bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of endothelin‐1 on portal‐systemic collaterals of common bile duct‐ligated cirrhotic rats
Authors: Chan C.‐C. , Wang S.‐S. , Lee F.‐Y. , Chang F.‐Y. , Lin H.‐C. , Hou M.‐C. , Huang H.‐C. , Lee S.‐D.
Published: April 2004

Background/Aims  Endothelin‐1 (ET‐1) may induce intrahepatic vasoconstriction and consequently increase portal pressure. Endothelin‐1 has been shown to exert a direct vasoconstrictive effect on the collateral vessels in partially portal vein‐ligated rats with a high degree of portal‐systemic shunting. This study investigated the collateral vascular responses to ET‐1, the receptors in mediation and the regulation of ET‐1 action by nitric oxide and prostaglandin in cirrhotic rats with a relatively low degree of portal‐systemic shunting.

Methods  The portal‐systemic collaterals of common bile duct‐ligated (BDL) cirrhotic rats were tested by in situ perfusion. The concentration‐response curves of collaterals to graded concentrations of ET‐1 (10−10−10−7 m) with or without BQ‐123 (ETA receptor antagonist, 2 × 10−6 m), BQ‐788 (ETB receptor antagonist, 10−7 m) or both were recorded. In addition, the collateral responses to ET‐1 with preincubation of Nω‐nitro‐L‐arginine (NNA, 10−4 M), indomethacin (INDO, 10−5 M) or in combination were assessed.

Results  Endothelin‐1 significantly increased the perfusion pressures of portal‐systemic collaterals. The ET‐1‐induced constrictive effects were inhibited by BQ‐123 or BQ‐123 plus BQ‐788 but not by BQ‐788 alone. The inhibitory effect was greater in the combination group. Pretreatment of NNA or NNA plus INDO equivalently enhanced the response of ET‐1 while pretreatment of INDO alone exerted no effect.

Conclusion  Endothelin‐1 has a direct vasoconstrictive effect on the collaterals of BDL cirrhotic rats, mainly mediated by ETA receptor. Endogenous nitric oxide may play an important role in modulating the effects of ET‐1 in the portal‐systemic collaterals of BDL cirrhotic rats.
Insulin‐like growth factors and pancreas beta cells
Authors: Van Haeften T. W. , Twickler Th. B.
Published: April 2004

Insulin‐like growth factors (IGFs) have been implicated in normal growth, and especially foetal pancreas beta‐cell development. As low birth weight has been implicated in the development of obesity and type 2 diabetes, much research has evolved into the importance of IGF and their signalling pathways for pancreas beta‐cell development, and for type 2 diabetes. Insulin‐like growth factor‐I signalling has a lot in common with insulin signalling, and is involved in diverse cellular effects such as antiapoptosis, protein synthesis, cell growth and mitogenesis. Insulin‐like growth factor‐II can be bound by the insulin receptor A subtype and the IGF‐1 receptor, which may explain its antiapoptotic effect.

Various knock‐out model studies indicate that absence of IGF‐I or the IGF‐1 receptor is critical for foetal and postnatal growth. Similarly, knock‐out models of post‐receptor molecules (such as IRS‐2) point to the physiological role of IGFs for pancreas beta‐cell development. A beta‐cell‐specific IGF‐1 receptor knock out model indicates the importance of IGF‐I for beta‐cell function. The Goto‐Kakizaki (GK) rat, a model for diabetes, has insufficient beta‐cell development, which may be related to its defective IGF‐II synthesis.

As normal pancreas beta cells adapt to the prevailing insulin resistance with increasing beta‐cell function, it is possible that insulin resistance interacts with IGF signalling in pancreas beta cells.
Diving behavior of immature, feeding Pacific bluefin tuna (Thunnus thynnus orientalis) in relation to season and area: the East China Sea and the Kuroshio–Oyashio transition region
Authors: Kitagawa Takashi , Kimura Shingo , Nakata Hideaki , Yamada Harumi
Published: April 2004

Twenty‐four archival tags were recovered from Pacific bluefin tuna previously released off Tsushima Island in the East China Sea. By analysis of the time‐series data of the pressure and the ambient and internal temperature from the 24 tags, we examined the relationship between the tuna's pattern of diving and the thermocline depth. In the East China Sea, diving and feeding events occurred throughout almost the entire day in both winter and summer, suggesting that the purpose of diving is for feeding. In summer, the feeding frequency was greater than that in winter, which corresponds to the fact that growth is more rapid in summer than in winter. During summer in the Kuroshio–Oyashio transition region, on the other hand, feeding events were much more frequent than those in the East China Sea, in spite of a lower diving frequency. The mean horizontal distance traveled was also significantly higher and it seems that in this area they may move horizontally to feed on prey accumulated at the surface. We conclude that, in addition to the ambient temperature structure, the vertical and horizontal distribution of prey species plays an important role in the feeding behavior of Pacific bluefin tuna. One bluefin tuna migrated to the Oyashio frontal area, where both the horizontal and the vertical thermal gradients are much steeper. The fish spent most of the time on the warmer side of the front and often traveled horizontally to the colder side during the day, perhaps to feed. This implies that there is a thermal barrier effect, in this case from the Oyashio front, on their behavior. The frequency of feeding events was low, although all the monitored fish dived every dawn and dusk, irrespective of the seasons or location. It is possible that these twice‐daily diving patterns occurred in response to the change in ambient light at sunrise and sunset.
Trends in carbon flux to seabirds in the Peruvian upwelling system: effects of wind and fisheries on population regulation
Authors: Jahncke J. , Checkley D. M. , Hunt G. L.
Published: April 2004

We hypothesized that change in the annual population size of guano‐producing seabirds (cormorant, Phalacrocorax bougainvillii; booby, Sula variegata; pelican, Pelecanus thagus) is a response to changes in primary and secondary production of the Peruvian upwelling system. We tested this hypothesis by modeling nitrate input through upwelling to the upper layers of the ocean off Peru between 6° and 14°S using data on wind stress and sea surface temperature. The model predicted the amount of carbon fixed by primary production each year from 1925 to 2000, which was then apportioned to the Peruvian anchovy (Engraulis ringens) biomass and ultimately to the seabird population and the anchovy fishery, the largest single‐species fishery on Earth. The model predicted a marked increase in primary production as a consequence of increasing wind stress. It overestimated the anchovy biomass after the collapse of the fishery in 1972, but closely predicted the growth of seabird populations from 1925 to the mid‐1960s, and their decline thereafter, explaining about 94% of the variation in seabird numbers from 1925 to 2000. The model indicates the seabirds consumed 14.4% of the available anchovies and, thus, that seabirds consumed 2.3% of the new production, before the development of the anchovy fishery, and only 2.2% of the available anchovies and 0.3% of the new production after the development of the fishery. The model results clarify the roles that environmental and anthropogenic factors may have had in regulating the guano‐producing seabird populations. It indicates that the growth of seabird populations from 1925 to 1955 was likely a response to increased productivity of the Peruvian upwelling system and that the subsequent drastic decline in seabird abundance was likely due to competition for food with the fishery, which caught ∼85% of the anchovies, which otherwise would have been available for the seabirds. This model also shows that an increase in oceanic primary production promotes reproductive success and population growth in higher trophic level organisms.
Simulating larval supply to estuarine nursery areas: how important are physical processes to the supply of larvae to the Aransas Pass Inlet?
Authors: Brown C. A. , Holt S. A. , Jackson G. A. , Brooks D. A. , Holt G. J.
Published: April 2004

Factors controlling the movement of fish larvae from coastal spawning environments to estuarine nursery areas are important to fish recruitment. In this paper, the role of physical processes in larval transport to estuarine nursery areas in the Aransas Pass region, Texas, is examined using a circulation model coupled with a fixed‐depth particle transport model. Two phases of transport are examined: transport on the shelf to the tidal inlet and transport through the inlet to estuarine nursery areas. Observed pulsing in the supply of red drum (Sciaenops ocellatus) larvae to the tidal inlet is significantly correlated with modeled particle supply. This pulsing is not correlated with a specific physical process, but results from the interaction of several factors affecting water movement, including low‐frequency variations in water level and wind forcing. Simulations suggest that the primary spawning region for red drum larvae that utilize nursery habitat in the Aransas Pass region is located north of the inlet. Patterns in the trajectories of particles that successfully enter the inlet reveal that they move alongshelf in the nearshore region and then move into the inlet, rather than moving directly across the shelf to the inlet. The approach path of particles outside the inlet determines the spatial transport patterns for inlets with branched channels and multiple bays. This study demonstrates that physical processes play an important role in determining larval supply to a tidal inlet.
Effect of customization of master gutta‐percha cone on apical control of obturation using different techniques: an in vitro study
Authors: Van Zyl S. P. , Gulabivala K. , Ng Y.‐L.
Published: April 2004

Aims  (i) To compare the prevalence of root filling extrusion placed using three different obturation techniques, each with or without customization of the master gutta‐percha cone; and (ii) to investigate the effects of various factors on the prevalence of root filling extrusion.

Methodology  A total of 180 roots were selected and randomly allocated into three groups. Five general dental practitioners were recruited; each obturated one group of the roots using three techniques, namely cold lateral condensation (n = 20), Schilder's warm vertical condensation (n = 20) or continuous wave condensation (n = 20). Each technique was completed with (n = 10) or without (n = 10) customization of the master gutta‐percha cone using chloroform. Two groups of the roots were recycled to allow all five operators to use them. Two observers examined the preinstrumentation, working length, master apical file and postobturation radiographs, and determined the presence of root filling extrusion and voids independently; they were blinded regarding the obturation technique used. The presence of root filling extrusion was also assessed by inspecting the root apex after obturation. The data were analysed using logistic regression models.

Results  A total of 300 root fillings were performed and 291 were included for analysis. Most of the root fillings were placed within 0.5 mm of the working length (80%, n = 233); only 20% (n = 58) were placed >0.5 mm beyond the working length. The odds of prevalence of extrusion >0.5 mm were significantly reduced by approximately 50% when cold lateral condensation (OR = 0.50; 95% CI = 0.26, 0.99; P = 0.04) or customization of master gutta‐percha cone (OR = 0.55; 95% CI = 0.30, 0.99; P = 0.04) was used. One operator produced 2.5 times more extruded root fillings than the other operators (OR = 2.50; 95% CI = 1.31, 4.78; P = 0.006). Other factors, such as root canal curvature and length, apical size of the prepared canal, as well as the operator's preferred obturation technique, were shown to have no significant influence on the prevalence of extrusion.

Conclusions  The prevalence of extrusion was significantly lower when cold lateral condensation and customization of the master cone were used. The ‘operator’ emerged as a significant factor affecting the prevalence of root filling extrusion.
Population structure of California coyotes corresponds to habitat‐specific breaks and illuminates species history
Authors: Sacks Benjamin N. , Brown Sarah K. , Ernest Holly B.
Published: April 2004

Little is known about the relationship between animal movements and the emergent structure of populations, especially for species occupying large continuous distributions. Some such mammals disperse disproportionately into habitat similar to their natal habitat, a behavioural bias that might be expected to lead to habitat‐conforming genetic structure. We hypothesized that coyotes (Canis latrans) would exhibit such natal‐biased dispersal, and used 13 microsatellite loci to test, correspondingly, whether genetic structure conformed to major habitat breaks. First, we used a model‐based approach to assign coyote genotypes to distinct genetic clusters irrespective of geographical location. Visualization on a geographical information system revealed a strong concordance between the locations of cluster assignments and habitat bioregions, not explainable in terms of physical dispersal barriers or intervening low‐quality habitat. Next, we used a multiple Mantel test, which controlled for effects of geographical distance (itself, marginally significant; P = 0.06), to statistically determine that genetic distance was indeed higher between than within bioregions (P < 0.001). Whereas previously published examples of landscape effects on gene flow have typically been explainable in terms of species‐wide habitat affinities or dispersal barriers, our finding that genetic subdivisions were associated with unobstructed boundaries between contiguous habitats suggests a role for intraspecific variability in habitat affinities as a factor underlying genetic structure. In addition, our data combined with previously published data suggest a pattern of genetic isolation‐by‐distance throughout western North America, consistent with independent evidence that the western half of the coyote range predates European settlement.
Solanum nigrum: A model ecological expression system and its tools
Authors: Schmidt Dominik D. , Kessler André , Kessler Danny , Schmidt Silvia , Lim Michelle , Gase Klaus , Baldwin Ian T.
Published: April 2004

Plants respond to environmental stresses through a series of complicated phenotypic responses, which can be understood only with field studies because other organisms must be recruited for their function. If ecologists are to fully participate in the genomics revolution and if molecular biologists are to understand adaptive phenotypic responses, native plant ecological expression systems that offer both molecular tools and interesting natural histories are needed. Here, we present Solanum nigrum L., a Solanaceous relative of potato and tomato for which many genomic tools are being developed, as a model plant ecological expression system. To facilitate manipulative ecological studies with S. nigrum, we describe: (i) an Agrobacterium‐based transformation system and illustrate its utility with an example of the antisense expression of RuBPCase, as verified by Southern gel blot analysis and real‐time quantitative PCR; (ii) a 789‐oligonucleotide microarray and illustrate its utility with hybridizations of herbivore‐elicited plants, and verify responses with RNA gel blot analysis and real‐time quantitative PCR; (iii) analyses of secondary metabolites that function as direct (proteinase inhibitor activity) and indirect (herbivore‐induced volatile organic compounds) defences; and (iv) growth and fitness‐estimates for plants grown under field conditions. Using these tools, we demonstrate that attack from flea beetles elicits: (i) a large transcriptional change consistent with elicitation of both jasmonate and salicylate signalling; and (ii) increases in proteinase inhibitor transcripts and activity, and volatile organic compound release. Both flea beetle attack and jasmonate elicitation increased proteinase inhibitors and jasmonate elicitation decreased fitness in field‐grown plants. Hence, proteinase inhibitors and jasmonate‐signalling are targets for manipulative studies.
On the neutrality of molecular genetic markers: pedigree analysis of genetic variation in fragmented populations
Authors: Van Oosterhout C. , Van Heuven M. K. , Brakefield P. M.
Published: April 2004

Many studies employ molecular markers to infer ecological and evolutionary processes, assuming that variation found at genetic loci offers a reliable representation of stochastic events in natural populations. Increasingly, evidence emerges that molecular markers might not always be selectively neutral. However, only a few studies have analysed how deviations from neutrality could affect estimates of genetic variation, using populations with known genealogy. We monitored changes in allozyme variation over eight generations in captive metapopulations of the butterfly Bicyclus anynana. Population demography was recorded by individually marking 35 000 butterflies and constructing pedigrees. We designed a computer program that simulated the inheritance of founder allozyme alleles in butterfly pedigrees. We thus tested whether the observed transmission of allozyme alleles could be explained by random genetic drift alone, or whether there was evidence for positive or negative selection. This analysis showed that in the smallest metapopulations the loss of allozyme variation exceeded the neutral rate. Possibly, linkage disequilibria between deleterious mutations and marker alleles resulted in background selection and a faster erosion of allozyme variation. In larger metapopulations, one locus (MDH) showed a significant heterozygote excess and smaller than expected loss in heterozygosity, observations consistent with (associative) overdominance. This study demonstrates that the neutrality of molecular markers cannot always be assumed, particularly in small populations with a high mutation load.
Genetic diversity ofRanunculus acrisL. (Ranunculaceae) populations in relation to species diversity and habitat type in grassland communities
Authors: Odat Nidal , Jetschke Gottfried , Hellwig Frank H.
Published: April 2004

Correlates between genetic diversity at intra‐ and interpopulation levels and the species diversity in plant communities are rarely investigated. Such correlates may give insights into the effect of local selective forces across different communities on the genetic diversity of local plant populations. This study has employed amplified fragment length polymorphism to assess the genetic diversity within and between 10 populations ofRanunculus acrisin relation to the species diversity (richness and evenness) of grassland communities of two different habitat types, ‘seminatural’ and ‘agriculturally improved’, located in central Germany. Within‐population genetic diversity estimated by Nei's unbiased gene diversity (HE) was high (0.258–0.334), and was not correlated with species richness (Pearson'sr = −0.17;P = 0.64) or species evenness (Pearson'sr = 0.15;P = 0.68) of the plant communities. However, the genetic differentiation betweenR. acrispopulations was significantly correlated with the difference in species evenness (Mantel'sr = 0.62,P = 0.02), but not with difference in species richness of plant communities (r = −0.17,P = 0.22). Moreover, we also found that populations ofR. acrisfrom the ‘seminatural’ habitat were genetically different (amova,P < 0.05) from those in ‘agriculturally improved’ habitats, suggesting that gene flow between these habitat types is limited. The results reported in this study may indicate that habitat characteristics influence the genetic diversity of plant species.
Microsatellite DNA markers: evaluating their potential for estimating the proportion of hatchery‐reared offspring in a stock enhancement programme
Authors: Bravington M. V. , Ward R. D.
Published: April 2004

We describe a statistical method for estimating the effectiveness of a stock enhancement programme using nuclear DNA loci. It is based on knowing the population allele frequencies and the genotypes of the hatchery parents (mother only, or mother and father), and on determining the probability that a wild‐born animal will by chance have a genotype consistent with hatchery origin. We show how to estimate the proportion of released animals in the wild population, and its standard error. The method is applied to a data set of eight microsatellite loci in brown tiger prawns (Penaeus esculentus), prior to the start of a possible enhancement programme. We conclude that, for this particular data set, the effectiveness of such an enhancement programme could be quantified accurately if both maternal and paternal genotypes are known, but not if maternal genotypes only are known. Full paternal genotyping would require offspring genotyping and thus would be expensive, but a partly typed paternal genotype from a mass homogenate of offspring would be almost as effective and much cheaper. The experiment would become feasible based on maternal genotypes alone, if a further three typical microsatellite loci could be found to add to the existing panel of eight. The methods detailed should be of interest to any enhancement project that relies on nuclear DNA markers to provide tags.
Heterogeneous genetic structure in a Fagus crenata population in an old‐growth beech forest revealed by microsatellite markers
Authors: Asuka Y. , Tomaru N. , Nisimura N. , Tsumura Y. , Yamamoto S.
Published: April 2004

The within‐population genetic structure of Fagus crenata in a 4‐ha plot (200 × 200 m) of an old‐growth beech forest was analysed using microsatellite markers. To assess the genetic structure, Moran's I spatial autocorrelation coefficient was calculated. Correlograms of Moran's I showed significant positive values less than 0.100 for short‐distance classes, indicating weak genetic structure. The genetic structure within the population is created by limited seed dispersal, and is probably weakened by overlapping seed shadow, secondary seed dispersal, extensive pollen flow and the thinning process. Genetic structure was detected in a western subplot of 50 × 200 m with immature soils and almost no dwarf bamboos (Sasa spp.), where small and intermediate‐sized individuals were distributed in aggregations with high density because of successful regeneration. By contrast, genetic structure was not found in an eastern subplot of the same size with mature soils and Sasa cover, where successful regeneration was prevented, and the density of the small and intermediate‐sized individuals was low. Moreover, genetic structure of individuals in a small‐size class (diameter at breast height < 12 cm) was more obvious than in a large‐size class (diameter at breast height ≥ 12 cm). The apparent genetic structure detected in the 4‐ha plot was therefore probably the result of the structure in the western portion of the plot and in small and intermediate‐sized individuals that successfully regenerated under the favourable environment. The heterogeneity in genetic structure presumably reflects variation in the density that should be affected by differences in regeneration dynamics associated with heterogeneity in environmental conditions.
Genetic divergence, population structure and historical demography of rare springsnails (Pyrgulopsis) in the lower Colorado River basin
Authors: Hurt Carla R.
Published: April 2004

Springsnails of the genus Pyrgulopsis are the most diverse group of freshwater gastropods in North America and current estimates show that Pyrgulopsis contains ~120 different species, many of which are at risk of extinction. Some factors contributing to their exceptional diversity include poor dispersal ability and extreme habitat specificity based on water availability, chemistry and depth. Most taxa exhibit high degrees of endemism, with many species occurring only in a single spring or seep, making springsnails ideal for studies of speciation and population structure. Here I present data from a survey of genetic variation at the mitochondrial gene cytochrome oxidase I from 37 populations and over 1000 individuals belonging to 16 species of Pyrgulopsis distributed throughout the lower Colorado River basin. High levels of interspecific sequence divergence indicate that Pyrgulopsis may have colonized this region multiple times beginning in the late Miocene (~6 Ma); earlier than previous estimates based on fossil evidence. Estimates of nucleotide diversity differ greatly among species and may reflect differences in demographic processes. These results are used to identify factors contributing to radiation of species in this region. The implications of this evolutionary history and genetic variation are discussed in relation to future management and conservation.
Genetic variation in piñon pine, Pinus edulis, associated with summer precipitation
Authors: Mitton Jeffry B. , Duran Kristy L.
Published: April 2004

Three previous reports of microgeographical variation of glycerate dehydrogenase (Gly) frequencies in piñon, Pinus edulis, established the hypothesis that Gly frequencies contribute to adaptation to heterogeneous environments, specifically to variation in soil moisture. In each of these studies, the frequency of the Gly‐3 allele or of Gly‐33 homozygotes was higher on dry sites than on nearby moist sites. Here we attempt to extend these observations by testing the hypothesis that Gly frequencies respond to soil moisture variation on a range‐wide scale. Gly frequencies were surveyed in 11 natural populations, and the frequency of the Gly‐3 allele varied from 0.27 to 0.65 among the sample sites. Elevation varied from 1650 to 3100 m, and summer precipitation, defined as precipitation from April to August, varied from 13.7 to 26.4 cm. The soil types at the collection sites were schist, quaternary volcanic or a mixture of shale and sandstone. Logistic regression revealed that Gly frequencies did not respond to either elevation or soil type, but were related to summer precipitation (P < 0.01). The correlation between summer precipitation and the frequency of the Gly‐3 allele was r = −0.92 (P < 0.001). Thus, the patterns of differentiation on microgeographical scales are consistent with greater differentiation on a range‐wide scale.
Development of microarray‐based diagnostics of voles and shrews for use in biodiversity monitoring studies, and evaluation of mitochondrial cytochrome oxidase I vs. cytochrome b as genetic markers
Authors: Pfunder M. , Holzgang O. , Frey J. E.
Published: April 2004

Molecular methods are widely used for species identification of mammals. In particular, the mitochondrial cytochrome b gene sequence has proven helpful for this purpose. Microarray technology can now open up new perspectives for biodiversity monitoring. With microarrays, many thousands of genetically based characteristics can be tested on one microscopic glass slide called a ‘chip’. A ‘Mammalia‐Chip’, for example, could include redundant diagnostic markers to unambiguously identify all European mammal species. Of broader use, and therefore economically more relevant, could be a ‘Biodiversity‐Chip’, containing diagnostic features to distinguish key species in the taxa of bacteria, lichen, molluscs, insects, fungi, mammals, etc. An important prerequisite for any mixed‐phyla chip is a standardization of methods. One of the most promising genes as a universal marker for all eukaryotes is cytochrome oxidase I. We show that cytochrome oxidase I is adequate for the discrimination of different species of voles and shrews with cluster analysis. Based on these results we present a diagnostic microarray‐chip using cytochrome oxidase I sequences for the identification of three species of Sorex (Soricidae, Insectivora) and four species of Microtus (Arvicolinae, Rodentia). We conclude that cytochrome oxidase I can be used as an alternative marker to cytochrome b in a mixed‐phyla chip, or both genes can be used in combination to enhance redundance and thus robustness of a specific chip including small mammals.
Long‐distance pollen flow and tolerance to selfing in a neotropical tree species
Authors: Latouche‐Hallé C. , Ramboer A. , Bandou E. , Caron H. , Kremer A.
Published: April 2004

Outcrossing rates, pollen dispersal and male mating success were assessed in Dicorynia guianensis Amshoff, a neotropical tree endemic to the Guiana shield. All adult trees within a continuous area of 40 ha (n = 157) were mapped, and were genotyped with six microsatellite loci. In addition, progenies were genotyped from 22 mature trees. At the population level, the species was mostly outcrossing (tm = 0.89) but there was marked variation among individuals. One tree exhibited mixed mating, confirming earlier results obtained with isozymes that D. guianensis can tolerate selfing. A Bayesian extension of the fractional paternity method was used for paternity analysis, and was compared with the neighbourhood method used widely for forest trees. Both methods indicated that pollen dispersal was only weakly related to distance between trees within the study area, and that the majority (62%) of pollen came from outside the study stand. Using maximum likelihood, male potential population size was estimated to be 1119, corresponding to a neighbourhood size of 560 hectares. Male mating success was, however, related to the diameter of the stem and to flowering intensity assessed visually. The mating behaviour of D. guianensis is a combination of long‐distance pollen flow and occasional selfing. The species can still reproduce when it is extremely rare, either by selfing or by dispersing pollen at long distances. These results, together with the observation that male mating success was correlated with the size of the trees, could be implemented in management procedures aiming at regenerating the species.
Individual assignment test reveals differential restriction to dispersal between two salmonids despite no increase of genetic differences with distance
Authors: Castric Vincent , Bernatchez Louis
Published: April 2004

In many species genes move over limited distances, such that genetic differences among populations or individuals are expected to increase as a function of geographical distance. In other species, however, genes may move any distance over a single generation time, such that no increase of genetic differences is expected to occur with distance. Patterns of gene dispersal have been assessed typically using this theoretical property. In this study, this classical approach based on a Mantel test was compared to a new method using individual assignment to reveal contrasts in dispersal patterns between 15 populations of brook charrSalvelinus fontinalisand 10 populations of Atlantic salmonSalmo salarsampled in eastern Canada, where both species co‐occur naturally. Based on the Mantel test, we found evidence for neither an increase of genetic differences with distance in either species nor a significant contrast between them. The individual‐based method, in contrast, revealed that individual assignment in both species was non random, being significantly biased toward geographically proximate locations. Furthermore, brook charr were on average assigned to a closer river than were salmon, according to a priori expectations based on the dispersal behaviour of the two species. We thus propose that individual assignment methods might be a promising and more powerful alternative to Mantel tests when isolation by distance cannot be postulated a priori.
Speciation, phylogeography and evolution of life history and morphology in plethodontid salamanders of the Eurycea multiplicata complex
Authors: Bonett R. M. , Chippindale P. T.
Published: April 2004

Understanding the complex interactions among environment, genotype and ontogeny in determining organismal phenotypes is cental to many biological disciplines. The Eurycea multiplicata complex, endemic to the Interior Highlands (Ozark Plateau and Ouachita Mountains) of eastern North America, comprises a diverse radiation of paedomorphic surface‐dwelling (E. tynerensis), metamorphic surface‐dwelling (E. multiplicata multiplicata and E. m. griseogaster) and metamorphic subterranean (Typhlotriton spelaeus) hemidactyliine plethodontid salamanders. Portions of two mitochondrial genes, cytochrome‐b and NADH dehydrogenase‐4, totalling 1818 base pairs (bp) were sequenced for 70 ingroup individuals plus numerous outgroup taxa, to examine the biogeography and relationships among these morphologically disparate species. Results show the E. multiplicata complex to be monophyletic, with its two most divergent clades corresponding to geography, not morphology or life history. Transforming surface‐dwelling populations from the Ouachitas (E. m. multiplicata) are sister to the Ozark taxa, including paedomorphic surface‐dwelling (E. tynerensis), subterranean (T. spelaeus) and transforming surface‐dwelling salamanders assigned to the ‘subspecies’E. m. griseogaster. Among Ozark taxa T. spelaeus (deeply nested within Eurycea) is sister to a clade that includes E. m. griseogaster and E. tynerensis. Current taxonomy suggests that paedomorphic populations (E. tynerensis) from the western Ozarks are distinct from nearby transforming populations (E. m. griseogaster). However, paedomorphic and transforming salamanders do not form reciprocally monophyletic groups and many populations share almost identical haplotypes. Ancestral state reconstruction of life history traits shows that paedomorphosis arose independently from three to nine times. Most populations are either completely paedomorphic or completely transforming. This suggests that local habitat parameters strongly influence life history mode in this complex, either facultatively or by selection for particular genotypes.
Molecular insight into patterns of colony composition and paternity in the common mole‐ratCryptomys hottentotus hottentotus
Authors: Bishop J. M. , Jarvis J. U. M. , Spinks A. C. , Bennett N. C. , O'Ryan C.
Published: April 2004

We report the discovery of intraspecific variation in both colony composition and patterns of paternity in two populations of the social common mole‐ratCryptomys hottentotus hottentotus. These two populations represent the mesic and arid habitat extremes of the species’ broad ecological range in South Africa. Until recently colonies of the common mole‐rat were thought to consist of familial groups whereby all colony members were the offspring of a monogamous reproductive pair. The remaining colony members were thought to forego reproduction until both social and ecological conditions favoured dispersal and opportunities for independent outbreeding. Results from genetic assignment tests using microsatellite markers indicate that while colony composition is dominated by familial groups, colonies within both populations included both adult and subadult foreign conspecifics. Analysis of parentage reveals that the social organization ofC. h. hottentotusis not that of strict monogamy; paternity of offspring was not assigned consistently to the largest, most dominant male within the colony. Moreover, a number of significantly smaller males were found to sire offspring, suggesting a sneak‐mating strategy by subordinate within‐colony males. Extra‐colony extra‐pair paternity (ECP) was also found to characterizeC. h. hottentotuscolonies, occurring with similar frequencies in both habitats. Both dominant established breeding males and subordinate males were identified as siring young in nonsource colonies. Furthermore, established breeding males were found to sire extra‐colony young in the same season as siring young within their source colonies. We discuss the significance of these results within the context of the divergent ecological regimes characterizing the two sites and observe that our results revisit the accuracy of using behavioural and morphological characters, which have structured the basis of our understanding of the behavioural ecology of this species, as indicators of breeding status in mark–recapture studies.
Genetic differentiation and local adaptation in the salt‐marsh beetle Pogonus chalceus: a comparison between allozyme and microsatellite loci
Authors: Dhuyvetter H. , Gaublomme E. , Desender K.
Published: April 2004

The genetic structure of Pogonus chalceus from 11 Atlantic and seven Mediterranean Western European populations was analysed. Results from seven allozyme loci were compared to five microsatellites to test the hypothesis that some enzymatic loci undergo selection. Both allozyme and microsatellite results showed that Mediterranean beetle populations are genetically distinct from Atlantic populations. The analysis of the genetic structure showed that FST values derived from all microsatellite loci were much smaller than those obtained from allozymes. The enzymatic locus Idh‐1 exhibited a high value compared to the other loci, suggesting that it is non‐neutral. The same Idh‐1 locus was implicated in differentiation between temporary and stable populations, as followed also from a highly significant relationship between the allele two of this Idh‐1 locus and dispersal power population estimates. The ‘parallel evolution’ model may account for the diversification of locally adapted Pogonus chalceus populations between different microhabitats.
An ancient bottleneck in the Lost Pines of central Texas
Authors: Al‐Rabab’ah Mohammad A. , Williams Claire G.
Published: April 2004

The retreating edge hypothesis for species responding to climate change predicts severe bottlenecks and eventual extinction. The disjunct Lost Pines population at the westernmost edge of the widespread Pinus taeda range is well suited for testing this prediction. The occurrence of one or more genetic bottlenecks in the Lost Pines population was tested using 34 nuclear microsatellite markers and a control sample from the larger, more continuous east Texas P. taeda forests. The Lost Pines population has undergone drastic contractions in effective population size between 3000 and 30 000 years bp. These results were supported by: (i) detection of transient heterozygosity excess, (ii) a mode‐shift indicator of allele frequencies, and (iii) a ratio of allele number to allele size range. No bottleneck was detected for the east Texas control using any of the three methods. The distribution of allele frequencies was skewed for the Lost Pines population compared to the control, indicating a loss of rare alleles. However, allelic diversity was similar between the Lost Pines population and its east Texas control; the mean allele number per locus was 5.29 and 5.38, respectively. It is proposed that the Lost Pines population was the western refugium for P. taeda during Pleistocene glaciation and that East Texas P. taeda forests descended from the bottlenecked Lost Pines population.
Genetic diversity and divergence among freshwater mussel (Anodonta) populations in the Bonneville Basin of Utah
Authors: Mock K. E. , Brim‐Box J. C. , Miller M. P. , Downing M. E. , Hoeh W. R.
Published: April 2004

Populations of the freshwater mussel genus Anodonta appear to be in a state of rapid decline in western North America, following a trend that unfortunately seems to be prevalent among these animals (Mollusca: Unionoida). Here we describe the patterns of molecular divergence and diversity among Anodonta populations in the Bonneville Basin, a large sub‐basin of the Great Basin in western North America. Using amplified fragment length polymorphism (AFLP) analysis, we found a striking lack of nuclear diversity within some of these populations, along with a high degree of structuring among populations (FST = 0.61), suggesting post‐Pleistocene isolation, due either to a long‐term loss of hydrologic connectivity among populations or to more recent fish introductions. We also found evidence of recent hybridization in one of these populations, possibly mediated by fish‐stocking practices. Using mitochondrial sequence data, we compared the Bonneville Basin populations to Anodonta in several other drainages in western North America. We found a general lack of resolution in these phylogenetic reconstructions, although there was a tendency for the Bonneville Basin Anodonta (tentatively A. californiensis) to cluster with A. oregonensis from the adjacent Lahontan Basin in Nevada. We recommend further investigation of anthropogenic factors that may be contributing to the decline of western Anodonta and a broad‐scale analysis and synthesis of genetic and morphological variation among Anodonta in western North America.
Mectizan Donation Program: evaluation of a public–private partnership
Authors: Peters David H. , Phillips Traci
Published: April 2004

The Mectizan Donation Program (MDP) has been perceived as a highly effective public health programme, and as a possible model for addressing future problems in international health. This evaluation examines how the MDP partnership has been functioning from the perspectives of partner organizations. The results of a survey of 25 partners show that the perceived benefits far outweigh the problems, and that the direct costs to the organizations have been minimal. The partnership is rated highly on many aspects of governance and management, with relatively few problems identified. A factor analysis demonstrated that a wide range of factors have influenced the partners’ perceptions. The benefits with the largest weights appear to be those related to external perceptions of the organization, and those indicating that the organization feels that its opinions will matter and lead to action in the partnership. The biggest factors influencing the positive perceptions on the governance and management of the MDP partnership appear to be the involvement of senior leaders from different organizations, and being able to agree on priorities. The MDP has been able to involve a large and heterogeneous number of partner organizations through relatively informal mechanisms that rely on goodwill and reciprocity. The survey results show how there was a strong alignment of the MDP with the interests of the various partners, and that a manageable number of problems were addressed and services provided. While having long‐term goals, the MDP and the onchocerciasis control programmes have been effective at demonstrating the effectiveness of the approach through regular, professional, and outcome‐oriented evaluations. Although the MDP is considered to be central to concerns of national officials, this feature is not rated as high as public perceptions, the internal characteristics of the partnership, or its accomplishments. Similarly, the need to secure resources is not viewed as a major determinant of the partnership's success, perhaps because resources were readily available through Merck and the partner organizations and programmes. These findings, along with the strategic and operational success of the MDP confirm the view that this type of public–private partnership should be pursued vigorously in other areas of public health. Other potential partnerships would do well to examine the characteristics of the MDP partnership, with careful attention to the features of its governance and the management, including a strong alignment of interests with partners, balancing a long‐term vision with clarity of roles and intensive management of coordination, and professional and results‐oriented accountability.
Economic evaluation of Mectizan distribution
Authors: Waters H. R. , Rehwinkel J. A. , Burnham G.
Published: April 2004

The distribution of ivermectin has dramatically altered the nature of onchocerciasis control. Existing economic analyses of ivermectin distribution programmes show that these programmes have a highly beneficial impact. Most analyses have estimated the economic benefits in terms of increased labour productivity as a result of reductions in blindness, and in terms of additional land‐availability because of a reduced transmission of the parasite. Economic evaluations of the Onchocerciasis Control Program (OPC) in West Africa have calculated a net present value – equivalent discounted benefits minus discounted costs – of $485 million for the programme over a 39‐year period, using a conservative 10% rate to discount future health and productivity gains. The net present value for the African Program for Onchocerciasis Control (APOC) is calculated at $88 million over a 21‐year time period, also using a 10% discount rate. Cost‐effectiveness analyses of ivermectin distribution have found a cost of $14–$30 per disability‐adjusted life‐year prevented – estimates comparable with other priority disease control programmes. However, the economic success of ivermectin distribution is sensitive to the fact that the drug itself has been donated free of charge. The market value of Merck's donations to the APOC for just 1 year considerably outweighs the benefits calculated for both the OPC and the APOC over the life of these projects. Pending the development of an effective macrofilaricide, the distribution of ivermectin will remain a public health priority into the foreseeable future.
Review: The delivery of ivermectin (Mectizan®)
Authors: Burnham G. , Mebrahtu T.
Published: April 2004

Over a comparatively short period of time, the development and distribution of ivermectin (Mectizan®) has radically altered the consequences of infection with Onchocerca volvulus. To achieve this required the fostering of many partnerships and the development of new tools and methods. The long‐term commitment of Merck, the World Bank and other sponsors, as well as governments and non‐governmental organizations, has been crucial. Yet the enthusiasm with which communities have taken up the delivery of ivermectin among themselves is perhaps the greatest reason for the success of this programme. The present challenge is sustaining the methods that have brought success so far, and making them part of health services and disease control programmes in some of the world's most impoverished and unstable areas. A major part of this challenge is continuing the commitment to controlling onchocerciasis as memory of the disease is fading, and while the hope of elimination or eradication for most endemic countries remains distant.
Impact of ivermectin on illness and disability associated with onchocerciasis
Authors: Tielsch James M. , Beeche Arlyne
Published: April 2004

The Onchocerciasis Control Program (OCP), one of the most successful vertical disease control programs in the history of public health, came to an end in 2003 with devolvement of responsibilities for control program activities passed to the countries affected. Fortunately, 15 years ago the Mectizan® Distribution Program (MDP) was founded to provide a complementary approach to controlling the disabling consequences of this parasitic infection. With over 250 million doses of ivermectin distributed over the past 15 years, the MDP is well on its way to both solidifying the progress made by the OCP and extending program reach well beyond the boundaries of the OCP. Through the extensive clinical testing protocols implemented in a variety of countries in Aftica, ivermectin has been proven to be a safe and highly effective treatment for onchocerciasis. Regular distribution to populations living in endemic areas has demonstrated significant reductions in blinding ocular complications, transmission, and disability caused by onchocercal skin disease. As yet undocumented, are the likely significant impact regular population dosing with ivermectin has on intestinal helminth infections, lymphatic filariasis, and human scabies infection. While there are significant barriers to continued program success, focussed attention on expanding and improving community‐directed ivermectin distribution is likely to lead to further progress against this resilient infection.