Scientists have found a way to stop sperm swimming, making the long-awaited male contraceptive pill a step closer to fruition.
Studies by researchers at King’s College Hospital, London, suggest the pill works within three hours and lasts for two days, so it is taken when required.
Published: 12:53 BST, 9 October 2012| Updated: 15:12 BST, 9 October 2012 114 View comments.
The mutation resulted in sperm tails that were 17 per cent shorter than normal, with a 50 per cent reduction in sperm production.
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In laboratory tests using mice, the team engineered a mutation in a gene called RABL2, which delivers protein fuel to the engine in a sperm's tail, known as the axoneme.
And because the gene is found elsewhere in the body, such as tissues in the brain, liver and kidneys, the pill would need to be programmed to work only on the testes.
Other forms of male contraception being developed include an injection given to men once a month.
A two-year trial in China involving 1,000 men found the injections were 95 per cent effective at preventing pregnancy.
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The research, led by scientists at Monash University in Melbourne, may also provide clues on possible causes of male infertility.
These paralyse certain muscles in the male reproductive system, causing a temporary block of the release of semen while having no adverse effects on libido, sexual performance or sensation, so the man still has an orgasm, but produces no fluid.
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All of the males carrying this mutation were sterile. 'But there were no pups born after six weeks.
The pill uses compounds found in blood pressure and anti-psychotic medication used in the Sixties, which were found to have the side-effect of ‘dry ejaculation’
Previous research has found that 55 per cent of men would be willing to take a male contraceptive pill.
The testosterone jab is administered in the buttocks and works by regulating two brain chemicals to block sperm production temporarily.
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Alternative therapy: A jab to halt sperm production is also being developed.
'The challenge with developing the male pill isn't rendering the sperm infertile, but turning them back on again,' she added.
Swimmers: By disrupting the fuel source that powers sperm to swim, men can be made temporarily infertile.
Lead researcher Professor Moira O'Bryan, of Monash University's School of Biomedical Sciences, said a future male pill might work to inhibit the RABL2 gene rather than change it permanently.
But a third of the dropped out of the trial, suggesting they were unwilling to undergo the ordeal of monthly injections and potential side-effects that include mood swings, lower sex drive and acne.
Another option is a pill that prevents sperm from being released on ejaculation.
The research was done in conjunction with the universities of Cambridge and Newcastle in the UK and published in the journal PLoS Genetics.
They all behaved normally,' Professor O'Bryan told the Sydney Morning Herald.
But a British study published in 2010 found that women didn’t trust men to take a contraceptive pill every day.
All the mice with the mutated gene were infertile and their sperm unable to swim.
By ascertaining how to cut off the power supply that enables sperm to move, a man's wrigglers can now left twitching rather than swimming.
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