[Multidrug resistance increase of tumor cells at the effect of radiation and phorbol ether depends on protein kinase C and reactive oxygen species].

The effects of phorbol ether (PMA) and ionizing radiation on multidrug resistance (MDR) of human larynx cancer cells HEp-2 and the dependences of these effects on protein kinase C (PKC) activity and reactive oxygen species (ROS) production were studied. MDR was determined by transport rate of rhodamine 123 off cells and production of ROS in cells was measured by means of 2'7'-dichlorodigidrofuorescein oxidation to fluorescent 2',7'-dichlorofluorescein. ROS production was increased in cells at PMA treatment.

[Antitumor effect of low-intensity extremely high-frequency electromagnetic radiation on a model of solid Ehrlich carcinoma].

The influence of different exposure regimes of low-intensity extremely high-frequency electromagnetic radiation on the growth rate of solid Ehrlich carcinoma in mice has been studied. It was shown that, at an optimum repetition factor of exposure (20 min daily for five consecutive days after the tumor inoculation), there is a clearly pronounced frequency dependence of the antitumor effect. The analysis of experimental data indicates that the mechanisms of antitumor effects of the radiation may be related to the modification of the immune status of the organism.

[Modification of antitumor effect of vincristine by natural avermectins].

The effect of avermectins (aversectin C, aversectin C1 and avermectin B1) on the vincristine antitumor action with respect to murine transplantable tumors was studied. It was shown that both the natural avermectins mixtures and the individual avermectin B1 potentiated the antitumor action of vincristine on Ehrlich carcinoma, melanoma B16 and P388 lymphoid leukemia, including the vincristine resistant strain P388. Such an effect of the avermectins was observed only when they were administered after vincristine.

[Analysis of 15-lipoxygenase activity in irradiated thymocytes].

We studied the effect of gamma-radiation on 15-lipoxygenase activity in rat thymocytes. The enzyme activity was determined as the rate of linoleic acid oxidation by the protein fraction isolated from the control and irradiated thymocytes under standard conditions. We demonstrate lipoxygenase activation immediately after irradiation of thymocytes.

[Apoptosis in P388 leukemia cells induced by specific inhibitors of 5- and 12-lipoxygenase and the product of cyclooxygenase, prostaglandin E2].

We studied the effect of specific inhibitors of 5- and 12-lipoxygenases as well as the product of cyclooxygenase activity, prostaglandin E2, on proliferation and death of P388 leukemia cells. Inhibition of 5- and 12-lipoxygenases in the cells inhibits proliferation and induces apoptosis. The concentrations of baicalein, an inhibitor of 12-lipoxygenase, and AA861, an inhibitor of 5-lipoxygenase, causing a 50% death rate (LC50) proved to be the same, 50 microM.

[A study of the role of lipoxygenases in radiation-induced apoptosis of thymocytes. Inhibitory analysis].

The radiation-induced apoptosis of thymocytes is suppressed by the common inhibitor of lipoxygenases nordihydroguaiaretic acid but not the inhibitors of cyclooxygenases or cytochrome P-450, which indicates the key role of lipoxygenases in apoptosis. However, the specific inhibitors of 5-lipoxygenase (AA861) and of 12-lipoxygenase (baicalein) do not suppress apoptosis and even enhance it. This effect can be explained by an increase in the yield of the 15-lipoxygenase product upon inhibition of 5- and 12-lipoxygenases.

[Changes in sensitivity of lymphocytic leukemia P388 cells to oxidative stress and platidiam upon tumor growth].

We studied the effect of oxidative stress induced by hyperoxia, hydrogen peroxide, or menadione on mouse leukemia P388 cells at early (4 days) and late (7 days) stages of tumor growth. Oxidative stress proved to inhibit cell division and to induce apoptosis. Seven-day leukemia cells feature lower proliferative potential and higher sensitivity to oxidative stress and platidiam.

[Antitumor effect of combined treatment with ionizing radiation and vitamin B12-C complex].

The combined effect of ionizing radiation (0.5-4 Gy) and the vitamin B12-C complex on life-span of mice with Ehrlich carcinomas was studied. It was shown that antitumor effect of the combined treatment strictly depends on the sequence of the agent applying and on the time interval between them.

[Growth inhibition and induction of tumor cell death by phospholipase A2 and lipoxygenase inhibitors].

We studied the effect of arachidonic acid metabolism inhibitors in a wide concentration range on the proliferation and death of lympholeukemia cells P-388. Proliferation of the cells was estimated by metaphase frequency and the proportion of cells in S phase; cellular death was determined by their lysis, trypan blue staining, damaged nuclei, the proportion of cells with subdiploid DNA content, and DNA fragmentation. Low concentrations of phospholipase A2 and lipoxygenase inhibitors were shown to stimulate cell division, while higher concentrations inhibited it by blocking G1-S transition and inducing apoptotic cellular death.

[Cytotoxic and cytostatic effect of avermectines on tumor cells in vitro].

Effect of natural avermectin complex (aversectin C) and separate avermectins A1, A2, B1 and B2 in the cell culture of murine myeloma Ns/o, Erlich carcinoma ascites and human larynx carcinoma Hep-2 was investigated. It was shown that aversectin C within the concentrations of 0.1 to 1.

[Action of avermectins on lymphoid leukemia P-388 cells in vitro].

Avermectins are final products in the fermentation process with Streptomyces avermitilis. They have parasitocidic activity and are used as the main substances of insectoacaronematocides. The study of the activity of the natural avermectin complex (aversectin C) and separate avermectins A1, A2, B1 and B2 in the cell culture of lymphoid leukemia P-388 showed that within the concentrations of 0.

[Signalling during radiation-induced apoptosis of thymocytes].

The mechanisms of signal triggering, enhancement and transduction during radiation-induced apoptosis of the thymocytes are discussed. Apoptosis is triggered by aggregation of receptors accompanied by activation of protein tyrosine kinases. The receptor aggregation is caused by radiation-induced cross-links.

[Emotions, stress, smoking, alcohol consumption and cancer--the correlational and causal connections].

Correlative and causal relationships are discussed between emotions, stress, smoking, drinking, and cancer. The following conclusions have been drawn. Emotions control the physiological stress reactions: the negative emotions initiate and maintain stress, and positive emotions stop it.

[The model of age dependent frequency of neoplasms].

The equation for the increase of tumor frequency with age is deduced from the supposition about the errors of DNA replication as the main cause of oncogenic mutations. The quantitative expression of the organ specificity of tumor frequency is concluded also. The age function coincide qualitative with epidemiologic date: the tumor frequency is in proportion to age with the exponents of 5 and higher.

[The stimulation of cell growth in human lymphoma by ionizing radiation at low doses].

The effect of low-dose radiation (1-100 cGy) on the growth of lymphoma Raji cells in vitro was examined. It was shown that irradiation with doses of 2-20 cGy stimulates the cells growth. This effect was caused by shortening of the lag-phase of growth.

[The cause-effect relationships between different indices of radiation lesions of the thymocytes].

The dependence of the kinetics of different thymocyte injuries of the experimental conditions was investigated. It was shown that the rate of cell death detecting by cell staining decreases with the increase of the dye molecular size. Different organic substances decrease the staining rate of the dead cells with trypan blue but increase the rate of DNA fragmentation.

[Stimulation of fibroblasts' growth in culture by low-dose ionizing radiation in acute irradiation].

The effect of low irradiation doses (10-100 cGy) on the growth of Chinese hamster fibroblasts was examined. It was shown that the number and the mean size of colonies increased after irradiation with doses of 10-40 cGy. Dependence of the effect on dose is extremal with maximum at 10-20 cGy.

[The intercellular interactions in the interphase death of irradiated thymocytes. A study of the nature of the mediator of the interaction of irradiated thymocytes].

A study was made of the influence of cytosol and conditioned medium, obtained at different times of incubation of irradiated thymocytes, on native thymocytes, as well as of the influence of mixing the suspension and changing the medium and the enzyme inhibitors, involved in metabolism of arachidonic acid, on the radiation injury to thymocytes. Cytosol of thymocytes, incubated for 60 min after irradiation, was shown to exert an insignificant toxic effect on native thymocytes. The conditioned medium of irradiated thymocytes is virtually ineffective.

[The intercellular interactions in the interphase death of irradiated thymocytes. A study of the influence of different cells on thymocyte interphase death].

The influence of different cells on death and pycnosis of thymocyte nuclei after in vitro irradiation has been investigated. It has been shown that the removal from the thymocyte suspension of cells, having the activity of natural killers, medullar thymocytes, and macrophages, does not influence the radiation-induced damage to cortical thymocytes. The injury of exposed thymocytes decreases, however, after incubation them with nonirradiated thymocytes or cultured cells, the efficiency of the latter being dependent on the type of cells.

[The role of changes in the cytoplasmic concentration of Ca2+ in dexamethasone-induced thymocyte death].

The putative role of changes in cytosolic Ca2+ concentration ([Ca2+]i) in the dexamethasone (DM) induced thymocyte death was investigated. Incubation of rat thymocytes with 10(-7) M DM for different time intervals from 0.1 to 8 h did not change the basal [Ca2+]i level ca 100 nM as measured with Ca(2+)-fluorescent probe Quin-2.

[The interphase death of dividing cells. The relation of interphase death to cell energy requirements].

In experiments with irradiated cells of Chinese hamster and Ehrlich ascites tumor a study was made of the influence of energy provision on their interphase death rate. The presence of the uncoupler of respiration and oxidative phosphorylation--carbonyl cyanide-3-chlorophenylhydrazone--in a medium without glucose was shown to drastically increase the interphase death rate of cells of both types, whereas this effect was not observed in a medium with glucose.

[The interphase death of dividing cells. The effect of oxygen and the pH of the medium on the interphase death of Ehrlich ascites carcinoma cells under the action of ionizing radiation].

Interphase death of in vitro irradiated (200 Gy) Ehrlich ascites tumor cells was studied as a function of oxygenation level and medium pH. The presence of oxygen both during and after irradiation as well as the increase in pH from 7.4 to 8.

[Modification of the interphase death of thymocytes: the effect of agents inhibiting the killing process].

The influence of different killing inhibiting agents on the interphase death of irradiated rat thymocytes has been investigated. The results confirm the previously proposed hypothesis of the interphase death mechanism involving activation of killing potency in the irradiated population of thymus cells.