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
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    The @China quarterly 45 (1971), S. 183-184 
    ISSN: 0305-7410
    Source: Cambridge Journals Digital Archives
    Topics: Linguistics and Literary Studies , History , Political Science , Sociology , Economics
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1912
    Keywords: Adenosine ; 2-Chloroadenosine ; Neurotransmission ; Vas deferens ; Uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the isolated rat vas deferens, various 2-substituted adenosine derivatives and adenosine inhibited contractions elicited by field stimulation but had little effect on responses to exogenous noradrenaline. 2-Chloroadenosine, 2-bromoadenosine, 2-hydroxyadenosine and 2-fluoroadenosine were all more potent than adenosine. Theophylline antagonized the action of the 2-substituted derivatives. The inhibitory action of adenosine was potentiated by dipyridamole, 2-amino-6-[(2-hydroxy-5-nitro)benzylthio]-9-β-d-ribofuranosylpurine (HNBTG) or 2′-deoxycoformycin while that of 2-chloroadenosine was not altered by any of these drugs or by phenoxybenzamine, atropine or indomethacin. Pretreatment of the vas deferens with both HNBTG and 2′-deoxycoformycin eliminated the difference in inhibitory potency between adenosine and 2-chloroadenosine. These results indicate that 2-substituted adenosine derivatives, like adenosine, produce inhibition of transmission by acting on a presynaptic site which can be blocked by theophylline. The high apparent potency of 2-chloroadenosine compared to adenosine appears to be duc to the former being neither taken up nor deaminated, while the apparent potency of adenosine is masked by uptake and deamination in this tissue.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 317 (1981), S. 110-114 
    ISSN: 1432-1912
    Keywords: Adenosine-Adenine nucleotides ; Neurotransmission ; Vas deferens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the isolated rat vas deferens stimulated at 0.2 Hz, [14C]labelled 5′-AMP, 5′-ADP and 5′-ATP (10 μM) inhibited twitch responses, were broken down to [14C]adenosine in the medium and incorporated into [14C]adenine ribonucleotides in the tissue. Pretreatment of tissues with 6-(2-hydroxy-5-nitrobenzyl)-thioguanosine (NBTGR), a potent inhibitor of adenosine transport, potentiated the presynaptic inhibitory action of these 5′ nucleotides and reduced their incorporation in [14C]adenine nucleotides, but did not alter the appearance of [14C]adenosine in the medium. A series of 2′, 3′ and 5′-substituted adenine nucleotides (10 μM) inhibited the twitch responses of the vas deferens stimulated at 0.2 Hz. This effect was potentiated by NBTGR. Addition of exogenous adenosine deaminase very significantly reduced the inhibitory actions of adenosine, 5′-AMP, 5′-ADP and 5′-ATP and also reduced those of 2′, 5′-ADP, NAD+ and dePCoA. The inhibitory actions of the other 2′, 3′ and 5′ adenine nucleotides studied were not altered by exogenous adenosine deaminase. These results indicated that the presynaptic inhibitory actions of 5′-AMP, 5′-ADP and 5′-ATP in rat vas deferens predominantly result from their prior hydrolysis to adenosine whereas the 2′, 3′ and 5′-substituted adenine nucleotides appear to act mainly directly to inhibit transmitter release.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 335 (1987), S. 301-304 
    ISSN: 1432-1912
    Keywords: Adenosine ; Adenosine-5′-uronamides ; Guinea-pig ileum ; Neurotransmission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ability of a series of N6-modified N-alkyl-5′-uronamides to cause presynaptic inhibition of transmitter release was examined in isolated guinea-pig ileum stimulated at 0.2 Hz. These analogs inhibited the twitch responses to nerve stimulation, the majority being full agonists with their inhibitory effects being antagonised by theophylline. These analogs had no significant effects on responses of ileum to carbachol. N-ethyl 5′-uronamide substitution resulted in an up to four-fold reduction in activity of N6-substituted adenosine analogs, while stereoselectivity of the N6-substituted analogs continued to be present. 5′-Uronamide substitutions to N6-(3-pentyl)-adenosine resulted in a marked loss of activity when there were large alkyl groups at the amide or with amides of secondary amines. It was concluded that adenosine analogs interact with both the N6 and C-5′ regions of the adenosine receptor in this tissue, with the interaction being less than additive.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-1912
    Keywords: Adenosine ; Adenine nucleotides ; Vas deferens ; Neurotransmission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the isolated rat vas deferens stimulated at 0.2 Hz, a series of 2′, 3′-, and 5′-substituted adenine nucleotides all inhibited the twitch responses, their actions being potentiated by the nucleoside transport inhibitors, HNBTGR, NBMPR and dipyridamole. The metabolism of these nucleotides was examined utilising HPLC analysis of the bathing medium after exposure to 30 μM nucleoside or nucleotide for 5 min. 5′-AMP, 5′-ADP, 5′-ATP, and NAD+ were all partially hydrolysed to adenosine, the relative extent of this being 5′-AMP〉5′-ADP=5′-ATP≫NAD+. However, the other nucleotides examined were not detectably converted to adenosine or to adenosine deamination products. These results indicate that the 2′-, 3′- and 5′-substituted nucleotides studied act at a P1-purinoceptor in rat vas deferens to inhibit neurotransmission and, with the exception of 5′-AMP, 5′-ADP, 5′-ATP and NAD+, all appear to act directly at this receptor. However, the 5′-adenine nucleotides (AMP, ADP and ATP) and NAD+ all appear to act at least partially indirectly subsequent to their hydrolysis to adenosine.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 333 (1986), S. 313-322 
    ISSN: 1432-1912
    Keywords: Adenosine/Adenosine analogs ; Neurotransmission ; N6 region ; Purinergic receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study explored the nature of the purine domain N6 regions of the presynaptic adenosine receptors of guinea-pig ileum and of rat vas deferens. The experimental design tested a model of these receptors which is complementary to the structure of the N6 substituent of the classical A1 adenosine receptor agonist N6-1-phenyl-2R-propyladenosine, (R-PIA). Assays of activity employed ileal segments or the midportions of vasa deferentia under continuous electrical stimulation at 0.2 Hz. Structure activity correlations compared the EC-50s for twitch inhibition. As shown previously, R-PIA was 60–80 times more potent than its S diastereomer, the resultant of the positive contribution of propyl C-3 to activity as well as the negative influence of steric hindrance exerted by propyl C-3 of the S diastereomer. Other pairs of diastereomers having a chiral center adjacent to N6 showed that the stereoselectivity of the PIAs was generalizable. Biological activity appears to reside wholly in the N6 alkyl moiety; the phenyl or aryl groups of similar size actually diminished potency. The receptor subregions interacting with propyl C-1 and C-3 of R-PIA are each large enough to accomodate two — but not three — methylene residues, each methylene contributing additively to activity. Hydrophobicity is a prominent attribute of the propyl C-1 and C-3 subregions. The potencies of these analogs as inhibitors of presynaptic transmission in ileum or vas deferens are covariant with inhibition of [3H]N6-cyclohexyl-adenosine binding to rat cerebral cortical membranes. Singular exceptions to this generalization may represent organ- or species-dependent differences in receptor fine structure.
    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...