At the proximal part of mouse chromosome 17 there are three well-defined genes affecting the axis of the embryo and consequently tail length: Brachyury, Brachyury the second, and the t-complex tail interaction (T1, T2, and tct). The existence of T1 and tct in fact defines the classical ''t-complex'' that occupies 40 cM of mouse chromosome 17. Their relationship to each other and various unlinked interacting genes has been enigmatic. The tint gene was the first of the latter to be identified. We report here its genetic mapping using a microsatellite scan together with outcrosses to Mus spretus and M. castaneous followed by a subsequent testcross to T, T1, and T2 mutants. Surprisingly, tint interacts with T2 but not with T1. The implications of our data suggest that T2 may be part of the T1 regulatory region through direct or indirect participation of tint.
Spores of Bacillus megaterium and the bacteriophage T7 were sensitized to X-rays by NaBr in N2 purged systems up to the 0 2 level of sensitivity. This sensitivity is due to the action of -Br,-formed by reaction of '0H with Br -.Many additives, representing biologically significant compounds or portions of their structure were tested for their effect on the NaBr-induced sensitization . Proposals are made from these results as to the mechanisms of sensitization by NaBr, as well as reactivities of various additives with 'Br2 .
A rhodium compound, Rh(NH3)3Cl3, does not sensitize the spores of Bacillus megaterium to X-rays. However, it is a very effective sensitizer of vegetative cells of Staphylococcus aureus, raising the sensitivity four times in O2 and over 100 times in anoxia. The inhibition by oxygen of the sensitizing action of Rh(III), which operates over a wide range of [O2], is noteworthy. These experiments were performed in saline-phosphate buffer using 50 kVp X-rays. The results are discussed in terms of the known radiation chemistry of this compound.
The radiation sensitivity of spores of Bacillus megaterium is markedly increased by transplatin in both N2 and O2, and in a manner suggesting the involvement of hydroxyl radicals in both instances, thus differing mechanistically from its isomer cisplatin.
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