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  • 1985-1989  (4)
  • Chemistry  (2)
  • Fictive locomotion  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Modulation of short latency cutaneous excitation in flexor and extensor motoneurons during fictive locomotion in the cat (1989)
    Springer
    Experimental brain research 77 (1989), S. 57-68 
    Details
    ISSN: 1432-1106
    Keywords: Cutaneous EPSPs ; Fictive locomotion ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We examined modulation of transmission in short-latency, distal hindlimb cutaneous reflex pathways during fictive locomotion in 19 decerebrate cats. Fictive stepping was produced either by electrical stimulation of the mesencephalic locomotor region (MLR) or by administration of Nialamide and 1-DOPA to acutely spinalized animals. Postsynaptic potentials (PSPs) produced by electrical stimulation of low threshold afferents (〈 2.5 times threshold) in the superficial peroneal (SP), sural, saphenous or medial plantar nerves were recorded intracellularly from various extensor (n = 28) and flexor (n = 24) motoneurons and averaged throughout the step cycle, together with voltage responses to intrasomatic constant current pulses (in order to monitor relative cell input resistance). Each motoneuron studied displayed rhythmic background oscillations in membrane potential and correlated variations in input resistance. The average input resistance of extensor motoneurons was lowest during mid-flexion, when the cells were relatively hyperpolarized and silent. Conversely, average input resistance of flexor motoneurons was highest during mid-flexion, when they were depolarized and active. The amplitude of the minimum-latency excitatory components of PSPs produced by cutaneous nerve stimulation were measured from computer averaged records representing six subdivisions of the fictive step cycle. Oligosynaptic EPSP components were consistently modulated only in the superficial peroneal responses in flexor motoneurons, which exhibited enhanced amplitude during the flexion phase. With the other skin nerves tested (sural, saphenous, and plantar), no consistent patterns of modulation were observed during fictive locomotion. We conclude that transmission through some, but not all, oligosynaptic excitatory cutaneous pathways is enhanced by premotoneuronal mechanisms during the flexion phase of fictive stepping in several cat hindlimb motor nuclei. The present results suggest that the patterns of interaction between the locomotor central pattern generator and excitatory cutaneous reflex pathways depend on the source of afferent input and on the identity of the target motoneuron population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250567
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  • 2
    Electronic Resource
    Electronic Resource
    Phasic modulation of short latency cutaneous excitation in flexor digitorum longus motoneurons during fictive locomotion (1988)
    Springer
    Experimental brain research 71 (1988), S. 568-578 
    Details
    ISSN: 1432-1106
    Keywords: Fictive locomotion ; Cutaneous reflex pathways ; Flexor digitorum longus muscle ; Motoneurons ; Interneurons ; Reflex modulation ; Spinal cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We examined modulation of transmission of short-latency excitation produced by distal hindlimb cutaneous input, as well as fluctuations in motoneuron membrane potential and input resistance, in flexor digitorum longus (FDL) motoneurons during fictive locomotion. Fictive stepping was induced in unaesthetized, decerebrate cats either by repetitive stimulation of the mesencephalic locomotor region (MLR) or by administration of Nialamide and 1 DOPA after low spinal section. In the MLR preparations, brief depolarizing waves occurred in FDL cells during the early flexion phase of fictive stepping, immediately after cessation of activity in extensor muscles. In some FDL cells, plateau-like depolarizations also occurred during the extensor phase. Fictive stepping induced in acutely spinalized cats by administration of l-DOPA was slower and more variable; peak polarization in FDL motoneurons always occurred during the early flexion phase but there was usually no distinct depolarization during extension. In both types of preparation, the initial EPSP components in synaptic potentials (SP-EPSPs) produced by electrical stimulation of the cutaneous division of the superficial peroneal nerve (SP) were maximally facilitated during early flexion, coincident with the peak of background depolarization. This enhancement was manifested by an increase in the amplitude of initial SP-EPSP components or by decreased central latency of the initial EPSP components, or both. In most FDL motoneurons, input resistance decreased systematically during late flexion, coincident with relative membrane hyperpolarization. Correction of SP-EPSP amplitudes for changes in input resistance suggested that SP-EPSP facilitation persisted throughout the flexion phase These findings are discussed with reference to modulation of cutaneous reflexes during locomotion and the possibility that excitatory last-order interneurons in particular cutaneous reflex pathways may distribute excitatory drive from the central pattern generator for locomotion to FDL α-motoneurons
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248749
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  • 3
    Electronic Resource
    Electronic Resource
    Mg2IrB2-x, ein Magnesium-Iridiumborid mit W2CoB2 -verwandter Struktur (1986)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 543 (1986), S. 89-96 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Mg2IrB2-x, a Magnesium Iridium Boride with a Structure Related to the W2CoB2-TypeThe new compound Mg2IrB2-x with a small homogeneity range determined approximately as 0,2 ≤ x ≤ 0,35 crystallizes monoclinically in the space group C2/m, Z=4 (lattice constants see Inhaltsübersicht). The structure which was solved by single crystal X-ray and powder neutron diffraction methods is related to the W2CoB2-type and contains distorted Mg4Ir2-prisms. The boron atoms are partly disordered. They are situated either inside the prisms forming pairs or with very short Ir-B distances (199 pm) on an elongated prism edge formed by two iridium atoms.
    Notes: Die neue Verbindung Mg2IrB2-x mit einem schmalen Homogenitätsbereich, der näherungsweise zu 0,2 ≤ x ≤ 0,35 bestimmt wurde, kristallisiert monoklin in der Raumgruppe C2/m, Z = 4. Bei x = 0,35 betragen die Gitterkonstanten a = 858,0(1) pm, b = 484,6(1) pm, c = 683,6(1) pm, β = 115°43′(1). Die Struktur, die mit Röntgen-Einkristall- und Pulver-Neutronenbeugungsmethoden bestimmt wurde, leitet sich vom W2CoB2-Typ ab und enthält verzerrte Mg4Ir2-Prismen. Die Boratome sind zum Teil fehlgeordnet. Sie befinden sich entweder innerhalb der Prismen und bilden Paare, oder sie liegen auf einer aufgeweiteten, aus zwei Iridiumatomen bestehenden Prismenkante, wobei sehr kurze Ir-B-Abstände ausgebildet werden (199pm).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19865431211
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  • 4
    Electronic Resource
    Electronic Resource
    Zur Umsetzung von Bis(2-mercaptoethyl)phosphinen mit Organozinn-Verbindungen Molekülstruktur eines zinnhaltigen Sechzehnringes (1988)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 556 (1988), S. 161-169 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaction of Bis(2-mercaptoethyl)phosphines with Organotin Compounds. Molecular Structure of a Tin Containing Sixteen-membered RingThe reaction of bis(2-mercaptoethyl)phosphine with di-t-butyltin dimethoxide yields mixture of oligomers of the type [t-Bu2Sn(SCH2CH2)2Pr]n (R = Me, Ph) from which the trans-configurated dimers (n = 2) have been isolated. By the reaction with sulphur and selenium, respectively, these dimers were transformed to the corresponding thioxo and selenoxo derivatives.The sixteen-membered ring trans-[t-Bu2Sn(SCH2CH2)2P(S)Ph]2 crystallizes in the space group P21/n with the unit cell dimensions a 1350.9, b 1310.2, c 1500.3 pm, β 96.36° and does not exhibit any intramolecular Sn—P interaction: The 1,5-diorgano-1-chloro-5-elementa-1-stanna(IV)-bicyclo-[3.3.01,5]octanes R(Cl)Sn(SCH2CH2)2E (6, R = Ph, E = PPh; 7, R = Ph, E = NMe) have been prepared from the corresponding sodium dithiolates and phenyltrichlorostannane. The transannulare Sn—P and Sn—N interactions in 6 and 7 are confirmed by 31P and 119Sn NMR investigations.
    Notes: Die Reaktion von Bis(2-mercaptoethyl)phosphinen mit Di-t-butylzinndimethoxid liefert Mischungen von Oligomeren des Typs [t-Bu2Sn(SCH2CH2)2PR]n (R = Me, Ph), von denen die trans-konfigurierten Dimere (n = 2) isoliert wurden. Durch Reaktion mit Schwefel bzw. Selen wurden diese in die entsprechenden Thio- bzw. Selenoderivate überführt. Der Sechzehnring trans-[t-Bu2Sn(SCH2CH2)2P(S)Ph]2 4 kristallisiert in der Raumgruppe P21/n mit den Gitterkonstanten a 1350,9, b 1310,2, c 1500,3 pm und β 96,36°, er enthält keine intramolekularen Sn—P.-Wechselwirkungen. Die 1,5-Diorgano-1-chloro-5-element-1-stanna(IV)-bicyclo[3.3.01,5]-octaneR(Cl)Sn(SCH2CH2)2E (6, R = Ph, E = PPh; 7, R = Ph, E = NMe) wurden aus den entsprechenden Natriumdithiolaten und Phenyltrichlorstannan erhalten. Die transannularen Sn—P- und Sn—N- Wechselwirkungen in 6 und 7 werden durch 31P- und 119Sn-NMR-Untersuchungen bestätigt.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19885560117
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