SEARCH · PubMed Health

Results for “MONOAMINE OXIDASE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources

PubMed1984

Isoelectric focusing of isoenzymes of monkey brain monoamine oxidase.

The multiple forms of monoamine oxidase (MAO) in monkey brain were investigated using an electrofocusing technique. When beta-phenylethylamine (beta-PEA) was used as substrate, two peaks (peak I and peak II) could be clearly distinguished from the profile; the isoelectric point (pI) values were near 7.8 and 6.3, respectively. When serotonin (5-HT) was used, MAO activity was observed in peak I enzyme. The peak I enzyme with a pI value of 7.8 contains AB-form MAO and oxidizes 5-HT and beta-PEA, while peak II enzyme with a pI value of 6.3 contains B-form MAO and oxidizes beta-PEA, respectively. However, when peak II enzyme was incubated in a pH 8.8 reaction medium, MAO activity toward 5-HT in peak II enzyme was seen.

Animals↗

PubMed1983

Comparative studies of purified and reconstituted monoamine oxidase from bovine liver mitochondria.

Monoamine oxidase, a strictly membrane-bound flavoenzyme, has been purified using a modified procedure recently developed. Probably similarly to other preparations known from the literature, the enzyme solubilizes to a clear suspension, which represents large clusters ranging in size from 5 to 50 nm containing appreciable amounts of residual lipids. The purified and reconstituted enzymes are inhibited differently by deoxycholate. In contrast to deoxycholate, Triton X-100 does not inhibit the purified enzyme, but rather disintegrates the lipid-enzyme clusters to the smallest active units. However, removal of the detergent leads to reconglomeration to larger lipid-enzyme aggregates. Using the irreversible destruction of the enzyme by deoxycholate as assay, reconstitution of the enzyme with exogeneous lipids has been studied. All basic enzyme properties, such as stability, maximal activity (V), Michaelis constant (Km), pH- and temperature-dependence of the purified and reconstituted systems, are significantly different.

Animals↗

PubMed1981

Activity of platelet monoamine oxidase in apparently health subjects.

Monoamine oxidase activity was assayed in platelets from 32 apparently healthy subjects using phenethylamine as substrate and two concentrations of oxygen (0.06 and 0.12 mM). Apparent Km (microM) and Vmax (nmol/mg protein/5 min) values were estimated from double reciprocal plots. The means of the Km and Vmax values were both increased by a factor of about 1.6 when the oxygen concentration was elevated from 0.06 mM (Km = 2.96 and Vmax = 4.47) to 0.12 mM (Km = 4.82 and Vmax = 7.18). The frequency distribution of the Vmax values was not clearly unimodal, especially at the higher oxygen concentration. The Vmax values of the women were significantly higher than those of the men but no sex difference was obtained for the Km values. The overall velocity (v) at 10 microM phenethylamine was highly correlated to the Vmax values both at low and high oxygen concentrations (r = 0.99 and 0.98, respectively).

Blood Platelets↗

PubMed1993

Structure and promoter organization of the human monoamine oxidase A and B genes.

Monoamine oxidase (MAO) A and B play an important role in regulating levels of biogenic amines. MAO A and B cDNAs have been cloned and the deduced amino acids share 73% sequence identity. The genes for MAOA and B are comprised of 15 exons interspersed by 14 introns, span at least 60 kb and exhibit identical exon-intron organization. These findings suggest that the MAOA and MAOB genes are derived from the duplication of a common ancestral gene. The core promoter region of MAOA is comprised of two 90 bp repeats, each of which contains two Spl elements and lacks a TATA box. The MAOB core promoter region contains two sets of overlapping Spl sites which flank a CACCC element all upstream of a TATA box. The different organization of the MAOA and MAOB promoters may underlie their different cell and tissue specific expression.

Base Sequence↗

PubMed1990

Tissue distribution of human monoamine oxidase A and B mRNA.

Monoamine oxidase (MAO) A and B play important roles in the metabolism of biogenic amines. Northern analysis using 32P-labeled subfragments of human liver MAO A and B cDNA clones detected a 5- and a 3-kb transcript, respectively, in most human tissues examined. However, fetal heart and thymus express minute amounts of MAO A transcript, whereas fetal brain, muscle, thymus, spleen, meninges, and placenta express minute amounts of MAO B transcript. Small intestine and placenta express, in addition to the MAO A 5-kb transcript, a 2-kb transcript, which may arise from an alternative polyadenylation site. MAO A and B transcripts are expressed in similar regions of adult human brain. The highest concentrations of these transcripts were located in frontal cortex and locus coeruleus. This study demonstrates the tissue-specific distribution of the MAO genes and will provide insight into the physiological functions of MAO A and B.

Brain↗

PubMed1988

Monoamine oxidase inhibitors in anxiety disorders.

Monoamine oxidase inhibitors (MAOI's) have been shown to be significantly superior to placebo in the treatment of some anxiety disorders, particularly agoraphobia and mixed anxiety--depressive states. There is no convincing evidence that MAOI's are effective treatment in pure anxiety states, whether or not panic is present as a major symptom, although they are effective in so-called endogenous anxiety. Many past published studies of MAOI's have yielded poor results because the drugs have been prescribed for insufficient time (less than four weeks) or at too low dosage. There are no important therapeutic differences between the MAOI's apart from the faster speed of response with the nonhydrazine compound, tranylcypromine. Treatment often has to be long-term, and some degree of pharmacological dependence may develop. A few clinical studies have compared the efficacy of MAOI's and tricyclic antidepressants in anxious disorders. There is growing evidence that MAOI's are somewhat more effective than tricyclic antidepressants in the treatment of anxiety disorders and when phobic anxiety is an important component of a depressive disorder.

Antidepressive Agents, Tricyclic↗

PubMed2002

Smoking only explains part of the associations between platelet monoamine oxidase activity and personality.

Platelet monoamine oxidase (MAO) activity has been shown to be inversely associated with personality traits such as sensation seeking, impulsiveness and extraversion. Those personality traits have also been linked to vulnerability for substance abuse, e.g. tobacco smoking and early onset or "type 2" alcoholism. Compounds in cigarette smoke have been shown to be inhibitors of MAO, which has led several authors to claim that there is no association between alcoholism, which is the most studied psychiatric condition, and platelet MAO if the effect of smoking is removed. With regard to the association between personality and platelet MAO, authors have in general been cautious. In the present paper we describe a number of results which show that there is such an association, both in clinical series if the effect of smoking is removed and in series where smoking have never taken place. A cornerstone in this regard is the significant association between platelet MAO activity and both behaviour/personality, voluntary alcohol intake and biochemical measures of CNS serotonergic activity in non-human primates. Strong evidence that the regulation of platelet MAO activity takes place on a transcriptional level with an involvement of transcription factors, likely to also regulate central monoaminergic activity, are presented.

Blood Platelets↗

PubMed1982

Regulation of rat pineal melatonin synthesis: effect of monoamine oxidase inhibition.

Inhibition of pineal monoamine oxidase (MAO) activity either by harmine or pargyline in adult male Sprague-Dawley rats housed in a 12 : 12 LD cycle resulted in increase pineal N-acetyltransferase (NAT) activity. Pineal MAO inhibition also increased pineal melatonin content, presumably as a result of the increased NAT activity. Conjunct treatment with propranolol, a beta-adrenergic receptor antagonist, nullified these effects, regardless of the MAO inhibitor (harmine, pargyline or both) used or the inhibitor dose given. MAO inhibition during continuous light resulted in increased NAT activity greater than that observed following MAO inhibition during a 12 : 12 LD cycle. On the other hand, the increase in melatonin content following MAO inhibition during continuous light was not significantly different from that following MAO inhibition during a 12 : 12 LD cycle. Conjunct propranolol administration negated the effects of MAO inhibition on both the level of NAT activity and melatonin content, regardless of the lighting conditions. The level of pineal NAT activity is apparently regulated by the level of pineal beta-adrenergic receptor stimulation. While melatonin production appears to be dependent on increases in NAT activity, biosynthesis of this methoxyindole may also be regulated, in part, by other factors or processes in metabolic pathway.

Acetyltransferases↗

PubMed1992

Developmental aspects of the monoamine-degrading enzyme monoamine oxidase.

In the rat heart, monoamine oxidase (MAO)-B activity was shown to predominate in 2- to 3-week-old animals, whereas MAO-A activity was reported to be very low in newborn rats and to increase considerably with age until it predominates. These results are in contrast with those found in the mouse heart, where an age-dependent increase in MAO-B activity with no changes in 5-hydroxytryptamine deaminating activity was found to occur. There is evidence that the adult values of MAO activity are reached early in development in rat kidney and liver. In the rat lung the adult values of MAO-A activity are reached by day 40, whereas MAO-B activity is still increasing by day 80. Important differences have been reported in the developmental pattern of the two forms of MAO in the rat and mouse brain, with a decrease in the MAO-A/MAO-B ratio during postnatal development. In the human brain, the ontogenetic development of MAO-A and MAO-B appears to parallel that observed in the rodent brain. It is worth noting that most of the available data have to be considered with reservation owing to many methodological problems. Further studies are clearly needed to get reliable information on the ontogenesis of MAO in mammalian tissues.

Animals↗

PubMed1984

Personality traits related to monoamine oxidase activity in platelets.

Platelet monoamine oxidase (MAO) activity and intellectual level were examined in a large series of 1,129 18-year-old boys, selected from the general population. Personality traits were determined by means of selected subscales from several personality inventories such as the Zuckerman Sensation Seeking Scale, the Eysenck Personality Inventory, and the Karolinska Hospital Personality Inventory. Information was also gathered concerning alcohol consumption habits, signs of alcohol dependence, and use and abuse of tobacco, cannabis, glue, opiates, and amphetamine. Low MAO subjects were found to be more sensation seeking and to have higher scores on impulsivity and monotony avoidance. They also had higher use of tobacco and alcohol, showed more signs of possible alcohol dependence, and showed more drug abuse. When low MAO subjects were subdivided according to intellectual level, low MAO subjects with high intellectual level were found to have higher psychological functioning as judged by a psychologist after a clinical interview. Low MAO subjects with low intellectual level were found to have more use and abuse of alcohol and drugs, i.e., less accepted forms of sensation seeking, and they had a significantly lower level of psychological functioning. This subgroup seems to be the real "high risk" group that according to the high risk paradigm could be expected to show more alcohol abuse and higher tendencies to suicidal behavior.

Adolescent↗

PubMed1998

Localization of monoamine oxidase mRNA in human placenta.

Monoamine oxidase (MAO) oxidatively deaminates vasoactive and biogenic amines and exists in two distinct forms (A and B), coded for by separate genes, which exhibit distinct substrate specificities and inhibitor sensitivities. Using specific primers for MAO-A and MAO-B mRNA in a reverse transcription-polymerase chain reaction (RT-PCR) on RNA from human liver, the predicted products for both enzymes were detected. Furthermore, RT-PCR on RNA from human placenta, believed to contain predominantly (or only) MAO-A protein, also indicated the presence of both A and B gene transcripts. The cellular distribution of MAO mRNA in placental tissue was analyzed by in situ hybridization of MAO-A and MAO-B mRNA-specific cRNA probes on paraffin sections. MAO-A mRNA was mainly evident in the syncytiotrophoblastic layer. None was detected in the vascular endothelium/smooth muscles. Significantly, MAO-B mRNA signal was also evident in the placental villi, notably in the syncytiotrophoblasts, intermediate trophoblasts, cytotrophoblasts, and the vascular endothelium. To our knowledge, this is the first demonstration of the cellular distribution of MAO mRNA in human placenta via in situ hybridization. The expression of MAO-B in placental tissue rather than in blood elements within placenta is also unequivocally demonstrated. These highly specific cRNA probes can now be used to study the distribution of MAO-A and MAO-B expression in other tissues.

Blotting, Northern↗

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↗

PubMed1993

Rescue of axotomized immature rat facial motoneurons by R(-)-deprenyl: stereospecificity and independence from monoamine oxidase inhibition.

The role of monoamine oxidase B (MAO-B) in R(-)-deprenyl-mediated rescue of rat facial motoneurons axotomized at postnatal day 14 (P14) was investigated using the (+)- and (-)-enantiomers of deprenyl [S(+)-deprenyl and R(-)-deprenyl]. Previously, doses of R(-)-deprenyl sufficient to inhibit MAO-B were shown to increase the survival of motoneurons following an apparent loss of target-derived trophic support caused by axotomy in P14 rats. In the present experiments, motoneuronal survival was measured 21 d after unilateral facial nerve transection at P14. The animals were treated with saline or doses of R(-)- or S(+)-deprenyl ranging from 0.001 to 10 mg/kg every 2 days (/2d). Frontal serial 10 microns sections were taken through the length of the facial nuclei ipsilaterally and contralaterally to the facial nerve transections. Every third section was immunoreacted for an antibody against ChAT to identify the motoneuron somata, while every adjacent third section was Nissl stained to assess motoneuronal survival. A second series of P14 rats was treated with similar doses of the two deprenyl enantiomers or saline and the brainstems removed for measurement of MAO-A and MAO-B activity at 4 hr after the treatments. Averages of 24% of the facial motoneurons survived axotomy with either saline treatment or 0.001 mg/kg/2d doses of R(-)-deprenyl. Doses of R(-)-deprenyl of 0.005, 0.01, and 10.0 mg/kg/2d increased the surviving facial motoneuron to 38%, 51%, and 48%, respectively, indicating an ED50 of about 0.005 mg/kg/2d. Doses of S(+)-deprenyl as high as 10 mg/kg/2d did not increase motoneuronal survival, revealing a stereospecificity for the increased survival of at least 2000-fold. The ED50 for MAO-B inhibition in the P14 brainstem was approximately 0.1 mg/kg for the (-)-enantiomer and 2.0 mg/kg for the (+)-enantiomer, revealing a 20-fold higher sensitivity of the enzyme toward the (-)-enantiomer in the P14 rat brainstem. A dose of 10 mg/kg of S(+)-deprenyl inhibited about 65% of brainstem MAO-B activity without increasing motoneuronal survival, whereas 0.005 and 0.01 mg/kg of R(-)-deprenyl increased motoneuronal survival without significant inhibition of brainstem MAO-B activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗

PubMed1978

Effect of p-chloramphetamine on the inactivation of monoamine oxidase in rat brain by 3-amino-2-oxazolidinone, 2-hydroxyethylhydrazine and pheylisopropylhydrazine.

p-Chloroamphetamine protected against the irreversible inactivation of monoamine oxidase in rat brain and liver by 3-amino-2-oxazolidinone, an agent that leads to monoamine oxidase inhibition through conversion to an active metabolite, probably 2-hydroxyethyl-hydrazine. In contrast, p-chloramphetamine did not protect against the inactivation of monoamine oxidase by 2-hydroxyethylhydrazine itself or by phenylisoprophylhydrazine. The effect on 3-amino-2-oxazolidinone may have been due to interference with its metabolism rather than to occupancy of active sites on monoamine oxidase by p-chloroamphetamine. Some implications of these findings relating ot the use of 3-amino-2-oxazolidinone in evaluating reversible monoamine oxidase inhibitors and to the pharmacological effects of p-chloroamphetamine are discussed.

Amphetamines↗

PubMed1978

Effect of phospholipid depletion by phospholipases on the properties and formation of the multiple monoamine oxidase forms in the rat liver.

The effect of phospholipid depletion by phospholipases on the properties and formation of monoamine oxidase A and B been investigated. The enzyme was solubilized, partially purified, treated with phospholipases and subjected to get filtration to reduce the amount of enzyme-associated phospholipids. Phospholipase A treatment of the purified monoamine oxidase fraction had no effect on the deprenil inhibition pattern or the observed transition temperatures in the Arrhenius plots. However, the rate of enzyme inactivation by heat and trypsin were greatly increased but differences in rates of inactivation of monoamine oxidase A and B were still observed. Phospholipase C treatment of the enzyme fraction had no effect on the deprenil inhibition pattern, Arrhenius plots, heat stability or trypsin digestibility. The inhibition pattern of membrane-bound monoamine oxidase and the phospholipase-treated fractions by propargylamine showed a reduced substrate specificity compared to deprenil suggesting a hydrophobic region in the enzyme is a factor involved in the structural differences of monoamine oxidase A and B.

Animals↗

PubMed1997

Effects of monoamine oxidase and catechol-O-methyltransferase inhibition on dopamine turnover: a PET study with 6-[18F]L-DOPA.

The consequences of monoamine oxidase and catechol-O-methyltransferase inhibition on the effective turnover of dopamine were investigated using 6-[18F]L-3-4-dihydroxyphenylalanine (6-[18F]L-DOPA) and positron emission tomography. The effective dopamine turnover was expressed as the ratio between the rate of reversibility of 6-[18F]L-DOPA trapping (k[loss]) and the rate of uptake of 6-[81F]L-DOPA (Ki) in the striatum of normal cynomolgus monkeys. The monkeys received 6-[18F]L-DOPA scans, untreated or after pretreatment with either the peripheral catechol-O-methyltransferase inhibitor nitecapone; the peripheral and central catechol-O-methyltransferase inhibitor tolcapone; the monoamine oxidase inhibitors deprenyl or pargyline; a combination of tolcapone and the monoamine oxidase inhibitors. Tolcapone alone or combined with the monoamine oxidase inhibitors produced a significant decrease in the dopamine turnover (55 to 65%). Neither nitecapone nor monoamine oxidase inhibition alone produced significant changes. These results may have implications for the use of central catechol-O-methyltransferase inhibitors added to routine levodopa therapy in parkinsonian patients.

Animals↗

PubMed1975

Human platelet monoamine oxidase activity in iron-deficiency anaemia.

1. The activity of monoamine oxidase, when assayed with four substrates, was significantly lowered in platelets prepared from the blood of patients with iron-deficiency anaemia. 2. Treatment with oral iron preparations restored platelet monoamine oxidase activity to normal in those patients whose serum iron concentrations also returned to normal. 3. Platelet monoamine oxidase activity remained low if treatment failed to restore serum iron concentration to within normal limits.

Adult↗

PubMed1981

Human platelet monoamine oxidase activity in health and disease: a review.

The most readily available source of monoamine oxidase in man is the platelet, although only the B form of the enzyme is represented in this site. Platelet activity is higher in women than in men. The enzyme activity is generally stable and is partly under genetic control. There is some evidence that individuals with low activity have a higher psychiatric morbidity than those with high activity. Despite some negative studies, the consensus of publication dealing with schizophrenia, migraine, and alcoholism find that mean platelet monoamine oxidase activity in the patient group is lower than in the controls. Values are raised in unipolar depression. Technical differences, or patient or control group heterogeneity, might well account for the absence of unanimity in the literature. A considerable degree of overlap between patient and control values, whatever the clinical diagnosis, appears to be the standard finding. Apart from these neuropsychiatric disturbances, platelet monoamine oxidase activity is raised in megaloblastic anaemia and reduced in iron deficiency anaemia. Although altered enzyme activity values may be linked to abnormal platelet populations in some of the haematological disorders discussed, in general the causes of abnormal platelet monoamine oxidase activity are unknown.

Adolescent↗