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  • 1
    Electronic Resource
    Electronic Resource
    Calcium containing particles in mitochondria of heart muscle cells as shown by cryo-ultramicrotomy and X-ray microanalysis (1977)
    Springer
    Cell & tissue research 182 (1977), S. 17-31 
    Details
    ISSN: 1432-0878
    Keywords: Myocardium, mitochondria, calcium ; Cryo-ultramicrotomy-X-ray microanalysis ; Ultrahistochemistry ; Cardiac surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mitochondria of normal myocardial cells of the sand rat and the mouse as well as of the left ventricle of man, have been examined for their content of calcium. Ultrahistochemistry and X-ray microanalysis revealed two basically different inclusions: Osmiophilic mitochondrial granules and Spherical mitochondrial particles. Osmiophilic mitochondrial granules were found in conventionally fixed and plastic embedded tissues as well as in cryosections of chemically fixed and sucrose infused tissues. Such granules lacked inert electron density and probably consisted mainly of unsaturated lipids. X-ray spectra obtained from these tissues revealed no peaks for calcium. Spherical mitochondrial particles were present in dry-cut cryo-sections of N2-frozen tissues not treated by fixatives and/or cryoprotectants. These particles were deeply electron dense in unstained, freeze-dried cryo-sections. They usually measured from 600Å–900Å in diameter in the normal myocardium of the sand rat and the mouse and from 250 Å–400Å in diameter in the left ventricular myocardium of man. Significant calcium peaks could be identified in the X-ray spectra of these particles, whereas none occurred in the analyses of other tissue regions. Potassium was detected with about equal frequency in the particles and in other parts of the tissue. On the basis of the inert electron density of the particles and their absence in chemically fixed tissues as well as of the results of the X-ray analysis, it is concluded that they contain precipitates of extremely labile ions of mitochondrial calcium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222051
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructural localization of calcium in the pigeon papillary muscle as demonstrated by cytochemical studies and X-ray microanalysis (1974)
    Springer
    Cell & tissue research 155 (1974), S. 57-74 
    Details
    ISSN: 1432-0878
    Keywords: Cardiac ultrastructure ; Sarcoplasmic reticulum ; Myocardial calcium localization ; EDTA/EGTA ; X-ray microanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The intracellular localization of calcium as an antimonate precipitate is studied in myocardial cells of a non-mammalian vertebrate. Pigeon papillary muscles are pretreated in a calcium-free potassium solution containing 60 mM KSb (OH)6, and fixed in 1 % OsO1 containing the same concentration of antimonate. Calcium is chelated by K-EDTA or K-BGTA, in part separating it from the sodium-calcium antimonate. Atomic absorption spectrophotometry is employed to study the precipitate formation when sodium and calcium ions are added to a pH controlled antimonate solution. The chelating effect of K-EDTA and K-EGTA on the precipitates is studied by the same method. Both sodium and calcium cations are heavily precipitated by the antimonate anion. More calcium ions are precipitated when sodium ions are also present in the solution. K-EDTA and K-EGTA do not redissolve more than about 50% of the calcium antimonate from a sodium-calcium antimonate precipitate. When calcium cations only are added to the antimonate solution, K-EGTA redissolves about 95% of the calcium antimonate precipitate. A direct evidence for the presence of calcium in the tissue precipitates is given by X-ray microanalyses of 2500 Å thick sections. Calcium antimonate is located to the sarcoplasmic reticulum (SR), the myofibrils, the mitochondria and the nuclei. In the SR, calcium antimonate is consistently found in the subsarcolemmal cisternae of the peripheral couplings (Sommer and Johnson, 1969) and in the Z line cisternae (Saetersdal and Myklebust, 1975) or extended junctional SR (Sommer and Johnson, 1970). Along the myofibrils, calcium antimonate is found at the overlap of thick and thin filaments. In sarcomeres with short I bands, a dense antimonate precipitate consisting of large granules is found at the A-I junction. No calcium is found at the Z lines. The calcium antimonate granules along the myofilaments seem to be related to the length of the sarcomeres. The significance of these findings is discussed in relation to functional aspects of the myocardial cell
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220284
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