bluuebunny/crossref_metadata_2025 huggingface dataset:
Molluscan shellfish biomarker study of the Quebec, Canada, Saguenay Fjord with the soft‐shell clam,Mya arenaria
Authors: Blaise C. , Gagné F. , Pellerin J. , Hansen P.‐D. , Trottier S.
Published: October 2002

A spatial and temporal survey of six sites in the Saguenay Fjord and of one adjacent site in the St. Lawrence River estuary (Quebec, Canada) was undertaken to study the possible effects of anthropogenic contaminant input on soft‐shell clam (Mya arenaria) populations. Bivalve sampling sites were selected because they reflected a range of areas representative of either no known (or apparent) pollution sources or of areas potentially influenced by different gradients and types of contamination sources. The most upstream site selected in the Saguenay Fjord, nearest to a highly populated and industrialized sector, and the most downstream site, near its mouth with the St. Lawrence River estuary, spanned a distance of some 70 km and encompassed the entire intertidal area suitable forMya arenariahabitat. To measure effects in collected animals, we used a comprehensive battery of biomarkers composed of metallothionein‐like proteins (MT), 7‐ethoxyresorufin O‐deethylase activity (EROD), DNA damage (DD), lipid peroxidation (LPO), vitellinlike proteins (Vn), phagocytosis (PHAG), nonspecific esterase (NspE) activity, and condition factor (weight‐to‐length ratio of clams). Vn, PHAG, DD, and NspE biomarkers were assayed in hemolymph (or hemocytes), whereas others (MT, EROD, LPO) were determined in the digestive gland. Whole‐tissue metal content was also quantified in clams collected in the spatial survey. The spatial survey conducted in June 1997 showed significant effects at all sites, and principal component analysis indicated in addition that the more important responses were linked to the MT, LPO, and NspE biomarkers. Clams collected from sites closest to the upstream reaches of the fjord generally displayed higher levels of tissue metals (cadmium, manganese), as well as greater responses of NspE activity, MT, LPO, and PHAG. Animals collected from sites influenced by municipal wastewaters had higher levels of Vn, suggesting the presence of environmental estrogens. The results of the temporal survey (six monthly samplings of clams at three sites from May through October, 1997) showed that the bivalve reproductive cycle (vitellogenesis and spawning) can modulate the expression of several biomarkers. Vn levels, for example, were positively correlated with DD and EROD and negatively correlated with MT, suggesting that reproduction can influence the susceptibility of clams to some contaminants. Discrimination analysis over the 6 months of sampling revealed that the mean value of the discriminant function changed significantly over time, suggesting important changes in the relative contribution of each biomarker. In short, this study has provided evidence that clam populations in the Saguenay Fjord are impacted by multiple sources of contamination whose effects can be modulated by reproduction. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 170–186, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10048
Microcystin‐producing cyanobacteria in recreational waters in southwestern Germany
Authors: Frank Christian A. P.
Published: October 2002

Toxin‐forming species of freshwater cyanobacteria have been detected in all parts of Germany. Because of the high number of lakes (more than 2000) in Baden‐Württemberg, in southwestern Germany, only a representative selection of lakes (155) was intensively monitored for mass development of cyanobacteria and the formation of toxins in 1999. Nutrients, dominant algal species, chlorophyll, and toxins were determined from waters with cyanobacterial blooms. Toxin analyses were performed using HPLC, the PP1 inhibition test, and the microcystin ELISA. In 45% of the monitored lakes, the phytoplankton assemblage consisted mainly of cyanobacteria; in an additional 24% of the lakes cyanobacteria were detected. More than 26% of the lakes contained toxigenic cyanobacteria. The highest amount of microcystins detected outside scum areas was 11–560 μg/L. In relation to biomass, cyanobacteria contained up to 1100 μg/g dry matter and up to 2.6 μg/μg Chl a. The dominant form of microcystin detected was microcystin‐LR, one of the most toxic known microcystins. The results of the present study have been used to develop a stepwise monitoring scheme for lakes with permanent cyanobacterial populations to protect human health and livestock. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 361–366, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10068
Carbon disulfide cytotoxicity on cultured cardiac myocytes of rats
Authors: Tan Xiaodong , Peng Xiaoxia , Wang Yongdi , Wang Fuyuan , Joyeux Michel , Hartemann Philippe
Published: October 2002

Although epidemiological studies have suggested that carbon disulfide produces cardiovascular effects in occupationally exposed workers, little is known about its cellular mechanism. The purpose of the present study was to evaluate the functional and histological effects on cardiac myocytes cultured under a condition of carbon disulfide exposure. Cardiac myocytes were isolated from neonatal rat ventricles by trypsin, dispersed and cultured for 3 days in a full Dulbecco's Modified Eagle Medium containing 2% calf serum. Then the myocytes (106 myocytes/mL) were incubated with carbon disulfide at concentrations of 0, 20, 40, and 80 μmol/mL for 24 h. The beating arrest rate of myocytes for each group was examined, succinodehydrogenase (SDH) activity in the myocardial cells was assessed using a cytochemical method, and a morphological examination was performed. We found that the beating arrest rate of cardiac myocytes increased with increasing exposure levels. Vacuolization and pseudopodia could be seen in the cytoplasm of the exposed group. SDH activity decreased with increasing exposure levels. The results suggest that CS2 has a direct and dose‐dependent cytotoxic effect. The biochemical mechanism may be a reduction of the availability of energy (adenosine triphosphate) to cardiac myocytes, resulting in a decrease of contractility by lack of energy. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 324–328, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10070
Possible allelopathic effects of cyanotoxins, with reference to microcystin‐LR, in aquatic ecosystems
Authors: Pflugmacher Stephan
Published: October 2002

During recent years a shift from macrophyte‐dominated to more phytoplankton‐dominated lakes has been correlated to the process of eutrophication. The existence of numerous substances exhibiting allelopathic effects on the growth of algae has been shown in different aquatic macrophytes (e.g., Myriophyllum spicatum) and is thought to be an important mechanism in stabilizing the macrophyte‐dominated clear‐water state of a lake. A few recent studies have shown that algae themselves can produce special substances inhibiting growth or photosynthetic processes in other algae. A well‐known cyanobacterial secondary metabolite, microcystin‐LR, was tested for its allelopathic power on aquatic macrophytes such as Ceratophyllum demersum and Myriophyllum spicatum, resulting in growth inhibition, reduction in photosynthetic oxygen production, and changes in pigment pattern. This shows that microcystin‐LR has a possible role as an allelopathic infochemical. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 407–413, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10071
Rotational augmentation of horizontal axis wind turbine blade aerodynamic response
Authors: Schreck S. , Robinson M.
Published: October 2002

Surface pressure data were acquired using the NREL Unsteady Aerodynamics Experiment, a full‐scale horizontal axis wind turbine, which was erected in the NASA Ames 80 ft × 120 ft wind tunnel. Data were collected first for a stationary blade and then for a rotating blade with the rotor disc at zero yaw. Analyses compared aerodynamic forces and surface pressure distributions under rotating conditions against analogous baseline data acquired from the stationary blade. This comparison allowed rotational modifications to blade aerodynamics to be characterized in detail. Rotating conditions were seen to dramatically amplify aerodynamic forces and radically alter surface pressure distributions. These and subsequent findings will more fully reveal the structures and interactions responsible for these flow field enhancements and help establish the basis for formalizing comprehension in physics‐based models. Copyright © 2002 John Wiley & Sons, Ltd.
Building the San Francisco Beacons
Authors: Eldredge Sue , Piha Sam , Levin Jodi
Published: October 2002

San Francisco's Beacon Initiative is designed to foster youth development on a large scale. Its intermediary, Community Network for Youth Development, used a theory of change process to forge consensus and create a road map to guide this large collaborative toward its long‐term goals.
Homing at an extragenic locus mediated by VDE (PI‐SceI) in Saccharomyces cerevisiae
Authors: Nogami Satoru , Fukuda Tomoyuki , Nagai Yuri , Yabe Shizu , Sugiura Masako , Mizutani Ryuta , Satow Yoshinori , Anraku Yasuhiro , Ohya Yoshikazu
Published: October 2002

PI‐SceI (VDE), a homing endonuclease with protein splicing activity, is a genomic parasite in the VMA1 gene of Saccharomyces cerevisiae. In a heterozygous diploid of the VDE‐less VMA1 allele and a VDE‐containing VMA1 allele, VDE specifically cleaves its recognition sequence (VRS) in the VDE‐less VMA1 allele at meiosis, followed by ‘homing’, i.e. a conversion to a VDE‐containing allele. We found that upon VDE expression, homing of a marker gene at an extragenic locus occurs only when a 45 bp element containing the VRS is inserted at its allelic site, while mutants of VDE with no endonuclease activity lack authentic extragenic homing activity. Thus, both the VRS and VDE are required for homing. Insertion of the VRS in a homozygous diploid significantly lowered the spore germination ability, indicating that a template for gene repair at its allelic locus is essential for efficient homing and survival of yeast cells. Copyright © 2002 John Wiley & Sons, Ltd.
Duikers: Native food composition, micronutrient assessment, and implications for improving captive diets
Authors: Dierenfeld Ellen S. , Mueller Pamela J. , Hall Mary Beth
Published: October 2002

This review summarizes and contrasts published information on the proximate chemical composition of native fruits and leaves eaten by duikers, and adds new data concerning the soluble carbohydrate, mineral, and tannin content of duiker foods. Information on circulating plasma concentrations of minerals and the fat‐soluble vitamins A and E is also summarized in relation to free‐ranging vs. zoo‐held duikers and differences in the nutrient content of their respective diets. In nature, duikers consume diets containing low starch (in general <0.1% of dry matter (DM)) and moderate‐to‐high fiber (averaging 32% DM) and protein (fruits <10%, leaves <20% DM) levels, and do not avoid foodstuffs containing tannins. Native food samples were considered low to marginal in calcium (Ca) and phosphorus (P) content compared with domestic ruminant dietary requirements, but Ca levels were generally two‐ to threefold higher than P concentrations. Diets fed to duikers in captivity are often low in fiber and tannin content, and high in starch and protein, as well as low in Ca relative to P (compared with native plants), which may lead to nutrient imbalances and health problems. Plasma alpha‐tocopherol values measured in zoo duikers ranged from 0.4 to 8.3 μg/ml, and were less variable in free‐ranging animals (1.7–7.0 μg/ml). Retinol values did not differ among duiker species or between sample populations, and were within normal ranges (0.2–0.7 μg/ml) expected for herbivores. Domestic hoofstock appear to be suitable physiological models for evaluating fat‐soluble vitamin status, but mineral homeostasis appears to differ in duikers. Free‐ranging duikers have somewhat higher Ca, and lower P concentrations compared with captive‐held individuals, and inverse Ca:P ratios and copper (Cu) deficiency have been reported in captive duikers—both conditions in which captive diet may play a key role. A frugivorous browser pellet/diet that incorporates the findings summarized here, and better duplicates the chemical complement described for native foods eaten by duikers, may provide health benefits to these small concentrate selectors. Zoo Biol 21:185–196, 2002. © 2002 Wiley‐Liss, Inc.
Stimulation of DNA synthesis in skin fibroblasts by human hepatocyte growth factor/scatter factor.
Authors: Kataoka Hirotoshi , Gohda Eiichi , Matsunaga Tetsuhiko , Ishii Takehisa , Hara Hiroto , Yamamoto Itaru
Published: October 2002

The effect of hepatocyte growth factor/scatter factor (HGF/SF) on the proliferation of human skin fibroblasts was examined. At concentrations above 1.0 ng/ml, both native and recombinant human HGF/SF stimulated the DNA synthesis determined by [3H]thymidine incorporation, which was completely inhibited by an anti‐human HGF/SF monoclonal antibody. The maximal DNA synthesis in the treated cells was nearly twice that in untreated cells. HGF/SF also caused an increase in the labelling index, DNA content and cell number. The effect of HGF/SF was more than additive to the maximal effect of insulin and epidermal growth factor, other mitogens for the fibroblasts. These results indicate that human skin fibroblasts are sensitive to the mitogenic action of HGF/SF.
No change in bone‐specific alkaline phosphatase activities in cultured rat osteoblastic cells under L‐ascorbate and β‐glycerophosphate‐induced mineralization
Authors: Chak C. W. , Lee K. M. , Leung K. S. , Fung K. P.
Published: October 2002

Mineralization occurred both in fetal rat calvarial cells and UMR 106 osteoblastic cells when they were cultured in medium containing L‐ascorbate and β‐glycerophosphate as evidenced by von Kóssa staining as well as deposition of calcium ions and inorganic phosphate in the cells. When compared with corresponding non‐mineralized cell cultures, both the mineralized cultures of calvarial cells and UMR 106 cells did not exhibit any change in intracellular bone‐specific alkaline phosphatase activities which were measured by wheatgerm lectin precipitation method. Our results support the hypothesis that mineralization may not exert any direct negative feedback on matrix protein synthesis in osteoblasts during bone formation.
EFFECT OF MELATONIN ON NF‐κB DNA‐BINDING ACTIVITY IN THE RAT SPLEEN
Authors: CHUANG JIH‐ING , MOHAN NATARAJAN , MELTZ MARTIN L. , REITER RUSSEL J.
Published: October 2002

It was recently demonstrated that the pineal neurohormone melatonin is a hydroxyl radical scavenger and antioxidant, and that it plays an important role in the immune system. In studies reported herein, we have investigated the relationship of the melatonin level and the NF‐κ B DNA binding activity in the spleen of Sprague—Dawley rats. These in vivo results indicate that NF‐ κB DNA binding activity in the spleen is lower at night, when endogenous melatonin levels are elevated, than during the day, when endogenous melatonin levels are lower. Furthermore, exogenously administered melatonin (10mg/kg) was shown to cause a significant decrease in NF‐κB DNA binding activity in the spleen at 60min after intraperitoneal injection (as compared with vehicle‐treated rats). These new findings suggest that the normal night time rise which can be expected for melatonin may be associated with increased NF‐κB DNA binding activity in the spleen. The melatonin, therefore, could potentially act to modulate spleen function and/or the immune system by regulating the NF‐κB DNA binding activity in the spleen.
PRIMARY PEPTIDE SEQUENCES FROM SQUID MUSCLE AND OPTIC LOBE MYOSIN IIs: A STRATEGY TO IDENTIFY AN ORGANELLE MYOSIN
Authors: MEDEIROS NELSON A. , REESE THOMAS S. , JAFFE HOWARD , DEGIORGIS JOSEPH A. , BEARER ELAINE L.
Published: October 2002

The squid giant axon provides an excellent model system for the study of actin‐based organelle transport likely to be mediated by myosins, but the identification of these motors has proven to be difficult. Here the authors purified and obtained primary peptide sequence of squid muscle myosin as a first step in a strategy designed to identify myosins in the squid nervous system. Limited digestion yielded fourteen peptides derived from the muscle myosin which possess high amino acid sequence identities to myosin II from scallop (60–95%) and chick pectoralis muscle (31–83%). Antibodies generated to this purified muscle myosin were used to isolate a potential myosin from squid optic lobe which yielded 11 peptide fragments. Sequences from six of these fragments identified this protein as a myosin II. The other five sequences matched myosin II (50–60%, identities), and some also matched unconventional myosins (33–50%). A single band that has a molecular weight similar to the myosin purified from optic lobe copurifies with axoplasmic organelles, and, like the optic lobe myosin, this band is also recognized by the antibodies raised against squid muscle myosin II. Hence, this strategy provides an approach to the identification of a myosin associated with motile axoplasmic organelles.
OSTEOGENIC GROWTH PEPTIDE ENHANCES THE RATE OF FRACTURE HEALING IN RABBITS
Authors: SUN YAN QUN , ASHHURST DOREEN E.
Published: October 2002

The discovery of growth factors, such as osteogenic growth peptide (OGP), that stimulate bone formation led to experiments to discover whether they can accelerate fracture healing. To determine whether OGP enhances the rate of healing in rabbits, fractures were made in the tibiae of New Zealand White rabbits and immobilized with either a plastic plate (unstable mechanical conditions), or a dynamic compression plate (stable mechanical conditions). OGP was administered to experimental animals by intravenous injection from day 4 until the day before sacrifice; control animals were not injected. After treatment with OGP, callus development under unstable mechanical conditions was accelerated. At 7 days, the cartilage in the centre of the callus was covered by bone and endochondral ossification had started; these events occur at 10 days in control fractures. Subsequently, endochondral ossification is completed earlier which allows the invasion of the fracture gap by cells, so that cortical union is complete by 21 to 28 days. In control fractures, bone is only beginning to form in the gaps at 28 days. There was no increase in the size of the callus in any of the experimental fractures compared to the untreated controls. Treatment with OGP has no observable effect on the rate of healing of fractures under stable mechanical conditions. These observations suggest that under unstable mechanical conditions only, the rate of callus formation and subsequent cortical healing is enhanced by treatment with OGP, but that the size of the callus is determined by mechanical and other factors.
MALIGNANT TRANSFORMATION OF SYRIAN HAMSTER EMBRYO (SHE) CELLS IN PRIMARY CULTURE BY MALACHITE GREEN: TRANSFORMATION IS ASSOCIATED WITH ABROGATION OF G2/M CHECKPOINT CONTROL
Authors: RAO K. V. K. , MAHUDAWALA DAISY M. , REDKAR ALKA A.
Published: October 2002

Malachite green (MG), consisting of green crystals with a metallic lustre, is highly soluble in water, cytotoxic to various mammalian cells and also acts as a liver tumour promoter. In view of its industrial importance and possible exposure to human beings, MG poses a potential environmental health hazard. We have earlier reported the malignant transformation of Syrian hamster embryo (SHE) cells by MG. In this study, we have studied the effects of MG on cell cycle phase distribution of normal and MG transformed Syrian hamster embryo cells in asynchronous and synchronous cell population. DNA flow cytometric analysis indicated that culturing cells for 48h in medium containing MG at different concentrations induced dose‐dependent G2/M arrest in normal cells. Malignantly transformed cells showed no such dose‐responsive accumulation of cells at the G2/M phase of the cell cycle in response to MG. Synchronization studies indicated that in the control, both in the presence and absence of MG, cells followed a normal cell cycle pattern up to 16h. After 16h in the absence of MG, cells continued a normal cell cycle, whereas in the presence of MG they accumulated at G2/M phase of the cell cycle. This pattern of accumulation of cells at the G2/M checkpoint control was not observed in either untreated or MG‐treated transformed cells. The present study indicates efficient operation of G2/M checkpoint control in control SHE cells and its abrogation in transformed SHE cells.
TISSUE TRANSGLUTAMINASE EXPRESSION IN QUAIL EPIPHYSEAL CHONDROCYTES
Authors: Gionti Elisa , Sanchez Massimo , Arcella Antonietta , Pontarelli Gianfranco , Tavassi Simona , Gentile Vittorio , Cozzolino Anna , Porta Raffaele
Published: October 2002

Tissue transglutaminase (tTGase) is a GTP‐binding Ca2+‐dependent enzyme which catalyses the post‐translational modification via ∍(γ‐glutamyl)lysine bridges. The physiological role of tTGase is not fully understood. It has been shown that in cartilage the expression of tTGase correlates with terminal differentiation of chondrocytes. Recent evidence suggests that the GTP‐binding activity of tTGase may play a role in the control of cell cycle progression thus explaining some of the suggested roles for the enzyme.

tTGase activity is present in primary cultures of epiphyseal chondrocytes and increases transiently upon retinoic acid (RA) treatment. Increase in enzyme activity occurs upon RA addition and is accompanied by a parallel increase in protein and mRNA levels. Stimulation of tTGase expression by RA correlates with suppression of cell growth and occurs independently of cell adhesion and cell differentiation.

tTGase expression is not observed in MC2, a permanent chondrocyte cell line derived from retrovirus infected chondrocytes. RA treatment fails to activate tTGase expression in MC2 cells and to completely suppress cell proliferation.

Our findings lend support to the idea that tTGase might play a role in non‐dividing cultured chondrocytes.
DECREASED INTRACELLULAR PROTEOLYSIS CORRELATES WITH THE MAINTENANCE OF A SPECIFIC ISOENZYME OF CYTOCHROME P‐450
Authors: Evans Peter J.
Published: October 2002

The rates of intracellular protein degradation, of identically labelled populations of proteins, were compared in hepatocytes cultured at 37° (on an adsorbed collagen layer) and in cells preserved on gelatin gels at 10°C. The half‐lives of the long‐lived proteins were 35.4±8.6h (N=4) and 692.9±216.9h (N=4) respectively. Proteolysis was substantially decreased at 10°C but the rate of decrease remained constant. Hepatocytes rapidly removed resorufin from the culture medium. The resorufin was not being conjugated or accumulated within the cells. Dicumarol, a potent inhibitor of quinone oxidoreductase, at high concentration (500μm) caused only a 72% decrease in the utilization of resorufin. The microsomal detoxifying enzyme, cytochrome P‐450 1A1 remained at a constant level in the preserved hepatocyte monolayers. The results of this study strongly favour storing hepatocytes at 10°C rather than at 4° or 37°C.
Vasopressin stimulates tyrosine phosphorylation by activation of pkc in the rat smooth muscle cell line, a‐10
Authors: Gonzalez CARLOS B. , Reyes Carlos E. , Figueroa Carlos D. , Barra Valeria , Troncoso Silvia
Published: October 2002

Arginine vasopressin (AVP)‐induced tyrosine phosphorylation was studied in a rat smooth muscle cell line, A‐10, by western blotting, using a monoclonal antibody against phosphotyrosine. AVP stimulated the phosphorylation of several cellular proteins of molecular mass 60–130kDa in a time‐ and dose‐dependent manner. Phosphorylation was mediated largely by V1receptor subtype since it was inhibited by selective V1antagonist and was only partially elicited by the V2agonist, desmopressin. Heterotrimeric G‐proteins seemed to be involved in the phosphorylation mechanism because fluoraluminates, an activator of heterotrimeric G‐proteins (and thus an uncoupler of the receptor—G‐protein interaction) inhibited the AVP‐induced phosphorylation. The protein kinase C (PKC) inhibitors: staurosporine, H7 and GF109203X are able to block the AVP‐stimulated phosphorylation. The last of these has been shown to be one of the most selective inhibitors of PKC. These results indicate that PKC is upstream of the phosphorylation, a motion which is supported by the fact that the AVP‐stimulated phosphorylation was downregulated by phorbol esters.
DIRECT CHEMOTACTIC EFFECT OF BRADYKININ AND RELATED PEPTIDES—SIGNIFICANCE OF AMINO‐ AND CARBOXYTERMINAL CHARACTER OF OLIGOPEPTIDES IN CHEMOTAXIS OF TETRAHYMENA PYRIFORMIS
Authors: Koőhidai László , Kovács Krisztina , Csaba György
Published: October 2002

The chemotactic character of the nonapeptide bradykinin (BK1–9) and its derivatives was studied in the eukaryotic ciliated model Tetrahymena pyriformis. The results demonstrate that BK1–9 has a direct and ligand‐specific chemoattractant effect (maximal at 10−11m) without any intermediate substance as is essential in some mammalian test systems. Evaluation of the chemotactic effect elicited by derivatives showed that the presence of N‐ and C‐terminal arginines can influence chemotactic potency of the molecule via expression of pyrrolidine and aromatic ring structures of terminal amino acid residues. Removal of the N‐terminal Arg (expression of Pro) results in a significant decrease in chemotaxis (BK2–9), while further truncation of the C‐terminal, causing expression of the aromatic ring of Phe (BK2–8), results in a highly chemoattractant variant. A single pyrrolidine ring on the C‐terminus BK1–7 also has a positive effect on the chemotactic character, however further truncation (BK1–6, BK1–5) causes the chemoattractant character to become chemorepellent. Study of chemotactic selection with BK derivatives supports our previous findings that only phylogenetically selected ligands or their close derivatives are able to induce long‐term selection with chemotaxis.
HUMAN ARTICULAR CHONDROCYTES EXPRESS THREE FACILITATIVE GLUCOSE TRANSPORTER ISOFORMS: GLUT1, GLUT3 AND GLUT9
Authors: Mobasheri A. , Neama G. , Bell S. , Richardson S. , Carter S. D.
Published: October 2002

Glucose is an important metabolite and a structural precursor for articular cartilage and its transport has significant consequences for cartilage development and functional integrity. In this study the expression of facilitative glucose transporters (GLUTs) in human chondrocytes was investigated. Results showed that at least three GLUT isoforms (GLUT1, GLUT3 and GLUT9) are expressed by normal chondrocytes. Given the central role of glucose in chondrocyte physiology and metabolism, its regular provision via GLUTs will influence the metabolic activity and survival of chondrocytes in cartilage matrices.
A New Species in the Lichen Genus Fuscoderma from New Guinea
Authors: Jørgensen P. M. , Sipman H. J. M.
Published: October 2002

Fuscoderma papuanorum is described as the first species of this genus to occur so close to the Equator, being part of the austral element of the New Guinea flora. The genus appears to be of considerable age.
Unstable Behavior of the Laurentide Ice Sheet over Deforming Sediment and Its Implications for Climate Change
Authors: Clark Peter U.
Published: October 2002

Geologic records of fluctuations of the Laurentide ice sheet margin following the most recent glacial maximum (ca.20,00014C yr B.P.) identify fundamental differences in ice-sheet behavior depending on subglacial bed conditions. Rapid and irregular icemargin fluctuations occurred only over areas of deforming sediment, indicating nonclimatic forcing controlled by the inherent instability of coupled ice sheet-deforming sediment dynamics. In contrast, largely uninterrupted ice-margin retreat with no evidence of significant readvance occurred over rigid-bed areas, indicating stable behavior. Unstable ice-sheet behavior was most pronounced from 15,000 until 10,00014C yr B.P., by which time most of the ice margin had retreated onto a rigid bed. Unstable ice-sheet behavior would have been an integral component in controlling variable fluxes of icebergs and meltwater, as well as meltwater routing, to the North Atlantic, thus affecting thermohaline circulation. The abrupt climate oscillations in the North Atlantic region that ended at 10,00014C yr B.P. may thus have their origin in the inherently unstable behavior of the Laurentide ice sheet overriding deforming sediment.
Paleoecological Studies of a Holocene Lacustrine Record from the Kangerlussuaq (Søndre Strømfjord) Region of West Greenland
Authors: Eisner Wendy R. , Törnqvist Torbjörn E. , Koster Eduard A. , Bennike Ole , van Leeuwen Jacqueline F.N.
Published: October 2002

A lacustrine sediment record from the Kangerlussuaq region, West Greenland, has resulted in a pollen, macrofossil, and sediment stratigraphy that encompasses the last 500014C yr. Deglaciation of the area and subsequent development of a nearby floodplain occurred before 5000 yr B.P. Since that time eolian sand and silt deposition appear to have been continuous, with a significant increase ca. 100014C yr B.P. Pollen analysis shows little change in the character of the vegetation throughout the record. Fluctuations in herb pollen taxa indicate changes in the extent and development of eolian sand sheets. The oldest pollen zone records relatively little pollen accumulation and low taxa diversity. This is followed by a zone of high pollen accumulation, presumably a phase of highest vegetation density, from 4400 to 340014C yr B.P. Thereafter, declining pollen accumulation rates reveal a gradual environmental deterioration. Macrofossil analyses record significant limnological changes, with an early eutrophic phase followed by a masotrophic phase and a reversal to more eutrophic conditions in the final phase. The preserved record illustrates the interactions of deglaciation, eolian activity, regional vegetation, and limnological change.
Postglacial Vegetation and Climate of the Cascade Range, Central Oregon
Authors: Sea Debra S. , Whitlock Cathy
Published: October 2002

Pollen data from two sites provide information on the postglacial vegetation and climate history of the Cascade Range. Indian Prairie in the western Cascade Range was colonized by subalpine forests ofPinus, Picea,andTsugaand open meadows prior to ca. 12,40014C yr B.P. The treeline lay 500 to 1000 m below its modern elevation and conditions were cooler than at present. From ca. 12,400 to ca. 995014C yr B.P.Abiesbecame important and the forest resembled that presently found at middle elevations in the western Cascade Range. The pollen record implies a rise in treeline and warmer conditions than before. From ca. 10,000 to 4000-450014C yr B.P., conditions that were warmer and effectively drier than today led to the establishment of a closed forest composed ofPseudotsuga, Abies, and, at lower elevations,QuercusandCorylus. During this period, Gold Lake Bog in the High Cascades was surrounded by closed forest ofPinusandAbies. The early-Holocene pollen assemblages at both Indian Prairie and Gold Lake Bog lack modern analogues, and it is likely that greater-than-present summer radiation fostered unique climatic conditions and vegetation associations at middle and high elevations. In the late Holocene, beginning ca. 4000-450014C yr B.P., cooler and more humid conditions prevailed and the modern vegetation was established. A comparison of these sites with others in the Pacific Northwest suggests that major patterns of vegetational change at individual sites were a response to large-scale changes in the climate system that affected the entire region.
Vegetation and Seasonality Shifts during the Late Quaternary Deduced from 13C/12C Ratios of Grazers at Equus Cave, South Africa
Authors: Lee-Thorp Julia A. , Beaumont Peter B.
Published: October 2002

Season of rainfall can be a major influence on the relative proportions of C3 and C4 grasses in a landscape, since their relative distribution is essentially constrained by temperatures during the growing season; cool growing seasons favor C3 grasses, whereas warm ones favor C4 grasses. 13C/12C ratios in tooth enamel carbonate of grazers from the site of Equus Cave, northern Cape Province, South Africa, were used to determine vegetation and rainfall seasonality shifts during the late Quaternary. The results show shifts in the relative proportion of C3 and C4 grasses during the latter stages of the Pleistocene, and domination by C4 grasses in the Holocene. The data show that the northwestern Cape did not fall within a winter rainfall zone during this period as has been postulated in recent climate models. Instead, a more complex situation is suggested in which at least two periods of enhanced winter rainfall occurred within a predominantly summer rainfall regime.
Modern and Holocene Pollen Assemblages from Some Small Arctic Lakes on Somerset Island, NWT, Canada
Authors: Gajewski Konrad
Published: October 2002

Modern pollen samples from 15 lakes along a north-south transect on western Somerset Island, NWT, Canada, show a decrease in pollen concentrations from the high arctic to the mid-arctic zone, but there are few differences in the pollen percentages between these sites. Long-distance transport accounts for up to 50% of the pollen in these lake sediments. Cores from two lakes show few changes in the percentages of important pollen types, except for an initial period, before 6000 yr B.P., of increased Salix. The pollen concentration of lake RS36 from the mid-arctic is twice that of lake RS29 from the high arctic, and at both sites the concentrations decreased during the past 6000 yr B.P. This suggests a climatic deterioration during the past 6000 yr which has caused a decrease in the abundance of plants on the landscape.
New Radiocarbon Dates for the Vedde Ash and the Saksunarvatn Ash from Western Norway
Authors: Birks Hilary H. , Gulliksen Steinar , Haflidason Haflidi , Mangerud Jan , Possnert Göran
Published: October 2002

The Vedde Ash Bed (mid-Younger Dryas) and the Saksunarvatn Ash (early Holocene) are important regional stratigraphic event markers in the North Atlantic, the Norwegian Sea, and the adjacent land area. It is thus essential to date them as precisely as possible. The occurrence of the Saksunarvatn Ash is reported for the first time from western Norway, and both tephras are dated precisely by AMS analyses of terrestrial plant material and lake sediment at Kråkenes. The Vedde Ash has been previously dated at sites in western Norway to about 10,600 yr B.P. It is obvious in the Younger Dryas sediments at Kråkenes, and its identity is confirmed geochemically. The mean of four AMS dates of samples of Salix herbacea leaves adjacent to the tephra is 10,310 ± 50 yr B.P. The Saksunarvatn Ash is not visible in the early Holocene lake sediment at Kråkenes. After removal of organic material and diatoms, the identity of the tephra particles was confirmed geochemically, and their stratigraphic concentration was estimated. From curve matching of a series of seven AMS dates of terrestrial plant macrofossils and whole sediment, the radiocarbon age of the ash is 8930–9060 yr B.P., corresponding to an age of 9930–10,010 cal yr B.P. (7980–8060 cal yr B.C.).
Late Quaternary Lake-Level Record from Northern Eurasia
Authors: Harrison Sandy P. , Yu Ge , Tarasov Pavel E.
Published: October 2002

Lake records from northern Eurasia show regionally coherent patterns of changes during the late Quaternary. Lakes peripheral to the Scandinavian ice sheet were lower than those today but lakes in the Mediterranean zone were high at the glacial maximum, reflecting the dominance of glacial anticyclonic conditions in northern Europe and a southward shift of the Westerlies. The influence of the glacial anticyclonic circulation attenuated through the late glacial period, and the Westerlies gradually shifted northward, such that drier conditions south of the ice sheet were confined to a progressively narrower zone and the Mediterranean became drier. The early Holocene shows a gradual shift to conditions wetter than present in central Asia, associated with the expanded Asian monsoon, and in the Mediterranean, in response to local, monsoon-type circulation. There is no evidence of mid-continental aridity in northern Eurasia during the mid-Holocene. In contrast, the circum-Baltic region was drier, reflecting the increased incidence of blocking anticyclones centered on Scandinavia in summer. There is a gradual transition to modern conditions after ca. 5000 yr B.P. Although these broad-scale patterns are interrupted by shorter term fluctuations, the long-term trends in lake behavior show a clear response to changes in insolation and glaciation.
Climate Variability on the Yucatan Peninsula (Mexico) during the Past 3500 Years, and Implications for Maya Cultural Evolution
Authors: Curtis Jason H. , Hodell David A. , Brenner Mark
Published: October 2002

Climate variability on the Yucatan Peninsula during the past 3500 yrs is reconstructed from the measurement of δ18O in monospecific ostracods and gastropods in a 6.3-m sediment core from Lake Punta Laguna, Mexico. This late Holocene record is divided into three periods based on changes in mean δ18O values. From ∼3310 to ∼1785 14C yr B.P. (Period I), low mean δ18O values indicate relatively wet conditions (i.e., low evaporation to precipitation ratio, E/P). Mean oxygen isotopic values increased ∼1785 14C yr B.P., and the interval between ∼1785 and ∼930 14C yr B.P. (Period II) was distinctly drier than the periods before or after. The climate during the latter part of Period II was persistently dry, with exceptionally arid events centered at ∼1171, 1019, and 943 14C yr B.P. (equivalent to 862, 986, and 1051 A.D.). This interval of frequent drought was recorded at several other localities in Mexico and Central America, and coincided with the collapse of Classic Maya civilization. Following the last arid event, δ18O values decreased abruptly at ∼930 14C yr B.P. (beginning of Period III), signaling a return to wetter conditions that have generally prevailed to the present, with the exception of a dry episode centered at 559 14C yr B.P. (1391 A.D.). The paleoclimatic record from Punta Laguna provides evidence that multi-decadal and millennial-scale changes in E/Poccurred on the Yucatan Peninsula during the late Holocene. These wet/dry episodes may have influenced cultural evolution in Mesoamerica.
Late Quaternary Earthquake Chronology from Luminescence Dating of Colluvial and Alluvial Deposits of the Arava Valley, Israel
Authors: Porat Naomi , Wintle Ann G. , Amit Rivka , Enzel Yehouda
Published: October 2002

Luminescence ages help provide a time scale for recurrent surface ruptures on a normal fault in the southern Arava, Israel. The dated samples come from alluvium and colluvium along a fault scarp north of Elat. The ages, obtained mainly by infrared stimulation of sand-size potassium feldspar grains, accord with geomorphic age estimates from soils and degraded scarps. Four large earthquakes occurred between 37,000 and 14,000 yr ago. Five smaller earthquakes occurred thereafter continuing until recent times. The mean recurrence interval for earthquakes of magnitudes greater than 6 is about 4000 yr.
Climate Variation and the Rise and Fall of an Andean Civilization
Authors: Binford Michael W. , Kolata Alan L. , Brenner Mark , Janusek John W. , Seddon Matthew T. , Abbott Mark , Curtis Jason H.
Published: October 2002

Paleolimnological and archaeological records that span 3500 years from Lake Titicaca and the surrounding Bolivian–Peruvian altiplano demonstrate that the emergence of agriculture (ca. 1500 B.C.) and the collapse of the Tiwanaku civilization (ca. A.D. 1100) coincided with periods of abrupt, profound climate change. The timing and magnitude of climate changes are inferred from stratigraphic evidence of lake-level variation recorded in14C-dated lake-sediment cores. Paleo-lake levels provide estimates of drainage basin water balance. Archaeological evidence establishes spatial and temporal patterns of agricultural field use and abandonment. Prior to 1500 B.C., aridity in the altiplano precluded intensive agriculture. During a wetter period from 1500 B.C. to A.D. 1100, the Tiwanaku civilization and its immediate predecessors developed specialized agricultural methods that stimulated population growth and sustained large human settlements. A prolonged drier period (ca. A.D. 1100–1400) caused declining agricultural production, field abandonment, and cultural collapse.
Magnetic Polarity and Fission-Track Chronology of a Late Pliocene–Pleistocene Paleoclimatic Proxy Record in the Tropical Andes
Authors: Helmens Karin F. , Barendregt Rene W. , Enkin Randolph J. , Baker Judith , Andriessen Paul A.M.
Published: October 2002

Two sections exposing a Late Pliocene–Pleistocene sedimentary sequence in the marginal valleys of the Bogotá Basin (Colombian Andes, South America) were sampled for paleomagnetic analysis. Magnetostratigraphy and fission-track dates of tephra beds provide a detailed geochronologic calibration for the sedimentary basin. Measurements of magnetic susceptibility complement the regional environmental record provided by lithological and palynological evidence. Sedimentation in the Bogota Basin started in the early part of the Gauss Chron at ca. 3.2 myr. The oldest recorded sediments belong to the Guasca Member of the Upper Tilatá Formation. They were deposited in a lacustrine/paludal environment, near the end of the tectonic uplift in the Bogotá area, and/or under Pliocene climatic conditions that were warmer than today. Repeated climate cooling associated with glaciations in the surrounding mountains resulted in the deposition of a fluvial–lacustrine complex referred to as the Subachoque Formation. The first glaciation is placed near the Gauss/Matuyama polarity reversal at 2.6 myr. A lithologic change in the Subachoque Formation marked by coarser-grained fluvial deposits and a possible increase in amplitude of the magnetic susceptibility signal occurs near the Matuyama/Brunhes boundary at 0.8 myr, indicating a shift toward higher magnitude climate oscillations.
Implications of Subfossil Coleoptera for the Evolution of the Mima Mounds of Southwestern Puget Lowland, Washington
Authors: Nelson Robert E.
Published: October 2002

The origin of Washington State's Mima Mounds has been debated for over a century, with numerous mechanisms being postulated. Subfossil Coleopteran (beetle) remains recovered from the base of a mound at Mima Prairie consist of species that would be expected in rodent burrows and nests; all but one species are obligate burrow inhabitants. These results suggest the past presence of fossorial rodents (probably pocket gophers,Thomomys mazama) in the mounds, although none live there at present. Whether or not the gophers created the mounds, they may well have been instrumental in maintaining mound geometry until very recently.
Reliable Late-Pleistocene Stratigraphic Ages and Shorter Groundwater Travel Times from14C in Fossil Snails from the Southern Great Basin
Authors: Brennan Robert , Quade Jay
Published: October 2002

Both aquatic and land snails are common in the geologic record, but their utility in dating is greatly restricted by their well-documented tendency to yield14C dates inconsistent with true14C ages. In this study, we examine the use of14C ages from (1) small, previously unstudied, terrestrial snails to date hosting spring deposits and from (2) cooccuring aquatic snails to constrain groundwater travel times during the last glacial period. Our study area in the southern Great Basin encompasses Yucca Mountain, site of the proposed high-level nuclear waste repository, where information on the age and extent of past high water tables and on groundwater flow times is crucial to several licensing issues. Our results show that shells of small terrestrial snails belonging toValloniasp. yield14C dates consistent with14C ages of associated carbonized wood. These results imply that these taxa can provide reliable14C age control on the broadly distributed deposits in which they have been described. In contrast, cooccurring aquatic snails from fossil spring deposits yield14C ages generally greater than the control age. This is because the aquatic shells often formed in spring waters that had an initial14C deficiency. However, the magnitude of the deficiency is much less than that observed in nearby modern springs, arguing for much higher average14C contents in late Pleistocene groundwaters in these basins. If representative, this implies shorter groundwater travel times through aquifers in southern Nevada during late-glacial time.
A Reassessment of U-Th and14C Ages for Late-Glacial High-Frequency Hydrological Events at Searles Lake, California
Authors: Lin Jo C. , Broecker Wallace S. , Hemming Sidney R. , Hajdas Irena , Anderson Robert F. , Smith George I. , Kelley Maxwell , Bonani Georges
Published: October 2002

U-Th isochron ages of tufas formed on shorelines suggest that the last pluvial event in Lake Lahontan and Searles Lake was synchronous at about 16,500 cal yr B.P. (equivalent to a radiocarbon age of between 14,000 and 13,500 yr B.P.), whereas the timing of this pluvial event determined by radiocarbon dating is on the order of 1000 yr younger. The timing of seven distinct periods of near desiccation in Searles Lake during late-glacial time has been reinvestigated for U-Th age determination by mass spectrometry. U-Th dating of evaporite layers in the interbedded mud and salt unit called the Lower Salt in Searles Lake was hampered by the uncertainty in assessing the initial230Th/232Th of the samples. The resulting ages, corrected by a conservative range of initial230Th/232Th ratios, suggest close correlation of the abrupt changes recorded in Greenland ice cores (Dansgaard-Oeschger events) and wet–dry conditions in Searles Lake between 35,000 and 24,000 cal yr B.P.
Black Mats, Spring-Fed Streams, and Late-Glacial-Age Recharge in the Southern Great Basin
Authors: Quade Jay , Forester Richard M. , Pratt William L. , Carter Claire
Published: October 2002

Black mats are prominent features of the late Pleistocene and Holocene stratigraphic record in the southern Great Basin. Faunal, geochemical, and sedimentological evidence shows that the black mats formed in several microenvironments related to spring discharge, ranging from wet meadows to shallow ponds. Small land snails such asGastrocopta tappanianaandVertigo berryiare the most common mollusk taxa present. Semiaquatic and aquatic taxa are less abundant and include Catinellids,Fossaria parva, Gyraulus parvus,and others living today in and around perennial seeps and ponds. The ostracodesCypridopsis okeechobiandScottia tumida,typical of seeps and low-discharge springs today, as well as other taxa typical of springs and wetlands, are common in the black mats. Several new species that lived in the saturated subsurface also are present, but lacustrine ostracodes are absent. The δ13C values of organic matter in the black mats range from −12 to −26‰, reflecting contributions of tissue from both C3(sedges, most shrubs and trees) and C4(saltbush, saltgrass) plants. Carbon-14 dates on the humate fraction of 55 black mats fall between 11,800 to 6300 and 230014C yr B.P. to modern. The total absence of mats in our sample between 6300 and 230014C yr B.P. likely reflects increased aridity associated with the mid-Holocene Altithermal. The oldest black mats date to 11,800–11,60014C yr B.P., and the peak in the14C black mat distribution falls at ∼10,00014C yr B.P. As the formation of black mats is spring related, their abundance reflects refilling of valley aquifers starting no later than 11,800 and peaking after 11,00014C yr B.P. Reactivation of spring-fed channels shortly before 11,20014C yr B.P. is also apparent in the stratigraphic records from the Las Vegas and Pahrump Valleys. This age distribution suggests that black mats and related spring-fed channels in part may have formed in response to Younger Dryas (YD)-age recharge in the region. However, the inception of black mat formation precedes that of the YD by at least 40014C yr, and hydrological change is gradual, not rapid.