bluuebunny/crossref_metadata_2025_split huggingface dataset:
Urinary iodine and thyroid volume in a Swedish population
Authors: Milakovic M. , Berg G. , Nyström E. , Lindstedt G. , Gebre‐Medhin M. , Eggertsen R. 
Published: December 2004

Abstract.Objective.  To evaluate the present efficacy of an iodine supplementation programme working in Sweden since 1936 by studying the iodine excretion in urine and determining the thyroid volume in a population in a semi‐rural community.Design.  A cross‐sectional population screening comprising three age groups with randomly selected individuals: group 1 (children): 7–9 years, n = 61 (invited 70); group 2 (teenagers): 15–17 years, n = 61 (invited 63), and group 3 (adults): 60–65 years; n = 57 (invited 73).Main measurements.  Urinary iodine was measured spectrophotometrically; thyroid volume by ultrasonography.Results.  The median values for urinary iodine concentration in the three age groups were 194 μg L−1, 246 μg L−1 and 190 μg L−1, respectively, indicating an adequate iodine intake. In the 7–9 year olds, the median value of the thyroid volume was 4.7 mL, which coincides with the recently established upper limit of normal children of that age, 4.0–4.8 mL (ICCIDD, International Council for control iodine deficiency disorders). One eight‐year‐old boy had a pronounced goiter. Four teenagers and one adult were found to have an enlarged thyroid gland according to earlier established reference volumes (15 years >16 mL; adults > 25 mL).Conclusion.  We conclude that the iodine intake in our region is sufficient in age groups ranging from young children to pre‐retirement adults.
Genetic evaluation of a proposed introduction: the case of the greater prairie chicken and the extinct heath hen
Authors: Palkovacs Eric P. , Oppenheimer Adam J. , Gladyshev Eugene , Toepfer John E. , Amato George , Chase Thomas , Caccone Adalgisa 
Published: December 2004

AbstractPopulation introduction is an important tool for ecosystem restoration. However, before introductions should be conducted, it is important to evaluate the genetic, phenotypic and ecological suitability of possible replacement populations. Careful genetic analysis is particularly important if it is suspected that the extirpated population was unique or genetically divergent. On the island of Martha's Vineyard, Massachusetts, the introduction of greater prairie chickens (Tympanuchus cupido pinnatus) to replace the extinct heath hen (T. cupido cupido) is being considered as part of an ecosystem restoration project. Martha's Vineyard was home to the last remaining heath hen population until its extinction in 1932. We conducted this study to aid in determining the suitability of greater prairie chickens as a possible replacement for the heath hen. We examined mitochondrial control region sequences from extant populations of all prairie grouse species (Tympanuchus) and from museum skin heath hen specimens. Our data suggest that the Martha's Vineyard heath hen population represents a divergent mitochondrial lineage. This result is attributable either to a long period of geographical isolation from other prairie grouse populations or to a population bottleneck resulting from human disturbance. The mtDNA diagnosability of the heath hen contrasts with the network of mtDNA haplotypes of other prairie grouse (T. cupido attwateri, T. pallidicinctus and T. phasianellus), which do not form distinguishable mtDNA groupings. Our findings suggest that the Martha's Vineyard heath hen was more genetically isolated than are current populations of prairie grouse and place the emphasis for future research on examining prairie grouse adaptations to different habitat types to assess ecological exchangeability between heath hens and greater prairie chickens.
Evidence of genetic selection for growth in new recruits of a marine fish
Authors: PLANES S. , ROMANS P. 
Published: December 2004

AbstractA cohort of Diplodus sargus, a coastal marine fish abundant in the Mediterranean Sea, has been surveyed from its settlement following the pelagic larval stage up to 4 months of age, when the juveniles are moving to adult habitats in order to assess selective processes. We followed the mortality by looking at the decrease in population abundance and, simultaneously, the genetic structure using allozymes and the growth associated with each genotype to test for a relationship between genotype and phenotype. The recruitment survey demonstrated that 80% of individuals arrived within a single night and that they show very similar age providing a discrete pulse of new recruits that we followed for changes in survival and allele frequencies. After 4 months, there was a total mortality of 80.8%, with the disappearance of 181 of 224 fish that initially colonized the rocky barrier. The decrease in number followed a logarithmic model with a maximum decrease in the early period (first 30 days). The model derived from the 4 months of data demonstrates that most of the mortality in the cohort occurs over the first 120 days following settlement and the model predicted a final abundance of 10 individuals after 1 year. Within the same period of 4 months, we observed significant decrease in multilocus heterozygosity. Such a decrease in heterozygosity partly resulted from a purge of the Pgm‐80* allele. Together with this major change in a natural population, an aquarium experiment demonstrated that individuals with Pgm‐80* alleles show significantly lower growth than other new recruits. We propose that the decrease in frequency of Pgm‐80* in the natural environment is the result of targeted predation that eliminates smaller individuals and therefore individuals bearing Pgm‐80*. The potential metabolic effect as well as a scenario that could lead to the maintenance of polymorphism is discussed.
Hybridization and contemporary evolution in an introduced cichlid fish from Lake Malawi National Park
Authors: STREELMAN J. TODD , GMYREK S. L. , KIDD M. R. , KIDD C. , ROBINSON R. L. , HERT E. , AMBALI A. J. , KOCHER T. D. 
Published: December 2004

AbstractRapidly evolving systems offer the chance to observe genetic and phenotypic change in real time. We exploit a well‐characterized introduction of cichlid fish into Lake Malawi National Park to document a short history of habitat colonization and the evolution of genes and colour pattern. In the early 1960s, a fish exporter introduced individuals of Cynotilapia afra to a single site (Mitande Point) of Thumbi West Island and, as late as 1983, the species was confined to this location. In 2001, C. afra had colonized the entire perimeter of Thumbi West. In July of that year, we sampled C. afra individuals from six sites around the island and scored variation in dorsal fin colour as well as allelic diversity at six microsatellite loci. We found that, in two decades, C. afra had diverged into genetically distinct, phenotypically different northern and southern populations. We observed a high proportion of hybrids between the introduced C. afra and the native Metriaclima zebra on the southern coast of Thumbi West, and speculate that hybridization is facilitated by low water clarity at these windward sites. The short history of C. afra at Thumbi West is a microcosm of contemporary evolutionary divergence and may provide the opportunity to study the process from start to finish in genetic detail.
Admixture and diversity in West African cattle populations
Authors: FREEMAN A. R. , MEGHEN C. M. , MacHUGH D. E. , LOFTUS R. T. , ACHUKWI M. D. , BADO A. , SAUVEROCHE B. , BRADLEY D. G. 
Published: December 2004

AbstractWe present a population genetic analysis of microsatellite variation in 16 West African cattle populations. West Africa represents a unique juxtaposition of different climatic and ecological zones in a relatively small geographical area. While more humid coastal regions are inhabited by the tsetse fly, a vector which spreads trypanosomiasis among cattle, the disease is not transmitted in the drier areas outside this zone. This is the most thorough study of genetic diversity in cattle within this area, which contains genetically important trypanotolerant Bos taurus breeds. Genetic relationships among the many breeds are examined and levels of diversity are assessed. Admixture levels were determined using a variety of methods. Ancestry informative or population‐associated alleles (PAAs) were selected using populations from India, the Near East and Europe. Multivariate analysis, the admix program and model‐based Bayesian admixture analysis approaches were also employed. These analyses reveal the direct impact of ecological factors and the profound effect of admixture on the cattle of this region. They also highlight the importance of efforts to prevent further dilution of African taurine breeds by B. indicus cattle.
Genetic structuring of Patagonian toothfish populations in the Southwest Atlantic Ocean: the effect of the Antarctic Polar Front and deep‐water troughs as barriers to genetic exchange
Authors: SHAW P. W. , ARKHIPKIN A. I. , AL‐KHAIRULLA H. 
Published: December 2004

AbstractThe environmental and/or life history factors affecting genetic exchange in marine species with potential for high dispersal are of great interest, not only from an evolutionary standpoint but also with regard to effective management. Previous genetic studies have demonstrated substantial differentiation among populations of the Patagonian toothfish around the Southern Ocean, indicating breakdown of gene flow across large distances between inhabited shelf areas. The present study examined genetic structuring through analysis of microsatellite loci and restriction fragment length poymorphism (RFLP) of the mitochondrial ND2 gene and control region of the toothfish population in the SW Atlantic, allowing examination of the relative effects of the Antarctic Polar Front (APF), deep‐water troughs and distance between sites. Mitochondrial DNA (mtDNA) data indicated a sharp genetic division between the Patagonian Shelf/North Scotia Ridge and the Shag Rocks/South Georgia samples, whereas microsatellite data showed much less distinct structuring and an intermediate position of the North Scotia Ridge samples. We suggest these data indicate that the APF, as a barrier to larval dispersal, is the major inhibitor of genetic exchange between toothfish populations, with deep‐water troughs and distance between sites contributing to genetic differentiation by inhibiting migration of relatively sedentary adults. We also suggest that differences between mtDNA and nuclear DNA population patterns may reflect either genome population size effects or (putative) male‐biased dispersal.
Nonallopatric and parallel origin of local reproductive barriers between two snail ecotypes
Authors: ROLÁN‐ALVAREZ EMILIO , CARBALLO MONICA , GALINDO JUAN , MORÁN PALOMA , FERNÁNDEZ BLANCA , CABALLERO ARMANDO , CRUZ RAQUEL , BOULDING ELIZABETH G. , JOHANNESSON KERSTIN 
Published: December 2004

AbstractTheory suggests that speciation is possible without physical isolation of populations (hereafter, nonallopatric speciation), but recent nonallopatric models need the support of irrefutable empirical examples. We collected snails (Littorina saxatilis) from three areas on the NW coast of Spain to investigate the population genetic structure of two ecotypes. Earlier studies suggest that these ecotypes may represent incipient species: a large, thick‐shelled ‘RB’ ecotype living among the barnacles in the upper intertidal zone and a small, thin‐shelled ‘SU’ ecotype living among the mussels in the lower intertidal zone only 10–30 m away. The two ecotypes overlap and hybridize in a midshore zone only 1–3 m wide. Three different types of molecular markers [allozymes, mitochondrial DNA (mtDNA) and microsatellites] consistently indicated partial reproductive isolation between the RB and the SU ecotypes at a particular site. However, each ecotype was related more closely to the other ecotype from the same site than to the same ecotype from another site further along the Galician coast (25–77 km away). These findings supported earlier results based solely on allozyme variation and we could now reject the possibility that selection produced these patterns. The patterns of genetic variation supported a nonallopatric model in which the ecotypes are formed independently at each site by parallel evolution and where the reproductive barriers are a byproduct of divergent selection for body size. We argue that neither our laboratory hybridization experiments nor our molecular data are compatible with a model based on allopatric ecotype formation, secondary overlap and introgression.
Molecular evidence for Pleistocene glacial cycles driving diversification of a North American desert spider, Agelenopsis aperta
Authors: AYOUB NADIA A. , RIECHERT SUSAN E. 
Published: December 2004

AbstractThe influence of historical climatic vs. geological changes on species diversification patterns was investigated in a widely distributed North American desert spider, Agelenopsis aperta (Araneae: Agelenidae), with particular reference to Pleistocene glacial cycles and earlier patterns of mountain building. Levels of sequence divergence obtained from the mitochondrial gene, cytochrome oxidase I, dated to the Pleistocene, eliminating Rocky Mountain orogeny as a cause of diversification, as orogeny ended 4 million years ago. The results of phylogenetic and network analyses showed the presence of three geographically defined clades, which were consistent with the presence of at least three glacial refugia: (i) east of the Rocky Mountains; (ii) between the Rocky Mountains and Sierra Nevadas; and (iii) west of the Sierra Nevadas. In addition, populations within the Rocky Mountains exhibited significantly lower genetic diversity than populations east of the Rocky Mountains and the haplotypes found within the Rockies were a subset of eastern haplotypes. These patterns suggest that a post‐Pleistocene range expansion occurred out of an eastern glacial refugium into the Rocky Mountains. Examination of phylogeographical studies of other North American desert taxa indicated that mountain building explained diversification patterns more effectively for some taxa but Pleistocene climate change was more important for others, including A. aperta.
Reconciling geography and genealogy: phylogeography of giant freshwater prawns from the Lake Carpentaria region
Authors: DE BRUYN MARK , WILSON JOHN C. , MATHER PETER B. 
Published: December 2004

AbstractThere is convincing geological evidence for the historical existence of an ancient lake on the Australian–New Guinea continental shelf during the late Pleistocene. Lake Carpentaria was a vast fresh‐ to brackishwater lake that would presumably have provided habitat for, and facilitated gene flow among, aquatic taxa that tolerate low to moderate salinities in this region. Moreover, it has been argued that the outflow of Papua New Guinea's Fly River was diverted westward into Lake Carpentaria during this period, although this hypothesis is controversial. We predicted that these events, if a true history, would have promoted gene flow and population growth via range‐expansion events in the giant freshwater prawn (Macrobrachium rosenbergii) and restricted gene flow subsequently by way of a vicariant event as sea levels rose during the late Pleistocene, and a marine environment replaced Lake Carpentaria. We tested these hypotheses using phylogeographical and phylogenetic analyses of mitochondrial DNA variation in M. rosenbergii populations sampled from the Lake Carpentaria region. Our results support the hypothesis that Lake Carpentaria facilitated gene flow among populations of M. rosenbergii that are today isolated, but contest claims of a westward diversion of the Fly River. We inferred the timing of initial expansion in the ‘Lake Carpentaria lineage’ and found the timing of this event to be broadly concordant with geological dating of the formation of Lake Carpentaria. Reconciling geological and molecular data, as presented here, provides a powerful framework for investigating the influence of historical earth history events on the distribution of biological (i.e. molecular) diversity.
Mitochondrial DNA variation and population structure of the island endemic Azorean bat (Nyctalus azoreum)
Authors: SALGUEIRO P. , COELHO M. M. , PALMEIRIM J. M. , RUEDI M. 
Published: December 2004

AbstractThe Azorean batNyctalus azoreumis the only endemic mammal native to the remote archipelago of the Azores. It evolved from a continental ancestor related to the Leisler's batNyctalus leisleriand is considered threatened because of its restricted and highly fragmented distribution. We studied the genetic variability in 159 individuals from 14 colonies sampled throughout the archipelago. Sequences of the D‐loop region revealed moderate but highly structured genetic variability. Half of the 15 distinct haplotypes were restricted to a single island, but the most common was found throughout the archipelago, suggesting a single colonization event followed by limited interisland female gene flow. AllN. azoreumhaplotypes were closely related and formed a star‐like structure typical of expanded populations. The inferred age of demographic expansions was consistent with the arrival of founder animals during the Holocene, well before the first humans inhabited the Azores. Comparisons with a population ofN. leislerifrom continental Portugal confirmed not only that allN. azoreumlineages were unique to the archipelago, but also that the current levels of genetic diversity were surprisingly high for an insular species. Our data imply that the Azorean bat has a high conservation value. We argue that geographical patterns of genetic structuring indicate the existence of two management units.
Identification of a PEST‐like motif in listeriolysin O required for phagosomal escape and for virulence in Listeria monocytogenes
Authors: Lety Marie‐Annick , Frehel Claude , Dubail Iharilalao , Beretti Jean‐Luc , Kayal Samer , Berche Patrick , Charbit Alain 
Published: December 2004

The hly‐encoded listeriolysin O (LLO) is a major virulence factor secreted by the intracellular pathogen Listeria monocytogenes, which plays a crucial role in the escape of bacteria from the phagosomal compartment. Here, we identify a putative PEST sequence close to the N‐terminus of LLO and focus on the role of this motif in the biological activities of LLO. Two LLO variants were constructed: a deletion mutant protein, lacking the 19 residues comprising this sequence (residues 32–50), and a recombinant protein of wild‐type size, in which all the P, E, S or T residues within this motif have been substituted. The two mutant proteins were fully haemolytic and were secreted in culture supernatants of L. monocytogenes in quantities comparable with that of the wild‐type protein. Strikingly, both mutants failed to restore virulence to a hly‐negative strain in vivo. In vitro assays showed that L. monocytogenes expressing the LLO deletion mutant was strongly impaired in its ability to escape from the phagosomal vacuole and, subsequently, to divide in the cytosol of infected cells. This work reveals for the first time that the N‐terminal portion of LLO plays an important role in the development of the infectious process of L. monocytogenes.
Generation and characterization of a PhoP homologue mutant of Neisseria meningitidis
Authors: Johnson C. R. , Newcombe J. , Thorne S. , Borde H. A. , Eales‐Reynolds L.‐J. , Gorringe A. R. , Funnell S. G. P. , McFadden J. J. 
Published: December 2004

Two‐component regulatory systems are important regulators of virulence genes in a number of bacteria. Genes encoding a two‐component regulator system, with homology to the phoP/phoQ system in salmonella, were identified in the meningococcal genome. Allele replacement was used to generate a meningococcal knock‐out mutant of the regulator component of this system, and its phenotype was examined. The mutant displayed many differences in protein profiles compared with wild type, consistent with it being a gene‐regulatory mutation. Many of the growth characteristics of the mutant were similar to those of phoP mutants of salmonella: it was unable to grow at low concentrations of magnesium and was sensitive to defensins and other environmental stresses. Magnesium‐regulated differences in protein expression were abrogated in the mutant, indicating that the meningococcal PhoP/PhoQ system may, as in salmonella, respond to changes in environmental magnesium levels. These results are consistent with the PhoP homologue playing a similar role in the meningococcus to PhoP in salmonella and suggest that it may similarly be involved in the regulation of virulence genes in response to environmental stimuli in the meningococcus. In support of this conclusion, we found the mutant grew was unable to grow in mouse serum and was attenuated in its ability to traverse through a layer of human epithelial cells. Identification of those genes regulated by the meningococcal PhoP may provide a route towards the identification of virulence genes in the meningococcus.
Genome plasticity in Streptomyces: identification of 1 Mb TIRs in the S. coelicolor A3(2) chromosome
Authors: Weaver David , Karoonuthaisiri Nitsara , Tsai Hsiu‐Hwei , Huang Chih‐Hung , Ho Mai‐Lan , Gai Shuning , Patel Kedar G. , Huang Jianqiang , Cohen Stanley N. , Hopwood David A. , Chen Carton W. , Kao Camilla M. 
Published: December 2004

SummaryThe chromosomes of several widely used laboratory derivatives of Streptomyces coelicolor A3(2) were found to have 1.06 Mb inverted repeat sequences at their termini (i.e. long‐terminal inverted repeats; L‐TIRs), which are 50 times the length of the 22 kb TIRs of the sequenced S. coelicolor strain M145. The L‐TIRs include 1005 annotated genes and increase the overall chromosome size to 9.7 Mb. The 1.06 Mb L‐TIRs are the longest reported thus far for an actinomycete, and are proposed to represent the chromosomal state of the original soil isolate of S. coelicolor A3(2). S. coelicolor A3(2), M600 and J1501 possess L‐TIRs, whereas approximately half the examined early mutants of A3(2) generated by ultraviolet (UV) or X‐ray mutagenesis have truncated their TIRs to the 22 kb length. UV radiation was found to stimulate L‐TIR truncation. Two copies of a transposase gene (SCO0020) flank 1.04 Mb of DNA in the right L‐TIR, and recombination between them appears to generate strains containing short TIRs. This TIR reduction mechanism may represent a general strategy by which transposable elements can modulate the structure of chromosome ends. The presence of L‐TIRs in certain S. coelicolor strains represents a major chromosomal alteration in strains previously thought to be genetically similar.
Transcription activation at the Escherichia coli melAB promoter: interactions of MelR with the C‐terminal domain of the RNA polymerase α subunit
Authors: Grainger David C. , Belyaeva Tamara A. , Lee David J. , Hyde Eva I. , Busby Stephen J. W. 
Published: December 2004

SummaryWe have investigated the role of the RNA polymerase α subunit during MelR‐dependent activation of transcription at the Escherichia coli melAB promoter. To do this, we used a simplified melAB promoter derivative that is dependent on MelR binding at two 18 bp sites, located from position −34 to −51 and from position −54 to −71, upstream of the transcription start site. Results from experiments with hydroxyl radical footprinting, and with RNA polymerase, carrying α subunits that were tagged with a chemical nuclease, show that the C‐terminal domains of the RNA polymerase α subunits are located near position −52 and near position −72 during transcription activation. We demonstrate that the C‐terminal domain of the RNA polymerase α subunit is needed for open complex formation, and we describe two experiments showing that the RNA polymerase α subunit can interact with MelR. Finally, we used alanine scanning to identify determinants in the C‐terminal domain of the RNA polymerase α subunit that are important for MelR‐dependent activation of the melAB promoter.