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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 16 (1981), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Sulcular penetration patterns of phenytoin (PHT) and albumin (BSA), in New Zealand white rabbits, were followed through the sulcular lining tissue, overlying gingiva, interposed connective tissue, proximating periosteum and blood over 180 minutes. The time course study revealed that a steady-state uptake of both molecules from the sulcus into the sulcular lining tissue was reached approximately 60 minutes after local tracer application. It was also found that PHT, after penetrating the sulcular lining tissue, was maintained at higher levels in gingiva than in other adjacent tissues while BSA levels were found highest in periosteum. Kinetic studies of these tissues demonstrated that sulcular tissue had a greater capacity for PHT than BSA and that uptake by this tissue had a capacity-limited characteristic. The other adjacent tissues and blood also showed capacity-limited characteristics probably reflecting uptake by the sulcular tissues. BSA degradation or PHT metabolism did not occur in any of these tissues or in serum.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 51 (1981), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The ability of intact primary roots of corn (Zea mays L. Bear Hybrid WF 9 × 38) to adapt to growth-inhibitory concentrations of auxin was studied using a highly sensitive position sensor transducer to measure growth. The timing, concentration dependence and temperature dependence of adaptation were studied as well as the time course of loss of adaptation upon removal of auxin. The rate of root elongation is inhibited 80% within 40 min after application of 10−7M IAA. Within 90 min growth rate begins to recover. For concentrations of IAA equal to or greater than 10−7M, recovery of growth rate (adaptation) is incomplete. Corn roots show a similar pattern of adaptation to the synthetic auxins NAA and 2,4-D. The Q10 for adaptation is high (3.2) and comparable to that for root growth (3.3). Upon removal of exogenous IAA, loss of adaptation occurs with full sensitivity to the hormone regained within 20 min.Based on the auxin specificity and the Q10 for adaptation it is concluded that adaptation occurs neither by a change in the auxin degradation capacity of the root nor by a diffusional redistribution of applied auxin. It is suggested that adaptation involves metabolic processes, perhaps a metabolically dependent alteration of the number or affinity of auxin binding sites.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 67 (1986), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We investigated the effect of Ca2+ on ethylene production in 2-cm long apical segments from primary roots of corn (Zea mays L., B73 × Missouri 17) seedlings. The seedlings were raised under different conditions of Ca2+ availability. Low-Ca and high-Ca seedlings were raised by soaking the grains and watering the seedlings with distilled water or 10 mM CaCl2, respectively. Segments from high-Ca roots produced more than twice as much ethylene as segments from low-Ca roots. Indoleacetic acid (IAA; 1 μM) enhanced ethylene production in segments from both low-Ca and high-Ca roots but auxin-induced promotion of ethylene production was consistently higher in segments from high-Ca roots. Addition of I-aminocyclopropane-I-carboxylic acid (ACC) to root segments from low-Ca seedlings doubled total ethylene production and the rate of production remained fairly constant during a 24 h period of monitoring. In segments from high-Ca seedlings ACC also increased total ethylene production but most of the ethylene was produced within the first 6 h. The data suggest that Ca2+ enhances the conversion of ACC to ethylene. The terminal 2 mm of the root tip were found to be especially important to ethylene biosynthesis by apical segments and, experiments using 45Ca2+ as tracer indicated that the apical 2 mm of the root is the region of strongest Ca2+ accumulation. Other cations such as Mn2+, Mg2+, and K+ could largely substitute for Ca2+. The significance of these findings is discussed with respect to recent evidence for gravity-induced Ca2+ redistribution and its relationship to the establishment of asymmetric growth during gravitropic curvature.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 72 (1988), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hasenstein, K. H. and Evans, M. L. 1988. The influence of calcium and pH on growth in primary roots of Zea mays. - Physiol. Plant. 72: 466–470.We investigated the interaction of Ca2+ and pH on root elongation in Zea mays L. cv. B73 × Missouri 17 and cv. Merit. Seedlings were raised to contain high levels of Ca2+ (HC, imbibed and raised in 10 mM CaCl2) or low levels of Ca2+ (LC, imbibed and raised in distilled water). In HC roots, lowering the pH (5 mM MES/Tris) from 6.5 to 4.5 resulted in strong, long-lasting growth promotion. Surprisingly, increasing the pH from 6.5 to 8.5 also resulted in strong growth promotion. In LC roots acidification of the medium (pH 6.5 to 4.5) resulted in transient growth stimulation followed by a gradual decline in the growth rate toward zero. Exposure of LC roots to high pH (pH shift from 6.5 to 8.5) also promoted growth. Addition of EGTA resulted in strong growth promotion in both LC and HC roots. The ability of EGTA to stimulate growth appeared not to be related to H+ release from EGTA upon Ca2+ chelation since, 1) LC roots showed a strong and prolonged response to EGTA, but only a transient response to acid pH, and 2) promotion of growth by EGTA was observed in strongly buffered solutions. We also examined the pH dependence of the release of 45Ca2+ from roots of 3-day-old seedlings grown from grains imbibed in 45Ca2+. Release of 45Ca2+ from the root into agar blocks placed on the root surface was greater the more acidic the pH of the blocks. The results indicate that Ca2+ may be necessary for the acid growth response in roots.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 6 (1979), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 11 (1981), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of plant growth regulation 5 (1986), S. 73-83 
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A computer-based video digitizer system is described which allows automated tracking of markers placed on a plant surface. The system uses customized software to calculate relative growth rates at selected positions along the plant surface and to determine rates of gravitropic curvature based on the changing pattern of distribution of the surface markers. The system was used to study the time course of gravitropic curvature and changes in relative growth rate along the upper and lower surface of horizontally-oriented roots of maize (Zea mays L.). The growing region of the root was found to extend from about 1 mm behind the tip to approximately 6 mm behind the tip. In vertically-oriented roots the relative growth rate was maximal at about 2.5 mm behind the tip and declined smoothly on either side of the maximum. Curvature was initiated approximately 30 min after horizontal orientation with maximal (50°) curvature being attained in 3 h. Analysis of surface extension patterns during the response indicated that curvature results from a reduction in growth rate along both the upper and lower surfaces with stronger reduction along the lower surface.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 83 (1996), S. 97-102 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 83 (1996), S. 97-102 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: 10 Be concentration. This pedogenic component closely parallels paleorainfall, so that regional precipitation history during the Quaternary can be derived.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 93 (1986), S. 75-83 
    ISSN: 1432-1424
    Keywords: single channel ; chloride ; selectivity ; conductance state ; Aplysia neurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Single-channel recordings from outside-out patches ofAplysia neurones in K-free solutions revealed the presence in most membrane patches of ionic channels showing surprising selectivity properties, as deduced from reversal potential measurements. After complete substitution of external NaCl by mannitol (in the presence of internal CsCl), these channels are more permeable to Cl than to Cs, but are also slightly permeable to Cs:P Cl/P Cs=4. Furthermore, in the presence of external NaCl, their ability to discriminate cations from anions seems lower than in external mannitol. Substitutions of external Cl by various anions showed that the channels are more permeable to NO3 than to Cl, and that they are appreciably permeable to isethionate, SO4 and methanesulfonate. Their elementary conductance is about 100 pS in 600mm symmetrical Cl. However, different conductance states (usually 2 or 3) can often be detected in the same membrane patch. By using voltage ramps, we established theI–V curves corresponding to each of these states and found small but significant differences between the reversal potentials of each state.
    Type of Medium: Electronic Resource
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