Table I.

The Density of Gap Junctions in Control and FGF4-treated Mesenchyme Cultures

						Anterior mesenchyme: gap junctions per 3,600 μm2 ± SEM N experiments (n) fields						Posterior mesenchyme: gap junctions per 3,600 μm2 ± SEM N experiments (n) fields
		Plating density		Cx		No FGF4		With FGF4		P		No FGF4		With FGF4		P
		cells/10 μl
Chick		4 × 104				169 ± 21		155 ± 18 (a)		>0.5		164 ± 28		382 ± 53		<0.001
				43		3 (30)		3(30)				3 (26)		3 (26)
						264 ± 24						200 ± 20				<0.02
						5 (46)						5 (42)
		2 × 104		43								14 ± 1.1		31 ± 3		<0.007
												2 (30)		2 (30)
		1 × 104		43								18.5 ± 1.4		28.9 ± 2.3		< 0.01
												3 (40)		3 (40)
Mouse		4 × 104		43		378 ± 83		369 ± 82		>0.6		209 ± 22		418 ± 50		<0.001
						3 (43)		3 (43)				6 (90)		6 (80)
				43		248 ± 16						213 ± 10				>0.1
						2 (22)						2 (22)
				32		111 ± 17		121 ± 17		>0.8		76 ± 7		164 ± 19		<0.001
						4 (43)		4 (43)				5 (28)		5 (28)
				32		47.6 ± 4						83.6 ± 5				<0.001
						4 (42)						4 (42)

Results from all experiments, grouped appropriately. Data taken from single optical sections through the monolayer region of the cultures. One experiment comparing chick control and FGF4-treated anterior mesenchyme was counted as a projection and has been omitted; there was no difference (P > 0.6) between untreated and FGF4-treated cultures. The average number of gap junctions between cells at very low density (1 × 10⁴) cells/10 μl) is probably overestimated because gap junctions were patchy and counts were made over regions where gap junctions could clearly be identified.