Myocardial Electrophysiological Alterations In Pacing-induced Heart Failure And Defibrillation Shock Delivery

Heart failure patients frequently have ventricular arrhythmias and high incidence of sudden death. Current antiarrhythmic drug therapies have failed to improve the survival of these patients as the arrhythmogenesis is poorly understood. The only effective therapy for lethal arrhythmia, ventricular fibrillation, is electrical shock (defibrillation). Studies on arrhythmogenesis and potential antiarrhythmic therapies in heart failure are needed.;This thesis investigated: (1) cardiac electrophysiological changes and arrhythmogenesis in a heart failure model; (2) cellular electrophysiological effects of defibrillation shocks.;Heart failure was produced by rapid ventricular pacing (240 beats/min, 4-5 weeks) in 35 dogs. Twenty-one operated, non-paced dogs served as control. Increased impulse conduction time, ventricular refractory period and action potential duration, and decreased action potential duration and resting membrane potential of Purkinje fibers were observed in association with heart failure. Despite a high incidence of ventricular fibrillation during heart failure, programmed electrical stimulation failed to induce significant arrhythmia, suggesting a non-reentrant mechanism for the arrhythmia initiation. The arrhythmogenic effect of norepinephrine and myocardial responsiveness to isoproterenol were both decreased, suggesting a decreased importance of catecholamines in the arrhythmogenesis of heart failure. The failing heart showed an increased susceptibility to cesium-induced ventricular tachycardia and triggered activity, implying a possible important role for triggered activity in the arrhythmogenesis of heart failure.;Defibrillation shocks to guinea pig papillary muscle caused refractory states which were related to shock intensity and waveforms. This refractoriness lasted longer than one activation and may be important for successful defibrillation. Shocks also increased stimulation threshold, which may contribute to post-defibrillation pacing failure in patients with an implanted pacemaker. In canine Purkinje fibers, shocks induced rapid firing, which may be responsible for unsuccessful defibrillation and post-defibrillation arrhythmias.;Conclusions: (1) Heart failure is associated with arrhythmogenic electrophysiological abnormalities and increased susceptibility to ventricular fibrillation. The arrhythmogenesis is unlikely to be mainly due to reentry or catecholamines whereas triggered activity may play an important role. (2) Defibrillation shock-induced refractoriness lasts longer than one activation, which may be important for successful defibrillation. The shock-induced increase of pacing threshold and rapid firing may constitute potential complications of defibrillation, including reinitiation of ventricular fibrillation

Identification of a major QTL and candidate genes analysis for branch angle in rapeseed (Brassica napus L.) using QTL-seq and RNA-seq

IntroductionBranching angle is an essential trait in determining the planting density of rapeseed (Brassica napus L.) and hence the yield per unit area. However, the mechanism of branching angle formation in rapeseed is not well understood.MethodsIn this study, two rapeseed germplasm with extreme branching angles were used to construct an F2 segregating population; then bulked segregant analysis sequencing (BSA-seq) and quantitative trait loci (QTL) mapping were utilized to localize branching anglerelated loci and combined with transcriptome sequencing (RNA-seq) and quantitative real-time PCR (qPCR) for candidate gene miningResults and discussionA branching angle-associated quantitative trait loci (QTL) was mapped on chromosome C3 (C3: 1.54-2.65 Mb) by combining BSA-seq as well as traditional QTL mapping. A total of 54 genes had SNP/Indel variants within the QTL interval were identified. Further, RNA-seq of the two parents revealed that 12 of the 54 genes were differentially expressed between the two parents. Finally, we further validated the differentially expressed genes using qPCR and found that six of them presented consistent differential expression in all small branching angle samples and large branching angles, and thus were considered as candidate genes related to branching angles in rapeseed. Our results introduce new candidate genes for the regulation of branching angle formation in rapeseed, and provide an important reference for the subsequent exploration of its formation mechanism

Curing of Plasmid pXO1 from Bacillus anthracis Using Plasmid Incompatibility

The large plasmid pXO1 encoding the anthrax toxin is important for the virulence of Bacillus anthracis. It is essential to cure pXO1 from B. anthracis to evaluate its role in the pathogenesis of anthrax infection. Because conventional methods for curing plasmids (e.g., curing agents or growth at elevated temperatures) can induce mutations in the host chromosomal DNA, we developed a specific and reliable method to eliminate pXO1 from B. anthracis using plasmid incompatibility. Three putative replication origins of pXO1 were inserted into a temperature-sensitive plasmid to generate three incompatible plasmids. One of the three plasmids successfully eliminated the large plasmid pXO1 from B. anthracis vaccine strain A16R and wild type strain A16. These findings provided additional information about the replication/partitioning of pXO1 and demonstrated that introducing a small incompatible plasmid can generate plasmid-cured strains of B. anthracis without inducing spontaneous mutations in the host chromosome

One dimensional hierarchical nanostructures composed of CdS nanosheets/nanoparticles and Ag nanowires with promoted photocatalytic performance

Constructing one-dimensional (1D) hierarchical photocatalysts is deemed to be central to promoting photocatalytic capacity. In this paper, 1D hierarchical structures composed of CdS nanosheets/nanoparticles on Ag nanowires (denoted as 1D Ag@CdS core-shell hierarchical hetero-nanowires) have been fabricated via a wet-chemistry approach at low temperature. The optimization of the synthetic parameters indicates that the amounts of Cd(NO 3 ) 2 ·4H 2 O and thiourea play important roles in the construction of the 1D hierarchical structures. The as-prepared 1D hierarchical Ag@CdS core-shell hetero-nanowires exhibit efficient photocatalytic performance in both methyl orange (MO) degradation (degrade 96% of MO within 240 min) and hydrogen generation (73.5 μmol h -1 ) from water splitting due to the unique hybrid nano-architecture. It is expected that this Ag@CdS hierarchical nanostructure could have potential in solar energy conversion and this fabrication technique could be used as a reference to design other 1D metal@semiconductor core-shell heteronanowires

Self-supported bimodal-pore structured nitrogen-doped carbon fiber aerogel as electrocatalyst for oxygen reduction reaction

Self-supported 3-dimensional (3D) nitrogen-doped bimodal-pore structured carbon fiber aerogel is synthesized via a facile carbonization process using prawn shells as the raw material. The fabricated N-doped carbon fiber aerogel possesses micro- and meso-porous pores with an N doping level of 5.9% and a high surface area of 526 m2 g−1. As an electrocatalyst, the resultant N-doped carbon fiber aerogel exhibits superior electrocatalytic activity towards oxygen reduction reaction (ORR) with a more positive ORR onset-potential, better stability and high resistance to crossover effect compared to the commercial Pt/C electrocatalyst. Keywords: 3D, N-doped carbon fiber aerogel, Bimodal-pore structure, Electrocatalyst, OR

A Rigid–Flexible and Multi-Siloxane Bridge Strategy for Toughening Epoxy Resin with Promising Flame Retardancy, Mechanical, and Dielectric Properties

Developing highly efficient and multifunctional epoxy resins (EPs) that overcome the shortcomings of flammability and brittleness is crucial for pursuing sustainable and safe application but remains a huge challenge. In this paper, a novel biomass-containing intumescent flame retardant containing a rigid–flexible and multi-siloxane bridge structure (DPB) was synthesized using siloxane; 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO); and biomass vanillin. DPB could facilitate the formation of a carbon residual with an intumescent structure, which effectively blocked the propagation of heat and oxygen. As a result, the peak heat release rate (pHRR) and total heat release (THR) of DPB/EP-7.5 decreased by 38.8% and 45.0%, respectively. In terms of mechanical properties, the tensile and flexural elongations at break of DPB/EP-7.5 increased by 77.2% and 105.3%, respectively. Impressively, DPB/EP-7.5 had excellent dielectric properties, with a dielectric constant of 2.5–2.9. This was due to the Si-O bonds (multi-siloxane bridges) contained in DPB/EP, which can quench the polarization behavior of the hydroxyl group. This paper provides a facile strategy for the preparation of multifunctional EP, which will pave the way for the promotion and application of EP in the high-end field

The association between morphological characteristics of paraspinal muscle and spinal disorders

AbstractBackground Spinal disorders affect millions of people worldwide, and can cause significant disability and pain. The paraspinal muscles, located on either side of the spinal column, play a crucial role in the movement, support, and stabilization of the spine. Many spinal disorders can affect paraspinal muscles, as evidenced by changes in their morphology, including hypertrophy, atrophy, and degeneration.Objectives The objectives of this review were to examine the current literature on the relationship between the paraspinal muscles and spinal disorders, summarize the methods used in previous studies, and identify areas for future research.Methods We reviewed studies on the morphological characteristics of the paravertebral muscle and discussed their relationship with spinal disorders, as well as the current limitations and future research directions.Results The paraspinal muscles play a critical role in spinal disorders and are important targets for the treatment and prevention of spinal disorders. Clinicians should consider the role of the paraspinal muscles in the development and progression of spinal disorders and incorporate assessments of the paraspinal muscle function in clinical practice.Conclusion The findings of this review highlight the need for further research to better understand the relationship between the paraspinal muscles and spinal disorders, and to develop effective interventions to improve spinal health and reduce the burden of spinal disorders