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The amount of ultraviolet irradiation and ablation experienced by a planet depends strongly on the temperature of its host star. Of the thousands of extrasolar planets now known, only six have been found that transit hot, A-type stars (with temperatures of 7,300-10,000 kelvin), and no planets are known to transit the even hotter B-type stars. For example, WASP-33 is an A-type star with a temperature of about 7,430 kelvin, which hosts the hottest known transiting planet, WASP-33b (ref. 1); the planet is itself as hot as a red dwarf star of type M (ref. 2). WASP-33b displays a large heat differential between its dayside and nightside, and is highly inflated-traits that have been linked to high insolation. However, even at the temperature of its dayside, its atmosphere probably resembles the molecule-dominated atmospheres of other planets and, given the level of ultraviolet irradiation it experiences, its atmosphere is unlikely to be substantially ablated over the lifetime of its star. Here we report observations of the bright star HD 195689 (also known as KELT-9), which reveal a close-in (orbital period of about 1.48 days) transiting giant planet, KELT-9b. At approximately 10,170 kelvin, the host star is at the dividing line between stars of type A and B, and we measure the dayside temperature of KELT-9b to be about 4,600 kelvin. This is as hot as stars of stellar type K4 (ref. 5). The molecules in K stars are entirely dissociated, and so the primary sources of opacity in the dayside atmosphere of KELT-9b are probably atomic metals. Furthermore, KELT-9b receives 700 times more extreme-ultraviolet radiation (that is, with wavelengths shorter than 91.2 nanometres) than WASP-33b, leading to a predicted range of mass-loss rates that could leave the planet largely stripped of its envelope during the main-sequence lifetime of the host star.
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OPINION STATEMENT: The mainstay of treatment for men with three or fewer non-castrate metastatic lesions outside of the prostate remains morbid palliative androgen deprivation therapy. We believe there is now a significant body of retrospective literature to suggest a survival benefit if these men have radical treatment to their primary tumour alongside 'metastasis-directed therapy' to the metastatic deposits. However, this regimen should be reserved to high-volume centres with quality assurance programmes and excellent outcomes. Patients should be made clear as to the uncertainty of benefit for this multi-site treatment strategy, and we await the publication of randomised controlled trials reporting in the next 5 years.
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Neoplasias da Próstata/patologia , Neoplasias da Próstata/terapia , Terapia Combinada , Gerenciamento Clínico , Humanos , Masculino , Metástase Neoplásica , Resultado do TratamentoRESUMO
Unplanned general surgery represents a major workload and requires comprehensive evaluation with appropriate outcomes. This study aimed to summarize current reporting of patient-reported outcomes (PROs) in randomized clinical trials (RCTs) in unplanned general surgery. A systematic review identified RCTs reporting PROs in the commonest six areas of unplanned general surgery. Details of the PRO measures were examined using the CONSORT extension for PRO reporting in RCTs. Extracted information about each PRO domain included the reporting of baseline PROs, rationale for PRO selection and whether PRO findings were used in conjunction with clinical outcomes to inform treatment recommendations. The internal validity of included studies was assessed using the Cochrane risk of bias tool. 12,519 abstracts were screened and 20 RCTs containing data from 2037 patients included. Included studies used 14 separate PRO measures covering 35 different health domains. A visual analogue assessment of pain was most frequently reported (n = 13). Reporting of baseline PRO data was uncommon (11/35 PRO domains). The rationale for PRO data collection and a PRO-specific hypothesis were provided for 9 (25.7 %) and 5 (14.3 %) domains, respectively. Seventeen RCTs (85.0 %) used the PRO data alongside clinical outcomes to inform treatment recommendations. Of the 116 risk of bias assessments, 77 (66.0 %) were judged as high or unclear. There is a lack of well designed, and conducted RCTs in unplanned general surgery that include PROs. Future work to define relevant PROs and methods for optimal assessment are needed to inform health care decision-making.
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Cirurgia Geral/normas , Avaliação de Resultados da Assistência ao Paciente , Ensaios Clínicos Controlados Aleatórios como Assunto/métodos , Viés , Interpretação Estatística de Dados , Emergências , Humanos , Masculino , Projetos de PesquisaRESUMO
Treatment possibilities for clinically localised prostate cancer include radical prostatectomy (RP), external beam radiotherapy, brachytherapy, focal therapy and active surveillance. Conflicting and methodologically flawed observational data from the last two decades have led to uncertainty as to the best oncological option. However, recently, there has been a series of high-quality studies that point to disease specific and overall survival advantages for those men undergoing RP. This article reviews the latest evidence and argues that at the current time, RP must be considered the gold standard treatment for the majority of men with clinically localised prostate cancer.
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Tomada de Decisões , Estadiamento de Neoplasias , Prostatectomia , Neoplasias da Próstata/diagnóstico , Humanos , Masculino , Neoplasias da Próstata/cirurgiaRESUMO
During urinary tract infections (UTIs), uropathogenic Escherichia coli must maintain a delicate balance between sessility and motility to achieve successful infection of both the bladder and kidneys. Previous studies showed that cyclic dimeric GMP (c-di-GMP) levels aid in the control of the transition between motile and nonmotile states in E. coli. The yfiRNB locus in E. coli CFT073 contains genes for YfiN, a diguanylate cyclase, and its activity regulators, YfiR and YfiB. Deletion of yfiR yielded a mutant that was attenuated in both the bladder and the kidneys when tested in competition with the wild-type strain in the murine model of UTI. A double yfiRN mutant was not attenuated in the mouse model, suggesting that unregulated YfiN activity and likely increased cytoplasmic c-di-GMP levels cause a survival defect. Curli fimbriae and cellulose production were increased in the yfiR mutant. Expression of yhjH, a gene encoding a proven phosphodiesterase, in CFT073 ΔyfiR suppressed the overproduction of curli fimbriae and cellulose and further verified that deletion of yfiR results in c-di-GMP accumulation. Additional deletion of csgD and bcsA, genes necessary for curli fimbriae and cellulose production, respectively, returned colonization levels of the yfiR deletion mutant to wild-type levels. Peroxide sensitivity assays and iron acquisition assays displayed no significant differences between the yfiR mutant and the wild-type strain. These results indicate that dysregulation of c-di-GMP production results in pleiotropic effects that disable E. coli in the urinary tract and implicate the c-di-GMP regulatory system as an important factor in the persistence of uropathogenic E. coli in vivo.
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GMP Cíclico/análogos & derivados , Infecções por Escherichia coli/microbiologia , Proteínas de Escherichia coli/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Fósforo-Oxigênio Liases/genética , Infecções Urinárias/microbiologia , Sistema Urinário/microbiologia , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Celulose/genética , Celulose/metabolismo , GMP Cíclico/genética , GMP Cíclico/metabolismo , Citoplasma/metabolismo , Citoplasma/microbiologia , Escherichia coli/enzimologia , Infecções por Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , Feminino , Fímbrias Bacterianas/genética , Fímbrias Bacterianas/metabolismo , Deleção de Genes , Peróxido de Hidrogênio/metabolismo , Ferro/metabolismo , Camundongos , Fósforo-Oxigênio Liases/metabolismo , Sistema Urinário/metabolismo , Infecções Urinárias/metabolismo , Urina/microbiologia , Escherichia coli Uropatogênica/genética , Escherichia coli Uropatogênica/metabolismoRESUMO
Cystathionine ß-synthase (CBS) is an essential pyridoxal 5'-phosphate (PLP)-dependent enzyme of the transsulfuration pathway that condenses serine with homocysteine to form cystathionine; intriguingly, human CBS also contains a heme b cofactor of unknown function. Herein we describe the enzymatic and spectroscopic properties of a disease-associated R266K hCBS variant, which has an altered hydrogen-bonding environment. The R266K hCBS contains a low-spin, six-coordinate Fe(III) heme bearing a His/Cys ligation motif, like that of WT hCBS; however, there is a geometric distortion that exists at the R266K heme. Using rR spectroscopy, we show that the Fe(III)-Cys(thiolate) bond is longer and weaker in R266K, as evidenced by an 8 cm(-1) downshift in the ν(Fe-S) resonance. Presence of this longer and weaker Fe(III)-Cys(thiolate) bond is correlated with alteration of the fluorescence spectrum of the active PLP ketoenamine tautomer. Activity data demonstrate that, relative to WT, the R266K variant is more impaired in the alternative cysteine-synthesis reaction than in the canonical cystathionine-synthesis reaction. This diminished cysteine synthesis activity and a greater sensitivity to exogenous PLP correlate with the change in PLP environment. Fe-S(Cys) bond weakening causes a nearly 300-fold increase in the rate of ligand switching upon reduction of the R266K heme. Combined, these data demonstrate cross talk between the heme and PLP active sites, consistent with previous proposals, revealing that alteration of the Arg(266)-Cys(52) interaction affects PLP-dependent activity and dramatically destabilizes the ferrous thiolate-ligated heme complex, underscoring the importance of this hydrogen-bonding residue pair.
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Cistationina beta-Sintase/química , Heme/genética , Fosfato de Piridoxal/química , Domínio Catalítico , Dicroísmo Circular , Cistationina beta-Sintase/genética , Espectroscopia de Ressonância de Spin Eletrônica , Estabilidade Enzimática , Compostos Ferrosos/química , Homocistinúria/genética , Humanos , Modelos Moleculares , Mutação , Oxirredução , Ligação Proteica , Espectrometria de Fluorescência , Análise Espectral Raman , TemperaturaRESUMO
Insertional mutations leading to expansion of the octarepeat domain of the prion protein (PrP) are directly linked to prion disease. While normal PrP has four PHGGGWGQ octapeptide segments in its flexible N-terminal domain, expanded forms may have up to nine additional octapeptide inserts. The type of prion disease segregates with the degree of expansion. With up to four extra octarepeats, the average onset age is above 60 years, whereas five to nine extra octarepeats results in an average onset age between 30 and 40 years, a difference of almost three decades. In wild-type PrP, the octarepeat domain takes up copper (Cu(2+)) and is considered essential for in vivo function. Work from our lab demonstrates that the copper coordination mode depends on the precise ratio of Cu(2+) to protein. At low Cu(2+) levels, coordination involves histidine side chains from adjacent octarepeats, whereas at high levels each repeat takes up a single copper ion through interactions with the histidine side chain and neighboring backbone amides. Here we use both octarepeat constructs and recombinant PrP to examine how copper coordination modes are influenced by octarepeat expansion. We find that there is little change in affinity or coordination mode populations for octarepeat domains with up to seven segments (three inserts). However, domains with eight or nine total repeats (four or five inserts) become energetically arrested in the multi-histidine coordination mode, as dictated by higher copper uptake capacity and also by increased binding affinity. We next pooled all published cases of human prion disease resulting from octarepeat expansion and find remarkable agreement between the sudden length-dependent change in copper coordination and onset age. Together, these findings suggest that either loss of PrP copper-dependent function or loss of copper-mediated protection against PrP polymerization makes a significant contribution to early onset prion disease.
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Cobre/metabolismo , Doenças Priônicas/etiologia , Príons/química , Sequências Repetitivas de Aminoácidos/fisiologia , Adulto , Idade de Início , Animais , Cobre/química , Cricetinae , Histidina/química , Humanos , Mesocricetus , Camundongos , Pessoa de Meia-Idade , Modelos Moleculares , Proteínas PrPSc/metabolismo , Príons/metabolismoRESUMO
Pharmacokinetic and efficacy studies with levofloxacin were performed in the common marmoset (Callithrix jacchus) model of inhalational tularemia. Plasma levofloxacin pharmacokinetics were determined in six animals in separate single-dose and multidose studies. Plasma drug concentrations were analyzed using liquid chromatography-tandem mass spectrometry-electrospray ionization. On day 7 of a twice-daily dosing regimen of 40 mg/kg, the levofloxacin half-life, maximum concentration, and area under the curve in marmoset plasma were 2.3 h, 20.9 microg/ml, and 81.4 microg/liter/h, respectively. An efficacy study was undertaken using eight treated and two untreated control animals. Marmosets were challenged with a mean of 1.5 x 10(2) CFU of Francisella tularensis by the airborne route. Treated animals were administered 16.5 mg/kg levofloxacin by mouth twice daily, based on the pharmacokinetic parameters, beginning 24 h after challenge. Control animals had a raised core body temperature by 57 h postchallenge and died from infection by day 5. All of the other animals survived, remained afebrile, and lacked overt clinical signs. No bacteria were recovered from the organs of these animals at postmortem after culling at day 24 postchallenge. In conclusion, postexposure prophylaxis with orally administered levofloxacin was efficacious against acute inhalational tularemia in the common marmoset. The marmoset appears to be an appropriate animal model for the evaluation of postexposure therapies.
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Antibacterianos/farmacocinética , Antibacterianos/uso terapêutico , Francisella tularensis/efeitos dos fármacos , Francisella tularensis/patogenicidade , Levofloxacino , Ofloxacino/farmacocinética , Ofloxacino/uso terapêutico , Animais , Antibacterianos/administração & dosagem , Callithrix , Cromatografia Líquida , Esquema de Medicação , Feminino , Masculino , Ofloxacino/administração & dosagem , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas em Tandem , Resultado do Tratamento , Tularemia/tratamento farmacológico , Tularemia/microbiologiaRESUMO
Susceptibility and lethality studies of inhalational tularaemia were undertaken using the common marmoset (Callithrix jacchus) to determine its suitability as a non-human primate model. Pairs of marmosets were exposed to varying challenge doses of Francisella tularensis by the airborne route and monitored for up to 14 days postchallenge (p.c.). Lethal infection was achieved following a retained dose of less than 10 bacterial colony-forming units (CFU). However, precise LD(50) determination was not possible. The model was characterized using a target challenge dose of approximately 100 CFU. Increased core body temperature was the first indicator of disease, at approximately 2.5 days p.c. Overt clinical signs were first observed 12-18 h after the temperature increase. Significantly decreased activity was observed after approximately 3 days. All animals succumbed to infection between 4.5 and 7 days p.c. At postmortem examination, gross pathology was evident in the liver, spleen and lungs of all animals and high bacterial numbers were detected in all the organs assessed. Bacteraemia was demonstrated in all animals postmortem. Histopathological observations included severe suppurative bronchopneumonia, severe multifocal pyogranulomatous hepatitis, splenitis and lymphadenitis. Tularaemia disease progression in the common marmoset therefore appears to be consistent with the disease seen in humans and other animal models. The common marmoset may therefore be considered a suitable model for further studies of inhalational tularaemia.
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Francisella tularensis/patogenicidade , Tularemia/patologia , Animais , Callithrix , Contagem de Colônia Microbiana , Modelos Animais de Doenças , Progressão da Doença , Suscetibilidade a Doenças , Feminino , Francisella tularensis/crescimento & desenvolvimento , Francisella tularensis/isolamento & purificação , Exposição por Inalação , Rim/microbiologia , Rim/patologia , Dose Letal Mediana , Fígado/microbiologia , Fígado/patologia , Pulmão/microbiologia , Pulmão/patologia , Masculino , Pneumonia Bacteriana/microbiologia , Pneumonia Bacteriana/patologia , Baço/microbiologia , Baço/patologia , Tularemia/microbiologia , VirulênciaRESUMO
Inhalational anthrax is a rare but potentially fatal infection in man. The common marmoset (Callithrix jacchus) was evaluated as a small non-human primate (NHP) model of inhalational anthrax infection, as an alternative to larger NHP species. The marmoset was found to be susceptible to inhalational exposure to Bacillus anthracis Ames strain. The pathophysiology of infection following inhalational exposure was similar to that previously reported in the rhesus and cynomolgus macaque and humans. The calculated LD(50) for B. anthracis Ames strain in the marmoset was 1.47 x 10(3) colony-forming units, compared with a published LD(50) of 5.5 x 10(4) spores in the rhesus macaque and 4.13 x 10(3) spores in the cynomolgus macaque. This suggests that the common marmoset is an appropriate alternative NHP and will be used for the evaluation of medical countermeasures against respiratory anthrax infection.
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Antraz/patologia , Bacillus anthracis/patogenicidade , Modelos Animais de Doenças , Infecções Respiratórias/patologia , Aerossóis , Animais , Antraz/microbiologia , Bacillus anthracis/isolamento & purificação , Peso Corporal , Callithrix , Contagem de Colônia Microbiana , Feminino , Exposição por Inalação , Dose Letal Mediana , Masculino , Infecções Respiratórias/microbiologia , VirulênciaRESUMO
The transcriptional activator CooA belongs to the CRP/FNR (cAMP receptor protein/fumarate and nitrate reductase) superfamily of transcriptional regulators and uses heme to sense carbon monoxide (CO). Effector-driven allosteric activation is well understood in CRP, a CooA homologue. A structural allosteric activation model for CooA exists which parallels that of CRP; however, the role of protein dynamics, which is crucial in CRP, is not well understood in CooA. We employed site-directed spin labeling electron paramagnetic resonance spectroscopy to probe CooA motions on the µs-ms timescale. We created a series of Cys substitution variants, each with a cysteine residue introduced into a key functional region of the protein: K26C, E60C, F132C, D134C, and S175C. The heme environment and DNA binding affinity of each variant were comparable to those of wild-type CooA, with the exception of F132C, which displayed reduced DNA binding affinity. This observation confirms a previously hypothesized role for Phe132 in transmitting the allosteric CO binding signal. Osmolyte perturbation studies of Fe(III) "locked-off" CooA variants labeled with either MTSL or MAL-6 nitroxide spin labels revealed that multicomponent EPR spectra report on conformational flexibility on the µs-ms timescale. Multiple dynamic populations exist at every site examined in the structurally uncharacterized Fe(III) "locked-off" CooA. This observation suggests that, in direct contrast to effector-free CRP, Fe(III) "locked-off" CooA undergoes conformational exchange on the µs-ms timescale. Importantly, we establish MAL-6 as a spin label with a redox-stable linkage that may be utilized to compare conformational dynamics between functional states of CooA.
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Proteínas de Bactérias/química , Monóxido de Carbono/química , Compostos Férricos/química , Hemeproteínas/química , Transativadores/química , DNA/química , Espectroscopia de Ressonância de Spin Eletrônica , Modelos MolecularesRESUMO
We present near infrared high-precision photometry for eight transiting hot Jupiters observed during their predicted secondary eclipses. Our observations were carried out using the staring mode of the WIRCam instrument on the Canada-France-Hawaii Telescope (CFHT). We present the observing strategies and data reduction methods which delivered time series photometry with statistical photometric precision as low as 0.11%. We performed a Bayesian analysis to model the eclipse parameters and systematics simultaneously. The measured planet-to-star flux ratios allowed us to constrain the thermal emission from the day side of these hot Jupiters, as we derived the planet brightness temperatures. Our results combined with previously observed eclipses reveal an excess in the brightness temperatures relative to the blackbody prediction for the equilibrium temperatures of the planets for a wide range of heat redistribution factors. We find a trend that this excess appears to be larger for planets with lower equilibrium temperatures. This may imply some additional sources of radiation, such as reflected light from the host star and/or thermal emission from residual internal heat from the formation of the planet.
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Surface enhanced Raman scattering (SERS) has been conducted on tryptophan (W), proline (P) and tyrosine (Y) containing peptides that include W-P-Y, Y-P-W, W-P-P-P-Y, Y-P-P-P-W, W-P-P-P-P-P-Y, and Y-P-P-P-P-P-W to gain insight into molecular binding behavior on a metal substrate to eventually apply in protein SERS detection. The peptides are shown to bind through the molecule's carboxylic end, but the strong affinity of the tryptophan residue to the substrate surface, in conjunction with its large polarizability, dominates each molecule's SERS signal with the strong presence of its ring modes in all samples. These results are important for understanding SERS of protein molecules.
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BACKGROUND: Randomised controlled trials (RCTs) in surgery can be challenging to conduct, and trials in the emergency surgical setting when patients have unplanned hospital admissions are particularly difficult. One area of challenge is capturing baseline patient-reported outcome (PRO) data. This study examined the feasibility and optimal methods for the collection of baseline and follow-up PRO data in the setting of unplanned surgical hospital admissions. METHODS: Clinically stable adult patients with unplanned admissions through the day and night under the care of general surgeons at two acute NHS trusts were approached during working week days and asked to complete validated PRO measures (European Quality of Life-5 Dimension, Short Form-12, and Gastrointestinal Quality of Life Index) on admission and 6 weeks following discharge. Feasibility of PRO data collection was determined by the proportions of admitted patients eligible and recruited and by questionnaire-response rates at baseline and follow up. Reasons for non-recruitment and non-completion of questionnaires were sought and recorded. RESULTS: There were 276 admissions, of whom 235 (85.1 %) were eligible. Reasons for ineligibility were the following: age under 18 years old (n = 5, 1.8 %), non-surgical presenting complaint (n = 6, 2.2 %) and clinical instability (n = 30, 10.9 %). One hundred and sixty-six patients (70.6 %) were recruited (98 female, 59.0 %); median age 53, range 19-100). Common reasons for non-recruitment included patients being discharged home before approached by researchers (n = 29, 12.3 %) or declining participation because they felt unwell (n = 15, 6.4 %). The most common reason for admission to the hospital was abdominal pain (n = 120, 72.3 % recruited patients), of whom 50 (30.1 %) required operative intervention. Baseline PRO data was obtained from 153 patients (93.3 %), and 74 (48.4 %) returned follow-up questionnaires. CONCLUSIONS: Collection of baseline PRO data amongst unplanned admissions in general surgery is feasible. Methods for optimising retention and follow up are needed.
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BACKGROUND: The purpose of this study are to review available smartphone applications ('apps') relating to weight loss surgery, and assess the level of medical professional involvement in their design METHODS: Smartphone apps relating to weight loss surgery were identified by searching the three app stores: Apple's App Store, Google Play (Android) and Blackberry AppWorld. A data search was undertaken using keywords and phrases relating to weight loss surgery. Apps designed for the non-surgical treatment of obesity were excluded. RESULTS: A total of 38 apps were identified (Google Play = 17, Apple App Store = 21, Blackberry World = 0). Ten of 38 apps were duplicated therefore 28 apps were reviewed. Mean app rating was 3.6/5 and mean app cost was £1.89. Twenty-six of 28 (92.9%) apps were designed for use by patients. Apps were categorised into the following categories: patient information (ten), patient support forums (six), patient record tools (six), weight loss clinic advertisements (four), a journal app (one) and a conference tool (one). Health professional involvement was evident in 12 of 28 (42.9%) apps. CONCLUSIONS: This study has identified that the majority of available apps relating to weight loss surgery do not have health professional input. The establishment of a 'quality stamp' provided by an established bariatric surgical body could improve the confidence with which patients and clinicians use these new information sources. Weight loss surgery apps offer a unique opportunity to provide accurate and reliable patient information and their use as part of the informed consent process should be explored.
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Cirurgia Bariátrica , Aplicativos Móveis/normas , Obesidade/cirurgia , Telefone Celular , Humanos , InternetAssuntos
Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Cobre/metabolismo , Príons/química , Príons/metabolismo , Zinco/química , Zinco/metabolismo , Cobre/química , Espectroscopia de Ressonância de Spin Eletrônica , Modelos Moleculares , Ligação Proteica , Estrutura Terciária de ProteínaRESUMO
The aim of this study was to compare the pharmacokinetics and efficacy of ciprofloxacin as post-exposure therapy against inhalational anthrax in the common marmoset (Callithrix jacchus) with other non-human primate models in order to determine whether the marmoset is a suitable model to test post-exposure therapies for anthrax. Pharmacokinetic (PK) and efficacy studies with ciprofloxacin were performed in the marmoset. Ciprofloxacin plasma pharmacokinetics were determined in six animals in separate single-dose and multiple-dose studies and were analysed by high-performance liquid chromatography (HPLC). A separate group of marmosets was exposed to ca. 100× the 50% lethal dose (LD(50)) of Bacillus anthracis Ames strain by the airborne route. On Day 5 of a twice-daily dosing regimen of 17.5 mg/kg, the ciprofloxacin half-life (t(1/2)), maximum drug concentration (C(max)) and area under the concentration-time curve (AUC) in marmoset plasma were 1.9 h, 2.1 µg/mL and 7.9 µg/mL/h, respectively. Naïve untreated control animals succumbed to infection by Day 9. All animals treated with ciprofloxacin, started on the day of exposure and continued for 10 days, remained healthy during the treatment period. Two antibiotic-treated animals (33%) died after withdrawal of antibiotic therapy, attributed to the germination of residual spores. In conclusion, in many respects the marmoset appears to respond to B. anthracis in a similar way to the macaque, suggesting that this small non-human primate is an acceptable, practical alternative model for the evaluation of medical countermeasures against respiratory anthrax infection.