[Retention of tumorigenicity in radioresistant progeny of cells surviving exposure to high doses of gamma irradiation]. / Sokhranenie tumorogennosti u radiorezistentnykh potomkov kletok, vyzhivshikh posle vozdeistviia gamma-izlucheniia v bol'shikh dozakh.

The cell tumorigenic ability and the cell clonogenicity in semi-solid medium of highly radioresistant variant cell line, PIC-20 (the progeny of djungarian hamster fibroblast cell line DX-TK- surviving acute exposure to 20 Gy of gamma-irradiation), were examined. In the absence of additional radiation, no differences between tested features of non-irradiated PIC-20 cells and parental DX-TK- cells were observed. On the contrary, after gamma-irradiation with high doses the essential differences in the properties of the examined cell lines were revealed. After exposure to 10 Gy the surviving fraction of PIC-20 cells was 20 times higher than that of the parental cells. Both irradiated and non-irradiated PIC-20 cells produced colonies of similar size. It is revealed that even after irradiation with doses of 5, 10 or 15 Gy, the PIC-20 cells kept their tumorigenicity as high as non-irradiated ones. In all these cases the 90-100% of animals had the tumour, with the average latent period of tumour appearance after inoculation being the same both for irradiated and non-irradiated PIC-20 cells. After irradiation of parental DX-TK- cells with the highest dose of 15 Gy, the amount animals with tumour decreased by 70% and the average latent period of tumour appearance increased fivefold as compared with that for non-irradiated DX-TK- cells. The data obtained indicate that PIC-20 is highly radioresistant cells, which are able to proliferate both in semi-solid medium and in an animal organism even after radiation exposure to high doses.

[Different levels of radiation protection in tumor cell population]. / Razlichnye urovni radiozashchity v populiatsii opukholevykh kletok.

It is postulated the presence of various systems of protection in tumor cell population. This systems have different mechanisms and are induced by the level of damage. From the analysis of the literature and own experiments the author maintains that there are not less than three levels of tumor cell population protection. 1. The radiation induced protection system is engaged after relative low radiation doses (1-4 Gy). Basic mechanism is stimulation of intracell DNA repair. 2. Repopulation is restore of number of cells, which were in a radioresistant state at the moment of irradiation. This second protection level is induced by radiation with doses 4.5-10 Gy. 3. Nonspecific protection mechanism opposing hard destruction effects functions at cell population level after irradiation with doses above 10 Gy. As a result of radioinduced fusion of lethally damaged cells, and also as a result of generation of polyploid and multinuclear cells and other reorganization processes aroused by radiation in high doses, viable somatic cell hybrids and genetically changed cells may be formed. In this case repopulation may occur owing to irradiated tumor cell progeny proliferation appeared after indicated processes.

Cell attachment to extracellular matrices is modulated by pulsed radiation at 820 nm and chemicals that modify the activity of enzymes in the plasma membrane.

BACKGROUND AND OBJECTIVES: Adhesive interactions between cells and extracellular matrices play a regulative role in wound repair processes. The objective of this investigation is to study action mechanisms of pulsed radiation at 820 nm on cellular adhesion in vitro. Light emitting diodes (LED) at 820 nm are widely used for treatment of wounds of various etiology. STUDY DESIGN/MATERIALS AND METHODS: The LED (820 +/- 10 nm, 10 Hz, 16-120 J/m(2)) is used for the irradiation of HeLa cell suspension. In parallel experiments, amiloride (5 x 10(-4) M), ouabain (7 x 10(-5) M, 7 x 10(-4) M), quinacrine (6 x 10(-4) M), arachidonic acid (1 x 10(-5) M), glucose (2 x 10(-4) M), and ATP (5 x 10(-5) M) are added to the cell suspension before or after the irradiation procedure. The cell-glass adhesion is studied using the adhesion assay technique described in Lasers Surg Med 1996; 18:171. RESULTS: Cell-glass adhesion increases in a dose-dependent manner following the irradiation. Preirradiation eliminates the inhibition of cell attachment caused by ouabain, arachidonic acid, and ATP. The inhibitive effect of quinacrine on the cell attachment is eliminated by the irradiation performed after the treatment with the chemical. Irradiation and amiloride have a synergetic stimulative effect on the cell attachment. The threshold dose for the cell attachment stimulation by the irradiation is decreased by the treatment of the cell suspension with amiloride or ouabain. CONCLUSIONS: The results obtained indicate that pulsed IR radiation at 820 nm increases the cell-matrix attachment. It is the modulation of the monovalent ion fluxes through the plasma membrane and not the release of arachidonic acid that is involved in the cellular signaling pathways activated by irradiation at 820 nm. Preirradiation has a protective effect against the inhibitive action of ouabain, arachidonic acid, ATP, and quinacrine on cell attachment process. It is supposed that irradiation activates those signaling pathways in cells which attenuate the inhibitive action of these chemicals.

[Small doses of ionizing radiation as radiation modifying factor]. / Malye dozy ioniziruiushchego izlucheniia kak radiomodifitsiruiushchii faktor.

To investigate the biological effects of small dose ionizing radiation has been acquiring greater importance. The awareness of how and in what direction it show its modifying effects in small doses is an essential scientific basis for developing standards, living conditions under specific environmental conditions. Cultured Hela cells and DEF 4/21 fibroblasts were used to evaluate the biological effects of small-dose ionizing radiation, by examining the conditions under which it showed its modifying effect in small doses (0.1 Gy) in particular. Preexposure to small-dose radiation was shown to alter cell responses to subsequent radiation in large doses. The modifying effects of small-dose radiation turned out to depend on the interval of exposure to small and large doses. Sensitization was recorded at an interval of 2-3 min; an adaptive response was achieved when the interval increased up to 3-5 hours. Upon exposure, intercellular contacts contribute to the modifying effects of small-dose radiation. There was neither effect of sensitization nor adaptive response if single cells were exposed to radiation.

Donors of NO and pulsed radiation at lambda = 820 nm exert effects on cell attachment to extracellular matrices.

The adhesion of HeLa cells to a glass matrix was evaluated after the irradiation of the cell suspension with a pulsed near-infrared light-emitting diode (lambda = 820 nm, frequency 10 Hz, dose 8-120 J/m(2)) and treatment with two donors of nitric oxide, sodium nitroprusside (SNP, 5 x 10(-4) M) and NaNO(2) (4 x 10(-4) M). It was found that in an irradiated cell suspension, the cell-glass adhesion increases in a dose-dependent manner (a bell-shaped curve with a maximum at 60 J/m(2)). The treatment of cells with SNP or NaNO(2) before the irradiation eliminates the radiation-induced attachment stimulation. Pretreatment of cells with SNP not only eliminates the radiation-induced attachment stimulation but inhibits the attachment of irradiated (but not non-irradiated) cells. It is suggested that a modulation of the activity of respiratory chain (probably the alteration of the activity of cytochrome c oxidase) is involved in radiation-induced increase of cell attachment.

Cell attachment modulation by radiation from a pulsed light diode (lambda = 820 nm) and various chemicals.

BACKGROUND AND OBJECTIVE: Adhesive interactions between cells and extracellular matrices play a regulative role in wound repair processes. The objective of this investigation is to study the mechanisms of light action on cellular adhesion in vitro. The adhesion of HeLa cells to a glass matrix is evaluated after irradiation with a pulsed near-infrared (IR) diode and treatment with various chemicals. STUDY DESIGN/MATERIALS AND METHODS: A semiconductor diode (820 +/- 10 nm, 10Hz, 16--120 J/m(2)) is used for irradiation of the cell suspension. In parallel experiments, various chemicals (mannitol, melatonin, ethanol, ascorbic acid, superoxide dismutase, catalase, rotenone, azide, dinitrophenol (DNP), methylene blue, and hydrogen peroxide) are added to the cell suspension before or after the irradiation procedure. The cell-glass adhesion is studied by using the adhesion assay technique (Lasers Surg. Med. 1996;18:171). RESULTS: It has been found that cell-glass adhesion increases in a dose-dependent manner after irradiation. The treatment of the cells with antioxidants (free radical scavengers), e.g., mannitol, melatonin, ethanol, and ascorbic acid, as well as with the ionophore DNP, eliminated the light effect. The respiratory chain inhibitors rotenone and azide strongly modified the light effect, depending on the dose. The oxidative agents hydrogen peroxide (in a low concentration) and methylene blue increased the cell adhesion. Superoxide dismutase did not modify the light effect. The effect of the catalase (stimulative or suppressive) was dependent on its concentration and treatment sequence. Preirradiation was found to decrease (or normalize to the control level) the suppressive effects of some chemicals. CONCLUSION: The results obtained are evidence that first, pulsed IR radiation with certain parameters modulates the cell-matrix attachment. second, free radical and redox processes are involved in the cell-matrix interaction, probably at some stage(s) of the photosignal transduction. Third, both types of the primary reactions in the respiratory chain, namely, the increase of the electron flow and production of the reactive oxygen species, cause a transient oxidative stress in the cytoplasm.

[Systemic radiation reaction of tumor cell populations to high dose irradiation]. / Sistemnaia zashchitnaia reaktsiia populiatsii opukholevykh kletok na obluchenie v bol'khikh dozakh.

The work presents the results of the experiments confirming supposition of existence of a protection mechanism opposing hard destruction effects and acting at cell population level. The experiments were carried out with cultures of tumour cells HeLa and DEF 4/21. By technique of hybrid selection in selective HAT medium it was found that radioinduced cell fusion led to formation of viable and clonogenic cell hybrids. By electron microscopic methods, microinjections of fluorescent dye-stuff into cells and autoradiography it was discovered that tight cell communications were formed in irradiated culture before cell fusion. After high dose radiation posterity of survivor cells was by far the most radioresistant comparing with the parent cells and had more greater ability for repopulation. It was supposed that the ability was based on property of rapid transition from mitotic reproduction to non-mitotic division.

[The appearance of a fracture of radioresistant cells in a fibroblast population irradiated at high doses]. / Vozniknovenie fraktsii radiorezistentnykh kletok v obluchennoi bol'shimi dozami populiatsii fibroblastov.

Two sublines of Djungarian DEF 4/21 hamster cells survived after gamma irradiation with the doses of 10 and 20 Gy were obtained. The survived cell posterity (SCP) of both cell lines are considerably more clonogenic. They show a higher proliferative activity and a shorter period of generation than the control cells. The sublines are several times more radioresistant as compared to the original cells. After exposure to high doses of radiation, the cell culture of the SCP exhibits a 17 to 20% high-resistant fraction. Supposedly, the cells of this fraction are responsible for repopulation after exposure to lethal doses of gamma irradiation.

[The effect of gamma irradiation under different regimens on isolated and contacting cells of a HeLa culture]. / Vliianie gamma-oblucheniia v razlichnykh rezhimakh na odinochnye i kontaktiruiushchie kletki kul'tury HeLa.

It was shown that isolated and united HeLa cells in culture responded to single irradiation and repeated low dose irradiation by different ways. The effect on radiosensitivity was revealed in united cells only.

Effects of monochromatic low-intensity light and laser irradiation on adhesion of HeLa cells in vitro.

BACKGROUND AND OBJECTIVE: The adhesion of HeLa cells was evaluated after irradiation with monochromatic low-intensity light or laser irradiation. It is well known that the cell-cell and cell-matrix adhesion changes during wound repair. For better understanding of low-power laser light action on the wound healing process, it would be of interest to study the light action on cellular adhesion in vitro. STUDY DESIGN/MATERIALS AND METHODS: The monochomatic light was in the range 580-860 nm (bandwidth 10 nm, 5-150 J/m2 1.3 W/m2) and the He-Ne laser irradiation was 632.8 nm (100 J/m2, 10 W/m2). Cell-cell and cell-glass adhesion were evaluated after irradiation of HeLa cells. RESULTS: It was found that cell-cell and cell-glass adhesion increased following irradiation depending on the irradiation conditions (wavelength, dose) and the time elapsed after the irradiation. The cell attachment to glass surface increased after irradiation of samples of HeLa cells in suspension. CONCLUSION: The adhesion was stimulated in the wavelength ranges 600-625, 645-700, and 720-850 nm with maxima at 620, 680, 750, and 820-830 nm, respectively.

[The kinetics of polykaryon formation in a HeLa cell culture after irradiation at doses of 5 and 10 Gy]. / Kinetika obrazovaniia polikarionov v kul'ture kletok HeLa posle oblucheniia v dozakh 5 i 10 Gr.

Monolayer culture of HeLa tumor cells irradiated at 5 Gy and 10 Gy doses was followed up in kinetics for 14 days. It was shown that starting with day 3 the cell monolayer is modified in such a way that some cells occur in 2- to 8-cell accumulations. The rate of formation of such groups and the number of cells in them were dose-related. The labeling index in these formations was several times higher than that in the irradiated population on the whole. The analysis of the grade of DNA synthesis synchronization in these accumulations showed that complete cell fusion and polykaryon formation after irradiation at the dose of 10 Gy occurred on day 4 whereas after 5 Gy, only on day 7. In both cases the status of complete fusion was 3 days in duration.

[Changes in the amount of ATP in HeLa cells under the action of He-Ne laser radiation]. / Izmenenie kolichestva ATF v kletkakh HeLa pod vozdeistviem izlucheniia He-Ne lazera.

Amount of ATP in HeLa cells in various phases of growth was measured after He-Ne laser irradiation (100 J/m2, 10 W/m2, 10 s) by a bioluminescent luciferin-luciferase method. In cells of the exponential phase of growth, the amount of ATP (basal level 8 x 10(-16) mole/cell) starts to increase in 15 min after the irradiation with a maximum (170% above the basal level) at 20 min, and then decreases gradually to the basal level. The sensitivity of the cells to He-Ne laser radiation is lowest in lag-phase of growth, then increases to a plateau (approximately 185% above the control level) from 5th day of cultivation.

[The effect of He-Ne laser radiation on the adhesive properties of the cell membrane]. / Vliianie izlucheniia He-Ne lazera na adgezivnye svoistva kletochnoi membrany.

Changes in the number of individual cells and cellular complexes after a standard dispergation procedure were used as a criterion for evaluating the strength of the cellular contacts at various time-points after the irradiation of HeLa monolayers with a He-Ne laser (100 J/m2, 10 W/m2, 10 s). The per cent of cellular complexes increased after the irradiation, being maximal (19.5 +/- 0.6) at 30 minutes of post-irradiation, and then decreased to the control level (12.1 +/- 0.5). Per cent of cellular complexes increased again at longer intervals (90-180 min) after the irradiation.

Evidence for formation of somatic cell hybrids in a population of irradiated cells.

Experiments using two genetically marked lines of Djungarian hamster cells (DM-15 HPRT- and DH-TK-) and the technique of hybrid selection in selective HAT medium revealed viable colonies in a mixed culture irradiated with a dose of 5 Gy. The sublines grown from these colonies were examined. Chromosome analysis showed that about 45% of those cells were hybrids inheriting chromosome markers of both parent strains. Formation of radio-induced hybrids occurs as a function of time after irradiation, 6 days proving to be the optimal interval. It is postulated that radiation-induced cell fusion and formation of viable somatic cell hybrids may be essential for cell population survival in the course of tumour radiotherapy.