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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 157 (1990), S. 193-202 
    ISSN: 1615-6102
    Keywords: Current vectors ; Elodea canadensis ; Ionic currentPolarity ; Vibrating probe (3-d recording)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The pattern and density of ionic currents near the surface ofElodea canadensis leaves were investigated using a 3-d recording vibrating probe. Positive current always entered the adaxial (upper) surface, and left the abaxial (lower) surface of mature leaves. Current densities ranged from 1 to 15μAcm−2 in leaves irradiated with white light submerged in artificial pond water of pH 8. When the pH of the medium was lowered from 8 to 6, a rapid, approximate 40% reduction in current density on both sides of the leaf occured. Within 15 min of turning the light off, the current at the surface almost vanished. After re-introducing light, current began to rise after 10 to 15 min. Immature leaves exhibited no polarity in the current pattern, i.e., inward and outward current was found on both surfaces. Immature leaves also produced less current than mature ones, and responded less strongly to darkness. The results support the conclusion thatElodea leaves pump H+ out at the lower surface, and leak OH− at the upper surface. The H+ current at the lower surface presumably facilitates the intake of carbon in form of CO2.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 187 (1995), S. 132-137 
    ISSN: 1615-6102
    Keywords: Electroporation ; Electropermeabilization ; Lilium longiflorum ; Pollen grains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electroporation was used to introduce plasma membrane impermeable molecules into the cytoplasm of pollen grains ofLilium longiflorum. Ungerminated pollen grains were exposed to the fluorescent dye quin2 or FITC-labelled dextrans and electroporated with exponentially decaying voltage pulses of 250 to 2000 V/cm and time constants of 0.01 to 10 μs. The number of electroporated pollen grains increased with the strength and duration of the voltage pulses, and with the osmolarity of the external medium. Optimal results were obtained with pulses of 1000 V/cm and 10 μs time constant, and with 900 mM mannitol in the electroporation buffer. The size of the pores produced in the plasma membrane by electroporation allowed uptake of 40 kDa dextran but not 70 kDa dextran. The rate of germination of pollen grains was low immediately after electroporation, but increased with time in pollen growth medium. The conditions of electroporation reported here may be used to load genetic material into pollen grains for the production of transgenic plants.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 113 (1982), S. 89-96 
    ISSN: 1615-6102
    Keywords: Bioelectric currents ; Extracellular current measurements ; Vibrating probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper summarizes the fundamentals and describes advances in the vibrating probe, a tool that was developed and introduced into biological research byJaffe andNuccitelli in 1974. The improvements reported are concerned on the one hand with the construction, micropositioning and maintenance of the probe itself and, on the other hand, with the origin of artifacts and possible ways to avoid or, at least, to detect and monitor them. The advances in construction and the elucidation of possible artifacts may help extend the usefulness of this unique tool in investigations of ionic currents which cells and tissues drive through themselves during development and movement.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1615-6102
    Keywords: Achlya ; Development ; Electrophysiology ; Sporogenesis ; Vibrating probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study explores natural ionic currents traversing hyphae and sporangia during the asexual life cycle of the mycelial water moldAchlya debaryana. Ionic current enters the extending hyphal apex at a density of 1–2μAcm−2 in the form of current spikes. Current normal to the surface enters hyphae up to 600 μm behind the growing tip. A large efflux of current lasting 1–2 minutes occurs during the homogeneous stage of sporangium development. Spore release is accompanied by a few spikes of inward current. The results obtained so far suggest that the developmental processes of hyphal elongation and sporangium formation in the asexual life cycle of water molds are correlated with particular ionic currents.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1615-6102
    Keywords: Immunolocalization ; H+-ATPase ; Tip growth ; Lilium longiflorum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A heterogeneous distribution of H+-ATPase was visualized in germinated pollen ofLilium longiflorum using monoclonal antibodies raised against plasma membrane H+-ATPase. Immunolocalization studies of protoplasts and subprotoplasts derived from pollen tubes and sectioned pollen grains and pollen tubes show that H+-ATPases are abundant in the plasma membrane of pollen grains but are absent or sparsely distributed in the plasma membrane of pollen tubes. This polar distribution of H+-ATPases is probably the basis of the endogenous current pattern measured in growing lily pollen and involved in pollen tube tip growth.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of K+ deficiency on the plasma membrane (PM) H+-ATPase was studied in young stems of poplar plants (Populus tremula × tremuloides) grown with low or full-strength K+ supply. Immunological assays using different antibodies were applied to test if K+ deficiency affects the amount of immunodetectable PM H+-ATPases in the stem tissue. The monoclonal antibody clone 46 E5 B11 revealed an increased abundance of PM H+-ATPases under conditions of low K+ supply, and immunolabelling experiments showed that this increase was restricted to vessel-associated cells (VACs) of the wood ray parenchyma. Replacement of the monoclonal antibody by a polyclonal antibody against PM H+-ATPase gave a specific immunoreactivity on blots as well as tissue sections too, but the labelling intensity showed no difference between plants with low or full-strength K+ supply. Measurements of extracellular H+ concentrations using non-invasive, H+-selective microelectrodes revealed a lowering of the pH at the surface of VACs and an enhancement of net efflux of H+ in plants grown with low K+ supply. The present results indicate an up-regulation of specific isoforms of the PM H+-ATPase in VACs under K+-deficient conditions and suggest a key role for these PM H+-ATPases in unloading K+ from the xylem stream.
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  • 7
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The patterns of naturally growing ion currents associated with horizontally growing roots of Trifolium repens L. seedlings were measured in a simple low-salt bathing medium using a highly sensitive vibrating electrode. Current consistently enters the main elongation zone of the root and leaves from mature, elongated tissue. This current enters and leaves with densities of ca. 4.0–11.0 mA m−2 and 4.0 mA m−2, respectively. Current was also delected entering the zone of emerging root hairs and also the root-hair tips themselves.These results are a further example of the involvement of self-generated electrical fields in plant developmental processes. Possible, secondary rhizosphere-associated effects of the extracellular loop of the developmental current are also suggested.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Planta 146 (1979), S. 31-39 
    ISSN: 1432-2048
    Keywords: Autoradiography ; Calcium ; Mougeotia ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ca2+ is proposed to function as a messenger in such phytochrome-mediated responses as localized cell growth, intracellular movements, and control of plasma membrane properties. To test this hypothesis, the uptake of Ca2+ in irradiated and non-irradiated regions of individual threads of the green alga Mougeotia was studied with the aid of 45Ca2+ and low temperature autoradiography: 10–20 cells within 40–60 cell-long threads were irradiated for up to 1 min, transferred to darkness for 3 to 10 min, submersed in a radioactive medium for 1 min, washed in an unlabelled medium for 30 min, and then autoradiographed at-80° C for several days. The autoradiographs show that those cells which had been pre-irradiated with red light did take up 2–10 times more Ca2+ than the adjacent non-irradiated cells of the same thread. Cells pre-irradiated with farred light or red light followed by far-red light showed no enhanced uptake of Ca2+. These results might be interpreted to indicate, firstly, that phytochrome-Pfr is involved in the enhanced uptake of Ca2+ and secondly, that the accumulation of radioactive Ca2+ in red light irradiated cells is an expression of an increased intracellular concentration of Ca2+. This interpretation is based on the data that (i) the dark interval between irradiation and labelling precluded the involvement of photosynthesis, (ii) the effect of red light was reversible with far-red light, and (iii) the accumulation of Ca2+ persisted during the long wash-out period. We speculate, that the red light-enhanced accumulation of Ca2+ in Mougeotia cells is caused by a Pfr-mediated increase of the Ca-permeability of the plasma membrane, and perhaps by a Pfr-impeding of an active Ca2+-extrusion.
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  • 9
    ISSN: 1432-2048
    Keywords: Calcium Ions ; Membrane potential ; Nitella ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolated internodes of Nitella (N. opaca, N. flexilis) and Nitellopsis spec. were punctured with single microelectrodes and their membrane potentials were recorded continuously during various light treatments. In red light the initial response was always a depolarization. This depolarization began with a lag-time of 0.4-3.5s and reached a steady state within 1–2 min of continuous illumination. Repolarization began within several seconds after turning off the light. The magnitude of the red-light-induced depolarization increased with the Ca2+-concentration of the medium. The largest depolarizations were recorded in 5 m mol l-1 Ca2+. Ca2+ could not be replaced in this function by Na+, Mg2+, La3+ or mannitol. Far-red light alone had no effect on the resting membrane potential. Far-red light applied immediately after red light accelerated the repolarization of the membrane potential. Far-red light applied simultaneously with red light reduced the amount of depolarization and increased the rate of repolarization. The results indicate that phytochrome and Ca2+ are involved in the light-induced depolarization of the membrane. They are consistent with the hypothesis that phytochrome may act by triggering a Ca2+-influx at the plasma membrane.
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  • 10
    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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