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Biomedical subjects

M T Subbiah

Publications and source records attributed to M T Subbiah.

At least 91 records · Page 5Linked to original sources
PubMed1981

Regional aortic differences in atherosclerosis-susceptibility: changes in prostaglandin biosynthesis and cholesterol accumulation in response to desoxycorticosterone (DOCA)-salt induced hypertension.

In spontaneously atherosclerosis-susceptible White Carneau pigeons, intimal cushions that appear at birth near the coeliac branch of aorta do not progress into atherosclerotic lesions. However, the area across from the intimal cushion (so called 'lesion area') a) accumulates cholesteryl esters b) synthesizes more PGE2 and c) eventually develops into complicated atherosclerotic plaques. When DOCA-salt hypertension is induced in the pigeons, the 'initimal cushion' area displays a) accumulation of increasing amounts of cholesteryl esters and b) increase in the synthesis of all prostaglandins (particularly PGE2) from C14-arachidonic acid and c) approaches similarity to the 'lesion area' in the magnitude of these changes. These results suggest that under the influence of a risk factor, the 'intimal cushion' can acquire biochemical properties of the atherogenic areas of the aorta.

Animals↗
PubMed1981

Regional aortic differences in atherosclerosis susceptibility. Relationship to lipid concentration and prostaglandin biosynthesis.

In spontaneously atherosclerosis-susceptible White Carneau pigeons intimal cushions are noted consistently at the coeliac branch of aorta at birth. While these cushions do not progress into atherosclerotic lesions, the area across from the cushion (so called "lesion area") develop a classic atherosclerotic plaque by three years of age. In order to explain this regional aortic susceptibility to atherosclerosis, cholesterol and cholesteryl ester concentrations and prostaglandin biosynthesis in the two aortic regions were examined. It was found that the concentration of free and esterified cholesterol was higher in the intimal cushion area. Examination of the formation of various prostaglandins from C14-arachidonic acid indicates a striking increase in PGE2 synthesis in the lesion area with no difference in the formation of 6-keto PGF1 alpha (stable product of PGI2). These studies suggest that one of the earliest changes noted in the "lesion area" that differs from the intimal cushion is the enhanced formation of PGE2.

Animals↗
PubMed1981

Persistent enhancement of bile acid synthesis in guinea pigs following stimulation of cholesterol catabolism in neonatal life.

Cholesterol catabolism to bile acids was stimulated in neonatal guinea pigs by feeding 1.11% cholestyramine (CT)-containing diet for 8 weeks. The animals were then switched to standard laboratory diet for an additional 4 weeks. At the end of the laboratory diet period: a) CT-pre-treated guinea pigs continued to excrete significantly higher (p less than 0.05) amounts of bile acids, b) the activity of hepatic 7 alpha-hydroxylase was significantly elevated (p less than 0.01) in CT-pre-treated animals, and c) isolated hepatocytes from CT-pre-treated guinea pigs secreted significantly higher (p less than 0.05) amounts of bile acid when compared to controls during a 4-hour incubation. These data provide biochemical support for our contention that stimulation of cholesterol catabolism during neonatal life can have effects that persist into adult life.

Animals↗
PubMed1981

Effect of feeding a low protein diet during neonatal life on subsequent cholesterol and bile acid metabolism in adult guinea pigs.

The effect of feeding a low-protein (LP) diet during neonatal life of guinea pigs on subsequent cholesterol and bile acid metabolism when the animals were being fed a) stock diet and b) 0.25% cholesterol-containing diet, was investigated. Feeding a 10% protein diet caused a significant (P less than 0.05) increase in the fecal excretion of neutral sterols and bile acids without any change in plasma cholesterol. The LP-fed guinea pigs continued to excrete significantly (P less than 0.05) greater amount of neutral sterols and bile acids level after they had been switched to stock diet for several weeks. The pool sizes of lithocholic and chenodeoxycholic acids were lower in the LP group during the stock diet period. Upon challenge with 0.25% cholesterol diet, no significant differences between the two groups, regarding the above-mentioned parameters, were noted. The data suggest that neonatal exposure to a low-protein diet can affect sterol and bile acid metabolism such that the effect persists even when the animals have been switched to stock diet for several weeks.

Aging↗
PubMed1981

Decreased bile acid pool neonates of guinea pigs fed cholesterol during pregnancy.

Feeding 0.25% cholesterol-containing chow to guinea pigs during pregnancy resulted in a) significantly higher plasma cholesterol in the neonates, b) a striking decrease in the total bile acid pool of the neonates, with a significant reduction in the pool of chenodeoxycholic acid, and c) and increase in the proportion of bile acids associated with the neonatal liver. These results suggest that feeding cholesterol to guinea pigs during pregnancy has undesirable effects in the neonate in terms of the development of cholesterol degradation mechanisms.

Animals↗
PubMed1981

Estrogen administration early in life and the development of atherosclerosis.

Effect of high doses of estrogen administration early in life on aortic atherosclerosis and cholesteryl ester metabolism was investigated in female atherosclerosis-susceptible (White Carneau) pigeons. Long-term estrogen (in doses of 0.25 mg/kg/day) administration significantly increased the severity of aortic atherosclerosis. Following short-term administration of estrogens, the concentration of aortic cholesterol was significantly higher in estrogen-treated pigeons with a marked increase in cholesteryl esters. Determination of activities of enzymes concerned with cholesteryl ester metabolism in aorta indicated an increase in cholesteryl ester synthetase, while no difference was noted in the three cholesteryl ester hydrolases located in various subcellular fractions of aorta. These results suggest that the increase in aortic cholesterol content following estrogen treatment may be partly responsible for the noted increase in atherosclerosis following long-term administration of estrogens to female pigeons.

Animals↗
PubMed1980

Studies of aggregation and thromboxane B2 synthesis in avian thrombocytes: comparison between atherosclerosis-susceptible and resistant breeds.

Comparison of thrombocyte aggregation in response to arachidonic acid and synthesis of prostaglandins from C14-arachidonic acid by thrombocytes was made between atherosclerosis-susceptible White Carneau and atherosclerosis-resistant Show Racer Pigeons. Contrary to the expectations, thrombocytes from atherosclerosis-susceptible pigeons were a) less sensitive to arachidonic acid induced aggregation and b) synthesized less thromboxane B2 (stable product of proaggregatory thromboxane A2) from C14-arachidonic acid. Analysis of fatty acid composition of thrombocyte phospholipids indicated a higher concentration of arachidonic acid in White Carneau Pigeons. These results suggest that thrombocytes from atherosclerosis-susceptible pigeons are altered early and as a defense mechanism display less responsiveness towards aggregation.

Animals↗
PubMed1980

Incorporation of 14C-mevalonate into biliary cholesterol and bile acids by perfused rat liver: effect of plasma and individual lipoproteins.

Effect of plasma and individual lipoproteins on the incorporation of 14C-mevalonate into biliary bile acids and cholesterol by perfused rat liver was investigated. Use of plasma free perfusate (instead of whole blood) gave similar rates of incorporation of 14C-mevalonate into biliary bile acids, but showed a decrease in percent distribution in cholic acid and a increase in beta-muricholic acid. Addition of VLDL (isolated from Zucker rats) into the plasma free perfusate caused a significant increase in the incorporation of the label into bile acids, but LDL and HDL had no effect. HDL caused an increase in biliary excretion of 14C-cholesterol.

Animals↗
PubMed1980

Bile acids in the fetal rat: effect of maternal bile duct ligation.

The effect of bile duct ligation during pregnancy in rats (thereby increasing maternal plasma bile acids levels) on the bile acid content and composition in the fetus was examined. In spite of 30-fold increase in maternal plasma cholic acid, the bile acid content in the fetus of bile duct ligated rats was significantly lower (p less than 0.05) with a significant reduction in cholic acid content. Plasma cholesterol levels of fetuses from bile duct ligated rats were also significantly lower (p less than 0.05). In addition to the commonly expected bile acids, gas-liquid chromatographic analysis of the fetal bile acid pool showed peaks corresponding to several secondary bile acids. These results suggest that the transfer of primary bile acids of maternal origin into the fetus is minimal.

Animals↗
PubMed1980

Effect of sucrose polyester on fecal bile acid excretion and composition in normal men.

The effects of sucrose polyester (SPE) (a nonabsorbable mixture of hex-a, hepta,- and octa-fatty acid esters of sucrose with physical properties similar to those of common dietary fats) on fecal bile acid excretion and composition were assessed in 24 healthy, nonobese, normolipemic male volunteers, in a 40-day, inpatient, metabolic balance study. Isocaloric diets provided either 800, 300, or less than 50 mg of cholesterol/day (P/S ratios respectively 0.4, 1.0, and 1.5). After diet-only perids of 10 days (for the 800 and 300 mg cholesterol regimens), and 21 days (for the 50 mg diet), the diets were continued for 30 days, with addition of SPE to diets over three successive treatment periods of 10 days each, with 8, 16, and 35 g of liquid SPE/day, or 15, 30, and 50 g SPE/day in a SPE-hydrogenated palm oil mix. On both the liquid SPE and SPE-hydrogenated palm oil mix, there were no significant changes in fecal bile acid excretion as a function of dietary SPE, at any level of cholesterol intake, P > 0.1. In most subjects SPE changed fecal bile acid composition; lithocholic acid was decreased, and in most instances this was accompanied by the appearance and increase in chenodeoxycholic acid. In one subject, both deoxycholic and 3 beta, 12 alpha-dihydroxycholanic acid were reduced, with an accompanying increase in cholic acid. The hypocholesterolemic effect of SPE appears to be mediated through its reduction of intestinal absorption of cholesterol, not through effects on bile acid excretion.

Adult↗
PubMed1980

Enhancement of thrombocyte aggregation and thromboxane B2 synthesis by diethylstilbestrol.

Effect of diethylstilbestrol administration on thrombocyte aggregation and thromboxane B2 synthesis was investigated in atherosclerosis-susceptible pigeons. Platelet aggregatory response to arachidonic acid and synthesis of thromboxane B2 from 14C-arachidonic acid was enhanced in thrombocytes derived from diethylstilbestrol-treated pigeons. Platelet total phospholipid concentration was increased in pigeons with diethylstilbestrol treatment. Enhanced thromboxane synthesis might be responsible for increased platelet aggregation, which in turn might contribute to the severe atherosclerosis noted following diethylstilbestrol treatment in several avian species.

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