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| Conventional maize implicated in Zentek/Austrian mouse study |
Posted: Friday, December 5, 2008 10:52 am
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Scientists around the world
are scrutinizing the Zentek
mouse study, and we are sure to hear
from more of them in due course. Politicians are a far less reticent
crowd, but they're being uncharacteristically quiet about their
deliberations -- despite Austria's efforts to promote the study. The
press are mostly copying each other's coverage,
while inventing claims
regarding 'impotence' and 'infertility'. In sum, the study
appears to be a bombshell that won't go off -- possibly because a bit
of scrutiny shows the report is either largely inconclusive,
or a
blow to the anti-biotech camp. The main problem? Conventional
maize has far more impact on mice than engineered maize.
The promotional effort
On
November 13, Dr. Eva Claudia Lang of Austria's Federal Ministry of
Health, Family and Children (Bundesministerium für Gesundheit, Familie
und Jugend) circulated an email to over 400 public officials in the
European Commission and EU member states urging them to download
Zentek's study, "Biological effects of transgenic maize NK603 x MON810
fed in long term reproduction studies in mice", from the
ministry's website.
This was two days after Greenpeace first broke the story of Zentek's
study, which was revealed on Nov. 11 at
a seminar in Vienna.
With publicity from Greenpeace's media
experts, Austria's
promotion, and "potential unknown long-term side-effects" near the top
of the
activist wish list, the impact of the Zentek study should have
been on a par with similarly-promoted studies by Ermakova, Pusztai and
others.
Promotional effort fails
It's
possible that skepticism is emerging over research findings that are
not peer-reviewed, at least in the field of GMOs. There may even be an
emerging consensus that dodging peer review, at least in the field of
GMOs, is an admission that the paper would fail
peer-review, and that the authors have a keener interest in
sensationalism than in
science.
In this case, it's far more likely that scrutiny is
silently at work -- because Dr. Zentek's preliminary findings, freely
available online, paint a picture quite opposite to what Austria and
Greenpeace would prefer regulators and the world at large to perceive.
The main problem? Conventional maize has far more
impact on mice than engineered maize.
Problems with the paper - multi-generation study
a. comparison with GM feed.
In
the multi-generation study, mice gave issue to successive generations
of offspring -- i.e., parents gave birth to infant mice, who, in their
turn, became parents for the next generation. Regardless of diet, the
report finds "[n]o differences were seen in performance of the parental
mice in all
generations", and [n]o statistically significant differences were seen
in reproduction data
between the two feeding groups".
b. comparisons between non-GM feeds.
When the scientists compared results between the non-GM equivalent
of the mouse feed (ISO), and a mouse feed based on maize grown in
Austria (A REF), a startling picture emerged.
Differences in parental performance of females at delivery in
the F1 and F3 generation where females
from the ISO group were significantly lighter than females from the A
REF group. In those generations, the body mass of
females 3 weeks after delivery was
significantly different and again females from the ISO group were
significantly lighter than females from the A REF group.
Differences in body mass of males was seen in
the F2 generation and males from the ISO group were significantly
lighter than males from the A REF group. In the ISO group body
mass of females and males at mating,
females at delivery, and 3 weeks after delivery, differed significantly
over several
generations. In the A REF body mass differed significantly at mating in
the F2 > F1 in females and F3>F1 in males.
In other words, conventional maize appears to have
been an unhealthy diet for the mice.
d. comparing GM organ weights.
Comparing GM feed to feed made from ISO, the scientists looked at organ
weights. The best they could say was, "Relative organ weights showed
significant differences between groups
that were not consistent through the investigation."
Consistent inconsistency is another way of saying "random", or
"inconclusive".
Things were not quite so inconclusive when it came to comparing the
non-GM ISO and A REF results.
e. comparing non-GM organ weights.
The authors downplayed the significance of their findings.
"Although a number of significant differences concerning relative organ
weights had been found", they said, "these differences could not be
corroborated by
the microscopic comparisons between the feeding groups in any of the
above mentioned organs."
In this portion of the study, they concluded: "[t]here was no evidence
of diet related changes in the
tissues of the gastrointestinal tract, liver, pancreas, kidneys,
spleen, lungs and testes."
f. immunochemistry.
Immunohistochemistry was equally inconclusive. "The
differences
are inconsistent between the two sexes and were not
found in all segments. For the CD3+ immune population the impact of
feed seems rather low", the scientists wrote. The same was true
of CD20 + B-lymphocytes and macrophages: there was either too
much
"inter-individual variability of
the results", or "[n]o statistically significant differences were seen
between the groups."
g. ultrastructural investigation.
Ultrastructural
investigation showed dramatic differences. Comparing the ISO to its GM
version, the scientists could find "[n]o significant divergences
... in the spleen and pancreatic
cells."
The dramatic difference emerged when comparing ISO
and A REF feeds. [em added] "A significant variation
regarding the nuclear shape
irregularity was
only ascertained in liver cells of female mice", they said, "which was
lower
(0.025) in the A REF group in comparison to the ISO group (Table
47) The pore density of lymphocyte nuclei in the spleen was
significantly
lower in males (p=0.026) in the A REF group than in the ISO Group."
h. gene micorarrays.
The authors admit that the value of their gene microarray analyses
are questionable, but their results are nonetheless suggestive.
When
comparing ISO to GM feed, they found "439 genes were
... expressed
differentially". Comparing ISO to A REF, they said: "In total, 1016
genes were found to be differentially expressed".
Problems with the paper - continuous breeding.
In continuous breeding, a set of parent mice give birth to successive
litters, and these litters are compared and evaluated.
The proponents of the Zentek study point almost solely to this section
of the paper as proof that GM feed damages mice.
As a slap in the face to interpretations rendered by Greenpeace,
the Daily Mail, et. al.
regarding offspring performance, the scientists actually
said, "all the consecutive average litter weights
failed to meet the level of significance by a small margin".
Before authors explain observed differences between mice fed GM and
non-GM feed, they will need to explain the far greater
observed
differences between mice fed two versions of
conventional maize.
Coda.
On p. 14, the authors explain that "A difference was considered
statistical[ly] significant at p
< 0.05." At
this level of significance, the author(s) of a paper should expect to
discover at least one 'false positive' among twenty tests.
This
paper lacks a working hypothesis, i.e., a plausible statement of fact
which tests would verify or falsify. Instead, it describes a program to
establish a low level of significance, and then conduct so many tests
that something was bound to emerge "significantly".
With such a low criterion for "significance", and so many tests,
"significant" results were were nearly guaranteed.
Even so, the results they got suggest the most "significant" impacts on
the mice come from conventional feed -- leading to
the silence of credible media and cautious
politicians about whether this paper means anything at all.
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