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M E Chavarría

Publications and source records attributed to M E Chavarría.

13 recordsLinked to original sources
PubMed2001

Effect of bafilomycin A1, a specific inhibitor of vacuolar (V-type) proton ATPases, on the capacitation of rabbit spermatozoa.

Mammalian spermatozoa maintain precisely regulated ionic gradients that must be modified during capacitation and the acrosome reaction. In other cell types, ionic gradients are mainly regulated by the presence in plasma membranes of three metabolically different types of ATPases. The modifications induced during in vitro capacitation of rabbit spermatozoa by the specific inhibition of V-type H+-ATPases with bafilomycin A were studied. We used chlortetracycline binding to rabbit spermatozoa to monitor capacitation, and the coomassie brilliant blue method to identify acrosome-reacted sperm cells. There was a significant difference between the percentage of epididymal (66 +/- 7%) and ejaculated (43 +/- 11%) spermatozoa capacitated in vitro, after a 6-h incubation period in the presence of Ca2+ without ATPase inhibitor. The presence of bafilomycin significantly reduced these numbers (25 +/- 11 and 16+/- 8%, epididymal and ejaculated spermatozoa, respectively) and eliminated the difference. Ejaculated spermatozoa capacitated in the absence of bafilomycin showed a linear increase in the percentage of acrosome reactions induced by the addition of A23187 (12 +/- 5, 23+/- 6 and 31 +/- 5 after 15, 30 and 45 min). The presence of 0.2 micromol l-1 bafilomycin during the capacitation incubation induced a significant decrease in the acrosome reaction percentages (4 +/- 2, 8 +/- 3 and 14 +/- 4 after 15, 30 and 45 min). The addition of bafilomycin after the capacitating period had no effect upon the induction of the acrosome reaction by A23187. These results indicate that vacuolar ATPases play an important role during rabbit sperm capacitation. However, once the spermatozoa have been capacitated, V-type ATPases do not have a significant participation during the acrosome reaction.

Acrosome Reaction↗
PubMed1997

Deconvolution analysis of bioassayable LH secretion and half-life in men with idiopathic oligoasthenospermia.

To further investigate the nature of neuroendocrine disturbances of the hypothalamopituitary-gonadal axis in idiopathic male infertility, we studied 12 infertile men with oligoasthenozoospermia and 13 euspermic controls, matched for age and body mass index, by blood withdrawal at 10-min intervals for 8 h to analyse pulsatile release of bioactive LH (b-LH). The rat interstitial cell testosterone (RICT) bioassay was used in conjunction with a recently validated multiparameter deconvolution algorithm, to estimate the endogenous half-life of b-LH, its secretory burst frequency, amplitude, duration and mass. Oligoasthenospermic men exhibited significant (p < 0.05) alterations within the LH axis; namely: (1) a prolonged half-life of b-LH (92 min in euspermic men, 127 min in oligoasthenospermic men); (2) a reduced b-LH secretory burst amplitude (2.2 +/- 1.2 IU/l/min in euspermic men, 1.7 +/- 0.8 IU/l/min in oligoasthenospermic men); (3) a lower bioactive/immunoactive (b/i) ratio for LH secretory burst amplitude (14 in euspermic men, 4 in oligoasthenospermic men); (4) a reduced b/i ratio in the mass of LH secreted per burst (5.4 in euspermic men, 4.1 in oligoasthenospermic men) and (5) decreased coordinate release of b-LH and testosterone in infertile men, as assessed by cross-correlation analysis. These disturbances differ from the neuroendocrine dysregulation described in other states of male hypogonadotrophism.

Activity Cycles↗
PubMed1997

[The male factor. II. Spermatozoa. Structure and function].

In the "male factor" entity, the structural and functional correlation determining the sperm fertilizing capacity is constituted by a group of cellular factors that must be evaluated in the semen of the infertile men. Structurally the spermatozoa of the head, the middle piece and the flagellum. The head has a highly condensed haploid nucleus, surrounded by a thin layer of cytoplasmic material, which is covered in a cap-like fashion by the membrane limiting the acrosome. This last organelle, which has characteristics similar to those of a secretory granule, secretes in a programmed way the hydrolytic enzymes that facilitate the fertilization process. The middle piece contains the mitocondrail sheet, responsible for the energy metabolism of the sperm cell. The flagellum has the same basic structure of other cilia or flagella, but also has particular characteristics due to the presence of the outer dense fibers and the fibrous sheath. In the semen analysis from infertile men the abnormalities most frequently observed belong to the number, morphology, variability, motility of capacitation-acrosome reaction of the sperm cells. However, due to the apparent multifactorial etiology of the male factor, now a days we only have few options for medical or pharmacological treatment. In this paper we review the morphology and ultrastructure considered as "normal" in the human spermatozoa, as well as we describe the most frequent alterations in these parameters. At the same time, we discuss the impact of sperm motility and of the capacitation-acrosome reaction process in male fertility.

Acrosome↗
PubMed1996

Alterations in pulsatile luteinizing hormone and follicle-stimulating hormone secretion in idiopathic oligoasthenospermic men: assessment by deconvolution analysis--a clinical research center study.

To investigate the nature of neuroendocrine disturbances of the hypothalamo-pituitary-gonadal axis in idiopathic male infertility, we studied 14 infertile men with oligoasthenozoospermia (OLIGO) and 15 age-, body mass index-, and community-matched euspermic controls by blood withdrawal at 10-min intervals for 12 h to encompass basal (8-h) and exogenous GnRH-stimulated (4-h) pulsatile release of LH and FSH (by immunoradiometric assay) as well as testosterone (by RIA). Deconvolution analysis was used to estimate endogenous LH and FSH half-lives, secretory burst frequency, amplitude, duration, and mass. OLIGO men exhibited normal serum concentrations of total, free, and percent dialyzable testosterone and estradiol, but distinct dynamic alterations within the LH and FSH axes; namely (P < 0.05), 1) a prolonged half-life of LH (OLIGO, 95 +/- 19 min; control, 80 +/- 9.3 min) and a reduced half-life of FSH (OLIGO, 260 +/- 79 min; control, 320 +/- 93 min); 2) a low LH, but normal FSH, secretory burst frequency (OLIGO, 12 +/- 3.4; control, 15 +/- 3.0 LH pulses/day); 3) a decreased serum testosterone peak frequency (OLIGO, 16 +/- 4.3; control, 21 +/- 3.2 peaks/day); and 4) an amplified mass of LH (1.1- to 1.3-fold higher in OLIGO) and FSH (2.4- to 2.7-fold higher in OLIGO) secreted per burst basally as well as after GnRH injection. These disturbances were readily distinguishable from the neuroendocrine dysregulation described in other states of male hypogonadotropism (e.g. uremia, fasting, and aging).

Adult↗
PubMed1992

Capacitation and acrosome reaction of human spermatozoa. An assisted reproduction approach.

In this paper we briefly review the recent advances in the understanding of human sperm capacitation, fundamentally focused to give help to the practitioners involved in assisted reproduction. Sperm capacitation has been the subject of study for many years in several animal species, but during the past ten years the advances in assisted reproduction procedures have made important contributions in the progress of this topic in relation to human spermatozoa. In this manuscript we analyze the metabolic, membranal and physiological changes observed in these cells during in vitro capacitation and their relationships with the female genital tract secretions, as well as with the homologous oocytes.

Acrosome↗
PubMed1991

[Comparative study of the morpho-functional features of the sperm of fertile and infertile men and their relation to fertilizing ability].

The recent advances in assisted reproduction procedures have helped to the better understanding of the female reproductive physiology and pathology, however, male infertility remains as a poor explained medical problem, nevertheless it occurs in almost 50% of infertile couples. Oligoasthenozoospermia is one of the more common causes of male infertility, therefore we measured in 10 patients with this diagnosis and in 10 fertile euspermic men, besides the parameters included in the standard semen analysis, the quantitative motility (photography method), capacitation-acrosome reaction and the sperm ability to fertilize zona-free hamster oocytes, with the aim to correlate the morphofunctional characteristics of the male gametes with their fertilizing capacity. The results showed significant differences in every parameter studied, including the correlation analysis. In relation with the in vitro induction of the acrosome reaction in both groups, we found significant correlations of the sperm fertilizing ability and the progressive sperm motility with this parameter (fertile group: RS = 0.834, P less than 0.005 & RS = 0.612, P less than 0.05; infertile group: RS = 0.986, P less than 0.001 & RS = 0.536, P less than 0.05 respectively), nevertheless the sperm rate which completed this process was low in relation to the total sperm population even in the fertile men (9.4 +/- 2.0% & 4.4 +/- 2.5% acrosome reacted cells after 18 h of incubation, in the fertile and infertile males respectively). The results also showed the presence of fully capacitated spermatozoa in both groups, since they penetrated the zona-free hamster eggs and decondensed their chromatin (73.9 +/- 13.4% & 10.4 +/- 7.7% penetrated eggs in the euspermic and oligoasthenozoospermic individuals respectively), however, the spermatozoa from the oligoasthenozoospermic men showed low polyspermy indexes too (0.1 penetrated spermatozoa/inseminated oocyte). In this last group we found, in addition, that the mean sperm velocity and the abnormal sperm morphology rate showed significant correlations with the fertilizing ability of the male gametes too (RS = 0.986, P less than 0.005 & RS = -0.942, P less than 0.005. respectively). These data allow us to suggest that before an infertile man is involved in any assisted reproduction program, the presence of possible morphofunctional alterations in the spermatozoa be analyzed, with the aim to be able to make a better prognosis about the success with these patients.

Acrosome↗
PubMed1991

[Inhibin, steroid hormone, and gonadotropin concentration in blood from fertile and infertile males and its relationship with testicular function].

The role of inhibin in the testicular function and its relation with other hormone regulation spermatogenesis have not been elucidated in the human, therefore we studied by RIA the serum concentrations of this testicular secretion product, as well as those of LH, FSH, T and E2 and their possible correlation with some parameters evaluated by spermatobioscopy (cell number, motility, morphology and immature germinal cells) in fertile, oligozoospermic and azoospermic men. We did not find significant differences in inhibin concentration between fertile and oligozoospermic males; however in the azoospermic group the mean inhibin concentration was significantly higher (722.9 +/- 137.9 U/l in the fertile men; 658.5 +/- 147.1 and 963.1 +/- 300.9 U/l in the oligozoospermic and azoospermic groups respectively), in spite of data dispersion in the 3 study groups. Among the fertile males we found a negative significant correlation between the inhibin and the LH and FSH concentrations (p less than 0.05), while in the oligozoospermic patients this negative correlation was observed with T concentration. In the fertile males inhibin also showed correlation with the sperm percentage with normal morphology and with the immature germinal cells in semen; in the oligozoospermic group this glycoprotein showed correlation with the sperm count and the germinal cells concentration. We also found correlation between testosterone and/or LH concentrations and sperm count in both groups. These results indicate modifications in the hormonal concentrations regulating the testicular function and in their relationship, in men with testicular damage, which can render a change in the mechanisms controlling this function.(ABSTRACT TRUNCATED AT 250 WORDS)

Estradiol↗
PubMed1990

[Several new concepts on the terminal mechanism of mammal fertilization].

We briefly reviewed some ionic mechanisms participating in the fulfillment of the acrosome reaction processes, indicating the results obtained by the simultaneous and dynamic quantitation of sodium, potassium, calcium and hydrogen concentrations in the in incubation medium of human spermatozoa induced to achieve the acrosome reaction through the addition of cAMP and follicular fluid. At the same time, the participation of zinc and some enzymatic activities, like phospholipase A2, in the occurrence of this process, is indicated. A study is done about the sperm nuclear decondensation mechanisms, pointing at the importance of various participants in this event, like the disulfide groups reducing agents, some metalic ions and the glycosaminoglycanes, as well as a proposal of a mechanism which could be physiologically functional for the in vivo occurrence of this phenomenon. Finally we present some results explaining the DNA synthesis activation, which is repressed in the spermatozoa since the spermiogenesis final stages, and is indispensable for the chromosomic duplication required during egg segmentation.

Acrosome↗
PubMed1990

[New concepts about the terminal mechanism of fertilization in mammals].

We briefly reviewed some ionic mechanisms participating in the fulfillment of the acrosome reaction processes, indicating the results obtained by the simultaneous and dynamic quantitation of sodium, potassium, calcium and hydrogen concentrations in the in incubation medium of human spermatozoa induced to achieve the acrosome reaction through the addition of cAMP and follicular fluid. At the same time, the participation of zinc and some enzymatic activities, like phospholipase A2, in the occurrence of this process, is indicated. A study is done about the sperm nuclear decondensation mechanisms, pointing at the importance of various participants in this event, like the disulfide groups reducing agents, some metal ions and the glycosaminoglycans, as well as a proposal of a mechanism which could be physiologically functional for the in vivo occurrence of this phenomenon. Finally we present some results explaining the DNA synthesis activation, which is repressed in the spermatozoa since the spermiogenesis final stages, and is indispensable for the chromosomic duplication required during egg segmentation.

Acrosome↗
PubMed1987

Concentrations of calmodulin in sperm in relation to their motility in fertile euspermic and infertile asthenozoospermic men.

The relationship between calmodulin and sperm motility was assessed in euspermic and asthenozoospermic men using radioimmunoassay and time-lapse photography, respectively. There was a significant decrease in the % sperm motility, mean sperm velocity, motility index and % of progressively motile sperm in the asthenozoospermic group when compared with euspermic men. The former also exhibited a higher % of sperm with erratic or circular motility. Calmodulin concentration in sperm from the asthenozoospermic men was 4.8 +/- 1.4 micrograms/mg protein compared with 12.6 +/- 2.3 in euspermic men (P less than 0.0005). The differences observed in sperm motility characteristics between the two groups may, thus, be due to the observed differences in the concentration of calmodulin.

Adult↗
PubMed1984

Quantitative evaluation of the human spermatozoal motility and acrosome reaction in infertile oligozoospermic and fertile euspermic men.

Idiopathic oligozoospermia is one of the most important problems in Andrology, but up to now it is poorly understood because the often routine conventional semen parameters, unquestionably are not directly related to the evaluation of the morphological and functional integrity that determines the spermatozoan fertilizing capacity. A non complex strategy was designed to determine the presence of alterations in the functional integrity of the spermatozoa from infertile men with idiopathic oligozoospermia and from euspermic fertile men, by the quantitative analysis of the spermatozoan motility and the acrosome reaction. There was a lower percentage of acrosome reacted spermatozoa within the semen of the infertile men, accompanied with a significant decrease in the motility percentage, sperm velocity and motility index in comparison with semen from fertile men. These data strongly support a possible detrimental structural and functional integrity of the spermatozoa from the oligozoospermic men.

Acrosome↗
PubMedDate not supplied

Secretions of ovine uterus and oviduct induce in vitro capacitation of ram spermatozoa.

Interaction between spermatozoa and female reproductive tract fluids involves both losses of surface proteins and adsorption of exogenous fluids' components. To study the functional consequences of this interaction, sperm acrosome reaction was evaluated after incubation at 37 degrees C in uterine (UF) and/or oviductal (OF) fluid collected at estrus from conscious ewes. Ram spermatozoa were collected through the catheterized vas deferens. The fluids had previously been diluted with equal volumes of BWW medium or dialyzed against BWW. Control incubations were in BWW. Twenty minutes before the end of incubation, Ca2+ (2.5 mM) was added to induce the acrosome reaction, which was assessed using a triple stain technique. Results showed that 22-24% of the sperm experienced acrosome reaction after sequential incubation in UF (1 h) and OF (4 h), or in UF alone (5 h). Exposure to OF alone induced 13% of acrosome reaction. When the spermatozoa were preincubated in UF followed by OF, the acrosome reaction percentage increased almost linearly with time. When incubated in UF alone, this percentage increased steadily with time, whereas a plateau was reached after 1 h of incubation in OF alone. Dialysis of the fluids did not modify the results. These results show that ewe reproductive tract secretions may capacitate ram spermatozoa in vitro, evaluated by their efficacy to induce acrosome reaction.

Acrosome↗