Recent Studies in the Pre-Excitation Syndrome

The Wolff-Parkinson-White syndrome has held an unusual fascination for cardiologists ever since its original description in 1930. Over 60 different theories have been postulated to describe the mechanism of pre-excitation. The recent development of epicardial mapping techniques to define the sequence of ventricular activation, and the introduction of His bundle electrocardiography have provided valuable procedures for studying pre-excitation. This presentation will discuss some of the insights into the mechanism of pre-excitation that have been derived from these two electrophysiological procedures

Electrophysiology of Concealed Conduction

Several figures are presented here to demonstrate the different mechanisms of concealed conduction in which microelectrodes were used to record from the A-V node and His-Purkinje system together with simultaneously recorded atrial and ventricular electrograms. Of course, in a standard ECG, one would not be able to determine what was occurring within the specialized A-V conduction system, since only the information provided by the atrial and ventricular electrograms (P wave and QRS complex) would be available for interpretation

Microelectrode and His Bundle Studies on Type I and II Second Degree A-V Block

Mobitz classified second degree A-V block into two categories. Mobitz type I, or Wenckebach block, is characterized by a gradual prolongation of the P-R interval preceding the dropped ventricular beat. In Mobitz type II block, the dropped beat occurs without preceding prolongation of the P-R interval. Bundle branch block usually is present in patients with Mobitz type II block. The importance of distinguishing between these two types of A-V block lies in the usual irreversibility and higher mortality of patients with type II A-V block, as contrasted with type I or Wenckebach block. Also, Mobitz type II block frequently progresses to complete A-V block and Adams-Stokes attacks, thus necessitating a cardiac pacemaker

Highly effective yet simple transmembrane anion transporters based upon ortho-phenylenediamine bis-ureas

Simple, highly fluorinated receptors are shown to function as highly effective transmembrane anion antiporters with the most active transporters rivalling the transport efficacy of natural anion transporter prodigiosin for bicarbonate

Tobacco exposure inhibits SPLUNC1-dependent antimicrobial activity

Background: Tobacco smoke exposure impairs the lung´s innate immune response, leading to an increased risk of chronic infections. SPLUNC1 is a secreted, multifunctional innate defense protein that has antimicrobial activity against Gram negative organisms. We hypothesize that tobacco smoke-induced SPLUNC1 dysfunction contributes to the observed defect in innate immunity in tobacco smokers and that this dysfunction can be used as a potential biomarker of harm. Methods: We collected sputum from never-smokers and otherwise healthy smokers. We performed Western blotting to determine SPLUNC1 levels and determined antimicrobial activity against nontypeable Haemophilus influenzae. An in vitro exposure model was utilized to measure the effect of tobacco exposure on human bronchial epithelial culture (HBEC) antimicrobial activity against H. influenzae. The direct effects of cigarette and little cigar smoke exposure on SPLUNC1 function was determined using 24 h growth measurements and LPS binding assays. Results: H. influenzae growth in cigarette smoker´s sputum was significantly greater compared to never-smokers sputum over 24 h. HBEC supernatants and lysates contained significantly higher numbers of H. influenzae following chronic cigarette and little cigar smoke exposure compared to air-exposed controls. Furthermore, SPLUNC1´s antimicrobial activity and LPS-binding capability against both H. influenzae and P. aeruginosa was attenuated following cigarette and little cigar exposure. Conclusions: These data suggest that cigarette and little cigar exposure impairs SPLUNC1´s antimicrobial ability and that this inhibition may serve as a novel biomarker of harm that can be used to assess the toxicity of commercial tobacco products.Fil: Moore, Patrick J.. University of North Carolina; Estados UnidosFil: Sesma, Juliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Médicas; ArgentinaFil: Alexis, Neil E.. University of North Carolina; Estados UnidosFil: Tarran, Robert. University of North Carolina; Estados Unido

Effects of Nitrogen Fertilization on Biomass Yield and Quality in Large Fields of Established Switchgrass in Southern Iowa, USA

Switchgrass (Panicum virgatum L.) is a potential biofuel crop in the midwestern United States. The objective of this experiment was to test the effect of nitrogen application on biomass dry matter yield and fiber and mineral concentrations in large field plots in Lucas and Wayne counties in southern Iowa. Two established switchgrass fields with a previous history of limited management were evaluated from 1998 through 2002. Nitrogen was applied in the spring at rates of 0, 56, 112, and 224 kg N ha−1, and a single biomass harvest was made in autumn. Biomass production averaged across locations and N levels increased by 3.6 mg ha−1 between 1998 and 2002 to 6.5 mg ha−1. Nitrogen improved yields, with the response declining as N levels increased. The highest yield throughout the experiment was 8.5 mg ha−1 at the Lucas location in 2002. Changes in fiber and mineral concentrations did not follow any trend over years but were likely due to differences in harvest date among years. Nitrogen fertilization had no meaningful effect on the quality of the biofuel produced. This study clearly shows that nitrogen application and proper agronomic management can substantially increase the yield of established switchgrass fields over time without affecting the quality of the feedstock. As this experiment was conducted in large plots using commercial farm machinery, the results should be broadly applicable to real world situations