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Biomedical subjects

R Prasad

Publications and source records attributed to R Prasad.

At least 271 records · Page 15Linked to original sources
PubMed1987

Status of calcium influx in cell cycle of S. cerevisiae.

The transport of calcium was assayed in exponentially growing and G1 arrested temperature sensitive cdc mutants of Saccharomyces cerevisiae. There was no statistically significant difference in the rate of Ca2+ influx in cdc 28, cdc 37 and cdc 4 arrested cells, as well as in wild type cells arrested in G1 phase in comparison to exponentially growing cells. There was however a significant increase in Ca2+ uptake in cdc 7 and cdc 24 arrested cells. The former is known to arrest before bud emergence and initiation of DNA synthesis; arrest of the latter affects bud formation while DNA synthesis continues. The results suggest that Ca2+ may have a role in bud formation and growth.

Biological Transport↗
PubMed1987

Relevance of cation-exchange capacity of cell wall in detecting H+-symport in yeasts.

Addition of mono- or divalent cations to unbuffered yeast suspensions causes acidification of the medium. In some yeasts (Rhodotorula glutinis and Metschnikowia reukaufii) this represented a mediated H+ extrusion in exchange for cations (mostly K+). However, in some other yeasts (Pichia humboldtii and Candida albicans) the pH change was very rapid. The rapid acidification of the media by Pichia humboldtii was found to be due to high cation-exchange capacity of its cell wall. This cation-exchange was saturable, exhibited high affinity for divalent cations and was stoichiometric under appropriate experimental conditions. Results suggest that such cation exchange capacity of some yeasts could hamper the measurements related to H+-symport mechanisms.

Cell Wall↗
PubMed1986

Tetraphenylphosphonium is an indicator of negative membrane potential in Candida albicans.

The characteristics of the uptake of lipophilic cations tetraphenylphosphonium (TPP+) into Candida albicans have been investigated to establish whether TPP+ can be used as a membrane potential probe for this yeast. A membrane potential (delta psi, negative inside) across the plasma membrane of C. albicans was indicated by the intracellular accumulation of TPP+. The steady-state distribution of TPP+ was reached within 60 min and varied according to the expected changes of delta psi. Agents known to depolarize membrane potential caused a rapid and complete efflux of accumulated TPP+. The initial influx of TPP+ was linear over a wide range of TPP+ concentrations (2.5-600 microM), indicating a non mediated uptake. Thus, TPP+ is a suitable delta psi probe for this yeast.

Biological Transport↗
PubMed1986

Transport of basic amino acids in Candida albicans.

In Candida albicans, ATCC 46977, transport of basic amino acids is mediated by two systems (S1 and S2). Kinetic data and competitive inhibition studies of the different systems showed that transport of L-lysine, L-arginine and L-histidine have distinct specificities. System S1 of L-lysine and L-arginine was highly specific for the respective single basic amino acid. However, S2 of L-lysine and S1 of L-histidine were shown to be specific systems for most of basic amino acids. S2 of L-arginine was different from S2 of L-lysine and S1 of L-histidine. The effect of a thiol reagent, N-ethylmalemide, revealed that S2 of L-lysine and S1 of L-histidine were sensitive to this reagent, while all other systems were insensitive. The transport activity of different systems of L-lysine, L-arginine and L-histidine was followed during the growth of C. albicans. It was observed that different basic amino-acid systems have maximum activity during different stages of C. albicans growth.

Amino Acids↗
PubMed1986

Survival rates and prehospital delay during myocardial infarction among black persons.

Over a 12-month period, a consecutive series of 111 black patients admitted to a municipal hospital in Chicago was studied. The 2-week mortality rate for the entire group was 19% (95% confidence intervals, 11.7 to 26.3), and the rate was twice as high for women as for men. A history of systemic hypertension was encountered in 75% of the patients, and diabetes mellitus was present in 33%, although they were not significant predictors of mortality within this group. The delay time from onset of symptoms to arrival at the hospital was markedly prolonged compared with studies of predominantly white populations--twice as long at the median and 3 times as long at the mean. Preventive campaigns aimed at this population should include educating patients on the symptoms of coronary artery disease and encouraging them to seek prompt medical care. Attention must also be given to eliminating obstacles to access to care in this group.

Adult↗
PubMed1986

The effects of level of difficulty of mental arithmetic challenge on heart rate and oxygen consumption.

Heart rate plus various metabolic and ventilatory indices were monitored while 18 young males engaged in a mental arithmetic task, structured to include 3 levels of difficulty; easy, difficult and impossible. Measurements were also taken while subjects undertook graded isotonic exercise on a bicycle ergometer; for each subject heart rate was plotted against oxygen consumption over the various exercise loads. Knowing oxygen consumption during the psychological tasks, these regression equations permitted the calculation of expected heart rates during each task condition and thus the computation of 'additional heart rate' as the difference between actual and predicted heart rate values. Additional heart rate was sensitive to variations in difficulty level; the difficult condition elicited reliably more additional heart rate than the easy and impossible conditions. Subjects' performance as well as their perceptions closely reflected the a priori classification of difficulty. Although subjects rated the easy condition as particularly unengaging, the impossible condition attracted relatively high rates of task involvement. It was argued that self-reports of this sort are probably more susceptible than cardiac activity to social demand characteristics.

Adolescent↗
PubMed1986

Spontaneous subhyaloid and retinal haemorrhages in an infant.

A 6 week old girl from a socially isolated family presented with seizures and was found to have a full fontanelle, retinal and subhyaloid haemorrhages, and anaemia. These findings were not the result of a shaking injury but of a ruptured intracerebral arterial aneurysm.

Cerebral Hemorrhage↗
PubMed1986

Metabolism of 3H-proline in riboflavin deficiency.

Riboflavin deficiency and food restriction were associated with greater solubility and lesser total and insoluble collagen concentration in rat skin. Studies using 3H-proline suggest that the lower collagen concentration under these conditions could be due to a decrease in synthesis as well as slow maturation of collagen. The mechanisms underlying defective cross-link formation appear to be different in food-restricted and riboflavin-deficient rats. Half-life of soluble collagen was not affected in riboflavin deficiency, but it was slightly shorter in food-restricted weight-matched animals.

Animals↗
PubMed1986

Purification and characterization of extracellular caseinolytic enzyme of Micrococcus sp. MCC-315 isolated from cheddar cheese.

Micrococcus sp. MCC-315, an organism isolated from Cheddar cheese, produced an extracellular calcium metalloenzyme. This protease was purified to homogeneity from culture supernatant by precipitation with ammonium sulfate (50 to 70% saturation) and gel filtration through Sephadex G-100, resulting in about 82 times increase of specific activity and 53% recovery of the enzyme. The protease exhibited a pH optimum at 10.6 for both whole casein and beta-casein. It had optimum activity for whole casein in the presence and absence of calcium++ at 60 and 50 degrees C, respectively, and at 37 to 40 degrees C for beta-casein with or without calcium++. The enzyme was stable at 45 degrees C but lost activity at higher temperatures. It was inhibited by heavy metal ions but calcium++, cobalt++, manganese++, strontium++, and iron++ had a slight stimulatory effect. The enzyme was inhibited completely and irreversibly by metal chelating agents. Calcium ions were required for maintenance of an active conformation of the enzyme. The enzyme had molecular weight of 28,900 and Michaelis constants 6.66 and 5.00 mg/ml for whole casein and beta-casein. Amino acid analysis of the hydrolyzed enzyme revealed the absence of sulfhydryl groups as was indicated also by lack of inhibition by thiol reagents.

Caseins↗
PubMed1986

Transdermal nitroglycerin patches in angina pectoris. Dose titration, duration of effect, and rapid tolerance.

The duration of effect of transdermal nitroglycerin patches was studied in 14 patients with angina pectoris. By titrating the dose to achieve specific circulatory effects, we chose a patch size that produced a consistent fall in systolic blood pressure of 10 mm Hg or greater for each patient (10 cm2 in 7 patients, 20 cm2 in 5, and 40 cm2 in 2; releasing 5, 10, and 20 mg of nitroglycerin per 24 hours, respectively). The effects of these individualized patches were compared with those of placebo patches. Compared with placebo, nitroglycerin patches increased exercise duration to the onset of angina (257 +/- 72 compared with 383 +/- 130 seconds, p less than 0.0001) and total exercise time (338 +/- 89 compared with 456 +/- 119 seconds, p less than 0.0001) and decreased ST segment depression (1.0 +/- 0.5 compared with 0.6 +/- 0.4 mm, p less than 0.05) at 4 hours but not at 24 and 48 hours. We conclude that nitroglycerin patches do not show objective evidence of antianginal or antiischemic effects for 24 hours. Tolerance to the circulatory and antianginal effects probably develops within 24 hours of patch application.

Administration, Topical↗
PubMed1986

Effect of short-term cyclosporine A administration on urinary acidification.

This study was designed to investigate the short-term effect of cyclosporine A (CyA) at a dose of 25 mg/kg body weight, on urinary acidification and renal potassium handling. Rats treated with CyA for 8 days developed metabolic acidosis (Blood pH 7.34 +/- 0.01, Blood HCO3 20 +/- 0.9 mEq/l) while those treated for 3 days did not (Blood pH 7.39 +/- 0.01, HCO3 24 +/- 1.0 mEq/l). Fractional HCO3 excretion was low in both groups indicating that bicarbonate reabsorption in the proximal nephron was unimpaired. Distal hydrogen ion secretion evaluated by the ability to increase urinary pCO2 in a highly alkaline urine was impaired in both groups (urinary pCO2 61 +/- 2.3 mmHg and 50 +/- 2.5 mmHg in rats treated with CyA for 3 and 8 days, respectively as compared to controls 72 +/- 3.0 mmHg, p less than 0.01). Under basal conditions, renal potassium excretion was lower in CyA treated rats than in controls. This was observed in association with a decrease in GFR in rats treated with CyA for 8 days (GFR 1.3 +/- 0.3 ml/min) but not in those treated for 3 days (GFR 2.2 +/- 0.4 ml/min). Rats treated with CyA for 3 days were able to increase potassium excretion normally in response to both sodium sulfate infusion and to an acute potassium infusion. In rats treated with CyA for 8 days, acute potassium loading failed to elicit an increase in fractional potassium excretion (from 32 +/- 5.3 to 28 +/- 2.3%) despite an increase in plasma K (from 3.0 +/- 0.2 to 8.4 +/- 0.3 mEq/l) and urine flow (from 11 to 36 mu ml/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonium Chloride↗