Effects of source distribution, dose, and linear energy transfer capacity on inactivation and mutation of mycobacteria after 2H, 35S, and 32P incorporation

Using a selected model, the paper makes a contribution to the question whether the energy dose as a macroscopically-physically defined quantity can be usefully applied in cell ranges with linear dimensions of the order of 1 μm, i.e. whether there is still a correlation between the energy dose and quantitatively measurable biological radiation effects. The problem is investigated with the aid of the intracellular β decay of the 3H, 35S, and 32P nuclei on mycobacteria (BCG) in liquid media. Quantitative findings of radiobiological experiments are linked with model dose calculations to form dose-effect curves. The experimental principle consists in adding radioactively labelled compounds to the nutrient solution of bacteria at normal growth temperatures, thus obtaining an intracellular β source region caused by their uptake. The uptake conditions for the three radionuclides are varied by using different chemical bonds (2H) or carrier concentrations (3H, 35S). As biological reactions, inactivation in the form of growth inhibition and mutagenic induction of resistance to isonicotinic acid hydrazide are recorded. (orig./MG)