A sound way towards reversible vasectomies
THE MOST reliable means of contraception for men—and one that cannot fail or be forgone in the heat of the moment—is a vasectomy. But the procedure is largely irreversible: it involves stopping the flow of sperm from the testes by cutting conduits known as the vas deferens and sealing them or tying them off. A reconnection, after a reconsideration, is no small task.文章源自The Economist Digest-https://te.qinghe.me/187.html
Researchers are now examining a different tack: blocking the vas deferens using compounds that combine to form a barrier that can later be removed. Lab trials have involved four separate injections to establish a sperm-proof barrier, which could later be dissolved using a blast of focused, infrared light.文章源自The Economist Digest-https://te.qinghe.me/187.html
Aware that repeated injections into the penis might affect men’s willingness to undergo such a procedure, Wanhai Xu, a urologist at Harbin Medical University in China, and colleagues propose a different idea: a barrier that can be put in place with one injection and broken down with ultrasound.文章源自The Economist Digest-https://te.qinghe.me/187.html
Dr Xu’s recipe includes three parts, principally a polymer known as a hydrogel that thickens inside the body and is already approved for medical use. Crucially, in that gel were plenty of thioketals, compounds that fall apart when exposed to reactive, oxygen-containing molecules, plus just a sprinkle of titanium dioxide—an inert material that, when exposed to ultrasound, releases just those molecules.文章源自The Economist Digest-https://te.qinghe.me/187.html
To check their work, Dr Xu’s team employed a few dozen male rats. Some were given a traditional vasectomy, others an injection of the new material and the rest injected with saline, as a control. Each was then permitted to follow its essential nature with four females. Only those rats given the saline sired offspring.文章源自The Economist Digest-https://te.qinghe.me/187.html
The real test, as the team reports in ACS Nano, a nanotechnology journal, came next: half the rats given the new treatment were exposed to a blast of ultrasound. That evidently dissolved the hydrogel in the creatures’ pipes: they could again reproduce, while those not thusly blasted stayed sterile.文章源自The Economist Digest-https://te.qinghe.me/187.html
What works in rats, alas, does not always work in humans, so further trials will be needed. But Dr Xu is hopeful that these findings represent a sound idea for a reversible contraceptive—with fewer sticking points.文章源自The Economist Digest-https://te.qinghe.me/187.html 文章源自The Economist Digest-https://te.qinghe.me/187.html
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