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To study the role of active programmed cell death induced by Vibrio cholerae antigens in alteration of peritoneal macrophages of experimental animals.Apoptosis was assessed by cytofluorometric analysis with propidium iodide using cytofluorometer "Coulter" as well as on characteristic morphological changes of cells in stained histological preparations.Performed experiments carried out by both methods provide evidence that V. cholerae and its antigens (cholera toxin, neuraminidase, chitinase, and lypopolysaccharide) cause apoptosis of mice peritoneal macrophages, which leads to their alteration.Our results demonstrate that programmed cell death of phagocytes is one of the causes of cytotoxic effect of V.cholerae and its antigens. Performed experiments show the role of apoptosis of macrophages in formation of postimmunization immunosuppression after vaccination against cholera.

The comparative study of the genomes of V. cholerae O139 isolated from humans and from water of surface reservoirs was carried out with the use of single- and double-primer polymerase chain reaction (PCR). The profiles of polymorphic DNA fragments obtained in this study made it possible to find out differences between groups of strains, as well as the individual features of some of them. The comparison of strains isolated from humans and from water in single-primer PCR revealed that they, in spite of the general similarity of their genomes, essentially differed, which was probably due to changes in the genome of this infective agent. Strains of aqueous origin lacked genes ctx and tcpA, which made them epidemiologically unimportant.

Neuraminidase isolated from Yersinia pestis [correction of the plaque microbe] and purified has been studied for its effect on the peritoneal leukocytes of the white mice with results presented. Neuraminidase exerted the insulin-like effect on the peritoneal leukocytes of the white mice and this effect depended on the used dose. The priming of leukocytes by neuraminidase preparation was accompanied by the sharp increase of hydrogen peroxide production under effect of the capsule antigen of the plaque microbe and, apparently, by the appearance of additional binding sites for the adhesion piles of the plaque agent.

Comparative study of the properties of initial capsular (cap+) and non-capsular (cap-) F. tularensis strains has revealed that the non-capsular variants have their specific biological features. The characteristic features of these variants are avirulence and inability to produce an immunogenic effect in sensitive laboratory animals. Cap- mutants, depending on the method of their obtaining, may exhibit different sensitivity to some antibacterial preparations. In contrast to the initial virulent strains, cap- variants are intensively phagocytosed by peritoneal macrophages of white mice and capable of multiplication and survival in these macrophages. F. tularensis non-capsular forms are characterized by higher superoxide-dismutase and neuraminidase activity than the initial strains, which may be the explanation of the phenomenon of their intracellular survival. At the same time the main biochemical signs of cap- strains (citrullinureidase, phosphatase and penicillinidase) remain unchanged, which determines the possibility of their classification with this subspecies.

In Y. pestis a cyclic AMP-binding protein was detected, isolated to a homogeneous state, and its physico-chemical properties were studied. The protein is a highly molecular compound with a molecular weight of 180 kD, capable of being released into the environment in the process of cell growth and having protein kinase activity, not depending on the presence of cyclic AMP. Y. pestis neuraminidase is one of the substrates appearing due to the action of protein kinase detected in this study. Y. pestis protein kinase may alter the spectrum of protein phosphorylation in the leukocytes of white mice. The direct participation of this protein in the development of infection is supposed.

In two Francisella species (F. tularensis and F. novicida) neuraminidase activity, heretofore unknown, was detected. The enzyme exhibited specificity with respect to the substrates used in the investigation, neutralizing natural mucins, but not other compounds (glycoproteins and glycoproteins). All F. tularensis strains were found to have enzymatic activity irrespective of their subspecies, but neuraminidase activity was higher in the strains belonging to the American subspecies. Experimentally obtained F. tularensis noncapsular variants possessed higher neuraminidase activity than the capsular parent strains. The conclusion on the possible role of this enzyme in F. tularensis colonization of the host body was made.

Superoxide dismutase (SOD) activity has been registered in representatives of the genus Francisella. The electrophoretic mobility of the enzyme and a number of its isoforms in F. tularensis are linked with the subdivision of this species into several subspecies. Avirulent and noncapsular variants of F. tularensis are characterized by a higher SOD activity than the initial virulent strains. Attempts to detect catalase activity in F. tularensis have failed.

Studies of biological activity of cholera vibrios in cultures of chinese hamster ovary cells (CHO) have revealed their strong dependence on culture conditions. Elongation of CHO cells is caused only by choleragenic strains. Under stationary conditions of culture the vibrios were found to release haemolisin into the medium and had a cytotoxic effect. Most of cytotoxic supernatants exhibited a neuraminidase activity. Proteolytic activity was less dependent on the vibrio culture conditions. Strains with a high proteolytic activity caused rounding of the CHO cells.

The data on the influence of the preparation of Y. pestis adhesion pili on peritoneal macrophages in white mice and guinea pigs are presented. Y. pestis adhesion pili have been found to induce the dose-dependent increase of cell chemiluminescence. They have also been found to induce a number of biochemical changes in target cells: the secretion of myeloperoxidase, an increase in the activity of cAMP-dependent protein kinases.

Vibrio cholerae 01 and non 01 neuraminidase may be rapidly detected with the use of a synthetic 4-methylumbelliferyl-neuraminic acid substrate. Other vibrios and Enterobacteriaceae show no neuraminidase activity against this substrate. The method may be used with microorganism cultures grown in solid and liquid nutrient media. The time of analysis is 15-20 min.

The intracellular form of neuraminidase has been detected in E. coli and Proteus vulgaris. Neuraminidase has been isolated from E. coli HB 101 cells and purified 118-fold. Some physico-chemical properties of this enzyme have been studied.

beta-Lactamase was isolated from the cells of a penicillinase-producing strain of the tularemia causative agent. It was purified 100 times. By its properties (the substrate profile, Km, temperature optimum and thermostability) beta-lactamase differed from penicillinases isolated from other sources.

It was shown that serum of albino mice infected with plague microbe cells inactivated benzylpenicillin. Such deacetylating activity reached its peak by the 3rd day and after that decreased reaching by the 5th--7th day the level registered in non-infected animal and being apparently of non-specific character. Ampicillin proved to be 2 times more resistant to the effect of serum acylase as compared to benzylpenicillin. It was supposed that the ability of serum of infected animals to inactivate benzylpenicillin by splitting off phenylace acid was the cause of ineffective treatment of experimental plague of albino mice with comparatively low doses of the drug.

The authors demonstrated the presence of neuraminidase in Past. pestis. Optimal conditions for its formation and detection were chosen. Extracellular form of neuraminidase was revealed. An increase of cultivation temperature led to the elevation of the neuraminidase activity in Past. pestis cells. Neuraminidase was revealed in bacteria affiliated to Past. pestis (causative agents of pseudotuberculosis and Y. enterocolitica).

beta-Lactamase and penicillinacylase were detected in the tularemia causative agent. These enzymes participated in the mechanism of natural resistance of the microorganisms to penicillins. It was shown that the growth temperature had a significant effect on the beta-lactamase activity. The penicillin resistance marker was not eliminated with the use of acridine orange, ethidium bromide or sodium dodecylsulfate.

The biological action of Y. pestis adenylate cyclase on peritoneal leukocytes of guinea pigs has been studied by means of chemiluminescence. Y. pestis adenylate cyclase is supposed to contribute to the "oxidation" explosion of phagocytes in plague.

The quantitative method for determination of penicillinacylase activity is described. The method is based on detection of phenylacetic acid (PAA) formed during hydrolysis of benzylpenicillin. PAA is extracted with toluol and nitrated with potassium nitrate solution in concentrated sulphuric acid followed by reduction of nitrophenylacetic acid into aminophenylacetic acid with zinc powder. Aminophenylacetic acid interacts with p-dimethylaminobenzaldehyde in acid medium forming a coloured compound (Schiff base). The optic density of the latter was determined with spectrophotometer SF-16 at 430 nm. The method was used for determination of acylase in Yersinia species and some other bacteria.