| 51. |
- Sabounchei, J. S., et al.
(författare)
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Rhodium complexes containing O-bonded NHxMe2-xCHO (x=0, 1, 2) : X-ray structure of Rh(PPh3)(3)(OCHNHMe) CIO4
- 2001
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Ingår i: Helvetica Chimica Acta. - 0018-019X .- 1522-2675. ; 84:10, s. 3075-3083
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Tidskriftsartikel (refereegranskat)abstract
- Displacement of norbornadiene (nbd; bicyclo[2.2.1]hepta-2,5-diene) from [Rh(PPh3)(2)(nbd)]ClO4 by hydrogenation in the presence of PPh3 and formamide or Me-substituted derivatives, results in the formation of O-bonded formamide complexes [Rh(PPh3)(3)(OCHNHxMe2-x)]ClO4 (x=0, 1, 2) rather than N-bonded derivatives. These have been characterised by spectroscopic measurements and, in the case of [Rh(PPh3)(3)(OCHNHMe)]ClO4, by X-ray crystallography. All undergo oxidative addition with H-2, and the rates of ligand exchange in the Rh-I and Rh-III complexes have been determined by magnetisation-transfer measurements.
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| 52. |
- Saether, Stein Are, et al.
(författare)
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Inferring local adaptation from QST-FST comparisons : neutral genetic and quantitative trait variation in European populations of great snipe
- 2007
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 20:4, s. 1563-1576
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Tidskriftsartikel (refereegranskat)abstract
- We applied a phenotypic QST (PST) vs. FST approach to study spatial variation in selection among great snipe (Gallinago media) populations in two regions of northern Europe. Morphological divergence between regions was high despite low differentiation in selectively neutral genetic markers, whereas populations within regions showed very little neutral divergence and trait differentiation. QST > FST was robust against altering assumptions about the additive genetic proportions of variance components. The homogenizing effect of gene flow (or a short time available for neutral divergence) has apparently been effectively counterbalanced by differential natural selection, although one trait showed some evidence of being under uniform stabilizing selection. Neutral markers can hence be misleading for identifying evolutionary significant units, and adopting the PST–FST approach might therefore be valuable when common garden experiments is not an option. We discuss the statistical difficulties of documenting uniform selection as opposed to divergent selection, and the need for estimating measurement error. Instead of only comparing overall QST and FST values, we advocate the use of partial matrix permutation tests to analyse pairwise QST differences among populations, while statistically controlling for neutral differentiation.
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| 53. |
- Sahlman, Tobias, 1976-
(författare)
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Population Genetic Analyses of Natal Dispersal and Substructure in Three Bird Species
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Genetic variation within and among populations is a result of past and ongoing processes. Among the most important of such processes are dispersal, habitat fragmentation and selection. This thesis use neutral genetic variation as a tool to investigate these processes in three bird species.In the Siberian jay, the timing of dispersal is dependent on social dominance among siblings. Mark-recapture data, radio-tracking and genetic variation was used to investigate whether timing of dispersal had an effect on dispersal distance. The results show that early dispersing individuals also disperse longer. In the same species, genetic correlation between neighbours was used to find areas with high production of philopatric individuals, which could be indicative of high habitat quality.Great snipe populations in northern Europe have a breeding range divided into two regions. A QST-FST approach was applied to study variation in selection between regions. Differentiation between the regions in neutral molecular markers was low, indicating high gene flow, or short time available for neutral divergence. Morphological divergence between the regions was high, and QST > FST, which indicates divergent selection. Thus, neutral genetic markers can be misleading in identifying evolutionary significant units, and the QST-FST approach might be valuable to identify targets for conservation.Rock ptarmigan, or its ancestors, originated in Beringia, and spread throughout the Holarctic region. Their distribution has subsequently been affected by glaciations, most likely leading to withdrawals and re-colonisations. Neutral genetic variation among five populations around the northern Atlantic was investigated. There was strong genetic structure among the populations, and evidence that Scandinavian rock ptarmigan has been isolated from other populations for considerable time. Rock ptarmigan in Svalbard showed slightly lower genetic variation than others, and comparisons with other studies suggested an eastern colonisation route to Svalbard.
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| 54. |
- Sandalova, T., et al.
(författare)
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A structural basis for CD8(+) T cell-dependent recognition of non-homologous peptide ligands - Implications for molecular mimicry in autoreactivity
- 2005
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 280:29, s. 27069-27075
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Tidskriftsartikel (refereegranskat)abstract
- Molecular mimicry of self-epitopes by viral antigens is one possible pathogenic mechanism underlying induction of autoimmunity. A self-epitope, mDBM, derived from mouse dopamine beta-mono-oxygenase (KALYDYAPI) sharing 44% sequence identity with the lymphocytic choriomeningitis virus-derived immunodominant epitope gp33 (KAVYNFATC/ M), has previously been identified as a cross-reactive self-ligand, presentation of which results in autoimmunity. A rat peptide homologue, rDBM (KALYNYAPI, 56% identity to gp33), which displayed similar properties to mDBM, has also been identified. We herein report the crystal structure of H-2D(b)center dot rDBM and a comparison with the crystal structures of the cross-reactive H-2D(b)center dot gp33 and non- cross- reactive H-2D(b)center dot gp33 (V3L) escape variant (KALYNFATM, 88% identity to gp33). Despite the large sequence disparity, rDBM and gp33 peptides are presented in nearly identical manners by H-2D(b), with a striking juxtaposition of the central sections of both peptides from residues p3 to p7. The structural similarity provides H-2D(b) in complex with either a virus-derived or a dopamine beta-mono-oxygenase-derived peptide with a shared antigenic identity that conserves the positioning of the heavy chain and peptide residues that interact with the T cell receptor (TCR). This stands in contrast to the structure of H-2D(b) center dot gp33 (V3L), in which a single conserved mutation, also present in rDBM, induces large movements of both the peptide backbone and the side chains that interact with the TCR. The TCR-interacting surfaces of the H-2D(b) center dot rDBM and H-2D(b) center dot gp33 major histocompatibility complexes are very similar with regard to shape, topology, and charge distribution, providing a structural basis for CD8 T cell activation by molecular mimicry and potential subsequent development of autoreactivity.
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| 55. |
- Sosnoff, Jacob J., et al.
(författare)
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Coherence of EMG activity and single motor unit discharge patterns in human rhythmical force production.
- 2005
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Ingår i: Behavioural Brain Research. - : Elsevier BV. - 0166-4328 .- 1872-7549. ; 158:2, s. 301-310
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to examine the modulation of the motor neuronal pool as a function of task dynamics. Specifically, we investigated the effects of task frequency on the single motor unit discharge pattern, electromyogram (EMG) activity and effector force output. Myoelectric activity and effector force were recorded while young adults isometrically abducted their first dorsal interosseus at five sinusoidal targets (0.5 Hz, 1 Hz, 2 Hz, 3Hz and 4 Hz) and at two force levels (5% and 25% maximum voluntary contraction (MVC)). Individual motor unit spike trains were isolated from the EMG. Auto-spectral and coherence analyses were performed on the force output, EMG and motor unit spike trains. The frequency of maximal coherence between the EMG and force output closely corresponded to the target frequency in all conditions. There was a broadband distribution of power with multiple peaks in the EMG and motor unit spectrums in the 0.5 Hz and 1Hz targets. However, the EMG and motor unit spectrums in the 2 Hz, 3Hz and 4Hz targets were characterized by an increasingly narrower band of activity with one dominant peak that closely corresponded to the target. There is high coherence between EMG output and target force frequency, but the relative contribution of the fast and slow neuromuscular bands are differentially influenced by the task frequency. The rhythmical organization of neuromuscular output in the 0.5 Hz task is relatively broadband and similar to that shown previously for constant level force output. The frequency structure of neuromuscular organization becomes increasingly more narrowband as the frequency of the target increases (2–4 Hz). The modulation of the motor neuronal pool is adaptive and depends on the relative contribution of feedback and feedforward control processes, which are driven by the task demands.
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| 56. |
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| 57. |
- Sprigg, Nikola, et al.
(författare)
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elationship between outcome and baseline blood pressure and other haemodynamic measures in acute ischaemic stroke : Data from the TAIST trial
- 2006
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Ingår i: Journal of Hypertension. - : Ovid Technologies (Wolters Kluwer Health). - 0263-6352 .- 1473-5598. ; 24:7, s. 1413-1417
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A poor outcome after stroke is associated independently with high blood pressure during the acute phase, however, relationships with other haemodynamic measures [heart rate (HR), pulse pressure (PP), rate-pressure product (RPP)] remain less clear. METHODS: The Tinzaparin in Acute Ischaemic Stroke Trial is a randomised, controlled trial assessing the safety and efficacy of tinzaparin versus aspirin in 1484 patients with acute ischaemic stroke. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and HR measurements taken immediately prior to randomization were averaged, and the mid-blood pressure (MBP), PP, mean arterial pressure (MAP), pulse pressure index, and RPP were calculated. The relationship between these haemodynamic measures and functional outcome (death or dependency, modified Rankin Scale > 2) and early recurrent stroke, were studied with adjustment for baseline prognostic factors and treatment group. Odds ratios (OR) and 95% confidence intervals (CI) refer to a change in haemodynamic measure by 10 points. RESULTS: A poor functional outcome was associated with SBP (adjusted OR, 1.11, 95% CI, 1.03-1.21), HR (adjusted OR, 1.15, 95% CI, 1.00-1.31), MBP (adjusted OR, 1.15, 95% CI, 1.03-1.29), PP (adjusted OR, 1.14, 95% CI, 1.02-1.26), MAP (adjusted OR, 1.15, 95% CI, 1.02-1.31) and RPP (adjusted OR, 1.01, 95% CI, 1.00-1.02). Early recurrent stroke was associated with SBP, DBP, MBP and MAP. CONCLUSIONS: A poor outcome is independently associated with elevations in blood pressure, HR and their derived haemodynamic variables, including PP and the RPP. Agents that modify these measures may improve functional outcome after stroke. © 2006 Lippincott Williams & Wilkins.
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| 58. |
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| 59. |
- Sundström, Johan, et al.
(författare)
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Relations of plasma homocysteine to left ventricular structure and function : the Framingham Heart Study.
- 2004
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Ingår i: Eur Heart J. - 0195-668X. ; 25:6, s. 523-30
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: Hyperhomocysteinaemia is a risk factor for congestive heart failure, especially in women. We investigated if homocysteine promotes left ventricular (LV) remodelling. METHODS AND RESULTS: We examined cross-sectional relations of plasma total homocysteine to echocardiographic LV structure and function in 2697 Framingham Heart Study participants (mean age 58 years, 58% women) free of heart failure and previous myocardial infarction. Adjusting for age and height, plasma homocysteine was positively related to LV mass, wall thickness, and relative wall thickness in women (p=0.0004-0.04), but not in men (p=0.28-0.68). Adjusting additionally for other clinical covariates, the relations of plasma homocysteine to LV mass and wall thickness in women remained statistically significant, but the relation to relative wall thickness became of borderline significance (1.92 g, 0.01 cm, and 0.29% increase, respectively, for a 1-SD increase in ln[homocysteine], p=0.01-0.08). LV mass and wall thickness were higher in the fourth quartile of plasma homocysteine compared to the lower three in all models in women (p=0.0003-0.02), but not in men (p=0.25-0.78). Plasma homocysteine was not related to left atrial size or LV fractional shortening in either sex. CONCLUSION: In our community-based sample, plasma homocysteine was directly related to LV mass and wall thickness in women but not in men.
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| 60. |
- Söderman, Fredrik, 1968-
(författare)
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Comparative Population Ecology in Moor Frogs with Particular Reference to Acidity
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is an attempt to describe how different environmental factors influence life history traits in different populations, sexes and developmental stages in the moor frog, Rana arvalis. The studied populations are located along 1100 km latitudinal gradient, with pH varying between 4.0 and 8.5. I have used data from both natural populations and common garden experiments. Reproducing moor frogs were larger and older at high latitudes, indicating a selective advantage of large size at high latitudes and/or earlier reproduction at low latitudes. When controlling for age I found that frogs were older and smaller at low pH, which may be a result of a reduced growth rate due to acid stress. The both sexes respond differently to different environments, with the lowest sexual dimorphism in body size found in the acid environments. This is possibly caused by a trade-off between growth and reproduction. Being large is considered to be advantageous, in females due to increased fecundity, and in males due to higher ability to compete for mates, while the cost of high growth is a reduced possibility to survive until the next mating season. Moor frog embryos originating from an acid population survived better under acid stress than embryos from a neutral population. Using quantitative genetic techniques I found strong maternal effects and small additive genetic variation for the traits in acid and non acid populations. The variation in acid stress tolerance owed largely to non-genetic effects. Females from acid localities lay larger eggs, which probably improves the performance of tadpoles under acid conditions. The trade-off between egg size and fecundity was stronger in acid populations indicating that females in acid populations reduced fecundity to increase offspring size. Finally, frogs from acidified environments were more asymmetric in skeletal traits further indicating the developmental stress created by acidification.
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