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  • 2000-2004  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Effects of Melanocortin Receptor Ligands on Thyrotropin-Releasing Hormone Release: Evidence for the Differential Roles of Melanocortin 3 and 4 Receptors (2002)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 14 (2002), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The hypothalamic melanocortin system is important in the central regulation of food intake and body weight. We have previously demonstrated that intracerebroventricular administration of α-melanocyte stimulating hormone (α-MSH), a nonselective MC3 and MC4 receptor agonist, stimulated plasma thyroid-stimulating hormone, and agouti-related protein (AgRP), an MC3 and MC4 receptor antagonist, suppressed it. In this study, we investigated the effects of MC3 and MC4 receptor (MC3-R and MC4-R) selective agonists and antagonists on the release of thyrotropin-releasing hormone (TRH) from hypothalamic explants in vitro. α-MSH stimulated TRH release from the rat hypothalamic explants (α-MSH 100 nM 230 ± 22.9% basal, P 〈 0.005). In contrast, γ2-MSH, a selective MC3-R agonist, suppressed TRH release (γ2-MSH 10 µM 76.2 ± 7.4% basal, P 〈 0.05). AgRP (83-132), a nonselective MC3/4-R antagonist, induced no change in TRH release whilst JKC-363 (cyclic [Mpr11, D-Nal14, Cys18, Asp22-NH2]-β-MSH 11-22), a selective MC4-R antagonist, suppressed it (JKC-363 10 nM 57.2 ± 11.5% basal, P 〈 0.05). Both AgRP (83-132) and JKC-363 blocked α-MSH stimulated TRH release but only AgRP (83-132) blocked the inhibitory effect of γ2-MSH on TRH release. These data suggest differential roles for the MC3 and MC4 receptors in TRH release; MC3-R agonism inhibiting and MC4-R agonism stimulating TRH release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.2002.00769.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Cholesterol requirement of subadult black tiger shrimp Penaeus monodon (Fabricius) (2001)
    Oxford, UK : Blackwell Science, Ltd
    Aquaculture research 32 (2001), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The high cost of cholesterol used in aquaculture diets for shrimp makes it important to precisely define their requirement for this essential nutrient in order to avoid excess supplementation of the diet. Two experiments were carried out to determine the cholesterol requirement of subadult (about 3 g) Penaeus monodon (Fabricius). The growth response and survival of shrimp were compared following feeding for up to 8 weeks with diets in which the cholesterol content varied between 0.7 and 8.5 g kg−1. Feed intake was quantified and the retention of ingested cholesterol determined by whole body analysis. The cholesterol requirement of subadult P. monodon was found to be about 75 mg kg−1 body weight d−1. The optimum dietary cholesterol content was approximately 1.7 g kg−1 (dry matter), which is appreciably lower than the current recommendation of 2.5–4 g kg−1. In most practical shrimp diets, the endogenous cholesterol in the ingredients provides more than 1.7 g kg−1 of cholesterol. Hence, our research suggests that it may be unnecessary to add expensive, supplementary cholesterol to commercial shrimp diets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1355-557x.2001.00030.x
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  • 3
    Electronic Resource
    Electronic Resource
    Arylamine N-acetyltransferase of Mycobacterium tuberculosis is a polymorphic enzyme and a site of isoniazid metabolism (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 42 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Arylamine N-acetyltransferases (NATs; E.C 2.3.1.5) N-acetylate arylhydralazine and arylamine substrates using acetyl coenzyme A. Human NAT2 acetylates and inactivates the antituberculosis drug, isoniazid (INH), and is polymorphic. We previously demonstrated that there is a homologue of human NAT2 in Mycobacterium tuberculosis, whose product N-acetylates INH in vitro. We now demonstrate that the nat gene is expressed in M. tuberculosis and M. bovis Bacille Calmette-Guerin (BCG), using reverse transcription–polymerase chain reaction and Western blotting. The NAT protein is active in M. bovis BCG in vivo, as detected by the presence of N-acetyl INH in M. bovis BCG lysates grown in INH. Sequence analysis of the M. tuberculosis nat coding region reveals a single nucleotide polymorphism in 18% of a random cohort of M. tuberculosis clinical isolates, conferring a G to R change. The recombinant mutant protein appears less stable than the wild type, and has an apparent affinity for INH of 10-fold less than the wild type. Modelling the change in M. tuberculosis NAT shows that the G to R change is close to the active site, and supports the experimental findings. Minimum inhibitory concentration data suggest that this polymorphism in nat is linked to low-level changes in the INH susceptibility of M. tuberculosis clinical isolates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02648.x
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  • 4
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    A Theoretical Investigation of the Effects of Electronegative Substitution on the Strength of C-H...N Hydrogen Bonds (2001)
    In:  EPIC3Journal of Physical Chemistry, 105, pp. 8718-8726
    Details
    Publication Date: 2019-07-17
    Description: The effects of electronegative substitution (as modeled using fluoro substituents) on the strength of C-HâââNinteractions, and how these effects change with hybridization or with acidity of the proton donor, are examinedthrough the use of quantum chemistry. The binding energies (Do) in complexes between fluorinated derivativesof acetylene, ethylene, ethane and methane (the donors) and ammonia (the acceptor) are considered. We findthat fluoro substitution leads to a strengthening of the C-HâââN hydrogen bonds in all cases. The effect ofreplacing a beta hydrogen by fluorine increases as the hybridization of the proton donor goes from sp 〈 sp2〈 sp3. This trend is the opposite of the propensity of the unsubstituted C-H donors to participate in a hydrogenbond. The magnitude of the effect of an alpha fluorine is significantly greater than that of a beta fluorine forthe ethylene-ammonia complex, but the difference is much smaller for the ethane-ammonia complex. Ingeneral, the increase in the hydrogen-bond strength upon fluoro substitution of the proton donor qualitativelyparallels an increase in the acidity of the donor. We find that the strength of even the most weakly boundsystems (i.e., those with sp2- and sp3-hybridized proton donors) can be made comparable to, or larger than,that of the acetylene-ammonia complex through electronegative (fluoro) substitution.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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