Biomedical subjects
Publications and source records attributed to G Peres.
The authors describe a technique of portacaval shunt in a fish (small dogfish) using microsurgery. The techniques of anaesthesia and surgery are described and the results of eight operations are given, which show the problems of this kind of surgery, particularly with healing.
The effect of phorbol ester tumour promoters on the release of superoxide anion radicals .O2- by human peripheral leukocytes and the role of such radicals in tumour promotion of mouse skin was studied. No significant difference was found between complete [12-O-tetradecanoylphorbol-13-acetate (TPA)] as compared with incomplete [12-O-retinoylphorbol-13-acetate (RPA), 12-O-(2Z,4E,6,8)tetradecatetraenoylphorbol-13-acetate (Ti8), mezerein] tumour promoters upon induction of .O2- when measured by the reduction of ferricytochrome c. The semisynthetic phorbol esters 12-O-ethacrynylphorbol-13-acetate (EPA) and 4-O-methyl-TPA were less active, and phorbol diacetate, phorbol and ionophore A 23187 were found to be inactive in stimulating superoxide anion radicals. TPA-induced .O2- release from leukocytes was strongly inhibited by Cu(II)-(diisopropylsalicylate)2 (CuDIPS), and, to a lesser extent, by ethacrynic acid, nordihydroguaiaretic acid and quercetin. Retinoic acid exhibited only a moderate inhibitory effect. No .O2- release was observed in epidermal cell cultures upon TPA treatment. When analysed by the alkaline elution technique, TPA-induced .O2- release from leukocytes did not lead to measurable DNA damage in co-cultivated keratinocytes even in the presence of DNA repair inhibitors. In multi-stage-tumourigenesis experiments including two-stage promotion, retinoic acid, ethacrynic acid and CuDIPS were unable to inhibit tumour promotion in mouse skin when applied in combination with TPA in first stage promotion. gamma-Irradiation at a dose level shown to cause DNA damage in vitro could not replace TPA as a stage I-promoting agent. It is concluded that superoxide anion radicals--if related to promotion at all--may play a role in stage II rather than in stage I of mouse skin tumour promotion.
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1. The main perchlorosoluble fraction of rainbow trout serum has some physico-chemical characters kindred to those of human serum albumin (low molecular weight, solubility with ammonium sulfate, electrophoretic mobility, no glycoproteinic staining). 2. However, on account of obvious differences (heterogeneity and existence of various phenotypes, lack of bromophenol blue or bilirubin binding, low concentration, solubility in perchloric acid), the term "para-albumin" seems more suitable to name this compound. 3. The perchlorosoluble fraction binds hemoglobin causing an increase of peroxidasic activity. But, unlike to human haptoglobin, hemoglobin binding is partial, reversible and labile.
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The present study examined whether the reported lower values of anaerobic abilities in children and adolescents, both in absolute and related to bodyweight values, as compared to adults can be explained, partially at least, by a non-optimal testing apparatus. So, they cannot express their anaerobic abilities. Specifically, we examined the force-velocity (F-V) relationship on a mechanical cycle ergometer, in 23 adolescents and 11 adults, with two wheels of very different weights: 6.3 kg (Wh6) and 18 kg (Wh18). A higher wheel inertia might explain a late reach or no reach of the true peak velocity and the maximal anaerobic power (PmaxAn). The adolescent group showed higher Vo (V for zero braking force) values with Wh6 (238 +/- 14 vs 223 +/- 16 rpm) (P < 0.001) than with Wh18. The absolute or relative PmaxAn values for this group were slightly higher, but not significantly, with Wh6 (10.6 +/- 2.2 vs 10.2 +/- 1.9 W/kg). The delay to reach peak velocity was higher with Wh18 than with Wh6 (P < 0.001) in the two groups. In addition, the delay was always higher (P < 0.001) in the adolescent group compared to the adult group for both wheels. This suggests that the fatigue related to the observed late reach and the rapid decrease of power over time could lead to an underestimation of the PmaxAn peak in children.
The purpose of this study was to examine the effect of glutamate-arginine salt (AGs) or placebo (P1) on ammonemia during and after 1 hour exercise on sporting event bicycle under ergonomic device at 80% VO2max in 3 healthy male volunteers (age 18-25 years). Subjects were tested in three sessions, at rest after AGs and during exercise with placebo (Pl) or AGs. The subjects were given 20 g of AGs or Pl orally and 30 min later, exercised at 75-80% VO2max for 30 min. Blood samples were taken at 0, +30, +60, +90, +120 min after AGs and analyzed for ammonemia. Our results show a highly significant increase in plasma ammonia concentration during exercise. The magnitude of this increase was diminished when subjects were given AGs before the exercise session, suggesting that AGs may help reduce physiologic fatigue.
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Effects of non lethal concentrations of hexavalent chromium on intestinal enzymology of Salmo gairdneri and Dicentrarchus labrax (Pisces). The effects of an exposure to potassium dichromate on intestinal enzyme activities (Alkaline phosphatase, maltase, leucine amino peptidase and ATPases) have been studied on a fresh water fish (Salmo gairdneri) and a salt water fish (Dicentrarchus labrax). Fish were exposed at seasonal temperatures (13 or 21 degrees C) to toxic concentrations equal to 1/10 of the 24 h-LC 50 (i.e. 18 mg/l Cr for trout and 5 mg/l Cr for bass) during respectively 13 and 21 days. Intoxicated trout stopped feeding and showed a decrease in their intestinal weight at the end of the experiments. A decrease of brush border membrane activities (Alkaline phosphatase, maltase and leucine amino peptidase) were also observed. These alterations have been interpreted as the consequence of the chromium induces fasting. Intoxicated bass showed no alterations of their feeding habits. Two specific effects of chromium on enzyme activities have been found: a severe decrease of the alkaline phosphatase activity and an increase of the Na/K ATPase activity. These enzyme activities could be useful indicators of chromium intoxication in marine fish.
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The study of intestinal respiration in vitro showed that thermal rise up to 30 degrees C increases oxygen consumption and decreases it at the beginning of 35 degrees C. The Q10, equal to 1,80 and 1,51 between 15-25 degrees C and 20-30 degrees C, suggests a stimulation, by the temperature, of enzymatic reactions rate in the respiratory chain. The measures of oxygen consumption have been conducted every 10 minutes during 120 minutes. The study of glycine absorption at the concentration 0,5 mM have been effected with in vitro technic in presence of 14C glycine. The absorption time have been fixed at 30 minutes. The glycine absorption studied at 15-20 and 25 degrees C increase with the rise of temperature. The Q10, equal to 1,76 between 15 and 25 degrees C, suggests the mechanisms existence of metabolic complexions. The water movements, at different temperatures, are always directed from physiologic liquid to intestinal tissue.