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Biomedical subjects

S R Gupta

Publications and source records attributed to S R Gupta.

At least 55 records · Page 3Linked to original sources
PubMed1976

Interaction of aflatoxin B1 with some biologically important substances.

The interaction of aflatoxin B1 with a number of biologically important substances has been investigated by spectrophotometric and fluorimetric techniques. The ultra-violet absorption of tryptophan, adenosine, RNA and DNA were altered by the addition of aflatoxin B1. Some amino-acids, purine and pyrimidine derivatives, bovine-serum albumin and DNA quenched the fluorescence of aflatoxin B1. Fluorescence polarization data suggested that the interaction of aflatoxin B1 with bovine-serum albumin was stronger than that with DNA.

Adenosine↗
PubMed1976

Effect of some inhibitors on aflatoxin-production in a synthetic medium and on the incorporation of acetate-1- 14C into aflatoxins by resting mycelia of Aspergillus parasiticus.

The effect of a number of metabolic inhibitors on the incorporation of acetate-1-14C into aflatoxins was investigated, using resting mycelia of Aspergillus parasiticus suspended in phosphate buffer. Malonate, iodoacetate, sodium arsenite, 2:4 dinitrophenol, sodium fluoride and p-aminosalicylate stimulated the incorporation at low concentrations and inhibited the same at high concentrations. p-Nitrobenzoic acid was inhibitory at all the concentrations tried. Fluoride, arsenite, arsenate and iodoacetate inhibited both growth and aflatoxin production when added directly to the growth medium. In general, there was a greater inhibition in growth medium than with the suspended mycelia.

Acetates↗
PubMed1975

Fluorescence changes of aflatoxins B1 and G1.

The effects of various factors, such as pH, buffer, sodiumchloride and ultra-violet radiation on the fluorescence of aflatoxins B1 and G1 have been studied. The fluorescence characteristics of aflatoxins B1 and G1 underwent a marked change at pH values above 7.2. Prolonged exposure to ultra-violet radiation lead to some degradation of aflatoxins and the extent of degradation was dependent upon the nature of the solvent. Sodium chloride partially protected the toxins from degradation by ultra-violet radiation or alkaline conditions.

Aflatoxins↗
PubMed1975

The effect of inorganic salts and some biologically important compounds on the incorporation of 1-14C acetate into aflatoxins by resting mycelia of Aspergillus parasiticus.

Zn++, Mg++, and Mn++ ions at certain concentrations, stimulated the incorporation of [1-14C] acetate-into aflatoxins by resting mycelia of Aspergillus parasiticus suspended in tris-HCl buffer of pH 7.2. Ba++ gave consistant stimulation over a wide range of concentrations. Ethanol markedly inhibited the incorporation. Of the tricarboxylic acid cycle intermediates, citric acid gave the maximum stimulation.

Acetates↗
PubMed1975

Malonate as a precursor in the biosynthesis of aflatoxins.

Incorporation of [I-14C]acetate and [2-14C]malonate into aflatoxins by resting mycelia of Aspergillus parasiticus resuspended in different buffers was studied. A decrease in pH from 5-8 to 2-8, as well as addition of EDTA, markedly stimulated the incorporation of malonate but the effect on acetate incorporation was less pronounced. Mycelia took up comparatively more acetate than malonate, but more malonate (4-3%) entering mycelia was incorporated into aflatoxins than was acetate (1-6%). Furthermore, the addition of unlabelled acetate reduced the incorporation of label from [I-14C]acetate by 75% but from [2-14C]malonate by only 25%. These results suggest that malonate is an intermediate in aflatoxin synthesis and that is can be incorporated without prior conversion to acetate.

Acetates↗
PubMed1975

A comparative study of the effects of aflatoxin B1, alpha-amanitin and actinomycin-D on RNA synthesis by rat liver.

The effect of different combinations of aflatoxin B1, alpha-amanitin and actinomycin-D on the incorporation of orotic acid-6-14C into RNA was investigated using rat liver slices. The results support the view that the mode of action of aflatoxin B1 and alpha-amanitin are similar in some respects, and that aflatoxin B1 and actinomycin-D act according to different mechanisms. Evidence was also obtained about the formation of an active metabolite of aflatoxin B1 in this system.

Aflatoxins↗