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Biomedical subjects

A Halaris

Publications and source records attributed to A Halaris.

At least 37 records · Page 2Linked to original sources
PubMed1993

Hyperdopaminergia in schizophreniform psychosis: a chronobiological study.

Circadian rhythm abnormalities have been described in various psychiatric disorders, but they have not received much attention in studies of schizophrenia and schizophreniform psychosis. The present study used the cosine model to determine the circadian patterns of amino acids, dopamine, and prolactin concentrations, which were analyzed over a 24-hour period in serum of healthy subjects, drug-free schizophrenic patients, and neuroleptic-treated schizophrenic patients. The mesor (the daily mean) of phenylalanine was lower in drug-free schizophrenic women than in healthy women. The mesors of the ratio of phenylalanine or tyrosine to competing amino acids were similar in healthy subjects and patients. The ratio of phenylalanine/competing amino acids showed a phase advance (i.e., earlier onset of the time of highest concentration) in drug-free patients compared with healthy subjects. Schizophrenic patients displayed a higher dopamine mesor than healthy subjects. Female drug-free schizophrenic patients had lower prolactin mesors and lower amplitudes (i.e., half of the total predictable change in rhythm) than healthy women. Compared with healthy subjects, schizophrenic patients showed a phase advance of circadian prolactin concentrations. Neuroleptics raised the prolactin mesor and amplitudes but did not elicit any phase change in amino acids, dopamine, or prolactin. These data confirm the indirect pharmacologic evidence of increased dopaminergic activity in schizophrenic patients that relates to dopamine's precursors and to the neuroendocrine regulation of prolactin.

Adolescent↗
PubMed1991

Binding of [3H]-p-aminoclonidine to alpha 2-adrenoceptor states plus a non-adrenergic site on human platelet plasma membranes.

Characterization of the binding of [3H]p-aminoclonidine ([3H]PAC) to purified plasma membranes from human platelets has revealed multiple binding sites. [3H]PAC identified site-1 in the picomolar affinity range (site-1 KD estimates ranged from 13 to 94 pM). Site-1 displayed a rank order of competition by various compounds for [3H]PAC, indicative of an alpha 2-adrenoceptor, and was sensitive to 0.1 mM GTP. [3H]PAC also identified a second site with nanomolar affinity (site-2 KD estimates ranged from 0.7 to 1.7 nM). In the presence of 0.1 mM GTP, site-2 was not diminished significantly. Also in contrast to site-1, site-2 displayed low affinity for yohimbine (YOH), (-)-epinephrine and (-)-norepinephrine (NE). Therefore, site-2 could not be an active alpha 2-adrenoceptor; instead it had properties similar to a previously reported imidazoline-preferring binding site. A third site (site-3) bound [3H]PAC with a KD for site-3 of 26.6 +/- 10.0 nM (SD). Site-3 had a rank order of competition by various compounds for 5 nM [3H]yohimbine ([3H]YOH) binding which was indicative of an alpha 2-adrenoceptor. (-)-NE competed for 5 nM [3H]YOH binding at two sites: site-1 Ki = 32 pM, site-3 Ki = 239 nM. Treatment with 0.1 mM GTP completely removed site-1 and transferred the competitive binding of (-)-NE to low affinity (Ki = 437 nM). Thus, site-3 appears to be a free alpha 2-adrenoceptor. Bmax estimates for untreated membranes, derived from simultaneous multi-experiment curve-fitting analyses, were site-1 = 36 +/- 29 fmol/mg plasma membrane protein, site-2 = 95 +/- 34 fmol/mg and site-3 = 154 +/- 35 fmol/mg. We are the first to report a site for [3H]PAC binding on platelets (site-2) with properties uncharacteristic of an adrenoceptor. This observation appears to be due to our use of purified plasma membrane and low ionic strength buffer. These studies relate to reports of increased binding of [3H]PAC to platelets from depressed patients.

Adrenergic alpha-Agonists↗
PubMed1991

Desipramine lowers tritiated para-aminoclonidine binding in platelets of depressed patients.

Platelet adrenergic receptor binding has been studied by several groups of investigators as a possible marker for depression and other psychiatric conditions. Although some of the findings have been discrepant, the results of the majority of studies that have used imidazoline compounds as ligands have confirmed elevated alpha 2-adrenergic receptor binding in depression. We have emphasized the advantages of obtaining platelet-purified plasma membranes and using tritiated para-aminoclonidine as the ligand of choice. By using "site-selective" concentrations of tritiated para-aminoclonidine, we have identified two high-affinity-binding sites of the platelet alpha 2-adrenergic receptor that appear to be upregulated in depression before treatment. Depressed patients were treated with desipramine hydrochloride for 6 to 8 weeks, and platelet binding was reassessed. Desipramine reduced binding to nearly normal levels at both site-selective concentrations of tritiated para-aminoclonidine. The concentrations of plasma catecholamines could play a role in the downregulation of binding at posttreatment. We discuss these findings in the context of platelet imidazoline-binding sites being a possible state-dependent marker for depression.

Adrenergic alpha-Agonists↗
PubMed1991

Relationship between membrane fluidity and adrenoceptor binding in depression.

Membrane fluidity and adrenergic receptor binding were studied in platelets of depressed patients before and during treatment with desmethylimipramine to investigate the relationship between the alpha 2-adrenergic receptor and its membrane environment in depression. Most samples came from a previous study in which we observed higher 3H-para-aminoclonidine (3H-PAC) binding in platelets from depressed patients compared to healthy subjects. Fluidity was measured by steady state diphenylhexatriene (DPH) anisotropy in both purified plasma membranes and in intracellular membrane preparations from platelets. No differences were observed in DPH membrane fluidity, per se, indicating that fluidity changes probably do not underlie either the increased alpha 2-adrenergic receptor binding in depression or the normalization of binding during treatment. However, lower intracellular membrane fluidity was correlated with higher binding to 3H-PAC site-1 in healthy subjects, but not in depressed patients. Thus, during depression there may be a disruption in the normal relationship between the adrenergic receptor and its membrane environment.

Adrenergic alpha-Agonists↗
PubMed1990

Comparison of 3H-para-aminoclonidine binding to different platelet preparations.

The binding to human platelets of 3H-para-aminoclonidine (3H-PAC), an alpha2 adrenoceptor partial agonist, appears to be altered in depressed patients. We observed that the parameters of 3H-PAC binding to purified plasma membranes from platelets of normal Red Cross volunteers, compare favorably to those reported for binding to normal human autopsy prefrontal cortical lysates. However, only purified plasma membranes from platelets yielded a close comparison. 3H-PAC binding to intact platelets from healthy volunteers was less than 10% displaceable by an alpha2 adrenoceptor antagonist and was therefore unquantifiable. A low percent of specific binding (approx. 35%) was also observed in washed platelet lysates, and the binding was not of very high affinity (KD greater than 10 nM). In contrast, the binding of 3H-PAC to platelet purified plasma membranes from healthy subjects displayed two high affinity binding sites (KD1 = 10.6 pM and KD2 = 1.2 nM). These results are discussed in relation to our recent finding of elevated 3H-PAC binding to platelet purified plasma membranes from depressed patients as compared to healthy subjects.

Adrenergic alpha-Agonists↗
PubMed1990

Elevated 3H-para-aminoclonidine binding to platelet purified plasma membranes from depressed patients.

Purified platelet plasma membranes were used to compare 3H-para-aminoclonidine binding in 18 depressed patients and 24 sex- and age-matched, healthy control subjects. Two site-selective concentrations of the radioligand were used (0.06 and 1.5 nmol/L) to investigate two high-affinity 3H-para-aminoclonidine binding sites. Radioligand binding was significantly elevated in platelets of depressed patients at both concentrations of 3H-para-aminoclonidine whether expressed per milligram protein, per platelet, or per square micrometer of platelet surface area (each p less than 0.02). These data agree with most previous studies, suggesting that a subset of platelet alpha 2 adrenoceptors, recognized by clonidine and its derivative para-aminoclonidine, is upregulated in depressed patients. By using purified plasma membranes, our data rule out the possibility that an inhibitor may have masked receptor binding in previous studies which used total platelet lysates. The present findings thus support the alpha 2 adrenoceptor hypersensitivity theory of depression.

Adrenergic alpha-Antagonists↗
PubMed1989

Gas-liquid chromatographic method for routine detection of plasma sulfo-, gluco-, and free 3-methoxy-4-hydroxyphenylglycol.

A revised method is described for detection of human plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) using gas-liquid chromatography and electron capture detection. This method has comparable sensitivity and reproducibility as HPLC methods with amperometric detection but is less expensive. The extraction and detection of an internal standard of 3-ethoxy-4-hydroxyphenylglycol (EHPG) is identical to MHPG, making quantitation easier than with electrochemical detection. Techniques for measuring the sulfo-, gluco-, and free plasma MHPG fractions are described, and normal adult values are reported.

Adult↗
PubMed1989

Electroencephalographic changes and other indices of neurotoxicity with haloperidol-lithium therapy.

This prospective study was undertaken in order to establish indices of possible neurotoxicity due to the combination of lithium with haloperidol and a combination of lithium with other neuroleptics. Twenty-one subjects who were receiving neuroleptic-lithium combination were studied. Of them, 14 had a primary affective disorder-manic phase, and 7 had schizophrenia as judged by Feighner criteria. The subjects were evaluated on clinical, neuropsychological measures and EEG at baseline and 10-14 days after addition of lithium to the neuroleptic regimen. Of 11 subjects receiving the haloperidol-lithium combination, 5 (45.4%) showed abnormal responses on EEG. Of these 5 subjects, 3 showed abnormal photic responses, and 2 showed slowing in posterior alpha activity. These photoparoxysmal and photomyoclonic responses are indicative of cerebral pathophysiology resulting from the interactive effect of the haloperidol-lithium combination. The photic and other associated EEG abnormalities reported may be the earliest indication of neurotoxicity. No significant changes were observed in the EEG in 10 subjects treated with other neuroleptic-lithium combinations. In a statistical comparison the haloperidol-lithium combination had significantly more frequent EEG changes than the combination of lithium with other neuroleptics. This study presents sufficient evidence from reported photic and other associated EEG changes to pursue further investigation of neurotoxicity due to haloperidol-lithium therapy. Such a study should employ a larger number of subjects, random assignment of subjects to treatment and control groups, and blind evaluation of data.

Adult↗
PubMed1988

Super high affinity 3H-para-aminoclonidine binding to platelet adrenoceptors in depression.

1. An assay was developed using sucrose gradient purified platelet plasma membranes which allowed detection, for the first time in patients, of both super-high affinity (KD = 17 pM) and high affinity (KD = 1.7 nM) binding sites. 2. Limited Scatchard plot analyses were performed on platelet membranes from depressed patients and controls using 10 pM-2.5 nM 3H-p-aminoclonidine (3H-PAC). 3. Patients (n = 9) were age-paired with healthy control subjects for simultaneous blood drawing, platelet preparation and analysis. 4. All patients were endogenous depressives with Hamilton-Depression scores ranging from 19 to 30 at the time of pre-treatment. Seven of the nine patients were analyzed again at six weeks of treatment with antidepressant medication. 5. Using 60 pM 3H-PAC (a concentration determined to bind predominantly to the super-high affinity receptor state) pre-treatment patient values were higher then paired controls (p = 0.06). Post-treatment analysis of seven of the patients and paired controls showed no differences (p = 0.5) suggesting a normalization of receptor binding following treatment. 6. No differences were observed in platelet yield or morphology or in the percent of other blood cell contaminants in the platelet preparations between patients at pre-treatment and controls. However, the platelet yield was significantly lower in patients post-treatment (p = 0.06). 7. These results are in agreement with two previous studies showing elevated 3H-clonidine binding to high affinity sites from depressed patients. The data presented herein suggest that there is a modest 1.25-fold elevated super-high affinity platelet adrenoceptor binding in depressed patients pre-treatment. Receptor binding becomes normal post-treatment.

Adrenergic alpha-Agonists↗
PubMed1986

Evaluation of studies on platelet alpha 2 adrenoreceptors in depressive illness.

Discrepant results have been reported from at least ten laboratories regarding the status of platelet alpha 2 adrenoreceptors in depressed patients. Using a statistical test to combine those studies which utilized radioligand binding techniques, we find the overall data support an elevation in density of platelet alpha 2 adrenoreceptors from drug-free depressed patients (p less than 0.05) and suggest a normalization to lower binding values following antidepressant drug treatment (0.05 less than p less than 0.10). However, these positive results are attributable to highly significant findings by only three laboratories. Much of the discrepancy may be attributable to numerous methodological variables which distinguish the studies. Foremost amongst these variables are the use of different platelet size populations, the use of different medium, and the choice of radioactive ligand and competitor (non-radioactive ligand) in the assay. We present a rationale for the proper choice of each methodological condition used in the clinical assessment of platelet alpha 2 adrenoreceptor status, hoping that improved experimental designs will resolve the current controversy.

Adrenergic alpha-Antagonists↗
PubMed1986

3H-clonidine and 3H-yohimbine binding to glass fiber filters: implications for studies with platelet membranes.

3H-Clonidine and 3H-yohimbine were observed to bind to glass fiber filters. The binding was displaced by co-filtration with the corresponding non-radioactive ligand. Phentolamine and (--)-norepinephrine were ineffective in displacing either 3H-clonidine or 3H-yohimbine bound to filters. Failure to correct for filter binding resulted in an over-estimation of specific binding to platelet membranes. Certain published methodologies may have consequently misidentified up to 20% of the specific binding to platelets, that was actually due to displaced filter binding. Experimental conditions are described which eliminate filter binding. These results are significant for the interpretation of data from studies of platelet binding in depressed patients.

Binding Sites↗