704 research outputs found
Possible hybridization of Brazilian planorbid snails and its importance in population dynamics
Microbiological, histological, immunological, and toxin response to antibiotic treatment in the mouse model of Mycobacterium ulcerans disease.
Mycobacterium ulcerans infection causes a neglected tropical disease known as Buruli ulcer that is now found in poor rural areas of West Africa in numbers that sometimes exceed those reported for another significant mycobacterial disease, leprosy, caused by M. leprae. Unique among mycobacterial diseases, M. ulcerans produces a plasmid-encoded toxin called mycolactone (ML), which is the principal virulence factor and destroys fat cells in subcutaneous tissue. Disease is typically first manifested by the appearance of a nodule that eventually ulcerates and the lesions may continue to spread over limbs or occasionally the trunk. The current standard treatment is 8 weeks of daily rifampin and injections of streptomycin (RS). The treatment kills bacilli and wounds gradually heal. Whether RS treatment actually stops mycolactone production before killing bacilli has been suggested by histopathological analyses of patient lesions. Using a mouse footpad model of M. ulcerans infection where the time of infection and development of lesions can be followed in a controlled manner before and after antibiotic treatment, we have evaluated the progress of infection by assessing bacterial numbers, mycolactone production, the immune response, and lesion histopathology at regular intervals after infection and after antibiotic therapy. We found that RS treatment rapidly reduced gross lesions, bacterial numbers, and ML production as assessed by cytotoxicity assays and mass spectrometric analysis. Histopathological analysis revealed that RS treatment maintained the association of the bacilli with (or within) host cells where they were destroyed whereas lack of treatment resulted in extracellular infection, destruction of host cells, and ultimately lesion ulceration. We propose that RS treatment promotes healing in the host by blocking mycolactone production, which favors the survival of host cells, and by killing M. ulcerans bacilli
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Analysis of spatial variability for the development of reduced lead body surface maps
The spatial frequency of measurement points from standard ECG systems lacks accuracy to diagnose local variability in cardiac activity on the torso. Body Surface Mapping (BSM) improves this accuracy, but lacks the simplicity to be implemented in clinic on a regular basis. Reduced-lead BSM system improves applicability, but currently no standardization of lead reduction has been agreed upon. This research investigates the reduction of BSMs based on Lomb-Scargle Spectral Analysis to determine an appropriate electrode positioning through spatial frequency assessment. Based on the measurement of 13 healthy volunteers, a 128 electrode system could be reduced to a 36 electrode system and an 84 electrode system for ventricular and atrial activity measurements, respectively, with up to 10% loss of the full information provided by the original body surface potential map. Further research will investigate the appropriate positions of these electrodes and the effect of lead reduction for various cardiac abnormalities
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