Biomedical subjects

J Vitorica

Publications and source records attributed to J Vitorica.

41 records · Page 3Linked to original sources

PubMed1984

Age-dependent variations in peroxide-utilizing enzymes from rat brain mitochondria and cytoplasm.

The location of peroxide-utilizing enzymes has been studied in rat brain. Glutathione peroxidase and glutathione reductase distributions indicate that both enzymes are located in the cytoplasm and in the matrix space of "synaptosomal" and "free" mitochondria. On the other hand, catalase distribution parallels that of NADH-cytochrome c reductase (rotenone-insensitive), and appears to be associated with the outer membrane of brain mitochondria. Whereas no gross age-dependent changes in various marker enzymes were found, a gradual but significant increase in glutathione peroxidase from the soluble fraction of free mitochondria was detected. The consequences of such increase are discussed with regard to the reducing potential of the cell.

Aging↗

PubMed1981

Age-related quantitative changes in enzyme activities of rat brain.

The patterns of brain enzymes linked to energy metabolism have been determined in rats aged between 3 and 21 months and compared to those of the developing brain as an estimate of the senescent energy capacity of this organ. During aging, pyruvate kinase increases, pointing towards an enhancement of the glucose-dependence of this organ. However, NAD-isocitrate dehydrogenase declines, suggesting a reduction of Krebs cycle activity in the aged rat brain. An increase in cytoplasmic NAD-malate dehydrogenase found during aging could provide an alternative mechanism of NAD recovery.

Aging↗

PubMed1981

Comparison between developmental and senescent changes in enzyme activities linked to energy metabolism in rat heart.

The developmental and senescent patterns of a number of heart enzyme activities linked to energy metabolism have been studied in rats aged between 4 days and 21 months. A morphometric study of mitochondrial volume fractions and numbers has been also carried out. Developmental changes result in a rise of most mitochondrial enzymes (NADP+-isocitrate dehydrogenase, malic enzyme, succinate dehydrogenase, citrate synthase) and mitochondrial volume fractions. Exceptions are NAD+-isocitrate dehydrogenase, which declines from 4 days onwards, and NAD+-malate dehydrogenase, which declines and then rises over the same period. Senescent changes follow two different trends. While pyruvate kinase and those mitochondrial enzymes lying between citrate formation and isocitrate oxidation (citrate synthase, NADP+-and NAD+-isocitrate dehydrogenases) decline to some degree, mitochondrial succinate dehydrogenase and NAD+-malate dehydrogenase activities increase over the same period. This could point towards a partial impairment of Krebs cycle function, and a reduced energy-producing capacity in the aged rat heart.

Aging↗

PubMed1981

Metabolic implications of ageing: changes in activities of key lipogenic and gluconeogenic enzymes in the aged rat liver.

The variations in enzyme activities involved in the main pathways of liver energetic metabolism--glycolysis, Krebs cycle, gluconeogenesis and lipogenesis--have been studied in rats ranging between the age of 4 days and 21 months. The major changes observed are the following: (1) enzymes involved in glycolysis (pyruvate kinase) and lipogenesis (NADP-malic enzyme, ATP-citrate lyase) decrease in activity during ageing, and (2) gluconeogenic enzymes (phosphoenolpyruvate carboxykinase, glucose-6-phosphatase) are maintained or slightly increased over the same period. The results suggest that an increase in the capacity for gluconeogenesis with respect to that for lipogenesis takes place in the aged rat liver.

ATP Citrate (pro-S)-Lyase↗

PubMedDate not supplied

Changes of calcium homeostasis in nerve endings during aging.

Calcium uptake reduction in synaptosomes observed in old rats is partly due to a decreased calcium influx through brain voltage-dependent calcium channels. This defect is not due to differences in the polarization of the plasma membrane, but rather to the influx of calcium itself, and may be accentuated at lower concentrations of calcium. We found that the cytosolic calcium concentration in 24-month-old rats is higher than in adults, both at rest and under K-depolarization, and it is suggested that these high calcium levels may partially inactivate synaptosomal calcium channels. The mitochondrial defect may be partially responsible for the increase in cytosolic calcium with age in K-depolarized synaptosomes, but other factors are probably responsible for the increase in resting (Ca2+).

Aging↗