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Biomedical subjects

S Patel

Publications and source records attributed to S Patel.

At least 613 records · Page 34Linked to original sources
PubMed1989

Isolation of plasma membrane complexes from Xenopus oocytes.

A method for the isolation of plasma membrane fractions from Xenopus oocytes has been developed, and the membranes have been characterized biochemically and morphologically. Plasma membrane complexes prepared by this procedure consisted of large sheets of the membrane, with associated vitelline envelope (a nonmembranous meshwork of fibers) and cortical (secretory) granules still attached. The morphology of cell surface microvilli and coated pits was well preserved. Cortical granules were removed by gentle homogenization in a low ionic strength medium, and integral and peripheral membrane proteins were then separated from vitelline envelopes by detergent extraction and phase separation in Triton-X-114. Biochemical characterization of the plasma membrane fractions indicated substantial levels of 5'-nucleotidase and alkaline phosphodiesterase activity associated with the oocyte cell surface, with 44-66% recovery of these markers in the final membrane preparations. Lectin blotting and lectin affinity chromatography with Concanavalin A and wheat germ agglutinin were used to characterize the major glycoprotein species associated with the plasma membrane complexes. Plasma membrane fractions prepared by this procedure should be very useful in both biochemical and morphological studies of membrane protein sorting in the Xenopus oocyte system.

Animals↗
PubMed1989

Skinned muscle fibers of Aplysia: potentiation of contraction by "background" calcium and lack of effect of cyclic AMP.

1. Aplysia buccal muscle E1 can be skinned with saponin in a low ionic strength medium. Pulses of calcium, which were ineffective at causing contraction in intact fibers, elicited contraction in skinned fibers. 2. Tension in skinned fibers increased at [Ca2+] greater than 10(-7) M and was maximal at 6 x 10(-7) M. 10(-5) M [Ca2+] caused irreversible damage to the fibers. 3. Fibers did not exhibit "catch", i.e. they relaxed quickly upon removal of calcium. 4. Optimal pH for tension was 7.0. 5. Contractile responses to calcium pulses were increased by raising "background" [Ca2+] to 10(-7) M. 6. Cyclic AMP (10(-4) and 10(-3) M) had no effect on tension.

Animals↗
PubMed1989

N-methyl-D-aspartate receptors in the cortex and hippocampus of baboon (Papio anubis and Papio papio).

In vitro autoradiography was used to examine the N-methyl-D-aspartate receptor in the brain of a baboon species, Papio anubis, and compared to that of Papio papio which exhibits a photosensitive epilepsy. The epilepsy originates in the frontal cortex and is accompanied by an enhanced sensitivity to N-methyl-D-aspartate. In both Papio anubis and Papio papio, the density of N-methyl-D-aspartate receptors was greatest in the hippocampus, followed by associational areas including frontal cortex, and low in primary sensory areas such as the visual cortex. The receptors were concentrated in the outer cortical layers I-III, very low in layer IV except in primary visual cortex, and of intermediate density in layer V. The density of binding sites was approximately two-fold lower than previously observed in the rodent brain, whereas the affinity of the receptor for [3H]L-glutamate was greater in the primate versus the rodent brain. Glycine potentiated the binding of [3H]L-glutamate in both cortex and hippocampus. No significant differences in the properties of N-methyl-D-aspartate receptors were observed between the two baboon species, suggesting that the photosensitivity of Papio papio is not due to alterations in the binding of L-glutamate to the N-methyl-D-aspartate receptor complex.

Animals↗
PubMed1989

Effect of vitamin D metabolites on calcitriol metabolism in experimental renal failure.

Previous studies from our laboratory have demonstrated that metabolic clearance rate (MCR) of calcitriol is decreased in experimental renal failure. In this experiment, we examined the effects of calcitriol, 25-hydroxyvitamin D3 (25(OH)D3) and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) on the MCR of calcitriol in renal failure produced in rats by partial nephrectomy. The MCR of calcitriol in these rats with renal failure was significantly lower than in control rats with sham operations. Plasma concentrations of calcitriol did not differ between the rats with moderate renal failure and control rats (sham, 74.7 +/- 3.6 pg/ml, N = 7; renal failure, 67.7 +/- 6.0, N = 6; serum creatinine 0.56 +/- 0.02 mg/dl vs. 0.96 +/- 0.02); however, the levels were significantly lower in rats with severe renal failure (sham, 66.5 +/- 5.1 pg/ml, N = 7, severe renal failure, 49.6 +/- 2.1 pg/ml, N = 8; serum creatinine 0.53 +/- 0.01 mg/dl vs. 1.40 +/- 0.03). Subcutaneous infusion of calcitriol (10 ng/kg/day) in rats with severe renal failure for one week significantly increased the MCR of calcitriol (0.22 +/- .01 vs. 0.17 +/- .01 ml/min/kg, P less than 0.001). Infusion of 25(OH)D3 (600 ng/day) or 24,25(OH)2D3 (1 microgram/day) in rats with renal failure for one week also increased the MCR of calcitriol (25(OH)D3, 0.25 +/- 0.01 ml/min/kg; 24,25(OH)2D3, 0.25 +/- 0.01, both P less than 0.001) when compared to rats with renal failure infused with vehicle (0.21 +/- 0.01). Administration of 24,25(OH)2D3 significantly lowered the plasma levels of calcitriol in rats with renal failure (52.3 +/- 3.1 pg/ml, P less than 0.05) in comparison to the rats with renal failure infused with vehicle (67.7 +/- 6.0).(ABSTRACT TRUNCATED AT 250 WORDS)

24,25-Dihydroxyvitamin D 3↗
PubMed1989

Memory functioning following a left medial thalamic hematoma.

A patient with a discrete, left medial thalamic hematoma developed a severe anterograde amnesia. The memory deficit was most consistent for verbal materials, but was also observed on several tests of figural memory. The patient appeared to have a normal short-term memory (STM) capacity, performed normally on a STM distractor task and was not abnormally sensitive to proactive inhibition. This case is evidence that unilateral damage to the medial thalamus alone can produce a severe memory deficit.

Aged↗
PubMed1989

Age-related changes in precorneal tear film stability.

For several years it has been known that the production rate of tears declines as age increases. Reports suggest that this reduction is more apparent in females than in males. Using a noninvasive method we report that a significant linear reduction in precorneal tear film stability occurs between the ages of 8 and 80 years. However, we found no significant differences in tear film stability between males and females.

Adolescent↗
PubMed1989

The subclass of IgG antibody in allergic disease: II. The IgG subclass of antibodies produced following natural exposure to dust mite and grass pollen in atopic and non-atopic individuals.

In an attempt to understand the role of the different IgG subclasses in allergic disease, we have studied the subclass of IgG antibody to dust mite (HDM) and grass pollen (GP) produced as a result of natural exposure. Studies were carried out on 40 atopic children and 100 atopic adults who had never received immunotherapy. Thirty-two non-atopic adult controls were also studied. The specificity of the assay for IgG antibodies to dust mite was confirmed by inhibition with the homologous extract but not mite culture medium or fetal calf serum. IgG1 antibodies to HDM could be detected in most atopics (94%) and non-atopics (97%), and similar results were obtained for GP (81% and 100%, respectively). IgG4 antibodies to HDM were detected in more atopics (66%) than non-atopics (53%) and the difference was more marked for GP (72% vs. 19%). While the levels of IgG1 antibodies were not significantly different in the two groups, the levels of IgG4 antibodies were much lower in the non-atopics (P less than 0.001, Mann-Whitney U-test). These data show that all subjects were capable of recognizing and mounting an IgG1 antibody response to these inhaled antigens. Atopic individuals differed from normal subjects in the frequency with which they made IgG4 antibodies in response to natural exposure to both dust mites and pollen.

Adult↗
PubMed1989

Comparison of a new type of skin test (Phazet) with existing skin test methods and the radioallergosorbent test (RAST).

A new skin test method (Phazet) for diagnosis of immediate-type allergic disease was tested in 232 patients attending the Guy's Hospital Allergy Clinic, and compared with conventional skin test methods, using Bencard and Pharmalgen allergen solutions, and with serum IgE antibody tests (RAST). Six allergens (cat, dust mite, Cladosporium, grass pollen birch pollen and plantain pollen) were used, as well as histamine and a negative control. Phazet proved easy to use and was popular with inexperienced operators (medical and dental students). For the majority of allergens there was reasonably good agreement with the different tests, but overall Phazet and RAST produced fewer positive results than the other skin tests methods. In particular, the frequency of positive histamine tests was lower with Phazet (82%) than with Bencard or Pharmalgen (99%), but this discrepancy was lower in the second part of the study when the minimum time for the insertion of the needle (1 sec) was more scrupulously observed. Phazet offers a convenient and practical alternative to conventional 'wet' skin test methods.

Allergens↗
PubMed1989

Human tear film pre-rupture phase time (TP-RPT)--a non-invasive technique for evaluating the pre-corneal tear film using a novel keratometer mire.

A non-invasive method of assessing the stability of the human pre-corneal tear film is described using a novel keratometer mire designed in the form of a grid pattern (HIR-CAL Grid). In a laboratory environment, the technique measures with ease and little variability the time taken for the tear film to loose stability and enter the pre-rupture phase (TP-RPT) before rupturing (BUT). This technique may prove useful in evaluating the stability or otherwise of the pre-corneal tear film of prospective contact lens wearer and the pre-contact lens tear film stability on differing current and new contact lens materials.

Blinking↗
PubMed1989

Macrophage subpopulations in lamina propria of normal and inflamed colon and terminal ileum.

The aim of this study was to characterise human intestinal macrophages in normal and inflamed ileum and colon. Immunoperoxidase staining with a panel of monoclonal antibodies and histochemical staining for acid phosphatase and non-specific esterase was performed. In the superficial lamina propria, normal colonic macrophages were larger and more strongly positive for acid phosphatase and non-specific esterase than those in normal terminal ileum. There were more macrophages staining with monoclonal antibody RFD1 in the superficial lamina propria of the latter. Studies in inflammatory bowel disease tissue showed the presence of macrophages staining with monoclonal antibodies RFD9 and 3G8 which were rarely present in normal tissue and represented a different pattern from that seen in infectious colitis. Studies on isolated intestinal macrophages confirmed the findings in tissue sections. Subpopulations of intestinal macrophages are likely to have different functional roles. Phenotypic changes during inflammation may be induced by mediators of inflammation or may represent a recently recruited population of cells.

Adolescent↗
PubMed1989

IgG and IgE antibodies after immunotherapy with bee and wasp venom.

IgG and IgE antibody levels have been followed for a period of 2 years in patients receiving immunotherapy with bee and wasp venom. 106 adult patients who had had anaphylactic reactions to wasp stings had initially low IgG antibody levels to wasp venom which rose with therapy (p less than 0.001). IgE antibody levels also showed an initial rise but subsequently fell (p less than 0.001). The pattern was similar to that previously reported in children who had had anaphylactic reactions to bee stings, but who, after a course of immunotherapy, were able to tolerate stings with impunity. 60 adults who had had anaphylactic reactions to bee stings showed a different pattern, with initially high IgG antibody levels which did not rise further. Since two thirds of this group were beekeepers or members of beekeeper's families, the high initial IgG antibody levels could have been a response to the frequent stings to which such individuals are prone. The fact that high levels did not protect against anaphylaxis shows, however, that the classical concept of 'blocking antibody' is in need of revision.

Bee Venoms↗
PubMed1989

Acute effects of smoking on blood pressure and cerebral blood flow.

Chronic smoking, particularly in hypertensives, is associated with an increased frequency of cerebral infarction and subarachnoid haemorrhage; cerebral blood flow (CBF) is also decreased in chronic smokers. The acute effects of smoking upon CBF are less clear. The present study in six volunteers investigated the immediate effects of smoking (and inhaling) three cigarettes, each separated by a 2 hr gap, upon heart rate, blood pressure (BP) and CBF assessed by xenon inhalation and flow velocities in the middle cerebral artery by transcranial Doppler ultrasound. Smoking caused significant increases in heart rate, BP and middle cerebral artery flow velocities, and a significant fall in CBF (individual falls in hemispherical flow could be as great as 40%). These haemodynamic effects are probably caused by nicotine-induced changes in catecholamine release. The possible clinical significance of the BP and CBF changes induced by acute smoking in high-risk groups is discussed.

Administration, Inhalation↗
PubMed1989

Mononuclear phagocyte system of human Peyer's patches: an immunohistochemical study using monoclonal antibodies.

Macrophages in sections of human terminal ileal Peyer's patches were studied using a panel of monoclonal antibodies. Germinal centre macrophages were large and strongly positive for acid phosphatase and stained with antibodies RFD1, RFD9, UCHM1 and other macrophage-specific monoclonal antibodies, but not RFD7. In the macrophages of the dome region there was heterogeneity of size and staining for acid phosphatase. The majority of the RFD1 positive cells in this region appeared to be macrophages. However, no RFD9- or RFD7-positive cells were present. By contrast, RFD7-positive but RFD9-negative macrophages were present in the lamina propria. In the interfollicular areas there were cells with a dendritic morphology which were strongly HLA-DR, HLA-DQ and RFD1-positive, but which did not stain with the other macrophage specific monoclonal antibodies or for acid phosphatase. Some macrophages and lymphocytes in the germinal centre and dome regions expressed interleukin 2 and transferrin receptors. These cells were not present in the adjacent lamina propria.

Acid Phosphatase↗
PubMed1988

Design, synthesis, and fluorescence studies of fluorenyl fatty acids as new depth-dependent fluorescent probes for membranes: getting over the looping-back problem.

Fluorescent fatty acids have proved very useful in studying the membrane hydrophobic core. They readily partition into membranes or can be converted to phospholipids, which form integral components of membranes. By attaching the fluorescent chromophore to different positions along the alkyl chain of fatty acids, e.g., an anthroyloxy group attached via an ester linkage to n-hydroxystearic acid, membranes have been probed at different depths. While this is an interesting approach and has been extensively used, relatively little attention has been paid to the molecular design of these probes in order to have minimal membrane perturbation. In the present study we have looked into the general problem of design of such depth-dependent membrane probes. We report here a series of fluorenyl fatty acids with varying fatty acid chain lengths, i.e., (2-fluorenyl)acetic acid, -butyric acid, -hexanoic acid, and -octanoic acid, in order to obtain information at different depths in the membrane hydrophobic core. To see the effect of attachment of a hydrophobic tail on the orientation of such fatty acids in membranes, an n-butyl group was linked to the C-7 position of fluorene in (2-fluorenyl)butyric acid to get 4-(7-n-butylfluoren-2-yl)butyric acid. Further, to assess their ability to act as depth-dependent fluorescent probes, these fatty acids were incorporated in vesicles prepared from egg phosphatidylcholine, and their fluorescence quenching was studied with potassium iodide, Cu(II), 9,10-dibromostearic acid, and 12-bromostearic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Membrane↗