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Biomedical subjects

I Nagy

Publications and source records attributed to I Nagy.

At least 235 records · Page 13Linked to original sources
PubMed1982

Proteases and proteinase inhibitors in experimental glucocorticosteroid myopathy.

The unknown enzymatic mechanism of enhanced protein breakdown in steroid myopathy was studied in functionally and biochemically different muscles of rabbits treated with dexamethasone for three weeks. After glucocorticoid administration the fast-twitch glycolytic semimembraneous muscle of treated animals was atrophied, whereas the weight of the slow-twitch oxidative soleus muscle was not altered. The specific activity of the lysosomal endo- and exopeptidases (cathepsin D, E, B and L, lysosomal carboxypeptidase A and dipeptidylpeptidase I) was increased about 2-fold in the atrophied white muscle. The activity of the cytosol enzyme Ca++-activated neutral proteinase was also elevated, whereas that of the other cytosol endopeptidase, chymotrypsin-like enzyme, was unaltered. The level of alanine aminopeptidase was only slightly increased. On the other hand, there were no unequivocal changes in protease activity in the soleus muscle. These findings are in agreement with the known differences in glucocorticoid-sensitivity of the various muscles. Our results suggest that the lysosomal proteolytic system and the Ca++-activated neutral proteinase may play an important role in the glucocorticoid-induced intracellular protein catabolism in muscle. The inhibitor capacities of cathepsin B and trypsin detectable in muscle cytosol were not altered after steroid treatment. Consequently, the increase in cathepsin B activity was not due to the loss of its inhibitor.

Animals↗
PubMed1981

In vivo effects of vitamin E deficiency on the intracellular monovalent electrolyte concentrations in brain and liver of rat. An energy dispersive X-ray microanalytic study.

Vitamin E is known to play a protective role for cell membranes against free-radical attacks. Vitamin E deficiency causes a rapid macroscopic ageing of rats. On the other hand, during normal ageing, cell membranes undergo functional alterations resulting in an increased intracellular potassium concentration in brain and liver cells. Therefore, is was of interest to study whether vitamin E deficiency produces similar alterations in young rats. Female Wistar rats were fed with a vitamin E deficient diet from 1 month of age for 10 months. The parietal brain cortex and the liver were analyzed by means of a quantitative energy dispersive X-ray microanalytic method using a JEOL JSM-35C-EDAX-711-NOVA-3 system. Monovalent electrolyte contents as well as the water content of the cells were determined in 5 treated and 5 control animals. Water content was measured by analyzing the potassium content in aqueous, frozen state, and again in the dry mass of the cells. On the basis of these data, a computer program calculated the water proportions. Average values for 200 or more cells of each organ per group revealed a significant increase in the intracellular potassium content of the brain cells, whereas the sodium and chloride contents increased to a much lower extent. There was a 2.6% loss of intracellular water in the brain cells in the vitamin E deficient group. The liver monovalent ions and water content remained unchanged. The results obtained are discussed in terms of the membrane hypothesis of ageing.

Aging↗
PubMed1981

Restoration of pituitary prolactin synthesis and release by the administration of morphine to rats bearing a transplanted prolactin-secreting tumor.

Rats bearing transplanted prolactin-secreting tumors are known to have very high prolactin levels in the serum, reduced hypothalamic opiate concentrations, increasing hypothalamic dopamine synthesis and increased hypophyseal portal blood dopamine levels. Further, it has been shown that incubation in 3H-leucine of anterior pituitary glands from these tumor-bearing rats demonstrates a marked inhibition of 3H-prolactin synthesis and release. Using rats with the prolactin-secreting tumor MtTW15, we have found that 4 days of continuous administration of either morphine sulfate 1.44 mg daily or haloperidol 0.11 mg daily using and osmotic infusion pump caused a significant increase in the synthesis and release of 3H-prolactin from incubated pituitary gland compared to untreated tumor-bearing animals. Morphine may reduce hypothalamic dopamine release, whereas haloperidol is a direct dopamine receptor antagonist in achieving these effects.

Animals↗
PubMed1980

Effect of antiestrogens on pituitary prolactin production in normal and pituitary tumor-bearing rats.

Administration of the antiestrogen tamoxifen to normal Buffalo female rats caused a 45% reduction (p less than 0.01) in 3H-prolactin synthesis and release in vitro. Radioimmunoassayable prolactin in incubated glands and medium also decreased significantly. Similar results were observed in Wistar-Furth animals except for in vitro radioimmunoassayable prolactin, which decreased less markedly (by 33%, p less than 0.01). Serum prolactin concentration in treated rats was unchanged. Tamoxifen did not affect the extremely high serum prolactin concentration in rats bearing mammotropic tumors. It further reduced in vitro synthesis of radioactive prolactin but not of the radioimmunoassayable hormone. No interaction between antiestrogens and the dopamine agonist bromocriptine was observed. These observations suggest that the nonsteroidal antiestrogens decrease the synthesis of prolactin but have little effect on release of the hormone. Tamoxifen inhibits growth of transplantable mammotropic tumors MtTW15 and 7315a potently without altering tumor prolactin production. In vivo treatment of adult female rats with tamoxifen did not affect in vitro synthesis and release of radioactive growth hormone, but reversed the elevated growth hormone production of rats bearing 7315a tumors.

Animals↗
PubMed1980

Focal nodular hyperplasia of the liver and hepatic cell adenoma in women on oral contraceptives.

The article reports on the respective occurrence of focal nodular hyperplasia and hepatic cell adenoma in the liver of two women on oral contraceptives. The hepatic cell adenoma showed serious vascular lesions, including peliosis hepatis. Both tumors were removed surgically, and the patients are well. A possible relationship between oral contraception and benign hepatic tumor genesis is discussed under consideration of the pertinent literary data.

Adult↗
PubMed1979

Major metabolic pathways and hormone production in unstimulated monolayer cultures of the rat anterior pituitary.

In cell cultures derived from anterior pituitary glands of rats, enzyme activities of cell homogenates and hormone (GH, PRL, LH, and FSH) content of the culture media were measured. Sex differences in enzyme activities representing major metabolic pathways (citrate cycles, pentose cycles, and glycolysis) were demonstrated both in freshly dispersed cells and in 8-day-old cultures; in cultures of both sexes enzyme activities increased during cultivation. In cultures derived from female rats, cell protein doubled by the 12th day and remained constant for up to the 24th day in culture, whereas enzyme activities showed changes suggesting that cell metabolism shifted to anaerobic glycolysis during cultivation. In the culture media the presence of four pituitary hormones was demonstrated for as long as 3 weeks of cultivation with variable secretion dynamics; the release of gonadotropic hormones diminished gradually whereas that of GH remained constant and PRL levels increased with time. These results indicate that under strictly defined culture conditions pituitary cells may function in spite of profound metabolic changes.

Acid Phosphatase↗
PubMed1979

Some biochemical characteristics of hormone-secreting pituitary tumors and of the host's anterior pituitary gland.

The activity of some glycolytic, oxidative, and degradative enzymes was studied in transplanted rat hormone-secreting pituitary tumors MtTW15 and 7315a and in the host pituitary gland. The elevated serum-hormone concentrations produced by 7315a tumor decreased the size of the host's pituitary gland, its hormone content, and G6P-DH, LDH, PK, and ICDH, but produced no changes in MDH, acid phosphatase, cathepsin-D, and LYSAR enzyme activities (mU/mg tissue). LDH and PK activities were greater in unit weight of pituitary tumors than in pituitary glands. Although more G6P-DH was found in MtTW15 tumor than in normal pituitary tissue, less of the enzyme was detected in 7315a pituitary tumor. It is concluded that elevated serum pituitary hormones selectively decrease hormone production and the activity of some enzymes in the pituitary gland, presumably through a feedback mechanism.

Animals↗