Biomedical subjects

G Csaba

Publications and source records attributed to G Csaba.

At least 55 records · Page 3Linked to original sources

PubMed1998

The effects of ceramide and its analogues on the secretion of the mucocyst content of Tetrahymena.

Monoclonal antibody to Geodia lectin is bound by the mucocyst content of Tetrahymena. By using this (fluorescent-labelled) antibody and confocal microscopy, the actual state of the mucocyst (position, resting, filling or extruding) can be studied. Treatment with C2 ceramide and non-hydroxy fatty acid caused a rapid depletion of mucocyst material. Another ceramide analogue, psychosine caused fusion of mucocysts. In these cases--in contrast to the controls--the contractile vacuole was filled with mucocyst material and this was seen in the tubules in contact with the contractile vacuoles. Hydroxy fatty acid ceramide, sphingomyelin and sphingosine-1-phosphate were ineffective. As the former materials influence also the cytoskeleton, while the latter do not, the cytoskeleton is presumed to have a mediatory effect. Neither the connection of contractile vacuoles with tubular structures nor mucocyst fusion have been described before.

Animals↗

PubMed1997

Phospholipase D activity in the Tetrahymena pyriformis GL.

Phospholipase D (PLD) is an enzyme which participates in the signaling mechanism cleaving phosphatidylcholine (PC) to choline and phosphatidic acid (PA). In Tetrahymena pyriformis GL this enzyme activity is enhanced by different kinds of agonists (sodium orthovanadate, sodium fluoride and phorbol 12-myristate 13-acetate), and its activity can be inhibited by inhibitors such as pertussis toxin, calphostin C, genistein, trifluoperazine. These results suggest that the PLD signalling pathway is connected with the tyrosine kinase, phospholipase C, phosphatidylinositol and G-protein coupled signalling pathways. By demonstrating the PLD activity in Tetrahymena our knowledge on the signaling mechanisms at a unicellular level has been extended. The results support our view that most transducing mechanisms that are characteristic of mammalian cells are also in the protozoan Tetrahymena.

Animals↗

PubMed1997

Identification of lectins in the kinetids of Tetrahymena pyriformis.

Previously we described lectin-like molecules in the ciliate Tetrahymena pyriformis; by application of synthetic neoglycoconjugates it is now shown that T. pyriformis contains considerable amounts of both a beta-D-glucose- and a lactose-specific lectin. No evidence for the presence of alpha-D-mannose-, alpha-D-galactose- or of alpha-L-fucose-specific lectins could be obtained. The two lectins, identified in T. pyriformis, are associated with the kinetids. During cell division the lectins disappear or become masked in the fission furrow. Therefore, we assume that these lectins are involved in the organization of the distribution pattern of the kinetids during cell division perhaps due to lectin-glycoprotein interactions.

Albumins↗

PubMed1997

Time- and concentration-dependence of the growth-promoting activity of insulin and histamine in Tetrahymena. Application of the MTT-method for the determination of cell proliferation in a protozoan model.

The unicellular ciliate Tetrahymena pyriformis was treated with different concentrations of insulin or histamine and at different time points the cell density was measured, using a tetrazolium-based semiautomated colorimetric assay (MTT). The assay was suitable to determine the rate of cell proliferation of Tetrahymena. Insulin in each concentration significantly elevated the cell count up to 3 h. After that, it was neutral or its effect was insignificant. Histamine at 10(-5) M concentration diminished cell count at 3, 5, 7 and 24 h. At 10(-6) M concentration there was no difference and at 10(-7) M concentration it enhanced cell division up to 5 h, after that there being no difference. The two hormones have cell division promoting activity for cells of higher animals and the experiments demonstrate this effect already at a unicellular level.

Animals↗

PubMed1997

Effects of dipeptides containing the amino acid, proline on the chemotaxis of Tetrahymena pyriformis. Evolutionary conclusions on the formation of hormone receptors and hormones.

Our investigations demonstrate that proline-containing dipeptides can provoke a chemosensory response from the unicellular Tetrahymena pyriformis. The chemotactic effects of the dipeptides have a close relationship with the side chain and the lipophilicity of the amino-terminal amino acid. Comparison of 'mirror' variants of proline-containing dipeptides points to the fact that dipeptides with small side chain and non-polar character amino acids (Gly-Pro, Ala-Pro) are preferred on the amino-terminal end. In the case of amino acids with very variable side chains, small (Pro-Gly) and the large side chain and non-polar character amino acids (Pro-Leu, Pro-Phe) on the carboxyl-terminal end can induce significant chemotactic responses. With valine on any terminus the proline-containing dipeptide induced a weak repellent effect.

Animals↗

PubMed1997

Increased apoptosis of adult rat lymphocytes after single neonatal vitamin A treatment (hormonal imprinting). A flow cytometric analysis.

Newborn rats were treated with a single dose of vitamin A (retinol) and apoptosis of peripheral lymphocytes was studied by flow cytometry in adult age. Vitamin A treatment (hormonal imprinting) caused a moderate, however significant elevation in the number of apoptotic lymphocytes after three months. Dexamethasone or Concanavalin-A alone did not influence apoptosis significantly. However, in the neonatally retinol treated rats dexamathasone significantly elevated the quantity of apoptotic lymphocytes related to the control or Concanavalin-A treated control cells. The results call attention to the prolonged effect of hormonal imprinting in a new index and to the possible dangerous effects in human, neonatally treated with vitamin A.

Animals↗

PubMed1997

Effect of combined neonatal imprinting by vitamin A, vitamin D3, benzpyrene and allylestrenol on adult rat thymus glucocorticoid and uterine estrogen receptors.

1. Combined neonatal imprinting with allylestrenol, vitamins A and D3 and benzpyrene significantly increased thymic glucocorticoid receptor capacity in male and female animals and decreased receptors affinity in adult females only. 2. Uterine estrogen receptor affinity or density was not influenced. 3. Considering that perinatal treatment with allylestrenol or vitamin D3 decreased glucocorticoid receptor capacity, the dominance of the positive effect of retinol should be surmised. 4. The experiments call attention to the interrelation of different materials acting simultaneously in the perinatal period.

Allylestrenol↗

PubMed1997

Effect of 3-amino-1-propanol on the phosphatidylinositol (PI) and glycosyl phosphatidylinositol (GPI) systems of Tetrahymena.

3-Amino-1-propanol (AP), a substance replacing ethanolamine in phosphatidylethanolamine (PE) significantly reduced 32P incorporation to phosphatidylinositol (PI) and glycosyl-phosphatidylinositol (GPI) in the unicellular organism Tetrahymena pyriformis. At 10 mM, AP completely inhibited the incorporation of 32P into PI. 3H-arachidonate incorporation into PI was also inhibited, while that into diacylglycerol (DAG) was high. The experiments indicate the presence and metabolism of inositol phospholipids and GPI in T. pyriformis.

Animals↗

PubMed1997

Indomethacin alters phospholipid and arachidonate metabolism in Tetrahymena pyriformis.

Indomethacin an inhibitor of the cyclooxygenase pathway for arachidonate metabolism in vertebrates, totally inhibited 32P incorporation into phospholipids at a dose of 2.0 or 5.0 mM in Tetrahymena. Treatment with 0.1 mM indomethacin caused higher arachidonic acid (AA) incorporation into phosphatidylinositol (PI) and lower incorporation into phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (4,5) bisphosphate (PIP2). The same treatments in the presence of 3H-AA resulted in a significantly elevated 3H-diacylglycerol (DAG) level and free AA level compared with control cells. Indomethacin influences the lipid cycle and therefore the inositol phosphate cycle in Tetrahymena.

Animals↗

PubMed1997

PLA2 activity in Tetrahymena pyriformis. Effects of inhibitors and stimulators.

Phospholipase A2 (PLA2) is an enzyme which participates in signalling mechanisms cleaving arachidonate from sn-2 position of glycerophospholipids. In this study we have verified the existence of a PLA2-like activity in the free living protozoan, Tetrahymena pyriformis GL. This activity is Ca(2+)-independent, EDTA (10 mM) has no effect on its activity. Quinacrine (0.1 mM) and 4-bromophenacyl bromide (BPB; 0.1 mM) inhibited, melittin (20 micrograms/ml) significantly stimulated the PLA2 activity and the release of free arachidonic acid (AA) from 1-acyl 2-14C-arachidonyl-3-phosphatidylethanolamine substrate. Melittin stimulated PLA2 hyperactivity is CA(2+)-dependent. There was no considerable alteration in the PLA2 activity by stimulation of the activity by tyrosine kinase (with vanadate, H2O2), phospholipase C (PLC) (with phorbol 12, 13-dibutyrate) or G-proteins (with NaF, AlF4), thus in Tetrahymena PLA2 activity seems to be independent of these--in Tetrahymena (also functioning)--signalling pathways. Treatment with quinacrine and BPB leads to decreased synthesis and disturbed breakdown of phospholipids and phosphoinositides. These findings suggest that PLA2 activity is in connection with the phospholipid metabolism of Tetrahymena.

Acetophenones↗

PubMed1997

Mitochondrial dehydrogenases in different taxa of tetrahymena: effect of insulin.

Mitochondrial dehydrogenase activity was measured in seven taxa of Tetrahymena (T. pyriformis G1. T. hegewishi, T. malaccensis, T. pigmentosa, T. shapiro, T. thermophila CU-399, T. thermophila MS-1). Enzyme activity was different in the taxa investigated. Insulin reduced enzyme activity in six of the seven taxa studied. The duration of activity reduction was relatively long (5-10 min.) in most of the cases, and in T. hegewishi this lasted up to the end of the measurements (30 min.). There was no interrelation between the basic dehydrogenase activity of the taxon and the effect of insulin. There was also no correlation between the degree of relationship (of the taxa) and the dehydrogenase profile after insulin treatment.

Animals↗

PubMed1997

Imprinting effects of proline containing dipeptides (proline-glycine, proline-leucine, proline-valine and their retro variants) in tetrahymena. Evolutionary conclusions.

Proline-glycine, proline-leucine and proline-valine dipeptides and their retro variants were used in the experiments to study the effects of pretreatment (imprinting) in Tetrahymena, by investigating fluorescein isothiocyanate (FITC)-conjugated peptide binding. The protozoan organism could differentiate between the proline-dipeptides containing different partner amino-acids and between the dipeptides having the amino acids in reversed positions. The effect of imprinting was positive or negative and this was dependent on the type of the partner amino acid and on its position. Pro-Gly and Pro-Leu induced positive imprinting (elevated FITC-dipeptide binding) and Pro-Val induced negative imprinting (decrease of FITC-peptide binding). There was positive imprinting induction in two cases for the retro FITC-peptide and in one case for the FITC-conjugate of the imprinter peptide itself. The highest positive imprinting (almost 60% increase) was induced by Pro-Gly for FITC-Gly-Pro. Considering earlier--chemotaxis--experiments, the results of the present--binding--studies run parallel with the physiological effects. The experiments call attention to the sharp differentiating ability of small peptides at a unicellular level, that could have some role in the selection of molecules for hormone formation, during evolution.

Animals↗

PubMed1997

Effect of perinatal vitamin A or retinoic acid treatment (hormonal imprinting) on the sexual behavior of adult rats.

Single neonatal treatment with vitamin A (retinol) dramatically reduced the sexual activity of adult male rats. In females there was a significant decrease in the Meyerson index and a non significant decrease in the lordosis quotient. The effect of three perinatal treatments (at the first, third and fifth day) with all-trans retinoic acid was much weaker, causing only a significant increase in the time of the first ejaculation in males and non-significant decrease in the lordosis quotient of females. The experiments call attention to the false imprinting provoking effect of materials acting on members of the steroid receptor superfamily with possible human health aspect.

Animals↗

PubMed1997

Transgenerational effect of a single neonatal benzpyrene treatment (imprinting) on the sexual behavior of adult female rats.

Male and female rats were neonatally treated with a single dose of benzpyrene. The adult animals were mated inter se, forming control-control, benzpyrene (female)-control, benzpyrene (male)-control, and benzpyrene-benzpyrene treated couples. In the F1 and F2 generations (without any further treatment) the females's sexual behavior was tested to Meyerson index and lordosis quotient after ovariectomy and hormone treatment, using experienced males. In the F1 generation both indices were significantly reduced in the maternally treated, paternally untreated groups, however this reduction was not present in the group where the treatment was maternal and paternal alike. In the F2 generation, beside the more expressed reduction in the grandmaternally treated group, a moderate reduction in the sexual activity of progenies having treated grandfather or two treated grandparents were observed. The experiment call attention to the transgenerational sexual behavioral effect of a dangerous environment pollutant, benzpyrene.

Animals↗

PubMed1997

Effects of the amino sugars, glucosamine, mannosamine, or the fluorinated derivative 2-deoxy-fluoroglucose on the phosphatidyl inositol and glycosyl phosphatidyl inositol systems of Tetrahymena.

Sugar derivatives which have an inhibitory effect on glycosyl phosphatidyl inositol (GPI) synthesis in mammals, primarily prevented 32P incorporation in the unicellular Tetrahymena. Incorporation of 3H-mannose and 3H-inositol was induced by mannosamine. While there was a uniform effect of sugar analogues in mammals, they could not elicit totally similar effects in Tetrahymena. Analogues of sugar also affected synthesis in the phosphatidyl inositol (PI) system. Synthesis of GPI in Tetrahymena was different from that in mammals, but the metabolism of GPI and PI revealed similarities.

Animals↗

PubMed1997

Accumulation of insulin-gold particles in the oral apparatus of Tetrahymena after insulin pretreatment (imprinting).

The oral apparatus and body ciliature of untreated control cells bind insulin-gold very rarely. From 1 day to 1 week after insulin pretreatment (hormonal imprinting) an enormous quantity of insulin-gold was bound by the oral cilia, completely filling the region, while the insulin-gold on the body ciliature is scattered. The binding was specific for insulin, since polyethylene glycol (PEG)-gold was not bound at all. The results call attention to the binding and the increasing role of hormonal (insulin) imprinting, and particularly to the marked role of the oral region in this binding. The roles of mucocyst extrusion and specific binding by receptors are discussed.

Animals↗

PubMed1996

Investigations of receptor-mediated phagocytosis by hormone-induced (imprinted) Tetrahymena pyriformis.

Receptor-mediated endocytosis by Tetrahvmena pyriformis was studied using tetramethylrhodamine isothiocyanate-labeled concanavalin A (TRITC-Con A) with fluorescence and confocal microscopy. In the presence of insulin, or 24 h after insulin pretreatment (hormonal imprinting), the binding and uptake of TRITC-Con A increased when compared to controls, owing to the binding of TRITC-Con A to sugar oligomers of insulin receptors. Mannose inhibited the binding of Con A, thus demonstrating the specificity of binding. Histamine, a phagocytosis-promoting factor in mammals and Tetrahymena, and galactose, did not influence the uptake of TRITC-Con A.

Animals↗

PubMed1996

Effect of insulin on the phospholipase-D activity of untreated and insulin-pretreated (hormonally imprinted) Tetrahymena.

Insulin treatment of the unicellular Tetrahymena enormously increases the activity of phospholipase D (PLD) within 30 min. Insulin pretreatment (hormonal imprinting) does not influence basal PLD activity after 24 h. The second insulin treatment failed to stimulate PLD activity in insulin imprinted Tetrahymena. The results suggest the presence of the functional PLD activity in Tetrahymena and that hormonal imprinting modifies signal transduction to PLD, as previously reported in calmodulin activation and phophatidylinositol 4,5-bis-phosphate (PIP2) synthesis.

Animals↗