Factors influencing the nucleoprotein content of fibroblasts growing in vitro

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Abstract
The effect of various substances on the nucleoprotein phosphorus content (NPP) of fresh explants from the embryo chick heart growing in vitro in roller tubes was examined. Cultures grown in Tyrode soln. alone showed a fall in NPP. The addition of embryo extract to the cultures caused an appreciable rise in NPP and this rise was unaltered when the embryo extract had been heated to 100[degree] for 5 mins. Crystalline ribonuclease had no effect on the growth promoting properties of embryo extract, but crude ribonuclease preps. from pancreatin contained a factor which caused a marked stimulation of nucleoprotein synthesis in the presence of embryo extract. Cultures grown in embryo extract to which mucinase had been added in high conc. showed a smaller rise in NPP than control cultures grown in embryo extract without mucinase. Extracts of mammalian embryos caused an increase in NPP. Sheep embryo cartilage extract was particularly effective. Ant. pituitary extracts were without effect on the NPP of the cultures.