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Biomedical subjects

A Singh

Publications and source records attributed to A Singh.

At least 757 records · Page 42Linked to original sources
PubMed1982

Ultrastructure of turkey hepatocytes.

Hepatocytes of normal male and female turkey livers perfused in situ with a fixative containing 4% glutaraldehyde in 0.05 M phosphate buffer (pH 7.4) were examined by electron microscopy. The hepatocytes, arranged in two-cell-layered plates, were polygonal and had three spatially different surfaces. The vascular surface was formed by microvilli, which at times projected into the sinusoids past the space of Disse. The interhepatocytic surfaces were closely applied and contained an occasional gap junction. The biliary surface participated in bile canaliculus formation and had short, regular microvilli. Tight junctions and adherens junctions were close to the canalicular lumen. The hepatocyte nucleus was located towards the vascular pole. The cytoplasm of hepatocytes of the females had many lipid droplets. The pleomorphic mitochondria, with relatively electron dense matrices were surrounded by one or, rarely, two profiles of flattened rER. Golgi complex was often observed in the vicinity of the nucleus, whereas the centrioles were located in the pericanalicular area of the biliary pole, which was rich in microtubules. These microtubules were extremely long, at times covering a substantial distance between the Golgi complex and bile canaliculi; microtubules occasionally formed bundles near the biliary pole. Small vesicles in close proximity of the microtubules were frequently observed. The spatial relationship between Golgi complex, microtubules, vesicles, and centrioles at the biliary pole of the hepatocyte appears to support the concept that the bile secretory mechanism in avian hepatocytes may involve a centrioles-microtubules-vesicles-Golgi complex system.

Animals↗
PubMed1982

Ultrastructure of the thyroid glands of rats fed photomirex: an 18-month recovery study.

The thyroid glands, from rats which had received photomirex (0.05, 0.5, 5 or 50 ppm) or mirex (5 or 50 ppm) in their diets for 28 days and maintained for 18 months on clean diet, were examined by electron microscopy. A dose of 0.05-5 ppm photomirex resulted in an augmentation of principal follicular cell heights. Their cytoplasm exhibited a marked numerical increase of secondary lysosomes. In addition, at 5 ppm, follicular cells in some segments of the gland contained only a few secondary lysosomes. After dietary exposure to 50 ppm photomirex the number of lysosomal elements remained elevated in epithelial cell cytoplasm. Morphological aberrations in the follicles could not be detected after the 5 ppm mirex treatment. The most remarkable alterations in this experiment occurred in the thyroid glands of animals ingesting 50 ppm mirex where columnar follicular cells were engorged with deformed lysosomal bodies. Remaining components of the follicular cell architecture in all the treated groups were unaffected and were similar to those in the control group. These results demonstrated that following a 28-day dietary exposure of rats to photomirex (0.05-50 ppm) or mirex (50 ppm), alterations in the thyroid glands persisted for at least 18 months.

Administration, Oral↗
PubMed1982

Distribution of cytochemically detectable cholesterol in the electric organ of Torpedo marmorata.

A cytochemical probe for cholesterol, the polyene antibiotic filipin, was applied to aldehyde-fixed samples of the electric organ of Torpedo marmorata to identify filipin-binding sites in the various membrane components of the organ and, hence, the probable cholesterol content at these levels. In both thin-sectioned and freeze-fractured samples, filipin-cholesterol complexes appeared numerous and homogeneously distributed on the Schwann cell plasma membrane. On the presynaptic membrane, filipin-cholesterol complexes occurred in patches alternating with unlabeled membrane segments. The postsynaptic, acetylcholine receptor-rich plasma membrane of the electroplax showed no or few filipin-cholesterol complexes in the flat region and upper part of the invaginations (both areas characterized by a lattice of small intramembrane particles); however, the membrane of the bottom part of the postsynaptic invaginations contained several complexes. The ventral, noninnervated plasma membrane of the electroplax showed a moderate, homogeneous filipin labeling. These data suggest that the distribution of cholesterol among membranes of the electroplax is not homogeneous and that the acetylcholine receptor-rich region of the postsynaptic membrane (as characterized by the lattice of small intramembrane particles) may contain little cholesterol.

Animals↗
PubMed1982

An improved method of analysis of observer variation between pathologists.

An improved method of analysing interobserver variation in histopathological studies is described and illustrated, by use of data from a congruence survey of malignant melanoma. The method provides, between any number of pathologists, an assessment of overall agreement and of agreement on each individual category of a classification system. Adjustment for differences in chance agreement due to varying numbers of categories or an altered composition of cases is included in the analysis. A generalization of the procedure designed to measure the strength of associations between different categories is formulated and explained with the use of an example.

Humans↗
PubMed1982

Study of delusions in Kenyan schizophrenic patients diagnosed using a set of research diagnostic criteria.

Eighty 'psychotic' Kenyan patients of African origin were screened using the New Haven Schizophrenic Index (NHSI). Fifty-one of these (64%) were found positive. Delusions were found to be significantly more common (P less than 0.001) in the NHSI positive group than in the negative group. Sex and age had no effect on the distribution of delusions in general but level of education did. These findings are compared and contrasted with findings of similar investigations and some of their implications are discussed.

Adolescent↗
PubMed1982

Chemical and biochemical aspects of superoxide radicals and related species of activated oxygen.

The spectrum of biological processes in which oxygen is used by living systems is quite large, and the products include some damaging species of activated oxygen, particularly the superoxide radical (O-.2) and hydrogen peroxide (H2O2). Superoxide radicals and hydrogen peroxide, in turn, can lead to the formation of other damaging species: hydroxyl radicals (.OH) and singlet oxygen (1O2). Hydroxyl radicals react with organic compounds to give secondary free radicals that, in the presence of oxygen, yield peroxy radicals, peroxides, and hydroperoxides. Formation, interconversion, and reactivity of O-.2 and related activated oxygen species, methods available for their detection, and the basis of their biological toxicity are briefly reviewed.

Animals↗
PubMed1982

Isolation and characterization of glycoproteins in proteoglycan aggregates of calf rib cartilage.

Proteoglycan aggregates were prepared under associative conditions from calf rib cartilage extracts isolated with 4 M guanidine . HCl in the presence of proteinase inhibitors. Five Coomassie blue positive bands including two link proteins could be detected after treatment of proteoglycan aggregates with 2-mercaptoethanol. After dissociating these proteoglycan aggregates with 4 M guanidine . HCl three fractions were obtained by chromatography on Sepharose 2B under the same conditions. A large complex obtained in the excluded volume was partially soluble in the presence of 0.1% sodium dodecyl sulfate, but did not enter 7.5% polyacrylamide gel. It split into seven bands; five of them were not found in proteoglycan aggregates after 2-mercaptoethanol treatment. Neither link proteins nor hyaluronate could be detected in this complex, but chondroitin sulfate was present. Proteoglycan monomers and one included fraction were isolated in addition to this complex. From the included fraction, 8 glycoproteins including 2 link proteins were isolated by preparative polyacrylamide gel electrophoresis and their amino acid and sugar contents determined. These glycoproteins possessed the ability to bind hyaluronate. These results indicate the presence of other glycoproteins besides the two link proteins and a glycoprotein-proteoglycan complex in proteoglycan aggregates of calf rib cartilage.

Animals↗
PubMed1982

Sustained pectin ingestion delays gastric emptying.

The effects of sustained fiber ingestion on gastric emptying glucose tolerance, hormone responses, and jejunal absorption of glucose and lysine were studied in healthy volunteers. Subjects were placed on a low-fiber (3 g) diet for 2 wk, followed by 4 wk of an isocaloric diet supplemented with 20 g/day of either apple pectin (7 subjects) or alpha-cellulose (6 subjects). At the conclusion of each dietary period subjects ingested a low-fiber breakfast surface-labeled with 99mtechnetium sulfur-colloid. Gastric emptying half-time, plasma glucose, calcium, phosphorus, insulin, glucagon, gastrin, human pancreatic polypeptide, and motilin were determined. Gastric emptying half-time was prolonged approximately twofold after pectin supplementation (p less than 0.005) and returned to normal 3 wk after discontinuing pectin supplementation. Cellulose supplementation did not alter the gastric emptying rate. Plasma glucose, calcium, phosphorus, and hormonal responses to the meal were unchanged after either pectin or cellulose supplementation. Pectin ingestion did not impair intestinal absorption of glucose or lysine. In contrast to sustained cellulose ingestion, sustained pectin ingestion slows the gastric emptying rate; the mechanism underlying this adaptive effect is unknown.

Adolescent↗
PubMed1982

Desorption of atropine sulphate and hyoscyamine hydrobromide by various antacids in vitro.

Desorption of atropine sulphate and hyoscyamine hydrobromide by antacids such as magnesium trisilicate, magnesium oxide, aluminium hydroxide an bismuth carbonate was carried out i vitro. This was achieved by preparing a complex of the alkaloids with bromothymolblue and then partitioning th complex between aqueous buffer phase and non-aqueous chloroform phase. The latter was analyzed colorimetrically. The desorption followed the sequence: magnesium trisilicate greater than bismuth carbonate greater than aluminium hydroxide greater than magnesium oxide. The results also show that desorption is dependent on the amount of alkaloid adsorbed and the pH of the medium.

Adsorption↗