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E C Hall-Craggs

Publications and source records attributed to E C Hall-Craggs.

At least 19 recordsLinked to original sources
PubMed1986

Neuromuscular relationships in a muscle having segregated motor endplate zones. I. Anatomical and physiological considerations.

The cranial portion of the rat anterior gracilis muscle is innervated by the obturator nerve at two discrete motor endplate zones of which the distal is supplied by well-defined branches of the nerve. Prior to the use of this muscle in a study of motoneuron sprouting, further morphological and physiological studies have shown that its fibers vary in length but a number traverse the whole muscle or are long enough to extend through both endplate zones. The distribution of muscle fiber types is typical of a rat fast-twitch muscle, and each fiber is innervated at a single endplate. Myography showed that the spinal cord segments, which may contribute to the muscle's innervation, are L2, 3, and 4, of which L3 is constant and predominant, and that denervation of the distal endplate zone leads to a 50% reduction of the maximum isometric tension developed by the muscle. Antidromic stimulation of nerves supplying the distal endplate zone produced contraction of the proximal part of the muscle and, following similar antidromic stimulation, intracellular recordings made at proximal zone endplates showed the presence of endplate potentials. It was concluded from these data that endplates at both the proximal and distal zones can form part of the same motor unit.

Animals↗
PubMed1986

Neuromuscular relationships in a muscle having segregated motor endplate zones. II. The response to partial denervation.

The cranial belly of the anterior gracilis muscle of the rat has two discrete motor endplate zones. A proximal zone is innervated by short branches of the obturator nerve, and a distal zone is innervated by (usually) two longer branches. Each muscle fiber is innervated at a single motor endplate although a substantial number lie within both endplate zones. In addition, motor units are divided between the two zones. In order to dissociate the role of the denervated endplate from that of the denervated muscle fiber in the promotion of motoneuron sprouting, the distal endplate zone in this model was denervated and the response at the proximal zone was studied. Comparisons were made with partial denervation of the muscle by division of the L4 ventral ramus and with partial denervation of the distal endplate zone. Denervation of the distal endplate zone produced profuse terminal sprouting at the proximal zone whereas division of L4 predominantly produced nodal sprouting at both zones. Partial denervation of the distal zone resulted in nodal sprouts in that zone and again mainly terminal sprouts at the proximal zone. The repeated association of terminal sprouting with division of the motor axons supplying the distal zone together with the knowledge that motor units are distributed between the two zones led to the conclusion that the terminal sprouting was stimulated by the reduction in size of motor units rather than by the presence of denervated muscle fibers in the vicinity of the endplates.

Animals↗
PubMed1985

Fibre-type specificity and effect of thyroid hormone on glucose 6-phosphate dehydrogenase activity in normal and denervated skeletal muscles of the rat.

Glucose-6-phosphate dehydrogenase activity increases following denervation of rat skeletal muscle. The specificity of this effect to muscle fibre type was studied. Basal activity of the dehydrogenase was higher in soleus, a muscle composed predominantly of type I fibres, than in extensor digitorum longus, a muscle composed predominantly of type IIa and b fibres. The enzymatic activity of the soleus was also greater than that of the red (RQ) and white (WQ) portions of quadriceps muscle (predominantly type IIa and type IIb fibres, respectively). Following denervation, glucose-6-phosphate dehydrogenase increased in extensor digitorum longus and RQ, but not in WQ or the soleus. Following chronic treatment of rats with 3,3',5-triiodothyronine, which converts type I muscle fibres to type II, the dehydrogenase activity increased in both denervated soleus and extensor digitorum longus. It is concluded that the effect of denervation on glucose-6-phosphate dehydrogenase activity is selective for type IIa (fast oxidative-glycolytic) muscle fibres.

Animals↗
PubMed1983

Fiber type changes in denervated soleus muscles of the hyperthyroid rat.

The thyroid status of rats is known to influence the histochemical and biochemical myosin adenosine triphosphatase (M-ATPase) activity of the soleus muscle. In the hypothyroid state, denervated soleus muscles are not subject to that influence. Our experiments indicated that in the hyperthyroid state fibers of the denervated soleus muscle show a profound change from acid-stable M-ATPase positive to acid-stable M-ATPase negative. We concluded that this change was induced by the hyperthyroid state and was not neurally mediated.

Adenosine Triphosphatases↗
PubMed1983

Central core degeneration after tenotomy in soleus muscles of hyperthyroid rats.

Tenotomy of the rat soleus muscle is followed by a central degeneration of slow, fatigue-resistant muscle fibers. Previous experiments showed that fast, fatigable fibers of the gastrocnemius when transformed to slow, fatigue-resistant fibers by cross-reinnervation also develop lesions after tenotomy. The experiments described in this communication were carried out to discover whether the susceptibility of fibers to lesions was determined by their fiber type or the nature of their innervation. Rats were rendered hyperthyroid by the administration of sodium 3,3',5-triiodo-L-thyronine (T3) for 7 to 10 weeks. Tenotomy of the soleus muscles was then carried out and the experimental and contralateral muscles were removed and stained for myosin ATPase activity after a further 2 weeks. The hyperthyroid state of each animal was confirmed by the assay of succinate dehydrogenase activity of liver and the contralateral muscle. After acid preincubation, whole muscle fiber type counts of contralateral muscles showed a statistically significant change from a predominantly acid-stable population of fibers to acid-labile fibers. In addition, many fibers of intermediate staining properties were seen. When the experimental muscles were examined, all three varieties of fiber showed central degeneration. The nature of the fiber type change induced by T3 and the role that innervation might play in this is discussed. It was concluded that the susceptibility of fibers to the lesions that follow tenotomy is dependent on the nature of their innervation rather than their fiber type.

Animals↗
PubMed1982

A method demonstrating motor endplates for light and electron microscopy.

The cytochemical localization of acetylcholinesterase activity at motor endplates is commonly employed prior to electron microscopic examination. Methods which involve the use of thiocholine esters often lead to a loss of resolution due to the spread to surrounding tissues of an extremely dense reaction product. A method is presented in which esterase positive sites are revealed by incubation with hexazotized pararosaniline and indoxyl acetate. The osmiophilic property of the reaction product which remains localized to the synaptic cleft allows speedy identification and detailed examination of the endplate at the ultrastructural level. An application of the procedure is also described.

Animals↗
PubMed1981

The response of the rat soleus muscle to tenotomy after dorsal root section.

Both soleus muscles of rats were tenotomized 5-10 days after deafferentation of one side which was achieved by section of the 4th and 5th lumbar dorsal roots. When examined 2 weeks after tenotomy, all experimental muscles showed central degenerative changes in slow fatigue-resistant fibers. These changes were absent from muscles that had been only deafferented. Experimental deafferented muscles examined 6 weeks after tenotomy showed a substantial recovery which was comparable to that seen in tenotomized muscles with intact afferent innervation. It is concluded that (1) deafferentation does not inhibit the recovery of tenotomized fibers, and (2) the loss of afferent fibers plays no part in the protection from central degeneration known to be afforded by denervation of tenotomized muscles.

Afferent Pathways↗
PubMed1980

Survival of satellite cells following exposure to the local anesthetic bupivacaine (Marcaine).

Rat lumbrical muscles were incubated in a concentration of 10(-2) M bupivacaine for 5 or 15 min and examined after further incubation in the absence of the drug for periods totalling 1, 2, and 3h. Electron microscopy showed that muscle fibers and their component organelles and myonuclei underwent a series of irreversible degenerative changes. However, satellite cells retained their normal morphology under similar conditions. It is concluded that satellite cells are responsible for the rapid regeneration of muscles that follows degeneration induced by bupivacaine. The role of satellite cells in muscle regeneration is discussed.

Animals↗
PubMed1980

Early ultrastructural changes in skeletal muscle exposed to the local anaesthetic bupivacaine (Marcaine).

The local anaesthetic drug bupivacaine is known to produce a degeneration in mammalian muscle fibres which is followed by regeneration. In an attempt to define the site of action of this drug and the cell type responsible for the subsequent fibre regeneration, first lumbircal muscles of rats were exposed in vitro to concentrations of 10(-2), 5 X 10(-3), and 10(-3)M bupivacaine for periods ranging from 5 min to 3 h. An electron microscopic study of muscles exposed to 10(-2) and 5 X 10(-3)M bupivacaine revealed an initial supercontraction followed by evidence of severe and probably irreversible injury to plasma membrane, sarcoplasmic reticulum and mitochondria. Myonuclei showed signs of injury early, but satellite cells were found relatively resistant. The basal lamina remained intact throughout and myelinated axons did not suffer damage. However, both endothelial cells of capillaries and fibrocytes showed degenerative changes. Muscles exposed to 10(-3)M bupivacaine showed little change after incubation for 3 h. It is concluded that increased intracellular levels of Ca++ ions may play a part in the pathogenesis of muscle injury induced by bupivacaine and that their source may be the sarcoplasmic reticulum. The role of the satellite cell in the regeneration that follows this injury was not clearly established.

Animals↗
PubMed1978

Changes in length of sarcomeres following tenotomy of the rat soleus muscle.

Tenotomy of the proximal and distal tendons of the soleus muscle of female Wistar rats was performed and sarcomeric length and muscle fascicle length measured. On the first postoperative day muscle bellies were found shortened and their sarcomeric length considerably reduced. Four weeks following tenotomy, although the muscle bellies remained shortened, sarcomeric length was comparable with that of control muscles. Measurement of muscle fascicle lengths at this time showed that those of experimental muscles were nearly 50% less than those of control muscles. It was concluded from these experiments that a reduction of the number of sarcomeres in series had occurred, thus compensating for the reduced length of the muscle belly.

Animals↗