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Paula Bustamante, Jonathan R Iredell
The stable maintenance of certain plasmids in bacterial populations has contributed significantly to the current worldwide antibiotic resistance (AbR) emergency. IncX plasmids, long underestimated in this regard, have achieved recent notoriety for their roles in transmission of resistance to carbapenem and colistin, the last-line antibiotics for Gram-negative infections. Toxin-antitoxin (TA) systems contribute to stable maintenance of many AbR plasmids, and a few TA systems have been previously described in the IncX plasmids...
March 3, 2017: Plasmid
Michael B Liu, Christopher Y Ko, Zhen Song, Alan Garfinkel, James N Weiss, Zhilin Qu
Ventricular myocytes are excitable cells whose voltage threshold for action potential (AP) excitation is ∼-60 mV at which INa is activated to give rise to a fast upstroke. Therefore, for a short stimulus pulse to elicit an AP, a stronger stimulus is needed if the resting potential lies further away from the INa threshold, such as in hypokalemia. However, for an AP elicited by a long duration stimulus or a diastolic spontaneous calcium release, we observed that the stimulus needed was lower in hypokalemia than in normokalemia in both computer simulations and experiments of rabbit ventricular myocytes...
December 6, 2016: Biophysical Journal
Yasutaka Kurata, Kunichika Tsumoto, Kenshi Hayashi, Ichiro Hisatome, Mamoru Tanida, Yuhichi Kuda, Toshishige Shibamoto
Early afterdepolarization (EAD) is known as a cause of ventricular arrhythmias in long QT syndromes. We theoretically investigated how the rapid (IKr) and slow (IKs) components of delayed-rectifier K(+) channel currents, L-type Ca(2+) channel current (ICaL), Na(+)/Ca(2+) exchanger current (INCX), Na(+)-K(+) pump current (INaK), intracellular Ca(2+) (Cai) handling via sarcoplasmic reticulum (SR), and intracellular Na(+) concentration (Nai) contribute to initiation, termination, and modulation of phase-2 EADs, using two human ventricular myocyte models...
January 1, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Miyuki Tashiro, Yasuhide Watanabe, Tomomi Yamakawa, Kanna Yamashita, Satomi Kita, Takahiro Iwamoto, Junko Kimura
BACKGROUND AND AIMS: Carvedilol ((+/-)-1-(carbazol-4-yloxy)-3-[[2-(o-methoxyphenoxy)ethyl]amino]-2-propanol), a β-adrenoceptor-blocker, has multi-channel blocking and vasodilator properties. This agent dose-dependently improves left ventricular function and reduces mortality in patients with arrhythmia and chronic heart failure. However, the effect of carvedilol on the cardiac Na+/Ca2+ exchanger (NCX1) has not been investigated. METHODS AND RESULTS: We examined the effects of carvedilol and metoprolol, 2 β-blockers, on Na+/Ca2+ exchange current (INCX) in guinea-pig cardiac ventricular cells and fibroblasts expressing dog cardiac NCX1...
2017: Pharmacology
Chao Wang, Lei-Lei Wang, Chi Zhang, Zhen-Zhen Cao, An-Tao Luo, Pei-Hua Zhang, Xin-Rong Fan, Ji-Hua Ma
AIM: The augmentation of late sodium current (INa.L) not only causes intracellular Na(+) accumulation, which results in intracellular Ca(2+) overload via the reverse mode of the Na(+)/Ca(2+) exchange current (reverse-INCX), but also prolongs APD and induces early afterdepolarizations (EAD), which can lead to arrhythmia and cardiac dysfunction. Thus, the inhibition of INa.L is considered to be a potential way for therapeutic intervention in ischemia and heart failure. In this study we investigated the effects of tolterodine (Tol), a competitive muscarinic receptor antagonist, on normal and veratridine (Ver)-augmented INa...
November 2016: Acta Pharmacologica Sinica
Dongryeoul Bae, Ohgew Kweon, Ashraf A Khan
The objective of this study was to determine antimicrobial resistance and elucidate the resistance mechanism in nontyphoidal Salmonella enterica serovars isolated from food products imported into the United States from 2011 to 2013. Food products contaminated with antimicrobial-resistant nontyphoidal S. enterica were mainly imported from Taiwan, Indonesia, Vietnam, and China. PCR, DNA sequencing, and plasmid analyses were used to characterize antimicrobial resistance determinants. Twentythree of 110 S. enterica isolates were resistant to various antimicrobial classes, including β-lactam, aminoglycoside, phenicol, glycopeptide, sulfonamide, trimethoprim, and/or fluoroquinolone antimicrobial agents...
August 2016: Journal of Food Protection
Syevda G Sirenko, Victor A Maltsev, Yael Yaniv, Rostislav Bychkov, Daniel Yaeger, Tatiana Vinogradova, Harold A Spurgeon, Edward G Lakatta
Coupling of an intracellular Ca(2+) clock to surface membrane ion channels, i.e., a "membrane clock, " via coupling of electrochemical Na(+) and Ca(2+) gradients (ENa and ECa, respectively) has been theorized to regulate sinoatrial nodal cell (SANC) normal automaticity. To test this hypothesis, we measured responses of [Na(+)]i, [Ca(2+)]i, membrane potential, action potential cycle length (APCL), and rhythm in rabbit SANCs to Na(+)/K(+) pump inhibition by the digitalis glycoside, digoxigenin (DG, 10-20 μmol/l)...
July 1, 2016: American Journal of Physiology. Heart and Circulatory Physiology
Pinghua Shen, Ying Zhang, Gang Li, Xiaofei Jiang
Infection caused by carbapenem-resistant Klebsiella pneumoniae has become a major healthcare threat and KPC-2 enzyme is a dominant factor mediating carbapenems resistance in K. pneumoniae. This study was designed to determine the genetic environment of blaKPC-2, which prevailed in clinical K. pneumoniae isolates recovered in Huashan Hospital, Shanghai, China. Forty-two clinical isolates were included in this study by blaKPC-2 screening. After multilocus sequence typing and plasmid analyses of PCR-based replicon typing (PBRT), junction PCR, mapping PCR and crossing PCR assays, primer walking, and amplicon sequencing were used to analyze the genetic environment of the blaKPC-2 gene...
July 2016: Brazilian Journal of Infectious Diseases
Hana Dobiasova, Monika Dolejska
OBJECTIVES: To describe the prevalence and diversity of IncX plasmids with antibiotic resistance genes in Enterobacteriaceae and to identify the most disseminated lineages of the plasmid family. METHODS: IncX plasmids were screened in 1894 Enterobacteriaceae isolates resistant to cefotaxime (2 mg/L) or with reduced susceptibility to ciprofloxacin (0.05 mg/L) obtained from various sources in five continents using PCR. IncX plasmid-harbouring isolates were identified using MALDI-TOF or biochemical tests, and screened for antibiotic resistance genes using PCR and sequencing; their clonality was determined by PFGE...
August 2016: Journal of Antimicrobial Chemotherapy
Jingzhen Zhu, Xingyou Dong, Qian Liu, Chao Wu, Qingqing Wang, Zhou Long, Longkun Li
Hydrophobic bile acids (BAs) are thought to inhibit smooth muscle contractility in several organs. The present study was undertaken to investigate the effects of hydrophobic BAs on the detrusor contractility of rat bladder and to explore the possible mechanism. Lithocholic acid (LCA) treatment increased the micturition interval and induced a concentration-dependent relaxation of bladder detrusor strips. In addition, LCA reduced the concentration of intracellular free Ca(2+)([Ca(2+)]i) and inhibited both the outward and inward Na(+)/Ca(2+) exchanger (NCX) current (INCX) in primary isolated smooth muscle cells (SMCs)...
February 19, 2016: Scientific Reports
María Getino, Raúl Fernández-López, Carolina Palencia-Gándara, Javier Campos-Gómez, Jose M Sánchez-López, Marta Martínez, Antonio Fernández, Fernando de la Cruz
Bacterial conjugation is the main mechanism for the dissemination of multiple antibiotic resistance in human pathogens. This dissemination could be controlled by molecules that interfere with the conjugation process. A search for conjugation inhibitors among a collection of 1,632 natural compounds, identified tanzawaic acids A and B as best hits. They specially inhibited IncW and IncFII conjugative systems, including plasmids mobilized by them. Plasmids belonging to IncFI, IncI, IncL/M, IncX and IncH incompatibility groups were targeted to a lesser extent, whereas IncN and IncP plasmids were unaffected...
2016: PloS One
Seong Woo Choi, Hyang-Ae Lee, Sung-Hwan Moon, Soon-Jung Park, Hae Jin Kim, Ki-Suk Kim, Yin Hua Zhang, Jae Boum Youm, Sung Joon Kim
Na(+)/Ca(2+) exchanger current (INCX) triggered by spontaneous Ca(2+) release from sarcoplasmic reticulum (SR) has been suggested as one of the cardiac pacemaker mechanisms ("Ca(2+) clock model"). In human embryonic stem cell-derived cardiomyocytes (hESC-CMs) showing spontaneous action potentials (APs), we found that substantial population (35 %) showed regular oscillation of inward currents (SICs) in nystatin-perforated voltage clamp between -40 and 40 mV (-80 ± 10.6 pA, at -20 mV). SICs were similarly observed between nodal, atrial, and ventricular hESC-CMs...
April 2016: Pflügers Archiv: European Journal of Physiology
Hanne C Gadeberg, Simon M Bryant, Andrew F James, Clive H Orchard
In mammalian cardiac ventricular myocytes, Ca efflux via Na/Ca exchange (NCX) occurs predominantly at T tubules. Heart failure is associated with disrupted t-tubular structure, but its effect on t-tubular function is less clear. We therefore investigated t-tubular NCX activity in ventricular myocytes isolated from rat hearts ∼18 wk after coronary artery ligation (CAL) or corresponding sham operation (Sham). NCX current (INCX) and l-type Ca current (ICa) were recorded using the whole cell, voltage-clamp technique in intact and detubulated (DT) myocytes; intracellular free Ca concentration ([Ca]i) was monitored simultaneously using fluo-4...
January 15, 2016: American Journal of Physiology. Heart and Circulatory Physiology
An-tao Luo, Zhen-zhen Cao, Yu Xiang, Shuo Zhang, Chun-ping Qian, Chen Fu, Pei-hua Zhang, Ji-hua Ma
AIM: Intracellular Ca(2+) ([Ca(2+)]i) overload occurs in myocardial ischemia. An increase in the late sodium current (INaL) causes intracellular Na(+) overload and subsequently [Ca(2+)]i overload via the reverse-mode sodium-calcium exchanger (NCX). Thus, inhibition of INaL is a potential therapeutic target for cardiac diseases associated with [Ca(2+)]i overload. The aim of this study was to investigate the effects of ketamine on Na(+)-dependent Ca(2+) overload in ventricular myocytes in vitro...
November 2015: Acta Pharmacologica Sinica
Yuanfang Xie, Zhandi Liao, Eleonora Grandi, Yohannes Shiferaw, Donald M Bers
BACKGROUND: Most cardiac arrhythmias occur intermittently. As a cellular precursor of lethal cardiac arrhythmias, early afterdepolarizations (EADs) during action potentials(APs) have been extensively investigated, and mechanisms for the occurrence of EADs on a beat-to-beat basis have been proposed. However, no previous study explains slow fluctuations in EADs, which may underlie intermittency of EAD trains and consequent arrhythmias. We hypothesize that the feedback of intracellular calcium and sodium concentrations ([Na](i) and [Ca](i)) that influence membrane voltage (V) can explain EAD intermittency...
December 2015: Circulation. Arrhythmia and Electrophysiology
Elisa Passini, Ana Mincholé, Raffaele Coppini, Elisabetta Cerbai, Blanca Rodriguez, Stefano Severi, Alfonso Bueno-Orovio
INTRODUCTION: Hypertrophic cardiomyopathy (HCM) is a cause of sudden arrhythmic death, but the understanding of its pro-arrhythmic mechanisms and an effective pharmacological treatment are lacking. HCM electrophysiological remodelling includes both increased inward and reduced outward currents, but their role in promoting repolarisation abnormalities remains unknown. The goal of this study is to identify key ionic mechanisms driving repolarisation abnormalities in human HCM, and to evaluate anti-arrhythmic effects of single and multichannel inward current blocks...
July 2016: Journal of Molecular and Cellular Cardiology
María Getino, David J Sanabria-Ríos, Raúl Fernández-López, Javier Campos-Gómez, José M Sánchez-López, Antonio Fernández, Néstor M Carballeira, Fernando de la Cruz
UNLABELLED: Bacterial conjugation constitutes a major horizontal gene transfer mechanism for the dissemination of antibiotic resistance genes among human pathogens. Antibiotic resistance spread could be halted or diminished by molecules that interfere with the conjugation process. In this work, synthetic 2-alkynoic fatty acids were identified as a novel class of conjugation inhibitors. Their chemical properties were investigated by using the prototype 2-hexadecynoic acid and its derivatives...
2015: MBio
Lin Zuo, Yunhui Du, Jihua Ma, Ke Wang, Yuhui Zhao, Feng Bai, Bowei Wu, Xinliang Ma, Huirong Liu
OBJECTIVES: The incidence of arrhythmia is associated with autoantibodies against the second extracellular loop of β1-adrenergic receptor (β1-AAbs). The current study was designed to determine the mechanisms by which arrhythmia experimentally might be induced by β1-AAbs. METHODS: Blood samples were collected from patients with varied arrhythmias or coronary heart disease (CHD) and healthy subjects. The titer of β1-AAbs was assessed. Passive immunization rat models with β1-AAbs were established to determine whether β1-AAbs induced arrhythmia...
November 1, 2015: International Journal of Cardiology
Dongryeoul Bae, Chorng-Ming Cheng, Ashraf A Khan
Food contaminated with extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica has emerged as an important global issue due to the international food-product trade. Therefore, the purpose of this study was to investigate whether imported food products can serve as a reservoir for non-typhoidal Salmonella (NTS) that can transmit β-lactam-resistance to humans through ingestion of the contaminated food. NTS isolates (n=110) were collected from various imported food products (n=3480) from 2011 to 2013...
December 2, 2015: International Journal of Food Microbiology
Liang-Xing Fang, Jian Sun, Liang Li, Hui Deng, Ting Huang, Qiu-E Yang, Xue Li, Mu-Ya Chen, Xiao-Ping Liao, Ya-Hong Liu
In this study, 619 individual Escherichia coli isolates from food-producing and companion animals were analysed to determine the prevalence of the cephalosporinase gene blaCMY-2. In total, 18 CMY-2-producers (2.9%) were detected and exhibited multidrug-resistant phenotypes. One of the CMY-2-producers was found to possess a novel blaCMY-2-like allele, blaCMY-130. The isolates belonged to distinct pulsotypes, suggesting that the blaCMY-2 gene was not disseminated by clonal expansion of blaCMY-2-positive strains...
August 2015: International Journal of Antimicrobial Agents
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