Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Platelet monoamine oxidase (MAO) activity was measured in patients with nonaffective schizophrenic disorders (i.e., without prominent symptoms of depressions or manias), and in patients with schizophrenia-related depressions. MAO activity was significantly lower than control values in a subgroup of 16 patients with nonaffective schizophrenic disorders (most of whom were paranoid) characterized by the presence of auditory hallucinations and delusions. Platelet MAO activity was not reduced in 16 other nonaffective schizophrenic patients without auditory hallucinations. Platelet MAO activity was significantly higher than control values in a group of 8 depressed patients with schizophrenia-related depressions characterized by the presence of chronic asocial, eccentric, or bizarre behavior. These findings of differences in platelet MAO activity in clinically defined subgroups of nonaffective schizophrenic disorders and the schizophrenia-related depressive disorders may help to account for some of the discrepancies in findings among the various studies of platelet MAO activity in schizophrenic and affective disorders.
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PMID:Differences in platelet monoamine oxidase activity in subgroups of schizophrenic and depressive disorders. 73 52

Platelet monoamine oxidase (MAO) activity was investigated in a series of 60 patients with chronic schizophrenic illnesses free from neuroleptic medication, and 70 normal controls. No significant differences in platelet MAO activity or in substrate preference were detected between patients and controls, using tryptamine and tyramine as substrates. Platelet MAO activity did not distinguish patients with positive symptoms from those with negative symptoms alone and did not show any relationship with severity of disease or with a number of clinical features. These findings suggest that low platelet MAO activity cannot be regarded as a genetic marker for schizophrenia. Important determinants of platelet MAO activity yet to be discovered may have contributed to the discrepancies in recent observations of platelet MAO activity in schizophrenia.
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PMID:Platelet monamine oxidase in schizophrenia. An investigation in drug-free chronic hospitalized patients. 79 Nov 82

Both the amphetamines and MAO inhibitors share common clinical and pharmacological properties, namely, (i) to clinically induce euphoriant-stimulating type and psychotomimetic effects in certain individuals, and (ii) to increase, albeit by different mechanisms, the amount of functionally available neurotransmitter (catecholamines and indoleamines) at the receptor site. The present data now indicate that, like the amphetamines, the use of MAO inhibitors can be clinically associated with dependence-tolerance. Perhaps these clinical findings will converge with other clinical-biochemical data in helping to define the specific amine(s) responsible for not only the clinical effects of these drugs but also the etiopathogenesis of major psychiatric illnesses such as the affective disorders and schizophrenia.
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PMID:Monoamine oxidase inhibitors: potential for drug abuse. 96 35

Some 50 years ago the enzyme MAO was discovered by Hare and in the early 1930s Blaschko suggested that MAO may play an important role in the catabolism of monoamines in the central nervous system. With the discovery of iproniazid as an inhibitor of MAO and its introduction as an anti-depressant, many aspects of MAO activity and biogenic amine metabolism in experimental animals and man were examined. Although many other inhibitors of MAO were discovered and used therapeutically as anti-depressants, these drugs fell into disrepute largely because of their side-effects. Furthermore, their anti-depressant properties were questioned. After some years of relative inactivity there is now a revival of interest in the functional role of MAO in the central nervous system and drugs that inhibit or stimulate its activity "specifically". The basic reason for the upsurge of interest is that the enzyme from many tissues, including the brain of animals as well as man, has been purified and characterised. The evidence that neuronal MAO exist with different substrate and inhibitor specificities has led to the suggestion that they have physiological function and that deamination of non-methylated biogenic monoamines can take place in neurons. These findings have led to the advent of new drugs (clorgyline and depranil) with "selective" inhibition of enzyme forms. Their possible usage in the chemotherapy of depressive illness should be considered seriously. Fluctuation in peripheral organs as well as brain MAO is well documented. Recently they have been associated with changes in naturally occurring steroids. Although a decrease in platelet and brain MAO activity has been reported in a number of affect disorders (schizophrenia and bipolar depression) the results of these findings have recently been questioned (20, 141). Obviously further study in this area of research discussed is badly needed.
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PMID:Monoamine oxidase. Its inhibition. 110 Oct 49

Blood platelet monoamine oxidase (MAO) activity was evaluated in twenty-four anergic, schizophrenic outpatients during a double-blind study comparing a chlorpromazine-imipramine combination to thio-thixeneplacebo. Platelet MAO activity was determined on blood samples drawn after a two-week drug-free washout and once weekly over a four-week on-drug period. Schizophrenic patients could be classified according to their blood platelet MAO activity into either a low-MAO or a high-MAO group. In neither group of this population of schizophrenics did blood platelet MAO activity correlate with any of the primary or secondary symptoms of schizophrenia. Ten alcoholics and seven volunteer non-patients could similarly be divided into low- and high-MAO groups. Mean blood platelet MAO activity for these groups was not significantly different from the mean values of the low and high-MAO groups of the schizophrenics. These findings do not support published reports of low blood platelet activity as a genetic marker for schizophrenia. Discriminate function analysis of symptomatology ratings at baseline was used to characterize the low- and high-MAO schizophrenic patient groups. Individuals in the low-MAO group were distinguished by hyperactivity, anergia and sleep disturbance.
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PMID:Blood platelet monoamine oxidase activity in anergic schizophrenics. 123 83

We did a meta-analysis on all publications (English and other languages) concerned with platelet monoamine oxidase (MAO) in schizophrenia. Essentially, when patients were medicated with a neuroleptic, most studies found that schizophrenics had lower platelet MAO levels than controls. Administration of neuroleptic lowers MAO levels. MAO levels in drug-free schizophrenics were similar to controls. Only a minority of studies found drug-free schizophrenics had decreased platelet MAO levels.
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PMID:Platelet monoamine oxidase in schizophrenia: a meta-analysis. 135 26

1. PE is present in the brain in tiny quantities; it is heterogeneously distributed and present in synaptosomes. 2. It is synthesised from phenylalanine by L-AADC and oxidatively deaminated by MAO-B. Its turnover is remarkably fast. 3. Its concentration, particularly in the caudate nucleus, is affected by MAO inhibition (increased), lesion of the Substantia nigra (decreased), amine depletion (increased) and antipsychotic drugs (increased). 4. When iontophoresed (or injected) it amplifies the effects of DA and NA (and their agonists) but is without effect on other neurotransmitters. 5. It is suggested that it acts postsynaptically as a neuromodulator of catecholaminergic neurotransmission and that it is involved in the mechanism of action of Deprenyl; it is also suggested that it, or its principal metabolite PAA, may be involved in the aetiology of schizophrenia, depression and aggression as well as perhaps in other neuropsychiatric conditions.
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PMID:Phenylethylaminergic modulation of catecholaminergic neurotransmission. 165 28

In subtypes of schizophrenia and unipolar depression, both increased and decreased levels of platelet serotonin were found. Hyperserotonemia was usually observed in patients with psychotic features (i.e., in paranoid schizophrenia and psychotic depression). Hyposerotonemia, although less common than hyperserotonemia, was present in nonparanoid schizophrenia and nonpsychotic depression (i.e., in patients without psychotic symptoms). A sex difference in platelet monoamine oxidase activity was observed among healthy subjects, but not among schizophrenic patients. The activity of platelet monoamine oxidase in paranoid and nonparanoid schizophrenic patients did not differ from that in healthy subjects. The findings in this study suggest that biological differences between subtypes of unipolar depression or schizophrenia might depend upon the presence of psychotic symptoms.
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PMID:Platelet serotonin in subtypes of schizophrenia and unipolar depression. 175 25

We have previously reported that the activity in platelets of the important antioxidant enzyme glutathione peroxidase (GPx) is inversely correlated with computed tomographic (CT) measures of brain atrophy in a population of patients with chronic schizophrenia, suggesting that low GPx may be a vulnerability factor in those schizophrenic patients with structural brain abnormalities. The significance of this finding has now been explored in a larger clinical population by examining the relation of GPx and CT parameters to psychosocial variables and to the activity of platelet monoamine oxidase (MAO), which has also been reported to be altered in certain schizophrenic populations. In the present study, low platelet GPx and high brain atrophy were found to be associated with DSM-III diagnoses of nonparanoid schizophrenia, a high degree of chronicity, and a predominance of negative symptoms. Contrary to some literature reports, atrophy also correlated with age and length of illness among the schizophrenic patients, although the contribution of these factors was less than that of low GPx, which was itself not age dependent. The ventricle-brain ratio (VBR) and atrophy were highly correlated in a control group of affective disorder patients, but not in the schizophrenic group, where large VBRs were found predominantly in the DSM-III undifferentiated subgroup. The low-GPx/high-atrophy schizophrenic patients had normal platelet MAO levels, and MAO was significantly lower only in the paranoid subgroup, consistent with reported observations. There was no evidence for a neuroleptic-induced effect on either enzyme.
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PMID:Platelet glutathione peroxidase and monoamine oxidase activity in schizophrenics with CT scan abnormalities: relation to psychosocial variables. 196 70

Platelet MAO activity has been reported by several investigators to differentiate schizophrenia, schizophrenia related depressive disorders, alcoholism, unipolar and bipolar depression from normal controls. Evoked potentials likewise have differentiated schizophrenic and affective patients. However, the precise relationship between MAO activity, evoked potentials (EP), and psychiatric illness has not been clarified. A possible association between psychopathology and high MAO activity/EP reducing and low MAO activity/EP augmenting has been reported. Such a bidirectionality further confounds results. This study was undertaken to determine the association of psychopathological dimensions found in a group of subjects whose platelet MAO activity and evoked responses were obtained two years earlier. Utilizing the Gottschalk-Gleser verbal behavior scales of Anxiety, Depression, Social Alienation-Personal Disorganization and Cognitive Impairment a significant correlation was revealed between low platelet MAO activity and high Total Anxiety scale and Shame Anxiety subscale scores. Additionally, a significant correlation was demonstrated between reducing evoked potentials and elevated Death Anxiety, Somatic Concerns, and Total Death and Mutilation Depression subscales scores, combined and separately. Furthermore, a significant positive correlation was found between augmenting evoked potentials and Overt Hostility Outward scores. No significant correlations were demonstrated between platelet MAO activity or evoked potentials and Social Alienation-Personal Disorganization or Cognitive Impairment scores. These findings lend support to the position that biological markers may predict predispositions to anxiety and depression.
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PMID:Platelet monoamine oxidase activity and evoked response as predictors of anxiety and depression derived from the content analysis of speech. 221 39


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