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Biomedical subjects

S C Patel

Publications and source records attributed to S C Patel.

At least 37 records · Page 2Linked to original sources
PubMed2000

Regional distribution of NPC1 protein in monkey brain.

NPC1 is a member of a family of polytopic membrane-bound proteins with sterol-sensing domains. Inactivating mutations of NPC1 are responsible for most cases of Niemann-Pick type C disease, whose hallmark is progressive neurodegeneration. The precise molecular mechanisms whereby defective NPC1 function leads to neurodegeneration are unknown. In the brain, we have previously found NPC1 to localize predominantly within perisynaptic astrocytic processes. Here we have mapped the regional distribution of NPC1 in the monkey brain. Dense NPC1 immunoreactivity was observed in telencephalic structures, including the cerebral neocortex, hippocampus, caudate nucleus and putamen, whilst light immunostaining was observed in diencephalic structures, including the globus pallidus, thalamus and hypothalamus. Light staining was also generally observed in the midbrain, pons, medulla oblongata and cerebellum, except the inferior olive, which was densely stained. By light microscopy, only a few indistinctly labeled cell bodies were observed even within densely labeled regions, where most of the immunoreactivity appeared to be due to the large numbers of labeled cellular processes. On electron microscopy, these processes were identified as glial, and not neuronal. The astrocytic localization of NPC1 was further confirmed by double labeling for NPC1 and GFAP. The regional pattern of NPC1 expression suggests that areas normally expressing low levels of the NPC1 protein are more susceptible to neuronal degeneration in Niemann-Pick type C disease.

Animals↗
PubMed2000

Reporting and concordance of methodologic criteria between abstracts and articles in diagnostic test studies.

OBJECTIVE: To evaluate the quality and concordance of methodologic criteria in abstracts versus articles regarding the diagnosis of trichomoniasis. STUDY DESIGN: Survey of published literature. DATA SOURCES: Studies indexed in MEDLINE (1976-1998). STUDY SELECTION: Studies that used culture as the gold or reference standard. DATA EXTRACTION: Data from abstract and articles were independently abstracted using 4 methodologic criteria: (1) prospective evaluation of consecutive patients; (2) test results did not influence the decision to do gold standard; (3) independent and blind comparison with gold standard; and (4) broad spectrum of patients used. The total number of criteria met for each report was calculated to create a quality score (0-4). MEASUREMENTS AND MAIN RESULTS: None of the 33 abstracts or full articles reported all 4 criteria. Three criteria were reported in none of the abstracts and in 18% of articles (95% confidence interval [95% CI] 8.6% to 34%). Two criteria were reported in 18% of abstracts (95% CI, 8.6% to 34%) and 42% of articles (95% CI, 27% to 59%). One criterion was reported in 42% of abstracts (95% CI, 27% to 59%) and 27% of articles (95% CI, 15% to 44%). No criteria were reported in 13 (39%) of 33 abstracts (95% CI, 25% to 56%) and 4 (12%) of 33 articles (95% CI, 4.8% to 27%). The agreement of the criteria between the abstract and the article was poor (kappa -0.09; 95% CI, -0.18 to 0) to moderate (kappa 0.53; 95% CI, 0.22 to 0.83). CONCLUSIONS: Information on methods basic to study validity is often absent from both abstract and paper. The concordance of such criteria between the abstract and article needs to improve.

Clinical Laboratory Techniques↗
PubMed2000

Systematic review of diagnostic tests for vaginal trichomoniasis.

OBJECTIVE: To review critically and to summarize the evidence of diagnostic tests and culture media for the diagnosis of Trichomonas vaginitis. METHODS: We performed a systematic review of literature indexed in MEDLINE of studies that used Trichomonas culture as the reference standard (9,882 patients, 35 studies). Level I studies (5,047 patients, 13 studies) fulfilled at least two of three criteria: 1) consecutive patients were evaluated prospectively, 2) decision to culture was not influenced by test results, and 3) there was independent and blind comparison to culture. RESULTS: The sensitivity of the polymerase chain reaction technique (PCR) was 95% (95% CI 91% to 99%), and the specificity was 98% (95% CI 96% to 100%). One study was classified as Level I evidence (52 patients). The sensitivity of the enzyme-linked immunosorbent assay was 82% (95% CI 74% to 90%), and the specificity was 73% (95% CI 35% to 100%). The sensitivity of the direct fluorescence antibody was 85% (95% CI 79% to 90%), and the specificity was 99% (95% CI 98% to 100%). Sensitivities of culture media were 95% for Diamond's, 96% for Hollander, and 95% for CPLM. CONCLUSIONS: The sensitivity and specificity of tests to diagnose trichomoniasis vary widely.

Animals↗
PubMed2000

Laparoscopic cholecystectomy at the Aga Khan Hospital, Nairobi.

OBJECTIVE: To evaluate our experience of laparoscopic cholecystectomies at the Aga Khan Hospital, Nairobi over a three-year period from the inception of the technique, and to assess its value and advantages to the patients. DESIGN: A prospective case series study. SETTING: The Aga Khan Hospital, Nairobi. PATIENTS: One hundred and thirty five cases operated from February 1996 to April 1999. All patients were subjected to the American method of laparoscopic cholecystectomy, which is described in detail in this paper. MAIN OUTCOME MEASURES: Clinical presentation, age and sex demographics, average hospital stay, intraoperative and postoperative complications and outcome. RESULTS: There was a female preponderance with a female to male ratio of 5:1. Mean age was forty nine years. Majority of patients suffered from chronic cholecystitis. The conversion rate to an open procedure was five per cent. There were two cases of significant bile leakage which required laparotomy. No mortality was reported in this series. CONCLUSION: This technique was found to have distinct advantages such as shorter hospital stay, lesser postoperative pain and very good cosmesis. It is a safe procedure if performed by a well trained surgeon.

Adolescent↗
PubMed2000

The persistent stapedial artery.

The persistent stapedial artery is a rare congenital vascular anomaly that may present as a pulsatile middle ear mass or that may appear as an incidental finding. Five cases of persistent stapedial artery are presented. The CT findings include the absence of the ipsilateral foramen spinosum and a soft-tissue prominence in the region of the tympanic segment of the facial nerve. Three cases were associated with an aberrant internal carotid artery. Imaging identification of this variant may obviate unnecessary surgery and may help in planning surgical or endovascular interventions.

Adolescent↗
PubMed2000

Human fetal retinal pigment epithelium-induced cell cycle arrest, loss of mitochondrial membrane potential and apoptosis.

PURPOSE: To investigate the mechanism of action of the soluble immune suppressive product secreted by human fetal retinal pigment epithelial (HFRPE) cells in a model system using the human T-cell line Jurkat (Jkt). METHODS: Pure HFRPE cells were isolated and cultured. The supernatants of both nonactivated and IFN-gamma-activated HFRPE cells were isolated. Cells from the human T-cell line Jkt were incubated either in standard culture medium or in the supernatant isolated from HFRPE cells. In the first assay Jkt cell proliferation was measured by [(3)H]thymidine incorporation. In the second assay Jkt cell apoptosis was examined for annexin V staining by flow cytometry. In the third assay Jkt cell division was evaluated with carboxyfluorescein succinimidyl ester (CFSE) fluorescent dye. In the last assay the mitochondrial transmembrane potential of Jkt cells was measured with the cationic lipophilic fluorochrome 3,3'-dihexyloxacarbocyanine iodide [DiOC(6)]. In all the assays the effect of supernatants isolated from both nonactivated and IFN-gamma-activated HFRPE cells were compared with standard culture medium. The involvement of antiapoptotic human gene bcl-x(L:)was determined by using a Jkt cell line that was stably transfected with bcl-x(L:). RESULTS: The supernatant isolated from HFRPE cells significantly suppressed the cell division in Jkt cells and induced apoptosis. These effects were stronger when the supernatant was isolated from IFN-gamma-activated HFRPE cells. The apoptosis pathway induced by the secreted product of HFRPE cells involved the early disruption of mitochondrial transmembrane potential. Although the overexpression of bcl-x(L) gene rescued the Jkt cells from supernatant-induced apoptosis, it could not restore the proliferation of Jkt cells. CONCLUSIONS: These data suggest that HFRPE cells secrete a product that initiates an early cell cycle arrest in the human T-cell line Jkt, which is followed by the activation of an apoptotic pathway that involves the loss of mitochondrial membrane potential. The latter could be prevented by bcl-x(L) overexpression. Also these data suggest that the HFRPE-induced T-cell apoptosis may play a significant role in maintaining the immune privilege in the subretinal space.

Annexin A5↗
PubMed1999

Initial clinical experience with IV tissue plasminogen activator for acute ischemic stroke: a multicenter survey. The t-PA Stroke Survey Group.

We assessed initial clinical experience with IV tissue plasminogen activator (t-PA) treatment of acute ischemic stroke in a standardized retrospective survey of hospitals with experienced acute stroke treatment systems. The incidence of symptomatic intracerebral hemorrhage (ICH) was 6% (11 of 189 patients; 95% CI 3 to 11%), similar to that in the National Institute of Neurological Disorders and Stroke (NINDS) t-PA Stroke Study. Deviations from the NINDS protocol guidelines were identified in 30% of patients (56 of 189). The incidence of symptomatic ICH was 11% among patients with protocol deviations as compared with 4% in patients who were treated according to the NINDS protocol guidelines, suggesting that strict adherence to protocol guidelines is prudent.

Aged↗
PubMed1999

Localization of Niemann-Pick C1 protein in astrocytes: implications for neuronal degeneration in Niemann- Pick type C disease.

Niemann-Pick type C disease (NP-C) is an inherited neurovisceral lipid storage disorder characterized by progressive neurodegeneration. Most cases of NP-C result from inactivating mutations of NPC1, a recently identified member of a family of genes encoding membrane-bound proteins containing putative sterol sensing domains. By using a specific antipeptide antibody to human NPC1, we have here investigated the cellular and subcellular localization and regulation of NPC1. By light and electron microscopic immunocytochemistry of monkey brain, NPC1 was expressed predominantly in perisynaptic astrocytic glial processes. At a subcellular level, NPC1 localized to vesicles with the morphological characteristics of lysosomes and to sites near the plasma membrane. Analysis of the temporal and spatial pattern of neurodegeneration in the NP-C mouse, a spontaneous mutant model of human NP-C, by amino-cupric-silver staining, showed that the terminal fields of axons and dendrites are the earliest sites of degeneration that occur well before the appearance of a neurological phenotype. Western blots of cultured human fibroblasts and monkey brain homogenates revealed NPC1 as a 165-kDa protein. NPC1 levels in cultured fibroblasts were unchanged by incubation with low density lipoproteins or oxysterols but were increased 2- to 3-fold by the drugs progesterone and U-18666A, which block cholesterol transport out of lysosomes, and by the lysosomotropic agent NH4Cl. These studies show that NPC1 in brain is predominantly a glial protein present in astrocytic processes closely associated with nerve terminals, the earliest site of degeneration in NP-C. Given the vesicular localization of NPC1 and its proposed role in mediating retroendocytic trafficking of cholesterol and other lysosomal cargo, these results suggest that disruption of NPC1-mediated vesicular trafficking in astrocytes may be linked to neuronal degeneration in NP-C.

Amino Acid Sequence↗
PubMed1999

A new model of retinal pigment epithelium transplantation with microspheres.

OBJECTIVES: To develop a 3-dimensional carrier system for subretinal transplantation of human fetal retinal pigment epithelial (HFRPE) cells and to assess their growth pattern in the rabbit subretinal space. METHODS: After a standard 3-port vitrectomy, HFRPE cells grown as microspheres on cross-linked fibrinogen were introduced into the subretinal space of rabbits. The eyes were studied at 7, 14, and 30 days after surgery by ophthalmoscopy and light microscopy. RESULTS: Ophthalmoscopically, at day 7, 11 (61%) of the 18 eyes showed radiating hyperpigmentation around the transplanted HFRPE microspheres. The results of a histological examination revealed a monolayer outgrowth of HFRPE cells, overlying host retinal pigment epithelium. The control eyes revealed a patch of chorioretinal atrophy with lymphocytic infiltration around the microspheres. CONCLUSIONS: Human fetal retinal pigment epithelial cells grown as microspheres on cross-linked fibrinogen can be successfully transplanted into the subretinal space. Cells can survive for at least 1 month and form a monolayer over the host retinal pigment epithelium cells, with a mild local inflammatory response. The difference in inflammatory responses between the eyes that underwent transplantation and the control eyes may suggest a modulating effect of the HFRPE cells on inflammation, immunity, or both. This new xenogenic model may have importance in the study of subretinal transplant cell biology and the associated immune response. CLINICAL RELEVANCE: The results of this study may be important for better understanding of the mechanisms of retinal pigment epithelium cell behavior after transplantation. The proposed model may be applicable for future clinical and experimental investigations in the area of retinal pigment epithelium transplantation.

Animals↗
PubMed1999

Growth of human fetal retinal pigment epithelium as microspheres.

BACKGROUND: The aim was to develop a three-dimensional cell culture system for human fetal retinal pigment epithelial (HFRPE) cells for in vitro cellular studies and for possible application in subretinal transplantation. METHODS: Pieces of freshly isolated HFRPE monolayer tissue were grown on crosslinked fibrinogen (CLF) films. The growth pattern and morphologic characteristics of the implanted tissue were studied using phase-contrast microscopy, photography, and light and electron microscopy. The cells were screened immunohistochemically for HLA-ABC, HLA-DR, ICAM-1, B7, and Cytokeratin. Cell proliferation was studied using 5-bromo-2-deoxyuridine incorporation. RESULTS: After attachment to CLF, HFRPE monolayer tissue formed small tumor-like formations, i.e. microspheres. HFRPE microspheres survived and proliferated in a floating state for at least 4 months. After attachment of the microspheres to the culture dish floor, formation of a confluent HFRPE cell monolayer with high proliferative activity was noted around the microspheres. HFRPE cells stained positive for HLA-ABC, ICAM-1, and cytokeratin and negative for B7 and HLA-DR. The microspheres could be easily detached from the dish and they were able to initiate similar growth after reattachment. CONCLUSION: HFRPE grown on CLF resemble a three-dimensional culture system with high yield of pure cells that can be useful for a wide variety of in vitro studies. Because of their adjustable size, spherical shape, and ability to initiate growth of cells with a high proliferative potential, HFRPE microspheres may be successfully utilized as a source of donor cells for subretinal transplantation.

B7-1 Antigen↗
PubMed1999

Cellular response in rabbit eyes after human fetal RPE cell transplantation.

BACKGROUND: This study was carried out to study inflammatory and proliferative cellular responses in the rabbit eye after subretinal transplantation of human fetal retinal pigment epithelial (HFRPE) cells. METHODS: 5-Bromo-2-deoxyuridine (BrdU)-labeled HFRPE cells were injected subretinally into rabbit eyes at three different concentrations. Macrophage, glial, and proliferative responses of the eye tissues were studied by immunohistochemistry and light microscopy at different times after the surgery. RESULTS: In transplanted eyes, the HFRPE cells were distributed irregularly either as multilayers or monolayers. In eyes receiving high-density cell suspensions, retinal breaks were seen. No retinal breaks were noted in the eyes receiving low-density HFRPE cell suspensions. The highest intensity of inflammatory response was seen at 4-14 days after surgery, with greater expression in transplanted eyes receiving high-density cell suspensions. The host cellular response was characterized initially by local infiltration of the retina and subretinal space by macrophages and glial cells. After day 14, a decline in the number of donor cells was noted in all eyes. At later stages the host cellular response was characterized mainly by local choroidal thickening and infiltration by inflammatory cells. Proliferative response was expressed mainly by retinal cells. CONCLUSION: Initial inflammatory and proliferative responses after the xenogenic human to rabbit HFRPE cell transplantation were expressed by retinal cells with later involvement of the choroid. Our results showed a decline in the number of donor cells starting from day 14 after the transplantation. This may suggest a possibility of rejection. The initial quantity of injected cells may be critical for the intensity of the immune and inflammatory responses.

Animals↗
PubMed1999

Human fetal retinal pigment epithelium suppresses the activation of CD4(+) and CD8(+) T-cells.

BACKGROUND: The suppressive effect of human fetal retinal pigment epithelium (HFRPE) on the activation of human CD4(+) and CD8(+) T-cells was evaluated in vitro. METHODS: Pure populations of CD4(+) and CD8(+) T-cells were isolated from human peripheral blood-derived buffy coats by negative immunomagnetic selection. The purity of the cells was examined by flow cytometry using anti-CD3-FITC, anti-CD4-FITC, anti-CD8-PE, and anti-CD20-PE mAbs. HFRPE cells were isolated from fetal eyes and pure cultures were obtained. The effect of normal or IFN-gamma-activated HFRPE cells at early (P3) or late (P6) passages on the activation of CD4(+) and CD8(+) T-cells was assessed in two different T-cell activation assays. In both activation models anti-CD3 mAb (OKT3) provided the antigen-specific signal. The secondary signal for the activation of CD4(+) and CD8(+) T-cells was provided with anti-CD18 mAb (TS1/18) and anti-CD28 mAb (9.3) in the first and the second assay respectively. Cross-linking of these soluble mAbs was performed with sheep-anti-mouse IgG-coated latex beads. The T-cell activation was determined by cell proliferation measured by [(3)H]thymidine incorporation. In each activation assay T-cells were incubated with HFRPE cells in a ratio of T-cells to HFRPE of 1:1 or 1:4. RESULTS: CD4(+) and CD8(+) T-cells were activated by cross-linking CD3 and CD18 in the first assay (CD3/CD18) and CD3 and CD28 in the second assay (CD3/CD28). In both assays HFRPE inhibited the activation of CD4(+) and CD8(+) T-cells. IFN-gamma-activated HFRPE cells totally suppressed the T-cell activation at a 1:1 ratio. This suppressive effect was weaker at lower cell ratios. Some donor variation was observed in the inhibition at the lower cell ratios, especially for the inhibition of CD8(+) T-cell activation with anti-CD3/CD18. The passaging of HFRPE cells did not alter their suppressive effect on CD4(+) and CD8(+) T-cells. CONCLUSIONS: HFRPE cells suppressed the activation of both CD4(+) and CD8(+) T-cells in vitro. These findings suggest that RPE-induced immune suppression may play a significant role in maintaining immune privilege in the subretinal space.

Antibodies, Monoclonal↗
PubMed1999

Apolipoprotein D gene expression in the rat brain and light and electron microscopic immunocytochemistry of apolipoprotein D expression in the cerebellum of neonatal, immature and adult rats.

Apolipoprotein D gene and protein expression were investigated in the rat brain and cerebellum, respectively, during development. Apolipoprotein D gene expression was first observed in embryonic day 12 rat brain, with a moderate increase in apolipoprotein D messenger RNA levels towards the later part (embryonic days 15-17) of gestation. In the postnatal rat brain, a marked induction of apolipoprotein D messenger RNA occurred at postnatal day 10, with progressively higher levels of apolipoprotein D messenger RNA observed up to postnatal day 20. Somewhat lower, but none the less high, levels of apolipoprotein D messenger RNA continued to be present in brains of adult animals. In the immature cerebellum (day 3 up to one- to two-week-old rats), there were many densely labeled apolipoprotein D-immunoreactive cells that had features of oligodendrocyte precursors. Purkinje neurons showed apolipoprotein D immunoreactivity in one- to two-week-old animals, after which there appeared to be some decrease in staining. Oligodendrocytes in the cerebella of two-week-old animals were strongly apolipoprotein D positive, with immunoreactivity declining in older animals. These results reveal a maturation-associated induction of apolipoprotein D gene expression in the rat brain, and expression of apolipoprotein D in glial (immature oligodendrocyte) cells in the immature cerebellum, followed by specific expression of apolipoprotein D in Purkinje neurons.

Aging↗
PubMed1999

Increased expression of apolipoprotein D following experimental traumatic brain injury.

Increasing evidence suggests that apolipoprotein D (apoD) could play a major role in mediating neuronal degeneration and regeneration in the CNS and the PNS. To investigate further the temporal pattern of apoD expression after experimental traumatic brain injury in the rat, male Sprague-Dawley rats were subjected to unilateral cortical impact injury. The animals were killed and examined for apoD mRNA and protein expression and for immunohistological analysis at intervals from 15 min to 14 days after injury. Increased apoD mRNA and protein levels were seen in the cortex and hippocampus ipsilateral to the injury site from 48 h to 14 days after the trauma. Immunohistological investigation demonstrated a differential pattern of apoD expression in the cortex and hippocampus, respectively: Increased apoD immunoreactivity in glial cells was detected from 2 to 3 days after the injury in cortex and hippocampus. In contrast, increased expression of apoD was seen in cortical and hippocampal neurons at later time points following impact injury. Concurrent histopathological examination using hematoxylin and eosin demonstrated dark, shrunken neurons in the cortex ipsilateral to the injury site. In contrast, no evidence of cell death was observed in the hippocampus ipsilateral to the injury site up to 14 days after the trauma. No evidence of increased apoD mRNA or protein expression or neuronal pathology by hematoxylin and eosin staining was detected in the contralateral cortex and hippocampus. Our results reveal induction of apoD expression in the cortex and hippocampus following traumatic brain injury in the rat. Our data also suggest that increased apoD expression may play an important role in cortical neuronal degeneration after brain injury in vivo. However, increased expression of apoD in the hippocampus may not necessarily be indicative of neuronal death.

Animals↗
PubMed1999

Human fetal retinal pigment epithelial cells induce apoptosis in allogenic T-cells in a Fas ligand and PGE2 independent pathway.

PURPOSE: To evaluate the inhibitory effect of human fetal retinal pigment epithelium (HFRPE) on the activation of human T-cells. METHODS: Pure cultures of HFRPE cells were incubated with purified human T-cells in three different activation assays: 1) allogenic peripheral blood mononuclear cells; 2) OKT3 coated beads in the presence of accessory cells; and 3) stimulation with phorbol ester and phytohemagglutinin. RESULTS: HFRPE cells suppressed the activation of T-cells in all three assays. The mechanism of HFRPE mediated T-cell suppression was apoptosis. The role of Fas ligand(FasL)/Fas-mediated T-cell suppression was excluded, since FasL protein or mRNA could not be detected on HFRPE cells with flow cytometry and by reverse transcriptase polymerase chain reaction, respectively. Additionally, the inhibitory effect of HFRPE cells could not be blocked by anti-Fas ligand or antagonistic anti-Fas antibodies. Moreover, HFRPE cells suppressed the proliferation of anti-CD3 mAb mediated T-cell proliferation of murine splenocytes isolated from lpr mice. The inhibitory effect of HFRPE cells was not PGE2 mediated, since indomethacin could not restore the T-cell activation. Although the HFRPE mediated T-cell apoptosis was cell-cell contact independent, it was not induced by secretion of TNF-alpha, TGF-beta, or IL-10. The ratio between HFRPE and T-cells had a major impact on the HFRPE's inhibitory effect. CONCLUSIONS: HFRPE cells suppressed the activation of human T-cells by induction of T-cell apoptosis through a process that involves the secretion of soluble factors. The HFRPE mediated T-cell suppression was dependent on the ratio between HFRPE and T-cells. This undefined pathway of T-cell apoptosis may play a role in the maintenance of immune privilege in the subretinal space and may reduce the severity of the immune response after HFRPE transplantation.

Animals↗
PubMed1999

Cryoprecipitate: An autologous substrate for human fetal retinal pigment epithelium.

PURPOSE: To harvest thin membranes from cryoprecipitates isolated from human blood donors and utilize them as substrates for the adhesion of human fetal retinal pigment epithelial (HFRPE) cells. METHODS: Frozen human cryoprecipitates from anonymous blood donors were obtained from the blood bank. Thin cryo-membranes were harvested by their mixture with riboflavin-5-phosphate (R5P) and overnight exposure to ultra-violet light. Sheets of retinal pigment epithelium (RPE) were isolated from fetal eyes at 17-22 weeks gestational age. The sheets were subsequently attached to cryo-membranes. The morphology of the cells was examined with phase contrast and electron microscope. Cell proliferation was evaluated by their incorporation of 5-bromo-2'-deoxyuridine (BrdU). Functional viability was assessed by rod outer segment (ROS) phagocytosis. RESULTS: Thin membrane films were made from isolated human cryoprecipitates. Isolated sheets of pure HFRPE cells were attached to the membranes. The cells maintained their cuboidal morphology and did not dedifferentiate. The cells subsequently proliferated and migrated onto the culture plate, forming cellular monolayers. The cultured cells phagocytized isolated ROS. CONCLUSIONS: Cryoprecipitate membranes may provide an ideal source for the adhesion, cultivation, and transfer of HFRPE cells. Their autologous isolation from the recipient's blood grants an additional advantage for their application as a carrier for HFRPE transplantation into the subretinal space.

Blood Preservation↗