Studies on Leukemia in The C58 Strain of Mice Part 1. Hematological and histological studies of normal mice, spontaneous and transplanted leukemia mice

Hematological and cytological studies, including peripheral blood counting, blood picture, myelogram, impressed preparation of spleen and lymph node, and phase contrast microscopic and electron microscopic observations of leukemic cells were performed on the high leukemic strain C58 mice. In the present observation, 61.4% of C58 mice developed leukemia spontaneously after the latent periods varing from 4 to 19 months. In non-leukemic mice, blood counting, peripheral-blood picture and myelogram did not show any significant change throughout the each age groups, but lymphocyt/neutrophile ratio decreased gradually after the age of 6 month. Old mice above 12 months of age showed a slight hypochromic anemia and relative neutrophilia. Most of the spontaneous leukemia occurred after the age of 6 month and 61.4% of them occurred between the age of 12 and 16 month. All of the spontaneous leukemias observed in this strain were lymphatic type. White cell count ranged from 4,500 to 225,000, averaging 109,600 with 47.2% lymphoblasts in average. Marked anemia and thrombocytopenia were present. Myelograms showed slight or moderate lymphoblastic infiltrations, but impressed preparation of spleen and lymph node always contained lymphoblasts over 90%. Morphological characteristics of the lymphoblast observed in spontaneous leukemia were narrow basophilic cytoplasm, large nucleus with a few deep indentations, coarse chromatin net work and nucleoles of vague chromatin borders. Phase contrast microscopy of lymphoblast showed nucleal indentations clearly and bright cytoplasm with a few rod-shaped mitocondrias in the Golgi area. Electron microscopic observations of lymphoblast also revealed the characteristic indentations of the nucleus. Spontaneous leukemia could be transplanted easely to the adult C58 mice by cell graft. A transplanted line named OHS-LL, No 1 is being maintained serially up to present. Serially transplanted leukemia mice often showed remarkable myeloid reaction and died after 7-8 days after cell graft. Blastic cells became to show atypical form suggesting of much more primitive and malignant character than that of the original leukemia by serial transplantations. Electron microscopic observations of lymph node and spleen of spontaneous leukemia revealed the presence of numerous virus particles located extracellularly. These particles were morphlolgically identical with the C particle observed in various other leukemic mice.