The Journal of Cell Biology, Vol 72, 424-440, Copyright © 1977 by The Rockefeller University Press
Dibutyryl cyclic AMP treatment of 3T3 and SV40 virus-transformed 3T3 cells in aggregates. Effects on mobility and cell contact ultrastructure
H Gershman, J Drumm and JJ Rosen
The random cell movement of BALB/c 3T3 and SV40 virus-transformed BALB/c
3T3 cells within homogeneous aggregates was studied by observing the degree
of penetration of newly attached [3H]thymidine-labeled cells into the
interior of the aggregates. The 3T3 cells penetrated into 3T3 aggregates an
average of 0.89 cell diameter in 1.5 days, whereas the SV40-3T3 cells
penetrated into SV40-3T3 aggregates an average of 3.20 cell diameters in
the same time. Treatment of the aggregates with theophylline, theophylline
plus prostaglandin E1, or theophylline plus dibutyryl cyclic AMP all
decreased the penetration of the SV40-3T3 cells into SV40-3T3 aggregates
(2.36, 1.22, and 0.79 cell diameters, respectively). The same treatments
had little effect on 3T3 aggregates. The ultrastructure of 3T3 and SV40-3T3
cells in aggregates was examined by transmission electron microscopy. The
3T3 cells in aggregates were surrounded by microvilli and lamellipodia
which were in contact with neighboring cells, whereas SV40-3T3 cells were
nearly devoid of microvilli and lamellipodia and made contact at broader,
less regular surface undulations. Treatment with theophylline plus
dibutyryl cyclic AMP resulted in the appearance of microvilli on SV40-3T3
cells and also appeared to increase the area of intercellular contacts in
both 3T3 and SV40-3T3 cells. These observations were supported for the
surface cells of the aggregates by scanning electron microscopy.
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