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  • 1
    Electronic Resource
    Electronic Resource
    Head-to-tail connected double calix[4]arenes (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 863-879 
    Details
    ISSN: 1434-4475
    Keywords: Calix[4]arenes ; Macrocycles ; Double calixarenes ; X-Ray analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Neue makrotricyclische Verbindungen, in denen zwei Calix[4]aren-Einheiten durch aliphatische Ketten unterschiedlicher Länge (drei bis fünf C-Atome) zwischen zwei gegenüberliegendenp-Positionen und zwei gegenüberliegenden Phenolsauerstoffen verknüpft sind, wurden hergestellt. Ausgehend vonp-tert-Butyl-calix[4]aren werden zunächst zwei O-geschützte Phenolbausteine in 1,3-Stellung durch Umsetzung mit den entsprechenden Tosylaten etherartig gebunden. Nach Abspaltung der Benzylether-Schutzgruppe wird durch Fragmentkondensation mit 2,6-bisbrommethylierten 4-Alkylphenolen das neue Calix[4]aren gebildet. Für8c wurde die Struktur durch Einkristallröntgenstrukturanalyse bestätigt. Beide Calixarenteile nehmen diecone-Konformation ein, wobei in die beiden Hohlräume je ein Molekül Acetonitril eingeschlossen wird.
    Notes: Summary New macrotricyclic compounds consisting of two calix[4]arene substructures connected by aliphatic chains of various length (three to five carbon atoms) between two oppositep-positions and two distal phenolic oxygens have been synthesized. Starting withp-tert-butyl-calix[4]arene, two O-protected phenolic units are attachedvia ether links in 1,3-position by reaction with the corresponding tosylates. After deprotection, the new calix[4]arene is formed by fragment condensation with 2,6-bisbromomethylated 4-alkylphenols. The structure of one example (8c) has been confirmed by single crystal X-ray analysis. Both calixarene parts assume the cone conformation, a molecule of acetonitrile being included in both cavities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807096
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  • 2
    Electronic Resource
    Electronic Resource
    Medullary respiratory-related neurons with axonal connections to rostral pons and their function in termination of inspiration (1985)
    Springer
    Pflügers Archiv 403 (1985), S. 58-65 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00583283
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of rubrospinal tract and the adjacent mesencephalic reticular formation on the activity of medullary respiratory neurons and the phrenic nerve discharge in the rabbit (1988)
    Springer
    Pflügers Archiv 413 (1988), S. 23-31 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00581224
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  • 4
    Electronic Resource
    Electronic Resource
    Special Calixarenes by Directed SynthesesDedicated to Professor C. David Gutsche. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2019-2030 
    Details
    ISSN: 0947-3440
    Keywords: Calixarenes ; Macrocycles ; Fragment condensation ; Stepwise strategies ; X-ray analysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of special calixarenes and calixarene-like macrocyclic compounds via stepwise procedures and fragment condensation is reviewed. Among the compounds available are exo- and endo-calixarenes consisting of different phenolic units, having bridges other than methylene or showing inherent chirality (Cn-symmetry). Macrobi- and -tricyclic molecules such as bridged calixarenes, double calixarenes, bicyclocalixarenes and annelated calixarenes are also described. Single crystal X-ray structures are reported for several compounds. Some properties like conformational barriers, pKa values or the ability to complex metal ions are discussed, showing the potential of these compounds which may (only) be produced by directed synthesis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971004
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