The signature of hot hydrogen in the atmosphere of the extrasolar planet HD 209458b

About ten per cent of the known extrasolar planets are gas giants that orbit very close to their parent stars. The atmospheres of these 'hot Jupiters' are heated by the immense stellar irradiation. In the case of the planet HD 209458b, this energy deposition results in a hydrodynamic state in the upper atmosphere, allowing for sizeable expansion and escape of neutral hydrogen gas. HD 209458b was the first extrasolar planet discovered that transits in front of its parent star. The size of the planet can be measured using the total optical obscuration of the stellar disk during an observed transit, and the structure and composition of the planetary atmosphere can be studied using additional planetary absorption signatures in the stellar spectrum. Here we report the detection of absorption by hot hydrogen in the atmosphere of HD 209458b. Previously, the lower atmosphere and the full extended upper atmosphere of HD 209458b have been observed, whereas here we probe a layer where the escaping gas forms in the upper atmosphere of HD 209458b.     

Influence of prey movement on the aim of predatory strikes of the western rattlesnake ( Crotalus Viridis )

The purpose of this study was to determine whether the western rattlesnake ( Crotalus viridis ) aims its predatory strike at the head/thorax region of mice primarily on the basis of cues related to the direction of prey movement. We hypothesized that when rattlesnakes strike at anesthetized, backward-moving mice, most strikes would be aimed at the forward-most-moving region, i.e., the posterior (abdomen/tail) region of prey. However, most mice were struck in the anterior (head/thorax) region, implying that the visual-infrared image of mice, rather than directional movement, guides the aim of predatory strikes.     

Mutations of the BRAF gene in human cancer

Cancers arise owing to the accumulation of mutations in critical genes that alter normal programmes of cell proliferation, differentiation and death. As the first stage of a systematic genome-wide screen for these genes, we have prioritized for analysis signalling pathways in which at least one gene is mutated in human cancer. The RAS RAF MEK ERK MAP kinase pathway mediates cellular responses to growth signals. RAS is mutated to an oncogenic form in about 15% of human cancer. The three RAF genes code for cytoplasmic serine/threonine kinases that are regulated by binding RAS. Here we report BRAF somatic missense mutations in 66% of malignant melanomas and at lower frequency in a wide range of human cancers. All mutations are within the kinase domain, with a single substitution (V599E) accounting for 80%. Mutated BRAF proteins have elevated kinase activity and are transforming in NIH3T3 cells. Furthermore, RAS function is not required for the growth of cancer cell lines with the V599E mutation. As BRAF is a serine/threonine kinase that is commonly activated by somatic point mutation in human cancer, it may provide new therapeutic opportunities in malignant melanoma.     

A natural allele of Nxf1 suppresses retrovirus insertional mutations

Endogenous retroviruses have shaped the evolution of mammalian genomes. Host genes that control the effects of retrovirus insertions are therefore of great interest. The modifier-of-vibrator-1 locus (Mvb1) controls levels of correctly processed mRNA from genes mutated by endogenous retrovirus insertions into introns, including the Pitpn(vb) tremor mutation and the Eya1(BOR) model of human branchiootorenal syndrome. Positional complementation cloning identifies Mvb1 as the nuclear export factor Nxf1, providing an unexpected link between the mRNA export receptor and pre-mRNA processing. Population structure of the suppressive allele in wild Mus musculus castaneus suggests selective advantage. A congenic Mvb1(CAST) allele is a useful tool for modifying gene expression from existing mutations and could be used to manipulate engineered mutations containing retroviral elements.     

SLC2A9 is a newly identified urate transporter influencing serum urate concentration, urate excretion and gout

Uric acid is the end product of purine metabolism in humans and great apes, which have lost hepatic uricase activity, leading to uniquely high serum uric acid concentrations (200-500 microM) compared with other mammals (3-120 microM). About 70% of daily urate disposal occurs via the kidneys, and in 5-25% of the human population, impaired renal excretion leads to hyperuricemia. About 10% of people with hyperuricemia develop gout, an inflammatory arthritis that results from deposition of monosodium urate crystals in the joint. We have identified genetic variants within a transporter gene, SLC2A9, that explain 1.7-5.3% of the variance in serum uric acid concentrations, following a genome-wide association scan in a Croatian population sample. SLC2A9 variants were also associated with low fractional excretion of uric acid and/or gout in UK, Croatian and German population samples. SLC2A9 is a known fructose transporter, and we now show that it has strong uric acid transport activity in Xenopus laevis oocytes.     

Activation of the carcinogen N-hydroxy-2-acetylaminofluorene by rat mammary peroxidase

Summary A peroxidase preparation from rat mammary gland parenchymal cells, a target tissue of arylamine carcinogens, was shown to activate the carcinogen N-hydroxy-2-acetylaminofluorene via a nitroxyl free radical intermediate to the more active carcinogens nitrosofluorene and N-acetoxy-2-acetylaminofluorene. Hydrogen peroxide, cumene hydroperoxide, and linoleic acid hydroperoxide were effective as substrates. The antioxidants ascorbate, propyl gallate and reduced glutathione prevented the free radical activation route.     

Cattle grazing behavior regulates tick populations

Summary Analysis of field population data showed that host-seeking larvae of the tickBoophilus microplus were less successful in attaching to their hosts when larval densities were high. Experimental results showed that cattle hosts detected and avoided high densities of larvae in pasture. The finding reveals a previously unknown population-regulating mechanism for ticks, which are important pests of livestock.Acknowledgment. The authors wish to thank G. Maywald, D. Stegeman, R. Tozer, A. Voll, G. Milne and J. Osborne who helped with the observations. The Australian Meat Research Committee (AMRC) and the Australian Centre for International Agricultural Research (ACIAR) provided some financial support for the project and A. Edwards assisted greatly with the photography.