Browsing by Author "HERRERA, E"

Now showing 1 - 7 of 7
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    EFFECT OF INVIVO OOCYTE AGING ON SPERM CHROMATIN DECONDENSATION IN THE GOLDEN-HAMSTER
    (1986) JEDLICKI, A; BARROS, C; SALGADO, AM; HERRERA, E
    Aged spontaneously activated hamster oocytes recovered from adult females 18 and 24 hours after ovulation were at the pronuclear stage. These oocytes and fresh controls were inseminated in vitro with capacitated hamster spermatozoa and observed with the phase-contrast microscope. The percentage of fertilization in fresh control oocytes was 98%, as compared to 36% and 18% when the oocytes were recovered 18 and 24 hours after ovulation, respectively. The mean number of sperm decondensations per egg in control oocytes was 10, and in the aged ones it was 0.69 and 0.12 when the oocytes were recovered 18 and 24 hours after ovulation, respectively. When similarly treated oocytes were studied with scanning and transmission electron microscopy, it was found that the degree of gamete membrane fusion was greater than that observed with the phase-contrast microscope, but that most of the spermatozoa failed to decondense the chromatin. We suggest that parthenogenetic oocytes at the pronuclear stage are in a similar stage of the cell cycle as in fertilized eggs, in which the cytoplasm does not have the ability to decondense the sperm chromatin.
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    HAMSTER OOCYTE FERTILIZABILITY AFTER 4-DEGREES-C STORAGE
    (1986) BARROS, C; HERRERA, E; FUENZALIDA, I; ARGUELLO, B
    The purpose of the present work was to study the feasibility of using hamster oocytes stored at 4.degree. C in M-2 culture medium for 24 and 48 hours in the evaluation of human sperm fertilizability. A total of 1,394 oocytes were stored for 24 hours and 1,234 were stored for 48 hours. After the storage period all the oocytes were stained with fluorescein diacetate, proving the physical integrity of the egg plasma membrane. Twenty-five and 22 semen samples were used to compare their ability to penetrate freshly ovulated and 24- and 48-hour-stored hamster oocytes. Freshly ovulated and 24-hour-stored oocytes were penetrated at percentages that in more than 95% of the cases showed no significant differences. The same experiments carried out with oocytes stored for 48 hours showed that in 75% of the cases no significant differences were found. The use of oocytes preserved at 4.degree. C when large numbers of semen samples are to be tested for fertilizability is recommended.
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    HUMAN SPERM-CERVICAL MUCUS INTERACTION AND THE ABILITY OF SPERMATOZOA TO FUSE WITH ZONA-FREE HAMSTER OOCYTES
    (1988) BARROS, C; JEDLICKI, A; FUENZALIDA, I; HERRERA, E; ARGUELLO, B; VIGIL, P; VILLASECA, P; LEONTIC, E
    Samples of semen and cervical mucus were provided by 18 couples. Cervical mucus was obtained for each day possible and stored at 4.degree.C until all the samples were collected. Flat capillary tubes were loaded with the mucous samples and spermatozoa from the husband''s semen sample were allowed to migrate through the cervical mucus (3 cm column) into culture medium. The spermatozoa recovered after migration through cervical mucus were assayed in vitro with zona-free hamster oocytes. Control experiments were carried out using spermatozoa from the same semen sample but prepared by the swimming-up technique. Altogether, 557 eggs in the control group and 1236 eggs in the experimental group were analysed, and the results demonstrated that the % of sperm penetration, the mean number of sperm decondensations per penetrated egg and the mean number of spermatozoa adhering per egg all had higher values (P < 0.05) for the control samples than for the experimental samples. We suggest that cervical mucus modifies human spermatozoa, as measured by their interaction with zona-free hamster oocytes.
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    ROUND-HEADED SPERMATOZOA - A MODEL TO STUDY THE ROLE OF THE ACROSOME IN EARLY EVENTS OF GAMETE INTERACTION
    (WILEY, 1990) VONBERNHARDI, R; DEIOANNES, AE; BLANCO, LP; HERRERA, E; BUSTOSOBREGON, E; VIGIL, P
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    SPERM MIGRATION THROUGH THE FEMALE GENITAL-TRACT OF THE NEW-WORLD MONKEY CEBUS-APELLA
    (1995) ORTIZ, ME; GAJARDO, G; LEON, CG; HERRERA, E; VALDEZ, E; CROXATTO, HB
    This study was designed to characterize sperm migration in the female genital tract of Cebus apella. Forty-eight cycles of eighteen females mated during the periovulatory period were studied. Eggs were searched for and spermatozoa were counted in segmental flushings of the genital tract performed in situ 1-7 h, 19-31 h, or 45-56 h after coitus. Of 14 eggs recovered, 8 were fertilized, thus assuring a reasonable normality of prefertilization phenomena in both males and females.
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    ULTRASTRUCTURAL OBSERVATIONS OF INCORPORATION OF GUINEA-PIG SPERMATOZOA INTO ZONA-FREE HAMSTER OOCYTES
    (1977) BARROS, C; HERRERA, E
    Zona-free hamster oocytes inseminated in vitro with acrosome-reacted guinea-pig spermatozoa were examined with the EM. Guinea-pig spermatozoa, in the vicinity of the oocytes, consistently lacked the whole acrosome including the equatorial segment region. In cross fertilization, sperm-egg membrane fusion does not differ significantly from that of normal fertilization. It was sometimes possible to observe protrusions of oocyte cytoplasm containing sperm chromatin in the process of dispersion.