INTRODUCTION Rare foci of sperm production may be found in up to 60% of men with nonobstructive azoospermia (NOA). Sperm production, if present, is minimal for sperm appearance in the ejaculate. Given that there are no treatment options to restore fertility, sperm retrieval is the only alternative to find testicular sperm than then can be used for in vitro fertilization (IVF). Among sperm acqui...

Male infertility is the result of a variety of highly treatable conditions. The critical step in treating male infertility is to evaluate properly every male partner of an infertile couple and to generate the proper treatment strategy. There are many medical and surgical options that can help most couples overcome male factor infertility. Male infertility can most easily be broken down into pro...

Mass-specific metabolic rate, the rate at which organisms consume energy per gram of body weight, is negatively associated with body size in metazoans. As a consequence, small species have higher cellular metabolic rates and are able to process resources at a faster rate than large species. Since mass-specific metabolic rate has been shown to constrain evolution of sperm traits, and most of the...

Spermatogenesis and sperm maturation are complex processes which are affected by a myriad of endocrine, paracrine and neural factors. In birds, regulation of testicular and excurrent duct growth, maturation and function are only poorly understood. As the quality and quantity of sperm produced may be altered at any of several points during sexual maturation, spermatogenesis or during extragonada...

Theory predicts that males should increase overall investment in ejaculate expenditure with increasing levels of sperm competition. Since ejaculate production is costly, we may expect males to tailor their reproductive investment according to anticipated levels of sperm competition. Here, we investigate plasticity in ejaculate investment in response to cues of population average levels of sperm...

BACKGROUND Metals can cause male infertility through affection of spermatogenesis and sperm quality. Strong evidences confirm that male infertility in metal-exposed humans is mediated via various mechanisms such as production of reactive oxygen species (ROS). Flavonoids have antioxidant and metal chelating properties which make them suitable candidates for neutralizing adverse effects of metals...

Sperm production is a crucial factor for the potential reproductive success of males in many species (Nakatsuru & Kramer, 1982). Especially under strong sperm competition, higher sperm numbers in the ejaculates are likely to increase a male’s chance of fertilization (Parker et al., 1996). But sperm production is limited by physiological constraints, e.g. by testis size, which often depends on t...

1. Testosterone (T) is a key mediator in the expression of numerous morphological and behavioural traits in mammals, but the factors underlying individual variation in circulating T levels are poorly understood. 2. The intimate structural integration of sperm and T production within the testes, alongside the dependency of sperm production on high levels of T, suggests that T requirements for sp...