E. M. Goodman

Effects of Electromagnetic Fields on Molecules and Cells

Evidence suggests that cell processes can be influenced by weak electromagnetic fields (EMFs). EMFs appear to represent a global interference or stress to which a cell can adapt without catastrophic consequences. There may be exceptions to this observation, however, such as the putative role of EMFs as promoters in the presence of a primary tumor initiator. The nature of the response suggests that the cell is viewing EMFs as it would another subtle environmental change. The age and state of the cell can profoundly affect the EMF bioresponse. There is no evidence that direct posttranscription effects occur as a result of EMF exposure. Although transcription alterations occur, no apparent disruption in routine physiological processes such as growth and division is immediately evident. What is usually observed is a transient perturbation followed by an adjustment by the normal homeostatic machinery of the cells. DNA does not appear to be significantly altered by EMF. If EMF exposure is associated with an increased risk of cancer, the paucity of genotoxic effects would support the suggestion that the fields act in tumor promotion rather than initiation. The site(s) and mechanisms of interaction remain to be elaborated. Although there are numerous studies and hypotheses that suggest the membrane represents the primary site of interaction, there are also several different studies showing that in vitro systems, including cell-free systems, are responsive to EMFs. The debate about potential hazards or therapeutic value of weak electromagnetic fields will continue until the mechanism of interaction has been clarified.

Physarum polycephalum: A Review of a Model System Using a Structure-Function Approach

Publisher Summary This chapter discusses the relationship between the structure and function of Physarum . Physarum amoebae undergo a true cell division involving karyokinesis and cytokinesis. The rRNA and tRNA transcripts from the amoeboid and plasmodial stages are similar with respect to their molecular weight, their location, and the fraction of the genome they represent. Amoebae are not pigmented and contain little or no slime on their surface. They have a discernible endoplasmic reticulum, Golgi bodies, and centrioles. Centrioles are part of the mitotic apparatus in amoebae; a mitotic tubule organizing center is found associated with the nucleolus in the plasmodium. A relationship between the two structures remains to be determined. Alleles at the two separate mating-type loci control zygote formation and the transformation of the zygote to a plasmodium; in the plasmodium, plasmogamy is under control of another separate and distinct fusion locus. Haploid plasmodia can develop by repeated karyokinesis in the absence of cytokinesis in the apogamic (C1) strain. The replication of chromosomal DNA is bidirectional, occurs in a sequential, temporal order and is completed within 3–4 hours. The replication of nucleolar DNA occurs in an unscheduled, nontemporal order; it is initiated in the latter part of the S phase and continues until prophase. Chromosomal and nucleolar DNA are arranged in a nucleosome configuration.

Low frequency electric and magnetic fields have different effects on the cell surface

There is a considerable controversy over the nature of weak electromagnetic‐field effects in living organisms. Part of the controversy can be traced to a lack of understanding of whether electric or magnetic fields are involved in producing bioeffects. We find that both 60 Hz electric and magnetic fields alter the cell surface of Physarum polycephalum. Exposure to electric fields increases the negative charge on the cell surface while magnetic‐field exposure decreases the hydrophobic character of the surface. These effects appear to be additive and independent of the waveform of the applied fields.

Effects of Extremely Low Frequency Electromagnetic Fields on Physarum polycephalum

Microplasmodia from the slime mold Physarum polycephalum have been continuously exposed to weak electromagnetic fields at 45, 60, and 75 Hz. To date, microplasmodia have been exposed to fields of 75 Hz, 2.0 G, 0.7 V/m for more than 700 days. Two other sets of cultures have been exposed to 45 and 60 Hz fields (2.0 G, 0.7 V/m) for 180 and 400 days, respectively. The time between successive mitotic divisions in cultures exposed to fields varied from 0.5 to 2 hr longer than their respective controls. The mitotic delay is reproducible, and the onset appears to be frequency dependent with approximately 14, 90, and 120 days exposure to 45, 60, and 75 Hz electromagnetic radiation required before a significant effect is observed. Removal of affected cultures from the electromagnetic field (75 Hz, 2.0 G, 0.7 V/m) results in the disappearance of the mitotic delay in approximately 40 days. In addition to the mitotic delay, a retardation in reversible protoplasmic streaming was observed at all frequencies.

Pulsed magnetic fields alter the cell surface

Pulsed magnetic fields (PMFS) are routinely used in the medical community to facilitate bone repair in clinical cases of non‐union or pseudarthoses [(1984) Orth. Clin. No. Am. 15, 61‐87]. Although this therapeutic regimen appears to be reasonably effective, the mechanism of action between specific PMFs and the target tissue remains unknown. Adding urgency to the need to understand the mechanism are a wide number of reports that have appeared which demonstrate that PMFs similar to those in clinical use can alter many basic physiological functions. We report that a 24 h exposure to PMFs alters the cell surface of Physarum polycephalum amoebae. Further, using the technique of aqueous two‐phase partitioning, we present evidence for individual magnetic and electric field, cell surface effects.

Bioeffects of Extremely Low-Frequency Electromagnetic Fields Variation with Intensity, Waveform, and Individual or Combined Electric and Magnetic Fields

Prolonged exposure of the myxomycete Physarum polycephalum to either continuous wave (75 Hz) or frequency modulated wave (76 Hz) electromagnetic fields (EMF) (0.1-2.0 G and 0.035-0.7 V/m) lengthens the mitotic cycle and depresses the respiration rate. Once induced, these effects persist indefinitely in the presence of EMF without increasing or decreasing in magnitude beyond that due to normal variability of the organism. Similar effects are observed when either individual electric fields (0.7 V/m) or magnetic fields (2.0 G) are applied; however, the magnitude of the response is less than that observed with simultaneous fields. The individual field effects appear to be additive for respiration but not for nuclear division rate. For fields applied simultaneously at levels below 0.14 V/m and 0.4 G the response was independent of field intensity. No threshold was observed for simultaneously applied electric and magnetic fields; however, indirect evidence is presented that suggests either the electric or magne...

Protein kinase C activity following exposure to magnetic field and phorbol ester

We examined the separate and combined effects of 60 Hz sinusoidal magnetic fields (MFs) and a phorbol ester on protein kinase C (PKC) activity in HL60 cells. No enhancement in PKC activity was observed when a cell culture was exposed to a 1.1 mT (rms) MF alone or to a combination of MF and 2 microM phorbol 12-myristate 13-acetate (PMA) for 1 h. In a second set of experiments, cells were preexposed to a less than optimal concentration of PMA (50 nM) for 45 min, followed by a 15 min exposure to both PMA and MF. The data showed a greater decrease in cytosolic PKC activity and a larger increase in membrane activity than was induced by either 1 h PMA treatment alone or PMA and sham MF exposure. One logical conclusion from these data is that MFs may be acting in a synergistic manner on a pathway that has already been activated. Therefore, we suggest that MFs, rather than producing biological effects by a new pathway or mechanism of interaction, exert their effect(s) by interacting with already functioning reactions or pathways. If correct, the question of an MFs mechanism of interaction refocuses on how weak fields might enhance or depress a molecular reaction in progress, rather than on finding a new transduction pathway.

Cell Surface Effect of 60-Hz Electromagnetic Fields

ing from 0.035 to 0.7 V/m and 0.01 to 0.3 mT (1 T = 104 G), measured in the growth medium, reduce the rate of respiration and slow mitotic activity in the plasmodial (vegetative) stage P. polycephalum (14-18). In this study haploid (gametic) P. polycephalum amoebae (RSD4) are grown axenically in liquid semidefined medium (19) (conductivity = 0.5 Siemens/m) at 25.0 ? 0.3?C in sinusoidal 60-Hz cw fields of 1.0 V/m (rms) and 0.1 mT (rms) which are applied perpendicular to each other in the plane parallel to the earth and in phase with one another. The growth flasks and exposure chamber are identical to those described in our earlier report (14). P. polycephalum amoebae are eukaryotic cells with an average diameter of 20 /,m; their life cycle and physiology have been reviewed by Goodman (20, 21). The cells are grown in the EM fields continuously except for short periods when they are removed for transfer to fresh medium. Cell partitioning behavior is measured after at least 2 weeks of field exposure after which time differences between exposed and

Effects of weak electromagnetic fields onPhysarum polycephalum: Mitotic delay in heterokaryons and decreased respiration

Continuous exposure ofPhysarum polycephalum to a 75 Hz, 2.0 G, and 0.7 V/m electromagnetic field results in a depressed respiration rate and a lengthening of the mitotic cell cycle. If unexposedPhysarum are mixed with exposedPhysarum the onset of synchronous mitosis in the mixed culture is delayed, occurring at a time between those of the 2 parent cultures.

Method for ensuring comparable temperatures in biological experiments using multiple incubators

We describe a method for overcoming the tendency of four separately controlled incubators to drift apart in temperature. One incubator acts as a master temperature control; the control circuits of the others sense and eliminate temperature differences between the master and the other incubators.