bluuebunny/crossref_metadata_2025_split huggingface dataset:
Remnants of ancient genetic diversity preserved within captive groups of scimitar‐horned oryx (Oryx dammah)
Authors: IYENGAR A. , GILBERT T. , WOODFINE T. , KNOWLES J. M. , DINIZ F. M. , BRENNEMAN R. A. , LOUIS E. E. , MACLEAN N. 
Published: March 2007

AbstractScimitar‐horned oryx, now considered extinct in the wild, persists in large numbers in captivity. In this first molecular genetic study on this species, we explore the patterns of genetic diversity across European, North American, and a few other captive groups using microsatellite markers and mitochondrial control region sequencing. Strong population structure was not evident from microsatellite data but we discovered deep divergence within the mitochondrial DNA haplotypes from a network analysis where three disconnected networks were obtained, with estimated divergence times ofc.2.1–2.7 million years. Mismatch distribution analyses suggest population expansionsc.1.2 and 0.5 million years ago. We discuss our findings in the context of historical climatic changes in North Africa and use information obtained on current patterns of genetic diversity within captive groups to make recommendations for future captive management and reintroduction strategies.
Population structure and the co‐evolution between social parasites and their hosts
Authors: BRANDT MIRIAM , FISCHER‐BLASS BIRGIT , HEINZE JÜRGEN , FOITZIK SUSANNE 
Published: March 2007

AbstractCo‐evolutionary trajectories of host–parasite interactions are strongly affected by the antagonists’ evolutionary potential, which in turn depends on population sizes as well as levels of recombination, mutation, and gene flow. Under similar selection pressures, the opponent with the higher evolutionary rate is expected to lead the co‐evolutionary arms race and to develop local adaptations. Here, we use mitochondrial DNA sequence data and microsatellite markers to assess the amount of genetic variability and levels of gene flow in two host–parasite systems, each consisting of an ant social parasite — the European slavemaker Harpagoxenus sublaevis and the North American slavemaker Protomognathus americanus— and its two main host species. Our population genetic analyses revealed limited gene flow between individual populations of both host and parasite species, allowing for a geographic mosaic of co‐evolution. In a between‐system comparison, we found less genetic variability and more pronounced structure in Europe, where previous behavioural studies demonstrated strong local adaptation. Within the European host–parasite system, the larger host species Leptothorax acervorum exhibited higher levels of both genetic variability and gene flow, and previous field data showed that it is less affected by the social parasite H. sublaevis than the smaller host Leptothorax muscorum, which has genetically depleted and isolated populations. In North America, the parasite P. americanus showed higher levels of gene flow between sites, but overall less genetic diversity than its hyper‐variable main host species, Temnothorax longispinosus. Interestingly, recent ecological and chemical studies demonstrated adaptation of P. americanus to local host populations, indicating the importance of migration in co‐evolutionary interactions.
Regulation of brassinosteroid responses by Phytochrome B in rice
Authors: JEONG DONG‐HOON , LEE SHINYOUNG , KIM SONG LIM , HWANG ILDOO , AN GYNHEUNG 
Published: March 2007

ABSTRACTPlant growth and development are coordinately controlled by environmental signals and internal factors. Light signals, mediated by phytochromes, regulate photomorphogenesis by interacting with endogenous programmes that involve multiple phytohormones. Brassinosteroids (BRs) are a group of growth‐promoting phytohormones with a crucial role in the light‐dependent development of plants. However, the interaction between light‐signalling pathways and BR signalling is not well understood. Here, we examined the responses of lamina joint inclination and coleoptile elongation to exogenous brassinolide (BL) under light or dark conditions. Both responses were more pronounced under darkness, implying that BR signalling is inhibited by light. To elucidate which phytochrome is involved in this interaction, we isolated rice phytochrome‐deficient mutants (osphyA, osphyB and osphyC) from a T‐DNA insertional population. Whereas the osphyA and osphyC knockout mutants did not differ from the wild‐type plants in their BL responses, osphyB mutants were more sensitive. In addition, RT‐PCR analysis revealed enhanced expression of BR‐inducible genes and decreased transcript levels of BR‐biosynthetic genes in osphyB plants. These results suggest that Phytochrome B acts as a negative regulator of BL‐regulated growth and development processes in rice.
Transcriptional profiling of hexaploid wheat (Triticum aestivum L.) roots identifies novel, dehydration‐responsive genes
Authors: MOHAMMADI MOHSEN , KAV NAT N. V. , DEYHOLOS MICHAEL K. 
Published: March 2007

ABSTRACTWe used a long‐oligonucleotide microarray to identify transcripts that increased or decreased in abundance in roots of dehydration‐tolerant hexaploid bread wheat, in response to withholding of water. We observed that the major classes of dehydration‐responsive genes (e.g. osmoprotectants, compatible solutes, proteases, glycosyltransferases/hydrolases, signal transducers components, ion transporters) were generally similar to those observed previously in other species and osmotic stresses. More specifically, we highlighted increases in transcript expression for specific genes including those putatively related to the synthesis of asparagine, trehalose, oligopeptide transporters, metal‐binding proteins, the gamma‐aminobutyric acid (GABA) shunt and transcription factors. Conversely, we noted a decrease in transcript abundance for diverse classes of glutathione and sulphur‐related enzymes, specific amino acids, as well as MATE‐efflux carrier proteins. From these data, we identified a novel, dehydration‐induced putative AP2/ERF transcription factor, which we predict to function as a transcriptional repressor. We also identified a dehydration‐induced ‘little protein’ (LitP; predicted mass: 8 kDa) that is highly conserved across spermatophytes. Using qRT‐PCR, we compared the expression patterns of selected genes between two related wheat genotypes that differed in their susceptibility to dehydration, and confirmed that these novel genes were highly inducible by water limitation in both genotypes, although the magnitude of induction differed.
The relationship between isoprene emission rate and dark respiration rate in white poplar (Populus alba L.) leaves
Authors: LORETO FRANCESCO , CENTRITTO MAURO , BARTA CSENGELE , CALFAPIETRA CARLO , FARES SILVANO , MONSON RUSSELL K. 
Published: March 2007

ABSTRACTIn past studies, it was hypothesized that reductions in chloroplast isoprene emissions at high atmospheric CO2 concentrations were caused by competition between cytosolic and mitochondrial processes for the same substrate, possibly phosphoenolpyruvate (PEP). We conducted field and laboratory experiments using leaves of white poplar (Populus alba L.) to identify whether an inverse relationship occurs between the dark respiration rate (a mitochondrial process) and the isoprene emission rate. Field experiments that were carried out in a free‐air CO2‐enriched (FACE) facility showed no clear effect of elevated CO2 on either isoprene emission rate or respiration rate by leaves. In young, not yet fully expanded leaves, low isoprene emission and high dark respiration rates were measured in both ambient and elevated CO2. In these leaves, isoprene emission was inversely correlated with dark respiration. It is possible to interpret from these results that, in young leaves, high rates of growth respiration compete with isoprene biosynthesis for the same substrate. However, it is also possible that the negative correlation reflects the contrasting reductions in growth respiration and increases in expression of the enzyme isoprene synthase at this final stage of leaf maturation. In contrast to our observations on young leaves, respiration rate and isoprene emission rate were positively correlated in older, fully expanded leaves (8 and 11 from apex). A positive correlation was also found between respiration rate and isoprene emission rate when these parameters were modulated using different ozone exposure, growth light intensity, growth temperature and exposure to different leaf temperatures in laboratory experiments. These data show that competition for substrate between isoprene biosynthesis and leaf respiration does not determine the rate of isoprene emission in most circumstances that affect both processes. A negative correlation was observed across all experiments between isoprene emission rate and the activity of phosphoenolpyruvate carboxylase (PEPc), a cytosolic enzyme that competes with isoprene biosynthesis for substrate. The cytosolic metabolite, PEP, occurs at a metabolic branch point from which substrate flows into three processes: (1) the production of pyruvate for mitochondrial respiration, (2) the production of oxaloacetate (OAA) by PEPc for anabolic support of mitochondrial respiration and (3) transport into the chloroplast to support chloroplastic demands for pyruvate, including isoprenoid biosynthesis. The results of our observations suggest that only the second process competes for substrate with isoprenoid synthesis, while the partitioning of PEP between mitochondrial respiration and chloroplast isoprenoid biosynthesis is controlled in a way that retains balance in substrate demand.
Measurement of stem respiration of sycamore (Platanus occidentalis L.) trees involves internal and external fluxes of CO2 and possible transport of CO2 from roots
Authors: TESKEY R. O. , MCGUIRE M. A. 
Published: March 2007

ABSTRACTCO2 released by respiring cells in tree stems can either diffuse to the atmosphere or dissolve in xylem sap. In this study, the internal and external fluxes of CO2 released from respiring stems of five sycamore (Platanus occidentalis L.) trees were calculated. Mean rates of stem respiration were highest in mid‐afternoon and lowest at night, and were positively correlated with air temperature. Over a 24 h period, on average 34% of the CO2 released by respiring cells in the measured stem segment remained within the tree. CO2 efflux to the atmosphere consisted of similar proportions of CO2 derived from local respiring cells (55%) and CO2 that had been transported in the xylem (45%), indicating that CO2 efflux does not accurately estimate respiration. A portion of the efflux of transported CO2 appeared to have originated in the root system. A modification of the method for calculating stem respiration based on internal and external fluxes of CO2 was developed to separate efflux due to local respiration from efflux of transported CO2.
Impacts of tree height on leaf hydraulic architecture and stomatal control in Douglas‐fir
Authors: WOODRUFF DAVID R. , MCCULLOH KATHERINE A. , WARREN JEFFREY M. , MEINZER FREDERICK C. , LACHENBRUCH BARBARA 
Published: March 2007

ABSTRACTThis study investigated the mechanisms involved in the regulation of stomatal closure in Douglas‐fir and evaluated the potential impact of compensatory adjustments in response to increasing tree height upon these mechanisms. In the laboratory, we measured leaf hydraulic conductance (Kleaf) as leaf water potential (Ψl) declined for comparison with in situ diurnal patterns of stomatal conductance (gs) and Ψl in Douglas‐fir across a height gradient, allowing us to infer linkages between diurnal changes in Kleaf and gs. A recently developed timed rehydration technique was used in conjunction with data from pressure–volume curves to develop hydraulic vulnerability curves for needles attached to small twigs. Laboratory‐measured Kleaf declined with increasing leaf water stress and was substantially reduced at Ψl values of −1.34, −1.45, −1.56 and −1.92 MPa for foliage sampled at mean heights of approximately 20, 35, 44 and 55 m, respectively. In situ gs measurements showed that stomatal closure was initiated at Ψl values of −1.21, −1.36, −1.74 and −1.86 MPa along the height gradient, which was highly correlated with Ψl values at loss of Kleaf. Cryogenic scanning electron microscopy (SEM) images showed that relative abundances of embolized tracheids in the central vein increased with increasing leaf water stress. Leaf embolism appeared to be coupled to changes in gs and might perform a vital function in stomatal regulation of plant water status and water transport in conifers. The observed trends in gs and Kleaf in response to changes in Ψl along a height gradient suggest that the foliage at the tops of tall trees is capable of maintaining stomatal conductance at more negative Ψl. This adaptation may allow taller trees to continue to photosynthesize during periods of greater water stress.
Thellungiella: an Arabidopsis‐related model plant adapted to cold temperatures
Authors: GRIFFITH MARILYN , TIMONIN MARY , WONG ANNIE C. E. , GRAY GORDON R. , AKHTER SAJJAD R. , SALDANHA MARSHA , ROGERS MICHAEL A. , WERETILNYK ELIZABETH A. , MOFFATT BARBARA 
Published: March 2007

ABSTRACT Thellungiella salsuginea, a wild crucifer that grows in subarctic Canada and is closely related to Arabidopsis thaliana, was examined for its suitability as a model plant for studies of tolerance to cold and freezing temperatures. Thellungiella completed its life cycle at 5 °C, demonstrating that temperature‐sensitive processes such as seed germination and the production of pollen and seeds were resistant to cold temperatures. Moreover, the plant exhibited dramatically different vegetative and flowering phenotypes in response to growth at cold temperature and shifts to cold temperature. Northern analyses showed that genes induced by cold in Arabidopsis, including CBF1, the transcriptional activator for the cold‐regulated (COR) genes COR15a and COR47, were also expressed in Thellungiella. Freezing tolerance, assayed by the regrowth of intact plants, increased from −13.0 to −18.5 °C after cold treatment. The plants lacked endogenous ice nucleation or anti‐freeze activity, indicating a potential for supercooling. As a close relative to Arabidopsis, Thellungiella exhibits extreme cold tolerance and should be an important model system in the elucidation of stress tolerance mechanisms.
Kaposi's sarcoma in Nigeria
Authors: Onunu Abel N. , Okoduwa Cynthia , Eze Emeka U. , Adeyekun Ademola A. , Kubeyinje Emmanuel P. , Schwartz Robert A. 
Published: March 2007

AbstractBackground  The prevalence of Kaposi's sarcoma (KS) in parts of Africa has been on the increase as a result of the human immunodeficiency virus (HIV) infection pandemic. However, there is a paucity of information for Nigeria.Objective  To describe the clinical and epidemiological characteristics of cutaneous KS in patients with HIV‐infection in Benin City, Nigeria.Methods  All patients presenting to the dermatology and infectious diseases clinics of the University of Benin Teaching Hospital, or admitted to its medical wards, within the period July 2000–June 2005 were examined retrospectively in a chart review for KS. Diagnosis of HIV was based upon ELISA testing. The CD4+ cell counts were performed using the Dyna Bead method and KS was diagnosed histologically.Results  In our survey, 31 patients, representing 0.84% of all new HIV patients seen during the study period, had cutaneous KS. There were 19 males and 12 females, giving a male to female ratio of 1.6 : 1. The mean age was 36.3 ± 9 years; mean CD4+ count was 127 ± 14 cells/dl. The lower limbs (74.2%), trunk (48.4%) and the face (22.6%) were the most frequent sites affected. The lesions were solitary in three patients (9.7%) and multiple in 28 patients (90.3%).Conclusion  The prevalence of HIV‐related KS is increasing in Nigeria. There is an increase in the number of women being diagnosed with this form of KS, probably owing to more females having HIV disease.
Balance module allows consistent monitoring and documentation of the pooling process for nucleic acid amplification technology testing
Authors: Hourfar M. K. , Koller M. , Roth W. K. , Kehrli R. , Seifried E. , Schmidt M. 
Published: March 2007

Background and Aims  When performing minipool testing of blood donations for transfusion‐transmissible viruses, it is crucial to correctly dispense plasma from each donation into the pools. However, concerns regarding the monitoring and documentation of the pooling process exist.Methods  A balance module with a tube holder has been developed, which can be easily integrated into liquid handling platforms. The existing software monitors and evaluates every single dispensing from primary samples to the minipool to confirm liquid arrival. The weighing accuracy of the balance module is approximately 2 mg per dispensing episode.Results  Ten thousand one hundred and fifty‐six blood donations were tested on a Tecan Genesis RSP‘ pipetting system. Thirty‐one donations were not pipetted because the pipetting workstation identified a clot or sample shortage in the primary tube. The balance module exclusively detected another 18 mispipettings, which were outside of the acceptance criteria of 100 ± 10%. The mean pipetted volume for these samples was 34.2 µl (range 0–87 µl). Visual inspection of the corresponding primary tubes showed blood clots, short sample or no apparent cause. The average deceleration of the pooling process, using the balance, was determined to be about 22%.Conclusions  With the novel liquid arrival check system, complete and consistent process documentation of pooling for nucleic acid amplification technology (NAT) testing is feasible. It enables blood banks to monitor and compare every single dispense made with predefined, required volumes. Results can be transferred to the laboratory information management system for automated selective exclusion of inaccurately dispensed samples.One sentence summary   Monitoring and documenting the pooling process for NAT testing using a balance‐based liquid arrival check system.
Experimental evidence of habitat provision by aggregations of Riftia pachyptila at hydrothermal vents on the East Pacific Rise
Authors: Govenar Breea , Fisher Charles R. 
Published: March 2007

AbstractHabitat created or modified by the physical architecture of large or spatially dominant species plays an important role in structuring communities in a variety of terrestrial, aquatic, and marine habitats. At hydrothermal vents, the giant tubeworm Riftia pachyptila forms large and dense aggregations in a spatially and temporally variable environment. The density and diversity of smaller invertebrates is higher in association with aggregations of R. pachyptila than on the surrounding basalt rock seafloor. Artificial substrata designed to mimic R. pachyptila aggregations were deployed along a gradient of productivity to test the hypothesis that high local species diversity is maintained by the provision of complex physical structure in areas of diffuse hydrothermal flow. After 1 year, species assemblages were compared among artificial aggregations in low‐, intermediate‐, and high‐productivity zones and compared to natural aggregations of R. pachyptila from the same site. Hydrothermal vent fauna colonized every artificial aggregation, and both epifaunal density and species richness were highest in areas of high chemosynthetic primary production. The species richness was also similar between natural aggregations of R. pachyptila and artificial aggregations in intermediate‐ and high‐productivity zones, suggesting that complex physical structure alone can support local species diversity in areas of chemosynthetic primary production. Differences in the community composition between natural and artificial aggregations reflect the variability in microhabitat conditions and biological interactions associated with hydrothermal fluid flux at low‐temperature hydrothermal vents. Moreover, these local ecological factors may further contribute to the maintenance of regional species diversity in hydrothermal vent communities on the East Pacific Rise.
On the experimental evolution of specialization and diversity in heterogeneous environments
Authors: Jasmin Jean‐Nicolas , Kassen Rees 
Published: March 2007

AbstractEnvironmental variance can be decomposed into two components: the contrast among patches in the optimal phenotype and the variance in productivity among patches. Both components can influence the outcome of selection in heterogeneous environments. In general genetic diversity within a population should increase as the contrast among patches increases. As the variance in productivity increases, on the other hand, individual niche breadth should decrease since the response to selection becomes dominated by adaptation to the most productive patch. We tested this interpretation of diversity in heterogeneous environments by selecting the bacterium Pseudomonas fluorescens over several hundred generations in pair‐wise mixtures of four carbon substrates. We then assessed the response to selection in the mixtures in terms of performance on each component substrate. The results provide general support for this interpretation of the environmental variance and suggest further that competition among genotypes promotes diversification in heterogeneous environments.
Plasticity in metabolic allometry: the role of dietary stoichiometry
Authors: Jeyasingh Punidan D. 
Published: March 2007

AbstractMetabolism involves multiple elements. While we know much about the allometry in metabolic response of organisms to energy (carbon, C) availability, little is known about how different‐sized organisms respond to the relative availability of elements. I experimentally manipulated availability of phosphorus (P) relative to C, to test whether dietary C : P affects metabolism in four species of Daphnia, spanning an order of magnitude in body mass. Results indicated that the slope of the relationship between individual respiration and body mass was M0.83 under a balanced diet (C : P c. 150), and M0.67 under an imbalanced diet (C : P c. 800). Increased respiration under dietary imbalance was not due to increased ingestion. The change in the scaling exponent was due to the greater respiratory response of smaller species to altered diets. Diet‐induced metabolic plasticity contributes to variation in metabolic allometry, at least at such small scales of body size.
Escape in space from enemies: a comparison between stands with and without enhanced densities of the spruce bark beetle
Authors: Schroeder Leif Martin 
Published: March 2007

Abstract1 Populations of the spruce bark beetle, Ips typographus (L.), are known to grow rapidly in storm‐disturbed stands as a result of relaxation from intraspecific competition. In the present study, it was tested whether a second mechanism, escape in space from natural enemies, also contributes to the rapid population increase.2 The experiment was conducted during the initiation phase of five local outbreaks of I. typographus triggered by a storm‐disturbance in November 1995 in southern Sweden.3 The impact of natural enemies on the ratio of increase (number of daughters per mother) of I. typographus was compared pairwise between disturbed stands with high numbers of storm‐felled trees and undisturbed stands without wind‐felled trees.4 Enemy impact was assessed by comparing the ratio of increase in uncaged (exposed to enemies) and caged (protected from enemies) bolts colonized by I. typographus prior to being placed in the stands. The experiment was conducted in the second and third summers after the storm‐felling.5 Enemy impact was about twice as high in stands without wind‐felled trees compared with in stands with wind‐felled trees in the second summer whereas there was no significant difference between the stand types in the third summer.6 The result demonstrates that spatial escape from enemies contributes to the rapid population growth of I. typographus after storm‐disturbances.