Fears that sex-linked chromosomes, such as the male Y chromosome, are doomed to extinction have been refuted in a new genetic study which examines the sex chromosomes of chickens.

Scientists have shed new light on how sperm navigate the female reproductive tract, "crawling" along the channel walls and swimming around corners -- with frequent collisions.

A long-term follow-up analysis of participants in the Step Study, an international HIV-vaccine trial, has confirmed that certain subgroups of male study participants were at higher risk of becoming infected after receiving the experimental vaccine compared to those who received a placebo. The vaccine used in the study did not contain the HIV virus, but it did contain HIV genes which were delivered to cells using a vector that employed a type of cold virus known as adenovirus serotype 5 (Ad5).

A new study has identified the risk of major birth defects associated with different types of assisted reproductive technology. In the most comprehensive study of its kind in the world, researchers compared the risk of major birth defects for each of the reproductive therapies commonly available internationally, such as: IVF (in vitro fertilization), ICSI (intracytoplasmic sperm injection) and ovulation induction. They also compared the risk of birth defects after fresh and frozen embryo transfer.

The proportion of insured girls and young women completing the human papillomavirus (HPV) vaccine among those who initiated the series has dropped significantly -- as much as 63 percent -- since the vaccine was approved in 2006, according to new research.

Prostate cancer cells that defy treatment and display heightened tumor-generating capacity can be identified by levels of prostate specific antigen (PSA) expressed in the tumor cells, scientists have found.

Insect glands are responsible for producing a host of secretions that allow bees to sting and ants to lay down trails. New research focuses on secretions from glands in the reproductive tract that help sperm survive and guide the sperm on the trip to fertilize an egg. The gene that controls the development of these glands in fruit flies provides important information about gland development in all insects, as well as potential clues to similar human reproductive glands.

A new study suggests that exposure to estrogenic chemicals in the womb or during childhood could have a long-term effect on female fertility. Limiting such exposures, including minimizing use of soy-based baby formula, would be a step toward maintaining female reproductive health.

Researchers report that male pseudoscorpions treated with the antibiotic tetracycline suffer significantly reduced sperm viability and pass this toxic effect on to their untreated sons. They suggest a similar effect could occur in humans and other species.

Researchers are a step closer to launching human clinical trials involving the use of an innovative stem cell therapy to fight the virus that causes AIDS.