bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon dioxide assimilation by a wetland sedge canopy exposed to ambient and elevated CO2: measurements and model analysis
Authors: Rasse D. P. , Li J.‐H. , Drake B. G. 
Published: December 2004

Summary

The wetland sedge Scirpus olneyi Gray displays fast rates of CO2 assimilation and responds positively to increased atmospheric CO2 concentration. The present study was aimed at identifying the ecophysiological traits specific to S. olneyi that drive these CO2‐assimilation patterns under ambient and elevated CO2 conditions.
The net ecosystem exchange (NEE) of CO2 between S. olneyi communities and the atmosphere was measured in open‐top chambers.
We developed a new mechanistic model for S. olneyi communities based on published ecophysiological data and additional measurements of photosynthetic parameters.
Our NEE measurements confirmed that S. olneyi communities have a high rate of summertime CO2 assimilation, with noontime peaks reaching 40 µmol CO2 m−2 ground s−1 on productive summer days, and that elevated CO2 increased S. olneyi CO2 assimilation by c. 35–40%.
Using S. olneyi‐specific ecophysiological parameters, comparison with measured NEE showed that the model accurately simulated these high rates of CO2 uptake under ambient or elevated CO2.
The model pointed to the Rubisco capacity of Scirpus leaves associated with their high total nitrogen content as the primary explanation for the high rates of CO2 assimilation, and indicated that the vertical‐leaf canopy structure of S. olneyi had comparatively little influence on CO2 assimilation.
Structure–function analysis of human Spt4: evidence that hSpt4 and hSpt5 exert their roles in transcriptional elongation as parts of the DSIF complex
Authors: Kim Dong‐ki , Inukai Naoto , Yamada Tomoko , Furuya Akiko , Sato Hiroe , Yamaguchi Yuki , Wada Tadashi , Handa Hiroshi 
Published: December 2004

AbstractBackground:The human Spt4/Spt5 complex, termed DRB‐sensitivity inducing factor (DSIF) is a dual regulator of transcription that stimulates, or, when cooperating with negative elongation factor (NELF), represses RNA polymerase II (RNAPII) elongation. Spt4 and Spt5 are also thought to be involved in mRNA capping, homologous DNA recombination, and transcription‐coupled DNA repair. As a first step to understanding how these proteins regulate diverse cellular processes, we investigated the structure and function of hSpt4in vitro.Results:Immunodepletion of hSpt5 from HeLa nuclear extracts resulted in the efficient co‐depletion of hSpt4. Using DSIF‐depleted nuclear extracts and a series of Spt4 mutants, we examined the amino acid sequence of hSpt4 which was important for hSpt5 binding and for transcriptional repression and activation by DSIF. Unexpectedly, the zinc finger of hSpt4, which is critical for the yeast counterpart to functionin vivo, was dispensable for hSpt5 binding and for transcriptional regulationin vitro.Conclusion:These and other results suggest: (i) that the central region of hSpt4 is necessary and sufficient for its functionin vitroand (ii) that there is no free hSpt4 or hSpt5 in cells. We propose that hSpt4 and hSpt5 exert their roles in transcriptional regulation, and possibly in other nuclear processes, as parts of the DSIF complex.
Enforced cytokinesis without complete nuclear division in embryonic cells depleting the activity of DNA topoisomerase IIα
Authors: Akimitsu Nobuyoshi , Adachi Noritaka , Hirai Hiroshi , Hossain Muktadir S. , Hamamoto Hiroshi , Kobayashi Masao , Aratani Yasuaki , Koyama Hideki , Sekimizu Kazuhisa 
Published: December 2004

AbstractBackground: There are two distinct DNA topoisomerase II (topo II) isoforms, designated topo IIα and topo IIβ, in mammalian cells. The function of topo IIα in the development of mammalian cells has not been elucidated because of a lack of topo IIα mutants.Results: We generated mice with a targeted disruption of the topo IIα gene. The development of topo IIα−/– embryos was terminated at the 4‐ or 8‐cell stage. When wild‐type embryos at the 2‐ or 4‐cell stage were treated with ICRF‐193, a catalytic inhibitor of topo II, nuclear division occurred followed by cytokinesis to form 4 or 8 cells, respectively, then development was terminated. Microscope analysis of 4,6‐diamidino‐2‐phenylindole (DAPI)‐stained nuclei of both topo IIα−/– and ICFR‐193‐treated embryonic cells revealed a droplet‐like structure connecting the terminals of two adjacent nuclei forming a bridge‐like structure. Phosphorylated histone H3, a marker for the M phases, disappeared from the nuclei of the topo IIα‐depleted embryonic cells. Laser scanning cytometry of the topo IIα‐depleted cells revealed the presence of 2N DNA cells.Conclusions: Our results indicate that topo IIα has an essential role in the early stages of mouse development and that depletion of topo IIα from the embryonic cells causes incomplete nuclear division followed by enforced cytokinesis.
Cell cycle regulation of chromatin binding and nuclear localization of human Cdc7‐ASK kinase complex
Authors: Sato Noriko , Sato Megumi , Nakayama Masahito , Saitoh Rika , Arai Ken‐ichi , Masai Hisao 
Published: December 2004

AbstractBackground: During the course of DNA replication, regulation of cellular localization and chromatin binding of involved factors plays critical roles. Cdc7 kinase is required for DNA replication and its kinase activity is cell cycle‐regulated by its activation subunit Dbf4/ASK. In mammals, it is not known at which time point during the cell cycle Cdc7 and Dbf4/ASK proteins are imported into nuclei and loaded on to chromatin.Results: We have constructed a series of truncation and deletion derivatives of ASK and expressed them as fusion proteins with GFP in mammalian cells. Both Dbf4‐motif‐M and ‐C conserved in Dbf4/ASK protein family are required for huCdc7 kinase activation. Two stretches of amino acid sequences, NLS1 (P346KKKRIK) and NLS2 (K201RVGSGAQKTRTGRLKK), are important for ASK nuclear localization. In stable transformants expressing GFP‐fused full‐length ASK under the tetracycline inducible promoter, GFP‐ASK protein accumulates in nuclei at the telophase, but its binding to chromatin does not reach a maximum until late G1, whereas huCdc7 is imported into nuclei and binds to chromatin at early G1. An important substrate of Cdc7‐ASK at the G1/S transition is likely to be MCM. Indeed, over‐expression of both huCdc7 and ASK results in the elevated phosphorylation of endogenous MCM2 protein, as manifested by appearance of the mobility‐shifted form on SDS‐PAGE, but does not cause any significant effects on cell cycle progression.Conclusions: Nuclear localization and chromatin binding of endogenous huCdc7 and GFP‐ASK expressed during the post‐mitotic phase are independently regulated. Although GFP‐ASK is presumably imported into nuclei through its two nuclear localization signals at telophase, it may require additional signals for chromatin binding, the level of which increases at late G1 phase.Cell cycle regulation of cellular localization and chromatin binding of Cdc7 and ASK proteins. See text for details.image
AKRL1 and AKRL2 activate the JNK pathway
Authors: Harada Takeshi , Matsuzaki Osamu , Hayashi Hideko , Sugano Sumio , Matsuda Akio , Nishida Eisuke 
Published: December 2004

AbstractBackground: c‐Jun N‐terminal kinase (JNK), a member of the mitogen‐activated protein kinase (MAPK) family, is activated by specific cytokines and various environmental stresses. MKK4 and MKK7 are shown to be direct activators of JNK. Although several upstream components of the JNK pathway, including members of the MAPKKK family have been described, the components lying between the receptors or sensors and JNK have not been fully characterized.Results: We have identified AKRL1 and AKRL2 (Akr1p‐like 1 and 2) as novel activators of the JNK pathway. AKRL1 and AKRL2 proteins have a considerable sequence similarity to Akr1p, a protein essential for endocytosis in Saccharomyces cerevisiae. Expression of AKRL1 or AKRL2 activates JNK and its activators MKK4 and MKK7. This AKRL1/2‐induced JNK activation is significantly suppressed by the expression of a kinase‐negative mutant of TAK1, a member of the MAPKKK family. AKRL1 and AKRL2 localize to the Golgi. Both the N‐terminal half and the C‐terminal transmembrane domain of AKRL1/2 are required for the JNK activation. The C‐terminal transmembrane domain of AKRL1/2 is required for localization to the Golgi.Conclusion: AKRL1 and AKRL2 are localized to Golgi and the novel activators of the JNK pathway.
VDE‐initiated intein homing in Saccharomyces cerevisiae proceeds in a meiotic recombination‐like manner
Authors: Fukuda Tomoyuki , Nogami Satoru , Ohya Yoshikazu 
Published: December 2004

AbstractBackground: Inteins and group I introns found in prokaryotic and eukaryotic organisms occasionally behave as mobile genetic elements. During meiosis of the yeast Saccharomyces cerevisiae, the site‐specific endonuclease encoded by VMA1 intein, VDE, triggers a single double‐strand break (DSB) at an inteinless allele, leading to VMA1 intein homing. Besides the accumulating information on the in vitro activity of VDE, very little has been known about the molecular mechanism of intein homing in yeast nucleus.Results: We developed an assay to detect the product of VMA1 intein homing in yeast genome. We analysed mutant phenotypes of RecA homologs, Rad51p and Dmc1p, and their interacting proteins, Rad54p and Tid1p, and found that they all play critical roles in intein inheritance. The absence of DSB end processing proteins, Sae2p and those in the Mre11‐Rad50‐Xrs2 complex, also causes partial reduction in homing efficiency. As with meiotic recombination, crossover events are frequently observed during intein homing. We also observed that the absence of premeiotic DNA replication caused by hydroxyurea (HU) or clb5Δ clb6Δ mutation reduces VDE‐mediated DSBs.Conclusion: The repairing system working in intein homing shares molecular machinery with meiotic recombination induced by Spo11p. Moreover, like Spo11p‐induced DNA cleavage, premeiotic DNA replication is a prerequisite for a VDE‐induced DSB. VMA1 intein thus utilizes several host factors involved in meiotic and recombinational processes to spread its genetic information and guarantee its progeny through establishment of a parasitic relationship with the organism.
[PHI+], a novel Sup35‐prion variant propagated with non‐Gln/Asn oligopeptide repeats in the absence of the chaperone protein Hsp104
Authors: Crist Colin G. , Nakayashiki Toru , Kurahashi Hiroshi , Nakamura Yoshikazu 
Published: December 2004

AbstractBackground: The [PSI+] element of the budding yeast is an aggregated form of the translation release factor Sup35 that is propagated and transmitted cytoplasmically in a manner analogous to that of mammalian prions. The N‐terminal of Sup35, necessary for [PSI+], contains oligopeptide repeats and multiple Gln/Asn residues.Results: We replaced the Gln/Asn‐rich prion repeats of Sup35 with non‐Gln/Asn repeats from heterologous yeast strains. These non‐Gln/Asn repeat Sup35s propagated a novel [PSI+] variant, [PHI+], that appeared de novo 103 times more frequent than [PSI+]. [PHI+] was stably inherited in a non‐Mendelian fashion, but not eliminated upon the inactivation of Hsp104, unlike known [PSI+] elements. In vitro, non‐Gln/Asn repeat domains formed amyloid fibres that were shorter and grew more slowly than did Gln/Asn‐rich prion domains, while [PHI+] aggregates were smaller than [PSI+] aggregates in vivo.Conclusions: These findings suggest the existence of an alternative, Hsp104‐independent pathway to replicate non‐Gln/Asn variant Sup35 prion seeds.
Consequences of wildfire on ecosystem CO2 and water vapour fluxes in the Great Basin
Authors: OBRIST DANIEL , DELUCIA EVAN H. , ARNONE JOHN A. 
Published: December 2004

AbstractIncreased fire frequency in the Great Basin of North America's intermountain West has led to large‐scale conversion of native sagebrush (Artemisia tridentata Nutt.) communities to postfire successional communities dominated by native and non‐native annual species during the last century. The consequences of this conversion for basic ecosystem functions, however, are poorly understood. We measured net ecosystem CO2 exchange (NEE) and evapotranspiration (ET) during the first two dry years after wildfire using a 4‐m diameter (16.4 m3) translucent static chamber (dome), and found that both NEE and ET were higher in a postfire successional ecosystem (−0.9–2.6 µmol CO2 m−2 s−1 and 0.0–1.0 mmol H2O m−2 s−2, respectively) than in an adjacent intact sagebrush ecosystem (−1.2–2.3 µmol CO2 m−2 s−1 and −0.1–0.8 mmol H2O m−2 s−2, respectively) during relatively moist periods. Higher NEE in the postfire ecosystem appears to be due to lower rates of above‐ground plant respiration while higher ET appears to be caused by higher surface soil temperatures and increased soil water recharge after rains. These patterns disappeared or were reversed, however, when the conditions were drier. Daily net ecosystem productivity (NEP; g C m−2 d−1), derived from multiple linear regressions of measured fluxes with continuously measured climate variables, was very small (close to zero) throughout most of the year. The wintertime was an exception in the intact sagebrush ecosystem with C losses exceeding C gains leading to negative NEP while C balance of the postfire ecosystem remained near zero. Taken together, our results indicate that wildfire‐induced conversion of native sagebrush steppe to ecosystems dominated by herbaceous annual species may have little effect on C balance during relatively dry years (except in winter months) but may stimulate water loss immediately following fires.
Climate change and sea turtles: a 150‐year reconstruction of incubation temperatures at a major marine turtle rookery
Authors: HAYS GRAEME C. , BRODERICK ANNETTE C. , GLEN FIONA , GODLEY BRENDAN J. 
Published: December 2004

AbstractSea turtles show temperature dependent sex determination. Using an empirical relationship between sand and air temperature, we reconstructed the nest temperatures since 1855 at Ascension Island, a major green turtle (Chelonia mydas) rookery. Our results show that inter‐beach thermal variations, previously ascribed to the albedo of the sand, which varies hugely from one beach to another, have persisted for the last century. Reconstructed nest temperatures varied by only 0.5 °C on individual beaches over the course of the nesting season, while the temperature difference between two key nesting beaches was always around 3 °C. Hence inter‐beach thermal variations are the main factor causing a large range of incubation temperatures at this rookery. There was a general warming trend for nests, with a mean increase in reconstructed nest temperatures for different months of between 0.36 and 0.49 °C for the last 100 years.
Changes in carbon storage and fluxes in a chronosequence of ponderosa pine
Authors: LAW B. E. , SUN O. J. , CAMPBELL J. , VAN TUYL S. , THORNTON P. E. 
Published: December 2004

AbstractForest development following stand‐replacing disturbance influences a variety of ecosystem processes including carbon exchange with the atmosphere. On a series of ponderosa pine (Pinius ponderosa var. Laws.) stands ranging from 9 to> 300 years in central Oregon, USA, we used biological measurements to estimate carbon storage in vegetation and soil pools, net primary productivity (NPP) and net ecosystem productivity (NEP) to examine variation with stand age. Measurements were made on plots representing four age classes with three replications: initiation (I, 9–23 years), young (Y, 56–89 years), mature (M, 95–106 years), and old (O, 190–316 years) stands typical of the forest type in the region. Net ecosystem productivity was lowest in the I stands (−124 g C m−2 yr−1), moderate in Y stands (118 g C m−2 yr−1), highest in M stands (170 g C m−2 yr−1), and low in the O stands (35 g C m−2 yr−1). Net primary productivity followed similar trends, but did not decline as much in the O stands. The ratio of fine root to foliage carbon was highest in the I stands, which is likely necessary for establishment in the semiarid environment, where forests are subject to drought during the growing season (300–800 mm precipitation per year). Carbon storage in live mass was the highest in the O stands (mean 17.6 kg C m−2). Total ecosystem carbon storage and the fraction of ecosystem carbon in aboveground wood mass increased rapidly until 150–200 years, and did not decline in older stands. Forest inventory data on 950 ponderosa pine plots in Oregon show that the greatest proportion of plots exist in stands ∼ 100 years old, indicating that a majority of stands are approaching maximum carbon storage and net carbon uptake. Our data suggests that NEP averages ∼ 70 g C m−2 year−1 for ponderosa pine forests in Oregon. About 85% of the total carbon storage in biomass on the survey plots exists in stands greater than 100 years, which has implications for managing forests for carbon sequestration. To investigate variation in carbon storage and fluxes with disturbance, simulation with process models requires a dynamic parameterization for biomass allocation that depends on stand age, and should include a representation of competition between multiple plant functional types for space, water, and nutrients.
A reciprocal transplant experiment within a climatic gradient in a semiarid shrub‐steppe ecosystem: effects on bunchgrass growth and reproduction, soil carbon, and soil nitrogen
Authors: LINK STEVEN O. , SMITH JEFFREY L. , HALVORSON JONATHAN J. , BOLTON HARVEY 
Published: December 2004

AbstractWe investigated the effect of climate change on Poa secunda Presl. and soils in a shrub‐steppe ecosystem in south‐eastern Washington. Intact soil cores containing P. secunda were reciprocally transplanted between two elevations. Plants and soils were examined, respectively, 4.5 and 5 years later. The lower elevation (310 m) site is warmer (28.5 °C air average monthly maximum) and drier (224 mm yr−1) than the upper elevation (844 m) site (23.5 °C air average monthly maximum, 272 mm yr−1). Observations were also made on undisturbed plants at both sites. There was no effect of climate change on plant density, shoot biomass, or carbon isotope discrimination in either transplanted plant population. The cooler, wetter environment significantly reduced percent cover and leaf length, while the warmer, drier environment had no effect. Warming and drying reduced percent shoot nitrogen, while the cooler, wetter environment had no effect. Culm density was zero for the lower elevation plants transplanted to the upper site and was 10.3 culms m−2 at the lower site. There was no effect of warming and drying on the culm density of the upper elevation plants. Culm density of in situ lower elevation plants was greater than that of the in situ upper elevation plants. Warming and drying reduced total soil carbon 32% and total soil nitrogen 40%. The cooler, wetter environment had no effect on total soil C or N. Of the C and N that was lost over time, 64% of both came from the particulate organic matter fraction (POM, > 53 µm). There was no effect of warming and drying on the upper population of P. secunda while exposing the lower population to the cooler, wetter environment reduced reproductive effort and percent cover. With the warmer and drier conditions that may develop with climate change, total C and N of semiarid soils may decrease with the active fraction of soil C also rapidly decreasing, which may alter ecosystem diversity and function.
Major disturbance events in terrestrial ecosystems detected using global satellite data sets
Authors: POTTER CHRISTOPHER , TAN PANG‐NING , STEINBACH MICHAEL , KLOOSTER STEVEN , KUMAR VIPIN , MYNENI RANGA , GENOVESE VANESSA 
Published: December 2004

AbstractEcosystem scientists have yet to develop a proven methodology to monitor and understand major disturbance events and their historical regimes at a global scale. This study was conducted to evaluate patterns in an 18‐year record of global satellite observations of vegetation phenology from the Advanced Very High Resolution Radiometer (AVHRR) as a means to characterize major ecosystem disturbance events and regimes. The fraction absorbed of photosynthetically active radiation (FPAR) by vegetation canopies worldwide has been computed at a monthly time interval from 1982 to 1999 and gridded at a spatial resolution of 0.5° latitude/longitude. Potential disturbance events of large extent (> 0.5 Mha) were identified in the FPAR time series by locating anomalously low values (FPAR‐LO) that lasted longer than 12 consecutive months at any 0.5° pixel. We find that nearly 400 Mha of the global land surface could be identified with at least one FPAR‐LO event over the 18‐year time series. The majority of these potential disturbance events occurred in tropical savanna and shrublands or in boreal forest ecosystem classes. Verification of potential disturbance events from our FPAR‐LO analysis was carried out using documented records of the timing of large‐scale wildfires at locations throughout the world. Disturbance regimes were further characterized by association analysis with historical climate anomalies. Assuming accuracy of the FPAR satellite record to characterize major ecosystem disturbance events, we estimate that nearly 9 Pg of carbon could have been lost from the terrestrial biosphere to the atmosphere as a result of large‐scale ecosystem disturbance over this 18‐year time series.
Successful induction of immune tolerance in a patient with haemophilia B with inhibitor
Authors: Suzuki N. , Watanabe J. , Kudoh T. , Hori T. , Hatakeyama N. , Mizue N. , Oda T. , Tsutsumi H. 
Published: December 2004

Summary.We describe successful induction of immune tolerance (IT) in a 10‐month‐old boy with severe haemophilia B. Urticaria developed soon after starting prophylactic treatment and was associated with an inhibitor at 7 Bethesda units mL−1. Initially, we tried low dose factor IX therapy to induce IT with only a transient effect. The patient experienced an intracranial haemorrhage. A simple bolus dose of FIX eradicated the inhibitor. Thereafter he has been free from inhibitor and nephrotic syndrome for more than 5 years, although he receives FIX three times a week.
Control of bleeding in patients with haemophilia A with inhibitors: a systematic review
Authors: Lloyd Jones M. , Wight J. , Paisley S. , Knight C. 
Published: December 2004

Summary.This paper reports a systematic review of the best available evidence of clinical effectiveness in the treatment of acute bleeding in haemophilia A patients with inhibitors. Because of the lack of randomized controlled trials (RCTs) on this topic, broad inclusion criteria with regard to study design were applied in order to assess the best available evidence for each intervention. Because of the clinical and methodological heterogeneity of the evidence, it was not appropriate to pool data across studies; instead, data were synthesized using tabulation and qualitative narrative assessment. No evidence was found to support the use of high‐dose factor VIII (FVIII) in bleeding episodes. However in surgery it was found to be highly successful (100%) for low‐titre, low‐responding inhibitors although not reliable for high‐responding inhibitors. Porcine FVIII (pFVIII) was effective in the control of severe bleeding episodes with high‐titre or high‐responding inhibitors (100%) and in 60–90% of surgical procedures. Activated prothrombin complex concentrates (APCCs) appear to be more effective than prothrombin complex concentrates (PCCs) in the control of mild to severe bleeding episodes. There was no good evidence for the use of PCCs in surgery. APCCs controlled bleeding in approximately 90% of surgical episodes. Recombinant factor VIIa (rFVIIa) controlled 70–100% of mild to severe bleeding episodes with high‐responding inhibitors, and achieved better results when used early. It was effective in 60–100% of surgical episodes. Doses varied from study to study, and side‐effects from mild to infrequent but serious adverse events were reported. The quality of the evidence is variable. Limited evidence relating to other treatment options is also included in the review.