Coordination of electromechanical and metabolic properties of cat soleus motor units

1988 ◽  
Vol 255 (5) ◽  
pp. C684-C693 ◽  
Author(s):  
T. P. Martin ◽  
S. Bodine-Fowler ◽  
V. R. Edgerton
Keyword(s):  
Spinal Cord ◽  
Muscle Fibers ◽  
Motor Units ◽  
Cross Sectional Area ◽  
Spinal Cord Transection ◽  
Sectional Area ◽  
Cross Sectional ◽  
Physiological Properties ◽  
Metabolic Properties ◽  
Adult Cats

Motor units were studied in the soleus muscle of normal adult cats and adult cats that had undergone complete spinal cord transection approximately 4 mo earlier. Intracellular recording and stimulation techniques were used to study selected electrical properties of the motoneuron and isometric contractile properties of the muscle unit. Motor unit fibers were depleted of their glycogen through repetitive stimulation of the motoneuron and identified by a quantitative histochemical determination of glycogen. A sample of muscle fibers from the glycogen-depleted unit and from fibers not depleted of glycogen were analyzed for cross-sectional area, succinate dehydrogenase (SDH), alpha-glycerolphosphate dehydrogenase (GPD), and alkaline myofibrillar adenosine triphosphatase. It was observed that the fiber-to-fiber variability in cross-sectional area and SDH and GPD activity within units of normal and transected cats was significantly larger than that measured in repeated samples from a single fiber. Additionally, for each of these properties, the range found among fibers within a unit was similar to that found among nondepleted fibers of the same myosin type. The influence of spinal cord transection on some muscle fibers seemed to result in a metabolic shift from the generalized category of slow-oxidative toward fast-oxidative glycolytic. This shift in metabolic properties appeared to be coupled with a similar shift in the physiological properties of the muscle unit and motoneuron from slow to fast.

Maximal force as a function of anatomical features of motor units in the cat tibialis anterior

1987 ◽  
Vol 57 (6) ◽  
pp. 1730-1745 ◽  
Author(s):  
S. C. Bodine ◽  
R. R. Roy ◽  
E. Eldred ◽  
V. R. Edgerton
Keyword(s):  
Motor Unit ◽  
Tibialis Anterior ◽  
Periodic Acid ◽  
Muscle Fibers ◽  
Motor Units ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Periodic Acid Schiff ◽  
Cross Sectional ◽  
Single Motor Unit

In 11 tibialis anterior muscles of the cat, a single motor unit was characterized physiologically and subsequently depleted of its glycogen through repetitive stimulation of an isolated ventral root filament. Muscle cross sections were stained for glycogen using a periodic acid-Schiff reaction, and single-fiber optical densities were determined to identify those fibers belonging to the stimulated motor unit. Innervation ratios were determined by counting the total number of muscle fibers in a motor unit in sections taken through several levels of the muscle. The average innervation ratios for the fast, fatigueable (FF) and fast, fatigue-resistant (FR) units were similar. However, the slow units (S) contained 61% fewer fibers than the fast units (FF and FR). Muscle fibers belonging to S and FR units were similar in cross-sectional area, whereas fibers belonging to FF units were significantly larger than fibers belonging to either S or FR units. Additionally, muscle fibers innervated by a single motoneuron varied by two- to eightfold in cross-sectional area. Specific tensions, based on total cross-sectional area determined by summing the areas of all muscle fibers of each unit, showed a modest difference between fast and slow units, the means being 23.5 and 17.2 N X cm-2, respectively. Variations in maximum tension among units could be explained principally by innervation ratio, although fiber cross-sectional area and specific tension did contribute to differences between unit types.

Morphological observations of motor units connected in-series to Golgi tendon organs

1986 ◽  
Vol 55 (1) ◽  
pp. 147-162 ◽  
Author(s):  
J. M. Spielmann ◽  
E. K. Stauffer
Keyword(s):  
Discharge Rate ◽  
Muscle Fibers ◽  
Motor Units ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Golgi Tendon Organs ◽  
In Series ◽  
The Cross ◽  
Tendon Organs

The glycogen-depletion technique (17, 32) has been used to examine the functional and morphological relationships between single isolated motor units (MUs) and single isolated Golgi tendon organs (GTOs) that were excited by the MUs in the soleus muscle of the cat. All MUs whose twitch contraction generated a brisk discharge from the GTOs during the rising and plateau phase of force development had a muscle fiber attached specifically to the proximal end of the GTOs. A significant (P less than 0.05) linear relationship was found between GTO discharge rate and the cross-sectional area of the muscle fibers that connected to a receptor. This was true when the correlation was calculated between firing rate and 1) the cross-sectional area of the entire collection of muscle fibers that connected in series to the GTOs; and 2) for the cross-sectional areas of the individually depleted muscle fibers that inserted on the GTO sample. These findings support the notion that the most physiologically relevant input for GTOs arises from the MUs that are attached directly in-series with the receptor.

Neonatal Spinal Cord Transection Decreases Hindlimb Weight-Bearing and Affects Formation of Achilles and Tail Tendons

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Sophia K. Theodossiou ◽  
Nicholas M. Pancheri ◽  
Alleyna C. Martes ◽  
Aimee L. Bozeman ◽  
Michele R. Brumley ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Spinal Cord ◽  
Locomotor Activity ◽  
Mechanical Loading ◽  
Weight Bearing ◽  
Cross Sectional Area ◽  
Spinal Cord Transection ◽  
Sectional Area ◽  
Cross Sectional ◽  
Partial Weight

Abstract Mechanical loading may be required for proper tendon formation. However, it is not well understood how tendon formation is impacted by the development of weight-bearing locomotor activity in the neonate. This study assessed tendon mechanical properties, and concomitant changes in weight-bearing locomotion, in neonatal rats subjected to a low thoracic spinal cord transection or a sham surgery at postnatal day (P)1. On P10, spontaneous locomotion was evaluated in spinal cord transected and sham controls to determine impacts on weight-bearing hindlimb movement. The mechanical properties of P10 Achilles tendons (ATs), as representative energy-storing, weight-bearing tendons, and tail tendons (TTs), as representative positional, non-weight-bearing tendons were evaluated. Non- and partial weight-bearing hindlimb activity decreased in spinal cord transected rats compared to sham controls. No spinal cord transected rats showed full weight-bearing locomotion. ATs from spinal cord transected rats had increased elastic modulus, while cross-sectional area trended lower compared to sham rats. TTs from spinal cord transected rats had higher stiffness and cross-sectional area. Collagen structure of ATs and TTs did not appear impacted by surgery condition, and no significant differences were detected in the collagen crimp pattern. Our findings suggest that mechanical loading from weight-bearing locomotor activity during development regulates neonatal AT lateral expansion and maintains tendon compliance, and that TTs may be differentially regulated. The onset and gradual increase of weight-bearing movement in the neonate may provide the mechanical loading needed to direct functional postnatal tendon formation.

Observations on the number of nuclei within the fibres of some red and white muscles

1977 ◽  
Vol 23 (1) ◽  
pp. 269-284 ◽  
Author(s):  
I.G. Burleigh
Keyword(s):  
Cross Sectional Area ◽  
Growth Potential ◽  
Muscle Fibres ◽  
Sectional Area ◽  
Adult Rats ◽  
Cross Sectional ◽  
Physiological Properties ◽  
Phasic Type ◽  
The One ◽  
Red And White Muscles

Nuclei have been enumerated in muscle fibres of different physiological properties within adult rats and rabbits. Almost invariably, and regardless of muscle type, there is a direct relationship between the cross-sectional area (or fibre breadth) of muscle fibres and the number of nuclei within them. The one exception occurred in muscles of older rats where increased nuclear numbers do not always appear to result in broader muscle fibres. The greater complement of nuclei in broader fibres is accompanied by larger amounts of cell substance per nucleus. Confirming early observations in the literature, red fibres of the slow-phasic type have more nuclei than have white, fast-phasic fibres of similar breadth. These conclusions are not vitiated by differences in the number of nuclei within capillaries or in satellite cells, by differences in nuclear length or by variation in the degree to which fibres are contracted. In respect of their complement of nuclei, and the average amount of cell substance formed per nucleus the small red fibres that occur within muscles of predominantly fast-phasic character appear to be fast-rather than slow-phasic in type. When the number of nuclei observed per fibre is plotted against fibre cross-sectional area, the shapes of the resulting distributions suggest that estimates of muscle nuclei may be valuable not only as an index of growth potential, but of the extent to which that potential is expressed. In one muscle, the above distribution was of a form which indicated that some fibres may have formed abnormally large amounts of protein per nucleus. However, this was not adequately confirmed. Various factors have been investigated that are relevant to the accuracy of enumerating nuclei and measuring fibre breadths.

scholarly journals Morphological peculiarities of neuromuscular junctions among different fiber types: Effect of exercise

2017 ◽  
Vol 27 (3) ◽  
Author(s):  
Teet Seene ◽  
Maria Umnova ◽  
Priit Kaasik
Keyword(s):  
Axon Terminal ◽  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Cross Sectional Area ◽  
Fiber Types ◽  
Sectional Area ◽  
Cross Sectional ◽  
Thin Sections ◽  
Axon Terminals ◽  
Ultrastructural Studies

The aim of our research was to examine whether there are differences in the morphology of neuromuscular junctions of different types of muscle fibers in rodents, and after their adaptation to six weeks endurance exercise training. After 5-day acclimation, Wistar rats were subjected to run with the speed 35 m/min during 6 week, 5 days per week and the training volume reached 60 min per day. Muscle samples for ultrastructural studies were fixed, dehydrated and embedded in Epon-812. Ultra-thin sections were cut from longitudinally and transversely oriented blocs, using 4 blocks from each animal. The area of axon terminals on fast- twitch fibers is 1.5 time large (p<0.001) and the perimeter of terminals is 1.7 time large in comparison with slow- twitch oxidative fibers (p<0.001) in control group. There are correlation between cross-sectional area of different muscle fibers and length of axon terminals (r=0.72), between cross-sectional area and with of axon terminal (r=-0.62), and between turnover rate of contractile proteins and length of axon terminal (r=0.75). Fast remodeling of synapse on oxidative and oxidative-glycolytic muscle fibers during endurance training seems to guarantees the intensive renewal of the structures of muscle fibers with higher oxidative capacity.

scholarly journals Dehydration affects spinal cord cross-sectional area measurement on MRI in healthy subjects

Spinal Cord ◽  
2014 ◽  
Vol 52 (8) ◽  
pp. 616-620 ◽  
Author(s):  
C Wang ◽  
R C Tam ◽  
E Mackie ◽  
D K B Li ◽  
A L Traboulsee
Keyword(s):  
Spinal Cord ◽  
Healthy Subjects ◽  
Cross Sectional Area ◽  
Area Measurement ◽  
Sectional Area ◽  
Cross Sectional
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