Biological mechanisms of male infertility.
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Humans↗
Biomedical subjects
W C Ford
Publications and source records attributed to W C Ford.
Value of the hamster oocyte test and computerised measurements of sperm motility in predicting if four or more viable embryos will be obtained in an IVF cycle.
The experimental group consisted of men from 81 couples waiting for in vitro fertilization (IVF), about half of whom had sperm dysfunction defined by a negative post-coital test. A diagnostic semen sample was subjected to a hamster oocyte penetration test (HOPT) after stimulation of the acrosome reaction with A23187 +/- pentoxifylline and to computerized sperm motility measurements (CASA) as well as conventional semen analysis according to the WHO protocol. Logistic regression was used to identify parameters that predicted the probability of achieving four or more viable embryos at IVF among the 65 couples from whom four or more oocytes were collected. The number of oocytes available and whether the woman had previously been pregnant (ever pregnant) were important factors but once these had been taken into account a number of sperm parameters had additional predictive power. The most useful of these were the percentage sperm static (CASA) or the percent sperm progressively motile (conventional semen analysis) in the Percoll preparation. A model incorporating the number of oocytes collected, ever pregnant and percentage sperm static achieved 85% correct prediction of outcome in the experimental dataset but only 62% correct prediction in an independent set of 280 IVF cycles. The percentage of hamster oocytes penetrated was a significant predictor but had no advantage over simple motility measurements. The results illustrate the difficulty of basing a prognosis for achieving satisfactory fertilization in IVF on the properties of spermatozoa.
Adult↗
The motility of demembranated human spermatozoa is inhibited by free calcium ion activities of 500 nmol/L or more.
A number of studies have demonstrated that high calcium ion activities inhibit sperm motility, but little is known about the effect of different calcium activities close to the physiological range. Therefore, we investigated whether raising calcium activities within the submicromolar range would inhibit the motility of demembranated human spermatozoa. Spermatozoa were demembranated with Triton X-100 and motility was measured objectively by computer assisted semen analysis. Motility, reactivated by 1 mol adenosine 5'-triphosphate (AlphaTauP)/L, was short lived, with maximum activity only sustained for about 1 min. Reactivated motility was not affected by 50 micromol cAMP/L. The amplitude of lateral head displacement was significantly greater at room temperature than at 37 degrees C, but there were no significant differences between the percentage of sperm motile or their velocity at the two temperatures. The calcium buffer 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) at 1 mmol/L was included in the demembranation-reactivation medium, and free calcium ion activities were calibrated using the fluorescent calcium probe Fura-2. Calcium ion activities of > or =500 nmol/L significantly inhibited the percentage of demembranated-reactivated spermatozoa that were motile, and the velocity and lateral head displacement of these cells. The range of intracellular calcium activities in spermatozoa from 24 cryopreserved ejaculates was 110-534 nmol/L; roughly twice the value in fresh spermatozoa. Therefore, calcium ion activities in the range observed in cryopreserved spermatozoa can inhibit the activity of demembranated human spermatozoa.
Adult↗
Reactive oxygen species and sperm.
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Humans↗
A critical investigation of NADPH oxidase activity in human spermatozoa.
It has been suggested that human spermatozoa contain an NADPH oxidase that could generate reactive oxygen species involved in signalling pathways to promote fertility. The proposal depends on observations that the addition of NADPH to purified human spermatozoa stimulates chemiluminescence by the superoxide (O2-) probe, lucigenin. We confirmed these observations, but demonstrated that lucigenin increases NADPH consumption by spermatozoa and stimulates artefactual O2- production via a diphenyleneiodonium (DPI) sensitive flavoprotein. In the absence of cytochrome c, DPI-inhibitable NADPH oxidation by permeabilized spermatozoa was 8 times too small to account for the rate of NADPH-stimulated cytochrome c reduction. Thus NADPH can directly reduce cytochrome c by a flavoprotein dependent mechanism making this O2- assay also unreliable in sperm suspensions. We were unable to observe O2- production by 40 x 10(6) spermatozoa/ml using electron paramagnetic resonance spectroscopy but could identify O(2)(-) generation from 2000 4beta-phorbol-12-myristate-13-actetate (PMA)-stimulated leukocytes. Using spectrophotometry, we did not detect the reduced cytochrome b(558) component of the neutrophil NADPH oxidase in human spermatozoa. No hydrogen peroxide generation was observed using a sensitive Amplex Red assay. We conclude that human spermatozoa do not possess significant NADPH oxidase activity and that the mechanism by which NADPH promotes capacitation must be re-evaluated.
Acridines↗
Delayed conception and active and passive smoking. The Avon Longitudinal Study of Pregnancy and Childhood Study Team.
OBJECTIVE: To determine whether passive as well as active smoking by women or smoking by men is associated with delayed conception, after adjustment for confounding factors. DESIGN: Population study of couples expecting a baby. Logistic regression was performed to identify factors associated with delayed conception. SETTING: The Avon Health Authority area, United Kingdom. PATIENT(S): All couples expected to deliver between April 1991 and December 1992. INTERVENTION(S): Questionnaires administered early in pregnancy. MAIN OUTCOME MEASURE(S): Time taken to conceive, categorized as <6 months, 6-11 months, 1-3 years, and >3 years. RESULT(S): After correction for confounding factors, delayed conception was statistically significantly associated with both active smoking by the woman (odds ratio [OR] 1.23 [95% CI 0.98-1.49] for > 6 months and 1.54 [95% CI 1.19-2.01] for >12 months) and her exposure to passive smoking (OR 1.17 [95% CI 1.02-1.37] and 1.14 [95% CI 0.92-1.42]) compared with women with no exposure to tobacco smoke (referent). Heavy smoking by men was independently associated with delayed conception. In active smokers, the effect increased with the number of cigarettes. CONCLUSION(S): Smoking by men and passive and active smoking by women are associated with delayed conception.
Adult↗
Sucralose: lack of effects on sperm glycolysis and reproduction in the rat.
Certain chlorine-substituted sugars with chemical similarities to sucralose have been demonstrated previously to diminish or inhibit sperm glycolysis and fertility in the rat ([Ford]). In order to investigate this potential for sucralose, epididymal spermatozoa were recovered from rats exposed in vivo to oral doses of one of three of these substituted sugars: 6-chloroglucose (6-CG, 24mg/kg/day, positive control), sucralose (500mg/kg/day, over 300 times the expected human daily intake), or a 6'-substituted isomer of sucralose, trichloro de-oxy sucrose (TCDS, 100mg/kg/day, a potential trace impurity in commercial sucralose); distilled water served as the negative control. After incubation of the spermatozoa with D-[U-(14)C] glucose, measurements of (14)CO(2) and of ATP content showed no impairment of the glycolytic ability of spermatozoa in any of the groups except for a marked inhibition for those exposed to 6-CG, the positive control. In order to determine whether other parameters of reproduction and fertility could be affected, reproductive endpoints were examined following oral exposure of male and female rats to sucralose. Sucralose was fed in the diet at concentrations of 0, 0.3, 1.0 and 3.0% (approx. 100, 365 and 1150 times the EDI) to groups of 30 male and 30 female rats for 10 weeks prior to mating, and continued through two subsequent generations until weaning of the F(2) pups. Two litters were produced per generation. Food consumption and weight gain in the F(0) and F(1) generations were depressed in all sucralose groups before mating and in all four litters prior to weaning. The decrease in initial average weight for newborn pups probably reflects the increased litter sizes noted for sucralose-treated groups and the reduced food consumption of the dams during gestation and lactation. The latter is a result primarily of the unpalatability of sucralose to rats ([McNeil,]). Caecal enlargement (a common animal response to large doses of indigestible material) occurred in both the F(0) and F(1) parents. Increased kidney weights, possibly associated with increased water intake, were observed primarily among animals receiving 3% sucralose (no renal histopathology has been detected). Decreased thymus weights occurred in F(1) males and in both F(1) and F(2) females at the 3% level. Subsequent studies specifically designed to investigate the potential for adverse immune system effects of sucralose ([McNeil,]) showed no adverse effects. These findings are consistent with investigations by others showing that decreases in thymus weights occur in young rats in response to stressful conditions associated with reductions in weight gain. All reproductive indices (oestrous cycles, mating behaviour, fertility, gestation, maternal and foetal viability, foetal development, parturition, pup maturation and lactation) were comparable between the control and sucralose-treated groups. We conclude from these results that sucralose has no effect on sperm glycolysis or on male or female reproductive performance in the rat.
Adenosine Triphosphate↗
Gender reassignment and assisted reproduction: An ethical analysis. Bristol Centre for Reproductive Medicine Ethics Advisory Committee.
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Adolescent↗
Increasing paternal age is associated with delayed conception in a large population of fertile couples: evidence for declining fecundity in older men. The ALSPAC Study Team (Avon Longitudinal Study of Pregnancy and Childhood).
The impact of male age on fecundity remains controversial. Here, a large population study was used to investigate the effect of paternal age on time to conception. All couples in the Avon Health district expecting a baby between 1 April 1991 and 31 December 1992 were eligible. Questionnaires completed by both the man and the woman at 18 weeks gestation covered specific fertility factors, e.g. parity, paternity, cohabitation and oral contraception; and non-specific factors, e.g. educational achievement, housing, cigarette smoking, alcohol consumption, obesity. Logistic regression was used to identify factors independently related to conception in < or =6 or < or =12 months. Of 8515 planned pregnancies, 74% were conceived in < or =6 months, 14% in the second 6 months and 12% after more than a year. Nine variables, including the age of the woman, were independently related to time to conception. After adjustment for these, the likelihood of conception within 6 or 12 months was lower in older men. Compared to men <25 years old, the adjusted odds ratios (95% confidence interval) for conception in < or =12 months were 0.62 (0.40, 0.98), 0.50 (0.31, 0.81) and 0.51 (0.31, 0.86) in men aged 30-34, 35-39 and > or =40 years respectively.
Adult↗
The prognostic power of the post-coital test for natural conception depends on duration of infertility.
Controversy about the value of the post-coital test (PCT) has prompted us to re-analyse data from 207 couples, originally studied between 1982 and 1983, with at least 12 months' infertility at presentation, complete diagnostic information and exclusion of female factors, to clarify the effect of duration of infertility on the prediction of conception. In couples with less than 3 years infertility and a positive PCT, 68% conceived within 2 years compared with 17% of those with a negative result. After 3 years, corresponding rates were 14% and 11%. The relative risks of conception [95% confidence interval (CI)] calculated using the Cox's proportional hazards model were 0.23 (0.12-0.43) for a negative PCT (reference positive PCT) and 0.25 (0.13-0.51) for more than 36 months infertility (reference 12-23 months). Semen analysis had no extra predictive power given the duration of infertility and the PCT. The PCT is an effective predictor of conception where defined female causes of infertility are absent and duration of infertility is less than 3 years. Once infertility is prolonged (beyond 3 years) the conception rate is low even with a positive test because a large proportion of couples remaining childless so long have true unexplained infertility. Use of the PCT will enable clinicians to allocate scarce, expensive and invasive resources effectively.
Adult↗
Relative contribution of leukocytes and of spermatozoa to reactive oxygen species production in human sperm suspensions.
The contribution of leukocytes and of spermatozoa to reactive oxygen species (ROS) production in prepared sperm suspensions from donors and subfertility patients was compared. In both groups, more leukocytes/10(6) spermatozoa were counted in samples which produced detectable ROS than in those that did not: Donors-645 vs. 170 (medians, n = 7; p < 0.01, Kruskal-Wallis), Subfertile group-1785 (n = 18) vs. 11 (n = 8) (p < 0.005, Kruskal-Wallis), respectively. Leukocyte concentrations were correlated with basal (r = 0.826, p < 0.001) and with ROS production stimulated with 50 mumol N-formyl, met, leu, phe l-1 (N-FMLP) (r = 0.835, p < 0.001) and 100 nmol phorbol 12-myristate 13-acetate l-1 (PMA) (r = 0.835, p < 0.001) measured using a chemiluminescence assay. Leukocytes were removed from the sperm suspensions of 6 donors and from 96 ejaculates from 21 subfertility patients and ROS production was determined. Subsequently, in all 6 donors, N-FMLP did not stimulate ROS production indicating that leukocyte removal was complete, though in one case PMA stimulated low levels of ROS production. In 65 ejaculates from subfertile men the N-FMLP response was completely eliminated but in 7 of these samples PMA continued to stimulate ROS production. We conclude that infiltrating leukocytes are the predominant source of ROS production in unpurified sperm preparations. Some purified sperm suspensions could be stimulated to produce ROS by the addition of PMA indicating that spermatozoa themselves may produce ROS, albeit in much smaller amounts.
Humans↗
Reactive oxygen species (ROS) production and the outcome of diagnostic tests of sperm function.
Washed sperm suspensions from 64 out of 89 (72%) randomly selected infertility patients produced detectable reactive oxygen species (ROS) compared to 17 out of 67 (25%) prospective semen donors (p < 0.01, Chi-square test). Among patients, the median sperm concentration in ejaculates which yielded sperm suspensions that generated detectable levels of ROS was lower than in those which did not: 36.2 (15.63-57.64) vs. 71.5 (22-108) x 10(6)/mL, respectively (median (interquartile range), p < 0.05, Kruskal-Wallis test). In samples that produced ROS, the basal rate of production and the rates after stimulation with 50 mumol N-formyl met leu phe (N-FMLP) l-1 or with 100 nmol phorbol 12-myristate 13-acetate (PMA) l-1 were significantly and inversely correlated with sperm concentration in the ejaculate (r = -0.43, -0.41 and -0.35, respectively, p < 0.01 Spearman's rank correlation). The rate of ROS production showed no relationship to the motility of spermatozoa in semen, whether evaluated visually or via computer assisted semen analysis. However, there was a significant negative correlation (r = -0.370) between the motile, normal sperm concentration (MNSC) and basal ROS production, and when stimulated with N-FMLP (r = -0.311) or with PMA (r = -0.249) (all p < 0.05). In patient samples that generated detectable ROS, the ability of the spermatozoa to retain motility for 24 h after preparation on a 40/80% Percoll gradient was negatively correlated with basal ROS production (r = -0.310, p < 0.05). ROS production was also related to the outcome of in vitro sperm mucus penetration tests. Unstimulated levels of ROS production showed a significant (p < 0.05), negative correlation with the number of progressively motile spermatozoa present in mucus after 15 (r = -0.379) and 60 (r = -0.362) min. These results suggest that sperm samples with increased ROS tend to have poor semen quality and reduced performance in a number of routine, diagnostic sperm function tests.
Adult↗
The contribution of subtle oocyte or sperm dysfunction affecting fertilization in endometriosis-associated or unexplained infertility: a controlled comparison with tubal infertility and use of donor spermatozoa.
This study aims to determine the relative contribution of oocyte and/or sperm dysfunction to the reduction of fertilization rates in vitro in cases of minor endometriosis and prolonged unexplained infertility. The results of in-vitro fertilization (IVF) treatment with ovarian stimulation have been compared between couples with the above conditions and women with tubal infertility (as control for oocyte function) and the use of donor spermatozoa (as control for sperm function). Fertilization and cleavage rates using husband's spermatozoa were significantly reduced in endometriosis couples (56%, n = 194, P < 0.001) and further significantly reduced in couples with unexplained infertility (52%, n = 327, P < 0.001) compared with tubal infertility (60%, n = 509). Using donor spermatozoa the rates were the same as using husband's spermatozoa in tubal infertility (61%, n = 27) or endometriosis (55%, n = 21) but significantly though only partly improved with unexplained infertility (57%, n = 60, P < 0.02). In unexplained infertility, a significantly increased proportion of couples experienced complete failure of fertilization and cleavage in a cycle (5-6% versus 2-3%). However, complete failure was not usually repetitive, and the affected couples did not account for the overall reduction in fertilization and cleavage rates, which remained significantly lower in the rest of the unexplained and endometriosis groups. Implantation and pregnancy rates appeared similar in all groups. The benefit of IVF treatment in cases of minor endometriosis and prolonged unexplained infertility is due to superabundance of oocytes obtained by stimulation. The reduction in natural fertility associated with endometriosis appears to be at least partly due to a reduced fertilizing ability of the oocyte. In unexplained infertility, there is distinct impairment due to otherwise unsuspected sperm dysfunction but probably also oocyte dysfunction.
Adult↗
The effect of incubation periods under 95% oxygen on the stimulated acrosome reaction and motility of human spermatozoa.
Human sperm samples were prepared on a 30% Percoll gradient and reactive oxygen species (ROS) production was measured. In samples that generated ROS incubation under 95%O2:5%CO2 for 30 min decreased the proportion of spermatozoa capable of the stimulated acrosome reaction by 40% in comparison to samples incubated under 95%N2:5%CO2 (P< 0.001, repeated measures analysis of variance), but the degree of inhibition did not increase after more prolonged incubation periods (up to 6 h). The addition of the antioxidants catalase and superoxide dismutase prevented the inhibitory effect of 95%O2:5%CO2. Leukocyte removal from samples prior to 95%O2:5%CO2 incubation preserved the ability of the spermatozoa to acrosome react. Sperm motility parameters were less affected by 95%O2:5%CO2 but track velocity was 64.1 microm/s+/-1.96 after 2 h incubation under 95%N2:5%CO2 compared with 54.7 microm/s+/-1.41 after 2 h incubation under 95%O2:5%CO2 (P < 0.05, repeated measures analysis of variance). Sperm samples that did not generate detectable ROS were not affected by 95%O2:5%CO2. The toxic effects of incubation under 95%O2:5%CO2 on human spermatozoa result from increased endogenous ROS production, mostly from leukocytes. High ROS levels inhibit sperm function, with the stimulated acrosome reaction being more susceptible than motility parameters.
Acrosome Reaction↗
Antioxidant treatment for male subfertility: a promise that remains unfulfilled.
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Animals↗
Intrauterine insemination: is it an effective treatment for male factor infertility?
Results were collected from 11 studies comparing intrauterine insemination (IUI) with intracervical insemination (ICI) of frozen donor semen, 10 studies comparing IUI with timed natural intercourse (NI) or ICI in couples with semen defects and seven studies comparing ICI with NI or ICI in couples with unexplained infertility. IUI significantly increased the pregnancy rate relative to favourably timed ICI in donor insemination (DI) with frozen semen both with and without gonadotrophin stimulation of the female partner (odds ratios (95% confidence interval) 1.92 (1.02-3.61) and 2.63 (1.52-4.54) respectively). The benefit of IUI tended to be less when the pregnancy rate for ICI was high and IUI had no benefit with fresh donor semen. Overall IUI was of significant benefit in the male factor couples compared with NI-ICI (odds ratio 2.20 (1.43-3.39) and the advantage appeared to be maintained when comparison was confined to properly timed ICI although the odds ratios were not significantly greater than 1. IUI had no benefit relative to favourably timed NI-ICI for couples with unexplained infertility; an apparent advantage overall was produced by studies where NI was late. None of the studies on male factor used a sperm function test to define male subfertility and three only included couples with good mucus penetration by sperm. The range of semen defects defined was such that many couples would have had a good chance of conceiving naturally given a normal female partner but nevertheless the overall pregnancy rate (4.8%) was considerably less than in the unexplained group (11.6%), suggesting that some sperm dysfunction was present. We conclude that the available evidence suggests that IUI is valuable for DI with cryopreserved semen and for couples with mild to moderately impaired semen quality and postulate that it overcomes failure to fertilize due to impaired mucus penetration and poor survival in the female reproductive tract.
Cryopreservation↗
Evidence that peptides derived from the disintegrin domain of primate fertilin and containing the ECD motif block the binding of human spermatozoa to the zona-free hamster oocyte.
The binding of human spermatozoa to, and penetration of, zona-free hamster oocytes were significantly inhibited in the presence of (i) a 28-residue peptide corresponding to part of the disintegrin-like domain of monkey fertilin beta, or (ii) a hexapeptide containing the ECD motif found in the disintegrin-like domain of monkey and human fertilin beta, or (iii) a hexapeptide containing an RGD motif, implicated in integrin recognition. Polyclonal antibodies raised against the 28-residue peptide were used in conjunction with immunobeads to demonstrate that this peptide bound to the oolemma of zona-free hamster oocytes. These data support the view that the ECD motif is involved in the recognition of the oolemma receptor by human fertilin.
ADAM Proteins↗
Cloning and sequence analysis of rat fertilin alpha and beta--developmental expression, processing and immunolocalization.
Fertilin alpha and beta are members of the MDC (metalloproteinase-like, disintegrin-like, cysteine-rich) protein family and are expressed on the sperm surface where they have been proposed to play a role in mammalian fertilization. Inhibition of sperm-oocyte binding and sperm-oocyte fusion make fertilin an attractive target for the development of an immunocontraceptive vaccine. Full-length cDNAs encoding alpha and beta fertilin subunits were isolated from a rat testis cDNA library and sequenced. Using reverse transcription-polymerase chain reaction (RT-PCR), the developmental expression of fertilin alpha and beta was determined in pre-pubertal and mature rat testes. Fertilin alpha mRNA was present at all stages of development, suggesting that it is not exclusively expressed in post-meiotic germ cells. In contrast, fertilin beta mRNA was first identified in day 19 testes, coincident with the presence of pachytene spermatocytes. Polyclonal antisera raised against a 28-residue peptide (corresponding to part of the disintegrin domain) and two recombinant fusion proteins identified a 90 kDa protein in testicular sperm extracts and a 60 kDa protein in caput and cauda epididymidal sperm extracts, the predicted sizes for rat fertilin beta precursor and mature protein respectively. Indirect immunofluorescence using the anti-peptide antisera stained the acrosomal cap of permeabilized testicular, caput and caudal spermatozoa and elongating spermatids in testicular sections.
ADAM Proteins↗