Muscle fibre type composition in distal myopathy (Welander). An analysis with enzyme- and immuno-histochemical, gel-electrophoretic and ultrastructural techniques

Fiber-type phenotype of the jaw-closing muscles in Gorilla gorilla, Pan troglodytes, and Pan paniscus: A test of the Frequent Recruitment Hypothesis

Skeletal muscle fiber types are important determinants of the contractile properties of muscle fibers, such as fatigue resistance and shortening velocity. Yet little is known about how jaw-adductor fiber types correlate with feeding behavior in primates. Compared with chimpanzees and bonobos, gorillas spend a greater percentage of their daily time feeding and shift to herbaceous vegetation when fruits are scarce. We thus used the African apes to test the hypothesis that chewing with unusually high frequency is correlated with the expression in the jaw adductors of a high proportion of type 1 (slow, fatigue-resistant) fibers at the expense of other fiber types (the Frequent Recruitment Hypothesis). We used immunohistochemistry to determine the presence and distribution of the four major myosin heavy chain (MHC) isoforms in the anterior superficial masseter (ASM), superficial anterior temporalis, and deep anterior temporalis of four Gorilla gorilla, two Pan paniscus, and four Pan troglodytes. Serial sections were stained against slow (MHC-1/-α-cardiac) and fast (MHC-2/-M) fibers. Fibers were counted and scored for staining intensity, and fiber cross-sectional areas (CSAs) were measured and used to estimate percentage of CSA of each MHC isoform. Hybrid fibers accounted for nearly 100% of fiber types in the masseter and temporalis of all three species, resulting in three main hybrid phenotypes. As predicted, the gorilla ASM and deep anterior temporalis comprised a greater percentage of CSA of the slower, fatigue-resistant hybrid fiber type, significantly so for the ASM (p = 0.015). Finally, the results suggest that fiber phenotype of the chewing muscles contributes to behavioral flexibility in ways that would go undetected in paleontological studies relying solely on morphology of the bony masticatory apparatus.

Abnormal palatopharyngeal muscle morphology in sleep-disordered breathing

The aim of the present study was to investigate whether histopathological changes can be detected in two soft palate muscles, the palatopharyngeus and the uvula, in 11 patients with long duration of sleep-disordered breathing (SDB). Muscle samples were collected from patients undergoing uvulo-palatopharyngoplasty (UPPP). Reference samples from the corresponding areas were obtained at autopsy from five previously healthy subjects. Muscle morphology, fibre type and myosin heavy chain (MyHC) compositions were analysed with enzyme-histochemical, immunohistochemical and biochemical techniques. The muscle samples from the patients, and especially those from the palatopharyngeus, showed several morphological abnormalities. The most striking findings were (i) increased amount of connective tissue, (ii) abnormal variability in fibre size, (iii) increased proportion of small-sized fibres, (iv) alterations in fibre type and MyHC compositions, (v) increased frequency of fibres containing developmental MyHC isoforms. Our findings point towards a pathological process of denervation and degeneration in the patient samples. Conclusively, the morphological abnormalities suggest a neuromuscular disorder of the soft palate in SDB patients.

Distal myopathies

Among various previously described distal myopathies, several diseases have now been established as clinically and genetically distinct entities. The most representative diseases are dominantly inherited Welander distal myopathy and tibial muscular dystrophy, and the recessively inherited distal myopathy with rimmed vacuoles and distal muscular dystrophy (Miyoshi myopathy). Since the discovery of the gene loci for several distal myopathies, several diseases previously categorized as different disorders have now proven to be the same or allelic disorders (e.g. distal myopathy with rimmed vacuoles and hereditary inclusion body myopathy, Miyoshi myopathy and limb-girdle muscular dystrophy with gene locus at 2p13). Except for Miyoshi myopathy, which has the typical findings of muscular dystrophy, most of the distal myopathies share the common pathologic features of myopathic changes with rimmed vacuoles. The pathologic changes are somewhat similar to those seen in chronic muscular dystrophy, but necrotic and regenerative processes are less prominent and creatine kinase levels are either normal or only mildly elevated. Further study is necessary to determine why rimmed vacuoles are so common in the distal myopathies, and what role they play in the pathogenesis of muscle fibre atrophy and loss, predominantly in the distal portions of the extremities.

Welander distal myopathy--an overview

Welander distal myopathy has an autosomal dominant inheritance and a late onset. The onset of symptoms is in the hands and gradually distal muscles of the lower extremities are involved. The most-affected muscles are the long extensors of the hands and feet. CK-values are normal or slightly elevated. There is never any cardiac involvement in Welander distal myopathy. Neurophysiological findings are of both myopathic and neuropathic character. Histopathological findings in muscle biopsies are mainly of myopathic type and include rimmed vacuoles which correspond to autophagic vacuoles on the ultrastructural level. Tubulo-filamentous inclusions with a diameter of 16-21 nm, i.e. of the same type as found in patients with Inclusion Body Myositis, are found in the sarcoplasm and in myofibre nuclei. A neurogenic component in Welander distal myopathy has been suggested, on the grounds of a sensory dysfunction, neuropathic findings on neurophysiology and muscle biopsy and a decrease of A-delta nerve fibres on sural nerve biopsy. Genetic analysis has excluded linkage to other defined distal myopathies and hereditary Inclusion Body Myopathy loci.

Hereditary distal myopathy with granulo-filamentous cytoplasmic inclusions containing desmin, dystrophin and vimentin

A 56-year-old female and her 34-year-old daughter presented with a predominantly distal myopathy affecting the peroneal and calf muscles, neck flexors and hand muscles. Both patients and two other daughters had cardiac arrhythmias, three requiring the insertion of cardiac pacemakers. Skeletal muscle biopsies revealed a complex myopathic process with granular degeneration, rimmed vacuoles and eosinophilic cytoplasmic inclusions. Ultrastructurally, the inclusions were composed of electron dense granular material and filaments forming linear masses beneath the sarcolemma and rounded masses within the cytoplasm of the fibres. Immunohistochemistry revealed labelling of the inclusions for desmin, dystrophin and vimentin, but not for alpha-actinin, spectrin, utrophin or myosin heavy chains. This family shows a hereditary distal myopathy with some features in common with previously-reported cases in which biopsies showed cytoplasmic inclusion bodies containing desmin. This group of diseases is clinically and pathologically heterogeneous. In the present cases, the accumulation of cytoplasmic filaments may reflect a generalised disturbance of filamentous protein metabolism rather than a specific disorder of desmin.

Immunohistochemical characterization of human masseter muscle spindles

An enzyme- and immunohistochemical study has been performed on human masseter muscle spindles. Antibodies selective for different myosin heavy chain (MHC) isoforms and M-band proteins (M-protein, myomesin, and MM-CK) were used. The expression of these proteins was determined in the different intrafusal fiber types. Nuclear bag1 and nuclear bag2 fibers expressed predominantly slow-twitch and slow-tonic MHCs. The bag2 fibers in addition contained fetal MHC. Nuclear chain fibers coexpressed embryonic, fetal, and fast-twitch MHCs. The bag2 and chain fibers contained all three M-band proteins, whereas the bag1 fibers contained only myomesin. In general the MHC expression in the human masseter intrafusal fiber types was similar to that previously reported for limb muscles in man as well as for limb and masseter muscles in other species. However, the number of intrafusal fibers per spindle was unusually high (up to 36). This reinforces the idea that masseter muscle spindles have a strong proprioceptive impact during the control of jaw movements.

Muscle fibre degeneration in distal myopathy (Welander)--ultrastructure related to immunohistochemical observations on cytoskeletal proteins and Leu-19 antigen

In seven patients with long-standing and six patients with early symptoms of Welander distal myopathy (WDM), monoclonal antibodies directed against such cytoskeletal proteins as dystrophin, spectrin and desmin and against Leu-19, a myoblast and satellite cell related antigen, were applied to muscle biopsies from the anterior tibial and soleus muscles. In addition, ultrastructural studies were carried out on biopsies from the soleus muscle. In muscle fibres from patients with early symptoms there was normal immunostaining for dystrophin, spectrin, desmin and Leu-19. In the patients with long-standing symptoms, there was also a normal expression of dystrophin, and a normal staining for spectrin and desmin was found in normal sized muscle fibres. Occasionally normal sized muscle fibres showed staining for Leu-19. Increased staining for spectrin and desmin and a strong Leu-19 staining was seen in normal sized muscle fibres with rimmed vacuoles and in atrophic fibres. Increased staining for spectrin, desmin and Leu-19 has been described in denervated muscle fibres and, thus, the present findings may support earlier findings of a neurogenic component in Welander distal myopathy. In the soleus muscle, ultrastructural muscle fibre abnormalities conformed to those in the anterior tibial muscle. Many rimmed vacuoles were observed which corresponded, at the ultrastructural level, to autophagic vacuoles. Intranuclear and cytoplasmic filamentous inclusions of the same shape and diameter as in inclusion body myositis were observed.

Intranuclear and cytoplasmic filamentous inclusions in distal myopathy (Welander)

Ultrastructural examination of anterior tibial muscle from four patients with late-onset autosomal dominant distal myopathy of Welander-type revealed intrasarcoplasmic filamentous inclusions in association with rimmed vacuoles. In one of the patients, identical intranuclear filamentous inclusions were also found. These filamentous inclusions are similar to those described in inclusion body myositis (IBM). They have also been observed in hereditary neuromuscular disorders including autosomal recessive distal myopathy. Thus, the filamentous inclusions occur in different neuromuscular conditions with different etiologies. These findings further raise the question of the specificity of the filamentous inclusions in IBM.

Welander's distal myopathy: clinical, neurophysiological and muscle biopsy observations in young and middle aged adults with early symptoms

Nine young or middle aged patients with early symptoms of Welander's distal myopathy were subjected to a detailed neurological examination including quantitative sensory testing, determination of motor and sensory nerve conduction velocity (NCV), sensory nerve action potentials, electromyography (EMG) and muscle biopsy from the tibialis anterior muscle (TA). Slight weakness of the extensors of the fingers and hands was found in all nine patients, and of the dorsiflexors of the feet in seven. All patients had a distal sensory disturbance most prominent for temperature which agrees with earlier observations. EMG changes in TA and extensor digitorum communis (EDC) muscles were of myopathic type. Slight abnormalities compatible with either myopathy or early neuropathy were found in one muscle biopsy. These findings indicate that a neurogenic lesion affecting at least the peripheral sensory system is present at an early stage of Welander's distal myopathy and that the neurogenic lesion might precede the myopathic changes.

Inclusion body myositis and Welander distal myopathy: a clinical, neurophysiological and morphological comparison

Five patients with inclusion body myositis (IBM), an acquired inflammatory myopathy, and five patients with Welander hereditary distal myopathy (WDM) were compared clinically and with neurophysiological and morphological techniques. Both diseases have a late insidious onset, but the course of IBM is more severe. IBM mainly affects proximal muscles in the lower extremities, while distal muscle groups are involved in both upper and lower extremities. In WDM there is always a strict distal muscle involvement. The neurophysiological characteristics of the two conditions include both myopathic and neurogenic components. In both diseases there were rimmed vacuoles in muscle fibres and at the ultrastructural level cytoplasmic 15-18 nm filamentous inclusions. Although the histopathology of muscle in IBM and WDM has some common features, inflammatory infiltrates were never found in WDM. Such infiltrates seem to be an important clue to the correct diagnosis of IBM.

Muscle lipofuscin content and satellite cell volume is increased after high altitude exposure in humans

Muscle ultrastructural changes during a typical expedition to the Himalayas were analyzed by taking muscle biopsies from seven climbers before and after their sojourn at high altitude (over 5000 m for 8 weeks). M. vastus lateralis samples were analyzed morphometrically from electron micrographs. A quantitative evaluation was made of lipofuscin, satellite cells and myonuclei. Significant increases of the volume densities of lipofuscin (+ 235%) and satellite cells (+ 215%) were observed.

Neurogenic involvement in distal myopathy (Welander). Histochemical and morphological observations on muscle and nerve biopsies

Patients with distal myopathy (Welander) were subjected to muscle biopsy from the anterior tibial muscle (n = 4) and to nerve biopsy from the sural nerve at the ankle (n = 5) in order to elucidate a possible neurogenic component of the disease. The type I muscle fibres had a larger mean cross-sectional area as compared to normal controls and an increased variation in fibre size with both hypertrophic and atrophic fibres in one and the same biopsy. A normal muscle fibre type composition was found in the patients. Structural muscle fibre abnormalities such as atrophic fibres, mainly angulated, split fibres, rimmed vacuoles and centrally located nuclei were found in all biopsies. A disorganization and loss of myofibrils as well as autolytic vacuoles were the most prominent findings at the ultrastructural level. Two patients had a moderate loss of myelinated sural nerve fibres. The mean nerve fibre density was decreased as compared to normal controls while the mean nerve fibre area and circular diameter were increased due to selective loss of small diameter (A-delta) nerve fibres. The muscle and nerve fibre abnormalities are discussed with reference to neuropathic and myopathic changes. Some muscle fibre abnormalities are typical for a neurogenic disorder while some others are mostly seen in myopathies but may also appear in neurogenic conditions. A neurogenic etiology in Welander distal myopathy is further supported by the finding of loss of small diameter nerve fibres in the sural nerve.

Sequential studies of a childhood myopathy: a clinical, histochemical and morphometric investigation

An unusual inherited progressive distal myopathy of early childhood onset is described in two sisters from a consanguineous Asian family. Motor milestones were normal but gait deteriorated slowly thereafter with development of generalized hypotonia and muscle weakness particularly in the wrist extensors and hand muscles. Muscle biopsies obtained at the ages of 6 and 10 years respectively (Case 1) showed significant differences. At 6 years muscle morphology and histochemical appearance were normal although type I fibres predominated (79%) and a substantial pool of 'undifferentiated' fibres (12%) was present. By 10 years there was a significant reduction in type I fibres (-13%) and in 'undifferentiated' fibres (-10%) with a concomitant increase in type II fibres (+23%). Fibre size and shape were normal at the age of 6 years but no further fibre growth was evident 4 years later. The older sister (Case 2, age 13 years) was similarly affected. The possibility of this progressive myopathy being caused by loss of neural control at two separate stages of development is discussed. The importance of performing sequential morphometric studies of muscle biopsies from patients with unusual childhood myopathies is emphasized.

Effects of excessive use of remaining muscle fibers in prior polio and LV lesion

Twenty-three subjects with weakness of musculus tibialis anterior (TA) due to prior poliomyelitis (n = 19) or prior LV lesion (n = 4) were examined regarding the use of remaining TA motor units during walking and the consequences of long-term overuse for the TA muscle fibers. Subjects with an excessive overuse exhibited almost only type 1 muscle fibers and with marked hypertrophy. Subjects who did not use remaining TA fibers because of too-severe paralysis had a normal fiber type differentiation and fiber atrophy. The use of remaining TA motor units was correlated to the type 1 muscle fiber percentage (r = 0.69) and to the type 1 fiber size (r = 0.78). Identical changes were observed in subjects with prior poliomyelitis and in subjects with prior LV lesion and were, thus, not specific for poliomyelitis. The changes in fiber type composition may be explained by a transition of type 2 to type 1 muscle fibers in accordance with previously reported experimental transneuronal stimulation through implanted electrodes in animals.

Adult human masseter muscle fibers express myosin isozymes characteristic of development

Masseter muscle biopsies were obtained from nine patients undergoing orthognatic surgery or surgery for parotid tumors. A detailed enzyme-histochemical and immunocytochemical study of these muscles was performed using antibodies specific to the various isozymes of the myosin heavy chain (MHC) in order to identify the MHC isozymes that were present in the different fiber types. The contractile proteins in these same biopsies were analyzed by two-dimensional gel electrophoresis, native pyrophosphate gel electrophoresis, and by an immunopolypeptide mapping approach. These studies have shown that there is a very heterogeneous distribution of the myosin isozymes, with many fibers containing more than one myosin type. We also present evidence that in addition to adult fast and slow myosin, the human masseter muscle contains two proteins, neonatal MHC and embryonic myosin light chain, that are characteristic of developing muscle.

Autonomic cardiovascular responses in distal myopathy (Welander)

Autonomically mediated cardiovascular responses were evaluated in 9 patients with Welander distal myopathy and compared to data from an age- and sex-matched control group. The myopathy patients had a normal respiratory sinus arrhythmia and a normal heart rate response to the Valsalva menoeuvre, indicating a normal vagal function. They had a normal initial heart rate response to the orthostatic position, indicating a normal function of the sympathetic nerves. The main difference between the groups was found in the orthostatic position. The myopathy patients reacted with a greater increase in systolic blood pressure and a smaller heart rate increase than the controls. This suggests an altered peripheral vasomotor function, possibly with a more predominant activation of alfa than beta adrenergic receptors leading to vasoconstriction. In addition, a low forearm blood flow at rest and a les pronounced blood flow increase during the isometric handgrip were found in the myopathy patients. This finding could also be explained by proneness to vasoconstriction. It is concluded that patients with Welander distal myopathy have no signs of dysfunction of the peripheral autonomic nerves.

Sensory involvement in distal myopathy (Welander)

Eleven patients with Welander distal myopathy were subjected to detailed sensory testing including measurements of perception thresholds for vibration and temperature in both hands and feet. The threshold values were compared with normal, age-corrected values and also with data from an age-matched control group consisting of patients with antecedent poliomyelitis with the same degree of paresis. The screening examination indicated impaired thermal sensibility in all 11 patients and impairment for at least one other sensory modality in 9 patients. In comparison with age-corrected normal values, the measured warm-cold difference limen was abnormal in the feet of 9 patients and the vibratory threshold at least at one test point in 6 patients. When compared with the data from the paretic controls, the thermal abnormality was significant with regard to warm and cold thresholds, the warm-cold difference limen and the heat pain threshold. The vibration threshold abnormality was significant in the feet. It is concluded that sensibility impairment is present in Welander's myopathy indicating a peripheral sensory neuropathy involving both unmyelinated (C-fibers) and myelinated fibers.

Muscle fibre type composition, motoneuron firing properties, axonal conduction velocity and refractory period for foot extensor motor units in dystrophia myotonica

Seven patients with dystrophia myotonica were investigated using neurophysiological combined with histochemical techniques to elucidate motor unit properties in foot extensor muscles, which are often involved in the early stages of this disorder. For the 25 extensor digitorum brevis motor units studied the axonal conduction velocity, the axonal refractory period and the voluntary firing properties were within normal limits. However, high threshold motor units were not observed and the mean value of the axonal conduction velocities was lower (p less than 0.02) for the dystrophia myotonica motor units when compared with corresponding data from healthy subjects. There were also signs of impaired impulse propagation in the terminal part of the motor unit. In muscle biopsy specimens from the anterior tibial muscle, fibre type composition and structure were demonstrated using enzyme histochemical techniques for adenosine-triphosphate and immunohistochemical techniques for identification of the types of myosin isoform present. The histochemical findings indicated a type I fibre dominance, which was most obvious in the more seriously affected muscles. Neonatal myosin was observed preferentially in small but also in some normal sized fibres. Furthermore, some ring fibres were present and these showed staining with antineonatal myosin in their superficial portion. This indicates that an abnormal regeneration is one cause of the myopathic appearance of the muscle fibres in dystrophia myotonica. These investigations show that there is a reduced proportion of type II motor units in foot extensor muscles involved in the myopathy in dystrophia myotonica although it cannot definitely be established whether this is due to a loss of high threshold type II motor units or type II to type I transformation.

High serum levels of creatine kinase: asymptomatic prelude to distal myopathy

Two brothers and an unrelated man had serum creatine kinase values of 3000-8000 units when they were asymptomatic, and there was no weakness on examination. EMG and muscle biopsy showed changes indicative of myopathy. Years later, all three developed weakness that was limited to the gastrocnemius. Because siblings were affected, the disorder can be regarded as a form of muscular dystrophy. The distribution of weakness, serum enzyme changes, and histologic changes resembled an autosomal recessive distal myopathy first described by Miyoshi and differed from many other reported cases of distal myopathy. Our cases also indicate that myopathy may be asymptomatic.