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Biomedical subjects

J Prost

Publications and source records attributed to J Prost.

At least 73 records · Page 4Linked to original sources
PubMed1993

Comparative changes between pancreas and pancreatic juice digestive enzyme contents during nutritional rehabilitation following severe protein malnutrition in the rat.

The relationship between digestive enzyme activities in the pancreas and pancreatic juice was studied in post-weaning rats fed on a low-protein diet (30 g cereal protein/kg) for 1 month and a refeeding balanced diet (235 g mixed protein/kg) for the following 3 months. A control group was fed on the balanced diet for 4 months. At the end of malnutrition and at various times of refeeding, activities of amylase (EC 3.2.1.1), trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1), lipase (EC 3.1.1.3), phospholipase A2 (EC 3.1.1.4) and cholesterolesterase (EC 3.1.1.13) in pancreas and pancreatic juice were measured. Recovery of body and pancreas weights was obtained after 3 months of refeeding. Pancreas offered a higher resistance to the low-protein diet; a quicker recovery than that of the whole organism was observed during refeeding. Protein and RNA contents of pancreatic cells were depressed by protein depletion. At the end of refeeding, pancreatic and cell RNA contents were still depressed. In pancreas and pancreatic juice, protein depletion produced a decrease in enzyme activities, with the exception of phospholipase A2 and cholesterolesterase. During refeeding, activities were increased to various levels in pancreatic juice and pancreas. In pancreatic juice, a deficit in enzyme activities still prevailed at the end of refeeding. The retention thresholds (total activity in pancreas v. activity per h in pancreatic juice) of hydrolases were increased by malnutrition. They were all decreased by refeeding at various rates, but after 3 months of refeeding the thresholds were still markedly increased for all enzymes studied. After malnutrition and during refeeding, the dissociated enzyme activities in pancreas and pancreatic juice could be the expression of an alteration at different stages: synthesis, intracellular transport, storage mechanisms and secretion.

Amylases↗
PubMed1992

Changes in serum and lipoprotein fatty acids of growing rats fed protein-deficient diets with low or adequate linolenic acid concentrations.

The effects of a protein-deficient diet associated with sunflower oil [adequate in 18:2(n-6), poor in 18:3(n-3)] or soybean oil [adequate in both 18:2(n-6) and 18:3(n-3)] on lipid serum and lipoprotein compositions were studied in growing rats. Four groups of rats were fed different diets: SFC (20% casein + 5% sunflower oil); SFd (2% casein + 5% sunflower oil); SC (20% casein + 5% soybean oil); Sd (2% casein + 5% soybean oil). After 28 d, both protein-deficient groups exhibited low concentrations of protein, phospholipid, triacylglycerol and total cholesterol in serum and VLDL. Compared with rats fed 20% casein diets, those fed low protein diets had lower 18:2(n-6) and 20:4(n-6) in phospholipids of serum, VLDL and HDL2-3, and the 20:4(n-6)/18:2(n-6) ratio was twofold higher in triacylglycerols of serum and VLDL. In the SFd-fed group, 22:5(n-6) was higher than in the SFC-fed group for both triacylglycerols and phospholipids in overall lipoprotein fractions studied. In addition, the 20:3(n-9)/20:4(n-6) ratio was 0.1 in HDL2-3 phospholipids of the SFd-fed group. Sunflower oil-fed rats compared with soybean oil-fed rats had greater monounsaturated fatty acids and lower total (n-3) fatty acids in both triacylglycerols and phospholipids of serum, VLDL and HDL2-3, as well as lower total (n-6) fatty acids in serum and VLDL triacylglycerols. Apolipoproteins (apo) of VLDL were drastically depressed in rats fed protein-deficient diets, whereas apo-AI of HDL2-3 showed a particular resistance. Likewise, sunflower oil-fed rats had enhanced apo-B48 of VLDL and apo-C, apo-AII and apo-AIV of HDL2-3. The present findings show that some effects of protein malnutrition were enhanced by alpha-linolenic acid deficiency, in particular reduced (n-6) and (n-3) fatty acid bioavailability.

Animals↗
PubMed1992

[Malondialdehyde production and erythrocyte membrane resistance to free radicals, in function of adequate or inadequate protein intake, associated with different oils (sunflower, soybean, coconut, salmon)].

Requirements in polyunsaturated fatty acids (PUFA) of series n-3 and n-6 may be amplified and their metabolism, transport, and utilization may be impaired in the long term, by protein depletion. The aim of this study was to evaluate, in young rats, malondialdehyde (MDA) production and erythrocyte membrane antioxidative defense, when they were fed balanced (20% casein) or depleted (2% casein) protein diet associated with various oils (sunflower, soybean, coconut or salmon). Over a short period (28 days), eight groups of 10 male Wistar rats were fed eight different diets: TOC (20% casein + 5% sunflower oil), TOd (2% casein + 5% soybean oil), SOC (20% casein + 5% soybean oil), SOd (2% casein + 5% soybean oil), COC (20% casein + 5% coconut oil), COd (2% casein + 5% coconut oil), SAC (20% casein + 5% salmon oil), SAd (2% casein + 5% salmon oil). Blood was removed, MDA was assessed in plasma (reaction with thiobarbituric acid). Washed erythrocytes were subjected to organic free radical generator (Kit KGRL 400 Spiral R.D., Couternon, 21560 France). The haemoglobin released was analysed by spectrophotometry. The total anti-radical defense status was expressed as the length of time to reach 50% hemolysis (T 50% in min). Plasma of deficient groups (2% casein) exhibited low concentrations of protein, particularly with coconut and salmon oils; phospholipid and total cholesterol, excepted with diet containing coconut oil; triacylglycerol; and VLDL. Malondialdehyde. In groups fed balanced protein diets, the lowest values were obtained with salmon and coconut oils. MDA contents of groups TOd, COd and SAd were higher than those of their respective control groups, but significantly only in group COd. Antiradical defense status. Total anti-radical defence status in erythrocytes was not modified in the short term by balanced or depleted protein diets which ever oil was used, despite deep changes in fatty acid composition of membrane phospholipids. In particular, phospholipid contents in eicosapentaenoic, docosahexaenoic acids were greatly enhanced by the consumption of salmon oil compared to the values obtained with coconut oil.

Animals↗
PubMed1991

Free-flow electrophoresis with trapping by a transverse inhomogeneous field.

We propose an electrophoretic technique combining the use of a series of dielectric traps controlled by an ac electric field and conventional continuous field free-flow electrophoresis. From the theoretical model that we describe, one can expect, for DNA electrophoresis, an improvement of one to two orders of magnitude in the selectivities or experimental durations.

Chemical Phenomena↗
PubMed1991

Structures in colloidal physical chemistry.

The vast range of technological and industrial application of colloidal systems is largely a direct result of their diversity of structure on microscopic and mesoscopic scales. Recent progress in understanding these structures allows for greater control of the macroscopic properties, as well as providing new avenues of fundamental research in physics, chemistry and materials science.

Animals↗
PubMed1991

Age and protein restriction followed by balanced refeeding affect pancreatic digestive enzyme outputs and turnover times in rats.

Outputs and turnover times of trypsinogen 2, chymotrypsinogen 1, lipase and amylase were determined in pancreatic juice of growing male Wistar rats at various times during protein restriction (5% protein) followed by balanced refeeding (20% protein). In control rats fed a 20% protein diet, trypsinogen 2, chymotrypsinogen 1 and amylase outputs increased progressively with age, those of lipase remained constant and the turnover times of the four hydrolases were shortened. With time, protein restriction induced the most rapid decrease in trypsinogen 2 output, followed by that of amylase, then by those of trypsinogen 1 and lipase. Compared with controls, protein restriction enhanced specific radioactivity in total proteins and each hydrolase and diminished the enzyme turnover times at the beginning of the experiment. Refeeding returned each hydrolase output to control values, but the turnover times remained shortened to the end of experiment. Pancreatic lobules were isolated from control and protein-depleted rat pancreata after 23 d of dietary treatment. After a pulse of [3H]leucine, lobules were incubated in Krebs-Ringer-bicarbonate-HEPES. Basal and stimulated (50 pmol cholecystokinin/L) secretions of total proteins, amylase and radioactive proteins were measured. Protein restriction resulted in a lower response of acinar cells to cholecystokinin. The reduced ability of cholecystokinin to stimulate secretion may be attributable to a lower number and/or to the reduced affinity of cholecystokinin receptors in acinar cells. Therefore, the observed output and turnover changes during protein restriction could be partly due to an impairment of cholecystokinin efficiency.

Aging↗
PubMed1988

Effects of age, and protein malnutrition followed by a balanced diet on the non-parallel change in digestive enzymes in the pancreas and their secretion in the rat.

1. Ninety male Wistar rats were divided into two groups. A control group (C) was fed on a balanced diet, containing 200 g protein/kg for 51 d. An experimental group (E) was fed on a low-protein diet containing 50 g protein/kg for 28 d (PM), and then on a balanced diet for 23 d (BR). At different days of PM and BR, the pancreas and the pancreatic juice were collected 40 min after injection of 0.1 mCi [3H]leucine. The amounts of amylase (EC 3.2.1.1), trypsinogen 2 (EC 3.4.21.4), chymotrypsinogen 1 (EC 3.4.21.1) and lipase (EC 3.1.1.3) were determined after separation by the isoelectric focussing technique. Incorporation of [3H]leucine into the four hydrolases of pancreatic juice and pancreas was also determined. 2. In control rats a progressive increase in the concentration of digestive enzymes and the amounts secreted were observed with age. Maturation was reached when the rats were 9 weeks old. In rats E, PM inhibited maturation of the pancreas. However, individual enzymes were not affected to the same extent and at the same time. As soon as re-feeding was initiated, pancreas maturation took place and a significant increase in these variables was observed. The increases varied according to the hydrolase and did not appear at the same time. 3. In control rats, a preferential secretion of newly synthesized enzymes was observed in young rats, whereas with age, the proportion of newly synthesized enzymes excreted decreased slowly. In group E rats, at the beginning of PM, the proportion of newly synthesized enzymes secreted was very low and increased with time. 4. In rats C and E, our results indicated a non-parallelism between pancreatic enzyme levels and amounts secreted. This non-parallelism was different in both groups, it was changed with age and pancreas maturation in group C, and according to nutritional state in group E.

Aging↗
PubMed1988

[Protein malnutrition and response of pancreatic acinar cells to stimulation by cholecystokinin].

Pancreatic lobules were isolated from 2 groups of male Wistar rats after 23 days of diet. A control group (C) fed on a 20% protein diet (16% gluten + 4% casein) and an experimental group (E) on a 5% protein diet (4% gluten + 1% casein). After isolation, lobules were preincubated 10 min with 10 muCi [3H]-leucine, washed, then incubate within Krebs Ringer bicarbonate Hepes. Basal secretion, then stimulated secretion (50 pM of cholecystokinin (CCK] of radioactive and non-radioactive protein and amylase outputs were measured. During basal secretion, in (E) group, lobules secreted more proteins than (C) one, the same outputs of amylase and radioactive protein were observed in both groups. The stimulated secretion by CCK increased the outputs of non-radioactive protein and amylase of lobules (T) (2-3 fold), but was without effect on lobule (E) outputs. Therefore, a low-protein diet involved a decrease of CCK sensibility on acinar cells, this fact might be mediated by a decreasing number and/or affinity of their CCK receptors.

Amylases↗
PubMed1988

[Evidence for several storage and exportation pathways of pancreatic digestive enzymes during protein malnutrition followed by refeeding].

Outputs of pancreatic juice hydrolase were constant during a three-hour collection in control rats fed 20% protein and in malnourished rats fed on a low protein diet (5% protein). However, during the same time after a 3H-Leucine pulse, the relative proportion of each labelled enzyme (newly synthesized) were changed. In control rats, this phenomenon was specially obvious for trypsinogen 2 (Tg2) and chymotrypsinogen 1 (Chtg1), and support the existence of separate pools for various pancreatic hydrolases. In malnourished rats, the relative proportion of labelled Tg2 is not modified by protein malnutrition, whereas the proportion of labelled amylase, lipase and Chtg1 were decreased. Refeeding carried out the same labelling profile of each enzyme in the two groups.

Animals↗