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Biomedical subjects

G Csaba

Publications and source records attributed to G Csaba.

At least 289 records · Page 16Linked to original sources
PubMed1987

The role of Ca2+ in hormonal imprinting of the Tetrahymena.

It is known from model experiments on Tetrahymena that primary exposure to a hormone induces receptor formation or amplification, in other words a hormonal imprinting. Substances acting on the intracellular Ca2+ level of the Tetrahymena, such as TMB-8, EDTA, EGTA, NiCl2 and La(NO3)3, interfered with hormonal imprinting of the unicellular to different degrees, and some of them influenced hormone (insulin, TSH) binding also independently of imprinting. Interference with the intracellular Ca-metabolism generally influenced imprinting by insulin and TSH, which were mediated by different mechanisms, to dissimilar degrees, or in opposite directions. On combined application of the agents acting on Ca-metabolism, their effects were additive. It appears that intact Ca-mediation is an essential prerequisite for normal hormonal imprinting.

Calcium↗
PubMed1987

Influence of hormonal imprinting on hormone level. Permanent receptor damaging effect of pituitary hormones administered to newly-hatched cockerels.

The overlapping effect of TSH and FSH on the gonad and on the thyroid gland can be demonstrated in cockerels even at the age of five weeks. These hormones influence the secretion of testosterone in a similar way and to a similar extent, while on the thyroxine level the influence of the specific hormone is more pronounced. Neonatal FSH and TSH treatment considerably decreased the basal testosterone level measured at the age of five weeks. Neonatal FSH treatment increased the basal T4 level while TSH treatment decreased it. The effect of TSH treatment administered at the age of five weeks in increasing the testosterone level was weakened after neonatal pretreatment with any iodine hormone. The effect of TSH treatment could only be inhibited by neonatal FSH pretreatment. Neonatal pretreatment with any of the trophormones caused a diminution of the T4 level augmenting of FSH and TSH administered at the age of five weeks.

Animals↗
PubMed1987

Effect of embryonic and/or neonatal diethylstilbestrol and allylestrenol treatment on postnatal development of the chick testis.

The synthetic steroid diethylstilbestrol (DES) and the steroid-like allylestrenol (AE) have been used for years in human medicine for the protection of pregnancy. The hazards to the fetus of gestational DES treatment are well established [2, 17, 18]. Knowledge of a similar effect of AE is still fragmentary. Therefore, further studies are required of the after-effects of embryonic and perinatal AE exposure. In our earlier experiments with polypeptide hormones [4, 5, 6] we have observed that perinatal age is a critical period in the maturation of hormone receptors. In this period the presence of hormone induces the development of its specific receptors. The phenomenon is termed hormonal imprinting [4, 5, 6]. During its maturation the receptor is flexible and the presence of non-specific hormones capable of binding to it may alter its normal development Accordingly, even a single hormone injection in the perinatal period may alter the hormone-sensitivity of the target organ.

Allylestrenol↗
PubMed1987

The effect of varying illumination on imprinting of Tetrahymena by insulin.

Tetrahymena pyriformis cultures were imprinted with insulin. Hormone binding was reduced in the dark, but alternation of dark and light periods were in this respect more effective than the dark itself. The deviations observed may be attributed, besides the reduced insulin binding by the imprinted cells in the dark, to an enhanced binding by the non-imprinted control cells kept in the dark. It is suggested that the dark-induced structural transformation of the membrane, manifesting among others in a changed hormone binding, may be caused by alterations in haem synthesis due to varying illumination.

Animals↗
PubMed1987

Presence (hPL, prostaglandin) and absence (triiodothyronine, thyroxine) of hormones in Tetrahymena: experimental facts and open questions.

The RIA technique detected prostaglandin (PGF2) and human placetal lactogen (hPL) in Tetrahymena cultures grown in bacto tryptone + yeast extract medium which, however, itself contained these hormones. About one to two per cent of the total hormone content of the medium was demonstrated intracellularly. Treatment with diiodotyrosine (T2), which is known to stimulate the growth of Tetrahymena, was followed by a decrease in the intracellular prostaglandin level. Triiodothyronine and thyroxine were not detected in Tetrahymena or in the medium, and did not appear in it on induction with TSH either. In the light of these observations it might well be doubted that prostaglandin was native in Tetrahymena: the use of synthetic media, and/or a reliable demonstration of the hormone content of the growth medium is recommended for evidence of hormone biosynthesis by unicellular organisms.

Animals↗
PubMed1987

A single neonatal treatment with methylcholanthrene or benzo(a)pyrene alters microsomal enzyme activity for life.

A single neonatal exposure to methylcholanthrene or benzo(a)-pyrene altered the hepatic microsomal enzyme activity of rats for a long time. Methylcholanthrene depressed, whereas benzo(a)pyrene enhanced the activity of the microsomal enzyme system. The former had a greater influence on males than on females, whereas the latter acted practically uniformly on both sexes.

Animals↗
PubMed1987

Localisation of 3H-corticosterone inside thymocytes at different stages of ontogenetic development.

The thymocytes of newborn rats incorporated considerably greater amounts of labeled corticosterone in culture than those of two or four weeks old rats. The incorporation of label tended to increase up to 5 min of exposure in all age groups, but did not further increase in any during longer exposures. The hormone entered the nucleus of the thymocytes and assumed primarily a heterochromatic localisation.

Aging↗
PubMed1987

Internalization of receptor and hormone after hormonal imprinting, as detected with colloidal gold labeled insulin in cultures of a permanent liver cell line.

The intracellular localization of internalized colloidal gold-labeled hormone differed markedly between Chang liver cells pretreated and not pretreated with insulin. While the non-imprinted cells bound little hormone in the coated pits and internalized it mainly inside smooth vesicles, the imprinted cells bound the bulk of hormone in coated pits and coated vesicles. Later the label appeared inside the lysosomes and in the imprinted cells it was abundantly present also in extra-lysosomal localizations, mainly on the nuclear membrane and inside the nucleus. These observations disclosed some new information on the internalization of the receptor-hormone complex, and on the mechanism of hormonal imprinting as well.

Animals↗
PubMed1986

Simultaneous electron microscopic detection of colloidal gold labeled ligand and adenylate cyclase. Influence of concanavalin-A on adenylate cyclase activity of fibroblasts.

Concanavalin-A-colloidal gold (Con-A-G) complex and adenylate cyclase activity were detected simultaneously in electron microscopic preparations of human fibroblast cultures, by a combined histochemical technique. The colloidal gold particles appeared as round bodies which could be readily differentiated from the amorphous product of the adenylate cyclase enzyme reaction. The combined technique makes possible the simultaneous visualization of the bound ligand (i.e. of its binding site), and of the enzyme activated by the ligand. Treatment of the cells with Con-A accounted for a considerable increase in intracellular adenylate cyclase activity. The activity increase was disproportionally greater than the amount of bound ligand, and it also appeared in localizations showing no indication of ligand binding. Treatment of the fibroblasts with Con-A was followed by internalization of the ligand and the enzyme inside at least seemingly segregated vesicles.

Adenylyl Cyclases↗
PubMed1986

Suitability of oligopeptides for induction of hormonal imprinting--implications on receptor and hormone evolution.

Hormonal imprinting induced in Tetrahymena and in Chang liver cells with di-, tri-, tetra- and pentapeptides (synthetic opioids and their fragments) has shown that both cell types are able to differentiate the related molecules from one another. The dipeptide phenylalanine + proline induced a measurable imprinting in the liver cells, and chain length increase, especially terminal coupling with tyrosine enhanced the imprinting potential enormously. Intra-chain changes in the amino acid sequence had a measurable effect on the intensity of imprinting. The molecules showing the relatively strongest physiological action accounted for the most intensive imprinting in both cell types; this indicates that, in all probability, induction of binding site formation plays a key role in the development of signal molecules, and thereby in hormone evolution.

Animals↗
PubMed1986

Receptor-level interrelationships of amino acids and the adequate amino acid type hormones in Tetrahymena: a receptor evolution model.

Histidine stimulates the phagocytosis of Tetrahymena to the same extent as histamine, and also stimulates its division, which histamine does not. Tyrosine and diiodotyrosine equally stimulate the growth of the Tetrahymena. Both amino acids inhibit the characteristic influence of the adequate amino acid hormone when added to Tetrahymena culture 72 h in advance of it. Primary interaction with diiodotyrosine and tyrosine notably increases the cellular growth rate. Histamine has a similar, although less notable effect than histidine. In the light of these experimental observations there is reason to postulate that the receptors of the amino acid hormones have developed from amino acid receptors.

Animals↗
PubMed1986

Studies on internalization and intracellular localization of membrane DNA in mouse peritoneal macrophages, by means of lactoferrin-gold complex.

It is an experimental fact that lactoferrin binds to DNA. In the present study, a lactoferrin-gold complex was first bound by the cell surface, then became internalized (inside coated or smooth vesicles). Intracellularly the complex appeared in tube-like or vesicle-like structures, which approximated the nucleus, and some vesicles even showed indications of association with the external nuclear membrane. Neither membrane binding, nor internization of the lactoferrin-gold complex had taken place in cells pretreated with DNase.

Animals↗
PubMed1986

Internalization and localization of membrane-associated DNA in the Tetrahymena.

The Tetrahymena does possess membrane-associated DNA, which binds the DNA-ase-gold complex. After binding, the DNA-DNA-ase-gold complex entered the cells mainly in vacuoles delimited by unilamellar membranes, less often in coated vesicles, which released the complex near to the nucleus, to judge from appearance of gold colloid particles along the nuclear membrane and, occasionally, above the nuclear pore or, infrequently, inside the nucleus itself.

Animals↗