Showing papers on "Sperm published in 1991"

Ascorbic acid protects against endogenous oxidative DNA damage in human sperm.

Abstract: Damage to the DNA of germ cells can lead to mutation, which may result in birth defects, genetic diseases, and cancer. The very high endogenous rate of oxidative DNA damage and the importance of dietary ascorbic acid (AA) in preventing this damage has prompted an examination of these factors in human sperm DNA. The oxidized nucleoside 8-hydroxy-2'-deoxyguanosine (8-oxo-7,8-dihydro-2'-deoxyguanosine; oxo8dG), 1 of approximately 20 major products of oxidative damage to DNA, was measured in DNA isolated from human sperm provided by healthy subjects and compared to the seminal fluid AA levels. This relationship was studied in two groups. In a group of 24 free-living individuals 20-50 years old high levels of oxo8dG were correlated with low seminal plasma AA. The endogenous level of oxo8dG in this group was 13 fmol per microgram of DNA or approximately 25,000 adducts per sperm cell. The second group of individuals was maintained on a controlled diet that varied only in AA content. When dietary AA was decreased from 250 to 5 mg/day, the seminal fluid AA decreased by half and the level of oxo8dG in sperm DNA increased 91%. Repletion of dietary AA for 28 days (from 5 mg/day to 250 or 60 mg/day) caused a doubling in seminal fluid AA and reduced oxo8dG by 36%. These results indicate that dietary AA protects human sperm from endogenous oxidative DNA damage that could affect sperm quality and increase risk of genetic defects, particularly in populations with low AA such as smokers.

DNA packaging and organization in mammalian spermatozoa: comparison with somatic cells.

Abstract: Mammalian sperm DNA is the most tightly compacted eukaryotic DNA, being at least sixfold more highly condensed than the DNA in mitotic chromosomes. To achieve this high degree of packaging, sperm DNA interacts with protamines to form linear, side-by-side arrays of chromatin. This differs markedly from the bulkier DNA packaging of somatic cell nuclei and mitotic chromosomes, in which the DNA is coiled around histone octamers to form nucleosomes. The overall organization of mammalian sperm DNA, however, resembles that of somatic cells in that both the linear arrays of sperm chromatin and the 30-nm solenoid filaments of somatic cell chromatin are organized into loop domains attached at their bases to a nuclear matrix. In addition to the sperm nuclear matrix, sperm nuclei contain a unique structure termed the sperm nuclear annulus to which the entire complement of DNA appears to be anchored when the nuclear matrix is disrupted during decondensation. In somatic cells, proper function of DNA is dependent upon the structural organization of the DNA by the nuclear matrix, and the structural organization of sperm DNA is likely to be just as vital to the proper functioning of the spermatozoa.

Abnormal Morphology of Bovine Spermatozoa

Abstract: 1. Introduction. 2. Preparation of Semen for Morphological Examination. 3. Normal Bovine Spermatogenesis and Sperm Maturation. 4. Photomicrographic Features of Bovine Sperm Cell Abnormalities. 5. Defects of the Sperm Head. 6. Mechanisms of Development of Sperm Tail Defects. 7. Defects of the Sperm Tail. 8. Evaluation of the Spermiogram. Index.

Sperm Competition Influences Sperm Size in Mammals

Abstract: Among mammals sperm competition leads to selection for increased sperm numbers but it is not known whether it also leads to changes in sperm size. Two contrasting theoretical predictions have been made. The first hypothesis relies on the assumption that there is a trade-off between sperm numbers and sperm size and predicts that, in species confronting sperm competition, there will be a concomitant decrease in sperm size as sperm numbers increase. In contrast, the second hypothesis suggests that longer sperm may outcompete rival sperm; if longer sperm may swim faster, they will reach the ova sooner and will be selected when sperm competition prevails. We tested these hypotheses in both primates and rodents. We report that males from species in which females mate promiscuously have longer sperm than species in which females mate with one male. In addition, we also found that sperm length is positively correlated with maximum sperm velocity. Our findings thus support the view that longer sperm may be adaptive in the context of sperm competition.

Influence of body size and population density on fertilization success and reproductive output in a free-spawning invertebrate

Abstract: Gamete production and fertilization influence zygote production. While gamete production is correlated positively with body size, individual fertilization success may be a function of population density. Usually it is assumed that when high population density leads to reduced body size and gamete production, per capita zygote production is diminished. This field study of the sea urchin Diadema antillarum Philippi provides a test of this assumption. Three experiments were conducted to determine the effect of male spawning on fertilization success. In the first experiment, unfertilized eggs were placed in Nitex bags at three distances up and downstream from a spawning male. In the second experiment, unfertilized eggs were released and captured at three distances downstream from a sperm source. In both experiments, fertilization decreased with distance from the sperm source. The final experiment tested the influences of male size and population density on fertilization success; the effect of density was sign...

Methylation levels of maternal and paternal genomes during preimplantation development.

Abstract: The methylation status of three highly repeated sequences was studied in sperm, eggs and preimplantation embryos with different combinations of parental chromosomes. High levels of methylation of the IAP and MUP sequence families were found in sperm and in eggs, whereas the L1 repeat was found to be highly methylated in sperm but only about 42% methylated in eggs. To assess how the two parental genomes behaved during preimplantation development, normal, fertilised embryos were compared with parthenogenetic embryos where the chromosomes are exclusively of maternal origin. It was observed that the high levels of methylation at the IAP and MUP sequences were retained through early development, with the first signs of demethylation at the IAP sequences apparent on both parental chromosomes in the blastocyst. Methylation at the sperm-derived L1 sequences dropped to about the same level as that of the egg-derived sequences by the late 2-cell stage, both then remain at this intermediate level until around the time of cavitation when levels fell to about 10% in the blastocyst. High levels of DNA methylase were detected in germinal vesicle and metaphase II oocytes; these high levels were maintained in fertilised and parthenogenetic embryos through into the morula and then declined to be undetectable in the blastocyst. Our comparison of maternal and paternal genomes suggests that methylation levels at repeat sequences are remarkably similar at the time of fertilisation or, as in the case of the L1 sequences, they become so during the first few cell cycles. Hence, there do not appear to be global methylation differences between the genomes that are retained through preimplantation development.(ABSTRACT TRUNCATED AT 250 WORDS)

Fertilizing capacity of bovine sperm may be maintained by binding of oviductal epithelial cells.

Abstract: The ability of the bovine oviduct to maintain the motility and fertilizing capacity of bovine sperm was investigated by incubating frozen-thawed sperm with endosalpingeal epithelial cells cultured on either tissue culture plastic (nonpolarizing) or Matrigel.coated Millicell (polarizing) substrata, Sperm were also incubated in medium alone or with cultured bovine tracheal epithelial cells, Motility was determined at 6-h intervals over a 48-h period. The fertilizing capacity of sperm was evaluated after 0, 24, and 30 h of incubation by adding oocytes to the culture and determining the incidences of fertilization and polyspermy. Motility was maintained for 48 h in sperm that bound to endosalpingeal epithelial cells, but to a greater extent with polarized cells (38.4% motile) than with nonpolarized cells (0.8%). Fertilizing capacity was maintained for 30 h in sperm incubated with endosalpingeal epithelial cells on Matrigel/Millicell, but not in sperm incubated in medium alone or with tracheal cells. Only sperm incubated with oviductal cells developed hyperactivated motility. Scanning electron micrographs revealed that sperm were bound by the rostral portion of the intact acrosome to the apical surface of polarized endosalpingeal cells, These results suggest that the oviduct may not only store sperm but may also maintain sperm viability and fertilizing capacity during the preovulatory period,

Intracellular Calcium Accumulation and Responsiveness to Progesterone in Capacitating Human Spermatozoa

Abstract: Progesterone induced a rapid, long-lasting, dose- dependent increase of intracellular free calcium concentration ((Ca2+)i) in human sperm capacitated overnight. This effect was not counteracted by the cytosolic progesterone receptor antagonist RU486 (1 �mol/L) nor by the GABA-A receptor antag- onists bicuculline (10 �mol/L) and picrotoxin (50 �mol/L). Also, the rank order of potency of several progestative steroids on (Ca2+)i differed from that previously reported for uterine intra- cellular progesterone receptor or for P-GABA interaction in the central nervous system, indicating a different pathway for pro- gesterone stimulation of human sperm. Modifications of basal and progesterone-stimulated (Ca2+)i during sperm capacita- tion were also studied. A progressive, parallel increase of basal and progesterone-stimulated (Ca2+)i in capacitating spermato- zoa was found. In particular, progesterone-stimulated (Ca2+)i increased from a basal concentration of 147% ± 17% at 10 mm- utes to 327% ± 65% after 120 minutes of incubation in capaci- tating medium. This increase was well correlated with basal (Ca2+li (r = 0.93). In contrast, basal and progesterone- stimulated (Ca2+)i concentrations were constantly low in sper- matozoa incubated in noncapacitating medium. In capacitated spermatozoa, initial responsiveness to progesterone and basal (Ca2+)i was higher than in capacitating and noncapacitated samples,and remained constantthroughout the duration of the experiment.The progressive,parallelincreaseof (Ca2-f-)i and response to progesterone observed during in vitro capacitatlon ofhuman spermatozoa might be physiologically relevantinvivo duringcapacitationof sperm in the female genital tract.

Sperm Competition, Sperm Depletion, Paternal Care, and Relative Testis Size in Birds

Abstract: Testis mass in birds scales allometrically to body mass, the exponent being signifi- cantly smaller than unity. Two hypotheses were formulated in order to account for variation in relative testis size: (1) the sperm competition hypothesis, according to which males of taxa with a high intensity of sperm competition have larger testes than males of other taxa; and (2) the sperm depletion hypothesis, which proposes that taxa in which males copulate often also have large testes. Variation in testis mass after controlling for the effects of body mass and phylogeny was investigated in relation to copulation frequency per female (as a measure of the intensity of sperm competition) and per male (as a measure of the intensity of sperm depletion). Variation in relative testis mass was positively related to variation in copulation frequency per female, and the variation was significant; the sperm competition hypothesis was therefore supported by data. The sperm depletion hypothesis could not account for variation in testis size. Variation in relative testis mass was positively correlated with variation in social dispersion and was nega- tively correlated with variation in mate-guarding behavior.The extent of paternal care was re- lated to certainty of paternity as estimated from the presence of mate guarding, but not from relative testis mass.

More is not better: brood size and population growth in a self-fertilizing nematode.

Abstract: The normal form of the nematode Caenorhabditis elegans is a self-fertilizing hermaphrodite, which produces from the same germ-line tissue first a limited number of sperm and then a larger number of oocytes. Self-progeny brood sizes are determined by the number of sperm, and most of the oocytes remain unfertilized. Therefore it might seem selectively advantageous to increase the number of sperm, and hence the size of the brood. A mutation that leads to a 50% increase in sperm production allows a comparison of population growth rates between the wild type (mean brood 327 progeny) and the mutant (mean brood 499 progeny). Wild-type populations grow faster, as measured by food consumption, indicating that increased brood size is not advantageous. The mutant appears to be at a disadvantage because the additional spermatogenesis leads to a delay in the onset of oogenesis, and hence to an increase in the minimum generation time. In support of the notion of an optimal brood size, it was found that different natural isolates of this species have self-fertilities similar to that of the standard laboratory strain, in the range 250-350 progeny per worm.

Control of the sperm–oocyte switch in Caenorhabditis elegans hermaphrodites by the fem-3 3′ untranslated region

Abstract: IN the Caenorhabditis elegans hermaphrodite germ line, sperm and then oocytes are made from a common pool of germ-cell precursors. The decision to differentiate as a sperm or an oocyte is regulated by the sex-determining gene,fem-3. Expression of fem-3 in the hermaphrodite germ line directs spermatogenesis and must be negatively regulated to allow the switch to oogenesis1,2. In adult hermaphrodites (which are producing oocytes), mostfem-3 RNA is found in the germ line3, consistent with both the requirement for fem-3 in hermaphrodite spermatogenesis and the maternal effects of fem-3 on embryonic sex determination1,2Whereas loss-of-function mutants in fem-3 produce only oocytes, hermaphrodites carrying any of nine fem-3 gain-of-function (gf) mutations make none; instead sperm are produced continuously and in vast excess over wild-type amounts1Genetic analyses suggest that fem-3(gf) mutations have escaped a negative control required for the switch to oogenesis1. Here we report that all nine fem-3(gf) mutants carry sequence alterations in the fem-3 3′ untranslated region (3′ UTR). There is no increase in the steady-state level of fem-3(gf) RNA over wild-type, but there is an increase in the polyadenylation of fem-3(gf) RNA that is coincident with the unregulated fem-3 sactivity. Results of a titration experiment support the hypothesis that a regulatory factor may bind the fem-3 3′ UTR. We speculate that fem-3 RNA is regulated through its 3′ UTR by binding a factor that inhibits translation, and discuss the idea that this control may be part of a more general regulation of maternal RNAs.

A test of the human sperm acrosome reaction following ionophore challenge. Relationship to fertility and other seminal parameters.

Abstract: Acrosome reaction capacity was tested on semen samples from 53 fertile and 26 subfertile men. Preparations were divided into two aliquots after 3 or 24 hours of culture. One aliquot received 10 mumol/L calcium ionophore A23187 in dimethyl sulfoxide (DMSO) and the other received DMSO alone. Acrosome reactions were scored on ethanol-permeabilized smears using fluorescein isothiocyanate (FITC)-conjugated Pisum sativum lectin. The following factors were analyzed: the spontaneous reaction rates (control); induced reaction rates (ionophore-challenged); and the difference between the two, being the proportion of spermatozoa in the population capable of reacting in response to calcium influx (acrosome reaction to ionophore challenge [ARIC]). While spontaneous reactions bore no relation to fertility, induced reactions and ARICs were significantly reduced or absent in subfertile men, indicating acrosomal dysfunction as a likely cause of fertilization failure. The test was shown to have a predictive value for fertility comparable to that of the hamster ovum sperm penetration assay and to be a simple and cost-effective addition to existing semenology.

Evidence for the function of hyperactivated motility in sperm.

Abstract: After insemination, mammalian sperm undergo a striking change in flagellar beat pattern, termed hyperactivation. In low-viscosity culture medium, nonhyperactivated sperm flagella generate relatively symmetrical, low-amplitude waves, while hyperactivated sperm flagella generate an asymetrical beating pattern that results in nonprogressive movement. Since sperm encounter highly viscous and viscoelastic fluids in the female reproductive tract, the progress of hyperactivated sperm was compared with that of nonhyperactivated and transitional sperm in media of increasing viscosity. Hamster sperm obtained from the caudal epididymis were incubated in a medium that promotes capacitation. After 0, 3, and 4 h of incubation, the majority of the sperm exhibited, respectively, activated, transitional, and hyperactivated motility. At each of these time points, aliquots of sperm were removed from incubation and added to solutions of 0, 5%, 10%, 20%, and 30% Ficoll in medium. Samples containing mostly hyperactivated sperm (4 h) maintained higher swimming and flagellar velocities and were able to generate greater forces in response to increased viscous loading than activated sperm (0 h). Transitional sperm (3 h) showed an intermediate response. The paths of hyperactivated sperm through solutions of 20% and 30% Ficoll were considerably straighter than those made through medium alone. This is the first demonstration that hyperactivation can confer a mechanical advantage upon sperm in the oviduct where they may encounter viscous oviductal fluid and a viscoelastic cumulus matrix.

Kinetics of Fertilization in the Sea Urchin Strongylocentrotus franciscanus: Interaction of Gamete Dilution, Age, and Contact Time.

Abstract: Determining fertilization success of free spawning organisms in the field requires knowledge of how eggs and sperm interact under varying encounter fre- quencies and durations. In the laboratory, we investigated the relative influence of sperm concentration, egg con- centration, sperm-egg contact time, and sperm age on fer- tilization in the sea urchin Strongylocentrotus francis- canus. Our results indicated that sperm concentration, sperm-egg contact time, sperm age, and individual vari- ability were sequentially the most important factors in- fluencing fertilization success. Egg concentration was not significant over the range tested. A theoretical model of fertilization (Vogel-Czihak-Chang-Wolf model) was used to estimate the two rate constants of fertilization kinetics: the rate constant of sperm-egg encounter and rate constant of fertilization. This model explained 9 1% of the variation in fertilization success, provided estimates of the rate con- stants involved in fertilization, and indicated the propor- tion (3%) of sperm-egg contacts that result in fertilization. Estimates of sperm swimming velocity and egg diameter were used to independently calculate the rate of sperm- egg encounter and confirm the predictions of the model. This model also predicts the non-significant effect of egg concentration on fertilization success found empirically.

In vitro fertilization of single, isolated gametes of maize mediated by electrofusion

Abstract: Electrofusion-mediated in vitro fertilization of maize using single sperm and egg cells was performed. Sperm cells were released from pollen grains after rupture of the latter by osmotic shock in the fusion medium (0.55 M mannitol). Egg cells were isolated by enzyme treatment (pectinase, pectolyase, hemicellulase, and cellulase) followed by mechanical isolation. The conditions generally used for the electrical fusion of protoplasts of somatic cells were also applied to the protoplasts of gametic cells of maize. Electrofusion was performed with single pairs of gametes under microscopic observation. The mean fusion frequency was 79%. Isolated egg cells of maize showed protoplasmic streaming during 22 days of culture, but they did not divide. However, after fusion of the sperm with the egg cells, these fused cells did develop, with a mean division frequency of 83%, and grew to multicellular structures. Egg cells and fusion products were cultivated with a maize feeder-cell system.

Bicarbonate: carbon-dioxide regulation of sperm capacitation, hyperactivated motility, and acrosome reactions.

Abstract: The bicarbonate: CO2 (HCO3-:CO2) concentration dependencies of hamster sperm motility, spontaneous acrosome reactions, and zona penetration (used to assay the zona-induced acrosome reaction) were examined. A cross-over experimental design was used to segregate effects on early stages of capacitation, spanning the first 5 h of incubation, from those on acrosome reactions and zona penetration during the last 1 h. After 5 h, HCO3-:CO2 concentrations were increased, decreased, or kept the same for 1 h. Compared to no HCO3-:CO2, as little as 2.9 mM: 0.6% HCO3-:CO2 increased the sperm motility index (MI) by 2.7-3.6 times. When HCO3-:CO2 was continuously present, both progressive and hyperactivated motility were stimulated by HCO3-:CO2 in a dose-dependent manner by 3-4 h, well before completion of capacitation. Stimulation of acrosome reactions or zona penetration, by addition of HCO3-:CO2 to sperm for 1 h late in capacitation, depended mainly on levels of HCO3-:CO2 present earlier in capacitation. When 25 mM: 5% HCO3-:CO2 was added only at 5 h, responses were significantly lower than with sperm treated continuously with the same concentration of HCO3-:CO2, being 2.5 times lower for MI, 2 times lower for acrosome reactions, and 6.3 times lower for zona penetration. In contrast, decreasing HCO3-:CO2 to suboptimal levels after 5 h did not decrease any 6-h sperm responses significantly. The average maximal and one-half maximal preincubation HCO3- concentrations for all responses were 34.2 +/- 1.0 and 9.2 +/- 0.3 mM, respectively. Zona penetration and hyperactivation were highly correlated.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective role of superoxide dismutase in human sperm motifity: superoxide dismutase activity and lipid peroxide in human seminal plasma and spermatozoa

Abstract: The levels of superoxide dismutase (SOD), a highly specific scavenging enzyme for superoxide anion radicals (O2-), and lipid peroxide produced by oxygen free radicals were measured in human seminal plasma and spermatozoa. Seminal plasma contained 366.8 +/- 20.9 U/ml (mean +/- SE) of SOD activity. SOD activity in human spermatozoa showed a significant correlation to the number of motile spermatozoa, while the activity in seminal plasma did not relate to the sperm concentration or motility. The lipid peroxide concentration in seminal plasma was 6.22 +/- 0.46 nmol/ml and had no significant relationship to sperm concentration or motility. The malondialdehyde (MDA) concentration in spermatozoa was significantly related to the number of immotile spermatozoa. A decrease in the motility of spermatozoa incubated in medium without seminal plasma was observed after 120 min, while the MDA concentration of the spermatozoa increased. Addition of exogenous SOD (400 U/ml) to the sperm suspension significantly decreased this loss of motility and the increase of the MDA concentration. These data suggest a significant role for SOD in sperm motility. It seems that lipid peroxidation of human spermatozoa may cause loss of motility and that SOD may inhibit this lipid peroxidation. These results suggest that SOD may have a possible clinical application in the use of spermatozoa for in-vitro fertilization (IVF) or artificial insemination.

Attachment of boar sperm to mucosal explants of oviduct in vitro: possible role in formation of a sperm reservoir.

Abstract: Ejaculated boar sperm were incubated with explants of porcine oviductal mucosa that had been dissected from the isthmic and ampullar regions of gilts. Sperm bound within minutes to the epithelial surfaces of the explants. Binding was not affected by region (isthmus or ampulla) nor day of estrous cycle (Day 0 or Day 10), but was increased by addition of 70 pg/ml 17 beta-estradiol to the medium. Scanning electron micrographs indicated that sperm bound, via the acrosomal region, to ciliated cells. After 24 h, the numbers of bound sperm dropped significantly, but the motility of the bound sperm did not. A mucous material that entrapped sperm was observed on the epithelial surfaces of 23/32 isthmic and only 4/32 ampullar explants. These results indicate that sperm sticking to ciliated cells and mucus can create a sperm reservoir in the isthmus, but the means by which sperm are released remain unknown.

Relationship between sperm motility assessed with the Hamilton-Thorn motility analyzer and fertilization rates in vitro.

Abstract: To determine which sperm movement characteristics are related to in vitro fertilization rates, semen and swim-up preparations used for in vitro fertilization in 108 patients were assessed using the Hamilton-Thorn HTM-2030 Motility Analyzer (HTMA) and other sperm tests. There were highly significant correlations between manual and HTMA results for sperm concentration (Spearman r = 0.881; P less than 0.001) and the percentage of motile spermatozoa (Spearman r = 0.580; P less than 0.001). The percentage of motile spermatozoa with average path velocities greater than 10 microns/s and greater than 20 microns/s, straight line and curvilinear velocity, linearity (straight line velocity vs curvilinear velocity), amplitude of lateral head displacement, and beat-cross frequency were significantly higher in the insemination medium after selection of motile spermatozoa by the swim-up technique than in the semen. Linearity (P less than 0.01), the percentage of morphologically normal spermatozoa (P less than 0.05) and straight line velocity (P less than 0.05) in semen, and the percentage of motile spermatozoa with average path velocities greater than 10 microns/s in both semen (P less than 0.05) and insemination medium (P less than 0.05) were significantly correlated with in vitro fertilization rate when examined by a nonparametric (Spearman) test. With logistic regression analysis of all data, only the diagnoses of male infertility and tubal disease, linearity in semen, and the percentage of motile spermatozoa with average path velocities between 10 and 20 microns/s in insemination medium were significantly related to in vitro fertilization rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrogen peroxide is involved in hamster sperm capacitation in vitro.

Abstract: We have investigated the possibility that the generation of hydrogen peroxide (H2O2) by spermatozoa plays a physiological role during capacitation. Capacitation is defined as the incubation period required for fertilization in mammals. Capacitation culminates in an exocytotic event, the acrosome reaction (AR). Mammalian sperm generate H2O2 during aerobic incubation and do not contain catalase, the enzyme that promotes scavenging of H2O2. In the present work we show that added catalase inhibited the AR, while glucose oxidase (GO), an enzyme that generates H2O2, accelerated the onset of the AR. Direct addition of H2O2 also stimulated the AR; catalase inhibited both the stimulation by GO and by H2O2. The onset of the AR was always preceded by the appearance of hyperactivated motility. The stimulation of the AR by H2O2 was manifest 1-2 h after the addition of H2O2. Catalase added at 3 h of incubation was less effective in inhibiting the AR than catalase added at the beginning. Incubation of sperm with catalase prevented the induction of the AR by the membrane-perturbing lipid, lysophosphatidyl choline. Taken together, these results suggest that H2O2 produced by hamster sperm plays a significant role during capacitation, possibly in membrane reorganization to facilitate the fusion that takes place during exocytosis of the acrosomal contents.

Sperm attraction to a follicular factor(s) correlates with human egg fertilizability

Abstract: Spermatozoa normally encounter the egg at the fertilization site (in the Fallopian tube) within 24 hr after ovulation. A considerable fraction of the spermatozoa ejaculated into the female reproductive tract of mammals remains motionless in storage sites until ovulation, when the spermatozoa resume maximal motility and reach the fertilization site within minutes. The nature of the signal for sperm movement is not known, but one possible mechanism is attraction of spermatozoa to a factor(s) released from the egg. We have obtained evidence in favor of such a possibility by showing that human spermatozoa accumulate in follicular fluid in vitro. This accumulation into follicular fluid was higher by 30-260% than that observed with buffer alone and was highly significant (P less than 10(-8)). Not all of the follicular fluids caused sperm accumulation; however, there was a remarkably strong correlation (P less than 0.0001) between the ability of follicular fluid from a particular follicle to cause sperm accumulation and the ability of the egg, obtained from the same follicle, to be fertilized. These findings suggest that attraction may be a key event in the fertilization process and may give an insight into the mechanism underlying early egg-sperm communication.

Distribution of aneuploidy in human gametes: comparison between human sperm and oocytes.

Abstract: The frequency and distribution of aneuploidy was compared in 11,615 karyotyped human sperm and 772 karyotyped human oocytes to determine if all chromosomes are equally likely to be involved in aneuploid events or if some chromosomes are particularly susceptible to nondisjunction. The frequency of hypohaploidy and hyperhaploidy was compared among different chromosome groups and individual chromosomes for human sperm and oocytes. In general, hypohaploid chromosome complements were more frequent than hyperhaploid complements, in sperm and oocytes. The distribution of chromosome loss in the hypohaploid complements indicated that significantly fewer of the large chromosomes and significantly more of the small chromosomes were lost, suggesting that technical loss predominantly affects small chromosomes. A conservative estimate of aneuploidy (2 X hyperhaploidy) was approximately 3-4% in the human sperm and 18-19% in human oocytes. All chromosome groups were represented among hyperhaploid human sperm and oocytes. For human sperm, the observed frequency of hyperhaploidy equaled the expected frequency based on the assumption that the frequency of nondisjunction is equal for all chromosome groups, with two exceptions: group G and the sex chromosomes. Among individual chromosomes in human sperm, chromosomes 1 and 21 and the sex chromosomes had a significant excess of hyperhaploidy. For human oocytes, there were fewer hyperhaploid oocytes than expected for chromosome groups C and F and more than expected for chromosome groups D and G. Among individual chromosomes there was a significant excess for chromosome 21. These results indicate that all chromosomes are susceptible to nondisjunction but that chromosome 21 is particularly prone to aneuploidy in both human sperm and oocytes. They also demonstrate that sex chromosome aneuploidy is common in human sperm but not in human oocytes.