TABLE III.

Distribution of Cell in C2 Cultures Doubly Stained with Antibodies Against Myogenin and MEF2A

		Averaged Per Ten Fieldsa
Days in 2% FCS	Growth Factor Added	Total Number of Cells	MyoD+ Cells	Myogenin/MEF2A			Myosin+ Cells
				Myogenin+ Cells	MEF2A+ Cells	Myog+/MRF2A+ Cells
1	None	177.4 ± 4	18.2 ± 0.7	4	0	0	-
	PDGF	201 ± 19	6.7 ± 0.7	0	0	0	-
	FGF	253 ± 14	6 ± 1	0	0	0	-
2	None	410.5 ± 20.5	25.5 ± 10.5	14.2 ± 7.7	0b	0	-
	PDGF	433 ± 67	44.2 ± 15.7	21.2 ± 3.2	2.5 ± 0.5	2.5 ± 1.5	-
	FGF	643 ± 3	56 ± 6	10.5 ± 2.5	4.2 ± 2.2	2.5 ± 1.5	-
3	None	730 ± 47	110.5 ± 11.5(15.1%)c	111.7 ± 6.7(15.3%)c	63.3 ± 4.8(8.9%)c	60.2 ± 4.7(53.9%)d	28.2 ± 7.7
	PDGF	1342 ± 111	168 ± 12(10.4%)	116 ± 3.2(8.7%)	62.3 ± 2.3(4.4%)	62.0 ± 2.5(53.4%)	50.5 ± 7.5
	FGF	1868 ± 232	195 ± 41(12.5%)	164 ± 16.5(8.6%)	81.8 ± 1.3(4.5%)	81.2 ± 1.7(49.5%)	32.5 ± 3

^aCultures were initiated at 4.8 × 10⁴ cells per plate in proliferation medium and 24 hours later the medium was replaced with the 2% FCS medium ( ± growth factors). Only infrequent cells fused into myotubes by day 3 (total of 0–5 nuclei within myotubes per ten fields). Total cell numbers and the numbers of MyoD+ cells were examined using the same plates; ten fields per plate were analyzed for day 3 plates; more fields were analyzed for day 1 and day 2 plates so that minimum of 500 cells were counted. The analysis of myogenin ± /MEF2A ± cells or of myosin+ cells was done by scoring twenty fields per plate for all time points (day 2 results for the analysis of myogenin ± /MEF2A ± were further confirmed by scoring 100 myogenin+ cells). All results shown were eventually averaged per ten fields per plate using duplicate plates.

^bAnalyzing 100 myogenin+ cells we found infrequent myogenin+/MEF2A+ cells as in the growth factor-treated cultures.

^cNumbers in parentheses show the percent cells with the specific phenotype out of total cells.

^dNumbers in parentheses show the percent of Myog+/MFF2A+ cells out of all myogenin+ cells.