亚硒酸钠和硒酸钠对小白菜生长生理特性的影响

以小白菜品种'秦白2号'为材料,采用盆栽试验研究了不同浓度亚硒酸钠[Se(IV)]和硒酸钠[Se(VI)]胁迫对小白菜生长生理特性的影响及其生理机制,为土壤硒污染修复及其合理开发利用提供理论依据.结果表明,Se(IV)≤10.0 mg·kg-1时,小白菜的叶长、叶宽显著下降,而生物量没有受到显著影响;Se(VI)≤1.0 mg·kg-1时,叶长、叶宽、生物量没有显著变化;更高浓度处理时,叶长、叶宽、生物量均随外源Se(IV)和Se(VI)处理浓度的增大而急速下降.Se(IV)≤40.0 mg·kg-1和Se(VI)≤20.0 mg·kg-1处理均对小白菜叶片叶绿素含量无显著影响,但更高浓度外源Se(IV)和Se(VI)却显著抑制了叶绿素合成.低浓度外源Se(IV)和Se(VI)均使小白菜叶片谷胱甘肽过氧化物酶(GSH-Px)活性上升,膜质过氧化物(MDA)含量下降,对超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性及脯氨酸含量无显著影响;高浓度硒使MDA含量、脯氨酸含量及SOD活性上升,而使GSH-Px活性和CAT活性下降;外源Se(IV)和Se(VI)均使过氧化物酶(POD)活性降低.研究发现,低浓度外源Se(IV)和Se(VI)均提高了小白菜的抗氧化作用,从而促进小白菜叶片叶绿素的合成和生长,高浓度时则相反;低浓度硒的抗氧化作用和高浓度硒的过氧化作用均以Se(VI)大于Se(IV).说明硒酸钠的有效性和毒害作用均大于亚硒酸钠.     

不同浓度亚硒酸钠溶液对水杉种子萌发的影响

硒元素是植物生长所需的微量元素。在水杉母树主要生长所在地恩施境内形成立体的硒资源环境,而该区的水杉群落天然更新困难,林下鲜见更新幼苗或幼树。因此,结合硒资源,研究硒元素与水杉种子萌发的相互关系对水杉的天然更新繁育具有重要意义。为了揭示硒元素对水杉种子发芽的影响,该研究通过测定不同环境条件(温度:20、25、30 ℃; 光照:12 h光照/12 h黑暗、24 h全黑暗; 是否浸种)下原生水杉种子的萌发率,筛选出最适萌发条件,并在此条件下采用不同浓度(0、0.25、0.5、1.0、2.0、4.0、8.0、16.0 mg·L^-1)的亚硒酸钠对水杉种子进行处理,观察其萌发的变化。结果表明:当使用浓度为0.25 mg·L^-1的亚硒酸钠溶液处理水杉种子时,种子的发芽率、发芽势和发芽指数都为最高,分别为34.0%、29.0%、13.9; 当亚硒酸钠浓度大于0.25 mg·L^-1时,水杉种子的发芽率、发芽势和发芽指数开始随着浓度的增加而降低,在亚硒酸钠浓度为16.0 mg·L^-1时,三个指标都达到最低值,分别为0.5%、0%、0.025。由此可知,低浓度(0～0.25 mg·L^-1)的亚硒酸钠处理对水杉种子的萌发有一定的促进作用,而高浓度(>0.25 mg·L^-1)的亚硒酸钠处理对水杉种子的萌发则有一定的抑制作用。     

亚硒酸钠诱导SW480细胞凋亡过程中活性氧的作用

为探讨亚硒酸钠诱导人结肠癌SW480细胞凋亡的机理,将荧光探针2′,7′－二氯荧光黄乙二脂（2′,7′－DCFH－DA）、罗丹明123（rhodamine123）负载人结肠癌细胞,利用多光子成像系统测定胞内活性氧（ROS）、线粒体跨膜电位（△Ψm）的变化。结果发现（1）Na2SeO3作用SW480细胞,可导致细胞凋亡和胞内的ROS增加。SOD、过氧化氢酶可降低凋亡率并抑制ROS的增加。（2）线粒体电子传递链抑制剂鲁藤酮及氰化钠可抑制OS增加。（3）Na2SeO3可导致线粒体的跨膜电位的下降。表明Na2SeO3作用细胞可导致来源于线粒体的ROS增加,ROS介导亚硒酸钠诱导细胞凋亡。     

富硒酵母和亚硒酸钠对肉仔鸡生长后期日增重影响的Meta分析

富硒酵母和亚硒酸钠对肉仔鸡日增重的影响是否具有差异一直是学界探讨的热点,目前的研究存在着分歧,并因研究众多,实验设计纷繁复杂及传统的综述分析无法定量等原因而不能得出明确的结论,急需尽快判定二者间作用效率的差异．Meta分析是一种统计方法,可将前人具有共同研究目的相互独立的多个研究结果合并、定量分析,得出精确和可靠的结论,避免主观性．本研究中,Meta分析结果表明,在饲料硒浓度0．2mg／kg水平下,亚硒酸钠对肉仔鸡生长后期日增重的作用略大于富硒酵母,但二者无差异显著性（p〉0．05）．     

亚硒酸钠对糖尿病肾病大鼠肾脏Nephrin表达的影响与意义

探讨亚硒酸钠对糖尿病肾病大鼠肾脏Nephrin表达的影响及二者间的关系,从而研究亚硒酸钠和Nephrin在糖尿病肾病中的作用机制.通过链脲佐菌素法及给予高脂饮食诱导模拟大鼠糖尿病肾病模型,实验设空白对照组、糖尿病肾病对照组、亚硒酸钠干预组,亚硒酸钠干预组每日给予亚硒酸钠溶液灌胃,其它组给予等量生理盐水灌胃.灌胃10周后处死大鼠,取血、尿标本测相关生化指标.取肾脏组织戊二醛固定制作切片电镜下观察超微结构改变,取肾脏组织多聚甲醛固定制石蜡切片光镜下观察病理改变和免疫组化定位蛋白表达.取肾脏组织RT-PCR检测Nephrin的mRNA表达、Western Blotting检测nephrin的蛋白表达,分析各组数据的统计差异.结果发现亚硒酸钠干预组大鼠基本状况和生化指标较糖尿病肾病对照组明显改善,光镜和电镜下观察病理改变和超微结构病变较糖尿病肾病对照组明显减轻.免疫组化nephrin蛋白表达着色糖尿病肾病对照组较空白对照组减少,亚硒酸钠干预组较糖尿病肾病对照组着色明显增多.Nephrin mRNA和蛋白表达糖尿病肾病对照组较空白对照组明显降低,而亚硒酸钠干预组较糖尿病肾病对照组升高,但低于空白对照组,差异均有统计学意义（P〈0．05）．亚硒酸钠明显促进肾脏Nephrin表达,改善了糖尿病肾病,表明亚硒酸钠和Nephrin在防治和延缓糖尿病肾病的发生发展中可能起重要作用．     

亚硒酸钠诱发的晶状体上皮细胞DNA损伤及修复

观察了亚硒酸钠（Ｎａ２ＳｅＯ３）在体外作用于大鼠晶状体上皮细胞（ＲＬＥ ｃｅｌｌｓ）而造成的ＤＮＡ单链断裂（ＳＳＢ）,并对其ＤＮＡ损伤、修复动力学做了初步研究。发现ＳＳＢ严重程度与亚硒酸钠的浓度呈线性相关,其ＳＳＢ重接修复约在３０￣６０ｍｉｎ内完成,还作了有关非程序ＤＮＡ合居（ＵＤＳ）的检测,发现与ＳＳＢ相比,ＵＤＳ发生迟且持续时间更长,提示Ｎａ２ＳｅＯ３可能在体外对大鼠晶状体上皮细胞除造成ＳＳＢ     

亚硒酸钠对P16蛋白在Wistar大鼠生精细胞表达的影响

目的探讨亚硒酸钠对P16蛋白在Wistar大鼠生精细胞表达的影响.方法断乳雄性Wistar大鼠30只随即分为正常对照组、低硒(2mg/L)和高硒(4mg/L)组,连续饮用含硒水43周后,取大鼠睾丸组织,用免疫组织化学SP法显示P16蛋白在大鼠睾丸中的表达,并对免疫组织化学结果进行定性、定位、图像分析和统计学处理.结果P16蛋白主要表达在精原细胞和精子的核内,免疫组织化学阳性细胞的平均光密度(MOD)和面数密度(NA)加硒组略高于正常对照组(P>0.05).结论本实验结果提示:饮水中加入2mg/L,4mg/L亚硒酸钠对生精细胞P16蛋白的表达无显著的影响.     

Regulation of reactive oxygen species in stem cells and cancer stem cells

Stem cells are defined by their ability to self-renew and their multi-potent differentiation capacity. As such, stem cells maintain tissue homeostasis throughout the life of a multicellular organism. Aerobic metabolism, while enabling efficient energy production, also generates reactive oxygen species (ROS), which damage cellular components. Until recently, the focus in stem cell biology has been on the adverse effects of ROS, particularly the damaging effects of ROS accumulation on tissue aging and the development of cancer, and various anti-oxidative and anti-stress mechanisms of stem cells have been characterized. However, it has become increasingly clear that, in some cases, redox status plays an important role in stem cell maintenance, i.e., regulation of the cell cycle. An active area of current research is redox regulation in various cancer stem cells, the malignant counterparts of normal stem cells that are viewed as good targets of cancer therapy. In contrast to cancer cells, in which ROS levels are increased, some cancer stem cells maintain low ROS levels, exhibiting redox patterns that are similar to the corresponding normal stem cell. To fully elucidate the mechanisms involved in stem cell maintenance and to effectively target cancer stem cells, it is essential to understand ROS regulatory mechanisms in these different cell types. Here, the mechanisms of redox regulation in normal stem cells, cancer cells, and cancer stem cells are reviewed.     

Implication of CpG-ODN and reactive oxygen species in the inhibition of intracellular growth of Salmonella typhimurium in hepatocytes

Bacterial DNA acts as an alert signal for eukaryotic cells through immunostimulatory CpG motifs. These sequences have therapeutic properties promoting protective immune TH1 responses and are recognized by a membrane protein belonging to the Toll-like receptor (TLR) family, named TLR-9. The aim of this study was to test the capability of murine hepatocytes to sense bacterial DNA and to develop antibacterial mechanisms against Salmonella typhimurium. We show that hepatocyte cell lines and mRNA extracts from murine liver constitutively express TLR-9, which is down-regulated by LPS and the mix of IFNgamma, IL-1beta and LPS. Also, we have found that hepatocyte cell lines can sense the presence of bacterial DNA and respond to it by increasing the pool of intracellular peroxides. This results in inhibition of intracellular growth of S. typhimurium when infected cells were incubated in the presence of CpG synthetic oligonucleotides (CpG-ODN). Expression of hepatocyte Mn-SOD is also induced by stimulation with CpG-oligodeoxynucleotides, LPS, and the mix of IFNgamma, IL-1beta and LPS. These results reinforce the prominent role of hepatocytes as a microbial product-responsive cell and the capabilities of CpG-ODN sequences as potent inducers of the innate immune response through the activation of a broad range of cell types.     

Effects of reactive oxygen species on eicosanoid metabolism in human endothelial cells.

The influence of reactive oxygen species (H2O2 was used as model substance) on the formation and release of PGI2 and TXA2 by cultured human endothelial cells was analyzed. In the presence of H2O2 concentrations which did not induce a general cell damage (analyzed by estimation of the cellular concentration of energy rich phosphates and extent of lipid peroxidation), the formation of both eicosanoids exhibited a sigmoidal shape with respect to time. Increasing H2O2 concentration shortened the half time of PGI2 and TXA2 production. The maximum rates of PGI2 and TXA2 formation were separated by a delay of the TXA2 production. The ratio of PGI2 and TXA2 formation was 100 to 1 at the time of maximum PGI2 formation and 1-2 to 1 at the time of maximum TXA2 formation. This effect of reactive oxygen species could contribute to the reduction of the protective function of the endothelium in hemostasis and vascular tone. Using antioxidants, the modulating function of reactive oxygen species on the eicosanoid metabolism in endothelial cells was verified.     

Vanadate-induced cell growth regulation and the role of reactive oxygen species

While vanadium compounds are known as potent toxicants as well as carcinogens, the mechanisms of their toxic and carcinogenic actions remain to be investigated. It is believed that an improper cell growth regulation leads to cancer development. The present study examines the effects of vanadate on cell cycle control and involvement of reactive oxygen species (ROS) in these vanadate-mediated responses in a human lung epithelial cell line, A549. Under vanadate stimulation, A549 cells generated hydroxyl radical (*OH), as determined by electron spin resonance (ESR), and hydrogen peroxide (H2O2) and superoxide anion (O2*-), as detected by flow cytometry using specific dyes. The mechanism of ROS generation involved the reduction of molecular oxygen to O2*- by both a flavoenzyme-containing NADPH complex and the mitochondria electron transport chain. The O2*- in turn generated H2O2, which reacted with vanadium(IV) to generate *OH radical through a Fenton-type reaction (V(IV) + H2O2 --> V(V) +*OH + OH-). The ROS generated by vanadate induced G2/M phase arrest in a time- and dose-dependent manner as determined by measuring DNA content. Vanadate also increased p21 and Chk1 levels and reduced Cdc25C expression, leading to phosphorylation of Cdc2 and a slight increase in cyclin B1 expression as analyzed by Western blot. Catalase, a specific antioxidant for H2O2, decreased vanadate-induced expression of p21 and Chk1, reduced phosphorylation of Cdc2Tyr15, and decreased cyclin B1 levels. Superoxide dismutase, a scavenger of O2*-, or sodium formate, an inhibitor of *OH, had no significant effects. The results obtained from the present study demonstrate that among ROS, H2O2 is the species responsible for vanadate-induced G2/M phase arrest. Several regulatory pathways are involved: (1) activation of p21, (2) an increase of Chk1 expression and inhibition of Cdc25C, which results in phosphorylation of Cdc2 and possible inactivation of cyclin B1/Cdc2 complex.     

Rodent and human mast cells produce functionally significant intracellular reactive oxygen species but not nitric oxide

In immunity, reactive oxygen species (ROS) and nitric oxide (NO) are important antimicrobial agents and regulators of cell signaling and activation pathways. However, the cellular sources of ROS and NO are much debated. Particularly, there is contention over whether mast cells, key secretory cells in allergy and immunity, can generate these chemical species, and if so, whether they are of functional significance. We therefore examined directly by flow cytometry the capacity of mast cells to generate intracellular ROS and NO using the respective cell-permeable fluorescent probes dichlorodihydrofluorescein and diaminofluorescein and evaluated the effects of inhibitors of ROS and NO synthesis on cell degranulation. For each of three mast cell types (rat peritoneal mast cells, mouse bone marrow-derived mast cells, and human blood-derived mast cells), degranulation stimulated by IgE/antigen was accompanied by production of intracellular ROS but not NO. Inhibition of ROS production led to reduced degranulation, indicating a facilitatory role for ROS, whereas NO synthase inhibitors were without effect. Likewise, bacterial lipopolysaccharide and interferon-gamma over a wide range of conditions failed to generate intracellular NO in mast cells, whereas these agents readily induced intracellular NO in macrophages. NO synthase protein, as assessed by Western blotting, was readily induced in macrophages but not mast cells. We conclude that rodent and human mast cells generate intracellular ROS but not NO and that intracellular ROS but not intracellular NO are functionally linked to mast cell degranulation.     

Trichostatin a modulates intracellular reactive oxygen species through SOD2 and FOXO1 in human bone marrow‐mesenchymal stem cells

Engraft cells are often exposed to oxidative stress and inflammation; therefore, any factor that can provide the stem cells resistance to these stresses may yield better efficacy in stem cell therapy. Studies indicate that histone deacetylase (HDACs) inhibitors alleviate damage induced by oxidative stress. In this study, we investigated whether regulation of reactive oxygen species (ROS) occurs through the HDAC inhibitor trichostatin A (TSA) in human bone marrow‐mesenchymal stem cells (hBM‐MSCs). Intracellular ROS levels increased following exposure to hydrogen peroxide (H₂O₂), and were suppressed by TSA treatment. Levels of the antioxidant enzyme superoxide dismutase 2 (SOD2) increased following treatment with 200 nM TSA and to a lesser level at 1–5 μM TSA. Cell protective effects against oxidative stress were significantly increased in TSA‐MSCs after treatment with low doses of TSA (50–500 nM) and decreased with high doses of TSA (5–10 μM). Consistent results were obtained with immunoblot analysis for caspase3. Investigation of Forkhead box O1 (FOXO1), superoxide dismutase 2 (SOD2), and p53 levels to determine intracellular signaling by TSA in oxidative stress‐induced MSCs demonstrated that expression of phosphorylated‐FOXO1 and phosphorylated‐SOD2 decreased in H₂O₂‐treated MSCs while levels of p53 increased. These effects were reversed by the treatment of 200 nM TSA. These results suggest that the main function of ROS modulation by TSA is activated through SOD2 and FOXO1. Thus, optimal treatment with TSA may protect hBM‐MSCs against oxidative stress. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrical stimulation of human embryonic stem cells: Cardiac differentiation and the generation of reactive oxygen species

Exogenous electric fields have been implied in cardiac differentiation of mouse embryonic stem cells and the generation of reactive oxygen species (ROS). In this work, we explored the effects of electrical field stimulation on ROS generation and cardiogenesis in embryoid bodies (EBs) derived from human embryonic stem cells (hESC, line H13), using a custom-built electrical stimulation bioreactor. Electrical properties of the bioreactor system were characterized by electrochemical impedance spectroscopy (EIS) and analysis of electrical currents. The effects of the electrode material (stainless steel, titanium-nitride-coated titanium, titanium), length of stimulus (1 and 90 s) and age of EBs at the onset of electrical stimulation (4 and 8 days) were investigated with respect to ROS generation. The amplitude of the applied electrical field was 1 V/mm. The highest rate of ROS generation was observed for stainless steel electrodes, for signal duration of 90 s and for 4-day-old EBs. Notably, comparable ROS generation was achieved by incubation of EBs with 1 nM H₂O₂. Cardiac differentiation in these EBs was evidenced by spontaneous contractions, expression of troponin T and its sarcomeric organization. These results imply that electrical stimulation plays a role in cardiac differentiation of hESCs, through mechanisms associated with the intracellular generation of ROS.     

In vitro differential effects of sodium selenite on the growth of human hepatoma cells and human embryonic liver cells

The effects of various concentrations of Na₂SeO₃ on human hepatoma cells and human embryonic liver cells was investigated in vitro. For human hepatoma cells, mitotic index and cell count decreased with increasing selenium concentrations. At 1 μg/mL Na₂SeO₃, mitotic activity of human hepatoma cells were partially arrested. In human embryonic liver cells continuously treated with Na₂SeO₃, (1 μg/mL) cell count of the treated group decreased only by d 7; mitotic index, labeled index, and mean silver grain number per 50 labeled nuclei were the same as in the control group on exposure to 1, 3, and 5 μg/mL for up to 72 h. In mixed cultures of human hepatoma and embryonic liver cells treated with 3 and 5 μg/mL of Na₂SeO₃ for 24 h, hepatoma cells showed vacuolated cytoplasms, distorted nuclei, condensed chromatin, and even pyknosis, whereas the embryonic liver cells retained a normal morphology under the same treatment.     

Caudatin induces caspase-dependent apoptosis in human glioma cells with involvement of mitochondrial dysfunction and reactive oxygen species generation

Caudatin as one species of C-21 steroidal from Cynanchum bungei decne displays potential anticancer activity. However, the underlying mechanisms remain elusive. In the present study, the growth suppressive effect and mechanism of caudatin on human glioma U251 and U87 cells were evaluated in vitro. The results indicated that caudatin significantly inhibited U251 and U87 cell growth in both a time- and dose-dependent manner. Flow cytometry analysis revealed that caudatin-induced cell growth inhibition was achieved by induction of cell apoptosis, as convinced by the increase of Sub-G1 peak, PARP cleavage and activation of caspase-3, caspase-7 and caspase-9. Caudatin treatment also resulted in mitochondrial dysfunction which correlated with an imbalance of Bcl-2 family members. Further investigation revealed that caudatin triggered U251 cell apoptosis by inducing reactive oxygen species (ROS) generation through disturbing the redox homeostasis. Moreover, pretreatment of caspase inhibitors apparently weakens caudatin-induced cell killing, PARP cleavage and caspase activation and eventually reverses caudatin-mediated apoptosis. Importantly, caudatin significantly inhibited U251 tumour xenografts in vivo through induction of cell apoptosis involving the inhibition of cell proliferation and angiogenesis, which further validate its value in combating human glioma in vivo. Taken together, the results described above all suggest that caudatin inhibited human glioma cell growth by induction of caspase-dependent apoptosis with involvement of mitochondrial dysfunction and ROS generation.