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Biomedical subjects

J Arnaud

Publications and source records attributed to J Arnaud.

At least 163 records · Page 9Linked to original sources
PubMed1978

Studies on the midgut of Centropages typicus (copepod, calanoid). I. Structural and Ultrastructural Data.

From a structural study of the midgut of Centropages typicus, three main zones presenting different cellular associations may be defined. The ultrastructural study carried out allows us to distinguish several cell types. The four principal cell categories (E, R, F and B) show a more or less marked resemblance with those identified in the Malacostraceans, especially in the hepatopancreas of Decapods. The three types R, F and B, which are subdivided according to their localization (R and R') or their developing stages (F1, F2; B1 to B5), are recognized by the following characteristics: R-cells with smooth endoplasmic reticulum and high microvilli (zones I and III); F-cells with rough endoplasmic reticulum and short or spherical microvilli (zones I and II); B-cells with a large vacuolar apparatus made up of lysosome-like dense bodies associated with vacuoles originating from pinocytosis (zone II). From the comparisons of morphological, ultrastructural and histochemical results concerning Centropages typicus with author's data, we propose and discuss these functions for the three principal cell types: synthesis and secretion of pre-digestive enzymes (F1 and F2-cells); enzyme synthesis, intracellular digestion and extrusion (B1 to B5-cells); absorption (R and R'-cells).

Animals↗
PubMed1977

Hydrolysis and uptake of an aliphatic fatty ester by whole isolated fat cells.

During 9-min incubations at 37 degrees C, whole isolated fat cells are able to hydrolyze a water-insoluble ester, ethyl [3H]oleate, added as an emulsion to the extracellular medium. The monoester lipase exerts its activity as a membrane-bound enzyme and is not releasable by heparin. Variation of the reaction rate with substrate concentration suggests a diffusion-limited process, consonant with the fact that enzyme and substrate are associated with particles of enormous sizes (the fat cell and the lipid droplet, respectively). Variation of lipase activity with increasing temperature in the incubation medium shows a break at 46 degrees C +/-1 degrees C, most probably related to a phase transition in the membrane structure. During incubation, 30-60% of the amount of [3H]oleic chains formed by hydrolysis are incorporated into the cell, mainly as triacylglycerols. Controls of cell viability indicate that under the experimental conditions the framework of the membrane and the internal organization of the cell appear to be maintained. Such an experimental model might duplicate physiological conditions since aliphatic fatty esters are thought to be hydrolyzed at the cell surface during uptake.

Adipose Tissue↗
PubMed1976

Lipolytic activity of whole isolated liver cells in aqueous suspension.

1. Liver contains a lipase which catalyzes in vitro the hydrolysis of esters of short-chain normal primary alcohols and fatty acids. It is shown that this enzymatic activity can be measured by using intact liver cells as source of enzyme. During short-term incubations of suspensions of cells isolated from rat liver, the lipase acts as a membrane-bound enzyme and readily attacks [3H] oleoylethanol added as an emulsion into the bathing medium. The lipolytic reaction proceeds linearly for at least 20 min at 37 degrees C, at the pH optimum of 8.5. [3H] Oleic acid, a reaction product, is mostly retained in the medium and is used to monitor the lipolytic process. 2. In the presence of heparin, the bound lipase is released in the medium in amounts representing one-third to one half the total activity contained in the cells. This release is very rapid and associated in all cases with a concomitant release of lactate dehydrogenase activity. Such effects are consistent with the interpretation that heparin, at concentrations comprised between 10 and 100 mug per ml, causes alterations of the plasma membrane of the isolated cells, resulting in the dispersion of membrane-bound and cytoplasmtic material. This action of heparin is totally blocked by protamine sulfate (1 mg/ml). No specific effect of heparin directed towards the selective release of lipase could be demonstrated under these conditions. 3. During incubations in the presence of heparin, it was observed that the release of monoester lipase was quantitatively related to a simultaneous decrease in membrane-bound as well as in total monoester lipase activity measureable in the cells after homogenization. This, along with the reappearance of membrane-bound activity immediately after heparin withdrawal, suggest that under the experimental conditions, the membrane-bound enzyme is replaced from inside the cell in proportion of its release by heparin.

Animals↗
PubMedDate not supplied

Effects of adriamycin on chronic cardiotoxicity in selenium-deficient rats.

Adriamycin (doxorubicin) is an antineoplastic drug used to treat various cancers; however, its chronic use is unfortunately accompanied by cardiotoxicity. This toxicity can be reduced by antioxidant agents such as selenium, and it is particularly interesting that cancer patients are usually deficient in this trace element, which suggests that its supplementation could contribute to beneficial treatment. We have examined the effect of adriamycin on chronic cardiotoxicity in 6-week selenium deficiency in rats. Selenium-deficient rats showed a considerable reduction of selenium levels and of selenium-containing glutathione peroxidase. Cardiac lipid peroxides increased slightly in the deficient rats, whereas plasma and heart lipid peroxides increased markedly in adriamycin-treated rats. This increase was greatly accentuated in selenium deficiency. These results suggest that free radical mechanism may be contributing to adriamycin toxicity, and above all show the importance of balancing the selenium levels in adriamycin-treated subjects to limit its harmful myocardial action. A decrease in adriamycin cardiotoxicity with no concomitant decrease in its antineoplastic activity would be of considerable value by improving the therapeutic benefit of the drug.

Animals↗
PubMedDate not supplied

Reversal of selenium and zinc deficiencies in chronic hemodialysis patients by intravenous sodium selenite and zinc gluconate supplementation. Time-course of glutathione peroxidase repletion and lipid peroxidation decrease.

In six chronic dialyzed uremic patients, an intravenous sodium selenite (Se 50 micrograms during 5 wk and then 100 micrograms) and zinc gluconate (Zn 5 mg) supplementation was performed during 20 wk at each dialysis session three times weekly. Before supplementation, plasma Se and Zn, plasma and erythrocytes (RBC) antioxidant metallo-enzymes glutathione peroxidase (GPX), and superoxide dismutase (SOD) were significantly decreased, whereas lipid peroxidation (as thiobarbituric acid reactants TBARs) was increased. To obtain a significative change in plasma selenium, we had to use an Se dose of 100 micrograms/dialysis session. Then, treatment-increased plasma Se (from 0.58 +/- 0.09 to 0.89 +/- 0.16 mumol/L) led to a repletion of RBC-GPX (from 29.6 +/- 6 to 43 +/- 5.8 U/g Hb) and increased plasma GPX levels (from 62 +/- 13 to 151 +/- 43 U/L). Plasma Zn and RBC-SOD did not vary significantly. The change of TBARs was not observed between wk 1 and 4. They decreased significantly between wk 4 (4.80 +/- 0.21 mumol/L) and wk 20 (4.16 +/- 0.26 mumol/L). We noted a low correlation between TBARs and plasma GPX. A strong correlation was observed between Se and plasma GPX. The reversal of Se deficiencies should reduce oxidative damage observed in these patients.

Aged↗
PubMedDate not supplied

Effects of a multivitamin mineral supplement on zinc and copper status during pregnancy.

The effect of a multivitamin-mineral supplement was investigated during pregnancy according to a double-blind protocol by determining zinc and copper in maternal plasma, mononuclear and polynuclear zinc and copper at the third, sixth, eighth, and ninth months of gestation. The subjects were supplemented from the first trimester until delivery. A significant decrease was observed in plasma zinc that varied from 11.5 mumol/L to 10.8 mumol/L in the supplemented group (n = 29) and from 11 mumol/L to 10 mumol/L in the placebo group (n = 33) at 3 and 9 mo of gestation, respectively. In contrast, plasma copper levels increased in a way depending upon the stage of gestation in both groups: from 24.7 to 28.2 mumol/L in the treated group and from 24.9 to 30.9 mumol/L in the placebo group at 3 and 9 mo of gestation, respectively, but the difference was only significant in the placebo group. No difference between groups was observed in mononuclear and polynuclear zinc or copper levels. These trace elements were also determined in cord blood at delivery. There were no statistically significant differences in zinc and copper concentration found in placebo group and supplemented group. Finally, the beneficial effect of supplementation on muscular cramps and appearance of vergetures was noted.

Adolescent↗
PubMedDate not supplied

Effect of ischemia/reperfusion sequence on cytosolic iron status and its release in the coronary effluent in isolated rat hearts.

The hypothesis that oxygen-derived free radicals play an important role in myocardial ischemic and reperfusion injury has received a lot of support. In the presence of catalytic amounts of transition metals such as iron, superoxide anions, and hydrogen peroxide can be transformed into a highly reactive hydroxyl radical .OH (Haber-Weiss reaction). In view of this, we have undertaken this study to investigate whether iron is involved in the reperfusion syndrome and therefore could aggravate free radicals injury. Coronary effluent iron concentrations and cardiac cytosolic iron levels were evaluated in rat hearts subjected to an ischemia/reperfusion sequences. In the case of total ischemia, iron concentration in coronary effluents peaked immediately in the first sample collected upon reperfusion. However, in the case of partial ischemia, iron concentration in coronary effluents peaked rather exclusively during ischemia period. Cardiac cytosolic iron level augmented significantly after 30 min of total ischemia and non significantly in the other ischemia protocols compared to perfused control hearts. It also appears that the iron released is not protein-bound, and could therefore have a marked catalytic activity. The results of the present study suggest that in the oxygen paradox, iron plays an important role in inducing alterations during reoxygenation.

Animals↗
PubMedDate not supplied

"The SU.VI.MAX Study": a primary prevention trial using nutritional doses of antioxidant vitamins and minerals in cardiovascular diseases and cancers. SUpplementation on VItamines et Minéraux AntioXydants.

The "SUpplementation en VItamines et Minéraux AntioXydants" (SU.VI.MAX) Study is a randomized double-blind, placebo-controlled, primary-prevention trial which started in 1994 in France. This epidemiologic study is designed to test the efficacy of a daily supplementation with antioxidant vitamins (vitamin C, 120 mg, vitamin E, 30 mg, and beta-carotene, 6 mg) and minerals (selenium, 100 microg, and zinc, 20 mg) at nutritional doses, in reducing the main causes of premature death (cancers and cardiovascular diseases); 12,735 eligible subjects (women aged 35 to 60 years, and men aged 45 to 60 years) were included in 1994 and and will be followed up for 8 years. Participants undergo a yearly visit consisting, every other year, of either biological sampling or clinical examination. They also regularly provide information on health events and dietary intake by filling out computerized questionnaires using the Minitel Telematic Network. After 2 years of supplementation, biochemical indicators of vitamin and trace element status reach reasonable level without reaching concentrations as high as those observed in intervention studies, which tested relatively high doses of antioxidants, and ended up with higher risk of pathology.

Adult↗