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Cosmic particle accelerator shock
In brief–
JOHN CHUMACK/SCIENCE PHOTO LIBRARY
COULD blasts of gas from deep beneath the lunar surface be giving the moon a surprisingly fresh-faced look? If they are, our picture of the moon’s geological past will have to change just as dramatically. The moon was thought to be geologically inactive. The last volcanoes erupted on it nearly a billion years ago, and meteor impacts were believed to be the only thing that could be altering its surface. That belief is set to change. Carle Pieters of Brown University in Providence, Rhode Island, and her colleagues studied images from the Apollo missions of the 1960s and ’70s along with spectrographic readings from more recent space probes. The team focused on the Ina structure, an unusual-looking area nearly 3 kilometres in diameter near the moon’s equator. It has fewer craters, sharper topography, and is far brighter than the surrounding surface. This “freshness” suggests it has not been suffered many major impacts or much weathering by solar wind and microscopic meteors, which can dull and blunt surface features (Nature, vol 444, p 184). The researchers think that the fresh features were created when gas emissions blew off a previous layer of rock to expose a fresh surface as recently as 10 million years ago – a phenomenon that could still be under way. “The freshness of these surfaces is hard to account for in any other way,” says Pieters.
18 | NewScientist | 11 November 2006
061111_N_In Brief_p17_18.indd 18
Have we misunderstood a crucial part of HIV? IN cash-starved regions of the world, deciding who should get anti-retroviral drugs for HIV is a tough call. Now it seems that one of the main tools for making that decision may be less reliable than it appeared. World Health Organization guidelines recommend starting anti-retroviral drugs when someone’s CD4 cell count has fallen below 350 cells per microlitre, an indicator of HIV infection, or for people with symptoms of AIDS whose CD4 count has dropped to below 200.
Brian Williams of the WHO and his colleagues studied HIV-positive and HIV-negative populations in eight African countries including Ethiopia, South Africa, Uganda and Zambia. They found that between 3 and 5 per cent of HIV-negative people had CD4 counts below 350. What’s more, when people with low pre-infection cell counts did contract HIV, and received anti-retrovirals, they survived for about nine years – the same as people with high counts (Journal of Infectious
Diseases, vol 194, p 1450). The new findings call into question just how much we understand about CD4 cells and their interaction with HIV, says Williams. “Generally, if you have high CD4 counts you can be considered to be doing pretty well and if you have very low counts, you’re in trouble,” says Williams. But CD4 counts can vary a lot naturally so if you follow the WHO guidelines to the letter, then some people started on antiretrovirals would not even be infected with HIV, he concludes. TOM MCHUGH/SPL
How the moon sheds its old skin
Cosmic particle accelerator shock SHOCK waves radiating out from galaxy clusters could be the puzzling powerhouses that have boosted some cosmic rays to ultra-high energies. Joydeep Bagchi at the University of Pune, India, and his team picked up giant arcs of radio waves around the Abell 3376 galaxy cluster using the Very Large Array radio telescope in New Mexico. “We’ve seen similar structures produced by shock waves around supernovae, but never on this scale – 6 million light years across,” he says. The team believes that these shock waves could have been produced either by collisions of matter as galaxies are pulled into the cluster or by gas falling into it (Science, vol 314, p 791). To produce the radio signals, the shock waves must be speeding up electrons to almost the speed of light, says Bagchi. He thinks that the same process might also accelerate larger charged particles to extraordinary speeds – possibly creating the mysterious ultrahigh-energy cosmic rays that have been detected on Earth. “Until now, we have had no idea what their source is,” says Bagchi. “This could be it.”
Bite like a spider, sting like a chilli A TARANTULA’S bite is hot stuff. It causes pain by triggering the same receptors on nerve cells as chillies do. The venom of Psalmopoeus cambridgei – the Trinidad chevron tarantula, a native of the West Indies – activates a nerve cell receptor called TRPV1, say David Julius and colleagues at the University of California, San Francisco. This receptor also responds to capsaicin, the chemical that gives chilli its hot, burning taste. Julius’s team tested the venom on normal human embryonic kidney cells, which contain the TRPV1 receptor, and other, modified cells
without the receptor. Normal kidney cells produced a surge of calcium ions when exposed to the venom, whereas cells lacking the receptor did not, proving that the receptor is activated by the venom. The team then pinpointed the three compounds in the venom that were responsible and applied them to the feet of mice with or without the TRPV1 receptor. Mice with the receptor showed signs of pain, and their feet swelled up (Nature, DOI: 10.1038/nature05285). Further tests revealed that crude venom from at least one other species of tarantula, which is found in southeast Asia, also activates the capsaicin receptor, leading the team to suggest that many other spiders and perhaps other species use a similar hot trick to catch prey or deter predators.
www.newscientist.com
6/11/06 5:10:26 pm
JOHN CHUMACK/SCIENCE PHOTO LIBRARY
COULD blasts of gas from deep beneath the lunar surface be giving the moon a surprisingly fresh-faced look? If they are, our picture of the moon’s geological past will have to change just as dramatically. The moon was thought to be geologically inactive. The last volcanoes erupted on it nearly a billion years ago, and meteor impacts were believed to be the only thing that could be altering its surface. That belief is set to change. Carle Pieters of Brown University in Providence, Rhode Island, and her colleagues studied images from the Apollo missions of the 1960s and ’70s along with spectrographic readings from more recent space probes. The team focused on the Ina structure, an unusual-looking area nearly 3 kilometres in diameter near the moon’s equator. It has fewer craters, sharper topography, and is far brighter than the surrounding surface. This “freshness” suggests it has not been suffered many major impacts or much weathering by solar wind and microscopic meteors, which can dull and blunt surface features (Nature, vol 444, p 184). The researchers think that the fresh features were created when gas emissions blew off a previous layer of rock to expose a fresh surface as recently as 10 million years ago – a phenomenon that could still be under way. “The freshness of these surfaces is hard to account for in any other way,” says Pieters.
18 | NewScientist | 11 November 2006
061111_N_In Brief_p17_18.indd 18
Have we misunderstood a crucial part of HIV? IN cash-starved regions of the world, deciding who should get anti-retroviral drugs for HIV is a tough call. Now it seems that one of the main tools for making that decision may be less reliable than it appeared. World Health Organization guidelines recommend starting anti-retroviral drugs when someone’s CD4 cell count has fallen below 350 cells per microlitre, an indicator of HIV infection, or for people with symptoms of AIDS whose CD4 count has dropped to below 200.
Brian Williams of the WHO and his colleagues studied HIV-positive and HIV-negative populations in eight African countries including Ethiopia, South Africa, Uganda and Zambia. They found that between 3 and 5 per cent of HIV-negative people had CD4 counts below 350. What’s more, when people with low pre-infection cell counts did contract HIV, and received anti-retrovirals, they survived for about nine years – the same as people with high counts (Journal of Infectious
Diseases, vol 194, p 1450). The new findings call into question just how much we understand about CD4 cells and their interaction with HIV, says Williams. “Generally, if you have high CD4 counts you can be considered to be doing pretty well and if you have very low counts, you’re in trouble,” says Williams. But CD4 counts can vary a lot naturally so if you follow the WHO guidelines to the letter, then some people started on antiretrovirals would not even be infected with HIV, he concludes. TOM MCHUGH/SPL
How the moon sheds its old skin
Cosmic particle accelerator shock SHOCK waves radiating out from galaxy clusters could be the puzzling powerhouses that have boosted some cosmic rays to ultra-high energies. Joydeep Bagchi at the University of Pune, India, and his team picked up giant arcs of radio waves around the Abell 3376 galaxy cluster using the Very Large Array radio telescope in New Mexico. “We’ve seen similar structures produced by shock waves around supernovae, but never on this scale – 6 million light years across,” he says. The team believes that these shock waves could have been produced either by collisions of matter as galaxies are pulled into the cluster or by gas falling into it (Science, vol 314, p 791). To produce the radio signals, the shock waves must be speeding up electrons to almost the speed of light, says Bagchi. He thinks that the same process might also accelerate larger charged particles to extraordinary speeds – possibly creating the mysterious ultrahigh-energy cosmic rays that have been detected on Earth. “Until now, we have had no idea what their source is,” says Bagchi. “This could be it.”
Bite like a spider, sting like a chilli A TARANTULA’S bite is hot stuff. It causes pain by triggering the same receptors on nerve cells as chillies do. The venom of Psalmopoeus cambridgei – the Trinidad chevron tarantula, a native of the West Indies – activates a nerve cell receptor called TRPV1, say David Julius and colleagues at the University of California, San Francisco. This receptor also responds to capsaicin, the chemical that gives chilli its hot, burning taste. Julius’s team tested the venom on normal human embryonic kidney cells, which contain the TRPV1 receptor, and other, modified cells
without the receptor. Normal kidney cells produced a surge of calcium ions when exposed to the venom, whereas cells lacking the receptor did not, proving that the receptor is activated by the venom. The team then pinpointed the three compounds in the venom that were responsible and applied them to the feet of mice with or without the TRPV1 receptor. Mice with the receptor showed signs of pain, and their feet swelled up (Nature, DOI: 10.1038/nature05285). Further tests revealed that crude venom from at least one other species of tarantula, which is found in southeast Asia, also activates the capsaicin receptor, leading the team to suggest that many other spiders and perhaps other species use a similar hot trick to catch prey or deter predators.
www.newscientist.com
6/11/06 5:10:26 pm