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转基因作物伤害动物内脏(论文全文)(3)

The raw biochemical data, necessary to allow a statistical re-evaluation, should be made publically available according to European Union Directive CE/2001/18 but unfortunately this is not always the case in practice. On this occasion, the data we required for this analysis were obtained either through court actions (lost by Monsanto) to obtain the MON 863 feeding study material (June 2005), or by courtesy of governments or Greenpeace lawyers. We thank the Swedish Board of Agriculture, May 30, 2006 for making public the NK 603 data upon request from Greenpeace Denmark and lawyers from Greenpeace Germany, November 8, 2006 for MON 810 material. This allowed us to conduct for the first time a precise and direct side-by-side comparison of these data from the three feeding trials with these GMOs.

Approximately 80 different biochemical and weight parameters, including crude and relative measures (Table , Annexes), were evaluated in serum and urine after 5 and 14 weeks of feeding. We classified these per organ (markers by site of synthesis or regulation). These organs weighed at the end of the experimental period, along with the whole body were: adrenal glands, brain, gonads, heart, kidneys, liver, and spleen. In addition, some parameters measured were related to bone marrow (blood cells) and pancreas (glucose) function. Unfortunately, some important measurements serving as markers for liver function were not conducted for technical or unknown reasons. This included gamma glutamyl transferase after 90 days feeding, cholesterol and triglyceride levels in the NK 603 and MON 810 trials, and cytochrome P450 family members in all cases. In addition, important sex difference markers were also ignored such as blood sex or pituitary hormone levels. Furthermore, it is well known and present in OECD guidelines that measurements should be conducted for at least 3 different experimental points to study dose- or time-related effects. Contrastingly and for reasons that are not stated, in all three studies for all three GMOs, only 2 doses and periods of feeding were measured, which makes it difficult to evaluate dose and cumulative effects. We have in a first instance indicated lacking values for different parameters (Annexes, Tables , , ).

2.3. Statistical power related to the experimental design

The most fundamental point to bear in mind from the outset is that a sample size of 10 for biochemical parameters measured two times in 90 days is largely insufficient to ensure an acceptable degree of power to the statistical analysis performed and presented by Monsanto. For example, concerning the statistical power in a t test at 5%, with the comparison of 2 samples of 10 rats, there is 44% chance to miss a significant effect of 1 standard deviation (SD; power 56%). In this case to have a power of 80% would necessitate a sample size of 17 rats. Therefore, the statistical power is insufficient in these studies to allow an a priori dismissal of all significant effects. Indeed, this is true overall with the amplitude of the effects that can usually be observed within three months, in the case of usual chronic toxicity appearing after one year of treatment. Hence, the lack of rejection of the null hypothesis at 5% does not mean that this hypothesis is true. Thus, the assessment of statistical power is absolutely necessary to understand the undetectable size effect; the statistical power depends on the sample and effect size, and the level of the test. This is exemplified when Monsanto performed one-way analysis of variance (ANOVA) calculations at 5% with a sample size of 10 animals for 10 groups. In this case the probability of not detecting a medium size effect [] (0.5 SD for a t test for instance) is about 70% (power of the test 30%). However, the fact is that within 90 days, a chronic toxicity has a maximum chance of giving rise to a medium rather than large size effects. The disturbance of parameters at the beginning of a disease is generally less important than at its end or as time progresses. Therefore, the protocol has to be drastically improved at this level, and as a result we consider that based on the analysis as presented by Monsanto that it fails to demonstrate that the consumption of these GM maize feeds was indeed safe as claimed. Any sign of toxicity should be taken into consideration to justify the prolongation of the experiment, or, if this is not possible, to reassess the statistical analysis, and to propose a scientifically valid physiological interpretation of any findings relating to disturbed functional parameters on a per organ basis. This was the ultimate objective of this investigation.

In reality, in their report containing the raw data and statistical analysis, Monsanto did not apply in any case their chosen and described statistical methods. Only parametric tests (one-way ANOVA under homoscedasticity hypothesis and Student t tests on contrasts) were employed. Moreover, to select significant results, they only contrasted the data sets from the 33% GM maize feeding groups (for NK 603 and MON 810) with all reference groups. Moreover, their biological interpretation of statistically significant results differs from case to case. In particular, sex differences were frequently used to reject pathological significance, despite the fact that this was without measuring effects on sex hormone levels. They also used the lack of linear dose-related effects, which is almost inevitable given that only two feeding doses were measured, to declare the diet as safe, as proposed for MON 863 GM maize []. In the MON 863 experiments, the authors still failed to apply their declared methodology, which was slightly different. The ANOVA and contrast analysis (33% GM feeding dose versus controls) were in this case the determining criteria for evaluation of statistical significance, but only if the mean of the 33% GM feeding group was outside the range of the mean of the reference cohorts. All this increases noticeably the risks of false negative results.

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