SPECTRAL-ANALYSIS OF MUSCLE-FIBER IMAGES AS A MEANS OF ASSESSING SARCOMERE HETEROGENEITY

A new image-analysis-based method is described for assessing sarcomere heterogeneity in skinned rabbit psoas muscle fiber segments. This met hod consists of off-line, two-dimensional Fourier spectral analysis of video-taped muscle images. Local sarcomere length is assessed by part itioning the muscle images into half and quarter images spanning the o riginal image and analyzing the associated spectra. The spectra are an alyzed in two different ways, yielding two measures of sarcomere lengt h. The first measure is obtained by calculating and inverting the cent roid frequency of the first-order peak associated with each two-dimens ional Fourier spectrum. The second measure is obtained in a similar ma nner, the only difference being that the two-dimensional spectra are f irst collapsed into one-dimensional line spectra by summing the pixels perpendicular to the fiber axis. Comparison of the two measures provi des a measure of striation skewness that cannot be obtained by other i mage analysis based methods that determine sarcomere length by analyzi ng selected line luminance profiles.