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Biomedical subjects

R Sinha

Publications and source records attributed to R Sinha.

At least 163 records · Page 9Linked to original sources
PubMed1989

Retinoic acid treatment of fibroblasts causes a rapid decrease in [3H]inositol uptake.

NIH 3T3 fibroblasts treated with all-trans-retinoic acid (RA) showed a dramatic decrease in the uptake of [3H]inositol compared to solvent-treated controls. The onset of RA-induced inhibition of [3H]inositol uptake was rapid with a 10-15% decrease occurring after 2-3 h of RA exposure and 60-70% reduction after 16 h of RA treatment. A progressive dose-dependent decrease in inositol uptake was found as the concentration of RA increased from 10(-8) to 10(-5) M and the effect was fully reversible within 48 h after RA removal. The Vmax and Kt for the controls were 10 nmol/2.5 x 10(6) cells/2 h and 51 microM; and for RA-treated cells the values were 4 nmol/2.5 x 10(6) cells/2 h and 52 microM. The decreased [3H]inositol uptake was not due to a change in the affinity (Kt) of the transporter for the inositol but to a decrease in the Vmax. The maximal effect on inositol uptake was dependent on RA treatment of the cells after they reached saturation density or if made quiescent by serum starvation. RA was the most active of the different retinoids examined in the order RA greater than 13-cis-RA = retinyl acetate greater than all-trans-retinol greater than 5,6-dihydroxyretinoic acid methyl ester greater than N-4-hydroxyphenyl retinamide. In contrast to this effect on inositol, the uptake of fucose, mannose, galactose, and glucose was either not affected or enhanced (for mannose and fucose) by RA treatment. RA inhibition of inositol uptake was also observed in 3T3-Swiss and Balb/3T3 cells but not in two virally transformed 3T3 cell lines. Phlorizin, amiloride, and monensin inhibited inositol uptake by 66, 74, and 58%, respectively, and this inhibition was additive when the cells were treated with RA as well as these inhibitors. A decreased incorporation of [3H]inositol into polyphosphoinositides was also observed in RA-treated cells but not to the same extent as for [3H]inositol uptake. In conclusion, RA treatment of 3T3 fibroblasts decreases the uptake of [3H]inositol by up to 70% within 8 to 10 h at near physiological concentrations in a reversible and specific manner.

Animals↗
PubMed1989

Responses of thoracolumbar spinal neurons to renal artery occlusion.

Experiments were performed to examine responses of spinal neurons to activation of renal chemoreceptors during renal artery occlusion (RAO). One hundred twenty-two spinal neurons were studied in 33 cats that were anesthetized with alpha-chloralose. Cells studied in the L2-T11 segments were excited by electrical stimulation of the renal nerves and responded to stimulation of somatic structures. RAO (90 s) excited 67 cells (55%). Twenty-eight cells were excited at the onset of occlusion (from 5 +/- 1 to 27 +/- 5 spikes/s) and then either completely or partially adapted (ON responses). Another 39 cells were excited at the onset of occlusion, adapted to varying degrees, and then exhibited a second increase in activity beginning 41 +/- 7 s into the occlusion period [onset-ischemic (ON/IS) responses]. The secondary increase reached a peak of 15 +/- 2 spikes/s 65 s after occlusion. Among the responding cells, ON responses were associated with cells receiving A delta only or with cells with A delta- and C-fiber renal inputs. In contrast, 100% of cells with ON/IS response received both A delta- and C-fiber inputs. Probability of finding responding cells was greatest in the most rostral segments. We conclude that ON responses to RAO are due to activation of mechanoreceptors in the renal artery. ON/IS responses must have resulted from activation of mechanoreceptors followed by activation of renal chemoreceptors in association with development of renal ischemia. These data provide evidence for activation of spinal neurons by RAO. These neurons may be important for renal reflexes of chemoreceptor origin.

Animals↗
PubMed1989

The relationship between neuropsychological and late component evoked potential measures in chronic alcoholics.

The relationships between event-related potential (ERP) measures and neuropsychological measures were investigated in a group of 39 male alcoholics and 22 age-matched male controls. Late component ERP measures such as N1, Nd, and P3 components and neuropsychological measures of perceptual-motor function, semantic and figural memory and verbal abstracting functions were included in a correlational analysis. No significant correlations between N1 amplitude or latency and neuropsychological tests were obtained. However, visual Nd amplitude correlated significantly with perceptual-motor tests and figural memory scores in the alcoholics. Significant correlations were found in alcoholics for visual P3 amplitude at PZ and delayed figural memory scores and two of the perceptual-motor tests. No significant correlations were obtained among the controls. These data indicate that significant relationships exist between some neuropsychological and ERP measures but that these relationships are restricted to measures of perceptual-motor functioning and to delayed figural memory.

Adult↗
PubMed1988

Calcium and vitamin D in bone metabolism: analyses of their effects with a short-term in vivo bone model in rats.

A short-term in vivo system was developed to examine simultaneously bone formation and resorption, and the effects of dietary calcium and vitamin D on these processes. In experiment 1, 25 male Long-Evans rats were each implanted with two gelatin capsules containing mineralized bone (MB) powder subcutaneously in the thorax region. At 4, 6, 8, 10 and 12 d after implantation the acid phosphatase activity (resorption) increased significantly (P less than 0.01), whereas alkaline phosphatase activity (formation) did not change. In experiment 2, both MB and demineralized bone (DB) powder were implanted on contralateral dorsal sites of the thorax in 40 male Long-Evans rats and harvested after 7, 9, 11 and 13 d. Enzyme, mineral and histological assessment indicated bone formation in DB implants with bone resorption in MB implants. In experiment 3, the effects of dietary calcium (0.2 or 1.0%) and vitamin D (cholecalciferol at 300 ng/d or 1,25-dihydroxycholecalciferol [1,25(OH)2D3] at 75 ng/d) were examined using 40 male Long-Evans rats. These rats were implanted with both DB and MB powders and the implants were harvested on d 12. Both low (0.2%) dietary calcium and 1,25(OH)2D3 stimulated resorption of MB implants. Therefore, the physiological processes of bone formation and resorption were mimicked in this system of bone powder implants. Further, dietary calcium and 1,25(OH)2D3 were shown to modulate these processes.

Acid Phosphatase↗
PubMed1988

The effect of dietary calcium on bone metabolism in young and aged female rats using a short-term in vivo model.

The use of high dietary calcium supplementation in the treatment of patients with osteoporosis is controversial. The present study examined the mechanisms underlying the effects of calcium supplementation by investigating the influence of dietary calcium on bone dynamics in young and aged rats. A 2 x 2 x 2 factorial design was utilized with 0.2% (low) or 1.0% (high) calcium, 2- or 24-m-old female Long-Evans rats that were implanted subcutaneously with demineralized (DB) and mineralized (MB) bone powder. The four groups of rats were fed each of the respective diets for 11 wk and then implanted with one #5 gelatin capsule containing 30 mg of DB and another containing 100 mg of MB powder. The animals were injected intraperitoneally with 0.1 microCi/g body weight with 45Ca 14 h before the end of experiment. The ectopic bone as well as the right femurs were harvested 14 d after the rats were implanted. Marker enzyme activities (alkaline-formation and acid-resorption phosphatase), 45Ca uptake and calcium content were measured in the implants and the distal epiphyses of the right femurs. Bone turnover was higher in the young rats than in the old animals, and high dietary calcium in the young animals increased bone formation, as indicated by alkaline phosphatase activity. Dietary calcium level did not affect ectopic bone formation or resorption in the aged rats. The results indicate that high dietary intake of calcium does not affect bone dynamics in aged female rats but does increase bone formation in young rats.

Acid Phosphatase↗
PubMed1988

The effects of repeated withdrawals from alcohol on the memory of male and female alcoholics.

The measure of number of withdrawals, as a separate drinking variable of relevance to cognitive functioning in alcoholics, is a relatively uninvestigated measure. An ethanol withdrawal hypothesis has been suggested that would predict poorer cognitive performance with increased number of withdrawals from alcohol. In this study, the effects of withdrawals (defined as a 24 hr period of abstinence following the consumption of alcohol) on tests of learning and memory were examined. Using 76 male and 67 female alcoholics, results indicate that greater number of withdrawals is related to poorer memory test performance. Results provide support for the ethanol hypothesis of poorer cognitive performance with increasing number of withdrawals, and suggest that females may exhibit accelerated responses to the effects of alcohol misuse.

Adult↗
PubMed1987

A modified anthrone-sulfuric acid method for the determination of fructose in the presence of certain proteins.

Two milliliters of a reagent consisting of anthrone and tryptophan each at a 0.01% concentration in 75% sulfuric acid, when added to 0.9 ml of solution containing D-fructose, produced on heating (55 degrees C, 90 min) a pink color (lambdamax 520 nm) with an absorbance of 0.009 A/nmol. The absorbance is about three times higher than that of the standard anthrone-sulfuric acid reagent. Glucose yields a color only about 1% as intense as that yielded by fructose. The method is useful for the estimation of fructose in the presence of proteins. Synthetic Amadori compounds and glycosylated proteins containing ketoamine-linked fructose, however, were unreactive.

Anthracenes↗