Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 44
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Nutr Health Aging ; 24(1): 9-15, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31886802

RESUMO

OBJECTIVES: The association between telomeres length (TL) and cancer mortality is uncertain. We tested the hypotheses that long TL are associated with reduced cancer mortality. DESIGN: Prospective cohort study. SETTING: the National Health and Nutrition Survey (NHANES, 1999-2002). PARTICIPANTS: The analytic sample included adults (n = 7183) who had TL measurements. MEASUREMENTS: DNA was obtained via blood samples. Telomere length was assessed using the quantitative polymerase chain reaction method. RESULTS: During follow-up (0.08-12.7 person-years, median = 9.5 years), we observed 195 participants had cancer as causes of death. TL was negatively corelated with age, body mass index (BMI), systolic blood pressure (SBP), C-reactive protein (CRP), race, diabetes, hypertension, cardiovascular diseases (CVD) and cancer mortality, conversely, positively corelated with alcohol use, but not related to diastolic blood pressure (DBP) and smoking. Kaplan-Meier analysis revealed that TL was significantly associated with cancer mortality (log-rank, P <0.001). CONCLUSIONS: Our study expands upon previous evidence of a relationship between TL and cancer mortality. TL may be a useful tool for evaluating risk of cancer mortality in American adults.

2.
Zhonghua Zhong Liu Za Zhi ; 41(12): 918-922, 2019 Dec 23.
Artigo em Chinês | MEDLINE | ID: mdl-31874549

RESUMO

Objective: To investigate the expression level of antisense transcript of pseudogene, general transcription factor Ⅱi psedugen23 (GTF2IP23), in breast cancer and its effect on the host gene general transcription factor Ⅱi (GTF2I). Methods: The expressions of GTF2IP23 and GTF2I were detected in 40 cases of invasive breast cancer tumors and their counterparts by using quantitative real-time polymerase chain reaction (qRT-PCR). The effects of GTF2IP23 on the expression of GTF2I gene and cell proliferation and migration were analyzed by overexpression of GTF2IP23 in breast cancer cells. Results: The expression of GTF2IP23 mRNA in breast cancer tissues was significantly higher than that in adjacent tissues (P<0.001), while the expression of GTF2I mRNA was significantly lower than that in adjacent tissues (P=0.007). The expression of GTF2IP23 was negatively correlated with GTF2I (r=-0.335, P=0.025). The expression of GTF2IP23 in breast cancer cells was significantly higher than in normal breast cells (P<0.01), while GTF2I expression in breast cancer cells was significantly lower than that in normal breast cells (P<0.01). Overexpression of GTF2IP23 in ZR-75-30 cells significantly reduced the expression of GTF2I (P=0.034) and enhanced cell proliferation (P=0.017) and migration (P=0.026) capacity. Conclusions: GTF2IP23 is distinctly upregulated in breast cancer, it inhibits the expression of real gene GTF2I and promotes the proliferation of breast cancer cells.


Assuntos
Neoplasias da Mama/sangue , Proteínas Musculares/metabolismo , Proteínas Nucleares/metabolismo , Transativadores/metabolismo , Fatores de Transcrição TFII/genética , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Proteínas Musculares/genética , Proteínas Nucleares/genética , Reação em Cadeia da Polimerase em Tempo Real , Transativadores/genética , Fatores de Transcrição TFII/metabolismo
6.
J Appl Microbiol ; 124(3): 829-841, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29253325

RESUMO

AIMS: Increasing attention has been attracted to intestinal microbiota, due to interactions with nutrition, metabolism and immune defence of the host. Traditional Chinese medicine (TCM) feed additives have been applied in aquaculture to improve fish health, but the interaction with fish gut microbiota is still poorly understood. This study aimed to explore the effect of adding TCM in feed on the intestinal microbiota of gibel carp (Carassius auratus gibelio). METHODS AND RESULTS: Bacterial communities of 16 fish intestinal contents and one water sample were characterized by high-throughput sequencing and analysis of the V4-V5 region of the 16S rRNA gene. The results showed that the composition and structure of the bacterial community were significantly altered by the TCM feeding. Some phyla increased markedly (Proteobacteria, Actinobacteria, Acidobacteria, etc.), while Fusobacteria were significantly reduced. Concurrently, the richness and diversity of the taxonomic units increased, and the microbiota composition of TCM-treated fish was more homogeneous among individuals. At the genus level, the addition of TCM tended to reduce the incidence of potential pathogens (Aeromonas, Acinetobacter and Shewanella), while stimulating the emergence of some potential probiotics (Lactobacillus, Lactococcus, Bacillus and Pseudomonas). CONCLUSIONS: These data suggested that the feed additive could regulate the fish intestinal microbiota by reinforcing the microbial balance. SIGNIFICANCE AND IMPACT OF THE STUDY: This study may provide useful information for further application of TCM for diseases prevention and stress management in aquaculture.


Assuntos
Bactérias/isolamento & purificação , Medicamentos de Ervas Chinesas/metabolismo , Microbioma Gastrointestinal , Carpa Dourada/microbiologia , Animais , Aquicultura , Bactérias/classificação , Bactérias/genética , Biodiversidade , Carpa Dourada/metabolismo , Sequenciamento de Nucleotídeos em Larga Escala , Medicina Tradicional Chinesa
7.
J Hum Hypertens ; 31(12): 843-847, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28816229

RESUMO

MicroRNAs (miRNA, miR) play vital part in the pathophysiology of arterial remodeling in hypertension patients, and are increasingly becoming novel biomarkers in cardiovascular disease. The study was designed to evaluate the correlation between let-7 expression level and subclinical atherosclerosis in untreated patients with newly diagnosed essential hypertension. We assessed 240 participants including 60 healthy volunteers with normal carotid intima-media thickness (nCIMT), 60 healthy volunteers with increased CIMT (iCIMT), 60 hypertension patients with nCIMT and 60 hypertension patients with iCIMT. All patients underwent measurements of CIMT and ambulatory blood pressure (BP) monitoring. The level of let-7 was quantified using real-time reverse transcription polymerase chain reaction. Correlations of let-7 expression with BP parameters and CIMT were assessed using multiple linear regression analysis. We observed the lowest miRNA let-7 expression (21.70±1.45 vs 29.33±2.58 vs 31.50±1.80 vs 35.49±2.33; P<0.001) in healthy controls with nCIMT, followed by healthy controls with iCIMT, then hypertension patients with nCIMT and highest expression in hypertension patients with iCIMT. Let-7 was independently correlated with CIMT(r=0.587, P<0.001), and multiple linear regression analysis showed that let-7 was independently correlated with CIMT (ß=0.031, P<0.001). Our findings provide significant evidence that plasma let-7 could represent a non-invasive marker for atherosclerosis in hypertensive patients and herald the emergence of a potential indicator to monitor end-organ damage in hypertension.


Assuntos
Espessura Intima-Media Carotídea , Hipertensão/sangue , MicroRNAs/sangue , Adulto , Estudos Transversais , Feminino , Humanos , Hipertensão/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
8.
Genet Mol Res ; 16(1)2017 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-28362993

RESUMO

IL-17 is associated with the occurrence and development of laryngeal cancer. However, no study has reported the association between IL-17 polymorphisms and laryngeal cancer susceptibility. Therefore, we analyzed the association of three polymorphism loci (rs2275913, 197 G/A; rs3748067, 383 A/G; and rs763780, 7488 T/C) of IL-17A and IL-17F with laryngeal cancer in the Chinese population. A case-control study was performed with 325 patients and 325 controls. Polymorphisms were detected by polymerase chain reaction and sequencing methods. SPSS17.0 software was used for statistical analysis. Allele and genotype frequencies of IL-17A rs2275913 were significantly different between patients and controls (P < 0.05). Frequencies of rs2275913 (197 G/A) AA and GA+AA genotypes compared to the GG genotype were significantly higher in patients than in controls, indicating the association of these genes with laryngeal cancer susceptibility; adjusted OR values were 2.54 (1.50-4.23) and 1.62 (1.19-2.17), respectively. Furthermore, individuals with the GA+AA genotype, compared to the GG genotype, aged ≤60 years, with smoking and alcohol consumption habits, and without a family history of cancer showed a higher cancer risk (OR = 2.74, 95%CI = 1.41-5.23; OR = 2.11, 95%CI = 1.21-3.55; OR = 1.91, 95%CI = 1.02-3.70; OR = 1.99, 95%CI = 1.08-3.39, respectively). In conclusion, the rs2275913 IL-17A (197 G/A) is associated with the incidence and development of laryngeal cancer in the Chinese population, and the AA and GA+AA genotypes harbor a high laryngeal cancer risk.


Assuntos
Interleucina-17/genética , Neoplasias Laríngeas/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Alelos , Grupo com Ancestrais do Continente Asiático/genética , Estudos de Casos e Controles , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Humanos , Interleucina-17/metabolismo , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , Fatores de Risco , Fumar/efeitos adversos
9.
J Hum Hypertens ; 31(3): 200-205, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27629245

RESUMO

MicroRNAs (miRs) are key posttranscriptional regulators of gene expression in all eukaryotic cells and have a vital role in the evolution of hypertension and cardiovascular remodelling and, therefore, have emerged as potential biomarkers for cardiovascular disease. We assessed 240 participants, including 60 healthy volunteers with normal carotid intima-media thickness (nCIMT), 60 healthy volunteers with increased CIMT (iCIMT), 60 hypertensive patients with nCIMT and 60 hypertensive patients with iCIMT. All patients underwent measurements of CIMT, carotid-femoral pulse wave velocity (cfPWV) and ambulatory blood pressure (BP) monitoring. Plasma miR-92a expression was quantified by real-time reverse transcription PCR. Correlations between miR-92a expression and BP parameters, CIMT and cfPWV were assessed using the Spearman correlation coefficient. We observed the lowest miR-92a expression (24.59±1.30 vs 27.76±2.13 vs 29.29±1.89 vs 33.76±2.08; P<0.001) in healthy controls with nCIMT, followed by healthy controls with iCIMT, then hypertensive patients with nCIMT and the highest expression in hypertensive patients with iCIMT. Additionally, MiR-92a levels showed a significant positive correlation with 24-h mean systolic BP (r=0.807, P<0.001), 24-h mean diastolic BP (r=0.649, P<0.001), 24-h mean pulse pressure (PP) (r=0.697, P<0.001), 24-h daytime PP (r=0.654, P<0.001), 24-h nighttime PP (r=0.573, P<0.001), CIMT (r=0.571, P<0.001) and cfPWV (r=0.601, P<0.001). Our data present significant evidence that circulating miR-92a represents a potential noninvasive atherosclerosis marker in essential hypertensive patients.


Assuntos
Aterosclerose/sangue , Hipertensão Essencial/sangue , MicroRNAs/sangue , Adulto , Aterosclerose/diagnóstico por imagem , Biomarcadores/sangue , Pressão Sanguínea , Espessura Intima-Media Carotídea , Hipertensão Essencial/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Análise de Onda de Pulso , Estudos Retrospectivos
10.
Zhonghua Yi Xue Za Zhi ; 96(12): 971-4, 2016 Mar 29.
Artigo em Chinês | MEDLINE | ID: mdl-27045724

RESUMO

OBJECTIVE: To establish the isolation, culture and identification methods of primary rat skeletal muscle satellite cells (SMSC) and observe its characterization of differentiation in vitro. METHODS: Skeletal muscle satellite cells were obtained by tissue block culture method in combination with pre-plating techniques, and the purity of these cells was detected by both immunocytochemistry and fluorescence activated cell sorter (FACS) with Pax7 as marker of SMSC. Myogenesis of these cells was induced in differentiation medium and the mRNA expressions of myogenic differentiation gene (MyoD) and Myogenin were determined by Real-time polymerase chain reaction (PCR). RESULTS: Cells crawled out from the edge of tissue blocks after 1 week of culture. After purification by pre-plating techniques, more than 97.6% of the cells expressed Pax7, a unique marker of satellite cells. The mRNA of MyoD and Myogenin showed time-specific expression in the myogenesis induction process in vitro. CONCLUSION: Skeletal muscle satellite cells with high purity and strong differentiation ability can be obtained by means of tissue block culture method.


Assuntos
Desenvolvimento Muscular/genética , Proteína MyoD/genética , Miogenina/genética , Fator de Transcrição PAX7/genética , Células Satélites de Músculo Esquelético , Animais , Diferenciação Celular , Ratos , Reação em Cadeia da Polimerase em Tempo Real
11.
Neoplasma ; 63(2): 215-22, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26774143

RESUMO

To explore the potential clinical anti-tumor roles of Bacillus subtilis fmbJ-derived fengycin on cell growth and apoptosis in colon cancer HT29 cell line.Fengycin was extracted from Bacillus subtilis fmbJ and detected using HPLC. The effects of different concentration of fengycin on colon cell HT29 cell activity at different time points were analyzed using MTT assay. ROS level in colon HT29 cells affected by fengycin was detected using DCFH-DA method, followed by measuring the effects of fengycin on HT29 cell apoptosis and cell cycle by flow cytometry. The effects of fengycin on Bax/Bcl-2, CDK4/cyclin D1, Caspase-6 and Caspase-3 expressions in HT29 cells were analyzed using western blot. Also, mRNA levels of Bax/Bcl-2 and CDK4/cyclin D1 in HT29 cells affected by fengycin were analyzed using qRT-PCR.Compared with controlss, 20 µg/mL of fengycin performed an inhibit role on HT29 cell growth of at 3 day (P<0.05), and high dose of fengycin showed more excellent effect on inhibiting HT29 cell growth with time increasing. Besides, fengycin could induce HT29 cell apoptosis and affect the cell cycle arrest at G1. ROS level in HT29 cells treated by fengycin was significantly increased compared with that in control group (P<0.05). Western blot analysis showed that after being treated with fengycin, Bax, Caspase-3, and Caspase-6 expressions were increased, however, Bcl-2, and CDK4/cyclin D1 expressions were decreased (P<0.05).Our study suggested that fengycin may play certain inhibit roles in the development and progression of colon cancer through involving in the cell apoptosis and cell cycle processes by targeting the Bax/Bcl-2 pathway.


Assuntos
Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Bacillus subtilis/metabolismo , Proliferação de Células/efeitos dos fármacos , Neoplasias do Colo/tratamento farmacológico , Pontos de Checagem da Fase G1 do Ciclo Celular/efeitos dos fármacos , Lipopeptídeos/farmacologia , Caspase 3/metabolismo , Caspase 6/metabolismo , Linhagem Celular Tumoral , Ciclina D1/metabolismo , Quinase 4 Dependente de Ciclina/metabolismo , Células HT29 , Humanos , Espécies Reativas de Oxigênio/metabolismo , Proteína X Associada a bcl-2/metabolismo
12.
Genet Mol Res ; 14(4): 13391-402, 2015 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-26535654

RESUMO

The aim of this study was to investigate the association between the cyclooxygenase 2 (COX2) -765G>C (rs20417) polymorphism and prostate cancer (PC) risk using meta-analysis. A systematic literature search was performed using the PubMed, Embase, Cochrane Library, and Google Scholar databases by using the terms "cyclooxygenase-2/COX-2/PTGs2", "polymorphism" or "variation", and "prostate" and "cancer" or "carcinoma" to identify relevant articles up to June 14, 2014. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were assessed for PC risk associated with COX2 -765G>C polymorphism using fixed- and random-effect models. We identified a total of nine publications, including 5952 cases and 5078 controls, to investigate the effect of COX2 -765G>C on PC risk, and found no significant association in any genetic model tested (CC vs GG: OR = 0.993, 95%CI = 0.923-1.068; GC+CC vs GG: OR = 1.041, 95%CI = 0.931-1.103; CC vs GC+GG: OR = 0.858, 95%CI = 0.689-1.067; CC vs GG: OR = 0.871, 95%CI = 0.689-1.086; GC vs GG: OR = 1.032, 95%CI = 0.945-1.127). Power analysis and tests for publication bias ensured the reliability of our results. This meta-analysis suggested that the functional COX2 -765G>C polymorphism, located in the COX2 gene promoter, is unlikely to be associated with PC risk. However, additional larger, well-designed studies are still required to reach a conclusive result on this issue.


Assuntos
Ciclo-Oxigenase 2/genética , Polimorfismo de Nucleotídeo Único , Neoplasias da Próstata/genética , Alelos , Estudos de Casos e Controles , Predisposição Genética para Doença , Genótipo , Humanos , Masculino , Razão de Chances , Viés de Publicação
13.
Eur Rev Med Pharmacol Sci ; 18(19): 2789-97, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25339471

RESUMO

OBJECTIVE: Inducible nitric oxide (NO) synthase (iNOS) inhibitor S-methylisothiourea (SMT) has been reported to have anti-tumor effects on several types of cancers.  We aimed to investigate whether SMT can inhibit nasopharyngeal carcinoma cells CNE-2 proliferation through raise chemotherapy effect of diaminodichloroplatinum (DDP). MATERIALS AND METHODS: CNE-2 cells were treated with SMT, DDP and both of them respectively. MTT and colony-forming assay was performed to detect the proliferation effect of the treatment. Hoechst 33258 staining and apoptosis analysis were performed to investigate the apoptosis effect of chemotherapy. Additionally, the NO level was detected to estimate the activity of iNOS. RESULTS: CNE-2 cells expressed high level of iNOS. SMT can inhibit CNE-2 cells growth in a dose-dependent manner and have the effect on reducing dosage of DDP as well as enhancing the anti-tumor efficacy by promote cell apoptosis. CONCLUSIONS: Our findings suggested that SMT play a synergism role in the inhibition process of DDP on nasopharyngeal carcinoma, and SMT could be a promising therapeutic factor for cancer prevention.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Apoptose/efeitos dos fármacos , Cisplatino/farmacologia , Isotiurônio/análogos & derivados , Neoplasias Nasofaríngeas/tratamento farmacológico , Óxido Nítrico Sintase Tipo II/antagonistas & inibidores , Carcinoma , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Cisplatino/administração & dosagem , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Humanos , Isotiurônio/farmacologia , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/enzimologia , Neoplasias Pulmonares/patologia , Carcinoma Nasofaríngeo , Neoplasias Nasofaríngeas/enzimologia , Neoplasias Nasofaríngeas/patologia
14.
Placenta ; 33(12): 977-81, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23103204

RESUMO

Cocaine abuse in pregnant women is currently a significant public hygiene problem and is tightly associated with elevated risk for preterm delivery. Placental steroidogenesis especially progesterone production was essential for success and maintenance of pregnancy in humans and rodents. In the present study, we determined the impact of prenatal cocaine exposure on pathways of placental progesterone synthesis in rats. Pregnant rats were treated cocaine twice daily (15 mg/kg/day) during the third trimester, and the maternal and fetal plasma progesterone and pregnenolone concentrations were detected. We also examined both the protein and mRNA expression of some key enzymes and regulators for progesterone production in placenta. Results showed that, after maternal cocaine use during pregnancy, progesterone and pregnenolone concentrations in both maternal and fetal rats were significantly decreased. Although prenatal cocaine exposure had no effects on placental 3ß-hydroxysteroid dehydrogenase type 1 (3ßHSD1) expression, protein and mRNA expression of the cholesterol side-chain cleavage enzyme (P450scc/CYP11a) in placenta was significantly inhibited. Moreover, protein and mRNA expressions of MLN64 that regulating cholesterol transport and activating protein 2γ (AP2γ/Tfap2c) that controlling P450scc/CYP11a gene expression in placenta were both decreased following maternal cocaine use in pregnancy. Collectively, this study suggested that prenatal cocaine exposure could insult the placental progesterone production in rats possibly associated with the high risk for preterm delivery.


Assuntos
Cocaína/toxicidade , Regulação para Baixo/efeitos dos fármacos , Placenta/efeitos dos fármacos , Progesterona/biossíntese , Animais , Enzima de Clivagem da Cadeia Lateral do Colesterol/genética , Enzima de Clivagem da Cadeia Lateral do Colesterol/metabolismo , Transtornos Relacionados ao Uso de Cocaína/metabolismo , Inibidores da Captação de Dopamina/toxicidade , Feminino , Sangue Fetal , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Placenta/enzimologia , Placenta/metabolismo , Gravidez , Complicações na Gravidez/metabolismo , Pregnenolona/sangue , Progesterona/sangue , RNA Mensageiro/metabolismo , Distribuição Aleatória , Ratos , Ratos Sprague-Dawley , Natimorto , Fator de Transcrição AP-2/genética , Fator de Transcrição AP-2/metabolismo , Vasoconstritores/toxicidade
15.
Talanta ; 63(3): 593-8, 2004 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-18969474

RESUMO

Silica monoliths were fabricated inside fused-silica capillaries. Then the monolithic columns were coated with membrane-like zirconia. The zirconia-coated silica monoliths exhibited different EOF behavior comparing with that of bare silica monoliths. The magnitude and direction could be manipulated by changing the running buffers. Due to the amphoteric characteristic of zirconia, the silica monoliths with zirconia surface facilitate the separation of basic compounds. Aromatic amines and alkaloids were separated without obvious peak tailing. The zirconia surface was easily modified with octadecylphosphonic acid for the separation of neutral compounds. Column efficiency as high as 90,000 and 80,000m(-1) was obtained for beberine and naphthalene, respectively. Furthermore, the zirconia coating increased the stability of the monolithic columns. Even after being exposed to severe condition, there was no apparently efficiency decrease for the test samples.

16.
Acta Neurochir Suppl ; 81: 343-5, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12168342

RESUMO

To examine the feasibility of measuring the nitric oxide (NO) metabolites nitrate and nitrite in microdialysate samples from the human brain, microdialysis probes were placed in normal appearing cerebral cortex of severely head injured patients in the Neurosurgical Intensive Care Unit at Ben Taub General Hospital. Nitrate/nitrite analysis was performed using NO chemiluminescence. Low micromolar levels of NO metabolites were consistently and easily detected. These levels seen are comparable to levels reported in CSF but tissue tortuosity and probe recovery considerations suggest that the absolute concentrations at the probe site are probably ten fold higher. Microdialysis with measurement of nitric oxide metabolites is technically feasible and may provide valuable insights into both normal neurochemistry and neurochemical derangements in disease.


Assuntos
Encéfalo/metabolismo , Córtex Cerebral/metabolismo , Traumatismos Craniocerebrais/metabolismo , Monitorização Fisiológica/métodos , Nitratos/metabolismo , Óxido Nítrico/metabolismo , Nitritos/metabolismo , Biomarcadores/análise , Humanos , Microdiálise/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
17.
Mol Cell Biol ; 21(9): 2969-80, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11287603

RESUMO

The major distal regulatory sequence for the beta-globin gene locus, the locus control region (LCR), is composed of multiple hypersensitive sites (HSs). Different models for LCR function postulate that the HSs act either independently or synergistically. To test these possibilities, we have constructed a series of expression cassettes in which the gene encoding the enhanced green fluorescent protein (EGFP) is under the control of DNA fragments containing single and multiple HSs of the LCR. LCR DNA fragments containing only the minimal region needed for position-independent expression (HS cores) or containing cores plus flanking sequences (HS units) were compared to ascertain whether conserved sequences between the HS cores contributed to enhancement. Expression of these constructs was measured after targeted integration into three defined loci in murine erythroleukemia cells using recombinase-mediated cassette exchange. At all three marked loci, synergistic enhancement of expression was observed in cassettes containing a combination of HS2, HS3, and HS4 units. In contrast, HS2, HS3, and HS4 cores (without flanking sequences) give an activity equivalent to the sum of the activities of the individual HS cores. These data suggest a model in which an HS core plus flanking regions, bound by specific proteins, forms a structure needed for interaction with other HS units to confer strong enhancement by the LCR. The three targeted integration sites differ substantially in their permissivity for expression, but even the largest LCR construct tested could not overcome these position effects to confer equal expression at all three sites.


Assuntos
Elementos Facilitadores Genéticos , Globinas/genética , Região de Controle de Locus Gênico , Sítios de Ligação , Humanos
18.
Mol Cell Biol ; 21(1): 298-309, 2001 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-11113204

RESUMO

We have inserted two expression cassettes at tagged reference chromosomal sites by using recombinase-mediated cassette exchange in mammalian cells. The three sites of integration displayed either stable or silencing position effects that were dominant over the different enhancers present in the cassettes. These position effects were strongly dependent on the orientation of the construct within the locus, with one orientation being permissive for expression and the other being nonpermissive. Orientation-specific silencing, which was observed at two of the three site tested, was associated with hypermethylation but not with changes in chromatin structure, as judged by DNase I hypersensitivity assays. Using CRE recombinase, we were able to switch in vivo the orientation of the transgenes from the permissive to the nonpermissive orientation and vice versa. Switching from the permissive to the nonpermissive orientation led to silencing, but switching from the nonpermissive to the permissive orientation did not lead to reactivation of the transgene. Instead, transgene expression occurred dynamically by transcriptional oscillations, with 10 to 20% of the cells expressing at any given time. This result suggested that the cassette had been imprinted (epigenetically tagged) while it was in the nonpermissive orientation. Methylation analysis revealed that the methylation state of the inverted cassettes resembled that of silenced cassettes except that the enhancer had selectively lost some of its methylation. Sorting of the expressing and nonexpressing cell populations provided evidence that the transcriptional oscillations of the epigenetically tagged cassette are associated with changes in the methylation status of regulatory elements in the transgene. This suggests that transgene methylation is more dynamic than was previously assumed.


Assuntos
Cromatina/genética , Regulação da Expressão Gênica/genética , Mutagênese Insercional/genética , Transgenes/genética , Proteínas Virais , Animais , Azacitidina/farmacologia , Metilação de DNA/efeitos dos fármacos , Desoxirribonuclease I/metabolismo , Elementos Facilitadores Genéticos/genética , Citometria de Fluxo , Regulação da Expressão Gênica/efeitos dos fármacos , Inativação Gênica/efeitos dos fármacos , Genes Reporter/genética , Impressão Genômica/genética , Globinas/genética , Ácidos Hidroxâmicos/farmacologia , Hibridização in Situ Fluorescente , Integrases/metabolismo , Região de Controle de Locus Gênico/genética , Camundongos , Regiões Promotoras Genéticas/genética , Ativação Transcricional/efeitos dos fármacos , Transfecção , Células Tumorais Cultivadas
19.
Se Pu ; 19(6): 497-502, 2001 Nov.
Artigo em Chinês | MEDLINE | ID: mdl-12545458

RESUMO

Solid phase microextraction (SPME) is a solvent-free technique with high extraction efficiency and easy to perform automatically. It can be coupled with high performance liquid chromatography to perform efficient analysis of compounds with high polarity. The advances in solid phase microextraction coupled with high performance liquid chromatography, including its theory, interfaces, coating materials and applications, are reviewed with 36 references.


Assuntos
Cromatografia Gasosa/métodos , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia Gasosa/instrumentação , Cromatografia Líquida de Alta Pressão/instrumentação , Inseticidas/análise , Lidocaína/análise , Compostos Organofosforados , Solventes
20.
Talanta ; 54(1): 79-88, 2001 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-18968228

RESUMO

Porous ceria-zirconia composite with narrow particle size distribution and large specific surface area was synthesized by a sol-gel process. Chromatographic properties of the native supports was investigated in normal phase mode for the separation of test mixtures of basic, neutral and acidic compounds. The new packing material exhibited polar and basic properties, which are suitable for the separation of basic compounds. Lypophilic packing has been obtained by the modification of the ceria-zirconia with stearic acid, which exhibited strong hydrophobicity relative to the native packing. Therefore, the modified ceria-zirconia behaves as a reversed-phase packing material. Different selectivity towards basic compounds was observed on the new packing compared to the native ceria-zirconia and conventional ODS stationary phase.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA