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  • 1
    ISSN: 1432-2013
    Keywords: Axonal connections ; Medullary respiratory neurons ; Pneumotaxic centre ; Termination of inspiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In urethane-anaesthetized, paralyzed and artificially ventilated rabbits, medullary respiration-related neurons (RRU) were classified according to the phase relation of their burst discharge to phrenic nerve activity. Phase-bound inspiratory (I) or expiratory (E) neurons were discriminated from phase-spanning expiratory-inspiratory (EI) or inspiratory-expiratory (IE) units. Mechanisms of termination of inspiration by electrical stimulation of rostral pontine nuclei (Nc. parabrachialis medialis; Lc. coeruleus) were examined firstly to demonstrate whether RRU receive descending excitatory and inhibitory afferents as well as ascending efferents and secondly to analyse the time course of the neuronal pathways involved. Of 120 RRU, 38 neurons were demonstrated to receive pontine afferents. About 33% of all E neurons became orthodromically excited during rostral pons stimulation whereas 18.2% of all I cells became orthodromically inhibited. Some RRU were shown to project up to the rostral pons. 50% of these were of the phase-spanning IE type. The onset of inspiratory inhibition induced by rostral pons stimulation occurred 3.4 ms after the onset of single electrical pulse stimulation. Based on these results a neuronal model for a pontine mechanism terminating inspiration is proposed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Axonal connections ; Control of breathing ; Medullary respiratory neurons ; Midbrain ; Reticular formation ; Rubrospinal tract
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Suprapontine brain sites acting on the central respiratory system have been demonstrated to give rise to inspiratory as well as expiratory facilitatory effects. In the present study the inspiratory inhibitory effect which has been reported in the cat to be elicited consistently by electrical stimulation of the rubrospinal tract and the adjacent mesencephalic reticular formation was examined in the urethane-anaesthetized rabbit. Stimulation of these sites with single electrical shocks of moderate intensity induced a short latency (onset after 3.0 ms) transient (duration: 29 ms) inhibition of the phrenic nerve activity (PHR). Short volleys of stimuli applied in mid- to late-inspiration led to a premature off-switch of inspiration. The extracellularly recorded discharge activity of the different types of medullary respiration-related units (RRU) reflected these alterations, accordingly. Axonal connections of RRU with mesencephalic structures were evaluated. Examination of orthodromic responses of medullary RRU to stimulation of this pathway revealed that most bulbospinal inspiratory neurons (10 out of 13) were paucisynaptically inhibited after short latency (at least 1.2 ms). The conduction time from bulbospinal inspiratory neurons to the recording site of PHR was 1.6 ms. Thus, a disynaptic pathway — including bulbospinal inspiratory neurons — is suggested inducing inspiratory inhibition 3.0 ms after single shock midbrain stimulation. This inhibition results in disfacilitation of phrenic motoneurons. The fact that extensive electrolytic lesions of the pneumotaxic center in rostral pons did not abolish the observed inspiratory inhibitions excludes these structures from being involved. A direct pathway from the red nucleus and the adjacent reticular formation to phrenic nuclei of the spinal cord, however, can not be excluded from being involved in the demonstrated inspiratory inhibition. The described effects may play a role in behavioral or voluntary control of respiration.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 107 (1995), S. 785-818 
    ISSN: 0044-8249
    Keywords: Calixarene ; Metacyclophane ; Resorcarene ; Supramolekulare Chemie ; Wirt-Gast-Verbindungen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Durch Kondensation von p-tert-Butylphenol mit Formaldehyd sind in einem Schritt in guten Ausbeuten cyclische Oligomere erhältlich, in denen je nach Reaktionsbedingungen vier, sechs oder acht Phenolbausteine über Methylenbrücken verknüpft sind. Die kelchartige Gestalt der stabilsten Konformation des Tetramers erklärt den Namen Calixaren (calix = Kelch). In ähnlicher Weise liefert Resorcin bei der Kondensation mit einer Vielzahl von Aldehyden cyclische Tetramere mit dem gleichen Grundgerüst (Resorcarene). In beiden Fällen erfordert die Herstellung keine Verdünnungsbedingungen, so daß auch größere Mengen leicht zugänglich sind. Überdies können die Stammverbindungen vielfältig modifiziert werden, wobei die phenolischen Hydroxygruppen und die Phenylringe zwei Ansatzpunkte bieten, die getrennt oder in Kombination genutzt werden können. Calixarene sind deshalb ideale Edukte für die Synthese der unterschiedlichsten Wirtverbindungen und Bausteine für die Konstruktion größerer molekularer Systeme mit definierter Struktur und Funktion. Die potentiellen Anwendungen reichen vom Einsatz als hochspezifische Liganden für die Analytik, die Sensortechnik und die medizinische Diagnostik über die Verwendung zur Decontaminierung von Abwässern bis hin zur Konstruktion künstlicher Enzyme und zur Herstellung neuer Materialien für die nichtlineare Optik oder für ultradünne Schichten und Siebmembranen mit molekularen Poren.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0044-8249
    Keywords: Calixarene ; Solvatation ; Supramolekulare Chemie ; Wasserstoffbrücken ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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