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  • 1
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The heart ultrastructure of the anostracan Crustacea Branchinecta paludosa, Artemia salina, Branchipus schaefferi, and Streptocephalus sp. is essentially similar. All lack an endocardium and an epicardium, and the heart wall consists of a single layered myocardium. Only in the posterior end of the heart does the myocardium form a tube. In the remaining, anterior part of the heart, the myocardium forms a trough. The dorsal edges of this trough are firmly attached to the basement membrane of the epidermis, which thus forms the lid of the trough. The Z-bands of the sarcomere are diffuse, and H- and M-bands were not seen. Interior couplings are as a rule found at Z-levels.
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  • 2
    ISSN: 1572-8404
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Philosophy
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biology and philosophy 3 (1988), S. 497-499 
    ISSN: 1572-8404
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Philosophy
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  • 4
    ISSN: 1432-1971
    Keywords: Cerebral perfusion ; Cardiac surgery ; Pediatric surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Six children undergoing major cardiac surgery had extensive cerebral monitoring during cardiopulmonary bypass (CPB). The monitoring included continuous recording of arterial blood pressure (BP), central venous pressure (CVP), cerebral electrical activity by a cerebral function monitor (CFM), and middle cerebral artery (MCA) flow velocity by the transcranial pulsed Doppler (TCD) technique. Introduction of the precooled blood containing priming solution resulted in rapid fall in BP as well as MCA velocities in these children at the start of CPB. During steady-state CPB at 20°C, MCA flow velocities were reduced in five of six children, range 45%–105% of pre-bypass value. These flow velocity values were recorded at cerebral perfusion pressures (CPP=BP−CVP) in the range of 14–26 mmHg. This reduced cerebral perfusion during steady-state CPB appears to be more than sufficient to meet the cerebral metabolic demands at the particular temperature. The reduced cerebral perfusion is in contrast to the enhanced perfusion found in adults during moderately hypothermic (28°–30°C) low-flow, low-pressure CPB previously reported. It was presumably due to the reduced temperature, reduced perfusion pressure, and less hemodilution. During periods of constant temperature, hematocrit, and partial pressure of carbon dioxide (PaCO 2), MCA flow velocities varied passively with changes in CPP, demonstrating that cerebral autoregulation was not operative. Transcranial Doppler appears to be a suitable tool for investigating CPB techniques optimal with respect to cerebral circulation.
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  • 5
    ISSN: 1432-0878
    Keywords: Cardiac sarcomeres ; Circolana borealis (Isopod) ; T-tubules ; Sarcoplasmic reticulum ; Couplings ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The membrane systems of the cardiac muscle cell of the isopod Cirolana borealis Lilljeborg are described. The sarcolemma invaginates at the level of the Z band, forming transverse tubules. Narrow tubules branch off in a longitudinal direction from these transverse and radially arranged TZ-tubules forming a transverse collar at each A-I level, where dyadic and triadic junctions are formed with the sarcoplasmic reticulum. Two different orientations of the coupling discs have been detected in the supercontracted sarcomere, and this observation has been discussed. Adjacent myofibrils are separated by a double layer of sarcoplasmic reticulum.
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  • 6
    ISSN: 1432-0878
    Keywords: Cardiac sarcomere ; Munida tenuimana (crustacea) ; T tubule system ; Sarcoplasmic reticulum ; Couplings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The membrane systems of the cardiac muscle cell of Munida tenuimana G. O. Sars are described. The sarcolemma invaginates at the Z level, forming tubules. Narrow tubules branch off in a longitudinal direction from these transverse and radially arranged tubules, forming a narrow transverse collar at the H level where dyadic and triadic junctions are formed with the sarcoplasmic reticulum.
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  • 7
    ISSN: 1432-0878
    Keywords: Cardiac sarcomeres ; Tmetonyx cicada (Crustacea) ; T-tubules ; Sarcoplasmic reticulum ; Couplings ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The membrane systems of the cardiac muscle cell of the amphipod Tmetonyx cicada (O. Fabricius) are described. The sarcolemma invaginates and forms a transverse network of tubules at the level of the Z band. Narrow longitudinal tubules branch from the network and connect to another transverse network of tubules at the H band level, where dyadic and triadic junctions are formed with the sarcoplasmic reticulum. Adjacent myofibrils are normally separated by a well developed double layer of the sarcoplasmic reticulum. In areas where the myofibrils closely approach the outer sarcolemma, peripheral couplings have been found at the level of the H band.
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  • 8
    ISSN: 1432-0878
    Keywords: Cardiac sarcomeres ; Euchaeta norvegica (Copepoda) ; T-tubules ; sarcoplasmic reticulum ; Couplings ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The membrane systems of the cardiac muscle cell of the copepod Euchaeta norvegica Boeck are described. The heart wall, which is between 0.12 and 1.36 μm thick, consists of an epicardium and a single layer of muscle cells. Invaginations of the sarcolemma forming transverse tubules have been found at all levels of the sarcomere with the exception of the H-band level. The longitudinal tubules of the same system are closely associated with the sarcoplasmic reticulum to form interior couplings at the A-I level of the sarcomere. Triadic couplings at the Z band level were not seen in E. norvegica, but peripheral couplings were demonstrated. Nexuses were found in the intercalated discs.
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  • 9
    ISSN: 1432-0878
    Keywords: Cardiovascular system ; Rossia macrosoma (Cephalopoda) ; Myofibrils ; Intercalated discs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The muscle cells of the ventricle, the branchial heart and the branchial heart appendages of Rossia macrosoma (Delle Chiaje) are studied. The ventricle myocardium has three muscle layers, while the other two organs exhibit a loose arrangement of muscle cells. The muscle cells of the ventricle, the branchial heart and the branchial heart appendages are similar in structure. The nuclei are surrounded by myofibrils. In the myofibrils A-, I- and discontinuous Z-bands are seen. The diameters of the thick filaments are 300–400Å, their length varies from 1.7 to 3.9 μ. Thin filaments have a diameter of approximately 85Å. The ratio between thick and thin filaments is roughly 1 to 11. The SR runs mostly as a longitudinal network within the myofibrils. A few short T-tubules are observed in the Z-regions. Peripheral and internal couplings exist. The latter are few in number. Intercalated discs are small and rarely observed. They have been found in all three organs. A difference in the function of these organs is not reflected in the ultrastructure of the intercalated discs. These discs are often of the interdigitating type with interfibrillar junctions and unspecialized regions. Peripheral couplings are seen at the unspecialized regions. The intercalar surfaces of the muscle cells “shoulder off” into the lateral surface, and the transition between the two surfaces is not a sharp one. Attachment plaques are found scattered over the whole sarcolemma.
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  • 10
    ISSN: 1432-0878
    Keywords: Heart ultrastructure ; Lepidurus arcticus (Branchiopoda) ; Myofibrils ; T-system ; Sarcoplasmic reticulum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The heart of Lepidurus arcticus consists of an epicardium and a single layer of strongly polarized myocardial cells, 10–50 μm thick, with the myofibrillar part facing the epicardium. The Z-bands are diffuse and some Z-material forms attachment plaques. Relaxed sarcomeres show a hexagonal arrangement of thick filaments and 6 thin filaments in orbit, but filaments often diverge in their orientation. The sarcolemma invaginates from both the epicardial and the endocardial side of the cell, forming clefts and T-tubules. The sarcoplasmic reticulum is loosely reticular, cisternae associate with sarcolemma to form large and typical peripheral and interior couplings. The latter are of the “button-to-button” type and they tend to be located at the A-I level.
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