ISSN:0197-8462    

DOI:10.1002/bem.2250110102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

ISSN:0197-8462    

DOI:10.1002/bem.2250110103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIdentified cells ofHelix lucorumL. received 20 min exposures to 23, 120, or 200 mT stationary magnetic field (MFs). Resting potentials and input resistances were measured. Controls were instituted for temperature changes and for mechanical and other sources of artifact. Resting potentials did not change with MF exposure. Input resistances decreased significantly in normally silent cells during MF exposure, but increased significantly in spontaneously active cells. The magnitudes of changes were monotonically related to strength of the MF. Changes in excitatory postsynaptic potentials were observed during MF exposure. Elimination of perineuronal glia by proteolytic enzymes eliminated the MF effects.

ISSN:0197-8462    

DOI:10.1002/bem.2250110104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractEffects of extremely‐low‐frequency (ELF) electromagnetic fields on proliferation of rabbit‐ligament fibroblasts were examined. Markedly different effects, ranging from inhibition to stimulation of proliferation, were obtained, depending on the signal parameters of amplitude, frequency, and DC magnetic field. These results demonstrate that simple, single‐frequency signals can have dramatic effects on ligament cells, which may be useful for bioelectrical stimulation of growth and repair. Also, the range of frequencies examined in this study covered those commonly used in transmission of electrical energy (50 or 60 Hz), which indicates that further study of possible effects of exposure to fields generated by power transmission equipment is wa

ISSN:0197-8462    

DOI:10.1002/bem.2250110105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractContinuous exposure of sea urchin (Strongylocentrotus purpuratus) embryos at 18°C to a cyclic 60‐Hz magnetic field at 0.1 mT rms beginning 4 min after insemination caused a significant developmental delay during the subsequent 23 hours. No delay in development was recorded for periods up to 18 hours after fertilization. At 18 h, most embryos were in the mesenchyme blastula stage. At 23 h, most control embryos were in mid‐gastrula whereas most magnetic‐field‐exposed embryos were in the early gastrula stage. Thus an estimated 1‐h delay occurred between these developmental stages. The results are discussed in terms of possible magnetic‐field modification of transcription as well as interference with cell migration during gastrulation. The present study extends and supports the growing body of information about potential effects of exposures to extremely‐low‐frequency (ELF) magnetic fields on deve

ISSN:0197-8462    

DOI:10.1002/bem.2250110106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractWhole human blood was exposed or sham‐exposed in vitro for 2 h to 27 or 2,450 MHz radio‐frequency electromagnetic (RF) radiation under isothermal conditions (i.e., 37 ± 0.2 °C). Immediately after exposure, mononuclear cells were separated from blood by Ficoll density‐gradient centrifugation and cultured for 3 days at 37°C with or without mitogenic stimulation by phytohemagglutinin (PHA). Lymphocyte proliferation was assayed at the end of the culture period by 6 h of pulse labeling with3H‐thymidine3H‐TdR). Exposure to radiation at either frequency at specific absorption rates (SARs) below 50 W/kg resulted in a dose‐dependent, statistically significant increase of3H‐TdR uptake in PHA‐activated or unstimulated lymphocytes. Exposure at 50 W/kg or higher suppressed3H‐TdR uptake relative to that of sham‐exposed cells. There were no detectable effects of RF radiation on lymphocyte morphology or viability. Notwithstanding the characteristic temperature dependence of lymphocyte activation in vitro, the isothermal exposure conditions of this study warrant the conclusion that the biphasic, dose‐dependent effects of the radiation on lymphocyte proliferation were

ISSN:0197-8462    

DOI:10.1002/bem.2250110107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractA new experimental approach has been developed to determine kinetic and thermodynamic parameters of the inactivation of an enzyme under labile conditions both with and without exposure to electrical currents as sources of perturbation. Studies were undertaken to investigate if low‐frequency electric currents can accelerate the thermal inactivation of an enzyme through interactions with dipole moments in enzymatic molecules and through related mechanical stresses. The experiments were conducted with the enzyme acid posphatase. The enzyme was exposed to a 50‐Hz current at different densities (10 to 60 mA/cm2rms) or to a sinusoidal or square‐wave current at an average density of 3 mA/cm2and frequencies from, respectively, 50 Hz to 20 kHz and 500 pulses per second (pps) to 50,000 pps. Positive‐control experiments were performed in the presence of a stabilizer or a deactivator. The results indicate that the technique is sensitive to conformational changes that otherwise may be impossible to detect. However, exposure to electric currents under the experimental conditions described herein showed no effects of the c

ISSN:0197-8462    

DOI:10.1002/bem.2250110108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractA user‐friendly, numerical program has been developed to permit the calculation of induced currents in modeled bodies of human and infrahuman subjects. The program is based on a charge‐simulation method (CSM), and it takes into account the three‐dimensional (3‐D) character of the extremely‐low‐frequency (ELF) electric field and of the models to be exposed. The principle of the method is to simulate a 3‐D object, for example, an animal model, by a combination of several parts (blocks) having simple geometric forms such as a sphere, a cylinder, or a cone. This approach permits easy preparation of input data on the dimensions of the blocks and their positions in a 3‐D arrangement. Other input data, such as the coordinates of the contour points and the imaginary values of charges inside objects, which are necessary in the calculations by CSM, are produced automatically by selecting an appropriate “level” for each block, according to its importance. To simulate parts having irregular shapes, special blocks may be added. In one series of experiments, induced currents were calculated for a baboon model in various postures: standing upright, positioned on four legs, and sitting on the floor. Calculated currents. the total induced current in particular, agreed very well with experimental values. Local currents in parts of the baboon models were more variable, ranging from 5% to 17% of measured values in the case of induced currents in the head. Some problems with this method, such as the effect of the dimensions of blocks or the choice of block le

ISSN:0197-8462    

DOI:10.1002/bem.2250110109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe reported association between the risk of human cancer and exposure to 50‐ or 60‐Hz electric and magnetic fields is difficult to evaluate from studies published to date. The association is now being reexamined in several large epidemiologic studies. In most of the studies, exposure will be assessed with newly designed, portable meters that allow direct and precise measurements of exposure to be performed easily for large numbers of individuals. The main features of the studies are summarized. At a meeting of principal investigators held in 1988 at the International Agency for Research on Cancer, broad guidelines were agreed for the design of this new generation of studies. These guidelines should improve the comparability of results and eventually provide a clearer assessment of human‐cancer risk from exposure to extremely low‐frequency electric and magnetic

ISSN:0197-8462    

DOI:10.1002/bem.2250110110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

ISSN:0197-8462    

DOI:10.1002/bem.2250110111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY