CHEMICAL AND MORPHOLOGICAL CHARACTERISTICS OF CELLS CULTIVATED IN CHEMICALLY DEFINED MEDIUM COMPARED TO CULTURES SUPPLEMENTED WITH HORSE OR FETAL-CALF SERA1 ' 2

Cultures (NCTC-designated) of kidney cells of Cercopithecus aethiops were grown in a chemically defined medium (NCTC-135) and were then examined morphologically and cytochemically. Comparisons were made with cultures of the same cell line in medium supplemented with either 10 % fetal-calf or 10 % horse sera. The epitheloid cells of the serum-free cultures demonstrated only a slight difference in enzymatic activity when compared to the cultures supplemented by 10 % fetal-calf and 10 % horse sera. The use of a particular serum supplement in combination with a chemically defined medium did not appear to determine if a cell culture would be reactive or nonreactive to alkaline or acid phosphatase. Results indicated also that alkaline-phosphatase activity was altered very little by freezing of the cells prior to testing. Variability of alkaline-phosphatase was interpreted as a result of a combination of environmental factors and "age " in vitro. The strong activity of acid phosphatase, noted both in the serum-free culture (NCTC-4952) and in the culture (NCTC-6314) supplemented by 10 % fetal-calf serum, was regarded as reflection of the number of culture passages in vitro and the constitutive nature of the enzyme