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Biomedical subjects

G Curzon

Publications and source records attributed to G Curzon.

At least 217 records · Page 12Linked to original sources
PubMed1972

A method for obtaining linear reciprocal plots with caeruloplasmin and its application in a study of the kinetic parameters of caeruloplasmin substrates.

1. The curved plots of 1/v against 1/[S] obtained when caeruloplasmin oxidizes NN-dimethyl-p-phenylenediamine were investigated. The first free-radical oxidation product of caeruloplasmin oxidation of NN-dimethyl-p-phenylenediamine is required for curvature, as straight-line plots were obtained when activities were measured either before appreciable free-radical product had appeared or in the presence of ascorbate, which reduced it back to NN-dimethyl-p-phenylenediamine. 2. In the presence of ascorbate linear reciprocal-plots were obtained with all of the 37 substrates tested. V(max.) values varied over only an eightfold range and those for the 20 p-amino compounds over only a twofold range. K(m) values, however, varied over a 10(4)-fold range. The small range of V(max.) values indicates that the rate-limiting step in caeruloplasmin action is relatively independent of the nature of the substrate. K(m) values suggest that substrates bind primarily by ring electrons, although certain side-chain groups increased the K(m) in a manner unrelated to likely changes of ring-electron densities. A mechanism involving repulsion between negative charges on the substrate and the enzyme was supported by the variation of the K(m) of 5-hydroxyindol-3-ylacetic acid with pH.

Aniline Compounds↗
PubMed1972

Amine metabolites in the cerbrospinal fluid in Huntington's chorea.

The amine metabolites HVA and 5-HIAA in the lumbar CSF of 15 patients with Huntington's chorea were determined. A negative correlation was found between the severity of symptoms and the CSF HVA, but not 5-HIAA levels. The mean HVA concentration was lower than that of a group of patients with miscellaneous neurological disorders, similar to that of a group with miscellaneous psychiatric disorders and higher than that of a group with Parkinson's disease. The mean 5-HIAA concentration was similar to that of the neurological group and higher than those of the groups with psychiatric disorders or Parkinson's disease. CSF HVA and 5-HIAA concentrations of a single patient with severe akinetic rigid Huntington's chorea were similar to those found in Parkinson's disease. The findings are discussed in relation to previous neuropathological observations and to reported effects of drugs on the choreic symptoms.

Adult↗
PubMed1971

Regional and subcellular changes in the concentration of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in the rat brain caused by hydrocortisone, DL- -methyl-tryptophan l-kynurenine and immobilization.

1. In agreement with previous findings on whole brain, the intraperitoneal injection of hydrocortisone, DL-alpha-methyltryptophan or L-kynurenine decreased the concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxy-indoleacetic acid (5-HIAA) in different regions of the rat brain.2. Hydrocortisone caused similar decreases in the concentrations of both 5-HT and 5-HIAA, suggesting decreased 5-HT synthesis.3. Changes in the concentration of 5-HIAA after hydrocortisone corresponded significantly to those after alpha-methyltryptophan. Changes in the concentration of 5-HT did not correspond, possibly due to falsely high 5-HT values because of interfering material derived from alpha-methyltryptophan.4. In general, kynurenine caused larger decreases in the concentration of 5-HT than in the concentration of 5-HIAA.5. In agreement with previous findings with whole brain, immobilization of rats for 5 h decreased the concentration of 5-HT and increased that of 5-HIAA in most brain regions.6. The order of the percentage decreases in the concentrations of 5-HIAA 6 h after hydrocortisone injection was, in decreasing order: hypothalamus, striatum, cerebellum, mid-brain, pons + medulla and cortex. The percentage increases after immobilization for 5 h were in the reverse order.7. The differences between the percentage decreases in the concentration of 5-HIAA after hydrocortisone and the percentage increases after immobilization were very similar in all regions except the hypothalamus. This is consistent with immobilization stress increasing the firing rate of 5-hydroxytryptaminergic neurones similarly in different regions.8. During the first 3 h of immobilization the concentrations of 5-HIAA in the hypothalamus and in the rest of the brain increased approximately in parallel. Between 3 and 5 h, 5-HIAA returned to control concentrations in the hypothalamus while continuing to rise in the rest of the brain.9. Relative changes in the concentration of 5-HT in particulate and supernatant fractions after the various treatments were comparable except 2 h after kynurenine injection when the concentration 5-HT fell in the particulate but not in the supernatant fraction. The concentration of 5-HT did fall in the latter, though more slowly than in the former fraction, suggesting a concentration of amine synthesizing organelles in particulate material.

Animals↗
PubMed1971

Effect of folic acid by mouth on cerebrospinal fluid homovanillic acid and 5-hydroxyindoleacetic acid concentration.

Administration of 30 mg folic acid by mouth caused a significant fall in cerebrospinal fluid homovanillic acid concentration in 11 subjects. There was no significant change of 5-hydroxyindoleacetic acid concentration. The fall was less marked in five patients on anticonvulsant medication and failed to reach statistical significance. Neither homovanillic acid nor 5-hydroxyindoleacetic acid concentrations changed significantly when 15 mg folic acid was given in divided dosage for one, two, and four weeks. The effect appeared to be related to the height of serum-folate levels reached and to be independent of cerebrospinal fluid-folate levels, which did not change significantly. Possible mechanisms and their potential therapeutic application are discussed.

Administration, Oral↗
PubMed1970

Tryptophan metabolism in depression.

Psychiatric patients suffering from endogenous depression and a control group without endogenous depression were given oral loads of L-tryptophan and urinary excretion determined of the tryptophan metabolites on the pyrrolase pathway: kynurenine, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid. Female endogenously depressed subjects excreted significantly more kynurenine and 3-hydroxykynurenine but not the subsequent metabolite 3-hydroxyanthranilic acid than did female control subjects. Variability of excretion of kynurenine and 3-hydroxykynurenine at different times by the same subject was much greater in the endogenously depressed than in the control group. There was no consistent temporal relationship between excretion of metabolites and severity of the depressive illness. The possible significance of the findings in relation to defective tryptophan metabolism in the brain in endogenous depression is commented upon.

Administration, Oral↗