Brain regional distributions of monoamine oxidase activities in postnatal development in normal and chronically manganese-treated rats

To investigate the hypothesis that manganese toxicity may affect the development of the monoamine oxidases (MAOs) in brain, the regional distributions of the A (serotonin-oxidizing) and B (benzylamine-oxidizing) forms of MAO were determined in manganese-treated (1 mg or 10 mg of MnCl₂·4H₂O per ml of drinking water from conception onwards until the rats were used for experiments) and untreated male rats during various stages of postnatal development. The age-related variations in regional M AO-A activities (especially in pons and medulla and in cerebellum) were more marked than those in regional MAO-B activities. The MAO-A:MAO-B activity ratios decreased in all regions during development. Chronic manganese treatment (at the specified doses) did not significantly alter the age-related changes in regional MAO-A and MAO-B activities; nor were the A:B activity ratios affected. The results suggest that there is differential expression of MAO isoforms in various brain regions during postnatal development but the expression is not affected by chronic manganese toxicity.     

Heterogeneity of monoamine oxidase activities in synaptic and non-synaptic mitochondria derived from three brain regions: Some functional implications

The heterogeneity of monoamine oxidase (MAO; EC 1.4.3.4) activities was studied in two fractions of synaptic mitochondria (SM & SM2) and one fraction of non-synaptic ("free") mitochondria (M) isolated from three rat brain regions (cerebral cortex, striatum, and pons & medulla) by the Lai and Clark (1979, 1989) method in order to elucidate the heterogeneity of MAO at the subcellular and brain regional levels. The activities toward serotonin (MAO-A), benzylamine (MAO-B), and dopamine (MAO-DA) in SM2 from all three regions were different from the corresponding values in SM. In addition, the various MAO activities in SM and SM2 showed heterogeneous distribution with respect to the three brain regions investigated. Both the distribution of MAO-A and MAO-B in non-synaptic mitochondria (M) did not show marked regional differences although MAO-DA in M varied depending on the region. These results clearly demonstrate that the distribution of MAO activities toward different substrates is heterogeneous both at the subcellular and the brain regional levels. The MAO-A:MAO-B ratios in the various mitochondrial fractions also showed trends that are consistent with this hypothesis. Furthermore, in fraction SM of synaptic mitochondria, this ratio was consistently higher than values in the other two mitochondrial fractions (SM2 & M) irrespective of the region from which they were isolated. In view of the functional importance of MAO in the regulation and compartmentation of amine metabolism, the heterogeneity of MAO at subcellular and regional levels may assume pathophysiological importance in neurological diseases (e.g., Parkinsonism) with which altered amine metabolism is associated.     

Circadian variations in the monoamine levels and monoamine oxidase activity in different regions of the rat brain as a function of age

Time-related changes in the levels of norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT) and monoamine oxidase (EC 1.4.3.4, MAO) activity have been studied in the cerebral cortex, cerebellum, medulla oblongata, hypothalamus, striatum and midbrain of 21 day, 3, 6, 12 and 24 month old rats maintained at 12 hours of light and 12 hours of dark condition. Maximum NE level was seen during the dark phase in all the regions of 3, 6, 12 and 24 month old rats, whereas in 21 day old, the maximum NE level occurred during the light phase. In the cerebral cortex and in the cerebellum of 21 day old rat DA was absent at all times. In all the other age groups, the maximum DA level was seen during the dark phase, while for 5-HT higher level was during the light phase in all the age groups. MAO activity of 3, 6, 12 and 24 month old rats showed the peak activity at the beginning of the light phase (06:00 hours), whereas cerebral cortex, cerebellum and medulla oblongata of 21 day old rat had its peak MAO activity at 14:00 hours and at 22:00 hours in other regions.     

Immunocytochemical demonstration of monoamine oxidase B in brain astrocytes and serotonergic neurons.

An antiserum to monoamine oxidase B (MAO-B) was used to define the distribution of this metabolic enzyme in the adult rat brain immunocytochemically. MAO-B is specifically located in two major central nervous system cell classes, astrocytes and serotonin-containing neurons. Double-immunofluorescence experiments using antisera to glial fibrillary acidic protein and MAO-B showed that both protoplasmic and fibrillary astrocytes throughout the brain contain MAO-B, whereas oligodendrocytes do not contain the enzyme. Areas lacking a blood-brain barrier, such as the specialized circumventricular organs, also contain MAO-B-positive cells. A double-immunofluorescence experiment using antisera to serotonin and MAO-B enabled the positive identification of neurons containing both molecules. The catecholamine-containing neurons of the brain did not contain detectable amounts of MAO-B. The specific distribution of MAO-B in the adult central nervous system indicates that the role of MAO-B in monoamine metabolism may be more specifically defined than previously believed.     

Comparative effects of thyroid hormone analogs on the activities of brain and liver mitochondria and nuclei in thyroidectomized rats

Several thyroid hormone analogs have been tested for thyromimetic activity on rat brain and liver subcellular organelles. The compounds were administered immediately after thyroidectomy to 90 g male S-D rats for 10 days, by daily s.c. injection. In cerebral cortex and liver we measured the activities of mitochondrial succinate cytochrome c reductase and a-GPD, and nuclear RNA polymerase I. Brain mitochondrial enzymes were unchanged in thyroidectomized (Tx) and in Tx-treated rats, whereas the activities of these enzymes in liver mitochondria were partially restored by the treatments. RNA polymerase I activity in brain and liver dropped significantly 10 days after thyroidectomy and daily injection of thyroid hormones or analogs maintained the nuclear activity at a normal level. Correlation between the structure of thyroid hormone analogs and their subcellular effects is in good agreement with previous binding and in vivo studies. Enzyme activities stimulated by T₃ were lowered by replacing the T₃ side-chain by an acetic acid group or by substituting the bridged oxygen atom by atom by CO. In contrast, the activity was enhanced by substituting iodine with a 3' isopropyl group. Although less active than iodine, the 3,5-dimethyl substituents may be introduced without a complete loss of nuclear activity.     

大鼠脑单胺氧化酶对甲状腺激素反应的实验观察

目的 探讨甲状腺激素对甲状腺功能低下（甲低）鼠脑单胺氧化酶（MAO）活性的影响和保护作用。方法 用1%NaClO4诱发大鼠甲状腺功能低下,实验组大鼠分别注射T3、T4,观察脑MAO活性变化,同时观察生后不同时期甲低仔鼠MAO活性。结果 甲低大鼠脑MAO活性增强,20日龄仔鼠MAO活性增加的百分比高于成熟鼠。注射T4脑MAO活性恢复,脑MAO活性与血清T4呈负相关。结论 大鼠甲低时脑MAO活性变化反映了MAO在维持大脑发育和功能上起重要作用,T4对脑MAO活性有保持作用。     

Differential effects of L-thyroxine on cardiac and hepatic monoamine oxidase activity toward benzylamine and serotonin.

Male and female rats of 2 age groups were given subcutaneous injections of L-thyroxine (500 mug/kg) at 12 h intervals for a period of 10 days. The activity of monoamine oxidase (MAO) in normal and thyrotoxic rats was studied with two substrates: benzylamine and serotonin. The results showed that a thyroxine effect on cardiac and liver MAO activity is dependent on the substrate used in the assay. Kinetic studies of cardiac and liver MAO after thyroxine-treatment showed an unaltered Km for benzylamine but a change in Km for serotonin. Both findings may indicate a discriminative action of thyroid hormones on different forms of MAO. The possible presence of a soluble activator and inhibitor for MAO was investigated.     

不同碘营养状态对大鼠肝组织Ⅰ型脱碘酶和脑组织Ⅱ型脱碘酶活性的影响

不同碘营养状态Wistar大鼠分别于饲养3、6、12个月时处死,放射免疫法测定血清甲状腺激素水平.放射性核素分析法检测大鼠脑组织Ⅱ型脱碘酶(DⅡ)和肝组织Ⅰ型脱碘酶(DⅠ)的活性.结果 显示在早期碘缺乏状态下,动物出现以低T4为主要表现的甲减,DⅠ和DⅡ活性代偿性上调.高碘在转录后直接抑制DⅠ的活性,使血清TT3和FT3下降,而DⅡ的活性增高,可能是由于T4和T3对酶的底物诱导失活所致.     

Effect of phase shift on monoamine oxidase activity in different regions of the rat brain as a function of age

The effect of reversed light-dark cycle on the monoamine oxidase activity of different regions of the rat brain in various age groups was studied. Twenty-one-day-old rats showed an irregular pattern of shift in the appearance of the peak activity. In the case of 3-, 6-, and 12-month-old rats, all the regions of the brain became synchronized to the altered environmental condition, and the peak MAO activity was shifted by 180 degrees. In the cerebral cortex of 24-month-old rats the peak was shifted by only 60 degrees, whereas a 120 degrees shift was observed for all the other regions. The present study suggests that the synchronizing effect of the light-dark cycle is age dependent.     

Effect of experimental thyrotoxicosis on oxidative phosphorylation in rat liver, kidney and brain mitochondria

Coupled phosphorylation was examined in liver, kidney and brain mitochondria from rats made thyrotoxic by injecting repeated doses of triiodothyronine. Liver and kidney mitochondria were maximally affected under these conditions, whereas effects on brain mitochondria were marginal. State-3 respiration rates with succinate decreased considerably in all the tissues, whereas glutamate oxidation increased in liver, but decreased in kidney and brain mitochondria. Oxidation rates of beta-hydroxybutyrate decreased in kidney and brain mitochondria but were not significantly affected in liver mitochondria. Oxidation of ascorbate + TMPD was not affected. State-4 respiration rates increased in general with all the substrates resulting in lowering of the RCI. The ADP/O ratios decreased in a site-specific manner in the mitochondria from the three tissues. The content of cytochrome b decreased in all three tissues, whereas the content of cytochrome c + c1 increased in liver and kidney but decreased in brain. The content of cytochrome a, however, was not significantly affected. Basal and Mg2+-stimulated ATPase activities increased in mitochondria of liver and kidney but not in those of brain; total ATPase activities, however, were not altered. The results imply that excessive levels of thyroid hormones over normal in the serum can lead to impairment of mitochondrial energy metabolism in a tissue-specific manner.     

Differential activities of putative subsarcolemmal and interfibrillar mitochondria from cardiac muscle

Mitochondria were isolated from rat hearts by Polytron treatment in a low ionic strength medium. The mitochondria that remained in the tissue after Polytron treatment were then isolated by Nagarse treatment in a high ionic strength medium. Properties of these two preparations were compared. The state 3 rate of respiration was not significantly different between Polytron and Nagarse prepared mitochondria if the assay was carried out in a low ionic strength sucrose medium. On the other hand, when the assay was carried out in a high ionic strength KCl medium, a significant difference in state 3 rate was observed between these two preparations of mitochondria, mainly due to the decreased state 3 rate of Polytron mitochondria. The total cytochrome c and a + a₃ content and enzyme activities were similar in Polytron and Nagarse mitochondria. Although no release of cytochrome c was observed in low ionic strength assay medium, about 25% of the total cytochrome c was released from Polytron mitochondria in the high ionic strength assay medium. It was, therefore, concluded that the difference in state 3 rate of respiration in KCl assay medium is probably due to the loss of cytochrome c into the medium and may not represent any physiological difference between them.     

Effects of chronic manganese treatment on rat brain regional sodium-potassium-activated and magnesium-activated adenosine triphosphatase activities during development

The effects of chronic manganese (Mn) treatments (1 and 10 mg MnCl₂.4H₂O per ml of drinking water) from conception onwards on brain regional development of sodium-potassium-activated and magnesium-activated adenosine triphosphatascs (Na-K-ATPase and Mg-ATPase) were studied. The activities of these enzymes were determined in hypothalamus, cerebellum, pons and medulla, striatum, midbrain and cerebral cortex (which included the hippocampus) of Mn-treated and age-matched control rats at 5 postnatal ages. Both ATPase activities doubled in most brain regions between day 5 and day 20 postnatal. In pons and medulla, striatum, midbrain, and cerebral cortex, adult levels of both enzymatic activities were attained by day 20 postnatal. Na-K-ATPase activities transiently increased in the midbrain (+25%) at day 12 with the lower Mn dose and in the cerebral cortex (+31%) at day 20 with the higher Mn dose. With the higher Mn dose only, Mg-ATPase activities were increased in the hypothalamus (+20%) at day 12 and in the pons and medulla (+22%) at day 20 but were decreased in the pons and medulla (–20%) at day 60. Thus, only transient changes in enzymatic activities were observed despite dose-dependent increases in the brain levels of Mn resulting from the Mn treatment. A hypothesis regarding the role of early but transient changes in brain metabolism in the pathogenesis of the initial psychotic symptoms in Mn intoxication was proposed and discussed in relation to several other observations of a similar nature.     

cDNA cloning of human liver monoamine oxidase A and B: molecular basis of differences in enzymatic properties.

The monoamine oxidases play a vital role in the metabolism of biogenic amines in the central nervous system and in peripheral tissues. Using oligonucleotide probes derived from three sequenced peptide fragments, we have isolated cDNA clones that encode the A and B forms of monoamine oxidase and have determined the nucleotide sequences of these cDNAs. Comparison of the deduced amino acid sequences shows that the A and B forms have subunit molecular weights of 59,700 and 58,800, respectively, and have 70% sequence identity. Both sequences contain the pentapeptide Ser-Gly-Gly-Cys-Tyr, in which the obligatory cofactor FAD is covalently bound to cysteine. Based on differences in primary amino acid sequences and RNA gel blot analysis of mRNAs, the A and B forms of monoamine oxidase appear to be derived from separate genes.     

Effect of dehydroepiandrosterone (DHEA) on monoamine oxidase activity,lipid peroxidation and lipofuscin accumulation in aging rat brain regions

Dehydroepiandrosterone (DHEA), one of the major steroid hormones, and its ester have recently received attention with regard to aging and age-related diseases like Alzheimer and others. DHEA is synthesized de novo in the brain and its substantial fall with age has been shown to be associated with neuronal vulnerability to neurotoxicity processes. Thus, DHEA is considered to be a neuroactive pharmacological substance with potential antiaging properties. A prominent feature that accompanies aging is an increase in monoamine oxidase (MAO). Increased MAO activity with correlated increase in lipid peroxidation in the aging rat brain supports the hypothesis that catecholamine oxidation is an important source of oxidative stress. The progressive accumulation of lipofuscin in neuronal cells is one of the most characteristic age related changes, an increase in body weight was also observed at 24 months. The objective of this study was to observe the changes in monoamine oxidase activity, lipid peroxidation levels and lipofuscin accumulation occurring in aging rat brain regions, and to see whether these changes are restored to normal levels after exogenous administration of DHEA (30 mg/kg/day for 1 month). The results obtained in the present work revealed that normal aging was associated with significant increases in the activity of monoamine oxidase, lipid peroxidation levels and lipofuscin accumulation in brain regions of 4, 14 and 24 months age group male rats. The present study showed that DHEA treatment significantly decreased monoamine oxidase activity, lipid peroxidation and lipofuscin accumulation in brain regions of aging rats, the increased body weight at 24 months also decreased more than the age matched controls. It can therefore be suggested that DHEA's beneficial effects seemed to arise from its antioxidant, antiobesity, antilipofuscin, antilipidperoxidative and thereby anti-aging actions. The results of this study will be useful for pharmacological modification of the aging process and development of new drugs for age related disorders.     

Differential effects of chronic ethanol administration and withdrawal on gamma-aminobutyric acid type A and NMDA receptor subunit proteins in male and female rat brain

BACKGROUND: Investigations have shown that chronic ethanol exposure results in selective alterations in levels of gamma-aminobutyric acid (GABA)A and NMDA receptor subunits. We previously reported significant sex differences in these chronic ethanol-induced adaptations. Because we have more recently found important sex differences in timing for the development of and recovery from ethanol dependence, we wanted to ascertain whether there were associations between overt expression of withdrawal and neuroadaptations at the level of GABAA and NMDA receptors. METHODS: Western blot analysis was used to assay protein levels for several GABAA and NMDA receptor subunits in rat cerebral cortex and hippocampus by using subunit-selective antibodies. Rats were fed 6% ethanol in a liquid diet with pair-fed controls. Feeding, harvesting of tissue, and Western blot experiments were all conducted while maintaining the paired design. Tissue was harvested after 3 days of ethanol exposure, 9 days of ethanol exposure, or 3 days of ethanol withdrawal after 14 days of liquid diet administration. RESULTS: We again found sex-, subunit-, and brain region-selective effects of ethanol administration and withdrawal for GABAA and NMDA receptors. There was a strong association between increased GABAA receptor alpha4 subunit levels and previously determined withdrawal-induced changes in seizure susceptibility, highlighted by the sex differences in ethanol exposure length required to cause withdrawal signs. In addition, results obtained after 9 days of ethanol administration were in general agreement with previous findings after 14 days of ethanol administration. CONCLUSIONS: These data further support the suggestion that alterations in subunit assembly of GABAA and NMDA receptors may have some mechanistic role in neuroadaptations underlying ethanol dependence and withdrawal. Furthermore, significant sex differences in these adaptations suggest that multiple types of adaptations may be elicited, depending on innate differences in the actions/effects of ethanol.     

Effects of alloxan diabetes and insulin on morphology and certain functional activities of mitochondria of the rat liver and heart

Summary The authors studied the ultrastructural appearance and metabolic behaviour of mitochondria in the liver and heart of rats suffering from alloxan diabetes. Liver mitochondria did not show significant morphological and biochemical changes compared to normal, whereas heart mitochondria were decreased in number, their structure was altered and the phosphorylating activity was obviously impaired. Insulin treatment significantly improved the P/O ratio although, as far as the myocardium was concerned, it could not normalize it. The differences in behaviour of liver and heart mitochondria related to the changes of lipid and carbohydrate metabolism and to the disordered ion balance occurring in this experimental endocrine disease, are discussed. This work was in part supported by a grant from theConsiglio Nazionale delle Ricerche (Rome).     

异甘草酸镁与复方甘草酸单胺治疗药物性肝损伤患者疗效比较研究

目的 分析比较异甘草酸镁与复方甘草酸单胺治疗药物性肝损伤(DILI)患者的疗效。方法 2018年1月～2020年1月我院收治的DILI患者102例,随机分为观察组51例和对照组51例,分别给予异甘草酸镁或复方甘草酸单胺静脉滴注治疗14～28 d。采用放射免疫法检测层粘连蛋白(LN)、透明质酸酶(HA)、III型前胶原(PC-III)和IV型胶原(IV-Col)水平,采用ELISA法检测超氧化物歧化酶(SOD)、一氧化氮(NO)、白介素-6(IL-6)和肿瘤坏死因子-α(TNF-α)。结果 治疗后,观察组血清ALT和AST水平分别为(42.7±12.5)U/L和(38.2±9.4)U/L,显著低于对照组【分别为(64.5±21.9)U/L和(55.6±15.2)U/L,P<0.05】;血清HA、PC-III和IV-Col水平分别为(138.2±21.5)mg/L、(85.6±17.4)μg/L和(141.5±16.4)μg/L,显著低于对照组【分别为(182.1±23.9)mg/L、(123.8±19.4)μg/L和(175.4±18.7)μg/L,P<0.05】;血清SOD...     

Studies on age related changes in cytochrome P-450, cytochrome b-5 and mixed function oxidase activity in mouse liver microsomes,in relation to their phospholipid composition

Liver microsomes were isolated from male mice of various defined ages, and their ability to metabolise ethylmorphine, p-nitroanisole, p-aminobenzoic acid and aniline was assessed as was their content of cytochrome P-450, cytochrome b-5 and protein, and their lipid composition.The rising capacity of the microsomes to metabolise these substrates in the first half of the lifespan was associated with a rise in the cytochrome P-450 and cytochrome b-5 content as well as an increase in the ratio of phosphatidylcholine to both phosphatidylethanolamine and sphingomyelin and, in early adult life, decreasing saturation of phospholipid fatty acids. The lipid changes would be expected to increase microsomal membrane fluidity.Declining mixed function oxidase activity in later life paralleled a decline in the ratio of phosphatidylcholine to phosphatidylethanolamine and sphingomyelin, and progressively reduced saturation of phospholipid fatty acids. Cytochrome content showed only a slight irregular decline with advancing age until the oldest animals were investigated, in which cytochrome b-5 was considerably reduced. Unfortunately, cytochrome P-450 was not measured in the oldest available group.Inducing the mixed function oxidase system with daily phenobarbitone injections for 4 days substantially increased enzyme activity in animals up to the middle of the age range tested. Older animals showed progressively reduced induction and none at all was seen in the oldest group. In contrast with the situation in non-induced mice, these changes were more closely associated with changes in cytochrome P-450 content than with alterations of lipid composition.     

Effect of hypo- and hyperthyroidism on regional monoamine metabolism in the adult rat brain

The effects of hypo- and hyperthyroidism were investigated on brain levels and accumulation rates (after pargyline) of 5-hydroxytryptamine (5-HT), norepinephrine (NE) and dopamine (DA) in discrete brain regions of the adult rat. Whereas NE remained unchanged in all brain areas except in the cerebellum, alterations in brain 5-HT and DA suggest that the behavioral abnormalities associated with thyroid dysfunction in adulthood may be related to neurotransmission disturbances. In hypothyroidism, 5-HT content decreased in cerebral hemispheres and mesodiencephalon and DA content decreased in these regions and also in cerebellum and pons-medulla. Concomitantly, accumulation rate of 5-HT was lower in pons-medulla whereas that of DA was increased in cerebral hemispheres and mesodiencephalon. In hyperthyroidism, 5-HT levels increased in cerebral hemispheres alone. Accumulation rate of 5-HT increased in pons-medulla and that of DA increased in mesodiencephalon. These data indicate that the influence of thyroid hormones on monoamines (MAs) in the adult brain varies with the neurotransmitter and the brain area considered.