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)

The 'binding' of IgE to particulate preparations derived from sonicated purified rat mast cells was measured by the blocking of PCA titrations of the supernatant solutions from incubations with such preparations. It was found that the PCA blocking reaction was inhibited by the addition of calcium ion to the incubations. The blocking reaction was strongly dependent on the pH of the incubations, being maximal at pH values lower than 5-0. The blocking reaction proceeded in a linear manner for at least 3 h provided that no more than 70 percent of the amount of IgE initially supplied had been removed by the particulate fraction. Only mast cell-derived preparations were capable of effecting PCA blocking.
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PMID:On the nature of the presumed receptor for IgE on mast cells. III. Kinetics of the blocking of the PCA reaction by cell-free particulate preparations from rat peritoneal mast cells and effect of pH and calcium concentration on the reaction. 0 50

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

Astemizole (0.5-5 mg/kg, p.o.) dose-dependently inhibited heterologous and homologous PCA reactions in rats at ID50 values of 1.48 mg/kg and 2.37 mg/kg, respectively. The inhibitory effect of astemizole on heterologous PCA was most remarkable when this compound was given p.o. 2 h prior to antigen challenge. Astemizole (0.1-5 mg/kg, p.o.) dose-dependently inhibited experimentally-induced asthma in guinea pigs at an ID50 of 0.86 mg/kg. Ex vivo, astemizole (0.5-5 mg/kg, p.o.) inhibited antigen-induced histamine release from lung pieces of sensitized guinea pigs. In in vitro experiments, the drug dose-dependently inhibited antigen-induced histamine and SRS-A releases from guinea pig lung pieces at concentrations of 0.05-10 microM. Furthermore, astemizole (0.1-10 microM) inhibited the histamine release induced by compound 48/80 and antigen-antibody reaction from rat peritoneal mast cells, and at 0.1-500 nM inhibited both leukotriene C4- and platelet-activating factor (PAF)-induced contraction of isolated guinea pig trachea at submicromolar concentrations. Astemizole not only inhibited 45Ca uptake into rat mast cells but also prevented the Ca2+ release from the intracellular Ca store induced by compound 48/80, although this compound did not affect the histamine release from permeabilized mast cells induced by Ca2+. Our results suggest that one of the antiallergic mechanisms of astemizole may be an inhibition of signal transduction from the mast cell membrane to the intracellular systems.
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PMID:Antiallergic effects of astemizole on immediate type hypersensitivity reactions. 170 34

The effect of various analogues of the neurotoxic amphetamine derivative, MDA (3,4-methylenedioxyamphetamine) on carrier-mediated, calcium-independent release of 3H-5-HT and 3H-DA from rat brain synaptosomes was investigated. Both enantiomers of the neurotoxic analogues MDA and MDMA (3,4-methylenedioxymethamphetamine) induce synaptosomal release of 3H-5-HT and 3H-DA in vitro. The release of 3H-5-HT induced by MDMA is partially blocked by 10(-6) M fluoxetine. The (+) enantiomers of both MDA and MDMA are more potent than the (-) enantiomers as releasers of both 3H-5-HT and 3H-DA. Eleven analogues, differing from MDA with respect to the nature and number of ring and/or side chain substituents, also show some activity in the release experiments, and are more potent as releasers of 3H-5-HT than of 3H-DA. The amphetamine derivatives (+/-)fenfluramine, (+/-)norfenfluramine, (+/-)MDE, (+/-)PCA, and d-methamphetamine are all potent releasers of 3H-5-HT and show varying degrees of activity as 3H-DA releasers. The hallucinogen DOM does not cause significant release of either 3H-monoamine. Possible long-term serotonergic neurotoxicity was assessed by quantifying the density of 5-HT uptake sites in rats treated with multiple doses of selected analogues using 3H-paroxetine to label 5-HT uptake sites. In the neurotoxicity study of the compounds investigated, only (+)MDA caused a significant loss of 5-HT uptake sites in comparison to saline-treated controls. These results are discussed in terms of the apparent structure-activity properties affecting 3H-monoamine release and their possible relevance to neurotoxicity in this series of MDA congeners.
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PMID:3,4-Methylenedioxyamphetamine (MDA) analogues exhibit differential effects on synaptosomal release of 3H-dopamine and 3H-5-hydroxytryptamine. 182 38

PCA 4233 [2-(phenylthio)ethyl-5-ethoxycarbonyl-2,4,6-trimethyl- 1,4-dihydropyridine-3-carboxylate] and PCA 4248 [2-(phenylthio) ethyl-5-methoxycarbonyl-2, 4, 6-trimethyl-1, 4-dihydropyridine-3-carboxylate], two compounds developed from a series of 1,4-dihydropyridines that lack pharmacologic effects on voltage-operated calcium channels, were found to block selectively rabbit operated calcium channels, were found to block selectively rabbit and human platelet aggregation and secretion, and binding of [3H]-labeled platelet-activating factor (PAF) to human platelet and polymorphonuclear PAF receptors. Rabbit platelet aggregation was tested with 1.9 nM PAF, i.e., a concentration producing maximal response, and was completely blocked with 10 microM PCA 4233 and 3 microM 4248 (IC50 values, 2.55 and 1.05 microM, respectively). Human platelet aggregation in platelet-rich plasma was studied with 1 microM PAF, a concentration that caused a response comparable with that of 1.9 nM PAF in rabbit platelets. The IC50 of PCA 4248 for ATP release under these conditions was 3.6 microM. PCA 4248 behaved as a competitive and selective antagonist in [3H]serotonin secretion studies on rabbit platelets, since it displaced rightwards log dose-response curves and lacked any effect on thrombin- and ionophore A23187-induced platelet secretion. A pA2 value of 7.5 was obtained from Schild plots on [3H]serotonin secretion studies. PCA 4248 also produced a dose-dependent inhibition of [3H]PAF binding to human platelets and to human polymorphonuclear leukocytes. These data indicate that PCA 4233 and PCA 4248 belong to a new class of selective PAF-receptor antagonists.
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PMID:1,4-Dihydropyridines, a new class of platelet-activating factor receptor antagonists: in vitro pharmacologic studies. 217 Jun 24

The effect of mitogens and/or recombinant B-cell growth factors (M/GFs) on the in vitro growth of hairy cells was examined. Tumor cells were isolated from the spleens of four patients with hairy cell leukemia (HCL) by Ficoll-Hypaque sedimentation and E-rosetting. Enrichment for tumor cells was confirmed with intracytoplasmic immunoglobulin (Ig) staining, tartrate resistant acid phosphatase (TRAP) staining, and staining using monoclonal antibodies (MoAbs) directed at B, T, myeloid, and monocytoid antigens (Ags) in indirect immunofluorescence assays. Tumor cells were B1(CD20)+ B2(CD21)- B4(CD19)+ IL-2R(CD25)+ PCA-1 +/- TRAP+. HCLs neither synthesized DNA nor secreted Ig in response to culture with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-2, IL-3, IL-4, IL-5, or IL-6. However, a proliferative response (stimulation index greater than or equal to 3.0) without Ig secretion was triggered in HCLs by mitogens or combinations of GFs. Specifically, DNA synthesis was induced at 3 days in three of four HCL samples cultured with Staphylococcus aureus Cowan A (SAC) or the combination of phorbol ester (TPA) and the calcium ionophore A 23187 (Ca2+); DNA synthesis was triggered later (day 7) by tumor necrosis factor (TNF) or by IL-4 and IL-5. In contrast, the fourth patient, a nonresponder to SAC or TPA/Ca2+, demonstrated increased DNA synthesis at day 3 when cocultured with IL-4 and IL-5. Both autoradiography and staining with antibromodeoxyuridine (BrdU) MoAb conjugated to fluorescein confirmed DNA synthesis by only a minority (5% to 23%) of tumor cells within each patient. Dual staining confirmed that responsive cells were both BrdU+ and TRAP+. DNA synthesis induced by TPA/Ca2+ was blocked specifically by anti-IL-6 Ab; in contrast, the HCL proliferative response to SAC, TNF, or IL-4 and IL-5 was not inhibited by anti-IL-6 Ab. alpha-Interferon inhibited the response to TPA/Ca2+, TNF, or IL-4 and IL-5 without any effect on response to SAC. Finally, peroxidase-antiperoxidase staining demonstrated that HCLs are induced by TPA/Ca2+, but not by SAC, to produce intracytoplasmic IL-6. These data demonstrate IL-4, IL-5, and IL-6 mediated DNA synthesis by HCLs in vitro and suggest a possible in vivo role for these growth factors in the pathophysiology of HCL.
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PMID:Response patterns of hairy cell leukemia to B-cell mitogens and growth factors. 224 29

Amoxanox inhibited immunologically stimulated and LTD4-induced bronchoconstriction in laboratory animals. Amoxanox, like DSCG, inhibited rat IgE-mediated PCA and histamine release from rat peritoneal mast cells, and suppressed immunologically stimulated or calcium ionophore A23187-induced SRS-A generation in rat peritoneal cavity and guinea pig lung fragments. This compound also reduced the contractile response of guinea pig lung parenchymal and ileal strips to LTD4, but did not significantly affect the response of the ileum to either histamine or acetylcholine. Therefore, the antiallergic action of amoxanox seems to be associated with inhibition of chemical mediator release and antagonistic activity on SRS-A.
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PMID:Mechanism of the action of amoxanox (AA-673), an orally active antiallergic agent. 241 69

Antiallergic effects of 4-[2-oxo-3-(1H-tetrazol-5-yl)-2H-chromen-8-yloxy]-buty ric acid (C4C) were studied. C4C is an active principal metabolite of an orally effective antiallergic agent, KP-136. C4C (0.2-1 mg/kg, i.v.) markedly inhibited the mast cell-mediated homologous PCA of rats and the experimental allergic asthma of rats and guinea pigs, although it had almost no effects on heterologous PCA and compound 48/80-induced cutaneous response in rats. C4C (0.2 mg/kg, i.v.) was scarcely effective on cutaneous responses induced by intradermal injection of histamine and serotonin which are principal chemical mediators of rat homologous PCA, and it blocked the decrease of skin histamine content after the PCA. In addition, C4C (0.01-0.5 micrograms/ml) inhibited the increase of 45Ca uptake of mast cells, the histamine release and the degranulation induced by the antigen-antibody interaction. These effects of C4C were much the same as those of KP-136. From the above findings, C4C is considered to be an antiallergic agent that inhibits the mast cell activation by blocking the calcium influx, and it shares similar pharmacological properties with KP-136.
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PMID:Antiallergic effects of 4-[2-oxo-3-(1H-tetrazol-5-yl)-2H-chromen-8-yloxy]-bu tyric acid. 247 59

The effects of RU-31156 on type I allergic reactions were studied and the following results were obtained. Seven-day homologous PCA in guinea pigs was significantly inhibited by oral doses of this drug. The maximum inhibition was observed when the drug was given 30 minutes prior to challenge. Forty-eight-hour homologous PCA was significantly inhibited in rats, and this inhibition was maximal when the drug was given 10 minutes prior to challenge. Orally-administered RU-31156 gave significant inhibition of induction of experimental asthma symptoms in guinea pigs when it was given one or two hours prior to challenge. In addition, the drug significantly inhibited the asthmatic reaction of experimental asthma in rats when it was given 10 minutes prior to challenge. RU-31156 significantly inhibited histamine and SRS-A release from the lung tissue of passively sensitized guinea pigs. The combined use of isoproterenol or theophylline with RU-31156 did not enhance the inhibitory activity of the drug. RU-31156 did not produce any effect on the histamine release induced by calcium ionophore A 23187. RU-31156 inhibited the Schultz-Dale reaction in the tracheal muscle and the ileum of guinea pigs, but it did not show any antihistaminic in these organs.
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PMID:Inhibition of immediate hypersensitivity reaction by a new drug, RU-31156. 620 30

The x-ray pictures have principal significance in the clinical estimation of morphology of the skeleton. Roentgenometrical investigations of second metacarpal bone allow to assess the value of PCA (percentage cortical area), which is adequate to the mineral contents of the bone structure. PCA value of 100 equals the density of 2,3 g/cm3. The standard values of PCA and density equivalents were established in a group of 600 healthy children. The study was based on a group of 50 sick children aged from 1 to 16 years. The urolithiasis in all cases was diagnosed and all children were treated in the National Research Institute of Mother and Child in the years 1978-1979. The concrements in all cases contained the calcium salts as the main component. In 32 cases the following mixed stones: whewellite and weddellite, struvite and apatite, brushite and apatite, struvite and oxalate were found out. It was stated on the ground of mineralogical examinations that one component clearly preponderated the other ones.
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PMID:[The assessment of skeletal mineralization in children with urolithiasis]. 717 94


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