Search PubMed⌕ Search

Biomedical subjects

T L Perry

Publications and source records attributed to T L Perry.

At least 91 records · Page 5Linked to original sources
PubMed1982

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 Parkinson's 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 Parkinson's disease.

Adult↗
PubMed1982

Normal cerebrospinal fluid and brain glutamate levels in schizophrenia do not support the hypothesis of glutamatergic neuronal dysfunction.

A recently proposed hypothesis to explain schizophrenia is based on reports of reduced concentrations of glutamic acid in the cerebrospinal fluid (CFS) of schizophrenic patients. This hypothesis suggests that there may be a dysfunction of glutamatergic neurons in schizophrenia, with either a degeneration of these neurons, or their failure to release glutamate as a neurotransmitter. Direct measurement of glutamate levels in CSF and autopsied brain of schizophrenic patient showed no differences from glutamate levels in suitable adult control subjects. The data presented here do not offer support for the new hypothesis.

Adult↗
PubMed1982

Human CSF GABA concentrations: revised downward for controls, but not decreased in Huntington's chorea.

gamma-Aminobutyric acid (GABA) concentrations were measured in CSF specimens from two large groups of control subjects, one without neurological or psychiatric disease, and one with a variety of neurological disorders not known to involve altered GABAergic function in brain. CSF GABA was also measured in patients with Huntington's chorea and in patients with other choreiform disorders. GABA was measured in CSF by a modification of the ion exchange-fluorometric method that featured use of a relatively large cation exchange column, and a markedly decreased quantity of sulfosalicylic acid for deproteinization of CSF. Mean BABA concentrations in CSF were 87 and 77 nmol/liter for neurologically normal and abnormal control subjects, 82 nmol/liter for the Huntington's chorea patients, and 105 nmol/liter for patients with other forms of chorea. The mean concentration of homocarnosine was not reduced in CSF of Huntington's chorea patients as compared with controls. Mean CSF GABA concentrations found in control subjects were less than half the lowest control means previously reported. These low values are attributable in part to a reduction in on-column hydrolysis of conjugated forms of GABA in CSF, which can be produced by excessive sulfosalicylic acid, and in part to improved chromatographic resolution of GABA from other unknown o-phthalaldehyde-reactive compounds in CSF. Analysis of free GABA in CSF does not appear useful for diagnosis of suspected Huntington's chorea, nor as a possible predictive test for persons genetically at risk for Huntington's chorea.

Carbon Radioisotopes↗
PubMed1982

Concentrations of GABA and other amino acids in CSF from torsion dystonia patients.

Free amino acid concentrations were measured by conventional amino acid analysis, and gamma-aminobutyric acid (GABA) concentrations were determined, by an ion-exchange fluorometric technique, in CSF specimens from 16 patients with torsion dystonias and in CSF from a large number of control subjects. The mean CSF GABA concentration of the dystonia patients (97 +/- 11 nmol/L) did not differ significantly from the means for CSF GABA in two groups of adult control subjects. Mean concentrations of all commonly determined amino compounds were normal in the CSF of torsion dystonia patients, except for ornithine, which was modestly but significantly reduced.

Adolescent↗
PubMed1982

A double-blind clinical trial of isoniazid in Huntington disease.

Isoniazid (INH) was given to nine patients with Huntington disease (HD) in a double-blind, placebo-controlled crossover trial. In an earlier open trial, three of six patients had improved, and one of them remained improved after 7 years on INH. Only one patient benefited in the present trial. All patients excreted small amounts of hydrazine in their urine while taking INH, and it is this INH metabolic that elevates GABA content in brain. GABA concentrations were markedly increased in CSF during INH therapy. Lack of clinical improvement in most HD patients despite elevation of brain GABA content suggests that in the minority who are benefited, INH may be acting by some mechanism other than increase of GABAergic neuronal function.

Adult↗
PubMed1981

Cystinylglycine in plasma: diagnostic relevance for pyroglutamic acidemia, homocystinuria, and phenylketonuria.

Cystinylglycine, recently identified as a normal small peptide in human plasma, has diagnostic importance for several genetically determined disorders. We found cystinylglycine absent from the plasma of a patient with pyroglutamic acidemia, and the peptide was either absent or greatly reduced in plasma from patients with homosyctinuria. In the latter disorder, a different small peptide replaced cystinylglycine. It was identified as the mixed disulfide of homocysteine and cysteinylglycine. The mean plasma concentration of cystinylglycine was 13.6 +/- 3.6 mumol/l in adult control subjects, and concentrations of the mixed disulfide of homocysteine and cysteinylglycine varied between 2 and 10 mumol/l in the plasma of homocystinuric patients. Failure to separate cystinylglycine from phenylalanine with many rapid amino acid analyzer systems can lead to a misclassification of persons as heterozygotes for the phenylketonuria gene when heterozygosity testing is based on the phenylalanine/tyrosine molar ratio in fasting plasma.

Autoanalysis↗
PubMed1981

Mild elevations of plasma ornithine in homocystinuria.

Hyperornithinemia was found on many occasions during monitoring of amino acids in the fasting plasma of homocystinuric patients. Ornithine concentrations were elevated 2- to 3-fold above the normal mean value. Hyperornithinemia was of much less marked degree than that seen in gyrate atrophy of the choroid and retina, and was not accompanied by overflow ornithinuria or hypolysinemia. Elevations in plasma ornithine concentrations in homocystinuric patients were generally proportional to elevations in the plasma concentration of homocystine, but not that of methionine.

Adolescent↗
PubMed1981

Studies of amino acid content and transport in glutathione-deficient erythrocytes from a patient with pyroglutamic acidemia (5-oxoprolinemia).

Repeated biochemical studies of the erythrocytes of a patient with pyroglutamic acidemia have shown a varying biochemical disorder in these cells. Whereas earlier studies demonstrated absence of glutathione and massive amino acid loading in erythrocytes, these cells later contained small but readily measurable amounts of glutathione and had a relatively normal amino acid content. The marked increase in amino acids after acid hydrolysis of erythrocytes had also disappeared. Transport studies showed a significant increase in the active transport of glycine, while the transport of other amino acids was comparable to that of normal cells. We are unable to detect any activity of gamma-glutamyl transpeptidase in human erythrocytes. Our observations suggest a role for glutathione in the transport of amino acids by erythrocytes, but at present no definite conclusion can be drawn with regard to the participation of the gamma-glutamyl cycle in this process. The biochemical variability in our patient's erythrocytes is unexplained and should be searched for in other patients with pyroglutamic acidemia.

Amino Acids↗
PubMed1981

Lactic acidosis due to pyruvate carboxylase deficiency.

Two unrelated Canadian Indian infants presented with metabolic acidosis. Lactate, pyruvate, glutamic acid, proline and alanine were greatly elevated in plasma. Urinary excretion of alpha-ketoglutarate and pyruvate was increased. Pyruvate carboxylase activity was very low in skin fibroblasts and liver. Phosphoenolpyruvate carboxykinase was low in liver. Both infants were unresponsive to several enzyme cofactors, including biotin. Both survive at age 2 years with severe mental retardation..

Acidosis↗
PubMed1981

Postmortem changes of amino compounds in human and rat brain.

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.

Amines↗
PubMed1981

Elevation of brain GABA content by chronic low-dosage administration of hydrazine, a metabolite of isoniazid.

When gamma-aminobutyric acid aminotransferase (GABA-T) activity was measured in vitro in rat brain, neither isoniazid (INH) nor for of its known metabolites (isonicotinic acid, acetylisoniazid, acetylhydrazine, diacetylhydrazine) inhibited the enzyme in concentrations (5 mM) far higher than those likely to be achieved when INH is administered to man. In contrast, hydrazine (5 micrometers) caused a 50% inhibition of GABA-T without inhibiting glutamic acid decarboxylase (GAD). Rats were injected daily for 109 days with hydrazine (0.08 or 0.16 mmol/kg/day), after which amino acid contents and enzyme activities were measured in their brains. Both hydrazine doses caused significant elevations of whole brain GABA content and reductions of GABA-T activity, but did not affect GAD activity. Chronic administration of hydrazine at these doses did not reduce weight gain or alter rat behavior, nor did it produce any irreversible pathologic changes in liver or alterations in hepatic aryl hydrocarbon hydroxylase activity. However, hydrazine treatment caused changes in the contents of many brain amino acids besides GABA, and markedly increased concentrations of ornithine, tyrosine, and alpha-aminoadipic acid in rat plasma. Inhibition of GABA-T activity and the other biochemical alterations observed in patients given high doses of INH probably result from hydrazine formed in the metabolic degradation of INH. Thus administration of hydrazine might be a more direct means of elevating brain GABA content in patients where this seems indicated, and might not entail a greater risk of adverse effects.

4-Aminobutyrate Transaminase↗
PubMed1981

Neurotransmitter amino acids in dominantly inherited cerebellar disorders.

We measured amino acid contents in the brains of 11 patients with dominantly inherited cerebellar disorders. Despite clinical similarities, three biochemically different disorders were found. One disorder, with demonstrated HLA linkage in one pedigree, was characterized by moderate reduction of aspartate and glutamate contents in cerebellar cortex alone. In a second disorder, aspartate and glutamate contents were reduced markedly in other brain areas as well as in cerebellar cortex. Aspartate and glutamate contents were normal in cerebellar cortex in the third disorder. GABA content in cerebellar cortex and dentate nucleus was reduced in some patients with each disorder, whereas cerebellar taurine content was normal in all patients. Aspartate deficiency in cerebellar cortex did not result from lack of aspartate aminotransferase or pyruvate carboxylase activity. These amino acid abnormalities probably imply loss of specific cerebellar neurons.

Amino Acids↗
PubMed1981

Amino acid abnormalities in epileptogenic foci.

We compared amino acid contents of 54 epileptogenic foci removed neurosurgically from temporal or frontal cortex of 35 patients with focal epilepsy with those of biopsies from the same cortical regions of 14 nonepileptic patients. Neither taurine nor GABA content was reduced in epileptogenic foci. Glycine content was elevated markedly in some foci, whereas aspartic acid content was normal. Mean glutamic acid content was significantly higher in epileptogenic foci than in control cortex, and six foci contained amounts of glutamate more than 2 SD above the control mean. Our findings do not support hypotheses that deficiencies of taurine or GABA are involved in the pathogenesis of focal epilepsy but do suggest a possible etiologic role for the excitatory neurotransmitter, glutamic acid.

Adolescent↗
PubMed1980

Amino acid and enzyme studies of brain and other tissues in an infant with argininosuccinic aciduria.

Amino acid contents were measured in four regions of autopsied brain from an infant who presented in coma at the age of 7 weeks and died with argininosuccinic aciduria. Argininosuccinic acid lyase activity was greatly reduced in liver, kidney and cultured skin fibroblasts; incorporation of [14C]citrulline into protein by fibroblasts was minimal. Argininosuccinic acid lyase activity in brain was only slightly lower than that in control infant brain. Nevertheless, the brain showed extensive microscopic changes and a marked accumulation of argininosuccinic acid, varying between regions from 1.8 to 4.4 mmol/l. Brain contents of glutamine, glutamic acid, and alpha-amino-n-butyric acid were also greatly elevated, with a lesser elevation of citrulline, and a normal arginine content. These studies suggest genetic heterogeneity of tissue enzymes in argininosuccinic aciduria and offer some clues about pathogenesis of the neurological damage often seen in this disorder.

Amino Acids↗