| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Central Nervous System, Tokyo Metropolitan Institute of Gerontology, Japan.
1. The isometric contractile properties and morphological characteristics of the muscle unit portion of motor units were investigated in the medial gastrocnemius (MG) muscle of Fischer 344 rats. Individual motor units were functionally isolated by stimulating single MG axons in finely dissected ventral root filaments. 2. To study the mechanical properties of the motor units in the rat MG muscle, ninety-six motor units in five animals were classified into three categories (type FF, FR and S units) using two physiological criteria: presence or absence of the 'sag' property and fatigability. The relative distribution of the different motor unit types in the sample was 35.4% for type FF, 47.9% for type FR, and 16.7% for type S units. 3. There was little overlap in the distribution of twitch contraction time between type F (including types FF and FR) and type S units. The mean value was 17.1 ms for type FF, 15.7 ms for type FR, and 28.0 ms for type S units. Type FF units produced the largest tetanic tension (mean +/- S.D.; 201 +/- 75 mN). Tension output of type S units was the smallest (15 +/- 6 mN), and that of type FR units was intermediate (100 +/- 45 mN). These values were significantly different. 4. A muscle unit portion of twenty-three motor units (8 FF, 6 FR, and 9 S units) was depleted of its glycogen through repetitive stimulation after characterization of its mechanical properties. Cross-sectional areas of units fibres and innervation ratio were directly measured in sections stained for glycogen using a periodic and acid-Schiff (PAS) reaction. Specific tension of unit fibres was calculated by dividing the maximum tetanic tension of a unit by its total fibre area. 5. The number of unit fibres ranged from 44 to 77 for type S, 116 to 198 for type FR, and 221 to 356 for type FF units, and differences among their means (66, 154 and 271, respectively) were significant. Tetanic tension was correlated with innervation ratio for all of the twenty-three units, or units within a particular type. 6. Mean fibre area for type S units (1983 microns2) was significantly smaller than that for type FF units (3489 microns2). Fibres belonging to type FR units had an intermediate size (2648 microns2). Correlation between tetanic tension and fibre area was significant for either all units or units within a particular type. 7. Total cross-sectional area was significantly different among the motor unit types, and was highly correlated to the maximum tetanic tension.(ABSTRACT TRUNCATED AT 400 WORDS)
This article has been cited by other articles:
|
|
 |
|
  T. E. Higham and A. A. Biewener Integration within and between muscles during terrestrial locomotion: effects of incline and speed J. Exp. Biol., July 15, 2008; 211(14): 2303 - 2316. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. G. Keenan and F. J. Valero-Cuevas Experimentally Valid Predictions of Muscle Force and EMG in Models of Motor-Unit Function Are Most Sensitive to Neural Properties J Neurophysiol, September 1, 2007; 98(3): 1581 - 1590. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. H. Kim, S. Suzuki, and K. Kanda Age-related physiological and morphological changes of muscle spindles in rats J. Physiol., July 15, 2007; 582(2): 525 - 538. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. G. Keenan, D. Farina, F. G. Meyer, R. Merletti, and R. M. Enoka Sensitivity of the cross-correlaton between simulated surface EMGs for two muscles to detect motor unit synchronization J Appl Physiol, March 1, 2007; 102(3): 1193 - 1201. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Celichowski, W. Mrowczynski, P. Krutki, T. Gorska, H. Majczynski, and U. Slawinska Changes in contractile properties of motor units of the rat medial gastrocnemius muscle after spinal cord transection Exp Physiol, September 1, 2006; 91(5): 887 - 895. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. G. Keenan, D. Farina, R. Merletti, and R. M. Enoka Amplitude cancellation reduces the size of motor unit potentials averaged from the surface EMG J Appl Physiol, June 1, 2006; 100(6): 1928 - 1937. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. G. Keenan, D. Farina, K. S. Maluf, R. Merletti, and R. M. Enoka Influence of amplitude cancellation on the simulated surface electromyogram J Appl Physiol, January 1, 2005; 98(1): 120 - 131. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. M. Damon and J. C. Gore Physiological basis of muscle functional MRI: predictions using a computer model J Appl Physiol, January 1, 2005; 98(1): 264 - 273. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Sugiura and K. Kanda Progress of Age-Related Changes in Properties of Motor Units in the Gastrocnemius Muscle of Rats J Neurophysiol, September 1, 2004; 92(3): 1357 - 1365. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. L. Messi and O. Delbono Target-Derived Trophic Effect on Skeletal Muscle Innervation in Senescent Mice J. Neurosci., February 15, 2003; 23(4): 1351 - 1359. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. N. Maganaris, V. Baltzopoulos, D. Ball, and A. J. Sargeant In vivo specific tension of human skeletal muscle J Appl Physiol, March 1, 2001; 90(3): 865 - 872. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. L. Tam, V. Archibald, B. Jassar, N. Tyreman, and T. Gordon Increased Neuromuscular Activity Reduces Sprouting in Partially Denervated Muscles J. Neurosci., January 15, 2001; 21(2): 654 - 667. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. J. Sokoloff Localization and Contractile Properties of Intrinsic Longitudinal Motor Units of the Rat Tongue J Neurophysiol, August 1, 2000; 84(2): 827 - 835. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. S. Carp, P. A. Herchenroder, X. Y. Chen, and J. R. Wolpaw Sag During Unfused Tetanic Contractions in Rat Triceps Surae Motor Units J Neurophysiol, June 1, 1999; 81(6): 2647 - 2661. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. J. Fuglevand, V. G. Macefield, and B. Bigland-Ritchie Force-Frequency and Fatigue Properties of Motor Units in Muscles That Control Digits of the Human Hand J Neurophysiol, April 1, 1999; 81(4): 1718 - 1729. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. J. Fuglevand and S. S. Segal Simulation of motor unit recruitment and microvascular unit perfusion: spatial considerations J Appl Physiol, October 1, 1997; 83(4): 1223 - 1234. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
