Search PubMed⌕ Search

Biomedical subjects

A Valenzuela

Publications and source records attributed to A Valenzuela.

At least 109 records · Page 6Linked to original sources
PubMed1987

Effects of chronic administration of dextroamphetamine on enzymes of energy metabolism in regions of the rat brain.

In the present study the effects of chronic administration of dextroamphetamine on energy metabolism in the brain of the rat were examined. The enzymes studied were: hexokinase (soluble and particulate forms), phosphofructokinase, pyruvate kinase, lactate dehydrogenase, citrate synthase, NAD+ and NADP+-dependent isocitrate dehydrogenases, succinate dehydrogenase and malate dehydrogenase. All the activities of the enzymes were assayed in four regions of the brain of the rat (cerebellum, medulla oblongata and pons, cererbral cortex and diencephalon). Rats were injected intaperitoneally once daily with dextroamphetamine for 20 consecutive days. The initial dose was 5 mg/kg/day and the dose was then increased by 1 mg/kg/every 5 days up to a total of 8 mg/kg/day on days 16-20. In the glycolytic enzymes a reduction of the activity of phosphofructokinase was found in the diencephalon and an increase of the activity of pyruvate kinase and lactate dehydrogenase in the diencephalon and medulla oblongata and pons, respectively. Citrate synthase was the only enzyme in the Krebs' cycle affected by chronic administration of dextroamphetamine. The results presented here show that chronic administration of dextroamphetamine produced important changes in some enzymes of glycolysis and the Krebs' cycle in the brain of the rat.

Animals↗
PubMed1987

Effects of pindolol and clopamide on blood lipids in arterial hypertensive patients.

The effects of clopamide, pindolol and its combination on plasma lipids in 49 hypertensive patients (WHO I-II), divided into three parallel randomized groups, were studied over a 6 months period. Total cholesterol, triglycerides, HDL and LDL cholesterol fractions were determined twice during an initial 4-week washout phase, and after a 1-, 3- and 6-month active hypotensive drug phase. Patients were instructed to maintain their usual dietary habits. Daily drug doses were adjusted progressively to attain optimal hypotensive effects. In the clopamide monotherapy group, total cholesterol increased significantly (p less than 0.05); triglycerides and LDL showed a tendency to increase while for HDL a tendency to decrease was observed. In the pindolol monotherapy group, a significant reduction of triglycerides (p less than 0.01) and a significant increase of HDL cholesterol (p less than 0.05) were recorded. No significant changes in total cholesterol or LDL fraction were observed. Combined pindolol-clopamide therapy decreased total triglycerides (NS), increased HDL significantly (p less than 0.05) and did not influence total cholesterol and LDL fraction. It is concluded that pindolol does not negatively influence blood lipids as the thiazide-type diuretic clopamide does, and that when both drugs are used together, the beta-blocker can probably counterbalance the diuretic-induced negative effects on blood lipids. Accordingly, it is suggested that pindolol could be a more favorable beta-blocker drug to be used on hypertensive subjects with metabolic coronary risk factors.

Adult↗
PubMed1987

Differences in the lipid peroxidative status, cytochrome P-450 content and microsomal oxygen consumption between right and left lobes of the liver in fetal sheep. Comparison with maternal liver.

The existence of the ductus venosus in mammalian fetal liver determines a different blood flow in the right and left lobes. This asymmetry is associated to a decrease in oxygen delivery to the right lobe. Some stages in oxygen metabolism are related to the formation of free radicals that can induce cellular damage dependent on the tissue oxygen concentration and on the activity of the enzymatic and non enzymatic systems involved in the tissue protection. In the present study, the differences in the lipid peroxidative status and some parameters related to the protection against oxygen toxicity between both lobes in the sheep fetal liver were analyzed and compared to the same parameters in the dam liver.

Animals↗
PubMed1987

Differences in the distribution of energy-metabolizing enzymes in rat brain regions.

The activities of several enzymes of glucose metabolism (glycolytic and tricarboxylic acid pathways) in four different regions of rat brain (cerebellum, medulla oblongata and pons, cerebral cortex and diencephalon) have been studied. Statistical differences were found in the activities of all the enzymes analyzed in the four regions, except in the case of the soluble hexokinase and pyruvate kinase. The changes observed in citrate synthase activity may account for physiological differences in those areas related to myelin formation and energy metabolism. Cerebral cortex and diencephalon showed enzyme activities which were generally greater than those of the cerebellum and medulla oblongata and pons. The results obtained lend support to the concept of a differential energy metabolism in brain regions.

Animals↗
PubMed1986

Differential prooxidative effect of adult and fetal hemoglobin.

Human fetal hemoglobin assayed in a peroxidizing system shows an increased prooxidative effect when compared to human adult hemoglobin. This effect is related only to the oxyhemoglobin form since both fetal and adult methemoglobins did not show any prooxidative effect. The prooxidative effect of the oxyhemoglobin form is ascribed to its increased sensitivity to form superoxide free radicals when transformed to the methemoglobin form. It is proposed that the structure of the heme pocket of fetal oxyhemoglobin enhances free radical release when compared to adult oxyhemoglobin. This difference may be important in some hematological disorders presented by the newborn.

Female↗
PubMed1986

Differential effect of silybin on the Fe2+-ADP and t-butyl hydroperoxide-induced microsomal lipid peroxidation.

We have observed a differential effect of silybin dihemisuccinate on rat liver microsomal oxygen consumption and on lipid peroxidation induced by NADPH-Fe2+-ADP and t-butyl hydroperoxide. These results are ascribed to the antioxidant properties of the flavonoid. The differences observed in the effect of the catalysts may be a consequence of the different capacity of silybin to act as a scavenger of free radicals formed by NADPH-Fe2+-ADP or t-butyl hydroperoxide.

Adenosine Diphosphate↗
PubMed1986

Postmortem activity of the key enzymes of glycolysis. In rat brain regions in relation to time after death.

The activities of the rate-limiting enzymes of glycolytic pathway were measured in various areas of rat brains kept at a temperature of +25 degrees C for various intervals after death by cervical dislocation. Hexokinase shows a substantial decline in activity over a period of 24 h, reaching 41%, 57%, 44%, and 51% of the controls in cerebellum, medulla oblongata and pons, cerebral cortex, and diencephalon, respectively. In the same areas the phosphofructokinase reached 28%, 61%, 60%, and 40% of the zero-time activity, respectively. Lactate dehydrogenase behaves differently in the four areas, with an increase in cerebral cortex and diencephalon and a decrease in cerebellum and medulla oblongata and pons. Pyruvate kinase activity was quite stable over the 24 h period studied. Therefore, the activities of hexokinase and phosphofructokinase in brain tissue were of little value for diagnosis of the time of death.

Animals↗
PubMed1985

Protective effect of the flavonoid silybin dihemisuccinate on the toxicity of phenylhydrazine on rat liver.

Phenylhydrazine is a hemolytic agent whose mechanism of action is related with the formation of free radicals and the induction of lipid peroxidation. The flavonoid silybin dihemisuccinate is an antihepatotoxic principle used in the treatment of many liver diseases; its mechanism of action has been ascribed to its antioxidant properties. This work demonstrates, using a hemoglobin-free perfusion system, the protective effect of the in vivo treatment of the rat with silybin dihemisuccinate on the hepatic glutathione depletion and lipid peroxidation induced by the infusion of phenylhydrazine into the perfusion buffer.

Animals↗
PubMed1985

Inhibitory effect of the flavonoid silymarin on the erythrocyte hemolysis induced by phenylhydrazine.

The flavonoid silymarin, which is used as a therapeutical agent in the treatment of liver diseases, can inhibit the hemolysis and lipid peroxidation induced by phenylhydrazine on erythrocytes obtained from rats treated with the flavonoid. This effect is ascribed to the antioxidant properties as a free radical scavenger exhibited by the flavonoid. Silymarin failed to inhibit the glutathione depletion induced by phenylhydrazine on erythrocytes. It is proposed that the flavonoid acts at the membrane level of the cell avoiding the lipid peroxidative and fluidizing effect of phenylhydrazine.

Animals↗
PubMed1985

Red cell superoxide dismutase activity as an index of human copper nutrition.

Red cell superoxide dismutase (SOD) activity was evaluated as a biochemical index of copper nutrition in a double-blind study of 17 infants recovering from malnutrition and receiving marginal copper intakes. Children were paired on admission by sex, birth weight, nutritional status and antecedents of diarrhea and breast feeding. Nine served as controls receiving a copper sulfate supplement (80 micrograms/kg daily for 120 d; eight received a placebo and were supplemented only if plasma copper levels dropped below 90 micrograms/dl or on d 90 for at least 30 d. After copper supplementation there was a significant rise (paired t-test; P less than 0.05) in plasma copper (96 vs. 165 micrograms/dl); ceruloplasmin (33 vs. 50 mg/dl) and SOD (1073 vs. 1371 U/g Hb). After supplementation these values were similar to those of the controls. SOD was correlated with plasma copper (r = 0.78; P less than 0.001) and not with weight-for-age or weight-for-length. Addition of copper in vitro did not modify the SOD activity. Red cell SOD is a good marker of copper nutrition in humans and correlates well with plasma copper.

Clinical Enzyme Tests↗
PubMed1985

Superoxide radical generation, NADPH oxidase activity, and cytochrome P-450 content of rat liver microsomal fractions in an experimental hyperthyroid state: relation to lipid peroxidation.

The effect of thyroid hormone treatment on hepatic microsomal functions related to NADPH-dependent electron transfer reactions was studied in rats given 0.1 mg T3/kg BW for 1, 2, 3, and 7 consecutive days. This treatment resulted in increased rates of O2-. generation by microsomal fractions, concomitantly with an enhancement in NADPH oxidase activity and decreased cytochrome P-450 content, in livers exhibiting increased respiration. Subsequent studies showed elevated levels of malondialdehyde in microsomal fractions and liver homogenates, as well as augmented chemiluminescent response in the latter system. These results indicate that the calorigenic effect of T3 on the liver tissue is accompanied by a stimulation of microsomal functions involving univalent reduction of oxygen. This cellular response might lead to a greater lipid peroxidative rate and cytochrome P-450 loss as secondary events of thyroid hormone action.

Animals↗
PubMed1985

How to detect bacterial contamination prior to transplantation.

The mortality of kidney transplantation generally amounts to 10% due to infections and GIT complications. Once grafting a Staphylococcus aureus and Streptococcus contaminated kidney the recipient had to undergo emergency surgery four times. Hence it has become our routine to sample the perfusate on blood culture media. Among 145 donor nephrectomies the microbiologic examination of the kidney perfusate in which the graft is stored and transported turned out to be positive in 28%. Four out of five germs isolated after incubation on blood culture media were of the non-pathogenic type seen in the normal flora of the skin. Making use of the CIT (24-30 hours) we cultured the perfusate on blood media. Since the temporary results of the microbiological examination are obtained within 12 hours we can initiate the first choice antibiotic therapy already at the time of transplantation. Though there was proof of highly pathogenic bacteria clinical infection occurred in none of our patients among a total of 114 grafts. The outstanding clinical importance of this diagnostic tool arises from the time sparing information of any contamination and the early hint at the first choice of antibiotics. The distinct application of antibiotics according to the result of the perfusate culture on blood culture media is superior to a general antibiotic cover.

Abdominal Injuries↗