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1.
Nat Astron ; 8(5): 567-576, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38798715

RESUMO

Jupiter's moon Europa has a predominantly water-ice surface that is modified by exposure to its space environment. Charged particles break molecular bonds in surface ice, thus dissociating the water to ultimately produce H2 and O2, which provides a potential oxygenation mechanism for Europa's subsurface ocean. These species are understood to form Europa's primary atmospheric constituents. Although remote observations provide important global constraints on Europa's atmosphere, the molecular O2 abundance has been inferred from atomic O emissions. Europa's atmospheric composition had never been directly sampled and model-derived oxygen production estimates ranged over several orders of magnitude. Here, we report direct observations of H2+ and O2+ pickup ions from the dissociation of Europa's water-ice surface and confirm these species are primary atmospheric constituents. In contrast to expectations, we find the H2 neutral atmosphere is dominated by a non-thermal, escaping population. We find 12 ± 6 kg s-1 (2.2 ± 1.2 × 1026 s-1) O2 are produced within Europa's surface, less than previously thought, with a narrower range to support habitability in Europa's ocean. This process is found to be Europa's dominant exogenic surface erosion mechanism over meteoroid bombardment.

2.
Nat Commun ; 13(1): 7390, 2022 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-36450728

RESUMO

Mercury's southern inner magnetosphere is an unexplored region as it was not observed by earlier space missions. In October 2021, BepiColombo mission has passed through this region during its first Mercury flyby. Here, we describe the observations of SERENA ion sensors nearby and inside Mercury's magnetosphere. An intermittent high-energy signal, possibly due to an interplanetary magnetic flux rope, has been observed downstream Mercury, together with low energy solar wind. Low energy ions, possibly due to satellite outgassing, were detected outside the magnetosphere. The dayside magnetopause and bow-shock crossing were much closer to the planet than expected, signature of a highly eroded magnetosphere. Different ion populations have been observed inside the magnetosphere, like low latitude boundary layer at magnetopause inbound and partial ring current at dawn close to the planet. These observations are important for understanding the weak magnetosphere behavior so close to the Sun, revealing details never reached before.

3.
Geophys Res Lett ; 49(9): e2022GL098111, 2022 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-35864892

RESUMO

Water-group gas continuously escapes from Jupiter's icy moons to form co-orbiting populations of particles or neutral toroidal clouds. These clouds provide insights into their source moons as they reveal loss processes and compositions of their parent bodies, alter local plasma composition, and act as sources and sinks for magnetospheric particles. We report the first observations of H2 + pickup ions in Jupiter's magnetosphere from 13 to 18 Jovian radii and find a density ratio of H2 +/H+ = 8 ± 4%, confirming the presence of a neutral H2 toroidal cloud. Pickup ion densities monotonically decrease radially beyond 13 R J consistent with an advecting Europa-genic toroidal cloud source. From these observations, we derive a total H2 neutral loss rate from Europa of 1.2 ± 0.7 kg s-1. This provides the most direct estimate of Europa's H2 neutral loss rate to date and underscores the importance of both ion composition and neutral toroidal clouds in understanding satellite-magnetosphere interactions.

4.
Space Sci Rev ; 217(1): 11, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33487762

RESUMO

The ESA-JAXA BepiColombo mission to Mercury will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric particle dynamics at Mercury as well as their interactions with solar wind, solar radiation, and interplanetary dust. The particle instrument suite SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) is flying in space on-board the BepiColombo Mercury Planetary Orbiter (MPO) and is the only instrument for ion and neutral particle detection aboard the MPO. It comprises four independent sensors: ELENA for neutral particle flow detection, Strofio for neutral gas detection, PICAM for planetary ions observations, and MIPA, mostly for solar wind ion measurements. SERENA is managed by a System Control Unit located inside the ELENA box. In the present paper the scientific goals of this suite are described, and then the four units are detailed, as well as their major features and calibration results. Finally, the SERENA operational activities are shown during the orbital path around Mercury, with also some reference to the activities planned during the long cruise phase.

5.
Science ; 362(6410)2018 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-30287631

RESUMO

Saturn has a sufficiently strong dipole magnetic field to trap high-energy charged particles and form radiation belts, which have been observed outside its rings. Whether stable radiation belts exist near the planet and inward of the rings was previously unknown. The Cassini spacecraft's Magnetosphere Imaging Instrument obtained measurements of a radiation belt that lies just above Saturn's dense atmosphere and is decoupled from the rest of the magnetosphere by the planet's A- to C-rings. The belt extends across the D-ring and comprises protons produced through cosmic ray albedo neutron decay and multiple charge-exchange reactions. These protons are lost to atmospheric neutrals and D-ring dust. Strong proton depletions that map onto features on the D-ring indicate a highly structured and diverse dust environment near Saturn.

6.
Science ; 362(6410)2018 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-30287633

RESUMO

The sizes of Saturn's ring particles range from meters (boulders) to nanometers (dust). Determination of the rings' ages depends on loss processes, including the transport of dust into Saturn's atmosphere. During the Grand Finale orbits of the Cassini spacecraft, its instruments measured tiny dust grains that compose the innermost D-ring of Saturn. The nanometer-sized dust experiences collisions with exospheric (upper atmosphere) hydrogen and molecular hydrogen, which forces it to fall from the ring into the ionosphere and lower atmosphere. We used the Magnetospheric Imaging Instrument to detect and characterize this dust transport and also found that diffusion dominates above and near the altitude of peak ionospheric density. This mechanism results in a mass deposition into the equatorial atmosphere of ~5 kilograms per second, constraining the age of the D-ring.

8.
Diabet Med ; 29(8): e191-8, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22507537

RESUMO

AIMS: This study characterized UK primary care patients with Type 2 diabetes who initiated insulin treatment, and described the initial insulin regimens used, overall metabolic changes and health-care resource usage. METHODS: A retrospective cohort study was performed using quality-checked patient data from The Health Improvement Network database. Eligible patients who initiated insulin for the first time between 2004 and 2006 were grouped into four cohorts according to the type of insulin regimen initiated. Data on patient characteristics, metabolic and clinical outcomes and health-care resource use were collected at baseline and during 6 months of follow-up. RESULTS: In total, 4045 eligible adults [2269 male, 1776 female; mean age 62.6 ± 13.3 years; mean baseline HbA(1c) 82 ± 22 mmol/mol (9.6% ± 2.0%)] initiated insulin. Approximately half (52.4%) initiated insulin as basal insulin only, 41.6% as premixed only, 4.0% as basal-bolus and 2.1% as prandial insulin only. Among patients with ≥ 180 days follow-up (n=3815), the initial insulin regimen was not changed during follow-up in 75.1% of patients, while 13.7% discontinued, 7.0% switched and 4.7% intensified insulin therapy. The mean change in HbA(1c) was -14 mmol/mol (-1.3%, n=2881), with 17.3% of patients achieving an HbA(1c) of <53 mmol/mol (7%, n=3024). The mean weight change was +0.9 kg (n=2345). CONCLUSIONS: Basal and premixed insulin were the most common types of insulin initiated and in most patients no changes were made to the initial regimen over 6 months. However, few patients achieved glycemic control targets.


Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Insulina/uso terapêutico , Idoso , Índice de Massa Corporal , Peso Corporal , Bases de Dados Factuais , Diabetes Mellitus Tipo 2/sangue , Substituição de Medicamentos , Medicina de Família e Comunidade/estatística & dados numéricos , Feminino , Hemoglobinas Glicadas/metabolismo , Recursos em Saúde/estatística & dados numéricos , Humanos , Masculino , Pessoa de Meia-Idade , Aceitação pelo Paciente de Cuidados de Saúde/estatística & dados numéricos , Estudos Retrospectivos , Reino Unido
9.
Diabet Med ; 29(7): e13-20, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22268988

RESUMO

AIMS: To describe patients with Type 2 diabetes mellitus treated with basal insulin, with or without oral antidiabetics in UK primary care, and evaluate insulin treatment patterns and factors explaining changes in therapy. METHODS: Retrospective analysis of patients with Type 2 diabetes within The Health Improvement Network UK primary care database. Patients receiving basal insulin between January and June 2006 were followed until July 2009. RESULTS: Analysis included 3185 patients, mean age 65.6 years [standard deviation (SD) 12.4], 50.9% men, median diabetes duration 9.6 years, median basal insulin use 1.3 years, 86.5% had received oral antidiabetics in the previous 12 months. Mean follow-up was 2.9 years (SD 1.0), 59.8% patients maintained basal insulin throughout follow-up with a mean HbA(1C) of 69 mmol/mol (SD 19; 8.4%, SD 1.7) at baseline and 65 mmol/mol (SD 17; 8.1%, SD 1.6) during follow-up. During follow-up, 6.9% of patients discontinued, 19.3% intensified with and 14.1% switched to prandial or premixed insulin. Patients who intensified (prandial) had a mean HbA(1c) of 77 mmol/mol (SD 18; 9.2%, SD 1.6) before change and a mean HbA(1c) of 71 mmol/mol (SD 21; 8.6%, SD 2.0) at the end of the study. Those switching to premixed insulin had a mean HbA(1c) of 80 mmol/mol (SD 18; 9.5%, SD 1.7) before change and a mean HbA(1c) of 69 mmol/mol (SD 17; 8.5%, SD 1.5) at the end of the study. Increasing HbA(1c) and longer diabetes duration explained intensification and switch. CONCLUSIONS: The majority of patients had HbA(1c) above the 53 mmol/mol (< 7%) target at baseline and post-intensification/switch. The HbA(1c) levels were reduced by intensification/switch suggesting that insulin changes did have some impact. Most patients did not change insulin treatment despite having higher than recommended HbA(1c) levels. Reasons for not changing treatment in face of unsatisfactory clinical outcomes are unclear. Further research is warranted to explore barriers towards therapy change.


Assuntos
Glicemia/metabolismo , Diabetes Mellitus Tipo 2/tratamento farmacológico , Hemoglobinas Glicadas/metabolismo , Hipoglicemiantes/uso terapêutico , Insulina/uso terapêutico , Idoso , Automonitorização da Glicemia , Diabetes Mellitus Tipo 2/sangue , Diabetes Mellitus Tipo 2/epidemiologia , Feminino , Seguimentos , Humanos , Hipoglicemiantes/sangue , Insulina/sangue , Insulina de Ação Prolongada , Masculino , Pessoa de Meia-Idade , Período Pós-Prandial , Estudos Retrospectivos , Fatores de Tempo , Resultado do Tratamento , Reino Unido/epidemiologia
10.
Int J Clin Pract ; 65(5): 586-91, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21489082

RESUMO

OBJECTIVE: To investigate switching from thiazolidinediones, and predictors for switching treatment, after publication of a meta-analysis reporting an increased risk of myocardial infarction associated with rosiglitazone use. RESEARCH DESIGN AND METHODS: Using the Health Information Network (THIN) UK primary care database, the number of people with type 2 diabetes prescribed either thiazolidinedione, rosiglitazone (n = 10,062) or pioglitazone (n = 4454), and the rate of switching from thiazolidinediones (n = 3301 and 1106, respectively), were computed for each month, May 2006 to January 2008. The probability of switching post-publication, May 2007 to January 2008, was modelled by logistic regression in a forward stepwise model. Variables included demographics, history of ischaemic heart disease (IHD), heart failure (HF) or stroke, risk factors for IHD, glucose-lowering and cardiovascular drug use, HbA(1c) and diabetes duration. RESULTS: There was a sharp increase in switching from both thiazolidinediones in summer 2007; rosiglitazone prescription numbers then decreased while pioglitazone prescribing increased. Switching from rosiglitazone was associated with IHD [adjusted odds ratio (OR) 1.72; 95% confidence intervals (CI) 1.47-2.00], insulin treatment (OR 5.10; 95% CI 3.21-8.10), HF (OR 2.26; 95% CI 1.62-3.18), a recent sulphonylurea prescription (OR 1.33; 95% CI 1.17-1.51) gender (OR men vs. women 0.79; 95% CI 0.70, 0.90) and duration of therapy. Switching from pioglitazone was associated with HF (OR 3.05; 95% CI 1.77-5.26), duration of therapy, and number of glucose-lowering treatments. CONCLUSIONS: Prescribing habits for both thiazolidinediones changed immediately following the safety warning. IHD was associated with switching from rosiglitazone; otherwise reasons for change appear to be complex, not directly related to the findings of the meta-analysis.


Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Padrões de Prática Médica/estatística & dados numéricos , Tiazolidinedionas/efeitos adversos , Tiazolidinedionas/uso terapêutico , Adulto , Idoso , Substituição de Medicamentos , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos , Medicina de Família e Comunidade/estatística & dados numéricos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pioglitazona , Fatores de Risco , Rosiglitazona , Retirada de Medicamento Baseada em Segurança , Reino Unido
11.
Diabet Med ; 26(8): 803-14, 2009 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-19709151

RESUMO

AIMS: To determine the long-term health economic benefits associated with lispro vs. regular human insulin (RHI) in UK Type 1 diabetic (T1DM) patients using the previously published and validated CORE Diabetes Model. METHODS: A literature review designed to capture clinical benefits associated with lispro and T1DM cohort characteristics specific to UK was undertaken. Clinical benefits were derived from a Cochrane meta-analysis. The estimated difference (weighted mean) in glycated haemoglobin (HbA(1c)) was -0.1% (95% confidence interval -0.2 to 0.0%) for lispro vs. RHI. Severe hypoglycaemia rates for lispro and RHI were 21.8 and 46.1 events per 100 patient years, respectively. Costs and disutilities were accounted for severe hypoglycaemia rates. All costs were accounted in 2007 poundUK from a National Health Service (NHS) perspective. Future costs and clinical benefits were discounted at 3.5% annually. RESULTS: In the base-case analysis, lispro was projected to be dominant compared with RHI. Lispro was associated with improvements in quality-adjusted life expectancy (QALE) of approximately 0.10 quality-adjusted life years (QALYs) vs. RHI (7.60 vs. 7.50 QALYs). Lifetime direct medical costs per patient were lower with lispro treatment, pound70 576 vs. pound72 529. Severe hypoglycaemia rates were the key driver in terms of differences in QALE and lifetime costs. Sensitivity analyses with assumptions around time horizon, discounting rates and benefits in terms of glycaemic control or hypoglycaemic event rates revealed that lispro remained dominant. CONCLUSIONS: Our findings suggest that lispro is likely to improve QALE, reduce frequency of diabetes-related complications and lifetime medical costs compared with RHI.


Assuntos
Diabetes Mellitus Tipo 1/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Insulina/análogos & derivados , Insulina/uso terapêutico , Análise Custo-Benefício , Diabetes Mellitus Tipo 1/economia , Humanos , Hipoglicemiantes/economia , Insulina/economia , Insulina Lispro , Expectativa de Vida , Anos de Vida Ajustados por Qualidade de Vida , Estatística como Assunto , Fatores de Tempo
12.
Science ; 307(5713): 1262-6, 2005 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-15731443

RESUMO

During Cassini's initial orbit, we observed a dynamic magnetosphere composed primarily of a complex mixture of water-derived atomic and molecular ions. We have identified four distinct regions characterized by differences in both bulk plasma properties and ion composition. Protons are the dominant species outside about 9 RS (where RS is the radial distance from the center of Saturn), whereas inside, the plasma consists primarily of a corotating comet-like mix of water-derived ions with approximately 3% N+. Over the A and B rings, we found an ionosphere in which O2+ and O+ are dominant, which suggests the possible existence of a layer of O2 gas similar to the atmospheres of Europa and Ganymede.


Assuntos
Magnetismo , Oxigênio , Saturno , Atmosfera , Meio Ambiente Extraterreno , Hidrogênio , Gelo , Íons , Prótons , Astronave , Análise Espectral
13.
Rheumatology (Oxford) ; 42(8): 989-94, 2003 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12730515

RESUMO

OBJECTIVE: To study the pharmacokinetics of methotrexate (MTX) plus cyclosporin A (CSA) in patients with rheumatoid arthritis (RA). METHODS: On day 1 of the study, patients with RA receiving stable doses of MTX had blood and urine levels of MTX and its metabolite 7-hydroxymethotrexate (7-OH-MTX) measured post oral dosing of the drug. MTX was then discontinued and CSA therapy was started on day 8. On day 20, blood levels of CSA and CSA metabolites were measured post drug dosing. On day 23, MTX therapy was restarted and levels of MTX, CSA and their metabolites were again measured as described above. RESULTS: In the 30 patients, coadministration of CSA and MTX led to a 26% increase in mean peak plasma MTX concentration (P < 0.01), an 18% increase in the mean plasma MTX concentration area under the curve (AUC, P=0.01) and an 80% decrease in plasma 7-OH-MTX AUC (P < 0.01). In 13 patients receiving a 10 mg MTX dose, CSA reduced urinary 7-OH-MTX excretion by 87% (P < 0.01) without altering MTX excretion. MTX did not alter the pharmacokinetics of CSA or its metabolites. CONCLUSION: CSA may block oxidation of MTX to its relatively inactive metabolite, 7-OH-MTX, thereby potentiating MTX efficacy.


Assuntos
Artrite Reumatoide/tratamento farmacológico , Ciclosporina/farmacocinética , Imunossupressores/farmacocinética , Metotrexato/análogos & derivados , Metotrexato/farmacocinética , Administração Oral , Adulto , Idoso , Artrite Reumatoide/sangue , Artrite Reumatoide/urina , Ciclosporina/sangue , Ciclosporina/uso terapêutico , Esquema de Medicação , Sinergismo Farmacológico , Quimioterapia Combinada , Feminino , Humanos , Imunossupressores/análise , Imunossupressores/uso terapêutico , Masculino , Metotrexato/análise , Metotrexato/sangue , Metotrexato/uso terapêutico , Metotrexato/urina , Pessoa de Meia-Idade
14.
Environ Manage ; 28(1): 31-7, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11436998

RESUMO

The endangered snail kite (Rostrhamus sociabilis) feeds primarily on the freshwater apple snail (Pomacea paludosa) in Florida. The nonindigenous, floating water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) impede kites from finding snails. Effective control of these aquatic plants in the littoral zone of central and south Florida lakes benefits kites by maintaining open foraging habitat. However, incidental herbicide spraying of nesting substrates result in nest collapse when kites breed in nonwoody, emergent plants [cattail (Typha spp.) and giant bulrush (Scirpus validus)] in the outer littoral zone during lower lake levels. Many endangered species recovery plans and their implementation have experienced problems due to inaction and/or noncooperation by various governmental agencies and their personnel. Herein, we describe the development and implementation of a buffer zone strategy to prevent secondary impacts from an aquatic plant control program to snail kites nesting on lakes in central and south Florida. A strategy was jointly developed by personnel of five state and federal agencies to control herbicide application near kite nesting areas during the normal breeding season. Although requiring various modifications during its implementation, this cooperative effort successfully integrated aquatic plant control objectives with snail kite conservation on Lake Okeechobee during 1988. The program was expanded the following year to lakes Kissimmee and Tohopekaliga. Since the implementation of the snail kite impact preclusion program, no nest loss was attributed to incidental herbicide applications on lakes Okeechobee, Kissimmee, and Tohopekaliga.


Assuntos
Conservação dos Recursos Naturais/métodos , Meio Ambiente , Herbicidas/efeitos adversos , Comportamento de Nidação/efeitos dos fármacos , Aves Predatórias , Caramujos , Animais , Cruzamento , Florida , Água Doce
15.
J Cardiovasc Pharmacol ; 37(5): 502-11, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11336101

RESUMO

Fluvastatin sodium (Lescol, Novartis Pharmaceutical Corp., East Hanover, NJ, U.S.A.), a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG Co-A) reductase inhibitor that limits cholesterol biosynthesis, is available as a 40-mg immediate-release formulation capsule. An extended-release formulation for once-daily administration has been developed for patients with primary hypercholesterolemia who may benefit from doses higher than 40 mg/day. This phase I study evaluated the safety, tolerability, and pharmacokinetics of a new fluvastatin extended-release formulation at doses ranging from 80-640 mg/day in 40 hypercholesterolemic patients. After a 2-week dietary stabilization phase, patients (Fredrickson type IIa/IIb), 18-55 years of age, were randomly assigned to four groups to receive oral fluvastatin extended-release (80, 160, 320, or 640 mg) or matching placebo once daily for 13 days. Fluvastatin extended-release was generally safe and well tolerated at doses of 80-320 mg/day. Within this dose range, linear pharmacokinetics was observed after single and multiple dosing. At 640 mg, fluvastatin extended-release was not well tolerated. Six of the seven actively treated patients at this dose experienced adverse events, including diarrhea, headache, and clinically relevant elevations in serum transaminase concentrations. In addition, nonlinear pharmacokinetics, possibly due to saturation of first-pass metabolism, was observed at this dose, causing higher than expected serum drug concentrations. Once-daily administration of fluvastatin extended-release at doses of 80-320 mg/day was generally safe and well tolerated in patients with primary hypercholesterolemia over a 13-day dosing period.


Assuntos
Anticolesterolemiantes/administração & dosagem , Anticolesterolemiantes/efeitos adversos , Ácidos Graxos Monoinsaturados/administração & dosagem , Ácidos Graxos Monoinsaturados/efeitos adversos , Hipercolesterolemia/tratamento farmacológico , Indóis/administração & dosagem , Indóis/efeitos adversos , Adolescente , Adulto , Anticolesterolemiantes/farmacocinética , Área Sob a Curva , Preparações de Ação Retardada , Relação Dose-Resposta a Droga , Método Duplo-Cego , Esquema de Medicação , Ácidos Graxos Monoinsaturados/farmacocinética , Feminino , Fluvastatina , Humanos , Hipercolesterolemia/sangue , Indóis/farmacocinética , Lipoproteínas/sangue , Testes de Função Hepática , Masculino , Pessoa de Meia-Idade
16.
J Heart Lung Transplant ; 20(3): 330-9, 2001 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-11257560

RESUMO

BACKGROUND: RAD is a novel macrolide with potent immunosuppressive and antiproliferative activities. This study characterizes the safety, tolerability, and pharmacokinetics of two different single oral doses of RAD in stable lung and heart/lung transplant recipients with and without cystic fibrosis (CF). METHODS: This was a Phase I, multicenter, randomized, double-blind, two-period, two-sequence, crossover study. Single doses of RAD capsules at doses of 0.035 mg/kg (2.5 mg maximum) or 0.10 mg/kg (7.5 mg maximum) were administered with cyclosporine (Neoral [cyclosporine, USP] modified), steroids, and azathioprine on Day 1. The alternate dose was administered on Day 16. Laboratory assessments, vital signs, and adverse events were recorded throughout the study. RAD pharmacokinetic profiles were assessed over a 7-day period following each dose. Steady-state cyclosporine (CsA) profiles were assessed at baseline and with each RAD dose; RAD and CsA trough concentrations were obtained throughout the study period. RESULTS: Of the 20 patients randomized, 8 had CF and 12 did not. Single doses of RAD were safe and well tolerated. Headache was the most common side effect. RAD produced a mild, dose-dependent, reversible decrease in platelet and leukocyte counts. Cholesterol and triglycerides were minimally affected. At both doses, CF patients had significantly lower peak concentrations of RAD than did non-CF patients (p = 0.03); however, overall exposure (area under the curve/dose) was not different between the groups (p = 0.63). At the higher dose, there was a clinically minor under-proportionality in AUC, averaging -11%. Steady-state pharmacokinetics of CsA were not affected by RAD co-administration.RAD was safe and well tolerated by stable lung and heart/lung transplant recipients with and without CF. The presence of CF did not influence the extent of RAD exposure. Single doses of RAD did not affect the pharmacokinetics of CsA. Ongoing studies are assessing the long-term safety and efficacy of RAD in lung and heart/lung transplantation.


Assuntos
Imunossupressores/uso terapêutico , Transplante de Pulmão , Macrolídeos/uso terapêutico , Adolescente , Adulto , Estudos Cross-Over , Ciclosporina/uso terapêutico , Fibrose Cística/complicações , Método Duplo-Cego , Feminino , Transplante de Coração-Pulmão/imunologia , Humanos , Imunossupressores/administração & dosagem , Imunossupressores/farmacocinética , Transplante de Pulmão/imunologia , Macrolídeos/administração & dosagem , Macrolídeos/farmacocinética , Masculino , Pessoa de Meia-Idade
17.
Arch Biochem Biophys ; 364(1): 19-29, 1999 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-10087161

RESUMO

Lck encodes a 56-kDa protein-tyrosine kinase, predominantly expressed in T lymphocytes, crucial for initiating T cell antigen receptor (TCR) signal transduction pathways, culminating in T cell cytokine gene expression and effector functions. As a consequence of a high-throughput screen for selective, novel inhibitors of p56(lck), an isothiazolone compound was identified, methyl-3-(N-isothiazolone)-2-thiophenecarboxylate(A-125800), which inhibits p56(lck) kinase activity with IC50 = 1-7 microM. Under similar assay conditions, the isothiazolone compound was equipotent in blocking the ZAP-70 tyrosine kinase activity but was 50 to 100 times less potent against the catalytic activities of p38 MAP kinase and c-Jun N-terminal kinase 2alpha. A-125800 blocked activation-dependent TCR tyrosine phosphorylation and intracellular calcium mobilization in Jurkat T cells (IC50 = 35 microM) and blocked T cell proliferation in response to alloantigen (IC50 = 14 microM) and CD3/CD28-induced IL-2 secretion (IC50 = 2.2 microM) in primary T cell cultures. Inhibition of p56(lck )by A-125800 was dose- and time-dependent and was irreversible. A substitution of methylene for the sulfur atom in the isothiazolone ring of the compound completely abrogated the ability to inhibit p56(lck) kinase activity and TCR-dependent signal transduction. Incubation with thiols such as beta-ME or DTT also blocked the ability of the isothiazolone to inhibit p56(lck) kinase activity. LC/MS analysis established the covalent modification of p56(lck) at cysteine residues 378, 465, and 476. Together these data support an inhibitory mechanism, whereby cysteine -SH groups within the p56(lck) catalytic domain react with the isothiazolone ring, leading to ring opening and disulfide bond formation with the p56(lck) enzyme. Loss of p56(lck) activity due to -SH oxidation has been suggested to play a role in the pathology of AIDS. Consequently, a similar mechanism of sulfhydryl oxidation leading to p56(lck) inhibition, described in this report, may occur in the intact T cell and may underlie certain T cell pathologies.


Assuntos
Inibidores Enzimáticos/farmacologia , Proteína Tirosina Quinase p56(lck) Linfócito-Específica/antagonistas & inibidores , Tiazóis/farmacologia , Trifosfato de Adenosina/metabolismo , Sequência de Aminoácidos , Animais , Sítios de Ligação/efeitos dos fármacos , Catálise/efeitos dos fármacos , Linhagem Celular , Cisteína/metabolismo , Relação Dose-Resposta a Droga , Humanos , Células Jurkat , Ativação Linfocitária/efeitos dos fármacos , Dados de Sequência Molecular , Fosforilação/efeitos dos fármacos , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais/efeitos dos fármacos , Compostos de Sulfidrila/farmacologia , Tiazóis/metabolismo , Fatores de Tempo
18.
Liver Transpl Surg ; 5(2): 112-8, 1999 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10071350

RESUMO

Black transplant recipients are associated with low cyclosporine bioavailability, which may contribute to the poorer clinical outcomes observed with these patients. In this analysis, we compared cyclosporine exposure in black (n = 9) and nonblack (n = 18) pediatric maintenance liver transplant recipients by using steady-state pharmacokinetic profiles obtained after administration of the original and microemulsion formulations of cyclosporine. Treatment with the original cyclosporine formulation resulted in lower mean dose-normalized, area under the concentration-versus-time curve values for black compared with nonblack pediatric liver transplant recipients. On conversion to the microemulsion formulation of cyclosporine, black and nonblack patients experienced increases in cyclosporine bioavailability of 102% and 39%, respectively (P =.009 and P =.001). Because the increase in mean bioavailability was substantially greater for blacks, area under the concentration-versus-time curve values for this pediatric subpopulation became similar to those levels obtained for nonblacks receiving the microemulsion formulation for cyclosporine. When patients were further stratified by age, ethnic differences in bioavailability with the original formulation of cyclosporine were most apparent in the 1- to 5-year age group. Conversion to the microemulsion formulation resulted in a 164% increase (P =.05) in bioavailability for black patients within this age group such that, again, these levels became similar to area under the concentration-versus-time curve values obtained for young nonblacks receiving cyclosporine for microemulsion. Improvements in cyclosporine bioavailability after administration of the microemulsion formulation of cyclosporine may translate to improved long-term graft and patient outcomes for black pediatric liver transplant recipients.


Assuntos
População Negra , Ciclosporina/farmacocinética , Emulsões/uso terapêutico , Imunossupressores/farmacocinética , Transplante de Fígado , Adolescente , Envelhecimento/metabolismo , Disponibilidade Biológica , Criança , Pré-Escolar , Estudos Cross-Over , Feminino , Humanos , Masculino , Estudos Retrospectivos
20.
Transplantation ; 63(12): 1762-7, 1997 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-9210501

RESUMO

BACKGROUND: A comparison of the oral bioavailability of cyclosporine from the original formulation (CsA) and from the new formulation, cyclosporine for microemulsion (CsA-ME), was made in pediatric maintenance liver transplant patients within two age groups (group 1, ages 1-5 years; group 2, ages 6-17 years) in an open-label, multicenter, randomized crossover trial. All patients were at least 6 months past transplantation and were receiving CsA maintenance therapy. METHODS: In study period 1 (days 1 through 14), patients were administered either CsA or CsA-ME at the same b.i.d. dosage as their maintenance therapy. Upon entry into period 2 (days 15 through 28), patients were converted to the alternate formulation at a 1:1 mg dose ratio. On day 29, all patients returned to the CsA treatment administered at study entry, with follow-up on day 35. Dosage adjustments were not allowed with either CsA or CsA-ME. Twelve-hour pharmacokinetic profiling was performed at the end of periods 1 and 2. RESULTS: Both the mean area under the concentration-versus-time curve and the mean maximum blood concentration of cyclosporine-both normalized for dose-were significantly increased: by 66% and 109%, respectively, in patients receiving CsA-ME compared with those receiving CsA in group 1 and by 39% and 75%, respectively, in group 2. During this study, liver function remained stable, and serum creatinine and blood pressure did not differ significantly between treatment groups. CONCLUSIONS: This study shows increased bioavailability in all patients converted to CsA-ME, with the greatest increase seen in patients with the lowest initial cyclosporine bioavailability. The tolerability was similar between the two formulations during this study.


Assuntos
Ciclosporina/farmacocinética , Sistemas de Liberação de Medicamentos , Imunossupressores/farmacocinética , Transplante de Fígado , Absorção , Administração Oral , Adolescente , Fatores Etários , Disponibilidade Biológica , Criança , Pré-Escolar , Estudos Cross-Over , Ciclosporina/administração & dosagem , Emulsões , Feminino , Humanos , Imunossupressores/administração & dosagem , Lactente , Masculino
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