Biomedical subjects

Deborah M Grzybowski

Publications and source records attributed to Deborah M Grzybowski.

4 recordsLinked to original sources

PubMed2006

In vitro model of cerebrospinal fluid outflow through human arachnoid granulations.

PURPOSE: To describe and validate an in vitro model of the arachnoid granulation (AG) outflow pathway for cerebrospinal fluid (CSF), by using human AG cells grown on a filter membrane support and perfused in a modified Ussing chamber at pressures analogous to normal human intracranial pressures. METHODS: Human AG cells were grown, characterized, seeded onto filter membranes, and perfused in the physiologic (basal to apical, B-->A) or nonphysiologic (apical to basal, A-->B) directions. Cells were fixed under pressure after perfusion and prepared for electron microscopy (EM). RESULTS: The average cellular hydraulic conductivity in the B-->A direction (10 total) was 4.52 +/- 0.43 microL/min per mm Hg/cm(2) with an average transcellular pressure decrease of 3.13 +/- 0.09 mm Hg. The average cellular hydraulic conductivity in the A-->B direction (six total) was 0.29 +/- 0.16 microL/min per mm Hg/cm(2) with an average transcellular decrease in pressure of 3.33 +/- 0.16 mm Hg. Cells perfused nonphysiologically showed a large number of dead and dying cells. EM postperfusion analysis showed that AG cells were integrally attached to the underlying filter membrane. Large extracellular cisternal spaces were visible between overlapping AG cells and vacuoles within the cytoplasm. It is possible that these spaces within and between cells represent pathways for transcellular and paracellular transport of fluid. CONCLUSIONS: The results demonstrate that AG cells in vitro show a statistically significant greater flow rate and cellular hydraulic conductivity when perfused in the physiologic versus the nonphysiologic direction under normal intracranial pressures. These results suggest that this in vitro model of the AGs can accurately replicate the unidirectional flow of CSF in vivo.

Arachnoid↗

PubMed2005

Characterization of cytoskeletal and junctional proteins expressed by cells cultured from human arachnoid granulation tissue.

BACKGROUND: The arachnoid granulations (AGs) are projections of the arachnoid membrane into the dural venous sinuses. They function, along with the extracranial lymphatics, to circulate the cerebrospinal fluid (CSF) to the systemic venous circulation. Disruption of normal CSF dynamics may result in increased intracranial pressures causing many problems including headaches and visual loss, as in idiopathic intracranial hypertension and hydrocephalus. To study the role of AGs in CSF egress, we have grown cells from human AG tissue in vitro and have characterized their expression of those cytoskeletal and junctional proteins that may function in the regulation of CSF outflow. METHODS: Human AG tissue was obtained at autopsy, and explanted to cell culture dishes coated with fibronectin. Typically, cells migrated from the explanted tissue after 7-10 days in vitro. Second or third passage cells were seeded onto fibronectin-coated coverslips at confluent densities and grown to confluency for 7-10 days. Arachnoidal cells were tested using immunocytochemical methods for the expression of several common cytoskeletal and junctional proteins. Second and third passage cultures were also labeled with the common endothelial markers CD-31 or VE-cadherin (CD144) and their expression was quantified using flow cytometry analysis. RESULTS: Confluent cultures of arachnoidal cells expressed the intermediate filament protein vimentin. Cytokeratin intermediate filaments were expressed variably in a subpopulation of cells. The cultures also expressed the junctional proteins connexin43, desmoplakin 1 and 2, E-cadherin, and zonula occludens-1. Flow cytometry analysis indicated that second and third passage cultures failed to express the endothelial cell markers CD31 or VE-cadherin in significant quantities, thereby showing that these cultures did not consist of endothelial cells from the venous sinus wall. CONCLUSION: To our knowledge, this is the first report of the in vitro culture of arachnoidal cells grown from human AG tissue. We demonstrated that these cells in vitro continue to express some of the cytoskeletal and junctional proteins characterized previously in human AG tissue, such as proteins involved in the formation of gap junctions, desmosomes, epithelial specific adherens junctions, as well as tight junctions. These junctional proteins in particular may be important in allowing these arachnoidal cells to regulate CSF outflow.

Journal Article↗

PubMed2005

Model for nonectatic increase in posterior corneal elevation after ablative procedures.

PURPOSE: To evaluate the response of the posterior cornea after uneventful laser in situ keratomileusis (LASIK) with scanning-slit videokeratography using the change in elevation as a measure of biomechanical remodeling. SETTING: Hong Kong Sanatorium and Hospital, Hong Kong, China. METHODS: Three schematic models of possible posterior corneal response mechanisms to laser refractive surgery were proposed: model A, isolated central bulging; model B, forward shift over a large region of the posterior surface; model C, backward peripheral movement into the anterior chamber. A retrospective study was performed to determine which model was consistent with posterior corneal behavior in 2380 eyes of 1255 patients after myopic LASIK performed with the Technolas 217 laser (Bausch & Lomb). Patients received preoperative and 6-month postoperative Orbscan I (version 2.0, Bausch & Lomb) examinations. Preoperative posterior elevation maps were subtracted from postoperative maps of 2380 eyes using 3 fitting protocols. Difference maps were averaged and the results compared to the proposed schematic models. All topography data processing was done using the Ohio State University Corneal Topography Tool. RESULTS: Significant central increases in posterior elevation corresponded with significant peripheral decreases in posterior elevation. This pattern is consistent with schematic model C, backward peripheral movement of the posterior cornea, possibly due to a differential pattern of swelling. CONCLUSIONS: Increases in central posterior corneal elevation after LASIK appear to be dominated by backward peripheral corneal swelling into the anterior chamber rather than forward "bulging" of the central posterior cornea. This is consistent with stable remodeling of the corneal shape due to a surgically induced change in structure and fluid balance, rather than an ectatic event.

Astigmatism↗

PubMed2004

Spatial comparison between wall shear stress measures and porcine arterial endothelial permeability.

A better understanding of how hemodynamic factors affect the integrity and function of the vascular endothelium is necessary to appreciate more fully how atherosclerosis is initiated and promoted. A novel technique is presented to assess the relation between fluid dynamic variables and the permeability of the endothelium to macromolecules. Fully anesthetized, domestic swine were intravenously injected with the albumin marker Evans blue dye, which was allowed to circulate for 90 min. After the animals were euthanized, silicone casts were made of the abdominal aorta and its iliac branches. Pulsatile flow calculations were subsequently made in computational regions derived from the casts. The distribution of the calculated time-dependent wall shear stress in the external iliac branches was directly compared on a point-by-point basis with the spatially varying in vivo uptake of Evans blue dye in the same arteries. The results indicate that in vivo endothelial permeability to albumin decreases with increasing time-average shear stress over the normal range. Additionally, endothelial permeability increases slightly with oscillatory shear index.

Albumins↗