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Biomedical subjects

A Singh

Publications and source records attributed to A Singh.

At least 559 records · Page 31Linked to original sources
PubMed1990

Discovery of a novel and alternate hydrogen peroxide generation machinery in the mammalian thyroid gland that modulates iodination of tyrosine.

The hydrogen peroxide-dependent and peroxidase-mediated iodination of tyrosine, a pivotal step in the thyroxine biosynthesis in thyroid glands of mammals, has always been thought to be dependent on a glucose-glucose oxidase system to meet its demand for hydrogen peroxide. This report documents a novel and probably kinetically faster hydrogen peroxide-generating system operating in the thyroid gland cells involving the superoxide dismutase and superoxide anion radical. In the female cycling mice, the superoxide radical and superoxide dismutase activity are shown to be at persistently high levels, quite likely acting as a potent hydrogen peroxide synthesizer in the mammalian thyroid gland. The significance of this discovery in relation to the thyroid physiology is discussed.

Animals↗
PubMed1990

Effect of treatment with 4-hydroxyandrostenedione on the peripheral conversion of androstenedione to estrone and in vitro tumor aromatase activity in postmenopausal women with breast cancer.

The effect of treatment with the aromatase inhibitor, 4-hydroxyandrostenedione (4-OHA) on the peripheral conversion of androstenedione to estrone has been examined in eight postmenopausal women with advanced breast cancer. Before treatment conversion of androstenedione to estrone ([p]AEIBB) ranged from 0.81 to 3.7% and was almost completely inhibited after treatment with 4-OHA (two doses of 500 mg i.m. with an interval of 12 days between doses). Transfer constants were also measured by the urinary method ([p]AEIBU) for some subjects and decreased from 2.3 +/- 0.52% to 0.24 +/- 0.11% after treatment, a mean reduction of 90%. Mean plasma concentration of estradiol (37.4 +/- 16.6 pmol/liter) and estrone (99.0 +/- 32.2 pmol/liter) decreased significantly (P less than 0.01) to 15.7 +/- 4.6 pmol/liter and 52.4 +/- 8.9 pmol/liter, respectively, after treatment. Aromatase and DNA polymerase alpha (a marker of cell proliferation) activities were measured in seven samples of breast tumor tissue obtained before and after treatment. For three samples there was a marked (67 +/- 17%) decrease in tumor aromatase activity after treatment, for two, little change occurred, while tumor aromatase activity in the other two samples appeared to be resistant to the effect of 4-OHA. The correlation between tumor aromatase and DNA polymerase alpha activities (r = 0.45) failed to reach a significant level.

Aged↗
PubMed1990

Biochemical and histopathological changes following dermal exposure to paraphenylene diamine in guinea pigs.

The guinea pigs were dermally exposed to paraphenylene diamine (PPD) at a dose level of 0.1 ml day-1 of a 1.0% (w/v) solution of PPD for 1, 3, 5 and 7 days. The absorption of PPD and its effects on lipid peroxidation, glutathione, histamine and several enzymes were assessed in skin and serum. Histopathological changes in liver, kidney and skin were examined also. The findings of the study indicated that PPD exposure resulted in significantly increased levels of lipid peroxidation and histamine contents in skin. The activity of enzymes increased significantly in skin and serum. PPD exposure also showed degenerative changes in liver and hyperkeratosis together with infiltration of cells in the dermis. Biochemical defects and histopathological changes in skin and serum correlated with the duration of exposure.

Administration, Topical↗
PubMed1990

Conformation and expression of the albumin gene of young and old rats.

The conformation and expression of the albumin gene in the liver of young (21-) and old (85-week) rats were studied. Digestion of nuclei with MNase shows no differences in the nucleosomal organization in the coding region of the gene in the two ages. The gene has a DNase I hypersensitive site which is distinctly less sensitive in old rats. Its 5'-CCGG-3' sequences are more methylated in the old in which its rate of transcription is also lower.

Aging↗
PubMed1990

Production of cellulolytic enzymes by immobilized Sporotrichum thermophile.

Spores of Sporotrichum thermophile were immobilized in agar, polyacrylamide, and sodium alginate to generate in situ mycelium for production of cellulolytic enzymes. Immobilized mycelium was considerably less effective than free cells for cellulase productivity. Of the three gel types, agar beads proved to be the best carrier for the immobilized spores and subsequently generated mycelium. Results of repeated batch experiments suggested that the immobilized mycelia could be reused but at much reduced efficiency.

Acrylic Resins↗
PubMed1990

Dot immunobinding assay in comparison with enzyme-linked immunosorbent assay for the detection of bluetongue virus antibodies in sheep.

A total of 384 sheep serum samples collected from two organised sheep farms was tested by dot immunobinding assay (DIA) and indirect enzyme-linked immunosorbent assay (I-ELISA) for the presence of bluetongue virus (BTV) antibodies. The results of both these assays were compared to find a sensitive, specific, rapid, easily performed and economical test for the diagnosis of bluetongue disease. DIA detected BTV antibodies in 210 samples (54.94%) and I-ELISA detected 157 positive samples (40.88%). Competitive ELISA (C-ELISA) was performed to check the discrepancies in I-ELISA and DIA. On the basis of these tests the overall agreement, relative specificity and sensitivity between ELISA and DIA were 75%, 87.6% and 100%, respectively. DIA was found to be a rapid, sensitive, easily performed and economical test as compared to ELISA.

Animals↗
PubMed1990

Dietary intakes and biochemical markers of selected minerals: comparison of highly trained runners and untrained women.

Mineral status of highly trained (HT) women runners (n = 14) and untrained (UT) women (n = 11), as determined from 3-day dietary records, blood, and urine samples, was compared. HT women had significantly higher energy (HT: 2331 +/- 121 vs UT: 1973 +/- 107 kcal/day; p less than 0.05), magnesium (Mg) (HT: 369 +/- 29 vs UT: 262 +/- 18 mg/day, p less than 0.05), and potassium (K) (HT: 3874 +/- 384 vs UT: 2646 +/- 244 mg/day; p less than 0.05) intakes than UT women. However, mean daily intakes of calcium (Ca), iron (Fe), copper (Cu), and sodium (Na) were not different for the two groups. Plasma concentrations and urinary excretion of Ca, Mg, and Cu of HT and UT women did not differ. Plasma Fe concentrations of the two groups were also similar (HT: 21 +/- 2 vs UT: 22 +/- 1 mumol/L), and, although serum ferritin concentrations of HT women were lower than UT women (HT: 18 +/- 4 vs UT: 30 +/- 6 micrograms/L), the difference was not significant. Urinary Na excretion of the two groups did not differ. HT women had a higher K intake than UT women but urinary K excretion of the two groups did not differ. Whether present mineral intakes by HT women are adequate during periods of intensive training remains to be determined.

Biomarkers↗
PubMed1990

Dietary patterns, gastrointestinal complaints, and nutrition knowledge of recreational triathletes.

Dietary habits, nutrition knowledge, and gastrointestinal complaints were evaluated in 21 female and 50 male triathletes; 30 completed hemoccult slides to determine the frequency of gastrointestinal bleeding. Triathletes trained 11 h/wk with weekly distances of 5.3, 116.5, and 40.9 km for swimming, biking, and running, respectively. Mean daily energy intake averaged 9058 and 11,591 kJ for women and men, respectively; 53.8% of the energy was from carbohydrates. Mean intakes of vitamins and most minerals exceeded the Recommended Dietary Allowances (RDAs), but many had intakes below RDAs for some nutrients; greater than 60% had low zinc and copper intakes. Because 39% took a daily multivitamin-mineral supplement, some had intakes 200-600% above the RDA. Although there were notable misconceptions about nutrition, nutrition knowledge was high. Upper-gastrointestinal complaints, reported by 50%, included bloating and abdominal gas; the incidence of positive hemoccult slides was 27%. The relation among performance, dietary patterns, nutrition knowledge, and gastrointestinal function remains to be established.

Adult↗
PubMed1990

Impaired trapping of Tc-99m pertechnetate in the salivary glands of patients with congenital hypothyroidism.

This paper describes diminished concentration of Tc-99m pertechnetate in the salivary glands of infants with congenital hypothyroidism. The salivary glands' abnormalities were incidentally noted on the neck images acquired for suspected lingual thyroid or athyrosis. None of the 11 infants with congenital hypothyroidism revealed normal Tc-99m pertechnetate trapping in the salivary glands.

Congenital Hypothyroidism↗
PubMed1990

Erythrocyte aggregation: the roles of cell deformability and geometry.

The sedimentation rate of erythrocyte under controlled conditions was used to study the influence of cell deformability and geometry on erythrocyte aggregation. The cell deformability, which is determined by the viscoelastic properties of the membrane, the cell geometry, and the cellular viscosity, was systematically altered. The viscoelasticity of the membrane was gradually decreased with increasing concentrations of glutaraldehyde (0.01-1.0%) or heat treatment at 47.5 degrees C for increasing time intervals (0-80 min), which led to an increase at low concentrations and short incubation and then to a progressive decrease of erythrocyte aggregation. Changes of the osmolality were used to simultaneously alter the cell geometry and cellular viscosity in opposing directions. When the haematocrit level was held constant, the sedimentation rate decreased with increasing osmolality. With a constant erythrocyte number per volume, but changing haematocrit level, the highest sedimentation rate was observed at isotonicity. These results indicate that cell deformability and geometry play an important role in erythrocyte aggregation and sedimentation and may have implications on other cell-cell interactions as well.

Blood Sedimentation↗