248 research outputs found
Coupling between pore formation and phase separation in charged lipid membranes
We investigated the effect of charge on the membrane morphology of giant
unilamellar vesicles (GUVs) composed of various mixtures containing charged
lipids. We observed the membrane morphologies by fluorescent and confocal laser
microscopy in lipid mixtures consisting of a neutral unsaturated lipid
[dioleoylphosphatidylcholine (DOPC)], a neutral saturated lipid
[dipalmitoylphosphatidylcholine (DPPC)], a charged unsaturated lipid
[dioleoylphosphatidylglycerol (DOPG)], a charged saturated
lipid [dipalmitoylphosphatidylglycerol (DPPG)], and
cholesterol (Chol). In binary mixtures of neutral DOPC/DPPC and charged
DOPC/DPPG, spherical vesicles were formed. On the other
hand, pore formation was often observed with GUVs consisting of
DOPG and DPPC. In a DPPC/DPPG/Chol
ternary mixture, pore-formed vesicles were also frequently observed. The
percentage of pore-formed vesicles increased with the DPPG
concentration. Moreover, when the head group charges of charged lipids were
screened by the addition of salt, pore-formed vesicles were suppressed in both
the binary and ternary charged lipid mixtures. We discuss the mechanisms of
pore formation in charged lipid mixtures and the relationship between phase
separation and the membrane morphology. Finally, we reproduce the results seen
in experimental systems by using coarse-grained molecular dynamics simulations.Comment: 34 pages, 10 figure
Revisiting Discrete Dark Matter Model:\theta_{13}\neq0 and \nu_{R} Dark Matter
We revisit the discrete dark matter model with flavor symmetry
originally introduced by M.Hirsch {\it et.al}. We show that radiative
corrections can lead to non-zero and non-zero mass for the
lightest neutrino. We find an interesting relation among neutrino mixing
parameters and it indicates the sizable deviation of from the maximal
angle and the degenerate mass spectrum for neutrinos. Also we
study the possibilities that the right-handed neutrino is a dark matter
candidate. Assuming the thermal freeze-out explains observed dark matter
abundance, TeV-scale right-handed neutrino and flavored scalar bosons are
required. In such a case, flavor symmetry plays an important role for the
suppression of lepton flavor violating processes as well as for the stability
of dark matter. We show that this scenario can be viable against currently
existing constraints from collider, low energy experiments and cosmological
observations.Comment: The wrong estimations in Eq(4.9) and Fig.14 in the published version
of this paper are corrected. As the result, the prefered mass range for
bosons are lowered. Some comments on constraints from rare lepton
decays and SM precision test adde
Partially Folded Structure of Flavin Adenine Dinucleotide-depleted Ferredoxin-NADP+ Reductase with Residual NADP+ Binding Domain
This research was originally published in the Journal of Biological Chemistry. Masahiro Maeda, Daizo Hamada, Masaru Hoshino, Yayoi Onda, Toshiharu Hase and Yuji Goto. Partially Folded Structure of Flavin Adenine Dinucleotide-depleted Ferredoxin-NADP+ Reductase with Residual NADP+ Binding Domain. J. Biol. Chem. 2002; 277, 17101-17107. © the American Society for Biochemistry and Molecular Biolog
Risk for atrial fibrillation in patients with hypertrophic cardiomyopathy: Association with insulin resistance
SummaryBackgroundWe undertook a cross-sectional study to test the hypothesis that patients with hypertrophic cardiomyopathy (HCM) who have impaired left ventricular (LV) diastolic function are insulin resistant. We also evaluated the relation between the development of atrial fibrillation (AF) and insulin resistance (IR) in patients with HCM.Methods and resultsEighty-eight patients with HCM (71 men, 17 women) were enrolled in the study. IR was estimated using the homeostasis model assessment (HOMA) index. Echocardiographically determined left atrial (LA) dimension was measured as a marker of LA size. The ratio of trasmitral early LV filling velocity to early diastolic mitral annulus velocity (E/e′) was also measured as a marker of LV diastolic function. Twenty-seven patients (31%) had IR. Multivariate logistic regression analyses showed that independent determinants of AF were increased LA size [odds ratio (OR) 3.5, 95% confidence interval (CI) 1.2–9.8] and impaired LV diastolic function [OR 4.6, 95% CI 1.6–12.8]. The strongest determinant of LA size was the HOMA index (p=0.0005). Similarly, the HOMA index (p=0.0019) was an independent determinant of LV diastolic function.ConclusionIR is highly prevalent among non-diabetic patients with HCM. A possible mechanism by which IR affects the development of AF is mediated through its association with increased LA size or impaired LV diastolic function. IR may be an important underlying mechanism for the genesis of AF in HCM
nsPEFs induce the ISR via ROS-mediated HRI activation
The integrated stress response (ISR) is one of the most important cytoprotective mechanisms and is integrated by phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α). Four eIF2α kinases, heme-regulated inhibitor (HRI), double-stranded RNA-dependent protein kinase (PKR), PKR-like endoplasmic reticulum kinase (PERK), and general control nonderepressible 2 (GCN2), are activated in response to several stress conditions. We previously reported that nanosecond pulsed electric fields (nsPEFs) are a potential therapeutic tool for ISR activation. In this study, we examined which eIF2α kinase is activated by nsPEF treatment. To assess the responsible eIF2α kinase, we used previously established eIF2α kinase quadruple knockout (4KO) and single eIF2α kinase-rescued 4KO mouse embryonic fibroblast (MEF) cells. nsPEFs 70 ns in duration with 30 kV/cm electric fields caused eIF2α phosphorylation in wild-type (WT) MEF cells. On the other hand, nsPEF-induced eIF2α phosphorylation was completely abolished in 4KO MEF cells and was recovered by HRI overexpression. CM-H2DCFDA staining showed that nsPEFs generated reactive oxygen species (ROS), which activated HRI. nsPEF-induced eIF2α phosphorylation was blocked by treatment with the ROS scavenger N-acetyl-L-cysteine (NAC). Our results indicate that the eIF2α kinase HRI is responsible for nsPEF-induced ISR activation and is activated by nsPEF-generated ROS
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