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Biomedical subjects

P Vargha

Publications and source records attributed to P Vargha.

At least 55 records · Page 3Linked to original sources
PubMed1985

Influence of low and high temperature on diiodotyrosine imprinting in Tetrahymena.

Hormonal imprinting takes place at the primary interaction between target cell and hormone, and alters cellular response to the hormone for lifetime (at the unicellular level in many subsequent generations). Imprinting induced in Tetrahymena cells by diiodotyrosine at the optimum temperature of 25 degrees C took effect on re-exposure to the hormone at 25 degrees C and 15 degrees C, but failed to take effect if the cells were first exposed to the hormone at 15 degrees C or 32 degrees C.

Animals↗
PubMed1984

Receptor 'memory' in Tetrahymena: does it satisfy the general criteria of memory? An experimental study on induction and extinction by retroactive interference in a unicellular organism.

Diiodotyrosine induced receptor 'memory' at a concentration as low as 10(-18) M. Repeated exposure enhanced cellular responsiveness. Treatment with diiodotyrosine for 1 h, 4 times, induced receptor 'memory' more efficiently than a single uninterrupted treatment for 4 h. Immediately after induction, the receptor 'memory' is subject to retroactive interference by foreign hormonal stimuli, and can be extinguished completely by combined hormone treatment. Thus, the phenomenon of retroactive interference also takes effect at the unicellular level. The experimental observations indicate that receptor 'memory', induced in Tetrahymena by hormonal imprinting, has certain common features with the neuronal memory of higher organisms.

Diiodotyrosine↗
PubMed1984

Influence of prolonged life span on receptor 'memory' in a unicellular organism, Tetrahymena.

The first interaction of the Tetrahymena with a hormone-like molecule-diiodo-tyrosine (T2) in the present study - gives rise to hormonal imprinting, the effect of which is being preserved by receptor 'memory' over as many as 500 generations. The first interaction with the hormone modifies the growth potential of the cell also without reexposure. In the present study, we followed up the fate of receptor 'memory' in Tetrahymena cells maintained without exchange of medium, and thereby inhibited in division, over the period of a year. The cells continued to display increased responsiveness - receptor 'memory' - over the first 3 months which normally cover the change of 500 generations, and to a lesser degree over the next 3 months (after 6 months) as well, but they showed loss of 'memory' after 9 and 12 months, as judged from the similarity of their growth response to the control. At 9 months, the cells were able to recover their original growth potential within 4 days of return to normal medium, but the 'memory' of the behavioral (growth response) modification induced by T2 returned, in a not fully convincing form, only after 48 days. Receptor 'memory' returned in 21 days. It follows that receptor 'memory' can equally persist by cell-cell transmission or within the same nondividing cell of extremely prolonged life span. Evidence has also been presented that loss of receptor 'memory' with ageing is only virtual, because it can be reactivated if the aged cells are 'rejuvenated' under appropriate conditions.

Animals↗
PubMed1983

Attempt to disturb receptor memory in a unicellular (Tetrahymena) model system.

The effect of a hormone-like substance first reaching a receptor is of decisive importance in the unicellular (Tetrahymena) model system. The effect of the similar or dissimilar molecule after the first or second pretreatment depends to a great extent on pretreatment if it was carried out by a similar substance, but it does not depend on it if the agent used for pretreatment was different chemically. Receptor memory developing after hormonal imprinting can thus be disturbed by molecules of similar nature, but the effect of a different molecule--if it acts immediately after the imprinting--cannot be neglected, either.

Alkaloids↗
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

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

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↗
PubMed1981

Experimental study of hormone receptor development in a unicellular model system.

It was shown earlier that diiodotyrosine (T2) stimulates the growth of Tetrahymena. In the present study clonal populations of Tetrahymena, derived from subcultures propagated in the presence of T2, showed a highly significant increase of intra-clone variance over the control, while inter-clone variation was significant, but not decisive. This suggests that genetic factors play a smaller role in the development of the cell membrane receptor pattern tha the genetic variability of the membrane itself, which seems to account for the stabilization of the adequate receptors on first exposure to a hormone.

Analysis of Variance↗
PubMed1980

Receptor amplifying effect of serotonin and serotonin analogues in a protozoan (Tetrahymena) model system.

A 72-hour treatment of Tetrahymena with serotonin analogues at a concentration of 10(-9) mmole/l resulted in a decrease of the reproduction rate, whereas serotonin itself was ineffective. On the second exposure to antagonists, cellular division was enhanced but its rate remained around or below the control value, while the second exposure to serotonin produced a more marked effect than the first one did, which finding implies a receptor amplification. The most pronounced receptor amplification was caused by the first exposure to serotonin. This observation indicates that the receptor is rather selective as regards the amplification effect.

Animals↗
PubMed1978

Long-lasting effect of single ecdysone injections in newborn rats.

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.

Adrenal Glands↗
PubMedDate not supplied

Validation studies of drug exposures in pregnant women.

The aim of these studies was to check the quality of data collection concerning drug use during pregnancy in the Hungarian Case-Control Surveillance of Congenital Abnormalities from four different aspects. (a) The parents of non-respondent cases were visited at home to collect data, but the Ethics Committee did not allow collection of comparable data from non-respondent control women. Thus only 200 selected non-respondent controls were visited at home and questioned about drug use as part of a validation study. There was no difference in the distribution and occurrence of frequently used drugs between the respondent and non-respondent control groups. (b) Data collection was compared between the usual method of the Case-Control Surveillance and personal interview in case with congenital limb deficiencies. In general, the two methods produced similar results with respect to drug use, but the personal interview revealed a higher use of unintended contraceptive pills while the use of antenatal care logbooks in the Case-Control Surveillance showed a higher use of drugs to prevent threatened abortion and preterm delivery. (c) A check of source and completeness of drug exposure showed that about one-quarter of the drugs used during pregnancy were not recorded in the Case-Control Surveillance, and the proportion of lack of recall was about 23%. A small group of women (2.4%) did not use prescribed drugs due to the suspected teratogenic risk. (d) The teratogenic labelling of drugs deters pregnant patients from the use of prescribed drugs, or at least shortens the duration of drug intake. Thus the evaluation of drug use on the basis of medically recorded prescribed drugs and/or usual recommendations produces a bias thus it is necessary to complete it with information from the patients.

Adolescent↗
PubMedDate not supplied

Evaluation of the peripapillary circulation in healthy and glaucoma eyes with scanning laser Doppler flowmetry.

In order to study peripapillary perfusion, one randomly selected eye of 34 of healthy volunteers and 40 glaucoma patients (27 suffering from primary open-angle glaucoma (POAG) 10 from normal pressure glaucoma (NPG) nd three from other types of glaucoma) was studied with a Heidelberg Retina Flowmeter. Temporal flow adjacent to the disc edge was significantly higher than the nasal flow (p < 0.01). It was reduced significantly in myopia both in controls (p < 0.05) and in glaucoma patients (p < 0.001). However, there was no difference between either controls and glaucoma patients or between POAG and NPG patients. It was independent of treatment type in glaucoma. Within the temporal peripapillary area extremely high flow values (values higher than the mean + 2 SD of the corresponding individual retinal flow) seemed to represent deep peripapillary vascular rings. They were significantly more frequent in glaucoma (72%) than in healthy volunteers (44%, p < 0.05). Their frequency was 83% in myopic and 23% in non-myopic eyes in the control group (p < 0.001). However, in glaucoma patients they were common both in myopic eyes (71%) and in non-myopic ones (75%). The results suggest that capillary perfusion adjacent to the temporal edge of the disc is significantly reduced in myopia. Deep peripapillary vascular structures can be measured on images focused on the surface of the retina, especially if the retina is thinner than normal (healthy myopic eyes and glaucomatous eyes independently of the refraction). This may mask a deficient function of the retinal capillary bed.

Adult↗
PubMedDate not supplied

Changes in thyroid hormones and serum lipids of aged women following thyroidectomy.

Thyrotropin (TSH), thyroxine (T24) 3,5,3403 triiodothyronine (T23), serum lipid levels and ECG findings in females who underwent thyroidectomy 2-44 years earlier, were compared to those of similar controls with intact thyroid. Pathological ECG is more frequent in thyroidectomized persons who also exhibit higher thyrotropin and lower HDL-cholesterol levels. The results indicate that thyroidectomized state should be regarded and controlled as a possible condition of subclinical hypothyreosis, being a risk factor of cardiovascular diseases.

Aged↗
PubMedDate not supplied

Correlation between polarimetric retinal nerve fiber layer thickness and retinal sensitivity determined with frequency-doubling technology.

BACKGROUND AND OBJECTIVE: Correlation between polarimetric retinal nerve fiber layer thickness measured with variable corneal compensation and retinal sensitivity measured with frequency-doubling technology (FDT) and standard automated perimetry (SAP) was investigated. PATIENTS AND METHODS: Twenty-four consecutive patients with chronic open-angle glaucoma and 17 healthy control subjects (1 randomly selected eye for each subject) were evaluated. RESULTS: For all subjects, quadrant scanning laser polarimetry parameters correlated positively with both FDT and SAP mean sensitivity of the opposite hemifield (P< .001). Global scanning laser polarimetry parameters correlated positively with FDT-mean sensitivity, SAP-mean sensitivity, and FDT-mean deviation, and negatively with SAP-mean deviation (in SAP, mean deviation is positive in case of sensitivity loss) (P < or = .02). The nerve fiber indicator also correlated with FDT-pattern standard deviation and SAP-corrected loss variance (P < or = .01). Using un-logged sensitivity values, no further correlations were found. CONCLUSION: Our results show that a similar structure-function relationship exists between polarimetric retinal nerve fiber layer thickness determined with variable corneal compensation and retinal sensitivity measured with SAP and FDT.

Adult↗