Response to spontaneous and induced His refractory ventricular premature beats during long RP tachycardia: What is the mechanism?

This electrophysiology tracing demonstrates a graded postexcitation response of the retrograde limb of an orthodromic reentrant tachycardia circuit with varying His refractory VPB coupling intervals, which reiterates the decrementally conducting retrograde limb of the tachycardia circuit.

Bacillus thuringiensis Bt_UNVM-84, a Novel Strain Showing Insecticidal Activity against Anthonomus grandis Boheman (Coleoptera: Curculionidae).

Bacillus thuringiensis is a Gram-positive bacterium known for its insecticidal proteins effective against various insect pests. However, limited strains and proteins target coleopteran pests like Anthonomous grandis Boheman, causing substantial economic losses in the cotton industry. This study focuses on characterizing a Bacillus sp. strain, isolated from Oncativo (Argentina), which exhibits ovoid to amorphous parasporal crystals and was designated Bt_UNVM-84. Its genome encodes genes for the production of two pairs of binary Vpb1/Vpa2 proteins and three Cry-like proteins showing similarity with different Cry8 proteins. Interestingly, this gene content was found to be conserved in a previously characterized Argentine isolate of B. thuringiensis designated INTA Fr7-4. SDS-PAGE analysis revealed a major band of 130 kDa that is proteolytically processed to an approximately 66-kDa protein fragment by trypsin. Bioassays performed with spore-crystal mixtures demonstrated an interesting insecticidal activity against the cotton boll weevil A. grandis neonate larvae, resulting in 91% mortality. Strain Bt_UNVM-84 is, therefore, an interesting candidate for the efficient biological control of this species, causing significant economic losses in the cotton industry in the Americas.

The Efficacy Comparison Between Guan-Fu Base A Hydrochloric Injection vs. Propafenone Hydrochloric Injection in the Treatment of Arrhythmia: Systemic Review and Meta-Analysis.

Objective: To determine using a systematic assessment and meta-analysis if GFA injection is an appropriate substitute of propafenone for arrhythmic. Design: Conduct a systematic review and meta-analysis of randomized controlled trials. Data Source: PubMed, Web of Science, Cochrane Library, Embase, Wan-Fang Database, VIP, CNKI, and Sino Med from their inception to 7 March 2021. Eligibility Criteria for Selecting Studies: Inclusion of randomized controlled trials, which draws a comparison between GFA and propafenone. Evaluation of study integrity and conducted an extraction of independent data. Main Outcome Measure: Efficacy for supraventricular tachycardia, it is considered effective if it is reversed within 40 min (without considering recurrence); for premature ventricular beats, if they are reduced by more than 50% within 6 h. Results: Included in this current study are 1,294 research subjects pooled from 14 clinical studies. From the pooled assessment, GFA is demonstrated to be the equivalent of propafenone regarding the potency of effectiveness for tachycardia (RR = 1.11, 95% CI: 0.96, 1.28, P = 0.15). The subset analysis indicated that GFA has a better effect on premature ventricular beats (RR = 1.35, 95% CI: 1.07, 1.70, P = 0.01) and a similar effect on supraventricular tachycardia (RR = 1.07, 95% CI: 0.98, 1.12, P = 0.21). GFA effectiveness is lesser than propafenone in the case of mean converting time (WMD = -1.18, 95% CI: -2.30, -0.07, P = 0.04), systolic blood pressure (WMD = -3.53, 95% CI: -6.97, -0.09, P = 0.04), and QRS complex (WMD = -3.82, 95% CI: -6.96, -0.69, P = 0.02). Both GFA and propafenone have identical effects for diastolic blood pressure, heart rate, P-R interval, and QTc interval. Conclusion: A meta-analysis of RCTs was performed across 14 clinical trials, whereby 1,294 patients are used as research subjects. From the results, it is revealed that the effect exhibited by GFA injection is similar to the propafenone injection when treating premature ventricular beats or supraventricular tachycardia. Nevertheless, in certain academic disciplines, it was found that GFA is safer and beneficial compared to propafenone. Based on facts from relevant studies, GFA is deemed applicable during clinical practice. Systematic Review Registration: https://www.inplasy.com/inplasy-2021-3-0077/, identifier: INPLASY202130077.

Baculovirus Expression and Functional Analysis of Vpa2 Proteins from Bacillus thuringiensis.

The mode of action underlying the insecticidal activity of the Bacillus thuringiensis (Bt) binary pesticidal protein Vpb/Vpa (formerly Vip1/Vip2) is uncertain. In this study, three recombinant baculoviruses were constructed using Bac-to-Bac technology to express Vpa2Ac1 and two novel Vpa2-like genes, Vpa2-like1 and Vpa2-like2, under the baculovirus p10 promoter in transfected Sf9 cells. Pairwise amino acid analyses revealed a higher percentage of identity and a lower number of gaps between Vpa2Ac1 and Vpa2-like2 than to Vpa2-like1. Moreover, Vpa2-like1 lacked the conserved Ser-Thr-Ser motif, involved in NAD binding, and the (F/Y)xx(Q/E)xE consensus sequence, characteristic of the ARTT toxin family involved in actin polymerization. Vpa2Ac1, Vpa2-like1 and Vpa2-like2 transcripts and proteins were detected in Sf9 culture cells, but the signals of Vpa2Ac1 and Vpa2-like2 were weak and decreased over time. Sf9 cells infected by a recombinant bacmid expressing Vpa2-like1 showed typical circular morphology and produced viral occlusion bodies (OBs) at the same level as the control virus. However, expression of Vpa2Ac1 and Vpa2-like2 induced cell polarization, similar to that produced by the microfilament-destabilizing agent cytochalasin D and OBs were not produced. The presence of filament disrupting agents, such as nicotinamide and nocodazole, during transfection prevented cell polarization and OB production was observed. We conclude that Vpa2Ac1 and Vpa2-like2 proteins likely possess ADP-ribosyltransferase activity that modulated actin polarization, whereas Vpa2-like1 is not a typical Vpa2 protein. Vpa2-like2 has now been designated Vpa2Ca1 (accession number AAO86513) by the Bacillus thuringiensis delta-endotoxin nomenclature committee.

Acute dietary zinc deficiency in rats exacerbates myocardial ischaemia-reperfusion injury through depletion of glutathione.

Zn plays an important role in maintaining the anti-oxidant status within the heart and helps to counter the acute redox stress that occurs during myocardial ischaemia and reperfusion. Individuals with low Zn levels are at greater risk of developing an acute myocardial infarction; however, the impact of this on the extent of myocardial injury is unknown. The present study aimed to compare the effects of dietary Zn depletion with in vitro removal of Zn (N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN)) on the outcome of acute myocardial infarction and vascular function. Male Sprague-Dawley rats were fed either a Zn-adequate (35 mg Zn/kg diet) or Zn-deficient (<1 mg Zn/kg diet) diet for 2 weeks before heart isolation. Perfused hearts were subjected to a 30 min ischaemia/2 h reperfusion (I/R) protocol, during which time ventricular arrhythmias were recorded and after which infarct size was measured, along with markers of anti-oxidant status. In separate experiments, hearts were challenged with the Zn chelator TPEN (10 µm) before ischaemia onset. Both dietary and TPEN-induced Zn depletion significantly extended infarct size; dietary Zn depletion was associated with reduced total cardiac glutathione (GSH) levels, while TPEN decreased cardiac superoxide dismutase 1 levels. TPEN, but not dietary Zn depletion, also suppressed ventricular arrhythmias and depressed vascular responses to nitric oxide. These findings demonstrate that both modes of Zn depletion worsen the outcome from I/R but through different mechanisms. Dietary Zn deficiency, resulting in reduced cardiac GSH, is the most appropriate model for determining the role of endogenous Zn in I/R injury.

Propranolol prevents life-threatening arrhythmias in LQT3 transgenic mice: implications for the clinical management of LQT3 patients.

BACKGROUND: The efficacy of beta-blockers for treatment of patients with long QT syndrome type 3 (LQT3) has been repeatedly questioned, and it has been suggested that they might be detrimental for this genetic subgroup of patients with long QT syndrome (LQTS). The disquieting consequence has been that cardiologists confronted with LQT3 patients often do not even attempt pharmacologic therapy and implant cardioverter-defibrillators as first-choice treatment. However, the most recent clinical data indicate high efficacy of beta-blocker therapy in LQT3 patients. OBJECTIVE: The purpose of this study was to test the antiarrhythmic efficacy of beta-blockers in an established experimental model for LQT3. METHODS: After phenotypic validation of 65 ∆KPQ-SCN5A knock-in transgenic (TG) mice compared to 32 wild-type (WT) mice, we tested the effect of the arrhythmogenic cholinergic muscarinic agonist carbachol in 19 WT and 39 TG anesthetized mice, with and without pretreatment with propranolol given intraperitoneally. RESULTS: At the same heart rates, TG mice had a markedly longer QT interval than WT mice. Whereas carbachol had minor arrhythmic effects in the WT mice, it produced ventricular tachycardia (VT) and ventricular fibrillation (VF) in 55% of 20 TG mice. By contrast, in none of 19 TG mice pretreated with propranolol did VT/VF occur after carbachol injection. CONCLUSION: These experimental data indicate that, contrary to previous reports, beta-blockade effectively prevents VT/VF in a validated LQT3 model. Together with the most recent clinical data, these findings indicate that there is no reason for not initiating protective therapy with beta-blockers in LQT3 patients.

Heart rate turbulence.

Heart rate turbulence (HRT) is a baroreflex-mediated biphasic reaction of heart rate in response to premature ventricular beats. Heart rate turbulence is quantified by: turbulence onset (TO) reflecting the initial acceleration of heart rate following premature beat and turbulence slope (TS) describing subsequent deceleration of heart rate. Abnormal HRT identifies patients with autonomic dysfunction or impaired baroreflex sensitivity due to variety of disorders, but also may reflect changes in autonomic nervous system induced by different therapeutic modalities such as drugs, revascularization, or cardiac resynchronization therapy. More importantly, impaired HRT has been shown to identify patients at high risk of all-cause mortality and sudden death, particularly in postinfarction and congestive heart failure patients. It should be emphasized that abnormal HRT has a well-established role in stratification of postinfarction and heart failure patients with relatively preserved left ventricular ejection fraction. The ongoing clinical trials will document whether HRT can be used to guide implantation of cardioverter-defibrillators in this subset of patients, not covered yet by ICD guidelines. This review focuses on the current state-of-the-art knowledge regarding clinical significance of HRT in detection of autonomic dysfunction and regarding the prognostic significance of this parameter in predicting all-cause mortality and sudden death.

The Effect of Oxygen Therapy on VPB in Patients with Chronic Obstructive Pulmonary Disease / 결핵

BACKGROUND: In patients with chronic obstructive pulmonary disease(COPD), it is well known that hypoxemia increases the frequency of VPB, which is associated with the poor prognosis such as sudden death. The aim of this study is to evaluate the effect of short and long-term low flow oxygen therapy on the development of VPBs in patients with COPD by correcting the hypoxemia. METHOD: In 19 patients with COPD, oxygen saturation and VPB are monitored by pulse oxymeter and 24-hour Holter EKG, with room air and the 1st and the 8th day during oxygen therapy by nasal prong (2L/min). RESULTS: The arterial oxygen saturation was significantly higher on the 1st day of oxygen therapy compared with breathing room air, and also higher on the 8th day of oxygen therapy than on the 1st day. We found that there was significant correlation between the minimal value of the arterial oxygen saturation and the mean value of the arterial oxygen saturation. The number of VPBs per hour was significantly higher on the 1st day of oxygen therapy compared with breathing room air, and also higher on the 8th day of oxygen therapy than on the 1st day. There was no significant correlation between the decrease of the frequency of VPBs and the increase of the minimal arterial oxygen saturation. But, because of the low p value as 0.056, The correlation is highly suggested. CONCLUSION: With oxygen therapy, the arterial oxygen saturation was increased and the number of VPBs was decreased, and with long-term oxygen therapy more than 7days, the number of VPBs was more decreased in patients with COPD.