bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Dendroclimatic Reconstruction of Annual Precipitation on the Western Canadian Prairies since A.D. 1505 from Pinus flexilis James
Authors: Case Roslyn A. , MacDonald Glen M. 
Published: September 2002

AbstractTree-ring chronologies from living and sub-fossil Pinus flexilis James (limber pine) trees extend back more than 500 yr on the western edge of the Great Plains in Alberta. Living trees were found to be as old as 526 yr. Tree-ring growth in Pinus flexilis is most sensitive to annual precipitation over the annualization period August to July. The longevity of the trees coupled with their sensitivity to variations in annual precipitation make them an important resource for constructing annually resolved multicentury records of paleohydrology on the northwestern Great Plains. A 487-yr reconstruction of annual precipitation in southwestern Alberta was produced from the tree-ring series. This is the longest dendroclimatological reconstruction of precipitation available from the northern plains. The reconstruction has some similarity to reconstructions from the western Great Plains of the United States. However, there are also many divergences in the timing of droughts. Some of this divergence may reflect the importance of orographic uplift in producing precipitation along the eastern flanks of the Rocky Mountains. Our reconstruction shows that the frequency of droughts in Alberta during the period of instrumental records, about the last 100 yr, has not been appreciably different from conditions of the preceding four centuries. In addition, the most severe drought of this century, which led to widespread farm abandonment between 1918 and 1922, was not the most severe drought in the past 487 yr.
Enhanced Age Resolution of the Marine Quaternary Record in the Arctic Using Aspartic Acid Racemization Dating of Bivalve Shells
Authors: Goodfriend Glenn A. , Brigham-Grette Julie , Miller Gifford H. 
Published: September 2002

AbstractAspartic acid (Asp) racemization occurs at a significantly higher rate than isoleucine epimerization and consequently provides better temporal resolution of Arctic marine deposits (from Alaska, Spitsbergen, and Baffin Island). Heating experiments (at 100°C) on the bivalves Mya and Hiatella show the Asp racemization rate decreases with increasing D/L values, as is typical for biogenic carbonates. Based on these experimental racemization rates and rates determined from racemization of samples radiocarbon dated to ca. 10,000–12,000 yr B.P., activation energies for Mya and Hiatella are estimated to be 30.6 and 30.0 kcal/mol, respectively, for Asp racemization, and 29.0 and 29.5 for isoleucine epimerization. Analysis of a time series of Plio–Pleistocene Hiatella from the north coast of Alaska shows that last-interglacial mollusks can be readily distinguished from modern samples by Asp but not by isoleucine. D/L Asp values indicate a younger age for the Fishcreekian transgression than does isoleucine epimerization. For Spitsbergen, D/L Asp shows a slight age difference (ca. 12,000 yr) between two units of the “episode B” interstadial and suggests that the age of these units may be closer to 65,000 than to 80,000 yr B.P., two possible ages suggested by other evidence. The age of the Loks Land Interstadial on Baffin Island is likely to be greater than that indicated by radiocarbon ages. Within deposits from each region, D/L Asp values are less variable among individual shells than isoleucine epimerization values. This may indicate better reliability of Asp for geochronology.
Amino Acids and Stable Carbon Isotope Distributions in Taihu Lake, China, Over the Last 15,000 Years, and Their Paleoecological Implications
Authors: Jinquan Wang , Jinling Liu 
Published: September 2002

AbstractAmino acid, organic nitrogen, and stable carbon isotope (13C/12C) profiles through a core from East Taihu Lake are interpreted in terms of paleoecology and paleoclimate over the last ca. 15,000 yr. Lower amino acid contents and higher δ13C values at the base of the core represent a cool and arid climate, and coincide with low organic productivity. A marked increase in total amino acids and organic nitrogen, with a decrease in δ13C values from 193 to 90 cm (ca. 6500–6000 yr B.P.), indicates a warmer and moist climate, and greater organic productivity. Amino acids then decrease in abundance, while δ13C values increase progressively, beginning at 73 cm (ca. 6000 yr B.P.), reflecting cooling and lower organic productivity. The average δ13C values from a core from West Taihu Lake are evidently higher than values from East Taihu Lake. The latter may reflect a stream environment, whereas the high δ13C values from West Taihu Lake likely reflect autotrophic carbon sources and a lacustrine environment since 11,000 yr B.P.
A Late Holocene Paleoecological Record from Torrey Pines State Reserve, California
Authors: Cole Kenneth L. , Wahl Eugene 
Published: September 2002

AbstractPaleoenvironments of the Torrey Pines State Reserve were reconstructed from a 3600-yr core from Los Peñasquitos Lagoon using fossil pollen, spores, charcoal, chemical stratigraphy, particle size, and magnetic susceptibility. Late Holocene sediments were radiocarbon dated, while the historical sediments were dated using sediment chemistry, fossil pollen, and historical records. At 3600 yr B.P., the estuary was a brackish-water lagoon. By 2800 yr B.P., Poaceae (grass) pollen increased to high levels, suggesting that the rising level of the core site led to its colonization bySpartina foliosa(cord-grass), the lowest-elevation plant type within regional estuaries. An increase in pollen and spores of moisture-dependent species suggests a climate with more available moisture after 2600 yr B.P. This change is similar to that found 280 km to the north at 3250 yr B.P., implying that regional climate changes were time-transgressive from north to south. Increased postsettlement sediment input resulted from nineteenth-century land disturbances caused by grazing and fire. Sedimentation rates increased further in the twentieth century due to closure of the estuarine mouth. The endemicPinus torreyana(Torrey pine) was present at the site throughout this 3600-yr interval but was less numerous prior to 2100 yr B.P. This history may have contributed to the low genetic diversity of this species.
Luminescence Dating of Sediments from the Luthern Valley, Central Switzerland, and Implications for the Chronology of the Last Glacial Cycle
Authors: Preusser Frank , Müller Benjamin U. , Schlüchter Christian 
Published: September 2002

AbstractThe advancing glaciers of the last glacial maximum either eroded or deeply buried older sediments in the Swiss Alpine Foreland. However, part of the Swiss Plateau was not covered by ice and is therefore an excellent area for investigating climate and environmental change during the Upper Pleistocene. Repeated fluvial sequences can be studied in several pits along the Luthern Valley. The chronological framework is based on lithostratigraphy, pollen analysis, U/Th dating, and recently, heavy mineral analysis and luminescence dating. The oldest unit, the Untere Zeller Schotter braided river deposit, represents cold climate conditions and presumably a glaciation prior to the Eemian Interglaciation. The last interglacial period and the very beginning of the last glacial cycle is represented by the Mittlere Zeller Schotter, sediments of a meandering fluvial system. Younger braided river sediments, the Obere Zeller Schotter, seem to correlate with the cold climate of oxygen isotope stage (OIS) 4. Weathering of the top of the Obere Zeller Schotter is likely to represent the OIS 3. The advancing Reuss glacier caused erosion of the recent Luthern Valley, cutting into older sediments, with local loess accumulation during the last glacial maximum as indicated by cover sediments on top of the fluvial sequence.
Late Quaternary Stratigraphy, Glacial Limits, and Paleoenvironments of the Marresale Area, Western Yamal Peninsula, Russia
Authors: Forman Steven L. , Ingólfsson Ólafur , Gataullin Valery , Manley William , Lokrantz Hanna 
Published: September 2002

AbstractStratigraphic records from coastal cliff sections near the Marresale Station on the Yamal Peninsula, Russia, yield new insight on ice-sheet dynamics and paleoenvironments for northern Eurasia. Field studies identify nine informal stratigraphic units from oldest to youngest (the Marresale formation, Labsuyakha sand, Kara diamicton, Varjakha peat and silt, Oleny sand, Baidarata sand, Betula horizon, Nenets peat, and Chum sand) that show a single glaciation and a varied terrestrial environment during the late Pleistocene. The Kara diamicton reflects regional glaciation and is associated with glaciotectonic deformation from the southwest of the underlying Labsuyakha sand and Marresale formation. Finite radiocarbon and luminescence ages of ca. 35,000 to 45,000 yr from Varjakha peat and silt that immediately overlies Kara diamicton place the glaciation >40,000 yr ago. Eolian and fluvial deposition ensued with concomitant cryogenesis between ca. 35,000 and 12,000 cal yr B.P. associated with the Oleny and the Baidarata sands. There is no geomorphic or stratigraphic evidence of coverage or proximity of the Yamal Peninsula to a Late Weichselian ice sheet. The Nenets peat accumulated over the Baidarata sand during much of the past 10,000 yr, with local additions of the eolian Chum sand starting ca. 1000 yr ago. A prominent Betula horizon at the base of the Nenets peat contains rooted birch trees ca. 10,000 to 9000 cal yr old and indicates a >200-km shift northward of the treeline from the present limits, corresponding to a 2° to 4°C summer warming across northern Eurasia.
Geomorphic Expression of Abrupt Climate Change in Southwestern North America at the Glacial Termination
Authors: Anderson Roger Y. , Allen Bruce D. , Menking Kirsten M. 
Published: September 2002

AbstractEolian and subaqueous landforms composed of gypsum sand provide geomorphic evidence for a wet episode at the termination of glacial climate in southwestern North America. Drying of pluvial Lake Estancia, central New Mexico, occurred after ca. 12,00014C yr B.P. Thereafter, eolian landforms on the old lake floor, constructed of gypsum sand, were overridden by rising lake water, modified by subaqueous processes, and organized into beach ridges along the lake's eastern shore. Preservation of preexisting eolian landforms in the shallow lake suggests abupt changes in lake level and climate. Available radiocarbon ages suggest that the final highstand recorded by beach ridges may have developed during the Younger Dryas (YD) stade. The beach ridges provide information about lake surface area, which was 45% of the lake area reached during the maximum highstands of the late Pleistocene. A similar proportional response has been reported for YD climate changes outside the North Atlantic region.
Tree-Ring-Based Spring Temperature Patterns over the Past Four Centuries in Western Himalaya
Authors: Yadav Ram R. , Singh Jayendra 
Published: September 2002

AbstractA network of 12 tree-ring width chronologies of Himalayan cedar (Cedrus deodara) from the western Himalayan region, India, has been used to reconstruct mean spring (March–May) temperature variations back to A.D. 1600. The most conspicuous feature of the temperature reconstruction is the long-term cooling trend since the late 17th century that ended early in the 20th century. The warmest 30-yr mean for the 20th century was recorded during 1945–1974. However, this warming, in the context of the past four centuries is well within the range of natural variability, since warmer springs of greater magnitude occurred in the later part of the 17th century (1662–1691).
Consequences of reduced production of NO on vascular reactivity of porcine coronary arteries after angioplasty: importance of EDHF
Authors: Thollon Catherine , Fournet‐Bourguignon Marie Pierre , Saboureau Delphine , Lesage Ludovic , Reure Hélène , Vanhoutte Paul M , Vilaine Jean Paul 
Published: September 2002

The consequences of the reduced production of nitric oxide (NO) by cells from regenerated endothelium were investigated by measuring membrane potential of smooth muscle cells (SMCs), isometric tension and cyclic nucleotides content in porcine coronary arteries with intimal thickening, four weeks following angioplasty.
Under basal conditions, SMCs of coronary arteries with regenerated endothelium were depolarized by 10 mV. This depolarization was associated with 82% decreased level of cGMP without alteration in cAMP.
Sodium nitroprusside (SNP, 1 μM) repolarized SMCs of the previously denuded coronary arteries. This repolarization was abolished by 1H‐[1,2,4]‐oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ, 10 μM) and not suppressed by glibenclamide (10 μM), iberiotoxin (IbTX, 100 nM) and the combination of charybdotoxin (ChTX, 40 nM) plus apamin (100 nM).
Four‐aminopyridine (4‐AP, 1‐5 mM) generated spontaneous rhythmic activities only in coronary arteries with regenerated endothelium which were abolished by SNP. Nevertheless, 4‐AP did not suppress the repolarization induced by SNP.
In vascular segments with regenerated endothelium, contracted with prostaglandin F2α (PGF2α), relaxation to bradykinin (BK, 30 nM) was unaltered despite a reduced production of cGMP (−70%). Indomethacin (10 μM) plus Nω‐nitro‐L‐arginine (L‐NA, 30 μM) reduced relaxation (−12% and −35% for native and regenerated endothelium, respectively) but did not abolish it.
The hyperpolarizations induced by BK were not altered by the presence of indomethacin and L‐NA and were unchanged in segments with regenerated endothelium.
These data are consistent with a contribution of impairment in NO production to the depolarization of SMCs. Nevertheless, EDHF responses to BK are sufficient to maintain a normal relaxation after angioplasty.

British Journal of Pharmacology (2002) 136, 1153–1161. doi:10.1038/sj.bjp.0704828
An N‐terminal histidine regulates Zn2+ inhibition on the murine GABAA receptor β3 subunit
Authors: Dunne Emma L , Hosie Alastair M , Wooltorton Julian R A , Duguid Ian C , Harvey Kirsten , Moss Stephen J , Harvey Robert J , Smart Trevor G 
Published: September 2002

Whole‐cell currents were recorded from Xenopus laevis oocytes and human embryonic kidney cells expressing GABAA receptor β3 subunit homomers to search for additional residues affecting Zn2+ inhibition. These residues would complement the previously identified histidine (H267), present just within the external portal of the ion channel, which modulates Zn2+ inhibition.
Zinc inhibited the pentobarbitone‐gated current on β3H267A homomers at pH 7.4, but this effect was abolished at pH 5.4. The Zn2+‐sensitive spontaneous β3 subunit‐mediated conductance was also insensitive to block by Zn2+ at pH 5.4.
Changing external pH enabled the titration of the Zn2+ sensitive binding site or signal transduction domain. The pKa was estimated at 6.8±0.03 implying the involvement of histidine residues.
External histidine residues in the β3 receptor subunit were substituted with alanine, in addition to the background mutation, H267A, to assess their sensitivity to Zn2+ inhibition. The Zn2+ IC50 was unaffected by either the H119A or H191A mutations.
The remaining histidine, H107, the only other candidate likely to participate in Zn2+ inhibition, was substituted with various residues. Most mutants were expressed at the cell surface but they disrupted functional expression of β3 homomers. However, H107G was functional and demonstrated a marked reduction in sensitivity to Zn2+.
GABAA receptor β3 subunits form functional ion channels that can be inhibited by Zn2+. Two histidine residues are largely responsible for this effect, H267 in the pore lining region and H107 residing in the extracellular N‐terminal domain.

British Journal of Pharmacology (2002) 137, 29–38. doi:10.1038/sj.bjp.0704835
Characterization of two novel forms of the rat sulphonylurea receptor SUR1A2 and SUR1BΔ31
Authors: Gros Laurent , Trapp Stefan , Dabrowski Michael , Ashcroft Frances M , Bataille Dominique , Blache Philippe 
Published: September 2002

The ATP‐sensitive potassium channel (KATP) of pancreatic β‐cells is composed of the sulphonylurea‐binding protein, SUR1, and the inwardly rectifying K+ channel subunit, Kir6.2. We have characterized two novel isoforms of rat SUR1 in the RINm5F insulin‐secreting cell line.
SUR1A2 is an allelic variant with a single amino acid change in the first nucleotide‐binding domain. Coinjection of SUR1A2 plus Kir6.2 into Xenopus oocytes or expression of a SUR1A2–Kir6.2 tandem in HEK‐293 cells yielded large currents with characteristics similar to the wild‐type KATP channel.
SUR1BΔ31, detected in several human tissues, is a splice variant of the rat SUR1 gene that lacks exon 31 of the corresponding human SUR1 gene. SUR1BΔ31 lacks the TM16–TM17 transmembrane‐spanning helices leading to a protein with a different transmembrane topology. Coinjection of SUR1BΔ31 plus Kir6.2 into Xenopus oocytes or expression of the Kir6.2/SUR1BΔ31 tandem construct in HEK‐293 cells did not result in any current, and a surface expression assay indicated that this channel does not reach the plasma membrane.
SUR1A2 and SUR1A1 proteins expressed in HEK‐293 cells display similar binding affinities for [3H]‐glibenclamide, while SUR1BΔ31 shows a 500‐fold lower affinity.
These findings confirm that TM16–TM17 of SUR1 are important for high‐affinity glibenclamide binding and that their deletion impairs trafficking of the KATP channel to the surface membrane.

British Journal of Pharmacology (2002) 137, 98–106. doi:10.1038/sj.bjp.0704836
Natural history of asthma from childhood to adulthood
Authors: Kay A. B. , Gelfand E. W. , Smith L. J. , Tashkin D. 
Published: September 2002

SummaryAsthma is a common and complex condition, with considerable heterogeneity both in phenotype and in the underlying pathophysiology. This paper aims to address some of the recent advances in the understanding of asthma, as well as indicating how these advances reveal potential new avenues for therapeutic intervention. Current drug treatments, although effective at alleviating inflammatory symptoms, do little to target the underlying causative factors. The onset of asthma is controlled by a combination of genetic and environmental factors, and a greater understanding of these has highlighted the importance of early‐life infections, allergen avoidance and fetal and postnatal nutrition. An imbalance in the expression of T‐cell phenotypes is thought to play an important role in the pathophysiology of asthma, and further elucidation of the underlying immune mechanisms has identified new ways of modulating the course of the disease. It is clear that there is also a need for new drug strategies that are aimed at the diverse factors that both trigger the disease and determine its course and severity, as well as the immune mechanisms contributing to its pathophysiology. Treatment plans that address this diversity are likely to provide a more effective means of asthma management and, combined with current knowledge of causative factors, might even act to modulate the course and severity of the disease.
Bacterial expression and membrane targeting of the rat complement regulator Crry: A new model anticomplement therapeutic
Authors: Fraser Deborah A. , Harris Claire L. , Smith Richard A.G. , Morgan B. Paul 
Published: September 2002

AbstractInappropriate or unregulated activation of complement can contribute to pathology in inflammatory diseases. Previous studies have shown that soluble recombinant regulators of complement are effective in animal models and some human diseases. However, limitations include cost, rapid clearance, and unwanted systemic effects. To avoid some of these problems, bacterial expression of regulators has been optimized and methods for the addition of a membrane‐targeting moiety to the complement regulator developed. When administered directly to sites of inflammation, membrane‐targeted human regulators are retained and inhibit complement‐activation locally. To test the efficacy of membrane‐targeted complement regulators in vivo, we have undertaken the expression and membrane targeting of the rat‐complement regulator Crry. A soluble recombinant form of Crry, containing only the first four short consensus repeats, was expressed in a mammalian expression system and shown to be functional as a fluid phase regulator. To generate the quantities required for testing in vivo, Crry was expressed in bacteria and refolded successfully. Refolded protein had full‐complement regulatory activity in vitro. Attachment of a membrane address tag conferred membrane‐binding capacity and greatly increased complement regulatory function in vitro. This novel anticomplement agent can now be applied to rat models of arthritis and other inflammatory diseases.
Molecular dynamics simulations of alanine rich β‐sheet oligomers: Insight into amyloid formation
Authors: Ma Buyong , Nussinov Ruth 
Published: September 2002

AbstractThe aggregation observed in protein conformational diseases is the outcome of significant new β‐sheet structure not present in the native state. Peptide model systems have been useful in studies of fibril aggregate formation. Experimentally, it was found that a short peptide AGAAAAGA is one of the most highly amyloidogenic peptides. This peptide corresponds to the Syrian hamster prion protein (ShPrP) residues 113–120. The peptide was observed to be conserved in all species for which the PrP sequence has been determined. We have simulated the stabilities of oligomeric AGAAAAGA and AAAAAAAA (A8) by molecular dynamic simulations. Oligomers of both AGAAAAGA and AAAAAAAA were found to be stable when the size is 6 to 8 (hexamer to octamer). Subsequent simulation of an additional α‐helical AAAAAAAA placed on the A8‐octamer surface has revealed molecular events related to conformational change and oligomer growth. Our study addresses both the minimal oligomeric size of an aggregate seed and the mechanism of seed growth. Our simulations of the prion‐derived 8‐residue amyloidogenic peptide and its variant have indicated that an octamer is stable enough to be a seed and that the driving force for stabilization is the hydrophobic effect.