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zoom RSS 超音波による避妊治療の可能性

<<   作成日時 : 2012/02/02 20:10   >>

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超音波で精子数を減らす

画像 ラットについての研究によれば音波により不妊レベルまで精子数を減らせるという。
 ビル&メリンダゲイツ財団からの助成金を獲得したノースカロライナ大学の研究者によって研究が進められている。15分2回で精子数を大幅に減らせるという。
 人の場合、精子数が1ミリリットルあたり1500万未満になると妊娠させにくくなる。ラットの精子数は1000万以下にまで低下した。
 実際に避妊治療に使うまでにはまだまだ研究が必要である。

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30 January 2012 Last updated at 01:38 GMT
Testicular zap 'may stop sperm'
http://www.bbc.co.uk/news/health-16756381

A dose of ultrasound to the testicles can stop the production of sperm, according to researchers investigating a new form of contraception.

A study on rats published in Reproductive Biology and Endocrinology showed that sound waves could be used to reduce sperm counts to levels that would cause infertility in humans.
Researchers described ultrasound as a "promising candidate" in contraception.
However, far more tests are required before it could be used.
The concept was first proposed in the 1970s, but is now being pursued by researchers at the University of North Carolina who won a grant from the Bill & Melinda Gates Foundation.
They found that two, 15-minute doses "significantly reduced" the number of sperm-producing cells and sperm levels.
It was most effective when delivered two days apart and through warm salt water.
In humans, the researchers said men were considered to be "sub-fertile" when sperm counts dropped below 15 million sperm per millilitre.
The sperm count in rats dropped to below 10 million sperm per millilitre.
Lead researcher Dr James Tsuruta said: "Further studies are required to determine how long the contraceptive effect lasts and if it is safe to use multiple times."
The team needs to ensure that the ultrasound produces a reversible effect, contraception not sterilisation, as well as investigate whether there would be cumulative damage from repeated doses.
Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, said: "It's a nice idea, but a lot more work is needed."
He said that it was likely that there would be recovery of sperm production, but the "sperm might be damaged and any baby might be damaged" when sperm production resumed.
"The last thing we want is a lingering damage to sperm," he said.

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Therapeutic ultrasound as a potential male contraceptive: power, frequency and temperature required to deplete rat testes of meiotic cells and epididymides of sperm determined using a commercially available system
James K Tsuruta, Paul A Dayton, Caterina M Gallippi, Michael G O'Rand, Michael A Streicker, Ryan C Gessner, Thomas S Gregory, Erick JR Silva, Katherine G Hamil, Glenda J Moser and David C Sokal

Reproductive Biology and Endocrinology 2012, 10:7 doi:10.1186/1477-7827-10-7
Published: 30 January 2012
Abstract (provisional)
Background
Studies published in the 1970s by Mostafa S. Fahim and colleagues showed that a short treatment with ultrasound caused the depletion of germ cells and infertility. The goal of the current study was to determine if a commercially available therapeutic ultrasound generator and transducer could be used as the basis for a male contraceptive.

Methods
Sprague-Dawley rats were anesthetized and their testes were treated with 1 MHz or 3 MHz ultrasound while varying power, duration and temperature of treatment.

Results
We found that 3 MHz ultrasound delivered with 2.2 Watt per square cm power for fifteen minutes was necessary to deplete spermatocytes and spermatids from the testis and that this treatment significantly reduced epididymal sperm reserves. 3 MHz ultrasound treatment reduced total epididymal sperm count 10-fold lower than the wet-heat control and decreased motile sperm counts 1,000-fold lower than wet-heat alone. The current treatment regimen provided nominally more energy to the treatment chamber than Fahim's originally reported conditions of 1 MHz ultrasound delivered at 1 Watt per square cm for ten minutes. However, the true spatial average intensity, effective radiating area and power output of the transducers used by Fahim were not reported, making a direct comparison impossible. We found that germ cell depletion was most uniform and effective when we rotated the therapeutic transducer to mitigate non-uniformity of the beam field. The lowest sperm count was achieved when the coupling medium (3% saline) was held at 37 degrees C and two consecutive 15-minute treatments of 3 MHz ultrasound at 2.2 Watt per square cm were separated by 2 days.

Conclusions
The non-invasive nature of ultrasound and its efficacy in reducing sperm count make therapeutic ultrasound a promising candidate for a male contraceptive. However, further studies must be conducted to confirm its efficacy in providing a contraceptive effect, to test the result of repeated use, to verify that the contraceptive effect is reversible and to demonstrate that there are no detrimental, long-term effects from using ultrasound as a method of male contraception.

The complete article is available as a provisional PDF. The fully formatted PDF and HTML versions are in production.

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