Nitrosomethylurea-Induced Lymphomas in Thymectomized Mice, in Relation to Thymus-Dependent and Independent Systems

Abstract

The present paper describes lymphomagenesis in Swiss mice given nitrosomethylurea (NMU) at birth, and thymectomized at 12 days of age. In mice, at this age, migration of T lymphocytes to other parts of the body has already taken place. On the other hand, the precocious thymectomy prevents any possible interference between thymus and the extrathymic lymphoid system in lymphomagenesis since the major target organ for NMU lymphoma induction is absent. No lymphatic tumours developed in NMU-treated thymectomized mice, although they survived for a long time after thymectomy and about twice as long as the time required for thymus lymphoma production. It can be concluded that NMU in the present experimental system induces lymphomas exclusively in the thymus, while the thymus-dependent and independent areas of the peripheral lymphatic tissues are not affected.

Morphology and pathogenesis of tumors of the thymus and stomach in sprague‐dawley rats following intragastric administration of methyl nitrosourea (MNU)

“…Among the latter, DMBA and MNU were used successfully in newborn mice (Rappaport and Baroni, 1962;Palestro and Stramignoni, 1975). Rappaport induced malignant lymphomas in Swiss mice with DMBA at an incidence of 34% in survivors over 8 weeks of age (Rappaport and Baroni, 1962).…”

“…MNU was used by Palestro and Stramignoni (1975) in random-bred Swiss mice to induce generalized lymphomas. The thymus was involved in 62 % of the animals between 1 1 and 20 weeks post partum.…”

“…In mice, thymic lymphomas have been induced experimentally with oncogenic viruses (Butler et a]., 1967), ionizing radiation (Lagerlof, 1968), and chemical carcinogens. Among the latter, DMBA and MNU were used successfully in newborn mice (Rappaport and Baroni, 1962;Palestro and Stramignoni, 1975). Rappaport induced malignant lymphomas in Swiss mice with DMBA at an incidence of 34% in survivors over 8 weeks of age (Rappaport and Baroni, 1962).…”