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Serial measurements were made of the cerebrospinal fluid and plasma amino-acid concentrations in 12 patients with purulent meningitis. Marked increases in the concentrations of most CSF amino-acids were found, possibly caused by altered transport mechanisms in the inflamed meninges and choroid plexuses.

Serial measurements have been made of the cerebrospinal fluid and plasma amino acid concentrations in 11 patients with viral meningitis and in four with tuberculous meningitis. A small increase in the concentrations of a few amino acids in cerebrospinal fluid has been found in a viral meningitis in contrast to a marked increase in most amino acids in tuberculous meningitis. The findings are compared with those found in patients with purulent meningitis and the possible causes and the diagnostic significance of these findings are discussed.

The concentration of free amino acids in the plasma and lumbar CSF of 11 patients with steady-state chronic renal failure has been measured and the CSF: plasma concentration ratios calculated. The results have been compared with the corresponding data from 37 control subjects. In renal failure, elevation of the mean plasma concentration of total amino acids and a reduction in the ratio of essential to total amino acids have been found. Whereas some individual plasma amino acid concentrations in renal failure were higher than normal, others were lower. Striking abnormalities of the CSF amino acid concentration have been observed. Some amino acids have shown similar patterns of abnormality in both CSF and plasma, whereas in the case of others, the changes have been restricted to either CSF or plasma. Significant variations from normal of the CSF: plasma concentration ratios were observed for four amino acids.

The concentration of free amino acids in CSF and plasma has been measured in 19 patients with renal disease undergoing haemodialysis therapy. The values obtained have been compared with those measured in non-haemodialysed patients. At the end of a 10-h dialysis period, the total CSF amino acid concentration had fallen by only 23.3% compared with a 57.7% fall in plasma. Examination of the results for individual amino acid concentrations showed 3 different patterns of inter-relationship between plasma and CSF.

Measurements of cerebrospinal fluid (CSF) and plasma amino acid concentrations have been made in 12 patients with the Guillain-Barré syndrome. The CSF protein concentration was normal in seven specimens and raised in 13. Abnormalities of the CSF amino acid profile were found in all specimens but were more marked in those with a raised CSF protein concentration. The possible causes and diagnostic significance of these changes are discussed.