Thomas L. Perry

Huntington's Chorea

Abstract Amino acids and related compounds were measured in various regions of brain obtained at autopsy from eight neurologically normal persons, one patient with Parkinsons disease, and eight patients with Huntingtons chorea. γ-Aminobutyric acid (GABA) and homocarnosine, a related dipeptide, were reduced in the substantia nlgra, putamen-globus-pallidus, and caudate nucleus of the choreic patients, as compared to the normal subjects and the patient with Parkinsonism. Glycerophosphoethanolamine concentration was elevated in these three regions of choreic brain. Deficiency of γ-aminobutyric acid, a possible inhibitory synaptic transmitter in brain, might produce the symptoms characteristic of Huntingtons chorea. Such a deficiency could result from reduced activity of the enzyme glutamic acid decarboxylase, or might reflect a decrease in the number of neurons that normally utilize γ-aminobutyric acid as a transmitter.

Parkinson's disease: A disorder due to nigral glutathione deficiency?

Amino acid analysis of autopsied human brain showed reduced glutathione (GSH) content significantly lower in the substantia nigra than in other brain regions. GSH was virtually absent in the nigra of patients with Parkinsons disease. Oxidative degradation of L-DOPA and dopamine in vivo may generate reactive oxygen species (hydrogen peroxide, superoxide, hydroxyl radical, or singlet oxygen) which can damage membranes and other cellular components. Since GSH is an important natural antioxidant, a deficiency of GSH in the substantia nigra could make this region vulnerable to oxidative injury. If confirmed, the hypothesis that loss of nigrostriatal dopaminergic neurons results from a regional GSH deficiency could have important therapeutic implications for the management and prevention of Parkinsons disease.

Technical pitfalls leading to errors in the quantitation of plasma amino acids

Abstract This paper describes seemingly trivial variations in the preparation of blood plasma for amino acid analysis, and in the operation of the automatic amino acid analyzer, that can lead to major errors in the quantitative determination of taurine, phosphoethanolamine, the dicarboxylic amino acids, glutamine, the disulphide amino acids, and tryptophan. These technical pitfalls can easily be avoided. The resulting improved accuracy in measurement of plasma amino acids may be essential for meaningful studies of some metabolic or nutritional disorders where differences from normal are subtle.

Postmortem changes of amino compounds in human and rat brain.

Abstract: Contents of 35 amino acids and related compounds were measured in whole rat brain, and in superficial areas of biopsied and autopsied human brain, after incubation for various intervals at temperatures simulating those likely to occur in cadavers under mortuary conditions. These data should aid interpretation of values for amino compounds determined in autopsied brain from patients with neurological or psychiatric disorders. The contents of glutamic acid, glutamine, taurine, phosphoethanolamine, cystathionine, and homocarnosine remain unchanged for long periods in human brain. Aspartic acid content is stable for 4 h after death, but thereafter rises rapidly. Glycine content rises rapidly, as do the contents of most amino acid components of proteins. Glutathione content drops rapidly in human brain after death. GABA content is stable for about 30 min, and rises to a maximum 2 to 3 h after death, after which it remains unchanged for at least 24 h. In rat brain, GABA content rises more rapidly, aspartate content rises more slowly, homocarnosine content decreases progressively, and glycerophosphoethanolamine content decreases more rapidly than in human brain.

A versatile lithium buffer elution system for single column automatic amino acid chromatography.

Abstract A new chromatographic system employing lithium citrate buffers is described for use on a single 120 cm resin column of the Technicon amino acid analyzer. With this system, adequate resolution of a large number of amino acids up to and including arginine can be achieved in a chromatographic run of 21 hours. The amides asparagine and glutamine are well separated from other amino acids. This chromatographic procedure should prove useful when it is necessary to quantitate each of a large number of amino acids and related compounds in physiological fluids or tissue homogenates.

Partial protection from the dopaminergic neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine by four different antioxidants in the mouse

C57 black mice given a single injection of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 40 mg/kg, developed marked reduction of striatal dopamine content and loss of dopaminergic neurons in the zona compacta of the substantia nigra. However, pretreatment with any one of four different antioxidants, alpha-tocopherol, beta-carotene, ascorbic acid or N-acetylcysteine, significantly decreased MPTP-induced striatal dopamine loss, and alpha-tocopherol prevented neuronal loss in the substantia nigra. Four chemical analogues of MPTP (cinnamaldehyde, N,N-dimethylcinnamylamine, arecoline and 2-methyl-1,2,3,4-tetrahydro-6,7-isoquinolinediol) were all found to lack dopaminergic nigrostriatal neurotoxicity in the mouse.

Nigrostriatal dopaminergic neurons remain undamaged in rats given high doses of L-DOPA and carbidopa chronically.

Abstract: Rats were fed maximally tolerated doses of l‐3,4‐Dihydroxyphenylalanine (l‐DOPA) and carbidopa daily for 120 days in order to achieve a sustained elevation in brain dopamine levels. Some animals were also given buthionine sulfoximine, a γ‐glutamylcysteine synthetase inhibitor, in an unsuccessful effort to reduce brain glutathione contents. l‐DOPA‐ and carbidopa‐treated animals displayed no behavioral changes suggestive of nigrostriatal dopaminergic neuronal loss. When sacrificed 60 days after L‐DOPA treatment ended, all rats had normal tyrosine hydroxylase activities and dopamine contents in their striata, and cell counts were normal in the substantia nigra. It therefore seems unlikely that a model of Parkinsons disease, suitable for exploring the etiological importance of glutathione deficiency, can be produced in rats merely by administering the largest tolerable doses of l‐DOPA.

Depletion of glutathione in brainstem of mice caused by N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine is prevented by antioxidant pretreatment.

C57 black mice showed significantly decreased glutathione (GSH) content in the brainstem 24 h after a single s.c. injection of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 40 mg/kg. This loss of GSH could be prevented by pretreating animals with large amounts of alpha-tocopherol or beta-carotene. Increasing dopamine turnover of nigrostriatal neurons in mice by dietary administration of L-dihydroxy-phenylalanine and carbidopa did not accentuate the neurotoxic effects of MPTP. It seems likely that MPTP metabolites directly damage dopaminergic nigrostriatal neurons and that GSH is consumed in attempts to detoxify these metabolites in the substantia nigra.

Brain glutamate deficiency in amyotrophic lateral sclerosis

Amino acid contents were measured in autopsied brains of eight patients with the sporadic form of amyotrophic lateral sclerosis (ALS) and in brains of control subjects dying without neurologic or psychiatric disease. Glutamic acid content was reduced in most brain regions and in the cervical cord in the ALS patients, while glutamine contents were normal. Taurine contents were increased, and γ-aminobutyric acid contents were decreased in some brain regions in the ALS patients. The brain glutamate deficiency in ALS is unexplained, but insufficient production or release of this excitatory neurotransmitter might have important secondary effects on motor neurons.

Nonketotic hyperglycinemia. Glycine accumulation due to absence of glycerine cleavage in brain.

Glycine concentrations were measured in plasma and cerebrospinal fluid of five patients in different types of hyperglycinemia to determine why severe neurologic deterioration is confined to the so-called nonketotic form of hyperglycinemia. Glycine content and glycine-cleavage enzyme activity were also determined in brain obtained in autopsy from three of these patients. Spinal-fluid glycine concentrations were 15 to 30 times above normal in patients with nonketotic hyperglycinemia, but were normal in those with hyperglycinemias of undetermined type who had comparable elevations of plasma glycine. Glycine content was two to four times above normal in several brain regions, and brain glycine cleavage enzyme activity was absent in two patients dying of nonketotic hyperglycinemia. By contrast, glycine content was normal and glycine cleavage activity present in the brain of an infant who died of hyperglycinemia of unknown cause. These results suggest that elevated glycine levels may be harmless in blood, but lethal in brain.