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Biomedical subjects

A M Preaux

Publications and source records attributed to A M Preaux.

24 records · Page 2Linked to original sources
PubMedDate not supplied

Effect of fasting on organic anion uptake by isolated rat liver cells.

In order to determine if the delayed clearance of organic anions observed in vivo after fasting can be related to an alteration of cell membrane carriers, kinetics of sulfobromophthalein (BSP) uptake were determined in isolated rat liver cells obtained from 48-hr starved rats. Surprisingly, in fasted rats the existence of two carriers can be directly revealed by classical kinetic plots. The high-affinity component, inhibited by Na+-taurocholate, has a Km of 0.5 +/- 0.2 microM and a Vmax of 0.2 +/- 0.1 nmole per min per 10(6) cells; the low-affinity component, which is not sensitive to Na+-taurocholate, has a Km of 21.2 +/- 3.2 microM and a Vmax of 4.8 +/- 0.9 nmoles per min per 10(6) cells. Comparison with control cells shows that fasting does not modify the total capacity of the liver cell membrane carriers to take up BSP. However, alterations in the kinetic parameters of the two uptake components were observed: a 53% decrease in the affinity of the low-affinity component and a 50% reduction in the capacity of the high-affinity uptake. These alterations, together with the observed decrease in hepatic blood flow and/or the increase in BSP efflux from the hepatocytes, could be involved in the delayed clearance of BSP and other anionic compounds occurring in vivo after fasting.

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PubMedDate not supplied

The usefulness of microscopic bile examination in patients with suspected microlithiasis: a prospective evaluation.

Gallbladder bile collected by duodenal intubation or during surgery was examined microscopically in patients who were free of stones and in patients with proven stones. None of the 16 patients free of stones had cholesterol monohydrate crystals or calcium bilirubinate granules in bile. Among the 17 patients with proven cholelithiasis, 13 with cholesterol stones had cholesterol monohydrate crystals in their bile, but only 2 of the 4 patients with pigment stones had calcium bilirubinate granules. These data confirm that cholesterol monohydrate crystals are sensitive and specific for cholesterol stones, whereas calcium bilirubinate granules lack sensitivity for the diagnosis of pigment stones. From these results, the diagnostic usefulness of microscopic examination of bile collected from the duodenum was studied prospectively in 46 patients with symptoms suggestive of cholelithiasis but in whom stones had not been visualized at cholecystography and ultrasonography. In 15 of them, bile was found to be abnormal: cholesterol monohydrate crystals were seen in 11, cholesterol crystals + calcium bilirubinate granules in 2 and calcium bilirubinate granules in 2. To date, nine of these patients have been operated on: 6 (all with cholesterol monohydrate crystals) had small cholesterol gallstones and 3 (2 with cholesterol monohydrate crystals and 1 with calcium bilirubinate granules) had signs strongly suggestive of the recent migration of gallstones. One patient refused operation, but minute pigment stones were found to be associated with calcium bilirubinate granules at duodenal intubation. In the other 31 patients, bile contained neither cholesterol monohydrate crystals nor calcium bilirubinate granules. They were not operated on and were followed up with repeated investigations for 12 to 24 months.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMedDate not supplied

In vitro toxicity of polymorphonuclear neutrophils to rat hepatocytes: evidence for a proteinase-mediated mechanism.

Human polymorphonuclear neutrophils, when exposed to soluble or particulate stimuli, can destroy various types of cells. The aim of this study was to investigate their toxicity against hepatocytes. Human polymorphonuclear neutrophils were incubated in basal conditions and after stimulation with 5 mg per ml opsonized zymosan in the presence of rat hepatocytes isolated by collagenase digestion. Cytotoxicity was quantified by the percentage of ALT activity released by hepatocytes in culture medium. Whereas unstimulated neutrophils exhibited only minor effects, opsonized zymosan-stimulated neutrophils induced, after 16 hr incubation, a 24.0 +/- 4.1% (mean +/- 1 S.E.) ALT activity release at a neutrophil/hepatocyte ratio of 5, and a 51.7 +/- 6.8% ALT activity release at a ratio of 20. At this ratio of 20, the ALT activity release was 9.0% at 1 hr and 24.0% at 4 hr. Three proteinase inhibitors (i.e., soybean trypsin inhibitor, alpha 1-proteinase inhibitor and fetal calf serum) decrease cytotoxicity by 78, 76 and 78%, respectively. The protective effect of proteinase inhibitors was not due to a nonspecific effect of proteins, since bovine serum albumin did not decrease the toxicity of stimulated polymorphonuclear cells. The supernatant of stimulated neutrophils was also found to be toxic against hepatocytes, and again, this effect was inhibited by soybean trypsin inhibitor, alpha 1-proteinase inhibitor and fetal calf serum. Finally, the role of proteinases was supported by the demonstration of a cytotoxic effect of two purified proteinases: porcine pancreatic elastase and human neutrophil cathepsin G. The toxicity of these proteinases was also markedly reduced by the specific inhibitors used in the study.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMedDate not supplied

In vitro toxicity of hydrogen peroxide against normal vs. tumor rat hepatocytes: role of catalase and of the glutathione redox cycle.

Hydrogen peroxide produced by stimulated phagocytic cells or during the metabolism of drugs, is toxic to various cell types. The aim of this study was to investigate its toxicity against normal vs. tumor rat hepatocytes. Isolated normal hepatocytes and tumor hepatocytes from three hepatocarcinoma cell lines, Fao, C2 (Faof1C2) and HTC, were incubated in the presence of a H2O2-generating system consisting of glucose and varied concentrations of glucose oxidase. The toxicity of H2O2 was quantified by measuring the percentage of lactate dehydrogenase activity released in the culture medium after various times of incubation. By comparison to normal hepatocytes, tumor hepatocytes exhibited an increased susceptibility to lysis by H2O2. At a concentration of 100 mU per ml, glucose oxidase induced a lactate dehydrogenase activity release of only 6.1 +/- 2.2% (mean +/- S.E.) from normal hepatocytes and of 71.0 +/- 2.9, 45.5 +/- 2.5 and 34.7 +/- 3.4% from Fao, C2 and HTC cells, respectively, after an 18-hr incubation. At a concentration of 10 mU per ml, glucose oxidase had no toxic effect to normal hepatocytes or HTC cells, whereas it induced a lactate dehydrogenase activity release of 58.7 +/- 7.6 and 51.2 +/- 5.6% from Fao and C2 cells, respectively. In addition, the time courses of lactate dehydrogenase activity release, studied with 500 mU per ml glucose oxidase, demonstrated that Fao cells, C2 cells and, to a lesser degree, HTC cells were lysed more rapidly than normal hepatocytes. The toxicity of glucose oxidase was suppressed by the addition of catalase, indicating that it was actually mediated by H2O2.(ABSTRACT TRUNCATED AT 250 WORDS)

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