RESUMEN
The delayed effects of the combined action of hyperthermia and ionizing radiation on yeast cells Saccharomyces cereviciae were investigated and compared with analogous effects of gamma-irradiation alone. It was shown that cells, survived after thermoradiate exposure, as well as cells, survived after gamma-irradiation form different in size colonies. The diminishing of size is accompanied by the increasing of the radiosensitivity of cells from these colonies. No significant difference between the radiosensitivity of the progeny of cells, survived the combined exposure, and the radiosensitivity of the progeny of gamma-irradiated cells was observed. A preposition can be made, that the thermal exposure of yeast cells before gamma-irradiation don't practically influence on the delayed effects. The magnitude of recovery (liquid holding recovery) on progeny of surviving cells is essentially smaller then the magnitude of recovery of irradiated parent culture without dependence on the type of initial exposure: combined action or just gamma-irradiation. This magnitude is correlated with the degree of the parental cell damage.
Asunto(s)
Rayos gamma , Calor , Saccharomyces cerevisiae/efectos de la radiación , Saccharomyces cerevisiae/fisiologíaRESUMEN
The incontact action of penicillin and ethidium bromide on dividing bacterial culture Escherichia coli through ampoule glass or by means of antennae was studied. No statistically significant differences in cell division between samples exposed to distant action and control were found, though contact action of both substances reduced division considerably.
Asunto(s)
Antibacterianos/farmacología , Escherichia coli/efectos de los fármacos , Etidio/farmacología , Penicilinas/farmacología , Medios de Cultivo , Escherichia coli/crecimiento & desarrollo , Vidrio , Metales , CuarzoRESUMEN
Various cellular systems have been analysed for synergistic interactions of the simultaneous action of hyperthermia with physical agents including ionizing radiation, ultraviolet light, and ultrasound, and with chemical agents including thio-TEPA and cis-DDP. Some general rules of synergistic interaction were revealed. First, for every constant rate or intensity of exposure to physical factors or concentration of chemical agents, synergy can be observed only within a certain temperature range that is different for various cellular systems. Secondly, within this range, there is a specific temperature that maximizes the synergistic effect. Any deviation of temperature from the optimal one results in a reduction in synergy. Thirdly, the rate of exposure to physical agents or the concentration of chemical agents strongly influences the synergy; i.e. as the dose rate or concentration is reduced, the temperature for maximum synergism decreases. Possible interpretations of the mechanisms responsible for these relationships of synergy are discussed.
Asunto(s)
Hipertermia Inducida , Saccharomyces cerevisiae/efectos de los fármacos , Saccharomyces cerevisiae/efectos de la radiación , Saccharomycetales/efectos de los fármacos , Saccharomycetales/efectos de la radiación , Antineoplásicos/farmacología , Antineoplásicos Alquilantes/farmacología , Cisplatino/farmacología , Sinergismo Farmacológico , Calor , Radiación Ionizante , Saccharomyces cerevisiae/crecimiento & desarrollo , Saccharomycetales/crecimiento & desarrollo , Tiotepa/farmacología , Ultrasonografía Intervencional , Rayos UltravioletaRESUMEN
The influence of media with different osmotic pressure (NaCl water solutions) on survival and permeability of Escherichia coli B/r and Escherichia coli Bs-1 cells heated up to 50, 52 and 60 degrees C was investigated. Hypotonic media increased, while hypertonic media, within a certain range of sodium chloride concentrations, decreased the damaging action of heating independently of the temperature. The effectiveness of thermoprotection was seen to increase, and the range of osmolyte concentrations, at which the highest effect of protection takes place, to move markedly towards higher concentrations of NaCl with increase in heating temperature. A certain relationship is suggested between the observed phenomenon and the osmotic homeostasis system of microorganisms under condition of thermogenic and tonic stress.
Asunto(s)
Escherichia coli/metabolismo , Calor , Permeabilidad de la Membrana Celular , Concentración Osmolar , Estrés Oxidativo , Cloruro de SodioRESUMEN
The kinetics of microwave (7 GHz) heating of yeast and bacterial cell suspensions of different concentrations was investigated in the conditions of various thermoisolation of irradiated samples. It was established that independently of type of microorganisms, microwaves produced a more intensive heating of cell suspension in comparison with suspension fluid. The degree of heating was shown to increase with cell concentration. This effect was more expressed under conditions of thermoisolation. At the same irradiation doses and cell concentrations the yeast suspension was heated more vigorously than bacterial one. These differences disappeared when the rise in sample temperature was related to the total cell volume.
Asunto(s)
Escherichia coli/efectos de la radiación , Microondas , Saccharomyces cerevisiae/efectos de la radiación , Escherichia coli/citología , Cinética , Saccharomyces cerevisiae/citologíaRESUMEN
The survival of bacterial cells Escherichia coli exposed to sodium nitrate (1-5 M) simultaneously with 60Co gamma rays was shown to be smaller than that expected for independent addition of the effects induced by each of agents applied separately. The synergistic effect was quantitatively estimated by the factor k, which is the ratio of the isoeffective doses on the calculated additive survival curve and the experimental one. The dependencies of k on the exposition of combined action of gamma rays and different NaNO3 solutions (1, 3 and 5 M) are presented. It was demonstrated that the synergistic ratio k was increased with exposure duration increasing. It is suggested that in this case the synergistic effect may be related with the formation of some additional lethal damage due to NaNO3 radiochemical transformation products.
Asunto(s)
Escherichia coli/efectos de los fármacos , Escherichia coli/efectos de la radiación , Nitratos/farmacología , Radioisótopos de Cobalto , Relación Dosis-Respuesta a Droga , Relación Dosis-Respuesta en la Radiación , Rayos gamma , Soluciones , Factores de TiempoRESUMEN
The influence of microwaves and heat on dynamics of heating of samples of intact and inactivated bacteria Escherichia coli and solutions of some basic molecular components of cell was investigated. It was shown that microwaves induce different dynamics of heating of all samples. On the contrary, thermal action induces identical dynamics of heating of all this samples except vegetable oil which was heated more intensively.
Asunto(s)
Células/efectos de la radiación , Calefacción , Calor , Microondas , Células/citología , Campos Electromagnéticos , Escherichia coli/citología , Escherichia coli/efectos de la radiación , Peptonas , Aceites de Plantas , Cloruro de Sodio , Soluciones , Sacarosa , SuspensionesRESUMEN
The object of this work was to study the effect of a short incubation in 0.01 M tris buffer, pH 7.0, with a different NaCl content (0-10%) on the viability, optic density and permeability of intact and heated at 52 degrees C Escherichia coli B/r cells. In contrast to the intact cells, the viability of the heated cells depended on osmotic pressure in the medium into which they were transferred after heating. The survival rate was highest when the cells were transferred into an isotonic buffer. In the case of hypotonic and hypertonic media, the survival rate of the cells decreased owing to the death of cells which were responsible for the formation of small colonies under the isotonic conditions. This was accompanied with a more intensive drop in the optic density of bacterial suspensions while their permeability increased (when the cells were transferred into the hypotonic conditions). The role of membranes in the processes of bacterial heat inactivation is discussed on the basis of the results obtained.