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  • 1
    Electronic Resource
    Electronic Resource
    The role of erythropoietin in the production of principal erythrocyte proteins other than hemoglobin during terminal erythroid differentiation (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 126 (1986), S. 259-265 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Erythropoietin (EP) controls the terminal phase of differentiation in which proerythroblasts and their precursors, the colony forming units-erythroid (CFU-e), develop into erythrocytes. Biochemical studies of this hormone-directed terminal differentiation have been hindered by the lack of a homogeneous population of erythroid cells at the developmental stages of CFU-e and proerythroblasts that will synchronously differentiate in response to EP. Such a population of cells can be prepared from the spleens of mice with the acute erythroblastosis resulting from infection with anemia-inducing Friend virus (FVA). Using these FVA-infected erythroid cells, which were induced to differentiate with EP, four proteins other than hemoglobin that have key functions in mature erythrocytes were monitored during the 48-hour period of terminal differentiation. Synthesis of spectrin and membrane band 3 proteins were determined by immunoprecipitation and SDS-polyacrylamide gel electrophoresis; accumulation of the cytoskeletal protein band 4.1 was monitored by immunoblotting; carbonic anhydrase activity was measured electro-metrically. Band 3 synthesis and band 4.1 accumulation could be detected only after exposure of the cells to EP. Spectrin synthesis was ongoing prior to culture with EP, but it did increase after exposure to the hormone. Carbonic anhydrase-specific activity changed very little throughout the terminal differentiation process. These results reveal at least three patterns of production of principal erythrocyte proteins during EP-mediated terminal differentiation of FVA-infected erythroid cells. Depending on the specific protein examined, de novo synthesis can be induced by EP, an ongoing production can be enhanced by EP, or the production of a protein can be completed at a developmental stage prior to EP-mediated differentiation in these cells.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041260216
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Monolayer freeze-fracture - a modified procedure (1986)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 3 (1986), S. 439-451 
    Details
    ISSN: 0741-0581
    Keywords: Monolayer freeze-fracture ; Trans-membrane proteins ; Erythrocyte membrane proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Monolayer freeze-fracture of biological membranes is a valuable tool for integrating membrane morphology with biochemical analysis of membrane components. This correlation has been restricted by the purity of the biochemical sample. In this article, the method is reviewed, and an improved method is described. The essential modification was the use of a polysaccharide-coated microscope slide, instead of a copper plate, to cover cells attached to a polylysine-coated coverslip. It was found that proper freeze-fracture will not occur unless there is a distinct temperature gradient, with its accompanying stresses, across the cell monolayer during the freezing process. This gradient is achieved by using glass slides of different thickness to cover each side of the monolayer. Comparison of the results with those obtained when using a copper-glass system demonstrated a consistently purer sample for the glass-glass system, with whole-cell contamination of the external membrane leaflet being reduced to 0.4%. Problems associated with obtaining pure samples for biochemical analysis are discussed, and the results of freeze-fracture with the glass-glass and glass-copper systems are compared. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of polypeptides associated with the separate halves of the erythrocyte membrane demonstrated that band 3, the anion transport protein, separates with the cytoplasmic face, whereas only sialoglycoproteins and their fragments are retained in the external face. This finding, obtained with the glass-glass system, is consistent with results of our earlier freeze-fracture study that used a copper-glass system which showed that covalent bonds may be broken during this procedure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060030407
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    Paper (German National Licenses)
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  • 3
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    Estimates of the mean circulation in the deep (〉2,000m) layer of the Eastern North Atlantic (1985)
    Elsevier
    In:  Progress in Oceanography, 14 . pp. 103-127.
    Details
    Publication Date: 2017-07-10
    Description: A total of 131 current meter records of between 6 and 24 month duration are analysed to describe the deep flow field of the eastern North Atlantic from 19° to 54°N and from the Continental Slope to the Mid Atlantic Ridge. Mean flows are weak and may be statistically indeterminate in some records and locations, but appear to indicate cyclonic circulations around the Iberia and Porcupine abyssal plains with a generally southward flow along the Mid Atlantic ridge and a deep northward slope current (where measurements exist) along the eastern boundary. The deepest inflow to the north-eastern basin that has been identified to date takes place through the Discovery Gap of 〉4,700 m sill-depth at 37° 25′N 15° 45′W in the Azores-Portugal ridge. South of that ridge, observations are sparse and no systematic circulation is yet evident. These observations are discussed in relation to recent geostrophic estimates of the deep circulation.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0079-6611(85)90008-4
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Pathways and variability of the Antarctic Intermediate Water in the western equatorial Pacific Ocean. (2005)
    Elsevier
    In:  Progress in Oceanography, 67 . pp. 245-281.
    Details
    Publication Date: 2016-10-05
    Description: In the western equatorial Pacific the low-salinity core of Antarctic Intermediate Water (AAIW) is found at about 800 m depth between potential density levels σθ = 27.2 and 27.3. The pathways of AAIW and the degradation of its core are studied, from the Bismarck Sea to the Caroline Basins and into the zonal equatorial current system. Both historical and new observational data, and results from numerical circulation model runs are used. The observations include hydrographic stations from German and Japanese research vessels, and Eulerian and Lagrangian current measurements. The model is the JAMSTEC high-resolution numerical model based on the Modular Ocean Model (MOM 2). The general agreement between results from the observations and from the model enables us to diagnose properties and to provide new information on the AAIW. The analysis confirms the paramount influence of topography on the spreading of the AAIW tongue north of New Guinea. Two cores of AAIW are found in the eastern Bismarck Sea. One core originates from Vitiaz Strait and one from St. George’s Channel, probably arriving on a cyclonic pathway. They merge in the western Bismarck Sea without much change in their total salt content, and the uniform core then increases considerably in salt content when subjected to mixing in the Caroline Basins. Hydrographic and moored current observations as well as model results show a distinct annual signal in salinity and velocity in the AAIW core off New Guinea. It appears to be related to the monsoonal change that is typically found in the near-surface waters in the region. Lagrangian data are used to investigate the structure of the deep New Guinea Coastal Undercurrent, the related cross-equatorial flow and eddy-structure, and the embedment in the zonal equatorial current system. Results from 17 neutrally buoyant RAFOS floats, ballasted to drift in the AAIW core layer, are compared with a numerical tracking experiment. In the model 73 particles are released at five-day intervals from Station J (2.5°N, 142°E), simulating currents at a moored time series station north of New Guinea. Observed and model track patterns are fairly consistent in space and season. Floats cross the equator preferably north of Cenderawasih Bay, with a maximum range in eddy-motion in this region north of New Guinea. The northward route at 135°E is also reflected in a low-salinity tongue reaching up to 3°N. At that longitude the floats seem to ignore the zonally aligned equatorial undercurrents. Farther to the east (139 145°E), however, the float observations are consistent with low-latitude bands of intermediate currents.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.pocean.2005.05.003
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Interannual variability of deep water particle flux in relation to production and lateral sources in the northeast Atlantic (2005)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 52 (1). pp. 33-50.
    Details
    Publication Date: 2019-09-23
    Description: Results of particle flux studies using sediment traps in the northeast Atlantic Ocean at 33oN, 22oW, a time-series station (L1/K276) operated within the German contribution to the international Joint Global Ocean Flux Study (JGOFS) between summer 1993 and summer 2001, are presented. The particle flux at 2000 m depth is highly seasonal with only one main peak in February and March and is characterized by strong interannual variability. The comparison of the particle flux time series with the measurements of chlorophyll and phaeopigments in the sediment trap material, and chlorophyll-a concentrations at surface from SeaWiFS together with the similarity of the pattern observed in the alkenone flux, particulate organic carbon (POC) and calcium carbonate (CaCO3) leads to the conclusion that the particle flux at this position is fast and directly coupled to the phytoplankton development and decay in the overlying euphotic zone. SeaWiFS chlorophyll-a data (1997-2001) and characteristics of the upper water column (mixed layer depth, depth of nitracline, primary production) as predicted by an eddy-permitting model of the North Atlantic coupled with a simple nitrate-phytoplankton-zooplankton-detritus (NPZD) pelagic-ecosystem model are used to understand the observed interannual differences in particle flux at 2000 m. Our results suggest that the interannual differences in the observed particle flux are a direct consequence of the variability of phytoplankton biomass and primary production in the euphotic zone in this region.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr.2004.08.008
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Meddies and decadal changes at the Azores Front from 1980 to 2000 (2005)
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 52 (3-4). pp. 583-604.
    Details
    Publication Date: 2020-08-05
    Description: Twenty years of time series observations from the deep-sea mooring KIEL276 are used to obtain information on the frequency and propagation of meddies (Mediterranean Water eddies), on long-term changes in flow properties, and on a possible relation to the North Atlantic Oscillation. The mooring was set at the nominal position 33°N, 22°W at a water depth of more than 5200 m in the northern Canary Basin. It is located near the southern boundary of the Azores Current (AC), which is part of the North Atlantic subtropical gyre, and also in the large-scale Mediterranean Water (MW) tongue originating from the Strait of Gibraltar. The amplitudes of time-varying vertical quasi-geostrophic modes and the correlation of current and temperature changes at levels in the MW and the North Atlantic Central Water above are used to identify meddies. A total of 10 meddies passed the mooring during the period 1980–2000. Half of the events can be related to earlier observations. Directional changes in meddy-related velocities are used to estimate speeds and directions of meddy propagation. Directions of propagation are very homogeneous, with all the 10 meddies observed propagating with a southward velocity component within a sector of 90°, and typical speeds are 2–3 cm/s. Meddy occurrence was uneven in time, with six meddies found during the first four years and only four meddies during the remaining 16 years. Decadal changes show the annual-mean and the fluctuating kinetic energy levels at the site changing from lower values in the 1980s to high values in the 1990s. This change appears to be correlated with variations in the North Atlantic Oscillation (NAO) index, with a delay in oceanic response of about 3 years. A conceptual model of AC meanders is used to identify meander signals in the upper-layer time series. The AC axis appears to be closer to the site during the 1990s than during the preceding decade and indicates a southward or southwestward displacement of the AC with increasingly positive values of the NAO index. Meddy frequency is lower when the AC gets closer from the north. A reduction in meddy occurrence in the region just south of the AC is possibly caused by the shear-induced blocking of some meddies crossing the front from the north.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr2.2004.12.010
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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