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S Durand

Publications and source records attributed to S Durand.

At least 55 records · Page 3Linked to original sources
PubMed1989

Stimulation of xylanase synthesis in Cryptococcus albidus by cyclic AMP.

Cryptococcus albidus secretes a xylanase when induced by xylan or beta-methylxyloside, a non-metabolizable inducer, and production of the enzyme is repressed by xylose. The effect of exogenous cAMP on xylanase production was tested under different growth conditions. The cAMP elicited a 1.5 to 2 fold increase in xylanase production during the induction by xylan and B-methylxyloside but did not relieve the repression observed during growth on xylose. Cyclic AMP also affected the growth rate of the cells and did not modulate the activity of pure xylanase in vitro. A 15-nucleotide sequence located upstream from the xylanase gene could be part of a cAMP regulatory sequence.

Base Sequence↗
PubMed1988

Effect of tunicamycin on xylanase secretion in the yeast Cryptococcus albidus.

The yeast Cryptococcus albidus secretes a glycosylated xylanase (48 kDa) in the culture medium in response to beta-methylxyloside as inducer. Addition of tunicamycin to the medium results in the formation of a modified xylanase (40 kDa) which is depleted in carbohydrate content and whose enzymatic activity is 2.5 times less than that of the glycosylated xylanase. The secretion of xylanase was followed under both conditions by pulse-chase experiments. The half-time of secretion of the glycosylated and nonglycosylated forms was 5 and 2 h, respectively. Cell-associated xylanase activity was not detected when the cells were treated with the antibiotic. The absence of cell wall-associated xylanase, after tunicamycin treatment, was confirmed by immunolocalization with anti-xylanase antibodies at the electron microscopic level. The results suggest that the interactions of carbohydrate moiety within the cell wall retarded the secretion of the enzyme to the medium.

Cryptococcus↗
PubMed1987

Distribution of high-density lipoprotein 2 and 3 constituents during in vitro phospholipid hydrolysis.

Human high-density lipoproteins HDL2 (d = 1.068-1.125) and HDL3 (d = 1.125-1.210) doubly labelled with [3H]cholesterol/cholesteryl ester and with [acyl-14C]phosphatidylcholine were further incubated with phospholipases. Highly purified phospholipase A2 from Crotalus adamanteus allowed gradual degrees of lipolysis (30-90%) on both HDL2 and HDL3. Moderate phospholipid hydrolyses were achieved using hepatic triacylglycerol lipase, partially purified from post-heparin plasma. Moreover, the latter enzyme seemed to exert a lysophospholipase activity, acting on the 2-acyl-sn-glycero-3-phosphocholine generated. A purified sphingomyelinase C from Staphylococcus aureus was also used and completely hydrolysed HDL sphingomyelin. After incubation, doubly labelled HDL2/HDL3 were reisolated in their appropriate density interval. In the presence of albumin, which bound most of the lipolysis products, phospholipolysis induced a phospholipid depletion of the particles and a heterogeneous partition of all HDL2 constituents between the HDL2 and HDL3 density intervals. Radioactivity distributions correlated with mass movements. The 'HDL3-like' particles isolated after HDL2 lipolysis were twice as rich in cholesterol as plasma HDL3. No loss of apoprotein A1 was recorded due to phospholipolysis. In the absence of albumin, the density distributions of HDL2 or HDL3 constituents were unaffected by phospholipolysis, the products of lipolysis being reisolated with the stable particles. Control and treated HDL were also reisolated by equilibrium density gradient ultracentrifugation, gel chromatography or by gradient gel electrophoresis. Phospholipase treatment in the presence of albumin induced a shift of the HDL2 or HDL3 whole distribution towards particles of higher density and lower apparent size. Lipolysed HDL2 thus showed characteristics intermediate between those of HDL2 and HDL3. So, phospholipolysis may affect the physical parameters of HDL particles, but additional pathways such as cholesterol movements and apoprotein loss must be linked to achieve the HDL2----HDL3 interconversion.

Humans↗
PubMed1987

Lipid content of human and rat pancreas.

We analyzed the lipid composition of the human pancreas and performed a parallel study on rat pancreas. Some precautions were taken in order to keep the secretory zymogens as inactive precursors in both tissues. The lipid content of the human pancreas corresponded to 5.5% of the tissue wet weight, lower than that found in pancreas of two-month-old Wistar rats (10%). In man, triglycerides and phospholipids were found at comparable levels, respectively, 37 and 30 mg/g of pancreas wet weight, not far from the values of the rat pancreas. In human pancreas, phosphatidylcholines and lysophosphatidylcholines represented about 40% of the total phospholipid fraction, phosphatidylethanolamines and lysophosphatidylethanolamines 21%, and phosphatidylserines and -inositols were found equally represented with 7.5%. The total cholesterol content accounted for about 4.5% of the total lipids; only 30% was esterified. By comparison, in rat, total cholesterol represented 3.3% of lipids and 90% was esterified. The phospholipids in human pancreas contained high amounts of saturated fatty acids (92%) mainly stearic and palmitic, whereas triglycerides contained equal amounts of saturated and unsaturated fatty acids, principally represented by oleic and palmitic acids. In rats the phospholipids contained only 63% saturated fatty acids (palmitic and stearic) and triglycerides contained 61% unsaturated fatty acids (mainly oleic and linoleic). In terms of lipid composition, there is a greater similarity between human and rat pancreas than with other known pancreas, such as the guinea pig and the ox.

Adult↗
PubMed1982

The decrease of the non secretory phospholipase A in rat pancreas during a chronic alcohol intoxication.

It is known that ethanol induces morphological lesions in the exocrine pancreas of man and of experimental animals. We showed recently that ethanol is metabolized by the rat pancreas. It has also been demonstrated that ethanol acts on the lipid metabolism of the pancreas by stimulating the lipid biosynthesis and by inhibiting fatty acids oxidation. We recently characterised a non secretory phospholipase A in the rat pancreas, probably involved in the intracellular phospholipid turnover. The actions of chronic alcoholic intoxication on the level of this enzyme is investigated in this paper. The ethanol intoxication was prolonged for two years and resulted in a progressive decrease in the level of the pancreatic non secretory phospholipase (p less than 0.01). This result confirms the chronic metabolic modifications induced by alcohol on the pancreas and emphasizes its metabolic participation in chronic alcoholic pancreatitis.

Alcoholism↗
PubMed1980

Ethionine and methionine distribution and toxicity in the rat kidney.

Autoradiographic studies demonstrated that in the rat kidney radioactivity was localized mainly in the medulla in animals injected with [14C]ethionine, whereas it was distributed homogeneously throughout the whole parenchyma in rats given [14C]methionine. This difference of distribution was consistent with a difference in renal toxicity: a single i.p. dose (1 g/kg) of ethionine induced a slight but persistent (6 days) damage to kidney tubule cells evidenced by an increase of urinary GGT and slight disturbance of renal function, such damage was not observed with methionine.

Animals↗
PubMed1980

A non-secretory phospholipase A2 in the rat pancreas.

The rat pancreas shows a phospholipase activity in the absence of the tryptic activation of the zymogens. We verified that this activity was not due to the zymogen of the secretory phospholipase. Indeed unlike the prophospholipase, the enzyme responsible for the spontaneous phospholipase activity shows a higher catalytic rate at substrate concentrations higher than the critical micelle concentration. This enzyme has a positional specificity of the A2 type and possesses a molecular weight of about 9,500.

Animals↗
PubMed1980

Distribution of radioactivity in rats injected with L-14C methionine as studied by whole body autoradiography.

14C-L methionine was given intraperitoneally to rats. The delivered dose was 2.7 mg . kg-1 and the injected activity was 100 microCi . kg-1. Whole body autoradiography was performed on all rats. We noted the highest uptake of radioactivity in the liver and the pancreas. In the liver, there was an accumulation of radioactivity which occurs in the two hours after the injection. In the pancreas, both exocrine and endocrine portions were labelled. All the other organs were labelled but the highest activities are found in high protein turn-over tissues (glands, bone-marrow, spleen). This suggests that methionine is rapidly incorporated into proteins which can explain the persistence of radioactivity in the body of rats injected with this amino acid.

Animals↗
PubMed1977

[Spontaneous phospholipase A activity of rat pancreatic homogenates].

Rat pancreas presents a spontaneous phospholipase A activity which appears before trypsin activation at optimal pH 6.5. The responsible enzyme is independent of pancreatic prophospholipase A, as can be seen through experiments done in the presence of trypsin inhibitors. On the other hand, this enzyme is distinct from excretory phospholipase which is more active and whose optimal pH is 8.8. Thermostability and insensibility of spontaneously active phospholipase A to DFP differentiate it from lipase, carboxyl-esterhydrolase and lysophospholipase, respectively.

Animals↗
PubMed1975

[Comparative diffusion of 14C-ethionine and 14C-methionine in rat tissue].

The pancreas is the tissue which traps the most intensively the trace-dosis injected ethionine -14C; 30 min after the injection, the pancreas fixes the labelled product twice more than the liver and five times more than the stomach. This trapping might explain the pancreatic modifications occuring during the intoxication. In the same experimental conditions, the pancreas fixes the ethionine -14C twice less than methionine. Urinary excretion of ethionine is faster and more important than that of methionine.

Adipose Tissue↗