Low potency toxins reveal dense interaction networks in metabolism

Background The chemicals of metabolism are constructed of a small set of atoms and bonds. This may be because chemical structures outside the chemical space in which life operates are incompatible with biochemistry, or because mechanisms to make or utilize such excluded structures has not evolved. In this paper I address the extent to which biochemistry is restricted to a small fraction of the chemical space of possible chemicals, a restricted subset that I call Biochemical Space. I explore evidence that this restriction is at least in part due to selection again specific structures, and suggest a mechanism by which this occurs. Results Chemicals that contain structures that our outside Biochemical Space (UnBiological groups) are more likely to be toxic to a wide range of organisms, even though they have no specifically toxic groups and no obvious mechanism of toxicity. This correlation of UnBiological with toxicity is stronger for low potency (millimolar) toxins. I relate this to the observation that most chemicals interact with many biological structures at low millimolar toxicity. I hypothesise that life has to select its components not only to have a specific set of functions but also to avoid interactions with all the other components of life that might degrade their function. Conclusions The chemistry of life has to form a dense, self-consistent network of chemical structures, and cannot easily be arbitrarily extended. The toxicity of arbitrary chemicals is a reflection of the disruption to that network occasioned by trying to insert a chemical into it without also selecting all the other components to tolerate that chemical. This suggests new ways to test for the toxicity of chemicals, and that engineering organisms to make high concentrations of materials such as chemical precursors or fuels may require more substantial engineering than just of the synthetic pathways involved

Light and Electron Microscopy Study of First Generation Development of Eimeria papillata (Apicomplexa: Eimeriidae) in Polarized MDCK-Cells in vitro

The early development of Eimeria papillata (Apicomplexa) was studied in vitro using light and electron microscopy. The first developmental stages observed were elongated, sporozoite-shaped schizonts with two nuclei and two refractile bodies which appeared 17 hours p.i.; the schizonts retained this shape until the 8-nuclei-stage. At 23 hours p.i. they had changed into a spherical shape, the refractile bodies had multiplied and the development of merozoites was observed. Each merozoite of the first generation contained two refractile bodies. An improved method for in vitro cultivation of Eimeria in polarized host cells and subsequent fine structural investigation is described © 1995, Gustav Fischer Verlag Jena. All rights reserved

Monoclonal antibodies identify two neutralization-sensitive epitopes in Besnoitia besnoiti endocytes

Four monoclonal antibodies were produced against endozoite membrane and cytoplasmic antigens of B. besnoiti. In immunofluorescence antibody tests, three of the clones, designated 2M3C5, 2M1G8 and 2M9G3 recognized antigens restricted to the anterior pole of the endozoites. The fourth clone, 2M9C4, recognized a membrane-associated component in a beaded pattern, cytoplasmic granules and extracellular background. The staining characteristics differed from the solid diffuse staining of polyclonal serum. On Western blots of detergent-soluble extracts fractionated under non-reducing conditions in 10% SDS-PAGE gels, mAbs 2M3C5, 2M1G8 and 2M9G3 recognized a common antigen at >200 kDa. Recognition with mAb 2M3C5 was consistently different in intensity and extent. Monoclonal antibody 2M9C4 recognized a single antigen at 75 kDa. The antibodies significantly reduced infectivity of Besnoitia endozoites into cultured cells, demonstrating the potential role of the antigens in the invasion process and raising the possibility of development of a vaccine and diagnostic tests for the disease

Scanning and Transmission Electron Microscopy of Host Cell Pathology Associated with Penetration by Eimeria Papillata Sporozoites

Scanning and electron microscopy was used to study the pathogenesis that occurred in mouse epithelial cells that had been penetrated by Eimeria papillata sporozoites. Optimal penetration of parasites injected into nonligated and ligated mouse intestine was found to occur at 4-15 min post-inoculation. During initial penetration, the parasite caused disruption of the microvilli of the intestinal cells, which led to detachment of the microvilli from the plasma membrane of the penetrated cell. Host cells penetrated by the parasite showed extensive destruction of the internal cellular organization together with blebbing of host-cell cytoplasm and release of internal organelles such as mitochondria. Ultimately, the penetrated cells completely broke down, leaving vacuolated areas next to ultrastructurally normal epithelial cells. © 1992 Springer-Verlag