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Twenty-one amino acids were determined in serum and cerebrospinal fluid of 12 patients with endemic, and in the cerebrospinal fluid of 22 patients with epidemic optic neuropathy. For the endemic patients, there was a decrease in aspartate and taurine in the serum with respect to controls. The ratios aspartate/taurine and taurine/valine were decreased, and glutamate/taurine was increased in the serum. Some of the altered amino acid ratios indicate preponderance of excitatory to inhibitory molecules. The ratio with valine corresponded to the decrease in taurine and the maintenance of valine concentration, an amino acid related to anthropometric parameters. A typical malnutrition pattern was not observed, as the levels of essential amino acids were not significantly modified. In the cerebrospinal fluid there were increases in aspartate, glutamate and threonine, the first two probably indicating a neurodegenerative disorder or some type of metabolic alteration, primary or secondary to the disease. The increase in threonine could be related to lipid metabolism, but it is not clear at present. A wide variety of amino acid ratios were increased in the cerebrospinal fluid of patients with endemic optic neuropathy, mainly pointing to an excitatory condition and some metabolic alterations. In the cerebrospinal fluid of patients with epidemic optic neuropathy there was an increase in aspartate and glutamate, and increase in glutamate/taurine, glutamate/glycine, and gamma-aminobutyric acid/glycine ratios. Interesting differences were also observed between patients from different periods of time, but with the same clinical features, and the modifications of amino acid concentrations in the cerebrospinal fluid, such as glutamine, threonine and tryptophan. The present results indicate a disorder in the metabolism of amino acids, support a specific deficit, especially for taurine, an imbalance between excitatory and inhibitory amino acids, and a possible relation to viral infections.

A form of dominantly inherited olivopontocerebellar atrophy (OPCA) occurs commonly in persons of Spanish ancestry in northeastern Cuba. Its prevalence in the Province of Holguin is 41 per 100,000, a figure much higher than that found in western Cuba or in other parts of the world. The high prevalence is probably the result of a founder effect, but might be due to an interaction between a mutant gene and an unidentified environmental neurotoxin. We describe the clinical features of this disorder, and the neuropathological abnormalities in 7 autopsied patients. In addition, we report biochemical findings in plasma, cerebrospinal fluid (CSF) and urine obtained from 10 living OPCA patients. Quantitation of amino acids in fasting plasma showed a number of differences between the Cuban patients and healthy Canadian controls, but these are likely to have been caused by dietary differences. Amino acid concentrations in the CSF of the Cuban OPCA patients were similar to those of healthy Cuban controls, except for a decreased concentration of ethanolamine. Mean concentrations of dopamine metabolites were significantly low in the CSF of the OPCA patients, corresponding to neuronal depletion observed in the substantia nigra of autopsied cases. Examination of the patients' urines provided no evidence that either cyanide or 3-acetylpyridine is involved in causing this form of OPCA.