Population genetics and phylogenetics of DNA sequence variation at multiple loci within the Drosophila melanogaster species complex

Two regions of the genome, a 1-kbp portion of the zeste locus and a 1.1- kbp portion of the yolk protein 2 locus, were sequenced in six individuals from each of four species: Drosophila melanogaster, D. simulans, D. mauritiana, and D. sechellia. The species and strains were the same as those of a previous study of a 1.9-kbp region of the period locus. No evidence was found for recent balancing or directional selection or for the accumulation of selected differences between species. Yolk protein 2 has a high level of amino acid replacement variation and a low level of synonymous variation, while zeste has the opposite pattern. This contrast is consistent with information on gene function and patterns of codon bias. Polymorphism levels are consistent with a ranking of effective population sizes, from low to high, in the following order: D. sechellia, D. melanogaster, D.mauritiana, and D. simulans. The apparent species relationships are very similar to those suggested by the period locus study. In particular, D. simulans appears to be a large population that is still segregating variation that arose before the separation of D. mauritiana and D. sechellia. It is estimated that the separation of ancestral D. melanogaster from the other species occurred 2.5-3.4 Mya. The separations of D. sechellia and D. mauritiana from ancestral D. simulans appear to have occurred 0.58- 0.86 Mya, with D. mauritiana having diverged from ancestral D. simulans 0.1 Myr more recently than D. sechellia.      

Invasive Crayfish Threaten the Development of Submerged Macrophytes in Lake Restoration

Submerged macrophytes enhance water transparency and aquatic biodiversity in shallow water ecosystems. Therefore, the return of submerged macrophytes is the target of many lake restoration projects. However, at present, north-western European aquatic ecosystems are increasingly invaded by omnivorous exotic crayfish. We hypothesize that invasive crayfish pose a novel constraint on the regeneration of submerged macrophytes in restored lakes and may jeopardize restoration efforts. We experimentally investigated whether the invasive crayfish (Procambarus clarkii Girard) affects submerged macrophyte development in a Dutch peat lake where these crayfish are expanding rapidly. Seemingly favourable abiotic conditions for macrophyte growth existed in two 0.5 ha lake enclosures, which provided shelter and reduced turbidity, and in one lake enclosure iron was added to reduce internal nutrient loading, but macrophytes did not emerge. We transplanted three submerged macrophyte species in a full factorial exclosure experiment, where we separated the effect of crayfish from large vertebrates using different mesh sizes combined with a caging treatment stocked with crayfish only. The three transplanted macrophytes grew rapidly when protected from grazing in both lake enclosures, demonstrating that abiotic conditions for growth were suitable. Crayfish strongly reduced biomass and survival of all three macrophyte species while waterfowl and fish had no additive effects. Gut contents showed that crayfish were mostly carnivorous, but also consumed macrophytes. We show that P. clarkii strongly inhibit macrophyte development once favourable abiotic conditions for macrophyte growth are restored. Therefore, expansion of invasive crayfish poses a novel threat to the restoration of shallow water bodies in north-western Europe. Prevention of introduction and spread of crayfish is urgent, as management of invasive crayfish populations is very difficult.     

Neuroactive diol and acyloin metabolites from cone snail-associated bacteria

The bacterium Gordonia sp. 647 W.R.1a.05 was cultivated from the venom duct of the cone snail, Conus circumcisus. The Gordonia sp. organic extract modulated the action potential of mouse dorsal root ganglion neurons. Assay-guided fractionation led to the identification of the new compound circumcin A (1) and 11 known analogs (2–12). Two of these compounds, kurasoin B (7) and soraphinol A (8), were active in a human norepinephrine transporter assay with K_i values of 2575 and 867 nM, respectively. No neuroactivity had previously been reported for compounds in this structural class. Gordonia species have been reproducibly isolated from four different cone snail species, indicating a consistent association between these organisms.     

Digital image analysis of AgNORs in cervical smears of women with premalignant and malignant lesions of the uterine cervix

We performed a hospital-based, unmatched case-control study to investigate the association between progressive stages of cervical neoplasia and digital analysis of cell proliferation by silver stained nucleolus organizer region associated proteins (AgNORs). We measured cell proliferation levels in the cervical epithelial cells of 10 women with low grade squamous intraepithelial lesions (LG-SIL), eight with high grade squamous intraepithelial lesions (HG-SIL), 11 with cervical cancer (CC) and eight with no cervical lesions (controls) using the AgNORs technique. Cell proliferation was measured by digital image analysis (DIA). DIA revealed increased total areas of AgNORs in HG-SIL and CC compared to LG-SIL and control patients. AgNORs with a kidney or cluster shape exhibited greater areas than those with a spherical or long shape. We propose a cut-off of 118 pixels to differentiate benign (control and LG-SIL) from malignant (HG-SIL and CC) lesions. DIA of AgNORs is a simple and inexpensive method for studying proliferation. The increased total area of AgNORs in malignant lesions provides information regarding cell behavior and may be related to cervical carcinogenesis; however, further validation studies are required to establish its usefulness in cytological analysis.     

1-Thio-beta-D-galactofuranosides: synthesis and evaluation as beta-D- galactofuranosidase inhibitors

Beta-D-galactofuranosidase is a good chemotherapeutic target for the design of inhibitors, since beta-D-galactofuranose is a constituent of important parasite glycoconjugates but is not present in the host mammals. With this aim, we have synthesized for the first time alkyl, benzyl and aryl 1-thio-beta-D-galactofuranosides by condensation of penta-O-benzoyl-alpha,beta-D-galactofuranose with the corresponding thiols, in the presence of SnCl4as catalyst. The complete chemical and spectroscopical characterization of these compounds showed that the reaction was stereoselective. Debenzoylation with sodium methoxide afforded the beta-S-galactofuranosides in high yield. The thioglycosides were tested as inhibitors of the beta-D- galactofuranosidase of Penicillium fellutanum, using for the first time 4-nitrophenyl-beta-D-galactofuranoside as chromogenic substrate. The 4- aminophenyl-1-thio-beta-D-galactofuranoside, obtained by catalytic hydrogenation of the nitrophenyl derivative, was the best inhibitor being then an adequate ligand for the preparation of an affinity phase aimed at the isolation of beta-d-galactofuranosidases from different sources. Also the inhibitory activity of d-galactono-1, 4-lactone was shown.