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Biomedical subjects

R Vyas

Publications and source records attributed to R Vyas.

At least 37 records · Page 2Linked to original sources
PubMed1990

A restriction fragment length polymorphism for human topoisomerase II: possible relationship to drug-resistance.

In previous studies we used Southern blotting to examine the topoisomerase II locus (on chromosome 17) in human leukemia cell lines and noted a difference in the XmnI restriction endonuclease digestion pattern between an m-AMSA-resistant line and its m-AMSA-sensitive parent line (Zwelling, L. A.; Hinds, M,; Chan, D.; Mayes, J.; Sie, K. L.; Parker, E.; Silberman, L.; Radcliffe, A.; Beran, M.; Blick, M. Characterization of an amsacrine-resistant line of human leukemia cells. Evidence for a drug-resistant form of topoisomerase II. Journal of Biological Chemistry 264:16411-16420; 1989). We now demonstrate that the variable XmnI digestion pattern represents a normal restriction fragment length polymorphism (RFLP) which is observed in subjects without malignant disease and exhibits an autosomal pattern of inheritance. These data suggest that the previously described deviation in the genomic structure of topoisomerase II in the m-AMSA-resistant cell line did not reflect a new mutation, but rather a reduction to homozygosity at the topoisomerase II locus. This reduction to homozygosity is not due to chromosomal loss, as chromosome 17-specific gene probes clearly identify two chromosome 17's in the sensitive line and four in the resistant line, using chromosome painting with a chromosome 17-specific library. Some other genetic change must be the cause of the resistance of HL-60/AMSA and its topoisomerase II to the inhibiting actions of m-AMSA.

Alleles↗
PubMed1990

Cardiovascular response to dynamic treadmill exercise in patients with essential hypertension before and after therapy with atenolol or captopril.

Thirty eight patients with essential hypertension and 20 healthy volunteers were subjected to treadmill exercise test. The hypertensives were then controlled with atenolol or captopril by randomly forming two groups of 19 patients each, and treadmill evaluation was repeated. The resting rate-pressure product (RPP) and myocardial oxygen consumption (MVO2), as well as peak RPP and MVO2 and recovery time, were increased and exercise duration decreased significantly in uncontrolled hypertensives (p less than 0.001). Control of hypertension resulted in significant improvement of exercise performance in both the groups. Atenolol, when compared to captopril, resulted in better exercise conditioning with considerable lowering of resting and peak RPP and MVO2 (p less than 0.001), though the difference in exercise duration, maximum work load and recovery time were not significant (p greater than 0.05). Thus, where myocardial oxygen consumption is an important consideration while treating hypertension, atenolol offers a better choice.

Adult↗
PubMed1984

1-Acetyl-3-acetoxy-5'5-diphenylhydantoin has colchicine-like activity.

1-Acetyl-3-acetoxy-5'5-diphenylhydantoin (Ac-DPH) is a synthetic derivative of diphenylhydantoin with unusual properties: 1) it inhibits microtubular polymerization and depolymerizes established microtubules; 2) it blocks colchicine binding and displaces colchicine from microtubular protein, although it bears no resemblance to colchicine; and 3) it does not arrest human lymphocytes in metaphase, in contrast to diphenylhydantoin or its metabolite, 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH).

Animals↗
PubMed1978

Morphologic effect of hydantoin drugs on mitosis and microtubules of cultured human lymphocytes.

A new class of mitotic inhibitors is described. Diphenylhydantoin and 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH), its metabolite, increase the mitotic index of cultured human lymphocytes without affecting the second resting phase (G2). Mitotic inhibition by these compounds is time dependent, and not a property of hydantoins in general. HPPH proved to be more potent than diphenylhydantoin. Electron micrographs of HPPH-treated human lymphocytes showed changes in 45% of the cells in metaphase: a decrease in microtubules or the appearance of 100 A microfilaments. These changes resemble those induced by colchicine.

Cells, Cultured↗
PubMed1975

The effect of parahydroxylation of diphenylhydantoin on metaphase accumulation.

DPH has a colchicine-like action on metaphase arrest of cultured human lymphocytes. The first step in detoxification of DPH increased its power to accumulate metaphases 3-fold. This hydroxy derivative [5-[4-hydroxyphenyl]-5-phenylhydantoin, HPPH] 3.6 X 10(-4) M was equivalent colchicine 1 x 10(-5) M in its power to inhibit metaphase completion. The effect of HPPH on mitosis was reversible; colchicine effect was not reversed and vincristine effect was partially reversed by washing drug from the medium. Hydroxylation of DPH did not change its inhibition of DNA synthesis and enhanced inhibition of protein synthesis to a minor degree. Detoxification increased the colchicine-like action of DPH.

Cells, Cultured↗
PubMedDate not supplied

Green's function solution to the tissue bioheat equation.

A Green's function solution to the tissue bioheat equation including blood flow in cylindrical geometry is obtained. Numerical results for temperature variation in the bovine muscle are reported when the tissue is exposed to neodymium-yttrium-aluminum garnett (Nd:YAG) lasers with Gaussian profile and a comparison with recent measurements is made. A strong dependence of the tissue temperature on the beam radius and pulse time is found.

Animals↗