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Biomedical subjects

J Boyer

Publications and source records attributed to J Boyer.

At least 181 records · Page 10Linked to original sources
PubMed1988

Lipolytic activities of freshly isolated rat liver parenchymal cells.

By using a specific collagenase preparation preserving lipolytic enzymes, we could isolate intact rat liver cells with monoester lipase (MEL) and, for the first time, substantial amounts of endogenous neutral triester lipase (TEL) activities assayable as cell-bound enzymes. TEL and MEL activities were found exclusively in parenchymal cells. Virtually all TEL was located on plasma membrane from which it was rapidly released at 37 degrees C in the absence of any additive. MEL was distributed almost equally inside the cell and in the membrane, to which it was firmly attached. Infusion of heparin to the whole animal before liver exposure decreased by 80% the TEL content of parenchymal cells (a property typical of hepatic lipase) whilst MEL was unchanged. These results question the concept that heparin-releasable hepatic lipase acts at the surface of endothelial liver cells and further suggest that TEL and MEL refer to distinct catalytic entities.

Animals↗
PubMed1988

Altered acylation of erythrocyte phospholipids in alcoholism.

The composition and metabolism of erythrocyte lipids were studied in 10 chronic alcoholic patients within 48 hr after discontinuation of alcohol intake and in 10 nonalcoholic control subjects. Chronic alcoholism produced no change in contents of cholesterol, total phospholipids, and proportions of phosphatidylcholine and phosphatidylethanolamine in erythrocyte phospholipids. The mean values of the rates of acylation of phosphatidylcholine and phosphatidylethanolamine with oleic acid were increased respectively by 59% (p less than 0.001) and 38% (p less than 0.05) as compared with the controls. There was no correlation between acylation rates and mean cellular volumes. Increases in acylation rates normalized over several weeks after alcohol withdrawal and were not related to a direct effect of alcohol on the intact erythrocyte, suggesting that these alterations result from ethanol-induced changes in the membrane during erythrocyte formation. The increased rates of acylation might modify the remodeling of the lipid matrix and thereby the membrane function.

Acylation↗
PubMed1988

Decreased acylation of phosphatidylcholine in diabetic rat erythrocytes.

We investigated the effects of streptozocin-induced diabetes on composition and metabolism of rat erythrocyte lipids. Diabetes produced no change in contents of cholesterol, total phospholipids, and proportions of phosphatidylcholine and phosphatidylethanolamine in phospholipids. The acylation of total phospholipids with palmitic, oleic, or arachidonic acids was decreased (P less than .01) in intact erythrocytes from diabetic versus control animals. This anomaly was underlaid by a decrease (P less than .01) in acylation of phosphatidylcholine, whereas phosphatidylethanolamine was unaffected. The impaired acylation of phosphatidylcholine was unchanged in vitro by insulin or coenzyme A but was restored to control values by ATP and by insulin treatment of the diabetic rats. We conclude that diabetes specifically alters the acylation of at least phosphatidylcholine in rat erythrocyte, an effect that might modify the remodeling of erythrocyte phospholipids and thereby the membrane function.

Acylation↗
PubMed1988

[Clinico-immunological profile of hepatic and extrahepatic diseases accompanied by anti-mitochondrial antibodies].

In a 13 year retrospective study mitochondrial antibodies were found in 1.71 p. 100 of patients about 60 years old with a strong female predominance. The presence of these antibodies was associated with a significantly increased level of the three classes of immunoglobulin and a marked cholestatic syndrome. In 76.9 p. 100 of cases the antibodies were associated with hepatic disease, mainly of immunological origin (67.7 p. 100). Primary biliary cirrhosis was the most frequent with significantly increased levels of mitochondrial antibodies, immunoglobin M, alkaline phosphatase and cholesterol. However, there was no correlation between the antibody levels and the clinical, biological and histological stages, thus ruling out any prognostic significance. The use of human cultured cells in the antibody detection assay increased the positivity of antinuclear antibodies compared with assays using classical rat liver substrates. Six sera were positive for anticentromere antibodies: 5/6 showed signs of the CRST syndrome with a primary biliary cirrhosis in 3/5 cases. The frequency of the association of primary biliary cirrhosis and other autoimmune diseases supports the results of previous reports as well as the finding of an association between mitochondrial antibodies and other auto-antibodies. In 3 cases primary biliary cirrhosis was associated with a chronic pancreatitis, suggesting a pluriglandular sicca syndrome, and in 3 other cases with a monoclonal IgA gammopathy. Mitochondrial antibodies are associated with other auto-immune non-hepatic diseases in 15.4 p. 100 of cases. The presence of increased levels of mitochondrial antibodies without any other auto-antibody associated with a chronic non-surgical cholestasis and an increased level of immunoglobulin M is still strongly suggestive of primary biliary cirrhosis.

Adult↗
PubMed1987

Lipases operative at the fat cell surface: attempt at an integrated approach.

Extracellular acylglycerols are hydrolysed by lipases active at the surface of intact fat cells isolated from rat or human adipose tissue. During short-term incubation, rat fat cells hydrolyse di-[3H]oleyl-[14C]glycerol at a rate of 70 +/- 7.7 mU/10(6) cells (mean +/- S.E.) versus 440 +/- 62 mU/10(6) cells for the hydrolysis of mono-[3H]oleylglycerol; these relatively high lipolytic potencies may serve, among other functions, to counteract the cytolytic effect of both esters. Reaction rates with both substrates are unchanged by addition of various apolipoproteins C and by the nutritional state of the animals. Fat cells incorporate 15-20 per cent of the total [3H]-oleic chains liberated by hydrolysis, with no correlation between uptake and hydrolysis rates. [3H]-oleic chains in cell lipids are found mainly as diacylglycerol (15 per cent) and triacylglycerol (80 per cent). Both lipolytic processes differ from the hydrolysis of trioleylglycerol by cell-bound lipoprotein lipase, which occurs at lower rates (6.5 +/- 0.6 mU/10(6) cells) and depends on apolipoprotein C-II and nutritional state of the animals. The results support the accepted view that lipoprotein lipase and monoacylglycerol lipase are distinct enzymes. Differences between lipoprotein lipase and diacylglycerol lipase activities raise the possibility of different catalytic entities. In conclusion, isolated fat cells in suspension hydrolyse and incorporate lipids. This model should approximate physiological conditions more closely than the use of lipases in the free state.

Adipose Tissue↗
PubMed1987

Nutritional dependence of the effect of estrogen on fat cell lipoprotein lipase.

We investigated the effects of ethynylestradiol (EE) at low dose (1.2 micrograms/day) injected s.c. for 10 days on lipoprotein lipase (LPL) in fat cells of female rats fed a standard diet (5% lipid, 49.5% glucid, 23.5% protein) as a function of the nutritional state. EE caused a 150% increase in LPL activity in the fed state, and a 65% decrease in the fasting state, resulting in a large increment in the physiological feeding-fasting difference. Feeding the rats a diet supplemented with 20% lard reversed the estrogen-dependent LPL increase in the fed state. Under all experimental conditions, EE caused a depletion of fat stores and an increase in plasma levels of triacyglycerol.

Adipose Tissue↗
PubMed1987

In vivo insulin effect on ATPase activities in erythrocyte membrane from insulin-dependent diabetics.

Na+-K+-dependent ouabain-sensitive ATPase and Mg2+-ATPase have been assayed in the erythrocyte membranes of control subjects and in uncontrolled type I (insulin-dependent) diabetics. A decrease in Na+-K+-ATPase activity was observed in the patients that was significantly correlated with glycemia. The Mg2+-ATPase was increased moderately, and no correlation with glycemia was found. To study the in vivo effect of insulin, ATPase activities were measured in uncontrolled diabetics before and after a 24-h continuous insulin perfusion administered by means of an artificial pancreas. ATPase activities were corrected after normalization of glycemia. It therefore seems that glycemia and/or insulinemia are involved in the regulation of erythrocyte Na+-K+ ouabain-sensitive ATPase and to a lesser extent in that of Mg2+-dependent ATPase.

Adenosine Triphosphatases↗