[Postnatal development of the masticatory muscles of the Wistar rat (Rattus norvegicus Berkenhout). A histochemical study]. / Postnatale Entwicklung der Kaumuskulatur der Wistarratte (Rattus norvegicus BERKENHOUT). Eine histochemische Studie.

Muscle biopsies of the mandible adductors of the Wistar rat (Rattus norvegicus Berkenhout) have been analyzed enzyme-histochemically for the investigation of the postnatal development (42.-126. d post partum) of their muscle fibers with special regards to the fiber types. The following methods have been used in this investigation: myofibrillar adenosine triphosphatase (ATP-ase) with different pre-incubations, Sudan black B (triglycerides), periodic acid-Schiff reagent (PAS) (glycogen), Gomori modified Trichrome staining. Quantitative analysis of muscle fibre-type composition and muscle fibre size was done from different regions of muscle sections. Estimation of the fiber size was carried out by measuring the minimum diameter of each type of muscle fibre.

The adductor mandibulae muscle in teleost fish with protrusible or non protrusible jaws: a histochemical and immunohistochemical study.

A study was made of the morphology and fibre type composition of the adductor mandibulae (AM) muscle in Teleosts with very protrusible (carp), moderately protrusible (cod) and non-protrusible (trout and cat-fish) jaws. In contrast to the trout and cat-fish, in which the AM is formed by only 2 components (mandibular and mental), in the carp and cod there is a third portion (maxillary) which is more or less developed in relation to the extent of jaw protrusion. Fibre types were identified by means of histochemical staining for succinate dehydrogenase and myosin ATPase activities, and by immunohistochemistry with anti-sera specific for fish fast and slow myosins. In all the species AM is composed principally of white (fast) fibres, with a smaller proportion of red (slow) fibres. The red fibres, which appear in the deep layers only of the muscle are not found in all of the components, and in the different species are not always present in the same parts. In those parts of the AM which are mixed, a transition zone lies between the red and white areas, and is usually composed of a third, or intermediate, type of fibre with histochemical and immunohistochemical properties similar to those of the pink zone of lateral muscle. The anatomical characteristics and different fibre type compositions of the various components forming the AM are discussed in relation to the extent of jaw protrusion and the relevant physiological data concerning other movements in which this muscle participants.

Histochemical characteristics of masseter and temporalis muscles after 5 weeks of maxillomandibular fixation--an investigation in Macaca mulatta.

This study describes the histochemical characteristics and cross-sectional areas of the superficial masseter and temporalis muscles in juvenile rhesus monkeys after 5 weeks of maxillomandibular fixation. Four juvenile male Macaca mulatta underwent mandibular surgery and 5 weeks of maxillomandibular fixation as part of a study of temporomandibular joint (TMJ) adaptations after condylar replacement. Immediately before the time the animals were killed (5 weeks postsurgically), biopsies of the masseter and temporalis muscles were obtained and submitted to histochemical analysis and calculation of muscle-fiber areas. The data were compared to histochemistry from 12 juvenile control Macaca mulatta. Significant decreases in mean cross-sectional area were exhibited in both type I (p less than 0.05) and type II (p less than 0.01) fibers in all muscles when compared to controls (n = 12). The ratio of type I to type II fibers, however, remained constant during maxillomandibular fixation in masseter and temporalis muscle samples, indicating no change in relative types of fibers. We conclude from this experimental investigation that (1) significant atrophy occurs in the temporalis and masseter muscles after 5 weeks of maxillomandibular fixation, and (2) this atrophy occurs in both type I and type II fibers, indicating that overall recruitment of the muscle (and not just of one fiber type of motor unit) was affected during fixation.

Immunocytochemical and electrophoretic analyses of changes in myosin gene expression in cat posterior temporalis muscle during postnatal development.

Changes in myosin gene expression during the postnatal development of the homogeneously superfast kitten posterior temporalis muscle were examined using immunocytochemical techniques supplemented by pyrophosphate gel electrophoresis and gel electrophoresis-derived enzyme linked immunosorbent assay (GEDELISA) of myosin isoforms. The antibodies used were polyclonals directed against the heavy chains of superfast and foetal myosins and monoclonals against the heavy chains of slow and fast myosins. The fibres of the posterior temporalis in the newborn kitten stained almost uniformly with the anti-foetal myosin antibody and the largest of these fibres stained strongly for superfast myosin. A subpopulation of fibres staining for superfast myosin also stained lightly for slow myosin. These slow staining fibres were evenly distributed in the centres of muscle fibre bundles, reminiscent of primary fibres in limb fast muscle. During subsequent development, slow myosin staining disappeared and superfast myosin replaced foetal myosin so that by 50 days the muscle was virtually homogeneously superfast as in the adult. Fast myosin was never expressed at any stage. It is proposed that fibres staining transiently for slow myosin are superfast primary fibres which are homologous to fast primary fibres recently described in regions of limb muscles devoid of slow fibres in the matured animal. Other jaw-closing muscles have significant populations of slow fibres in the mature animal and it is postulated that there exists in these muscles a second class of jaw primary fibres, the slow primary fibres, in which slow myosin synthesis would be sustained in the adult. It is suggested that the myogenic cells of jaw-closing and limb muscles are of two distinct types preprogrammed to express different muscle genes.

Sexual dimorphism in the distribution of estrogen receptors in the temporomandibular joint complex of the baboon.

The localization of radiolabeled estradiol was examined in the temporomandibular complex of male baboons by means of an autoradiographic technique. Five baboons were studied. Four animals received only the tritiated estrogen (1 microgram/kgm) and one animal, which served as the control, received both the tritiated estrogen and the unlabeled estrogen (100 micrograms/kgm). The study failed to demonstrate nuclear uptake and retention of tritiated estrogen in any of the tissues of the temporomandibular joint complex, including the articular surface of the condyle, articular disk, capsule, and muscles of mastication. However, estrogen receptors were identified in other tissues, including the pituitary. All tissues examined in the control animal were negative for estrogen receptors. It was concluded that there were no estrogen receptors in the temporomandibular joint complex of aged male baboons. As in previous studies, these findings provide additional evidence of a sexual dimorphism with respect to estrogen receptor distribution in the temporomandibular joint complex of the baboon. Furthermore, it is reasonable to speculate that estrogens may modulate a variety of metabolic functions in these tissues that could be important in the maintenance, repair, and/or pathogenesis of the temporomandibular joint.

Muscle fibre types and muscle spindles in the jaw musculature of the rat.

The fibre composition and occurrence of muscle spindles was studied in the masticatory, the suprahyoid and the infrahyoid muscles of the rat. Muscle fibres were typed as fast-white, fast-intermediate, fast-red and slow-red according to their ATPase and SDH activity. Fibre type appeared to be closely related to fibre diameter. In most of the muscles, all four fibre types were found. Slow-red fibres were absent in the superficial masseter, the transverse mandibular and the omohyoid muscles; fast-white fibres were absent in the mylohyoid muscle. The masticatory muscles were mainly composed of the three fast-fibre types; the jaw-opener muscles (the anterior digastric, the posterior digastric, the posterior digastric, the stylohyoid and the lateral pterygoid muscle) showed more slow-red fibres. In the masticatory and most of the suprahyoid muscles, the slow-red fibres were restricted to an area with high SDH activity. In the infrahyoid muscles, the fibre types were evenly distributed. Many muscle spindles, often clustered, were found in the masticatory muscles, except in the lateral pterygoid. In most of the suprahyoid muscles, these sensory structures were absent. In the infrahyoid muscles, solitary muscle spindles were found.

Heterogeneous distribution of myosin in human masticatory muscle fibres as shown by immunocytochemistry.

On the basis of enzymic properties, different fibre types can be distinguished in human skeletal muscle (type I fibres and type II fibres with subtypes) and there is a correlation between fibre types and the occurrence of slow and fast myosin. In human masticatory muscles, fibres with ATPase activity at pH 9.4, intermediate between that of type I (low activity) and type II (high activity), are frequent. On cryostat-sectioned material, highly specific antibodies against fast myosin, slow myosin and slow light chains were applied. The myosin composition of human masticatory muscles was very heterogeneous, in contrast to that in limb muscles, with various proportions of slow and fast myosins, heavy as well as light chains. Type I fibres contained slow myosin only and type II mainly fast myosin, ATPase IM and type IIC fibres contained a mixture of slow and fast myosins in variable amounts. The findings conform with physiological evidence of a continuum of contraction times for motor units in the human masticatory muscles and suggests that these muscles are highly adapted to the special and complicated functions of the stomatognathic system.

Microprobe analysis of human masseter muscle biopsies.

Biopsies of the human masseter muscle were made using an intraoral approach. Sections were cut in a cryostat and freeze-dried. Using the myosin ATPase method at pH 9.3 the recognized heterogeneity of the muscle with respect to type I and type II fibers was confirmed. Sections were examined in an SEM by the method of energy dispersive X-ray analysis using a computer assisted semi-quantitative method (bulk analysis-thick sections) to determine the distribution of Na, P, S, Cl and K and their relative masses. Element concentrations in descending order were K, S, P, Na and Cl. Some element ratios were compared with results in the literature for other muscle (biochemical and microprobe analysis) and found to be generally in reasonable agreement. The results form a basis for the study of a prominent and accessible masticatory muscle in altered states.

The histochemical profile of the human masseter. An autopsy and biopsy study.

A histochemical study has been carried out upon samples of muscle obtained from the human masseter. Sixteen specimens obtained either at autopsy or biopsy have shown that the middle and deep portions of the muscle contain fibres which in their size, histochemical staining properties and number correspond to the appearances noted in most human limb skeletal muscles. By contrast, samples taken from the superficial portion of the masseter demonstrated several unusual characteristics: these included a striking inequality of muscle fibre size in that the Type II fibres were much smaller than those of Type I but exceeded the latter in total number. This part of the muscle also contained, in 6 out of 10 samples, substantial numbers of intermediate fibres identified by myofibrillar ATPase staining. This study has confirmed that the superficial part of the human masseter is different morphologically and presumably functionally from the middle and deep parts of the muscle.