Intercellular Communication via Gap Junctions Influences Cell Survival During Hypoxia

Stem cell therapy can be beneficial following myocardial infarction. However, when murine bone marrow-derived mesenchymal stem cells (mBM-MSCs) are injected into the ischemic area, a large percentage of these cells undergo apoptosis resulting in decreased therapeutic benefits. We hypothesize that the loss of these mBM-MSCs is regulated by intercellular channels or gap junctions (GJs) that provide apoptotic signals passed between ischemic cardiomyocytes and mBM-MSCs. Our research aims to attenuate these GJs by suppressing Connexin-43 (Cx43) expression, the predominant channel-forming protein. We will accomplish this by transiently transfecting a Cx43 siRNA into mBM-MSCs. Our data demonstrate that intracellular fluorescent dyes and FACS analysis can quantify cell-cell coupling between mBM-MSCs in co-culture. Disrupting Cx43 expression will identify a potential therapeutic target for increasing the retention of mBM-MSCs following myocardial infarction

Fluorescence and Hybrid Detection Aperture of the Pierre Auger Observatory

The aperture of the Fluorescence Detector (FD) of the Pierre Auger Observatory is evaluated from simulated events using different detector configurations: mono, stereo, 3-FD and 4-FD. The trigger efficiency has been modeled using shower profiles with ground impacts in the field of view of a single telescope and studying the trigger response (at the different levels) by that telescope and by its neighbours. In addition, analysis cuts imposed by event reconstruction have been applied. The hybrid aperture is then derived for the Auger final extension. Taking into account the actual Surface Detector (SD) array configuration and its trigger response, the aperture is also calculated for a typical configuration of the present phase.Comment: contribution to the 29th International Cosmic Ray Conference, Pune, India, 3-10 August 200

Gap Junctions in Stem Cells Provide an Essential Conduit for Cell-Cell Communication

Introduction: Myocardial infarction (MI) results from the death of cardiomyocytes (CM) following obstruction of blood flow and diminished oxygen supply to the tissue (hypoxia). Human adipose tissue-derived stem cells (hADSCs) used in pre-clinical models can replace damaged CM, however, this has not been replicated in human clinical trials due to early loss of hADSCs. We hypothesize that coupling of hADSCs to dying CMs may account for part of this loss. Furthermore, cell culturing is essential aspect of any in-vitro experiment. Through multiple trials we sought to maximize the efficiency of our culturing procedures in order to best facilitate the work in our lab. Methods: Four aliquots of hADSCs were cultured and the effects of various reagents and culturing practices were investigated. To examine cell coupling, hADSCs will be cultured for different lengths of time with fluorescent dyes that are either permeable or impermeable to the cell membrane. We will assess the time course of coupling between hADSCs under both normoxic and hypoxic conditions by using fluorescent-activated cell sorting (FACS). Results: Our previous studies demonstrate that adult mesenchymal stem cells possess membrane proteins (connexins) that contribute to cell-cell coupling. The proposed studies will address the functional significance of connexins related to hADSC coupling. The results of our hADSC culturing trials found we can optimize our cultures to facilitate these experiments through several procedural and reagent modifications. Key modifications to culturing protocols include, 1. decreased time spent in culture, 2. utilization of pure, established cell lots, 3. using smaller flasks

Formalizing artisanal and small-scale gold mining : A grand challenge of the Minamata Convention

Artisanal and small-scale gold mining (ASGM) is the world's largest source of anthropogenic mercury emissions and releases. These have devastating consequences for miners' health and the environment. Most of the >20 million ASGM miners worldwide are not officially recognized, registered, regulated, or protected by state laws. Formalization-the process of organizing, registering, and reforming ASGM-is mandated by the Minamata Convention on Mercury. Previous attempts to reduce mercury emissions from ASGM have largely failed. Our perspective argues that signatories to the Convention will only succeed in reducing ASGM mercury emissions and releases with comprehensive bottom-up formalization approaches centered around working with miners, and significant external funding from consumers, large mining corporations, and governments. The approximate global 5-year cost of this approach could be US$355 million (upper and lower estimate bounds: US$213-742 million) if scaled per country, or US$808 million (US$248 million-US$2.17 billion) if scaled per miner.Peer reviewe

Hypertension-induced renal fibrosis and spironolactone response vary by rat strain and mineralocorticoid receptor gene expression

Introduction. Aldosterone promotes renal fibrosis via the mineralocorticoid receptor (MR), thus contributing to hypertension-induced nephropathy. We investigated whether MR gene expression influences renal fibrosis and MR antagonist response in a two-kidney, one-clip hypertensive rat model. Materials and methods. Brown Norway (BN), Lewis, and ACI rats were randomised to spironolactone 20 mg/kg/day or water by gavage, starting four weeks after left renal artery clipping. Blood pressure was measured bi-weekly by tail cuff. After eight weeks of treatment, right kidneys were removed and examined for fibrosis and gene expression. Rats of each strain undergoing no intervention served as controls. Results. Blood pressure increased similarly among strains after clipping and was unaffected by spironolactone. Hypertension caused the greatest renal fibrosis in BN rats (p \u3c 0.001 by ANOVA compared to other strains). Real-time PCR analysis showed greater renal collagen type I and MR gene expression in untreated, hypertensive BN rats (both p \u3c 0.05 compared to other strains). Spironolactone attenuated fibrosis, with similar fibrosis among strains of spironolactone-treated rats. Conclusion. Hypertension-induced renal fibrosis was greatest in rats with the highest MR gene expression. Spironolactone abolished inter-strain differences in fibrosis. Our data suggest that MR genotype may influence aldosterone-induced renal damage, and consequently, renal response to aldosterone antagonism

Functional Conservation of Asxl2, a Murine Homolog for the Drosophila Enhancer of Trithorax and Polycomb Group Gene Asx

Polycomb-group (PcG) and trithorax-group (trxG) proteins regulate histone methylation to establish repressive and active chromatin configurations at target loci, respectively. These chromatin configurations are passed on from mother to daughter cells, thereby causing heritable changes in gene expression. The activities of PcG and trxG proteins are regulated by a special class of proteins known as Enhancers of trithorax and Polycomb (ETP). The Drosophila gene Additional sex combs (Asx) encodes an ETP protein and mutations in Asx enhance both PcG and trxG mutant phenotypes. The mouse and human genomes each contain three Asx homologues, Asx-like 1, 2, and 3. In order to understand the functions of mammalian Asx-like (Asxl) proteins, we generated an Asxl2 mutant mouse from a gene-trap ES cell line.We show that the Asxl2 gene trap is expressed at high levels in specific tissues including the heart, the axial skeleton, the neocortex, the retina, spermatogonia and developing oocytes. The gene trap mutation is partially embryonic lethal and approximately half of homozygous animals die before birth. Homozygotes that survive embryogenesis are significantly smaller than controls and have a shortened life span. Asxl2(-/-) mice display both posterior transformations and anterior transformation in the axial skeleton, suggesting that the loss of Asxl2 disrupts the activities of both PcG and trxG proteins. The PcG-associated histone modification, trimethylation of histone H3 lysine 27, is reduced in Asxl2(-/-) heart. Necropsy and histological analysis show that mutant mice have enlarged hearts and may have impaired heart function.Our results suggest that murine Asxl2 has conserved ETP function and plays dual roles in the promotion of PcG and trxG activity. We have also revealed an unexpected role for Asxl2 in the heart, suggesting that the PcG/trxG system may be involved in the regulation of cardiac function

Extraction of the atmospheric neutrino fluxes from experimental event rate data

The precise knowledge of the atmospheric neutrino fluxes is a key ingredient in the interpretation of the results from any atmospheric neutrino experiment. In the standard atmospheric neutrino data analysis, these fluxes are theoretical inputs obtained from sophisticated numerical calculations. In this contribution we present an alternative approach to the determination of the atmospheric neutrino fluxes based on the direct extraction from the experimental data on neutrino event rates. The extraction is achieved by means of a combination of artificial neural networks as interpolants and Monte Carlo methods.Comment: 6 pages, 2 figs, to appear in the proceedings of the 2nd International Conference on Quantum Theories and Renormalization Group in Gravity and Cosmology, Barcelona, July 200

Protein Kinase G-I Deficiency Induces Pulmonary Hypertension through Rho A/Rho Kinase Activation

Protein kinase G (PKG) plays an important role in the regulation of vascular smooth cell contractility and is a critical mediator of nitric oxide signaling, which regulates cardiovascular homeostasis. PKG-I–knockout (Prkg1−/−) mice exhibit impaired nitric oxide/cGMP-dependent vasorelaxation and systemic hypertension. However, it remains unknown whether PKG-I deficiency induces pulmonary hypertension. In this study, we characterized the hypertensive pulmonary phenotypes in Prkg1−/− mice and delineated the underlying molecular basis. We observed a significant increase in right ventricular systolic pressure in Prkg1−/− mice in the absence of systemic hypertension and left-sided heart dysfunction. In addition, we observed marked muscularization of distal pulmonary vessels in Prkg1−/− mice. Microangiography revealed impaired integrity of the pulmonary vasculature in Prkg1−/− mice. Mechanistically, PKG-I–mediated phosphorylation of Rho A Ser188 was markedly decreased, and the resultant Rho A activation was significantly increased in Prkg1−/− lung tissues, which resulted in Rho kinase activation. The i.t. administration of fasudil, a Rho kinase inhibitor, reversed the hypertensive pulmonary phenotype in Prkg1−/− mice. Taken together, these data show that PKG-I deficiency induces pulmonary hypertension through Rho A/Rho kinase activation–mediated vasoconstriction and pulmonary vascular remodeling

Measuring diffuse neutrino fluxes with IceCube

In this paper the sensitivity of a future kilometer-sized neutrino detector to detect and measure the diffuse flux of high energy neutrinos is evaluated. Event rates in established detection channels, such as muon events from charged current muon neutrino interactions or cascade events from electron neutrino and tau neutrino interactions, are calculated using a detailed Monte Carlo simulation. Neutrino fluxes as expected from prompt charm decay in the atmosphere or from astrophysical sources such as Active Galactic Nuclei are modeled assuming power laws. The ability to measure the normalization and slope of these spectra is then analyzed. It is found that the cascade channel generally has a high sensitivity for the detection and characterization of the diffuse flux, when compared to what is expected for the upgoing- and downgoing-muon channels. A flux at the level of the Waxman-Bahcall upper bound should be detectable in all channels separately while a combination of the information of the different channels will allow detection of a flux more than one order of magnitude lower. Neutrinos from the prompt decay of charmed mesons in the atmosphere should be detectable in future measurements for all but the lowest predictions.Comment: 12 pages, 3 figure