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  • Articles  (11)
  • Articles: DFG German National Licenses  (11)
  • Life and Medical Sciences  (7)
  • Artemisia tridentata  (4)
  • 550 - Earth sciences
  • Humans
  • 1
    Electronic Resource
    Electronic Resource
    Species interactions at the level of fine roots in the field: influence of soil nutrient heterogeneity and plant size (1996)
    Springer
    Oecologia 106 (1996), S. 440-447 
    Details
    ISSN: 1432-1939
    Keywords: Artemisia tridentata ; Tussock grasses ; Competition ; Roots ; Soil heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Interference at the level of fine roots in the field was studied by detailed examination of fine root distribution in small soil patches. To capture roots as they occur in natural three-dimensional soil space, we used a freezing and slicing technique for microscale root mapping. The location of individual roots intersecting a sliced soil core surface was digitized and the identity of shrub and grass roots was established by a chemical technique. Soil patches were created midway between the shrub, Artemisia tridentata, and one of two tussock grasses, Pseudoroegneria spicata or Agropyron desertorum. Some soil patches were enriched with nutrients and others given only deionized water (control); in addition, patches were located between plants of different size combination (large shrubs with small tussock grasses and small shrubs with large tussock grasses). The abundance of shrub and grass roots sharing soil patches and the inter-root distances of individual fine roots were measured. Total average rooting density in patches varied among these different treatment combinations by only a factor of 2, but the proportion of shrub and grass roots in the patches varied sixfold. For the shrub, the species of grass roots sharing the patches had a pronounced influence on shrub root density; shrub roots were more abundant if the patch was shared with Pseudoroegneria roots than if shared with Agropyron roots. The relative size of plants whose roots shared the soil patches also influenced the proportion of shrub and grass roots; larger plants were able to place more roots in the patches than were the smaller plants. In the nutrient-enriched patches, these influences of grass species and size combination were amplified. At the millimeter- to centimeter-scale within patches, shrub and grass roots tended to segregate, i.e., avoid each other, based on nearest-neighbor distances. At this scale, there was no indication that the species-specific interactions were the result of resource competition, since there were no obvious patterns between the proportion of shrub and grass roots of the two species combinations with microsite nutrient concentrations. Other potential mechanisms are discussed. Interference at the fine-root level, and its species-specific character, is likely an influential component of competitive success, but one that is not easily assessed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329699
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of competition on stable carbon isotope ratios of two tussock grass species (1991)
    Springer
    Oecologia 88 (1991), S. 148-151 
    Details
    ISSN: 1432-1939
    Keywords: Agropyron desertorum ; Agropyron spicatum ; Pseudoroegneria spicata ; Artemisia tridentata ; Stable carbon isotope composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous studies have shown that plant carbon isotope composition varies when plants experience differences in water and nutrient availability. However, none have addressed the effect of root interactions, including competition for these soil resources, on carbon isotope ratios. We studied the effect of interspecific root interactions on the productivity and carbon isotope ratios of two Great Basin tussock grass species (Agropyron desertorum and Pseudoroegneria spicata). We compared grasses grown in mixture with sagebrush (Artemisia tridentara) to grasses in similar mixtures but where root interactions with sagebrush were limited by fiberglass partitions. During both years of the study, tussocks growing in competition with sagebrush produced tissue with more negative δ13C values than grasses experiencing limited root interaction with sagebrush. The magnitude of this difference (0.5 to 0.9%) is similar to that found in other studies when soil fertility and moisture availability were altered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328416
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  • 3
    Electronic Resource
    Electronic Resource
    Soil solution phosphate, root uptake kinetics and nutrient acquisition: implications for a patchy soil environment (1992)
    Springer
    Oecologia 89 (1992), S. 305-309 
    Details
    ISSN: 1432-1939
    Keywords: Soil phosphate ; Root kinetics ; Root proliferation ; Agropyron desertorum ; Artemisia tridentata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The importance of increased root phosphate (P) uptake kinetics, root proliferation and local increases of soil solution P (P1) for P acquisition from fertile soil microsites was explored with a simulation model and calculated uptake was compared with experimental data. Based on the partitioning of added P in microsites to P1 and P adsorbed on soil particles and the results of a dual-isotope-labeling experiment (Caldwell et al. 1991a), acquisition of P from the fertile microsites was some 20 X that of uptake from an equal volume of soil which received only water. Simulations were in general agreement and also showed that elevation of root P uptake kinetics could contribute more to the increased acquisition than did root proliferation under these circumstances. Although increased physiological uptake capacity for P has generally been considered to be of little benefit because of diffusion limitation, in patchy soil environments selective elevation of P uptake kinetics in fertile microsites may be of considerable benefit. These tests were conducted in calcareous soil which releases much less P into the soil solution than do many other soils. In many noncalcareous soils the benefits of selective elevation of root uptake kinetics would likely be greater.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317406
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  • 4
    Electronic Resource
    Electronic Resource
    Temporal dynamics of soil spatial heterogeneity in sagebrush-wheatgrass steppe during a growing season (1996)
    Springer
    Plant and soil 184 (1996), S. 299-309 
    Details
    ISSN: 1573-5036
    Keywords: Agropyron desertorum ; Artemisia tridentata ; nutrient availability ; resource patchiness ; sagebrush-grass steppe ; temporal variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Variability in five soil resources essential for plant growth (NH4 +, NO3 -, P, K and soil moisture) was quantified using univariate, multivariate and geostatistical techniques in a sagebrush-grass steppe ecosystem at three times (early April, June and August) during the 1994 growing season. Samples were collected every meter in a 10 × 10-m ‘macrogrid’, every 20 cm within nested 1 × 1-m ‘minigrids’, and every 3 cm within additionally nested 15 × 15-cm ‘microgrids’. Strong autocorrelation for all variables in the three sample periods was only found over distances less than 2 m, indicating that patches of high internal uniformity in this soil were smaller than 2 m during the growing season. Differences in semivariograms between sample periods were most pronounced for NO3 -, NH4 + and soil moisture, variables that we consider to primarily limit plant growth in this system. The distance over which sample points were autocorrelated for NO3 -, NH4 + and soil moisture increased from April to June. In contrast P and K, which are relatively more abundant at the study site, exhibited relatively constant semivariance patterns over the three sample periods. Weak correlation was found between samples collected in the three sample periods for N and soil moisture indicating that the spatial pattern of these limiting resources changed between sample periods. However, P and K had highly significant correlations (p〈0.00001) among sample periods, indicating that the distributional patterns of these relatively more abundant resources remained rather constant. There were strong negative correlations between P and K and distance from the base of shrubs for all sample times (p〈0.001), indicating an increase in P and K close to shrubs. Similar strong negative correlations were not found between distance from the shrubs and levels of NH4 +, NO3 -, or soil moisture, nor for any soil variable and distance from perennial tussock grasses. Changes in patterns of nutrient and soil moisture variability within a growing season suggest that not only must plants acquire soil resources that vary in time and space, but that they may also have to adjust to different scales of resource patchiness during the season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010459
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  • 5
    Electronic Resource
    Electronic Resource
    Variant cDNAs encoding proteins similar to the α subunit of chicken CapZ (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 204-214 
    Details
    ISSN: 0886-1544
    Keywords: actin-binding ; muscle ; Z-line ; capping ; isoform ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chicken adult muscle and liver cDNA libraries were screened with a cDNA, α1, previously isolated from a chicken embryo library by screening with antibodies against the α subunit of chicken CapZ. cDNAs with a new coding region, called α2, were found in addition to ones with the α1 coding region. α2 predicts a protein sequence that matches exactly the N-terminal sequence of 5 peptides prepared from CapZ α purified from chicken muscle, while the protein sequence predicted by α1 matches the peptides well, but not exactly. The predicted protein sequences of α1 and α2 are very similar to each other, and they are similar to those of the α subunit of capping protein from Dictyostelium [Hartmann et al., J. Biol. Chem. 163:5254-5254, 1989] and an actin-binding protein from Xenopus [Ankenbauer et al., Nature 342:822-824, 1989]. Other conserved features of the predicted primary and secondary structures are noted. Chicken α1 and α2 are transcribed in all of 7 adult chicken muscle and non-muscle tissues in comparable amounts by Northern analysis. α2 has four poly(A)+ RNA transcripts, one of which is rare in liver. α1 has two transcripts. α1 and α2 are encoded by different single-copy genes by Southern analysis of chicken genomic DNA.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970180306
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  • 6
    Electronic Resource
    Electronic Resource
    Biochemical and morphological properties of bovine erythrocyte membrane glycoproteins (1982)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 19 (1982), S. 157-170 
    Details
    ISSN: 0730-2312
    Keywords: erythrocyte ; membranes ; glycoproteins ; electronmicroscope ; gel electrophoresis ; bovine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The major and minor sialoglycoproteins of the bovine erythrocyte have been solubilized and extensively purified. A comparison of composition revealed that the major glycoprotein had 77% carbohydrate and 23% peptide, and the minor one had 27% carbohydrate and 73% peptide. Molar ratios of sugars were related, however, the major glycoprotein had twice as much galactose and sialic acid as did the minor glycoprotein. Molecular weights, estimated from retardation coefficients of mobility in sodium dodecyl sulfate gel electrophoresis, were 55,000 for the major glycoprotein and 34,000 for the minor glycoprotein. The glycoproteins were studied by electron microscopy before and after delipidation and after ultracentrifugation. The major glycoprotein, prior to delipidation, formed large micelles. After delipidation, the major glycoprotein could not be visualized suggesting that it did not form aggregates in aqueous solution. The minor glycoprotein was visualized as rather uniform spherical aggregates (62 Å average diameter) which tended to form short chains and small clumps. These characteristic aggregates were seen both before and after delipidation. After ultracentrifugation, fixation and sectioning both glycoproteins appeared to have formed microcrystalline arrays with average periodicity of 49 Å.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240190206
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  • 7
    Electronic Resource
    Electronic Resource
    Distribution of lysosomal enzymes in animal tissuesThis research was supported by grant RG-5759 from the National Institutes of Health and project WM-33 of the U. S. Department of Agriculture. (1963)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 61 (1963), S. 85-92 
    Details
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030610109
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  • 8
    Electronic Resource
    Electronic Resource
    Culture perfusion schedules influence the metabolic activity and granulocyte-macrophage colony-stimulating factor production rates of human bone marrow stromal cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 147 (1991), S. 344-353 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The metabolic function and GM-CSF production rates of adherent human bone marrow stromal cells were investigated as functions of medium and serum feeding rates. A range of medium exchange schedules was studied, ranging from a typical Dexter culture protocol of one weekly medium exchange to a full media exchange daily, which more closely approximates what bone marrow cells experience in situ. Glucose consumption was found to be significantly higher at full daily exchange rate than at any other exchange schedule examined. However, the lactate yield on glucose was a constant, at 1.8 mol/mol, under all conditions considered. Differential serum vs. medium exchange experiment showed that both serum supply and medium nutrients were responsible for the altered behavior at high exchange rates. Glutamine consumption was found to be insignificant under all culture conditions examined. A change in exchange schedule from 50% daily medium exchange to full daily medium exchange after 14 days of culture was found to result in a transient production of GM-CSF and a change in metabolic behavior to resemble that of cultures which had full daily exchange from day one. These results suggest that both stromal cell metabolism and GM-CSF production are sensitive to medium exchange schedules. Taken together, the data presented indicate that attempts to model the function of human bone marrow in vitro may be well served by beginning with medium exchange schedules that more closely mimic the in vivo physiologic state of bone marrow.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041470221
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  • 9
    Electronic Resource
    Electronic Resource
    IL-1α and TNFα act synergistically to stimulate production of myeloid colony-stimulating factors by cultured human bone marrow stromal cells and cloned stromal cell strains (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 159 (1994), S. 221-228 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human bone marrow stromal cells repond to stimulation by the monokines IL-1 and TNF by producing colony-stimulating factors such as GM-CSF and G-CSF. In this study we show that IL-1α and TNFα act synergistically to stimulate GM-CSF and G-CSF production by cultured marrow stromal cells. We further show that IL-1α and TNFα synergistically stimulate production of GM-CSF and G-CSF by a clonal stroma-derived cell strain. Although IL-1 and TNF share many of the same biological activities, we show that IL-1α and TNFα have an unequal ability to induce myeloid-CSF production by both cultures, with IL-1α being the more potent inducer. We found that induction by IL-1α and TNFα was independent of cell proliferation. The effect of IL-1α and TNFα on production of the two myeloid-CSFs by the clonal cells was significantly greater than the unfractionated passaged stromal cultures, having the greater effect on G-CSF production. The clonally derived stromal cells constitutively produced colony-stimulating activity, in particular GM-CSF, at levels easily detected by ELISA. These findings show that, in addition to the overlapping and additive activities of IL-1α and TNFα, they can interact synergistically. Our findings further suggest that a small subpopulation of stroma cells may be the major producer of G-CSF in the marrow microenvironment during immune response. © 1994 wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041590205
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  • 10
    Electronic Resource
    Electronic Resource
    Culture of pachytene spermatocytes for analysis of meiosis (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 16 (1995), S. 128-139 
    Details
    ISSN: 0192-253X
    Keywords: Spermatogenesis ; meiosis ; synapsis ; synaptonemal complex ; G2-M transition ; okadaic acid ; actinomycin D ; camptothecin ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: An impediment to the investigation of mammalian spermatogenic meiosis has been the lack of an appropriate system for experimental manipulation of meiotic prophase cells. We report here the use of a simple system for the short-term culture of pachytene spermatocytes. We have assayed parameters of cell function pertinent to meiotic prophase, namely chromosome pairing and synapsis. During the culture period of 24-48 hr, cells maintained typical pachytene morphology, chromatin condensation patterns, and chromosome pairing, as assessed by light and electron microscopy. Uridine incorporation, monitored by autoradiography, reflected the chromosomal distribution found in vivo in that the autosomal chromosomes were transcriptionally active, while the sex chromosomes were not. Thus features of chromosome pairing and sex chromatin inactivation are maintained in these cultures. We have conducted experiments to demonstrate that cultured pachytene spermatocytes can be useful for the analysis of agents, some of which may be suspected mutagens, that might affect chromosome structure and function during meiosis. Treatment of cells with actinomycin D revealed a differential effect on chromatin condensation in the autosomes versus the sex chromosomes. Carnptothecin, a topoisomerase inhibitor, induced desynapsis of paired chromosomes. Okadaic acid, a phosphatase inhibitor, induced premature metaphase-I condensation of pachytene chromosomes. This last experiment suggests that these cultured cells may be useful for analysis of meiotic cell cycle controls. Taken together, these results demonstrate a culture system that can be useful for analysis of meiotic events as well as in screening for potential mutagenic agents that might affect meiotic chromosome structure and function. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020160206
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