Cu-doped ZnO nanoparticles composited with Ag were synthesized by a one-step sol-gel method in this work, aiming at highly photocatalytic activity and possible application under sunlight (especially near ultraviolet and visible light regions, 300–760 nm) irradiation. Scanning electron microscopy (SEM) shows that the introduction of Cu inhibits particle aggregation. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) reveal that Zn(Cu)O–Ag nanoparticles (CZA NPs) are composed of metallic Ag (Ag0) and Zn(Cu)O nanocrystals; while at the Cu concentration of higher than 2%, a few CuO nanocrystals appear. Transmission electron microscopy (TEM) results evidenced the well-defined formation of Zn(Cu)O–Ag and/or CuO–ZnO–Ag heterojunctions. UV–vis spectra display that the visible absorption of the samples is obviously enhanced after the Cu introduction. At a low Cu doping level (0.2%) and moderate Cu concentration (3%–5%), the blue and green photoluminescence (PL) emission strength of the samples becomes very weak in comparison to other samples, indicative of the high separation of photogenerated electron-hole pairs. Reasonably, the higher photocatalytic degradation (complete degradation of methylene blue (MB) and methyl orange (MO) within 40 min under the simulated sunlight irradiation) are achieved in these cases: low Cu doping level (0.2%) and moderate Cu concentration (3%–5%) in CZA NPs. Further, we checked the effects of other factors on the photocatalytic degradation for possible application. Our results suggest that one well-designed composite type such as element-doped Zn(M)O–Ag nano-heterojunction or complicated metal oxide–ZnO–Ag nanocomposites possessing suitable band structures for the separation and utilization of photo-generated carriers, will remarkably improve the photocatalytic performance of nano-ZnO under sunlight irradiation.
Small RNA represents several unique non-coding RNA classes that have important function in a wide range of biological processes including development of germ cells and early embryonic, cell differentiation, cell proliferation and apoptosis in diverse organisms. However, little is known about their expression profiles and effects in yak oocytes maturation and early development. To investigate the function of small RNAs in the maturation process of yak oocyte and early development, two small RNA libraries of oocytes were constructed from germinal vesicle stage (GV) and maturation in vitro to metaphase II-arrested stage (M II) and then sequenced using small RNA high-throughput sequencing technology. A total of 9,742,592 and 12,168,523 clean reads were obtained from GV and M II oocytes, respectively. In total, 801 and 1,018 known miRNAs were acquired from GV and M II oocytes, and 75 miRNAs were found to be significantly differentially expressed: 47 miRNAs were upregulated and 28 miRNAs were downregulated in the M II oocytes compared to the GV stage. Among the upregulated miRNAs, miR-342 has the largest fold change (9.25-fold). Six highly expressed miRNAs (let-7i, miR-10b, miR-10c, miR-143, miR-146b and miR-148) were validated by real-time quantitative PCR (RT-qPCR) and consistent with the sequencing results. Furthermore, the expression patterns of two miRNAs and their potential targets were analysed in different developmental stages of oocytes and early embryos. This study provides the first miRNA profile in the mature process of yak oocyte. Seventy-five miRNAs are expressed differentially in GV and M II oocytes as well as among different development stages of early embryos, suggesting miRNAs involved in regulating oocyte maturation and early development of yak. These results showed specific miRNAs in yak oocytes had dynamic changes during meiosis. Further functional and mechanistic studies on the miRNAs during meiosis may beneficial to understanding the role of miRNAs on meiotic division.
With an aim to improve the efficiency of yak-bovine interspecies somatic cell nuclear transfer (iSCNT), this study investigated the effect of different culture systems on the development, quality and gene expression profile of yak-bovine iSCNT embryo. Reconstructed embryos were cultured in modified synthetic oviductal fluid (mSOF) or relative defined culture medium (RDCM) with 5% or 20% oxygen tension. Relative mRNA abundance of Oct-4, IFNT, IGF-2, Bax, GPX-1, SOD-1, CAT and GSS was analysed in blastocysts with qRT-PCR. The blastocyst formation rate in RDCM under 5% oxygen tension was significantly higher than that under 20% oxygen tension (P < 0.05). The total cell number of blastocyst derived from RDCM with 20% oxygen tension was lower than that of other groups, whereas the group of RDCM with 5% oxygen tension showed a beneficial effect on apoptosis index and tolerance to cryopreservation (P < 0.05). However, under the same oxygen tension, the mRNA abundance of IFNT of RDCM groups was higher than that of the mSOF groups. In addition, high oxygen tension during in vitro culture (IVC) with RDCM significantly increases the mRNA expression of oxidative stress-related genes (GPX-1, SOD-1, CAT and GSS) (P < 0.05). 3, 4-Dihydroxyflavone (DHF) during high oxygen tension was able to improve the cloned blastocyst formation rate in RDCM (P < 0.05). These results for the first time showed that low oxygen tension and RDCM could improve the developmental competence and quality and alleviate the oxidative stress for yak-bovine iSCNT embryo during IVC.
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