Interaction of alcohol dehydrogenase with tert-butylhydroperoxide: stimulation of the horse liver and inhibition of the yeast enzymes

Preincubation of horse liver alcohol dehydrogenase (HLADH) with the oxidative agent, tert-butyl hydroperoxide (tBOOH) results in a twofold stimulation of the ethanol dehydrogenase activity of this enzyme. This stimulation was dependent on tBOOH concentration up to 100 mM; above this concentration tBOOH did not further stimulate ethanol oxidation by HLADH. Active-site-directed reagents and classical ADH binary complexes were used to probe the possible mechanism of this activating effect. The rate and extent of stimulation by tBOOH is strongly reduced by binary complexes with NAD(+) or NADH, whose pyrophosphate groups bind to Arg-47 and Arg-369. In contrast stimulation by tBOOH was not prevented by AMP or the sulfhydryl reagents dithiothreitol and glutathione, suggesting, respectively, a lack of role for Lys-228 and sulfhydryl group oxidation in the stimulation by tBOOH. In contrast to the liver enzyme, treatment of yeast ADH (YADH) with tBOOH irreversibly inhibited its ethanol dehydrogenase activity. Inhibition of YADH by tBOOH approximated first-order rate kinetics with respect to enzyme at fixed concentrations of tBOOH between 0.5 to 300 mM. Four -SH groups per molecule of YADH were modified by tBOOH, whereas only two -SH groups were modified in HLADH. The stimulation of HLADH by tBOOH is suggested to be due to destabilization of the catalytic Zn-coordination sphere and amino acids associated with coenzyme binding in the active site, while inactivation of YADH appears to be associated with -SH group oxidation by the peroxide.     

Fish species-environment and abundance relationships in a Great Plains river system

Fish assemblages in the upper Red River system of southwestern Oklahoma (USA) were predictable along measured environmental gradients Conductivity was the most important variable predicting structure of fish assemblages followed by stream size, alkalinity woody debris and water clarity Classification of abundance data identified four groups each of species and sites Species groups were separated on a habitat template indicating similar environmental responses within groups However, site groups showed considerable overlap on the template Correlations among species environmental preferences were significantly associated with correlations of species abundances Likewise, site correlations on the basis of measured environmental variables and on the basis of species abundances were significantly similar
We tested abundance and distribution data for agreement with the hierarchical model of Kolasa Several testable predictions of the model described our data well specialist species outnumbered generalist species and were less abundant on average, than generalist species Average abundance of species was highly correlated with their ecological ranges and species were clumped along both ecological range and abundance axes     

Clinical examination or whole-body magnetic resonance imaging: the Holy Grail of spondyloarthritis imaging

Whole-body magnetic resonance imaging allows acquisition of diagnostic images in the shortest scan time, leading to better patient compliance and artifact-free images. Methods of clinical examination of the anterior chest wall joints vary between physician groups and consideration of the rules of rib motion is suggested. The type of joint and its synovial lining may also aid imaging/clinical correlation. This well-written study by experts in the field with a standardized design and methodology allows good scientific analysis and suggests the advantages of whole-body magnetic resonance imaging in anterior chest wall imaging. Selection of clinical examination criteria and specific joints may have had an influence on the study results and the lack of association reported.     

Use of Two-Dimensional Polyacrylamide Electrophoresis to Demonstrate that Putative Rhizobium Cross-Inoculation Mutants Actually Are Contaminants

Two-dimensional polyacrylamide electrophoresis was used to determine that mutants of Rhizobium trifolii DT6, claimed to be capable of effectively nodulating soybeans, were actually Rhizobium japonicum 110 contaminants isolated from the parent DT6 culture.     

Synthesis and ex vivo evaluation of carbon-11 labelled N-(4-methoxybenzyl)-N'-(5-nitro-1,3-thiazol-2-yl)urea ([11C]AR-A014418): a radiolabelled glycogen synthase kinase-3beta specific inhibitor for PET studies

N-(4-Methoxybenzyl)-N'-(5-nitro-1,3-thiazol-2-yl)urea (AR-A014418), a highly selective inhibitor of glycogen synthase kinase-3beta (GSK-3beta), was radiolabelled with carbon-11 (half-life=20.4min) for cerebral positron emission tomography (PET) studies. Reaction of desmethyl AR-A014418 with [(11)C]CH(3)I produced [(11)C]AR-A014418 in 17% decay-corrected radiochemical yield, based on [(11)C]CO(2), with 3230mCi/micromol specific activity after a 30min synthesis time. The desmethyl precursor of AR-A014418 was synthesized in 23% yield by a novel one-pot reaction of 2-amino-5-nitrothiazole with in situ generated TMS-protected 4-hydroxybenzylisocyanate, following deprotection with acid. Ex vivo biodistribution studies were conducted after [(11)C]AR-A014418 was administered via tail vein injection into Sprague-Dawley rats. Very low levels of radioactivity were found in all brain regions (0.08% injected dose/gram of tissue) at 5 and 30min post-injection, uncorrected for vascular compartment. Considering the extremely poor brain penetration of [(11)C]AR-A014418 this compound cannot be used to study GSK-3beta in cerebral PET studies. Furthermore, the specific pharmacological mechanism(s) of antidepressant-like activity attributed to AR-A014418 should be investigated.