Answers to the comments of A. Lerchl on the paper 'No effects of intermittent 50-Hz EMF on cytoplasmic free calcium and on the mitochondrial membrane potential in human diploid fibroblasts' by Pilger et al. (Radiat Environ Biophys (2004) 43:203–207)

Autor: Alexander Pilger
Rok vydání: 2010
Předmět:
Zdroj: Radiation and Environmental Biophysics. 49:495-497
ISSN: 1432-2099
0301-634X
DOI: 10.1007/s00411-010-0281-5
Popis: Dr. Lerchl expresses his concern about the low variability of results from the comet assay reported in our publication (Pilger et al. 2004). He argues that the findings are suspicious for statistical as well as technical reasons. In addition, he suspects that the blinding of the experiments could have been circumvented. These allegations are mainly derived from controversies in the context of experiments with highfrequency electromagnetic fields (Lerchl and Wilhelm 2010; Rudiger and Adlkofer 2010; Rudiger 2009a, b; Lerchl 2009). However, it should be pointed out that, apart from the objections raised by Lerchl, the results of Rudiger’s group on genotoxic effects of extremely low-frequency electromagnetic fields (ELF-EMF) were unexpected in a completely different sense. In contrast to expectations, intermittent exposure to ELF-EMF was found to induce DNA strand breaks, whereas no changes in DNA fragmentation have been observed upon treatment with continuous ELF-EMF (Ivancsits et al. 2002). Recently, this phenomenon which seems to lack biological plausibility was corroborated by Focke et al. (2010) using the same cells and the same exposure system. One of the main reasons for Lerchl’s claim that the data of the comet tail factors must have been fabricated is rooted in the argument that one E-cell classification more or less would result in a much greater variation than the reported standard deviation of 0.04. Lerchl argues that the resulting range assuming a tail factor of 4.08 would be 3.985–4.175. However, this argument is fundamentally flawed. There cannot be a miraculous addition or loss of one E-cell but this cell must be balanced by the reduction or addition of a cell exhibiting another tail type. The most likely case is that the addition of one E-cell is balanced by the reduction of one D-cell and vice versa. By simple arithmetic, this results in an effect on the tail factor of 0.03 and not in the more than threefold higher figure of 0.095 given by Lerchl. It has to be borne in mind that the five tail types A to E have, under the assumption of only random variation, a multinomial distribution with a variance of each cell type count proportional to p(1 p), where p is the probability for observing a cell of that type. Under control conditions, the fraction of E-cells is very low (about 0.0015). Hence, the average number of E-cells among 1,000 cells is 1.5, and the theoretical standard deviation is about 1.22. Single counts for the data reported in this paper (Pilger et al. 2004) could not be retrieved, and only the tail factors were kept on file, but examination of records from fibroblast controls (n = 50) yielded a standard deviation of 1.25 counts for E-cells. This value is quite close to expectation. The statement by Lerchl ‘‘The effect of one E-cell more or less in one of the 5 replicates on the standard deviation of the mean value is also significant since the standard deviation would change by 0.04’’ is not correct, and it is incomprehensible how Lerchl arrived at this statement. The standard deviation—under the conditions stated by Lerchl—will change according to the following formula
Databáze: OpenAIRE
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