USE OF COMPUTER-ASSISTED ANALYSIS FOR MYOFIBER SIRE MEASUREMENTS OF RAT SOLEUS MUSCLES FROM PHOTOGRAPHED IMAGES

Since myofiber cross-sectional area measurements are important in desc ribing myofiber adaptations to physiological and pathological changes, we developed a reproducible method for measuring myofiber size using fluorescent stains. Several 35-mm slides of dystrophin-, laminin-, and concanavalin A (ConA)-stained muscle sections were used to calculate myofiber cross-sectional areas and to compare different techniques and settings of an image capture system. Although variation in equipment settings did result in variation in myofiber area, the overall effect was of little practical significance (<6%). Using midrange values for the settings of illumination, black level, and gain, reproducible quan titative data were collected and analyzed from 35-mm slides of FITC-la beled conA taken from atrophic, normal, and hypertrophic muscle sample s. As expected, the atrophic muscle fibers were smaller. However, in h ypertrophic muscle from compensatory overload, the fibers were compose d of both large and small fibers. We found it important that the myofi ber cross-sectional area measurements be expressed both in terms of av erage fiber areas and as frequency distribution histograms. In additio n, detailed methodology of fiber area measurement must be provided.