Role of carbon dioxide fixation,blood aspartate and glutamate in the adaptation of amphibian brain tissues to a hyperosmotic internal environment

Mechanisms have been examined by which hyperosmotic blood plasma might elevate the levels of aspartate and glutamate in the brain of the toadBufo boreas. CO₂ fixation was assessed by two in vivo methods using [2-¹⁴C]glucose injected intracisternally. Thirty minutes after injection, the¹⁴C labeling of glutamate and aspartate was more than 100 times greater in brain than in liver. In brain tissues, 40+% of¹⁴C atoms appeared to be incorporated into aspartate via the pyruvate carboxylase pathway. Brain tissues of control toads and toads adapting or adapted to hyperosmotic plasma osmolality revealed no differences in the rate of CO₂ fixation as related to glucose utilization or tissue pool sizes of glutamate and aspartate. Elevated levels of these amino acids in blood plasma preceded increases in brain tissues. Carbon atoms required during hyperosmotic adaptation for expansion of amino acid pools in brain tissues may, in part, originate from amino acids in blood but apparently not from CO₂ fixation in brain.     

Decrease in serum receptor-reactive somatomedin in diabetes.

Somatomedin in rat serum has been measured by a sensitive radioreceptor assay using 125I-labelled human somatomedin and human placental membrane. In rats made diabetic with strepotzotocin, receptor-reactive somatomedin levels were decrease by up to 75%. The decrease followed the time course of increasing serum glucose and occurred to the same extent in rats aged between 4 and 40 weeks. Endogenous serum receptor-reactive somatomedin appeared exclusively in high molecular weight fractions on gel chromatography. In diabetes the decreased somatomedin was due to a fall in this high molecular weight activity, but was not accompanied by a fall in somatomedin binding protein. These results suggest a role for insulin in maintaining serum somatomedin levels.     

A genetic link between leaf carbon isotope composition and whole‐plant water use efficiency in the C4 grass Setaria

Genetic selection for whole‐plant water use efficiency (yield per transpiration; WUE_plant) in any crop‐breeding programme requires high‐throughput phenotyping of component traits of WUE_plant such as intrinsic water use efficiency (WUE_i; CO₂ assimilation rate per stomatal conductance). Measuring WUE_i by gas exchange measurements is laborious and time consuming and may not reflect an integrated WUE_i over the life of the leaf. Alternatively, leaf carbon stable isotope composition (δ¹³C_leaf) has been suggested as a potential time‐integrated proxy for WUE_i that may provide a tool to screen for WUE_plant. However, a genetic link between δ¹³C_leaf and WUE_plant in a C₄ species has not been well established. Therefore, to determine if there is a genetic relationship in a C₄ plant between δ¹³C_leaf and WUE_plant under well watered and water‐limited growth conditions, a high‐throughput phenotyping facility was used to measure WUE_plant in a recombinant inbred line (RIL) population created between the C₄ grasses Setaria viridis and S. italica. Three quantitative trait loci (QTL) for δ¹³C_leaf were found and co‐localized with transpiration, biomass accumulation, and WUE_plant. Additionally, WUE_plant for each of the δ¹³C_leaf QTL allele classes was negatively correlated with δ¹³C_leaf, as would be predicted when WUE_i influences WUE_plant. These results demonstrate that δ¹³C_leaf is genetically linked to WUE_plant, likely to be through their relationship with WUE_i, and can be used as a high‐throughput proxy to screen for WUE_plant in these C₄ species.     

Does it matter what a hospital is “high volume” for? Specificity of hospital volume-outcome associations for surgical procedures: analysis of administrative data

Objective To determine whether the improved outcome of a surgical procedure in high volume hospitals is specific to the volume of the same procedure.Design and setting Analysis of secondary data in Ontario, Canada.Participants Patients having an oesophagectomy, colorectal resection for cancer, pancreaticoduodenectomy, major lung resection for cancer, or repair of an unruptured abdominal aortic aneurysm between 1994 and 1999.Main outcome measures Odds ratio for death within 30 days of surgery in relation to the hospital volume of the same surgical procedure and the hospital volume of the other four procedures. Estimates were adjusted for age, sex, and comorbidity and accounted for hospital level clustering.Results With the exception of colorectal resection, 30 day mortality seemed to be inversely related not only to the hospital volume of the same procedure but also to the hospital volume of most of the other procedures. In some cases the effect of the volume of a different procedure was stronger than the effect of the volume of the same procedure. For example, the association of mortality from pancreaticoduodenectomy with hospital volume of lung resection (odds ratio for death in hospitals with a high volume of lung resection compared with low volume 0.36, 95% confidence interval 0.23 to 0.57) was much stronger than the association of mortality from pancreaticoduodenectomy with hospital volume of pancreaticoduodenectomy (0.76, 0.44 to 1.32).Conclusion The inverse association between high volume of procedure and risk of operative death is not specific to the volume of the procedure being studied.     

How IGF-1 activates its receptor

This study presents a new model for IGF-I receptor activation in which the transmembrane domains are held apart until ligand binding brings them together in an activated state.