Retrospective estimation of the electric and magnetic field exposure conditions in in vitro experimental reports reveal considerable potential for uncertainty.

Experiments on cell cultures exposed to extremely low frequency (ELF, 3-300 Hz) magnetic fields are often subject to multiple sources of uncertainty associated with specific electric and magnetic field exposure conditions. Here we systemically quantify these uncertainties based on exposure conditions described in a group of bioelectromagnetic experimental reports for a representative sampling of the existing literature. The resulting uncertainties, stemming from insufficient, ambiguous, or erroneous description, design, implementation, or validation of the experimental methods and systems, were often substantial enough to potentially make any successful reproduction of the original experimental conditions difficult or impossible. Without making any assumption about the true biological relevance of ELF electric and magnetic fields, these findings suggest another contributing factor which may add to the overall variability and irreproducibility traditionally associated with experimental results of in vitro exposures to low-level ELF magnetic fields. Bioelectromagnetics. 39:231-243, 2018. © 2017 Wiley Periodicals, Inc.

Calcium homeostasis and low-frequency magnetic and electric field exposure: A systematic review and meta-analysis of in vitro studies.

Low frequency magnetic field (LF MF) exposure is recurrently suggested to have the ability to induce health effects in society. Therefore, in vitro model systems are used to investigate biological effects of exposure. LF MF induced changes of the cellular calcium homeostasis are frequently hypothesised to be the possible target, but this hypothesis is both substantiated and rejected by numerous studies in literature. Despite the large amount of data, no systematic analysis of in vitro studies has been conducted to address the strength of evidence for an association between LF MF exposure and calcium homeostasis. Our systematic review, with inclusion of 42 studies, showed evidence for an association of LF MF with internal calcium concentrations and calcium oscillation patterns. The oscillation frequency increased, while the amplitude and the percentage of oscillating cells remained constant. The intracellular calcium concentration increased (SMD 0.351, 95% CI 0.126, 0.576). Subgroup analysis revealed heterogeneous effects associated with the exposure frequency, magnetic flux density and duration. Moreover, we found support for the presence of MF-sensitive cell types. Nevertheless, some of the included studies may introduce a great risk of bias as a result of uncontrolled or not reported exposure conditions, temperature ranges and ambient fields. In addition, mathematical calculations of the parasitic induced electric fields (IEFs) disclosed their association with increased intracellular calcium. Our results demonstrate that LF MF might influence the calcium homeostasis in cells in vitro, but the risk of bias and high heterogeneity (I(2)>75%) weakens the analyses. Therefore any potential clinical implications await further investigation.

Inhibition of cellular proliferation and enhancement of hydrogen peroxide production in fibrosarcoma cell line by weak radio frequency magnetic fields.

This study presents experimental data for the effects of weak radio frequency (RF) magnetic fields on hydrogen peroxide (H2O2) production and cellular growth rates of fibrosarcoma HT1080 cells in vitro. Cells were exposed either to 45 µT static magnetic fields (SMFs)-oriented vertical to the plane of growth or to SMFs combined with weak 5 and 10 MHz RF magnetic fields of 10 µTRMS intensity perpendicular to the static field. Cell numbers were reduced up to 30% on Day 2 for the cells exposed to the combination of SMF and a 10 MHz RF magnetic field compared with the SMF control cells. In addition, cells exposed to 10 MHz RF magnetic fields for 8 h increased H2O2 production by 55%. The results demonstrate an overall magnetic field-induced biological effect that shows elevated H2O2 levels with accompanying decrease in cellular growth rates.

Inhomogeneous background magnetic field in biological incubators is a potential confounder for experimental variability and reproducibility.

This report shows that the background magnetic field in biological incubators can vary by orders of magnitude within and between incubators. These variations can be observed within the same incubator in locations that are centimeters apart from each other as well as between incubators that are identical and located in the same laboratory. Additionally, the values measured were frequently outside the range of magnitudes found naturally on the Earth's surface or ordinary habitation spaces. Exposure to such altered magnetic field environments has been experimentally shown to be sufficient to cause numerous effects in cell cultures. Examples of the effects reported span from differential generation of free radicals and heat shock proteins to differences in cellular proliferation, differentiation, and death. Although the effects are not well established and the molecular mechanism of action is currently under debate, these observations alone support the notion that the inhomogeneity of the background magnetic field in incubators is a potential confounding source of the variability and reproducibility for studies performed on cell cultures. In this regard, it is recommended that special measures be adopted to control the background magnetic fields in incubators when investigating the biological effects of exposure to magnetic fields of comparable characteristics as the ones measured in this study, or when studying small biological effects in general.

Reduction of the background magnetic field inhibits ability of Drosophila melanogaster to survive ionizing radiation.

The effects of exposure to an environment where the background magnetic field (BMF) has been reduced were studied on wild-type Drosophila melanogaster by measuring its ability to survive a single exposure to ionizing radiation (IR) during its larval stage. The experimental design presented shows a timeframe, IR dose, and BMF parameters that will cause a significant and reproducible reduction of survival on this insect model. These results suggest that BMFs may play a fundamental role in the recovery or harm of a biological system that is exposed to single doses of IR.

Reduction of the Earth's magnetic field inhibits growth rates of model cancer cell lines.

Small alterations in static magnetic fields have been shown to affect certain chemical reaction rates ex vivo. In this manuscript, we present data demonstrating that similar small changes in static magnetic fields between individual cell culture incubators results in significantly altered cell cycle rates for multiple cancer-derived cell lines. This change as assessed by cell number is not a result of apoptosis, necrosis, or cell cycle alterations. While the underlying mechanism is unclear, the implications for all cell culture experiments are clear; static magnetic field conditions within incubators must be considered and/or controlled just as one does for temperature, humidity, and carbon dioxide concentration.