Some peculiarities of the sequential action of heat and ionizing radiation on yeast cells

Figures & data

Figure 1. Survival curves for diploid yeast cells of Saccharomyces cerevisiae, strain XS800. Cells were exposed to a sequential treatment with ionizing radiation (⁶⁰Co γ-ray, 2 Gy/min) and hyperthermia (50°C) and the reverse order of these agents. Different lines are labelled with the duration of heat exposure (hours).

Figure 2. The dependence of the thermal enhancement ratio on the duration of heat exposure (50°C) after the sequential action of ionizing radiation (⁶⁰Co γ-rays) and hyperthermia on diploid yeast cells.

Figure 3. Survival curves for diploid yeast cells exposed to a sequential treatment with ionizing radiation (⁶⁰Co γ-ray, 80 Gy/min) and hyperthermia (50°C) and the reverse order of these agents. Different lines are labelled with the duration of heat exposure (hours).

Figure 4. Survival curves for diploid yeast cells exposed to a sequential treatment with ionizing radiation (⁶⁰Co γ-ray, 2 Gy/min) and hyperthermia (58°C) and the reverse order of these agents. Different lines are labelled with the duration of heat exposure (minutes).

Figure 5. The dependence of the thermal enhancement ratio on the duration of heat exposure (58°C) after the sequential action of ionizing radiation (⁶⁰Co γ-rays) and hyperthermia on diploid yeast cells.

Figure 6. Survival curves for diploid yeast cells exposed to a sequential treatment with ionizing radiation (⁶⁰Co γ-ray, 80 Gy/min) and hyperthermia (58°C) and the reverse order of these agents. Different lines are labelled with the duration of heat exposure (minutes).

Table I.  The dependence of the basic model parameters (p₁, p₂) and the greatest TER after different conditions of the sequential action of ionizing radiation (γ-rays) and hyperthermia (H).

Treatment conditions			Model parameters		The greatest value of TER
Temperature, °C	Dose rate, Gy/min	Order of treatment	p1	p2	Experiment	Theory
50	2	γ-ray + H	1.9	4.5	3.0	2.9
50	2	H + γ-ray	0.8	2.8	1.7	1.8
50	80	γ-ray + H	1.9	4.5	3.0	2.9
50	80	H + γ-ray	0.8	2.8	1.7	1.8
58	2	γ-ray + H	0.5	0.8	1.5	1.5
58	2	H + γ-ray	0.5	0.8	1.5	1.5
58	80	γ-ray + H	0.8	0.8	1.9	1.8
58	80	H + γ-ray	0.8	1.8	1.9	1.8