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1.
Rev Sci Instrum ; 94(3): 033508, 2023 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-37012805

RESUMO

The fast-ion D-alpha diagnostic (FIDA) is employed to detect Dα light emitted by neutralized fast ions during neutral beam injection. A tangentially viewing FIDA has been developed for the HuanLiuqi-2A (HL-2A) tokamak and typically achieves temporal and transverse spatial resolutions of ∼30 ms and ∼5 cm, respectively. A fast-ion tail on the red shifted wing of the FIDA spectrum is obtained and analyzed with the Monte Carlo code FIDASIM. Good agreement has been presented between the measured and simulated spectra. As the FIDA diagnostic's lines of sight intersect the central axis of neutral beam injection with small angles, the beam emission spectrum is observed with a large Doppler shift. Thus, tangentially viewing FIDA could detect only a small portion of fast ions with an energy of ≈ 20 ∼ 31 keV and a pitch angle of ≈ -1 ∼ -0.8. A second FIDA installation with oblique viewing is designed to minimize spectral contaminants.

2.
Rev Sci Instrum ; 93(11): 113507, 2022 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-36461440

RESUMO

A new neutral particle analyzer (NPA) diagnostic based on single crystal chemical vapor deposition (sCVD) diamond detector that provides measurements of fast ions has been designed and installed on HL-2A tokamak. Diamond detectors have been applied in some magnetic confinement fusion devices due to their outstanding properties of compact size and radiation hardness. This DNPA can measure energies above 13.4 keV. The line of sight (LOS) of the DNPA intersects with the NBI No. 2 with a tangency radius of 154.8 cm. Due to the pitch angle defined by the LOS and geometry of the diagnostic, the DNPA is mainly sensitive to trapped ions. To interpret the energy spectrum and verify the feasibility of the design of the DNPA, a Monte Carlo code called FIDASIM, which is a synthetic diagnostic code that simulates fast ion D-alpha and NPA signals, is applied to model the neutral flux reaching the detector. The results show that the flux is mainly contributed by the low energy fast ions (E < 10 keV) and it is mainly coming from the active components, the passive signal is dominant in the high energy region (E > 15 keV). The modeling features the ability to distinguish between active and passive signals, and the simulated strong passive signals are suggested to come from charge exchange between cold neutrals and fast ions around the plasma edge. In addition, despite the large ratio of halo neutrals, essentially it has a limited contribution to the energy spectrum.

3.
Eur Rev Med Pharmacol Sci ; 25(18): 5610-5618, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34604953

RESUMO

OBJECTIVE: This study aims to explore the biological roles of long non-coding RNA (lncRNA) ZNF281 and KLF15 in regulating cervical carcinoma progression. PATIENTS AND METHODS: Differential expressions of ZNF281 in 58 collected cervical carcinoma and normal tissues were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The relationship between ZNF281 and clinicopathologic characteristics in cervical carcinoma patients was analyzed. By generating ZNF281 knockdown model in HeLa and SiHa cells through the transfection of shZNF281, migratory ability changes were examined via transwell and wound healing assay. The role of ZNF281 in in vivo tumorgenicity of cervical carcinoma was examined by implanting xenografted cancers in nude mice. The downstream target of ZNF281 and their interaction were assessed by bioinformatics tool and Dual-Luciferase reporter assay, respectively. Finally, co-regulations of ZNF281 and KLF15 on cervical carcinoma progression were elucidated. RESULTS: ZNF281 was upregulated in cervical carcinoma tissues and cell lines. It was correlated to TNM staging, and incidences of lymphatic metastasis and distant metastasis in cervical carcinoma patients, while it was unrelated to age and tumor size. The knockdown of ZNF281 effectively attenuated migratory ability in HeLa and SiHa cells. Besides, knockdown of ZNF281 also reduced tumorigenicity of cervical carcinoma in nude mice. KLF15 was the downstream gene binding ZNF281, and they were negatively correlated to each other in cervical carcinoma tissues. Notably, KLF15 was responsible for ZNF281-induced regulation on cervical carcinoma migration. CONCLUSIONS: LncRNA ZNF281 is upregulated in cervical carcinoma samples, and it is correlated to lymphatic metastasis, distant metastasis, and poor prognosis in cervical carcinoma patients. By targeting KLF15, ZNF281 triggers migratory potential in cervical carcinoma. We believed that ZNF281 is a promising biomarker for cervical carcinoma.


Assuntos
Regulação Neoplásica da Expressão Gênica/genética , Fatores de Transcrição Kruppel-Like/metabolismo , Fatores de Transcrição Kruppel-Like/fisiologia , RNA Longo não Codificante/metabolismo , RNA Longo não Codificante/fisiologia , Proteínas Repressoras/metabolismo , Proteínas Repressoras/fisiologia , Neoplasias do Colo do Útero/genética , Animais , Carcinogênese/genética , Linhagem Celular Tumoral , Movimento Celular/genética , Progressão da Doença , Feminino , Células HeLa , Humanos , Metástase Linfática/genética , Camundongos Nus , Ligação Proteica/genética , Neoplasias do Colo do Útero/patologia
4.
Plant Dis ; 103(8): 1889-1901, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31161920

RESUMO

Apple fruit spot disease has caused serious economic losses for years in China since the widespread application of fruit bagging in production. Although the three genera Trichothecium, Alternaria, and Acremonium have been reported to be the causal agents, studies on the disease etiology and pathogen biology are still sparse. Here, we report characterization of eight fungal isolates from lesions on 126 symptomatic fruit samples collected in Shaanxi Province, China. Pathogenicity of the isolates was assessed. DNA sequences were obtained at four loci, including D1/D2 domains of the large-subunit nrRNA gene, internal transcribed spacer regions 1 and 2, 5.8S nrDAN gene, a fragment of the actin gene, and a fragment of the ß-tubulin. Based on phylogenetic analysis and morphological features, three new species were found: Acremonium mali, Sarocladium liquanensis, and Sarocladium mali. In addition, we made the first report of Sarocladium terricola as a plant pathogen. Temperature and moisture significantly affected in vitro conidial germination of five Acremonium-like species, and their impact on infection of apple fruit was tested using Acremonium sclerotigenum. Conidia of five species germinated from 15 to 35°C in free water; four of the species had optimum temperature around 25°C, whereas conidia of S. terricola had an optimum temperature of 30°C. Conidial germination rate increased as relative humidity (RH) increased. The five isolates had relatively high conidial germination rates at RH > 97%, with a significant decline at 95% RH. Incidence of infection also increased in proportion to RH. In free water, conidial germination was relatively unaffected by temperature.


Assuntos
Acremonium , Ascomicetos , Frutas , Malus , Acremonium/classificação , Acremonium/fisiologia , Ascomicetos/classificação , Ascomicetos/fisiologia , China , Frutas/microbiologia , Malus/microbiologia , Filogenia , Temperatura
5.
Rev Sci Instrum ; 87(11): 11E552, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27910605

RESUMO

In toroidal magnetic fusion devices, fast-ion D-alpha diagnostic (FIDA) is a powerful method to study the fast-ion feature. The fast-ion characteristics can be inferred from the Doppler shifted spectrum of Dα light according to charge exchange recombination process between fast ions and probe beam. Since conceptual design presented in the last HTPD conference, significant progress has been made to apply FIDA systems on the Experimental Advanced Superconducting Tokamak (EAST). Both co-current and counter-current neutral beam injectors are available, and each can deliver 2-4 MW beam power with 50-80 keV beam energy. Presently, two sets of high throughput spectrometer systems have been installed on EAST, allowing to capture passing and trapped fast-ion characteristics simultaneously, using Kaiser HoloSpec transmission grating spectrometer and Bunkoukeiki FLP-200 volume phase holographic spectrometer coupled with Princeton Instruments ProEM 1024B eXcelon and Andor DU-888 iXon3 1024 CCD camera, respectively. This paper will present the details of the hardware descriptions and experimental spectrum.

6.
Rev Sci Instrum ; 87(11): 11D616, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27910316

RESUMO

Volume recombination plays an important role towards plasma detachment for magnetically confined fusion devices. High quantum number states of the Balmer series of deuterium are used to study recombination. On EAST (Experimental Advanced Superconducting Tokamak), two visible spectroscopic measurements are applied for the upper/lower divertor with 13 channels, respectively. Both systems are coupled with Princeton Instruments ProEM EMCCD 1024B camera: one is equipped on an Acton SP2750 spectrometer, which has a high spectral resolution ∼0.0049 nm with 2400 gr/mm grating to measure the Dα(Hα) spectral line and with 1200 gr/mm grating to measure deuterium molecular Fulcher band emissions and another is equipped on IsoPlane SCT320 using 600 gr/mm to measure high-n Balmer series emission lines, allowing us to study volume recombination on EAST and to obtain the related line averaged plasma parameters (Te, ne) during EAST detached phases. This paper will present the details of the measurements and the characteristics of deuterium Balmer series line emissions during density ramp-up L-mode USN plasma on EAST.

7.
Rev Sci Instrum ; 87(11): 11E542, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27910390

RESUMO

To investigate the fast ion behavior, a fast ion D-alpha (FIDA) diagnostic system has been installed on EAST. Fast ion features can be inferred from the Doppler shifted spectrum of Balmer-alpha light from energetic hydrogenic atoms. This paper will focus on the validation of FIDA measurements performed using MHD-quiescent discharges in 2015 campaign. Two codes have been applied to calculate the Dα spectrum: one is a Monte Carlo code, Fortran 90 version FIDASIM, and the other is an analytical code, Simulation of Spectra (SOS). The predicted SOS fast-ion spectrum agrees well with the measurement; however, the level of fast-ion part from FIDASIM is lower. The discrepancy is possibly due to the difference between FIDASIM and SOS velocity distribution function. The details will be presented in the paper to primarily address comparisons of predicted and observed spectrum shapes/amplitudes.

8.
Rev Sci Instrum ; 87(11): 11D429, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27910502

RESUMO

A filterscope diagnostic system has been mounted to observe the line emission and visible bremsstrahlung emission from plasma on the experimental advanced superconducting tokamak during the 2014 campaign. By this diagnostic system, multiple wavelengths including Dα (656.1 nm), Dγ (433.9 nm), He ii (468.5 nm), Li i (670.8 nm), Li ii (548.3 nm), C iii (465.0 nm), O ii (441.5 nm), Mo i (386.4 nm), W i (400.9 nm), and visible bremsstrahlung radiation (538.0 nm) are monitored with corresponding wavelength filters. All these multi-channel signals are digitized at up to 200 kHz simultaneously. This diagnostic plays a crucial role in studying edge localized modes and H-mode plasmas, due to the high temporal resolution and spatial resolution that have been designed into it.

9.
Genet Mol Res ; 14(2): 5699-709, 2015 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-26125769

RESUMO

Three-dimensional ultrasound speckle tracking imaging was used to evaluate the effects of recombinant human brain natriuretic peptide (rhBNP) in acute anterior and extensive anterior myocardial infarction. Ninety patients with acute anterior or extensive myocardial infarction were randomly divided into 3 groups: Group A [emergency percutaneous coronary intervention (PCI)], Group B (emergency PCI + rhBNP early treatment), and Group C (emergency PCI + late rhBNP treatment). Within 6 h of admission and at 1 week and 3 and 6 months after PCI, patients underwent routine transthoracic echocardiography and real-time three-dimensional echocardiography. At 1 week, 1 month, 3 months, 6 months, and 12 months, ejection fraction values in groups B and C were significantly greater than those in group A (P < 0.05), and left ventricular end-diastolic volume and left ventricular end-systolic volume values in groups B and C were less than those in group A (P < 0.05). Within 6 h of admission in each group, long-axis, radial, circumferential, and area variables corresponding to anterior descending artery segments showed no significant difference (all P > 0.05). However, at 1 week, 1 month, 3 months, 6 months, and 12 months, long-axis, radial, circumferential and area variables in groups B and C were significantly less than those in group A (P < 0.05). Intervention with rhBNP can im-prove resilience of the local myocardium, left ventricular mechanical function, and cardiac remodeling. Within 6 h of admission or after PCI, rhBNP application showed no significant difference in heart function improvement or myocardial remodeling inhibition.


Assuntos
Infarto Miocárdico de Parede Anterior/tratamento farmacológico , Peptídeo Natriurético Encefálico/administração & dosagem , Proteínas Recombinantes/administração & dosagem , Função Ventricular/efeitos dos fármacos , Adulto , Idoso , Infarto Miocárdico de Parede Anterior/diagnóstico por imagem , Infarto Miocárdico de Parede Anterior/genética , Infarto Miocárdico de Parede Anterior/patologia , Infarto Miocárdico de Parede Anterior/cirurgia , Ecocardiografia Tridimensional , Feminino , Humanos , Imageamento Tridimensional , Masculino , Pessoa de Meia-Idade , Peptídeo Natriurético Encefálico/genética , Radiografia , Proteínas Recombinantes/genética , Função Ventricular/genética
10.
Eur Rev Med Pharmacol Sci ; 19(6): 1101-16, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25855938

RESUMO

OBJECTIVE: DESs have been proved to be beneficial for patients with chronic total coronary occlusions (CTO) in terms of cardiac function and other prognosis. We aim to compare the efficacy and safety of drug-eluting stent (DES) and bare-metal stent (BMS) in CTO recanalization at different follow-up duration. METHODS: Articles comparing outcomes between DES and BMS implantation in patients with CTO was searched. A fixed-effect (inverse-variance weighted) and random-effect (DerSimonian and Laird) model were used to analyze the pooling results. RESULTS: A total of 29 comparative studies including 24 cohort studies and 5 randomized controlled studies were identified with a total of 9140 patients (5008 received BMS and 4132 received DES). The risk of all cause death for DES was higher at 6 months and lower at 12 months than BMS, and no significant difference was shown at 24, 36 and 60 months. DES group had lower risk of MI after 12 months implantation, and no difference was shown at 6, 24, 36 and 60 months. Major adverse cardiovascular event (MACE)-free survival was clinically and significantly improved by 73%, 68%, 49%, 40% and 37% respectively in DES group at 6,12, 24, 36, and 60 months. CONCLUSIONS: DES is superior to BMS in binary restenosis, reocclusion and MACE-free survival during long-term follow up. The occurrences of all-cause death and MI show that the risk rate of BMS is higher than that of DES at 12 months. The frequency of all-cause death of DES is higher than BMS at 6 months. DES has higher risk of in-stent thrombosis than BMS at 36 months of implantation.


Assuntos
Oclusão Coronária/diagnóstico , Oclusão Coronária/cirurgia , Stents Farmacológicos , Causas de Morte/tendências , Doença Crônica , Estudos de Coortes , Oclusão Coronária/mortalidade , Seguimentos , Humanos , Ensaios Clínicos Controlados Aleatórios como Assunto/mortalidade , Fatores de Tempo , Resultado do Tratamento
11.
Bull Entomol Res ; 104(6): 742-50, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25208627

RESUMO

Rhynchophorus ferrugineus (Coleoptera, Curculionidae) is the most destructive pest of palm trees worldwide containing it invasive areas, such as the southern part of China. It is always emphasized to develop integrated pest management based on biological agents, but their success is not very exciting. Presently, the immune defenses of this pest against biological agents attract scarce attention. It is still unclear whether immune priming also generally occurs in insect pests and in response to different pathogens. Our results indicated that previous challenge of bacteria pathogen enhanced the magnitude of phenoloxidase activity and antibacterial activity in R. ferrugineus larvae against the secondary infection. Furthermore, trans-generational immune priming was also determined in this pest, and only challenged R. ferrugineus mothers transferred the immune protection to their offspring which suggested males and females of this pest might have evolved different strategies on the investment of delivering immune protection to their offspring. Importantly, our data provide the evidence to suggest that different kinds of biological control agents might be used alternatively or in combination to fight against R. ferrugineus because of the existence of immune priming with low species-specific level. On the other hand, for this invasive pest, the immune priming may also facilitate its adaptation and dispersal in the new regions.


Assuntos
Gorgulhos/imunologia , Gorgulhos/microbiologia , Animais , Escherichia coli/fisiologia , Feminino , Imunidade Inata , Larva/imunologia , Larva/microbiologia , Masculino , Gorgulhos/crescimento & desenvolvimento
12.
Eur Rev Med Pharmacol Sci ; 17(12): 1583-9, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23832722

RESUMO

BACKGROUND: Coronary chronic total occlusion (CTO) is the end stage of coronary artery atherosclerosis. CTO revascularization can be performed by percutaneous transluminal coronary angioplasty (PTCA), bare metal stent (BMS) or drug-eluting stent (DES). It is important to scientifically evaluate the effectiveness of CTO interventional treatments. METHODS: Relevant studies of long term outcomes for several kinds of CTO treatments were examined. Data were extracted and assessed by two independent clinical experts, pooled and analyzed using meta-analysis. RESULTS: (1) Totally 8 articles comparing outcomes between PTCA and BMS treatment were analyzed. Follow-up variables such as mortality, subsequent coronary artery bypass graft surgery (CABG), re-occlusion, re-stenosis and target lesion revascularization (TLR) were analyzed by meta-analysis. Compared with BMS intervention, PTCA was associated with significant higher rate of re-occlusion, re-stenosis, subsequent PTCA and TLR. (2) Totally 12 articles compared long term outcomes between BMS groups and DES groups, encompassed 3605 CTO patients. During the long-term follow-up, six variables as major adverse cardiac events (MACE), myocardial infarction, all-cause death, subsequent CABG, accumulated MACE-free survival rate, re-stenosis/re-occlusion rate were analyzed by meta-analysis. Compared with patients in DES groups, patients in BMS groups had significant higher MACE, subsequent CABG, re-stenosis/re-occlusion rate, TLR, target vessel revascularization, while lower MACE-free survival rate. CONCLUSIONS: Incidence of re-occlusion, re-stenosis, subsequent PTCA and TLR were significantly lower for BMS implantation than for PTCA procedure. Variables, including MACE, subsequent CABG, re-stenosis/re-occlusion rate were higher while accumulated MACE-free survival rate was lower in BMS groups than in DES groups.


Assuntos
Oclusão Coronária/cirurgia , Angioplastia Coronária com Balão , Humanos , Stents
13.
Chem Commun (Camb) ; 48(91): 11235-7, 2012 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-23069792

RESUMO

A postsynthesis assembly approach, an ex situ ligand exchange route, was developed for fast (within 2 h) and high loading (34% coverage) deposition of CdSe QDs on TiO(2) films. With the combination of high-quality QD sensitizers and the effective deposition technique, a record photovoltaic performance with an efficiency of 5.4% was observed for the resulting cell device.

14.
Mol Psychiatry ; 16(5): 548-56, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-20386566

RESUMO

We report the first genome-wide association study in 1000 bipolar I patients and 1000 controls, with a replication of the top hits in another 409 cases and 1000 controls in the Han Chinese population. Four regions with most strongly associated single-nucleotide polymorphisms (SNPs) were detected, of which three were not found in previous GWA studies in the Caucasian populations. Among them, SNPs close to specificity protein 8 (SP8) and ST8 α-N-acetyl- neuraminide α-2,8-sialyltransferase (ST8SIA2) are associated with Bipolar I, with P-values of 4.87 × 10(-7) (rs2709736) and 6.05 × 10(-6) (rs8040009), respectively. We have also identified SNPs in potassium channel tetramerization domain containing 12 gene (KCTD12) (rs2073831, P=9.74 × 10(-6)) and in CACNB2 (Calcium channel, voltage-dependent, ß-2 subunit) gene (rs11013860, P=5.15 × 10(-5)), One SNP nearby the rs1938526 SNP of ANK3 gene and another SNP nearby the SNP rs11720452 in chromosome 3 reported in previous GWA studies also showed suggestive association in this study (P=6.55 × 10(-5) and P=1.48 × 10(-5), respectively). This may suggest that there are common and population-specific susceptibility genes for bipolar I disorder.


Assuntos
Transtorno Bipolar/etnologia , Transtorno Bipolar/genética , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Polimorfismo de Nucleotídeo Único/genética , Anquirinas/genética , Povo Asiático/etnologia , Povo Asiático/genética , Transtorno Bipolar/epidemiologia , Canais de Cálcio Tipo L/genética , Proteínas de Ligação a DNA/genética , Feminino , Genótipo , Humanos , Masculino , Razão de Chances , Fenótipo , Proteínas/genética , Reprodutibilidade dos Testes , Sialiltransferases/genética , Fatores de Transcrição/genética
15.
J Phys Condens Matter ; 22(1): 016002, 2010 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-21386237

RESUMO

Room temperature ferromagnetic Cu-doped ZnO nanowires have been synthesized using the chemical vapor deposition method. By combining structural characterizations and comparative annealing experiments, it has been found that both extrinsic (CuO nanoparticles) and intrinsic (Zn(1-x)Cu(x)O nanowires) sources are responsible for the observed ferromagnetic ordering of the as-grown samples. As regards the former, annealing in Zn vapor led to a dramatic decrease of the ferromagnetism. For the latter, a reversible switching of the ferromagnetism was observed with sequential annealings in Zn vapor and oxygen ambience respectively, which agreed well with previous reports for Cu-doped ZnO films. In addition, we have for the first time observed low temperature photoluminescence changed with magnetic properties upon annealing in different conditions, which revealed the crucial role played by interstitial zinc in directly mediating high T(c) ferromagnetism and indirectly modulating the Cu-related structured green emission via different charge transfer transitions.

16.
J Bacteriol ; 185(23): 6893-901, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14617653

RESUMO

The Vibrio pathogenicity island (VPI) in epidemic Vibrio cholerae is an essential virulence gene cluster. Like many pathogenicity islands, the VPI has at its termini a phage-like integrase gene (int), a transposase-like gene (vpiT), and phage-like attachment (att) sites, and is inserted at a tRNA-like locus (ssrA). We report that the VPI precisely excises from the chromosome and that its left and right ends join to form an extrachromosomal circular excision product (pVPI). Two-stage nested PCR analysis and DNA sequencing confirmed the int-att-vpiT junction and that the core attP of pVPI is identical to the chromosomal VPI attR site. Excision was independent of toxR and toxT. Excision was independent of recA, suggesting that it is mediated by site-specific recombination. Interestingly, while excision was detected in int and vpiT mutants, excision was abolished in a double (int vpiT) mutant and was restored by plasmids containing genes for either recombinase. Excision results in deletion of A361 in the ssrA locus, which flanks the right junction of the VPI. Since A361 encodes U70 in the critical G. U base pair in the acceptor stem of the ssrA RNA that is the determinant for aminoacylation with alanine, this deletion might have deleterious effects on ssrA function. Also, vpiT may have undergone interchromosomal translocation or may represent an independent integration event, as it was found downstream of hutA in some isolates. Our results provide new insight into the molecular biology of the VPI, and we propose that the process of excision and circularization is important in the emergence, pathogenesis, and persistence of epidemic V. cholerae.


Assuntos
Cromossomos Bacterianos/genética , Genes Bacterianos , Família Multigênica , Vibrio cholerae/genética , Mutação , Reação em Cadeia da Polimerase , Recombinases/fisiologia , Recombinação Genética , Translocação Genética , Vibrio cholerae/patogenicidade , Virulência
17.
Nature ; 413(6854): 413-7, 2001 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-11574886

RESUMO

The timing of the earliest habitation and oldest stone technologies in different regions of the world remains a contentious topic in the study of human evolution. Here we contribute to this debate with detailed magnetostratigraphic results on two exposed parallel sections of lacustrine sediments at Xiaochangliang in the Nihewan Basin, north China; these results place stringent controls on the age of Palaeolithic stone artifacts that were originally reported over two decades ago. Our palaeomagnetic findings indicate that the artifact layer resides in a reverse polarity magnetozone bounded by the Olduvai and Jaramillo subchrons. Coupled with an estimated rate of sedimentation, these findings constrain the layer's age to roughly 1.36 million years ago. This result represents the age of the oldest known stone assemblage comprising recognizable types of Palaeolithic tool in east Asia, and the earliest definite occupation in this region as far north as 40 degrees N.


Assuntos
Evolução Biológica , Hominidae , Animais , Arqueologia , China , Fósseis , Sedimentos Geológicos , Humanos , Tempo
18.
Biochemistry ; 40(27): 8118-25, 2001 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-11434781

RESUMO

Valyl-tRNA synthetase (ValRS) has difficulty discriminating between its cognate amino acid, valine, and structurally similar amino acids. To minimize translational errors, the enzyme catalyzes a tRNA-dependent editing reaction that prevents accumulation of misacylated tRNA(Val). Editing occurs with threonine, alanine, serine, and cysteine, as well as with several nonprotein amino acids. The 3'-end of tRNA plays a vital role in promoting the tRNA-dependent editing reaction. Valine tRNA having the universally conserved 3'-terminal adenosine replaced by any other nucleoside does not stimulate the editing activity of ValRS. As a result 3'-end tRNA(Val) mutants, particularly those with 3'-terminal pyrimidines, are stably misacylated with threonine, alanine, serine, and cysteine. Valyl-tRNA synthetase is unable to hydrolytically deacylate misacylated tRNA(Val) terminating in 3'-pyrimidines but does deacylate mischarged tRNA(Val) terminating in adenosine or guanosine. Evidently, a purine at position 76 of tRNA(Val) is essential for translational editing by ValRS. We also observe misacylation of wild-type and 3'-end mutants of tRNA(Val) with isoleucine. Valyl-tRNA synthetase does not edit wild-type tRNA(Val)(A76) mischarged with isoleucine, presumably because isoleucine is only poorly accommodated at the editing site of the enzyme. Misacylated mutant tRNAs as well as 3'-end-truncated tRNA(Val) are mixed noncompetitive inhibitors of the aminoacylation reaction, suggesting that ValRS, a monomeric enzyme, may bind more than one tRNA(Val) molecule. Gel-mobility-shift experiments to characterize the interaction of tRNA(Val) with the enzyme provide evidence for two tRNA binding sites on ValRS.


Assuntos
Escherichia coli/enzimologia , Edição de RNA , RNA de Transferência de Valina/metabolismo , Valina-tRNA Ligase/metabolismo , Regiões 3' não Traduzidas/metabolismo , Acilação , Sítios de Ligação , Escherichia coli/genética , Hidrólise , Isoleucina/metabolismo , RNA Bacteriano/metabolismo , Aminoacil-RNA de Transferência/metabolismo , Aminoacilação de RNA de Transferência , Valina-tRNA Ligase/antagonistas & inibidores
19.
J Biol Chem ; 276(23): 20286-91, 2001 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-11342535

RESUMO

Analysis of prolyl-tRNA synthetase (ProRS) across all three taxonomic domains (Eubacteria, Eucarya, and Archaea) reveals that the sequences are divided into two distinct groups. Recent studies show that Escherichia coli ProRS, a member of the "prokaryotic-like" group, recognizes specific tRNA bases at both the acceptor and anticodon ends, whereas human ProRS, a member of the "eukaryotic-like" group, recognizes nucleotide bases primarily in the anticodon. The archaeal Methanococcus jannaschii ProRS is a member of the eukaryotic-like group, although its tRNA(Pro) possesses prokaryotic features in the acceptor stem. We show here that, in some respects, recognition of tRNA(Pro) by M. jannaschii ProRS parallels that of human, with a strong emphasis on the anticodon and only weak recognition of the acceptor stem. However, our data also indicate differences in the details of the anticodon recognition between these two eukaryotic-like synthetases. Although the human enzyme places a stronger emphasis on G35, the M. jannaschii enzyme places a stronger emphasis on G36, a feature that is shared by E. coli ProRS. These results, interpreted in the context of an extensive sequence alignment, provide evidence of divergent adaptation by M. jannaschii ProRS; recognition of the tRNA acceptor end is eukaryotic-like, whereas the details of the anticodon recognition are prokaryotic-like. This divergence may be a reflection of the unusual dual function of this enzyme, which catalyzes specific aminoacylation with proline as well as with cysteine.


Assuntos
Aminoacil-tRNA Sintetases/metabolismo , Mathanococcus/enzimologia , RNA de Transferência de Prolina/metabolismo , Sequência de Aminoácidos , Aminoacil-tRNA Sintetases/química , Sítios de Ligação , Dados de Sequência Molecular , Conformação de Ácido Nucleico , RNA de Transferência de Prolina/química , Homologia de Sequência de Aminoácidos
20.
Biol Chem ; 382(3): 399-406, 2001 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-11347887

RESUMO

Cysteinyl-tRNA synthetase catalyzes the addition of cysteine to its cognate tRNA. The available eukaryotic sequences for this enzyme contain several insertions that are absent from bacterial sequences. To gain insights into the differences between the bacterial and eukaryotic forms, we previously studied the E. coli cysteinyl-tRNA synthetase. In this study, we sought to clone and express the full-length gene for the human cytoplasmic cysteinyl-tRNA synthetase. Although a gene encoding the human enzyme has been described, the predicted protein sequence, consisting of 638 amino acids, lacks homology with other eukaryotic enzymes in the carboxyl-terminus. This suggested that a further investigation was necessary to obtain the definitive sequence for the human enzyme. Here we report the isolation of a full-length cDNA that encodes a protein of 748 amino acids. The predicted protein sequence shows considerable similarity to other eukaryotic cysteinyl-tRNA synthetases in the carboxyl-terminus. We also found that approximately 20% of the mRNA encoding the cytoplasmic cysteinyl-tRNA synthetase contained an insertion of 8 bases in the 3' coding region of the mRNA. This insertion arises from an alternative splicing between the last two exons of the gene. The alternative splicing alters the reading frame and results in the replacement of the carboxy-terminal 44 amino acids with a novel sequence of 22 amino acids. Expression of the full-length and alternative forms of the enzyme in E. coli generated functional proteins that were active in aminoacylation of human cytoplasmic tRNA(Cys) with cysteine.


Assuntos
Aminoacil-tRNA Sintetases/genética , Aminoacil-tRNA Sintetases/metabolismo , Citoplasma/enzimologia , Processamento Alternativo , Sequência de Aminoácidos , Aminoacil-tRNA Sintetases/química , Sequência de Bases , Clonagem Molecular , DNA Complementar , Escherichia coli/genética , Etiquetas de Sequências Expressas , Humanos , Isoenzimas/genética , Isoenzimas/metabolismo , Dados de Sequência Molecular , Estrutura Quaternária de Proteína , Homologia de Sequência de Aminoácidos , Células Tumorais Cultivadas
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