Magnetic Fields Trump Oxygen in Controlling the Death of Erythro-Leukemia Cells
Round 1
Reviewer 1 Report
The manuscript is much improved. However, there are still some concerns 1:Oxygen levels as low as 0.4% normally reduce proliferation. In this study there are only measurements of cells in the process of dying at certain time points as fractions of the number of cells present at that time. However, the cell death between measurements is not recorded. Inclusion of cell survival (cell number as a function of time after re-seeding or doubling time) would improve the study.
2: The experiments used a malignent leukemia cell line. Most cancer cells have decreased OXPHOS (Warburg effect). The conclusions regarding OXPHOS should take this into account. The whole conclusion is highly speculative and there is not not enough evidence from the data for the claims l. 559-565 and section 5.
It should be included in the manuscript how the oxygen levels were measured and that it was measured in the gas, not the cell medium.
Also, the origin of the K562 cells should be stated.
table 2: It is said that n is the number of re-seedings (l. 302), and the cell number is nx1000 (table legend)? Does this mean that the values in the table are average values from different time point in one experiment? This should be written more clearly. How many times was the experiment repeated? Are the data from only one sample in each bay?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors are convincingly proving the effect of low electromagnetic fields and the effect of transition into these fields combined with physiologically relevant changes in oxygen levels using as an end point the measurement of apoptotic/necrotic cell death. The elegant and careful design of the cell culture conditions and sampling gives a valuable tool for scientist interested in the study of the effect of low electromagnetic fields.
It is unfortunate that the data has no statistical significance. Would it be possible to revaluate the results presented on Figure 3. and calculate statistical significance?
Regarding Table 2., presenting the dead cells in baseline culture I have difficulties in understanding what the numbers represent. What is (n)? If n is the number of culture weeks, how can the authors calculate the actual cell number by multiplying the percentages by 1000 x n? Furthermore, if the table represents the cell death values of the 4 different culture conditions, why are these values averaged in the last line of the table?
Finally, in line 315 there is the sentence: “The rate and mechanism of cell death in culture can forecast the destiny of human tissues, particularly when considering chronic diseases”. This is a very general statement, normally, cells cultured in vitro are not undergoing apoptosis of course, but this or other types of cell death can be triggered on the same culture using different initiators. I would suggest to delete this sentence.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript is improved and I accept the arguments in the response.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
This study aims to investigate the impact of the increased expose to electromagnetic radiation in modern society. This was done by cultivating cells in an incubator with or without shielding. Two different oxygen levels were also tested. However, the rationale for this is not well explained. The material and method section is much too long, with parts that should be in results or discussion.
For 19% oxygen: L.43 states that arterial oxygen level is 19% with reference to Höckel et al. In this reference the only value for arterial blood was 90-100 mmHg, corresponding to about 13%. A value of 19% is not physiological.
Choosing 0% oxygen does not make sense. 0% oxygen is so low that all cells will die and growing cells for a week at 0% is not possible. The values for cell apoptosis and necrosis in 0% oxygen in table 2 do not seem probable.
It is stated that the value measured was 0.4% before and 0.7% after experiment which is very different from 0% However, it is not described how it was measured. Was the measurements done in air or the cell medium and with what kind of sensor? The pericellular oxygen concentration depends on cell number, cell respiration and oxygen diffusion and will decrease in a growing cell culture, so it will change during an experiment. Also, how can oxygen be measured after apoptosis measurements (0.7%)?
In all, the experiments do not appear robust or sound.
