| 1. |
- Ammoun, Sylwia, et al.
(författare)
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OX1 orexin receptors activate extracellular signal-regulated kinase in Chinese hamster ovary cells via multiple mechanisms : the role of Ca2+ influx in OX1 receptor signaling
- 2006
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Ingår i: Molecular Endocrinology. - : The Endocrine Society. - 0888-8809 .- 1944-9917. ; 20:1, s. 80-99
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Tidskriftsartikel (refereegranskat)abstract
- Activation of OX1 orexin receptors heterologously expressedin Chinese hamster ovary (CHO) cells led to a rapid, strong,and long-lasting increase in ERK phosphorylation (activation).Dissection of the signal pathways to ERK using multiple inhibitorsand dominant-negative constructs indicated involvement of Ras,protein kinase C, phosphoinositide-3-kinase, and Src. Most interestingly,Ca2+ influx appeared central for the ERK response in CHO cells,and the same was indicated in recombinant neuro-2a cells andcultured rat striatal neurons. Detailed investigations in CHOcells showed that inhibition of the receptor- and store-operatedCa2+ influx pathways could fully attenuate the response, whereasinhibition of the store-operated Ca2+ influx pathway alone orthe Ca2+ release was ineffective. If the receptor-operated pathwaywas blocked, an exogenously activated store-operated pathwaycould take its place and restore the coupling of OX1 receptorsto ERK. Further experiments suggested that Ca2+ influx, as such,may not be required for ERK phosphorylation, but that Ca2+,elevated via influx, acts as a switch enabling OX1 receptorsto couple to cascades leading to ERK phosphorylation, cAMP elevation,and phospholipase C activation. In conclusion, the data suggestthat the primary coupling of orexin receptors to Ca2+ influxallows them to couple to other signal pathways; in the absenceof coupling to Ca2+ influx, orexin receptors can act as signalintegrators by taking advantage of other Ca2+ influx pathways.
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| 2. |
- Biglarnia, Ali-Reza, 1973-
(författare)
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Minimizing Risks and Morbidity in Live Kidney Donors
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Live kidney donors are healthy volunteers who are exposed to major surgical procedure and physical harms with no direct therapeutic benefits. Efforts to minimize their risks and morbidity are therefore of utmost importance. The current thesis describes studies on donor evaluation, surgical procedure and postoperative management of live kidney donors. The overall purpose is to evaluate and possibly improve routines and treatments in order to reduce risks and the overall morbidity of live kidney donors. In Study I, we evaluated the assessment of kidney function during donor evaluation and found that the accuracy of iohexol glomerular filtration rate (GFR) is compromised by large variations in repeated measurements in presumably healthy donors. We proposed that there is a need for improvement of GFR measurements and that the assessment of predonation kidney function should be more comprehensive, involving GFR, laboratory investigations, functional and morphological examinations and sound clinical judgment. In Study II, we addressed the risk of perioperative venous thromboembolism (VTE) and concluded that expanding the standard screening protocol for VTE to include perioperative venous duplex can potentially decrease the VTE-related morbidity. In studies III and IV, we investigated the impact of hand-assisted retroperitoneoscopic (HARS) nephrectomy on donor safety and perioperative morbidity. The HARS nephrectomy uses the hand-assisted approach, which enables immediate manual compression for hemostasis in case of sudden and severe bleeding. Additionally, the pure retroperitoneal access further increases the safety margin of laparoscopic donor nephrectomy by 1) minimizing the risk of intestinal injury, and 2) exposure of the retroperitoneal nerves, making HARS suitable for continuous infusion of local anesthetics (CILA). CILA effectively reduces the need for opioid consumption and has the potential to totally obviate opiate analgesics postoperatively. Consequently, CILA in combination with HARS reduces morphine-related morbidity and promotes postoperative recovery. In accordance with these data, we recommend improvement and modification of the donor evaluation process as well as a broad introduction of HARS nephrectomy in combination with CILA to increase the safety margin for live kidney donors.
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| 3. |
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| 4. |
- Borisov, Denis, et al.
(författare)
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Spectrum of the Magnetic Schrödinger Operator in a Waveguide with Combined Boundary Conditions
- 2005
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Ingår i: Annales de l'Institute Henri Poincare. Physique theorique. - : Springer Science and Business Media LLC. - 1424-0637 .- 1424-0661. ; 6:2, s. 327-342
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Tidskriftsartikel (refereegranskat)abstract
- We consider the magnetic Schrodinger operator in a two-dimensional strip. On the boundary of the strip the Dirichlet boundary condition is imposed except for a fixed segment (window), where it switches to magnetic Neumann(1). We deal with a smooth compactly supported field as well as with the Aharonov-Bohm field. We give an estimate on the maximal length of the window, for which the discrete spectrum of the considered operator will be empty. In the case of a compactly supported field we also give a sufficient condition for the presence of eigenvalues below the essential spectrum.
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| 5. |
- Ekholm, Adam, et al.
(författare)
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Community phenology of insects on oak : local differentiation along a climatic gradient
- 2021
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Ingår i: Ecosphere. - : Wiley. - 2150-8925. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is advancing the onset of phenological events, with the rate of advance varying among species and trophic levels. In addition, local populations of the same species may show genetic differences in their response to seasonal cues. If populations of interacting species differ in their response, then climate change may result in geographically varying shifts in the community-level distribution of interaction strength. We explored the magnitude of trophic- and species-level responses to temperature in a tritrophic system comprising pedunculate oak, insect herbivores, and their associated parasitoids. We sampled local realizations of this community at five sites along a transect spanning fifteen degrees of latitude. Samples from each trophic level at each site were exposed to the same set of five climatic regimes during overwintering in climate chambers. We then recorded the number of days and degree-days required for oak acorns to develop and insects to emerge. In terms of dates of events, phenology differed among populations. In terms of degree-days, we found that for two species pairs, the heat sum required to develop in spring differed by an additional ˜500 degree-days between trophic levels when overwintering at the highest temperature. For three species, within-population variation in the number of degree-days required for emergence was higher at warmer temperatures. Our findings suggest that changing temperatures can modify interactions within a community by altering the relative phenology of interacting species and that some interactions are more vulnerable than others to a shift in temperature. The geographic variation in the phenological response of a species suggests that there is a genetic component in determining the phenology of local populations. Such local variation blended with interspecific differences in responses makes it complex to understand how communities will respond to warmer temperatures.
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| 6. |
- Ekholm, Adam, et al.
(författare)
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Dispersal, host genotype and environment shape the spatial dynamics of a parasite in the wild
- 2017
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 98:10, s. 2574-2584
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Tidskriftsartikel (refereegranskat)abstract
- Dispersal, environment and genetic variation may all play a role in shaping host-parasite dynamics. Yet, in natural systems, their relative importance remains unresolved. Here, we do so for the epidemiology of a specialist parasite (Erysiphe alphitoides) on the pedunculate oak (Quercus robur). For this purpose, we combine evidence from a multi-year field survey and two dispersal experiments, all conducted at the landscape scale. Patterns detected in the field survey suggest that the parasite is structured as a metapopulation, with trees in denser oak stands characterized by higher parasite occupancy, higher colonization rates and lower extinction rates. The dispersal experiments revealed a major impact of the environment and of host genotype on the presence and abundance of the parasite, with a weaker but detectable imprint of dispersal limitation. Overall, our findings emphasize that dispersal, host genotype and the environment jointly shape the spatial dynamics of a parasite in the wild.
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| 7. |
- Ekholm, Adam, et al.
(författare)
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Herbivory in a changing climate-Effects of plant genotype and experimentally induced variation in plant phenology on two summer-active lepidopteran herbivores and one fungal pathogen
- 2022
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- With climate change, spring warming tends to advance plant leaf-out. While the timing of leaf-out has been shown to affect the quality of leaves for herbivores in spring, it is unclear whether such effects extend to herbivores active in summer. In this study, we first examined how spring and autumn phenology of seven Quercus robur genotypes responded to elevated temperatures in spring. We then tested whether the performance of two summer-active insect herbivores (Orthosia gothica and Polia nebulosa) and infection by a pathogen (Erysiphe alphitoides) were influenced by plant phenology, traits associated with genotype or the interaction between these two. Warm spring temperatures advanced both bud development and leaf senescence in Q. robur. Plants of different genotype differed in terms of both spring and autumn phenology. Plant phenology did not influence the performance of two insect herbivores and a pathogen, while traits associated with oak genotype had an effect on herbivore performance. Weight gain for O. gothica and ingestion for P. nebulosa differed by a factor of 4.38 and 2.23 among genotypes, respectively. Herbivore species active in summer were influenced by traits associated with plant genotype but not by phenology. This suggest that plant attackers active in summer may prove tolerant to shifts in host plant phenology-a pattern contrasting with previously documented effects on plant attackers active in spring and autumn.
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| 8. |
- Ekholm, Adam, et al.
(författare)
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Host plant phenology, insect outbreaks and herbivore communities - The importance of timing
- 2020
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 89:3, s. 829-841
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Tidskriftsartikel (refereegranskat)abstract
- Climate change may alter the dynamics of outbreak species by changing the phenological synchrony between herbivores and their host plants. As host plant phenology has a genotypic component that may interact with climate, infestation levels among genotypes might change accordingly. When the outbreaking herbivore is active early in the season, its infestation levels may also leave a detectable imprint on herbivores colonizing the plant later in the season. In this study, we first investigated how the spring phenology and genotype of Quercus robur influenced the density of the spring-active, outbreaking leaf miner Acrocercops brongniardellus. We then assessed how intraspecific density affected the performance of A. brongniardellus and how oak genotype and density of A. brongniardellus affected the insect herbivore community. We found that Q. robur individuals of late spring phenology were more strongly infested by A. brongniardellus. Conspecific pupae on heavily infested oaks tended to be lighter, and fewer heterospecific insect herbivores colonized the oak later in the season. Beyond its effects through phenology, plant genotype left an imprint on herbivore species richness and on two insect herbivores. Our results suggest a chain of knock-on effects from plant phenology, through the outbreaking species to the insect herbivore community. Given the finding of how phenological synchrony between the outbreak species and its host plant influences infestation levels, a shift in synchrony may then change outbreak dynamics and cause cascading effects on the insect community.
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| 9. |
- Ekholm, Adam, et al.
(författare)
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Long-term yield and biodiversity in stands managed with the selection system and the rotation forestry system: A qualitative review
- 2023
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 537
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Forskningsöversikt (refereegranskat)abstract
- There is an increasing interest in implementing Continuous Cover Forestry (CCF) as a tool to mitigate negative effects of the traditional rotation forestry system on biodiversity. However, the effects of CCF on forest growth and yield and on biodiversity is still poorly known. In this qualitative review, we compare biodiversity and longterm yield between the selection system, which is a type of CCF practiced in full-storied forests, and the traditional rotation forestry system. We specifically focus on forests dominated by Picea abies, which is a tree species of high economic relevance. Our literature search resulted in 17 publications on stand growth and yield and 21 publications on biodiversity. A majority of simulation studies found a higher long-term yield in the rotation forestry system, but it is challenging to conclude which system is the most productive. The magnitude of the difference in yield between systems, and how it varies across different environmental conditions, remains to be determined. For biodiversity, comparisons of species assemblage and individual species were only made to certain phases of the rotation cycle (recent clearcuts and middle-aged stands). Nevertheless, two aspects can be highlighted: i) the species assemblage in clearcuts differ substantially from stands managed with the selection system. Some of these effects may however be short lasting as examplified by studies on beetle assamblages showing that middle-aged rotation forestry stands become more similar to stands managed with the selection system, ii) the selection system maintains a similar species assemblage as the uncut control during the first years after cutting. In conclusion, management with the selection system may come with a loss in long-term stand yield, but much of the species assemblage is maintained after logging. We recommend future studies to specifically focus on long-term effects on biodiversity - in particular on species of conservation concern. There is also a need to establish a long-term research infrastructure to further develop the field.
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| 10. |
- Ekholm, Adam, et al.
(författare)
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Short-term effects of continuous cover forestry on forest biomass production and biodiversity: Applying single-tree selection in forests dominated by Picea abies
- 2022
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Ingår i: AMBIO: A Journal of the Human Environment. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 51, s. 2478-2495
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Tidskriftsartikel (refereegranskat)abstract
- The rotation forestry system provides high biomass production, but could also have a negative impact on species sensitive to disturbance. Continuous cover forestry (CCF) could contribute to solving these conflicting goals, but its feasibility in nutrient limited boreal forests is yet unresolved. In a unique experiment, we simultaneously assessed the short-term effect of single-tree selection on both biomass production and biodiversity (vascular plants, bryophytes, wood-inhabiting fungi), and tested fertilization as a way to mediate growth-biodiversity trade-offs. We found that unharvested stands and stands subjected to single-tree selection had a similar species assemblage of vascular plants, bryophytes, and wood-inhabiting fungi. Fertilization increased growth by 37% and induced shifts in two understory species (favoring the grass Avenella flexuosa and disfavoring the bryophyte Hylocomium splendens). We conclude that single-tree selection may become a useful tool to enhance biodiversity in managed forests.
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