Incorporation of neutral C-terminal residues in 3-amidinophenylalanine-derived matriptase inhibitors

A novel series of matriptase inhibitors based on previously identified tribasic 3-amidinophenylalanine derivatives was prepared. The C-terminal basic group was replaced by neutral residues to reduce the hydrophilicity of the inhibitors. The most potent compound 22 inhibits matriptase with a K_i value of 0.43 nM, but lacks selectivity towards factor Xa. By combination with neutral N-terminal sulfonyl residues several potent thrombin inhibitors were identified, which had reduced matriptase affinity.     

Generation of a 3D model for human GABA transporter hGAT-1 using molecular modeling and investigation of the binding of GABA

A three-dimensional model of the human Na⁺/Cl^?-dependent γ-aminobutyric acid (GABA) transporter hGAT-1 was developed by homology modeling and refined by subsequent molecular modeling using the crystal structure of a bacterial homologue leucine transporter from Aquifex aeolicus (LeuT_Aa) as the template. Protein structure quality checks show that the resulting structure is particularly suited for the analysis of the substrate binding pocket and virtual screening experiments. Interactions of GABA and the substrate binding pocket were investigated using docking studies. The difference of 6 out of 13 substrate interacting side chains between hGAT-1 and LeuT_Aa lead to the different substrate preference which can be explained using our three-dimensional model of hGAT-1. In particular the replacement of serine 256 and isoleucine 359 in LeuT_Aa with glycine and threonine in hGAT-1 seems to facilitate the selection of GABA as the main substrate by changing the hydrogen bonding pattern in the active site to the amino group of the substrate. For a set of 12 compounds flexible docking experiments were performed using LigandFit in combination with the Jain scoring function. With few exceptions the obtained rank order of potency was in line with experimental data. Thus, the method can be assumed to give at least a rough estimate of the potency of the potential of GABA uptake inhibitors.     

Metabolic basis for contractile dysfunction following chronic partial bladder outlet obstruction in rabbits

Our study is designed to correlate nitrite concentration, an index of nitric oxide (NO) release with mast cell peroxidase (MPO), a marker of cardiac mast cell degranulation and cardioprotective effect of ischaemic preconditioning in isolated perfused rat heart subjected to 30 min of global ischaemia and 30 min of reperfusion. Ischaemic preconditioning, comprised of four episodes of 5 min global ischaemia and 5 min of reperfusion, markedly reduced the release of lactate dehydrogenase (LDH) and creatine kinase (CK) in coronary effluent and incidence of ventricular premature beats (VPBs) and ventricular tachycardia and fibrillation (VT/VF) during reperfusion phase. Ischaemia-reperfusion induced release of MPO was markedly reduced in ischaemic preconditioned hearts. Increased release of nitrite was noted during reperfusion phase after sustained ischaemia in preconditioned hearts as compared to control hearts. No alterations in the release of nitrite was observed immediately after ischaemic preconditioning. However, ischaemic preconditioning markedly increased the release of MPO prior to global ischaemia. It is proposed that cardioprotective and antiarrhythmic effect of ischaemic preconditioning may be ascribed to degranulation of cardiac mast cells. Depletion of cytotoxic mediators during ischaemic preconditioning and consequent decreased release of these mediators during sustained ischaemia-reperfusion may be associated with preservation of structures in isolated rat heart responsible for NO release.     

RGS9 modulates dopamine signaling in the basal ganglia

Regulators of G protein signaling (RGS) modulate heterotrimeric G proteins in part by serving as GTPase-activating proteins for Galpha subunits. We examined a role for RGS9-2, an RGS subtype highly enriched in striatum, in modulating dopamine D2 receptor function. Viral-mediated overexpression of RGS9-2 in rat nucleus accumbens (ventral striatum) reduced locomotor responses to cocaine (an indirect dopamine agonist) and to D2 but not to D1 receptor agonists. Conversely, RGS9 knockout mice showed heightened locomotor and rewarding responses to cocaine and related psychostimulants. In vitro expression of RGS9-2 in Xenopus oocytes accelerated the off-kinetics of D2 receptor-induced GIRK currents, consistent with the in vivo data. Finally, chronic cocaine exposure increased RGS9-2 levels in nucleus accumbens. Together, these data demonstrate a functional interaction between RGS9-2 and D2 receptor signaling and the behavioral actions of psychostimulants and suggest that psychostimulant induction of RGS9-2 represents a compensatory adaptation that diminishes drug responsiveness.     

A mathematical model of the impact of infused targeted cytotoxic agents on brain tumours: implications for detection,design and delivery

Abstract. Motivated by the recent development of highly specific agents for brain tumours, we develop a mathematical model of the spatio-temporal dynamics of a brain tumour that receives an infusion of a highly specific cytotoxic agent (e.g. IL-4-PE, a cytotoxin comprised of IL-4 and a mutated form of Pseudomonas exotoxin). We derive an approximate but accurate mathematical formula for the tumour cure probability in terms of the tumour characteristics (size at time of detection, proliferation rate, diffusion coefficient), drug design (killing rate, loss rate and convection constants for tumour and tissue), and drug delivery (infusion rate, infusion duration). Our results suggest that high specificity is necessary but not sufficient to cure malignant gliomas; a nondispersed spatial profile of pretreatment tumour cells and/or good drug penetration are also required. The most important levers to improve tumour cure appear to be earlier detection, higher infusion rate, lower drug clearance rate and better convection into tumour, but not tissue. In contrast, the tumour cure probability is less sensitive to a longer infusion duration and enhancements in drug potency and drug specificity.     

The structure of Ro 09-0198 in different environments.

The constitution and configuration of Ro 09-0198 (cinnamycin) have been determined in DMSO. Further investigations in aqueous solution, in SDS micelles and in a lipid bilayer have been done to study the influence of different environments on the conformation of the peptide. It turned out that in spite of the polycyclic structure of the molecule, the conformation is drastically changed going from water to SDS micelles. Ro 09-0198 orients itself in lipid bilayers as expected from its amphiphilic structure. According to a nuclear Overhauser effect spectroscopy experiment under magic angle spinning (MAS) conditions, the molecule is incorporated into the membrane with its hydrophobic part inside the bilayer.     

Wading bird use of established and newly created reactor cooling reservoirs at the Savannah River Site,near Aiken,South Carolina,USA

We compared wading bird use of a newly created 405-ha reactor cooling reservoir (L-Lake) at the Savannah River Site, near Aiken, South Carolina, with that of two similar > 25-year-old reservoirs (1130-ha Par Pond and 87-ha Pond B) at the same site. L-Lake was constructed in 1984–1985 and filled in late 1985. Approximately 25% of the shoreline of L-Lake was planted with lacustrine vegetation in early 1987 in an attempt to speed the establishment of a self-sustaining balanced biological community (BBC) at the reservoir. Even so, during the course of our studies, L-Lake had considerably less wetland vegetation, especially floating-leaved species such as yellow nelumbo (Nelumbo lutea), than did either of the two older reservoirs.Sixty-three surveys of the avian communities using the three reservoirs were conducted between fall of 1987 and summer of 1989. These surveys indicated that (1) at least seven species of wading birds (order: Ciconiiformes) used L-Lake, (2) wading bird density was higher at L-Lake than at the other two reservoirs, (3) wading birds represented a higher proportion of the total avian community at L-Lake than at the other two, older reservoirs, and (4) wading birds at L-Lake used planted portions of the shoreline more than unplanted portions. We suggest that the inter-reservoir differences we observed represent a trophic upsurge (sensu O'Brien, 1990) resulting from the increased availability of fishes at L-Lake compared with the two older reservoirs.Work was performed at the University of Georgia's Savannah River Ecology Laboratory, Aiken, South Carolina 29802.     

Metabolic studies on rabbit bladder smooth muscle and mucosa

Recent studies indicate that the mucosa of the urinary bladder may play a major role in the maintenance of normal bladder function. The mucosal surface of the urinary bladder serves as a protective layer against the irritative solutes found in the urine. The integrity of this barrier can be broken by overdistension, anoxia, detergents, alcohols, bacterial infection and by contact with agents to which the mucosa has been sensitized.In view that both anoxia and ischemia can mediate a breakdown in the role of the mucosal layer as a permeability barrier, it is reasonable to assume that this function is dependent on cellular metabolism. As an initial investigation we have compared a variety of biochemical and metabolic parameters between the mucosal layer (consisting of the lamina propria, urothelium, and any connective tissue and vascular tissue within this layer); and the muscularis layer.The results of these studies demonstrated that the rate of glucose metabolism to lactic acid (LA) of the mucosa was more than three-fold greater than that of the smooth muscle. The rate of CO₂ production of the mucosa was 60% greater than that of the unstimulated smooth muscle. The maximal activity of the mitochondrial enzyme citrate synthase was significantly greater in the mucosa than in the smooth muscle, however, the activity of malate dehydrogenase was similar for both tissues. The maximal activity of the cytosolic enzyme creatine kinase was more than two-fold greater in the bladder smooth muscle than in the mucosa; although the affinities of the creatine kinase isoforms of the mucosa were sigificantly greater than those of the muscle.Although the concentrations of ATP and ADP were similar in both muscle and mucosa, the level of creatine phosphate (CP) was over four-fold greater in the bladder muscle while the level of AMP in the muscle was only 58% of that in the mucosal epithelium.In summary, the rate of glucose metabolism was greater in the mucosa than in the smooth muscle although the concentrations of high energy phosphates (ATP+CP) was significantly greater in the smooth muscle. Future studies will be directed at identifying the specific cellular processes within the mucosal layer that relate to the function of the urothelium as a permeability barrier.     

呼吸道菌群种类和数量与小儿毛细支气管炎的关系

目的 分析呼吸道菌群定植种类和数量与小儿毛细支气管炎之间的关联性.方法 选择2017年5月至2018年5月我院收治的296例毛细支气管炎患儿,将患儿按照疾病严重程度分为重症毛细支气管炎组(n=92)和轻症毛细支气管炎组(n=204),另纳入同期在我院体检的62例健康儿童为对照组,分析各组对象呼吸道菌群的种类及数量.结果...