Disaggrcgatcd mouse embryo cells, grown in monolaycrs, undcrwcnt a progrcssivc dcclinc in growth ratc upon succcssivc transfer, the rapidity of the decline dcpcnding, among othcr things, on the inoculation density. Ncvcrthclcss, ncarly all culturcs dcvclopcd into cstablishcd lincs within 3 months of culture. Thc first sign of thc emcrgcncc of an established line was the ability of thc cells to maintain a constant or rising potential growth ratc. This occurred while thc cultures wcrc morphologically unchangcd. Thc growth rate continued to incrcasc until it cqualcd or cxcccdcd that of the original culturc. The carly cstablishcd cclls showed an increasing mctabolic autonomy, as indicated by dccrcasing dependence on ccll-to-ccll fccding. It is suggcstcd that the process of cstablishmcnt involvcs an altcration in ccll pcrmcability propcrtics. Chromosome studics indicatcd that thc cells rcsponsiblc for thc upturn in growth rate wcrc diploid, but latcr the population shifted to the tctraploid range, often very rapidly. Still later, marker chromosomes appcarcd. Different lines acquired diffcrcnt propcrtics, dcpcnding on thc culture conditions cmploycd; one line dcvclopcd which is cxtrcmcly scnsitivc to contact inhibition.

No abstract

The A549 tumor-cell line, initiated from a human alveolar cell carcinoma, has been continuously propagated in vitro for more than 3 years (more than 1,000 cell generations). These cells have a human karyotype and appear to have been derived from a single parent cell. All A549 cells examined by electron microscopy at both early and late passage levels contain multilamellar cytoplasmic inclusion bodies typical of those found in type II alveolar epithelial cells of the lung. At early and late passage levels, the cells synthesize lecithin with a high percentage of disaturated fatty acids utilizing the cytidine diphosphocholine pathway; such a pattern of phospholipid synthesis is expected for cells believed to be responsible for pulmonary surfactant synthesis. The A549 cell line should permit in vitro analysis of human surfactant synthesis and secretion and possibly provide a source of human surfactant for therapeutic intervention in pulmonary disease states characterized by surfactant deficiency.

Murine sarcoma virus-transformed mouse fibroblasts produce polypeptide growth factors and release them into serum-free medium. These factors stimulate cells to divide in monolayer cultures and also to form colonies that grow progressively in soft agar. Three major peaks of activity are seen, with apparent molecular weights of 25,000, 12,000, and 7000.