首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The metric of prime interest in power line epidemiological studies has been AC magnetic intensity. To consider also possible geomagnetic involvement, the orientation of a long straight power line is examined relative to a uniform geomagnetic field (GMF) with dip angle α. An expression is derived for the component of the total GMF that is parallel, at an elevation β, to the circuital magnetic field that surrounds the line. This component is a function of the angles α and β, the total geomagnetic intensity BT, and the angle θ between the axis of the power line and magnetic north. Plotting these geomagnetic parameters for known leukemia residences allows one to test for possible ion cyclotron resonance or other GMF interactions. This approach, in principle, is an easy addition to existing or planned studies, because residential access is not required to obtain local values for α, β, θ, and BT. We recommend including these parameters in the design of epidemiological studies examining power line fields and childhood leukemia. © 1995 Wiley-Liss, Inc.  相似文献   

2.
We advance the hypothesis that biological systems utilize the geomagnetic field (GMF) for functional purposes by means of ion cyclotron resonance-like (ICR) mechanisms. Numerous ICR-designed experiments have demonstrated that living things are sensitive, in varying degrees, to magnetic fields that are equivalent to both changes in the general magnetostatic intensity of the GMF, as well as its temporal perturbations. We propose the existence of ICR-like cell regulation processes, homologous to the way that biochemical messengers alter the net biological state through competing processes of enhancement and inhibition. In like manner, combinations of different resonance frequencies all coupled to the same local magnetic field provide a unique means for cell regulation. Recent work on ultraweak ICR magnetic fields by Zhadin and others fits into our proposed framework if one assumes that cellular systems generate time-varying electric fields of the order 100 mV/cm with bandwidths that include relevant ICR frequencies.  相似文献   

3.
The purpose of the work was to further investigate the effect of zero magnetic field (ZMF) on the concentration of ions in the human blood compared to the effect of the normal geomagnetic field (GMF). We have investigated the total Zn and Cu concentrations in the blood serum during in vitro aging of blood. The investigation was carried out both on blood from healthy donors as well as from chronic bronchial asthma (BA) patients. Blood samples were kept for 48 hours in a Helmholtz coil compensating system to remove the static component of the geomagnetic field, at room temperature. We found that zinc concentrations in the plasma were not significantly influenced by the exposure to ZMF compared to GMF for both healthy and pathological samples. In contrast, copper concentration was found to be significantly sensitive to the magnetic environment. Healthy blood showed a slight loss of copper from the blood serum in GMF, which further increased in ZMF. BA pathology is characterized by four distinct types of disease, which showed both qualitative and quantitative distinctive sensitivity to the magnetic environment, as compared to healthy blood. The aging effect appeared to be slowed down for most of the BA types of pathologies. These results point to the sensitivity of ion binding to serum proteins and/or transport through cell membranes in the magnetic environment, in our case in the absence of the normal geomagnetic field.  相似文献   

4.
Some magnetobiological problems of orbital (in the geomagnetic field--GMF) and interplanetary (in hypomagnetic conditions) flights are considered. The influence of electromagnetic fields (EMF) created by systems and equipment of the space vehicle (SV) are touched also. A level of the geomagnetic field (GMF) onboard during the orbital flights is discussed. Its periodic variations onboard owing to movement of SV on an orbit are analyzed. The reader's attention in attracted to the papers by R.M. Baevsky et al. in which the influence of magnetic storms and periodic variations of GMS on the cardiovascular system of astronauts onboard are shown. Possible ways and mechanisms of the influence are discussed. The wrong assertions in a number of works namely that at orbital flights an appreciable electrical field is induced in an organism of an astronaut in a space-craft and the electrical field may by responsible for some biological impacts are analyzed. The situation at the future in the terplanetary flights (for example Martian missions) when a crew and biological objects for a long time will be in the interplanetary magnetic field (by several orders less then GMF) is considered. As applied to the flights the opportunities of generation onboard the "artificial" GMF are outlined. The ensuing biological and technical questions are discussed.  相似文献   

5.
It was shown that the 250-fold screening of the geomagnetic field (GMF) (“zero” magnetic field with an induction of 0.2?μT) affects early embryogenesis and the reproduction capacity of mice in vivo. Pregnant NMRI mice at the zygote stage placed in this “zero” magnetic field (MF) lost the ability to bear offspring babies although their embryos developed up to the blastocyst stage without any visible deviations from the norm. The abortion of development in the “zero” MF occurred after the exit of the blastocysts from the zona pellicida and invasion into the uterus during implantation. Histological analysis indicates that possible reasons of the abnormalities of postimplantation development are a decrease in the proliferative activity of embryonic cells and the impairment of the interaction between the trophoblast and endometrium, which finally results in the resorption of embryos in the uterus.  相似文献   

6.
Living organisms are exposed to the geomagnetic field (GMF) throughout their lifespan. Elimination of the GMF, resulting in a hypogeomagnetic field (HMF), leads to central nervous system dysfunction and abnormal development in animals. However, the cellular mechanisms underlying these effects have not been identified so far. Here, we show that exposure to an HMF (<200 nT), produced by a magnetic field shielding chamber, promotes the proliferation of neural progenitor/stem cells (NPCs/NSCs) from C57BL/6 mice. Following seven-day HMF-exposure, the primary neurospheres (NSs) were significantly larger in size, and twice more NPCs/NSCs were harvested from neonatal NSs, when compared to the GMF controls. The self-renewal capacity and multipotency of the NSs were maintained, as HMF-exposed NSs were positive for NSC markers (Nestin and Sox2), and could differentiate into neurons and astrocyte/glial cells and be passaged continuously. In addition, adult mice exposed to the HMF for one month were observed to have a greater number of proliferative cells in the subventricular zone. These findings indicate that continuous HMF-exposure increases the proliferation of NPCs/NSCs,in vitro and in vivo. HMF-disturbed NPCs/ NSCs production probably Affects brain development and function, which provides a novel clue for elucidating the cellular mechanisms of the bio-HMF response.  相似文献   

7.
If it is more fundamental to formulate biological expression in terms of electromagnetic fields, does this also imply that living things are especially sensitive to the external electromagnetic environment? Specifically, we examine possible genomic effects due to reversals of the geomagnetic field. To maintain sensitivity following a reversal, the Wiltschko hypothesis for the avian magnetic compass can be subsumed under an NB imprinting paradigm, where N is the horizontal vector pointing to magnetic north and B the geomagnetic field vector. Even with a compass that is invariant under reversals, there are nevertheless potential difficulties due to discontinuities in the magnitude of the field during the transition between one chron and the next. Indeed, transitions may be one reason for other-than-magnetic avian auxiliary compasses. Additional problems may also arise during transitions because of high rates of change in B. However, the largest reported dB/dt (Steens Mountain event) is estimated at 1 /u.T/day, seemingly too small to induce significant Faraday current density. Reversals may have also helped determine the nature of the interaction mechanism between GMF and living systems. Mechanisms based on fixed magnetic moments may not be capable of adapting to the reversal process. A better case can be made for an ion cyclotron resonance interaction. Direct involvement in the cell-signaling activities of biological ions would provide such flexibility, and also point to a broader role for the GMF in modulating CNS function than merely to provide orientation.  相似文献   

8.
The geomagnetic field (GMF) is an environmental cue that provides directional information for animals. The intensity of GMF is varied over space and time. Variations in the GMF intensity affect the navigation of animals and their physiology. In this study, the phototaxis of the migratory insect rice planthopper Nilaparvata lugens (N. lugens) and frataxin in N. lugens (Nl‐fh), which is a mitochondrial protein required for cellular iron homeostasis and iron‐sulfur cluster assembly, were investigated by using different intensities of magnetic field. From the results, individuals of N. lugens showed decreased phototaxis when reared and tested in a behavioral arena under a strong magnetic field. Besides the reduction in performance, an accompanying effect of the strong magnetic field condition was a reduced level of Nl‐fh‐messenger RNA, and a Nl‐fh knockdown indeed impaired the phototactic behavior in a tested sample of insects. This leads to the conclusion that the expression of frataxin is dependent on the strength of the surrounding magnetic field and that functional frataxin facilitates phototactic behavior in N. lugens.  相似文献   

9.
Zhang X  Li JF  Wu QJ  Li B  Jiang JC 《Bioelectromagnetics》2007,28(2):155-158
Previous studies found that elimination of the geomagnetic field (GMF) interferes with the normal brain functions, but the underlying mechanism remains unknown. The present study examined the effects of long-term exposures to a near-zero magnetic environment on the noradrenergic activities in the brainstem of golden hamsters. Both the content of norepinephrine (NE) and the density of NE-immunopositive neurons in the tissue decreased significantly after the treatment, and the effects could be progressive with time. These variations may substantially contribute to behavioral and mood disorders reported in other studies when animals are shielded from the GMF.  相似文献   

10.
Except for relatively few polarity reversals the magnitude of the magnetic dipole moment of the earth has remained constant since life first began, allowing evolutionary processes to integrate the geomagnetic field (GMF) into several biological functions. One of these, bearing the classical signature of an ion cyclotron resonance (ICR)-like interaction, results in biological change associated with enhanced proton transport. The wide range of cation masses over which this effect is found suggest a fundamental biological dependence on the GMF, one that functions equally well for electric as well as magnetic fields. Such generalization of ICR requires two things: transparency of tissues to the GMF and suitably tuned ELF resonant magnetic or electric fields. To complement the widely reported ICR responses to applied AC magnetic fields, we hypothesize the existence of weak endogenous ICR electric field oscillations within the cell. This equivalence implies that even in the absence of applied AC magnetic fields, biological systems will exhibit intrinsic GMF-dependent ion cyclotron resonance intracellular interactions. Many ICR effects that have been reported appear as antagonist pairs suggesting that the characteristics of the GMF have not only been incorporated into the genome but also appear to function in an endocrine-like manner.  相似文献   

11.
Magnetotactic bacteria are microorganisms that orient and migrate along magnetic field lines. The classical model of polar magnetotaxis predicts that the field-parallel migration velocity of magnetotactic bacteria increases monotonically with the strength of an applied magnetic field. We here test this model experimentally on magnetotactic coccoid bacteria that swim along helical trajectories. It turns out that the contribution of the field-parallel migration velocity decreases with increasing field strength from 0.1 to 1.5 mT. This unexpected observation can be explained and reproduced in a mathematical model under the assumption that the magnetosome chain is inclined with respect to the flagellar propulsion axis. The magnetic disadvantage, however, becomes apparent only in stronger than geomagnetic fields, which suggests that magnetotaxis is optimized under geomagnetic field conditions. It is therefore not beneficial for these bacteria to increase their intracellular magnetic dipole moment beyond the value needed to overcome Brownian motion in geomagnetic field conditions.  相似文献   

12.
The Earth's geomagnetic field (GMF) is known to act as a sensory cue for magnetoreceptive animals such as birds, sea turtles, and butterflies in long‐distance migration, as well as in flies, cockroaches, and cattle in short‐distance movement or body alignment. Despite a wealth of information, the way that GMF components are used and the functional modality of the magnetic sense are not clear. A GMF component, declination, has never been proven to be a sensory cue in a defined biological context. Here, we show that declination acts as a compass for horizontal food foraging in fruit flies. In an open‐field test, adopting the food conditioning paradigm, food‐trained flies significantly orientated toward the food direction under ambient GMF and under eastward‐turned magnetic field in the absence of other sensory cues. Moreover, a declination change within the natural range, by alteration only of either the east–west or north–south component of the GMF, produced significant orientation of the trained flies, indicating that they can detect and use the difference in these horizontal GMF components. This study proves that declination difference can be used for horizontal foraging, and suggests that flies have been evolutionarily adapted to incorporate a declination compass into their multi‐modal sensorimotor system.  相似文献   

13.
Attenuation of the ambient magnetic field to 200 nT (1/250 of normal GMF) is shown to be detrimental for cultured primary embryonic fibroblasts (lowered adhesion and viability, disruption of preformed monolayer, and permeabilization) and two-cell murine embryos (abrupt cessation of development, blastomere disorientation, permeabilization and cytoskeletal alterations). These data further demonstrate the importance of the geomagnetic field for normal cell proliferation and embryogenesis in mammals.  相似文献   

14.
Previously we found an opposite effect of artificial static magnetic field (SMF) and natural geomagnetic field (GMF) on arterial baroreceptors. A 0.35 T SMF increased baroreflex sensitivity (BRS), whereas GMF disturbance decreased BRS. Here, we investigated interrelated impacts on arterial baroreceptors of 0.35 T SMF, generated by Nd(2)-Fe(14)-B alloy magnets, GMF, and verapamil, a Ca(2+) channel blocking agent. We measured BRS in rabbits before and after local SMF exposure of sinocarotid baroreceptors or after simultaneous SMF and verapamil application, in conjunction with geomagnetic disturbance during actual experimental run (determined by K-index) and geomagnetic disturbance over the preceding 24 h of each experiment (A(k)-index). BRS was estimated from peak responses of mean arterial pressure (MAP) and heart rate, expressed as percentages of the resting values preceding each pair of pressure (phenylephrine) and depressor drug (nitroprusside) injections. Prior to verapamil and/or SMF application we found a significant positive correlation of K-index with MAP (t = 2.39, P =.021, n = 44), but negative with BRS (t = -4.60, P =.0003, n = 44), and found a negative correlation of A(k)-index with BRS (t = -2.7, P = 0.01, n = 44). SMF induced an increase in BRS (0.79 +/- 0.1 vs. 1.15 +/- 0.1 bpm%/mmHg%, initial value vs. SMF exposure, P <.0002, n = 26). Verapamil infusion blocked the SMF and GMF effect on BRS, indicating Ca(2+) channels as a possible site of both fields' impact. SMF and GMF probably affect baroreceptor sensory transduction, modulating baroreceptor membranes' Ca(2+) channel permeability.  相似文献   

15.
The aim of this study was to find out how a long-term shielding of the geomagnetic field (GMF) affected the immune system of rats. Male and female Wistar rats were kept up to an age of 2 months in a natural GMF (about 37 microT). Afterwards, the rats were divided into four groups (males and females separately): control rats were maintained in ambient GMF, while experimental animals were housed under conditions of a weakened GMF (below 12 microT) achieved with steel cages. After 6 months, the rats were sacrificed by decapitation. Spleens and thymuses were isolated and weighed. Peritoneal cells were eluted and cultured in vitro to study their ability to produce nitric oxide (NO) and to synthesize superoxide anion (O2(-)), important microbicidal molecules of macrophages. The number of macrophages was estimated by a crystal violet staining method. We found that the long-term shielding of the GMF could influence the functioning of the immune system in a sex-dependent manner. The deprivation of the GMF delayed physiological thymus involution, that effect being more strongly expressed in females. The weakening of the GMF resulted in an increased number of peritoneal macrophages, especially in males. The shielding of the GMF diminished the ability of macrophages to release NO and to synthesize O2(-), those effects being more powerfully expressed in males and females, respectively. It is proposed that the observed changes in the immune system occur as a consequence of the protective effect of GMF shielding on the circadian rhythm-dependent level of melatonin.  相似文献   

16.
Spreading evidence suggests that environmental and artificial magnetic fields have a significant impact on cardiovascular system. The modulation of cardiovascular regulatory mechanisms may play a key role in observed effects. The objective was to study interrelated impacts of artificial static magnetic field (SMF) and natural geomagnetic field (GMF) on arterial baroreceptors. We studied baroreflex sensitivity (BRS) in conscious rabbits before and after 40 min of sham (n = 20) or application of Nd2-Fe14-B alloy magnets (n = 26) to the sinocarotid baroreceptor region in conjunction with GMF disturbance during the actual experiment, determined by K- and A(k)-indexes from a local geomagnetic observatory. SMF at the position of baroreceptors was 0.35 T. BRS was estimated from peak responses of mean arterial pressure (MAP) and heart rate expressed as percentages of the resting values preceding each pair of pressure (phenylephrine) and depressor drug (nitroprusside) injections. We observed a significant increase in BRS for the nitroprusside depressor test (0.78 +/- 0.1 vs. 1.15 +/- 0.14 bpm/mmHg%, initial value vs. SMF exposure, P <.0002) and a tendency for phenylephrine pressor test to increase in BRS. Prior to SMF exposure, a significant positive correlation was found between actual K index values and MAP (t = 2.33, P =.025, n = 46) and a negative correlation of the K index with BRS (t = -3.6, P =.001, n = 46). After SMF exposure we observed attenuation of the geomagnetic disturbance induced a decrease in BRS. Clinical trials should be performed to support these results, but there is a strong expectation that 0.35 T SMF local exposure to sinocarotid baroreceptors will be effective in cardiovascular conditions with arterial hypertension and decreased BRS, due to a favorable SMF effect on the arterial baroreflex. Magnets to the sinocarotid triangle along with modification of the pharmacotherapy for hypertension should be especially effective on days with intense geomagnetic disturbance, in moderating sympathetic activation and baroreceptor dysfunction.  相似文献   

17.
Organisms have been exposed to the geomagnetic field (GMF) throughout evolutionary history. Exposure to the hypomagnetic field (HMF) by deep magnetic shielding has recently been suggested to have a negative effect on the structure and function of the central nervous system, particularly during early development. Although changes in cell growth and differentiation have been observed in the HMF, the effects of the HMF on cell cycle progression still remain unclear. Here we show that continuous HMF exposure significantly increases the proliferation of human neuroblastoma (SH-SY5Y) cells. The acceleration of proliferation results from a forward shift of the cell cycle in G1-phase. The G2/M-phase progression is not affected in the HMF. Our data is the first to demonstrate that the HMF can stimulate the proliferation of SH-SY5Y cells by promoting cell cycle progression in the G1-phase. This provides a novel way to study the mechanism of cells in response to changes of environmental magnetic field including the GMF.  相似文献   

18.
The influence of partial screening of EMF on the composition of white blood cells was studied in the experiments on rats. Two kinds of copper rings were used in these experiments: individual for each rat and common for the cage. It was shown that inside the ring the composition of blood cells was changed--in 3-5 hours the number of granulocytes increased and in 24 hours it restored to the initial level. The effect was more expressive in the experiments using individual rings. In control groups the experiment with plastic rings didn't reveal this effect. It was presumed that EMF prevented the decay of granulocytes. It leads to the increase of their guantity. It was revealed that there was a positive correlation between Ki-indexes of geomagnetic field (GMF) in 1-2 days before the experiments and the number of granulocytes in rats during 1995-2002. Ki-indexes reflect the degree of GMF disturbance. During magnetic storms the spreading of EMF in radio-frequency range changes. It was presumed that the effect of partial screening of EMF of rats and the activity of magnetic storms are similar in their influence on the composition of white blood cells of rats.  相似文献   

19.
In this study, we measured and analyzed the spectral characteristics of a low-frequency magnetic field (MF) inside several gasoline-powered cars while driving on busy city roads. The spectra obtained upon measurements in the interior of the cars are compared with those measured in office locations at different times of the day and with different disturbances of the geomagnetic field (k-index of disturbance 2–8). The power spectral density of the electromagnetic field in cars moving on busy roads in the frequency range of 10−3–102 Hz is one to three orders of magnitude higher than that in urban offices. This raises a question regarding the possible influence of these MFs on the psychophysiological state of drivers. In turn, in the daytime, the MF power in the range from 10−3 to 1 Hz inside the locations is three times higher compared with the power of a strong geomagnetic storm. Despite such an overwhelming magnetic background, geomagnetic storms affect various organisms. The nonspecific effect of magnetic storms is supposed to be associated with relatively long (lasting several hours or more [frequency range of 10−4−10−5 Hz]) periods of enhancement or weakening of the local geomagnetic field. In this range, especially at night, the power spectral density of geomagnetic disturbances is comparable to and can even exceed the power density of urban MFs. © 2020 Bioelectromagnetics Society.  相似文献   

20.
Clinical, microbiological and hormonal examination of women with chronic cervicitis revealed lesions in the upper section of the reproductive tract in a high proportion of those examined, hormonal disturbances being registered in 96.7% of women. Dysbiotic manifestations (suppression of lacto- and bifidoflora and the excessive growth of opportunistic microorganisms) in the uterus cervix and vagina observed in patients with chronic cervititis were not associated with the etiology of the inflammatory process. The degree of dysmicrobiocenosis in the lower section of the genital tract in women with chronic cervicitis depends on the character of hormonal disturbances. The most significant inhibition of the resident flora was observed when ovarian dysfunction occurred and less significant--in cases of hyperprolactinemia and changes in the level of hypophysial hormones. Hormonal disturbances led to contamination of vagina and cervical canal with opportunistic microorganisms that was inversely proportional to the presence of lactic acid bacteria and bifidobacteria in these organs. Complex therapy of women with chronic cervicitis with the use of preparations for the correction of hormonal disturbances made it possible to restore the normal microflora of the genital tract and to improve the results of treatment.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号