Mohamed Lassaad Ammari

Impairment of emotional behavior and spatial learning in adult Wistar rats by ferrous sulfate.

The aim of this study was to investigate the effects of FeSO(4) on the behavior of adult Wistar rats. Rats were treated with moderate doses of iron (1.5 or 3.0 mg/kg) for 5 consecutive days, and the effects of iron supplementation on emotional behavior were studied. One group of rats was tested in elevated plus-maze and in open field, and other group was tested for learning abilities in water maze and for motor skills in rotarod task. Iron level in the brain was measured in the frontal cortex, cerebellum, basal ganglia and hippocampus. The effects of the iron treatment (in particular, a dose of 3.0 mg/kg) on emotional behavior in the elevated plus maze and in the open field were significant. The effects of iron on spatial learning were less pronounced, but significant impairments due to the treatment were observed during the probe test. Motor skills and procedural learning in the rotarod task were not significantly affected by the treatment. These behavioral impairments were associated with significant iron accumulations in the hippocampus and basal ganglia of rats treated with 3.0 mg/kg iron and are discussed in terms of possible neuronal impairments of these structures. Thus, FeSO(4) administration at 3.0 mg/kg for 5 consecutive days in adult rats overcomes the mechanisms that shield the brain from iron intoxication and leads to behavioral impairments, in particular with respect to emotional behavior.

Effect of a chronic GSM 900 MHz exposure on glia in the rat brain.

Extension of the mobile phone technology raises concern about the health effects of 900 MHz microwaves on the central nervous system (CNS). In this study we measured GFAP expression using immunocytochemistry method, to evaluate glial evolution 10 days after a chronic exposure (5 days a week for 24 weeks) to GSM signal for 45 min/day at a brain-averaged specific absorption rate (SAR)=1.5 W/kg and for 15 min/day at a SAR=6 W/kg in the following rat brain areas: prefrontal cortex (PfCx), caudate putamen (Cpu), lateral globus pallidus of striatum (LGP), dentate gyrus of hippocampus (DG) and cerebellum cortex (CCx). In comparison to sham or cage control animals, rats exposed to chronic GSM signal at 6 W/kg have increased GFAP stained surface areas in the brain (p<0.05). But the chronic exposure to GSM at 1.5 W/kg did not increase GFAP expression. Our results indicated that chronic exposure to GSM 900 MHz microwaves (SAR=6 W/kg) may induce persistent astroglia activation in the rat brain (sign of a potential gliosis).

Exposure to GSM 900 MHz electromagnetic fields affects cerebral cytochrome c oxidase activity.

The world-wide and rapidly growing use of mobile phones has raised serious concerns about the biological and health-related effects of radio frequency (RF) radiation, particularly concerns about the effects of RFs upon the nervous system. The goal of this study was conducted to measure cytochrome oxidase (CO) levels using histochemical methods in order to evaluate regional brain metabolic activity in rat brain after exposure to a GSM 900 MHz signal for 45 min/day at a brain-averaged specific absorption rate (SAR) of 1.5 W/Kg or for 15 min/day at a SAR of 6 W/Kg over seven days. Compared to the sham and control cage groups, rats exposed to a GSM signal at 6 W/Kg showed decreased CO activity in some areas of the prefrontal and frontal cortex (infralimbic cortex, prelimbic cortex, primary motor cortex, secondary motor cortex, anterior cingulate cortex areas 1 and 2 (Cg1 and Cg2)), the septum (dorsal and ventral parts of the lateral septal nucleus), the hippocampus (dorsal field CA1, CA2 and CA3 of the hippocampus and dental gyrus) and the posterior cortex (retrosplenial agranular cortex, primary and secondary visual cortex, perirhinal cortex and lateral entorhinal cortex). However, the exposure to GSM at 1.5 W/Kg did not affect brain activity. Our results indicate that 6 W/Kg GSM 900 MHz microwaves may affect brain metabolism and neuronal activity in rats.

Effect of head-only sub-chronic and chronic exposure to 900-MHz GSM electromagnetic fields on spatial memory in rats

Primary objective: This study was carried out to investigate the behavioural effects of sub-chronic and chronic head-only exposure to 900 MHz GSM (Global System for Mobile communications) in male rats. Methods: Rats were exposed for 45 minutes per day, at a brain-averaged specific absorption rate (SAR) = 1.5 W Kg−1or 15 minutes per day at a SAR = 6 W Kg−1, during 8 or 24 weeks. Then, their spatial memory was tested using the radial-arm maze. In the first phase (10 days), rats were trained to visit the eight arms of the maze without returning to an arm already visited. In the second phase (8 days), a 45-minute intra-trial delay was introduced after four visited arms. Results: Performance of exposed rats (1.5 or 6 W Kg−1) was compared with that of sham, negative control and positive control rats. Scopolamine treatment in the positive control rats induced deficit in spatial memory task in the second phase of the test. However, spatial memory task was unaffected in exposed rats. Conclusion: Sub-chronic and chronic head-only exposure of rats to GSM 900 MHz signal (45-minutes, SAR = 1.5 or 15-minutes, SAR = 6 W Kg−1) did not induce spatial memory deficit in the radial-arm maze.

GFAP expression in the rat brain following sub-chronic exposure to a 900 MHz electromagnetic field signal

Purpose: The rapid development and expansion of mobile communications contributes to the general debate on the effects of electromagnetic fields emitted by mobile phones on the nervous system. This study aims at measuring the glial fibrillary acidic protein (GFAP) expression in 48 rat brains to evaluate reactive astrocytosis, three and 10 days after long-term head-only sub-chronic exposure to a 900 MHz electromagnetic field (EMF) signal, in male rats. Methods: Sprague-Dawley rats were exposed for 45 min/day at a brain-averaged specific absorption rate (SAR) = 1.5 W/kg or 15 min/day at a SAR = 6 W/kg for five days per week during an eight-week period. GFAP expression was measured by the immunocytochemistry method in the following rat brain areas: Prefrontal cortex, cerebellar cortex, dentate gyrus of the hippocampus, lateral globus pallidus of the striatum, and the caudate putamen. Results: Compared to the sham-treated rats, those exposed to the sub-chronic GSM (Global System for mobile communications) signal at 1.5 or 6 W/kg showed an increase in GFAP levels in the different brain areas, three and ten days after treatment. Conclusion: Our results show that sub-chronic exposures to a 900 MHz EMF signal for two months could adversely affect rat brain (sign of a potential gliosis).

Static Magnetic Field Exposure Affects Behavior and Learning in Rats

The present work investigated the behavioral effects of a moderate exposure (1 h per day for 5 consecutive days) to a static magnetic field (SMF, 128 mT) in male rats. SMF effects were evaluated in two sets of control and SMF-exposed rats. One set of animals was used for evaluation of SMF potential effects on emotional behaviors in the elevated plus maze and in the open field. The other set of animals was tested for learning and memory abilities in different procedures of the Morris water maze task. We found no significant difference between control and SMF-exposed rats in anxiety tests. However, the ratio of open arms time in the plus maze was reduced by half in SMF-exposed rats. In the Morris water maze, SMF-exposed rats were partially impaired during the initial learning task as well as in the retention task at one week. We conclude that static magnetic field exposure altered emotional behaviors in the plus maze and led to cognitive impairments, or at least to substantial attention disorders, in the Morris water maze.

Iterative channel estimation and decoding of turbo-coded OFDM symbols in selective Rayleigh channel

This work deals with the detection of turbo-coded symbols in orthogonal frequency-division multiplexed (OFDM) systems. OFDM symbol detection requires channel estimation, which is often carried out using known pilots. In this paper, an iterative detector composed of a turbo decoder and a channel estimator is proposed. These modules perform jointly and exchange soft information through an iterative process. The decoder consists of the maximum a posteriori Bahl-Cocke-Jelinek-Raviv (MAP-BCJR) algorithm, and the channel estimator is based on the minimum mean-square error (MMSE) criterion. The proposed approach allows for the use of all available information, increases the quality of channel estimation, and improves the system performance. This paper also proposes a new expression of the channel reliability factor used by the MAP-BCJR decoding algorithm. This metric depends on signal-to-noise ratio and the channel estimation error variance. The effect of the channel reliability factor and of the channel estimation error are investigated.

Neural network equalization for frequency selective nonlinear MIMO channels

In order to provide high data rate over wireless channels and improve the system capacity, Multiple-Input Multiple-Output (MIMO) wireless communication systems exploit spatial diversity by using multiple transmit and receive antennas. Moreover, to achieve high date rate and fulfill the power, MIMO systems are equipped with High Power Amplifiers (HPAs). However, HPAs cause nonlinear distortions and affect the receivers performance. In this paper, we investigate the joint effects of HPA nonlinearity and frequency selective channel on the performance of MIMO receiver. Then, we propose two equalization schemes to compensate simultaneously nonlinear distortions and frequency selective channel effects. The first one is based on a feedforward Neural Network (NN) named (NN-MIMO-Receiver) and the second uses NN technique and LMS equalizer (LMS-NN-MIMO). The Levenberg-Marquardt algorithm (LM) is used for neural network training, which has proven [1] to exhibit a very good performance with lower computation complexity and faster convergence than other algorithms used in literature. These proposed methods are compared in term of Symbol Error Rate (SER) running under nonlinear frequency selective channel.

On the Capacity of ASTC-MIMO-OFDM System in a Correlated Rayleigh Frequency-Selective Channel

Algebraic Space-Time Codes (ASTC) for MIMO systems are based on quaternion algebras. Thanks to their algebraic construction, the ASTC codes are full-rank, full-rate and have the non-vanishing determinant property. These codes have been proposed for MIMO flat fading channels in order to increase the spectral efficiency and to maximize the coding gain. The purpose of this work is to analyze the performance of the ASTC in a frequency selective Rayleigh channel. To deal with the frequency selectivity, we use the OFDM modulation. The capacity performances of an ASTC-MIMO-OFDM system, under correlated Rayleigh frequency-selective channel, have been evaluated. Index Terms-

Effects of combined ferrous sulphate administration and exposure to static magnetic field on spatial learning and motor abilities in rats

Primary objective: Occupational exposure to static magnetic fields (SMF) increases, in particular due to the widespread use of Magnetic Resonance Imaging (MRI) for medical diagnosis, thus raising health concerns. This study investigated the behavioural effects of 128 mT SMF in rats and examined the hypothesis that iron supplementation (3 mg kg−1 for 5 days) potentiate the effects of SMF. Methods: Spatial learning abilities in the water maze, motor co-ordination in the rotarod and motor skills in the stationary beam and suspending string tests were assessed in iron-treated, SMF-exposed and co-exposed SMF–iron rats. Results: Acquisition of the water maze navigation task was unaffected in all groups. SMF-exposed and iron-treated rats showed a deficit in the 7-day retention test. No deficit was found in the rotarod and suspended string tests in all groups. Only iron-treated rats were impaired in the stationary beam test. A combination of iron and SMF treatments did not produce additional degradation of performance in all tests. Conclusion: SMF exposure had no massive effect but affected long-term spatial memory. Iron supplementation and 128 mT SMF had no synergistic effects.