Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0220723 (PCA)
 4,687 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Immediately after stimulation with glucose in vitro, isolated rat pancreatic islets prelabeled with [32P]orthophosphate release a pulse of [32P]orthophosphate into the media (the "phosphate flush"). Islets have been rapidly frozen before, during, and after this pulse to assess the concurrent changes in the distribution of tissue radioactivity. Under the present experimental conditions, approximately 90% of the islet radioactivity was soluble in perchloric acid (PCA-soluble) immediately before stimulation and slightly more than half of that was present as [32P]orthophosphate. The tissue pool of [32P]orthophosphate declined 55% and 62% after 7 and 14 min of stimulation which, respectively, incorporated the peak and the end of the heightened efflux of radioactivity. The net decrementa in tissue orthophosphate could account for all of the radioactivity which was released during the "phosphate flush." During the 14-min period of stimulation, labeled ATP and GTP (which had accounted for 13% and 4% of total PCA-soluble radioactivity before stimulation) increased 51% and 35%, respectively, and labeled ADP and AMP (which had accounted for 5.4% and 1.5% of PCA-soluble counts) fell 36% and 77%, respectively. Certain other PCA-soluble components, such as phosphorylcholine and phosphorylethanolamine, and total PCA-insoluble radioactivity were not demonstrably altered. The findings indicate that the "phosphate flush" originates from a labile pool of tissue orthophosphate. It remains to be established whether the simultaneous changes in the turnover of selected nucleotides are coupled to the translocation of orthophosphate or are mediated separately.
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PMID:32P-labeling patterns in rat pancreatic islets: tissue source of the radiophosphate released after glucose stimulation. 36 45

PCA was measured for human PRP by determining recalcification times assayed in a minimal-dilution, controlled PH/PCO2 system in a siliconized cuvette, with the use of light transmission measurements (aggregometry). Platelet shape, aggregation, and plasma clotting end points were assayed photometrically, with platelet morphology and aggregation studied in parallel by light microscopy. With varying concentrations of ADP preincubated with PRP initially containing essentially disc-shaped platelets, it was found that induced shape change in the absence of an aggregation is necessary and sufficient for the development of PCA. This was consistently measurable as a shortening of recalcification times by approximately 50% for suspensions of shape-changed platelets vs. disc-shaped platelets. The pharmacologic inhibition of the endoperoxide pathway-mediated platelet secondary aggregation and release by aspirin administered in vivo does not impair the ability of human platelets to develop this PCA. Inhibition of shape change with amounts of 5'-adenosine monophosphate insufficient to affect coagulation tests in the absence of platelets leads to 80% to 90% inhibition of the ADP-induced PCA. This PCA is shown to be fully reversible, with morphologic reversion of shape-changed platelets to the discoid form, and is shown to be distinct from other PCAs previously described for platelets activated in different ways, such as PF3 activity. It is suggested that the binding of coagulation factors to the platelet membrane may be regulated concomitantly with shape change.
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PMID:A platelet procoagulant activity associated with platelet shape change. 68 25

We have studied the effects of the antithrombitic agent PCA 4230 on the entry of Mn2+, used here as a Ca2+ surrogate for Ca2+ channels, and on the release of Ca2+ from the intracellular stores in stimulated human platelets loaded with fura-2. PCA 4230 prevented receptor-operated calcium entry activated by thrombin, ADP and collagen with no modification of the Ca2+ release from the intracellular stores. PCA 4230 also inhibited cytochrome P-450-mediated O-dealkylase activity with the same concentration-dependence as the thrombin-induced Mn2+ entry. These results suggest that the inhibitory effects of PCA 4230 on Ca2+ influx may be due to its interaction with cytochrome P-450, which has been proposed recently to be involved in the activation of receptor-operated Ca2+ channels. In addition, PCA 4230 inhibited both PAF-induced Ca2+ entry and Ca2+ release, behaving as a PAF-antagonist. All these effects contribute to explain the antithrombitic action of PCA 4230.
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PMID:Effects of the antithrombitic agent PCA 4230 on agonist-induced Ca2+ entry and Ca2+ release in human platelets. 131 57

A method for a simultaneous separation of malondialdehyde (MDA), ascorbic acid and adenine nucleotide derivatives in biological samples by ion-pairing high-performance liquid chromatography is presented. The separation is obtained by an LC-18-T 15 cm x 4.6 mm 3 microns particle size column using tetrabutylammonium as the pairing ion. The starting buffer consists of 10 mM tetrabutylammonium hydroxide, 10 mM KH2PO4 plus 1% methanol, pH 7.00. A step gradient is formed using a second buffer consisting of 2.8 mM tetrabutylammonium hydroxide, 100 mM KH2PO4 plus 30% methanol, pH 5.5. Under these chromatographic conditions a highly resolved separation of MDA, ATP, ADP, AMP, adenosine, ascorbic acid, GTP, GDP, IMP, inosine, Hypoxanthine, Xanthine, uric acid, NAD, and NADP can be performed in about 36 min. In addition, the separation of NADH and NADPH can also be obtained; this renders the present method suitable for the detection of these reduced coenzymes in alkaline extracts from tissue samples. Data referring to PCA extracts from ischemic and reperfused isolated rat hearts and from human erythrocytes peroxidized in vitro by a challenge with 1 mM NaN3 and various concentrations of H2O2 are reported. The relevance of this chromatographic method lies in the possibility to determine directly MDA concentrations avoiding the unspecific thiobarbituric acid colorimetric test, any other manipulation of the sample out of the PCA extraction, and any possible coelution of other acid soluble compounds. The simultaneous determination of MDA, ascorbic acid, and of ATP and its degradation products gives the opportunity to correlate, by a single chromatographic run, peroxidative damages with the energy state of the cell which is of great importance in studies of ischemic and reperfused tissues.
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PMID:Simultaneous separation of malondialdehyde, ascorbic acid, and adenine nucleotide derivatives from biological samples by ion-pairing high-performance liquid chromatography. 195 65

Plasma levels of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) and the in vitro ability of platelets to aggregate and of monocytes to express procoagulant (tissue factor) activity (PCA) were evaluated in five patients who are homozygous for familial hypercholesterolemia (FH) before and after a single and a regular 5-month cholesterol removal by low density lipoprotein (LDL) apheresis. The biweekly procedure resulted in a 25% to 30% reduction (approximately 150 mg/dl) in total and LDL cholesterol (both were greater than 550 mg/dl at the beginning of the study). The basal levels of t-PA antigen and fibrinolytic activity before and after 10 minutes of venous stasis, basal PAI activity, and PAI-1 antigen were comparable to controls and were not affected by LDL apheresis. Likewise, regardless of the cholesterol removal, the PCA of freshly isolated monocytes and that of monocytes incubated with lipopolysaccharide did not differ from control values. Finally, the pre-apheresis sensitivity of platelets to adenosine diphosphate, arachidonic acid, and collagen was 1.5 to 2 times the normal value. This ratio was unchanged throughout the 5-month procedure. We conclude that fibrinolysis and monocyte PCA are normal in FH patients, whereas platelet aggregation is abnormally high, and none of these parameters is significantly affected by a 25% to 30% reduction in total and LDL cholesterol by LDL apheresis. Furthermore, our data suggest that removal of cholesterol from plasma by LDL apheresis is important for gaining insight into the mechanisms involved in the ischemic complications of arteriosclerosis in FH patients.
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PMID:Hemostatic variables in homozygous familial hypercholesterolemia. Effect of regular plasma cholesterol removal by low density lipoprotein apheresis. 212 91

A bioassay, using high-performance liquid chromatography (HPLC) analysis of platelet adenosine nucleotides and hypoxanthine, was studied for its potential use as a test for MH susceptibility. A protocol for the assay was developed, based on the method outlined by Solomons and Masson. The HPLC procedure was a rapid, efficient, sensitive, and highly reproducible technique for measuring ATP, ADP, AMP, and hypoxanthine in platelets. Conditions of extraction and storage were critical for preventing degradation of the nucleotides. Extraction of nucleotides at icebath temperature was found necessary. Storage of platelet extract in PCA, even at -20 degrees C, showed loss of ATP and ADP; hence, neutralization with KOH was essential before storage. Contrary to the findings of Solomons et al., the present study demonstrated that neither ATP depletion nor per cent reduction in nucleotide ratios in platelets treated with halothane can be used as a definitive test for the diagnosis of MH susceptibility. The reason for this disagreement is unclear; however, differences in methods and altitude are implicated. It is possible that the platelet is not affected by malignant hyperthermia and thus cannot serve as a test system for the detection of the syndrome.
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PMID:The use of a platelet nucleotide assay as a possible diagnostic test for malignant hyperthermia. 402 92

The spectrum of low molecular weight compounds, in particular of ribonucleotides, within first cleavage stage embryos of the polar lobe-forming mollusc Nassarius reticulatus and the distribution of the compounds within the embryo at the trefoil stage of first cleavage are analysed by means of capillary isotachophoresis after 0.5 M PCA extraction. The compounds which are found in the whole trefoil embryo (T), the lobeless part (LL), and the polar lobe (PL) respectively, and the mean quantities (nmol. microliter-1; n = 6) are: UTP (11.5, 4.8, 5.6), ITP (8.5, 3.6, 5.0), GTP (10.3, 3.0, 9.0), ATP (29.8, 13.4, 18.8), UDP (11.8, 3.4, 8.7), CTP (8.0, 3.1, 4.5), GDP (5.3, 2.6, 3.4), ADP (16.5, 6.1, 11.6), CDP (4.0, 1.4, 2.6), GMP (4.7, 2.7, 4.3), glucose-6-phosphate (G6P) (53.5, 38.8, 13.0). These compounds appear to be localized in the non-yolk cytoplasmic pool. As the volume ratio of PL/LL for total volume and for non-yolk cytoplasmic volume is about 0.74 and 0.60 respectively, the concentration of all nucleotides in PL as compared to LL is significantly higher (HO, p less than 0.001), both relative to the total volume and to the non-yolk cytoplasmic volume. The G6P concentration is considerably higher in the lobeless part. The morphogenetic role of the vegetal pole compartment of the egg apparently is correlated with a relatively high level of its nucleotide contents.
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PMID:Composition of the nucleotides pool in a morphogenetic compartment in eggs of Nassarius reticulatus (Mollusca) analysed by capillary isotachophoresis. 406 27

ATP, ADP, AMP and glycerate 2, 3-bisphosphate in blood are frequently analyzed in order to evaluate erythrocytes for blood donation and to diagnose hemolytic anemias. In order to find an uncomplicated and safe procedure for the preanalytical treatment of blood a freezing-storing procedure using dry ice was worked out and combined with a later PCA precipitation. The pre-freezing stability of the components was also investigated and found to be best at room temperature.
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PMID:Specimen handling for the assay of adenylates and glycerate 2, 3-bisphosphate in erythrocytes. 731 20

To evaluate the antithrombotic and antiallergic properties of rhaponticin extracted from Rhei Rhizoma, the in vitro and ex vivo inhibitory activities of rhaponticin and its metabolite, rhapontigenin, were measured. These compounds inhibited in vitro ADP- and collagen-induced platelet aggregation. Rhapontigenin was more potent, with IC50 values of 4 and 70 microg/ml, respectively. In ex vivo ADP- and collagen-induced rat platelet aggregation, these compounds also exhibited a potent inhibitory effect. The antiplatelet aggregation effects of rhaponticin and rhapontigenin were more potent than those of aspirin. Rhapontigenin showed significant protection from death due to pulmonary thrombosis in mice. Rhapontigenin also showed the strongest inhibitory activity against beta-hexosaminidase release induced by DNP-BSA. These compounds inhibited PCA reaction in mice. Rhapontigenin intraperitoneally administered showed the strongest inhibitory activity and significantly inhibited PCA at doses of 25 and 50 mg/kg, with inhibitory activities of 48 and 85%, respectively. The inhibitory activity of orally administered rhaponticin was stronger than that of intraperitoneally administered rhaponticin. These results suggest that rhaponticin, in the rhizome of Rhei Rhizoma, is a prodrug that has extensive antiallergic and antithrombotic properties.
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PMID:Antithrombotic and antiallergic activities of rhaponticin from Rhei Rhizoma are activated by human intestinal bacteria. 1221 67

Monocytes express tissue factor (TF) as a result of cytokine stimulation or endothelial adherence. We evaluated monocyte-platelet interaction in vitro as another trigger for monocyte TF enhancement in human mononuclear cells isolated by density gradient centrifugation from peripheral blood. Cell TF procoagulant activity (TF-PCA) was quantitated by a one-stage recalcification clotting time assay. Platelets were counted and identified by whole blood flow cytometry as CD61 positive particles, activated platelets were characterized by P-Selectin (CD62) expression, and monocytes by surface CD14 expression. A significant correlation between normalized TF-PCA of isolated mononuclear cells and platelet count was shown (r = 0.43, P < 0.001). Percentage of activated platelets in baseline samples was 4.2 +/- 3.5 while adenosine diphosphate (ADP) increased platelet positivity to 34 +/- 17% (P < 0.001). After isolation, 52 +/- 12% of platelets within suspensions were activated (P < 0.0001). Percentage of CD62-positive monocytes (CD14+ particles) increased from baseline 5% to 13 +/- 6% in ADP-stimulated samples to 53 +/- 17% after isolation (P < 0.001). These findings suggest that density gradient centrifugation activates platelets and that an adhesive interaction between monocytes and platelets may promote TF-PCA expression in isolated mononuclear suspensions. Enhanced monocyte TF expression as a result of an activated platelet-monocyte interaction seems to be an important laboratory effect requiring consideration when utilizing this technique in an experimental setup.
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PMID:Platelet-induced expression of tissue factor procoagulant activity in freshly isolated human mononuclear cells: implications for experimental use. 1297 24


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