| 11. |
- Rupert, A. E., et al.
(författare)
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Assessment of tissue viability following electroosmotic push-pull perfusion from organotypic hippocampal slice cultures
- 2013
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Ingår i: ACS Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 4:5, s. 849-857
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a novel sampling technique that allows both introduction and removal of fluid from the extracellular space of living tissue. This method is based on the fluidics of push-pull perfusion but flow is driven by electroosmosis. We have applied this method to organotypic hippocampal cultures. A source capillary is inserted into the tissue and a collection capillary is in contact with the tissue surface through a thin layer of fluid. A voltage is applied across the proximal ends of source and collection capillary. In the applied field, fluid will move from source, into the tissue, and then be collected. In this process, damage to cells may occur. To understand better what sampling conditions influence damage most, we tested various sampling geometries and applied voltages, quantifying damage 16-24 h later using propidium iodide as a cell death marker. We found that damage correlates with both voltage drop and power dissipated in the tissue, but that voltage drop is a better indicator of damage when comparing models in which capillary arrangement and length are different. © 2013 American Chemical Society.
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| 12. |
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| 13. |
- Sandberg, Mats, 1953, et al.
(författare)
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NRF2-regulation in brain health and disease: Implication of cerebral inflammation
- 2014
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Ingår i: Neuropharmacology. - : Elsevier BV. - 0028-3908. ; 79, s. 298-306
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Tidskriftsartikel (refereegranskat)abstract
- The nuclear factor erythroid 2 related factor 2 (NRF2) is a key regulator of endogenous inducible defense systems in the body. Under physiological conditions NRF2 is mainly located in the cytoplasm. However, in response to oxidative stress, NRF2 translocates to the nucleus and binds to specific DNA sites termed "anti-oxidant response elements"or "electrophile response elements"to initiate transcription of cytoprotective genes. Acute oxidative stress to the brain, such as stroke and traumatic brain injury is increased in animals that are deficient in NRF2. Insufficient NRF2 activation in humans has been linked to chronic diseases such as Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis. New findings have also linked activation of the NRF2 system to anti-inflammatory effects via interactions with NF-κB. Here we review literature on cellular mechanisms of NRF2 regulation, how to maintain and restore NRF2 function and the relationship between NRF2 regulation and brain damage. We bring forward the hypothesis that inflammation via prolonged activation of key kinases (p38 and GSK-3β) and activation of histone deacetylases gives rise to dysregulation of the NRF2 system in the brain, which contributes to oxidative stress and injury. © 2013 Elsevier B.V. All rights reserved.
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| 14. |
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| 15. |
- Taghi, Karimipanah, 1953-, et al.
(författare)
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The confinement effects on jet kinetic momentum flux quantified by measuring the reaction force
- 2014
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Ingår i: The International Journal of Ventilation. - 1473-3315 .- 2044-4044. ; 13:3, s. 285-298
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Tidskriftsartikel (refereegranskat)abstract
- A turbulent jet is the most important flow element in mechanical ventilation. Mixing ventilation is basedon the properties of turbulent jets. By entrainment into the jet the ambient air is set into motion. For ajet supplied within a room the enclosure may affect the jet in several ways, through: a) Coanda effect which is the tendency of a fluid to be attracted to a nearby surface. A free jet is turned into a wall jet and the momentum flux of the jet decreases by friction against the room surfaces.b) The jet collides with the opposing wall and the jet is transformed into a wall jet. c) The size of the cross sectional area relative to the supply opening will affect the flow pattern withinthe enclosure. One can expect the direction of the inflow (entrainment) to the jet to be affected. d) Location of supply and extract. The location of the supply is a factor that influences the pressure gradient within the room. This paper considers the items b), c) and d). The main characteristic of a jet is its momentum flux, but determining the momentum flux is not an easy task and has lead to contradicting results. Standard methods require velocity field measurements which have their restrictions and uncertainties. To overcome these problems a direct and more reliable method was used by recording the flow force, caused by an impinging jet, with a digital balance. Thetests were carried out both for unenclosed (free jet) and enclosed cases. In the latter case tests were conducted with supply and extract both located on the same wall and located on opposite walls. Detailed pressure measurements were conducted to describe the details of the reaction force. There was a clear effect of the confinement on the reaction force and a Reynolds number dependence.
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| 16. |
- Wu, J. F., et al.
(författare)
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Integrated Electroosmotic Perfusion of Tissue with Online Microfluidic Analysis to Track the Metabolism of Cystamine, Pantethine, and Coenzyme A
- 2013
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 85:24, s. 12020-12027
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an approach that integrates electroosmotic perfusion of tissue with a substrate-containing solution and online microfluidic analysis of products, in this case thiols. Using this approach we have tracked the metabolism of cystamine, pantethine and CoA in the extracellular space of organotypic hippocampal slice cultures (OHSCs). Currently, little is known about coenzyme A (CoA) biodegradation and even less is known about the regulation and kinetic characteristics for this sequential multienzyme reaction. We found that the steady state percentage yields of cysteamine from cystamine and pantethine during the transit through OHSCs were 91% +/- 4% (SEM) and 0.01% - 0.03%, respectively. The large difference in the yields of cysteamine can be used to explain the drugs' different toxicities and clinical effectiveness against cystinosis. The kinetic parameters of the enzyme reaction catalyzed by the ectoenzyme pantetheinase are K-M,K-C/alpha = 4.4 +/- 1.1 mM and V-max,V-C = 29 +/- 3 nM/s, where alpha is the percentage yield of pantethine to pantetheine through disulfide exchange. We estimate that the percentage yield of pantethine to pantetheine through disulfide exchange is approximately 0.5%. Based on the formation rate of cysteamine in the OHSCs, we obtained the overall apparent Michaelis constant and maximum reaction rate for sequential, extracellular CoA degradation in an in situ environment, which are K'(M) = 16 +/- 4 mu M, V'(max) = 7.1 +/- 0.5 nM/s. Kinetic parameters obtained in situ, although difficult to measure, are better representations of the biochemical flux in the living organism than those from isolated enzymes in vitro.
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| 17. |
- Xu, Hongjuan, et al.
(författare)
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Electroosmotic sampling. Application to determination of ectopeptidase activity in organotypic hippocampal slice cultures.
- 2010
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Ingår i: Analytical chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 82:15, s. 6377-83
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Tidskriftsartikel (refereegranskat)abstract
- We hypothesize that peptide-containing solutions pulled through tissue should reveal the presence and activity of peptidases in the tissue. Using the natural zeta-potential in the organotypic hippocampal slice culture (OHSC), physiological fluids can be pulled through the tissue with an electric field. The hydrolysis of the peptides present in the fluid drawn through the tissue can be determined using capillary HPLC with electrochemical detection of the biuret complexes of the peptides following a postcolumn reaction. We have characterized this new sampling method by measuring the flow rate, examining the use of internal standards, and examining cell death caused by sampling. The sampling flow rate ranges from 60 to 150 nL/min with a 150 microm (ID) sampling capillary with an electric field (at the tip of the capillary) from 30 to 60 V/cm. Cell death can be negligible with controlled sampling conditions. Using this sampling approach, we have electroosmotically pulled Leu-enkephalin through OHSCs to identify ectopeptidase activity in the CA3 region. These studies show that a bestatin-sensitive aminopeptidase may be critical for the hydrolysis of exogenous Leu-enkephalin, a neuropeptide present in the CA3 region of OHSCs.
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