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Find video protocols related to scientific articles indexed in Pubmed.
Galanin-3 receptor antagonism by SNAP 37889 reduces motivation to self-administer alcohol and attenuates cue-induced reinstatement of alcohol-seeking in iP rats.
J. Pharmacol. Sci.
PUBLISHED: 05-30-2014
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The neuropeptide galanin has a role in promoting alcohol consumption and general feeding behavior. The galanin-3 receptor (GALR3) subtype is implicated in modulating the consumption of alcohol and has therefore been identified as a potential target for new pharmacotherapies to treat alcohol use disorders. We have previously shown that the selective GALR3 antagonist SNAP 37889 reduced voluntary alcohol consumption in iP (alcohol-preferring) rats. The present study firstly aimed to investigate the effect of GALR3 antagonism on the motivational properties of alcohol. Secondly, the potential of GALR3 as a therapeutic target in the prevention of relapse was investigated in response to alcohol-conditioned cues. Administration of SNAP 37889 (30 mg/kg, i.p.) significantly reduced the breakpoint for ethanol under a progressive-ratio operant responding schedule of reinforcement. SNAP 37889 also significantly reduced reinstatement of alcohol-seeking in response to re-exposure to conditioned cues that were previously associated with the availability of alcohol. Collectively, results from the current study provide new evidence of GALR3 involvement in cue-induced relapse and provide further evidence that GALR3 antagonism reduces the motivational drive to consume alcohol. These findings validate further research in to the potential use of SNAP 37889 and other GALR3 antagonists to treat alcohol abuse disorders in humans.
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Targeted delivery of a model immunomodulator to the lymphatic system: comparison of alkyl ester versus triglyceride mimetic lipid prodrug strategies.
J Control Release
PUBLISHED: 01-05-2014
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A lipophilic prodrug approach has been used to promote the delivery of a model immunomodulator, mycophenolic acid (MPA), to the lymphatic system after oral administration. Lymphatic transport was employed to facilitate enhanced drug uptake into lymphocytes, as recent studies demonstrate that targeted drug delivery to lymph resident lymphocytes may enhance immunomodulatory effects. Two classes of lymph-directing prodrugs were synthesised. Alkyl chain derivatives (octyl mycophenolate, MPA-C8E; octadecyl mycophenolate, MPA-C18E; and octadecyl mycophenolamide, MPA-C18AM), to promote passive partitioning into lipids in lymphatic transport pathways, and a triglyceride mimetic prodrug (1,3-dipalmitoyl-2-mycophenoloyl glycerol, 2-MPA-TG) to facilitate metabolic integration into triglyceride deacylation-reacylation pathways. Lymphatic transport, lymphocyte uptake and plasma pharmacokinetics were assessed in mesenteric lymph and carotid artery cannulated rats following intraduodenal infusion of lipid-based formulations containing MPA or MPA prodrugs. Patterns of prodrug hydrolysis in rat digestive fluid, and cellular re-esterification in vivo, were evaluated to examine the mechanisms responsible for lymphatic transport. Poor enzyme stability and low absorption appeared to limit lymphatic transport of the alkyl derivatives, although two of the three alkyl chain prodrugs - MPA-C18AM (6-fold) and MPA-C18E (13-fold) still increased lymphatic drug transport when compared to MPA. In contrast, 2-MPA-TG markedly increased lymphatic drug transport (80-fold) and drug concentrations in lymphocytes (103-fold), and this was achieved via biochemical incorporation into triglyceride deacylation-reacylation pathways. The prodrug was hydrolysed rapidly to 2-mycophenoloyl glycerol (2-MPA-MG) in the presence of rat digestive fluid, and 2-MPA-MG was subsequently re-esterified in the enterocyte with oleic acid (most likely originating from the co-administered formulation) prior to accessing the lymphatics and lymphocytes. Importantly, after administration of 2-MPA-TG, the concentrations of free MPA in the mesenteric lymph nodes were significantly enhanced (up to 28 fold) when compared to animals administered equimolar quantities of MPA, suggesting the efficient conversion of the esterified prodrug back to the pharmacologically active parent drug. The data suggest that triglyceride mimetic prodrugs have potential as a means of enhancing immunotherapy via drug targeting to lymphocytes and lymph nodes.
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Intestinal bile secretion promotes drug absorption from lipid colloidal phases via induction of supersaturation.
Mol. Pharm.
PUBLISHED: 03-27-2013
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The oral bioavailability of poorly water-soluble drugs (PWSD) is often significantly enhanced by coadministration with lipids in food or lipid-based oral formulations. Coadministration with lipids promotes drug solubilization in intestinal mixed micelles and vesicles, however, the mechanism(s) by which PWSD are absorbed from these dispersed phases remain poorly understood. Classically, drug absorption is believed to be a product of the drug concentration in free solution and the apparent permeability across the absorptive membrane. Solubilization in colloidal phases such as mixed micelles increases dissolution rate and total solubilized drug concentrations, but does not directly enhance (and may reduce) the free drug concentration. In the absence of changes to cellular permeability (which is often high for lipophilic, PWSD), significant changes to membrane flux are therefore unexpected. Realizing that increases in effective dissolution rate may be a significant driver of increases in drug absorption for PWSD, we explore here two alternate mechanisms by which membrane flux might also be enhanced: (1) collisional drug absorption where drug is directly transferred from lipid colloidal phases to the absorptive membrane, and (2) supersaturation-enhanced drug absorption where bile mediated dilution of lipid colloidal phases leads to a transient increase in supersaturation, thermodynamic activity and absorption. In the current study, collisional uptake mechanisms did not play a significant role in the absorption of a model PWSD, cinnarizine, from lipid colloidal phases. In contrast, bile-mediated dilution of model intestinal mixed micelles and vesicles led to drug supersaturation. For colloids that were principally micellar, supersaturation was maintained for a period sufficient to promote absorption. In contrast, for primarily vesicular systems, supersaturation resulted in rapid drug precipitation and no increase in drug absorption. This work suggests that ongoing dilution by bile in the gastrointestinal tract may invoke supersaturation in intestinal colloids and promote absorption, and thus presents a new mechanism by which lipids may enhance the oral absorption of PWSD.
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Copper(I)-catalyzed cycloaddition of silver acetylides and azides: incorporation of volatile acetylenes into the triazole core.
Org. Biomol. Chem.
PUBLISHED: 07-12-2011
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Silver acetylides and organic azides react under copper(I) catalysis to afford 1,4-disubstituted 1,2,3-triazoles. Mechanistic studies implicate a process involving transmetallation to copper acetylides prior to cycloaddition. This work demonstrates that silver acetylides serve as suitable precursors for entry into copper-mediated coupling reactions. This methodology allows the incorporation of volatile and difficult-to-handle acetylenes into the triazole core.
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Total synthesis of 8-deshydroxyajudazol B.
Org. Lett.
PUBLISHED: 03-16-2011
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The total synthesis of a stereoisomer of 8-deshydroxyajudazol B (4), the putative biosynthetic intermediate of the ajudazols A (1) and B (2), is described. The key steps in the synthesis included an intramolecular Diels-Alder (IMDA) reaction to secure the isochromanone fragment, a novel selective acylation/O,N-shift to give a hydroxyamide which was cyclized to the oxazole and a high yielding Sonogashira coupling to form the C18-C19 bond. Partial alkyne reduction then afforded the target 4.
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Total synthesis of enigmazole A from Cinachyrella enigmatica. Bidirectional bond constructions with an ambident 2,4-disubstituted oxazole synthon.
J. Am. Chem. Soc.
PUBLISHED: 07-02-2010
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The first total synthesis of the cytotoxic marine macrolide enigmazole A has been completed in 22 steps (longest linear sequence). The sensitive, densely functionalized 2,4-disubstituted oxazole fragment was constructed using an efficient Negishi-type coupling of an oxazol-2-ylzinc reagent formed directly from the parent ethyl 2-iodooxazole-4-carboxylate by zinc insertion. Other key steps include a hetero-Diels-Alder cycloaddition to form the central embedded pyran ring, a Wittig reaction to unite Eastern and Western hemispheres, and a ring size-selective Keck macrolactonization.
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Liposomal circular dichroism. Assignment of remote stereocenters in plakinic acids K and L from a Plakortis-Xestospongia sponge association.
Org. Lett.
PUBLISHED: 03-09-2010
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Two new omega-phenyl polyketide peroxides, plakinic acids K and L, were isolated from a two-sponge association of Plakortis halichondroides and Xestospongia deweerdtae. The absolute configurations of the remote dimethyl-branched stereocenters in plakinic acid K were assigned by degradation of plakinic acid K to a long-chain naphthamide and analysis by liposomal circular dichroism (L-CD) and comparison with synthetic standards.
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Oxazoline-oxazinone oxidative rearrangement. divergent syntheses of (2S,3S)-4,4,4-trifluorovaline and (2S,4S)-5,5,5-Trifluoroleucine.
J. Org. Chem.
PUBLISHED: 06-23-2009
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Stereoselective syntheses of the valuable fluorinated amino acids (2S,3S)-4,4,4-trifluorovaline and (2S,4S)-5,5,5-trifluoroleucine have been achieved starting from 4,4,4-trifluoro-3-methylbutanoic acid by using a conceptually simple transformation: conversion to a chiral oxazoline, SeO2-promoted oxidative rearrangement to the dihydro-2H-oxazinone, and face-selective hydrogenation of the C=N bond, followed by hydrogenolysis-hydrolysis. The transformation is limited by the tendency of the intermediate beta-trifluoromethyldihydrooxazinone to undergo imine-enamine isomerization. Both amino acids were obtained as configurationally pure hydrochloride salts identical in all respects with those in literature reports.
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Amplification of the Cotton effect of a single chromophore through liposomal ordering-stereochemical assignment of plakinic acids I and J.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 05-14-2009
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A dramatic effect is observed when acyclic N-(2-naphthamides) of medium-chain 1-amino-2-methylalkanes are partially ordered with the help of liposomes: the Cotton effect arising from pi-pi* transitions of the terminal naphthamide chromophor is enormously enhanced. This effect was exploited to assign the configuration of new polyketide peroxides such as 1 from the sponge Plakortis halichondroides.
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Total synthesis of the proposed structure of 8-deshydroxyajudazol A: a modified approach to 2,4-disubstituted oxazoles.
J. Org. Chem.
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The total synthesis of the proposed structure for the minor myxobacterial metabolite 8-deshydroxyajudazol A (3) is described. The isochromanone moiety present in the eastern fragment was constructed by an intramolecular-Diels-Alder (IMDA). Difficulties were encountered with the formation of the 2,4-disubstituted oxazole, so this was synthesized via a modified approach. This involved selective acylation of the diol 7 with acid 8, azide displacement of the secondary alcohol, and subsequent azide reduction in the presence of base which induced an O,N shift to give the hydroxyamide 23. Cyclodehydration then gave the desired oxazole 24 and deprotection followed by mesylation and elimination produced the C15 alkene 5. Sonogashira coupling with the eastern fragment vinyl iodide 6 and partial reduction yielded 8-deshydroxyajudazol A (3).
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Localization of oleuropeyl glucose esters and a flavanone to secretory cavities of Myrtaceae.
PLoS ONE
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We report the widespread occurrence of structurally diverse oleuropeyl glucose esters, including the new diester eucaglobulin B, localized specifically to the essential oil secretory cavities of myrtaceous species. Clear taxonomic patterns in the composition of cavity extracts within the genus Eucalyptus are shown with species from subgenus Symphyomyrtus dominated by oleuropeyl glucose esters and species from subgenus Eucalyptus dominated instead by the flavanone, pinocembrin. We also examined the intra-species occurrence of oleuropeyl glucose esters by quantifying the abundant constituents cuniloside B and froggattiside A in trees from two populations of Eucalyptus polybractea R.T. Baker. All trees contained both compounds, which were positively correlated with total essential oil concentration. This apparent ubiquity of oleuropeyl glucose esters at both intra- and inter-specific levels in Eucalyptus is indicative of important physiological or ecological functions. The significance of their prevalence and the sequestration of these esters and also pinocembrin to the extracellular domain of secretory cavities is discussed in light of their potential biological activities and our findings that they are spatially segregated to the exterior of cavity lumina. The localization of oleuropeyl glucose esters to a specific and isolatable tissue type has the potential to aid in future elucidation of function and biosynthesis.
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