The effects of experimental denervation and reinnervation on skeletal muscle fiber type and intramuscular innervation.

Porcine muscle has a unique grouped arrangement with 3-70 Type I fibers occurring in clusters surrounded by Type II fibers. The deep medial portion of the porcine semitendinosus exhibits a regular pattern of extensive Type I grouping whereas the superficial or lateral portion of the muscle exhibits Type II predominance. Mean values for terminal innervation ratios were 1.00 +/- 0.01 and 1.02 +/- 0.01 in normal superficial and deep semitendinosus respectively. Subterminal axons, therefore, do not branch intramuscularly and innervate only one muscle fiber in normal porcine muscle. Following nerve crush and subsequent reinnervation, fiber type conversion occurred which resulted in a fiber type grouping pattern dissimilar to the normal grouped arrangement. Significantly (P less than 0.01) elevated terminal innervation ratios (1.45-2.15) were measured in reinnervated muscle as a result of extensive branching of subterminal axons, but the percentage of Type I and Type II muscle fibers was unchanged. It was concluded that: (1) nerve crush causes distal nerve degeneration, loss of the normal fiber type pattern, and extensive collateral ramification of subterminal axons; (2) collateral reinnervation imposes a neuronal influence on muscle fibers which dictates transformation of all muscle fibers innervated by a single subterminal axon to a uniform histochemical profile; and (3) the type grouping observed in normal porcine muscle is not a result of neuronal influence mediated by collateral branching of subterminal axons.     

Congenital muscular dystrophy. A histochemical study with morphometric analysis on biopsied muscles

Muscle biopsies from 10 Japanese patients (9 females and 1 male) with congenital muscular dystrophy (CMD) were studied. Their clinical features varied remarkably in severity; one patient died at 6 years of age. Family history was negative in all but one patient who had an affected sibling. Muscle biopsy findings varied from mild myopathic to advanced dystrophic changes. Hypertrophic fibers associated with occasional fiber splitting were assumed to reflect a chronic dystrophic process. Histochemical examination revealed type 1 fiber predominance in 5 patients, and type 2 fiber predominance in one. Eight patients had a slight to moderate increase in the number of undifferentiated type 2C fibers suggesting a regenerating process after fiber necrosis. Type 2B fibers were fairly well preserved in 8 patients. The overall findings differed from those of the Fukuyama type congenital muscular dystrophy (FCMD) and Duchenne muscular dystrophy (DMD) in which more active fiber necrosis and regeneration are seen. We conclude that the present CMD patients suffered from a chronic dystrophic process similar to that in limb-girdle muscular dystrophy.     

Nemaline myopathy: comparative muscle histochemistry in the severe neonatal, moderate congenital, and adult-onset forms

A histochemical study of biopsied muscle specimens from patients with the 3 forms of nemaline myopathy (i.e., severe neonatal, moderate congenital, and adult-onset), classified on the basis of clinical symptoms, was conducted. A close relationship could not be found between the number of rods and the severity of weakness in any form. Type 1 fiber atrophy and predominance or type 2B fiber deficiency was the usual finding in all forms. In the moderate congenital form, type 1 fiber atrophy and predominance became more apparent in patients with a protracted course, suggesting that the histochemical abnormalities are progressive. The abnormal fiber type distribution is assumed to be related to the pathogenetic mechanism of nemaline myopathy in all forms. Because acid phosphatase activity was increased in muscle fibers of patients with rapid progression, an autodegenerative process inducing lysosomal enzyme activation may be responsible for the acute clinical progression and muscle fiber loss in this disorder.     

Muscle fiber type transformation in nemaline myopathy and congenital fiber type disproportion

In a morphometric study on biopsied muscles from 5 patients with nemaline myopathy (NM) and 5 with congenital fiber type disproportion (CFTD), the common findings were relative type 1 fiber smallness, type 1 fiber predominance and occasional hypertrophic type 2 fibers. In NM, the relatively larger type 1 fibers increased in number with age in parallel with a decrease in the number of normal to hypertrophic type 2 fibers, reflecting active fiber type transformation from type 2 to type 1, which resulted in striking type 1 fiber predominance. The presence of scattered non-atrophic type 2C fibers also reflected active fiber type transformation because the fibers during the maturational or degenerating process are known to show the type 2C reaction on ATPase staining. On the other hand, the type 1 fibers in CFTD were small in caliber and showed minimal variation in size, suggesting practically no fiber type transformation from hypertrophic type 2 to type 1.     

Arthrogryposis multiplex congenita: histochemical study of biopsied muscles

Morphometric analysis was performed after histochemical staining on 12 biopsied muscles of the affected limbs from 12 patients with arthrogryposis multiplex congenita. Except for one muscle, samples demonstrated variation in fiber size associated with abnormal fiber type distribution suggesting abnormal innervation: large groups of atrophic fibers in one muscle, either type 1 or 2 fiber predominance with occasional fiber type grouping in five, a complete lack of type 2 fibers in one, type one fiber atrophy in one, both type 2A and 2B fiber atrophy in two, and increased number of type 2C fibers in four. In most patients with arthrogryposis multiplex congenita, a defect in neural influence on the developing muscles may be responsible for the absence or maldevelopment of some muscle groups. Underdeveloped muscles are then assumed to induce imbalance of agonists and antagonists resulting in permanent contractures.     

Predominant fiber atrophy and fiber type disproportion in early ullrich disease

Ullrich disease (congenital muscular dystrophy type Ullrich, UCMD) is a severe congenital disorder of muscle caused by recessive and dominant mutations in the three genes that encode the alpha-chains of collagen type VI. Little is known about the early pathogenesis of this myopathy. The aim of this study was to investigate early histological changes in muscle of patients with molecularly confirmed UCMD. Muscle biopsies were analyzed from 8 UCMD patients ranging in age from 6 to 30 months. Type I fiber atrophy and predominance were seen early, together with a widening of the fiber diameter spectrum, whereas no dystrophic features were apparent. A subpopulation of more severely atrophic type I fibers was apparent subsequently, including one biopsy that fulfilled the formal diagnostic criteria of histopathological fiber type disproportion (FTD). Thus, early in the disease, UCMD presents as a non-dystrophic myopathy with predominant fiber atrophy. Collagen VI mutations also qualify as a cause of fiber type disproportion.     

Nemaline myopathy with type 2 fiber predominance; a case report]

A 4-year-old boy was admitted to our hospital because of dyspnea and muscle-weakness. His developmental milestones were delayed. His face was long with opened mouth. He spoke with nasal voice. He had proximally dominant muscle weakness and his deep tendon reflexes were absent. Laboratory examination revealed normal serum creatine kinase level and a myopathic EMG pattern. Blood gas analysis revealed metabolic acidosis with PH 7.35, PCO2 55.4 mmHg, PO2 62.4 mmHg, BE 3.0, probably from the metabolic acidosis by respiratory muscle weakness. In the biopsied left biceps brachii muscle, there were scattered fibers with nemaline bodies and abnormal fiber type distribution; type 1, 2 A, 2 B and 2 C fibers comprised 7%, 70%, 21% and 2% respectively. Small type 1 fibers and type 1 fiber predominance are the characteristic and common histochemical findings in nemaline myopathy. Accordingly, type 2 fiber predominance in the present patient is a unique, rare phenomenon. The finding might result from a preferential loss of type 1 motoneurons or muscle fiber type transformation from type 1 to type 2 fibers due to a certain abnormal neuronal influence on developing muscles.     

Long-term effects of spinal cord transection on fast and slow rat skeletal muscle: II. Morphometric properties

Morphometric properties of rat soleus and extensor digitorum longus muscles were studied 1 year following complete thoracic spinal cord transection (spinal cord level T9). Both muscles demonstrated almost complete type 1 to type 2 muscle fiber type conversion after 1 year. Muscle fiber atrophy was observed in both muscles. Type 2 fiber atrophy occurred to about the same extent in both muscles. Atrophy was most severe for the soleus type 1 fibers (50% decrease in size). Calculations based on the fiber type and size changes observed indicate that the percentage of the muscle cross-sectional area occupied by each fiber type was almost the same for both muscles 1 year after transection. Discriminant analysis of the data indicated that the percentage of type 2 fibers present in the muscle was the best discriminator between the various groups. These morphometric data provided a basis for understanding the contractile results presented in the previous study as well as insights into the mechanism of transformation in skeletal muscle. Furthermore, inherent differences between type 1 and type 2 fibers were demonstrated between predominantly slow and predominantly fast muscles. Thus, after almost one-half a lifetime of transection, rat muscles are almost completely transformed to fast muscle, and, regardless of initial conditions, have nearly identical properties.     

肉毒神经毒素A诱导兔咬肌萎缩及其组织形态学研究

目的探讨肉毒神经毒素A诱导兔咬肌萎缩及对骨骼肌组织形态学影响。方法健康成年新西兰白兔30只,随机取5只共10个咬肌不作任何处理作为正常对照组(N组),另25只进行肉毒素诱导咬肌萎缩试验,一侧咬肌内注射肉毒毒素A(B组),另一侧注射生理盐水作自身对照(S组)。试验组25只动物分5组,分别进行2周、4周、8周、12周和24周试验,于试验结束时用B型超声测两侧咬肌厚度,切除两侧咬肌称其湿重,并留取部份肌组织做切片进行HE染色、三磷酸腺苷(ATP酶)染色和还原型辅酶I还原酶(NADH—TR)染色,光镜下观察及图像分析。结果 N组与S组咬肌各项指标均无差异,咬肌厚度和湿重测量显示B组咬肌厚度和湿重减少,与N组和S组之间差异有显著性,咬肌萎缩程度逐渐加重,至第12周达到最重,第24周时维持与第12周时相等的水平。切片光镜检查显示肌纤维面积减小。ATP酶和NADH-TR染色见Ⅱ型肌纤维横截面积(CSA)减小,Ⅱb型纤维更加明显,I型纤维无明显变化。结论肉毒素A有肯定的诱导肌萎缩作用．其肌萎缩主要为Ⅱ型肌纤维,对I型肌纤维无明显影响。     

Muscular dystrophy in a litter of golden retriever dogs

Clinicopathologic findings from two golden retriever dogs with an inherited, progressive, degenerative muscle disease that were studied until 27 and 40 months of age are described. Initial clinical signs included stilted gait and simultaneous advancement of their pelvic limbs. Further gait restriction and muscle hypertrophy eventually occurred. Serum creatine kinase was dramatically elevated (greater than 10,000 U/L). There were persistent "spontaneous" high-frequency discharges (pseudomyotonia) on electromyographic evaluation. Features of both muscle fiber degeneration (hyaline fibers, myophagocytosis) and regeneration (small basophilic fibers) were seen on light microscopy. Similar ultrastructural changes (fiber hypercontraction, increased myoblasts) were present. On morphometric histochemical evaluation, mean fiber diameter of both type 1 and 2 fibers was increased compared with controls in two of three muscles examined. There was no apparent fiber type predominance. Scattered ragged red fibers were seen, but this appeared to be a nonspecific finding of either muscle fiber regeneration or degeneration. These findings and potential contributing pathophysiologic mechanisms are discussed in relation to Duchenne muscular dystrophy.     

Preferential central nucleation of type 2 myofibers is an invariable feature of myotonic dystrophy type 2

The clinical features of myotonic dystrophy type 1 (DM1) and type 2 (DM2) may present striking similarity, whereas, in some cases, the DM2 phenotype may be so mild that the diagnosis may be missed. Therefore, the identification of disease-specific histopathological patterns for DM1 and DM2 may help clinicians to correctly address genetic studies. We performed a comparative morphological and morphometric analysis on muscle biopsies from 10 DM1 and 11 DM2 patients, comparing type 1 and type 2 fibers as to: fiber type predominance, transverse diameter, atrophy and hypertrophy factors, and prevalence of central nuclei. In DM1 cases we observed preferential type 1 fiber atrophy and a higher prevalence of central nucleation among type 1 fibers in all cases. In DM2 muscle biopsies, high rates of atrophic and hypertrophic type 2 fibers were observed in most cases, and preferential central nucleation in type 2 fibers was present in all cases. As opposed to DM1, in which type 1 fibers display most of the histological changes, preferential atrophy and hypertrophy of type 2 fibers may be considered as markers of DM2. A higher prevalence of central nuclei among hypertrophic type 2 fibers has a predictive value for the diagnosis of DM2. Thus, morphometric and fiber type-based histological analysis of muscle biopsies may help differentiate between DM1 and DM2 and guide molecular analysis.     

Congenital fiber type disproportion in identical twins

Eighteen-month-old identical twins with the muscle histological characteristics of congenital fiber type disproportion are reported. The fiber typing system of pH-dependent adenosine triphosphatase was used to analyze the size and percentage of type 1, 2A, and 2B fibers in muscle tissue obtained by needle biopsy. Both twins had significantly larger type 2 than type 1 fibers, with 2B fibers representing the largest type. One patient also had type 1 predominance at the expense of a reduction in 2B (2B deficiency). The probands as well as other family members had transient delayed motor development, macrocephaly, and normal intelligence. A biopsy obtained from 1 of these family members failed to demonstrate a similar histological abnormality. The disorder is nonprogressive in this family, as evidenced by minimal disability in the older members and gradual improvement in the probands.     

Type 2 fiber predominance in Lambert-Eaton myasthenic syndrome

Serial muscle biopsies in a noncarcinomatous case of Lambert-Eaton myasthenic syndrome (LEMS) have shown progressive atrophy and loss of type 1 fibers, resulting in overwhelming type 2 predominance. A similar abnormality was found in a single biopsy from a second case of LEMS without associated carcinoma. Review of the literature suggests that type 2 fiber predominance has been observed in at least one other biopsied case. Interference with transmitter release caused by anti-voltage-gated calcium channel antibodies may deprive type 1 muscle fibers of the low frequency discharge necessary to maintain their metabolic properties.     

Progressive centripetal degeneration in polyneuropathies (author's transl)

This is a clinicopathologic report on three patients with sensory polyneuropathies of different origin. Sensory loss involved all four limbs reaching the upper third of the thighs and the elbow level or higher, in all three patients. In addition to the limbs the central region of the anterior aspect of the trunk, from lower abdomen up to level T2, and on the top of the scalp were involved. There was minimal weakness. This pattern of sensory deficit can best be explained by a length dependent degeneration of fibers. Familial amyloidosis, Portugese type, was responsible for the neuropathy in the first patient, diabetes mellitus in the second and alcoholism in the third one. On teased nerve fiber study, single regenerating fibers were isolated on sural nerve biopsy specimens from patients 1 and 2. Segmental demyelination and/or remyelination occurred in 11 per cent of the fibres in patient 1, in 36 per cent in patient 2 and in 4 of the 19 fibres isolated in patient 3. On cross sections of nerve specimens embedded in Epon there was a striking loss of myelinated fibres which was less important and predominated on smaller fibres in patients 1 and 2. On electron microscopic examination loss of unmyelinated fibres was conspicuous in all three patients. On single fiber studies as well as on sections of embedded specimens, myelinated fibres occasionally showed demyelination in contact to amyloid deposits. The present study demonstrates that in this pattern of neuropathy degeneration of myelinated fibers begins in the distal part of longest axons and may be associated with axonal sprouting in more proximal parts of degenerating axons. As the neuropathy progresses axons of shorter and shorter length become involved.     

A freeze-fracture study of fiber types in normal human muscle.

The sarcoplasmic reticulum (SR) and plasma membranes of Type 1 and Type 2 fibers of normal human muscle were examined by the freeze-fracture technique. Total particle counts in the SR appeared much lower than in other mammals and a packing density of about 1200 particles/micrometer 2 was found in both longitudinal and cisternal components of SR. There was no difference in particle density of Type 1 and Type 2 fibers. In freeze-fracture replicas of plasma membranes several fiber type differences were seen. The surface caveolae were uniformly distributed in Type 1 fibers whereas in Type 2 they were clustered preferentially at the I-band levels. Total density of intramembranous particles was greater in Type 1 fibers (347 +/- 68/micrometer 2 in P-face, 58 +/- 11/micrometer 2 in E face) than in Type 2 fibers (207 +/- 30/micrometer 2 in P-face, 80 +/- 9/micrometer 2 in E-face). There was a striking difference in respect to rectilinear arrays which were virtually absent in Type 1 fibers (0--2/micrometer 2) and numberous (up to 50--70/micrometer 2) in Type 2 fibers.     

Both type 1 and type 2a muscle fibers can respond to enzyme therapy in Pompe disease

Muscle weakness is the main symptom of Pompe disease, a lysosomal storage disorder for which major clinical benefits of enzyme replacement therapy (ERT) have been documented recently. Restoration of skeletal muscle function is a challenging goal. Type 2 muscle fibers of mice with Pompe disease have proven resistant to therapy. To investigate the response in humans, we studied muscle biopsies of a severely affected infant before and after 17 months of therapy. Type 1 and 2a fibers were marked with antibodies, and lysosome-associated membrane protein-1 (Lamp1) was used as the lysosomal membrane marker. Quantitative measurements showed a 2.5-3-fold increase of fiber cross-sectional area of both fiber types during therapy and normalization of the Lamp1 signal in approximately 95% of type 1 and approximately 75% of type 2a fibers. The response of both type 1 and 2a muscle fibers in the patient studied herein corroborates the beneficial effects of enzyme therapy seen in patients with Pompe disease.     

Muscle histochemistry in myotubular (centronuclear) myopathy

We report the clinical and histochemical findings in 7 patients with myotubular (centronuclear) myopathy aged from 2 months to 32 years. The clinical symptoms varied from patient to patient. Three patients developed severe muscle weakness and hypotonia with respiratory distress from infancy, and 4 had muscle weakness from 2-5 years of age with no apparent delay in developmental milestones. In addition to an increased number of fibers with centrally placed nuclei, there were 3 other histochemical characteristics of this disorder, i.e., type 1 fiber predominance, type 1 fiber hypotrophy and type 2B fiber deficiency. Other histological findings included a peripheral halo in the sarcoplasm on NADH-TR staining and an increased number of undifferentiated type 2C fibers, indicating a delay in muscle fiber growth and differentiation due to a probable defective neural supply in the developing muscles.     

A case of progressive hemiatrophy with type 2 muscle atrophy in muscle biopsy]

We reported a case of progressive hemiatrophy, whose skeletal muscle biopsy revealed type 2 fiber atrophy. This patient, a 40-year-old woman, noticed left leg atrophy at the age of 39. She had a history of minor trauma of the left thigh at the age of 30. On admission, physical examination revealed atrophy of various parts of her left side of body, predominantly in the left leg. There was no dermatological or neurological abnormalities except these atrophies. Hematological and biochemical examinations were normal. EEG, EMG, nerve conduction studies and autonomic function tests were normal in either side of the body. MRI study showed reduced muscle bulk as well as subcutaneous fatty tissue especially in her left leg. Skeletal muscle biopsy of her left quadriceps femoris muscle revealed type 2 fiber atrophy and type 1 fiber predominance. However, no abnormality was found in the intramuscular nerves. We considered that type 2 muscle fiber atrophy was one of the cause of atrophy of this case.     

STUDIES ON EPIDEMIOLOGICAL, CLINICAL AND ETIOLOGICAL ASPECTS OF ALS DISEASE IN SARDINIA, SOUTHERN ITALY

This investigation was conducted to clarify the epidemiology of ALS disease in Sardinia. During the years 1965–1974, the average annual incidence was found to be 0.64/100,000 inhabitants. On prevalence day, October 24st, 1971, the prevalence rate was 1.56/100,000 inhabitants. A significant male predominance was found, the average annual incidence rates for men and women being 0.88 and 0.40 respectively. The peak in both sexes was reached between 60 and 69 years. ALS distribution in the study area was uniform but its occurrence was significantly higher among agricultural workers (5.28/100,000). ALS started on average at 56.58 years and its duration was 2.5 years, being significantly longer in patients under 40-years-old. The distribution of the various clinical forms was: 66 per cent conventional forms, 20 per cent bulbar and 14 per cent pseudo-polyneuritic. In the bulbar type, a female predominance was found. About 96 per cent of cases were sporadic and 4 per cent familial. Familial cases presented no difference from sporadic cases. Trauma was present in 10.5 per cent of the cases and gastrointestinal disfunction in 13 per cent. This probably reflects some relationship between trauma and ALS, and between malnutrition and ALS. No combination of ALS, dementia and parkinsonism was observed. Dementia was associated with ALS in four cases and Parkinson's disease in one case, separately. The combination of other disease states with ALS in the present study may be simple coincidence.     

骨关节病患者肌纤维萎缩类型及其与日常活动的相关性

背景：骨关节病患者因制动等原因可出现严重的肌纤维萎缩,但目前对这类肌纤维萎缩的微观分类及其与日常活动的研究较少。 目的：观察骨关节病患者肌肉萎缩类型以及其与日常活动的相关性。 方法：纳入24例老年女性骨关节病患者,应用功能独立性评定量表对患者习惯性的日常运动进行了评价,在进行关节置换过程中对患者肌纤维进行了测定并通过活检进行组织病理学侧量。同时选取同期因骨折需要进行修复的4例女性患者为对照组。观察患者的肌纤维(Ⅰ型、ⅡA型和ⅡB型)发生萎缩类型和比率变化。 结果与结论：骨关节病患者根据发生萎缩的肌纤维类型不同,分为1型、2B型何1+2AB型。Ⅰ型的肌纤维肌横截面积明显小于ⅡA型和ⅡB型肌纤维(P < 0.05)。大部分骨关节病患者在得病过程中仅发生同一种肌纤维类型的萎缩,而非所有的肌纤维均出现萎缩。功能独立性评定量表评分从1+2AB型,2B型和1型逐渐减少(P < 0.05)。结果证实,肌肉萎缩1+2AB型对骨关节病患者日常活动影响最大,而单纯的2B型影响最小。