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71.
Johan R. Vikan Bård G. Stokke Frode Fossøy Craig Jackson Esa Huhta† Jarkko Rutila‡ Arne Moksnes & Eivin Røskaft 《Ethology : formerly Zeitschrift fur Tierpsychologie》2009,115(9):840-850
Previous studies have shown that the tendency to reject parasitic eggs among certain hosts is strongly dependent on the degree of similarity with own eggs, whereas other conditional cues do not affect rejection decisions. This paper examines whether two such hosts, the closely related brambling and chaffinch, show a different tendency to reject parasitic eggs if they are multiply parasitized. Some individuals were experimentally parasitized with both a non-mimetic and a low–intermediate contrasting egg in the same breeding attempt. The non-mimetic egg was rejected almost without exception. In chaffinches, the low–intermediate contrasting egg was introduced shortly after rejection of the non-mimetic egg whereas in bramblings, both eggs were introduced simultaneously. A control group consisted of individuals that were parasitized with one low–intermediate contrasting egg. There was no significant difference in the tendency to reject the low–medium contrasting eggs between the experimental and control group in any of the species, implying that the same acceptance threshold is applied to each parasitic egg independently. Moreover, the rejection rate of non-mimetic eggs was high (>90%) regardless of whether the egg was introduced alone or together with a low–medium contrasting egg. The results are discussed in relation to recent studies with great reed warblers Acrocephalus arundinaceus that obtained contrasting results in similar experimental designs. The different degrees of flexibility displayed by Fringilla and great reed warbler hosts are likely to reflect differences in both the perception and action component of the recognition system. 相似文献
72.
73.
Suzanne C. Mills Alessandro Grapputo Ilmari Jokinen Esa Koskela Tapio Mappes Tanja Poikonen 《Evolution; international journal of organic evolution》2010,64(1):166-179
Trade-offs are widespread between life-history traits, such as reproduction and survival. However, their underlying physiological and behavioral mechanisms are less clear. One proposed physiological factor involves the trade-off between investment in male reproductive effort and immunity. Based on this hypothesis, we investigated differences in fitness between artificially selected immune response bank vole groups, Myodes glareolus . Significant heritability of immune response was found and a correlated response in testosterone levels to selection on immune function. Male reproductive effort, reproductive success, and survival of first generation offspring were assessed and we demonstrate a relationship between laboratory measured immune parameters and fitness parameters in field enclosures. We identify a trade-off between reproductive effort and survival with immune response and parasites as mediators. However, this trade-off results in equal male fitness in natural conditions, potentially demonstrating different male signaling strategies for either reproductive effort or survival. Females gain indirect genetic benefits for either genetic disease resistance or male reproductive effort, but not both. Immune response is genetically variable, genetically linked to testosterone and may indirectly maintain genetic variation for sexually selected traits. Evidence for both a genetic and a field trade-off between reproductive effort and survival indicates an evolutionary constraint on fitness traits. 相似文献
74.
Johan Reinert Vikan Bård Gunnar Stokke Jarkko Rutila Esa Huhta Arne Moksnes Eivin Røskaft 《Evolutionary ecology》2010,24(5):1141-1157
The brood parasitic common cuckoo Cuculus canorus has a history of coevolution that involves numerous passerine hosts, but today only a subset is known to be regularly parasitised
in any area. In some hosts, there is significant variation in the occurrence of parasitism between populations, but still
individuals in non-parasitised populations show strong antiparasite defences. In the present study we compared the strength
of egg rejection of four distant Fennoscandian brambling Fringilla montifringilla populations experiencing different levels of cuckoo parasitism (0–6%). Egg rejection ability was in general very well developed
and we did not find any population differences in the relationship between egg rejection probability and similarity between
host and experimental parasitic eggs. Furthermore, bramblings very rarely made errors in rejection, indicating that selection
against rejection behaviour is likely to be very weak. The brambling-cuckoo system therefore differs from other well studied
systems which are characterised by pronounced spatial and temporal variation in the host’s level of defence. This result is
unlikely to reflect independent replication of the same evolutionary trajectory because the weak breeding site tenacity of
bramblings should result in an extreme amount of gene flow within the distribution area and thus strongly impede localised
responses to selection. Instead, lack of geographic variation has more likely arisen because bramblings respond to selection
as one evolutionary unit, and because the average parasitism pressures have been high enough in the past to cause regional
fixation of rejection alleles and evolution of clutch characteristics that facilitate cost free egg recognition. 相似文献
75.
Eva R. Kallio Michael Begon Heikki Henttonen Esa Koskela Tapio Mappes Antti Vaheri Olli Vapalahti 《Proceedings. Biological sciences / The Royal Society》2010,277(1701):3783-3791
Infected females may transfer maternal antibodies (MatAbs) to their offspring, which may then be transiently protected against infections the mother has encountered. However, the role of maternal protection in infectious disease dynamics in wildlife has largely been neglected. Here, we investigate the effects of Puumala hantavirus (PUUV)-specific MatAbs on PUUV dynamics, using 7 years'' data from a cyclic bank vole population in Finland. For the first time to our knowledge, we partition seropositivity data from a natural population into separate dynamic patterns for MatAbs and infection. The likelihood of young of the year carrying PUUV-specific MatAbs during the breeding season correlated positively with infection prevalence in the overwintered parent population in the preceding spring. The probability of PUUV infection varied between seasons (highest in spring, lowest in late summer) and depended on population structure, but was also, in late autumn, notably, negatively related to summer MatAb prevalence, as well as to infection prevalence earlier in the breeding season. Hence, our results suggest that high infection prevalence in the early breeding season leads to a high proportion of transiently immune young individuals, which causes delays in transmission. This suggests, in turn, that MatAb protection has the potential to affect infection dynamics in natural populations. 相似文献
76.
Sarah K. Coleman Tommi M?ykkynen Sami Hinkkuri Lauri Vaahtera Esa R. Korpi Olli T. Pentik?inen Kari Kein?nen 《The Journal of biological chemistry》2010,285(46):36032-36039
AMPA receptors (AMPARs) are tetrameric ion channels that mediate rapid glutamate signaling in neurons and many non-neuronal cell types. Endoplasmic reticulum (ER) quality control mechanisms permit only correctly folded functional receptors to be delivered to the cell surface. We analyzed the biosynthetic maturation and transport of all 12 GluA1–4 subunit splice variants as homomeric receptors and observed robust isoform-dependent differences in ER exit competence and surface expression. In contrast to inefficient ER exit of both GluA3 splice forms and the flop variants of GluA1 and GluA4, prominent plasma membrane expression was observed for the other AMPAR isoforms. Surprisingly, deletion of the entire N-terminal domain did not alter the transport phenotype, nor did the different cytosolic C-terminal tail splice variants. Detailed analysis of mutant receptors led to the identification of distinct residues in the ligand-binding domain as primary determinants for isoform-specific maturation. Considered together with the essential role of bound agonist, our findings reveal the ligand-binding domain as the critical quality control target in AMPAR biogenesis. 相似文献
77.
Ye L Haider HKh Esa WB Su L Law PK Zhang W Lim Y Poh KK Sim EK 《Journal of cellular and molecular medicine》2010,14(1-2):323-336
The study aims to use cholesterol (Chol) + DOTAP liposome (CD liposome) based human vascular endothelial growth factor-165 (VEGF(165)) gene transfer into skeletal myoblasts (SkMs) for treatment of acute hind limb ischaemia in a rabbit model. The feasibility and efficacy of CD liposome mediated gene transfer with rabbit SkMs were characterized using plasmid carrying enhanced green fluorescent protein (pEGFP) and assessed by flow cytometry. After optimization, SkMs were transfected with CD lipoplexes carrying plasmid-VEGF(165) (CD-pVEGF(165)) and transplanted into rabbit ischaemic limb. Animals were randomized to receive intramuscular injection of Medium199 (M199; group 1), non-transfected SkM (group 2) or CD-pVEGF(165) transfected SkM (group 3). Flow cytometry revealed that up to 16% rabbit SkMs were successfully transfected with pEGFP. Based on the optimized transfection condition, transfected rabbit SkM expressed VEGF(165) up to day 18 with peak at day 2. SkMs were observed in all cell-transplanted groups, as visualized with 6-diamidino-2-phenylindole and bromodeoxyuridine. Angiographic blood vessel score revealed increased collateral vessel development in group 3 (39.7 +/- 2.0) compared with group 2 (21.6 +/- 1.1%, P < 0.001) and group 1 (16.9 +/- 1.1%, P < 0.001). Immunostaining for CD31 showed significantly increased capillary density in group 3 (14.88 +/- 0.9) compared with group 2 (8.5 +/- 0.49, P < 0.001) and group 1 (5.69 +/- 0.3, P < 0.001). Improved blood flow (ml/min./g) was achieved in animal group 3 (0.173 +/- 0.04) as compared with animal group 2 (0.122 +/- 0.016; P= 0.047) and group 1 (0.062 +/- 0.012; P < 0.001). In conclusion, CD liposome mediated VEGF(165) gene transfer with SkMs effectively induced neovascularization in the ischaemic hind limb and may serve as a safe and new therapeutic modality for the repair of acute ischaemic limb disease. 相似文献
78.
Tøttrup AP Rainio K Coppack T Lehikoinen E Rahbek C Thorup K 《Integrative and comparative biology》2010,50(3):293-304
Evidence for climate-driven phenological changes is rapidly increasing at all trophic levels. Our current poor knowledge of the detailed control of bird migration from the level of genes and hormonal control to direct physiological and behavioral responses hampers our ability to understand and predict consequences of climatic change for migratory birds. In order to better understand migration phenology and adaptation in environmental changes, we here assess the scale at which weather affects timing of spring migration in passerine birds. We use three commonly used proxies of spring-time climatic conditions: (1) vegetation "greenness" (NDVI) in Europe, (2) local spring temperatures in northern Europe, and (3) the North Atlantic Oscillation Index (NAO) as predictors of the phenology of avian migration as well as the strength of their effect on different subsets of populations and the dependence of correlations on species-specific migratory strategy. We analyze phenological patterns of the entire spring migration period in 12 Palaearctic passerine species, drawing on long-term data collected at three locations along a longitudinal gradient situated close to their northern European breeding area. Local temperature was the best single predictor of phenology with the highest explanatory power achieved in combination with NAO. Furthermore, early individuals are more affected by climatic variation compared to individuals on later passage, indicating that climatic change affects subsets of migratory populations differentially. Species wintering closer to the breeding areas were affected more than were those travelling longer distances and this pattern was strongest for the earliest subsets of the population. Overall, our results suggest that at least early subsets of the population are affected by local conditions and early birds use local conditions to fine-tune the date of their spring arrival while individuals arriving later are driven by other factors than local conditions e.g. endogenous control. Understanding what cues migratory organisms use to arrive at an optimum time is important for increasing our knowledge of fundamental issues like decision making in organisms during migration and is crucial for future protection of migratory organisms. 相似文献
79.
Rytkönen AK Vaara M Nethanel T Kaufmann G Sormunen R Läärä E Nasheuer HP Rahmeh A Lee MY Syväoja JE Pospiech H 《The FEBS journal》2006,273(13):2984-3001
The contributions of human DNA polymerases (pols) alpha, delta and epsilon during S-phase progression were studied in order to elaborate how these enzymes co-ordinate their functions during nuclear DNA replication. Pol delta was three to four times more intensely UV cross-linked to nascent DNA in late compared with early S phase, whereas the cross-linking of pols alpha and epsilon remained nearly constant throughout the S phase. Consistently, the chromatin-bound fraction of pol delta, unlike pols alpha and epsilon, increased in the late S phase. Moreover, pol delta neutralizing antibodies inhibited replicative DNA synthesis most efficiently in late S-phase nuclei, whereas antibodies against pol epsilon were most potent in early S phase. Ultrastructural localization of the pols by immuno-electron microscopy revealed pol epsilon to localize predominantly to ring-shaped clusters at electron-dense regions of the nucleus, whereas pol delta was mainly dispersed on fibrous structures. Pol alpha and proliferating cell nuclear antigen displayed partial colocalization with pol delta and epsilon, despite the very limited colocalization of the latter two pols. These data are consistent with models where pols delta and epsilon pursue their functions at least partly independently during DNA replication. 相似文献
80.
Due to its net positive charge histone H1 readily associates with liposomes containing acidic phospholipids, such as phosphatidylserine (PS). Interestingly, circular dichroism reveals that while histone H1 in aqueous solutions appears as a random coil, its binding to liposomes containing PS is associated with a pronounced increase in alpha-helicity and beta-sheet content, estimated at 7% and 24%, respectively. This interaction further results in vesicle aggregation and lipid mixing. Fluorescence microscopy revealed rapid binding of Texas Red-labeled H1 (TR-H1) to giant liposomes composed of phosphatidylcholine and PS (SOPC/brain PS, 9/1 molar ratio), followed by lateral segregation and subsequent translocation of the membrane-bound H1 into the giant liposome. The above processes in giant liposomes did depend on the presence of the negatively charged PS. Comparison of the behavior of H1 in giant liposomes to that in cultured leukemic T cells demonstrated very similar patterns. More specifically, fluorescence microscopy revealed binding of TR-H1 to the plasma membrane as lateral segregated microdomains, followed by translocation into the cell. H1 also triggered membrane blebbing and fragmentation of the nuclei of these cells, thus suggesting induction of apoptosis. Our findings indicate that histone H1 and acidic phospholipids form supramolecular aggregates in the plasma membrane of T cells, subsequently resulting in major rearrangements of cellular membranes. Our results allow us to conclude that the minimal requirement for the interaction of histone H1 with the leukemia cell plasma membrane is reproduced by giant liposomes composed of unsaturated phosphatidylcholine and phosphatidylserine, the latter being mandatory for the observed changes in the secondary structure of H1 as well as the macroscopic consequences of the H1-PS interactions. 相似文献