The development of immunoassays to four biological threat agents in a bidiffractive grating biosensor.

A critical need exists for a field deployable biosensor to detect environmental infectious agents in collected air samples rapidly, with sensitivity and specificity approaching that of standard laboratory procedures. The ideal sensor would analyze unknown samples in minutes, have programmable operation for unattended sample analysis, and be capable of multiple agent analysis for a number of agents. The goal of this project was to further the development of the bidiffractive grating biosensor (BDG) created through collaboration between Battelle Memorial Institute (BMI), Hoffman LaRoche (HLR), and the Naval Medical Research Command (NMRC). This manuscript details the development, optimization, and evaluation of this device as a potential field deployable biosensor. Well-characterized immunochemical reagents developed by the Biological Defense Research Department (BDRD) at NMRI were employed to develop assays in the BDG. These results were compared to those obtained with antigen capture enzyme linked immunosorbent assays (ELISAs). Four separate antigens were evaluated: Staphylococcus aureus enterotoxin B (SEB), ricin (RIC), Francisella tularensis (FT), and Clostridium botulinum toxin (BOT).

Electrocardiographic manifestations and clinical significance of atrioventricular nodal alternating Wenckbach periods.

Atrioventricular nodal alternating Wenckebach periods were defined as episodes of 2:1 atrioventricular block in which there was a gradual increase in transmission intervals of conducted beats ending in two or three consecutively blocked atrial impulses. This is one of the mechanisms whereby 2:1 atrioventricular block progresses into 3:1 or 4:1 atrioventricular block. Alternating Wenckebach periods appear during rapid atrial pac,ng (even in the absence of depressed atrioventricular nodal function), provided that the atria can be captured at a rate fast enough to allow for the occurrence of this phenomenon. Treatment of atrial flutter with digoxin and quinidine produces alternating Wenckebach's periods, with associated electrocardiographic changes specific for the type of drug given. In patients with "atrial tachycardia with atrioventricular block" due to digitalis intoxication or with primary disease of the conducting system or with acute myocardial infarction, there are coexisting severe arrhythmias and clinical symptoms requiring almost immediate pharmacologic or electrical therapy. We conclude that atrioventricular nodal alternating Wenckebach's periods are common and frequentyly transient and that they occur in a variety of clinical conditions, most of which are benign; however, contrary to what is commonly accepted, some episodes appear in clinical settings requiring prompt pharmacologic or electrical treatment.