主题：【讨论】不明白转基因有啥好争论的 -- 没那么美好
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Effect of diets containing genetically modified potatoes expressing Galanthus nivalis lectin on rat small intestine
Dr Stanley WB Ewen FRCPath a Corresponding AuthorEmail Address, Arpad Pusztai PhD a
Summary
Diets containing genetically modified (GM) potatoes expressing the lectin Galanthus nivalis agglutinin (GNA) had variable effects on different parts of the rat gastrointestinal tract. Some effects, such as the proliferation of the gastric mucosa, were mainly due to the expression of the GNA transgene. However, other parts of the construct or the genetic transformation (or both) could also have contributed to the overall biological effects of the GNA-GM potatoes, particularly on the small intestine and caecum.
Genetically modified (GM) plant products are becoming increasingly common in the human food-chain, yet in contrast to the general acceptance of the need for the biological testing of novel foods and feedstuffs, few studies have been carried out on the possible effects of GM products on the mammalian ut mucosa. GM potatoes expressing a snowdrop lectin (Galanthus nivalis agglutinin [GNA]) under the CaMV35s promoter have been developed to increase insect and nematode resistance.1 GNA was selected for insertion into potatoes because the initial effect of this mannose-specific lectin on the rat small bowel has been shown to be minimal,2 and because its binding to mannose present on the epithelial surface of rat jejunal villi is demonstrable only after feeding for 10 days. We compared the histological indices of the gut of rats fed potato diets containing GM potatoes, non-GM potatoes, or non-GM potatoes supplemented with GNA, to find out whether GNA gene insertion had affected the nutritional and physiological impact of potatoes on the mammalian gut.
ELISA analysis confirmed that the expression level of GNA in raw GM potatoes was 25·4 μg/g dry matter; the concentration was decreased to 4·9 μg/g after boiling for 1 h. Six rats were randomly allocated to each group, and were fed diets containing either raw or boiled GNA-GM potatoes, parent potatoes (Desiree), or parent-line potatoes supplemented with 25·4 μg/g GNA for 10 days. All potato diets were isocaloric and contained an average of 6% protein. Histological samples of stomach, jejunum, ileum, caecum, and colon were taken 10 days after the start of feeding. The samples, each 2 cm in length, were opened along the antimesenteric border. The serosal surface was allowed to adhere to card for 3 min and was then fixed in 10% neutral buffered formalin for 18 h at 20°C. Paraffin sections (4 μm) were stained with haematoxylin and eosin, and mucosal thickness (stomach) or crypt length (jejunum, ileum, caecum, and colon) was measured by videoimage analysis. Intraepithelial lymphocytes are equally distributed in all parts of the small intestine, and are known to increase when non-specific intestinal damage occurs. Thus, to assess potential damage, intraepithelial lymphocytes were counted in eight jejunal villi from each of the six rats fed diets containing GNA-GM potatoes or parent potatoes, both raw and boiled. No such measurements were made for the group fed parent potatoes spiked with GNA because dietary GNA or other lectins do not induce lymphocyte infiltration. GNA binding to the jejunum and ileum was measured by elution with 0·1 mol/L mannose, followed by ELISA.
The presence of GNA in the diets, irrespective of whether originating from GNA-GM potatoes or from parent-potato diets supplemented with GNA, was associated with significantly greater mucosal thickness of the stomach when compared with parent-potato diets (table 1). This effect was observed with both raw and boiled potatoes. Crypt length in the jejunum of rats fed on raw GNA-GM potato diets was significantly greater than in those given parent-line or parent-line plus GNA potato diets. However, the increase in jejunal crypt length was not seen in rats fed boiled GNA-GM potatoes (table 1). GNA had no significant effects on the ileum, but rats fed boiled potatoes had shorter ileal crypts than rats given respective raw potato diets. Rats fed boiled GNA-GM potatoes had significantly thinner caecal mucosae than rats given boiled parent potatoes, with or without GNA supplementation (table 1). Intraepithelial lymphocyte counts per 48 villi were 7·6 (SD 2·7) in rats fed on boiled parent potatoes, compared with 10·3 (3·3) in rats fed boiled transgenic potatoes (p<0·01). With raw potato diets, the intraepithelial lymphocyte counts were again significantly different: 5·3 (2·0) and 9·3 (2·6) in parent and GM potatoes, respectively (p<0·01). Peyer's patches appeared normal in all rats. GNA binding in the jejunum and ileum was about the same, irrespective of whether spiked GNA potatoes or GM potatoes were fed (table 2). Measurement of GNA binding by immunocytochemistry also showed a similar pattern.2
Click to open table
Table 1Table imageOpens in a new browser window
Effect of raw and cooked parent, parent+GNA, and GNA+GM potatoes on histological indices of rat gut
Click to open table
Table 2Table imageOpens in a new browser window
GNA binding to the jejunum and ileum of rats given diets containing GNA-GM potatoes or parent potato diets spiked with GNA
We suggest that the promotion of jejunal growth was the result of the transformation of the potato with the GNA gene, since the jejunum of rats was shown to be stimulated only by GM potatoes but not by dietary GNA (table 1), in agreement with a previous study in which the dietary GNA concentration was 1000-fold higher than the one used in this study.2 Thus, we propose that the unexpected proliferative effect was caused by either the expression of other genes of the construct, or by some form of positioning effect in the potato genome caused by GNA gene insertion. Because caecal thickness was similar in rats given boiled parent potatoes in the presence or absence of spiked GNA, we suggest that the decrease in caecal mucosal thickness seen in rats fed boiled GM-potato diets was the consequence of the transfer of the GNA gene into the potato. Caecal mucosal thickness in rats given raw potato diets was significantly higher than in those given the corresponding boiled potatoes. Thus, the main effect of boiling was to decrease mucosal thickness; this binding was fully in line with expectations. The raw parent-line potato diets supplemented with GNA were associated with a significantly thinner caecal mucosa than that of rats given parent-line potato diets. A similar trend was also observed in rats fed raw GNA-GM potatoes, but the difference did not reach significance (table 1).
As expected, colonic crypt lengths were generally higher in rats given raw potato diets than in those given boiled potatoes, except for animals fed GNA-supplemented raw or boiled potato diets, between which there was no significant difference. Feeding rats on diets containing GM potatoes, irrespective of whether raw or boiled, had no significant effect on colonic crypt length compared with that in animals fed the corresponding parent-line potatoes (table 1). Rats fed on GNA-supplemented parent potatoes had significantly shorter colonic crypt lengths than those fed on parent potatoes of GNA-GM potatoes; the reason for this finding is not clear.
In conclusion, the stimulatory effect of GNA-GM potatoes on the stomach was mainly due to the expression of the GNA transgene in the potato. By contrast, the potent proliferative effect of raw GNA-GM potatoes on the jejunum, and the antiproliferative effect of boiled transgenic potatoes on the caecum can be attributed only partly to GNA gene expression. Other parts of the GM construct, or the transformation, could have contributed to the overall effects. Once bound, GNA is internalised by endocytosis;2 some other component of the construct in the GNA-GM potato or its expressed gene product might also be able to penetrate and affect the rat mucosal cells in a similar manner. The growth-promoting effect of raw GNA-GM potatoes in the jejunum, evident as crypt hyperplasia, is probably due to a direct stimulatory effect on crypt cells; the increase in T lymphocyte infiltration may be important in the elimination of damaged enterocytes.3 The possibility that a plant vector in common use in some GM plants can affect the mucosa of the gastrointestinal tract and exert powerful biological effects may also apply to GM plants containing similar constructs, particularly those containing lectins, such as soya beans or any plants expressing lectin genes or transgenes.
This study was supported by Scottish Office: Agriculture, Environment, and Fishery Department (grant number FF 818).
References
1 Gatehouse AMR, Down RE, Powell KS, et al. Transgenic potato plants with enhanced resistance to the peach-potato aphid. Myzus persicae. Ent Exp Appl 1996; 79: 295-307. PubMed
2 Pusztai A, Ewen SWB, Grant G, et al. Relationship between survival and binding of plant lectins during small intestinal passage and their effectiveness as growth factors. Digestion 1990; 46 (suppl 2): 306-316. CrossRef | PubMed
3 Marsh NM, Ensari A. The gut associated lymphoid tissue and immune system. In: Whitehead R, ed. Gastrointestinal and oesophageal pathology. Edinburgh: Churchill Livingstone, 1995: 201-225.
a Department of Pathology, University of Aberdeen, Aberdeen AB25 2ZD, UK
Corresponding Author Information Correspondence to: Dr Stanley W B Ewen
不管是在制备，使用和食用三个步骤上出现毒性现象，而化学农药在上述三个步骤上都出现大规模中毒现象。
反转基因一派在争论Bt蛋白的可能有毒问题上都忽视了很多生物学的基本常识，这是一个遗憾：
比如Bt蛋白基因编码一个昆虫胃毒原蛋白，这个原蛋白在昆虫体外对昆虫无毒，只有被昆虫摄入其碱性环境的胃内后，经过一种特殊蛋白酶的切割后释放毒素核心肽段，产生毒性效应。毒素蛋白结合害虫胃部细胞受体嵌合于细胞膜，破坏渗透平衡导致细胞破裂。
由于其它动物和人体没有这种特殊蛋白酶，这个Bt原蛋白进入人胃后，动物和人类没有害虫那种碱性的胃液环境，蛋白会被胃部的酸性蛋白酶消化，不能产生具有毒性的核心肽；胃部细胞也没有可以和结合核心肽的受体，因此毒性核心肽不能对人类产生毒性作用，因此使用Bt毒蛋白相对安全。
苏云杆菌昆虫毒蛋白能有效杀死昆虫，从1975年开始人们大规模制备苏云杆菌菌剂，大规模作为外用生物农药进行喷洒，植保人员大量接触这种细菌和蛋白，也没出现中毒现象和过敏现象。庄稼在大量喷涂了苏云杆菌后必然也大量污染了Bt蛋白，这么长时期也没有报道喷洒苏云杆菌制剂的植物食品的消费者有任何不良反应，也没有看到使用这种生物农药于饲料作物后对家畜有不良影响。
如果转基因作物和农药的上市一视同仁地受到食品和药物管理局的审核批准，那么大多数现役农药将被淘汰。
很可惜，农药的批准和使用不在食品和药物管理局的职权范围，食品和药物管理局只有决定农药残留量的权力。
我们经常看到新闻某人想不开就喝了XXX农药几瓶，但从来没有看到想不开就去吃几公斤转基因的。
一方面是现在对转基因是否有害没有明确、统一的认识，不能匆忙推广。二是现在推广的话，在技术上必然受制于人，也是不明智的。最重要的是，以过去多年的经验，如果美国积极的向中国推销什么东西的话，百分之百可以肯定是危险的，有副作用的。
您给出链接的右侧有评论
第一篇
The Lancet, Volume 354, Issue 9187, Pages 1315 - 1316, 16 October 1999 Adequacy of methods for testing the safety of genetically modified foods
摘抄
The experiments done by Ewen and Pusztai were incomplete, included too few animals per diet group,5 and lacked controls such as a standard rodent diet containing about 15% protein (lactalbumin) as a balanced source of aminoacids6 and a test diet with potatoes containing an “empty” vector. Therefore the results are difficult to interpret and do not allow the conclusion that the genetic modification of potatoes accounts for adverse effects in animals. Similar criticisms of this work have been made by the Royal Society
实验是不完整的，每个饮食组的参试动物数量过少，缺少对应含量氨基酸的对照组，缺少带有空载体的对照组（即土豆为不含转入基因，但带有转基因载体的土豆--苏迅）。因此结论难以解释，无法得出转基因食品有副作用的结论。皇家协会也作出了同样的批评。
第二篇
The Lancet, Volume 354, Issue 9187, Pages 1314 - 1315, 16 October 1999 Genetically modified foods: “absurd” concern or welcome dialogue?
The Research Letter by Stanley Ewen and Pusztai was received by the journal towards the end of 1998. Since then, it has been peer reviewed by six specialist advisers—a nutritionist, a human pathologist, a veterinary pathologist, an agricultural geneticist, a plant molecular biologist, and a statistician—who had several requests for clarification about the design of the study, the laboratory methods used, and the statistical tests applied. Some advised rejection; others encouraged us to go ahead and publish. The authors revised their letter three times to try to meet our reviewers' criticisms. The Royal Society's own internal review of the Pusztai data had led to the damning verdict that the study “is flawed in many aspects of design, execution, and analysis and that no conclusions should be drawn from it”. So why publish the paper?
The answer lihes partly in a February, 1999, statement from the UK's chief scientific adviser, Robert May.4 While criticising the researchers' “sweeping conclusions about the unpredictability and safety of GM foods”, he pointed to the frustration that had dogged this entire debate: “Pusztai's work has never been submitted for peer review, much less published, and so the usual evaluation of confusing claim and counter-claim effectively cannot be made”. This problem was underlined by our reviewers, one of whom, while arguing that the data were “flawed”, also noted that, “I would like to see [this work] published in the public domain so that fellow scientists can judge for themselves… if the paper is not published, it will be claimed there is a conspiracy to suppress information”. Publication of Ewen and Pusztai's findings is not, as some newspapers have reported,5 a “vindication” of Pusztai's earlier claims. On the contrary, publication of a paper after substantial review and revision provides a report that deserves further scientific attention.
Stanley Ewen和Pusztai的论文在98年底就提交到了《柳叶刀》。之后由6名专家进行了评审，包括营养学家，人类病理学家，兽医病理学家，农业遗传学家，植物分子生物学专家和统计学专家，他们提出了许多实验设计，实验手段，统计方法中需要澄清的问题。有一些认为应该拒绝，其他的鼓励杂志发表。作者把自己的文章修改了3次来回应批评。皇家协会对本实验的内部评阅结论是负面的“在设计，实行，分析方面存在许多缺陷，其结论不可信”。那为什么要发表呢？
英国首席科学顾问Robert May1999年2月的声明给出了部分答案。一方面批评了研究“对于转基因食品不可预测性和安全性的结论过于笼统”，他同时指出整个辩论的沮丧之处“Pusztai的工作从未提交同行评议，很少有发表过，所以无法对其进行正常的评论”。这个问题也受到我们评委的重视，其中一位认为数据是“有缺陷的”，也指出“我希望这个工作能公诸于众从而其余科学家能够自己进行评价……如果此论文没有发表，就会引起压制信息的阴谋论的猜疑。”Stanley Ewen和Pusztai发现的发表不是像某些报纸所宣称的对Pusztai的辩护。相反，在评阅和修订之后本文的发表应该引起科学界的注意。
参见： 外链出处
缺乏基本的学科背景的情况下，说的话只能是有心或无意的曲解甚至篡改。河里现在无论是所谓“急转”还是“反转”。对这个技术的风险和利益的理解都存在很多问题。当我发觉自己无力同时给过于激动的双方说情况的时候，我只能选择闭嘴。
您说别人乱扣帽子，您这“为民请命”的帽子却也扣得杠杠的。网上各类关于转基因的民意调查，都是反转完全占上风，何来为民请命的需要。
其次，“不讲科学”也是没道理的。转基因是不是百分百安全，不经过长期的人体试验怎么能得出结论呢。要是转派能拿出长期的试验报告，论证安全性，反转的自然会服气。或者转派自己带头，每天吃，顿顿吃，也可以啊，问题是转派肯自己去做小白鼠么？
只给链接是理直气壮的表现吗？hwd99网友，你太懒了，给大家介绍介绍内容啊，科学界对这篇文章，到底是支持的多还是反对的多啊？
不过还是谢谢给出链接，我去看了作者的自辩以及其他科学家的评论，发现原来这篇文章当年就已经成为被痛打的落水狗了。不止一位科学家从纯实验的角度对其的不严谨做了说明。这种浑身漏气的文章被发表真是柳叶刀及编辑的耻辱。不过有人说，初衷是不能压制言论，即使是有缺陷的实验和结论，发表了也有利于其他科学家的验证和评论。换句话说，这种尝试发表在顶级科学期刊的用科学实验证明转基因作物有害的文章是非常稀少的，反转人士们都看着呢，你柳叶刀如果敢不发表，那你是什么阶级立场？于是有人对这种看法评论说，这是政治介入科学的恶劣例子，打破底线。这篇文章一发，反转/反科技人士如获至宝，因为能在这种顶级杂志发表就已经证明文章的内容是无可辩驳的铁证！没错，就是这么一篇当年就被从科学上批倒批臭的文章，至今仍是反转人士爱不释手的宝贝。其作者后来因为学术水平问题丢了工作，于是更悲情了，更阴谋论了。这么多年，反转人士们手中的宝贝，实在太少了点，所以这一件愈显珍贵。下面是一篇深得我心的comment：外链出处
Your decision to publish the research of Stanley Ewen and Arpad Pusztai1 breaks unfortunate new ground for a scientific journal. Put simply, The Lancet has placed politics and-tabloid sensationalism above its responsibility to report and assess new science. Most peer-reviewed journals are respected, and read, for the integrity of the research they publish and their dependability in weeding out irresponsible work.
Richard Horton (Oct 16, p 1314)2 argues that The Lancet might have been criticised for suppressing information by not publishing Ewen and Pusztai's work, but I believe he has jeopardised the journal's credibility, especially among readers and contributors in the scientific community. This pandering to popular debate rather than promoting responsible scientific inquiry may appeal to some, but I believe that the editor's poor judgment will strengthen the resolve of other scientific journals to adhere to the publication standards The Lancet saw fit to abandon.
I doubt if The Lancet would have published Ewen and Pusztai's research if it had implied the safety of biotech foods. But that is fine. Those who work hard to apply biotechnology to agriculture have no interest in flawed data.
Horton is nave if he really believes that “publication of Ewen and Pusztai's findings is not, as some newspapers have reported, a `vindication' of Pusztai's earlier claims”. Antitechnology activists already have seized on The Lancet's publication of this work as precisely that. They claim that publication, in itself, is proof the research is valid because that is the standard scientific journals are supposed to apply.
In the USA, biotech crops and foods have been tested more than any other agricultural products in history. We have a regulatory system that applies science-based policies to guard the health of consumers and the environment. That system would have trashed Pusztai's potatoes if they had been submitted for approval. Too bad The Lancet failed to exercise such oversight on research submissions.
转派好像一直没有理直气壮地回答这个“跟领导吃”的问题。回答起来也简单，在目前阶段，转基因食品是为穷人准备的。将来转基因技术可能会给人们带来更可口营养更好更安全的食物，但不是现在。现在的转基因技术主要是为了降低成本和增产。因此转基因食品必然是以廉价性来吸引人的。
领导要吃特供，富豪也要吃好吃精。另外从安全角度，如果保守的话，当然是吃那种产量低价格高的有机食品了。转基因毕竟是新事物。这个世界是不平等的，每个人需要根据自己的社会经济地位作出选择。如果你买不起有机食品，就只能吃工业化生产出来的农产品；如果你孩子想吃三文鱼而你买不起，就可以选择转基因三文鱼或者不吃。
没有人强迫你吃转基因食品，一切都得根据自己的经济情况来。地球人太多了，而且大家想吃更多的大鱼大肉。怎么办？
问题是，反转派想对穷人说，转基因坏，不许吃。
您说当年不止一位科学家从纯实验的角度对其的不严谨做了说明，您说来说去，一点也没有谈到，当年是如何说明Ewen和Pusztai结果是不严谨的，最后您转载了一篇深得您心的英文评论，我从这篇英文评论中，一点也没有看到，它是如何评论，Ewen和Pusztai结果不严谨的。而我给出的链接，Ewen和Pusztai仔细从技术上回复其他人疑问，大家很容易访问，这里转载到这里：
SWB Ewen , A Pusztai
Authors' reply
Sir—In their Oct 16 commentary Harry A Kuiper and colleagues discuss methods for testing the safety of GM foods. Our research letter only addressed the biological effects of GNA-GM potato diets on the morphology of the rat gut. However, since the safety testing issue has been raised we would like to respond.
According to the Rowett Institute's audit report the parent and transgenic lines we used were “substantially equivalent”. At least for protein content this was confirmed in the alternative report put on the internet by the Rowett (not by Pusztai, as stated by Kuiper et al). All experimental diets were isoproteinic and isocaloric and supplemented with vitamins and minerals for optimal growth, and the food intake of all rats was the same. Although 6% protein is suboptimal, the diet was not protein-free, as it was in the paper cited by Kuiper et al. Since the rats were growing, to use emotional terms such as “starvation” is misleading. Furthermore, starvation reduces gut size and crypt length, precisely the opposite what we found. Since trypsin and chymotrypsin inhibitors have no effect on gut morphology, reference to them is irrelevant. The potato lectin is antimitogenic2 so its effect should be a reduction in crypt cell proliferation rate and crypt size, not an increase. Moreover, GNA was selected for GM insertion because its effect on the gut is minimal so differences in lectin content, as an explanation for the biological effects reported, are also irrelevant.
Kuiper et al refer to “no consistency” in the changes. Is there any reason why changes in the different gut compartments should be the same? The ingestion of potatoes may indeed be associated with several adaptive changes, including caecal hypertrophy, but all the rats were given essentially the same potato diet containing the same starch component. Our study was about the effects of GM potatoes on gut morphology, not on their toxicology. The number of rats used (six per treatment group) was more than sufficient and most peer-reviewed, published papers on the biological and nutritional effects of similar diets (including over 40 from our laboratory) use three to four animals per group. Our controls were also sufficient. For both raw and cooked GM potatoes we used as controls both parent potato and parent potato supplemented with purified GNA, at the level expressed in GM potatoes. With this experimental design we could discriminate between the effects of the transgene product, the transformation, or the cooking and the interactions between these effects. The use of standard rodent diet of undefined composition as a control would have been inappropriate, and the effects of high-protein and low-protein diets would not have been comparable. We agree with Kuiper et al that attention should be paid to bioavailability and toxic effects. Kuiper et al cite their study done with a recombinant form of Bacillus thuringiensis toxin and not with toxin isolated from the GM-tomato. They themselves point out that since the stability, survival in the gut, and toxicity of a recombinant protein usually differ from those of the plantgene product, the two forms can not be used for comparisons. Biotech companies, in their submissions to regulatory authorities, also rely on toxicity studies with E coli recombinants. We, by contrast, have been comparing the gene product from the GM plant with that of the non-transformed original.3
Indeed it would have been desirable for testing methods recommended by FAO/WHO and so on to have been used for GM food crops currently approved. Unfortunately, no such tests were required, carried out, or their results published. It is therefore surprising for Kuiper et al to state that “the data so far indicate GM-crops… that have been introduced into the environment do not differ from traditionally grown crops except for the inserted traits”. Several traits having nothing to do with the transgene save the insertion have been found to differ in GM lines. The Monsanto analyses of glyphosate-resistant soya showed that the GM-line contained about 28% more Kunitz trypsin inhibitor, a known antinutrient and allergen.4 GM-soya contained significantly less phyto-oestrogens than the parent lines.5 Why is it that current GM crops need not be examined as thoroughly as the next generation?
We agree that “particular attention must be given to the detection and characterisation of unintended effects of genetic modification” but how will unknown toxins or allergens be found without first biologically testing the GM crop for toxicity? Writing of the sequence to be followed in future safety testing procedures, Kuiper et al say “depending on the outcome… further toxicological and nutritional studies may be needed”. The admission by people close to the decision-making committees of the European Union that the biological testing of GM food is needed appears to be an acknowledgment that previous safety testing could not have been rigorous enough.
Allan Mowat comments on the tissue fixation. This has long been a contentious topic. There may not be an ideal fixative but it is mischievous to suggest that the fixative upon which the whole of human histopathology relies could be responsible for different crypt-length measurements. The histology was part of a large series of synchronous physiological measurements on the same animal, demanding rapid tissue handling. Our animals were young (about 85 g) and, at that stage of development, the gut can easily be dissected from the mesentery to provide an unwashed, undistended histological sample at a constant distance from the pylorus. Orientation and plane-of-section problems were minimised by “splinting” tissue samples on card during standardised fixation. The jejunal crypt length of our 85 g rats has not varied and the data reported are similar to those obtained from 5000 jejunal crypts over the past 10 years. Rat intestinal crypt length depends on diet, animal supplier, and housing conditions, all of which are standardised in our rat colony, and the chemical composition of the potato diet was subjected to the exhaustive chemical analysis.
Intraepithelial lymphocytes (IEL) are thought to provide a surveillance function for damaged or virally infected cells, and any increase in the IEL population need not be limited to hypersensitivity reactions. Our young animals could not have been exposed to GNA previously, and any difference between groups is likely to be due to luminal factors in the diet. Moreover, IEL numbers are unaffected by lectin treatment. 1 The only difference in the diets is the presence of unidentified factors caused by genetic modification. Epithelial cell damage induced by the genetic modification cannot be excluded, and we would have studied it if our experiments had not been aborted. IELs averaged 7—11 per villus based on 48 villi counted, and we believe that our estimate is a useful indicator of unspecified immunological events of comparative value between groups. The suggestion that the lowprotein content of the diet caused intestinal infection can be rejected; parasites were not evident in the unwashed histological preparations and the lamina propria did not contain excess eosinophils.
Hyperplasia refers specifically to an increased cell number, frequently, but not necessarily, accompanied by increased mitotic activity although increased crypt mitotic activity is indeed present in our GM-potato fed animals. If, after 10 days of ingestion of GM potatoes villus pathology had been evident we would have described the damage. We reject the notion that potato or GNA lectin could have produced the changes that caused us concern.
Peter Lachmann's points (1) and (2) are addressed in our reply to Mowat. To point (3) the answer is yes, the measurements were done double-blind. With regard to point (4), Lachmann does not understand that the significant changes in mucosal indices represent another nail in the coffin of “substantial equivalence” on which the GM regulatory system is based. The differences in gut metabolic responses demonstrate that GM potatoes were not “metabolically equivalent”, and this is important whether the changes are pathological or not. Increased epithelial cell proliferation in the colon is not regarded desirable and the high energy cost of small-intestinal hyperplasia may compromise growth and development.
In his point (5) Lachmann asserts that we had no prior hypothesis. Because the experimental design was obvious from the introductory part of our letter, to save space, a part of our sentence was omitted. Here it is: “It was thought that comparison of the histological parameters of the gut of rats fed potato diets containing either GM potatoes, or non-GM potatoes with or without being supplemented with GNA should give a clear indication whether GNA gene insertion had affected the nutritional and physiological impact of potatoes on the mammalian gut”. Our table 1 clearly gives the statistical methods used and the number of comparisons. These methods were approved by independent statisticians. Lachmann says that the experiments need to be repeated. We would be happy to oblige. If our experiments are so poor why have they not been repeated in the past 16 months? It was not we who stopped the work on testing GM potatoes expressing GNA or other lectins or even potatoes transformed with the empty vector, which are now available. If Lachmann represents the view of the Academy of Medical Sciences on GM-food safety he should use his influence to make funds available for the continuation of this work in the UK.
References
1 Herzig KH, Bardocz S, Grant G, Nustede R, Folsch UR, Pusztai A. Red kidney bean lectin is a potent cholecystokinin releasing simulus in the rat inducing pancreatic growth.. Gut 1997; 41: 333-338. CrossRef | PubMed
2 Kilpatrick DC. Isolation of a lectin from the pericarp of potato (Solanum tuberosum) fruits.. Biochem J 1980; 191: 273-275. PubMed
3 Pusztai A, Grant G, Bardocz S, Alonso R, Chrispeels MJ, Schroeder HE, Tabe LM, Higgins TJV. Expressin of the insecticidal bean alpha-amylase inhibitor transgene has minimal detrimental effect on the nutritional value of peas fed to rats at 30% of the diet.. J Nutr 1999; 129: 1597-1603. PubMed
4 Padgett SR, Taylor NB, Nida DL, Bailey MR, MacDonald J, Holden LR, Fuchs RL. The composition of glyphosatetolerant soybean seeds is equivalent to that of conventional soybeans.. J Nutr 1996; 126: 702-716. PubMed
5 Lappe MA, Bailey EB, Childress C, Setchell C. Alterations in clinically important phytoestrogens in genetically modified herbicide-tolerant soybeans.. J Medic Food 1999; 1: 241-243. PubMed
更不代表现在就可以急匆匆的把转基因投入市场，就中国现在这市场状况，一放开转基因以次充好、掺杂造假那是必然的。
转基因还没有任何国家标准和长期试吃案例，将来另说，现在就放开转基因是自绝于人民。
PS：现在中国不吃转基因就饿死人了？
一篇一篇贴英文文献没意思，大家自己可以去看，我概述一下就行了。结果到您嘴里就成了“您说当年不止一位科学家从纯实验的角度对其的不严谨做了说明，您说来说去，一点也没有谈到，当年是如何说明Ewen和Pusztai结果是不严谨的”。按说你如此勤力，那些批评的文章你不可能没看到，你这种希望网友们不去探究的侥幸心理就比较可笑了。好吧，我虽然不喜欢这样做，就满足你或者说揭露你一次，贴过来吧：
Stanley Ewen and Arpad Pusztai (Oct 16, p 1353)1 raise intriguing questions about the potential of Galanthus nivalis agglutinin (GNA) to cause morphological alterations in the intestinal tract and suggest that the lectin's effects may be exacerbated in genetically modified potatoes. However, the ways in which Ewen and Pusztai assess the enteropathic properties of GNA mean that their findings must be interpreted with extreme caution.
The indices of crypt length and jejunal intraepithelial lymphocyte (IEL) count have been used to study intestinal immunopathology for 20 years or more2, 3 but several aspects of Ewen and Pusztai's methodology warrant attention. First, the study relies entirely on image analysis of formalin—fixed, paraffin-embedded sections, which are notoriously subject to shrinkage, distortion, and other fixation artifacts. These problems can be partly overcome by careful choice of well-oriented villuscrypt units combined with exhaustive measurement techniques, but Ewen and Pusztai do not indicate whether they did this. Errors created by measuring crypts in different planes of section on the sample could account for the high variation reported. The fact that the crypt lengths reported (60-90 μm in the jejunum) are much smaller than those normally found in the rat4 reinforces the view that the measurements may not have been accurate. More sensitive methods for processing and measuring intestinal tissues include non-formalin-based fixatives, microdissection, and direct morphometry of crypt and villus lengths.2—4 The enterocyte mitotic rate is probably the most sensitive index of intestinal pathology,2 and this can be measured easily by metaphase arrest or incorporation of bromodeoxyuridine.
Ewen and Pusztai use IEL counts to support their hypothesis that genetically modified potatoes cause jejunal lesions. They state that “IEL are known to increase when non-specific intestinal damage occurs”, but an increase in IEL count is specifically a feature of enteropathies associated with activated T lymphocytes.3 Thus an increased IEL count in animals receiving lectins could be compelling evidence for these materials inducing immunologically mediated damage to the gut. However, Ewen and Pusztai have not shown this conclusively. They do not seem to have counted IELs by a well-established method in which IEL are counted per 100 enterocyte nuclei or as an absolute number per length, volume or area of mucosa. That the technique they used is not ideal is underlined by the numbers of IEL they report, which are in the region of 7-11 per 48 villi. To reconcile these estimates, given that a single column of villus enterocytes in the rat jejunum contains 200-300 enterocytes and the density of IEL in the normal small intestine is 10-20 per 100 epithelial cells, is difficult. The low protein content of some of the diets, referred to by other commentators as a possible source of error,5 could account for some deviation of IEL numbers from normal but not for such a gross change. However, it is feasible that such a diet might have made the rats more susceptible to the intestinal infections known to cause the kind of changes in IEL and crypts3 noted here.
The speculation that the lectin caused jejunal crypt hyperplasia via a direct stimulatory effect on crypt cells cannot be substantiated by the data. Hyperplasia implies increased mitotic activity, which was not measured. Also, the time course for these changes is not described, and no parameters of villus pathology are provided. In the absence of this information, it is impossible to say whether the changes in crypt morphology are primary effects of the lectin or secondary to villus damage.
Interactions between lectins, intestinal epithelial cells, and the local immune apparatus is an important and poorly understood area. Appropriate methods for studying the enteropathic effects of lectins are available and are comparatively simple and inexpensive. Application of these techniques may help elucidate the issues raised by this provocative study.
还有
While much of the debate has focused on the nature of the diets studied by Stanley Ewen and Arpad Pusztai1 and possible differences between them, one central question is the effects of these on cell proliferation in the gut. Ewen and Pusztai talk about “proliferative effects” when they have not measured intestinal cell proliferation but merely crypt depth. Crypt depth might reflect hypoplasia and hyperplasia but this has yet to be shown. Various methods can be used to measure intestinal epithelial cell proliferation, such as the numbers of dividing cells in optimally sectioned crypts, but for definitive conclusions we need measurements related to the rate of crypt or gland cell production;2 the size of the epithelial population also needs to be assessed appropriately. Perhaps the best way of doing this is to use metaphase arrest and the microdissection method,3 in which not only the rate of crypt cell production but also good measurements of crypt and villus size can be captured simultaneously.
Another point is that many such studies can be confounded by concomitant changes in the denominator,4, 5 and the data on intraepithelial lymphocytes, with sectioned villus as the denominator, could be subject to the same criticism.
We hope these comments will help to ensure that if these studies are repeated (as they should be), robust, rapid, and reliable methods for assessment of cell proliferation are used.
再一篇批评，这篇科学细节较少：
The Lancet criticised the Royal Society last May1 for its “breathtaking impertinence” in reviewing Arpad Pusztai's work before it had been published. Richard Horton now repeats that criticism.2 We commented on Pusztai's unpublished work because he himself had commented on it, so extensively that it had become a matter of public interest. Since a one-sided debate was raging on the back of unvalidated experimental data, the Royal Society had a duty to examine such evidence as it could secure from all sources, including Pusztai himself. That is impertinence only if you endorse scientists flouting normal practice and rushing to the press with unvalidated data and invalid conclusions.
In introducing the Ewen and Pusztai research letter3 Horton helpfully describes the ambivalence of the referees and emphasises the value of having the data out in the open. He also states that the data are nongeneralisable. It is therefore surprising that the journal allowed the paper to appear with two general conclusions in the final paragraph.
In the circumstances, Horton's comments on the “failure to understand the… dialogue of accountability” are somewhat ironic.
好吧，您能不能诚实地回答，就在柳叶刀的相关链接中，肯定这一实验的科学家多还是批评的多。我比较惊讶你还没有推出如下结论：这些科学家都被利益集团收买啦！
前面指责别人不提供出处，不给全文，到自己这，连出处也不给，我依据你所说来分析你的观点，你还批评我不对，要求为何如此不一样啊？
再说，我们前面讨论的问题是，到底老百姓有没有权利谈论转基因粮食的危害？ 我批评的是那位黑岛民不准大家谈论转基因危害，您反对，却给不出任何理由。现在谈这些，可实在扯淡得太远了，与我所指出，你们存在的问题，一点关系也没有。
每个食物组6只小白鼠，数量太少，很多人都指出了这个实验设计上存在的缺陷。
记得您是从事工科科研的，相比您也知道实验设计对于一个实验结果的影响有多大，可能工科实验重复数无需太多，但生物学实验，特别是这种观察食物对生物影响的实验，处理数量太少对结果的影响很大，因为实验周期长，影响因素多。