Sunday, 31 August 2008

Signal jamming

A compound that acts like a jamming device, preventing bacteria from detecting host signalling and bacterial signaling, provides promise for a broad-spectrum approach to treating bacterial infection.

At least 25 bacteria succeed as pathogens, in part, because they can spy on their hosts and communicate with other bacteria. When bacteria detect certain signals, they respond by expressing bacterial proteins that increase their virulence. Sperandio and colleagues now report that they can reduce the effects of bacterial infection by jamming the bacterial signal decoder.

Sperandio and colleagues found that a small molecule, dubbed LED209, binds QseC, the bacterial protein that normally detects external signalling. LED209-treatment not only prevented the upregulation of virulence genes in infected cultured cells, it also protected animals against Esherichia coli, Salmonella typhimurium and Francisella tularensis in animal models. For example, 9 days after innoculation with F. tularensis, 80% of LED209-treated mice were still alive, compared with only 10% of untreated mice.

Although bacteria tend to evolve resistance to drugs that affect bacterial health, LED209 does not have adverse effects on bacterial health, but just prevents the expression of virulence proteins. Consequently, bacteria are less likely to develop resistance to LED209 and similar drugs, suggesting that that such drugs could make excellent broad-spectrum antibiotics.

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Saturday, 23 August 2008

Got the not-so blues

For blue-footed boobies, foot colour is a big deal -- such a big deal, in fact, that females lose their enthusiasm for laying healthy eggs when their mates feet lose their blue brilliance.

Blue-footed boobies, who live on the Galapagos Islands and the eastern Pacific coastline, tend to lead monogamous lifestyles. Each year, females usually lay 2 eggs, of equal size, about 4 days apart. Roxana Torres and colleagues let females lay the first egg, and then used a non-toxic marker to make their partners' feet look duller, suggesting the partners were unhealthy. Consequently, they found, second eggs were layed later and were considerably smaller than expected.

This finding meets with predictions: if females want the best for their babies, then they should vary how much energy they invest into producing offspring depending on how well they suspect their offspring will survive. If the males are unhealthy -- or in the case of blue-footed boobies, are less blue -- then the offspring may have a harder time surviving. Moreover, if the female blue-footed boobies invest more attention to the older egg, then at least one offspring is likely to survive. Perhaps there is something to putting all your eggs in one basket after all.

Presumably, the fact that the second egg is smaller than the first and comes later than expected (making it altogether less likely to succeed) is not the consequence of a decision on the part of the lady bird, but is rather an involuntary response. Do such responses occur in humans too? Is it possible that women coupled with unhealthy (or even seemingly unhealthy) men don't invest as much in as-yet unborn offspring as they could -- unconsciously of course?

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Friday, 22 August 2008

Phenomenal photos

Red veined darter

Some truly amazing photos of wet insects, taken by German Photographer Martin Amm.
More of these available at Zooillogix.

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Thursday, 21 August 2008

Getting nosey with skin cancer

Scientists have identified the compounds that give skin cancer its unique smell, suggesting that an electronic nose could help doctors sniff out skin cancer.

Studies have previously established that dogs can smell cancer and that cancerous skin has a different odor profile than non-cancerous skin. Building on these finding, Michelle Gallagher and colleagues used gas chromatography/mass spectrometry to sample the air above cancerous and non-cancerous skin and, for the first time, determined the chemical composition of cancer's unique smell.

These findings were announced yesterday at the American Chemical Society Meeting in Philadelphia. The authors hope to develop an electronic nose that could be used by doctors to quickly, and non-invasively, identify skin cancer. Skin cancer, the most common form of cancer is the US, is currently diagnosed by time consuming, and invasive, biopsies. Lung cancer may also be detectable with an electronic nose.

Interestingly, TB also has a unique odor, which rats and honeybees can detect. In trials, however (and perhaps unsurprisingly), patients have balked at the idea of being diagnosed by a rat. Perhaps odor profiles of other diseases can also be detected electronically. Who nose?

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Tuesday, 19 August 2008

Conniving courters

When it comes to courting, male fish sometimes pretend they’re after love when they actually want something else -- eggs for dinner.

Reporting in the Journal of Fish Biology, Suzanne Grey and colleagues followed male Telmatherina sarasinorum, also known as sailfin silversides, as they foraged for food in their native habitat, the Malili Lakes of Indonesia. Curiously, the brightly coloured male T. sarasinorum would occasionally display ritual courting behaviour to the females of a related species, Telmatherina antoniae. But whereas males and females normally quiver at the end of the courting ritual, indicating that eggs and sperm have been released, only the female fish would quiver in these curious courtships. And when the females swam off, these males would immediatly begin eating the eggs. This deceptive behaviour, dubbed ‘sneaky egg-eating’, has never been described before.

Sneaky-egg eating occurs at a low but appreciable frequency, the authors note, and probably evolved in part because of a lack of alternative sources of nutrition.

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