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Search Results: 1 - 10 of 149753 matches for " H Criss Hartzell "
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Drosophila Bestrophin-1 Currents Are Regulated by Phosphorylation via a CaMKII Dependent Mechanism
Charity Duran, Li-Ting Chien, H. Criss Hartzell
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0058875
Abstract: Cell swelling induced by hypo-osmotic stress results in activation of volume-regulated anion channels (VRAC) that drive a compensatory regulatory volume decrease. We have previously shown that the Best1 gene in Drosophila encodes a VRAC that is also activated by increases in intracellular Ca2+. The role of Best1 as a VRAC has recently been independently confirmed by the Clapham lab in an unbiased RNAi screen. Although dBest1 is clearly a volume-regulated channel, its mechanisms of regulation remain unknown. Here we investigate Drosophila Best1 (dBest1) regulation using the Drosophila S2 cell model system. Because dBest1 activates slowly after establishing whole-cell recording, we tested the hypothesis that the channel is activated by phosphorylation. Two experiments indicate that phosphorylation is required for dBest1 activation: nonspecific protein kinase inhibitors or intracellular perfusion with the non-hydrolyzable ATP analog AMP-PNP dramatically reduce the amplitude of dBest1 currents. Furthermore, intracellular perfusion with ATP-γ-S augments channel activation. The kinase responsible for dBest1 activation is likely Ca2+/calmodulin dependent kinase II (CaMKII), because specific inhibitors of this kinase dramatically inhibit dBest1 current activation. Neither specific PKA inhibitors nor inactive control inhibitors have effects on dBest1currents. Our results demonstrate that dBest1 currents are regulated by phosphorylation via a CaMKII dependent mechanism.
Inhibition of AMPA receptor trafficking at hippocampal synapses by β-amyloid oligomers: the mitochondrial contribution
Yanfang Rui, Jiaping Gu, Kuai Yu, H Criss Hartzell, James Q Zheng
Molecular Brain , 2010, DOI: 10.1186/1756-6606-3-10
Abstract: We found that a brief exposure of hippocampal neurons to Aβ oligomers not only led to marked removal of AMPARs from postsynaptic surface but also impaired rapid AMPAR insertion during chemically-induced synaptic potentiation. We also found that Aβ oligomers exerted acute impairment of fast mitochondrial transport, as well as mitochondrial translocation into dendritic spines in response to repetitive membrane depolarization. Quantitative analyses at the single spine level showed a positive correlation between spine-mitochondria association and the surface accumulation of AMPARs. In particular, we found that spines associated with mitochondria tended to be more resistant to Aβ inhibition on AMPAR trafficking. Finally, we showed that inhibition of GSK3β alleviated Aβ impairment of mitochondrial transport, and effectively abolished Aβ-induced AMPAR loss and inhibition of AMPAR insertion at spines during cLTP.Our findings indicate that mitochondrial association with dendritic spines may play an important role in supporting AMPAR presence on or trafficking to the postsynaptic membrane. Aβ disruption of mitochondrial trafficking could contribute to AMPAR removal and trafficking defects leading to synaptic inhibition.Alzheimer's disease (AD) often attacks aged populations and is highlighted by progressive loss of memory and cognitive abilities [4]. AD brains exhibit two major pathological hallmarks: extracellular senile plaques containing β-amyloid aggregates and intracellular neurofibrillary tangles consisting of hyperphosphorylated microtubule-associated tau proteins [5,6]. β-amyloid (Aβ) molecules are generated by proteolytic cleavage of the transmembrane β-amyloid precursor protein (APP) [7,8]. Aggregated Aβ fibrils constitute the core of neuritic plaques and are believed to be a major culprit for neurodegeneration and subsequent cognitive abnormalities in AD patients [9-11]. Recent studies, however, indicate that Aβ molecules exert adverse effects on neuronal functions
改进的模拟退火-单纯形综合反演方法
刘鹏程,纪晨,Stephen,H.,Hartzell
地球物理学报 , 1995,
Abstract: 实际中的大量地球物理反演是一个多参数、非线性优化问题,所采用的目标函数,即度量由参数化的理论模型得出的预测值与观测值的吻合程度,往往具有多个局部极值.针对这类问题,本文综合全局反演方法具有的全域搜索能力强、局部方法收敛速度快和“均匀设计”布点效率高的特点,提出了模拟退火-单纯性综合反演方法,并通过一维声波非线性反演验证了这种综合方法的搜索能力和效率.
Allergic Dermatitis due to Topical Antibiotics
Jonathan H. Shahbazian,Tristan L. Hartzell,Amit K. Pandey,Kodi K. Azari
Western Journal of Emergency Medicine : Integrating Emergency Care with Population Health , 2012,
Abstract: In this report we present a case of allergic dermatitis from chronic use of antibiotic ointment mistakenly diagnosed as a localized finger infection.
Impaired Sulfate Metabolism and Epigenetics: Is There a Link in Autism?
Samantha Hartzell,Stephanie Seneff
Entropy , 2012, DOI: 10.3390/e14101953
Abstract: Autism is a brain disorder involving social, memory, and learning deficits, that normally develops prenatally or early in childhood. Frustratingly, many research dollars have as yet failed to identify the cause of autism. While twin concordance studies indicate a strong genetic component, the alarming rise in the incidence of autism in the last three decades suggests that environmental factors play a key role as well. This dichotomy can be easily explained if we invoke a heritable epigenetic effect as the primary factor. Researchers are just beginning to realize the huge significance of epigenetic effects taking place during gestation in influencing the phenotypical expression. Here, we propose the novel hypothesis that sulfates deficiency in both the mother and the child, brought on mainly by excess exposure to environmental toxins and inadequate sunlight exposure to the skin, leads to widespread hypomethylation in the fetal brain with devastating consequences. We show that many seemingly disparate observations regarding serum markers, neuronal pathologies, and nutritional deficiencies associated with autism can be integrated to support our hypothesis.
Ampère-Class Pulsed Field Emission from Carbon-Nanotube Cathodes in a Radiofrequency Resonator
D. Mihalcea,L. Faillace,J. Hartzell,H. Panuganti,S. M. Boucher,A. Murokh,P. Piot,J. C. T. Thangaraj
Physics , 2015, DOI: 10.1063/1.4927052
Abstract: Pulsed field emission from cold carbon-nanotube cathodes placed in a radiofrequency resonant cavity was observed. The cathodes were located on the backplate of a conventional $1+\frac{1}{2}$-cell resonant cavity operating at 1.3-GHz and resulted in the production of bunch train with maximum average current close to 0.7 Amp\`ere. The measured Fowler-Nordheim characteristic, transverse emittance, and pulse duration are presented and, when possible, compared to numerical simulations. The implications of our results to high-average-current electron sources are briefly discussed.
The effect of the dust size distribution on asteroid polarization
Joseph Masiero,Christine Hartzell,Dan Scheeres
Physics , 2009, DOI: 10.1088/0004-6256/138/6/1557
Abstract: We have developed a theoretical description of how of an asteroid's polarization-phase curve will be affected by the removal of the dust from the surface due to a size-dependent phenomenon such as radiation pressure-driven escape of levitated particles. We test our calculations against new observations of four small (D ~ 1 km) near-Earth asteroids [(85236), (142348), (162900) and 2006 SZ_217] obtained with the Dual Beam Imaging Polarimeter on the University of Hawaii's 2.2 m telescope, as well as previous observations of (25143) Itokawa and (433) Eros. We find that the polarization of the light reflected from an asteroid is controlled by the mineralogical and chemical composition of the surface and is independent of dust particle. The relation between the slope of the polarization-phase curve beyond the inversion angle and the albedo of an asteroid is thus independent of the surface regolith size distribution and is valid for both Main Belt and Near-Earth asteroids.
RIFLE is not RIFLE: on the comparability of results
Lars Englberger, Rakesh M Suri, Hartzell V Schaff
Critical Care , 2009, DOI: 10.1186/cc8175
Abstract: As an example of the possible discrepancy, a 1.5-fold increase (50%) in sCr from a baseline of 1.0 mg/dL in a 60-year-old white male corresponds to only a 37% eGFR decrease using the MDRD formula. In this scenario the patient is classified in RIFLE class R by both methods. In the same patient an only 30% increase in sCr (1.0 mg/dL to 1.3 mg/dL), however, corresponds to a 26% decrease of eGFR. Therefore, the patient would consequently be classified as having AKI in RIFLE class R by the GFR threshold but not based on sCr changes. This theoretical disagreement in defining and staging AKI by RIFLE has been outlined previously [2], but data to estimate potential discrepancy in a 'real world' scenario are not available.Furthermore, the use of different versions of RIFLE criteria counteracts the original goal of a consensus definition and hinders comparability.To understand the differences better, we applied these two methods of calculating RIFLE to consecutive patients undergoing cardiac surgery with cardiopulmonary bypass between 2005 and 2007 at our institution. AKI was defined by using either largest sCr increase or eGFR decrease (MDRD formula) within the first postoperative week compared to baseline. In all patients a preoperative baseline sCr was available. We did not use urine output criteria to define AKI.Among the total cohort, 9.3% patients were diagnosed as having AKI by the sCr criteria versus 18.9% with eGFR criteria (Table 2). The largest disagreement was detected in class R. Overall, the diagnosis of AKI using eGFR thresholds was more sensitive than sCr changes, and this was also true for staging of patients in RIFLE classes R and I. However, for patients staged in the highest AKI class F, sensitivity was higher for sCr criteria. These discrepancies can be expected to be found in other patient populations when non-uniform methods of determining RIFLE criteria are utilized. Our findings may assist in interpretation of other clinical studies.Recently the RIFLE
Effects of site-directed mutagenesis of mglA on motility and swarming of Myxococcus xanthus
Sarah A Fremgen, Neal S Burke, Patricia L Hartzell
BMC Microbiology , 2010, DOI: 10.1186/1471-2180-10-295
Abstract: Nine mutants, with mutations predicted to alter residues that bind the guanine base or coordinate magnesium, did not produce detectable MglA. As expected, these mutants were mot- dev- because MglA is essential for these processes. Of the remaining nine mutants, seven showed a wild-type distribution pattern for MglA but fell into two categories with regard to function. Five of the seven mutants exhibited mild phenotypes, but two mutants, T78D and P80A, abolished motility and development. The localization pattern of MglA was abolished in two mutants that were mot- spo- and dev-. These two mutants were predicted to alter surface residues at Asp52 and Thr54, which suggests that these residues are critical for proper localization and may define a protein interaction site. Improving the consensus match with Ras at Thr78 abolished function of MglA. Only the conservative serine substitution was tolerated at this position. Merodiploid constructs revealed that a subset of alleles, including mglAD52A, were dominant and also illustrated that changing the balance of MglA and its co-transcribed partner, MglB, affects A-motility.Our results suggest that GTP binding is critical for stability of MglA because MglA does not accumulate in mutants that cannot bind GTP. The threonine in PM3 of MglA proteins represents a novel modification of the highly conserved GTPase consensus at this position. The requirement for a hydroxyl group at this position may indicate that MglA is subject to modification under certain conditions. Proper localization of MglA is critical for both motility and development and likely involves protein interactions mediated by residues Asp52 and Thr54.The Gram-negative soil bacterium Myxococcus xanthus is a model prokaryote for understanding the complexity of intercellular interactions that occur during multicellular development. When nutrients are limiting, groups of (>105) M. xanthus cells can aggregate and assemble fruiting bodies. Inside fruiting bodies, cells d
Alguns aspectos da fun??o endotelial em cirurgia cardíaca
évora, Paulo Roberto B;Pearson, Paul J;Schaff, Hartzell V;
Revista Brasileira de Cirurgia Cardiovascular , 1993, DOI: 10.1590/S0102-76381993000300004
Abstract: this study shows some aspects of endothelial function closely related with cardiac surgery: 1) following global myocardial ischemia and reperfusion, the coronary endothelium has an impaired ability to express endothelium-dependent vasodilation to the receptor-dependent agonists while endothelium-dependent relaxation to the receptor-independent a23187 and phospholipase c is unaltered. the relaxation to sodium fluoride, which acts on a pertussis toxin-sensitive g-protein is impaired. these experiments indicate that impaired receptor-mediated production of edrf/no following reperfusion injury could be due to g-protein dysfunction in the pathway which links endothelial cell receptors to the pathway of edrf/no synthesis; 2) forty-five minutes of cardioplegic arrest of the canine heart does not alter the production edrf/no in the epicardial coronary artery. similar experiments support the concept that uw solution is safe for cardiac preservation during heart transplantation; 3) in coronary, renal, femoral and pulmonary arterial segments, protamine induced endothelium-dependent vasodilation mediated by the stimulated release of edrf/no. in the pulmonary circulation, differently of the coronary, renal and femoral arteries, protamine-induced endothelium-dependent vasodilation could be inhibited by comparable amounts of heparin, and this effect was overcome by adding additional protamine; 4)ln 83% of the superfusion experiments, effluent from the left ima induced greater relaxation of the bioassay ring than did the right ima due to the basal release of edrf/no. because edrf/no induces vasodilation and also inhibits platelet adhesion, platelet aggregation, and atherogenesis, luminal release of edrf/no by the ima could contribute to superior results when the artery is used in bypass grafting. upon exposure of the grafts to hypoxia, the vasodilator activity of effluent from both ima and saphenous vein grafts was augmented.this hypoxic augmentation could be inhibited by indometha
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