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Biomedical subjects

B Radhakrishnamurthy

Publications and source records attributed to B Radhakrishnamurthy.

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

Plasma glucose level related to blood pressure in 272 children, ages 7-15 years, sampled from a total biracial population.

Since a positive association between blood pressure and plasma glucose level in child populations has been observed previously, we studied this relationship in a stratified random sample of children ages 7-15 years drawn from a total geographic population. We stratified this population (N = 3524) by diastolic blood pressure and weighted the extreme strata. The sample of children (N = 272) was free of secondary hypertensives and was tested by a restricted glucose tolerance test. As a parameter of cellular glucose kinetics, a "peripheral insulin resistance" was defined as one-hour glucose (mg/dl) X one-hour insulin (microU/ml). For white boys, this product showed an increase from 2745 in the low blood pressure strata to 6615 in the high blood pressure strata. To assess the relationship between blood pressure measured during the reexamination and fasting plasma glucose level, we classified the children according to their peripheral insulin resistance in a low, medium, and high group. After controlling for body weight, only white children in the high blood pressure strata with high insulin resistance had a positive association between fasting plasma glucose and systolic blood pressure. The relationship may be initiated by inappropriate intravascular water retention influencing the blood pressure in children with high peripheral insulin resistance and susceptible to hypertension.

Adolescent↗
PubMed1981

Chemical changes in the arterial wall during regression of atherosclerosis in monkeys.

Changes of arterial wall lipid and connective tissue components were studied under various regression regimes on experimental high fat-cholesterol diet induced atherosclerosis in non-human primates. Levels of plasma lipids and aorta tissue lipids were closely related, while an inverse relationship between plasma cholesterol levels was noted with the ratio of aorta tissue free/ester cholesterol. Although the total content of glycosaminoglycan increased slightly with increasing disease, changes of individual glycosaminoglycans were most closely related to the severity of aorta atherosclerosis associated with both induction and regression of disease. With increasing atherosclerosis hyaluronic acid tended to decrease, while chondroitin sulfates decreased. Heparan sulfate decreased considerably with increasing severity of atherosclerosis. Consequently, regression regimens reducing the severity reversed the glycosominoglycan changes. Withdrawal of the dietary stimulus and cholestryamine produced the greatest reversal of atherosclerosis. In contrast, D-thyroxine treatment resulted in severe aorta atherosclerosis comparable to controls receiving no treatment. The effectiveness of regression depends on favorably altering plasma lipids but without adversely affecting the arterial wall structural elements.

Animals↗
PubMed1980

Isolation and characterization of proteoglycans from bovine lung.

Proteoglycans were extracted from bovine lung gas exchange tissue, pleura, and bronchioles with 4.0 M guanidinium chloride at 5 degrees C in the presence of protease inhibitors. Preliminary purification of the proteoglycans was achieved by an initial CsCl isopycnic centrifugation (rho 0 = 1.33) and through precipitation with cetylpyridinium chloride in 0.5 M KCl. Further purification and fractionation of proteoglycans was achieved by a second CsCl isopycnic centrifugation (rho 0 = 1.45) in 4.0 M guanidinium chloride. Based on the ultracentrifuge profiles and electrophoretic behavior, the major fractions were pooled. They were purified further by gel filtration on Sepharose CL-2B and characterized by extensive analyses. A heparan sulfate proteoglycan was the major proteoglycan identified in the gas exchange tissue and in the pleura. The major proteoglycan component from the bronchioles was a chondroitin sulfate proteoglycan. Approximate molecular weight of 2 x 10(6) for the heparan sulfate proteoglycan from the pleura and chondroitin sulfate proteoglycan from the bronchioles and 1 x 10(6) for the heparan sulfate proteoglycan from the gas exchange tissue were estimated from gel filtration analyses. After incubation with hyaluronic acid, the chondroitin sulfate proteoglycans from the bronchioles showed an increase in specific viscosity and a higher molecular weight compound eluting near the void volume in Sepharose CL-2B column chromatography. The proteoglycans exhibited varied anticoagulant activities in Stypven, partial thromboplastin and thrombin clotting times and inhibited thrombin-induced platelet aggregation.

Amino Acids↗
PubMed1980

Determination of mulecular-weight distribution of aorta glycosaminoglycans by automated gel filtration.

This report describes an automated gel filtration procedure for estimation of molecular weights of glycosaminoglycans using Technicon sugar analyzer. A Sepharose CL-6B column was used for filtration. The method has been applied to determining the distribution of molecular weights of glycosaminoglycans from human aorta. The glycosaminoglycans were fractionated on a Dowex 1 (Cl-) column prior to gel filtration. On gel filtration, hyaluronic acid resolved into two components with estimated molecular weights of 38,000 and 8000. A molecular weight of 22,000 was estimated for heparan sulfate. Chondroitin 6-sulfate and dermatan sulfate eluted from the column in one peak, suggesting these two glycosaminoglycans have a similar molecular weight, 18,000. The procedure was found suitable for studying the gel filtration behavior of proteoglycans from bovine aorta and lung.

Animals↗
PubMed1980

Lipid changes in atherosclerotic aortas of Macaca fascicularis after various regression regimens.

plasma and aortic tissue lipid changes in atherosclerotic Macaca fascicularis monkeys were studied following various regression regimens for 18 months. Atherosclerosis was induced in groups of 18 Macaca fascicularis monkeys by feeding a semipurified diet containing 43% of the calories as fat and 1.2 mg/kcal cholesterol for 6 months. Five groups of animals were continued on the same diet containing 0.34 mg/kcal cholesterol during the regression period, and were given the following hypocholesterolemic regimens: none (positive controls); D-thyroxine; pyrimidine derivative; cholestyramine; and alfalfa. Another group of animals was maintained on regular monkey chow alone during the regression period (negative control). Among the hypocholesterolemic agents, cholestyramine very effectively reduced the plasma cholesterol, and aorta free- and esterified cholesterol and phospholipids. D-Thyroxine significantly lowered the plasma cholesterol levels but, surprisingly, tissue lipid levels were the highest among the groups studied. Alfalfa, although not as effective as cholestyramine, tended to reduce the plasma and tissue lipids more than other drugs. Pyrimidine derivative actually increased the mean levels of plasma and tissue cholesterol. Plasma cholesterol correlated positively with aortic tissue cholesterol, free and esterified cholesterol. Both the plasma percentage distribution of alpha-lipoprotein and the phospholipid/cholesterol ratio were inversely related to all tissues lipids. Plasma cholesterol accounted for 43% and 30% respectively of the variability in tissue total and esterified cholesterol. Thus the effectiveness of any hypocholesterolemic regimen is probably dependent on achieving a favorable lipoprotein distribution in plasma without any adverse effect on the arterial wall metabolism.

Animals↗
PubMed1980

Lipoprotein-hyaluronate associations in human aorta fibrous plaque lesions.

Lipoproteins and glycosaminoglycans were isolated from human aorta fibrous plaque lesions by isotonic saline extraction and treatment with elastase. Hydrolysis by elastase, using suitable inhibitors of nonspecific proteases, yielded about twice the amount of cholesterol and four times more GAG than saline extraction. Bio-Gel A-50m column chromatography of elastase-solubilized materials gave a fraction which contained lipoproteins of 1.006 and 1.063 floating densities and hyaluronic acid. Immunologically the lipoproteins resembled serum apoB-containing lipoproteins. Two species of hyaluronates with estimated molecular weights of 400,000 and 75,000 were observed. In addition to hyaluronate, elastase solubilized other GAG which were not associated with lipoproteins. Association of hyaluronate as the only GAG in the elastase-solubilized lipoprotein fraction emphasizes the important role that hyaluronate may play in the aggregation or entrapment of macromolecules such as lipoproteins in the arterial connective tissue matrix.

Animals↗
PubMed1980

A rapid method of isolation and fractionation of proteoglycans using a vertical tube rotor for isopycnic centrifugation.

A comparison was made between a vertical tube rotor and a fixed angle rotor for isopycnic centrifugation of proteoglycans. In the vertical tube rotor, isopycnic gradient was achieved much faster than in the conventional fixed angle rotor. The use of a vertical tube rotor for isopycnic centrifugation shortens the time considerably for the isolation of proteoglycans from various tissues.

Animals↗
PubMed1980

Studies of glycoproteins from bovine aorta.

Glycoproteins from bovine aorta intima were isolated by a sequential digestion of the tissue with collagenase and elastase after extration of the tissue with saline. The proteins in the extracts were precipitated by (NH4)2SO4 and fractionated by Con-A sepharose affinity chromatography. The fractions were analyzed for their carbohydrate composition and by polyacrylamide disc gel electrophoresis. These studies show that considerable heterogeneity of aorta glycoproteins exists. Some of the glycoprotein materials are likely intimately associated with fibrous structures, collagen and elastin, of the aorta intima.

Animals↗
PubMed1980

Studies of biologic properties of proteoglycans from bovine aorta.

Chondroitin sulfate-dermatan sulfate proteoglycans (PG) were isolated from bovine aorta-intima by extraction with 4.0 M guanidinium chloride in the presence of protease inhibitors and purified through cetylpyridinium complexes. The PG were fractionated by CsCl isopyknic centrifugation into three fractions with different chemical composition. The anticoagulant activity of the PG fractions was studied by Stypven time, partial thromboplastin clotting time (PTT), and thrombin time assays. The three PG fractions delayed coagulation in the three assays. The PG fractions did not affect the ADP and collagen-induced platelet aggregation but inhibited the aggregation induced by 0.2 units per ml. of thrombin. The PG fractions released lipoprotein lipase in rabbits when injected, and the enzyme activity released by the major PG fraction was approximately 60 per cent of that of heparin. This PG fraction interacted with serum low density lipoproteins but not with high density lipoproteins. Certain biologic properties are probably due to the presence of dermatan sulfate in the PG fractions. These studies suggest important functional roles for PG in the arterial wall.

Animals↗
PubMed1980

Photometric determination of glycosylation of hemoglobin in diabetes mellitus.

We evaluated glycosylation of hemoglobin (HbA + HbA1) in 25 control subjects and in 133 diabetic patients who were in various stages of blood glucose control, by measuring ketoamine-linked hexoses in hemoglobin. These hexoses were converted by digestion with 10 mol/L acetic acid for 16 h at 100 +/- 5 degrees C to 5-hydroxymethylfurfuraldehyde, which was quantitated by reaction with 2-thiobarbituric acid. Glycosylation of hemoglobin was expressed as micromoles of hydroxymethylfurfuraldehyde per gram of globin protein (the "HMF index"). A mean HMF index of 1.67 (SD = 0.23) was obtained for controls; that for diabetic patients was 2.93 (SD 0.95). The index correlated well (r = 0.83, p < 0.001) with average blood glucose concentration as measured during the preceding 16 weeks, over a wide range of glucose values (1 to 6 g/L). It correlated even better (r = 0.92, p < 0.001) when corrected for variations in hemoglobin concentration. Thus measurement of ketoamine-linked hexoses of hemoglobin or HMF index provides an independent and useful alternative to the currently used methods that measure only HbA1 or HbA1c.

Blood Glucose↗
PubMed1980

Proteoglycan synthesis and secretion by bovine aortic tissue in organ culture.

The incorporation of 35S into proteoglycans (PG) of bovine aorta segments maintained in short term culture was investigated. The labeled PG were isolated by 4.0 M guanidinium chloride extraction and collagenase and elastase digestion and specific activities determined. The culture medium contained about 10% of the total uronate. In the sequential extraction of tissue PG, elastase treatment released the most uronate material. Guanidinium chloride extracted PG showed the highest degree of sulfation while the elastase solubilized PG had the lowest sulfate content. In the culture medium the highest specific activity was noted in heparan sulfate PG, followed by the chondroitin sulfates PG and then dermatan sulfate PG. Among the PG from tissue extracts, dermatan sulfate chains from guanidinium chloride extracted and collagenase solubilized PG showed similar specific activity. The highest specific activity of haparan sulfate was observed in the elastase solubilized PG. The specific activity of chondroitin sulfate chains was the lowest in all tissue PG preparations. These studies provide further evidence of the metabolic heterogeneity of aorta PG.

Animals↗
PubMed1979

Isolation of proteoglycan-hyaluronate complexes from bovine aorta.

Two proteoglycan-hyaluronate complexes were extracted from bovine aorta with 4.0 M guanidinium chloride in the presence of protease inhibitors and purified by cesium chloride density gradient centrifugation under associative conditions. Complex I with higher buoyant density had 22% protein and 18% uronate, whereas Complex II had 11% protein and 23.6% uronate. Glycosaminoglycan (GAG) analysis of the complexes indicated that both complexes contained large amounts of hyaluronic acid, 13.6% and 24.0% of the total GAG in Complexes I and II, respectively. Chondroitin sulfates and dermatan sulfate constituted the remainder of the GAG. Chromatography on Sepharose CL 6B suggested that Complex I had an estimated molecular weight of 800,000 and Complex II, 250,000. The complexes were dissociated into proteoglycan and hyaluronate by cesium chloride density gradient centrifugation under dissociative conditions. The proteoglycans free of hyaluronic obtained from the complexes had similar protein and GAG composition. The molecular weight of the proteoglycan was estimated to be 80,000 and that of the hyaluronate of the complex, 90,000.

Animals↗