Time-related changes of motor unit properties in the rat medial gastrocnemius muscle after the spinal cord injury. II. Effects of a spinal cord hemisection

Celichowski, Jan; Kryściak, Katarzyna; Krutki, Piotr; Majczyński, Henryk; Górska, T; Sławińska, Urszula

doi:10.1016/j.jelekin.2009.07.003

Cited by 11 publications

(12 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We examine the enlargement of motor units following partial denervation using force as an indirect measure of size in a large sample of motor units and using counts of the muscle fibres innervated by single motoneurons (muscle units) as a direct measure in a subset of motor units. Our findings demonstrate that the capacity for axon sprouting of flexor motoneurons is the same in normally active motoneurons and in those whose neuromuscular activity is dramatically diminished by spinal cord hemisection (Celichowski et al 2009).…”

Section: Introductionmentioning

confidence: 64%

“…We cut either L4 or L5 spinal root simultaneously with hemisection of the lower thoracic spinal cord at T12 to dramatically reduce but not eliminate neuromuscular transmission during the first 10 days of axon sprouting when almost all the reinnervation of denervated endplates occurs (Tam & Gordon, 2003 b ). Neuromuscular activity is dramatically reduced immediately after thoracic hemisection with progressive recovery of activity over a period of a month (Celichowski et al 2009). We will refer to the rats with spinal cord thoracic hemisection as the hemisected rats to distinguish them from the rats in which the spinal cord was intact.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Sprouting capacity of lumbar motoneurons in normal and hemisected spinal cords of the rat

Gordon

Tyreman

2010

The Journal of Physiology

View full text Add to dashboard Cite

Nerve sprouting to reinnervate partially denervated muscles is important in several disease and injury states. To examine the effectiveness of sprouting of active and inactive motor units (MUs) and the basis for a limit to sprouting, one of three rat lumbar spinal roots was cut under normal conditions and when the spinal cord was hemisected at T12. Muscle and MU isometric contractile forces were recorded and muscle fibres in glycogen-depleted single muscle units enumerated 23 to 380 days after surgery. Enlargement of intact MUs by sprouting was effective in compensating for up to 80% loss of innervation. For injuries that removed >70-80% of the intact MUs, muscle contractile force and weight dropped sharply. For partial denervation of <70%, all MUs increased contractile force by the same factor in both normally active muscles and muscles whose activity was reduced by T12 hemisection. Direct measurements of MU size by counting glycogen-depleted muscle fibres in physiologically and histochemically defined muscle units, provided direct evidence for a limit in MU size, whether or not the activity of the muscles was reduced by spinal cord hemisection. Analysis of spatial distribution of muscle fibres within the outer boundaries of the muscle unit demonstrated a progressive increase in fibres within the territory to the limit of sprouting when most of the muscle unit fibres were adjacent to each other. We conclude that the upper limit of MU enlargement may be explained by the reinnervation of denervated muscle fibres by axon sprouts within the spatial territory of the muscle unit, formerly distributed in a mosaic pattern.

show abstract

Section: Introductionmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Sprouting capacity of lumbar motoneurons in normal and hemisected spinal cords of the rat

Gordon

Tyreman

2010

The Journal of Physiology

View full text Add to dashboard Cite

show abstract

“…However, just 1 month after complete cord transection in rats, gastrocnemius motor units showed only minor changes in fatigue parameters (Celichowski et al . , , see Fig. ).…”

Section: Motor Units Paralysed By Spinal Cord Injury Become Weaker Anmentioning

confidence: 86%

“…, Celichowski et al . , Mrówczyński et al . [data were calculated over all unit types together) and human muscles (Häger‐Ross et al .…”

Section: Motor Axon Properties Are Altered By Spinal Cord Injurymentioning

confidence: 99%

Human spinal cord injury: motor unit properties and behaviour

et al. 2013

View full text Add to dashboard Cite

Spinal cord injury (SCI) results in widespread variation in muscle function. Review of motor unit data shows that changes in the amount and balance of excitatory and inhibitory inputs after SCI alter management of motoneurons. Not only are units recruited up to higher than usual relative forces when SCI leaves few units under voluntary control, the force contribution from recruitment increases due to elevation of twitch/tetanic force ratios. Force gradation and precision are also coarser with reduced unit numbers. Maximal unit firing rates are low in hand muscles, limiting voluntary strength, but are low, normal or high in limb muscles. Unit firing rates during spasms can exceed voluntary rates, emphasizing that deficits in descending drive limit force production. SCI also changes muscle properties. Motor unit weakness and fatigability seem universal across muscles and species, increasing the muscle weakness that arises from paralysis of units, motoneuron death and sensory impairment. Motor axon conduction velocity decreases after human SCI. Muscle contractile speed is also reduced, which lowers the stimulation frequencies needed to grade force when paralysed muscles are activated with patterned electrical stimulation. This slowing does not necessarily occur in hind limb muscles after cord transection in cats and rats. The nature, duration and level of SCI underlie some of these species differences, as do variations in muscle function, daily usage, tract control and fibre-type composition. Exploring this diversity is important to promote recovery of the hand, bowel, bladder and locomotor function most wanted by people with SCI.

show abstract

“…MUs with values of the ratio lower or equal to 2.0 were accepted as fast, whereas MUs with higher values of this ratio were slow. This classification method was also used in our earlier reports Celichowski et al 2010;Mrówczyński et al 2010).…”

Section: Methodsmentioning

confidence: 99%

Changes of the force-frequency relationship in the rat medial gastrocnemius muscle after total transection and hemisection of the spinal cord

Mrówczyński

Celichowski

Krutki

et al. 2011

Journal of Neurophysiology

Self Cite

View full text Add to dashboard Cite

The relationships between the stimulation frequency and the force developed by motor units (MUs) of the medial gastrocnemius muscle were compared between intact rats and animals after total transection or hemisection of the spinal cord at the low thoracic level. The experiments on functionally isolated MUs were carried out 14, 30, 90, and 180 days after the spinal cord injury. Axons of investigated MUs were stimulated with trains of pulses at 10 progressively increased frequencies (from 1 to 150 Hz), and the force-frequency curves were plotted. Spinal cord hemisection resulted in a considerable leftward shift of force-frequency curves in all types of MUs. After the total transection, a leftward shift of the curve was observed in fast MUs, whereas there was a rightward shift in slow MUs. These changes coincided with a decrease of stimulation frequencies necessary to evoke 60% of maximal force. Moreover, the linear correlation between these stimulation frequencies and the twitch contraction time observed in intact rats was disrupted in all groups of animals with spinal cord injury. The majority of the observed changes reached the maximum 1 mo after injury, whereas the effects evoked by spinal cord hemisection were significantly smaller and nearly constant in the studied period. The results of this study can be important for the prediction of changes in force regulation in human muscles after various extends of spinal cord injury and in evaluation of the frequency of functional electrical stimulation used for training of impaired muscles.

show abstract

Time-related changes of motor unit properties in the rat medial gastrocnemius muscle after the spinal cord injury. II. Effects of a spinal cord hemisection

Cited by 11 publications

References 39 publications

Sprouting capacity of lumbar motoneurons in normal and hemisected spinal cords of the rat

Sprouting capacity of lumbar motoneurons in normal and hemisected spinal cords of the rat

Human spinal cord injury: motor unit properties and behaviour

Changes of the force-frequency relationship in the rat medial gastrocnemius muscle after total transection and hemisection of the spinal cord

Contact Info

Product

Resources

About