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At least 1,729 records · Page 96Linked to original sources
PubMed1984

Regulation of sarcomere number in skeletal muscle: a comparison of hypotheses.

Sarcomere lengths from 16 locations in the muscles of mastication were measured from pigs fixed in maximum excursion (wide jaw opening) and in postural position (near occlusion). These data, plus published data on sarcomere lengths in rabbit jaw muscles, were used to evaluate conflicting hypotheses about the factors which regulate serial sarcomere number in striated muscles. According to the most successful hypothesis, sarcomere number is adjusted so as to achieve an optimum sarcomere length when the muscle is experiencing a high level of tension. Most often, this occurs at jaw positions where the muscle is electrically active.

Animals↗
PubMed2007

Malignant triton tumor in a patient with Li-Fraumeni syndrome and a novel TP53 mutation.

We report a 3-year-old boy with a malignant triton tumor (MTT) involving the left masticator space with local invasion and regional lymph node metastasis. Family history and detection of a novel germline TP53 mutation confirmed his diagnosis of Li Fraumeni syndrome (LFS). MTT has not been previously described in association with LFS. This case along with a comprehensive review of the literature, illustrate the importance of both somatic and germline TP53 mutations in the pathogenesis MTT. The tumor could not be resected and he was successfully treated with intensive induction chemotherapy, irradiation, and high-dose chemotherapy with autologous stem cell transplantation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2002

Orexin B immunoreactive fibers and terminals innervate the sensory and motor neurons of jaw-elevator muscles in the rat.

The relationship between orexinergic terminals and the sensory and motor neurons of jaw-elevator muscles was examined by means of anti-orexin B (OXB) immunohistochemistry combined with horseradish peroxidase (HRP) retrograde tracing in the rat. HRP was initially injected into the jaw-elevator muscles; 48 h later the animals were sacrificed and fixed for HRP reaction and anti-OXB immunohistochemistry. OXB-like terminals were observed to distribute in the trigeminal mesencephalic nucleus (Vme) and the trigeminal motor nucleus (Vmo) where they closely contact the Vme neuronal somata and the Vmo neuronal somata and dendrites retrogradely labeled with HRP. The results of this study provide anatomical evidence of a direct OXB orexinergic innervation of the sensory and motor neurons controlling jaw-elevator muscles involved in mastication. Its functional significance related to the feeding behavior and bruxism is discussed.

Animals↗
PubMed1994

Immunohistochemical evidence for GABA and glycine-containing trigeminal premotoneurons in the guinea pig.

Electrophysiological studies have suggested that inhibition of trigeminal motoneurons during mastication and the jaw-opening reflex are mediated by last-order interneurons (premotoneurons) utilizing GABA and glycine [Chandler et al. (1985), Brain Res., 325:181-186; Enomoto et al. (1987), Neurosci. Res., 4:396-412; Goldberg and Nakamura (1968), Experientia, 24:371-373; Kidokoro et al. (1968), J. Neurophysiol., 31:695-708; Nakamura et al. (1978), Exp. Neurol., 61:1-14]. In the present study we performed a series of double-labeling experiments in guinea pigs to determine the location of neurons which contain GABA (gamma aminobutyric acid) or glycine that project to the trigeminal motor nucleus (Mo5). This was accomplished by performing immunohistochemical staining in combination with a retrograde tract tracing technique using colloidal gold bound to inactivated WGA-HRP (wheat germ agglutin-horseradish peroxidase) (gWGA-HRP) as our retrograde tracer. Neurons which had a positive immunoreactivity to GABA or GAD (glutamic acid decarboxylase) and contained the retrograde marker were located in regions adjacent to the Mo5 such as the intertrigeminal, supratrigeminal, peritrigeminal and rostral portions of the parvocellular reticular formation alpha. Neurons which had a positive immunoreactivity to glycine and contained the retrograde marker were identified in the parvocellular reticular formation, the spinal trigeminal nucleus oralis, supratrigeminal and intertrigeminal regions. These data provide anatomical evidence for GABAergic and glycinergic projections to Mo5.

Animals↗
PubMed1982

An anatomical study of three cases of alobar holoprosencephaly.

One case of median cleft lip with hypotelorism and two cases of cyclopia, all with brains exhibiting alobar holoprosencephaly, were examined by detailed anatomical dissection. The results indicate that the variations of the skull and associated soft structures form a continuum, as do the brain, eye, and face, from the mild to severe end of the syndrome. At the mild end, the bony malformations were primarily limited to the structures derived from the frontonasal promience, within which the ethmoid bone was the focal point. Malformed soft structures included the muscles of the anterior and posterior neck regions. At the severe end of the spectrum, these structures were more severely malformed, and the sphere of malformations widened to include more peripherally located bones and soft structures such as the mandible, ear ossicles, muscles of mastication, and salivary glands. Possible mechanisms for the generation of the malformations are addressed.

Abnormalities, Multiple↗
PubMed1984

An anatomical study of human otocephaly.

This study describes the gross anatomic variations observed in a 32-week male fetus diagnosed as having otocephaly. Special attention was given to the muscular, peripheral nervous, and vascular systems of the entire body. External features included approximation of the ears on the front of the neck, underdevelopment of the lower jaw, and a small oral cavity. The mandible, maxillae, and zygomatic bones were smaller than normal and appeared shifted in a ventrocaudal direction. The middle ear ossicles were fused and abnormally positioned. The tongue was positioned abnormally and malformed. The muscles of mastication were fused in the midline and formed the floor of the oral cavity. The variations were similar to the spectrum of abnormalities reported in two cases in the literature. Because of this finding, it is possible that the causative events leading to these deviations were similar in the three cases. Possible mechanisms are considered which could lead to the observed malformations seen in these cases. There were also several muscle and nerve anomalies outside of the head region.

Abnormalities, Multiple↗
PubMed1993

Dynamic contrast: a sensory contribution to palatability.

By focusing on a sensory model for palatability, the "ice-cream effect", we speculate on some principles underlying palatability. We propose that the most highly palatable foods are likely to have higher levels of "dynamic contrast" (moment-to-moment sensory contrast from the everchanging properties of foods manipulated in the mouth). The sensory feature contributing most to dynamic contrast seems to be somatosensation. Texture, for example, over the course of masticating a crunchy food, changes markedly such that each alteration contributes differently and dynamically to sensory contrast. Our purpose herein is to propose that dynamic contrast contributes significantly to palatability of foods and beverages.

Animals↗
PubMed2001

A role for Engrailed-2 in determination of skeletal muscle physiologic properties.

The molecular basis underlying the establishment of the myogenic lineage, subsequent differentiation, and the establishment of specific fiber types (i.e., fast versus slow) is becoming well understood. In contrast, the regulation of the general properties of a specific anatomical muscle group (e.g., leg versus jaw muscles) and the regulation of muscle-fiber properties within a particular group are less well characterized. We have investigated the potential role of the homeobox-containing gene, Engrailed-2 (En-2), in the mouse, which is specifically expressed in myoblasts in the first arch and maintained in the muscles of mastication in the adult. We have generated mice that ectopically express En-2 in all muscles during early development and primarily in fast muscles in the adult. Ectopic En-2 in nonjaw muscles leads to a decrease in fiber size, whereas overexpression in the jaw muscles leads to a shift in fiber metabolic properties as well as a decrease in fiber size. In contrast, loss of En-2 in the jaw leads to a shift in fiber metabolic properties in the jaw of female mice only. Jaw muscles are sexually dimorphic, and we propose that the function of En-2 and mechanisms guiding sexual dimorphism of the jaw muscles are integrated. We conclude that the specific expression of En-2 in the jaw therefore plays a role in specifying muscle-fiber characteristics that contribute to the physiologic properties of specific muscle groups.

Animals↗
PubMed1998

Force production in the primate masticatory system: electromyographic tests of biomechanical hypotheses.

Studies of the influence of dietary selection pressures in living and extinct primate taxa frequently interpret cranial diversity using a simple lever model. When this model is applied to functional or evolutionary questions, it is commonly assumed that the muscles of mastication vary little in activity during biting at points along the tooth row. A pattern of smoothly increasing maximum bite force magnitudes is therefore predicted as the bite point is moved posteriorly along the dental arcade. Diverse adaptive explanations are mapped onto this pattern. In this study, the activity of the superficial masseter and anterior temporalis muscles in humans was quantified during high magnitude bite force production at points along the tooth row. These data indicate that there are substantial changes in muscle activity with bite point, and that the standard lever model is therefore an incomplete description of masticatory force production. Maximum muscle force magnitudes were found to be greatest during first molar biting and to decrease as the bite point moved anteriorly and posteriorly. Additionally, relative balancing and working side muscle activity changed by bite point. This latter pattern is consistent with the predictions of Greaves' constrained lever model, which assumes that masticatory muscle activity is restricted by the need to maintain compressive forces at both temporomandibular joints. However, these results also imply that additional factors influence muscle activity--such as dental morphology, mandibular kinematics, and the need to safeguard against joint distraction during diverse loading conditions--and that the constrained lever model of Greaves is therefore also incomplete. These considerations suggest that masticatory system morphology in primates will respond differently to dietary selection pressures than is commonly hypothesized. Intepretations of cranial morphology in fossil taxa may therefore also differ.

Adult↗
PubMed2000

Masticatory stress, orbital orientation and the evolution of the primate postorbital bar.

A postorbital bar is one of a suite of derived features which distinguishes basal primates from their putative sister taxon, plesiadapiforms. Two hypotheses have been put forward to explain postorbital bar development and variation in circumorbital form: the facial torsion model and visual predation hypothesis. To test the facial torsion model, we employ strain data on circumorbital and mandibular loading patterns in representative primates with a postorbital bar and masticatory apparatus similar to basal primates. To examine the visual predation hypothesis, we employ metric data on orbit orientation in Paleocene and Eocene primates, as well as several clades of visual predators and foragers that vary interspecifically in postorbital bar formation.A comparison of galago circumorbital and mandibular peak strains during powerful mastication demonstrates that circumorbital strains are quite low. This indicates that, as in anthropoids, the strepsirhine circumorbital region is excessively overbuilt for countering routine masticatory loads. The fact that circumorbital peak-strain levels are uniformly low in both primate suborders undermines any model which posits that masticatory stresses are determinants of circumorbital form, function and evolution. This is interpreted to mean that sufficient cortical bone must exist to prevent structural failure due to non-masticatory traumatic forces. Preliminary data also indicate that the difference between circumorbital and mandibular strains is greater in larger taxa.Comparative analyses of several extant analogs suggest that the postorbital bar apparently provides rigidity to the lateral orbital margins to ensure a high level of visual acuity during chewing and biting. The origin of the primate postorbital bar is linked to changes in orbital convergence and frontation at smaller sizes due to nocturnal visual predation and increased encephalization. By incorporating in vivo and fossil data, we reformulate the visual predation hypothesis of primate origins and thus offer new insights into major adaptive transformations in the primate skull.

Animals↗
PubMed1988

Innervation of periodontal ligament and dental pulp in the rat incisor: an immunohistochemical investigation of neurofilament protein and glia-specific S-100 protein.

Nervous elements in the periodontal ligament and dental pulp of rat incisors were investigated by means of immunohistochemistry for neurofilament protein (NFP) and glia-specific S-100 protein. The periodontal ligament in the incisors was densely innervated by NFP-immunoreactive nerve fibers; the distribution of the nerve fibers and their terminations differed markedly from those in molars. NFP-positive, thick nerve bundles entered the lingual periodontal ligament through slits located in the mid-region of the alveolar socket, and immediately formed numerous Ruffini-like corpuscles. In the labial periodontal ligament, all of the NFP-immunoreactive nerve fibers terminated in free endings. The restricted location of the stretch receptor, Ruffini-like corpuscle, in the lingual periodontal ligament appears to be an essential element, because this region is regularly extended during mastication. The nervous elements were restricted to the alveolar half of the periodontal ligament in every region; they avoided the dental half of the periodontal ligament, which presumably moves continuously with the tooth. Pulpal nerve fibers in incisors also showed a characteristic distribution different from those in molars; individual nerve fibers with beaded structures ran in the center of the pulp toward the incisal edge, and did not form the subodontoblastic nerve plexus of Raschkow. Immunostaining for S-100 protein revealed a distribution pattern of nervous elements similar to that for NFP, suggesting that the nerves supplying the periodontal ligament and dental pulp were mostly covered by a Schwann sheath.

Animals↗
PubMed1987

Velocity curves of human arm and speech movements.

The velocity curves of human arm and speech movements were examined as a function of amplitude and rate in both continuous and discrete movement tasks. Evidence for invariance under scalar transformation was assessed and a quantitative measure of the form of the curve was used to provide information on the implicit cost function in the production of voluntary movement. Arm, tongue and jaw movements were studied separately. The velocity curves of tongue and jaw movement were found to differ in form as a function of movement duration but were similar for movements of different amplitude. In contrast, the velocity curves for elbow movements were similar in form over differences in both amplitude and duration. Thus, the curves of arm movement, but not those of tongue or jaw movement, were geometrically equivalent in form. Measurements of the ratio of maximum to average velocity in arm movement were compared with the theoretical values calculated for a number of criterion functions. For continuous movements, the data corresponded best to values computed for the minimum energy criterion; for discrete movement, values were in the range of those predicted for the minimum jerk and best stiffness criteria. The source of a rate dependent asymmetry in the form of the velocity curve of speech movements was assessed in a control study in which subjects produced simple raising and lowering movements of the jaw without talking. The velocity curves of the non-speech control gesture were similar in form to those of jaw movement in speech. These data, in combination with similar findings for human jaw movement in mastication, suggest that the asymmetry is not a direct consequence of the requirements of the task. The biomechanics and neural control of the orofacial system may be possible sources of this effect.

Arm↗
PubMed1979

Location of interganglionic neurons in the stomatogastric system of the spiny lobster.

The stomatogastric ganglion produces distinct and complex patterned output driving the mastication and filtration of food. It does so with a small number of neurons whose properties and interconnections have been extensively examined. The motor patterns are subject to modulation and integration by neurons of other ganglia. This paper reports a search for interneurons of the four interconnecting ganglia of this system, using cobalt chloride backfilling techniques. It was determined that only a small number of neurons may interconnect these ganglia: (1) In the stomatogastric ganglion there are two to three small neurons and six large neurons with neurites projecting anteriorly towards the other ganglia. (2) In the two commissural ganglia there are one to three small neurons whose neurites project to the primary input nerve of the stomatogastric ganglion. (3) In the oesophageal ganglion there are three small neurons whose location would allow them to play a co-ordinating role in the output of all four ganglia.

Animals↗
PubMed1992

Gastric surgery and bezoars.

We present a series of 56 patients with gastrointestinal bezoar following previous gastric surgery for gastroduodenal peptic ulcer. The following parameters were studied: factors predisposing to bezoar formation (type of previous surgery, alimentation, and mastication), form of clinical presentation, diagnostic tests, and treatment. A bilateral truncal vagotomy plus pyloroplasty had been performed previously on 84% of patients, 44% revealed excessive intake of vegetable fiber, and 30% presented with bad dentition. The most frequent clinical presentation was intestinal obstruction (80%). This was diagnosed mainly by clinical data and simple abdominal radiology. The main exploratory technique for diagnosing cases of gastric bezoar was endoscopy. Surgery is necessary for treating the intestinal forms, and one should always attempt to fragment the bezoar and milk it to the cecum, reserving enterotomy and extraction for cases where this is not possible. The small intestine and stomach should always be explored for retained bezoars. Gastric bezoars should always receive conservative treatment, endoscopic extraction, and/or enzymatic dissolution; gastrotomy and extraction should be performed when this fails.

Adult↗
PubMed1993

The role of the cerebral cortex in swallowing.

This paper reviews clinical, neuroanatomical, and neurophysiological studies that have implicated the cerebral cortex in the initiation and/or regulation of swallowing as well as related functions such as mastication. Cortical dysfunction has been reported to result in a variety of swallowing impairments. Furthermore, swallowing can be evoked and/or modulated by stimulation applied to restricted regions of the cortex. Neuroanatomical investigations and single neuron recording studies also provide some insights into the cortical structures, pathways, and mechanisms that may mediate deglutition.

Cerebral Cortex↗
PubMed1991

Facial pain. IV. A prospective study of 1052 patients with a view of: precipitating factors, associated symptoms, objective psychiatric and neurological symptoms.

In a prospective material of 1052 patients the precipitating factors, associated symptoms, psychological and neurological deficits have been examined. Mastication and talking are the most frequently occurring precipitating factors, 76% as regards Neuralgia, with typical starting difficulties. As regards Non-neuralgiform Pain 24%, with precipitation late in the masticatory process. There were trigger zones in 50% of the cases of Typical Trigeminal Neuralgia and in 9% of the patients with Non-neuralgiform Pain. In a series of cases the jaw joint is perceived as a trigger zone. Cold precipitates pain in 48%-39%. Other precipitating factors are much more rare--psychological stress in 15% of the patients with Non-neuralgiform Pain, however. "Vegetative" associated symptoms were relatively frequent, lacrimation occurred in 31% of the cases of Typical Trigeminal Neuralgia and in 20% of the cases of Non-neuralgiform Pain. Rhinorrhea and salivation were less frequent. In terms of figures migrainoid associated symptoms had no connection with vegetative associated symptoms or with pain in the eye. In 11% of the patients pain occurred most frequently during the night and in 20% the frequency of pain was the same day and night. About 1/3 of the patients with Neuralgia experienced seasonal variations. Tenderness of foramina is a symptom of no significance. Very few patients had primary sensory loss. No eye or ear symptoms have been found which may be referred to as the patho-anatomical basis of the pain. About 1/3 of the patients with Non-neuralgiform Pain had psychological symptoms whereas hardly any patients with Neuralgia had them. MMPI test performed on a small matched material showed no difference between Neuralgia and Non-neuralgiform Pain. In material B an examination has been made of the jaw joint arthrosis symptoms. A restriction of the diagnosis of arthrosis has had the effect that it must be recognized that patients with facial pain do not have the high frequency of jaw joint diseases previously assumed. As was also the case in a series of normal material previously published, between 1, 5 and 1, 3 of the patients with Neuralgia had jaw joint arthrosis which was due to old age. This study has not revealed any connection between previous diseases, the onset of pain, the character and course of the pain, the character of the attack, the localization of pain, precipitating factors, associated symptoms and symptoms of loss on the one hand and the patho-anatomical substratum on the other.

Arousal↗
PubMed1994

Masseter muscle hyperactivity and myofascial pain dysfunction syndrome: a relationship under stress.

Myofascial pain dysfunction syndrome (MPD) of the temporomandibular joint (TMJ) is a psychophysiological disorder that develops because of hyperactive muscles of mastication. Ten women meeting criteria for MPD and 12 symptom-free women participated in the study. The rationale for this study was to observe cardiovascular and masseter muscle changes during four contiguous experimental periods: baseline/adaptation, reaction time, recovery, and relaxation. MPD patients showed less masseter muscle activity and higher heart rates at baseline than controls. Controls had significantly higher masseter EMG activity during reaction time. Both groups showed significant elevation in masseter muscle activity and heart rate over the 14-min reaction period. MPD patients' recovery from stress was equivalent to controls' for both heart rate and masseter muscle activity. MPD patients exhibited significantly slower reaction times than controls. The results suggest that masseter muscle hyperactivity may not account for the development and maintenance of MPD.

Adult↗
PubMed1990

Herpes simplex virus and intraoral ulcers in immunocompromised patients with haematologic malignancies.

Possible factors predisposing to the development of intraoral ulcers in immunocompromised patients with haematologic malignancies were investigated. Among 46 patients undergoing antineoplastic treatment, 18 developed an intraoral ulcer during the prospective study. Patients with or without ulcers were comparable with respect to underlying disease, presence of teeth, the qualitative composition of the aerobic and facultatively anaerobic oral microflora, herpes simplex virus (HSV) titer positivity, a past history of herpes labialis, leukocyte and thrombocyte counts, and duration of fever. Viral cultures from saliva revealed an association between the presence of HSV in saliva and the presence of intraoral ulcers. HSV was not isolated from the saliva of any patient without ulcers. Viral cultures from the ulcers revealed growth of HSV in 11 (61%) of the 18 patients with ulcers. HSV-positive ulcers were located more often on the alveolar process than elsewhere in the oral cavity. Ulcers on the lateral borders of the tongue and on the buccal mucosa were found only in dentate patients. Development of intraoral ulcers was not associated with an increase of the HSV titer in serum in any patient. It is concluded that some intraoral ulcers, especially when located on the alveolar process, are associated with and probably caused by HSV, while mechanical trauma during mastication seems likely to be involved in the pathogenesis of ulcers elsewhere in the oral cavity.

Adult↗