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Adult neurogenesis from reprogrammed astrocytes. Neural regeneration research Griffiths, B. B., Bhutani, A., Stary, C. M. 2020; 15 (6): 973?79
Abstract

The details of adult neurogenesis, including environmental triggers, region specificity, and species homology remain an area of intense investigation. Slowing or halting age-related cognitive dysfunction, or restoring neurons lost to disease or injury represent just a fraction of potential therapeutic applications. New neurons can derive from stem cells, pluripotent neural progenitor cells, or non-neuronal glial cells, such as astrocytes. Astrocytes must be epigenetically "reprogrammed" to become neurons, which can occur both naturally in vivo, and via artificial exogenous treatments. While neural progenitor cells are localized to a few neurogenic zones in the adult brain, astrocytes populate almost every brain structure. In this review, we will summarize recent research into neurogenesis that arises from conversion of post-mitotic astrocytes, detail the genetic and epigenetic pathways that regulate this process, and discuss the possible clinical relevance in supplementing stem-cell neurogenic therapies.

View details for DOI 10.4103/1673-5374.270292

View details for PubMedID 31823866
Methods of Mitochondrial and Redox Measurements in Ischemic Stroke STROKE BIOMARKERS Arvola, O., Rao, A., Stary, C. M., Dambinova, S., Peplow, P. V., Martinez, B. 2020: 61?78
View details for DOI 10.1007/978-1-4939-9682-7_5

View details for Web of Science ID 000555477000007
Stem Cell-Derived Exosomes Protect Astrocyte Cultures From in vitro Ischemia and Decrease Injury as Post-stroke Intravenous Therapy FRONTIERS IN CELLULAR NEUROSCIENCE Sun, X., Jung, J., Arvola, O., Santoso, M. R., Giffard, R. G., Yang, P. C., Stary, C. M. 2019; 13
View details for DOI 10.3389/fncel.2019.00394

View details for Web of Science ID 000483577400001
Pre-treatment with microRNA-181a Antagomir Prevents Loss of Parvalbumin Expression and Preserves Novel Object Recognition Following Mild Traumatic Brain Injury NEUROMOLECULAR MEDICINE Griffiths, B. B., Sahbaie, P., Rao, A., Arvola, O., Xu, L., Liang, D., Ouyang, Y., Clark, D. J., Giffard, R. G., Stary, C. M. 2019; 21 (2): 170?81
View details for DOI 10.1007/s12017-019-08532-y

View details for Web of Science ID 000467933200008
Age-dependent sexual dimorphism in hippocampal cornu ammonis-1 perineuronal net expression in rats BRAIN AND BEHAVIOR Griffiths, B. B., Madden, A. K., Edwards, K. A., Zup, S. L., Stary, C. M. 2019; 9 (5)
View details for DOI 10.1002/brb3.1265

View details for Web of Science ID 000471349100006
Elucidating sex differences in response to cerebral ischemia: immunoregulatory mechanisms and the role of microRNAs PROGRESS IN NEUROBIOLOGY Kaidonis, G., Rao, A. N., Ouyang, Y., Stary, C. M. 2019; 176: 73?85
View details for DOI 10.1016/j.pneurobio.2018.08.001

View details for Web of Science ID 000466257100005
Sexually Dimorphic Response to Stroke of miR-181a and miR-200c in Aged Mice Griffiths, B. B., Arvola, O., Bhutani, A., Pastroudis, J., Xu Lijun, Stary, C. LIPPINCOTT WILLIAMS & WILKINS. 2019
View details for Web of Science ID 000478733401457
Ferroptosis Contributes to Isoflurane Neurotoxicity FRONTIERS IN MOLECULAR NEUROSCIENCE Xia, Y., Sun, X., Luo, Y., Stary, C. M. 2019; 11
View details for DOI 10.3389/fnmol.2018.00486

View details for Web of Science ID 000455338600003
Stem Cell-Derived Exosomes Protect Astrocyte Cultures From in vitro Ischemia and Decrease Injury as Post-stroke Intravenous Therapy. Frontiers in cellular neuroscience Sun, X., Jung, J. H., Arvola, O., Santoso, M. R., Giffard, R. G., Yang, P. C., Stary, C. M. 2019; 13: 394
Abstract

In the present study, we assessed efficacy of exosomes harvested from human and mouse stem cell cultures in protection of mouse primary astrocyte and neuronal cell cultures following in vitro ischemia, and against ischemic stroke in vivo. Cell media was collected from primary mouse neural stem cell (NSC) cultures or from human induced pluripotent stem cell-derived cardiomyocyte (iCM) cultures. Exosomes were extracted and purified by polyethylene glycol complexing and centrifugation, and exosome size and concentration were determined with a NanoSiteTM particle analyzer. Exosomes were applied to primary mouse cortical astrocyte or neuronal cultures prior to, and/or during, combined oxygen-glucose deprivation (OGD) injury. Cell death was assessed via lactate dehydrogenase (LHD) and propidium iodide staining 24 h after injury. NSC-derived exosomes afforded marked protection to astrocytes following OGD. A more modest (but significant) level of protection was observed with human iCM-derived exosomes applied to astrocytes, and with NSC-derived exosomes applied to primary neuronal cultures. In subsequent experiments, NSC-derived exosomes were injected intravenously into adult male mice 2 h after transient (1 h) middle cerebral artery occlusion (MCAO). Gross motor function was assessed 1 day after reperfusion and infarct volume was assessed 4 days after reperfusion. Mice treated post-stroke with intravenous NSC-derived exosomes exhibited significantly reduced infarct volumes. Together, these results suggest that exosomes isolated from mouse NSCs provide neuroprotection against experimental stroke possibly via preservation of astrocyte function. Intravenous NSC-derived exosome treatment may therefore provide a novel clinical adjuvant for stroke in the immediate post-injury period.

View details for DOI 10.3389/fncel.2019.00394

View details for PubMedID 31551712

View details for PubMedCentralID PMC6733914
Post-injury inhibition of miR-181a promotes restoration of hippocampal CA1 neurons after transient forebrain ischemia in rats. eNeuro Griffiths, B. B., Ouyang, Y. B., Xu, L., Sun, X., Giffard, R. G., Stary, C. M. 2019
Abstract

The cellular and molecular mechanisms regulating post-injury neurogenesis in the adult hippocampus remain undefined. We have previously demonstrated that pre-injury treatment with anti-microRNA-181a preserved neurons and prevented astrocyte dysfunction in the hippocampal CA1 following transient forebrain ischemia. In the present study we assessed post-injury treatment with anti-miR-181a on recovery of CA1 neurons following transient forebrain ischemia in rats. Stereotactic CA1 injection of miR-181a antagomir at either 2h or 7d post-injury resulted in improved restoration of CA1 measured at 28d post-injury. Treatment with antagomir was associated with overexpression of the mir-181a target cell-adhesion associated/related oncogene (CDON) protein and enhanced expression of the neuroprogenitor cell marker doublecortin (DCX) in the CA1. Assessment of GFAP+ cell fate by Cre/Lox-mediated deletion demonstrated that some GFAP+ cells in CA1 exhibited de novo DCX expression in response to injury. In vitro experiments using primary neuronal stem cells confirmed that miR-181a inhibition augmented expression of DCX and directed cellular differentiation towards a neuronal fate. These results suggest that miR-181a inhibition plays a central role in restoration of CA1 neurons via augmentation of early latent neurogenic gene activation in neuralprogenitor cells, including some reactive astrocytes. Therapeutic interventions targeting this restorative process may represent a novel post-injury approach to improve clinical outcomes in survivors of forebrain ischemia.Significance Statement Persistent cognitive impairment is a major source of decreased quality of life for survivors of cardiac arrest, with impaired memory cited as the most severe long-term deficit (Moulaert et al., 2009). Interruptions in cerebral blood flow result in delayed death of hippocampal CA1 neurons (Horn and Schlote, 1992). Pharmaceutical therapies given during this two-week therapeutic window could drastically reduce the cognitive deficits experienced by survivors of forebrain ischemia. However, interventions that have attempted to directly target neurons after forebrain ischemia have so far failed to translate to effective therapies. Therefore, there is an urgent need for novel treatments that either provide protection against loss or hasten functional recovery of CA1 neurons.

View details for DOI 10.1523/ENEURO.0002-19.2019

View details for PubMedID 31427401
Nursing Markedly Protects Postpartum Mice From Stroke: Associated Central and Peripheral Neuroimmune Changes and a Role for Oxytocin. Frontiers in neuroscience Stary, C. M., Xu, L., Voloboueva, L. A., Alc�ntara-Hern�ndez, M., Arvola, O. J., Idoyaga, J., Giffard, R. G. 2019; 13: 609
Abstract

Recent studies demonstrate significant neuroimmune changes in postpartum females, a period that also carries an increased risk of stroke. Oxytocin, a major hormone upregulated in the brains of nursing mothers, has been shown to both modulate neuroinflammation and protect against stroke. In the present study we assessed whether and how nursing modulates the neuroimmune response and injury after stroke. We observed that postpartum nursing mice were markedly protected from 1 h of transient middle cerebral artery occlusion (MCAO) relative to either non-pregnant/non-postpartum or non-nursing (pups removed) postpartum females. Nursing mice also expressed reduced levels of pro-inflammatory cytokines, had decreased migration of blood leukocytes into the brain following MCAO, and displayed peripheral neuroimmune changes characterized by increased spleen weight and increased fraction of spleen monocytes. Intranasal oxytocin treatment in non-pregnant females in part recapitulated the protective and anti-inflammatory effects associated with nursing. In summary, the results of the present study demonstrate that nursing in the postpartum period provides relative protection against transient ischemic stroke associated with decreased brain leukocytes and increased splenic monocytes. These effects appear to be regulated, at least in part, by oxytocin.

View details for DOI 10.3389/fnins.2019.00609

View details for PubMedID 31354401

View details for PubMedCentralID PMC6637858
Ferroptosis Contributes to Isoflurane Neurotoxicity. Frontiers in molecular neuroscience Xia, Y., Sun, X., Luo, Y., Stary, C. M. 2018; 11: 486
Abstract

The underlying mechanisms of isoflurane neurotoxicity in the developing brain remain unclear. Ferroptosis is a recently characterized form of programmed cell death distinct from apoptosis or autophagy, characterized by iron-dependent reactive oxygen species (ROS) generation secondary to failure of glutathione-dependent antioxidant defenses. The results of the present study are the first to demonstrate in vitro that ferroptosis is a central mechanism contributing to isoflurane neurotoxicity. We observed in embryonic mouse primary cortical neuronal cultures (day-in-vitro 7) that 6 h of 2% isoflurane exposure was associated with decreased transcription and protein expression of the lipid repair enzyme glutathione peroxidase 4. In parallel, isoflurane exposure resulted in increased ROS generation, disruption in mitochondrial membrane potential, and cell death. These effects were significantly attenuated by pre-treatment with the selective ferroptosis inhibitor ferrostatin-1 (Fer-1). Collectively, these observations provide a novel mechanism for isoflurane-induced injury in the developing brain and suggest that pre-treatment with Fer-1 may be a potential clinical intervention for neuroprotection.

View details for PubMedID 30687003

View details for PubMedCentralID PMC6333734
Inhibition of miR-181a protects female mice from transient focal cerebral ischemia by targeting astrocyte estrogen receptor-a. Molecular and cellular neurosciences Stary, C. M., Xu, L., Li, L., Sun, X., Ouyang, Y., Xiong, X., Zhao, J., Giffard, R. G. 2017; 82: 118-125
Abstract

Whether the effect of miR-181a is sexually dimorphic in stroke is unknown. Prior work showed protection of male mice with miR-181a inhibition. Estrogen receptor-? (ER?) is an identified target of miR181 in endometrium. Therefore we investigated the separate and joint effects of miR-181a inhibition and 17?-estradiol (E2) replacement after ovariectomy. Adult female mice were ovariectomized and implanted with an E2- or vehicle-containing capsule for 14d prior to 1h middle cerebral artery occlusion (MCAO). Each group received either miR-181a antagomir or mismatch control by intracerebroventricular injection 24h before MCAO. After MCAO neurologic deficit and infarct volume were assessed. Primary male and female astrocyte cultures were subjected to glucose deprivation with miR-181a inhibitor or transfection control, and E2 or vehicle control, with/without ESR? knockdown with small interfering RNA. Cell death was assessed by propidium iodide staining, and lactate dehydrogenase assay. A miR-181a/ER? target site blocker (TSB), with/without miR-181a mimic, was used to confirm targeting of ER? by miR-181a in astrocytes. Individually, miR-181a inhibition or E2 decreased infarct volume and improved neurologic score in female mice, and protected male and female astrocyte cultures. Combined miR-181a inhibition plus E2 afforded greater protection of female mice and female astrocyte cultures, but not in male astrocyte cultures. MiR-181a inhibition only increased ER? levels in vivo and in female cultures, while ER? knockdown with siRNA increased cell death in both sexes. Treatment with ER? TSB was strongly protective in both sexes. In conclusion, the results of the present study suggest miR-181a inhibition enhances E2-mediated stroke protection in females in part by augmenting ER? production, a mechanism detected in female mice and female astrocytes. Sex differences were observed with combined miR-181a inhibition/E2 treatment, and miR-181a targeting of ER?.

View details for DOI 10.1016/j.mcn.2017.05.004

View details for PubMedID 28522364
miR-29a differentially regulates cell survival in astrocytes from cornu ammonis 1 and dentate gyrus by targeting VDAC1. Mitochondrion Stary, C. M., Sun, X., Ouyang, Y., Li, L., Giffard, R. G. 2016; 30: 248-254
Abstract

Neurons in the cornu ammonis 1 (CA1) region of the hippocampus are vulnerable to cerebral ischemia, while dentate gyrus (DG) neurons are more resistant. This effect is mediated by local astrocytes, and may reflect differences in subregional hippocampal expression of miR-29a. We investigated the role of miR-29a on survival of hippocampal astrocytes cultured selectively from CA1 and DG in response to glucose deprivation (GD). CA1 astrocytes exhibited more cell death and a greater decrease in miR-29a than DG astrocytes. A reciprocal change was observed in the mitochondrial voltage dependent cation channel-1 (VDAC1), a regulator of mitochondria and target of miR-29a. In CA1 astrocytes, increasing miR-29a decreased VDAC1 and improved cell survival, while knockdown of VDAC1 improved survival. Finally, the protective effect of miR-29a was eliminated by inhibition of miR-29a/VDAC1 binding. These findings suggest that the selective vulnerability of the CA1 to injury may be due in part to a limited miR-29a response in CA1 astrocytes, allowing a greater increase in VDAC1-mediated cellular dysfunction in CA1 astrocytes.

View details for DOI 10.1016/j.mito.2016.08.013

View details for PubMedID 27553862
Astrocytes Protect against Isoflurane Neurotoxicity by Buffering pro-brain-derived Neurotrophic Factor. Anesthesiology Stary, C. M., Sun, X., Giffard, R. G. 2015; 123 (4): 810-819
Abstract

Isoflurane induces cell death in neurons undergoing synaptogenesis via increased production of pro-brain-derived neurotrophic factor (proBDNF) and activation of postsynaptic p75 neurotrophin receptor (p75). Astrocytes express p75, but their role in neuronal p75-mediated cell death remains unclear. The authors investigated whether astrocytes have the capacity to buffer increases in proBDNF and protect against isoflurane/p75 neurotoxicity.Cell death was assessed in day in vitro (DIV) 7 mouse primary neuronal cultures alone or in co-culture with age-matched or DIV 21 astrocytes with propidium iodide 24 h after 1 h exposure to 2% isoflurane or recombinant proBDNF. Astrocyte-targeted knockdown of p75 in co-culture was achieved with small-interfering RNA and astrocyte-specific transfection reagent and verified with immunofluorescence microscopy. proBDNF levels were assessed by enzyme-linked immunosorbent assay. Each experiment used six to eight replicate cultures/condition and was repeated at least three times.Exposure to isoflurane significantly (P < 0.05) increased neuronal cell death in primary neuronal cultures (1.5 � 0.7 fold, mean � SD) but not in co-culture with DIV 7 (1.0 � 0.5 fold) or DIV 21 astrocytes (1.2 � 1.2 fold). Exogenous proBDNF dose dependently induced neuronal cell death in both primary neuronal and co-cultures, an effect enhanced by astrocyte p75 inhibition. Astrocyte-targeted p75 knockdown in co-cultures increased media proBDNF (1.2 � 0.1 fold) and augmented isoflurane-induced neuronal cell death (3.8 � 3.1 fold).The presence of astrocytes provides protection to growing neurons by buffering increased levels of proBDNF induced by isoflurane. These findings may hold clinical significance for the neonatal and injured brain where increased levels of proBDNF impair neurogenesis.

View details for DOI 10.1097/ALN.0000000000000824

View details for PubMedID 26270940
MicroRNA-200c Contributes to Injury From Transient Focal Cerebral Ischemia by Targeting Reelin. Stroke; a journal of cerebral circulation Stary, C. M., Xu, L., Sun, X., Ouyang, Y., White, R. E., Leong, J., Li, J., Xiong, X., Giffard, R. G. 2015; 46 (2): 551-556
View details for DOI 10.1161/STROKEAHA.114.007041

View details for PubMedID 25604249
Pre-treatment with miR-182 Antagomir Mitigates Ischemic Brain Damage by Reducing Astrocytes Injury and Inflammation Alhadidi, Q., Xu, L., Sun, X., Althobaiti, Y., Almalki, A., Alsaab, H., Stary, C. WILEY. 2020
View details for DOI 10.1096/fasebj.2020.34.s1.08888

View details for Web of Science ID 000546023103610
Systematic Study of the Immune Components after Ischemic Stroke Using CyTOF Techniques. Journal of immunology research Li, Y., Wang, Y., Yao, Y., Griffiths, B. B., Feng, L., Tao, T., Wang, F., Xu, B., Stary, C. M., Zhao, H. 2020; 2020: 9132410
Abstract

Stroke induces a robust inflammatory response. However, it still lacks a systematic view of the various immune cell types due to the limited numbers of fluorophore used in the traditional FACS technique. In our current study, we utilized the novel technique mass cytometry (CyTOF) to analyze multiple immune cell types. We detected these immune cells from the ischemic brain, peripheral blood, spleen, and bone marrow at different time courses after stroke. Our data showed (1) dynamic changes in the immune cell numbers in the ischemic brain and peripheral organs. (2) The expression levels of cell surface markers indicate the inflammation response status after stroke. Interestingly, CD62L, a key adhesion molecule, regulates the migration of leukocytes from blood vessels into secondary lymphoid tissues and peripheral tissues. (3) A strong leukocyte network across the brain and peripheral immune organs was identified using the R program at day 1 after ischemia, suggesting that the peripheral immune cells dramatically migrated into the ischemic areas after stroke. This study provides a systematic, wide view of the immune components in the brain and peripheral organs for a deep understanding of the immune response after ischemic stroke.

View details for DOI 10.1155/2020/9132410

View details for PubMedID 32908941

View details for PubMedCentralID PMC7474762
Pregabalin: Potential for Addiction and a Possible Glutamatergic Mechanism. Scientific reports Althobaiti, Y. S., Almalki, A., Alsaab, H., Alsanie, W., Gaber, A., Alhadidi, Q., Hardy, A. M., Nasr, A., Alzahrani, O., Stary, C. M., Shah, Z. A. 2019; 9 (1): 15136
Abstract

Drug addiction remains a prevalent and fatal disease worldwide that carries significant social and economic impacts. Recent reports suggest illicit pregabalin (Lyrica) use may be increasing among youth, however the addictive potential of pregabalin has not been well established. Drug seeking behavior and chronic drug use are associated with deficits in glutamate clearance and activation of postsynaptic glutamatergic receptors. In the current study, we investigated the abuse potential of pregabalin using conditioned place preference (CPP) paradigm. Different doses of pregabalin (30, 60, 90, and 120mg/kg) were used to assess the seeking behavior in mice. Glutamate homeostasis is maintained by glutamate transporter type-1 (GLT-1), which plays a vital role in clearing the released glutamate from synapses and drug seeking behavior. Therefore, we investigated the role of glutamate in pregabalin-seeking behavior with ceftriaxone (CEF), a potent GLT-1 upregulator. Mice treated with pregabalin 60 and 90mg/kg doses demonstrated drug seeking-like behavior, which was significantly blocked by CEF pretreatment. These results suggest that pregabalin-induced CPP was successfully modulated by CEF which could serve as a lead compound for developing treatment for pregabalin abuse.

View details for DOI 10.1038/s41598-019-51556-4

View details for PubMedID 31641170
Nursing Markedly Protects Postpartum Mice From Stroke: Associated Central and Peripheral Neuroimmune Changes and a Role for Oxytocin FRONTIERS IN NEUROSCIENCE Stary, C. M., Xu, L., Voloboueva, L. A., Alcantara-Hernandez, M., Arvola, O. J., Idoyaga, J., Giffard, R. G. 2019; 13
View details for DOI 10.3389/fnins.2019.00609

View details for Web of Science ID 000474791200001
Hippocampal sub-regional differences in the microRNA response to forebrain ischemia. Molecular and cellular neurosciences Arvola, O., Kaidonis, G., Xu, L., Griffiths, B., Stary, C. M. 2019
Abstract

Transient forebrain ischemia, as occurs with cardiac arrest and resuscitation, results in impaired cognitive function secondary to delayed neuronal cell death in hippocampal cornu ammonis-1 (CA1). Comparatively, hippocampal neurons in the adjacent dentate gyrus (DG) survive, suggesting that elucidating the molecular mechanisms underpinning hippocampal sub-regional differences in ischemic tolerance could be central in the development of novel interventions to improve outcome in survivors of forebrain ischemia. MicroRNAs (miRNAs) are non-coding RNAs that modulate the translation of target genes and have been established as an effective therapeutic target for other models of injury. The objective of the present study was to assess and compare post-injury miRNA profiles between CA1 and DG using a rat model of forebrain ischemia. CA1 and DG sub-regions were dissected from rat hippocampi following 10?min of forebrain ischemia at three time points (3?h, 24?h, and 72?h) and at baseline. Pronounced differences between CA1 and DG were observed for several select miRNAs, including miR-181a-5p, a known regulator of cerebral ischemic injury. We complexed fluorescent in situ hybridization with immunohistochemistry to observe cell-type specific and temporal differences in mir-181a-5p expression between CA1 and DG in response to injury. Using established miRNA-mRNA prediction algorithms, we extended our observations in CA1 miRNA dysregulation to identify key functional pathways as potential modulators of CA1 ischemic vulnerability. In summary, our observations support a central role for miRNAs in selective CA1 ischemic vulnerability and suggest that cell-specific miRNA targeting could be a viable clinical approach to preserve CA1 neurons and improve cognitive outcomes for survivors of transient forebrain ischemia.

View details for DOI 10.1016/j.mcn.2019.05.003

View details for PubMedID 31128240
Bidirectional gut-brain-microbiota axis as a potential link between inflammatory bowel disease and ischemic stroke. Journal of neuroinflammation Zhao, L., Xiong, Q., Stary, C. M., Mahgoub, O. K., Ye, Y., Gu, L., Xiong, X., Zhu, S. 2018; 15 (1): 339
Abstract

Emerging evidence suggests that gut-brain-microbiota axis (GBMAx) may play a pivotal role linking gastrointestinal and neuronal disease. In this review, we summarize the latest advances in studies of GBMAx in inflammatory bowel disease (IBD) and ischemic stroke. A more thorough understanding of the GBMAx could advance our knowledge about the pathophysiology of IBD and ischemic stroke and help to identify novel therapeutic targets via modulation of the GBMAx.

View details for PubMedID 30537997
Elucidating sex differences in response to cerebral ischemia: immunoregulatory mechanisms and the role of microRNAs. Progress in neurobiology Kaidonis, G., Rao, A. N., Ouyang, Y., Stary, C. M. 2018
Abstract

Cerebral ischemia remains a major cause of death and disability worldwide, yet therapeutic options remain limited. Differences in sex and age play an important role in the final outcome in response to cerebral ischemia in both experimental and clinical studies: males have a higher risk and worse outcome than females at younger ages and this trend reverses in older ages. Although the molecular mechanisms underlying sex dimorphism are complex and are still not well understood, studies suggest steroid hormones, sex chromosomes, differential cell death and immune pathways, and sex-specific microRNAs may contribute to the outcome following cerebral ischemia. This review focuses on differential effects between males and females on cell death and immunological pathways in response to cerebral ischemia, the central role of innate sex differences in steroid hormone signaling, and upstream regulation of sexually dimorphic gene expression by microRNAs.

View details for PubMedID 30121237
Micro-RNAs in the pathogenesis of epiretinal membrane (ERM) formation Kaidonis, G., Stary, C. M., Leng, T. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2018
View details for Web of Science ID 000442932805293
Engineering chimeric antigen receptor-T cells for cancer treatment MOLECULAR CANCER Ye, B., Stary, C. M., Li, X., Gao, Q., Kang, C., Xiong, X. 2018; 17: 32
Abstract

Intratumor heterogeneity of tumor clones and an immunosuppressive microenvironment in cancer ecosystems contribute to inherent difficulties for tumor treatment. Recently, chimeric antigen receptor (CAR) T-cell therapy has been successfully applied in the treatment of B-cell malignancies, underscoring its great potential in antitumor therapy. However, functional challenges of CAR-T cell therapy, especially in solid tumors, remain. Here, we describe cancer-immunity phenotypes from a clonal-stromal-immune perspective and elucidate mechanisms of T-cell exhaustion that contribute to tumor immune evasion. Then we assess the functional challenges of CAR-T cell therapy, including cell trafficking and infiltration, targeted-recognition and killing of tumor cells, T-cell proliferation and persistence, immunosuppressive microenvironment and self-control regulation. Finally, we delineate tumor precision informatics and advancements in engineered CAR-T cells to counteract inherent challenges of the CAR-T cell therapy, either alone or in combination with traditional therapeutics, and highlight the therapeutic potential of this approach in future tumor precision treatment.

View details for PubMedID 29448937
Anesthetic neurotoxicity: an emerging role for glia in neuroprotection JOURNAL OF MOLECULAR MEDICINE-JMM Bell, J. D., Stary, C. M. 2017; 95 (4): 349-351
View details for DOI 10.1007/s00109-017-1523-7

View details for Web of Science ID 000398516800001

View details for PubMedID 28246725
Genetically Modified T-Cell-Based Adoptive Immunotherapy in Hematological Malignancies JOURNAL OF IMMUNOLOGY RESEARCH Ye, B., Stary, C. M., Gao, Q., Wang, Q., Zeng, Z., Jian, Z., Gu, L., Xiong, X. 2017
Abstract

A significant proportion of hematological malignancies remain limited in treatment options. Immune system modulation serves as a promising therapeutic approach to eliminate malignant cells. Cytotoxic T lymphocytes (CTLs) play a central role in antitumor immunity; unfortunately, nonspecific approaches for targeted recognition of tumor cells by CTLs to mediate tumor immune evasion in hematological malignancies imply multiple mechanisms, which may or may not be clinically relevant. Recently, genetically modified T-cell-based adoptive immunotherapy approaches, including chimeric antigen receptor (CAR) T-cell therapy and engineered T-cell receptor (TCR) T-cell therapy, promise to overcome immune evasion by redirecting the specificity of CTLs to tumor cells. In clinic trials, CAR-T-cell- and TCR-T-cell-based adoptive immunotherapy have produced encouraging clinical outcomes, thereby demonstrating their therapeutic potential in mitigating tumor development. The purpose of the present review is to (1) provide a detailed overview of the multiple mechanisms for immune evasion related with T-cell-based therapies; (2) provide a current summary of the applications of CAR-T-cell- as well as neoantigen-specific TCR-T-cell-based adoptive immunotherapy and routes taken to overcome immune evasion; and (3) evaluate alternative approaches targeting immune evasion via optimization of CAR-T and TCR-T-cell immunotherapies.

View details for DOI 10.1155/2017/5210459

View details for Web of Science ID 000392609000001

View details for PubMedID 28116322

View details for PubMedCentralID PMC5237740
Serum prealbumin as an effective prognostic indicator for determining clinical status and prognosis in patients with hemorrhagic stroke. Neural regeneration research Zhang, S. Q., Peng, B., Stary, C. M., Jian, Z. H., Xiong, X. X., Chen, Q. X. 2017; 12 (7): 1097?1102
Abstract

Serum prealbumin is a recognized marker of malnutrition, but its prognostic role in patients with hemorrhagic stroke remains unclear. In this study, we retrospectively reviewed the records of 105 patients with hemorrhagic stroke admitted to Renmin Hospital of Wuhan University, China, from January to December 2015. We collected demographic and radiological data, and recorded serum prealbumin levels at admission and on days 1, 3, 6, 9, and 14-21. The existence of infections and gastrointestinal hemorrhage, and clinical condition at discharge were also recorded. Serum prealbumin levels during hospitalization were significantly lower in patients with infections compared with those without infections, and also significantly lower in patients with gastrointestinal hemorrhage compared with those without. Serum prealbumin levels at discharge were significantly higher in patients with good recovery than in those with poor recovery. We conclude that regular serum prealbumin measurements in patients with hemorrhagic stroke may be a useful indicator for determining clinical status and prognosis, which may therefore help to guide clinical decision-making.

View details for PubMedID 28852391

View details for PubMedCentralID PMC5558488
Exaggerated Oculocardiac Reflex Elicited by Local Anesthetic Injection of an Empty Orbit: A Case Report. A & A case reports Nicholson, D., Kossler, A., Topping, K., Stary, C. M. 2017
Abstract

We report the first description of oculocardiac reflex elicited with injection of local anesthetic in an empty orbit, and highlight clinical indicators for patients that may be at risk for an exaggerated oculocardiac reflex. We describe a patient with prior head and eye trauma treated for anophthalmic socket reconstruction at an outpatient eye surgery center. Injection of local anesthetic into the empty orbit induced an extended sinus arrest. This exaggerated response was avoided in a subsequent surgery by pretreatment with high-dose anticholinergics.

View details for DOI 10.1213/XAA.0000000000000609

View details for PubMedID 28767475
Advances in Immunotherapy for Glioblastoma Multiforme JOURNAL OF IMMUNOLOGY RESEARCH Huang, B., Zhang, H., Gu, L., Ye, B., Jian, Z., Stary, C., Xiong, X. 2017
Abstract

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults. Patients with GBM have poor outcomes, even with the current gold-standard first-line treatment: maximal safe resection combined with radiotherapy and temozolomide chemotherapy. Accumulating evidence suggests that advances in antigen-specific cancer vaccines and immune checkpoint blockade in other advanced tumors may provide an appealing promise for immunotherapy in glioma. The future of therapy for GBM will likely incorporate a combinatorial, personalized approach, including current conventional treatments, active immunotherapeutics, plus agents targeting immunosuppressive checkpoints.

View details for DOI 10.1155/2017/3597613

View details for Web of Science ID 000396149400001

View details for PubMedID 28299344
The inflammasome as a target for pain therapy BRITISH JOURNAL OF ANAESTHESIA Zhang, H., Li, F., Li, W., Stary, C., Clark, J. D., Xu, S., Xiong, X. 2016; 117 (6): 693-707
Abstract

The interleukin-1 family of cytokines are potent inducers of inflammation and pain. Proteolytic activation of this family of cytokines is under the control of several innate immune receptors that coordinate to form large multiprotein signalling platforms, termed inflammasomes. Recent evidence suggests that a wide range of inflammatory diseases, cancers, and metabolic and autoimmune disorders, in which pain is a common complaint, may be coordinated by inflammasomes. Activation of inflammasomes results in cleavage of caspase-1, which subsequently induces downstream initiation of several potent pro-inflammatory cascades. Therefore, it has been proposed that targeting inflammasome activity may be a novel and effective therapeutic strategy for these pain-related diseases. The purpose of this narrative review article is to provide the reader with an overview of the activation and regulation of inflammasomes and to investigate the potential therapeutic role of inflammasome inhibition in the treatment of diseases characterized by pain, including the following: complex regional pain syndrome, gout, rheumatoid arthritis, inflammatory pain, neuropathic pain, chronic prostatitis, chronic pelvic pain syndrome, and fibromyalgia. We conclude that the role of the inflammasome in pain-associated diseases is likely to be inflammasome subtype and disease specific. The currently available evidence suggests that disease-specific targeting of the assembly and activity of the inflammasome complex may be a novel therapeutic opportunity for the treatment of refractory pain in many settings.

View details for DOI 10.1093/bja/aew376

View details for Web of Science ID 000389640900005

View details for PubMedID 27956668

View details for PubMedCentralID PMC5155560
Transient Receptor Potential Vanilloid 1 Regulates Mitochondrial Membrane Potential and Myocardial Reperfusion Injury. Journal of the American Heart Association Hurt, C. M., Lu, Y., M Stary, C., Piplani, H., Small, B. A., Urban, T. J., Qvit, N., Gross, G. J., Mochly-Rosen, D., Gross, E. R. 2016; 5 (9)
Abstract

The transient receptor potential vanilloid 1 (TRPV1) mediates cellular responses to pain, heat, or noxious stimuli by calcium influx; however, the cellular localization and function of TRPV1 in the cardiomyocyte is largely unknown. We studied whether myocardial injury is regulated by TRPV1 and whether we could mitigate reperfusion injury by limiting the calcineurin interaction with TRPV1.In primary cardiomyocytes, confocal and electron microscopy demonstrates that TRPV1 is localized to the mitochondria. Capsaicin, the specific TRPV1 agonist, dose-dependently reduced mitochondrial membrane potential and was blocked by the TRPV1 antagonist capsazepine or the calcineurin inhibitor cyclosporine. Using in silico analysis, we discovered an interaction site for TRPV1 with calcineurin. We synthesized a peptide, V1-cal, to inhibit the interaction between TRPV1 and calcineurin. In an in�vivo rat myocardial infarction model, V1-cal given just prior to reperfusion substantially mitigated myocardial infarct size compared with vehicle, capsaicin, or cyclosporine (24�3% versus 61�2%, 45�1%, and 49�2%, respectively; n=6 per group; P<0.01 versus all groups). Infarct size reduction by V1-cal was also not seen in TRPV1 knockout rats.TRPV1 is localized at the mitochondria in cardiomyocytes and regulates mitochondrial membrane potential through an interaction with calcineurin. We developed a novel therapeutic, V1-cal, that substantially reduces reperfusion injury by inhibiting the interaction of calcineurin with TRPV1. These data suggest that TRPV1 is an end-effector of cardioprotection and that modulating the TRPV1 protein interaction with calcineurin limits reperfusion injury.

View details for PubMedID 27671317
A high-resolution method for assessing cellular oxidative phosphorylation efficiency: bringing mitochondrial bioenergetics into focus. Focus on "Direct real-time quantification of mitochondrial oxidative phosphorylation efficiency in permeabilized skeletal muscle myofibers". American journal of physiology. Cell physiology Stary, C. M. 2016; 311 (2): C237-8
View details for DOI 10.1152/ajpcell.00203.2016

View details for PubMedID 27413172
Cytosolic calcium transients are a determinant of contraction-induced HSP72 transcription in single skeletal muscle fibers JOURNAL OF APPLIED PHYSIOLOGY Stary, C. M., Hogan, M. C. 2016; 120 (10): 1260-1266
Abstract

The intrinsic activating factors that induce transcription of heat shock protein 72 (HSP72) in skeletal muscle following exercise remain unclear. We hypothesized that the cytosolic Ca(2+) transient that occurs with depolarization is a determinant. We utilized intact, single skeletal muscle fibers from Xenopus laevis to test the role of the cytosolic Ca(2+) transient and several other exercise-related factors (fatigue, hypoxia, AMP kinase, and cross-bridge cycling) on the activation of HSP72 transcription. HSP72 and HSP60 mRNA levels were assessed with real-time quantitative PCR; cytosolic Ca(2+) concentration ([Ca(2+)]cyt) was assessed with fura-2. Both fatiguing and nonfatiguing contractions resulted in a significant increase in HSP72 mRNA. As expected, peak [Ca(2+)]cyt remained tightly coupled with peak developed tension in contracting fibers. Pretreatment with N-benzyl-p-toluene sulfonamide (BTS) resulted in depressed peak developed tension with stimulation, while peak [Ca(2+)]cyt remained largely unchanged from control values. Despite excitation-contraction uncoupling, BTS-treated fibers displayed a significant increase in HSP72 mRNA. Treatment of fibers with hypoxia (Po2: <3 mmHg) or AMP kinase activation had no effect on HSP72 mRNA levels. These results suggest that the intermittent cytosolic Ca(2+) transient that occurs with skeletal muscle depolarization provides a sufficient activating stimulus for HSP72 transcription. Metabolic or mechanical factors associated with fatigue development and cross-bridge cycling likely play a more limited role.

View details for DOI 10.1152/japplphysiol.01060.2015

View details for Web of Science ID 000376691800018

View details for PubMedID 26869714

View details for PubMedCentralID PMC4867320
Targeting Glial Mitochondrial Function for Protection from Cerebral Ischemia: Relevance, Mechanisms, and the Role of MicroRNAs OXIDATIVE MEDICINE AND CELLULAR LONGEVITY Li, L., Stary, C. M. 2016
Abstract

Astrocytes and microglia play crucial roles in the response to cerebral ischemia and are effective targets for stroke therapy in animal models. MicroRNAs (miRs) are important posttranscriptional regulators of gene expression that function by inhibiting the translation of select target genes. In astrocytes, miR expression patterns regulate mitochondrial function in response to oxidative stress via targeting of Bcl2 and heat shock protein 70 family members. Mitochondria play an active role in microglial activation, and miRs regulate the microglial neuroinflammatory response. As endogenous miR expression patterns can be altered with exogenous mimics and inhibitors, miR-targeted therapies represent a viable intervention to optimize glial mitochondrial function and improve clinical outcome following cerebral ischemia. In the present article, we review the role that astrocytes and microglia play in neuronal function and fate following ischemic stress, discuss the relevance of mitochondria in the glial response to injury, and present current evidence implicating miRs as critical regulators in the glial mitochondrial response to cerebral ischemia.

View details for DOI 10.1155/2016/6032306

View details for Web of Science ID 000385104800001

View details for PubMedID 27777645

View details for PubMedCentralID PMC5061974
Exploring and exploiting unique properties of the hippocampal dentate gyrus for post-stroke therapy: astrocytes link ischemic resistance with neurogenic potential. Neural regeneration research Stary, C. M. 2016; 11 (11): 1756?57
View details for PubMedID 28123412

View details for PubMedCentralID PMC5204224
Single-Cell Sequencing Technology in Oncology: Applications for Clinical Therapies and Research. Analytical cellular pathology Ye, B., Gao, Q., Zeng, Z., Stary, C. M., Jian, Z., Xiong, X., Gu, L. 2016; 2016: 9369240-?
Abstract

Cellular heterogeneity is a fundamental characteristic of many cancers. A lack of cellular homogeneity contributes to difficulty in designing targeted oncological therapies. Therefore, the development of novel methods to determine and characterize oncologic cellular heterogeneity is a critical next step in the development of novel cancer therapies. Single-cell sequencing (SCS) technology has been recently employed for analyzing the genetic polymorphisms of individual cells at the genome-wide level. SCS requires (1) precise isolation of the single cell of interest; (2) isolation and amplification of genetic material; and (3) descriptive analysis of genomic, transcriptomic, and epigenomic data. In addition to targeted analysis of single cells isolated from tumor biopsies, SCS technology may be applied to circulating tumor cells, which may aid in predicting tumor progression and metastasis. In this paper, we provide an overview of SCS technology and review the current literature on the potential application of SCS to clinical oncology and research.

View details for DOI 10.1155/2016/9369240

View details for PubMedID 27313981

View details for PubMedCentralID PMC4897661
Physiologically normal 5% O2 supports neuronal differentiation and resistance to inflammatory injury in neural stem cell cultures. Journal of neuroscience research Sun, X., Voloboueva, L. A., Stary, C. M., Giffard, R. G. 2015; 93 (11): 1703-1712
Abstract

Recent studies have demonstrated that neural stem cell (NSC) culture at physiologically normoxic conditions (2-5% O2 ) is advantageous in terms of neuronal differentiation and survival. Neuronal differentiation is accompanied by a remarkable shift to mitochondrial oxidative metabolism compared with preferentially glycolytic metabolism of proliferating cells. However, metabolic changes induced by growth in a normoxic (5%) O2 culture environment in NSCs have been minimally explored. This study demonstrates that culturing under 5% O2 conditions results in higher levels of mitochondrial oxidative metabolism, decreased glycolysis, and reduced levels of reactive oxygen species in NSC cultures. Inflammation is one of the major environmental factors limiting postinjury NSC neuronal differentiation and survival. Our results show that NSCs differentiated under 5% O2 conditions possess better resistance to in vitro inflammatory injury compared with those exposed to 20% O2 . The present work demonstrates that lower, more physiologically normal O2 levels support metabolic changes induced during NSC neuronal differentiation and provide increased resistance to inflammatory injury, thus highlighting O2 tension as an important determinant of cell fate and survival in various stem cell therapies. � 2015 Wiley Periodicals, Inc.

View details for DOI 10.1002/jnr.23615

View details for PubMedID 26147710

View details for PubMedCentralID PMC4575628
Physiologically normal 5% O2 supports neuronal differentiation and resistance to inflammatory injury in neural stem cell cultures. Journal of neuroscience research Sun, X., Voloboueva, L. A., Stary, C. M., Giffard, R. G. 2015; 93 (11): Spc1-?
Abstract

Recent studies have demonstrated that neural stem cell (NSC) culture at physiologically normoxic conditions (2-5% O2 ) is advantageous in terms of neuronal differentiation and survival. Neuronal differentiation is accompanied by a remarkable shift to mitochondrial oxidative metabolism compared with preferentially glycolytic metabolism of proliferating cells. However, metabolic changes induced by growth in a normoxic (5%) O2 culture environment in NSCs have been minimally explored. This study demonstrates that culturing under 5% O2 conditions results in higher levels of mitochondrial oxidative metabolism, decreased glycolysis, and reduced levels of reactive oxygen species in NSC cultures. Inflammation is one of the major environmental factors limiting postinjury NSC neuronal differentiation and survival. Our results show that NSCs differentiated under 5% O2 conditions possess better resistance to in vitro inflammatory injury compared with those exposed to 20% O2 . The present work demonstrates that lower, more physiologically normal O2 levels support metabolic changes induced during NSC neuronal differentiation and provide increased resistance to inflammatory injury, thus highlighting O2 tension as an important determinant of cell fate and survival in various stem cell therapies. � 2015 Wiley Periodicals, Inc.

View details for DOI 10.1002/jnr.23675

View details for PubMedID 26384084
Epigenetics: The Epicenter for Future Anesthesia Research? Anesthesiology Stary, C. M., Patel, H. H., Roth, D. M. 2015; 123 (4): 743-744
View details for DOI 10.1097/ALN.0000000000000808

View details for PubMedID 26259141
T Cells and Cerebral Ischemic Stroke NEUROCHEMICAL RESEARCH Gu, L., Jian, Z., Stary, C., Xiong, X. 2015; 40 (9): 1786-1791
View details for DOI 10.1007/s11064-015-1676-0

View details for Web of Science ID 000360546600002
Advances in Astrocyte-targeted Approaches for Stroke Therapy: An Emerging Role for Mitochondria and microRNAS. Neurochemical research Stary, C. M., Giffard, R. G. 2015; 40 (2): 301-307
Abstract

Astrocytes are critical regulators of neuronal function and an effective target for stroke therapy in animal models. Identifying individual targets with the potential for simultaneous activation of multiple downstream pathways that regulate astrocyte homeostasis may be a necessary element for successful clinical translation. Mitochondria and microRNAs each represent individual targets with multi-modal therapeutic potential. Mitochondria regulate metabolism and apoptosis, while microRNAs have the capacity to bind and inhibit numerous mRNAs. By combining strategies targeted at maintaining astrocyte function during and following cerebral ischemia, a synergistic therapeutic effect may be achieved.

View details for DOI 10.1007/s11064-014-1373-4

View details for PubMedID 24993363
Post-stroke treatment with miR-181 antagomir reduces injury and improves long-term behavioral recovery in mice after focal cerebral ischemia. Experimental neurology Xu, L., Ouyang, Y., Xiong, X., Stary, C. M., Giffard, R. G. 2015; 264: 1-7
Abstract

miR-181 has deleterious effects on stroke outcome, and reducing miR-181a levels prior to middle cerebral artery occlusion (MCAO) was shown previously to be protective. Here we tested the effect of post-ischemic treatment with miR-181a antagomir by intracerebroventricular and intravenous routes of administration on infarct size, neurological outcome, inflammatory response and long term behavioral outcome. Post-treatment with miR-181a antagomir significantly reduced infarction size, improved neurological deficits and reduced NF-?B activation, numbers of infiltrating leukocytes and levels of Iba1. Targets affected by miR-181a antagomir administered after stroke onset include BCL2 and X-linked inhibitor of apoptosis protein (XIAP). Post-treatment with miR-181a antagomir significantly improved behavioral outcome assessed by rotarod at one month. These findings indicate that post-treatment with miR-181a antagomir has neuroprotective effects against ischemic neuronal damage and neurological impairment in mice, and the protection is long lasting including recovery of motor function and coordination over one month. The ability to protect the brain with post-treatment with miR-181a antagomir with long lasting effect makes this a promising therapeutic target and may be an innovative and effective new approach for stroke therapy.

View details for DOI 10.1016/j.expneurol.2014.11.007

View details for PubMedID 25433215
Role of caveolin-3 in lymphocyte activation. Life sciences Tran, C., Stary, C. M., Schilling, J. M., Bentley, B., Patel, H. H., Roth, D. M. 2015; 121: 35-39
Abstract

Caveolins are structural proteins clustered in lipid-rich regions of plasma membrane involved in coordinating signal transduction in various organ systems. While caveolin-1 (Cav-1) has been shown to regulate lymphocyte activation, the role of caveolin-3 (Cav-3) in immune system signaling has not been investigated. We tested the hypothesis that Cav-3 modulates lymphocyte activation.Lymphocyte/leukocyte subpopulations from WT and Cav-3 mice were profiled with flow cytometry. Cytokine production in quiescent and activated splenocytes from WT and Cav-3 mice was assessed with ELISA.Levels of T-cells, monocytes, and natural killer cells were not different between WT and KO mice, however KO mice had lower B-cell population-percentage. Functionally, activated lymphocytes from Cav-3 KO mice demonstrated significantly reduced expression of IL-2 compared to WT, while expression of TNF?, IL-6, and IL-10 was not different. Finally, expression of IL-17 was significantly reduced in T-helper cells from KO mice, while IFN? was not, suggesting that Cav-3 is a determinant in the development of the Th-17 subpopulation.This study is the first to demonstrate that Cav-3 may be a novel participant in B-cell expression, T-cell cytokine production and activation of inflammation.

View details for DOI 10.1016/j.lfs.2014.11.017

View details for PubMedID 25476831
The Use of microRNAs to Modulate Redox and Immune Response to Stroke. Antioxidants & redox signaling Ouyang, Y., Stary, C. M., White, R. E., Giffard, R. G. 2015; 22 (2): 187-202
Abstract

Significance: Cerebral ischemia is a major cause of death and disability throughout the world, yet therapeutic options remain limited. The interplay between cellular redox state and the immune response plays a critical role in determining the extent of neural cell injury after ischemia and reperfusion. Excessive amounts of reactive oxygen species (ROS) generated by mitochondria and other sources act both as triggers and effectors of inflammation. This review will focus on the interplay between these two mechanisms. Recent Advances: MicroRNAs (miRNAs) are important post-transcriptional regulators that interact with multiple target messenger RNAs (mRNAs) coordinately regulating target genes including those involved in controlling mitochondrial function, redox state, and inflammatory pathways. This review will focus on the regulation of mitochondria, ROS, and inflammation by miRNAs in the chain of deleterious intra- and intercellular events that lead to brain cell death after cerebral ischemia. Critical Issues: Although pretreatment using miRNAs was effective in cerebral ischemia in rodents, testing treatment after the onset of ischemia is an essential next step in the development of acute stroke treatment. In addition, miRNA formulation and delivery into the CNS remain a challenge in the clinical translation of miRNA therapy. Future Directions: Future research should focus on post-treatment and potential clinical use of miRNAs.

View details for DOI 10.1089/ars.2013.5757

View details for PubMedID 24359188
Molecular Pathogenesis of Anti-NMDAR Encephalitis BIOMED RESEARCH INTERNATIONAL Ding, H., Jian, Z., Stary, C. M., Yi, W., Xiong, X. 2015
Abstract

Anti-NMDAR encephalitis is a recently identified autoimmune disease, described by an immune-mediated loss of NMDA glutamate receptors, resulting in progressive mental deterioration. To date, literature on anti-NMDAR encephalitis has been largely clinically oriented, including descriptions of the clinical presentation and course, diagnostic methods, and potential clinical treatments. However, the underlying molecular mechanisms contributing to the complex immunological cellular transformation that is associated with the progression of anti-NMDAR encephalitis remain to be adequately explored. This review will provide a summary of the current literature on anti-NMDAR encephalitis, including the immunologic molecular mechanisms contributing to disease progression. In particular this review will focus on the effect of anti-NMDAR on GluN2-NMDAR expression and the molecular transformation of B and T leukocytes in the loss of self-tolerance. Further research on the immunologic mechanisms contributing to anti-NMDAR encephalitis may provide an avenue for future novel diagnostic approaches, such as immunologic surveillance, as well as new therapeutic strategies for this recently identified autoimmune disease.

View details for DOI 10.1155/2015/643409

View details for Web of Science ID 000357828300001

View details for PubMedID 26221602

View details for PubMedCentralID PMC4499418
microRNAs: Innovative Targets for Cerebral Ischemia and Stroke CURRENT DRUG TARGETS Ouyang, Y., Stary, C. M., Yang, G., Giffard, R. 2013; 14 (1): 90-101
Abstract

Stroke is one of the leading causes of death and disability worldwide. Because stroke is a multifactorial disease with a short therapeutic window many clinical stroke trials have failed and the only currently approved therapy is thrombolysis. MicroRNAs (miRNA) are endogenously expressed noncoding short single-stranded RNAs that play a role in the regulation of gene expression at the post-transcriptional level, via degradation or translational inhibition of their target mRNAs. The study of miRNAs is rapidly growing and recent studies have revealed a significant role of miRNAs in ischemic disease. miRNAs are especially important candidates for stroke therapeutics because of their ability to simultaneously regulate many target genes and since to date targeting single genes for therapeutic intervention has not yet succeeded in the clinic. Although there are already quite a few review articles about miRNA in ischemic heart disease, much less is currently known about miRNAs in cerebral ischemia. This review summarizes current knowledge about miRNAs and cerebral ischemia, focusing on the role of miRNAs in ischemia, both changes in expression and identification of potential targets, as well as the potential of miRNAs as biomarkers and therapeutic targets in cerebral ischemia.

View details for Web of Science ID 000316871200010

View details for PubMedID 23170800
Caveolins: targeting pro-survival signaling in the heart and brain. Frontiers in physiology Stary, C. M., Tsutsumi, Y. M., Patel, P. M., Head, B. P., Patel, H. H., Roth, D. M. 2012; 3: 393-?
Abstract

The present review discusses intracellular signaling moieties specific to membrane lipid rafts (MLRs) and the scaffolding proteins caveolin and introduces current data promoting their potential role in the treatment of pathologies of the heart and brain. MLRs are discreet microdomains of the plasma membrane enriched in gylcosphingolipids and cholesterol that concentrate and localize signaling molecules. Caveolin proteins are necessary for the formation of MLRs, and are responsible for coordinating signaling events by scaffolding and enriching numerous signaling moieties in close proximity. Specifically in the heart and brain, caveolins are necessary for the cytoprotective phenomenon termed ischemic and anesthetic preconditioning. Targeted overexpression of caveolin in the heart and brain leads to induction of multiple pro-survival and pro-growth signaling pathways; thus, caveolins represent a potential novel therapeutic target for cardiac and neurological pathologies.

View details for DOI 10.3389/fphys.2012.00393

View details for PubMedID 23060817

View details for PubMedCentralID PMC3464704
Caveolins: targeting pro-survival signaling in the heart and brain FRONTIERS IN PHYSIOLOGY Stary, C. M., Tsutsumi, Y. M., Patel, P. M., Head, B. P., Patel, H. H., Roth, D. M. 2012; 3
View details for DOI 10.3389/fphys.2012.00393

View details for Web of Science ID 000209173000386
Idiopathic granulomatous mastitis associated with corynebacterium sp. Infection. Hawaii medical journal Stary, C. M., Lee, Y. S., Balfour, J. 2011; 70 (5): 99-101
Abstract

Idiopathic granulomatous mastitis (IGM) is a rare inflammatory condition of the breast. The etiology and treatments options of IGM remain controversial. Previous case reports have suggested that Corynebacterium sp., a gram-positive bacillus endogenous to the skin, may be associated with IGM. In the present report, we describe the first case of IGM with a positive culture for Corynebacterium sp. reported in the United States.

View details for PubMedID 21857740
The O-2 cost of the tension-time integral in isolated single myocytes during fatigue AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Hepple, R. T., Howlett, R. A., Kindig, C. A., Stary, C. M., Hogan, M. C. 2010; 298 (4): R983-R988
Abstract

One proposed explanation for the Vo(2) slow component is that lower-threshold motor units may fatigue and develop little or no tension but continue to use O(2), thereby resulting in a dissociation of cellular respiration from force generation. The present study used intact isolated single myocytes with differing fatigue resistance profiles to investigate the relationship between fatigue, tension development, and aerobic metabolism. Single Xenopus skeletal muscle myofibers were allocated to a fast-fatiguing (FF) or a slow-fatiguing (SF) group, based on the contraction frequency required to elicit a fall in tension to 60% of peak. Phosphorescence quenching of a porphyrin compound was used to determine Delta intracellular Po(2) (Pi(O(2)); a proxy for Vo(2)), and developed isometric tension was monitored to allow calculation of the time-integrated tension (TxT). Although peak DeltaPi(O(2)) was not different between groups (P = 0.36), peak tension was lower (P < 0.05) in SF vs. FF (1.97 +/- 0. 17 V vs. 2. 73 +/- 0.30 V, respectively) and time to 60% of peak tension was significantly longer in SF vs. FF (242 +/- 10 s vs. 203 +/- 10 s, respectively). Before fatigue, both DeltaPi(O(2)) and TxT rose proportionally with contraction frequency in SF and FF, resulting in DeltaPi(O(2))/TxT being identical between groups. At fatigue, TxT fell dramatically in both groups, but DeltaPi(O(2)) decreased proportionately only in the FF group, resulting in an increase in DeltaPi(O(2))/TxT in the SF group relative to the prefatigue condition. These data show that more fatigue-resistant fibers maintain aerobic metabolism as they fatigue, resulting in an increased O(2) cost of contractions that could contribute to the Vo(2) slow component seen in whole body exercise.

View details for DOI 10.1152/ajpregu.00715.2009

View details for Web of Science ID 000275857800014

View details for PubMedID 20130224
Glycolytic activation at the onset of contractions in isolated Xenopus laevis single myofibres EXPERIMENTAL PHYSIOLOGY Walsh, B., Stary, C. M., Howlett, R. A., Kelley, K. M., Hogan, M. C. 2008; 93 (9): 1076-1084
Abstract

Intracellular pH (pHi) was measured in isolated Xenopus laevis single myofibres at the onset of contractions, with and without glycolytic blockade, to investigate the time course of glycolytic activation. Single myofibres (n=8; CON) were incubated in 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein acetoyxmethyl ester (10 microM; for fluorescence measurement of pHi) and stimulated for 15 s at 0.67 Hz in anoxia in the absence (control condition; CON) and presence of a glycolytic inhibitor (1 mM iodoacetic acid; IAA). Intracellular pHi and tension were continuously recorded, and the differences in pHi between conditions were used to estimate the activation time of glycolysis. An immediate and steady increase in pHi (initial alkalosis) at the onset of contractions was similar between CON and IAA trials for the first 9 s of the contractile bout. However, from six contractions (approximately 10 s) throughout the remainder of the bout, IAA demonstrated a continued rise in pHi, in contrast to a progressive decrease in pHi in CON (P<0.05). These results demonstrate, with high temporal resolution, that glycolysis is activated within six contractions (10 s at 0.67 Hz) in single Xenopus skeletal muscle fibres.

View details for DOI 10.1113/expphysiol.2008.042440

View details for Web of Science ID 000258442700008

View details for PubMedID 18515473
Elevation in heat shock protein 72 mRNA following contractions in isolated single skeletal muscle fibers AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Stary, C. M., Walsh, B. J., Knapp, A. E., Brafman, D., Hogan, M. C. 2008; 295 (2): R642-R648
Abstract

The purpose of the present study was 1) to develop a stable model for measuring contraction-induced elevations in mRNA in single skeletal muscle fibers and 2) to utilize this model to investigate the response of heat shock protein 72 (HSP72) mRNA following an acute bout of fatiguing contractions. Living, intact skeletal muscle fibers were microdissected from lumbrical muscle of Xenopus laevis and either electrically stimulated for 15 min of tetanic contractions (EX; n=26) or not stimulated to contract (REST; n=14). The relative mean developed tension of EX fibers decreased to 29+/-7% of initial peak tension at the stimulation end point. Following treatment, individual fibers were allowed to recover for 1 (n=9), 2 (n=8), or 4 h (n=9) prior to isolation of total cellular mRNA. HSP72, HSP60, and cardiac alpha-actin mRNA content were then assessed in individual fibers using quantitative PCR detection. Relative HSP72 mRNA content was significantly (P<0.05) elevated at the 2-h postcontraction time point relative to REST fibers when normalized to either HSP60 (18.5+/-7.5-fold) or cardiac alpha-actin (14.7+/-4.3-fold), although not at the 1- or 4-h time points. These data indicate that 1) extraction of RNA followed by relative quantification of mRNA of select genes in isolated single skeletal muscle fibers can be reliably performed, 2) HSP60 and cardiac alpha-actin are suitable endogenous normalizing genes in skeletal muscle following contractions, and 3) a significantly elevated content of HSP72 mRNA is detectable in skeletal muscle 2 h after a single bout of fatiguing contractions, despite minimal temperature changes and without influence from extracellular sources.

View details for DOI 10.1152/ajpregu.00852.2007

View details for Web of Science ID 000258322700032

View details for PubMedID 18525012
Measurement of activation energy and oxidative phosphorylation onset kinetics in isolated muscle fibers in the absence of cross-bridge cycling AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Walsh, B., Howlett, R. A., Stary, C. M., Kindig, C. A., Hogan, M. C. 2006; 290 (6): R1707-R1713
Abstract

This study utilized N-benzyl-p-toluene sulfonamide (BTS), a potent inhibitor of cross-bridge cycling, to measure 1) the relative metabolic costs of cross-bridge cycling and activation energy during contraction, and 2) oxygen uptake kinetics in the presence and absence of myosin ATPase activity, in isolated Xenopus laevis muscle fibers. Isometric tension development and either cytosolic Ca2+ concentration ([Ca2+]c) or intracellular Po2 (PiO2) were measured during contractions at 20 degrees C in control conditions (Con) and after exposure to 12.5 microM BTS. BTS attenuated tension development to 5+/-0.4% of Con but did not affect either resting or peak [Ca2+]c during repeated isometric contractions. To determine the relative metabolic cost of cross-bridge cycling, we measured the fall in PiO2) (DeltaPiO2; a proxy for Vo2) during contractions in Con and BTS groups. BTS attenuated DeltaP(iO2) by 55+/-6%, reflecting the relative ATP cost of cross-bridge cycling. Thus, extrapolating DeltaPiO2 to a value that would occur at 0% tension suggests that actomyosin ATP requirement is approximately 58% of overall ATP consumption during isometric contractions in mixed fiber types. BTS also slowed the fall in PiO2) (time to 63% of overall DeltaPiO2) from 75+/-9 s (Con) to 101+/-9 s (BTS) (P<0.05), suggesting an important role of the products of ATP hydrolysis in determining the Vo2 onset kinetics. These results demonstrate in isolated skeletal muscle fibers that 1) activation energy accounts for a substantial proportion (approximately 42%) of total ATP cost during isometric contractions, and 2) despite unchanged [Ca2+]c transients, a reduced rate of ATP consumption results in slower Vo2 onset kinetics.

View details for DOI 10.1152/ajpregu.00687.2005

View details for Web of Science ID 000237368500031

View details for PubMedID 16424084
Determinants of oxidative phosphorylation onset kinetics in isolated myocytes MEDICINE AND SCIENCE IN SPORTS AND EXERCISE Walsh, B., Howlett, R. A., Stary, C. M., Kindig, C. A., Hogan, M. C. 2005; 37 (9): 1551-1558
Abstract

At the onset of constant-load exercise, pulmonary oxygen uptake (VO(2)) exhibits a monoexponential increase, following a brief time delay, to a new steady state. To date, the specific factors controlling VO(2) onset kinetics during the transition to higher rates of work remain largely unknown. To study the control of respiration in the absence of confounding factors such as blood flow heterogeneity and fiber type recruitment patterns, the onset kinetics of mitochondrial respiration were studied at the start of contractions in isolated single myocytes. Individual myocytes were microinjected with a porphyrin compound to allow phosphorescent measurement of intracellular PO(2) (P(i)O(2), an analog of VO(2)). Peak tension and P(i)O(2) were continuously monitored under a variety of conditions designed to test the role of work intensity, extracellular PO(2), cellular metabolites, and enzyme activation on the regulation of VO(2) onset kinetics.

View details for DOI 10.1249/01.mss.0000177469.25763.25

View details for Web of Science ID 000232078100015

View details for PubMedID 16177608
Intracellular pH during sequential, fatiguing contractile periods in isolated single Xenopus skeletal muscle fibers JOURNAL OF APPLIED PHYSIOLOGY Stary, C. M., Hogan, M. C. 2005; 99 (1): 308-312
Abstract

The purpose of the present study was to test the hypothesis that a preceding contractile period in isolated single skeletal muscle fibers would attenuate the decrease in pH during an identical, subsequent contractile period, thereby reducing the rate of fatigue. Intact single skeletal muscle fibers (n = 9) were isolated from Xenopus lumbrical muscle and incubated with the fluorescent cytosolic H+ indicator 2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) AM for 30 min. Two identical contractile periods were performed in each fiber, separated by a 1-h recovery period. Force and intracellular pH (pHi) fluorescence were measured simultaneously while fibers were stimulated (tetanic contractions of 350-ms trains with 70-Hz stimuli at 9 V) at progressively increasing frequencies (0.25, 0.33, 0.5, and 1 contraction/s) until the development of fatigue (to 60% initial force). No significant difference (P < 0.05) was observed between the first and second contractile periods in initial force development, resting pHi, or time to fatigue (5.3 +/- 0.5 vs. 5.1 +/- 0.6 min). However, the relative decrease in the BCECF fluorescence ratio (and therefore pHi) from rest to the fatigue time point was significantly greater (P < 0.05) during the first contractile period (to 65 +/- 4% of initial resting values) compared with the second (77 +/- 4%). The results of the present study demonstrated that, when preceded by an initial fatiguing contractile period, the rise in cytosolic H+ concentration in contracting single skeletal muscle fibers during a second contractile period was significantly reduced but did not attenuate the fatigue process in the second contractile period. These results suggest that intracellular factors other than H+ accumulation contribute to the fall in force development under these conditions.

View details for DOI 10.1152/japplphysiol.01361.2004

View details for Web of Science ID 000230385800041

View details for PubMedID 15761085
Relationship between intracellular PO2 recovery kinetics and fatigability in isolated single frog myocytes JOURNAL OF APPLIED PHYSIOLOGY Kindig, C. A., Walsh, B., Howlett, R. A., Stary, C. M., Hogan, M. C. 2005; 98 (6): 2316-2319
Abstract

In single frog skeletal myocytes, a linear relationship exists between "fatigability" and oxidative capacity. The purpose of this investigation was to study the relationship between the intracellular Po(2) (Pi(O(2))) offset kinetics and fatigability in single Xenopus laevis myocytes to test the hypothesis that Pi(O(2)) offset kinetics would be related linearly with myocyte fatigability and, by inference, oxidative capacity. Individual myocytes (n = 30) isolated from lumbrical muscle were subjected to a 2-min bout of isometric peak tetanic contractions at either 0.25- or 0.33-Hz frequency while Pi(O(2)) was measured continuously via phosphorescence quenching techniques. The mean response time (MRT; time to 63% of the overall response) for Pi(O(2)) recovery from contracting values to resting baseline was calculated. After the initial square-wave constant-frequency contraction trial, each cell performed an incremental contraction protocol [i.e., frequency increase every 2 min from 0.167, 0.25, 0.33, 0.5, 1.0, and 2.0 Hz until peak tension fell below 50% of initial values (TTF)]. TTF values ranged from 3.39 to 10.04 min for the myocytes. The Pi(O(2)) recovery MRT ranged from 26 to 146 s. A significant (P < 0.05), negative relationship (MRT = -12.68TTF + 168.3, r(2) = 0.605) between TTF and Pi(O(2)) recovery MRT existed. These data demonstrate a significant correlation between fatigability and oxidative phosphorylation recovery kinetics consistent with the notion that oxidative capacity determines, in part, the speed with which skeletal muscle can recover energetically to alterations in metabolic demand.

View details for DOI 10.1152/japplphysiol.00355.2004

View details for Web of Science ID 000229365500047

View details for PubMedID 15691906
NAD(P)H fluorescence imaging of mitochondrial metabolism in contracting Xenopus skeletal muscle fibers: effect of oxygen availability JOURNAL OF APPLIED PHYSIOLOGY Hogan, M. C., Stary, C. M., Balaban, R. S., Combs, C. A. 2005; 98 (4): 1420-1426
Abstract

The blue autofluorescence (351 nm excitation, 450 nm emission) of single skeletal muscle fibers from Xenopus was characterized to be originating from mitochondrial NAD(P)H on the basis of morphological and functional correlations. This fluorescence signal was used to estimate the oxygen availability to isolated single Xenopus muscle fibers during work level transitions by confocal microscopy. Fibers were stimulated to generate two contractile periods that were only different in the PO2 of the solution perfusing the single fibers (PO2 of 30 or 0-2 Torr; pH = 7.2). During contractions, mean cellular NAD(P)H increased significantly from rest in the low PO2 condition with the core (inner 10%) increasing to a greater extent than the periphery (outer 10%). After the cessation of work, NAD(P)H decreased in a manner consistent with oxygen tensions sufficient to oxidize the surplus NAD(P)H. In contrast, NAD(P)H decreased significantly with work in 30 Torr PO2. However, the rate of NAD(P)H oxidation was slower and significantly increased with the cessation of work in the core of the fiber compared with the peripheral region, consistent with a remaining limitation in oxygen availability. These results suggest that the blue autofluorescence signal in Xenopus skeletal muscle fibers is from mitochondrial NAD(P)H and that the rate of NAD(P)H oxidation within the cell is influenced by extracellular PO2 even at high extracellular PO2 during the contraction cycle. These results also demonstrate that although oxygen availability influences the rate of NAD(P)H oxidation, it does not prevent NAD(P)H from being oxidized through the process of oxidative phosphorylation at the onset of contractions.

View details for DOI 10.1152/japplphysiol.00849.2004

View details for Web of Science ID 000227665400037

View details for PubMedID 15591295
Effects of acute creatine kinase inhibition on metabolism and tension development in isolated single myocytes JOURNAL OF APPLIED PHYSIOLOGY Kindig, C. A., Howlett, R. A., Stary, C. M., Walsh, B., Hogan, M. C. 2005; 98 (2): 541-549
Abstract

This study investigated the effects of acute creatine kinase (CK) inhibition (CKi) on contractile performance, cytosolic Ca2+ concentration ([Ca2+]c), and intracellular PO2 (PIO2) in Xenopus laevis isolated myocytes during a 2-min bout of isometric tetanic contractions (0.33-Hz frequency). Peak tension was similar between trials during the first contraction but was significantly (P < 0.05) attenuated for all subsequent contractions in CKi vs. control (Con). The fall in PIO2 (DeltaPIO2) from resting values was significantly greater in Con (26.0 +/- 2.2 Torr) compared with CKi (17.8 +/- 1.8 Torr). However, the ratios of Con to CKi end-peak tension (1.53 +/- 0.11) and DeltaPO2 (1.49 +/- 0.11) were similar, suggesting an unaltered aerobic cost of contractions. Additionally, the mean response time (MRT) of DeltaPIO2was significantly faster in CKi vs. Con during both the onset (31.8 +/- 5.5 vs. 49.3 +/- 5.7 s; P < 0.05) and cessation (21.2 +/- 4.1 vs. 68.0 +/- 3.2 s; P < 0.001) of contractions. These data demonstrate that initial phosphocreatine hydrolysis in single skeletal muscle fibers is crucial for maintenance of sarcoplasmic reticulum Ca2+ release and peak tension during a bout of repetitive tetanic contractions. Furthermore, as PIO2 fell more rapidly at contraction onset in CKi compared with Con, these data suggest that CK activity temporally buffers the initial ATP-to-ADP concentration ratio at the transition to an augmented energetic demand, thereby slowing the initial mitochondrial activation by mitigating the energetic control signal (i.e., ADP concentration, phosphorylation potential, etc.) between sites of ATP supply and demand.

View details for DOI 10.1152/japplphysiol.00354.2004

View details for Web of Science ID 000226282400017

View details for PubMedID 15333609
Effect of dissociating cytosolic calcium and metabolic rate of intracellular Po-2 kinetics in single frog myocytes JOURNAL OF PHYSIOLOGY-LONDON Kindig, C. A., Stary, C. M., Hogan, M. C. 2005; 562 (2): 527-534
Abstract

The purpose of this investigation was to utilize 2,3-butanedione monoxime (BDM; an inhibitor of contractile activation) to dissociate cytosolic [Ca(2+)] ([Ca(2+)](c)) from the putative respiratory regulators that arise from muscle contraction-induced ATP utilization in order to determine the relative contribution of [Ca(2+)](c) on intracellular P(O(2)) (P(iO(2))) kinetics during the transition from rest to contractions in single skeletal myocytes isolated from Xenopus laevis lumbrical muscle. Myocytes were subjected to electrically induced isometric tetanic contractions (0.25 Hz; 2-min bouts) while peak tension and either [Ca(2+)](c) (n= 7; ratiometric fluorescence microscopy) or P(iO(2)) (n= 7; phosphorescence microscopy) was measured continuously. Cells were studied under both control and 3 mm BDM conditions in randomized order. Initial (control, 100 +/- 0%; BDM, 72.6 +/- 4.6%), midpoint (control, 86.7 +/- 1.8%; BDM, 61.6 +/- 4.1%) and end (control, 85.0 +/- 2.8%; BDM, 57.5 +/- 5.0%) peak tensions (normalized to initial control values) were significantly reduced (P < 0.05) with BDM compared with control (n= 14). Despite the reduced peak tension, peak [Ca(2+)](c) was not altered (P > 0.05) between control and BDM trials. Thus, the peak tension-to-peak [Ca(2+)](c) ratio was reduced with BDM compared with control. The absolute fall in P(iO(2)) with contractions, which is proportional to the rise in , was significantly reduced with BDM (13.2 +/- 1.3 mmHg) compared with control (22.0 +/- 2.0 mmHg). However, P(iO(2)) onset kinetics (i.e. mean response time (MRT)) was not altered between BDM (66.8 +/- 8.0 s) and control (64.9 +/- 6.3 s) trials. Therefore, the initial rate of change (defined as the fall in P(iO(2))/MRT) was significantly slower in BDM fibres compared with control. These data demonstrate in these isolated single skeletal muscle fibres that unchanged peak [Ca(2+)](c) in the face of reduced metabolic feedback from the contractile sites evoked with BDM did not alter P(iO(2)) onset kinetics in isolated single frog myocytes, suggesting that metabolic signals arising from the contractile sites play a more substantial role than [Ca(2+)](c) in the signalling pathway to oxidative phosphorylation during the transition from rest to repeated tetanic contractions.

View details for DOI 10.1113/jphysiol.2004.074922

View details for Web of Science ID 000226528000016

View details for PubMedID 15550463
Resistance to fatigue of individual Xenopus single skeletal muscle fibres is correlated with mitochondrial volume density EXPERIMENTAL PHYSIOLOGY Stary, C. M., Mathieu-Costello, O., Hogan, M. C. 2004; 89 (5): 617-621
Abstract

The purpose of the present study was to compare the individual fatigue characteristics of isolated single skeletal muscle fibres with their mitochondrial volume density (MVD), using direct histological morphometry. Single muscle fibres (n= 14) were microdissected from lumbrical muscle of adult female Xenopus laevis, and force was measured while fibres were stimulated (tetanic contractions of 200 ms trains with 70 Hz stimuli at 9 V) at progressively increasing frequencies (2 min each at 0.25, 0.33, 0.5 and 1 contractions s(-1)) until fatigue (<50% initial maximal force) had been established. Following the end of the fatigue protocol, MVD was determined by electron microscopy. Time to fatigue varied among the individual fibres from 3.3 to 10 min. MVD of individual fibres ranged from 3.0 to 9.2% and was positively correlated (r= 0.93) with time to fatigue of corresponding fibres. These results, using direct histological measurements of MVD: (1) support on a single cell basis the notion that oxidative capacity is a major determinant of muscle fatigue resistance; and (2) show that the fatigue profile of a single cell can be used to predict oxidative capacity.

View details for DOI 10.1113/expphysiol.2004.027763

View details for Web of Science ID 000223470200012

View details for PubMedID 15258122
Effect of contraction frequency on the contractile and noncontractile phases of muscle venous blood flow JOURNAL OF APPLIED PHYSIOLOGY Hogan, M. C., Grassi, B., Samaja, M., Stary, C. M., Gladden, L. B. 2003; 95 (3): 1139-1144
Abstract

The purpose of this study was to test the hypothesis that increasing muscle contraction frequency, which alters the duty cycle and metabolic rate, would increase the contribution of the contractile phase to mean venous blood flow in isolated skeletal muscle during rhythmic contractions. Canine gastrocnemius muscle (n = 5) was isolated, and 3-min stimulation periods of isometric, tetanic contractions were elicited sequentially at rates of 0.25, 0.33, and 0.5 contractions/s. The O2 uptake, tension-time integral, and mean venous blood flow increased significantly (P < 0.05) with each contraction frequency. Venous blood flow during both the contractile (106 +/- 6, 139 +/- 8, and 145 +/- 8 ml x 100 g-1 x min-1) and noncontractile phases (64 +/- 3, 78 +/- 4, and 91 +/- 5 ml x 100 g-1 x min-1) increased with contraction frequency. Although developed force and duration of the contractile phase were never significantly different for a single contraction during the three contraction frequencies, the amount of blood expelled from the muscle during an individual contraction increased significantly with contraction frequency (0.24 +/- 0.03, 0.32 +/- 0.02, and 0.36 +/- 0.03 ml x N-1 x min-1, respectively). This increased blood expulsion per contraction, coupled with the decreased time in the noncontractile phase as contraction frequency increased, resulted in the contractile phase contribution to mean venous blood flow becoming significantly greater (21 +/- 4, 30 +/- 4, and 38 +/- 6%) as contraction frequency increased. These results demonstrate that the percent contribution of the muscle contractile phase to mean venous blood flow becomes significantly greater as contraction frequency (and thereby duty cycle and metabolic rate) increases and that this is in part due to increased blood expulsion per contraction.

View details for DOI 10.1152/japplphysiol.00226.2003

View details for Web of Science ID 000184733800031

View details for PubMedID 12794032
Trimetazidine reduces basal cytosolic Ca2+ concentration during hypoxia in single Xenopus skeletal myocytes EXPERIMENTAL PHYSIOLOGY Stary, C. M., Kohin, S., Samaja, M., Howlett, R. A., Hogan, M. C. 2003; 88 (3): 415-421
Abstract

We tested the hypotheses that: (1) Ca(2+) handling and force production would be irreversibly altered in skeletal muscle during steady-state contractions when subjected to severe, prolonged hypoxia and subsequent reoxygenation; and (2) application of the cardio-protective drug trimetazidine would attenuate these alterations. Single, living skeletal muscle fibres from Xenopus laevis were injected with the Ca(2+) indicator fura 2, and incubated for 1 h prior to stimulation in 100 micro M TMZ-Ringer solution (TMZ; n = 6) or standard Ringer solution (CON; n = 6). Force and relative free cytosolic Ca(2+) concentration ([Ca(2+)](c)) were measured during continuous tetanic contractions produced every 5 s as fibres were sequentially perfused in the following manner: 3 min high extracellular P(O(2)) (159 mmHg), 15 min hypoxic perfusion (3-5 mmHg) then 3 min high P(O(2)). Hypoxia caused a decrease in force and peak [Ca(2+)](c) in both the TMZ and CON fibres, with no significant (P < 0.05) difference between groups. However, basal [Ca(2+)](c) was significantly lower during hypoxia in the TMZ group vs. the CON group. While reoxygenation generated only modest recovery of relative force and peak [Ca(2+)](c) in both groups, basal [Ca(2+)](c) remained significantly less in the TMZ group. These results demonstrated that in contracting, single skeletal muscle fibres, TMZ prevented increases in basal [Ca(2+)](c) generated during a severe hypoxic insult and subsequent reoxygenation, yet failed to protect the cell from the deleterious effects of prolonged hypoxia followed by reoxygenation.

View details for Web of Science ID 000183476900013

View details for PubMedID 12719766
No effect of trans sodium crocetinate on maximal O-2 conductance or V-O2,V-max in moderate hypoxia RESPIRATORY PHYSIOLOGY & NEUROBIOLOGY Hepple, R. T., Stary, C. M., Kohin, S., Wagner, P. D., Hogan, M. C. 2003; 134 (3): 239-246
Abstract

The lumped parameter describing skeletal muscle diffusional conductance for O(2), DM(O(2)), reflects all of the resistances for O(2) in moving from red cell to muscle fiber mitochondria. The purpose of our study was to determine if the carotenoid compound, trans sodium crocetinate (TSC), which has been reported to increase the diffusivity of O(2) in plasma, improves DM(O(2)) and thus, V(O(2),max) in maximally contracting in situ skeletal muscle. V(O(2),max) was measured in the isolated perfused canine gastrocnemius (n=5) during 3 min of isometric tetanic contractions at 1 Hz, while the animal was breathing 12% O(2) (PA(O(2))=32+/-2 Torr, mean+/-S.E.) under two experimental conditions. The first was a control contraction period and the second (following 60 min recovery) was performed within 5 min after infusion of a 0.1 mg x ml(-1) solution of TSC (total dose 100 microg kg(-1)). There were no significant differences in convective O(2) delivery (11.9+/-2.3 vs. 12.1+/-2.2 ml x min(-1) x 100 g(-1)), V(O(2),max) (9.5+/-1.5 vs. 9.6+/-1.5 ml x min(-1) x 100 g(-1)) or calculated DM(O(2)) (0.37+/-0.03 vs. 0.37+/-0.04 ml x min(-1) x 100 g(-1) x Torr(-1)) between contraction periods. As such, our results show that TSC does not improve performance in maximally contracting canine gastrocnemius muscle in situ under moderately hypoxic conditions, suggesting either that TSC in this situation does not increase plasma O(2) diffusivity or that this step in O(2) diffusion from red cell to myocyte does not constrain DM(O(2)).

View details for Web of Science ID 000182101900006

View details for PubMedID 12660103
Assessment of O-2 uptake dynamics in isolated single skeletal myocytes JOURNAL OF APPLIED PHYSIOLOGY Kindig, C. A., Kelley, K. M., Howlett, R. A., Stary, C. M., Hogan, M. C. 2003; 94 (1): 353-357
Abstract

The purpose of this research was to develop a technique for rapid measurement of O(2) uptake (Vo(2)) kinetics in single isolated skeletal muscle cells. Previous attempts to measure single cell Vo(2) have utilized polarographic-style electrodes, thereby mandating large fluid volumes and relatively poor sensitivity. Thus our laboratory has developed an approximately 100-microl, well-stirred chamber for the measurement of Vo(2) in isolated Xenopus laevis myocytes using a phosphorescence quenching technique [Ringer solution with 0.05 mM Pd-meso-tetra(4-carboxyphenyl)porphine] to monitor the fall in extracellular Po(2) (which is proportional to cellular Vo(2) within the sealed chamber). Vo(2) in single living myocytes dissected from Xenopus lumbrical muscles was measured from rest across a bout of repetitive tetanic contractions (0.33 Hz) and in response to a ramp protocol utilizing an increasing contraction frequency. In response to the square-wave contraction bout, the increase in Vo(2) to steady state (SS) was 16.7 +/- 1.3 ml x 100 g(-1) x min(-1) (range 13.0-21.9 ml x 100 g(-1) x min(-1); n = 6). The rise in Vo(2) at contractions onset (n = 6) was fit with a time delay (2.1 +/- 1.2 s, range 0.0-7.7 s) plus monoexponential rise to SS (time constant = 9.4 +/- 1.5 s, range 5.2-14.9 s). Furthermore, in two additional myocytes, Vo(2) increased progressively as contraction frequency increased (ramp protocol). This technique for measuring Vo(2) in isolated, single skeletal myocytes represents a novel and powerful investigative tool for gaining mechanistic insight into mitochondrial function and Vo(2) dynamics without potential complications of the circulation and other myocytes.

View details for DOI 10.1152/japplphysiol.00559.2002

View details for Web of Science ID 000179815700045

View details for PubMedID 12391049
Preconditioning improves function and recovery of single muscle fibers during severe hypoxia and reoxygenation AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY Kohin, S., Stary, C. M., Howlett, R. A., Hogan, M. C. 2001; 281 (1): C142-C146
Abstract

Reperfusion following prolonged ischemia induces cellular damage in whole skeletal muscle models. Ischemic preconditioning attenuates the deleterious effects. We tested whether individual skeletal muscle fibers would be similarly affected by severe hypoxia and reoxygenation (H/R) in the absence of extracellular factors and whether cellular damage could be alleviated by hypoxic preconditioning. Force and free cytosolic Ca2+ ([Ca2+]c) were monitored in Xenopus single muscle fibers (n = 24) contracting tetanically at 0.2 Hz during 5 min of severe hypoxia and 5 min of reoxygenation. Twelve cells were preconditioned by a shorter bout of H/R 1 h before the experimental trial. In preconditioned cells, force relative to initial maximal values (P/P(o)) and relative peak [Ca2+]c fell (P < 0.05) during 5 min of hypoxia and recovered during reoxygenation. In contrast, P/P(o) and relative peak [Ca2+]c fell more during hypoxia (P < 0.05) and recovered less during reoxygenation (P < 0.05) in control cells. The ratio of force to [Ca2+]c was significantly higher in the preconditioned cells during severe hypoxia, suggesting that changes in [Ca2+]c were not solely responsible for the loss in force. We conclude that 1) isolated skeletal muscle fibers contracting in the absence of extracellular factors are susceptible to H/R injury associated with changes in Ca2+ handling; and 2) hypoxic preconditioning improves contractility, Ca2+ handling, and cell recovery during subsequent hypoxic insult.

View details for Web of Science ID 000169384100017

View details for PubMedID 11401836
Recovery of force during postcontractile depression in single Xenopus muscle fibers AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Howlett, R. A., Stary, C. M., Hogan, M. C. 2001; 280 (5): R1469-R1475
Abstract

This study examined the relationship between force and cytosolic free calcium concentration ([Ca2+]c) in different fiber types from Xenopus before, during, and after cells underwent postcontractile depression (PCD). During a standardized fatigue run, force in the two fast fatiguing (FF) fiber types (types 1 and 2, n = 10) fell more quickly (5.8 vs. 8.1 min) and to a greater degree [0.36 vs. 0.51 of initial (P(o))] than in the slow fatiguing (SF) fiber type (type 3, n = 11). After the initial fatigue run, both FF and SF experienced a drop in force to <15% P(o) (PCD) at a similar time (20.6 vs. 21.4 min). A second stimulation period, undertaken during PCD, produced significant recovery of force in both groups, but significantly more so in SF than FF (64 +/- 7 vs. 29 +/- 2% P(o)). This force recovery during PCD was accompanied by a significant increase in peak [Ca2+]c, particularly in SF. However, despite the significant recovery of force during stimulation while in PCD, the amount of force produced for a given peak [Ca2+]c was significantly lower in both groups during PCD than at any other point in the experiment. A final stimulation period, initiated when all fibers had recovered from PCD, demonstrated a recovery of both force and peak [Ca2+]c in both groups, but this recovery was significantly greater in SF vs. FF. These data demonstrate that with continuous electrical stimulation, it is possible to produce a significant recovery of force production during the normally quiescent period of PCD, but that it occurs with a decreased muscle force production for a given peak [Ca2+]c. This suggests that factors other than structural alterations of the sarcoplasmic reticulum are likely the cause of PCD in these fibers.

View details for Web of Science ID 000167973400029

View details for PubMedID 11294770
Impairment of Ca2+ release in single Xenopus muscle fibers fatigued at varied extracellular Po-2 JOURNAL OF APPLIED PHYSIOLOGY Stary, C. M., Hogan, M. C. 2000; 88 (5): 1743-1748
Abstract

We tested the hypothesis that the mechanisms involved in the more rapid onset of fatigue when O(2) availability is reduced in contracting skeletal muscle are similar to those when O(2) availability is more sufficient. Two series of experiments were performed in isolated, single skeletal muscle fibers from Xenopus laevis. First, relative force and free cytosolic Ca(2+) concentrations ([Ca(2+)](c)) were measured simultaneously in single fibers (n = 6) stimulated at increasing frequencies (0.25, 0.33, 0.5, and 1 Hz) at an extracellular PO(2) of either 22 or 159 Torr. Muscle fatigue (force = 50% of initial peak tension) occurred significantly sooner (P < 0.05) during the low- (237 +/- 40 s) vs. high-PO(2) treatments (280 +/- 38 s). Relative [Ca(2+)](c) was significantly decreased from maximal values at the fatigue time point during both the high- (72 +/- 4%) and low-PO(2) conditions (78 +/- 4%), but no significant difference was observed between the treatments. In the second series of experiments, using the same stimulation regime as the first, fibers (n = 6) exposed to 5 mM caffeine immediately after fatigue demonstrated an immediate but incomplete relative force recovery during both the low- (89 +/- 4%) and high-PO(2) treatments (82 +/- 3%), with no significant difference between treatments. Additionally, there was no significant difference in relative [Ca(2+)](c) between the high- (100 +/- 12% of prefatigue values) and low-PO(2) treatments (108 +/- 12%) on application of caffeine. These results suggest that in isolated, single skeletal muscle fibers, the earlier onset of fatigue that occurred during the low-extracellular PO(2) condition was modulated through similar pathways as the fatigue process during the high and involved a decrease in relative peak [Ca(2+)](c).

View details for Web of Science ID 000086985000034

View details for PubMedID 10797138
Phosphorylating pathways and fatigue development in contracting Xenopus single skeletal muscle fibers AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Stary, C. M., Hogan, M. C. 2000; 278 (3): R587-R591
Abstract

To investigate the differential contribution of oxidative and substrate-level phosphorylation to force production during repetitive, maximal tetanic contractions, single skeletal muscle fiber performance was examined under conditions of high-oxygen availability and anoxia. Tetanic force development (P) was measured in isolated, single type-1 muscle fibers (fast twitch; n = 6) dissected from Xenopus lumbrical muscle while being stimulated at increasing frequencies (0.25, 0.33, and 0.5 Hz), with each frequency lasting 2 min. Two separate work bouts were conducted, with the perfusate PO(2) being either 0 or 159 mmHg. No significant (P < 0. 05) difference was found in the initial peak tensions (P(0)) between the high (334 +/- 57 kPa) and the low (325 +/- 41 kPa) PO(2) treatment. No significant difference in P was observed between the treatments during the first 50 s. However, a significant difference in force production was observed between the high (P/P(0) = 0.96 +/- 0.02) and the low PO(2) condition (P/P(0) = 0.92 +/- 0.02) by 60 s of work. After 60 s, steady-state force production was maintained during the high compared with the low PO(2) condition until stimulation frequency was increased, at which point developed tension during the high PO(2) condition began to decline. Time to fatigue (P/P(0) = 0.3) was reached significantly sooner during the low (250 +/- 16 s) than the high PO(2) condition (367 +/- 28 s). These results demonstrate that during the first 50 s of 0.25-Hz contractions, substrate-level phosphorylation has the capacity to maintain force and ATP hydrolysis when oxidative phosphorylation is absent. This period was followed by an oxygen-dependent phase in which force generation was maintained during the high PO(2) condition (but not during the low PO(2) condition) until the onset of a final fatiguing phase, at which a calculated maximal rate of oxidative phosphorylation was reached.

View details for Web of Science ID 000085808000006

View details for PubMedID 10712276
Structural basis of muscle O-2 diffusing capacity: evidence from muscle function in situ JOURNAL OF APPLIED PHYSIOLOGY Hepple, R. T., Hogan, M. C., Stary, C., Bebout, D. E., Mathieu-Costello, O., Wagner, P. D. 2000; 88 (2): 560-566
Abstract

Although evidence for muscle O(2) diffusion limitation of maximal O(2) uptake has been found in the intact organism and isolated muscle, its relationship to diffusion distance has not been examined. Thus we studied six sets of three purpose-bred littermate dogs (aged 10-12 mo), with 1 dog per litter allocated to each of three groups: control (C), exercise trained for 8 wk (T), or left leg immobilized for 3 wk (I). The left gastrocnemius muscle from each animal was surgically isolated, pump-perfused, and electrically stimulated to peak O(2) uptake at three randomly applied levels of arterial oxygenation [normoxia, arterial PO(2) (Pa(O(2))) 77 +/- 2 (SE) Torr; moderate hypoxia, Pa(O(2)): 33 +/- 1 Torr; and severe hypoxia, Pa(O(2)): 22 +/- 1 Torr]. O(2) delivery (ml. min(-1). 100 g(-1)) was kept constant among groups for each level of oxygenation, with O(2) delivery decreasing with decreasing Pa(O(2)). O(2) extraction (%) was lower in I than T or C for each condition, but calculated muscle O(2) diffusing capacity (Dmus(O(2))) per 100 grams of muscle was not different among groups. After the experiment, the muscle was perfusion fixed in situ, and a sample from the midbelly was processed for microscopy. Immobilized muscle showed a 45% reduction of muscle fiber cross-sectional area (P < 0.05), and a resulting 59% increase in capillary density (P < 0.05) but minimal reduction in capillary-to-fiber ratio (not significant). In contrast, capillarity was not significantly different in T vs. C muscle. The results show that a dramatically increased capillary density (and reduced diffusion distance) after short-term immobilization does not improve Dmus(O(2)) in heavily working skeletal muscle.

View details for Web of Science ID 000085188100025

View details for PubMedID 10658023
Rapid force recovery in contracting skeletal muscle after brief ischemia is dependent on O-2 availability JOURNAL OF APPLIED PHYSIOLOGY Hogan, M. C., Kohin, S., Stary, C. M., Hepple, R. T. 1999; 87 (6): 2225-2229
Abstract

We tested the hypothesis that contracting skeletal muscle can rapidly restore force development during reperfusion after brief total ischemia and that this rapid recovery depends on O(2) availability and not an alternate factor related to blood flow. Isolated canine gastrocnemius muscle (n = 5) was stimulated to contract tetanically (isometric contraction elicited by 8 V, 0.2-ms duration, 200-ms trains, at 50-Hz stimulation) every 2 s until steady-state conditions of muscle blood flow (controlled by pump perfusion) and developed force were attained (3 min). While maintaining the same stimulation pattern, muscle blood flow was then reduced to zero (complete ischemia) for 2 min. Normal blood flow was then restored to the contracting muscle; however, two distinct conditions of oxygenation (at the same blood flow) were sequentially imposed: deoxygenated blood (30 s), blood with normal arterial O(2) content (30 s), a return to deoxygenated blood (30 s), and finally a return to normal arterial O(2) content (90 s). During the ischemic period, force development fell to 39 +/- 6 (SE)% of normal (from 460 +/- 40 to 170 +/- 20 N/100 g). When muscle blood flow was restored to normal by perfusion with deoxygenated blood, developed force continued to decline to 140 +/- 20 N/100 g. Muscle force rapidly recovered to 310 +/- 30 N/100 g (P < 0.05) during the 30 s in which the contracting muscle was perfused with oxygenated blood and then fell again to 180 +/- 30 N/100 g when perfused with blood with low PO(2). These findings demonstrate that contracting skeletal muscle has the capacity for rapid recovery of force development during reperfusion after a short period of complete ischemia and that this recovery depends on O(2) availability and not an alternate factor related to blood flow restoration.

View details for Web of Science ID 000084182000031

View details for PubMedID 10601171
Effect of varied extracellular PO2 on muscle performance in Xenopus single skeletal muscle fibers JOURNAL OF APPLIED PHYSIOLOGY Stary, C. M., Hogan, M. C. 1999; 86 (6): 1812-1816
Abstract

The purpose of this study was to examine the development of fatigue in isolated, single skeletal muscle fibers when O2 availability was reduced but not to levels considered rate limiting to mitochondrial respiration. Tetanic force was measured in single living muscle fibers (n = 6) from Xenopus laevis while being stimulated at increasing contraction rates (0.25, 0.33, 0.5, and 1 Hz) in a sequential manner, with each stimulation frequency lasting 2 min. Muscle fatigue (determined as 75% of initial maximum force) was measured during three separate work bouts (with 45 min of rest between) as the perfusate PO2 was switched between values of 30 +/- 1.9, 76 +/- 3.0, or 159 Torr in a blocked-order design. No significant differences were found in the initial peak tensions between the high-, intermediate-, and low-PO2 treatments (323 +/- 22, 298 +/- 27, and 331 +/- 24 kPa, respectively). The time to fatigue was reached significantly sooner (P < 0.05) during the 30-Torr treatment (233 +/- 39 s) compared with the 76- (385 +/- 62 s) or 159-Torr (416 +/- 65 s) treatments. The calculated critical extracellular PO2 necessary to develop an anoxic core within these fibers was 13 +/- 1 Torr, indicating that the extracellular PO2 of 30 Torr should not have been rate limiting to mitochondrial respiration. The magnitude of an unstirred layer (243 +/- 64 micron) or an intracellular O2 diffusion coefficient (0.45 +/- 0.04 x 10(-5) cm2/s) necessary to develop an anoxic core under the conditions of the study was unlikely. The earlier initiation of fatigue during the lowest extracellular PO2 condition, at physiologically high intracellular PO2 levels, suggests that muscle performance may be O2 dependent even when mitochondrial respiration is not necessarily compromised.

View details for Web of Science ID 000080781400014

View details for PubMedID 10368342
Pulmonary gas exchange during exercise in pigs JOURNAL OF APPLIED PHYSIOLOGY Hopkins, S. R., Stary, C. M., Falor, E., Wagner, H., Wagner, P. D., McKirnan, M. D. 1999; 86 (1): 93-100
Abstract

Increased ventilation-perfusion (VA/Q) inequality is observed in approximately 50% of humans during heavy exercise and contributes to the widening of the alveolar-arterial O2 difference (A-aDO2). Despite extensive investigation, the cause remains unknown. As a first step to more direct examination of this problem, we developed an animal model. Eight Yucatan miniswine were studied at rest and during treadmill exercise at approximately 30, 50, and 85% of maximal O2 consumption (VO2 max). Multiple inert-gas, blood-gas, and metabolic data were obtained. The A-aDO2 increased from 0 +/- 3 (SE) Torr at rest to 14 +/- 2 Torr during the heaviest exercise level, but arterial PO2 (PaO2) remained at resting levels during exercise. There was normal VA/Q inequality [log SD of the perfusion distribution (log) = 0.42 +/- 0.04] at rest, and moderate increases (log = 0.68 +/- 0.04, P < 0.0001) were observed with exercise. This result was reproducible on a separate day. The VA/Q inequality changes are similar to those reported in highly trained humans. However, in swine, unlike in humans, there was no inert gas evidence for pulmonary end-capillary diffusion limitation during heavy exercise; there was no systematic difference in the measured PaO2 and the PaO2 as predicted from the inert gases. These data suggest that the pig animal model is well suited for studying the mechanism of exercise-induced VA/Q inequality.

View details for Web of Science ID 000080009600014

View details for PubMedID 9887118
Faster adjustment of O-2 delivery does not affect Vo(2) on-kinetics in isolated in situ canine muscle JOURNAL OF APPLIED PHYSIOLOGY Grassi, B., Gladden, L. B., Samaja, M., Stary, C. M., Hogan, M. C. 1998; 85 (4): 1394-1403
Abstract

The mechanism(s) limiting muscle O2 uptake (VO2) kinetics was investigated in isolated canine gastrocnemius muscles (n = 7) during transitions from rest to 3 min of electrically stimulated isometric tetanic contractions (200-ms trains, 50 Hz; 1 contraction/2 s; 60-70% of peak V(O2)). Two conditions were mainly compared: 1) spontaneous adjustment of blood flow (Q) [control, spontaneous Q (C Spont)]; and 2) pump-perfused Q, adjusted approximately 15 s before contractions at a constant level corresponding to the steady-state value during contractions in C Spont [faster adjustment of O2 delivery (Fast O2 Delivery)]. During Fast O2 Delivery, 1-2 ml/min of 10(-2) M adenosine were infused intra-arterially to prevent inordinate pressure increases with the elevated Q. The purpose of the study was to determine whether a faster adjustment of O2 delivery would affect V(O2) kinetics. Q was measured continuously; arterial (Ca(O2)) and popliteal venous (Cv(O2)) O2 contents were determined at rest and at 5- to 7-s intervals during contractions; O2 delivery was calculated as Q x Ca(O2), and V(O2) was calculated as Q x arteriovenous O2 content difference. Times to reach 63% of the difference between baseline and steady-state VO2 during contractions were 23.8 +/- 2.0 (SE) s in C Spont and 21.8 +/- 0.9 s in Fast O2 Delivery (not significant). In the present experimental model, elimination of any delay in O2 delivery during the rest-to-contraction transition did not affect muscle V(O2) kinetics, which suggests that this kinetics was mainly set by an intrinsic inertia of oxidative metabolism.

View details for Web of Science ID 000076306700029

View details for PubMedID 9760333
Peripheral O-2 diffusion does not affect Vo(2) on-kinetics in isolated in situ canine muscle JOURNAL OF APPLIED PHYSIOLOGY Grassi, B., Gladden, L. B., Stary, C. M., Wagner, P. D., Hogan, M. C. 1998; 85 (4): 1404-1412
Abstract

To test the hypothesis that muscle O2 uptake (V(O2)) on-kinetics is limited, at least in part, by peripheral O2 diffusion, we determined the V(O2) on-kinetics in 1) normoxia (Control); 2) hyperoxic gas breathing (Hyperoxia); and 3) hyperoxia and the administration of a drug (RSR-13, Allos Therapeutics), which right-shifts the Hb-O2 dissociation curve (Hyperoxia+RSR-13). The study was conducted in isolated canine gastrocnemius muscles (n = 5) during transitions from rest to 3 min of electrically stimulated isometric tetanic contractions (200-ms trains, 50 Hz; 1 contraction/2 s; 60-70% peak V(O2)). In all conditions, before and during contractions, muscle was pump perfused with constantly elevated blood flow (Q), at a level measured at steady state during contractions in preliminary trials with spontaneous Q x Adenosine was infused intra-arterially to prevent inordinate pressure increases with the elevated Q x Q was measured continuously, arterial and popliteal venous O2 concentrations were determined at rest and at 5- to 7-s intervals during contractions, and V(O2) was calculated as Q x arteriovenous O2 content difference. PO2 at 50% HbO2 saturation (P50) was calculated. Mean capillary PO2 (Pc(O2)) was estimated by numerical integration. P50 was higher in Hyperoxia+RSR-13 [40 +/- 1 (SE) Torr] than in Control and in Hyperoxia (31 +/- 1 Torr). After 15 s of contractions, Pc(O2) was higher in Hyperoxia (97 +/- 9 Torr) vs. Control (53 +/- 3 Torr) and in Hyperoxia+RSR-13 (197 +/- 39 Torr) vs. Hyperoxia. The time to reach 63% of the difference between baseline and steady-state V(O2) during contractions was 24.7 +/- 2.7 s in Control, 26.3 +/- 0.8 s in Hyperoxia, and 24.7 +/- 1.1 s in Hyperoxia+RSR-13 (not significant). Enhancement of peripheral O2 diffusion (obtained by increased PcO2 at constant O2 delivery) during the rest-to-contraction (60-70% of peak V(O2)) transition did not affect muscle V(O2) on- kinetics.

View details for Web of Science ID 000076306700030

View details for PubMedID 9760334
Bioenergetics of contracting skeletal muscle after partial reduction of blood flow JOURNAL OF APPLIED PHYSIOLOGY Hogan, M. C., Gladden, L. B., Grassi, B., Stary, C. M., Samaja, M. 1998; 84 (6): 1882-1888
Abstract

The purpose of this study was to examine the bioenergetics and regulation of O2 uptake (VO2) and force production in contracting muscle when blood flow was moderately reduced during a steady-state contractile period. Canine gastrocnemius muscle (n = 5) was isolated, and 3-min stimulation periods of isometric, tetanic contractions were elicited sequentially at rates of 0.25, 0.33, and 0.5 contractions/s (Hz) immediately followed by a reduction of blood flow [ischemic (I) condition] to 46 +/- 3% of the value obtained at 0.5 Hz with normal blood flow. The VO2 of the contracting muscle was significantly (P < 0.05) reduced during the I condition [6.5 +/- 0.8 (SE) ml . 100 g-1 . min-1] compared with the same stimulation frequency with normal flow (11.2 +/- 1.5 ml . 100 g-1 . min-1), as was the tension-time index (79 +/- 12 vs. 123 +/- 22 N . g-1 . min-1, respectively). The ratio of VO2 to tension-time index remained constant throughout all contraction periods. Muscle phosphocreatine concentration, ATP concentration, and lactate efflux were not significantly different during the I condition compared with the 0. 5-Hz condition with normal blood flow. However, at comparable rates of VO2 and tension-time index, muscle phosphocreatine concentration and ATP concentration were significantly less during the I condition compared with normal-flow conditions. These results demonstrate that, in this highly oxidative muscle, the normal balance of O2 supply to force output was maintained during moderate ischemia by downregulation of force production. In addition, 1) the minimal disruption in intracellular homeostasis after the initiation of ischemia was likely a result of steady-state metabolic conditions having already been activated, and 2) the difference in intracellular conditions at comparable rates of VO2 and tension-time index between the normal flow and I condition may have been due to altered intracellular O2 tension.

View details for Web of Science ID 000073960000009

View details for PubMedID 9609780

Creed Stary

Associate Professor of Anesthesiology, Perioperative and Pain Medicine (Adult MSD) and, by courtesy, of Ophthalmology at the Stanford University Medical Center

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