Factors From Mouse Tissues Stimulating Colony Growth of Mouse Bone Marrow Cells in Vitro

Summary When tested either by use as “organ culture feeder layers” or alternatively, by extraction prior to plating, several mouse tissues have been demonstrated to contain activity which stimulated colony development of mouse bone marrow cells in vitro By the “feeder layer” technique adrenal, tail tendon, bladder, heart, skeletal muscle, uterus and lung tissues consistently showed activity. By the extraction technique skeletal muscle, thymus, lung, spleen and kidney tissue from 12–14 day old mice and heart, thymus, brain, gut, spleen and lung tissue from 3–4 month old mice were active. Activity was also extracted from whole embryo, placenta, foetal membrane and pregnant uterus tissue, the last three tissues showing approximately 10–50 times more activity than other tissues on a wet weight of tissue per volume of extract basis. The active factor in an extract of pooled placenta, membrane and pregnant uterus tissues migrated in the β to α 2 ‐globulin region on starch‐Geon block clectrophoresis. had an apparent sedimentation coefficient (S 20,w ) of 3·8 S and was partially purified by batch chromatography on calcium phosphate gel.