A stereological method for estimating volume and surface of sarcoplasmic reticulum

The stereological analysis of volume and surface of sarcoplasmic reticulum tubules in muscle cells meets with particular problems because these structures are (a) highly oriented in the longitudinal direction of the muscle cells, (b) lined up in parallel, (c) periodically arranged in relation to sarcomeres and (d) internally symmetrical in analogy to sarcomere symmetry. On the whole this system may be characterized as a parallel linear array of units with translational‐reflexive symmetry. On the basis of a simple model it is demonstrated that the problems of sampling and stereological measurement can be overcome if a combination of oblique and transverse sections are used. The procedure can be simplified to operate exclusively with oblique sections only slightly inclined to the transverse plane if a small systematic error can be accepted.