Fibre hybrids in type groups. An investigation of human muscle biopsies

[Histochemical and morphometric study of the fibrillar population of the diaphragm muscle. II. Cow and pig]

M-ATPase techniques, at different pH levels prior to incubation, as well as metabolic procedures (alpha-MGPDH and NADH-TR), were used to determine the fibre-type content of the lumbar and costal portions in the bovine and porcine diaphragm. The fibre samples were exposed to image analysis in order to evaluate both the morphometrical and statistical values. On the basis of staining reactions, the fibre types IA, IB and IIC were found in the lumbar portion of the bovine diaphragm; in the costal portion of the same diaphragm, IA, IB, IIA and IIC fibre types were observed. With regard to the porcine diaphragm, the I, IIA, IIB, IIC fibre types were present in both portions of the muscle. Further morphometrical and statistical data concerning all the fibre types are obtained and discussed.

Myosin ATPase intermediate density fibers for diagnosis of reinnervation

Myosin ATPase (pH 9.4) differentiates two muscle fiber types in healthy human muscle, while diseased muscle often contains intermediate density fibers (IDFs). We evaluated the possibility that, since almost all IDFs in pathologic muscle biopsies are changing type after reinnervation by a motor axon of the opposite type, IDFs are useful in diagnosis. In a retrospective study of 208 muscle biopsies, IDFs were seen as often as were esterase-positive angular atrophic fibers (EPAAFs). In denervation identified by EMG and by histopathology, EPAAFs and IDFs were found much more often than were other indicators. Of biopsies diagnosed without use of IDFs as minimal histologic change or no pathologic diagnosis, 16% had IDFs with sparse EPAAFs and 21% had IDFs without EPAAFs, suggesting mild denervation with rapid reinnervation. IDFs correlate well with EPAAFs, identifying reinnervated versus denervated fibers. Type grouping reveals completed reinnervation change that may be many years old, while IDFs are changing type when biopsied and thus reveal recent reinnervation and preceding denervation. IDFs usefully belong with the histochemical indicators used to evaluate muscle disease.

Muscle morphometry in motor neuron disease

It has previously been suggested that the pathological abnormalities seen in muscle biopsies from patients with motor neuron disease (MND) are of predictive value in relation to the rate of progression of the disease. In this study, quadriceps muscle biopsies from 19 patients with MND and 20 age matched controls were prepared for histochemistry and analysed morphometrically. Pathological features of denervation and reinnervation were observed in all MND patients although considerable variation between patients was noted. Motor neuron disease biopsies also showed increased connective tissue, an increased variation in fibre size, and a random fibre type distribution. Several of these abnormalities were more severe in female patients. Many of these 'abnormalities' were also frequent, albeit to a milder degree, in control biopsies and emphasize the need for age matched controls. The morphometric data was not related to the age of the patient, disease duration, type of MND or muscle strength, thus suggesting that the progression and severity of MND and its prognosis cannot be judged on the basis of quadriceps muscle pathology alone.

Motor innervation and fiber type pattern in amyotrophic lateral sclerosis and in Charcot-Marie-Tooth disease

A quantitive study of the terminal innervation ratio (TIR) was conducted using 18 amyotrophic lateral sclerosis (ALS) and 12 Charcot-Marie-Tooth disease (CMT) muscle biopsies. Morphometric and histochemical analyses of muscle fibers were performed in 9 ALS and 6 CMT biopsies. The results revealed that TIR and type grouping were significantly greater in CMT than in ALS. The proportion of type 3 fibers was higher in ALS, though the proportion of intermediate and type 0 fibers was significantly higher in CMT. The atrophy factor was significantly greater in type 3 than in types 1 and 2 fibers, but it was not significantly different in type 0 and intermediate fibers as compared to types 1 and 2, It appears, therefore, that CMT has a better capacity for collateral reinnervation than ALS. Type 0 and intermediate fibers may represent altered endproducts of successful collateral reinnervation.

[Selective muscle fiber type anomalies in neuromusclar disorders. An analysis of 124 consecutive muscle biopsies (author's transl)]

The following parameters were measured and calculated in 124 consecutive muscle biopsies: mean fiber diameter, standard deviation, percentage of type I and Type II fibers, variability coefficient, hypertrophy and atrophy factor. Twenty percent of the histometrically analyzed biopsies showed a type II atrophy and four percent a type I atrophy. Type II atrophy was found particularly in the following disorders: collagen vascular diseases, steroid myopathies, cachexia and as a result of inactivity. Some neurogenic processes also demonstrated a selective type II atrophy. The combination of a grouped type II atrophy with a type I hypertrophy is characteristic of chronic and usually heredodegenerative disorders of the motoneurons. The presence of a selective type II atrophy argues against a genetically determined muscular dystrophy. A mixed atrophy classified here as strong or very strong primarily suggests a neuropathy. A selective type I hypertrophy has been found exclusively in neurogenic processes, and type II hypertrophy predominantly in the cases of chronic heredodegenerative neurogenic and primarily myopathic diseases. An increase of the variability coefficient of both types of muscle fibers is more frequent and pronounced in neurogenic processes than in myopathic syndromes. Type II fibers show a selective increase in the variability coefficient considerably more often than type I fibers. In contrast to other reports we seldom found a fiber type predominance or a pathological type-grouping. Only two out of five biopsies with pathological fiber type-grouping were definitely neurogenic. In special cases the histometric analysis of muscle fiber types improves the diagnostic efficiency of muscle biopsies.

Human muscle fiber types in power lifters, distance runners and untrained subjects

Muscle biopsies were taken from the vastus lateralis of 12 males: 5 control subjects, 4 power lifters and 3 distance runners. Three fiber "types" were distinguished by comparing serial sections for alkaline myofibrillar adenosine triphosphatase (ATPase) and succinic dehydrogenase (SDH) activities: 1. high ATPase and low SDH; fast-twitch-glycolytic (FG). 2. High ATPase and high SDH; fast-twitch-oxidative-glycolytic (FOG). 3. Low ATPase and high SDH; slow-twitch-oxidative (SO). In some cases the distinction between the FOG and FG classess was not clear and a group termed "transitional" was employed. A variation in percentage of fiber types and fiber area was found among individuals. The percentage of SO fibers varied from 19.6-60.1% within all 3 groups, with a mean of 40.5%. In the control group approximately 75% of the fibers were oxidative (FOG + SO). The major characteristics of the lifters were a decrease in the percentage of FOG fibers and a hypertrophy of FOG and FG fibers. The distance runners had a high percentage of oxidative fibers with few FG fibers. It is suggested that the fast-twitch fibers are mainly involved in the adaptation of muscle to exercise since the percentage of SO fibers varies greatly among individuals within and between the 3 groups studied.

Limitations to the neuroregulation of enzymes in mammalian skeletal muscle

Muscle fibers of the sternomastoid and the tongue of the rat were characterized histochemically according to mitochondrial distribution (succinic dehydrogenase), as well as reactivity for the alkali- and acid-stabile "myofibrillar" adenosine triphosphatases. The principal fiber types of the sternomastoid was the large, "white" AalphabetaM fibers and the smaller, "intermediate" BbetaD and "red CalphaL fibers (figs. 1, 2, 3). The unusual musculature of the tongue was populated by diminutive AalphaM and CalphaM fibers, and variants thereof; all with relatively high mitochondrial content (figs. 4, 5, 6). Reinnervation of the sternomastoid muscle by the hypoglossal nerve caused most fibers of the sternomastoid to assume histochemical profiles reminiscent of those commonly observed in the tongue. However, the BbetaD fibers of the sternomastoid persisted in near usual numbers and disposition (fig. 17), despite their reinnervation by a nerve normally destined for a muscle lacking that particular fiber type. Thus, there are as yet unrecognized factors, possibly of neural origin, though more likely of muscle origin (genetic), that impose restrictions on the metabolism-regulating functions of substitute motoneurons.