Isolation and characterization of highly radioresistant malignant hamster fibroblasts that survive acute gamma irradiation with 20 Gy.

To study the acquired radioresistance of tumor cells, a model system of two cell lines, Djungarian hamster fibroblasts (DH-TK-) and their radioresistant progeny, was established. The progeny of irradiated cells were isolated by treating the parental cell monolayer with a single dose of 20 Gy (PIC-20). The genetic and morphological features, clonogenic ability, radiosensitivity, cell growth kinetics, ability to grow in methylcellulose, and tumorigenicity of these cell lines were compared.

Photobiological modulation of cell attachment via cytochrome c oxidase.

The number of cells attached to glass substrates increases if HeLa cell suspensions are irradiated with monochromatic visible-to-near infrared radiation (600-860 nm, 52 J m(-2)) prior to plating. The well-structured relationship between this biological response and the radiation wavelength (action spectrum with maxima at 620, 680, 760, and 820 nm) suggests the existence of a photoacceptor responsible for the enhancement of attachment (presumably cytochrome c oxidase, the terminal enzyme of the respiratory chain) and, secondly, the existence of signaling pathways between the mitochondria, the plasma membrane, and the nucleus of the cell. Treating the cell suspension with ouabain (a Na(+), K(+)-ATPase inhibitor), amiloride (an inhibitor of N(+)/H(+) exchangers), or sodium azide (a cytochrome c oxidase inhibitor) prior to irradiation significantly modifies the action spectrum of cell attachment enhancement.

[Retention of tumorigenicity in radioresistant progeny of cells surviving exposure to high doses of gamma irradiation].

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.

[Different levels of radiation protection in tumor cell population].

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.

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.