Molecular dynamics simulation of human neurohypophyseal hormone receptors complexed with oxytocin-modeling of an activated state.

The neurohypophyseal hormone oxytocin (CYIQNCPLG-NH(2), OT) is involved in the control of labor, secretion of milk and many social and behavioral functions via interaction with its receptors (OTR) located in the uterus, mammary glands and peripheral tissues, respectively. In this paper we propose the interactions responsible for OT binding and selectivity to OTR versus vasopressin ([F3,R8]OT, AVP) receptors: V1aR and V2R, all three belonging to the Class A G protein-coupled receptors (GPCRs). Three-dimensional models of the activated receptors were constructed using a multiple sequence alignment and the activated rhodopsin-transducin (MII-Gt) prototype [Slusarz and Ciarkowski, 2004] as a template. The 1 ns unconstrained molecular dynamics (MD) of three pairs of receptor-OT complexes (two complexes per each receptor) immersed in the fully hydrated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) lipid bilayer was conducted in the AMBER 7.0 force field. The relaxed models of ligand-receptor complexes were used to identify the putative binding sites of OT. The stabilizing interactions with conserved Gln residues in all complexes were identified. The nonconserved hydrophobic residues were proposed as responsible for OTR-OT selectivity and ligand recognition. These results provide guidelines for experimental site-directed mutagenesis and if confirmed, they may be helpful in designing new selective OT analogs with both agonistic or antagonistic properties.     

Destruction of Salmonella typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes in chicken manure by drying and/or gassing with ammonia

Escherichia coli O157:H7 and Listeria monocytogenes were able to grow for a period of 2 days in fresh chicken manure at 20 degrees C with a resulting 1-2 log units increase in CFU; Salmonella typhimurium remained stable. Prolongation of the storage time to 6 days resulted in a 1-2 log decreases of S. typhimurium compared to the initial count and a 3-4 log decrease of E. coli O157:H7; the number of L. monocytogenes did not decrease below the initial. These changes were accompanied by an increase in pH and accumulation of ammonia in the manure. The destruction of the three microorganisms was greatly increased by drying the manure to a moisture content of 10% followed by exposure to ammonia gas in an amount of 1% of the manure wet weight; S. typhimurium and E. coli O157:H7 were reduced by 8 log units, L. monocytogenes by 4.     

Probing the pharmacological properties of distinct subunit interfaces within heteromeric glycine receptors reveals a functional ββ agonist-binding site

Synaptic glycine receptors (GlyRs) are hetero-pentameric chloride channels composed of α and β subunits, which are activated by agonist binding at subunit interfaces. To examine the pharmacological properties of each potential agonist-binding site, we substituted residues of the GlyR α(1) subunit by the corresponding residues of the β subunit, as deduced from sequence alignment and homology modeling based on the recently published crystal structure of the glutamate-gated chloride channel GluCl. These exchange substitutions allowed us to reproduce the βα, αβ and ββ subunit interfaces present in synaptic heteromeric GlyRs by generating recombinant homomeric receptors. When the engineered α(1) GlyR mutants were expressed in Xenopus oocytes, all subunit interface combinations were found to form functional agonist-binding sites as revealed by voltage clamp recording. The ββ-binding site displayed the most distinct pharmacological profile towards a range of agonists and modulators tested, indicating that it might be selectively targeted to modulate the activity of synaptic GlyRs. The mutational approach described here should be generally applicable to heteromeric ligand-gated ion channels composed of homologous subunits and facilitate screening efforts aimed at targeting inter-subunit specific binding sites.     

Ephedrine accelerates psychomotor recovery from anesthesia in macaque monkeys

Background Ephedrine is used in treatment of hypotension during anesthesia. We investigated its effects on the psychomotor recovery and its potential adverse reactions on cardiorespiratory functions in rhesus monkeys. Methods The monkeys received 50 μg/kg medetomidine, 2.0 mg/kg S‐ketamine with 150 IU hyaluronidase i.m. Pulse rate, blood pressure and saturation of haemoglobin were monitored for 20 minutes. Thereafter, 1 mg/kg of ephedrine or a placebo was administered i.m. and behavioural changes, pulse rate, blood pressure and saturation of haemoglobin were monitored every 5 minutes. Results Ephedrine shortened recovery from anaesthesia from 80.4 ± 25.8 to 14.83 ± 13.70 minutes. Ephedrine also increased oxygen saturation of haemoglobin and systolic blood pressure and caused significant decrease in pulse rate 5 minutes after its administration. Conclusions Ephedrine can be successfully used to accelerate psychomotor recovery after the use of common anesthetic protocols combining dissociative anesthetic agent and alpha 2‐adrenoceptor agonist in primates.     

High-throughput sex identification by melting curve analysis in blue-breasted quail and chicken

The objective was to develop a high-throughput method of identifying sex in both Coturnix chinensis and Gallus gallus, which would be useful for biomedical research and hatcheries. Because chromo-helicase-DNA binding protein (CHD)-based Griffiths P2/P8 primers do not produce polymerase chain reaction (PCR) products with distinguishable sex-specific curves in melting curve analysis (MCA), these primers are unsuitable for high throughput application in either species. Conserved regions were identified by basic local alignment search tool (BLAST) analyses of cloned CHD-Z and CHD-W genes of C. chinensis. Based on sequence alignment, a female-specific CHD-W primer (W-cot-F1) and a female/male (or CHD-W/CHD-Z)-common primer (ZW-cot-F1) were redesigned for use in combination with the Griffiths P2 primer for MCA-based PCR reaction. In C. chinensis and G. gallus, W-cot-F1/P2 and ZW-cot-F1/P2 had amplicon lengths of 315/318 and 114 base pairs and melting temperatures (Tm) of approximately 79.5 °C to 80 °C and approximately 78.5 °C to 79°C, respectively. Thus, MCA distinguished sex based on two distinct Tm peaks in females versus only one Tm peak in males. The MCA-based real-time PCR combined with the proposed primer redesign provided a high-throughput method of identifying sex in C. chinensis and G. gallus.     

双重实时荧光PCR法检测食品和饲料中的鸡源性成分

根据鸡线粒体DNA细胞色素b基因序列和内参照基因PUC18质粒基因序列设计特异性引物和以不同荧光素标记的TaqMan探针。通过对反应条件的优化筛选,建立能同时扩增鸡源性成分和内参照基因成分的双重实时荧光PCR检测方法。设置内参照反应是为了监控反应体系中是否含有PCR反应的抑制物,避免出现假阴性结果。分别以鸡、鸭、鹅、火鸡、牛、羊、猪、鱼、兔、驴、鹿、狗、马、鸽子、大豆、玉米、小麦、大米、马铃薯及番茄的线粒体DNA作为模板进行特异性试验,结果表明该方法仅能特异性扩增鸡源性成分,而对其它物种未见有效扩增。通过灵敏度测试,该方法检出限达0.01%。所制定的方法特异性高,灵敏度好,可以作为食品和饲料中鸡源性成分的高效检测方法。     

Amino acids outside of the loops that define the agonist binding site are important for ligand binding to insect nicotinic acetylcholine receptors

Nicotinic acetylcholine (ACh) receptors (nAChRs) are the targets of several kinds of insecticides. Based on the mutagenesis studies of Torpedo californica nAChRs and solved structure of a molluscan, glial-derived soluble ACh-binding protein, a model of the agonist site was constructed with contributing amino acids from three distinct loops (A, B, and C) of the α subunits and another three loops (D, E, and F) of the non-α subunits. According to this model, most insect nAChR subunits can form the functional heteromeric or homomeric receptors. Actually, insect subunits themselves did not form any functional receptor at various combinations as yet, and only part of them can form the functional receptors with vertebrate non-α subunits. These findings suggested that the agonist binding for insect nAChRs was not only contributed by those key amino acids in six loops, but also some unidentified amino acids from other regions. In our previous studies on nAChRs for Nilaparvata lugens , a target-site mutation (Y151S) was found within two α subunits (Nlα1 and Nlα3). In Drosophila S2 cells and Xenopus oocytes, Nlα1 can form functional receptors with rat β2 subunit. However, the same thing was not observed in Nlα3. In the present paper, by exchanging the corresponding regions between Nlα1 and Nlα3 to generate different chimeras, amino acid residues or residue clusters in the regions outside the six loops were found to play essential roles in agonist binding, especially for the amino acid clusters between loop B and C. This result indicated that the residues in the six loops could be necessary, but not enough for the activity of agonist binding.     

Recent improvements in the development of A<Subscript>2B</Subscript> adenosine receptor agonists

Adenosine is known to exert most of its physiological functions by acting as local modulator at four receptor subtypes named A₁, A_2A, A_2B and A₃ (ARs). Principally as a result of the difficulty in identifying potent and selective agonists, the A_2B AR is the least extensively characterised of the adenosine receptors family. Despite these limitations, growing understanding of the physiological meaning of this target indicates promising therapeutic perspectives for specific ligands. As A_2B AR signalling seems to be associated with pre/postconditioning cardioprotective and anti-inflammatory mechanisms, selective agonists may represent a new therapeutic group for patients suffering from coronary artery disease. Herein we present an overview of the recent advancements in identifying potent and selective A_2B AR agonists reported in scientific and patent literature. These compounds can be classified into adenosine-like and nonadenosine ligands. Nucleoside-based agonists are the result of modifying adenosine by substitution at the N ⁶-, C²-positions of the purine heterocycle and/or at the 5′-position of the ribose moiety or combinations of these substitutions. Compounds 1-deoxy-1-{6-[N′-(furan-2-carbonyl)-hydrazino]-9H-purin-9-yl}-N-ethyl-β-D-ribofuranuronamide (19, hA₁ K _i = 1050 nM, hA_2A K _i = 1550 nM, hA_2B EC₅₀ = 82 nM, hA₃ K _i > 5 μM) and its 2-chloro analogue 23 (hA₁ K _i = 3500 nM, hA_2A K _i = 4950 nM, hA_2B EC₅₀ = 210 nM, hA₃ K _i > 5 μM) were confirmed to be potent and selective full agonists in a cyclic adenosine monophosphate (cAMP) functional assay in Chinese hamster ovary (CHO) cells expressing hA_2B AR. Nonribose ligands are represented by conveniently substituted dicarbonitrilepyridines, among which 2-[6-amino-3,5-dicyano-4-[4-(cyclopropylmethoxy)phenyl]pyridin-2-ylsulfanyl]acetamide (BAY-60–6583, hA₁, hA_2A, hA₃ EC₅₀ > 10 μM; hA_2B EC₅₀ = 3 nM) is currently under preclinical-phase investigation for treating coronary artery disorders and atherosclerosis.