Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Muscle Spindles”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked 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↗
PubMed1997

Expression of myosin heavy chain isoforms in regenerated muscle spindle fibres after muscle grafting in young and adult rats--plasticity of intrafusal satellite cells.

Satellite cells are the myogenic precursor cells of postnatal skeletal muscles. After muscle injury they can proliferate, differentiate, fuse and form myofibres. We have analysed regeneration of distinctly different types of intrafusal fibres in rat muscle spindles. We have introduced the new technique of heterochronous allotransplantation and compared it with the previously used standard autografting method. The allotransplantation method enables one to graft muscles from very young animals; we have used the extensor digitorum longus (EDL) muscles from 2- to 28-day-old rats, which were grafted into EDL muscles of adult inbred recipients. The regenerated "intrafusal" fibres did not express the spindle-specific slow tonic and alpha cardiac-like myosin heavy chain (MyHC) isoforms and they did not exhibit the dual mATPase reaction typical of the nuclear bag2 fibres and the characteristic regional differences in MyHC expression and in the mATPase reaction of nuclear bag1 and nuclear bag2 fibres. On the other hand, they expressed either fast twitch or slow twitch/beta cardiac MyHC isoforms and exhibited an alkali or acid stable mATPase reaction along their whole length, like extrafusal fast type 2 and slow type 1 muscle fibres, respectively. In all regenerated muscle spindles only motor, but no sensory axons were found. More than 85% of muscle spindles in our sample contained regenerated spindle fibres of the same extrafusal fibre type (either type 2 or type 1), in contrast to control muscle spindles, which always contained intrafusal fibres of three different intrafusal fibre types (nuclear bag1, nuclear bag2 and nuclear chain fibres). There were no differences in MyHC expression and mATPase activity between spindle fibres regenerated in grafts taken from young rats of various ages or between allotransplanted and autotransplanted EDL muscles. The present results demonstrate that regenerated "intrafusal" fibres resemble, according to MyHC expression, extrafusal fast or slow muscle fibres. It can thus be concluded that intrafusal satellite cells derived from distinctly different nuclear bag1, nuclear bag2 and nuclear chain fibres show great plasticity, as their MyHC expression can be respecified towards the extrafusal muscle fibre phenotype by foreign alpha-motor innervation.

Animals↗
PubMed1983

Ultrastructure of muscle spindle in congenital myotonic dystrophy. A study of preterm infant muscle spindles.

The muscle spindle in the preterm infants with congenital myotonic dystrophy consisted of numerous, unfused intrafusal fibers. These fibers showed immature myofilament arrangement at 27 weeks but had the nuclear arrangement of bag and chain type. The motor endings were very sparse while prominent sensory endings were seen. At 34-37 weeks, even though the muscle fibers were unfused, the nuclear bag and chain fibers could be differentiated by the presence and absence of M line. Immature motor endings were seen at this stage. In conclusion, the muscle spindle in the preterm infants is immature.

Cytoskeleton↗
PubMed1988

Effects of the infraorbital nerve-transection on the formation of Ia fibers in muscle spindles of the masseter muscle in developing mice.

The effect of the transection of the infraorbital nerve on d 20 after birth on the formation of the annulospiral ending of Ia fibers of muscle spindles in the masseter muscle was investigated in developing mice. On the 20th d after the operation, there were significant differences between control and treated animals in the ratio of muscle spindles with non-coiled endings to all muscle spindles, and the ratios of muscle spindles with non-coiled endings in the masseter muscle on the operated and sham-operated sides were about equal to each other. On the 30th d after the operation, the ratio for the masseter muscle on the operated side was approximately twice that for the one on the sham-operated side. The ratio for the operated side was about equal to that for 15-d-old control mice, and about twice that for 20-d-old control animals. Thus, the present results indicate that disorder of sensory inputs following the transection of the infraorbital nerve leads to degeneration and/or inhibition of the formation of annulospiral endings in muscle spindles of the masseter muscle, and suggest that disorder of the masticatory mechanism may be caused by the degeneration and/or inhibition of the formation of the endings in many muscle spindles of the masseter muscle.

Animals↗
PubMed1997

Microscopic study of muscle spindles in recti muscles of human fetal eye.

Muscle spindles of recti muscles of the eyebulb appear in the 11th week of intrauterine life. At first, the spindle manifests the stage of myotube with 2-3 intrafusal fibers and is surrounded by the monolayer of internal capsule. In the course of subsequent development, the number of intrafusal fibers increases. Internal capsule begins to demonstrate two layers (14th week) and, then, external capsule develops (17th week). In the 20th week, mature spindles have been observed with a multilayered external capsule.

Embryonic and Fetal Development↗
PubMed2003

[Histochemical study of the sensory endings of muscle spindles in rat longissimus muscles].

Most studies concerning the structure and function of muscle spindles have utilized the hind limbs of experimental animals. However, little is known about muscle spindles of the back muscles. The purpose of this study was to investigate the sensory innervation of muscle spindles of the paravertebral muscle in the rat. The subjects were 10 normal male rats. The longissimus muscles were isolated and frozen in cooled isopentane (-160 degrees C), and serial transverse sections were made with a cryostat. Histochemical preparations were then made using nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) stain and modified Gomori-trichrome stain. The muscle spindles in each segment were identified microscopically by observing the equatorial and polar regions. NADH-TR staining was employed to distinguish nuclear bag1, nuclear bag2, and nuclear chain intrafusal muscle fibers. A total of 20 spindle poles were surveyed. The mean polar length of intrafusal fibers as well as that of each region (A, B, and C) were measured. NADH-TR staining also demonstrated the terminal sites of sensory fibers along intrafusal fibers. All spindle poles surveyed were innervated by secondary sensory fibers in addition to primary sensory fibers. Eight spindle poles were intermediate type muscle spindles that were innervated by one primary sensory fiber and one secondary sensory fiber. Twelve spindle poles were complex type muscle spindles that were innervated by one primary sensory fiber and multiple secondary sensory fibers. The mean length of the A region was 223.1+/-37.9 microm (n=8) for intermediate type spindles and 493.8+/-157.0 microm (n=12) for complex type spindles. The length of the A region was significantly longer in the complex type spindles than in the intermediate type spindles (p<0.001). The results suggest that the innervations of secondary sensory fibers were well developed in the longissimus muscle spindles in the rat. The morphological features of muscle spindles of the longissimus muscle may represent the structural basis for qualitatively different afferent discharges that relate to the characteristic types of locomotion served by paravertebral muscles.

Animals↗
PubMed1993

Influences on the gamma-muscle spindle system from muscle afferents stimulated by KCl and lactic acid.

It is known that accumulation of contraction metabolites in muscles stimulates group III and IV afferents and induces excitation of gamma-efferents to the homonymous muscle. The aim of the present study was to investigate whether increased concentrations of lactic acid and KCl in one muscle may influence the activity in primary and secondary muscle spindle afferents (MSAs) from the chemically affected muscle and from surrounding muscles. The experiments were made on 7 cats anesthetized with alpha-chloralose. Recordings were made simultaneously from 2-8 single MSAs from the triceps surae (GS) and the posterior biceps and semitendinosus muscles (PBSt). The mean rate of firing and the depth of modulation of MSA responses to sinusoidal stretching of the receptor-bearing muscles were determined. Responses of 27 primary MSAs (11 from PBSt and 16 from GS) were recorded. On 24 of these clear-cut alterations in sinusoidal response were evoked by injection of 1 ml of KCl (50-600 mM) or 1 ml of lactic acid (20-200 mM) into the artery supply of the GS muscle. Also, all secondary MSAs recorded (4 from PBSt and 1 from GS) showed sizable effects to increased intramuscular concentrations of KCl and/or lactic acid. On both primary and secondary MSAs, from GS as well as from PBSt muscles, nearly all effects observed were compatible with activation of static fusimotor neurons. Effects on MSAs were completely abolished when the ipsilateral L7-L6 ventral roots were cut and when the GS nerve was anesthetized. Intravenous injections of KCl and lactic acid, as well as arterial injections of 0.9% NaCl, were ineffective in changing the MSA responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Local↗
PubMed1982

One-bag-fiber muscle spindles in tenuissimus muscles of the cat.

Over 150 complete and 139 incomplete single muscle spindles were examined in serial transverse sections of cat tenuissimus muscles in search for spindles lacking one of the two types of nuclear bag intrafusal fiber. Several histochemical reactions were used to type the intrafusal muscle fibers and assess the spindle motor and sensory innervation. One complete spindle lacked a bag1 fiber, and another spindle lacked a bag2 fiber. Several incomplete spindles also lacked bag1 fibers. In addition, ten double tandem spindles contained one capsular unit each that lacked the bag1 fiber, and one triple tandem spindle had two such capsules. All one-bag-fiber spindles had primary sensory innervation, but none had secondary sensory innervation. Their motor innervation was similar to that of the usual two-bag-fiber spindles in the number and disposition of intrafusal motor endings. It is unclear whether the one-bag fiber spindles, either single or tandem-linked, are products of an aberrant spindle development or represent a true anatomical and functional subcategory of the cat muscle spindle.

Adenosine Triphosphatases↗
PubMed1998

Muscle spindle activity following muscle tendon vibration in man.

Muscle spindle primary endings originating from the Tibialis anterior, Extensor Digitorum Longus and Lateral Peroneal muscles were recorded by the microneurographic technique. Their resting activity and stretch sensitivity after muscle tendon vibration (80 Hz, 30 s) were compared with those in the previbratory period. Most of the units (73%) exhibited a decreased spontaneous firing rate whereas a few others either conserved (13.5%) or increased (13.5%) their resting discharge after vibration. A complete recovery necessitated 40 s. The static stretch sensitivity of the units was decreased during the 3 s following vibration exposure and returned to the control level (about 14 s). The results are discussed in the light of previous psychophysiological studies reporting an altered position sense and a development of involuntary muscle contractions in postvibratory periods.

Adult↗
PubMed1999

Vibration sensitivity of cat muscle spindles at short muscle lengths.

Experiments are described in which the vibration sensitivity was tested for primary and secondary endings of soleus muscle spindles of the anaesthetised cat. The vibratory stimulus was applied longitudinally to the muscle tendon and, after locating the site of the spindle in the muscle, applied transversely to muscle fibres directly overlying the spindle. All measurements were made with the muscle slack, at 20 mm shorter than its maximum physiological length (Lm-20 mm). Spindles were separated into two groups: spontaneous spindles, which maintained background activity at this length, and silent spindles, which did not. Two forms of muscle conditioning were used: hold-long, in which the muscle was stretched by 5 mm, contracted and then returned to the test length, and hold-test, in which a conditioning contraction was given at the test length. After hold-test, most spindles responded to longitudinal vibration; after hold-long, most did not. This difference in responsiveness was attributed to the presence or absence of slack in intrafusal and extrafusal fibres, due to the muscle's thixotropic property. When the vibration was applied transversely, at a site directly overlying the spindle, responses of silent spindles continued to show thixotropic behaviour, whereas responses of spontaneous spindles were almost independent of the form of muscle conditioning. It is proposed that the ability of spontaneous spindles to maintain background activity at short muscle lengths is due to connective tissue or elastic fibre links between the sensory ending and the spindle capsule. The vibratory stimulus, applied transversely, reaches the sensory ending via these strands which, as non-muscle tissue, do not alter their mechanical state as a result of muscle conditioning.

Animals↗
PubMed1983

Multiple-bag-fiber muscle spindles in tenuissimus muscles of the cat.

Over 300 complete and incomplete cat muscle spindles were examined in serial transverse sections of tenuissimus muscles in search of spindles with more than two nuclear bag intrafusal muscle fibers. Several histochemical and histological stains were used to identify the intrafusal fibers and assess their motor and sensory innervation. About 13% of the spindles contained either three or four bag fibers rather than the usual two. Every multiple-bag-fiber spindle possessed at least one nuclear bag1 and one nuclear bag2 fiber. The supernumerary bag fibers were either another bag1 and/or bag2 fiber, or a mixed bag fiber. The extra bag fibers had the usual morphologic and histochemical properties of cat nuclear bag fibers. All multiple-bag spindles received primary sensory innervation, and most had secondary sensory endings in addition. Their motor pattern was similar in the number, appearance and disposition of intrafusal motor endings to that of the usual two-bag-fiber spindles. Bag fibers of the same kind shared motor nerve supply in three multiple-bag spindles in which tracings of individual motor axons were obtained histologically. It is unclear whether any functional advantage is conveyed to a muscle spindle by its having more than one bag1 and one bag2 fiber.

Adenosine Triphosphatases↗
PubMed1982

Development of immunohistochemical characteristics of intrafusal fibres in normal and de-efferented rat muscle spindles.

Intrafusal muscle fibres in adult muscle spindles differ in their myosin composition. After selective motor denervation intrafusal muscle fibres develop mature ultrastructural characteristics. In order to evaluate the role of fusimotor innervation on the maturation of the myosin composition of intrafusal muscle fibres we have examined with immunohistochemical techniques i) the postnatal development of muscle spindles in new-born rats and in 7-21 day old rats; ii) muscle spindles in the EDL of 21-day-old rats de-efferented at birth. For the characterization of myosins in intrafusal fibres we used three myosin antisera: antipectoral myosin, antiheart myosin and antiheart myosin adsorbed with muscle powder from the soleus muscle of guinea pig. We show in this study that during development intrafusal fibres change immunoreactivity and that in the absence of motor innervation bag fibres do not fully develop the myosin characteristics of control spindles. We conclude that the maturation of bag1 and bag2 fibres apparently requires next to the inductive influence of sensory axon terminals the presence and activity of fusimotor axons.

Animals↗
PubMed1990

[Ultrastructure of the muscle spindles in the extraocular muscles of pigs].

To define the morphological properties of muscle spindles relative to the accurate control of eyeball movement, muscle spindles were investigated in 6 extraocular muscles of three white pigs by an electron microscope. The muscle spindles were composed mainly of a thin outer capsule, nuclear bag and chain fibers. The bag fibers seem to be slow fibers and the chain fibers to be fast fibers in the external fashion, in so far as the former has a greater myofibril density than the latter. The intrafusal muscle fibers were innervated by three categories of nerve terminals; annulospiral and flower spray sensory terminals and gamma motor terminals. The annulospiral terminal was coiled sparsely on the bag fiber and densely on the chain fiber. The cross terminals were found in the pairing muscle fibers. We frequently observed that the satellite cells were controlled by the sensory terminals. It was also frequently observed that the muscle spindles were composed of only one intrafusal bag muscle fiber. It was suggested that the extraocular muscle spindles of the pig remained a primordial profile in the structure.

Animals↗
PubMed1997

Increased intramuscular concentration of bradykinin increases the static fusimotor drive to muscle spindles in neck muscles of the cat.

The aim of the present study was to investigate if increased intramuscular concentrations of bradykinin (BK) in one muscle influence the activity in primary and secondary muscle spindle afferents (MSAs) originating from both ipsi- and contralateral muscles, via fusimotor reflexes. The ipsilateral trapezius (TR) and the splenius (SP) muscles were subjected to sinusoidal stretches and 2-3 MSAs were simultaneously recorded from these muscles. Responses of 29 MSAs (15 SP and 14 TR) were registered in five adult cats anaesthetised with alpha-chloralose. Intramuscular injections of 0.5 ml BK (6-86 micrograms/ml) were administered to both the ipsi- and contralateral SP and TR muscles. Similar doses of BK (5-10 micrograms) have been shown to induce muscle pain when injected into the temporal muscle in man. The responsiveness of the MSAs to the injections of BK was 86% and 87.5% from the contralateral TR and SP muscles, respectively. The effects were predominantly static onto the MSAs. The duration of the effects was on average 3.5-4 min, however some effects lasted for more than 15 min. The effects were always abolished after cutting the nerve to the injected muscle. The large majority of the spindle afferents were unresponsive to i.m. Tyrode injections (23 of 29). For the afferents that were responsive to injection of Tyrode, the effects were always considerably smaller and with shorter duration than those evoked by BK injections. Thus, increased intramuscular concentrations of BK may excite primary and secondary MSAs from ipsi- and contralateral muscles, via fusimotor reflexes evoked most probably by activity in chemosensitive muscle afferents. The results are discussed in relation to a recent hypothesis on pathophysiological mechanisms behind genesis, spread and perpetuation of muscle tension and pain in chronic musculoskeletal pain syndromes.

Animals↗