Development of normal and dystrophic chick muscle in tissue culture. Production and release of creatine kinase and acetylcholinesterase

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.

Creatine kinase isozyme transition in chicks with hereditary muscular dystrophy

In both normal chicks and chicks with hereditary muscular dystrophy the BB (brain) and MB (hybrid) isozymes were the predominant forms of creatine kinase (CK) activity in embryonic skeletal muscle. As myogenesis progressed, activity due to the MM (muscle) isozyme progressively increased, and by 1 week ex ovo, the MM isozyme accounted for approximately 97% of total muscle activity in both genotypes. During this time, the proportion of the MM isozyme was slightly but significantly lower in dystrophic muscles. After hatching the proportion of the MB isozyme and its total activity decreased in normal muscle, but increased in dystrophic pectoral muscle, and by 5 months ex ovo, the MB isozyme accounted for 10% of total CK activity. Prior to hatching there was no consistent difference in total CK activity between normal and dystrophic tissues, but by 1 week after hatching and thereafter, total CK activity was significantly lower in dystrophic pectoral muscle.

Altered protein synthesis and creatine kinase in breast muscle cell cultures from dystrophic chick embryos

The total protein synthesis (TPS), myosin synthesis (MS) and creatine kinase (CK) levels in muscle cell cultures obtained from 400 normal (strain 454) and 400 dystrophic chick embryos (strain 455) were investigated. The cultures were obtained from breast muscles of 12 day chick embryos by dissociation in 0.25% trypsin, preplating and plating of 5 x 10(5) floating cells on gelatin coated dishes in Minimal Essential Medium, 10% horse serum and 2% chick embryo extract. After 6 days, when electron-microscopic studies demonstrated good muscle differentiation, cell cultures were labeled with [3H]leucine. TPS and MS, respectively, showed 85% and 65% increases in breast muscle cell cultures from dystrophic chick embryos. The half-life times for total protein and myosin from dystrophics were 19 and 32 hr, respectively as compared with 36 and 48 hr from controls. Noncollagen protein content (NCP) showed 27% decrease in postfusion stage (12 days) of cell cultures from dystrophics. The CK level showed 30% lower values in the cells from dystrophics but 50% higher values in their culture medium. The addition of leupeptin plus pepstatin (50 microgram/ml) to these cultures resotred NCP content, total protein and myosin turnover to normal values and significantly increased TPS and MS. The addition of diphenylhydantoin (DPH) (20 microgram/ml) to cell cultures from dystrophics did not change the NCP content nor the turnover for total protein and myosin but significantly increased TPS, MS and CK while medium CK significantly decreased. The addition of leupeptin plus pepstatin or DPH to muscle cell cultures from normal chick embryos also significantly stimulated TPS and MS.