Messing with the plugs that male mosquitoes deposit in female reproductive tracts could be a way to slow the spread of malaria, says a new study in PLOS Biology.

Such ‘mating plugs’, formed by proteins found in semen, are seen in many species. They are thought to prevent re-mating and / or help with sperm storage. In the new paper, Flaminia Catteruccia, of Imperial College London, and colleagues detail the composition of the plug used by males of the malarial mosquito species Anopheles gambiae.

They demonstrate that inhibiting plug formation prevents sperm storage but is not a major barrier to re-insemination. Given these mosquitoes only mate once, inhibition of plugs and the consequent problems with sperm retention could clearly severely restrict the animal’s numbers were it to be widespread.

“If in the future we can develop an inhibitor that prevents the coagulating enzyme doing its job inside male An. gambiae mosquitoes in such a way that can be deployed easily in the field – for example in the form of a spray as it is done with insecticides – then we could effectively induce sterility in female mosquitoes in the wild,” says Catteruccia (press release). “This could provide a new way of limiting the population of this species of mosquito, and could be one more weapon in the arsenal against malaria.”

Catteruccia and colleagues show that the plug is formed of cross-linking of seminal proteins mediated by a transglutaminase enzyme specific to male glands that produce the semen. They demonstrate that interfering with the expression of this transglutaminase in males inhibits plug formation.

“This is a very novel idea, which is really neat,” Steve Lindsay, of the London School of Hygiene and Tropical Medicine, told the BBC. “We will need a whole variety of different tools to combat malaria, and this may have a function, but there is no one magic bullet.”

See also: Finding the Right Plugin: Mosquitoes Have the Answer, PLOS Biology.

Image: mosquitoes courtesy of Sam Cotton, University College London.

An exploratory stem cell therapy developed in the UK has successfully restored vision to eight partially sighted patients. (Times, FT)

The treatment, developed by scientists at the North East England Stem Cell Institute in Newcastle, UK, will now be further tested in a larger trial of 25 patients.

All eight of the patients who took part in the first trial of the treatment reported improved vision, reduced eye pain and a better quality of life. Russell Turnbull, 38, was one of the participants. He lost most of the sight from his right eye in 1994 when he was sprayed in the face with ammonia while trying to break up a fight. The chemical burnt his cornea, leaving him with cloudy vision, pain on every blink and extreme sensitivity to light. His vision was restored after stem cells from his good eye were used to repair his damaged one.

“This has transformed my life,” Turnbull, told the Financial Times. “I’m working, I can go jet skiing and also ride horses,” he adds.