Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 71
Filtrar
1.
Nature ; 627(8003): 281-285, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38286342

RESUMO

Tight relationships exist in the local Universe between the central stellar properties of galaxies and the mass of their supermassive black hole (SMBH)1-3. These suggest that galaxies and black holes co-evolve, with the main regulation mechanism being energetic feedback from accretion onto the black hole during its quasar phase4-6. A crucial question is how the relationship between black holes and galaxies evolves with time; a key epoch to examine this relationship is at the peaks of star formation and black hole growth 8-12 billion years ago (redshifts 1-3)7. Here we report a dynamical measurement of the mass of the black hole in a luminous quasar at a redshift of 2, with a look back in time of 11 billion years, by spatially resolving the broad-line region (BLR). We detect a 40-µas (0.31-pc) spatial offset between the red and blue photocentres of the Hα line that traces the velocity gradient of a rotating BLR. The flux and differential phase spectra are well reproduced by a thick, moderately inclined disk of gas clouds within the sphere of influence of a central black hole with a mass of 3.2 × 108 solar masses. Molecular gas data reveal a dynamical mass for the host galaxy of 6 × 1011 solar masses, which indicates an undermassive black hole accreting at a super-Eddington rate. This suggests a host galaxy that grew faster than the SMBH, indicating a delay between galaxy and black hole formation for some systems.

2.
Rev Med Liege ; 76(12): 837-839, 2021 Dec.
Artigo em Francês | MEDLINE | ID: mdl-34881824

RESUMO

The complete dislocation of the talus or «missing talus¼ corresponds to a simultaneous dislocation of the tibiotalar, talocalcaneal and talonavicular joints, without associated talar fracture. This lesion occurs as part of high energy trauma and accounts for 3 to 5 % of talus injuries. It is most frequently anterolateral and in more than 75 % of cases, this dislocation is open. Among the soft tissue lesions that are often associated with the dislocation, vascular lesions leading to avascular necrosis of the talus are found in almost 100 % of cases. This necrosis is generally well tolerated by the patient. A conservative treatment by reimplantation of the talus after debridement of the site should be performed as a first-line treatment as fast as possible. When the avascular necrosis of the talus is not well tolerated by the patient, a talectomy associated with tibiocalcaneal arthrodesis can be performed as a secondary procedure. Talectomy alone should not be done.


La dislocation complète du talus ou «missing talus¼ correspond à une dislocation simultanée des articulations tibiotalienne, talocalcanéenne et talonaviculaire, sans fracture talienne associée. Cette lésion survient dans le cadre d'un traumatisme à haute énergie et représente 3 à 5 % des lésions du talus. Elle est le plus fréquemment antéro-latérale et, dans plus de 75 % des cas, cette dislocation est ouverte. Parmi les lésions des tissus mous qui y sont souvent associées, les lésions vasculaires conduisant à une nécrose avasculaire du talus sont retrouvées dans presque 100 % des cas. Cette nécrose est généralement bien tolérée par le patient. Un traitement conservateur par réimplantation du talus après débridement du site doit être réalisé en première intention et ce, de manière urgente. Lorsque la nécrose avasculaire du talus n'est pas bien tolérée par le patient sur le long terme, une talectomie associée à une arthrodèse tibio-calcannénne peut être réalisée dans un second temps. La talectomie seule doit, quant à elle, être proscrite.


Assuntos
Traumatismos do Tornozelo , Luxações Articulares , Osteonecrose , Tálus , Traumatismos do Tornozelo/diagnóstico por imagem , Traumatismos do Tornozelo/cirurgia , Humanos , Luxações Articulares/cirurgia , Tálus/diagnóstico por imagem , Tálus/cirurgia
3.
Phys Rev Lett ; 122(10): 101102, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30932663

RESUMO

During its orbit around the four million solar mass black hole Sagittarius A* the star S2 experiences significant changes in gravitational potential. We use this change of potential to test one part of the Einstein equivalence principle: the local position invariance (LPI). We study the dependency of different atomic transitions on the gravitational potential to give an upper limit on violations of the LPI. This is done by separately measuring the redshift from hydrogen and helium absorption lines in the stellar spectrum during its closest approach to the black hole. For this measurement we use radial velocity data from 2015 to 2018 and combine it with the gravitational potential at the position of S2, which is calculated from the precisely known orbit of S2 around the black hole. This results in a limit on a violation of the LPI of |ß_{He}-ß_{H}|=(2.4±5.1)×10^{-2}. The variation in potential that we probe with this measurement is six magnitudes larger than possible for measurements on Earth, and a factor of 10 larger than in experiments using white dwarfs. We are therefore testing the LPI in a regime where it has not been tested before.

4.
Nature ; 553(7688): 310-312, 2018 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-29258298

RESUMO

Convection plays a major part in many astrophysical processes, including energy transport, pulsation, dynamos and winds on evolved stars, in dust clouds and on brown dwarfs. Most of our knowledge about stellar convection has come from studying the Sun: about two million convective cells with typical sizes of around 2,000 kilometres across are present on the surface of the Sun-a phenomenon known as granulation. But on the surfaces of giant and supergiant stars there should be only a few large (several tens of thousands of times larger than those on the Sun) convective cells, owing to low surface gravity. Deriving the characteristic properties of convection (such as granule size and contrast) for the most evolved giant and supergiant stars is challenging because their photospheres are obscured by dust, which partially masks the convective patterns. These properties can be inferred from geometric model fitting, but this indirect method does not provide information about the physical origin of the convective cells. Here we report interferometric images of the surface of the evolved giant star π1 Gruis, of spectral type S5,7. Our images show a nearly circular, dust-free atmosphere, which is very compact and only weakly affected by molecular opacity. We find that the stellar surface has a complex convective pattern with an average intensity contrast of 12 per cent, which increases towards shorter wavelengths. We derive a characteristic horizontal granule size of about 1.2 × 1011 metres, which corresponds to 27 per cent of the diameter of the star. Our measurements fall along the scaling relations between granule size, effective temperature and surface gravity that are predicted by simulations of stellar surface convection.

5.
BJOG ; 124(2): 306-312, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27704657

RESUMO

OBJECTIVE: To report pregnancy outcomes of SHiP (spontaneous haemoperitoneum in pregnancy) and the association with endometriosis. DESIGN: Retrospective case note review. SETTING: Dutch referral hospitals for endometriosis. SAMPLE: Eleven women presenting with 15 events of SHiP. METHODS: In collaboration with the Dutch Working Group on Endometriosis, unpublished cases of SHiP that occurred in the Netherlands between 2010 and 2015 were retrieved. MAIN OUTCOME MEASURES: Maternal and perinatal mortality and morbidity. RESULTS: SHiP occurred predominantly in the second and third trimester of pregnancy. The earliest and major presenting symptom was an acute onset of abdominal pain, often combined with low haemoglobin levels or signs of fetal distress. Imaging was a diagnostic tool when free peritoneal fluid could be observed. For surgical treatment of the bleeding site, a midline laparotomy was mostly needed, the median estimated amount of blood loss was 2000 mL. No fetomaternal or perinatal mortality was reported, despite a high rate of preterm births (54.5%). In all women, endometriosis was diagnosed at a certain moment in time and therefore was probably involved in the pathogenesis of SHiP. Four women showed recurrence of SHiP. In one of these cases the second event of SHiP occurred in a subsequent pregnancy. CONCLUSION: Pregnancy outcomes of SHiP are improving when compared with previous reports, with absent fetomaternal and perinatal mortality in this recent series. Growing knowledge and adequate multidisciplinary intervention may have contributed to these favourable results. Increasing awareness of this serious complication of pregnancy is advocated, especially in women diagnosed with endometriosis. TWEETABLE ABSTRACT: Growing awareness of SHiP is advocated, especially in women diagnosed with endometriosis.


Assuntos
Endometriose/complicações , Hemoperitônio/etiologia , Complicações na Gravidez/etiologia , Dor Abdominal/etiologia , Adulto , Feminino , Sofrimento Fetal/etiologia , Humanos , Países Baixos , Gravidez , Resultado da Gravidez , Nascimento Prematuro/etiologia , Estudos Retrospectivos
6.
Hist Sci Med ; 48(4): 469-74, 2014.
Artigo em Francês | MEDLINE | ID: mdl-25962214

RESUMO

Chemotherapy stands today for cancer. In 1909, Paul Ehrlich (1854-1915) advocates the use of arsphenamine by infusion. So, he is considered as the father of chemotherapy. In fact, the first to have thought through chemotherapy was Sir Christopher Wren (1632-1723). In 1676, ideas and experiments on animals had sufficiently progressed to allow Michel Ettmuller (1644-1683) to publish the first edition of his book and several others were printed until 1753. In this book, he describes the first intravenous treatment, it sets the first indications, dosages and different products which can be used. However this method has been forgotten until the late 19th century.


Assuntos
Antineoplásicos/história , Neoplasias/história , Administração Intravenosa , Animais , Antineoplásicos/administração & dosagem , História do Século XVII , História do Século XVIII , História do Século XIX , História do Século XX , Humanos , Neoplasias/tratamento farmacológico
8.
Int J Obes (Lond) ; 35(2): 217-25, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20603627

RESUMO

OBJECTIVE: To investigate the impact of reduced adipocyte fatty acid-binding protein 4 (FABP4) in control of body weight, glucose and lipid homeostasis in diet-induced obese (DIO) mice. METHODS: We applied RNA interference (RNAi) technology to generate FABP4 germline knockdown mice to investigate their metabolic phenotype. RESULTS: RNAi-mediated knockdown reduced FABP4 mRNA expression and protein levels by almost 90% in adipocytes of standard chow-fed mice. In adipocytes of DIO mice, RNAi reduced FABP4 expression and protein levels by 70 and 80%, respectively. There was no increase in adipocyte FABP5 expression in FABP4 knockdown mice. The knockdown of FABP4 significantly increased body weight and fat mass in DIO mice. However, FABP4 knockdown did not affect plasma glucose and lipid homeostasis in DIO mice; nor did it improve their insulin sensitivity. CONCLUSION: Our data indicate that robust knockdown of FABP4 increases body weight and fat mass without improving glucose and lipid homeostasis in DIO mice.


Assuntos
Adipócitos/metabolismo , Peso Corporal/genética , Proteínas de Ligação a Ácido Graxo/metabolismo , Obesidade/genética , Interferência de RNA , Animais , Ingestão de Energia/fisiologia , Metabolismo Energético/fisiologia , Proteínas de Ligação a Ácido Graxo/genética , Técnicas de Silenciamento de Genes/métodos , Mutação em Linhagem Germinativa , Resistência à Insulina/genética , Resistência à Insulina/fisiologia , Metabolismo dos Lipídeos/genética , Camundongos , Camundongos Knockout , Camundongos Obesos , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Obesidade/metabolismo , RNA Mensageiro/metabolismo
9.
Int J Obes (Lond) ; 33(5): 601-4, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19223847

RESUMO

Both 11beta-hydroxysteroid dehydrogenase (11beta-HSD1) inhibition and peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonism reduce liver and plasma lipids in rodents through partly distinct mechanisms. This study aimed to assess their additivity of action on liver and plasma lipids in a model of diet-induced steatosis. Rats were fed an obesogenic diet and were treated either with an 11beta-HSD1 inhibitor (Compound A, 3 mg kg(-1) day(-1)) or rosiglitazone (RSG, 5 mg kg(-1) day(-1)) or both for 6 weeks. Compound A and RSG reduced liver steatosis and triglyceridemia, and did so additively when given in combination. The 11beta-HSD1 inhibitor had no effect on serum adiponectin, but increased liver adiponectin receptor type 2 (Adipo-R2) mRNA levels. Conversely, RSG increased serum adiponectin, a likely mediator of its antisteatotic action, but had no effect per se on the Adipo-R2 expression. mRNA levels of representative genes of fatty acid oxidation tended to be increased by both compounds. The study shows that combined 11beta-HSD1 inhibition and PPAR-gamma agonism additively reduce liver steatosis and triglyceridemia, which may eventually prove therapeutically useful.


Assuntos
11-beta-Hidroxiesteroide Desidrogenase Tipo 1/antagonistas & inibidores , Fígado Gorduroso/metabolismo , PPAR gama/agonistas , Triglicerídeos/metabolismo , Adiponectina/sangue , Animais , Modelos Animais de Doenças , Fígado Gorduroso/prevenção & controle , Masculino , Obesidade/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Adiponectina/sangue , Rosiglitazona , Tiazolidinedionas/farmacologia , Triazóis/farmacologia
10.
Science ; 317(5836): 342-5, 2007 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-17540860

RESUMO

Spatially resolving the surfaces of nearby stars promises to advance our knowledge of stellar physics. Using optical long-baseline interferometry, we constructed a near-infrared image of the rapidly rotating hot star Altair with a resolution of <1 milliarcsecond. The image clearly reveals the strong effect of gravity darkening on the highly distorted stellar photosphere. Standard models for a uniformly rotating star cannot explain our findings, which appear to result from differential rotation, alternative gravity-darkening laws, or both.

12.
Cytogenet Genome Res ; 105(2-4): 363-74, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15237224

RESUMO

The reconstruction of genetic networks in mammalian systems is one of the primary goals in biological research, especially as such reconstructions relate to elucidating not only common, polygenic human diseases, but living systems more generally. Here we propose a novel gene network reconstruction algorithm, derived from classic Bayesian network methods, that utilizes naturally occurring genetic variations as a source of perturbations to elucidate the network. This algorithm incorporates relative transcript abundance and genotypic data from segregating populations by employing a generalized scoring function of maximum likelihood commonly used in Bayesian network reconstruction problems. The utility of this novel algorithm is demonstrated via application to liver gene expression data from a segregating mouse population. We demonstrate that the network derived from these data using our novel network reconstruction algorithm is able to capture causal associations between genes that result in increased predictive power, compared to more classically reconstructed networks derived from the same data.


Assuntos
Algoritmos , Genética Populacional , Genômica , 11-beta-Hidroxiesteroide Desidrogenases/genética , Animais , Teorema de Bayes , Análise por Conglomerados , Feminino , Perfilação da Expressão Gênica , Desequilíbrio de Ligação , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Modelos Genéticos , Locos de Características Quantitativas
13.
Acta Orthop Belg ; 69(2): 197-200, 2003 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-12769023

RESUMO

Anterior elbow dislocations are often associated with severe soft tissue lesions. The mechanism of dislocation is usually an anteriorly directed blow on the proximal ulna after a fall on a flexed elbow. Simple anterior elbow dislocations are traditionally treated by closed reduction followed by a short period of immobilisation. Fracture-dislocations are usually unstable after reduction and necessitate surgical management. The authors report a case of acute anterior dislocation with a concomitant radial head fracture that was complicated by recurrent instability. The literature is reviewed to discuss a treatment strategy.


Assuntos
Lesões no Cotovelo , Luxações Articulares/diagnóstico por imagem , Idoso , Idoso de 80 Anos ou mais , Articulação do Cotovelo/diagnóstico por imagem , Feminino , Humanos , Luxações Articulares/terapia , Radiografia , Recidiva
14.
Int J Obes Relat Metab Disord ; 27 Suppl 3: S17-21, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14704738

RESUMO

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor isoforms with key roles in the regulation of lipid and glucose metabolism. Synthetic ligands for PPAR gamma (and PPAR alpha) have effects of promoting insulin sensitization in the context of obesity. Recent evidence suggests that activation of PPAR delta might produce similar effects. Both PPAR gamma and PPAR alpha have also been shown to produce selected anti-inflammatory effects and to reduce the progression of atherosclerosis in animals (alpha and gamma) or in humans (alpha). Mechanisms underlying insulin-sensitizing effects are complex. For PPAR gamma, direct effects on adipose tissue lipid metabolism with secondary benefits in liver and/or muscle (lipid levels and insulin signaling) have been implicated. For PPAR alpha, accelerated lipid catabolism may contribute to reduced muscle or liver 'steatosis'. Anti-inflammatory mechanisms as contributors to the beneficial metabolic effects of PPAR activation are also worth considering for the following reasons: (1) obesity and insulin resistance are associated with a proinflammatory milieu. (2) PPAR gamma has clear effects to oppose the effects of tumor necrosis factor-alpha (TNFalpha) in adipocytes. (3) effects of PPAR ligands on cytokine-mediated signaling (eg via NF-kappa B) may be expected to enhance insulin action. (4) Adipose production of several molecules that are implicated as markers or mediators of inflammation is reduced. (5) In humans, treatment with either PPAR alpha or PPAR gamma agonists has been shown to reduce circulating levels of proteins that serve as markers of inflammation. (6) Adiponectin, a fat-derived circulating factor that has been implicated as having anti-inflammatory activity, is induced by PPAR gamma agonism.


Assuntos
Inflamação/fisiopatologia , Resistência à Insulina , Obesidade/fisiopatologia , Receptores Citoplasmáticos e Nucleares/fisiologia , Fatores de Transcrição/fisiologia , Animais , Anti-Inflamatórios/farmacologia , Humanos , Ligantes
17.
J Biol Chem ; 276(45): 42077-83, 2001 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-11546817

RESUMO

Chronic elevation of systemic levels of acute phase reactants and inflammatory cytokines found in patients with diabetes and the often-associated metabolic syndrome X (hypertriglyceridemia, low serum high density lipoprotein cholesterol, hypertension, and accelerated atherosclerosis) may be responsible for the increased incidence of cardiovascular problems in this population. Here we examine the contribution of adipose tissue to the systemic elevation of acute phase reactants associated with chronic hyperglycemia. We demonstrate that adipose tissue expresses a number of acute phase reactants at high levels, including serum amyloid A3 (SAA3), alphal-acid glycoprotein, the lipocalin 24p3 as well as plasminogen activator inhibitor-1 (PAI-1). Additionally, we show SAA3 is expressed at low levels under normal conditions but in the diabetic state is dramatically up-regulated in adipose tissue while down-regulated in liver. Furthermore, pro-inflammatory stimuli and high glucose can lead to the induction of SAA3 in adipose tissue in vivo as well as in the 3T3-L1 adipocyte cell line. Adipose tissue may therefore play a major role in the pathogenic sequelae of Type II diabetes, in particular the cardiovascular problems associated with prolonged hyperglycemia.


Assuntos
Proteínas de Fase Aguda/biossíntese , Tecido Adiposo/metabolismo , Hiperglicemia/metabolismo , Células 3T3 , Adipócitos/metabolismo , Sequência de Aminoácidos , Animais , Diabetes Mellitus Experimental/metabolismo , Hiperinsulinismo/metabolismo , Lipopolissacarídeos/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Orosomucoide/biossíntese , Inibidor 1 de Ativador de Plasminogênio/biossíntese , Proteína Amiloide A Sérica/biossíntese , Fator de Necrose Tumoral alfa/farmacologia
19.
J Biol Chem ; 276(34): 31521-7, 2001 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-11418601

RESUMO

We compared the ability of rat and human hepatocytes to respond to fenofibric acid and a novel potent phenylacetic acid peroxisome proliferator-activated receptor (PPAR) alpha agonist (compound 1). Fatty acyl-CoA oxidase (FACO) activity and mRNA were increased after treatment with either fenofibric acid or compound 1 in rat hepatocytes. In addition, apolipoprotein CIII mRNA was decreased by both fenofibric acid and compound 1 in rat hepatocytes. Both agonists decreased apolipoprotein CIII mRNA in human hepatocytes; however, very little change in FACO activity or mRNA was observed. Furthermore, other peroxisome proliferation (PP)-associated genes including peroxisomal 3-oxoacyl-CoA thiolase (THIO), peroxisomal enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (HD), peroxisomal membrane protein-70 (PMP-70) were not regulated by PPAR alpha agonists in human hepatocytes. Moreover, other genes that are regulated by PPAR alpha ligands in human hepatocytes such as mitochondrial HMG-CoA synthase and carnitine palmitoyl transferase-1 (CPT-1) were also regulated in HepG2 cells by PPAR alpha agonists. Several stably transfected HepG2 cell lines were established that overexpressed human PPAR alpha to levels between 6- and 26-fold over normal human hepatocytes. These PPAR alpha-overexpressing cells had higher basal mRNA levels of mitochondrial HMG-CoA synthase and CPT-1; however, basal FACO mRNA levels and other PP-associated genes including THIO, HD, or PMP-70 mRNA were not substantially affected. In addition, FACO, THIO, HD, and PMP-70 mRNA levels did not increase in response to PPAR alpha agonist treatment in the PPAR alpha-overexpressing cells, although mitochondrial HMG-CoA synthase and CPT-1 mRNAs were both induced. These results suggest that other factors besides PPAR alpha levels determine the species-specific response of human and rat hepatocytes to the induction of PP.


Assuntos
Transportadores de Cassetes de Ligação de ATP , Apolipoproteínas C/genética , Regulação da Expressão Gênica/fisiologia , Hepatócitos/metabolismo , Peroxissomos/metabolismo , Receptores Citoplasmáticos e Nucleares/fisiologia , Fatores de Transcrição/fisiologia , 3-Hidroxiacil-CoA Desidrogenases/genética , Acetil-CoA C-Aciltransferase/genética , Animais , Apolipoproteína C-III , Sequência de Bases , Primers do DNA , Enoil-CoA Hidratase/genética , Hepatócitos/enzimologia , Hepatócitos/ultraestrutura , Humanos , Isomerases/genética , Proteínas de Membrana/genética , Complexos Multienzimáticos/genética , Enzima Bifuncional do Peroxissomo , Peroxissomos/enzimologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Receptores Citoplasmáticos e Nucleares/agonistas , Receptores Citoplasmáticos e Nucleares/genética , Fatores de Transcrição/agonistas , Fatores de Transcrição/genética
20.
Appl Opt ; 39(13): 2130-9, 2000 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-18345117

RESUMO

The optical characterization of a fiber-connected planar optics beam combiner dedicated to astronomical interferometry for two telescopes is presented. The beam combiner, fully integrated on a single 5 mm x 40 mm glass chip, is tested as the central part of an astronomical instrument. The single-mode waveguides are made by silver-ion-exchange technology upon glass substrates and provide spatial filtering, which improves the visibility measurement accuracy by selecting only the fundamental mode of the beams at the telescope focal plane. A global optical throughput of 43% is measured, and the sources of losses are identified and examined in detail. Solutions for improving this throughput are proposed. High and stable contrasts are obtained with a 1.55-mum laser diode (?96%) and with a white-light source (~92%) in the astronomical H filter (1.43 mum; 1.77 mum). The need for accurate control of differential instrumental polarization is demonstrated. In this context the intrinsic polarization-maintaining property of the planar optics component is characterized. This validation of the important potential uses of integrated planar optics should be valuable for future design of optical telescope arrays.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA