title: Ca+2-accumulating components in developing skeletal muscle.
abstract: This ultrastructural study on the localization of Ca+2 in developing skeletal muscle indicates that the formation of calcium-accumulating components begins during embryonic development. Both oxalate and pyroantimonate techniques are used to localize Ca+2 in distinct cellular components of chick pectoral and sartorius muscles. Two major sites for Ca+2 accumulation are present in ultrathin sections of embryonic and post-embryonic muscles: the terminal cisternae of the sarcoplasmic reticulum and specific lines in the I-bands. Calcium oxalate-accumulating vesicles are present in the smallest recognizable myotubes at the twelfth day of incubation, but calcium-accumulating components are not seen at myofibrillar I-band sites until the fourteenth to seventeenth days of incubation. The fact that myofibrils first form and later in development accumulate a Ca+2-binding component suggests that this Ca+2-binding component is not necessary for the formation of myofibrils, but is added to myofibrils before hatching to serve a probable regulatory role in contraction.
mesh_terms: D000367:Age Factors; D000818:Animals; D000965:Antimony; D002118:Calcium / Q000378:metabolism*; D002642:Chick Embryo; D002645:Chickens; D008854:Microscopy, Electron; D024510:Muscle Development; D009132:Muscles / Q000196:embryology / Q000378:metabolism* / Q000648:ultrastructure; D009992:Osmium; D010070:Oxalates; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013194:Staining and Labeling
chemical_list: D010070:Oxalates; D009992:Osmium; D000965:Antimony; D002118:Calcium