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Effects of Fractionated Doses of X-radiation on Normal and Tumor Tissue^*

L. C. Fogg and R. F. Cowing

( Department of Public Health, Pondville Hospital, Walpole, Mass.)

Fractionated doses of 294 r produce a greater effect on spermatogonia and spermatocytes in partially shielded mice than does an equivalent acute dose.

After irradiation has caused depopulation of the tubules of spermatogonia, subsequent recovery is from capsular cells, called prespermatogonia.

The prespermatogonia are more resistant to radiation than are spermatogonia.

Oocytes and spermatocytes are relatively comparable in their response to doses of irradiation.

As compared to the testis, recovery following depopulation of germinal cells in the ovary is greatly delayed.

The fractionated dose required to depopulate the testis or ovary of germinal cells is not sufficient to cause destruction of all tumor cells in the tumors studied, namely, spontaneous mammary adenocarcinoma in C3H mice and the transplantable S 180 in the C57BL mice.

Apparently, induced resistance has not been achieved by repeated doses of irradiation under the conditions of our procedure.

^* This work was supported by Grant C-1478 from the U.S. Public Health Service and by the Department of Public Health, Pondville, Hospital.

Chief of Research Laboratory, Pondville Hospital; Instructor in Pathology, Harvard University.

Radiological physicist.

Received 10/ 6/52.