Extracellular Killing of Trypanosoma cruzi Amastigotes by Human Eosinophils1

Granules released from human eosinophils upon interaction with Trypanosoma cruzi amastigotes in vitro were seen attached to the surface of non-internalized parasites by electron microscopy. Amastigote damage was preceded by the binding of eosinophil granule material to its membrane, and eosinophil granule major basic protein (MBP) bound to the parasite surface was readily detectable. Additional evidence of eosinophil cytotoxicity for extracellular amastigotes was the observation that amastigotes trapped between two eosinophils, without being ingested by either one, were destroyed at the interface. Amastigotes isolated from the spleens of infected mice or grown in culture were similarly sensitive to the lytic effects of purified MBP. These results demonstrate the ability of human eosinophils to lyse T. cruzi amastigotes extracellularly in the absence of antibody and suggest that MBP may be involved in the effect. Thus, eosinophils, known to be capable of destroying phagocytosed amastigotes, could also contribute to the clearance of these parasites through extracellular killing.     

Ultrastructural and Chemical Changes in Spores of Bacillus cereus after Action of Disinfectants

Spores of Bacillus cereus subjected to 5% NaOH at 50° and 0.25% NaOCl at 20° undergo a 99% loss in viability in 11 and 19.5 min, respectively. Kinetic studies show that the release of Ca²⁺ and dipicolinic acid occur at different rates and that extensive loss of both ribonucleic and deoxyribonucleic acids occur under these conditions of disinfection. Electron micrographic studies reveal a progressive degradation of the spore integuments. Both chemical and ultrastructural observations made in this study lead to the conclusion that the primary lethal effect of either disinfectant is the modification of outer spore coats leading to a disruption of normal permeability barriers.