title: Scanning transmission electron microscope studies of deep-frozen unfixed muscle correlated with spatial localization of intracellular elements by fluorescent x-ray analysis.
abstract: Thin sections of deep-frozen unfixed muscle were studied in a scanning electron microscope modified for transmission imaging and equipped with a "cryostage" for vacuum compatibility of hydrated tissue. With an energy-dispersive x-ray analysis system, intracellular atomic species in the scan beam path were identified by their fluorescent x-rays and spatially localized in correlation with the electron optical image of the microstructure. Marked differences are noted between the ultrastructure of deep-frozen hydrated muscle and that of fixed dehydrated muscle. In frozen muscle, myofibrils appear to be composed of previously undescribed longitudinal structures between 400-1000 A wide ("macromyofilaments"). The usual myofilaments, mitochondria, and sarcoplasmic reticulum were not seen unless the tissue was "fixed" before examination. Fluorescent x-ray analysis of the spatial location of constituent elements clearly identified all elements heavier than Na. Intracellular Cl was relatively higher than expected.
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D005453:Fluorescence; D005615:Freezing; D006651:Histocytochemistry; D006652:Histological Techniques; D008855:Microscopy, Electron, Scanning; D008931:Mitochondria, Muscle; D009132:Muscles / Q000032:analysis / Q000166:cytology*; D009210:Myofibrils; D010758:Phosphorus / Q000032:analysis; D011188:Potassium / Q000032:analysis; D011817:Rabbits; D011827:Radiation; D012519:Sarcoplasmic Reticulum; D013455:Sulfur / Q000032:analysis
chemical_list: D010758:Phosphorus; D002713:Chlorine; D013455:Sulfur; D011188:Potassium; D002118:Calcium