Changes in the T4/T3 molar ratio following thyrotropin releasing hormone injection in cattle.

The injection of thyrotropin releasing hormone into cattle resulted in a rapid decrease in the T4/T3 molar ratio. 2 breeds of cattle, Shorthorn and Africander Cross were studied. The decrease in the T4/T3 molar ratio was significantly greater in the Shorthorn breed. It is concluded that acute stimulation of the thyroid gland with TRH results in enhanced release of both T3 and T4 and that T3 is discharged more rapidly than T4.     

Intensification of amphetamine-induced excitation by methysergide,a serotonergic receptor blocker

Summary Methysergide, a serotonergic receptor blocker, was studied to determine its effects against d-amphetamine-induced excitation as measured by convulsions elicited by handling in mice. Significant intensification (p<0.01) of the action of d-amphetamine was observed in mice. These results indicate that reduction in serotonergic activity in the central nervous system enhances excitation induced by d-amphetamine.This work was supported by the Pharmaceutical Manufacturer Association Starter Grant, No. 5 S01 RR 05654-06 and the Air Force Office of Scientific Research Grant. The authors are grateful to Ben Wiggins, Michael Wallace, Maria Salazar, and Sanford Futterman for their technical assistance. The authors are also grateful to Dr Boris Tabakoff for supplying the formula of the CSF used in this experiment and we are indebted to San Antonio College for the use of their computer facilities. Dr Blum is a Career Teacher in drug addiction sponsored by NIDA, grant No. 1-T01-DA00290-01.     

Implications of symbiotic nitrogen fixation by desert plants

There is little information available regarding symbiotic nitrogen fixation by desert plants, particularly with respect to the group of nodulated non-legumes. Early investigations of nodules on non-legumes were contemporary with early studies of the Leguminoseae; however, comparatively little is known even now regarding the extent to which non-legumes fix nitrogen. A review of literature regarding changes in concepts of nitrogen fixation by legumes and nodulated non-legumes is presented. Evidence from recent studies on nodulated non-legumes, including those in desert areas, indicates some 31 species of 21 genera in 12 new or previously unrecognized plant families show nodulation with implications of nitrogen fixation. Some biological aspects of symbiotic nitrogen fixation are discussed, and reports in the literature of nitrogen fixation in natural plant populations are reviewed. Nitrogen fixation reactions in the desert environment are considered in terms of the areas of investigation needed to help define (1) the magnitude of nitrogen fixation, (2) the extent of nodulation in non-legume plants, and (3) factors affecting this nodulation in the desert ecosystem.     

Home-range size and overlap of sympatric male mule and white-tailed deer in Texas

Information about the ecology of sympatric male deer is limited, which may influence management strategies for these species. We estimated home-range and core-area sizes and overlap, and survival of sympatric male desert mule deer ( Odocoileus hemionus eremicus ) and white-tailed deer ( Odocoileus virginianus ) in west central Texas. We captured 18 males of each species, fitted them with radio-collars, and monitored them for mortality from 2000 through 2003. We calculated home ranges for 7 males of each species in 2001 and 2002. Home-range sizes of mule deer (8.8 km 2 ) and white-tailed deer (7.4 km 2 ) were similar. Interspecific home-range overlap was less common than intraspecific overlap. Mean annual survival was 0.76 (SE = 0.04) for mule deer and 0.80 (SE = 0.06) for white-tailed deer. The high degree of home-range overlap and similar survival between the 2 deer species suggest that management targeting only 1 species may be unfeasible.     

Object retrieval preferences of Norway rats: An evolutionary generalization of behavior

Summary Prior studies have shown that object retrieval (including food hoarding) by domestic rats can occur in the context of different motivations. The present experiments show that retrieval preferences related to two motivational systems, feeding and gnawing, are ordered by object features related to either or both systems. Object retrieval in this species is apparently guided by a generalized value system. The capacity to order alternatives across specific motivational systems has evident selective advantage and may reflect a general adaptive principle.     

Local action of vitamin A on amphibian limb regeneration

Summary Axolotl forearms isolated from upper arm tissue either surgically or by local irradiation regenerate excessive structures after vitamin A treatment. This demonstration excludes the possibility of regeneration being altered by enhanced cellular migration and thus indicates that vitamin A respecifies cells close to the site of amputation.     

Phosphorylation fails to activate chloride channels from cystic fibrosis airway cells

Chloride impermeability of epithelial cells can account for many of the experimental and clinical manifestations of cystic fibrosis (CF). Activation of apical-membrane Cl- channels by cyclic AMP-mediated stimuli is defective in CF airway epithelial cells, despite normal agonist-induced increases in cellular cAMP levels. This defect in Cl- channel regulation has been localized to the apical membrane by exposing the cytoplasmic surface of excised membrane patches to the catalytic subunit (C subunit) of cAMP-dependent protein kinase and ATP. In membranes from normal cells, C-subunit activated Cl- channels with properties identical to those stimulated by cAMP-dependent agonists during cell-attached recording. Activation by the C subunit was not observed in CF membranes, but the presence of Cl- channels was verified by voltage-induced activation. The failure of the C subunit to activate the Cl- channels of CF membranes indicates that the block in their cAMP-mediated activation lies distal to induction of cAMP-dependent protein kinase activity and focuses our attention on the Cl- channel and its membrane-associated regulatory proteins as the probable site of the CF defect.     

A polymorphic DNA marker genetically linked to Huntington's disease

Family studies show that the Huntington's disease gene is linked to a polymorphic DNA marker that maps to human chromosome 4. The chromosomal localization of the Huntington's disease gene is the first step in using recombinant DNA technology to identify the primary genetic defect in this disorder.     

Gut microbiota composition correlates with diet and health in the elderly

Alterations in intestinal microbiota composition are associated with several chronic conditions, including obesity and inflammatory diseases. The microbiota of older people displays greater inter-individual variation than that of younger adults. Here we show that the faecal microbiota composition from 178 elderly subjects formed groups, correlating with residence location in the community, day-hospital, rehabilitation or in long-term residential care. However, clustering of subjects by diet separated them by the same residence location and microbiota groupings. The separation of microbiota composition significantly correlated with measures of frailty, co-morbidity, nutritional status, markers of inflammation and with metabolites in faecal water. The individual microbiota of people in long-stay care was significantly less diverse than that of community dwellers. Loss of community-associated microbiota correlated with increased frailty. Collectively, the data support a relationship between diet, microbiota and health status, and indicate a role for diet-driven microbiota alterations in varying rates of health decline upon ageing.