# Sensitivity of Cell Cultures on Time-Varying Low-Frequency Magnetic Field Changes
## 2 Materials and Methodology
### Cell Cultures and Cultivation Conditions  
The experimental biological samples are prepared from pure strain BY4741 yeast cells, _Saccharomyces cerevisiae_, stored in a refrigerator, and cultivated on yeast-peptone-dextrose (YPD) agar at 4 \({}^{\circ}\)C in a Petri dish. The samples are regularly reinoculated on a 2-month basis to maintain pure strain and living cells.  
The experimental protocol comprises pre-cultivation, followed by dilution for sample preparation, cultivation during experimental irradiation, and finally quantification. For the pre-cultivation, a solution of YPD (1% yeast extract, 2% peptone, and 2% dextrose) medium is prepared and diluted with 95% distilled water. After the solution is prepared, the yeasts  
Figure 2: Exposure system. Letters A–E indicate exact position of each investigated sample.  
are inoculated into a 20 mL flask with prepared YPD. The final medium is cultured for 24 h on a shaker at 180 rpm, at an ambient temperature of 23 \({}^{\circ}\)C. Precultured yeast solution is pipetted (0.05 mL) into Erlenmeyer flasks (100 mL), producing five control, and five exposed samples containing 25 mL of experimental medium. To ensure air access, the closure of a cotton-wool plug is inserted on top of each flask. The prepared experimental samples are fixed into an exact place within the electromagnetic coil cavity and then transported into the incubator.  
Cell counting method using Burker chambers is performed to evaluate the proliferation reaction on applied LF MF. The microscopic pictures were taken by Axiocam ERc 5s mounted on an inverted microscope Zeiss Primovert (Oberkochen, Germany). Cell counting is performed before and after each experiment in every exposed and control sample, which is meant to establish a quantification procedure based on the growth dynamics ratio depicted in Figure 3.  
If the growth coefficient \(X>1\), this indicates stimulation of cell growth as a reaction to the external field. If the coefficient \(X<1\), the applied field has an inhibitory effect on yeast reproduction.  
The presented work focuses on a biological response expressed as a percentage. First, the response rate parameter \(S\) [%] is determined. It corresponds to:  
\[S=(X-1)\cdot 100, \tag{2}\]  
The value \(X=1\) represents an unchanged state, the exposed and control samples reproduced equally, and the response rate parameter is \(S=0\%\). If, for example, value \(X=1.2\), the cell counts in the exposed sample are 20% greater than in the control sample, the value of the response rate parameter is \(S=20\%\) and a stimulating effect is observed. On the other hand, at the value of \(X=0.8\), there are 20% fewer cells present in the exposed sample than in the control sample; the response rate parameter is \(S=-20\%\), and the inhibitory effect is observed.  
The experiment performance reflects the common methods and practice for scientific work in laboratories, with main emphasis on precision and accuracy. Developed laboratory protocol incorporates a manual for the implementation of experimental procedures to ensure repeatability and further verification. In addition, the parameters such as conductivity and sample internal temperature are measured; records were archived for further comparison or repetition. Ambient temperature was also monitored during the whole  
Figure 3: The calculation method developed for quantification of the MF effect—representing a growth dynamics coefficient ratio.  
experiment and is stored with corresponding microscopic photos of samples on the Burker chamber, as well as the cell counts of each sample before and after the experiment.