bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic variation and migration in the Mexican free‐tailed bat (Tadarida brasiliensis mexicana)
Authors: RUSSELL A. L. , MEDELLÍN R. A. , MCCRACKEN G. F. 
Published: June 2005

AbstractIncomplete lineage sorting can genetically link populations long after they have diverged, and will exert a more powerful influence on larger populations. The effects of this stochastic process can easily be confounded with those of gene flow, potentially leading to inaccurate estimates of dispersal capabilities or erroneous designation of evolutionarily significant units (ESUs). We have used phylogenetic, population genetic, and coalescent methods to examine genetic structuring in large populations of a widely dispersing bat species and to test hypotheses concerning the influences of coalescent stochasticity vs. gene flow. The Mexican free‐tailed bat, Tadarida brasiliensis mexicana, exhibits variation in both migratory tendency and route over its range. Observations of the species’ migratory behaviour have led to the description of behaviourally and geographically defined migratory groups, with the prediction that these groups compose structured gene pools. Here, we used mtDNA sequence analyses coupled with existing information from allozyme, banding, and natural history studies to evaluate hypotheses regarding the relationship between migration and genetic structure. Analyses of molecular variance revealed no significant genetic structuring of behaviourally distinct migratory groups. Demographic analyses were consistent with population growth, although the timing of population expansion events differs between migratory and nonmigratory populations. Hypotheses concerning the role of gene flow vs. incomplete lineage sorting on these data are explored using coalescent simulations. Our study demonstrates the importance of accounting for coalescent stochasticity in formulating phylogeographical hypotheses, and indicates that analyses that do not take such processes into account can lead to false conclusions regarding a species’ phylogeographical history.
MHC diversity and the association to nematode parasitism in the yellow‐necked mouse (Apodemus flavicollis)
Authors: MEYER‐LUCHT Y. , SOMMER S. 
Published: June 2005

AbstractIn vertebrates, the genes of the major histocompatibility complex (MHC) are among the most debated candidates accounting for co‐evolutionary processes of host–parasite interaction at the molecular level. The exceptionally high allelic polymorphism found in MHC loci is believed to be maintained by pathogen‐driven selection, mediated either through heterozygous advantage or rare allele advantage (= frequency dependent selection). While investigations under natural conditions are still very rare, studies on humans or mice under laboratory conditions revealed support for both hypotheses. We investigated nematode burden and allelic diversity of a functional important MHC class II gene (DRB exon2) in free‐ranging yellow‐necked mice (Apodemus flavicollis). Twenty‐seven distinctApfl‐DRB alleles were detected in 146 individuals with high levels of amino acid sequence divergence, especially at the antigen binding sites (ABS), indicating selection processes acting on this locus. Heterozygosity had no influence on the infection status (being infected or not), the number of different nematode infections (NNI) or the intensity of infection, measured as the individual faecal egg count (FEC). However, significant associations of specificApfl‐DRB alleles to both nematode susceptibility and resistance were found, for all nematodes as well as in separate analyses of the two most common nematodes.Apodemus flavicollisindividuals carrying the allelesApfl‐DRB*5 orApfl‐DRB*15 revealed significantly higher FEC than individuals with other alleles. In contrast, the alleleApfl‐DRB*23 showed a significant association to low FEC of the most common nematode. Thus, our results provide evidence for pathogen‐driven selection acting through rare allele advantage under natural conditions.
Analysis of sex‐linked sequences supports a new mammal species in Europe
Authors: HELLBORG LINDA , GÜNDÜZ İSLAM , JAAROLA MAARIT 
Published: June 2005

AbstractEuropean mammals have been the focus of particularly detailed taxonomic studies by traditional morphological methods. However, DNA analyses have the potential to reveal additional, cryptic species. We describe two highly divergent evolutionary lineages within a small Eurasian mammal, the field vole (Microtus agrestis). We show that the two lineages can be detected not only with maternally (mitochondrial DNA), but also with paternally (Y chromosome) and biparentally (X chromosome) inherited DNA sequences. Reciprocal monophyly of all genealogies and their congruent geographical distributions is consistent with reproductive isolation. Our results suggest that the field vole should be reclassified as two separate species.
Tests of spatial and temporal factors influencing extra‐pair paternity in red‐winged blackbirds
Authors: WESTNEAT DAVID F. , MAYS HERMAN L. 
Published: June 2005

AbstractExtra‐pair paternity (EPP) is a widespread and highly variable reproductive phenomenon in birds. We tested the effects of habitat, spatial factors, and timing of breeding on the occurrence of EPP in red‐winged blackbirds (Agelaius phoeniceus). We used PCR‐amplified microsatellites to assess the paternity of 1479 nestlings from 537 broods on 235 territories over four breeding seasons. Over 4 years, 40% of nestlings were extra‐pair. At least 27% of actual sires were non‐neighbours, suggesting that males or females interacted over longer distances than in other populations of red‐winged blackbirds. The level of EPP was significantly clumped within broods and males but not within females across broods. EPP was negatively related to the area of a male's territory. The spatial proximity of a female's nest to the territory boundary had no effect on total EPP, but tended to increase the probability of an EPP by a nearby male. We found no influence on EPP of the type of habitat on the territory or the level of nesting activity nearby. The time in the season when a nest was started and the synchrony of breeding also had no significant effect on the level of EPP. The age of the male, the age of his neighbours, and the interaction between the two had no effect on total EPP. However, older males were less likely to have an offspring sired by a neighbour on their territory. Males with older neighbours were also less likely to have offspring sired by a neighbour, particularly if they were new territory owners. The high variability in who gained and lost paternity, and the limited impact of spatial and temporal factors influencing it, have some interesting implications for theories seeking to explain mating patterns.
Genetic differentiation and gene flow among populations of the alpine butterfly, Parnassius smintheus, vary with landscape connectivity
Authors: KEYGHOBADI NUSHA , ROLAND JENS , STROBECK CURTIS 
Published: June 2005

AbstractLevels of gene flow among populations vary both inter‐ and intraspecifically, and understanding the ecological bases of variation in levels of gene flow represents an important link between the ecological and evolutionary dynamics of populations. The effects of habitat spatial structure on gene flow have received considerable attention; however, most studies have been conducted at a single spatial scale and without background data on how individual movement is affected by landscape features. We examined the influence of habitat connectivity on inferred levels of gene flow in a high‐altitude, meadow‐dwelling butterfly, Parnassius smintheus. For this species, we had background data on the effects of landscape structure on both individual movement and on small‐scale population genetic differentiation. We compared genetic differentiation and patterns of isolation by distance, based on variation at seven microsatellite loci, among three regions representing two levels of connectivity of high‐altitude, nonforested habitats. We found that reduced connectivity of habitats, resulting from more forest cover at high altitudes, was associated with greater genetic differentiation among populations (higher estimated FST), a breakdown of isolation by distance, and overall lower levels of inferred gene flow. These observed differences were consistent with expectations based on our knowledge of the movement behaviour of this species and on previous population genetic analyses conducted at the smaller spatial scale. Our results indicate that the role of gene flow may vary among groups of populations depending on the interplay between individual movement and the structure of the surrounding landscape.
Processes of diversification and dispersion of Rice yellow mottle virus inferred from large‐scale and high‐resolution phylogeographical studies
Authors: TRAORE O. , SORHO F. , PINEL A. , ABUBAKAR Z. , BANWO O. , MALEY J. , HEBRARD E. , WINTER S. , SERE Y. , KONATE G. , FARGETTE D. 
Published: June 2005

AbstractPhylogeography of Rice yellow mottle virus (RYMV) was reconstructed from the coat protein gene sequences of a selection of 173 isolates from the 14 countries of mainland Africa where the disease occurred and from the full sequences of 16 representative isolates. Genetic variation was linked to geographical distribution and not to host species as isolates from wild rice always clustered with isolates from cultivated rice of the same region. Genetic variation was not associated to agro‐ecology, viral interference and insect vector species. Distinct RYMV lineages occurred in East, Central and West Africa, although the Central African lineage included isolates from Benin, Togo and Niger at the west, adjacent to countries of the West African lineage. Genetic subdivision at finer geographical scales was apparent within lineages of Central and West Africa, although less pronounced than in East Africa. Physical obstacles, but also habitat fragmentation, as exemplified by the small low‐lying island of Pemba offshore Tanzania mainland, explained strain localization. Three new highly divergent strains were found in eastern Tanzania. By contrast, intensive surveys in Côte d’Ivoire and Guinea at the west of Africa did not reveal any new variant. Altogether, this supported the view that the Eastern Arc Mountains biodiversity hotspot was the centre of origin of RYMV and that the virus spread subsequently from east to west across Africa. In West Africa, specific strains occurred in the Inner Niger Delta and suggested it was a secondary centre of diversification. Processes for diversification and dispersion of RYMV are proposed.
Stomatal density, anatomy and nutrient concentrations of Scots pine needles are affected by elevated CO2 and temperature
Authors: LUOMALA EEVA‐MARIA , LAITINEN KAISA , SUTINEN SIRKKA , KELLOMÄKI SEPPO , VAPAAVUORI ELINA 
Published: June 2005

ABSTRACTStomatal density, anatomy and nutrient concentrations of Scots pine (Pinus sylvestris L.) needles were studied during 3 years of growth at elevated CO2 (693 ± 30 µmol mol−1), at elevated temperature (ambient +2·8–6·2 °C depending on the time of the year) and in a combination of elevated CO2 and temperature in closed‐top chambers. The treatments were started in August 1996. At elevated temperature, the needles that were grown in the first year (i.e. the 1997 cohort) were thinner, had thinner mesophyll in the abaxial side, thinner vascular cylinder and lower stomatal density than those grown at ambient temperature. The proportion of mesophyll area occupied by vascular cylinder or intercellular spaces were not changed. Lower stomatal density apparently did not lead to decreased use of water, as these needles had higher concentrations of less mobile nutrients (Ca, Mg, B, Zn and Mn), which could indicate increased total transpiration. In the 1997 and 1998 cohorts, elevation of temperature decreased concentrations of N, P, K, S and Cu. In the 1999 cohort, contradictory, higher concentrations of N and S at elevated temperature may be related to increased nutrient mineralization in the soil. Elevation of CO2 did not affect stomatal density, needle thickness, thickness of epidermis or hypodermis, vascular cylinder or intercellular spaces. Concentrations of N, P, S and Cu decreased at elevated CO2. Reductions were transient and most distinct in the 1997 cohort. The effects of CO2 and temperature were in some cases interactive, which meant that in the combined treatment stomatal density decreased less than at elevated temperature, and concentrations of nutrients decreased less than expected on the basis of separate treatments, whereas the thickness of the epidermis and hypodermis decreased more than in the separate treatments. In conclusion, alterations in the anatomy and stomatal density of Scots pine needles were more distinct at elevated temperature than at elevated CO2. Both elevated CO2 and temperature‐induced changes in nutrient concentrations that partly corresponded to the biochemical and photosynthetic alterations in the same cohorts (Luomala et al. Plant, Cell and Environment26, 645–660, 2003) Reductions in nutrient concentrations and alterations in the anatomy were transient and more evident in the needle cohort that was grown in the first treatment year.
Differential accumulation of maysin and rhamnosylisoorientin in leaves of high‐altitude landraces of maize after UV‐B exposure
Authors: CASATI PAULA , WALBOT VIRGINIA 
Published: June 2005

ABSTRACTFlavonoid induction by UV‐B was investigated in five maize landraces from high altitudes and a W23 inbred line lacking the B1 and Pl1 transcription factors required for anthocyanin synthesis. In their natural habitats these landraces receive much higher UV‐B fluence than plants at lower altitudes at similar latitudes and would be predicted to have UV‐B tolerance by recurrent selection against UV‐B stress. We identified two flavones that are induced by UV‐B in leaves of high‐altitude lines: maysin and its biosynthetic precursor rhamnosylisoorientin. Accumulation is controlled by a p‐homologous transcription factor expressed in leaves, and this factor is regulated by UV‐B. The levels of either maysin or rhamnosylisoorientin are higher in seedling leaves than in subsequent leaves; the highest flavone concentration was detected in silks. Some landraces have only rhamnosylisoorientin; this likely reflects a mutation in salmon silk1 (sm1) or in a duplicate locus, as genetic crosses with W23 restore the production of maysin in heterozygous F1 plants. In conclusion, it is demonstrated that maize plants from high altitudes respond to UV‐B radiation by accumulating UV‐absorbing flavones in leaves; in contrast, these compounds are present at only very low levels in inbred lines such as W23 and are not regulated by UV‐B.
Inter‐vessel pitting and cavitation in woody Rosaceae and other vesselled plants: a basis for a safety versus efficiency trade‐off in xylem transport
Authors: WHEELER JAMES K. , SPERRY JOHN S. , HACKE UWE G. , HOANG NGUYEN 
Published: June 2005

ABSTRACTThe hypothesis that greater safety from cavitation by air‐seeding through inter‐vessel pits comes at the cost of less porous pit membranes with greater flow resistance was tested . Sixteen vessel‐bearing species were compared: 11 from the Rosaceae, four from other angiosperm families, and one fern. Unexpectedly, there was no relationship between pit resistance (and hence the prevailing membrane porosity) and cavitation pressure. There was, however, an inverse relationship between pit area per vessel and vulnerability to cavitation (r2 = 0.75). This suggests that cavitation is caused by the rare largest membrane pore per vessel, the average size of which increases with total pit area per vessel. If safety from cavitation constrains pit membrane surface area, it also limits vessel surface area and the minimum vessel resistivity. This trade‐off was consistent with an approximately three‐fold increase in vessel resistivity with cavitation pressure dropping from −0.8 to −6.6 MPa. The trade‐off was compensated for by a reduction in the percentage of vessel wall pitted: from 10–16% in vulnerable species to 2–4% in resistant species. Across species, end‐wall pitting accounted for 53 ± 3% of the total xylem resistivity. This corresponded to vessels achieving on average 94 ± 2% of their maximum possible conductivity if vessel surface area is constrained.
Respiratory Vaccination of Mice Against Influenza Virus: Dissection of T‐ and B‐Cell Priming Functions
Authors: Coleclough C. , Sealy R. , Surman S. , Marshall D. R. , Hurwitz J. L. 
Published: June 2005

AbstractWe find that a single respiratory administration of replicationally inactivated influenza A viral particles most often elicits a waning serum antibody response, as the long‐sustained bone marrow antiviral plasma cell populations characteristically induced by viral infection are lacking, though antiviral plasma cells at other sites may occasionally persist for a long time. To determine whether this alteration in the pattern of the B‐cell response is a reflection of the nature of T‐helper (Th) priming, we simultaneously primed B cells with inactivated influenza A/PR8(H1N1) and Th cells with infectious A/x31(H3N2). We show that Th cells cross‐react extensively between these two viruses, although the antibody response to viral envelope glycoproteins is completely non‐cross‐reactive. Th cells primed by infectious A/x31 have little impact on the antibody response specifically elicted from naïve B cells by inactivated A/PR8 viruses, suggesting that the characteristic vigour of the antibody response to influenza viral infection depends on the direct interaction of antiviral B cells with virally infected dendritic cells. Memory B cells primed by inactivated influenza viral particles however, respond rapidly to secondary challenge with live or inactivated viruses, promptly populating bone marrow with antiviral plasma cells. Moreover, Th cells primed by previous live A/x31 viral challenge alter the pattern of the response of naïve B cells to live A/PR8 challenge by accelerating the appearance of anti‐H1/N1 plasma cells in bone marrow, eliminating the early spike of anti‐H1/N1 plasma cells in the mediastinal node, and generally diminishing the magnitude of the lymph node response. Inactivated A/PR8 and infectious A/x31 are both effective vaccines against A/PR8 infection, as mice preimmunized with either vaccine exhibit much more rapid viral clearance from the lung after infectious A/PR8 challenge. In fact, even when given during a course of anti‐CD8 treatment to preempt cross‐reactive cytotoxic T cells, live A/x31 is a more effective vaccine against A/PR8 infection than is inactivated A/PR8 itself.
Mobile Classification in Microarray Experiments
Authors: Dozmorov I. M. , Centola M. , Knowlton N. , Tang Y. 
Published: June 2005

AbstractIn a homogeneous group of samples, there are genes whose expression variations can be attributed to factors other than experimental errors. These factors can include natural biological oscillations or metabolic processes. These genes are rarely classified as ‘interesting’ based on their variability profile. However, their dynamic behaviour can tease out important clues about naturally occurring biological processes in the organism under study and can be used for group classification. Dynamical discriminate function analysis was developed on the concept that stable classification parameters (roots) can be derived from highly variable gene‐expression data. Stability of these combinations implies a strongly compensatory relationship that may divulge functional interconnections.
Induction of Systemic Antitumour Resistance with Targeted Polymers
Authors: Rihova B. , Strohalm J. , Kovar M. , Mrkvan T. , Subr V. , Hovorka O. , Sirova M. , Rozprimova L. , Kubackova K. , Ulbrich K. 
Published: June 2005

AbstractConjugates based on N‐(2‐hydroxypropyl)methacrylamide (HPMA) represent a new generation of antibody‐targeted polymeric anticancer drugs with both cytotoxic and immunoprotecting/immunomobilizing activity. 20–90% of mice that are cured of EL4 mouse T‐cell lymphoma, BCL1 mouse B‐cell leukaemia and 38C13 mouse B‐cell lymphoma by injection of doxorubicin‐HPMA conjugate develop a long‐lasting memory and systemic antitumour resistance. It is suggested that the main activity of the polymeric drug, directly after application is – due to the high level of the drug – of cytotoxic and cytostatic nature. Thereafter, long‐term conjugates persist at low concentration in the circulation, which are capable of mobilizing the defence mechanisms of the host. Until now, seven patients with generalized carcinoma were treated with doxorubicin‐HPMA–human‐Ig conjugate. Disease stabilization, lasting from 6 to more than 18 months, was recorded.
Coding Joint Diversity in Mature and Immature B‐Cell Lines
Authors: Yuan S. W. , Agard E. A. , Larijani M. , Wu G. E. 
Published: June 2005

AbstractAntigen receptor gene rearrangement is regulated by many factors in B and T lymphocytes. The sequences of the gene segments themselves, their associated recombination signal sequences (RSS), expression of the RAG genes and the chromatin accessibility of the particular gene segments to be rearranged all influence the outcome of recombination and thus antigen receptor diversity. In the present study, we have evaluated the effect of variations in RAG activity level on the junctional diversity of coding joint sequences. Using the pre‐B‐like 204‐1‐8 and the mature B DR3 cell lines under different transfection conditions, we were able to investigate recombination activity levels that varied 100‐fold. We evaluated the sequences of the coding joints for junctional diversity resulting from nucleotide addition or deletion. Surprisingly, we found that the sequence of coding joints of these recombinants did not exhibit significant variation despite the large difference in recombination frequency. Our results indicate that the fidelity of the joining phase of V(D)J recombination is not jeopardized by varying RAG activity.
Malaria infection among pregnant women attending antenatal clinics in six Rwandan districts
Authors: Geertruyden Jean‐Pierre Van , Ntakirutimana Dorothee , Erhart Annette , Rwagacondo Claude , Kabano Augustin , D'Alessandro Umberto 
Published: June 2005

SummaryObjectives  The aim of the study was to assess the knowledge, attitude and practices of pregnant women towards malaria and their association with malaria morbidity.Methods  Cross‐sectional malaria survey of 1432 pregnant women attending six health centres, each of them situated in a specific health district in Rwanda from September to October 2002.Results  The overall prevalence of malaria infection was 13.6% and all infections but two were caused by Plasmodium falciparum. The six health districts were significantly different in terms of malaria prevalence, which varied between 11.5% and 15.4% in four and was <5% in the other two districts. The prevalence of anaemia and splenomegaly mirrored that of malaria infection. In three districts, the prevalence of infection was significantly higher in primigravidae than in secundigravidae and multigravidae (P = 0.01), while in two others it did not vary with parity. Bed net use was low – only 13.1% of the women had at least one bed net at home and 8.3% of them slept under it – and significantly different between districts. Most women knew that malaria might have serious consequences for their pregnancy and that insecticide‐treated bed nets are useful for malaria prevention. However, the bed net market price [1525 Rwandan Francs (RFr), approximately 1.6€] was much higher than that considered as affordable and acceptable (389 RFr, approximately 0.3€).Conclusion  Malaria in pregnancy is a major problem in Rwanda, even in the districts of low transmission. Bed net use among pregnant women is low. The option of providing free insecticide‐treated bed nets to pregnant women should be explored and possibly implemented; it could rapidly increase bed net use and earlier attendance to antenatal clinics with clear benefits for the women's health.