Advanced Simultaneous Isolation, Culture, and Identification of Myoblasts and Fibroblasts From Sternocleidomastoid Muscle of Congenital Muscular Torticollis.

BACKGROUND: Congenital muscular torticollis (CMT) is a common pediatric disease caused by contracture of sternocleidomastoid muscle (SCM) that leads to neck stiffness and deformity. Based on the adhesion characteristics of different cells in affected SCM of CMT, myoblasts and fibroblasts can be isolated simultaneously by advanced culture conditions. Our study aimed to explore and optimize the isolation, culture, and identification of myoblasts and fibroblasts in SCM of CMT. METHODS: Myoblasts and fibroblasts were separated by combined digestion with trypsin and collagenase. With this improved method, the morphology of isolated myoblasts and fibroblasts was observed under the microscope, the cell growth curve was drawn, and the purity of myoblasts and fibroblasts was determined by immunofluorescence. RESULTS: The method allowed to satisfactorily culture myoblasts and fibroblasts. The cells could stably grow and be passaged, provided they were at least 80% confluent. Immunofluorescence of myoblasts and fibroblasts showed high rate of positive staining, and cell count showed excellent growth state. Moreover, according to the growth curve, fibroblasts grew at a higher rate than myoblasts. CONCLUSIONS: The isolated myoblasts and fibroblasts have high purity, intact structure, and relatively high vitality. This method can be used to establish a cell model with myoblasts and fibroblasts, which can be applied to investigate etiology of CMT or mechanisms of drug action.

Fiber types of the anterior and lateral cervical muscles in elderly males.

PURPOSE: The anterior and lateral cervical muscles (ALCM) are generally considered to be postural, yet few studies have investigated ALCM fiber types to help clarify the function of these muscles. This study aimed to systematically investigate ALCM fiber types in cadavers. METHODS: Anterior and lateral cervical muscles (four scalenus anterior, medius, posterior muscles; five longus colli, five longus capitis taken bilaterally from one cadaver) were removed from four male embalmed cadavers (mean age 87.25 years). Paraffin-embedded specimens were sectioned then stained immunohistochemically to identify type I and II skeletal muscle fibers. Proportional fiber type numbers and cross-sectional area (CSA) occupied by fiber types were determined using stereology (random systematic sampling). Results were analyzed using ANOVA (P < 0.05) and descriptive statistics. RESULTS: Scalenus anterior had the greatest average number and CSA of type I fibers (71.9 and 83.7%, respectively); longus capitis had the lowest number (48.5%) and CSA (61.4%). All scalene muscles had significantly greater type I CSA than longus capitis and longus colli; scalenus anterior and medius had significantly greater type I numbers than longus capitis and longus colli. Some significant differences were observed between individual cadavers in longus colli for CSA, and longus capitis for number. CONCLUSION: The ALCM do not share a common functional fiber type distribution, although similar fiber type distributions are shared by longus colli and longus capitis, and by the scalene muscles. Contrary to conventional descriptions, longus colli and longus capitis have type I fiber proportions indicative of postural as well as phasic muscle function.

Neck muscle afferents influence oromotor and cardiorespiratory brainstem neural circuits.

Sensory information arising from the upper neck is important in the reflex control of posture and eye position. It has also been linked to the autonomic control of the cardiovascular and respiratory systems. Whiplash associated disorders (WAD) and cervical dystonia, which involve disturbance to the neck region, can often present with abnormalities to the oromotor, respiratory and cardiovascular systems. We investigated the potential neural pathways underlying such symptoms. Simulating neck afferent activity by electrical stimulation of the second cervical nerve in a working heart brainstem preparation (WHBP) altered the pattern of central respiratory drive and increased perfusion pressure. Tracing central targets of these sensory afferents revealed projections to the intermedius nucleus of the medulla (InM). These anterogradely labelled afferents co-localised with parvalbumin and vesicular glutamate transporter 1 indicating that they are proprioceptive. Anterograde tracing from the InM identified projections to brain regions involved in respiratory, cardiovascular, postural and oro-facial behaviours--the neighbouring hypoglossal nucleus, facial and motor trigeminal nuclei, parabrachial nuclei, rostral and caudal ventrolateral medulla and nucleus ambiguus. In brain slices, electrical stimulation of afferent fibre tracts lateral to the cuneate nucleus monosynaptically excited InM neurones. Direct stimulation of the InM in the WHBP mimicked the response of second cervical nerve stimulation. These results provide evidence of pathways linking upper cervical sensory afferents with CNS areas involved in autonomic and oromotor control, via the InM. Disruption of these neuronal pathways could, therefore, explain the dysphagic and cardiorespiratory abnormalities which may accompany cervical dystonia and WAD.

Reduced masticatory function is related to lower satellite cell numbers in masseter muscle.

The physiology of masseter muscles is known to change in response to functional demands, but the effect on the satellite cell (SC) population is not known. In this study, the hypothesis is tested that a decreased functional demand of the masseter muscle causes a reduction of SCs. To this end, twelve 5-week-old male Sprague-Dawley rats were put on a soft diet (SD, n = 6) or a hard diet (HD, n = 6) and sacrificed after 14 days. Paraffin sections of the superficial masseter and the m. digastricus (control muscle) were stained with haematoxylin and eosin for tissue survey and with anti-myosin heavy chain (MHC) for slow and fast fibres. Frozen sections of both muscles were double-stained for collagen type IV and Pax7. Slow MHC fibres were equally distributed in the m. digastricus but only localized in a small area of the m. masseter. No differences between HD or SD for the m. digastricus were found. The m. masseter had more SCs per fibre in HD than in SD (0.093 ± 0.007 and 0.081 ± 0.008, respectively; P = 0.027). The m. masseter had more fibres per surface area than the m. digastricus in rats with an SD group (758.1 ± 101.6 and 568.4 ± 85.6, P = 0.047) and a HD group (737.7 ± 32.6 and 592.2 ± 82.2; P = 0.007). The m. digastricus had more SCs per fibre than the m. masseter in the SD group (0.094 ± 0.01 and 0.081 ± 0.008; P = 0.039). These results suggest that reduced masseter muscle function is related to a lower number of SCs. Reduced muscle function might decrease microdamage and hence the requirement of SCs in the muscle fibres.

Intermuscular relationship of human muscle fiber type proportions: slow leg muscles predict slow neck muscles.

INTRODUCTION: Our aim in this study was to examine whether the muscle fiber type proportions in different muscles from the same individual are interrelated. METHODS: Samples were excised from five skeletal muscles in each of 12 human autopsy cases, and the fiber type proportions were determined by immunohistochemistry. We further examined the intermuscular relationship in fiber type proportion by reanalyzing three previously published data sets involving other muscles. RESULTS: Subjects demonstrated a predominantly high or low proportion of type 1 fibers in all examined muscles, and the overall difference between individuals was statistically significant (P < 0.001). Accordingly, the type 1 fiber proportions in most muscles were positively correlated (median r = 0.42, range -0.03-0.80). Similar results were also obtained from the three reanalyzed data sets. CONCLUSIONS: We suggest the existence of an across-muscle phenotype with respect to fiber type proportions; some individuals display generally faster muscles and some individuals slower muscles when compared with others.

Serial histologic and immunohistochemical changes in anterior digastric myocytes in response to distraction osteogenesis.

PURPOSE: To document histologic and immunohistochemical changes in the anterior digastric muscle during distraction osteogenesis (DO). MATERIALS AND METHODS: Nineteen Yucatan minipigs with mixed dentition were used for these experiments. Group A (n = 16) underwent unilateral mandibular distraction at a rate of 1 mm/day (no latency) for 12 days. Animals were killed at mid-DO (n = 5), end-DO (n = 5), mid-fixation (n = 4), and end-fixation (n = 2). Group B (n = 2) underwent acute 12-mm advancement, and group C (n = 1) dissection and osteotomy. Animals from groups B and C were killed at the end-DO time point. Digastric muscles from treatment and contralateral sides of all animals were harvested and embedded in paraffin. Specimens were stained with hematoxylin/eosin or immunohistochemically for proliferating cell nuclear antigen (PCNA; total cell proliferation), paired Box-7 gene protein (Pax7; satellite cells), or myogenic differentiation 1 protein (MyoD; differentiating myoblasts). Descriptive and bivariate statistics were computed to compare groups (P ≤ .05 statistically significant). RESULTS: All animals survived the operation and observation period; there were no device failures. Two animals (1 at mid-DO, 1 at mid-fixation) were eliminated from the study because of postoperative infection. There was minimal digastric inflammation, fibrosis, and muscle fiber size variability during active DO. Immunohistochemical analysis showed statistically significant increases in PCNA (cellular proliferation), Pax7 (satellite cells), and MyoD (differentiating myoblasts) positive nuclei in digastrics at mid-DO and end-DO. CONCLUSIONS: Results of this study indicate that there are minimal pathologic changes but significant increases in PCNA, Pax7, and MyoD positive nuclei during active distraction. This supports the hypothesis that the digastric muscle response to DO consists of proliferation and hypertrophy.

Discharge rate of sternohyoid motor units activated with surface EMG feedback.

We analyzed individual motor units of the sternohyoid muscle with the aim of characterizing their minimum and maximum discharge rates and their variability in discharge during voluntary contractions. Surface EMG signals were recorded with an array of eight electrodes from the sternohyoid muscle of seven healthy men (age: 30.2+/-3.5 yr). The multichannel surface EMG signals were displayed as feedback for the subjects who identified and modulated the activity of one target motor unit in 30-s contractions during which the discharge rate was increased from minimum to maximum (ramp contraction), sustained at maximum level (sustained), or increased in brief bursts (burst). During the ramp contractions, the minimum average discharge rate over epochs of 1 s was 11.6+/-1.5 pulses per second (pps) and the maximum 57.0+/-5.7 pps (P<0.001). During the sustained contractions, the motor unit discharge rate decreased from 65.5+/-8.4 pps at the beginning to 52.9+/-7.6 pps at the end of the contraction (P<0.05). The coefficient of variation for the interspike interval during the sustained contractions was 40.2+/-9.8% and a large percentage of discharges had instantaneous rates>50 pps (52.2+/-12.5%) and>100 pps (8.0+/-1.2%), with peak values>150 pps. During the burst contractions, the instantaneous discharge rate reached average maximum values of 97.6+/-36.8 pps. The observed discharge rates and their variability are higher than those reported for limb muscles, which may be due to large synaptic input and noise received by these motor neurons.

Heterogeneity of fiber characteristics in the rat masseter and digastric muscles.

The functional requirements in muscle use are related to the fiber type composition of the muscles and the cross-sectional area of the individual fibers. We investigated the heterogeneity in the fiber type composition and fiber cross-sectional area in two muscles with an opposing function, namely the digastric and masseter muscles (n = 5 for each muscle) of adult male rats, by means of immunohistochemical staining according to their myosin heavy chain (MyHC) content. The digastric and masseter muscles were taken from Wistar strain male rats 10 weeks old. In the masseter six predefined sample locations were examined; in the digastric four. Most regions showed dominant proportions of type IIA and IIX fibers. However, both muscles also revealed a regional heterogeneity in their fiber type distribution. In the digastric, type I fibers were detected only at the central and deep areas of the anterior and posterior belly, respectively. Meanwhile, the peripheral area of the anterior belly contained a higher proportion of type IIB fibers. In the masseter, the type I fibers were absent. In the superficial masseter the distribution of IIA and IIB fibers was significantly different between the superior and inferior regions. In the deep masseter, regional differences were observed among all four examined areas, of which the posterolateral region contained the highest proportion of type IIB fibers. The cross-sectional areas of type IIB fibers were always the largest, followed by the type IIX and IIA fibers. Only a few differences in cross-sectional area of corresponding fiber types were detected between the various sites. In conclusion, the masseter and digastric muscles showed an obvious heterogeneity of fiber type composition and fiber cross-sectional area. Their heterogeneity reflects the complex role of the both muscles during function. This detailed description of the fiber type composition can serve as a reference for future studies examining the muscular adaptations after the onset of various diseases in the masticatory system.

Slow-tonic muscle fibers and their potential innervation in the turtle, Pseudemys (Trachemys) scripta elegans.

A description is provided of the ratio of slow-tonic vs. slow- and fast-twitch fibers for five muscles in the adult turtle, Pseudemys (Trachemys) scripta elegans. The cross-sectional area of each fiber type and an estimation of the relative (weighted) cross-sectional area occupied by the different fiber types are also provided. Two hindlimb muscles (flexor digitorum longus, FDL; external gastrocnemius, EG) were selected on the basis of their suitability for future motor-unit studies. Three neck muscles (the fourth head of testo-cervicis, TeC4; the fourth head of retrahens capitus collique, RCCQ4; transversalis cervicis, TrC) were chosen for their progressively decreasing oxidative capacity. Serial sections were stained for myosin adenosine triphosphatase (ATPase), NADH-diaphorase, and alpha-glycerophosphate dehydrogenase (alpha-GPDH). Conventional fiber-type classification was then performed using indirect markers for contraction speed and oxidative (aerobic) vs. glycolytic (anaerobic) metabolism: i.e., slow oxidative (SO, including slow-twitch and possibly slow-tonic fibers), fast-twitch, oxidative-glycolytic (FOG), and fast-twitch glycolytic (Fg) fibers. Slow-tonic fibers in the SO class were then revealed by directing the monoclonal antibody, ALD-58 (raised against the slow-tonic fiber myosin heavy chain of chicken anterior latissimus dorsi), to additional muscle cross sections. All five of the tested muscles contained the four fiber types, with the ATPase-stained fibers including both slow-tonic and slow-twitch fibers. The extreme distributions of SO fibers were in the predominately glycolytic TrC vs. the predominately oxidative TeC4 muscle (TrC-SO, 9%; FOG, 20%; Fg, 71% vs. TeC4-SO, 58%: FOG, 16%; Fg, 25%). Across the five muscles, the relative prevalence of slow-tonic fibers (4-47%) paralleled that of the SO fibers (9-58%). TeC4 had the highest prevalence of slow-tonic fibers (47%). The test muscles exhibited varying degrees of regional concentration of each fiber type, with the distribution of slow-tonic fibers paralleling that of the SO fibers. In the five test muscles, fiber cross-sectional area was usually ranked Fg > FOG > SO, and slow-twitch always > slow-tonic. In terms of weighted cross-sectional area, which provides a coarse-grain measure of each fiber type's potential contribution to whole muscle force, all five muscles exhibited a higher Fg and lower SO contribution to cross-sectional area than suggested by their corresponding fiber-type prevalence. This was also the case for the slow-twitch vs. slow-tonic fibers. We conclude that slow-tonic fibers are widespread in turtle muscle. The weighted cross-sectional area evidence suggested, however, that their contribution to force generation is minor except in highly oxidative muscles, with a special functional role, like TeC4. There is discussion of: 1) the relationship between the present results and previous work on homologous neck and hindlimb muscles in other nonmammalian species, and 2) the potential motoneuronal innervation of slow-tonic fibers in turtle hindlimb muscles.

Neck muscles in the rhesus monkey. I. Muscle morphometry and histochemistry.

Morphometric methods were used to describe the musculotendinous lengths, fascicle lengths, pennation angles, and cross-sectional areas of neck muscles in adult Macaca mulatta monkeys. Additionally, muscles were frozen, sectioned, and stained for ATPase activity to determine fiber-type composition. Individual rhesus muscles were found to vary widely in their degree of similarity to feline and human muscles studied previously. Suboccipital muscles and muscles supplied by the spinal accessory nerve were most similar to human homologs, whereas most other muscles exhibited architectural specializations. Many neck muscles were architecturally complex, with multiple attachments and internal aponeuroses or tendinous inscriptions that affected the determination of their cross-sectional areas. All muscles were composed of a mixture of type I, IIa, and IIb fiber types the relative proportions of which varied. Typically, head-turning muscles had lower proportions of type II (fast) fibers than homologous feline muscles, whereas extensor muscles contained higher proportions of type II fibers. The physical and histochemical specializations described here are known to have a direct bearing on functional properties, such as force-developing capacity and fatigue-resistance. These specializations must be recognized if muscles are to be modeled accurately or studied electrophysiologically.

Marked non-uniformity of fiber-type composition in the primate suboccipital muscle obliquus capitis inferior.

Obliquus capitis inferior (OCI) is a monoarticular suboccipital muscle linking the transverse process of the atlas (C1) to the spinous process of the axis (C2). Histochemical analysis of fiber-type composition showed that the muscle has a marked gradient of fiber-type distribution in which type I fibers comprise 95-100% of fibers in the deepest region but less than 10% of fibers in the superficial layer. Step-like changes in fiber-type proportions occurred between groups of fascicles. In most instances the boundaries between these fascicles did not exhibit different perimysial features from those fascicles with similar fiber-type proportions. OCI contained large numbers of muscle spindles, which were concentrated in deep regions rich in type I fibers. The degree of nonuniformity in fiber-type distribution seen in OCI is unusually large when compared with patterns described in other primate muscles, and has implications for the way that the muscle is studied anatomically and physiologically.

Functional morphology of the pterygoid hamulus.

The pterygoid hamulus (PH), a structure on the under surface of the skull base which has so far hardly been described, is in a peculiar situation biomechanically. The aim of this study is to accumulate sufficient morphological data to enable a functional interpretation to be provided. A total of 93 adult skulls and 24 children's skulls have been examined, and also an additional 20 heads in which the relationship to the surrounding muscles could be investigated. Measurements were made with a sliding gauge, and sections cut from specimens embedded in methyl methacrylate were examined histologically. The hamulus is a variable structure which can, however, be allotted to one of a few basic types. As nomenclature we suggest the following terms: the base: Basis; body: Corpus, sulcus: Sulcus; neck: Collum; head: Caput of the hamulus. The average measurements are: length 7.2 mm, sagittal breadth 1.4 mm, transverse breadth 2.3 mm. The sections show that the medial cortical lamella is thicker than the lateral, and that the 2 are bound together by oblique trabeculae. The medial gradient angle of the collagen fibers is smaller than that of the lateral. A few muscles take origin from the hamulus, the tensor veli palatini turns round the neck, and a few of its fibers take origin here. The distribution of the material within the hamulus suggests that its body is subjected to greater loading in the medio-dorsal direction, but that the head is freely pulled away laterally and caudally. Its exposed position at the distal end of the upper dental arch and the formation of a bursa or sliding layer in the sulcus suggest that it may be a potential source of irritation.

Muscle fiber type compartmentalization and expression of an immature myosin isoform in the sternocleidomastoid muscle of rabbits and primates.

The sternocleidomastoid muscle is located in the neck and is both a neck rotator and flexor. Cervical dystonia, a focal dystonia disorder, is characterized by forceful involuntary contraction of a group of neck muscles, usually including the sternocleidomastoid. Little is known about the fiber type composition, fiber type compartmentalization and innervation patterns in this muscle in rabbit and primates. Sternocleidomastoid muscles from rabbit and monkey were analyzed for muscle fiber type composition and number, muscle fiber cross-sectional area and patterns of innervation. The sternocleidomastoid muscle was composed of two distinct regions, or compartments, with different fiber type compositions: an outer or superficial region composed of mostly type 2 myofibers and an inner deep region composed of both type 2 and type 1 myofibers. Neonatal myosin heavy chain isoform was detected in approximately 25% of the myofibers in both regions of the muscle. Neuromuscular junctions were located in seven endplate bands approximately 1-3 cm apart throughout the length of the muscle. There is clear evidence of anatomical subdivisions within this muscle. Not only is there variation in fiber type composition between superficial and deep regions of the muscle, but unlike most other mature skeletal muscles, it continues to express neonatal myosin heavy chain isoform in the adult. The motor program for neck movements is extremely complex, and the histological complexity plays a role in allowing for a continuum of movements of the head and neck, from maintenance of posture to rapid head movements.

Effect of hypothyroidism on myosin heavy chain expression in rat pharyngeal dilator muscles.

Although the association between hypothyroidism and obstructive sleep apnea is well established, the effect of thyroid hormone deficiency on contractile proteins in pharyngeal dilator muscles responsible for maintaining upper airway patency is unknown. In the present study, the effects of hypothyroidism on myosin heavy chain (MHC) expression were examined in the sternohyoid, geniohyoid, and genioglossus muscles of adult rats (n = 20). The relative proportions of MHC isoforms present were determined using MHC-specific monoclonal antibodies and oligonucleotide probes. All control muscles showed a paucity of type I MHC fibers, with greater than 90% of fibers containing fast-twitch type II MHCs. In the genioglossus muscle, a population of non-IIa non-IIb fast-twitch type II fibers (putatively identified as type IIx MHC fibers) were detected. Hypothyroidism induced significant changes in MHC expression in all muscles studied. In the sternohyoid, type I fibers increased from 6.2 to 16.9%, whereas type IIa fibers increased from 25.9 to 30.7%. Type I fibers in the geniohyoid increased from 1.2 to 12.8%, whereas type IIa fibers increased from 34.1 to 42.7%. The genioglossus showed the smallest relative increase in type I expression but the greatest induction of type IIa MHC. None of the muscles examined demonstrated reinduction of embryonic or neonatal MHC in response to thyroid hormone deficiency. In summary, hypothyroidism alters the MHC profile of pharyngeal dilators in a muscle-specific manner. These changes may play a role in the pathogenesis of obstructive apnea in hypothyroid patients.

Musculotopic organization of the hypoglossal nucleus in the grass frog, Rana pipiens.

Recent neural tracer studies in several mammalian species have demonstrated a similar musculotopic organization of the hypoglossal motoneurons which innervate individual tongue muscles. The distribution of this musculotopic organization in nonmammalian tetrapods, however, has not received detailed investigation. As part of an ongoing study on the comparative organization of the vertebrate hypoglossal nucleus, the musculotopic organization of the hypoglossal nucleus of Rana pipiens was studied by injection of lectin-conjugated horseradish peroxidase into four distinct tongue muscles and the geniohyoid muscle. Injections into the hyoglossus muscle label neurons in dorsal regions of the hypoglossal nucleus in middle and rostral nucleus levels. Injections into the genioglossus basalis muscle label neurons in ventral and lateral regions of the hypoglossal nucleus in caudal nucleus levels. Injections into the genioglossus medialis muscle label neurons in dorsal regions in caudal levels, throughout the nucleus in middle levels, and in ventral regions in more rostral levels. Injections into the geniohyoid muscle label neurons in the ventral tip of the hypoglossal nucleus and in the ventromedial corner of the medullary gray matter in middle and rostral nucleus levels. These results demonstrate that the organization of the hypoglossal nucleus in Rana pipiens is more complex than previous tracer studies indicated. Similarities in the musculotopic organization of the amphibian and mammalian hypoglossal nuclei suggest an evolutionary conservatism of the motor system controlling tongue movement.

Tendinous insertions in the human thyroid cartilage plate: macroscopic and histologic studies.

The zones of tendinuous insertion and origin of the sternothyroid muscle, the thyrohyoid muscle, the inferior constrictor muscle of the pharynx and the external part of the cricothyroid muscle were studied in adult larynges by macroscopy and light microscopy. The sternothyroid muscle is inserted in the superior and inferior thyroid tubercula and also in a tendinous arch, which extends between the two tubercula. In contrast to the descriptions found in most textbooks, the sternothyroid muscle has no attachment to the oblique line. The thyrohyoid muscle and the thyropharyngeal part of the inferior constrictor muscle of the pharynx originate in ventral and dorsal symmetry at the oblique line. X-rays permit a measurement of their original angles, resulting in a mean value of 36 degrees. According to these measurements, and electromyographic findings by other authors, both muscles can be regarded as a bipennate muscle from a functional point of view. Histologic studies indicate that the oblique line's zone of origin structurally resembles an areal periosteal-diaphysary tendinous insertion. In the non-ossified thyroid cartilage, the insertions in the region of the thyroid tubercula are similar to chondral-apophysary insertions of tendons in the limb skeleton. After ossification of the thyroid cartilage, they show the shape of circumscribed periosteal-diaphysary insertions. Osteogenesis of the laryngeal skeleton therefore affects the structure of the thyroid tubercula's tendinous insertions. From a mechanical point of view, the insertions in the thyroid cartilage function as extension-checking mechanisms, and also serve to balance the different elastic modules of the tendinous tissue and the cartilaginous or bony tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of hetero-reinnervation within the rat tongue.

This study centred on the effects of hetero-reinnervation within the rat tongue. Lingual, greater auricular and vagus nerves were used. Proximal segments of each of these nerves were joined to the distal hypoglossal stump using 10/0 nylon suture. Histological sections of the tongue were examined. In lingual hypoglossal cross-union, histological evidence indicated that neuromuscular junction (nmj) reinnervation was present to some degree in all intrinsic tongue muscles and within geniohyoid. Lingual nerve fibres were also found within the dorsal keratinised lingual epithelium, reinnervating taste buds and intralingual ganglia. Greater auricular nerve fibres were unable to make contact with nmjs, nor were they found to any appreciable degree within the lingual mucosa. Vagal nerve fibres were found close to, but not innervating, nmjs, but did reinnervate taste buds, lingual vasculature and intralingual ganglia. It was concluded that nodose cells are unable to reinnervate vacated nmjs, but like lingual fibres can reinnervate lingual mucosa, intralingual ganglia and vasculature.

Fiber architecture and histochemistry in the cat neck muscle, biventer cervicis.

1. Biventer cervicis (BC) is an anatomically complex muscle that is divided by tendinous inscriptions into five in-series compartments of motor units. We have analyzed the fiber architecture and fiber-type composition of these different compartments using microdissection and histochemical methods. 2. BC narrows as it runs rostrally, but its in-series compartments have similar cross-sectional areas. The tapered shape of BC comes about because tendinous inscriptions and the tendon of insertion are oriented obliquely and muscle fibers attach in a progressively offset fashion from the medial to the lateral muscle edge. 3. Individual compartments of BC differ from one another in their architecture. The rostral two compartments (1 and 2) contain fibers of similar length that run between two plates of tendinous tissue. Compartments 3 and 4 are divided into two or three in-parallel subvolumes whose fiber bundles differ in their lengths and sites of attachment. Compartment 5 is the most variable in its structure. In some cats it is separated from compartment 4 by a tendinous inscription, but in other cats, it blends with a dorsomedial part of compartment 4 to form a single subvolume. 4. The relative lengths of fibers in different compartments were analyzed when the head and neck were held in different postures. Fibers in rostromedial regions were stretched more effectively when the head was flexed at suboccipital joints, and appeared to be less sensitive to movements at lower cervical joints. Movements across lower cervical joints produced substantial length changes in caudolateral parts of BC. 5. Muscle fibers of different histochemical types were not distributed evenly within each muscle compartment. Slow, oxidative (SO) fibers accounted for the majority of fibers near the nuchal midline but for only 30%-45% of fibers in lateral muscle regions. Proportions of fast, glycolytic (FG) fibers were greatest in lateral regions. Fast, oxidative-glycolytic (FOG) fibers were distributed quite uniformly throughout each compartment. 6. The specialized architecture of BC may shape its physiological capabilities. The complex internal structures of different compartments may alter the length-tension properties of BC.(ABSTRACT TRUNCATED AT 400 WORDS)