Search PubMed⌕ Search

Biomedical subjects

S K Gupta

Publications and source records attributed to S K Gupta.

At least 883 records · Page 49Linked to original sources
PubMed1977

Clinical significance of completely subdivided maxillary antrum.

A rare case of a completely subdivided maxillary antrum is reported. The lower compartment was a closed cavity in which infection resulted in the persistence of an oroantral fistula. Healing occurred only after the septum was broken and proper intranasal drainage by antrostomy was established.

Adult↗
PubMed1977

Effect of Zinc on tricarboxylic acid cycle intermediates and enzymes in relation to aflatoxin biosynthesis.

The stimulatory action of zinc on aflatoxin production by Aspergillus parasiticus NRRL3240 has been investigated by studying the levels of tricarboxylic acid (TCA) cycle intermediates and related enzymes in the fungal mycelium. During the stationary phase of growth, the levels of alpha-keto acids declined in zinc-sufficient cultures compared with those in zinc-dificient cultures. TCA cycle enzymes did not show any significant changes due to zinc availability. In zinc-deficient cultures, enzymes of the TCA cycle had maximum activity on the fourth day, after which their activity declined. In zinc-sufficient cultures, some enzymes showed maximum activity on the fourth day, others on the second day.

Aflatoxins↗
PubMed1977

Regulation of aflatoxin biosynthesis. 1 Comparative study of mycelial composition and glycolysis in aflatoxigen and nonaflatoxigenic strains.

A comparative biochemical study of an aflatoxigenic strain Aspergillus parasiticus NRRL 3240 and a nonaflatoxigenic strain A. flavus NRRL 3237 was carried out in order to have a better idea of regulation of aflatoxin biosynthesis. The results obtained revealed continuous primary metabolic activity (protein synthesis) in the nonaflatoxigenic strain while the aflatoxigenic stain showed inhibition of protein and nucleic acid synthesis. The aflatoxigenic strain showed higher levels of oxygen uptake, RNA, NAD, FMN and activities of glycolytic enzymes. Furthermore, it had lower of lipids and reduced activity of glucose-6-phosphate dehydrogenase, which is a source for NADPH. The differences observed have been discussed in relation to aflatoxin biosynthesis and its regulation.

Aflatoxins↗
PubMed1977

Biosynthesis of aflatoxins.

The role of zinc on the primary metabolism of Aspergillus parasiticus in relation to aflatoxin biosynthesis was studied. Zinc deficiency impaired growth and metabolism of nucleic acid and protein while stimulating that of lipid. The activities of enzymes of glycolytic cycle were affected indicating that these are zinc dependent enzymes. Impaired glycolytic cycle tends to reduce the level of primary metabolites like pyruvate, citrate and oxaloacetate which trigger aflatoxin formation. During stationary phase these precursors accumulate as these are not used up for the synthesis of secondary metabolites (aflatoxins) due to zinc deficiency. ATP and energy-charge (E.C.) which are important for various physiological processes like growth are reduced in zinc deficiency. Also zinc deficiency results in low levels of AMP which favour synthesis of lipid. Inorganic phosphate accumulated due to zinc deficiency and this may be unfavourable for aflatoxin synthesis.

Adenine Nucleotides↗
PubMed1977

Regulation of aflatoxin biosynthesis. III. Comparative study of adenine nucleotide pool in aflatoxigenic and non-aflatoxigenic strains.

The adenine nucleotide pools were studied in toxigenic (NRRL 3240) and non-toxigenic (NRRL 3537) strains of Aspergillus flavus group in relation to aflatoxin biosynthesis. The levels of ADP and AMP were comparatively low in the non-toxigenic strain throughout the growth period. In the toxigenic strain the levels of ADP and AMP increased significantly during the stationary phase. The ATP content of the toxigencic strain had higher ATP levels during the stationary phase compared to the toxigenic strain. The inorganic phosphate levels of the non-aflatoxigenic strain were higher when compared with the aflatoxigenic strain. High levels of inorganic phosphate have been reported to be inhibitory for secondary biosynthesis including aflatoxins. The energy charge values of the non-toxigenic strain, compared to the toxigenic strain, were lower during exponential phase but higher during stationary phase. The observed changes have been correlated with aflatoxin biosynthesis.

Adenine Nucleotides↗
PubMed1977

Regulation of aflatoxin biosynthesis. 2 Comparative study of tricarboxylic acid cycle in aflatoxigenic and non-aflatoxigenic strains of Aspergillus flavus.

The presence of a functional TCA cycle and its intermediates has been shown in Aspergillus parasiticus and Aspergillus flavus. The role of the TCA cycle in aflatoxin biosynthesis has been studied. In A. parasiticus the TCA cycle was activated on the second day of growth (exponential growth phase) resulting in the onset of aflatoxin biosynthesis. Pyruvate accumulation to toxic levels in A. parasiticus is suggested to shift the growth phase from exponential to stationary with the onset of aflatoxin biosynthesis. In A. flavus, a non-aflatoxigenic strain, no pyruvate accumulation was observed. Moreover, the onset of aflatoxin production in A. parasiticus was followed by a decline in the levels of TCA cycle intermediates indicating their possible utilization in secondary metabolite synthesis. Accumulation of TCA cycle intermediates in A. flavus is suggested to be due to non-diversion to aflatoxin biosynthesis.

Aflatoxins↗
PubMed1976

Phosphoglycerate kinase from young and old Turbatrix aceti.

Phosphoglycerate kinase (ATP:3-phospho-D-glycerate-1-phosphotransferase, EC 2.7.2.3) from young and old Turbatrix aceti has been purified to homogeneity. The "old" enzyme exhibits a marked reduction in specific activity both in crude homogenates and in pure form when compared to preparations from young nematodes. The specific activities for pure "young" and "old" enzymes are 650-750 and 300-400 units/mg, respectively. All other properties of "young" and "old" enzymes were nearly identical, including molecular weight (43 000), Km, behavior on columns, thermal stability and mobility during gel electrophoresis at three pH values. The results are discussed in terms of the possible mechanism of formation of "altered" enzymes. In addition, certain properteis of the nematode phosphoglycerate kinase are compared with those of the enzyme from yeast and rabbit muscle.

Aging↗