PubMed Health⌕ Search

Biomedical subjects

V L Popov

Publications and source records attributed to V L Popov.

At least 55 records · Page 3Linked to original sources
PubMed1994

Depletion of gamma interferon and tumor necrosis factor alpha in mice with Rickettsia conorii-infected endothelium: impairment of rickettsicidal nitric oxide production resulting in fatal, overwhelming rickettsial disease.

C3H/HeN mice infected intravenously with a dose of Rickettsia conorii (Malish 7 strain) that is sublethal for immunocompetent animals (1.1 x 10(3) PFU) developed disseminated infection of endothelial cells of the brain, lungs, heart, liver, kidney, testis, and testicular adnexa. In R. conorii-infected mice depleted of gamma interferon (IFN-gamma) and/or tumor necrosis factor alpha (TNF-alpha) by intravenous administration of neutralizing monoclonal antibodies on days 0, 2, and 4, the mortality rate was 100%. Death of the cytokine-depleted animals on days 5 and 6 was associated with overwhelming rickettsial infection documented by titration of rickettsial content in the brain and liver and by immunohistologic demonstration of massive quantities of R. conorii in endothelial cells of all organs examined, in macrophages of the liver and spleen, and in hepatocytes. Nondepleted, immunocompetent animals showed markedly reduced rickettsial content in the tissues on day 6, with rickettsial destruction in phagolysosomes not only in macrophages but also in endothelial cells and hepatocytes. All nondepleted, infected mice recovered and appeared completely healthy by day 9. Assay of liver infiltrated by lymphocytes and macrophages revealed mRNA of IFN-gamma and TNF-alpha, indicating that the host defenses were activated at the site of infection. Treatment of mice with an analog of L-arginine reduced the synthesis of nitric oxide and impaired rickettsial killing. Nitric oxide production was also impaired in cytokine-depleted infected mice. These observations support the hypothesis that IFN-gamma secreted by T lymphocytes and natural killer cells and TNF-alpha secreted by macrophages act in a synergistic, paracrine fashion on adjacent rickettsia-infected endothelial cells, hepatocytes, and macrophages to stimulate synthesis of nitric oxide, which kills intracellular R. conorii.

Animals↗
PubMed1994

Rickettsia conorii infection of C3H/HeN mice. A model of endothelial-target rickettsiosis.

BACKGROUND: Rickettsial diseases result from disseminated intraendothelial cell infection. The clinically critical conditions, meningoencephalitis and interstitial pneumonia, are associated with multifocal rickettsial vascular injury. EXPERIMENTAL DESIGN: C3H/HeN mice inoculated intravenously with either 2.25 x 10(3) or 2.25 x 10(5) Rickettsia conorii (Malish 7 strain) were observed for illness with sacrifice of animals for evaluation of pathologic lesions and host responses by light and electron microscopy, rickettsial content and location by plaque assay, immunohistology, and electron microscopy, and immune response by cytokine analyses and serology. RESULTS: Mice inoculated with a high dose of rickettsiae established disseminated endothelial infection on day 1, became ill with progressive increase in rickettsiae on day 4, and died with vascular injury-based meningoencephalitis and interstitial pneumonia on day 5 or 6. Mice inoculated with the low rickettsial dose became ill on day 5 and recovered by day 10. Clearance of rickettsiae was associated with lymphohistiocytic perivasculitis. Rickettsial infection of Kupffer cells and hepatocytes led to the formation of transient hepatic granulomas. Infection-associated loss of the ability of spleen cells to secrete interleukin-2 on stimulation with concanavalin A suggested transient immunosuppression. CONCLUSIONS: This experimental infection provides the best available model for rickettsial disease with endothelial infection and injury, immune rickettsial clearance, regeneration of endothelium, and repair of the vascular lesions.

Animals↗
PubMed1992

[Changes in the skin and sciatic nerve after soft-tissue damage to the extremity by a high-speed small-caliber bullet].

The character of contusive changes has been determined in the skin and sciatic nerve after lesion of soft tissues of the extremity with a high-speed small-bore bullet. A high-speed filming, tensiometry have been used. They allow to observe and measure processes of formation of the temporal pulsating cavity appearing at the moment of injury in the block of 20% gelatin and its influence on the imitator of the vascular-neural bundle. In the investigation performed on test-animals by means of neuromorphological, histological and histochemical techniques certain contusive changes are stated in the skin and sciatic nerve at various distances from the edge of the entrance and axis of the wound canal. The investigation of the material in 1, 3, 5 days after the lesion makes it possible to differentiate initial changes connected mainly with the effect of contusion from the secondary ones.

Animals↗
PubMed1992

Persistence of Rickettsia prowazekii in cotton rat macrophage cultures.

Rickettsia prowazekii is able to multiply and persist for a long time in cotton rat macrophage culture (29-days observation period). Electron microscopic studies showed that the structure of Rickettsiae remained intact at different intervals post-inoculation (p.i.). In the course of persistence Rickettsiae revealed a reduced capacity to infect chick embryos and guinea pigs, however, the infectious agent could be isolated at all stages of persistence of cultured cells such as fibroblasts of the guinea pig embryo, macrophages of intact cotton rats.

Animals↗
PubMed1992

Ultrastructure of viable and inactivated Coxiella burnetii after inoculation of mice.

C3HA mice were inoculated intraperitoneally (i.p.) with viable Coxiella burnetii (C.b.) (strain Apodemus flavicollis-Luga, phase I) or C.b. antigen (formalin-inactivated C.b.); pieces of spleen, liver, omentum, kidney, and suspension of peritoneal macrophages were examined by electron microscopy at 1, 7, 14, 21, 28, and 42 days post-infection (p.i.). Two main types of viable C.b. cells--small dense (DC) and bacteria-like (BC)--were found in omentum, spleen, and peritoneal exudate cells beginning from the 1st day p.i. but maximal amount they reached in spleen at day 14. Some parasitophorous vacuoles contained damaged BC or lysing C.b. cells. C.b. corpuscular antigen was found in phagosomes in ultrathin sections of spleen macrophages until 28 days p.i. By 7 days p.i. in omentum 3 types of parasitophorous phagosomes were described which were supposed to be the sites of the antigen utilization. It is assumed that most BC are destroyed in omentum macrophages during the 1st week after i.p. injection of the antigen, and DC can persist in spleen at least for one month.

Animals↗
PubMed1992

[Pseudomonads as parasites of protozoa].

The experimental study of the interaction of Tetrahymena pyriformis with different microorganisms of the genus Pseudomonas, isolated from the soil, was made. The study revealed that T. pyriformis phagocytosed some Pseudomonas pigment-forming species (P. cepacia, P. putida, P. fluorescens, P. pirkettii). The most pronounced cytopathogenic effect was produced by P. cepacia. The dynamic observations of the ultrastructural features of interaction between P. cepacia and protozoa were made. Even at early stages of this interaction some types of parasitiferous phagosomes containing both intact bacteria capable of multiplication by binary division and Pseudomonas cells exhibiting different degrees of destruction were registered. In several phagosomes morphologically intact bacteria differing in their cell-wall profiles and the density of their cytoplasm and nucleotide were present simultaneously. More dense cells with sinuous cell-wall membranes were more virulent. By hour 18 one giant parasitiferous vacuole was formed by fusion of smaller phagosomes, which subsequently broke up, liberating a new generation of bacteria. In infected cells disturbances in the structure of their mitochondria and macronucleus appeared. During the first 2 days of the joint cultivation of P. cepacia and T. pyriformis the accumulation of bacteria occurred due to the selection and multiplication of digestion-resistant bacterial cells, which ensured the resistance of this Pseudomonas population in association with protozoa.

Animals↗
PubMed1992

[The ultrastructure of a new species of Chlamydia--Chlamydia pneumoniae].

The dynamic study of a new Chlamydia species, C. pneumoniae (strain TWAR, isolate TW-480), inoculated into the monolayer culture of cells L-929 was made 24, 48, 72 and 96 hours after inoculation. When compared with C. trachomatis and C. psittaci, C. pneumoniae were found to stand between these two species with respect to the morphology of their intracytoplasmic microcolonies (inclusions): they were round, almost bubble-like, but more densely packed with chlamydiae, surrounded by an undulate membrane, preserving its integrity until the late stages of their development cycle. In cells L-929 C. pneumoniae had a typical development cycle accompanied by the formation of vegetative and spore-like cells, reticular and elementary bodies, as well as intermediate cells, though this process was slower than in C. trachomatis and C. psittaci. Besides normal elementary bodies, many altered ones were formed in the process of the development of C. pneumoniae in cells L-929. Most of these alterations were similar to the process of bacterial L-transformation and could be regarded as the manifestation of chlamydial pathology related to the adaptation to new host cells.

Animals↗
PubMed1991

Ultrastructure of Chlamydia pneumoniae in cell culture.

The electron microscopic appearance of Chlamydia pneumoniae elementary bodies with pear-shaped, loose outer membrane has been suggested as one criterion of its classification as a new chlamydial species. The study of the original strain TW 183 in LCL 929 and HL cells and a low-passage isolate of Kajaani-6 isolate in HL cells revealed spherical compact elementary bodies common to other chlamydia.

Chlamydophila pneumoniae↗
PubMed1991

Mixed Rickettsia-virus infection in Dermacentor reticulatus imago.

Electron microscopic examination revealed replication and accumulation of Rickettsia sibirica in the fat body of experimentally infected Dermacentor reticulatus ticks. Rickettsia are released from the fat body cells by budding being surrounded with cytoplasm and plasmalemma of the host cell. Eukaryotic cell structures have been detected consisting of lamella layers whirled around the intact rickettsiae. In addition to rickettsia, microorganisms morphologically resembling Francisella tularensis and an orbivirus were found in tick tissues at morphological examination. The morphology of the virus and stages of its morphogenesis are described. Mixed viral and rickettsial infection has been shown to develop in the same ticks and even in the same fat body cells in a very close association.

Animals↗
PubMed1991

[The ultrastructure of the interaction of Rickettsia sibirica and R. slovaca with the cells of ixodid ticks].

The ultrastructural aspects of the interaction of R. sibirica and R. slovaca with cells of mites of the species Dermacentor reticulatus, D. marginatus and Ixodes ricinus after their parenteral infection, as well as in the organs of D. marginatus infected naturally in the environment, have been studied. Both rickettsial species have similar morphology in different organs of the vector. These rickettsiae not only multiply, their populations are also partly destroyed in phagolysosomes. The natural mixed infection of R. sibirica and orbivirus in cells of D. reticulatus is described. As shown in this study, both associates pass through the complete ontogenetic cycle of development on the level of the host body and also on the level of an individual cell.

Animals↗
PubMed1991

[The ultrastructural characteristics of the interaction of Legionella pneumophila with the infusorian protozoon Tetrahymena pyriformis].

In this work the morphological features of the interaction of L. pneumophila virulent strain and T. pyriformis have been studied on the submicroscopic level in the time course of the process. The study has shown the process of the destruction of the bacterial population and the penetration of individual intact Legionella cells from the phagosome into the endoplasm of T. pyriformis after 6-9 hours of interaction in the form of the budding of the phagosome and further multiplication of Legionella in the endoplasm. As revealed in this study, T. pyriformis have two types of phagosomes characterized by different variants of the destruction of Legionella. In T. pyriformis lysosomes-like granules, mitochondria and the granular endoplasmatic network take part in the process of interaction. The process of interaction has been found to end by day 7 in the death of all protozoal cells taking part in interaction.

Animals↗
PubMed1990

[An analysis of the mechanisms of interpopulation interaction of Yersinia with Tetrahymena pyriformis infusorians at the cellular and subcellular levels].

The mechanisms of interaction between the populations of Yersinia and T. pyriformis have been analyzed on the cellular and subcellular levels. As shown in this investigation, Yersinia, when phagocytized by T. pyriformis, may undergo morphological changes, remain unchanged and also multiply, destroying the host cell in the process.

Animals↗
PubMed1989

[Inactivation of concentrated biomasses of Rickettsia prowazekii].

The methods used for the sparing inactivation of highly concentrated R. prowazekii biomass and for the decrease of its infectious activity are described. These methods are recommended for use in experiments in the field of molecular biology, as well as for disinfection of different materials contaminated with rickettsiae. As conditions for complete inactivation, incubation at 50 degrees C for 1 hour without chemical disinfectants, treatment with 0.5% phenol solution at 30 degrees C for 12 hours and with 0.1% formaldehyde solution at 4 degrees C for 24 hours have been selected. Treatment with 0.5% phenol solution at 36 degrees C for 1 hour or incubation at 45 degrees C without the use of disinfectants ensures an essential decrease in the infectivity of the material if the work with viable infective agents is necessary. Ultraviolet irradiation for 1.5 hours and exposure to the action of 0.1-0.5% sodium azide are less effective.

Azides↗
PubMed1989

[Dissociation and ultrastructure of the cells of Shigella sonnei isolated from gnotobiotes and obtained in vitro].

The dissociation variants of S. sonnei in phase I, isolated from germ-free rats and obtained in vitro, have been studied. Such dissociation variants have been found to form colonies with classical and atypical morphology. The electronmicroscopic study has revealed that different dissociation variants include small dense cells with the markedly thickened cell wall and pronounced microcapsule and spheroplasts with the damaged cell wall and less pronounced microcapsule. The formation of these cells is supposed to be the way of the adaptation of S. sonnei in the course of the infectious process and linked with changes in their virulence in the population cycle.

Animals↗
PubMed1988

[Electron microscopic study of the interaction of virulent and avirulent Shigella flexneri strains with the macrophages of murine peritoneal exudate].

The electron microscopic dynamic study of the interaction of S. flexneri virulent strain 2a and S. flexneri avirulent strain, genetically related to strain 2a and having the same antigenic structure, with peritoneal macrophages of CBA mice at an early period showed differences in the cytotoxic action of these strains. Even at the early period of the interaction between macrophages and virulent shigellae structural changes were observed in macrophages: ruptures in the membranes of parasitophore phagosomes, the vacuolization of the cytoplasm, the destruction of mitochondria. These changes were indicative of the early cytotoxic action of shigellae belonging to the virulent strain. In macrophages infected with avirulent shigellae the manifestations of this cytotoxicity were less pronounced and appeared later than in macrophages infected with S. flexneri virulent strain.

Adsorption↗