In vitro and in vivo aspects of N-acyl-phosphatidylethanolamine-containing liposomes.

Incorporation of the phospholipid, N-acyl-phosphatidylethanolamine (NAPE), has shown to increase the liposomal stability towards plasma components in vitro. Besides increasing the circulation-time, NAPE has been shown to contain fusiogenic properties. Hence, fusion between NAPE-liposomes and target cells may be expected, resulting in a favorable delivery of drug to the target cell.

Secondary structure alterations in insulin and growth hormone water-in-oil emulsions.

Water-in-oil (w/o) emulsions have shown a promising release profile of small drug molecules and proteins. However, the major concerns are the structural stability, the retention of the activity and to avoid unwanted immunological reactions caused by the changes in protein structure. In the present study, the secondary structure of insulin and growth hormone is investigated after manufacture of w/o emulsions, using Fourier transform infrared (FTIR) spectroscopy.

Role of astrocytes in the maintenance and modulation of glutamatergic and GABAergic neurotransmission.

The functional activity in the brain is primarily composed of an interplay between excitation and inhibition. In any given region the output is based upon a complex processing of incoming signals that require both excitatory and inhibitory units. Moreover, these units must be regulated and balanced such that an integrated and finely tuned response is generated.

Non-randomness in Shine-Dalgarno regions: links to gene characteristics.

A probabilistic approach to the study of the Shine-Dalgarno region was used to identify the most non-random positions based on parsing of genomes in four species: Escherichia coli, Bacillus subtilis, the AT-rich Clostridium perfringens, and the GC-rich Streptomyces coelicolor. The compositional non-randomness shows a clear peak centered around 9-11 nucleotides upstream of the start codon. This peak was in all species associated with guanine as the most abundant nucleotide, flanked by guanine in the closest proximity and adenines farther away (cytosine in case of S.

A sequential high-yielding large-scale solution-method for synthesis of philanthotoxin analogues.

A general, improved procedure for rapid synthesis of philanthotoxin analogues, a pharmacologically important class of polyamine conjugates, is described. The solution-phase procedure is illustrated by gram-scale synthesis of philanthotoxins PhTX-343 and PhTX-12. Selectively protected polyamines are coupled to N(alpha)-Fmoc-protected amino acid pentafluorophenyl esters.

Phosphinic, phosphonic and seleninic acid bioisosteres of isonipecotic acid as novel and selective GABA(C) receptor antagonists.

A number of amino acids bioisosterically derived from the specific GABA(A) agonist, isonipecotic acid, were electrophysiologically characterized as antagonists at GABA(C) rho(1) receptors expressed in Xenopus oocytes. The phosphinic acid analogue of isonipecotic acid, piperidin-4-ylphosphinic acid (2), was comparable with the standard GABA(C) antagonist, (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA), in terms of potency and GABA(C) versus GABA(A) receptor selectivity. Whereas the phosphonic acid analogue, piperidin-4-ylphosphonic acid (4), was at least an order of magnitude weaker than piperidin-4-ylphosphinic acid as a GABA(C) antagonist, the seleninic acid analogue, piperidin-4-ylseleninic acid (SEPI, 6), was the most potent and selective GABA(C) antagonist within the group of isonipecotic acid derived amino acids studied.

Characterisation of the abiotic degradation pathways of oxytetracyclines in soil interstitial water using LC-MS-MS.

The fate of oxytetracyclines (OTCs) in soil interstitial water was investigated and the structure of a number of degradation products elucidated in a time-related experiment. A previously developed separation method for LC-MS-MS able to base separate and quantify OTC and three of its epimers and degradation products was applied. Compounds detected were 4-epi-oxytetracycline (EOTC) (t(R)=3.

Rational design, synthesis, and pharmacological evaluation of 2-azanorbornane-3-exo,5-endo-dicarboxylic acid: a novel conformationally restricted glutamic acid analogue.

The design and synthesis of conformationally restricted analogues of alpha-amino acids is an often used strategy in medicinal chemistry research. Here we present the rational design, synthesis, and pharmacological evaluation of 2-azanorbornane-3-exo,5-endo-dicarboxylic acid (1), a novel conformationally restricted (S)-glutamic acid (Glu) analogue intended as a mimic of the folded Glu conformation. The synthesis of 1 was completed in its racemic form in eight steps from commercially available starting materials.

Effect of dextran as a run buffer additive in drug-protein binding studies using capillary electrophoresis frontal analysis.

The study of drug-protein interactions by capillary electrophoresis frontal analysis requires establishment of a sufficient mobility difference between the mobility of the ligand and protein. The potential utility of dextran as a run buffer additive to manipulate the electrophoretic mobilities of low molecular weight ligands and protein in capillary electrophoresis frontal analysis binding studies was assessed. It was demonstrated that dextran was effective in improving the separation between the ligands warfarin and flurbiprofen and human serum albumin.

Sodium glycocholate transport across Caco-2 cell monolayers, and the enhancement of mannitol transport relative to transepithelial electrical resistance.

Ideally, the amount of enhancer remaining at the donor side during an in vitro transport study should be known, in order to know the true enhancer concentration during a permeability study. The purpose of the present study is to estimate the flux of the enhancer, sodium glycocholate (GC), through Caco-2 cell monolayers, and to study the effect of various enhancer concentrations on the permeability of GC itself, the permeability of mannitol and the transepithelial electrical resistance (TEER). Apical to basolateral permeability was measured with various concentrations 0.

From experimental design to uncertainty estimation for the European Pharmacopoeia HPLC analysis of human insulin.

In this paper the process from experimental design (e.g. ruggedness test) to uncertainty estimation is described.

Identification of the amino acids of human serum albumin involved in the reaction with the naproxen acyl coenzyme A thioester using liquid chromatography combined with fluorescence and mass spectrometric detection.

Xenobiotic carboxylic acids, that via their metabolites covalently modify proteins, have been associated with serious side effects in man. Such reactive metabolites may be acyl glucuronides or alternatively, the corresponding acyl-CoA thioesters. In this study, the reaction of a model xenobiotic acyl-CoA, the naproxen-CoA, with human serum albumin (HSA), was characterized by high-performance liquid chromatography employing fluorescence and mass spectrometric detection.

Stereostructure-activity studies on agonists at the AMPA and kainate subtypes of ionotropic glutamate receptors.

(S)-Glutamic acid (Glu), the major excitatory neurotransmitter in the central nervous system, operates through ionotropic as well as metabotropic receptors and is considered to be involved in certain neurological disorders and degenerative brain diseases that are currently without any satisfactory therapeutic treatment. Until recently, development of selective Glu receptor agonists had mainly been based on lead compounds, which were frequently naturally occurring excitants structurally related to Glu. These Glu receptor agonists generally contain heterocyclic acidic moieties, which has stimulated the use of bioisosteric replacement approaches for the design of subtype-selective agonists.

Competitive antagonism of AMPA receptors by ligands of different classes: crystal structure of ATPO bound to the GluR2 ligand-binding core, in comparison with DNQX.

Ionotropic glutamate receptors (iGluRs) constitute a family of ligand-gated ion channels that are essential for mediating fast synaptic transmission in the central nervous system. This study presents a high-resolution X-ray structure of the competitive antagonist (S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid (ATPO) in complex with the ligand-binding core of the receptor. Comparison with the only previous structure of the ligand-binding core in complex with an antagonist, 6,7-dinitro-2,3-quinoxalinedione (DNQX) (Armstrong, N.

Demonstration of pyruvate recycling in primary cultures of neocortical astrocytes but not in neurons.

Pyruvate recycling was studied in primary cultures of mouse cerebrocortical astrocytes, GABAergic cerebrocortical interneurons, and co-cultures consisting of both cell types by measuring production of [4-(13)C]glutamate from [3-(13)C]glutamate by aid of nuclear magnetic resonance spectroscopy. This change in the position of the label can only occur by entry of [3-(13)C]glutamate into the tricarboxylic acid (TCA) cycle, conversion of labeled alpha-ketoglutarate to malate or oxaloacetate, malic enzyme-mediated decarboxylation of malate to pyruvate or phosphoenolpyruvate carboxykinase-mediated conversion of oxaloacetate to phosphoenolpyruvate and subsequent hydrolysis of the latter to pyruvate, and introduction of the labeled pyruvate into the TCA cycle, i.e.

Secreted phospholipase A(2) as a new enzymatic trigger mechanism for localised liposomal drug release and absorption in diseased tissue.

Polymer-coated liposomes can act as versatile drug-delivery systems due to long vascular circulation time and passive targeting by leaky blood vessels in diseased tissue. We present an experimental model system illustrating a new principle for improved and programmable drug-delivery, which takes advantage of an elevated activity of secretory phospholipase A(2) (PLA(2)) at the diseased target tissue. The secretory PLA(2) hydrolyses a lipid-based proenhancer in the carrier liposome, producing lyso-phospholipids and free fatty acids, which are shown in a synergistic way to lead to enhanced liposome destabilization and drug release at the same time as the permeability of the target membrane is enhanced.

An antiplasmodial lignan from Euterpe precatoria.

As a part of a study on new antiplasmodial natural products, a new 8-5' linked lignan dehydrodiconiferyl dibenzoate (2) and p-hydroxybenzoic acid (1) were isolated from the roots of the palm Euterpe precatoria. In contrast to compound 1, compound 2 showed a moderate antiplasmodial activity.

New dammarane and malabaricane triterpenes from Caloncoba echinata.

Three novel triterpenes, (11R,20R)-11,20-dihydroxy-24-dammaren-3-one (1), (17S,20R,24R)-17,25-dihydroxy-20,24-epoxy-14(18)-malabaricen-3-one (2), and (17R,20S,24R)-17,25-dihydroxy-20,24-epoxy-14(18)-malabaricen-3-one (3), were isolated from leaves of Caloncoba echinata. The structures were established using mainly 800 MHz NOESY and HMBC connectivities. The absolute stereochemistry of C-11 in 1 and that of C-17 in 2 were established by the Mosher method.

Leishmanicidal and antiplasmodial activity of constituents of Smirnowia iranica.

Three unusual, highly oxygenated novel phenylpropanoids (1-3) and two novel isoflavans, 8-prenylmucronulatol (4) and smiranicin (6), were isolated from Smirnowia iranica together with a previously described isoflavan, glyasperin H (5). The structures were established using homo- and heteronuclear two-dimensional NMR experiments. The isoflavans significantly inhibited the growth of extracellular stages of three Leishmania species in vitro, their activity against the intracellular stages being considerably lower.

Calcium-stimulated short-circuit currents in the canine proximal colonic epithelium: effects of DK-PGD2, a metabolite of prostaglandin D2.

Prostaglandin D2 (PGD2) has marked inhibitory effects on the canine proximal colonic epithelium set up in Ussing chambers. These effects involved a receptor that is pharmacologically distinct from the classical DP, presumably the recently identified CRTH2/DP2 variety. The mechanism underlying these effects was studied using 13,14-dihydro-15-keto-PGD2 (DK-PGD2), a stable metabolite of the parent prostanoid.

A new sheathless electrospray interface for coupling of capillary electrophoresis to ion-trap mass spectrometry.

A simple laboratory-made sheathless electrospray interface for coupling of capillary electrophoresis to ion-trap mass spectrometry (CE/MS) was developed. The interface was machined in-house and it was designed to be freely interchangeable with the commercially available ionization sources for the mass spectrometer. Sharpened fused-silica capillaries were coated with nickel by a simple electrodeless plating procedure and were used as all-in-one columns/emitters.

Solid-phase synthesis of polyamine toxin analogues: potent and selective antagonists of Ca2+-permeable AMPA receptors.

The wasp toxin philanthotoxin-433 (PhTX-433) is a nonselective and noncompetitive antagonist of ionotropic receptors, such as ionotropic glutamate receptors and nicotinic acetylcholine receptors. Polyamine toxins are extensively used for the characterization of subtypes of ionotropic glutamate receptors, in particular Ca(2+)-permeable AMPA and kainate receptors. We have previously shown that an analogue of PhTX-433 with one of the amino groups replaced by a methylene group, philanthotoxin-83 (PhTX-83) is a selective and potent antagonist of AMPA receptors.

Development of fast-disintegrating pellets in a rotary processor.

The aim of the present work was to formulate fast-disintegrating pellets by direct pelletization in a rotary processor. Formulations containing kaolin or bentonite and lactose were agglomerated with or without the addition of crospovidone in an instrumented rotary processor. The effects of the excipients on the amount of wall adhesion, the size and size distribution, the disintegration time, and the shape of the agglomerates, as well as the content of agglomerates > 2800 microns, were investigated.

Specific GABA(A) agonists and partial agonists.

The GABA(A) receptor system is implicated in a number of neurological and psychiatric diseases, making GABA(A) receptor ligands interesting as potential therapeutic agents. Only a few different classes of structures are currently known as ligands for the GABA recognition site on the hetero-pentameric GABA(A) receptor complex, reflecting the very strict structural requirements for GABA(A) receptor recognition and activation. Within the series of compounds showing agonist activity at the GABA(A) receptor site that have been developed, most of the ligands are structurally derived from the GABA(A) agonists muscimol, THIP, or isoguvacine, which we developed in the initial stages of the project.