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  • 1
    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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    Paper (German National Licenses)
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  • 2
    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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    Paper (German National Licenses)
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  • 3
    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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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Nucellar projection transfer cells in the developing wheat grain (1994)
    Springer
    Protoplasma 182 (1994), S. 39-52 
    Details
    ISSN: 1615-6102
    Keywords: Nucellar projection ; Symplast/apoplast sucrose exchange ; Transfer cell ; Wall ingrowth development ; Wheat grain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transfer cells in the nucellar projection of wheat grains at 25 ±3 days after anthesis have been examined using light and electron microscopy. Within the nucellar tissue, a sequential increase in non-polarized wall ingrowth differentiation and cytoplasmic density was evident. Cells located near the pigment strand were the least differentiated. The degree of differentiation increased progressively in cells further removed from the pigment strand and the cells bordering the endosperm cavity had degenerated. Four stages of transfer cell development were identified at the light microscope level. Wall ingrowth differentiation followed a sequence from a papillate form through increased branching (antler-shaped ingrowths) which ultimately anastomosed to form a complex labyrinth. The final stage of wall ingrowth differentiation was compression which resulted in massive ingrowths. In parallel with wall ingrowth deposition cytoplasmic density increased. During wall deposition, paramural and multivesicular bodies were prominent and were in close association with the wall ingrowths. The degeneration phase involved infilling of cytoplasmic islets within the wall ingrowths. This was accompanied by complete loss of the protoplast. The significance of this transfer cell development for sucrose efflux to the endosperm cavity was assessed by computing potential sucrose fluxes across the plasma membrane surface areas of the nucellar projection cells. Transfer cell development amplified the total plasma membrane surface area by 22 fold. The potential sucrose flux, when compared with maximal rates of facilitated membrane transport of sugars, indicated spare capacity for sucrose efflux to the endosperm cavity. Indeed, when the total flux was partitioned between the nucellar projection cells at the three stages of transfer cell development, the fully differentiated stage III cells located proximally to the endosperm cavity alone exhibited spare transport capacity. Stage II cells could accommodate the total rate of sucrose transfer, but stage I cells could not. It is concluded that the nucellar projection tissue of wheat provides a unique opportunity to study transfer cell development and the functional role of these cells in supporting sucrose transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403687
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    Paper (German National Licenses)
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