In their recent article, Takahashi et al. (1) suggest that heatinduced DNA double strand breaks contribute to heat-induced cell killing because heat treatment induces histone gH2AX-containing foci. Such foci have been associated with double strand breaks induced by ionizing radiation, other agents, and other stresses (2). However, the authors disregard the hyperthermia biology literature, which...

We have observed the enzymatic production of deoxyribonucleic acid (DNA) doublestrand breaks in Escherichia coli K12 after ultraviolet irradiation. Doublestrand breaks appeared in wild-type, polA1, recB21, recA, and exrA strains after incubation in minimal medium. THE UVRA6 strain showed no evidence of double-strand breakage under the same conditions. Our data suggest that uvr+ cells, which are...

Alkaline and neutral elution techniques were used to charac terize the production of singleand double-strand DMA breaks in human diploid fibroblasts by incorporated radionuclides. 125I was incorporated in DMA as [125l]iododeoxyuridine, 3H as [3H]thymidine, and 14C as [14C]thymidine. Under frozen conditions, 125Iwas 3 times as efficient as 3H per decay in inducing singlestrand breaks and 6 times...