摘要:

AbstractAfter 45 min of exposure to pulsed 2450 MHz microwaves (2 μsec pulses, 500 pps, 1 mW/cm2, average whole body SAR 0.6 W/kg), rats showed retarded learning while performing in the radial‐arm maze to obtain food rewards, indicating a deficit in spatial “working memory” function. This behavioral deficit was reversed by pretreatment before exposure with the cholinergic agonist physostigmine or the opiate antagonist naltrexone, whereas pretreatment with the peripheral opiate antagonist naloxone methiodide showed no reversal of effect. These data indicate that both cholinergic and endogenous opioid neurotransmitter systems in the brain are involved in the microwave‐induced spatial memory deficit. © 1994 Wiley

ISSN:0197-8462    

DOI:10.1002/bem.2250150202

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

年代:1994

数据来源: WILEY

摘要:

AbstractLiving cells exist in an electrically noisy environment. This has led to the so‐called “signal‐to‐noise” problem whereby cells are observed to respond to extremely‐low‐frequency (ELF) exogenous fields that are several orders of magnitude weaker than local endogenous fields associated with thermal fluctuations. To resolve this dilemma, we propose that living cells are affected only by electromagnetic fields that are spatially coherent over their surface. The basic idea is that a significant number of receptors must be simultaneously and coherently activated (biological cooperativity) to produce effects on the biochemical functioning of the cell. However, like all physical detection systems, cells are subject to the laws of conventional physics and can be confused by noise. This suggests that a spatially coherent but temporally random noise field superimposed on a coherent ELF signal will defeat the mechanism of discrimination against noise, and any observed field‐induced bioeffects would be suppressed. An experimental test of this idea was conducted using morphological abnormalities in developing chick embryos caused by electromagnetic field exposure as the endpoint. At an impressed noise amplitude comparable to the ELF field strength (but roughly one‐thousandth of the thermal noise field), the increased abnormality rate observed with only the ELF field present was reduced to a level essentially the same as for the control embryos. © 19

ISSN:0197-8462    

DOI:10.1002/bem.2250150203

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

年代:1994

数据来源: WILEY

摘要:

AbstractAn energy efficient electromagnetic stimulator device for fracture healing was compared to a commercially available device in stimulating cell growth in tissue cultures. The energy efficient device, which conserves energy by using a bidirectional time‐dependent magnetic wave form, and the commercially available stimulator, which uses a unidirectionaltime‐dependent magnetic wave form, were tested on chick tendon fibroblasts in primary culture. Comparing non‐stimulated control and cells electromagnetically stimulated with unidirectional and bidirectional waveforms showed that at the growth phase between days 2 and 3, both electrical stimulation techniques increased cell division as measured by DNA synthesis. When cells were dividing rapidly, collagen synthesis was reduced. When the cells reached the confluence there was no difference among the groups (control, unidirectionally stimulated, and bidirectionally stimulated) in terms of number of cells or collagen produced. © 1994 Wiley‐L

ISSN:0197-8462    

DOI:10.1002/bem.2250150204

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

年代:1994

数据来源: WILEY

摘要:

AbstractCalcium chloride and snail physiological salt solutions were exposed to static magnetic fields (2.3–350 mT), and the physical properties of the solutions as well as their biologic effects were studied. Our preliminary observations show that these fields alter physicochemical properties of CaCl2solutions and the functional effects of physiological solutions. Experiments on CaCl2solutions demonstrated field‐dependent changes of electrical conductivity, with the magnitude and the direction of conductivity change being a function of both concentration and field intensity. The changes in conductivity were maintained for periods in excess of 1 h after exposure. Conductivity changes were not found after exposure of physiological solutions to static magnetic fields, but changes of biological consequence did occur. Other experiments showed that there were several changes in cellular function observed in ganglia and isolated neurons ofHelix pomatiawhen the perfusing medium was changed from the normal physiologic solution to the same solution after exposure to magnetic fields. These changes include membrane depolarization and increased action potential discharge, reduced uptake of Ca into cells, altered content of cyclic nucleotides in ganglia, and increased volume of isolated cell bodies. A change in hydration of calcium ions may be one of the consequences of magnetic‐field exposure, and in physiological solutions this change may have functional consequences. © 1994 Wiley‐L

ISSN:0197-8462    

DOI:10.1002/bem.2250150205

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

年代:1994

数据来源: WILEY

摘要:

AbstractMicrowave evoked body movements were studied in mice. A resonant cavity was used to provide head and neck exposure of the mouse to pulsed and gated continuous wave (CW) 1.25 GHz microwaves. No difference in response to pulsed and gated CW stimuli of equal average power was found. The incidence of the microwave evoked body movements increased proportionally with specific absorption (dose) when the whole‐body average specific absorption rate was at a constant level (7300 W/kg). Under a constant average specific absorption rate, the response incidence reached a plateau at 0.9 kJ/kg. For doses higher than 0.9 kJ/kg, response incidence was proportional to the specific absorption rate and reached a plateau at 900 W/kg. Body movements could be evoked by a single microwave pulse. The lowest whole‐body specific absorption (SA) tested was 0.18 kJ/kg, and the corresponding brain SA was 0.29 kJ/kg. Bulk heating potentials of these SAs were less than 0.1 °C. For doses higher than 0.9 kJ/kg, the response incidence was also proportional to subcutaneous temperature increment and subcutaneous heating rate. The extrapolated absolute thresholds (0% incidence) were 1.21 °C temperature increment and 0.24 °C/s heating rate. Due to high subcutaneous heating rates, these microwaves must be perceived by the mouse as an intense thermal sensation but not a pain sensation because the temperature increment was well below the threshold for thermal pain. Results of the present study should be considered in promulgation of personnel protection guideline against high peak power but low average power microwaves. © 1994 Wiley‐

ISSN:0197-8462    

DOI:10.1002/bem.2250150206

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

年代:1994

数据来源: WILEY

摘要:

AbstractLimits on the exposure to high‐peak‐power, short‐duration microwave pulses have only recently been adopted. Additional data, however, are needed to understand the effects that may be produced by exposure to high‐peak‐power pulsed microwaves. Four male rhesus monkeys (Macaca mulatta) were trained on an operant task for food pellet reward to investigate the behavioral effects of very high‐peak‐power 5.62 GHz microwaves. The operant task required monkeys to pull one plastic lever on a variable interval schedule (VI‐25 s) and then respond to color signals and pull a second lever to obtain food. The monkeys were conditioned to perform a color discrimination task using one of three colors displayed by a fiber‐optic cable. A red signal was the discriminative stimulus for responding on the first lever. A response on the second lever when a green signal was presented (1 s duration) delivered a food pellet. If a response on the second lever was made in the presence of a white signal, a 30‐s timeout occurred. While performing the behavioral task, the monkeys were exposed to microwave pulses produced by either a military radar (FPS‐26A) operating at 5.62 GHz or the same radar coupled to a Stanford linear energy doubler (SLED) pulse‐forming device (ITT‐2972) that enhanced peak power by a factor of nine by adding a high power pulse to the radar pulse. The effects of both types of pulses were compared to sham exposure. Peak field power densities tested were 518, 1270, and 2520 W/cm2for SLED pulses and 56, 128, and 277 W/cm2for the radar pulses. The microwave pulses (radar or SLED) were delivered at 100 pps (2.8 μs radar pulse duration, ≈ 50 ns SLED pulse duration) for 20 min and produced averaged whole‐body SARs of 2,4, or 6 W/kg. Compared to sham exposures, significant alterations of lever responding, reaction time, and earned food pellets occurred during microwave exposure at 4 and 6 W/kg but not 2 W/kg. There were no differences between radar or SLED pulses in producing behavioral effects. ©1994 Wiley‐Liss, Inc.This is a US Government work and, as such, is in the public domai

ISSN:0197-8462    

DOI:10.1002/bem.2250150207

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

年代:1994

数据来源: WILEY

ISSN:0197-8462    

DOI:10.1002/bem.2250150201

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

年代:1994

数据来源: WILEY