bluuebunny/crossref_metadata_2025_split huggingface dataset:
Salinity and sea level mediate elevated CO2 effects on C3–C4 plant interactions and tissue nitrogen in a Chesapeake Bay tidal wetland
Authors: ERICKSON JOHN E. , MEGONIGAL J. PATRICK , PERESTA GARY , DRAKE BERT G. 
Published: November 2006

AbstractElevated atmospheric carbon dioxide concentrations ([CO2]) generally increase plant photosynthesis in C3 species, but not in C4 species, and reduce stomatal conductance in both C3 and C4 plants. In addition, tissue nitrogen concentration ([N]) often fails to keep pace with enhanced carbon gain under elevated CO2, particularly in C3 species. While these responses are well documented in many species, implications for plant growth and nutrient cycling in native ecosystems are not clear. Here we present data on 18 years of measurement of above and belowground biomass, tissue [N] and total standing crop of N for a Scirpus olneyi‐dominated (C3 sedge) community, a Spartina patens‐dominated (C4 grass) community and a C3–C4‐mixed species community exposed to ambient and elevated (ambient +340 ppm) atmospheric [CO2] in natural salinity and sea level conditions of a Chesapeake Bay wetland. Increased biomass production (shoots plus roots) under elevated [CO2] in the S. olneyi‐dominated community was sustained throughout the study, averaging approximately 35%, while no significant effect of elevated [CO2] was found for total biomass in the C4‐dominated community. We found a significant decline in C4 biomass (correlated with rising sea level) and a concomitant increase in C3 biomass in the mixed community. This shift from C4 to C3 was accelerated by the elevated [CO2] treatment. The elevated [CO2] stimulation of total biomass accumulation was greatest during rainy, low salinity years: the average increase above the ambient treatment during the three wettest years (1994, 1996, 2003) was 2.9 t ha−1 but in the three driest years (1995, 1999, 2002), it was 1.2 t ha−1. Elevated [CO2] depressed tissue [N] in both species, but especially in the S. olneyi where the relative depression was positively correlated with salinity and negatively related with the relative enhancement of total biomass production. Thus, the greatest amount of carbon was added to the S. olneyi‐dominated community during years when shoot [N] was reduced the most, suggesting that the availability of N was not the most or even the main limitation to elevated [CO2] stimulation of carbon accumulation in this ecosystem.
Climate impacts on Mediterranean blue tit survival: an investigation across seasons and spatial scales
Authors: GROSBOIS VLADIMIR , HENRY PIERRE‐YVES , BLONDEL JACQUES , PERRET PHILIPPE , LEBRETON JEAN‐DOMINIQUE , THOMAS DONALD W. , LAMBRECHTS MARCEL M. 
Published: November 2006

AbstractIn some hole nesting passerine species, long‐term monitoring data are available for several geographically independent populations. Climate forcing can then be documented and predictions made on the scale of distribution ranges. Several demographic studies of Paridae report dramatic impacts of wintertime climatic factors. However, these studies were undertaken in populations located in the northern parts of the species' ranges. Studies on the survival of Paridae in their southern ranges are necessary in order to assess potential latitudinal variation in climate forcing on survival. Based on monitoring of individual adult blue tits (Parus caeruleus), the effects of climatic factors on annual survival were assessed in three distinct Mediterranean populations. In these regions, climatic conditions in early summer might be expected to have a strong impact because they can be extremely hot and dry and because at this time of year Paridae are subjected to intrinsic constraints that stem from energetically costly postbreeding moult, recovery from reproductive costs, and from population densities inflated by the new cohort of fledglings. The impact of climatic conditions in early summer was, thus, addressed in addition to that prevailing in winter. In order to consider a large number of local climatic variables while limiting statistical power loss, integrative indices of local climate were built using multivariate techniques. In addition, the NAO and three large‐scale factors that are closely linked with atmospheric and oceanic circulation in the intertropical zone were considered as potentially influential factors in winter and early summer. Relationships between blue tit survival and indices of local temperature and precipitation in winter and in early summer were detected. Adult survival also correlated with a large‐scale tropical index in early summer: rainfall in the Sahel. This is one of the first quantitative indications that fluctuations in summer climatic conditions explain a significant part of the temporal variation in adult survival in unconnected populations of a sedentary European vertebrate. Furthermore, the results support the hypothesis that summertime local climates in Western Europe are closely linked with atmospheric and oceanic circulation in the intertropical zone.
Niche pre‐emption increases with species richness in experimental plant communities
Authors: MWANGI PETER N. , SCHMITZ MARTIN , SCHERBER CHRISTOPH , ROSCHER CHRISTIANE , SCHUMACHER JENS , SCHERER‐LORENZEN MICHAEL , WEISSER WOLFGANG W. , SCHMID BERNHARD 
Published: November 2006

SummaryIn plant communities, invasion resistance may increase with diversity because empty niche space decreases simultaneously. However, it is not clear if this only applies to exotic species or also to native species arriving at a site with few other native species during community assembly. We tested the latter by transplanting four native species into experimental grassland communities varying in species richness form 1–16 (−60) species. In addition, we tested the hypothesis that invasion is less successful if the invading species belongs to a functional group that is already present in the community. The test invaders included a grass species (Festuca pratensis, FP), a short (Plantago lanceolata, PL) and a tall herb species (Knautia arvensis, KA), and a legume species (Trifolium pratense, TP). The same four functional groups also occurred alone or in all possible combinations in the different experimental communities. The overall performance of the transplants was negatively related to the logarithm of the species richness of host communities. Plant biomass declined by 58%, 90%, 84% and 62% in FP, PL, KA and TP, respectively, from monocultures to 16‐species mixtures, indicating lower invasiveness of the two herbs than of the grass and the legume. Resident grasses showed a strong negative effect on the performance of all test invaders, whereas resident small and tall herbs had neutral, and resident legumes had positive effects. The case of the legumes indicates that contributions to invasion resistance need not parallel invasiveness. Communities containing resident species of only one functional group were most inhibitive to transplants of the same functional group. These results indicate that invasion resistance of experimental plant communities is related to the degree of niche overlap between resident species and invaders. This niche overlap can be high due to generally low amounts of empty niche space in species‐rich resident communities or due to the occurrence of the same functional group as the one of the invader in the resident community. Stronger within‐ than between‐functional‐group invasion resistance may be the key mechanism underlying diversity effects on invasion resistance in grassland and other ecosystems at large.
Assessing the trade‐offs between crossover and parallel group designs in sleep research
Authors: BERRY CHARLES C. , MOORE POLLY , DIMSDALE JOEL E. 
Published: November 2006

SummarySleep researchers invariably struggle with decisions regarding the optimal design for their studies. Whether such studies involve treatment for insomnia, obstructive sleep apnea, or any other sleep disorder, questions arise regarding the respective trade‐offs between a parallel group and a crossover design. This study analyzed the variance structure of commonly measured polysomnographic variables in an effort to describe the statistical impact of these alternate designs. The study examined the effects of opioids on sleep and employed multiple crossovers between placebo, MS‐contin, and methadone using a double‐blind, randomized crossover design. Thirty‐seven healthy subjects were studied. Four of the subjects were unable to complete the protocol for a variety of reasons, and polysomnogram data was unavailable for one subject. Data from 37 subjects provide the basis for this analysis. Despite dropouts, the crossover study was approximately four times as efficient as the parallel group design in terms of being able to recognize differences in deep sleep across these conditions. Other polysomnographic variables also favored the crossover design to varying extents. Despite the operational complexity of a crossover design, the statistical efficiency of this approach makes it a preferable approach for designing intervention studies in sleep research.
Total sleep deprivation can increase vestibulo‐ocular responses
Authors: QUARCK G. , VENTRE J. , ETARD O. , DENISE P. 
Published: November 2006

SummaryThe effect of sleep deprivation on the vestibular function is largely unknown. Some studies have found that postural balance or vestibular reflexes are decreased in sleep‐deprived subjects while others found no change. The aim of this study was to evaluate the effect of sleep deprivation on the vestibulo‐ocular reflex (VOR). Horizontal eye movements were recorded in healthy subjects during earth vertical axis rotation in darkness once after an ordinary night sleep and once after 26–29 h of sleep deprivation. In the first experiment (n = 8), for which rotation was a 60° s−1 velocity step, sleep deprivation induced a significant increase in VOR gain. In the second experiment (n = 12), for which rotation was sinusoidal (0.2 Hz ± 25° s−1), sleep deprivation induced no significant modification in VOR gain. The difference between the two studies was the abrupt onset of the step stimulation in comparison with the sinusoidal rotation. Because of its unexpected onset and the potential threat to postural balance, the step stimulation may activate the system specialized in reorienting attention towards salient or behaviourally relevant events. This system includes the right temporoparietal cortex, an area also involved in VOR control. A number of studies have found that sleep deprivation alters the activity of this cortical area during attentional tasks. It is therefore our hypothesis that the difference between the effects of these two vestibular stimulations results from a sleep deprivation‐induced modulation of the right temporoparietal cortex.
N‐terminal pro‐brain natriuretic peptide for detection of cardiovascular stress in patients with obstructive sleep apnea syndrome
Authors: VARTANY EDMOND , IMEVBORE MICHAEL , O'MALLEY MARY , MANFREDI CHRISTOPHER , PASQUARELLA CAROL , SCINTO LEONARD , FINE JONATHAN 
Published: November 2006

SummaryPatients with obstructive sleep apnea syndrome (OSAS) have an elevated incidence of cardiovascular events that may be related to an increased ventricular load and hypoxemia caused by apneas and hypopneas. N‐terminal pro‐brain natriuretic peptide (NTproBNP) appears to be an excellent marker of myocardial stretch and could serve as an indicator of subclinical cardiac stress, thereby identifying a patient population at risk for cardiac effects from OSAS. Adult patients presenting with suspected OSAS and scheduled for nocturnal polysomnography were recruited. Patients with heart or renal failure or severe lung disease were excluded. NTproBNP was measured the evening before and the morning after sleep. Blood pressure (BP) was monitored intermittently throughout the night. Fifteen male and 15 female subjects with a mean ± SD body mass index of 38.2 ± 9.8 were studied. Mean Apnea–Hypopnea Index (AHI) was 38.4 ± 26, with 17 subjects having severe OSAS (AHI > 30). No subject had a significant rise in BP. NTproBNP values overnight decreased in 19 patients and rose in 11 (mean change 3.8 ± 33 pg mL−1), but only one patient had an abnormal morning value. Three patients had an abnormal NTproBNP value prior to sleep, but their levels decreased with sleep. No correlations were detected between the evening baseline or postsleep NTproBNP levels and OSAS. Monitoring pre‐ and postsleep NTproBNP levels revealed no association with the occurrence or degree of OSAS, making it unlikely that NTproBNP could serve as a marker of cardiac stress in OSAS patients with stable BP and without overt heart failure.
Screening for sleep‐related breathing disorders by transthoracic impedance recording integrated into a Holter ECG system
Authors: MUELLER ANDREAS , FIETZE INGO , VOELKER RICHARD , EDDICKS STEPHAN , GLOS MARTIN , BAUMANN GERT , THERES HEINZ 
Published: November 2006

SummaryIn patients with arrhythmias, coincidence with sleep‐related breathing disorders (SRBD) is high and of clinical relevance. Electrocardiogram‐derived (ECG) parameters have been developed for SRBD screening, but it has proved necessary to exclude patients with frequent arrhythmias. Holter‐based screening tools, easy to use, are therefore warranted. The goal of our study was to evaluate the diagnostic accuracy, with respect to SRBD detection, of transthoracic impedance recording (TTIR) integrated into a Holter System. Our investigation consisted of 2 phases. In phase 1 we compared the performance of TTIR to that of in‐hospital polysomnography (PSG) in 56 patients (46 male, mean age 57). In phase 2 we compared TTIR to results from an ambulatory polygraphy (PG) system in 180 patients (143 male, mean age 56). We scored apnea and hypopnea from P(S)G, and derived a respiratory‐disturbance index (P(S)G‐RDI). TTIR was analyzed semi‐automatically. Reduction of the impedance amplitude by more than 50% over 10 s was scored as apnea/hypopnea, with consequent calculation of TTIR‐RDI. In phase 1, 20 out of 56 patients revealed a PSG‐RDI > 10 h−1. TTIR‐RDI in 19 patients from this group was >10 h−1 (sensitivity 95%, specificity 97.2%, positive predictive value 95%, negative predictive value 97.2%, interclass correlation coefficient 0.98). In phase 2, 46 of 180 patients revealed a PSG‐RDI > 10 h−1. TTIR‐RDI in 37 out of this group was >10 h−1 (sensitivity 80.4%, specificity 92.5%, positive predictive value 78.7%, negative predictive value 93.2%, interclass correlation coefficient 0.92). TTIR integrated into a Holter ECG system and tested in a large patient cohort demonstrates acceptable high accuracy in detection of SRBD. Arrhythmia analysis and screening for SRBD can be performed in a single‐step approch.
A phylogenetic analysis of the correlates of sleep in birds
Authors: ROTH TIMOTHY C. , LESKU JOHN A. , AMLANER CHARLES J. , LIMA STEVEN L. 
Published: November 2006

SummaryQuantitative comparative studies of sleep have focused exclusively on mammals. Such studies have repeatedly found strong relationships between the time spent in various sleep states and constitutive variables related to morphology, physiology, and life history. These studies influenced the development of several prominent hypotheses for the functions of sleep, but the applicability of these patterns and hypotheses to non‐mammalian taxa is unclear. Here, we present the first quantitative analysis of sleep in a non‐mammalian taxon (birds), focusing on the daily amount of time spent in slow‐wave sleep (SWS) and rapid‐eye movement (REM) sleep as determined by electrophysiological methods. We examined the relationships between constitutive and sleep variables in 23 avian species following earlier studies in mammals, but also considered an index of exposure to predators while asleep and controlled for shared evolutionary history among taxa. Overall, our results were very different from those obtained for mammals. Most remarkably, the relationships between both SWS time and REM sleep time and all constitutive variables were very weak and markedly non‐significant, even though we had adequate power to detect correlations typical of the mammalian data. Only an index of exposure to predation during sleep was significantly related to sleep time, which is the only result common to both birds and mammals. Our results suggest that further insight into the function(s) of sleep across the animal kingdom may require an expansion of sleep research beyond the current mammalian paradigm.
Comparative genomics and repetitive sequence divergence in the species of diploidNicotianasection Alatae
Authors: Yoong Lim K. , Kovarik Ales , Matyasek Roman , Chase Mark W. , Knapp Sandra , McCarthy Elizabeth , Clarkson James J. , Leitch Andrew R. 
Published: November 2006

SummaryCombining phylogenetic reconstructions of species relationships with comparative genomic approaches is a powerful way to decipher evolutionary events associated with genome divergence. Here, we reconstruct the history of karyotype and tandem repeat evolution in species of diploidNicotianasection Alatae. By analysis of plastid DNA, we resolved two clades with high bootstrap support, one containingN. alata,N. langsdorffii,N. forgetianaandN. bonariensis(called then = 9 group) and another containingN. plumbaginifoliaandN. longiflora(called then = 10 group). Despite little plastid DNA sequence divergence, we observed, via fluorescentin situhybridization, substantial chromosomal repatterning, including altered chromosome numbers, structure and distribution of repeats. Effort was focussed on 35S and 5S nuclear ribosomal DNA (rDNA) and the HRS60 satellite family of tandem repeats comprising the elements HRS60, NP3R and NP4R. We compared divergence of these repeats in diploids and polyploids ofNicotiana. There are dramatic shifts in the distribution of the satellite repeats and complete replacement of intergenic spacers (IGSs) of 35S rDNA associated with divergence of the species in section Alatae. We suggest that sequence homogenization has replaced HRS60 family repeats at sub‐telomeric regions, but that this process may not occur, or occurs more slowly, when the repeats are found at intercalary locations. Sequence homogenization acts more rapidly (at least two orders of magnitude) on 35S rDNA than 5S rDNA and sub‐telomeric satellite sequences. This rapid rate of divergence is analogous to that found in polyploid species, and is therefore, in plants, not only associated with polyploidy.
ATR and ATM play both distinct and additive roles in response to ionizing radiation
Authors: Culligan Kevin M. , Robertson Clare E. , Foreman Julia , Doerner Peter , Britt Anne B. 
Published: November 2006

SummaryThe ATR and ATM protein kinases are known to be involved in a wide variety of responses to DNA damage. The Arabidopsis thaliana genome includes both ATR and ATM orthologs, and plants with null alleles of these genes are viable. Arabidopsis atr and atm mutants display hypersensitivity to γ‐irradiation. To further characterize the roles of ATM and ATR in response to ionizing radiation, we performed a short‐term global transcription analysis in wild‐type and mutant lines. We found that hundreds of genes are upregulated in response to γ‐irradiation, and that the induction of virtually all of these genes is dependent on ATM, but not ATR. The transcript of CYCB1;1 is unique among the cyclin transcripts in being rapidly and powerfully upregulated in response to ionizing radiation, while other G2‐associated transcripts are suppressed. We found that both ATM and ATR contribute to the induction of a CYCB1;1:GUS fusion by IR, but only ATR is required for the persistence of this response. We propose that this upregulation of CYCB1;1 does not reflect the accumulation of cells in G2, but instead reflects a still unknown role for this cyclin in DNA damage response.
Time of day modulates low‐temperature Ca2+ signals in Arabidopsis
Authors: Dodd Antony N. , Jakobsen Mia Kyed , Baker Andrew J. , Telzerow Anja , Hou Sui‐Wen , Laplaze Laurent , Barrot Laure , Scott Poethig R. , Haseloff Jim , Webb Alex A. R. 
Published: November 2006

SummaryWe tested the hypothesis that the circadian clock modulates Ca2+‐based signalling pathways, using low‐temperature (LT)‐induced Ca2+ signals. We investigated the relationship between diurnal and circadian modulation of LT‐induced increases in cytosolic‐free calcium ([Ca2+]cyt), and regulation of [Ca2+]cyt‐dependent outputs of the LT‐signalling network (RD29A transcript abundance and stomatal closure). We measured [Ca2+]cyt non‐invasively using aequorin, and targeted aequorin to the guard cell using a guard cell‐specific GAL4‐green fluorescent protein enhancer trap line. LT caused transient increases in whole plant and guard cell [Ca2+]cyt. In guard cells, the LT‐induced [Ca2+]cyt elevation preceded stomatal closure. In whole plants, the magnitude of LT‐induced [Ca2+]cyt transients, measured from the entire plant or specifically the guard cell, varied with the time of day: LT‐induced [Ca2+]cyt transients were significantly higher during the mid‐photoperiod than at the beginning or end. Diurnal variation in LT‐induced guard cell [Ca2+]cyt increases was not correlated to diurnal variation in LT‐induced stomatal closure. There was circadian modulation of LT‐induced whole plant [Ca2+]cyt increases, which were correlated to the circadian pattern of RD29A induction. In order to understand the significance of LT‐induced [Ca2+]cyt increases, we used a computer simulation to demonstrate that, in guard cells, LT‐induced [Ca2+]cyt increases measured from a population of cells are likely to represent the summation of cold‐induced single‐cell [Ca2+]cyt oscillations.
Identification of novel QTL for resistance to crown rot in the doubled haploid wheat population ‘W21MMT70’ × ‘Mendos’
Authors: Bovill W. D. , Ma W. , Ritter K. , Collard B. C. Y. , Davis M. , Wildermuth G. B. , Sutherland M. W. 
Published: November 2006

AbstractCrown rot (causal agent Fusarium pseudograminearum) is a fungal disease of major significance to wheat cultivation in Australia. A doubled haploid wheat population was produced from a cross between line ‘W21MMT70’, which displays partial seedling and adult plant (field) resistance to crown rot, and ‘Mendos’, which is moderately susceptible in seedling tests but partially resistant in field trials. Bulked segregant analysis (BSA) based on seedling trial data did not reveal markers for crown rot resistance. A framework map was produced consisting of 128 microsatellite markers, four phenotypic markers, and one sequence tagged site marker. To this map 331 previously screened AFLP markers were then added. Three quantitative trait loci (QTL) were identified with composite interval mapping across all of the three seedling trials conducted. These QTL are located on chromosomes 2B, 2D and 5D. The 2D and 5D QTL are inherited from the line ‘W21MMT70’, whereas the 2B QTL is inherited from ‘Mendos’. These loci are different from those associated with crown rot resistance in other wheat populations that have been examined, and may represent an opportunity for pyramiding QTL to provide more durable resistance to crown rot.