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  • 1
    Electronic Resource
    Electronic Resource
    Mechanics of root elongation and the effects of 3,5-diiodo-4-hydroxybenzoic acid (DIHB) (1987)
    Springer
    Plant and soil 99 (1987), S. 211-218 
    Details
    ISSN: 1573-5036
    Keywords: Aeration ; Barley ; 3,5-Diiodo-4-hydroxybenzoic acid ; Extensibility ; Mechanical impedance ; Osmotic potential ; Pea ; Root elongation ; Wheat ; Young's modulus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This paper reports the results of two series of experiments. In the first the effects of DIHB on the rate of root elongation were compared on unstressed roots and on roots stressed by mechanical impedance and by inadequate levels of aeration. Barley plants were grown in beds of small glass spheres through which nutrient solution was circulated. Mechanical impedance of 25 kPa was applied by subjecting the beds to a confining pressure. Inadequate aeration was obtained by reducing the oxygen concentration in the nutrient solution to 5%. The second series examined possible effects of DIHB on the elastic modulus of root tips of wheat and pea. Elastic modulus gives an indication of the behaviour of roots in structured soil where penetration of peds can be limited by the buckling of root tips. The elastic modulus was measured in experiments of the static cantilever type on roots previously immersed in solutions of polyethylene glycol of different osmotic potential. Elastic modulus measurements can also detect any changes in turgor pressure and wilting characteristics of roots and can therefore help to identify the mechanisms of action of DIHB. DIHB caused increases in root elongation relative to controls in all cases: 26±5.7% in unstressed roots, 14±6.4% in mechanically impeded roots and 54±9.8% in roots growing in 5% oxygen. DIHB had no effect on the elastic modulus, osmotic or turgor pressure of the roots. It is concluded that DIHB acts by modifying the cell wall extensibility factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370868
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  • 2
    Electronic Resource
    Electronic Resource
    The behaviour of roots encountering cracks in soil (1984)
    Springer
    Plant and soil 79 (1984), S. 11-28 
    Details
    ISSN: 1573-5036
    Keywords: Beta distribution ; Buckling ; Cracks ; Crack width ; Lateral roots ; Pea ; Penetration ; Penetrometer ; Rape ; Remoulded soil ; Roots ; Safflower ; Seminal axes ; Soil strength ; Undisturbed soil ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary It is shown that probabilities of root penetration across cracks in soil can be calculated effectively using a mathematical model involving root stress and soil distributions and penetrometer/root stress ratios. Penetration criteria are developed, and it is found that the effective penetrometer/root stress ratios take values of about 4 for crack widths smaller than about 2 mm and about 8 for wider cracks. Root swelling does not appear to contribute significantly to the probability of root penetration through any effect on root buckling stress. Suggestions are made for further work on the effects of soil structure and strength on root behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182140
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  • 3
    Electronic Resource
    Electronic Resource
    Model experiments on the behaviour of roots at the interface between a tilled seed-bed and a compacted sub-soil (1986)
    Springer
    Plant and soil 95 (1986), S. 123-133 
    Details
    ISSN: 1573-5036
    Keywords: Aggregate ; Compaction pan ; Penetrometer ; Root penetration ; Seed-bed ; Soil strength ; Triticum aestivum ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary When elongating seminal roots of developing plants reach the base of a tilled seedbed, they often encounter a layer of dense, strong untilled soil. At this interface, they may be deflected horizontally and instead of penetrating the sub-soil, they may form a horizontal mat of roots at the base of the seed-bed. If this occurs, the plants are unable to absorb the reserves of water in the sub-soil, and are very sensitive to short periods of drought. Model experiments were done with artificial sub-soil layers having a range of strengths and with artificial seed-beds having sieved soil aggregates in the 4–7.7, 2–4 and 1–2 mm size ranges. Roots of wheat were grown through the aggregate beds and the proportions of roots which penetrated into the sub-soil were investigated as functions of sub-soil strength and diameter of the aggregates in the seed-bed. The proportion penetrating was found to decrease exponentially with sub-soil strength. The rate of decrease was similar for the 2–4 and 1–2 mm aggregates but was greater for the 4–6.7 mm aggregates. It is concluded that, provided that the roots of different plant species behave similarly, the base of the seed-bed should be composed of fine aggregates and that the penetrometer strength of the underlying untilled sub-soil should not exceed 0.4 MPa for plants with a single seminal axis or 3 MPa for plants such as wheat with 4 seminal axes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02378858
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  • 4
    Electronic Resource
    Electronic Resource
    Model experiments on the behaviour of roots at the interface between a tilled seed-bed and a compacted sub-soil (1986)
    Springer
    Plant and soil 95 (1986), S. 149-161 
    Details
    ISSN: 1573-5036
    Keywords: Compaction pan Earthworms ; Pea ; Pisum sativum ; Root channels ; Root entry ; Trematotropism ; Triticum aestivum ; Tunnels ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Roots which grow down through a seed-bed and encounter a strong, untilled sub-soil beneath may be unable to penetrate the sub-soil and may be deflected horizontally. They will continue to grow horizontally along the top of the sub-soil either until the seed-bed dries out and the roots wilt and cease elongating, or until they find some path of low resistance down through the sub-soil. Such paths are often cylindrical biopores such as earthworm tunnels or channels left after the decay of previous root systems. Model experiments were done with artificial impenetrable sub-soils containing arrays of round holes of various diameters. Roots of pea and wheat were grown down through beds of aggregates to encounter the artificial sub-soils at random positions. The roots were deflected horizontally until they encountered the vertical holes. The proportions of roots which entered the holes were found to decrease with decreasing hole diameter. Computer simulation studies were done to investigate some aspects of roots encountering impenetrable sub-soils containing random arrays of round holes. The distances that randomly-deflected roots would have to travel before encountering holes were studied as functions of hole diameter and hole density. The experimental results were combined and compared with the results from the computer simulations. It was found that the numbers of roots encountering holes within certain distances in practice were not significantly different from those simulated on the basis of random chance. Therefore there was no evidence for the roots sensing and growing preferentially towards the holes (trematotropism) in the well-aerated system used in the experiments. However, limited evidence shows that the possibility of trematotropism cannot be ruled out for poorly-aerated systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02378860
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  • 5
    Electronic Resource
    Electronic Resource
    The behaviour of roots encountering cracks in soil (1984)
    Springer
    Plant and soil 77 (1984), S. 141-149 
    Details
    ISSN: 1573-5036
    Keywords: Cracks ; Crack width ; Lateral roots ; Pea ; Penetration ; Penetrometer ; Rape ; Remoulded soil ; Roots ; Safflower ; Seminal axes ; Soil strength ; Undisturbed soil ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Experimental methods are described for observing the behaviour of roots encountering cracks in soil. The proportions of roots which enter a second soil block after crossing a crack of known width were measured. Soil strength was measured with a penetrometer. Results are presented for the proportions of seminal roots of wheat and primary lateral roots of pea which enter moulded soil of various strengths after crossing cracks. Results are also presented for the proportions of seminal roots of pea, rape and safflower which enter undisturbed soil after crossing cracks. It was found that, in all cases, the proportion of roots penetrating the second soil block decreased with increasing crack width and increasing soil strength. Also, a smaller proportion of thinner roots penetrated the second soil block than thicker roots under similar conditions. Root diameter in the cracks was influenced by both crack width and soil strength, and an empirical equation is presented to describe this effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182918
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  • 6
    Electronic Resource
    Electronic Resource
    Lipid synthesis and secretion by primary cultures of rat mammary epithelial cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 157 (1993), S. 469-480 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Lipid synthesis and secretion was measured in primary rat mammary epithelial cells cultured on basement matrix in medium supplemented with lactogenic hormones. The cells grew and differentiated to form alveolar-like structures reminiscent of lactating mammary gland. They synthesized abundant triacylglycerol, containing fatty acids characteristic of rat milk (C10:O-C14:0), using 14C-glucose, 14C-oleic acid or 14C-glycerol as precursors. Basal levels of triacylglycerol secretion were measured using 14C-oleic acid labeling; 1.3±0.3% of the labeled cellular triacylglycerol was secreted into the medium in 24 hours. Secreted lipid droplets were surrounded by a bilayer membrane with an electron-dense inner coat characteristic of fat globules secreted by the mammary gland. The rate of triglycerol secretion was increased to 998±98% of control (P〈0.01) by the addition of phorbol 12-myristate 13-acetate (PMA) in combination with staurosporine, a protein kinase inhibitcn. Several other protein kinase inhibitors, when combined with PMA, also markedly stimulated secretion. Effective protein kinase inhibitors included sphingosine (has diverse cellular effects including the inhibition of protein kinase C; 13-fold increase in secretion), and KT5823 (a cGMP dependent protein kinase inhibitor; 5-fold increase). KT5720 (a cAMP-dependent protein kinase inhibitor) did not alter secretion. Kinase inhibitors were effective only in the presence of a phorbol ester. 4α-phorbol-12,13-didecanoate, a phorbol ester which does not activate protein kinase C (PKC), could substitute for PMA. Lipid release was not mediated by disruption of cell-cell tight junctions, as EGTA did not release lipid. Based on these observations we suggest that two signals are needed to enable or stimulate lipid secretion in cultured rat mammary epithelial cells: (1) inhibition of a protein kinase and (2) a PKC-independent effect of phorbol ester. We have, for the first time, characterized a cell culture model suitable for studying lipid synthesis and secretion by mammary epithelial cells. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041570306
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  • 7
    Electronic Resource
    Electronic Resource
    The role of growth factors in haemopoiesis (1985)
    New York, NY : Wiley-Blackwell
    BioEssays 2 (1985), S. 154-158 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Many of the haemopoietic cell growth factors have now been purified to homogeneity and their structural genes cloned. Methods are also now available for obtaining pure populations of haemopoietic cells. The use of such cells, in combination with pure growth factors, has provided intriguing information about the biological activities and mode of action of the factors in faciliating survival, proliferation and differentiation of the haemopoietic cells.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950020404
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  • 8
    Electronic Resource
    Electronic Resource
    Some tensile properties of nerveThis investigation was supported (in part) by a grant-in-aid from the Agnes Anderson Fund, University of Washington. (1956)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 48 (1956), S. 87-94 
    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 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030480106
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  • 9
    Electronic Resource
    Electronic Resource
    Excitability related to spike size in crab nerve fibersAcknowledgment is made of funds provided for support of this research by Initiative 171, State of Washington, U.S.A. (1952)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 40 (1952), S. 303-315 
    Details
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030400210
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  • 10
    Electronic Resource
    Electronic Resource
    Conditions controlling the proliferation of haemopoietic stem cells in vitro (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 91 (1977), S. 335-344 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A liquid culture system is described whereby proliferation of haemopoietic stem cells (CFU-S), production of granulocyte precursor cells (CFU-C), and extensive granulopoiesis can be maintained in vitro for several months. Such cultures consist of adherent and non-adherent populations of cells. The adherent population contains phagocytic mononuclear cells, “epithelial” cells, and “giant fat” cells. The latter appear to be particularly important for stem cell maintenance and furthermore there is a strong tendency for maturing granulocytes to selectively cluster in and around areas of “giant fat” cell aggregations. By “feeding” the cultures at weekly intervals, between 10 to 15 “population doublings” of functionally normal CFU-S regularly occurs. Increased “population doublings” may be obtained by feeding twice weekly. The cultures show initially extensive granulopoiesis followed, in a majority of cases, by an accumulation of blast cells. Eventually both blast cells and granulocytes decline and the cultures contain predominantly phagocytic mononuclear cells.Culturing at 33°C leads to the development of a more profuse growth of adherent cells and these cultures show better maintenance of stem cells and increased cell density.When tested for colony stimulating activity (CSA) the cultures were uniformly negative. Addition of exogenous CSA caused a rapid decline in stem cells, reduced granulopoiesis and an accumulation of phagocytic mononuclear cells.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040910303
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