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Biomedical subjects

K Shirai

Publications and source records attributed to K Shirai.

At least 235 records · Page 13Linked to original sources
PubMed1980

Preparation and properties of immobilized lipoprotein lipase.

Purified bovine milk lipoprotein lipase has been covalently attached to CH-Sepharose with water-soluble carbodiimide. The immobilized enzyme retained enzymic activity and was stimulated 7-fold by the addition of human apolipoprotein C-II. Both [3H]heparin and 125I-labeled apolipoprotein C-II bound to the immobilized enzyme; unlabeled heparin and apolipoprotein C-II competed for binding of their respective labeled compounds. Apolipoprotein C-II did not compete for binding of [3H]heparin and vice versa. Human apolipoprotein C-III did not bind to the immobilized enzyme nor did it compete for apolipoprotein C-II binding. We conclude from these studies that both apolipoprotein C-II and heparin interact with immobilized lipoprotein lipase and that they have different binding sites.

Animals↗
PubMed1980

Clinical study of niceritrol on serum lipids in the treatment of hyperlipidemia.

The effects of niceritrol, a nicotinic acid derivative, on the levels of HDL-cholesterol (HDL-Ch) and a mixture of VLDL- and LDL-Ch (VLDL- + LDL-Ch) were studied in hyperlipidemic patients. Serum total cholesterol (sTC) and serum triglyceride (sTG) were significantly reduced during niceritrol administration. Lipoprotein electrophoresis showed that niceritrol increased the alpha:beta ratio. HDL-Ch showed a significant increase of 12.5% by the 16th week of therapy. This increase was more marked in patients with lower pre-treatment HDL-Ch levels and significant in patients whose pre-treatment sTG levels were in excess of 200 mg/dl. Females displayed higher pre-treatment HDL-Ch levels (38.5 mg/dl) than males (30.6 mg/dl). However, niceritrol increased HDL-Ch significantly in both groups. At 16 weeks, the VLDL- + LDL-Ch level showed a significant decrease of 9.2%; the HDL-Ch:VLDL + LDL-Ch and HDL-CH:sTC ratios were significantly increased throughout niceritrol administration. Niceritrol is thought to be effective in preventing the development and progression of atherosclerosis because it raises the level of anti-atherogenic HDL-Ch and lowers the level of atherogenic VLDL- + LDL-Ch.

Cholesterol↗
PubMed1980

Effect of pantethine on cholesterol ester metabolism in rat arterial wall.

The total serum cholesterol level in rats fed on a high cholesterol diet (HCD) for 16 weeks was markedly higher than that in rats fed on a normal diet (ND), but pantethine reduced the increased level in rats fed on HCD (P less than 0.05). Acid cholesterol esterase activity (acid CEase) of arterial wall homogenates from rats fed on HCD was significantly lower than that of rats fed on ND (P less than 0.005). Acid CEase activity in the arterial wall of rats fed on HCD for 8 weeks and then ND for 8 weeks was less than that of rats fed on ND for 16 weeks. Acid CEase activity in the arterial wall was increased in rats fed on pantethine-containing diet. The ratio of cholesterol ester synthesizing activity to neutral cholesterol esterase (neutral CEase) activity was higher in rats fed on NCD than in those fed on ND. The ratio was lower in rats on the pantethine-containing diet than in those on NCD. The relationship between hypercholesterolemia and lipid metabolism in the arterial wall and effects of pantethine are discussed on the basis of these results.

Alanine Transaminase↗
PubMed1980

Effects of tocopherol deficiency on lipid metabolism in the arterial wall of rats on normal and high cholesterol diets.

The effects of dietary tocopherol deficiency on arterial wall enzymes involved in lipid synthesis and hydrolysis were studied in rats receiving normal diets and diets supplemented with 1% cholesterol. Arterial wall lipase and cholesterol esterase were associated with both the lysosome and microsome fractions, whereas acyl CoA synthetase, triglyceride synthesizing activity, cholesteryl ester synthesizing activity and cytidine diphosphatecholine-1,2-diacyl glycerol choline phosphotransferase (CPT) were found mainly in the microsomal fraction. When tocopherol was depleted from either the normal or high cholesterol diets, the following changes occurred in the arterial wall: (1) increase in thiobarbituric acid reactive substances; (2) decrease in lysosomal acid lipase and acid cholesteryl esterase; (3) decrease in the microsomal enzymes, acyl CoA synthetase, triglyceride synthesizing activity, cholesteryl ester synthesizing activity, neutral lipase and neutral cholesteryl esterase; and (4) increase in microsomal CPT. The results of these studies suggest that dietary tocopherol plays an important role in both lipid synthesis and degradation in the arterial wall, and the results may account for the accumulation of lipids and lipoperoxides in atherosclerotic lesions.

Animals↗
PubMed1980

Purification and properties of bovine aortic lipoprotein lipase.

Lipoprotein lipase of bovine aortic intima has been purified to homogeneity by affinity chromatography on heparin-Sepharose. As determine by polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the purified enzyme had a molecular weight of approximately 60,000, required apolipoprotein C-II for activity and was inhibited by 1.0 M NaCl. Optimum lipolytic activity was in the pH range of 8.0-8.5. Bovine skimmed milk lipoprotein lipase was also purified and its properties compared to those of the aortic enzyme. Based on these comparative studies, we conclude that bovine aortic and milk lipoprotein lipase have similar properties.

Animals↗
PubMed1979

Studies of cholesterol esterase in rat arterial wall.

Cholesterol esterase activity was estimated in homogenates of rat arterial wall using radioactive cholesteryl oleate incorporated into phospholipid vesicles as a substrate. The labeled oleic acid was separated from the ester by addition of benzene-chloroform-methanol mixture. Under these conditions, two pH optima were found at about 4.5 and 7.5. Most of the activities at pH 4.5 and 7.5 were found in the lysosomal and microsomal fraction, respectively. No enzyme activity was detected when the substrate vesicles were prepared with phosphatidylethanolamine or sphingomyelin, but the activity was higher when the substrate vesicles were prepared with phosphatidylserine and highest when they were prepared with phosphatidylcholine. The relationship between enzyme regulation and lipid deposition in the arterial wall is discussed.

Animals↗
PubMed1979

Effects of pantetheine on cholesteryl ester synthesis in the arterial wall of rats on high cholesterol diet.

Increase of acyl-CoA synthesis was observed when extracts of rat arterial wall were incubated with pantetheine [D-bis-(N-pantothenyl-beta-aminoethyl)-disulfide]. Cholesteryl ester synthesis from palmitate in the arterial wall extract in vitro was higher with arteries from rats on high cholesterol diet than with those from rats on normal diet, but the synthesis was reduced in the arteries of rats on high cholesterol diet with pantetheine. Triglyceride synthesis was higher with arterial wall extracts of rats on high cholesterol diet than with preparations from rats on normal diet and was not reduced with those of rats on high cholesterol diet plus pantetheine. The value of the effects of pantetheine on lipid metabolism in the prevention of atherosclerosis is pointed out.

Acyl Coenzyme A↗
PubMed1978

Studies on the mechanism of action of ACTH on triglyceride synthesis in fat cells.

It was found that ACTH greatly reduced lipogenesis in fat cells in the presence of calcium ion, but not in the absence of calcium ion. Of the enzymes involved in triglyceride synthesis from fatty acid in lipid micelle membranes, only acyl-CoA synthetase was inhibited by calcium ion, the apparent Ki value of calcium ion being 4.2 X 10(-4) M. The Km values of the enzyme for palmitate and ATP were 2.0 X 10(-4) M and 2.5 X 10(-4) M, respectively and calcium ion caused non-competitive inhibition with both palmitate and ATP. The acyl-CoA synthetase activity of lipid micelle membranes was inhibited by treatment with phospholipase A or C, but not by treatment with phospholipase D. The mechanism of inhibition of triglyceride synthesis by ACTH is discussed on the basis of these results.

Adipose Tissue↗
PubMed1978

Quantitative and qualitative estimation of urinary kallikrein in a patient with Bartter's syndrome.

Urinary kallikrein in a patient with Bartter's syndrome was remarkably higher than normal. Indomethacin treatments increased serum potassium concentration and urinary Na/K ratio, and improved the response of blood pressure to angiotensin II infusion, while it decreased plasma renin activity, plasma aldosterone and urinary kallikrein. The purified urinary kallikrein had one component of the iso-electric point 4.3 by isoelectric focusing using Ampholine system, and its molecular weight was 4.2 x 10(4), which was greater than those of three components of normal human urinary kallikreins (normal HUK). Also Km values with TAME and BAME of urinary kallikrein in our patient with Bartter's syndrome did not correspond to those of normal HUK. Thus it can be said that urinary kallikrein in our patient with Bartter's syndrome was qualitatively different from normal HUK. The present observation might be a reflection of renal tubular dysfunction in this patient with Bartter's syndrome.

Angiotensin II↗