Mechanism of silicate binding to the bacterial cell wall in Bacillus subtilis.

To investigate the chemical mechanism of silicate binding to the surface of Bacillus subtilis, we chemically modified cell wall carboxylates to reverse their charge by the addition of an ethylenediamine ligand. For up to 9 weeks, mixtures of Si, Al-Fe-Si, and Al-Fe-Si plus toxic heavy metals were reacted with these cells for comparison with control cells and abiotic solutions. In general, more Si and less metal were bound to the chemically modified surfaces, thereby showing the importance of an electropositive charge in cell walls for fine-grain silicate mineral development. The predominant reaction for this development was the initial silicate-to-amine complexation in the peptidoglycan of ethylenediamine-modified and control cell walls, although metal ion bridging between electronegative sites and silicate had an additive effect. The binding of silicate to these bacterial surfaces can thus be described as outer sphere complex formation because it occurs through electrostatic interaction.     

Virulence of infecting Helicobacter pyloristrains and intensity of mononuclear cell infiltration are associated with levels of DNA hypermethylation in gastric mucosae

DNA methylation changes are known to occur in gastric cancers and in premalignant lesions of the gastric mucosae. In order to examine variables associated with methylation levels, we quantitatively evaluated DNA methylation in tumors, non-tumor gastric mucosae, and in gastric biopsies at promoters of 5 genes with methylation alterations that discriminate gastric cancers from non-tumor epithelia (EN1, PCDH10, RSPO2, ZIC1, and ZNF610). Among Colombian subjects at high and low risk for gastric cancer, biopsies from subjects from the high-risk region had significantly higher levels of methylation at these 5 genes than samples from subjects in the low risk region (p ≤ 0.003). When results were stratified by Helicobacter pylori infection status, infection with a cagA positive, vacA s1m1 strain was significantly associated with highest methylation levels, compared with other strains (p = 0.024 to 0.001). More severe gastric inflammation and more advanced precancerous lesions were also associated with higher levels of DNA methylation (p ≤ 0.001). In a multivariate model, location of residence of the subject and the presence of cagA and vacA s1m1 in the H. pylori strain were independent variables associated with higher methylation in all 5 genes. High levels of mononuclear cell infiltration were significantly related to methylation in PCDH10, RSPO2, and ZIC1 genes. These results indicate that for these genes, levels of methylation in precancerous lesions are related to H. pylori virulence, geographic region and measures of chronic inflammation. These genes seem predisposed to sustain significant quantitative changes in DNA methylation at early stages of the gastric precancerous process.     

Positive genetic associations among fitness traits support evolvability of a reef‐building coral under multiple stressors

Climate change threatens organisms in a variety of interactive ways that requires simultaneous adaptation of multiple traits. Predicting evolutionary responses requires an understanding of the potential for interactions among stressors and the genetic variance and covariance among fitness‐related traits that may reinforce or constrain an adaptive response. Here we investigate the capacity of Acropora millepora, a reef‐building coral, to adapt to multiple environmental stressors: rising sea surface temperature, ocean acidification, and increased prevalence of infectious diseases. We measured growth rates (weight gain), coral color (a proxy for Symbiodiniaceae density), and survival, in addition to nine physiological indicators of coral and algal health in 40 coral genets exposed to each of these three stressors singly and combined. Individual stressors resulted in predicted responses (e.g., corals developed lesions after bacterial challenge and bleached under thermal stress). However, corals did not suffer substantially more when all three stressors were combined. Nor were trade‐offs observed between tolerances to different stressors; instead, individuals performing well under one stressor also tended to perform well under every other stressor. An analysis of genetic correlations between traits revealed positive covariances, suggesting that selection to multiple stressors will reinforce rather than constrain the simultaneous evolution of traits related to holobiont health (e.g., weight gain and algal density). These findings support the potential for rapid coral adaptation under climate change and emphasize the importance of accounting for corals’ adaptive capacity when predicting the future of coral reefs.     

Synthesis of novel 1-alkyl-8-substituted-3-(3-methoxypropyl) xanthines as putative A2B receptor antagonists

In order to identify a high-affinity, selective antagonist for the A_2B subtype adenosine receptor, more than 40 1,8-disubstituted-3-(3-methoxypropyl) xanthines were prepared and evaluated for their binding affinity at recombinant human adenosine receptors, mainly of the A_2A and A_2B subtypes. Some of the 1-ethyl-3-(3-methoxypropyl)-8-aryl substituted derivatives 15(a–m) showed moderate-to-high affinity at human A_2B receptors, with compound 15d showing A_2B selectivity over the other A receptors assayed (A₁, A_2A, A₃) of 34-fold or over.     

Use of plate-wash samples to monitor the fates of culturable bacteria in mercury- and trichloroethylene-contaminated soils

With the ultimate aim of developing bioremediation technology that use the optimum bacterial community for each pollutant, we performed polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis and identified communities of culturable bacteria in HgCl(2)- and trichloroethylene (TCE)-contaminated soil microcosms. PCR-DGGE band patterns were similar at 0 and 1 ppm HgCl(2), but changes in specific bands occurred at 10 ppm HgCl(2). Band patterns appearing at 10 and 100 ppm TCE were very different from those at 0 ppm. Phylogenetic analysis showed four bacterial groups in the HgCl(2)-contaminatied cultures: Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes. Most high-density bands, decreased-density bands, and common bands were classified into the phyla Proteobacteria, Actinobacteria, and Firmicutes, respectively; the effects of HgCl(2) on culturable bacteria appeared to differ among phyla. Duganella violaceinigra [98.4% similarity to DNA Data Bank of Japan (DDBJ) strain], Lysobacter koreensis (98.2%), and Bacillus panaciterrae (98.6%) were identified as bacteria specific to HgCl(2)-contaminated soils. Bacteria specific to TCE-contaminated soils were distributed into three phyla (Firmicutes, Proteobacteria, and Actinobacteria), but there was no clear relationship between phylum and TCE effects on culturable bacteria. Paenibacillus kobensis (97.3%), Paenibacillus curdlanolyticus (96.3%), Paenibacillus wynnii (99.8%), and Sphingomonas herbicidovorans (99.4%) were identified as bacteria specific to TCE-contaminated soils. These bacteria may be involved in pollutant degradation.     

Transduction of phosphatase and tensin homolog deleted on chromosome 10 into eosinophils attenuates survival, chemotaxis, and airway inflammation

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is part of a complex signaling system that affects a variety of important cell functions. PTEN antagonizes the action of PI3K by dephosphorylating the signaling lipid phosphatidylinositol 3,4,5-triphosphate. In the present study, we used a TAT fusion protein transduction system to elucidate the role of PTEN in eosinophils and airway inflammation. A small region of the HIV TAT protein (YGRKKRRQRRR), a protein transduction domain known to enter mammalian cells efficiently, was fused to the N terminus of PTEN. Flow cytometric analysis of annexin V- and propidium iodide-stained cells was used to assess eosinophil survival. A chemotaxis assay was performed using a Boyden chamber. Cell analysis in bronchoalveolar lavage fluid and histological examinations were performed using OVA-challenged A/J mice. We found that TAT-PTEN was successfully internalized into eosinophils and functioned as a phosphatase in situ. TAT-PTEN, but not a TAT-GFP control protein, blocked the ability of IL-5 to prevent the apoptosis of eosinophils from allergic subjects. The eotaxin-induced eosinophil chemotaxis was inhibited by TAT-PTEN in a dose-dependent manner. Intranasal pretreatment with TAT-PTEN, but not TAT-GFP, significantly inhibited the OVA-induced eosinophil infiltration in bronchoalveolar lavage fluid. Histological examination of the lung, including H&E and Alcian blue/periodic acid-Schiff staining, revealed that TAT-PTEN, but not TAT-GFP, abrogated eosinophilic inflammation and mucus production. Our results suggest that PTEN negatively regulates eosinophil survival, chemotaxis, and allergic inflammation. The pharmacological targeting of PTEN may constitute a new strategy for the treatment of eosinophilic disorders.     

The effect of repetitive transcranial magnetic stimulation on gamma oscillatory activity in schizophrenia

Background

Gamma (γ) oscillations (30–50 Hz) have been shown to be excessive in patients with schizophrenia (SCZ) during working memory (WM). WM is a cognitive process that involves the online maintenance and manipulation of information that is mediated largely by the dorsolateral prefrontal cortex (DLPFC). Repetitive transcranial magnetic stimulation (rTMS) represents a non-invasive method to stimulate the cortex that has been shown to enhance cognition and γ oscillatory activity during WM.

Methodology and Principal Findings

We examined the effect of 20 Hz rTMS over the DLPFC on γ oscillatory activity elicited during the N-back task in 24 patients with SCZ compared to 22 healthy subjects. Prior to rTMS, patients with SCZ elicited excessive γ oscillatory activity compared to healthy subjects across WM load. Active rTMS resulted in the reduction of frontal γ oscillatory activity in patients with SCZ, while potentiating activity in healthy subjects in the 3-back, the most difficult condition. Further, these effects on γ oscillatory activity were found to be specific to the frontal brain region and were absent in the parieto-occipital brain region.

Conclusions and Significance

We suggest that this opposing effect of rTMS on γ oscillatory activity in patients with SCZ versus healthy subjects may be related to homeostatic plasticity leading to differential effects of rTMS on γ oscillatory activity depending on baseline differences. These findings provide important insights into the neurophysiological mechanisms underlying WM deficits in SCZ and demonstrated that rTMS can modulate γ oscillatory activity that may be a possible avenue for cognitive potentiation in this disorder.     

Centrally administered adrenomedullin 2 activates hypothalamic oxytocin-secreting neurons, causing elevated plasma oxytocin level in rats

We examined the effects of intracerebroventricular (i.c.v.) administration of adrenomedullin 2 (AM2) on plasma oxytocin (OXT) and arginine vasopressin (AVP) levels in conscious rats. Plasma OXT levels were markedly increased 5 min after i.c.v. administration of AM2 (1 nmol/rat) compared with vehicle and remained elevated in samples taken at 10, 15, 30, and 60 min. By contrast, plasma AVP levels were not significantly elevated in samples taken between 5 and 180 min after i.c.v. administration of AM2 except at the 30-min time point. Fos-like immunoreactivity (Fos-LI) was observed in various brain areas, including the paraventricular (PVN) and the supraoptic nuclei (SON) after i.c.v. administration of AM2 (2 nmol/rat) in conscious rats (measured at 90 min post-AM2 infusion). Dual immunostaining for OXT/Fos and AVP/Fos showed that OXT-LI neurons predominantly exhibited nuclear Fos-LI compared with AVP-LI neurons in the PVN and the SON. In situ hybridization histochemistry showed that i.c.v. administration of AM2 (0.2, 1, and 2 nmol/rat) caused marked induction of the expression of the c-fos gene in the PVN and the SON. This induction was significantly reduced by pretreatment with both the calcitonin gene-related peptide (CGRP) antagonist CGRP-(8-37) (3 nmol/rat) and the AM receptor antagonist AM-(22-52) (27 nmol/rat). These results suggest that centrally administered AM2 mainly activates OXT-secreting neurons in the PVN and the SON, at least in part through the CGRP and/or AM receptors with marked elevation of plasma OXT levels in conscious rats.     

Fatty acid composition of the tropical lichen Teloschistes flavicans and its cultivated symbionts

Fatty acid components, in both the free and combined form of the intact tropical lichen Teloschistes flavicans, and its isolated photobiont and mycobiont, were analyzed by GC-MS of derived methyl esters. Its rDNA analysis confirmed that the isolated cultured symbionts belong to the genera Trebouxia and Teloschistes, respectively. The fatty acid composition of the lichen did not correspond to those found in the isolated symbionts, suggesting that the fatty acid metabolism is markedly influenced by the symbiosis. Differences in the fatty acid composition in the lichen were observed during the summer (27 degrees C), when the main fatty acids were saturated and in the winter (22 degrees C) when an increase of unsaturated fatty acids occurred. Similar differences of composition were also observed for the cultured mycobiont at different temperatures. The increase in the unsaturation level at low temperatures would maintain the membrane fluidity. Our results are the first on the fatty acids of a tropical lichen and suggest that it is sensitive to small temperature variations, which influences its saturated and unsaturated fatty acid composition.     

Atheroma development in apolipoprotein E-null mice is not regulated by phosphorylation of p27(Kip1) on threonine 187

Excessive cellular proliferation is thought to contribute to neointimal lesion development during atherosclerosis and restenosis after angioplasty. Inhibition of cyclin-dependent kinase (CDK) activity by p27 inhibits mammalian cell growth. Mounting evidence indicates that p27 negatively regulates neointimal thickening in animal models of restenosis and atherosclerosis, and its expression in human neointimal lesions is consistent with such a protective role. Cell cycle progression is facilitated by cyclinE/CDK2-dependent phosphorylation of p27 on threonine 187 (T187) during late G1. The purpose of this study was to assess whether this phosphorylation event plays a role during atherosclerosis. To this end, we generated apolipoprotein E-null mice with both p27 alleles replaced by a mutated form non-phosphorylatable at T187 (apoE-/-p27T187A mice) and investigated the kinetics of atheroma development in these animals compared to apoE-/- controls with an intact p27 gene. Fat feeding resulted in comparable level of hypercholesterolemia in both groups of mice. Surprisingly, aortic p27 expression was not increased in fat-fed apoE-/-p27T187A mice compared with apoE-/- controls. Moreover, atheroma size, lesion cellularity, proliferation, and apoptotic rates were undistinguishable in both groups of fat-fed mice. Thus, in contrast to previous studies that highlight the importance of p27 phosphorylation at T187 on the control of p27 expression and function in different tissues and pathophysiological scenarios, our findings demonstrate that this phosphorylation event is not implicated in the control of aortic p27 expression and atheroma progression in hypercholesterolemic mice.