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Biomedical subjects

V L Popov

Publications and source records attributed to V L Popov.

At least 73 records · Page 4Linked to original sources
PubMed1988

[Invasiveness and cytotoxicity as criteria in assessing Yersinia attenuation].

The electron microscopic study of cells HEp-2 and the complex microbiological and morphological study of tissues and organs of guinea pigs and mice infected with the isogenic pairs of Yersinia strains (Y. pseudotuberculosis I and Y. enterocolitica 09) differing in the presence of the calcium-dependence plasmid, as well as Y. pseudotuberculosis mutants resistant to rifampicin, nalidixic acid or crystal violet without this plasmid, have revealed that the invasiveness and cytotoxicity of the infective agents are not directly related to the presence of the above-mentioned plasmid in these bacteria. The use of the quantitative characteristics of virulence, such as penetration ability, intracellular multiplication, dissemination and the formation of degenerative changes, has made it possible to find out that the mutants of Y. pseudotuberculosis I, yielding the negative result in the keratoconjunctivitis test and resistant to the above-mentioned antimicrobial substances, can be arranged in the following order according to the degree of attenuation: rifr mutants--nalr mutants--kvlr mutants. In contrast to Y. pseudotuberculosis I, the loss of the calcium-dependence plasmid by Y. enterocolitica 09 is accompanied by an essential decrease in their invasive and cytotoxic properties, but this relationship is indirect and unstable. The proposed criteria intended for use in the evaluation of the degree of the manifestation of the invasive and cytotoxic properties of bacteria can be useful for the selection of optimally attenuated Yersinia strains showing promise as vaccine strains.

Animals↗
PubMed1987

Electron microscopic analysis of in vitro interaction of Rickettsia prowazekii with guinea pig macrophages. I. Macrophages from nonimmune animals.

Monolayer cultures of peritoneal macrophages of intact guinea pigs were infected with Rickettsia prowazekii (strain Breinl) and examined by electron microscopy after 30 min, 4 and 24 hr post-infection (p.i.). Three parallel processes developed in infected macrophages: reproduction of rickettsiae in macrophage cytoplasm, destruction in phagolysosomes and production of spheroplast-like forms. Reproduction of rickettsiae yielded 2 cell types: those with dense and with light cytoplasm; they were located side by side in the microcolony and seemed to have a common capsule-like coat. Relatively small spheroplast-like forms of about 1 micron in size were regularly detected. Addition of immune serum to macrophages increased the number of rickettsiae, both of rod-shaped as well as of spheroplast-like ones located within phagosomes, but elicited no increase in the number of digested pathogen cells.

Animals↗
PubMed1987

Electron microscopic analysis of in vitro interaction of Rickettsia prowazekii with guinea pig macrophages. II. Macrophages from immune animals.

Alike to macrophages from intact animals, reproduction, destruction and formation of spheroplast-like forms were observed in macrophages from immune guinea pigs 2 months post-infection (p.i.) with the virulent Breinl strain of Rickettsia prowazekii. Unlike to the former, immune macrophages revealed phagolysosomes which were larger in size and contained more rickettsiae showing morphologic signs of destruction. Spheroplast-like forms occurred more often and were more numerous than in intact animals. Structures morphologically similar to L-forms of gram-negative bacteria and that of chlamydiae were also detected. After adding immune serum, more intact rickettsiae and spheroplasts were found in phagosomes as well as more phagolysosomes contained rickettsiae and spheroplasts with morphologic signs of destruction. It is suggested that clearance of immune macrophages from rickettsiae is mediated by at least two processes: on one hand by destruction of rod-shaped rickettsiae within phagolysosomes and, on the other hand, by formation and subsequent destruction of spheroplast-like forms within vacuoles, which probably also function as phagolysosomes.

Animals↗
PubMed1986

Peculiarities of Rickettsia prowazekii in the cell culture as revealed by cryoultramicrotomy.

Ultrastructure of Rickettsia prowazekii has been followed in L-929 cells 4 days post-infection (p.i.) by cryoultramicrotomy. Groups of rickettsiae were present in the cytoplasm outside of vacuoles forming microcolonies. The size of rickettsiae amounted to 400 X 700 nm, the average thickness of the cell wall was 5 nm, that of periplasmic space and cytoplasmic membrane 14 and 6 nm, respectively. Within intracytoplasmic colonies the rickettsiae were tightly packed and their cell walls were closely adjacent to each other. No halo or capsule-like coating around them was detected. No ultrastructural details were observed in the light translucent spaces between cells. Marginal rickettsiae of the microcolonies were often in close contact with the host cell mitochondria.

Animals↗
PubMed1986

Ultrastructure of Rickettsia sibirica during interaction with the host cell.

Rickettsia sibirica (strain Netsvetaev) was found within large translucent spaces in the cytoplasm of L-929 cell monolayer cultures on day 6 postinfection (p.i.). These rickettsiae were rod shaped 0.3 X 10 microns in size encircled by a halo of up to 200 nm wide corresponding to a capsule-like coat. Directly on the cell wall was a 12 nm thick microcapsule in which subunit structures with 12 nm thick spacing could be recognized. The cell wall membrane was 14 nm thick with a wider internal layer occasionally in a section found split into two electron-dense lamels; the internal layer corresponded to peptidoglycan. The periplasmic space with an average thickness of 5 nm separated the cell wall from a 7 nm thick cytoplasmic membrane. The ultrastructure of R. sibirica was similar to that of other rickettsiae, although the capsule-like coat was thicker than in spotted fever (SF) group rickettsiae.

Animals↗
PubMed1985

[Biological characteristics of bacteria during the Cytos-2 Soviet-French space experiment].

The experiment "Cytos-2" made it possible to reveal a certain increase in the antibiotic resistance of bacteria constituting the opportunistic pathogenic microflora of man (Staphylococcus, Escherichia coli and Pseudomonas aeruginosa) to oxacillin, erythromycin, colistin and kanamycin under the conditions of space flight. The electron-microscopic study of the postflight staphylococcal cultures revealed the thickening of the cell membrane in staphylococci. The conditions of the experiment did not affect the stability of the biochemical characteristics of P. aeruginosa cultures, as well as their virulence, immunogenic properties and type specificity.

Anti-Bacterial Agents↗
PubMed1985

[Characteristics of rickettsial morphology during intracellular development].

The normal anatomy of rickettsiae has been characterized with the use of R. prowazekii, R. conorii and R. akari in continuous cell cultures L-929, Al, FL and in primary chick embryo fibroblast culture. Rickettsiae are short rod-shaped cells with the dense cytoplasm and the regular structure of the cell wall--cytoplasmic membrane complex. The study has shown the absence of polymorphism in rickettsiae growing under permissive conditions, but at the same time these organisms easily develop into pathological forms. Pathological forms can be detected alongside normal rickettsiae in the same cells. The classification of the pathological forms of rickettsiae is presented. In this classification the compensating (reversible) and destructive (irreversible) forms of alterations, as well as hypertrophic and dystrophic processes on the level of the whole rickettsial cell or its organelles, are pointed out.

Animals↗
PubMed1984

Rickettsiaceae and Chlamydiaceae: comparative electron microscopic studies.

The structure and cytopathology of obligate intracellular bacteria belonging to families Rickettsiaceae and Chlamydiaceae and their interaction with eukaryotic host cells were compared in electron microscopic studies. "Rickettsia-like" and "chlamydia-like" types of organization of bacterial cells and their interaction with host cells are presented. The rickettsia-like type is characterized by short rod-shaped cells multiplying freely ( extravacuolarly ) in the cytoplasm or nucleoplasm of the host cell; the chlamydia-like type has spherical cells multiplying inside the cytoplasmic vacuole limited by the host membrane. The rickettsia-like type includes the genus Rickettsia and rod-shaped symbionts from genera Wolbachia and Symbiotes ; the chlamydia-like type falls into genera Chlamydia, Ehrlichia, Cowdria and Neorickettsia . The transitional types represented by Wolbachia persica (type 1), Coxiella and Rickettsiella (type 2) are also described. The possible evolutional relationships of the genera comprising both families are considered and their classification is proposed.

Chlamydia↗
PubMed1984

[Electron microscopic characteristics of the action of penicillin and vancomycin on Rickettsia conorii and Rickettsia akari in vitro].

The possibility of L-transformation for two species of Rickettsia of the tick group (R. conorii and R. akari) was studied with light and electron microscopy. The experiments were performed on the cultures of L-cells (murine fibroblasts). Penicillin and vancomycin were used as the transforming agents. Electron microscopy revealed clear changes in the morphological structure of both species when the doses of penicillin and vancomycin were 50-100 and 250-1500 micrograms/ml, respectively. The antibiotics had a morphologically analogous effect on both species of Rickettsia. The resulting morphological structures were large oval spheroplast-like cells with significant expansion of the periplasmic space up to 1 X 1.75 micron under the effect of penicillin and 0.5 X 0.7 micron under the effect of vancomycin. R. akari was somewhat more sensitive to the antibiotics. Electron microscopy of the morphological changes in the Rickettsia induced by penicillin and vancomycin showed that they were similar to the changes observed in gram-negative bacteria on their L-transformation and to the penicillin forms of chlamydia (galprovia) and R. prowazekii. They may be considered as a phase of unbalanced growth and represent the initial stage of L-transformation.

Cell Wall↗
PubMed1984

[Interaction of Rickettsia akari with the host cell in vitro: multiplication, formation of spheroplast-like forms and its destruction in phagolyosomes].

The electron microscopic study of the interaction of R. akari, strain CK, with the monolayer culture of L-cells was made 4 days after inoculation. Rickettsiae multiplied by transverse binary fission immediately in the cytoplasm of the cells and left the cells by gemmation, surrounded with plasmolemma and a fragment of the host cytoplasm. Alongside with multiplying rickettsiae, spheroplast-like rickettsiae and rickettsiae at the stage of destruction were regularly observed in phagolysosomes. The authors suggest that the normal interaction of rickettsiae with the host cell may be realized by three following routes (1) reproduction, (2) destruction in phagolysosomes and (3) formation of altered (anomalous) forms. The ability of the vegetative forms of rickettsiae and chlamydiae to yield spheroplast-like forms (the initial phase of bacterial L-transformation) indicates that these organisms are similar to bacteria and cannot be themselves regarded as L-forms.

Animals↗
PubMed1984

[Yield of Chlamydia from an infected cell studied by scanning electron microscopy].

The study of the monolayer cell culture L-929, infected with strain CP-1 isolated from a patient with Reiter's syndrome, by means of scanning electron microscopy demonstrated that the release of chlamydiae from infected cells occurred in two ways: (1) by active ejection, probably as the consequence of the local rupture of the host cell, and (2) by more quiet "eruption" due to rupture in the plasmolemma . Elementary chlamydial bodies released from the cell had a spherical form, and reticular bodies had an irregularly spherical form, often with recesses and digitiform protrusions.

Animals↗
PubMed1984

[Surface structure of the elementary bodies of Chlamydia].

The surface structure of chlamydial elementary bodies (strain PL-B577 causing enzootic abortion of ewes and strain CP-1 isolated from a patient with Reiter's syndrome), concentrated directly on the grid of an electron microscope, was studied by the method of negative staining. The surface of the cell wall of chlamydial elementary bodies in the preparations of crude cultures, not subjected to enzymatic purification, was formed by spherical subunits 4 nm in diameter. The surface of the cell wall of elementary bodies was found to have projections 10-20 nm long and 3-4 nm in diameter, as well as annular structures 15-22 nm in diameter in hexagonal arrangement, spaced at 45 nm and probably traversed by these projections. The number of such structures in a group was 12-15. These data correspond to the model representing the structure of the surface of chlamydiae, which was proposed by Matsumoto in 1979.

Abortion, Spontaneous↗
PubMed1984

[Floating cell cultures of the fetal pancreas].

A simple method for preparing human and animal fetal pancreatic cell cultures has been developed. It is based on enzymatic treatment of the fetal pancreatic tissue with collalitine in combination with microdissection. As a result of subsequent cultivation there form floating cytotypic and organotypic cultures consisting mainly of B cells in different phases of the secretory cycle. The floating cultures prepared by the above-described method produce insulin and can be successfully used in experimental and clinical transplantology.

Culture Techniques↗
PubMed1983

Comparison of the ultrastructure of small dense forms of chlamydiae and Coxiella burnetii.

In the course of passaging of Coxiella burnetii (C.b.) in Alveonasus lahorensis ticks, the haemocytes contained cell forms with electrondense cytoplasm, intracytoplasmic lamellar membranes, and a peculiar limiting membrane--25 to 30 nm thick "envelope complex". Similar small forms occurred when C.b. had been cultured in the yolk sack of chick embryos. The dense forms of C.b. were similar to those of Rickettsiella cells. Dense forms (elementary bodies) surrounded by an "envelope complex" were found also in some chlamydiae cultured in yolk sacs of chick embryos.

Animals↗
PubMed1983

[Antigenic characteristics of the L forms of Streptococcus group B].

Stable L-forms of group B streptococci (GBS) have been obtained and their antigenic features have been studied by the serological methods (the passive hemagglutination test, the aggregate agglutination test, the gel diffusion test), as well as by using ferritin and peroxidase labels with the subsequent electron microscopy. The use of the serological methods has made it possible to reveal the antigenic differences between the stable L-forms of GBS and their bacterial forms. Specific antigenic substances can be found in the supernatant fluid obtained after the sedimentation of the ultrasonically disintegrated cellular mass of streptococcal L-forms and bacterial cultures. The use of ferritin and peroxidase labels has revealed the specificity of GBS L-form antigen and its localization on the cytoplasmic membrane of all L-form structural elements.

Animals↗