Genetically modified organisms and biological risks
Institute of Higher Nervous Activity and Neurophysiology RAS, Moscow,
Russia, e-mail: I_Ermakova@mail.ru
Widespread distribution of genetically modified organisms (GMO) causes
great biological risks for human and the Environment. Three kind of biological
risks are described usually: ecological, nutrition and agrotechnical. The term
genetically modified organisms (GMOs) refers to plants, microbes and animals
with genes transferred from other species in order to produce certain novel
characteristics (for example resistance to pests, or herbicides). Neither
methods are perfect and do not guarantee that the rest of the plant genome
remains unchanged. The hazard of genetically modified organisms (GMO) was shown
for human, animals and the Environment in many scientific investigations. Four
main sources of the hazards of GMO are accepted by scientists worldwide: 1)
those due to the new genes, and gene products introduced; 2) unintended effects
inherent to the technology; 3) interactions between foreign genes and host
genes; and 4) those arising from the spread of the introduced genes by ordinary
cross-pollination as well as by horizontal gene transfer (World Scientists'
Statement, 2000). Natural infectious agents exist which can transfer genes
horizontally between individuals. There are viruses and other pieces of
parasitic genetic material, called plasmids and transposons, which
are able to get into cells and then make use of the cell's resources to multiply
many copies of themselves or to jump into (as well as out of) the cell's genome
(World Scientists' Statement 2000).
Experimental researches showed the negative effect of GMO on insects. Larvae of
the monarch butterfly, Danaus plexippus, reared on milkweed leaves dusted with
pollen from Bt corn, ate less, grew more slowly and suffered higher mortality
than larvae reared on leaves dusted with untransformed corn pollen or on leaves
without pollen (Losey, 1999). In an other investigation it was shown that Bt
corn could have adverse sublethal effects on black swallowtails in the field.
Reduction of life expectancy of ladybirds, fed by pest aphid, planted in
GM-potatoes, was found also.
The genetically modified (or transgenic) plants could be used by mammals for
their nutrition in the fields of GM-crops. It was shown that consumption of
GM-food by animals led to the negative changes in their organs. Experiments,
conducted by A. Pusztai (1998), found that potatoes modified by the insertion of
snowdrop genes that code for insecticidal proteins stunted the growth of rats
and damaged their immune system. Feeding rats with baked transgenic potatoes
significantly affected some of their vital organs including the kidneys, thymus,
gastrocnemius muscle and others. Negative effect of GM-potatoes, GM-pears, GM-soya
on mammals was shown in many other investigations.
For understanding of the GMO dangerous it is better to know the methods that
usually used to introduce a new DNA (gene) into the cell of a plant that is
going to be modified. There are two standard methods: the “shot-gun” technique
and agrobacterium tumefaciens method. Both methods are not perfect and don’t
guarantee safety for the Environment those GM-organisms, which were created with
their help. Experimental researches in mice showed that ingested foreign DNA
survived in the gastrointestinal tract and entered the blood stream of mice.
Important data were obtained in pregnant mice that were fed regularly during
pregnancy with a daily dose of plasmids containing the gene for the green
fluorescent protein (pEGFP-C1) or bacteriofaphage M13 DNA. Foreign DNA, orally
ingested by pregnant mice, was discovered in white blood cells, spleen, liver
cells of foetuses and newborn animals. Authors concluded, that maternally
ingested foreign DNA could be potential mutagen for the developing fetus (Schubbert
et al., 1998).
Our own experiments showed the dangerous of Ready Roundup soya-bean (line
40.3.2), modified by the transgene CP4 EPSPS, for rats and their offspring.
Female rats were divided into groups, housed and kept under normal laboratory
conditions (3 rats/cage).
Experiments with rat females were repeated three times in four groups: “GM-soya”
group, “Trad-soya” group, “Protein-isolate GM-soya” group and “Control” group.
One group of female rats of 180-200g weights was allocated to the experimental
group, and received 5-7g soy flour prepared by the grinding the raw whole
Roundup-Ready soybean seeds. In two other groups females the diet was
supplemented with the same amount of soya flour, prepared from protein isolate
GM-soya (RR, line 40.3.2) or from traditional soya Arcon SJ 91-330. Soy flour
was mixed with water and added to the rat chow for two weeks before mating,
during mating, pregnancy and lactation. In a positive control group females have
only got the standard laboratory chow, without any supplementation. After two
weeks on the diets all females were mated with healthy males of the same age,
who have never been exposed to soya flour supplements. Lab chow and water was
available ad libitum during the experimental period, for all animals. 30 females
and 221 pups were investigated during three series of similar experiments.
Supplementation of the diet of the females with GM soy led to the high mortality
of rat pups (51.6%) in comparison with the pups from “Trad-soya” group (10%),
“Protein-isolate GM soy” group (15.1%) and “Control” group (8.1%) (Tabl). High
pup mortality was characteristic of every litter from mothers fed the GM soy
flour. Pups from “GM-soy” group have higher mortality and third of them were
sick and weighed several times less, than pups from the control groups. No
lethality of females and survived young pups eating the GM-soya flour
supplemented diet was observed. The level of mortality was analyzed by the
one-way ANOVA, using of Newman-Keuls test for share distribution.
The anxiety (model “light and dark”) and aggression were analysed in females and
their offspring. The behaviour of females and young rat pups of GM-group was
compared with those of control groups. Obtained data showed a high level of
anxiety and aggression in rats from GM-soy group: females and rat pups attacked
and bit each other and the worker, who took care about them.
Our data allow us to speculate and presume that the negative effect of GM-soy on
the newborn pups could be mediated by three possible factors. Firstly, it can be
the result of transformation, and insertion of the foreign genes, which could
penetrate into the sexual/stem cells, or/and into cells of the fetus, as it was
observed by Schubbert and colleagues (1998). In their experiments the plasmid
containing the green fluorescent protein (pEGFP-C1) gene, or the bacteriofaphage
M13 DNA was fed to pregnant mice. Using the polymerase chain reaction (PCR) or
the fluorescent in situ hybridization (FISH) method, foreign DNA, orally
ingested by pregnant mice, was discovered in various organs of fetuses and of
newborn animals. GM-soy is one of the plants, created by the help of bacterial
DNA plasmids (Agrobacter tumefaciensis method). So, we can presume that
able for replication plazmids are kept in the cells of GM-plants (in our case in
GM-soya). The affecting of sexual cells and reproductive organs of rats by
plasmids with foreign DNA from GM soy could be occurred.
Secondly, the negative effect of GM-soya could be connected with the highly
mutagenic nature of the GM transformation process. Also, the instability of gene
constructs was described for GM-soya (Windels et al., 2001).
Thirdly, the adverse effect of GM-soya could be mediated by the accumulation of
Roundup residues in GM-soya. However, no mortality was observed with female
rats, nor with the young pups survived, although they also began to eat the GM-soya,
it was supposed that the effect could be mediated by two first factors.
Confirmation of this assumption could be also the fact of weak negative effect
of protein-isolate GM-soya.
In order to understand the mechanism of GM soy influence on the reproductive
performance of mammals and their offspring, it would be necessary to perform
complex researches, including histological, genetical, and embryo-toxicological
investigations. We had to restrict our experiments only for a short time-span.
At the present time one of the main global goals is the protection of the
Environment from the uncontrolled distribution and the contamination of
imperfect genetically modified organisms, which can cause the human diseases,
the decrease of biovariety, and the destruction of nature.
Table. Mortality of rat pups in three weeks after birth
Groups | Delivered females/total females | Number of newborn pups | Number of died pups | Dead pups/total born (%) |
Control | 7/9 | 74 | 6 p<0.001* |
8,1% |
GM-soya | 6/9 | 64 |
33 |
51,6% |
Protein-isolate GM soya | 4/6 | 33 | 5 p<0.01* |
15% |
Traditional soya | 5/6 | 50 | 5 p<0.001* |
10% |