Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 32
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Nanoscale ; 11(40): 18790-18796, 2019 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-31595929

RESUMO

Microfluidics has been considered as an effective platform in the mechanism study and large-scale manufacturing of nanomaterials. In this work, we report the facile synthesis of quantum-confined CsPbBr3 nanowires (NWs) by using a continuous-flow microfluidic reactor. The optimized reaction temperature is around 50 °C, and one "synthesis run" by microfluidics requires only ten minutes. This study reveals that the formation of CsPbBr3 NWs takes place by a hybrid growth mechanism of seed-mediated growth and oriented attachment growth. This microfluidic approach benefits the alignment of the short quantum-confined NWs and promotes their oriented attachment to form long NWs, while conventional flask synthesis results in large and irregular nanorods under the same reaction conditions. This work not only provides a new synthetic path for the preparation of CsPbX3 NWs but also sheds some light on the fundamental study of CsPbX3 NWs.

2.
Angew Chem Int Ed Engl ; 58(49): 17631-17635, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31560445

RESUMO

Fundamental insights into the reaction kinetics of organic-inorganic lead halide perovskite nanocrystals (LHP NCs) are still limited due to their ultrafast formation rate. Herein, we develop a water-oil interfacial synthesis of MAPbBr3 NCs (MA=CH3 NH3 + ), which prolongs the reaction time to tens of minutes. This method makes it possible to monitor in situ the formation process of MAPbBr3 NCs and observe successive spectral evolutions from 438 to 534 nm in a single reaction by extending reaction time. The implementation of this method depends on reducing the formation rate of PbBr6 4- octahedra and the diffusion rate of MA. The formation of PbBr6 4- is a rate-determining step, and the biphasic system offers a favorable reaction condition to control the mass transfer of MA. The effects of temperature and concentration of precursor and ligand are investigated in detail.

3.
Nanoscale Res Lett ; 14(1): 152, 2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-31049739

RESUMO

Perovskite quantum dots (QDs) have been widely used in white light-emitting diodes (WLEDs), due to their high quantum yield (QY), tunable bandgap, and simple preparation. However, the red-emitting perovskite QDs are usually containing iodine (I), which is not stable under continuous light irradiation. Herein, perovskite-based WLED is fabricated by lead-free bismuth (Bi)-doped inorganic perovskites Cs2SnCl6 and less-lead Mn-doped CsPbCl3 QDs, which emits white light with color coordinates of (0.334, 0.297). The Bi-doped Cs2SnCl6 and Mn-doped CsPbCl3 QDs both show excellent stability when kept in the ambient air. As benefits from this desired characteristic, the as-prepared WLED shows excellent stability along with operating time. These results can promote the application of inorganic perovskite QDs in the field of WLEDs.

4.
Huan Jing Ke Xue ; 40(5): 2019-2026, 2019 May 08.
Artigo em Chinês | MEDLINE | ID: mdl-31087836

RESUMO

In this study, the size distribution of aerosol number concentration (10 nm-10µm), particulate matter (PM2.5 and PM10), and meteorological data were collected from June 1 to 25, 2017, at the summit of Mountain Taishan by using a wide-range particle spectrometer (WPS), a ß-ray continuous ambient particulate monitor, and an automatic weather station. Consequently, the characteristic of the aerosol size distribution and their impact factors were analyzed. The results indicated that the average mass concentration of PM2.5 and PM10 were 20.7 µg·m-3 and 82.4 µg·m-3, respectively, and the ratio of PM2.5/PM10 was only 25.1%. The average number concentration, surface area concentration, and volume concentration were 8672.8 cm-3, 408.3µm2·cm-3, and 24.2µm3·cm-3, respectively. The spectrum distribution was unimodal for number concentration, and trimodal for surface area and volume concentration. The dominant sizes of the number concentration and the surface area concentration were located at 10-20 nm and 100-500 nm, respectively. The volume concentration had dominant sizes at 100-500 nm and 2.5-10 µm. Wind direction was proved to have a greater influence on PM and number concentration compared with wind speed. With the enhancement of RH, the spectrum of number concentration was converted from bimodal to unimodal distribution, while the surface area concentration changed from unimodal to trimodal distribution.

5.
Nanotechnology ; 30(24): 245201, 2019 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-30812014

RESUMO

CsPbX3 perovskite nanocrystals (NCs) are becoming a promising material for optoelectronic devices that possess an optically tunable bandgap, and bright photoluminescence. However, the toxic Pb is not environmentally friendly and the quantum yield (QY) of blue emitting NCs is relatively low. In addition, the red emitting perovskite containing iodine is not stable under light illumination. In this paper, high QY, blue emitting, non-toxic fluorescent nanomaterial carbon dots and orange-emitting CsPb0.81Mn0.19Cl3 NCs with partial Pb replacement are combined to fabricate white light-emitting diodes (WLEDs). A WLED with color coordinates of (0.337, 0.324) and a correlated color temperature of 4804 K is fabricated. Compared to red emitting perovskite containing iodine, the CsPb0.81Mn0.19Cl3 NCs are stable no matter whether they are stored in the air or exposed under ultraviolet light. Therefore, the as-fabricated WLED shows good color stability against increasing currents and long-term working stability.

6.
Sci Total Environ ; 661: 1-9, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30660033

RESUMO

Based on a field campaign in Shouxian, a rural site on the Yangtze River Delta, China, from December 14, 2016 to January 4, 2017, the vertical profiles of black carbon (BC) and planetary boundary layer (PBL) structures were studied. In total, 58 vertical profiles were obtained, including of the PM2.5, BC mass concentration (mBC) and relevant meteorological parameters. Four profile types were categorized: I: uniform vertical distributions (38%), II: higher values at lower altitudes (29%), III: bimodal distributions with high values near the ground and at higher altitudes (17%), and IV: unimodal distributions with high values at higher altitudes (11%). A further analysis confirmed that all types were mainly influenced by the PBL diurnal evolution and local emissions, while types III and IV were strongly associated with the temperature inversions at low altitudes. The diurnal variations of the BC vertical profiles mainly followed the evolution of the PBL. In the early morning, the average mBC within the PBL (MBL, BC) increased significantly, reaching the highest level in the diurnal cycles, i.e., approximately 13.0 µg m-3. The pollutants were confined to a thin layer <0.2 km above the ground, which contributed to the smoke produced by local residential biomass burning. Around noon, the accumulated BC in the layer was diluted as a result of the development of the PBL. The height of the PBL (HPBL) reached its maximum in the afternoon, with an average of 0.65 km, while MBL, BC dropped to its minimum, with an average of 7.8 µg m-3. As evening approached, the BC produced by local residential biomass burning gradually accumulated near the ground and linearly declined along the standardized height (HS) within the nocturnal boundary layer (NBL). There were large differences in the BC concentration within and above the PBL both in the daytime and at night.

7.
Huan Jing Ke Xue ; 39(3): 961-971, 2018 Mar 08.
Artigo em Chinês | MEDLINE | ID: mdl-29965438

RESUMO

Two hundred seventy-nine PM2.5 samples were collected from January 9, 2015 to January 31, 2015 in Lin'an, Nanjing, and Suzhou. They were analyzed for organic carbon (OC) and elemental carbon (EC) following the thermal/optical reflection protocol. The pollution characteristics of OC and EC in PM2.5 during the winter in the Yangtze River Delta were discussed in detail.The average mass concentrations of PM2.5 in the three sample sites were (123.56±61.11), (144.77±62.91), and (156.5±68.97) µg·m-3, respectively, which were in excess of the Ambient Air Quality Standard (GB 3095-2012) 24-hr mass-based standard of 75 µg·m-3. The average mass concentration of OC and EC were (21.93±11.69)/(6±3.6), (20.32±10.3)/(5.39±3.07), and (27.08±14.35)/(6.4±4.29) µg·m-3, respectively. Lin'an, which is regarded as the background site for the atmospheric environment in the Yangtze River Delta, is also polluted seriously. The OC was strongly correlated with EC in Lin'an (R2=0.83), Nanjing (R2=0.72), and Suzhou (R2=0.72). This shows that the carbonaceous aerosols have similar sources during the winter in the Yangtze River Delta. All of the samples' OC/EC ratios exceeded 2.0, with the sample OC/EC ratios mainly distributed in the range of 2.5-6.0, indicating that coal combustion and vehicle exhaust are the main sources of OC and EC. The estimated mass concentrations of SOC were (9.23±5.26), (6.82±4.36), and (12.56±7.52) µg·m-3, respectively, which contributed 42%, 34%, and 46% to the OC, indicating that SOC is an important part of OC. Backward-trajectory shows that the mass concentrations of PM2.5, OC, and EC have a good correlation with the transmission path of the main air mass. The mass concentrations of PM2.5, OC, and EC controlled by the air mass from poor air quality areas are 1.14-1.7 times, 1.55-2.1 times, and 1.94-2.47 times higher than that in the air mass from good air quality areas.

8.
Dalton Trans ; 47(18): 6598-6604, 2018 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-29700544

RESUMO

Two new centric alkali metal bismuth selenite fluorides, ABi2SeO3F5 (A = K and Rb), have been synthesized through a soft hydrothermal method. KBi2SeO3F5 crystallizes in an orthorhombic crystal system with the centric space group Pbcm possessing a three-dimensional (3D) network made up of SeO3 trigonal pyramids and asymmetric BiO3F5 polyhedra. As regards compound RbBi2SeO3F5, it crystallizes in a triclinic crystal system with a centric space group of P1[combining macron], which contains alternant two-dimensional (2D) [Bi2SeO3F5]∞1- layers separated by Rb+ cations. In terms of structure, the differences between KBi2SeO3F5 and RbBi2SeO3F5 originate from the size of alkali metal cations, which has a great influence on the framework geometry and the dimensionalities of crystals. The UV-vis diffuse reflectance spectroscopy study of powder samples indicates that the band gaps of KBi2SeO3F5 and RbBi2SeO3F5 are approximately 4.08 and 4.18 eV, respectively, which are the largest ones among the known bismuth selenites owing to the existence of alkali metal cations as well as fluorine anions in crystals. Furthermore, theoretical calculations show that the optical absorption of two compounds is mainly attributed to the contribution of BiOxFy polyhedra and [SeO3]2- anionic groups.

9.
Sci Total Environ ; 621: 507-515, 2018 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-29195199

RESUMO

A more precise atmospheric extinction coefficient would be advantageous for improving air quality (visibility) forecasting. In this study, the size distribution, chemical composition and relative humidity were measured in Lin'an from January 9 to 31, 2015. The merits and weaknesses of three parameterization schemes are discussed in this paper, including the non-linear fitting scheme, the IMPROVE (Interagency Monitoring of Protected Visual Environment) algorithm and the κ-elemental carbon (EC)-Mie model. Comparing the three schemes mentioned above, we find that the non-linear fitting equation requires the least amount of data, and its calculation process is the simplest. However, its calculated values are significantly influenced by specific data and fitting formulas. The uncertainty of the variable coefficients makes it difficult to directly implement this method for other datasets. The calculated values of the three versions of the IMPROVE algorithm strongly correlate with the measured values, with slopes near 1.0 and statistical indexes (R2) of 0.848, 0.858 and 0.866. However, this method is affected by the chemical compositions of the particles in different regions; for example, when the quality of PM2.5 is reconstructed from the measured data, the coefficients of different components change, thus affecting the final results. The κ-EC-Mie model objectively reflects the changes in the law of visibility, as the model considers both the chemical composition and size distribution of particles, and its predominant merit is derived from the fact that it is calculated without an empirical formula, which may eliminate the computational errors caused by the uncertainties of coefficients.

10.
Arch Environ Contam Toxicol ; 72(4): 481-495, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28434030

RESUMO

The origins and spatial and temporal distributions of air pollutants (PM2.5, PM10, CO, SO2, NO2 and O3) during May to June of 2015 were investigated using data from 1490 monitoring sites in China. Aerosol number concentrations and meteorological data from Shijiazhuang, Nanjing, and Suzhou were combined with the MIX Asian emission data and the HYSPLIT model. Furthermore, the diurnal variation, size distribution, and main sources of air pollutants and aerosols were selectively characterized in the North China Plain (NCP) and the Yangtze River Delta (YRD). High values of particulate matter concentrations (PM), including PM2.5 and PM10, occurred in the northwestern and central regions of eastern China. Elevated PM2.5 and PM10 concentrations represented natural dust sources and anthropogenic resident, power plant, industry, and traffic emissions sources, respectively. The concentrated distributions of SO2 were similar to those of PM. The CO concentrations were distributed uniformly in China. High O3 values occurred above the Qinghai province. During the observation period, the air masses mainly originated from the northwest NCP and from the southwest or northeastern ocean in the YRD, resulting in high concentrations of PM2.5, PM10, SO2, and CO in the NCP, the average values of which were 61.8 ± 40.0, 118.8 ± 66.4, 24.1 ± 24.6 µg m-3, and 1.2 ± 0.9 mg m-3, respectively, and were 1.2, 1.4, 1.5, and 1.3 times larger than those in the YRD. NO2 had higher concentrations in the YRD with an average of 43.7 ± 24.8 µg m-3, which was 1.2 times larger than that in the NCP. The diurnal variations of PM, NO2 and CO had bimodal distributions and SO2 and O3 had unimodal distributions in the NCP and YRD. The aerosol number concentrations had average values of 12,661 ± 5266, 11,189 ± 5905, and 12,797 ± 5931 cm-3 in Shijiazhuang, Nanjing, and Suzhou. Their diurnal variations displayed trimodal peaks at 18:00-21:00, 11:00-14:00, and 06:00-08:00, and their spectra distributions were all unimodal with peaks at 60-70, 60-70, and 100-110 nm, respectively.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Monitoramento Ambiental , China , Poeira , Modelos Químicos , Material Particulado/análise
11.
Huan Jing Ke Xue ; 38(5): 1743-1752, 2017 May 08.
Artigo em Chinês | MEDLINE | ID: mdl-29965076

RESUMO

The particles number concentrations were determined by Wide-range Particle Spectrometer (WPS) in northern suburb of Nanjing in January and April 2015. The information of size distributions was applied in the multiple-path particle dosimetry model (MPPD) v.3.04 to quantify deposition fractions (DF) and number concentration (NC) depositions of fine particles in different regions of human airway, at different air quality levels, at rest and exercise. DF of nucleation mode and Aitken mode at rest and exercise were similar, while DF of accumulation mode at exercise was 2.49 times of that at rest. DF of nucleation mode and Aitken mode in pulmonary (PUL) was the highest, about 48.17% of total deposition fractions (TDF) at rest and 54.23% of TDF at exercise. DF of accumulation mode in head was the highest, about 41.23% of TDF at rest and 80.47% of TDF at exercise. The particle NC deposition in human airway in winter was lower than that in spring, and the total NC deposition in 3 regions was in the order of PUL > tracheobronchial(TB) > head. Compared with resting, nucleation mode deposition in PUL and accumulation mode deposition in TB and head increased at exercise. The worse the air quality, the higher the deposition growth rate of exercising to resting in head. DF difference among regions was mainly due to the different physiological parameters, while NC deposition difference was mainly due to the different particle NC in the local environment.


Assuntos
Poluentes Atmosféricos/análise , Sistema Respiratório , Aerossóis , Poluição do Ar , China , Cidades , Exercício Físico , Humanos , Tamanho da Partícula , Estações do Ano
12.
Huan Jing Ke Xue ; 38(10): 4024-4033, 2017 Oct 08.
Artigo em Chinês | MEDLINE | ID: mdl-29965184

RESUMO

Using a wide-range particle spectrometer (WPS), an environmental management system (EMS), KC-120H middle volume sampler, a 850 professional ion chromatography analyzer, and heat/light carbon analyzer (DRI2001A), we observed the number concentration of aerosols with sizes ranging from 10 nm to 10 µm, gas concentrations, and concentrations of PM2.5, water-soluble ions, OC, and EC in a Lin'an atmospheric background station from January 9 to 31, 2015. The positive matrix factorization (PMF) model was applied for source apportionment, and the size distribution and diurnal variations of emission sources were analyzed based on the meteorological data. The average aerosol concentration was 5062 cm-3·nm-1 and PM2.5 mass concentration was 123.6 µg·m-3. The average concentrations of NO3-, SO42-, and NH4+, the main water-soluble ions in PM2.5 were 19.2, 15.4, and 10.8 µg·m-3, which accounted for 37.9%, 30.4%, and 21.4% of total water-soluble ions, respectively. Theaverage concentrations of OC and EC were 24.4 µg·m-3 and 6.6 µg·m-3. Secondary aerosol formation, coal combustion, motor vehicle emissions, dust, andbiomass burning were the main sources of PM2.5 in Lin'an during winter with contributions of 42.3%, 21.4%, 17.1%, 8.7%, and 10.6%, respectively. Different sources had different aerosol number concentration distributions. The aerosol number concentration spectra of secondary sources, vehicle emissions, dust, and biomass burning followed unimodal-type distributions with peaks at 120, 50, 100, and 90 nm. Coal particle number concentration was a bimodal distribution which exhibited peak values at 25 nm and 100 nm (19842 cm-3·nm-1 and 18372 cm-3·nm-1, respectively). The spectra of surface concentrations of secondary sources, coal combustion, motor vehicle emissions, dust, and biomass burning followed a three-peak distribution. The peaks were at 650, 210, 160, 180, and 575 nm. The diurnal variations of particle number concentrations influenced by diurnal variations in the boundary layer and human activities were consistent with the variations in surface concentrations, which displayed bimodal-type distribution.

13.
Drug Dev Ind Pharm ; 41(3): 458-63, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24471512

RESUMO

OBJECTIVE: The objective of this study was to fabricate a novel nano-bioceramics incorporated lysozyme poly (d, l-lactide-co-glycolide) (PLGA) microsphere. METHODS: The nano-bioceramics was used as a biodegradable and sustained-release antacid to stabilize the lysozyme in the drug release process. First, the nano-bioceramics were prepared by sol-gel method, and then were characterized by energy dispersive X-ray analysis, dynamic light scattering and in vitro degradation test. Second, the lysozyme PLGA microsphere incorporated with nano-bioceramic was fabricated by the S/W/O/W emulsion solvent evaporation method. The microsphere was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and UV circular dichroism (UV CD). Finally the in vitro drug release and bioactivity test was carried out. RESULTS: The composition of the nano-bioceramics was 58% SiO2, 36% CaO, 6% P2O5, and the average particle size was 295 nm. The nano-bioceramics incorporated lysozyme PLGA microspheres were prepared by the multi-emulsion method. The SEM results showed that the bioceramics was uniformly distributed in the PLGA microsphere. Results from in vitro lysozyme release test exhibited a prolonged release time for 1month. The FTIR and UVCD results suggested that the lysozyme in the drug release process had a similar secondary structure conformation to the native one. The Micrococcus lysodeikticus test showed that the microspheres incorporated with bioceramics provided long-term protein stability against the acidic environment resulted from PLGA's degradates and more than 90% of the lysozyme released over the 1 month period was preserved in a bioactive form. CONCLUSION: A novel bioceramics incorporated lysozyme PLGA microsphere was prepared with potentials for sustained protein release formulation.


Assuntos
Vidro/química , Ácido Láctico/síntese química , Microesferas , Muramidase/síntese química , Ácido Poliglicólico/síntese química , Animais , Galinhas , Avaliação Pré-Clínica de Medicamentos/métodos , Ácido Láctico/metabolismo , Muramidase/metabolismo , Ácido Poliglicólico/metabolismo , Copolímero de Ácido Poliláctico e Ácido Poliglicólico
14.
Iran J Pharm Res ; 13(3): 835-42, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25276183

RESUMO

The main objective of this study was to investigate biocompatibility and provide in-vivo pharmacological and toxicological evidence for further investigation of the possibility of pH sensitive ion exchange resin microsphere for clinical utilizations. Acute toxicity study and general pharmacological studies were conducted on the pH sensitive ion exchange resin microsphere we prepared. The general pharmacological studies consist of the effects of the pH sensitive ion exchange resin microsphere on the nervous system of mice, the functional coordination of mice, the hypnosis of mice treated with nembutal at subliminal dose, the autonomic activities of tested mice, and the heart rate, blood pressure, ECG and breathing of the anesthetic cats. The LD50 of pH sensitive ion exchange resin microsphere after oral administration was more than 18.84 g·Kg(-1). Mice were orally administered with 16 mg·Kg(-1), 32 mg·Kg(-1) and 64 mg·Kg(-1) of pH sensitive ion exchange resin microsphere and there was no significant influence on mice nervous system, general behavior, function coordination, hypnotic effect treated with nembutal at subliminal dose and frequency of autonomic activities. Within the 90 min after 5 mg·Kg(-1), 10 mg·Kg(-1), 20 mg·Kg(-1) pH sensitive ion exchange resin microsphere was injected to cat duodenum, the heart rate, blood pressure, breathing and ECG of the cats didn't make significant changes in each experimental group compared with the control group. The desirable pharmacological and toxicological behaviors of the pH sensitive ion exchange resin microsphere exhibited that it has safe biocompatibility and is possible for clinical use.

15.
Cell Reprogram ; 14(1): 88-97, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22313114

RESUMO

Blood cells transfusion and hematopoietic stem cells (HSCs) transplantation are important methods for cell therapy. They are widely used in the treatment of incurable hematological disorder, infectious diseases, genetic diseases, and immunologic deficiency. However, their availability is limited by quantity, capacity of proliferation and the risk of blood transfusion complications. Recently, human embryonic stem cells (hESCs) have been shown to be an alternative resource for the generation of hematopoietic cells. In the current study, we describe a novel method for the efficient production of hematopoietic cells from hESCs. The stable human fetal liver stromal cell lines (hFLSCs) expressing erythropoietin (EPO) were established using the lentiviral system. We observed that the supernatant from the EPO transfected hFLSCs could induce the hESCs differentiation into hematopoietic cells, especially erythroid cells. They not only expressed fetal and embryonic globins but also expressed the adult-globin chain on further maturation. In addition, these hESCs-derived erythroid cells possess oxygen-transporting capacity, which indicated hESCs could generate terminally mature progenies. This should be useful for ultimately developing an animal-free culture system to generate large numbers of erythroid cells from hESCs and provide an experimental model to study early human erythropoiesis.


Assuntos
Células-Tronco Embrionárias/citologia , Eritropoetina/metabolismo , Feto/citologia , Hematopoese/fisiologia , Fígado/citologia , Células Estromais/citologia , Células Estromais/metabolismo , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Linhagem Celular , Células Cultivadas , Meios de Cultivo Condicionados/farmacologia , Células-Tronco Embrionárias/fisiologia , Células Eritroides/citologia , Células Eritroides/metabolismo , Eritropoetina/genética , Globulinas Fetais/metabolismo , Humanos , Lentivirus/genética , Fígado/embriologia , Fígado/metabolismo , Transfecção
16.
Cell Biol Int ; 36(3): 267-71, 2012 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-22003828

RESUMO

The Wnt/ß-catenin signalling pathway is important in regulating not only self-renewal of haemopoietic progenitors and stem cells but also haemopoietic differentiation of ESCs (embryonic stem cells). However, it is still not clear how it affects haemopoietic differentiation. We have used a co-culture system for haemopoietic differentiation of mouse ESCs and iPSCs (induced pluripotent stem cells) in which the Wnt3a gene-modified OP9 cell line is used as stromal cells. The number of both Flk1+ and CD41+ cells generated from both co-cultured mouse ESCs and mouse iPSCs increased significantly, which suggest that Wnt3a is involved in the early stages of haemopoietic differentiation of mouse ESCs and mouse iPSCs in vitro.


Assuntos
Diferenciação Celular , Células-Tronco Embrionárias/citologia , Células-Tronco Pluripotentes Induzidas/citologia , Proteína Wnt3A/metabolismo , Animais , Proliferação de Células , Células-Tronco Embrionárias/metabolismo , Sistema Hematopoético , Células-Tronco Pluripotentes Induzidas/metabolismo , Camundongos
17.
PLoS One ; 6(3): e17687, 2011 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-21394208

RESUMO

Abnormal activation of the Sonic hedgehog (SHH) pathway has been described in a wide variety of human cancers and in cancer stem cells (CSCs), however, the role of SHH pathway in gastric CSCs has not been reported. In this study, we investigated the possibility that abnormal activation of the SHH pathway maintained the characteristics of gastric CSCs. First, we identified cancer stem-like cells (CSLCs) from human gastric cancer cell lines (HGC-27, MGC-803 and MKN-45) using tumorsphere culture. Compared with adherent cells, the floating tumorsphere cells had more self-renewing capacity and chemoresistance. The cells expressing CSCs markers (CD44, CD24 and CD133) were also significantly more in tumorsphere cells than in adherent cells. More importantly, in vivo xenograft studies showed that tumors could be generated with 2 x 104 tumorsphere cells, which was 100-fold less than those required for tumors seeding by adherent cells. Next, RT-PCR and Western blot showed that the expression levels of Ptch and Gli1 (SHH pathway target genes) were significantly higher in tumorsphere cells than in adherent cells. The results of quantitative real-time PCR were similar to those of RT-PCR and Western blot. Further analysis revealed that SHH pathway blocked by cyclopamine or 5E1 caused a higher reduction in self-renewing capacity of HGC-27 tumorsphere cells than that of adherent cells. We also found that SHH pathway blocking strongly enhanced the efficacy of chemotherapeutic drugs in HGC-27 tumorsphere cells in vitro and in vivo but had no significant effect in adherent cells. Finally, we isolated the tumorspheres from gastric cancer specimen, these cells also had chemoresistance and tumorigenic capacity, and SHH pathway maintained the gastric CSLCs characteristics of tumorsphere cells from primary tumor samples. In conclusion, our data suggested that SHH pathway was essential for maintenance of CSLCs in human gastric cancer.


Assuntos
Proteínas Hedgehog/metabolismo , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologia , Transdução de Sinais , Neoplasias Gástricas/metabolismo , Neoplasias Gástricas/patologia , Animais , Antineoplásicos/farmacologia , Adesão Celular/efeitos dos fármacos , Agregação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Humanos , Masculino , Camundongos , Camundongos Nus , Células-Tronco Neoplásicas/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Tela Subcutânea/efeitos dos fármacos , Tela Subcutânea/patologia , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de Xenoenxerto
18.
PLoS One ; 5(3): e9732, 2010 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-20305811

RESUMO

Understanding how hepatic precursor cells can generate differentiated bile ducts is crucial for studies on epithelial morphogenesis and for development of cell therapies for hepatobiliary diseases. Epimorphin (EPM) is a key morphogen for duct morphogenesis in various epithelial organs. The role of EPM in bile duct formation (DF) from hepatic precursor cells, however, is not known. To address this issue, we used WB-F344 rat epithelial stem-like cells as model for bile duct formation. A micropattern and a uniaxial static stretch device was used to investigate the effects of EPM and stress fiber bundles on the mitosis orientation (MO) of WB cells. Immunohistochemistry of liver tissue sections demonstrated high EPM expression around bile ducts in vivo. In vitro, recombinant EPM selectively induced DF through upregulation of CK19 expression and suppression of HNF3alpha and HNF6, with no effects on other hepatocytic genes investigated. Our data provide evidence that EPM guides MO of WB-F344 cells via effects on stress fiber bundles and focal adhesion assembly, as supported by blockade EPM, beta1 integrin, and F-actin assembly. These blockers can also inhibit EPM-induced DF. These results demonstrate a new biophysical action of EPM in bile duct formation, during which determination of MO plays a crucial role.


Assuntos
Ductos Biliares/fisiologia , Células Epiteliais/citologia , Fígado/metabolismo , Glicoproteínas de Membrana/biossíntese , Mitose , Células-Tronco/citologia , Animais , Biofísica/métodos , Imuno-Histoquímica/métodos , Masculino , Glicoproteínas de Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Microscopia de Fluorescência/métodos , Ratos , Ratos Endogâmicos F344
19.
J Cell Physiol ; 221(1): 54-66, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19492421

RESUMO

Human embryonic stem (hES) cells are typically maintained on mouse embryonic fibroblast (MEF) feeders or with MEF-conditioned medium. However, these xenosupport systems greatly limit the therapeutic applications of hES cells because of the risk of cross-transfer of animal pathogens. The stem cell niche is a unique tissue microenvironment that regulates the self-renewal and differentiation of stem cells. Recent evidence suggests that stem cells are localized in the microenvironment of low oxygen. We hypothesized that hypoxia could maintain the undifferentiated phenotype of embryonic stem cells. We have co-cultured a human embryonic cell line with human fetal liver stromal cells (hFLSCs) feeder cells stably expressing hypoxia-inducible factor-1 alpha (HIF-1alpha), which is known as the key transcription factor in hypoxia. The results suggested HIF-1alpha was critical for preventing differentiation of hES cells in culture. Consistent with this observation, hypoxia upregulated the expression of Nanog and Oct-4, the key factors expressed in undifferentiated stem cells. We further demonstrated that HIF-1alpha could upregulate the expression of some soluble factors including bFGF and SDF-1alpha, which are released into the microenvironment to maintain the undifferentiated status of hES cells. This suggests that the targets of HIF-1alpha are secreted soluble factors rather than a cell-cell contact mechanism, and defines an important mechanism for the inhibition of hESCs differentiation by hypoxia. Our findings developed a transgene feeder co-culture system and will provide a more reliable alternative for future therapeutic applications of hES cells.


Assuntos
Células-Tronco Embrionárias/citologia , Feto/citologia , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Fígado/citologia , Células-Tronco Pluripotentes/citologia , Células Estromais/citologia , Células Estromais/metabolismo , Proteína Morfogenética Óssea 4/genética , Proteína Morfogenética Óssea 4/metabolismo , Diferenciação Celular , Proliferação de Células , Forma Celular , Quimiocina CXCL12/genética , Quimiocina CXCL12/metabolismo , Técnicas de Cocultura , Embrião de Mamíferos/citologia , Embrião de Mamíferos/metabolismo , Células-Tronco Embrionárias/metabolismo , Fator 2 de Crescimento de Fibroblastos/genética , Fator 2 de Crescimento de Fibroblastos/metabolismo , Proteínas de Homeodomínio/metabolismo , Humanos , Cariotipagem , Proteína Homeobox Nanog , Fator 3 de Transcrição de Octâmero/metabolismo , Células-Tronco Pluripotentes/metabolismo , Solubilidade
20.
Clin Dev Immunol ; 2008: 531317, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18695740

RESUMO

In vitro maintenance of stem cells is crucial for many clinical applications. Stem cell preservation factor FRIL (Flt3 receptor-interacting lectin) is a plant lectin extracted from Dolichos Lablab and has been found preserve hematopoietic stem cells in vitro for a month in our previous studies. To investigate whether FRIL can preserve neural progenitor cells (NPCs), it was supplemented into serum-free suspension culture media. FRIL made NPC grow slowly, induced cell adhesion, and delayed neurospheres formation. However, FRIL did not initiate NPC differentiation according to immunofluorescence and semiquantitive RT-PCR results. In conclusion, FRIL could also preserve neural progenitor cells in vitro by inhibiting both cell proliferation and differentiation.


Assuntos
Fabaceae/química , Lectinas de Ligação a Manose/farmacologia , Lectinas de Plantas/farmacologia , Células-Tronco/efeitos dos fármacos , Animais , Técnicas de Cultura de Células , Células Cultivadas , Meios de Cultura Livres de Soro , Lectinas/química , Lectinas/genética , Ratos , Células-Tronco/citologia , Células-Tronco/fisiologia , Preservação de Tecido
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA