Bacillus thuringiensis mosquitocidal toxin Cry4Ba has no significant natural activity against Culex quinquefasciatus or Culex pipiens (50% lethal concentrations [LC 50 ], >80,000 and >20,000 ng/ml, respectively). We introduced amino acid substitutions in three putative loops of domain II of Cry4Ba. The mutant proteins were tested on four different species of mosquitoes, Aedes aegypti, Anopheles quadrimaculatus, C. quinquefasciatus, and C. pipiens. Putative loop 1 and 2 exchanges eliminated activity towards A. aegypti and A. quadrimaculatus. Mutations in a putative loop 3 resulted in a final increase in toxicity of >700-fold and >285-fold against C. quinquefasciatus (LC 50 Х 114 ng/ml) and C. pipiens (LC 50 ‫י‬ 37 ng/ml), respectively. The enhanced protein (mutein) has very little negative effect on the activity against Anopheles or Aedes. These results suggest that the introduction of short variable sequences of the loop regions from one toxin into another might provide a general rational design approach to enhancing B. thuringiensis Cry toxins.

Postischemic myocardial contractile dysfunction is in part mediated by the burst of reactive oxygen species (ROS), which occurs with the reintroduction of oxygen. We hypothesized that tissue oxygen tension modulates this ROS burst at reperfusion. After 20 min of global ischemia, isolated rat hearts were reperfused with temperature-controlled (37.4°C) Krebs-Henseleit buffer saturated with one of three different O2 concentrations (95, 20, or 2%) for the first 5 min of reperfusion and then changed to 95% O 2. Additional hearts were loaded with 1) allopurinol (1 mM), a xanthine oxidase inhibitor, 2) diphenyleneiodonium (DPI; 1 M), an NAD(P)H oxidase inhibitor, or 3) Tiron (10 mM), a superoxide scavenger, and were then reperfused with either 95 or 2% O 2 for the first 5 min. ROS production and tissue oxygen tension were quantitated using electron paramagnetic resonance spectroscopy. Tissue oxygen tension was significantly higher in the 95% O2 group. However, the largest radical burst occurred in the 2% O 2 reperfusion group (P Ͻ 0.001). Recovery of left ventricular (LV) contractile function and aconitase activity during reperfusion were inversely related to the burst of radical production and were significantly higher in hearts initially reperfused with 95% O2 (P Ͻ 0.001). Allopurinol, DPI, and Tiron reduced the burst of radical formation in the 2% O2 reperfusion groups (P Ͻ 0.05). Hypoxic reperfusion generates an increased ROS burst originating from multiple pathways. Recovery of LV function during reperfusion is inversely related to this oxygen radical burst, highlighting the importance of myocardial oxygen tension during initial reperfusion.reactive oxygen species; contractile function; cardiac arrest REPERFUSION, FOLLOWING GLOBAL ISCHEMIA of the heart, restores oxygen delivery to the ischemic tissue. During ischemia, there is a strong reductive pressure, which, with the reintroduction of oxygen, results in the burst of reactive oxygen species (ROS), which are thought to primarily be responsible for the postischemic myocardial contractile dysfunction (2, 4, 5). This phenomenon of postischemic contractile dysfunction may result from either cell injury or myocardial stunning (6), or a combination of both. This postischemic myocardial dysfunction is seen after a number of clinical syndromes including both regional (acute myocardial infarction) and global (cardiac arrest) myocardial ischemia (15,20).ROS, particularly superoxide, may be generated from multiple sources and mechanisms depending on the duration of preceding ischemia. Earlier studies identified endothelial cells as a major source of ROS at reperfusion that could be inhibited by xanthine oxidase blockers (31) and react with iron to form the very reactive hydroxyl radical (30). After prolonged periods of ischemia sufficient to result in necrosis, a major source of ROS appears to be neutrophils, which can be blocked with anti-neutrophil interventions causing a reduction of infarct size (7). However, after shorter periods of ischemia resulting in myocardial s...

The pervasive technology of cardiac monitoring has greatly advanced patient care for several decades. Since its advent, telemetry has been used in a variety of settings to guide medical management in patients who are either acutely or non-acutely ill. Evidence from several studies supports the benefits of the 2004 American Heart Association (AHA) telemetry guidelines in stratifying patients into 3 groups based on their individual cardiac event risk. It has been shown to reduce hospital costs without compromising patient care as well as eliminate overflow of telemetry units. This article reviews the AHA cardiac telemetry guidelines and evaluates the current status of its implementation, the general benefits, as well as its limitations.

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