Factors Influencing the Concentration of Enzymes in Various Muscles.

The genetic form of muscular dystrophy in the chicken is by now a well recognized entity (1, 2), and is a condition of some importance, since in many features it approximates the corresponding disease in the human. We have elsewhere reported our preliminary findings with lactic dehydrogenases in dystrophic chickens (3). Further investigations have centered on analysis of the content of the lactic dehydrogenases and of cr-glycerophosphate dehydrogenase in the affected muscles during the lifespan of dystrophic chickens, since our early studies had indicated that a defect in the synthesis of protein or its replacement by the muscle was present. The relationship of a-glycerophosphate dehydrogenases to the type of lactic dehydrogenase present in various muscles will also be discussed. The disease is inherited as a strict autosomal recessive. There is considerable variation in the time of onset of overt symptoms, but the majority of homozygous birds are noticeably affected by the age of 8 weeks, i.e. before they are mature. It is possible to select genetic strains for early or late onset (2). The disease progresses slowly and it is rarely lethal, except when an affected bird falls or is placed on its back, in which position it is quite helpless. Most affected chickens live a normal life-span and are fertile. The clinical and histological characteristics of the disease have been reviewed by Julian and Asmundson (2).