Thymidine phosphorylation and thymidylate kinase in developing breast muscle of normal and dystrophic chickens

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.

Dystrophic spinal cord transplants induce abnormal thymidine kinase activity in normal muscles

The role of the neural tube in the pathogenesis of muscular dystrophy was tested directly. Neural tubes from chicken embryos with hereditary muscular dystrophy and from genetically normal embryos were transplanted into normal recipient embryos. Dystrophic neural tissue induced in muscles of normal hosts high thymidine kinase activity characteristic of dystrophic muscle; normal neural tubes did not. We propose an early inductive effect of the neural tube on the presumptive myoblasts that sets their subsequent course of development, either normal or dystrophic.