bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of phosphorylated MAPIB in neuritogenesis
Authors: Avila Jesus , Ulloa Luis , Diez‐Guerra Javier , Diaz‐Nido Javier
Published: October 2002

The distribution of microtubule‐associated protein lB (MAPlB) phosphorylated by either proline‐directed protein kinase (PDPK) or casein kinase II (CK II) in neuroblastoma cells and hippocampal neurons has been studied by immunofluorescence using specific antibodies to distinct phosphorylation‐sensitive epitopes. A proximo‐distal gradient of increasing PDPK‐catalyzed phosphorylation of MAPlB is superimposed on a proximo distal gradient of decreasing CK II‐catalyzed MAPlB phosphorylation within growing axon‐like neurites. Additionally, CK II‐phosphorylated MAPlB is present in cell bodies and dendrites where no PDPK‐phosphorylated MAPlB is observed. These results suggest distinct roles for both types of modifications of MAPlB in developing neurons.
WHY DOES BONE MATRIX CONTAIN NON‐COLLAGENOUS PROTEINS? THE POSSIBLE ROLES OF OSTEOCALCIN, OSTEONECTIN, OSTEOPONTIN AND BONE SIALOPROTEIN IN BONE MINERALISATION AND RESORPTION
Authors: Roach H. I.
Published: October 2002

Four major non‐collagenous bone proteins were localised by single and double immuno‐histochemistry during de novo mineralisation and bone resorption. Both osteopontin and bone sialoprotein were localised ahead of the mineralisation front, suggesting that both proteins are necessary for the initiation of bone mineralisation. This supports previous suggestions that bone sialoprotein acts as a crystal nucleator. The role of osteopontin is less certain, but might be related to ensuring that only the right type of crystal is formed. Osteocalcin and osteonectin were not present in areas of first crystal formation, but were present in the fully mineralised matrix. Their role may be to control the size and speed of crystal formation.

Osteopontin, bone sialoproteins and osteocalcin (but not osteonectin) were also present at reversal lines. Interpreting this localisation together with information from the literature, the following functions are suggested during resorption: Osteocalcin may act as a chemoattractant for osteoclasts, while both osteopontin and bone sialoprotein may facilitate the binding of osteoclasts via the arg‐gly‐asp motif.
GLUCOSE STRONGLY STIMULATES RATE OF THE RRNA SYNTHESIS IN EHRLICH ASCITES CARCINOMA CELLS
Authors: Buzhurina I. M. , Chernaya N. G. , Panov M. A.
Published: October 2002

A change in glucose concentration in an Ehrlich ascites carcinoma cell suspension from 0.1 mM to 20 mM causes a more than 50‐fold stimulation of the rate of ribosomal RNA synthesis. Such an effect occurs without any dramatic effect on the rate of protein synthesis in cells. This process parallels a decrease in intracellular pH which may be a reason of Na+/H+‐antiport activation.
A confocal microscopic evaluation of the effects of insulin imprinting on the binding of Concanavalin A by Tetrahymena pyriformis.
Authors: Kovcs Peter , Sundermann Christine , Estridge Barbara H. , Csaba György
Published: October 2002

With confocal microscopy it is possible to study the Concanavalin A (Con A) binding characteristics of the surface and interior of a single cell by viewing optical sections. It was observed in Tetrahymena pyriformis that Con A bound both to the plasma membrane and to intracellular structures. Incubation of cells with a competing sugar a‐methylmannopyranoside, decreased binding. Hormonal imprinting with insulin resulted in an increase in binding of Con A to the cell surface and a decrease in intracellular binding. It is possible that the intracellular binding sites may migrate to the plasma membrane.
EPR study of the sea anemone cytolysin, equinatoxin II, cytotoxicity on V‐79 cells
Authors: Batista Urška , Šentjurc Marjeta
Published: October 2002

Electron paramagnetic resonance (EPR) was used to study the effect of equinatoxin II (EqT II), a cytolytic protein isolated from the sea anemone Actinia equina L., on membrane fluidity and cell metabolism of V‐79 cells; the reduction of the spin probe incorporated into the cell membranes as well as the oxygen consumption in the cell suspension were measured. The results were compared with the results obtained by the cell viability study. Under the influence of EqT II (less than 37.5 μg/106 cells) no significant changes in cell membrane fluidity were observed, while reduction kinetics of the spin probe and the oxygen consumption decreased when the cells were kept in Tris buffer solution. However, in the presence of 10% fetal calf serum, which prevented cell lysis, the effects of EqT II were diminished. The oxygen consumption corresponds to the cell viability changes but the reduction kinetics alterations indicate that some oxidation‐reduction processes other than cell respiration are affected by EqT II in the absence of serum. The effect seems to be indirect, probably due to the formation of pores which are associated with changed permeability of plasmalemma for metabolites and ions.
Maternal nicotine exposure: reponse of type II pneumocytes of neonatal rat pups.
Authors: Maritz G. S. , Thomas R.‐A.
Published: October 2002

The influence of maternal nicotine exposure during pregnancy and lactation on the Type II cells of lung tissue of one day old neonatal rat pups was investigated. The results clearly show that maternal nicotine exposure resulted in an increase in the type II cell count in the lungs of the offspring. In addition the lamellar body content of the type II cells of the nicotine exposed rat pups were significantly (P< 0.01) higher than that of the control animals. The type II cell mitochondria of lung tissue of nicotine exposed rat pups were swollen and no microvilli occurred on the alveolar surface. This clearly illustrates that nicotine interfered with type II cell integrity of tlte neonatal lung and may subsequently interfere with the normal development of the alveolar region of the lung.
Morphological alterations caused by lithium in various cell lines
Authors: Matthopoulos Demetrios P. , Tzaphlidou Margaret , Leontiou Ioannis
Published: October 2002

Lithium is being used for the treatment of mental diseases and for the attenuation of muelosuppression during chemotherapy. As during long term lithium treatment kidney damage has been reported, we studied morphological alterations in cells of kidney origin after exposure to lithium chloride. Above the level of 4 mmol, lithium has fatal effects in CV1 cells while HeLa cells that are not originating from kidneys, tolerate higher lithium concentrations. Cellular morphology alters during treatment duration. At early stages, cells become flatter on their substrate and upon longer than 4 days treatment begin to detach from their substrate and eventually cell death comes in a concentration dependent manner. The only morphological alteration observed in a lymphoblastoid cell line was a statistically significant cellular swelling.
A MOVING IMAGE OF FLAGELLA: NEWS AND VIEWS ON THE MECHANISMS INVOLVED IN AXONEMAL BEATING
Authors: COSSON J.
Published: October 2002

Beating of cilia and flagellae allows movement of the fluid surrounding isolated cells (for example: protists) or epithelia (bronchial tissue) but is also responsible for the movement of unicellular organisms in this medium (such as spermatozoa or protists). This paper aims to describe: (1) the biochemical and structural elements of the ‘9 +2’ structure called the axoneme; (2) the mechanisms of wave generation and propagation along the axoneme of cilia and flagellae are then described, stating that in most models of wave propagation, a clear distinction is made between the dynein‐dependent microtubule sliding which represents the oscillatory motor and the bending mechanism which regulates wave propagation. In current models, the bending propagation is supported by a bind /relax cyclic mechanism which propagates in register, but frame‐shifted, with the powering action of the dynein motor along the axoneme. While a large amount of knowledge was accumulated about the motor, little is known about the resisting elements regulating the bending. (3) The present study also puts forward ideas as to how these organelles have been highly conserved throughout eucaryotic evolution, and concludes with suggestions for further fields of investigation into this unique mechanical device used for cell movement.
PROTEIN RETENTION IN THE ENDOPLASMIC RETICULUM OF INSECT CELLS IS NOT COMPROMISED BY BACULOVIRUS INFECTION
Authors: HENDERSON JANEY , MACDONALD HEATHER , LAZARUS COLIN M. , NAPIER RICHARD M. , HAWES CHRIS R.
Published: October 2002

High level expression of the major auxin‐binding protein (ABP1) from maize (Zea maysL.) has been used to demonstrate that the machinery for retaining proteins in the endoplasmic reticulum (ER) of insect cells functions efficiently throughout the baculovirus infection cycle. Immuno‐localization showed wild‐type ABP1 (ABP1‐KDEL) to be targeted to the lumen of the ER, in accordance with its signal peptide and carboxyterminal KDEL ER‐retention signal. The protein accumulated in dilations of the ER, and none was detected at the cell surface. Immunoblotting of concentrated culture medium confirmed that ABP1‐KDEL was not secreted at a detectable level. In contrast, when the carboxyterminus was mutated to KEQL, secretion of the baculovirus‐expressed protein was readily detected. Immunolocalization and immunoblotting demonstrated that a high proportion of the ABP1‐KEQL protein was secreted at the cell surface and into the culture medium. The data demonstrate that the ER of insect cells has a great capacity to retain proteins and that this property is largely unaffected by the cellular disruption caused by baculovirus replication.
THE INTER‐SERTOLI CELL TIGHT JUNCTIONS IN GERM CELL‐FREE SEMINIFEROUS TUBULES FROM PRENATALLY IRRADIATED RATS: A FREEZE‐FRACTURE STUDY
Authors: RIBEIRO ALBERTO F. , DAVID‐FERREIRA JOSÉ F.
Published: October 2002

The tight junctions between Sertoli cells were examined by freeze‐fracture in 3‐month‐old prenatally irradiated rats, whose seminiferous tubules are devoid of germ cells. The replicas from irradiated tubules show elaborate interdigitations of the lateral membranes of Sertoli cells and very extensive tight junctions. These junctions are characterized by a great number of continuous parallel or complex interweaving strands of intramembranous particles, preferentially associated with E fracture faces. The presence of highly cross‐linked tight junctional strands is compatible with an epithelium deprived of germ cells, with a reduced need for flexibility. Anomalous ectoplasmic specializations, consisting of groups of cisternae arranged perpendicularly to the lateral surface, are found in the irradiated tubules. These structures may be involved in a storage mechanism of redundant lateral membrane resulting from the elimination of germ cells. Typical gap junctions, intercalated between the tight junctional strands, are larger and more frequently found in treated animals than in controls. These findings indicate that a very tight permeability barrier seems to be established in the irradiated testis even in the absence of germ cells. Thus, the formation and maintenance of Sertoli tight junctions do not appear to be directly dependent on the presence of germ cells. Nevertheless, the alterations detected in the tight junction architecture and in the ectoplasmic specializations indicate that maturing germ cells probably contribute to the functional organization of the blood—testis barrier in the normal testis.
ANTIPROLIFERATIVE EFFECT OF ILLIMAQUINONE ON LEISHMANIA MEXICANA
Authors: RANGEL HECTOR R. , DAGGER FRACEHULI , COMPAGNONE REINALDO S.
Published: October 2002

Illimaquinone, a sponge metabolite that disrupts the Golgi complex in mammalian cells, stopped proliferation and induced morphological and ultrastructural changes in promastigotes of L. mexicana Radioactive labeling of proteins demonstrates an increased excretion function and diminution of membrane acid phosphatase activity, due probably to the vesiculation of the Golgi complex and alteration of the cell protein sorting mechanism. The result indicated that illimaquinone could be useful for the study of intracellular traffic in Trypanosomatidae.
PRODUCTION OF GERMLINE CHIMERIC CHICKENS BY TRANSFER OF CULTURED PRIMORDIAL GERM CELLS
Authors: CHANG IL‐KUK , JEONG DONG KEE , HONG YEONG HO , PARK TAE SUB , MOON YANGHA KIM , OHNO TADAO , HAN JAE YONG
Published: October 2002

Primordial germ cells (PGCs) from stage 27 (5.5‐day‐old) Korean native ogol chicken embryonic germinal ridges were cultured in vitro for 5 days. As in in vivo culture, these cultured PGCs were expected to have already passed beyond the migration stage. Approximately 200 of these PGCs were transferred into 2.5‐day‐old white leghorn embryonic blood stream, and then the recipient embryos were incubated until hatching. The rate of hatching was 58.8% in the manipulated eggs. Six out of 60 recipients were identified as germline chimeric chickens by their feather colour. The frequency of germline transmission of donor PGCs was 1.3–3.1% regardless of sex. The stage 27 PGCs will be very useful for collecting large numbers of PGCs, handling of exogenous DNA transfection during culture, and for the production of desired transgenic chickens.
POLYAMINE REGULATORY PROCESSES AND OXIDATIVE STRESS IN MONOCROTALINE‐TREATED PULMONARY ARTERY ENDOTHELIAL CELLS
Authors: AZIZ SHEWAN M. , TOBOREK MICHAL , HENNIG BERNHARD , ENDEAN ERIC , LIPKE DAVID W.
Published: October 2002

Alterations in polyamine metabolism may be a critical mechanism of monocrotaline (MCT)‐induced structural remodeling of the pulmonary vasculature. In the present study, the hypothesis that MCT, through the induction of oxidative stress, modulates cellular polyamine regulatory mechanisms which in turn might be involved in the upregulation of fibronectin production in pulmonary artery endothelial cells (PAEC) was examined. A 24‐h treatment with MCT significantly increased PAEC polyamine concentrations as compared to vehicle‐treated cells. In addition, exposure to MCT caused an increase in abundance of ornithine decarboxylase (ODC) mRNA, upregulation of ODC activity and enhancement of spermidine import into PAEC. Inhibition ofde novopolyamine synthesis further increased spermidine uptake in MCT‐treated cells. The depletion of cellular polyamine contents through the blockade of bothde novopolyamine biosynthesis and polyamine transport prevented MCT‐induced increases in the medium level of fibronectin. In addition, PAEC treatment with MCT stimulated cellular oxidative stress as determined by increased levels of thiobarbituric acid reactive substances, enhanced dichlorofluorescein fluorescence and activation of NF‐KB. A co‐treatment with dimethylthiourea, an oxygen radical scavenger, prevented MCT‐induced increases in cellular oxidation and attenuated disturbances in polyamine metabolism. These data suggest that MCT can stimulate polyamine regulatory processes in PAEC possibly through an increase in cellular oxidative stress. The present study may have significant implication in understanding mechanisms of MCT‐induced pulmonary hypertension and remodeling of pulmonary vasculature.
Partial characterization of mosquito larvae extract modulating mouse and human cell proliferation
Authors: Ronderos J.R , Rimoldi O.J , Salas M.A , Brenner R.R
Published: October 2002

Mosquito larvae crude extract have been found to alter the mitotic rate of several mouse epithelial cell populations such as enterocytes and tongue keratinocytes. Also, the dialysed fraction inhibits hepatocyte proliferation in hepatectomized males. These experiments suggested an inhibitory effect on the G1/S interphase. Consequently, we suggested the presence of some molecule or molecules related to the TGF‐β superfamily. In the present paper, we have assayed the crude extract on human mononuclear cells and the dialysed fraction of the extract on tongue keratinocyte proliferation. Furthermore, different protein fractions obtained using a molecular exclusion chromatographic column were assayed on hepatocyte proliferation of hepatectomized mice. Three groups of proteins have been isolated. Results show a dose‐dependent effect of crude extract on mononuclear cell proliferation and the dialysed extract caused an inhibitory effect on tongue keratinocyte proliferation. With regard to the hepatocyte mitotic rate, an inhibitory effect appeared only in animals receiving the fraction with lower molecular weight. These results suggest the presence in mosquito larvae of some peptidic molecule or molecules resembling the activity of members of the TGF‐β superfamily.
Effects of TGFβ and BFGF on the differentiation of human bone marrow stromal fibroblasts
Authors: Locklin Rachel M. , Oreffo Richard O.C , Triffitt James T.
Published: October 2002

Adipocytes and osteoblasts have common origins from fibroblastic stem cells. Consequently, modulation of the processes of adipogenesis and osteogenesis has implications for the possible treatment of metabolic bone diseases, such as osteoporosis, in which medullary fat accumulates and trabecular bone volume decreases. It is likely that the balance between these two systems is affected by particular endogenous growth factors which are known to affect bone metabolism. We have therefore investigated the effects of transforming growth factor beta (TGFβ), basic fibroblast growth factor (bFGF) and dexamethasone (Dex) on cultured human bone marrow (HBM) fibroblastic cells to observe the effects on adipogenesis and osteogenesis. In the absence of fetal calf serum (FCS), TGFβ caused a dose‐dependent increase in cell growth and alkaline phosphatase activity (AP); however, in the presence of FCS growth was inhibited at high concentrations and AP unaffected. TGFβ increased matrix proteoglycan and collagen synthesis. bFGF inhibited AP and increased colony number and size, while Dex treatment increased AP activity and colony number, and both factors in combination resulted in an additive increase in growth. Dex‐induced adipocyte formation was accelerated but not increased by bFGF. A significant inhibition of adipogenesis by TGFβ was observed within 7 days. These results demonstrate the importance of biological factors known to be involved in bone remodelling in the regulation of osteogenesis and adipogenesis.
PDGF‐BB AND IGF‐I USE DIFFERENT SIGNALING PATHWAYS TO INDUCE NaK‐ATPase SUBUNITS IN CULTURED RAT THORACIC AORTIC SMOOTH MUSCLE CELLS
Authors: Lo Chu S.
Published: October 2002

(Na++K+)‐adenosine triphosphatase (NaK‐ATPase), an ubiquitous membrane transport protein consisting of α and β subunits, regulates Na+/K+fluxes and maintains many vital physiological functions, including cell growth. Results have indicated that platelet‐derived growth factor (PDGF) and insulin‐like growth factor‐I (IGF‐I) both enhance NaK‐ATPase subunits. Genistein, an inhibitor of tyrosine phosphorylation, inhibits serum‐ and PDGF‐BB‐induced NaK‐ATPase α1subunit protein levels without inhibiting IGF‐I‐induced NaK‐ATPase α1subunit protein levels. These results indicate that PDGF‐BB and IGF‐I utilize separate signaling pathways to induce the synthesis of NaK‐ATPase α1subunits. In addition, genistein failed to inhibit PDGF‐BB‐stimulated NaK‐ATPase β1subunit levels, suggesting that two separate pathways are involved to induce the synthesis of the NaK‐ATPase α1and β1subunits, respectively.
THE EFFECT OF OXIDATIVE STRESS INDUCED BY t‐BUTYL HYDROPEROXIDE ON THE STRUCTURAL DYNAMICS OF MEMBRANE PROTEINS OF CHINESE HAMSTER FIBROBLASTS
Authors: Mazhul V. , Shcherbin D. , Zavodnik I. , Rekawiecka K. , Bryszewska M.
Published: October 2002

A method based on the measurement at room temperature of tryptophan phosphorescence (RTTP) gives the unique possibility to investigate the dynamic structure of membrane proteins without their isolation from cells. This method was used to study the influence of tert‐ butyl hydroperoxide (t ‐BHP) on Chinese hamster fibroblasts. The treatment of fibroblasts with t ‐BHP in a concentration range of 0.5–2m m for 60min caused an increase of frequency and amplitude of membrane protein motions with lifetimes of hundreds miliseconds (a decrease of RTTP τ2). In parallel, cell viability was studied by trypan blue exclusion test and the content of thiobarbituric acid reactive substances was measured in cells. The dependences of the RTTP τ2and cell viability on t ‐BHP concentration were similar. Contrary to this, t ‐BHP did not induce the activation of lipid peroxidation processes in cells. This indicates that cell death is connected with the excessive increase of intramolecular dynamics of membrane proteins during t ‐BHP action.
IDENTIFICATION OF APOPTOTIC CELL DEATH IN DISTRACTION OSTEOGENESIS
Authors: Meyer Thomas , Meyer Ulrich , Stratmann Udo , Wiesmann Hans Peter , Joos Ulrich
Published: October 2002

The purpose of this experimental work was to investigate whether apoptosis contributes to tissue remodelling during distraction bone healing. In a rabbit model of mandibular distraction osteogenesis, we quantitatively analysed the extent of apoptotic cell death in relation to differently applied mechanical loadings. Apoptotic cells were identified by means of an in situ detection assay for nuclear DNA fragmentation using a modified TUNEL procedure and by electron microscopical examination for typical morphological features of programmed cell death. TUNEL‐positive cells were frequently detected in samples distracted at higher strain magnitudes. Ultrastructurally, these apoptotic cells displayed a condensed chromatin and fragmented nuclei, while the continuity of their plasma membranes remained intact. Our results clearly indicated that the discontinuous traction of osteotomized mandibles induced enhanced apoptosis. In contrast to non‐distracted samples and mandibles distracted at low strain magnitudes, in which only minimal evidence of apoptotic cell death was detected, the application of hyperphysiological strain magnitudes resulted in an increased apoptosis rate. Thus, mechanical loading seems to be a triggering factor for apoptotic changes in osteoblastic cells. These findings suggest a pathophysiological role of apoptotic cell death in the control of tissue integrity during distraction osteogenesis.
4‐1BB‐LIKE MOLECULE IS EXPRESSED IN ISLET‐INFILTRATING MONONUCLEAR CELLS AND IN THE GRAY MATTER OF THE BRAIN
Authors: Lim Ho Y. , Kim Kack K. , Zhou Feng C. , Yoon Ji‐Won , Hill James M. , Kwon Byoung S.
Published: October 2002

4‐1BB is an inducible costimulatory molecule that can exert regulatory effects on T cells. Polyclonal antibodies against oligopeptides representing an evolutionarily‐conserved region of murine 4‐1BB, were prepared and used to stain tissues in normal and inflammatory conditions. The 4‐1BB mRNA was detected in the PMA‐treated spleen and heart, and constitutively in the brain, kidneys and lungs. The 4‐1BB‐like protein (BBLP) was expressed on mononuclear cells infiltrating islet cells in the pancreata of NOD mice. Expression was prominent in the early phase of insulitis and the level of expression diminished or disappeared in the later phase. BBLP was identified in the gray matter of brain where neuronal cell bodies, dendrites, and fiber terminals reside but was almost entirely absent in the white matter where axonal fibers dwell. A peculiar rosette pattern was observed in a granular layer of cerebellum and scattered in the stria terminalis. The staining pattern strongly resembled the receptor/nerve terminals in the brain and in the peripheral nervous system. Taken together, BBLP may be associated with the early phase of inflammation and with brain function.
EX VIVO APOPTOTIC POTENTIAL OF PERIPHERAL BLOOD MONONUCLEAR CELLS OF THE ELDERLY HUMAN SUBJECT
Authors: Szmit Ewa , Trzonkowski Piotr , Myśliwska Jolanta , Foerster Jerzy , Myśliwski Andrzej
Published: October 2002

Studies of immunosenescence have led to a detailed knowledge of immune system dysfunctions in the ageing human being. Apoptosis seems to be one of the process regulating an immune response after the antigenic stimulation. We examined whether commonly used methods of assessing apoptosis in the elderly human subject produce comparable results to young subjects. PBMC of young and elderly volunteers were isolated from the venous blood and cultured for 6 or 24h with antigens of anti‐influenza vaccine or PMA. The intensity of apoptosis was measured using the annexinV test, flow cytometric evaluation of DNA content (sub‐G1 peak in DNA histograms), ‘ladder’ by DNA gel electrophoresis, and fluorescence microscope. Apoptosis in 6h‐lasting cultures of the elderly was more intense in annexinV test, while it was decreased assessing subG1 peak. Additionally, in the aged group, those changes were associated with cell cycle arrest. Our results suggest that the apoptosis after the stimulation with the vaccine antigens seems to be some kind of activation‐induced cell death (AICD). Different patterns of apoptosis after stimulation may be associated with the cell cycle arrest of the PBMC in the elderly.
Pollen and Macrofossils from Wisconsinan Interstadial Sediments in Northeastern Georgia
Authors: Jackson Stephen T. , Whitehead Donald R.
Published: October 2002

Pollen and plant macrofossil analyses and dating (both TAMS and conventional14C) of wetland sediments from the Nodoroc Site in the Piedmont region of northeastern Georgia identified two depositional episodes of interstadial (ca. 26,000-22,000 yr B.P.) and mid- to late Holocene (<3600 yr B.P.) age. Interstadial pollen assemblages were dominated byPinusandQuercus,withCarya, Picea,andAbiesalso present in significant amounts. The interstadial assemblages had lowerPinusand higherQuercuspollen percentages than apparently contemporaneous assemblages from sites in the southern Appalachians and Coastal Plain. Interstadial macrofossils included two needle morphotypes ofPinussubgenusPinus,possibly indicating local occurrence of twoPinusspecies. One of the needle morphotypes is consistent withPinus banksiana,but other species cannot be ruled out. Comparison of conventional and TAMS14C dates illustrates problems in obtaining accurate age models from wetlands and ponds characterized by shallow or fluctuating water levels, low sedimentation rates, and vegetation growing on the depositional surface.
Packrat Midden Evidence of Late Quaternary Vegetation Change in the White Mountains, California-Nevada
Authors: Jennings Steven A. , Elliott-Fisk Deborah L.
Published: October 2002

Packrat (Neotomaspp.) middens from the White Mountains indicate climatic and plant community conditions for the last 19,000 yr. During full-glacial times (ca. 19,000 yr B.P.) and at the Pleistocene/Holocene boundary juniper woodlands were 600 m lower in elevation than at present. Midden assemblages and stable-isotope data suggest lower temperatures and increased precipitation relative to the present into the early Holocene. Two early Holocene middens (ca. 8000 yr B.P.) from lower elevations of the White Mountains contain fragments of pinyon pine and indicate that both pinyon and juniper grew at a site that today supports only a pinyon woodland. Two middle Holocene middens (ca. 5000 yr B.P.) indicate that there was an upward migration of pinyon-juniper woodlands along a high-elevation ecotone, but little change in the middle of the pinyon-juniper woodland. Middens from the late Holocene indicate that present-day plant communities were in place by ca. 2000 yr B.P. or before.
Stick-Nest Rat Middens as Sources of Paleoecological Data in Australian Deserts
Authors: Pearson Stuart , Dodson John R.
Published: October 2002

The existing paleoenvironmental data from the Australian arid zone lack sensitivity and come from only a few sites. Macrofossils and pollen from four dated middens of the stick-nest rat (Leporillus spp.) were analyzed from two sites in Western Australia. Animal and plant macrofossil remains were well preserved and provided evidence of change in species distribution within the last 1150 yr. Brush-tail possum and golden bandicoot have contracted their ranges in the recent past, possibly since the introduction of cats into Australia. An undescribed lacewing was also a significant find. Pollen preserved in parts of the same midden and in middens from different sites indicates that records are sensitive to the composition of the local vegetation when the midden was built. Pollen spectra are quite different from playa lakes, which record largely regional vegetation. Pollen preserved in the fecal pellets, desiccated urine, and grass mat nesting material provided similar information but some differences were apparent, suggesting dietary preferences were reflected in the fecal component. The pollen record suggested a trend to less-wooded vegetation cover in central Australia between 900 and 300 yr B.P.
Inverse Multiparameter Modeling of Paleoclimate Carbon Cycle Indices
Authors: Heinze C. , Hasselmann K.
Published: October 2002

A simple linear response model describing the functional relationship between ocean carbon cycle parameters and paleoclimate tracers (atmospheric pCO2, δ13C, CaCO3 saturation) was derived from a set of sensitivity experiments performed previously using a three-dimensional carbon cycle model. The linear model is optimally fitted to ice and marine sediment core records for the last 120,000 yr to estimate the carbon cycle parameter changes that could have caused the observed reduction of atmospheric CO2 partial pressure during the last glaciation. The analysis indicates that the glacial pCO2 reduction was primarily caused by a strengthening of the biological POC pump and a retardation of the oceanic circulation. An increase in deep-sea alkalinity and a change in the advective pattern of the ocean circulation have a smaller impact on atmospheric CO2 but are necessary to explain the full set of paleoclimate tracers.
Late Quaternary Biomass Changes from 13C Measurements in a Highland Peatbog from Equatorial Africa (Burundi)
Authors: Aucour Anne-Marie , Hillaire-Marcel Claude , Bonnefille Raymonde
Published: October 2002

Stable carbon isotope ratios of total organic matter were measured in two cores collected from the Kashiru peatbog in Burundi, Equatorial Africa. The record, which spans at least the last 40,000 yr, documents the C3-C4 biomass balance in the organic sediment. Among the major modern peat formers, most plants are C3 species and are characterized by δ13C values of -25.5 ± 2.3% (vs PDB). The C4 plants, which are characterized by higher δ13C values (-11.3 ± 0.7%) belong to the Gramineae (Miscanthidium sp.) and Cyperaceae families (Cyperus latifolius, C. papyrus, Pycreus nigricans). In the fossil record, δ13C values of total organic matter vary between -28 and -15% in response to the relative fluxes of C3 and C4 plants. Before 30,000 yr B.P., low δ13C values (-23.5 ± 1.1%) match high arboreal pollen contents. From 30,000 to 15,000 yr B.P., higher δ13C values (-17.6 ± 1.1%) correspond to a significant increase in percentages of grass pollen. During this episode, a short and sharp shift toward lighter carbon isotopic compositions at 21,000 yr B.P. is synchronous with higher input of arboreal pollen. From 15,000 to 12,000 yr B.P., the 13C content decreases (δ13C = -22.9 ± 1.4%). This shift, which cannot be explained by an increase in the arboreal vegetation, could be explained by the spreading of C3 Gramineae or C3 Cyperaceae. The interval from 12,000 to 7000 yr B.P. is poorly documented in these cores due to much lower organic matter accumulation. Low δ13C values (δ13C = -25.2 ± 1.3%) are observed from 7000 to 5000 yr B.P., when the pollen data show development of C3 mountain forest. The Late Holocene is characterized by a mixed C3-C4 organic matter accumulation (δ13C = -20.9 ± 1.6%). This study depicts a change in the dominant photosynthetic pathway among the herbaceous components, notably at the glacial-interglacial transition, when C3 plants were favored by increased water supply and/or higher atmospheric CO2 concentration.
Sea-Surface Temperature Estimates for the Tropical Western Pacific during the Last Glaciation and Their Implications for the Pacific Warm Pool
Authors: Thunell Robert , Anderson David , Gellar Debrorah , Miao Qingmin
Published: October 2002

Twenty deep-sea sediment cores from the western Pacific between 30°N and 30°S provide evidence of sea-surface temperature (SST) changes throughout the tropics and subtropics. Glacial SSTs were estimated using the modern analog technique (MAT) applied to planktonic foraminifers and planktonic foraminiferal δ18O changes. We used δ18O to identify the last glacial maximum. The MAT method differs from the traditional transfer function approach in that it utilizes a global coretop database, and estimates paleotemperature by finding analogs from the modern coretop samples. In addition, the MAT approach appears to be less susceptible than the transfer function technique to biases introduced by carbonate dissolution. Our results indicate that tropical SSTs differed by less than 2°C from present; away from the tropics (30°N and 30°S) SSTs were at least 3°C cooler. Our results differ from those of previous studies in the western Pacific by using a set of well-preserved, high-sedimentation rate cores from shallow regions. The results of this study clearly indicate that a western Pacific warm pool existed during the last glacial maximum (LGM), providing a heat and moisture source for a Walker Circulation cell similar to that of today. We propose that a steeper lapse rate existed during the last glacial maximum and that this can explain at least part of the discrepancy between marine and terrestrial temperature estimates adjacent to New Guinea for the LGM.
Stability of Holocene Climate Regimes in the Yellowstone Region
Authors: Whitlock Cathy , Bartlein Patrick J. , Van Norman Kelli J.
Published: October 2002

A 12,500-yr pollen record from Loon Lake, Wyoming provides information on the climate history of the southwestern margin of Yellowstone National Park. The environmental reconstruction was used to evaluate hypotheses that address spatial variations in the Holocene climate of mountainous regions. Loon Lake lies within the summer-dry/winter-wet climate regime. An increase in xerophytic pollen taxa suggests drier-than-present conditions between ca. 9500 and 5500 14C yr B.P. This response is consistent with the hypothesis that increased summer radiation and the expansion of the east Pacific subtropical high-pressure system in the early Holocene intensified summer drought at locations within the summer-dry/winter-wet regime. This climate history contrasts with that of nearby sites in the summer-wet/winter-dry region, which were under the influence of stronger summer monsoonal circulation in the early Holocene. The Loon Lake record implies that the location of contrasting climate regimes did not change in the Yellowstone region during the Holocene. The amplitude of the regimes, however, was determined by the intensity of circulation features and these varied with temporal changes in the seasonal distribution of solar radiation.
The California Storm of January 1862
Authors: Engstrom Wayne N.
Published: October 2002

The greatest storm in the written history of California struck the region in the winter of 1861–1862. The unusual weather began on Christmas Eve, 1861, and persisted for some 45 days as a series of middle-latitude cyclones made landfall along the California coast. Episodes of very cold and very warm temperatures occurred both during the storm and in the spring of 1862 as meridional flow prevailed. Heavy precipitation swelled the Santa Ana River to more than triple the highest estimated discharge in this century. High water levels in coastal streams between Los Angeles and San Diego persisted into the spring. Lakes were created in the Los Angeles Basin and the Mojave Desert. Arroyos were cut. Sediments from the flood may be preserved in offshore basins.
Preservation and Recognition of Middle and Early Pleistocene Loess in the Driftless Area, Wisconsin
Authors: Jacobs Peter M. , Knox James C. , Mason Joseph A.
Published: October 2002

An exceptional stratigraphic and pedologic record of Pleistocene environmental conditions occurs at the Kieler Site in the Driftless Area of southwestern Wisconsin. Peoria, Roxana, Loveland, and pre-Loveland loesses overlie weathered bedrock residuum. The pre-Loveland unit previously has been included as part of the residuum at other Driftless Area sites. Early and middle Pleistocene loesses in the Mississippi Valley are normally absent at most localities. Rather than nondeposition, we suggest the apparent absence of pre-Illinoian loess units is due in part to erosion, but also to weathering that renders loesses unrecognizable so they are classified as “residuum.”
Biogenic Silica Record in Lake Biwa of Central Japan over the Past 145,000 Years
Authors: Xiao Jule , Inouchi Yoshio , Kumai Hisao , Yoshikawa Shusaku , Kondo Yoichi , Liu Tungsheng , An Zhisheng
Published: October 2002

The record of the biogenic silica flux (BSF, g cm−2(103yr)−1) in Lake Biwa reflects changes in diatom productivity in the lake and provides information regarding changes in paleoclimatic conditions. The BSF record of Lake Biwa demonstrates five periods over the past ca. 145,000 yr when the BSF values were significantly greater than 7.5 g cm−2(103yr)−1, and five intervals when they were lower. The data imply that paleoclimatic conditions were warmer and wetter from ca. 123,000 to 115,000, 103,000 to 95,000, 88,000 to 72,000, 57,000 to 32,000 yr B.P., and around ca. 6000 yr B.P. when the BSF values were greater, and relatively dry and cold from ca. 141,000 to 123,000 yr B.P. and during intervals between two of the five warm and wet episodes when the BSF values were lower. Time series of the BSF record can be correlated with the record of biogenic silica content in Lake Baikal and the marine oxygen isotope stages 1 through 6. Furthermore, the BSF values varied with much higher amplitude during the last interglaciation than during the last glaciation, probably implying that the diatom productivity in Lake Biwa was likewise more variable and had a larger range under interglacial conditions than under glacial conditions.
Tsunami Deposits Beneath Tidal Marshes on Northwestern Vancouver Island, British Columbia
Authors: Benson Boyd E. , Grimm Kurt A. , Clague John J.
Published: October 2002

Two sand sheets underlying tidal marshes at Fair Harbour, Neroutsos Inlet, and Koprino Harbour on the northwestern coast of Vancouver Island, British Columbia, were probably deposited by tsunamis. The sand sheets become thinner and finer-grained landward, drape former land surfaces, contain marine microfossils, are locally graded or internally stratified, and can be correlated with earthquakes that generated tsunamis in the region. 137Cs dating and historical accounts indicate that the upper sand sheet was deposited by the tsunami from the great Alaska earthquake in 1964. Radiocarbon ages on plant fossils within and on top of the lower sand sheet show that it was deposited sometime after about A.D. 1660. We attribute the lower sand sheet to a tsunami from the most recent plate-boundary earthquake on the Cascadia subduction zone about 300 yr ago, extending the documented effects of this earthquake north of the Nootka fault zone. The 1964 tsunami deposits differ little in thickness and continuity among the three marshes. In contrast, the lower sand sheet becomes thinner and less continuous to the north, implying a tsunami source south of the study area.
Late Pleistocene C4Plant Dominance and Summer Rainfall in the Southwestern United States from Isotopic Study of Herbivore Teeth
Authors: Connin Sean L. , Betancourt Julio , Quade Jay
Published: October 2002

Patterns of climate and C4plant abundance in the southwestern United States during the last glaciation were evaluated from isotopic study of herbivore tooth enamel. Enamel δ13C values revealed a substantial eastward increase in C4plant consumption forMammuthusspp.,Bisonspp.,Equusspp., andCamelopsspp. The δ13C values were greatest inBisonspp. (−6.9 to +1.7‰) andMammuthusspp. (−9.0 to +0.3‰), and in some locales indicated C4-dominated grazing. The δ13C values of Antilocaprids were lowest among taxa (−12.5 to −7.9‰) and indicated C3feeding at all sites. On the basis of modern correlations between climate and C4grass abundance, the enamel data imply significant summer rain in parts of southern Arizona and New Mexico throughout the last glaciation. Enamel δ18O values range from +19.0 to +31.0‰ and generally increase to the east. This pattern could point to a tropical or subtropical source of summer rainfall. At a synoptic scale, the isotope data indicate that interactions of seasonal moisture, temperature, and lowered atmospheric pCO2determined glacial-age C4abundance patterns.
Paleoclimatic Significance of Late Quaternary Lacustrine and Alluvial Stratigraphy, Animas Valley, New Mexico
Authors: Krider P.Reed
Published: October 2002

Lacustrine and alluvial stratigraphic sequences in the southern Animas Valley of New Mexico allow reconstruction of late Quaternary climates. Four separate stands of late Quaternary Lake Cloverdale in the southern Animas Valley are recorded by lacustrine shoreline deposits. Soils and stratigraphic evidence show that three young lake highstands occurred during the Holocene and that a higher lake stand occurred 18,000 to 20,00014C yr B.P. Fluvial systems aggraded the southern Animas Valley during the middle to late Holocene. The late Quaternary stratigraphy shows that several periods during the late Holocene were characterized by higher effective precipitation than at any time since the last glacial maximum.
Radiocarbon Age Constraints on Rates of Advance and Retreat of the Puget Lobe of the Cordilleran Ice Sheet during the Last Glaciation
Authors: Porter Stephen C. , Swanson Terry W.
Published: October 2002

Calibrated radiocarbon dates of organic matter below and above till of the last (Fraser) glaciation provide limiting ages that constrain the chronology and duration of the last advance–retreat cycle of the Puget Lobe in the central and southeastern Puget Lowland. Seven dates for wood near the top of a thick proglacial delta have a weighted mean age of 17,420 ± 90 cal yr B.P., which is the closest limiting age for arrival of the glacier near the latitude of Seattle. A time–distance curve constructed along a flowline extending south from southwestern British Columbia to the central Puget Lowland implies an average glacier advance rate of ca. 135 m/yr. The glacier terminus reached its southernmost limit ca. 16,950 yr ago and likely remained there for ca. 100 yr. In the vicinity of Seattle, where the glacier reached a maximum thickness of 1000 m, ice covered the landscape for ca. 1020 yr. Postglacial dates constraining the timing of ice retreat in the central lowland are as old as 16,420 cal yr B.P. and show that the terminus had retreated to the northern limit of the lowland within three to four centuries after the glacial maximum. The average rate of retreat was about twice the rate of advance and was enhanced by rapid calving recession along flowline sectors where the glacier front crossed deep proglacial lakes.
Lake-Level Chronology on the Southern Bolivian Altiplano (18°–23°S) During Late-Glacial Time and the Early Holocene
Authors: Sylvestre Florence , Servant Michel , Servant-Vildary Simone , Causse Christiane , Fournier Marc , Ybert Jean-Pierre
Published: October 2002

Stratigraphic analyses of outcrops, shorelines, and diatoms from the southern Bolivian Altiplano (Uyuni-Coipasa basin) reveal two major lacustrine phases during the late-glacial period and the early Holocene, based on a chronology established by radiocarbon and U/Th control. A comparison of14C and230Th/234U ages shows that during times of high lake level, radiocarbon ages are valid. However, during low-water periods,14C ages must be corrected for a reservoir effect. The lacustrine Tauca phase started a little before 16,00014C yr B.P., and the lake level reached its maximum between 13,000 and 12,00014C yr B.P. A dry event (Ticaña) occurred after ca. 12,000 and before 950014C yr B.P. A moderate lacustrine oscillation (Coipasa event) occurred between ca. 9500 and 850014C yr B.P., using a reservoir-corrected conventional14C chronology. Comparisons between the lake-level chronology in the Uyuni-Coipasa basin and data from other southern tropical areas of South America suggest that the lacustrine evolution may reflect large-scale climatic changes.
Dating the Lower Paleolithic Open-Air Site of Holon, Israel by Luminescence and ESR Techniques
Authors: Porat Naomi , Zhou Li Ping , Chazan Michael , Noy Tamar , Horwitz Liora Kolska
Published: October 2002

The open-air Acheulian site in Holon, Israel, was dated by the luminescence methods and by electron spin resonance (ESR). Situated in the coastal plain Quaternary Kurkar Group, the Holon site was first excavated in the late 1960s, when typical lower Paleolithic lithics and middle Pleistocene fauna were found. In order to date the site, new test pits were dug adjacent to the earlier excavations and the archaeological bed was exposed in a section comprising a series of paleosols and aeolianites. Alkali feldspars separated from the sediments were dated using the infrared stimulated luminescence and thermoluminescence signals, and quartz was dated using the optically stimulated luminescence signal. The age of the archaeological bed is constrained by two samples to 198,000 ± 22,000–201,000 ± 17,000 yr. The age of the base of the section is 240,000 ± 29,000 yr, and the age of the top is 81,000 ± 8000 yr. Two teeth from the archaeological bed, recovered from the original excavation collection, yielded an average ESR age of 204,000 ± 16,000 yr, calculated using the linear uptake model, which is in a very good agreement with the luminescence ages. These dates place Holon within the range of other late Acheulian and Acheulo-Yabrudian sites in this region such as Tabun E (younger chronology), Yabrud I (archaeological level 18), and Berekhat Ram.
Glacio-Eustatic Control of Continental–Shallow Marine Cyclicity from Late Quaternary Deposits of the Southeastern Po Plain, Northern Italy
Authors: Amorosi Alessandro , Colalongo Maria Luisa , Fusco Fabio , Pasini Giancarlo , Fiorini Flavia
Published: October 2002

Integrated sedimentological and micropaleontological (foraminifera, ostracods, pollens) investigations of a 173-m-long continuous core in the subsurface of the SE Po Plain reveal a cyclic facies distribution of continental to shallow-marine deposits. Radiometric and pollen data enable an age attribution of the study units to the late Middle Pleistocene–Holocene. Glacioeustasy appears to have exerted a major control on facies development, as documented by the close relationships between cyclic lithofacies patterns and the curves of eustatic fluctuation. Particularly, relative sea-level falls and lowstand phases were characterized by the development of alluvial sedimentation, whereas major transgressive pulses and subsequent highstands are reflected by abrupt shifts to paralic and shallow-marine deposits. This facies architecture is paralleled by a distinctive pollen distribution, reflecting the alternation of a glacial type of vegetation, dominated by Pinus and nonarboreal pollen types, with interglacial mixed deciduous broad-leaved forests.