Mouse mammary gland has a finite life span when serially transplanted in isogenic female
hosts, using declining rate of ductal growth as an indicator of aging. In the experiments
reported here, young and old hosts were transplanted with mammary tissues from young
and old donors, and the transplants were propagated serially until they were lost due to
diminished capacity for growth. Mammary tissue derived from both young and old donors
behaved similarly when propagated in young hosts, and no consistent effect of donor age …