Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 427-432 
    ISSN: 0009-2940
    Keywords: [1n]Metabiphenylophanes ; Calixarenes ; Spherands ; Diastereoselectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Condensation of 5,5′-di-tert-butyl-2,2′-dihydroxybiphenyl (1) with formaldehyde yields a cyclic trimer 2 (and tetramer 3) having three (four) methylene groups less than a calix[6]-arene (calix[8]arene). Alkylation of the (flexible) trimer with ethyl bromoacetate gives exclusively the stereoisomer 4 with C2 symmetry, while the isomer with D3 symmetry is not observed. Two isomers 6a and 6b (C2 and C1 symmetry) are obtained by treatment with tert-butyl bromoacetate which both are converted by transesterification with methanol into the same hexamethyl ester 5 having C2 symmetry. These results are rationalized by restricted rotation around Ar—Ar bonds for larger O-alkyl groups also around Ar—CH2—Ar bonds. The structure of the hexaethyl ester 4 is also confirmed by single crystal X-ray analysis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2019-2030 
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 155-161 
    ISSN: 1434-193X
    Keywords: Mechanical bonding ; Interlocked molecules ; Template synthesis ; Calixarenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the amide-based rotaxane 7a bearing calix[4]arene blocking groups is described for the first time. While rotaxane formation fails if a calix[4]arene is functionalized at the upper rim with only an amino or methylamino group lacking any spacer, the prolonged amine 5a works successfully as stopper unit preventing dethreading of the dimeric wheel 1a by its size. Rotaxane formation of 8b was observed only by MALDI-TOF mass spectrometry of the reaction mixture of the amine 5b, the axle 6 and 1a. With the larger trimeric wheel 1b no stable rotaxane could be obtained. It either does not act as a concave template or its opening is too wide, even for the bulky calixarene stoppers.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 34 (1995), S. 713-745 
    ISSN: 0570-0833
    Keywords: calixarenes ; host-guest compounds ; metacyclophanes ; resorcarenes ; supramolecular chemistry ; Calixarenes ; Host-guest chemistry ; Supramolecular chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The condensation reaction between p-tert-butylphenol and formaldehyde leads in a single step to good yields of cyclic oligomers in which, depending on the reaction conditions, either four, six, or eight phenol units are joined by methylene bridges. The beakerlike shape of the most stable conformation of the tetramer has led to their being given the name “calixarenes” (calix = chalice). Resorcinol can undergo condensation in a similar manner with a variety of aldehydes to afford cyclic tetramers with the same basic structure (the resorcarenes). In both cases the reaction does not require the use of dilution techniques, so that large quantities of product can be readily obtained. In addition, the parent compounds can be modified in various ways, in particular at the phenolic hydroxy groups or the phenyl residues; these approaches can be used separately or in combination. Calixarenes are thus ideal starting materials for the synthesis of various types of host molecules and can also act as building blocks for the construction of larger molecular systems with defined structures and functions. Their potential applications range from use as highly specific ligands for analytical chemistry, sensor techniques and medical diagnostics to their use in the decontamination of waste water and the construction of artificial enzymes and the synthesis of new materials for non-linear optics or for ultrathin layers and sieve membranes with molecular pores.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...