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Biomedical subjects

G B Nadkarni

Publications and source records attributed to G B Nadkarni.

At least 19 recordsLinked to original sources
PubMed1985

Possible implications of reciprocity between ethylene and aflatoxin biogenesis in Aspergillus flavus and Aspergillus parasiticus.

Aspergillus flavus and Aspergillus parasiticus produced ethylene during early growth. However, the onset of toxin biosynthesis was marked by the absence of ethylene evolution. 2-Chloroethyl phosphonic acid, an ethylene-generating compound, inhibited aflatoxin biosynthesis in vivo. The reciprocal relationship between the production of aflatoxin and ethylene by the organism may indicate the involvement of the latter in the regulation of aflatoxin biogenesis.

Aflatoxins↗
PubMed1982

Radiation-induced changes in purified prothrombin and thrombin.

The effect of gamma-irradiation on purified prothrombin and thrombin in aqueous solution has been assessed with reference to bifunctional activities, e.g., clotting and esterase functions, physico-chemical changes in structure, and kinetics. The inactivation curves indicated that the clotting activity was more susceptible to gamma-radiation than the esterolytic function in both the proteins. Prothrombin was comparatively more sensitive to radiation than thrombin. The irradiation of prothrombin (100 kR) caused modifications in the protein resulting in reduced formation of thrombin after activation by Factor Xa. The modifications caused by irradiation were assessed in these proteins by changes in spectral characteristics, levels of tryptophan and disulphides, electrophoretic mobility and amino acid composition. Radiation-induced changes in thrombin were reflected in its kinetic behaviour. The clotting activity of thrombin was almost completely lost at 100 kR, while esterolysis was relatively less affected. The modification of tyrosine and tryptophan residues in thrombin influenced the clotting activity, while these were not involved for esterolysis. Histidine had involvement in both these activities.

Amino Acids↗
PubMed1980

Functional multiplicity of phosphoglucose isomerase from Lactobacillus casei.

Phosphoglucose isomerase (D-glucose-6-phosphate ketolisomerase, EC 5.3.1.9), purified from Lactobacillus casei, showed multiplicity with respect to electrophoretic mobility, molecular weight, kinetic properties and responses to erythrose 4-phosphate. Among the three forms isolated, one having a dimeric conformation, was specific for glucose 6-phosphate. Erythrose 4-phosphate inhibited this preparation in a sigmoid fashion, while this compound activated the enzyme for isomerization of ribose 5-phosphate. In tetrameric conformation of the similar subunits, the enzyme was more specific for ribose 5-phosphate and the inhibition exerted by erythrose 4-phosphate was hyperbolic. The possible implications of these observations have been discussed.

Chromatography, Gel↗
PubMed1980

Effect of heavy water (2H2O) on regulatory properties of phosphoglucose isomerase from Lactobacillus casei.

Phosphoglucose isomerase (D-glucose-6-phosphate ketolisomerase, EC 5.3.1.9) purified to homogeneity from Lactobacillus casei was used for studies on 2H2O effects. This preparation showed distinct differences in functional properties in H2O and 2H2O, respectively. Erythrose-4-phosphate which exerted sigmoidal inhibition in H2O, acted as a competitive inhibitor in 2H2O. The enzyme also showed reduced rate of fructose 6-phosphate formation in 2H2O. The enzyme was found to be dimeric in water and monomeric in 2H2O. The loss of regulatory properties of the enzyme has been correlated with disaggregation of the protein in heavy water, similar to that caused by sodium dodecyl sulphate treatment.

Deuterium↗
PubMed1980

Influence of inoculum size of Aspergillus parasiticus spores on aflatoxin production.

The influence of the inoculum size on growth and aflatoxin production was examined in Aspergillus parasiticus (NRRL 3145) by using a synthetic medium. The reduction in the number of spores by 4 to 5 log cycles either by serial dilution or by gamma irradiation caused a two fold increase in the toxin production. The decrease in the inoculum size induced a lag in growth of the culture, though the final yield of the mycelium over the 28-day experimental period was the same. The maximal accumulation of aflatoxin was observed on day 14 of incubation. A transition from the biphasic to monophasic pattern in aflatoxin production could be correlated with the size of the inoculum. The enhanced toxin production from dilute inocula was similar to that obtained with the surviving fraction of the spores after gamma irradiation (0 to 150 krads).

Aflatoxins↗