A new colimetric assay for monoamine oxidase in serum and its clinical application.

A new colimetric assay for serum monoamine oxidase and clinical findings based on this method are described. This rapid, precise procedure employs 1-[(4-aminomethylphenyl)azol]-2-naphthol as a substrate. The enzymatically generated 1-[(4-formyl phenyl)azo]-2-naphthol is extracted into cyclohexane to form a colored solution whose absorbance is determined at 500 nm. The method proved to be extremely simple, and the results obtained correlated well with those given by the standard method of McEwen.     

Dangerous monoamine oxidase inhibitor interactions are still occurring in the 1990s.

The clinical course is described of a 28-year-old woman who was severely ill following ingestion of a Do-Do tablet (which consists of ephedrine, caffeine and theophylline), 24 h after discontinuing phenelzine treatment. Signs and symptoms were delayed for 8 h after which she developed encephalopathy, neuromuscular irritability, hypotension, sinus tachycardia, rhabdomyolysis and hyperthermia. Her illness was complicated by pneumonia and adult respiratory distress syndrome (ARDS). The management of monoamine oxidase inhibitor (MAOI) toxicity, which can arise from interactions and overdoses, is discussed. It should be remembered that, despite the increase in use of alternative and safer antidepressants, MAOI interactions still occur and unless they are managed appropriately, are potentially fatal. Patients need to be warned that restrictions apply for up to 2 weeks after stopping the medication, and doctors need to be aware that serious interactions can occur in this time period.     

Imidazoline-binding domains on monoamine oxidase B and subpopulations of enzyme

A series of phenoxy-substituted methylimidazoline derivatives were synthesized and used to define the ligand recognition properties of the imidazoline-binding domain (IBD) on monoamine oxidase (MAO)-B and its role in substrate processing. The rank order of potency for selected compounds in competitive binding studies with the imidazoline [(3)H]idazoxan was different from that in enzyme activity assays, suggesting that the IBD and the site involved in enzyme inhibition are distinct. IC(50) values for inhibition of MAO-B activity by imidazoline/guanidinium ligands were one to two orders of magnitude greater than ligand concentrations that probably saturate the IBD, but were equal to the K(d) values of these ligands in competitive binding assays with the reversible MAO-B inhibitor [(3)H]Ro 19-6327. In addition, the degree of enzyme inhibition by these ligands was similar in platelet and liver, tissues exhibiting 10-fold differences in the amount of the IBD-accessible enzyme subpopulation. These data suggested that the inhibitory effect of these compounds on MAO-B activity involved a secondary interaction with the enzyme domain recognizing the inhibitor Ro 19-6327 and does not involve interaction with the IBD. Subsequent radioligand-binding studies indicated that human liver MAO-B actually existed as two distinct populations that differed in the accessibility of their IBD. The relatively small amounts of MAO-B possessing an accessible IBD ( approximately 5% in human liver) precludes determination of the functional consequences of ligand binding to the IBD. This subpopulation of MAO-B may be selectively regulated or generated in different individuals or tissues and targeted by pharmacologically active compounds in a cell type-specific manner.     

The macrolide-lincosamide-streptogramin B resistance phenotypes characterized by using a specifically deleted, antibiotic-sensitive strain of Streptomyces lividans.

Genes conferring resistance to macrolide, lincosamide, and streptogramin B (MLS) antibiotics via ribosomal modification are widespread in bacteria, including clinical isolates and MLS-producing actinomycetes. Such erm-type genes encode enzymes that mono- or dimethylate residue A-2058 of 23S rRNA. The different phenotypes resulting from monomethylation (MLS-I phenotype, conferred by erm type I genes) or dimethylation (MLS-II phenotype due to erm type II genes) have been characterized by introducing tlrD or ermE, respectively, into an MLS-sensitive derivative of Streptomyces lividans TK21. This strain (designated OS456) was generated by specific replacement of the endogenous resistance genes lrm and mgt. The MLS-I phenotype is characterized by high-level resistance to lincomycin with only marginal resistance to macrolides such as chalcomycin or tylosin, whereas the MLS-II phenotype involves high-level resistance to all MLS drugs. Mono- and dimethylated ribosomes were introduced into a cell-free protein-synthesizing system prepared from S. lividans and compared with unmodified particles in their response to antibiotics. There was no simple correlation between the relative potencies of MLS drugs at the level of the target site (i.e., the ribosome) and their antibacterial activities expressed as MICs.     

SR 95191, a selective inhibitor of type A monoamine oxidase with dopaminergic properties. II. Biochemical characterization of monoamine oxidase inhibition

SR 95191 [3-(2-morpholino-ethyl-amino)-4-cyano-6-phenylpyridazine] is a novel psychotropic drug which possesses the pharmacological properties of a selective, reversible type A monoamine oxidase inhibitor (MAOI). The MAOI activity of SR 95191 was examined in the rat brain, liver and duodenum and compared to that of clorgyline, harmaline, l-deprenyl, moclobemide and cimoxatone. In vitro, SR 95191 selectively inhibited MAO-A and was less potent than cimoxatone, clorgyline and harmaline, but was more potent than moclobemide. Ex vivo, SR 95191 also preferentially inhibited MAO-A in the brain and was 6 and 13 times less potent than cimoxatone and moclobemide, respectively. Like all MAO-A inhibitors, SR 95191 in vivo caused a dose-dependent increase in striatal 3-methoxytyramine, dopamine, serotonin and in hypothalamic norepinephrine contents. A concomitant decrease in deaminated metabolites was observed. SR 95191 inhibited peripheral MAO activity in liver and duodenum. In brain, liver and duodenum, MAO inhibition induced by SR 95191 was short-lasting. Repeated dosing for 14 days did not enhance MAO-A inhibition. Like all reversible MAOIs, SR 95191 antagonized the long-lasting MAO-A inhibition induced by clorgyline. Finally, SR 95191 did not affect monoamine uptake either in vitro or in vivo and did not interact in vitro with a variety of neurotransmitter or drug receptor sites. Based on these results it is postulated that SR 95191 is a selective and reversible type A MAOI of medium potency, which may be of therapeutic benefit in depressed patients.     

Inhibition of A and B N-acetyl-beta-D-glucosaminidase urinary isoenzymes by urea

A urinary fraction which inhibits the activity of N-acetyl-beta-D-glucosaminidase (NAG) has been isolated and identified as being urea. Usually present in high concentration, urea appears to be the only urinary component responsible for the frequently observed urinary NAG inhibition. The inhibition of the two urinary NAG isoenzymes A and B is competitive with respective Ki values of about 70 mmol/l and 60 mmol/l. With routine assay conditions, it seems that a dilution of urine prior to enzyme assay is sufficient to abolish the inhibition of the two isoenzymes A and B by endogenous urea.     

Effect of cadmium and copper on monoamine oxidase type A and B in brain and liver mitochondria

The effect of cadmium and copper on monoamine oxidase type A and B in mitochondrial preparations from brain and liver was determined in vitro. The results showed a dose-related inhibition of the enzyme. Both the A and B forms of the enzyme were similarly inhibited by the presence of either cadmium or copper. Copper has been shown to be a 7-8 times more potent inhibitor of monoamine oxidase than cadmium. The data suggest that the intracellular concentration of unbound copper (13 mumol/l) or cadmium (100 mumol/l) may inhibit monoamine oxidase in brain and liver by 50%.     

HBV感染者单胺氧化酶活性分析的临床价值

目的分析乙型肝炎病毒（HBV）感染者的血清单胺氧化酶（MAO）活性,探讨MAO活性分析在HBV感染者的临床应用价值。方法回顾分析了284例HBV感染者及123例正常对照者的血清MAO活性水平。结果与正常对照组比较,A组（ALT升高,大三阳者）、B组（ALT升高,小三阳、HBV-DNA阳性者）、D组（ALT正常,大三阳）MAO均呈明显升高（P〈0.01）;C组（ALT升高,小三阳、HBV-DNA阴性者）、E组（ALT正常,小三阳、HBV-DNA阳性者）、F组（ALT正常,小三阳、HBV-DNA阴性者）MAO水平无显著性变化（P〉0.05）。结论对HBV感染者进行血清MAO活性分析,有助于了解肝细胞损害情况,预测肝纤维化的发生,对病情判断有重要意义。     

Potentiation of para-hydroxyamphetamine-induced head-twitch response by inhibition of monoamine oxidase type A in the brain

After pretreatment with either clorgyline, a monoamine oxidase (MAO)-A-selective inhibitor, or pargyline, an MAO-B-selective inhibitor with less selectivity than l-deprenyl, i.c.v. administration of para-hydroxyamphetamine (p-OHA) significantly increased both the frequency and total number of head-twitches in mice. A typical MAO-B-selective inhibitor, l-deprenyl, however, did not change the total count of the p-OHA-induced head-twitch response (HTR). These effects were also found with fixed doses of the selective MAO inhibitors when p-OHA was varied. Administration of clorgyline (1 mg/kg) or pargyline (5 mg/kg) almost inhibited completely MAO-A in the mouse forebrain, and pargyline also almost inhibited completely MAO-B. l-Deprenyl, in contrast, almost inhibited completely MAO-B without affecting MAO-A activity. Systemic administration of l-5-hydroxytryptophan also induced HTR and the total number of twitches was enhanced by clorgyline, but not by pargyline or l-deprenyl. Chlorimipramine or cocaine significantly reduced p-OHA-induced HTR, suggesting an intraneuronal site of action. Together with the presence of considerable MAO-A in 5-hydroxytryptamine (5-HT) neurons of various animal species, and possible accumulation and subsequent monoamine-releasing properties of p-OHA, the present results indicate that p-OHA might induce the HTR by interaction with intraneuronally increased 5-HT. This mechanism probably results in 5-HT release onto the postsynaptic 5-HT2 receptors. Taken together, different roles of MAO-B in "the hyperactivity syndrome" and the HTR are discussed.     

新疆维吾尔族单胺氧化酶B基因多态性与帕金森病的关系

目的 探讨新疆维吾尔族多巴胺代谢酶-单胺氧化酶B(monoamine oxidase B,MAOB)基因内含子13G/A多态性与帕金森病(Parkinson disease,PD)遗传易感性的关系.方法 采用聚合酶链反应-限制性片段长度多态性分析法(PCR-RLFP),经卡方检验,分析95例PD患者与104例健康对照的MAOB基因的等位基因和基因型频率分布情况.结果 PD组与健康对照组MAOB基因G/A等位基因频率、各基因型频率差异无统计学意义;男性PD组与男性健康对照组、女性PD组和女性健康对照组等住基因频率、各基因型频率差异无统计学意义;男性PD组与女性PD组等位基因、各基因型频率差异有统计学意义(x2=3.944,P＜0.05;x2=18.030,P＜0.01).结论 新疆维吾尔族MAOB基因内含子13 G/A多态性可能与PD遗传易感性无关,男性PD组与女性PD组基因型分布不一致.     

Characteristic cardiac phenotypes are detected by cardiovascular magnetic resonance in patients with different clinical phenotypes and genotypes of mitochondrial myopathy

Background

Mitochondrial myopathies (MM) are a heterogeneous group of inherited conditions resulting from a primary defect in the mitochondrial respiratory chain with consecutively impaired cellular energy metabolism. Small sized studies using mainly electrocardiography (ECG) and echocardiography have revealed cardiac abnormalities ranging from conduction abnormalities and arrhythmias to hypertrophic or dilated cardiomyopathy in these patients. Recently, characteristic patterns of cardiac involvement were documented by cardiovascular magnetic resonance (CMR) in patients with chronic progressive external ophthalmoplegia (CPEO)/Kearns-Sayre syndrome (KSS) and with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS). The present study aimed to characterize the prevalence and pattern of cardiac abnormalities and to test the additional diagnostic value of CMR in this patient population. The hypothesis that different neuromuscular MM syndromes present with different cardiac disease phenotypes was evaluated.

Methods

Sixty-four MM patients (50 ± 15 years, 44 % male) and 25 matched controls (52 ± 14 years, 36 % male) prospectively underwent cardiac evaluations including CMR (comprising cine- and late-gadolinium-enhancement (LGE) imaging). Based on the neuromuscular phenotype and genotype, the patients were grouped: a) CPEO/KSS (N = 33); b) MELAS/–like (N = 11); c) myoclonic epilepsy with ragged-red fibers (MERRF) (N = 3) and d) other non-specific MM forms (N = 17).

Results

Among the 64 MM patients, 34 (53 %) had at least one abnormal CMR finding: 18 (28 %) demonstrated an impaired left ventricular ejection-fraction (LV-EF <60 %), 14 (22 %) had unexplained LV hypertrophy and 21 (33 %) were LGE-positive. Compared to controls, MM patients showed significantly higher maximal wall thickness (10 ± 3 vs. 8 ± 2 mm, p = 0.005) and concentricity (LV mass to end-diastolic volume: 0.84 ± 0.27 vs. 0.67 ± 0.11, p < 0.0001) with frequent presence of non-ischemic LGE (30 % vs. 0 %, p = 0.001). CPEO/KSS showed a predominantly intramural pattern of LGE mostly confined to the basal LV inferolateral wall (8/10; 80 %) in addition to a tendency toward concentric remodelling. MELAS/-like patients showed the highest frequency of cardiac disease (in 10/11 (91 %)), a mostly concentric LV hypertrophy (6/9; 67 %) with or without LV systolic dysfunction and a predominantly focal, patchy LGE equally distributed among LV segments (8/11; 73 %). Patients with MERRF and non-specific MM had no particular findings. Pathological CMR findings indicating cardiac involvement were detected significantly more often than pathological ECG results or elevated cardiac serum biomarkers (34 (53 %) vs. 18 (28 %) vs. 21 (33 %); p = 0.008).

Conclusion

Cardiac involvement is a frequent finding in MM patients – and particularly present in KSS/CPEO as well as MELAS/-like patients. Despite a high variability in clinical presentation, CPEO/KSS patients typically show an intramural pattern of LGE in the basal inferolateral wall whereas MELAS patients are characterized by overt concentric hypertrophy and a rather unique, focally accentuated and diffusely distributed LGE.

Electronic supplementary material

The online version of this article (doi:10.1186/s12968-015-0145-x) contains supplementary material, which is available to authorized users.     

帕金森病发病风险与单胺氧化酶B基因微卫星多态性的相关研究

目的:探讨单胺氧化酶B(monoamineoxidaseB,MAOB)基因内含子2区(GT)n微卫星多态与散发性帕金森病发病风险间的关系。方法:采用扩增片段长度多态法(Amp-FLP)和微卫星荧光标记-半自动基因分型技术,对142例符合诊断标准的中国帕金森病患者和210例健康正常人,进行MAOB基因(GT)n微卫星多态分型,并通过相对风险率(relativerate,RR)与帕金森病发病风险作相关分析。结果:①病例-对照组间各等位基因频率分布差异有显著性意义(χ2=25.11,df=15,P=0.048)。其中168,170,184,186bp等位基因与帕金森病正相关,而172bp和182bp等位基因与帕金森病发病风险负相关。②按性别分层后,男性帕金森病患者中仅184bp等位基因频率明显增加(χ2=17.54,P=0.00003),182bp等位基因频率明显减少(χ2=9.10,P=0.026)。女性帕金森病患者中168,170,186,188bp等位基因频率明显增加(168bpχ2=9.55,P=0.002;170bpχ2=5.30,P=0.021;184bpχ2=24.76,P=0.000001;186bpχ2=4.35,P=0.037)。结论:MAOB基因内含子2中(GT)n多态与散发性帕金森病的发病风险有关。这种关联关系有性别差异。     

Effects of imipramine, nomifensine and d-amphetamine on type B monoamine oxidase, cyclic AMP phosphodiesterase and dopamine-beta-hydroxylase.

The three dissimilar structural antidepressant drugs, imipramine, nomifensine and d-amphetamine, were compared for their effects on type B monoamine oxidase, cyclic AMP phosphodiesterase and dopamine-beta-hydroxylase. Three antidepressant drugs caused a dose-dependent inhibition on type B monoamine oxidase. Of the three drugs, imipramine had a most potent effect. Unlike d-amphetamine, both imipramine and nomifensine inhibited the cyclic AMP phosphodiesterase activity at concentrations more than 10(-4)M. No effect was observed below this concentration. All drugs seemed to have little or no effects on the partially purified dopamine-beta-hydroxylase activity. The weak inhibitory effects of nomifensine on these three enzymes may not be attributable to its antidepressant properties. Morphine had no effect on the three enzyme activities.     

The role of monoamine oxidase in the metabolism of exogenous noradrenaline by the human saphenous vein.

Human saphenous vein segments were obtained from patients subjected to coronary bypass surgery. As determined by HPLC-ED, the veins had a relatively low content of noradrenaline and high content of the deaminated metabolites, dihydroxyphenylglycol (DOPEG) and dihydroxymandelic acid (DOMA). In vein segments which had been incubated with 3H-noradrenaline (0.1 mumol/l), the oxidative deamination pathway predominated over the O-methylating one. Deamination occurred both at the neuronal and extraneuronal level; DOPEG appearing to be a good index of intraneuronal deamination, whereas DOMA and O-methylated and deaminated metabolites were mainly formed extraneuronally. Both MAO type A and MAO type B selective inhibitors reduced the deamination of noradrenaline; deamination was also found to be partially sensitive to semicarbazide. Inhibition of neuronal uptake or of deamination increased O-methylation. The human saphenous vein thus metabolizes exogenous noradrenaline following a pattern which substantially differs from that shown to occur in various blood vessels from other animal species.     

Biochemical basis of prolidase deficiency. Polypeptide and RNA phenotypes and the relation to clinical phenotypes.

Cultured skin fibroblasts or lymphoblastoid cells from eight patients with clinical symptoms of prolidase deficiency were analyzed in terms of enzyme activity, presence of material crossreacting with specific antibodies, biosynthesis of the polypeptide, and mRNA corresponding to the enzyme. There are at least two enzymes that hydrolyze imidodipeptides in these cells and these two enzymes could be separated by an immunochemical procedure. The specific assay for prolidase showed that the enzyme activity was virtually absent in six cell strains and was markedly reduced in two (less than 3% of controls). The activities of the labile enzyme that did not immunoprecipitate with the anti-prolidase antibody were decreased in the cells (30-60% of controls). Cell strains with residual activities of prolidase had immunological polypeptides crossreacting with a Mr 56,000, similar to findings in the normal enzyme. The polypeptide biosynthesis in these cells and the controls was similar. Northern blot analyses revealed the presence of mRNA in the polypeptide-positive cells, yet it was absent in the polypeptide-negative cells. The substrate specificities analyzed in the partially purified enzymes from the polypeptide-positive cell strains differed, presumably due to different mutations. Thus, there seems to be a molecular heterogeneity in prolidase deficiency. There was no apparent relation between the clinical symptoms and the biochemical phenotypes, except that mental retardation was present in the polypeptide-negative patients. The activities of the labile enzyme may not be a major factor in modifying the clinical symptoms.     

Senescence-associated phenotypes in Akita diabetic mice are enhanced by absence of bradykinin B2 receptors

We have previously reported that genetically increased angiotensin-converting enzyme levels, or absence of the bradykinin B2 receptor, increase kidney damage in diabetic mice. We demonstrate here that this is part of a more general phenomenon - diabetes and, to a lesser degree, absence of the B2 receptor, independently but also largely additively when combined, enhance senescence-associated phenotypes in multiple tissues. Thus, at 12 months of age, indicators of senescence (alopecia, skin atrophy, kyphosis, osteoporosis, testicular atrophy, lipofuscin accumulation in renal proximal tubule and testicular Leydig cells, and apoptosis in the testis and intestine) are virtually absent in WT mice, detectable in B2 receptor-null mice, clearly apparent in mice diabetic because of a dominant mutation (Akita) in the Ins2 gene, and most obvious in Akita diabetic plus B2 receptor-null mice. Renal expression of several genes that encode proteins associated with senescence and/or apoptosis (TGF-beta1, connective tissue growth factor, p53, alpha-synuclein, and forkhead box O1) increases in the same progression. Concomitant increases occur in 8-hydroxy-2'-deoxyguanosine, point mutations and deletions in kidney mitochondrial DNA, and thiobarbituric acid-reactive substances in plasma, together with decreases in the reduced form of glutathione in erythrocytes. Thus, absence of the bradykinin B2 receptor increases the oxidative stress, mitochondrial DNA damage, and many senescence-associated phenotypes already present in untreated Akita diabetic mice.