Conditioning of gray crows (Corvus cornix L.) in a "giant" eight-arm radial maze

Twelve adult hooded crows (Corvus cornix) were trained to perform a standard radial-maze task in a giant eight-arm outdoor radial maze constructed at the "Chistyi les" Biological Station (Tver oblast) for comparative investigations of spatial memory in birds and mammals. The maze consists of a central part of 250 cm diameter, and has arms of 650 cm length, 170 cm height and 80 cm width. The examined hooded crows showed good task performance. Errors (repeated visits to empty arms) were few in number and were predominantly connected with the tendency to avoid arms close to an observer.     

Electrical capacitance of lipid bilayer membranes of hydrogenated egg lecithin at the temperature phase transition

Electrical capacitance of the planar bilayer lipid membrane (BLM) formed from hydrogenated egg lecithin (HEL) has been studied during many passages through the phase transition temperature. In contrast to the BLM from individual synthetic phospholipids, membranes from HEL did not demonstrate any capacitance change at the phase transition temperature maximum, as measured by differential scanning calorimeter at 52 degrees C. Instead, two temperatures have been discerned by capacitance records: thickening at 42-43 degrees C and thinning at 57-59 degrees C. The first temperature region is close to the transition temperature of dipalmitoyllecithin, whereas the second is close to that of distearoyllecithin, two main components of the HEL. It was suggested that capacitance measurements were able to reveal a phase separation in the BLM from HEL which was not detected by differential scanning calorimetry. The phase transition of the BLM from the liquid crystal state to the gel state is followed by thickening of the bilayer structure, partly due to a gauche- trans transition of lipid molecules but mainly due to redistribution of the solvent n-decane.     

Isolation and phenotyping of Vibrio cholerae strains with the enhanced production of main protective antigens

Two V. cholerae strains of classical biovar, 2414 (serovar Ogawa) and 2415 (serovar Inaba), with of increased production of main protective antigens--cholera toxin, toxin-coregulated pili of adhesion (TCP), outer membrane protein OmpU, as well as phospholipases and proteases, have been detected among natural and recombinant strains under study. A simultaneous increase in the production of the above-mentioned main immunogenicity factors in strains 2414 and 2415 is seemingly linked with the presence of recombinant plasmid pCT105 with cloned genes of cholera toxin in these microbial cells. As the result of plasmid-chromosomal relationships, this plasmid probably ensures the effective expression of global regulating gene toxR. The strains capable of the hyperproduction of cholera toxin, TCP and protein OmpU may be used for the manufacture of more effective chemical vaccine (choleragen-toxoid).     

TNF-alpha in the regulation of MUC5AC secretion: some aspects of cytokine-induced mucin hypersecretion on the in vitro model

TNF-alpha has been implicated in the aetiology of otitis media with effusion (OME), where goblet cells proliferate in a modified respiratory epithelium, leading to the accumulation of a mucin-rich effusion in the middle-ear cleft. The MUC5AC mucin gene product has been identified as a component of these effusions. Here we have used the HT29-MTX goblet cell line, which secretes MUC5AC mucin, as a model to study the effect of TNF-alpha on goblet cells. MUC5AC mucin was identified and quantitated with a monoclonal antibody NCL-HGM-45M1. TNF-alpha stimulates MUC5AC mucin secretion in a dose-dependent manner, with 20 ng/ml producing maximal stimulation. Both pre-confluent and confluent cells showed peak stimulation after 7 h, however the pre-confluent cells showed twice the level of mucin hypersecretion. These results suggest that TNF-alpha stimulation of mucin secretion could play an important role in the early acute phase of the development of OME. This hypersecretion of mucin could then lead to the failure of the mucociliary clearance system, resulting in the accumulation of a mucin-rich effusion in the middle ear and the movement to a more chronic phase of the disease.     

Genetic markers of epidemic strains of Vibrio cholerae

In this review new data on the key pathogenicity genes of V. cholerae are presented. As shown on the basis of the analysis of the latest information on the structure of the genomes of different V. cholerae strains, structural genes ctxAB coding cholera toxin may not serve as the only marker of epidemically dangerous strains. More complete and reliable information for the evaluation of the epidemic potential of V. cholerae isolated from the environment may be obtained by the simultaneous detection of 4 genetic markers: genes ctxAB, tcpA and hap coding, respectively, cholera toxin, toxin-corregulated adhesion pili and soluble hemagglutinin/protease, as well as regulatory virulence gene toxR.     

Noncapsular mutants of Vibrio cholerae serogroup O139: their isolation, identification and use for the preparation of an O139 diagnostic antiserum

On the basis of V. cholerae strain P16064, serogroup O139, spontaneous and transposon mutants with the stable lose of the capacity for producing the polysaccharide capsule, but retaining antigen O139, have been obtained. As revealed in this study, capsular and noncapsular strains differ in their sensitivity to cholera phages 20 and Inaba, as well as in agglutination with O139-antiserum. These data make it possible to use of bacteriophages for the differentiation of capsular and noncapsular strains. The use of noncapsular mutants ensure obtaining rabbit O139-antisera with higher antibody titer.     

Strains of Vibrio cholerae serogroups O1 and O139 that produce the basic protective antigens

To find out stable and effective producers of major protective antigens intended for use as components of cholera chemical vaccine against V. cholerae strains of serogroups O and O139, the comparative analysis of the production of cholera toxin, toxin-coregulated pili (TCP), antigens O1 and O139, polysaccharide capsule and outer membrane protein OmpU in different V. cholerae strains groups O1 and O139 has been made. V. cholerae strain KM68, serogroup O1, has been found capable of the production of antigen O1, serovar Ogawa, protein OmpU at a sufficiently high level and the hyperproduction of cholera toxin and TCP, and thus suitable for use in the manufacture of cholera bivalent vaccine as the source of these antigens. Specially selected alysogenic noncapsular strain KM137 of serogroup O139, characterized by a high and stable level of the biosynthesis of this somatic antigen when grown in both laboratory and production conditions, may serve as the produces of antigen O139.