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ORIGINAL ARTICLES

The prenatal effects of mobile microwave radiation on mice

Hamdi, Khaled Naim

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doi: 10.1097/01.MJX.0000397212.31669.36
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Abstract

Introduction

Mobile phones and cell towers are the most common sources of microwave radiations (MWR). Electromagnetic radiations are waves of electric and magnetic energy moving through space. Microwave is used in telephone links, aircrafts, ships, radar, and kitchen utensils. The first mobile phone system was analog and used frequencies of 450–900 MHz. The digital system of mobile phone is operated at 1800–2100 MHz. Mobile phones are two-way radio transmitters. A part of the emitted radiation is absorbed by the user; the power of absorption is expressed as the specific absorption rate (SAR) in watts per kilogram. The effects of radiofrequency electromagnetic waves (RF-EMW) emitted from cell phones have been debated [1,2]. The effects of RF-EMW on the brain seem to be the most researched area [3]. RF-EMW emitted from the cell phones can reduce the fertilizing potential of men [4]. The RF-EMW effects on cellular organelles are controversial. RF-EMW stimulate plasma membrane NADH oxidase and extracellular superoxide production [5]. This can lead to oxidative stress and subsequent carcinogenesis [6,7]. RF-EMW can increase free-radical activity in cells [8]. MWR at cellular telephone frequency of 1.95 GHZ signal may influence the repair of radiograph-induced DNA breaks or alter the cell death pathways of the damage response [9]. RF-EMW of the commercially available cell phones may affect the fertilizing potential of spermatozoa, and this can explain the RF-EMW-related infertility cases observed in numerous studies [10]. Microwaves of mobile phones may decrease the number of ovarian follicles in rats. The decreased number of follicles in fetuses exposed during the prenatal life to mobile phone microwaves suggested that intrauterine exposure has toxic effects on ovaries [11].

This study aimed to evaluate the prenatal effects of mobile MWR on mice, especially on the liver. The liver cells may be vulnerable to MWR because of their high iron content; iron molecules may act similar to an antenna or a receptor for receiving MWR, much like the antenna of a TV and cell phone.

Materials and methods

This study was carried out in CD-1 mice that were mainly females. The average body weight was 24–30 g. The animals were obtained from the breeding unit of Theodor Bilharz Research Institute (Imbaba, Giza, Egypt). The animals were housed in 30×40×40 cm (W×L×H) plastic cages. The cage was free from all kinds of materials that could affect the electromagnetic fields. Animals were fed on cubes of crude protein minerals and fibers. Fresh vegetables and milk were also provided along with tap water ad libitum. The housing room in the Animal House of the Ain Shams Medical School, was maintained at 24°C with 42±5% relative humidity and had a 12-h light–dark cycle (light on during 06:00–18:00h).

Breeding

The gestational period of the CD-1 mice is approximately 20–21 days. Two adult virgin female mice with one adult male mouse were housed in a wire cage overnight from 18:00 to 09:00 h. The presence of vaginal plug indicated the occurrence of fertilization. The pregnant female mice were divided into three groups of 10 animals each.

  • (1) G1: this was used as a control group without exposure near any source of electromagnetic field.
  • (2) G2: mice were exposed for half-hour every day during the gestational period with the cell phone in answering state.
  • (3) G3: mice were exposed during the gestational period for 1 h every day with the cell phone in answering state, and 12 h while the cell phone was in standby state.

The MWR was produced by a mobile phone operating with a microwave frequency range of 900–1800 MHz [12]. The mobile phone was situated in the center of the cage; the distance between the phone and mice was approximately 10 cm.

Maternal body weight of all groups was recorded daily through the gestational period. After delivery, fetuses were taken out for morphological, histological, and ultrastructural studies. The average number and average body weight of fetuses were recorded and statistically analyzed. The fetuses were examined for morphological malformation using a binocular microscope. Fetuses were killed with an overdose of ether; a piece of liver of approximately 2×1×1 cm was excised for biopsy. A part of the specimen was fixed in 10% neutral formalin, then dehydrated in ethanol, cleaned with xylene, and embedded in paraffin. Tissue sections were stained with hematoxylin and eosin and examined by light microscopy. The other parts of the specimen were cut into approximately 1-mm3; fixed in phosphate-buffered glutaraldehyde, 2–4%; then treated with 1% osmium tetraoxide, and dehydrated in ethanol. This was followed by addition of toluene, equal volumes of toluene and epon, and pure epon, and then they were embedded in epoxy resin (Epon 812 resin, Heidelberg, Baden-Württemberg, Germany). Semithin sections were stained using toluidine blue and ultrathin sections were stained using uranyl acetate and lead citrate, and then examined with an electron microscope (Philips 400, Amsterdam, Netherlands).

Statistical analyses

Data were collected and analyzed by using the commercially available statistics software SPSS-10 package (release 3, SPSS Inc., Chicago, Illinois, USA). An analysis of variance test was used to compare between the means of the different parameters of the three studied groups. A difference was considered significant at a probability of P less than 0.05.

Results

The morphological results of the pregnant mice and fetuses are illustrated in Tables 1–3.

Table 1
Table 1:
The effects of microwave radiation on body weight (grams) during the gestational period
Table 2
Table 2:
The effects of microwave radiation on body length (centimeter) of 21-day-old fetuses
Table 3
Table 3:
The effects of microwave radiation on body weight (grams) of fetuses

The pregnant mothers

In this study, there was a steady increase in body weight during the gestational period. The highest mean body weight was observed in G1 (44.9±0.64 g); the lowest mean body weight was in G3 (36.96±1.92 g). The maternal mortality rate was zero; no abortions were recorded among mothers of all groups.

Fetuses

The mean body length of fetuses showed decreases in G3 (1.76±0.15 cm) and G2 (2.01±0.12 cm) compared with G1 (2.2±0.105 cm) with a statistical significant difference. Furthermore, there was a decrease in the mean fetal body weight in G2 (0.92±0.103) and G3 (0.75±0.11), respectively, compared with G1 (1.14±0.084) with a statistical significant difference. There were no morphological malformations in all groups.

Histological and ultrastructural results of mice liver

The results of the control group (G1) are seen in Figs 1–4. The hepatocytes are polygonal in shape with ill-defined cell boundaries and granular cytoplasm. The nuclei of hepatocytes usually are large and vesicular with prominent nuclei. The blood sinusoids are lined by thin endothelial cells (Fig. 1). The ultrastructural results of G1 showed the cytoplasm of hepatocytes containing a variety of organelles. The mitochondria appeared in different shapes, showed sac-like structures, and were limited by double membranes; the cristae are folds of the inner membrane inside the mitochondria. The endoplasmic reticulum in its two forms rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum is seen; free ribosomes are found singly or in aggregates as electron-dense granules. Golgi apparatus is seen near the nucleus as curved flattened sacs surrounded by clusters of vesicles. The nuclei are limited by prominent nuclear membrane; the hepatocytic nuclear chromatin exists in two forms as heterochromatin and euchromatin. The nucleoli of most hepatocytes show an electron-dense amorphous structure (Figs 2–4).

Fig. 1
Fig. 1:
Light micrograph of a control liver section, [group 1 (G1)]. The central vein (C) and the characteristic pattern of the hepatocytes and blood sinusoids are indicated by arrows (hematoxylin and eosin, ×640).
Fig. 2
Fig. 2:
Electron micrograph of control liver [group 1 (G1)]. The mitochondria with cristae (M), rough endoplasmic reticulum (R), bile canaliculus (B), and electron-dense vacuoles (V) (×3000) are observed.
Fig. 3
Fig. 3:
Electron micrograph of control liver [group 1 (G1)]. The mitochondria with cristae (M), rough endoplasmic reticulum (R), hepatocytes nucleus (N), and electron-dense vacuoles (V) (×3000) are observed.
Fig. 4
Fig. 4:
Electron micrograph of control liver [group 1 (G1)]. The mitochondria with cristae (M), rough endoplasmic reticulum (R), bile canaliculus (B), hepatocytes nucleus (N), and electron-dense vacuoles (V) (×3000) are observed.

The histopathological picture of G2 showed congestion of the central vein and dilated blood sinusoids. This was apparent in G3 with damaged endothelial lining of the central vein and hemolyzed blood cells, in addition to hepatocytic vacuolar degeneration, some pyknotic nuclei, and scattered focal areas of inflammatory cells in the periportal areas.

The ultrastructural examination of G2 and G3 (Figs 5–8) showed damaged mitochondria. Generalized mitochondrial swelling was common; the mitochondrial cristae were irregular, incomplete, and in some cases were destructed and appeared as empty vacuoles akin to structureless bodies. The RER and smooth endoplasmic reticulum were fragmented and swollen in many hepatocytes, and showed marked dilated and broken cisternae with vesiculate rounded vesicles. The cytoplasm of many hepatocytes showed numerous vacuoles and fatty changes and an increase in the amount of free ribosomes. Some nuclei of the hepatocytes showed irregular shapes, nuclear inclusions, and a slightly increased number of micronuclei. The space of Disse showed dilation with fragmentation of RBCs and Kupffer cells. The periportal space showed scattered focal areas of inflammatory cell infiltrations, mainly of lymphocytes.

Fig. 5
Fig. 5:
Electron micrograph of group 2 (G2). The mitochondria have lost their cristae (M) and many of them are pleomorphic; Kupffer cells (K) with numerous microvilli and abundance of heterochromatin aggregated on the nuclear membrane within the blood sinusoids (×3000).
Fig. 6
Fig. 6:
Electron micrograph of group 3 (G3) showing dilated vacuolated smooth endoplasmic reticulum (S) and pleomorphic mitochondria that have lost their cristae (M) (×4500).
Fig. 7
Fig. 7:
Electron micrograph of group 3 (G3) showing dilated vacuolated smooth endoplasmic reticulum (S), pleomorphic mitochondria that have lost their cristae (M), and nuclear inclusion (I) within the hepatocytes nuclei (N) along with irregular nuclear membranes (×3000).
Fig. 8
Fig. 8:
Electron micrograph of group 3 (G3) showing dilated vacuolated smooth endoplasmic reticulum (S), pleomorphic mitochondria that have lost their cristae (M); each of the inflammatory cells, mainly lymphocytes (L), contains a relatively large nucleus that fills most of the cel (×3000).

Discussion

MWRs have been involved in many diverse affiliations besetting our life. The possibility of embryonic and fetal damage is now greater as radiating cell phone units are brought into close contact to our bodies.

There is no epidemiologic evidence of daily-life exposure to microwaves being harmful to human reproductive processes [13]. However, a reduction of the uteroplacental blood flow as a result of microwave exposure of 915 MHz at 0.6 mW/cm2 incident power density corresponding to an SAR of 0.4 W/kg, which could induce congenital malformations and abortion, was observed [14].

In this study, there was a significant reduction in the average body weight and body length of the fetuses of G2 and G3 that were exposed to MWR compared with the control group (G1). This reduction may be due to impairment of the placental blood flow and reduction of nutrients and gases to the fetal circulation, as reported by Chazan et al. [15]. Fetal malformations and deaths in experimental animals could be attributed to the thermal effect of the microwave [14]. Microwave energy might lead to elevation of the pelvic temperature and in turn injure embryonic tissues. Fetal mass reduction is due to the exposure to RF [16]. Significant differences in the body weight of chick embryos exposed to 50 Hz during the first 24 h of incubation have been reported [17]. An increase in mortality rate of chick embryos exposed to mobile phone has been shown by Grigor'ev [18].

In this study, there were no congenital malformations detected in G2 and G3. No significant differences between the RF and sham groups in the percentages of normal and abnormal fetuses were observed [19]. There was no effect in developing fetuses exposed to 2450 MHz of microwave at a power density of 28 mW/cm2 for 100 min daily from day 6 to day 15 of gestation [20]. Meanwhile, fetal malformations in rats irradiated with 27.12 MHz RF on days 7 and 9 of gestation have been reported [21].

The congestion and dilation of the central veins of the liver cells observed in this study could confirm results of Bermanet al. [20] and Gökcimenet al. [22] which reported sinusoidal dilation, cell infiltration in the peripheral areas, necrosis, and vascular degeneration in liver cells of young male Wister Albino rats exposed to EMW at a frequency of 27.17 MHz and a power density of 0.2 mW/cm2 for 6 min daily for 2 weeks. Low energy of ultrahigh frequency electromagnetic field emitted from a cellular phone was able to induce a genotoxic response in hematopoietic tissues during the embryogenesis through an unknown mechanism [23]. In contrast, no pathological changes in animal growth rate and in the hepatocytes in rats exposed to 50-HMz electromagnetic field have been observed [24,25]. There were no mutagenic effects on hepatocytes of mice exposed in utero to 2.45 GHz with SAR of 0.71 W/kg for 16 h daily from the begining of gestational age up to day 15 [26].

In this study, the ultrastructural changes in hepatocytes in G2 and G3 were apparent clearly as mitochondrial degeneration and fragmentations of the endoplasmic reticulum. The damage caused to the mitochondria could be attributed to liberation of lysosomal enzymes, in addition to oxidative damage of the mitochondrial RNA. Mitochondrial swelling and fragmentation of its cristae were probably due to influx of water into the inner and outer mitochondrial membranes [27]. Mitochondrial swelling has been attributed to the change in the mitochondrial membrane permeability [28]. As mitochondria are the powerhouse of the cell, their damage might result in lowered energy output. This could be a cause for cellular degeneration. Swelling mitochondria and loss of their cristae were observed in rat hepatocytes exposed to electromagnetic fields [29]. A significant increase in alanine aminotransferase and aspartate aminotransferase enzymes following the increased duration of microwave exposure has been observed [30]. These two enzymes (alanine aminotransferase and aspartate aminotransferase) are specific liver enzymes that increased with toxic damage of the liver cells [31].

The hepatic cell injury caused by exposure to MWR could be due to increased potassium serum concentration and cellular membrane damage, induced by oxidative damage or by impaired function of ions. The increase in lipid per oxidation and the complex reaction of free radicals might lead to destruction of the membrane proteins [32]. The endoplasmic reticulum in this study was fragmented and vesiculated into short rounded cisternae, especially RER. The hepatocytic nuclei of the irradiated groups showed noticeable features of alteration and this could be due to DNA damage by the MWRs.

In conclusion, people should restrict their usage of mobile phones. This study showed a significant decrease in weight and length of fetuses exposed to MWR during the gestational period in mice. Prenatal exposure to MWR might be hepatotoxic, but considerable study is required to provide scientific support. Data from animal studies are limited in their human application.

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Keywords:

hepatocytes; mice; mobile phone microwave radiation; ultra structure; uteroplacental blood flow

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