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Biomedical subjects

A Machado

Publications and source records attributed to A Machado.

At least 199 records · Page 11Linked to original sources
PubMed1980

Development of NADPH-producing pathways in rat heart.

The behaviours of the principal NADPH-producing enzymes (glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, cytoplasmic and mitochondrial 'malic' enzyme and NAPD+-dependent isocitrate dehydrogenase) were studied during the development of rat heart and compared with those in brain and liver. 1. The enzymes belonging to the pentose phosphate pathway exhibit lower activities in heart than in other tissues throughout development. 2. The pattern of induction of heart cytoplasmic and mitochondrial 'malic' enzymes does not parallel that found in liver. Heart mitochondrial enzyme is slowly induced from birth onwards. 3. NADP+-dependent isocitrate dehydrogenase has similar activities in all tissues in 18-day foetuses. 4. Heart mitochondrial NADP+-dependent isocitrate dehydrogenase is greatly induced in the adult, where it attains a 10-fold higher activity than in liver. 5. The physiological functions of mitochondrial 'malic' enzyme and NADP+-dependent isocitrate dehydrogenase are discussed.

Animals↗
PubMed1980

Effect of cerebellar lesions on monoamine levels in various brain areas of the cat.

Modifications in thee content of monoamines after different lesions of the cerebellar cortex were investigated in eight prosencephalic structures of cat's brain. Apart from other minor changes, lesions of the posterior vermis induced significant changes in the thalamus (decrease of DA and increase of 5-HT). Lesions of the cortex of a cerebellar hemisphere, on the other hand, produced an increase of 5-HT in the caudate nucleus and an increase of DA in the hippocampus in addition to a generalized increase of 5-HT in all the prosencephalic structures studied. These findings are discussed in relation to the anatomical connections of the lesioned areas and their expected role in the sleep-wakefulness cycle.

Animals↗
PubMed1977

Isocitrate dehydrogenase of Tetrahymena pyriformis.

We have studied the isocitrate dehydrogenase of Tetrahymena pyriformis. This enzyme is able to utilize both NAD and NADP, but kinetic studies suggest that the enzymatic activity with NAD is not of physiological signifance. Some of the factors that might regualte the NADP-dependent isocitrate dehydrogenase were also studied. This enzyme has an absolute requirement for divalent cations; Mg,+ and Mn2+ will serve as cofactors but the latter is more effective than the former. It is known that this enzyme is subject to a concerted inhibition by oxaloacetate and glyoxylate. Either glyoxylate or oxaloacetate alone also are capable of inhibiting the enzyme although higher concentrations are required. We have found concerted inhibition also for the NAD-dependent isocitrate dehydrogenase from rat liver and yeast. The activity of the Tetrahymena pyriformis enzyme is inhibited by NADPH. This inhibition is competitive with NADP. The Ki and Km values are, respectively, 20 micrometers and 18 micrometers.

Animals↗
PubMed1976

Regulation of the level of yeasts citrate synthase by oxygen availability.

The activity of yeasts citrate synthase in cells grown under different hypoxic conditions has been investigated. A linear relationship between the citrate synthase activity and the respiratory capacity of the cells has been found. When Saccharomyces cerevisiae was grown on fermentable substrates the activity decreased as the concentration of sugars in the medium increased. The enzyme of the yeast Rhodoturula showed a high activity in spite of the existence of high sugar concentration in the culture medium. Neither feed-back repression by glutamate nor feed-forward induction by ammonia has been found in bakers' yeast. The results suggest that the regulation of the enzyme by oxygen availability takes place by the ""de novo'' synthesis of the enzyme.

Acetates↗
PubMed1976

Annular subvalvular left ventricular aneurysm in Bahia, Brazil.

Two cases of left ventricular aneurysm, a 16-year-old black boy and a 23-year-old white girl, from Bahia, Brazil, are presented. In both patients there was enlargement of the cardiac silhouette and a prominent bulge of the left inferior border. On the right oblique view a ring of calcium at the ventricular opening of the aneurysms was visualized. A left ventriculogram showed a huge aneurysm in the first case and a bulge on the lateral wall of the left ventricle in the other. Cardiac catheterization showed a rise in left and right ventricular end-diastolic pressures and in the mean pulmonary artery pressure. In the first case the contour of the right ventricular pressure curve showed a restrictive pattern. The similarities of these aneurysms with the annular submitral type described in young black Africans are stressed.

Adolescent↗
PubMed1975

Isocitrate dehydrogenases and oxoglutarate dehydrogenase activities of baker's yeast grown in a variety of hypoxic conditions.

The activities of isocitrate dehydrogenase (NAD), isocitrate dehydrogenase (NADP) and oxoglutarate dehydrogenase have been investigated in Saccharomyces cerevisiae grown in a variety of aerobic and hypoxic conditions, the latter including oxygen deprivation, high glucose concentration, addition of inhibitors of mitochondrial protein synthesis, respiratory inhibition by azide, and impaired respiration mutants. All hypoxic conditions led to a marked decrease of oxoglutarate dehydrogenase and significant decreases of the two isocitrate dehydrogenases. According to its kinetic properties, the NAD-isocitrate dehydrogenase will not be operative in hypoxia "in vivo". From these and other related facts it is concluded that hypoxic conditions in yeast generally lead to a splitting of the tricarboxylic acid cycle and that glutamate synthesis in these conditions takes place through the coupling of the NADP-linked isocitrate and glutamate dehydrogenases.

Aerobiosis↗
PubMedDate not supplied

Effects of development and ageing on pulmonary NADPH-cytochrome c reductase, glutathione peroxidase, glutathione reductase and thioredoxin reductase activities in male and female rats.

The behaviour of the principal NADPH-consuming detoxification enzymes (NADPH-cytochrome c reductase, glutathione peroxidase-glutathione reductase system, and thioredoxin reductase) was studied during development and senescence of the rat lung. We have also studied the influence of sex on the development and senescent values. The NADPH-cytochrome c reductase activity increases at birth and afterwards remains constant until the 25th day after birth, at which age there is a maximum activity. Its activity decreases during the ageing period in both sexes. The glutathione reductase and thioredoxin reductase activities show significant differences with respect to sex during the adult stage, however during ageing these differences disappear. These enzymes show maximum activity at 25 days after birth, and afterwards the activity decreases continuously until the adult levels are reached. The activity of glutathione reductase is increased during the ageing period, especially in the female rats, however, in senescence the levels of thioredoxin reductase are lower than in the adult stage. The glutathione peroxidase shows a significant difference between both sexes during senescence and in the male its activity in this stage is higher than during development and adulthood.

Aging↗
PubMedDate not supplied

Relationship between enzymatic activity loss and post-translational protein modification in aging.

During aging, there is a decrease in the activity of many enzymes. The mechanism causing the loss of activity is still not well understood in most cases. We have studied the decrease in the activities of the malic, 6-phosphogluconate dehydrogenase and superoxide dismutase enzymes. The old malic enzyme is about 36% less active than the young enzyme and the old 6-phosphogluconic dehydrogenase enzyme is about 26% less active than the young enzyme. In this paper, some chemical properties of these enzymes are studied. Diethyl pyrocarbonate measurements indicate that the old malic enzyme has 1 histidine residue less than the young malic enzyme. Moreover, the treatment of the young malic enzyme with ascorbate for 15 min produces the loss of 36% of enzymatic activity and the loss of 1.2 histidine residues. 2,4,6-trinitrobenzenesulfonic acid measurements indicate that the old 6-phosphogluconate dehydrogenase enzyme has 11 lysine residues less than the young 6-phosphogluconate dehydrogenase enzyme. The proteolysis with trypsin produces more peptides in the young 6-phosphogluconate dehydrogenase enzyme than in the old one. However, similar numbers of peptides were produced when endoproteinase Arg-C was used in both enzymes, young and old 6-phosphogluconate dehydrogenase. Moreover, the treatment of young 6-phosphogluconate dehydrogenase enzyme with ascorbate for 15 min produces the loss of 8 lysine residues. These results suggest that during aging the modification of histidine residue could be involved in the loss of malic enzyme activity, and the modification of lysine residues could be involved in the loss of 6-phosphogluconate dehydrogenase activity. These results could also suggest that the modification of histidine and lysine residues during aging could be produced by oxidation. This could be a general process in aging, with an increase in the oxidation of many proteins. The relevance of this process in the aging effects must be related to the kind of proteins that are susceptible of oxidation and that this oxidation affects their enzymatic or biological function. We have also studied other enzymes one of which is the superoxide dismutase enzyme involved in the protection against oxidative damage. Our results are similar to those described for malic enzyme. In the latter case, the failure to measure one of the histidines in the Cu/Zn SOD is due to a chemical modification, probably caused by oxidation of the residue.

Journal Article↗