Lifespan, age changes and tumour incidence in an ageing C57BL mouse colony.

Detailed data from a colony of C57BL mice kept for research into ageing processes are given on weights of 13 organs between the ages of 6 and 30 months; pathological findings and x-ray results from animals aged 6, 24 and 30 months; age-specific tumour incidences in 24 organs in 3-month period up to 36 months of age. Results of previously published age-related studies of reproductive capacity, dental abnormalities and brain changes are summarised.

Immunological control of polyoma virus oncogenesis in mice.

Adult CBA mice thymectomized, treated with antilymphocytic globulin (ALG) and inoculated with human leprosy organisms were accidentally infected with polyoma virus and all developed tumours. After cessation of ALG administration, some animals were given spleen cells from syngeneic donors immunized with polyoma virus; none developed tumours. Similar results were obtained in mice deliberately infected with polyoma virus but not with leprosy organisms. Passive transfer of antibody before but not after virus inoculation prevented tumour formation in immunosuppressed recipients. Virus infection in thymectomized, lethally irradiated and bone marrow reconstituted mice resulted in only a very low incidence of tumours. These results emphasize the role of immunological surveillance in preventing polyoma tumour formation under natural conditions.

The structure of tumours derived from mouse cells after "spontaneous" transformation in vitro.

The histological structure of 58 primary tumours derived from spontaneously transformed tissue culture cell lines from embryonic (14-16 days), young (3-20 days) and old (28-34 months) C3H and C57 mice is described. Although the cell lines were derived from a number of different organs the tumours were similar in morphology. The pattern was mixed, with "fibrosarcomatous", "myxoid", "epithelioid" and giant cell areas. The tumours resemble some types of haemangiopericytoma.