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Peripheral Sites (peripheral + site)
Selected AbstractsKinetic analysis of effector modulation of butyrylcholinesterase-catalysed hydrolysis of acetanilides and homologous estersFEBS JOURNAL, Issue 10 2008Patrick Masson The effects of tyramine, serotonin and benzalkonium on the esterase and aryl acylamidase activities of wild-type human butyrylcholinesterase and its peripheral anionic site mutant, D70G, were investigated. The kinetic study was carried out under steady-state conditions with neutral and positively charged aryl acylamides [o -nitrophenylacetanilide, o -nitrotrifluorophenylacetanilide and m -(acetamido) N,N,N -trimethylanilinium] and homologous esters (o -nitrophenyl acetate and acetylthiocholine). Tyramine was an activator of hydrolysis for neutral substrates and an inhibitor of hydrolysis for positively charged substrates. The affinity of D70G for tyramine was lower than that of the wild-type enzyme. Tyramine activation of hydrolysis for neutral substrates by D70G was linear. Tyramine was found to be a pure competitive inhibitor of hydrolysis for positively charged substrates with both wild-type butyrylcholinesterase and D70G. Serotonin inhibited both esterase and aryl acylamidase activities for both positively charged and neutral substrates. Inhibition of wild-type butyrylcholinesterase was hyperbolic (i.e. partial) with neutral substrates and linear with positively charged substrates. Inhibition of D70G was linear with all substrates. A comparison of the effects of tyramine and serotonin on D70G versus the wild-type enzyme indicated that: (a) the peripheral anionic site is involved in the nonlinear activation and inhibition of the wild-type enzyme; and (b) in the presence of charged substrates, the ligand does not bind to the peripheral anionic site, so that ligand effects are linear, reflecting their sole interaction with the active site binding locus. Benzalkonium acted as an activator at low concentrations with neutral substrates. High concentrations of benzalkonium caused parabolic inhibition of the activity with neutral substrates for both wild-type butyrylcholinesterase and D70G, suggesting multiple binding sites. Benzalkonium caused linear, noncompetitive inhibition of the positively charged aryl acetanilide m -(acetamido) N,N,N -trimethylanilinium for D70G, and an unusual mixed-type inhibition/activation (, > , > 1) for wild-type butyrylcholinesterase with this substrate. No fundamental difference was observed between the effects of ligands on the butyrylcholinesterase-catalysed hydrolysis of esters and amides. Thus, butyrylcholinesterase uses the same machinery, i.e. the catalytic triad S198/H448/E325, for the hydrolysis of both types of substrate. The differences in response to ligand binding depend on whether the substrates are neutral or positively charged, i.e. the differences depend on the function of the peripheral site in wild-type butyrylcholinesterase, or the absence of its function in the D70G mutant. The complex inhibition/activation effects of effectors, depending on the integrity of the peripheral anionic site, reflect the allosteric ,cross-talk' between the peripheral anionic site and the catalytic centre. [source] Refined structures of placental alkaline phosphatase show a consistent pattern of interactions at the peripheral siteACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2010Boguslaw Stec In order to gain deeper insights into the functional sites of human placental alkaline phosphatase, the structures of the enzyme with the putative regulators l -Phe, pNPP and 5,-AMP [Llinas et al. (2005), J. Mol. Biol.350, 441,451] were re-refined. Significant variations in ligand positioning and identity were found compared with the previous report. The multiple corrections to the model improved the phases and the electron-density maps, allowing the modeling of omitted side chains and multiple disordered residues. These improvements led to a change in the position of l -Phe at the peripheral binding site, which appeared to be reversed. The structure with pNPP contained only p -nitrophenol in three distinct sites, while the structure with 5,-AMP contained the p -nitrophenyl group in two of the sites instead of 5,-AMP. Comparison of the re-refined models shows a consistent pattern of interactions at the peripheral site. [source] Surface Action Potential and Contractile Properties of the Human Triceps Surae Muscle: Effect of ,Dry' Water ImmersionEXPERIMENTAL PHYSIOLOGY, Issue 1 2002Yuri A. Koryak The effects of 7 days of ,dry' water immersion were investigated in six subjects. Changes in the contraction properties were studied in the triceps surae muscle. After immersion, the maximal voluntary contraction (MVC) was reduced by 18.9% (P < 0.01), and the electrically evoked (150 impulses s,1) maximal tension during tetanic contraction (Po) was reduced by 8.2% (P > 0.05). The difference between Po and MVC expressed as a percentage of Po and referred to as force deficiency was also calculated. The force deficiency increased by 44.1% (P < 0.001) after immersion. The decrease in Po was associated with increased maximal rates of tension development (7.2%) and relaxation. The twitch time-to-peak was not significantly changed, and half-relaxation and total contraction time were decreased by 5.3% and 2.8%, respectively, but the twitch tension (Pt) was not significantly changed and the Pt/Po ratio was decreased by 8.7%. The 60 s intermittent contractions (50 impulses s,1) decreased tetanic force to 57% (P < 0.05) of initial values, but force reduction was not significantly different in the two fatigue-inducing tests: fatigue index (the mean loss of force of the last five contractions, expressed as a percentage of the mean value of the first five contractions) was 36.2 ± 5.4% vs. 38.6 ± 2.8%, respectively (P > 0.05). While identical force reduction was present in the two fatigue-inducing tests, it would appear that concomitant electrical failure was considerably different. Comparison of the electrical and mechanical alterations recorded during voluntary contractions, and in contractions evoked by electrical stimulation of the motor nerve, suggests that immersion not only modifies the peripheral processes associated with contraction, but also changes central and/or neural command of the contraction. At peripheral sites, it is proposed that the intracellular processes of contraction play a role in the contractile impairment recorded during immersion. [source] Tetrakis-phthalocyanines bearing electron-withdrawing fluoro functionality: Synthesis, spectroscopy, and electrochemistryHETEROATOM CHEMISTRY, Issue 5 2009Ahmet T. Bilgiçli In this study, 2,9,16,23-tetrakis-4,-(2,3,5,6-tetrafluoro)-phenoxy-phthalocyaninatometalfree and metal(II) complexes, (H2PcBzF16, ZnPcOBzF16, CuPcOBzF16, and CoPcOBzF16) (Bz: Benzene) (2H, Zn, Cu, and Co), have been prepared directly from the corresponding 4,-(2,3,5,6-fluorophenylthio)-phthalonitrile compounds in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in high boiling quinoline solvent. Tetrafluoro atoms on 2,3,5,6-position of benzene at the peripheral sites of phthalocyanines (Pcs) give rise interesting solubility to tetrakismetallophthalocyanines. Although all complexes were soluble in DCM, CHCl3, THF, DMF, and DMSO with increasing order, complexes synthesized, particularly H2PcBzF16, CuPcOBzF16, have very limited solubility in DMF and DMSO. The complexes have been characterized by elemental analysis, FTIR, 1H NMR, UV,vis, and MALDI,TOF mass spectral data. The cyclic voltammetry and differential pulsed voltammetry of the complexes show that while H2PcBzF16, CuPcOBzF16, and ZnPcOBzF16 give ligand-based reduction and oxidation processes, CoPcOBzF16 gives both ligand and metal-based redox processes, in harmony with the common metallophthalocyanine complexes. Redox processes due to both aggregated and disaggregated species were simultaneously observed during the first reduction process. The nature of the metal-based redox processes was confirmed using spectroelectrochemical measurements. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:262,271, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20545 [source] Cross-presentation, dendritic cell subsets, and the generation of immunity to cellular antigensIMMUNOLOGICAL REVIEWS, Issue 1 2004William R. Heath Summary:, Cross-presentation involves the uptake and processing of exogenous antigens within the major histocompatibility complex (MHC) class I pathway. This process is primarily performed by dendritic cells (DCs), which are not a single cell type but may be divided into several distinct subsets. Those expressing CD8, together with CD205, found primarily in the T-cell areas of the spleen and lymph nodes, are the major subset responsible for cross-presenting cellular antigens. This ability is likely to be important for the generation of cytotoxic T-cell immunity to a variety of antigens, particularly those associated with viral infection, tumorigenesis, and DNA vaccination. At present, it is unclear whether the CD8,-expressing DC subset captures antigen directly from target cells or obtains it indirectly from intermediary DCs that traffic from peripheral sites. In this review, we examine the molecular basis for cross-presentation, discuss the role of DC subsets, and examine the contribution of this process to immunity, with some emphasis on DNA vaccination. [source] Suppression of experimental colitis in mice by CD11c+ dendritic cellsINFLAMMATORY BOWEL DISEASES, Issue 2 2009Joseph E. Qualls PhD Abstract Background: The innate immune system serves a critical role in homeostasis of the gastrointestinal (GI) tract. Both macrophages (MØs) and dendritic cells (DCs) have been shown to have pathogenic roles in animal models of inflammatory bowel disease. However, studies by several labs have established that resident MØs and DCs within the normal GI tract maintain an immunosuppressive phenotype compared to that seen in other peripheral sites. Recent studies by our lab demonstrated that the depletion of both MØs and DCs before the initiation of dextran sodium sulfate (DSS)-induced colitis resulted in exacerbation of disease, partly caused by increased neutrophil influx. Methods/Results: In this current report, DSS-induced colitis was shown to be significantly more severe when DCs were selectively depleted in mice as indicated by changes in weight loss, stool consistency, rectal bleeding, and histopathology. In contrast to enhanced colitis in MØ/DC-depleted mice, which was associated with increased neutrophil influx, increased colitis in DC-depleted mice was not associated with an increase in neutrophils in the colon, as shown by CXCL1 chemokine levels and myeloperoxidase (MPO) activity. However, increased IL-6 gene and protein expression in colon tissues correlated positively with increased colitis severity in DC-depleted mice compared to colitis in DC-intact mice. Conclusions: This study demonstrates that resident DCs can suppress the severity of acute DSS colitis and that regulation of IL-6 production may contribute to DC-mediated control of intestinal inflammation. (Inflamm Bowel Dis 2008) [source] Severity of Vertebral Fractures Is Associated With Alterations of Cortical Architecture in Postmenopausal Women,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2009Elisabeth Sornay-Rendu Abstract Patients with vertebral fractures (VFx) have trabecular architectural disruption on iliac biopsies. Because cortical bone is an important determinant of bone strength, we assessed cortical and trabecular microarchitecture at peripheral sites in patients with VFx of varying number (N) and severity (S). Bone architecture and volumetric density (vBMD) were assessed at the distal radius and tibia with HR-pQCT (XTreme CT; Scanco Medical, Bassersdorf, Switzerland) in 100 women with VFx (age, 74 ± 9 yr) of different S (GI, n = 23; GII, n = 35; GIII, n = 42) and in 362 women (age, 69 ± 7 yr) without peripheral or VFx (G0) from the OFELY study. Spine areal BMD (aBMD) was assessed by DXA. Among all women, at the radius and after adjustment for age and aBMD, there were significant trends in lower vBMD, cortical thickness (Cort.Th), trabecular number (Tb.N) and thickness (Tb.Th), higher trabecular separation (Tb.Sp), and distribution of separation (Tb.Sp.SD) with greater VFx S and N. Among women with VFx, lower Cort.Th and cortical vBMD (D.Cort) were associated with severe (GIII) and multiple (n > 2) VFx (p < 0.05). The age-adjusted OR for each SD decrease of Cort.Th was 2.04 (95% CI, 1.02,4.00) after adjustment for aBMD. At the tibia, there were trends for lower vBMD, Tb.N, Tb.Th, and higher Tb.Sp and Tb.Sp.SD with greater VFx S and N (p < 0.001). Among women with VFx, lower Cort.Th and D.Cort were associated with severe and multiple (n > 3) VFx (p < 0.01). In postmenopausal women, VFx are associated with low vBMD and architectural decay of trabecular and cortical bone at the radius and tibia, independently of spine aBMD. Severe and multiple VFx are associated with even more alterations of cortical bone. [source] Neuropeptide Y Cotransmission with Norepinephrine in the Sympathetic Nerve,Macrophage InterplayJOURNAL OF NEUROCHEMISTRY, Issue 6 2000Rainer H. Straub Abstract: The CNS modulates immune cells by direct synaptic-likecontacts in the brain and at peripheral sites, such as lymphoid organs. Tostudy the nerve-macrophage communication, a superfusion method was used toinvestigate cotransmission of neuropeptide Y (NPY) with norepinephrine (NE),with interleukin (IL)-6 secretion used as the macrophage read-out parameter.Spleen tissue slices spontaneously released NE, NPY, and IL-6 leading to asuperfusate concentration at 3-4 h of 1 nM, 10 pM, and 120pg/ml, respectively. Under these conditions, NPY dose-dependently inhibitedIL-6 secretion with a maximum effect at 10 -10M(p = 0.012) and 10 -9M (p < 0.001).Simultaneous addition of NPY at 10 -9M and the,-2-adrenergic agonist p -aminoclonidine further inhibited IL-6secretion (p < 0.05). However, simultaneous administration of NPYat 10 -9M and the ,-adrenergic agonist isoproterenolat 10 -6M or NE at 10 -6Msignificantly increased IL-6 secretion (p < 0.005). To objectifythese differential effects of NPY, electrical field stimulation of spleenslices was applied to release endogenous NPY and NE. Electrical fieldstimulation markedly reduced IL-6 secretion, which was attenuated by the NPYY1 receptor antagonist BIBP 3226 (10 -7M, p = 0.039;10 -8M, p = 0.035). This indicates that NPY increases theinhibitory effect of endogenous NE, which is mediated at low NE concentrationsvia ,-adrenoceptors. Blockade of ,-adrenoceptors attenuatedelectrically induced inhibition of IL-6 secretion (p < 0.001),which was dose-dependently abrogated by BIBP 3226. This indicates that underblockade of ,-adrenoceptors endogenous NPY supports the stimulatingeffect of endogenous NE via ,-adrenoceptors. These experimentsdemonstrate the ambiguity of NPY, which functions as a cotransmitter of NE inthe nerve-macrophage interplay. [source] Nausea and Vomiting Side Effects with Opioid Analgesics during Treatment of Chronic Pain: Mechanisms, Implications, and Management OptionsPAIN MEDICINE, Issue 4 2009Frank Porreca PhD ABSTRACT Objectives., Gastrointestinal (GI) side effects such as nausea and vomiting are common following opioid analgesia and represent a significant cause of patient discomfort and treatment dissatisfaction. This review examines the mechanisms that produce these side effects, their impact on treatment outcomes in chronic pain patients, and counteractive strategies. Results., A number of mechanisms by which opioids produce nausea and vomiting have been identified. These involve both central and peripheral sites including the vomiting center, chemoreceptor trigger zones, cerebral cortex, and the vestibular apparatus of the brain, as well as the GI tract itself. Nausea and vomiting have a negative impact on treatment efficacy and successful patient management because they limit the effective analgesic dosage that can be achieved and are frequently reported as the reason for discontinuation of opioid pain medication or missed doses. While various strategies such as antiemetic agents or opioid switching can be employed to control these side effects, neither option is ideal because they are not always effective and incur additional costs and inconvenience. Opioid-sparing analgesic agents may provide a further alternative to avoid nausea and vomiting due to their reduced reliance on mu-opioid signalling pathways to induce analgesia. Conclusions., Nausea and vomiting side effects limit the analgesic efficiency of current opioid therapies. There is a clear need for the development of improved opioid-based analgesics that mitigate these intolerable effects. [source] Schistosomiasis delays lesion resolution during Leishmania major infection by impairing parasite killing by macrophagesPARASITE IMMUNOLOGY, Issue 7 2002Anne Camille La Flamme Summary Infection of mice with Schistosoma mansoni delays the resolution of cutaneous lesions and parasitaemia during Leishmania major infection. In contrast, L. major infection does not appear to alter the course of schistosomiasis. Analysis of the cytokine responses in the draining lymph nodes (LN) indicates that, while L. major infection had no effect on schistosome-specific interleukin (IL)-4 production by mesenteric LN (MLN) cells, coinfection with S. mansoni resulted in decreased leishmania-induced interferon (IFN)-,, tumour necrosis factor-, and nitric oxide production by popliteal LN (PLN) cells 4 weeks after L. major infection. In addition, PLN cells produced higher levels of IL-4 4 weeks after L. major infection in coinfected mice. Finally, IFN-,-stimulated macrophages isolated from S. mansoni -infected mice were impaired in their ability to kill L. major after in vitro infection. These results suggest that pre-existence of a strong Th2 response-dominated infection can alter the responses to Th1-inducing pathogens at peripheral sites and impair Th1-mediated effector functions. [source] B cell differentiation in the bursa of Fabricius and spleen of embryos and chicks immediately after hatchingANIMAL SCIENCE JOURNAL, Issue 6 2009Kiyoaki NARABARA ABSTRACT Flow cytometric analysis and immunohistochemical observation were used to qualitatively and quantitatively clarify the nature of B cell differentiation in the bursa of Fabricius of chick embryos and to determine the timing of antibody class switching in chicken spleens based on positivity of IgM and IgG on and in the cells. In the bursa, the sIgM-positive cell population formed from the 12th to 15th day of embryogenesis. The proportion of sIgM-high expressing (sIgMhigh) cells was lower among bursacytes than splenocytes of hatched chicks, suggesting that the sIgMhigh bursacytes are to be released to peripheral sites. The proportion of sIgMhigh cells was higher at 0 days old than at any other examined stage of development. Colonization of the spleen by B cells occurred between the 18th day of embryogenesis and 0 days old. Antibody class switching was thought to start in the spleen between 1 and 2 weeks of age, because IgG-positive cells were present in the spleen of 2-week-old chicks, but not 0-day-old or 1-week-old chicks. [source] Use of a `caged' analogue to study the traffic of choline within acetylcholinesterase by kinetic crystallographyACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2007Jacques-Philippe Colletier Acetylcholinesterase plays a crucial role in nerve-impulse transmission at cholinergic synapses. The apparent paradox that it displays high turnover despite its active site being buried raises cogent questions as to how the traffic of substrates and products to and from the active site can occur so rapidly in such circumstances. Here, a kinetic crystallography strategy aimed at structurally addressing the issue of product traffic in acetylcholinesterase is presented, in which UV-laser-induced cleavage of a photolabile precursor of the enzymatic product analogue arsenocholine, `caged' arsenocholine, is performed in a temperature-controlled X-ray crystallography regime. The `caged' arsenocholine was shown to bind at both the active and peripheral sites of acetylcholinesterase. UV irradiation of a complex with acetylcholinesterase during a brief temperature excursion from 100,K to room temperature is most likely to have resulted in a decrease in occupancy by the caged compound. Microspectrophotometric experiments showed that the caged compound had indeed been photocleaved. It is proposed that a fraction of the arsenocholine molecules released within the crystal had been expelled from both the active and the peripheral sites. Partial q -weighted difference refinement revealed a relative movement of the two domains in acetylcholinesterase after photolysis and the room-temperature excursion, resulting in an increase in the active-site gorge volume of 30% and 35% in monomers A and B of the asymmetric unit, respectively. Moreover, an alternative route to the active-site gorge of the enzyme appeared to open. This structural characterization of acetylcholinesterase `at work' is consistent with the idea that choline exits from the enzyme after catalysis either via the gorge or via an alternative `backdoor' trajectory. [source] Frontal fibrosing alopecia associated with generalized hair lossAUSTRALASIAN JOURNAL OF DERMATOLOGY, Issue 3 2010Paul Armenores ABSTRACT We present six cases of frontal fibrosing alopecia, in which generalized hair loss is a feature. Although this variant of lichen planopilaris has been reported clinically in a number of patients, there is very little histological evidence that the condition exists in peripheral sites. We believe this pattern of involvement may be more common than is reported, and have provided histological evidence of lichen planopilaris being present at sites beyond the scalp and eyebrows. [source] | ||||||||||||||||