bluuebunny/crossref_metadata_2025_split huggingface dataset:
TAXOL REDUCES THE RATE OF CYTOKINESIS IN PtK1CELLS
Authors: SNYDER JUDITH A. , MCLELLAND SANDRA L. 
Published: October 2002

AbstractMitotic PtK1cells were treated both during mid‐anaphase and at furrow initiation with the potent microtubule (MT) stabilizing agent, taxol, to determine the role of MTs in the rate of cytokinetic events. Rates of cytokinesis (μm/min) were measured by changes in furrow diameter. Incubation of PtK1cells during mid‐anaphase with 5 μg/ml taxol slows the rate of cytokinesis by an average of 43%. Instead of furrow initiation to midbody formation taking an average of 10.7 min (1.6 μm/min), furrowing to midbody formation was completed in an average of 19.0 min (0.9 μm/min), which does not include the 7‐min period between taxol application in mid‐anaphase and furrow initiation. Application of 5 μg/ml taxol to cells at furrow initiation had a reduced effect on decreasing the rate of cytokinesis and midbody formation; furrowing to midbody formation took an average of 14.6 min (1.2 μm/min). These data suggest that delays in the rate of cytokinesis is dependent on the mitotic stage at which taxol is applied. Ultrastructural analysis shows that taxol treatment of anaphase cells prevents midbody formation during early G1, yet MT number and organization in the furrowed region is not significantly altered from untreated cells. There is little change in the organization and amount of contractile ring microfilaments, yet filaments are also found parallel to midbody MTs. Our results may be explained by the fact that taxol tends to stabilize MTs which probably affects the rate at which they depolymerize in the terminal phases of cytokinesis. Reduction in depolymerization rates of a stable population of MTs could serve to regulate the rate of cytokinesis.
ALZHEIMER'S SOLUBLE AMYLOID BETA PROTEIN IS SECRETED BY HEPG2 CELLS AS AN APOLIPOPROTEIN
Authors: KOUDINOV ALEXEI R. , KOUDINOVA NATALIA V. 
Published: October 2002

AbstractRecently we reported that the soluble form of amyloid beta protein (sAβ) in normal human plasma and cerebrospinal fluid is associated with lipoprotein (LP) particles. In this paper we tested the sAβ secretion by cells in association with LP in the model of the human hepatoma HepG2 cell line. These cells secreted sAβ to the culture media and expressed intracellular sAβ immunoreactivity. Soluble Aβ in the cell supernatant was detected in 200–300kDa LP complexes in association with apoA‐I, apoJ, transthyrethin and phospholipids, triglycerides and free and esterified cholesterol. This was assessed by size exclusion HPLC, immunoprecipitation with corresponding antibodies and by analysis of sAβ associated metabolically‐labeled lipids, respectively. Our results suggest that sAβ to LP association represents a unique mechanism, governing the normal biology of sAβ.
CONTACT GUIDANCE OF CHICK EMBRYO NEURONS ON SINGLE SCRATCHES IN GLASS AND ON UNDERLYING ALIGNED HUMAN SKIN FIBROBLASTS
Authors: Stepień E. , Stanisz J. , Korohoda W. 
Published: October 2002

AbstractThe influence of substratum topography on the morphology and orientation of neurites of chick embryo neurons was studied.Two series of experiments are reported. One concerned the behaviour of growth cones when the axons become contact‐guided by the surface texture. The second studied contact guidance of neurites extending on a compact layer of fixed aligned human skin fibroblasts (HSF).It was observed that when the growth cones of sensory neurons isolated from dorsal root ganglions encountered a single scratch in a glass surface (0.1–2μm in depth and diameter) they turned and continued movement following the axis of the scratch. These neurons became contact‐guided as a result of the sequence of events. The growth cone filopodia recognized the irregularity in the substratum surface, whereas the growth cone lamella stabilized contact with the scratch and moved forward along the scratch axis. Scanning electron microscope revealed that the single scratches 150nm in width and ca. 100nm deep growth cone filopodia less than 200nm in diameter could detect and react by turning into them. These filopodia extensions followed the edge of scratches. However, phase contrast and Nomarski's differential interference contrast appeared insufficient for analysis of primary contact guidance of fine growth cone filopodia which themselves are often less than 200nm. In neuron cultures on fixed aligned HSF, the neuron aggregates assumed spindle‐like shapes, and sparsely seeded individual neurons extended axons along the long axes of the fibroblasts. The axons extended significantly further on the fixed underlying fibroblasts than on collagen‐covered glass. In crowded cultures of neurons, the cells extended neurites ignoring both the surface anisotropy (the scratches) and the orientation of the aligned fibroblasts. Immunofluorescence staining of neurons with antibodies against neurofilaments made it possible to analyse their shape and orientation on the fibroblasts. Computer‐assisted image analysis permitted the observed alignment of the neurites to be characteriezed quantitatively.
INVOLVEMENT OF GLUTATHIONE AND GLUTATHIONE‐RELATED ENZYMES IN THE PROTECTION OF NORMAL AND TRISOMIC HUMAN FIBROBLASTS AGAINST DAUNORUBICIN
Authors: Zatorska Agnieszka , Józwiak Zofia 
Published: October 2002

AbstractWe measured the glutathione content, and the activity of glutathione‐related enzymes and DT‐diaphorase in cultured normal (cell line: S‐126) and trisomic (cell lines: S‐158, S‐240) human fibroblasts exposed to daunorubicin (DNR). Determination of reduced and total glutathione levels, and measurement of the activity of glutathione peroxidase, glutathione reductase, glutathione‐S‐transferase and DT‐diaphorase were performed spectrophotometrically. Human fibroblasts were exposed to 4μ m DNR for 2h, and the cells placed in drug‐free medium for 6, 12, 24, 48, and 72h. Cellular levels of GSH and total glutathione decreased following exposure to DNR. However, the ratio of GSH to total glutathione returned to control levels only in trisomic cells. These changes were concomitant with increasing glutathione‐S‐transferase and glutathione reductase activities. DNR also significantly increased the activity of Se‐independent peroxidase and DT‐diaphorase in trisomic fibroblasts. Marked increases in the activity of Se‐dependent peroxidase and DT‐diaphorase alone were seen in normal cells. The results provide the first evidence that DNR can induce alterations in the level of glutathione and glutathione‐dependent enzymes in trisomic fibroblasts as compared to normal cells, which may provide additional protection against daunorubicin‐induced oxidative stress in trisomic fibroblasts.
EXTREMELY LOW FREQUENCY (ELF) PULSED‐GRADIENT MAGNETIC FIELDS INHIBIT MALIGNANT TUMOUR GROWTH AT DIFFERENT BIOLOGICAL LEVELS
Authors: Zhang Xinchen , Zhang Husheng , Zheng Congyi , Li Chaoyang , Zhang Xinsong , Xiong Wei 
Published: October 2002

AbstractExtremely low frequency (ELF) pulsed‐gradient magnetic field (with the maximum intensity of 0.6–2.0T, gradient of 10–100T·M−1, pulse width of 20–200ms and frequency of 0.16–1.34Hz treatment of mice can inhibit murine malignant tumour growth, as seen from analyses at different hierarchical levels, from organism, organ, to tissue, and down to cell and macromolecules. Such magnetic fields induce apoptosis of cancer cells, and arrest neoangiogenesis, preventing a supply developing to the tumour. The growth of sarcomas might be amenable to such new method of treatment.
Late Quaternary Environmental and Climatic Changes in Central Brazil
Authors: Ledru Marie-Pierre 
Published: October 2002

AbstractPaleoenvironmental changes dating back to 30,000 yr B.P. documented in a pollen record from central Brazil (lat. 19°S) permit the reconstruction of climatic changes related to shifts of the Antarctic polar fronts. The paleoclimatic inferences were obtained by a study of modern vegetation and pollen distribution, taking into account present-day climatic parameters. At 30,000 yr B.P. the climate must have been warmer and moister than today judging from the high amount of tree pollen taxa characteristic of floodplain forest. From 17,000 to 14,000 yr B.P. the climate was drier although tree pollen percentages were relatively high. After 12,000 yr B.P.Araucariaforest elements increased, suggesting a moister and cooler climate. TheAraucariaforest disappeared during a short interval between 11,000 and 10,000 yr B.P. This could be related to the Younger Dryas event. At the beginning of the Holocene the climate became cool and moist again, as indicated by the reexpansion of theAraucariaforest. The latter was progressively replaced by a mesophytic semideciduous forest indicating warmer and drier climate after 8500 yr B.P. At 5000 yr B.P. an arid interval was followed by the expansion of mesophytic semideciduous forest elements.
A Model of Pollen Source Area for an Entire Lake Surface
Authors: Sugita Shinya 
Published: October 2002

AbstractA model of pollen deposition on the surface of an entire basin is developed to estimate pollen source area, and results are compared with those for a point at the center of a basin (I. C. Prentice, 1985,Quaternary Research23, 76-86; 1988, "Vegetation History," (pp. 17-42, Kluwer Academic). This model is more appropriate for approximating the source area of pollen in lake sediment, since mixing in lake water and focusing of sediment redistribute pollen originally deposited over the entire surface. In general, the pollen source radius for the entire basin surface is 10-30% smaller than the source radius for a point at the center; the difference in the source radius is more profound for heavier pollen types such as spruce and sugar maple than for lighter types such as oak and ragweed. The average pollen input to the entire surface is more strongly influenced by nearby pollen sources than pollen deposition at the center. The pollen record from a lake may therefore provide different spatial resolution than the record from a bog of similar radius.
Late Quaternary Records of the Atmospheric Input of Eolian Dust to the Center of the Chinese Loess Plateau
Authors: Zhang Xiaoye , An Zhisheng , Chen Tuo , Zhang Guangyu , Arimoto Richard , Ray Barbara J. 
Published: October 2002

AbstractThe concentrations of 15 elements and mineral grain-size distributions were determined for Late Quaternary loess sediments from the Chinese Loess Plateau. Particle-size distributions of the loess were approximately log-normal for each of three modes (i.e., 0.04 to 1 μm diameter, 2 to 20 μm, and 20 to 200 μm) that integrate the transport and deposition of eolian dust. The mass particle-size distributions of typical crustal elements (Si, Ca, Fe, Ti, K, Mn, and V) in paleosol and loess samples show patterns similar to those of mineral aerosols, but higher concentrations occur in the submicrometer sediment particles. Absolute principal component analysis of the elemental data suggests that the loess can be described in terms of synsedimentary and postdepositional concentration and subvertical migration of CaCO3 and various elements through the deposit. A variety of geochemical indicators in the loess are apparently sensitive to Asian monsoon variations; these include the mass ratio of course to fine particles, the concentration ratios of certain trace elements, the elemental fluxes associated with eolian dust, and the bulk concentration of Ca in the sediments.
Climatic Interpretation of Alpine Snowline Variations on Millennial Time Scales
Authors: Seltzer Geoffrey O. 
Published: October 2002

AbstractThe depression of snowlines, or equilibrium-line altitudes, of alpine glaciers is often used by glacial geologists to infer variations in mass balance. The climatic interpretation of snowline depression, however, is complicated by the number of factors that control glacier mass balance. The simple lapse-rate method of temperature interpretation ignores the effects of changes in radiation and snow accumulation. The statistical approach to temperature interpretation, which regresses precipitation and temperature against snowline altitude, neglects the effect of radiation. The most comprehensive approach for the climatic interpretation of snowline depression couples the heat and mass balances of a glacier surface. A sensitivity analysis that utilizes the coupled heat- and mass-balance approach indicates that the ∼1000-m variation in snowline of alpine glaciers on glacial-to-interglacial time scales could be a result of significant changes in temperature, and to a lesser extent changes in insolation. Snowline variations are sensitive only to relatively large changes in annual accumulation, which should also be evident in other proxy records of moisture change. The approaches outlined here provide glacial geologists with a summary of how various climatic forcings associated with glaciation may be quantified from snowline data.
Evidence for a Large Earthquake and Tsunami 100-400 Years Ago on Western Vancouver Island, British Columbia
Authors: Clague John J. , Bobrowsky Peter T. 
Published: October 2002

AbstractA peaty marsh soil is sharply overlain by a sand sheet and intertidal mud at tidal marshes near Tofino and Ucluelet, Vancouver Island, British Columbia. Foraminifera and vascular plant fossils show that the buried soil was submerged suddenly and was covered quickly by sand. Radiocarbon ages place this event between 100 and 400 yr ago. The coastal subsidence suggested by the submergence occurred in an area of net late Holocene emergence, perhaps during the most recent great earthquake on the northern part of the Cascadia subduction zone. The sand sheet overlying the peaty soil records the tsunami triggered by this earthquake. Similar stratigraphic sequences of about the same age have been reported from estuaries along the outer coasts of Washington and northern Oregon, suggesting that hundreds of kilometers of the Cascadia subduction zone may have ruptured during one, or a series of plate-boundary earthquakes less than 400 yr ago.
Glacier Modeling and the Climate of Patagonia during the Last Glacial Maximum
Authors: Hulton Nick , Sugden David , Payne Antony , Clapperton Chalmers 
Published: October 2002

AbstractIce cap modeling constrained by empirical studies provides an effective way of reconstructing past climates. The former Patagonian ice sheet is in a climatically significant location since it lies athwart the Southern Hemisphere westerlies and responds to the latitudinal migration of climatic belts during glacial cycles. A numerical model of the Patagonian ice cap for the last glacial maximum (LGM) is developed, which is time-dependent and driven by changing the mass balance/altitude relationship. It relies on a vertically integrated continuity model of ice mass solved over a finite difference grid. The model is relatively insensitive to ice flow parameters but highly sensitive to mass balance. The climatic input is adjusted to produce the best fit with the known limits of the ice cap at the LGM. The ice cap extends 1800 km along the Andes and has a volume of 440,000 km3. During the LGM the equilibrium line altitude (ELA) was lower than at present by at least 560 m near latitude 40°S, 160 m near latitude 50°S, and 360 m near latitude 56°S. The latitudinal variation in ELA depression can be explained by an overall fall in temperature of about 3.0°C and the northward migration of precipitation belts by about 5° latitude. Annual precipitation totals may have decreased by about 0.7 m at latitude 50°S and increased by about 0.7 m at latitude 40°S. The ELA rises steeply by up to 4 m per kilometer from west to east as the westerlies cross the Andes and this prevents ice growth to the east. The limited decrease in temperature during the LGM could be related to the modest migration of the Antarctic convergence between South America and the Antarctic Peninsula.
Continuous Holocene Record of Diatom Stratigraphy, Paleohydrology, and Anthropogenic Activity in a Spring-Mound in Southwestern United States
Authors: Blinn Dean W. , Hevly Richard H. , Davis Owen K. 
Published: October 2002

AbstractThis study presents the first continuous record of fossil diatoms taken from an open spring-mound in southwestern United States. Diatoms were analyzed from a radiocarbon-dated core taken from Montezuma Well, a near thermally constant spring in northcentral Arizona. Fluctuations in total diatom density, oscillations in the relative abundance of Anomoeoneis sphaerophora, and intermittent deposition of calcite suggest that water levels in Montezuma Well underwent dramatic fluctuations to the degree of being intermittently dry, or at least very shallow, during the middle Holocene (∼8000-5000 yr B.P.). The fluctuations in water level probably correspond to oscillations in regional temperature and precipitation, which regulate hydrologic input and evaporation rates. The dramatic fluctuations in water level during the middle Holocene suggest that the endemic biota of Montezuma Well underwent relatively rapid speciation within the past ∼5000 yr. The appearance of endemic species (Gomphonema montezumense and Cyclotella pseudostelligera f. parva ) at ∼5000-3000 yr B.P. supports this hypothesis. Diatom indicators for organic enrichment (Aulacoseira granulata and A. islandica) closely coincide with the prehistoric native occupation of Montezuma Well.
A Multiproxy Investigation of Late-Glacial Climate and Vegetation Change at Pine Ridge Pond, Southwest New Brunswick, Canada
Authors: Levesque André J. , Cwynar Les C. , Walker Ian R. 
Published: October 2002

AbstractPollen, plant macrofossil, chironomid, and lithological analyses of late-glacial sediment from Pine Ridge Pond all indicate that the warming following deglaciation was punctuated on two separate occasions by a return to colder climes; initially by a brief and moderate cold episode (the Killarney Oscillation), followed shortly by the Younger Dryas. The Killarney Oscillation, AMS 14C dated at between 11,290 and 10,960 yr B.P., is characterized by abrupt and simultaneous increases in Betula (birch) pollen and Betula glandulosa (dwarf birch) macrofossils and a decline in tree pollen. The Younger Dryas is distinguished by the reversion of a short-lived closed Picea (spruce) forest to a prolonged forest-tundra stage (ca. 10, 820 to 9500(?) yr B.P.), during which macrofossils of arctic/alpine plants such as Salix herbaces, Cassiope hypnoides, Armeria maritima, and Thalictrum alpinum make their sole late-glacial appearance. Chironomid-inferred summer surface-water temperatures indicate a cooling of approximately 8 and 12°C during the Killarney Oscillation and Younger Dryas, respectively, and coarse-sand analysis indicates increased erosion on the landscape during these same intervals.
Particle-Size Evidence for Source Areas of Charcoal Accumulation in Late Holocene Sediments of Eastern North American Lakes
Authors: Clark James S. , Royall P.Dan 
Published: October 2002

AbstractTwo methods of analyzing charcoal in sediment reveal changes in charcoal accumulation across temperate eastern North America during the last several hundred years. In one method the analyst counts mostly small particles that reflect regional emissions; in the other, the analyst counts only larger particles derived mostly from such local sources as catchment fires. We used these methods to compare charcoal accumulation at 14 lakes from the prairie/forest border in Minnesota to eastern Maine. The two methods gave concordant accumulation rates for sediments of pre-1850 age at each of 4 lakes analyzed by both methods. This concordance is consistent with the interpretation that pre-1850 emissions were controlled by broad-scale factors, such as climatically controlled regional differences in fuels and moisture. Since 1900 large particles decreased greatly, and small particles decreased slightly, in Minnesota and Wisconsin. By contrast in the Northeast the large particle accumulation has remained at the low values measured in pre-1900 sediments at most sites, while small particles increased everywhere east of central New York and Pennsylvania. The observed patterns suggest that (1) large particles primarily reflect local fires that were common in the Midwest before fire suppression became effective, (2) large particles were rare in the Northeast, especially before extensive land clearance, (3) small particles reflect regional combustion that increased in the Northeast after extensive use of fire for land clearance and wood burning for industrial purposes of the 19th century, and (4) small particles remain abundant in the Midwest long after effective fire suppression, probably because these well-dispersed small particles have a large source area that extends beyond the local wildfires that account for large particles before European settlement.
Sedimentary and Paleoclimatic Controls on Caddisfly (Insecta: Trichoptera) Assemblages during the Last Interglacial-to-Glacial Transition in Southern Ontario
Authors: Williams Nancy E. , Eyles Nicholas 
Published: October 2002

AbstractSouthern Ontario, Canada, has late Pleistocene deposits that contain evidence for climatic cooling during the last interglacial/glacial transition and much of the succeeding Wisconsin glaciation. Fossils of lacustrine and riverine caddisflies (Insecta: Trichoptera) are abundant and well-preserved in these deposits. We examined 26 samples from the interglacial section exposed in the Don Valley Brickyard and compared their caddisfly assemblages with those recovered from the overlying early Wisconsin Scarborough Formation deposits at nearby Scarborough Bluffs. Fifty-one caddisfly taxa in 16 families were recovered from the Don Valley site. Fossil abundance and species richness appear related to the storm or fair-weather conditions inferred from the sedimentary facies. Caddisfly fossils were most abundant and species richness highest in fair-weather, peaty, rippled sands. Highest proportions of river species as opposed to lake species were recovered from sands (storm and fair-weather). Assemblages from both sites indicate the presence of a large and productive river flowing into ancestral Lake Ontario. However, the river assemblage appeared to be far more sensitive to environmental change than the relatively stable assemblage representing the thermally buffered lake. Warm temperate river species such asHydropsyche bidens, Hydropsyche mississippiensis, Macrostemum carolina, and Potamyia flavaare present in the lower Don samples but absent from the Scarborough Bluffs deposits, while indicators of cooler than present climatic conditions such asArctopsyche IndogensisandHagenella canadensisare present in the Scarborough Bluffs sediments but absent from the lower Don samples. For the interval from about 80,000 to 55,000 yr B.P., we infer a climatic cooling from temperature about 2°C warmer than present to about 3°C cooler than present.