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Biomedical subjects

J Mourek

Publications and source records attributed to J Mourek.

At least 73 records · Page 4Linked to original sources
PubMed1982

Adenylate cyclase activity in crude plasma membranes of subcutaneous adipocytes during ontogenetic development of rats.

In order to explain the differences in the hormone stimulated lipolysis during ontogenic development of rats, the activity of adenylate cyclase was determined in crude plasma membranes of subcutaneous adipocytes of 5, 14, 21 and 45 to 55-day-old animals. Stimulatory effects of nonhormonal and hormonal agents were expressed as the increment in percentage of basal values which were not significantly changed in the age groups studied. The highest stimulatory effect was observed after sodium fluoride in 14 and 21-day-old rats. Guanylylimidodiphosphate and GTP revealed the lowest stimulatory effects in adult animals (greater than 45-day-old). The beta-adrenergic agent isoproterenol revealed the highest stimulatory effect in the 5 and 45-day-old group while in the preparation from 14-day-old rats the adenylate cyclase activity was significantly lower. On the other hand, tetracosactide (beta 1-24-corticotropin) revealed the smallest stimulatory effect on the preparation from 5-day-old rats; its stimulatory effect steadily increased and reached the highest value in adenylate cyclase preparations from adult animals. It can be concluded that the adenylate cyclase system in subcutaneous adipocytes is already basically mature at early ontogenic stages of development in rats. Nevertheless, the explanation for the small variations of the enzyme activity in different age groups requires further study.

Adenylyl Cyclases↗
PubMed1982

Ontogenetic studies on adrenergic lipolysis in rat adipocytes from subcutaneous adipose tissue.

The in vitro release of free fatty acids from small adipocytes (mean diameter 24.4 +/- 0.4 micrometer; 11-42 micrometer) isolated from subcutaneous adipose tissue of rats aged 5, 14, 21 and 35 days was induced by l-isoprenaline (ISO), l-noradrenaline (NA) or l-adrenaline (ADR). The results were related to a cell count of 10(6) and compared to results in adult rats [both sexes, fed ad libitum, mean weight 180-210 g). The cell yield decreased with development, i.e. it was highest in the youngest rats. In adult rats, increasing catecholamine (CA) concentrations produced pronounced concentration-dependent lipolysis in the potency order ISO greater than NA greater than ADR which is typical of beta 1-adrenergic functions. Qualitatively the same results in 5- and 35-day-old rats were observed, the latter showing greater sensitivity towards CA. Practically no lipolytic response was recorded in 14 and 21-day-old animals, however. Not one of the CA, nor any of the concentrations used, could evoke lipolysis in these animals. The experiments were carried out simultaneously on different age groups, technical errors can therefore be excluded.

Adipose Tissue↗
PubMed1981

Effect of a short-term fasting and altitude hypoxia on the cytochrome oxidase activity of rat brain mitochondria.

The effect of short-term fasting and thirst, prolonged fasting and hypoxic hypoxia upon the activity of cytochrome oxidase was studied in mitochondrial fractions obtained from the brain and the liver. The investigation was carried out in two groups of rats, 5 and 60 days old. a) The activity of cytochrome oxidase in mitochondria isolated from the brain cortex, subcortical regions and the medulla oblongata rises, while the changes in liver mitochondrial fractions are reverse. b) A significant increase of mitochondrial cytochrome oxidase was found in 5-day-old rats after both types of fasting and hypoxia in all regions of the brain, as well as in the liver. c) The cytochrome oxidase activity in brain and liver mitochondria of 60-day-old rats was not affected appreciably after 24 h nutritional deprivation, with the exception of a significant rise of activity in the medulla oblongata. Prolonged fasting and hypoxia again markedly increased the activity of this enzyme in all regions of the brain and in the liver.

Animals↗
PubMed1981

Influence of age and of short-term and repeated fasting on the cytochrome concentration in mitochondria isolated from different parts of the rat CNS and liver.

The authors measured the cytochrome a+a3, b and c+c1 content of mitochondria isolated from the cerebral cortex, subcortical structures, medulla oblongata and liver of male rats aged 5 and 60 days. They found that the amount of cytochrome a+a3, b and c+c1 in the cerebral cortex, of cytochrome a+a3 and b in subcortical structures and of only cytochrome a+a3 in medulla oblongata and liver mitochondria rose during ontogenesis. A single short-term (24 h) fast reduced the cytochrome a+a3 and b content of the cerebral cortex and the cytochrome a+a3 content of the medulla oblongata in 5-day-old rats. In 60-day-old animals, there was a drop in the cytochrome a+a3 and b concentration in the cerebral cortex and in the a+a3 concentration in liver mitochondria. Repeated fasting (3 X 18 hours) reduced the cytochrome a+a3 content of mitochondria isolated from all the given parts of the CNS in 5-day-old rats.

Aging↗
PubMed1979

Effect of altitude hypoxia on ATPase activity in the brain of rats of different ages.

In experiments on 5-day-old and adult rats of both sexes, the authors investigated Na+--K+-stimulated and Mg2+-dependent ATPase activity in the cerebral cortex, subcortical formations and the medulla oblongata. They studied the effect of 20 min acute altitude hypoxia corresponding to either 7,000 or 9,000 m, in a thermostable chamber (30 degrees C). ATPase activity was found to increase during ontogenesis -- this being the greatest in cortical tissue and the least in the medulla oblongata. Hypoxia corresponding to 7,000 m altitude significantly depressed total ATPase activity in 5-day-old rats, but significantly stimulated it in adult animals. Changes in Na+--K+-stimulated ATPase activity played the major role in these changes. Hypoxia corresponding to 9,000 m altitude likewise depressed total ATPase activity in 5-day-old rats and to practically the same extent as moderate hypoxia (7,000 m). In adult rats, marked hypoxia (9,000 m) significantly reduced only Mg2+-dependent ATPase activity. Mg2+ activity rose during ontogenesis to a lesser degree than Na+--K+-stimulated ATPase and the reciprocal ratio of these ATPase and the reciprocal ratio of these ATPase activities, in the given parts of the brain, fell progressively in adult animals to values close to 1.

Adenosine Triphosphatases↗