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1.
J Psychiatr Pract ; 6(3): 140-6, 2000 May.
Article in English | MEDLINE | ID: mdl-15990481

ABSTRACT

The author followed 67 patients with panic disorder with agoraphobia (PDA) for a minimum of 5 years in a private practice setting. They were treated with a combination of pharmacotherapy (antidepressants or benzodiazepines) and cognitive-behavioral psychotherapy. The author examines outcomes for three groups: A) 11 male patients, 10 of whom had comorbid conditions; B) 21 female patients with comorbid conditions; and C) 35 female patients without comorbid conditions. Symptom severity was assessed using the Panic Disorder Severity Scale (PDSS). Patients in all groups showed marked improvement in all the domains measured by the PDSS, with the greatest improvement in PDSS scores occurring during the first year in all three groups. Patients in groups A and B tended to plateau after 5 years of treatment and show no additional improvement thereafter, whereas patients in group C (women with "pure PDA") continued to improve, although at a gradually slower rate. However, after an average of 11 years of treatment, the majority of patients remained symptomatic. The presence of comorbid alcohol abuse or depression was associated with poorer outcomes. The results in this effectiveness study are generally not as good as the outcomes of published PDA follow-up efficacy studies, but appear to be superior to outcomes in cohorts of chronically anxious patients treated decades ago.

2.
Drug Saf ; 20(2): 187-93, 1999 Feb.
Article in English | MEDLINE | ID: mdl-10082074

ABSTRACT

Antipsychotic-induced tardive dyskinesia is a common and clinically significant hazard of long term antipsychotic therapy. The arrival of atypical antipsychotics has markedly improved the outlook: atypical antipsychotics are emerging as effective treatments and may also reduce the prevalence and incidence of tardive dyskinesia. In mild cases, careful monitoring of tardive dyskinesia by serial Abnormal Involuntary Movements Scale (AIMS) assessments may be the appropriate course. More severe tardive dyskinesia calls for intervention in order to treat the dyskinesia. Atypical antipsychotics and tocopherol (vitamin E) are effective and generally well tolerated treatment options for tardive dyskinesia. Tardive dyskinesia variants such as tardive dystonia and tardive akathisia tend to be more severe and difficult to treat compared with typical tardive dyskinesia. Prevention of tardive dyskinesia is possible through careful selection of patients for antipsychotic therapy, use of the lowest effective antipsychotic dosages, use of atypical rather than traditional antipsychotics and concurrent tocopherol administration. The clinician can now undertake the management of tardive dyskinesia with growing confidence.


Subject(s)
Antipsychotic Agents/adverse effects , Dyskinesia, Drug-Induced/etiology , Dyskinesia, Drug-Induced/therapy , Humans
4.
Harv Rev Psychiatry ; 3(3): 130-9, 1995.
Article in English | MEDLINE | ID: mdl-9384940

ABSTRACT

Tardive dyskinesia, tardive akathisia, and tardive dystonia are reviewed from a clinical perspective. The evaluation of each syndrome is discussed, and its clinical presentation and course are illustrated with case vignettes. Drugs used in the treatment of tardive dyskinesia are presented, with greater emphasis on the more recently introduced therapies such as clozapine and vitamin E. Although effective treatments remain elusive, neuroleptic-induced movement disorders can be managed satisfactorily in the majority of clinical situations. Algorithms are presented to outline treatment approaches for mild and moderate/severe tardive dyskinesia.


Subject(s)
Akathisia, Drug-Induced , Antipsychotic Agents/adverse effects , Dyskinesia, Drug-Induced , Dystonia/chemically induced , Adult , Aged , Akathisia, Drug-Induced/complications , Akathisia, Drug-Induced/diagnosis , Akathisia, Drug-Induced/drug therapy , Akathisia, Drug-Induced/epidemiology , Akathisia, Drug-Induced/etiology , Decision Trees , Dyskinesia, Drug-Induced/diagnosis , Dyskinesia, Drug-Induced/drug therapy , Dyskinesia, Drug-Induced/epidemiology , Dyskinesia, Drug-Induced/etiology , Dystonia/complications , Dystonia/diagnosis , Dystonia/drug therapy , Female , Humans , Male , Middle Aged , Risk Factors
5.
Am J Psychiatry ; 151(6): 836-41, 1994 Jun.
Article in English | MEDLINE | ID: mdl-7910437

ABSTRACT

OBJECTIVE: The purpose of this study was to assess the long-term outcome of patients with tardive dyskinesia. METHOD: A group of 122 neuroleptic-treated Hungarian outpatients were assessed for tardive dyskinesia on the Abnormal Involuntary Movement Scale and the Tardive Dyskinesia Rating Scale by the same rater over a 10-year period. RESULTS: Sixty-three of the patients received both 5- and 10-year follow-up assessments and are the subjects of this report. The overall prevalence of tardive dyskinesia in this group changed little over time; it was 30.2% at baseline, 36.5% at 5 years, and 31.7% at 10 years. However, there were changes in the tardive dyskinesia status of individual patients; 11 patients had remissions, and 12 who did not have tardive dyskinesia at the baseline assessment had developed it by the 10-year assessment. These two subgroups did not differ significantly on demographic and drug history variables. Outcome of tardive dyskinesia was not significantly related to neuroleptic treatment or to age. CONCLUSIONS: The data of this 10-year follow-up study provide evidence for the long-term stability of tardive dyskinesia and for the feasibility of maintenance neuroleptic therapy for chronic psychotic patients who have tardive dyskinesia.


Subject(s)
Dyskinesia, Drug-Induced/epidemiology , Adult , Ambulatory Care , Antipsychotic Agents/adverse effects , Dyskinesia, Drug-Induced/diagnosis , Dyskinesia, Drug-Induced/etiology , Female , Follow-Up Studies , Humans , Hungary/epidemiology , Longitudinal Studies , Male , Physical Examination , Prevalence , Prognosis , Psychotic Disorders/drug therapy , Severity of Illness Index
6.
Article in English | MEDLINE | ID: mdl-7911586

ABSTRACT

1. Two types of psychiatric diagnoses were obtained in a study of the course of early dyskinesia: DSM-III-R and Dimensional Global Ratings of Schizophrenia, Paranoia, Mania and Depression. 2. The strength of association between measures of vulnerability to developing tardive dyskinesia (TD), and clinical components from each of the two methods of obtaining psychiatric diagnoses was established by canonical correlations. 3. Overall, little difference was obtained between DSM-III-R categories and Global Ratings in terms of correlations with TD vulnerability measures. Using components from global diagnostic ratings, the Depression and Schizophrenia Scales made stronger contributions to the canonical functions than Mania and Paranoia. 4. Unipolar depressed patients appear more sensitive to NL: they developed TD after less NL exposure. 5. Dimensional classification appears to be a promising approach to capturing important characteristics of psychoses.


Subject(s)
Dyskinesia, Drug-Induced/diagnosis , Dyskinesia, Drug-Induced/psychology , Psychotic Disorders/diagnosis , Psychotic Disorders/psychology , Antipsychotic Agents/adverse effects , Antipsychotic Agents/therapeutic use , Bipolar Disorder/complications , Bipolar Disorder/psychology , Depressive Disorder/complications , Depressive Disorder/psychology , Humans , Paranoid Disorders/complications , Paranoid Disorders/psychology , Psychiatric Status Rating Scales , Psychotic Disorders/drug therapy , Schizophrenic Psychology
7.
Cell Calcium ; 14(7): 531-8, 1993 Jul.
Article in English | MEDLINE | ID: mdl-8402836

ABSTRACT

In mixed platelet membrane vesicles the presence of two distinct endoplasmic reticulum-type calcium pump enzymes of 100 and 97 kD molecular mass has been demonstrated. We have previously shown that both calcium pumps were recognized by polyclonal anti-sarcoplasmic reticulum calcium pump antisera [11]. In the present work we studied the effects of several calcium pump inhibitors on active calcium transport and inositol trisphosphate-induced calcium release in these vesicles in an attempt to assign the two calcium pump isoenzymes to specific calcium pools. The effect of the PL/IM 430 inhibitory anti-calcium pump antibody was compared to that of other calcium pump inhibitors acting predominantly on the 100 and the 97 kD calcium pump isoforms, respectively. The PL/IM 430 antibody, which recognized the 97 kD pump on Western blots and 2,5-di-(tert-butyl)-1,4-benzohydroquinone, which inhibited phosphoenzyme formation of the same pump isoform, inhibited calcium accumulation predominantly into an inositol trisphosphate-releasable calcium pool. On the other hand, low concentration of thapsigargin, which inhibited phosphoenzyme formation mainly of the 100 kD pump isozyme, had a more pronounced effect on calcium uptake into an inositol trisphosphate-resistant pool. These data suggest that in platelets the 97 kD calcium pump isoform is likely to be associated with the inositol trisphosphate-sensitive calcium storage organelle.


Subject(s)
Blood Platelets/metabolism , Calcium-Transporting ATPases/antagonists & inhibitors , Calcium/metabolism , Endoplasmic Reticulum/enzymology , Inositol 1,4,5-Trisphosphate/physiology , Intracellular Membranes/metabolism , Isoenzymes/antagonists & inhibitors , Antibodies, Monoclonal/pharmacology , Benzoquinones/pharmacology , Biological Transport , Calcium-Transporting ATPases/immunology , Cell Compartmentation , Humans , Indoles/pharmacology , Isoenzymes/immunology , Signal Transduction , Terpenes/pharmacology , Thapsigargin
8.
Biochem J ; 288 ( Pt 1): 297-302, 1992 Nov 15.
Article in English | MEDLINE | ID: mdl-1332697

ABSTRACT

Phosphorylation, immunoblotting, limited proteolysis and drug-sensitivity analysis were used to characterize the sarcoendoplasmic-reticulum Ca2+ ATPases in a variety of human cell types. In platelets, several megakaryoblastoid and lymphoblastoid cell lines two distinct autophosphorylated forms of these ATPases with molecular mass of 100 and 97 kDa could be observed, whereas in several other cell types the 97 kDa form was absent. On immunoblots the 97 kDa species was specifically recognized by an inhibitory monoclonal antibody raised against the Ca2+ pump of platelet internal membranes, yielded on trypsinolysis a major fragment of 80 kDa, exhibited a distinct electrophoretic migration pattern as compared with the skeletal-, cardiac- and smooth-muscle Ca2+ pumps, and its autophosphorylation was strongly inhibited by the Ca(2+)-mobilizing agent 2,5-di-(t-butyl)-1,4-benzohydroquinone (tBHQ). The 100 kDa species reacted with an antibody specific for the cardiac- and smooth-muscle Ca2+ pumps, yielded on trypsinolysis fragments of 55 and 35 kDa, and its autophosphorylation was much less sensitive to tBHQ inhibition. These findings indicate the simultaneous presence of two different endoplasmic-reticulum Ca2+ pumps in a variety of human cell types, and may explain the previously observed differences in the Ca(2+)-handling characteristics of different intracellular Ca2+ pools and cell types.


Subject(s)
Calcium-Transporting ATPases/analysis , Calcium-Transporting ATPases/physiology , Endoplasmic Reticulum/enzymology , Hydroquinones/pharmacology , Antibodies, Monoclonal , Blood Platelets/enzymology , Calcium-Transporting ATPases/antagonists & inhibitors , Humans , Immunoblotting , Lymphocytes/enzymology , Megakaryocytes/enzymology , Molecular Weight , Muscle, Smooth/enzymology , Myocardium/enzymology , Peptide Fragments/metabolism , Phosphorylation , Trypsin/metabolism , Tumor Cells, Cultured
9.
Neuropsychopharmacology ; 6(4): 241-7, 1992 Jun.
Article in English | MEDLINE | ID: mdl-1352977

ABSTRACT

The effects of a loading dose of 100 mg/kg phenylalanine (PHE) were assessed in three groups of DSM-III-R diagnosed unipolar depressed patients: patients with tardive dyskinesia (TD) (n = 11); patients exposed to neuroleptics (NLs) but without TD (n = 10); and patients never exposed to NLs (n = 10). No significant differences were obtained in fasting and 2 hour postloading PHE plasma levels between the groups. A statistically significant correlation was found between Abnormal Involuntary Movements Scale total scores and postloading PHE plasma levels (p less than .05). Three TD patients showed unusually large increases in PHE plasma levels and PHE:large neutral amino acid ratios. Abnormalities in PHE metabolism may contribute to the development and severity of TD in some NL-treated unipolar depressed patients.


Subject(s)
Depressive Disorder/drug therapy , Dyskinesia, Drug-Induced/complications , Phenylalanine/administration & dosage , Adolescent , Adult , Affect/drug effects , Amino Acids/blood , Antipsychotic Agents/adverse effects , Depressive Disorder/complications , Depressive Disorder/psychology , Female , Humans , Male , Middle Aged , Phenylalanine/blood , Phenylalanine/therapeutic use
10.
Article in English | MEDLINE | ID: mdl-1348369

ABSTRACT

1. An ambulatory activity monitor with solid-state memory was employed to obtain 24-hour activity data in 29 neuroleptic-treated hospitalized patients and 9 normal controls. 2. The activity monitor is a piezoelectric device which was strapped to the non-dominant ankle. Activity was recorded in 5-minute epochs throughout the 24-hour period. 3. In contrast to patients with mania (N = 15) and schizophrenia (N = 4), depressed patients (N = 9) had higher clinical ratings of akathisia and lower levels of daytime activity. 4. Manic and depressed patients showed a delay of peak activity (= acrophase). 5. Quantifiable alterations in rest-activity rhythms may occur in neuroleptic-induced akathisia but measurement of activity may be complicated by the patient's psychiatric disorder.


Subject(s)
Antipsychotic Agents/adverse effects , Motor Activity/drug effects , Psychomotor Agitation/psychology , Adolescent , Adult , Bipolar Disorder/chemically induced , Bipolar Disorder/psychology , Circadian Rhythm/drug effects , Depression/psychology , Female , Humans , Male , Middle Aged , Schizophrenic Psychology
11.
Psychopharmacology (Berl) ; 107(4): 503-10, 1992.
Article in English | MEDLINE | ID: mdl-1603892

ABSTRACT

Relative vulnerability to dyskinesia in terms of exposure to antipsychotic drugs prior to onset of dyskinesia was studied in a sample of 100 psychiatric patients with dyskinesia onset generally within a year or less of the point of study entry. Unipolar and bipolar patients were more vulnerable to dyskinesia than other diagnostic groups. In the total sample, lithium exposure did not appear to delay development of dyskinesia. Longer exposure to antiparkinson drugs was associated with delayed onset of dyskinesia. Past exposure to electroconvulsive therapy was related to decreased vulnerability to dyskinesia.


Subject(s)
Dyskinesia, Drug-Induced/etiology , Psychotic Disorders/complications , Adult , Bipolar Disorder/complications , Depressive Disorder/complications , Electroconvulsive Therapy , Female , Humans , Lithium/therapeutic use , Male , Psychiatric Status Rating Scales , Psychotic Disorders/psychology , Schizophrenia/complications
12.
J Biol Chem ; 266(22): 14593-6, 1991 Aug 05.
Article in English | MEDLINE | ID: mdl-1830588

ABSTRACT

In mixed membrane vesicles prepared from human platelets, the presence of two distinct calcium pump enzymes (molecular mass 100 and 97 kDa) was demonstrated by 32P autoradiography, immunoblotting, and thapsigargin inhibition. Both the 100- and 97-kDa membrane proteins showed calcium-dependent phosphoenzyme formation and reacted with a polyclonal anti-sarcoplasmic reticulum calcium pump antiserum, while only the 100-kDa protein reacted with the antiserum specific for the sarco-endoplasmic reticulum-type calcium transport ATPase 2b isoform. Thapsigargin, inhibiting active calcium transport in platelet membrane vesicles, predominantly blocked the phosphoenzyme formation of the 100-kDa isoform and of the tryptic calcium pump fragments of 55 and 35 kDa, while lanthanum specifically increased the phosphoenzyme formation of the 97-kDa enzyme and of the tryptic fragment of 80 kDa. These results indicate the presence of the sarco-endoplasmic reticulum-type calcium transport ATPase 2b isoform and of a yet unidentified, 97-kDa calcium pump protein in human platelet membranes.


Subject(s)
Blood Platelets/enzymology , Calcium-Transporting ATPases/analysis , Isoenzymes/analysis , Terpenes/pharmacology , Antibodies/immunology , Autoradiography , Blotting, Western , Calcium-Transporting ATPases/antagonists & inhibitors , Calcium-Transporting ATPases/immunology , Cell Membrane/enzymology , Humans , Hydrolysis , Isoenzymes/antagonists & inhibitors , Isoenzymes/immunology , Sarcoplasmic Reticulum/enzymology , Thapsigargin , Trypsin
13.
J Membr Biol ; 123(1): 9-21, 1991 Jul.
Article in English | MEDLINE | ID: mdl-1723105

ABSTRACT

Jurkat and MOLT-4 cultured T lymphoblasts were loaded with low concentrations (30-50 microM) of indo-1 and with high concentrations (3.5-4.5 mM) of quin-2, respectively, in order to follow the activation of calcium transport pathways after stimulation of the cells by a monoclonal antibody against the T cell antigen receptor (aCD3), or after the addition of thapsigargin, a presumed inhibitor of endoplasmic reticulum calcium pump. In the indo-1 loaded cells the dynamics of the intracellular calcium release and the calcium influx could be studied, while in the quin-2 overloaded cells the changes in cytoplasmic free calcium concentration ([Ca2+]i) were strongly buffered and the rate of calcium influx could be quantitatively determined. We found that in Jurkat lymphoblasts, in the absence of external calcium, both aCD3 and thapsigargin induced a rapid calcium release from internal stores, while upon the readdition of external calcium an increased rate of calcium influx could be observed in both cases. aCD3 and thapsigargin released calcium from the same intracellular pools. The calcium influx induced by either agent was of similar magnitude and had a nonadditive character if the two agents were applied simultaneously. As demonstrated in quin-2 overloaded cells, a significant initial rise in [Ca2+]i or a pronounced depletion of internal calcium pools was not required to obtain a rapid calcium influx. The activation of protein kinase C by phorbol ester abolished the internal calcium release and the calcium influx induced by aCD3, while having only a small effect on these phenomena when evoked by thapsigargin. Membrane depolarization by gramicidin inhibited the rapid calcium influx in both aCD3- and thapsigargin-treated cells, although it did not affect the internal calcium release produced by either agent. In MOLT-4 cells, which have no functioning antigen receptors, aCD3 was ineffective in inducing a calcium signal, while thapsigargin produced similar internal calcium release and external calcium influx to those observed in Jurkat cells.


Subject(s)
Antibodies, Monoclonal/immunology , Antigens, Differentiation, T-Lymphocyte/immunology , Calcium/metabolism , Receptors, Antigen, T-Cell/immunology , T-Lymphocytes/metabolism , Terpenes/pharmacology , Aminoquinolines/pharmacology , Biological Transport, Active , CD3 Complex , Cell Line , Cells, Cultured , Endoplasmic Reticulum , Fluorescent Antibody Technique , Gramicidin/pharmacology , Humans , Indoles/pharmacology , T-Lymphocytes/drug effects , Thapsigargin , Valinomycin
14.
J Biol Chem ; 266(14): 8952-6, 1991 May 15.
Article in English | MEDLINE | ID: mdl-1827440

ABSTRACT

Peptides C28R2 and C28R1A, representing the two main alternative classes of calmodulin-binding domains from the plasma membrane Ca2+ pump, were tested for their calmodulin-binding properties and for their capacity to interact with pump from which the calmodulin-binding domain had been removed by chymotryptic proteolysis. Peptide C28R2 was more effective in both capacities. Binding of peptide to calmodulin was measured by competition experiments. Such experiments indicated that Ki for C28R2 as an inhibitor of the pump-calmodulin interaction was 0.1 nM, whereas C28R1A had a Ki of 1 nM. Interaction of peptide with chymotryptically activated Ca2+ pump was measured by observing the inhibition by peptide of active Ca2+ transport into inside-out membrane vesicles at low Ca2+. Those experiments showed that C28R2 interacted relatively strongly (an IC50 of 1 microM), whereas C28R1A had an IC50 of 15 microM. The calmodulin-binding peptides had effects on both the K1/2 for Ca2+ and the Vmax of the proteolyzed pump. The effects on the K1/2 for Ca2+ were related to the net plus charge on the peptide, with the most positive peptides being most effective in competing with Ca2+. The substantial differences between C28R2 and C28R1A suggest that Ca2+ pumps containing calmodulin-binding domains like C28R1A have lower calmodulin affinities and higher activities in the absence of activator.


Subject(s)
Calcium-Transporting ATPases/chemistry , Calmodulin-Binding Proteins/chemistry , Calmodulin/metabolism , Amino Acid Sequence , Calcium/metabolism , Calcium-Transporting ATPases/metabolism , Chymotrypsin , Erythrocytes/enzymology , Humans , In Vitro Techniques , Kinetics , Molecular Sequence Data , Peptide Fragments/chemistry
15.
Mol Immunol ; 27(12): 1297-306, 1990 Dec.
Article in English | MEDLINE | ID: mdl-1703278

ABSTRACT

In human T (Jurkat) lymphoblasts we have studied the calcium signals induced by monoclonal antibodies reacting with the T-cell antigen receptor complex (TCR and CD3). Jurkat cells were preloaded with the fluorescent calcium indicator Indo-1 and the stimulus-induced rise in cytoplasmic free calcium concn was followed in the absence or in the presence of external calcium. The technique allowed the separate investigation of the intracellular calcium release and the external calcium influx processes. The changes in the membrane potential of Jurkat cells were followed simultaneously by using fluorescent indicators. We found that the activation of protein kinase C by phorbol ester (PMA) or by the permeable diacyl glycerol, DiC8, rapidly eliminated the calcium signal, independently of the presence or absence of external calcium, while these treatments did not appreciably change the membrane potential. In contrast, cell membrane depolarization achieved by various treatments selectively blocked the stimulus-induced calcium influx, while did not affect stimulus-induced calcium release from internal stores. The magnitude of the stimulus-induced calcium influx was found to be largely independent of the external calcium concns between about 2-2500 microM. It is demonstrated that the inhibitory effect of membrane depolarization on calcium influx is not simply due to the reduction of the inward calcium gradient under these conditions. These observations indicate a significant down-regulation of the stimulus-induced calcium signal by protein kinase C activation and a selective inhibition of the receptor-operated calcium channels by membrane depolarization.


Subject(s)
Calcium/metabolism , T-Lymphocytes/metabolism , 4-Chloromercuribenzenesulfonate/pharmacology , Antibodies, Monoclonal , Benzothiazoles , Biological Transport , Carbocyanines/pharmacology , Cell Line , Diglycerides/pharmacology , Gramicidin/pharmacology , Humans , Membrane Potentials/drug effects , Membrane Potentials/physiology , Muromonab-CD3 , Protein Kinase C/drug effects , Protein Kinase C/physiology , Tetradecanoylphorbol Acetate/pharmacology
17.
Biochim Biophys Acta ; 1027(2): 130-40, 1990 Aug 24.
Article in English | MEDLINE | ID: mdl-2168754

ABSTRACT

Jurkat lymphoblasts were stimulated by a monoclonal antibody against the CD3 membrane antigen and the evoked calcium signal was followed by the intracellular fluorescent calcium indicator indo-1. The technique applied allowed us to separately investigate the stimulus-induced intracellular calcium release and the calcium-influx pathways, respectively. In the same cells membrane potential was estimated by the fluorescent dye diS-C3-(5). The resting membrane potential of Jurkat lymphoblasts under normal conditions was between -55 and -60 mV. Membrane depolarization, obtained by increasing external K+ concentration, removing external Cl-, or by increasing the Na+/K+ leak permeability with gramicidin or PCMBS, did not induce calcium influx in the resting cells and did not influence the CD3 receptor-mediated internal calcium release, while strongly inhibited the receptor-mediated calcium influx pathway. Half-maximum inhibition of this calcium influx was observed at membrane potential values of about -35 to -40 mV and this inhibition did not depend on the external calcium concentration varied between 5 and 2500 microM. Membrane hyperpolarization by valinomycin did not affect either component of the calcium signal. The observed selective inhibition of the receptor-operated calcium influx pathway by membrane depolarization is probably an important modulator of calcium-dependent cell stimulation.


Subject(s)
Calcium Channels/physiology , Calcium/metabolism , 4-Chloromercuribenzenesulfonate/pharmacology , Antibodies, Monoclonal , Antigens, CD/immunology , Antigens, Differentiation, T-Lymphocyte/immunology , CD3 Complex , Calcium Channels/drug effects , Cell Line , Fluorescent Dyes , Humans , Indoles , Kinetics , Membrane Potentials/drug effects , Receptors, Antigen, T-Cell/immunology , Signal Transduction , T-Lymphocytes
18.
FEBS Lett ; 266(1-2): 171-4, 1990 Jun 18.
Article in English | MEDLINE | ID: mdl-1694785

ABSTRACT

The relationship between thrombin-evoked changes in intracellular calcium concentration [( Ca2+]i) and aggregation was examined in Indo-1-loaded human platelets. The stimulus-induced intracellular calcium release and external calcium influx, as well as platelet aggregation, were studied in the same cell preparation. A close correlation between the sustained high [Ca2+]i level, depending on calcium entry, and the aggregation response was found. Gramicidin, at a concentration high enough to induce membrane depolarization, strongly inhibited the calcium influx and aggregation, but did not influence the thrombin-induced intracellular calcium release. We conclude that calcium influx through depolarization-inhibited calcium channels is a prerequisite of thrombin-induced platelet aggregation.


Subject(s)
Blood Platelets/physiology , Calcium/physiology , Platelet Aggregation , Thrombin/pharmacology , Cytoplasm/physiology , Egtazic Acid/pharmacology , Gramicidin/pharmacology , Humans , In Vitro Techniques , Membrane Potentials , Signal Transduction
19.
Biochim Biophys Acta ; 984(1): 88-96, 1989 Aug 21.
Article in English | MEDLINE | ID: mdl-2548622

ABSTRACT

In human platelets thrombin-induced calcium release from intracellular stores, the consequent influx of extracellular calcium, as well as their role in the aggregation and ATP-secretion reactions were examined. In indo-1-loaded platelets intracellular calcium release was studied in the presence of excess EGTA in the incubation medium, while calcium influx was followed after a rapid repletion of external calcium. After thrombin-stimulation both calcium release and calcium influx produced about the same peak levels of cytoplasmic free calcium but in the first case it was only a transient response, while in the latter one a sustained calcium signal was observed. Increased calcium influx could be evoked for several minutes after the addition of thrombin, it was selectively inhibited by Mg2+ (20 mM) and Ni2+ (1 mM) ions, by neomycin and by PCMB, a non-penetrating SH-group reagent. This calcium influx was practically insensitive to organic calcium channel blockers. Thrombin-induced platelet aggregation was only partial in the absence of external calcium, even if excess magnesium was present in the media, while the aggregation response became complete if external calcium was repleted. A significantly reduced aggregation could be seen in calcium-containing media if calcium influx was selectively inhibited. Platelet ATP-secretion under the same conditions did not depend on external calcium or on calcium influx. These data indicate that in thrombin-stimulated platelets the opening of specific plasma membrane calcium channels can be selectively modulated and these channels play a major role in the development of a full-scale aggregation.


Subject(s)
Blood Platelets/physiology , Calcium/metabolism , Thrombin/pharmacology , Adenosine Triphosphate/metabolism , Biological Transport/drug effects , Calcium Channel Blockers/pharmacology , Humans , Neomycin/pharmacology , Phosphatidylinositols/physiology , Platelet Aggregation
20.
J Biol Chem ; 264(8): 4577-82, 1989 Mar 15.
Article in English | MEDLINE | ID: mdl-2538449

ABSTRACT

The functional domains of the in situ red cell membrane calcium pump were mapped by a double labeling technique. In inside-out vesicles (IOVs) the calcium pump was phosphorylated by [gamma-32P]ATP, the proteins blotted onto nitrocellulose and tagged by monoclonal antibodies raised against the purified pump protein. After proteolytic treatment of the IOVs by trypsin, chymotrypsin, or calpain-I, the fragmentation pattern of the enzyme was followed on the double-labeled immunoblots. The changes in the kinetics of the pump were examined by parallel measurements of the active calcium uptake in IOVs. By analysis of the results of tryptic digestion, it was possible to show that the antibodies recognized three different domains of the pump: 1) a Mr = 10,000-15,000 fragment (not seen directly) which includes the calmodulin-binding domain, 2) a nonphosphorylated Mr = 35,000 tryptic fragment, and 3) a phosphorylated fragment of Mr = 76,000-81,000. Chymotrypsin or calpain-I digestion of the membranes produced one major, Mr = 125,000 fragment, which had lost antibody-binding region 1. Production of this fragment coincided with the loss of calmodulin dependence and with a calmodulin-like activation of IOV calcium uptake (high Vmax, cooperativity in calcium activation). The Mr = 125,000 fragment was further activated by acidic lipids producing high Vmax and low K 1/2 (Ca2+) with no cooperativity. Based on these data a kinetic model and a functional map of the plasma membrane calcium pump is suggested.


Subject(s)
Calcium Channels/metabolism , Calpain/pharmacology , Erythrocyte Membrane/analysis , Phosphatidylinositols/pharmacology , Adenosine Triphosphate/metabolism , Antibodies, Monoclonal , Biological Transport , Calcium/metabolism , Calcium Channels/analysis , Calcium Channels/drug effects , Calpain/metabolism , Chymotrypsin/metabolism , Humans , Immunoblotting , Kinetics , Molecular Weight , Peptide Fragments/metabolism , Phosphatidylinositol Phosphates , Phosphorylation , Trypsin/metabolism
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