Effects Of Irradiated Medium Research Articles

Effects of irradiated medium with or without cells on bystander cell responses

Recent studies have indicated that extranuclear or extracellular targets are important in mediating the bystander genotoxic effects of α-particles. In the present study, human–hamster hybrid (A L) cells were plated on either one or both sides of double-mylar dishes 2–4 days before irradiation, depending on the density requirement of experiments. One side (with or without cells) was irradiated with α-particles (from 0.1 to 100 Gy) using the track segment mode of a 4 MeV Van de Graaff accelerator. After irradiation, cells were kept in the dishes for either 1 or 48 h. The non-irradiated cells were then collected and assayed for both survival and mutation. When one side with cells was irradiated by α-particles (1, 10 and 100 Gy), the surviving fraction among the non-irradiated cells was significantly lower than that of control after 48 h co-culture. However, such a change was not detected after 1 h co-culture or when medium alone was irradiated. Furthermore, co-cultivation with irradiated cells had no significant effect on the spontaneous mutagenic yield of non-irradiated cells collected from the other half of the double-mylar dishes. These results suggested that irradiated cells released certain cytotoxic factor(s) into the culture medium that killed the non-irradiated cells. However, such factor(s) had little effect on mutation induction. Our results suggest that different bystander end points may involve different mechanisms with different cell types.

Effects of gamma radiation on the in vitro response of Dactylis glomerata leaf segments

60Co γ radiation dose-response curves for callus induction/somatic embryo formation and plantlet regeneration from in vitro cultured leaf segments of orchardgrass ( Dactylis glomerata L.) were established. The effect of irradiated medium on callus/embryo formation was nil up to 30 Gy. After irradiation, leaf segments were plated onto Schenk and Hildebrandt medium containing 30 μM 3,6-dichloro- o-anisic acid and cultured at 25°C in the dark. D 50s in two separate experiments for callus induction/somatic embryo formation were 14.6 and 11.1 Gy, respectively. Embryo germination and plantlet development were more sensitive; the D 50 being 6.0 Gy. Shoot development was suppressed more than root development. No chlorophyll deficient plantlets were observed among the several hundred regenerated.

Radiation-induced organogenesis : effects of irradiated medium and its components on tobacco tissue culture

Gamma irradiated medium induces the formation of buds in non-irradiated dark grown tobacco callus ( Nicotiana tabacum Var. Wisconsin no. 38). Experiments were conducted to determine the component(s) of the medium that is effective in this radiation-induced organogenesis. Fractions of medium were irradiated singly and in combination, then combined with non-irradiated fractions to form the complete growth medium. The results show that irradiated indoleacetic acid (IAA) was not the effective component in the induction of organogenesis. Omission of IAA from the medium resulted in the formation of buds, as expected. Irradiated myo-inositol induced organogenesis more consistently than the other irradiated components. The age of the inoculum tissue and its passage number from the tobacco stem affected the potency of the tobacco callus to organise.

Effects of irradiated medium on growth characteristics of mammalian cells in tissue culture

Exposure of tissue culture cells to irradiated medium is known to induce mitotic delay, and impair growth and reproductive integrity. Studies were undertaken to elucidate the nature of radiation damage to the medium and how this damage is expressed in the effects on cells. Growth characteristics of mouse lymphoma cells (L5178Y) were used as an index of the concentration of toxic radiation products in the medium, for a range of delivered doses. The effects of various incubation times and intervals between irradiation and cell inoculation were examined. The use of radioprotectors to reduce and reverse the observed effects was studied.

The Effect of Ionizing Radiation on Genetic Transcription: Aspects of the Mechanism

Bacteria would appear to be excellent model systems for the study of the effect of ionizing radiation, such as Xor y-radiation, on living cells. In many respects this is true, but it is also true that even the processes by which bacterial cells are damaged are not understood. Thus, the model system has not contributed as much as it should. To understand individual processes in bacterial cells, Hollaender et al. (1) studied respiration, and Billen and Lichtstein (2)and Pauly et al. (3) studied the formation of induced enzyme as affected by ionizing radiation. Pollard and Vogler (4) and Pollard and Macauley (5) studied the effect of radiation on the incorporation of phosphate and sulfate, the amount of DNA, the amount of /-galactosidase, and the induction of ,/-galactosidase. The effect of a-particle bombardment on enzyme induction was studied by Frey and Pollard (6). In all these experiments the action of radiation is seemingly less than the action of radiation on the ability of the cells to divide and form colonies, and some experiments show a rather interesting time course in that the effect of radiation is not very apparent until after a delayed time; then a relatively sharp diminution in the metabolic processes takes place (5). In the light of modem molecular biology these experiments suggest that one action taking place is on genetic transcription. Recent work by Clayton and Adler (7) and by Pollard (8) has shown that there is an effect of ionizing radiation on the process of enzyme induction. In the latter experiments the half-life of messenger RNA and the rate of transcription were measured over a wide temperature range by using ionizing radiation to turn off transcription and observing the rate of cessation of enzyme synthesis. However, recent studies of the effect of ionizing radiation on the metabolic processes of bacteria have shown that there are varied and separable effects. Pollard et al. (9) have shown that there is an inhibiting effect of irradiated medium on the synthesis of DNA, RNA, and protein and on the formation of an induced enzyme. Stuy (10), Miletic et al. (11), and Pollard and Achey (12) have demonstrated the