Human sperm penetration into zona-free hamster oocytes as a test to evaluate the sperm fertilizing ability

Validation of a laboratory-developed test of human sperm capacitation

Sperm must undergo capacitation to become fertilization competent. Here we validated that monosialotetrahexosylganglioside (GM1 ) localization patterns, which were assessed in the Cap-Score™ Sperm Function Test, reflect a capacitated state in human sperm. First, we defined patterns representing sperm that do or do not respond to stimuli for capacitation. Sperm with "capacitated" patterns had exposed acrosomal carbohydrates and underwent acrosome exocytosis in response to calcium ionophore (A23187). Precision was evaluated by percent change of the Cap-Score measured for 50, 100, 150, and 200 sperm. Changes of 11%, 6%, and 5% were observed (n ≥ 23); therefore, we counted ≥150 sperm per condition. Variance within and between readers was evaluated using 20 stitched image files generated from unique ejaculates. Two trained readers randomly resampled each image 20 times, reporting an average standard deviation of 3 Cap-Score units and coefficient of variation of 13% when rescoring samples, with no difference between readers. Semen liquefaction times ≤2 hr and mechanical liquefaction with Pasteur or wide-orifice transfer pipettes did not alter Cap-Score values. However, liquefaction with chymotrypsin (p = 0.002) and bromelain (p = 0.049) reduced response to capacitating stimuli and induced membrane damage, while counterintuitively improving sperm motility. Together, these data validate the Cap-Score assay for the intended purpose of providing information on sperm capacitation and male fertility. In addition to its clinical utility as a diagnostic tool, this test of sperm function can reveal the impact of common practices of semen handling on the ability of sperm to respond to capacitation stimuli.

The polysulphate binding domain of human proacrosin/acrosin is involved in both the enzyme activation and spermatozoa-zona pellucida interaction

Mammalian acrosin is a protease present as a zymogen in the acrosome of a non-reacted mammalian sperm, and in vitro is able to carry out limited hydrolysis of homologous and heterologous zonae pellucidae. On the other hand, sulphated polymers and zona pellucida glycoproteins bind to acrosin on a domain different from the active site, named the polysulphate binding domain (PSBD). Thus it is believed that acrosome-reacted spermatozoa bind to glycan chains of the zona pellucida through PSBD participating as secondary binding receptor. The aim of the present work was to study the role of PSBD during both human gamete interaction and acrosin activation. In this work we present evidence that the anti-human acrosin monoclonal antibody C5F10 is directed to an epitope located on or near the PSBD on human proacrosin/acrosin. Moreover, we show that this antibody is able to inhibit both proacrosin activation induced by fucoidan and the sperm binding to the zona pellucida. Our results suggest that the same PSBD is involved in both sperm secondary binding, during zona pellucida penetration, and proacrosin activation.

Influence of incubation time/temperature on acrosome reaction/sperm penetration assay

The acrosomal status of human spermatozoa was studied in relation to the score of the sperm penetration assay (SPA) at low-temperature (4 degrees C) incubation for induction and synchronization of the acrosome reaction (AR) and the incubation time of spermatozoa in conventional SPA. Spermatozoa were collected from 18 patients, selected by the "swim-up" method and treated in three different ways: (1) short-term incubation group (SIG): 3 h incubation at 37 degrees C, and (2) long-term incubation group (LIG): 20 h incubation at 37 degrees C, and (3) low temperature group (LTG): 24 h incubation at 4 degrees C followed by additional incubation at 37 degrees C for 3 h. The conventional methods of incubation, i.e. SIG (3 h) and LIG (20 h) did not show any significant differences as evaluated by the sperm penetration rate and the number of decondensing sperm heads per oocyte. In contrast, in the LTG all parameters were significantly increased, especially those of penetration rate (p less than 0.0005) and decondensing sperm heads per oocyte (p less than 0.0005). The percentage of AR significantly increased (p less than 0.0005) in the LTG (14.7%) compared with SIG (6.1%) and LIG (10.6%). A significant correlation was demonstrated between AR and the parameters used for evaluation of the SPA. The penetration rate (Spearman test, r = 0.462, n = 54, p less than 0.003) was the most significant parameter correlated with AR. It would appear that only human spermatozoa having completed AR are capable of fusing with the zona-free hamster ova.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of microinjection and two types of electrical stimuli on bovine sperm-hamster egg penetration

These experiments were designed to test the effects of an electrofusion and an electroporation pulse on bovine sperm-hamster egg development. In experiment 1, single motile sperm were injected into the perivitelline space of each egg. A 4,500 V/cm, 30 microseconds fusion pulse (FP) was applied while sperm-egg membrane contact was maintained. It was observed that single motile sperm were rendered immotile immediately after FP application whereas nonpulsed single motile sperm remained motile for up to 36 h postinjection. In addition, both motile and sonicated spermatozoa were injected directly into the ooplasm prior to receiving an FP to determine whether the FP was detrimental to sperm viability. In experiment 2, to induce the acrosome reaction, an 1,150 V/cm electroporation pulse was applied to washed bovine sperm suspended in TALP medium containing 5 mM Ca2+. Treated and nontreated sperm were coincubated with zona-free hamster ova, and sperm-pentrating ability was measured. Results from experiment 1 indicate that FP failed to induce sperm-egg fusion (0/69). FP did not, however, inhibit decondensation or pronuclear formation of sperm injected into hamster egg ooplasm. Single motile sperm injected into the ooplasm resulted in development of both pulsed (19/28) and nonpulsed (21/28) groups. Sonicated tail-free sperm heads injected into the ooplasm resulted in no detectable difference between treated (18/30) and nontreated (19/30) groups. In experiment 2, treatment of sperm with electroporation pulse +5 mM Ca2+ increased zona-free hamster ova penetration scores over nontreated sperm within bulls (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation of the hypo-osmotic swelling test, semen score and the zona-free hamster egg penetration assay in humans

The correlation between the hypo-osmotic swelling test, the modified Eliasson score for human semen analysis and the hamster egg penetration assay was examined. The results showed a weak but significant correlation between the group of subjects with swelling rates below 50% and the above 80% group. These groups showed hamster egg penetration assay rates of 9 +/- 14% and 39 +/- 29%, respectively (P less than 0.035). A significant correlation was also found between modified Eliasson scores (17 +/- 10 and 5 +/- 7, respectively) and swelling rates below 50% and above 70% (P less than 0.001). These results suggest that spermatozoa showing a low swelling rate have a poor fertilizing capacity. Therefore, the swelling tests and analysis of the patients semen can be used to discriminate sperm quality.

The significance of the zona-free hamster oocyte test for the evaluation of male fertility

Results of the zona-free hamster oocyte test were compared with pregnancy rates after coitus and after artificial insemination with donor semen (AID) in 322 primary infertile couples. Artificial donor insemination was offered if in the test the percentage of hamster oocytes with at least one decondensed sperm head (oocyte-sperm interaction rate) was less than 20. If the rate was less than 5, the pregnancy rate after coitus was significantly lower than in the group with a rate of greater than or equal to 5 to less than 20. In the former group, the pregnancy rate by AID was significantly higher than the pregnancy rate by coitus. We conclude that the zona-free hamster oocyte test is useful to predict the chance to achieve pregnancy in couples with unexplained infertility and to determine whether AID can increase this chance.

The measurement of hyaluronidase activity in human spermatozoa by substrate slide assay and its clinical application

Acrosomal hyaluronidase activity of individual sperm can be detected by a halo formation around the sperm head on hyaluronic acid substrate slides. The following results were obtained by this method in clinical practice. A significant correlation was found between hyaluronidase activity and sperm concentration in male infertility. Hyaluronidase activity increased as the concentration of sperm increased, and the least hyaluronidase activity was determined at less than 10 X 10(6)/ml. The group with more than 40% motility had a higher hyaluronidase activity than other groups with poor motility. Although there was no significant correlation between hyaluronidase and cumulus dispersion and fertilization rates in immature oocytes, there was an excellent correlation in mature oocytes in human in vitro fertilization. These findings suggest that a newly developed assay will be useful for evaluating sperm fertilizing capacity.

Individual variation for in vitro fertilization success in dairy bulls

Individual semen samples from 29 bulls in routine artificial breeding service were tested for their capability to achieve in vitro fertilization. Ejaculated semen was diluted, .1 ml of semen in 2 ml of a modified Tyrode's medium with an osmolality of 340 mOsmol/kg, washed thrice, incubated 3 h at 37 degrees C before being used for in vitro fertilization, or incubated 4 h and 8 h before assessment of motility, capacitation, and acrosome integrity. The degree of variability in percentage of oocytes fertilized was assessed along with several factors that might contribute to this variation. Variation among bulls was not significantly different. Variation from one replicate to another was high. Variation was found in motility, capacitation, and frequency of acrosome reaction, but these variables were not significantly correlated to fertilization rate in vitro.

In vitro fertilization of hamster and human oocytes by microinjection of human sperm

In this study, swollen sperm heads were obtained after the injection of human sperm into the perivitelline space of hamster oocytes. The number of injected sperm and the sperm concentration in the preincubation medium were found to have an influence on the rate of penetrated hamster oocytes. The optimal injected sperm number was always between five to 12 to obtain 8, 37, and 36% penetration for donors A, B, and C, respectively. The optimal sperm concentration in preincubation medium was between 6 and 22 x 10(6) sperm/ml to obtain 16, 47, and 43% penetration for donors A, B, and C, respectively. The rate of polyspermic oocytes was related to the injected sperm number (0, 55, and 100% for one to four, five to 12, and more than 12 injected sperm respectively). Ten human mature oocytes were injected with the sperm from six normal donors. Five fertilized eggs were obtained, and of these four cleaved in in vitro culture.

Cryopreservation of hamster oocytes: effects of vitrification or freezing on human sperm penetration of zona-free hamster oocytes

Three experiments were conducted for evaluation of the efficacy of conventional freezing or vitrification of hamster oocytes for use in a human sperm penetration assay (hSPA). In experiment 1, oocytes were cryopreserved and evaluated for survival on the basis of morphologic criteria. Survival of vitrified oocytes and that of frozen oocytes were not different, whereas all cryopreserved groups had lower survival than noncryopreserved controls. In experiment 2, oocytes were conventionally frozen or vitrified and evaluated in an hSPA. Vitrified oocytes had a lower frequency of sperm penetration than frozen oocytes, and all cryopreserved groups had lower penetration rates than untreated controls. In experiment 3, oocytes were exposed to the cryoprotectant used to vitrify (VS1) or freeze (DMSO) but not cooled prior to evaluation in an hSPA. Exposure to DMSO but not VS1 reduced hSPA values. It is concluded from these experiments that while all cryopreserved oocytes do not survive, at current stages of development conventionally frozen oocytes perform better than vitrified oocytes in the hSPA and losses associated with conventional freezing procedures may be related to cryoprotectant exposure, whereas vitrification losses are more probably due to events associated with rapid cooling and/or warming of the oocytes.

The split ejaculate: assessment of fertility potential using two in vitro test systems

Semen samples (split & whole ejaculates) were obtained from 12 normal men (group A) and 8 oligospermic infertile men with sperm concentrations of less than 20 x 10(6) sperm/ml (group B). All samples were evaluated by standard semen analysis, bovine cervical mucus penetration assay (CMPT), and, in all cases with sufficient sperm, in the human spermatozoa zona-free hamster in vitro penetration assay (SPA). In group A the motile sperm concentration was significantly higher in the ejaculated material of the first two contractions (fraction I or FI) than in the remainder of the ejaculate (fraction II or FII) (p less than 0.02). No significant differences were observed in sperm penetration into zona-free hamster ova or bovine cervical mucus by sperm from FI, FII or the whole ejaculate. Motile sperm concentration was significantly correlated with sperm penetration into bovine cervical mucus (r = 0.65, p less than 0.01), but not into zona-free hamster ova (r = 0.01 NS). In the samples collected by group B, the mean sperm concentration and motile sperm concentration were higher in the first (FI) than in the second (FII) fractions of the split ejaculate or the whole ejaculate (p less than 0.05). No significant differences were found among the FI, FII and the whole ejaculate semen samples for penetration of sperm into bovine cervical mucus. Sperm concentration and motile sperm concentration were significantly correlated with sperm penetration into bovine cervical mucus (r = 0.58, p less than 0.01 and r = 0.57, p less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of the concentration of motile sperm inseminated on the ovum penetration assay results: toward a standardized method

The influence of the concentration of motile sperm inseminated on the zona-free hamster egg penetration rate has been studied. In 3 fertile men, the higher the concentration of motile sperm inseminated, the higher the ovum penetration rate. This correlation emphasizes the usefulness of standardizing the technical conditions under which the ovum penetration assay is performed. It is also suggested to refer to a standard curve for results analysis. In the 22 patients studied, the outcome of the heterologous ovum assay was in most cases related to the initial sperm parameters. However, some disagreement was also observed. In the absence of a correlation between the initial sperm parameters and the ovum penetration rates, further investigation is needed in order to either more precisely determine the aetiology of unexplained couple infertility, or, in case of intrauterine insemination or in vitro fertilization, to better understand the conditions under which spermatozoa are capacitated in vitro.

Semen parameters and capacitation

A relationship exists between several semen parameters and the ability of spermatozoa to capacitate. The increase of oligoteratozoospermia, which could be related to testicular dysfunction, is correlated with the decrease of the percentage of spermatozoa able to "capacitate". The increase of loss of motility with time, which could be related to abnormalities of the seminal fluid, is also correlated with a decreased number of spermatozoa able to "capacitate".

Prognostic value of the heterologous ovum penetration test for human in vitro fertilization

In order to evaluate the prognostic value of the heterologous ovum penetration test (HOP-test) the results of this test were compared with the fertilization rate of human ova in a programme for in vitro fertilization and embryo transfer (IVF/ET). Sperm from 29 husbands (23 normozoospermic and 6 with an abnormal semen profile) were exposed on one occasion to approximately 30 hamster ova in the HOP-test and on 1 to 3 occasions to 1 to 4 preovulatory oocytes obtained from the respective wives. The mean penetration rate (+/- SEM) of the hamster ova was 43 +/- 4% (range: 0-62%) for the normozoospermic men, and 23 +/- 6% (range: 0-47%) for the men with abnormal semen profiles. In 20 out of 23 couples in which the husbands were normozoospermic, sperm penetrated the hamster ova as well as they fertilized human ova; however, in one couple, a false-positive result was obtained (penetration of the hamster ova and no fertilization of the human oocytes) and in one couple a false-negative result occurred. One negative IVF result was correctly predicted by the HOP-test. In the 6 patients with disturbed sperm motility no correct positive or negative results were obtained, whilst 4 false-positive and 2 false-negative results occurred using the HOP-test. Although the number of patients with disturbed sperm motility was small, the data suggest that the HOP-test is of limited value in predicting fertility in an IVF program for couples with reduced fertility.

Histoincompatibility in couples with unexplained infertility

Class I human leukocyte antigens (HLA-A, -B) and class II (HLA-DR) antigens were determined in 18 carefully selected couples suffering from unexplained infertility and subsequently compared with 30 normal fertile couples with no history of secondary sterility and with a control group consisting of randomly matched women and men from our laboratory cell panel. No significant differences in the frequencies of HLA antigens were detected between infertile and control groups. The frequency of shared HLA-A, -B, and -DR antigens among members of the couples was similar in all the groups. Finally, the one-way mixed lymphocyte culture showed normal reactivity of both infertile parental pairs in all combinations tested.

The effect of Mycoplasma hominis and Ureaplasma urealyticum on hamster egg in vitro penetration by human spermatozoa

The effects of some genital mycoplasmas on the in vitro penetration of human spermatozoa into the master egg were studied. Ureaplasma urealyticum serotypes 4, 8, and 6 showed high interfering activity: 6.3% (P less than 0.01), 12.3%, and 14.5%, respectively, against the 55.6% penetration rate of untreated sperm. Neither a cytotoxic effect of mycoplasmas on gametes nor a masking of the binding sites on the egg surface were demonstrated. In experiments carried out with U. urealyticum serotype 4, the production of diffusible relatively heat-labile factor(s) responsible for the inhibition of sperm penetration was postulated.

Zona-free hamster egg-sperm penetration assay: I. Testing of human semen fertilizability

The zona-free hamster egg penetration test was performed on semen samples from 21 fertile donors, 57 infertile patients with normal semen parameters, and 63 infertile patients with subnormal spermiogram, as well as on 19 frozen semen samples. In the donor group 100% of the samples gave a positive range of penetration (PRP) of 20-96% with a mean penetration rate (MPR) of 53%, while 84% of the frozen samples showed a PRP of 18-44% and an MPR of 31%. Although 74% of the samples from infertile patients with normal spermiograms gave a PRP of 11-92% and an MPR of 34%, only 46% of the semen samples from the infertile patients with subnormal spermiogram showed a PRP of 21-100% but an MRP of 43%.

A regimen for obtaining mature human oocytes from donors for research into human fertilization in vitro

Patients awaiting laparoscopic sterilization were canvassed to allow oocytes to be aspirated from their ovaries at the time of operation for the purpose of testing the fertilizing capacity of spermatozoa from clinically infertile men. Because these patients were volunteers, the standard techniques for stimulation, ovulation prediction, operation, and oocyte recovery had to be modified for maximum safety and for convenience to both patient and staff. Superovulation was induced with 100 mg or 150 mg clomiphene citrate on days 2 to 6 or 5 to 9 of the menstrual cycle. Final maturation of oocytes was stimulated with 5000 IU of human chorionic gonadotropin administered between days 11 and 15 of the cycle, and the operation was performed 34 to 36 hours later on the routine gynecology operation lists. Of the 157 patients canvassed , 47% were willing to donate oocytes to the project. Despite the variability of the stimulation regimens, the simplified operative technique, and the fact that more than half the patients were on oral contraceptives in the previous cycle, one or more oocytes were retrieved in 75% of the patients. At the initial assessment, 83% of these were considered suitable for in vitro fertilization.

Molecular events leading to fertilization--a review

Fertilization consists of a sequence of complex events which culminates in the fusion of the genetic information provided by two parent cells, thus leading to the formation of a new individuum. The male gamete develops in the testis, acquires forward motility and fertilizing capacity during maturation in the epididymis, and after capacitation undergoes the acrosome reaction in the female reproductive tract. The female gamete matures in the cyclically developing follicles and, by the time of ovulation, reaches a quiescent stage at metaphase II of meiosis. Gamete fusion occurs in the distal tube, and involves a series of modifications on the egg surface and its investments, intended to protect the developing embryo from polyspermy.

Relationships of seminal plasma prolactin with spermatozoal characteristics and fertilizing capacity in vitro

Seminal plasma prolactin (PRL) levels were determined in 224 semen samples collected from fertile and suspected infertile men, and their relationships with spermatozoal characteristics and fertilizing capacity in vitro were evaluated. PRL concentrations were similar in normospermic and oligospermic samples, but were significantly lower in azoospermic samples. PRL concentrations were significantly higher in samples with high spermatozoal motility than in those with low spermatozoal motility. There were no significant differences in PRL concentrations between normal-morphology and abnormal-morphology samples, and between high-fertilizing capacity and low-fertilizing capacity samples. A low degree of positive correlation was observed between the PRL concentration and the spermatozoal motility. There were no significant correlations between the PRL levels, the other spermatozoal characteristics, and the spermatozoal fertilizing capacity in vitro. These findings indicate that the seminal plasma PRL levels are significantly depressed in azoospermic subjects and suggest that the seminal plasma PRL may play a role in the maintenance of spermatozoal motility. Whether there is a potential function of prolactin in semen on spermatozoal fertilizing capacity, however, cannot be inferred from the present study.

Effects of androgens on fertilizing capacity of human spermatozoa

The potential functions of testosterone and 5 alpha-dihydrotestosterone, the androgens normally present in human seminal plasma, on human spermatozoal physiology were evaluated by studying the effects of these two steroid hormones on the in vitro fertilizing capacity of human spermatozoa. Spermatozoa collected from presumably fertile men were washed in BWW medium and incubated with different concentrations (0, 100, 250, 500, 1000 pg/ml) of testosterone or 5 alpha-dihydrotestosterone for 5 hr before insemination of the zona-free hamster ova. Penetration of the zona-free hamster ova was scored 6 hr later and the results were analyzed statistically. Both testosterone and 5 alpha-dihydrotestosterone, at the concentrations tested, significantly decreased the in vitro penetration of the denuded hamster ova in comparison to the controls (p less than 0.05). A dose-dependent response was also observed for the 5 alpha-dihydrotestosterone tested. These findings indicate that exogenous testosterone and 5 alpha-dihydrotestosterone can inhibit the fertilizing capacity of human spermatozoa in vitro, and suggest that the androgens normally present in human seminal plasma may serve, in part, to prevent premature spermatozoal capacitation before the spermatozoa reach the site of fertilization in vivo.

Efforts to correlate laboratory with field observations on bull sperm fertility

This work represents efforts towards development of the zona-free hamster ovum sperm penetration assay for predicting relative levels of fertility for semen from individual bulls. Results reported here followed insemination of hamster vitelli with bull sperm, after frozen storage, with observations of sperm acrosomes and parallel inseminations of more than 1000 cows with semen from each bull. The average 75-day non-return rate for the four bulls was 74.0% (range 71.6 to 75.6). Laboratory studies indicated the following: the percentage of sperm with intact acrosomes varied from 55 to 73 between bulls, the percentage of motile sperm varied from 41 to 64, the percentage of sperm with progressive motility ranged from 24 to 40, the number of sperm interacting per (zona-free hamster) ovum ranged from 1.6 to 3.8, the number of sperm attached per ovum ranged from 1.4 to 2.9, the number of sperm within each penetrated ovum ranged from 1.5 to 1.8, the percentage of ova interacting with sperm ranged from 76 to 92, the percentage of ova penetrated ranged from 62 to 85, and the percentage of ova with male pronuclei ranged from 33 to 49. Although predictive ranking in the laboratory of these bulls with less than 4% variation in fertility levels was not possible, the zone-free hamster ovum test could be useful in identifying potentially subfertile bulls before they enter a young sire-sampling program.

A critical method of evaluating tests for male infertility

Considerable uncertainty surrounds the selection of test values that separate infertile from fertile men in the evaluation of male infertility. We herein describe an objective method of determining these values, referred to as threshold values, for different infertility tests. Using test results from fertile men threshold values were chosen such that 96 per cent of the semen samples from the fertile men were scored as fertile. These threshold values then were used to evaluate 100 semen samples from 74 men presenting for evaluation of infertility. Using this method we constructed infertility profiles on each of the 100 semen samples presented for infertility evaluation and found that the zona pellucida-free hamster egg penetration test (a measure of a spermatozoon's ability to undergo capacitation and penetrate an egg) identified 66 per cent of these samples as infertile, while multiple exposure photomicrography (a quantitative measure of sperm motility) identified 54 per cent of these samples as infertile. This compares with results from routine semen analyses using the same method, which identified none of the samples as infertile by sperm motility grade, 1 per cent by semen pH, 4 per cent by the percentage of motile sperm, 7 per cent by the total count of motile sperm, 10 per cent by the total sperm count, 11 per cent by the semen leukocyte concentration, 12 per cent by the concentration of motile sperm, 13 per cent by ejaculate volume, 16 per cent by sperm concentration and 27 per cent by sperm morphology. This method of analyzing infertility test results provides insight into the potential causes of male infertility and offers a critical approach towards understanding the complex problem of male fertility dysfunction.

Stimulation of the human spermatozoal fertilizing ability by dibutyryl 3',5'-CAMP and theophylline in vitro

The stimulation of the human spermatozoal fertilizing ability by dibutyryl 3',5'-CAMP (diCAMP) and theophylline in suspected fertile and subfertile semen samples was demonstrated with the zona-free hamster ova penetration test. The penetration rates for the untreated (control) fertile and subfertile samples were 30% and 17%, respectively. DiCAMP increased the penetration rates to 54% and 37% (with 5 mM diCAMP) and to 46% and 36% (with 10 mM diCAMP) in the fertile and subfertile samples, respectively; theophylline increased the penetration rates to 56% and 35% (with 10 mM theophylline) and to 49% and 42% (with 20 mM theophylline) in the fertile and subfertile samples, respectively. These results indicate that diCAMP and theophylline can affect the fertilizing ability of human spermatozoa in vitro.

Human sperm penetration of zona-free hamster eggs after storage of the semen for 48 hours at 2 degrees C to 5 degrees C

The motility of human spermatozoa and their ability to penetrate zona-free hamster eggs were examined after dilution of the semen with TES-Tris (TEST) yolk buffer and storage for 48 hours at 2 degrees C to 5 degrees C. Semen samples from 10 fertile donors and 19 infertility patients were studied. More than 65% of the spermatozoa which were initially motile in the TEST yolk buffer remained active after storage. During storage, the mean swimming speed of the sperm declined to approximately 60% of the prestorage value. The percentage of zona-free hamster eggs that were penetrated by spermatozoa from patients and donors increased significantly following 48 hours of storage at 2 degrees C to 5 degrees C. Normal semen and abnormal semen were equally preserved by this storage method. This procedure may be used to ship semen samples by commercial transportation to specialized laboratories for testing. Low temperature storage in the TEST yolk buffer appears to enhance the fertilizing capacity of human spermatozoa in vitro.

The influence of medium composition, osmolarity and albumin content on the acrosome reaction and fertilizing capacity of human spermatozoa: development of an improved zona-free hamster egg penetration test

The influence of medium composition, osmolarity and albumin concentration on the ability of human spermatozoa to undergo the acrosome reaction and penetrate zona-free hamster ova has been investigated. Raising the osmolarity but not the albumin concentration of the media was found to significantly increase the proportion of spermatozoa exhibiting an acrosome reaction and penetrating hamster ova, without influencing motility. There was, however, no correlation between the size of the acrosome reacted population and penetration rates between samples, suggesting that the zona-free hamster egg penetration test is more than just a measure of the availability of acrosome reacted cells. As a result of this study, a revised protocol for the hamster egg assay is described which is shorter and considerably more sensitive than conventional procedures.

Sperm morphology assessment as an indicator of human fertilizing capacity

Semen samples from 95 men were examined by routine semen analysis and specific histologic staining for sperm morphology. The men were classified into fertile and infertile groups on the basis of clinical evaluation and in vitro testing, using the zona-free hamster egg penetration assay. Thirty men were designated as fertile, as they had fathered children and their sperm showed penetration of greater than 20% of the zona-free hamster eggs with the in vitro fertilization test. Subjects classified as infertile were men from infertile couples whose wives showed no evidence of infertility and whose in vitro fertilization ability was 10% or less. The semen analysis parameters of the fertile and infertile groups were significantly different. Fertile men had mean values of 108 X 10(6) sperm/ml, 61% motile, 64% normal forms (sperm with oval morphology), and 69% penetration in vitro. The mean values for infertile men were significantly lower: 42 X 10(6) sperm/ml, 45% motile, 32% normal forms, and 3.2% penetration in vitro. The importance of the morphology parameter was revealed by comparison of the percentage of penetration with count, motility, and morphology. Penetration correlated best with morphology (r = 0.730) as compared with motility (r = 0.451) and count (r = 0.605). The distribution of abnormalities in the infertile group revealed 81.6% with abnormal morphology (less than 50%), 53.8% with abnormal motility (less than 50%), and 38.5% with abnormal count (less than 20 million/ml). As a single parameter, decreased number of normal forms appears to be a good indicator for clinical infertility if in vitro fertilization testing is not available.

Factors affecting human sperm penetration of zona-free hamster ova

The effects of in vivo and in vitro aging of hamster ova, protein supplementation of culture media, sperm concentration, and sperm motility on penetration of zona-free hamster ova by human sperm were investigated. Penetrability of ova was significantly lowered by 2 to 4 additional hours of in vivo aging or by an additional 3 hours of in vitro aging. A comparison was made of the effects of the addition to the media of human preovulatory serum and human serum albumin, and the penetrating ability of human sperm was increased with the addition of 10% human preovulatory serum. Sperm motility was also better maintained in the presence of 10% serum. Maximum penetration occurred after 3 hours of sperm-egg interaction following a 3-hour preincubation period with a sperm concentration of 5 x 10(6) motile sperm per milliliter. When motile sperm concentration was maintained at 1 X 10(7) motile sperm per milliliter, there was no correlation between penetrating ability and percentage of motility. These factors should be controlled to allow reproducible results with the hamster test.

Unexplained infertility

To recapitulate, four questions must be raised when the couple has been evaluated and found to be normal: (1) Was the infertility evaluation complete in terms of modern standards? (2) Were the results of studies and observations appropriately interpreted? (3) Has a factor which was considered within normal limits and compatible with fertility at the onset of the workup changed during the course of the evaluation? (4) How accessible for evaluation are processes necessary for conception which occur within the reproductive tract? Both members of the couple as well as the managing physician are frustrated and plagued by feelings of inadequacy when no positive findings can be identified during the course of an infertility evaluation. This situation obviously requires of the physician a combination of delicacy, patience, and considerable attention to each detail of the evaluation which has just been completed. The material herein was designed to raise suggestions for approaches to such couples when faced with the designation of "unexplained infertility."

Stimulation of the zona-free hamster ova penetration efficiency by human spermatozoa after 17 beta-estradiol treatment

17 beta-Estradiol (E2) stimulated the zona-free hamster ova penetration by human spermatozoa from both fertile and subfertile men after 5 hours of incubation in vitro. For spermatozoa samples from fertile men, the mean penetration rates increased significantly (P less than 0.05), from 35.6% +/- 3.5% (control) to 60.1% +/- 5.8% (E2 = 50 ng/ ml) and 50.5% +/- 2.6% (E2 = 100 ng/ml), respectively. E2 also increased the mean penetration rates of spermatozoa samples from subfertile men significantly (P less than 0.05), from 10.2% +/- 1.8% (control) to 30.5% +/- 7.2% (E2 = 50 ng/ml) and 33.1% +/- 6.6% (E2 = 100 ng/ml), respectively. These findings indicate that E2 can affect the fertilizing ability of human spermatozoa in vitro.

Reliability and accuracy of the zona-free hamster ova assay in the assessment of male fertility

The efficacy of the zona-free hamster ova assay in assessing male fertility was studied in 22 men of proven fertility, 16 of unproven fertility, and 31 who were members of infertile couples. The mean hamster ova penetration rates were significantly higher in males of proven fertility (34%) and unproven fertility (30%) than in infertile males (11%). Sperm from 21 of 22 men of proven fertility penetrated greater than 15% of ova; one man had a zero penetration rate. Sperm from 8 of 16 men of unproven fertility and 24 of 31 men of infertile couples penetrated less than 15% of ova. There was no correlation between penetration rates and any of the traditional measures of semen analysis. Two assays were performed on every male and six assays were performed on six males. There was good interassay reliability in all 69 males (r = 0.86) and in the six males with six tests (r = 0.97). The mean interassay variation was 8.6%.