Histochemical and physiological properties of cat motor units after self‐ and cross‐reinnervation

Abstract

SUMMARY1. This report describes selected histochemical and physiological properties of the motor units of adult cat soleus muscle approximately one year after self-and cross-reinnervation with the nerve of the heterogenous flexor hallucis longus (f.h.l.). Self-reinnervated f.h.l. motor units are also considered. Whole muscles were tested for fibre reaction to alkaline pre-incubated ATPase, cz-glycerophosphate dehydrogenase (a-GPD) and reduced nicotinamide adenine dinucleotide diaphorase (NADH-D). Motor units were isolated and studied by splitting the ventral root in acute preparations.2. The histochemical fibre type profile in the self-reinnervated muscle was comparable to normal muscle as was mean twitch contraction time, twitch-tetanus ratio and fatigue index. The mean tetanic tension of the soleus self-and cross-reinnervated motor units appeared close to a normal soleus whereas the mean tetanic tension of the f.h.l. self-reinnervated units was significantly less than a normal f.h.l.3. An average of 14 % of the fibres of the soleus cross-reinnervated muscles had high ATPase and a c-GPD staining intensity in contrast to normal and selfreinnervated soleus in which such fibres are absent. Thus alkaline lability of myofibrillar ATPase increased in some fibres of what was originally a homogeneous population. The small increase in the number of densely staining fibres for ATPase at an alkaline pH (14 %) was associated with a 73 % decrease in (mean) contraction time (41 + 11 ms) of the thirty-three cross-reinnervated muscle units studied, with no unit's contraction time greater than 60 ms. Mean contraction times for the self-reinnervated soleus and f.h.l. muscles were 78 + 31 ms and 27 + 8 ms respectively.4. All fibres of the soleus cross-reinnervated muscles showed intense reaction to NADH-D, as was true of self-reinnervated soleus. This staining pattern is typical of normal soleus. In concordance, these motor units consistently demonstrated a high resistance to fatigue when stimulated for a four-minute period.5. These results suggest that in the adult self-and cross-reinnervated soleus muscle,

Trophic effects on the contractile and histochemical properties of rat soleus muscle

“…The finding of substantial muscular wasting as a result of virtually complete paralysis lasting 2 or 4 weeks is in accord with a significant role of some factor(s) associated with neuromuscular activity in regulating the mass of rat soleus muscle. The stimulus of active or passive lengthening has also been shown (Goldspink, 1978;Spector et al, 1982) to influence dramatically both MW and F-CSA. Nevertheless, the present results also demonstrate an additional factor that appears to influence muscle mass.…”

“…The extreme fluctuations in skeletal muscle mass due to such perturbations as high resistance weight training (Edgerton, 1976) joint immobilization (Solandt et al, 1943;Spector et al, 1982) or spinal cord transection (Johnson et al, 1982;Mayer et al, 1984) are attributed to changes in the pattern (Salmons and Sreter, 1976) or degree (Sreter et al, 1982) of neuromuscular activity. The finding of substantial muscular wasting as a result of virtually complete paralysis lasting 2 or 4 weeks is in accord with a significant role of some factor(s) associated with neuromuscular activity in regulating the mass of rat soleus muscle.…”

“…The cross-rernnervation experiments of Buller et al (1960) and others (Buller et al, 1969;Close, 1969;Bagust et al, 1981;Chan et al, 1982) demonstrated that the motoneuron regulates a variety of contractile, biochemical, and histochemical properties of skeletal muscle. The signals responsible for this muscular plasticity were hypothesized to derive from newly directed activity patterns and/or the supply of a neurotrophic substance to the muscle by the innervating nerve (Buller et al, 1960).…”

Expression of Myosin Isoforms in Denervated, Cross‐Reinnervated, and Electrically Stimulated Rabbit Muscles

“…It has been shown that the almost complete transformation usually observed on crossreinnervated fast-twitch muscles is in marked contrast to the very incomplete transformation produced by cross-reinnervation of slow-twitch muscles (Dum et al, 198Sa,b;for review, see Jolesz and SrCter, 1981). Particularly, although contraction time of slow-twitch muscle is faster when cross-reinnervated by a nerve from a fast muscle, this may not be accompanied by change in the histochemical pattern of myosin ATPase activity (Buller et al, 1969;Chan et al, 1982;Gauthier et al, 1983). Thus, the transformations of the biochemical properties do not parallel in every respect those of the physiological ones (SrCter et al, 197.5;Srihari et al, 1981).…”

“…Myosin preparation. Myosin was prepared as prey iously described (d 'Albis et al, 1979). Briefly, small pieces of f'rozen muscles previously thawed on ice were washed in five volumes 20 mM NaCl, 5 mM sodium phosphate, 1 mM EGTA, pH 6.5.…”