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2.
Rev Sci Instrum ; 92(5): 053516, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-34243235

RESUMO

The Faraday-effect based polarimeter and interferometer are developed for non-perturbation magnetic field and density measurements on the Keda Reconnection eXperiment (KRX) device. The magnetic reconnection is externally driven by a pair of parallel current plates. To design this instrument and provide an alternative way to facilitate theory-experiment comparisons via forward modeling of the diagnostics process with full plasma dynamics given by simulation, we develop a synthetic diagnostics based on 2D photonic integrated circuit simulation for magnetic reconnection on the KRX. The view-line geometry is optimized and wavelengths (1 mm) of the polarimeter and interferometer are selected to ensure the sensitivity of measurement on the KRX. We have simulated magnetic reconnection on the x-line (x-z plane) with horizontal viewing and vertical viewing for line of sight measurements. It is found that the current sheet width and indicator of magnetic reconnection can be inferred directly from the dynamics of Faraday rotation even with the line-integrated character of polarimeter-interferometer diagnostics.

3.
Epidemiol Infect ; 148: e237, 2020 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-32829720

RESUMO

Bordetella bronchiseptica is a potential zoonotic pathogen, which mainly causes respiratory diseases in humans and a variety of animal species. B. bronchiseptica is one of the important pathogens isolated from rabbits in Fujian Province. However, the knowledge of the epidemiology and characteristics of the B. bronchiseptica in rabbits in Fujian Province is largely unknown. In this study, 219 B. bronchiseptica isolates recovered from lung samples of dead rabbits with respiratory diseases in Fujian Province were characterised by multi-locus sequencing typing, screening virulence genes and testing antimicrobial susceptibility. The results showed that the 219 isolates were typed into 11 sequence types (STs) including five known STs (ST6, ST10, ST12, ST14 and ST33) and six new STs (ST88, ST89, ST90, ST91, ST92 and ST93) and the ST33 (30.14%, 66/219), ST14 (26.94%, 59/219) and ST12 (16.44%, 36/219) were the three most prevalent STs. Surprisingly, all the 219 isolates carried the five virulence genes (fhaB, prn, cyaA, dnt and bteA) in the polymerase chain reaction screening. Moreover, the isolates were resistant to cefixime, ceftizoxime, cefatriaxone and ampicillin at rates of 33.33%, 31.05%, 11.87% and 3.20%, respectively. This study showed the genetic diversity of B. bronchiseptica in rabbits in Fujian Province, and the colonisation of the human-associated ST12 strain in rabbits in Fujian Province. The results might be useful for monitoring the epidemic strains, developing preventive methods and preventing the transmission of epidemic strains from rabbits to humans.


Assuntos
Infecções por Bordetella/veterinária , Bordetella bronchiseptica/genética , Coelhos/microbiologia , Doenças Respiratórias/veterinária , Animais , Antibacterianos/farmacologia , Infecções por Bordetella/epidemiologia , Infecções por Bordetella/microbiologia , Bordetella bronchiseptica/efeitos dos fármacos , Bordetella bronchiseptica/isolamento & purificação , China/epidemiologia , Farmacorresistência Bacteriana , Variação Genética , Filogenia , Doenças Respiratórias/epidemiologia , Doenças Respiratórias/microbiologia
5.
Epidemiol Infect ; 147: e256, 2019 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-31441395

RESUMO

Staphylococcus aureus has been recognised as one of the important zoonotic pathogens. However, knowledge about the epidemiology and genetic characteristics of S. aureus in rabbits was limited. The aim of this study was to determine the characteristics of 281 S. aureus isolated from dead rabbits of nine rabbit farms in Fujian Province, China. All the isolates were characterised by multi-locus sequencing typing, detection of virulence factors and antimicrobial susceptibility test. The results showed that the 281 isolates were grouped into two sequence types, ST121 (13.52%, 38/281) and ST398 (86.48%, 243/281). Surprisingly, the ST121 strains were only recovered from the lung samples from one of the nine rabbit farms studied. In the 281 isolates, the virulence genes of nuc, hla, hlb, clfA, clfB and fnbpA were positive, whereas the sea, seb, tsst, eta and etb genes were negative. Notably, the 38 ST121 isolates carried the pvl gene. All the 281 isolates were methicillin-susceptible S. aureus, and the isolates were susceptible to most of the used antibiotics, except for streptomycin, kanamycin, azithromycin and penicillin, and the resistance rates of which were 23.84%, 19.57%, 16.01% and 11.03%, respectively. This study first described the epidemiology and characteristics of S. aureus in rabbits in Fujian Province, which will help in tracking the evolution of epidemic strains and preventing the rabbit-human transmission events.


Assuntos
Infecções Estafilocócicas/veterinária , Staphylococcus aureus/isolamento & purificação , Animais , China/epidemiologia , Genótipo , Testes de Sensibilidade Microbiana , Epidemiologia Molecular , Tipagem de Sequências Multilocus , Coelhos , Infecções Estafilocócicas/epidemiologia , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/classificação , Staphylococcus aureus/genética , Fatores de Virulência/genética
6.
Transfus Med ; 25(6): 399-405, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26578423

RESUMO

BACKGROUND: Little information about the occupational exposures to blood and body fluid (BBF) among blood service workers (BSWs) in blood stations in China is available currently. OBJECTIVES: To assess current status of occupational exposure to BBF and assess the knowledge about occupational blood-borne pathogen exposures and universal precaution among BSWs in blood donations in China. To understand the incidence of occupational exposure in five blood centres in China. METHODS: A cross-sectional study was conducted from January 2008 to December 2013. RESULTS: There were a total of 99 BBF exposures reported during the study period. The total incidence of BBF exposures was 4.4 per 100 person-years. Higher rates were observed for persons employed less than five years and persons less than 45 years old. Nurses have the highest percentage (49.5%) of BBF exposures. BBF exposures occurred most commonly during the afternoon (62.7%). Percutaneous injuries were the most common BBF exposures. Most incidents occurred during sharps use (73.4%). The major cause of occupational exposure was that there was no continuous training (48.4%) and improper use of equipment (23.2%). Only 56.6% of BBF exposures had appropriate first aid measures. During this research work, one staff member was reported to have seroconverted to syphilis after BBF exposure. CONCLUSIONS: To reduce BBF exposures, it is urgent to take several effective actions in China, including improved occupational health systems, adequate education, administrative support, increased use of standard precautions, better safety devices/products and work practices.


Assuntos
Bancos de Sangue , Doadores de Sangue , Patógenos Transmitidos pelo Sangue , Sangue , Enfermeiras e Enfermeiros , Exposição Ocupacional , Adulto , China/epidemiologia , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
7.
Sci Rep ; 5: 14386, 2015 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-26395756

RESUMO

AlGaN/GaN quantum structure is an excellent candidate for high speed infrared detectors based on intersubband transitions. However, fabrication of AlGaN/GaN quantum well infrared detectors suffers from polarization-induced internal electric field, which greatly limits the carrier vertical transport. In this article, a step quantum well is proposed to attempt solving this problem, in which a novel spacer barrier layer is used to balance the internal electric field. As a result, a nearly flat band potential profile is obtained in the step barrier layers of the AlGaN/GaN step quantum wells and a bound-to-quasi-continuum (B-to-QC) type intersubband prototype device with detectable photocurrent at atmosphere window (3-5 µm) is achieved in such nitride semiconductors.

8.
Acta Physiol (Oxf) ; 215(1): 24-36, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26031185

RESUMO

AIM: Voluntary exercise has been shown to protect against the development of ulcerative colitis, but the mechanism is not fully understood. We hypothesized that prior voluntary exercise would attenuate colonic inflammation and ameliorate clinical symptoms in dextran sulphate sodium (DSS)-induced ulcerative colitis by increasing glucocorticoid production and up-regulating PPAR-γ activity in the colon. METHODS: Male C57Bl/6J mice were assigned to sedentary, exercise, exercise with PPAR-γ antagonist GW9662 or glucocorticoid synthesis inhibitor metyrapone. Following the completion of the 30 days' exercise training programme, they were treated with or without 2% DSS in drinking water for 5 days, followed by 5 days of regular water. RESULTS: Compared with sedentary mice, exercise mice exhibited improved clinical symptoms (weight loss and diarrhoea) and less inflammation (expression of pro-inflammatory cytokines and histological injury) in response to DSS, whereas these beneficial effects were abolished by both GW9662 and metyrapone treatment. Molecular studies revealed that exercise significantly increased the expression of PPAR-γ, augmented the expression of steroidogenic enzymes (CYP11A1 and CYP11B1) and elevated corticosterone levels in the colon. GW9662 treatment reversed the expression of PPAR-γ without altering the expression of steroidogenic enzymes and corticosterone secretion in the colon, while metyrapone treatment blocked glucocorticoid secretion and abrogated the increase in PPAR-γ expression in the colon. CONCLUSION: These findings suggest that prior voluntary exercise suppresses the expression of pro-inflammatory cytokines in the colon in response to inflammatory challenge by up-regulating glucocorticoid-mediated PPAR-γ activity, contributing to protection against the development of ulcerative colitis.


Assuntos
Colite Ulcerativa/metabolismo , PPAR gama/metabolismo , Ativação Transcricional/fisiologia , Animais , Colite Ulcerativa/terapia , Corticosterona/metabolismo , Inflamação/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Condicionamento Físico Animal , Regulação para Cima
9.
J Dairy Sci ; 94(4): 2060-70, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21426997

RESUMO

This study was designed to identify sex-specific antibodies (SSAb) in rabbit antisera against bovine sex-sorted sperm, and capture sex-specific proteins of bovine X- or Y- proteins by SSAb. The rabbit antisera against bovine X- or Y-sperm were first produced by a series of immunological approaches, and further purified through immuno-neutralization with excess sex-sorted Y- or X-sperm, respectively, to remove non-sex specific antibodies and enrich sex-specific antibodies. After removal of non-sex specific antibodies, the purified rabbit sera with enriched sex-specific antibodies were screened for sex-specific antibodies by immunofluorescence staining and flow cytometry. The results showed that 3.0, 2.2, and 4.2% of unsorted sperm, sex-sorted X-sperm, and sex-sorted Y-sperm were recognized by the purified rabbit antisera against Y-sperm, respectively, whereas 29.2, 19.7, and 3.9% of unsorted sperm, sex-sorted X-sperm, and sex-sorted Y-sperm were recognized by the purified rabbit antisera against X-sperm. These results suggested that the purified rabbit antisera against X-sperm contained SSAb that preferentially bound to sex-sorted X-sperm. Subsequently, the purified rabbit antisera against X- or Y-sperm were used to immunoprecipitate sex-specific proteins in bovine sperm proteins, and a 30-kDa protein was specifically captured by the rabbit antisera against X-sperm. In conclusion, our results implied that this 30-kDa protein might be a sex-specific protein in bovine X-sperm, which has the potential to be used in immunological procedures for sexing sperm.


Assuntos
Proteínas de Membrana/imunologia , Pré-Seleção do Sexo/veterinária , Espermatozoides/imunologia , Cromossomo X/imunologia , Cromossomo Y/imunologia , Animais , Anticorpos/análise , Bovinos , Soros Imunes , Masculino , Proteínas de Membrana/isolamento & purificação , Coelhos , Pré-Seleção do Sexo/métodos
10.
Plant Dis ; 95(4): 494, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30743347

RESUMO

Coleus (Coleus blumei) is an ornamental plant that is susceptible to infection by several viroids of the genus Coleviroid, which is a member of the family Pospiviroidae. Coleus blumei viroid (CbVd) -1 was first reported in commercial yellow coleus fields in Brazil in 1989 (1). In addition, CbVd-2, CbVd-3, and CbVd-4 have only been detected from coleus in Germany in 1996 (4). CbVd-5 and CbVd-6 were recently identified in China (2). In March 2010, leaves were collected from 50 symptomless coleus plants from a commercial nursery in Hainan Province, China. Total RNA was extracted from the leaves (3). Reverse transcription (RT)-PCR using CbVd-2 specific primers (forward: 5'-AGCTTACCTGGGTTCCCT-3' and reverse: 5'-CTCTCCTCTATTTACTCTCTTCTC-3') corresponding to positions 76 to 93 and 52 to 75 on the CbVd-2 reference sequence, respectively (GenBank Accession No. NC003682). Amplification of a 301-bp product was obtained from one sample. This PCR product was then cloned into pMD18-T (Takara, Dalian, China). Twelve positive clones were sequenced and the results were subjected to BLAST analysis. Sequence analysis showed that two sequences (GenBank Accessions Nos. HQ727542 and HQ727544) shared 99% identity with the reference sequence of CbVd-2 (NC003682), and four sequences (HQ727541, HQ727543, HQ727545 and HQ727547) had 99.34% identity with the reference sequence of CbVd-2 (NC003682). The proposed secondary structures of these variants have approximately 75% paired nucleotides. Results suggested the presence of CbVd-2, which is a member of the Coleviroid genus, Pospoviroidae family. To our knowledge, this is the first report of CbVd-2 from commercial coleus in China. References: (1) M. E. N. Fonseca et al. Fitopatol. Bras. 14:94, 1989. (2) W. Y. Hou et al. Arch. Virol. 154:993, 2009. (3) S. F. Li et al. Ann. Phytopathol. Soc. Jpn. 61:381, 1995. (4) R. L. Spieker et al. J. Gen. Virol. 77:2839, 1996.

11.
East Afr Med J ; 87(1): 32-7, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23057301

RESUMO

BACKGROUND: Despite the diverse conservative and surgical modalities for the management of temporomandibular joint (TMJ) dislocation and the controversy that surrounds them, very little has been done within the East-African setup in terms of highlighting and provoking greater interest in the epidemiology and management of TMJ dislocation. OBJECTIVE: To audit the pattern of occurrence, demographics, aetiology and enumerate the treatment modalities of TMJ dislocation at the oral and maxillofacial surgery division (OMFS) of the University of Nairobi Dental Hospital. DESIGN: Descriptive cross-sectional study. SETTING: University of Nairobi Dental Hospital (UNDH) from January 1995 to July 2005. RESULTS: Twenty nine patients had been diagnosed and managed for TMJ dislocation. Twenty (69%) were females and nine (31%) were males. Their ages ranged from 10-95 years with a mean of 42 years. The cases managed were primarily chronic in nature. The most common form being anterior TMJ dislocation, accounting for twenty-five (86.2%) cases. Trauma was implicated as an aetiology in only five (17%) of the cases while the remaining majority of twenty four (83%) cases were spontaneous. Amongst the causes of spontaneous TMJ dislocation, yawning was the most common accounting for fourteen cases (48.3%). Dislocations caused by trauma were found to be 12.6 times more likely to be associated with other injuries than spontaneous dislocations. Anterior TMJ dislocations were found to be 1.3 times more likely to be associated with absence of molars than posterior TMJ dislocations. Anatomical aberrations, as predisposing factors, were not a significant finding in this research. Eight (28%) of the cases were managed conservatively. Twenty one (72%) of the cases were managed surgically. The eminectomy was the most common technique with a 75% success rate. The highest incidence of TMJ dislocation occurs in the 3rd-5th decade with a female preponderance with bilateral anterior TMJ dislocation being the most common. Most of the cases were managed surgically with eminectomy being the preferred technique with the highest success rate. A study needs to be undertaken to determine reasons' why conservative modalities are least employed in the management of TMJ dislocation in our setup and what can be done about it.


Assuntos
Luxações Articulares/epidemiologia , Transtornos da Articulação Temporomandibular/epidemiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Feminino , Humanos , Luxações Articulares/diagnóstico , Luxações Articulares/terapia , Quênia , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Transtornos da Articulação Temporomandibular/diagnóstico , Transtornos da Articulação Temporomandibular/terapia , Adulto Jovem
12.
Br J Sports Med ; 43(12): 928-31, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19136506

RESUMO

OBJECTIVE: This study aims to investigate the association between mode of transportation to work and dyslipidaemia. METHODS: During the period between January and February 2006, telephone interviews were conducted with 2506 randomly selected urban residents aged 18 years or older in the 8 districts of Beijing, using a multiple stratified random sampling technique. Of the selected individuals, 1024 (40.86%) members of the workforce were subsequently tested for biomarkers (ie, total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C)). Multiple logistic regression modelling was used, adjusted for potential confounders. RESULTS: The probability of dyslipidaemia in workers who travel to work by bus, car or taxi is higher than that of workers who walk to work, with prevalence odds ratios (PORs) of 1.99 (95% CI 1.33 to 2.97) and 2.21 (95% CI 1.28 to 3.84), respectively. There is no significant difference in the risk of experiencing dyslipidaemia when workers who ride bicycles are compared with those who walk to work (POR = 1.22, 95% CI 0.83 to 1.78). CONCLUSIONS: These findings indicate that modes of transportation to work are significantly associated with the prevalence of dyslipidaemia. Prevention education should be emphasised among higher-risk people who usually go to work by car, bus or taxi.


Assuntos
Dislipidemias/epidemiologia , Doenças Profissionais/epidemiologia , Transportes/estatística & dados numéricos , Adolescente , Adulto , Idoso , Biomarcadores/sangue , China/epidemiologia , Dislipidemias/sangue , Exercício Físico/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doenças Profissionais/sangue , Saúde da População Urbana , Adulto Jovem
13.
Biologicals ; 37(1): 37-43, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19008122

RESUMO

A novel plasmid pGS/2SS-M4GFP was constructed in the present study by recombination of GS/2SS gene and enhanced green fluorescent protein (M4GFP) sequence. The GS/2SS fusion gene encoding two copies of somatostatin genes was firstly introduced into pVAX-asd vector in which the kanamycin resistance cassette was replaced by the asd cassette. The M4GFP gene was then fused into 3' end of GS/2SS gene in the proper reading frame. After purified, plasmid pGS/2SS-M4GFP was transfected into different cell lines derived from pig kidney and human cancer cells. The transcription process of GS/2SS gene was confirmed by RT-PCR, and the localization as well as expression of GS/2SS-M4GFP fusion protein was observed by confocal microscopy and ELISA. Transfection results revealed that sole M4GFP was localized within the cytosol and the nucleus, while fusion protein GS/2SS-M4GFP was localized only in the cytoplasm. Furthermore, it should be noted that subcellular localization of GS/2SS-M4GFP was not specific to one cell line, but appeared to be common across a variety of cell lines. These results provide for the first time valuable evidence that M4GFP is a versatile tool to trace GS/2SS protein and pave the way for further study on its tissue distribution and immunological mechanism in vivo.


Assuntos
Linhagem Celular/metabolismo , Vetores Genéticos/síntese química , Vetores Genéticos/metabolismo , Proteínas de Fluorescência Verde/genética , Transgenes , Animais , Clonagem Molecular , Resistência Microbiana a Medicamentos/genética , Células HeLa , Antígenos de Superfície da Hepatite B/genética , Humanos , Modelos Biológicos , Proteínas Recombinantes de Fusão/genética , Somatostatina/genética , Suínos , Distribuição Tecidual , Transfecção
14.
Animal ; 2(11): 1569-74, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22444007

RESUMO

Somatostatin (SS) is a hormone that inhibits the secretion of growth hormone. Immunization against SS can promote the growth of animals. A novel SS-VP22 fused vaccine, pEGS2SS-V, was constructed from pEGS2SS plasmid with a VP22 gene fragment. Two times of immunization with pEGS2SS-V-induced anti-SS antibodies in mice. Compared with mice immunized with pEGS2SS and 0.85% saline, the growth performance of mice immunized with pEGS2SS-V was increased by 14.1% (P < 0.05) and 48.4% (P < 0.01) on the 2nd week after the first vaccination, respectively. The results indicated that the effects of the somatostatin DNA vaccine could be improved effectively by VP22 gene adjuvant.

15.
Nature ; 414(6862): 457-62, 2001 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-11719808

RESUMO

The retinoblastoma tumour suppressor (Rb) pathway is believed to have a critical role in the control of cellular proliferation by regulating E2F activities. E2F1, E2F2 and E2F3 belong to a subclass of E2F factors thought to act as transcriptional activators important for progression through the G1/S transition. Here we show, by taking a conditional gene targeting approach, that the combined loss of these three E2F factors severely affects E2F target expression and completely abolishes the ability of mouse embryonic fibroblasts to enter S phase, progress through mitosis and proliferate. Loss of E2F function results in an elevation of p21Cip1 protein, leading to a decrease in cyclin-dependent kinase activity and Rb phosphorylation. These findings suggest a function for this subclass of E2F transcriptional activators in a positive feedback loop, through down-modulation of p21Cip1, that leads to the inactivation of Rb-dependent repression and S phase entry. By targeting the entire subclass of E2F transcriptional activators we provide direct genetic evidence for their essential role in cell cycle progression, proliferation and development.


Assuntos
Proteínas de Ciclo Celular/fisiologia , Divisão Celular/fisiologia , Proteínas de Ligação a DNA , Fatores de Transcrição/fisiologia , Animais , Proteínas de Ciclo Celular/genética , Divisão Celular/genética , Linhagem Celular , Inibidor de Quinase Dependente de Ciclina p21 , Ciclinas/genética , Regulação para Baixo , Fatores de Transcrição E2F , Fator de Transcrição E2F1 , Fator de Transcrição E2F2 , Fator de Transcrição E2F3 , Fibroblastos/citologia , Marcação de Genes , Integrases/genética , Integrases/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína do Retinoblastoma/metabolismo , Fase S/genética , Fase S/fisiologia , Fatores de Transcrição/genética , Proteínas Virais/genética , Proteínas Virais/metabolismo
16.
Guang Pu Xue Yu Guang Pu Fen Xi ; 21(5): 691-3, 2001 Oct.
Artigo em Chinês | MEDLINE | ID: mdl-12945334

RESUMO

Factors effecting the fluorescence characteristics of the reaction CPFX-Tb were studied thoroughly. The effect of the experimental conditions on the fluorescence intensity was defined. In the pH 6.0 media, CPFX-Tb complex fluorescence system can emit intrinsic fluorescence of Tb. The excitation and emission wavelengths are 328 nm and 545 nm. The linear range is 1.0 x 10(-8)-1.0 x 10(-6) mol.L-1. The regression equation is F = 1.57 + 4.87 x 10(8) c, r = 0.9999 with the detection limit of 5.0 x 10(-9) mol.L-1. It has been satisfactory for the determination of trace ciprofloxacin in urine by using terbium ion as fluorescent probe.


Assuntos
Anti-Infecciosos/urina , Ciprofloxacina/urina , Térbio , Quelantes , Corantes Fluorescentes , Humanos , Espectrometria de Fluorescência
18.
Mol Cell Biol ; 20(11): 4169-80, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10805758

RESUMO

Aberrant expression of developmentally silenced genes, characteristic of tumor cells and regenerating tissue, is highly correlated with increased cell proliferation. By modeling this process in vitro in synthetic nuclei, we find that DNA replication leads to deregulation of established developmental expression patterns. Chromatin assembly in the presence of adult mouse liver nuclear extract mediates developmental stage-specific silencing of the tumor marker gene alpha-fetoprotein (AFP). Replication of silenced AFP chromatin in synthetic nuclei depletes sequence-specific transcription repressors, thereby disrupting developmentally regulated repression. Hepatoma-derived factors can target partial derepression of AFP, but full transcription activation requires DNA replication. Thus, unscheduled entry into S phase directly mediates activation of a developmentally silenced gene by (i) depleting developmental stage-specific transcription repressors and (ii) facilitating binding of transactivators.


Assuntos
Inativação Gênica , Ativação Transcricional , alfa-Fetoproteínas/genética , Animais , Carcinoma Hepatocelular , Cromatina , Replicação do DNA , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Células HeLa , Humanos , Fator 1 de Ligação ao Facilitador Linfoide , Camundongos , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Fase S , Moldes Genéticos , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Genética , Células Tumorais Cultivadas , Xenopus
19.
J Biol Chem ; 274(35): 25113-20, 1999 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-10455192

RESUMO

The alpha-fetoprotein gene (AFP) is tightly regulated at the tissue-specific level, with expression confined to endoderm-derived cells. We have reconstituted AFP transcription on chromatin-assembled DNA templates in vitro. Our studies show that chromatin assembly is essential for hepatic-specific expression of the AFP gene. While nucleosome-free AFP DNA is robustly transcribed in vitro by both cervical (HeLa) and hepatocellular (HepG2) carcinoma extracts, the general transcription factors and transactivators present in HeLa extract cannot relieve chromatin-mediated repression of AFP. In contrast, preincubation with either HepG2 extract or HeLa extract supplemented with recombinant hepatocyte nuclear factor 3 alpha (HNF3alpha), a hepatic-enriched factor expressed very early during liver development, is sufficient to confer transcriptional activation on a chromatin-repressed AFP template. Transient transfection studies illustrate that HNF3alpha can activate AFP expression in a non-liver cellular environment, confirming a pivotal role for HNF3alpha in establishing hepatic-specific gene expression. Restriction enzyme accessibility assays reveal that HNF3alpha promotes the assembly of an open chromatin structure at the AFP promoter. Combined, these functional and structural data suggest that chromatin assembly establishes a barrier to block inappropriate expression of AFP in non-hepatic tissues and that tissue-specific factors, such as HNF3alpha, are required to alleviate the chromatin-mediated repression.


Assuntos
Cromatina/metabolismo , Proteínas de Ligação a DNA/farmacologia , Fígado/metabolismo , Proteínas Nucleares/farmacologia , Fatores de Transcrição/farmacologia , alfa-Fetoproteínas/genética , Animais , Extratos Celulares , Linhagem Celular , Células Cultivadas , Cromatina/química , Regulação da Expressão Gênica/efeitos dos fármacos , Fator 3-alfa Nuclear de Hepatócito , Histonas/metabolismo , Fator C1 de Célula Hospedeira , Humanos , Técnicas In Vitro , Nucleossomos/metabolismo , Fator 1 de Transcrição de Octâmero , Oócitos , Moldes Genéticos , Fatores de Transcrição/genética , Ativação Transcricional/genética , Transfecção , Proteínas de Xenopus , Xenopus laevis
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