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  • 1
    Electronic Resource
    Electronic Resource
    Physiological role of brain angiotensin III in drinking behavior in the rat (1996)
    Springer
    Journal of biomedical science 3 (1996), S. 203-210 
    Details
    ISSN: 1423-0127
    Keywords: Ile7-angiotensin III ; Bestatin ; Osmotic minipump ; Drinking response ; Spontaneously hypertensive rats ; Normotensive rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We examined the physiologic role of endogenous brain angiotensin III (AIII), an active degradative product of angiotensin II, in drinking behavior. Adult, male spontaneously hypertensive (SH) and Wistar-Kyoto normotensive (WKY) rats that were instrumented with an intracerebroventricular (i.c.v.) cannula connected to an osmotic minipump for chronic infusion were used. 7-day i.c.v. infusion of the specific AIII antagonist, Ile7-AIII (10 or 100 pmol/min), resulted in no significant alteration in daily (24 h), diurnal (8:00 a.m.-8:00 p.m.) or nocturnal (8:00 p.m.-8:00 a.m.) basal water intake in both SH and WKY rats. Similar results were obtained with i.c.v. infusion of the aminopeptidase inhibitor, bestatin (150 or 300 pmol/min), given alone or simultaneously with Ile7-AIII (10 pmol/min). Rats that were water-deprived for the first 3 days of 7-day infusion of Ile7-AIII consumed significantly less water during the first 2 h after water became available. Furthermore, the accumulated water intake during the first 24 h was appreciably greater in SH than WKY rats. We interpret these results to suggest that the endogenous brain AIII may not be tonically involved in fluid homeostasis. Instead, it must be activated under conditions of dehydration, such as water deprivation, particularly in the SHRs, to initiate drinking behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253101
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  • 2
    Electronic Resource
    Electronic Resource
    Role of the N-terminal region of the a chain in β1-bungarotoxin from the venom ofBungarus multicinctus (Taiwan-banded krait) (1988)
    Springer
    The protein journal 7 (1988), S. 713-727 
    Details
    ISSN: 1573-4943
    Keywords: snake venom ; presynaptic neurotoxin ; β1-bungarotoxin ; role of N-terminal region in β1-bungarotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The N-terminal α-amino groups of β1-bungarotoxin (β1-Bgt) fromBungarus multicinctus venom were modified with trinitrobenzene sulfonic acid and the modified derivative was separated by high performance liquid chromatography. The trinitrophenylated (TNP) derivative contained two TNP groups at the α-amino groups of A chain and B chain and showed a marked decrease in enzymatic activity. Methionine residues at positions 6 and 8 of the A chain were oxidized with chloramine T or cleaved with cyanogen bromide to remove the N-terminal octapeptide. Oxidation of methionine residues and removal of the N-terminal octapeptide caused a precipitous decrease in enzymatic activity, whereas antigenicity remained unchanged. The presence of dihexanoyllecithin influenced the interaction between β1-Bgt and 8-antilinonaphthalene sulfonate (ANS) and revealed that β1-Bgt consists of two types of ANS-binding sites, one at the substrate binding site of the A chain and the other might be at the B chain. The modified derivatives still retained their affinity for Ca2+ and ANS, indicating that the N-terminal region is not involved in Ca2+ and substrate binding. A fluorescence study revealed that the α-amino group of the A chain was in the vicinity of substrate binding site and that the TNP α-amino groups were in proximity to Trp-19 of the A chain. In addition, the study showed that the N-terminal region is important for stabilizing the architectural environment of Trp-19. The results, together with the proposal that Trp-19 of the A chain is involved in substrate binding, suggest that the N-terminal region of the A chain plays a crucial role in maintaining a functional active site for β1-Bgt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025579
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  • 3
    Electronic Resource
    Electronic Resource
    Tryptophan modification of phospholipase A2 enzymes and presynaptic neurotoxins from snake venoms (1984)
    Springer
    The protein journal 3 (1984), S. 195-213 
    Details
    ISSN: 1573-4943
    Keywords: snake venom ; phospholipase A2 ; presynaptic neurotoxin ; tryptophan modification of phospholipase A2 ; tryptophan modification of presynaptic neurotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three phospholipases A2 purified from cobra venoms and two presynaptically acting neurotoxins that exhibit phospholipase A2 activity were subjected to tryptophan modification with 2-hydroxy-5-nitrobenzyl bromide. Associated with the modification of an increasing number of Trp residues were marked decreases in enzymatic activity and lethality, whereas antigenicity remained unchanged. The degree of exposure of tryptophanyl groups as determined by acrylamide quenching was consistent with the relative reactivity toward 2-hydroxy-5-nitrobenzyl bromide, except for Hemachatushaemachatus phospholipase A2, which showed unusually high reactivity due to its characteristic dimeric conformation. Difference spectra of Trp-modified derivatives differed from those of their native enzymes by the presence of a new positive perturbation between 350 and 500 nm, with a maximum at 415 nm. Scatchard plots revealed only one type of binding site for Ca2+, and the binding abilities of the modified enzymes were not impaired. At pH 8.0, all native enzymes enhanced the emission intensity of 8-anilinonaphthalene sulfonate (ANS) dramatically, and the emission intensity of the ANS-enzyme complex increased or decreased in parallel with increasing concentration of Ca2+ for the respective enzyme. The Trp-modified derivatives did not enhance the emission intensity of ANS at all either in the presence or absence of Ca2+. By means of tryptophan modification, we were able to infer that the tryptophan residues are in the vicinity of the Ca2+ binding site and are directly involved in the binding with ANS. This, together with the suggestion that the hydrophobic pocket that interacts with ANS might be the site of binding of the phospholipase A2 enzyme with the substrate, suggests that the Trp residues in phospholipase A2 enzymes and presynaptic toxins are involved in substrate binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01040500
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  • 4
    Electronic Resource
    Electronic Resource
    Selective modification of tyrosine-68 in β1-bungarotoxin from the venom ofBungarus multicinctus (Taiwan banded krait) (1986)
    Springer
    The protein journal 5 (1986), S. 15-28 
    Details
    ISSN: 1573-4943
    Keywords: Snake venom ; presynaptic neurotoxin ; β1-bungarotoxin ; tyrosine modification of β1-bungarotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract β1-Bungarotoxin (β1-Bgt) fromBungarus multicinctus (Taiwan banded krait) snake venom was subjected to tyrosine modification withp-nitrobenzenesulfonyl fluoride (NBSF) atpH 8.0 and the NBS derivatives were separated by high-performance liquid chromatography. The results of amino acid analysis revealed that only one Tyr residue out of 14 was modified, and the modified residue was identified to be Tyr-68 in the A chain of β1-Bgt. Spectrophotometric titration indicated that the phenolic group of Tyr-68 has apK of 10.1. Modification of Tyr-68 in the A chain caused a selective loss in lethal toxicity, but had no effect on either enzymatic or antigenic activities. The Ca2+-induced difference spectra and fluorescence study indicated that β1-Bgt possesses at least two different types of Ca2+-binding sites. However, modification of Tyr-68 in β1-Bgt did not cause any change of the Ca2+-induced difference spectra and fluorescence spectra in native toxin and the two types of Ca2+-binding sites were retained. Moreover, the affinity of Tyr-68-modified β1-Bgt for 8-anilinonaphthalene sulfonate was also unaffected in both the presence and absence of Ca2+. All of the results indicated that Tyr-68 is not involved in the Ca2+ and substrate bindings in the A chain of β1-Bgt. It is concluded that lethal toxicity is not necessarily associated with enzymatic, antigenic, and Ca2+-binding activities in β1-Bgt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025581
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  • 5
    Electronic Resource
    Electronic Resource
    Separation and characterization of the A chain and B chain in β1-bungarotoxin fromBungarus multicinctus (Taiwan banded krait) venom (1993)
    Springer
    The protein journal 12 (1993), S. 469-475 
    Details
    ISSN: 1573-4943
    Keywords: Snake venom ; presynaptic neurotoxin ; β1-bungarotoxin ; A chain and B chain of β1-bungarotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The interchain disulfide bond between A chain and B chain of β1-bungarotoxin (β1-Bgt) was selectively cleaved by dithiothreitol, and the A and B chains were separated by HPLC. The separated A and B chains did not show detectable enzymatic activity and lethal toxicity, but exhibited an immunoreactivity with anti-β1-Bgt antibody. Analytical isoelectrofocusing revealed that the A chain is a neutral subunit with pI=7.4, and the B chain is a basic one with pI=9.6. The A chain exhibited a Ca2+-binding ability as revealed by fluorescence measurement. Moreover, fluorescence studies showed that the intact interchain disulfide bond is essential for maintaining the hydrophobic character of substrate binding site in β1-Bgt and stabilizing the architectural environment of Trp-19 in the A chain. However, combination of the A chain and B chain failed to restore the biological activities and physicochemical properties which the intact β1-Bgt possessed. These, together with our previous result that the Trp-19 of the A chain is involved in substrate binding, suggest that the integrity of the interchain disulfide bond favors the maintenance of the active conformation of β1-Bgt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025047
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