Measuring Male-to-Male Differences in Fertility or Effects of Semen Treatments.

Fertility is a convenient but meaningless term unless the outcome measure is stipulated and accounts for dependence of male fertility on the female population. We describe outcome measures and detail the impacts of the physiological status of each female and her external environment, as well as management imposed by humans. We explain the dominant role of the female reproductive tract as a series of hurdles for sperm seeking an ovum. Each spermatozoon in an ejaculate is unique, although usually most are morphologically similar. Semen seemingly contains three subpopulations of sperm, based on fate within a female and role in hampering the success of the ultimate winning spermatozoon; we define these subpopulations. The numerical size of each subpopulation placed into a female determines the shape of the dose-response curve leading to possible live young. Heterospermic artificial insemination provides far greater sensitivity to detect differences, partly because the female environment is identical for each comparison.

Testis and antler dysgenesis in sitka black-tailed deer on Kodiak Island, Alaska: Sequela of environmental endocrine disruption?

It had been observed that many male Sitka black-tailed deer (Odocoileus hemionus sitkensis) on Kodiak Island, Alaska, had abnormal antlers, were cryptorchid, and presented no evidence of hypospadias. We sought to better understand the problem and investigated 171 male deer for phenotypic aberrations and 12 for detailed testicular histopathology. For the low-lying Aliulik Peninsula (AP), 61 of 94 deer were bilateral cryptorchids (BCOs); 70% of these had abnormal antlers. Elsewhere on the Kodiak Archipelago, only 5 of 65 deer were BCOs. All 11 abdominal testes examined had no spermatogenesis but contained abnormalities including carcinoma in situ-like cells, possible precursors of seminoma; Sertoli cell, Leydig cell, and stromal cell tumors; carcinoma and adenoma of rete testis; and microlithiasis or calcifications. Cysts also were evident within the excurrent ducts. Two of 10 scrotal testes contained similar abnormalities, although spermatogenesis was ongoing. We cannot rule out that these abnormalities are linked sequelae of a mutation(s) in a founder animal, followed by transmission over many years and causing high prevalence only on the AP. However, based on lesions observed, we hypothesize that it is more likely that this testis-antler dysgenesis resulted from continuing exposure of pregnant females to an estrogenic environmental agent(s), thereby transforming testicular cells, affecting development of primordial antler pedicles, and blocking transabdominal descent of fetal testes. A browse (e.g., kelp) favored by deer in this locale might carry the putative estrogenic agent(s).

Weaknesses in reports of "fertility" for horses and other species.

Apparent fertility of a male or group of females is considered frequently by veterinarians or animal scientists. Unfortunately, concepts of experimental design and statistics impacting validity and interpretation of values for average pregnancy rate frequently are ignored. The magnitude of this problem was documented by examination of published papers; 51 of 67 (76%) were considered flawed for one or more reasons. The discussion considers why: (a) conclusions from most published fertility studies reporting no significant difference due to treatment(s) are suspect, because too few males and/or females were used; (b) the experimental unit in an IVF study should be a droplet of co-incubating gametes rather than an ovum; (c) apparent fertility of a male is profoundly influenced by the range in actual fertility of the females with which he was mated, and thus might shift over a two- to three-fold range; and (d) scientists should refrain from conduct of studies destined to be inconclusive, and should be candid in reporting each fertility trial. It was emphasized that no fertility data were better than an imprecise average value for a given male or a conclusion based on an inadequate research study or incomplete report of what was done.

Computer-assisted sperm analysis (CASA): capabilities and potential developments.

Computer-assisted sperm analysis (CASA) systems have evolved over approximately 40 years, through advances in devices to capture the image from a microscope, huge increases in computational power concurrent with amazing reduction in size of computers, new computer languages, and updated/expanded software algorithms. Remarkably, basic concepts for identifying sperm and their motion patterns are little changed. Older and slower systems remain in use. Most major spermatology laboratories and semen processing facilities have a CASA system, but the extent of reliance thereon ranges widely. This review describes capabilities and limitations of present CASA technology used with boar, bull, and stallion sperm, followed by possible future developments. Each marketed system is different. Modern CASA systems can automatically view multiple fields in a shallow specimen chamber to capture strobe-like images of 500 to >2000 sperm, at 50 or 60 frames per second, in clear or complex extenders, and in <2 minutes, store information for ≥ 30 frames and provide summary data for each spermatozoon and the population. A few systems evaluate sperm morphology concurrent with motion. CASA cannot accurately predict 'fertility' that will be obtained with a semen sample or subject. However, when carefully validated, current CASA systems provide information important for quality assurance of semen planned for marketing, and for the understanding of the diversity of sperm responses to changes in the microenvironment in research. The four take-home messages from this review are: (1) animal species, extender or medium, specimen chamber, intensity of illumination, imaging hardware and software, instrument settings, technician, etc., all affect accuracy and precision of output values; (2) semen production facilities probably do not need a substantially different CASA system whereas biology laboratories would benefit from systems capable of imaging and tracking sperm in deep chambers for a flexible period of time; (3) software should enable grouping of individual sperm based on one or more attributes so outputs reflect subpopulations or clusters of similar sperm with unique properties; means or medians for the total population are insufficient; and (4) a field-use, portable CASA system for measuring one motion and two or three morphology attributes of individual sperm is needed for field theriogenologists or andrologists working with human sperm outside urban centers; appropriate hardware to capture images and process data apparently are available.

Tests to measure the quality of spermatozoa at spermiation.

This commentary is to critique the revised World Health Organization (WHO) semen analysis manual as it pertains to characteristics of a spermatozoon at spermiation. The aims of the revised WHO manual include improving the 'quality of semen analysis' without any restriction to clinical use. Furthermore, the manual states that semen analysis may be useful for (a) 'investigating male fertility status' and (b) 'monitoring spermatogenesis during and following male fertility regulation.' However, if the analysis of ejaculated spermatozoa is intended for the purposes described in (b), then cells that are abnormal at spermiation must be identified. This paper takes the position that the manual does not identify methods to estimate the quality of spermatozoa at spermiation. Instead, it uses a 'gold standard' of sperm passing through the cervical mucus or arriving near the site of fertilization. Although this standard is appropriate for drawing conclusions regarding the probability that an individual could impregnate his partner, it is not appropriate for studying illness of the testes per se. Herein, the measures of sperm quality presented in the WHO manual are critiqued with respect to the detection of spermatozoa that were abnormal at spermiation vs. those that became abnormal subsequently. Quality assessments based on the percentage of motile or 'viable' spermatozoa are meaningless. Alternative quality attributes defining spermatozoa at spermiation are presented in this paper. In conclusion, assessment of spermatozoal quality at spermiation, on the basis of quality attributes of individual ejaculated spermatozoa, is best achieved through application of (a) a new paradigm for the morphological evaluation of sperm quality and (b) modern analytical techniques to evaluate, in an adequate sample, several appropriate independent attributes in each spermatozoon in order to more accurately identify the proportion of abnormal spermatozoa.

Considerations in evaluating human spermatogenesis on the basis of total sperm per ejaculate.

Total number of sperm per ejaculate (TSperm) is an important measure for clinicians to provide advice to patient couples. However, TSperm per hour of abstinence (TSperm/h) is a better measure for epidemiologist-andrologist teams or clinicians to evaluate spermatogenesis because it is a rate function. This review looks at the interplay and impacts of rate of sperm accumulation in the excurrent duct system, abstinence interval, sexual arousal, and masturbation vs intercourse on observed TSperm. It also examines why and when TSperm/h might provide a meaningful quantitative evaluation of spermatogenesis (ie, rate of sperm production). There is no doubt that TSperm increases with longer abstinence, and in different men plateaus after 2-9 days. Clinicians wishing to maximize number of fully functional sperm available during intercourse, or for artificial insemination, might wish to recommend 6-7 days of abstinence. Diagnostically, the important feature is TSperm/h. After abstinence interval exceeds 64-72 hours, TSperm/h has started to decline in most nonoligozoospermic men as rate of sperm accumulation in the excurrent ducts approaches zero; apparently increasingly more sperm are voided in urine. Clinicians or epidemiologist-andrologist teams wishing to have optimal distinction among individuals with high, typical, or low sperm production (ie, normal or abnormal spermatogenesis) should accurately measure TSperm/h for samples provided after 42-54 hours' abstinence (never 64 hours). Longer abstinence intervals reward men with poor sperm production, because sperm accumulate in the excurrent ducts for 7 days or more of abstinence, and penalize men with good sperm production, because after 3 days or less of abstinence their excurrent ducts probably are full.

Total sperm per ejaculate of men: obtaining a meaningful value or a mean value with appropriate precision.

UNLABELLED: We retrospectively mined and modeled data to answer 3 questions. 1) Relative to an estimate based on approximately 20 semen samples, how imprecise is an estimate of an individual's total sperm per ejaculate (TSperm) based on 1 sample? 2) What is the impact of abstinence interval on TSperm and TSperm/h? 3) How many samples are needed to provide a meaningful estimate of an individual's mean TSperm or TSperm/h? Data were for 18-20 consecutive masturbation samples from each of 48 semen donors. Modeling exploited the gamma distribution of values for TSperm and a unique approach to project to future samples. Answers: 1) Within-individual coefficients of variation were similar for TSperm or TSperm/h abstinence and ranged from 17% to 51%; average approximately 34%. TSperm or TSperm/h in any individual sample from a given donor was between -20% and +20% of the mean value in 48% of 18-20 samples per individual. 2) For a majority of individuals, TSperm increased in a nearly linear manner through approximately 72 hours of abstinence. TSperm and TSperm/h after 18-36 hours' abstinence are high. To obtain meaningful values for diagnostic purposes and maximize distinction of individuals with relatively low or high sperm production, the requested abstinence should be 42-54 hours with an upper limit of 64 hours. For individuals producing few sperm, 7 days or more of abstinence might be appropriate to obtain sperm for insemination. 3) At least 3 samples from a hypothetical future subject are recommended for most applications. Assuming 60 hours' abstinence, 80% confidence limits for TSperm/h for 1, 3, or 6 samples would be 70%-163%, 80%-130%, or 85%-120% of the mean for observed values. In only approximately 50% of cases would TSperm/h for a single sample be within -16% and +30% of the true mean value for that subject. CONCLUSIONS: Pooling values for TSperm in samples obtained after 18-36 or 72-168 hours' abstinence with values for TSperm obtained after 42-64 hours is inappropriate. Reliance on TSperm for a single sample per subject is unwise.

The cycle of the seminiferous epithelium in humans: a need to revisit?

Understanding the dynamics of spermatogenesis is central to clinical andrology or to probing environmental effects on human testes. This review considers what is known about renewal and proliferation of spermatogonia, how germ cells are organized in cellular associations constituting the cycle of the seminiferous epithelium, relative frequencies of cellular associations, durations of the cycle of the seminiferous epithelium and spermatogenesis, and measurement of daily sperm production. Daily sperm production (DSP) per testis tends to decline with advancing age. Regardless of age, there is substantial loss of potential sperm from degeneration of spermatocytes, but not spermatids. DSP per gram testis parenchyma or DSP per testis cannot be predicted on the basis of testis size or age of a man. The review shows why our 1960s data base is neither robust nor precise and suggests how deficiencies might be rectified. New cellular associations should be defined, with none representing >15% of the cycle of the seminiferous epithelium. Then determine when A(pale)-spermatogonia become committed to proliferate or how many mitotic divisions occur thereafter. Restudy the duration of spermatogenesis because the accepted value might be in error by approximately 6 days. Restudying human spermatogenesis will benefit clinicians, toxicologists, and epidemiologists probing testis function by direct evaluations or indirectly via evaluations of quantity and quality of sperm ejaculated. It also will benefit scientists interested in renewal and proliferation of spermatogonia, or a spermatogonium as a prototype stem cell.