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Biomedical subjects

S Mahadevan

Publications and source records attributed to S Mahadevan.

At least 145 records · Page 8Linked to original sources
PubMed1977

Purification and properties of urease from bovine rumen.

Urease (urea amidohydrolase, EC 3.5.1.5) was extracted from the mixed rumen bacterial fraction of bovine rumen contents and purified 60-fold by (NH4)2SO4 precipitation, calcium phosphate-gel adsorption and chromatography on hydroxyapatite. The purified enzyme had maximum activity at pH 8.0. The molecular weight was estimated to be 120000-130000. The Km for urea was 8.3 X 10(-4) M+/-1.7 X 10(-4) M. The maximum velocity was 3.2+/-0.25 mmol of urea hydrolysed/h per mg of protein. The enzyme was stabilized by 50 mM-dithiothreitol. The enzyme was not inhibited by high concentrations of EDTA or phosphate but was inhibited by Mn2+, Mg2+, Ba2+, Hg2+, Cu2+, Zn2+, Cd2+, Ni2+ and Co2+. p-Chloromercuribenzenesulfphonate and N-ethylmaleimide inhibited the enzyme almost completely at 0.1 mM. Hydroxyurea and acetohydroxamate reversibly inhibited the enzyme. Polyacrylamide-gel electrophoresis showed that the mixed rumen bacteria produce ureases which have identical molecular weights and electrophoretic mobility. No multiple forms of urease were detected.

Animals↗
PubMed1976

Protein components in the very low density lipoproteins of hen's egg yolks. Identification of highly aggregating (gelling) and less aggregating (non-gelling) proteins.

Apoproteins of hen's egg yolk very low density lipoprotein has been separated by Sephadex G-200 gel filtration in 0.5% sodium dodecyl sulfate into three categories of proteins termed apoprotein A, apoprotein B and apoprotein C. Apoprotein A fraction consists of several aggregated proteins (linked possibly by -S-S- bridges) as shown by acrylamide gel electrophoresis in the presence of 2-mercaptoethanol. Apoprotein B contains two major protein components, B1 and B2, with molecular weights of 78 000 and 64 000, respectively, and two minor proteins components. Apoprotein C was obtained in a pure form as a low molecular weight, -S-S- linked dimer protein and accounted for about 30% of the total protein. In the monomeric form, apoprotein C has a molecular weight of 9400. Apoprotein A and apoprotein B have similar amino acid composition, except in isoleucine content which is over two times in apoprotein B as compared to apoprotein A. Apoprotein C lacks histidine and is richer in arginine than apoproteins A or B. Apoprotein C has lysine as N-terminal, while apoproteins A and B have predominantly arginine as the N-terminal amino acid. All the three fractions contain carbohydrate residues, apoprotein B being the richest in carbohydrate content. Cold-stored apoproteins A forms a clear gel when dispersed in 0.5% sodium dodecyl sulfate at concentration of above 2 mg/ml, while apoprotein B forms a gel only above 10 mg/ml. Apoprotein C, even at 35 mg/ml, forms a clear solution with no tendency to gel.

Amino Acid Sequence↗
PubMed1976

Effect of cold stress on rapeseed oil fed rats.

No mortality was observed in 6 week old male Sprague-Dawley rats subjected to cold at 4 C for 3 weeks and fed either a control diet (Chow) or a semisynthetic diet containing 20% by wt rapeseed oil high in erucic acid (23.6%). All rats fed the Chow diet and 17 of 20 rats fed the rapeseed oil-containing diet survived 4 weeks in the same environment. Three rats on the latter diet died of self-mutilation. Marked myocardial lipidosis as well as a large acumulation of 20:1 and 22:1 was observed in the hearts of rats fed the rapeseed oil-containing diet. Five of 20 rats on the Chow diet and 2 of 20 rats on the rapeseed oil-containing diet had focal necrotic areas in the myocardium.

Animals↗
PubMed1976

Relationship between erucic acid and myocardial changes in male rats.

The back and belly fat of pigs fed a diet containing 20% by wt rapeseed oil (22% erucic acid) for 16 weeks was rendered into oil. This rendered pig fat, which contained 5.6% erucic acid, was fed to male rats in three separate experiments at 20% by wt of the diet for 16 weeks. In experiment I rendered pig fat was compared only to Brassica campestris var. Span rapeseed oil containing 4.8% erucic acid. In experiments II and III, rendered pig fat was compared to commercial lard containing 0.2% docosenoic acid, commercial lard to which 5.4% free erucic acid was added, and Span rapeseed oil. There was no significant (P less than 0.01) differences observed in the level of erucic acid in the hearts of rats fed diets of rendered pig fat, Span rapeseed oil, or commercial lard plus erucic acid. However, the incidence (P less than 0.001) and severity (P less than 0.01) of cardiac lesions were significantly higher in Span rapeseed oil fed rats compared to rats fed control diets. The number of rats affected or the severity of lesions in the rendered pig fat fed group was not significantly different from controls. The results of this study indicate that the myocardial lesions associated with feeding 20% rapeseed oil diets are not related to the content of erucic acid per se. The possible reasons why rapeseed oil causes cardiac lesions in rats are discussed. It is suggested that a triglyceride imbalance in the oil might play an important role in causing these lesions in rats.

Animals↗
PubMed1976

The development of dermal lesions and alopecia in male rats fed rapeseed oil.

For 8 weeks 10 male weanling Sprague-Dawley rats were fed a semisynthetic diet containing by weight either 20% corn oil or rapeseed oils containing different amounts of erucic acid (Brassica napus var. Zephyr, 0.6%; B. napus var. Oro, 1.8%; B. campestris var. Span, 4.8%; or B. campestris var. Echo and Arlo, i.e., regular rapeseed oil, 23.6%). At 4-5 weeks after the experiment began, rats receiving the diets containing rapeseed oil showed evidence of alopecia and developed scaly, hemorrhagic, and necrotic tails, as well as scaliness of the feet, similar to the lesions described in essential fatty acid (EFA) deficiency. This condition became most severe between 5 and 8 weeks and had disappeared by 14 weeks. Fatty acid analysis of the diets and tissues of the animals did not reveal any evidence of EFA deficiency. It is suggested that these symptoms observed might be related to a possible inhibition of prostaglandin biosynthesis in rats fed rapeseed oils.

Alopecia↗
PubMed1975

Failure of dietary erucic acid to impair oxidative capacity or APT production of rat heart mitochondria isolated under controlled conditions.

1. Male, 8-week old rats were fed Purina Rat Chow for semisynthetic diets containing 20% by weight of rapeseed oil or corn oil for 3 days. 2. The hearts from the animals fed the three diets were analyzed for total lipid, phospholipid, free fatty acids, cholesterol esters, tri-, di- and monoacylglyerols. There was a seven-fold increase in the levels of triacylglycerols in the hearts of rats fed rapeseed oil diet compared to the levels in the hearts of animals fed the other two diets. Smaller increases in the content of other neutral lipid fractions were also observed. 3. Heart mitochondria from the three groups of animals were isolated under controlled conditions in the presence or absence of heparin. The rats of oxidation of different substrates and of ATP synthesis by these mitochondria were compared. 4. Mitochondria isolated in the absence of heparin from rapeseed oil-fed rats had much lower rates of oxidation and ATP synthesis than mitochondria isolated similarly from rats fed the other two diets. 5. With mitochondria freshly isolated in the presence of heparin, no significant differences in rates of oxidation or ATP synthesis were found among the three groups of animals. 6. It is concluded that, when properly isolated, mitochondria from rapeseed oil-fed rats are functionally intact with respect to oxidation and energy-coupling capacity.

Adenosine Triphosphate↗
PubMed1975

Brassica compestris var. Span: I. Fractionation of rapeseed oil by molecular distillation and adsorption chromatography.

Procedures for the large scale isolation of pure triglycerides and fractions rich in nontriglyceride components from Span rapeseed oil are described. Fractionation of Brassica campestris var. Span rapeseed oil by molecular distillation yielded 4 triglyceride fractions, all of which contained traces of sterol esters. An additional triglyceride fraction rich in free and esterified sterols and other volatile components was obtained from the oil. Separation by adsorption chromatography of Span rapeseed oil yielded three fractions; A) a pure triglyceride ffaction; B) a triglyceride fraction rich in sterol esters; and C) another fraction containing free sterols and other polar components.

Chromatography↗
PubMed1975

Brassica campestris var. Span: II. Cardiopathogenicity of fractions isolated from span rapeseed oil when fed to male rats.

Rapeseed oils low in erucic acid caused myocardial lesions when fed to weanling male rats for 16 weeks. The cardiopathogenic properties appear to be associated with the triglycerides of the oil, and not to nontriglyceride components present in fully refined rapeseed oil. Cardiac lipid analysis confirmed that erucic acid accumulation was proportional to the concentration of this acid in the diet.

Animals↗
PubMed1975

Oxidase-peroxidase enzymes of Datura innoxia. Oxidation of formylphenylacetic acid ethyl ester.

An enzyme system from Datura innoxia roots oxidizing formylphenylacetic acid ethyl ester was purified 38-fold by conventional methods such as (NH4)2SO4 fractionation, negative adsorption on alumina Cy gel and chromatography on DEAE-cellulose. The purified enzyme was shown to catalyse the stoicheiometric oxidation of formylphenylacetic acid ethyl ester to benzoylformic acid ethyl ester and formic acid, utilizing molecular O2. Substrate analogues such as phenylacetaldehyde and phenylpyruvate were oxidized at a very low rate, and formylphenylacetonitrile was an inhilating agents, cyanide, thiol compounds and ascorbic acid. This enzyme was identical with an oxidase-peroxidase isoenzyme. Another oxidase-peroxidase isoenzyme which separated on DEAE-chromatography also showed formylphenylacetic acid ethyl ester oxidase activity, albeit to a lesser extent. The properties of the two isoenzymes of the oxidase were compared and shown to differ in their oxidation and peroxidation properties. The oxidation of formylphenylacetic acid ethyl ester was also catalysed by horseradish peroxidase. The Datura isoenzymes exhibited typical haemoprotein spectra. The oxidation of formylphenylacetic acid ethyl ester was different from other peroxidase-catalysed reactions in not being activated by either Mn2+ or monophenols. The oxidation was inhibited by several mono- and poly-phenols and by catalase. A reaction mechanism for the oxidation is proposed.

Formates↗
PubMed1975

Oxidase-peroxidase enzymes of Datura innoxia. Oxidation of reduced nicotinamide-adenine dinucleotide in the presence of formylphenylacetic acid ethyl ester.

The oxidase-peroxidase from Datura innoxia which catalyses the oxidation of formylphenylacetic acid ethyl ester to benzoylformic acid ethyl ester and formic acid was also found to catalyse the oxidation of NADH in the presence of Mn2+ and formylphenylacetic acid ethyl ester. NADH was not oxidized in the absence of formylphenylacetic acid ethyl ester, although formylphenylacetonitrile or phenylacetaldehyde could replace it in the reaction. The reaction appeared to be complex and for every mol of NADH oxidized 3-4 g-atoms of oxygen were utilized, with a concomitant formation of approx. 0.8 mol of H2O2, the latter being identified by the starch-iodide test and decomposition by catalase. Benzoylformic acid ethyl ester was also formed in the reaction, but in a nonlinear fashion, indicating a lag phase. In the absence of Mn2+, NADH oxidation was not only very low, but itself inhibited the formation of benzoylformic acid ethyl ester from formylphenylacetic acid ethyl ester. A reaction mechanism for the oxidation of NADH in the presence of formylphenylacetic acid ethyl ester is proposed.

Catalase↗
PubMed1975

Amino acid biosynthesis in mixed rumen cultures.

Mixed rumen micro-organisms, maintained in continuous culture readily incorporated labelled HCO3- and acetate into amino acids. Labelled propionate, in contrast, was utilized only for isoleucine biosynthesis, but failed to label other amino acids to any significant extent. Evidence was obtained showing that in these mixed, i.e. symbiotic, cultures foward tricarboxylic acid-cycle reactions only proceed to 2-oxoglutarate. 14C distribution in amino acids clearly shows that 2-oxoglutarate is not oxidized further by tricarboxylic acid-cycle enzymes. Instead, acetate is carboxylated to pyruvate which is then carboxylated to oxaloacetate. Oxaloacetate equilibrates with fumarate and thereby carbon atoms 1 and 4 as well as carbon atoms 2 and 3 are randomized. Evidence was also obtained for the carboxylation of propionate to 2-oxobutyrate, isovalerate to 4-methyl-2-oxopentanoate, phenylacetate and hydroxyphentlacetate to the corresponding phenyl- and hydroxyphenyl-pyruvic acids and succinate to 2-oxoglutarate. Of the amino acid precursors investigated, only 3-hydroxypyruvate, the precursor of serine, appeared to be synthesized via an oxidative step, i.e. 3-phosphoglyceric acid to 3-phosphohydroxypyruvic acid. Most 2-oxo precursors of amino acids in these organisms appear to be formed via reductive carboxylation of the precursor acid.

Alanine↗
PubMed1975

Cardiac lesions in rats fed rapeseed oils.

Fully refined rapeseed oils containing different amounts of erucic acid (1.6%, 4.3% and 22.3%) were fed, at 20% by weight of diet, to weanling male and female Sprague-Dawley rats for periods up to 112 days. Transient myocardial lipidosis characterized by accumulation of fat droplets in myocardial fibers was marked in male and female rats fed oxidized and unoxidized rapeseed oil containing 22.3% erucic acid, moderate with rapeseed oil containing 4.3% erucic acid and very slight in rats fed rapeseed oil containing 1.6% erucic acid. Peak intensity of myocardial lipidosis occurred at three to seven days and regressed thereafter. Focal myocardial necrosis and fibrosis occurred in male rats fed rapeseed oils containing different levels of erucic acid for 112 days. The incidence of myocardial necrosis and fibrosis was markedly lower in female rats, and the incidence of these lesions in either sex was not affected by the state of oxidation of these oils. In a second experiment, male rats were fed diets containing crude, partially refined or fully refined rapeseed oils. There was no correlation between the number of foci of myocardial necrosis and fibrosis and the state of refinement of the oils, but there were generally fewer lesions in rats fed those oils having the lowest levels of erucic acid.

Animals↗