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- Li, Lizhen, 1977, et al.
(författare)
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Protective role of reactive astrocytes in brain ischemia.
- 2008
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Ingår i: Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 0271-678X .- 1559-7016. ; 28:3, s. 468-81
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Tidskriftsartikel (refereegranskat)abstract
- Reactive astrocytes are thought to protect the penumbra during brain ischemia, but direct evidence has been lacking due to the absence of suitable experimental models. Previously, we generated mice deficient in two intermediate filament (IF) proteins, glial fibrillary acidic protein (GFAP) and vimentin, whose upregulation is the hallmark of reactive astrocytes. GFAP(-/-)Vim(-/-) mice exhibit attenuated posttraumatic reactive gliosis, improved integration of neural grafts, and posttraumatic regeneration. Seven days after middle cerebral artery (MCA) transection, infarct volume was 210 to 350% higher in GFAP(-/-)Vim(-/-) than in wild-type (WT) mice; GFAP(-/-), Vim(-/-) and WT mice had the same infarct volume. Endothelin B receptor (ET(B)R) immunoreactivity was strong on cultured astrocytes and reactive astrocytes around infarct in WT mice but undetectable in GFAP(-/-)Vim(-/-) astrocytes. In WT astrocytes, ET(B)R colocalized extensively with bundles of IFs. GFAP(-/-)Vim(-/-) astrocytes showed attenuated endothelin-3-induced blockage of gap junctions. Total and glutamate transporter-1 (GLT-1)-mediated glutamate transport was lower in GFAP(-/-)Vim(-/-) than in WT mice. DNA array analysis and quantitative real-time PCR showed downregulation of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of tissue plasminogen activator. Thus, reactive astrocytes have a protective role in brain ischemia, and the absence of astrocyte IFs is linked to changes in glutamate transport, ET(B)R-mediated control of gap junctions, and PAI-1 expression.
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| 5. |
- Eriksson, Maja, 1975, et al.
(författare)
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Comparing mono- and divalent DNA groove binding cyanine dyes--Binding geometries, dissociation rates, and fluorescence properties
- 2006
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Ingår i: Biophysical Chemistry. - : Elsevier BV. - 1873-4200 .- 0301-4622. ; 122:3, s. 195-205
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Tidskriftsartikel (refereegranskat)abstract
- The unsymmetrical cyanine dyes BOXTO-PRO and BOXTO-MEE were derived from the DNA groove binder BOXTO, by adding a positively charged or a non-ionic hydrophilic tail to BOXTO, respectively. The main objective was to obtain more efficient DNA probes, for instance in electrophoresis and microscopy, by slowing down the dissociation of BOXTO from DNA. The interactions with mixed sequence DNA was studied with fluorescence and absorbance spectroscopy, stopped-flow dissociation and gel electrophoresis. Both the derivatives are groove bound as BOXTO, and have similar fluorescence properties when bound to mixed sequence DNA in free solution. BOXTO-PRO exhibits a slower dissociation than BOXTO from DNA, whereas the dissociation rate for BOXTO-MEE is faster and, unexpectedly independent of the ionic strength. During gel electrophoresis both BOXTO-PRO and BOXTO-MEE exhibit a faster dissociation rate than BOXTO. Still, BOXTO-PRO seems to be a good alternative as DNA probe, especially for applications in free solution where the dissociation is slower than for the corresponding intercalator TOPRO-1.
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| 6. |
- Hellberg, Fredrik, 1975-
(författare)
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Investigations of the breakup dynamics of small molecular ions recombining with electrons
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dissociative recombination is the process in which a molecular ion recombines with an electron and then fragments into neutral products. This process has been studied in many experiments over the years at the ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm University. In this thesis the experimental methods and data analysis procedures used to investigate dissociative recombination are presented together with the results for several diatomic and triatomic ions. Cross sections and branching fractions of the different breakup channels have been determined. An imaging system was introduced to study the fragmentation channels in detail. The main focus is on the dynamics of the three-body breakup of triatomic dihydride ions. This work includes the results from the dissociative recombination of NO+, SH2+, SD2+, PD2+, NH2+, CH2+, H2O+ and H3+.
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| 8. |
- Holmström, Andreas, 1978, et al.
(författare)
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Efficient Space-time FE for a Simplified Thermo-metallurgical Problem Relevent to Casting
- 2005
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Ingår i: Computational Methods for Coupled Problems in Science and Engineering, COUPLED PROBLEMS 2005 Santorini Island, Greece, May 25-27, 2005. - 8495999714 ; , s. 227-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Solving the non-linear thermo-metallurgical problem such as the thermal cooling of a molten metal or the macro-segregation during a cooling process are problems that needs careful consideration. The strong non-linearities of the problem makes it difficult to solve without having a prohibitive high cost arising from the high spatial and time-domain discretization needed to solve the problem. For the studied application of design optimization of cast components a low computational time is important since a lot of computations are necessary in an optimization.From the first law of thermodynamics we derive a space-timeFE-discretization for a hierarchy of discontinuous Galerkin in time, dG(k) k>=0. This formulation integratesthe stored energy exact. As a special case we regain theenthalpy-method with suitable average of the energygeneration over time.For the macro-segregation, the problem is reformulated so that the phase-transition drives a flow of species. Diffusion is possible throughout the domain in this model. This can then be further rewritten using a potential approach. We can by this aproch arrive in discretizations that guaranties that the balance equation is satisfied and can solve phase-transition problem as a fieldproblem or as a local problem.The coupled problems of cooling-transformation are solved. The possibility of using adaptivity in space-time for the coupled problem is discussed.
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| 10. |
- Holmström, Andreas, 1978, et al.
(författare)
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Optimization of Cast Components in the Development Process
- 2005
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Ingår i: WCSMO6- 6th World Congress on Structural and Multidisciplinary Optimization, Rio de Janeiro, 30 May-3 June, 2005. ; , s. 26-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In structural optimization, we wish to design a component such that we fulfill a set of functional requirements while minimizing, for instance, the cost or weight of a component. Here we focus on the optimization of cast components in trucks. Of the functional requirements, several are related to strength issues. For a cast component, the resulting mechanical behavior depends on the casting process, and it must be taken into account that strong couplings exist between the geometry, the production process and the material properties. As a result, one is faced with a complex multidisciplinary optimization problem.In this contribution, a generic process for optimizing complex multi-physics problems is presented using a succession of more and more complex analyzes. The strategy that we propose is to use low level analyzes to scan a large number of different solutions in order to find the most viable ones. These are then further narrowed down during a chain of analyzes with successively higher level of detail, while trying not to remove good solutions. During the very latest stages of the analysis, only a few solutions are considered, and therefore, more time and resource consuming analyzes can be used in order to fully investigate the properties of the component.A principal problem of a cast component is discussed for a given a set of mechanical load demands and with consideration to the production process in order to exemplify the process and some possible pitfalls. The explicit computational procedure, based on FE-analysis, is applied to a simplified mechanical and thermal problems involved in the casting of a typical load-bearing structural component.
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