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At least 559 records · Page 31Linked to original sources
PubMed1996

[Leiomyoma of the masseter muscle. Report of a case].

The authors present a clinical case of leiomyoma, localized in the anterior margin of the masticator muscle. The clinical diagnosis was formulated following the histological test on the operating part. It is a case a rare pathology of the oral cavity that isn't commonly suspected. The symptoms of the patient let think a pathology of ATM and it was not typical of benign or malign neoplasm of the soft tissue of oral cavity. Only the use of a special clinical test, permitted the possibility to diagnose the exceptional case of masseter muscle on the left. The surgical therapy, being the neoplasm case benign and well capsuled resulted to be treatable and permitted the definitive resolution of the case.

Adult↗
PubMed1991

Estimation of tendon-plane orientation within human masseter muscle from reconstructed magnetic resonance images.

The human masseter is a powerful multipennate jaw elevator with complex internal architecture. The three-dimensional disposition of tendon planes within the muscle is thought to be an important determinant of function. We selected five adult subjects and used cephalometric radiography, magnetic resonance imaging and graphical, three-dimensional reconstruction to describe the organization of these planes within the muscle. Putative tendon planes were fitted to the surfaces of the three-dimensional reconstructions, and these were related to the mid-sagittal plane in the coronal and transverse views. To confirm whether putative planes disclosed by magnetic resonance represented true anatomical entities, a fresh human cadaver head was imaged and the magnetic resonance slices were compared with cryosections obtained in the same planes. Tendon-plane angulation appeared to be related to ramal length and lower face height measured cephalometrically. In the transverse view, the tendon planes appeared roughly to follow the angulations of the zygomatic arch and the lateral face of the mandibular ramus. These findings suggest that the angulation of tendon planes, and possibly pennation angles, are different depending on the viewing angle. Rather than reporting pennation angle as a single angle, alpha, which has been the convention, it may be more appropriate to express it as a three-dimensional angle relative to the normal of a particular tendon plane. The inference is that muscle fibres inserting on either side of a central tendon may need to develop different tensile forces if translation is to occur directly along the tendon axis.

Adipose Tissue↗
PubMed2001

Comparative evolution of muscular dystrophy in diaphragm, gastrocnemius and masseter muscles from old male mdx mice.

X chromosome-linked muscular dystrophic mdx mouse lacks the sarcolemmal protein dystrophin and represents a genetic homologue of human Duchenne muscular dystrophy (DMD). The present study analysed some aspects of pathological processes such as fibrosis, frequency of centralized nuclei, presence of degenerative or regenerative fibres, expression of utrophin and associated protein complexes, and myosin heavy chain isoforms in three muscles [diaphragm (DIA), gastrocnemius (GTC) and masseter (MAS)] from old male mdx mice. All parameters investigated comparatively in these pathological muscles provided evidence that the MAS mdx muscle presents a slight deterioration pattern in comparison to that of DIA and GTC muscles. Utrophin and associated proteins are present in many cell clusters with continuous membrane labelling in MAS muscle. Respective proportions of myosin heavy chain isoforms, measured by electrophoresis/densitometry, showed only slight change in GTC muscle, significant evolution in DIA muscle but drastic isoform conversions in MAS muscle. These results highlighted the difference in deterioration susceptibility of various muscles to muscular dystrophy. The reason why this occurs in MAS muscles is still obscure and discussed in terms of the comparative developmental origins of these muscles.

Aging↗
PubMed1996

Fetal myosin heavy chain increases in human masseter muscle during aging.

Biochemical, immunohistochemical and molecular biological methods were used to detect fetal myosin heavy chain (MyHC) in the human masseter of elderly and young subjects. Samples from the elderly subjects contained larger amounts of fetal MyHC than those of young adults. Only a very small amount of embryonic MyHC could be detected in both age groups. Embryonic and fetal MyHCs were never detected in the control adult orofacial, limb and trunk muscles. Polymerase chain reaction (PCR) analysis revealed the presence of fetal mRNA sequences in elderly and young masseter muscles. We conclude that fetal MyHC is present in the human masseter throughout the life span and that there is an increase in the relative amount of this protein with age.

Adult↗
PubMed1986

Development of the masseter muscle and oral behavior in the pig.

During mastication the adult pig masseter contracts with a complex pattern involving a wave of electromyographic (EMG) activity moving from the ventro-rostral corner to the dorso-caudal corner. The present study was undertaken to ascertain the ontogeny of that contraction pattern. Anatomical measurements were made on masseters from fetal, infant, and juvenile pigs. EMG activity from different parts of the masseter was recorded along with oral movements in infant and juvenile pigs as they suckled, drank, and chewed on food and non-food objects. The basic arrangement of muscle fibers and tendinous aponeuroses was found to be the same in all ages. The longest and most vertical fibers were found rostrally and ventrally, whereas the shortest and most horizontal fibers were found caudally and dorsally. The length of fasciculi decreased with age, relative to muscle weight. Variance in length among different parts of the muscle increased with age. Fetal masseters were oriented generally more horizontally than the masseters of older animals, except that the dorso-caudal corner, usually the most horizontal portion, is not developed in fetuses. The contraction patterns within the infant masseter were less complex than those of older animals; only the dorso-caudal corner was distinct. The further development of intramuscular differences in activity may be associated with the increasing anatomical complexity of the masseter, which augments its functional capabilities.

Aging↗
PubMed1997

Ultrastructural analysis of inputs around the soma of an intra-cellularly labeled masseter muscle spindle afferent in cat mesencephalic trigeminal nucleus.

Intra-axonal recording and labeling with HRP was performed to examine synaptic inputs around soma of mesencephalic trigeminal neuron (Vme) innervating the masseter muscle-spindles on electron microscopy. Intra-axonal injection of HRP was made in the mesencephalic tract. About twelve boutons contacting the labeled soma were observed from serial ultrathin sections. Among them eight boutons synapsed on the labeled soma, one bouton contacted on the soma but synapsed on an unlabeled dendrite nearby. Serially observing the other three boutons, no synaptic junctions were identified. The synapses between boutons and soma were mainly asymmetrical. Six boutons contained clear spherical vesicles (S-ending) and the other six contained spherical, oviod and flattened, namely pleomorphic clear vesicles (P-ending). Both S-endings and P-endings frequently contained large or small dense-core vesicles. Typical F-endings with predominantly flattened vesicles was not seen, though some P-endings contained more flattened vesicles. The significance of these observations was discussed.

Animals↗
PubMed1992

[Quantitative topographic characterization of the myoelectric activity distribution of the masseter muscle: mapping of spectral EMG parameters].

A new method for quantitative characterization of myoelectrical masseter activity distribution by mapping of spectral EMG-parameters is described. The surface electromyograms of M. masseter were monopolarly recorded (16 channels). On the basis of registered EMG intervals (512 ms) the spectral EMG power of several frequency bands was calculated (Fast Fourier Transformation). The spectral EMG parameters between the 16 electrode positions were estimated by linear interpolation (4-nearest neighbours algorithm). Afterwards the spectral EMG parameters were fitted in a grey-tone or colour scale with 10 intervals. The so obtained EMG activity maps ("EMG-Maps") permit a quantitative-topographic characterization of myoelectrical masseter activity during different functional load procedures. The frequency range which is to consider in masseter surface-EMG investigations encloses frequencies between 15 and 500 Hz. The topography of EMG activation pattern of M. masseter is only described in a comprehensive manner when the electrode array consists of 16 electrodes and more. During defined motor tasks like clenching with controlled forces the reproducibility of EMG-Maps which respect to the topography of EMG activity pattern is very high. The absolute values of spectral EMG power as well as power changes of selected band ranges during clenching correlate to the extent of chewing forces.

Adult↗
PubMed1982

[Morphohistochemical characteristics of the myons of the masseter muscle of the mammals and man].

In the musculus masseter of the man, dog, rabbit and rat (5 specimens for each) optic density of diformasan deposition [after succinatedehydrogenase (SDG) activity has been revealed], transversal section areas of myons, number of capillaries around them and thickness of the Z-line have been studied. In each muscle subjected to the investigation parameters for 150 myons randomly chosen have been defined. According to SDG activity, muscle fibres of three types have been visibly selected: red, white and intermediate. According to all signs investigated, the muscle tissue is a single complex without a sharp division into various fibre types.

Adult↗