Mice heterozygous for mutation in Atm,the gene involved in ataxia-telangiectasia,have heightened susceptibility to cancer

Ataxia-telangiectasia is characterized by radiosensitivity, genome instability and predisposition to cancer. Heterozygous carriers of ATM, the gene defective in ataxia-telangiectasia, have a higher than normal risk of developing breast and other cancers. We demonstrate here that Atm 'knock-in' (Atm-Delta SRI) heterozygous mice harboring an in-frame deletion corresponding to the human 7636del9 mutation show an increased susceptibility to developing tumors. In contrast, no tumors are observed in Atm knockout (Atm(+/-)) heterozygous mice. In parallel, we report the appearance of tumors in 6 humans from 12 families who are heterozygous for the 7636del9 mutation. Expression of ATM cDNA containing the 7636del9 mutation had a dominant-negative effect in control cells, inhibiting radiation-induced ATM kinase activity in vivo and in vitro. This reduces the survival of these cells after radiation exposure and enhances the level of radiation-induced chromosomal aberrations. These results show for the first time that mouse carriers of a mutated Atm that are capable of expressing Atm have a higher risk of cancer. This finding provides further support for cancer predisposition in human ataxia-telangiectasia carriers.     

Overlap of internal models in motor cortex for mechanical loads during reaching

A hallmark of the human motor system is its ability to adapt motor patterns for different environmental conditions, such as when a skilled ice-hockey player accurately shoots a puck with or without protective equipment. Each object (stick, shoulder pad, elbow pad) imparts a distinct load upon the limb, and a key problem in motor neuroscience is to understand how the brain controls movement for different mechanical contexts. We addressed this issue by training non-human primates to make reaching movements with and without viscous loads applied to the shoulder and/or elbow joints, and then examined neural representations in primary motor cortex (MI) for each load condition. Even though the shoulder and elbow loads are mechanically independent, we found that some neurons responded to both of these single-joint loads. Furthermore, changes in activity of individual neurons during multi-joint loads could be predicted from their response to subordinate single-joint loads. These findings suggest that neural representations of different mechanical contexts in MI are organized in a highly structured manner that may provide a neural basis for how complex motor behaviour is learned from simpler motor tasks.     

The sizes and characteristics of the minority ethnic populations of Great Britain--latest estimates

This article presents estimates of the minority ethnic populations of Great Britain in 2000 and describes the regional distributions of the different groups. It also discusses changes in the sizes of the different minority ethnic populations during the 1990s. The paper provides information on some key demographic features of these populations at the end of the 1990s--age and sex structures, proportions born in the United Kingdom and whether children lived with their natural parents.     

Breeding and parental care in the endangered Tehuantepec jackrabbit ( Lepus flavigularis )

We documented date and duration of each breeding phase, breeding rate, nursing behavior, parental care, and leveret survival of the Tehuantepec jackrabbit ( Lepus flavigularis ), a critically endangered lagomorph. Between June 2006 and May 2008, we observed 60 adult radio-collared jackrabbits in Oaxaca, México. Tehuantepec jackrabbits exhibit breeding behaviors 250 days out of the year, with a high-intensity period during the rainy season (May–October). Females give birth to 2 leverets 32 days after copulation. Directly after birth, leverets are put into “beds” or “nests,” which are depressions in the ground covered by prairie grass ( Jouvea pilosa ). Females return to nurse and groom the leverets once per day until the leverets are weaned (12 days after birth). The breeding season and parental care behaviors of Tehuantepec jackrabbits are similar to those of other jackrabbits. Females produced an average of 2 litters per breeding season. The breeding rate for the Tehuantepec jackrabbit (4 leverets per breeding female per breeding season) is lower than the average of other species in the genus Lepus. The survival rate of Tehuantepec jackrabbit leverets (50% at day 19) is higher than that of other leporids. Predation by domestic dogs ( Canis familiaris ) is the main cause of mortality. Understanding reproductive behavior is critical for captive breeding, reintro duction, and conservation efforts for endangered leporids such as the Tehuantepec jackrabbit. Documentamos la fecha y la duración de cada fase de la reproducción, la tasa reproductiva, el amamantamiento, el cuidado parental y los instintos de supervivencia de los lebratos de la liebre de Tehuantepec ( Lepus flavigularis ), un lagomorfo en peligro crítico de extinción. Entre junio de 2006 y mayo de 2008 observamos 60 liebres adultas con collares radiotransmisores en Oaxaca, Mexico. Las liebres de Tehuantepec se reproducen 250 días del año, con un período de alta intensidad durante la estación lluviosa (de mayo a octubre). Las hembras paren 2 lebratos 32 días después de la cópula; colocan a los lebratos en “camas”, o huecos en el suelo cubiertos del pasto Jouvea pilosa, justo después de nacer. Las hembras regresan para amamantar y limpiar a los lebratos una vez cada tarde hasta destetarlos 12 días después de nacer. La temporada de reproducción y el cuidado parental de la liebre de Tehuantepec son parecidos a los de otras liebres. En promedio, las hembras producen 2 crías cada temporada de reproducción. La tasa de reproducción de la liebre de Tehuantepec (4 lebratos por hembra reproductora por temporada de reproducción) está por debajo del promedio de otras especies del género Lepus. La tasa de supervivencia de los lebratos de la liebre de Tehuantepec (50% al día 19) es superior a la que se ha documentado para otros lepóridos, siendo la principal causa de mortalidad la depredación por los perros domésticos ( Canis familiaris ). Es crucial entender el comportamiento reproductor para la crianza en cautiverio, la reintroducción y para los esfuerzos de conservación de lepóridos que están en peligro de extinción tal como occure con la liebre de Tehuantepec.     

A GIS model to predict the location of fossil packrat ( Neotoma ) middens in central Nevada

Fossil packrat ( Neotoma ) middens provide an important source of paleoecologic data in the arid West. This study describes and tests a predictive GIS model that uses the eights-of-evidence method for determining areas with a high probability of containing fossil middens in central Nevada. Model variables included geology, elevation, and aspect. Geology was found to be the most important variable tested. We produced a map of 4 probability classes validated by field-checking 21 randomly selected 1-km 2 sites throughout the study area. Our high-probability category reduced the search area to only 3.5% of the total study area. Fossil middens were found on 8 of 21 sites (38%). Geologic types that contained middens were granite, limestone, and volcanic tuff. A 2nd run of the model with the new midden localities added to the training set helped narrow the total search area even further. This analysis demonstrates that the weights-of-evidence method provides an effective tool both for guiding research design and for helping locate midden sites within specific localities. With only a limited training dataset and a simple set of mapped criteria, a model can be constructed that is both predictive and testable. We intend to continue development of the model to improve our ability to predict the location of Pleistocene-age middens and to locate middens on low-probability sites. This method, designed for mineral exploration, has wide potential application within the natural sciences.     

Full-glacial shoreline vegetation during the maximum highstand at Owens Lake, California

Owens Valley, California, was markedly different during the Wisconsin glacial stage from what it is today. Alpine glaciers bounded the Sierra Nevada, and pluvial Owens Lake reached highstands and overflowed its natural basin. We analyzed three layers from two packrat middens, dated to ca 23,000-14,500 yr BP, obtained from Haystack Mountain (1155 m) only 10 m above and Juniperus osteosperma ) and single-needle pinyon pine ( Pinus monophylla ) woodland existed at the site. In the layers dated to ca 17,500 and 16,000 yr BP, macrofossils document the presence of Rocky Mountain juniper ( Juniperus scopulorum ), a species that no longer occurs in California. It is suggested that meltwater from the retreating glacial ice inundated the Owens River Lake chain causing pluvial Owens Lake to reach its highstand. This caused an increase in effective moisture, due to high groundwater, allowing the mesophytic Rocky Mountain juniper to exist at the site.