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PubMed1997

Possible contribution of active MMP2 to lymph-node metastasis and secreted cathepsin L to bone invasion of newly established human oral-squamous-cancer cell lines.

We have established human oral-squamous-cancer cell lines, BHY and HN, derived from non-metastatic cancer and metastatic cancer respectively. We examined the expression of matrix-degrading enzymes and their inhibitors in these cell lines. Both cell lines expressed pro-matrix metalloproteinase (MMP)1, proMMP2, proMMP9, membrane-type MMP and urokinase-type plasminogen activator. In addition to these enzymes, BHY cells secreted proMMP7 and procathepsin L, while HN cells secreted a large amount of active MMP2. BHY cells secreted a tissue inhibitor of matrix metalloproteinase, TIMP2, but only a trace level of TIMP1. Contrary to BHY cells, HN cells secreted TIMP1, but only a trace level of TIMP2. When we inoculated these cells into the masseter muscle of nude mice, both types of cell formed solid tumors, whose microscopic appearance was identical to that of the original tumors. BHY tumors were highly differentiated squamous-cell carcinomas, and invasive to the masseter muscle and the mandibular bone. Despite their local aggressiveness, BHY tumors did not metastasize to any distant organs. HN tumors were poorly differentiated squamous-cell carcinomas, weakly invasive to the muscle, but not to the mandibular bone. However, HN tumors frequently metastasized to cervical lymph nodes. These results suggest that the net activity of MMP2 (active MMP2/TIMP2) and cathepsin L secreted from cancer cells may contribute respectively to lymph-node metastasis and to bone invasion by oral cancer cells.

Animals↗
PubMed1985

A cineradiographic and electromyographic study of mastication in Tenrec ecaudatus.

Regular chewing was studied in the specialized Malagasy insectivore Tenrec ecaudatus with the aid of precisely correlated electromyography of the main adductors, digastrics, and two hyoid muscles and cineradiography for which metallic markers were placed in the mandibles, tongue, and hyoid bone. During the power stroke the body of the mandible moves dorsally and medially. The medially directed component of movement at this time is greatly increased by simultaneous rotation of the mandible about its longitudinal axis. The highly mobile symphysis, spherical dentary condyle, loss of superficial masseter muscle and zygoma, and the simplified zalamnodont molars all appear to be related to the large amount of mandibular rotation that occurs during occlusion. The balancing side lateral pterygoid muscle (inferior head) apparently shifts the working side mandible laterally during the last part of opening and the first part of closing. The working side temporalis and the superficial masseter muscle are both responsible for the shift back to the midline. The temporalis is usually active to the same extent on the working and balancing sides during the power stroke. The level of activity (amplitude) of the temporalis and duration of the power stroke increase with harder foods. Whenever soft foods are chewed, the superficial masseter is only active on the working side; whenever foods of increasing hardness are chewed, its level of activity on the balancing side increases to approach that of the working side. Mandibular rotation is greatly reduced when hard foods are chewed.

Animals↗
PubMed1990

[Morphological and functional analysis of dento-orofacial complex in monozygotic twins with Duchenne type muscular dystrophy].

The form of dento-orofacial complex and masticatory muscle function of monozygotic twins with Duchenne type muscular dystrophy were investigated. They had no environmental difference. Morphological analysis were performed on the dental casts and cephalograms. EMG recordings were derived from the bipolar surface electrodes on the masseter muscle and the anterior belly of digastric muscle on the left side. Each consisted of the data for three years. Results obtained are as follows: 1) Based on the average data, these patients showed an elongated dental arch in the maxilla and mandible, which might be caused by enlarged tongues. There were little difference in the tooth and dental arch sizes between them. 2) Cephalometric findings indicated that the elder brother showed a clockwise rotation of the mandible with larger gonial angle than the younger brother. Both of them showed a larger gonial angle based on the mean values. 3) Analysis of EMG recordings revealed an elongated silent period induced by teeth tapping and chin tapping, and a variable masticatory rhythm compared with that of normal sample. Moreover an annually increased imbalance between masseter muscle and digastric muscle was evident, which were parallel to the change of the blood creatine kinase value. Differences in the form and function of orofacial complex between them might be caused by their polygene heredity and the large size of DMD gene (XP 21).

Adolescent↗
PubMed2006

Patterns of experimentally induced pain in pericranial muscles.

Nociceptive mechanisms in the craniofacial muscle tissue are poorly understood. The pain pattern in individual pericranial muscles has not been described before. Experimental muscle pain was induced by standardized infusions of 0.2 ml 1 m hypertonic saline into six craniofacial muscles (masseter, anterior temporalis, posterior temporalis, trapezius, splenius capitis and sternocleidomastoid) in 20 healthy subjects. The pressure pain thresholds (PPTs) were determined before and after infusions. The subjects continuously reported intensity of saline-induced pain on an electronic visual analogue scale (VAS) and the perceived area of pain was drawn on anatomical maps. The pain areas were measured and the localization determined by a new centre-of-gravity method. The PPTs were lowest on the sternocleidomastoid muscle (anova: P<0.001), but the saline-evoked VAS pain scored highest following injection into the masseter muscle (anova: P<0.05). The centre-of-gravity measures demonstrated significantly different localization of the pain areas (anova: P<0.001). The trigeminally vs. the cervically innervated muscles had significantly different patterns of spread and referral of pain according to trigeminally vs. cervically innervated dermatomes (P<0.005). In conclusion, there appear to be characteristic pain patterns and pain sensitivity in different craniofacial muscles in healthy volunteers, which may be of importance for further research on different craniofacial pain conditions.

Face↗
PubMed1991

[Mastication and the electromyographic silent period in denture wearers].

The purpose of this study is to compare the masticatory efficiency and the physiological activity of masticatory muscles among patients with removable partial dentures (R.P.D.) and patients with natural dentition. The masticatory efficiency is assessed from the duration of chewing sequences for various foods, from the first masticatory cycle to the swallowing. The physiological activity is tested by the duration of the inhibition reflex called the "silent period" (S.P.) obtained upon each muscle examined: 29 subjects are examined, 24 of them had a R.P.D.; they were divided into four groups according to the extent of their edentation; 5 control subjects have full natural dentition. The study is performed using global electromyography of the two masseter muscles and the two anterior temporal muscles. The mastication of the control subjects appears to have a regular alternance of working potential and periods of rest. The duration of the chewing sequences is determined by the nature of the food, brief for soft food, long for hard food. The mastication of patients with R.P.D. appears more irregular with a lengthening of active phases. The duration of chewing sequences is significantly longer for the control subjects. The duration of the S.P. is 19-21 milliseconds for the masseter muscles of the patients with dentures and the control patients, and 20-22 milliseconds for the temporal muscles for the same individuals. The differences of the S.P. durations between control subjects and patients with R.P.D. is never significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Postoperative changes after bilateral mandibular osteotomies: a computed tomography study.

Twelve patients undergoing bilateral osteotomy of the ramus of the mandible were examined with CT preoperatively and postoperatively. The maximum area of the cheek and oropharynx was measured together with the thickness of the masseter muscle and the overlying subcutaneous tissue. The preoperative CT examinations showed wide anatomic variations. The postoperative examinations showed a diminished oropharynx lumen of approximately 43%. Swelling of the cheek averaged 61% and was associated with the well-vascularized masseter muscle. The TMJs were measured and a slight widening of the joint space was found postoperatively.

Adult↗
PubMed1998

Heterogeneity among muscle precursor cells in adult skeletal muscles with differing regenerative capacities.

Skeletal muscle has a remarkable capacity to regenerate after injury, although studies of muscle regeneration have heretofore been limited almost exclusively to limb musculature. Muscle precursor cells in skeletal muscle are responsible for the repair of damaged muscle. Heterogeneity exists in the growth and differentiation properties of muscle precursor cell (myoblast) populations throughout limb development but whether the muscle precursor cells differ among adult skeletal muscles is unknown. Such heterogeneity among myoblasts in the adult may give rise to skeletal muscles with different regenerative capacities. Here we compare the regenerative response of a masticatory muscle, the masseter, to that of limb muscles. After exogenous trauma (freeze or crush injuries), masseter muscle regenerated much less effectively than limb muscle. In limb muscle, normal architecture was restored 12 days after injury, whereas in masseter muscle, minimal regeneration occurred during the same time period. Indeed, at late time points, masseter muscles exhibited increased fibrous connective tissue in the region of damage, evidence of ineffective muscle regeneration. Similarly, in response to endogenous muscle injury due to a muscular dystrophy, widespread evidence of impaired regeneration was present in masseter muscle but not in limb muscle. To explore the cellular basis of these different regenerative capacities, we analyzed the myoblast populations of limb and masseter muscles both in vivo and in vitro. From in vivo analyses, the number of myoblasts in regenerating muscle was less in masseter compared with limb muscle. Assessment of population growth in vitro indicated that masseter myoblasts grow more slowly than limb myoblasts under identical conditions. We conclude that the impaired regeneration in masseter muscles is due to differences in the intrinsic myoblast populations compared to limb muscles.

Animals↗
PubMed1984

Thyrotropin-releasing hormone (TRH) causes sympathetic activation and cerebral vasodilation in the rabbit.

The effects of TRH on regional blood flow were studied in rabbits under urethane anesthesia. Four types of experiments were performed with the following results. (1) I.v. injection of 2 mg/kg b.w. TRH in animals with unilateral cervical sympathotomy caused a rise in mean arterial blood pressure from 10.0 +/- 0.5 to 13.3 +/- 0.5 kPa. Total cerebral blood flow, measured with labeled microspheres, increased from 75 +/- 5 to 126 +/- 16 g/min/100 g tissue on the intact side. There was a similar increase on the side with sympathotomy. The greatest increase, about 70%, was observed in cortical gray matter, caudate nucleus and thalamic region. There were marked reductions in blood flows in the spleen, gastric mucosa, skin and skeletal muscle. Mydriasis occurred on the side with an intact sympathetic supply. (2) I.v. infusion of 0.06 mg/kg b.w. per min TRH in animals with unilateral cervical sympathotomy and stabilized blood pressure increased total cerebral blood flow from 84 +/- 10 to 139 +/- 7 g/min/100 g. Blood flows to the masseter muscle, submandibular gland and facial skin but not to the eye or tongue were markedly reduced on the side with an intact sympathetic supply while little or no effect was observed on the side with sympathotomy. (3) Unilateral peripheral stimulation of the sympathetic chain at 1 Hz after bilateral sympathotomy caused a reduction in blood flows in the tongue, masseter muscle, submandibular gland and facial skin in animals with stabilized blood pressure. No potentiation of the stimulation effect was observed during TRH infusion. (4) The arteriovenous difference in oxygen saturation in the brain decreased from 39.1 +/- 2.8 to 26.4 +/- 3.7% after i.v. injection of 2 mg/kg b.w. TRH. The results indicate that TRH caused cerebral vasodilation in excess of that required by possible changes in cerebral metabolism. The vasoconstriction in the head region and the mydriasis was caused mainly by an increase in the activity of the cervical sympathetic nerves.

Acid-Base Equilibrium↗
PubMed1983

Role of the infraorbital nerve in retrieving behavior in lactating rats.

Injecting the local lidocaine into the mystacial pads of primiparous rats rendered the snout insensitive to touch and abolished the dams' ability to retrieve. Injecting the drug into the masseter muscles or intraperitoneally did not render the snout anaptic or abolish retrieval, results indicating that the effect of intramystacial lidocaine treatment could not be attributed to systemic toxicity or to the drug's spreading from the mystacial pads to affect the nearby masseter muscles. Cutting the intraorbital nerves produced a temporary retrieval impairment that was indistinguishable from that produced by intramystacial lidocaine injection. Surgical deafferentation did not affect the latency of dams to approach pups that had been displaced from the nest site, which indicates that the retrieval deficit was not due to postoperative debilitation. In addition, infraorbital section did not interfere with the ability to locate and consume a piece of cheese that had been buried in the home cage, which indicates that the operation did not produce anosmia or interfere with the muscles used to grasp pups. Cutting the facial nerves abolished vibrissal movement but did not disrupt retrieval, results indicating that the effect of infraorbital lesions could not be attributed to the loss of vibrissal cues or to nonspecific effects of nerve section. The possibility was tested that infraorbital deafferentation has a profound effect on retrieval because anaptic dams, in their initial attempts at picking up pups, elicit distress vocalizations from their offspring. Dams injected with lidocaine in the mystacial pads failed to retrieve pups that had been anesthetized with a barbiturate to abolish their distress vocalizations. Thus pup-produced vocalizations are not responsible for the retrieval impairment exhibited by anaptic mothers. It is concluded that perioral tactile sensation plays an important role in the ability of lactating rats to retrieve.

Animals↗
PubMed1993

Digastric muscle response as a function of knowledge of the task to be performed.

Whether the motor programme executed by the digastric muscles during a forceful bite is modified according to a subject's expectation that the resistance between the teeth will change was investigated. There were two experimental conditions: (1) tracking a ramp (drawn on an oscilloscope screen) by biting (isometrically) on a force transducer and holding it at 120 N, and (2) tracking the same ramp with a sudden unloading at 100 N. There were two groups of experiments: (1) control experiments in which subjects underwent a sudden and unexpected unloading of the jaw, and (2) experiments in which subjects were previously informed whether or not there was to be an unloading. In all experiments the subjects co-contracted their digastric muscles during the bite as compared to the state at rest. The subjects' responses fell into the three different types: (i) those who varied the level of tonic digastric activity only as a function of the experimental condition, (ii) those who co-contracted the digastric muscles at the same time as the masseter muscles, and (iii) those who changed the contraction pattern of the digastric muscles as a function of the experimental condition. If modulation of the digastric muscles occurred this is a 'feedforward' strategy mainly based on immediate past performance.

Bite Force↗
PubMed1990

[Studies on the cybernetic aspects of occlusal splint therapy].

This study was focussed on the effects of changes in interocclusal clearance on the activity of oral muscles. Two types of occlusal splints were incorporated in 20 subjects without TMJ-syndrome. Their muscle reactions were recorded electromyographically in the masseter muscle. The results show 5 groups of muscle reaction correlated with the mean postural face height. The changed height of the postural position has a significant influence on the control pattern of the masticatory system.

Adult↗
PubMed1984

Response of elevator activity during mastication to treatment of functional disorders.

The pattern of elevator activity during mastication in temporal and masseter muscles of 37 patients with functional disorders and pain in the masticatory system was studied before and after conventional treatment and compared with a control group of 43 subjects. As compared to controls, patients before treatment chewed with greater relative strength (percent of maximal elevator activity), longer relative contraction times (percent of total duration of chewing cycle) and stronger intermediary activity between strokes. These parameters of muscle coordination are proposed as quantitative estimates of "hyperactivity". Conventional treatment abolished pain, tenderness and other symptoms and signs completely in 18 patients in whom the most significant findings in the muscles under study were reductions in absolute and relative contraction times ascribed to increased stability produced by occlusal adjustment. It is suggested that relatively shorter pauses before treatment impaired blood flow and that their prolongation following treatment improved circulation. During the strong, dynamic contractions of mastication, masseter muscles tended to be more susceptible to hyperactivity than the temporal muscles.

Dental Occlusion↗
PubMed1985

Morphological and electrophysiological determination of the projections of jaw-elevator muscle spindle afferents in rats.

The fluorescent compound Lucifer Yellow was injected into the somata of nine identified jaw-elevator muscle spindle afferents, located in the V mesencephalic nucleus. Reconstructions of the central course of their axons were subsequently made from serial, transverse, sections to identify sites of projection. Three sites of termination were identified on the basis of collaterals that ended in varicosities and/or boutons. All afferents projected to the V nucleus oralis and, all but one, also to the V motor nucleus. Two out of nine afferents had terminations in the supra-trigeminal nucleus, though a further four appeared to send collaterals to this area. The relative density of projection, judged by the number of collaterals supplied to each area, decreased in the order: V nucleus oralis, V motor nucleus and supra-trigeminal nucleus. The central course of the afferent axons was such that impulses from the periphery would arrive first at the V motor nucleus, then the V nucleus oralis, the supra-trigeminal nucleus, and finally the afferent somata in the V mesencephalic nucleus. In animals in which the masseter nerve was exposed in-continuity for electrical stimulation, electrophysiological recordings were made in the three areas described above to identify units that received a monosynaptic input from spindles in the masseter muscle. Criteria were formulated on the basis of the pattern of responses on stimulation of the masseter nerve, and the morphology of labelled neurones, for differentiating between afferents, interneurones, and motoneurones. In the V motor nucleus, monosynaptic excitatory post-synaptic potentials (e.p.s.p.s) were obtained in both synergist and masseter motoneurones. These were assumed to arise from a masseter muscle spindle input as the thresholds for exciting such afferents and eliciting e.p.s.p.s were similar. Some interneurones, chiefly in the V nucleus oralis, were activated at thresholds close to that of muscle spindle afferents and could also fire in response to muscle stretch. As their latencies (measured extracellularly) were similar to that of e.p.s.p.s in motoneurones, they were assumed to receive a monosynaptic muscle spindle input. However, most interneurones were activated at longer latencies (up to 7 ms) and some also fired to muscle stretch. Arguments are advanced, based on the long rise time of e.p.s.p.s recorded in some, that the majority of these may also be candidates for monosynaptic activation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

The anatomy and electrical activity of the platysma muscle.

Dissection of seven cadavers showed that the platysma muscle may cover large parts of the masseter muscle. The platysma may thus be a significant source of artefact activity when recording the masseteric activity with surface electrodes. This is illustrated by a patient-case. The electrical activity of the platysma muscle was studied during jaw movements in normal, healthy subjects. Activity was regularly recorded during the latter half of large vertical jaw opening movements and, in five of the seven subjects, in the ipsilateral platysma muscle also during combined lateral-vertical jaw opening movements. The platysma may, therefore, in some individuals, have a functional role during the opening phase of chewing cycles when this has a marked lateral component.

Adolescent↗
PubMed1991

Effects of cervical sympathetic nerve stimulation and neuropeptide Y (NPY) on cranial blood flow in the cat.

Effects of cervical sympathetic nerve stimulation (SNS) at 10 Hz and intravenous infusion of neuropeptide Y (NPY), 10 and 100 pmol x kg body wt-1 x min-1 for 5 min, on regional blood flow in the cat were investigated with radioactive microspheres. Sympathetic nerve stimulation caused significant reductions in blood flows in the facial tissues including the eye. Alpha-adrenoceptor blockade with phenoxybenzamine and combined beta- and alpha-adrenoceptor blockade with propranolol and phenoxybenzamine abolished the effects of sympathetic nerve stimulation in most facial tissues except in the tongue, upper eyelid and masseter muscle. In most cranial tissues, neuropeptide Y reduced regional blood flow and increased vascular resistance. No effect of neuropeptide Y on vascular resistance was observed in the choroid. In the present study, evidence for a non-adrenergic component in sympathetic vasoconstriction was found in the tongue, upper eyelid and masseter muscle but not in the majority of feline facial tissues. Neuropeptide Y was a potent vasoconstrictor in many cranial tissues, while in parts of the uvea, the effects of neuropeptide Y were less pronounced.

Animals↗
PubMed2000

Gelatinase-B (matrix metalloproteinase-9; MMP-9) secretion is involved in the migratory phase of human and murine muscle cell cultures.

The remodelling of connective tissue components is a fundamental requirement for a number of pivotal processes in cell biology. These may include myoblast migration and fusion during development and regeneration. In other systems, similar biological processes are facilitated by secretion of the matrix metalloproteinases (MMPs), especially the gelatinases. This study investigated the activity of the gelatinases MMP-2 and 9 by zymography on cell conditioned media in cultures of cells derived from explants of the human masseter muscle and in the murine myoblast cell-line C2C12. Expression of MMP-9 by western blotting and TIMP-1, the major inhibitor of MMPs, by northern blotting, during all phases of myoblast proliferation, migration, alignment and fusion, was also measured. Irrespective of the origin of the cultures, MMP-9 activity was secreted only by single cell and pre-fusion cultures whilst MMP-2 activity was secreted at all stages as well as by myotubes. The loss of MMP-9 activity was due to the loss of MMP-9 protein expression. TIMP-1 mRNA was not detectable at the single cell stage but its expression increased as cells progressed through the pre-fusion and post-fusion stages to reach a maximal in myotube containing cultures. Migration of cells derived from human masseter muscle was inhibited, using a specific anti-MMP-9 blocking monoclonal antibody (6-6B). These data are consistent with the concept that regulation of matrix turnover via MMP-9 may be involved in the events leading to myotube formation, including migration. Loss of expression of this enzyme and expression of TIMP-1 mRNA is associated with myotube containing cultures. Consequently, the ratio between MMPs and TIMPs maybe important in determining myoblast migration and differentiation.

Animals↗
PubMed1994

Hyperalgesic change over the craniofacial area following urate crystal injection into the rabbit's temporomandibular joint.

The aim of this investigation was to study the characteristics of hyperalgesia and inflammatory change in the craniofacial area following the production of an acute arthritis of the temporomandibular joint (TMJ) in the rabbit. Unilateral arthritis was produced by the injection of monosodium urate (MSU) into the TMJ of the rabbits. Hyperalgesia was evaluated by the reduction in the threshold of the head-withdrawal response to pressure stimulation, and inflammatory change was determined by the quantitative Evans-blue test and light-microscopic examination of histological sections. Several hours after an injection of MSU (0.15, 0.5, 1.5 mg), hyperalgesic changes were observed over not only the MSU-administered condyle, but also over the ipsilateral masseter muscle and temporal muscle in a dose dependent manner, and lasted for more than 24 h before gradual recovery. The other craniofacial region showed no significant threshold-reduction. Although a very intense inflammatory sign was found in the region of the MSU-treated TMJ, a decreased or negative sign was found in the masseter muscle with a very low threshold. Local block of the TMJ using Bupivacaine suggested that the hyperalgesic change in the masseteric region was partly due to prolonged excitation of TMJ afferents.

Analysis of Variance↗
PubMed1991

[Newly devised subcutaneous needle electrodes for EMG recording].

Subcutaneous needle electrodes made of stainless steel were newly devised for ease of handling and perfect insulation. This needle (phi 0.20 mm) is used for acupuncture. The electrodes had the capability to record the EMG activity easily from a certain muscle. Then, the EMG activities of the masseter muscle were recorded with both these needle electrodes and surface electrodes and the results were compared. 1. Insertion of the electrodes into the subcutaneous tissue was easily performed because of the application of the acupuncture needle and their lightness of 0.2g was effective in fixing the electrodes on the skin without causing any tension. 2. After the insertion of the needle electrodes, the impedance showed below 5 kohm immediately, and the EMG recordings during biting could be simply achieved with great stability. 3. The action potential from the needle electrodes was less than that from the surface ones. The former reacted more sensitively to the change in the distance between the electrodes, compared with the latter.

Action Potentials↗