OBJECTIVETo find out the characteristic topographic distribution of the muscle spindles in human masseter and temporal muscle, and to clarify the neurobiology roles of masticatory muscles during chew and adjusting mandibular position.

METHODSThe muscle spindles of masseter and temporal muscle on both sides of 5 human corpses fixed in formalin for more than 1 year were observed and quantitatively analyzed by picture analysis equipment.

RESULTSThe muscle spindles were maldistributed and spindles were commonly clustered in some individual portions, and the muscle spindle figures were diversiform, which were predominantly composed of the spindle simple and spindle complexes. The masseter spindles of the deep portion were obviously more than that of the superficial. Spindles of temporal muscle were concentrated in the anterior approach to the coracoid.

CONCLUSIONThe distribution of muscle spindles in the masseter and temporal muscle is heterogeneous, spindle density in the deep portion of masseter and the anterior of temporolis muscle is greater than others. The deep of masseter and the anterior of temporal muscle play an important part in maintaining mandibular position and balance.

Cytoskeleton ; Humans ; Mandible ; Masseter Muscle ; Masticatory Muscles ; Muscle Spindles ; Temporal Muscle

OBJECTIVETo investigate the changes in the afferent discharge activities of the sensory nerve endings in muscle spindles of rats with hindlimb immobilization.

METHODSPlaster cast was used immobilize the hindllimbs of rats. Using air-gap technique, the spontaneous discharge of the muscle spindles and its responses to perfusion with succinylcholine (0.05 mg/ml) and suspension in an extended position were observed in isolated muscle spindles from rats with hindlimb immobilization for 3, 7, and 14 days.

RESULTSThe muscle spindles of rat soleus showed a sharp decrease in spontaneous discharge frequency (P<0.01) and response to succinylcholine perfusion after 3 days of hindlimb immobilization (P<0.05). Significant changes of the firing rate in an extended position was observed in rats after a 14-day immobilization (P<0.01). The duration of individual spikes was significantly prolonged following hindlimb immobilization (P<0.01).

CONCLUSIONMuscle spindle discharges decrease significantly in rats following hindlimb immobilization, which might be related to reduced contractile properties of the muscle spindle.

Animals ; Hindlimb Suspension ; Muscle Spindles ; innervation ; Muscle, Skeletal ; innervation ; Rats

Muscle spindle is the key proprioceptor in skeletal muscles and plays important roles in many physiological activities, such as maintaining posture, regulating movement and controlling speed variation. It has significant clinical relevance and is emerging as a promising therapeutic target for the treatment of motor functional impairment and metabolic diseases. In this review, we summarized muscle spindle distribution and the mechanism of mechanical signal transmission, and reviewed the research progress on morphological and structural characteristics of muscle spindles.
Muscle Spindles/physiology* ; Muscle, Skeletal/physiology* ; Clinical Relevance

Fifteen young pigs were used in this study. The animals were divided into three groups; 1. Group for removal of the temporal muscle, 2. Group for removal of the masseter muscle, 3. Group for removal of masseter and internal pterygoid muscles. The animals were anesthetized with 3.5% chloral hydrate intraperitoneaily. In the right side the head was shaved. The masticatory muscle was removed. The animals were sacrificed four .months later. The head was separated from trunk and cleaned by boiling in a solution of potassiumm hydroxide. The results were as follows; 1. In the group for removal of the temporal muscle, the Coronoid process of the mandible was resorbed. 2. In the group for removal of the masseter muscle, there was produced asymmetrical growth of the mandible, attrition of the molar teeth in the control side, and resorption of the mandibular angle. 3. In the group for removahof the Masseter and Internal muscles, the changes were more severe than that of the group for removal of the masseter muscle. The mandibular angle was completely absent. 4. The growth of the bone seems definitely related to the presence of the muscular tissue actively pulling upon it.
Animals ; Chloral Hydrate ; Guinea Pigs* ; Guinea* ; Head ; Mandible* ; Masseter Muscle ; Masticatory Muscles* ; Molar ; Muscles ; Pterygoid Muscles ; Swine ; Temporal Muscle ; Tooth

Hemangiomas are the most common benign tumors in infancy, occurring most often on cutaneous and mucosal surfaces. Although less than 1% of hemangiomas occur in skeletal muscle, 15% of intramuscular hemangiomas arise in the head and neck musculature. Less than 10 cases of the sternocleidomastoid muscle have been reported in the English literatures. The masseter muscle is most commonly involved in the head and neck. Clinically, these tumors are present as distinct, localized, rubbery swelling. Neck computed tomography scan with enhancement may suggest a vascular mass within the muscle while angiography may detect feeding arteries in large intramuscular hemangiomas. The treatment of the hemangiomas is based on location, accessibility, depth of invasion, age, and cosmetic considerations. The optimal treatment is complete wide resection including the cuff of surrounding muscle. We report a case of hemangioma that occurred in the sternocleidomastoid muscle along with a with literature review.
Angiography ; Arteries ; Head ; Hemangioma ; Hemangioma, Capillary ; Masseter Muscle ; Muscle, Skeletal ; Neck Muscles ; Neck

Capsule restricts the further study on muscle spindle function and the involved mechanism. The aim of this study was to establish the isolation method of intrafusal fibres from the isolated rat muscle spindle. Intrafusal fibres were harvested from muscle spindle of soleus muscle in rats using neutrase-collagenase digestion. A variety of incubation mediums have been tested to find out an appropriate medium of intrafusal fibers in vitro. Trypan blue staining was used to detect cell death, and patch clamp was used to record resting potential. The results showed that the intrafusal fibres incubated with amine acid-saline solution were almost all dead. DMEM could maintain good condition of the fibres, but excess CO2 ventilation would induce cellular swelling or even death. While Leiboviz's 15 (L-15) medium can guarantee 1-2 h of physiological condition of the intrafusal fibres. Coverslips treated with gelatin, polylysine and serum was the better interfaces for the intrafusal fibres to adhere easily, compared with regularly treated coverslip. The resting potential of intrafusal fibres was (-45.3 ± 5.1) mV, consistent with others obtained from in vivo muscle spindle from cats and frogs. These results suggest that the isolation method of the intrafusal fibres has been successfully established in the present study, providing a new approach in better understanding of muscle spindle activities and the involved mechanism.
Animals ; Cell Culture Techniques ; methods ; Muscle Spindles ; physiology ; Muscle, Skeletal ; physiology ; Rats

One of the most important and urgent issues in the field of space medicine is to reveal the potential mechanism underlying the disused muscle atrophy during the weightlessness or microgravity environment. It will conduce to find out effective methods for the prevention and treatment of muscle atrophy during a long-term space flight. Increasing data show that muscle spindle discharges are significantly altered following the hindlimb unloading, suggesting a vital role in the progress of muscle atrophy. In the last decades, we have made a series of studies on changes in the morphological structure and function of muscle spindle following simulated weightlessness. This review will discuss our main results and related researches for understanding of muscle spindle activities during microgravity environment, which may provide a theoretic basis for effective prevention and treatment of muscle atrophy induced by weightlessness.
Animals ; Hindlimb Suspension ; Muscle Spindles ; physiopathology ; Muscle, Skeletal ; physiopathology ; Muscular Atrophy ; physiopathology ; Space Flight ; Weightlessness Simulation

OBJECTIVE: To investigate the effects of Jendrassik maneuver on latency and amplitude of the T-reflex and H-reflex of the soleus muscle in normal adults. METHOD: The T-reflex and H-reflex tests were performed on sixty normal adults with standardized technique using the soleus muscle. The shortest latency and the largest peak-to-peak amplitude were chosen for representative values. RESULTS: The results were as follows: 1) There was a significant difference in latency of the T-reflex between with and without Jendrassik maneuver. 2) The increment ratio of the amplitude with Jendrassik maneuver was 88% in the T-reflex and 18% in the H-reflex. There were a significant difference in the amplitude of both reflexes between with and without Jendrassik maneuver. 3) A high correlation was present between the latency of H- & T-reflex and the length. CONCLUSION: According to these results, we suggest that Jendrassik maneuver primarily increases the sensitivity of muscle spindles and decreases the presynaptic inhibition of the Ia terminals at cortical, subcortical and spinal levels. Jendrassik maneuver can be a useful tool in cases of clinically decreased or absent deep tendon reflex.
Adult ; H-Reflex* ; Humans ; Muscle Spindles ; Muscle, Skeletal* ; Reflex ; Reflex, Stretch

OBJECTIVETo study the effects of repeated + Gz forces on masticatory muscles.

METHODS48 male Wistar rats were randomly divided into 4 groups. Group A was normally fed. Group B was only fixed with rat-kept devices for 5 minutes. Group C was borne + 1 Gz for 5 minutes. Group D was repeatedly exposed + 10 Gz (each for 30 s, onset rate about 0.5 G/s, 5 times/d with + 1 Gz 1 minute intervals, 4 d/wk, 3 weeks in total). The histological changes of the masseter, temporal and lateral pterygoid muscles were observed.

RESULTSNo abnormal changes were observed in Group A, B and C. But pathological changes could be found in group D. The wrench and deformation of muscular fibers, the dissolution of partial myofibril, the swelling of mitochondria, the reduce of hepatin from the masseter and lateral pterygoid muscles could be found.

CONCLUSIONSRepeated + Gz stresses could induce the damage of masticatory muscles in different degrees.

Animals ; Hypergravity ; Male ; Masseter Muscle ; pathology ; ultrastructure ; Masticatory Muscles ; pathology ; ultrastructure ; Microscopy, Electron ; Pterygoid Muscles ; pathology ; ultrastructure ; Rats ; Rats, Wistar ; Temporal Muscle ; pathology ; ultrastructure ; Time Factors

The management of chronic empyema remains still disturbing. These patients always have chances to exposure septic conditions. We presents 4 patients of chronic empyema with sepsis who underwent E-flap and Myoplasty with extrathoracic skeletal muscles between December 1994 and March 1997. Two patients who had BPF were treated with intercostal muscle flap as co-procedures. Intervals between first E-flap and second Myoplasty ranged from 5 to 10 months. There was no morbidity or mortality. We think these stepwise procedure offers a chance to terminate these debilitating disease.
Empyema* ; Humans ; Intercostal Muscles ; Mortality ; Muscle, Skeletal ; Sepsis*