Biomedical subjects

G Vieitez

Publications and source records attributed to G Vieitez.

26 records · Page 2Linked to original sources

PubMed1993

Comparison between fluorescent peanut agglutinin lectin and GB24 antibody techniques for the assessment of acrosomal status.

In order to compare fluorescent peanut (Arachis hypogaea) agglutinin lectin and GB24 antibody (specific for the inner acrosomal membrane) techniques for the assessment of acrosome reaction, both methods were applied on semen specimens obtained from patients undergoing in-vitro fertilization (IVF). The acrosome status was evaluated after a 4 h incubation in B2 medium with and without calcium ionophore A23187. Results obtained with both techniques were compared and studied as a function of IVF outcome. The percentage of spontaneous acrosome-reacted spermatozoa was higher when assessed by lectin than by GB24 (19 +/- 2% versus 11 +/- 1%; P < 0.001). The difference between the two methods (lectins minus GB24) was significantly higher in abnormal than in normal spermatozoa (10 +/- 2% versus 4 +/- 2%; P < 0.05), but did not significantly correlate with the percentage of acrosomes with abnormal morphology (r = 0.28; NS). When studied in relation to the IVF results, the response to A23187 was higher in successes than in failures (45 +/- 2% versus 34 +/- 4%; P < 0.05) but there was no significant difference between methods. Thus the assessment of acrosome reaction is strongly influenced by the method used, particularly in abnormal spermatozoa. Since the results obtained with lectins were higher in abnormal spermatozoa, GB24 seems to be more effective for assessment of true acrosome reaction.

Acrosome↗

PubMed1993

Effect of clomiphene citrate on sperm cell function.

Experiments were performed to determine time and dose-dependent effects of clomiphene citrate on the function of fertile donor spermatozoa. The percentages of acrosome-reacted, motile and live spermatozoa were assessed. Incubation with clomiphene citrate (1-1000 mumol/l; 1-4 h) induced a dose- and time-dependent increase in the percentage of acrosome-reacted spermatozoa (up to 100%). Acrosome reaction was associated with an impairment of both motility and viability. The maximal value for percentage of live reacted spermatozoa (37 +/- 1%) was obtained when cells were incubated for 1 h with 100 mumol/l of clomiphene citrate. Oestradiol neither affected sperm function when used alone nor inhibited clomiphene action. These results show that clomiphene strongly triggers the acrosome reaction, but that this action is not related to its anti-oestrogenic properties.

Acrosome↗

PubMed1992

High progesterone concentrations induce acrosome reaction with a low cytotoxic effect.

OBJECTIVE: To determine the optimal conditions to obtain live acrosome-reacted spermatozoa for micromanipulation. DESIGN: Experiments were performed to determine time and dose-dependent effects of calcium ionophore A23187 or steroids on acrosome reaction of fertile donor sperm. The percentages of total reacted and live reacted spermatozoa were assessed with the peanut agglutinin lectin procedure. RESULTS: Incubation with 1 mmol/L progesterone (P) induced 48% +/- 17% acrosome reaction after 6 hours. Motility and viability remained high (49% +/- 3% and 70% +/- 2%, respectively) and thus the percentage of live reacted spermatozoa was 27% +/- 5%. Incubation with A23187 (5 mumol/L for 30 minutes) gave similar results for the percentage of live reacted spermatozoa (26% +/- 4%) but with a lower motility and viability (25% +/- 7% and 53% +/- 2%, respectively; P less than 0.05). CONCLUSIONS: These results show that high concentration of P is an effective way to induce acrosome reaction in preparation for micromanipulation.

Acrosome↗

PubMed1991

The effect of oxytocin on oestradiol-17 beta and testosterone secretion by cultured human granulosa cells.

The effect of oxytocin at different concentrations was tested on the secretion of oestradiol-17 beta and testosterone by cultured human granulosa cells obtained by follicular punctures during in-vitro fertilization (IVF) attempts. Oxytocin had no effect on testosterone secretion, either in the absence or the presence of follicle stimulating hormone (FSH). It had no effect on oestradiol-17 beta in the absence of FSH. However, it decreased the FSH-stimulated secretion of oestradiol-17 beta in a certain number of cases. This inhibitory effect appears to be associated with cells more responsive to FSH and was identified in women found to be successful in achieving pregnancy during IVF attempts.

Androstenedione↗

PubMed1990

Effect of clomiphene citrate on oestrogen secretion by human granulosa cells in culture.

The effect of clomiphene citrate (CC) and 17 beta-oestradiol (E2) on oestrogen secretion was studied in human preovulatory granulosa cells in culture. CC stimulated E2 secretion at 1 and 10 ng/ml (respectively, +36 +/- 14% and +33 +/- 5%) in basal conditions but had no effect on FSH-stimulated E2 secretion. On the other hand, E2 had no effect at any of the tested concentrations (0.1 ng/ml to 1000 ng/ml) on its own production. Since the plasma level of CC obtained in clinical use ranges from 1 to 10 ng/ml, this finding could explain the higher plasma oestrogen levels obtained with CC as compared to human menopausal gonadotrophin.

Androstenedione↗

PubMed1990

Effects of RU486 on progesterone secretion by human preovulatory granulosa cells in culture.

The effects of RU486 on progesterone synthesis were studied in human preovulatory granulosa cells in culture. No effect was observed at 1 and 10 micrograms/mL, but at 100 micrograms/mL, RU486 inhibited the simulation of progesterone secretion induced by LH and cAMP. It is suggested that the main target of RU486 is the cytochrome P450scc function [catalyzing the formation of pregnenolone (D5P) from cholesterol], since no accumulation of D5P or hydroxy derivatives of progesterone was observed. As RU486 is an antiglucocorticosteroid and antiprogesterone agent, the effects of dexamethasone and progesterone were also investigated. Dexamethasone did not modify progesterone secretion, but progesterone inhibited its own synthesis in both the presence and absence of LH. Thus, under these experimental conditions RU486 displayed a progesterone-like effect. However, since the effect of RU486 was observed only at a concentration around 10(-4) M, the mechanism of action may not involve a receptor pathway and may not apply to most clinical circumstances.

Cells, Cultured↗

PubMed1988

Effect of a luteinizing hormone-releasing hormone agonist (Buserelin) on steroidogenesis of cultured human preovulatory granulosa cells.

In order to ascertain whether there is a direct effect of luteinizing hormone-releasing hormone (LH-RH) agonists on ovarian steroidogenesis, human preovulatory granulosa cells were cultured in the presence of an LH-RH agonist (Buserelin, Hoechst Roussel Pharmaceuticals, Paris, France). Cultures were performed without serum but with precursors of estrogens and progestins. In basal conditions, Buserelin, at 1 ng/ml, increased estradiol and progesterone (P) secretion, while at concentrations of 10 and 100 ng/ml, no effect was observed. In the presence of follicle-stimulating hormone (FSH) or LH, Buserelin at 1 and 10 ng/ml did not modify the cell's steroidogenesis. However, at a concentration of 100 ng/ml, Buserelin decreased LH stimulation of P secretion. These results suggest that LH-RH agonists, at concentrations in the range of those obtained in clinical use, can modulate ovarian steroidogenesis by direct action.

17-alpha-Hydroxyprogesterone↗

PubMedDate not supplied

[Selection and characterization of human acrosome-reacted sperm: application to subzonal insemination].

Acrosome reacted spermatozoa were selected with immunobeads coated with an antibody directed against the inner acrosomal membrane (GB24) and then detached immunologically using an anti-Fab'2 antibody. Using this method, we have shown that acrosome reaction occurs in the most morphologically normal spermatozoa and is followed by a loss in motility and a decrease in longevity. Moreover, when injected in the perivitelline space of hamster oocytes, the selected spermatozoa had a higher fertilization rate than unselected spermatozoa, confirming that acrosome reaction is necessary for the fusion with the oocyte plasma membrane and that the selection method does not alter the fertilizing ability of the spermatozoa. Therefore, this method represents a new way for understanding the sperm functions.

Acrosome↗