Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.21 (CPT)
 4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Based on the observation (Bradbury et al. (1992) Am. J. Physiol. 262, C752-C759) that conditions known to activate the cystic fibrosis transmembrane regulator protein (CFTR) increase the rate of exocytosis and decrease the rate of endocytosis, it was proposed that activation of the CFTR may involved cAMP-dependent fusion of CFTR containing endosomes with the apical membrane. We have tested this hypothesis in two cell lines derived from epithelia that express defective chloride transport in cystic fibrosis (CF): the human colonic cell line, T84, and the tracheal cell line 9HTEo-. The dose-dependence of forskolin- and CPT-cAMP-induced inhibition of endocytosis were compared with the dose-dependence of chloride channel activation. Endocytosis was determined from the uptake of FITC-dextran, and assayed in purified endosomes. Chloride channel activity was measured from the rate of I-efflux. If the fusion hypothesis is correct: (1) concentrations of agonist that inhibit endocytosis should activate chloride channel activity, and (2) the relationship between endocytosis and channel activation should be similar for forskolin and CPT-cAMP. Results in both cell lines were inconsistent with these postulates, suggesting that either chloride channel activation and the inhibition of endocytosis are separate effects of cAMP, or that the increase in apical CFTR resulting from agonist-dependent inhibition of endosomal fusion is minimal.
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PMID:Activation of the cystic fibrosis transmembrane regulator by cyclic AMP is not correlated with inhibition of endocytosis. 752 69

Chloride conductance across the isolated skin of Rana pipiens shows a voltage-activated component (G(Cl)(V)) which requires the presence of mucosal Cl. G(Cl)(V) is normally low or dormant. It is stimulated by elevated intracellular cAMP, irrespective whether originating from application of ss-adrenergic agonists (isoproterenol), stimulators of the adenylyl-cyclase (forskolin), inhibitors of the phosphodiesterases (isobutyl-methyl-xanthine) or membrane-permeable cAMP analogues (CPT-cAMP). Baseline G(Cl) under inactivating conditions increases also with cAMP dose-dependently. The data indicate that cAMP is a central regulator of the passive, conductive chloride transport across amphibian skin.
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PMID:Chloride conductance in amphibian skin: regulatory control in the skin of Rana pipiens. 1859 32

Mercury is a contaminant of global concern. The use of elemental mercury in various (former) industrial processes, such as chlorine production at chlor-alkali plants, is known to have resulted in soil and groundwater contaminations worldwide. However, the subsurface transport behaviour of elemental mercury as an immiscible dense non-aqueous phase liquid (DNAPL) in porous media has received minimal attention to date. Even though, such insight would aid in the remediation effort of mercury contaminated sites. Therefore, in this study a detailed field characterization of elemental mercury DNAPL distribution with depth was performed together with two-phase flow modelling, using STOMP. This is to evaluate the dynamics of mercury DNAPL migration and the controls on its distribution in saturated porous media. Using a CPT-probe mounted with a digital camera, in-situ mercury DNAPL depth distribution was obtained at a former chlor-alkali-plant, down to 9 m below ground surface. Images revealing the presence of silvery mercury DNAPL droplets were used to quantify its distribution, characteristics and saturation, using an image analysis method. These field-observations with depth were compared with results from a one-dimensional two-phase flow model simulation for the same transect. Considering the limitations of this approach, simulations reasonably reflected the variability and range of the mercury DNAPL distribution. To further explore the impact of mercury's physical properties in comparison with more common DNAPLs, the migration of mercury and PCE DNAPL in several typical hydrological scenarios was simulated. Comparison of the simulations suggest that mercury's higher density is the overall controlling factor in controlling its penetration in saturated porous media, despite its higher resistance to flow due to its higher viscosity. Based on these results the hazard of spilled mercury DNAPL to cause deep contamination of groundwater systems seems larger than for any other DNAPL.
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PMID:The transport behaviour of elemental mercury DNAPL in saturated porous media: analysis of field observations and two-phase flow modelling. 2474 26