| 1. |
- Jokiranta, T S, et al.
(author)
-
Complement C3b interactions studied with surface plasmon resonance technique
- 2001
-
In: International Immunopharmacology. - 1567-5769 .- 1878-1705. ; 1:3, s. 495-506
-
Journal article (peer-reviewed)abstract
- The surface plasmon resonance (SPR) phenomenon is utilized in a number of new real time biosensors. In this study, we have used this technique to study interactions between the central complement component C3b and its multiple ligands by using the Biacore equipment. The SPR technique is particularly suitable for analysis of the alternative complement pathway (AP) because the inherent nature of the latter is to amplify deposition of C3b on various surfaces. C3b was coupled onto the sensor surface and the coupling efficiency was compared under various conditions on both polystyrene and carboxymethylated dextran surfaces. After enzymatic C3b coupling or standard amine C3b coupling, we analyzed and compared the binding of four C3b ligands to the surface: factor B, factor H, C5 and the soluble complement receptor 1 (sCR1, CD35). Binding of each ligand to C3b was detected when C3b had been coupled either enzymatically or using the amine coupling, but the half-lives of the interactions were found to vary depending on the coupling procedure. Factor H binds to C3b via three interaction sites. The target sites are exposed on the C3b, C3c and C3d fragments of C3, respectively. Therefore, we also tested by using the Biacore whether factor B, C5 and sCR1 bind to C3c and/or C3d. It was found that factor B bound to C3d, but not to C3c. On the other hand, both C5 and sCR1 bound to C3c, but not to C3d. In conclusion, this study shows that SPR is a powerful tool in analyzing and mapping the interactions of C3b with its multiple ligands.
|
|
| 2. |
- Sha, Yongcui, et al.
(author)
-
Diel vertical migration of copepods and its environmental drivers in subtropical Bahamian blue holes
- 2021
-
In: Aquatic Ecology. - : Springer. - 1386-2588 .- 1573-5125. ; 55:4, s. 1157-1169
-
Journal article (peer-reviewed)abstract
- Diel vertical migration (DVM) is the most common behavioral phenomenon in zooplankton, and numerous studies have evaluated DVM under strong seasonality at higher latitudes. Yet, our understanding of the environmental drivers of DVM at low latitudes, where seasonal variation is less pronounced, remains limited. Therefore, we here examined patterns of vertical distribution in copepods in six subtropical Bahamian blue holes with different food web structure and tested the role of several key environmental variables potentially affecting this behavior. Day and night samplings showed that copepods generally performed DVM, characterized by downward migration to deeper depths during the day and upward migration to surface waters at night. Across all blue holes, the daytime vertical depth distribution of calanoid copepods correlated positively with both predation risk and depth of food resources (Chlorophyll a), but was less affected by ultraviolet radiation (UVR). A potential explanation is that since UVR is a continuous threat across seasons, zooplankton have established photoprotective pigmentation making them less vulnerable to this threat. The copepods also showed a size-structured depth segregation, where larger individuals were found at deeper depths during the day, which further strengthens the suggestion that predation is a major driver of DVM in these systems. Hence, in contrast to studies performed at higher latitudes, we show that despite the constant exposure to UVR, predator avoidance and food availability are the most pronounced drivers of copepod DVM at those low latitudes, suggesting that the main driver of DVM may vary among systems, but also systematically by latitude.
|
|
| 3. |
- Vinterstare, Jerker, et al.
(author)
-
Antipredator phenotype in crucian carp altered by a psychoactive drug
- 2021
-
In: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 11:14, s. 9435-9446
-
Journal article (peer-reviewed)abstract
- Predator-inducible defenses constitute a widespread form of adaptive phenotypic plasticity, and such defenses have recently been suggested linked with the neuroendocrine system. The neuroendocrine system is a target of endocrine disruptors, such as psychoactive pharmaceuticals, which are common aquatic contaminants. We hypothesized that exposure to an antidepressant pollutant, fluoxetine, influences the physiological stress response in our model species, crucian carp, affecting its behavioral and morphological responses to predation threat. We examined short- and long-term effects of fluoxetine and predator exposure on behavior and morphology in crucian carp. Seventeen days of exposure to a high dose of fluoxetine (100 µg/L) resulted in a shyer phenotype, regardless of the presence/absence of a pike predator, but this effect disappeared after long-term exposure. Fluoxetine effects on morphological plasticity were context-dependent as a low dose (1 µg/L) only influenced crucian carp body shape in pike presence. A high dose of fluoxetine strongly influenced body shape regardless of predator treatment. Our results highlight that environmental pollution by pharmaceuticals could disrupt physiological regulation of ecologically important inducible defenses.
|
|
| 4. |
- Vinterstare, Jerker, et al.
(author)
-
Experimental manipulation of perceived predation risk and cortisol generates contrasting trait trajectories in plastic crucian carp
- 2020
-
In: Journal of Experimental Biology. - : COMPANY BIOLOGISTS LTD. - 0022-0949 .- 1477-9145. ; 223:4
-
Journal article (peer-reviewed)abstract
- Most animals constitute potential prey and must respond appropriately to predator-mediated stress in order to survive. Numerous prey also adaptively tailor their response to the prevailing level of risk and stress imposed by their natural enemies, i.e. they adopt an inducible defence strategy. Predator exposure may activate the stress axis, and drive the expression of anti-predator traits that facilitate survival in a high-risk environment (the predation-stress hypothesis). Here, we quantified two key morphological anti-predator traits, body morphology and coloration, in crucian carp reared in the presence or absence of a predator ( pike) in addition to experimental manipulation of physiological stress via implants containing either cortisol or a cortisol inhibitor. We found that predator-exposed fish expressed a deeper-bodied phenotype and darker body coloration as compared with non-exposed individuals. Skin analyses revealed that an increase in the amount of melanophores caused the dramatic colour change in predator-exposed fish. Increased melanization is costly, and the darker body coloration may act as an inducible defence against predation, via a conspicuous signal of the morphological defence or by crypsis towards dark environments and a nocturnal lifestyle. By contrast, the phenotype of individuals carrying cortisol implants did not mirror the phenotype of predatorexposed fish but instead exhibited opposite trajectories of trait change: a shallow-bodied morphology with a lighter body coloration as compared with sham-treated fish. The cortisol inhibitor did not influence the phenotype of fish i.e. neither body depth nor body coloration differed between this group and predator-exposed fish with a sham implant. However, our results illuminate a potential link between stress physiology and morphological defence expression.
|
|
| 5. |
- Vinterstare, Jerker, et al.
(author)
-
More than meets the eye : Predator-induced pupil size plasticity in a teleost fish
- 2020
-
In: Journal of Animal Ecology. - : Wiley-Blackwell. - 0021-8790 .- 1365-2656. ; 89:10, s. 2258-2267
-
Journal article (peer-reviewed)abstract
- Most animals are visually oriented, and their eyes provide their ‘window to the world’. Eye size correlates positively with visual performance, because larger eyes can house larger pupils that increase photon catch and contrast discrimination, particularly under dim light, which have positive effects on behaviours that enhance fitness, including predator avoidance and foraging. Recent studies have linked predation risk to selection for larger eyes and pupils, and such changes should be of importance for the majority of teleost fishes as they have a pupil that is fixed in size (eyes lack a pupillary sphincter muscle) and, hence, do not respond to changes in light conditions. Here, we quantify eye and pupil size of individual crucian carp, a common freshwater fish, following controlled manipulations of perceived predation risk (presence/absence). We also tested if crucian carp responded to increased predation risk by shifts in diel activity patterns. We found that crucian carp show phenotypic plasticity with regards to pupil size, but not eye size, as pupil size increased when exposed to predators (pike). Predator-exposed crucian carp also shifted from diurnal to nocturnal activity. Using a modelling exercise, we moreover show that the plastically enlarged pupils significantly increase visual range, especially for small objects under dim light conditions. Overall, our results provide compelling evidence for predator-induced pupil enlargement resulting in enhanced visual capabilities in a teleost fish. Pupil size plasticity in combination with the observed shift towards nocturnal activity may allow for efficient foraging also under dark conditions when predation risk from diurnal and visually oriented predators is reduced. The data highlight the powerful role of predation risk for eye development and evolution.
|
|
| 6. |
- Ahlberg, Joakim, 1966-
(author)
-
Multi-unit common value auctions : theory and experiments
- 2012
-
Doctoral thesis (other academic/artistic)abstract
- Research on auctions that involve more than one identical item for sale was,almost non-existing in the 90’s, but has since then been getting increasing attention. External incentives for this research have come from the US spectrum, sales, the European 3G mobile-phone auctions, and Internet auctions. The policy relevance and the huge amount of money involved in many of them have helped the theory and experimental research advance. But in auctions where values are equal across bidders, common value auctions, that is, when the value depends on some outside parameter, equal to all bidders, the research is still embryonic.This thesis contributes to the topic with three studies. The first uses a Bayesian game to model a simple multi-unit common value auction, the task being to compare equilibrium strategies and the seller’s revenue from three auction formats; the discriminatory, the uniform and the Vickrey auction. The second study conducts an economic laboratory experiment on basis of the first study. The third study comprises an experiment on the multi-unit common value uniform auction and compares the dynamic and the static environments of this format.The most salient result in both experiments is that subjects overbid. They are victims of the winner’s curse and bid above the expected value, thus earning a negative profit. There is some learning, but most bidders continue to earn a negative profit also in later rounds. The competitive effect when participating in an auction seems to be stronger than the rationality concerns. In the first experiment, subjects in the Vickrey auction do somewhat better in small groups than subjects in the other auction types and, in the second experiment, subjects in the dynamic auction format perform much better than subjects in the static auction format; but still, they overbid.Due to this overbidding, the theoretical (but not the behavioral) prediction that the dynamic auction should render more revenue than the static fails inthe second experiment. Nonetheless, the higher revenue of the static auction comes at a cost; half of the auctions yield negative profits to the bidders, and the winner’s curse is more severely widespread in this format. Besides, only a minority of the bidders use the equilibrium bidding strategy.The bottom line is that the choice between the open and sealed-bid formats may be more important than the choice of price mechanism, especially in common value settings.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Björklund, Thomas, et al.
(author)
-
Kalkyleringsmodeller i lantbruksföretag
- 2014
-
Reports (other academic/artistic)abstract
- Denna studie syftar till att kartlägga och förklara hur företagare gör kalkyler inför sina investeringsbeslut. Projektet utreder i vilken utsträckning användande av olika kalkyleringsmodeller förekommer samt om företagarna kan tillämpa de för de olika beslutssituationerna mest lämpliga kalkyleringsmodellerna. Med hjälp av sådan kunskap är det möjligt att hjälpa företagare till ökad kompetens om ekonomistyrning så att de kan fatta bättre beslut om prissättning och investeringar. Studien omfattar företagare inom "de gröna näringarna". Fokus ligger på lantbruksföretagare. Det empiriska materialet utgörs av spannmålsodlare. Lantbruksföretagare är en mera intressant målgrupp än andra flertalet andra kategorier av småföretagare i och med att lantbruk kännetecknas av stora fasta investeringar. På basis av en genomgång av beteendevetenskaplig litteratur redovisas förutsättningar och begränsningar för människors möjligheter att agera rationellt vid sitt beslutsfattande. Det empirska underlaget för studien består i sexton personliga intervjuer med spannmålsodlare, varav hälften i Skåne och hälften i Östergötland. Företagarna fick berätta om hur de resonerade, när de under de senaste åren investerade i maskinhallar, maskiner, fastigheter och grödor. En del av intervjupersonerna använde formella kalkyleringsmetoder, medan andra använde informella metoder, dvs intuition, magkänsla, erfarenheter och synpunkter från personer i den sociala omgivningen. De formella metoder som respondenterna använde var endast investeringskalkyler och bidragskalkyler. Då de valda kalkyleringsmetoderna ställs i relation till typ av investeringsbeslut, framkommer mönstret att fastighetsinvesteringar ofta bygger på investeringskalkyler, men det finns också lantbrukare som inte gör några beräkningar. Val av gröda görs ofta utifrån en bidragskalkyl, som är datorbaserad. Då det gäller byggande av en maskinhall eller inköp av en traktor, tröska eller annan maskin är bilden olikartad. Anmärkningsvärt många beslutsfattare använder inte alls någon kalkyl. Lantbrukare med en universitetsutbildning är mera benägna att göra kalkyler inför sina investeringsbeslut. Två av respondenterna är direktörer för mycket stora gårdar, som därför har en styrelse. Dessa två är förpliktade att genomföra kalkyler. Egenföretagarna beslutar mycket ofta om investeringar utan någon kalkyl utan de ser i hög grad till sin likviditet. Om de på sina konton har tillräckligt med pengar, kan de göra stora investeringar. De är ofta inte villiga att ta lån. Det finns vissa skillnader mellan gårdar av olika storlekar, men mönstret är inte helt klart. När dessa resultat tolkas i skenet av beteendevetenskaplig litteratur är det inte svårt att förstå företagarnas ibland till synes irrationella beteende. Deras undlåtenhet att göra kalkyler kan förklaras av att man som egenföretagare är inneboende riskovillig, eftersom företaget ekonomi och den personliga ekonomin är sammankopplade. Vidare är kalkyleringsarbetet resurskrävand i sig, vilket innebär att förtagarna kan mena att värdet av kalkyleringen är mindre än vad ett bättre investeringsbeslut vore värt. En övergripande slutsats är att undervisningen i ekonomistyrning måste inkludera inte endast olika kalkyleringsmetoder utan också frågor om hur kunskapen ska komma till användning.
|
|
| 10. |
- Björnerås, Caroline, et al.
(author)
-
Inland blue holes of The Bahamas - chemistry and biology in a unique aquatic environment
- 2020
-
In: Fundamental and Applied Limnology. - : Schweizerbart science publishers. - 1863-9135. ; 194:2, s. 95-106
-
Journal article (peer-reviewed)abstract
- While lake systems in temperate regions have been extensively studied, tropical and subtropical systems have received less attention. Here, we describe the water chemistry and biota of ten inland blue holes on Andros Island, The Bahamas, representative of the morphological, abiotic, and biotic variation among Androsian inland blue holes. The majority of the studied blue holes were vertically stratified with oxic freshwater overlying anoxic saline groundwater of marine origin. Water chemistry (e.g. total phosphorus and nitrogen) in shallow waters was similar among blue holes, while turbidity and water color varied. Presence of hydrogen sulfide and reduced iron in and below the halocline indicate reducing conditions in all stratified blue holes. The biota above the halocline was also similar among blue holes with a few taxa dominating the phytoplankton community, and the zooplankton community consisting of copepods and rotifers. The Bahamas mosquitofish (Gambusia hubbsi) was present in all investigated blue holes, often accompanied by other small planktivorous fish, while the piscivorous bigmouth sleeper (Gobiomorus donnitor) was only present in some of the blue holes. Our field study reinforces that inland blue holes are highly interesting for biogeochemical research, and provide naturally replicated systems for evolutionary studies.
|
|
