Multistate Shigellosis Outbreak and Commercially Prepared Food, United States

In 2000, shigellosis traced to a commercially prepared dip developed in 406 persons nationwide. An ill employee may have inadvertently contaminated processing equipment. This outbreak demonstrates the vulnerability of the food supply and how infectious organisms can rapidly disseminate through point-source contamination of a widely distributed food item

Effects of cardiac anisotropy on modeling transvenous defibrillation in the human thorax

The objective of this study is to determine the effects of cardiac tissue anisotropy on transvenous defibrillation fields in a human torso model. The study is implemented with a physiologically realistic 3-D finite element model of the human thorax. The model computes potential and potential gradient distributions within the heart from a knowledge of defibrillation shock strength, defibrillation electrode location, and the relative conductivities of the interior thorax. Coil electrodes were placed in the right ventricular cavity and the superior vena cava. Results are compared between a model with an isotropic myocardium and a model with an anisotropic myocardium. Comparison of the potential and potential gradient distributions within the myocardium between the isotropic and anisotropic models yielded root mean square errors of 4.9% and 19.4%, respectively, and correlation coefficients of 0.999 and 0.981, respectively. These results indicate that cardiac anisotropy and fiber orientation do not significantly affect transvenous defibrillation fields

Extracting isovolumes from three-dimensional torso geometry using PROLOG

Three-dimensional (3-D) Imite element torso models are widely used to simulate deflbrillation field quantities, such as potential, gradient, and current density. These quantities are computed at spatial nodes that comprise the torso model. These spatial nodes typically number between 105 and 106, which makes the comprehension of torso deli brillat ion simulation output difficult. Therefore, the objective of this study is to rapidly prototype software to extract a subset of the geometric model of the torso for visualization in which the nodal information associated with the geometry of the model meets a specified threshold value (e.g., minimum gradient). The data extraction software is implemented in PROLOG, which is used to correlate the coordinate, structural, and nodal data of the torso model. A PROLOG-based environment has been developed and is used to rapidly design and test new methods for sorting, collecting, and optimizing data extractions from defibrillation simulations in a human torso model for subsequent visualization. © 1998 IEEE

Defibrillation efficacy of different electrode placements in a human thorax model

The objective of this study was to measure the defibrillation threshold (DFT) associated with different electrode placements using a three- dimensional anatomically realistic finite element model of the human thorax. Coil electrodes (Endotak DSP, model 125, Guidant/CPI) were placed in the RV apex along the lateral wall (RV), withdrawn 10 mm away from the RV apex along the lateral wall (RVprox), in the RV apex along the anterior septum (RVseptal), and in the SVC. An active pulse generator (can) was placed in the subcutaneous prepectoral space. Five electrode configurations were studied: RV→SVC, Rv(prox)→SVC, RV(SEPTAL)→SVC, RV→Can, and RV→SVC+Can. DFTs are defined as the energy required to produce a potential gradient of at least 5 V/cm in 95% of the ventricular myocardium. DFTs for RV→SVC, RV(prox) →SVC, RV(septal)→SVC, RV→Can, and RV→SVC+Can were 10, 16, 7, 9, and 6J, respectively. The DFTs measured at each configuration fell within one standard deviation of the mean DFTs reported in clinical studies using the Endotak leads. The relative changes in DFT among electrode configurations also compared favorably. This computer model allows measurements of DFT or other defibrillation parameters with several different electrode configurations saving time and cost of clinical studies

Proteins secreted by root-knot nematodes accumulate in the extracellular compartment during root infection

Root-knot nematodes are biotrophic parasites that invade the root apex of host plants and migrate towards the vascular cylinder where they induce the differentiation of root cells into hypertrophied multinucleated giant cells. Giant cells are part of the permanent feeding site required for nematode development into the adult stage. To date, a repertoire of candidate effectors potentially secreted by the nematode into the plant tissues to promote infection has been identified. However, the precise role of these candidate effectors during root invasion or during giant cell induction and maintenance remains largely unknown. Primarily, the identification of the destination of nematode effectors within plant cell compartment(s) is crucial to decipher their actual functions. We analyzed the fine localization in root tissues of five nematode effectors throughout the migratory and sedentary phases of parasitism using an adapted immunocytochemical method that preserves host and pathogen tissues. We showed that secretion of effectors from the amphids or the oesophageal glands is tightly regulated during the course of infection. The analyzed effectors accumulated in the root tissues along the nematode migratory path and along the cell wall of giant cells, showing the apoplasm as an important destination compartment for these effectors during migration and feeding cell formation