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Biomedical subjects

G Csaba

Publications and source records attributed to G Csaba.

At least 397 records · Page 22Linked to original sources
PubMed1982

Involvement of selection and amplification mechanisms in hormone receptor development in a unicellular model system.

It was demonstrated earlier, that long lasting exposure of Tetrahymena to a hormone (histamine) resulted in an increased responsiveness to a later re-exposure. However, it was difficult to establish whether selection or amplification plays a role in receptor differentiation. As diiodotyrosine (T2) enhances the growth of Tetrahymena, in the present experiment the effect of T2-treatment on a long-term culture of Tetrahymena pyriformis was analysed by mathematical-statistical methods to differentiate the effects of selection and amplification mechanisms on hormone receptor development. Although continuous and periodic treatment with T2 enhanced cell division equally, the resulting populations differed in structure. On continuous treatment the population tended to become inhomogenous. The variance tended to increase for 9 days and decreased afterwards without, however, returning to the control level. On periodic treatment the variance was the same as in the control group, but the second and third exposure were significantly more effective than the first treatment, suggesting that the primary encounter with the hormone had given rise to lasting alterations (hormonal imprinting). It follows that continuous exposure involves a selection process which does not, however, account for a steady increase of the growth rate; for initial amplification, taking place also in this condition, and selection which takes effect later, compensate one another's effects. Regarding the unicellular experimental system as a phylo- and ontogenetic model, the conclusion lies close at hand that the selection and amplication mechanisms promote hormone receptor development by joint rather than alternate action.

Analysis of Variance↗
PubMed1982

Influence of hormone concentration and time factor on development of receptor memory in a unicellular (Tetrahymena) model system.

1. Treatment of Tetrahymena pyriformis cells with diiodotyrosine (T2) gave rise to a considerable, concentration-dependent increase of the growth rate within the range of 10(-15) and 10(-9) M, but did not influence it at the level of 10(-18) M. 2. Re-exposure of the cells 1, 2 and 4 weeks later to the hormone concentrations originally used accounted for a marked increase of growth rate at all hormone levels tested, indicating that the extremely low concentration of 10(-18) M, which failed to stimulate growth on first exposure, did nevertheless give rise to hormonal imprinting, which caused the cells to "remember" the hormone, as judged from their increased responsiveness to it on re-exposure. 3. The degree of growth response was concentration-dependent on both first and second exposure: higher levels of treatment gave rise to firmer imprinting, and to greater response on re-exposure. 4. The length of exposure time proved to be more decisive than the level of treatment in respect of the development of hormonal imprinting. 5. Short-term exposures up to 60 min, although they stimulated cell growth by direct effect, gave rise to lasting inhibition of cellular response to re-exposure(s) rather than to hormonal imprinting.

Animals↗
PubMed1982

Detection of different functional states of the cellular nucleus with a new trichrome staining technique.

The new trichrome stain ASTRIN, prepared from alcian blue, safranine, thionine, and resorcin, stains the cell nuclei red or blue, depending on their functional state. Activation of salivary gland cells with pilocarpin, or of liver cell with prednisolone, equally resulted in a quantitative increase of cells with active (blue) nuclei. Changes in nuclear staining after digestion with trypsin, pronase, or ribonuclease, and after extraction of cellular DNA and RNA with perchloric acid, unequivocally suggest that alteration of the protein-DNA ratio, i.e. the hetero- or euchromatic state of nuclear chromatin, is responsible for the disparity of the nuclear staining reaction with ASTRIN. The new trichrome stain seems to be suitable for routine cytodiagnostic use.

Animals↗
PubMed1982

Development and persistence of receptor 'memory' in a unicellular model system.

A single exposure of Tetrahymena to diiodotyrosine stimulated replication of the unicellular organism significantly relative to the control. The stimulatory effect tended to decrease with progressing time, but was still demonstrable after as many as 500 generations. Reexposures to diiodotyrosine also enhanced cell growth, indicating the existence of a receptor 'memory' in respect to the initial exposure, but their effect tended to decline soon after initial stimulation, and did not, in all probability, contribute to the preservation of the 'memory' which itself tends to vanish gradually in due course.

Animals↗
PubMed1982

ASTRIN - a new trichrome staining technique.

The new trichrome stain ASTRIN, composed of alcian blue, safranine, thionine and resorcin, differentiates myocytes from fibrocytes, mature from immature cartilagineous elements, heterochromatic from euchromatic state of nuclear chromatin, and detects neurosecretions. The great differential staining potential of ASTRIN is in all probability due to the dissimilar diffusion rates of its components, for no new dye molecule arises from the combination, as shown by spectrophotometric and thin-layer chromatographic analysis.

Alcian Blue↗
PubMed1982

Effect of polypeptide hormones (insulin, thyrotropin, gonadotropin, adrenocorticotropin) on RNA synthesis in Tetrahymena, as assessed from incorporation of 3H-uridine.

Incorporation of 3H-uridine by RNA in Tetrahymena was differently influenced by insulin, glucagon, follicle-stimulating hormone (FSH), thyrotropic hormone (TSH), adrenocorticotropic hormone (ACTH) and chorion-gonadotropic hormone (PMSG). TSH caused it to increase considerably and durably after an initial depression, while glucagon caused it to rise over the control throughout. Insulin, and especially PMSG, depressed the incorporation of label considerably, the latter to 3-6% of the control value by 120 min. ACTH and FSH accounted for an initial depression of RNA synthesis which, however, returned to normal 30 min after treatment. Remarkably, while the chemically similar hormones acted differently, insulin and glucagon showed the same trend of positive and negative influence, respectively.

Adrenocorticotropic Hormone↗
PubMed1982

The overlapping effects of thyrotropin and gonadotropins on chick embryo gonads in vitro.

Pieces of 12- and 15-day-old chick embryo testes and ovaries were cultured in vitro in the presence of thyrotropin (TSH), gonadotropins (FSH + LH) and adrenocorticotropin (ACTH) for different periods. All the explants of treated gonads differentiated into typical testes or ovaries according to their genetic sex. The gonads of 12-and 15-day-old chick embryos showed a good response to both thyrotropic and gonadotropic stimulation. On the other hand, they did not respond to adrenocorticotropic stimulation. Fifteen-day-old chick embryo testes were grown in tissue culture in the presence of the said hormones. Gonadotropins and TSH enhanced the growth and migration of testicular cells as compared with the control or ACTH treated group. In addition, they maintained the germ cells on the upper surface of epithelial cells. These results have confirmed our previous results in vivo in that gonadotropins and thyrotropin hormones accelerated the development of 12- or 15-day-old chick embryo gonads.

Adrenocorticotropic Hormone↗
PubMed1982

Experimental observations on the mechanism of hormonal imprinting: influence of actinomycin D, methylamine and colchicine on receptor memory in a unicellular model system.

The first interaction between target cell and hormone gives rise to hormonal imprinting, which accounts for greater responsiveness of the cell at later interactions. The mechanism of hormonal imprinting is obscure; we based experimental approach to its closer study on combined treatment of Tetrahymena, as model cells, with diiodotyrosine (T2), which stimulates the division, and cell growth inhibitors, which interfere with different stages of cell reproduction, and methylamine, which inhibits cluster formation in the membrane. Of these, actinomycin D and methylamine inhibited the growth of the Tetrahymena, while colchicine did not, and all three suppressed the division stimulating action of T2, but could not prevent hormonal imprinting, as demonstrated on later re-exposure to T2 of cells preexposed and not preexposed to T2 in combination with the inhibitors. It appears that the underlying mechanism of hormonal imprinting is highly complex, and involves many subcellular mechanisms and structures, but suppression of, or gross interference with, one or another of these cannot delete, only quantitatively reduce, the consequence of the first interaction with the hormone, i.e. hormonal imprinting.

Animals↗
PubMed1982

Overlapping effect of follicle stimulating hormone (FSH) and thyrotropin (TSH) on the ultrastructure of immature chicken testes.

In newly hatched chicken testes the gonadotropin receptors due to their immaturity are not specific but still structurally versatile and so they can bind both FSH and TSH which have a chemically related structure. The functional overlapping effect of FSH and TSH on the ultrastructure of Sertoli and Leydig cells of immature chicken testes was investigated. The activity of Sertoli cells was increased by FSH treatment and this increase correlated well with the amount of SER and RER in cells and with their increased surface activity. The vacuolization and degeneration observed at the apical part of the cells may refer to the formation of testicular tubules. After TSH treatment cell activity increased and in addition a considerable increase in RER and lipid droplets was observed. Fenestrated cisternae were often found in the Sertoli cells of the treated animals. In the Leydig cells, both hormones increased lysosomal activity and the number of lipid droplets. After FSH treatment the amount of SER increased while after TSH treatment the Golgi activity.

Age Factors↗
PubMed1982

Further experiments in unicellular model system to substantiate receptor amplification.

In a previous experiment histamine, a phagocytosis promoting hormone of vertebrates, was employed to enhance the phagocytosis of Tetrahymena to demonstrate the possibility of receptor amplification by a short treatment. A long-term treatment with histamine also stimulated the phagocytotic activity of the Tetrahymena, and the stimulatory effect persisted for some time after return to plain medium. In this experiment the function was observed and the hormone binding of cells was not taken into consideration. In the present study evidence was obtained that a lasting first exposure to histamine durably enhanced the histamine binding capacity of the unicellular. This indicates a parallelism of alterations in the histamine binding capacity and phagocytotic function of Tetrahymena. It was also shown that lasting re-exposure to histamine depressed rather than enhanced the histamine binding.

Animals↗