Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0043167 (pertussis)
19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the mechanisms underlying the increase in automaticity induced by alpha 1-adrenergic stimulation of normal and "ischemic" canine Purkinje fibers. Fibers were superfused with a control Tyrode's solution, followed by an ischemic superfusate that included 10 mM KCl, 5 mM NaHCO3, Po2 of 10-25 mm Hg, and pH 6.7. To exclude beta-adrenergic actions, propranolol was added to all solutions. In the presence of phenylephrine, normal automaticity at high membrane potentials usually decreased, whereas the incidence of abnormal automaticity during ischemia was increased from a control value of 10% to 30%. Block of an alpha 1-receptor subtype with chloroethylclonidine in the presence of phenylephrine caused normal automaticity to increase in all fibers studied and significantly increased abnormal automaticity to 70%. The alpha-adrenergic-induced increase in automaticity did not occur in ischemic fibers from animals pretreated with pertussis toxin (PTX), which ADP-ribosylated and functionally inactivated the 41-kd family of GTP regulatory proteins. In contrast, the use of PTX enhanced the increase in automaticity induced by phenylephrine in normally polarized Purkinje fibers. Ryanodine, which blocks sarcoplasmic reticulum Ca2+ release, attenuated the increase in normal automaticity in nonischemic fibers but had no effect on abnormal automaticity in ischemic fibers. The increase in abnormal automaticity was, however, blocked by the alpha 1 subtype blocker WB 4101, which also blocks the increase in automaticity in normal fibers. In conclusion, the increase in abnormal automaticity in ischemic Purkinje fibers depends on a WB 4101-sensitive alpha 1-adrenergic receptor subtype whose actions are transduced by a PTX-sensitive 41-kd G protein and are not blocked by ryanodine.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Positive chronotropic responses induced by alpha 1-adrenergic stimulation of normal and "ischemic" Purkinje fibers have different receptor-effector coupling mechanisms. 132 30

The N-methyl-D-aspartate (NMDA)-sensitive subtype of glutamate receptor, which gates Ca(2+)-permeable ion channels, is known for its role in learning and memory formation, in the induction of long-term potentiation, and also in seizure activity and neurotoxicity. In primary cultures of cerebellar neurons, agonists of NMDA receptors induce a dose-dependent release of [3H]arachidonic acid ([3H]AA), which is potentiated by activation of the glycine-positive modulatory site and inhibited by NMDA receptor antagonists. NMDA receptor-induced [3H]AA release is inhibited by quinacrine and partially depends on the presence of extracellular calcium. The [3H]AA release is not sensitive, however, to pretreatment with pertussis or cholera toxin, which suggests a Ca(2+)-dependent activation of phospholipase A2 not employing G proteins. Pretreatment of cultures with the natural and semisynthetic sphingolipids GT1b and PKS 3, respectively, inhibits NMDA receptor-mediated [3H]AA release. We also demonstrated glutamate-evoked [3H]AA release from rat hippocampal slices, which is NMDA receptor mediated, calcium dependent and sensitive to quinacrine. Arachidonic acid and its metabolites have been shown to play a role as second messengers and to modulate neuronal activity. Moreover, they are thought to act as transsynaptic modulators in the mechanism of NMDA receptor-induced long-term potentiation in the hippocampus. Their role in ischemic brain pathology has also been postulated. Our experiments on cultured cerebellar granule cells, incubated in a Mg(2+)-free medium deprived of glucose and oxygen, demonstrated a time-dependent stimulation of [3H]AA release. This release was inhibited by antagonists of NMDA receptors and by quinacrine. Stimulation of NMDA-sensitive glutamate receptors and the subsequent calcium-mediated activation of phospholipase A2 may play a role in the in vivo release of arachidonic acid during brain ischemia. This hypothesis is supported by the observation that the enhanced level of thromboxane B2 in the gerbil brain after 5 min of global ischemia is reduced by the systemic application of either the NMDA antagonist MK-801 or the ganglioside GM1.
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PMID:NMDA receptor-mediated arachidonic acid release in neurons: role in signal transduction and pathological aspects. 138 78

Cerebral ischemia produces perturbation of signal transduction systems in neurons. In order to estimate the contribution of guanine nucleotide-binding protein (G-protein) to hippocampal neuronal death, the effect of pertussis toxin (PTX) on the CA1 pyramidal cell damage after transient forebrain ischemia in rats was examined. PTX was administered 3 days before 20 min of transient forebrain ischemia. PTX injection into the CA1 subfield failed to alter the number of ischemic-damaged CA1 pyramidal cells. In contrast, ventricular PTX injection exacerbated CA1 pyramidal cell damage. We also studied postischemic alteration of GTP binding sites in the hippocampal formation using quantitative in vitro autoradiography. Autoradiographic imaging demonstrated predominant distribution of GTP binding sites in synaptic areas in the hippocampus. No significant change of GTP binding activity was observed in the hippocampus until 2 days after recirculation. Seven days after ischemia, when the CA1 pyramidal cells were depleted, the GTP binding sites of the strata oriens and radiatum in the CA1 subfield had reduced by 32% and 31%, respectively. In contrast, GTP binding in the CA3 subfield and the dentate gyrus remained unaltered throughout the reperfusion period. These results suggest that the amount of G-proteins as estimated by GTP binding remained unaltered in the hippocampus during the early recirculation period, when the CA1 pyramidal cells were morphologically intact, and that signal transduction pathways mediated by Gi and Go do not play a major role in delayed death of the CA1 pyramidal cells.
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PMID:The role of GTP binding proteins in ischemic brain damage: autoradiographic and histopathological study. 161 6

As an approach to understanding the molecular basis of the pathophysiology of cerebral ischemia, we examined qualitative and quantitative changes in pertussis toxin substrates, Gi1 and G0, in the membrane of rat cerebral cortex after decapitation. Within 1 min after decapitation, the extent of pertussis toxin-catalyzed [32P]ADP ribosylation of the G proteins in the cerebral cortex membrane was significantly decreased and the magnitude of the decrease became slightly larger upon further incubation of the decapitated brain. Addition of guanine nucleotides, GTP and GDP, or the purified beta gamma subunits of transducin to the membranes of control and ischemic cerebral cortex stimulated [32P]ADP ribosylation of the G proteins. The stimulation of [32P]ADP ribosylation in the control situation by guanine nucleotides was almost to the same extent as that in ischemia. However, the stimulation by transducin beta gamma subunits was different; the control stimulation was greater than that in ischemia. In immunoblots probed with antibodies against Gi1 alpha, G0 alpha, and T beta, the immunoreactivity of the corresponding proteins in ischemia was similar to that in control, suggesting that the amounts of G proteins were not changed in ischemia. These results suggest that ischemia accelerates the dissociation of alpha-GDP-beta gamma to alpha-GDP and free beta gamma and causes the denaturation of the dissociated alpha-GDP, thereby decreasing [32P]ADP ribosylation.
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PMID:Ischemia of rat brain decreases pertussis toxin-catalyzed [32P]ADP ribosylation of GTP-binding proteins (Gi1 and G0) in membranes. 189 6

The heat-labile toxin (HTL) was purified from sonic extracts of Bordetella bronchiseptica and Bordetella pertussis cells by a series of hydrophobic interactions, density gradient centrifugation, gel filtration, isoelectric precipitation, and isoelectric focusing. A 114-fold purification was regularly obtained with a yield of 31%. A dose of 0.75 ng was dermonecrotizing in guinea pigs. HLT is a simple protein (pI 6.9) with a molecular weight by gel filtration of 102,000 which consists of two polypeptides of 30,000 and 24,000 molecular weight. Amino acid analysis showed 15 common amino acids and the absence of methionine. The dermonecrotizing activity was inactivated at 56 degrees C, and at above pH 10 or below pH 5. Effects of various ions, detergents, enzymes and other chemical agents on HLT were determined. When instilled on the surgically exposed peripheral blood vessels of guinea pigs or suckling mice, HLT induced vasoconstriction within 15 min resulting in the decrease of blood flow, followed by manifestations of ischemia, diapedesis and petechial hemorrhage during the following 5 h. HLT activity on arterioles was unaffected by adrenergic or cholinergic blockades. Biochemically, HLT significantly inhibited in vitro the activity of Na+ - K+ ATPase prepared from rat kidney. A possible mechanism by which HLT induces dermohemorrhagic necrosis and splenic atrophy, is discussed.
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PMID:Bordetella heat-labile toxin: further purification, characterization and mode of action. 301 69

A variety of pharmacological agents were used as experimental probes to determine with greater precision the site(s) of damage to cerebral adenylate cyclase as a consequence of postischemic reperfusion in the gerbil. A paradigm of 60-min bilateral ischemia followed by 40-min reperfusion results in a decreased sensitivity of the catalytic site of adenylate cyclase to Mn2+. Likewise, the GTP-transducer site (guanine nucleotide regulatory or G protein) revealed depressed responses to GTP in the absence or presence of norepinephrine, dopamine agonists, substance P, yohimbine, and cholera and pertussis toxins. Moreover, a crude preparation of GTPase disclosed that damage elicited by postischemic reperfusion was directed to the higher-affinity form of this enzyme, which is associated with the overall function of the guanine nucleotide regulatory protein. Injury to adenylate cyclase was unrelated either to the ability of adrenergic ligands to bind to associated receptor sites or to the capacity of the brain to generate visual evoked potentials in response to visual stimuli.
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PMID:Further probes into the molecular sites of damage to cerebral adenylate cyclase following postischemic reperfusion. 310 40

We examined alterations in the cyclic AMP generating system and G protein subunits in gerbil hippocampus following 10 min of transient ischemia. In hippocampal slices, basal and isoproterenol- and forskolin-stimulated cyclic AMP accumulations were markedly increased at 6 and 24 h after ischemia. Interestingly, both the inhibition of forskolin-stimulated cyclic AMP and the potentiation of beta-adrenoceptor-stimulated cyclic AMP by a gamma-aminobutyric acidB receptor agonist were attenuated at these time points. Ischemia did not affect the immunolabeling of any of the G protein alpha subunits; only that of beta subunits was significantly decreased, by 28.2%, 4 days after ischemia. In contrast, pertussis toxin-catalyzed [32P]ADP ribosylation declined progressively during the late recirculation period, reaching a significant reduction (25.4%) at 6 h after ischemia. These results suggest that ischemia affects the heterotrimeric conformation (alpha beta gamma) of Gi/Go during the recirculation period, thereby leading to increased cyclic AMP production. Because cyclic AMP-dependent protein kinase A modulates the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-kainate receptor channels, postischemic sensitization of the cyclic AMP generating system may contribute to neuronal degeneration in the hippocampus.
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PMID:Alterations in cyclic AMP generation and G protein subunits following transient ischemia in gerbil hippocampus. 767 81

Platelet-activating factor (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine [PAF]) is a potent lipid autocoid produced by many cell types. PAF is produced by cultured rat cerebellar neurons and human fetal brain cells, and has been extracted from brain tissue. Multiple PAF receptors have been demonstrated in brain tissue. PAF stimulates intracellular Ca2+ mobilization and phosphatidylinositol (PI) metabolism in transformed neuronal cell lines via the PAF receptor, to which both pertussis toxin (PTX)-sensitive and -insensitive G protein appear to couple. PAF has potent actions on cerebral vessels and cerebral metabolism when administered in vivo. Direct neuronal effects of PAF, such as inhibition of acetylcholine release, are observed in vitro. Excessive PAF production in pathological states of the nervous system, such as neurotrauma and stroke, has been shown. In multiple studies in rodent and non-rodent models using highly specific and potent PAF antagonists, reversal or prevention of key consequences of brain injury, such as hypoperfusion following ischemia, reperfusion and edema, inflammatory cell accumulation, neurologic/motor deficits, and neuronal salvage, has been demonstrated. These studies taken together support a role for PAF as an important mediator in the pathophysiology of brain injury.
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PMID:Platelet-activating factor: a putative neuromodulator and mediator in the pathophysiology of brain injury. 790 80

We studied the receptor-effector coupling mechanism responsible for alpha 1-adrenergic receptor-induced increases in abnormal automaticity (AA) occurring at low membrane potentials in "ischemic" Purkinje fibers, superfused with Tyrode's solution containing [K+]o 10 mmol/L, pH 6.8, PO2 < 25 mm Hg. To exclude beta-adrenergic actions, propranolol was added to all solutions. We derived membrane slope resistance (Rsl) from the current-voltage relation obtained with two microelectrodes for intracellular current injection and transmembrane voltage recording. We also measured the membrane time constant, Tm, to assess changes in membrane resistance (Rm). Phenylephrine effects on Rsl in simulated ischemia were studied in the absence or presence of the alpha 1-subtype blockers WB 4101 (WB) or chloroethylclonidine (CEC), both 0.1 mumol/L, and in Purkinje fibers from dogs injected with pertussis toxin (PTX) (30 micrograms/kg i.v., 60 to 72 hours before study). There were no significant differences in mean values of Rsl before phenylephrine superfusion among all groups of Purkinje fibers. Tm increased by 23% during phenylephrine 0.1 mumol/L superfusion, and Rsl increased by 11%. These two results suggest a 23% increase in Rm with no concordant change in longitudinal resistance. In the presence of CEC, phenylephrine increased Rsl by 12%. In contrast, WB blocked phenylephrine effects on Rsl (0.3%). In PTX-treated Purkinje fibers, the levels of PTX-sensitive G protein as well as phenylephrine effects on Rsl (3%) were significantly reduced. In the absence of WB and of CEC, the phenylephrine effects both on Rsl and on the incidence of AA were directly related to the level of PTX-sensitive substrate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Receptor-effector coupling pathway for alpha 1-adrenergic modulation of abnormal automaticity in 'ischemic' canine Purkinje fibers. 790 61

GTP-binding regulatory proteins (G proteins) regulate various biological functions, but their participation in controlling coronary microvascular tone has not been established yet. The goal of the present study was to elucidate the role of pertussis toxin (PTX)-sensitive G protein in regulating coronary microvascular tone during autoregulation and ischemia. In 42 open-chest dogs, coronary arterial microvessels on the surface of the left ventricle were directly observed by epi-illuminated fluorescence microangiography using a floating objective system. PTX (300 ng/mL) was superfused onto the surface of the left ventricle for 2 hours to block Gi and G(o) protein in epimyocardial coronary microvessels in vivo. PTX superfusion caused no change in the resting diameters of microvessels and significantly blocked the vasoconstriction induced by BHT 920 (a selective alpha 2-agonist). After pretreatment with PTX or its vehicle, the left anterior descending coronary artery (LAD) was occluded by a hydraulic occluder to reduce coronary perfusion pressure (CPP) in a stepwise fashion. A mild stenosis (CPP, 60 mm Hg), a severe stenosis (CPP, 40 mm Hg), and complete occlusion were sequentially produced. Coronary flow velocity in the LAD distal to the stenotic site was continuously monitored. In both PTX and vehicle groups, flow velocity did not significantly decrease during mild stenosis, proving that transmural coronary autoregulatory function was well preserved in the preparation. During severe stenosis and complete occlusion, the coronary flow velocity significantly decreased. In the vehicle group, microvessels < 100 microns in inner diameter significantly dilated in response to the reduction in perfusion pressure (mild stenosis, 6.2 +/- 1.9%; severe stenosis, 21.1 +/- 4.4%; and complete occlusion, 16.8 +/- 5.9%; P < .05 versus baseline diameters). In the PTX group, microvessels did not dilate during each occlusion level (mild stenosis, -2.0 +/- 0.9%; severe stenosis, -3.9 +/- 1.9%; and complete occlusion, -13.4 +/- 2.9%; P < .05 versus vehicle group). PTX did not affect the microvascular dilation caused by nitroprusside. The present data indicate that PTX-sensitive G protein is crucially involved in microvascular control during autoregulation and ischemia.
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PMID:Pertussis toxin-sensitive G protein mediates coronary microvascular control during autoregulation and ischemia in canine heart. 791 38


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