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Biomedical subjects

J Polonovski

Publications and source records attributed to J Polonovski.

At least 73 records · Page 4Linked to original sources
PubMed1984

[Dissociation of human serum low density lipoproteins in several immunologically distinct subunits. Isolation and characterization of a B-III subunit].

Low density lipoproteins (d = 1.030-1.055) were partially delipidated with ethyl-ether (LDLe). These LDLe exhibit a spontaneous dissociation several days after delipidation. Four different immunoprecipitation complexes (B-I to B-IV) are observed when using two dimensional immunoelectrophoresis against anti LDLe immunserum. The various subunits of LDLe have different behaviour upon electrophoresis. On disc gel electrophoresis containing urea three bands can be seen; all are phospholipoproteins. The apolipoprotein moiety of LDL and LDLe have the same apparent molecular weight around 550 000. With time several subunits appear in LDLe, the majority of them have a molecular weight around 370 000, 260 000 and 125 000. One of the components from dissociated LDLe containing the immunodeterminant B-III, has been separated by chromatography on heparin-agarose. This LDLe-B-III has the same phospholipid/protein ratio as total LDLe and a protein moiety with an apparent molecular weight of 110 000. This part of apolipoprotein B has no affinity for heparin. Immunocompetition studies by the ELISA technique indicated that sialic acid, one of terminal residues of LDL glycoprotein, is involved in the immunological recognition of LDL and of its derivatives by anti LDL and anti LDLe antisera.

Amino Acids↗
PubMed1984

[Comparison of the effects of orally or percutaneously administered estradiol on carbohydrates and lipids after the menopause].

The metabolic changes in carbohydrate (fasting blood sugar and blood sugar levels two hours after taking 70 g of glucose orally as well as insulin and glycosylated A1c haemoglobin) and also lipid metabolism as total and fractional HDL, triglycerides and alphaprotein B, were compared in 43 patients of a mean age of 48.6 years who had hysterectomy with castration. These patients were divided into two random groups: the first group (23 women) received hormone replacement treatment in a dose of 1.5 mg of oestradiol percutaneously, the second group of 20 women received 2 mg of oestradiol specially prepared for oral administration. Biological control was carried out immediately after the treatment and 3 and 6 months later. It consisted of levels of carbohydrates and of lipids and of oestriol, oestradiol and FSH. Both treatments, whether percutaneous or oral, were similar in their beneficial action on the changes brought about by castration. When 17 Beta oestradiol was administered percutaneously a better control over the carbohydrate and lipid (triglyceride) metabolism was obtained. This confirms that when oestradiol is administered orally the same respect has to be given to the contrary indications to its administration and to controlling the metabolic effects as when any other form of oestrogen therapy is administered orally.

Administration, Oral↗
PubMed1983

Effects of phenothiazines on low density lipoprotein metabolism in cultured human fibroblasts.

Treatment of cultured human fibroblasts with trifluoperazine or chlorpromazine resulted in a biphasic effect on low density lipoprotein (LDL) catabolism, depending upon the dose. At up to 10(-5) M, a marked increase in LDL binding, internalization and degradation was observed. This phenomenon took place within the first hours of incubation with the drugs, suggesting a direct effect on cell membrane physical characteristics, probably related to the lipophilic properties of phenothiazines. Concentrations above 2 X 10(-5) M resulted in a relative decrease in LDL binding and internalization, and in a dramatic decrease in LDL degradation, which may be related to an inhibition of calmodulin-dependent processes.

Calmodulin↗
PubMed1983

Effect of cyclic AMP on low density lipoprotein binding and internalization by cultured human fibroblasts.

Pretreatment of cultured human fibroblasts by cyclic AMP resulted in a marked decrease in the binding and internalization of the low density lipoproteins (about 55% of controls for cyclic AMP 2.10(-3) M). This effect was dose dependent and increased by theophyllin. DL propranolol, an inhibitor of adenylcyclase, had an opposite effect. Isoproterenol, which stimulates adenylcyclase, reproduced the effect of cyclic AMP. The cholesterol synthesis from [2-14C] acetate was decreased by cyclic AMP, theophyllin and isoproterenol, and increased by propranolol. The incorporation of [1-14C] oleate into cholesteryl esters was reduced by cyclic AMP, theophyllin, isoproterenol and propranolol.

Cells, Cultured↗
PubMed1983

Cholesterol and 7-dehydrocholesterol inhibit the in situ degradation of sphingomyelin by cultured human fibroblasts.

Feeding cultured human fibroblasts with cholesterol and 7-dehydrocholesterol resulted in a strong decrease of the in situ degradation of sphingomyelin (about 20 and 40 fold reduction for cholesterol and 7-dehydrocholesterol respectively, at 50 micrograms/ml of medium, and for 24 h incubation). Measurement performed on cell homogenates showed a slight decrease of the sphingomyelinase activity (about 75% of controls), whereas the activities of other lysosomal enzymes (beta glucosaminidase, beta galactosidase) were not significantly affected.

Cells, Cultured↗
PubMed1983

[Structure and metabolism of plasma lipoproteins].

Blood plasma contains lipoproteins of which the structure and the composition are not constant during the time and that depend on their metabolic evolution from their synthesis rate in intestine or liver to their utilization in the liver or the peripheral tissues. The composition and the pathway of the different lipoprotein classes (chylomicrons, VLDL, LDL, HDL) are reviewed, as also the main pathological perturbations that attack them.

Chemical Phenomena↗
PubMed1983

The role of serum lipoproteins on the in vitro proliferative potential of human hematopoietic progenitors CFUC and CFUE.

The influence of various lipoprotein fractions on the proliferation of normal human hematopoietic progenitors, CFUC and CFUE, was studied in vitro. The lipoprotein fractions, very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), low density lipoproteins (LDL), high density lipoproteins (HDL2 and HDL3), were isolated by sequential ultracentrifugation. The addition of each subfraction to lipoprotein deficient medium allowed us to distinguish two categories of lipoproteins: firstly, those with density d greater than 1.030, LDL, HDL2 and HDL3 which showed a marked inhibitory activity on CFUC and CFUE proliferation and, secondly, those with density d less than 1.030, VLDL and IDL which did not show any inhibitory activity. The regulatory role of lipoproteins on progenitor cell proliferation is discussed.

Cell Division↗
PubMed1982

Incorporation of exogenous fatty acids into phospholipids by cultured hamster fibroblasts. Effect of SV40 transformation.

In situ incorporation of two saturated (palmitic, 16:0; stearic, 18:0) and three unsaturated fatty acids (oleic, 18:1; linoleic, 18:2; arachidonic, 20:4) into the four major phospholipids, sphingomyelin, PC, PI and PE, was followed. Transformed cells incorporated unsaturated fatty acids more rapidly, whereas no significant differences were found concerning saturated fatty acids. In vitro determination of phospholipid acylation showed that incorporation of coenzyme A-activated forms of two saturated fatty acids (16:0 and 18:0) and one unsaturated fatty acid (18:1) into phospholipids was increased in transformed cells. Comparison of results obtained in situ and in vitro strongly suggests that incorporation of fatty acids into phospholipids in cultured cells is not limited by acyltransferase activities.

Animals↗
PubMed1982

[Lipoproteins associated with lipoprotein B in human serum low density lipoproteins].

Small amounts of lipoprotein C and lipoprotein D could be observed in low density lipoproteins (1.030-1.055 g/ml), using electroimmunomigration and polyacrylamide gel electrophoresis. Lipoprotein structures containing several apolipoproteins such as lipoprotein (B+C) or (B+D) were not detected in these low density lipoproteins. Lipoproteins C and D could not be separated from lipoprotein B by using gel filtration and affinity chromatography on heparin-Sepharose. Apolipoproteins C-III and D measured by electroimmunoassay are 3.2 +/- 1.2% and 1.15 +/- 0.6%, respectively, of the proteins found in the density range 1.030-1.055 g/ml, so there is, therefore, about 1 mol of apolipoprotein C-III and 0.1 mol of apolipoprotein D per mol of apolipoprotein B.

Apolipoproteins↗
PubMed1982

[Activable phospholipase a2 of rat blood platelets].

Rat blood platelet lysate showed high phospholipase A2 activity and contained much less than activating factor much greater than which increased phospholipase A2 activity. The phospholipase A2 and the much less than activating factor much greater than were eluted together in the same first protein fraction obtained by chromatography on a G 100 Sephadex column washed with tris-HCl buffer (pH 7.2). This mixture of proteins can be further fractionated on a Sepharose Blue CL 6B column in 2 protein fractions. The first fraction eluted by tris-HCl buffer (pH 7.2) showed 10 percent of the initial phospholipase activity; the second fraction eluted by NaCl 1 M-tris HCl buffer (pH 7.2) which showed no phospholipase activity, contains activating factor; if both fractions are mixed the initial phospholipase activity is almost totally restored. In conclusion, in rat blood platelets, phospholipase activity originates in a great part from the association of an much less than activable phospholipase much greater than and an much less than activating factor much greater than.

Animals↗
PubMed1982

[Immunological assay of apolipoprotein A-I].

Since lipid free apo A-I and lipid rich apo A-I (HDL, LP A, LP A-I) have different accessible antigenic sites, the electroimmunoassay ("rocket") does not allow the determination of the apo A-I concentration in both lipoproteins and serum when lipid free apo A-I are taken as controls. The results are found more significant when an isolated HDL or serum are used as reference. A comparison is made with the results (height of the pics) obtained for the same sample with different antibodies anti apo A-I, checked with the same HDL control, great differences two to one is observed. It is only explained by the various composition of antibodies directed against different apo A-I antigenic sites. Differences obtained in the levels of apo A-I in HDL2 and in HDL3 by immunoprecipitation show that the more lipoproteins are lipid rich the less their apo A-I are reached by antibodies.

Animals↗