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Objective To locate the distribution of muscle spindles in tibialis anterior (TA) and extensor digitorum longus muscle (EDL) and the anchoring mode of muscle spindles in skeletal muscles, and perform statistics analysis of their morphological character by anatomical parameters. Methods Five adult wild type C57BL/6 mice were sacrificed, and TA and EDL were dissected and frozen with improved ultra-low temperature cryopreservation technology avoiding myofibers damaged by possible ice crystal. Continuous frozen transections were obtained and operated by HE staining, followed by microimaging to spot the muscle spindles location. Some parameters including regions length and cross section area (CSA) of muscle spindles were noticed for the discovery of some general characteristics of spindles by statistics. Results For TA and EDL, the scattered characters of muscle spindles were distributed as follows: the spindles were located at the upper third of the mid-belly of both TA and EDL from caudal to rostral position, while near the enter point to muscle of the deep peroneal nerve in dorsal-ventral orientation. The peripheral of muscle spindles anchored to extrafusal fibers to hold in the muscle. And in term of length, region A, connected with sensory nerve ending, demonstrated a significant correlation with region B, which located at the poles of region A and twined by motor nerve ending (correlation index = 0. 75) when considering the muscle spindles with four intrafusal fibers only. And no correlation was discovered in any others pairwise parameters. Conclusion The scattered diagram of muscle spindles in TA and EDL of C57BL/6 mice might provide anatomic basis for evaluation of lower limb motor function, especially for the spinal cord injury and recovery research. And the correlationship between the length of region A and B might improve exploring the variability of electrophysiological characters.
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Abstract Aim: The present study aimed to compare the strength performance and the neuromuscular activity during one maximum repetition test (1RM), and the maximum voluntary isometric contractions (MVIC) performed with whole-body vibration (WBV), local vibration (LV), and no vibration (NV). Methods: The sample consisted of 15 males, experienced in strength training for at least 6 months, which performed all strength tests in the barbell curl exercise across randomized trials on the following conditions: NV, WBV, and LV. During all tests, the normalized root means square values of the electromyographic signals (EMGRMS) of the biceps brachii and brachioradialis were recorded and compared between the conditions. The one-way ANOVAs with repeated measures were used to compare the results of 1RM and MVIC tests and the normalized EMGRMS between the conditions. When necessary, a post hoc Scott-Knott test was used to identify the differences reported in the ANOVAs. The significance level adopted was α < 0.05. Results: The EMGRMS response of the biceps brachii and brachioradialis muscles during the 1RM and MVIC tests presented significantly higher values at LV compared to WBV, and NV (p < 0.001). The 1RM tests, and the MVIC results were similar between conditions (p = 0.9803; p = 0.061, respectively). Conclusion: These results indicate that the application of MV was not sufficient to increase strength performance.
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Humans , Exercise , Muscle Spindles , Electromyography/instrumentation , Resistance Training/instrumentation , Isometric ContractionABSTRACT
SUMMARY: This study aimed to accurately localize the location and depth of the centre of the highest region of muscle spindle abundance (CHRMSA) of the triceps brachii muscle. Twenty-four adult cadavers were placed in the prone position. The curve connecting the acromion and lateral epicondyle of the humerus close to the skin was designed as the longitudinal reference line (L), and the curve connecting the lateral and the medial epicondyle of the humerus was designed as the horizontal reference line (H). Sihler's staining was used to visualize the dense intramuscular nerve region of the triceps brachii muscle. The abundance of muscle spindle was calculated after hematoxylin and eosin stain. CHRMSA was labelled by barium sulphate, and spiral computed tomography scanning and three- dimensional reconstruction were performed. Using the Syngo system, the projection points of CHRMSA on the posterior and anterior arm surface (P and P' points), the position of P points projected to the L and H lines (PL and PH points), and the depth of CHRMSA were determined. The PL of the CHRMSA of the long, medial, and lateral heads of the triceps brachii muscle were located at 34.83 %, 75.63 %, and 63.93 % of the L line, respectively, and the PH was located at 63.46 %, 69.62 %, and 56.07 % of the H line, respectively. In addition, the depth was located at 34.73 %, 35.48 %, and 35.85 % of the PP' line, respectively. These percentage values are all the means. These body surface locations and depths are suggested to be the optimal blocking targets for botulinum toxin A in the treatment of triceps brachii muscle spasticity.
RESUMEN: Este estudio tuvo como objetivo localizar con precisión la ubicación y la profundidad del centro de la región más alta del huso muscular (CHRMSA) del músculo tríceps braquial. Se colocaron veinticuatro cadáveres adultos en posición prona y se designó la curva que conecta el acromion y el epicóndilo lateral del húmero cerca de la piel como la línea de referencia longitudinal (L), y la curva que conecta los epicóndilos lateral y medial del húmero fue designada como la línea de referencia horizontal (H). Se usó la tinción de Sihler para visualizar la región nerviosa intramuscular densa del músculo tríceps braquial. La abundancia de huso muscular se calculó después de la tinción con hematoxilina y eosina. CHRMSA se marcó con sulfato de bario y se realizó una tomografía computarizada espiral y una reconstrucción tridimensional. Usando el sistema Syngo, fueron determinados los puntos de proyección de CHRMSA en la superficie posterior y anterior del brazo (puntos P y P'), la posición de los puntos P pro- yectados en las líneas L y H (puntos PL y PH) y la profundidad de CHRMSA. Los PL de la CHRMSA de las cabezas larga, medial y lateral del músculo tríceps braquial se ubicaron en el 34,83 %, 75,63 % y 63,93 % de la línea L, respectivamente, y el PH se ubicó en el 63,46 %, 69,62 %, y 56,07 % de la línea H, respectivamente. La profundidad se ubicó en el 34,73 %, 35,48 % y 35,85 % de la línea PP', respectivamente. Estos valores porcentuales son todas las medias. Se sugiere que estas ubicaciones y profundidades de la superficie corporal son los objetivos de bloqueo óptimos para la toxina botulínica A en el tratamiento de la espasticidad del músculo tríceps braquial.
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Humans , Male , Female , Adult , Middle Aged , Aged , Muscle, Skeletal/anatomy & histology , Muscle Spasticity , Arm/innervation , Cadaver , Muscle, Skeletal/innervation , Muscle, Skeletal/diagnostic imaging , HumerusABSTRACT
Objective:To observe the denervation and reinnervation of the neuromuscular junction (NMJ) and muscle spindle after sciatic nerve crush in mice.Methods:From January, 2019 to October, 2019, 18 C57BL/6 mice were randomly and evenly divided into injured groups (sciatic nerve crush group, 12 mice) and control groups (sham group, 6 mice). Mice in the injured group were sacrificed at day-1, day-2, day-3 and 4 weeks after the sciatic nerve injury. Mice in the control group were sacrificed at day-3 and 4 weeks from the day of experiment. The tibialis anterior muscles with crushed nerve were collected for immunohistochemistry staining by neurofilament (NF), synaptophysin (Syn) and α-bungarotoxin (α-BTX). Data were analysed by unpaired t-test. P<0.05 was considered significant difference. Results:The completely denervation of NMJ reached (92.4±8.85)% at day-3 after the nerve crush, compared with (5.19±1.32)% in the control group ( P<0.05). However, the muscle spindle lost γ-motor neuron innervation at day-2 after the nerve crush and completely denervated at day-3 after the surgery. For the reinnervation, no difference of no reinnervation of NMJ [(3.02±0.78)% vs. (4.22±2.08)%], partial reinnervation of NMJ [(6.44±1.91)% vs. (7.94±2.12)%] and completely reinnervation of NMJ [(90.54±10.44)% vs. (87.84±13.89)%] were observed between the control group and the injured group 4 weeks after the injury. While, for the muscle spindle, only the acetylcholine receptors at each end were partly reinnervated. The innervation of the middle part of the muscle spindle was thin and discontinued without typical spiral winding structure. Conclusion:The denervation speed of NMJ and muscle spindle was comparable after the peripheral nerve injury. The γ-motor neuron lost innervation ahead of the sensory neuron in the muscle spindle. The reinnervation of NMJ is earlier than that of the muscle spindle, and the re-innervation of the γ-motor neuron is prior to the sensory neuron in the muscle spindle.
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@#Spasticity often results in motor dysfunction, lowering individual abilities of daily living, and limitation of social particitation of the patients, prolonging function recovery, deteriorating quality of life. Drug is helpful to improve spasiticity and reduce complications. But there are some adverse effects in cognition function. Individual medication should be recommended as proposal.
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Objective To investigate changes induced by hindlimb unloading in morphology of nerve endings in soleus muscle spindles.Method Hindlimb unloading model was simulated by tail suspension in female rats.Fast silver-staining was used to observe morphology of nerve endings of single muscle spindle in 7 d,14 d,21 d and 28 d tail-suspended and control rats.Result Nerve endings of muscle spindles in control rats were intact and clear,and there was no obvious abnormality in single soleus muscle spindle of 7 d tail-suspended rats.Slight fragmentation of nerve endings was observed in Equatorial Region of soleus muscle spindle in 14 d tail-suspended rats,while reduction in density and disruption of nerve endings were observed in soleus muscle spindle in 21 d tail-suspended rats.Serious degeneration and distortion of nerve endings were found in soleus muscle spindle in 28 d tail-suspended rats.Conclusion Hindlimb-unloading can induce time-related changes in morphology of nerve endings of muscle spindle in rats soleus muscle.
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Objective To observe the effect of inosine on afferent discharge of muscle spindle.Methods The afferent discharge of isolated toad muscle spindle was recorded using air-gap technique.The effects of inosine on the discharge rate of muscle spindle was observed.Results After administration of 0.2mmol/L,0.4mmol/L and 0.8mmol/L inosine,the spontaneous discharge of muscle spindle increased from(0.86?(0.12))Hz,(0.88?(0.12))Hz and(0.85?0.10)Hz to(11.42?2.48)Hz,(21.75?3.03)Hz and(32.25?4.08)Hz,respectively.Conclusion Inosine can increase the afferent discharge rate of muscle spindle,and this effect is dose-dependent.
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Neurotrophin 3(NT-3) is required for proprioceptive neuron survival and physiological function.During embryonic development,NT-3 deficient in developing muscle dues to loss of proprioceptive neurons in dorsal root ganglia or their axons by apoptosis,and then to the absence of muscle spindles.The chemoattractant effect of NT-3 on dorsal root ganglion axons has been improved that NT-3 is a key requirement for the development of proprioceptive projection to motor neurons.Depletion of NT-3 in the period of adult educes to the decline of the function of proprioception.NT-3 has extensive protective effect on proprioceptive neuron and enhances them to restore the normal physiological function under the pathological state.
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Objective To study the effect of gallamine triethiodide (GT) on the increased afferent discharge from the muscle spindle caused by succinylcholine (SCh). Methods The nervous filaments of rats were separated from tibial nerve innervating the gastrocnemius muscle, and afferent discharge from the muscle spindle was recorded. SCh of a certain dose was injected after 4 minutes of injection of a certain dose of GT. The effect of suppression by GT on the increased afferent discharge from the muscle spindle caused by SCh was measured by counting the decrease in discharge peak frequency (DPF) and maximum increase frequency (MIF) and by counting the time of peak frequency (PF) appearing delayed than the controls. Results When the dose of SCh was 0.005mmol/kg, the dose of GT was 0.005mmol/kg, 0.010mmol/kg and 0.020mmol/kg, DPF reduced to 67.2%, 52.5% and 37.1% of the controls, respectively; MIF reduced to 61.4%, 40.2.% and 25.4%; PF appearing time delayed 43.9s, 64.3s and 80.4s than the controls. When the dose of GT was 0.005mmol/kg but the dose of SCh was 0.010mmol/kg, DPF and MIF reduced to 83.3% and 77.8% of the controls, respectively; PF appearing time delayed 22.5s than the controls. Conclusion GT has a remarkably suppressive effect on the increase in afferent discharge from the muscle spindle induced by SCh. The suppression of GT is dose-dependent, and the action of SCh and GT on muscle spindle is in competition.
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ObjectiveTo study wether muscle spindle afferents have the regulating effects on res piratory movement. MethodsExperiments were performed on 36 anesthetized, immobilized, bilater ally vagotomized and artificially ventilated rabbits. Using the phrenic nerve discharge as the respira tory index, this experiment have assessed the effects of muscle spindle afferents invoked by intraarte rial injection of succinylcholine(Sch) on respiration. Results①In 40(63.49% ) cases which had the facilitated effects, 23 (36.51%) cases had the effect of prolonged inspiratory phase and 17 (26.98 % ) cases had the effect of attenuated expiratory phase and augmented respiratory frequency. In addition,there were 11(17.46% ) cases which had the attenuated effects,and 4(6.35% ) cases which had the biphasic effects,and 8(12.7% ) cases which had no effects;②The effect of prolonged inspiratory phase mainly showed the prolongation of inspiratory duration(Ti), but the effect of at tenuated expiratory phase and augmented respiratory frequency mainly showed the decrease of expi ratory duration (Te) and the augmentation of respiratory frequency(RF) ;③The above facilitated ef fects of Sch were significantly attenuated by intramuscular application of bupivacaine to destroy the muscle spindles. ConclusionThese results suggest that muscle spindle afferents induced by intraar terial injection Sch have a significant facilitated effect on respiration.
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ObjectiveTo investigate the role of NRM in the antinociceptive effect of muscle spindle afferents, the influence of NRM lesion on the inhibitory effect of muscle spindle afferents on the nociceptive responses of wide dynamic range (WDR) neurons and the effects of the muscle spindle afferents on the NRM neuronal activities were observed. MethodsThe single units of WDR neurons in the spinal dorsal horn were recorded extracellularly, and the inhibitory effects of activating muscle spindle afferents by intravenous administration of succinyicholine (SCH) on the C-fibers evoked responses (C-responses) of WDR neurons were tested before and after lesion of NRM. The ef- fects of the muscle spindle afferents activated by administrating SCH on the single NRM neurons were also examined. Results①lt was found that the C-responses of WDR neurons were significantly inhibited by intravenously adminis- tration of SCH, and the inhibitory effect was reduced after lesion of NRM ;②The activities of most of the NRM neu- rons could be changed significantly by administrating SCH. According to their responses, NRM neurons could be classified into three types:excitatory, inhibitory and non-responsive neurons, and the responses were dose-depen- dent. ConclusionThese results suggest that the muscle spindle afferents evoked by SCH may activate the NRM neu- rons, which plays an important role in the antinociception of muscle spindle afferents.
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Using the bullforg and toad in experi ments, and making the dorsal root potential (DRP) and ventral rool potential (VRP) as the indexes of the presynaptic inhibition, we examined and analysed the central effects produced by the spindle a fferents during stretching muscle. The results indicat that, aftet muscle paralysis, the phase DRP recorded on dorsal root simultanesously with stretching M. Semitendinosus is produced by spindle afferents, so it is named spindle-DRP'. The characteristic of the spindle-DRP has been discussed in detail. Meanwhile it was found that continual spindle afferents could increase the DRP evoked by electro-stimulating N. peronaeus, can decrease the nerve VRP evoked in this way. These results suggest that the spindle afferents are involved in the acupuncture anaesthesia, perhaps through the presynaptic inhibition. This result may be a new data for the research of the theory of presynaptic inhibition and the principle of acupuncture anaesthesia.