Diet containing glyphosate-resistant soybeans affected the nuclei of
liver cells in mice.
Manipulated Organism:
Soybean (Glycine max).
Inserted Transgenes and Target Effect:
CP4 EPSPS gene derived from the common soil bacterium
Agrobacterium sp. Strain CP4. The gene was fused to the cauliflower
mosaic virus (CaMV-35S) promoter so that the target gene would be
expressed in all parts of the plant. The transgenic soybeans are resistant
to glyphosate which is the active ingredient of the herbicide Roundup.
Goal of This Study:
Investigation of livers of mice that were fed a diet containing
glyphosate-resistant soybeans. The researchers focused on the liver
since it is "a primary site for biotransformation of the products of
digestion and is strategically located between the intestinal tract
and the general circulation. Moreover, it degrades and detoxifies toxic
compounds received from the intestines or from the general circulation
and excretes them in the bile" ( p.173).
Swiss mice were fed 14% GM soybean in a standard laboratory chow. Control
mice were fed on the same diet but with unmodified soybeans. Feeding
experiment began with pregnant mice and the offspring were fed for 8
months under constant environmental conditions. Mice were killed and
their liver cells investigated when 1, 2, 5 or 8 months old.
Nontarget Effects:
-
Electron microscopic examination of liver samples showed that the shapes
of the cell nuclei in liver cells differ in GM fed mice and controls:
"In fact, except for 1 month-old animals, all GM fed mice showed irregular
shaped nuclei, while control animals generally showed roundish nuclei. An
irregular nuclear shape generally represents an index of high metabolic
rate . . ." (p. 177). The irregular shape appeared as fine waving and
increases the surface area between the nucleus and the cytoplasm.
-
Nuclear pores were more frequent in the irregular shaped nuclei of GM
fed-mice.
-
In GM fed mice, the nucleoli of liver cells had an irregular
shape, numerous small fibrillar centers (FCs), and abundant dense
fibrillar component (DFC). "It is known that when the metabolic
rate increases the number of small FCs as well as the amount of DFC
increase. . . . Interestingly, in our animals the modifications of FC size
as well as of DFC . . . amounts are related to food only" (p. 178).
-
Nucleoplasmic (snRNPs and SC-35) and nucleolar (fibrillarin) splicing
factors were more abundant in GM-fed mice. Splicing factors play an
essential role in the initial stages of gene expression leading to
protein formation and enzyme activity.
The authors conclude: "The present work demonstrates that GM soybean
intake can influence hepatocyte [liver cell] nuclear features in young and
adult mice and, although the mechanisms responsible for such alterations
are still unknown, our data encourage further investigations on this
subject of relevant scientific interest" (p. 179).
Source:
Malatesta, M., C. Caporaloni, S. Gavaudan, M. B. L. Rocchi et al.
(2002). “Ultrastructural Morphometrical and Immunocytochemical Analyses of
Hepatocyte Nuclei from Mice Fed on Genetically Modified Soybean,” Cell
Structure and Function vol. 27, pp. 173-80.
Author Affiliations:
University of Urbino, Italy; Instituto Zooprofilattico Sperimentale,
Perugia, Italy.
Funding:
Not mentioned.
Product Status:
Glyphosate-resistant soybeans are commercially grown and have been on
the market in the United States since 1996. Most of these soybeans are
used for animal feed (cattle, pigs, and chicken).
Copyright 2008 The Nature
Institute.
|
|
