conclusions the extract contains substances that are effective on the delivery rate, sex ratio, and the number of newborns in the female rats. it may affect through the ionic changes in the rats, by modifying the activity of follicle-stimulating and testosterone hormones, and/or changing the rate of fertilizing ability of sperms containing y chromosome. this phenomenon may also be due to loweri...

BACKGROUND Adolescents display sexual behaviours and developmental characteristics that place them at risk for Sexually Transmitted Diseases (STDs). Because young people experiment sexually and because of the consequences of indiscriminate sexual activities on the youth, there is the need to mount sex education programmes that are geared towards enlightenment and appropriate education about sex...

Studies of sex-ratio conflict in the eusocial Hymenoptera (ants, bees and wasps) have provided the most rigorous tests of kin selection theory. The hymenopteran haplodiploid system of sex determination generally renders workers more closely related to their sisters than to their brothers, whereas queens are equally related to their sons and daughters. Kin selection theory therefore predicts tha...

Throughout the animal kingdom, nervous systems differ between sexes. Sexual dimorphisms in neuroanatomical, physiological, and neurochemical parameters are reflected by sex-specific forms of behavior, in particular with regard to reproduction, and sex differences in neuroendocrine regulation. The present volume of Biomedical Reviews is mainly concerned with sex differences in the mammalian and ...

The facultative control of primary sex ratio by breeding birds has become a major focus in evolutionary biology in recent years. A combination of well-developed theoretical literature and rapid publication of empirical results has created considerable confusion, with controversial claims for both extreme control of primary sex ratio versus no control around inherent random variability. We prese...

BACKGROUND Women's perceived control over condom use has been found to be an important determinant of actual condom use in some studies. However, many existing analyses used cross-sectional data and little quantitative information exists to characterize the relationships between perceived control and actual condom use among sex worker populations. METHODS We assessed the association between m...

The effects of sex control and twinning techniques on determination of optimal culling parity of cows in beef cow-calf production systems were deterministically analyzed using a herd model simulation. The model simulated the annualized net revenue as an economic indicator during the whole life cycle of a cow. Biological factors (survivability, growth, reproduction, and feed requirements) and ec...