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At least 19 recordsLinked to original sources
PubMed1979

Morphometric comparison of capillaries in muscle spindles, nerve, and muscle.

Morphometric study was performed on transverse sections of microdissected muscle spindles from rabbit tenuissimus muscles. It showed a statistically significant difference in size and structure between the intrafusal capillaries and those of extrafusal muscle. The former are larger in diameter, circumference, and area due to a proportionate increase in the number of endothelial cells. Vesicles within spindle endothelial cells are fewer, mitochondrial counts are greater, but in proportion to the increased number of endothelial cells, intercellular junctions are tight and pericyte coverage is greater. The basement membrane around endothelial cells and pericytes is thicker and more often multilayered. The endoneurial capillaries of tenuissimus intramuscular nerve are morphologically identical to intrafusal capillaries. The similarity of the capillaries of spindles to those in brain suggests that a blood-nervous system barrier extends from brain into the peripheral nerves and muscle spindles.

Animals↗
PubMed1979

[Decrease in the frequency of muscle spindle discharges during muscle stretching].

When studying responses of 500 muscle receptors to stretching of the m. triceps of the cat deafferented hindlimb, 23 cases revealed a transient decrease in the firing rate (DFR) of muscle spindles' receptors. The DFR occurs in the same receptor at different forms and rates of stretching approximately at the same area of stretching ("the DFR area"). When increasing the rate of stretching, the DFR effect is enhanced. The DFR effect seems to be due to a short-lasting unloading of the spindle area which contains the receptor terminals. The unhomogenous structure of the extrafusal muscle as well as various mechanical properties of the intrafusal muscle fibers can provide necessary conditions for the above effect.

Animals↗
PubMed1976

[Muscle spindles in denervated and reinnervated m. soleus of the rat. I. Changes in number, distribution and length of muscle spindles].

After a transient or permanent unilateral denervation of the soleus muscle of the rat the number, distribution and length of muscle spindles were determined. The results were compared with those of the contralateral innervated muscle and with the data received from investigating soleus muscles of normal uninjured rats. Denervation (with or without reinnervation) reduces the number of muscle spindles by nearly 50%. The typical uniform distribution of muscle spindles in the muscle remains almost unchanged. The remaining muscle spindles grow longer. The same findings are observed in the contralateral still innervated muscles, too. Consequently a comparison of the denervated (reinnervated) muscle exclusively with its contralateral muscle does not show different counts of muscle spindles. Therefore in such investigations the contralateral muscle is of dubious value as a mean of control. As regards number, distribution and length of muscle spindles there exist only small differences between the various strains of rats.

Animals↗
PubMed1975

The responses of muscle spindles in sheep extraocular muscles.

1. Responses from de-efferented muscle spindles in sheep extraocular muscles have been recorded in the Gasserian ganglion using glass microelectrodes. 2. The afferent fibre conduction velocities ranged from 32 to 106 m/sec and most were intermediate. The distribution was unimodal. 3. The afferent responses to ramp stretches and longitudinal vibration of the muscle could not be divided into two groups, but both the dynamic indices and vibration sensitivities of the afferents increased with their conduction velocities. 4. Injection of suxamethonium did not help to classify afferents with intermediate conduction velocity. 5. It is concluded that the afferents from sheep extraocular muscle spindles form a single population whose properties are correlated with their nerve fibre diameters.

Animals↗
PubMed1979

Muscle spindle supply to the masticatory muscles in the Japane ermine (Carnivora).

Histological examination of the jaw muscles of the Japanese ermine showed that 4 jaw-closing muscles have 13 muscle spindles on one side of the face. The temporal muscle has 99 muscle spindles, 68 being in the anterior vertical and 31 in the posterior horizontal belly. The masseter muscle has 33 muscle spindles, 23 being in the profound and 10 in the superficial belly. The medial pterygoid muscle has 7 muscle spindles and the zygomaticomandibular muscle contains 4 muscle spindles. The lateral pterygoid and the jaw-opening muscles have no spindles.

Animals↗
PubMed1979

An ultrastructural study of nerve terminal degeneration in muscle spindles of the tenuissimus muscle of the cat.

Muscle spindles in the tenuissimus muscle of the cat were studied between 12 and 168 h after cutting or freezing the nerve to this muscle. Degenerative changes in sensory and motor nerve terminals on intrafusal muscle fibres were observed using the electron microscope. Comparisons were made with spindles from unoperated or sham-operated cats. The earliest degenerative changes were seen in sensory and motor terminals at 20-24 h after the lesion. No nerve endings were seen by 114 h after denervation. The most consistent initial signs of degeneration were: (1) the presence of abnormal mitochondria and dense bodies in sensory terminals, and (2) a decrease in the number and clumping of synaptic vesicles combined with an increase in glycogen and neurofilaments in motor endings. Intrafusal fibres participate in the removal of degenerating sensory endings. Schwann cells phagocytose degenerating motor terminals. The disappearance of nerve terminals precedes the complete degeneration of preterminal myelinated fibres within the muscle spindle.

Animals↗
PubMed1979

Modification by lidocaine of the discharges of primary endings of muscle spindles in cat tenuissimus muscle.

The effects of lidocaine (1--20 microgram/ml) on afferent discharge patterns of primary endings of muscle spindles in cat tenuissimus muscle were investigated. Discharge from the endings, recorded in Ia afferent axons, was evoked by ramp stretch of the muscle, stimulation of single static or dynamic fusimotor axons or by a combination of stretch and fusimotor stimulation. Spontaneous discharge of the endings at the initial length of the muscles was reduced by 2--5 microgram/ml and abolished by 10--15 microgram/ml lidocaine. The static but not the dynamic discharge elicited by muscle stretch was blocked by concentrations of 10--15 microgram/ml. The same concentrations abolished static and dynamic fusimotor influences on primary ending discharge. However, in one experiment where the spindle was microscopically observed, fusimotor stimulation still resulted in contraction of the intrafusal muscle even when fusimotor stimulation failed to elicit changes in discharge response patterns of the primary endings. These findings indicate that lidocaine interferes with the encoding mechanism prior to block of impulse conduction in either the fusimotor or afferent axons.

Animals↗
PubMed1978

Effect of diazepam on the gamma motor system indicated by the responses of the muscle spindle of the triceps surae muscle of the decerebrate cat to the muscle stretch.

The experiments were performed on 37 intercollicularly decerebrate cats. The triceps surae muscle was subjected to trapezoidal stretches of 10 mm/s or 2 mm/s over a length of 14 mm. The reflex arc was left partially or fully intact. The effect of diazepam given intravenously on the discharge frequencies of group Ia afferent fibres from muscle spindles in the belly of the triceps surae muscle was studied. Diazepam depressed both the dynamic and the static gamma motor responses. When gamma motor fibres were selectively blocked by procaine a parallel shift of the tension-extension curve was observed. From comparison of the effect of procaine and diazepam on the phasic and static responses of the muscle spindle it was concluded that directly after the injection of diazepam the gamma motor activity was completely abolished at a dose as low as 0.1 mg/kg whereas the alpha motor system was only partly depressed even at higher doses. Differences in the effect of diazepam on the dynamic and static gamma system respectively, could not be found.

Action Potentials↗
PubMed1976

[Responses of the muscle spindles of tenotomized and hypertrophied muscles to stretch and vibration].

Responses of primary and secondary endings of muscle spindles were studied after tenotomy and hypertrophy in the cat soleus muscles. Under constant load (100 g) background activity of primary endings in a control muscle was 17 +/- 1.5 imp/s. It did not change in hypertrophic muscle and increased after tenotomy to 26 +/- 1.5 imp/s. Responses of secondary endings did not change under the same conditions. The frequency of a response from primary and secondary endings of tenotomized and hypertrophic muscles were higher during dynamic and static phase of stretching as compared to response of normal muscle spindles. Primary endings of tenotomized and hypertrophic muscles were able to repeat vibration up to 200 Hz, while secondary endings responded only with some increase in the discharge frequency.

Animals↗
PubMed1979

Occurrence and distribution of muscle spindles in masticatory and suprahyoid muscles of the rat.

The occurrence and distribution of muscle spindles was studied in histochemically and conventionally stained serial cross sections of 6-week-old and adult rat masticatory and suprahyoid muscles. Spindles were present in moderate to large numbers in jaw closers, but they were absent in jaw openers and two of four muscles of an accessory suprahyoid group. In jaw closers, 67% or more of the total spindle population was concentrated relatively distant from the temporomandibular joint, in muscle portions which contained large numbers of extrafusal fibers reacting strongly for oxidative enzymes. Because of their location, spindles in these portions should be stretched more and, subsequently, should respond with a greater afferent discharge at any given muscle length than spindles situated nearer to the joint. Spindles in jaw closers, especially the medial pterygoid and deep masseter, often occurred in clusters and complex forms near the terminal branching of intramuscular nerve trunks. No such concentrations were seen in the two muscles of the accessory suprahyoid group that had spindles. The association in jaw closers of spindles with extrafusal fibers high in oxidative enzyme activity is consistent with the view that spindles are the sensory component of a reflex system that recruits these fibers for finely-graded contractions in response to small internal length-changes of the muscle (Botterman et al., '78); however, in jaw openers and two muscles of the accessory suprahyoid group, the absence of spindles, coupled with the presence of large populations of extrafusal fibers high in oxidative enzyme activity, is not easily reconciled with this concept.

Animals↗
PubMed1978

Myelinated nerve fiber supply and muscle spindles in the respiratory muscles of cat: quantitative study.

The present study was undertaken to provide quantitative data on the myelinated fibers of the phrenic and intercostal nerves and the number of spindles in the main respiratory muscles of the cat. The myelinated component of the phrenic and intercostal nerves was studied in the cat. Histograms of sequency distributions as a function of nerve fiber diameter were established for normal nerves. Certain nerves were then examined 35 to 40 days after excision of the dorsal spinal ganglia. The muscle spindles of the corresponding muscles were counted and localized, and, on the basis of several morphological criteria, were classified with those usually described in the interosseous muscles. The study of the nerves, as that of the spindles, demonstrates clear differences of proprioceptive innervation among the respirator muscles. The lateral part of the diaphragm and the Triangularis sterni have practically no spindles. The external muscles of the first thoracic spaces are very rich in spindles. Respiratory muscles can be ranged in an almost continuous manner between these two extremes.

Animals↗
PubMed1977

Histochemical study of normal human muscle spindle. Histochemical classification of intrafusal muscle fibers and intrafusal nerve endings.

Normal muscle spindles of human skeletal muscle were studied histochemically. 1) Four histochemical types of intrafusal muscle fibers were classified by ATPase stain: Bag I fiber, Bag II fiber, Chain I fiber and Chain II fiber. Moreover, two types of nuclear bag fibers were classified by NADH Tetrazolium Reductase stain and PAS stain: Bag I fiber and Bag II fiber. 2) Three kinds of fusimotor endings were verified by the cholinesterase technic: en plaque, en grappe and diffuse endings. 3) Two kinds of fusisensory endings were verified by NADH TR stain and also electron-microscopically: primary and secondary sensory endings.

Adenosine Triphosphatases↗