Muscle biopsy evaluation in neuromuscular disorders

Effects of different aerobic exercise frequencies on streptozotocin-nicotinamide-induced type 2 diabetic rats: Continuous versus short bouts and weekend warrior exercises

BACKGROUND

Exercise training is known to have multiple beneficial effects on type 2 diabetes mellitus (T2DM). The aim of this study was to explore the effects of aerobic exercise frequency on diabetic parameters, the histopathological structure of skeletal muscle, diabetic myopathy, and mitochondrial enzyme activity in an experimental model of T2DM.

METHODS

Sprague-Dawley rats (n = 35) were rendered diabetic by injection of nicotinamide (110 mg/kg) and streptozotocin (65 mg/kg). Rats with blood glucose concentrations between 7 and 17 mmol/L were used. Diabetic rats were randomly allocated to one of the following groups: (i) control sedentary; (ii) diabetic sedentary; (iii) diabetic with continuous exercise (30 min/day, 5 days/week); (iv) diabetic with short bouts of exercise (3 × 10 min/day, 5 days/week); and (v) diabetic rats as "weekend warriors" (35 + 40 min/day, 2 days/week). After 6 weeks swimming exercise (total duration 150 min/week), biochemical tests were performed to measure insulin, glucose, cytokines, serum and muscle myeloperoxidase (MPO), and malondialdehyde (MDA) levels. Histologic analysis (histomorphometric and mitochondrial enzyme analysis) was also performed.

RESULTS

Compared with diabetic sedentary rats, significant improvements were observed in all exercise groups in terms of glucose levels, weight loss, tissue MPO and MDA levels, muscular connective tissue, muscle atrophy, mitochondrial enzyme, and all histomorphometric analyses.

CONCLUSIONS

The results of the study emphasize the effects of training on inflammation, increased oxidative stress, myopathy, and mitochondrial damage in a rat model of T2DM, and demonstrate that there is no major difference between exercise modalities provided that the total duration of exercise remains the same.

Dystrophia myotonica type 1 presenting with dysarthria: A case report and literature review

Dystrophia myotonica (DM) type 1 is an autosomal dominant disorder, caused by a trinucleotide CTG repeat expansion in the 3′ untranslated region of the dystrophia myotonica protein kinase (DMPK) gene (chromosome 19q13.3). The disorder affects different organ systems, including the skeletal muscles, ocular lens, lungs, heart and gastrointestinal tract, as well as the endocrine and central nervous systems. The skeletal muscles are most frequently involved, whereby the disorder manifests as myotonia, muscle weakness and amyotrophy. However, DM type 1 presenting with dysarthria is rare. The current study presents a case of a 28-year-old male with DM type 1 presenting with dysarthria and associated multifocal hyperintense lesions in the white matter. Although electromyogram measurements identified myotonic discharges in all extremities, a muscle biopsy failed to detect the characteristic pathological features of DM type 1. A lack of a positive family history for DM type 1 also obscured diagnosis. However, genetic analysis detected a single allele in the P12 segment of the DMPK gene that included a CTG expansion of 13 repeats and a three-base gradient fragment in the P134 segment that included a CTG expansion of >600 repeats. According to the characteristics of dysarthria, multifocal hyperintense lesions in the white matter, electromyogram measurement results and genetic testing results, a diagnosis of DM type 1 was confirmed.

Effect of mesenchymal stem cells on induced skeletal muscle chemodenervation atrophy in adult male albino rats

The present research was conducted to evaluate the effect of bone marrow derived mesenchymal stem cells (BM-MSCs) as a potential therapeutic tool for improvement of skeletal muscle recovery after induced chemodenervation atrophy by repeated local injection of botulinum toxin-A in the right tibialis anterior muscle of adult male albino rats. Forty five adult Wistar male albino rats were classified into control and experimental groups. Experimental group was further subdivided into 3 equal subgroups; induced atrophy, BM-MSCs treated and recovery groups. Biochemical analysis of serum LDH, CK and Real-time PCR for Bcl-2, caspase 3 and caspase 9 was measured. Skeletal muscle sections were stained with H and E, Mallory trichrome, and Immunohistochemical reaction for Bax and CD34. Improvement in the skeletal muscle histological structure was noticed in BM-MSCs treated group, however, in the recovery group, some sections showed apparent transverse striations and others still affected. Immunohistochemical reaction of Bax protein showed strong positive immunoreaction in the cytoplasm of muscle fibers in the induced atrophy group. BM-MSCs treated group showed weak positive reaction while the recovery group showed moderate reaction in the cytoplasm of muscle fibers. Immunohistochemical reaction for CD34 revealed occasional positive CD34 stained cells in the induced atrophy group. In BM-MSCs treated group, multiple positive CD34 stained cells were detected. However, recovery group showed some positive CD34 stained cells at the periphery of the muscle fibers. Marked improvement in the regenerative capacity of skeletal muscles after BM-MSCs therapy. Hence, stem cell therapy provides a new hope for patients suffering from myopathies and severe injuries.

Longitudinal follow-up of muscle echotexture in infants with congenital muscular torticollis

Unilateral fibrous contracture of the sternocleidomastoid (SCM) muscle is the major pathophysiology in infants with congenital muscular torticollis (CMT). Physical examination is not always sufficient to detect minimal muscle fibrosis in involved SCM muscles.A prospective study for SCM muscle fibrosis in CMT infants by quantifying echotexture and muscle thickness during the course of treatment is highlighted in the study.Convenience samples of 21 female and 29 male infants with CMT, who were 1 to 12 months old, underwent physiotherapy for at least 3 months and were followed for 4.7 ± 0.4 months. All infants had at least 2 clinical assessments and ultrasonographic examinations for bilateral SCM muscles during follow-up. The K value, derived from the difference in echo intensities between the involved and uninvolved SCM muscles on longitudinal sonograms, was used to represent the severity of muscle fibrosis. Bilateral SCM muscle thickness and ratio of involved to uninvolved muscle thickness (Ratio I/U) were obtained simultaneously. Clinical outcome was also recorded.No subjects underwent surgical intervention during follow-up. The K value decreased from 6.85 ± 0.58 to 1.30 ± 0.36 at the end of follow-up (P < 0.001), which reflected the decrease of muscle fibrosis. The Ratio I/U decreased from 1.11 ± 0.04 to 0.97 ± 0.02 during treatment, which was possibly related to the increased uninvolved SCM muscle thickness.In conclusion, echotexture is an efficient indicator for reflecting a wide degree of muscle fibrosis in infants with CMT and is informative during the treatment course.

Analysis of RNA Expression in Adult Zebrafish Skeletal Muscle

The zebrafish is an excellent vertebrate model system to investigate skeletal muscle development and disease. During early muscle formation the small size of the developing zebrafish allows for the characterization of gene expression in whole embryos. However, as the zebrafish develops, access to the underlying skeletal muscle is limited, requiring the skeletal muscle to be sectioned for a more detailed examination. Here, we describe a straightforward and effective method to prepare adult zebrafish skeletal muscle sections, preserving muscle morphology, to characterize gene expression in the zebrafish adult skeletal muscle.

Clinical approach to the diagnostic evaluation of hereditary and acquired neuromuscular diseases

For diagnostic evaluation of a neuromuscular disease, the clinician must be able to obtain a relevant patient and family history and perform focused general, musculoskeletal, neurologic, and functional physical examinations to direct further diagnostic evaluations. Laboratory studies for hereditary neuromuscular diseases include the relevant molecular genetic studies. The electromyogram and nerve-conduction studies remain an extension of the physical examination, and help to guide further diagnostic studies such as molecular genetics and muscle and nerve biopsies. All diagnostic information needs are to be interpreted within the context of relevant historical information, family history, physical examination, laboratory data, electrophysiology, pathology, and molecular genetics.