Biomedical subjects

T Ramasarma

Publications and source records attributed to T Ramasarma.

At least 163 records · Page 9Linked to original sources

PubMed1970

Effect of alpha-p-chlorophenoxyisobutyrate on the metabolism of isoprenoid compounds in the rat.

1. Feeding of alpha-p-chlorophenoxyisobutyrate (CPIB) to rats increased ubiquinone concentration in the liver but not in other tissues. The increase was progressive with the time of feeding and related to the concentration of CPIB in the diet. 2. Incorporation of [1-(14)C]acetate, but not of [2-(14)C]mevalonate, into sterols in the liver in vivo or by liver slices in vitro was decreased on feeding the rats with CPIB. However, incorporation of mevalonate into ubiquinone increased. 3. CPIB, when added in low concentrations to liver slices, had no effect on isoprene synthesis from acetate; higher concentrations, however, were inhibitory. 4. No activation of ubiquinone synthesis from mevalonate was observed when CPIB was added to the liver slices synthesizing ubiquinone. 5. The increase in ubiquinone in CPIB-fed animals appears to be due to increased synthesis in the initial stages and to decreased catabolism in the later stages. 6. An inverse relationship was found between the concentration of ubiquinone in the liver and the serum sterol concentration in CPIB-fed rats.

Acetates↗

PubMed1970

Increase of hepatic mitochondria on administration of ethyl alpha-p-chlorophenoxyisobutyrate to the rat.

1. The antihypercholesterolaemic drug ethyl alpha-p-chlorophenoxyisobutyrate when fed to the rat orally or mixed with the diet increased the content of mitochondria in the liver by 50-100%. Other subcellular fractions did not show any significant change. 2. In oxidative activity, respiratory control and phosphorylating ability no significant difference was observed between the mitochondria isolated from the livers of the drug-treated rats and those from normal animals. 3. In agreement with earlier reports, administration of the drug depressed the concentration of serum cholesterol and increased liver weight and the liver content of ubiquinone. However, the increase of ubiquinone was greater in the nuclear than in the mitochondrial protein.

Animals↗

PubMed1970

Effect of administration of alpha-p-chlorophenoxyisobutyrate on hepatic mitochondria and ubiquinone during cold exposure.

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Adaptation, Physiological↗

PubMed1969

The cryptic nature of hepatic microsomal sulphite oxidase.

1. The activity of rat liver microsomal sulphite oxidase (EC 1.8.3.1) was increased several-fold on aging of microsomes, on delipidation by extraction with acetone or on solubilization with deoxycholate, suggesting its existence in a cryptic state. 2. In rat liver most of the sulphite oxidase was present in the nuclear fraction and only a small portion in the microsomes. 3. Microsomal sulphite oxidase activity was low in the developing embryo and increased rapidly after birth.

Acetone↗

PubMed1969

Metabolism of ubiquinone in relation to thyroxine status.

1. Under conditions of thyrotoxicosis induced by feeding rats with iodinated casein, ubiquinone concentration was found to increase in the liver by increased synthesis and by partly decreased catabolism leading to its accumulation. The increased ubiquinone was found primarily in the mitochondrial and supernatant fractions. 2. Supplementing the diet with thyroxine, at less than toxic doses, also increased the synthesis and the concentration of ubiquinone in the liver. 3. In the condition of hypothyroidism obtained by feeding rats with thiouracil the concentration and the synthesis of ubiquinone in the liver showed a small decrease. 4. Synthesis of ubiquinone in liver slices was partially inhibited by addition of thyroxine in vitro. Therefore the activation effect on ubiquinone synthesis of excess of thyroxine in the intact animals appears to be by an indirect mechanism.

Animals↗

PubMed1969

Activation of liver succinate dehydrogenase in rats exposed to hypobaric conditions.

1. On brief exposure of rats to hypobaric conditions, the activity of hepatic mitochondrial succinate dehydrogenase was raised from the basal state to a ;partially activated state'. This was further raised to ;fully activated state' by preincubation of mitochondria with succinate, as was the activity in mitochondria from normal rats. 2. On washing mitochondria with the homogenizing sucrose medium the activity excess obtained on preincubation with succinate was lost in mitochondria from both normal and treated rats. 3. The enzyme in the ;partially activated state' from animals exposed to hypobaric conditions was stable to the washing procedure but was labilized and reverted to a low basal state of activity on freezing and thawing of the isolated mitochondria. 4. The results suggest that activation of succinate dehydrogenase under hypobaric conditions represents a conformational change leading to a stable, partially activated, form of the enzyme system: this is the first evidence of physiological modulation of this rate-limiting step in the control of the rate of oxidation of succinate.

Animals↗

PubMed1968