ATP involvement in plant tissue responses to low temperature

The effects of chilling and freezing temperature on membrane permeability and ATP content were studied in the leaves of cucumber ( Cucumis sativus L.) and winter rape ( Brassica napus L. var. oleifera L.) leaves, grown at different temperatures. In the winter rape leaves, the endogenous ATP content was modified by application of dinitrophenol (DNP) solutions of different concentrations. The low temperature-induced changes in membrane permeability (as monitored by the conductivity method) were found to be associated with ATP decrease, both in the chilling-sensitive and chilling-resistant (subjected to freezing) plants. In tissues showing reversible injuries, changes in ATP content preceded those in membrane permeability and the adenylate energy charge was affected slightly. In tissues showing irreversible membrane damage, the ATP content was always below 0.4 μmol (g dry weight)⁻¹ and the adenylate energy charge was near 0.5. DNP treatment increased freezing sensitivity of winter rape leaves. In the cold-hardened winter rape leaves, however, freezing and thawing did not significantly affect ATP content or the energy charge, although the specimen showed a rather large increase in membrane permeability. In these leaves ATP content recovered about 20 h after a freezing and thawing treatment. It is proposed that a decrease in ATP supply might be the primary reason for the membrane leakiness at low temperature, both in chilling-sensitive and chilling-resistant (subjected to freezing) plants. The conclusion is, however, not true for the cold-acclimated, frostadapted cells.     

Extremely low frequency electromagnetic fields as effectors of cellular responses in vitro: possible immune cell activation

There is presently an intense discussion if electromagnetic field (EMF) exposure has consequences for human health. This include exposure to structures and appliances that emit in the extremely low frequency (ELF) range of the electromagnetic spectrum, as well as emission coming from communication devices using the radiofrequency part of the spectrum. Biological effects of such exposures have been noted frequently, although the implication for specific health effects is not that clear. The basic interaction mechanism(s) between such fields and living matter is unknown. Numerous hypotheses have been suggested, although none is convincingly supported by experimental data. Various cellular components, processes, and systems can be affected by EMF exposure. Since it is unlikely that EMF can induce DNA damage directly, most studies have examined EMF effects on the cell membrane level, general and specific gene expression, and signal transduction pathways. In addition, a large number of studies have been performed regarding cell proliferation, cell cycle regulation, cell differentiation, metabolism, and various physiological characteristics of cells. Although 50/60 Hz EMF do not directly lead to genotoxic effects, it is possible that certain cellular processes altered by exposure to EMF indirectly affect the structure of DNA causing strand breaks and other chromosomal aberrations. The aim of this article is to present a hypothesis of a possible initial cellular event affected by exposure to ELF EMF, an event which is compatible with the multitude of effects observed after exposure. Based on an extensive literature review, we suggest that ELF EMF exposure is able to perform such activation by means of increasing levels of free radicals. Such a general activation is compatible with the diverse nature of observed effects. Free radicals are intermediates in natural processes like mitochondrial metabolism and are also a key feature of phagocytosis. Free radical release is inducible by ionizing radiation or phorbol ester treatment, both leading to genomic instability. EMF might be a stimulus to induce an "activated state" of the cell such as phagocytosis, which then enhances the release of free radicals, in turn leading to genotoxic events. We envisage that EMF exposure can cause both acute and chronic effects that are mediated by increased free radical levels: (1) Direct activation of, for example macrophages (or other cells) by short-term exposure to EMF leads to phagocytosis (or other cell specific responses) and consequently, free radical production. This pathway may be utilized to positively influence certain aspects of the immune response, and could be useful for specific therapeutic applications. (2) EMF-induced macrophage (cell) activation includes direct stimulation of free radical production. (3) An increase in the lifetime of free radicals by EMF leads to persistently elevated free radical concentrations. In general, reactions in which radicals are involved become more frequent, increasing the possibility of DNA damage. (4) Long-term EMF exposure leads to a chronically increased level of free radicals, subsequently causing an inhibition of the effects of the pineal gland hormone melatonin. Taken together, these EMF induced reactions could lead to a higher incidence of DNA damage and therefore, to an increased risk of tumour development. While the effects on melatonin and the extension of the lifetime of radicals can explain the link between EMF exposure and the incidence of for example leukaemia, the two additional mechanisms described here specifically for mouse macrophages, can explain the possible correlation between immune cell system stimulation and EMF exposure.     

A role for Ca2+ in the effect of very low frequency electromagnetic field on the blastogenesis of human lymphocytes

Methicillin-resistant clinical isolates of Staphylococcus aureus are intrinsically resistant to beta-lactam antibiotics in that the resistance mechanism is unrelated to the possession of beta-lactamases. We have demonstrated that a new, high-molecular-mass penicillin-binding protein (PBP) is present in these strains with a low affinity for beta-lactams and that its amount is regulated by the growth conditions. The new PBP from all strains that have been examined has an identical mobility on SDS gel electrophoresis and is the only PBP still present in an uncomplexed state with beta-lactams (and therefore the only functional PBP when these strains are grown in media containing concentrations of beta-lactam antibiotics sufficient to kill sensitive strains.     

DNA fragmentation in human fibroblasts under extremely low frequency electromagnetic field exposure

Extremely low frequency electromagnetic fields (ELF-EMFs) were reported to affect DNA integrity in human cells with evidence based on the Comet assay. These findings were heavily debated for two main reasons; the lack of reproducibility, and the absence of a plausible scientific rationale for how EMFs could damage DNA. Starting out from a replication of the relevant experiments, we performed this study to clarify the existence and explore origin and nature of ELF-EMF induced DNA effects. Our data confirm that intermittent (but not continuous) exposure of human primary fibroblasts to a 50 Hz EMF at a flux density of 1 mT induces a slight but significant increase of DNA fragmentation in the Comet assay, and we provide first evidence for this to be caused by the magnetic rather than the electric field. Moreover, we show that EMF-induced responses in the Comet assay are dependent on cell proliferation, suggesting that processes of DNA replication rather than the DNA itself may be affected. Consistently, the Comet effects correlated with a reduction of actively replicating cells and a concomitant increase of apoptotic cells in exposed cultures, whereas a combined Fpg-Comet test failed to produce evidence for a notable contribution of oxidative DNA base damage. Hence, ELF-EMF induced effects in the Comet assay are reproducible under specific conditions and can be explained by minor disturbances in S-phase processes and occasional triggering of apoptosis rather than by the generation of DNA damage.     

Extremely low frequency electromagnetic field exposure affects fertilization outcome in swine animal model

Modern society continuously exposes the population to electromagnetic radiation, the effects of which on human health, in particular reproduction, are still unknown. The aim of this research was to assess the effect of acute (1 h) exposure of boar spermatozoa to a 50 Hz extremely low frequency electromagnetic field (ELF-EMF) on early fertility outcome. The effect of intensities ranging from 0 to 2 mT on morpho-functional integrity of capacitated spermatozoa was examined in vitro. The oviducts containing or without spermatozoa were then exposed to the minimum in vivo, TD_50, and maximum intensities determined in vitro, 4 h before ovulation. The effects of ELF-EMF on spermatozoa in terms of early embryo development were evaluated after 12 h and 6 days. It was found that in vitro ELF-EMF >0.5 mT induced a progressive acrosome damage, thus compromising the ability of spermatozoa to undergo acrosomal reaction after zona pellucida stimulation and reducing the in vitro fertilization outcome. These effects became evident at 0.75 mT and reached the plateau at 1 mT. Under in vivo conditions, the ELF-EMF intensity of 1 mT was able to compromise sperm function, significantly reducing the fertilization rate. In addition, the exposure of oviducts to fields ≥ 0.75 mT in the absence of spermatozoa was able to negatively affect early embryo development. In fact, it was found to cause a slowdown in the embryo cleavage. In conclusion, it was demonstrated how and at which intensities ELF-EMF negatively affect early fertility outcome in a highly predictive animal model.     

Physiological responses of Plantago media to electromagnetic field of power-line frequency (50 Hz)

Experimental evidence is presented that continuous exposure of hoary plantain (Plantago media L.) seedlings to the electromagnetic field (EMF) of power-line frequency may disturb physiological, biochemical, and cytological characteristics of these plants. The increase in EMF strength in the range from 230 to 1800 V/m (350–2000 nT) was found to reduce the percentage of seed germination, the rate of cell division, and the rates of DNA and protein biosyntheses in tissues of 8-day-old seedlings. The action of EMF with the strength of 500–1000 V/m (800–1150 nT) stimulated root growth, elevated the content of malondialdehyde and low-molecular antioxidants, and enhanced the activity of superoxide dismutase. Direct correlation was revealed between lipid peroxidation rates and the activity of cellular antioxidant defense system. The wavelike changes in the content of photosynthetic pigments were observed in plantain seedlings exposed to EMF of various strengths.     

Extremely low frequency pulsed electromagnetic field designed for antinociception does not affect microvascular responsiveness to the vasodilator acetylcholine

A 225 µT, extremely low frequency, pulsed electromagnetic field (PEMF) that was designed for the induction of antinociception, was tested for its effectiveness to influence blood flow within the skeletal microvasculature of a male Sprague–Dawley rat model (n = 103). Acetylcholine (0.1, 1.0, or 10 mM) was used to perturb normal blood flow and to delineate differential effects of the PEMF, based on degree of vessel dilation. After both 30 and 60 min of PEMF exposure, we report no effects on peak perfusion response to acetylcholine (with only 0.2% of the group difference attributed to exposure). Spectral analysis of blood flow data was generated to obtain information related to myogenic activity (0.15–0.40 Hz), respiratory rate (0.4–2.0 Hz), and heart rate (2.0–7.0 Hz), including the peak frequency within each of the three frequency regions identified above, peak power, full width at half maximum (FWHM), and mean within band. No significant effects due to exposure were observed on myogenic activity of examined blood vessels, or on heart rate parameters. Anesthesia‐induced respiratory depression was, however, significantly reduced following PEMF exposure compared to shams (although exposure only accounted for 9.4% of the group difference). This set of data suggest that there are no significant acute physiological effects of 225 µT PEMF after 30 and 60 min of exposure on peak blood flow, heart rate, and myogenic activity, but perhaps a small attenuation effect on anesthetic‐induced respiratory depression. Bioelectromagnetics 31:64–76, 2010. © 2009 Wiley‐Liss, Inc.     

A possible involvement of beta-endorphin, substance P, and serotonin in rat analgesia induced by extremely low frequency magnetic field

Most of the research concerning magnetic antinociception was focused on brief exposure less than 1 h. The main purpose of the present study was to determine the effect of extremely low frequency (ELF) magnetic field (MF) repeated exposures on rats in inducing antinociception and to find the effective analgesic "time window." Meanwhile this investigation was to examine the role of central beta-endorphin, substance P, and 5-HT in magnetic analgesia. We found tail flick latencies (TFLs) increased significantly after the rats were exposed to 55.6 Hz, 8.1 mT magnetic field for 4 days, 6 h each day. The analgesic effects seemed to decrease gradually when the rats were exposed daily for another 10 days. Their levels of TFLs decreased within 1 day when the rats were removed after a 4-day exposure. The concentrations of hypothalamus beta-endorphin, substance P, and brainstem serotonin (5-HT) were increased significantly on Day 4. However, no differences were found when rats were exposed for another 10 days, and there were no significant increases when rats were removed after the fourth day of exposure and tested for nociception on Days 5 and 7 with no changes in the biochemical markers at 7 days. These results suggest that the ELF magnetic field has analgesic effect, but only on Days 3 and 4. The effect may be associated with increases in endogenous beta-endorphin, substance P, and 5-HT stimulated by the 55.6 Hz, 8.1 mT magnetic field.     

Behavioral effects in monkeys exposed to extremely low frequency electromagnetic fields

Several experiments with rhesus and squirrel monkeys on the influence of extremely low frequency (ELF) electromagnetic fields found no effects on behavior. Magnetic fields of 0.3 and 1.0 mT with electric fields of below 1 to 29 V/m at frequencies of 7, 10, 15, 45, 60 and 75 Hz were used. Small differences in ambulatory activity and response rate were occasionally observed, but no consistent effects between or within animals on any measures were obtained. No effects on reaction time, interresponse time, match-to-sample performance, and blood constituents were observed. Such previously reported effects may not be a consequence of ELF values alone, but are probably related to other environmental variables.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

Effects of extremely low frequency electromagnetic field on the health of workers in automotive industry

Objective. To observe the effects of extremely low frequency electromagnetic fields (ELF-EMFs) in automotive industry on occupational workers. Methods. A total of 704 workers were investigated, and 374 workers were chosen and divided into two groups (control group and exposure group) according to the inclusive criteria, namely male with age 20–40 years old and ≥ 2 years of exposure. The intensities of ELF-EMFs and noise were detected with EFA-300 Field Analyzer (Narda company, Pfullingen, Germany) and AWA5610D integrating sound level meter (Hangzhou Aihua Instruments Co., Ltd, Hangzhou, China), respectively. Survey data were collected by questionnaire, and the physical check-up was done in hospital. All the data were input into SPSS17.0 software (SPSS Inc, Chicago, USA), and the appropriate statistic analyses were carried out. Results. The intensity of EMFs in exposure group was significantly higher than that in control group (p < 0.05), while the noise in two workplaces showed no difference (p>0.05). The survey data collected by questionnaires showed that the symptoms of loss of hair in exposure group were significantly different as compared with that in control group (p < 0.05). The check-up parameters of cardiovascular, liver and hematology system showed significant differences between the two groups (p < 0.05). Conclusions. Survey and check-up data suggest that exposure to ELF-EMFs might have effects on the nervous, cardiovascular, liver, and hematology system of workers.     

A semiclassical theory for nerve excitation by a low intensity electromagnetic field

A possible mechanism for microwave-neuron interaction, when the nerve is irradiated by a thermally insignificant electromagnetic field, is described. The radiation field is treated classically, but the atomic system which interacts with this field is treated quantum mechanically using the density matrix approach. Attention is given to both homogeneous and inhomogeneous broadening effects, and the degrading influence of inhomogeneous broadening upon the neural membrane's ability to interact with the electromagnetic field is shown.     

Non-H-2 linked control of low versus high responses of antigen-induced lymph node cell proliferation: possible role for antigen-presenting cells.

Quantitative differences in the magnitude of antigen-induced proliferative responses of sensitized lymph node cells between low (C3H/Anf or C3H/Cr) and high (C3H/Hej or CBA/j) responder H-2k mice have been observed 1 to 2 weeks after in vivo sensitization with antigen (OVA, PPD, and GAT). We have shown that antigen presentation is less effective in the sensitized lymph node cell populations from low responder mice compared with those from high responder mice, suggesting that the number and/or functional status of antigen-presenting cells in the regional lymph nodes may be a key factor in determining the magnitude of antigen-induced proliferative responses. These data are consistent with the hypothesis that cell traffic after sensitization plays an important role in determining the immune responsiveness of lymph nodes.