| 1. |
- Stubberud, Karin, et al.
(författare)
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Partial filling micellar electrokinetic chromatography optimisation studies of ibuprofen, codeine and degradation products, and coupling to mass spectrometry : Part I
- 2002
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Ingår i: Electrophoresis. - 0173-0835 .- 1522-2683. ; 23:4, s. 572-577
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Tidskriftsartikel (refereegranskat)abstract
- Studies have been performed to evaluate whether an on-line partial filling-micellar electrokinetic chromatography (PF-MEKC) system could be applied to a recently developed MEKC method for the separation of ibuprofen, codeine and one of the degradation products. Attempts to couple the PF-MEKC system to MS have also been performed. SDS concentration, micellar zone length and concentration of acetonitrile in the buffer were optimized using factorial design. When a small micelle zone was injected directly after the sample introduction, the results improved markedly. The MS parameters have not been optimized, but the studies show promising results for the use of PF-MEKC-mass spectrometry for identification of the degradation products.
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| 2. |
- Enarsson, Maria, et al.
(författare)
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Extracellular signal-regulated protein kinase signaling is uncoupled from initial differentiation of central nervous system stem cells to neurons
- 2002
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Ingår i: Molecular Cancer Research. - 1541-7786 .- 1557-3125. ; 1:2, s. 147-154
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge about signaling pathways in response to external signals is needed to understand the regulation of stem cell proliferation and differentiation toward particular cell fates. The Ras/extracellular signal-regulated kinase (ERK) pathway has been suggested to play an essential role in neuronal differentiation. We have examined ERK signaling in the transition from multipotent stem cell to post-mitotic progeny using primary stem cells from the rat embryonic cortex. Fibroblast growth factor-2 (FGF-2) is a stem cell mitogen, whereas platelet-derived growth factor AA (PDGF-AA) expands a pool of committed neuronal precursors from stem cells. When comparing ERK activation by these growth factors, we found that FGF-2 stimulates high and PDGF-AA lower levels of ERK phosphorylation in stem cells. Differentiation was monitored as down-regulation of the bHLH transcription factor mammalian achaete-scute homologue-1 (MASH1). Even in the absence of active ERK, MASH1 became down-regulated and microtubule-associated protein 2-positive cells could form. Thus, ERK activation seems dispensable for the earliest steps of CNS stem cell differentiation.
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| 3. |
- Erlandsson, Anna, et al.
(författare)
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Immature neurons from CNS stem cells proliferate in response toplatelet-derived growth factor
- 2001
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Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 21:10, s. 3483-3491
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Tidskriftsartikel (refereegranskat)abstract
- Identifying external signals involved in the regulation of neural stem cell proliferation and differentiation is fundamental to the understanding of CNS development. In this study we show that platelet-derived growth factor (PDGF) can act as a mitogen for neural precursor cells. Multipotent stem cells from developing CNS can be maintained in a proliferative state under serum-free conditions in the presence of fibroblast growth factor-2 (FGF2) and induced to differentiate into neurons, astrocytes, and oligodendrocytes on withdrawal of the mitogen. PDGF has been suggested to play a role during the differentiation into neurons. We have investigated the effect of PDGF on cultured stem cells from embryonic rat cortex. The PDGF alpha-receptor is constantly expressed during differentiation of neural stem cells but is phosphorylated only after PDGF-AA treatment. In contrast, the PDGF beta-receptor is hardly detectable in uncommitted cells, but its expression increases during differentiation. We show that PDGF stimulation leads to c-fos induction, 5'-bromo-2'deoxyuridine incorporation, and an increase in the number of immature cells stained with antibodies to neuronal markers. Our findings suggest that PDGF acts as a mitogen in the early phase of stem cell differentiation to expand the pool of immature neurons.
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| 4. |
- Erlandsson, Anna, 1973-
(författare)
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Neural Stem Cell Differentiation and Migration
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Neural stem cells are the precursors of neurons, astrocytes and oligodendrocytes. During neural development, the division of stem cells takes place close to the lumen of the neural tube, after which they migrate to their final positions within the central nervous system (CNS). Soluble factors, including growth factors, regulate neural stem cell proliferation, survival, migration and differentiation towards specific cell lineages.This thesis describes the function of platelet-derived growth factor (PDGF) and stem cell factor (SCF) in neural stem cell regulation. PDGF was previously suggested to stimulate neuronal differentiation, but the mechanisms were not defined. This study shows that PDGF is a mitogen and a survival factor that expands a pool of immature cells from neural stem cells. The PDGF-treated cells can be stained by neuronal markers, but need further stimuli to continue their maturation. They can become either neurons or glia depending on the secondary instructive cues. Moreover, neural stem cells produce PDGF. Inhibition of this endogenous PDGF negatively affects the cell number in stem cell cultures. We find that SCF stimulates migration and supports the survival of neural stem cells, but that it has no effect on their proliferation or differentiation into neurons and glia. Intracellular signaling downstream from the receptors for PDGF and SCF includes activation of extracellular signal-regulated kinase (ERK). This investigation shows that active ERK is not needed for the differentiation of stem cells into neurons, at least not during early stages.Neural stem cells have a future potential in the treatment of CNS disorders. To be able to use neural stem cells clinically we need to understand how their proliferation, differentiation, survival and migration are controlled. The results presented in this thesis increase our knowledge of how neural stem cells are regulated by growth factors.
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| 5. |
- Erlandsson, Anna, et al.
(författare)
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Stem cell factor is a chemoattractant and a survival factor for CNS stem cells
- 2004
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827 .- 1090-2422. ; 301:2, s. 201-210
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Tidskriftsartikel (refereegranskat)abstract
- Migration of neural cells to their final positions is crucial for the correct formation of the central nervous system. Several extrinsic factors are known to be involved in the regulation of neural migration. We asked if stem cell factor (SCF), well known as a chemoattractant and survival factor in the hematopoietic lineage, could elicit similar responses in neural stem cells. For that purpose, a microchemotaxis assay was used to study the effect of SCF on migration of neural stem cells from the embryonic rat cortex. Our results show that SCF-induced chemotaxis and that specific antibodies to SCF or tyrosine kinase inhibitors abolished the migratory response. The SCF-receptor, Kit, was expressed in neural stem cells and in their differentiated progeny. We also show that SCF is a survival factor, but not a mitogen or a differentiation factor for neural stem cells. These data suggest a role for SCF in cell migration and survival in the developing cortex.
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| 6. |
- Forsberg-Nilsson, Karin, et al.
(författare)
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Oligodendrocyte precursor hypercellularity and abnormal retina development in mice overexpressing PDGF-B in myelinating tracts
- 2003
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Ingår i: Glia. - : Wiley. - 0894-1491 .- 1098-1136. ; 41:3, s. 276-89
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Tidskriftsartikel (refereegranskat)abstract
- Platelet-derived growth factor (PDGF) influences the generation of neurons and glia during embryogenesis and in early postnatal life. In an attempt to determine the consequences of an overexpression of PDGF-B during the first weeks of life, we targeted transgenic expression of a human PDGF-B cDNA to myelinating tracts using the promoter region of the myelin basic protein (MBP) gene. Transgenic mRNA and protein were expressed in the brain and the expression profile of the human PDGF-B during early postnatal development closely paralleled that of the endogenous mouse MBP gene. The gross morphological appearance of transgenic brains was normal but at the cellular level several phenotypic alterations could be identified. In white matter tracts such as the corpus callosum and cerebellar medulla, there was a marked hypercellularity. The number of oligodendrocyte precursors was increased and astrocytes were more abundant. In adult mice carrying the MBP-PDGF-B transgene, however, myelination appeared normal and the amount of oligodendrocytes was similar to that of control littermates. In addition to the phenotypic alterations in the brain, investigation of eye structure revealed a striking disorganization of retinal architecture. The retina was folded with cells collected in papillar or follicular-like structures. Retinal whole mount preparations after India ink perfusion revealed capillary disorganization with large-caliber vessels supporting only a few fine branches. Our observations strengthen the notion that PDGF is an important effector molecule in postnatal CNS development.
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| 7. |
- Gäbel, Karin, 1969, et al.
(författare)
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The design and building of a lifecycle-based process model for simulating environmental performance, product performance and cost in cement manufacturing
- 2004
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Ingår i: Journal of Cleaner Production. - 0959-6526. ; 12:1, s. 77-93
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Tidskriftsartikel (refereegranskat)abstract
- State of the art lifecycle inventory (LCI) models are typically used to relate resource use and emissions to manufacturing and use of a certain product. Corresponding software tools are generally specialised to perform normalisation of the flows to the functional unit. In some cases it is, however, desirable to make use of the LCI model for other types of environmental assessments. In this paper, an alternative modelling technique resulting in a more flexible model is investigated. We exemplify the above by designing and building a model of a cement plant. The commissioner's, in this case Cementa AB's, requirements on a flexible model that generates information on environmental performance, product performance and the economic cost were seen as important. The work reported here, thus, has two purposes: on the one hand, to explore the possibility of building more flexible LCI models, and on the other hand, to provide the commissioner with a model that fulfils their needs and requirements. Making use of a calculational a-causal and object-oriented modelling approach satisfied the commissioner's special requirements on flexibility in terms of modularity and the types of calculations it was possible to perform. In addition, this model supports non-linear and dynamic elements for future use. The result is a model that can be used for a number of purposes, such as assessment of cement quality and environmental performance of the process using alternative fuels. It is also shown that by using the above modelling approach, flexibility and modularity can be greatly enhanced. © 2003 Elsevier Science Ltd. All rights reserved.
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| 8. |
- Göktürk, Camilla, et al.
(författare)
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Semicarbazide-sensitive amine oxidase in transgenic mice with diabetes
- 2004
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 325:3, s. 1013-1020
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Tidskriftsartikel (refereegranskat)abstract
- Semicarbazide-sensitive amine oxidase (SSAO) activity in plasma is increased in diabetes, and in particular, in diabetic patients with vascular complications. It has been speculated that SSAO is involved in the development of such complications due to the production of cytotoxic compounds. In this work, we have induced diabetes in a previously described mouse-model, overexpressing SSAO in smooth muscle cells. SSAO activity was estimated as well as expression of the endogenous mouse gene and human transgene using real-time PCR. Diabetes induced an increase in SSAO activity in serum, kidney, and adipose tissue of transgenic animals. An inverse correlation between SSAO activity and mouse SSAO mRNA levels was observed in transgenic animals with diabetes. These results further support the suggestion of a negative feedback control of the SSAO gene expression. The increased SSAO activity in diabetes is most likely dependent on post-transcriptional modifications or activation of existing inactive enzyme molecules.
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| 9. |
- Göktürk, Camilla, 1967-
(författare)
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Semicarbazide-sensitive Amine Oxidase (SSAO) – Regulation and Involvement in Blood Vessel Damage with Special Regard to Diabetes : A Study on Mice Overexpressing Human SSAO
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Semicarbazide-sensitive amine oxidase (SSAO, EC 1.4.3.6) belongs to a family of copper-containing amine oxidases. SSAO exists as a membrane bound protein in endothelial-, smooth muscle-, and adipose cells as well as soluble in plasma. SSAO catalyses oxidative deamination of primary monoamines, which results in the production of corresponding aldehydes, hydrogen peroxide and ammonia. These compounds are very reactive and potentially cytotoxic, and are able to induce vascular damage if produced in high levels. Patients with diabetes mellitus, and with diabetic complications in particular, have a higher SSAO activity in plasma compared to healthy controls. It has therefore been speculated that high SSAO activity is involved in the development of vascular complications associated with diabetes. The aim of this thesis is to investigate the importance of SSAO in the development of disorders of a vascular origin. We have studied the transcriptional regulation of the SSAO gene, by inducing diabetes in NMRI and in transgenic mice, overexpressing the human form of SSAO in smooth muscle cells. We found that the increase in SSAO activity in diabetes is accompanied by reduced mRNA levels of the endogenous mouse gene, suggesting a negative feedback on the transcription of the SSAO gene. In addition, the transgenic mice exhibited an abnormal phenotype in the elastic tissue of aorta and renal artery. These mice have a lower mean artery pressure and an elevated pulse pressure. These results indicate that high SSAO activity in smooth muscle cells is associated with a change in the morphology of large arteries. This is likely contributing to the development of vascular complications in diabetes.
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| 10. |
- Håkansson, M., et al.
(författare)
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The crystal structure of staphylococcal enterotoxin H : Implications for binding properties to MHC class II and TcR molecules
- 2000
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836. ; 302:3, s. 527-537
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Tidskriftsartikel (refereegranskat)abstract
- The X-ray structure of the superantigen staphylococcal enterotoxin H (SEH) has been determined at 1.69 Å resolution. In this paper we present two structures of zinc-free SEH (apoSEH) and one zinc-loaded form of SEH (ZnSEH). SEH exhibits the conventional superantigen (SAg) fold with two characteristic domains. In ZnSEH one zinc ion per SEH molecule is bound to the C-terminal β-sheet in the region implicated for major histocompatibility complex class II (MHC class II) binding in SEA, SED and SEE. Surprisingly, the zinc ion has only two ligating amino acid residues His206 and Asp208. The other ligands to the zinc ion are two water molecules. An extensive packing interaction between two symmetry-related molecules in the crystal, 834 Å2/molecule, forms a cavity that buries the zinc ions of the molecules. This dimer-like interaction is found in two crystal forms. Nevertheless, zinc-dependent dimerisation is not observed in solution, as seen in the case of SED. A unique feature of SEH as compared to other staphylococcal enterotoxins is a large negatively charged surface close to the Zn2+ site. The interaction of SEH with MHC class II is the strongest known among the staphylococcal enterotoxins. However, SEH seems to lack a SEB-like MHC class II binding site, since the side-chain properties of structurally equivalent amino acid residues in SEH and those in SEB-binding MHC class II differ dramatically. There is also a structural flexibility between the domains of SEH. The domains of two apoSEH structures are related by a 5°rotation leading to at most 3 Å difference in C(α) positions. Since the T-cell receptor probably interacts with both domains, SEH by this rotation may modulate its binding to different TcR Vβ-chains. (C) 2000 Academic Press.
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