EFFECT OF AGING ON SPONTANEOUS MICRONUCLEUS FREQUENCIES IN PERIPHERAL-BLOOD OF 9 MOUSE STRAINS - THE RESULTS OF THE 7TH COLLABORATIVE STUDYORGANIZED BY CSGMT JEMS-CENTER-DOT-MMS (VOL 338, PG 51, 1995)/

The spontaneous frequencies of micronucleated reticulocytes (MNRETS) w ere examined monthly over the life spans of animals belonging to nine mouse strains for the 7th collaborative study organized by the CSGMT/J EMS . MMS. Both sexes of the BDF1 strain and females of the A/J strain showed a statistically significant increase in mean spontaneous MNRET frequency in their last month of life, suggesting the possibility of strain-specific, age-dependent chromosomal instability. SAMP6/Tan, an accelerated senescence-prone strain, showed the same tendency, althoug h it was not statistically significant. The other strains studied, ddY , CD-1, B6C3F1, SAMR1, and MS/Ae, did not show significant age-related differences in mean of MNRET frequencies. More extensive statistical analyses are underway, and the outcomes will be reported separately.