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Biomedical subjects

H Loo

Publications and source records attributed to H Loo.

At least 55 records · Page 3Linked to original sources
PubMed1986

Reduced Bmax of [3H]-imipramine binding to platelets of depressed patients free of previous medication with 5HT uptake inhibitors.

The high-affinity binding sites for [3H]-imipramine (IMI) present in human platelets are associated with the neuronal uptake system for 5HT. It was recently demonstrated that previous antidepressant therapy with drugs which inhibit 5HT uptake could down-regulate [3H]-IMI binding and that this effect could persist up to 1 month after the end of treatment. We therefore re-examined the reported differences in Bmax of [3H]-IMI binding in platelets between control and depressed untreated patients, to evaluate the residual influence of previous antidepressant medication. The saturation characteristics of [3H]-IMI binding were compared in platelets from 17 depressed patients carefully selected according to previous antidepressant therapy and washout period, who were closely matched, for age and sex, with a group of control healthy volunteers. The results reveal a significant decrease by 47% in the Bmax of [3H]-IMI binding in platelets of untreated depressed patients when compared with controls. There was no significant modification of Kd values for platelet [3H]-IMI binding between the depressed and the control groups. Our results support the view that platelet [3H]-IMI binding is a useful tool as a biological marker in depression.

Adult↗
PubMed1986

Dementia--a semantic definition.

The word 'dementia' has different meanings according to its literary, judicial or medical use. So it seems useful to recall the semantic definition in order to enable practitioners and researchers to use a common language avoiding any risk of misunderstanding. According to etymology, the word means 'loss of mind'. Its definition evolved in France from the time of Pinel, who named dementia all kinds of thought abolition, until one of the alienists of the late 19th century stated the present meaning of the word: a global, progressive and nonreversible impairment of the intellectual abilities. The DSM 3 criteria are not in perfect accordance with this definition, giving some precisions, perhaps not yet sufficient.

Dementia↗
PubMed1985

[Study of the metabolism of cerebral noradrenaline in depressed patients by the assay of plasma dihydroxyphenylethylene glycol].

Dihydroxy-phenyl-ethylene-glycol (DOPEG or DHPG), a deaminated catabolite of noradrenaline formed after presynaptic re-uptake, is a good marker of metabolic activity in noradrenergic pathways. Plasma levels of free, conjugated and total DOPEG were measured by a radioenzymatic method in 45 patients with major depression selected according to the DSM 3 criteria and in 45 matched controls. A significant decrease in man DOPEG levels was observed in all depressive patients. A dexamethasone suppression test performed in these patients showed no difference in DOPEG levels between responders and non-responders, thus failing to support the hypothesis that subjects with low noradrenergic drive escape suppression. There was no correlation between plasma DOPEG levels and urinary excretion of methoxy-hydroxy-phenylglycol (MOPEG), another marker of noradrenaline metabolic activity. Thirty-one patients were treated with a specific monoaminergic antidepressant: maprotiline or indalpine; contrary to urinary MOPEG levels, plasma DOPEG levels had no predictive value concerning the response to this category of antidepressants. The various possible reasons for the fall in DOPEG observed in depressive patients are discussed.

Adult↗
PubMed1985

Dopaminergic receptor sites in human brain: positron emission tomography.

Positron emission tomography (PET) and 11C-labeled pimozide were used to study the dopaminergic (DA) receptor sites in the human striatum by comparing the latter with the cerebellum, which lacks DA receptors. Although 11C-pimozide concentration was not different in these two brain structures up to 53 minutes after IV injection (thus implying large nonspecific binding), a significant retention of radioactivity in striatum relative to cerebellum was found in controls but not in subjects pretreated with the unlabeled competitor haloperidol. This suggests that the striatal retention seen in controls was due to specific binding of 11C-pimozide to DA receptor sites, whereas prior occupation of the receptor sites by the unlabeled competitor was achieved in pretreated subjects.

Adult↗
PubMed1984

[3H]Imipramine binding and [3H]5HT uptake in human blood platelets: changes after one week chlorimipramine treatment.

In platelets of normal volunteers taking chlorimipramine (50 mg/day) for one week, the saturable uptake of [3H]5HT was fully inhibited at day 8, but returned to control values at day 15. The Bmax of [3H]imipramine binding was decreased by 65% at day 8 and remained significantly below control values at day 15. If the present findings can be extrapolated to other antidepressants, the reported decreases in [3H]imipramine binding in depression may partly reflect residual treatment effects. It cannot be excluded that, in depression, the platelet [3H]imipramine receptor already is down-regulated maximally which would preclude a further down-regulation due to antidepressant drug therapy.

Adult↗
PubMed1984

Lithium, sodium and potassium transport in erythrocytes of manic-depressive patients.

Different Li, Na and K transport pathways were assessed in erythrocytes from manic-depressive patients. No alteration in the Li-Na countertransport, Na,K cotransport or passive permeabilities was observed in either unipolar or bipolar manic-depressive patients. In addition, acute or chronic lithium treatment did not alter the maximal velocity of either the Li-Na countertransport or the Na,K cotransport. A two-fold reduction of the ouabain-sensitive Na efflux was observed among manic-depressive patients without alteration in the affinity of the Na pump for internal Na.

Adult↗
PubMed1984

[X-ray computed tomography (CT scanner) in schizophrenia. Comparison of its results with other studies].

This paper concerns the tomodensitometric (TDM) study, with the same clinical and radiological criteria, of 78 schizophrenic patients (age: less than 60 years) from psychiatric hospitals in Madrid and from Sainte-Anne hospital (Paris). The length of evolution and the severity of disturbances seemed to be the most important causal elements of cerebral atrophy. Some TDM peculiarities appeared correlated with some clinical forms (paranoid or hebephrenic). The review of previous works illustrates the importance of some etiological conditions for the production of cerebral atrophy: age, length of evolution and, more particularly, the severity of the disease. The confrontation of the anatomo-pathological and pneumoencephalographic studies with the TDM results suggests that, if the TDM is a good indicator of ventricular dilatation, appreciation of the widening of the cerebral sulci remains difficult.

Adult↗
PubMed1984

[Decrease in transcortin binding activity in depression].

In a preliminary study, Cortico-Binding Globuline (CBG) has been determined in 10 depressed major inpatients (DSM3) and compared with healthy volunteers. A clear cut fall of binding activity of transcortin is reported in depressed patients associated with an increase of total and free plasmatic cortisol.

Adult↗
PubMed1983

[3H]spiroperidol binding on lymphocytes: changes in two different groups of schizophrenic patients and effect of neuroleptic treatment.

[3H]spiroperidol binding to lymphocytes was measured in untreated paranoid or disorganized and treated paranoid schizophrenic patients. An increase in the Bmax was detected in untreated paranoid patients but a decrease was found in the disorganized patients. No difference was detected in the KD value. Neuroleptic treatment produced a decrease in the Bmax without affecting the KD value. Such results did not comply with the down regulation but might be explained by a change in membrane viscosity as [3H]spiroperidol binding sites on lymphocytes were coupled to phospholipid methylation.

Adult↗
PubMed1983

3H-Rauwolscine binding in platelets from depressed patients and healthy volunteers.

3H-Rauwolscine binds specifically and with high affinity to alpha 2-adrenoceptors in human platelets. In a study comparing the binding of 3H-rauwolscine in platelets obtained from 26 control volunteers with 19 hospitalised, untreated, severely depressed patients, the mean maximal binding (Bmax) and mean dissociation constant (Kd) of 3H-rauwolscine binding were found to be identical in both groups. After 7-12 days, treatment with different tricyclic antidepressant drugs there was a significant improvement in the depressive symptoms but no change in the 3H-rauwolscine binding. After an average of 23 days treatment with tricyclic antidepressants, and when the Hamilton Depression Rating Scores had returned to normal, the Kd and Bmax of 3H-rauwolscine binding were still unchanged.

Adjustment Disorders↗
PubMed1982

[Biochemistry of schizophrenia and mechanism of action of neuroleptics].

Among the biochemical theories proposed for schizophrenia the best-founded appears to be the dopaminergic theory. Dopaminergic agonists exacerbate schizophrenic symptoms. Neuroleptics, which are the most effective drugs in schizophrenia, are dopaminergic-blocking agents. Other biochemical disorders have been demonstrated in some cases of schizophrenia but results are not always consonant. The presence of abnormal compounds, i.e. methylated derivatives or phenylethylamine, has often been mentioned. Several disorders of enzymes have also been reported, such as a defect in beta-dopamine hydroxylase or an abnormal activity of the MAO which metabolizes the indolamines and catecholamines. Disorders of the metabolism of noradrenaline and serotonin have also been suggested, mainly on experimental evidence. Other compounds have been incriminated, such as endorphins, gamma-aminobutyric acid, lysine-8 vasopressin or prostaglandins. The action of neuroleptics can be ascribed to dopaminergic respector blockade, as a safe approximation. However, the demonstration of several dopaminergic pathways and of several types of receptors makes the understanding of their mode of action all the more difficult that they interplay with many other neurotransmittors.

Antipsychotic Agents↗
PubMed1982

[3H-Imipramine binding to human platelets. A peripheral index in depressive syndromes (author's transl)].

3H-imipramine shows specific, high-affinity binding to human platelet sites. The characteristics of these specific binding sites are very similar to those previously described in the rat brain. The inhibitory effects of 11 tricyclic antidepressants on 3H-imipramine binding to human platelets were investigated. There was a significant correlation between the inhibition observed and the average therapeutic doses of antidepressants, which suggests that the binding sites may be involved in the mode of action of these drugs. The number of binding sites (Bmax) for 3H-imipramine was compared in 39 controls and in 37 hospital patients with untreated severe depressive syndrome and was found to be significantly smaller in depressed patients, without any modification of the affinity constant Kd. The significance of these findings and their changes under treatment are discussed.

Adult↗