Abstract: A device for analyzing biological samples comprises first, second, third, and fourth layers. The first layer comprises a sample chamber in which a sample is positioned. The second layer comprises first, second, and third channels. A third, porous layer is positioned between the first layer and the second layer. A fourth layer composed of a substantially liquid-impermeable material is positioned between the second layer and the third layer. The fourth layer includes first and second pass-through channels that are aligned with the first and second channel, respectively. Fluids that flow in the first and second channels pass through the pass-through channels and diffuse into the sample chamber, establishing a chemical concentration gradient therein. A gas in the sample chamber can diffuse through the third and fourth layers and interact with a fluid flowing in the third channel, establishing a gas concentration gradient in the sample chamber.

Abstract: Human cell lines have been obtained which elaborate colony stimulating activity (CSA) for marrow cells, i.e., which enable cells to be grown in vitro for use in bioassay methods in diagnostics and therapy. One cell line, GCT, was obtained from a lung metastasis of a fibrous histiocytoma and another, RC4 from a monocyte enriched fraction of normal blood. These cell lines provide a continuous source of large quantities of conditioned medium from purification of CSA and is more potent in stimulating human narrow growth in vitro than conditioned mediums heretofore available, i.e., human embryo kidney cell or human leukocyte feeder layers, having finite life spans in culture.