Infectious allergy. XIV. Histochemical changes in redox enzymes in cells of the small intestine smooth muscle during sensitization with diphtheria exotoxin]

Administration to guinea pigs of 1/Dlm of diphtheria exotoxin twice at an interval of 1 and 24 hours, or once in a dose of 25/100 Dlm caused changes in the activity of the redox enzymes. The character of their changes in the animals to which the whole dose of the exotoxin was administered once or repeatedly was directly reverse: in the first case the activity of the enzymes was uniformly increased, and in the second--ununiformly depressed; besides, there was a marked disturbance of coordination between the enzymes. An increased sensitivity of the infectious allergy type following injection of low doses of diphtheria exotoxin was not accompanied by immunity formation. Specific antibodies against diphtheria exotoxin formed only in the organism of animals to which 1/100 Dlm of diphtheria toxin was injected once a day for 15 days, but in this case as well no immunity against diphtheria exotoxin was observed.     

Monoclonal antibodies against chordin. Use in structural and immunohistochemical studies

Eight MAbs have been developed against chordin and designated as At2-At9. It is shown that all antibodies are directed against identical, spatially overlapping or closely positioned epitopes of chordin. The chordin molecule has repetitive sites wherein epitopes for the eight MAbs are located. This site lies within a proteinase-resistant fragment of chordin, presumably a glycopeptide, of molecular mass between 2 and 10 kDa. Fluorescence staining of cryostat sections from stellate sturgeon with the use of At5 (indirect Coons' method) has revealed a positive reaction with notochord cells and sheath and with the spinal cord. No significant reaction with cartilage, muscle and kidney was detected.     

Sialic acid in F. tularensis and F. novicida antigens]

Sialic acid was revealed in the antigens of virulent (503/830 and Schu) and vaccine (Schu-attenuated and 15-reduced) strains of F. tularensis and also in the antigens of F. novicida isolated by the treatment with trichloracetic acid, by the thiobarbiturate method of Warren. Its content depended on the culture virulence. Sialic acid was absent in the antigens of avirulent strains of the causative agent of tularemia (503-attenuated, 15-attenuated and 21/400), but, in difference from the virulent strains, there was revealed 2-desoxyribose on account of the presence of DNA. Serological activity of F. tularensis antigen decreased only 15 times in the antibody neutralization reaction after a complete release of sialic acid as a result of hydrolysis of the preparation in 0.1 N, H2SO4 at 80 degrees C for one hour, i.e. it persisted at a sufficiently high level. On the basis of investigations carried out it can be admitted that there existed a chemical association between the sialic acid and other composites in the polysaccharide of the virulent and the vaccine strains of F. tularensis, but that this acid played no significant role in the manifestation of specific properties by the antigen.     

Mechanisms of gravity-dependent changes in the bone tissue

The most typical changes for the bone under the space flight conditions and a long-term hypokinesia are the following: the decreasing in bone mass, the demineralization and a reducing of a mechanical strength. It can lead to osteopenia and osteoporosis development. Also it increases the risk of fractures of supporting bones. Osteopenies, caused by the microgravity, are partially connected with the increasing of a reduction of trabecular bones. [Cytological mechanisms of gravity-dependent reactions in a bone tissue remain in many respects not clear. The study purpose was the analysis of some ultrastructural changes in bone tissue cells of the monkeys (Macaca mulatta), staying during 2 weeks onboard the biosatellite "Bion-11".     

Interactions of cells in zones of bone resorption under microgravity and hypokinesia

With the use of the methods of electron microscopy and autoradiography employing 3H-glycine the study was made of some morpho-functional cells-cells interactions (osteoblasts, osteocytes, macrophages, fibroblasts) in zones of adaptive remodeling of bone structures of the metaepiphyseal femoral bones of white rats which were during 28 days under experimental hypokinesia conditions, as well as of rats, flown on SLS-2 during 2 weeks. It is established that in zones of an increase of mineral matrix resorption some osteoblasts and osteocytes undergo destruction; a part of osteoblasts remains intact. The osteoclasts don't take part in destruction of osteoblasts and osteocytes. The utilization of the osteogenic cells detritus is accomplished by macrophages, coming to these zones. The resorption loci are filled not with the differentiating osteoblastic cells, as it is the case in the norm, but with fibroblasts and the bundles of collagen fibrils (fibrotic tissue) which do not undergo mineralization. Such changes are considered as one of the mechanisms of bone tissue response to a reduction of the supporting load.