Reversible ultrastructural changes in human fibroblasts grown in hepes buffered MCDB-104 supplemented with human serum.

Prolonged maintenance of human dermal fibroblasts in MCDB-104 medium supplemented with pooled human serum or platelet factor deficient preparations of human serum led to appearance of a large number of membrane bound inclusions, resembling lysosomes, and proliferation of small, Golgi associated vesicles. These inclusions did not appear if the cells were grown in Dulbecco-Vogt's modification of Eagle's minimal essential medium or in minimal essential medium supplemented with the same human serum fractions. Cells that acquired inclusions during a 10 d incubation in MCDB-104 subsequently lost these inclusions when transferred to Dulbecco'Vogt's medium for 4 d. Similar reversal of effects of MCDB-104 was also produced by MCDB-104 buffered with bicarbonate instead of HEPES.