New conformational constraints in isotopically (13C) enriched oligosaccharides

Multidimensional heteronuclear NMR studies have been applied to the resonance assignment and conformational analysis of 13C-enriched Neu5Acalpha2-3Galbeta1-4Glc. It is demonstrated that three-dimensional ROESY-HSQC experiments provide through-space distance restraints which cannot be observed with conventional homonuclear 1H techniques due to resonance overlap. In particular, connectivities demonstrating the existence of the "anti" conformation about the Galbeta1-4Glc glycosidic linkage are unambiguously observed. It is shown that 13C isotopic enrichment of the trisaccharide at a level >95% enables straightforward measurement of trans-glycosidic 1H-13C and 13C-13C coupling constants and a Karplus-type relation is derived for the latter. In total 15 conformational restraints were obtained for the trisaccharide in aqueous solution, all of which were in excellent agreement with theoretical parameters computed from a 5 ns molecular dynamics simulation of the glycan.      

Load-insensitive measurements from an isolated perfused biventricular working rat heart

To determine whether a rat heart model can provide load-insensitive measurements of cardiac function, a recently developed biventricular perfused preparation was tested. Using 29 Sprague-Dawley rat hearts perfused with modified Krebs-Henseleit buffer, ventricles functioned simultaneously with adjustable independent preload (venous reservoirs) and afterload (compliance chambers). Ultrasonic crystal pairs provided continuous left (LV) and right ventricular (RV) short-axis dimensions. LV and RV pressure-length loops (loop area = work) were generated from paired intraventricular pressure and short-axis dimensions. Load-insensitive measurements were obtained from the slopes (elastance) and x-intercepts (L₀) of regression lines generated from the end-systolic coordinates of these pressure-length loops over ranges of RV and LV preloads. Measurements were made after 15 min of stable function and after 20 min of warm (37°C) ischemia. During perturbations in LV afterload, there were linear changes in dP/dt, but loop work remained relatively unchanged. RV dP/dt and work varied little with physiologic ranges of afterload. Increased RV afterload had little effect on LV function. Ischemia affected LV function more than RV function using these measurements. Elastance, however, increased after ischemia with diastolic creep (increased L₀) for both ventricles. Load-insensitive and other sophisticated hemodynamic measurements are possible with this new preparation.     

The effect of isoniazid (INH) on Chinese hamster and mouse spermatogonia

Acute and chronic treatment of Chinese hamsters and mice with 5, 25 and 125 mg/kg isoniazid (INH) given by oral intubation did not enhance the chromosomal aberration frequencies in spermatogonia. The structural and numerical aberration rates remained in the range of spontaneous events even after the chronic treatment over 12 weeks with 3 x 125 mg/kg INH per week. This dose is much higher than normally used for prevention and therapy in man (3--16 mg/kg).     

Mass-Spectrometry-Linked Screening of Protein Fractions for Enzymatic Activities—A Tool for Functional Genomics

A simple and rapid strategy is described to screen protein fractions for defined enzymatic activity. A protein fraction from a porcine kidney extract was immobilized by covalent coupling to activated affinity beads. The immobilized proteins were incubated with probes specific for different enzyme activities. The reaction products were analyzed by matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry. The MALDI spectra indicate the presence of 5′-nucleotidase, phosphatase, kinase, glutathione reductase, and renin activities in the kidney protein extract. Furthermore, the method can be used to screen for inhibitors of enzymatic reactions. The method is adaptable to high-throughput sample handling and automated mass spectrometric analysis and therefore suited for functional genomics.     

The replicative helicase MCM recruits cohesin acetyltransferase ESCO2 to mediate centromeric sister chromatid cohesion

Chromosome segregation depends on sister chromatid cohesion which is established by cohesin during DNA replication. Cohesive cohesin complexes become acetylated to prevent their precocious release by WAPL before cells have reached mitosis. To obtain insight into how DNA replication, cohesion establishment and cohesin acetylation are coordinated, we analysed the interaction partners of 55 human proteins implicated in these processes by mass spectrometry. This proteomic screen revealed that on chromatin the cohesin acetyltransferase ESCO2 associates with the MCM2‐7 subcomplex of the replicative Cdc45‐MCM‐GINS helicase. The analysis of ESCO2 mutants defective in MCM binding indicates that these interactions are required for proper recruitment of ESCO2 to chromatin, cohesin acetylation during DNA replication, and centromeric cohesion. We propose that MCM binding enables ESCO2 to travel with replisomes to acetylate cohesive cohesin complexes in the vicinity of replication forks so that these complexes can be protected from precocious release by WAPL. Our results also indicate that ESCO1 and ESCO2 have distinct functions in maintaining cohesion between chromosome arms and centromeres, respectively.     

Population differences in density and resource allocation of ornamental tail feathers in the barn swallow

Many organisms show well‐defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost tail feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of tail feathers in relation to body size and wing size. Tail feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer tails. The extra enlargement of the tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying feather structure to produce longer feathers of lower density. These two separate processes accounting for the production of longer and more costly tail feathers and less dense feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 925–936.     

The phylogenetic status of arthropods, as inferred from 18S rRNA sequences

Partial 18S rRNA sequences of five chelicerate arthropods plus a crustacean, myriapod, insect, chordate, echinoderm, annelid, and platyhelminth were compared. The sequence data were used to infer phylogeny by using a maximum-parsimony method, an evolutionary-distance method, and the evolutionary-parsimony method. The phylogenetic inferences generated by maximum-parsimony and distance methods support both monophyly of the Arthropoda and monophyly of the Chelicerata within the Arthropoda. These results are congruent with phylogenies based on rigorous cladistic analyses of morphological characters. Results support the inclusion of the Arthropoda within a spiralian or protostome coelomate clade that is the sister group of a deuterostome clade, refuting the hypothesis that the arthropods represent the "primitive" sister group of a protostome coelomate clade. Bootstrap analyses and consideration of all trees within 1% of the length of the most parsimonious tree suggest that relationships between the nonchelicerate arthropods and relationships within the chelicerate clade cannot be reliably inferred with the partial 18S rRNA sequence data. With the evolutionary-parsimony method, support for monophyly of the Arthropoda is found in the majority of the combinations analyzed if the coelomates are used as "outgroups." Monophyly of the Chelicerata is supported in most combinations assessed. Our analyses also indicate that the evolutionary-parsimony method, like distance and parsimony, may be biased by taxa with long branches. We suggest that a previous study's inference of the Arthropoda as paraphyletic may be the result of (a) having two few arthropod taxa available for analysis and (b) including long-branched taxa.      

Baseline Levels of Potentially Toxic Elements in Pampas Soils

The soils of the Pampas are thought to be generally non-contaminated but there is growing evidence of trace element accumulation at some specific sites. The goal of this study was to measure the current levels of the main Potentially Toxic Elements (PTE) in the top horizon and in specific soil profiles so that we would establish the baseline concentrations of these elements. Eighty-eight top soils and three soil profiles were sampled. The samples were acid digested. Arsenic, boron, barium, cadmium, cobalt, chromium, copper, lead, manganese, mercury, molybdenum, nickel, silver, selenium and zinc were determined with inductively coupled argon plasma emission spectrometry (ICPES).

All of the values found are within the normal range for uncontaminated soils as reported from several continents. Elements with high environmental risk potential are lower than the admissible range of the European Union and some of them are orders of magnitude lower than those of the United States Environmental Protection Agency (US-EPA) 501 levels. Potentially Toxic Elements contents increased with depth or showed a maximum concentration at the B2 horizon. This is related to the parent material and the pedogenetic processes but not to recent contamination. Soil profiles showed higher concentrations of PTE in clayey horizons. However, these relationships did not appear in top soil samples in any soil Great Group studied. The shown data establishes a baseline for PTE concentrations for Pampas soils.