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H Bar-On

Publications and source records attributed to H Bar-On.

At least 73 records · Page 4Linked to original sources
PubMed1978

The metabolic fate of high density lipoprotein (HDL) in the diabetic rat.

Diabetic rats, pre-fed and maintained on a sucrose-rich diet, have marked hyperlipoproteinaemia, with an increase in both very low density (VLDL) and high density lipoproteins (HDL). HDL obtained from both diabetic and non-diabetic rats and labelled with 125I or 135I was injected simultaneously into diabetic and non-diabetic rats. The half life of the two HDL preparations was similar in both diabetic and non-diabetic rats and ranged between 11.4 to 12.0 hours. A-I apolipoprotein had a disappearance rate parallel to the whole HDL, in contrast to the apo-C peptides which had a faster rate of removal. Although the fractional catabolic rate (FCR) of HDL preparations was slower in the diabetic rats, there was a 16% increase in the calculated synthetic rate (SR) of HDL-protein. These observations could explain the increased plasma HDL levels in the sucrose-fed, streptozotocin-induced diabetic rat.

Animals↗
PubMed1977

Chloroquine-induced interference with degradation of serum lipoproteins in rat liver, studied in vivo and in vitro.

The effect of chloroquine, an inhibitor of certain lysosomal enzymes including cathepsin B (EC 3.4.22.1), on the degradation of serum lipoproteins in rat liver was studied in vivo and in liver homogenates. Chloroquine had no effect on the clearance from the circulation of 125I-labeled rat or human very low density lipoproteins or human low density lipoproteins. Pretreatment with chloroquine for 3 h, resulted in a 2-2.5 fold increase in 125i-labeled very low density lipoprotein recovered in the liver 45 min after injection of the homologous and heterologous lipoproteins. This effect was evident on both the 125I-labeled protein and 125I-labeled lipid moiety. 30 min after the injection of [3H]-cholesterol linoleate-labeled very low density lipoproteins, 70% of the injected label was recovered in the liver, both in control and chloroquine-treated rats. Since the perl and 20% in the experimental group, it was concluded that chloroquine interferes with the hydrolysis of [3H]cholesterol linoleate. Following injection of 125I-labeled human low density lipoproteins only 4% of the injected lipoprotein was recovered in the liver of control rats and not more than 10% after chloroquine treatment, when about 50% had been cleared from the circulation. Hence, while very low density lipoprotein protein and cholesterol ester are catabolized in the liver, the catabolism of low density lipoproteins occurs mainly in extra-hepatic tissues. Using post-nuclear liver suprnatant, optimal degradation of various serum lipoproteins was found at pH 4.4, and chloroquine inhibited their degradation. Degradation of very low density and low density lipoproteins was completely inhibited at 0.05 M chloroquine, while less pronounced inhibition was seen with high density lipoproteins, apolipoproteins and apolipoprotein AI. These results indicate that liver acid hydrolases in vivo participate in the degradation of serum lipoproteins. Cathepsin B is apparently responsible for the degradation of aplipoprotein B, while other cathepsins might also be active in the degradation of this and the other apolipoproteins.

Animals↗
PubMed1977

Correlation between thromboplastic activity and lecithin/sphingomyelin ratio in amniotic fluid preliminary report.

THe thromboplastic activity of amniotic fluid was correlated with the lecithin sphingomyelin (L/S) ratio in 59 pregnancies. It was shown that the thromboplastic activity and the L/S ratio in amniotic fluid had a coefficient of correlation of r = --0-73 (P less than 0-004). The thromboplastic activity was estimated by a modified method for prothrombin time, and a time of 113 seconds appeared to correspond to an L/S ratio of 2, in that it was the border line between maturity and immaturity of the fetal lungs. Thirty women were delivered within 24 hours of a sample of amniotic fluid being obtained. In the three patients whose babies developed the respiratory distress syndrome, the thromboplastic activity was estimated as being slower than 113 seconds.

Amniotic Fluid↗
PubMed1976

Serum lipoproteins and apolipoproteins in rats with streptozotocin-induced diabetes.

The lipoproteins of rats fed a high sucrose diet and made diabetic by administration of 45 mg/kg of streptozotocin were studied. All lipoprotein classes were found to be present in increased concentrations. The apolipoprotein composition of the various lipoprotein fractions was studied by polyacrylamide-gel electrophoresis in the presence of 8 M urea, isoelectric focusing in the presence of 8 M urea, and sodium dodecyl sulfate gel electrophoresis in polyacrylamide gels. In the very low density lipoproteins (VLDL) of diabetic rats, there was a marked alteration in the relative amounts of C proteins by polyacrylamide-gel electrophoresis, and this was found by isoelectric focusing to be primarily a relative increase in C-III-3 apoprotein and a decrease in C-III-O. In addition, in the diabetic rats, the VLDL contained a protein of mol wt 46,000, the A-IV protein, which normally is only present in the high density lipoproteins. In the high density lipoproteins, (HDL) the same alterations in pattern of the C proteins seen in the VLDL were present. Furthermore, the arginine-rich and A-IV protein normally present in HDL could not be detected in the HDL, although the other apolipoproteins are present. Apolipoprotein concentrations were determined by quantitative immunoelectrophoresis. It was found that in the diabetic rats there was an increase in the total amount of apo-B in the plasma, with the increment divided proportionately between the VLDL and the low density lipoprotein (LDL). The total apo-C concentration of plasma increased minimally. The A-IV concentration of plasma increased by 27%; it decreased markedly in the HDL, but appeared in increased amounts in both VLDL and in the d greater than 1.21 fraction. The arginine-rich protein decreased by 63% in the plasma and decreased significantly in the HDL, but increased in VLDL, LDL, and in the d greater than 1.21 fraction. These alterations in apolipoprotein patterns in diabetic animals suggest that the apolipoproteins may play an important role in determining the concentration of various lipoprotein fractions, or may be the result of altered metabolism of the lipoproteins. These lipoproteins with altered apolipoprotein composition may have important biologic differences from normal lipoporteins. Nevertheless, the HDL, despite the fact that it is deficient in some of its major constituents, was unchanged in its cholesterol content.

Animals↗
PubMed1976

Hyperlipoproteinemia in streptozotocin-treated rats.

In order to study hyperlipidemia in diabetes mellitus, rats were made diabetic by administration of streptozotocin and the optimal conditions for production of severe and persistent hyperlipoprotenemia determined. Two groups of rats were compared: rats fed sucrose-rich diets and rats fed laboratory chow. The optimal dose of streptozotocin was 45 mg/kg body weight for the sucrose-fed rats. With this dose, plasma glucose reached a maximum of over 600 mg/100 ml., and plasma insulin was reduced by 60 per cent. Plasma triglycerides rose in the sucrose-fed rats to over 1,000 mg/100 ml. two days after the streptozotocin was given and then decreased to over 770 mg./100 ml. 12 days after treatment and then to 585 mg./100 ml. 10 weeks after induction of diabetes. With this dose, ketonuria did not occur nor did any of the animals die, as occurred with higher doses. In the chow-fed rats, plasma triglyceride levels were elevated with the induction of diabetes to levels of approximately 300 mg./100 ml. The concentration of all the plasma lipoproteins increased with the induction of diabetes. The concentration of very-low density lipoprotein (VLDL) protein in the sucrose-fed diabetic increased fivefold, the low-density lipoprotein (LDL) protein increased, and especially striking was the increase in high-density lipoprotein (HDL) protein concentration, which became more pronounced with the duration of the diabetes. The diabetes produced by streptozotocin administration to sucrose-fed rats, thus, provides a useful model for the study of the hyperlipoproteinemia of diabetes.

Animals↗