Enhanced recovery from growth inhibition in irradiated M04 spheroids invading into embryonic chick heart fragments in organ culture.

We have studied recovery from growth inhibition in irradiated M04 mouse fibrosarcoma spheroids using various post-irradiation culture conditions. Recovery after irradiation with 18 Gy was significantly higher in M04 spheroids confronting fragments of embryonic chick heart in suspension culture as compared to M04 spheroids confronting pieces of Gel-foam in suspension culture (p less than 0.0007) or to M04 spheroids explanted on coverslips in static culture (p less than 0.006). These observations suggest that the normal tissue might contribute to recovery from growth inhibition in irradiated M04 cell populations.