Showing papers on "Monoamine oxidase B published in 1975"
01 Jan 1975
TL;DR: These studies suggest that aging processes may significantly affect monoamine mechanisms and be a predisposing factor to the development of clinical diseases in man such as depression, parkinsonism and other disorders of central nervous system homeostasis.
Abstract: A series of studies of monoamines and their metabolism in a variety of human tissues indicate that there are aging effects that may alter neurotransmitter substances. Monoamine oxidase (MAO) activity has a significant positive correlation with age in plasma and blood platelets of normal subjects and patients suffering from depressive disorders. Monoamine oxidase and age correlate positively in hindbrain and in eight separate areas of human brains from patients who died from a variety of causes. Hindbrain norepinephrine concentration progressively decreases with advancing age (r = −0.44, P < 0.01) while no changes were noted for serotonin (5-HT) and 5-hydroxy.indoleacetic acid (5-HIAA). Hindbrain norepinephrine concentration has a significant negative correlation with MAO (r = −0.41, P < 0.025) and hindbrain 5-HIAA has a significant positive correlation with MAO (r = +0.66, P = <0.05). These studies suggest that aging processes may significantly affect monoamine mechanisms and be a predisposing factor to the development of clinical diseases in man such as depression, parkinsonism and other disorders of central nervous system homeostasis.—Rorinson, D. S. Changes in monoamine oxidase and monoamines with human development and aging. Federation Proc. 34: 103–107, 1975.
144 citations
TL;DR: In this article, the authors compared l-deprenyl with clorgyline, an MAO A inhibitor, with regard to its inhibitory effect on the formation of three major catecholamine metabolites, homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), and 3-methoxy-4-hydroxymylglycol (MOPEG) in the rat brain in vivo.
129 citations
TL;DR: There was a tendency for patients in the low-MAO group to have more severely impaired reality testing, more paranoid and grandiose delusions, better prognostic scores, and less restlessness.
Abstract: The authors found normal monoamine oxidase (MAO) activity in 40 acute schizophrenic patients, in contrast to previous reports of a genetically linked platelet MAO deficit in chronic schizophrenia. Variations in MAO activity were not significantly associated with the 65 clinical variables analyzed, although there was a tendency for patients in the low-MAO group to have more severely impaired reality testing, more paranoid and grandiose delusions, better prognostic scores, and less restlessness.
75 citations
TL;DR: It is suggested that the competition among substrates of MA0 which is observed in uitro may have relevance to in uiuo mechanisms for control of biogenic amine concentrations.
Abstract: — Six endogenous substrates of monoamine oxidase (EC 1434) (serotonin, l-norepinephrine, dopamine, tyramine, tryptamine and β-phenethylamine) were used separately and in pairs with human brain mitochondrial extracts Apparent K1 values were obtained from experiments in which only 1 of 2 substrates was isotopically labelled, and these values were compared with experimental Km values β-Phenethylamine appears to be metabolized at enzyme active sites independent from those which bind serotonin The substrate l-norepinephrine competes with serotonin for an enzyme site, but also may be catalysed at an additional site which is independent of serotonin binding Experiments in which [14C]tryptamine was combined with [3E]serotonin indicated that tryptamine is a much more potent inhibitor of serotonin oxidation than was predicted from Km values It is suggested that the competition among substrates of MA0 which is observed in uitro may have relevance to in uiuo mechanisms for control of biogenic amine concentrations
57 citations
52 citations
46 citations
TL;DR: The biphasic inhibition of tyramine deamination by PCO is shown to result from ‘fast’ and ‘slow’ pseudo-first order reactions with the enzyme, and PCO has been shown to be a potent instantaneous competitive inhibitor of the enzyme.
35 citations
TL;DR: MAO activity in women was significantly higher than in men and exhibited greater variability and a circadian rhythm for free tryptophan was observed, but no diurnal variation in MAO activity could be established.
Abstract: A methodological study of healthy subjects was conducted to investigate factors influencing plasma free tryptophan and platelet monoamine oxidase (MAO) activity. The following changes were found during the menstrual cycle: free tryptophan was lower during the "ovulatory" phase than during the "premenstrual" phase, MAO activity was 20% lower during the "premenstrual" phase as compared with the "neutral" phase (days: menses-24 to -1). During pregnancy MAO activity was also lower than the values found six weeks postpartum. MAO activity in women was significantly higher than in men and exhibited greater variability. A circadian rhythm for free tryptophan was observed (minimum at midday, maximum at midnight). No diurnal variation in MAO activity could be established. Preliminary data from untreated endogenous depressive patients showed no difference in free tryptophan concentrations at 8 a.m. or 4 p.m. from control values.
35 citations
TL;DR: 6,7-dihydroxy-TIQ administered in uiuo to reserpinized mice markedly improves the accumulation of injected [3H]NE by sympathetic nerves or the heart, and is investigated to investigate the possibility that TIQs could inhibit M A 0 within peripheral sympathetic nerves in Uiuo.
Abstract: 1 , 2 , 3 , 4 T E T R A H Y ~ R O I ~ U I N O L l N ~ S (TIQS) hydroxylated the 6and 7-positions are ring-closed catecholamine analogues that possess neurotransmitter properties in some adrenergic systems (COHEN, 1973; MILLER et al., 1974; MYTILINEOU et al., 1974). TIQs can be formed by spontaneous condensation of catecholamines in tissues with aldehydes such as acctaldchyde or formaldehyde (COHEN & COLLINS, 1970; YAMANAKA et a!., 1970) and, therefore, they may play a role in modulating catecholaminergic actions during or after ingestion of alcoholic beverages. YAMANAKA (1971) and COLLINS et al. (1973) have reported that TIQs appear to be weak monoamine oxidase (MAO) inhibitors in uitro. The current study was undertaken to investigate the possibility that TIQs could inhibit M A 0 within peripheral sympathetic nerves in uiuo. We chose as an experimental model the in uiuo uptake of [3H]norepinephrine into adrenergic nerves of the heart in reserpine-treated mice. It is known that rescrpiiiized nerves lose their capacity to retain C3H]NE. Reserpine does not appear to affect transport into the nerves (IVEKSEN et al., 1965; SACHS, 1970; HERR & COSTA, 1969), but it docs prevent the uptake of C3H1NlX into the catecholamine-storage vesicles (CARLSSON et al., 1963; EULER & LISFIAIKO, 1963). As a rcsult, cytoplasmic ['HINE is subjected to rapid degradation by M A 0 and retention of C3H]NE is diminished. Inhibitors of M A 0 protect the cytoplasmic pool of NE and thereby increase the amount of C3H]NE that can be accumulated within the neuron. However, M A 0 inhibitors can not completely reverse the effect of reserpine because the MgZ '-ATP-dependent uptake-storage mechanism or the vesicles remains blocked. We worked with 6,7-dihydroxy-TJQ which is the condensation product of dopamine with formaldehyde. This TIQ can be taken up into sympathetic nerves of the mouse heart by means of the desmethylimipramine (DM1)-sensitive and cocaine-sensitive uptakc mechanism normally utilized by NE (L~CKC el al., 1973). Of particular interest, 6.7-dihydroxy-TIQ is readily accumulated within reserpinized adrenergic nerves where it enters the catecholamine-storage vesicles (COHEN et a/ . , 1972; TENNYSON et al., 1973; MYTILINEOU rt al., 1974). We report that 6,7-dihydroxy-TIQ administered in uiuo to reserpinized mice markedly improves the accumulation of injected [3H]NE by sympathetic nerves or the heart. Increased accumulation of 13H]NE was accompanied by some diminution in the presence of [3H]deaminated products.
29 citations
TL;DR: Studies with human platelet monoamine oxidase show that the enzyme contains two interacting catalytic sites, one of which has a high affinity for phenylethylamine and its activity is noncompetitively inhibited by either benzylamine or tryptamine.
27 citations
TL;DR: Each molecule of native enzyme and its multiple forms consists of two sub-units, only one of which possesses an active site, and evidence presented suggests that the preparation contains two types of MAO.
TL;DR: The distribution and characterization of MAO in various tissues of the snail were analyzed and data suggest that there is more than one type ofMAO.
Abstract: The distribution and characterization of MAO in various tissues of the snail were analyzed. Only low amounts of the enzyme exist in the different tissues and data suggest that there is more than one type of MAO.
TL;DR: The inhibitory effectiveness of these substituted benzylidinohydrazines was unrelated to their anticonvulsant activity and their ability to potentiate pentobarbital‐induced hypnosis, which was reflected by the protection afforded against pentylenetetrazol‐induced convulsions.
01 Jan 1975
TL;DR: This chapter discusses the monoamine oxidases (MAO) and the MAO inhibitor drugs and indicates that MAO B is more sensitive to heat than MAO A and the thermostability of MAO preparations was dependent on the presence of phospholipid.
Abstract: Publisher Summary
This chapter discusses the monoamine oxidases (MAO) and the MAO inhibitor drugs. Phenylethylamines and indolethylamines appear to be the endogenous substrates for tissue MAO. The m-O-methylated catecholamine metabolites have lower values than the parent amines. Normetanephrine is a preferred substrate for MAO A as is norepinephrine. Oxygen is also a required substrate and flavin-adenine dinucleotide is found in most MAOs. The relative efficiency with which the enzyme oxidizes low concentrations of amine increases as the oxygen concentrations fall rendering the enzyme relatively insensitive to large fluctuations of local oxygen concentrations. When crude preparations of MAO or MAO prepared by polyacrylamide gel electrophoresis are subjected to high temperatures and then tested for activity, a multiphasic loss of activity is observed suggesting the existence of multiple forms of the enzyme. By using specific inhibitor drugs and substrates, it appears that MAO B is more sensitive to heat than MAO A. The thermostability of the enzymes might be a useful indicator of the molecular nature of the enzymes. It is demonstrated that the thermostability of MAO preparations was dependent on the presence of phospholipid.
TL;DR: A case is reported in which platelet monoamine oxidase activity fluctuated in the course of a schizophreniform psychosis in a way which suggests a direct relationship between low levels of MAO activity and the psychosis.
Abstract: A case is reported in which platelet monoamine oxidase (MAO) activity fluctuated in the course of a schizophreniform psychosis in a way which suggests a direct relationship between low levels of MAO activity and the psychosis.
TL;DR: Replots of the slopes of Lineweaver-Burk plots against inhibiting substrate concentration were linear in most cases but were hyperbolic for serotonin and α-methyl-tryptamine inhibition of tyramine and dopamine oxidation, and parabolic for noradrenaline and dopamine inhibition of tryptamine oxidation.
TL;DR: The evolution of enzyme monoamine oxidase activity has been studied in various species and organs as discussed by the authors, and the results show that MAO activity is constant during adulthood and increases in old age.
TL;DR: A highly sensitive fluorescence assay is established for M A 0 activity which can permit the assay for the enzyme activity towards various biogenic amines as substrate in various regions from a single rat brain (HARADA & NACATSU, 1973).
Abstract: MONOAMINE oxidase (amine :oxygen oxidoreductase (deaminating) (flavin-containing), EC 1.4.3.4.) (MAO) in the brain is of physiological importance, since the enzyme inactivates transmitter monoamines such as dopamine, noradrenaline, and serotonin. Inhibition of the enzyme in the brain causes a significant increase in the amine levels (SHORE et a/., 1957; SPECTOR et al., 1958). Several reports have recently appeared concerning the multiple forms of M A 0 in the brain based on various criteria: selective inhibjtion by specific inhibitors (SQUIRES & LASSEN, 1968; JOHNSTON, 1968; SQUIRES 1968; FULLER, 1972; SQUIRES, 1972; NEFF et al., 1973); separation by disc gel electrophoresis (YOUDIM et al., 1969; YOUDIM, 1972). by continuous-flow electrophoresis (HARADA et al., 1971 ; NACATSU et al., 1972), or by Sephadex electrophoresis (SHIH & EIDUSQN, 1973); or immunoprecipitation (HIDAKA et al., 1972; HARTMAN & UDENFRIEND, 1972; MCCAULEY & RACER, 1973). Different regional distribution of biogenic monoamines (WEIL-MALHERBE & BONE, 1957; SANO et al., 1959) and also that of M A 0 activity towards serotonin (BOGDANSKI et nl., 1957) may also suggest the possible presence and physiological function of different forms of.MAO in several areas of the brain. We have recently established a highly sensitive fluorescence assay for M A 0 activity which can permit the assay for the enzyme activity towards various biogenic amines as substrate in various regions from a single rat brain (HARADA & NACATSU, 1973). By applying this new method, we have examined whether or not there is any regional difference in substrate specificity of M A 0 activity in order to obtain further information of the multiplicity and physiological significance of M A 0 in the brain.
TL;DR: This study discusses the function of the enzyme in vivo in terms of the known specificities and sensitivities to inhibition of the two kinetically distinguishable species present in this preparation.
TL;DR: In the cat brain the highest monoamine oxidase (MAO) activity is observed in the hypothalamus followed by hippocampus, caudate nucleus, pons and median cortex, and in vitro clorgyline was more selective in its inhibitory action and could distinguish between tyramine and dopamine MAO deaminating system.
Abstract: 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 clorgylinein vitro andin vivo.
TL;DR: No change in MAO activity was observed in the cerebellum, hypothalamus or anterior pituitary of ovariectomized rats after steroid treatment, and effects of the steroids in vivo were probably not due to a direct action on the enzyme since only at high concentration did they have any effect on the mitochondrial enzyme activity of the uterus in vivo.
Abstract: The monoamine oxidase (MAO) activity in the ovariectomized rat uterus was significantly increased above control levels in animals given testosterone: 33% (P smaller than 0.01) with tryptamine or 34% (P smaller than 0.05) with tyramine as substrate. Activity was also higher in hydrocortisone-treated animals: 30% (P smaller than 0.05) with tyramine or 25% (P smaller than 0.05) with tryptamine as substrate. Progesterone injection increased MAO activity toward tyramine by 20% but towards tryptamine by only 8%. The differences are not statistically significant but are believed to be real since they were reproducible. MAO activity in oestradiol-treated animals was 11% less than in the controls for both substrates. Although they are not significant differences, they were reproducible. No change in MAO activity was observed in the cerebellum, hypothalamus or anterior pituitary of ovariectomized rats after steroid treatment. At oestrus the enzyme activity in the uterus was lower than at dioestrus or prooestrus when beta-phenylethylamine was the substrate. When 5-hydroxytryptamine was used to measure enzyme activity, the same values were found at oestrus, dioestrus and prooestrus. Ovariectomy did not cause any changes in MAO activity in any of the tissues. Effects of the steroids in vivo were probably not due to a direct action on the enzyme since only at high concentration did they have any effect on the mitochondrial enzyme activity of the uterus in vivo.
TL;DR: In the striata of litter‐mate rats the development of the monoamine oxidase activity towards dopamine in vitro followed a similar time course with age as the tissue concentrations of homovanillic acid and dihydroxyphenylacetic acid, the two acid metabolites of dopamine formed by the action of MAO.
Abstract: In the striata of litter-mate rats the development of the monoamine oxidase (MAO) activity towards dopamine in vitro followed a similar time course with age as the tissue concentrations of homovanillic acid and dihydroxphenylacetic acid, the two acid metabolites of dopamine formed by the action of MAO.
TL;DR: The results of the present study did not demonstrate any relationship between a major catecholamine metabolite in urine, 3-methoxy-4-hydroxy phenylglycol, and dopamine-B-hydroxylase activity in plasma, monoamine oxidaseactivity in platelets, or monoamines oxidaseActivity in plasma.