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Biomedical subjects

P Datta

Publications and source records attributed to P Datta.

At least 109 records · Page 6Linked to original sources
PubMed1983

Aetiological studies on hospital in-patients with acute diarrhoea in Calcutta.

Bacterial enteropathogens and rotavirus were sought in 356 cases with acute diarrhoea admitted to the Infectious Diseases Hospital, Calcutta. One or more pathogens were isolated from 74.7% of the cases. Single enteropathogens could be detected from 66% and multiple enteropathogens from 8.7% of the patients. Vibrio cholerae biotype El Tor, rotavirus, V. parahaemolyticus, and enteropathogenic and enterotoxigenic Escherichia coli were the major pathogens detected. Rotavirus was detected from 7.6% of the cases. A higher rate of detection of rotavirus was seen in children younger than two years. Campylobacter jejuni could be isolated from the faeces of six (15%) of 40 cases either as a single pathogen or in association with V. cholerae biotype El Tor.

Acute Disease↗
PubMed1983

Synthesis of biodegradative threonine dehydratase in Escherichia coli: role of amino acids, electron acceptors, and certain intermediary metabolites.

The specific activity of inducible biodegradative threonine dehydratase (EC 4.2.1.16) in Escherichia coli K-12 increased significantly when the standard tryptone-yeast extract medium or a synthetic mixture of 18 L-amino acids was supplemented with 10 mM KNO3 or 50 mM fumarate and with 4 mM cyclic AMP. In absolute terms, almost four times as much enzyme was produced in the amino acid medium as in the tryptone-yeast extract medium. Enzyme induction in the amino acid medium was sensitive to catabolite repression by glucose, gluconate, glycerol, and pyruvate. An analysis of amino acid requirements for enzyme induction showed that a combination of only four amino acids, threonine, serine, valine, and isoleucine, produced high levels of threonine dehydratase provided that both fumarate and cyclic AMP were present. Immunochemical data revealed that the enzyme synthesized in the presence of these four amino acids was indistinguishable from that produced in the tryptone-yeast extract or the medium with 18 amino acids. We interpret these results to mean that not the amino acids themselves but some metabolites derived anaerobically in reactions involving an electron acceptor may function as putative regulatory molecule(s) in the anaerobic induction of this enzyme.

Amino Acids↗
PubMed1982

Altered expression of biodegradative threonine dehydratase in Escherichia coli mutants.

A number of strains of Escherichia coli K-12 failed to synthesize significant amounts of biodegradative threonine dehydratase (EC 4.2.1.16) when grown anaerobically in tryptone-yeast extract medium, a condition which is optimal for the induction of this enzyme. However, the addition of 10 mM potassium nitrate to the culture medium enabled a few of these strains, notably MB201, to induce the enzyme. An examination of the kinetic parameters, modifier sensitivity, and immunological cross-reactivity revealed that the enzyme produced by MB201 in nitrate-supplemented medium appeared indistinguishable from the dehydratase of a wild-type strain. The reduced expression of threonine dehydratase in MB201 appeared highly specific; the synthesis of two other inducible enzymes, D-serine deaminase and tryptophanase, and two "anaerobic" proteins, namely, fumarate reductase and cytochrome c551, remained unaffected. The mutation (tdcI) responsible for the altered expression of the dehydratase in MB201 was located at min 91 on the E. coli chromosome and appeared to tightly linked to if not identical with pgi, the gene encoding phosphoglucose isomerase, as judged by growth experiments on glucose and fructose, direct assay of phosphoglucose isomerase activity, spontaneous and simultaneous reversion of MB201 (tdcI) to TdcI+ and Pgi+ phenotype, and cosegregation of the two loci during transduction with P1 phage. Because not all strains lacking the dehydratase showed nitrate-dependent enzyme synthesis or had lesions at the pgi locus, it appears that mutations at multiple loci on the E. coli chromosome may influence the expression of the enzyme in vivo.

Adenosine Monophosphate↗
PubMed1981

Effect of environmental cooling on certain biochemical responses in broilers.

Investigations were undertaken to study the effect of different thermal environments of growth attributes of broilers. One hundred fifty-day old chicks of both sexes were kept each in control, foggers, exhaust fan and cooler groups during hot and dry, and hot and humid periods to assess the effect of cooling on growth efficiency of broilers in terms of blood cholesterol and ascorbic acid. The average cholesterol content (mg/100 ml) of blood plasma was highest in the control groups of both the periods. The birds of the control and exhaust groups were more stressed as compared to birds in fogger and cooler groups where the cholesterol content was least. The average values for the ascorbic acid content of blood plasma (mg/100 ml) were highest in the cooler groups of both the periods showing the greater resistance of these birds against the thermal stress. The increased amounts of ascorbic acid in the cooler groups were positively correlated to the heavier body weights of the birds in this particular group. In contrast, the birds in the control and exhaust groups had minimum amounts of ascorbic acid content at all ages irrespective of sexes. Therefore, from the above results of cholesterol content and ascorbic acid concentration, it is concluded that hot and humid period at Ludhiana is the most stressful and evaporative cooling is the most efficient method for alleviating summer stress in broilers.

Animals↗
PubMed1979

The role of glyoxylate in the regulation of biodegradative threonine dehydratase of Escherichia coli.

The activity of biodegradative threonine dehydratase of Escherichia coli K12 was reversibly inhibited by glyoxylate in the presence of AMP. Kinetic analysis showed that the inhibition was mixed with respect to L-threonine and competitive in terms of AMP; the inhibitory effect of glyoxylate was less pronounced at high protein concentrations. Incubation of dehydratase with L-threonine shifted the absorption maximum of the enzyme-bound pyridoxal phosphate from 413 to 425 nm; addition of glyoxylate completely prevented the threonine-mediated spectral shift. In addition to the inhibitory effect, incubation of purified enzyme with glyoxylate resulted in a progressive, irreversible inactivation of the enzyme and formation of inactive protein aggregates. The rates of inactivation were decreased with increasing concentrations of protein and AMP. During inactivation by glyoxylate, the 413-nm absorption maximum of the native enzyme was replaced by a new peak at 385 nm. Experiments with [14C]glyoxylate showed a rapid binding of 1 mol of glyoxylate per 147,000 g followed by a slow binding of 3 additional mol of glyoxylate; the glyoxylate-protein linkage was stable to acid precipitation and protein denaturants. Competition binding experiments revealed that pyruvate (which also inactivated the E. coli enzyme, Feldman, D.A., and Datta, P. (1975) Biochemistry 14, 1760-1767) did not interfere with the binding of glyoxylate or vice versa, suggesting that the two keto acids may occupy separate sites on the enzyme molecule. Nevertheless, experiments on enzyme inactivation using glyoxylate plus pyruvate reveal mutual interactions between these ligands in terms of lack of additive effect, retardation in the spectral shift due to glyoxylate, and stabilization of the enzyme in the presence and absence of AMP. We conclude from these results that the control of biodegradative threonine dehydratase is governed by a complex set of regulatory events resulting from reversible and irreversible association of these effectors with the enzyme molecule.

Adenosine Monophosphate↗
PubMed1978

Biodegradative threonine dehydratase. Reduction of ferricyanide by an intermediate of the enzyme-catalyzed reaction.

The threonine-dependent reduction of ferricyanide catalyzed by the purified biodegradative threonine dehydratase of Escherichia coli has been studied. The rate of production of 2-oxobutyrate in the presence of ferricyanide was lower than that found in the absence of ferricyanide. The concentrations of threonine required for half-maximal effects for the reduction of ferricyanide and, in the presence of the dye, for 2-oxobutyrate production, were 3 mM and 9mM, respectively. Reduction of ferricyanide was accompanied by evolution of CO2, and even within a very short incubation time with the enzyme, the ratio of ferricyanide reduced over CO2 evolved was approximately 7. Stopping the enzyme activity after a brief exposure to threonine at pH 9.7 resulted in the accumulation of an intermediate (with a half-life of 4 min at 25 degrees C) which formed an adduct with N-ethylmaleimide; the accumulated intermediate, in the absence of N-ethylmaleimide, reduced ferricyanide with concomitant evolution of CO2. We conclude from these results that 2-aminocrotonate is the intermediate which serves as a source of reducing equivalent for ferricyanide, and nonstoichiometric amount of ferricyanide reduction may be attributed to some secondary reactions of ferricyanide with compounds derived from the oxidation product of 2-aminocrotonate.

Escherichia coli↗