Growth of granulopoietic bone marrow cells of RF mice.

Mice of the RF strain are unusually susceptible to the development of leukemia, both spontaneously and after whole body irradiation. Cell culture and transplantation techniques were used to study the proliferative capacity of hematopoietic tissues of these mice. The growth characteristics of granulopoietic cells of young, non-irradiated RF mice were compared with those from a leukemia-resistant strain, C57BL/6J (B6). Marrow from RF mice showed a substantial reduction in the number of colony-forming units in culture (CFUC). The numbers of marrow cells capable of forming colonies in the spleen of lethally irradiated syngeneic mice (CFUS) were also reduced. The spleens from non-irradiated RF mice were almost twice the size of those from B6 mice. Despite these differences the numbers of circulating peripheral leukocytes and percent of polymorphonuclear leukocytes were similar in the two strains. Bone marrow from RF mice may be analogous to that of certain human "preleukemic" states in which alterations in marrow cells are demonstrable in culture.

Preparation and light-microscopic examination of fixed hematopoietic cells in soft agar.

Hematopoietic cells from the blood or bone marrow (of leukemic and nonleukemic patients) grown in vitro using soft agar tissue-culture technics may be fixed in formalin, embedded in paraffin, sectioned, and mounted on glass slides. Light microscopic examination of these sections stained with hematoxylin and eosin and with other histologic stains provides information useful in investigative and diagnostic hematology. Morphologic interpretation of the characteristics of cultured cells is within the capability of pathologists and clinical hematologists. The slides provide a permanent record of growth in vitro.

Proliferation of erythroid colonies in semi-solid agar.

Growth of human erythroid cells in soft-agar culture with no added erythropoietin was demonstrated. This growth was particularly marked in patients with diseases such as myelofibrosis (MF) in which patients had a previous history of polycythaemia vera (PV) characterized by excessive red cell production. A rapid assessment of the proportion of erythroid colonies was obtained by directly staining the culture with benzidine. Fixed and stained preparations of these agar-grown cells revealed elements in all stages of erythroid maturation. The morphology of these erythroid colonies was characteristic of 'erythroblastic islands' containing central, iron-containing macrophages, surrounded by erythrocytic precursors, with the more mature erythrocytes found at the periphery of the colony. These observations document that erythropoiesis may be maintained in agar cultures, and suggest that this technique may be of diagnostic value in disease states characterized by abnormalities of red cell production.

A study of alpha1-fetoprotein levels during exposure to 3'-methyl-4-dimethylaminoazobenzene and its analogs.

The serum concentration of alpha1-fetoprotein (alpha1F) was determined in rats following exposure to the hepatocarcinogen, 3'-methyl-4-dimethylaminoazobenzene, and its analogs. Small quantities of the carcinogen caused a rapid and significant elevation of alpha1F. Neither 2-methyl-4-dimethylaminoazobenzene nor p-aminoazobenzene resulted in any elevation of alpha1F. Further, under circumstances wherein 2-methyl-4-dimeth-laminoazobenzene is reported to become carcinogenic, i.e., when administered at the time of 70 percent hepatectomy, neither elevation of alpha1F nor histological alteration of the liver was noted. The increase in alpha1F after 3'-methyl-4-dimethylaminoazobenzene exposure is the result of a highly selective interaction. The possible contribution of hepatocyte mitosis to the elecation of alpha1F seen during chemical carcinogenesis is emphasized.