The solubility at 25 °C. of the sparingly soluble basic copper carbonate malachite has been determined by two methods. The constancy of the calculated value of the solubility product in solutions of varying ionic strength has shown it to be a comparatively well-defined material suitable for the study of the complexing ability of various organic chelating compounds. Evidence is presented for the existence of a cupric ion – carbonate ion complex under appropriate pH conditions.

The uptake of Crsl-chromate by thymocytes in suspension can be used as a sensitive quantitative criterion for the evaluation of early radiation damage to these cells, often under situations where other methods of assessing cell death such as morphological changes do not yield valid results. 'I'he development of a radiation lesion is characterized by a reduction in the uptake of Cr5l, which in vitro can be detected 1 hour following irradiation and with doses as low as 25 rads. By means of this technique thymocytes have been shown to be completely protected by anoxia to doses of up to 150 rads, but a t higher levels anoxia affords little protection. No protection of thymocytes could be demonstrated in vivo with S,P-aminoethylisothiouronium bromide hydrobromide (AET) or serotonin a t 0.72 mmoles per kg. L-Cysteine, cysteamine, and serotonin a t 1 m M concentration in vitro showed no protection of thymocytes provided they were removed from the cells iminediately subsequent to irradiation.

A number of thiol and disulfide compounds have been tested for their ability to inhibit the oxidation of α-ketoglutarate by rat-liver homogenates. In general, a correlation exists between the degree of inhibition and the radioprotective ability of the compound. It is possible that a better correlation exists for the corresponding disulfides.The inhibition involves oxidation of the thiol, and the disulfides were found to be more potent inhibitors than the thiols.There is no change in the ATP level of normal tissues after the administration of aminoethylisothiouronium bromide hydrobromide in vivo, and the protective ability of this compound is not considered to be related to any interference with mitochondrial oxidative phosphorylation. Mitochondrial respiration is, however, inhibited. The results support the mixed disulfide protection theory of Eldjarn and Pihl, and provide a physiologically significant test system for this hypothesis.

No abstract

The pyridine nucleotides of thymocytes have been examined following irradiation of the cells in vivo or in vitro. NAD was found to constitute about 95% of the total oxidized pyridine nucleotides in thymocytes while the level of NADH2 was found to be very low. There is a rapid loss of NAD from thymocytes following irradiation in vitro or in vivo which is evident with as little as 25 rads. There is no concomitant rise in the NADH2 levels following irradiation. The loss of NAD occurs principally from the nucleus of the cell and is characterized by an intracellular release of NADase from the mitochondria and nucleus into the cytoplasm. Following irradiation there is a reduced capacity for thymocytes to synthesize NAD from 7-C14-nicotinamide either in vitro or in vivo. The administration or presence of nicotinamide produces an unphysiological increase in the level of NAD in whole thymus or thymocytes in suspension. The level of NAD in treated cells is higher than in untreated controls following irradiation. This effect is not produced by nicotinic acid, cysteamine, L-cysteine, or promethazine. The administration of nicotinamide does not prevent the development of pyknotic degeneration in irradiated thymocytes. There is no change in the RNA content of the thymus under the conditions which reduce the NAD content.