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1.
Nature ; 563(7732): 532-535, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30464270

RESUMO

Since the first aeroplane flight more than 100 years ago, aeroplanes have been propelled using moving surfaces such as propellers and turbines. Most have been powered by fossil-fuel combustion. Electroaerodynamics, in which electrical forces accelerate ions in a fluid1,2, has been proposed as an alternative method of propelling aeroplanes-without moving parts, nearly silently and without combustion emissions3-6. However, no aeroplane with such a solid-state propulsion system has yet flown. Here we demonstrate that a solid-state propulsion system can sustain powered flight, by designing and flying an electroaerodynamically propelled heavier-than-air aeroplane. We flew a fixed-wing aeroplane with a five-metre wingspan ten times and showed that it achieved steady-level flight. All batteries and power systems, including a specifically developed ultralight high-voltage (40-kilovolt) power converter, were carried on-board. We show that conventionally accepted limitations in thrust-to-power ratio and thrust density4,6,7, which were previously thought to make electroaerodynamics unfeasible as a method of aeroplane propulsion, are surmountable. We provide a proof of concept for electroaerodynamic aeroplane propulsion, opening up possibilities for aircraft and aerodynamic devices that are quieter, mechanically simpler and do not emit combustion emissions.

2.
Am J Eval ; 44(1): 29-49, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37069836

RESUMO

Evaluation capacity building (ECB) continues to attract the attention and interest of scholars and practitioners. Over the years, models, frameworks, strategies, and practices related to ECB have been developed and implemented. Although ECB is highly contextual, the evolution of knowledge in this area depends on learning from past efforts in a structured approach. The purpose of the present article is to integrate the ECB literature in evaluation journals. More specifically, the article aims to answer three questions: What types of articles and themes comprise the current literature on ECB? How are current practices of ECB described in the literature? And what is the current status of research on ECB? Informed by the findings of the review, the article concludes with suggestions for future ECB practice and scholarship.

3.
EMBO J ; 30(18): 3714-28, 2011 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-21804532

RESUMO

C/EBPß is an auto-repressed protein that becomes post-translationally activated by Ras-MEK-ERK signalling. C/EBPß is required for oncogene-induced senescence (OIS) of primary fibroblasts, but also displays pro-oncogenic functions in many tumour cells. Here, we show that C/EBPß activation by H-Ras(V12) is suppressed in immortalized/transformed cells, but not in primary cells, by its 3' untranslated region (3'UTR). 3'UTR sequences inhibited Ras-induced cytostatic activity of C/EBPß, DNA binding, transactivation, phosphorylation, and homodimerization, without significantly affecting protein expression. The 3'UTR suppressed induction of senescence-associated C/EBPß target genes, while promoting expression of genes linked to cancers and TGFß signalling. An AU-rich element (ARE) and its cognate RNA-binding protein, HuR, were required for 3'UTR inhibition. These components also excluded the Cebpb mRNA from a perinuclear cytoplasmic region that contains activated ERK1/2, indicating that the site of C/EBPß translation controls de-repression by Ras signalling. Notably, 3'UTR inhibition and Cebpb mRNA compartmentalization were absent in primary fibroblasts, allowing Ras-induced C/EBPß activation and OIS to proceed. Our findings reveal a novel mechanism whereby non-coding mRNA sequences selectively regulate C/EBPß activity and suppress its anti-oncogenic functions.


Assuntos
Regiões 3' não Traduzidas , Envelhecimento , Proteína beta Intensificadora de Ligação a CCAAT/metabolismo , Regulação da Expressão Gênica , Proteína Oncogênica p21(ras)/metabolismo , Linhagem Celular , Humanos , Modelos Biológicos , RNA Mensageiro/metabolismo
4.
Genomics ; 99(2): 108-17, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22206861

RESUMO

TICs are characterized by their ability to self-renew, differentiate and initiate tumor formation. miRNAs are small noncoding RNAs that bind to mRNAs resulting in regulation of gene expression and biological functions. The role of miRNAs and TICs in cancer progression led us to hypothesize that miRNAs may regulate genes involved in TIC maintenance. Using whole genome miRNA and mRNA expression profiling of TICs from primary prostate cancer cells, we identified a set of up-regulated miRNAs and a set of genes down-regulated in PSs. Inhibition of these miRNAs results in a decrease of prostatosphere formation and an increase in target gene expression. This study uses genome-wide miRNA profiling to analyze expression in TICs. We connect aberrant miRNA expression and deregulated gene expression in TICs. These findings can contribute to a better understanding of the molecular mechanisms governing TIC development/maintenance and the role that miRNAs have in the fundamental biology of TICs.


Assuntos
Regulação Neoplásica da Expressão Gênica , MicroRNAs/genética , Neoplasias da Próstata/patologia , RNA Mensageiro/genética , Esferoides Celulares/metabolismo , Proliferação de Células , Perfilação da Expressão Gênica , Humanos , Masculino , MicroRNAs/metabolismo , Recidiva Local de Neoplasia/genética , Recidiva Local de Neoplasia/metabolismo , Recidiva Local de Neoplasia/patologia , Células-Tronco Neoplásicas/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Neoplasias da Próstata/genética , Neoplasias da Próstata/metabolismo , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Células Tumorais Cultivadas , Regulação para Cima
5.
Rev Sci Instrum ; 91(12): 125105, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-33379972

RESUMO

We report the construction and characterization of a comprehensive magnonic-opto-electronic oscillator (MOEO) system based on 1550-nm photonics and yttrium iron garnet (YIG) magnonics. The system exhibits a rich and synergistic parameter space because of the ability to control individual photonic, electronic, and magnonic components. Taking advantage of the spin wave dispersion of YIG, the frequency self-generation as well as the related nonlinear processes becomes sensitive to the external magnetic field. Besides being known as a band-pass filter and a delay element, the YIG delay line possesses spin wave modes that can be controlled to mix with the optoelectronic modes to generate higher-order harmonic beating modes. With the high sensitivity and external tunability, the MOEO system may find usefulness in sensing applications in magnetism and spintronics beyond optoelectronics and photonics.

6.
BMJ Case Rep ; 12(11)2019 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-31678923

RESUMO

Glomus tumours are atypical in extracutaneous locations and very rarely located in reproductive organs. We present an unusual case of an incidentally discovered glomus tumour arising from the testis of a 47-year-old man. The testicular occurrence of this tumour type is not only exceptionally rare but also serves to highlight the debate regarding the optimal management of incidentally discovered small testicular lesions.


Assuntos
Tumor Glômico/patologia , Neoplasias Testiculares/patologia , Diagnóstico Diferencial , Tumor Glômico/diagnóstico por imagem , Tumor Glômico/cirurgia , Humanos , Masculino , Pessoa de Meia-Idade , Orquiectomia , Neoplasias Testiculares/diagnóstico por imagem , Neoplasias Testiculares/cirurgia , Ultrassonografia
7.
Lab Chip ; 19(7): 1217-1225, 2019 03 27.
Artigo em Inglês | MEDLINE | ID: mdl-30801596

RESUMO

We describe a Lab-on-a-Film disposable that detects multidrug-resistant tuberculosis (MDR-TB) from sputum extracts. The Lab-on-a-Film disposable consists of 203 gel elements that include DNA sequences (probes) for 37 mutations, deletions, or insertion elements across 5 genes (including an internal control). These gel elements are printed on a flexible film, which costs approximately 500 times less than microarray glass. The film with printed gel elements is then laminated to additional rollable materials (films) to form a microfluidic flow cell. We combined multiplex amplification and hybridization steps in a single microfluidic chamber, without buffer exchanges or other manipulations up to and throughout hybridization. This flow cell also incorporates post hybridization wash steps while retaining an entirely closed-amplicon system, thus minimizing the potential for sample or amplicon cross-contamination. We report analytical sensitivity of 32 cfu mL-1 across all MDR-TB markers and detection of MDR-TB positive clinical specimens using an automated TruTip workstation for extraction and the Lab-on-a-Film disposable for amplification and detection of the extracts.


Assuntos
Equipamentos Descartáveis , Resistência a Múltiplos Medicamentos/genética , Técnicas de Genotipagem/instrumentação , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/genética , Escarro/microbiologia , Humanos
8.
J Biomed Sci ; 15(3): 317-31, 2008 May.
Artigo em Inglês | MEDLINE | ID: mdl-18204916

RESUMO

The cell division control protein (Cdc2) kinase is a catalytic subunit of a protein kinase complex, called the M phase promoting factor, which induces entry into mitosis and is universal among eukaryotes. This protein is believed to play a major role in cell division and control. The lives of biological cells are controlled by proteins interacting in metabolic and signaling pathways, in complexes that replicate genes and regulate gene activity, and in the assembly of the cytoskeletal infrastructure. Our knowledge of protein-protein (P-P) interactions has been accumulated from biochemical and genetic experiments, including the widely used yeast two-hybrid test. In this paper we examine if P-P interactions in regenerating tissues and cells of the anuran Xenopus laevis can be discovered from biomedical literature using computational and literature mining techniques. Using literature mining techniques, we have identified a set of implicitly interacting proteins in regenerating tissues and cells of Xenopus laevis that may interact with Cdc2 to control cell division. Genome sequence based bioinformatics tools were then applied to validate a set of proteins that appear to interact with the Cdc2 protein. Pathway analysis of these proteins suggests that Myc proteins function as the regulator of M phase initiation by controlling expression of the Akt1 molecule that ultimately inhibits the Cdc2-cyclin B complex in cells. P-P interactions that are implicitly appearing in literature can be effectively discovered using literature mining techniques. By applying evolutionary principles on the P-P interacting pairs, it is possible to quantitatively analyze the significance of the associations with biological relevance. The developed BioMap system allows discovering implicit P-P interactions from large quantity of biomedical literature data. The unique similarities and differences observed within the interacting proteins can lead to the development of the new hypotheses that can be used to design further laboratory experiments.


Assuntos
Ciclo Celular , Biologia Computacional , Proteínas/metabolismo , Animais , Bases de Dados de Proteínas , Xenopus laevis
9.
Focus (Am Psychiatr Publ) ; 16(3): 266-278, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31975921

RESUMO

Virtual reality (VR) technology offers new opportunities for the development of innovative clinical research, assessment, and intervention tools. VR-based testing, training, teaching, and treatment approaches that would be difficult, if not impossible, to deliver with traditional methods are now being developed that take advantage of the assets that are available with VR technology. As research evidence continues to indicate clinical efficacy, VR applications are being increasingly regarded as providing innovative options for targeting the cognitive, psychological, motor, and functional impairments that result from various clinical health conditions. VR allows for the precise presentation and control of stimuli in dynamic, multisensory, 3D computer-generated simulations as well as providing advanced methods for capturing and quantifying behavioral responses. These characteristics support the rationale for the use of VR applications in clinical assessment, intervention, and training. This article begins with a brief review of the history of and rationale for the use of VR with clinical populations. It then details one use case for the clinical application of VR-the exposure-therapy treatment of anxiety disorders and posttraumatic stress disorder. Although significant work is cited in other areas of clinical VR (e.g., pain management, cognitive and physical assessment and rehabilitation, eating disorders, social skills, and clinical training), a full overview of such a broad literature is beyond the scope of this article. Thus, the authors have opted to provide more in-depth analysis of one specific clinical area that clearly illustrates how VR has been successfully applied and is supported by an encouraging and evolving scientific literature.

10.
Disabil Rehabil ; 40(11): 1333-1344, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-28271907

RESUMO

PURPOSE: We developed and explored the feasibility and user acceptance of the Cognitive Assessment for Aphasia App: a non-immersive virtual reality cognitive assessment for stroke survivors, designed to be inclusive of individuals with aphasia. METHODS: Participants were assessed on a battery of pen-and-paper cognitive tests and the Cognitive Assessment for Aphasia App. Feasibility was explored by quantifying missing data for test completion, determining user acceptance for the app by measuring participants' preferred testing method, enjoyment and perceived task difficulty and time-taken to complete the test. RESULTS: Sixty-four stroke participants (35 with aphasia, 29 without aphasia) and 32 controls were recruited. Only one participant with aphasia was unable to complete all the Cognitive Assessment for Aphasia App tasks, whereas 13 participants were unable to complete all pen-and-paper tasks. Only 14% of participants preferred the pen-and-paper tests, and preference did not significantly differ between groups. Ninety-five per cent of participants were neutral or enjoyed the app and 4% perceived it to be very difficult. Higher age was negatively associated with user acceptance measures. CONCLUSION: The study shows preliminary evidence for the Cognitive Assessment for Aphasia App to be a feasible cognitive assessment for stroke survivors with and without aphasia. The app is currently being validated in stroke. Implications for rehabilitation The Cognitive Assessment for Aphasia App is a feasible tool for assessing post-stroke cognition in acute, inpatient rehabilitation and community settings. In research trials examining cognition, individuals with aphasia are often excluded. The Cognitive Assessment for Aphasia App permits the inclusion of these individuals, enhancing generalizability. The Cognitive Assessment for Aphasia App provides an alternative method to assess cognition that is quicker and preferred over standard neuropsychological tests.


Assuntos
Afasia/reabilitação , Aplicativos Móveis , Acidente Vascular Cerebral/complicações , Fatores Etários , Idoso , Afasia/etiologia , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Memória de Curto Prazo , Tempo de Reação , Realidade Virtual
11.
Mol Cell Biol ; 24(17): 7380-91, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15314150

RESUMO

CCAAT/enhancer binding protein beta (C/EBPbeta) is a widely expressed transcription factor whose activity is regulated by oncogenic Ha-RasV12 signaling. C/EBPbeta is essential for the development of mouse skin tumors containing Ras mutations and can cooperate with RasV12 to transform NIH 3T3 cells. Here we have investigated Ras-induced phosphorylation of C/EBPbeta in fibroblasts and report a novel proline-directed phosphoacceptor site at Ser64 within the transactivation domain. Ser64 phosphorylation was induced by activated Ras and Raf but was not blocked by chemical inhibitors of MEK1/2, phosphatidylinositol 3-kinase, JNK, or p38 mitogen-activated protein kinases. Ser64 was efficiently phosphorylated in vitro by the cyclin-dependent kinases Cdk2 and Cdc2. Thr189, previously identified as an ERK1/2 phosphorylation site that regulates C/EBPbeta activity, was also a substrate for Cdk phosphorylation. Ser64 and Thr189 phosphorylation was low in serum-starved (G0) cells but was strongly increased in mid-G1 cells and in cells arrested in S or M phase. In addition, phosphorylation on both sites was blocked by treating cells with the Cdk inhibitor roscovitine. In contrast to wild-type C/EBPbeta, which enhances transformation of NIH 3T3 cells, mutants bearing alanine substitutions at Ser64 and/or Thr189 inhibited RasV12-induced focus formation. Our findings support a role for C/EBPbeta as a nuclear effector of Ras signaling and transformation, and they indicate that cell cycle-dependent phosphorylation of C/EBPbeta on Ser64 and Thr189 is required to promote Ras-induced transformation of NIH 3T3 cells.


Assuntos
Proteína beta Intensificadora de Ligação a CCAAT/metabolismo , Ciclo Celular/fisiologia , Transformação Celular Neoplásica , Genes ras , Transdução de Sinais , Proteínas ras/metabolismo , Sequência de Aminoácidos , Animais , Proteína beta Intensificadora de Ligação a CCAAT/genética , Quinases relacionadas a CDC2 e CDC28/metabolismo , Quinase 2 Dependente de Ciclina , Inibidores Enzimáticos/metabolismo , Camundongos , Proteínas Quinases Ativadas por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Dados de Sequência Molecular , Células NIH 3T3 , Fosforilação , Proteínas Proto-Oncogênicas c-raf/genética , Proteínas Proto-Oncogênicas c-raf/metabolismo , Alinhamento de Sequência , Serina/metabolismo , Treonina/metabolismo , Proteínas ras/genética
12.
Neuropsychology ; 31(8): 877-899, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-29376669

RESUMO

OBJECTIVE: Since the mid-1990s, a significant scientific literature has evolved regarding the outcomes from the use of what we now refer to as clinical virtual reality (VR). This use of VR simulation technology has produced encouraging results when applied to address cognitive, psychological, motor, and functional impairments across a wide range of clinical health conditions. This article addresses the question, "Is clinical VR ready for primetime?" METHOD: After a brief description of the various forms of VR technology, we discuss the trajectory of clinical VR over the last 20 years and summarize the basic assets that VR offers for creating clinical applications. The discussion then addresses the question of readiness in terms of the theoretical basis for clinical VR assets, the research to date, the pragmatic factors regarding availability, usability, and costs of clinical VR content/systems, and the ethical issues for the safe use of VR with clinical populations. RESULTS: Our review of the theoretical underpinnings and research findings to date leads to the prediction that clinical VR will have a significant impact on future research and practice. Pragmatic issues that can influence adoption across many areas of psychology also appear favorable, but professional guidelines will be needed to promote its safe and ethical use. CONCLUSIONS: Although there is still much research needed to advance the science in this area, we strongly believe that clinical VR applications will become indispensable tools in the toolbox of psychological researchers and practitioners and will only grow in relevance and popularity in the future. (PsycINFO Database Record


Assuntos
Retroalimentação , Realidade Virtual , Humanos , Conhecimento Psicológico de Resultados , Transtornos Fóbicos/terapia , Interface Usuário-Computador , Terapia de Exposição à Realidade Virtual
13.
BMJ Case Rep ; 20152015 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-26400588

RESUMO

A previously healthy 16-year-old girl presented with signs of acute hepatitis. On initial enquiry, she had not taken any prescribed or 'over-the-counter' medications, and there was no recent travel history. Further investigations revealed no viral, autoimmune or metabolic cause of hepatitis. Only following specific questioning did she reveal that she had, in the preceding 3 months, regularly consumed internet ordered Chinese green tea, which contained Camellia sinensis. After ceasing green tea consumption, there was a rapid and sustained recovery of her hepatitis. The authors discuss the probable cause of herbal tea in this case of acute hepatitis, and the importance of awareness of this rare yet recurring theme for patients and clinicians alike.


Assuntos
Camellia sinensis/efeitos adversos , Doença Hepática Induzida por Substâncias e Drogas/etiologia , Hepatite/etiologia , Extratos Vegetais/efeitos adversos , Chá/efeitos adversos , Doença Aguda , Adolescente , Camellia sinensis/química , Catequina/análogos & derivados , Catequina/isolamento & purificação , Doença Hepática Induzida por Substâncias e Drogas/fisiopatologia , Feminino , Hepatite/fisiopatologia , Humanos , Extratos Vegetais/química , Recidiva , Resultado do Tratamento
14.
Med Image Anal ; 7(1): 21-45, 2003 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-12467720

RESUMO

The in vivo investigation of joint kinematics in normal and injured wrist requires the segmentation of carpal bones from 3D (CT) images, and their registration over time. The non-uniformity of bone tissue, ranging from dense cortical bone to textured spongy bone, the irregular shape of closely packed carpal bones, small inter-bone spaces compared to the resolution of CT images, along with the presence of blood vessels, and the inherent blurring of CT imaging render the segmentation of carpal bones a challenging task. We review the performance of statistical classification, deformable models (active contours), region growing, region competition, and morphological operations for this application. We then propose a model which combines several of these approaches in a unified framework. Specifically, our approach is to use a curve evolution implementation of region growing from initialized seeds, where growth is modulated by a skeletally-mediated competition between neighboring regions. The inter-seed skeleton, which we interpret as the predicted boundary of collision between two regions, is used to couple the growth of seeds and to mediate long-range competition between them. The implementation requires subpixel representations of each growing region as well as the inter-region skeleton. This method combines the advantages of active contour models, region growing, and both local and global region competition methods. We demonstrate the effectiveness of this approach for our application where many of the difficulties presented above are overcome as illustrated by synthetic and real examples. Since this segmentation method does not rely on domain-specific knowledge, it should be applicable to a range of other medical imaging segmentation tasks.


Assuntos
Ossos do Carpo/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Articulação do Punho , Algoritmos , Fenômenos Biomecânicos , Humanos , Imageamento Tridimensional
15.
IEEE Trans Pattern Anal Mach Intell ; 26(5): 550-71, 2004 May.
Artigo em Inglês | MEDLINE | ID: mdl-15460278

RESUMO

This paper presents a novel framework for the recognition of objects based on their silhouettes. The main idea is to measure the distance between two shapes as the minimum extent of deformation necessary for one shape to match the other. Since the space of deformations is very high-dimensional, three steps are taken to make the search practical: 1) define an equivalence class for shapes based on shock-graph topology, 2) define an equivalence class for deformation paths based on shock-graph transitions, and 3) avoid complexity-increasing deformation paths by moving toward shock-graph degeneracy. Despite these steps, which tremendously reduce the search requirement, there still remain numerous deformation paths to consider. To that end, we employ an edit-distance algorithm for shock graphs that finds the optimal deformation path in polynomial time. The proposed approach gives intuitive correspondences for a variety of shapes and is robust in the presence of a wide range of visual transformations. The recognition rates on two distinct databases of 99 and 216 shapes each indicate highly successful within category matches (100 percent in top three matches), which render the framework potentially usable in a range of shape-based recognition applications.


Assuntos
Algoritmos , Inteligência Artificial , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Reconhecimento Automatizado de Padrão , Gráficos por Computador , Simulação por Computador , Armazenamento e Recuperação da Informação/métodos , Análise Numérica Assistida por Computador , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Processamento de Sinais Assistido por Computador
16.
Clin Chim Acta ; 429: 198-205, 2014 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-24360850

RESUMO

BACKGROUND: Genetic polymorphisms in the CYP2C9 and VKORC1 genes have been linked to sensitivity of the anticoagulant drug warfarin. The aim of this study is to demonstrate a method for warfarin sensitivity genotyping using gel element microarray technology in a simplified workflow from sample collection to analysis and detection. METHODS: We developed an integrated amplification microarray system combining PCR amplification, target labeling, and microarray hybridization within a single, closed-amplicon "lateral flow cell" for genotyping three single nucleotide polymorphisms (SNPs) that influence warfarin response. We combined nucleic acid extraction of saliva using the TruTip technology together with the lateral flow cell assay and with fully automated array detection and analysis. RESULTS: The analytical performance of the assay was tested using 20 genotyped human genomic DNA samples and found to be sensitive down to 330 input genomic copies (1 ng). A follow-up pre-clinical evaluation was performed with 65 blinded saliva samples and the genotyping results were in agreement with those determined by bidirectional sequencing. CONCLUSIONS: Combined with the use of non-invasive saliva samples, rapid DNA extraction, the lateral flow cell, automatic imaging and data analysis provides a simple and fast sample-to-answer microarray test for warfarin sensitivity genotyping.


Assuntos
Técnicas de Genotipagem/métodos , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Reação em Cadeia da Polimerase/métodos , Saliva/citologia , Saliva/metabolismo , Varfarina/farmacologia , Alelos , Hidrocarboneto de Aril Hidroxilases/genética , Citocromo P-450 CYP2C9 , Humanos , Polimorfismo de Nucleotídeo Único , Integração de Sistemas , Vitamina K Epóxido Redutases/genética
18.
PLoS One ; 7(4): e35322, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22530006

RESUMO

Establishment of totipotency after somatic cell nuclear transfer (NT) requires not only reprogramming of gene expression, but also conversion of the cell cycle from quiescence to the precisely timed sequence of embryonic cleavage. Inadequate adaptation of the somatic nucleus to the embryonic cell cycle regime may lay the foundation for NT embryo failure and their reported lower cell counts. We combined bright field and fluorescence imaging of histone H(2b)-GFP expressing mouse embryos, to record cell divisions up to the blastocyst stage. This allowed us to quantitatively analyze cleavage kinetics of cloned embryos and revealed an extended and inconstant duration of the second and third cell cycles compared to fertilized controls generated by intracytoplasmic sperm injection (ICSI). Compared to fertilized embryos, slow and fast cleaving NT embryos presented similar rates of errors in M phase, but were considerably less tolerant to mitotic errors and underwent cleavage arrest. Although NT embryos vary substantially in their speed of cell cycle progression, transcriptome analysis did not detect systematic differences between fast and slow NT embryos. Profiling of amino acid turnover during pre-implantation development revealed that NT embryos consume lower amounts of amino acids, in particular arginine, than fertilized embryos until morula stage. An increased arginine supplementation enhanced development to blastocyst and increased embryo cell numbers. We conclude that a cell cycle delay, which is independent of pluripotency marker reactivation, and metabolic restraints reduce cell counts of NT embryos and impede their development.


Assuntos
Ciclo Celular/fisiologia , Reprogramação Celular/fisiologia , Aminoácidos/metabolismo , Animais , Arginina/metabolismo , Blastocisto/metabolismo , Análise por Conglomerados , Dano ao DNA , Transferência Embrionária , Embrião de Mamíferos/citologia , Embrião de Mamíferos/fisiologia , Desenvolvimento Embrionário/fisiologia , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Cinética , Masculino , Camundongos , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Técnicas de Transferência Nuclear , Imagem com Lapso de Tempo , Transgenes
19.
Aging Cell ; 10(1): 80-95, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20969722

RESUMO

The mammalian oocyte has the unique feature of supporting fertilization and normal development, while capable of reprogramming nuclei of somatic cells toward pluripotency, and occasionally even totipotency. While oocyte quality is known to decay with somatic aging, it is not a given that different biological functions decay concurrently. In this study, we tested whether oocyte's reprogramming ability decreases with aging. We show that oocytes isolated from mice aged beyond the usual reproductive age (climacteric) yield ooplasts that retain reprogramming capacity after somatic nuclear transfer (SCNT), giving rise to higher blastocysts rates compared to young donors ooplasts. Despite the differences in transcriptome between climacteric and young ooplasts, gene expression profiles of SCNT blastocysts were very similar. Importantly, embryonic stem cell lines with capacity to differentiate into tissues from all germ layers were derived from SCNT blastocysts obtained from climacteric ooplasts. Although apoptosis-related genes were down-regulated in climacteric ooplasts, and reprogramming by transcription factors (direct-induced pluripotency) benefits from the inhibition of p53-mediated apoptosis, reprogramming capacity of young ooplasts was not improved by blocking p53. However, more outgrowths were derived from SCNT blastocysts developed in the presence of a p53 inhibitor, indicating a beneficial effect on trophectoderm function. Results strongly suggest that oocyte-induced reprogramming outcome is determined by the availability and balance of intrinsic pro- and anti-reprogramming factors tightly regulated and even improved throughout aging, leading to the proposal that oocytes can still be a resource for somatic reprogramming when they cease to be considered safe for sexual reproduction.


Assuntos
Envelhecimento/metabolismo , Blastocisto/fisiologia , Reprogramação Celular/genética , Embrião de Mamíferos/metabolismo , Oócitos/fisiologia , Fatores Etários , Envelhecimento/genética , Animais , Apoptose/genética , Blastocisto/citologia , Linhagem Celular , Núcleo Celular/genética , Núcleo Celular/metabolismo , Climatério , Transferência Embrionária , Embrião de Mamíferos/citologia , Feminino , Fertilização/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Genes p53/fisiologia , Aptidão Genética/fisiologia , Cavalos , Humanos , Masculino , Camundongos , Técnicas de Transferência Nuclear , Oócitos/citologia , Gravidez , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
20.
Mol Cell Biol ; 30(11): 2621-35, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20351173

RESUMO

The bZIP transcription factor C/EBPbeta is a target of Ras signaling that has been implicated in Ras-induced transformation and oncogene-induced senescence (OIS). To gain insights into Ras-C/EBPbeta signaling, we investigated C/EBPbeta activation by oncogenic Ras. We show that C/EBPbeta DNA binding is autorepressed and becomes activated by the Ras-Raf-MEK-ERK-p90(RSK) cascade. Inducible phosphorylation by RSK on Ser273 in the leucine zipper was required for DNA binding. In addition, three other modifications (phosphorylation on Tyr109 [p-Tyr109], p-Ser111, and monomethylation of Arg114 [me-Arg114]) within an N-terminal autoinhibitory domain were important for Ras-induced C/EBPbeta activation and cytostatic activity. Apart from its role in DNA binding, Ser273 phosphorylation also creates an interhelical g<-->e' salt bridge with Lys268 that increases attractive electrostatic interactions between paired leucine zippers and promotes homodimerization. Mutating Ser273 to Ala or Lys268 to Glu decreased C/EBPbeta homodimer formation, whereas heterodimerization with C/EBPgamma was relatively unaffected. The S273A substitution also reduced the antiproliferative activity of C/EBPbeta in Ras(V12)-expressing fibroblasts and decreased binding to target cell cycle genes, while a phosphomimetic substitution (S273D) maintained growth arrest function. Our findings identify four novel C/EBPbeta-activating modifications, including RSK-mediated phosphorylation of a bifunctional residue in the leucine zipper that regulates DNA binding and homodimerization and thereby promotes cell cycle arrest.


Assuntos
Proteína beta Intensificadora de Ligação a CCAAT/metabolismo , Ciclo Celular/fisiologia , DNA/metabolismo , Zíper de Leucina , Proteínas Quinases S6 Ribossômicas/metabolismo , Sequência de Aminoácidos , Animais , Proteína beta Intensificadora de Ligação a CCAAT/química , Proteína beta Intensificadora de Ligação a CCAAT/genética , Linhagem Celular , DNA/genética , Substâncias de Crescimento/metabolismo , Humanos , Sistema de Sinalização das MAP Quinases/fisiologia , Camundongos , Proteínas Quinases Ativadas por Mitógeno/antagonistas & inibidores , Proteínas Quinases Ativadas por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Dados de Sequência Molecular , Fosforilação , Multimerização Proteica , Processamento de Proteína Pós-Traducional , Ratos , Proteínas Quinases S6 Ribossômicas/antagonistas & inibidores , Proteínas Quinases S6 Ribossômicas/genética , Alinhamento de Sequência , Ativação Transcricional , Proteínas ras/genética , Proteínas ras/metabolismo
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