Cardiac muscle fibers of the hummingbird and finch have no transverse tubules and are smaller in diameter than those of mammalian hearts. The fibers are connected by intercalated discs which are composed of desmosomes and f. adherentes; small nexuses are often interspersed. As in cardiac muscle of several other animals, the junctional SR of the couplings is highly structured in these two birds but, in addition, and after having lost sarcolemmal contact, the junctional SR continues beyond the coupling to extend deep into the interior of the cells and to form belts around the Z-I regions of the sarcomeres. This portion of the sarcoplasmic reticulum, which we have named "extended junctional SR," and which is so prominent and invariant a feature of cardiac cells of hummingbirds and finches, has not been observed in chicken cardiac cells. The morphological differences between these species of birds may be related to respective differences in heart rates characteristic for these birds.
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1 April 1971
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April 01 1971
CARDIAC MUSCLE : Its Ultrastructure in the Finch and Hummingbird with Special Reference to the Sarcoplasmic Reticulum
Paul H. Jewett,
Paul H. Jewett
From the Departments of Pediatrics, Pathology, and Physiology, Duke University Medical Center, and the Veterans Administration Hospital, Durham, North Carolina 27706
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J. R. Sommer,
J. R. Sommer
From the Departments of Pediatrics, Pathology, and Physiology, Duke University Medical Center, and the Veterans Administration Hospital, Durham, North Carolina 27706
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E. A. Johnson
E. A. Johnson
From the Departments of Pediatrics, Pathology, and Physiology, Duke University Medical Center, and the Veterans Administration Hospital, Durham, North Carolina 27706
Search for other works by this author on:
Paul H. Jewett
From the Departments of Pediatrics, Pathology, and Physiology, Duke University Medical Center, and the Veterans Administration Hospital, Durham, North Carolina 27706
J. R. Sommer
From the Departments of Pediatrics, Pathology, and Physiology, Duke University Medical Center, and the Veterans Administration Hospital, Durham, North Carolina 27706
E. A. Johnson
From the Departments of Pediatrics, Pathology, and Physiology, Duke University Medical Center, and the Veterans Administration Hospital, Durham, North Carolina 27706
Received:
July 07 1970
Revision Received:
November 16 1970
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1971 by The Rockefeller University Press
1971
J Cell Biol (1971) 49 (1): 50–65.
Article history
Received:
July 07 1970
Revision Received:
November 16 1970
Citation
Paul H. Jewett, J. R. Sommer, E. A. Johnson; CARDIAC MUSCLE : Its Ultrastructure in the Finch and Hummingbird with Special Reference to the Sarcoplasmic Reticulum . J Cell Biol 1 April 1971; 49 (1): 50–65. doi: https://doi.org/10.1083/jcb.49.1.50
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