转基因动物.doc

1. 准备假孕母鼠2. 受精卵的准备3. 基因导入4. 胚胎移植5. 对幼鼠鉴定1. 外源DNA大小基本不受控制（1-50kb）2. 导入过程直观3. 整合效率高1. 设备昂贵，环节较多2. 对操作人员有较高的技术要求3. 低效率（尤其是对大家畜）4. 对卵子伤害大，胚胎存活率低5. 基因整合随机性6. 转基因沉默基因导入的方法1. 受精卵雄原核显微注射法2. 胚胎干细胞法3. 逆转率病毒感染法A new study has found the amount of antibiotics given to farm animals is expected to increase by two-thirds over the next 15 years. Researchers are linking the growing dependence on the drugs to rising demand for meat, milk and eggs. The researchers warn the drugs could quicken the development of antibiotics-resistant infections. Such infections are already a major public health concern in the United States.Experts say when people stop living in poverty, the first thing they want to do is eat better. For most people, that means eating more meat.Increasing prosperity in Asia has meant people there are eating nearly four times as much meat, milk and dairy products as they did 50 years ago.To meet that demand, farms have put many animals into smaller spaces.Gail Hansen is a veterinarian - a doctor who treats animals - with the Pew Charitable Trusts, a research and advocacy group.As the animals are crowded together, oftentimes the easiest way to deal with some of the problems of crowding is to give them antibiotics.Dr. Hansen says antibiotics help the animals stay healthy in crowded environments and grow faster. But bacteria can develop resistance to the drugs, and that now-resistant bacteria can spread to people.Doctors find that antibiotics that once worked against the infections no longer do. The bacteria have learned ways to fight the medicine. Doctors say the heavy use of antibiotics in animals is one of several reasons for the growth of antibiotic resistance worldwide. In the United States, at least two million people get drug-resistant infections each year. At least 23,000 die from an infection.Ramanan Laxminarayan heads the Center for Disease Dynamics, Economics and Policy. He says the problem is expected to get worse. He believes the use of antibiotics in animals will soon increase sharply. He says that will not be good for human health.He and other researchers wrote a report on the study, which was published in the Proceedings of the National Academy of Sciences. They used data from the United Nations that tell how and where livestock are raised today. They then predicted how such production would change by 2030.The increase in demand is going to make agriculture shift to more intensive methods of production, which tend to use greater quantities of antibiotics.The researchers estimate a 67 percent increase in total antibiotics use in livestock worldwide. They believe such use will double in what they call middle-income countries like China, India and Brazil.But Dr. Hansen says it does not have to be that way.The developing world doesnt have to make all the same mistakes that we made - we being the United States and Europe.She notes that Europe has banned the use of antibiotics to increase animal growth. And she adds the United States is hoping to persuade farmers to stop using antibiotics for that purpose.Im Marsha James.ThelargestchickenmeatproducerintheUnitedStatessaysitwillstopgivingitsbirdsantibioticsthatdoctorsusetotreathumans.TysonFoodsmadetheannouncementApril28.Itsaiditplanstocompletethechangeby2017.Healthexpertssayoveruseofthemedicinesispartofthereasonmorebacteriaarebecomingresistanttothem.Farmershavefedlivestocksmallamountsofantibioticsformanyyears.Thedrugshelptheanimalsgrowfasterandpreventthespreadofsicknessamongfarmanimalsthatliveclosetogether.Butbacterialivinginandontheanimalsdevelopandbecomeimmunetothedrugs.Inotherwords,theantibioticsnolongerhaveanyeffect.Thesedrug-resistantbacteriathenenterthebodiesofpeoplewhoeatthebirdsorlivestock.Then,infectionsinhumansbecomemorecostlyanddifficulttotreat.Sometimes,treatmentdoesnotworkatall.DonnieSmithisthepresidentofTysonFoods.Hesaysthecompanyhasalreadybegunreducingitsuseofantibiotics.Asaresultofourefforts,onlyaverysmallpercentageofourchickenflocksreceivehumanantibioticstoday.Hesaysthecompanywillstopgivingitsbirdsantibioticsbytheendof2017.SashaStashwickisapolicyexpertattheNaturalResourcesDefenseCouncil,andenvironmentalgroup.TheNRDChasbeencallingforanendtotheuseofantibioticsinanimalsformanyyears.Ms.Stashwicksaysothercompanieshaverecentlyannouncedtheirdecisiontoendtheuseofthemedicineintheanimalstheyproduce.wereseeingthatoverathirdoftheindustryatthispointeitherhaseliminatedtheuseofmedically-importantantibioticsinitsproductionorhasmadeapubliccommitmenttodosowithinthenextfewyears.WhiletheuseofantibioticsinbirdsandlivestockisdecreasingintheU.S.andEurope,itisexpectedtoincreaseinthedevelopingworld.Thereisagrowingdemandformeatthere.Livestockproducersinthosecountriesareusingmethodsthatrequireantibioticstokeepanimalshealthy.RamananLaxminarayanisthedirectoroftheCenterforDiseaseDynamics,EconomicsandPolicy.HesaysTysonsannouncementshowsfoodproducerscancontinuetooperatewithoutusingthedrugs.Mr.Laxminarayansaysifproducersprovidecleanerlivingconditionsandbetternutritionfortheiranimals,theywillnotneedtogivethemantibiotics.Buthesaysthebuyingpublicmustpressurefarmerstostopusingthedrugs.ImMarshaJames.动物滥用抗生素“威胁”人类年英国细菌学家弗莱明发现青霉素，并在临床应用中取得惊人的效果，这标志着抗生素时代的到来，由此人类的平均寿命得以延长。可是由于抗生素的使用会导致耐药细菌的出现，短短几十年后，到世纪末，过分依赖和滥用抗生素就使人类陷于将“无药可救”的噩梦。为此，许多国家都对抗生素使用实施严格限制措施，我国也规定多种抗生素类药品须凭医生处方购买。可是这样就能彻底切断抗生素对人类健康的威胁链条吗？猪链球菌病疫情悬疑年月，四川省资阳、内江等地暴发猪链球菌病疫情致人死亡，畜牧养殖业安全敲响警钟。究竟是什么原因导致疫情暴发，人畜丧命？专家们的意见有多种，四川省微生物专家李明远教授认为，猪链球菌病在动物机体抵抗力降低和外部环境变化诱导下，会引起动物发病，这很有可能是养殖业长期在猪饲料里任意添加抗生素导致的。他认为，现在不少的生猪养殖户，为了让猪快速生长、膘肥体壮，在猪饲料添加剂中任意添加青霉素、镇静剂和激素等，直接导致猪细菌耐药性增高，而耐药性增高意味着细菌变异，当变异由量变累积到一定程度后产生质变，就可能导致由这种细菌产生的疾病流行。猪链球菌疫情暴发使人们开始反思畜牧养殖业的安全，更多专家将目光共同瞄准于饲料添加剂中抗生素的滥用。哈尔滨兽医研究所副研究员蔡雪辉说，目前养殖业中人们普遍采用的防疫方法是在猪饲料中长期添加低剂量的抗生素，以控制细菌类疾病。但通过细菌分析发现，这种方法反而会使猪产生耐药性。一旦发生新的病种，传统的抗生素将无能为力。他认为，四川省猪链球菌疫病暴发就属于这类情况。滥用抗生素“威胁链”还在延伸有不少人认为，只要自己和家人都尽量避免使用抗生素，特别是高级抗生素，耐药菌就不会在自己身上形成，健康将不会受到威胁。然而，事实远非如此乐观。孙诚谊等专家指出，凭处方购买抗生素的规定仍未能彻底斩断抗生素威胁健康的链条，动物滥用抗生素的危害，正在迅速地向人类传导。近年来，人畜共患病乃至死亡的事件在世界各地屡屡发生，这些现象必须引起高度警惕。据了解，我国每年约有万人死于药品不良反应，其中死于抗生素的滥用，这使我国成为世界上滥用抗生素问题最为严重的国家之一。孙诚谊说，目前人类滥用抗生素的问题得到了一定程度的控制，但是在动物身上使用抗菌素却成为监控盲区。动物使用抗生素主要是在养殖业中将抗生素作为饲料添加剂，这不仅可以使动物生长速度更快，喂食量降低，动物抗病能力也会非常高，养殖户自然可以增加获利。但是，动物广泛使用抗菌素，同样会导致“耐药菌株”的出现，使得原有的抗生素失去作用，导致动物细菌病难以控制。而且这些“耐药菌”极可能通过食物或动物与人的接触传播给人，进而使人产生耐药性。目前在农业中使用的抗生素种类已经囊括了人类自身使用的几乎全部抗生素种类，比如在畜牧业中，大肠杆菌、葡萄球菌、沙门氏菌等过去并不严重或较少发生的细菌病，现已上升为家禽的主要传染病，这与长期滥用抗生素有直接关系。据了解，抗生素作为饲料添加剂应用于动物生产已有多年的历史。抗生素在预防动物疾病，促进动物生长，提高畜牧业产量等方面作出了巨大贡献，但它给人类带来巨大经济效益的同时，潜在的危害更须引起高度警惕。拒绝抗生素：从人类食物链的“第一环”开始抗生素之所以在养殖业中广泛使用，因为它能给养殖户带来短期的经济利益。可是利益背后的健康危机，如果不从源头上加强管理，必将反过来对这个产业以沉重的打击。孙诚谊说，现在很多国家和地区都发出了禁用抗生素的命令，随着国际“绿色贸易壁垒”升温，滥用抗生素的动物生产业主将越来越多地遭遇产品出口方面的限制和障碍，这对我国的畜禽养殖业已经形成了严峻挑战。年初，欧盟从中国进口的虾、对虾中发现强力抗生素的药物残留，认为对人体健康构成潜在威胁，导致欧洲部分地区陷入食品恐慌。受到进口限制影响的中国动物产品包括：兔肉、禽肉、蜂蜜、软体动物肉类、甲壳类、冻虾、对虾和宠物产品等，几千万美元产品在荷兰港口销毁。目前，一些发达国家，诸如欧盟等已做出明确规定，对于已经注册用于人或动