Biomedical subjects
Publications and source records attributed to G Csaba.
A recently recognized bioactive substance of the parathyroid glands, gamma-L-glutamyl-taurine antagonises the metamorphosis enhancing effect of triiodothyronine. Shortening of the body-length of tadpoles is significantly delayed by the substance. The experimental results imply that it fulfills the role of a balance hormone.
In newborn rats serotonin was found to bind the membranes of adrenal medullary cells, to the wall of their vesicles and could be demonstrated also in the nucleus. The observations allowed conclusions concerning the cellular mechanisms of serotonin action.
3H-histamine was incorporated by Tetrahymena partly into membrane-associated structures (cilia), partly into intra-cytoplasmic localizations, and above all into food vacuoles. A considerable amount appeared in the nucleus, in practically exclusive association with the heterochromatin.
In the ovotestis of Helix pomatia both oogenesis and spermatogenesis were influenced by treatments with steroid hormones produced in the gonads of higher vertebrates. Testosterone influenced gametogenesis to a small degree. Progesterone and oestrone-acetate at first stimulated ovogenesis, but they also acted on spermatogenesis. All three hormones examined influenced oogenesis in a conspicuous and significant way, while their effect on spermatogenesis was indistinct.
1. Glutaurine (gamma-L-glutamyl-taurine) isolated from bovine parathyroid and later synthetized retards the metamorphosis of Rana arvalis. 2. From day 13 of treatment glutaurine moderates the metamorphosis inhibiting effect of antibiotics acting at the transcription and translation level.
A method for the demonstration of membrane-localized markers and receptors is described which results from the combination of autoradiography and scanning electronmicroscopy.
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After treatment of rats with 3H-5-hydroxytryptophan, grains indicating the presence of serotonin could be demonstrated in the adrenal medulla. In the beginning, the label is mainly found in the cytoplasm, later, more and more it appears in the nucleus, primarily above the heterochromatin.
Single injections of ecdysone to newborn rats were followed by increases in the weights of the adrenals and decreases in the weights of the thymuses in the adults. No change was registered in body weights and in the weights of the gonads. The plasma androsterone levels seemed to decrease; however, the interindividual differences proved to be too great to draw definite conclusions.
Single gonadotropin treatment of newborn rats caused a 63-71% decrease of TSH-binding on isolated thyroid cells prepared from thyroid glands of both 6- and 13-month-old animals. This fact points out that: (1) in newborn animals the hormone receptors are still plastic and deformable and (2) the damaging effect of the analogous hormone manifests itself at the receptor level.
In Tetrahymena pyriformis the phagocytotic rate increases in response to histamine, but neither the H1 antagonist phenindamine nor the H2 antagonist metiamide stimulate phagocytosis. The H1 antagonist counteracts the effect of histamine, whereas the H2 antagonist does not. The histamine receptor of Tetrahymena is of H1-type, since it cannot distinguish between histamine and antagonists which are closely related to it chemically. It does, however, distinguish between histamine and the chemically unrelated H1 antagonist, phenindamine. The H2 antagonist does not interact with the receptor.
Phagocytosis of Tetrahymena is inhibited by prednisolone-sodium-succinate and deoxy-corticosterone-glucoside, and stimulated by dexamethasone and prednisolone. Dexamethasone and estradiol enter the cells and are localized first in food vacuoles, and later on in the cytosol. They were never found in the nucleus. The demonstration by biochemical methods of a specific glucocorticoid binding protein failed in all three subcellular fractions examined.
Binding of 125I-triiodothyronine to the surface of Tetrahymena was studied by scanning autoradiography. Specific binding sites were found which were confined to cilia and the mouth region. The experiments contribute new data to the phylogenesis of the membrane pattern.
Gamma-L-glutmyl-taurine (Litoralon), a recently detected hormone of parathyroid gland, accelerates maturation of the gut of frog larvae and, similarly as vitamin A, it stimulates the synthesis of polysaccharides.
In Tetrahymena, an increase in the level of cAMP is accompanied by an increased phagocytotic rate, whereas increased sugar uptake is parallelled by a decreased cAMP level. The increase in cAMP level seems to be decisive with respect to phagocytosis as a basic phenomenon of life. In the action of epinephrine, however, some mechanism other than cAMP mediation may be involved. Depending on concentration, one hormone may provoke either an increase or a decrease in cAMP level, and this in turn triggers the corresponding function.
Epinephrine and insulin increased glucose uptake in Planaria, but epinephrine did so to a much grater extent. Glucagon proved to be without effect. The experiments support earlier results according to which in unicellular and invertebrate organisms membrane patterns can be found, which are similar to those of higher organisms and behave like receptors.
The hormone of the parathyroid gland, Glutaurine (gamma-L-glutamyl-taurine) exerts on rat thymus cultures an effect synergistic with vitamin A and antagonistic to prednisolone. When applied in itself, it increased the vitality and macrophage reaction of thymus cultures.