<P> While some groups and individuals have called for more human testing of GM food, multiple obstacles complicate such studies . The General Accounting Office (in a review of FDA procedures requested by Congress) and a working group of the Food and Agricultural and World Health organizations both said that long - term human studies of the effect of GM food are not feasible . The reasons included lack of a plausible hypothesis to test, lack of knowledge about the potential long - term effects of conventional foods, variability in the ways humans react to foods and that epidemiological studies were unlikely to differentiate modified from conventional foods, which come with their own suite of unhealthy characteristics . </P> <P> Additionally, ethical concerns guide human subject research . These mandate that each tested intervention must have a potential benefit for the human subjects, such as treatment for a disease or nutritional benefit (ruling out, e.g., human toxicity testing). Kimber claimed that the "ethical and technical constraints of conducting human trials, and the necessity of doing so, is a subject that requires considerable attention ." Food with nutritional benefits may escape this objection . E.g., GM rice has been tested for nutritional benefits, namely, increased levels of Vitamin A . </P> <P> Arpad Pusztai published the first peer - reviewed paper to find negative effects from GM food consumption in 1999 . Pusztai fed rats potatoes transformed with the Galanthus nivalis agglutinin (GNA) gene from the Galanthus (snowdrop) plant, allowing the tuber to synthesise the GNA lectin protein . While some companies were considering growing GM crops expressing lectin, GNA was an unlikely candidate . Lectin is toxic, especially to gut epithelia . Pusztai reported significant differences in the thickness of the gut epithelium, but no differences in growth or immune system function . </P> <P> On June 22, 1998, an interview on Granada Television's current affairs programme World in Action, Pusztai said that rats fed on the potatoes had stunted growth and a repressed immune system . A media frenzy resulted . Pusztai was suspended from the Rowett Institute . Misconduct procedures were used to seize his data and ban him from speaking publicly . The Rowett Institute and the Royal Society reviewed his work and concluded that the data did not support his conclusions . The work was criticized on the grounds that the unmodified potatoes were not a fair control diet and that any rat fed only potatoes would suffer from protein deficiency . Pusztai responded by stating that all diets had the same protein and energy content and that the food intake of all rats was the same . </P>

What is the major concern in cryopreservation of cells quizlet