953 resultados para Ca2 -activated K Current
Resumo:
The sediment redox potential was raised in the laboratory to estimate reduction of internal available phosphorus loads, such as soluble reactive phosphorus (SRP) and total phosphorus (TP), as well as the main elements of sediment extracts in Dianchi Lake. Several strongly reducing substances in sediments, which mainly originated from anaerobic decomposition of primary producer residues, were responsible for the lower redox potential. In a range of -400 to 200 mV raising the redox potential of sediments decreased TP and SRP in interstitial water. Redox potentials exceeding 320 mV caused increases in TP, whereas SRP maintained a relatively constant minimum level. The concentrations of Al, Fe, Ca2+, Mg2+, K+, Na+ and S in interstitial water were also related to the redox potential of sediments, suggesting that the mechanism for redox potential to regulate the concentration of phosphorus in interstitial water was complex.
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,pH,pH:(1),0.29 g/kg,101.56 g/kg,(EC)0.53 mS/cm,(EC>0.50 mS/cm);(2),6,pH6.55.5,pH(5.52),;(3)NO3-SO42-Cl-Ca2+Mg2+K+Na+,HCO3-,NO3-SO42-pH,Ca2+Na+pH
Resumo:
Ca2+Mg2+K+Na+(BS)(CEC)(EC),Ca2+(pH2.5)Mg2+K+Na+BS(pH2.5)CEC(pH3.5),;C a2+Mg2+K+Na+,pH2.5Ca2+Mg2+K+Na+;Ca2+BSCEC(BSP)EC,pH 2.5,Ca2+BSBSPpH 3.5,pH4.5,
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Radial distribution function of CaCl2-KCl (1:2 mol) melt was measured by X-ray scattering of high temperature liquid. The nearest neighbour distances of Ca2+-Cl-, K+-Cl- and Cl--Cl- ionic pairs are 0.278, 0.306 and 0.380 nm, respectively, Discussion on the relation between structure and physicochemical properties in the melt was simply done in this paper.
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The Grove Mountains, including 64 nunataks, is situated on an area about 3200km2 in the inland ice cap of east Antarctica in Princess Elizabeth land (72o20'-73101S, 7350'-75o40'E), between Zhongshan station and Dome A, about 450km away from Zhongshan station (6922'S, 7622'E). Many workers thought there was no pedogenesis in the areas because of the less precipitation and extreme lower temperature. However, during the austral summer in 1999-2000, the Chinaer 16 Antarctic expedition teams entered the inland East Antarctica and found three soil spots in the Southern Mount Harding, Grove Mountains, East Antarctica. It is the first case that soils are discovered in the inland in East Antarctica. Interestingly, the soils in this area show clay fraction migration, which is different from other cold desert soils. In addition, several moraine banks are discovered around the Mount Harding. The soil properties are discussed as below. Desert pavement commonly occurs on the three soil site surfaces, which is composed of pebbles and fragments formed slowly in typical desert zone. Many pebbles are subround and variegated. These pebbles are formed by abrasion caused by not only wind and wind selective transportation, but also salt weathering and thaw-freezing action on rocks. The wind blows the boulders and bedrocks with snow grains and small sands. This results in rock disintegration, paved on the soil surface, forming desert pavement, which protects the underground soil from wind-blow. The desert pavement is the typical feature in ice free zone in Antarctica. There developed desert varnish and ventifacts in this area. Rubification is a dominant process in cold desert Antarctic soils. In cold desert soils, rubification results in relatively high concentrations of Fed in soil profile. Stained depth increases progressively with time. The content of Fed is increasing up to surface in each profile. The reddish thin film is observed around the margin of mafic minerals such as biotite, hornblende, and magnetite in parent materials with the microscope analyzing on some soil profiles. So the Fed originates from the weathering of mafic minerals in soils. Accumulations of water-soluble salts, either as discrete horizons or dispersed within the soil, occur in the soil profiles, and the salt encrustations accumulate just beneath surface stones in this area. The results of X-ray diffraction analyses show that the crystalline salts consist of pentahydrite (MgSO4-5H2O), hexahydrite (MgSO4-6H2O), hurlbutite (CaBe2(PO4)2), bloedite (Na2Mg(S04)2-4H2O), et al., being mainly sulfate. The dominant cations in 1:5 soil-water extracts are Mg2+ and Na+, as well as Ca2+ and K+, while the dominant anion is SO42-, then NO3-, Cl- and HCO3-. There are white and yellowish sponge materials covered the stone underside surface, of which the main compounds are quartz (SiO2, 40.75%), rozenite (FeSOKkO, 37.39%), guyanaite (Cr2O3-1.5H2O, 9.30%), and starkeyite (MgSO4-4H2O, 12.56%). 4) The distribution of the clay fraction is related to the maximum content of moisture and salts. Clay fraction migration occurs in the soils, which is different from that of other cold desert soils. X-ray diffraction analyses show that the main clay minerals are illite, smectite, then illite-smectite, little kaolinite and veirniculite. Mica was changed to illite, even to vermiculite by hydration. Illite formed in the initial stage of weathering. The appearance of smectite suggests that it enriched in magnesium, but no strong eluviation, which belongs to cold and arid acid environment. 5) Three soil sites have different moisture. The effect moisture is in the form of little ice in site 1. There is no ice in site 2, and ice-cement horizon is 12 cm below the soil surface in site 3. Salt horizon is 5-10 cm up to the surface in Site 1 and Site 2, while about 26cm in site 3. The differentiation of the active layer and the permafrost are not distinct because of arid climate. The depth of active layer is about 10 cm in this area. Soils and Environment: On the basis of the characteristics of surface rocks, soil colors, horizon differentiation, salt in soils and soil depth, the soils age of the Grove Mountains is 0.5-3.5Ma. No remnants of glaciations are found on the soil sites of Mount Harding, which suggests that the Antarctic glaciations have not reached the soil sites since at least 0.5Ma, and the ice cap was not much higher than present, even during the Last Glacial Maximum. The average altitude of the contact line of level of blue ice and outcrop is 2050m, and the altitude of soil area is 2160m. The relative height deviation is about 110m, so the soils have developed and preserved until today. The parental material of the soils originated from alluvial sedimentary of baserocks nearby. Sporepollen were extracted from the soils, arbor pollen grains are dominant by Pinus and Betula, as well as a small amount Quercus, Juglans, Tilia and Artemisia etc. Judging from the shape and colour, the sporepollen group is likely attributed to Neogene or Pliocene in age. This indicates that there had been a warm period during the Neogene in the Grove Mountains, East Antarctica.
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,:,,,,,HCO -3 > SO2 -4 > Ca2 + >Mg2 + > K+ NO-3 Cl - > Na + > NH+4 > PO3 -4 ,HCO32Ca ;,PO3 -4 ,Ca2 + NO-3 ,,,HCO-3 Ca2 + Mg2 + ,K+ NH+4 ;,HCO-3 Mg2 + ,,NH+4 NO-3 ,
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, 20042005. , SO2 -4 , NH +4 , Ca2 + , NO -3 H+, pH, . 4, SO2 -4 , NH+4 , NO -3 , Ca2 +F- , K+Mg2 +, Na+Cl- , H+.
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TSPSO220051120051231TSPF-Cl-SO42-NO3-NH4+K+Na+Ca2+Mg2+TSP 1. TSP36.91313.44µg/m3106.60µg/m3SO42-> NH4+> Ca2+ > NO3-> K+ > Na+ > Cl- > Mg2+ > F-SO42- (23.0412.16µg/m3)NH4+(3.052.23µg/m3)3730TSPTSPCl-SO42-NO3-NH4+K+Na+Ca2+Mg2+/:1.295.231.352.371.731.221.841.231.02 2. TSPTSPTSPTSPTSPTSPTSPTSPTSPTSPTSPTSPTSPTSPCa2+Mg2+F-(RH)SO42-NO3-NH4+Cl- 3. TSPTSPpH6.270.41Q0.82TSPSO42-TSP 4. NH4+SO42-NO3-R0.850.65NH4+SO42-0.8TSPNH4+(NH4)2SO4Ca2+Mg2+R=0.72 5. 2005TSPSO42-/ Ca2+13.64SO42-/ Ca2+20NO3-/SO42-0.15
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The experiments in the Cole and Moore article in the first issue of the Biophysical Journal provided the first independent experimental confirmation of the Hodgkin-Huxley (HH) equations. A log-log plot of the K current versus time showed that raising the HH variable n to the sixth power provided the best fit to the data. Subsequent simulations using n(6) and setting the resting potential at the in vivo value simplifies the HH equations by eliminating the leakage term. Our article also reported that the K current in response to a depolarizing step to ENa was delayed if the step was preceded by a hyperpolarization. While the interpretation of this phenomenon in the article was flawed, subsequent simulations show that the effect completely arises from the original HH equations.
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Neuropeptide F is the most abundant neuropeptide in parasitic flatworms and is analogous to vertebrate neuropeptide Y. This paper examines the effects of neuropeptide F on tetrathyridia of the cestode Mesocestoides vogae and provides preliminary data on the signalling mechanisms employed. Neuropeptide F ( greater than or equal to 10 muM) had profound excitatory effects on larval motility in vitro. The effects were insensitive to high concentrations (I mM) of the anaesthetic procame hydrochloride suggesting extraneuronal sites of action. Neuropeptide F activity was not significantly blocked by a FMRFamide-related peptide analog (GNFFRdFamide) that was found to inhibit GNFFRFamide-induced excitation indicating the occurrence of distinct neuropeptide F and FMRFamide-related peptide receptors. Larval treatment with guanosine 5'-O-(2-thiodiphosphate) trilithium salt prior to the addition of neuropeptide F completely abolished the excitatory effects indicating the involvement of G-proteins and a G-protein coupled receptor in neuropeptide F activity. Addition of guanosine 5'-O-(2-thiodiphosphate) following neuropeptide F had limited inhibitory effects consistent with the activation of a signalling cascade by the neuropeptide. With respect to Ca2+ involvement in neuropeptide F-induced excitation of M. vogae larvae, the L-type Ca2+-channel blockers verapamil and nifedipine both abolished neuropeptide F activity as did high Mg+ concentrations and drugs which blocked sarcoplasmic reticulum Ca2+-activated Ca2+-channels (ryanodine) and sarcoplasmic reticulum Ca2+ pumps (cyclopiazonic acid). Therefore, both extracellular and intracellular Ca2+ is important for neuropeptide F excitation in M. vogae. With resepct to second messengers, the protein kinase C inhibitor chelerythrine chloride and the adenylate cyclase inhibitor MDL-2330A both abolished neuropeptide F-induced excitation. The involvement of a signalling pathway that involves protein kinase C was further supported by the fact that phorbol-12-myristate-13-acetate,known to directly activate protein kinase C, had direct excitatory effects on larval motility. Although neuropeptide F is structurally analogous to neuropeptide Y, its mode-of-action in flatworms appears quite distinct from the common signalling mechanism seen in vertebrates. (C) 2003 on behalf of Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.
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Les mcanismes cellulaires et molculaires qui sous-tendent la mmoire et lapprentissage chez les mammifres sont incompltement compris. Le rythme thta de lhippocampe constitue ltat en ligne de cette structure qui est cruciale pour la mmoire dclarative. Dans la rgion CA1 de lhippocampe, les interneurones inhibiteurs LM/RAD dmontrent des oscillations de potentiel membranaire (OPM) intrinsques qui pourraient se rvler importantes pour la gnration du rythme thta. Des travaux prliminaires ont suggr que le courant K+ I(A) pourrait tre impliqu dans la gnration de ces oscillations. Nanmoins, peu de choses sont connues au sujet de lidentit des sous-units protiques principales et auxiliaires qui soutiennent le courant I(A) ainsi que lampleur de la contribution fonctionnelle de ce courant K+ dans les interneurones. Ainsi, cette thse de doctorat dmontre que le courant I(A) soutient la gnration des OPM dans les interneurones LM/RAD et que des protines Kv4.3 forment des canaux qui contribuent ce courant. De plus, elle approfondit les connaissances sur les mcanismes qui rgissent les interactions entre les sous-units principales de canaux Kv4.3 et les protines accessoires KChIP1. Finalement, elle rvle que la protine KChIP1 module le courant I(A)-Kv4.3 natif et la frquence de dcharge des potentiels daction dans les interneurones. Nos travaux contribuent lavancement des connaissances dans le domaine de la modulation de lexcitabilit des interneurones inhibiteurs de lhippocampe et permettent ainsi de mieux saisir les mcanismes qui soutiennent la fonction de lhippocampe et possiblement la mmoire chez les mammifres.
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Laire tegmentaire ventrale (VTA) contient une forte densit de terminaisons neurotensinergiques ainsi que des rcepteurs la surface des neurones dopaminergiques et non-dopaminergiques. Le VTA a t impliqu dans des maladies comme la schizophrnie, les psychoses et labus de substance. Les drogues dabus sont connues pour induire le phnomne de sensibilisation - un processus de facilitation par lequel lexposition un stimulus produit une rponse augmente lors de lexposition subsquente au mme stimulus. La sensibilisation se dveloppe dans le VTA et implique mcanismes dopaminergiques et glutamatergiques. Il a t montr que les antagonistes neurotensinergiques bloquaient le dveloppement de la sensibilisation et certains mcanismes de rcompense et ces effets pourraient tre mdis indirectement par une modulation de la neurotransmission glutamatergique. Cependant, on connat peu les mcanismes de modulation de la transmission glutamatergique par la neurotensine (NT) dans le VTA. Le but de la prsente thse tait dtudier la modulation neurotensinergique de la neurotransmission glutamatergique dans les neurones dopaminergiques et non-dopaminergiques du VTA. Pour ce faire, nous avons utilis la technique du patch clamp dans la cellule entire dans des tranches horizontales du VTA pour tudier les effets de diffrents agonistes et antagonistes neurotensinergiques. Les neurones ont t identifi comme Ih+ (prsums dopaminergiques) ou Ih- (prsums non-dopaminergiques) selon quils exprimaient ou non un courant cationique activ par lhyperpolarisation (Ih). Des techniques dimmunocytochimie ont t utilises pour marquer les neurones et vrifier leur localisation dans le VTA. Dans une premire tude nous avons trouv que la neurotensine indigne (NT1-13) ou son fragment C-terminal, NT8-13, induisait une augmentation comparable des courants postsynaptiques excitateurs glutamatergiques (CPSEs) dans les neurones Ih+ ou Ih- du VTA. L'augmentation induite dans les neurones Ih+ par la NT8-13 a t bloque par le SR48692, un antagoniste des rcepteurs NTS1, et par le SR142948A, un antagoniste des rcepteurs NTS1 et NTS2, suggrant que l'augmentation tait mdie par lactivation des rcepteurs NTS1. Dans les neurones Ih- l'augmentation na t bloque que par le SR142948A indiquant une implication des rcepteurs NTS2. Dans une deuxime tude, nous avons test les effets de la D-Tyr[11]NT (un analogue neurotensinergique ayant diffrentes affinits de liaison pour les sous-types de rcepteurs neurotensinergiques) sur les CPSEs glutamatergiques dans les neurones Ih+ et Ih- en parallle avec une srie dexpriences comportementales utilisant un paradigme de prfrence de place conditionne (PPC) mene dans le laboratoire de Pierre-Paul Rompr. Nous avons constat que la D-Tyr[11]NT induisaient une inhibition dpendante de la dose dans les neurones Ih+ mdie par l'activation de rcepteurs NTS2. En revanche, la D-Tyr[11]NT a produit une augmentation des CPSEs glutamatergiques mdie par des rcepteurs NTS1 dans les neurones Ih-. Les rsultats des expriences comportementales ont montr que des microinjections bilatrales de D-Tyr[11]NT dans le VTA induisait une PPC bloque uniquement par la co-injection de SR142948A et SR48692, indiquant un rle pour les deux types de rcepteurs, NTS1 et NTS2. Cette tude nous a permis de conclure que i) la D-Tyr[11]NT agit dans le VTA via des rcepteurs NTS1 et NTS2 pour induire un effet de rcompense et ii) que cet effet est d, au moins en partie, une augmentation de la neurotransmission glutamatergique dans les neurones non-dopaminergiques (Ih-). Dans une troisime tude nous nous sommes intresss aux effets de la D-Tyr[11]NT sur les rponses isoles mdies par les rcepteurs N-mthyl-D-aspartate (NMDA) et acide -amino-3- hydroxy-5-mthyl-4-isoxazolepropionique (AMPA) dans les neurones du VTA. Nous avons constat que dans les neurones Ih+ lamplitude des CPSEs NMDA et AMPA taient attnues de la mme manire par la D-Tyr[11] NT. Cette modulation des rponses tait mdie par les rcepteurs NTS1 et NTS2. Au contraire, dans les neurones Ih-, lamplitude des rponses NMDA et AMPA taient augmentes en prsence de D-Tyr[11]NT et ces effets dpendaient de lactivation des rcepteurs NTS1 localiss sur les terminaisons glutamatergiques. Ces rsultats fournissent une preuve supplmentaire que le NT exerce une modulation bidirectionnelle sur la neurotransmission glutamatergique dans les neurones du VTA et met en vidence un nouveau type de modulation peptidergique des neurones non-dopaminergiques qui pourrait tre impliqu dans la sensibilisation. En conclusion, la modulation neurotensinergique de la neurotransmission glutamatergique dans les neurones dopaminergiques et non-dopaminergiques du VTA se fait en sens oppos soit, respectivement, par une inhibition ou par une excitation. De plus, ces effets sont mdis par diffrents types de rcepteurs neurotensinergiques. En outre, nos tudes mettent en vidence une modulation peptidergique de la neurotransmission glutamatergique dans le VTA qui pourrait jouer un rle important dans les mcanismes de lutte contre la toxicomanie.
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El propsito de este estudio es determinar la relacin entre la exposicin ocupacional y los niveles de audicin en trabajadores urbanos en espacio abierto (aseo urbano en general). Se realiz un estudio de corte transversal con 491 personas que incluyen hombres y mujeres, cuyo ambiente laboral es el espacio abierto de la ciudad. Los datos se obtuvieron durante los exmenes mdicos peridicos realizados en el ao 2014 a los empleados de una empresa cuya actividad econmica es el aseo urbano, que incluye recoleccin de basuras, cuidado forestal y de prados de uso comn, y limpieza del borde de los andenes. Se realiz estadstica descriptiva para las caractersticas demogrficas y razn de disparidad u Odds Ratio (OR) para buscar la relacin de antecedentes y hbitos personales con el riesgo de desarrollar prdida auditiva. De las 491 personas expuestas a niveles altos de ruido ocupacional, 62% present prdida auditiva, de los cuales la mayora se desempea como guadaadores y cortadores de csped, y son personas que llevan trabajando entre 1-5 aos en la empresa. Se encontr un aumento estadsticamente significativo entre la baja escolaridad y el riesgo de sufrir hipoacusia (p=0.0001) y un efecto protector del uso de motocicleta y audfonos. La enfermedad vascular perifrica, la prctica de tejo y la diabetes mostraron una fuerte tendencia a aumentar el riesgo. La prdida auditiva encontrada en este grupo no se puede relacionar directamente con la exposicin ocupacional a ruido, a pesar de ser trabajos que se llevan a cabo en el espacio urbano. Sin embargo, la baja escolaridad favorece la lesin auditiva y puede verse acelerada por enfermedades de alta prevalencia como diabetes y practicas recreacionales locales.
