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1.
Chemosphere ; 313: 137530, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36509187

RESUMO

BACKGROUND: Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants. The first exposure to PFAS occurs in utero, after birth it continues via breast milk, food intake, environment, and consumer products that contain these chemicals. Our aim was to identify determinants of PFAS concentrations in sensitive population subgroups- pregnant women and newborns. METHODS: Nine European birth cohorts provided exposure data on PFAS in pregnant women (INMA-Gipuzkoa, Sabadell, Valencia, ELFE and MoBa; total N = 5897) or newborns (3xG study, FLEHS 2, FLEHS 3 and PRENATAL; total N = 940). PFOS, PFOA, PFHxS and PFNA concentrations were measured in maternal or cord blood, depending on the cohort (FLEHS 2 measured only PFOS and PFOA). PFAS concentrations were analysed according to maternal characteristics (age, BMI, parity, previous breastfeeding, smoking, and food consumption during pregnancy) and parental educational level. The association between potential determinants and PFAS concentrations was evaluated using multiple linear regression models. RESULTS: We observed significant variations in PFAS concentrations among cohorts. Higher PFAS concentrations were associated with higher maternal age, primipara birth, and educational level, both for maternal blood and cord blood. Higher PFAS concentrations in maternal blood were associated with higher consumption of fish and seafood, meat, offal and eggs. In cord blood, higher PFHxS concentrations were associated with daily meat consumption and higher PFNA with offal consumption. Daily milk and dairy consumption were associated with lower concentrations of PFAS in both, pregnant women and newborns. CONCLUSION: High detection rates of the four most abundant PFAS demonstrate ubiquitous exposure of sensitive populations, which is of concern. This study identified several determinants of PFAS exposure in pregnant women and newborns, including dietary factors, and these findings can be used for proposing measures to reduce PFAS exposure, particularly from dietary sources.


Assuntos
Ácidos Alcanossulfônicos , Poluentes Ambientais , Fluorocarbonos , Animais , Gravidez , Feminino , Humanos , Populações Vulneráveis , Paridade , Dieta
2.
Crit Care Med ; 49(10): 1684-1693, 2021 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33938718

RESUMO

OBJECTIVES: Clinical trials evaluating the safety and effectiveness of sedative medication use in critically ill adults undergoing mechanical ventilation differ considerably in their methodological approach. This heterogeneity impedes the ability to compare results across studies. The Sedation Consortium on Endpoints and Procedures for Treatment, Education, and Research Recommendations convened a meeting of multidisciplinary experts to develop recommendations for key methodologic elements of sedation trials in the ICU to help guide academic and industry clinical investigators. DESIGN: A 2-day in-person meeting was held in Washington, DC, on March 28-29, 2019, followed by a three-round, online modified Delphi consensus process. PARTICIPANTS: Thirty-six participants from academia, industry, and the Food and Drug Administration with expertise in relevant content areas, including two former ICU patients attended the in-person meeting, and the majority completed an online follow-up survey and participated in the modified Delphi process. MEASUREMENTS AND MAIN RESULTS: The final recommendations were iteratively refined based on the survey results, participants' reactions to those results, summaries written by panel moderators, and a review of the meeting transcripts made from audio recordings. Fifteen recommendations were developed for study design and conduct, subject enrollment, outcomes, and measurement instruments. Consensus recommendations included obtaining input from ICU survivors and/or their families, ensuring adequate training for personnel using validated instruments for assessments of sedation, pain, and delirium in the ICU environment, and the need for methodological standardization. CONCLUSIONS: These recommendations are intended to assist researchers in the design, conduct, selection of endpoints, and reporting of clinical trials involving sedative medications and/or sedation protocols for adult ICU patients who require mechanical ventilation. These recommendations should be viewed as a starting point to improve clinical trials and help reduce methodological heterogeneity in future clinical trials.


Assuntos
Hipnóticos e Sedativos/farmacocinética , Hipnóticos e Sedativos/uso terapêutico , Congressos como Assunto , Consenso , Técnica Delphi , District of Columbia , Humanos , Hipnóticos e Sedativos/farmacologia , Respiração Artificial/instrumentação , Respiração Artificial/métodos , Fatores de Tempo
3.
Am J Health Syst Pharm ; 78(15): 1395-1401, 2021 07 22.
Artigo em Inglês | MEDLINE | ID: mdl-33872344

RESUMO

PURPOSE: Despite its availability for more than 70 years, many details concerning methadone remain contentious, such as the dosing equivalents for intravenous and enteral administration. A scoping review was performed to evaluate whether existing literature on methadone bioavailability in human subjects support the current recommendation that an equivalent enteral dose is twice the intravenous dose. METHODS: A librarian-assisted search of the PubMed and EMBASE databases identified all English-language articles with the terms methadone and bioavailability and/or conversion in the title or abstract published from inception though December 2019. A manual search of references was also performed to identify any additional articles. Studies were included in a scoping review if they were published in English and evaluated methadone bioavailability in human subjects. RESULTS: Among 65 publications initially identified, 6 studies involving a total of 50 patients were included in the review. Bioavailability data for healthy volunteers and patients with opioid use disorder, metastatic cancer, chronic pain from malignant or nonmalignant disease were available for analysis. The pooled mean (95% confidence interval) bioavailability (F) was 85.4% (75.2%-95.6%), with heterogeneity (I2) of 0. In the 4 studies that provided individual patient-level data, F was >50% in 40 of 42 patient measurements (95.2%) and ≥75% in 33 of 42 patient measurements (78.6%). CONCLUSION: Available evidence suggests the bioavailability of methadone is generally more than 75%, there is limited evidence for the currently recommended 1:2 ratio (intravenous:enteral), and a more appropriate dosing ratio may be 1:1.3. This scoping review underscores the need for further research to establish an effective and safe ratio when converting between intravenous and enteral dosing formulations of methadone.


Assuntos
Neoplasias , Transtornos Relacionados ao Uso de Opioides , Administração Intravenosa , Analgésicos Opioides/efeitos adversos , Disponibilidade Biológica , Humanos , Metadona , Neoplasias/tratamento farmacológico , Transtornos Relacionados ao Uso de Opioides/tratamento farmacológico
4.
Spine (Phila Pa 1976) ; 45(7): 483-490, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31658235

RESUMO

STUDY DESIGN: Prospective cohort study. OBJECTIVE: The aims of this study were to evaluate the outcome of surgical and nonsurgical treatment for patients with lumbar herniated disc (LHD) or lumbar spinal stenosis (LSS) after 2 years and to identify predictors for nonsuccess. SUMMARY OF BACKGROUND DATA: Studies regarding the clinician's ability to identify patients with a poor prognosis are not in concurrence and further studies are warranted. METHODS: This study included 390 patients with LHD or LSS referred for surgical evaluation after unsuccessful conservative treatment. Nonsuccess was defined as a Roland-Morris Disability score above 4 (0-23) or a Numeric Rating Scale back and leg pain score above 20 (0-60). Uni- and multivariate logistic regression analyses were used to investigate potential predictive factors including sociodemographic characteristics, history findings, levels of pain and disability, and magnetic resonance imaging findings. RESULTS: Rates of nonsuccess at 2 years were approximately 30% in surgically treated patients with LHD, approximately about 60% in patients with LSS for disability, and 30% and 40%, respectively for pain. For the main outcome variable, disability, in the final multiple logistic regression model, nonsuccess after surgery was associated with male sex (odds ratio [OR] 2.04, 95% confidence interval [CI]: 1.02-4.11, P = 0.04), low level of education (OR 2.60, 95% CI: 1.28-5.29, P = 0.01), high pain intensity (OR 3.06, 95% CI: 1.51-6.21, P < 0.01), and widespread pain (OR 3.59, 95% CI: 1.36-9.46, P = 0.01). CONCLUSION: The results indicate that the prognosis for patients referred for surgery with persistent LHD or LSS and unsuccessful conservative treatment is substantially better when surgery is performed as opposed to not performed. The predictive value of the variables male sex, low level of education, high pain intensity, and widespread pain location found in our study are partly in accordance with results of previous studies. Thus, our results warrant further investigation until firm conclusions can be made. LEVEL OF EVIDENCE: 3.


Assuntos
Dor Crônica/cirurgia , Tomada de Decisão Clínica/métodos , Degeneração do Disco Intervertebral/cirurgia , Deslocamento do Disco Intervertebral/cirurgia , Dor Lombar/cirurgia , Vértebras Lombares/cirurgia , Raízes Nervosas Espinhais/cirurgia , Adulto , Idoso , Dor Crônica/diagnóstico por imagem , Dor Crônica/epidemiologia , Estudos de Coortes , Dinamarca/epidemiologia , Feminino , Humanos , Degeneração do Disco Intervertebral/diagnóstico por imagem , Degeneração do Disco Intervertebral/epidemiologia , Deslocamento do Disco Intervertebral/diagnóstico por imagem , Deslocamento do Disco Intervertebral/epidemiologia , Dor Lombar/diagnóstico por imagem , Dor Lombar/epidemiologia , Vértebras Lombares/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Medição da Dor/métodos , Estudos Prospectivos , Raízes Nervosas Espinhais/diagnóstico por imagem
5.
Acta Physiol (Oxf) ; 214(1): 63-74, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25704169

RESUMO

AIMS: To investigate the regulation of cannabinoid receptors CB1 and CB2 on immune cells by pro-inflammatory cytokines and its potential relevance to the inflammatory neurological disease, multiple sclerosis (MS). CB1 and CB2 signalling may be anti-inflammatory and neuroprotective in neuroinflammatory diseases. Cannabinoids can suppress inflammatory cytokines but the effects of these cytokines on CB1 and CB2 expression and function are unknown. METHODS: Immune cells from peripheral blood were obtained from healthy volunteers and patients with MS. Expression of CB1 and CB2 mRNA in whole blood cells, peripheral blood mononuclear cells (PBMC) and T cells was determined by quantitative real-time polymerase chain reaction (qRT-PCR). Expression of CB1 and CB2 protein was determined by flow cytometry. CB1 and CB2 signalling in PBMC was determined by Western blotting for Erk1/2. RESULTS: Pro-inflammatory cytokines IL-1ß, IL-6 and TNF-α (the latter likely NF-κB dependently) can upregulate CB1 and CB2 on human whole blood and peripheral blood mononuclear cells (PBMC). We also demonstrate upregulation of CB1 and CB2 and increased IL-1ß, IL-6 and TNF-α mRNA in blood of patients with MS compared with controls. CONCLUSION: The levels of CB1 and CB2 can be upregulated by inflammatory cytokines, which can explain their increase in inflammatory conditions including MS.


Assuntos
Interleucina-1beta/farmacologia , Interleucina-6/farmacologia , Esclerose Múltipla/metabolismo , Receptor CB1 de Canabinoide/metabolismo , Receptor CB2 de Canabinoide/metabolismo , Linfócitos T/metabolismo , Fator de Necrose Tumoral alfa/farmacologia , Adulto , Feminino , Humanos , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/metabolismo , Masculino , Pessoa de Meia-Idade , Esclerose Múltipla/imunologia , Receptor CB1 de Canabinoide/genética , Receptor CB2 de Canabinoide/genética , Linfócitos T/efeitos dos fármacos , Adulto Jovem
6.
J Crit Care ; 29(5): 753-7, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24996761

RESUMO

PURPOSE: Nonbenzodiazepine sedation (eg, dexmedetomidine or propofol) may be more cost effective than benzodiazepine (BZ) sedation despite its higher acquisition cost. MATERIALS AND METHODS: A cost effectiveness (CE) analysis of noncardiac surgery, critically ill adults requiring at least 1 day of mechanical ventilation (MV) and administered either BZ or non-BZ sedation, that cycled health states and costs daily using a Markov model accounting for daily MV use until intensive care unit (ICU) discharge, was conducted from a third-party perspective. Transition probabilities were obtained from a published meta-analysis, and costs were estimated from best evidence. Sensitivity analyses were run for all extubation and discharge probabilities, for different cost estimates and for the specific non-BZ administered. RESULTS: When non-BZ rather than BZ sedation was used, the incremental cost-effectiveness ratio to avert 1 ICU day while MV or while either MV or non-MV was $3406 and $3136, respectively. The base-case analysis revealed that non-BZ sedation (vs BZ sedation) resulted in higher drug costs ($1327 vs $65) but lower total ICU costs (percent accounted for MV need): $35380 (71.0%) vs $45394 (70.6%). Sensitivity analysis revealed that BZ sedation would only be less costly if the daily rate of extubation was at least 16%, and the daily rate of ICU discharge without MV was at least 77%. The incremental CE ratio to avert 1 ICU day while MV or non-MV was similar between the dexmedetomidine and propofol non-BZ options. CONCLUSIONS: Among MV adults, non-BZ sedation has a more favorable CE ratio than BZ sedation over most cost estimates.


Assuntos
Benzodiazepinas/economia , Dexmedetomidina/economia , Custos de Medicamentos , Hipnóticos e Sedativos/economia , Propofol/economia , Respiração Artificial/economia , Adulto , Benzodiazepinas/administração & dosagem , Protocolos Clínicos , Análise Custo-Benefício , Estado Terminal , Dexmedetomidina/administração & dosagem , Humanos , Hipnóticos e Sedativos/administração & dosagem , Unidades de Terapia Intensiva/economia , Cadeias de Markov , Propofol/administração & dosagem , Respiração Artificial/métodos , Sensibilidade e Especificidade
7.
Cell Death Dis ; 5: e988, 2014 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-24407241

RESUMO

GATA1 mutations are tightly associated with transient myeloproliferative disorder (TMD) and acute megakaryoblstic leukemia (AMKL) in children with Down syndrome. Numerous genes are altered in GATA-1-deficient megakaryocytes, which may contribute to the hyperproliferation and abnormal terminal differentiation of these malignant cells. In this study, we demonstrate that Pstpip2 is a GATA-1-repressed gene that controls megakaryopoiesis. Ectopic expression of PSTPIP2 impaired megakaryocytic differentiation as evidenced by a decrease of CD41 expression and reduced DNA content in K562 cells. PSTPIP2 overexpression also caused enhanced activation of Src family kinases and subsequently reduced ERK phosphorylation. Consistently, PSTPIP2 knockdown showed the opposite effect on differentiation and signaling. Moreover, the W232A mutant of PSTPIP2, defective in its interaction with PEST family phosphatases that recruit c-Src terminal kinase (CSK) to suppress Src family kinases, failed to inhibit differentiation and lost its ability to enhance Src family kinases or reduce ERK phosphorylation. In fact, the W232A mutant of PSTPIP2 promoted megakaryocyte differentiation. These observations suggest that PSTPIP2 recruiting PEST phosphatases somehow blocked CSK activity and led to enhanced activation of Src family kinases and reduced ERK phosphorylation, which ultimately repressed megakaryocyte differentiation. Supporting this idea, PSTPIP2 interacted with LYN and the expression of a dominant negative LYN (LYN DN) overwhelmed the inhibitory effect of PSTPIP2 on differentiation and ERK signaling. In addition, a constitutively active LYN (LYN CA) normalized the enhanced megakaryocyte differentiation and repressed ERK signaling in PSTPIP2 knockdown cells. Finally, we found that PSTPIP2 repressed ERK signaling, differentiation, and proliferation and verified that PSTPIP2 upregulation repressed megakaryocyte development in primary mouse bone marrow cells. Our study thus reveals a novel mechanism by which dysregulation of PSTPIP2 due to GATA-1 deficiency may contribute to abnormal megakaryocyte proliferation and differentiation in pathogenesis of related diseases.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Diferenciação Celular , Proteínas do Citoesqueleto/genética , Regulação para Baixo , Fator de Transcrição GATA1/deficiência , Fator de Transcrição GATA1/metabolismo , Megacariócitos/citologia , Quinases da Família src/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Células Cultivadas , Proteínas do Citoesqueleto/metabolismo , Fator de Transcrição GATA1/genética , Regulação da Expressão Gênica , Humanos , Células K562 , Megacariócitos/enzimologia , Megacariócitos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Fosforilação , Transdução de Sinais , Quinases da Família src/genética
9.
Leukemia ; 27(9): 1882-90, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23748344

RESUMO

The majority of patients with BCR-ABL1-negative myeloproliferative neoplasms (MPN) harbor mutations in JAK2 or MPL, which lead to constitutive activation of the JAK/STAT, PI3K and ERK signaling pathways. JAK inhibitors by themselves are inadequate in producing selective clonal suppression in MPN and are associated with hematopoietic toxicities. MK-2206 is a potent allosteric AKT inhibitor that was well tolerated, including no evidence of myelosuppression, in a phase I study of solid tumors. Herein, we show that inhibition of PI3K/AKT signaling by MK-2206 affected the growth of both JAK2V617F- or MPLW515L-expressing cells via reduced phosphorylation of AKT and inhibition of its downstream signaling molecules. Moreover, we demonstrate that MK-2206 synergizes with ruxolitinib in suppressing the growth of JAK2V617F-mutant SET2 cells. Importantly, MK-2206 suppressed colony formation from hematopoietic progenitor cells in patients with primary myelofibrosis and alleviated hepatosplenomegaly and reduced megakaryocyte burden in the bone marrows, livers and spleens of mice with MPLW515L-induced MPN. Together, these findings establish AKT as a rational therapeutic target in the MPNs.


Assuntos
Transtornos Mieloproliferativos/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-akt/antagonistas & inibidores , Animais , Apoptose/efeitos dos fármacos , Medula Óssea/metabolismo , Medula Óssea/patologia , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Modelos Animais de Doenças , Feminino , Proteínas de Fusão bcr-abl/deficiência , Compostos Heterocíclicos com 3 Anéis/farmacologia , Compostos Heterocíclicos com 3 Anéis/uso terapêutico , Humanos , Janus Quinase 2/antagonistas & inibidores , Janus Quinase 2/genética , Fígado/metabolismo , Fígado/patologia , Megacariócitos/efeitos dos fármacos , Megacariócitos/metabolismo , Camundongos , Mutação , Transtornos Mieloproliferativos/tratamento farmacológico , Transtornos Mieloproliferativos/genética , Transtornos Mieloproliferativos/patologia , Células-Tronco Neoplásicas/efeitos dos fármacos , Células-Tronco Neoplásicas/metabolismo , Inibidores de Fosfoinositídeo-3 Quinase , Fosforilação/efeitos dos fármacos , Inibidores de Proteínas Quinases/uso terapêutico , Transdução de Sinais/efeitos dos fármacos , Baço/efeitos dos fármacos , Baço/metabolismo
11.
Bull Cancer ; 96(9): 839-49, 2009 Sep.
Artigo em Francês | MEDLINE | ID: mdl-19696008

RESUMO

Despite the publication of guidelines for handling antineoplastic agents, measurable amounts of these drugs are still found at various hospital sites. In this context, the French cancer network ONCORA supported the present study to assess the impact of environmental contamination controls on the quality of practices during the preparation of cytotoxic drugs. The first part of the study was conducted at five voluntary hospitals. A total of 65 wipe samples of objects and surfaces were taken in the drug preparation rooms and analyzed for the presence of 5-fluorouracil (5-FU). Measurable amounts of 5-FU were detected in 21 samples (32%). Many surfaces within Biological Safety Cabinets and isolators were found contaminated (36%). The worse results were obtained on gloves and on the outside of infusion bags. The same method was applied during the second part of the study, conducted six months after the end of the first audit. Global contamination was reduced to 17%. This study shows that appropriate handling helps decrease the number of samples contaminated, making it possible to recommend these controls for evaluating and improving the quality of practices. Since 2007, the network's laboratory has extended its activities to all French hospitals interested in this quality assurance programme.


Assuntos
Antimetabólitos Antineoplásicos/análise , Poluentes Ambientais/análise , Fluoruracila/análise , Exposição Ocupacional/análise , Antimetabólitos Antineoplásicos/química , Composição de Medicamentos/normas , Poluentes Ambientais/química , França , Luvas Protetoras , Hospitais/normas , Exposição Ocupacional/prevenção & controle
12.
Thorax ; 58(3): 211-6, 2003 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-12612295

RESUMO

BACKGROUND: Inhaled corticosteroids (ICS) affect many inflammatory pathways in asthma but have little impact on cysteinyl leukotrienes. This may partly explain persistent airway inflammation during chronic ICS treatment and failure to achieve adequate asthma control in some patients. This double blind, randomised, parallel group, non-inferiority, multicentre 16 week study compared the clinical benefits of adding montelukast to budesonide with doubling the budesonide dose in adults with asthma. METHODS: After a 1 month single blind run in period, patients inadequately controlled on inhaled budesonide (800 microg/day) were randomised to receive montelukast 10 mg + inhaled budesonide 800 microg/day (n=448) or budesonide 1600 microg/day (n=441) for 12 weeks. RESULTS: Both groups showed progressive improvement in several measures of asthma control compared with baseline. Mean morning peak expiratory flow (AM PEF) improved similarly in the last 10 weeks of treatment compared with baseline in both the montelukast + budesonide group and in the double dose budesonide group (33.5 v 30.1 l/min). During days 1-3 after start of treatment, the change in AM PEF from baseline was significantly greater in the montelukast + budesonide group than in the double dose budesonide group (20.1 v 9.6 l/min, p<0.001), indicating faster onset of action in the montelukast group. Both groups showed similar improvements with respect to "as needed" beta agonist use, mean daytime symptom score, nocturnal awakenings, exacerbations, asthma free days, peripheral eosinophil counts, and asthma specific quality of life. Both montelukast + budesonide and double dose budesonide were generally well tolerated. CONCLUSION: The addition of montelukast to inhaled budesonide is an effective and well tolerated alternative to doubling the dose of inhaled budesonide in adult asthma patients experiencing symptoms and inadequate control on budesonide alone.


Assuntos
Acetatos/administração & dosagem , Antiasmáticos/administração & dosagem , Asma/tratamento farmacológico , Broncodilatadores/administração & dosagem , Budesonida/administração & dosagem , Quinolinas/administração & dosagem , Administração por Inalação , Adolescente , Adulto , Idoso , Ciclopropanos , Método Duplo-Cego , Quimioterapia Combinada , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Método Simples-Cego , Sulfetos , Resultado do Tratamento
13.
Diagn Cytopathol ; 6(5): 313-6, 1990.
Artigo em Inglês | MEDLINE | ID: mdl-2292217

RESUMO

The authors studied 112 patients who received definitive radiotherapy/chemotherapy solely on the basis of positive cytologic findings in the appropriate clinical context. Eighty patients (71.4%) were treated on the basis of one or more positive sputum studies, while the remainder had at least one positive bronchial cytologic preparation. Eighty-six patients (76.3%) received radiotherapy alone; 19 received both radiotherapy and chemotherapy; only 7 were exclusively given chemotherapy. The utilization of stringent verification criteria revealed that none of our patients was falsely positive for malignancy. For those patients categorized as having malignant disease by verification criteria I-IV, there were no significant disparities between histologic and cytologic diagnoses. This study demonstrated, in a systematic fashion, that patients can be reliably and definitively treated for lung cancer on the basis of positive respiratory cytology findings without tissue corroboration.


Assuntos
Brônquios/patologia , Citodiagnóstico , Neoplasias Pulmonares/diagnóstico , Escarro/citologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Broncoscopia , Feminino , Humanos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/radioterapia , Masculino , Pessoa de Meia-Idade
14.
Biophys Chem ; 15(3): 177-90, 1982 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-6286003

RESUMO

The interaction of the radicals OH, t-BuO, Eaq, CO2 and O2 with the copper oxidase, laccase, from Polyporus, has been studied by the pulse-radiolysis technique. Each of these radicals formed transient adducts with a broad absorption maximum around 310 nm. Analysis of the optical properties and of the very fast rates of formation of these compounds shows that each radical interacts with a limited number of sites on the polypeptide part of the protein amongst R-S-S-R, histidine and aromatic residues. Interaction with the carbonyl group of some of the peptides bonds is also possible. The few target sites are probably hit simultaneously and electron transfer between these sites may also occur. In all cases, ina subsequent step, intramolecular electron transfer from the polypeptide radical adducts leads to a partial reduction of the blue type-1 Cu2+ with rates varying between 10(3) adn 10(4) s-1. Further reduction of the type-1 CU2+ occurs through a slow intermolecular reaction between two laccase radical transient adducts. In the case of CO2 and O2, this slow reduction could alternatively be due to an intermolecular reaction between laccase and CO2 or O2. The oxidation radicals OH, Br2 and (SCN)2, which formed radical adducts with fully ascorbate-reduced laccase, did not induce any type-1 copper reoxidation.


Assuntos
Oxirredutases , Butanóis , Dióxido de Carbono , Cobre , Transporte de Elétrons , Radicais Livres , Fungos/enzimologia , Hidróxidos , Lacase , Oxirredução , Superóxidos
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