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| 2. |
- French, Roger H., et al.
(författare)
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Long range interactions in nanoscale science
- 2010
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Ingår i: Reviews of Modern Physics. - 0034-6861. ; 82:2, s. 1887-1944
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Forskningsöversikt (refereegranskat)abstract
- Our understanding of the “long range” electrodynamic, electrostatic, and polar interactions that dominate the organization of small objects at separations beyond an interatomic bond length is reviewed. From this basic-forces perspective, a large number of systems are described from which one can learn about these organizing forces and how to modulate them. The many practical systems that harness these nanoscale forces are then surveyed. The survey reveals not only the promise of new devices and materials, but also the possibility of designing them more effectively.
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| 4. |
- Krettek, Alexandra, 1968-, et al.
(författare)
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Effect of phenotype on the transcription of the genes for platelet-derived growth factor (PDGF) isoforms in human smooth muscle cells, monocyte-derived macrophages, and endothelial cells in vitro
- 1997
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - : Lippincott Williams & Wilkins. - 1079-5642 .- 1524-4636. ; 17:11, s. 2897-2903
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Tidskriftsartikel (refereegranskat)abstract
- Proliferation of arterial smooth muscle cells (ASMCs) contributes considerably to enlargement of the arterial wall during atherosclerosis. The platelet-derived growth factor (PDGF) is a well-known mitogen and chemoattractant for ASMCs. Quantitative reverse transcription-polymerase chain reaction showed that cells appearing in atherosclerotic lesions, such as ASMCs, endothelial cells, and monocytes/macrophages, expressed mRNAs for both PDGF A and B chains in vitro, with the highest expression in endothelial cells. On proliferation, ASMCs and endothelial cells upregulated PDGF A mRNA. Differentiation of macrophages increased the amount of both mRNAs. Thus, the regulation of PDGF A- and B-chain expression depends on cell types and phenotypic states of the cells, which have also been found in vivo in human atherosclerotic lesions. PDGF A can be produced as short and long isoforms. The latter binds with high affinity to glycosaminoglycans. Irrespective of phenotype, only the minor part of total PDGF A mRNA consisted of the long variant in ASMCs, while endothelial cells produced 40% of total PDGF A as the long form. The differentiation of macrophages increased the production of the long PDGF A mRNA from 10% to 40%. Thus, increasing numbers of stimulated cells in the atherosclerotic lesion may increase the transcription of PDGF isoforms, and particularly of the long PDGF A isoform. Together with increasing amounts of ASMC-derived proteoglycans in developing lesions, this may contribute to accumulation of PDGF in the arterial wall matrix, resulting in prolonged stimulation of ASMCs.
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| 5. |
- Krettek, Alexandra, 1968-, et al.
(författare)
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Expression of PDGF receptors and ligand-induced migration of partially differentiated human monocyte-derived macrophages. Influence of IFN-gamma and TGF-beta
- 2001
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Ingår i: Atherosclerosis. - : Elsevier. - 0021-9150 .- 1879-1484. ; 156:2, s. 267-275
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Tidskriftsartikel (refereegranskat)abstract
- In the early atherosclerotic lesion, monocytes accumulate at sites of inflammation and endothelial injury. Platelet-derived growth factor (PDGF), produced for example by macrophages, is a chemoattractant for smooth muscle cells and possibly also for macrophages. During early differentiation into macrophages, human monocytes (early hMDM) showed lower expression of PDGF alpha-receptor (PDGF-Ralpha) than beta-receptor (PDGF-Rbeta) mRNA. Early hMDM showed increased random motility (chemokinesis) in the presence of PDGF of the long (BB(L)) but not short (BB(S)) B-chain homodimer. Neither PDGF-AA(S) nor PDGF-AA(L) affected early hMDM motility. Since increased cytokine levels accompany inflammation, the influence of interferon-gamma (IFN-gamma) and transforming growth factor-beta (TGF-beta) on PDGF-R expression and migratory response were studied. Only PDGF-Ralpha mRNA was highly upregulated by IFN-gamma. TGF-beta only had minor effects on receptor mRNAs. Upregulation of PDGF-Ralpha levels by IFN-gamma was accompanied by significantly increased migration (chemotaxis) towards PDGF-AA(L) only. Consequently, IFN-gamma modulates PDGF-Rs expression in early hMDM and, subsequently, the chemotactic activity of PDGF-AA(L) on IFN-gamma-stimulated early hMDM. This suggests that PDGF-AA(L) may be involved in attracting activated monocytes to sites of inflammation and injury.
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| 6. |
- Krettek, Alexandra, 1968-, et al.
(författare)
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Quantitation of platelet-derived growth factor receptors in human arterial smooth muscle cells in vitro
- 1997
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - : Lippincott Williams & Wilkins. - 1079-5642 .- 1524-4636. ; 17:11, s. 2395-2404
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Tidskriftsartikel (refereegranskat)abstract
- Platelet-derived growth factor (PDGF) is suggested to play an important role in the development of atherosclerosis as a migratory and mitogenic stimulus to arterial smooth muscle cells (ASMCs). Stimulated and unstimulated ASMCs were studied with respect to PDGF receptor (PDGF-R) mRNA and protein expression. Quantitative RT-PCR was developed for simultaneous evaluation of both PDGF-R alpha and -R beta mRNA expression and a quantitative ELISA for estimation of corresponding PDGF-R subunits. On the mRNA level, the overall PDGF-R beta expression was approximately 100 times lower than that of PDGF-R alpha. Furthermore, although PDGF-R alpha mRNA levels were high irrespective of hASMC phenotype, PDGF-R beta mRNA was influenced by serum stimulation with lower copy numbers in proliferating and confluent cells compared with quiescent cells. On the protein level, quiescent hASMCs expressed 10 times more PDGF-R beta than PDGF-R alpha. Serum stimulation decreased cell surface PDGF-Rs, with most prominent loss of PDGF-R alpha (ELISA and immunohistochemistry). Our results suggest a differential regulatory pattern for PDGF-R alpha and -R beta and are compatible with the usage of alternative promoters for regulation of -R alpha expression. Further, it seems that the number of available receptor subunits is not the only determinant of variations in cell stimulation with different PDGF isoforms.
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| 7. |
- Lustig, Florentina, 1948, et al.
(författare)
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Alternative splicing determines the binding of platelet-derived growth factor (PDGF-AA) to glycosaminoglycans.
- 1996
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 35:37, s. 12077-85
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Tidskriftsartikel (refereegranskat)abstract
- We have shown previously that the platelet-derived growth factor (PDGF) and a synthetic oligopeptide, corresponding to the basic carboxyl-terminal amino acid extension of the long PDGF-A isoform, bind to heparin. Here, we have expressed the long (rA125) and the short (rA109) variants of PDGF A-chains in Escherichia coli and produced the functional homodimers. Surface plasmon resonance analyses showed that while the dimeric rA125 bound with high affinity to low molecular weight heparin, the rA109, lacking the basic extension, did not. This strongly indicated that high affinity binding is due to the carboxyl-terminal extension. Investigations of kinetics and thermodynamics suggested an allosteric binding mechanism. Thus, dimeric rA125 contains two equivalent binding sites. Following low affinity binding of heparin to one binding site, the dimer undergoes a conformational change, increasing the affinity for heparin about 40 times. This positive cooperativity requires the basic amino acid extension in both monomers of the dimeric PDGF molecule. Thermodynamics of the reaction, showing an entropy-driven endothermic process, suggest the involvement of hydrophobic interactions in this rearrangement. Three amino acids in the basic carboxyl-terminal extension were essential for the interaction: the basic residues Arg111 and Lys116, and the polar Thr125. We also found that other glycosaminoglycan species, corresponding to those produced by human arterial smooth muscle cells, bound to dimeric rA125 and that heparan sulfate showed the highest affinity.
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| 9. |
- Lustig, S, et al.
(författare)
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The impact of school-based screening on service use in adolescents at risk for mental health problems and risk-behaviour
- 2023
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Ingår i: European child & adolescent psychiatry. - : Springer Science and Business Media LLC. - 1435-165X .- 1018-8827. ; 32:9, s. 1745-1754
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Tidskriftsartikel (refereegranskat)abstract
- Early detection and intervention can counteract mental disorders and risk behaviours among adolescents. However, help-seeking rates are low. School-based screenings are a promising tool to detect adolescents at risk for mental problems and to improve help-seeking behaviour. We assessed associations between the intervention “Screening by Professionals” (ProfScreen) and the use of mental health services and at-risk state at 12 month follow-up compared to a control group. School students (aged 15 ± 0.9 years) from 11 European countries participating in the “Saving and Empowering Young Lives in Europe” (SEYLE) study completed a self-report questionnaire on mental health problems and risk behaviours. ProfScreen students considered “at-risk” for mental illness or risk behaviour based on the screening were invited for a clinical interview with a mental health professional and, if necessary, referred for subsequent treatment. At follow-up, students completed another self-report, additionally reporting on service use. Of the total sample (N = 4,172), 61.9% were considered at-risk. 40.7% of the ProfScreen at-risk participants invited for the clinical interview attended the interview, and 10.1% of subsequently referred ProfScreen participants engaged in professional treatment. There were no differences between the ProfScreen and control group regarding follow-up service use and at-risk state. Attending the ProfScreen interview was positively associated with follow-up service use (OR = 1.783, 95% CI = 1.038–3.064), but had no effect on follow-up at-risk state. Service use rates of professional care as well as of the ProfScreen intervention itself were low. Future school-based interventions targeting help-seeking need to address barriers to intervention adherence.Clinical Trials Registration: The trial is registered at the US National Institute of Health (NIH) clinical trial registry (NCT00906620, registered on 21 May, 2009), and the German Clinical Trials Register (DRKS00000214, registered on 27 October, 2009).
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| 10. |
- Palacios, M.A., et al.
(författare)
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Platinum-group elements: quantification in collected exhaust fumes and studies of catalyst surfaces
- 2000
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Ingår i: The Science of the Total Environment. ; 257, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Automotive catalytic converters, in which Pt, Pd and Rh (platinum-group elements; PGEs) are the active components for eliminating several noxious components from exhaust fumes, have become the main source of environmental urban pollution by PGEs. This work reports on the catalyst morphology through changes in catalyst surface by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and laser-induced breakdown spectrometry (LIBS) from fresh to aged catalytic converters. The distribution of these elements in the fresh catalysts analysed (PtPdRh gasoline catalyst) is not uniform and occurs mainly in a longitudinal direction. This heterogeneity seems to be greater for Pt and Pd. PGEs released by the catalysts, fresh and aged 30 000 km, were studied in parallel. Whole raw exhaust fumes from four catalysts of three different types were also examined. Two of these were gasoline catalysts (PtPdRh and PdRh) and the other two were diesel catalysts (Pt). Samples were collected following the 91441 EUDC driving cycle for light-duty vehicle testing. The results show that at 0 km the samples collected first have the highest content of particulate PGEs and although the general tendency is for the release to decrease with increasing number of samples taken, exceptions are frequent. At 30 000 km the released PGEs in gasoline and diesel catalysts decreased significantly. For fresh gasoline catalysts the mean of the total amount released was approximately 100, 250 and 50 ng km−1 for Pt, Pd and Rh, respectively. In diesel catalysts the Pt release varied in the range 400800 ng km−1. After ageing the catalysts up to 30 000 km, the gasoline catalysts released amounts of Pt between 6 and 8 ng km−1, Pd between 12 and 16 ng km−1 and Rh between 3 and 12 ng km−1. In diesel catalysts the Pt release varied in the range 108150 ng km−1. The soluble portion of PGEs in the HNO3 collector solution represented less than 5% of the total amount for fresh catalysts. For 30 000 km the total amount of soluble PGEs released was similar or slightly higher than for 0 km.
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