Paper linking cell phones during pregnancy to behavior problems in mice corrected
The authors of a study published last year looking at the effects of cell phone exposure on mice in utero have corrected a figure after it was questioned. New experiments, they write, confirm the original conclusions they drew from the figure.
Here’s the corrected figure from the paper in Scientific Reports, published by Nature Publishing Group:
The authors identified an error in the determination of the maternal corticosterone levels as presented in Figure 4. The ELISA was repeated using stored serum samples from the original experiment. The levels have been corrected and are shown below in Figure 1 (the revised Figure 4). The mean corticosterone level in the pregnant control females was 5.4 ng/ml and in the exposed female mice was 6.1 ng/ml. There was no significant difference between the corticosterone levels of the control and experimental groups. The correction does not change the conclusions.
Corticosterone levels were measured on pregnant mice on day 12 of gestation. The mean corticosterone levels in pregnant control mice was 5.4 ng/ml and in exposed pregnant mice was 6.1 ng/ml. The differences were not statistically significant (P=0.786 by T test). Twelve representative mice housed separately were used, six from each exposure group.
Here’s the original Figure 4, which the authors used to rule out the effects of stress, rather than the cell phone radiation, on the mice:
The mean corticosterone level in the pregnant control females was 69.94 ng/ml and in the exposed female mice was 69.91 ng/ml.
Figure 4 (corticosterone data) is critical for the whole manuscript, as can be read in the text: “In order to exclude the possibility that impaired memory and behavior in exposed mice was caused by stress resulting from experimental manipulation, we measured serum corticosterone levels on day twelve of gestation using an ELISA assay. The mean corticosterone level in the exposed female mice (69.91?ng/ml, n = 6) was not significantly different from that in the control females (69.94?ng/ml, n = 6) [Figure 4], eliminating stress as a source of the observed behavioral and electrophysiologic differences.“
I have analyzed the data and the extremely small variations with the help of a ruler and found that the coefficients of variation in both the control as well as in the exposed animals is approximately 8%, thus in the same range as the unavoidable “noise” of this assay (so called intra-assay-variation), according to the manufacturer. In other words, if the data were correct, there was virtually zero biological variation within both groups and virtually zero difference between all animals’ values. And this for a stress marker which is known for being extremely variable within and between individual animals.
I have worked with assays like this one for many years, and I have never seen such small variations.
The original study garnered some media attention, and has been cited by one other paper, also in Scientific Reports, according to Thomson Scientific’s Web of Knowledge.