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PubMedDate not supplied

[Structure of an Escherichia coli bacterial suspension].

The structure of bacterial suspensions of Escherichia coli M-17 at the counting concentrations of the cells 10(7), 10(8), 10(9) i/ml and in the temperature range of (18-50) degrees C has been investigated by means of orientational conductometric, electron microscopic and UV-spectroscopic methods. On the basis of experimental relationships of the anisotropy of suspensions electric conductivity upon the intensity of a sinusoidal electric field and relaxation of anisotropy after switching off the field the function of the distribution of bacteria with respect to their sizes was evaluated at different temperatures and concentrations. The conductometric function of bacteria distribution is in a good agreement with the analogous function obtained with the help of the electron microscope. In accordance with the functions the suspension of E. coli contained three kinds of cells: high electronic density, low electronic density bacteria and bacteria aggregates. Relative amounts of every kind of bacteria depended on temperature and concentration of cells. The minimum of bacteria aggregates and maximum of low electronic density cells were obtained in the temperature range of (32-42) degrees C. This fact could be explained by the activation of the transport membrane systems in this temperature range. This hypothesis was confirmed by the UV-spectroscopic method.

Conductometry↗
PubMed1991

[The inhibition of mitosis in tissue culture cells by blue light].

Blue light (wavelength 350-480 nm) irradiation of the early mitotic (prophase and prometaphase) tissue culture cells at the dose of 50-3000 J/cm2 delay mitosis or completely block it at the metaphase. Cell sensitivity to the near UV light (wavelength 360 nm) was few times more as compared with the sensitivity to the visible light (wavelength 400-480 nm). Mitotic cells irradiated with the green light (wavelength more than 500 nm; dose up to 7500 J/cm2) completed division normally. The effect of the blue light did not depend on the presence of phenol red in tissue culture medium. Rhodamin 123 staining did not show any changes in the mitochondrial system in the irradiated mitotic cells. Blue light irradiation with the dose enough for the induction of mitotic delay appears to be insufficient to affect the proliferation of interphase cells.

Animals↗
PubMedDate not supplied

[Temperature changes of extracellular media state on a bacterial suspension].

Within temperature intervals 30-40 degrees C for bacterial suspension of E. coli and 24-34 degrees C for B. flavum the extracellular medium exists in a specific state. Water in the extracellular medium is stabilized by increased hydrophobicity of extracellular protein molecules surface due to proteins conformational change. The total amount of UV-absorbing metabolites is decreased as a result of activation of microorganisms transport systems. The temperature intervals of these processes are different for both types of the microorganisms and coincide with their temperature optima of vital activity.

Brevibacterium↗
PubMed1990

[Cytotoxic effect on human keratinocytes caused by anti-Ro-(SS-A) antibodies and UVA in vitro].

It is supposed that anti-Ro(SS-A) antibodies play an important role in the development of photosensitive skin disease in subacute cutaneous lupus erythematosus and neonatal lupus erythematosus. The aim of the experiments was to demonstrate that anti-Ro(SS-A) antibodies and UVA-light cause a cytotoxic effect on human keratinocytes in vitro. Keratinocytes are irradiated with UVA-light in presence of serum containing anti-Ro(SS-A) antibodies (62 E, ELISA). After application of 20 J/cm2 UVA-light only 48.5% of the irradiated cells are still vital (standard trypan blue exclusions test). Examination by scanning electron microscopy shows plain depressions on the surface of the keratinocytes, which were irradiated in presence of anti-Ro(SS-A) antibodies.

Antibodies, Antinuclear↗
PubMed1985

[Isolation of unbalanced growth forms from Listeria and their ultrastructure].

As the result of the action of penicillin, LiCl and UV irradiation on Listeria culture in the logarithmic phase, unbalanced growth forms (UGF) were obtained. Their viability was determined by the number of colony-forming units per ml. In this investigation the action of the above factors in a single cultivation and in consecutive subcultures was studied. Viable UGF were obtained under the action of all the above factors. UGF obtained under the action of penicillin were found to convert easily into L-forms in the process of subculturing. On the contrary, UGF obtained under the action of UV irradiation and LiCl produced no L-forms and reverted easily when the action of these factors stopped. In all three cases the formation of UGF was accompanied by changes in the structure of the cell wall and, partially, the cytoplasmic membrane, but in each case these changes had different character.

Cell Division↗
PubMed1978

Effects of 8-methoxypsoralen plus 365 nm UVA light on Candida albicans cells. An electron microscopic study.

Candida (C) albicans cells were exposed to 8-Methoxypsoralen (8-MOP) concentrations of 1.0 microgram/ml and 10.0 microgram/ml medium and irradiated with 365 nm light. The amount of energy emitted was 4.8 J/cm2. Two divergent types of cell damage occured concerning yeast cell cytoplasm and cell wall. Two hours after exposure cytoplasmic changes involving mitochondria, which showed irregularities in shape, blurred appearance or loss of mitochondrial cristae and outer membrane were seen. The number of vacuoles was increased. The cytoplasm showed large electron transparent areas, the cytoplasmic membrane disappeared in some areas completely. Nucleus and nuclear envelope usually remained intact in early stages. 24h after exposure conspicuous cell wall alterations were observed in addition to cytoplasmic changes. Newly produced cell wall material formed ball-like protrusions or was adherent sickle-shaped to the cell wall. The investigations strongly suggest that the results found after 8-MOP-UVA treatment of C. albicans cells can not be interpreted in the sense of a general cytotoxic effect. Apparently it takes the form of a combination of events involving regressive and progressive alterations.

Candida albicans↗
PubMed1987

Production of bacteriocin-like agents of Budvicia aquatica and "Pragia fontium".

In cultures of 9 budvicia aquatica and 5 "Pragia fontium" strains production of distinct bacteriocin-like agents was proved. It is suggested to call them aquaticins and fonticins. They display strain specific antibacterial activities towards both genera; however, they are not active towards Escherichia coli or Shigella sonnei indicators. Their inhibition zones are conspicuously narrow (turbid or clear). Their spontaneous production may be enhanced by UV-induction of producing bacteria. They are readily set free into the medium; no intracellular accumulation occurs. With only one exception, they are trypsin-resistant and remarkably heat-sensitive, being damaged at 45 degrees C to 55 degrees C. All these results suggest that aquaticins and fonticins are of corpuscular character. This assumption was proved true by electron microscopic observation of one of the fonticins: this resembles contracted tails of bacteriophage T4.

Bacteriocins↗
PubMed1985

Pasteurella haemolytica bacteriophage: identification, partial characterization, and relationship of temperate bacteriophages from isolates of Pasteurella haemolytica (biotype A, serotype 1).

Pasteurella haemolytica (biotype A, serotype 1) isolates (n = 15) from the upper respiratory tract of clinically normal cattle, as well as from lung lesions from cases of fatal bovine pasteurellosis, were examined for the presence of bacteriophage after irradiation with UV light. Treatment of all P haemolytica isolates with UV irradiation resulted in lysis of bacteria due to the induction of vegetative development of bacteriophages. The extent of growth inhibition and bacterial lysis in irradiated cultures was UV dose-dependent. Bacterial cultures exposed to UV light for 20 s reached peak culture density between 60 and 70 minutes after irradiation; thereafter, culture density declined rapidly, so that by 120 minutes, it was approximately 60% of the original value. When examined ultrastructurally, lytic cultures from each isolate revealed bacteriophages with an overall length of approximately 200 nm and that appeared to have a head with icosahedral symmetry and a contractile tail. Cell-free filtrate from each noninduced bacterial isolate was inoculated onto the other bacterial isolates in a cross-culture sensitivity assay for the presence of phages lytic for the host bacterial isolates. Zones of lysis (plaques) did not develop when bacterial lawns grown from the different isolates were inoculated with filtrates from the heterologous isolates.

Animals↗