Table 1.

Quantitative electron microscopic morphometry of ventricular cardiac myocytes

Genotype	1. jSR lumen width (nm)	2. jSR contact length (nm)	3. jSR contacts per IMS	4. jSR extent (arbitrary units)
Trdn+/+	21.7 ± 6.3 (179)	227 ± 142 (108)	0.42 ± 0.20 (85)	95 ± 28
Trdn−/−	37.1 ± 15.0* (192)	139 ± 62* (82)	0.30 ± 0.22* (89)	42 ± 13*

jSR lumen width was significantly larger and more variable in Trdn^−/− cells (see also Fig. 1 C and D). jSR extent (where feet are located) was obtained by multiplying the jSR contact length (column 2) by the frequency of dyads (= jSR contacts per intermyofibrillar space (IMS), column 3). jSR extent was reduced by 56% in the Trdn^−/− myocardium. Data are mean ± SD. All data are from 3 mice. In parenthesis are the number of dyads (columns 1 and 2) and number of images (column 3). *, P < 0.001, Student's t test.