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  • Polymer and Materials Science  (12)
  • Forelimb afferents  (3)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 56 (1984), S. 293-307 
    ISSN: 1432-1106
    Schlagwort(e): Descending pathways ; Forelimb afferents ; Disynaptic inhibition ; C3-C4 propriospinal neurones
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Intracellular recording was made in the C3-C4 segments from cell bodies of a previously described system of propriospinal neurones (PNs), which receive convergent monosynaptic excitation from different higher motor centres and mediate disynaptic excitation and inhibition from them to forelimb motoneurones. Inhibitory effects in these PNs have now been investigated with electrical stimulation of higher motor centres and forelimb nerves. Short-latency IPSPs were evoked by volleys in the cortico-, rubro- and tectospinal tracts and from the reticular formation. Latency measurements showed that those IPSPs which required temporal summation were disynaptically mediated. After transection of the corticospinal tract in C2, only small and infrequent disynaptic IPSPs were evoked from the pyramid. It is postulated that disynaptic pyramidal IPSPs only to a small extent are evoked by monosynaptic excitation of reticulospinal inhibitory neurones known to project directly to the PNs, and that they are mainly mediated by inhibitory interneurones in the C3-C4 segments. Tests with spatial facilitation revealed monosynaptic excitatory convergence from tecto-, rubro- and probably also from reticulospinal fibres on inhibitory interneurones monosynaptically excited from corticospinal fibres (interneuronal system I). Disynaptic IPSPs were also evoked in the great majority of the PNs by volleys in forelimb muscle and skin nerves. A short train of volleys was usually required to evoke these IPSPs from group I muscle afferents. In the case of cutaneous nerves and mixed nerves single volleys were often effective, and the lack of temporal facilitation of IPSPs produced by a train of volleys showed strong linkage from these nerves. The results obtained after transection of the dorsal column at different levels show that the relay is almost entirely rostral to the forelimb segments. Test with spatial facilitation revealed that interneurones monosynaptically activated from forelimb afferents receive convergent excitation from corticospinal but not or only weakly so from tecto- or rubrospinal fibres. There was also convergence from group I muscle afferents and low threshold cutaneous afferents on common interneurones. It is postulated that the disynaptic IPSPs from forelimb afferents are mediated by inhibitory interneurones (interneuronal system II) other than those receiving convergent descending excitation. Volleys in corticospinal fibres, in addition to the disynaptic IPSPs, evoke late IPSPs in the PNs. Similar late IPSPs were evoked from the ipsilateral forelimb by stimulation of the FRA. Monosynaptic IPSPs were evoked in the majority of the PNs on weak stimulation of the lateral reticular nucleus (LRN) and from regions dorsal to it. Results from threshold mapping suggest that these IPSPs are due to antidromic stimulation of ascending inhibitory neurones which also project to the C3-C4 PNs, and that the ascending collaterals terminate in the LRN or/and the base of the cuneate nuclei. Activity in the ascending collaterals may give higher centres information regarding inhibitory control of the PNs. It is postulated that interneuronal system I subserves descending feed-forward inhibition and interneuronal system II feed-back inhibition from the forelimb of transmission through the C3-C4 PNs to motoneurones.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 56 (1984), S. 279-292 
    ISSN: 1432-1106
    Schlagwort(e): Descending pathways ; Forelimb afferents ; Inhibitory C3-C4 propriospinal neurones ; Motoneurones
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A further analysis has been made of inhibitory pathways to motoneurones via C3-C4 propriospinal neurones (PNs). Intracellular recording was made from triceps brachi motoneurones and effects from higher centres and forelimb afferents on corticospinal IPSPs were investigated after transection of the corticospinal tract at the C5/C6 border. The shortest latencies of the IPSPs evoked by stimulation of the pyramid were as brief as those of the pyramidal EPSPs (Illert et al. 1977). It is postulated that the minimal linkage of the pyramidal IPSPs is disynaptic via inhibitory C3-C4 PNs projecting directly to motoneurones. It was confirmed that pyramidal IPSPs usually are depressed by volleys in forelimb motor axon collaterals (Illert and Tanaka 1978). A quantitative comparison was made of the recurrent depression of pyramidal IPSPs and of IPSPs caused by activation of the Ia inhibitory interneurones. The result support the hypothesis of two parallel inhibitory cortico-motoneuronal pathways via C3-C4 PNs, one disynaptic via the inhibitory PNs and the other trisynaptic via excitatory PNs and Ia inhibitory interneurones. Pyramidal volleys also evoked late IPSPs which in some cases were not depressed from forelimb motor axon collaterals. It is postulated that the late IPSPs are partly due to activation of inhibitory C3-C4 PNs. Disynaptic pyramidal IPSPs were effectively facilitated by volleys in rubro-, tecto- and reticulospinal fibres — but not from vestibulospinal fibres — showing a convergence from the former descending tracts on common inhibitory C3-C4 PNs. Projection from forelimb afferents and corticospinal fibres on common inhibitory C3-C4 PNs was revealed by strong facilitation of disynaptic pyramidal IPSPs from cutaneous forelimb afferents. No corresponding effect was evoked from C2 neck afferents. Stimulation in the lateral reticular nucleus (LRN) evoked monosynaptic IPSPs in some motoneurones. The results of threshold mapping in and around the LRN suggest that the IPSPs are caused by antidromic stimulation of ascending collaterals of inhibitory neurones also projecting to motoneurones, possibly the inhibitory C3-C4 PNs.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 56 (1984), S. 308-322 
    ISSN: 1432-1106
    Schlagwort(e): Descending pathways ; Forelimb afferents ; C3-C4 inhibition ; C3-C4 propriospinal neurones
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Extra- and intracellular recording was made from cells in the C3-C4 segments with the aim of finding interneurones of previously described inhibitory pathways to the C3-C4 propriospinal neurones, which may mediate descending feed-forward inhibition and feed-back inhibition from the forelimb, respectively. The lateral interneurones were found in the lateral part of lamina VII interspersed among the C3-C4 PNs and like them they receive convergent monosynaptic EPSPs and disynaptic IPSPs from the cortico-, rubro-, tecto- and reticulospinal tracts. Disynaptic IPSPs, but only rarely monosynaptic EPSPs, are evoked in them from forelimb nerves. The lateral interneurones do not project to the lateral reticular nucleus (LRN). The medial interneurones were found medially in laminae V and VI in a region where volleys in forelimb nerves evoke extracellular monosynaptic focal potentials (Rosén 1969). There is somatotopic organization of the projection from the forelimb to this region. Many neurones are strongly monosynaptically excited from group I muscle or/and cutaneous forelimb afferents. In addition, late discharges are evoked in many cells from cutaneous afferents and high threshold muscle afferents. Corticospinal volleys evoked monosynapic excitation in the great majority of these cells and usually also late EPSPs or IPSPs. Typically, rubrospinal and tectospinal volleys evoked neither monosynaptic excitation nor late effects as those elicited from corticospinal fibres. In some of the interneurones, IPSPs were evoked from forelimb nerves. About 20% of the medial “interneurones” have an ascending projection to the caudal brain stem. Threshold mapping for antidromic stimulation revealed termination in the main cuneate nucleus, the external cuneate nucleus and/or the LRN and also a branch projecting to more rostral levels in the brain. A few of the neurones in the medial region are PNs projecting to the forelimb segments. It is postulated that interneurones both of the lateral and medial type are inhibitory and project to the C3-C4 PNs. It is further postulated that the former are intercalated in the descending feed-forward inhibitory pathway to the C3-C4 PNs and the latter in the feed-back inhibitory pathway from the forelimb to these PNs. The role of feed-forward and feed-back inhibition of transmission from the brain to forelimb motoneurones via the C3-C4 PNs is discussed.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 1043-1060 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: In the absence of emulsifying agents, vinyl acetate polymerization in aqueous media was carried out at 50°C over a wide range of initial initiator and monomer concentrations to clarify the effect of reaction conditions on the kinetic behavior of the polymerization system. It was shown that the rate of polymerization was proportional to reaction time and initiator concentration and independent of the number of polymer particles present. The rate could also be successfully explained by the Smith and Ewart theory for emulsion polymerization when the dissolved monomer in water and the Trommsdorff effect were taken into consideration. A set of equations which could account for the effect of dissolved monomer in water on the rate of polymerization is proposed.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 323-331 
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of new polyimides containing fluorinated alkoxy side chains are prepared from novel fluorinated alkoxy diamines. The dieletric constant at 1 kHz in the fluorinated polyimides decreases from 3.3 to 2.6 as fluorine content increases. The refractive index also changes from 1.58 to 1.48, dependent on the fluorine content. In addition, the fluorinated polyimides exhibit lower water absorption than the reference polyimides prepared from m-phenylenediamine.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 24 (1986), S. 249-252 
    ISSN: 0887-6258
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 25 (1987), S. 377-382 
    ISSN: 0887-6258
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 2821-2823 
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 293-297 
    ISSN: 0887-6266
    Schlagwort(e): poly(p-phenylene) from organometallic polymerization, crystal structure of ; crystal structure of poly(p-phenylene) from organometallic preparation ; X-ray diffraction of organometallically produced poly(p-phenylene) ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The two-dimensional crystal structure of poly(p-phenylene) is investigated by linkedatom Rietveld analysis of the x-ray diffraction powder profile. Two molecular chains are packed in a rectangular pgg unit cell (a = 0.779 nm; b = 0.551 nm) with a paracrystalline shift distortion along the chain axis. The molecular conformation is not rigidly planar; rotations between adjacent phenyl-ring planes in a molecule alternate with an angle of about 20°. The setting angle between the mean molecular plane and the a axis is 55.5°.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 637-648 
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Blends composed of the α-helical polymers, poly-L-glutamates [(—NHCαHRC′O—)n, R = —CH2CH2COO—(CH2)m(C6H5] (Lm) and the corresponding D enantiomers (Dm), have been studied by x-ray diffraction and viscoelastic measurements. Binary blends of L2, D2, L3, and D3 are compatible and form isomorphous mixed crystals at all compositions, whereas other pairs, with the exception of L1/D1, are incompatible. The demixing process is described for a ternary system consisting of L1, D3, and a diluent chloroform at 40°C. The phase diagram comprises four regions, I, IA, A, and AA, with increasing polymer concentration; I: isotropic, A: anisotropic, IA: I-A biphasic, and AA: A-A biphasic. The IA biphasic gap is greater in the ternary system than in the binary ones. The high-molecular-weight component (D3) is partitioned into the A phase in the IA region. The AA separation originates from incompatibility of the polymers. The phase behavior is discussed on the basis of the Abe-Flory theory by incorporating the polymer-polymer interaction parameter.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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