The N-BAR domain protein,Bin3, regulates Rac1- and Cdc42-dependent processes in myogenesis

Actin dynamics are necessary at multiple steps in the formation of multinucleated muscle cells. BAR domain proteins can regulate actin dynamics in several cell types, but have been little studied in skeletal muscle. Here, we identify novel functions for the N-BAR domain protein, Bridging integrator 3 (Bin3), during myogenesis in mice. Bin3 plays an important role in regulating myofiber size in vitro and in vivo. During early myogenesis, Bin3 promotes migration of differentiated muscle cells, where it colocalizes with F-actin in lamellipodia. In addition, Bin3 forms a complex with Rac1 and Cdc42, Rho GTPases involved in actin polymerization, which are known to be essential for myotube formation. Importantly, a Bin3-dependent pathway is a major regulator of Rac1 and Cdc42 activity in differentiated muscle cells. Overall, these data classify N-BAR domain proteins as novel regulators of actin-dependent processes in myogenesis, and further implicate BAR domain proteins in muscle growth and repair.     

Differences in transpiration of Norway spruce drought stressed trees and trees well supplied with water

The paper focuses on the evaluation of transpiration as a physiological process, which is very sensitive to drought stress. Reactions of 25-year-old Norway spruce (Picea abies (L.) Karst.) trees to drought were examined during 2009 summer. Sap flow rate (SF), meteorological and soil characteristics were measured continually. Vapour pressure deficit of the air (VPD) and cumulative transpiration deficit (KTD) was calculated. During the second half of the vegetation period, the decrease in soil water content was observed and irrigation was applied to a group of spruce trees, while the second group was treated under natural soil drought. On the days, when the differences in transpiration between irrigated (IR) and non-irrigated (NIR) trees were significant (21 days), transpiration of NIR trees was only 23% of the transpiration of IR trees. We found significant differences in transpiration when the soil water content (SWC) of NIR variant at a depth of 5–15 cm ranged from 10.4 to 13.7%. Under both regimes of water availability, daily transpiration significantly responded to atmospheric conditions. However, the influence of all assessed meteorological parameters on SF of NIR trees was significantly lower than on IR tree. The dependency of transpiration on evaporative demands of atmosphere decreased with the decreasing soil moisture. Cumulative transpiration deficit of the stand during the entire evaluated period was 50.9 mm. The difference between the transpiration of the mean NIR tree and of the mean IR tree was 278.8 L over the assessed period of 47 days (5.9 L per day). The transpiration of NIR trees was 40.3% from the transpiration of IR trees during this period.     

Synthesis and antiplasmodial activity of some 1-azabenzanthrone derivatives

Some synthetic 1-azabenzanthrones (7H-dibenzo[de,h]quinolin-7-ones) are weakly to moderately cytotoxic, suggesting that they might also show antiparasitic activity. We have now tested a small collection of these compounds in vitro against a chloroquine-resistant Plasmodium falciparum strain, comparing their cytotoxicity against normal human fibroblasts. Our results indicate that 5-methoxy-1-azabenzanthrone and its 2,3-dihydro analogue have low micromolar antiplasmodial activities and showed more than 10-fold selectivity against the parasite, indicating that the dihydro compound, in particular, might serve as a lead compound for further development.     

27-Nor-Δ4-dafachronic acid is a synthetic ligand of Caenorhabditis elegans DAF-12 receptor

27-Nor-Δ⁴-dafachronic acid was prepared in nine steps and 14% overall yield by two sequential 2-carbon homologations from 20β-carboxyaldehyde-4-pregnen-3-one. Its activity was evaluated in vivo, where it rescued the Mig phenotype of daf-9(rh50) Caenorhabditis elegans mutants and restored their normal resistance to oxidative stress. 27-Nor-Δ⁴-dafachronic acid was also able to directly bind and activate DAF-12 in a transactivation cell-based luciferase reporter assay, although it was less active than the corresponding 25R-and 25S dafachronic acids. The binding mode of the 27-Nor steroid was studied by molecular dynamics using a homology model of the CeDAF-12 receptor.     

Phylogeographical pattern of Euplotes nobilii,a protist ciliate with a bipolar biogeographical distribution

Nuclear (18S and ITS) and mitochondrial (16S) ribosomal RNA gene sequences were determined from genetically distinct wild‐type strains of Antarctic (nine strains), Fuegian (four strains), Greenland (nine strains) and Svalbard (three strains) populations of the marine ciliate, Euplotes nobilii, and analysed for their nucleotide polymorphisms. A close genetic homogeneity was found within and between the Antarctic and Fuegian populations, while more significant levels of genetic differentiation were detected within and between the two Arctic populations, as well as between these populations and the Antarctic/Fuegian ones. The phylogeographical pattern that was derived from these data indicates that gene flow is not limited among Arctic populations; it equally connects the Arctic and Antarctic populations either directly, or through the Fuegian population. This indication reinforces previous evidence from laboratory assays of mating interactions between some of the strains analysed in this work that Southern and Northern polar populations of E. nobilii belong to a unique, panmictic population that substantially share the same gene pool.     

Metabolic fingerprinting reveals differences between northern and southern strains of the cryptic diatom Chaetoceros socialis

Morphology and molecular phylogeny constitute the structural elements of diatom taxonomy. These approaches do not, however, give information on the functioning of taxa. Additional methods to serve a more integrated and wide-ranging taxonomy have therefore been called for. Metabolic fingerprinting is one approach used within the field of metabolomics, often applied in classification of samples. Here we apply metabolic fingerprinting in a taxonomic study of a cryptic diatom species. Strains of the cosmopolitan diatom Chaetoceros socialis from two geographical areas; the north-east Atlantic and Arctic and the Gulf of Naples, were cultivated at three different temperatures; 2.5, 8 and 13°C. The strains from the two different geographical areas exhibited different growth rates as well as different photosynthetic efficiencies. Algal extracts, collected at the end of the growth experiments, were analysed by Ultra-Performance Liquid Chromatography High Resolution Mass Spectrometry. The two groups of strains were separated by principal component analysis of their metabolic fingerprints. Analysis of the data revealed both qualitative and quantitative differences in metabolite markers. These phenotypic differences reinforce differences also found for morphology, phylogenetic markers and growth rates, and point at different adaptive characteristics in organisms living under different temperature regimes.     

Falcipain-2 inhibition by suramin and suramin analogues

Falcipain-2 is a cysteine protease of the malaria parasite Plasmodium falciparum that plays a key role in the hydrolysis of hemoglobin, a process that is required by intraerythrocytic parasites to obtain amino acids. In this work we show that the polysulfonated napthylurea suramin is capable of binding to falcipain-2, inhibiting its catalytic activity at nanomolar concentrations against both synthetic substrates and the natural substrate hemoglobin. Kinetic measurements suggest that the inhibition occurs through an noncompetitive allosteric mechanism, eliciting substrate inhibition. Smaller suramin analogues and those with substituted methyl groups also showed inhibition within the nanomolar range. Our results identify the suramin family as a potential starting point for the design of falcipain-2 inhibitor antimalarials that act through a novel inhibition mechanism.     

Trypsin inhibitors in xoconostle seeds (Opuntia joconostle Weber.)

Seed proteins recovered after heating a seed extract from Opuntia joconostle Weber (xoconostle, an acid cactus pear) were screened for different biochemical activities, detecting only trypsin-like inhibitory activity. Two trypsin-like inhibitor forms from seeds were separated by RP-HPLC and partially sequenced and characterized as an enriched mixture. They were evaluated for inhibition on several serine proteinases, but only trypsin-like inhibition was detected by the inhibitor extract. The two isolated forms, OjTI 1 and OjTI 2 showed low molecular weights of 4.26 and 4.17 kDa as determined by mass spectrometry. An enriched inhibitory fraction showed a high thermal stability by retaining the activity after heating the sample for 1 h at 90 °C, as well as after heating for at 120 °C under 1 kg/cm² for 15 min at different pH values. Partial sequence of the two forms was determined by mass spectrometry indicating that they were similar and after alignments analysis they showed the highest similarity with the trypsin inhibitor from O. streptacantha and to a lesser extent to other trypsin inhibitors of the MEROPS database families. The inhibitory spectrum was evaluated against several digestive enzymes from pests and beneficial insects from several taxonomic orders.     

Trends of karyotypical evolution in the pearl cichlid,Geophagus brasiliensis,from southern Brazil

Chromosomal rearrangements such as inversions can facilitate speciation even in the presence of gene flow. The present study aims to analyze the karyotypic variation in six populations of Geophagus brasiliensis from southern Brazil. All specimens showed 2n = 48 chromosomes, but three karyotypes were found to have one, two or three pairs of submetacentric chromosomes. Although G. brasiliensis did not exhibit variation in the diploid number, it presented a wide interpopulational variation mainly regarding the karyotype formula and specific chromosomal markers. Differences in the location of the major and minor rDNA loci were observed among the populations. Moreover, different patterns were observed in the distribution of the constitutive heterochromatin, presenting intra- and interpopulational variation. This supports the hypothesis that this taxon represents a complex species or that cryptic species are included in this group, indicating a possibleprocess of sympatric speciation. By potentially restricting gene flow between heterokaryotypes, the segregating chromosome rearrangements we describe for G. brasiliensis may play a role in diversification in this species complex.