. 2001 Dec 1;118(6):653–678. doi: 10.1085/jgp.118.6.653

Table 1.

Spark Frequencies in R. pipiens (Continued)

1	2	3	4	5	6
Fiber No.	Ringer [K⁺]	Time	F′/F	No. of sparks	Frequency
	mM	min			sarcomere⁻¹ s⁻¹
z072600a	2.5	11		6	0.024
	13	19	1.30	379	0.662
	2.5	9		1	0.055 (2.29)
z072600b	2.5	9		23	0.104
	13	39	1.43	947	1.012
	2.5	10		63	0.215 (2.07)
z073100a^a	2.5	14		41	0.121
	13	56	1.37	477	1.021
	2.5	12		75	0.252 (2.08)
z080200a^a	2.5	9		1	0.003
	13	60	1.30	510	0.556
	2.5	18		23	0.069 (23.0)
z080800a	2.5	9		0	0.000
	13	27	1.29	178	0.403
	2.5	37		0	0.000
z080800b^a	2.5	10		3	0.010
	13	36	1.26	52	0.168
	2.5	14		22	0.061 (6.10)
z081800b^b	2.5	18		35	0.096
	13	44	1.23	262	0.510
	2.5	9		22	0.085 (0.88)
z082300a^b	2.5	10		6	0.023
	13	68	1.38	339	0.423
	2.5	17		75	0.162 (7.04)
z082300b	2.5	8		1	0.004
	13	32	1.08	8	0.030
z082800a^b	2.5	8		17	0.062
	13	41	1.34	492	0.893
	2.5	9		6	0.034 (0.55)
z082800b^b	2.5	7		9	0.038
	13	58	1.68	1,057	1.545
	2.5	11		31	0.086 (2.26)
z083000a	2.5	9		3	0.009
	13	13	1.64	293	0.711
z083000b	2.5	10		21	0.066
	13	11	1.26	286	0.804
z090700a	2.5	13		36	0.091
z090700b	2.5	10		34	0.109
	13	11	1.25	243	0.679
Mean ± SEM	2.5 (N = 15)	20.1 ± 2.6		37 ± 9	0.069 ± 0.014
	13 (N = 14)	36.8 ± 5.1	1.34 ± 0.04	395 ± 80	0.673 ± 0.102

Column 1 gives the fiber identification; column 2, the value of [K⁺]; column 3, the time in each [K⁺] solution; column 4, the ratio of resting fluorescence in elevated [K⁺] Ringer's (F′) to that in 2.5 mM [K⁺] Ringer's (F); column 5, the number of sparks detected in each solution; column 6, the spark frequency (equal to the number of sparks detected in each solution divided by the product of the number of sarcomeres studied times the total recording time for the images in that solution). For fibers that had measurements at early and late times in Normal Ringer's, the number in parentheses in column 6 gives the ratio of spark frequencies for the late and early exposures. Where possible, the value in column 4 was obtained from the average of two F′/F values: that estimated for the change from Normal Ringer's to elevated [K⁺] Ringer's and that for the change back to Normal Ringer's. For the calculation of the mean ± SEM values in the bottom row, a mean value for each solution (2.5 and 13 mM [K⁺] Ringer's) was first obtained for each experiment and these values were then averaged. Fiber numbers marked with superscript b and a denote experiments that contributed to the measurements summarized in Table and Table , respectively. Sarcomere length, 3.00 ± 0.06 μm.