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Biomedical subjects

M Unzeta

Publications and source records attributed to M Unzeta.

51 records · Page 3Linked to original sources
PubMed1991

Amine oxidase activities in rat breast cancer induced experimentally with 7,12-dimethylbenz(alpha)anthracene.

The activities and distribution of monoamine oxidase (MAO) and semicarbazide-sensitive amine oxidase (SSAO) in solid breast tumour induced in the rat by treatment with 7,12-dimethylbenz(alpha)anthracene (DMBA) were studied. The mammary tumours were classified according to anatomopathological criteria into: the benign fibroadenoma (FAD) and the malignant adenocarcinoma (ADC) and infiltrant adenocarcinoma (I-ADC). The proportions of total MAO (15%) and SSAO activities (85%) did not change with malignancy. However, an increasing degree of malignancy was associated with an increase in MAO-A activity and a decrease in MAO-B and SSAO activities. Kinetic constants were calculated for SSAO and for each MAO form separately, using specific substrates. The Km values did not change significantly with the degree of malignancy, but Vmax values for MAO-A increased whereas Vmax for SSAO and MAO-B diminished with malignancy. The dependence of SSAO activity on protein concentration indicated the presence of endogenous reversible inhibitory material in extracts from the more malign tumours. This inhibitor was associated with the microsomal fraction and was not removed by dialysis. It was also present in detergent-solubilized extracts, suggesting that the phenomenon might be due to an association of the enzyme itself producing an inactive species.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1991

The oxidation of dopamine by the semicarbazide-sensitive amine oxidase (SSAO) from rat vas deferens.

The activities of monoamine oxidase A and B and the semicarbazide-sensitive amine oxidase from rat vas deferens were compared towards benzylamine and dopamine. The selective inhibitors (-)-deprenyl and clorgyline were used to allow the contributions of the A and B forms of monoamine oxidase to be determined separately. Comparison of the kinetic constants of the three enzymes towards dopamine indicated that, although each of them had activity towards this substrate, their relative contributions to the total oxidative deamination would depend on the substrate concentration. At all concentrations in the range 1 microM to 10 mM monoamine oxidase-B would contribute about 50% of the total activity. In the range 1 to 10 microM the contributions made by activities of monoamine oxidase-A and the semicarbazide-sensitive enzyme were similar but at higher concentrations the activity of the latter enzyme became more important, its contribution to the total activity rising to some 35% of the total at 500 microM dopamine. The activity of the semicarbazide-sensitive enzyme towards dopamine might thus be important under conditions where either or both the monoamine oxidases were inhibited in pharmacological studies. Its possible relevance to Norrie disease, in which both forms of the human enzyme are deficient, requires further examination.

Amine Oxidase (Copper-Containing)↗
PubMed1991

Investigations of the possible glycosylation of monoamine oxidase B from pig leucocytes.

Monoamine oxidase B (MAO B) from pig liver has been reported to be a sialoglycoprotein. However, when that enzyme from pig lymphocytes and granulocytes was separated by polyacrylamide gel electrophoresis after labelling with the specific irreversible inhibitor [3H]pargyline, staining with 1-ethyl-2-[3-(1-ethyl-naphtho [1,2d] thiazolin-2-ylidene)-2-methylpropenyl] naphtho [1,2d] thiazolium bromide ("Stains-all") failed to detect the presence of sialic acid residues. Treatment of the enzyme in disrupted lymphocytes and granulocytes, or in mitochondrial fractions prepared from them, with neuraminidase resulted in a decrease in MAO activity. However, after the enzyme was rendered soluble by treatment with octylglucoside, treatment with neuraminidase had no effect on the activity. These results indicate that sialic acid residues are not an intrinsic component of MAO B, although associated material containing such groups appears to affect the activity of the membrane-bound enzyme. The activities of membrane-bound preparations of MAO B from pig lymphocytes and granulocytes were unaffected by treatment with trypsin or beta-chymotrypsin. After the preparations had been rendered soluble by treatment with octylglucoside there was a decrease in the activity on treatment with beta-chymotrypsin, but trypsin treatment had no effect. Thus solubilization resulted in residues sensitive to cleavage by the former enzyme becoming accessible to it. Tryptic and chymotryptic peptides separated from the sodium dodecyl sulphate denatured enzymes by polyacrylamide gel electrophoresis revealed no differences between MAO B prepared from lymphocytes and granulocytes.

Animals↗
PubMed1990

Inhibition of MAO by substituted tryptamine analogues.

Three different acetylenic analogues of tryptamine, in which the side chain is attached at the 2 position of the heterocyclic ring, were studied as inhibitors of MAO-A and MAO-B. IC50 values were determined after 30 min preincubation of the enzyme and inhibitor, at 37 degrees C before assay. Irreversibility and time-dependence of the inhibition were also established in each case. The kinetic parameters defining non-covalent complex formation and covalent adduct formation were calculated for the mechanism-based inhibition of both MAO-A and MAO-B by these compounds.

Animals↗
PubMed1990

Amine oxidase activities in chemically-induced mammary cancer in the rat.

The activities and distributions of monoamine oxidase (MAO) and semicarbazide-sensitive amine oxidase (SSAO) were studied in solid breast tumours induced in rat by treatment with 7,12-dimethylbenz(alpha)anthracene (DMBA). It was observed that increasing degree of malignancy was associated with an increase of MAO-A activity an decrease of MAO-B and SSAO activities. The Km values did not change significantly with malignancy but Vmax values for MAO-A increased whereas Vmax for MAO-B and SSAO diminished with malignancy. It was detected in the more malignant tumours the presence of endogenous reversible inhibitor of SSAO activity not removed by dialysis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Monoamine oxidase and semicarbazide-sensitive amine oxidase activities in bovine eye.

The activities of MAO-A, MAO-B and the semicarbazide-sensitive amine oxidase (SSAO) were determined in bovine lens, retina, optic nerve, iris and epithelium. No activities were detected in lens but the SSAO activity was found to be rather evenly distributed in the other tissues. The SSAO activities determined with 1 microM benzylamine were about half those determined for MAO-B. MAO-A activity, measured with 5-HT as substrate, was considerably greater than those of MAO-B and SSAO, determined with 2-phenylethylamine and benzylamine, respectively, in all the eye tissues.

Amine Oxidase (Copper-Containing)↗
PubMed1990

Amine oxidase activities in bovine lung.

The subcellular distributions of amine oxidase activities MAO-A, MAO-B and SSAO, in bovine lung have been determined. MAO activities are largely confined to the mitochondria whereas SSAO activity is concentrated in the microsomal fraction. The contribution of different type of amine oxidase present in the microsomal fraction to the metabolism of the benzylamine, tyramine, phenylethylamine, tryptamine and dopamine were determined. The kinetic constants towards benzylamine showed SSAO to have a higher affinity than MAO-B, and the comparison of the Vmax/Km relationship for both enzymes indicated that benzylamine would be oxidised more efficiently by SSAO than by MAO-B.

Amine Oxidase (Copper-Containing)↗
PubMed1989

Characterization of monoamine oxidase activity present in human granulocytes and lymphocytes.

The characterization of monoamine oxidase (MAO) activity in lymphocytes and granulocytes was studied by using cells prepared from human blood. The specific activities of the enzyme towards beta-phenylethylamine (PEA), benzylamine (Bz), tyramine (TYR) and 5-hydroxytryptamine (5-HT) were found to be 5-times higher in lymphocytes than in granulocytes. The absence of the semicarbazide-sensitive amine oxidase (SSAO) was confirmed by the lack of effect of semicarbazide on the benzylamine oxidation. The presence of MAO-B was corroborated by the inhibition of PEA oxidation with nanomolar deprenyl concentrations and by inhibition of TYR oxidation with high clorgyline concentrations, as well as by the simple sigmoid curve obtained in both cases. These results, together with the substrate preferences, suggest that the MAO activity of human granulocytes and lymphocytes is predominantly of the B form. For each fraction the kinetic constants were determined towards PEA, TYR and Bz as substrates. The Km values were similar for both cellular samples, whereas the Vmax values were higher in lymphocytes than in granulocytes. MAO-B was titrated with [3H]pargyline in order to find out the number of active sites. The corresponding molecular concentration, Kcat values and turnover number showed the presence of related enzymes in human granulocytes and lymphocytes.

Adult↗
PubMed1988

A comparative study of some kinetic and molecular properties of microsomal and mitochondrial monoamine oxidase.

This experimental work tries to characterize the monoamine oxidase of microsomal origin through its kinetic and molecular properties, and to establish a comparative study with the enzyme present in rat liver mitochondria. The temperature effect upon this catalytic activity was examined and similar behaviour of MAO A and MAO B between both cellular fractions was found. The study of the pH dependence of initial velocity showed similar results both in mitochondria and in microsomes. The FAD cofactor is covalently attached to the MAO of microsomal origin. The FAD containing subunits corresponding to MAO A and MAO B, previous binding of the enzyme with [3H]pargyline and posterior SDS electrophoresis and fluorography, showed molecular weights of 65,900 and 62,400, respectively, in both cellular fractions. The inhibition curves with clorgyline, deprenyl, semicarbazide and KCN, measuring the remaining activity towards 1 microM of benzylamine, indicated that in mitochondria 5% of the total activity is due to the presence of SSAO activity whereas in microsomes this activity represents about 20%. From all these results it appears that mitochondrial and microsomal MAO are related enzymes, although further structural studies are necessary to confirm their possible identity.

Amine Oxidase (Copper-Containing)↗
PubMed1988

Neurotransmitter systems and personality measurements: a study in psychosomatic patients and healthy subjects.

A comparative study performed in psychosomatic patients (PG) and healthy subjects (HG) reveals several correlations between personality measurements (Minnesota Multiphasic Personality Inventory, Sensation Seeking Scale, Susceptibility to Punishment), and biochemical variables (in serum: MHPG, acetylcholinesterase, calcium, melatonin; and in platelets: monoamine oxidase B, serotonin, calcium proteins). The relationship between some Sensation Seeking subscales and the enzymatic activities evaluated (negative with MAO and positive with AChase) and the opposite sign relationship between serotonin and some scales of MMPI in both groups studied (negative in the PG and positive in the HG) are noteworthy.

Acetylcholinesterase↗
PubMed1987

Monoamine oxidase activities in lymphocytes and granulocytes taken from pig blood.

The characterisation of monoamine oxidase activities in lymphocytes and granulocytes was studied using cells prepared from pig blood. The specific activities against beta-phenylethylamine, benzylamine, tyramine and 5-hydroxytryptamine as substrates in granulocytes (G) were approximately twice those found in lymphocytes (L). The absence of the semicarbazide-sensitive amine oxidase (SSAO) was confirmed by insensitivity of the latter to semicarbazide as inhibitor with benzylamine as substrate. MAO activity present in (G) and (L) was selectively inhibited by low deprenyl concentrations; this fact, in addition to the simple sigmoid inhibition curves obtained with increasing concentrations of clorgyline with tyramine as substrate, suggests that the MAO activity present both in (G) and (L) is predominantly of the MAO-B form. The absence of any contamination with plasma amine oxidase (EC 1.4.3.6) was confirmed by the fact that activity towards benzylamine (Bz) was insensitive to KCN-induced inhibition. Kinetic constants were determined for each fraction towards beta-phenylethylamine (PEA) and Bz as substrates. MAO-B was titrated with unlabelled pargyline, deprenyl and [3H]-pargyline; the corresponding Kcat values, turnover number and the active concentrations were then determined. The molecular weight of MAO-B present in both cellular fractions was calculated by SDS-electrophoresis and fluorography, after reaction with [3H]-pargyline. Some of these results are compared with those obtained with human blood leucocytes.

Amine Oxidase (Copper-Containing)↗
PubMed1987

Effects of nondenaturating zwitterionic detergent CHAPS, 3-[(3-cholamido propyl) dimethyl ammonio]-1-propanesulfonate, on rat liver mitochondrial and microsomal monoamine oxidase.

It has been reported that monoamine oxidase (MAO) activity (EC1.4.3.4) and, in general, enzymes possessing cationic substrates, were activated and inhibited by anionic and cationic detergents, respectively. In order to examine this hypothesis, the effect of the zwitterionic detergent CHAPS 3-[(3-cholamido propyl) dimethyl ammonio]-1-propanesulphonate was studied in comparison with the effects of cationic, anionic, and non-ionic detergents. The non-denaturating zwitterionic detergent CHAPS was used to solubilise rat liver monoamine oxidase MAO (EC1.4.3.4) of mitochondrial and microsomal origin; the solubilisation conditions, purification, inhibition and kinetic studies were then determined. These results are compared with those previously obtained with the non-ionic detergent Triton X-100, which would also be expected to have no net charge, and are interpreted in terms of specific ionic effects.

Animals↗
PubMed1986

Determination of monoamine oxidase concentrations in rat liver by inhibitor binding.

The concentrations of monoamine oxidase-A and -B have been determined in mitochondria, mitochondrial outer membranes and microsomes from Sprague-Dawley and Wistar rats by determining the binding of tritium-labelled pargyline. Although the amounts of each form present depended on the source and the preparation method, this was paralleled by the specific activity such that the molecular turnover number was found to remain constant. The catalytic constants, kcat/Km, which represents the apparent second-order rate constant for the combination of enzyme and substrate, were about 0.13 and 2.1 sec-1 X microM-1 for 5-hydroxytryptamine and 2-phenethylamine, respectively, regardless of the source. Estimations of the amounts of the two forms by determining the concentrations of the inhibitors clorgyline, (-)-deprenyl, J-508 or pargyline necessary to give complete inhibition were shown to give overestimates of the true values because of the non-specific binding of these inhibitors to sites other than the monoamine oxidase active site.

Animals↗