Causes of the Discontinuity of Growth of Fibroblasts Cultivated in Embryo-Juice

Abstract

Fibroblasts that are cultivated according to the flask-technic in a plasma-coagulum with embryo-juice as nutrient fluid do not proliferate continuously. Generally after 2 or 2 1/2 weeks'cultivation the cells stop multiplying, although only a small portion of the coagulum is covered with tissue. If a part of the tissue is transferred to a new coagulum, growth is resumed. If it is not so transferred the cells degenerate. Investigators who have attempted to find the cause for this cessation of growth and subsequent degeneration of the cells have attributed it either to changes that take place in the physical structure of the plasma-coagulum, or to the accumulation of toxic products therein. 1 The experiments reported here were designed to test another hypothesis, namely, that it might be the removal of serum from the coagulum that is responsible for the cessation of growth. Or, to express it in another way, it might be an inadequacy in the food supplied.

In the first experiment 2 fragments of tissue from a 23-year-old∗ strain of chick-heart fibroblasts were embedded in a flask 3 1/2 cm in diameter in a coagulum containing 33% plasma. They were then cultivated for 9 days in 33% embryo-juice.† By this time their initially rapid growth had already decreased to a noticeable degree. Two drops of chicken-serum were then given every 48 hours in addition to the embryo-juice that had previously been supplied. The cultures immediately resumed active growth. But, after 9 more days of cultivation their growth-rate diminished again. The concentration of embryo-juice was then increased to 66%, and serum was given as before. Again, active growth was resumed. This time it continued until the edge of the colony reached the vertical side of the flask.