RNA chains terminated prematurely on T2 DNA carrying ultraviolet lesion function as primer for the polymerization of ribonucleoside diphosphates by polynucleotide phosphorylase.

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The changes in the frequency of peripheral lymphocytes with chromosome aberrations were observed during or after irradiation of rabbits exposed to fractionated or single whole-body irradiations. In rabbits given daily fractionated whole-body irradiations the incidence of the aberrations showed a linear increase in the first week ; however, the incidence decreased thereafter though exposures were repeated. The lymphocyte count tended to decrease as the number of irradiations increased.
In rabbits exposed to a single dose of 250 R or 500 R the incidence of aberrations rapidly decreased over a period of 10 days following irradiation, and then showed a little change thereafter. The lymphocyte count in the peripheral blood reached a nadir 2-5 days after irradiation, and then started to increase gradually.
It was speculated that there are two types of lymphocytes, long-lived and short-lived, in the peripheral blood of rabbits, both of which are PHA-committed.

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The effect of whole body irradiation on antibody response to sheep erythrocytes was investigated in C57BL/6 mice.
1) The degree of reduction in antibody production observed shortly after irradiation increased with the increase in X-ray dose. Recovery from the damage of immunocompetent cells was not complete even one month after irradiation. 2) Some mice exposed to 300 R or more could not produce antibodies immediately after irradiation. Inability to produce antibodies in these mice may largely be attributable to the damage of B cells, since anti-2, 4, 6-trinitrophenyl (TNP) antibody was produced in all thymectomized mice, when they were irradiated with 300 R or more and immunized two months after irradiation. 3) Antibody production ceased in thymectomized mice sooner than non-thymectomized mice irrespective of radiation dose. 4) Neither nonthymectomized nor thymectomized mice could produce IgG antibodies after irradiation of 40O R or more. These irradiated mice, however, produced IgG antibody, when 1×10⁶ activated T cells were transferred together with sheep erythrocytes. These results indicate the inability to produce IgG antibody may be attributable to lack of T cells participating as helper cells in IgG antibody production.

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Radiation-induced chromosome aberrations were found to persist in cultured peripheral blood lymphocytes derived from Hiroshima and Nagasaki A-bomb survivors long after their radiation exposure. Earlier observations that the frequency of cells with chromosome aberrations increased in proportion with increasing dose in both cities were confirmed. However, in every dose group, the frequency of aberrant cells was consistently higher in Hiroshima than in Nagasaki. It is suggested that a higher neutron dose in Hiroshima than in Nagasaki may be a major component contributing to the difference in dose response between the two cities.
Among the types of chromosome aberrations so far identified, reciprocal translocations were observed to predominate, and they played an important role in determining the dose-aberration relationship.

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In this paper the structural and functional changes of gamma irradiated bovine hemoglobin are presented. Aqueous solutions/1%/of HbO₂ were irradiated in air with doses ranging from 1 to 4 Mrad. Isoelectric focusing indicated change of the charge of irradiated hemoglobin. The isoelectric point of hemoglobin was displaced towards more acid values with increasing doses, up from 1 Mrad. Fingerprint analysis and peptide column chromatography of irradiated hemoglobin demonstrated disturbances increasing with the dose. These changes were confirmed by amino acid analysis which showed that Cys, Met, Trp, His, Pro and Tyr residues were destroyed or modified following irradiation. At doses exceeding 1 Mrad the irradiated solutions of hemoglobin showed a decrease of heme-heme interaction and an increase of affinity for oxygen. Differences observed in oxygen-dissociation curves seem to be correlated with the radiation induced destruction of amino acid residues which are responsible for the functional properties of hemoglobin.

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Tritiated water was administered intraperitoneally at the dose rate of about 20 μCi/ml of body water to different six age groups of Swiss albino mice, ranging from 1 to 6 weeks old. They were autopsied at 48 hours post-injection. The liver of 5 weeks old mice is found most vulnerable and that of 4 weeks second but lesser than 5 weeks. Histopathologically, 1, 2, 3 and 6 weeks old mice liver showed lesser degree of damage. The distinct histopathological lesions include oedema, cytoplasmic vacuolation and degranulation, hyperaemia, increase number of Kupffer's cells etc.

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The 34×34 response matrix whose energy divisions were chosen as 0.02 MeV betwee 0 and 0.1 MeV and chosen as 0.1 MeV between 0.1 and 3 MeV was constructed, and pulse-height distributions obtained by 3"^φ spherical NaI (T1) scintillation spectrometer were unfolded by a response matrix method into true photon energy spectra. The derived spectra were discussed precisely in the energy region from 0 to 3 MeV. Exposure rates were calculated from the spectra, and these values were compared with those measured with an ionization chamber to make sure the total number of incident photons on the detector.

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Radiopathological study was undertaken on the mucosal layer of esophagus in mice after administration of P-32. Young adult mice were administered with P-32 at the dose rate 5 μCi/g body weight and autopsied at different intervals. An elevation of the mucosal epithelium is noted upto 15 day followed by a decline at 30 day. The number of pyknotic and necrotic cells increas markedly upto day 7 and it reaches to an extremely high levels at 15 and 30 days post-injection.

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