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Biomedical subjects

M Ramanadham

Publications and source records attributed to M Ramanadham.

28 records · Page 2Linked to original sources
PubMed1982

Mechanism for signaling initiation and termination of B lymphocyte proliferation induced by anti-immunoglobulin.

Several lines of evidence were explored which taken together indicate that both the initiation and the termination signal for activation of rabbit lymphocytes to synthesize DNA in response to anti-rabbit immunoglobulin occurs at an immunoglobulin receptor on the surface membrane of B cells. Thus, the premature removal of anti-rabbit immunoglobulin by simply washing the cells at the 31st hour of a 48-h incubation period caused a 60% decrease in the induction of DNA synthesis. The addition of rabbit immunoglobulin to compete with B cell surface immunoglobulin for the combining sites on anti-rabbit immunoglobulin yielded a markedly diminished activation. Addition of rabbit immunoglobulin even during the latter part of a pulse label period with [3H]-thymidine was sufficient to result in reduced activation. Finally, insoluble anti-rabbit immunoglobulin at the same nominal concentration as soluble anti-rabbit immunoglobulin also was effective in inducing cells to DNA synthesis. However, it is noteworthy that under the incubation conditions used it was not possible to derive a soluble component from insoluble anti-rabbit immunoglobulin which stimulated DNA synthesis. These data have been interpreted to indicate a need for a continuous surface presence of anti-rabbit immunoglobulin to stimulate activation in a process that is not dependent upon internalization of anti-rabbit immunoglobulin.

Animals↗
PubMed1979

Response of oxidative phosphorylation in liver of protein-energy malnourished rats.

State 3, state 4 respiratory rates, respiratory control ratio (RCR = state 3/state 4), ADP/O ratio and swelling in salt medium were determined in liver mitochondria from three groups of rats: group 1--controls; group 2--energy-restricted, and group 3--protein-deficient. Experiments were carried out between 3 and 5 weeks and between 7 and 9 weeks after initiation of the experimental diets. State 3 respiration of mitochondria from group 2 rats was reduced after 3-5 weeks on the experimental diet as compared to group 1 rats. However, state 4 respiration, RCR and ADP/O ratio were not different in groups 2 and 3 as compared to those in controls. Between 7 and 9 weeks it was found that state 3 respiration with both the substrates was higher in groups 2 and 3 as compared to group 1. State 4 respiration was increased in group 2 but was unaltered in group 3, compared to controls. Mitochondrial preparations from group 2 rats showed faster rates of swelling in KC1 medium, compared to group 1, at both periods. On the other hand, the rates of swelling were slower as compared to controls in the case of mitochondria isolated from group 3 rats. Results of these experiments indicate that the terminal effect of severe restriction of calories and protein on mitochondrial oxidative phosphorylation is similar.

Animals↗
PubMed1978

High erythrocyte membrane (Na+ + K+)-ATPase in kwashiorkor, in vivo reversal by diuretic.

Specific activity (mumol Pi released/h/mg membrane protein) of ouabain-sensitive (Na+ + K+)-ATPase has been shown to be higher in erythrocytes from children suffering from kwashiorkor, compared to that in normal children. Twenty four hours after treatment of these children with a diuretic, there was reduction in their body weights due to loss of oedema fluid. Ouabain sensitive (Na+ + K+)-ATPase of the erythrocyte membrane was inhibited by about 40% and this was associated with gain of 1.8 mequivalents Na+ per litre of erythrocytes. The results suggest that high ouabain-sensitive (Na+ + K+)-ATPase could be one of the mechanisms operative in erythrocytes to prevent accumulation of Na+ in kwashiorkor.

Adenosine Triphosphatases↗
PubMed1978

Rat liver mitochondrial cytochrome c oxidase and cytochromes in experimental protein-energy malnutrition.

Cytochrome c oxidase activity and cytochromes b, (c+c1) and a(+a3) concentrations were determined in liver mitochondria from rats fed the following diets: controls (group 1) fed ad libitum, energy-restricted (group 2) and protein-deficient (group 3). The animals were fed for two time intervals, 3--5 and 7--9 weeks. At 3--5 weeks, the cytochrome oxidase specific activity (nmol cytochrome c oxidized/mg protein/min) and cytochrome concentrations (nmol/mg protein) were not different in groups 2 and 3 as compared to group 1. At 7--9 weeks, the cytochrome oxidase specific activity and concentrations of cytochromes b, (c+c1) and a(+a3) were significantly reduced in group 2 rats as compared to well-fed controls. The Michaelis-Menten constant, Km apparent for ferrocytochrome c, was significantly higher in group 2 as compared to group 1. In group 3 rats, cytochrome oxidase specific activity and cytochrome b, a(+a3) concentrations were not different from group 1 at 7-9 weeks. However, cytochrome (c+c1) concentration was higher in group 3, resulting in an elevated ratio of cytochrome (c+c1) to cytochrome a(+a3) as compared to groups 1 and 2.

Animals↗
PubMedDate not supplied

Reduced cAMP levels and glycogen phosphorylase activation in isoproterenol perfused SHR myocardium.

The effect of isoproterenol perfusion on cAMP levels and phosphorylase activity was investigated in the spontaneously hypertensive rat (SHR) and Kyoto Wistar normotensive control rat (WKY) heart. The basal force of contraction in physiological salt solution perfused hearts was comparable between SHR and WKY. However, the force of contraction in response to 10 nM isoproterenol perfusion was decreased approximately 20-30% in SHR heart as compared to WKY heart. Basal cAMP levels were reduced in SHR hearts as compared to WKY hearts. Isoproterenol perfusion resulted in an increase in cAMP levels over the basal cAMP values which was 50% and 100% in SHR and WKY hearts, respectively. Basal phosphorylase activity was higher in SHR hearts as compared to WKY hearts. However, the percentage increase in phosphorylase activity by isoproterenol perfusion over the basal values was approximately 400% in WKY hearts and only 200% in SHR hearts. The ouabain-sensitive (Na+, K+)-ATPase activity, Ca2+ binding in the absence of ATP, sialic acid content, and 5'-nucleotidase activity of purified cardiac plasma membranes was not altered in SHR as compared to WKY. These results would suggest beta-adrenergic mediated adenylate cyclase stimulation is decreased in SHR myocardium while other plasma membrane properties and associated enzymes may not be altered.

Animals↗