Showing papers on "Sperm published in 1978"
TL;DR: Rats were considered to be pubertal at 50 days of age when spermatozoa were first found in the tail of the epididymis, but Wistar rats are not sexually mature until 100 years of age.
Abstract: Rats were considered to be pubertal at 50 days of age when spermatozoa were first found in the tail of the epididymis. Sperm production/g testis increased up to 75 days of age and testicular weight increased until 100 days of age. Sperm reserves in the tail of the epididymis were not maximal until 100 days of age. Therefore, Wistar rats are not sexually mature until 100 days. Sexually mature rats had testes weighing 3.7 g, produced 86 x 10(6) spermatozoa or 24 x 10(6) spermatozoa/g testicular parenchyma daily, and their paired epididymides contained 295 x 10(6) spermatozoa in the head + body and 440 x 10(6) spermatozoa in the tail.
705 citations
TL;DR: It is concluded that the fertilization wave in the medaka egg is propagated by calcium-stimulated calcium release, primarily from some internal sources other than the large cortical vesicles.
Abstract: Aequorin-injected eggs of the medaka (a fresh water fish) show an explosive rise in free calcium during fertilization, which is followed by a slow return to the resting level. Image intensification techniques now show a spreading wave of high free calcium during fertilization. The wave starts at the animal pole (where the sperm enters) and then traverses the egg as a shallow, roughly 20 degrees-wide band which vanishes at the antipode some minutes later. The peak free calcium concentration within this moving band is estimated to be about 30 microM (perhaps 100-1,000 times the resting level). Eggs activated by ionophore A23187 may show multiple initiation sites. The resulting multiple waves never spread through each other; rather, they fuse upon meeting so as to form spreading waves of compound origin. The fertilization wave is nearly independent of extracellular calcium because it is only slightly slowed (by perhaps 15%) in a medium containing 5 mM ethylene glycol-bis[beta-aminoethyl ether]N,N9-tetraacetic acid (EGTA) and no deliberately added calcium. It is also independent of the large cortical vesicles, which may be centrifugally displaced. Normally, however, it distinctly precedes the well-known wave of cortical vesicle exocytosis. We conclude that the fertilization wave in the medaka egg is propagated by calcium-stimulated calcium release, primarily from some internal sources other than the large cortical vesicles. A comparison of the characteristics of the exocytotic wave in the medaka with that in other eggs, particularly in echinoderm eggs, suggests that such a propagated calcium wave is a general feature of egg activation.
542 citations
TL;DR: The use of hamster eggs to activate human sperm to the point where their chromosomes can be studied directly is reported here and some claims have now been retracted.
Abstract: ALL available information on the chromosome constitution of human gametes is speculative, having been obtained by inference from the chromosome constitution of conceptuses that survive sufficiently long to produce a clinically recognisable pregnancy. A minimum of 10% of all recognised human conceptions are chromosomally abnormal, and it has been estimated that 1–2% are the result of fertilisation by a spermatozoon with a chromosome abnormality1. Cytological evaluation of the chromosome constitution of human spermatozoa has been restricted to the staining of fixed smears of whole sperm2–13. Certain chromosome regions with peculiar staining properties, such as the long arm of the Y chromosome and the heterochromatic region of chromosome 9, are presumed to be represented in appropriately stained sperm nuclei by differentially staining spots. By counting the number of these spots per nucleus, the frequency of aneuploidy in the sperm of normal males has been estimated to be around 40% (refs 5, 9–11). The precision of the data obtained from stained whole sperm is dubious, because several factors must be taken into consideration when blobs are counted in sperm head nuclei, all of which could contribute to biased estimates of nondisjunction7,8,12. For this reason, some claims have now been retracted12,13. To investigate the true contribution of male gametes to the production of chromosomally abnormal conceptuses and the factors influencing the production and survival of chromosomally abnormal sperm, it is necessary to analyse the sperm chromosomes directly. However, after meiotic metaphase II sperm chromosomes do not reappear until the male and female pronuclei of the fertilised egg prepare for the first cleavage division. We report here the use of hamster eggs to activate human sperm to the point where their chromosomes can be studied directly.
383 citations
TL;DR: The genetic basis of specificity of the acid phosphatase test is in question; the quantitative test can only be based on the extraordinarily high level of acidosphatase activity in semen; the low levels of activity often found in postcoital vaginal washings are thus equivocal with respect to the question of semen detection.
Abstract: The identification of semen is of paramount importance in the investigation of rape and other crimes involving sexual assault. The most commonly used procedures for semen identification center on the detection of sperm or the detection of prostatic acid phosphatase activity; methods involving the detection of spermine, choline, or semen antigens are less commonly employed. Unfortunately, none of these procedures is without one or more significant problems. For example, sperm will not be found in the semen of vasectomized or aspermic males; moreover, sperm are mechanically labile and their unequivocal identification in suspected semen stains is often difficult. Also, sperm are cleared from the vagina fairly rapidly and hence may not be found in postcoital vaginal washings. Thus the failure to detect sperm in suspect material by no means counterindicates semen. In the case of the acid phosphatase test, the problems are different. Acid phosphatase is not at all unique to semen or prostatic tissue; this enzyme activity is ubiquitous in nature. Moreover, there is evidence that prostatic acid phosphatase and the acid phosphatase found in normal vaginal secretions are genetically identical and that both are genetically identical to lysosomal acid phosphatase found in most tissues; therefore, the genetic basis of specificity of the acid phosphatase test is in question. The quantitative test can only be based on the extraordinarily high level of acid phosphatase activity in semen; the low levels of activity often found in postcoital vaginal washings are thus equivocal with respect to the question of semen detection. The other tests for semen identification are similarly suspect in reference to their specificity.
286 citations
TL;DR: The chapter describes the important roles played by intracellular calcium and cytoplasmic pH in turning on the cell metabolism and the consequences of sperm fusion with the egg that leads to the responses that result in the activation of embryonic development.
Abstract: Publisher Summary This chapter discusses the fertilization of the sea urchin egg. The metabolic and morphological changes of sea urchin gametes during fertilization are the best characterized of all embryos. In organization, this chapter explains the activation of both gametes, first considering the activation of the sperm upon its contact with egg jelly and the resultant cascade of the events leading to sperm–egg attachment and sperm–egg fusion. It then examines the consequences of sperm fusion with the egg that leads: (1) to the responses, excluding other sperm from fusing with the egg and (2) to the responses that result in the activation of embryonic development. The chapter describes the important roles played by intracellular calcium and cytoplasmic pH in turning on the cell metabolism. In sperm plasma membrane, the receptors interact with some component of the egg jelly or egg surface. This leads to increased Ca2+ content, the induction of membrane fusion, and the acrosomal exocytosis. At the same time, there is an acid efflux, polymerization of internal actin, and exposure of sperm lysins and sperm bindins that are attached to the newly formed membrane of the acrosomal process.
274 citations
TL;DR: It is concluded that a rise in intracellular pH induces the actin to disassociate from its binding proteins and thus it can polymerize.
Abstract: When Pisaster, Asterias, or Thyone sperm are treated with the ionophore A23187 or X537A, an acrosomal reaction similar but not identical to a normal acrosomal reaction is induced in all the sperm. Based upon the response of the sperm, the acrosomal reaction consists of a series of temporally related steps. These include the fusion of the acrosomal vacuole with the cell surface, the polymerization of the actin, the alignment of the actin filaments, an increase in volume, an increase in the limiting membrane, and changes in the shape of the nucleus. In this report, we have concentrated on the first two steps in this sequence. Although fusion of the acrosomal vacuole with the cell surface requires Ca++, we found that the polymerization of actin instead appears to be dependent upon an increase in intracellular pH. This conclusion was reached by applying to sperm A23187, X537A, or nigericin, ionophores which all carry H+ at high affinity, yet vary in their affinity for other cations. When sperm are suspended in isotonic NaCl, isotonic KCl, calcium-free seawater, or seawater, all at pH 8.0, and the ionophore is added, the actin polymerizes explosively and an efflux of H+ from the cell occurs. However, if the pH, of the external medium is maintained at 6.5, the presumed intracellular pH, no effect is observed. And, finally, if egg jelly is added to sperm (the natural stimulus for the acrosomal reaction) at pH 8.0, H+ is also released. On the basis of these observations and those presented in earlier papers in this series, we conclude that a rise in intracellular pH induces the actin to disassociate from its binding proteins. Now it can polymerize.
251 citations
TL;DR: Comparison of the electrophoretic patterns of histones from human testis, testicular sperm and ejaculated sperm implied that the histones may be removed in the order H2A and H1 before H3, H4 and H2B before TH2B.
208 citations
TL;DR: It is concluded that the effect of cAMP on modeled bull sperm reflects a naturally occurring balance which controls the motility of bull sperm, and that cAMP exerts its stimulatory action directly on the motile apparatus.
199 citations
TL;DR: Correlation of regeneration with fertility data demonstrated that fertility was reestablished when sperm production returned to about 15% of control levels, and only partially restored spermatogenesis.
Abstract: The regeneration of mouse testicular stem cells during 60 weeks after exposure to 600 or 1200 rad of ..gamma.. radiation was examined. Restoration of spermatogenesis depended on stem cell survival, regeneration, and differentiation. Several assays were employed to measure the number of stem cells and their ability to repopulate the seminiferous epithelium as follows. Assay 1: The percentage of repopulated tubular cross sections was determined histologically at various times after irradiation. Assay 2: Mice were irradiated and, after given time intervals to allow for regeneration of stem cell numbers, a second dose was given. The percentage of repopulated tubular cross sections was determined 5 weeks later. Assay 3: The ability of the stem cells to produce spermatocytes and spermatids was assayed by the levels of the germ cell specific isoenzyme, LDH-X. Assay 4: The ability of the stem cells to produce sperm was assayed by the number of sperm heads in the testes. In addition, the ability of the stem cells to produce functional spermatozoa was measured by the fertility of the animals. The results obtained were as follows. All assays demonstrated that gradual regeneration of stem cell number occurred simultaneously with repopulation of the seminiferous epithelium by differentiating cellsmore » derived from stem cells. The regeneration kinetics of stem cells followed an exponential increase approaching a dose-dependent plateau below the level prior to irradiation. The doubling time for stem cells during the exponential portion was about 2 weeks. The regeneration of stem cell number after depletion by irradiation was gradual and incomplete, and only partially restored spermatogenesis. Correlation of regeneration with fertility data demonstrated that fertility was reestablished when sperm production returned to about 15% of control levels.« less
195 citations
TL;DR: Sperm transport in the female rabbit proceeds by a sequential buildup of cells in ascending regions of the tract, which appears to involve the en masse migration of a limited number of cells from the lower isthmus to the upper oviduct and peritoneal cavity.
Abstract: The location of spermatozoa in the reproductive tract of the female rabbit was determined at 1.5, 4, 6, 8, 10, 12 and 16 h post coitum (p.c.). The posterior vagina, cervix, uterus, 5 regions of the oviduct and the ovarian surface were examined, the latter for evidence of sperm passage to the peritoneal cavity. The viability of spermatozoa recovered from the tract was assessed by counting the proportion of motile sperm and immotile cells with visibly disrupted head membranes. Sperm transport in the female rabbit proceeds by a sequential buildup of cells in ascending regions of the tract. The cervix may not be the principal site of sperm storage in the rabbit, since the viability of spermatozoa in the endocervical lumen is lower than in either the vagina or uterus. The tubal isthmus rather than the uterotubal junction, is the most important region restricting sperm ascent to the site of fertilization. Although a few sperm accumulate in the isthmus by 1.5 h p.c., there is no migration of sperm beyond the isthmus until 6 h p.c. and throughout sperm transport, more than 95% of the isthmic sperm population remain within 2 cm of the uterotubal junction. The majority of sperm reaching the site of fertilization ascend during the periovulation period and in many cases, after the arrival of the ova. The final ascent of spermatozoa to the site of fertilization appears to involve the en masse migration of a limited number of cells from the lower isthmus to the upper oviduct and peritoneal cavity. This transtubal migration occurs as a single event or as a series of events of limited duration which have ended by the time fertilization is completed.
TL;DR: The known properties of A23187 and the morphological similarity between the acrosome reaction and the secretory discharges of other secretory cells suggests that the immediate cause of the acosome reaction is an increase in the cytoplasmic free calcium concentration.
Abstract: The divalent metal cation ionophore A23187 induces an acrosome reaction in guinea-pig sperm which is dependent on external calcium. Examination of this acrosome reaction by electron microscopy shows that it is morphologically normal. The known properties of A23187 and the morphological similarity between the acrosome reaction and the secretory discharges of other secretory cells suggests that the immediate cause of the acrosome reaction is an increase in the cytoplasmic free calcium concentration.
TL;DR: The experiment examined the effect of supplementing a roughage diet with lupin grain on the capacity of testicular tissue to produce spermatozoa and found wide differences in total sperm production among rams fed on different diets.
Abstract: The experiment examined the effect of supplementing a roughage diet with lupin grain on the capacity of testicular tissue to produce spermatozoa. Changes in testicle size were estimated by comparative palpation. At the end of the experiment the rams were castrated and the morphology of the testes and their capacity to produce sperm were studied. At the highest level of feed intake, liveweight increased by 32% and testicle volume by 67% during the feeding period of 9 weeks. Rams on a diet that reduced testicle size produced 18 x l06 sperm/g testis per day, and those on a diet that increased testicle size produced 26 x l06 sperm/g testis per day. Those rams whose testes were increasing in size at castration had significantly larger seminiferous tubules, which occupied a significantly greater proportion of the testicle volume, than rams fed on diets that reduced the size of their testes. The variation in rates of sperm production, together with the large differences in testicle weight, resulted in wide differences in total sperm production among rams fed on different diets.
TL;DR: Recovery of fertility correlated with return of normal sperm counts and seminal fluid quality in the vas deferens on the testicular side of the obstruction at the time of vasovasostomy.
TL;DR: The identification, isolation, and partial characterization of a high molecular weight, trypsin-sensitive glycoprotein fraction from the sea urchin egg surface having species-specific affinity for bindin is reported, which may be the egg surface receptor for Bindin.
Abstract: Bindin is an insoluble protein coating the sperm acrosome process and mediating the adhesion of sperm to sea urchin eggs. Milligrams of bindin have been isolated. Here we report the identification, isolation, and partial characterization of a high molecular weight, trypsin-sensitive glycoprotein fraction from the sea urchin egg surface having species-specific affinity for bindin. This glycoprotein may be the egg surface receptor for bindin. The bindin receptor was released from 125-I-labeled eggs by parthenogenetic activation of eggs with ionophore A23187 in the presence of soybean trypsin inhibitor. The receptor has an isoelectric point of 4.02 and a molecular weight in sea water greater than or equal to 5 X 10(6), suggesting that it is an aggregate. It contains 34% neutral sugars, which are galactose and mannose.
TL;DR: Observations point to the chorion as the site at which the specific sperm-egg recognition occurs and as the primary site of one of the most stringent requirements of fertilization, namely the self-not-self recognition between gametes.
TL;DR: Methods for collection, freeze preservation and artificial insemination of domestic cat semen were developed and conception rate was low, but 6 pregnancies were achieved, 2 after hormonal induction of oestrus.
Abstract: Methods for collection, freeze preservation and artificial insemination of domestic cat semen were developed. Total sperm count and pre-freeze and post-thaw percent motility were significantly greater (P is less than 0.05) for samples collected by an artificial vagina method than for those collected by electroejaculation. Although conception rate was low (10.6%), 6 pregnancies were achieved, 2 after hormonal induction of oestrus.
TL;DR: Sperm bound to the zona surface following preincubation with Ca 2+ were capable of fertilization in vitro when the eggs were subsequently transferred to the culture medium and it is proposed that this binding reaction represents a part of capacitation and not the acrosome reaction.
TL;DR: Diet-induced atherosclerosis developed more extensively in vasectomized cynomolgus monkeys (Macaca fascicularis) than in sham-vasECTomized control monkeys fed the same diet.
Abstract: Diet-induced atherosclerosis developed more extensively in vasectomized cynomolgus monkeys (Macaca fascicularis) than in sham-vasectomized control monkeys fed the same diet. The effect was most pronounced in the abdominal aortas, carotid arteries, distal segments of the coronary arteries, and intracranial cerebral arteries. Antibodies to sperm developed in all vasectomized monkeys, and complement and immunoglobulins were associated with atherosclerotic plaques in some of the vasectomized animals. The immunological response to sperm antigens that often accompanies vasectomy may exacerbate atherosclerosis.
TL;DR: Observations show clearly that rapid passive transfer of rabbit spermatozoa to the upper oviduct and peritoneal cavity is a regular sequel to mating.
Abstract: Rabbit spermatozoa were recovered from the upper ampulla and the fimbrial and ovarian surfaces of all females examined at 1 mm post coitum (p.c.). As many as 1,000 spermatozoa could be recovered, on occasion, from the upper ampulla, fimbria and ovary of individual animals within the first 15 mm p.c. After artificial intravaginal insemination, the incidence of rapid transport and distribution of sperm in the female tract were the same as in mated females. The rapid transit phase of sperm transport is an asymmetric phenomenon, occurring predominantly in the left side of the female tract of both mated and artificially inseminated does. Most spermatozoa were not motile after rapid transport and in more than 90% of these, the membranes overlying the acrosome were disrupted. After rapid transport, spermatozoa were located almost exlcusively in the uppermost regions of the oviduct. Most of the spermatozoa were cleared to the peritoneal cavity between 15 mm and 4 h p.c. and none appeared to reenter the lower levels of the female tract. The sustained migration of motile spermatozoa from the uterus into the oviduct was first detected at 90 mm p.c., when small populations of motile sperm were recovered from the lower isthmus of all animals examined. These observations show clearly that rapid passive transfer of rabbit spermatozoa to the upper oviduct and peritoneal cavity is a regular sequel to mating. Most sperm in this vanguard are dead and are cleared to the peritoneal cavity before ovulation and thus can have no direct role in fertilization.
TL;DR: The phenotype of three Caenorhabditis elegans temperature-sensitive mutants is consistent with a primary defect in sperm motility, but the cause of this defect is not known.
Abstract: The isolation and characterization of three Caenorhabditis elegans temperature-sensitive mutants that are defective at fertilization are described. All three are alleles of the gene fer-1. At the restrictive temperature of 25°, mutant hermaphrodites make sperm and oocytes in normal numbers. No oocytes are fertilized, although they pass through the spermatheca and uterus normally. The oocytes can be fertilized by sperm transferred by wild-type males, indicating that the mutant defect is in the sperm. The temperature-sensitive period for the mutants coincides with spermatogenesis. Sperm made by mutants at 25° cannot be distinguished from wild-type sperm by light microscopy. The sperm do contact oocytes in mutant hermaphrodites, but do not fertilize. Mutant sperm appear to be nonmotile. Mutant males are also sterile when grown at 25°. They transfer normal numbers of sperm to hermaphrodites at mating, but these sperm fail to migrate to the spermatheca and are infertile. The phenotype of these mutants is consistent with a primary defect in sperm motility, but the cause of this defect is not known.
TL;DR: Human seminal plasma was found to contain a non-ultrafiltrable factor which effectively prevented, but did not reverse, the toxic effect upon spermatozoa of either endogenous or exogenous lipid peroxides.
Abstract: Peroxidation of the sperm cells' own phospholipids, closely bound up with declining motility, has been demonstrated in human spermatozoa; the rate of peroxidation was determined quantitatively by the reaction with thiobarbituric acid. Immotile or poorly motile spermatozoa from necrospermic or oligospermic semen exhibited a higher rate of peroxidation than highly motile spermatozoa from normal ejaculates. Peroxidized unsaturated fatty acids added to washed sperm suspensions immobilized the spermatozoa rapidly and permanently. Human seminal plasma was found to contain a non-ultrafiltrable factor which effectively prevented, but did not reverse, the toxic effect upon spermatozoa of either endogenous or exogenous lipid peroxides.
TL;DR: In male partners of infertile couples the presence of a varicocele is associated with compromised semen quality but not with diminished fertility when the female partners are treated, suggesting the importance of considering infertility as a problem of a couple, rather than a specific disorder of one of the partners.
TL;DR: It is reported here that early embryonic parthenogenetic cells are totipotent and can give rise to fully functional ova which, when fertilised by sperm, develop into normal individuals.
Abstract: IN strain LT/Sv mice, eggs often begin to develop parthenogenetically in the ovary after the first meiotic division1–3. They undergo apparently normal cleavage and blastocyst formation, but at the egg cylinder stage they become disorganised and form teratomas. They persist as tumours composed of many kinds of tissue, indicating that cells of parthenogenetic origin are viable. Spontaneous parthenogenesis is also common in ovulated strain LT eggs. They cleave, form blastocysts and implant in the uterus, but die shortly afterwards, in the same way that embryos derived from experimentally induced parthenogenesis die early4–7. However, parthenogenetic cells have been ‘rescued’ by removing embryos from the oviducts of virgin females and grafting them to extrauterine sites such as testis1 and kidney8. Those embryos become disorganised and can survive as teratomas composed of many kinds of viable tissues. Why, then, do cells of parthenogenetic origin fail to survive in utero? To investigate this problem we are using chimaeras derived from aggregates of eight-cell parthenogenetic and normal embryos2, transferred to the uteri of pseudopregnant females. We report here that early embryonic parthenogenetic cells are totipotent. They can give rise to fully functional ova which, when fertilised by sperm, develop into normal individuals.
TL;DR: The region within the epididymis where spontaneous sperm motility first appeared and the extent of later motility within that organ, as shown by microscopic observation of undiluted samples, varied with the species.
TL;DR: Adaptations of a male which increase the probability that his sperm is used by a female to inseminate her eggs will be favored by selection, may include behavioral and physiological characteristics of the male as well as competitive properties of the sperm itself.
Abstract: Females of many insect species store large numbers of sperm after mating, and mate numerous times, sometimes before sperm already stored is exhausted. The coincidence of these events results in sexual selection on males. Adaptations of a male which increase the probability that his sperm, and not the sperm of some other male, is used by a female to inseminate her eggs will be favored by selection. Such adaptations may include behavioral and physiological characteristics of the male as well as competitive properties of the sperm itself. Examples of such adaptations include 1) preand postcopulatory guarding behavior, 2) mating plugs, 3) chemical or physical characteristics of the ejaculate which reduce receptivity to remating, 4) sperm displacement (i.e. the replacement at a subsequent mating of the stored sperm of a previous mating), which could be effected either by the male during copulation or by some competitive aspect of the ejaculate, and 5) sperm precedence (i.e. nonrandom use). Parker (1970), in his stimulating review of this subject, has used the term "sperm competition" to describe the selection pressures operating on males to produce these adaptations. Note that adaptations arising in response to these pressures are not restricted in their mode of operation to properties of the sperm, per se, but can involve any feature of reproductive biology affecting sperm transfer or use. Studies of adaptations for sperm competition in Drosophila have focused on sperm displacement and, to a lesser extent, sperm precedence and the effect of
TL;DR: Electron micrographs of sperm undergoing an A23187-induced acrosome reaction in the presence of the acrosin inhibitors benzamidine, p-amino-benzamidine and phenylmethylsulphonyl fluoride show that the acosome reaction proceeds normally but that dispersal ofThe acrosomal contents is inhibited.
Abstract: The divalent metal cation ionophore A23187 rapidly induces a normal acrosome reaction in a population of guinea-pig sperm suspended in calcium medium. In the course of the acrosome reaction, proacrosin, the zymogen precursor of the protease acrosin, is activated. Although the acrosome reaction causes exocytosis of the acrosomal contents, ‘soluble’ acrosin is not released in significant amounts until well after the sperm population as a whole has undergone an acrosome reaction. This suggests that proacrosin is stored within the acrosome in an insoluble form and that exocytosis of the acrosomal contents in the acrosome reaction is insufficient, by itself, to cause its immediate dissolution. Electron micrographs of sperm undergoing an A23187-induced acrosome reaction in the presence of the acrosin inhibitors benzamidine, p-amino-benzamidine and phenylmethylsulphonyl fluoride show that the acrosome reaction proceeds normally but that dispersal of the acrosomal contents is inhibited. These morphological changes are, for the most part, below the limit of resolution of the light microscope and using light microscopy to assess whether an acrosome reaction has taken place, it can be mistakenly inferred that the reaction itself is inhibited by the acrosin inhibitors. The inhibition of the dispersal of the acrosomal contents by acrosin inhibitors suggests that acrosin activity is important in solubilizing acrosin. These experimental observations, taken with the evidence that the acrosome reaction is a response to an increase in intracellular free calcium, have been taken as the basis of a proposal for the mechanism of proacrosin activation in the acrosome reaction.
TL;DR: Easy performance, rapid sperm counts, and improvement of motility estimation make this chamber a useful tool where sperm analysis is carried out.
TL;DR: Despite the absence of sperm incorporation and gamete membrane fusion, CB-treated Arbacia and Spisula eggs mixed with sperm activated and possible mechanisms by which sperm may induce eggs to activate are discussed.
TL;DR: This chapter discusses the sperm–egg fusion in mammals, and the acrosome reaction appears to be essential for successful fusion of the spermatozoon with the egg.
Abstract: Publisher Summary This chapter discusses the sperm–egg fusion in mammals. Eggs fusing with spermatozoa can be obtained, by flushing the oviducts of mated females shortly after ovulation, but the chance of obtaining eggs in the initial stage of the fusion is very poor because of asynchronous sperm penetration and the rapidity of the fusion process. The fusion of a spermatozoon with an egg seems to be facilitated by the presence of numerous microvilli on the egg surface. The process of sperm–egg fusion in mammals can be readily studied by inseminating zona pellucida, free eggs, with acrosome reacted spermatozoa. The sperm membrane that initially fuses with the egg plasma membrane is the plasma membrane in the posterior region of the sperm head, not the inner acrosomal membrane. The inability of the acrosomal membrane to fuse with the egg membrane could be due to its lack of “fluidity.” The acrosome reaction appears to be essential for successful fusion of the spermatozoon with the egg. In some mammals (e.g., the hamster), the egg plasma membrane remains capable of fusing with the spermatozoa even long after the penetration of the fertilizing spermatozoon into the egg.