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Biomedical subjects

R Prasad

Publications and source records attributed to R Prasad.

At least 307 records · Page 17Linked to original sources
PubMed1984

Molecular basis of cadmium toxicity.

Cadmium has been shown to manifest its toxicity in human and animals by mainly accumulating in almost all of the organs and kidney is the main target organ where it is concentrated mainly in cortex. Environmental exposure of cadmium occurs via food, occupational industries, terrestrial and aquatic ecosystem. At molecular level, cadmium interferes with the utilization of essential metals e.g. Ca, Zn, Se, Cr and Fe and deficiencies of these essential metals including protein and vitamins, exaggerate cadmium toxicity, due to its increased absorption through the gut and greater retention in different organs as metallothionein (Cd-Mt). Cadmium transport, across the intestinal and renal brush border membrane vesicles, is carrier mediated and it competes with zinc and calcium. It has been postulated that cadmium shares the same transport system. Cadmium inhibits protein synthesis, carbohydrate metabolism and drug metabolizing enzymes in liver of animals. Chronic environmental exposure of cadmium produces hypertension in experimental animals. Functional changes accompanying cadmium nephropathy include low molecular weight proteinuria which is of tubular origin associated with excess excretion of proteins such as beta 2 microglobulin, metallothionein and high molecular weight proteinuria of glomerular origin (excretion of proteins such as albumin IgG, transferrin etc.). Recent data has shown that metallothionein is more nephrotoxic to animals. Cadmium is also toxic to central nervous system. It causes an alterations of cellular functions in lungs. Cadmium affects both humoral and cell mediated immune response in animals. Cadmium induces metallothionein in liver and kidney but under certain nutritional deficiencies like protein-calorie malnutrition and calcium deficiency, enhanced induction and greater accumulation of cadmium metallothionein has been observed.

Aging↗
PubMed1983

Effect of phosphatidylserine enrichment on amino acid transport in yeast.

A 1.5- to 3.5-fold accumulation of phosphatidylserine was observed when Candida albicans and Saccharomyces cerevisiae cells were grown in the presence of hydroxylamine, a known inhibitor of phosphatidylserine decarboxylase. However, as compared to S. cerevisiae cells, the levels of phosphatidylcholine and phosphatidylethanolamine were much lower in C. albicans cells. The enrichment of phosphatidylserine selectively affected the transport of several amino acids.

Amino Acids↗
PubMed1983

The possible functional significance of phosphatidylinositol in G1 arrest of Saccharomyces cerevisiae.

Individual phospholipids were assayed in exponentially growing and G1-arrested temperature-sensitive cell division cycle (cdc) mutants of Saccharomyces cerevisiae. It was observed that cdc28 cells which are known to arrest at 'start' when shifted to their non-permissive temperature, resulted in a 40% decrease in phosphatidylinositol (PI) level while the phosphatidylserine (PS) content was doubled in these cells. The reduced level of PI was restored in cdc4 and cdc7 mutants which are known to arrest past the 'start'. The increase in PS level in cdc28 mutant which was probably to compensate the intrinsic charging of membrane environment, was also reduced in cdc4 and cdc7 mutants. Our results demonstrate that PI may play a role in yeast cell division and growth and that the abnormalities of cdc28 could also be related to PI decrease.

Cell Division↗
PubMed1983

Combined effect of temperature and nutrients on protein turnover in Bacillus megaterium.

Protein turnover was followed in populations of Bacillus megaterium growing in temperature range of 17-48 degrees C in different media. Higher temperature stimulated the protein turnover (expressed as the amount of protein degraded during 3.3 h) in all the media tested up to the optimal growth temperature (40-42 degrees C). Protein turnover in a medium containing amino acids continued to be stimulated by temperature even above this point; no further significant increase of turnover was found in the other media.

Amino Acids↗
PubMed1983

Impaired collagen maturity in vitamins B2 and B6 deficiency--probable molecular basis of skin lesions.

Solubility of collagen was increased and the proportion of insoluble collagen was reduced in the skin of both riboflavin as well as pyridoxine-deficient rats. Collagen content of the skin, and aldehyde concentration of salt-soluble collagen were also lower in the deficient groups. The alpha:beta subunit ratio of salt-soluble collagen was higher in riboflavin deficiency. In food-restricted weight-matched control groups, similar changes in collagen solubility, but of lesser magnitude were observed. Both food restriction and riboflavin deficiency decreased plasma PLP concentration. Increase in the solubility of collagen, decrease in the aldehyde content of soluble collagen and increase in the alpha:beta subunit ratio of soluble collagen, suggest that the maturation of collagen may be affected in pyridoxine or riboflavin deficiency. These molecular events may be etiologically related to the pathogenesis of the skin lesions in vitamin B2 or B6 deficiency.

Animals↗
PubMed1983

Immunoglobulin levels in serum and cerebrospinal fluid in certain viral infections of the central nervous system.

It is seriously debated whether the presence of immunoglobulins in CSF is due to local production, diffusion of proteins through the blood-brain barrier, or both. Tourtellotte et al [1] strongly suggest that in both healthy and diseased individuals, immunoglobulins are synthesized extravascularly and subsequently diffuse into the CSF. Cohen and Bannister [2] demonstrated that lymphocytes from the CSF of patients with multiple sclerosis could produce IgA and IgG in vitro. Although such evidence suggests the likelihood of local production of immunoglobulins, others believe that elevated protein levels in CSF are due to migration of immunoglobulins from serum to CSF because of damage to the blood-brain barrier [3]. Thus, the elevated IgG level in CSF could be an expression of such an impaired blood-brain barrier. A further implication of this hypothesis is that the more the function of this barrier is impaired, the more extensive is the transudation. This includes the migration of large molecules such as IgM during the inflammatory state, a condition which increases not only the number of theoretical filters but also the size of the pores. IgG levels in CSF and serum were elevated in all five infections studied except viral encephalitis, in which this value remained normal. The serum IgA level was elevated in all five lesions, but the IgA level in CSF was elevated only in viral encephalitis, Guillain-Barré syndrome, and meningeal carcinomatosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Central Nervous System Diseases↗
PubMed1983

Effect of piperacillin on tobramycin pharmacokinetics in patients with normal renal function.

Aminoglycosides are inactivated by extended-spectrum penicillins in vitro and in patients with end-stage renal failure. In this prospective controlled study, we determined the effect of piperacillin on tobramycin pharmacokinetics. In 10 clinically stable male patients with calculated creatinine clearances of greater than or equal to 60 ml/min, serial levels in serum of tobramycin alone and after single 4-g intravenous doses of piperacillin were determined. No statistically significant changes in the concentration of drug in serum, the half-life (t1/2), the elimination rate constant (Ke), the volume of distribution (Vd), or the area under the serum concentration-time curve (AUC0-oo) occurred when tobramycin was used concurrently with piperacillin. Therefore, this antibiotic combination will not result in a clinically significant interaction in patients with normal renal function.

Adult↗
PubMed1983

Why choline supplementation did not enhance phosphatidylcholine level in Candida albicans.

In contrast to Saccharomyces cerevisiae cells, the supplementation of the growth media of Candida albicans cells with choline did not result in PC enrichment. The level of accumulation of choline uptake, which is the first step of its utilisation was found to be 50% higher in S. cerevisiae cells. However, the activity of choline kinase (EC 2.7.1.32), the first enzyme in CDP-choline pathway was identical between the two cell types. It appears that CTP: phosphocholine cytidylyl-transferase (EC 2.7.7.15) may be the regulatory enzymatic step in overall PC biosynthesis of C. albicans cells.

Biological Transport, Active↗
PubMed1983

Transport of purine, pyrimidine bases and nucleosides in Candida albicans, a pathogenic yeast.

Saturable, carrier mediated transport mechanism of adenine, guanine, thymine, uracil, adenosine, inosine, thymidine and uridine has been characterized in Candida albicans cells. Analysis of intracellular contents at short and long time intervals and kinetic data revealed that the uptake of all these bases and their nucleosides is independent of phosphoribosyltransferases and phosphorylases and their metabolic conversion starts only after an initial lag of 1-2 minutes. On the basis of competition experiments, different common and specific transport systems have also been identified.

Binding, Competitive↗
PubMed1983

Amino acid transport: its role in cell division and growth of Saccharomyces cerevisiae cells.

The transport of six amino acids was studied in exponentially growing and G1 arrested temperature sensitive mutants of the yeast Saccharomyces cerevisiae. The uptake of three amino acids viz. Gly, Ala and Val was selectively reduced in G1 arrested cells. The reduction in transport was only noticeable when cdc 28 mutant cells were arrested at their non-permissive temperature. Cdc 28 is known to arrest at the point of commitment to the cell cycle 'start'. The uptake, however, was unaffected in G1 arrested cdc 4 and cdc 7 cells. The wild type cells (A364A) when arrested at stationary phase, also demonstrated the reduction in the uptake of Ala and Val. It appears that amino acid transport may be involved in growth and cell division of Saccharomyces cerevisiae.

Amino Acids↗
PubMed1983

Absence of derepression of amino acids transport in Candida.

The transport of glycine, L-alanine, L-proline, L-leucine, L-lysine, L-phenylalanine and L-glutamic acid did not enhance in various strains of Candida cells, when they were grown in proline containing medium or preincubated with proline. However, under similar conditions, a significant enhancement in the level of accumulation of amino acids (derepression) was observed in Saccharomyces cerevisiae X-2180-A2 (GAP+) cells, which was sensitive to ammonium ions (NH4+). As expected, the derepression was absent in GAP- cells of S. cerevisiae X-2180 (GAP- mutant). In contrast to S. cerevisiae (GAP+) cells, the increase in few amino acids uptake in different Candida strains, grown in proline or preincubated in proline, could not be inhibited by cycloheximide, NH4+ or their D-stereoisomers. It appears that derepression of amino acids transport, a well known phenomenon in S. cerevisiae, may not exist in Candida species.

Amino Acids↗