Genetic diversity of Anaplasma marginale in Argentina

Bovine anaplasmosis caused by Anaplasma marginale is a worldwide major constraint to cattle production. The A. marginale major surface protein 1 alpha (msp1α) gene contains a variable number of tandem repeats in the amino terminal region and has been used for the characterization of pathogen genetic diversity. This study reports the first characterization of A. marginale genetic diversity in Argentina based on msp1α genotypes and its putative relationship with Rhipicephalus (Boophilus) microplus infestations. Herein, we analyzed whole blood bovine samples from anaplasmosis outbreaks in R. microplus infested (9 samples) and eradicated/free (14 samples) regions. Sequence analysis revealed the existence of 15 different msp1α genotypes with 31 different repeat units. Six new repeat sequences were discovered in this study and 13/31 (42%) repeats were unique to Argentinean strains. The analysis of msp1α repeat sequences according to R. microplus infestations resulted in three repeat groups: (i) found in tick-infested regions (20 repeats), (ii) found in tick free regions (6 repeats) and (iii) randomly distributed (5 repeats). Moreover, A. marginale msp1α genetic diversity was higher in tick-infested regions than in tick free areas. These results, together with previous evidence suggesting that A. marginale msp1α repeat units co-evolved with the tick vector, might represent an evidence of the role of tick-mediated transmission for the generation of pathogen genetic diversity.This work was supported by INCO Epigenevac project -UE FP6-, CONICET, ANPCyT and INTA, Argentina, Oklahoma Agricultural Experiment Station Project 1669.Peer reviewe

Hormonal Control of Cardiac Action Potential Phase 1 Currents in the Brugada Syndrome

Introduction: The Brugada syndrome is an inherited channelopathy with autosomal dominant genotype transmission patternpresenting marked gender bias in phenotype expression, with a male to female ratio of 9:1. A cellular model of the diseasesuggests a heterogeneous distribution in the phase 1 amplitude of the ventricular action potential as the origin for the developmentof the arrhythmogenic substrate.Objective: The aim of this study was to investigate the role of androgens on the cardiac action potential phase 1 regulationand its electrophysiological consequences in an experimental murine model of Brugada syndrome.Methods: Androgen control of gene expression was studied in HL-1 cells and rat hearts using real time polymerase chainreaction (PCR). For the electrophysiological studies, an experimental model of the Brugada syndrome was reproduced in aLangendorff system using Tyrode solution supplemented with pinacidil and terfenadine.Results: Treatment of HL-1 cells with di-hydro-testosterone increased the expression of the Kv4.3 potassium channel and thesodium/calcium exchanger (NCX). This effect was assessed in rats treated with testosterone and finasteride. The expressionof both genes decreased with finasteride, where as testosterone increased NCX messenger ribonucleic acid (mRNA) level.Testosterone produced action potential shortening at 90% repolarization (APD90) and decreased time to peak (TTP), whichin Brugada syndrome models correlate with increased arrhythmogenesis. In our model, this phenomenon was observed bothas an increase of sporadic and sustained ectopic ventricular action potentials. The frequency of ectopic action potentials inducedwith terfenadine and pinacidil in the control group was reduced by an order of magnitude with finasteride treatment.Conclusions: Androgens control the expression of key components of the cardiac action potential resulting in increased arrhythmogenesis.Finasteride treatment reverses these effects.El síndrome de Brugada es una canalopatía hereditaria con un patrón de transmisión autosómico dominante que presenta una marcado sesgo de genero en la expresión del fenotipo, con una razón hombre:mujer de 9:1. Un modelo celular de la enfermedad propone una distribución heterogénea de la amplitud de la fase 1 del potencial de acción ventrícular como la base para el desarrollo del sustrato arritmogénico. Nosotros hemos investigado el papel de los andrógenos en la regulación de la fase 1 del potencial de acción en corazones de ratas. El tratamiento de células HL-1 con di-hidro-testosterona produjo un aumento en la expresión de Kv4.3 y NCX. Evaluamos este efecto en ratas tratadas con Testosterona y Finasteride. La expresión de ambos genes fue disminuída por el Finasteride, mientras que la Testosterona aumentó el nivel de ARNm de NCX. Estudiamos los potenciales de acción en el corazón de rata aislado y perfundido en respuesta a un protocolo de arritmia luego de ser tratados con Terfenadina y Pinacidil. La Testosterona produjo un acortamiento del  APD90 y el TTP, lo cual en modelos del SBr se correlaciona con un aumento de la arritmogenicidad. En nuestro modelo, este fenómeno fue observado como un incremento en los potenciales de acción ventriculares ectópicos, esporádicos y sostenidos. La frecuencia de aparición de potenciales de acción ectópicos que se indujo con Terfenadina y Pinacidil en el grupo Control fue reducida en un orden de magnitud por el tratamiento con Finasteride