Peripheral neuropathy in the spontaneously diabetic WBN/Kob rat

We report that the morphological characteristics of the periperhal neuropathy in WBN/Kob rat, a diabetic animal model that develops persistent diabetes, were primary segmental demyelination and secondary axonal degeneration. These findings are similar to those in human patients with diabetes mellitus and unlike those in rodents with streptozotosin-induced diabetes. However, these changes were also indistinguishable from those of age-dependent neuropathy. In the spontaneous peripheral motor neuropathy of rats, pressure neuropathy from housing in wire-mesh cages has also been reported to be indistinguishable from the peripheral neuropathy in plantar nerve or tibial nerve. Therefore, we examined phrenic nerves that were free from the pressure of body weight in rats and described the changes with light and electron microscopy. The morphological changes of the nerve fibers consisted of myelin blebbing or distention, and early remyelination. The changes were seen with age. On morphometric analysis, a marked reduction of fiber occupancy was observed in WBN/Kob rats over 23 months old. The present study demonstrated that the peripheral neuropathy of WBN/Kob rats is myelinopathy. Since the phrenic nerve was not affected by pressure neuropathy anatomically, this study indicates that the peripheral neuropathy of WBN/Kob rats is not pressure neuropathy. Received: 15 January 1996 / Revised, accepted: 13 June 1996     

Peripheral motor neuropathy in spontaneously diabetic WBN/Kob rats: a morphometric and electron microscopic study

Summary The morphology and function of peripheral motor nerves of WBN/Kob rats of the newly identified strain with late onset and long-lasting diabetes were studied in comparison with those of nondiabetic age-matched rats. The most conspicuous and frequent change seen by electron microscopy in the diabetic rats was myelinopathy, initiated by vesicle formation in granular material accumulated in the myelin lamella. Initial changes developed into myelin blebbing or distention, demyelination and remyelination. A decreased population of nerve fibers in diabetic rats of advanced age suggested that the final stage of these changes was neuronal loss resulting from complete destruction of the neurons. The myelinopathy was consistently more frequent and conspicuous in diabetic rats than in age-matched nondiabetic rats, but the difference was not significant in rats of over 28 months old, because of the age-dependent increase of the change in older rats. The conduction velocity was significantly less in diabetic rats than in age-matched nondiabetic animals at 20 months but not at 28 months of age, because at the older age nondiabetic rats also showed a reduced conduction velocity. These findings showed that male WBN/Kob rats develop diabetic motor neuropathy, but that the essential changes in diabetic neuropathy are indistinguishable morphologically and functionally from those in age-dependent neuropathy.     

Age-related changes in coagulation, fibrinolysis, and platelet aggregation in male WBN/Kob rats

We investigated the age-related changes in blood coagulation, fibrinolysis, and platelet aggregation in male WBN/Kob rats, animals that exhibit spontaneously diabetes mellitus at more than 6 months of age. The rats aged 6 months or more showed significant hyperglycemia, hypoinsulinemia, and hyperlipidemia. As changes in coagulation parameters, the data indicated significant increases in factors II, V, VII, VIII, IX, X, and XII activities; a significant decrease in antithrombin III activity in rats more than 6 months of age; significant increases in fibrinogen level and factor XI activity; and significant decreases in prothrombin time and activated partial thromboplastin time in those more than 9 months of age. As changes in fibrinolytic parameters, the animals showed significant decreases in plasminogen and tissue-type plasminogen activator, and significant increases in ₂-plasmin inhibitor and plasminogen activator inhibitor at more than 6 months of age. In addition, there were significant correlations between the plasma levels of coagulation/fibrinolytic markers and the 4-hour fasting glucose or lipids. Furthermore, they displayed significant increases in ADP- or collagen-induced platelet aggregation and in cholesterol/phospholipid molar ratio in platelets at more than 9 months of age. The increase in cholesterol/phospholipid ratio may be responsible for hyperaggregation of platelets in diabetic animals. These findings suggest that WBN/Kob rats are suitable for research on blood coagulation abnormalities in diabetes. However, further studies are needed to clarify the details of the mechanisms involved.     

Histochemical study of the skeletal muscle in chronic alcoholism

Twenty-two chronic alcoholic patients were assessed by neurologic examination and muscle biopsy. The patients manifested proximal muscular weakness to a variable extent. One case presented as an acute bout of myopathy, according to the Manual Muscle Test, MMT. The most prominent histologic feature observed was muscle atrophy (95.3%) better evidenced through the ATPase stain with the predominance of type II A fibers (71.4%). Lack of the mosaic pattern (type grouping) seen in 76% of the cases and an important mitochondrial proliferation with intrasarcoplasmatic lipid accumulation in 63% of the patients. In case of acute presentation of muscle weakness the pathological substrate is quite different, i.e. presence of myositis mainly interstitial characterized by lymphoplasmocytic infiltrate and several spots of necrosis like Zencker degeneration. Based on histologic criteria, our data suggest that: the main determinant of muscle weakness seen in chronic alcoholic patients is neurogenic in origin (alcoholic polyneuropathy); the direct toxic action of ethanol under the skeletal muscle is closely related to the mitochondrial metabolism; the so-called acute alcoholic myopathy has probably viral etiology.     

Histochemical study of the skeletal muscle in multiple sclerosis

The authors present muscle histochemistry of ten patients of multiple sclerosis. The clinical diagnosis was based on criteria established by Poser et al. (1983). The main pathological findings observed were: lymphoplasmocitary vasculitis, increase in the number of 2B type fibers, inflammatory cells (macrophages) in the intramuscular ends of the motor nerves, amounts of lipids and 'moth-eaten' fibers. The presence of vasculitis observed in our cases contributes with the etiopathogenic hypothesis of an autoimmune lesion in multiple sclerosis. There is no correlation between the clinical and histological atrophy observed.     

Histochemical and ultrastructural pathology of skeletal muscle in a patient with abetalipoproteinemia

Pathological examination was carried out of the skeletal muscle of an 8-year-old boy with abetalipoproteinemia. The patient complained of diarrhea, and showed a deficiency of betalipoprotein, decreased fatsoluble vitamins, acanthocytosis and a mild incrase in serum creatine kinase. The prominent histochemical finding was punctate deposits of acid phosphatase activity in most fibers. Ultrastructural lesions revealed a number of giant lysosomes. Although these pathological findings seemed to be related to vitamin E deficiency, other pathological findings such as concentric laminated bodies of filamentous bodies were also observed. The clinical course and the changes in the pathological findings in our patient after long-term vitamin E therapy need to be observed.     

Heroin-induced myopathy in rat skeletal muscle

Summary The effects of heroin on rat skeletal muscle was studied. Heroin was injected intraperitoneally, and the soleus and tibial anterior muscles were studied using histological and histochemical techniques. Degenerative and regenerative changes were detected, the latter proving more significant. The soleus was the only muscle affected, the anterior tibial showing no sign of damage. The heroin myopathy model may be valuable in studying muscle fibre necrosis and regeneration.     

Histochemical changes in ATPase activity during regeneration of adult skeletal muscle fibers

Developing skeletal muscle fibers (myotubes) and fully differentiated (adult) muscle fibers can be distinguished according to their histochemical “myofibrillar” ATPase reaction. Myotubes stain darkly for the ATPase reaction at pH 9.4 following preincubation of sections in either alkali (pH 10.4) or acid (pH 4.35). This staining is exclusively localized to the myofibrils of these embryonic fibers. In the soleus muscle of the guinea pig, a progressive conversion to the adult staining pattern is completed 1 month following birth; fibers then stain lightly after alkaline-preincubation and darkly following acid-preincubation when staining is intermyofibrillar as well as myofibrillar. Thus the staining reaction can be used to follow developmental alterations in muscle fibers, and in the present study it was used to determine whether the regenerating fibers in an injured, fully differentiated muscle repeat the developmental changes. Fibers were transected in fully differentiated soleus muscles of guinea pigs, and at periodic intervals these injured muscles were examined histochemically. The sequence of histochemical and morphological changes in the regenerating muscle fibers essentially repeated normal development. Since regenerating fibers go through the same stages as during normal development, the restoration process probably involves the elaboration and fusion of undifferentiated myogenic cells or dedifferentiated muscle cells.     

Mechanisms of force loss in diabetic mouse skeletal muscle

Pathologic changes to alpha-motoneurons may contribute to decreases in skeletal muscle strength in diabetes. The present study examines this possibility. Female ICR mice (approximately 25 g) were given a single injection of streptozotocin (200 mg/kg). After 2, 4, and 8 weeks of diabetes, we measured maximum isometric tetanic torque of the fast-twitch anterior crural muscles at the ankle when stimulated through the common peroneal nerve, and maximal isometric tetanic force in the directly stimulated extensor digitorum longus (EDL) muscle. After 4 weeks, the relative loss of torque via nerve stimulation (-43%) was greater (P = 0.02) than the force loss in the directly stimulated muscle (-24%), indicating a functional neural deficit. However, the percent changes in strength in these two methods of stimulation were not different (P = 0.41) in the 8-week diabetic animals, indicating that functional impairment resided in the muscle. This suggests an early distal motoneuron or neuromuscular junction deficit that improved as the intrinsic muscle deficit worsened. Preliminary evidence also suggests excitation-contraction uncoupling may contribute to the loss of strength in fast-twitch muscles.     

The hyper-reinnervation of rat skeletal muscle

This study examines muscle recovery and related changes in the motor unit population of ‘hyper-reinnervated’ rat skeletal muscle. Medial gastrocnemius (MG) muscles were hyper-reinnervated by either cutting the MG nerve and implanting it on the MG muscle together with additional hind limb nerves, or by crushing the MG nerve and excising the medial portion (50–70%) of the MG muscle. Our findings were that muscles hyper-reinnervated with multiple nerves recovered muscle mass and strength more fully than did the self-reinnervated muscles, more motor units were formed (up to three times the normal number were found), and the mean motor unit size was significantly smaller. A relatively small percentage of muscle fibers became polyneuronally innervated. In contrast, the number of motor units that were formed in the muscle reduction experiments were not significantly larger than was expected considering the mass of the muscles. We conclude that hyper-reinnervation improves muscle recovery, it may be a useful technique for improving function in denervated muscle, and may serve to provide added sources of EMG control signals in some amputees.     

Differentiation of spontaneous activity from normal and denervated skeletal muscle.

The discrimination of fibrillation potentials and endplate potentials based on the conventional EMG methods is difficult if there is only discrete denervation. The reliability of discrimination can be highly improved if the frequency behaviour of the potentials is taken into account. The average proportional consecutive interval difference is the best discrimination variable with 90% correct findings per analysed potential sequence. When three analyses per muscle are made, the accuracy increases to 97.2%. The second best variable is the mean consecutive difference followed by interval bandwidth, standard deviation of interval, minimum interval and finally maximum interval. The mean duration of intervals does not allow of any differentiation. The frequency analysis can be restricted to spontaneous activity sequences of ten seconds. It is immaterial which part of a prolonged sequence is analysed for ten seconds. The conventional evaluation of registered spontaneous activity either alone or with observation at the monitor under simultaneous acoustic control is inferior to the frequency analysis. The results do not allow a statement of the probability of wrong diagnosis in clinical routine work.     

Histochemical and histopathological changes in skeletal muscle in late-onset hereditary distal myopathy (Welander).

Histochemical and histopathological staining methods were applied to muscle biopsy material from 13 patients with distal myopathy of late onset. Six cases showed slight to moderate histopathological changes and the normal distinction between Type I and Type II muscle fibres, based on their staining characteristics for myofibrillar ATPase, was well preserved. A selective Type I atrophy and an irregular distribution of oxidative enzyme and fat staining in Type I fibres were evident. In the other 7 cases, with moderate to advanced histopathological changes, there was a marked blurring of the normal difference observed in ATPase activity between Type I and TYpe II fibres. Thus, both types of fibre exhibited a high intensity of staining for myofibrillar ATPase at pH 9.4 without inhibition by acid preincubation (pH 4.3). These changes in phosphatase activity were found not only in atrophic fibres but also in normal-sized fibres without other signs of degeneration. Nuclear proliferation in chains and "ring fibres" were found. The early histopathological and histochemical changes in distal myopathy are strikingly similar to those of myotonic dystrophy.