bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOSPHOLIPIDS AND NUCLEAR RNA
Authors: ALBI E. , MICHELI M. , MAGNI VIOLA M. P.
Published: October 2002

It has been demonstrated that in hepatocyte nuclei the chromatin phospholipid fraction is localized near the RNA in decondensed chromatin. The aim of the present study was to see if there is any linkage between phospholipids and other nuclear components. Isolated hepatocyte nuclei and nuclear membranes were treated with deoxyribonuclease and ribonuclease. No loss of phospholipids was observed after DNA digestion, whereas 48% was lost following enzymatic RNA removal. This loss of phospholipids, localized either near the membrane or inside the nucleus, was not homogeneous for all phospholipids: phosphatidylserine and sphingomyelin being the most affected. It can be concluded that 48% of nuclear phospholipids, in particular sphingomyelin, is lost with RNA removal. This result is discussed in view of a possible role of phospholipids in DNA synthesis and RNA transcription.
INHIBITION OF CELLULAR GROWTH AND STEROID 11β‐HYDROXYLATION INRAS‐TRANSFORMED ADRENOCORTICAL CELLS BY THE FUNGAL TOXINS BETICOLINS
Authors: DING GUOQING , MAUME GABRIELLE , MILAT MARIE‐LOUISE , HUMBERT CLAUDE , BLEIN JEAN‐PIERRE , MAUME BERNARD F.
Published: October 2002

The proliferation of GM16 and 4CDTras‐transformed newborn rat adrenocortical (RTAC) cells and Y1 mouse adrenal tumor cells was inhibited by beticolins, the fungal toxins extracted fromCercospora beticola, at submicromolar concentrations in a dose‐dependent manner. Inhibitory concentrations for half the maximum inhibition were 150, 75 and 25 nmfor beticolin‐1 and 230, 150 and 50 nmfor beticolin‐2 in GM16, 4CDT and Y1 cells respectively. Beticolins strongly inhibited the production of 11β‐hydroxysteroids on the second and third days of treatment in a dose‐dependent manner between 0.1 and 1 μm. Beticolins were shown by confocal microscopy to be localized in cytoplasmic organelles about 30–40 min after treatment. This finding favors a direct action of beticolins on mitochondrial steroid 11β‐hydroxylase albeit another less direct mechanism involving a cytoplasmic signaling pathway cannot be excluded.
RETINOIC ACID: IDENTIFICATION OF SPECIFIC RECEPTORS THROUGH WHICH IT MAY MEDIATE TRANSCRIPTIONAL REGULATION OF FIBRONECTIN GENE IN BOVINE LENS EPITHELIAL CELLS
Authors: SHANKER GOURI , SAWHNEY RAJINDER
Published: October 2002

To elucidate in detail the regulatory mechanisms by which the fibronectin mRNA and protein are altered by all‐trans retinoic acid (RA) in bovine lens epithelial (LE) cells, we have investigated the transcription mechanism and the occurrence of nuclear receptors for RA in the nuclei of cultured LE cells. The rate of transcription of fibronectin (FN) mRNA increased by 130% in response to RA. The RA receptors in nuclear extracts prepared from LE cells show specific all‐trans [3H]‐RA binding sites. Saturation binding of all‐trans RA to these receptors and the Scatchard plot analyses of the binding data yielded an apparent dissociation constant (K d) of about 12nm and B maxof about 48pmoles/mg protein. Bovine retinoic acid receptors (RARs) have not been reported previously. Our results demonstrate for the first time that RA regulates FN expression and that regulation is at the transcriptional level in LE cells. Thus, retinoids may have an important role in the functional adhesion of epithelium to the lens capsule.
IMMUNOCHEMICAL IDENTIFICATION OF THE 1,25‐DIHYDROXYVITAMIN D3RECEPTOR PROTEIN IN HUMAN HEART
Authors: O'CONNELL TIMOTHY D. , SIMPSON ROBERT U.
Published: October 2002

A number of recent clinical observations suggest that vitamin D3plays an important role in maintaining normal cardiovascular function, either directly through its receptor in cardiac muscle, or indirectly through its infuence on circulating levels of calcium or on other regulatory factors. By using an antibody directed against the recombinant vitamin D3receptor, we have identified the receptor protein for 1,25(OH)2D3in tissue from two human hearts. The identification of the 1,25(OH)2D3receptor in human heart lends credence to the hypothesis that 1,25(OH)2D3directly effects the human heart and may be involved in several clinically relevant pathological conditions involving the vitamin D3endocrine system.
PRESENCE OF MULTIPLE CENTRIOLES AND PRIMARY CILIA DURING GROWTH AND EARLY DIFFERENTIATION IN THE MYOBLAST CO25 CELL LINE
Authors: ZEYTINOGLU MELIH , RITTER JEANETTE , WHEATLEY DENYS N. , WARN RICHARD M.
Published: October 2002

CO25 cells, a mouse myoblast line, contain multiple centrioles and primary cilia. A most unusual feature has been the finding of large numbers of separate structures in single cells—up to a maximum of nine centrioles, six primary cilia, and 12 of both organelles together. Aberrant multipolar spindles were occasionally seen containing variable numbers of centrioles. This strongly suggests that cells containing supernumerary centrioles and cilia are lost during mitosis, and that additional centriolar structures are generated during each interphase. No change in centriole or primary cilium frequency was detected after inducing the differentiation of myoblasts into myotubes. However, a significant migration of these structures occurred from a perinuclear to a supranuclear position prior to and during the phase of myoblast elongation. This shift was not maintained during cell fusion, when a net migration back to the periphery was observed, suggesting that it may have some function in relation to cell elongation and the change in the pattern of microtubule distribution which occurs as part of the process.
THE EFFECT OF HUMAN ENDOTHELIAL CELL‐DERIVED PROTEOGLYCANS ON HUMAN SMOOTH MUSCLE CELL GROWTH
Authors: WHITELOCK JOHN , MITCHELL SUE , UNDERWOOD P. ANNE
Published: October 2002

Extracellular proteoglycans (PGs) purified from cultured human arterial endothelial cells were tested for their effects on the proliferation of human vascular smooth muscle cells (VSMC). Fractions containing perlecan, the basement membrane heparan sulphate (HS) PG, the large chondrotin sulphate (CS) proteoglycan from connective tissue and other immunoreactive CS did not inhibit the proliferation of human VSMC. Native endothelial extracellular matrix, which was shown to contain the same PGs, demonstrated a pronounced stimulatory effect on the proliferation of human VSMCs. This stimulatory effect was not removed by pre‐incubation of the matrix with 1M NaCl, heparin, platelet extract or plasmin. These experiments demonstrate that PGs produced by human arterial endothelial cells do not inhibit the proliferation of VSMC. These data do not support the hypothesis that human endothelial cells, in vivo control the activation or proliferation of VSMCs directly by the secretion of a non‐proliferative molecule. Instead they support the hypothesis that the endothelial cells counteract intimal hyperplasia of VSMC indirectly by providing a barrier from activating factors in the plasma.
HUMAN B CELL DIFFERENTIATION: DEPENDENCE ON INTERACTIONS WITH MONOCYTES AND T LYMPHOCYTES VIA CD40, CD80 (B7.1), AND THE CD2‐LIGANDS CD48 AND CD58 (LFA‐3)
Authors: HOFFMANN JÖRG C , KRÜGER HARTMUT , ZIELEN STEFAN , BAYER BETTINA , ZEIDLER HENNING
Published: October 2002

B cell differentiation depends on cellular interactions with T lymphocytes and monocytes via adhesion molecules (AM). In order to characterize AM which are required for B cell differentiation immunoglobulin production using unseparated peripheral blood mononuclear cells (PBMC) was studied. Unstimulated human PBMC were cultured for 9 days with mAb directed at CD2/CD48, /CD58, CD59, CD5/CD72, CD11a—CD18/CD54, CD28/CD80, CD86, CD40/CD40L, or rat CD2 (control). B cell differentiation was quantified measuring IgM and in some cases IgA, IgG, and IgE production. IgM levels were significantly reduced by mAb against CD40, CD48, CD58 and CD80. The reduction was not due to isotype switching to IgA, IgG or IgE. The role of CD40, CD48, CD58 and CD80 was further investigated after depletion of different cell types. Depletion of monocytes and NK cells resulted in no detectable IgM production irrespective of added mAbs. In contrast, IgM production was still present after depletion of T cells and NK cells. Only mAb against CD80 and CD48 significantly reduced IgM production, the reduction of IgM production by anti‐CD40 mAb was less than in the presence of T cells. Importantly, anti‐CD58 mAb had no effect on IgM production after T cell and NK cell depletion. Taken together, the AM CD40, CD48, CD58, and CD80 are involved in Ig production of unseparated PBMCs. In this model of B cell differentiation only the AM CD58 depend on the presence of T cells while CD48 and CD80 help was found to be T cell independent.
FLOW CYTOMETRIC SCORING OF APOPTOSIS COMPARED TO ELECTRON MICROSCOPY IN γ IRRADIATED LYMPHOCYTES
Authors: LOUAGIE H. , CORNELISSEN M. , PHILIPPE J. , VRAL A. , THIERENS H. , DE RIDDER L.
Published: October 2002

One of the early events occurring at the cell membrane during apoptosis is the translocation of phosphatidylserine from the inner side of the plasma membrane to the outer layer. These phosphatidylserine groups can be bound by fluorescein isothiocyanate (FITC)‐labelled annexin V. The aim of this study was to evaluate the power of the annexin V flow cytometric assay in detecting apoptosis in γ irradiated peripheral blood lymphocytes and in differentiating between apoptosis and primary necrosis in these cells. Therefore, 5Gy and 20Gy γ irradiated peripheral blood mononuclear cells (PBMCs) were examined after a 24‐h culture period. The terminal deoxynucleotidyl transferase‐mediated dUTP—biotin nick end labeling (TUNEL) technique was performed as well. A comparison with an electron microscopic (EM) evaluation was made. EM is based on established morphological criteria allowing the classification of cells into four groups: viable, early apoptotic, secondary necrotic and primary necrotic cells. EM performed on annexin V positive sorted cells proved that a 5Gy γ irradiation of PBMCs mainly causes apoptosis, whereas a 20Gy γ irradiation mainly induces primary necrosis. Neither the annexin V flow cytometric assay nor the TUNEL assay were able to distinguish between primary and secondary necrotic cells. These results illustrate that if quantification of apoptosis is required, one should be careful in interpreting flow cytometric results obtained by annexin V or TUNEL staining in peripheral blood lymphocytes. Although in general primary necrotic cells show an increased forward scatter due to cellullar swelling, both early apoptotic and necrotic (primary or secondary) lymphocytes show a decreased forward scatter signal. Moreover, both primary and secondary necrotic lymphocytes are annexin V and propidium iodide (PI) positive and therefore indistinguishable. We conclude that if a new experiment focusing on apoptosis is set up, an initial EM evaluation is mandatory. If EM shows that the apoptosis inducing agent used in the design of the experiments is not causing primary necrosis, than the annexin V flow cytometric assay can provide rapid and quantitative information about apoptosis.
THE LEVEL AND PHOSPHORYLATION OF HSP70 IN THE RAT LIVER CYTOSOL AFTER ADRENALECTOMY AND HYPERTHERMIA
Authors: Čvoro Aleksandra , Dundjerski Jadranka , Trajković Divna , Matić Gordana
Published: October 2002

Hepatic heat shock protein Hsp70 synthesis and in vitro phosphorylation were studied in the liver cytosol of intact, adrenalectomized and dexamethasone‐administered adrenalectomized rats after 41°C whole body hyperthermic stress. Hsp70 was detected by immunoblotting with N27F3‐4 monoclonal antibody recognizing both constitutive and inducible forms of the protein. A comparison between basal and heat stress‐induced levels of the protein in the liver cytosol of the three groups of animals suggested that glucocorticoid hormones stimulate the basal synthesis of Hsp70 and inhibit its induction by stress. In both unstressed and hyperthermia‐exposed animals, hepatic Hsp70 was detected as a phosphoprotein. The extent of itsin vitro phosphorylation was found to be significantly reduced by heat stress or adrenalectomy, but dexamethasone failed to restore it to the original level.
G2RESTRICTION POINT WITHIN POPULATIONS OF HEPATOCYTES AND TONGUE KERATINOCYTES IN YOUNG, GROWING MICE
Authors: ERRECALDE ANA L. , GARCÍA ADRIANA L. , INDA ANA M. , BADRÁN AMADO F.
Published: October 2002

The authors studied the effect of either extracts from liver (LE) or the malignant tumour ES2 (TE) or plasma from intact mice (PI) or tumour‐bearing animals (PT) on the mitotic activity of the hepatocytes and tongue keratinocytes in young, growing C3H/s male mice (28±1 days old). Animals standardized for periodicity analysis were injected intraperitoneally with either TE, LE, PI, PT, or saline (S) at 16:00h with 0.01ml of sample/g of body weight and were then killed at (time of day/h post‐injection) 20:00/04, 00:00/08, and 04:00/12. Colchicine (2μg/g) was injected 4h before death. Samples of the liver and tongue from each animal were processed for histology and assessment of mitotic index. The results were expressed as colchicine‐arrested metaphases/1000 nuclei. The TE and LE stimulated the mitotic activity of hepatocytes and tongue keratinocytes. Taking into account the time elapsed between the injections and the measurements made in these light‐dark synchronized animals, we conclude that the increase in mitotic index observed in those tissues stemmed from a reinitiation of cell‐cycle traverse in a subpopulation of G2‐arrested, noncycling cells.
INTRACISTERNAL A‐PARTICLE (IAP)‐MEDIATED LEUKEMOGENESIS: LEVELS AND STABILITY OF IAP mRNA IN FDC‐P1 CELLS EXPOSED TO THE CONDITIONS OF AN IRRADIATED ENVIRONMENT
Authors: BLUMENSTEIN MARION , TESSMER UWE , HOSSFELD DIETER KURT , DÜHRSEN ULRICH
Published: October 2002

Following injection into sublethally irradiated DBA/2 or BALB/c mice, factor‐dependent FDC‐P1 cells undergo leukemic transformation due to oncogene activation by insertion of intracisternal A‐particle (IAP) genetic elements. Similar events are observed in vitro during coculture of FDC‐P1 cells with irradiated bone marrow stroma cells. To elucidate the mechanism of IAP transposition, we studied the level of IAP expression under the growth conditions preceding cell transformation. In vitro experiments showed that the type of growth factor, FDC‐P1 cell density, costimulation with steroid hormones or abrupt growth factor withdrawal had no effect on IAP mRNA levels (major transcripts of 7.4, 4.0 and 1.9kb). By contrast, stimulation with suboptimal concentrations of GM‐CSF or IL‐3 induced a mean 2.5‐fold increase in the intensity of the 7.4kb band, and induction of macrophage differentiation with retinoic acid resulted in an increased stability of the 4.0kb band. Although suboptimal growth stimulation and incipient macrophage differentiation have previously been shown to occur in the process of FDC‐P1 cell transformation, an increase in IAP expression could not convincingly be demonstrated in FDC‐P1 cell populations isolated from irradiated BALB/c mice or stroma cell cocultures. Further experiments are required to define the role of suboptimal growth stimulation and/or macrophage differentiation in this transformation model.
BINDING CONTRIBUTION BETWEEN SYNAPTIC VESICLE MEMBRANE AND PLASMA MEMBRANE PROTEINS IN NEURONS: AN AFM STUDY
Authors: Sritharan Kumudesh C. , Quinn Anthony S. , Taatjes Douglas J. , Jena Bhanu P.
Published: October 2002

The final step in the exocytotic process is the docking and fusion of membrane‐bound secretory vesicles at the cell plasma membrane. This docking and fusion is brought about by several participating vesicle membrane, plasma membrane and soluble cytosolic proteins. A clear understanding of the interactions between these participating proteins giving rise to vesicle docking and fusion is essential. In this study, the binding force profiles between synaptic vesicle membrane and plasma membrane proteins have been examined for the first time using the atomic force microscope. Binding force contributions of a synaptic vesicle membrane protein VAMP1, and the plasma membrane proteins SNAP‐25 and syntaxin, are also implicated from these studies. Our study suggests that these three proteins are the major, if not the only contributors to the interactive binding force that exist between the two membranes.
THE NATIVE MEMBRANE FUSION MACHINERY IN CELLS
Authors: Jeong Eun‐Hwan , Webster Paul , Khuong Chau Q. , Sattar Abdus A. K. M. , Satchi Mylan , Jena Bhanu P.
Published: October 2002

Recombinant SNAREs have been demonstrated as the minimal membrane fusion machinery. The participation of additional proteins in the regulation of membrane fusion has been suggested. In this study we provide nanometer‐resolution images of native NSF oligomers and SNARE complexes isolated from neurons and the pancreas. Our study reveals the presence of new coiled rod‐like structures in association with the SNARE complex only in neuronal tissue. Neuronal SNAREs were found coiled and super‐coiled with these structures. The existence of NSF as pentamers in its native state is also demonstrated. The extent of coiling and super‐coiling of SNAREs may regulate the potency and efficacy of membrane fusion in cells.
CONSERVED CELLULAR AND MOLECULAR MECHANISMS IN DEVELOPMENT
Authors: Giudice Giovanni
Published: October 2002

This review discusses examples of conserved cellular and molecular mechansims in development, including the pathway of signal transduction between the photoreceptors R8 and R7 in Drosophila, which is compared to vulval induction in Caenorhabditis elegans. The Wg pathway in Drosophila is compared, first, to theWnt pathway in dorsal mesoderm specification in Xenopus; second, to the same pathway in sea urchins; third, to the equivalent in the mom cascade of C. elegans; and finally, to parts of the equivalent pathway inDictyostelium discoideum. The conserved expression of some hox genes in vertebrate limb buds and in the heads or tails of several invertebrate and vertebrate embryos is also illustrated. Two further examples show the contrast between BMP4 and the proteins Noggin, Chordin, Follistatin and Gremlin. Another example concerns the binding of proteins to the 3′UTRs of several messages which inhibits their translation in Drosophila and C. elegans. The final example illustrates the selective transfer of transcription factors to nuclei in Drosophila and C. elegans.
MINIPODIA AND ROSETTE CONTACTS ARE ADHESIVE ORGANELLES PRESENT IN FREE‐LIVING AMOEBAE
Authors: Grbecki Andrzej , Grbecka Lucyna , Wasik Anna
Published: October 2002

Using scanning electron microscopy, Amoeba proteus cells migrating on the glass have been shown to develop dense coats of minipodia, which are discrete microprotrusions up to 8μm long and ∼0.5μm across. They cover the middle‐anterior area of the ventral cell surface, i.e. the region previously determined as the zone of most efficient adhesion of an amoeba to its substratum. Minipodia are sparse underneath the frontal zone and lacking from the tail region. In amoebae that adhere to the glass without moving, have just started moving, or show unstable motor polarity, minipodia are grouped in rosette contacts, cauliflower‐like papillae composed of supporting platforms with crowns of minipodia emerging from them. Both structures abound with cytoskeletal F‐actin, as shown by staining with fluorescein‐conjugated phalloidin. Amoebae experimentally prevented from adhering to the substratum neither develop discrete minipodia nor rosette contacts.
CD14‐DEPENDENT ACTIVATION OF NF‐κB BY FILARIAL PARASITIC SHEATH PROTEINS
Authors: Narayanan Kishore , Seufzer Bradly J. , Brockman‐Schneider Rebecca A. , Gern James E. , Balakrishnan Arun , Miyamoto Shigeki
Published: October 2002

Tropical pulmonary eosinophilia is in part caused by the hyperimmune responsiveness of the lung tissue against the antigens of degenerating microfilariae. We have previously shown that the activation of the transcription factor NF‐κB is essential for the synthesis and release of multiple pro‐inflammatory cytokines in HEp‐2 human airway epithelial cells following exposure to filarial parasitic sheath proteins (FPS). Neither the antigenic component nor the receptor involved in this activation is known. Herein we provide evidence that FPS activation of NF‐κB can be augmented by the cell surface expression of CD14. CD14 expression, however, is not sufficient to transduce FPS signals for NF‐κB activation, since its expression in different cell types does not always furnish the capacity to respond to FPS. We also show that NF‐κB activation by FPS treatment can be distinguished from that induced by bacterial lipolysaccharide, an agent that can also activate NF‐κB in a CD14‐dependent fashion. These observations suggest that the capacity of certain lung epithelial cells to interact with microfilarial antigens, activate NF‐κB in a CD14‐dependent manner and produce pro‐inflammatory cytokines may be a contributory factor to immune responses manifested by tropical pulmonary eosinophilia.
ANTIGENIC AND ULTRASTRUCTURAL MARKERS ASSOCIATED WITH UROTHELIAL CYTODIFFERENTIATION IN PRIMARY EXPLANT OUTGROWTHS OF MOUSE BLADDER
Authors: Kreft Mateja Erdani , Romih Rok , Sterle Maksimiljan
Published: October 2002

The purpose of this study was to establish an in vitro culture model that closely resembles whole mouse urothelial tissue. Primary explant cultures of mouse bladder were established on porous membrane supports and explant outgrowths were analysed for morphology and the presence of antigenic and ultrastructural markers associated with urothelial cytodifferentiation. When examined at the ultrastructural level, the cultured urothelium was polarized and organized as a multilayered epithelium. Differentiation was found to increase from the porous membrane towards the surface and from the explant towards the periphery of the culture. Scanning and transmission electron microscopical analysis of the most superficially‐located cells revealed four successive differentiation stages: cells with microvilli, cells with ropy microridges, cells with rounded microridges, and highly‐differentiated cells with asymmetric unit membrane (AUM) plaques forming rigid microridges and fusiform vesicles. The more highly‐differentiated cells were numerous at the periphery of the culture, but rare close to the explant. Epithelial organization was stabilized by well developed cell junctions. Immunolabeling demonstrated that superficial urothelial cells in culture: (1) develop tight junctions, E‐cadherin adherens junctions and abundant desmosomes and (2) express uroplakins and cytokeratin 20 (CK 20). Using a culture model of primary explant outgrowth we have shown that non‐differentiated mouse urothelial cells growing on a porous membrane show a high level of de novo differentiation.
MODIFICATION OF GLYCOSYLATION REDUCES MICROVILLI ON RAT LIVER EPITHELIAL CELLS
Authors: Zhao F. T. , Li J. , Shi G. X. , Liu Y. , Zhu L. P.
Published: October 2002

Effect of glycosylation modification on the shape of microvillus was investigated on rat liver epithelial cell line WB‐F344. Since rat ER α‐mannosidase has 89% identity to human 6A8 α‐mannosidase, we used an antisense 6A8 cDNA fragment to inhibit expression in WB‐F344 cells. Cells were transfected with antisense 6A8, the relevant sense fragment or the mock plasmid. Genomic PCR for neoR demonstrated integration of the transfected gene into host DNA. Enzymatic activity assay on p ‐nitro‐phenyl‐α‐D‐mannopyranoside showed suppression of ER α‐mannosidase expression in the cells transfected with antisense 6A8. Concanavalin A binding to these cells was enhanced, indicating a modification in glycosylation. Number reduction and blunting of microvillus on these cells was observed. Transduction with the sense fragment or the mock had no effect. Cells with suppressed ER α‐mannosidase expression grew slower in culture. Our results indicate an obvious effect of glycosylation modification on microvilli, which might be related with malfunctioning of cells.
EXAMINATION OF ACTIN POLYMERIZATION AND VISCOSITY INDUCED BY CATIONS AND IONIC STRENGTH WHEN CROSS‐LINKED BY α‐ACTININ
Authors: Goldmann Wolfgang H.
Published: October 2002

Increasing potassium chloride concentration from 0 to 100mM and magnesium chloride from 0 to 2mM show a parallel rate increase in polymerizing actin, whereas increasing calcium chloride concentration from 0 to 0.2mM decreases the rate of polymerizing actin. The presence of α‐actinin has little influence on the polymerization kinetics of actin under these conditions. Viscometric measurements indicate that the presence of various mono‐ and divalent cations, ionic strength, and α‐actinin in combination are responsible for changes in the mechanical properties of solutions containing actin. The actin filament dynamic behavior is drastically reduced under these conditions as confirmed by quasi‐elastic light scattering.
Implications of Peat Accumulation at Point Escuminac, New Brunswick
Authors: Warner Barry G. , Clymo Richard S. , Tolonen Kimmo
Published: October 2002

The world's peatlands contain about 450 GT of readily decomposeable organic carbon. Peat-forming systems have two main layers, of which the lowest is the thickest and includes the peat proper. The upper layer fixes carbon by photosynthesis, loses it by selective decay, and passes on about 15% to the lower zone; here decay continues, although very slowly. One consequence is that as for Point Escuminac, New Brunswick, the relation of age to depth may be concave. Although the surface of the peatland is as productive as ever, the true rate of carbon accumulation is decreasing; after 10,000 yr it is only 33% as efficient at sequestering carbon as it was when the peatland began to grow. Peatlands are usually thought to represent sinks for carbon, but a warming climate could make some peatlands carbon sources rather than sinks, thus initiating positive feedback.
Relationship of Temperature and Light Ring Formation at Subarctic Treeline and Implications for Climate Reconstruction
Authors: Yamaguchi David K. , Filion Louise , Savage Melissa
Published: October 2002

During the past 8 centuries, light rings (LRs) have occasionally formed in black spruce (Picea mariana) at treeline near Bush Lake, northern Quebec (L. Filion, S. Payette, L. Gauthier, and Y. Boutin, 1986, Quaternary Research 26, 272-279; A. Delwaide, L. Filion, and S. Fayette, 1991, Canadian Journal of Forest Research 21, 1828-1832). New analyses of climate data compiled during the period of overlapping tree-ring and instrumental records show that years of LR formation at Bush Lake have unusually cool May, June, August, and September temperatures. The analyses also show that August-September temperatures strongly correlate with May-July temperatures. Thus, late spring and entire growing-season temperatures influence LR formation at subarctic treeline. LRs formed in at least 5% of the trees at Bush Lake when May-September mean temperatures at Inukjuak fell below 4.2°C and August-September mean temperatures fell below 6.7°C. These threshold temperature/LR relationships can be used to infer limiting summer temperatures during the period preceding instrumental records. For example, the LR record suggests that May-September temperatures at northern Quebec treeline dropped below 4.2°C in A.D. 1601 after a major volcanic eruption of unknown source. Visual assessments of LR occurrence provide a new approach for extracting quantitative paleoclimatic information from tree rings.
New Geochemical Evidence for the Youngest Toba Tuff in India
Authors: Shane Phil , Westgate John , Williams Martin , Korisettar Ravi
Published: October 2002

New geochemical data on tephra samples from a layer present at several archeological sites in India support correlation of this layer to the Youngest Toba Tuff, erupted from northern Sumatra about 74,000 yr ago. The data show that the Indian tephra layer is not a correlative of older tephra erupted from Toba, as has been suggested on the basis of artifact assemblages. Previously published geochemical data on the Indian tephra beds was based on bulk ash samples containing mineral and clay contaminants, and the resulting variability in analyses did not allow identification or discrimination of individual eruptive events. Our new data were collected on individual glass shards and small, purified glass separates which have greater resolving power in fingerprinting. Acheulian and Paleolithic artifacts found at some of the Indian tephra sites do not reflect the antiquity of the tephra bed, as they occur in fluvial sediments and may be reworked.
An Alluvial Surface Chronology Based on Cosmogenic36Cl Dating, Ajo Mountains (Organ Pipe Cactus National Monument), Southern Arizona
Authors: Liu Beiling , Phillips Fred M. , Pohl Molly M. , Sharma Pankaj
Published: October 2002

A chronology of alluvial surfaces on piedmont slopes below the western Ajo Mountains, southern Arizona, has been obtained using cosmogenic36Cl accumulation and AMS radiocarbon dating. The apparent36Cl ages of individual boulders range from 520,000 to 13,000 yr, and the14C ages of organic material in the two young terraces are 2750–2350 and 17,800 cal yr B.P. The sequence of36Cl ages is consistent with the apparent stratigraphic order, but groupings of similar ages for different surfaces appear to result from repeated reworking of older surfaces associated with the deposition of younger ones. The youngest surface gave a distribution of36Cl ages about 30,000 yr older than the14C and soil ages; however, this distribution had36Cl ages that overlapped with36Cl ages from active channels and hillslopes. We attribute the older-than-expected exposure ages of sampled boulders to inheritance of36Cl while residing near the surface during very slow erosion on the mountain front. Our results show that although cosmogenic nuclide accumulation can help establish chronologies for surfaces in piedmont settings, care must be used in evaluating the effects of complex exposure histories.
Fossil Beetle Evidence for a Short Warm Interval near 40,000 yr B.P. at Titusville, Pennsylvania
Authors: Cong Shaoguang , Ashworth Allan C. , Schwert Donald P. , Totten Stanley M.
Published: October 2002

A brief cold–warm–cold climate change during the middle Wisconsinan is described for the first time in North America, based on fossil beetle assemblages at Titusville, Pennsylvania. AMS dating of insect chitin and wood suggests the change occurred between 39,000 and 43,500 yr B.P. Basal peats in river terrace deposits contain arctic–subarctic beetle species representing a climate similar to that found at treeline in Canada, where mean July temperatures range from 10° to 13°C. These cold-adapted beetles were replaced by species representing a climate similar to the mixed coniferous–deciduous forests of southern Canada, where mean July temperatures range from 18° to 20°C. In turn, these warmer-adapted beetles were replaced by arctic–subarctic species in the upper part of the section, representing a climate with mean July temperatures in the range 10°–13°C. The brief warm interval is informally designated the Titusville interstade. The difference in temperature between the colder and warmer intervals is about 5°–7°C. The Titusville interstade is correlated with the Upton Warren Interstade of the British Isles which is of similar age and intensity. It is also correlated with the high sea-surface temperature interval between Heinrich events 4 and 5 represented in North Atlantic sediment cores.
Paleoenvironmental Changes and Glacial Stades of the Last 50,000 Years in the Cordillera Central, Colombia
Authors: Thouret Jean-Claude , Van der Hammen Thomas , Salomons Barry , Juvigné Etienne
Published: October 2002

Using data from glacial geomorphology, tephra-soil stratigraphy and mineralogy, palynology, and radiocarbon dating, a sequence of glacial and bioclimatic stades and interstades has been identified for the past ca. 50,000 yr in the Ruı́z-Tolima massif, Cordillera Central. Six cold stades separated by warmer interstades occurred before 48,000, between 48,000 and 33,000, between 28,000 and 21,000, from ≥16,000 to ca. 14,000, ca. 13,000–12,400, and ca. 11,000–10,000 yr B.P. Although the radiocarbon ages are minimum-limiting ages obtained from tephra layers on top of tills, the tills are not significantly older because most are bracketed by dated tephra sets in measured stratigraphic sections. Two minor moraine stages likely reflect glacier pauses during cold intervals ca. 7400 yr B.P. and slightly earlier. Finally, glaciers readvanced between the 17th and 19th centuries. In contrast to the glacier cover (ca. 34 km2) on volcanoes of the massif during the last glacial maximum (LGM) the ice cover expanded to 1200 km2 and was still 800 km2 during late-glacial time (LGT). Glacier reconstructions based on the moraines suggest depression of the equilibrium line altitude (ELA) by ca. 1100 m during the LGM and 500–600 m during LGT relative to the modern ELA which lies at ca. 5100 m in the Cordillera Central. Glaciers in this region apparently reached their greatest extent when the climate was cold and moist, e.g., during stades corresponding to marine isotope stage 3; glaciers were still expanding during the LGM ca. 28,000–21,000 yr B.P., but they shrank considerably after 21,000 yr B.P. because of greatly reduced precipitation.
Origin of the Whewellite-Rich Rock Crust in the Lower Pecos Region of Southwest Texas and Its Significance to Paleoclimate Reconstructions
Authors: Russ Jon , Palma Russell L. , Loyd David H. , Boutton Thomas W. , Coy Michael A.
Published: October 2002

A calcium oxalate (whewellite)-rich crust occurs on exposed limestone surfaces in dry rock and open air shelters in the Lower Pecos region of southwest Texas. The crust, which also contains gypsum and clay, formed over silica-rich limestone during the Holocene. SEM and optical photomicrographs reveal similarities between whewellite microstructures and the lichenAspicilia calcarea.This desert lichen is known to produce calcium oxalate, and has been found in several sites in the region. The ubiquity of the whewellite-rich crust in the Lower Pecos shelters suggests that the lichen flourished in the past. SinceA. calcareais a desert species, the virulence of the organism likely peaked during xeric climate episodes then waned during mesic periods. Thus, radiocarbon ages of whewellite would correspond to dry climate periods experienced in the region, while periods with few or no14C data would indicate wet climate episodes. A preliminary paleoclimate reconstruction based on fourteen AMS14C dates indicates the Lower Pecos experienced dry to wet climate fluctuations during the late Holocene. This reconstruction generally agrees with other models established for Texas.
Holocene Key-Marker Tephra Layers in Kamchatka, Russia
Authors: Braitseva Olga A. , Ponomareva Vera V. , Sulerzhitsky Leopold D. , Melekestsev Ivan V. , Bailey John
Published: October 2002

Detailed tephrochronological studies in Kamchatka Peninsula, Russia, permitted documentation of 24 Holocene key-marker tephra layers related to the largest explosive eruptions from 11 volcanic centers. Each layer was traced for tens to hundreds of kilometers away from the source volcano; its stratigraphic position, area of dispersal, age, characteristic features of grain-size distribution, and chemical and mineral composition confirmed its identification. The most important marker tephra horizons covering a large part of the peninsula are (from north to south; ages given in14C yr B.P.) SH2(≈1000 yr B.P.) and SH3(≈1400 yr B.P.) from Shiveluch volcano; KZ (≈7500 yr B.P.) from Kizimen volcano; KRM (≈7900 yr B.P.) from Karymsky caldera; KHG (≈7000 yr B.P.) from Khangar volcano; AV1(≈3500 yr B.P.), AV2(≈4000 yr B.P.), AV4(≈5500 yr B.P.), and AV5(≈5600 yr B.P.) from Avachinsky volcano; OP (≈1500 yr B.P.) from the Baraniy Amfiteatr crater at Opala volcano; KHD (≈2800 yr B.P.) from the “maar” at Khodutka volcano; KS1(≈1800 yr B.P.) and KS2(≈6000 yr B.P.) from the Ksudach calderas; KSht3(A.D. 1907) from Shtyubel cone in Ksudach volcanic massif; and KO (≈7700 yr B.P.) from the Kuril Lake-Iliinsky caldera. Tephra layers SH5(≈2600 yr B.P.) from Shiveluch volcano, AV3(≈4500 yr B.P.) from Avachinsky volcano, OPtr(≈4600 yr B.P.) from Opala volcano, KS3(≈6100 yr B.P.) and KS4(≈8800 yr B.P.) from Ksudach calderas, KSht1(≈1100 yr B.P.) from Shtyubel cone, and ZLT (≈4600 yr B.P.) from Iliinsky volcano cover smaller areas and have local stratigraphic value, as do the ash layers from the historically recorded eruptions of Shiveluch (SH1964) and Bezymianny (B1956) volcanoes. The dated tephra layers provide a record of the most voluminous explosive events in Kamchatka during the Holocene and form a tephrochronological timescale for dating and correlating various deposits.
Holocene Tree Line and Climate Change on the Queen Charlotte Islands, Canada
Authors: Pellatt Marlow G. , Mathewes Rolf W.
Published: October 2002

Palynological study of two subalpine ponds on the Queen Charlotte Islands reveals changes in tree line and climate during the Holocene. The findings agree with previous reconstructions, from nearby Louise Pond on the Queen Charlotte Islands, that suggest a warmer-than-present climate and higher-than-present tree lines in the early Holocene (ca. 9600–660014C yr B.P.). Basal ages at SC1 Pond and Shangri-La Bog indicate that the basins did not hold permanent water before 720014C yr B.P., consistent with a warmer and drier early Holocene previously inferred from Louise Pond. Pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 ± 9014C yr B.P., similar to the 5790 ± 13014C yr B.P. age for cooling inferred from Louise Pond. Conditions similar to present were established at SC1 Pond by 3460 ± 10014C yr B.P., confirming the previous estimate of 340014C yr B.P. at Louise Pond. This 340014C yr B.P. vegetation shift on the Queen Charlotte Islands corresponds with the beginning of the Tiedemann glacial advance in the south-coastal mountains of British Columbia (ca. 330014C yr B.P.), the Peyto and Robson glacial advances between 3300 and 280014C yr B.P. in the Rocky Mountains, and climatic cooling inferred from palynological studies throughout southern British Columbia, northern Washington, and southeast Alaska. These findings confirm that changes in regional climate influenced changes in vegetation in coastal British Columbia.
Holocene Fluctuations of a Meromictic Lake in Southern British Columbia
Authors: Lowe David J. , Green John D. , Northcote Tom G. , Hall Ken J.
Published: October 2002

Holocene deposits of Mahoney Lake, a meromictic saline lake located in a closed basin in the semi-arid Okanagan Valley, contain evidence of frequent and marked changes in lake depth (up to >12 m/10014C yr) probably caused by short-term changes in effective precipitation. We studied a 5.45-m-long core comprising a basal layer of inorganic mud overlain by a succession of layers of calcareous laminated and nonlaminated organic mud, marl, and sand. We used Mazama tephra to adjust nine radiocarbon ages for the hardwater effect. Meromixis developed ca. 900014C yr B.P., and the lake has been episodically meromictic for about half the time since. Because of close linkages between sediments and depositional environments in meromictic and saline lakes, we infer that laminated sediments indicate meromictic conditions and high lake levels (>ca. 12 m water depth), whereas thick marl layers and nonlaminated sediments indicate nonmeromictic conditions and thus low lake levels (<ca. 8 m depth). Many of the inferred short-term climatic changes have not been identified in previous studies in northwestern North America, perhaps because of insensitive climatic proxies, inadequate temporal resolution, or discounting of anomalous findings.
North Atlantic Ice Sheet Fluctuations 10,000–70,000 Yr Ago as Inferred from Deposits on the Reykjanes Ridge, Southeast of Greenland
Authors: Lackschewitz Klas S. , Baumann Karl-Heinz , Gehrke Bettina , Wallrabe-Adams Hans-Joachim , Thiede Jörn , Bonani Georges , Endler Rudolf , Erlenkeuser Helmut , Heinemeier Jan
Published: October 2002

Marine records from the Reykjanes Ridge indicate ice sheet variations and abrupt climate changes. One of these records, ice-rafted detritus (IRD), serves as a proxy for iceberg discharges that probably indicates ice sheet fluctuations. The IRD records suggest that iceberg discharge 68,000–10,000 yr B.P. happened more frequently than the 7000- to 10,000-yr spacing of the Heinrich events. An IRD peak 67,000 to 63,000 yr B.P. further suggests that the Middle Weichselian glaciation started about 12,000 yr earlier in the North Atlantic than in the Norwegian Sea. Several later IRD events, in contrast, correlate with Norwegian Sea IRD-rich layers and imply coeval ice sheet advances in the North Atlantic and the Norwegian Sea. Coccoliths in a core from the Reykjanes Ridge show distinct peaks in species that record occasional inflow of warm surface water during the last glaciation, as previously reported from the eastern Labrador Sea. High abundances of coccoliths, together with a decrease of Neogloboquadrina pachyderma sin. and relatively low δ18O values, imply enhanced advection of the North Atlantic Current 69,000–67,000 yr B.P., 56,000–54,000 yr B.P., 35,000–33,000 yr B.P., and 26,000–23,000 yr B.P. This advection provided a regional moisture source for extension of ice sheets onto the shelf. In contrast, most of the IRD events are characterized by cold polar surface water masses indicating rapid variations in ocean surface conditions.
Late Weichselian Marine14C Reservoir Ages at the Western Coast of Norway
Authors: Bondevik Stein , Birks Hilary H. , Gulliksen Steinar , Mangerud Jan
Published: October 2002

A shallow marine Late Weichselian deposit on the outer coast of western Norway contains both terrestrial plant material and articulated marine shells. We have14C dated both types of material from eight different stratigraphic levels covering the time interval 12,300 to 11,10014C yr B.P. The difference between14C-dated terrestrial plant material and marine shell material (the marine reservoir age) ranges from 200 to 525 yr, with a weighted average of 380 ± 32 yr. This is almost identical to the present reservoir age of 379 ± 20 yr for southern Norway. In the mid-Younger Dryas (YD) interval the reservoir age in the North Atlantic (55°N–65°N) was 700–800 yr, considerably greater than the present reservoir age and the age we have measured for the Bølling–Allerød interval. The reason for this increase during the YD is probably a combination of reduced inflow of surface waters to the North Atlantic and more extensive sea-ice cover. Evidence from marine cores show that the southeastern Norwegian Sea experienced rapid fluctuations in the inflow of warm Atlantic surface water during the period 12,300 to 11,000 yr B.P. However, the reservoir age apparently did not increase during these colder periods (Older Dryas I and II). The reason is probably that, in contrast to the YD, these colder periods did not last long enough and/or were of too limited extent to alter the reservoir age of the ocean. A comparison of the obtained14C dates with the varve14C chronology from Lake Suigetsu indicates an age of 12,770 cal yr B.P. for the AL/YD boundary.
Highest Pluvial-Lake Shorelines and Pleistocene Climate of the Western Great Basin
Authors: Reheis Marith
Published: October 2002

Shoreline altitudes of several pluvial lakes in the western Great Basin of North America record successively smaller lakes from the early to the late Pleistocene. This decrease in lake size indicates a long-term drying trend in the regional climate that is not seen in global marine oxygen-isotope records. At +70 m above its late Pleistocene shoreline, Lake Lahontan in the early middle Pleistocene submerged some basins previously thought to have been isolated. Other basins known to contain records of older pluvial lakes that exceeded late Pleistocene levels include Columbus-Fish Lake (Lake Columbus-Rennie), Kobeh-Diamond (Lakes Jonathan and Diamond), Newark, Long (Lake Hubbs), and Clover. Very high stands of some of these lakes probably triggered overflows of previously internally drained basins, adding to the size of Lake Lahontan. Simple calculations based on differences in lake area suggest that the highest levels of these pluvial lakes required a regional increase in effective moisture by a factor of 1.2 to 3 relative to late Pleistocene pluvial amounts (assuming that effective moisture is directly proportional to the hydrologic index, or lake area/tributary basin area). These previously unknown lake levels reflect significant changes in climate, tectonics, and (or) drainage-basin configurations, and could have facilitated migration of aquatic species in the Great Basin.
Anatomie resection for severe blunt liver trauma in 100 patients: Significant differences between young and elderly
Authors: Tsugawa Kouji , Koyanagi Nobuhiro , Hashizume Makoto , Ayukawa Katsuhiko , Wada Hiroya , Tomikawa Morimasa , Ueyama Toshihiko , Sugimachi Keizo
Published: October 2002

The liver is the organ most commonly injured during blunt abdominal trauma. As our society ages, emergency surgery for active elderly patients increases, but data on aggressive emergency hepatic resection remain scarce in the literature. The purpose of this study was to determine whether the elderly (70 years of age or older) can tolerate major liver injury and subsequent hepatic resection. We investigated 100 patients who were treated by an anatomic resection for severe blunt liver trauma (29 elderly patients who were 70 years of age or older and 71 young patients who were younger than 70 years of age) in a retrospective study. The elderly patients were more severely injured as demonstrated by a higher Injury Severity Score, a lower Glascow Coma Scale, and lower survival (80.3% vs. 65.5%; p<0.05). The total number of associated injuries was greater in elderly patients. Motor vehicle accidents were responsible for 71.8% of the injuries in the young group, and the predominant mechanism in the elderly patients was also motor vehicle accidents (51.7%). The 71 anatomic hepatic resections performed on the young patients included right hemihepatectomy (n=45), left lateral segment resection (n=14), bisegmentectomy (n=5), and others. The 29 anatomic hepatic resections performed for the elderly patients were right hemihepatectomy (n=15), left lateral segment resection (n=5), left hemihepatectomy (n=4), and others. Pneumonia, subphrenic abscess, and urosepsis occurred at a significantly higher frequency in elderly patients than in young patients. Our data clearly indicated that (1) the mechanism of injury, grade of associated intraabdominal injuries, distribution of surgical procedures, and complications differ significantly between young and elderly patients; and (2) the survival rate (65.5%) in elderly patients may be sufficient to consider anatomic hepatic resection to be a useful, safe procedure.