Pathophysiology of microwave-induced traumatic brain injury

Abstract

Microwave technology has been widely used in numerous applications; however, excessive microwave exposure causes adverse effects, particularly in the brain. The present study aimed to evaluate the change in the number of neural cells and presence of apoptotic cells in rats for one month after exposure to excessive microwave radiation. The rats were exposed to 3.0 kW of microwaves for 0.1 sec and were sacrificed after 24 h (n=3), or 3 (n=3), 7 (n=3), 14 (n=3) or 28 days (n=4) of exposure. The neural cells were counted in the motor cortex and hippocampus [cornu ammonis 1 (CA1) and CA2] and the percentage of positive cells stained with terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) were also measured, which detected apoptotic cell death in the choroid plexus in the lateral ventricle, motor cortex and hippocampus. In the CA1, the number of neural cells decreased significantly by day 28 compared with that in the control (60.7 vs. 50.6, P=0.0358), but did not decrease before day 28. There were no significant differences on any day in the CA2 and the motor cortex. The number of cells showed a significant increase on day 7 compared to the control in the choroid plexus (2.1±1.1 vs. 21.8±19.1%, P=0.0318). There were no significant differences from the controls in the percentage of TUNEL-positive cells in the motor cortex and hippocampus. The effects of microwave exposure on the brain remain unclear; however, microwave-induced neurotrauma shows the same pathological changes as blast traumatic brain injury.

Exposure to radio-frequency electromagnetic waves alters acetylcholinesterase gene expression, exploratory and motor coordination-linked behaviour in male rats

“…It has been reported that AChE expression in normal brain is regulated by transcription factors such as c-fos and HNF 3α/β which are shown to control neuronal AChE expression under psychological and chemical stress conditions [17] , [28] . The observed alteration of AChE mRNA expression levels in exposed rats is in line with previous studies which ascertains cholinergic/inflammatory responses and molecular damage in the brain cells as stimulated by the microwave exposure [12] . Also, AChE levels have been found to be very low in all types of normal glia but increased in astrocytic tumors [16] .…”

Understanding blast-induced neurotrauma: how far have we come?

“…The existing rigid divide between blast physicists, engineers and biomedical researchers led to numerous systems claiming to generate ‘blast’, ‘shock wave’, blast injury and BINT; unfortunately, many of them reproduce faulty conditions and/or clinically irrelevant injuries. For example, recently, several experimental devices have been described that use ultrasound [ 149 , 150 ] or other means of generating overpressure, such as microwave [ 151 ] or laser [ 152 ]. Nevertheless, the resulting shockwaves do not have the physical properties of a blast (i.e., an explosion-generated shockwave) and do not replicate features of BINT seen in individuals exposed to blast.…”

Pulsed Microwave Energy Transduction of Acoustic Phonon Related Brain Injury

“…Igarashi et al (27) showed 50% mortality with extensive gross brain damage in rats directly exposed at close range to a single high pulse of 3 kW, 2.45 GHz microwaves for 0.1 s. Based upon the size of the rats and the microwave horn used, we estimate the incident power density to be ∼1 kW/cm 2 which would deliver to the target an average power of 1,000 W/cm 2 (27). By contrast, a 30-min application of 2.8 GHz pulses using power as low as 15-mWcm −2 was seen to damage rat brains (10).…”