To investigate the myelinotoxicity of cerebropsinal fluid in multiple sclerosis, we used an in vivo model of the myelinated central-nervous-system tract of tadpoles for quantitative double-blind tests of 46 cerebrospinal-fluid samples. Groups of xenopus tadpoles were injected with cerebrospinal fluid near the optic nerve. Forty-eight hours later, whole mounts of optic nerves were prepared, and a differential interference microscope was used to count myelin lesions. Cerebrospinal-fluid samples from 60 per cent of the patients with an acute attack of definite multiple sclerosis had myelinotoxic activity. This activity correlated best with the severity and duration of the disease, rather than with gamma-globulin or total protein concentrations. Activity was negative in 85 per cent of cerebrospinal-fluid samples from a control group with other neurologic diseases. This assay is a useful method for investigating myelinotoxic factors of cerebrospinal fluid in patients with multiple sclerosis, but was not helpful diagnostically.
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