Showing papers on "Sperm published in 1990"

Sperm Competition Games: Raffles and Roles

Abstract: Evolutionary games in which two males mate with the same female are examined by using an evolutionarily stable strategy (ESS) approach. These prospective models of competitive ejaculation seek ESS sperm numbers for cases when sperm competition obeys the \`raffle principle'. In a \`fair raffle', each male's fertilization probability equals his sperm number divided by the total sperm number in the female tract. In a loaded raffle, one male's sperm are \`devalued' relative to his competitor, e.g. a sperm from the second male to mate counts as only (say) half of a ticket in the fertilization lottery compared with one of the first male's sperm. The models assume that there is a trade-off between effort spent on sperm and effort spent on obtaining matings, and that fitness is the product of number of matings and the expected gain from each one. In a general sense, ESS sperm numbers increase with the probability that two males mate with the same female, and decrease with the degree of unfairness in the raffle. However, the ESS depends critically on the information available to the two competitors, and whether they occupy roles (of first or second to mate) randomly or non-randomly. If males \`know' whether they are the first or the second to mate, but these roles are assigned randomly, sperm numbers should be equal for the two males whether the raffle is fair or unfair. If roles are not random, so that (say) a given male tends to be first to mate, sperm numbers will not be equal unless the raffle is a fair one. In a loaded raffle, the male whose sperm are devalued should compensate by expending a greater reproductive effort on sperm. If sperm costs are equal for the two males, then the male in the favoured role should produce less sperm, but nevertheless achieves higher paternity because of the loading in the raffle. If sperm costs are asymmetric for the two roles, in a fair raffle the male that can produce sperm more cheaply ejaculates more sperm (and hence experiences higher paternity) although he expends less reproductive effort on sperm production.

A cytosolic sperm factor stimulates repetitive calcium increases and mimics fertilization in hamster eggs

Abstract: Microinjection of cytosolic sperm extracts into unfertilized golden hamster eggs caused a series of increases in cytoplasmic free calcium, Ca2+i, and membrane hyperpolarizing responses, HRs. These HRs and Ca2+i transients are similar to those seen during in vitro fertilization of hamster eggs. The sperm factor that is responsible for causing these effects appears to be of high molecular weight and protein based. Injection of sperm factor activated eggs and mimicked fertilization in causing repetitive HRs in the presence of phorbol esters and in sensitizing the egg to calcium-induced calcium release. Since these effects cannot be mimicked by injecting G-protein agonists or calcium-containing solutions, it seems unlikely that a receptor-G-protein signalling system is involved at fertilization. These data instead suggest a novel signal transduction system operates during mammalian fertilization in which a protein factor is transferred from the sperm into the egg cytoplasm after gamete membrane fusion.

Sperm competition games: sneaks and extra-pair copulations

Abstract: This paper examines ejaculation strategies for cases when an opportunist male ‘steals’ a mating with the female of a paired male This is an evolutionary game of competitive ejaculation in which two (or more) males mate with the same female Prospective evolutionarily stable strategy (ESS) models are analysed which seek ESS sperm numbers Sperm competition is assumed to obey the ‘raffle principle’ (i e fertilization probability increases with the proportion of a given male’s sperm in the female tract) The models assume a trade-off between sperm expenditure and other aspects of reproductive success Sperm costs may be unequal for the two males (paired male; opportunist male), especially if given phenotypes tend to adopt one or other pattern In the ‘sneaks and guarders’ (SG) game, certain males (guarders) are paired permanently to particular females, and others (sneaks) obtain matings opportunistically Roles are therefore constant Guarders are assumed to have no information whether a sneak mating has occurred (their strategy is tuned to the average risk of sperm competition) and the sperm costs are assumed to be unequal for sneaks and guarders If sneak matings are rare, guarding males should spend less effort on ejaculates than sneaks But if sneak matings are frequent, and if the marginal cost of sperm is very low for sneaks, the guarder may expend the greater effort on sperm If sperm are relatively very cheap for guarders, then in cases of double mating, the paternity prospects of guarders should be higher than for sneaks; otherwise sneaks should win However, if a guarder detects a sneak mating, he should increase his sperm dose in the female tract and achieve higher fertilization prospects (paternity) than the sneak A second model concerns cases of extra pair copulations (EPCS) where all males are paired to females, but all will mate with another male’s female if the opportunity should arise Thus roles are assigned randomly with fixed probability In this game, sperm costs relate to reduced paternal care (or to other losses with the ‘primary’ female) and are assumed to be equal to all males Predictions are very similar to the sneaks—guarders game: when performing an EPC a male should expend more effort on sperm (and hence gain higher paternity) than when mating as a paired males, unless the EPC is detected, in which case a paired male should greatly increase his sperm dose in the female (and hence should predominate at fertilization)

Profile of a mammalian sperm receptor

Abstract: Complementary molecules on the surface of eggs and sperm are responsible for species-specific interactions between gametes during fertilization in both plants and animals. In this essay, several aspects of current research on the mouse egg receptor for sperm, a zona pellucida glycoprotein called ZP3, are addressed. These include the structure, synthesis, and functions of the sperm receptor during oogenesis and fertilization in mice. Several conclusions are drawn from available information. These include (I) ZP3 is a member of a unique class of glycoproteins found exclusively in the extracellular coat (zona pellucida) of mammalian eggs. (II) ZP3 gene expression is an example of oocyte-specific and, therefore, sex-specific gene expression during mammalian development. (III) ZP3 is a structural glycoprotein involved in assembly of the egg extracellular coat during mammalian oogenesis. (IV) ZP3 is a sperm receptor involved in carbohydrate-mediated gamete recognition and adhesion during mammalian fertilization. (V) ZP3 is an inducer of sperm exocytosis (acrosome reaction) during mammalian fertilization. (VI) ZP3 participates in the secondary block to polyspermy following fertilization in mammals. (VII) The extracellular coat of other mammalian eggs contains a glycoprotein that is functionally analogous to mouse ZP3. The unique nature, highly restricted expression, and multiple roles of ZP3 during mammalian development make this glycoprotein a particularly attractive subject for investigation at both the cellular and molecular levels.

Analysis of the relationship between reactive oxygen species production and leucocyte infiltration in fractions of human semen separated on Percoll gradients.

Abstract: We have shown previously that the reactive oxygen species generated by washed human ejaculates originate from cells which can be isolated in the low density region of discontinuous Percoll gradients. In this study we have used a simplified two-step (40/80%) Percoll gradient to separate human ejaculates (n = 109) into two populations of spermatozoa, exhibiting either a high or a low capacity for reactive oxygen species generation. We have then examined the relationships between this activity and other properties of the isolated fractions, with particular emphasis on the presence of leucocytes, which we have quantified using a monoclonal antibody directed against the common leucocyte antigen. The low-density cells recovered from the 40%/80% interface of the Percoll gradients, differed from the high-density fraction in exhibiting significantly reduced sperm motility, poorer sperm morphology, and a considerably enhanced capacity for reactive oxygen species production (P less than 0.001). In six cases the elevated levels of reactive oxygen species generation were associated with leucocyte concentrations in excess of 1 x 10(6) per 10(7) sperm, suggesting that leucocytes enter the seminal compartment in an activated, oxygen-radical generating, state. However, in the majority of cases exhibiting high levels of reactive oxygen species production, leucocyte numbers were low or absent and the semen profiles were unremarkable, except that seminal sperm concentrations tended to be low. These results suggest that the oxidative stress responsible for defective sperm function involves reactive oxygen species originating from two sources; the sperm and infiltrating leucocytes.

Ploidy Manipulation and Gynogenesis in Fishes: Cytogenetic and Fisheries Applications

Abstract: Manipulation of fish chromosomes dates back to the early part of this century. The earliest experiments involved induction of gynogenesis with sperm inactivated by radiation or chemical treatments. Temperature or pressure shocks applied soon after fertilization resulted in the retention of the second polar body and reconstitution of diploidy; triploidy resulted from shocks to fish ova fertilized with normal sperm. More recently, it has been possible to suppress the first mitotic division offish eggs with high-pressure or -temperature treatments applied at the time of first cleavage to produce mitotic gynogenetic diploids and tetraploids. Androgenesis has been successfully induced in fish by irradiation of ova, fertilization of eggs with normal sperm, and suppression of the first mitosis with high-pressure treatments. Gynogenetic diploids have been used for cytogenetic studies of meiotic phenomena and gene mapping. The general finding to date is that the arrangement of genes on chromosomes is high...

Identification of a ZP3-binding protein on acrosome-intact mouse sperm by photoaffinity crosslinking.

Abstract: During the process of fertilization in mammals, sperm bind in a relatively species-specific manner to the zona pellucida (ZP) of ovulated eggs. ZP3, a glycoprotein found in the mouse egg zona pellucida, serves as receptor for sperm during gamete adhesion. We report here that a Mr 56,000 protein found on mouse sperm has properties expected for a sperm component that recognizes and binds to ZP3. This sperm protein is radiolabeled preferentially by a photoactivatable heterobifunctional crosslinker ("Denny-Jaffee reagent") covalently linked to purified ZP3, binds very tightly to ZP3-affinity columns, and is localized to heads of acrosome-intact but not acrosome-reacted sperm. These and other findings suggest that this protein may be a "ZP3-binding protein" that, together with the sperm receptor, supports species-specific binding of mouse sperm to unfertilized eggs.

Heparin-binding proteins from seminal plasma bind to bovine spermatozoa and modulate capacitation by heparin

Abstract: Bovine spermatozoa that have been exposed to seminal plasma possess more binding sites for heparin than sperm from the cauda epididymis that have not been exposed to accessory sex gland secretions. Seminal plasma exposure enables sperm, following incubation with heparin, to undergo zonae pellucidaeinduced exocytosis of the acrosome. In this study, the regulatory role of seminal plasma heparin-binding proteins in capacitation of bovine spermatozoa by heparin was investigated. Plasma membranes from sperm exposed to seminal plasma in vivo or in vitro contained a series of acidic 15-17 kDa proteins not found in cauda epididymal sperm. Western blots of membrane proteins indicated that these 15-17 kDa proteins bound [125 IJ-heparin. Heparin-binding proteins were isolated by heparin affinity chromatography from seminalplasma from vasectomized bulls. Gel electrophoresis indicated that the heparin-binding peaks contained 14-18 kDa proteins with isoelectric variation, a basic 24 kDa protein, and a 31 kDa protein. Western blots probed with [/25 I]-heparin confirmed the ability of each of these proteins to bind heparin. Each of these proteins, as well as controlproteins, bound to epididymal sperm. The seminalplasma proteins were peripherally associated with sperm since they were removed by hypertonic medium and did not segregate into the detergent phase of Triton X-1 14. Seminal plasma heparin-binding proteins potentiated zonae pellucidae-induced acrosome reactions in epididymal sperm. However, seminal plasma proteins that did not bind to the heparin affinity column were unable to stimulate zonae-sensitivity. Control proteins, including lysozyme-which binds to both heparin and sperm, were ineffective at enhancing zonae-induced acrosome reactions. These data provide evidence for a positive regulatory role of seminal plasma heparinbinding proteins in capacitation of bovine spermatozoa.

Proteolytic processing of a protein involved in sperm-egg fusion correlates with acquisition of fertilization competence.

Abstract: A protein located on the surface of guinea pig sperm (PH-30) has been implicated in the process of sperm-egg fusion (Primakoff, P., H. Hyatt, and J. Tredick-Kline. 1987. J. Cell Biol. 104:141-149). In this paper we have assessed basic biochemical properties of PH-30 and have analyzed the molecular forms of PH-30 present at different stages of sperm maturation. We show the following: (a) PH-30 is an integral membrane glycoprotein; (b) it is composed of two tightly associated and immunologically distinct subunits; (c) both subunits are made as larger precursors; (d) processing of the two subunits occurs at different developmental stages; (e) the final processing step occurs in the region of the epididymis where sperm become fertilization competent; (f) processing can be mimicked in vitro; (g) processing exposes at least two new epitopes on PH-30-one of the newly exposed epitopes is recognized by a fusion-inhibitory monoclonal antibody. These results are discussed in terms of the possible role of PH-30 in mediating fusion with the egg plasma membrane.

Teratospermic and normospermic domestic cats: ejaculate traits, pituitary-gonadal hormones, and improvement of spermatozoal motility and morphology after swim-up processing

Abstract: Electroejaculate traits, testicular volume, and circulating FSH, LH, and testosterone concentrations were compared between two populations of domestic cats consistently producing either a high (greater than 60%, normospermic) or low (less than 40%, teratospermic) incidence of structurally normal spermatozoa/ejaculate. The effects of semen dilution in Biggers, Whitten and Whittingham (BWW) or modified Krebs Ringer bicarbonate (mKRB) medium and swim-up processing on sperm viability and duration of motility in vitro also were assessed. Ejaculate volume, percent sperm motility, sperm progressive motility, motile spermatozoa/ejaculate, testes volume, and mean serum FSH and LH concentrations were similar (P greater than 0.05) between normospermic and teratospermic cats. However, sperm concentration/ml of ejaculate was greater and circulating testosterone levels were lower in teratospermic males. Swim-up processing increased (P less than 0.05) percent sperm motility, progressive motility, and the number of structurally normal sperm cells recovered and also prolonged the duration of sperm motility in both cat populations. In teratospermic ejaculates, swim-up separation increased the proportion of morphologically normal spermatozoa recovered by more than two-fold. Diluting cat semen with either BWW or mKRB increased flagellar bending in both normospermic and teratospermic cats. The sperm motility characteristics of only the teratospermic ejaculates were influenced by medium type; mKRB increased percent sperm motility and progressive motility whereas BWW had no effect. Compared with undiluted raw ejaculates, the duration of sperm motility was improved 18- to 24-fold by diluting semen in either BWW or mKRB medium followed by swim-up processing. This study demonstrates that the electroejaculate characteristics of domestic cats vary markedly and that some males consistently produce high proportions of morphologically abnormal spermatozoa. Diminished serum testosterone concentrations and normal pituitary secretion of FSH and LH in teratospermic males suggest that there is an inverse relationship between gonadal androgen production and pleiomorphic spermatozoa in the domestic cat. The swim-up procedure is effective for recovering motile, structurally normal spermatozoa from teratospermic cats.

Activation of mammalian oocytes by a factor obtained from rabbit sperm.

Abstract: In this study a fraction was prepared from rabbit sperm that activated rabbit and mouse oocytes following injection into the cytoplasm. The sperm factor activated oocytes exhibited cortical granule exocytosis, pronuclear formation, and cleavage. The sperm factor was soluble in aqueous solution and was not active extracellularly. Unlike most artificial activation methods that are only effective with aged oocytes, the sperm factor activated recently ovulated oocytes. The factor appears to be a protein or associated with a protein but not an acrosomal protein. Fractions from both mouse and bull sperm did not activate rabbit or mouse oocytes. Their inactivity may be owing to the techniques used to recover the fractions or differences between species in sperm morphology and fertilization processes. These observations support the hypothesis that oocyte activation is induced by a factor within sperm that is released into the cytoplasm of the oocyte at the time of sperm-oocyte fusion.

Analysing sperm competition data: simple models for predicting mechanisms.

Abstract: Prospective models are developed for analysing sperm competition data so as to predict the underlying mechanisms determining paternity in multiply mated females. The models require: 1) estimations of proportion of offspring sired by the last male to mate (P 2), 2) knowledge of the number of sperm transferred by each male, and 3) knowledge of the sperm storage capacity of the female, should this be limited. They will distinguish between “raffles” (sperm mixing without displacement) and sperm displacement mechanisms. The sensitivity of the techniques can be increased by manipulating the number of sperm transferred by each male. Typically, this can be done by manipulating copula duration or number of ejaculations, given a knowledge of the rate of sperm transfer. Data from two contrasting insect species are fitted to the models to demonstrate the techniques. These models are prospective only, and their limitations are discussed. The principal limitation is that we assume that sperm used for fertilization mix randomly in a “fertilization set” immediately prior to fertilization; in reality this may be difficult to identify. When sperm mixing is very rapid, the fertilization set will often be equivalent to the sperm stores, but with slow mixing, the fertilization set may be equivalent to a much more restricted zone and may change with time.

Congenital absence of the vas deferens. The fertilizing capacity of human epididymal sperm.

Abstract: Background. Congenital absence of the vas deferens has been considered a virtually untreatable cause of male sterility. Furthermore, sperm that have not passed through at least the head of the epididymis have been thought to be incapable of causing pregnancy. We attempted to determine whether human sperm that had never passed through the epididymis could fertilize eggs in vitro and whether the technique could be used for men with congenital absence of the vas deferens. Methods. Twenty-eight men with congenital absence of the vas deferens underwent microsurgical aspiration of sperm from the epididymis and vasa efferentia for attempted in vitro fertilization of their wives' oocytes, with subsequent transfer of embryos. Thirty-two treatment cycles were begun (four were repeat cycles). Results. The most motile sperm were found in the proximal epididymis, at or near the vasa efferentia. Embryos were obtained for transfer in 21 cases (66 percent). Ninety-three embryos resulted from 352 mature oocytes (...

Mechanisms of sperm competition.

Abstract: Sperm competition occurs when two (or more) males inseminate a single female during a reproductive cycle, but what determines which one of them will fertilize her eggs? Is it simply a lottery, or are there some more complex rules by which matings are translated into offspring? Several studies covering various animal groups have shown that mating order effects are often important in determining paternity patterns: in animals as different as insects and birds, the sperm from the last male to mate often has precedence over previously introduced sperm. Recently, behavioural ecologists and physiologists have started to examine the mechanisms by which sperm precedence is achieved. The study of sperm competition mechanisms complements the more behavioural studies, and a combination of the two approaches used on single species should prove to be particularly rewarding.

Sources of intraspecific variation in sperm precedence in red-flour beetles

Abstract: Sperm precedence, defined as nonrandom differential fertilization success among mating males, is likely to play a fundamental role in mediating male reproductive success in species with multiply mating females (Parker 1970a) The phenomenon of differential sperm usage from consecutive matings has now been documented across an extraordinary diversity of animal groups, including insects, spiders, birds, fish, reptiles, bats, and primates (review in Smith 1984) These studies typically have measured species-specific sperm precedence as mean P2 values, calculated as the mean proportion of eggs fertilized by the second of two mates (Boorman and Parker 1976; Gwynne 1984) However, nearly all species show an extremely wide, and as yet unexplained, range of variation around these mean P2 values (table 3; see also, eg, Schlager 1960; Fincke 1984; Nakano 1985) This intraspecific variability may be due to random variation, to differences among males in the competitive ability of their sperm, or to female sperm preference Further examination of such variation may contribute substantially to our understanding of the evolutionary significance of sperm precedence Our intent in this study was to examine the sources of variation in sperm precedence by sequentially mating pairs of males with replicate females We used the red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae), measuring P2 values and several behavioral and morphological traits in an attempt to understand the mechanisms underlying differences in sperm precedence

cDNA cloning reveals the molecular structure of a sperm surface protein, PH-20, involved in sperm-egg adhesion and the wide distribution of its gene among mammals

Abstract: Sperm binding to the egg zona pellucida in mammals is a cell-cell adhesion process that is generally species specific. The guinea pig sperm protein PH-20 has a required function in sperm adhesion to the zona pellucida of guinea pig eggs. PH-20 is located on both the sperm plasma membrane and acrosomal membrane. We report here the isolation and sequence of a full-length cDNA for PH-20 (available from EMBL/GenBank/DDBJ under accession number X56332). The derived amino acid sequence shows a mature protein of 468 amino acids containing six N-linked glycosylation sites and twelve cysteines, eight of which are tightly clustered near the COOH terminus. The sequence indicates PH-20 is a novel protein with no relationship to the mouse sperm adhesion protein galactosyl transferase and no significant homology with other known proteins. The two PH-20 populations, plasma membrane and acrosomal membrane, could arise because one form of PH-20 is encoded and differentially targeted at different spermatogenic stages. Alternatively, two different forms of PH-20 could be encoded. Our evidence thus far reveals only one sequence coding for PH-20: Southern blots of guinea pig genomic DNA indicated there is a single PH-20 gene, Northern blots showed a single size PH-20 message (approximately 2.2 kb), and no sequence variants were found among the sequenced cDNA clones. Cross-species Southern blots reveal the presence of a homologue of the PH-20 gene in mouse, rat, hamster, rabbit, bovine, monkey, and human genomic DNA, showing the PH-20 gene is conserved among mammals. Since genes for zona glycoproteins are also conserved among mammals, the general features of sperm and zona proteins involved in mammalian sperm-egg adhesion may have been evolutionarily maintained. Species specificity may result from limited changes in these molecules, either in their binding domains or in other regions that affect the ability of the binding domains to interact.

Evidence that proteolysis of the surface is an initial step in the mechanism of formation of sperm cell surface domains.

Abstract: On terminally differentiated sperm cells, surface proteins are segregated into distinct surface domains that include the anterior and posterior head domains. We have analyzed the formation of the anterior and posterior head domains of guinea pig sperm in terms of both the timing of protein localization and the mechanism(s) responsible. On testicular sperm, the surface proteins PH-20, PH-30 and AH-50 were found to be present on the whole cell (PH-20) or whole head surface (PH-30, AH-50). On sperm that have completed differentiation (cauda epididymal sperm), PH-20 and PH-30 proteins were restricted to the posterior head domain and AH-50 was restricted to the anterior head domain. Thus these proteins become restricted in their distribution late in sperm differentiation, after sperm leave the testis. We discovered that the differentiation process that localizes these proteins can be mimicked in vitro by treating testicular sperm with trypsin. After testicular sperm were treated with 20 micrograms/ml trypsin for 5 min at room temperature, PH-20, PH-30, and AH-50 were found localized to the same domains to which they are restricted during in vivo differentiation. The in vitro trypsin-induced localization of PH-20 to the posterior head mimicked the in vivo differentiation process quantitatively as well as qualitatively. The quantitative analysis showed the process of PH-20 localization involves the migration of surface PH-20 from other regions to the posterior head domain. Immunoprecipitation experiments confirmed that there is protease action in vivo on the sperm surface during the late stages of sperm differentiation. Both the PH-20 and PH-30 proteins were shown to be proteolytically cleaved late in sperm differentiation. These findings strongly implicate proteolysis of surface molecules as an initial step in the mechanism of formation of sperm head surface domains.

Dense fibers protect mammalian sperm against damage.

Abstract: The relative tensile strengths of the sperm of seven mammalian species and sea urchins have been measured by determining the minimum shear necessary to kill them (assayed by lack of motility) when they are suspended in a viscous fluid. In general, long sperm are killed by smaller shears than short sperm. However, the longer sperm are not as fragile as would be expected from theoretical predictions. Their additional tensile strength correlates well with the size of their dense fibers; a theory that Includes the dense fiber contributions accurately predicts the sperm tensile strength for most of the species in which this has been measured. This added strength may be necessary to protect sperm from shear forces encountered during epididymal transport and especially during ejaculation, as these forces are strong enough to kill long sperm if they are not strengthened.

Aniline blue staining as a marker of sperm chromatin defects associated with different semen characteristics discriminates between proven fertile and suspected infertile men

Abstract: A retrospective study of 49 men with proven fertility and 396 suspected infertile men was conducted with the primary objective of investigating the relationship between the nuclear maturity of sperm and male fertility. Acidic aniline blue staining was used to detect chromatin defects of sperm nuclei related to their nucleoprotein content as associated with DNA. The discriminant value of the percentage of unstained nuclei (= percentage of mature heads, MH) and of other semen characteristics, was analysed by a stepwise (forward) linear regression model. Semen characteristics that discriminated significantly between the two groups of subjects were, in descending order: (1) the percentage of normal sperm, (2) the percentage of amorphous heads, (3) the percentage of tapered heads, (4) semen volume, and (5) the percentage of MH. The discriminant value of each of the significant characteristics was studied by means of ROC-curves. MH had the best ROC-curve profile; its cut-off value was found to be equal to 70% (74.5 +/- 2.6% for the donor group versus 53.0 +/- 1.1% for the patient group). A simple infertility score (SIS) including MH, was built according to the cut-off values inferred from the ROC-curves. SIS allowed an overall satisfactory separation of the two groups (less than or equal to 4 = fertile, 5-6 = uncertainty zone, greater than 6 = infertile). Our results indicate that the addition of the evaluation of sperm head maturity to routine semen analysis improves the assessment of fertility in men.

Method to preselect the sex of offspring

Abstract: Intact X and Y chromosome bearing sperm populations of rabbits and swine were separated according to DNA content using a flow cytometer/cell sorter. Sperm viability was maintained by special staining techniques and by sorting and collecting the sperm in nutrient media. The sorted sperm were surgically inseminated into the uteri of rabbits or swine. Of the offspring born from does inseminated with the sorted population of X-bearing sperm, 94 % were females. Of offspring born from does inseminated with sorted Y-bearing sperm from the same ejaculate, 81 % were males.

Fertilization in teleost fishes: mechanisms of sperm-egg interactions

Abstract: Publisher Summary This chapter describes some of the principal morphological and cellular features of fertilization in fishes, from the initial encounter between sperm and egg to their fusion to form the zygote. The pathway leading to the fusion between a single sperm and a previously quiescent egg and the subsequent union of male and female pronuclei consists of a predictable, highly ordered sequence of events. The chapter describes the events and changes that take place during the sperm–egg interaction and their temporal relationships to each other. The eggs of fishes, particularly those of teleosts, appear to be particularly useful and advantageous for investigations of fertilization. Teleost eggs are generally large and possess the built-in advantage of having the location of sperm entry topographically restricted to a predetermined, identifiable site in the animal pole. The direct interaction of sperm and egg is mediated by complementary receptors located on their plasma membranes. Such receptors may function in sperm–egg recognition, binding, fusion, and even the activation of the egg in some species. An important functional component of these receptors is carbohydrate based on studies of the mouse sperm receptor (ZP3) and the sea urchin egg-binding protein (bindin).

Biochemical and morphological characterization of the intra-acrosomal antigen SP-10 from human sperm.

Abstract: The human sperm protein SP-10 was previously defined as a "primary vaccine candidate" by a World Health Organization Taskforce on Contraceptive Vaccines. By one- and two-dimensional immunoblots, we show that SP-10, extracted from ejaculated human sperm, demonstrated a polymorphism of immunogenic peptides from 18 to 34 kDa, a pattern that was conserved from individual to individual and was not altered by reducing agents. The majority of the antigenic peptides possessed isoelectric points of approximately 4.9. Immunocytochemistry on testis sections indicated that SP-10 was localized to round spermatids and spermatozoa within the adluminal compartment of the seminiferous epithelium. Immunofluorescence showed that SP-10 was not associated with the surface of acrosome-intact, ejaculated sperm. Light and electron microscopic immunocytochemistry localized SP-10 throughout the acrosome, and electron microscopic evidence demonstrated a bilaminar array in association with the inner aspect of the outer acrosomal membrane and the outer aspect of the inner acrosomal membrane. After induction of the acrosome reaction with the ionophore A23187, SP-10 remained displayed on the sperm head in association with the inner acrosomal membrane and equatorial segment. The results indicate that the MHS-10 monoclonal antibody may be used as a marker of acrosome development in the human and as a probe to evaluate acrosome status. The results also support the hypothesis that inhibition of sperm-egg interaction by anti-SP-10 monoclonal antibody may occur as a result of antigen exposure following the acrosome reaction.

Bovine oviductal fluid components and their potential role in sperm cholesterol efflux.

Abstract: Bovine oviductal fluid (OF) was collected and analyzed throughout the estrous cycle, and the capacity of the protein and lipoprotein components to support cholesterol efflux from bovine sperm was evaluated. Blood was collected and assayed for progesterone (P4) to monitor the estrous cycle. Protein and lipoprotein separation was achieved by density gradient centrifugation. Two major bands were identified. The first (1.056 less than delta 20 less than 1.140 g/ml) corresponded to bovine and rabbit plasma high-density lipoprotein (HDL) based on distribution in the density gradient and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The second band (1.235 less than delta 20 less than 1.243 g/ml) consisted predominantly of oviductal fluid albumin (OFA). Oviductal fluid protein concentration increased as serum P4 decreased around the time of estrus. Mean OF protein concentration was 21.3 mg/ml when serum P4 was lower than 0.5 ng/ml and 6.9 mg/ml when serum P4 was greater than 0.5 ng/ml. An inverse log relationship was found between HDL protein concentration and serum P4. Unesterified cholesterol (UC), cholesteryl ester, and phospholipid (PL) content of HDL for HDL protein concentrations of 3-56.1 micrograms/ml were 1.35-46.2 micrograms/ml, 1.91-44.48 micrograms/ml, and 1.69-59.8 micrograms/ml, respectively. Phosphatidylcholine and -ethanolamine were the major PLs present in the HDL fraction and their molar ratio (4:1 mol/mol) was relatively constant through the estrous cycle. The OFA fraction of the same samples accounted for more than 90% of total protein and for most of the variation in OF protein. To determine the ability of OF components to serve as sperm cholesterol acceptors, OF samples were incubated 1:1 (v/v) with and without 4 X 10(8) bovine sperm in 1.0 ml of modified Tyrode's solution and OF for 2 hr at 39 degrees C. After incubation, HDL and OFA fractions were isolated and analyzed for changes in protein and lipid content. After OF, samples were incubated with sperm, an increase in UC was found in the HDL fractions. UC in HDL increased by 12.1 +/- 1.0 micrograms/ml (means +/- SE) when serum P4 was less than or equal to 0.5 ng/ml. For samples corresponding to higher serum P4, the increase in UC was 3.60 +/- 0.89 micrograms/ml. Values for UC in HDL were corrected for the contribution of UC from OFA of OF samples. Cholesterol efflux from sperm has been implicated in the process of sperm capacitation. These results indicate that HDL from OF is elevated during the follicular phase of the estrous cycle and can serve as an acceptor for bovine sperm cholesterol.

Determination of the relationship between sperm morphologic classifications and fertility in stallions: 66 cases (1987-1988).

Abstract: The analysis of breeding records and sperm morphologic classifications from ejaculated semen during 99 stallion seasons, over a 2-year period, revealed a significant correlation (r = 0.34, P less than 0.01) between the percentage of morphologically normal sperm in ejaculates and the per cycle fertility estimate of the stallions studied. In addition, the percentage of sperm classified as having major defects (abnormal heads, proximal droplets, and abnormal midpieces) was significantly inversely correlated (r = -0.36, P less than 0.01) with the same fertility estimates. Multiple variable regression demonstrated that the variation in 2 morphologic features classified as major defects, abnormal heads, and proximal droplets, accounted for the largest amount of variation in fertility. It appears that in stallions, a large percentage of ejaculated sperm with major defects or other defects in combination with major defects is associated with a larger reduction in fertility than is associated with other defects.

Fluorescence in situ hybridization to Y chromosomes in decondensed human sperm nuclei.

Abstract: Human sperm nuclei were isolated with mixed alkyltrimethylammonium bromide and dithiothreitol (MATAB/DTT) and decondensed by treatments with lithium diiodosalicylate (LIS), sodium chloride, or Tris salts. Concentrations as low as 1 mM LIS induced measurable nuclear swelling compared to 600 mM required for the other two salts. As measured by image analyses, the projected nuclear area increased linearly up to approximately fivefold with LIS concentrations up to 10 mM. Swollen nuclei also maintained the elliptical shapes characteristic of the human sperm head. Expanded sperm nuclei of three men were hybridized with a fluorescently labeled 3.4 kb Y chromosome-specific repetitive DNA probe; 50.1% of the nuclei of each semen sample showed fluorescent labeling over a part of the nucleus indicating presence of the Y chromosome. In comparison, unswollen sperm did not yield reliable hybridization signals. This procedure is suitable for determining the proportion of human sperm with Y chromosomes and can be used to evaluate sperm separation techniques. The availability of probes specific for most human chromosomes suggests that this procedure may find general application in studies of sperm chromosomal constitution.