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  • Articles: DFG German National Licenses  (4)
  • 2000-2004
  • 1980-1984  (4)
  • 1915-1919
  • Clivia  (2)
  • Slow muscle fibres  (2)
  • ACh-sensitivity  (1)
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  • Articles: DFG German National Licenses  (4)
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Year
  • 1
    ISSN: 1432-2048
    Keywords: Clivia ; Cuticle development and fine structure ; Water permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fine structure of the upper cuticular membrane (CM) of Clivia miniata leaves was investigated using electron microscopy. The CM is made up of a thin (130 nm) lamellated cuticle proper (CP) and a thick (up to 7 μm over periclinal walls) cuticular layer (CL) of marbled appearance. Evidence is presented to show that the electron lucent lamellae of the CP do not simply represent layers of soluble cuticular lipids (SCL). Instead, the lamellation is probably due to layers of cutin differing in polarity. It is argued that the SCL in the Cp are the main barrier to water. Thickening of the CM during leaf development takes place by interposition of cutin between the CM and the cellin wall. The cutin of young, expanding leaves has a high affinity for KMnO4 and is therefore relatively polar. As leaves mature, the external CL underneath the CP becomes non-polar, as only little contrast can be obtained with permanganate as the post fixative.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 402 (1984), S. 88-93 
    ISSN: 1432-2013
    Keywords: Slow muscle fibres ; Denervation ; ACh-sensitivity ; Local electrical activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 1. The distribution of acetylcholine (ACh)-sensitive membrane areas was determined in 11–75 days denervated slow muscle fibres ofRana temporaria by iontophoretic application of acetylcholine. The fibres were also stimulated directly, and their electrical activity was recorded with an intra- and an extracellular electrode. 2. During the first two weeks following denervation the size of the ACh-sensitive fibre surface was similar to that of normal slow fibres, but a spreading out of ACh-sensitivity occurred between the 13th and 20th day. 3. The slow fibre membrane did not become homogeneously ACh-sensitive; even after long periods of denervation large local sensitivity gradients could be observed. Throughout the denervation period maximum values of ACh-sensitivity were in the same range as in normal slow fibres. 4. Action potentials were fully developed when ACh-sensitivity started to spread out. Extracellularly recorded inward currents varied in amplitude along the fibre surface, and either one or two peaks were observed in individual fibres. 5. The spatial relationship between inward current peaks and peaks of ACh-sensitivity was investigated in 12 fibres. Fifteen inward current peaks were located at distances of 30–640 μm from points of maximum ACh-sensitivity; only once did the centers of ACh-sensitivity and excitability coincide. 6. It is concluded that Na channels are incorporated into nonjunctional membrane areas of denervated slow fibres; this process preceds the incorporation of ACh-receptors by approximately one week.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Clivia ; Cuticle (fine structure and development) ; Cutin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of BF3-methanol treatment on the mass and fine structure of isolated Clivia leaf cuticles at different stages of development has been investigated. BF3-methanol cleaves ester linkages in cutin; however, the cuticles are not completely depolymerized. With increasing age, the residue left after BF3-methanol treatment increases in mass. In very young cuticles, 10% of the total cutin resisted BF3-methanol and the fraction of nonester cutin increased up to 62% in mature leaves. Transmission electron microscopy shows that fine structure of the cuticle proper is severely distorted but not destroyed. The internal cuticular layer, which exhibits a heavy contrast when fixed with KMnO4, is completely depolymerized, while the external cuticular layer is hardly affected. The results are discussed in relation to cuticle development and to the function of cuticles as transpiration resistances.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 397 (1983), S. 300-305 
    ISSN: 1432-2013
    Keywords: Slow muscle fibres ; ACh ; Sensitivity ; Distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 1) The distribution of acetylcholine-sensitive membrane areas in slow muscle fibres of pyriformis muscles of Rana temporaria was examined by iontophoretic application of acetylcholine from high resistance pipettes. 2) ACh-sensitivity varied considerably along individual slow fibres and from fibre to fibre. In some fibres the sensitivity was restricted to segments of less than 100 μm, in others it was continuous over several millimeter. Segments of variable length, but up to several millimeter, were completely insensitive to acetylcholine. Highly sensitive spots (〉1,000 mV/nC) were found occasionally, their diameter being of the order of 10–20 μm only. The occurrence at rather regular intervals of ACh-sensitive areas was a rare observation; no evidence was found for a generalized ACh-sensitivity. 3) There were marked differences in the lengths of ACh-sensitive segments between surface fibres and fibres located in deeper layers of the muscles. 4) It is concluded that the ACh-sensitive membrane areas correspond to individual nerve muscle contacts of the small motor system whose spatial distribution is extremely variable. In superficial slow fibres the synaptic contacts seem to be located predominantly on the internal circumference of the fibres.
    Type of Medium: Electronic Resource
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