Platelet mono-amine oxidase activity in the human fetus

Measurement of the platelet mono-amine oxidase (MAO) activity in the human fetus of 40 weeks gestation showed it to be equivalent to that found in the adult. The level represents a fully-developed mitochondrial MAO system in platelets and may reflect enzyme maturity in other tissues of the newborn.     

Classical conditioning modifies cytochrome oxidase activity in the auditory system

The effects of excitatory classical conditioning on cytochrome oxidase activity in the central auditory system were investigated using quantitative histochemistry. Rats in the conditioned group were trained with consistent pairings of a compound conditional stimulus (a tone and a light) with a mild footshock, to elicit conditioned suppression of drinking. Rats in the pseudorandom group were exposed to pseudorandom presentations of the same tone, light and shock stimuli without consistent pairings. Untrained rats in a naive group did not receive presentations of the experimental stimuli. The findings demonstrated that auditory fear conditioning modifies the metabolic neuronal responses of the auditory system, supporting the hypothesis that sensory neurons are responsive to behavioural stimulus properties acquired by learning. There was a clear distinction between thalamocortical and lower divisions of the auditory system based on the differences in metabolic activity evoked by classical conditioning, which lead to an overt learned behavioural response versus pseudorandom stimulus presentations, which lead to behavioural habituation. Increases in cytochrome oxidase activity indicated that tone processing is enhanced during associative conditioning at upper auditory structures (medial geniculate nucleus and secondary auditory cortices). In contrast, metabolic activation of lower auditory structures (cochlear nuclei and inferior colliculus) in response to the pseudorandom presentation of the experimental stimuli suggest that these areas may be activated during habituation to tone stimuli. Together these findings show that mapping the metabolic activity of cytochrome oxidase with quantitative histochemistry can be successfully used to map regional long-lasting effects of learning on brain systems.     

Platelet monoamine oxidase activity in subgroups of schizophrenic disorders

This article summarizes findings from a series of studies that examined platelet monoamine oxidase (MAO) activity in patients with nonaffective schizophrenic disorders and schizophrenia-related depressions. The findings indicate that mean platelet MAO activity was not different from control values in the subgroup of nonaffective schizophrenic disorders without auditory hallucinations (that is, the S-1 subgroup). However, mean platelet MAO activity was reduced in the subgroup of nonaffective schizophrenic disorders characterized by the presence of auditory hallucinations often occurring in conjunction with paranoid features (that is, the S-2 subgroup). Moreover, we found that mean platelet MAO activity was increased in schizophrenia-related depressions characterized by histories of chronic asocial, eccentric, or bizarre behavior.     

Mitochondrial fixation for the detection of cytochrome oxidase activity using microwave irradiation

We examined cell fixation with microwave irradiation (MWI) used in cytochemistry. MWI was applied to blocks of about 1 mm3 of mouse parotid glands at 500 W for about 5 sec in a fixative at 37 degrees C. The activities of endogenous peroxidase and mitochondrial cytochrome oxidase were demonstrated by using the DAB method with 3,3'-diaminobenzidine (DAB) and 0.01% H2O2. Under electron microscopy, peroxidase activity was localized in the nuclear envelope, endoplasmic reticulum and secretory granules. However, mitochondria cytochrome oxidase activity seemed to be rather weak against the MWI at 37 degrees C. Moreover, suspension of isolated hamster liver mitochondria was fixed by MWI and also demonstrated cytochrome oxidase activity by using the cytochemical methods with DAB, cytochrome c, catalase and sucrose. Such mitochondrial fractions were subjected to 6-second MWI given 10 or 18 times with an interval of 10 seconds with and without a chilled water bath. The final temperature of each fixative was kept at about 10 degrees C or rose to about 37 and 55 degrees C. When we took care to keep the temperature below 10 degrees C, the DAB reaction products accumulated in the mitochondrial intermembrane-intracristal space. No mitochondrial deposits were observed when the temperatures of the fixatives rose to 37 and 55 degrees C. These results indicated that peroxidase was very resistant to the heat with MWI fixation. Cytochrome oxidase is sensitive to the heat with MWI, so, a chilled water bath had to be used.     

Further characterization of NADPH oxidase activity of human polymorphonuclear leukocytes

Mn2+ was shown to catalyze a nonenzymatic oxidation of NADPH in the presence of superoxide anion by means of an isotopic assay for measurement of the oxidation of NADPH to NADP+. Human polymorphonuclear leukocyte granule NADPH oxidase activity was evaluated in the absence of Mn2+ and was found to be higher in granules from phagocytizing cells than in granules from resting cells. The drug phorbol myristate acetate, which affects the oxidative metabolism of the neutrophil like phagocytosis, was found to activate granule NADPH oxidase activity. Superoxide dismutase was shown to inhibit NADPH oxidase activity both in the presence and absence of added Mn2+. The NADPH oxidase reaction in the absence of Mn2+ was optimal at pH 5.5, and was more linear with increasing time and protein concentration than in the presence of Mn2+. No activity was measurable in granules isolated from resting cells until the level of NADPH added was above 0.25 mM. Activity was present in granules isolated from cells challenged with opsonized zymosan, even at 0.05 mM NADPH, and was higher than the activity found in granule fractions from resting cells at all levels of NADPH tested. The addition of as little as 0.1 muM NADH to the reaction mixture was found to inhibit granular NADPH oxidase activity, indicating a possible regulatory role for NADH. These results suggest that NADPH oxidase may be the enzyme that initiates the metabolic events accompanying phagocytosis.     

Beta-ethoxyacrolein contamination increases malondialdehyde inhibition of milk xanthine oxidase activity

beta-Ethoxyacrolein (BEA), a side product that forms during the preparation of malondialdehyde (MDA) by acidic hydrolysis of tetraethoxypropane (TEP), has been found to be an inhibitor of milk xanthine oxidase (XO) several times more potent than pure MDA (NaMDA). The incubation of XO with 10 microM BEA abolished 50% of the enzyme activity within 1 min; the inhibited enzyme was totally regenerated by dialysis and filtration through Sephadex. The BEA inhibition mode of the enzyme was mixed-type with the apparent inhibition constants (Ki) of 2.4 x 10(-6) M. An HPLC method for quantitation of BEA in the crude commonly used MDA preparation was set up.     

In situ detection of diamine oxidase activity using enhanced chemiluminescence

This study examines the early effects of 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone on cytosolic free calcium concentration ([Ca2+]i in primary cultures of fetal rat hypothalamic neurons. Microspectrofluorimetry of fluorescent Ca2+(-)sensitive indicator Fura-2 was used to quantify these changes. Allopregnanolone (1 pM to 100 nM) increased [Ca2+]i within 2-3 sec, in a dose dependent manner, with an EC50 of 10 +/- 4 nM. The stimulatory effect of allopregnanolone was attributable principally to a Ca2+ influx, as shown by the strong inhibition of external Ca2+ removal or by the calcium channel blocker nifedipine. The effect was stereospecific because the allopregnanolone isomer 3 beta-hydroxy-5 alpha-pregnan-20-one had no effect on [Ca2+]i. Among two other steroids examined, progesterone had no effect on [Ca2+]i, but 17 beta-estradiol evoked a rise in [Ca2+]i, although to a lesser extent than allopregnanolone. The allopregnanolone-induced [Ca2+]i rise was inhibited by picrotoxin and bicuculline but was unaffected by tetrodotoxin or by pretreatment of neurons with pertussis toxin. These results are consistent with a membrane site of action for allopregnanolone associated with GABAA receptors, leading to rapid changes in [Ca2+]i in fetal rat hypothalamic neurons.     

Effect of neurocatin on the activity of monoamine oxidase B in rat brain synaptosomes

When the phenotype of neurons in pre- and paravertebral sympathetic ganglia are compared, there are marked differences in NGF dependence, neuropeptide content, connectivity and electrophysiological properties. The trophic interactions that induce these differences are currently poorly understood. One explanation is that prevertebral neurons receive a second neurotrophic signal, other than NGF, from their target of innervation. If this is the case, neurons in the prevertebral ganglia should express another neurotrophin receptor, in addition to the NGF receptor (trkA). To test this prediction, the level of expression of three neurotrophin receptors, trkA, trkB and trkC, were examined in one paravertebral sympathetic ganglia, the SCG, and two prevertebral ganglia, the celiac and superior mesenteric ganglia. It was found that mRNA encoding the full-length form of the trkB receptor was barely expressed in the SCG. Significantly higher levels of full-length trkB mRNA expression were found in the prevertebral ganglia. Ligands of the trkB receptor may, therefore, contribute to the differentiation and/or survival of some prevertebral sympathetic neurons.     

Lipid peroxidation and changes in cytochrome c oxidase and xanthine oxidase activity in organophosphorus anticholinesterase induced myopathy

The data gained from clinical studies in the past years have indicated that the thrombolytic therapy (TL) has favourable effect on patients with acute myocardial infarction (AMI). It is aimed at reperfusion in the ischaemic area, a decrease in the extent of infarction site and a decrease in mortality. TL administered within the initial hours after the onset of AMI leads to better results than when administered after several hours. Currently, TL is not limited by age. The patients who were given streptokinase (SK) or anistreplase (APSAC) prior to more than 4 days, if necessary, urokinase or alteplase (rt-PA) should be given. There are differences in the opinions as to the optimal selection of thrombolytic drugs. However, all currently used drugs lead to a significant decrease in mortality due to AMI. The preferential use of accelerated administration of rt-PA in contrast to SK is justified in younger patients with extensive AMI of the anterior wall, in whom the therapy has begun within 4 hours since its onset. The occurrence of severe bleeding indicates that TL should be halted and coagulation factors should be replaced by freshly frozen plasma or fibrinogen concentrate, if necessary, transfusion of full blood should take place. If the severe bleeding occurs shortly after the administration of SK, the persisting plasminaemia can be arranged by antifibrinolytic drugs. An improvement in TL results can be achieved by adjuvant antithrombotic therapy. At the same time, in addition to acetylsalicylic acid, the patient treated with rt-PA should be given heparin. Heparin administration is not necessary in patients treated with SK or APSAC. However, heparin is indicated in patients at risk due to systemic embolization in congestive heart disease, extensive infarction or atrial fibrillation. (Tab. 1, Ref. 28.)     

Hypoxanthine-guanine phosphoribosyltransferase mutant glioma cells: diminished monamine oxidase activity

A defective capability of cultured rat glioma cells to reutilize purine bases (hypoxanthine-guanine phosphoribosyltransferase deficiency) was associated with a reduced capacity to oxidatively deaminate serotonin and tryptamine. The mutant glioma cells were also more sensitive to the cytotoxic effects of serotonin than were normal cells     

Determination of human plasma xanthine oxidase activity by high-performance liquid chromatography

An assay for human plasma xanthine oxidase activity was developed with pterin as the substrate and the separation of product (isoxanthopterin) by high-performance liquid chromatography with a fluorescence detector. The reaction mixture consists of 60 microliters of plasma and 240 microliters of 0.2 M Tris-HCl buffer (pH 9.0) containing 113 microM pterin. With this assay, the activity of plasma xanthine oxidase could be easily determined despite its low activity. As a result, it could be demonstrated that the intravenous administration of heparin or the oral administration of ethanol did not increase plasma xanthine oxidase activity in normal subjects, and also that plasma xanthine oxidase activity was higher in patients with hepatitis C virus infection than in healthy subjects or patients with gout. In addition, a single patient with von Gierke's disease showed a marked increase in the plasma activity of this enzyme, relative to that apparent in normal subjects.     

Higher activity of an aldehyde oxidase in the auxin-overproducing superroot1 mutant of Arabidopsis thaliana

Aldehyde oxidase (AO; EC 1.2.3.1) activity was measured in seedlings of wild type or an auxin-overproducing mutant, superroot1 (sur1), of Arabidopsis thaliana. Activity staining for AO after native polyacrylamide gel electrophoresis separation of seedling extracts revealed that there were three major bands with AO activity (AO1-3) in wild-type and mutant seedlings. One of them (AO1) had a higher substrate preference for indole-3-aldehyde. This AO activity was significantly higher in sur1 mutant seedlings than in the wild type. The difference in activity was most apparent 7 d after germination, the same time required for the appearance of the remarkable sur1 phenotype, which includes epinastic cotyledons, elongated hypocotyls, and enhanced root development. Higher activity was observed in the root and hypocotyl region of the mutant seedlings. We also assayed the indole-3-acetaldehyde oxidase activity in extracts by high-performance liquid chromatography detection of indole-3-acetic acid (IAA). The activity was about 5 times higher in the extract of the sur1 seedlings, indicating that AO1 also has a substrate preference for abscisic aldehyde. Treatment of the wild-type seedlings with picloram or IAA caused no significant increase in AO1 activity. This result suggested that the higher activity of AO1 in sur1 mutant seedlings was not induced by IAA accumulation and, thus, strongly supports the possible role of AO1 in IAA biosynthesis in Arabidopsis seedlings.     

Redox potentials and quinone reductase activity of L-aspartate oxidase from Escherichia coli

l-Aspartate oxidase (EC 1.4.3.16) is a flavoprotein that catalyzes the first step in the de novobiosynthetic pathway to pyridine nucleotides both under aerobic and under anaerobic conditions. Despite the physiological importance of this biosynthesis particularly in facultative aerobic organisms, such as Escherichia coli, little is known about the electron acceptor of reduced L-aspartate oxidase in the absence of oxygen. In this report, evidence is presented which suggests that in vitro quinones can play such a role. L-Aspartate oxidase binds menadione and 2, 3-dimethoxy-5-methyl-p-benzoquinone with Kd values of 11.5 and 2.4 microM, respectively. A new L-aspartate:quinone oxidoreductase activity is described in the presence and in the absence of phospholipids, and its possible physiological relevance is discussed. Moreover, considering the striking sequence similarity between L-aspartate oxidase and the highly conserved family of succinate-fumarate oxidoreductases, the redox properties of L-aspartate oxidase were investigated in detail. A value of -216 mV was calculated for the midpoint potential of the couple FAD/FADH2 bound to the enzyme. This result perfectly explains why L-aspartate oxidase may be considered as a very particular fumarate reductase unable to use succinate as the electron donor.     

The activity of catechol-O-methyltransferase and monoamine oxidase in the uterine artery of pigs during the oestrous cycle

Activities of catechol-O-methyltransferase (COMT), total monoamine oxidase (MAO) and both types of MAO-A and MAO-B activities were examined in uterine artery on the 0-2nd, 13-14th and 16-18th days of the oestrous cycle in pigs. It was shown that activity of COMT was the lowest on the 0-2nd day, while on the 16-18th day of the oestrous cycle it increased by 52.4% (p < 0.05). Total activity of MAO was the highest at periovulatory phase, whereas on days 13-14 and 16-18 of oestrous cycle is was lower by 83.5% (p < 0.01) and 58.1% (p < 0.01) compared with its activity at periovulatory phase, and was higher on day 16-18 by 153.3% (p < 0.01) in relation to the luteal phase (13-14th day). MAO-A activity was 31.3% (p < 0.01) and MAO-B 62.5% (p < 0.05) of the total activity of MAO. Their activities were also highest at periovulatory phase, then decreased by 86.8-87.4% (p < 0.01) on 13-14th day and by 54.8-57.5% (p < 0.01) or 16-18th day of oestrous cycle. Activities of MAO-A and MAO-B were higher by 223.0-258.2% (p < 0.01) on 16-18th day in relation to the luteal phase (13-14th day). On that base we suppose that variations of COMT and MAO activities can significantly change the catecholamines content in the blood vessels of reproductive organs of pigs.     

The intramitochondrial ATP/ADP-ratio controls cytochrome c oxidase activity allosterically

BACKGROUND: This study was carried out to evaluate intraocular or systemic factors associated with the visual field damage progression in eyes with normal-tension glaucoma (NTG). PATIENTS AND METHODS: Forty-seven NTG eyes with a minimum follow-up of 5 years were enrolled into the retrospective study. A stepwise regression analysis was performed to correlate the visual field damage progression, expressed as the mean deviation (MD) change per year, with several independent clinical factors including age, history of disc hemorrhage, initial MD, mean intraocular pressure (IOP), peak IOP, diurnal fluctuation of IOP, presence of a beta zone of peripapillary atrophy, and use of Ca(2+)-channel blockers. RESULTS: Statistical analysis revealed that non-use of Ca(2+)-channel blockers (P = 0.01), peripapillary atrophy (P = 0.03) and disc hemorrhage (P = 0.04) were associated with visual loss progression. CONCLUSIONS: Risk factors unrelated to IOP were suggested to be associated with progression of visual field loss. Systemic use of Ca(2+)-channel blockers has a favorable effect on visual field prognosis in NTG eyes.