Endocrine diseases of rodents.

The frequency of documented endocrine diseases in rodents and other small mammals varies considerably among the species maintained as pets, biomedical research animals, or display animals in zoos. The clinical diagnosis of endocrine diseases almost never occurs in free-ranging animals in their native habitat. Feral animals that have clinical endocrine disease, such as neoplasia, adrenal cortical hyperplasia, or diabetes, would exhibit clinical signs of altered behavior that would result in their removal by predators. The diagnosis of endocrine disease thus takes place in the relatively protective environment of captivity. This observation should forewarn pet owners and clinicians caring for these animals that the environment contributes to the development of endocrine diseases in these animals.     

Re-challenge of pigs following recovery from proliferative enteropathy

An experimental challenge model was developed to demonstrate Lawsonia intracellularis colonization and reproduction of proliferative enteropathy (PE) in naïve weaner pigs. Groups of pigs were orally dosed with between 10¹⁰ and 10⁵ L. intracellularis extracted from haemorrhagic PE affected mucosa. Pigs were monitored for clinical signs and intestinal lesions of PE and evidence of bacterial colonization by serology and faecal polymerase chain reaction (PCR). One group of challenged pigs were necropsied after 21 days to confirm the reproduction of PE. L. intracellularis colonization and seroconversion was delayed in pigs dosed with lower numbers of L. intracellularis. When faecal shedding of L. intracellularis ceased to be detected in all of the challenged pigs, they were re-dosed orally with approximately 10¹⁰ L. intracellularis and monitored for evidence of re-colonization and clinical disease. This study demonstrated that pigs previously challenged with L. intracellularis were protected from re-colonization and clinical disease on subsequent exposure 10 weeks later, regardless of the initial dose of L. intracellularis.     

Response of an aridland ecosystem to interannual climate variability and prolonged drought

Water is a key driver of ecosystem processes in aridland ecosystems. Thus, changes in climate could have significant impacts on ecosystem structure and function. In the southwestern US, interactions among regional climate drivers (e.g., El Niño Southern Oscillation) and topographically controlled convective storms create a spatially and temporally variable precipitation regime that governs the rate and magnitude of ecosystem processes. We quantified the spatial and temporal distribution of reduced grassland greenness in response to seasonal and annual variation in precipitation at two scales at the Sevilleta Long Term Ecological Research site in central New Mexico, using Normalized Difference Vegetation Index (NDVI) values from bi-weekly AVHRR data and seasonal ETM data from 1989 to 2005. We used spatially explicit NDVI Z-scores to identify times and places of significantly reduced greenness and related those to interactions between plant functional type, seasonal climate variation, and topography. Seasonal greenness was bimodal with a small peak in spring and a stronger peak following the summer monsoon. Greenness was generally spatially homogeneous in spring and more spatially variable in summer. From 2001 through spring 2002, drought effects were evidenced by a 4-fold increase in the number of pixels showing significantly low greenness. Spatial distribution of low greenness was initially modulated by topographic position, but as the drought intensified spread throughout the study area. Vegetation green up occurred rapidly when drought conditions ceased. We conclude that drought effects vary spatially over time, pervasive drought reduces broad-scale spatial heterogeneity, and greenness patterns recover rapidly when drought conditions end.     

Measurements of the equation of state of deuterium at the fluid insulator-metal transition

A high-intensity laser was used to shock-compress liquid deuterium to pressures from 22 to 340 gigapascals. In this regime deuterium is predicted to transform from an insulating molecular fluid to an atomic metallic fluid. Shock densities and pressures, determined by radiography, revealed an increase in compressibility near 100 gigapascals indicative of such a transition. Velocity interferometry measurements, obtained by reflecting a laser probe directly off the shock front in flight, demonstrated that deuterium shocked above 55 gigapascals has an electrical conductivity characteristic of a liquid metal and independently confirmed the radiography.