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Morphologic and morphometric analysis of the early effects of x-ray and heavy-ion irradiation of hamster lung.

Morphometric methods were to used to compare the early effects of graded single doses of x-rays with accelerated heavy particle (helium or neon) irradiation of hamster lung. Increased values in the volume densities of both capillary lumina and inflammatory cells at 2 weeks postirradiation were observed. Neon-ion irradiation wes statisically different from x-irradiation at all dose levels, while helium-ion irradiation showed significant increases only at higher doses (1000 to 1500 rads). At 1 month post-irradiation, the volume densities of capillary lumina after heavy particle irradiation began to return to control values, while those in x=irradiated lungs continued to be elevated. The volume density of inflammatory cells remained increased for all types of irradiation, and the highest values were obtained in neon-ion irradiated lungs. Accelerated heavy particle irradiation would therefore appear to elicit a more intense early radiation than does x-irradiation but the chronic significance of these findings is not yet known.

Animals

[Possibilities of variation in skip pendulum irradiation (author's transl)].

Irradiation techniques should be judged not by dose distribution only but also by the effort necessary for their realization. Skip pendulum irradiation is a technique excelling not only through suitable dose distribution but through effortless adjustment as well. The possibilities of variation in skip pendulum irradiation are examined, a schedule facilitates the choice of field breadth and pendulum angle. Skip pendulum irradiation should gain importance, too, for the bremsstrahlung from a linear accelerator.

Humans

Locus specificity for mutation induction in human cells exposed to accelerated heavy ions.

The relative efficiencies of two types of densely ionizing particles were compared for the induction of mutations at two distinct genetic loci in human cells. Mutations to 6-thioguanine resistance (hgprt locus) or to trifluorothymidine resistance (tk) locus were scored in TK6 human lymphoblastoid cells exposed to graded doses of 40Ar ions (470 MeV/amu, LET = 95-97 keV/microns) or 28Si ions (456 MeV/amu, 61 keV/microns). The autosomal tk locus was more efficiently mutated than the X-linked hgprt locus following heavy particle irradiations. This was predominantly due to the contribution of a class of slowly growing mutants scored at the tk locus. Silicon ions were more efficient per unit dose than argon ions for the induction of mutants at either locus. When the mutant yield for a particular ion was compared with particle fluence, similar numbers of hgprt mutants are induced by equal numbers of 40Ar or 28Si ions. Comparison of the number of tk mutants with particle fluence demonstrates an increased efficiency for 28Si ions over 40Ar. These data suggest that the LET-RBE relationship may be different for individual genetic loci in human cells.

Argon