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Biomedical subjects

M B Youdim

Publications and source records attributed to M B Youdim.

At least 289 records · Page 16Linked to original sources
PubMed1976

Physiological and pathological changes in tissue monoamine oxidase activity.

This article explores the possibility that malfunction of the enzyme monoamine oxidase (E.C. 1.4.3.4., MAO) could lead to aberrations in the catabolism of biogenic amines in the central nervous system and give rise to certain mental abnormalities. No conclusive evidence could be presented to substantiate this. Data on the normal function of the enyzme (for example its existence in multiple forms, the control of MAO activity by hormones or the independent development of MAO activities towards different substrates during maturation) are reviewed.

Adrenal Glands↗
PubMed1976

Variation in monoamine oxidase activity in rat brain crude mitochondrial fractions prepared by rate zonal centrifugation.

Rat brain crude mitochondrial fractionated by rate zonal centrifugation using an iso-osmotic gradient of Ficoll and sucrose. The results demonstrated that the isolated fractions were biochemically heterogeneous with regard to the enzymes, monoamine oxidase (MAO), NADH dehydrogenase and succinate dehydrogenase. When the activity of MAO was plotted as % of the highest specific activity towards tyramine, kynuramine oxidation remained fairly constant in fractions 10 to 30 but tyramine and dopamine showed separate peaks of activity in fractions 21 and 32 respectively. Sonic oscillations of separated particulate fractions did not change the ratios of various monoamine deamination when compared to the intact particles.

Animals↗
PubMed1976

Some histological and metabolic properties of an isolated perfused rat brain preparation with special reference to monoamine metabolism.

A method is described for perfusing the rat head which results in perfusion of the brain, its covering and the bony skull only. Dye and latex injection studies showed that there was no perfusion of extracranial tissue and thus it was not necessary to remove the lower jaw and facial tissues as described by previous authors. Perfusion with fluorescein demonstrated that the whole brain was perfused. Light microscopy after two hours of perfusion revealed no deterioration in brain-structure. Electron microscopy showed a small increase in the extracellular space and the perivascular space with good preservation of subcellular organelles. Glucose and acetoacetate removal were very similar to those reported for the adult rat in vivo as measured by arterio-venous differences. The concentrations of 5-hydroxytryptamine, dopamine and noradrenaline are maintained at values close to those in vivo during a 2-hr perfusion with a basal medium and the preparation will maintain linear rates of 5-hydroxytryptamine synthesis for 2 h when the medium contains L-tryptophan and tranylcypromine, at rates similar to those measured in vivo. The rate of uptake of L-tryptophan into the brain is similar to that reported after L-tryptophan loading in vivo. The histological and metabolic properties of the preparation are close to those observed in vivo. The method could provide a way in which monoamine metabolism in particular could be studied using an experimental model closer in its properties to the in vivo situation than tissue preparations such as slices or homogenates.

Acetoacetates↗
PubMed1976

Some properties of human platelet monoamine oxidase in iron-deficiency anaemia.

1. Monoamine oxidase activity in platelets prepared from the blood of patients with iron-deficiency anaemia was significantly lowered when compared with that in platelets from normal subjects. 2. The Km values of the platelet enzyme for the substrates dopamine, 5-hydroxytryptamine, phenylethylamine and kynuramine were similar for the platelet enzyme from iron-deficient and normal groups. 3. Heat-in-activation studies showed that the platelet monoamine oxidase from iron-deficient subjects was more labile to this treatment, when compared with the platelet enzyme from normal subjects. 4. The sensitivity of platelet monoamine oxidase to the inhibitors, clorgyline and deprenil, was increased in iron-deficiency anaemia. 5. Binding studies with the 14C-binding irreversible monoamine oxidase inhibitor, deprenil, showed that the amount of enzyme capable of binding this inhibitor was lowered by 48% in platelets from iron-deficient patients when compared with platelets from normal subjects. 6. The results show that there is a lowered amount of active enzyme in platelets from iron-deficient subjects. It is suggested that iron is necessary either for the synthesis of monoamine oxidase apoenzyme or is a cofactor for an enzyme which attaches flavin-adenine dinucleotide covalently to the monoamine oxidase apoenzyme.

Adult↗
PubMed1976

Metabolism of phenylethylamine in rat isolated perfused lung: evidence for monoamine oxidase 'type B' in lung.

Phenylethylamine is inactivated in a single passage through rat lung tissue by a process of uptake and deamination by a monoamine oxidase 'type B'. This enzyme is particularly susceptible to inhibition by deprenil and less sensitive to clorgyline. The monoamine oxidase of the lung, like that of other rat tissues, can be differentiated into 'type A' and 'type B' which appear to operate independently in the organized tissue.

Animals↗
PubMed1975

The nature of inhibition of cat brain mitochondrial monoamine oxidase by clorgyline.

In the cat brain the highest monoamine oxidase (MAO) activity is observed in the hypothalamus followed by hippocampus, caudate nucleus, pons and median cortex. Tyramine was the most actively deaminated substrate tested followed by dopamine. Clorgyline was more selective in its inhibitory action and could distinguish between tyramine and dopamine MAO deaminating system. The latter being more resistant to inhibition. The multiple forms of solubilized MAO as separated by polyacrylamide gel electrophoresis have varying phospholipid phosphorus content and sensitivity to inhibition by clorgyline in vitro and in vivo.

Animals↗
PubMed1975

The potentiation of the anti akinetic effect after L-dopa treatment by an inhibitor of MAO-B, Deprenil.

The potentiation of the anti akinetic effect after L-Dopa treatment by an inhibitor of monoamine oxidase (MAO) "B", Deprenil, has been demonstrated in parkinsonian patients with or without previous L-Dopa theapy. Application of the drug has been performed orally, intravenously and intramuscularly. Excellent kinetic effects resulted when combined with Madopar. The combined treatment with L-Dopa was highly effective when applicated i.v. or i.m. Deprenil is an inhibitor of MAO-B and is characterized by less frequent side effects. These are predominantly involuntary movements and confusion, which can be eliminated by lowering the dosage of Deprenil. A daily rhythm of MAO could be demonstrated in several areas of human brains as well as in a control group as in parkinsonian patients with or without L-Dopa therapy. Maximal activity of MAO occurs between noon and 6p.m. The clinical and biochemical data are discussed regarding the off-phenomenons as Deprenil is an excellent drug for preventing these.

Administration, Oral↗