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排序方式: 共有794条查询结果,搜索用时 15 毫秒
51.
We developed an experimental system to characterize the suppressive effect of extremely low-frequency (ELF) electric fields (EFs) on the stress response. We assessed differences in the EF effects by age and gender. Control, EF-alone, immobilization-alone, and co-treated groups were subjected to an EF (50 Hz, 10 kV/m). Co-treated mice were exposed to the EF for 60 min, with immobilization during the latter half. Our results indicate that the suppressive effects of ELF EFs on the stress response in immobilized mice occur regardless of gender or age. As stress plays an important role in the onset and progression of various diseases, these findings may have broad implications for understanding the efficacy of EFs in animal, and perhaps human, health. Bioelectromagnetics. 2020;41:156–163. © 2019 Bioelectromagnetics Society.  相似文献   
52.
化学药剂对水稻种子萌发和幼苗生长的影响   总被引:2,自引:0,他引:2  
以早丰 11号水稻种子为材料 ,用KNO3、KH2 PO4 、Na2 HPO4 等不同药液浸种 .结果显示 ,早丰 11号种子在适当浓度的KNO3、KH2 PO4 、Na2 HPO4 浸种后 ,发芽势、发芽率比对照有所提高 ,幼苗生长加快 ,表现在根长、发根数、苗高、鲜重比对照生长好 ,并且对水稻秧苗表现有抵抗低温的作用 .  相似文献   
53.
牛蛙胃肠胰系统内分泌细胞的免疫组织化学鉴定与定位   总被引:3,自引:0,他引:3  
应用过氧化物酶标记的链霉卵白素(S-P)免疫组织化学方法对牛蛙(Rana catesbeiana)胃肠胰系统5种内分泌细胞进行了鉴定与定位.在消化道中检测到了5-羟色胺(5-HT)、生长抑素(SS)、胃泌素(Gas)和胰高血糖素(Glu)细胞.5-HT细胞主要分布于胃幽门部和空肠,食道中偶见.SS细胞主要分布于胃,幽门部较密集,小肠各段少量,直肠和食道偶见.Gas细胞主要分布于小肠各段,胃和直肠中偶见,食道中未检测到.Glu细胞主要分布于胃和直肠,小肠各段偶见,食道中未检测到.在胰腺中检测出了5-HT、SS、Gas、Glu和胰多肽(PP)细胞.SS、Glu和PP细胞数量较多,成簇分布于胰岛中,5-HT和Gas细胞少量,散在分布于胰腺腺泡之间.胃腺部和胰腺内分泌细胞多呈圆形、椭圆形或形态不规则,有的可见明显胞突伸向邻近细胞,胃肠道上皮中的内分泌细胞多呈梭形、楔形或锥形,有的可见明显胞突伸向消化腔.与其它两栖动物相比,牛蛙胃肠胰系统内分泌细胞的存在与分布有一些共性,也存在着种间差异.  相似文献   
54.
Summary It has been reported that only certain types of pancreatic parenchymal cells survive transplantation. This study examines whether the extent of differentiation of the pancreas at the time of transplantation affects the resulting morphology or viability of its components. Segments of chick pancreas or its primordia from stages preceding formation of dorsal bud (60 h) through hatching (day 21) were implanted in the abdominal region of three-day chick embryos. After various periods of growth, grafts were examined by light- and electron microscopy. In all transplants, individual endocrine cells (A, B, D, PP) and islet structure were identical to those of normal embryos of comparable age. The exocrine portion also appeared normal in implants from embryos younger than seven days. In grafts from older donors, however, normal acini and ducts were replaced by dilated, irregularly shaped tubules from which new islets appeared to develop. These results suggest that transplantation causes structural modification of exocrine tissue, which may reflect its initial functional capabilities. These observations are compared with similar structural alterations that occur following experimental obstruction of ducts and in human pancreatic pathology.  相似文献   
55.
The oxidant Mn3+‐malonate, generated by the ligninolytic enzyme versatile peroxidase in a two‐stage system, was used for the continuous removal of endocrine disrupting compounds (EDCs) from synthetic and real wastewaters. One plasticizer (bisphenol‐A), one bactericide (triclosan) and three estrogenic compounds (estrone, 17β‐estradiol, and 17α‐ethinylestradiol) were removed from wastewater at degradation rates in the range of 28–58 µg/L·min, with low enzyme inactivation. First, the optimization of three main parameters affecting the generation of Mn3+‐malonate (hydraulic retention time as well as Na‐malonate and H2O2 feeding rates) was conducted following a response surface methodology (RSM). Under optimal conditions, the degradation of the EDCs was proven at high (1.3–8.8 mg/L) and environmental (1.2–6.1 µg/L) concentrations. Finally, when the two‐stage system was compared with a conventional enzymatic membrane reactor (EMR) using the same enzyme, a 14‐fold increase of the removal efficiency was observed. At the same time, operational problems found during EDCs removal in the EMR system (e.g., clogging of the membrane and enzyme inactivation) were avoided by physically separating the stages of complex formation and pollutant oxidation, allowing the system to be operated for a longer period (~8 h). This study demonstrates the feasibility of the two‐stage enzymatic system for removing EDCs both at high and environmental concentrations. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:908–916, 2015  相似文献   
56.
57.
Depolymerization of lignin biomass to its value-added chemicals and fuels is pivotal for achieving the goals for sustainable society, and therefore has acquired key interest among the researchers worldwide. A number of distinct approaches have evolved in literature for the deconstruction of lignin framework to its mixture of complex constituents in recent decades. Among the existing practices, special attention has been devoted for robust site selective chemical transformation in the complex structural frameworks of lignin. Despite the initial challenges over a period of time, oxidation and oxidative cleavage process of aromatic building blocks of lignin biomass toward the fine chemical synthesis and fuel generation has improved substantially. The development has improved in terms of cost effectiveness, milder reaction conditions, and purity of compound individuals. These aforementioned oxidative protocols mainly involve the breaking of C-C and C-O bonds of complex lignin frameworks. More precisely in the line with environmentally friendly greener approach, the catalytic oxidation/oxidative cleavage reactions have received wide spread interest for their mild and selective nature toward the lignin depolymerization. This mini-review aims to provide an overview of recent developments in the field of oxidative depolymerization of lignin under greener and environmentally benign conditions. Also, these oxidation protocols have been discussed in terms of scalability and recyclability as catalysts for different fields of applications.  相似文献   
58.
《Biomarkers》2013,18(2):172-180
Context:?The axon guidance cues netrin-1 is a secreted protein overexpressed in many different cancer tissues.

Objectives:?To determine whether plasma netrin-1 can be used as a diagnostic biomarker of human cancer.

Materials and Methods:?A total of 300 cancer plasma samples from breast, renal, prostate, liver, meningioma, pituitary adenoma, glioblastoma, lung, pancreatic and colon cancer patients were compared against 138 control plasma samples. Netrin-1 levels were quantified by ELISA and immunohistochemistry.

Results:?Plasma netrin-1 levels were significantly increased in breast, renal, prostate, liver, meningioma, pituitary adenoma, and glioblastoma cancers as compared to control samples.

Discussion and Conclusion:?Our results suggest that plasma netrin-1 can be used as a diagnostic biomarker for many human cancers.  相似文献   
59.
The effects on thyroid hormone-dependent gene biomarker responses of the persistent organochlorine pesticide metabolite 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) were investigated after exposure of 4-week-old European common frog (Rana temporaria) (stage 36) tadpoles to two (0.001 and 0.01 ppm) DDE concentrations. Total body weight, total length, and tail length and width increased after 3-day exposure to DDE. Expression patterns of genes encoding for growth hormone, thyroid-stimulating hormone (TSHβ) and thyroid hormone receptor (TRα and TRβ) isoforms were evaluated in the head, body and tail regions using a validated real-time polymerase chain reaction (PCR) method. The mRNA expression of growth hormone in the body, and TSHβ in the head showed significant DDE concentration-dependent decreases. While DDE caused variable effects on TRα mRNA steady-state, the expression of TRβ was significantly decreased in the tail by DDE in a concentration-specific manner. The effect of DDE exposure on TRβ mRNA expression showed a negative correlation with tail length and width during the exposure period. The unique pattern of a DDE-induced decrease of tail TRβ expression probably reflects the significant role of this thyroid hormone receptor isoform in tail re-absorption and overall metamorphosis in anuran species. Therefore, the present study shows that the evaluation of thyroid hormone-dependent genes may represent quantitative biomarkers of acute exposure to organochlorine pesticides in anuran species during critical developmental periods such as metamorphosis. Given the widespread environmental levels of DDT and its metabolites, these pollutants will remain a subject of concern and their effects on anuran species should be studied in more detail.  相似文献   
60.
During the differentiation of the male gamete, there is a massive remodeling in the shape and architecture of all the cells of the seminiferous epithelium. The cytoskeleton, as well as many associated proteins with it, plays a pivotal role in this process. The testis is particularly susceptible to environmental pollutant, which can lead to injury and impairment of normal spermatozoa production. Cadmium (Cd) is one of the major chemical environmental toxicants in economically developed countries. Food and cigarettes are the main sources of exposure to this element. Here, the protective role of zinc (Zn) to prevent the testicular toxicity in male adult rats after prenatal and during lactation exposure to Cd has been assessed. Altered testicular histology at the interstitial and germinal levels was found, whereas Zn supply completely corrected Cd toxicity. Moreover, the effects of these metals on the testicular expression and localization of the protease prolyl endopeptidase (PREP) were evaluated. Interestingly, the results showed an increase of PREP messenger RNA and protein. Data were corroborated by immunofluorescence. This study raises the possibility of using PREP as a new fertility marker.  相似文献   
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