X-irradiation of equine peripheral blood lymphocytes stimulated with phytohaemagglutinin in vitro

Non-effectivity of roentgen irradiation in an in vivo rapidly growing murine lymphosarcoma

The survival time of mice bearing a rapidly growing murine lymphosarcoma (cell doubling time 9.6 h) is hardly influenced by roentgen irradiation with fractions of 2 Gy, not even if delivered according to superfractionated schedules. Growth kinetic measurements reveal an almost complete mitotic block 6 h after exposure, followed by a large overshoot in cell proliferative activity. The dose-response curve for in vivo irradiated cells has a D0 of 1.9 and lacks a shoulder. Hence, repair of sublethal damage must be of restricted significance. The extremely strong proliferative capability appears to lead to rapid repopulation of the tumour. Typically, surviving cells show a high content of RNA and protein.

Low dose X-irradiation of thymus filler cells in limiting dilution cultures of LPS-reactive B cells reduces the background Ig-secreting cells without affecting growth-supporting capacity

Frequencies of lipopolysaccharide (LPS)-reactive B cells in the mouse can be determined in the limiting dilution culture system developed by Andersson et al. (1976, 1977a) which is completely dependent upon the presence of thymus filler cells, usually of rat origin. The assessment of B cell clones of mouse origin, however, can be hampered by the occurrence of varying numbers of thymus-derived immunoglobulin (Ig)-secreting cells. The number of these background Ig-secreting cells can be significantly reduced by low dose (110 mgray = 11 rad) X-irradiation of the rat thymus filler cells, without affecting their growth-supporting capacity.