• Korean Journal of Veterinary Research
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• v.33 no.2
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• pp.285-287
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• 1993

Toxoplasma gondii frozen by the method of very slow cooling ($-30^{\circ}C/3hrs.{\rightarrow}\;-60^{\circ}C/lhr.{\rightarrow}\;-196^{\circ}C$ of liquid nitrogen)were inoculated mice after storage in the liquid nitrogen for 5 years. The results obtained were as follows; 1. Toxoplasma gondii was detected in mice 4~5th day after intraperitoneal inoculation of organisms stored in the liquid nitrogen once a year for 5 years. 2. Toxoplasma gondii could be preserved longer than 5 years in liquid nitorgen being evidenced by the in vivo test.