| 61. |
- Ansar, Saema, et al.
(författare)
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Protein kinase C inhibition prevents upregulation of vascular ET(B) and 5-HT(1B) receptors and reverses cerebral blood flow reduction after subarachnoid haemorrhage in rats.
- 2007
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Ingår i: Journal of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 1559-7016 .- 0271-678X. ; 27:1, s. 21-32
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Tidskriftsartikel (refereegranskat)abstract
- The pathogenesis of cerebral ischaemia after subarachnoid haemorrhage (SAH) still remains elusive. The purpose of the present study was to examine whether specific protein kinas C (PKC) inhibition in rats could alter the transcriptional SAH induced Endothelin (ET) type B and 5-hydroxytryptamine type 1B (5-HT1B) receptor upregulation and prevent the associated cerebral blood flow (CBF) reduction. The PKC inhibitor RO-31-7549 or vehicle was injected intracisternally after the induced SAH in rats (n = 3 to 10 in each groups for each method). The involvement of the PKC isoforms was investigated with Western blot; only PKC delta and PKC alpha subtypes were increased after SAH RO-31-7549 treatment abolished this. At 2 days after the SAH basilar and middle cerebral arteries were harvested and the contractile response to endothelin-1 (ET-1; ETA and ETB receptor agonist) and 5-carboxamidotryptamine (5-CT; 5-HT1B receptor agonist) were investigated with a myograph. The contractile responses to ET-1 and 5-CT were increased (P < 0.05) after SAH compared with sham operated rats. In parallel, the ETB and 5-HT1B receptor mRNA and protein expression were significantly elevated after SAH, as analysed by quantitative real-time polymerase chain reaction and immunohistochemistry, respectively. Administration of RO-31-7549 prevented the upregulated contraction elicited by application of ET-1 and 5-CT in cerebral arteries and kept the ETB and 5-HT1B receptor mRNA and protein levels at pre-SAH levels. Regional and global CBF evaluated by an autoradiographic technique were reduced by 60% 64% after SAH (P < 0.05) and prevented by treatment with RO-31-7549. Our study suggests that PKC plays an important role in the pathogenesis of cerebral ischaemia after SAH.
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| 62. |
- Ansar, Saema, et al.
(författare)
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Subarachnoid Hemorrhage Induces Enhanced Expression of Thromboxane A(2) Receptors in Rat Cerebral Arteries.
- 2010
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Ingår i: Brain Research. - : Elsevier BV. - 1872-6240 .- 0006-8993. ; 1316, s. 163-172
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Tidskriftsartikel (refereegranskat)abstract
- Cerebral ischemia remains the key cause of morbidity and mortality after subarachnoid hemorrhage (SAH) with a pathogenesis that is still poorly understood. The aim of the present study was to examine the involvement of thromboxane A(2) receptors (TP) in the patophysiology of cerebral ischemia after SAH in cerebral arteries. SAH was induced in rats by injecting 250 microl blood into the prechiasmatic cistern. Two days after the SAH, cerebral arteries were harvested and contractile responses to the TP receptor agonist U46619 were investigated with myographs. In addition, the contractile responses were examined after pretreatment with selective TP receptor antagonist GR3219b. The TP receptor RNA and protein levels were analyzed by quantitative real-time PCR and immunohistochemistry, respectively. The global and regional cerebral blood flows (CBF) were quantified with an autoradiographic technique. SAH resulted in enhanced contractile responses to U46619 as compared to sham. The TP receptor antagonist GR3219b abolished the enhanced contractile responses to U46619 observed after SAH. The TP receptor mRNA level was elevated after SAH as compared to sham. The level of TP receptor protein on the smooth muscle cells (SMC) was increased in SAH compared to sham, Global and regional CBF was reduced in SAH as compared to sham. The results demonstrate that SAH results in CBF reduction and this is associated with enhanced expression of TP receptors in the SMC of cerebral arteries and microvessels.
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| 63. |
- Ansar, Saema, et al.
(författare)
-
Subarachnoid hemorrhage induces upregulation of vascular receptors and reduction in rCBF via an ERKI/2 mechanism
- 2008
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Ingår i: Cerebral Vasospasm: New Strategies in Research and Treatment. - Vienna : Springer Vienna. - 0065-1419. - 9783211757178 ; 104, s. 65-67
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Konferensbidrag (refereegranskat)abstract
- Previous studies have shown that endothelin type B (ETB) and 5-hydroxytryptamine type IB (5-HTIB) receptors are upregulated following subarachnoid hemorrhage (SAH). The purpose of the present study was to test whether extracellular signal-regulated kinase (ERKI/2) inhibition could alter the degree of SAH induced receptor upregulation in addition to prevent the cerebral blood flow (CBF) reduction. The ERKI/2 inhibitor SB386023-b was injected intra cisternally in conjunction with and after the induced SAH in rats. Two days after SAH cerebral arteries were harvested and the contractile response to endothelin-1 (ET-I) and 5-carboxamidotryptamine (5-CT) were investigated with a myograph. The contractile responses to ET-I and 5-CT were increased after SAH compared to sham. Administration of SB-386023-b prevented the upregulated contraction elicited by application of ET-I and 5-CT in cerebral arteries. Regional CBF evaluated by an autoradiographic technique, revealed a reduced CBF by 50% after SAH this was prevented by treatment with SB-386023-b. The results indicate that an ERKI/2 mechanism is involved in cerebral vasospasm and ischemia associated with SAH.
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| 64. |
- Ansar, Saema, et al.
(författare)
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Subtype activation and interaction of protein kinase C and mitogen-activated protein kinase controlling receptor expression in cerebral arteries and microvessels after subarachnoid hemorrhage
- 2008
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Ingår i: Stroke: a journal of cerebral circulation. - 1524-4628. ; 39:1, s. 185-190
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Tidskriftsartikel (refereegranskat)abstract
- Background and Purpose-The pathogenesis of cerebral ischemia associated with subarachnoid hemorrhage (SAH) still remains elusive. The aim of this study was to examine the involvement of mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) subtypes in the pathophysiology of cerebral ischemia after SAH in cerebral arteries and microvessels and to examine temporal activation of the kinases. We hypothesize that treatment with a MAPK or PKC inhibitor will prevent the SAH-induced kinase activation in brain vessels. Methods-SAH was induced by injecting 250 mu L blood into the prechiasmatic cistern in the rat. The activation of different MAPK and PKC isotypes in large circle of Willis cerebral arteries and intracerebral microvessels was examined at 0, 1, 3, 6, 12, 24, and 48 hours after SAH and after intrathecal treatment with PKC or MAPK inhibitor by use of Western blot. Results-Among the 8 investigated PKC isoforms, only PKC delta was activated at 1 hour and at 48 hours, whereas PKC alpha was activated at 48 hours after SAH. For the MAPKs, there was early phosphorylation at 1 hour of extracellular signal-regulated kinase 1/2, whereas c-jun N-terminal kinase and p38 showed enhanced phosphorylation only at 48 hours after SAH. The pattern was identical in large cerebral arteries and in intracerebral microvessels. Treatment with either the PKC (RO-31-7549) or the raf (SB386023-b) inhibitor prevented the kinase activation. Conclusions-The results show that specific subtypes of the MAPK and PKC pathways are activated in cerebral arteries after SAH and the PKC and raf inhibitors are able to prevent this activation.
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| 65. |
- Ansar, Saema, et al.
(författare)
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Vasospasm - Response
- 2007
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Ingår i: Journal of Neurosurgery. - 0022-3085. ; 106:5, s. 880-880
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 66. |
- Baun, Michael, et al.
(författare)
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Pharmacological characterization and expression of VIP and PACAP receptors in isolated cranial arteries of the rat
- 2011
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Ingår i: European Journal of Pharmacology. - : Elsevier BV. - 1879-0712 .- 0014-2999. ; 670:1, s. 186-194
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Tidskriftsartikel (refereegranskat)abstract
- Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide (PACAP) are potent vasodilators in animals and humans. PACAP infusion but not VIP infusion precipitates migraine attacks in migraine patients. The vascular effects of VIP and the two varieties of PACAP (PACAP-27 and PACAP-38) were investigated versus selective antagonists in segments of rat middle cerebral arteries (MCA), basilar arteries (BA) and middle meningeal arteries (MMA) using myographs. The luminal and abluminal effects of VIP were studied using perfusion myograph. mRNA expression of the relevant receptors (VPAC(1), VPAC(2) and PAC(1)) was examined by in situ hybridization. There was no significant difference in relaxant potency of the peptides in the MCA. In BA the relaxant potency was VIP>PACAP-27 = PACAP-38. Relaxant responses were either absent or very weak in MMA. VIP was found to be somewhat more potent in BA than in the MCA. Maxadilan, a selective PAC(1)-receptor agonist, showed no relaxant effect in either vessel. The VPAC(2)-antagonist PG 99-465 alone proved ineffective in the MCA, while it had a weak effect on BA. The VPAC(1)-antagonist PG 97269 inhibited relaxation induced by both VIP and the PACAPs in cerebral vessels. In combination, the two antagonists demonstrated better effect than either alone. VIP applied luminally via perfusion myograph caused no dilatation, indicating lack of endothelial involvement. In situ hybridization demonstrated the presence of mRNA for all three receptors in the smooth muscle cells of the vessels. In conclusion, migraine-like headache induced by PACAP-38 infusion is unlikely to be caused by direct vasodilator action on intracranial vessels. (C) 2011 Elsevier B.V. All rights reserved.
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| 67. |
- Bayrak Pehlivan, Ilknur, et al.
(författare)
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Bifunctional solar electrocatalytic water splitting using CIGS solar modules and WO3-based electrolyzers
- 2019
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Ingår i: EMRS Spring Meeting 2019.
-
Konferensbidrag (refereegranskat)abstract
- Using energy from the sun to produce a fuel and finally obtaining only water as an exhaust is a promising future technology for renewable energy and environmental sustainability. Solar driven water splitting is a method to produce hydrogen from solar energy. Coupling a solar cell with an electrolyzer is the approach with highest technological readiness. CuInxGa1-xSe2 (CIGS) is here a promising solar cell material for water splitting because it is possible to tune the band gap between 1.0 and 1.7 eV by changing the ratio between Ga and In, thus enabling maximum power point matching with an electrolyzer. Tungsten oxide is known as a photocatalytic material and mainly used for the oxygen evolution reaction in a water splitting process. However, WO3 films also show electrochromic activity together with hydrogen evolution. This result is interesting because it shows that WO3 films can be used as bifunctional materials for both hydrogen and oxygen evolution in water splitting, and provide additional functionalities to the system. In this study, WO3 films coated at different sputtering conditions on Ni foam and indium tin oxide substrates were investigated in the potential range of the hydrogen evolution reaction. The best overpotential of 164 mV vs. RHE at 10 mA/cm2 was obtained for WO3 films on Ni foam in 0.5 M H2SO4. The lowest potential needed for 10 mA/cm2 was measured 1.768 V for the electrolyzers consisting WO3 films on Ni foam as the cathode and non-coated Ni foam as the anode. Optimum solar-to-hydrogen (STH) efficiency of the CIGS solar cell modules and the electrolyzers was examined for different band gaps of the CIGS modules and sputtering conditions of WO3 films. Operation points of the combined system were calculated from the intersection of the voltage-current density curves for the CIGS modules and the electrolyzers. The results showed that the detailed sputtering conditions were not very critical to obtain high STH efficiency, indicating that the system could be robust and easily manufactured. The best-matched band gap of the CIGS was 1.19 eV and the highest STH efficiency of the CIGS driven WO3-based electrolyzers was 12.98 %.
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| 68. |
- Bayrak Pehlivan, Ilknur, et al.
(författare)
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Electrochromic solar water splitting using a cathodic WO3 electrocatalyst
- 2021
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 81
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Tidskriftsartikel (refereegranskat)abstract
- Solar-driven water splitting is an emerging technology with high potential to generate fuel cleanly and sustainably. In this work, we show that WO3 can be used as a cathodic electrocatalyst in combination with (Ag,Cu) InGaSe2 solar cell modules to produce hydrogen and provide electrochromic functionality to water splitting devices. This electrochromic effect can be used to monitor the charge state or performance of the catalyst for process control or for controlling the temperature and absorbed heat due to tunable optical modulation of the electrocatalyst. WO3 films coated on Ni foam, using a wide range of different sputtering conditions, were investigated as cathodic electrocatalysts for the water splitting reaction. The solar-to-hydrogen (STH) efficiency of solar-driven water electrolysis was extracted using (Ag,Cu)InGaSe2 solar cell modules with a cell band gap varied in between 1.15 and 1.25 eV with WO3 on Ni foam-based electrolyzers and yielded up to 13% STH efficiency. Electrochromic properties during water electrolysis were characterized for the WO3 films on transparent substrate (indium tin oxide). Transmittance varied between 10% and 78% and the coloration efficiency at a wavelength of 528 nm and the overpotential of 400 mV was 40 cm(2) C-1. Hydrogen ion consumption in ion intercalation for electrochromic and hydrogen gas production for water electrolysis processes was discussed.
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| 69. |
- Bayrak Pehlivan, Ilknur, et al.
(författare)
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NiMoV and NiO-based catalysts for efficient solar-driven water splitting using thermally integrated photovoltaics in a scalable approach
- 2021
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Ingår i: iScience. - : Cell Press. - 2589-0042. ; 24:1
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a trimetallic NiMoV catalyst is developed for the hydrogen evolution reaction and characterized with respect to structure, valence, and elemental distribution. The overpotential to drive a 10 mA cm−2 current density is lowered from 94 to 78 mV versus reversible hydrogen electrode by introducing V into NiMo. A scalable stand-alone system for solar-driven water splitting was examined for a laboratory-scale device with 1.6 cm2 photovoltaic (PV) module area to an up-scaled device with 100 cm2 area. The NiMoV cathodic catalyst is combined with a NiO anode in alkaline electrolyzer unit thermally connected to synthesized (Ag,Cu) (In,Ga)Se2 ((A)CIGS) PV modules. Performance of 3- and 4-cell interconnected PV modules, electrolyzer, and hydrogen production of the PV electrolyzer are examined between 25°C and 50°C. The PV-electrolysis device having a 4-cell (A)CIGS under 100 mW cm−2 illumination and NiMoV-NiO electrolyzer shows 9.1% maximum and 8.5% averaged efficiency for 100 h operation.
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| 70. |
- Bayrak Pehlivan, Ilknur, et al.
(författare)
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Optimum Band Gap Energy of ((Ag),Cu)(InGa)Se2 Materials for Combination with NiMo–NiO Catalysts for Thermally Integrated Solar-Driven Water Splitting Applications
- 2019
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Solar-driven water splitting is considered one of the promising future routes to generate fuel in a sustainable way. A carbon-free solar fuel, molecular hydrogen, can here be produced along two different but intimately related routes, photoelectrochemical (PEC) water splitting or photovoltaic electrolysis (PV-electrolysis), where the latter builds on well-established solar cell and electrolysis materials with high efficiency. The PV-electrolysis approach is also possible to construct from an integrated PEC/PV-system avoiding dc-dc converters and enabling heat exchange between the PV and electrolyzer part, to a conventionally wired PV-electrolysis system. In either case, the operating voltage at a certain current needs to be matched with the catalyst system in the electrolysis part. Here, we investigate ((Ag),Cu)(In,Ga)Se-2 ((A)CIGS)-materials with varying Ga-content modules for combination with NiMo-NiO catalysts in alkaline water splitting. The use of (A)CIGS is attractive because of the low cost-to-performance ratio and the possibility to optimize the performance of the system by tuning the band gap of (A)CIGS in contrast to Si technology. The band gap tuning is possible by changing the Ga/(Ga + In) ratio. Optoelectronic properties of the (A)CIGS materials with Ga/(Ga + In) ratios between 0.23 and 0.47 and the voltage and power output from the resulting water splitting modules are reported. Electrolysis is quantified at temperatures between 25 and 60 degrees C, an interval obtainable by varying the thermal heat exchange form a 1-sun illuminated PV module and an electrolyte system. The band gaps of the (A)CIGS thin films were between 1.08 to 1.25 eV and the three-cell module power conversion efficiencies (PCE) ranged from 16.44% with 1.08 eV band gap and 19.04% with 1.17 eV band gap. The highest solar-to-hydrogen (STH) efficiency was 13.33% for the (A)CIGS-NiMo-NiO system with 17.97% module efficiency and electrolysis at 60 degrees C compared to a STH efficiency of 12.98% at 25 degrees C. The increase in STH efficiency with increasing temperature was more notable for lower band gaps as these are closer to the overpotential threshold for performing efficient solar-driven catalysis, while only a modest improvement can be obtained by utilizing thermal exchange for a band gap matched PV-catalysts system. The results show that usage of cost-effective and stable thin film PV materials and earth abundant catalysts can provide STH efficiencies beyond 13% even with PV modules with modest efficiency.
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