Recruitment in the sea: bacterial genes required for inducing larval settlement in a polychaete worm

Metamorphically competent larvae of the marine tubeworm Hydroides elegans can be induced to metamorphose by biofilms of the bacterium Pseudoalteromonas luteoviolacea strain HI1. Mutational analysis was used to identify four genes that are necessary for metamorphic induction and encode functions that may be related to cell adhesion and bacterial secretion systems. No major differences in biofilm characteristics, such as biofilm cell density, thickness, biomass and EPS biomass, were seen between biofilms composed of P. luteoviolacea (HI1) and mutants lacking one of the four genes. The analysis indicates that factors other than those relating to physical characteristics of biofilms are critical to the inductive capacity of P. luteoviolacea (HI1), and that essential inductive molecular components are missing in the non-inductive deletion-mutant strains

A Glycoprotein in Shells of Conspecifics Induces Larval Settlement of the Pacific Oyster Crassostrea gigas

Settlement of larvae of Crassostrea gigas on shell chips (SC) prepared from shells of 11 different species of mollusks was investigated. Furthermore, the settlement inducing compound in the shell of C. gigas was extracted and subjected to various treatments to characterize the chemical cue. C. gigas larvae settled on SC of all species tested except on Patinopecten yessoensis and Atrina pinnata. In SC of species that induced C. gigas larvae to settle, settlement was proportionate to the amount of SC supplied to the larvae. When compared to C. gigas SC, all species except Crassostrea nippona showed lower settlement inducing activities, suggesting that the cue may be more abundant or in a more available form to the larvae in shells of conspecific and C. nippona than in other species. The settlement inducing activity of C. gigas SC remained intact after antibiotic treatment. Extraction of C. gigas SC with diethyl ether (Et2O-ex), ethanol (EtOH-ex), and water (Aq-ex) did not induce larval settlement of C. gigas larvae. However, extraction of C. gigas SC with 2N of hydrochloric acid (HCl-ex) induced larval settlement that was at the same level as the SC. The settlement inducing compound in the HCl-ex was stable at 100°C but was destroyed or degraded after pepsin, trypsin, PNGase F and trifluoromethanesulfonic acid treatments. This chemical cue eluted between the molecular mass range of 45 and 150 kDa after gel filtration and revealed a major band at 55 kDa on the SDS-PAGE gel after staining with Stains-all. Thus, a 55 kDa glycoprotein component in the organic matrix of C. gigas shells is hypothesized to be the chemical basis of larval settlement on conspecifics

Expression of acetylcholinesterase in alzheimer's disease brain: Role in neuritic dystrophy and synaptic scaling

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The beta-amyloid protein of Alzheimer's disease increases neuronal CRMP-2 phosphorylation by a Rho-GTP mechanism

Neuritic abnormalities are a major hallmark of Alzheimer's disease (AD) pathology. Accumulation of ?-amyloid protein (A?) in the brain causes changes in neuritic processes in individuals with this disease. In this study, we show that A? decreases neurite outgrowth from SH-SY5Y human neuroblastoma cells. To explore molecular pathways by which A? alters neurite outgrowth, we examined the activation and localization of RhoA and Rac1 which regulate the level and phosphorylation of the collapsin response mediator protein-2 (CRMP-2). A? increased the levels of the GTP-bound (active) form of RhoA in SH-SY5Y cells. This increase in GTP-RhoA correlated with an increase in an alternatively spliced form of CRMP-2 (CRMP-2A) and its threonine phosphorylated form. Both a constitutively active form of Rac1 (CA-Rac1) and the Rho kinase inhibitor, Y27632, decreased levels of the CRMP-2A variant and decreased threonine phosphorylation caused by A? stimulation. The amount of tubulin bound to CRMP-2 was decreased in the presence of A? but Y27632 increased the levels of tubulin bound to CRMP-2. Increased levels of both RhoA and CRMP-2 were found in neurons surrounding amyloid plaques in the cerebral cortex of the APP(Swe) Tg2576 mice. We found that there was an increase in threonine phosphorylation of CRMP-2 in Tg2576 mice and the increase correlated with a decrease in the ability of CRMP-2 to bind tubulin. The results suggest that A?-induced neurite outgrowth inhibition may be initiated through a mechanism in which A? causes an increase in Rho GTPase activity which, in turn, phosphorylates CRMP-2 to interfere with tubulin assembly in neurites

Data documenting the performance of the PT/INR line correction method for reconciling INR discrepancies between central laboratory coagulation analyzers using different thromboplastins during the evaluation of a portable Coagulometer

The data presented here was produced as part of an evaluation of the performance of the CoaguChek XS point-of-care coagulation analyzer, which is discussed in the research article “POCT PT INR – Is it adequate for Patient Care? A Comparison of the Roche Coaguchek XS vs. Stago Star vs. Siemens BCS in Patients Routinely Seen in an Anticoagulation Clinic” (Baker et al., in press) [1]. An effort to reconcile discrepancies in the patient INR result distributions from different central lab instruments (Stago Star and Siemens BCS) with the PT/INR line method is described (Poller et al., 2010, 2011; Ibrahim et al., 2011) [2-4]. While regression analysis of the ECAA Poller calibrant data provided a linear PT/INR line for all methods, Pearson's chi-squared and one-way repeated measures ANOVA analyses showed that central lab INR measurements continued to exhibit measurement site dependence after the PT/INR line correction was applied. According to paired t-test analysis, only the human thromboplastin dependent methods (CoaguChek XS and Siemens BCS both before and after PT/INR line correction) showed statistically significant agreement (p-value >0.05)

Conformational stability studies of a stapled hexa-β3-peptide library

A library of 14-helical hexa β(3)-peptides was synthesized in order to determine the influence of sequence variation as well as staple size and location on conformational stability. From this study we show that appropriately stapled hexa-β(3)-peptides can allow for a number of variations without significant perturbation of the 14-helix

The beta-amyloid protein of Alzheimer's disease does not bind to the alpha7 nicotinic acetylcholine receptor

Accumulation of the amyloid protein (Aß) in the brain is an important step in the pathogenesis of Alzheimer's disease. However, the mechanism by which Aß exerts its neurotoxic effect is largely unknown. It has been suggested that the peptide can bind to the a7 nicotinic acetylcholine receptor (a7nAChR). In this study, we examined the binding of Aß1-42 to endogenous and recombinantly expressed a7nAChRs. Aß1-42 did neither inhibit the specific binding of a7nAChR ligands to rat brain homogenate or slice preparations, nor did it influence the activity of a7nAChRs expressed in Xenopus oocytes. Similarly, Aß1-42 did not compete for a-bungarotoxin-binding sites on SH-SY5Y cells stably expressing a7nAChRs. The effect of the Aß1-42 on tau phosphorylation was also examined. Although Aß1-42 altered tau phosphorylation in a7nAChR-transfected SH-SY5Y cells, the effect of the peptide was unrelated to a7nAChR expression or activity. Binding studies using surface plasmon resonance indicated that the majority of the Aß bound to membrane lipid, rather than to a protein component. Fluorescence anisotropy experiments indicated that Aß may disrupt membrane lipid structure or fluidity. We conclude that the effects of Aß are unlikely to be mediated by direct binding to the a7nAChR. Instead, we speculate that Aß may exert its effects by altering the packing of lipids within the plasma membrane, which could, in turn, influence the function of a variety of receptors and channels on the cell surface. © 2007 The Author

Synthesis of stapled beta3 - peptides through ring - closing metathesis

The first synthesis of carbon-stapled beta(3)-peptides is reported. The precursor beta(3)-peptides, with O-allyl beta-serines located in an i/i+3 relationship, were prepared on solid phase. We show that efficient ring-closing metathesis (RCM) of these new beta(3)-peptides proceeds smoothly either in solution or on an appropriate solid support. All products were generated with high selectivity for the E-isomer