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  • 1
    Digitale Medien
    Digitale Medien
    Mathematical treatment of water movement in plant cells and tissue: a review (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 5 (1982), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract. Over the past three decades, many contributions have been made to the development of a mathematical basis for describing water transport in plant cells and tissue. This review paper attempts to summarize the more significant contributions and to outline the concepts upon which the various mathematical analyses are founded.The paper itself is divided into three major sections. Section I deals with the quantitative water relations of single plant cells. Basic equations are developed which describe the water statics and water dynamics of such cells. Included is a discussion of the theory and methods for measuring the various parameters (permeabilities, cell wall elastic moduli, etc.) which enter into the development. The section closes with a presentation of circuit analog models for single plant cells.Section II is devoted to a review and development of the water relations of plant tissues which contain numerous cells in series. Following a historical overview, various existing models are derived and physical tissue properties which enter the derivation are identified. The concept of ‘local equilibrium’ is discussed and circuit analog models for single cells are generalized and applied to several cells in series.The final section contains two example applications of water transport theory as it applies to plant tissue. One application involves radial water movement in a soybean hypocotyl while the other deals with water transport in a growing root tip. A summary at the end of the section is largely devoted to a discussion of the limitations of mathematical models dial are presently available.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1365-3040.ep11571715
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  • 2
    Digitale Medien
    Digitale Medien
    Collagenase and collagenase inhibitor activities in crevicular fluid of patients receiving treatment for localized juvenile periodontitis (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 21 (1986), S. 0 
    Details
    ISSN: 1600-0765
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Collagenolytic activity was monitored in crevicular fluids of 3 patients receiving treatment for localized juvenile periodontitis (LJP) and in 3 control, clinically healthy patients to study relationships between mammalian collagenase and disease activity. It was found that tissue collagenase activity initially was significantly higher in diseased patients compared to controls, but that in II of 13 diseased sites the activity decreased substantially following clinical treatment. In control sites, active collagenase was generally low or absent. Latent collagenase concentrations tended to remain high in diseased sites and in sites with gingival inflammation. Collagenase inhibitor activity was found only in clinically healthy sites sampled from both control subjects and LJP patients throughout the experiment, and in diseased sites following various phases of treatment. The collagenolytic activity observed was typical of mammalian collagenase in that the primary degradation products of collagen were 3/4- and 1/4-fragments. However, additional specific fragmentation of native collagen 3/4-fragments was also observed, which could be attributed to a novel collagenolytic activity generally present in crevicular fluid in a latent form. The results of this study suggest that the determination of active collagenase and collagenase inhibitor in crevicular fluid might be useful in assessing both the disease status of periodontal tissues and the efficacy of clinical treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1600-0765.1986.tb01508.x
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  • 3
    Digitale Medien
    Digitale Medien
    Frequency-dependent membrane impedance inChara corallina estimated by Fourier analysis (1985)
    Springer
    The journal of membrane biology 85 (1985), S. 233-243 
    Details
    ISSN: 1432-1424
    Schlagwort(e): Chara ; Fourier analysis ; fusicoccin ; inductive effect ; membrane impedance ; pH
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The white noise method of measuring membrane impedance has been applied to internodal cells ofChara corallina. Fourier analysis of a white noise transmembrane current signal and the voltage response has been used to obtain the frequency-dependent impedance of the in-series combination of the plasmalemma and tonoplast membranes. The results are similar to those of other workers who have measured membrane impedances by different techniques. At very low frequencies the equivalent capacitance of the membrane treated as an RC-circuit becomes negative, indicating a pseudoinductive effect. Membrane impedance has been measured over a range of pH values from pH 5.2 to pH 11; impedance magnitude reaches a maximum at pH 7. At interesting effect of fusicoccin at pH 11 has been observed, in which a decrease in membrane conductance occurs simultaneously with a small hyperpolarization of membrane PD.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01871518
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  • 4
    Digitale Medien
    Digitale Medien
    Theory of negative capacitance in membrane impedance measurements (1985)
    Springer
    The journal of membrane biology 85 (1985), S. 245-249 
    Details
    ISSN: 1432-1424
    Schlagwort(e): Chara ; membrane impedance ; negative capacitance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Three possible explanations of the negative capacitance seen in theChara corallina membrane impedance are critically examined. These explanations are based on: (1) voltage-dependent channel kinetics; (2) electro-osmosis; and (3) extracellular negative capacitance. It is shown that the first two can produce negative capacitance only with parameters which differ by several orders of magnitude from measured values. The last mechanism can produce a very large magnitude negative capacitance, in the appropriate frequency range. Possible experimental tests are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01871519
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  • 5
    Digitale Medien
    Digitale Medien
    Studies on the alignment of fibroblasts in uniform applied electrical fields (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 10 (1989), S. 371-384 
    Details
    ISSN: 0197-8462
    Schlagwort(e): human gingival fibroblasts ; statistics of directional data ; Ca2+ transport ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Uniform electrical fields have been applied to human gingival fibroblasts by means of uniform ionic currents passed through a thin chamber. Cells were observed to align in fields between 0.1 and 1.5 V/mm but did not display directed motion toward the anode or the cathode of the chamber. Statistical analysis of directional data was used to distinguish threshold levels of orientation at low field intensities, to quantify the dependence of alignment on time and field intensity, and to analyze differences between alignment of cells treated with the Ca2+ transport modifiers A23187, verapamil, and lanthanum. Alignment occurred at a steady rate and was dependent in a saturating fashion on field strength. The Ca2+ ionophore A23187 had a significant inhibitory effect on cell alignment in applied electrical fields; however, the Ca2+ channel blockers lanthanum and verapamil did not have a significant effect on alignment.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bem.2250100406
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