In situ anion-doped epitaxial strontium titanate films.

Misfit strains arising from a film-substrate mismatch can induce novel phases and properties in the epitaxial films of perovskite oxides. Here we employ yet another effect, namely, strain-assisted formation of oxygen vacancies. We demonstrate the misfit-promoted presence of oxygen vacancies and related substitutional incorporation of anion dopants in the epitaxial films of archetypal perovskite oxide SrTiO3. Both the oxygen vacancies and hydrogen or nitrogen dopants are introduced in situ during the pulsed-laser deposition of the films using compressive substrates. The films exhibit peculiar chemical expansion and optical properties, which are consistent with substitutional anion doping.

[Study of possibility of formation of Vibrio parahaemolyticus pandemic clones based on retrospective PCR-screening of clinical strains].

AIM: PCR-genotyping of Vibrio parahaemolyticus strains that had caused sporadic diseases in Novorossiysk from 1973 to 1976. MATERIALS AND METHODS: 24 clinical strains of V. parahaemolyticus isolated in Novorossiysk, most of which belonged to serogroups O4:K12 and O4:K8; 10 O3:K6 strains--causative agents of gastroenteritis outbreak in Vladivostok (1997) and 3 from Japan (1971) were used. PCR genotyping was performed by a set of marker genes of 7 pathogenicity islands (VPaI-1 - VPaI-7) and a number of other pathogenicity factors. RESULTS: All the strains isolated in 1970s differed significantly by sets of VPaI marker genes. In contrast to causative agents of outbreak in Vladivostok that contain all 7 VPaI genes (that is, members of the pandemic group that had spread globally since 1996) none of the O4:K12 and O4:K8 Novorossiysk strains contained the full set of all the VPaI genes. However this set was distributed among the members of the group. CONCLUSION: Taking into account that O4:K12 and O4:K8 serogroups are considered by a number of authors as O3:K6 serovariants, PCR-screening data obtained by us allows to assume that horizontal transfer of mobile elements (VPaI) between strains circulating in the region could have led to the formation of pandemic clones already in the 1970s. This implies that in several coastal regions in certain periods of time conditions that favor these process may form, and risk of infection with pandemic clones is associated not only with import of seafood.

The electronic properties of SrTiO3-δ with oxygen vacancies or substitutions.

The electronic properties, including bandgap and conductivity, are critical for nearly all applications of multifunctional perovskite oxide ferroelectrics. Here we analysed possibility to induce semiconductor behaviour in these materials, which are basically insulators, by replacement of several percent of oxygen atoms with nitrogen, hydrogen, or vacancies. We explored this approach for one of the best studied members of the large family of ABO3 perovskite ferroelectrics - strontium titanate (SrTiO3). The atomic and electronic structure of defects were theoretically investigated using the large-scale first-principles calculations for both bulk crystal and thin films. The results of calculations were experimentally verified by studies of the optical properties at photon energies from 25 meV to 8.8 eV for in-situ prepared thin films. It was demonstrated that substitutions and vacancies prefer locations at surfaces or phase boundaries over those inside crystallites. At the same time, local states in the bandgap can be produced by vacancies located both inside the crystals and at the surface, but by nitrogen substitution only inside crystals. Wide-bandgap insulator phases were evidenced for all defects. Compared to pure SrTiO3 films, bandgap widening due to defects was theoretically predicted and experimentally detected.

[Analysis of Vibrio cholerae hemolysins using monolayer continuous cell cultures]. / Analiz gemolizinov kholernykh vibrionov s pomoshch'iu monosloinykh perevivaemykh kletochnykh kul'tur.

The comparative study of the preparations of V.cholerae hemolysins of different serovars with the use of continuous cell lines CHO-K1, Vero, Hela, L-929 was carried out. The preparations of hemolysins isolated from such strains as V.cholerae 569B, V.eltor 9949, V.cholerae O-mut 461/67-34 differed in their biological activity on experimental animal models and had different cytotoxic activity. The preparations exhibiting no activity when tested in vivo (V.cholerae and V.eltor hemolysins) were cetotoxins, but in lower doses (1000 and 100 times respectively) than the preparation of V.cholerae O-mut hemolysin, active in vivo. Hemolysins induced the formation of anticytotoxic antibodies in low titers.

[Bactericidal properties of hemo-cytolysin from Vibrio cholerae non O1 P-11702 strain in a panel of indicator cultures for detection of vibriocins]. / [Bakteritsidnye svoistva gemotsitolizina iz shtamma Vibrio cholerae non O1 P-11702 na nabore indikatornykh kul'tur dlia vyiavleniia vibriotsinov.

The influence of the preparation of hemo-cytolysin, obtained from V. cholerae non O1 strain P-11702 and inducing lysis of both red blood cells and V. cholerae cultures using a panel of indicator cultures for the detection of vibriocins, was studied. The set of indicator cultures contained 2 Shigella flexneri strains, 1 S. dysenteriae strain, 3 S. sonnei strains, 3 Escherichia coli strains and 2 V. cholerae strains, one of them being atypical. Hemo-cytolysin exhibited lytic activity with respect to S. dysenteriae, S. sonnei strains and 1 V. cholerae strain. i.e. to 4 out of 11 indicator strains. V. cholerae atypical strain proved to be resistant to the preparation in contrast to 33 V. cholerae typical strains, studied previously.

[Bactericidal properties of the Vibrio cholerae non O1 bacteriolysin]. / Bakteritsidnye svoistva gemotsitolizina Vibrio cholerae non O1.

The influence of the preparation of hemocytolysin, obtained from V. cholerae non O1 (strain P-11702), on the growth of V. cholerae cells was studied. The study revealed that hemocytolysin is capable of inducing partial or complete bacterial lysis on the place of its application, depending on the protein load of the substance and the inoculation dose of microbes. Two electrophoretic fractions with molecular weights of 14 and 14.5 kD induced the cytolysis of sheep, rabbit, guinea-pig red blood cells and showed a bactericidal effect. The different sensitivity of Vct+ and Vct- strains of V. cholerae to different doses of hemocytolysin was studied.

[Quantitative parameters of the length of time of Vibrio eltor survival on household objects]. / Kolichestvennye parametry dlitel'nosti vyzhivaniia Vibrio eltor na nekotorykh predmetakh obikhoda.

On household articles contaminated with protein-containing excrements (as in the stool of cholera patients) V. eltor survive 4.6 times longer than on those contaminated with excrements without protein (as in the stool of vibriocarriers ). This is due to a lesser initial dose of vibrios and the absence of protein in the excrements of vibriocarriers . These differences in the survival time of V. eltor on household articles suggest that objects contaminated with the excrements of cholera patients are epidemiologically more dangerous than those contaminated with the excrements of vibriocarriers . The quantitative determination of the survival time of vibrios on household articles indicates that, probably, these articles merely play the role of intermediate factors in the transfer of V. eltor in the foci of cholera.

[A comparative study of the immunogenicity of a bacterial mass and of the cell membranes of Vibrio cholerae grown in vivo and in vitro]. / Sravnitel'noe izuchenie immunogennosti bakterial'noi massy i kletochnykh obolochek Vibrio cholerae, vyrashchennykh in vivo i in vitro.

The comparative study of the immunogenic and protective properties of V. cholerae, grown in vivo and in vitro, and cell walls and lysates obtained from these organisms. In the mouse protection test the efficacy of preparations obtained from vibrios grown in vivo did not exceed that of the preparations obtained from V. cholerae agar cultures.

[The use of immunoenzyme analysis and the vibriocidal antibody reaction in the serological examination of persons who have had cholera and of those in contact with them]. / Primenenie immunofermentnogo analiza i reaktsii vibriotsidnykh antitel pri serologicheskom obsledovanii liudei, perenesshikh kholeru, i obshchavshikhsia s nimi.

The preparation of cholera toxin obtained from Vibrio cholerae strain 1310 has been used for producing solid-phase immunosorbent intended for the enzyme immunoassay (EIA). The use of EIA and the vibriocidal antibody test (VAT) in the serological study of former cholera patients and persons having contacts with them has made it possible to show the excess of the antitoxic activity of sera over their vibriocidal activity in all subjects covered by the dynamic study (from 5-14 days to 8-10 months). EIA and VAT can be used as auxiliary methods in epidemiological survey and analysis.