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1.
Neurol Sci ; 45(1): 365-367, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-37792110

RESUMEN

A 27-year-old female patient suffered from recurrent episodes of dizziness, visual rotation, and intermittent right-hand numbness over one month. Symptoms persisted and were triggered by rotating the head to the right or left for more than 10 seconds. Neurological examination showed that the symptoms were most pronounced when the head was rotated over 45 degrees to the right. Dynamic digital subtraction angiography (dDSA) was performed to confirm the diagnosis. Leftward head rotation caused occlusion of the right vertebral artery(VA) . However, the symptoms were mild, owing to sufficient compensation by the right posterior communicating artery (PCA) . Rightward head rotation exceeding 45 degrees resulted in occlusion of the left VA. The resultant symptoms were pronounced due to inadequate compensation of the left PCA. CT angiographic reconstruction showed bilateral vertebral arteries with tortuous loops of vessels at the level of the C2 vertebrae . CT images showed no cleavage between the left VA and the anterior surface of the left C2 transverse foramen. Conservative treatment was recommended considering the patient's young age and limited severity of her symptoms. Bow Hunter's syndrome is a rare neurovascular disorder characterized by dynamic occlusion of the VAs during head rotation, leading to inadequate blood flow to the posterior cerebral circulation. Bow hunter syndrome, where bilateral dynamic occlusion occurs without a discernible dominant side of the VA, is uncommon. The medical community must acknowledge cervical vertigo as a distinct disorder. dDSA remains the gold standard for its diagnosis.


Asunto(s)
Mucopolisacaridosis II , Insuficiencia Vertebrobasilar , Humanos , Femenino , Adulto , Insuficiencia Vertebrobasilar/diagnóstico por imagen , Mucopolisacaridosis II/complicaciones , Angiografía de Substracción Digital/efectos adversos , Angiografía Cerebral , Arteria Vertebral/diagnóstico por imagen , Arteria Vertebral/cirugía
2.
BMC Cancer ; 22(1): 886, 2022 Aug 13.
Artículo en Inglés | MEDLINE | ID: mdl-35964108

RESUMEN

BACKGROUND: Obesity is a high-risk factor for development and poor prognosis of triple-negative breast cancer (TNBC), which was considered as a high malignant and poor clinical outcome breast cancer subtype. TNBC proliferation and migration regulated by obesity is complex. Here, we studied effects of cytokines secreted from adipose tissue on development of TNBC. METHODS: Forty postmenopausal cases by Yuebei People's Hospital of Shaoguan with stage I/IIA TNBC were enrolled. Cytokine concentrations were examined using ELISA analysis. Proliferation and migration of TNBC cell lines were performed using CCK8 assays and Transwell tests. The Log-rank (Mantel-Cox) test, two-tailed Mann-Whitney U test and two-tailed unpaired t test were performed using GraphPad Prism 8.4.2. RESULTS: Survival analysis indicated that obese patients with TNBC had worse disease free survival (DFS) as compared with normal weight group (Hazard Ratio 4.393, 95% confidence interval (CI) of ratio 1.071-18.02, p < 0.05). Obese patients with TNBC had severe insulin resistance and high plasma triglycerides. However, plasma adiponectin concentration was decreased and interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) concentration was increased in obese TNBC patients as compared with the nonobese group. The similar results were found in the cytokine secretion from adipose tissues and insulin-resistant adipocytes. The secretion of adipose tissue from obese TNBC patients could promote proliferation and migration of TNBC cell lines, including MDA-MB-157, MDA-MB-231, MDA-MB-453 and HCC38 cells. These TNBC cell lines co-incubated with insulin-resistant 3T3-L1 adipocytes or supplementing these cytokines medium also exhibited increase of proliferative and migratory capacity. CONCLUSION: TNBC patients with obesity had worse prognosis compared with the normal weight groups. Alteration of cytokines secreted from adipose tissues mediated proliferation and migration of TNBC, leading to tumor progression in TNBC patients with obesity.


Asunto(s)
Insulinas , Neoplasias de la Mama Triple Negativas , Tejido Adiposo/patología , Línea Celular Tumoral , Movimiento Celular , Proliferación Celular , Citocinas/metabolismo , Regulación Neoplásica de la Expresión Génica , Humanos , Insulinas/metabolismo , Procesos Neoplásicos , Obesidad/complicaciones , Neoplasias de la Mama Triple Negativas/patología
3.
Neurocrit Care ; 36(3): 822-830, 2022 06.
Artículo en Inglés | MEDLINE | ID: mdl-34751418

RESUMEN

BACKGROUND: Postinterventional cerebral hyperdensities are common on non-contrast-enhanced computed tomography (CT) after endovascular thrombectomy in patients with acute ischemic stroke, which may reflect blood-brain barrier damage. The disruption of the blood-brain barrier may lead to malignant brain edema. The relationship between the extent of postinterventional cerebral hyperdensities and malignant brain edema is unclear. METHODS: Patients with middle cerebral artery territory infarction and successful recanalization were consecutively enrolled. Postinterventional non-contrast-enhanced CT was performed to evaluate postinterventional cerebral hyperdensities within 24 h after endovascular thrombectomy. On the basis of the areas of the Alberta Stroke Program Early CT Score, we devised the Hyperdensity on CT Score to evaluate the extent of postinterventional cerebral hyperdensities. The primary outcome was malignant brain edema, defined as the development of clinical signs of herniation (including a decrease in consciousness and/or anisocoria), accompanied by imaging evidence of brain swelling. The component of postinterventional cerebral hyperdensities was divided into contrast staining and hemorrhage on the basis of persistency. RESULTS: Three hundred sixty patients were included (50.6% male, mean age 67.9 years), of whom 247 (68.6%) developed postinterventional cerebral hyperdensities and 66 (18.3%) developed malignant brain edema. After adjustment for confounders, including the component of postinterventional cerebral hyperdensities, the extent of postinterventional cerebral hyperdensities assessed by the Hyperdensity on CT Score was significantly associated with malignant brain edema (odds ratio 1.46, 95% confidence interval 1.20-1.77, p < 0.001). A Hyperdensity on CT Score greater than 3 had a sensitivity of 0.73 and a specificity of 0.87 for predicting malignant brain edema. CONCLUSIONS: The extent of postinterventional cerebral hyperdensities on postinterventional non-contrast-enhanced CT was associated with malignant brain edema. The Hyperdensity on CT Score could be used to predict malignant brain edema regardless of the component of postinterventional cerebral hyperdensities.


Asunto(s)
Edema Encefálico , Isquemia Encefálica , Accidente Cerebrovascular Isquémico , Accidente Cerebrovascular , Anciano , Edema Encefálico/diagnóstico por imagen , Edema Encefálico/etiología , Isquemia Encefálica/diagnóstico por imagen , Isquemia Encefálica/terapia , Edema , Femenino , Humanos , Infarto de la Arteria Cerebral Media/diagnóstico por imagen , Infarto de la Arteria Cerebral Media/cirugía , Accidente Cerebrovascular Isquémico/diagnóstico por imagen , Accidente Cerebrovascular Isquémico/cirugía , Masculino , Estudios Retrospectivos , Accidente Cerebrovascular/diagnóstico por imagen , Accidente Cerebrovascular/cirugía , Trombectomía/métodos
4.
J Stroke Cerebrovasc Dis ; 30(10): 106002, 2021 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-34333224

RESUMEN

In the present case, we directly visualized the pendulum movement of the contrast agent downstream of a carotid near-occlusion during digital subtraction angiography, suggesting the existence of "to-and-fro" stagnant flow created by the significant flow reduction and high back pressure from visible ophthalmic collaterals with blood stagnation distal to the stenosis. The pendular movement phenomenon represents a stagnation of blood that could be associated with an increased risk of thrombus formation and subsequent embolization to more distal arterial territories. This case may partially explain not only the embolic mechanism for stroke in carotid near-occlusion but the recent observation that collateral circulation through the ipsilateral ophthalmic artery is associated independently with an increased risk of the progression of carotid near-occlusion to complete occlusion.


Asunto(s)
Angiografía de Substracción Digital , Arteria Carótida Interna/diagnóstico por imagen , Estenosis Carotídea/diagnóstico por imagen , Medios de Contraste , Accidente Cerebrovascular/etiología , Anciano , Arteria Carótida Interna/fisiopatología , Estenosis Carotídea/complicaciones , Estenosis Carotídea/fisiopatología , Estenosis Carotídea/terapia , Humanos , Masculino , Valor Predictivo de las Pruebas , Flujo Sanguíneo Regional , Accidente Cerebrovascular/diagnóstico por imagen , Accidente Cerebrovascular/fisiopatología , Accidente Cerebrovascular/terapia , Resultado del Tratamiento
5.
Br J Anaesth ; 125(1): e28-e37, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32312571

RESUMEN

Tracheal intubation in coronavirus disease 2019 (COVID-19) patients creates a risk to physiologically compromised patients and to attending healthcare providers. Clinical information on airway management and expert recommendations in these patients are urgently needed. By analysing a two-centre retrospective observational case series from Wuhan, China, a panel of international airway management experts discussed the results and formulated consensus recommendations for the management of tracheal intubation in COVID-19 patients. Of 202 COVID-19 patients undergoing emergency tracheal intubation, most were males (n=136; 67.3%) and aged 65 yr or more (n=128; 63.4%). Most patients (n=152; 75.2%) were hypoxaemic (Sao2 <90%) before intubation. Personal protective equipment was worn by all intubating healthcare workers. Rapid sequence induction (RSI) or modified RSI was used with an intubation success rate of 89.1% on the first attempt and 100% overall. Hypoxaemia (Sao2 <90%) was common during intubation (n=148; 73.3%). Hypotension (arterial pressure <90/60 mm Hg) occurred in 36 (17.8%) patients during and 45 (22.3%) after intubation with cardiac arrest in four (2.0%). Pneumothorax occurred in 12 (5.9%) patients and death within 24 h in 21 (10.4%). Up to 14 days post-procedure, there was no evidence of cross infection in the anaesthesiologists who intubated the COVID-19 patients. Based on clinical information and expert recommendation, we propose detailed planning, strategy, and methods for tracheal intubation in COVID-19 patients.


Asunto(s)
Betacoronavirus , Infecciones por Coronavirus/terapia , Intubación Intratraqueal/métodos , Equipo de Protección Personal , Neumonía Viral/terapia , Anciano , COVID-19 , China , Infecciones por Coronavirus/complicaciones , Infecciones por Coronavirus/prevención & control , Femenino , Humanos , Hipotensión/etiología , Hipoxia/etiología , Masculino , Pandemias/prevención & control , Neumonía Viral/complicaciones , Neumonía Viral/prevención & control , Neumotórax/etiología , Guías de Práctica Clínica como Asunto , Estudios Retrospectivos , SARS-CoV-2
6.
Angew Chem Int Ed Engl ; 59(45): 19919-19923, 2020 11 02.
Artículo en Inglés | MEDLINE | ID: mdl-32696611

RESUMEN

A divergent synthetic approach to biogenetically related diterpenoids such as ent-kauranes, ent-trachylobanes, ent-beyerane, and ent-atisane has been developed. The unified synthetic route involves the De Mayo reaction to rapidly generate the bicyclo[3.2.1]-octane moiety of ent-kaurane. The key reactions also include bioinspired nucleophilic cyclopropanation generating the [3.2.1.02,7 ]-tricyclic core of ent-trachylobane and regioselective cyclopropane fragmentation furnishing ent-beyerane and ent-atisane through the nucleophilic attack and protonation of the cyclopropane ring. This strategy enables the asymmetric total syntheses of six diterpenoids from the commercially available geraniol.

7.
J Nat Prod ; 82(5): 1114-1119, 2019 05 24.
Artículo en Inglés | MEDLINE | ID: mdl-31013087

RESUMEN

Two new p-terphenyls, strepantibins A and B (1 and 2), along with the first representative of a naturally occurring bisphenyltropone, strepantibin C (3), were characterized from a Streptomyces sp. associated with the larvae of the mud dauber wasp Sceliphron madraspatanum. Their structures were determined by high-resolution electrospray ionization mass spectrometry, NMR, and X-ray crystallography data interpretation. Strepantibins A-C inhibited hexokinase II (HK2) activity and displayed antiproliferative activity against hepatoma carcinoma cells HepG-2, SMMC-7721 and plc-prf-5. In SMMC-7721 cells treated with strepantibin A, the morphological characteristics of apoptosis were observed.


Asunto(s)
Antineoplásicos/aislamiento & purificación , Inhibidores Enzimáticos/aislamiento & purificación , Hexoquinasa/antagonistas & inhibidores , Streptomyces/química , Avispas/microbiología , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Células Hep G2 , Humanos , Espectroscopía de Resonancia Magnética , Espectrometría de Masa por Ionización de Electrospray
8.
J Stroke Cerebrovasc Dis ; 28(12): 104440, 2019 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-31611167

RESUMEN

Carotid artery web has been frequently reported. However, the vertebral artery web has been less reported. It is difficult and seldom to diagnose vertebral artery web with noninvasive examinations. Here, we present a case of asymptomatic vertebral artery web diagnosed by ultrasound and confirmed by digital subtraction angiography.


Asunto(s)
Angiografía de Substracción Digital , Ultrasonografía Doppler en Color , Malformaciones Vasculares/diagnóstico por imagen , Arteria Vertebral/diagnóstico por imagen , Femenino , Humanos , Ataque Isquémico Transitorio/etiología , Persona de Mediana Edad , Paresia/etiología , Valor Predictivo de las Pruebas , Pronóstico , Malformaciones Vasculares/complicaciones , Malformaciones Vasculares/fisiopatología , Malformaciones Vasculares/terapia , Arteria Vertebral/anomalías , Arteria Vertebral/fisiopatología
9.
Bioorg Med Chem Lett ; 28(12): 2201-2205, 2018 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-29764742

RESUMEN

The sodium glucose co-transporter 2 (SGLT2) was considered as an important target for the treatment of type 2 diabetes mellitus in recent years. This report describes the design and synthesis of a series of novel SGLT2 inhibitors (11a-17a) as well as their dehydrate dihydrofuran derivatives (11b-17b), which were prepared by Mitsunobu reaction. Their SGLT2 inhibitory activity was also evaluated, and 16a and 17a were found to be the most potent compounds with IC50 values of 0.63 and 0.81 nM, respectively. However, all the dehydrate derivatives lose the SGLT2 inhibitory activity, with inhibition percentage no more than 66.5% at the concentration of 0.5 µM, which might because of the configuration inversion at C-2 of glucose. In conclusion, the present study improves understanding of the SAR of SGLT2 inhibitors, and provided more information that could be applied to design new molecules.


Asunto(s)
Glucósidos/farmacología , Inhibidores del Cotransportador de Sodio-Glucosa 2/farmacología , Transportador 2 de Sodio-Glucosa/metabolismo , Cristalografía por Rayos X , Relación Dosis-Respuesta a Droga , Glucósidos/síntesis química , Glucósidos/química , Humanos , Modelos Moleculares , Conformación Molecular , Inhibidores del Cotransportador de Sodio-Glucosa 2/síntesis química , Inhibidores del Cotransportador de Sodio-Glucosa 2/química , Relación Estructura-Actividad
10.
Bioorg Med Chem Lett ; 28(9): 1545-1549, 2018 05 15.
Artículo en Inglés | MEDLINE | ID: mdl-29606575

RESUMEN

Diversity-oriented synthesis of derivatives of natural products is an important approach for the discovery of novel drugs. In this paper, a series of novel 3,4-diaryl-1H-pyrazoles and 3,5-diaryl-1H-pyrazoles derivatives were synthesized through the one-pot reaction of flavones and isoflavones with the hydrazine hydrate and substituted hydrazine hydrate. Some of these novel compounds exhibited antifungal effects against Candida albicans SC5314, and displayed more potent inhibitory activities against the efflux-pump-deficient strain DSY654. In addition, compounds 25, 28 and 32a displayed outstanding reversal activity of azole resistance against clinical azole-resistant Candida albicans in combination with fluconazole (FLC), with FICI values ranging from 0.012 to 0.141. The preliminary structure-activity relationship (SAR) of these compounds was also discussed. In conclusion, this study provides several novel agents that displayed potent antifungal activities alone or together with fluconazole, which makes progress for development of antifungal drugs.


Asunto(s)
Antifúngicos/farmacología , Candida albicans/efectos de los fármacos , Descubrimiento de Drogas , Farmacorresistencia Fúngica/efectos de los fármacos , Flavonas/farmacología , Isoflavonas/farmacología , Pirazoles/farmacología , Antifúngicos/síntesis química , Antifúngicos/química , Relación Dosis-Respuesta a Droga , Flavonas/química , Fluconazol/química , Fluconazol/farmacología , Isoflavonas/química , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Pirazoles/síntesis química , Pirazoles/química , Relación Estructura-Actividad
11.
Bioorg Med Chem ; 26(14): 4320-4328, 2018 08 07.
Artículo en Inglés | MEDLINE | ID: mdl-30049584

RESUMEN

Four new diterpenoids scapanacins A-D (1-4) including one kaurane and three clerodane derivatives, along with eleven known compounds (9-15), were isolated from the Chinese liverwort Scapania carinthiaca J.B. Jack ex Lindb. Their structures were determined based on extensive spectroscopic analyses, and electronic circular dichroism (ECD) calculations. Vasorelaxant activity assays of the clerodane-type diterpenoids 2, and 4-8 revealed that they relaxed 3rd-order rat mesenteric arterioles pre-contracted with norepinephrine (NE). Further assays with scapanacin D (4) confirmed that the vasodilatation was mediated through inhibition of Ca2+ influx via voltage-dependent Ca2+ channels (VDCs), and this Ca2+ channel blocking effect was also confirmed by inhibiting the extracellular Ca2+ influx in MOVAS cells. Besides, very little decrease of the relaxant activity caused by 4 on endothelium-denuded mesenteric arterioles with NE also suggested the vasodilatation was mainly produced by inhibiting Ca2+-induced contraction of smooth muscle. In addition, cytotoxicity testing showed that compounds 1 and 9 with α,ß-unsaturated ketone exhibited inhibitory activities against a small panel of human cancer cell lines.


Asunto(s)
Antineoplásicos Fitogénicos/farmacología , Vasos Sanguíneos/efectos de los fármacos , Hepatophyta/química , Terpenos/farmacología , Vasodilatación/efectos de los fármacos , Vasodilatadores/farmacología , Animales , Antineoplásicos Fitogénicos/química , Antineoplásicos Fitogénicos/aislamiento & purificación , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , China , Relación Dosis-Respuesta a Droga , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Conformación Molecular , Ratas , Ratas Wistar , Relación Estructura-Actividad , Terpenos/química , Terpenos/aislamiento & purificación , Vasodilatadores/química , Vasodilatadores/aislamiento & purificación
12.
Proc Natl Acad Sci U S A ; 112(25): 7662-7, 2015 Jun 23.
Artículo en Inglés | MEDLINE | ID: mdl-26056281

RESUMEN

As the world's second largest sand sea and one of the most important dust sources to the global aerosol system, the formation of the Taklimakan Desert marks a major environmental event in central Asia during the Cenozoic. Determining when and how the desert formed holds the key to better understanding the tectonic-climatic linkage in this critical region. However, the age of the Taklimakan remains controversial, with the dominant view being from ∼ 3.4 Ma to ∼ 7 Ma based on magnetostratigraphy of sedimentary sequences within and along the margins of the desert. In this study, we applied radioisotopic methods to precisely date a volcanic tuff preserved in the stratigraphy. We constrained the initial desertification to be late Oligocene to early Miocene, between ∼ 26.7 Ma and 22.6 Ma. We suggest that the Taklimakan Desert was formed as a response to a combination of widespread regional aridification and increased erosion in the surrounding mountain fronts, both of which are closely linked to the tectonic uplift of the Tibetan-Pamir Plateau and Tian Shan, which had reached a climatically sensitive threshold at this time.

13.
Molecules ; 23(7)2018 07 04.
Artículo en Inglés | MEDLINE | ID: mdl-29973530

RESUMEN

Alkenal double bond reductases (DBRs), capable of catalyzing the NADPH-dependent reduction of the α,ß-unsaturated double bond, play key roles in the detoxication of alkenal carbonyls. Here, the isolation and characterization of two DBRs encoded by the liverwort species Marchantia paleacea are described. The two DBRs share a relatively low similarity, and phylogenetic analysis indicated that MpMDBRL is more closely related to microbial DBRs than to other plant DBRs, while MpDBR shares common ancestry with typical plant DBRs. Both DBR proteins exhibited hydrogenation ability towards hydroxycinnamyl aldehydes; however, their temperature optimums were strikingly different. MpMDBRL demonstrated slightly weaker catalytic efficiency compared to MpDBR, and the structural models of their active binding sites to the substrate may provide a parsimonious explanation. Furthermore, both DBRs significantly responded to phytohormone treatment. In conclusion, M. paleacea produces two distinct types of functional DBRs, both of which participate in the protection against environmental stress in liverwort. The presence of a microbial type of DBR in a plant is herein reported for the first time.


Asunto(s)
Marchantia/enzimología , Oxidorreductasas/genética , Oxidorreductasas/metabolismo , Dominio Catalítico , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Hidrogenación , Marchantia/química , Marchantia/genética , Modelos Moleculares , Oxidorreductasas/química , Filogenia , Reguladores del Crecimiento de las Plantas/farmacología , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo
15.
J Med Virol ; 89(10): 1865-1870, 2017 10.
Artículo en Inglés | MEDLINE | ID: mdl-28504470

RESUMEN

Hantavirus infection during pregnancy can influence both maternal and fetal outcomes. Here, we describe four cases of hemorrhagic fever with renal syndrome (HFRS) in pregnant Chinese women. The HFRS put these women at increased risk for severe illness, despite the patients' symptomologies in the onset phase were similar to those observed in non-pregnant HFRS patients, such as fever, headache, nausea, and thrombocytopenia. Pregnant women appeared to have a more severe status, presenting with severe complications, such as hypervolemia and pulmonary edema. Nevertheless, with appropriate management, mothers with HFRS may carry to full-term and breastfeeding maybe safe and feasible.


Asunto(s)
Virus Hantaan/aislamiento & purificación , Fiebre Hemorrágica con Síndrome Renal/virología , Riñón/virología , Complicaciones Infecciosas del Embarazo/virología , Adulto , Anticuerpos Antivirales/sangre , China/epidemiología , Femenino , Fiebre , Fiebre Hemorrágica con Síndrome Renal/epidemiología , Humanos , Riñón/fisiopatología , Embarazo , Adulto Joven
17.
Bioorg Med Chem Lett ; 26(15): 3617-20, 2016 08 01.
Artículo en Inglés | MEDLINE | ID: mdl-27297569

RESUMEN

We describe the synthesis and biological evaluation of riccardin D derivatives, a novel class of antimicrobial molecules. Structural diversification of these derivatives was achieved by introducing hydroxy, methoxy, and bromine into the aromatic rings of riccardin D. The antimicrobial evaluation of these compounds was performed as in vitro assays against clinically isolated bacteria and fungi. The introduction of bromine atom into the arene B of riccardin D led to several strongly active antibacterial compounds with a MIC value ranging from 0.5 to 4µg/mL for Staphylococcus aureus, both methicillin-sensitive and -resistant strains. Antifungal tests found compound 34 was the most potent molecule with a MIC value of 2µg/mL against Candida albicans. This initial biological evaluation suggests that these novel molecules merit further investigation as potential antimicrobial agents.


Asunto(s)
Antibacterianos/farmacología , Antifúngicos/farmacología , Bacterias/efectos de los fármacos , Hongos/efectos de los fármacos , Éteres Fenílicos/farmacología , Estilbenos/farmacología , Antibacterianos/síntesis química , Antibacterianos/química , Antifúngicos/síntesis química , Antifúngicos/química , Relación Dosis-Respuesta a Droga , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Éteres Fenílicos/síntesis química , Éteres Fenílicos/química , Estilbenos/síntesis química , Estilbenos/química , Relación Estructura-Actividad
20.
Proc Natl Acad Sci U S A ; 110(19): 7556-61, 2013 May 07.
Artículo en Inglés | MEDLINE | ID: mdl-23610418

RESUMEN

The development of fluvial systems in East Asia is closely linked to the evolving topography following India-Eurasia collision. Despite this, the age of the Yangtze River system has been strongly debated, with estimates ranging from 40 to 45 Ma, to a more recent initiation around 2 Ma. Here, we present (40)Ar/(39)Ar ages from basalts interbedded with fluvial sediments from the lower reaches of the Yangtze together with detrital zircon U-Pb ages from sand grains within these sediments. We show that a river containing sediments indistinguishable from the modern river was established before ~23 Ma. We argue that the connection through the Three Gorges must postdate 36.5 Ma because of evaporite and lacustrine sedimentation in the Jianghan Basin before that time. We propose that the present Yangtze River system formed in response to regional extension throughout eastern China, synchronous with the start of strike-slip tectonism and surface uplift in eastern Tibet and fed by strengthened rains caused by the newly intensified summer monsoon.

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