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  • Human triceps surae  (1)
  • Lengthening contraction  (1)
  • dye coupling  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The effect of muscle vibration on human position sense during movements controlled by lengthening muscle contraction (1991)
    Springer
    Experimental brain research 84 (1991), S. 631-634 
    Details
    ISSN: 1432-1106
    Keywords: Muscle vibration ; Kinesthesis ; Lengthening contraction ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Muscle vibration studies suggest that during voluntary movement limb position is coded by muscle spindle information derived from the lengthening, antagonist muscle. However, these investigations have been limited to movements controlled by shortening contractions. This study further examined this property of kinesthesia during movements controlled by lengthening contraction. Subjects performed a horizontal flexion of the right forearm to a mechanical stop randomly positioned at 30, 50 and 70° from the starting position. The movement was performed against a flexor load (1 kg) requiring contraction of the triceps muscle. Vision was occluded and movements were performed under three conditions: no vibration, vibration of the right biceps and vibration of the right triceps. The perceived position of the right forearm was assessed by instructing subjects to simultaneously match the right limb position with the left limb. Vibration of the shortening biceps muscle had no effect on limb matching accuracy. However, triceps vibration resulted in significant overestimation of the vibrated limb position (10–13°). The variability in movement distance was uninfluenced by muscle vibration. During movements controlled by lengthening contraction, there is a concurrent gamma dynamic fusimotor input that would enhance primary afferent discharge. Despite this additional regulating input to the muscle spindle, it appears that muscle spindle information from the lengthening muscle is important for the accurate perception of limb movement and/or position.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230975
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Permeability and structural studies of heart cell gap junctions under normal and altered ionic conditions (1982)
    Springer
    The journal of membrane biology 68 (1982), S. 227-238 
    Details
    ISSN: 1432-1424
    Keywords: intercellular communication ; dye coupling ; gap junctions ; A23187 ; monensin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The permeability and ultrastructure of communicating junctions of cultured neonatal rat ventricular cells are examined under control conditions and during treatments which raise intracellular Ca2+. Lucifer Yellow (487 mol wt) is used to examine junctional permeability. Under normal ionic conditions dye transfer from an injected muscle cell to neighboring muscle cells occurs rapidly (in less than 6 sec) while transfer to neighboring fibroblasts occurs more slowly. Application of monensin, which results in a partial contracture with superimposed asynchrony, or A23187, which results in a partial contracture, do not inhibit the transfer of dye between the muscle cells. A23187 did result in junctional blockade between muscle cells and fibroblasts. Freeze-fractured gap junctions from control and monensin-treated cells exhibit no distinguishable differences. Center-to-center spacing was not significantly different, 9.0 nm±1.4sd versus 9.2 nm±1.3sd, respectively; and particle diameters were virtually unchanged, 8.69 nm±0.9sd versus 8.61 nm±1.07sd, respectively. These results suggest that concentrations of intracellular Ca2+ sufficient to support a partial contracture and asynchronous contractile activity do not result in a block of intercellular junctions in cultured myocardial cells. These results are discussed in terms of intracellular Ca2+-buffering and junctional sensitivity to Ca2+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872267
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Twitch potentiation after fatiguing exercise in man (1987)
    Springer
    European journal of applied physiology 56 (1987), S. 461-466 
    Details
    ISSN: 1439-6327
    Keywords: Human triceps surae ; Twitch potentiation ; Twitch contraction time ; Twitch relaxation time ; Isometric contraction ; Muscle fatigue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Twitch potentiation was studied in the human triceps surae complex before and after intermittent maximal voluntary contractions or electrical stimulation at 20 Hz. Both forms of exercise were conducted with intact circulation for a maximum of 10 min or with circulatory occlusion until force output declined 50%. The relative potentiation was determined when a control twitch was compared to a twitch obtained after 5 s of maximal voluntary plantar flexion. The unpotentiated twitch torque (PT) and potentiated twitch torque (PT*) were reduced most severely after voluntary ischemic exercise (63.2% and 52.5% respectively, (P〈0.001)). However, the relative potentiation (PT*/PT) immediately after voluntary ischemic exercise increased to 1.65±0.18 from 1.22±0.13 at rest. Both PT and PT* recovered quickly after exercise. At rest, twitch contraction time (CT) and one-half relaxation time (1/2 RT) in the unpotentiated twitch were longer than that of contraction (CT*) and one-half relaxation time (1/2 RT*) in the potentiated twitch. Following non-occluded exercise, CT, CT*, 1/2 RT and 1/2 RT* were shortened relative to rest. After ischemic exercise CT and CT* were shortened although 1/2 RT and 1/2 RT* increased relative to rest. Both CT* and 1/2 RT* quickly recovered to pre-exercise values by 5 min post-exercise. Ratios of potentiated/control twitch parameters were not altered after nonoccluded exercise, but were increased after ischemic exercise. These results suggest that the mechanisms of fatigue which depress voluntary torque and twitch and potentiated twitch torques, do not interfere with the extent of potentiation after fatiguing exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417776
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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