Pacific Free Clinic
Service, Volunteer and Community Work
Pacific Free Clinic, Stanford University School of Medicine (9/1/2010)
San Jose, CA
San Jose, CA
Myelin sheaths, specialized segments of oligodendrocyte (OL) plasma membranes in the central nervous system (CNS), facilitate fast, saltatory conduction of action potentials down axons. Changes to the fine structure of myelin in a neural circuit, including sheath thickness and internode length (length of myelin segments between nodes of Ranvier), are expected to affect conduction velocity of action potentials. Myelination of the mammalian CNS occurs in a stereotyped, progressive pattern and continues well into adulthood in humans. Recent evidence from zebrafish, rodents, non-human primates, and humans suggests that myelination may be sensitive to experiences during development and adulthood, and that varying levels of neuronal activity may underlie these experience-dependent changes in myelin and myelin-forming cells. Several cellular, molecular, and epigenetic mechanisms have been investigated as contributors to myelin plasticity. A deeper understanding of myelin plasticity and its underlying mechanisms may provide insights into diseases involving myelin damage or dysregulation. This article is part of the Special Issue entitled 'Oligodendrocytes in Health and Disease'.
View details for DOI 10.1016/j.neuropharm.2015.08.001
View details for PubMedID 26282119
Neuromonitoring can be used to map out particular neuroanatomical tracts, define physiologic deficits secondary to specific pathology or intervention, or predict postoperative outcome and proves essential in the detection of central and peripheral ischemic events during neurosurgical intervention. Herein, we describe an instance of elective balloon-assisted coiling of a recurrent basilar tip aneurysm in a 61-year-old woman, where intraoperative somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (TcMEPs) were lost in the right lower extremity intraoperatively. We aim to highlight that targeted use of monitoring proves advantageous in both the open surgical and endovascular setting, even in the avoidance of potential iatrogenic peripheral nerve damage and limb ischemia as documented herein. Consideration of the increased risk for peripheral ischemia in the neurointerventional setting is especially imperative in particular populations where blood vessels might be of diminished size, such as in infants, young children, and severely deconditioned adults.
View details for DOI 10.1177/1591019915583219
View details for Web of Science ID 000356305000019
View details for PubMedID 26015519
View details for PubMedCentralID PMC4757266
Myelination of the central nervous system requires the generation of functionally mature oligodendrocytes from oligodendrocyte precursor cells (OPCs). Electrically active neurons may influence OPC function and selectively instruct myelination of an active neural circuit. In this work, we use optogenetic stimulation of the premotor cortex in awake, behaving mice to demonstrate that neuronal activity elicits a mitogenic response of neural progenitor cells and OPCs, promotes oligodendrogenesis, and increases myelination within the deep layers of the premotor cortex and subcortical white matter. We further show that this neuronal activity-regulated oligodendrogenesis and myelination is associated with improved motor function of the corresponding limb. Oligodendrogenesis and myelination appear necessary for the observed functional improvement, as epigenetic blockade of oligodendrocyte differentiation and myelin changes prevents the activity-regulated behavioral improvement.
View details for DOI 10.1126/science.1252304
View details for PubMedID 24727982
View details for PubMedCentralID PMC4096908
The C57BL/6J laboratory mouse is commonly used in neurobiological research. Digital atlases of the C57BL/6J brain have been used for visualization, genetic phenotyping and morphometry, but currently lack the ability to accurately calculate deviations between individual mice. We developed a fully three-dimensional digital atlas of the C57BL/6J brain based on the histology atlas of Paxinos and Franklin (2001 The Mouse Brain in Stereotaxic Coordinates 2nd edn (San Diego, CA: Academic)). The atlas uses triangular meshes to represent the various structures. The atlas structures can be overlaid and deformed to individual mouse MR images. For this study, we selected 18 structures from the histological atlas. Average atlases can be created for any group of mice of interest by calculating the mean three-dimensional positions of corresponding individual mesh vertices. As a validation of the atlas' accuracy, we performed deformable registration of the lateral ventricles to 13 MR brain scans of mice in three age groups: 5, 8 and 9 weeks old. Lateral ventricle structures from individual mice were compared to the corresponding average structures and the original histology structures. We found that the average structures created using our method more accurately represent individual anatomy than histology-based atlases alone, with mean vertex deviations of 0.044 mm versus 0.082 mm for the left lateral ventricle and 0.045 mm versus 0.068 mm for the right lateral ventricle. Our atlas representation gives direct spatial deviations for structures of interest. Our results indicate that MR-deformable histology-based atlases represent an accurate method to obtain accurate morphometric measurements of a population of mice, and that this method may be applied to phenotyping experiments in the future as well as precision targeting of surgical procedures or radiation treatment.
View details for DOI 10.1088/0031-9155/54/24/005
View details for Web of Science ID 000272364000005
View details for PubMedID 19926915
View details for PubMedCentralID PMC3365531
We describe a computerized (or virtual) model of a stereotactic head frame to enable planning prior to the day of radiosurgery. The location of the virtual frame acts as a guide to frame placement on the day of the procedure.The software consists of a triangular mesh representation of the essential frame hardware that can be overlaid with any MR scan of the patient and manipulated in three dimensions. The software calculates regions of the head that will actually be accessible for treatment, subject to the geometric constraints of the Leksell Gamma Knife hardware. DICOM-compliant MR images with virtual fiducial markers overlaid onto the image can then be generated for recognition by the treatment planning system.Retrospective evaluation of the software on 24 previously treated patients shows a mean deviation of the position of the virtual frame from the actual frame position of 1.6 +/- 1.3 mm. Initial clinical use on five patients indicates an average discrepancy of the virtual frame location and the actual frame location of <1 mm. MR images with virtual fiducial markers can be imported into radiosurgical treatment planning software and used to generate an initial treatment plan.The virtual frame provides a tool for prospective determination of lesion accessibility, optimization of the frame placement, and treatment planning before the day of the procedure. This promises to shorten overall treatment times, improve patient comfort, and reduce the need for repeat treatments due to suboptimally placed frames.
View details for DOI 10.1016/j.ijrobp.2008.06.1934
View details for Web of Science ID 000260592600039
View details for PubMedID 18954719