The authors of the World Health Organization Semen Analysis Manual are to be congratulated on producing a new edition; it is an essential tool to disseminate good practice in andrology. However, the tests described have poor prognostic power to predict a man's fertility and show little about the underlying causes of sub-fertility. This commentary urges a revival of research into the diagnosis o...

The silence about population growth in recent decades has hindered the ability of those concerned with ecological change, resource scarcity, health and educational systems, national security, and other global challenges to look with maximum objectivity at the problems they confront. Two central questions about population--(1) is population growth a problem? and (2) what causes fertility decline...

While demography has made many valuable contributions to the analysis of contemporary demographic reversals, the discipline seems as far as ever from explaining the dynamics of fertility change. Commentaries on “populations” routinely link fertility control and small families with progress, modernity, and western values; in “traditional” societies, fertility regulation is left to chance, God, a...

Most species with a long life span have few offspring while species with a short life span have many offspring. This evolutionary trade-off between fertility and body maintenance, based on the theory of r/K-selection, is a central theme in the theory of life history regulation. This trade-off is not only found between various species but also between individuals within one species. There is acc...

Freshly ejaculated spermatozoa are incapable or poorly capable of fertilizing an oocyte. The fertilization aptness of spermatozoa depends on the appropriate and time-dependent acquisition of hyperactivation, chemotaxis, capacitation, and the acrosome reaction, where calcium (Ca(2+)) is extensively involved in almost every step. A literature review showed that several ion channel proteins are li...

The queen conch Strombus gigas represents one of the most important fishery resources of the Caribbean but heavy fishing pressure has led to the depletion of stocks throughout the region, causing the inclusion of this species into CITES Appendix II and IUCN's Red-List. In Mexico, the queen conch is managed through a minimum fishing size of 200 mm shell length and a fishing quota which usually r...

Environmental factors influence the dynamics and regulation of biological populations through their influences on demographic variables, but demographic mechanisms of population regulation have received little attention. We investigated the demographic basis of regulation of Columbian ground squirrel (Spermophilus columbianus) populations under natural and experimentally food-supplemented condi...

BACKGROUND The task force on plants for fertility regulation in men continued with its program to identify novel prototypes in plants alleged to have fertility regulating properties. Nigella Sativa seeds are frequently used in folk medicine in the Middle East and some Asian countries for the promotion of good health and treatment of many ailments. OBJECTIVE To evaluated the role of alcoholic ...

The adipocyte-derived hormone leptin acts in the brain to modulate the central driver of fertility: the gonadotropin releasing hormone (GnRH) neuronal system. This effect is indirect, as GnRH neurons do not express leptin receptors (LEPRs). Here we test whether GABAergic or glutamatergic neurons provide the intermediate pathway between the site of leptin action and the GnRH neurons. Leptin rece...