Disposition of sulfadimethoxine in camels (Camelus dromedarius) following single intravenous and oral doses.

Single-dose pharmacokinetics of sulfadimethoxine were determined in six adult camels (Camelus dromedarius) following administration of a mean dosage of 17.5 +/- 2.7 mg/kg both i.v. and p.o. Serial blood samples were collected through an indwelling jugular catheter intermittently for 5 days for both routes. Sulfadimethoxine was assayed using high-performance liquid chromatography. Serum drug concentration versus time data for each animal was subjected to linear regression, with the best-fit model selected based on residual analysis. The data fit best into a two-compartment open model, with first-order input for oral administration. For orally administered drug, mean maximum serum concentration of 19.3 +/- 1.7 microg/ml was reached at 11.41 +/- 2.59 hr, with an elimination rate constant of 0.09/hr +/- 0.05/hr and an elimination half-life of 11.7 +/- 3 hr. Mean peak serum concentration following i.v. administration was 223 +/- 48 microg/ml. Mean volume of distribution at steady state was 0.393 +/- 0.049 L/kg. Elimination rate constants differed with i.v. and oral administration, suggesting a flip-flop model. Oral bioavailability was 103% +/- 38%. Comparison of maximum serum concentrations to the microbial breakpoint concentration reported for sulfadimethoxine (512 microg/ml) suggests that the dose used in this study, 17.5 +/- 2.7 mg/kg, is insufficient for achieving therapeutic serum levels.     

Post surgical development of inflammatory adhesions and reticular function in cows suffering from traumatic reticuloperitonitis

Inflammatory adhesions between reticulum and ventral abdomen in patients suffering traumatic reticuloperitonitis (TRP) may induce a massive inhibition of reticular contractions and thereby an impairment of the separation process of particles in the reticulorumen. However, a substantial disturbance of digesta passage (Hoflund-syndrome) is found only in a few TRP-cows. We hypothesized that this is due to a retrieval of reticular motility due to rebuilding and degradation of adhesions within months after the removal of the foreign body as the primary inflammatory stimulus. Accordingly, it was the objective of this study (a) to assess the extent and structure of inflammatory adhesions in cows with TRP over a period of six months following surgery and (b) to persecute reticular function by characterizing the sequence of reticular contractions sonographically and by assessment of particle size distribution in the faeces of patients by means of wet-sieving. Twenty-six cows suffering from TRP were studied on the day of rumenotomy (day 1) and on day 6, day 12 and 6 months post operationem. Additionally, six healthy control cows were investigated once. All cows were on a hay and concentrate diet. On day 1, the reticular floor and the reticular wall were affected by adhesions in varying extent in all cows; the contraction distance and contraction velocity of the reticulum were markedly reduced and the portion of large particles in the faces increased compared to healthy cows. On day 12, the portion of large particles did not vary any more from that of control cows; a tendency towards an increased contraction distance compared to day 1 was found. Sonographically, only marginal differences were detected in respect to extent and consistency of adhesions. Six months after rumenotomy, in 9 of 16 re-investigated cows sonography revealed no adhesions at the reticulum at all, in other cases the extent of adhesions shrunk considerably. Contraction distance and contraction velocity and particle size distribution in the faeces were found to be nearly comparable to that of control cows. It is concluded that inflammatory adhesions disappear in the majority of the TRP-patients, as a consequence reticular function normalizes. A serious disturbance of digesta passage seems to develop exclusively in those patients with the most extensive adhesions and may be also in such cows, where the primary adhesions cause the development of extensive abscesses.     

Advanced technology paths to global climate stability: energy for a greenhouse planet

Stabilizing the carbon dioxide-induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (approximately 10(13) watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission-free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non-primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.     

The Influence of Sorption Processes on the Phosphorus Mass Balance in a Eutrophic German Lowland River

Previous studies on sorption processes in running waters lack a quantification of phosphorus sorption in relation to phosphorus mass balances of entire river sections. The present study was designed to investigate the influence of sorption processes on the phosphorus mass balance in a medium-sized lowland river. Riverbed surface sediments were sampled in the lower River Spree in February and in July 2002, and used for sorption shaking experiments. Phosphorus analyses results were evaluated using Langmuir-isotherms. Organic sediments revealed sorption properties that were affected by incubation temperature in a manner opposite to those of clastic sediments. Particulate iron is assumed to be the dominant sorption site of phosphorus in the lower River Spree. Clastic sediments act as phosphorus sinks, especially in summer, when soluble reactive phosphorus (SRP) concentrations in the water body are relatively high. Organic river substrates were found to be a source rather than a sink of phosphorus for the water body, but even in the worst case of a storm event, including complete resuspension of an organic surface layer, the contribution of desorption to the riverine phosphorus load of a eutrophic river was negligible (at maximum 2.5% of SRP load during vegetation period).     

Genotypic Variability in Drought Performance and Recovery in Cowpea under Controlled Environment

Mid‐season drought is a factor frequently limiting crop production in the moist to dry savannah zones of the tropical and subtropical regions of the world. Ten cowpea genotypes were subjected to a cycle of drought at flowering followed by re‐watering to study variation in drought performance and recovery. Drought caused a reduction in leaf assimilation rate, transpiration rate and stomatal conductance with genotypic variances of 75.4, 57.9, and 83.3 %, respectively. Only genotypic variance in stomatal conductance increased appreciably under drought. Reductions in leaf water potential as a consequence of drought positively correlated with a decline in assimilation rate, which was associated with stomatal closure. One week after re‐watering, the three gas exchange parameters of stressed plants recovered fully and attained values 10–30 % higher than the well‐watered plants with increased genotypic variability. Reductions in the total dry matter during the drought interval varied from 11 to 50 % among genotypes, but were of minor importance for the total dry matter at maturity. After stress, the gain in dry matter varied considerably among the stressed genotypes, with stressed plants showing higher gain than the unstressed plants during this interval. This was associated with increased availability of assimilates due to enhanced green leaf area duration after stress release. Variability in drought recovery among genotypes was found, and appears to be more important for final yield than responses during drought.