Sperm Age Research Articles

Evaluation of the duration of sperm fertilizing ability in five lines of commercial broiler breeder and Delaware cross males

The ability to characterize the reproductive potential of male fowl can be affected by a number of factors, including age, type, insemination scheme, and number of sperm inseminated. Fertility is a complex interaction of traits involving two individuals of differing genetic composition: In modern broiler breeders, selected predominantly for growth and carcass characteristics, fertility problems may be exacerbated. In order to evaluate the male components of fertility, an experiment investigating the effects of male line on both average fertility and the duration of fertility was completed. Male chicks from five commercial broiler breeder male lines or sired by subfertile Delaware cross roosters were reared to adulthood. Between 30 and 60 wk of age, semen was collected from five males per line, extended and used to inseminate each of 10 to 12 hens from four broiler breeder female lines or Single Comb White Leghorn hens with 80 x 10(6) live sperm. Following a single insemination eggs were collected for 21 d and fertility determined by visual inspection following 4 d incubation. The percentages of live sperm and overall fertility data for the replicate trials were analyzed, following transformation, with a linear model and daily fertility data were analyzed by iterative least squares regression. Whereas there were large differences in fertility among individual males (durations from 3.4 to 14.5 d) within a line, there were no significant male line or replicate effects on overall fertility or the duration of fertility. However, there was a significant (P < 0.05) line-dependent reduction in the percentage of live sperm in broiler breeder males, with the subfertile Delaware cross males being intermediate. There were no significant female line or replicate effects on the duration of fertility; however, there were significant female line effects on overall fertility at both 7 and 21 d. These data suggest that although individual males varied widely, there were no male line effects on the duration of fertility in the lines of broiler breeders evaluated when analyzed by iterative least squares. Furthermore, these data suggest that although females may have significant affects on overall fertility, the duration of fertility appears to be a predominantly male characteristic. Therefore, iterative least squares regression may be a useful tool for identifying males with superior sperm fertilizing ability.

Fertility of rat epididymal sperm after chemically and surgically induced sympathectomy.

Guanethidine, a chemical that selectively blocks sympathetic noradrenergic neurons, was used to investigate the role of sympathetic innervation in the fertility of rat epididymal sperm, using both natural mating and in utero insemination protocols. This animal model correlates, at least in part, with spinal cord injury (SCI) in men. Adult male rats were treated daily by i.p. injections, for 21 or 42 days, with 0 or 6.25 mg/kg guanethidine. To compare the effects of guanethidine-induced sympathectomy with those following surgically induced sympathectomy, the inferior mesenteric ganglion and the proximal hypogastric nerves were removed in another group of rats. Both chemically and surgically induced sympathectomy increased the weight of the epididymis and seminal vesicles/coagulating glands as well as the number and the transit time of cauda epididymal sperm. Neither serum testosterone levels nor LH was affected by treatment with guanethidine. Using natural mating, no litters were produced by guanethidine-treated rats. Chemically denervated rats failed to produce copulatory plugs or ejaculate into the uterus. However, distal cauda epididymal sperm from chemically or surgically denervated rats displayed normal fertilization ability (80%) using in utero inseminations. In addition, the sperm of denervated rats did not show abnormal sperm chromatin structure using an assay that detects DNA damage. We conclude that sympathectomy delays the transit of sperm through the cauda epididymidis and produces ejaculatory dysfunction but does not compromise sperm quality in the distal cauda epididymidis. Moreover, these data provide compelling evidence that there is no association between the prolonged transit time of sperm within the epididymis, i.e., pre-ejaculatory sperm aging, and the fertility of those sperm, which has important implications for artificial insemination using sperm from men with SCI.

Modified sperm stress test: a simple assay that predicts sperm-related abnormal in-vitro fertilization

Loss of sperm motility is associated with the process of sperm senescence and occurs at different rates within a given normal or abnormal sperm population. Reactive oxygen species attack cell membrane phospholipids, generating fatty acid peroxides and other degradation products, that also have deleterious effects on sperm motility and fertilizing ability. The objective of this investigation was to study a modification of the original sperm stress test (MOST), changing the culture medium to one offering transitional metals and shortening the total test time, to ascertain whether it can predict fertilization under these laboratory conditions. A total of 41 semen samples was obtained from patients undergoing in-vitro fertilization (IVF) at our institution. Semen samples were grouped into those producing total fertilization rates (FR) within normal limits (>50%) and those showing low total FR (<50%). The normal FR group had a significantly greater MOST mean value than the low FR group (0.71 versus 0.44). Furthermore, there was a statistically significant correlation between the MOST score and ungrouped fertilization rates (r = 0.53, P = 0.0004). Diagnostic statistics for MOST ratio values predicting <50% FR showed an optimal threshold of 0.39. Collectively, sensitivity, specificity, positive predictive value and negative predictive value have their largest values at this threshold. Taking into account the above mentioned threshold figures, there is a significant association between MOST and FR categories (P = 0.0009). In conclusion, MOST is a simple assay that has significant predictive value for sperm related IVF abnormalities.

Snail sperm production characteristics vary with sperm competition risk

Sperm competition is widespread and influences both male investment in spermatogenic tissue and ejaculate characteristics. Sperm competition models assume trade-offs between sperm size and number, although such trade-offs may be difficult to detect. This study examines the effects of sperm competition risk on the sperm production characteristics of the freshwater snail Viviparus ater. In this prosobranch, females mate frequently and store sperm, generating sperm competition. Males produce two sperm morphs, fertile eupyrene sperm and non-fertilizing oligopyrene sperm. Non-fertilizing sperm may play a role in sperm competition and therefore, like fertilizing sperm, the number produced could vary relative to sperm competition risk. In addition, trade-offs between sperm number and sperm size may be expected. We manipulated the sex ratio of sexually mature snails and found the presence of rivals affected the ratio of oligopyrene/eupyrene sperm males produced. In experimental and natural populations, the number of oligopyrene sperm produced, but not the number of eupyrene sperm, was significantly higher when the sex ratio was male biased. Testis mass did not vary between experimental treatments. We also found a negative relationship between the number and size of oligopyrene sperm produced, which is consistent with evolutionary models of sperm competition, and is, to our knowledge, the first intraspecific demonstration of a trade-off between these traits.

The effects of walls, paternity and ageing on sperm motility.

The measurement of sperm motility is critical when studying fertilization kinetics and chemotaxis. Analysis of motility has traditionally been carried out on cells in small fluid volumes on microscope slides. Several theoretical treatments suggest that drag forces significantly affect flagellar motion within 10 sperm body lengths of the slide surface. Understanding how sperm move in the absence of surface drag is crucial when considering natural locomotory patterns. To examine the effects of solid surfaces, motile sperm from sea urchins (Arbacia punctulata) were placed in a Plexiglas chamber (69 mmx45 mmx15.5 mm; length x width x height). A system was constructed to minimize convective flow by limiting temperature differences within the chamber to less than 0.1 degrees C. The movement of sperm was video-recorded at two levels: (3/4)100 micron (3 body lengths) and 5 mm (150 body lengths) below the chamber lid. When swimming speeds were measured using a computerized video motion-analysis system, a highly significant difference (P<0. 0001) between cells at the two depths was found. Cells nearest the lid swam at 174.6+/-5.9 micron s-1 (mean +/- s.e.m.), whereas those farther away slowed to only 111.1+/-9.9 micron s-1 (mean +/- s.e.m.). Swimming speed was also found to be significantly (P<0.01) affected by paternity, but not by sperm age. We conclude that viscous wall effects must be carefully considered in studies of sperm motility and chemotaxis. The analysis of sperm on a microscope slide may substantially exaggerate swimming speed.

Biased primary sex ratio in the bushcricket Poecilimon veluchianus , an insect with sex chromosomes

Offspring sex ratio at hatching was examined in the bushcricket Poecilimon veluchianus. Offspring sex ratios varied significantly between females (Fig. 1). Low mortality prior to sex determination established that this heterogeneity was already present in the primary offspring sex ratio. Sperm age and female age had no influence on offspring sex ratio (Fig. 2). Male age at copulation, however, correlated significantly with offspring sex ratio (Fig. 3). There were two types of males: one type produced predominantly daughters when young and an increasing proportion of sons with age. The other type produced, independent of age, 1:1 offspring sex ratios (Fig. 4). The two types of males seem to occur in approximately equal numbers. Sex ratio variation (1) may adaptively compensate for local sex ratio biases caused by sex-specific motility, or (2) it may be adaptive if there is a sex-differential effect of laying date on offspring fitness.

Sperm segregants from the murine Rb(11.14) heterozygote fertilizing in vivo and in vitro.

Segregants of the Rb(11.14) translocation in 17 heterozygous male mice were analyzed in G- and C-banded first-cleavage metaphases after in vivo (n = 440) and in vitro (n = 267) fertilization. Mating intervals of 3 and 14 d provided unaged and physiologically aged sperm for the oocytes, which were from chromosomally normal females. Significantly more normal than balanced sperm segregants were seen in both the in vivo fertilized (P < 0.01) and in vitro fertilized (P < 0.001) study groups. The distortion was elevated in vitro (P < 0.02), unaccompanied by a sex-ratio distortion, and had a segregant distribution that was independent of sperm age; thus it differs from that seen for other translocations. The findings argue for chromosome-specific effects of Robertsonian translocations on sperm function. A significantly (P < 0.05) increased hyperhaploidy rate (unrelated to the translocation) supports the sperm-aging hypothesis.

Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival of the pregnancy, and sex of the baby.

The timing of sexual intercourse in relation to ovulation strongly influences the chance of conception, although the actual number of fertile days in a woman's menstrual cycle is uncertain. The timing of intercourse may also be associated with the sex of the baby. We recruited 221 healthy women who were planning to become pregnant. At the same time the women stopped using birth-control methods, they began collecting daily urine specimens and keeping daily records of whether they had sexual intercourse. We measured estrogen and progesterone metabolites in urine to estimate the day of ovulation. In a total of 625 menstrual cycles for which the dates of ovulation could be estimated, 192 pregnancies were initiated, as indicated by increases in the urinary concentration of human chorionic gonadotropin around the expected time of implantation. Two thirds (n = 129) ended in live births. Conception occurred only when intercourse took place during a six-day period that ended on the estimated day of ovulation. The probability of conception ranged from 0.10 when intercourse occurred five days before ovulation to 0.33 when it occurred on the day of ovulation itself. There was no evident relation between the age of sperm and the viability of the conceptus, although only 6 percent of the pregnancies could be firmly attributed to sperm that were three or more days old. Cycles producing male and female babies had similar patterns of intercourse in relation to ovulation. Among healthy women trying to conceive, nearly all pregnancies can be attributed to intercourse during a six-day period ending on the day of ovulation. For practical purposes, the timing of sexual intercourse in relation to ovulation has no influence on the sex of the baby.

Mouse chromosome 6 in Rb translocations: consequences in singly and doubly heterozygous males.

Previously it has been shown that male mice heterozygous for the Rb(6.16) translocation show a transmission distortion of the segregants in resulting zygotes, particularly for sexually active animals (Aranha and Martin-DeLeon, 1991). Sperm bearing the translocation have an impaired fertilizing ability, compared to chromosomally normal sperm, and this dysfunction is potentiated in X-bearing cells leading to a sex ratio distortion. Since earlier data suggested that a deficiency of Chromosome 6 was associated with sperm dysfunction (Zackowski and Martin-DeLeon, 1989), the present study was designed to determine the uniqueness of the coupling of the distortions for the Rb(6.16) translocation and the effect of 0 and 2 copies of Chr 6 on sperm function. First cleavage metaphases, resulting from chromosomally normal females that were mated to sexually active or rested Rb(6.15) or Rb(2.8) heterozygous males, were sequentially G- and C-banded. For unaged sperm from sexually active Rb(6.15) males, cytogenetic analysis showed that the ratio of normal (90) to balanced (37) zygotes deviated significantly (P < 0.001) from 1:1, as did the sex ratio, 46X:81Y (P < 0.01). The latter distortion was related to a deficiency of X-bearing sperm with the translocation (8X:29Y). Both segregation and sex ratio distortions disappeared for aged sperm (69:50, 51X:68Y) and a contingency table showed that segregant type was related to sperm age (P < 0.05). For the Rb(2.8) the ratio of normal to balanced zygotes (65:46) was not significantly different from 1:1 for unaged sperm, and although the ratio from aged sperm was 62:39, there was no relationship between segregant type and sperm age (P > 0.05). There was also no sex ratio distortion for either unaged or aged sperm (P > 0.05). To generate zygotes with sperm complements containing 0 and 2 copies of Chr 6, males doubly heterozygous for Rb(6.16) and Rb(6.15) were mated to chromosomally normal females. No zygotes were recovered and the males were shown histologically to have azoospermia and spermatogenic arrest. The results support the conclusion that the presence of Chr 6 in Rb translocations specifically affects segregant and sex ratio distributions. They also indicate, that as the common arm in compound heterozygotes, this chromosome grossly affects spermatogenesis.

The Effects of Sperm Concentration, Sperm:Egg Ratio, and Gamete Age on Fertilization Success in Crown-of-Thorns Starfish (Acanthaster planci) in the Laboratory

Laboratory experiments varying gamete concentrations and gamete age demonstrated significant reductions in fertilization success of the starfish Acanthaster planci (L.) with decreasing sperm concentration and increasing age of both eggs and sperm. The effect of aging in sperm was faster than that of eggs, and the speed of sperm aging increased with increasing dilution of sperm. Fertilization success was high over a wide range of sperm: egg ratios but declined rapidly at ratios less than 50, particularly at low sperm concentrations. A. planci gametes aged more slowly, and the loss of fertilizing capacity of sperm with dilution (the respiratory dilution effect) was far less, than in sea urchins. These characteristics provide a mechanism for enhanced fertilization success at given sperm concentrations and at greater distances and times from the point of gamete release, and may explain the higher fertilization rates achieved over longer distances in the wild by A. planci relative to sea urchins. Gametes would remain competent for longer periods at more dilute concentrations and so better achieve long-distance fertilization. Gametes obtained at the end of the breeding season were qualitatively different from those obtained early in the breeding season and showed reduced fertilization success for a given combination of variables, and different fertilization dynamics.

The genetic risks of in vitro fertilization techniques: the use of an animal model.

The influence of some technical and biological parameters on the genetic characteristics of embryos derived from in vitro fertilization (IVF) techniques was studied. Using a murine model, we assessed the effect of gamete manipulation, gamete maturation stage, and maternal age on the chromosome complements of first-cleavage embryos. We found a positive correlation between some of these parameters and the incidence of the different chromosome abnormalities studied. Regarding aneuploidy, we observed an influence of maternal age, using both prepubertal and old females. Polyspermy showed a positive correlation with in vitro fertilization, the immaturity and overmaturity of the oocytes employed, and the use of prepubertal females. The appearance of diploid female complements was related to oocyte immaturity and prepubertal females, while diploid male complements were directly related to in vitro fertilization. Premature chromosome condensation (PCC) had a direct relationship with oocyte immaturity and in vitro maturation of the oocyte. Finally, structural abnormalities were associated with the process of sperm aging in vitro.

Asymmetrical homogamy and unequal sex ratio from reciprocal mating-order crosses between Chorthippus parallelus subspecies

To study the evolution of this Pyrenean hybrid zone following postglacial secondary contact, a crossing programme was performed involving sequential mating of single females by males of both subspecies in both orders. Progeny were scored as embryos using Acridine orange and C-banding to identify their male parent. This revealed a number of significant departures from straightforward inheritance. There was an excess of pure over hybrid progeny. This homogamy is produced at fertilization but may have been determined before through sperm preference or competition. There was also sperm precedence with the second mating producing most of the progeny. This may be due to sperm ageing or differential storage and utilization by the female. The fundamental sex ratio in the progeny was biased towards males. Of particular interest is the finding that homogamy is markedly greater when C.p. parallelus is the mother, suggesting some form of differential biochemical recognition. This asymmetry should have important consequences for the dynamics of the hybrid zone. All these results are discussed in the light of the divergence of the two subspecies and the mixing of their genomes in the hybrid zone.

Sperm age, sex ratio, and hyperhaploidy frequency in mice.

Physiologically aged and unaged sperm from each of 12 sexually mature B6SJLF1/J mice were used to fertilize oocytes from females of the same strain, with each male serving as its own control. Male genomes in 323 and 307 first-cleavage metaphases obtained by in vivo and in vitro fertilization, respectively, were analyzed cytogenetically, using C-banding for detection of the Y chromosome. The sex (X:Y) ratio among all zygotes resulting from in vivo fertilization was 1.18; in zygotes resulting from in vivo fertilization by aged (14-d mating intervals) sperm, however, the ratio was 1.53, which differed significantly (chi 2 = 6.72, P less than 0.01) from the theoretical value of 1.00. Comparison of the sex ratio in zygotes resulting from in vivo fertilization by unaged sperm (3-d mating intervals), 0.94, with that in zygotes resulting from fertilization by aged sperm (using a 2 x 2 contingency table) showed a significant (chi c2 = 4.19, P less than 0.05) relationship between sex ratio and sperm age. In vitro neither the combined nor the individual 3- and 14-d data deviated significantly from the expected sex ratio of 1.00. The frequency of sperm-derived hyperhaploidy did not differ significantly between the in vivo (3.4%) and in vitro (5.9%) populations, but did between unaged (2.5%) and aged (6.8%) sperm (chi c2 = 5.74, P less than 0.01). All hyperhaploid zygotes had a complement of n + 1 chromosomes, except the 14-d in vitro group, where complements of n + 2 and n + 3 chromosomes were seen. Sperm-derived polyploidy, which was observed only in the in vitro group, was independent of sperm age and occurred in 6.8% of the zygotes. These data provide support for the sperm-aging hypothesis and indicate, for the first time, an influence of sperm aging in the male genital tract on the X:Y ratio of conceptuses resulting from natural matings of chromosomally normal males.

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

Determining fertilization success of free spawning organisms in the field requires knowledge of how eggs and sperm interact under varying encounter frequencies and durations. In the laboratory, we investigated the relative influence of sperm concentration, egg concentration, sperm-egg contact time, and sperm age on fertilization in the sea urchin Strongylocentrotus franciscanus. Our results indicated that sperm concentration, sperm-egg contact time, sperm age, and individual variability were sequentially the most important factors influencing 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 91% of the variation in fertilization success, provided estimates of the rate constants involved in fertilization, and indicated the proportion (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.

The murine Rb(6.16) translocation: evidence for sperm selection and a modulating effect of aging

The segregation products of the Rb(6.16) translocation were studied at first cleavage metaphase. Male mice heterozygous for the translocation mated at 3- and 14-day intervals to superovulated random-bred ICR females. Chromosome preparations of the recovered one-cell embryos were sequentially G- and C-banded and male and female complements analyzed cytogenetically. Of the 309 zygotes analyzed from both mating groups, no unbalanced segregants of the translocation were observed. In the 3-day group there was a highly significant difference (P less than 0.001) from the expected 1:1 ratio between sperm with normal (70.5%) and balanced segregants (26.2%) of alternate segregation. In the 14-day group the level of significance for the difference was ten times lower (P less than 0.01) as normal segregants were observed in 56.4% of the sperm and balanced ones in 36.5%. A comparison of the two groups using a 2 x 2 contingency table showed that segregant type was related to mating frequency (P less than 0.05). There was a highly significant distortion (P less than 0.01) of the sex ratio, with 178 Y-bearing and 131 X-bearing sperm in the combined populations. When sex ratio was analyzed according to mating intervals, the distortion was significant (P less than 0.01) only for the 3-day group. An analysis of the sex ratio according to the segregant type showed no significant deviation from 1:1 for type 1 segregants, which had normal chromosomes, while type 2 segregants, with the translocation, had a deficiency of X-bearing sperm. This deficiency was significant (P less than 0.05) only for the 3-day population. Analysis of meiotic preparations showed no association between the translocation trivalent and the X-Y bivalent. Our results, obtained under physiological conditions, provide definitive evidence for sperm selection and support previous findings that aging of sperm can modify the effect of selection.

The effect of in-vitro ageing on mouse sperm chromosomes

In-vitro ageing has long been suspected to affect adversely the ability of spermatozoa to fertilize and produce viable zygotes. A comparison of the first cleavage chromosome complement of 824 mouse embryos fertilized with fresh spermatozoa and 656 embryos fertilized with spermatozoa aged for 12, 24 or 48 h is reported herein. The chromosome analysis of first-cleavage embryos allows us to study directly the paternal and maternal chromosome complements which contribute to the embryo. Both chromosome clusters remain separate when an antimitotic agent is used to prevent metaphase synchronization, allowing identification of maternal and paternal chromosomes. We show that after sperm ageing, there is a decrease in the fertilization rate from 75% in the controls to 57.5% (12 h of ageing), 63.5% (24h of ageing) and 4.4% (48 h of ageing). Simultaneously, the level of chromosome structural abnormalities increase from 1.3% in the controls to 16.5% after 12 h of ageing, 18.8% after 24 h of ageing and 59% after 48 h of ageing. The incidence of aneuploidy and polyploidy is not affected by ageing of the spermatozoa. Most of the structural abnormalities are paternal in origin and are presumably induced by the ageing of spermatozoa.

Aging gametes in relation to incidence, gender, and twinning in Down syndrome

Sexual practices have been implicated in the causation of Down syndrome (DS). Two mechanisms have been hypothesized. The theory of the fertilisation of an overripe ovum due to a delay in fertilization, and more recently the aging of the sperm. The orthodox Jewish population have very specific, strict practices concerning menstruation, which provide a unique model for the study of births in relation to time of conception. Data on the incidence of DS in the Jewish population of Jerusalem between 1982 and 1988 were analyzed. Among a comparable group of mothers under age 37 years and for whom amniocentesis was not available, it was found that the incidence of DS was significantly higher in the religious than in the nonreligious population (P less than 0.001). The rate of twinning in the DS population was significantly higher than in the general population (P less than 0.015), as was the ratio of males to females, 62% and 38%, respectively compared with 51% males and 49% females in the newborn population (P less than 0.001). The association of these 3 factors in relation to the aging gamete of either maternal or paternal origin is discussed.

Modifications of sperm proteins leading to acquisition of fertilizing ability

Mammalian spermatozoa acquire their fertilizing ability following release from the seminiferous tubules, as they transverse the epididymis, the female tract and the egg investments. We have examined changes occurring in the distribution of antigens of rat spermatozoa during epididymal maturation and after ligation of the caput epididymis by using immunocytochemistry at the light microscopy and at the electron microscopy (EM) levels.Spermatozoa were collected from the test is and different segments of the epididymis. To obtain aging of sperm in vivo, male rats were operated and one side of the epididymis was ligated at the caput and corpus junction. Spermatozoa were washed, and divided into 4 tubes, and treated as follows: 1. no treatment; 2. permeabilization by freeze thawing; 3. Trypsin; 4. NP-40;. Sperm samples were washed and the nincubated for 30 min with monoclonal antibodies. Monoclonal antibodies were raised in mice against antigens on cauda sperm of rats.

Immunological Status of Patients before and after Vasovasostomy as Determined by the Immunobead Antisperm Antibody Test

With the immunobead antisperm antibody test a prospective study was conducted to evaluate the immune status of 55 men before and after vasectomy reversal. A third of the vasectomy patients (19 of 55) had significant serum-sperm antibodies (20 per cent binding or more) detected by the indirect immunobead antisperm antibody test. Of 31 vasovasostomy patients 12 (38 per cent) had significant sperm-surface antibodies (20 per cent binding or more) by the direct immunobead antisperm antibody test. Preoperative serum assays correctly classified the antibody status of 69 per cent of the vasectomy patients. The immunological impact of spermatic granuloma formation, duration of vasal obstruction, patient age and presence of sperm in the vasal fluid at operation also were assessed. An inverse relationship between the proportion of antibody-bound sperm and the percentage of motile sperm in the ejaculate of vas reversal patients was found with videomicrographic semen analysis. The percentage motility was significantly lower among patients with greater quantities of sperm-surface antibodies. No other parameter of semen analysis showed this difference when compared for positive or negative immunobead antisperm antibody test results.

Analysis of the chromosome complement in outbred mouse sperm fertilizing in vitro.

The chromosome complements in a population of mouse sperm from random-bred ICR donors were analyzed at first-cleavage metaphase after in vitro fertilization (IVF) of oocytes from females of the same strain. The sperm were aged as donations occurred within an average of 31 days, either since last mating or at arrival at the animal facility in the case of virgin males. Of a total of 598 sperm complements studied from 22 sexually mature males aged 10-26 weeks old, there was one diploid complement (0.17%). The frequencies of hyperhaploidy and structural aberrations that were studied in 338 complements were 4.4% and 3.6%, respectively, giving an overall frequency of 8.0%. The hyperhaploid complements consisted of n + 1, n + 2, n + 3, and n + 7 counts, while the structural abnormalities were of the chromosome type and included large and small fragments and a possible translocation. This is the highest frequency of sperm chromosome abnormalities reported for mouse sperm obtained from males under physiological conditions and fertilized in vitro or in vivo. Sperm aging, strain, and/or technique differences are among the factors that may be responsible for this high frequency. Since the 8.0% frequency of hyperhaploidy and structural abnormalities is similar to the frequency reported for human sperm after IVF, the outbred murine in vitro fertilization system may be a useful model to study the origin of human sperm chromosome abnormalities.