Human BIN3 complements the F-actin localization defects caused by loss of Hob3p, the fission yeast homolog of Rvs161p

The BAR adaptor proteins encoded by the RVS167 and RVS161 genes from Saccharomyces cerevisiae form a complex that regulates actin, endocytosis, and viability following starvation or osmotic stress. In this study, we identified a human homolog of RVS161, termed BIN3 (bridging integrator-3), and a Schizosaccharomyces pombe homolog of RVS161, termed hob3+ (homolog of Bin3). In human tissues, the BIN3 gene was expressed ubiquitously except for brain. S. pombe cells lacking Hob3p were often multinucleate and characterized by increased amounts of calcofluor-stained material and mislocalized F-actin. For example, while wild-type cells localized F-actin to cell ends during interphase, hob3Delta mutants had F-actin patches distributed randomly around the cell. In addition, medial F-actin rings were rarely found in hob3Delta mutants. Notably, in contrast to S. cerevisiae rvs161Delta mutants, hob3Delta mutants showed no measurable defects in endocytosis or response to osmotic stress, yet hob3+ complemented the osmosensitivity of a rvs161Delta mutant. BIN3 failed to rescue the osmosensitivity of rvs161Delta, but the actin localization defects of hob3Delta mutants were completely rescued by BIN3 and partially rescued by RVS161. These findings suggest that hob3+ and BIN3 regulate F-actin localization, like RVS161, but that other roles for this gene have diverged somewhat during evolution.     

Visual mate choice in poison frogs

We investigated female mate choice on the basis of visual cues in two populations of Dendrobates pumilio, the strawberry poison frog, from the Bocas del Toro Archipelago in Panama, Central America. Mate choice experiments were carried out by presenting subject females of each of two morphs of this species (orange and green) from two different island populations (Nancy Key and Pope Island) with object frogs (one of each morph) under glass at one end of a terrarium. Recorded calls were played simultaneously from behind both object frogs. The experiments were carried out under two light regimes: (i) white light, and (ii) relatively monochromatic filtered blue light. Subject females from each population displayed a significant preference for their own morph under white light, but not under blue light. These results indicate that female D. pumilio use visual cues in mate choice, and suggest that colour may be the visual cue they use.     

Effects of 17beta-oestradiol or oestrous stage-specific cow serum on the ability of bovine oviductal epithelial cell monolayers to prolong the viability of bull spermatozoa

The effect of 17beta-oestradiol and oestrous stage-specific cow serum on bovine oviductal epithelial cell monolayers to extend the viability of co-cultured bull spermatozoa was examined. Monolayers of cells from ampullary and isthmic segments were pre-treated with medium containing either oestrous cow serum, luteal-phase cow serum, 1 microg/ml 17beta-oestradiol + foetal bovine serum or foetal bovine serum alone (control) before the addition of motile frozen/thawed spermatozoa. Motility was visually assessed throughout a 48 h co-incubation period, while fertilising ability of spermatozoa was evaluated by adding in vitro matured bovine oocytes. Pre-treatment with 17beta-oestradiol or oestrous cow serum resulted in a higher percentage of motile spermatozoa after 18 h in isthmic and after 36 h in ampullary cultures compared with the control, but pre-treatment did not affect fertilisation rates. Only at 42 h in ampullary cultures was motility higher in luteal serum pre-treated cultures compared to the control. Motility was also assessed in medium conditioned by pre-treated monolayers. Pre-treatment with 17beta-oestradiol enhanced the ability of conditioned medium to prolong motility and medium conditioned with oestrous cow serum was superior to medium conditioned by luteal-phase serum at maintaining motility. In conclusion, the ability of oviductal epithelium to prolong the motility of spermatozoa is enhanced by 17beta-oestradiol.     

Bacterial diversity and ecosystem function of filamentous microbial mats from aphotic (cave) sulfidic springs dominated by chemolithoautotrophic "Epsilonproteobacteria"

Filamentous microbial mats from three aphotic sulfidic springs in Lower Kane Cave, Wyoming, were assessed with regard to bacterial diversity, community structure, and ecosystem function using a 16S rDNA-based phylogenetic approach combined with elemental content and stable carbon isotope ratio analyses. The most prevalent mat morphotype consisted of white filament bundles, with low C:N ratios (3.5-5.4) and high sulfur content (16.1-51.2%). White filament bundles and two other mat morphotypes had organic carbon isotope values (mean delta13C=-34.7 per thousand, 1sigma=3.6) consistent with chemolithoautotrophic carbon fixation from a dissolved inorganic carbon reservoir (cave water, mean delta13C=-7.4 per thousand for two springs, n=8). Bacterial diversity was low overall in the clone libraries, and the most abundant taxonomic group was affiliated with the "Epsilonproteobacteria" (68%), with other bacterial sequences affiliated with Gammaproteobacteria (12.2%), Betaproteobacteria (11.7%), Deltaproteobacteria (0.8%), and the Acidobacterium (5.6%) and Bacteriodetes/Chlorobi (1.7%) divisions. Six distinct epsilonproteobacterial taxonomic groups were identified from the microbial mats. Epsilonproteobacterial and bacterial group abundances and community structure shifted from the spring orifices downstream, corresponding to changes in dissolved sulfide and oxygen concentrations and metabolic requirements of certain bacterial groups. Most of the clone sequences for epsilonproteobacterial groups were retrieved from areas with high sulfide and low oxygen concentrations, whereas Thiothrix spp. and Thiobacillus spp. had higher retrieved clone abundances where conditions of low sulfide and high oxygen concentrations were measured. Genetic and metabolic diversity among the "Epsilonproteobacteria" maximizes overall cave ecosystem function, and these organisms play a significant role in providing chemolithoautotrophic energy to the otherwise nutrient-poor cave habitat. Our results demonstrate that sulfur cycling supports subsurface ecosystems through chemolithoautotrophy and expand the evolutionary and ecological views of "Epsilonproteobacteria" in terrestrial habitats.     

Rapid glucocorticoid stimulation and GABAergic inhibition of hippocampal serotonergic response: in vivo dialysis in the lizard anolis carolinensis

Central serotonin (5-HT) is activated during stressful situations and aggressive interactions in a number of species. Glucocorticoids secreted peripherally during stressful events feed back on central systems and may affect 5-HT mediation of stress-induced behavioral events. To test the neuromodulatory effect of stress hormone secretion, serotonin overflow was measured from the hippocampus of the lizard Anolis carolinensis. Microdialysis was used to collect repeated samples from anesthetized lizards, with perfusate measured by HPLC with electrochemical analysis. Following initially high levels of 5-HT, concentrations stabilized to basal levels after approximately 2 h. Intracortical infusion of 200 ng/ml corticosterone evoked transient increases in 5-HT release of approximately 400%. The effect of corticosterone on 5-HT overflow appears to be dose dependent as 20 ng/ml stimulated an increase of 200%, whereas 2 ng/ml stimulated a 50% increase. Administration of 0.1 and 1 ng/ml GABA via the dialysis probe significantly inhibited 5-HT overflow by 20 and 40%, respectively. The duration of GABA inhibition is greater than the stimulatory response for glucocorticoids. Short-lived glucocorticoid stimulation of 5-HT release suggests a possible mechanism for endocrine mediation of continuously changing social behavioral events.     

Molecular systematics and phylogeography of Amazonian poison frogs of the genus Dendrobates

The study of Amazonian biodiversity requires detailed knowledge of the phylogenetic relationships of closely related taxa distributed across Amazonia. The Amazonian poison frogs of the genus Dendrobates have undergone many taxonomic revisions, but the phylogenetic relationships within this group remain poorly understood. Most previous classifications were based on morphology and skin toxin analyses, with limited use of DNA sequence data. Using mtDNA sequence data from four gene regions (cytochrome b, cytochrome oxidase I, 16S rRNA, and 12S rRNA), we present a molecular phylogenetic analysis of the evolutionary relationships within a representative group of Amazonian Dendrobates. We use the resulting phylogenetic hypothesis to investigate different biogeographic hypotheses concerning genetic divergence and species diversity in Amazonia. The results of the analysis support the presence of ancient paleogeographic barriers to gene flow between eastern and western Amazonia, and indicate substantial genetic divergence between species found in the northern and southern regions of western Amazonia.     

NMR structure of stem-loop SL2 of the HIV-1 psi RNA packaging signal reveals a novel A-U-A base-triple platform

The genome of the human immunodeficiency virus type-1 (HIV-1) contains a stretch of approximately 120 nucleotides known as the psi-site that is essential for RNA packaging during virus assembly. These nucleotides have been proposed to form four stem-loops (SL1-SL4) that have both independent and overlapping functions. Stem-loop SL2 is important for efficient recognition and packaging of the full-length, unspliced viral genome, and also contains the major splice-donor site (SD) for mRNA splicing. We have determined the structure of the 19-residue SL2 oligoribonucleotide by heteronuclear NMR methods. The structure is generally consistent with the most recent of two earlier secondary structure predictions, with residues G1-G2-C3-G4 and C6-U7 forming standard Watson Crick base-pairs with self-complementary residues C16-G17-C18-C19 and A12-G13, respectively. However, residue A15, which is located near the center of the stem, does not form a predicted bulge, and residues A5 and U14 do not form an expected Watson-Crick base-pair. Instead, these residues form a novel A5-U14-A15 base-triple that appears to be stabilized by hydrogen bonds from A15-H61 and -H62 to A5-N1 and U14-O2, respectively; from A5-H61 to U14-O2, and from C16-H42 to U14-O2'. A kink in the backbone allows the aromatic rings of the sequential U14-A15 residues to be approximately co-planar, adopting a stable "platform motif" that is structurally similar to the A-A (adenosine) platforms observed in the P4-P6 ribozyme domain of the Tetrahymena group I intron. Platform motifs generally function in RNA by mediating long-range interactions, and it is therefore possible that the A-U-A base-triple platform mediates long-range interactions that either stabilize the psi-RNA or facilitate splicing and/or packaging. Residue G8 of the G8-G9-U10-G11 tetraloop is stacked above the U7-A12 base-pair, and the remaining tetraloop residues are disordered and available for potential interactions with either other RNA or protein components.