NAADP triggers the fertilization potential in starfish oocytes

In invertebrates oocytes or eggs, the fertilization or activation potential establishes the fast electrical block to polyspermy and, in some species, provides the Ca2+ influx which contributes to the following intracellular Ca2+ wave. In echinoderms, the molecule triggering the activation potential is still unknown. The aim of this study was to assess whether nicotinic acid-adenine dinucleotide phosphate (NAADP) elicited the fertilization potential in starfish oocytes. The changes in membrane potential induced by the sperm were measured in oocytes held at a low resting potential, so that the Ca2+-action potential was inactivated and only the initial slower depolarization caused by the sperm could be studied. Decreasing extracellular Na+ concentration did not prevent the onset of the fertilization potential, while removal of external Ca2+ abolished it. The pre-incubation with SK&F 96365 and verapamil and the pre-injection of BAPTA inhibited the fertilization potential, while the injection of heparin only reduced its duration. The biophysical and pharmacological properties of the sperm-elicited depolarization were similar to those displayed by the NAADP-activated Ca2+-mediated current recently described in starfish oocytes. Indeed, the desensitization of NAADP-receptors prevented the onset of the fertilization potential. Taken together, these data suggest that NAADP could trigger the fertilization potential in starfish oocytes.     

Non-stressful death of 23S rRNA mutant G2061C defective in puromycin reaction

Catalysis of peptide bond formation in the peptidyl transferase center is a major enzymatic activity of the ribosome. Mutations limiting peptidyl transferase activity are mostly lethal. However, cellular processes triggered by peptidyl transferase deficiency in the bacterial cell are largely unknown. Here we report a study of the lethal G2061C mutant of Escherichia coli 23S ribosomal RNA (rRNA). The G2061C mutation completely impaired the puromycin reaction and abolished formation of the active firefly luciferase in an in vitro translation system, while poly(U)- and short synthetic mRNA-directed peptidyl transferase reaction with aminoacylated tRNAs in vitro was seemingly unaffected. Study of the cellular proteome upon expression of the 23S rRNA gene carrying the G2061C mutation compared to cells expressing wild-type 23S rRNA gene revealed substantial differences. Most of the observed effects in the mutant were associated with reduced expression of stress response proteins and particularly proteins associated with the ppGpp-mediated stringent response.     

Trophic-based diversification in benthivorous charrs (Salvelinus) dwelling littoral zones of Northern lakes

Charrs of the genus Salvelinus form distinct trophic morphs living in sympatry in numerous postglacial lakes. Here we demonstrate that charrs can diversify into amphipod foraging specialists and sedentary macrobenthos consumers in the shallow-water ecosystems. This pattern was revealed in three out of six lakes under exploration supported by differences in stomach content, trophic-transmitted parasite, and stable isotope ratio analyzes. The body shape and growth rate comparison indicates that this kind of trophic-based diversification emerges at a juvenile stage and is maintained throughout the whole life. The restriction in gene flow found between the morphs allows to propose the possibility for the hereditable-based specialization to evolve. We found that those diversification phenomena are possible only in the lakes situated in vicinity of the ocean coastline, while no evidence of this split was found for inland mountain lakes. We suggest that the trophic-based diversification in the littoral ecosystems is accounted for the heterogeneity in the ecological conditions and food resources’ distribution linked to coastal wind action. This phenomenon was previously reported for the charr in Lake Fjellfrosvatn, Scandinavia, so it seems to be some universal yet poorly described kind of disruptive selection pressure for northern latitude fishes.

     

A central role for hepatocyte growth factor in adipose tissue angiogenesis

Hepatocyte growth factor (HGF) is a potent mitogenic and angiogenic factor produced in human adipose tissue. In this study, we use 3T3-F442A preadipocytes to study the contribution of HGF to angiogenesis in an in vivo fat pad development model. As observed for human adipocytes, HGF is synthesized and secreted by 3T3-F442A preadipocytes and mature adipocytes. HGF knockdown with small-interfering RNA reduced HGF mRNA expression 82.3 +/- 4.2% and protein secretion 82.9 +/- 1.4% from 3T3-F442A preadipocytes. Silencing of HGF resulted in a 70.5 +/- 19.0% reduction in endothelial progenitor cell migration to 3T3-F442A-conditioned medium in vitro. 3T3-F442A preadipocytes injected under the skin of mice form a fat pad containing mature, lipid-filled adipocytes and a functional vasculature. At 72 h postinjection, expression of the endothelial cell genes TIE-1 and platelet endothelial cell adhesion molecule (PECAM)-1 was decreased 94.4 +/- 2.2 and 91.5 +/- 2.5%, respectively, in 3T3-F442A fat pads with HGF silencing. Knockdown of HGF had no effect on differentiation of 3T3-F442A preadipocytes to mature adipocytes in vitro or in vivo. In developing fat pads under the skin of HGF overexpressing transgenic mice, TIE-1 and PECAM-1 mRNA was increased 16.5- and 21.4-fold, respectively, at 72 h postinjection. The increase in gene expression correlated with immunohistochemical evidence of endothelial cell migration in the developing fat pad. These data suggest that HGF has a central role in regulating angiogenesis in adipose tissue.     

Characterization of an acetylated heteroxylan from Eucalyptus globulus Labill

A heteroxylan was isolated from Eucalyptus globulus wood by extraction of peracetic acid delignified holocellulose with dimethyl sulfoxide. Besides (1-->4)-linked beta-D-xylopyranosyl units of the backbone and short side chains of terminal (1-->2)-linked 4-O-methyl-alpha-D-glucuronosyl residues (MeGlcA) in a 1:10 molar ratio, this hemicellulose contained galactosyl and glucosyl units attached at O-2 of MeGlcA originating from rhamnoarabinogalactan and glucan backbones, respectively. About 30% of MeGlcA units were branched at O-2. The O-acetyl-(4-O-methylglucurono)xylan showed an acetylation degree of 0.61, as determined by 1H NMR spectroscopy, and a weight-average molecular weight (M(w)) of about 36 kDa (P=1.05) as revealed from size-exclusion chromatography (SEC) analysis. About half of the beta-D-xylopyranosyl units of the backbone were found as acetylated moieties at O-3 (34 mol%), O-2 (15 mol%) or O-2,3 (6 mol%). Practically, all beta-D-xylopyranosyl units linked at O-2 with MeGlcA residues were 3-O-acetylated (10 mol%).     

Demographic expansion and genetic load of the halophyte model plant Eutrema salsugineum

The halophyte model plant Eutrema salsugineum (Brassicaceae) disjunctly occurs in temperate to subarctic Asia and North America. This vast, yet extremely discontinuous distribution constitutes an ideal system to examine long‐distance dispersal and the ensuing accumulation of deleterious mutations as expected in expanding populations of selfing plants. In this study, we resequenced individuals from 23 populations across the range of E. salsugineum. Our population genomic data indicate that E. salsugineum migrated “out of the Altai region” at least three times to colonize northern China, northeast Russia and western China. It then expanded its distribution into North America independently from northeast Russia and northern China, respectively. The species colonized northern China around 33.7 thousand years ago (kya) and underwent a considerable expansion in range size approximately 7–8 kya. The western China lineage is likely a hybrid derivative of the northern China and Altai lineages, originating approximately 25–30 kya. Deleterious alleles accumulated in a stepwise manner from (a) Altai to northern China and North America and (b) Altai to northeast Russia and North America. In summary, E. salsugineum dispersed from Asia to North America and deleterious mutations accumulated in a stepwise manner during the expansion of the species’ distribution.     

Orexinergic Neurotransmission in Temperature Responses to Methamphetamine and Stress: Mathematical Modeling as a Data Assimilation Approach

Experimental Data

Orexinergic neurotransmission is involved in mediating temperature responses to methamphetamine (Meth). In experiments in rats, SB-334867 (SB), an antagonist of orexin receptors (OX1R), at a dose of 10 mg/kg decreases late temperature responses (t>60 min) to an intermediate dose of Meth (5 mg/kg). A higher dose of SB (30 mg/kg) attenuates temperature responses to low dose (1 mg/kg) of Meth and to stress. In contrast, it significantly exaggerates early responses (t<60 min) to intermediate and high doses (5 and 10 mg/kg) of Meth. As pretreatment with SB also inhibits temperature response to the stress of injection, traditional statistical analysis of temperature responses is difficult.

Mathematical Modeling

We have developed a mathematical model that explains the complexity of temperature responses to Meth as the interplay between excitatory and inhibitory nodes. We have extended the developed model to include the stress of manipulations and the effects of SB. Stress is synergistic with Meth on the action on excitatory node. Orexin receptors mediate an activation of on both excitatory and inhibitory nodes by low doses of Meth, but not on the node activated by high doses (HD). Exaggeration of early responses to high doses of Meth involves disinhibition: low dose of SB decreases tonic inhibition of HD and lowers the activation threshold, while the higher dose suppresses the inhibitory component. Using a modeling approach to data assimilation appears efficient in separating individual components of complex response with statistical analysis unachievable by traditional data processing methods.     

High Levels of Heterogeneity in the HIV Cascade of Care across Different Population Subgroups in British Columbia,Canada

Background

The HIV cascade of care (cascade) is a comprehensive tool which identifies attrition along the HIV care continuum. We executed analyses to explicate heterogeneity in the cascade across key strata, as well as identify predictors of attrition across stages of the cascade.

Methods

Using linked individual-level data for the population of HIV-positive individuals in BC, we considered the 2011 calendar year, including individuals diagnosed at least 6 months prior, and excluding individuals that died or were lost to follow-up before January 1^st, 2011. We defined five stages in the cascade framework: HIV ‘diagnosed’, ‘linked’ to care, ‘retained’ in care, ‘on HAART’ and virologically ‘suppressed’. We stratified the cascade by sex, age, risk category, and regional health authority. Finally, multiple logistic regression models were built to predict attrition across each stage of the cascade, adjusting for stratification variables.

Results

We identified 7621 HIV diagnosed individuals during the study period; 80% were male and 5% were <30, 17% 30–39, 37% 40–49 and 40% were ≥50 years. Of these, 32% were MSM, 28% IDU, 8% MSM/IDU, 12% heterosexual, and 20% other. Overall, 85% of individuals ‘on HAART’ were ‘suppressed’; however, this proportion ranged from 60%–93% in our various stratifications. Most individuals, in all subgroups, were lost between the stages: ‘linked’ to ‘retained’ and ‘on HAART’ to ‘suppressed’. Subgroups with the highest attrition between these stages included females and individuals <30 years (regardless of transmission risk group). IDUs experienced the greatest attrition of all subgroups. Logistic regression results found extensive statistically significant heterogeneity in attrition across the cascade between subgroups and regional health authorities.

Conclusions

We found that extensive heterogeneity in attrition existed across subgroups and regional health authorities along the HIV cascade of care in B.C., Canada. Our results provide critical information to optimize engagement in care and health service delivery.     

Biodeterioration of crude oil and oil derived products: a review

Biodeterioration of crude oil and oil fuels is a serious economic and an environmental problem all over the world. It is impossible to prevent penetration of microorganisms in oil and fuels both stored in tanks or in oilfields after drilling. Both aerobic and anaerobic microorganisms tend to colonise oil pipelines and oil and fuel storage installations. Complex microbial communities consisting of both hydrocarbon oxidizing microorganisms and bacteria using the metabolites of the former form an ecological niche where they thrive. The accumulation of water at the bottom of storage tanks and in oil pipelines is a primary prerequisite for development of microorganisms in fuels and oil and their subsequent biological fouling. Ability of microorganisms to grow both in a water phase and on inter-phase of water/hydrocarbon as well as the generation of products of their metabolism worsen the physical and chemical properties of oils and fuels. This activity also increases the amount of suspended solids, leads to the formation of slimes and creates a variety of operational problems. Nowadays various test-systems are utilized for microbial monitoring in crude oils and fuels; thus allowing an express determination of both the species and the quantities of microorganisms present. To suppress microbial growth in oils and fuels, both physico-mechanical and chemical methods are applied. Among chemical methods, the preference is given to substances such as biocides, additives, the anti-freezing agents etc that do not deteriorate the quality of oil and fuels and are environmentally friendly. This review is devoted to the analysis of the present knowledge in the field of microbial fouling of crude oils and oil products. The methods utilized for monitoring of microbial contamination and prevention of their undesirable activities are also evaluated. The special focus is given to Russian scientific literature devoted to crude oil and oil products biodeterioration.     

Antiamoebin I in methanol solution: rapid exchange between right-handed and left-handed 3(10)-helical conformations

Antiamoebin I (Aam-I) is a membrane-active peptaibol antibiotic isolated from fungal species belonging to the genera Cephalosporium, Emericellopsis, Gliocladium, and Stilbella. Antiamoebin I has the amino acid sequence: Ac-Phe(1)-Aib-Aib-Aib-Iva-Gly-Leu-Aib(8)-Aib-Hyp-Gln-Iva-Hyp-Aib-Pro-Phl(16). By using the uniformly (13)C,(15)N-labeled sample of Aam-I, the set of conformationally dependent J couplings and (3h)J(NC) couplings through H-bonds were measured. Analysis of these data along with the data on magnetic nonequivalence of the (13)C(beta) nuclei (Deltadelta((13)C(beta))) in Aib and Iva residues allowed us to draw the univocal conclusion that the N-terminal part (Phe(1)-Gly(6)) of Aam-I in MeOH solution is in fast exchange between the right-handed and left-handed 3(10)-helical conformations, with an approximately equal population of both states. An additional conformational exchange process was found at the Aib(8) residue. The (15)N-NMR-relaxation and CD-spectroscopy measurements confirmed these findings. Molecular modeling and Monte Carlo simulations revealed that both exchange processes are correlated and coupled with significant hinge-bending motions around the Aib(8) residue. Our results explain relatively low activity of Aam-I with respect to other 15-amino acid residue peptaibols (for example, zervamicin) in functional and biological tests. The high dynamic 'propensity' possibly prevents both initial binding of the antiamoebin to the membrane and subsequent formation of stable ionic channels according to the barrel-stave mechanism.