Exposure to strong static magnetic field slows the growth of human cancer cells in vitro

Proposals to enhance the amount of radiation dose delivered to small tumors with radioimmunotherapy by constraining emitted electrons with very strong homogeneous static magnetic fields has renewed interest in the cellular effects of prolonged exposures to such fields. Past investigations have not studied the effects on tumor cell growth of lengthy exposures to very high magnetic fields. Three malignant human cell lines, HTB 63 (melanoma), HTB 77 IP3 (ovarian carcinoma), and CCL 86 (lymphoma; Raji cells), were exposed to a 7 Tesla uniform static magnetic field for 64 hours. Following exposure, the number of viable cells in each group was determined. In addition, multicycle flow cytometry was performed on all cell lines, and pulsed-field electrophoresis was performed solely on Raji cells to investigate changes in cell cycle patterns and the possibility of DNA fragmentation induced by the magnetic field. A 64 h exposure to the magnetic field produced a reduction in viable cell number in each of the three cell lines. Reductions of 19.04 ± 7.32%, 22.06 ± 6.19%, and 40.68 ± 8.31% were measured for the melanoma, ovarian carcinoma, and lymphoma cell lines, respectively, vs. control groups not exposed to the magnetic field. Multicycle flow cytometry revealed that the cell cycle was largely unaltered. Pulsed-field electrophoresis analysis revealed no increase in DNA breaks related to magnetic field exposure. In conclusion, prolonged exposure to a very strong magnetic field appeared to inhibit the growth of three human tumor cell lines in vitro. The mechanism underlying this effect has not, as yet, been identified, although alteration of cell growth cycle and gross fragmentation of DNA have been excluded as possible contributory factors. Future investigations of this phenomenon may have a significant impact on the future understanding and treatment of cancer. © 1996 Wiley-Liss, Inc.     

Are the young more sensitive than adults to the effects of radiofrequency fields? An examination of relevant data from cellular and animal studies

It has sometimes been assumed that children are more sensitive than adults to the effects of radiofrequency (RF) fields associated with cellular wireless telephones. However, relatively few in vitro or animal models have examined this possibility.In vitro studies have used several cell types, from both humans and rodents, including primary cells, embryonic cell lines, undifferentiated cancer cell lines, and stem cells. Overall, the balance of evidence does not suggest that field-related effects occur in any cell type: gene and protein expression were not significantly changed by exposure in nine out of 15 studies; genotoxicity was evaluated in 13 papers and in most, of these studies, no damage to DNA was detected; eight studies failed to demonstrate induction of apoptosis; and three studies reported lack of oxidative stress induction by RF-exposures. Five of eight studies investigating the effects of combined exposures to RF fields and chemical or physical agents reported a lack of field-related effects.In addition, few papers have been published on the effects of low level exposure of immature animals. The available results are very limited, both in terms of signals used and biological endpoints investigated, but the evidence does not indicate that prenatal or early postnatal exposures are associated with acute adverse responses or the development of detrimental changes in the long-term. Overall, this suggests that young animals may not be significantly more sensitive than adults, but there is clearly a need for further studies to be carried out.     

No effects of pulsed electromagnetic fields on expression of cell adhesion molecules (integrin, CD44) and matrix metalloproteinase-2/9 in osteosarcoma cell lines

Pulsed electromagnetic fields (PEMF) could enhance the cytocidal effects of chemotherapeutic drugs on malignant tumor cell lines, but metastasis effects of PEMF on tumor cells have not been investigated. We investigated the effects of PEMF exposure on the expression levels of some metastasis-related molecules, including integrin α subunits (α1, α2, α3, α4, α5, α6, αv), integrin β subunits (β1, β2, β3, β4), CD44, and matrix metalloproteinase-2/9 (MMP-2/9) in four human osteosarcoma cell lines (HOS, MG-63, SAOS-2, NY) and two mouse osteosarcoma cell lines (DOS, LM8) by using FACScan analysis, gelatin zymography, and Western blot analysis. Our results indicate that PEMF exposure has no effect on the expression of some molecules that are associated with tumor cell invasion and metastasis, and therefore suggest that PEMF exposure may be safely applied to chemotherapy for osteosarcoma.     

Transgenic Bacillus thuringiensis (Bt) Rice Is Safer to Aquatic Ecosystems than Its Non-Transgenic Counterpart

Rice lines genetically modified with the crystal toxin genes from Bacillus thuringiensis (Bt) have experienced rapid development, with biosafety certificates for two Bt rice lines issued in 2009. There has still been no commercial release of these lines yet due to public concerns about human health and environmental risks. Some studies confirmed that Bt rice was as safe as conventional rice to non-target organisms when pesticides were not applied, however, pesticides are still required in Bt rice to control non-lepidopteran pests. In this study, we assessed the environmental effects of two Bt rice lines expressing either the cry1Ab/1Ac or cry2A genes, respectively, by using zooplanktons as indicator species under normal field management practices using pesticides when required. In the whole rice growing season, non-Bt rice was sprayed 5 times while Bt rice was sprayed 2 times, which ensured both rice achieved a normal yield. Field investigations showed that rice type (Bt and non-Bt) significantly influenced zooplankton abundance and diversity, which were up to 95% and 80% lower in non-Bt rice fields than Bt rice fields. Laboratory rearing showed that water from non-Bt rice fields was significantly less suitable for the survival and reproduction of Daphnia magna and Paramecium caudatum in comparison with water from Bt rice fields. Higher pesticide residues were detected in the water from non-Bt than Bt rice fields, accounting for the bad performance of zooplankton in non-Bt field water. Our results demonstrate that Bt rice is safer to aquatic ecosystems than non-Bt rice, and its commercialization will be beneficial for biodiversity restoration in rice-based ecosystems.     

Zebra finch cell lines from naturally occurring tumors

The zebra finch (Taeniopygia guttata) has been intensively studied in many research fields including neuroscience, behavioral neurobiology, and evolution of the genome. Although numerous molecular and genomic resources are available for this model species, immortalized cell lines have been lacking. We have established two zebra finch cell lines derived from spontaneous tumors. ZFTMA is a tetraploid female cell line and G266 as a diploid male cell line. These first zebra finch cell lines should facilitate development of research on this model species.     

Maternal exposure to magnetic fields from high-voltage power lines and the risk of birth defects

The issue of adverse human health effects due to exposure to electromagnetic fields is still unclear, and congenital anomalies are among the outcomes that have been inconsistently associated with such exposure. We conducted a population-based, case-control study to examine the risk of congenital anomalies associated with maternal exposure to magnetic fields (MF) from high-voltage power lines during pregnancy in a community in northern Italy. We identified 228 cases of congenital malformations diagnosed in live births, stillbirths, and induced abortions among women living in the municipality of Reggio Emilia during the period 1998-2006, and a reference group of healthy newborns was matched for year of birth, maternal age, and hospital of birth. We identified maternal residence during early pregnancy and used Geographic Information System to determine whether the residences were within geocoded corridors with MF ≥0.1 μT near high-voltage power lines, then calculated the relative risk (RR) of congenital anomalies associated with maternal exposure. One case and 5 control mothers were classified as exposed, and the RR associated with MF ≥0.1 μT was 0.2 (95% CI: 0.0-2.0) after adjusting for maternal education. While small or moderate effects may have gone undetected due to low statistical power, the results of this study overall do not provide support for major effects of a teratogenic risk due to exposure to MF during early pregnancy.     

昆虫细胞系的培养和建立技术

迄今已经报道的昆虫细胞系有800株以上。昆虫细胞系在昆虫病理学、寄生虫学、内分泌学、遗传学和分子生物学等基础和应用研究中得到越来越广泛的应用。本文结合我们研究的结果和实践经验,概括了国内外昆虫细胞系建立技术的研究进展,包括昆虫细胞培养的发展、昆虫细胞系建立技术、不同昆虫组织来源细胞系的建立方法和过程,以及对昆虫细胞系特征的鉴定等方面。     

In vitro exposure to electromagnetic fields: changes in tumour cell properties

Two human colon cancer cell lines, Colo 205 and Colo 320 DM, have been studied for their responses to 60 Hz-generated electromagnetic fields (EMF) using soft agar cloning and monoclonal antibody binding assays to assess exposure-induced changes. Cellular responses have been studied after 24 h continuous exposure of cells concurrently to four experimental conditions; i.e. no EMF (E-M-), magnetic field only (M+, 1.0 G rms), electric field only (E+, 300 mA/m2 rms), and combined electric plus magnetic fields at these intensities (E+M+). Under these conditions, both cell lines demonstrated significantly increased colony formation in soft agar and increased expression of tumor associated antigens after exposure to E+M+ and to M+ as compared to unexposed controls.     

Influence of electric fields on photophobic reactions in blue-green algae

The effect of external electric fields on photo-accumulations of Phormidium uncinatum in light traps has been studied. 1. In direct current fields the phobic reaction of trichoms leaving the light field is not impaired if a voltage of 2.5 V is not exceeded. With voltages between 3 and 7 V the trichoms are motile, but phobic reactions are cancelled, provided the organisms are oriented more or less parallel to the electric field lines. Higher voltages cause the algae to die within minutes. 2. Only alternating current fields of very low frequencies (less than or equal 10(-3) Hz) have similar effects. Sine waves are more effective than triangular ones, but less than square waves. A hypothesis is proposed according to which sensory transduction of photophobic reactions in blue-green algae is mediated by changes in the endogenous membrane potential. This potential might be interfered with by the application of an external electric field, thus inhibiting photophobic reactions.     

Review of possible modulation-dependent biological effects of radiofrequency fields

The biological effects of modulated radiofrequency (RF) electromagnetic fields have been a subject of debate since early publications more than 30 years ago, suggesting that relatively weak amplitude-modulated RF electromagnetic fields have specific biological effects different from the well-known thermal effects of RF energy. This discussion has been recently activated by the increasing human exposure to RF fields from wireless communication systems. Modulation is used in all wireless communication systems to enable the signal to carry information. A previous review in 1998 indicated that experimental evidence for modulation-specific effects of RF energy is weak. This article reviews recent studies (published after 1998) on the biological effects of modulated RF fields. The focus is on studies that have compared the effects of modulated and unmodulated (continuous wave) RF fields, or compared the effects of different kinds of modulations; studies that used only one type of signal are not included. While the majority of recent studies have reported no modulation-specific effects, there are a few interesting exceptions indicating that there may be specific effects from amplitude-modulated RF fields on the human central nervous system. These findings warrant follow-up studies.     

Persistent use of false myeloma cell lines

Multiple myeloma (MM) is a neoplasm of a terminally differentiated B-cell. Human myeloma cell lines were shown to be suitable model systems for use in various fields of the biological sciences. Within the last 20 years more than 100 cell lines have been established. So-called 'myeloma cell lines' have been previously reported and are still widely used which are in reality Epstein-Barr virus (EBV)-positive B-lymphoblastoid cell lines. The presence of the EBV-genome in residual normal B-cells provides them with a selective growth advantage after explantation. Cell lines represent an extremely important resource for research in a variety of fields and disciplines. As the cell lines are used as in vitro model systems in lieu of primary material, it is crucial that the cells in the culture flasks faithfully correspond to the purported objects of study. On closer examination, the use of false cell lines may be seen to invalidate a significant percentage of scientific work, or at least cast doubts on the relevance of these in vitro results to the cell type or tumor in vivo. Ultimately, use of cross-contaminated cell lines is a waste of human and material resources. Henceforth, it should be mandatory to prove the proper derivation of each new cell line by comparing DNA fingerprints or karyotypes of the patient's primary cells and the cultured cells. The availability of well characterized and authenticated bona fide MM cell lines is of great importance for the study of the biology, etiology and treatment of the disease.     

Static magnetic fields: animal studies

Various experimental studies carried out over the last 30–40 years have examined the effects of the chronic or acute exposure of laboratory animals to static magnetic fields. Many of the earlier studies have been adequately reviewed elsewhere; few adverse effects were identified. This review focuses on studies carried out more recently, mostly those using vertebrates, particularly mammals. Four main areas of investigation have been covered, viz., nervous system and behavioural studies, cardiovascular system responses, reproduction and development, and genotoxicity and cancer. Work on the role of the natural geomagnetic field in animal orientation and migration has been omitted.

Generally, the acute responses found during exposure to static fields above about 4 T are consistent with those found in volunteer studies, namely the induction of flow potentials around the heart and the development of aversive/avoidance behaviour resulting from body movement in such fields. No consistently demonstrable effects of exposure to fields of 1 T and above have been seen on other behavioural or cardiovascular endpoints. In addition, no adverse effects of such fields on reproduction and development or on the growth and development of tumours have been firmly established. Overall, however, far too few animal studies have been carried out to reach any firm conclusions.     

Magnetic fields,radicals and cellular activity

Some effects of low-intensity magnetic fields on the concentration of radicals and their influence on cellular functions are reviewed. These fields have been implicated as a potential modulator of radical recombination rates. Experimental evidence has revealed a tight coupling between cellular function and radical pair chemistry from signaling pathways to damaging oxidative processes. The effects of externally applied magnetic fields on biological systems have been extensively studied, and the observed effects lack sufficient mechanistic understanding. Radical pair chemistry offers a reasonable explanation for some of the molecular effects of low-intensity magnetic fields, and changes in radical concentrations have been observed to modulate specific cellular functions. Applied external magnetic fields have been shown to induce observable cellular changes such as both inhibiting and accelerating cell growth. These and other mechanisms, such as cell membrane potential modulation, are of great interest in cancer research due to the variations between healthy and deleterious cells. Radical concentrations demonstrate similar variations and are indicative of a possible causal relationship. Radicals, therefore, present a possible mechanism for the modulation of cellular functions such as growth or regression by means of applied external magnetic fields.     

Microarray gene expression profiling of a human glioblastoma cell line exposed in vitro to a 1.9 GHz pulse-modulated radiofrequency field

The widespread use of mobile phones has led to public concerns about the health effects associated with exposure to radiofrequency (RF) fields. The paramount concern of most persons relates to the potential of these fields to cause cancer. Unlike ionizing radiation, RF fields used for mobile telecommunications (800-1900 MHz) do not possess sufficient energy to directly damage DNA. Most rodent bioassay and in vitro genotoxicity/mutation studies have reported that RF fields at non-thermal levels have no direct mutagenic, genotoxic or carcinogenic effects. However, some evidence has suggested that RF fields may cause detectable postexposure changes in gene expression. Therefore, the purpose of this study was to assess the ability of exposure to a 1.9 GHz pulse-modulated RF field for 4 h at specific absorption rates (SARs) of 0.1, 1.0 and 10.0 W/kg to affect global gene expression in U87MG glioblastoma cells. We found no evidence that non-thermal RF fields can affect gene expression in cultured U87MG cells relative to the nonirradiated control groups, whereas exposure to heat shock at 43 degrees C for 1 h up-regulated a number of typical stress-responsive genes in the positive control group. Future studies will assess the effect of RF fields on other cell lines and on gene expression in the mouse brain after in vivo exposure.     

Magnetic field direction differentially impacts the growth of different cell types

Magnetic resonance imaging (MRI) machines have horizontal or upright static magnetic field (SMF) of 0.1–3 T (Tesla) at sites of patients and operators, but the biological effects of these SMFs still remain elusive. We examined 12 different cell lines, including 5 human solid tumor cell lines, 2 human leukemia cell lines and 4 human non-cancer cell lines, as well as the Chinese hamster ovary cell line. Permanent magnets were used to provide 0.2–1 T SMFs with different magnetic field directions. We found that an upward magnetic field of 0.2–1 T could effectively reduce the cell numbers of all human solid tumor cell lines we tested, but a downward magnetic field mostly had no statistically significant effect. However, the leukemia cells in suspension, which do not have shape-induced anisotropy, were inhibited by both upward and downward magnetic fields. In contrast, the cell numbers of most non-cancer cells were not affected by magnetic fields of all directions. Moreover, the upward magnetic field inhibited GIST-T1 tumor growth in nude mice by 19.3% (p < 0.05) while the downward magnetic field did not produce significant effect. In conclusion, although still lack of mechanistical insights, our results show that different magnetic field directions produce divergent effects on cancer cell numbers as well as tumor growth in mice. This not only verified the safety of SMF exposure related to current MRI machines but also revealed the possible antitumor potential of magnetic field with an upward direction.     

50 Hz sinusoidal magnetic fields do not affect human lymphocyte activation and proliferation in vitro

In the last 30 years, an increasing public concern about the possible harmful effects of electromagnetic fields generated by power lines and domestic appliances has pushed the scientific community to search for a correct and comprehensive answer to this problem. In this work the effects of exposure to 50 Hz sinusoidal magnetic fields, with a magnetic flux density of 0.05 mT and 2.5 mT (peak values), were studied on human peripheral blood mononuclear cells (PBMCs) collected from healthy young and elderly donors. Cell activation and proliferation were investigated by using flow cytometry techniques and 3H-TdR incorporation assays, respectively. The results obtained indicated that exposure to the fields altered neither DNA synthesis nor the capacity of lymphocytes to enter the activation phase and progress into the cell cycle. Thus, the conclusions are that two important functional phases of human lymphocytes, such as activation and proliferation, are not affected by exposures to 50 Hz magnetic fields similar to those found under power lines.     

Review of russian literature on biological action of DC and low-frequency AC magnetic fields

This review considers the Russian scientific literature on the influence of weak static and of low-frequency alternating magnetic fields on biological systems. The review covers the most interesting works and the main lines of investigation during the period 1900 to the present. Shown here are the historical roots, beginning with the ideas of V. Vernadsky and A. Chizhevsky, which led in the field of Russian biology to an increasing interest in magnetic fields, based on an intimate connection between solar activity and life on the Earth, and which determined the peculiar development of Russian magnetobiology. The variety of studies on the effects of magnetic storms and extremely low-frequency, periodic variations of the geomagnetic field on human beings and animals as well as on social phenomena are described. The diverse experiments involving artificial laboratory magnetic fields acting on different biological entities under different conditions are also considered. A series of theoretical advances are reviewed that have paved the way for a step-by-step understanding of the mechanisms of magnetic field effects on biological systems. The predominantly unfavorable influence of magnetic fields on living beings is shown, but the cases of favorable influence of magnetic fields on human beings and lower animals are demonstrated as well. The majority of Russian investigations in this area of science has been unknown among the non-Russian speaking audience for many reasons, primarily because of a language barrier. Therefore, it is hoped that this review may be of interest to the international scientific community.     

Extremely low frequency electric fields and cancer: Assessing the evidence

Much of the research and reviews on extremely low frequency (ELF) electric and magnetic fields (EMFs) have focused on magnetic rather than electric fields. Some have considered such focus to be inappropriate and have argued that electric fields should be part of both epidemiologic and laboratory work. This paper fills the gap by systematically and critically reviewing electric‐fields literature and by comparing overall strength of evidence for electric versus magnetic fields. The review of possible mechanisms does not provide any specific basis for focusing on electric fields. While laboratory studies of electric fields are few, they do not indicate that electric fields should be the exposure of interest. The existing epidemiology on residential electric‐field exposures and appliance use does not support the conclusion of adverse health effects from electric‐field exposure. Workers in close proximity to high‐voltage transmission lines or substation equipment can be exposed to high electric fields. While there are sporadic reports of increase in cancer in some occupational studies, these are inconsistent and fraught with methodologic problems. Overall, there seems little basis to suppose there might be a risk for electric fields, and, in contrast to magnetic fields, and with a possible exception of occupational epidemiology, there seems little basis for continued research into electric fields. Bioelectromagnetics 31:89–101, 2010. © 2009 Wiley‐Liss, Inc.     

Residential exposure to magnetic fields generated by 110-400 kV power lines in Finland

In a specific case, the magnetic field generated in a building by a nearby power line is usually easy to calculate, although the accuracy of these calculations is sensitive to the quality of source information. To be able to study public health dimensions of magnetic field exposure (e.g., risk of cancer), it is necessary to evaluate the size and exposure of the population at risk. Relatively little quantitative information on public exposure to power-frequency magnetic fields of high-voltage power lines is available. This report describes residential exposure to magnetic fields from 110 kV, 220 kV, and 400 kV power lines in Finland at the national level, including 90% of the total line length in 1989. A geographical information system (GIS) was used to identify the buildings located near the power lines. After determining the distances between the lines and the buildings, historical data on load currents of these lines were used to calculate the magnetic fields. The residential magnetic field histories were then linked to the residents by means of a computerized central population register. The data obtained on personal exposure have also been utilized in a nationwide epidemiological study on magnetic field exposure of power lines and risk of cancer. The methods of exposure assessment and results of the number of buildings near 110 kV, 220 kV, and 400 kV power lines, their average annual magnetic fields, and personal exposure to magnetic fields from these lines are described. We found that 15,600 residents lived in an average residential magnetic field ≥0.1 μT caused by power lines in 1989. The number of these residents increased fivefold during 1970-1989. We estimated that 0.3% of the population was exposed in their residences to an annual average magnetic flux density from 110 kV, 220 kV, and 400 kV power lines higher than 0.1 μT, the level that the background magnetic flux density in general does not exceed in Finnish homes. Thus, the problem of magnetic field exposure generated by high-voltage lines concerns only a relatively small fraction of the total population in Finland. However, the size and exposure of the population at risk remain somewhat arbitrary in practical multisource situations, as the biological interaction mechanism, the concept of harmful dose, and, in particular, the significance of the duration of exposure are unknown. © 1995 Wiley-Liss, Inc.