The effect of exogenous testosterone on homospermic and heterospermic fertility in the cock

Cocks were administered testosterone (T) for 14 days via 0, 1, 2, or 4 Silastic capsules implanted subcutaneously. Each capsule released 1.04 mg of T per day. Concentrations of T in plasma and the proportion of eggs fertilized from homospermic insemination of hens were determined. Concentrations of T in plasma were variable and unaffected by treatment. The proportion of eggs that were fertilized by cocks decreased during treatment with 1 capsule, increased over the experiment in the group with 2 capsules, and increased after treatment ended in the group with 4 capsules. In heterospermic tests, cocks with distinguishable offspring were paired and semen was mixed within pairs. One cock in each pair received either 1 or 4 Silastic capsules containing T for 14 days; the other cock in the pair received none. The proportion of chicks sired by cocks treated with 1 capsule remained unchanged throughout the experiment, whereas the proportion sired by cocks treated with 4 capsules decreased markedly during the recovery period. The response to T was apparently dependent upon dosage and the sensitivity of the cock to T. The concentration of T in the plasma of the cock had little relationship to fertility. These results indicate that heterospermic insemination can be used as a sensitive method to detect the subtle effects of hormonal treatment.     

Correlations between heterospermic fertility and assays of porcine semen quality before and after cryopreservation

The relative fertilizing potential of frozen-thawed semen from four black and four white boars was determined following heterospermic insemination. A heterospermic index (HI) was computed for each of the 16 possible pairs of black and white boars. Correlation coefficients were computed between the HI and several in vitro tests of semen quality before and afttr cryopreservation of the semen. For the in vitro tests before cryopreservation, the HI were negatively correlated (-0.57) with spermatozoal motility before cooling the semen, but they were not correlated with spermatozoal motility after cooling to 5 degrees C. After freezing and thawing, the HI were correlated with the following in vitro tests: spermatozoal motility (0.50), spermatozoa with either normal or damaged apical ridges (0.31), spermatozoa with missing apical ridges (-0.51), spermatozoa filtered through sephadex columns (0.32), spermatozoa with acrosin-activity (0.38), percentage of maximal releasable glutamic oxalacetic transaminase (GOT) present extracellularly (0.54), spermatozoal intracellular GOT (-0.57), spermatozoa bound per zona-free hamster oocyte (0.64), and percentage of zona-free hamster oocytes penetrated (0.75). The HI were not correlated with the following in vitro tests after freezing and thawing: spermatozoa with normal apical ridges, damaged apical ridges and loose acrosomal caps, extracellular and maximal releasable GOT, and the number of penetrations per zona-free hamster oocyte. The multiple regression correlation coefficient between the HI and four selected variables from three in vitro tests was 0.94. This high correlation indicated that the fertilizing potential of the semen could be accurately predicted with four variables that appeared to measure different properties of the spermatozoa.     

Proportion of males with lower fertility spermatozoa estimated from heterospermic insemination

This study was designed to evaluate the proportion of males with spermatozoa detectably less fertile than the spermatozoa from other males. Previously unpublished and published data from heterospermic trials involving insemination with equal numbers of spermatozoa and resulting in at least 11 offspring from each pair of males were analyzed. The proportion of pairs in which the males sired equivalent numbers of offspring were 0.42, 0.18, 0.33 and 0.09 for trials with fresh boar semen, liquid-stored boar semen, frozen bull semen and fresh rabbit semen, respectively. The calculated proportion of males with less fertile spermatozoa were 0.36, 0.57, 0.42 and 0.70, respectively. Although these differences in fertility would not be apparent in some management systems, a high proportion of ejaculates had spermatozoa that were detectably less fertile.     

Do sire-dam interactions contribute significantly to fertility comparisons in heterospermic insemination trials

The percentage of offspring sired after heterospermic insemination of equal numbers of spermatozoa is believed to be a very sensitive measure of relative in vivo fertility of the inseminated samples. The objective of these trials was to evaluate whether there was a detectable male-female interaction in the fertilizing ability of spermatozoa. If there was such an interaction, we reasoned that the paternity of offspring from individual females in a heterospermic trial the second year would be similar to the paternity of offspring in the same individual females the first year if the same ejaculates were used. Five groups of ewes were inseminated with different combinations of semen (a single Merino ejaculate from one of five rams randomly paired with five different pools of Suffolk semen) in a heterospermic trial. Those ewes conceiving the first year were inseminated in a second breeding season with the same combination of semen used previously. The percentage of lambs sired by each ejaculate/pool of ejaculates was calculated for all lambs born from all ewes inseminated with each semen combination. These percentages would be the expected ratios of Merino-sired:Suffolk-sired lambs if there is no male-female interaction. Ewes in each group were divided into two subgroups: those conceiving only Merino-sired lambs the first year and those conceiving at least one Suffolk-sired lamb the first year. The ratio of Merino-sired lambs:Suffolk-sired lambs did not differ in either subgroup from those expected if there was no male-female interaction. These results are consistent with the absence of a male-female interaction in relative fertilizing ability of spermatozoa.     

Fertility differences among male rabbits determined by heterospermic insemination of fluorochrome-labeled spermatozoa

Spermatozoa from different bucks were stained with different fluorochromes, mixed, and inseminated heterospermically. By altering the interval between insemination and luteinizing hormone injection, spermatozoa were allowed to reside in the female tract approximately 5, 10, or 15 h prior to ovulation. The number of functional spermatozoa, from each male of a pair used, that was transported to the site of fertilization was estimated by counting total number of differently stained spermatozoa that surrounded or fertilized each oocyte. Spermatozoa from split ejaculates within a male competed against each other equally, indicating that the staining procedure did not affect fertilization or functional spermatozoal transport rates. Three pairs of males with high initial semen quality (greater than 80% motility) differed in fertility primarily due to functional spermatozoal transport. Spermatozoal survival in the female tract and capacitation time played a role in differences in male fertility when heterospermic insemination occurred at variable times relative to ovulation. Differences in fertilization not accounted for by spermatozoal transport ratio raised the possibility that rate of egg penetration due to acrosomal enzyme differences may be important in determining male fertility. Therefore, total acrosin, hyaluronidase, and arylsulfatase activity in spermatozoa from specific bucks used in fertilization experiments were determined. Although there were trends favoring high fertility when enzyme content was higher, the difference was significant only for arylsulfatase in one buck.     

Repeated inseminations required for natural fertility in a wild bird population

In most bird species, pairs copulate many times before egg laying. The exact function of repeated inseminations (i.e. successful copulations) is unknown, but several suggestions have been made. We tested the hypothesis that repeated inseminations are required to ensure fertilization of eggs, by using an experimental method where free-ranging male collared flycatchers (Ficedula albicollis) were prevented from inseminating their mates. We show that egg fertility was lower when females had not copulated during the studied part of their fertile period. By counting sperm on the inner perivitelline layer of eggs, we estimated that a minimum of 86 sperm must reach the site of fertilization to ensure average fertility. Using the timing of inseminations and the numbers of sperm on successive eggs, we show that repeated copulations are necessary to achieve an average rate of fertilization of a single clutch. Our results thus provide evidence that repeated inseminations function to ensure fertilization success. We discuss possible constraints on sperm production and utilization that may have contributed to this pattern.     

Radiations and male fertility

During recent years, an increasing percentage of male infertility has to be attributed to an array of environmental, health and lifestyle factors. Male infertility is likely to be affected by the intense exposure to heat and extreme exposure to pesticides, radiations, radioactivity and other hazardous substances. We are surrounded by several types of ionizing and non-ionizing radiations and both have recognized causative effects on spermatogenesis. Since it is impossible to cover all types of radiation sources and their biological effects under a single title, this review is focusing on radiation deriving from cell phones, laptops, Wi-Fi and microwave ovens, as these are the most common sources of non-ionizing radiations, which may contribute to the cause of infertility by exploring the effect of exposure to radiofrequency radiations on the male fertility pattern. From currently available studies it is clear that radiofrequency electromagnetic fields (RF-EMF) have deleterious effects on sperm parameters (like sperm count, morphology, motility), affects the role of kinases in cellular metabolism and the endocrine system, and produces genotoxicity, genomic instability and oxidative stress. This is followed with protective measures for these radiations and future recommendations. The study concludes that the RF-EMF may induce oxidative stress with an increased level of reactive oxygen species, which may lead to infertility. This has been concluded based on available evidences from in vitro and in vivo studies suggesting that RF-EMF exposure negatively affects sperm quality.     

The usefulness of combining traditional sperm assessments with in vitro heterospermic insemination to identify bulls of low fertility as estimated in vivo

To date, no single in vitro assessment can estimate bull fertility. This research was aimed at evaluating the ability of a series of laboratory assessments to assign 50 Holstein Friesian bulls grouped as low (ER-NRR<-1.5), medium (-0.5相似文献   

Grass phasiRNAs and male fertility

Recent studies have indicated that a special type of small noncoding RNAs, phased small-interfering RNAs (phasiRNAs) play crucial roles in many cellular processes of plant development. PhasiRNAs are generated from long RNA precursors at intervals of 21 or 24 nt in plants, and they are produced from both protein-coding gene and long noncoding RNA genes. Different from those in eudicots, grass phasiRNAs include a special class of small RNAs that are specifically expressed in reproductive organs. These grass phasiRNAs are associated with gametogenesis, especially with anther development and male fertility. In this review, we summarized current knowledge on these small noncoding RNAs in male germ cells and their possible biological functions and mechanisms in grass species.     

Observations as to male fertility in the Flemish environment and health studies

We report the observations made on 101 healthy non-smoking men aged 21-40 (50 from two industrial suburbs of the big city of Antwerp and 51 from Peer, a predominantly rural municipality with 14,622 inhabitants, 70 km east of Antwerp, chosen as the "control" area in spite of its intensive agriculture). Persons with known occupational exposures, persons working in a region with characteristics clearly different from the area of residence, and people commuting over long distances were excluded from the study. Sperm morphology was significantly worse in Peer than in Antwerp. Serum testosterone levels were significantly lower in Peer than in Antwerp. The proportions of men with very low and low serum testosterone levels, of men with very low and low spermatozoa concentrations and of men with very low and low percentages of spermatozoa with normal morphology, were all higher in Peer than in Antwerp. We speculate that both the lower testosterone concentrations and the poorer sperm quality are due to disturbance of the hypothalamic-pituitary-testicular function by hormone disrupters. Our data suggest that exposure to levels of environmental pollution which are widespread in developed nations, can have unfavourable effects on endocrine equilibrium and may disturb male fertiline disrupters.     

Sport,doping and male fertility

It is universally accepted that lifestyle interventions are the first step towards a good overall, reproductive and sexual health. Cessation of unhealthy habits, such as tobacco, alcohol and drug use, poor nutrition and sedentary behavior, is suggested in order to preserve/improve fertility in humans. However, the possible risks of physical exercise per se or sports on male fertility are less known. Being “fit” does not only improve the sense of well-being, but also has beneficial effects on general health: in fact physical exercise is by all means a low-cost, high-efficacy method for preventing or treating several conditions, ranging from purely physical (diabetes and obesity) to psychological (depression and anxiety), highly influencing male reproduction. If male sexual and reproductive health could be positively affected by a proper physical activity, inadequate bouts of strength – both excessive intensity and duration of exercise training – are more likely to have detrimental effects. In addition, the illicit use of prohibited drugs (i.e. doping) has reached pandemic proportions, and their actions, unfortunately very often underestimated by both amateur and professional athletes, are known to disrupt at different levels and throughout various mechanisms the male hypothalamic-pituitary-gonadal axis, resulting in hypogonadism and infertility.     

In vitro induction of the acrosome reaction in bull sperm and the relationship to field fertility using low-dose inseminations

The acrosome reaction (AR) is a prerequisite for normal sperm fertilizing capability and can be studied in vitro after induction by various agents. The efficacy of a sperm population to undergo the AR in vivo is expected to influence male fertilizing potential. During the past two decades, a number of attempts have been made to relate the in vitro-induced AR to field fertility in several species. However, to our knowledge, no studies have combined in vitro induction of the AR with the simultaneous detection of sperm viability and acrosomal status using a high-precision flow cytometric technique. Furthermore, large-scale fertility trials using low-dose inseminations are pending. In the current study, the relationship between field fertility and the in vitro-induced AR was investigated using three ejaculates from each of 195 bulls, 156 Holstein and 39 Jersey bulls (Bos taurus), participating in a progeny test program including low-dose inseminations. A range of insemination doses, varying from 2.0 × 10⁶ to 15 × 10⁶ sperm/dose, was obtained by a controlled dilution process applied to each ejaculate. Different insemination doses were distributed at random among 75,610 experimental first inseminations in 4721 herds and 208 artificial insemination (AI) technicians. Simultaneous detection of sperm viability and acrosomal status was achieved using a triple color flow cytometric technique. Sperm samples from the bulls displayed a wide range of ability to acrosome react in response to calcium ionophore A23187. Both reproducibility of the AR response after induction and relationship between ability to acrosome react and field fertility was highly dependent on the definition of AR inducibility. Six basic and six combined AR indices were assessed. The AR index expressing the fraction of acrosome reacted sperm in the live sperm population after induction by ionophore had the highest repeatability, best described the biological variation in the studied population, and yielded the best significant predictive values on field fertility among the 12 indices considered. Moreover, the ability of sperm to acrosome react appeared to be a noncompensable trait that affects fertility regardless of the number of sperm per insemination dose. The current results therefore indicate that this sperm parameter is important in the field and also may play a role in the IVF laboratory.     

The fertility of hypothyroid male mice

Male mice homozygous for the hypothyroid gene mutation were compared with normal siblings to determine whether hypothyroidism induced infertility by impairing sexual behaviour. In addition, the fertility of the hypothyroid mice was examined. The experimental results provide unequivocal evidence that genetically-induced hypothyroidism in male mice does not impair sexual behaviour or cause infertility.     

Lifestyle and fertility: the influence of stress and quality of life on male fertility

Background

Male infertility is a widespread condition among couples. In about 50% of cases, couple infertility is attributable to the male partner, mainly due to a failure in spermatogenesis. In recent times, the crucial role that modifiable lifestyle factors play in the development of infertility have generated a growing interest in this field of study, i.e. aging, psychological stress, nutrition, physical activity, caffeine, high scrotal temperature, hot water, mobile telephone use. Several studies have investigated associations between semen quality and the presence of lifestyle stressors i.e. occupational, life events (war, earthquake, etc.) or couple infertility; overall, these studies provide evidence that semen quality is impaired by psychological stress. In this review, we will discuss the impact of quality of life (modifiable lifestyle factors) and psychological stress on male fertility. In addition, the role that increased scrotal temperature along with inappropriate nutritional and physical exercise attitudes exert on male fertility will be presented.

Conclusion

The decline of male fertility, particularly associated with advancing age, incorrect lifestyles and environmental factors plays an important role on natality, and its consequences on the future on human population makes this an important public health issue in this century. Thus, modification of lifestyle through a structured program of educational, environmental, nutritional/physical exercise and psychological support, combined with the use of nutraceutical antioxidants can prevent infertility and therefore, may help couples to obtain better quality of life and improved possibility to conceive spontaneously or optimize their chances of conception.