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R Shalgi

Publications and source records attributed to R Shalgi.

At least 73 records · Page 4Linked to original sources
PubMed1988

Motility of rat spermatozoa at the site of fertilization.

This study was undertaken to examine the factors that may affect the numbers and motility patterns of spermatozoa at the site of fertilization. The contents of the oviductal ampullae of previously mated cycling or superovulated immature rats were examined microscopically. We determined whether spermatozoa were free or associated with cells and whether they exhibited hyperactivated motility, forward progressive motility, or were immotile. These data were correlated with the percentage of fertilized eggs. In addition, the beat pattern of hyperactivated spermatozoa was characterized by using high-speed video microscopy. At the time when half of the eggs were fertilized, ampullae of cycling rats contained an average of less than one motile spermatozoon per ampulla. Most of these motile spermatozoa were hyperactivated. About half of these were free in the ampulla and about half were in the cumulus or zona pellucida. Hyperactivated spermatozoa displayed a nonprogressive whiplash wave form with a high amplitude recovery stroke similar to that described in hamster and guinea pig spermatozoa capacitated in vitro. In addition to motile spermatozoa, we counted about three immotile spermatozoa for each motile spermatozoon. In superovulated, immature female rats, we found about ten times as many spermatozoa in each category as in cycling rats. From our observations, it is clear that very few spermatozoa reach the ampulla of the oviduct. Furthermore our observations suggest that in cycling rats progressively swimming spermatozoa may become hyperactivated shortly after entering the ampulla of the oviduct. They probably enter the cumulus mass within a short time or become immotile.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Fertilization in vitro of rat oocytes undergoing maturation in response to a GnRH analogue.

Oocytes were exposed to GnRHa to induce their maturation both in vivo, by administration of the hormone to hypophysectomized rats, and in vitro, in cultures of intact ovarian follicles. Mature oocytes obtained under both these conditions were then exposed in vitro to a sperm suspension for fertilization. Fertilization of control groups of oocytes, isolated from intact or hypophysectomized PMSG-primed hCG-induced ovulators, was 88.3 +/- 3.3% (n = 331) and 90.0 +/- 2.8% (n = 427), respectively, as compared to 82.8 +/- 3.2% (n = 413) for oocytes isolated from hypophysectomized PMSG-primed GnRHa-induced ovulators. Fertilization rate in oocytes treated by GnRHa in vitro was 78.5 +/- 3.1% (n = 247) as compared to 79.3 +/- 4.1% (n = 261) in LH-treated oocytes. These results demonstrate that fertilizability of oocytes undergoing maturation in response to GnRHa is similar to that of oocytes induced to mature by LH. No differences could be detected in the proportions of abnormal oocytes (polyspermic, fragmented and dead) and the zygotes obtained after fertilization of GnRHa- or LH-treated oocytes showed similar ability to cleave.

Animals↗
PubMed1986

The role of carbohydrates in sperm-egg interaction in rats.

The first step in fertilization is the interaction of the capacitated sperm with the zona pellucida. It has been proposed that the initial interaction, as in other types of cell adherence, is due to complementary interacting sites on the opposing surfaces of the gametes. This work intended to investigate the role of carbohydrates in sperm-egg binding in rats. Ejaculated sperm was collected from uterine horns of mated females. The sperm was suspended in Rat Fertilization Medium at final concentrations of 3-7 times 10(5) sperm/ml. After 5 1/2 h of sperm incubation, eggs were added to the sperm suspensions concomitantly with various carbohydrates to achieve a final concentration of up to 50 mM. The eggs were separated after 30 min, and the number of sperm bound to the zona pellucida was counted. Among a variety of monosaccharides tested at 50 mM concentration, it was found that alpha-methyl-mannoside was the most potent inhibitor (producing 80% inhibition); less potent was D-mannose and even less, L-fucose. A combination of alpha-methyl-mannoside and L-fucose showed a synergistic effect. Mannan was not more effective as an inhibitor than the monosugar mannose, while fucoidin was extremely potent, causing over 90% inhibition of binding at 0.1%. We assume the presence of macromolecules containing sugars on the zona pellucida because inhibition of sperm binding to this layer was observed: a) after preincubation of mannan or fucoidin with sperm, but not with the eggs; and b) after pretreatment of the egg with specific enzymes. The results obtained in this study in the rat are consistent with the hypothesis that carbohydrates are critical for the sperm-egg interaction.

Animals↗
PubMed1985

Mammalian fertilization as seen with the scanning electron microscope.

For several years we have been looking at mammalian gametes and their interactions with the scanning electron microscope (SEM). Examining the images produced by the SEM has given us a three-dimensional view of sperm, eggs, and egg investments. We are particularly impressed with the structural variation among gametes of different mammalian species. In this short report we examine the structure of mammalian spermatozoa, eggs, zonae pellucidae, and cumuli. Our observations and those of others have led us to believe that variation in gamete structure and function may have evolved as a mechanism for reproductive isolation of mammalian species.

Animals↗
PubMed1985

Penetration of sperm from teratospermic men into zona-free hamster eggs.

The ability of sperm samples from male partners of infertile couples, with isolated teratospermia (ITS), to penetrate zona-free hamster eggs was examined. The ITS patients had a significantly lower proportion of normal spermatozoa than did a control group of men of proven fertility (23.6% and 47.8%, respectively; P less than 0.001), while the mean total sperm count and the % motility did not differ between the two groups. The mean hamster egg penetration rate of sperm from ITS patients was 2.64% compared to 31.1% in the control group. A significant negative correlation was found in the ITS group between the proportion of a) abnormal forms and the ability to penetrate zona-free hamster eggs, and b) pyriform-shaped sperm and the penetration rate. Of the sperm parameters which were examined, only the morphology could be correlated with the rate of penetration.

Adult↗
PubMed1982

Sperm penetration into rat ova fertilized in vivo.

The mechanics of sperm entry into the oocyte were examined in rat ova fertilized in vivo. With the scanning electron microscope we observe that the spermatozoon is first associated with the oocyte by the region of the convex surface of the sperm head which is immediately anterior to the postacrosomal region. At this early stage the anterior tip of the sperm head is directed away from the oocyte surface. The spermatozoon subsequently appears to rotate so that it comes to lie on its "side." The membrane over the sperm head becomes free of microvilli and a large incorporation cone is subsequently formed. It is concluded that in the rat initial fusion of sperm and egg probably occurs between the oolemma and the sperm plasmalemma over the equatorial segment of the acrosome at the convex surface of the sperm head which is just anterior to the postacrosomal region.

Animals↗
PubMed1982

Comparison of cornual transfer via laparotomy with utero-cervical transfer of cultured preimplantation rat embryos.

Most work on embryo transfer has used the cornual route via laparotomy for implantation. This method is time-consuming and costly in operating materials. Cervical transfer seems to offer a simpler route and the promise of time and cost saving. Technical difficulties, however, have prevented this method from becoming widely used. It was thought that mastery of this technique is essential to allow large-scale experiments in order to determine the optimal time for reimplantation, the optimal stage whether 8 cells, morulae, or blastocysts, and to compare culture media. All of these will have significant clinical applications. In this work Vickery's method of cervical transfer in mice was modified to include direct vision of the cervix and dilatation before implantation. With this modification equivalent results were found on cervical or cornual transfer, but a higher failure rate on cervical transfer. The results and implications are discussed.

Animals↗
PubMed1981

The male factor in fertilization of rat eggs in vitro.

Both epididymal and ejaculated spermatozoa give usable rates of fertilization of superovulated oocytes in vitro. The epididymal sperm gave higher rates, but ejaculated sperm were preferred because intra-donor variation was lower than inter-donor variation. A selected population of 14 male donors had normally distributed fertilizing capacity with a mean and standard deviation of 77 +/- 14% (2,823 eggs). Successive ejaculates usually gave similar rates of fertilization. An attempt was made to eliminate dead and agglutinated cells from the ejaculated sperm by filtration through a column of glass beads. Despite the expected marked improvement in the average motility, the eluted spermatozoa were incapable of fertilizing. We concluded that the preferred source of spermatozoa for fertilization in vitro is ejaculated sperm. In the rat, motility and cell morphology are not adequate criteria for fertilizing capacity of treated spermatozoa.

Animals↗
PubMed1979

Scanning electron microscopy of the surface of normal and implantation-delayed mouse blastocysts during development in vitro.

Mouse blastocysts undergo developmental steps in culture analogous to those occurring during implantation in utero. We examined cultured blastocysts by scanning electron microscopy (SEM) as they passed through these stages. From the time of hatching to the acquisition of adhesiveness, most blastocysts were exhanded, with flattened cells possessing relatively small numbers of microvilli, centrally raised areas (presumably reflecting the location of the nuclei) and intercellular ridges often possessing microvilli. At, or shortly before, the trophoblast outgrowth stage, blastocysts appeared to contract; the cells bulged noticeably, microvilli covered the entire surface of most cells and intercellular ridges were no longer observable. Blastocysts removed from uteri on the seventh day of ovariectomy delay possessed a variety of morphologies and shapes. The blastocoel was frequently collapsed and cell outlines were difficult to discern. These blastocysts were initially adhesive in vitro, but subsequently disengaged from the substratum before becoming permanently adherent several hours later. During the initial phase of adhesiveness, blastocysts were elongated and had prominent intercellular ridges, particularly in the equatorial region. Detached blastocysts contained bulging cells with contours which obscured the intercellular ridges. Surface ultrastructure during subsequent phases resembled non-delayed blastocysts during attachment and outgrowth. On the basis of our studies, we propose that intercellular ridges play some role in blastocyst adhesiveness. However, we must conclude that there are other factors involved in the acquisition of adhesiveness by the blastocyst which are at least equally important but of a nature too subtle to be identified by our SEM analyses. Insofar as delayed blastocysts are concerned, we find that, within limits, the surface alterations that take place when blastocysts are activated in culture mirror those observed following reversal of delay in vivo by administration of hormones. Since delayed blastocysts placed in saline also undergo morphological changes resembling those seen at the onset of activation in utero, we suggest that reversal of implantation delay requires initially neither direct contact with steroid or macromolecular inducers nor an exogenous supply of metabolites.

Adhesiveness↗
PubMed1979

The effect of LH on the fertilizability and developmental capacity of rat oocytes matured in vitro.

The effect of adding LH (10 microgram NIH-LH-B8/ml) to the medium in which oocytes were undergoing maturation in vitro was studied. The fertilizability of the oocytes was evaluated in the sterile oviduct of a unilaterally ovariectomized, mated recipient. Freshly ovulated oocytes, used as a control of the method, were fertilized at a rate of 72%. Only 14% of oocytes matured in culture (without LH) were penetrated by spermatozoa, and 11% were fertilized normally. Addition of LH to the medium increased these proportions to 43 and 33% respectively. Oocytes matured in the presence of LH were able to develop into apparently normal rats. It is concluded that, although oocytes can mature in vitro spontaneously, and that these matured oocytes can be fertilized, addition of LH increases the numbers 3-fold. LH therefore has a direct maturation-promoting action on the rat oocyte-cumulus complex in vitro.

Animals↗
PubMed1978

Changes in the surface of the mouse blastocyst at implantation.

Implantation is a critical event, and perhaps the earliest one, in the maternal recognition of pregnancy. Information transfer from conceptus to mother might occur during, and subsequent to, implantation at the level of cell surface interaction. Therefore, attempts have been made both to identify the phases of implantation during which changes in the blastocyst surface occur and to characterized such changes. In vitro, blastocysts have been found to go through a series of discrete steps which are analogous to implantation in utero, and these steps can be retarded or prevented by the use of either suboptimal culture media or an inappropriate substratum. Morphological surface changes are not apparent when the blastocyst becomes adherent to the substratum; however, marked differences in blastocyst surface structure are revealed by scanning electron microscopy at the onset of trophoblast outgrowth. Studies at the molecular level implicate collagen as having a role in blastocyst adhesiveness, but other cell surface components are also likely to be involved.

Animals↗
PubMed1978

Timing of sperm transport, sperm penetration and cleavage in the rat.

Times of sperm entry into the oviduct from the uterus, into the ampulla from the isthmus; of sperm penetration into oocytes, and of cleavage, were determined using three mating regions. Time intervals and their errors of estimation were calculated. Spermatozoa were first found in the isthmus of the oviduct no earlier than 15 minutes after coitus, but required four hours to ascend the oviduct to the ampulla. The rate of sperm arrival was equal to the rate of sperm penetration, i.e., about 3 sperms/hour. Time of cleavage in vivo was 20.6 hours after sperm penetration in ad libitum mated animals. In culture, oocytes cleaved at exactly the same time as in vivo. Delaying sperm arrival to the site of fertilization (by delaying mating) shortened the time interval between median time of sperm penetration and median time of cleavage. It was concluded that the time of cleavage of the oocyte reflects primarily the time of sperm penetration, but is also influenced by the postovulatory age of the oocyte.

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