Sixteen normal young dogs were exposed to 1200 r of Co60 radiation over their entire bodies continuously at 5 to 6 r per minute. They were then given intravenous infusions of 1 to 5 billion of their own nucleated marrow cells that had been previously aspirated and stored frozen at -80 C. in dimethyl-sulphoxide.

Nine received samples stored in 10 per cent dimethyl-sulphoxide. All made prompt clinical and hematologic recoveries. Three dogs received samples stored in 5 per cent dimethyl-sulphoxide. One died. Three received samples stored in 15 per cent dimethyl-sulphoxide. Two died.

No toxicity of dimethyl-sulphoxide was recognized in these experiments. A disagreeable odor emanated from the injected animals and persisted for a number of hours.

Dimethyl-sulphoxide in 10 per cent concentration is suitable for the preservation of dog marrow at low temperature. Because the specimens preserved in it can be administered intravenously without prior dilution, this additive has an advantage over glycerol.

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