Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 11 de 11
Filtrar
1.
J Parasitol ; 103(2): 183-186, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-27874323

RESUMO

Toxocara canis is a common intestinal nematode of young dogs. Puppies contaminate the environment with large numbers of eggs that can embryonate and become infective in less than a month. Embryonated eggs are infectious for humans and other paratenic hosts. Most T. canis infections in humans are asymptomatic; however, migration of T. canis larvae in the eye and in the central nervous system can result in vision loss, blindness, and even death. The eggs of T. canis are highly resistant to harsh environmental conditions and routinely used chemical disinfectants. The objective of this study was to evaluate the effects of full-strength commercial bleach (5.25% sodium hypochlorite solution) treatment on development of T. canis eggs and to report our serendipitous finding that T. canis eggs in dog feces can float in passive fecal flotation tests using bleach. We also demonstrated that T. canis eggs could be identified using the McMaster's fecal eggs counting test using 100% bleach. Toxocara canis eggs collected from the feces of naturally infected 4-8 wk old puppies were treated with full-strength bleach (5.25% sodium hypochlorite solution) for 15 min, 30 min, 60 min, and 120 min; washed free of bleach smell by centrifugation; and resuspended in 0.1 N sulfuric acid solution to undergo larval development at room temperature for 18 days after exposure to bleach. Motile larvae were observed in T. canis eggs in all groups treated for 15-120 min and eggs continuously exposed to bleach for 18 days. Our results indicate that bleach may not be an appropriate disinfectant for dog kennels, cages, or laboratory utensils and work surfaces. Toxocara canis eggs are resistant to bleach treatment and continue to pose a risk for canine and human infections. Further study is needed to find the most appropriate methods for disinfection and removal of eggs to reduce the risk of transmission of this parasite.


Assuntos
Desinfetantes/farmacologia , Oxidantes/farmacologia , Hipoclorito de Sódio/farmacologia , Toxocara canis/crescimento & desenvolvimento , Animais , Desinfetantes/química , Cães , Fezes/parasitologia , Humanos , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Óvulo/efeitos dos fármacos , Óvulo/crescimento & desenvolvimento , Oxidantes/química , Contagem de Ovos de Parasitas , Hipoclorito de Sódio/química , Gravidade Específica , Fatores de Tempo , Toxocara canis/efeitos dos fármacos
2.
Health Technol Assess ; 20(60): 1-260, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27527344

RESUMO

BACKGROUND: Uncertainty about optimal red blood cell transfusion thresholds in cardiac surgery is reflected in widely varying transfusion rates between surgeons and cardiac centres. OBJECTIVE: To test the hypothesis that a restrictive compared with a liberal threshold for red blood cell transfusion after cardiac surgery reduces post-operative morbidity and health-care costs. DESIGN: Multicentre, parallel randomised controlled trial and within-trial cost-utility analysis from a UK NHS and Personal Social Services perspective. We could not blind health-care staff but tried to blind participants. Random allocations were generated by computer and minimised by centre and operation. SETTING: Seventeen specialist cardiac surgery centres in UK NHS hospitals. PARTICIPANTS: Patients aged > 16 years undergoing non-emergency cardiac surgery with post-operative haemoglobin < 9 g/dl. Exclusion criteria were: unwilling to have transfusion owing to beliefs; platelet, red blood cell or clotting disorder; ongoing or recurrent sepsis; and critical limb ischaemia. INTERVENTIONS: Participants in the liberal group were eligible for transfusion immediately after randomisation (post-operative haemoglobin < 9 g/dl); participants in the restrictive group were eligible for transfusion if their post-operative haemoglobin fell to < 7.5 g/dl during the index hospital stay. MAIN OUTCOME MEASURES: The primary outcome was a composite outcome of any serious infectious (sepsis or wound infection) or ischaemic event (permanent stroke, myocardial infarction, gut infarction or acute kidney injury) during the 3 months after randomisation. Events were verified or adjudicated by blinded personnel. Secondary outcomes included blood products transfused; infectious events; ischaemic events; quality of life (European Quality of Life-5 Dimensions); duration of intensive care or high-dependency unit stay; duration of hospital stay; significant pulmonary morbidity; all-cause mortality; resource use, costs and cost-effectiveness. RESULTS: We randomised 2007 participants between 15 July 2009 and 18 February 2013; four withdrew, leaving 1000 and 1003 in the restrictive and liberal groups, respectively. Transfusion rates after randomisation were 53.4% (534/1000) and 92.2% (925/1003). The primary outcome occurred in 35.1% (331/944) and 33.0% (317/962) of participants in the restrictive and liberal groups [odds ratio (OR) 1.11, 95% confidence interval (CI) 0.91 to 1.34; p = 0.30], respectively. There were no subgroup effects for the primary outcome, although some sensitivity analyses substantially altered the estimated OR. There were no differences for secondary clinical outcomes except for mortality, with more deaths in the restrictive group (4.2%, 42/1000 vs. 2.6%, 26/1003; hazard ratio 1.64, 95% CI 1.00 to 2.67; p = 0.045). Serious post-operative complications excluding primary outcome events occurred in 35.7% (354/991) and 34.2% (339/991) of participants in the restrictive and liberal groups, respectively. The total cost per participant from surgery to 3 months postoperatively differed little by group, just £182 less (standard error £488) in the restrictive group, largely owing to the difference in red blood cells cost. In the base-case cost-effectiveness results, the point estimate suggested that the restrictive threshold was cost-effective; however, this result was very uncertain partly owing to the negligible difference in quality-adjusted life-years gained. CONCLUSIONS: A restrictive transfusion threshold is not superior to a liberal threshold after cardiac surgery. This finding supports restrictive transfusion due to reduced consumption and costs of red blood cells. However, secondary findings create uncertainty about recommending restrictive transfusion and prompt a new hypothesis that liberal transfusion may be superior after cardiac surgery. Reanalyses of existing trial datasets, excluding all participants who did not breach the liberal threshold, followed by a meta-analysis of the reanalysed results are the most obvious research steps to address the new hypothesis about the possible harm of red blood cell transfusion. TRIAL REGISTRATION: Current Controlled Trials ISRCTN70923932. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 60. See the NIHR Journals Library website for further project information.


Assuntos
Anemia/terapia , Transfusão de Eritrócitos/métodos , Complicações Pós-Operatórias/epidemiologia , Idoso , Doenças Transmissíveis/epidemiologia , Análise Custo-Benefício , Transfusão de Eritrócitos/economia , Feminino , Hemoglobinas/análise , Humanos , Isquemia/epidemiologia , Tempo de Internação , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Modelos de Riscos Proporcionais , Qualidade de Vida , Anos de Vida Ajustados por Qualidade de Vida , Reprodutibilidade dos Testes , Fatores de Tempo , Reino Unido
3.
J Med Virol ; 88(9): 1641-5, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-26889628

RESUMO

Hepatitis E virus (HEV) is an important human pathogen with pigs and other species serving as natural animal reservoirs. Ample evidence documents sporadic cases of hepatitis E acquired via consumption of undercooked meat. Chronic hepatitis E cases in immunosuppressed individuals are mostly caused by zoonotic HEV of swine origin. We report here the identification of genotype 3 HEV from non-liver commercial pork from local grocery stores in southwest Virginia, and association of HEV seropositivity to the consumption of undercooked meat in healthy young adults at a university in the United States. These results raise concerns about foodborne HEV transmission in the United States. J. Med. Virol. 88:1641-1645, 2016. © 2016 Wiley Periodicals, Inc.


Assuntos
Reservatórios de Doenças/virologia , Doenças Transmitidas por Alimentos/virologia , Hepatite E/epidemiologia , Hepatite E/transmissão , Carne Vermelha/virologia , Doenças dos Suínos/transmissão , Adulto , Animais , Feminino , Doenças Transmitidas por Alimentos/prevenção & controle , Genótipo , Hepatite E/prevenção & controle , Hepatite E/virologia , Vírus da Hepatite E/genética , Vírus da Hepatite E/imunologia , Vírus da Hepatite E/isolamento & purificação , Humanos , Hospedeiro Imunocomprometido , Masculino , Pessoa de Meia-Idade , Fatores de Risco , Estudos Soroepidemiológicos , Suínos , Doenças dos Suínos/epidemiologia , Doenças dos Suínos/virologia , Estados Unidos/epidemiologia , Adulto Jovem
4.
Transfus Apher Sci ; 50(3): 451-61, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24675014

RESUMO

Thresholds for red blood cell transfusion following cardiac surgery vary by hospital and surgeon. The TITRe2 multi-centre randomised controlled trial aims to randomise 2000 patients from 17 United Kingdom centres, and tests the hypothesis that a restrictive transfusion threshold will reduce postoperative morbidity and health service costs compared to a liberal threshold. Patients consent to take part in the study pre-operatively but are only randomised if their haemoglobin falls below 9 g/dL during their post-operative hospital stay. The primary outcome is a binary composite outcome of any serious infectious or ischaemic event in the first three months after randomisation. Many challenges have been encountered in the set-up and running of the study.


Assuntos
Transfusão de Sangue , Complicações Pós-Operatórias , Procedimentos Cirúrgicos Cardíacos , Feminino , Seguimentos , Hemoglobinas/metabolismo , Humanos , Masculino , Complicações Pós-Operatórias/sangue , Complicações Pós-Operatórias/mortalidade , Complicações Pós-Operatórias/terapia , Estudos Retrospectivos , Fatores de Tempo , Reino Unido
5.
Am J Physiol Gastrointest Liver Physiol ; 294(5): G1257-67, 2008 May.
Artigo em Inglês | MEDLINE | ID: mdl-18308860

RESUMO

Inflammatory bowel disease is characterized by the recruitment of lymphocytes to the gut via mucosal vessels. Chemokines are believed to trigger alpha(4)beta(1)- and alpha(4)beta(7)-integrin-mediated adhesion to vascular cell adhesion molecule-1 (VCAM-1) and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) on mucosal vessels, although the contribution of each pathway and the chemokines involved are not well characterized. These interactions occur under conditions of hemodynamic shear, which is critical in determining how lymphocytes integrate chemokine signals to promote transmigration. To define the role of specific chemokines in mediating lymphocyte adhesion to VCAM-1 and MAdCAM-1, we studied the ability of immobilized chemokines to activate adhesion of human lymphocytes in a flow-based adhesion assay. Adhesion to immobilized MAdCAM-1 was alpha(4)beta(7) dependent, with no contribution from alpha(4)beta(1), whereas alpha(4)beta(1) mediated rolling and static adhesion on VCAM-1. Immobilized CC-chemokine ligand (CCL) 25 and CCL28 were both able to trigger alpha(4)beta(7)-dependent lymphocyte arrest on MAdCAM-1 under shear, highlighting a potential role for these chemokines in the arrest of lymphocytes on postcapillary venules in the gut. Neither had any effect on adhesion to VCAM-1, suggesting that they selectively trigger alpha(4)beta(7)-mediated adhesion. Immobilized CCL21, CCL25, CCL28, and CXC-chemokine ligand (CXCL) 12 all converted rolling adhesion to static arrest on MAdCAM-1 by activating lymphocyte integrins, but only CCL21 and CXCL12 also triggered a motile phenotype characterized by lamelipodia and uropod formation. Thus alpha(4)beta(1)/VCAM-1 and alpha(4)beta(7)/MAdCAM-1 operate independently to support lymphocyte adhesion from flow, and chemokines may act in concert with one chemokine triggering integrin-mediated arrest and a second chemokine promoting motility and transendothelial migration.


Assuntos
Quimiocinas CC/farmacologia , Imunoglobulinas/metabolismo , Integrinas/metabolismo , Linfócitos/efeitos dos fármacos , Mucoproteínas/metabolismo , Anticorpos/farmacologia , Adesão Celular/efeitos dos fármacos , Adesão Celular/fisiologia , Moléculas de Adesão Celular , Quimiocina CCL21/farmacologia , Quimiocina CXCL12/farmacologia , Células Endoteliais/citologia , Células Endoteliais/metabolismo , Proteínas de Ligação ao GTP/antagonistas & inibidores , Humanos , Imunoglobulinas/genética , Doenças Inflamatórias Intestinais/patologia , Integrina alfa4/análise , Integrina alfa4beta1/imunologia , Integrina alfa4beta1/metabolismo , Integrinas/análise , Integrinas/imunologia , Migração e Rolagem de Leucócitos/efeitos dos fármacos , Migração e Rolagem de Leucócitos/fisiologia , Linfócitos/citologia , Linfócitos/metabolismo , Mucoproteínas/genética , Toxina Pertussis/farmacologia , Receptores de Quimiocinas/análise , Reologia , Transdução de Sinais/efeitos dos fármacos , Linfócitos T/química , Transfecção , Molécula 1 de Adesão de Célula Vascular/metabolismo
6.
J Immunol ; 177(1): 593-603, 2006 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-16785557

RESUMO

Mucosal tissues require constant immune surveillance to clear harmful pathogens while maintaining tolerance to self Ags. Regulatory T cells (Tregs) play a central role in this process and expression of alpha(E)beta(7) has been reported to define a subset of Tregs with tropism for inflamed tissues. However, the signals responsible for recruiting Tregs to epithelial surfaces are poorly understood. We have isolated a subset of CCR10-expressing CD25+CD4+Foxp3+ Tregs with potent anti-inflammatory properties from chronically inflamed human liver. The CCR10+ Tregs were detected around bile ducts that expressed increased levels of the CCR10 ligand CCL28. CCL28 was secreted by primary human cholangiocytes in vitro in response to LPS, IL-1beta, or bile acids. Exposure of CCR10+ Tregs to CCL28 in vitro stimulated migration and adhesion to mucosal addressin cell adhesion molecule-1 and VCAM-1. Liver-derived CCR10+ Tregs expressed low levels of CCR7 but high levels of CXCR3, a chemokine receptor associated with infiltration into inflamed tissue and contained a subset of alpha(E)beta7(+) cells. We propose that CXCR3 promotes the recruitment of Tregs to inflamed tissues and CCR10 allows them to respond to CCL28 secreted by epithelial cells resulting in the accumulation of CCR10+ Tregs at mucosal surfaces.


Assuntos
Ductos Biliares/patologia , Quimiocinas/biossíntese , Quimiotaxia de Leucócito/imunologia , Células Epiteliais/imunologia , Células Epiteliais/patologia , Mediadores da Inflamação/fisiologia , Receptores de Quimiocinas/biossíntese , Linfócitos T Reguladores/patologia , Ductos Biliares/imunologia , Ductos Biliares/metabolismo , Células Cultivadas , Quimiocinas/metabolismo , Quimiocinas CC , Colangite Esclerosante/imunologia , Colangite Esclerosante/metabolismo , Colangite Esclerosante/patologia , Doença Crônica , Células Epiteliais/metabolismo , Fatores de Transcrição Forkhead/biossíntese , Humanos , Imunidade nas Mucosas , Mediadores da Inflamação/metabolismo , Interleucina-1/farmacologia , Interleucina-10/biossíntese , Interleucina-10/metabolismo , Lipopolissacarídeos/farmacologia , Cirrose Hepática Biliar/imunologia , Cirrose Hepática Biliar/metabolismo , Cirrose Hepática Biliar/patologia , Hepatopatias Alcoólicas/imunologia , Hepatopatias Alcoólicas/metabolismo , Hepatopatias Alcoólicas/patologia , Receptores CCR10 , Receptores CCR7 , Receptores CXCR3 , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Subpopulações de Linfócitos T/patologia , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/metabolismo , Regulação para Cima/imunologia
7.
Clin Cancer Res ; 12(7 Pt 1): 2004-13, 2006 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-16609009

RESUMO

PURPOSE: We hypothesized that deregulated corepressor actions, with associated histone deacetylation activity, epigenetically suppressed vitamin D receptor (VDR) responsiveness and drives resistance towards 1alpha,25-dihydroxyvitamin D(3). EXPERIMENTAL DESIGN: Profiling, transcriptional, and proliferation assays were undertaken in 1alpha,25(OH)(2)D(3)-sensitive MCF-12A nonmalignant breast epithelial cells, a panel of breast cancer cell lines, and a cohort of primary breast cancer tumors (n = 21). RESULTS: Elevated NCoR1 mRNA levels correlated with suppressed regulation of VDR target genes and the ability of cells to undergo arrest in G(1) of the cell cycle. A similar increased ratio of corepressor mRNA to VDR occurred in matched primary tumor and normal cells, noticeably in estrogen receptor alpha-negative (n = 7) tumors. 1alpha,25(OH)(2)D(3) resistance in cancer cell lines was targeted by cotreatments with either 1alpha,25(OH)(2)D(3) or a metabolically stable analogue (RO-26-2198) in combination with either trichostatin A (TSA; histone deacetylation inhibitor) or 5-aza-2'-deoxycytidine (DNA methyltransferase inhibitor). Combinations of vitamin D(3) compounds with TSA restored VDR antiproliferative signaling (target gene regulation, cell cycle arrest, and antiproliferative effects in liquid culture) to levels which were indistinguishable from MCF-12A cells. CONCLUSIONS: Increased NCoR1 mRNA is a novel molecular lesion in breast cancer cells, which acts to suppress responsiveness of VDR target genes, resulting in 1alpha,25(OH)(2)D(3) resistance and seems to be particularly associated with estrogen receptor negativity. This lesion provides a novel molecular diagnostic and can be targeted by combinations of vitamin D(3) compounds and low doses of TSA.


Assuntos
Neoplasias da Mama/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Receptores de Calcitriol/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Transdução de Sinais , Azacitidina/análogos & derivados , Azacitidina/farmacologia , Calcitriol/farmacologia , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Colecalciferol/análogos & derivados , Colecalciferol/farmacologia , Decitabina , Feminino , Humanos , Ácidos Hidroxâmicos/farmacologia , Proteínas Nucleares/efeitos dos fármacos , Correpressor 1 de Receptor Nuclear , RNA Mensageiro/efeitos dos fármacos , RNA Mensageiro/genética , Receptores de Calcitriol/efeitos dos fármacos , Proteínas Repressoras/efeitos dos fármacos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacos , Relação Estrutura-Atividade , Fatores de Tempo , Células Tumorais Cultivadas
8.
J Exp Med ; 200(11): 1511-7, 2004 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-15557349

RESUMO

Primary sclerosing cholangitis (PSC), a chronic inflammatory liver disease characterized by progressive bile duct destruction, develops as an extra-intestinal complication of inflammatory bowel disease (IBD) (Chapman, R.W. 1991. Gut. 32:1433-1435). However, the liver and bowel inflammation are rarely concomitant, and PSC can develop in patients whose colons have been removed previously. We hypothesized that PSC is mediated by long-lived memory T cells originally activated in the gut, but able to mediate extra-intestinal inflammation in the absence of active IBD (Grant, A.J., P.F. Lalor, M. Salmi, S. Jalkanen, and D.H. Adams. 2002. Lancet. 359:150-157). In support of this, we show that liver-infiltrating lymphocytes in PSC include mucosal T cells recruited to the liver by aberrant expression of the gut-specific chemokine CCL25 that activates alpha4beta7 binding to mucosal addressin cell adhesion molecule 1 on the hepatic endothelium. This is the first demonstration in humans that T cells activated in the gut can be recruited to an extra-intestinal site of disease and provides a paradigm to explain the pathogenesis of extra-intestinal complications of IBD.


Assuntos
Quimiocinas CC/fisiologia , Colangite Esclerosante/etiologia , Intestinos/patologia , Fígado/patologia , Linfócitos/fisiologia , Receptores de Quimiocinas/fisiologia , Movimento Celular , Endotélio/fisiologia , Humanos , Doenças Inflamatórias Intestinais/complicações , Receptores CCR , Receptores de Quimiocinas/análise
9.
Clin Med (Lond) ; 4(2): 173-80, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15139741

RESUMO

Inflammatory bowel disease is associated with extra-intestinal manifestations which occur either at the same time as flares of bowel inflammation (skin and eye disease) or run a course that is independent to inflammation in the bowel (liver and some joint syndromes). It has been suggested that the skin and eye complications occur as a consequence of the recruitment of activated effector cells released from the gut into the circulation to extra-intestinal site where they cause acute damage. However, this does not explain how patients can develop primary sclerosing cholangitis many years after having their colon removed for colitis. We propose that long-lived populations of memory lymphocytes arise as a consequence of bowel inflammation and that these cells express homing receptors that direct their subsequent migration not only to the gut but also to the liver. These long-lived cells may recirculate to the liver for many years and, in the absence of a local activating stimulus, will not cause damage. However, if they are subsequently activated in the liver this will lead to the development of inflammation and tissue damage which promotes the recruitment of more mucosal lymphocytes resulting in persistent inflammation and disease. The recent findings that MAdCAM-1 and CCL25, previously thought to be restricted to the gut, are up-regulated in the liver during inflammatory liver diseases that complicate IBD support the concept that common mechanisms control lymphocyte recruitment to the inflamed liver and gut.


Assuntos
Movimento Celular/fisiologia , Colangite Esclerosante/etiologia , Hepatite/etiologia , Doenças Inflamatórias Intestinais/fisiopatologia , Receptores de Retorno de Linfócitos/fisiologia , Colangite Esclerosante/fisiopatologia , Hepatite/fisiopatologia , Humanos , Mucosa Intestinal/fisiopatologia
10.
Eur J Biochem ; 270(23): 4681-8, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14622255

RESUMO

Defining how the agonist-receptor interaction differs from that of the antagonist-receptor and understanding the mechanisms of receptor activation are fundamental issues in cell signalling. The V1a vasopressin receptor (V1aR) is a member of a family of related G-protein coupled receptors that are activated by neurohypophysial peptide hormones, including vasopressin (AVP). It has recently been reported that an arginyl in the distal N-terminus of the V1aR is critical for binding agonists but not antagonists. To determine specific features required at this locus to support high affinity agonist binding and second messenger generation, Arg46 was substituted by all other 19 encoded amino acids. Our data establish that there is an absolute requirement for arginyl, as none of the [R46X]V1aR mutant constructs supported high affinity agonist binding and all 19 had defective signalling. In contrast, all of the mutant receptors possessed wildtype binding for both peptide and nonpeptide antagonists. The ratio of Ki to EC50, an indicator of efficacy, was increased for all substitutions. Consequently, although [R46X]V1aR constructs have a lower affinity for agonist, once AVP has bound all 19 are more likely than the wildtype V1aR to become activated. Therefore, in the wildtype V1aR, Arg46 constrains the inactive conformation of the receptor. On binding AVP this constraint is alleviated, promoting the transition to active V1aR. Our findings explain why arginyl is conserved at this locus throughout the evolutionary lineage of the neurohypophysial peptide hormone receptor family of G-protein coupled receptors.


Assuntos
Substituição de Aminoácidos , Arginina/metabolismo , Receptores de Vasopressinas/química , Receptores de Vasopressinas/metabolismo , Arginina/genética , Sítios de Ligação , Linhagem Celular , Humanos , Cinética , Conformação Proteica , Ensaio Radioligante , Receptores de Vasopressinas/genética , Transdução de Sinais , Relação Estrutura-Atividade
11.
Mol Endocrinol ; 16(3): 600-9, 2002 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-11875119

RESUMO

A fundamental issue in molecular endocrinology is to define how agonist:receptor interaction differs from antagonist:receptor interaction. The vasopressin V1a receptor (V1aR) is a member of a subfamily of related G protein-coupled receptors that are activated by the hormone AVP or related peptides. The N-terminus of the V1aR has recently been shown to be critical for binding agonists but not antagonists. Using a combination of N-terminally truncated constructs and alanine-scanning mutagenesis, individual residues that provide these agonist-specific binding epitopes have now been identified in this study. Our data establish that a single residue, Arg46, is critical for AVP binding to the V1aR. Systematic substitution revealed that Arg was required at this locus and could not be substituted by Lys, Glu, Leu, or Ala. In contrast, antagonist binding (cyclic or linear, peptide or nonpeptide) was unaffected. Disruption of Arg46 also resulted in defective intracellular signaling. Arginine is conserved at this locus in all members of the neurohypophysial peptide hormone receptor family cloned to date, indicative of a fundamental role in receptor function. In addition to Arg46, the residues Leu42, Gly43, Asp45 form a patch contributing to AVP binding. This study provides molecular insight into the role of the V1aR N-terminus and key differences between agonist and antagonist binding requirements.


Assuntos
Arginina , Receptores de Vasopressinas/química , Vasopressinas/antagonistas & inibidores , Vasopressinas/metabolismo , Sequência de Aminoácidos , Animais , Arginina Vasopressina/metabolismo , Sítios de Ligação , Linhagem Celular , Humanos , Dados de Sequência Molecular , Mutagênese , Ensaio Radioligante , Ratos , Receptores de Vasopressinas/genética , Receptores de Vasopressinas/metabolismo , Sistemas do Segundo Mensageiro , Relação Estrutura-Atividade , Transfecção , Trítio
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA