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  • Articles: DFG German National Licenses  (10)
  • 1995-1999  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Blue electroluminescent devices based on soluble poly(p-pyridine) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4264-4266 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated unilayer electroluminescent devices from soluble poly(p-pyridine) (PPy). The solubility of PPy in weak acids allows direct spin casting of the polymer films. The electroluminescence spectrum peaks at 2.5 eV (497 nm) corresponding to white light weighted towards the blue end of the spectrum. The photoluminescence spectrum peaks at 2.35 eV (530 nm). The operating voltages of the devices ranged from 4 to 12 V with current densities of 6 to 8 mA/mm2. We compare our devices with similar blue emitting devices based on poly(p-phenylene). © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359890
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Alternating-current light-emitting devices based on conjugated polymers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 894-896 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Most polymer electroluminescent devices to date are represented as tunnel diodes and operate under direct-current (dc) driving field. Here we report the fabrication of symmetrically configured alternating-current (ac) light-emitting (SCALE) devices based on conjugated polymers. The new devices consist of an emissive polymer layer sandwiched between two redox polymer layers. This configuration enables the SCALE devices to work under both forward and reverse dc bias as well as in ac modes. The nearly ohmic electrode/redox polymer contacts improve the charge injection efficiency significantly and make the SCALE device operation insensitive to electrode work functions. Symmetric operation supports the key role of redox polymer/emissive polymer interface states. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116222
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  • 3
    Electronic Resource
    Electronic Resource
    The cellular pathway of photosynthate transfer in the developing wheat grain. III. A structural analysis and physiological studies of the pathway from the endosperm cavity to the starchy endosperm (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The cellular pathway of sucrose transfer from the endosperm cavity to the starchy endosperm of developing grains of wheat (Triticum turgidum) has been elucidated. The modified aleurone and sub-aleurone cells exhibit a dense cytoplasm enriched in mitochondria and endoplasmic relicilium. Significantly, the sub-aleurone cells are characterized by secondary wall ingrowths. Numerous plasmodesmata interconnect all cells between the modified aleurone and starchy endosperm. The pro-tonophore carbonylcyanide-m-chlorophenyl hydrazone (CCCP) slowed [14C]sucrose uptake by grain tissue slices enriched in modified aleurone and sub-aleurone cells but had no effect on uptake by the starchy endosperm. The fluorescent weak acid sulphorhodamine G (SRG) was preferentially accumulated by the modified aleurone and sub-aleurone cells, and this uptake was sensitive to CCCP. The combined plasma membrane surface areas of the modified aleurone and sub-aleurone cells appeared to be sufficient to support the in vivo rates of sucrose transfer to the starchy endosperm. Plasmolysis of intact excised grain inhibited [14C]sucrose transfer from the endosperm cavity to the starchy endosperm. The sulphydryl group modifier p-chloromercuribenzenesulphonie acid (PCMBS) decreased [14C]sucrose uptake by the modified aleurone and sub-aleurone cells but had little effect on uptake by the starchy endosperm. In contrast, when PCMBS and [14C]sucrose were supplied to the endosperm cavity of intact excised grain, PCMBS slowed accumulation by all tissues equally. Estimates of potential sucrose fluxes through the interconnecting plasmodesmata were found to be within the published range. It is concluded that the bulk of sucrose is accumulated from the endosperm cavity by the modified aleurone and sub-aleurone cells and subsequently transferred through the symplast to the starchy endosperm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00374.x
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  • 4
    Electronic Resource
    Electronic Resource
    The cellular pathway of photosynthate transfer in the developing wheat grain. II. A structural analysis and histochemical studies of the pathway from the crease phloem to the endosperm cavity (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the developing wheat grain, photosynthate is transferred longitudinally along the crease phloem and then laterally into the endosperm cavity through the crease vascular parenchyma, pigment strand and nucellar projection. In order to clarify this cellular pathway of photosynthate unloading, and hence the controlling mechanism of grain filling, the potential for symplastic and apoplastic transfer was examined through structural and histochemical studies on these tissue types. It was found that cells in the crease region from the phloem to the nucellar projection are interconnected by numerous plasmodesmata and have dense cytoplasm with abundant mitochondria. Histochemical studies confirmed that, at the stage of grain development studied, an apoplastic barrier exists in the cell walls of the pigment strand. This barrier is composed of lignin, phenolics and suberin. The potential capacity for symplastic transfer, determined by measuring plasmodesmatal frequencies and computing potential sucrose fluxes through these plasmodesmata, indicated that there is sufficient plasmodesmatal cross-sectional area to support symplastic unloading of photosynthate at the rate required for normal grain growth. The potential capacity for membrane transport of sucrose to the apoplast was assessed by measuring plasma membrane surface areas of the various cell types and computing potential plasma membrane fluxes of sucrose. These fluxes indicated that the combined plasma membrane surface areas of the sieve element–companion cell (se–cc) complexes, vascular parenchyma and pigment strand are not sufficient to allow sucrose transfer to the apoplast at the observed rates. In contrast, the wall ingrowths of the transfer cells in the nucellar projection amplify the membrane surface area up to 22-fold, supporting the observed rates of sucrose transfer into the endosperm cavity. We conclude that photosynthate moves via the symplast from the se–cc complexes to the nucellar projection transfer cells, from where it is transferred across the plasma membrane into the endosperm cavity. The apoplastic barrier in the pigment strand is considered to restrict solute movement to the symplast and block apoplastic solute exchange between maternal and embryonic tissues. The implications of this cellular pathway in relation to the control of photosynthate transfer in the developing grain are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00373.x
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Corticotrophin-releasing factor produces a long-lasting enhancement of synaptic efficacy in the hippocampus (1998)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 10 (1998), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We have previously demonstrated that intra-hippocampal injection of corticotrophin-releasing factor improved memory retention of an inhibitory avoidance learning in rats; while the electrophysiological effects corticotrophin-releasing factor produces on hippocampal neurons are largely uncharacterized. In the present study, we found that corticotrophin-releasing factor injected into the dentate gyrus of hippocampus produced a dose-dependent and long-lasting enhancement in synaptic efficacy of these neurons, as measured by an increase in the amplitude and slope of population excitatory postsynaptic potentials, as well as the amplitude of population spike. The onset of corticotrophin-releasing factor-induced potentiation was slow. It was observed approximately 40–60 min after corticotrophin-releasing factor administration and lasted for more than 5 h. This effect of corticotrophin-releasing factor was blocked by pretreatment with the cyclase-adenosine-3,5-monophosphate (cAMP) inhibitor Rp-adenosine-3,5-cyclic monophosphothiolate triethylamine (Rp-cAMPS) and partially blocked by the N-methyl-D-aspartate receptor antagonist MK-801. Further, pretreatment with corticotrophin-releasing factor receptor antagonist dose-dependently diminished tetanization-induced long-term potentiation, and corticotrophin-releasing factor and tetanic stimuli had an additive effect on hippocampal neuron excitation. Moreover, direct injection of corticotrophin-releasing factor increased cAMP level in the dentate gyrus. These results together suggest that corticotrophin-releasing factor-induced potentiation simulates the late phase of tetanization-induced long-term potentiation and cAMP seems to be the messenger mediating this effect. Moreover, corticotrophin-releasing factor-induced potentiation and long-term potentiation may share some similar mechanisms, and corticotrophin-releasing factor is probably involved in the neural circuits underlying long-term potentiation. Thus, corticotrophin-releasing factor may play an important role in modulating synaptic plasticity in the hippocampus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.1998.00352.x
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  • 6
    Electronic Resource
    Electronic Resource
    Interactive effects of nicotine and MPTP on striatal tetrahydrobiopterin in mice (1996)
    Springer
    Journal of biomedical science 3 (1996), S. 47-53 
    Details
    ISSN: 1423-0127
    Keywords: Nicotine ; 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine ; Mecamylamine ; Biopterin ; Dopamine ; Striatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin known to cause dopamine (DA) neuron degeneration, while the psychoactive compound nicotine is known to excite DA neurons. Tetrahydrobiopterin is the cofactor for tyrosine hydroxylase (TOH) in the regulation of DA biosynthesis. The present study investigated the interactions between nicotine and MPTP on striatal biopterin, DA and TOH activity in BALB/c mice. The results indicated that both acute and chronic nicotine administrations at various concentrations significantly increased biopterin and DA levels in the striatum, while MPTP markedly decreased these measures. Pretreatment with nicotine at a dose having no significant effect alone, partially protected against MPTP's toxicity on biopterin and DA. Increasing the dose of nicotine did not have a further protective action. The toxicity of MPTP on TOH was also prevented by nicotine. Further, the above effects of nicotine were probably mediated through the cholinergic nicotinic receptors since mecamylamine reversed the effects of nicotine. These results suggest that nicotine interacts with the dopaminergic system probably at the level of DA biosynthesis through activating TOH and its coenzyme tetrahydrobiopterin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253578
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  • 7
    Electronic Resource
    Electronic Resource
    The cellular pathway of sucrose transport in developing cotyledons of Vicia faba L. and Phaseolus vulgaris L.: a physiological assessment (1995)
    Springer
    Planta 196 (1995), S. 659-667 
    Details
    ISSN: 1432-2048
    Keywords: Cotyledon (developing) ; Dermal cell complex (Phaseolus) ; Dermal transfer cell complex (Vicia) ; Phaseolus ; Sugar transport ; Vicia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cellular pathway of sugar uptake in developing cotyledons of Vicia faba L. and Phaseolus vulgaris L. seed was evaluated using a physiological approach. The cotyledon interface with the seed coat is characterised by a specialised dermal cell complex. In the case of Vicia faba cotyledons, the epidermal component of the dermal cell complex is composed of transfer cells. Sucrose is the major sugar presented to the outer surface of both cotyledons and it is taken up from the apoplasm unaltered. Estimated sucrose concentrations within the apparent free space of Vicia and Phaseolus cotyledons were 105 and 113 mM respectively. Rates of in-vitro uptake of [14C]sucrose by cotyledon segments or by whole cotyledons following physical removal or porter inactivation of the outer cells demonstrated that, for both Vicia and Phaseolus cotyledons, the dermal cell complexes are the most intense sites of sucrose uptake. Accumulation of [14C]sucrose in the storage parenchyma of whole cotyledons was directly affected by experimental manipulation of uptake by the outer cell layers and plasmolytic disruption of the interconnecting plasmodesmata. These findings indicated that sucrose accumulated by the dermal cell complexes is transported symplasmically to the storage parenchyma. Overall, it is concluded that the dermal cell complexes of the developing legume embryo, irrespective of the presence or absence of wall ingrowths, are the major sites for the uptake of sucrose released from the maternal tissues to the seed apoplasm. Thereafter, the accumulated sucrose is transported radially inward through the symplast to the storage parenchyma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197329
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  • 8
    Electronic Resource
    Electronic Resource
    The cellular pathway of sucrose transport in developing cotyledons ofVicia faba L. andPhaseolus vulgaris L.: a physiological assessment (1995)
    Springer
    Planta 196 (1995), S. 659-667 
    Details
    ISSN: 1432-2048
    Keywords: Cotyledon (developing) ; Dermal cell complex (Phaseolus) ; Dermal transfer cell complex (Vicia) ; Phaseolus ; Sugar transport ; Vicia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cellular pathway of sugar uptake in developing cotyledons ofVicia faba L. andPhaseolus vulgaris L. seed was evaluated using a physiological approach. The cotyledon interface with the seed coat is characterised by a specialised dermal cell complex. In the case ofVicia faba cotyledons, the epidermal component of the dermal cell complex is composed of transfer cells. Sucrose is the major sugar presented to the outer surface of both cotyledons and it is taken up from the apoplasm unaltered. Estimated sucrose concentrations within the apparent free space ofVicia andPhaseolus cotyledons were 105 and 113 mM respectively. Rates of in-vitro uptake of [14C]sucrose by cotyledon segments or by whole cotyledons following physical removal or porter inactivation of the outer cells demonstrated that, for bothVicia andPhaseolus cotyledons, the dermal cell complexes are the most intense sites of sucrose uptake. Accumulation of [14C]sucrose in the storage parenchyma of whole cotyledons was directly affected by experimental manipulation of uptake by the outer cell layers and plasmolytic disruption of the interconnecting plasmodesmata. These findings indicated that sucrose accumulated by the dermal cell complexes is transported symplasmically to the storage parenchyma. Overall, it is concluded that the dermal cell complexes of the developing legume embryo, irrespective of the presence or absence of wall ingrowths, are the major sites for the uptake of sucrose released from the maternal tissues to the seed apoplasm. Thereafter, the accumulated sucrose is transported radially inward through the symplast to the storage parenchyma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01106758
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of drug-protein interactions by combined microdialysis and high-performance liquid chromatography (1997)
    Springer
    Chromatographia 44 (1997), S. 205-208 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microdialysis ; Carbamazepine ; Human serum albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and rapid method for determination of the parameters of the interaction between drugs and protein, including the association constant and the number of binding sites, has been developed by use of a microdialysis sampling technique combined with high-performance liquid chromatography. The drug and protein (carbamazepine (5H-dibenz[b,f]flazepine-5-carboxamide, CBZ) and human serum albumin (HSA) were used as examples) were mixed in different molar ratios in 0.067 M potassium phosphate buffer, pH 7.4, and incubated at 37°C in a water-bath. The microdialysis probe was the used to sample the mixed CBZ-HSA solution at a perfusion rate of 1 μL min−1. The concentration of CBZ in the microdialysate was determined by reversed-phase high-performance liquid chromatography. Relative recovery (R), determined in vitro under similar conditions, was approximately 42.7%; theRSD ofR was approximately 1.85%. The estimated association constant (K) and the number of the binding sites,n, on one molecule of HSA were 1.06×104 M−1 and 0.880, respectively, which is in good agreement with the literature values determined by high-performance frontal analysis. The potential use of microdialysis is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466457
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  • 10
    Electronic Resource
    Electronic Resource
    Changes in Nuclear Ultrastructure during Callus Development in Tissue Culture of Allium Sativum (1998)
    Springer
    Biologia plantarum 41 (1998), S. 49-55 
    Details
    ISSN: 1573-8264
    Keywords: active phase cells ; dividing cells ; garlic ; nucleolus ; quiescent cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The changes in nuclear ultrastructure during garlic development were investigated. In quiescent cells, the nucleus was oblate and small, full of heterochromatin, and without nucleolus. In the active phase cells, the nucleus moved toward the center of the cell, and was enlarged with many deep fissures, and the heterochromatin in the nucleus turned to be euchromatin. One or more nucleoli were seen in active phase cells. Cell divisions were by means of amitosis. Relatively large nuclei with small distortions were seen in the callus cells. These results suggest that the metabolism of the active cells was higher than that of callus and quiescent cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001752214563
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