Headwater gas exchange quantified from O2 mass balances at the reach scale.

Headwater streams are important in the carbon cycle and there is a need to better parametrize and quantify exchange of carbon-relevant gases. Thus, we characterized variability in the gas exchange coefficient (k 2) and dissolved oxygen (O2) gas transfer velocity (k) in two lowland headwaters of the River Avon (UK). The traditional one-station open-water method was complemented by in situ quantification of riverine sources and sinks of O2 (i.e., groundwater inflow, photosynthesis, and respiration in both the water column and benthic compartment) enabling direct hourly estimates of k 2 at the reach-scale (~ 150 m) without relying on the nighttime regression method. Obtained k 2 values ranged from 0.001 h-1 to 0.600 h-1. Average daytime k 2 were a factor two higher than values at night, likely due to diel changes in water temperature and wind. Temperature contributed up to 46% of the variability in k on an hourly scale, but clustering temperature incrementally strengthened the statistical relationship. Our analysis suggested that k variability is aligned with dominant temperature trends rather than with short-term changes. Similarly, wind correlation with k increased when clustering wind speeds in increments correspondent with dominant variations (1 m s-1). Time scale is thus an important consideration when resolving physical drivers of gas exchange. Mean estimates of k 600 from recent parametrizations proposed for upscaling, when applied to the settings of this study, were found to be in agreement with our independent O2 budget assessment (within < 10%), adding further support to the validity of upscaling efforts aiming at quantifying large-scale riverine gas emissions.

Characterisation and chromosomal localisation of C-type low-molecular-weight glutenin subunits in the bread wheat cultivar Chinese Spring.

Low-molecular-weight glutenin subunits are classically divided into the B, C and D groups. Most attention has been paid to the characterisation of the B and D groups, whereas C subunits, although represented by a large number of protein components, have not been thoroughly characterised, mainly because they tend to separate with the gliadins in many fractionation procedures. Here we describe a procedure for obtaining a fraction strongly enriched in C subunits that has allowed us to determine the chromosomal location of these subunits in the bread wheat cultivar Chinese Spring. This analysis has shown that these subunits are coded on chromosome groups 1 and 6. Comparison between N-terminal amino acid sequencing of B and C subunits has shown that, whereas the former group includes mainly subunits with typical LMW-GS type sequences (76%), the C subunit group is made up almost completely of subunits with gliadin-like sequences (95%), including the alpha-type. These results indicate that the LMW-GSs are likely to be coded not only by the typical Glu-3 loci, but also by loci tightly linked to, and possibly included within, the Gli-1 and Gli-2 loci.

Effect of D-glucitol-hexanicotinate on platelet aggregability in patients with coronary heart disease.

D-glucitol-hexanicotinate (sorbinicate) was administered at a daily dose of 1.6 mg to 16 male patients who had survived myocardial infarction. Platelet aggregation induced by collagen (5 micrograms/ml), by ADP (2, 1.2, 0.8, and 0.4 X 10(-6)M), and by epinephrine (1 and 0.5 X 10(-6)M) was significantly decreased after 3 months of therapy. In a group of 13 comparable patients, who did not receive sorbinicate, platelet aggregation induced by ADP (1.2, 0.8, and 0.4 X 10(-6)M) and by epinephrine (1 X 10(-5)M and 1 X 10(-6)M) was significantly increased 3 months after entry into the study. Sorbinicate has effective lipid-lowering activity; the combination of hypolipidemic and anti-aggregating properties may prove important in primary and secondary prevention of atherosclerotic disease.