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C. Barros and E. Herrera

Summary. Zona-free hamster oocytes inseminated in vitro with acrosome-reacted guinea-pig spermatozoa were examined with the electron microscope. 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. However, it was sometimes possible to observe protrusions of oocyte cytoplasm containing sperm chromatin in the process of dispersion.

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Blood serum collected from female hamsters on each day of the oestrous cycle was assayed for its ability to induce the acrosome reaction. The maximum activity was found in sera obtained from females around the time of ovulation, and the minimum on Day 2. Ovariectomy did not affect the activity of the serum but oestrogen treatment significantly increased it. Blood serum from progesterone-treated and pregnant females significantly depressed the incidence of the acrosome reaction. Progesterone counteracted the effect of oestrogen with regard to the incidence of the acrosome reaction. The counteracting effect was maximal when both hormones were administered at the same time.

The possible rôle played by the hormones in this phenomenon is discussed.

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E Herrera, K Salas, N Lagos, DJ Benos and JG Reyes

The hypothesis that intracellular [Ca2+] is a cell parameter responsive to extreme temperatures in rat meiotic and postmeiotic spermatogenic cells was tested using intracellular fluorescent probes for Ca2+ and pH. In agreement with this hypothesis, extreme temperatures induced a rapid increase of cytosolic [Ca2+] in rat pachytene spermatocytes and round spermatids. Oscillatory changes in temperature can induce oscillations in cytosolic [Ca2+] in these cells. Intracellular [Ca2+] homeostasis in round spermatids was more sensitive to high temperatures compared with pachytene spermatocytes. The calculated activation energies for SERCA ATPase-mediated fluxes in pachytene spermatocytes and round spermatids were 62 and 75 kJ mol(-1), respectively. The activation energies for leak fluxes from intracellular Ca2+ stores were 55 and 68 kJ mol(-1) for pachytene spermatocytes and round spermatids, respectively. Together with changes in cytosolic [Ca2+], round spermatids undergo a decrease in pH(i) at high temperatures. This temperature-induced decrease in pH(i) appears to be partially responsible for the increase in cytosolic [Ca2+] of round spermatids induced by high temperatures. This characteristic of rat meiotic and postmeiotic spermatogenic cells to undergo an increment in cytosolic Ca2+ at temperatures > 33 degrees C can be related to the induction of programmed cell death by high temperatures in these cells.

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C. Barros, A. Jedlicki, I. Fuenzalida, E. Herrera, B. Arguello, P. Vigil, P. Villaseca and E. Leontic

Summary. Samples of semen and cervical mucus were provided by 18 couples. Cervical mucus was obtained for each day possible and stored at 4°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.

Keywords: human; cervical mucus; gamete membrane fusion test; spermatozoa

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JG Reyes, E Herrera, L Lobos, K Salas, N Lagos, RA Jorquera, P Labarca and DJ Benos

Glycolytic metabolism in meiotic and post-meiotic spermatogenic cells shows differentiation-related changes. The developmental and physiological significance of these metabolic changes is not known. The aim of the present study was to test the hypothesis that glucose and lactate metabolism can modulate intracellular calcium [Ca2+](i) in spermatogenic cells in an opposing and dynamic manner. Fluorescent probes were used to measure [Ca2+](i) and pH(i), and HPLC was used to measure intracellular adenine nucleotides and mitochondrial sensing of ATP turnover. [Ca2+](i) in pachytene spermatocytes and round spermatids was modulated by changes in lactate and glucose concentrations in the media. The kinetics and magnitude of the [Ca2+](i) changes induced by lactate and glucose were different in meiotic and post-meiotic spermatogenic cells. The presence of glucose in the medium induced a decrease in pH(i) in spermatogenic cells. This glucose-induced pH(i) decrease occurred later than the changes in [Ca2+](i), which were also observed when the pH(i) decrease was inhibited, indicating that the glucose-induced [Ca2+](i) increase was not a consequence of pH(i) changes. Hexose phosphorylation in glycolysis was part of the mechanism by which glucose metabolism induced a [Ca2+](i) increase in spermatogenic cells. The sensitivity of [Ca2+](i) to carbohydrate metabolism was higher in round spermatids than in pachytene spermatocytes. Thus, differentiation-related changes in carbohydrate metabolism in spermatogenic cells determine a dynamic and differential modulation of their [Ca2+](i) by glucose and lactate, two substrates secreted by the Sertoli cells.

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Brooke E Barton, Gerardo G Herrera, Prashanth Anamthathmakula, Jenna K Rock, Anna M Willie, Emily A Harris, Ken-Ichi Takemaru and Wipawee Winuthayanon

The oviduct (known as the fallopian tube in humans) is the site for fertilization and pre-implantation embryo development. Female steroid hormones, estrogen and progesterone, are known to modulate the morphology and function of cells in the oviduct. In this review, we focus on the actions of estrogen and progesterone on secretory, ciliated, and muscle cell functions and morphologies during fertilization, pre-implantation embryo development, and embryo transport in humans, laboratory rodents and farm animals. We review some aspects of oviductal anatomy and histology and discuss current assisted reproductive technologies (ARTs) that bypass the oviduct and their effects on embryo quality. Lastly, we review the causes of alterations in secretory, ciliated, and muscle cell functions that could result in embryo transport defects.