Browsing by Author "BIZE, I"

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    EPINEPHRINE DECREASES THE POTASSIUM REQUIREMENTS OF HAMSTER SPERM CAPACITATION - FUROSEMIDE BLOCKS THE EFFECT OF EPINEPHRINE
    (1985) BIZE, I; SANTANDER, G
    The possibility of an interaction between epinephrine and external K in the stimulation of the hamster sperm acrosome reaction and in vitro fertilizing ability were investigated. K+ is required late in capacitation and/or the acrosome reaction, but is not required for penetration of the zona pellucidae. The presence of epinephrine (50 .mu.M) in the capacitation medium lowers the K+ requirements of these processes and furosemide, a cotransport inhibitor, blocks the acrosome reaction, in vitro fertilization, and inhibits the stimulation by epinephrine. These results support the idea that there is an interaction between epinephrine as a stimulus to the secretion of the acrosomal content, and K+ as a mediator of the stimulus signal. K+ influx through the cotransport mechanism occurs during capacitation, that this mechanism is activated late during the process, and that it probably mediates the stimulatory effects of epinephrine. Apparently, the activation of passive cation transport mechanisms is a general phenomenon in biological signal transduction.
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    HYDROGEN-PEROXIDE IS INVOLVED IN HAMSTER SPERM CAPACITATION INVITRO
    (1991) BIZE, I; SANTANDER, G; CABELLO, P; DRISCOLL, D; SHARPE, C
    We have investigated the possibility that the generation of hydrogen peroxide (H2O2) by spermatozoa plays a physiological role during capacitation. Capacitation is defined as the incubation period required for fertilization in mammals. Capacitation culminates in an exocytotic event, the acrosome reaction (AR). Mammalian sperm generate H2O2 during aerobic incubation and do not contain catalase, the enzyme that promotes scavenging of H2O2. In the present work we show that added catalase inhibited the AR, while glucose oxidase (GO), an enzyme that generates H2O2, accelerated the onset of the AR. Direct addition of H2O2 also stimulated the AR; catalase inhibited both the stimulation by GO and by H2O2. The onset of the AR was always preceded by the appearance of hyperactivated motility. The stimulation of the AR by H2O2 was manifest 1-2 h after the addition of H2O2. Catalase added at 3 h of incubation was less effective in inhibiting the AR than catalase added at the beginning. Incubation of sperm with catalase prevented the induction of the AR by the membrane-perturbing lipid, lysophosphatidyl choline. Taken together, these results suggest that H2O2 produced by hamster sperm plays a significant role during capacitation, possibly in membrane reorganization to facilitate the fusion that takes place during exocytosis of the acrosomal contents.
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    RELATIONSHIP BETWEEN THE LENGTH OF SPERM PREINCUBATION AND ZONA PENETRATION IN THE GOLDEN-HAMSTER - A SCANNING ELECTRON-MICROSCOPY STUDY
    (1984) BARROS, C; JEDLICKI, A; BIZE, I; AGUIRRE, E
    Hamster spermatozoa are able to fertilize a high percentage of zona-intact hamster oocytes when they are preincubated for 2 h in a chemically defined medium. From this time on, the longer the preincubation time the lower the percentage penetration. Spermatozoa preincubated for > 6 h are unable to cross the zona pellucida, retaining their ability to fuse with zona-free hamster oocytes. Zona-intact hamster oocytes were observed with the scaning electron microscope. When the oocytes were inseminated with spermatozoa preincubated for 1-5 h the outer surface of the zona showed the penetrating spermatozoa and the sperm tracks made by those that failed to cross it. With longer preincubation times no penetrating spermatozoa were observed, and very few sperm tacks were present on the outer surface of the zona. Control experiments showed that neither eggs, spermatozoa, nor fertilization were affected by the medium recovered after long preincubations. Care should be taken regarding the preincubation time when using the in=vitro fertilization technique.