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Biomedical subjects

A Machado

Publications and source records attributed to A Machado.

65 records · Page 4Linked to original sources
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

The influence of age on neurotransmitter turnover in the rat's superior colliculus.

Measurements of the turnover of dopamine, noradrenaline and serotonin and their metabolites have been performed in the superior colliculus of adult and aged rats. The turnover of dopamine, noradrenaline and their metabolites after pargyline treatment was significantly lower in aged rats than in adults. On the contrary, the synthesis rate of serotonin (measured by accumulation of 5-hydroxytryptophan after decarboxylase blockade) and the turnover rate of serotonin (after pargyline treatment) did not change during aging. These findings suggest that aging has a different effect on catecholamines and serotonin turnover in the superior colliculus of the aged rats.

3,4-Dihydroxyphenylacetic Acid↗