The correlates of fertilizing capacity in normal fertile men

Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries

BACKGROUND

Numerous studies have reported declines in semen quality and other markers of male reproductive health. Our previous meta-analysis reported a significant decrease in sperm concentration (SC) and total sperm count (TSC) among men from North America-Europe-Australia (NEA) based on studies published during 1981-2013. At that time, there were too few studies with data from South/Central America-Asia-Africa (SAA) to reliably estimate trends among men from these continents.

OBJECTIVE AND RATIONALE

The aim of this study was to examine trends in sperm count among men from all continents. The broader implications of a global decline in sperm count, the knowledge gaps left unfilled by our prior analysis and the controversies surrounding this issue warranted an up-to-date meta-analysis.

SEARCH METHODS

We searched PubMed/MEDLINE and EMBASE to identify studies of human SC and TSC published during 2014-2019. After review of 2936 abstracts and 868 full articles, 44 estimates of SC and TSC from 38 studies met the protocol criteria. Data were extracted on semen parameters (SC, TSC, semen volume), collection year and covariates. Combining these new data with data from our previous meta-analysis, the current meta-analysis includes results from 223 studies, yielding 288 estimates based on semen samples collected 1973-2018. Slopes of SC and TSC were estimated as functions of sample collection year using simple linear regression as well as weighted meta-regression. The latter models were adjusted for predetermined covariates and examined for modification by fertility status (unselected by fertility versus fertile), and by two groups of continents: NEA and SAA. These analyses were repeated for data collected post-2000. Multiple sensitivity analyses were conducted to examine assumptions, including linearity.

OUTCOMES

Overall, SC declined appreciably between 1973 and 2018 (slope in the simple linear model: -0.87 million/ml/year, 95% CI: -0.89 to -0.86; P < 0.001). In an adjusted meta-regression model, which included two interaction terms [time × fertility group (P = 0.012) and time × continents (P = 0.058)], declines were seen among unselected men from NEA (-1.27; -1.78 to -0.77; P < 0.001) and unselected men from SAA (-0.65; -1.29 to -0.01; P = 0.045) and fertile men from NEA (-0.50; -1.00 to -0.01; P = 0.046). Among unselected men from all continents, the mean SC declined by 51.6% between 1973 and 2018 (-1.17: -1.66 to -0.68; P < 0.001). The slope for SC among unselected men was steeper in a model restricted to post-2000 data (-1.73: -3.23 to -0.24; P = 0.024) and the percent decline per year doubled, increasing from 1.16% post-1972 to 2.64% post-2000. Results were similar for TSC, with a 62.3% overall decline among unselected men (-4.70 million/year; -6.56 to -2.83; P < 0.001) in the adjusted meta-regression model. All results changed only minimally in multiple sensitivity analyses.

WIDER IMPLICATIONS

This analysis is the first to report a decline in sperm count among unselected men from South/Central America-Asia-Africa, in contrast to our previous meta-analysis that was underpowered to examine those continents. Furthermore, data suggest that this world-wide decline is continuing in the 21st century at an accelerated pace. Research on the causes of this continuing decline and actions to prevent further disruption of male reproductive health are urgently needed.

A Review of the Complex Relationship between Irritable Bowel Syndrome and Infertility

Irritable bowel syndrome (IBS) is a gastrointestinal disease that negatively affects up to 20% of the population. Infertility is defined as a disorder of the reproductive system described by lack of success in achieving pregnancy after more than a year of regular unprotected sexual intercourse. The main purpose of our review was to analyze the available literature regarding the IBS-infertility connection. Another secondary purpose of the present paper was to find out if oxidative stress may be the missing puzzle that may explain this possible correlation. After analyzing the available literature we concluded that oxidative stress is a plausible mediator of the connection between both female and male fertility and IBS. However, the data lacks in direct evidence to confirm this hypothesis. Nevertheless, it is recommended that certain levels of oxidative stress should not be exceeded in order to decrease IBS symptoms and increase the odds of conception given that generation of reactive oxygen species (ROS) is an aftermath of metabolically active cells. Therefore, reducing the oxidative stress by living a healthier lifestyle with a balanced diet, rich in micronutrients, limited in caffeine and alcohol, avoiding smoking and maintaining a normal body mass index with regular physical exercise may promote fertility and help diminishing IBS symptomatology. Studies with measurements of biological samples are needed in order to assess the complex relationship between oxidative stress, IBS and infertility.

Temporal trends in sperm count: a systematic review and meta-regression analysis

BACKGROUND

Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis is critical given the predictive value of sperm count for fertility, morbidity and mortality.

OBJECTIVE AND RATIONALE

To provide a systematic review and meta-regression analysis of recent trends in sperm counts as measured by sperm concentration (SC) and total sperm count (TSC), and their modification by fertility and geographic group.

SEARCH METHODS

PubMed/MEDLINE and EMBASE were searched for English language studies of human SC published in 1981-2013. Following a predefined protocol 7518 abstracts were screened and 2510 full articles reporting primary data on SC were reviewed. A total of 244 estimates of SC and TSC from 185 studies of 42 935 men who provided semen samples in 1973-2011 were extracted for meta-regression analysis, as well as information on years of sample collection and covariates [fertility group ('Unselected by fertility' versus 'Fertile'), geographic group ('Western', including North America, Europe Australia and New Zealand versus 'Other', including South America, Asia and Africa), age, ejaculation abstinence time, semen collection method, method of measuring SC and semen volume, exclusion criteria and indicators of completeness of covariate data]. The slopes of SC and TSC were estimated as functions of sample collection year using both simple linear regression and weighted meta-regression models and the latter were adjusted for pre-determined covariates and modification by fertility and geographic group. Assumptions were examined using multiple sensitivity analyses and nonlinear models.

OUTCOMES

SC declined significantly between 1973 and 2011 (slope in unadjusted simple regression models -0.70 million/ml/year; 95% CI: -0.72 to -0.69; P < 0.001; slope in adjusted meta-regression models = -0.64; -1.06 to -0.22; P = 0.003). The slopes in the meta-regression model were modified by fertility (P for interaction = 0.064) and geographic group (P for interaction = 0.027). There was a significant decline in SC between 1973 and 2011 among Unselected Western (-1.38; -2.02 to -0.74; P < 0.001) and among Fertile Western (-0.68; -1.31 to -0.05; P = 0.033), while no significant trends were seen among Unselected Other and Fertile Other. Among Unselected Western studies, the mean SC declined, on average, 1.4% per year with an overall decline of 52.4% between 1973 and 2011. Trends for TSC and SC were similar, with a steep decline among Unselected Western (-5.33 million/year, -7.56 to -3.11; P < 0.001), corresponding to an average decline in mean TSC of 1.6% per year and overall decline of 59.3%. Results changed minimally in multiple sensitivity analyses, and there was no statistical support for the use of a nonlinear model. In a model restricted to data post-1995, the slope both for SC and TSC among Unselected Western was similar to that for the entire period (-2.06 million/ml, -3.38 to -0.74; P = 0.004 and -8.12 million, -13.73 to -2.51, P = 0.006, respectively).

WIDER IMPLICATIONS

This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50-60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed.

Decline in sperm count in European men during the past 50 years

Purpose:

To investigate whether the sperm concentration of European men is deteriorating over the past 50 years of time.

Materials and Methods:

We analysed the data published in English language articles in the past 50 years in altering sperm concentration in European men.

Results:

A time-dependent decline of sperm concentration ( r = −0.307, p = 0.02) in the last 50 years and an overall 32.5% decrease in mean sperm concentration was noted.

Conclusion:

This comprehensive, evidence-based meta-analysis concisely presents the evidence of decreased sperm concentration in European male over the past 50 years to serve the scientific research zone related to male reproductive health.

T26248G-transversion mutation in exon7 of the putative methyltransferase Nsun7 gene causes a change in protein folding associated with reduced sperm motility in asthenospermic men

The NOP2/Sun domain family, member 7 (Nsun7) gene, which encodes putative methyltransferase Nsun7, has a role in sperm motility in mice. In humans, this gene is located on chromosome 4 with 12 exons. The aim of the present study was to investigate mutations of exon 7 in the normospermic and asthenospermic men. Semen samples were collected from the Fatemezahra IVF centre (Babol, Iran) and analysed on the basis of World Health Organization (WHO) guidelines using general phenol-chloroform DNA extraction methods. Exon 7 was amplified using Sun7-F and Sun7-R primers. Bands on samples from asthenospermic men that exhibited different patterns of movement on single-strand conformation polymorphism gels compared with normal samples were identified and subjected to sequencing for further identification of possible mutations. Direct sequencing of polymerase chain reaction (PCR) products, along with their analysis, confirmed C26232T-transition and T26248G-transversion mutations in asthenospermic men. Comparison of normal and mutant protein structures of Nsun7 indicated that the amino acid serine was converted to alanine, the structure of the helix, coil and strand was changed, and the protein folding and ligand binding sites were changed in samples from asthenospermic men with a transversion mutation in exon 7, indicating impairment of protein function. Because Nsun7 gene products have a role in sperm motility, if an impairment occurs in exon 7 of this gene, it may lead to infertility. The transversion mutation in exon 7 of the Nsun7 gene can be used as an infertility marker in asthenospermic men.

The Disappearing Sperms: Analysis of Reports Published Between 1980 and 2015

Reports regarding the changes in sperm concentration in different counties of the world are inconsistent. Furthermore, the reports that sprung up from specific epidemiological and experimental examinations did not include data of prior studies or geographical variations. The current study, following a previous report of massive fall in semen volume over the past 33 years, attempts to delineate the trend of altering sperm concentrations and factors responsible for this by reviewing article published from 1980 to July 2015 with geographic differences. The current study identified an overall 57% diminution in mean sperm concentration over the past 35 years ( r = -.313, p = .0002), which, when analyzed for each geographical region, identified a significant decline in North America, Europe, Asia, and Africa. An increasing trend of sperm concentration was identified only in Australia. The association of male age with such a trend ( R² = .979) is reported. The authors also correlated male fertility with sperm concentration. Thus, this comprehensive, evidence-based literature review aims to concisely and systematically present the available data on sperm concentration from 1980 to 2015, as well as to statistically analyze the same and correlate male health with the declining pattern of sperm count in a single scientific review to serve the scientific research zone related to reproductive health. It points to the threat of male infertility in times ahead.

WITHDRAWN: Effects of various glycerol concentrations and thawing temperatures on CASA parameters and acrosomal integrity of frozen-thawed canine spermatozoa

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Applications and interpretation of computer-assisted sperm analyses and sperm sorting methods in assisted breeding and comparative research

Theoretical and practical knowledge of sperm function is an essential requirement in almost every aspect of modern reproductive technology, if the overarching objective is the eventual production of live offspring. Artificial insemination (AI) techniques depend on the availability of high quality semen, whether fresh, diluted and stored, or frozen. Assessing such semen for quality and the likelihood of fertility is therefore also important, as much time, resources and effort can easily be wasted by using poor samples. Some semen technologies are aimed not at quality assessment, but at attempting to skew the breeding outcomes. Sex preselection by separating the male- and female-bearing spermatozoa using flow cytometry is now practised routinely in the agricultural industry, but speculatively it may eventually be possible to use other genetic markers besides the sex chromosomes. A moment's reflection shows that although sex-biasing flow cytometry technology is well developed and generally fulfils its purpose if presorting of sperm quality is adequate, other technologies aimed specifically at semen assessment are also sophisticated but provide inadequate data that say little about fertility. This is especially true of instrumentation for objective sperm motility assessment. Here we aim to examine this technological paradox and suggest that although the sperm assessment equipment might be sophisticated, the shortcomings probably lie largely with inappropriate objectives and data interpretation. We also aim to review the potential value and use of sperm sexing technology for non-domestic species, arguing in this case that the limitations also lie less with the technology itself than with the applications envisaged. Finally, the potential application of a sorting method directed at motility rather than sperm DNA content is discussed.

Utilisation of a sperm quality analyser to evaluate sperm quantity and quality of turkey breeders

1. A relatively new instrument known as a Sperm Quality Analyzer (SQA) offers a rapid assessment of sperm quality and quantity by providing a sperm quality index (SQI). The SQA measures a combination of the intensity of sperm activity and motile concentration by determining the number and amplitude of sperm movements per second in a capillary tube as detected through light beam interference. 2. Because the SQA has not been tested for its potential use in turkeys, the objective was to determine if the SQA could accurately respond to changes in turkey sperm concentration, viability, and motility in semen collected from turkey breeders. 3. The effect of varying concentrations of sperm on SQI values was evaluated by diluting replicate pools of semen from 4 different aged turkey breeder flocks with saline. Results from all 4 flocks showed that semen dilutions greater than 20-fold resulted in a linear decline in SQI values. 4. Additional in vitro analysis evaluated the effects of turkey sperm viability on the SQI under conditions of constant sperm concentration. Incubated, live sperm was mixed in various proportions with thawed, dead sperm to determine changes in viability. Increased proportions of dead sperm caused a decline in the SQI. 5. To assess sperm motility, turkey semen was incubated under either aerobic (motile) or anaerobic (immotile) conditions. Varied amounts of immotile and motile sperm samples were mixed. A linear increase in the SQI was observed as per cent motile sperm increased. 6. These results indicate that the SQA can respond to differences in turkey sperm concentration, viability, and motility using in vitro analyses.

Immunoreactive relaxin in seminal plasma of fertile boars and its correlation with sperm motility characteristics determined by computer-assisted digital image analysis

Ejaculates from 10 mature fertile large white Yorkshire boars were used to examine the correlation between immunoreactive relaxin levels in seminal plasma and sperm motility characteristics. Seminal plasma levels of immunoreactive relaxin were measured by a time-resolved fluoroimmunoassay (TR-FIA). Motility characteristics were assessed using a CellSoft computer-assisted digital image analysis system. The mean +/- SD level of immunoreactive relaxin in seminal plasma was 2.61 +/- 0.62 ng/mL. When the correlation between seminal plasma levels of immunoreactive relaxin and parameters of sperm movement was examined, it was found that relaxin levels were significantly correlated with the percentage of motile spermatozoa (r=0.687, p < 0.05), curvilinear velocity (r=0.745, p < 0.05), straight line velocity (r=0.651, p < 0.05), mean amplitude of lateral head displacement (mean ALH) (r=0.844, p < 0.01) and the maximum amplitude of lateral head displacement (max ALH) (r=0.830, p < 0.01), but not with linearity, beat-cross frequency, or percentage of circular cells. Among these parameters, seminal plasma levels of immunoreactive relaxin showed the strongest correlation with the ALH parameter related to fertilizing ability. These results indicate that immunoreactive relaxin in boar semen may be necessary not only for normal sperm motility but also for normal fertility, suggesting that determination of the profile of immunoreactive relaxin in ejaculates may have value as a potential marker for predicting sperm fertilizing ability of boars.

Effect of column filtration upon the quality parameters of fresh dog semen

We filtered dog semen through various resin columns to obtain a quick, simple system for improving semen quality. Fresh ejaculates were filtered through columns with either glasswool or a chemically-inert polypropylene network disc. The columns were filled with Sephadex G-15 (nonionic resin), Sephadex A-50 (anionic-exchange resin), Sephadex C-50 (cationic-exchange resin) or a combination of Sephadex A-50 and C-50. Filtration through glasswool improved semen quality, with a significant (P < 0.001) increase in the percentage of viability and decrease in the percentage of altered acrosomes (P < 0.001) and total abnormalities (P < 0.001). Total motility was not modified, but curvilinear velocity or linearity of the movement were improved using the glasswool bed. The effect of the glasswool was so intense that it masked the effects of the filtration resins. Substitution of glasswool by polypropylene discs resulted in an unmasking of the effects of the resins, although the polypropylene exerted slight effects on semen. Elution of the spermatozoa through Sephadex G-15 or Sephadex C-50 resulted in a decrease of altered acrosomes. However, filtration through Sephadex A-50 increased viability and decreased the percentage of altered acrosomes and total abnormalities. Combined filtration through Sephadex A-50 and C-50 yielded the combined results observed with the resins individually. Ultrastructural imaging of the interaction between spermatozoa and the beds and resins showed that the cells were loosely deposited upon the glasswool fibers and the Sephadex G-15 particles, whereas close interaction was observed between spermatozoa and Sephadex A-50 and C-50 particles. The whole of the sperm cell bound to C-50 particles, whereas spermatozoa were specifically bonded to A-50 particles in the apical region of the head and in segments of the tail, which were periodically distributed. The data suggest that filtration through glasswool or an anionic resin-exchange can significantly improve dog semen quality.

Role of reactive oxygen species in male infertility

Human spermatozoa exhibit a capacity to generate ROS and initiate peroxidation of the unsaturated fatty acids in the sperm plasma membrane, which plays a key role in the etiology of male infertility. The short half-life and limited diffusion of these molecules is consistent with their physiologic role in key biological events such as acrosome reaction and hyperactivation. The intrinsic reactivity of these metabolites in peroxidative damage induced by ROS, particularly H2O2 and the superoxide anion, has been proposed as a major cause of defective sperm function in cases of male infertility. The number of antioxidants known to attack different stages of peroxidative damage is growing, and it will be of interest to compare alpha-tocopherol and ascorbic acid with these for their therapeutic potential in vitro and in vivo. Both spermatozoa and leukocytes generate ROS, although leukocytes produce much higher levels. The clinical significance of leukocyte presence in semen is controversial. Seminal plasma confers some protection against ROS damage because it contains enzymes that scavenge ROS, such as catalase and superoxide dismutase. A variety of defense mechanisms comprising a number of anti-oxidants can be employed to reduce or overcome oxidative stress caused by excessive ROS. Determination of male infertility etiology is important, as it will help us develop effective therapies to overcome excessive ROS generation. ROS can have both beneficial and detrimental effects on the spermatozoa and the balancing between the amounts of ROS produced and the amounts scavenged at any moment will determine whether a given sperm function will be promoted or jeopardized. Accurate assessment of ROS levels and, subsequently, OS is vital, as this will help clinicians both elucidate the fertility status and identify the subgroups of patients that respond or do not respond to these therapeutic strategies. The overt commercial claims of antioxidant benefits and supplements for fertility purposes must be cautiously looked into, until proper multicentered clinical trials are studied. From the current data it appears that no single adjuvant will be able to enhance the fertilizing capacity of sperm in infertile men, and a combination of the possible strategies that are not toxic at the dosage used would be a feasible approach.

Adherence of human prostasomes to mouse spermatozoa and their displacement by monoclonal antibodies as revealed by free zone electrophoresis

Prostasomes, small corpuscular organelles derived from the prostate gland, were isolated from human seminal plasma by means of ultracentrifugation and Sephadex G 200 chromatography to examine their interactive ability with mouse spermatozoa as assessed by free zone electrophoresis. During the run, human prostasomes and mouse spermatozoa approached each other and finally fused into one single peak that was not further dissociated. In some cases the fusion of prostasomes and spermatozoa failed to appear following pretreatment of prostasomes with monoclonal antibodies raised against these organelles.

Evidence of deteriorating semen quality in the United Kingdom: birth cohort study in 577 men in Scotland over 11 years

OBJECTIVE

To determine whether the quality of semen has changed in a group of over 500 Scottish men born between 1951 and 1973.

DESIGN

Retrospective review of data on semen quality collected in a single laboratory over 11 years and according to World Health Organisation guidelines.

SETTING

Programme of gamete biology research funded by Medical Research Council.

SUBJECTS

577 volunteer semen donors. Of these, 171 were born before 1959, 120 were born in 1960-4, 171 in 1965-9, and 115 in 1970-4.

MAIN OUTCOME MEASURES

Conventional criteria of semen quality including semen volume (ml), sperm concentration (10(6)/ml), overall motility (% motile), total number of sperm in the ejaculate (10(6)), and total number of motile sperm in the ejaculate (10(6)).

RESULTS

When the four birth cohort groups were compared a later year of birth was associated with a lower sperm concentration, a lower total number of sperm in the ejaculate, and a lower number of motile sperm in the ejaculate. The median sperm concentration fell from 98x10(6)/ml among donors born before 1959 to 78x10(6)/ml among donors born after 1970 (P=0.002). The total number of sperm in the ejaculate fell from 301x10(6) to 214x10(6) (P=0.0005), and the total number of motile sperm in the ejaculate fell from 169.7x10(6) to 129.0x10(6) (P=0.0065).

CONCLUSION

This study provides direct evidence that semen quality is deteriorating, with a later year of birth being significantly associated with a reduced number of sperm in adult life.

Characterization of zebra mussel (Dreissena polymorpha) sperm morphology and their motility prior to and after spawning

In order to understand more about the reproductive physiology of the zebra mussel (Dreissena polymorpha), we have examined the effect of spawning on the kinematics and fertilization ability of their spermatozoa. Sperm morphology was characterized using scanning electron microscopy, differences in sperm kinematics were examined using CASA following manual collection of sperm from the gonad or spawning induced by 5-hydroxytryptamine (5-HT), and the fertilization ability of spawned and manually removed spermatozoa were compared. D. polymorpha sperm have a tail 50 microns long, a midpiece consisting of four spherical mitochondria-rich regions approximately 0.6 micron in diameter, a conical nucleus 2.52 microns in length, and a cylindrical acrosome 0.72 micron in height and width. Kinematic analysis revealed that manually removed sperm exhibit significantly lower motion characteristics as compared to spawned sperm. Treatment with 5-HT had no significant effect on the sperm kinematics of either manually removed or spawned spermatozoa. These data suggest that D. polymorpha spermatozoa have a similar morphology to other bivalve sperm, spawning results in a significant enhancement in sperm kinematics, and 5-HT does not directly alter sperm motion.

Complementary effects of propranolol and nonoxynol-9 upon human sperm motility

The inhibitory effects of nonoxynol-9, DL- and D-propranolol upon human sperm motility were determined in vitro. All three compounds were capable of causing complete cessation of sperm movement. However, greater efficacy was achieved using combinations of nonoxynol-9 and propranolol, suggesting a complementary interaction between these compounds. Investigations of the mechanism of action of propranolol revealed that an influx of calcium accompanied the loss of motility. However, since incubation in the absence of calcium enhanced the spermicidal effects of this compound, it was concluded that this calcium influx did not constitute the primary means by which motility was disrupted. Low doses of propranolol, which did not affect motility, were found to inhibit the capacity of human spermatozoa for sperm-oocyte fusion.

Effect of filtration on post-thaw quality of bull semen

Semen from 4 Holstein bulls was diluted in 4 different extenders, filtered with Sephadex ion-exchange column, and frozen in liquid nitrogen. Sperm motility, progressive motility, path velocity, progressive velocity and the percentage of normal acrosomes of filtered and nonfiltered semen were recorded before and after freezing. Semen characteristics were significantly influenced by extender, filtration and freezing. Before and after freezing, motility measurements and the percentage of normal acrosomes were higher (P < 0.001) in filtered than in nonfiltered spermatozoa. Post-thaw recovery rate of motile spermatozoa was higher in filtered semen than nonfiltered (68 vs 39%, P < 0.0001). The reduction in motility, progressive motility and the percentage of normal acrosomes during freezing and thawing processes were significantly lower (P < 0.0001) in filtered semen (34, 34 and 4%, respectively) than nonfiltered (59, 54 and 15%, respectively). Post-thaw viability of spermatozoa was significantly affected by extender, filtration and time (P < 0.0001). Immediate (0 h) post-thaw motility of nonfiltered semen (29%) was similar to 4-h post-thaw motility of filtered semen (25%; P > 0.05). In conclusion, bull spermatozoa recovered by Sephadex ion-exchange filtration showed better post-thaw viability.

Promotive effect by prostasomes on normal human spermatozoa exhibiting no forward motility due to buffer washings

Prostasomes, small corpuscular organelles derived from the prostate gland, were isolated from human seminal plasma by means of ultracentrifugation and Sephadex G 200 chromatography to assess objectively their promotive effect on the motility of buffer-washed normal human spermatozoa exhibiting no forward motility. Prostasomes were efficacious in about 70% of these spermatozoa, and a maximum value was obtained with prostasomes at a concentration corresponding to a protein content of 0.7-0.8 g/l followed by a plateau at higher concentrations. Addition of albumin alone resulted in a similar response although at a somewhat lower level and about 50% of the spermatozoa were rendered motile with a maximum effect of albumin at about 2.5 g/l. Albumin concentrations exceeding 3 g/l were less active. At protein concentrations of 0.25 g/l, prostasomes were superior to albumin in every respect concerning the effects on various sperm movement characteristics. These divergent effects were abolished when comparing prostasomes corresponding to a protein concentration of 0.75 g/l with albumin at 2.3 g/l, i.e. at their respective optimum concentration. Heat treatment and ultrasonication of prostasomes did not affect their motility-promoting properties. Some problem of sperm dysfunction has generally been considered to be a major contributory factor to infertility. By supplementing sperm preparations with postasomes in cases of established male factor, the already poor quality spermatozoa may more frequently be rendered capable of fertilization after insemination.

Predictive power of sperm motion analysis in in vitro fertilization

The correlation between sperm motion characteristics and in vitro fertilization was studied in 160 cycles, divided in two groups: those with male subfertility (N=42) and those with tubal disease (N=118). The group with male subfertility showed inferior performance, as indicated by a lower fertilization rate per oocyte (40% versus 66%) and per pick-up cycle (67% versus 93%). These two groups exhibited no significant difference in the mean sperm velocity, linearity, amplitude of lateral head displacement, and beat cross frequency in the pre swim-up and post swim-up specimens. The two groups differed in pre and post swim-up sperm motility, pre and post swim-up concentration, pre swim-up cumulative velocity at 110 to 140 Amicrom/sec and post swim-up cumulative velocity at 130 microm/sec. Logistic regression analysis was used to determine those variables that would predict fertilization; pre swim-up count and post swim-up motility proved to be the significant determinants. The results indicate that assessment of motion by automated semen analyzers does not supplement conventional semen analysis in the ability to predict fertilization.

Measurement of intracellular calcium levels of human spermatozoa acrosome reacted by electropermeabilization

Human spermatozoa readily undergo in vitro capacitation and the acrosome reaction when exposed to a single, brief, high-voltage electric pulse in a medium containing calcium. Using the fluorescent calcium indicator, Fura-2, the changes in the intracellular calcium concentration of human sperm following exposure to voltages in the range of 200-2000 V cm-1 were measured. The induction of the acrosome reaction by the electropermeabilization pulse was also monitored. In comparison, changes in calcium uptake during a standard capacitation procedure in which sperm samples were incubated for 7 h were analyzed. At hourly intervals, acrosome reaction induction and intracellular calcium uptake were measured. The results indicate that electropermeabilization rapidly and efficiently produces high populations of acrosome-reacted sperm and a corresponding and associated increase in the intracellular calcium concentration.

Computerized human sperm analysis

The recent introduction of various devices for computer-assisted sperm analysis allows us to have not only objective measurements of the seminal parameters but also to determine some characteristics of sperm motion such as curvilinear and linear velocity and amplitude of lateral head displacement that cannot be obtained by routine analysis. These new seminal parameters seem to be very useful in the diagnosis of male infertility and, among them, ALH seems to play a more important role; in one of our studies we found a significant correlation between this parameter and the results of the bovine cervical mucus penetration test (Penetrak). Furthermore it is possible to determine sperm subpopulations for each parameter and so it will be possible to express a more accurate judgement not only on the fertilizing capacity of semen but also to know the effects on spermatozoa of different activating and capacitating treatments.

Sperm motility analysis using multi-exposure photography (MEP): validity of the method with normal and abnormal patterns

Spermatozoon motility is an important semen parameter that can be correlated with fertilizing capacity. It can be evaluated by subjective or objective methods such as the multiple exposure photography technique (MEP). This technique was: (1) validated in terms of accuracy and sensitivity, and (2) used to investigate the possibility of differentiating patient subgroups on the basis of sperm motility. The method was shown to be accurate. The within and between assay variation coefficients were less than 6% and 17% respectively. Maximal sensitivity required 100 spermatozoa, since coefficients of variation were high when counting smaller numbers. A significant difference between fertile, normozoospermic and asthenozoospermic groups on the basis of the population pattern was found in a retrospective study. Moreover, the asthenozoospermic group could be divided into three subgroups, depending on whether one, two, or three motility variables were altered.

Prediction of in vitro fertilization rates from semen variables

OBJECTIVE

To assess the value of semen variables for predicting fertilization rates.

DESIGN

Measures of the fresh semen and the motile sperm fraction used for insemination were related to the fertilization rate by multiple regression analysis. The regression model was then used to construct a two-dimensional clinical chart.

SETTING

University-affiliated reproductive medicine unit.

PATIENTS

The results of 294 IVF cycles were analyzed retrospectively. Selection criteria were: [1] first cycle of IVF; [2] tubal and/or male factor infertility; and [3] four or more oocytes inseminated.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The fertilization rate was related to measured variables of the fresh semen and the motile sperm fraction used for insemination. Fertilization rate was categorized as poor (< 35%) or acceptable (> or = 35%).

RESULTS

Multiple regression analysis demonstrated a strong correlation between the fertilization rate and the combined indexes of percentage normal morphology and grade of motility in the fresh semen and percentage progressive motility in the motile sperm fraction. A two-dimensional chart that expressed these relationships was constructed. Its accuracy of prediction was 77% for poor fertilization and 95% for acceptable fertilization.

CONCLUSIONS

The fertilization rate is strongly correlated with percentage normal sperm morphology in the fresh semen and the percentage progressive motility in the motile sperm fraction used for insemination. The clinical chart provides a simple but powerful tool for predicting fertilization outcome.

Male infertility: current concepts

The purpose of the article is to review the current concepts regarding the etiology and treatment of male-factor infertility. The following general conclusions can be drawn: (a) conventional parameters for sperm quality and male fertility are inadequate and any assessment should involve several different tests of sperm cell function to increase the fertility prognosis; (b) the causes of disturbed sperm quality are still poorly understood; (c) the role of the varicocele is still controversial but some of the discrepancies reported in the literature may be explained by the negative influence of other factors such as smoking, epididymal pathology or glandular infections operating either in conjunction or independent of the varicocele; (d) the role of chronic inflammatory processes in the reproductive organs, in particular the involvement of chronic chlamydial infections, has been underestimated, largely because it is often asymptomatic and difficult to demonstrate objectively; (e) partial androgen insensitivity may account for a significant number of cases of severe oligozoospermia; (f) no major advances have been made in the medical treatment of poor sperm quality; (g) assisted fertilization techniques such as IVF and GIFT offer encouraging possibilities for the treatment of male-factor infertility; and (h) recent advances in microsurgical techniques are increasing the treatment possibilities for certain forms of obstructive azoospermia and severe oligozoospermia.

The fertilization antigen-1 does not have proteolytic/acrosin activity, but its monoclonal antibody inhibits sperm capacitation and acrosome reaction

OBJECTIVE

To determine if human sperm surface fertilization antigen exhibits proteolytic or acrosin activity and to investigate the mechanism(s) whereby monoclonal antibody (mAb) to fertilization antigen inhibits human sperm penetration of zona-free hamster ova.

DESIGN

Proteolytic and acrosin activities of human fertilization antigen were determined. Acrosomal status, acrosin activity, and motion characteristics were evaluated after incubation of human sperm with immunoaffinity-purified mAb to fertilization antigen.

SETTING

Academic research environment.

PARTICIPANTS

Fertile donors used as controls for infertile patients for fertility evaluation.

INTERVENTIONS

Human spermatozoa were treated with mAb to fertilization antigen and induced to undergo acrosome reaction using calcium ionophore A23187.

MAIN OUTCOME MEASURES

Proteolytic and acrosin activities of fertilization antigen. Sperm penetration assay, acrosomal status, and motion parameters.

RESULTS

Fertilization antigen does not exhibit proteolytic or acrosin activity; however, its mAb completely blocks human sperm penetration of zona-free hamster ova. The mAb to fertilization antigen inhibits ionophore-induced acrosome reaction and blocks development of the hyperactivated state of human sperm cells.

CONCLUSIONS

Monoclonal antibody to fertilization antigen blocks fertilization by inhibiting capacitation and acrosome reaction.

Preparation of human frozen-thawed seminal specimens using the SpermPrep filtration method: improvements over the conventional swim-up method

OBJECTIVE

To examine the qualitative and quantitative characteristics of frozen-thawed spermatozoa recovered through the SpermPrep (ZBL, Inc., Lexington, KY) filtration method or the swim-up technique for the purpose of intrauterine insemination (IUI) or other techniques for assisted reproduction.

DESIGN, SETTING, PATIENTS

Thirty pairs of frozen specimens purchased from three commercial semen suppliers were used in this study. Each pair consisted of two aliquots from the same semen specimen.

MAIN OUTCOME MEASURES

Spermatozoa recovered via the SpermPrep filtration and swim-up processes were evaluated for sperm numbers recovered, sperm motility, grade of sperm motility, percentage of morphologically normal spermatozoa, the response of spermatozoa to a hypo-osmotic environment (hypo-osmotic swelling test), and the amount of debris present.

RESULTS

Application of the SpermPrep filtration method resulted in recovery of significantly greater numbers of spermatozoa (P less than 0.01) than were recovered with the swim-up method (31.1 +/- 3.2 x 10(6) versus 10.2 +/- 1.8 x 10(6) spermatozoa, respectively). This represents a mean recovery of approximately one half (49%) of all spermatozoa applied to the filter, whereas for the swim-up method, it was only 15%. The overall quality of recovered spermatozoa was virtually identical between the two methods (P greater than 0.05). The percent motile sperm improved by a mean of 18% to 20%, the grade of motility improved by a mean of 0.4 points (scale 0 to 4), the percent of morphologically normal spermatozoa increased by a mean of approximately 10%, the percent of spermatozoa reactive to a hypo-osmotic medium test increased by a mean of approximately 9%, and the debris score decreased by a mean of 0.2 to 0.3 points (scale 0 to 4). Most importantly, the mean total number of motile, morphologically normal spermatozoa after filtration through the SpermPrep column was 20.2 +/- 1.1 x 10(6), representing a mean recovery of 73% of the normal spermatozoa originally applied to the column. This was 316% greater than the yield obtained with the swim-up method (6.4 +/- 0.8 x 10(6)), which was significantly greater (P less than 0.01) than that recovered via the swim-up method. Also, the time required to harvest sperm through SpermPrep filtration was 20 to 25 minutes versus 80 minutes required for the swim-up method (P less than 0.05).

CONCLUSION

Considering that the effectiveness of frozen-thawed semen is already limited when compared with fresh semen, SpermPrep filtration is the method of choice over the swim-up technique of sperm selection because the former provides significantly greater numbers of high quality sperm. It should be considered as an adjunct in semen preparation for IUI or other forms of assisted reproduction.

Movement characteristics and hyperactivation of human sperm on different epithelial cell monolayers

Studies of sperm movement characteristics concern mainly sperm swimming between two glass surfaces (as in the Makler chamber). Using automated videomicrography, (CellSoft, Cryo Resources, New York, USA), we have analysed the movements of human sperm swimming on monolayers of different origins: monkey kidney (Vero) cells, bovine oviduct cells, and human endometrial cells. About 10(5) sperm were deposited upon preparations consisting of monocellular layers adhering to a coverglass, and placed in a deep slide-coverglass system. Experiments were first performed at room temperature then at 37 degrees C. At room temperature, motion characteristics on Vero cell layers (six samples) were not different from those measured in either the conditioned or corresponding non-conditioned media, except for the amplitude of lateral head displacement (ALH) which was significantly lower. Comparison of the three different cell monolayers showed no difference between them for the corresponding motion parameters. The data were dramatically different at 37 degrees C: sperm swimming on cell monolayers of genital origin (oviduct or endometrium) exhibited high rates of hyperactivation (HA: 36.7% and 38.6% respectively), which was significantly more than on either Vero cells (10.9%) or in a control medium (12.6%). Moreover, HA rates were significantly higher on genital cell monolayers than in the corresponding conditioned medium. Hyperactivated sperm exhibited lasting 'star-spin' trajectories rather than 'transitional phases'. It is concluded that passage of sperm on either oviduct or endometrial epithelial cell monolayers can induce sperm hyperactivation and improve their fertilizing capacity.

Comparison of measurements of human sperm motility characteristics by the automated CellSoft system and time-exposure photomicrography

Human sperm motility characteristics in 28 semen samples with sperm concentrations less than 40 x 10(6) ml-1, as determined by the World Health Organization manual analysis (WHO, 1987), were measured by the automated CellSoft semen analyser (Cryo Resources Ltd, New York, NY, USA) using different system parameter settings (Mortimer & Mortimer, 1988a). The results were compared with those obtained by time-exposure photomicrographic (TEP) analysis. It was found that the settings of the minimum video frame rate and the threshold velocity used to distinguish motile from immotile sperm by the automated CellSoft system had a significant influence on measurements of percentage motility but not on linear velocity. At the five different parameter settings used in the present study, the automated CellSoft system gave significantly lower mean values for percentage motility in comparison with the WHO manual and TEP analyses. Measurements for linear velocity between the automated CellSoft system and TEP analyses were found not to be significantly different in these defined semen samples.

Motile sperm recovery from fresh and frozen-thawed ejaculates using a swim-up procedure

The recovery of motile sperm in swim-ups from fresh semen that was washed and centrifuged one time was 33% and after 2 washes and centrifugations was 22%. The recovery rates for frozen-thawed semen were only 7% and 5%, respectively. The straight line velocity of sperm was increased after sperm swim-up, whereas changes to the lateral sperm head movement were not as evident. However, the dramatic loss in motile sperm numbers especially after swim-up from thawed semen indicate that more efficient methods of isolating motile sperm from thawed semen may be required.

Prospective analysis of sperm-oocyte fusion and reactive oxygen species generation as criteria for the diagnosis of infertility

We have undertaken a prospective analysis of the diagnostic significance of three different criteria of human sperm function including the conventional semen profile, measurements of hamster-oocyte fusion, and determinations of reactive oxygen species generation in 139 couples. The latter, who were characterized by a lack of detectable abnormalities in the female partner, were followed up for a maximum of 4 years to determine the incidence of spontaneous pregnancy in the absence of therapeutic intervention. Assessments of monthly fecundity with life table analysis techniques revealed a highly significant, positive relationship between fertility and hamster-oocyte fusion rates that were measured in the presence of the ionophore, A23187. Conversely, reactive oxygen species generation was shown to be negatively associated with both the outcome of the sperm-oocyte fusion assay and fertility in vivo. The clinical significance of these diagnostic techniques was emphasized by the fact that within the same data set, the conventional semen profile was of no significant diagnostic value.

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

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

Studies on requirements for trackpoints in CellSoft automated semen analysis

The CellSoft (CRYO Resources, Ltd., New York, NY) system for computer-assisted sperm analysis was evaluated as to the appropriate settings for trackpoints. Fifty-eight human spermatozoa exhibiting complex swimming modes were chosen for analysis at room temperature. The accumulated measures for curvilinear velocity, linearity, mean and maximum amplitude of lateral head displacement, and beat cross frequency were determined over a range of trackpoints from 2 to 37. Stable measures (within the 95% confidence interval at 37 frames) were observed at 4 frames for curvilinear velocity and at 20 frames for linearity. The corresponding figure for mean amplitude of lateral head displacement and beat cross frequency was 8 frames. We conclude that the frame requirements concerning measures for curvilinear velocity/linearity and mean amplitude of lateral head displacement/beat cross frequency should be 20 and 8, respectively. Thus, 20 consecutive frames to analyze will suffice.

Analysis of sperm function in globozoospermia: implications for the mechanism of sperm-zona interaction

The globozoospermic condition has provided a unique opportunity to determine how the abnormal mitochondrial organization and acrosomal loss associated with this syndrome, influence sperm function. Despite the abnormal midpiece architecture, the movement characteristics of the spermatozoa, in terms of the curvilinear, path, and progressive velocities, amplitude of head displacement, and hyperactivation were all within the normal range. Similarly, the behavior of the spermatozoa on Percoll gradients was normal, although the capacity of the isolated fractions to generate reactive oxygen species was negligible. Of particular significance was the fact that the globozoospermic spermatozoa were incapable of sperm-oocyte fusion or binding the human zona pellucida, even after an intracellular calcium signal had been generated with the ionophore A23187. The sudden induction of sperm-zona interaction could, however, be achieved by the use of a ferrous ion promoter system to induce limited lipoperoxidation. This result demonstrates that the enhancing effect of peroxidation on sperm-zona adhesion involves a direct action on the properties of the sperm-plasma membrane, rather than an indirect consequence of acrosomal damage and acrosin leakage. Such findings emphasize the value of specific teratozoospermic conditions, such as globozoospermia, in dissecting the mechanisms that regulate human sperm function.

Establishment of TEST-yolk buffer enhanced sperm penetration assay limits for fertile males

TEST-yolk buffer has been shown to enhance sperm penetration of zona-free hamster eggs. Review of sperm penetration assay (SPA) data from a fertile population was undertaken to determine a normal range for SPA with TEST-yolk buffer enhancement. Thirty-eight intrauterine insemination patients and 4 artificial insemination donors who had successfully initiated a pregnancy within 18 months of SPA analysis were examined. All 42 enhanced SPAs demonstrated penetration of greater than 10%, and 37 of these (88%) yielded SPA values of greater than or equal to 20%. Thirty-three percent (14/42) of these individuals achieved 0% penetration in the SPA without TEST-yolk buffer. The SPA performed with the TEST-yolk modification has fewer false negatives than the assay done with the original methodology.

Variation of movement characteristics with washing and capacitation of spermatozoa. II. Multivariate statistical analysis and prediction of sperm penetrating ability

Fifty semen samples were studied by computer-assisted semen analysis before testing in the sperm penetration assay (SPA). Twenty-one concentration and movement measurements were obtained from each sample on sperm in semen, after washing and swim-up, and again after an 18-hour capacitation period. Discriminant analysis was then used to define a function from these measurements that would classify the SPA results as above or below a 10% penetration rate. A significant function was identified using the following variables: sperm concentration and motility in semen, and mean curvilinear velocity, linearity, and amplitude of lateral head displacement of washed sperm. Movement measurements of capacitated spermatozoa were not useful predictors in this analysis. The overall accuracy of this function for predicting SPA results was 72%. These findings demonstrate that computer-derived measurements of sperm movement provide biologically useful information regarding sperm function, and, in addition, emphasize the importance of multivariate techniques in the analysis and description of human sperm motion.

Enhanced penetration of zona-free hamster ova by sperm prepared by Nycodenz and Percoll gradient centrifugation

The effect of sperm penetration capacity after selection procedures using Percoll (Pharmacia AB, Uppsala, Sweden) and Nycodenz (Nycomed Diagnostics, Oslo, Norway) gradient centrifugation was compared with double-washed and swim-up in 47 subfertile men. The results of sperm motility, velocity, and amplitude lateral head displacement showed no significant improvement with the centrifugation procedures. The sperm penetration assay results obtained with double-washed and swim-up technique were poor (2.7% +/- 1.7%), however, a significant enhancement was obtained by Percoll (16.3% +/- 3.7%) and Nycodenz (15.8% +/- 3.3%) processing. Nycodenz centrifugation allowed sperm penetration of zona-free hamster ova at comparable rates to Percoll separation.

Transmembrane migration technique: reexamination of its usefulness in sperm motility assessments

A study was carried out using time-exposure photomicrography to investigate the potential usefulness of the transmembrane migration technique in the assessment of drug effects on human sperm motility. Significant but weak correlations were evident between the transmembrane migration ratio (TMMR%) and both % motility (r = 0.43; p less than 0.05) and the amplitude of lateral sperm head displacement (r = 0.40; p less than 0.05). However, no significant correlations were evident between TMMR% and the concentration of motile spermatozoa, mean path velocity, or frequency of sperm head rotation. Exposure to 2.5 mM 2-deoxyadenosine caused significant increases in % motility, mean path velocity, and frequency of sperm head rotation, with no concomitant rise in TMMR%, while 5.0 mM caffeine caused significant elevations in both TMMR% and in % motile cells. It is concluded that the transmembrane migration technique is a relatively insensitive method for detecting subtle but important changes in the movement characteristics of human spermatozoa.