Two different β-lactamase genes are present in Streptomycees cacaoi

Two beta-lactamase genes called blaL and blaU have been cloned independently in Liège and in Ume?, from Streptomyces cacaoi. Genes blaL and blaU were found to differ largely in their nucleotide sequences, although the encoded proteins both belonged to the class A of beta-lactamases (active-site serine penicillinases). DNA-hybridization and polymerase chain reaction assays have now demonstrated that both blaL and blaU genes were present in the S. cacaoi strains used in Liège and in Ume?.     

Increase in body size is correlated to warmer winters in a passerine bird as inferred from time series data

Climate change is expected to affect natural populations in many ways. One way of getting an understanding of the effects of a changing climate is to analyze time series of natural populations. Therefore, we analyzed time series of 25 and 20 years, respectively, in two populations of the citril finch (Carduelis citrinella) to understand the background of a dramatic increase in wing length in this species over this period, ranging between 1.3 and 2.9 phenotypic standard deviations. We found that the increase in wing length is closely correlated to warmer winters and in one case to rain in relation to temperature in the summer. In order to understand the process of change, we implemented seven simulation models, ranging from two nonadaptive models (drift and sampling), and five adaptive models with selection and/or phenotypic plasticity involved and tested these models against the time series of males and females from the two population separately. The nonadaptive models were rejected in each case, but the results were mixed when it comes to the adaptive models. The difference in fit of the models was sometimes not significant indicating that the models were not different enough. In conclusion, the dramatic change in mean wing length can best be explained as an adaptive response to a changing climate.     

Reactivation in Working Memory: An Attractor Network Model of Free Recall

The dynamic nature of human working memory, the general-purpose system for processing continuous input, while keeping no longer externally available information active in the background, is well captured in immediate free recall of supraspan word-lists. Free recall tasks produce several benchmark memory phenomena, like the U-shaped serial position curve, reflecting enhanced memory for early and late list items. To account for empirical data, including primacy and recency as well as contiguity effects, we propose here a neurobiologically based neural network model that unifies short- and long-term forms of memory and challenges both the standard view of working memory as persistent activity and dual-store accounts of free recall. Rapidly expressed and volatile synaptic plasticity, modulated intrinsic excitability, and spike-frequency adaptation are suggested as key cellular mechanisms underlying working memory encoding, reactivation and recall. Recent findings on the synaptic and molecular mechanisms behind early LTP and on spiking activity during delayed-match-to-sample tasks support this view.     

The transthyretin-related protein family.

A number of proteins related to the homotetrameric transport protein transthyretin (TTR) forms a highly conserved protein family, which we present in an integrated analysis of data from different sources combined with an initial biochemical characterization. Homologues of the transthyretin-related protein (TRP) can be found in a wide range of species including bacteria, plants and animals, whereas transthyretins have so far only been identified in vertebrates. A multiple sequence alignment of 49 TRP sequences from 47 species to TTR suggests that the tertiary and quaternary features of the three-dimensional structure are most likely preserved. Interestingly, while some of the TRP orthologues show as little as 30% identity, the residues at the putative ligand-binding site are almost entirely conserved. RT/PCR analysis in Caenorhabditis elegans confirms that one TRP gene is transcribed, spliced and predominantly expressed in the worm, which suggests that at least one of the two C. elegans TRP genes encodes a functional protein. We used double-stranded RNA-mediated interference techniques in order to determine the loss-of-function phenotype for the two TRP genes in C. elegans but detected no apparent phenotype. The cloning and initial characterization of purified TRP from Escherichia coli reveals that, while still forming a homotetramer, this protein does not recognize thyroid hormones that are the natural ligands of TTR. The ligand for TRP is not known; however, genomic data support a functional role involving purine catabolism especially linked to urate oxidase (uricase) activity.     

Synergistic effect of green tea extract and probiotics on the pathogenic bacteria, <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and <Emphasis Type="Italic">Streptococcus pyogenes</Emphasis>

The aim of this study was to assess the effect of a commercial green tea extract (TEAVIGO™) on the microbial growth of three probiotic strains (Lactobacillus and Bifidobacterium), as well as three pathogenic bacteria. MIC and co-culture studies were performed. The MICs of the green tea extract against Staphylococcus aureus and Streptococcus pyogenes (100 μg ml⁻¹) were considerably lower than those against the probiotic strains tested (>800 μg ml⁻¹) and Escherichia coli (800 μg ml⁻¹). In co-culture studies, a synergistic effect of the probiotic strains and the green tea extract was observed against both Staph. aureus and Strep. pyogenes. Green tea extract in combination with probiotics significantly reduced the viable count of both pathogens at 4 h and by 24 h had completely abolished the recovery of viable Staph. aureus and Strep. pyogenes. These reductions were more significant than the reductions induced by probiotics or green tea extracts used separately. These results demonstrate the potential for combined therapy using the green tea extract plus probiotics on microbial infections caused by Staph. aureus and Strep. pyogenes. As probiotics and the green tea extract are derived from natural products, treatment with these agents may represent important adjuncts to, or alternatives to, conventional antibiotic therapy.     

Free energy calculations and molecular dynamics simulations of wild-type and variants of the DNA-EcoRI complex.

Molecular dynamics simulations and free energy calculations of the wild-type EcoRI-DNA complex and several variants have been performed in aqueous solvent. In general, he theoretical estimations of the free energy differences (DeltaDeltaA) qualitatively agree well with the corresponding experimental data. The modifications which were experimentally found unfavorable compared to the wild-type complex were also found to be so in theoretical estimates. The mutant where the amino group of the base Ade(6) was replaced by a hydrogen atom eliminating one H-bond between the DNA and the protein, was experimentally found to be more stable than the wild-type complex. It was speculated that the modification also caused a structural relaxation in the DNA making DeltaDeltaA favorable. Our theoretical estimate yields a positive DeltaDeltaA in this case, but the difference is small, and no significant local structural relaxation was observed. The major H-bonds between the DNA and the protein in the wild-type complex are found to be maintained in the different mutants although the specific and non-specific interaction energies between the interacting the DNA bases and the protein residues are different in different mutants. The interaction pattern of the other nearby nucleotides are significantly influenced by each modification. Thus, the alteration of the non-specific interactions may also play an indirect role in determining the specificity of the complex. The interaction of the Gua(4) of the DNA with the protein is found to be most sensitive to any alteration in the recognition site. Because Gua(4) is the nucleotide closest to the scissile bond, this extra sensitivity seems to play an important role in altering the functional activity of the complex.     

The identity of Maerua macrocarpa Chiov. (Capparaceae)

It is argued that the original material of Maerua macrocarpa consists of elements from three different species: M. denhardtiorum, Thilachium thomasii and Capparis tornentosa . A lectotypification is proposed that makes M. macrocarpa a synonym of M. denhardtiorum .