226 



DISSOCIATION AND REAGGREGATION OF EMBRYONIC CELLS 



DISCUSSION: When embryonic cells are disassociated by trypsinization there appears to 

 form a viscous extracellular material derived from these disassociated cells, pos- 

 sibly a mucoprotein, which aids in the process of re-aggregation. This extra- 

 cellular material (ECM) may, in fact, be a variant of the ground substance which 

 binds together intact cells in tissues. Moscona says (I960) that this ECM may be 

 "elaborated in response to specific environmental situations by cells denuded of 

 their original matrix; that it provided cells with a controllable microenvironment, a 

 physiologically active intermediary zone between cells and culture medium, an op- 

 erational framework related to their native matrix yet adjusted to the particular 

 physical and metabolic conditions encountered. " 



V 



■J> -f 



k 







Fig. 1 - Smear of dissociated limb-bud cells from a 4-day chick 



embryo. 

 Fig. 2 - Aggregates of chick limb-bud cells at 24 hours obtained 



by rotation-culture of the cell suspension at 70 rpm. 

 Fig. 3 - Aggregates at 48 hours of chondrogenic cells showing 



early cartilage formation. 

 Fig. 4 - Aggregates of intermingled cells from embryonic chick 



limb-buds (4-day embryos) and mcsonephros {7-day 



embryos), showing mixture of cartilage and nephric 



tubules. 



(These available through courtesy of Dr. A. Moscona) 



