Determination of oxytetracycline and its degradation products by high-performance liquid chromatography-tandem mass spectrometry in manure-containing anaerobic test systems.

This paper describes the development of a HPLC-MS-MS (ESI) method with baseline separation of oxytetracycline, 4-epi-oxytetracycline, alpha-apo-oxytetracycline and beta-apo-oxytetracycline using an XTerra column and an MeOH-MilliQ-water (containing 8 mM formic acid) mobile phase. Limits of quantification for aqueous standards were in the range of 0.004 to 0.

The effect of mutations on the structure of insulin fibrils studied by Fourier transform infrared (FTIR) spectroscopy and electron microscopy.

Fibril formation (aggregation) of human and bovine insulin and six human insulin mutants in hydrochloric acid were investigated by visual inspection, Thioflavin T fluorescence spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The fibrillation tendencies of the wild-type insulins and the insulin mutants were (in order of decreasing fibrillation tendencies): Glu(B1) + Glu(B27) = bovine < human < des-(B1,B2)-insulin < Ser(B2) + Asp(B10) < Glu(A13) + Glu(B10) = Gln(B17) < Asp(B10). Transmission electron micrographs showed that the protofibrils of the mutants were similar to those of wild-type insulins and had a diameter of 5-10 nm and lengths varying from 50 nm to several microns.

Reduced antimicrobial potencies of oxytetracycline, tylosin, sulfadiazin, streptomycin, ciprofloxacin, and olaquindox due to environmental processes.

The stability of oxytetracycline (OTC), tylosin (TYL), sulfadiazin (SDZ), streptomycin (ST), ciprofloxacin (CF) and olaquindox (O) was examined in environmentally relevant matrices, such as soil interstitial water and sewage sludge water. Compounds were assessed in both aerobic (OTC, TYL, SDZ, ST, and CF) and anaerobic experiments (OTC, TYL, and O) using analytical measurements (UV spectrophotometry or HPLC) combined with a growth inhibition pour plate assay using activated sludge bacteria. (OTC was additionally assessed using a soil bacterial assay.

The lay user perspective on the quality of pharmaceuticals, drug therapy and pharmacy services--results of focus group discussions.

Background: This article presents the results of a study on quality of pharmacy services and perceived risk of pharmaceuticals. The results presented here are part of a multi-study evaluation of major changes in drug distribution in Iceland.

Objectives: This sub-study addressed the question: what is the lay user perspective on pharmaceuticals and pharmacy services, including their perception of risk?

Methods: To answer this question, seven focus group discussions were conducted with pharmacy customers in different locations in Iceland following new drug distribution legislation in 1996.

GluR2 ligand-binding core complexes: importance of the isoxazolol moiety and 5-substituent for the binding mode of AMPA-type agonists.

X-ray structures of the GluR2 ligand-binding core in complex with (S)-Des-Me-AMPA and in the presence and absence of zinc ions have been determined. (S)-Des-Me-AMPA, which is devoid of a substituent in the 5-position of the isoxazolol ring, only has limited interactions with the partly hydrophobic pocket of the ligand-binding site, and adopts an AMPA-like binding mode. The structures, in comparison with other agonist complex structures, disclose the relative importance of the isoxazolol ring and of the substituent in the 5-position for the mode of binding.

Hydrophilic carboxylic acids and iridoid glycosides in the juice of American and European cranberries (Vaccinium macrocarpon and V. oxycoccos), lingonberries (V. vitis-idaea), and blueberries (V. myrtillus).

Analysis of the hydrophilic fraction of cranberry juice by reversed-phase HPLC using an Aqua LUNA column with diode array or MS detection revealed the presence of quinic acid, malic acid, shikimic acid, and citric acid. For the first time, two iridoid glucosides were found in the juice. The two iridoid glucosides were shown to be monotropein and 6,7-dihydromonotropein by MS and NMR spectroscopy.

Structured triglyceride vehicles for oral delivery of halofantrine: examination of intestinal lymphatic transport and bioavailability in conscious rats.

Purpose: To compare the influence of triglyceride vehicle intramolecular structure on the intestinal lymphatic transport and systemic absorption of halofantrine in conscious rats.

Methods: Conscious, lymph cannulated and nonlymph cannulated rats were dosed orally with three structurally different triglycerides; sunflower oil, and two structured triglycerides containing different proportion and position of medium-(M) and long-chain (L) fatty acids on the glycerol backbone. The two structured triglycerides were abbreviated MLM and LML to reflect the structural position on the glycerol.

Transport of peptidomimetic drugs by the intestinal Di/tri-peptide transporter, PepT1.

The apical membrane of small intestinal enterocytes possess an uptake system for di- and tripeptides. The physiological function of the system is to transport small peptides resulting from digestion of dietary protein. Moreover, due to the broad substrate specificity of the system, it is also capable of transporting a number of orally administered peptidomimetic drugs.

A pharmacophore model for NK2 antagonist comprising compounds from several structurally diverse classes.

A neurokinin 2 (NK2) antagonist pharmacophore model has been developed on the basis of five non-peptide antagonists from several structurally diverse classes. To evaluate the pharmacophore model, another 20 antagonists were fitted to the model. By use of exhaustive conformational analysis (MMFFs force field and the GB/SA hydration model) and least-squares molecular superimposition studies, 23 of the 25 antagonists were fitted to the model in a low energy conformation with a low RMS value.

Characterization of mixtures of recombinant human cytochrome p450s as a screening model for metabolic stability in drug discovery.

1. Recombinant human cytochrome p450 (rhCYP) has become an important screening model in drug metabolism studies due to the high cost of human and animal hepatic tissue. Until now, rhCYPs have been evaluated and used as separate forms, but a mixture of CYP forms comparable with the human liver could be of value in early drug discovery.

Probing intermolecular protein-protein interactions in the calcium-sensing receptor homodimer using bioluminescence resonance energy transfer (BRET).

The calcium-sensing receptor (CaR) belongs to family C of the G-protein coupled receptor superfamily. The receptor is believed to exist as a homodimer due to covalent and non-covalent interactions between the two amino terminal domains (ATDs). It is well established that agonist binding to family C receptors takes place at the ATD and that this causes the ATD dimer to twist.

Recent advances in the medicinal chemistry of polyamine toxins.

This review describes the recent developments in the field of polyamine toxins, with focus on structure activity relationship investigations, including studies of importance of the polyamine moiety for biological activity, photolabeling studies using polyamine toxins as templates, as well as use of solid phase methods for the synthesis of polyamine toxins. The review is mainly concerned with effects of polyamine toxins on nicotinic acetylcholine receptors and ionotropic glutamate receptors.

Investigation of the metal binding site in methionine aminopeptidase by density functional theory.

All methionine aminopeptidases exhibit the same conserved metal binding site. The structure of this site with either Co2+ ions or Zn2+ ions was investigated using density functional theory. The calculations showed that the structure of the site was not influenced by the identity of the metal ions.

Cotrimoxazole prescribing by dispensing and non-dispensing doctors: do they differ in rationality?

Background: Dispensing doctors (DDs) have been found to prescribe significantly more drugs, more injections and more antibiotics per patient than non-dispensing doctors (NDDs). However, the rationality of prescription in relation to diagnoses and symptoms has not been studied.

Objectives: To identify and assess differences in the rationality of cotrimoxazole prescription by DDs and NDDs evaluated by drug choice and dosage in relation to diagnoses and symptoms.

Antiplasmodial compounds from Cochlospermum tinctorium.

Fractionation of an ethanol extract of roots of Cochlospermum tinctorium afforded five compounds: 3-O-E-p-coumaroylalphitolic acid (1), cochloxanthin (2), dihydrocochloxanthin (3), alphitolic acid (4), and 1-hydroxytetradecan-3-one (5). This is the first example of a 1-hydroxyalkan-3-one obtained from plant material after gentle workup. The antiplasmodial activities of the compounds were determined, and the IC(50) value of 3-O-E-p-coumaroylalphitolic acid was 2.

In vitro cytotoxic activity of phenanthroindolizidine alkaloids from Cynanchum vincetoxicum and Tylophora tanakae against drug-sensitive and multidrug-resistant cancer cells.

Two known phenanthroindolizidine alkaloids, (-)-(R)-13aalpha-antofine (1) and (-)-(R)-13aalpha-6-O-desmethylantofine (2), and two new natural products, (-)-(R)-13aalpha-secoantofine (3) and (-)-(R)-13aalpha-6-O-desmethylsecoantofine (4), were isolated from Cynanchum vincetoxicum. The structures of all compounds were established by means of NMR methods including COSY, NOESY, HSQC, and HMBC experiments, supported by HRMS and optical rotation data. Cytotoxic activity of the isolated alkaloids, and of three other alkaloids previously isolated from Tylophora tanakae, (-)-(R)-13aalpha-tylophorine (5), (-)-(R)-13aalpha-7-O-desmethyltylophorine (6), and (+)-(S)-13abeta-isotylocrebrine (7), was assessed in vitro using a drug-sensitive KB-3-1 and a multidrug-resistant KB-V1 cancer cell line.

Baclofen influences lipopolysaccharide-mediated interleukin-6 release from murine pituicytes.

Pituicytes, the glial cells of the neurohypophysis, secrete interleukin-6 upon stimulation with various inflammatory mediators, i.e. lipopolysaccharide.

Activity of novel 4-PIOL analogues at human alpha 1 beta 2 gamma 2S GABA(A) receptors--correlation with hydrophobicity.

A series of novel 5-(4-piperidyl)-3-isoxazolol (4-PIOL) analogues where the 4-position of the 3-isoxazolol ring was substituted with groups of different size, flexibility, and lipophilicity have been characterised. Their activity as agonists and/or antagonists on human alpha(1)beta(2)gamma(2S) GABA(A) receptors expressed in Xenopus oocytes was studied using two-electrode voltage clamp electrophysiology. Methyl- and ethyl-substituted 4-PIOL analogues were characterised as partial agonists since weak agonist responses could be potentiated with lorazepam and inhibited by the competitive antagonist 2-(3-carboxypropyl)-3-amino-6-methoxyphenyl-pyradizinum bromide (SR95531).

Evalution of capillary electrophoresis-frontal analysis for the study of low molecular weight drug-human serum albumin interactions.

Capillary electrophoresis frontal analysis was applied to 12 low molecular weight compounds including 8 drug substances displaying a range of different properties with respect to binding affinity, binding location, structure, lipophilicity, charge at physiological pH, and electrophoretic mobility. It was found that capillary electrophoresis frontal analysis can be used as a general method to study and quantify drug-human serum albumin interactions. The binding parameters obtained were consistent with literature values.

Structural basis for AMPA receptor activation and ligand selectivity: crystal structures of five agonist complexes with the GluR2 ligand-binding core.

Glutamate is the principal excitatory neurotransmitter within the mammalian CNS, playing an important role in many different functions in the brain such as learning and memory. In this study, a combination of molecular biology, X-ray structure determinations, as well as electrophysiology and binding experiments, has been used to increase our knowledge concerning the ionotropic glutamate receptor GluR2 at the molecular level. Five high-resolution X-ray structures of the ligand-binding domain of GluR2 (S1S2J) complexed with the three agonists (S)-2-amino-3-[3-hydroxy-5-(2-methyl-2H-tetrazol-5-yl)isoxazol-4-yl]propionic acid (2-Me-Tet-AMPA), (S)-2-amino-3-(3-carboxy-5-methylisoxazol-4-yl)propionic acid (ACPA), and (S)-2-amino-3-(4-bromo-3-hydroxy-isoxazol-5-yl)propionic acid (Br-HIBO), as well as of a mutant thereof (S1S2J-Y702F) in complex with ACPA and Br-HIBO, have been determined.

Changes in self-concept while using SSRI antidepressants.

In this study, the authors analyze how younger women see themselves within the context of using the antidepressants selective serotonin re-uptake inhibitors (SSRIs). Twelve in-depth interviews and 6 reinterviews were conducted with a community-based sample of women who had been taking SSRIs between 1 and 4 years. The empirical analysis revealed that SSRI users passed through stages in their careers as medicine users, these stages corresponding to how the users thought and felt about themselves.

Selective agonists at group II metabotropic glutamate receptors: synthesis, stereochemistry, and molecular pharmacology of (S)- and (R)-2-amino-4-(4-hydroxy[1,2,5]thiadiazol-3-yl)butyric acid.

Homologation of analogues of the central excitatory neurotransmitter glutamic acid (Glu), in which the distal carboxy group has been bioisosterically replaced by acidic heterocyclic units, has previously provided subtype selective ligands for metabotropic Glu receptors (mGluRs). The (S)-form of the 1,2,5-thiadiazol-3-ol Glu analogue, 2-amino-3-(4-hydroxy[1,2,5]thiadiazol-3-yl)propionic acid (TDPA, 6), is an 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptor agonist, which in addition stereospecifically activates group I mGluRs. We have now synthesized the (S)- and (R)-forms of 2-amino-4-(4-hydroxy[1,2,5]thiadiazol-3-yl)butyric acid (homo-TDPA, 7) and shown that whereas neither enantiomer interacts with AMPA receptors, (S)- and (R)-7 appear to be selective and equipotent agonists at group II mGluRs as represented by the mGluR2 subtype.

Putative neuroprotective actions of N-acyl-ethanolamines.

N-Acyl-ethanolamines (NAEs) and their precursors, N-acyl-ethanolamine phospholipids (NAPEs), are present in the mammalian brain at levels of a few hundred picomoles/gram tissue and a few nanomoles/gram tissue, respectively. NAE-containing arachidonic acid is called anandamide, and it has attracted particular attention since it is a partial agonist for the cannabinoid receptors, for which 2-arachidonoylglycerol is the full agonist. In addition, anandamide may also activate the vanilloid receptor.