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1.
Sci Rep ; 12(1): 2907, 2022 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-35190584

RESUMO

Physical activity (PA) helps prevention and aftercare of sporadic breast cancer (BC), cardiopulmonary fitness (CPF) being an age-independent predictor of tumor-specific mortality. Therefore, we wanted to identify predictors of CPF (represented by peak oxygen uptake: VO2peak) in BRCA1/2 mutation carriers whose risk of developing BC is high. We used cross-sectional data from 68 BRCA1/2 germline mutation carrying women participating in the randomized, prospective, controlled clinical study LIBRE-1. Assessments included cardiopulmonary exercise testing, medical and lifestyle history plus socioeconomic status. Additionally, the participants completed a psychological questionnaire regarding their attitude, subjective norms, perceived behavior control and intention towards PA. A multivariate logistic regression model was used to identify predictors for participants reaching their age- and sex-adjusted VO2peak reference values. 22 participants (median age: 40 years, interquartile range (IQR) 33-46) were cancer-unaffected and 46 cancer-affected (median age: 44 years, IQR 35-50). The strongest predictor for reaching the reference VO2peak value was attitude towards PA (Odds Ratio 3.0; 95% Confidence Interval 1.3-8.4; p = 0.021). None of the other predictors showed a significant association. A positive attitude towards PA seems to be associated with VO2peak, which should be considered in developing therapeutic and preventive strategies.Trial registrations: NCT02087592; DRKS00005736.


Assuntos
Atitude Frente a Saúde , Proteína BRCA1/genética , Proteína BRCA2/genética , Neoplasias da Mama/genética , Neoplasias da Mama/prevenção & controle , Teste de Esforço , Exercício Físico/psicologia , Mutação em Linhagem Germinativa , Consumo de Oxigênio , Adulto , Neoplasias da Mama/etiologia , Neoplasias da Mama/psicologia , Estudos Transversais , Feminino , Heterozigoto , Humanos , Pessoa de Meia-Idade , Estudos Prospectivos , Inquéritos e Questionários
2.
Ultrasound Obstet Gynecol ; 53(3): 367-375, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30014562

RESUMO

OBJECTIVES: The soluble fms-like tyrosine kinase-1 (sFlt-1) to placental growth factor (PlGF) ratio is generally elevated some time before and at the clinical onset of pre-eclampsia. The PROGNOSIS study validated a sFlt-1/PlGF ratio cut-off of ≤ 38 to rule out the onset of pre-eclampsia within 1 week of testing in women with suspected disease. The aim of this study was to assess the predictive value of the sFlt-1/PlGF ratio to rule out the onset of pre-eclampsia for up to 4 weeks, and to assess the value of repeat measurements. METHODS: This was an exploratory post-hoc analysis of data from the PROGNOSIS study performed in pregnant women aged ≥ 18 years with suspected pre-eclampsia, who were at 24 + 0 to 36 + 6 weeks' gestation at their first clinic visit. Serum samples were collected at the first visit and weekly thereafter. sFlt-1 and PlGF levels were measured using Elecsys® sFlt-1 and PlGF immunoassays. Whether the sFlt-1/PlGF ratio cut-off of ≤ 38 used to rule out the onset of pre-eclampsia within 1 week could predict the absence of pre-eclampsia 2, 3, and 4 weeks post-baseline was assessed. The value of repeat sFlt-1/PlGF testing was assessed by examining the difference in sFlt-1/PlGF ratio 2 and 3 weeks after the first measurement in women with, and those without, pre-eclampsia or adverse fetal outcome. RESULTS: On analysis of 550 women, sFlt-1/PlGF ratio ≤ 38 ruled out the onset of pre-eclampsia 2 and 3 weeks post-baseline with high negative predictive values (NPV) of 97.9% and 95.7%, respectively. The onset of pre-eclampsia within 4 weeks was ruled out with a high NPV (94.3%) and high sensitivity and specificity (66.2% and 83.1%, respectively). Compared with women who did not develop pre-eclampsia, those who developed pre-eclampsia had significantly larger median increases in sFlt-1/PlGF ratio at 2 weeks (∆, 31.22 vs 1.45; P < 0.001) and at 3 weeks (∆, 48.97 vs 2.39; P < 0.001) after their initial visit. Women who developed pre-eclampsia and/or adverse fetal outcome compared with those who did not had a significantly greater median increase in sFlt-1/PlGF ratio over the same period (∆, 21.22 vs 1.40; P < 0.001 at 2 weeks; ∆, 34.95 vs 2.30; P < 0.001 at 3 weeks). CONCLUSION: The Elecsys® immunoassay sFlt-1/PlGF ratio can help to rule out the onset of pre-eclampsia for 4 weeks in women with suspected pre-eclampsia. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.


Assuntos
Fator de Crescimento Placentário/sangue , Pré-Eclâmpsia/diagnóstico , Diagnóstico Pré-Natal/métodos , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/sangue , Adulto , Biomarcadores/metabolismo , Feminino , Feto , Idade Gestacional , Humanos , Pré-Eclâmpsia/sangue , Pré-Eclâmpsia/epidemiologia , Pré-Eclâmpsia/mortalidade , Valor Preditivo dos Testes , Gravidez , Prognóstico , Estudos Prospectivos , Estudos Retrospectivos
3.
Phys Rev Lett ; 110(4): 048103, 2013 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-25166204

RESUMO

We develop a generic description of thin active films that captures key features of flow and rotation patterns emerging from the activity of chiral motors which introduce torque dipoles. We highlight the role of the spin rotation field and show that fluid flows can occur in two ways: by coupling of the spin rotation rate to the velocity field via a surface or by spatial gradients of the spin rotation rate. We discuss our results in the context of patches of bacteria on solid surfaces and groups of rotating cilia. Our theory could apply to active chiral processes in the cell cytoskeleton and in epithelia.


Assuntos
Modelos Biológicos , Modelos Químicos , Actinas/química , Actinas/fisiologia , Aderência Bacteriana/fisiologia , Cílios/química , Cílios/fisiologia , Citoesqueleto/química , Citoesqueleto/fisiologia , Miosinas/química , Miosinas/fisiologia , Torque
4.
Eur Phys J E Soft Matter ; 35(9): 89, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23001784

RESUMO

Active processes in biological systems often exhibit chiral asymmetries. Examples are the chirality of cytoskeletal filaments which interact with motor proteins, the chirality of the beat of cilia and flagella as well as the helical trajectories of many biological microswimmers. Here, we derive constitutive material equations for active fluids which account for the effects of active chiral processes. We identify active contributions to the antisymmetric part of the stress as well as active angular momentum fluxes. We discuss four types of elementary chiral motors and their effects on a surrounding fluid. We show that large-scale chiral flows can result from the collective behavior of such motors even in cases where isolated motors do not create a hydrodynamic far field.


Assuntos
Hidrodinâmica , Modelos Moleculares , Citoesqueleto de Actina/química , Citoesqueleto de Actina/metabolismo , Cinética , Conformação Molecular , Torque
5.
Neurology ; 78(13): 998-1006, 2012 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-22422897

RESUMO

OBJECTIVE: The Methods of Optimal Depression Detection in Parkinson's Disease (MOOD-PD) study compared the psychometric properties of 9 depression scales to provide guidance on scale selection in Parkinson disease (PD). METHODS: Patients with PD (n = 229) from community-based neurology practices completed 6 self-report scales (Beck Depression Inventory [BDI]-II, Center for Epidemiologic Studies Depression Rating Scale-Revised [CESD-R], 30-item Geriatric Depression Scale [GDS-30], Inventory of Depressive Symptoms-Patient [IDS-SR], Patient Health Questionnaire-9 [PHQ-9], and Unified Parkinson's Disease Rating Scale [UPDRS]-Part I) and were administered 3 clinician-rated scales (17-item Hamilton Depression Rating Scale [HAM-D-17], Inventory of Depressive Symptoms-Clinician [IDS-C], and Montgomery-Åsberg Depression Rating Scale [MADRS] and a psychiatric interview. DSM-IV-TR diagnoses were established by an expert panel blinded to the self-reported rating scale data. Receiver operating characteristic curves were used to estimate the area under the curve (AUC) of each scale. RESULTS: All scales performed better than chance (AUC 0.75-0.85). Sensitivity ranged from 0.66 to 0.85 and specificity ranged from 0.60 to 0.88. The UPDRS Depression item had a smaller AUC than the BDI-II, HAM-D-17, IDS-C, and MADRS. The CESD-R also had a smaller AUC than the MADRS. The remaining AUCs were statistically similar. CONCLUSIONS: The GDS-30 may be the most efficient depression screening scale to use in PD because of its brevity, favorable psychometric properties, and lack of copyright protection. However, all scales studied, except for the UPDRS Depression, are valid screening tools when PD-specific cutoff scores are used.


Assuntos
Depressão/diagnóstico , Depressão/psicologia , Doença de Parkinson/diagnóstico , Doença de Parkinson/psicologia , Escalas de Graduação Psiquiátrica/normas , Autorrelato/normas , Inquéritos e Questionários/normas , Idoso , Depressão/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doença de Parkinson/epidemiologia
6.
Eur Phys J E Soft Matter ; 33(2): 99-103, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20852912

RESUMO

Cell sorting is a widespread phenomenon pivotal to the early development of multicellular organisms. In vitro cell sorting studies have been instrumental in revealing the cellular properties driving this process. However, these studies have as yet been limited to two-dimensional analysis of three-dimensional cell sorting events. Here we describe a method to record the sorting of primary zebrafish ectoderm and mesoderm germ layer progenitor cells in three dimensions over time, and quantitatively analyze their sorting behavior using an order parameter related to heterotypic interface length. We investigate the cell population size dependence of sorted aggregates and find that the germ layer progenitor cells engulfed in the final configuration display a relationship between total interfacial length and system size according to a simple geometrical argument, subject to a finite-size effect.


Assuntos
Separação Celular/métodos , Animais , Agregação Celular , Ectoderma/citologia , Mesoderma/citologia , Células-Tronco/citologia , Peixe-Zebra/embriologia
7.
Phys Rev E Stat Nonlin Soft Matter Phys ; 81(3 Pt 1): 030904, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20365690

RESUMO

The initial stages of transcription by RNA polymerase are frequently marked by pausing and stalling events. These events have been linked to an inactive backtracked state in which the polymerase diffuses along the template DNA. We investigate theoretically the influence of RNA secondary structure in confining this diffusion. The effective confinement length peaks at transcript lengths commensurate with early stalling. This finite-size effect accounts for slow progress at the beginning of transcription, which we illustrate via stochastic hopping models for backtracking polymerases.


Assuntos
RNA Polimerases Dirigidas por DNA/química , RNA Polimerases Dirigidas por DNA/genética , Modelos Químicos , Modelos Genéticos , RNA/química , RNA/genética , Transcrição Gênica/genética , Sítios de Ligação , RNA Polimerases Dirigidas por DNA/ultraestrutura , Ativação Enzimática , Modelos Moleculares , Conformação de Ácido Nucleico , Ligação Proteica , Estrutura Secundária de Proteína , RNA/ultraestrutura , Relação Estrutura-Atividade
8.
Eur Phys J E Soft Matter ; 30(4): 439-47, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19856004

RESUMO

We calculate the first-passage time distribution for diffusion through a cylindrical pore with sticky walls. A particle diffusively explores the interior of the pore through a series of binding and unbinding events with the cylinder wall. Through a diagrammatic expansion we obtain first-passage time statistics for the particle's exit from the pore. Connections between the model and nucleocytoplasmic transport in cells are discussed.


Assuntos
Difusão , Transporte Biológico , Modelos Químicos , Porosidade , Probabilidade , Fatores de Tempo
9.
J Eur Acad Dermatol Venereol ; 23(1): 52-7, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18702624

RESUMO

BACKGROUND: Dermatology in a penitentiary environment is an under-researched field. OBJECTIVES: To study the prison population seeking medical advice for skin diseases and to assess among detainees the life impact of these diseases, an approach that to the best of our knowledge has not previously been reported. METHODS: This prospective study was carried out in the male population of two penal institutions in the region of Toulouse, south-western France. RESULTS: One hundred seventy-eight men were seen, for a total of 234 diagnoses and 281 consultations. The five most frequent diagnoses, in order of decreasing frequency, were disorders of the pilosebaceous follicle, fungal diseases, benign skin tumours, warts and eczemas, which are common skin diseases. However, 72% of inmates believed their skin disease was directly related to detention. This belief was related to the conditions of life in prison (seclusion and its effects) and to frequent psychological problems. CONCLUSIONS: The disorders observed were generally benign skin conditions that could be expected in a population of young men living in a closed community. They led to a high demand for care and treatment: skin diseases represented the largest specialist consultation in our institutions. Skin problems can easily be managed in an outpatient unit, which confirms the usefulness of a dedicated dermatology clinic within the outpatient consultation units of penal institutions in order to provide care of equivalent quality to that available in a free environment. The dermatologist can have an important role in the medical management and the health education of prisoners.


Assuntos
Prisioneiros , Dermatopatias/epidemiologia , Adulto , França/epidemiologia , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Dermatopatias/classificação
10.
J Radiol ; 88(9 Pt 2): 1261-3, 2007 Sep.
Artigo em Francês | MEDLINE | ID: mdl-17878872

RESUMO

The daily practice of radiologists has evolved and radiologists are increasingly being directly involved with patient care and treatment. Consequently, radiologists have become a part of the therapeutic team available to patients. This active role, in hospital based or out-patient practices, does not only have an impact on the radiologist's professional activities. New liabilities related to interventional procedures or treatments are now added to already existing professional liability from diagnostic activities. Therefore, musculoskeletal radiologists performing interventional procedures must be aware and familiar with their obligations towards patients, including the requirement to provide adequate information to patients and documenting that informed consent was obtained.


Assuntos
Doenças Ósseas/terapia , Revelação/legislação & jurisprudência , Consentimento Livre e Esclarecido/legislação & jurisprudência , Responsabilidade Legal , Doenças Musculares/terapia , Radiologia Intervencionista/legislação & jurisprudência , Assistência Ambulatorial/legislação & jurisprudência , Termos de Consentimento/legislação & jurisprudência , França , Humanos , Corpo Clínico Hospitalar/legislação & jurisprudência , Equipe de Assistência ao Paciente/legislação & jurisprudência
11.
Neurology ; 63(2): 293-300, 2004 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-15277623

RESUMO

OBJECTIVE: To determine the prevalence and impact of comorbid psychiatric disturbances in Parkinson disease (PD) patients with psychosis. METHODS: Subject data were derived from a research database of 116 PD patients participating in standardized motor, cognitive, psychiatric, and caregiver assessments. RESULTS: There were 25 patients (22%) with psychosis manifest as hallucinations (n = 9), delusions (n = 1), or hallucinations and delusions (n = 15) and 25 patients (22%) who had no current or past psychiatric comorbidities (PDN). In the psychotic group, 44% had psychosis only (PSY), and 56% had psychosis plus at least one other comorbid psychiatric disturbance (PSY+), including depressive disorders (71%), anxiety disorders (21%), apathetic syndromes (14%), and delirium (14%). There were no differences in age, sex, education, or age onset or duration of PD among the PSY, PSY+, and PDN groups. Both psychotic groups had greater motor, functional, and frontal cognitive deficits and increased caregiver burden scores relative to PDN. PSY+ showed greater global and selective cognitive deficits compared to PDN. Psychosis was a primary predictor of caregiver burden, whereas depressive symptoms indirectly enhanced motor impairments. CONCLUSIONS: Nonpsychotic psychiatric disturbances, especially affective disturbances, are common comorbidities in PD patients with psychosis and warrant clinical attention to reduce morbidity and caregiver distress.


Assuntos
Transtornos Mentais/epidemiologia , Doença de Parkinson/epidemiologia , Transtornos Psicóticos/epidemiologia , Atividades Cotidianas , Idoso , Transtornos de Ansiedade/epidemiologia , Cuidadores/psicologia , Transtornos Cognitivos/epidemiologia , Comorbidade , Bases de Dados Factuais , Delusões/epidemiologia , Feminino , Alucinações/epidemiologia , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Transtornos do Humor/epidemiologia , Prevalência , Índice de Gravidade de Doença , Inquéritos e Questionários
12.
Novartis Found Symp ; 237: 164-75; discussion 176-81, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11444042

RESUMO

Cell division during development in many cases generates daughter cells that differ not only in fate, but also in size. We investigate the mechanisms that ensure proper spindle positioning during such asymmetric divisions using the one-cell stage Caenorhabditis elegans embryo as a model system. We utilized a UV laser microbeam as an in vivo microtubule-severing device to probe the forces driving spindle positioning. Our results indicate that extra-spindle pulling forces acting on the spindle poles dictate spindle position along the anterior-posterior embryonic axis. Importantly, forces acting on the posterior spindle pole appear more extensive than those acting on the anterior one, thus explaining the overall posterior spindle displacement that leads to the asymmetric division of the wild-type one-cell stage embryo. In separate work, we analysed a locus called zyg-8, which plays a key role in ensuring proper spindle positioning. Our data show that zyg-8 is required to promote microtubule growth and/or stability during anaphase. We identified the molecular nature of the zyg-8 locus in the course of a large-scale RNAi-based functional genomics screen. ZYG-8 harbours two notable protein domains: a Ca2+/calmodulin-dependent kinase domain, and a domain related to doublecortin, a human microtubule-associated protein involved in neuronal migration.


Assuntos
Caenorhabditis elegans/embriologia , Divisão Celular/fisiologia , Polaridade Celular/fisiologia , Embrião não Mamífero/fisiologia , Proteínas Associadas aos Microtúbulos , Fuso Acromático/metabolismo , Animais , Caenorhabditis elegans/fisiologia , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas do Domínio Duplacortina , Embrião não Mamífero/citologia , Lasers , Microtúbulos/metabolismo , Neuropeptídeos/metabolismo , Oócitos/fisiologia
13.
J Bacteriol ; 183(11): 3499-505, 2001 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-11344158

RESUMO

Based on the complementarity of the initial coding region (downstream box [db]) of several bacterial and phage mRNAs to bases 1469 to 1483 in helix 44 of 16S rRNA (anti-downstream box [adb]), it has been proposed that db-adb base pairing enhances translation in a way that is similar to that of the Shine-Dalgarno (SD)/anti-Shine-Dalgarno (aSD) interaction. Computer modeling of helix 44 on the 30S subunit shows that the topography of the 30S ribosome does not allow a simultaneous db-adb interaction and placement of the initiation codon in the ribosomal P site. Thus, the db-adb interaction cannot substitute for the SD-aSD interaction in translation initiation. We have always argued that any contribution of the db-adb interaction should be most apparent on mRNAs devoid of an SD sequence. Here, we show that 30S ribosomes do not bind to leaderless mRNA in the absence of initiator tRNA, even when the initial coding region shows a 15-nucleotide complementarity (optimal fit) with the putative adb. In addition, an optimized db did not affect the translational efficiency of a leaderless lambda cI-lacZ reporter construct. Thus, the db-adb interaction can hardly serve as an initial recruitment signal for ribosomes. Moreover, we show that different leaderless mRNAs are translated in heterologous systems although the sequence of the putative adb's within helix 44 of the 30S subunits of the corresponding bacteria differ largely. Taken our data together with those of others (M. O'Connor, T. Asai, C. L. Squires, and A. E. Dahlberg, Proc. Natl. Acad. Sci. USA 96:8973-8978, 1999; A. La Teana, A. Brandi, M. O'Connor, S. Freddi, and C. L. Pon, RNA 6:1393-1402, 2000), we conclude that the db does not base pair with the adb.


Assuntos
Biossíntese de Proteínas , RNA Mensageiro/metabolismo , RNA Ribossômico 16S/metabolismo , Pareamento de Bases , Sequência de Bases , Escherichia coli/genética , Escherichia coli/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Conformação de Ácido Nucleico , RNA Mensageiro/química , RNA Mensageiro/genética , RNA Ribossômico 16S/química , RNA Ribossômico 16S/genética , Thermus thermophilus/genética , Thermus thermophilus/metabolismo
14.
Mol Biol Cell ; 12(5): 1481-98, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11359937

RESUMO

To quantitatively investigate the trafficking of the transmembrane lectin VIP36 and its relation to cargo-containing transport carriers (TCs), we analyzed a C-terminal fluorescent-protein (FP) fusion, VIP36-SP-FP. When expressed at moderate levels, VIP36-SP-FP localized to the endoplasmic reticulum, Golgi apparatus, and intermediate transport structures, and colocalized with epitope-tagged VIP36. Temperature shift and pharmacological experiments indicated VIP36-SP-FP recycled in the early secretory pathway, exhibiting trafficking representative of a class of transmembrane cargo receptors, including the closely related lectin ERGIC53. VIP36-SP-FP trafficking structures comprised tubules and globular elements, which translocated in a saltatory manner. Simultaneous visualization of anterograde secretory cargo and VIP36-SP-FP indicated that the globular structures were pre-Golgi carriers, and that VIP36-SP-FP segregated from cargo within the Golgi and was not included in post-Golgi TCs. Organelle-specific bleach experiments directly measured the exchange of VIP36-SP-FP between the Golgi and endoplasmic reticulum (ER). Fitting a two-compartment model to the recovery data predicted first order rate constants of 1.22 +/- 0.44%/min for ER --> Golgi, and 7.68 +/- 1.94%/min for Golgi --> ER transport, revealing a half-time of 113 +/- 70 min for leaving the ER and 1.67 +/- 0.45 min for leaving the Golgi, and accounting for the measured steady-state distribution of VIP36-SP-FP (13% Golgi/87% ER). Perturbing transport with AlF(4)(-) treatment altered VIP36-SP-GFP distribution and changed the rate constants. The parameters of the model suggest that relatively small differences in the first order rate constants, perhaps manifested in subtle differences in the tendency to enter distinct TCs, result in large differences in the steady-state localization of secretory components.


Assuntos
Proteínas de Transporte/metabolismo , Retículo Endoplasmático/metabolismo , Complexo de Golgi/metabolismo , Lectinas de Ligação a Manose , Proteínas de Membrana/metabolismo , Proteínas de Membrana Transportadoras , Transporte Proteico , Vesículas Secretórias/metabolismo , Animais , Biomarcadores , Brefeldina A/farmacologia , Células COS , Cicloeximida/farmacologia , Humanos , Cinética , Proteínas Luminescentes/metabolismo , Microscopia Confocal , Microscopia de Vídeo , Inibidores da Síntese de Proteínas/farmacologia , Transporte Proteico/efeitos dos fármacos , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Vesículas Secretórias/química , Fatores de Tempo
15.
FEBS Lett ; 495(3): 167-71, 2001 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-11334885

RESUMO

Sequence determinants and structural features of the RNA govern mRNA-ribosome interaction in bacteria. However, ribosomal recruitment to leaderless mRNAs, which start directly with the AUG start codon and do not bear a Shine-Dalgarno sequence like canonical mRNAs, does not appear to rely on 16S rRNA-mRNA interactions. Here, we have studied the effects of translation initiation factors IF2 and IF3 on 30S initiation at a 5'-terminal AUG and at a competing downstream canonical ribosome binding site. We show that IF2 affects the forward kinetics of 30S initiation complex formation at the 5'-terminal AUG as well as the stability of these complexes. Moreover, the IF2:IF3 molar ratio was found to play a decisive role in translation initiation of a leaderless mRNA both in vitro and in vivo indicating that the translational efficiency of an mRNA is not only intrinsically determined but can be altered depending on the availability of components of the translational machinery.


Assuntos
Códon de Iniciação , Fatores de Iniciação de Peptídeos/farmacologia , Biossíntese de Proteínas , Ribossomos/metabolismo , Escherichia coli/genética , Fator de Iniciação 3 em Eucariotos , Genes Reporter , Substâncias Macromoleculares , Fatores de Iniciação de Peptídeos/metabolismo , Fator de Iniciação 2 em Procariotos , RNA de Transferência de Metionina/metabolismo , Transformação Genética
16.
Nature ; 409(6820): 630-3, 2001 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-11214323

RESUMO

Cell divisions that create daughter cells of different sizes are crucial for the generation of cell diversity during animal development. In such asymmetric divisions, the mitotic spindle must be asymmetrically positioned at the end of anaphase. The mechanisms by which cell polarity translates to asymmetric spindle positioning remain unclear. Here we examine the nature of the forces governing asymmetric spindle positioning in the single-cell-stage Caenorhabditis elegans embryo. To reveal the forces that act on each spindle pole, we removed the central spindle in living embryos either physically with an ultraviolet laser microbeam, or genetically by RNA-mediated interference of a kinesin. We show that pulling forces external to the spindle act on the two spindle poles. A stronger net force acts on the posterior pole, thereby explaining the overall posterior displacement seen in wild-type embryos. We also show that the net force acting on each spindle pole is under control of the par genes that are required for cell polarity along the anterior-posterior embryonic axis. Finally, we discuss simple mathematical models that describe the main features of spindle pole behaviour. Our work suggests a mechanism for generating asymmetry in spindle positioning by varying the net pulling force that acts on each spindle pole, thus allowing for the generation of daughter cells with different sizes.


Assuntos
Caenorhabditis elegans/embriologia , Polaridade Celular , Fuso Acromático/fisiologia , Animais , Fenômenos Biomecânicos , Caenorhabditis elegans/citologia , Divisão Celular , Embrião não Mamífero/citologia , Embrião não Mamífero/fisiologia , Modelos Biológicos
17.
Antimicrob Agents Chemother ; 44(12): 3278-84, 2000 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11083627

RESUMO

beta-L-5-Iododioxolane uracil was shown to have potent anti-Epstein-Barr virus (EBV) activity (50% effective concentration = 0.03 microM) with low cytotoxicity (50% cytotoxic concentration = 1,000 microM). It exerts its antiviral activity by suppressing replicative EBV DNA and viral protein synthesis. This compound is phosphorylated in cells where the EBV is replicating but not in cells where the EBV is latent. EBV-specific thymidine kinase could phosphorylate beta-L-5-iododioxolane uracil to the monophosphate metabolite. The K(m) of beta-L-5-iododioxolane uracil with EBV thymidine kinase was estimated to be 5.5 microM, which is similar to that obtained with thymidine but about fivefold higher than that obtained with 2' fluoro-5-methyl-beta-L-arabinofuranosyl uracil, the first L-nucleoside analogue discovered to have anti-EBV activity. The relative V(max) is seven times higher than that of thymidine. The anti-EBV activity of beta-L-5-iododioxolane uracil and its intracellular phosphorylation could be inhibited by 5'-ethynylthymidine, a potent EBV thymidine kinase inhibitor. The present study suggests that beta-L-5-iododioxolane uracil exerts its action after phosphorylation; therefore, EBV thymidine kinase is critical for the antiviral action of this drug.


Assuntos
Antivirais/farmacologia , Dioxolanos/farmacologia , Herpesvirus Humano 4/efeitos dos fármacos , Timidina Quinase/metabolismo , Timidina/análogos & derivados , Uracila/farmacologia , Antivirais/metabolismo , Dioxolanos/metabolismo , Interações Medicamentosas , Inibidores Enzimáticos/farmacologia , Humanos , Especificidade por Substrato , Timidina/farmacologia , Timidina Quinase/antagonistas & inibidores , Células Tumorais Cultivadas , Uracila/análogos & derivados , Uracila/metabolismo , Replicação Viral/efeitos dos fármacos
18.
Mol Pharmacol ; 58(5): 1109-14, 2000 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-11040060

RESUMO

A nonnaturally occurring L-configuration nucleoside analog, L-beta-5-bromovinyl-(2-hydroxymethyl)-1,3-(dioxolanyl)uracil (L-BVOddU) selectively inhibited varicella-zoster virus growth in human embryonic lung (HEL) 299 cell culture with an EC(50) of 0.055 microM, whereas no inhibition of CEM and HEL 299 cell growth or mitochondrial DNA synthesis was observed at concentrations up to 200 microM. L-BVOddU was phosphorylated by viral thymidine kinase but not by human cytosolic thymidine kinase, and the antiviral activity of this compound is dependent on the viral thymidine kinase. Unlike other D-configuration bromovinyl deoxyuridine analogs, such as E-5-(2-bromovinyl)-2'-deoxyuridine and 1-beta-arabinofuranosyl-E-5-(2-bromovinyl)uracil, this compound was metabolized only to its monophosphate metabolite. The di- or triphosphate metabolites were not detected. This suggested that the inhibitory mechanism may be unique and different from other anti-herpesvirus nucleoside analogs.


Assuntos
Antivirais/farmacologia , Herpesvirus Humano 3/efeitos dos fármacos , Nucleosídeos/farmacologia , Pró-Fármacos/metabolismo , Timidina Quinase/metabolismo , Uracila/farmacologia , Aciclovir/metabolismo , Aciclovir/farmacologia , Antivirais/metabolismo , Células Cultivadas , Herpesvirus Humano 3/enzimologia , Humanos , Cinética , Nucleosídeos/metabolismo , Fosforilação , Uracila/análogos & derivados , Uracila/metabolismo
19.
EMBO J ; 19(15): 4101-10, 2000 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-10921890

RESUMO

Translation initiation in bacteria involves a stochastic binding mechanism in which the 30S ribosomal subunit first binds either to mRNA or to initiator tRNA, fMet-tRNA(f)(Met). Leaderless lambda cI mRNA did not form a binary complex with 30S ribosomes, which argues against the view that ribosomal recruitment signals other than a 5'-terminal start codon are essential for translation initiation of these mRNAs. We show that, in Escherichia coli, translation initiation factor 2 (IF2) selectively stimulates translation of lambda cI mRNA in vivo and in vitro. These experiments suggest that the start codon of leaderless mRNAs is recognized by a 30S-fMet-tRNA(f)(Met)-IF2 complex, an intermediate equivalent to that obligatorily formed during translation initiation in eukaryotes. We further show that leaderless lambda cI mRNA is faithfully translated in vitro in both archaebacterial and eukaryotic translation systems. This suggests that translation of leaderless mRNAs reflects a fundamental capability of the translational apparatus of all three domains of life and lends support to the hypothesis that the translation initiation pathway is universally conserved.


Assuntos
Evolução Biológica , Proteínas de Ligação a DNA , Iniciação Traducional da Cadeia Peptídica , Fatores de Iniciação de Peptídeos/metabolismo , RNA Mensageiro/metabolismo , Ribossomos/metabolismo , Regiões 3' não Traduzidas , Animais , Proteínas da Membrana Bacteriana Externa/genética , Ligação Competitiva , Códon de Iniciação , Modelos Genéticos , Fator de Iniciação 2 em Procariotos , RNA de Transferência de Metionina/metabolismo , Coelhos , Proteínas Repressoras/genética , Reticulócitos/metabolismo , Sulfolobus/genética , Proteínas Virais , Proteínas Virais Reguladoras e Acessórias
20.
J Med Chem ; 43(13): 2538-46, 2000 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-10891113

RESUMO

A series of (E)-5-(2-bromovinyl)uracil analogues and related nucleosides was synthesized, and their antiviral activities were evaluated. (E)-5-(2-Bromovinyl)-2'-deoxy-L-uridine (L-BVDU, 2), 1-(beta-L-arabinofuranosyl)-(E)-5-(2-bromovinyl)uracil (L-BVAU, 4), (E)-5-(2-bromovinyl)-1-(2-deoxy-2-fluoro-beta-L-ribofuranosyl)uracil (L-FBVRU, 8) and (E)-5-(2-bromovinyl)-1-(2-deoxy-2-fluoro-beta-L-arabinofuranosyl)urac il (L-FBVAU, 10) were synthesized via appropriate 5-iodouracil analogues from L-arabinose. D- and L-Oxathiolane and -dioxolane derivatives 13, 16, 20, 21, and 29-34 were prepared by glycosylation reaction of the oxathiolane and dioxolane intermediates with silylated uracil analogues using TMSI as the coupling agent. The synthesized compounds were evaluated in cell cultures infected with the following viruses: varicella zoster virus (VZV), Epstein Barr virus (EBV), and herpes simplex virus types 1 and 2 (HSV-1 and HSV-2). Among the tested compounds, beta-L-CV-OddU (29), beta-L-BV-OddU (31), and beta-L-IV-OddU (33) exhibited potent in vitro antiviral activity against VZV with EC(50) values of 0.15, 0. 07, and 0.035 microM, respectively, and against EBV with EC(50) values of 0.49, 0.59, and 3.91 microM, respectively.


Assuntos
Antivirais/síntese química , Dioxolanos/síntese química , Herpesviridae/efeitos dos fármacos , Nucleosídeos de Pirimidina/síntese química , Uracila/análogos & derivados , Uracila/síntese química , Compostos de Vinila/síntese química , Antivirais/química , Antivirais/farmacologia , Divisão Celular/efeitos dos fármacos , Linhagem Celular , Dioxolanos/química , Dioxolanos/farmacologia , Herpesvirus Humano 1/efeitos dos fármacos , Herpesvirus Humano 2/efeitos dos fármacos , Herpesvirus Humano 3/efeitos dos fármacos , Herpesvirus Humano 4/efeitos dos fármacos , Humanos , Nucleosídeos de Pirimidina/química , Nucleosídeos de Pirimidina/farmacologia , Relação Estrutura-Atividade , Uracila/química , Uracila/farmacologia , Compostos de Vinila/química , Compostos de Vinila/farmacologia
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