Monoamine oxidase activity in Helix pomatia.

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.     

Methionine enkephalin inhibits the bursting activity of the Br-type neuron inHelix pomatia L.

Summary The present study demonstrates that methionine enkephalin can inhibit the normal bursting activity pattern of the RPal or Br-type neuron and this inhibition can be blocked by prior treatment with naloxone, the selective opiate antagonist. The study demonstrates indirectly the presence of opiate-like receptors inHelix pomatia.Acknowledgments. This work was funded by grant RR 08171 Division of Research Resources and NIMH, and a National Academy of Sciences Travel grant and a Hungarian Academy of Sciences research support award to G.B.S. We also gratefully acknowledge thoughtful comments from Dr J. Salanki.     

Monoamine oxidase activity in tissues of spontaneously hypertensive rats

Summary Monoamine oxidase (MAO) activity was assayed both in central and peripheral blood vessels of spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar Kyoto rats (WKR). The activity of MAO in the brain and peripheral vasculature was essentially the same in both SHR and WKR. It can therefore be concluded that central and peripheral vascular MAO activity is not altered in the genetically hypertensive animals.     

Naloxone selectively blocks dopamine response of Br-type neuron inHelix pomatia L.

Summary The present study demonstrates that the potent opiate antagonist, naloxone can selectively block the DA induced inhibition of the bursting activity pattern of the RPal or Br-type neuron. The dopamine inhibitory affect can also be blocked by haloperidol, a established dopamine receptor blocker.This work partially supported by a grant from the National Academy of Sciences and the Hungarian Academy of Sciences awarded to G.B.S. We also gratefully acknowledge thoughtful comments from Dr J. Salanki.     

Monoamine oxidase activity in membrane structures of rat liver cell

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Monoamine oxidase inhibitors and histamine metabolism

In rat, histamine metabolism is altered by some nonspecific inhibitors of monoamine oxidase (MAO) such as iproniazid, and, to a lesser extent, tranylcypromine. Type A MAO inhibitors, such as clorgyline and MD780515, do not seem to interfere with the metabolism of histamine. Deprenyl, a type B MAO inhibitor, shows some inhibition which is, however, much lower than that observed with iproniazid. The strong effect of iproniazid is probably due to its DAO inhibiting properties.     

Monoamine oxidase activities in human brain microvessels

Summary Microvessels can be easily isolated from human brain samples obtained at autopsy. Human frontal cortex MAO type A and B activities are similar in microvessel and microvessel-free preparations. In microvessels, enzyme activities and the ratio of MAO type A to type B vary among the areas studied and could selectively regulate the passage of certain amines through the blood vessel wall.Acknowledgment. The technical assistance of N. Gentile and the financial support by NIMH grant MH31156 is gratefully acknowledged.     

Organization of the multifunctional neural network regulating visceral organs inHelix pomatia L (Mollusca,Gastropoda)

Summary InHelix pomatia L. the overlapping neuronal network was found to regulate the visceral functions (e.g. cardiorenal, respiratory and genital functions). The neural network is organized around the multifunctional interneurons, which take part in forming both afferent and efferent pathways. The interneurons are sensitive to a wide range of neurotransmitters or transmitter candidates including low molecular weight substances (ACh, 5HT, DA, octopamine, glutamate) and several oligopeptides. In this system both selection of information and modification of membrane properties (for example habituation) are carried out by a combination of simultaneously liberated active agents.     

Monoamine oxidase activity in rat erythrocytes: Evidence for its localization in reticulocyte mitochondria

Summary During growth of young rats, monoamine oxidase activity in erythrocyte membrane preparations decreases more rapidly than reticulocyte concentrations in the respective blood samples. Since reticulocytes lose their mitochondria prior to the substantia reticulo-filamentosa, the non-linear correlation between monoamine oxidase activity and reticulocyte counts indicates that erythrocyte monoamine oxidase is located in reticulocyte mitochondria.This work was supported by a grant from the Deutsche Forschungsgemeinschaft.     

Monoamine oxidase activity in single nerve cell bodies from substantia nigra of rat and man

Summary In single nerve cell bodies isolated from the substantia nigra of man and rat the active forms of MAO A and MAO B were found by the use of the microdiver technique and specific inhibitors.     

Monoamine oxidase activity in single nerve cell bodies from substantia nigra of rat and man

In single nerve cell bodies isolated from the substantia nigra of man and rat the active forms of MAO A and MAO B were found by the use of the microdiver technique and specific inhibitors.     

Monoamine oxidase inhibition by d-amphetamine in ganglia and nerve endings

Summary The inhibition of monoamine oxidase (MAO) activity by d-amphetamine was measured in homogenates of cat superior cervical ganglion and nictitating membrane, using tyramine (TM) and noradrenaline (NA) as substrates. In both tissues, d-amphetamine was shown to be a competitive inhibitor of the oxidation of TM. The Ki for d-amphetamine, as a MAO inhibitor, was lower in the ganglia than in the peripheral nerve endings.Supported by a Contract from the National Research Council of Argentina (CONICET) (Res. 67/79).     

Monoamine oxidase activity of the brain of Locusta migratoria in normal conditions and after intoxication by two insecticides: chlordimeform and dieldrin]

Our investigations have shown up an MAO activity in locust brain, by the use of a radio-isotopic method, as much at larval as at adult stage. This MAO activity is in a sample of 34,3 dpm/mg of brain tissue (wet weight). Investigations have also been undertaken on effects of dieldrin and chlordimeform poisoning on this MAO activity. Even at sublethal dosages, chlordimeform causes a significant inhibition of MAO activity in vivo. This finding is in accordance with Beeman and Matsumura's work in vitro. Moreover, acute poisoning by dieldrin produces more than 60% of inhibition of MAO, 3 hours after administration of 115 microng of this insecticide by injection in the hoemocelian cavity.     

Monoamine oxidase activity of the hypothalamus and pituitary: alterations after pinealectomy, changes in photoperiod, or additions of melatonin in vitro.

Rat pituitary MAO activity was reduced by constant darkness and by additions of melatonin in vitro and was increased by constant light and by pinealectomy. Hypothalamic MAO activity followed the same pattern but was less dramatically affected. The data suggest that MAO may be a target enzyme for melatonin.     

Xanthine oxidase activity in the brain

Résumé La xanthine oxydase a été déterminée dans la partie surnageante des homogenéisats centrifugés de cerveau et cervelle de divers animaux (souris, rat, cobaye, lapin, vache) par spectrophotométrie de l'acide urique produit après incubation de 2 h avec l'hypoxanthine. Le cerveau du rat et du cobaye sont les plus riches en cette enzyme, mais la cervelle de la souris est dépourvue d'activité. La xanthine déhydrase s'est montrée plus active après incubation avec le NAD.