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Herbicide-resistant soybean: Studies have been conducted on the feeding value17 and possible toxicity18 for rats, broiler chickens, catfish and dairy cows of two GM lines of glyphosate-resistant soybean (GTS). The growth, feed conversion efficiency, catfish fillet composition, broiler breast muscle and fat pad weights and milk production, rumen fermentation and digestibilities in cows were claimed to be similar for GTS and non-GTS. However:
These experiments were poorly designed since the high dietary protein concentration and the low inclusion level of GTS could have masked any GM effect.
No individual feed intakes, body or organ weights were given and no histology was performed, except some qualitative microscopy on the pancreas.
The feeding value of the two GTS lines was not substantially equivalent either because the rats grew significantly better on one of the GTS lines than on the other.
The experiment with broiler chicken was a commercial and not a scientific study.
The catfish experiment showed again that the feeding value of one of the GTS lines was superior to the other.
Milk production and performance of lactating cows also showed significant differences between cows fed GM and non-GM feeds.
Moreover, testing of the safety of 5-enolpyruvylshikimate-3-phosphate synthase which renders soybeans glyphosate-resistant18 was irrelevant because in the gavage studies an E. coli recombinant and not the GTS product was used. Their effects could be different as the differences in post-translational modification could have impaired their stability to gut proteolysis.
Thus, the claim that the feeding value of GTS and non-GTS lines was substantially equivalent is at best premature.
In a separate study19 it was claimed that rats and mice which were fed 30% toasted GTS or non-GTS in their diet had no significant differences in nutritional performance, organ weights, histopathology and production of IgE and IgG antibodies. However, under the unphysiological — basically, starvation — conditions of these experiments when, instead of the normal daily growth of 5-8 g per day, the rats grew less than 0.3 g and mice not at all, no valid conclusions could be drawn.
GM corn: One broiler chicken feeding study with rations containing transgenic Event 176 derived Bt corn (Novartis) has been published.20 However, the results of this trial are more relevant to commercial than academic scientific studies.
GM peas: The nutritional value of diets containing GM peas expressing bean alpha-amylase inhibitor when fed to rats for 10 days at two different (30% or 65%) dietary inclusions, was shown to be similar to that of parent-line peas.21
Even at 65% level the difference was small mainly because the alpha-amylase inhibitor expressed in the peas was quickly digested in the rat gut and its antinutritive effect abolished. Unfortunately no gut histology was done or lymphocyte responsiveness measured.
Although some organ weights, mainly the caecum and pancreas were different, those of others were remarkably similar suggesting that GM peas may be used in the diets of farm animals at low/moderate levels if their progress was carefully monitored.
However, to establish its safety for humans a more rigorous specific risk assessment will have to be carried out with several GM lines. This should include:
An initial nutritional/toxicological testing on laboratory animals
If no harmful effects are then detected, it should be followed by clinical, double-blind, placebo-type tests with human volunteers, keeping in mind that any possible harmful effects would be particularly serious with the young, old, and disabled.
A protocol for such testing was given at the OECD conference in Edinburgh, February 2000 and subsequently published.22
GM potatoes: In a short feeding study to establish the safety of GM potatoes expressing the soybean glycinin gene, rats were daily force-fed with 2 g of GM or control potatoes/kg body weight.23 Although no differences in growth, feed intake, blood cell count and composition and organ weights between the groups was found, the potato intake of the animals was too low and unclear, whether the potatoes were raw or boiled.
Feeding mice with potatoes transformed with a Bacillus thuringiensis var. kurstaki Cry1 toxin gene or the toxin itself was shown24 to have caused villus epithelial cell hypertrophy and multinucleation, disrupted microvilli, mitochondrial degeneration, increased numbers of lysosomes and autophagic vacuoles and activation of crypt Paneth cells. The results showed that despite claims to the contrary, CryI toxin was stable in the mouse gut and therefore GM crops expressing it need to be subjected to “thorough tests…to avoid the risks before marketing.24
When the health risks of GM potatoes were revealed in some studies, a debate ensued.
In another study, young, growing rats were pair-fed on iso-proteinic and iso-caloric balanced diets containing raw or boiled non-GM potatoes and GM potatoes with the snowdrop (Galanthus nivalis) bulb lectin (GNA) gene.25 The results showed that the mucosal thickness of the stomach and the crypt length of the intestines of rats fed GM potatoes was significantly increased. Most of these effects were due to the insertion of the construct and not to GNA which had been been pre-selected as a non-mitotic lectin unable to induce hyperplastic intestinal growth26 and epithelial T lymphocyte infiltration. Although there is controversy about the tests, most of the adverse comments on this Lancet paper were personal, non-peer reviewed opinions and, as such, of limited scientific value. The findings, on the other hand, were published in a peer-reviewed publication25 and the criticism replied to.7 The work, however, has not been repeated nor results contradicted and it is therefore imperative that the effects on the gut structure and metabolism of all other GM crops developed using similar techniques and genetic vectors should be thoroughly investigated before their release into the food chain.
GM tomatoes: This study with a GM tomato expressing B. thuringiensis toxin CRYIA(b) gene was published in a book and not in a peer-reviewed journal. However, its importance was underlined by the immunocytochemical demonstration of in vitro binding of Bt toxin to the caecum/colon from humans and rhesus monkeys.27 Although in vivo the Bt toxin was not bound by the rat gut, this was possibly due to the authors’ use of recombinant Bt toxin.
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клеп, вот тебе механизмы воздействия гмо на организм (+) -- Филипп3 -- 19.04.13@23:02 (Чит.: 226)