Demyelination 105 



ataxia which occur frequently in Australian lambs are associated 

 with a deficiency in copper. In Australia this deficiency is due to 

 the lowered level of copper in the pasture, but in Great Britain 

 Swayback pastures contain adequate amounts of copper and it is 

 thought that the disease is caused by a failure in the intermediary 

 metabolism of copper in the ewe or by the copper in the pasture 

 being in an unavailable form (Hunter et al., 1945) . Our col- 

 leagues Gallagher, Judah and Rees (1956) have produced copper 

 deficiency in young rats and hens and shown that the copper con- 

 tent of the liver, kidney and brain is then reduced although 

 demyelination cannot be demonstrated. Growth is retarded, the 

 young rats become anaemic and there is reduced pigment forma- 

 tion in the skin. The latter quite likely is the result of deficiency 

 of tyrosinase which requires copper as its prosthetic group. The 

 anaemia is associated with decreased activity of cytochrome oxidase 

 which also requires copper. In addition, our colleagues have dis- 

 covered an impairment in the synthesis of phospholipid in their 

 copper-deficient animals possibly due once again to deficiency of 

 an enzyme that requires copper for its activity. Since myelin is 

 composed largely of phospholipids and synthesis goes on very 

 actively during the first few days of life we may have, in this dis- 

 covery, a suggestive pointer for further metabolic research into 

 demyelinisation. Already it has been shown that the copper con- 

 tent of the brain and liver from Swayback lambs is lower than 

 normal and that the copper-dependent enzyme cytochrome oxidase 

 in the brain of these lambs is also reduced (Howell and Davison, 

 1959) . 



Further studies are needed along these lines with special atten- 

 tion given to the Schwann cells and the oligodendrocytes whose 

 function it is to lay down the myelin sheath. It is to be hoped 

 that close cooperation between the biochemist, tissue culturist 

 and neurohistologist will yield fundamental information that may 

 solve the problems of these elusive diseases. 



REFERENCES 



Burt, N. S., McNabb, A. R. and Rossi ter, R. J. (1950) : Biochem. J., 47: 

 318. 



