Creatine kinase activity in normal and Duchenne muscular dystrophy fibroblasts

Decreased creatine kinase activity in cultured Duchenne dystrophic muscle cells

Muscle cells were cultured from six patients with Duchenne muscular dystrophy and nine normal subjects. Protein and myosin content and pyruvate kinase (PK) activity were similar in normal and Duchenne muscular dystrophy cultures. Creatine kinase (CK) activity was lower in Duchenne muscular dystrophy cultures and the isoenzyme distribution indicated MB-CK was significantly lower, while BB-CK was significantly higher in later Duchenne muscular dystrophy cultures. This abnormal isoenzyme pattern suggested aberrant or impaired maturation of Duchenne muscular dystrophy myotubes in vitro.

Normal and dystrophic hamster myoblast and fibroblast growth in culture

Normal and dystrophic hamster myoblasts and fibroblasts were compared for characteristic indicators of growth and differentiation. Clonal analysis of myoblast cultures indicated that 80% of colonies judged to be fusion-competent had differentiated. Dystrophic myoblasts were identical to normal in terms of their morphology, fusion potential (81.4%), and myokinase activity (59.6-49.1 mU/mg at 2-7 days), but displayed a significantly higher plating efficiency (normal: 52.6%; dystrophic: 82.1%), a longer doubling time (normal: 21.7 hours; dystrophic: 33.3 hours), and a lower day-7 creatine kinase activity (normal: 60.7 mU/mg; dystrophic: 41.3 mU/mg). Dystrophic fibroblasts were indistinguishable from normal ones in terms of their morphology, plating efficiency (90.4%), and doubling time (32.5 hours), but displayed a significantly lower day-2 creatine kinase activity (normal 58.3 mU/mg; dystrophic: 35.8 mU/mg) and day-7 myokinase activity (normal: 52.7 mU/mg; dystrophic: 39.9 mU/mg). The results are suggestive of an early and differential expression of the primary defect in dystrophic hamster myoblasts and fibroblasts in culture.

Tissue culture studies of muscle disorders: Part 2. Biochemical studies, nerve-muscle culture, metabolic myopathies, and animal models

This review continues with studies of protein, lipid, and purine metabolism of Duchenne muscular dystrophy (DMD) cells in vitro and of muscle cells in combined culture with nerve cells. In vitro studies of human metabolic myopathies are tabulated. Results using the hamster, chicken, and mouse (dy25, dy, mdg, and mdx) myopathies are discussed. Interesting findings include suggestions of altered collagen synthesis by DMD cells. Analysis of cell proteins by two-dimensional gel electrophoresis and the use of combined nerve-muscle cultures remain important areas of development. It is disappointing that so few attempts have been made to repeat significant findings in this field, and when a number of laboratories have examined the same phenomenon, the results are often contradictory. It remains to be shown how these various abnormalities found in cells in vitro are related to each other and to those pathologic features of diseased muscle observed in vivo.

Tissue culture studies of muscle disorders: Part 1. Techniques, cell growth, morphology, cell surface

Tissue culture has been used extensively in studies of human inherited disorders, and its application in the field of the neuromuscular disorders has increased rapidly in recent years. This review, covering the period 1977 to 1984, deals with tissue culture studies of both human and animal muscle disorders, although Duchenne muscular dystrophy (DMD) figures prominently because of the overwhelming interest in that disorder. The review is in two parts. In the first part, I discuss technical innovations in the field, the morphology and growth of cells, and a variety of studies related to the cell surface. Important findings in relation to DMD include reports of abnormal growth rates and reduced lifespan of DMD cells, hypersensitivity to DNA-damaging agents, abnormal cell-to-cell and cell-to-substratum adhesion, and a more "fluid" cell membrane. However, these findings are controversial or have so far been reported only by single laboratories.

Effect of vitamin D and its metabolites on developing myogenic cultures

Growth, protein synthesis and expression of creatine kinase (CK) by embryonic chick myogenic cells are inhibited by vitamin D and certain of its metabolites. 25-OH cholecalciferol was most active in concentrations of 10(-5) - 10(-6) M, with cholecalciferol and ergocalciferol less active in that order. Ergosterol had no activity of this sort. Inhibition of CK was most marked on the 4th and 5th day of culture and was due to suppression of the appearance of CK-NM and MB. CK-BB was not affected and CK-MB was more affected than CK-BB. Skin fibroblasts by comparison were slightly stimulated in growth at 10(-6) M and much less affected at 10(-5) M than the myogenic cells. It is suggested that vitamin D has a direct effect upon the muscle cell, to cause a selective diminution in the production of certain polypeptides.

The enzymology of skeletal muscle disorders

In myopathic disorders, abnormal serum enzyme activities are seen primarily in diseases of skeletal muscle where the condition involves the muscle fibers themselves. In denervation myopathies, serum enzyme activities are usually normal. The most dramatic increases of serum enzymes, particularly creatine kinase, are found in the dystrophic diseases, particularly Duchenne dystrophy. A review is given here of the many causes of abnormal serum enzyme activities where the source of enzymes is believed to be skeletal muscle. These include the dystrophies, various types of trauma, exercise, drug- and poison-induced causes including alcohol, malignant hyperthermia, inflammatory diseases, and miscellaneous causes. Tissue and serum activities are summarized for the commonly performed serum enzymes, i.e., CK, LD, AST, and aldolase. An extensive tabular and current description of the various types of dystrophies is given along with serum CK and pyruvate kinase activities.