Yaks and sheep trigger different changes in the grasshopper assemblages of the Qilian Mountains via differentially altering plant assemblages

1. The Qilian Mountains represent one of the key livestock‐raising grasslands in China. The two main herbivore species raised in this area – yaks and sheep – are of critical economical value. Grasshoppers compete with these animals for available nutrients, creating multifaceted relationships between livestock, grasshoppers and plants. A clear understanding of such relationships is lacking and is urgently needed to guide conservation efforts. 2. This study aims to document the effects of yak and sheep grazing on grasshopper assemblages and to elucidate the underlying mechanisms of such effects. 3. It is shown here that yaks and sheep impact grasshopper assemblages differently. Grasshopper assemblages exhibited lower density, biodiversity, richness, and evenness of distribution in yak‐grazed pastures than in grazing‐free grasslands. Sheep‐grazed pastures exhibited a dramatically divergent picture, with elevated density, biodiversity and richness, and a slightly decreased evenness of distribution. Grasshoppers were generally larger in grazed pastures than in grazing‐free grasslands, especially in yak‐grazed plots. 4. The present study suggests that differences between yak and sheep pastures in plant assemblage structure and plant traits are probably the underlying forces driving the differences in grasshopper assemblage structure and grasshopper traits, respectively. 5. The study shows that the grasshopper habitat indicator species differ between yak and sheep pastures, raising the possibility that such indicators can be used to monitor grassland usage and degradation in the Qilian Mountains. 6. These results provide novel insights into the dynamic interactions of common domesticated herbivore species, grasshoppers and plants in Qilian Mountains, which augment current knowledge and may ultimately lead to better conservation practices.     

Effect of oxygen tension on stability and expression of a killer toxin chimeric plasmid in a chemostat culture of Saccharomyces cerevisiae

Summary The effects of oxygen tension and dilution rate on expression and stability of killer toxin chimeric plasmid (pADH-10A) in transformants of wine yeast (Montrachet 522) were investigated using a glucose-limited chemostat culture. Killer toxin activity increased as a function of dilution rate when transformants were grown in N₂ or air, but not in 100% O₂. Killer transformants grown in the presence of N₂ had 2–4 fold and 10–15 fold higher toxin expression than that in the presence of air and 100% O₂, respectively. Plasmid stability increased as a function of dilution rate, regardless of the oxygen tension used. However, transformants grown in air gave the highest plasmid stability.Paper Number 10918 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named. nor criticism of similar ones not mentioned.     

Positioning of Subject and of Nasogastric Tube during a Gastric Secretion Study

The histamine-infusion test was conducted in 50 subjects with a modification that allowed the completeness of recovery of the maximal gastric secretion to be assessed. The effects of the exact position of the tube and the position of the subject on the completeness of recovery were investigated. A simple water-recovery test was found to be as reliable as fluoroscopy for showing that the tip of the tube was within the stomach. Provided that the tip was within the stomach, the exact position of the tube did not affect recovery. Furthermore, recovery in 19 subjects was not appreciably affected by changing the person from the left lateral to the supine semirecumbent position.