首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   78篇
  免费   5篇
  2023年   2篇
  2021年   1篇
  2020年   2篇
  2019年   1篇
  2018年   2篇
  2017年   2篇
  2016年   4篇
  2015年   3篇
  2014年   2篇
  2013年   7篇
  2012年   5篇
  2011年   7篇
  2010年   2篇
  2009年   5篇
  2008年   5篇
  2007年   3篇
  2006年   5篇
  2005年   5篇
  2004年   3篇
  2002年   1篇
  2001年   1篇
  1999年   1篇
  1995年   2篇
  1992年   1篇
  1990年   1篇
  1989年   1篇
  1988年   4篇
  1987年   3篇
  1985年   1篇
  1981年   1篇
排序方式: 共有83条查询结果,搜索用时 125 毫秒
1.
Spermatogonial cells (SCs) are key cells for spermatogenesis. These cells are affected by paracrine signals originated from nearby somatic cells, among them Leydig cells have receptors for osteocalcin, a hormone known for exerting positive roles in the promotion of spermatogenesis. The aim of this study was to evaluate roles for osteocalcin on SCs proliferative and differentiation features after coculture with Leydig cells. SCs and Leydig cells were isolated from neonate NMRI offspring mice and adult NMRI mice, respectively. SCs population were then enriched in a differential attachment technique and assessed for morphological features and identity. Then, SCs were cocultured with Leydig cells and incubated with osteocalcin for 4 weeks. Evaluation of proliferation and differentiation-related factors were surveyed using immunocytochemistry (ICC), Western blot, and quantitative real-time polymerase chain reaction (PCR). Finally, the rate of testosterone release to the culture media was measured at the end of 4th week. Morphological and flow cytometry results showed that the SCs were the population of cells able to form colonies and to express ID4, α6-, and β1-integrin markers, respectively. Leydig cells were also able to express Gprc6α as a specific marker for the cells. Incubation of SCs/Leydig coculture with osteocalcin has resulted in an increase in the rate of expressions for differentiation-related markers. Levels of testosterone in the culture media of SCs/Leydig was positively influenced by osteocalcin. It could be concluded that osteocalcin acts as a positive inducer of SCs in coculture with Leydig cells probably through stimulation of testosterone release from Leydig cells and associated signaling.  相似文献   
2.
3.
Hydroxytyrosol‐rich extract (HRE) and hydroxytyrosol‐rich olive mill wastewater (HROMW) were used as exogenous growth enhancers to stimulate tomato seedling vigor. The tomato seeds soaking in 10% w/v HROMW or HRE solutions were optimum in maximally enhancing seedling performance according to biochemical seed vigor parameters. Biochemical parameters as the average glucose‐6‐phosphate dehydrogenase (G6PDH) activity in HRE‐treated seeds (915.11 nmoles min?1 mg?1 protein) was higher than control (629.58 nmoles min?1 mg?1 protein) and correlated with the increased phenolic content (3530 μg g?1 fw) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH)‐based antioxidant activity (70.60%), respectively. Some key enzymes, guaiacol peroxidase (GPX) (6100.65 nmoles min?1 mg?1 protein) and catalase (2.04 μmoles min?1 mg?1 protein), were also higher in response to treatments and correlated with enhanced phenolic content and antioxidant activity. This study supports the hypothesis that the exogenous phenolic application stimulates the pentose phosphate pathway through an over‐expression of endogenous phenolic synthesis and an increase in free‐radical scavenging antioxidant activity. Therefore, the current study indicates the enhancement of seed vigor by HRE especially and HROMW as reflected by the stimulation of biochemical responses.  相似文献   
4.
Biological Trace Element Research - In low-income and middle-income countries such as Iran, smoking is becoming increasingly popular, especially among young people. This has led to additional...  相似文献   
5.
Metal pollution can produce many biological effects on aquatic environments. The marine diatom Amphora subtropica and the green alga Dunaliella sp. possess a high metal absorption capacity. Nickel (Ni) removal by living cells of A. subtropica and Dunaliella sp. was tested in cultures exposed to different Ni concentrations (100, 200, 300, and 500 mg L?1). The amount of Ni removed by the microalgae increased with the time of exposure and the initial Ni concentration in the medium. The metal, which was mainly removed by bioadsorption to Dunaliella sp. cell surfaces (93.63% of total Ni (for 500 mg Ni L?1) and by bioaccumulation (80.82% of total Ni (for 300 mg Ni L?1) into Amphora subtropica cells, also inhibited growth. Exposure to Ni drastically reduced the carbohydrate and protein concentrations and increased total lipids from 6.3 to 43.1 pg cell?1, phenolics 0.092 to 0.257 mg GAE g?1 (Fw), and carotenoid content, from 0.08 to 0.59 mg g?1 (Fw), in A. subtropica. In Dunaliella sp., total lipids increased from 26.1 to 65.3 pg cell?1, phenolics from 0.084 to 0.289 mg GAE g?1 (Fw), and carotenoid content from 0.41 to 0.97 mg g?1 (Fw). These compounds had an important role in protecting the algae against ROS generated by Ni. In order to cope with Ni stress shown by the increase of TBARS level, enzymatic (SOD, CAT, and GPx) ROS scavenging mechanisms were induced.  相似文献   
6.
Aspergillus niger broth culture on wheat bran was assessed for olive wastewater (OW) hydrolysis in order to release hydroxytyrosol (HT). The enzyme profiles of this culture broth gave essentially (IU/L): 3000 β-glucosidase and 100 esterase. Hydrolysis activity of A. niger enzyme preparation was evaluated by using three substrates: raw OW, phenolic fraction extracted from OW by ethyl acetate and its corresponding exhausted fraction. Large amounts of free simple phenolics were released from exhausted fraction and raw OW after enzymatic treatment. HPLC analyses show that HT was the main phenolic compound. One step of ethyl acetate extraction of hydrolysed OW allowed the recovery of 0.8 g of HT per litre of OW. The antioxidant activity of extracts from OW and exhausted fraction, measured by DPPH method, was drastically enhanced after hydrolysis treatment. This study demonstrates that hydrolysed OW is a potential source of bioactive phenolic compounds with promising applications in food and pharmaceutical industries.  相似文献   
7.
One-third of the 4,225 protein-coding genes of Escherichia coli K-12 remain functionally unannotated (orphans). Many map to distant clades such as Archaea, suggesting involvement in basic prokaryotic traits, whereas others appear restricted to E. coli, including pathogenic strains. To elucidate the orphans' biological roles, we performed an extensive proteomic survey using affinity-tagged E. coli strains and generated comprehensive genomic context inferences to derive a high-confidence compendium for virtually the entire proteome consisting of 5,993 putative physical interactions and 74,776 putative functional associations, most of which are novel. Clustering of the respective probabilistic networks revealed putative orphan membership in discrete multiprotein complexes and functional modules together with annotated gene products, whereas a machine-learning strategy based on network integration implicated the orphans in specific biological processes. We provide additional experimental evidence supporting orphan participation in protein synthesis, amino acid metabolism, biofilm formation, motility, and assembly of the bacterial cell envelope. This resource provides a “systems-wide” functional blueprint of a model microbe, with insights into the biological and evolutionary significance of previously uncharacterized proteins.  相似文献   
8.
Two-phase anaerobic digestion of cheese whey was investigated in a system consisting of a stirred acidogenic reactor followed by a stirred methanogenic reactor, the latter being coupled to a membrane filtration system to enable removal of soluble effluent whilst retaining solids. The acidogenic reactor was operated at a hydraulic retention time (HRT) of one day, giving maximum acidification of 52.25% with up to 5 g/l volatile fatty acids, of which 63.7% was acetic acid and 24.7% was propionic acid. The methanogenic reactor received an organic load up to 19.78 g COD/ld, corresponding to a HRT of 4 days, at which 79% CODs and 83% BOD(5) removal efficiencies were obtained. Average removals of COD, BOD(5) and TSS in the two-phase anaerobic digestion process were 98.5%, 99% and 100%, respectively. The daily biogas production exceeded 10 times reactor volume and biogas methane content was greater than 70%.  相似文献   
9.
Data from a nationally representative study in Bangladesh (BDHS 1996-97) were analysed to identify significant predictors of use of periodic abstinence, in comparison with other modern contraceptive methods. The study found that women in Bangladesh mostly use modern methods during their peak reproductive years, after which some of them switch to periodic abstinence. These women tend to be more from educated and from higher socioeconomic backgrounds and with at least one living son. Another set of data from the Matlab DSS was analysed and the results were in the same direction. Focus group discussions found that women were using the periodic abstinence method incorrectly, abstaining for more days than is necessary. For Bangladeshi contraceptive users to reach a higher degree of use-effectiveness for period abstinence, more IEC materials need to be developed.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号