| 1. |
- Sancho Pelluz, Javier, et al.
(författare)
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Sialoadhesin Expression in Intact Degenerating Retinas and Following Transplantation.
- 2008
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Ingår i: Investigative Ophthalmology & Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 1552-5783. ; 49, s. 5602-5610
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Resident microglial cells normally do not express sialoadhesin (a sialic acid binding receptor), whereas recruited inflammatory macrophages have been shown to do so. The expression of sialoadhesin was examined here in the course of photoreceptor cell degeneration and following transplantation. Methods: Sialoadhesin expression was analyzed in retinas of rd1 and rds mice. For transplantation studies, neonatal (P2) retinal cells derived from GFP mice were injected intraocularly in adult rd1 mice and controls. Antibodies recognizing different sialoadhesin epitopes, CD11b, and MHC-II were used to identify activated microglial cells in intact retinas and 21 days post-transplantation. Results: In rd1 mice, a few CD11b-positive cells were observed in the outer nuclear layer in the central retina at postnatal day (P) 11 and in increasing numbers between P12 21. In rds mice, CD11b-expressing cells were found from P16 and onwards. No sialoadhesin expressing cells were observed within the rd1 or rds mouse retinas at any of the ages examined (up to P150). Specific staining was only observed in cells found in the vitreal margin of the retina and in surrounding tissues (sclera, cornea, ciliary body, choroid). Following transplantation to normal and rd1 mice, a variable number of sialoadhesin-positive cells were detected within the grafts, in the graft-host interface, and in the subretinal space. Conclusions: The significant activation of microglia/macrophages observed in the various stages of degeneration in rd1 and rds mouse retinas is not accompanied by sialoadhesin expression. However, sialoadhesin-expressing cells are observed following transplantation. The occurrence of such cells could be of significance for the integration and long term survival of retinal grafts, as expression of sialoadhesin could facilitate other phagocytic receptors.
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| 2. |
- Bensch, Staffan, et al.
(författare)
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MalAvi : A public database of malaria parasites and related haemosporidians in avian hosts based on mitochondrial cytochrome b lineages
- 2009
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Ingår i: Molecular Ecology Resources. - : Wiley. - 1755-098X .- 1755-0998. ; 9:5, s. 1353-1358
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Tidskriftsartikel (refereegranskat)abstract
- Research in avian blood parasites has seen a remarkable increase since the introduction of polymerase chain reaction-based methods for parasite identification. New data are revealing complex multihost-multiparasite systems which are difficult to understand without good knowledge of the host range and geographical distribution of the parasite lineages. However, such information is currently difficult to obtain from the literature, or from general repositories such as GenBank, mainly because (i) different research groups use different parasite lineage names, (ii) GenBank entries frequently refer only to the first host and locality at which each parasite was sampled, and (iii) different researchers use different gene fragments to identify parasite lineages. We propose a unified database of avian blood parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon identified by a partial region of their cytochrome b sequences. The database uses a standardized nomenclature to remove synonymy, and concentrates all available information about each parasite in a public reference site, thereby facilitating access to all researchers. Initial data include a list of host species and localities, as well as genetic markers that can be used for phylogenetical analyses. The database is free to download and will be regularly updated by the authors. Prior to publication of new lineages, we encourage researchers to assign names to match the existing database. We anticipate that the value of the database as a source for determining host range and geographical distribution of the parasites will grow with its size and substantially enhance the understanding of this remarkably diverse group of parasites.
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| 3. |
- Bonneaud, C, et al.
(författare)
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Major histocompatibility alleles associated with local resistance to malaria in a passerine
- 2006
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Ingår i: Evolution. - 1558-5646. ; 60:2, s. 383-389
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Tidskriftsartikel (refereegranskat)abstract
- Malaria parasites are a major cause of human mortality in tropical countries and a potential threat for wildlife, as witnessed by the malaria-induced extinction of naive Hawaiian avifauna. Identifying resistance mechanisms is therefore crucial both for human health and wildlife conservation. Patterns of malaria resistance are known to be highly polygenic in both humans and mice, with marked contributions attributed to major histocompatibility (Mhc) genes. Here we show that specific Mhc variants are linked to both increased resistance and susceptibility to malaria infection in a wild passerine species, the house sparrow (Passer domesticus). In addition, links between host immunogenctics and resistance to malaria involved population-specific alleles, suggesting local adaptation in this host-parasite interaction. This is the first evidence for a population-specific genetic control of resistance to malaria in a wild species.
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| 4. |
- Diaz, JA, et al.
(författare)
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Reproductive investment of a lacertid lizard in fragmented habitat
- 2005
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Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 19:5, s. 1578-1585
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Tidskriftsartikel (refereegranskat)abstract
- We studied the effect of habitat fragmentation on female reproductive investment in a widespread lacertid lizard (Psammodromus algirus) in a mixed-forest archipelago of deciduous and evergreen oak woods in northern Spain. We captured gravid females in fragments (<= 10 ha) and forests (>= 200 ha) and brought them to the laboratory, where they laid their eggs. We incubated the eggs and released the first cohort of juveniles into the wild to monitor their survival. Females from fragments produced a smaller clutch mass and laid fewer eggs (relative to mean egg mass) than females of similar body size from forests. Lizards did not trade larger clutches for larger offspring, however, because females from fragments did not lay larger eggs (relative to their number) than females from forests. Among the first cohort of juveniles, larger egg mass and body size increased the probability of recapture the next year Thus, fragmentation decreased the relative fecundity of lizards without increasing the quality of their offspring. Reduced energy availability, increased predation risk, and demographic stochasticity could decrease the fitness of lizards in fragmented habitats, which could contribute to the regional scarcity of this species in agricultural areas sprinkled with small patches of otherwise suitable forest. Our results show that predictable reduction of reproductive output with decreasing size of habitat patches can be added to the already known processes that cause inverse density dependence at low population numbers.
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| 5. |
- Diéguez-Uribeondo, Javier, et al.
(författare)
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Re-evaluation of the enigmatic species complex Saprolegnia diclina-Saprolegnia parasitica based on morphological, physiological and molecular data
- 2007
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Ingår i: Fungal Genetics and Biology. - : Elsevier BV. - 1087-1845 .- 1096-0937. ; 44:7, s. 585-601
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Tidskriftsartikel (refereegranskat)abstract
- The phylogenetic relationships among isolates of the Saprolegnia diclina-Saprolegnia parasitica complex were investigated based on ITS rDNA sequences, and correlated with morphological and physiological characters. The isolates studied belong to five phylogenetically separate clades. The majority of presumed parasitic isolates, mostly isolated from fish lesions, fell within a clade that comprises isolates which has been variously named as S. diclina Type 1, S. parasitica, Saprolegnia salmonis or just as unnamed Saprolegnia sp. Presence of bundles of long-hooked hairs on secondary cysts, high frequency of retracted germination, and oogonia production at 7 degrees C (when occurring) were characteristic of this clade. A single isolate identified as S. diclina Type 2 clustered in a clade along with Saprolegnia ferax isolates. The isolates identified as S. diclina s. str. (S. diclina Type 3) distributed in two clades and appeared closely related to Saprolegnia multispora and to a number of Chilean isolates identified as Saprolegnia australis. The ITS sequences of clade I were almost identical even though the isolates were of diverse geographical origins and showed physiological and morphological differences and variations in their pathogenicity. This suggest these species reproduces clonally even in apparently sexually competent isolates. Adaptation to parasitism in Saprolegnia might have occurred at spore level by the development of long-hooked hairs to facilitate host attachment and selection of a retracting germination. The use of the name S. parasitica should be assigned to isolates of clade I that contained isolates forming cysts with bundles of long-hooked hairs.
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| 6. |
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| 7. |
- Hellgren, Olof, et al.
(författare)
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A jack-of-all-trades and still a master of some: prevalence and host range in avian malaria and related blood parasites
- 2009
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Ingår i: Ecology. - : Wiley. - 0012-9658. ; 90:10, s. 2840-2849
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Tidskriftsartikel (refereegranskat)abstract
- A parasite's ability to be a specialist vs. a generalist may have consequences for its prevalence within one or more if its host species. In this study we investigated the relationship between host specialization and prevalence in the highly species diverse avian blood parasites of the genera Plasmodium and Haemoproteus. Contrary to trade-off hypotheses that may explain host specialization, within both genera the parasites with the ability to complete their life cycles and be transmitted across a wide host range ( broad compatibility) were also the most common parasites within their compatible host species. These patterns remained unchanged when the host species with the highest prevalence were excluded, which reduces the possibility that the observed pattern was caused by parasites reaching high prevalence in a single main host, and being "spilled over" to other host species. We hypothesize that a positive relationship between parasite host range and prevalence might be explained by an overall higher encounter rate for the parasites with broad host range, which compensates for possibly reduced performance of parasites in each host species. Overall, these results show that parasites with the ability to successfully infect a wide variety of host species of broad ancestry also can have the ability to be the most prevalent in single host species.
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| 8. |
- Hellgren, Olof, et al.
(författare)
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Detecting shifts of transmission areas in avian blood parasites - a phylogenetic approach
- 2007
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Ingår i: Molecular Ecology. - 0962-1083. ; 16:6, s. 1281-1290
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the degree of geographical shifts of transmission areas of vector-borne avian blood parasites (Plasmodium, Haemoproteus and Leucocytozoon) over ecological and evolutionary timescales. Of 259 different parasite lineages obtained from 5886 screened birds sampled in Europe and Africa, only two lineages were confirmed to have current transmission in resident bird species in both geographical areas. We used a phylogenetic approach to show that parasites belonging to the genera Haemoproteus and Leucocytozoon rarely change transmission area and that these parasites are restricted to one resident bird fauna over a long evolutionary time span and are not freely spread between the continents with the help of migratory birds. Lineages of the genus Plasmodium seem more freely spread between the continents. We suggest that such a reduced transmission barrier of Plasmodium parasites is caused by their higher tendency to infect migratory bird species, which might facilitate shifting of transmission area. Although vector-borne parasites of these genera apparently can shift between a tropical and a temperate transmission area and these areas are linked with an immense amount of annual bird migration, our data suggest that novel introductions of these parasites into resident bird faunas are rather rare evolutionary events.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Perez-Tris, Javier, et al.
(författare)
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Diagnosing genetically diverse avian malarial infections using mixed-sequence analysis and TA-cloning
- 2005
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Ingår i: Parasitology. - 1469-8161. ; 131:1, s. 15-23
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Tidskriftsartikel (refereegranskat)abstract
- Birds harbouring several malarial parasites are common in the wild, and resolving such multiple infections is important for our understanding of host-parasite relationships. We propose a simple and reasonably accurate method for detecting and resolving multiple infections, based on the analysis of parasite cytochrome b DNA sequences: genetically mixed infections are first identified by double nucleotide peaks on sequence electropherograms, and later retrieved by TA-cloning. We applied this method to wild birds, and to experimentally created mixes with varying proportion of two parasites (Plasmodium spp. and Haemoproteus spp.). In general, the method was very efficient in detecting and resolving multiple infections, but some problems were encountered. Several multiple infections were erroneously scored as simple, either because one of the parasite lineages was a better target for the primers used, or because it was much more abundant in the mix. On the other hand, single nucleotide substitutions and template switching during PCR produced artificial sequences in some clones. We discuss the utility of the method, and propose a framework for its use when screening for genetically diverse avian malarial parasites.
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| 13. |
- Perez-Tris, Javier, et al.
(författare)
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Dispersal increases local transmission of avian malarial parasites
- 2005
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 8:8, s. 838-845
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Tidskriftsartikel (refereegranskat)abstract
- The relationships between dispersal and local transmission rate of parasites are essential to understanding host-parasite coevolution and the emergence and spread of novel disease threats. Here we show that year-round transmission, as opposed to summer transmission, has repeatedly evolved in malarial parasites (genera Plasmodium and Haemoproteus) of a migratory bird. Year-round transmission allows parasites to spread in sympatric host's wintering areas, and hence to colonize distantly located host's breeding areas connected by host-migration movements. Widespread parasites had higher local prevalence, revealing increased transmission, than geographically restricted parasites. Our results show a positive relationship between dispersal and local transmission of malarial parasites that is apparently mediated by frequent evolutionary changes in parasite transmission dynamics, which has important implications for the ecology and evolution of infectious diseases.
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| 14. |
- Perez-Tris, Javier, et al.
(författare)
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What are malaria parasites?
- 2005
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Ingår i: Trends in Parasitology. - : Elsevier BV. ; 21:5, s. 209-211
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Tidskriftsartikel (refereegranskat)
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| 15. |
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| 16. |
- Perez-Tris, Javier, et al.
(författare)
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Within-host speciation of malaria parasites
- 2007
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 2:2
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Tidskriftsartikel (refereegranskat)abstract
- Background Sympatric speciation—the divergence of populations into new species in absence of geographic barriers to hybridization—is the most debated mode of diversification of life forms. Parasitic organisms are prominent models for sympatric speciation, because they may colonise new hosts within the same geographic area and diverge through host specialization. However, it has been argued that this mode of parasite divergence is not strict sympatric speciation, because host shifts likely cause the sudden effective isolation of parasites, particularly if these are transmitted by vectors and therefore cannot select their hosts. Strict sympatric speciation would involve parasite lineages diverging within a single host species, without any population subdivision. Methodology/Principal Findings Here we report a case of extraordinary divergence of sympatric, ecologically distinct, and reproductively isolated malaria parasites within a single avian host species, which apparently occurred without historical or extant subdivision of parasite or host populations. Conclusions/Significance This discovery of within-host speciation changes our current view on the diversification potential of malaria parasites, because neither geographic isolation of host populations nor colonization of new host species are any longer necessary conditions to the formation of new parasite species.
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| 17. |
- Piersma, T, et al.
(författare)
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Is there a "migratory syndrome" common to all migrant birds?
- 2005
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Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923. ; 1046, s. 282-293
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Tidskriftsartikel (refereegranskat)abstract
- Bird migration has been assumed, mostly implicitly, to represent a distinct class of animal behavior, with deep and strong homologies in the various phenotypic expressions of migratory behavior between different taxa. Here the evidence for the existence of what could be called a "migratory syndrome," a tightly integrated, old group of adaptive traits that enables birds to commit themselves to highly organized seasonal migrations, is assessed. A list of problems faced by migratory birds is listed first and the traits that migratory birds have evolved to deal with these problems are discussed. The usefulness of comparative approaches to investigate which traits are unique to migrants is then discussed. A provisional conclusion that, perhaps apart from a capacity for night-time compass orientation, there is little evidence for deeply rooted co-adapted trait complexes that could make up such a migratory syndrome, is suggested. Detailed analyses of the genetic and physiological architecture of potential adaptations to migration, combined with a comparative approach to further identify the phylogenetic levels at which different adaptive traits for migration have evolved, are recommended.
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| 18. |
- Reullier, J, et al.
(författare)
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Diversity, distribution and exchange of blood parasites meeting at an avian moving contact zone
- 2006
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Ingår i: Molecular Ecology. - 0962-1083. ; 15:3, s. 753-763
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Tidskriftsartikel (refereegranskat)abstract
- Research on contact zones has paid relatively little attention to host-parasite interactions, although these situations have important but different implications depending on whether one considers the host or the parasite's perspective. We investigated both the role of a host contact zone in parasite expansion and whether parasites could influence contact zone dynamics. We studied the diversity and the patterns of parasite exchange (genera Haemoproteus and Plasmodium) infecting two parapatric sibling passerines meeting at a moving contact zone in western Europe. We amplified and sequenced a fragment of the parasite cytochrome b gene. The expanding host harboured more diverse parasites, which might indicate a superior ability to face a diverse parasite fauna than the receding host. Prevalence was very high in both hosts, due to the frequent occurrence of two sister Haemoproteus lineages. Despite the recent movement of the contact zone, these two parasites fitted almost perfectly to the geographic range of their main host species. Yet, we found several cases of cross-species infection in sympatric areas and evidences of asymmetrical spreading of parasites from the expanding host towards the receding host. Altogether, our results suggest that the host contact zone mainly acts as a barrier to parasite expansion even if recurrent host shifts are observed. Besides, they also support the idea that parasite-mediated competition might contribute to the displacement of hosts' contact zones, thereby emphasizing the role of parasitism on the population dynamics of sympatric species.
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| 19. |
- Telleria, J L, et al.
(författare)
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Conservation of seed-dispersing migrant birds in Mediterranean habitats: Shedding light on patterns to preserve processes
- 2005
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Ingår i: Biological Conservation. - : Elsevier BV. - 1873-2917 .- 0006-3207. ; 124:4, s. 493-502
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Tidskriftsartikel (refereegranskat)abstract
- Migratory frugivorous birds disperse the seeds of many plant species, forming mutualistic associations that render frugivores a priority for conservation in many habitats worldwide. We analysed the distribution of seed-dispersing frugivorous passerines in southern Spain, which is an important area for the conservation of European birds during winter. Frugivorous birds showed similar regional abundance and richness during four winters, although fruit availability changed among years. However, the spatial distribution of frugivorous birds in the area changed among years. These changes were principally determined by annual variation in the distribution of fruits in the area, revealing a clear ability of birds to track the distribution of fruits. The unpredictable distribution of fruits each year suggests that regional fruit crops, rather than selected habitat patches, need to be protected for the long-term conservation of frugivorous bird populations in wintering grounds. Remarkably, the distribution of frugivores was independent of forest development or general cover of shrubs, which helps to reconcile the protection of fruiting shrubs with forest cleaning, an usual management to prevent devastating summer fires that is destroying fleshy-fruited plant communities in many areas of southern Spain. Thus, leaving a part of the fruiting shrubs untouched when cleaning forest undergrowth will allow the settlement of frugivorous birds. Interestingly, both abundance and richness of frugivores decreased with elevation, probably as a consequence of impaired climatic conditions at high altitude, revealing the importance of lowland shrublands as wintering grounds for frugivorous birds. These habitats deserve special conservation efforts, as they are seriously threatened by the ongoing encroachment of agricultural and urban areas along the Mediterranean coasts.
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| 20. |
- Telleria, J L, et al.
(författare)
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Habitat effects on resource tracking ability: do wintering Blackcaps Sylvia atricapilla track fruit availability?
- 2007
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Ingår i: Ibis. - 0019-1019. ; 149:1, s. 18-25
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Tidskriftsartikel (refereegranskat)abstract
- If resource availability shapes population distribution, changes in resource abundance should cause parallel changes in population numbers. However, tracking ability may be disrupted by different environmental and behavioural factors that act at different spatial and temporal scales. Here we analyse the ability of wintering Blackcap Sylvia atricapilla populations to track spatio-temporal variation in fruit availability in southern Spain in two habitats (forests and shrublands) with different population structure. Former studies had shown that forests are equally used by both adult migrant and local Blackcaps, whereas shrublands are nearly monopolized by juvenile migrants. These differences might affect resource tracking: it should be disrupted in forests, as local birds remain over winter in their breeding territories, but not in shrublands where similarly competitive juvenile migrants can freely track the spatial distribution of fruits. We analysed the fruit-tracking ability of Blackcap populations among sites and years in both habitat types using a habitat-matching model, which predicts spatio-temporal changes in population abundance proportional to changes in resource availability. We counted Blackcaps and fruiting shrubs (dominated by Lentiscs Pistacia lentiscus and Wild Olives Olea europaea sylvestris) during four winters in forest and shrubland patches. The abundance of fruits was always higher in shrublands than in forests. In shrublands, Blackcaps seemed to move freely across fruit-rich habitat patches, tracking changes in fruiting-shrub abundance among sites and years. However, such tracking was not observed in forests. This supports the view that fruit-tracking ability may be constrained by local factors, such as the social structure of populations occurring in different habitat types, which introduces spatio-temporal variation in the way fruit availability shapes the abundance distribution of these birds in their Mediterranean wintering grounds.
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| 21. |
- van Noordwijk, AJ, et al.
(författare)
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A framework for the study of genetic variation in migratory behaviour
- 2006
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Ingår i: Journal of Ornithology. - : Springer Science and Business Media LLC. - 2193-7192 .- 2193-7206. ; 147:2, s. 221-233
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Evolutionary change results from selection acting on genetic variation. For migration to be successful, many different aspects of an animal's physiology and behaviour need to function in a co-coordinated way. Changes in one migratory trait are therefore likely to be accompanied by changes in other migratory and life-history traits. At present, we have some knowledge of the pressures that operate at the various stages of migration, but we know very little about the extent of genetic variation in various aspects of the migratory syndrome. As a consequence, our ability to predict which species is capable of what kind of evolutionary change, and at which rate, is limited. Here, we review how our evolutionary understanding of migration may benefit from taking a quantitative-genetic approach and present a framework for studying the causes of phenotypic variation. We review past research, that has mainly studied single migratory traits in captive birds, and discuss how this work could be extended to study genetic variation in the wild and to account for genetic correlations and correlated selection. In the future, reaction-norm approaches may become very important, as they allow the study of genetic and environmental effects on phenotypic expression within a single framework, as well as of their interactions. We advocate making more use of repeated measurements on single individuals to study the causes of among-individual variation in the wild, as they are easier to obtain than data on relatives and can provide valuable information for identifying and selecting traits. This approach will be particularly informative if it involves systematic testing of individuals under different environmental conditions. We propose extending this research agenda by using optimality models to predict levels of variation and covariation among traits and constraints. This may help us to select traits in which we might expect genetic variation, and to identify the most informative environmental axes. We also recommend an expansion of the passerine model, as this model does not apply to birds, like geese, where cultural transmission of spatio-temporal information is an important determinant of migration patterns and their variation.
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| 22. |
- Vilar, Eduardo, et al.
(författare)
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Chemotherapy and role of the proliferation marker Ki-67 in digestive neuroendocrine tumors
- 2007
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Ingår i: Endocrine-Related Cancer. - 1351-0088 .- 1479-6821. ; 14:2, s. 221-232
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Forskningsöversikt (refereegranskat)abstract
- Neuroendocrine tumors (NETs) of the digestive tract are a heterogeneous group of rare malignancies. Three major subgroups can be defined: pancreatic endocrine tumors, carcinoid tumors, and poorly differentiated gastroenteropancreatic NETs. Classically, digestive NETS have been considered to have an indolent course characterized for prolonged stabilizations or slow progressions, but there are clear differences in terms of aggressiveness, clinical course, and response to treatment among them. Retrospective studies have identified several clinicopathological and immunohistochemical factors as angioinvasion and proliferative index assessed by Ki-67 expression, which predict biological behavior and correlate with survival. Chemotherapy regimens based on the combination of several active drugs such as streptozocin, doxorubicin, 5-fluorouracil, dacarbazine, and temozolomide show low response rates, which sets the need to improve the results of the medical treatment of these malignancies. This review will analyze the role of Ki-67 in digestive NETs under a clinical perspective and will suggest future fields for development of this approach that enable a better patient selection for chemotherapy. Also a comprehensive review of the literature about chemotherapy in NETs is presented.
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