首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 109 毫秒
1.
Antibiotics have been uded in animal feeding for long history.In recent years,much attention has been received for their negative effects on animal and human being as well.Technology has been focused on alternatives of antibotics,such as probiotics,oligosaccharides,acidifiers,Chinese herds,chemical drugs,and other environmental measures.Their mechanism,effects,relatd factors and their prospect in the future were discussed in this paper.  相似文献   

2.
In the present experiment, effects of sodium hydrosulfide (NaHS), a H2S donor, on the oxidative damage, antioxidant capacity and the growth of cucumber hypocotyls and radicles were studied under 100 mmol L-1 NaCl stress. NaCl treatment significantly induced accumulation of H2O2 and thiobarbituric acid-reactive substances (TBARS) in cucumber hypocotyls and radicles, and application of NaHS dramatically reduced the accumulation of H2O2 and lipid peroxidation. However, the alleviating effects greatly depended on the concentrations of NaHS, and 400 μmol L-1 NaHS treatment showed the most significant effects. Corresponding to the change of lipid peroxidation, higher activities of antioxidant enzymes as well as the antioxidant capacity indicated as DPPH scavenging activity, chelating activity of ferrous ions and hydroxyl radical (·OH) scavenging activity were induced by NaHS treatment under NaCl stress, especially by 400 μmol L-1 NaHS treatment. With the alleviating lipid peroxidation, the amylase activities in cotyledons were increased, and the length of cucumber hypocotyls and radicles were significantly promoted by NaHS treatment under NaCl stress. Unlike the effects of NaHS, pretreatment with other sodium salts including Na2S, Na2SO4 , NaHSO4 , Na2SO3 , NaHSO3 and NaAc did not show significant effects on the growth of cucumber hypocotyls and radicles. These salts do not release H2S. Based on above results, it can be concluded that the effects of NaHS in the experiment depended on the H2S rather than other compounds derived from NaHS, and the alleviating effects might related with its function in modulating antioxidant capacity and amylase activities.  相似文献   

3.
Ultrafiltration(UF) experiments were subjected to the concentration of Shiitake polyphenol(SP) with ultrasound(US) enhancement, by which the effects of the main parameters such as ultrasonic power, transmembrane pressure, temperature and axial flow-rate on the membrane fluxes were analyzed, and then the SP of the ultrafiltrate after follow-up resin adsorption by HPLC was investigated. The results indicated that US could significantly enhance the membrane fluxes. The optimal conditions obtained was as follows: 0.60 W/cm2 US power, axial flow-rate of 80 L/h,operation temperature 30 ℃, transmembrane pressure 0.10 MPa. US increased the absorption capacity of the absorbent resin during the following stage. The HPLC analysis also showed that catechins were purified to some extent as the ultrafiltrate was treated by US and macroporous resin, indicating the technology of US enhancement coupled with UF showed the potential for concentration and purification of SP by absorbent resins.  相似文献   

4.
1 Introduction   Currently,the consumers made higher and higher demands on quality of food and beganto pay attention to methods and ways of animal production for ensuring food safety andhuman health Antibiotics have been used in animal feeding as growth promoters for longhistory.In recent years,this has increasingly become a focus of heated debate.Much attentionhas been received for their negative effects on animal and human being as well.On one hand,the positive influence of feeding growt…  相似文献   

5.
Covariance functions have been proposed as an alternative to model longitudinal data in animal breeding because of their various merits in comparison to the classical analytical methods.In practical estimation,different models and polynomial orders fitted can influence the estimates of covariance functions and thus genetic parameters.The objective of this study was to select model for estimation of covariance functions for body weights of Angora goats at 7 time points.Covariance functions were estimated by fitting 6 random regression models with birth year,birth month,sex,age of dam,birth type,and relative birth date as fixed effects.Random effects involved were direct and maternal additive genetic,and animal and maternal permanent environmental effects with different orders of fit.Selection of model and orders of fit were carried out by likelihood ratio test and 4 types of information criteria.The results showed that model with 6 orders of polynomial fit for direct additive genetic and animal permanent environmental effects and 4 and 5 orders for maternal genetic and permanent environmental effects,respectively,were preferable for estimation of covariance functions.Models with and without maternal effects influenced the estimates of covariance functions greatly.Maternal permanent environmental effect does not explain the variation of all permanent environments,well suggesting different sources of permanent environmental effects also has large influence on covariance function estimates.  相似文献   

6.
J.  R.  Qasem 《农业科学与技术》2010,(6):104-120
Allelopathy importance and its application under field conditions are reviewed. Recent achievements in the field of plant protection are mainly considered and presented. Natural chemicals of potential use as pesticides, commercialized natural products of pesticidal properties are included. Reported plants of pest control properties, their targeted agricultural pests, formulations, methods of application and activity under field conditions are presented. Allelopathic plant species and implications on their use in the field, positive and negative impacts on cultivated crop species and agricultural pests are discussed. Some research difficulties and experimental methodology problems are mentioned. Prospects of allelopathy as a future strategy for pest management, development of eco-friendly biopesticides and importance for sustainable agriculture and recent developments in allelopathy research are discussed.  相似文献   

7.
MicroRNAs(miRNAs)are small endogenous non-protein coding RNAs that range in size from 19–25 nucleotides. Thousands of miRNA genes have been identified in a variety of organisms,suggesting genetic exchange and distribution among species. miRNAs negatively regulate gene expression by binding to the 3′-untranslated regions(3′-UTRs)of their target genes and play an important role in growth,development and the occurrence of diseases. In this review,we summarize the recent advances in the understanding of the role of miRNAs in exosomes and their therapeutic potential,as well as provide an overview of the basic characteristics of miRNAs.  相似文献   

8.
Soybean(Glycine max(L.) Merr.) is a typical short-day and warm season plant, and the interval between emergence and flowering has long been known to be regulated by environmental factors, primarily photoperiod and temperature. While the effects of photoperiod and temperature on soybean flowering have been extensively studied, a dissection of the component photo-thermal effects has not been documented for Chinese germplasm. Our objective of the current study was to evaluate the independent- and interactive-photo-thermal responses of 71 cultivars from 6 ecotypes spanning the soybean production regions in China. These cultivars were subjected in pot experiments to different temperature regimes by planting in spring(low temperature(LT)) and summer(high temperature(HT)), and integrating with short day(SD, 12 h), natural day(ND, variable day-length), and long day(LD, 16 h) treatments over two years. The duration of the vegetative phase from emergence to first bloom(R1) was recorded, and the photo-thermal response was calculated. The outcome of this characterization led to the following conclusions:(1) There were significant differences in photo-thermal response among the different ecotypes. High-latitude ecotypes were less sensitive to the independent- and interactive-photo-thermal effects than low-latitude ecotypes; and(2) there was an interaction between photoperiod and temperature, with the effect of photoperiod on thermal sensitivity being greater under the LD than the SD condition, and with the effect of temperature on photoperiodic sensitivity being greater under the LT than the HT condition. The strengths and limitations of this study are discussed in terms of implications for current knowledge and future research directions. The study provides better understanding of photo-thermal effects on flowering in soybean genotypes from different ecotypes throughout China and of the implications for their adaptation more broadly.  相似文献   

9.
A 2-yr field study was conducted to assess the effects of transgenic japonica rice(KMD1 and KMD2) with a synthetic cry1 Ab gene from Bacillus thuingiensis Berliner on population dynamics and seasonal average densities of five thrips species including Stenchaetothrips biformis(Bagnall),Frankliniella intonsa(Trybom),F.tenuicornis(Uzel),Haplothrips aculeatus(Fabricius),Haplothrips tritici(Kurd) and their general predatory flower bug,Orius similis Zheng as compared to the parental control rice line using the white,blue and yellow sticky card traps.Population dynamics and seasonal average densities of these five thrips species and their general predatory flower bug were not significantly affected by rice type.Additionally,the white sticky card trap was suggested to be the most suitable for monitoring the population of these five thrips species and their general predator.These results show that our tested Bt rice lines do not interrupt the population of non-target thrips species and their general predatory flower bug in the field,and also cannot result in more occurrence of these thrips species in the rice ecosystem.  相似文献   

10.
Effects of silicon on photosynthetic parameters and antioxidant enzymes of chloroplast in cucumber seedlings under excess Mn were studied. Compared with the control, excess Mn significantly inhibited net photosynthetic rate (Pn), stomatal conductance, as well as the maximum yield of the photosystem II photochemical reactions (Fv/Fm) and the quantum yield of photosysytem II electron transport (Φ PSII), application of Si reversed the negative effects of excess Mn. In the further investigation, it was obtained that application of Si significantly increased the activities of enzymes related with ascorbate-glutathione cycle including ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) in cucumber chloroplast under excess Mn, this could be responsible for the lower accumulation of H2O2 and lower lipid peroxidation of chloroplast induced by Mn, and resulted in keeping higher photosynthesis.  相似文献   

11.
探讨了4种儿茶素单体对Na2S2O4诱导的3T3-L1细胞缺氧损伤和H2O2诱导的细胞氧化损伤的保护与修复作用。体外培养3T3-L1细胞,利用Na2S2O4诱导细胞缺氧损伤和H2O2诱导细胞氧化损伤,采用先加入诱导剂后加入儿茶素单体和先加入儿茶素单体后加入诱导剂两种处理方式,MTT法检测3T3-L1细胞存活率的变化。结果表明,先加入诱导剂可严重损伤3T3-L1细胞,再加入4种儿茶素单体均能对3T3-L1细胞进行修复,显著地提高细胞的存活率;而先加入4种儿茶素单体再加入诱导剂,细胞受损程度则显著降低,表明4种儿茶素单体对3T3-L1细胞缺氧或氧化损伤都具有较好的保护与修复作用。  相似文献   

12.
茶树酯型儿茶素生物合成及水解途径研究进展   总被引:2,自引:0,他引:2  
茶树酯型儿茶素对于茶叶加工产品品质的影响及人类健康的药理功效均高于非酯型儿茶素。酯型儿茶素合成及水解途径及分子调控机理,既是长期困扰茶业界的重点难题,也是富含原花青素(PAs)或缩合单宁(CAs)植物如葡萄、柿子的未解科学问题之一。作者在文中介绍了茶树酯型儿茶素合成及水解途径研究上取得的进展,儿茶素的没食子酰基化过程与水解单宁合成具有相似性;没食子酰基葡糖糖(βG)是它们合成的酰基供体,与葡萄糖基转移酶(UGGT)和没食子酰基转移酶(ECGT) 等有关;在茶树中酯型儿茶素很容易被水解酶(GCH)水解为没食子酸和非酯型儿茶素。此外,还综述了国际上有关flavan-3-ols的合成、聚合、糖苷化和甲基化研究进展。  相似文献   

13.
[目的]研究乙酰化儿茶素的相关性质,,以期改善儿茶素的应用特性。[方法]以乙酸酐为酰化剂对表没食子儿茶素没食子酸酯(EGCG)、茶多酚(TP)进行O-酰化修饰,分别合成了2种取代度的乙酰化儿茶素,考察了乙酰化程度对儿茶素溶解性、抗氧化性和紫外吸收能力的影响。[结果]随着取代度的增加,乙酰化儿茶素脂溶性增加,总抗氧化能力和清除超氧阴离子能力降低,清除羟自由基能力增加,紫外吸收带蓝移,吸收强度降低。[结论]研究筛选出高乙酰化儿茶素活性取代产物,从而为定向合成高活性的乙酰化儿茶素提供参考。  相似文献   

14.
采用高效液相色谱法对杭州地区有机毛峰茶叶4个等级(特级、一级、二级、三级)的氨基酸、嘌呤碱、儿茶素进行检测,并结合其感官审评分析,对杭州地区有机毛峰茶叶品质与其化学成分的关联性进行研究。结果表明,该毛峰茶叶中氨基酸、嘌呤碱总量随着品质级别的降低而减少;儿茶素指数除了特级比一级略低外,有随茶叶品质级别的降低而降低,儿茶素与氨基酸比值有随茶叶品质级别的降低而增加的规律;基于外形、汤色、香气、滋味、叶底感官审评因子来看,该批次的毛峰茶叶有随着等级呈现出与品质的正相关性。  相似文献   

15.
植物中分离的儿茶素类及其聚合物的抑菌作用   总被引:6,自引:0,他引:6  
以儿茶素类和4种儿茶素类聚合物为材料,采用平板打孔药敏法,对蜡状芽孢杆菌、大肠杆菌和枯草杆菌等3种细菌进行抑菌试验。结果表明,上述5种试样对3种细菌均具有显著的抑制作用,各试样的抑菌能力依次为TP>GOPC>LOPC>LPPC>LPR。其中,儿茶素类的抑菌能力强于它的聚合物,在本实验条件下,儿茶素类的MIC为0·12mg/mL,IC50为0·87~1·33mg/mL;儿茶素类聚合物的抑菌能力强弱顺序为低聚物(GOPC、LOPC)>多聚物(LPPC)>高聚物(LPR),其抑菌能力强弱与聚合度大小相关;其中的儿茶素类低聚物(GOPC、LOPC)的抑菌能力与儿茶素接近,具有一定应用价值。  相似文献   

16.
类黄酮及茶儿茶素生物合成途径及其调控研究进展   总被引:17,自引:2,他引:15  
夏涛  高丽萍 《中国农业科学》2009,42(8):2899-2908
 类黄酮化合物是植物的次生代谢产物,广泛分布于植物界且具有较强的生物活性。儿茶素是主要的类黄酮化合物之一,其含量占茶树鲜叶干重的12%~25%。作为茶叶的主要风味物质,儿茶素还具有抗氧化、抗诱变与防癌、抗心血管疾病、抗紫外线辐射等功能。本文从类黄酮及茶儿茶素的生物合成途径、组织化学定位、合成调控措施等方面,综述有关茶树儿茶素的生物合成代谢及其调控的研究进展,旨在为茶儿茶素生物合成的基因调控、代谢工程提供新的思路。  相似文献   

17.
做青强度对乌龙茶做青叶生化成分含量的影响   总被引:12,自引:5,他引:7  
以武夷肉桂鲜叶为原料 ,研究做青强度对做青叶生化成分的影响 .结果表明 ,做青过程中水浸出物总量、多酚类总量、儿茶素总量、氨基酸总量和可溶性总糖减少 ;做青强度越大 ,水浸出物总量、多酚类总量、儿茶素总量和氨基酸总量也减少较多 ;可溶性糖含量持续下降 ,但强度不同 ,下降幅度有差异 .还讨论了上述生化成分的变化与乌龙茶品质的关系  相似文献   

18.
茶多酚氧化实验研究   总被引:19,自引:1,他引:18  
进行茶多酚酶(PPO)促氧化、碱性氧化、酸性氧化试验,结果发现:茶多酚在3种氧化条件下均可氧化并形成茶黄素(Ts);酶促氧化形成茶黄素的含量比化学氧化形成量低。在双液相体系中茶多酚进行碱性氧化和酸性氧化,茶黄素形成量较接近。并就儿茶杯素氧化方法对茶色素制影响进行了讨论。  相似文献   

19.
遮荫对茶叶中儿茶素总量及构成的影响   总被引:1,自引:0,他引:1  
采用不同遮荫度覆盖黄旦茶园,对茶样内儿茶素总量及酯型、非酯型儿茶素含量进行检测分析。结果显示:与CK比较,蒸青样和成茶样中儿茶素总量均随遮荫度增大而呈整体下降趋势,其质量分数分别下降了3.08%-10.61%和2.65%-21.52%;其中酯型儿茶素变幅,蒸青样为-1.63%-5.28%,小于成茶样的-19.96%-10.35%;而非酯型儿茶素的降幅,蒸青样为9.90%-24.18%,大于成茶样的2.90%-19.82%。蒸青样中酯型与非酯型儿茶素的质量分数总体虽随遮荫度增大而减少,但酯型儿茶素占总儿茶素的百分比却随之增大,增幅为4.32%-10.05%;而非酯型儿茶素占比却与之相反,下降了5.10%-15.17%;因而酯型与非酯型儿茶素含量的比值是随遮荫度增加而增大的。遮荫对茶叶内儿茶素总量及其构成的影响程度达到了或接近于种间差异水平。  相似文献   

20.
短期遮阴对茶树嘌呤碱、氨基酸和儿茶素生物合成的影响   总被引:1,自引:0,他引:1  
研究了遮阴处理对茶树嘌呤碱、氨基酸和多酚类化合物生物合成的影响。对一年生茶树扦插苗短期遮阴处理后,通过高效液相色谱和荧光定量PCR技术分别对茶树三大代谢产物含量(嘌呤碱代谢,氨基酸代谢,多酚类代谢)及生物合成途径中关键基因的表达水平进行检测。结果表明,短期遮阴处理使得儿茶素总量略下调,可抑制咖啡碱的合成,大幅提高氨基酸的合成。遮阴8 d可以使其氨基酸总量增加58.5%,其中茶氨酸含量增加了近6倍。从基因表达差异分析来看,短期遮阴处理对一些基因的表达影响很大,如TCS1、PAL、F3'H和ANR2。遮阴处理对茶树扦插苗中嘌呤碱、氨基酸和多酚类化合物的生物合成有一定的影响作用。  相似文献   

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