Biomedical subjects

E Comoy

Publications and source records attributed to E Comoy.

At least 91 records · Page 5Linked to original sources

PubMed1979

Purification and properties of human erythrocyte delta-amino-levulinic acid dehydratase (EC 4-2-1-24).

Human delta-aminolevulinic acid dehydratase (ALA-D) was purified 9 000-fold by salt precipitation, ion-exchange chromatography and gel filtration. These methods resulted into an electrophoretically and immunologically pure protein. The optimum pH of the enzyme is 6.6 and its Km with ALA : 4.8 X 10(-4) M. The enzymatic activity was increased by thiol-containing substances, such as dithiothreitol (DTT), which protect the -SH groups of the protein. Zinc, a portion of the enzyme molecule, was partly lost during the purification procedure; its addition enhances the enzymatic activity. Determination of molecular weights and electron microscopy study are in favor of an octameric structure.

Animals↗

PubMed1979

[Arterial hypertension from secretion of catecholamines in an infant with a ganglioneuroblastoma].

The case of a 16 month old infant presenting with an abdominal tumour and systemic hypertension is reported. The profile of urinary plasma and tumour catecholamine levels corresponded with that of a pheochromocitoma. The combination of alphablockers and betablockers was the only effective treatment of the peaks of preoperative hypetension. The tumour was completely excised and was found to be a ganglioneuroblastoma. No recurrence has been observed after 3 years post-operative follow-up. The incidence and mechanisms of hypertension in neuroblastoma are reviewed. Only these histological forms of ganglioblastoma have the enzymatic set up for the synthesis and release of pressor amines.

Abdominal Neoplasms↗

PubMed1977

Postulated mode of action of metals on purified human ALA-dehydratase (EC 4-2-1-24).

The effects of twelve metals at various concentrations ranging from 10(-41 to 10(-7) M have been studied on delta-aminolaevulinic acid dehydratase 9000 fold (ALA-D), isolated and purified from human red cells. The results obtained are in very good agreement with those of many authors: zinc, a constitutive element of the enzyme, behaves as an activator at low concentration, and an inhibitor at higher concentrations. The same effect is noted with aluminium, cadmium, mercury and tin. The manganese has a poor inhibitory action, copper and lead are powerful inhibitors of the enzyme. The other metals studies have no noticiable effect on ALA-D. These results agree with the following hypothesis: according to their structure, metals would bind the enzyme in one or several allosteric sites, and induce an allosteric transposition to the active or inactive form of enzyme.

Aluminum↗

PubMed1977

[Abnormal movements of patients with Parkinsonism treated with L-dopa and anomalies of dopamine metabolism].

The authors describe the results of biochemical analysis carried out on 28 patients with Parkinson's disease who had been treated by L-dopa. Twenty of them showed either no abnormal movements at all or very few, eight others had considerable dyskinesia. Biochemical analysis of the urinary degradation products of L-Dopa revealed the existence of a swing in the degradation of dopamine towards 4-O-methylate derivatives in dyskinetic patients (significant difference at .01). The results confirm those obtained in their initial analysis carried out in 1973. The authors express the view that abnormal movements while under L-Dopa treatment are dependent on two factors: one, the hypersensitivity of dopaminergic reception, the other, the greater or lesser preponderance of the COMT isozyme giving rise to 4-O-methylates;

Dopamine↗

PubMed1976

Catecholamine metabolism in neuroblastoma.

Previous studies indicating the importance of catecholamine metabolism in neuroblastoma were briefly reviewed. Metabolic pathways were presented showing how the major urinary metabolites 3-methoxy-4-hydroxymandelic acid (VMA) and 3-methoxy-4-hydroxy-phenylacetic acid (HVA) are formed from norepinephrine and from dopamine plus 3,4-dihydroxyphenylalanine (DOPA), respectively. For 289 neuroblastoma patients at the time of diagnosis, the urinary excretion of VMA was significantly elevated in 75%, and HVA was elevated in 80%. Periodic assay of these metabolites during the course of the disease revealed that the excretion trends were of prognostic value with 80-90% reliability. By contrast, when the excretion in only the initial urine specimens was considered, the survival rate was the same for patients with normal, and with significantly elevated, excretion. Review of the results of tracer studies aimed at elucidating the in vivo metabolic origins of the urinary metabolites suggested that a) in neuroblastoma, the catecholamines were largely inactivated by intracellular metabolism in the tumor cells; b) there was excess production and excretion of the norepinephrine precursors, DOPA and dopamine; and c) in the tumors of most neuroblastoma patients, the initial enzyme in catecholamine synthesis, tyrosine hydroxylase, had an activity comparable with that in normal adrenal glands. The importance of the metabolism of catecholamines in patients with neuroblastoma was stressed: a) The excretion of elevated levels of urinary catecholamine metabolites were useful in diagnosis and in following the course of the disease, and b) study of the catecholamine metabolism in these patients permitted examination of possible relationships between the activity of the enzymes involved in catecholamine synthesis and the malignancy of this tumor.

Catecholamines↗

PubMed1974