Biomedical subjects

A Török

Publications and source records attributed to A Török.

At least 19 recordsLinked to original sources

PubMed2003

Organic hydroperoxide-induced chemiluminescence of follicular fluid and blood serum samples obtained from women pretreated for in vitro fertilization.

The organic hydroperoxide-induced chemiluminescence of follicular fluid obtained from in vitro fertilized patients and its differently separated fractions were evaluated. Peroxidative stress causes a different photo-emission in the samples which alludes to some factors playing a role in the maintenance of the pro-oxidant/antioxidant balance. Interactions between the protein compounds of the samples and the organic hydroperoxide associate with formation of excited species contributing to the distinctive light emission processes. The technique offers a special re-interpretation of the scavenger state relating to the components of follicular fluid.

Cells, Cultured↗

PubMed2003

Issues to debate on the Women's Health Initiative: estrogen: an instrument or the conductor of the orchestra?

Although it is well known that cyclic production of sex hormones is essential to establish reproductive function and female characteristics, distant impacts of the activity of the female endocrine system result from a concert of delicate mechanisms. Estrogen is rather an instrument than a conductor in this physiological orchestra of the female. Thus, controversies in the explanation of results from studies on hormone replacement therapy (HRT) and cardiovascular disease (CVD) prevention might be eliminated, if we analyse not only the role of estrogen but a broader spectrum of factors leading to CVD. Authors would like to hypothesize that haemorheological changes in women around menopause, such as increased blood and plasma viscosity, haematocrit and fibrinogen, are largely responsible for the increased mortality in the post-menopausal life period. We believe that a cyclic withdrawal bleeding establishes a more favourable haemorheological condition, thus, sequentially administered estrogen might be protective in post-menopausal women. Nevertheless, other factors, that decrease blood viscosity, such as daily exercise, intake of ample amount of fluids as well as ideal nutrition, are equally important. We are confident that sequential HRT, as well as healthy life style and risk prevention programmes have their proper place in the management of this issue.

Cardiovascular Diseases↗

PubMed2002

The effect of catecholamines, acetylcholine and histamine on progesterone release by human granulosa cells in a granulosa cell superfusion system.

There are experimental data demonstrating the presence and actions of various neurotransmitters in the ovary, thus supporting the view that they might play a role in intraovarian regulatory mechanisms, although their exact function in the regulation of ovarian hormone secretion is unclear. The objective of the present study was to investigate the direct action of catecholamines, acetylcholine and histamine on progesterone secretion of human granulosa cells in a superfused cell system. Human granulosa cells were isolated from preovulatory follicular fluid using a Percoll gradient centrifugation method. Approximately 2 x 10(6) cells were mixed with Sephadex G-10 and were transferred into two chambers of the superfusion apparatus. The system was perfused with a culture medium and test materials were added to the system at a dose of 100 pmol/ml. The progesterone concentration of samples was measured using an (125)I radioimmunoassay. Administration of epinephrine (adrenaline), norepinephrine (noradrenaline), dopamine and histamine had no effect on progesterone release. However, acetylcholine produced a significant progesterone release, which could be blocked by atropine. The observed effect of acetylcholine on progesterone release of superfused human granulosa cells may reflect a physiological role of acetylcholine in the regulation of granulosa cell function during the menstrual cycle.

Acetylcholine↗

PubMed2001

Modulatory effect of acetylcholine on gonadotropin-stimulated human granulosa cell steroid secretion.

The aim of this study was to explore the direct action of acetylcholine on gonadotropin-stimulated progesterone (P) and estradiol (E(2)) secretion of human granulosa cells (GCs) cultured in serum-free medium. Human GCs were isolated from preovulatory follicular fluid aspirated from 22 women undergoing in vitro fertilization at the University Women's Hospital of Tübingen. The production of progesterone and E(2) was measured in the presence and absence of acetylcholine, carbachol, atropine, luteinizing hormone (LH) or follicle-stimulating hormone (FSH) using radioimmunoassay. Statistical analysis of the data was performed by ANOVA and Newman-Keuls test. Administration of acetylcholine or carbachol (10(-5) M) resulted in a significant increase in P and E(2) secretion. This response was specifically blocked by the muscarinic receptor antagonist atropine. Similarly, carbachol resulted in a significant increase in P and E(2) output, though the response to it was somewhat reduced when compared to that evoked by acetylcholine. Acetylcholine did not show any additive effect on LH-stimulated P secretion, while it augmented the stimulatory effect of FSH on P release. In contrast, carbachol markedly diminished the stimulatory effect of LH on P secretion, while it caused no change in FSH-induced P output. When administered together, acetylcholine did not modify the stimulatory effect of FSH on E(2) secretion, however, it markedly elevated LH-induced E(2) output. Similar to this, carbachol significantly increased LH-induced E(2) release, however it decreased FSH-stimulated E(2) secretion. We suggest that acetylcholine has a direct modulatory effect on gonadotropin-stimulated steroid production of GCs, an effect that is mediated via muscarinic receptors. This effect may have a physiological role in the regulation of GC function during the menstrual cycle.

Acetylcholine↗

PubMed2001

Influence of melatonin on basal and gonadotropin-stimulated progesterone and estradiol secretion of cultured human granulosa cells and in the superfused granulosa cell system.

The aim of this study was to explore the direct action of melatonin (Me) on basal and gonadotropin-stimulated progesterone (PG) and estradiol (E2) secretion of human granulosa cells (GCs) cultured in serum-free medium and in a superfused GC system. Human GCs were isolated from preovulatory follicular fluid aspirated from 34 women undergoing in vitro fertilization at the University Women's Hospital of Tübingen. PG and E2 production was measured in the presence and absence of Me, propranolol, LH or FSH using radioimmunoassay. Statistical analysis of the data was performed by ANOVA and Newman-Keuls test. Me stimulated E2 secretion in a dose-dependent manner. Propranolol did not cause any change in E2 secretion, and when given with Me, it only partially blocked but could not entirely prevent E2 output. There was no statistically significant effect of Me on PG production when Me was administered at concentrations between 10(-4) and 10(-8) M. However, at 10(-3) M Me significantly suppressed PG output of granulosa cells. LH and FSH significantly stimulated the secretion of both steroid hormones. Me significantly reduced LH- and FSH-induced E2 secretion, as well as LH-stimulated PG output, while it caused only a slight, yet significant decrease in PG secretion. In the superfused GC system, FSH and LH resulted in a significant stimulatory effect on PG release. Me did not modify the stimulatory effect of FSH on PG, while it caused some delay in LH-stimulated PG release. Propranolol and Me had no stimulatory effect on PG release. On the basis of our results we suggest that Me has a direct modulatory effect on basal E2 and gonadotropin-stimulated E2 and PG secretion of human GCs. The observed effect may play a physiological role in the regulation of GC function during the menstrual cycle.

Adrenergic beta-Agonists↗

PubMed2000

A dynamic in vitro investigation of the characteristics of the granulosa cells hormone secretion.

OBJECTIVE: Basic characteristics of ovarian steroid production has largely been clarified by the use of human granulosa cell cultures in vitro. This technique made also possible to test different stimulatory and blocking hormones and chemicals in the cell cultures to clarify regulatory mechanisms of the granulosa cells. However, these cell cultures are static systems that do not give information about the dynamics of steroid production of the granulosa cells. Therefore, in the present study we have tried to establish a dynamic model using the so called superfusion method. METHODS: Granulosa cells were isolated from follicular fluid obtained by aspiration from patients undergoing in vitro fertilization program. The granulosa cells were packed into a closed Sephadex G10 column which was continuously kept at 37 degrees C and washed with McCoy's 5A culture medium. Samples of the medium leaving the column were collected in every 30 minutes with a fraction collector. Stimulation with LH and blocking with cycloheximide were carried out by adding the materials into the perfusing culture medium. Progesterone levels of the samples were measured by RIA-s. RESULTS: We found that the basal progesterone secretion is pulsatile even in the absence of any stimulation. After stimulation with LH there is a rapid, but a slight increase in the steroid levels, followed by a delayed and also pulsatile definite increase of progesterone levels starting at about 30 minutes. CONCLUSIONS: From the data obtained it is clear that human granulosa cells are storing progesterone in a small quantity that is LH releasable. The delayed progesterone increase is due to de novo synthesis of the hormones after the gonadotropin stimulation, which takes about 60 minutes.

Cell Culture Techniques↗

PubMed1998