Sperm Motility
 Sperm need to be activated by chemicals in the vagina before they can set off for their rendezvous with an egg, say researchers who have discovered a new set of molecular "keys" responsible for turning their engines on.
Australian scientist Dr Gerard Gibbs from the Monash Institute of Reproduction and Development in Melbourne will present his research at the Australian Health and Medical Research Congress in Sydney next week.
Sperm tails are the molecular motors that drive the cells towards the waiting egg. As such, they are essential to fertility. Gibbs and his team have revealed that the rod-like structures on the surface of these tails, known as outer dense fibres, are important in telling sperm when to start swimming.
activating sperm
It appears that chemicals in the vagina activate proteins along the fibres, setting the tail into action.
Scientists discovered some 40 years ago that sperm need to incubate in the female reproductive tract before becoming mobile.
With in vitro fertilisation scientists artificially activate the tails by exposing them to certain chemicals. The period of incubation, known as capacitation, takes around two hours. During this time the sperm undergo a complex series of molecular steps that eventually activate their tails.
"Sperm, when they come out of the male, are not immediately able to fertilise an egg and there's this period of incubation in the female reproductive tract where there's a whole lot of molecular changes which take place on the surface of the sperm," Gibbs said.
"Those molecular changes have to tell the inside of the sperm tail to start beating furiously so that it can swim and get to the egg."
To date only 14 molecules had been identified. Gibbs and his team have now observed about 80 molecules and identified 20.
The findings will be submitted for publication in the next 12 months after identification is confirmed.
The research could lead to a new male contraceptive that disables the sperm's tail and so prevents the sperm from fertilising an egg, Gibbs said.
Paul Ellis - Men's Health 
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