Showing papers on "Acrosome reaction published in 1976"

The Use of Zona-Free Animal Ova as a Test-System for the Assessment of the Fertilizing Capacity of Human Spermatozoa

Abstract: The zona-free hamster ovum was evaluated as a substitute for human o va in the assessment of the fertilizing capacity of human spermatozoa. Zona-intact ova completely resisted sperm penetration. Using nonpreincu bated spermatozoa sperm penetration of zona-free ova began 4-5 hours after insemination. However when spermatozoa were preincubated in a modified Krebs-Ringer solution for 4 hours sperm penetration began within 1 hour. There is some evidence that this is associated with the completion of sperm capacitation and the acrosome reaction. The results suggest that zona-free hamster ova can be substituted for human ova in the preliminary assessment of the fertilizing capacity of human spermatozoa.

Maturation and sperm penetration of canine ovarian oocytes in vitro.

Abstract: Canine ovarian oocytes were cultured in a medium consisting of TC medium 199, fetal calf serum and antibiotics. Ninety-nine percent of the apparently healthy oocytes were in the germinal vesicle (dictyate) stage when recovered from the ovaries; 25% of them reached metaphase I or II by 72 hours of culture. Washed ejaculated spermatozoa were added to BWW medium containing oocytes which had either been removed directly from the follicles or which had been cultured for 24--72 hours. The earliest acrosome reaction and zona penetration by spermatozoa were seen at seven hours after insemination. Seventy-four percent of the oocytes examined between 11 and 24 hours after insemination showed evidence of zona penetration by spermatozoa. Neither the condition of the oocyte vitellus nor the stage of nuclear maturation influenced the incidence of zona penetration. Decondensing sperm nuclei were found in the vitellus of 27% of the oocytes which had not been cultured and in the vitellus of 20% of those which had been cultured for 24--72 hours and were in various stages of maturation. These results indicate that (1) canine ovarian oocytes can be matured in vitro, (2) the spermatozoa require capacitation which takes approximately seven hours in vitro and (3) maturation of the oocytes is not required for sperm passage through the zona pellucida or entry into the vitellus nor for sperm nuclear decondensation.

The role of calcium in the acrosome reaction: An analysis using ionophore A23187

Abstract: The role of Ca+2 in the acrosome reaction of echinoid and mammalian sperm was investigated using the Ca+2 transporting ionophore A23187. The ionophore induced morphologically normal acrosome reactions in both types of sperm (as assessed by electron microscopic observation of echinoid sperm and phase contrast microscopic observation of mammalian sperm). In echinoids, these reactions were immediate. In the guinea pig and hamster, ionophore significantly decreased the capacitation interval; early reactions were accompanied by activation of motility. Ionophore induced reactions were affected by sperm, ionophore and Ca+2 concentrations. Since both ionophore induced and natural reactions require extracellular Ca+2, it is suggested that an influx of Ca+2 represents the initial step of the acrosome reaction. Under natural conditions, the permeability change which results in Ca+2 influx may be induced in echinoid sperm by egg jelly and may occur in mammalian sperm during capacitation. Ionophore A23187 should prove an experimentally useful drug for further study of the acrosome reaction since its effect on cells is understood, it induces synchronous reactions in a high percentage of sperm, and it conveniently reduces the capacitation interval in mammalian sperm.

Evidence for the role of a trypsin-like enzyme in the hamster sperm acrosome reaction†

Abstract: Acrosome reactions occurring in vitro in hamster sperm capacitated by bovine follicular fluid were severely inhibited by four synthetic trypsin inhibitors and by Zn2 +. Three polypeptide trypsin inhibitors and a synthetic chymotrypsin inhibitor did not inhibit the acrosome reaction, and Ca2 + overcame the inhibition by Zn2. These results suggest that a trypsin-like enzyme (possibly acrosin) plays a role in the acrosome reaction.

The sperm acrosome reaction and fertilization in the guinea-pig: a study in vivo

Abstract: Female guinea-pigs were naturally or artificially inseminated before or after ovulation and the distribution of spermatozoa in the oviducts and the time of sperm penetration into the eggs were determined. When animals were inseminated before ovulation, the spermatozoa stayed in the distal half of the oviduct until about the time of ovulation. Only a very few spermatozoa were present in the proximal half of the oviduct at the time of ovulation, but these were sufficient to effect fertilization. When animals were inseminated after ovulation, the spermatozoa ascended the oviduct faster than when animals were inseminated before ovulation, and fertilization commenced in 4 hr. Regardless of the time of insemination, the spermatozoa participating in fertilization appeared to undergo the acrosome reaction after they reached the proximal part of the oviduct or when they were very near the eggs.

Ionophore A23187 induces acrosome reactions in sea urchin and guinea pig spermatozoa.

Abstract: Ionophore A23187, in the presence of extracellular Ca+2, induces a morphologically normal acrosome reaction in sperm of the sea urchin and precocious acrosome reaction and activation of guinea pig sperm. Increased membrane permeability to Ca+2 is responsible for initiating the acrosome reaction in both sea urchin and guinea pig sperm. In sea urchin sperm, the permeability change is brought about by egg jelly, whereas in the guinea pig sperm it accompanies capacitation.

Phospholipase activity of sea urchin sperm: its possible involvement in membrane fusion.

Abstract: Phospholipase activity of egg-water treated Arbacia punctulata and Lytechinus variegatus sperm was shown to result from the sequential action of phospholipase A and lysophospholipase. A transient burst of phospholipase A activity followed induction of the acrosome reaction with egg water. The time of appearance suggested an acrosomal localization of the enzyme. The peak activity of phospholipase A correlated with initiation of sperm-egg fusion, suggesting a role for sea urchin sperm phospholipase A in membrane fusion and/or egg activation during fertilization.

Morphology and kinetics of the hamster sperm acrosome reaction

Abstract: The morphology and kinetics of the normal acrosome reaction were examined in vitro using hamster sperm incubated in detoxified sera. The reaction involved either swelling and elevation or crenulation and fragmentation of the acrosomal cap. Swelling and elevation occurred during both normal and degenerative reactions, as reported by others. Crenulation with subsequent fragmentation of the cap was observed during normal reactions. Early crenulation of the acrosome could be induced by cold shock (5 degrees C, 25 minutes), but this did not decrease the incubation time required (at 37 degrees C) for completion of the normal reaction. In appropriate sera, the occurrence of normal and degenerative acrosome reactions in motile sperm was significantly separated in time to study the reactions independently. The duration of the normal reaction, i.e., the time between the first morphological change in the acrosome (initiation)until the actual detachment of the cap (termination) was estimated to be 20 minutes. Saline dilution of these sera delayed initiation of the reaction and increased the duration of the reaction once it had started. Data from cold-shock and serum dilution experiments indicate that the mechanisms which govern the initiation and termination of the normal reaction are independently variable, and further suggest that initiation involves a change in membrane permeability and that termination includes membrane vesiculation.

Evidence for a polyspermy block at the level of sperm‐egg plasma membrane fusion in Urechis caupo

Abstract: The results of sperm binding experiments reveal no change in the sperm binding properties of the egg surface coat at fertilization of Urechis caupo eggs. When fertilized eggs are reinseminated, sperm continue to attach to the egg surface coat. The acrosomal tubules of supernumerary sperm are observed in the perivitelline space closely apposed to the egg membrane. Thus, the polyspermy block in Urechis eggs involves neither alteration of sperm binding sites nor inhibition of the acrosome reaction. Our results suggest that the block is at the level of sperm-egg membrane fusion.

Scanning electron-microscopical and other observations of sperm fertilization reactions in Limulus polyphemus L. (Merostomata: Xiphosura).

Abstract: Sperm fertilization reactions of Limulus polyphemus were examined by scanning electron and/or light microscopy. The following were considered: sperm motility, attachment of sperm to egg, acrosome reaction, and penetration of the acrosomal filament. The spermatozoa after semination are non-motile and become active only in close proximity to a defined region surrounding the egg. Egg materials diffusing into this region induce sperm motility and stimulate large numbers of spermatozoa to move towards the egg surface. Each sperm initially attaches by the apical tip and undergoes the acrosome reaction which causes a more permanent secondary attachment by the adhesion of acrosomal contents to the egg surface. The acrosome reaction also initiates the penetration of the acrosomal filament through the egg envelope, an event occurring in 70–80% of the attached spermatozoa (about 10(6). Shortly after this penetration, a secondary reaction occurs which involves a spiralling of the flagellum and an incorporation into the sperm body of the flagellar fibrous components, which then become closely apposed to the sperm nucleus. These sperm fertilization reactions were performed or initiated with 0-34 M CaCl2 in whole eggs, egg sections, excised egg envelopes and/or the outer basement lamina of the egg envelope. The Limulus fertilization system is very valuable since sperm reactions can be examined biochemically, which may lead to a better understanding of the chemical mechanisms involved in sperm-egg interactions in all animal species.

Fertilization in swine and cattle

Abstract: Fertilization and its prerequisites, i.e. sperm transport, capacitation and oocyte maturation, were discussed with emphasis on the occurrence of these processes in the pig and cow. Attempts to fertilize porcine and bovine ova in a micro-droplet system which was used successfully to fertilize mouse and hamster ova were not successful. Many droplets contained highly motile spermatozoa which were effective in removing the follicular cells from around the zonae. Spermatozoa attached to the zonae but did not penetrate the ova in vitro. No motile bull or boar spermatozoa with an "acrosome reaction" were observed in the droplets. When droplets which contained boar spermatozoa and pig follicular oocytes for 4 h were transferred into the oviducts of estrous females, spermatozoa exhibited acrosome reactions and ova were penetrated. Reducing oocyte maturation time and injecting progesterone before ovulation increased (P < 0.05) the incidence of polyspermy in pigs. Bovine oocytes underwent maturation and were penetra...

Effects of epididymal occlusion on sperm maturation in the hamster.

Abstract: The effects of occlusion of the hamster epididymis by clips on the maturation of epididymal spermatozoa were studied. Normal mature spermatozoa from the caudal region had a fertilization rate of 77% and showed a 50-80% incidence of acrosome reactions after 6 hours in medium. Conversely immature spermatozoa from the caput and corpus regions were infertile showed poor motility and did not exhibit an acrosome reaction. Isolation of these spermatozoa for 1 or 2 days improved motility and produced a distal migration of the cytoplasmic droplet similar to that observed in normal maturation. However these sperm remained infertile and failed to show an acrosome reaction in vitro. The results suggest that the ability of hamster epididymal spermatozoa to fertilize is related to the ability to exhibit an acrosome reaction in vitro and that the completion of sperm maturation appears to require the environment of the cauda epididymis.

Fertilization of sea urchins needs magnesium ions in seawater

Abstract: When sea urchin eggs were inseminated in seawater free of magnesium, the fertilization rate was very low. Spermatozoa that had been treated with egg jelly to induce the acrosome reaction also failed to fertilize eggs in seawater free of magnesium. These results indicate that magnesium is indispensable for some process or processes at fertilization, such as membrane, fusion or sperm penetration.

In-vitro fertilization of hamster eggs in different media and the stimulating effect of heterologous and homologous spermatozoa

Abstract: Hamster eggs with follicular cells were fertilized by epididymal spermatozoa in two chemically defined media. The proportion of penetrated eggs was significantly higher in a medium for rabbit (16%) than in a medium for rat eggs (6%), but much lower than in Tyrode's solution containing follicular fluid or blood serum as reported by others. The optimal sperm concentration for sperm penetration ranged from 0.5 to 5 X 10(6)/ml but penetration of denuded eggs failed in these media. When exposed to hamster spermatozoa in the rabbit medium containing living or dead spermatozoa of guinea-pig, rat, mouse or hamster, high proportions of denuded eggs (24-96%) and eggs with follicular cells (93%) were penetrated. By exposure of denuded hamster eggs to hamster spermatozoa in supernatant fluid of frozen-thawed guinea-pig spermatozoa, 97% of eggs were penetrated in 8 hr compared to 0% in the control group. Sperm capacitation was also efficiently induced by preincubation of hamster spermatozoa in the supernatant fluid. The fertilizing capacity of hamster spermatozoa was maintained for 12 hr during incubation with frozen-thawed guinea-pig spermatozoa when the concentration of hamster spermatozoa ranged between 10 and 20 X 10(6)/ml. The beneficial factor of guinea-pig spermatozoa appeared to be from spermatozoa themselves, not from the vasal or epididymal fluids. The presence of follicular cells, blood serum, bovine serum albumin, or even polyvinylpyrrolidone in the media is essential for the capacitation and acrosome reaction of hamster spermatozoa. The components of guinea-pig spermatozoa appear to maintain the fertilizing capacity of hamster spermatozoa and stimulate the process of capacitation.