bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in Progesterone Receptor Isoforms Content in the Rat Brain During the Oestrous Cycle and After Oestradiol and Progesterone Treatments
Authors: Guerra‐Araiza C. , Villamar‐Cruz O. , González‐Arenas A. , Chavira R. , Camacho‐Arroyo I. 
Published: September 2003

AbstractWe studied the effects of oestradiol and progesterone on progesterone receptor (PR) isoform content in the brain of ovariectomized rats and in intact rats during the oestrous cycle by Western blot analysis. In the hypothalamus and the preoptic area of ovariectomized rats, PR‐A and PR‐B content was increased by oestradiol, whereas progesterone significantly diminished the content of both PR isoforms after 3 h of treatment in the hypothalamus, but not in the preoptic area. In the hippocampus, only PR‐A content was significantly increased by oestradiol while progesterone significantly diminished it after 12 h of treatment. In the frontal cortex, no treatment significantly modified PR isoform content. During the oestrous cycle, the lowest content of PR isoforms in the hypothalamus was observed on diestrus day and, by contrast, in the preoptic area, the highest content of both PR isoforms was observed on diestrus day. We observed no changes in PR isoform content in the hippocampus during the oestrous cycle. These results indicate that the expression of PR isoforms is differentially regulated by sex steroid hormones in a regionally specific manner.
Double Oestrogen Receptor α and β Knockout Mice Reveal Differences in Neural Oestrogen‐Mediated Progestin Receptor Induction and Female Sexual Behaviour
Authors: Kudwa A. E. , Rissman E. F. 
Published: September 2003

AbstractTo test the hypothesis that oestrogen receptor α (ERα) and ERβ act together to mediate the actions of oestrogen in the ventromedial hypothalamus (VMH), we used mice with single or double knockout mutations of the ERα and ERβ genes. Ovariectomized mice were implanted with 17β‐oestradiol and killed 5 days later. Oestradiol treatment promoted progestin receptor (PR)‐immunoreactivity (‐ir) in the VMH of all genotypes, but was maximal in brains of wild‐type and ERβKO females. Analysis of specific VMH subregions revealed that PR‐ir induction was limited to the caudal VMH in ERαKO and ERαβKO mice. In the rostral VMH, oestradiol only induced PR‐ir in wild‐type and ERβKO mice, and the number of PR‐ir neurones in this region was greater in ERβKO than wild‐type females. Next, we tested the ability of a dopamine agonist and progesterone to facilitate sexual behaviour in females lacking functional ERα, ERβ, or both receptors. Ovariectomized mice were implanted with oestradiol, and tested for sexual behaviour three times after administration of the dopamine agonist, apomorphine, followed by two tests concurrent with progesterone treatment and a final test with just apomorphine treatment. ERαKO and ERαβKO females failed to display lordosis under any testing conditions, while ERβKO females exhibited lordosis behaviour equal to that of wild‐type females. Our data show that a subpopulation of PR‐ir neurones is induced by oestradiol in the caudal VMH of female mice lacking both ERα and ERβ genes. We hypothesize that this action of oestradiol is either mediated by a novel ER or by the mutant portion of the AF2 subregion of the ERα gene present in ERαKO brain. However, despite the presence of PR in VMH, females lacking a functional ERα gene do not display sexual behaviour, via either ligand‐dependent or ‐independent activation.
A retrospective study of pre‐fabricated carbon fibre root canal posts
Authors: Hedlund S.‐O. , Johansson N. G. , Sjögren G. 
Published: September 2003

summary Although pre‐fabricated carbon fibre posts have been used during the past decade clinical evaluations of the technique are still few. Using dental records and radiographs the clinical performance of 65 pre‐fabricated carbon fibre posts (Composipost and Endopost) placed in 48 patients who regularly visited a general practice were evaluated in the present study. After an average time of 2.3 ± 0·8 years (median 2·1 years, range 1–4·9 years) of clinical service the failure rate was 3%. Failure occurred in one tooth with a single crown restoration and in one tooth that was part of a cantilever fixed partial denture. Although the failure rate is lower than those mostly reported for metallic posts and cores more clinical studies are necessary to assess the suitability of pre‐fabricated carbon fibre posts for routine use as an alternative to individually cast posts.
Effects of habitat fragmentation and changes of dispersal behaviour after a recent population decline on the genetic variability of noncoding and coding DNA of a monogamous Malagasy rodent
Authors: Sommer S. 
Published: September 2003

AbstractWhile interactions among demography, behaviour and genetic structure are well‐documented for neutral genetic markers, the role of these parameters and the effects of genetic drift and selection are considerably less well understood in functional genes, such as the major histocompatibility complex (MHC). In this study, the consequences of habitat fragmentation and the effects of a current population decline on noncoding (mitochondrial DNA) and two coding MHC loci (DQA, DRB) with different functional importance were investigated in the small remnant subdivided population of the endangered Malagasy giant jumping rat (Hypogeomys antimena). Both neutral and selective markers revealed a significant genetic differentiation between the two remnant subpopulations. The FST values were much lower in the MHC DQA and DRB genes than in the mitochondrial data. The MHC DRB loci display the effects of both balancing selection (high sequence diversity, four times higher nonsynonymous than synonymous substitutions in the functionally important antigen‐binding site positions, twice the average heterozygosity of individual amino acids at the positions identified as part of the antigen‐binding site (ABS) than those outside the ABS and nonselective forces including genetic drift. Simultaneously with a current population decline offspring reduced their dispersal distances. No substantial effects were detected within the first 6 years of reduced gene flow in either mitochondrial or MHC markers.
Huge populations and old species of Costa Rican and Panamanian dirt frogs inferred from mitochondrial and nuclear gene sequences
Authors: Crawford A. J. 
Published: September 2003

AbstractMolecular genetic data were used to investigate population sizes and ages of Eleutherodactylus (Anura: Leptodactylidae), a species‐rich group of small leaf‐litter frogs endemic to Central America. Population genetic structure and divergence was investigated for four closely related species surveyed across nine localities in Costa Rica and Panama. DNA sequence data were collected from a mitochondrial gene (ND2) and a nuclear gene (c‐myc). Phylogenetic analyses yielded concordant results between loci, with reciprocal monophyly of mitochondrial DNA haplotypes for all species and of c‐myc haplotypes for three of the four species. Estimates of genetic differentiation among populations (FST) based upon mitochondrial data were always higher than nuclear‐based FST estimates, even after correcting for the expected fourfold lower effective population size (Ne) of the mitochondrial genome. Comparing within‐population variation and the relative mutation rates of the two genes revealed that the Ne of the mitochondrial genome was 15‐fold lower than the estimate of the nuclear genome based on c‐myc. Nuclear FST estimates were ≈ 0 for the most proximal pairs of populations, but ranged from 0.5 to 1.0 for all other pairs, even within the same nominal species. The nuclear locus yielded estimates of Ne within localities on the order of 105. This value is two to three orders of magnitude larger than any previous Ne estimate from frogs, but is nonetheless consistent with published demographic data. Applying a molecular clock model suggested that morphologically indistinguishable populations within one species may be 107 years old. These results demonstrate that even a geologically young and dynamic region of the tropics can support very old lineages that harbour great levels of genetic diversity within populations. The association of high nucleotide diversity within populations, large divergence between populations, and high species diversity is also discussed in light of neutral community models.
Evidence for the existence of some dissociation in an otherwise strong linkage disequilibrium between mitochondrial and chloroplastic genomes in Cyclobalanopsis glauca
Authors: Lin T.‐P. , Chuang W.‐J. , Huang S. S. F. , Hwang S.‐Y. 
Published: September 2003

AbstractVariations in mitochondrial DNA in Cyclobalanopsis glauca (Thunb. ex Murray) Oerst. were studied in 140 trees from 32 populations collected from within the tree's natural range. By sequencing two mitochondrial DNA intron fragments (nad4/3‐nad4/4r and nad7/2‐nad7/3r), we revealed a total of 1788 bp and five polymorphic sites which allowed us to distinguish six mitotypes. The mitochondrial DNA markers provided replicated data to support population phylogeographical scenarios suggested previously using chloroplastic DNA markers. The gene genealogical tree of mitochondrial DNA was partially congruent with the chloroplastic DNA tree owing to the slower mutation rate and different mutational direction. Significant linkage disequilibrium existed between the two organellar genomes. Further paring analyses between fragments synthesized using different primers, accompanied by exclusion of polymorphic sites, showed that the random association could be attributed specifically to one of the polymorphic sites of the petG‐trnP fragment of the chloroplastic genome, and the three polymorphic sites of the nad4/3‐nad4/4r fragment of the mitochondrial genome. The former was inferred to derive from paternal leakage, and the latter from recurrent mutation. These polymorphic sites were also responsible for uncoupling of the combined gene tree of mitotype and chlorotype. In conclusion, specific fragments found in this study contribute to the incomplete congruence of the two organellar lineages that otherwise associate well phylogeographically.
Phylogeography of the harlequin beetle‐riding pseudoscorpion and the rise of the Isthmus of Panamá
Authors: Zeh J. A. , Zeh D. W. , Bonilla M. M. 
Published: September 2003

AbstractMolecular and geological evidence indicates that the emergence of the Isthmus of Panamá influenced the historical biogeography of the Neotropics in a complex, staggered manner dating back at least 9 Myr bp. To assess the influence of Isthmus formation on the biogeography of the harlequin beetle‐riding pseudoscorpion, Cordylochernes scorpioides, we analysed mitochondrial COI sequence data from 71 individuals from 13 locations in Panamá and northern South America. Parsimony and likelihood‐based phylogenies identified deep divergence between South American and Panamanian clades. In contrast to low haplotype diversity in South America, the Panamanian Cordylochernes clade is comprised of three highly divergent lineages: one clade consisting predominantly of individuals from central Panamá (PAN A), and two sister clades (PAN B1 and PAN B2) of western Panamanian pseudoscorpions. Breeding experiments demonstrated a strictly maternal mode of inheritance, indicating that our analyses were not confounded by nuclear‐mitochondrial pseudogenes. Haplotype diversity is striking in western Atlantic Panamá, where all three Panamanian clades can occur in a single host tree. This sympatry points to the existence of a cryptic species hybrid zone in western Panamá, a conclusion supported by interclade crosses and coalescence‐based migration rates. Molecular clock estimates yield a divergence time of ≈ 3 Myr between the central and western Panamanian clades. Taken together, these results are consistent with a recent model in which a transitory proto‐Isthmus enabled an early wave of colonization out of South America at the close of the Miocene, followed by sea level rise, inundation of the terrestrial corridor and then a second wave of colonization that occurred when the Isthmus was completed ≈ 3 Myr bp.
Low genetic differentiation among seasonal cohorts inSenecio vulgarisas revealed by amplified fragment length polymorphism analysis
Authors: Haldimann P. , Steinger T. , Müller‐Schärer H. 
Published: September 2003

AbstractCommon groundsel,Senecio vulgaris(Asteraceae), is a highly selfing semelparous ephemeral weed that belongs to the few plant species in central Europe capable of growing, flowering and fruiting all year round. In temperate climates, floweringS. vulgariscohorts were found to appear up to three times per year. Using amplified fragment length polymorphism (AFLP) molecular markers we examined temporal genetic differentiation among spring, summer and autumn cohorts at each of seven sites located in two regions in Switzerland. Strong genetic differentiation among cohorts may indicate the existence of seasonal races ofS. vulgaris, reproductively isolated by nonoverlapping flowering phenologies. Analysis of molecular variance (amova) revealed that < 2.5% of the AFLP variation resided among cohorts within sites, whereas there was significant genetic differentiation among plants from different sites (15.6%) and among individuals within cohorts (81.9%). Significant genetic differentiation was also observed between the two regions. Isolation‐by‐distance was found on a regional scale, but not on a local scale. Gene flow was estimated to be ≈ 15‐fold higher among cohorts within sites than among sites. We further found, on average, similar levels of genetic diversity within the three seasonal cohorts. The results of this study demonstrate that season of growth represents a weak barrier for genetic exchange amongS. vulgarispopulations and does not affect molecular variance. Therefore, there is no evidence for the existence of seasonally specialized races ofS. vulgaris. We discuss some implications of the results for the biological control ofS. vulgarisusing a native rust fungus.
Evidence for gene flow in parasitic nematodes between two host species of shrews
Authors: Brant Sara V. , Ortí Guillermo 
Published: September 2003

AbstractWe describe the genetic structure of populations of the intestinal nematode Longistriata caudabullata (Trichostrongyloidea: Heligmosomidae), a common parasite of short‐tailed shrews (genus Blarina, Insectivora: Soricidae). Parasites and hosts were collected from a transect across a contact zone between two species of hosts, Blarina brevicauda and B. hylophaga, in central North America. An 800‐base pairs (bp) fragment of the ND4 mitochondrial DNA (mtDNA) gene was sequenced for 28 worms and a 783‐bp fragment of the mtDNA control region was analysed for 16 shrews. Phylogenetic analyses of mtDNA sequences revealed reciprocal monophyly for the shrew species, concordant with morphological diagnosis, and supported the idea that the transect cuts through a secondary contact zone between well‐differentiated B. brevicauda and B. hylophaga. In contrast to this pattern, the parasitic nematode mtDNA phylogeny was not subdivided according to host affiliation. Genealogical discordance between parasite and host phylogenies suggests extensive gene flow among parasites across the host species boundary.
Methods of parentage analysis in natural populations
Authors: Jones Adam G. , Ardren William R. 
Published: September 2003

AbstractThe recent proliferation of hypervariable molecular markers has ushered in a surge of techniques for the analysis of parentage in natural and experimental populations. Consequently, the potential for meaningful studies of paternity and maternity is at an all‐time high. However, the details and implementation of the multifarious techniques often differ in subtle ways that can influence the results of parentage analyses. Now is a good time to reflect on the available techniques and to consider their strengths and weaknesses. Here, we review the leading techniques in parentage analysis, with a particular emphasis on those that have been implemented in readily useable software packages. Our survey leads to some important insights with respect to the utility of the different approaches. This review should serve as a useful guide to anyone who wishes to embark on the study of parentage.
Global patterns in peatmoss biodiversity
Authors: Shaw A. Jonathan , Cox Cymon J. , Boles Sandra B. 
Published: September 2003

AbstractDNA sequence data from the nuclear ribosomal internal transcribed spacers (ITS) and thetrnL‐trnFchloroplast DNA regions were used to quantify geographical partitioning of global biodiversity in peatmosses (Sphagnum), and to compare patterns of molecular diversity with patterns of species richness. Molecular diversity was estimated for boreal, tropical, Neotropical, nonboreal (tropical plus Southern Hemisphere), Old World and New World partitions, based on a total of 436 accessions. Diversity was partitioned among geographical regions in terms of combined nuclear and chloroplast sequence data and separately for theITSandtrnL‐trnFdata sets. Levels of variation were estimated using phylogenetic diversity (PD), which incorporates branch lengths from a phylogenetic tree, and the number of polymorphic nucleotide sites. Estimates of species richness suggest that peatmoss diversity is higher in New World than Old World regions, and that the Neotropics constitute a ‘hotspot’ of diversity. Molecular estimates, in contrast, indicate that peatmoss biodiversity is almost evenly divided between New and Old World regions, and that the Neotropics account for only 20–35% of global peatmoss diversity. In general, levels of tropical and boreal peatmoss molecular diversity were comparable. Two species,S. sericeumfrom the Old World tropics andS. lapazensefrom Bolivia, are remarkably divergent in nucleotide sequences from all other Sphagna and together account for almost 20% of all peatmoss diversity, although they are represented by only three of the 436 accessions (0.7%). These species clearly demonstrate the nonequivalence of species biodiversity value.
Plastid DNA variation in theDactylorhiza incarnata/maculatapolyploid complex and the origin of allotetraploidD. sphagnicola(Orchidaceae)
Authors: Hedrén M. 
Published: September 2003

AbstractTo obtain further information on the polyploid dynamics of the theDactylorhiza incarnata/maculatapolyploid complex and the origin of the allotetraploidD. sphagnicola(Orchidaceae), plastid DNA variation was studied in 400 plants from from Sweden and elsewhere in Europe and Asia Minor by means of polymerase chain reaction–restriction fragment length polymorphisms (PCR‐RFLPs) and sequencing. Allotetraploid taxa in Europe are known have evolved by multiple independent polyploidization events following hybridization between the same set of two distinct ancestral lineages. Most allotetraploids have inherited the plastid genome from parents similar toD. maculata sensu lato, which includes, e.g. the diploidD. fuchsiiand the autotetraploidD. maculata sensu stricto.D. sphagnicolacarries a separate plastid haplotype different from the one found in other allotetraploid taxa, which is in agreement with an independent origin from the parental lineages. Some of the remaining allotetraploids have local distributions and appear to be of postglacial origin, whereas still other allotetraploids may be of higher age, carrying plastid haplotypes that have not been encountered in present day representatives of the parental lineages. Introgression and hybridization between diploids and allotetraploids, and between different independently derived allotetraploids may further have contributed to genetic diversity at the tetraploid level. Overall, theDactylorhizapolyploid complex illustrates how taxon diversity and genetic diversity may be replenished rapidly in a recently glaciated area.
Inter‐island movements and population differentiation in a pelagic seabird
Authors: Dearborn Donald C. , Anders Angela D. , Schreiber E. A. , Adams Rachelle M. M. , Mueller Ulrich G. 
Published: September 2003

AbstractWe used mark–resight data and amplified fragment length polymorphism (AFLP) markers to assess movements and gene flow between Central Pacific breeding colonies of the great frigatebird, Fregata minor. Of 715 adult frigatebirds marked on Tern Island and Johnston Atoll, 21.3% were resighted at other frigatebird colonies at least 582 km away. Mark–resight data indicated regular movement of males and females between Tern Island and Johnston Atoll (873 km apart), and less frequent movements to other islands; no birds marked on Tern or Johnston were seen on Christmas Island, but one was seen in the Philippines, 7627 km from where it was marked. Despite the regular occurrence of interisland movements, Bayesian analyses of AFLP data showed significant genetic differentiation between Tern Island and Johnston Atoll, and more pronounced differentiation between these two islands and the more distant Christmas Island. The AFLP profiles of three birds breeding on Tern Island fell within the profile‐cluster typical for Christmas Island birds, both in a nonmetric multidimensional scaling analysis and in a population assignment test, suggesting dispersal events from Christmas Island to Tern Island. Several factors could explain the persistence of genetic structure despite frequent movements between colonies: many movements occurred during the nonbreeding season, many breeding‐season movements did not involve mate‐acquisition behaviours and individuals that do disperse may be selected against, as suggested by morphometric differences between colonies. The persistence of genetic structure among breeding colonies despite significant interisland movements suggests limits to the effectiveness of migration as a homogenizing force in this broadly distributed, extremely mobile species.
Census vs. effective population size in chinook salmon: large‐ and small‐scale environmental perturbation effects
Authors: Shrimpton J. Mark , Heath Daniel D. 
Published: September 2003

AbstractPopulation viability has often been assessed by census of reproducing adults. Recently this method has been called into question and estimation of the effective population size (Ne) proposed as a complementary method to determine population health. We examined genetic diversity in five populations of chinook salmon (Oncorhynchus tshawytscha) from the upper Fraser River watershed (British Columbia, Canada) at 11 microsatellite loci over 20 years using DNA extracted from archived scale samples. We tested for changes in genetic diversity, calculated the ratio of the number of alleles to the range in allele size to give the statistic M, calculated Ne from the temporal change in allele frequency, used the maximum likelihood method to calculate effective population size (NeM), calculated the harmonic mean of population size, and compared these statistics to annual census estimates. Over the last two decades population size has increased in all five populations of chinook examined; however, Ne calculated for each population was low (81–691) and decreasing over the time interval measured. Values of NeM were low, but substantially higher than Ne calculated using the temporal method. The calculated values for M were generally low (M < 0.70), indicating recent population reductions for all five populations. Large‐scale historic barriers to migration and development activities do not appear to account for the low values of Ne; however, available spawning area is positively correlated with Ne. Both Ne and M estimates indicate that these populations are potentially susceptible to inbreeding effects and may lack the ability to respond adaptively to stochastic events. Our findings question the practice of relying exclusively on census estimates for interpreting population health and show the importance of determining genetic diversity within populations.