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Clinical Applications of Immunoassays
Published in Richard O’Kennedy, Caroline Murphy, Immunoassays, 2017
Dermatomyositis (DM) and polymyositis (PM) are idiopathic inflammatory disorders of skeletal muscle. Although both inflammatory conditions share the same clinical feature of muscle weakness, dermatomyositis is also associated with cutaneous lesions. A muscle biopsy is the definitive test for establishing a diagnosis of inflammatory myositis. A variety of autoantibodies detected by immunoassay in patient sera are associated with the disease. Antinuclear antibodies (ANA) are present in over 80% of patients with DM and PM [62]. The detection of anti-Ro, anti-La, anti-Sm, anti-ribonucleoprotein (RNP) and anti-TIF1 antibodies are highly suggestive of an inflammatory muscle condition; however, these antibodies also overlap with other connective tissue diseases and an associated diagnosis of cancer [63, 64]. Cytoplasmic RNA synthetases and other cytoplasmic proteins, including ribonucleoproteins are known as myositis-specific autoantibodies and are found in 30% of patients with DM and PM. Anti-Jo-1 antibodies are the most common type of myositis-specific autoantibody and are associated with interstitial lung disease, Raynaud’s phenomenon and arthritis [65]. Anti-SRP antibodies, primarily found in PM, are associated with a more severe myopathy with aggressive disease. In addition to autoantibodies, muscle enzyme analysis is important in diagnosing myopathy. Creatine kinase, lactate dehydrogenase, aldolase and the liver enzymes, aspartate aminotransferase and alanine aminotransferase are routinely measured with immunoassay. Muscle weakness with normal enzyme levels is more commonly seen in DM when compared to PM.
Down stair walking: A simple method to increase muscle mass and performance in 65+ year healthy people
Published in European Journal of Sport Science, 2022
Signe Regnersgaard, Anna K. Knudsen, Filippa O. Lindskov, Marija Mratinkovic, Eckart Pressel, Arthur Ingersen, Flemming Dela
A percutaneous muscle biopsy of the vastus lateralis muscle was obtained, using local anaesthetics and a 5 mm Bergström muscle biopsy needle. The specimen was flash-frozen directly in liquid nitrogen. Biopsies were stored in separate containers at −80°C until analyses of enzymes activities of citrate synthase (CS) and beta-hydroxyacyl CoA dehydrogenase (HAD), and of intramuscular glycogen content by spectrophotometry (Cobas 6000 c 501, Roche, Glostrup, Denmark).