bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term numerical changes and regulation in a river stock of European eelAnguilla anguilla
Authors: LOBÓN‐CERVIÁ JAVIER , IGLESIAS TANIA 
Published: April 2008

Summary1. The objective was to explore the regulatory mechanisms underlying the numerical dynamics of a river stock of European eelAnguilla anguillabased on a purely observational study. We used a 21‐year data set on the Rio Esva (Asturias, northwestern Spain) stock of eels, encompassing eel density at an estuary site and at nine sites distributed among three tributaries selected to differ in the distance from the tidal limit and fishery data on glass eels from the nearby Rio Nalón estuary.2. The abundance of glass eels and estuarine and in‐stream densities declined simultaneously over a 15‐year period. However, following a historical minimum in the abundance of glass eels around the year 2000, the density continued to decline in the estuary whereas density in the streams began an increase that has continued to the present.3. In‐stream cohort mortality rate (Z) varied from 0.0016 day−1to only 0.0003 day−1(on an annual basis from 0.57 to 0.099 year−1). The negative effects of intra‐cohort and inter‐cohort densities on mortality rate emphasized the responses of the riverine stock to compensatory density‐dependence. As a consequence, the number of eels surviving to commence the silvering stage was similar in magnitude in the strongest and weakest cohorts.4. These results suggest that, even if the low abundance of glass eels persists, in‐stream density may increase towards a stable value regulated by in‐stream density‐dependence.
Partitioning net ecosystem carbon exchange and the carbon isotopic disequilibrium in a subalpine forest
Authors: ZOBITZ JOHN M. , BURNS SEAN P. , REICHSTEIN MARKUS , BOWLING DAVID R. 
Published: April 2008

AbstractWe investigate the utility of an improved isotopic method to partition the net ecosystem exchange of CO2 (F) into net photosynthesis (FA) and nonfoliar respiration (FR). Measurements of F and the carbon isotopic content in air at a high‐elevation coniferous forest (the Niwot Ridge AmeriFlux site) were used to partition F into FA and FR. Isotopically partitioned fluxes were then compared with an independent flux partitioning method that estimated gross photosynthesis (GEE) and total ecosystem respiration (TER) based on statistical regressions of night‐time F and air temperature. We compared the estimates of FA and FR with expected canopy physiological relationships with light (photosynthetically active radiation) and air temperature. Estimates of FA and GEE were dependent on light as expected, and TER, but not FR, exhibited the expected dependence on temperature. Estimates of the isotopic disequilibrium D, or the difference between the isotopic signatures of net photosynthesis (δA, mean value −24.6‰) and ecosystem respiration (δR, mean value −25.1‰) were generally positive (δA>δR). The sign of D observed here is inconsistent with many other studies. The key parameters of the improved isotopic flux partitioning method presented here are ecosystem scale mesophyll conductance (gm) and maximal vegetative stomatal conductance (gcmax). The sensitivity analyses of FA, FR, and D to gcmax indicated a critical value of gcmax (0.15 mol m−2 s−1) above which estimates of FA and FR became larger in magnitude relative to GEE and TER. The value of D decreased with increasing values of gm and gcmax, but was still positive across all values of gm and gcmax. We conclude that the characterization of canopy‐scale mesophyll and stomatal conductances are important for further progress with the isotope partitioning method, and to confirm our anomalous isotopic disequilibrium findings.
Impact of severe dry season on net ecosystem exchange in the Neotropical rainforest of French Guiana
Authors: BONAL DAMIEN , BOSC ALEXANDRE , PONTON STÉPHANE , GORET JEAN‐YVES , BURBAN BENOÎT , GROSS PATRICK , BONNEFOND JEAN‐MARC , ELBERS JAN , LONGDOZ BERNARD , EPRON DANIEL , GUEHL JEAN‐MARC , GRANIER ANDRÉ 
Published: April 2008

AbstractThe lack of information on the ways seasonal drought modifies the CO2 exchange between Neotropical rainforest ecosystems and the atmosphere and the resulting carbon balance hinders our ability to precisely predict how these ecosystems will respond as global environmental changes force them to face increasingly contrasting conditions in the future. To address this issue, seasonal variations in daily net ecosystem productivity (NEPd) and two main components of this productivity, daily total ecosystem respiration (REd) and daily gross ecosystem productivity (GEPd), were estimated over 2 years at a flux tower site in French Guiana, South America (5 °16′54″N, 52 °54′44″W). We compared seasonal variations between wet and dry periods and between dry periods of contrasting levels of intensity (i.e. mild vs. severe) during equivalent 93‐day periods. During the wet periods, the ecosystem was almost in balance with the atmosphere (storage of 9.0 g C m−2). Seasonal dry periods, regardless of their severity, are associated with higher incident radiation and lower REd combined with reduced soil respiration associated with low soil water availability. During the mild dry period, as is normally the case in this region, the amount of carbon stored in the ecosystem was 32.7 g C m−2. Severe drought conditions resulted in even lower REd, whereas the photosynthetic activity was only moderately reduced and no change in canopy structure was observed. Thus, the severe dry period was characterized by greater carbon storage (64.6 g C m−2), emphasizing that environmental conditions, such as during a severe drought, modify the CO2 exchange between Neotropical rainforest ecosystems and the atmosphere and potentially the resulting carbon balance.
Age‐dependent response of boreal forest to temperature and rainfall variability
Authors: McMILLAN ANDREW M. S. , WINSTON GREGORY C. , GOULDEN MICHAEL L. 
Published: April 2008

AbstractWe used measurements of CO2 exchange by six Canadian boreal forest stands to determine how sites of contrasting age respond to interannual temperature and precipitation variation. The stands ranged in age (time since last burn) from 4 to 155 years. The study included years that were anomalously cool and moist, warm and dry, cool and dry, and warm and moist. Warmer than average springs accelerated the onset of older stand (> 20 years) photosynthesis by as much as 37 days and younger stand (< 20 years) photosynthesis by as much as 25 days. The warm–dry year resulted in a marked reduction of mid‐summer CO2 uptake by the younger, but not older, stands. The mid‐summer decline in young stand photosynthesis reflected the combination of warmth and drought; similar declines were not observed during the cool–dry or warm–moist years. The annual carbon gain by the oldest stands was greatest during the warm–dry year as a result of the expanded growing season. The annual carbon gain by the youngest stands was consistent from year to year, largely as a result of offsets between increased spring photosynthesis and reduced mid‐summer photosynthesis during the warm–dry year. Night‐time CO2 efflux increased by 2–29% during the warm–moist year relative to the warm–dry year. This increase was not systematically related to age. We conclude that the major source of interannual CO2 exchange variation at the landscape scale is the ability of older, evergreen canopies to respond to warm springs by advancing the onset of photosynthesis. Drought‐related reductions in photosynthesis, moisture‐driven respiratory losses, and the effects of spring warmth on young‐stand photosynthesis are of secondary importance. The advantage conferred on older, evergreen stands during warmer years carries implications for the possible effects of climate change on boreal forest succession. Warmer temperatures may increase the competitive advantage of late successional species relative to early successional species, and also the incidence of fire, thereby accelerating plant succession and shortening the fire‐return interval.
Bird migration times, climate change, and changing population sizes
Authors: MILLER‐RUSHING ABRAHAM J. , LLOYD‐EVANS TREVOR L. , PRIMACK RICHARD B. , SATZINGER PAUL 
Published: April 2008

AbstractPast studies of bird migration times have shown great variation in migratory responses to climate change. We used 33 years of bird capture data (1970–2002) from Manomet, Massachusetts to examine variation in spring migration times for 32 species of North American passerines. We found that changes in first arrival dates – the unit of observation used in most studies of bird migration times – often differ dramatically from changes in the mean arrival date of the migration cohort as a whole. In our study, the earliest recorded springtime arrival date for each species occurred 0.20 days later each decade. In contrast, the mean arrival dates for birds of each species occurred 0.78 days earlier each decade. The difference in the two trends was largely explained by declining migration cohort sizes, a factor not examined in many previous studies. We found that changes in migration cohort or population sizes may account for a substantial amount of the variation in previously documented changes in migration times. After controlling for changes in migration cohort size, we found that climate variables, migration distance, and date of migration explained portions of the variation in migratory changes over time. In particular, short‐distance migrants appeared to respond to changes in temperature, while mid‐distance migrants responded particularly strongly to changes in the Southern Oscillation Index. The migration times of long‐distance migrants tended not to change over time. Our findings suggest that previously reported changes in migration times may need to be reinterpreted to incorporate changes in migration cohort sizes.
Will climate change be beneficial or detrimental to the invasive swede midge in North America? Contrasting predictions using climate projections from different general circulation models
Authors: MIKA ANNA M. , WEISS ROSS M. , OLFERT OWEN , HALLETT REBECCA H. , NEWMAN JONATHAN A. 
Published: April 2008

AbstractClimate change may dramatically affect the distribution and abundance of organisms. With the world's population size expected to increase significantly during the next 100 years, we need to know how climate change might impact our food production systems. In particular, we need estimates of how future climate might alter the distribution of agricultural pests. We used the climate projections from two general circulation models (GCMs) of global climate, the Canadian Centre for Climate Modelling and Analysis GCM (CGCM2) and the Hadley Centre model (HadCM3), for the A2 and B2 scenarios from the Special Report on Emissions Scenarios in conjunction with a previously published bioclimatic envelope model (BEM) to predict the potential changes in distribution and abundance of the swede midge, Contarinia nasturtii, in North America. The BEM in conjunction with either GCM predicted that C. nasturtii would spread from its current initial invasion in southern Ontario and northwestern New York State into the Canadian prairies, northern Canada, and midwestern United States, but the magnitude of risk depended strongly on the GCM and the scenario used. When the CGCM2 projections were used, the BEM predicted an extensive shift in the location of the midges' climatic envelope through most of Ontario, Quebec, and the maritime and prairie provinces by the 2080s. In the United States, C. nasturtii was predicted to spread to all the Great Lake states, into midwestern states as far south as Colorado, and west into Washington State. When the HadCM3 was applied, southern Ontario, Saskatchewan, and Washington State were not as favourable for C. nasturtii by the 2080s. Indeed, when used with the HadCM3 climate projections, the BEM predicted the virtual disappearance of ‘very favourable’ regions for C. nasturtii. The CGCM2 projections generally caused the BEM to predict a small increase in the mean number of midge generations throughout the course of the century, whereas, the HadCM3 projections resulted in roughly the same mean number of generations but decreased variance. Predictions of the likely potential of C. nasturtii spatial spread are thus strongly dependent on the source of climate projections. This study illustrates the importance of using multiple GCMs in combination with multiple scenarios when studying the potential for spatial spread of an organism in response to climate change.
Quantitative trait loci affecting stomatal density and growth in a Quercus robur progeny: implications for the adaptation to changing environments
Authors: GAILING OLIVER , LANGENFELD‐HEYSER ROSEMARIE , POLLE ANDREA , FINKELDEY REINER 
Published: April 2008

AbstractStomatal traits are important to cope with changes in levels of atmospheric carbon dioxide (CO2) and with changing availability of water. Thus, they are expected to be involved in the reactions of plants to climate change. They are known to show a plastic physiological response to environmental factors such as elevated CO2 concentrations, but they are also under genetic control and should undergo evolutionary change if selection differs among environments. Stomatal development is regulated by several environmental and genetic signals suggesting a polygenic inheritance. In the present study, F1 progeny derived from a cross between Quercus robur and Q. robur subsp. slavonica were used to map QTLs (quantitative trait loci) for stomatal densities and growth parameters under nonwater stress conditions in 2 and 3 consecutive years, respectively. The positions of QTLs for stomatal density and growth coincided on six linkage groups. The QTL allele associated with the higher stomatal density was generally associated with taller plants and size increment indicating pleiotropic gene effects or close linkage. The phenotypic effects of the individual QTLs were mostly moderate in terms of phenotypic variance explained. However, a considerable amount of the genetically determined variation was explained by QTLs for stomatal density (from 63.6% to 94.4%). Especially, the QTL on linkage group 11 had a strong and highly significant effect on stomatal densities and growth parameters in all years suggesting a major QTL on this linkage group. The importance to analyse the genetic variation controlling complex adaptive traits in keystone species as oaks is discussed with regard to a better understanding of the reactions of ecosystems to global change.
Climatic effects on the breeding phenology and reproductive success of an arctic‐nesting goose species
Authors: DICKEY MARIE‐HÉLÈNE , GAUTHIER GILLES , CADIEUX MARIE‐CHRISTINE 
Published: April 2008

AbstractClimate warming is pronounced in the Arctic and migratory birds are expected to be among the most affected species. We examined the effects of local and regional climatic variations on the breeding phenology and reproductive success of greater snow geese (Chen caerulescens atlantica), a migratory species nesting in the Canadian Arctic. We used a long‐term dataset based on the monitoring of 5447 nests and the measurements of 19 234 goslings over 16 years (1989–2004) on Bylot Island. About 50% of variation in the reproductive phenology of individuals was explained by spring climatic factors. High mean temperatures and, to a lesser extent, low snow cover in spring were associated with an increase in nest density and early egg‐laying and hatching dates. High temperature in spring and high early summer rainfall were positively related to nesting success. These effects may result from a reduction in egg predation rate when the density of nesting geese is high and when increased water availability allows females to stay close to their nest during incubation recesses. Summer brood loss and production of young at the end of the summer increased when values of the summer Arctic Oscillation (AO) index were either very positive (low temperatures) or very negative (high temperatures), indicating that these components of the breeding success were most influenced by the regional summer climate. Gosling mass and size near fledging were reduced in years with high spring temperatures. This effect is likely due to a reduced availability of high quality food in years with early spring, either due to food depletion resulting from high brood density or a mismatch between hatching date of goslings and the timing of the peak of plant quality. Our analysis suggests that climate warming should advance the reproductive phenology of geese, but that high spring temperatures and extreme values of the summer AO index may decrease their reproductive success up to fledging.
Capacitation‐associated changes in membrane fluidity in asthenozoospermic human spermatozoa
Authors: Buffone Mariano G. , Doncel Gustavo F. , Calamera Juan C. , Verstraeten Sandra V. 
Published: April 2008

SummaryThe fertilizing potential of human spermatozoa relies on their ability to capacitate as they travel through the female reproductive tract. During this process, cholesterol is released from the plasma membrane, altering its architecture and dynamics. Using ISolate® gradients, we obtained high (L90)‐ and low (L45)‐quality spermatozoa from asthenozoospermic human semen samples. We tested the hypothesis that the lower fertilizing ability of asthenozoospermic L90 cells could be related to a lower ability to increase their membrane fluidity during capacitation. We assessed two sets of fluorescent probes: (i) DPH, TMA‐DPH and PA‐DPH which senses the hydrophobic core, cytosolic and exofacial leaflets of the bilayer, respectively and (ii) Laurdan, sensitive to the amount of water molecules intercalated between lipid moieties of the membrane (membrane hydration). Before capacitation, membrane fluidity of asthenozoospermic sperm populations was similar to the corresponding fractions of normozoospermic cells when evaluated with DPH, TMA‐DPH or PA‐DPH. Asthenozoospermic whole samples displayed lower plasma membrane hydration than normozoospermic cells as evidenced with Laurdan. After capacitation, asthenozoospermic L45 and L90 cells failed to increase their membrane fluidity in opposition to normozoospermic cells. Interestingly, membrane hydration significantly correlated with the main sperm motion parameters analysed, being a low membrane hydration associated with poor sperm movement. These results show that low‐motility spermatozoa are unable to respond to capacitation with the necessary changes in membrane fluidity. This defect in sperm plasma membrane rheology may be responsible for their poor functional quality and low fertilizing ability.
Construction of cavernosum smooth muscle using umbilical artery smooth muscle cells seeded on acellular corporal collagen matrices
Authors: Song Lu‐Jie , Xu Yue‐Min , Li Chao , Fu Qiang , Cui Lei , Hu Xiao‐Yong 
Published: April 2008

SummaryThe objective of this study was to investigate the feasibility of tissue engineering of corpus cavernosal smooth muscle. Acellular corporal collagen matrices (ACCMs) were obtained from the penis of adult rabbits by a cell removal procedure. ACCMs were implanted into the back muscles of allogenic rabbits to investigate the resulting immunological reaction. Human umbilical artery smooth muscle cells (HUASMCs) were isolated from human umbilical arteries through explant techniques and expanded in vitro. Subsequently, third and fifth passage HUASMCs were seeded to ACCMs at a concentration of 30 × 106 cells/mL. Then, seeded ACCMs were implanted subcutaneously in athymic mice. The implants were retrieved at 10, 20 and 40 days after implantation. Histochemistry, immunohistochemistry and scanning electron microscopy were performed to analyse the morphological characteristics of the engineered tissues. Additionally, organ bath studies were performed to address the contractility of the engineered tissues. The decellularization process successfully extracted all cellular components while preserving the original collagen fibers. The immunological reaction to ACCMs consisted of only a transient nonspecific inflammatory response. Light and scanning electron microscopy demonstrated that HUASMCs extended onto the three‐dimensional ACCMs scaffolds in vitro. Histological analyses of the explants from all time points demonstrated a progressive regeneration of smooth muscle, with structures very similar to native corpus cavernosum smooth muscle. The maximum contraction force induced by phenylephrine and electrical stimulation were 3.64 ± 0.18 g/100 mg and 2.50 ± 0.21 g/100 mg, respectively. Our study demonstrates that HUASMCs can be seeded on three‐dimensional ACCM scaffolds and will develop tissues similar to that of the native corpus cavernosum smooth muscle.
An evolutionary perspective on Y‐chromosomal variation and male infertility
Authors: Tyler‐Smith Chris 
Published: April 2008

SummaryGenetic variation on the Y chromosome is one of the best‐documented causes of male infertility, but the genes responsible have still not been identified. This review discusses how an evolutionary perspective may help with interpretation of the data available and suggest novel approaches to identify key genes. Comparison with the chimpanzee Y chromosome indicates that USP9Y is dispensable in apes, but that multiple copies of TSPY1 may have an important role. Comparisons between infertile and control groups in search of genetic susceptibility factors are more complex for the Y chromosome than for the rest of the genome because of population stratification and require unusual levels of confirmation. But the extreme population stratification exhibited by the Y also allows populations particularly suitable for some studies to be identified, such as the partial AZFc deletions common in Northern European populations where further dissection of this complex structural region would be facilitated.
Structure of the exosporium and sublayers of spores of the Bacillus cereus family revealed by electron crystallography
Authors: Ball David A. , Taylor Robert , Todd Sarah J. , Redmond Caroline , Couture‐Tosi Evelyne , Sylvestre Patricia , Moir Anne , Bullough Per A. 
Published: April 2008

SummaryWe report on the first step in mapping out the spatial location of structural proteins within the exosporium, namely a description of its three‐dimensional architecture. Using electron microscopy and image analysis, we have characterized crystalline fragments from the exosporium of Bacillus cereus, B. thuringiensis and B. anthracis strains and identified up to three distinct crystal types. Type I and type II crystals were examined in three dimensions and shown to form arrays of interlinked crown‐like structures each enclosing a cavity ∼26–34 Å deep with threefold symmetry. The arrays appear to be permeated by tunnels allowing access from one surface to the other, possibly indicating that the exosporium forms a semi‐permeable barrier. The pore size of ∼23–34 Å would allow passage of the endospore germinants, alanine or inosine but not degradative enzymes or antibodies. Thus the structures appear compatible with a protective role for the exosporium. Furthermore the outermost crystalline layer must act as a scaffold for binding the BclA protein that contributes to the ‘hairy nap’ layer. The array of crowns may also act as a matrix for the binding or adsorption of other proteins that have been identified in the exosporium such as GroEL, immune inhibitor A and arginase.