原浆型星形胶质细胞调控神经干细胞定向分化的优化比例筛选

目的将神经干细胞（NSC）与原浆型星形胶质细胞（PAS）以不同比例进行体外共培养，观察NSC的定向分化的差异，筛选出有利于向神经元分化的最佳方案，为体内实验提供依据。方法根据NSC与PAS的比例进行分组：3：1组；2：1组；1：1组；1：2组，共培养10天后，采用免疫组化法对分化神经元进行DAPI荧光标记，在显微镜下随机选取20个视野，每次计数100个细胞，计算神经元在NSC中所占的比例，并进行统计学处理。结果NSC：PAS2：1组分化得到的神经元数量最多，与分化的胶质细胞比例为65％：35％；而1：1组、3：1组稍低一些，比例分别为61％：39％和59％：41％；1：2组比例最低为57％：43％。结论在离体细胞共培养的实验中，因细胞的比例不同，NSC分化亦存在差异，其中NSC：PAS为2：1时，NSC分化为神经元的比例最高。     

15 Hz磁场刺激对大鼠局灶性脑创伤影响的实验研究

目的：研究15Hz磁场对大鼠脑创伤的影响。方法：采用大鼠局灶性左脑创伤模型，每天对大鼠头部进行正弦交变磁场（15Hz、18mT）刺激2h，分别作用3d或8d，同时设立对照组。双盲法病理切片观察。结果：与对照组相比，磁场组炎细胞反应减轻，神经元变性坏死程度减轻，8d时更为明显；远离创伤灶的皮层二、三层出现深染的呈长形（或变形）的特殊神经元，且磁场组的这种特殊神经元的数量和分布面积均明显高于对照组，尤以8d时更为显著。结论：所用ELMF可在一定程度上促进脑创伤的恢复，远离创伤区的特殊神经元的产生机制及其在脑创伤后恢复过程中的作用，有待进一步研究。     

5Hz和20Hz磁场刺激对大鼠脑缺血影响的比较研究

目的 观察5Hz和20Hz磁场对脑缺血损害的影响。方法 采用左侧颈总动脉阻断致大鼠急性脑缺血,缺血后给予5Hz和20Hz的磁场刺激3h或5h。观察脑细胞的缺血性病理变化。结果 锥体细胞和星形胶质细胞表现出不同的缺血性病理变化;对锥体细胞的缺血性损害5Hz组轻于对照组和20Hz组,而对星形胶质细胞则表现为5Hz组的缺血性损害程度重于对照组和20Hz组;20Hz组的缺血性损害程度与对照组相似。结论 不同频率的磁场对大鼠脑急性缺血性损害有不同的影响,磁场的频率效应可能与磁场作用机制及细胞的不同特性有关。     

原浆型和纤维型星形胶质细胞调控神经干细胞定向分化的比较研究

目的探讨原浆型星形胶质细胞（protoplasmic astrocyte，PAS）和纤维型星形胶质细胞（fibrous astrocyte，FAS）对神经干细胞（neural stem cell，NSC）定向分化的调控作用。方法将4＇，6-二脒基-2-苯基吲哚（4’，6-Diamidino-2-phenyindole，dilactate，DAPI）标记的NSC分别与PAS、FAS共培养，10天后免疫组化法对分化神经元进行鉴定，显微镜下随机选取20个视野，每次计数100个细胞，计算NSC分化为神经元的比例。结果NSC与PAS共培养后分化成的神经元比例较高，与胶质细胞的比例约为61％：39％；FAS与NSC共培养后分化神经元数量相对较少，以胶质细胞居多，其比例约为41％：59％。结论PAS与FAS相比更能促进NSC向神经元分化。     

原浆型星形胶质细胞调控神经干细胞定向分化的优化比例筛选

目的 将神经干细胞(NSC)与原浆型星形胶质细胞(PAS)以不同比例进行体外共培养,观察NSC的定向分化的差异,筛选出有利于向神经元分化的最佳方案,为体内实验提供依据.方法 根据NSC与PAS的比例进行分组: 3:1组;2:1组;1:1组;1:2组,共培养10天后,采用免疫组化法对分化神经元进行DAPI荧光标记,在显微镜下随机选取20个视野,每次计数100个细胞,计算神经元在NSC中所占的比例,并进行统计学处理.结果 NSC:PAS 2:1组分化得到的神经元数量最多,与分化的胶质细胞比例为65%:35%;而1:1组、3:1组稍低一些,比例分别为61%:39%和59%:41%;1:2组比例最低为57%:43%.结论 在离体细胞共培养的实验中,因细胞的比例不同,NSC分化亦存在差异,其中NSC:PAS为2:1时,NSC分化为神经元的比例最高.     

嗅鞘细胞对脊髓源性神经干细胞分化的影响

目的 探讨嗅鞘细胞对脊髓源性神经干细胞分化的作用。方法 应用Millicell插入式细胞培养皿，大鼠脊髓源性神经干细胞与嗅鞘细胞在无血清培养液中共培养，通过免疫化学染色方法，检测脊髓源性神经干细胞分化为神经元、星形胶质细胞和少突胶质细胞的比例。结果 共培养7d后，脊髓源性神经干细胞分化为神经元的比例高达43．5％，明显高于对照组的21．4％。结论 嗅鞘细胞提供的微环境可促进脊髓源性神经干细胞分化为神经元。     

短期强磁场暴露对金黄地鼠视网膜内多巴胺含量的影响

目的研究0．1Hz极低频交变磁场全身暴露对金黄地鼠眼视网膜内多巴胺含量的影响。方法36只成熟雄性金黄地鼠随机分为4组，每组9只，1组为对照组，另3组分别全身间断暴露于50、75、100mT交变磁场7d，每天暴露8h，然后测定视网膜内神经递质多巴胺含量。结果场强在50mT时，地鼠视网膜内多巴胺含量变化无统计学意义（P〉0．05），而在75、100mT时地鼠视网膜内多巴胺含量增加有统计学意义（P〈0．01）。100mT比75mT时地鼠视网膜内多巴胺含量增加有统计学意义（P〈0．05）。结论全身暴露磁场强度到达一定水平时可刺激金黄地鼠视网膜内多巴胺的合成和分泌，强度越强作用越明显，若长期的强磁场暴露将可能因视网膜内多巴胺含量的变化而影响视网膜的功能。     

模拟舰船强磁场生物效应的实验研究(论著)

目的：研究舰船上０．１Ｈｚ极低频交变磁场和恒定磁场全身暴露的生物效应及其作用阈值。方法：实验动物全身间断暴露于２５～１００ｍＴ交变或恒定磁场７或１４天，或连续暴露于３ｍＴ交变磁场５或１０天；然后分别测定其对微血管、神经肽、骨髓及免疫功能的影响。结果：当场强在７５和１００ｍＴ时，实验兔球结膜毛细血管和微静脉显著扩张，而在２５和５０ｍＴ时也有扩张趋势。场强在７５和１００ｍＴ时，大鼠下丘脑和垂体及血浆中β－内啡肽（β－Ｅｐ）和精氨酸加压素（ＡＶＰ）含量显著升高，在２５和５０ｍＴ时作用不明显，而３ｍＴ交变磁场使含量下降。场强在７５ｍＴ时，对实验兔和大鼠骨髓细胞增生活力有非常显著的促进作用。结论：磁场具有扩张微血管、改善微循环的作用，且随着场强的增大，作用逐渐加强。低强度磁场抑制神经肽的合成与分泌，高强度促进合成与分泌。强场在７５ｍＴ时，对骨髓细胞增生活力有非常显著的促进作用。交变和恒定磁场的场强和暴露时间相同时，对机体的影响基本一致     

5-氮杂胞苷诱导间充质干细胞分化为成肌细胞的实验研究

目的：探讨5－氮杂胞苷（5－Aza）诱导间充质干细胞（MSCs)分化为成肌细胞的相关机制。方法：分离纯化4－6周龄Balb/C小鼠骨髓MSCs，以不同浓度5－Aza作用，用四唑盐（MTT）法测定细胞生长活力；逆转录－聚合酶链反应（RT－PCR）鉴定肌形成调节因子5（Myf5)，成肌素（myogenin)表达，免疫组织化学染色鉴定结蛋白（desmin)，肌凝蛋白（myosin)表达；观察细胞形态变化。结果：1，3umol/L5－Aza对细胞增殖无明显影响，20umol/L 5-Aza对细胞有毒性作用，影响其增殖，10umol/L 5-Aza对细胞增殖无明显影响。20umol/L 5-Aza对细胞有毒性作用，影响其增殖，10umol/L5-Aza诱导后6h,MSCs表达Myf5,9h达最高；5umol/L 5-Aza诱导后9h，MSCs表达Myf5,12h达高峰。10umol/L 5-Aza诱导后24h，MSCs表达myogenin,48h达最高；5umol/L5-Aza诱导后6d，MSCs表达myogenin,且为高峰。10umol/L 5-Aza诱导后7d，部分细胞表达desmin;14d部分细胞表达myosin.10umol/L 5-Aza诱导后9d，部分细胞体明显增粗，14－16d后可见有肌管样细胞,出现。结论：5－Aza诱导MSCs向成肌细胞定向分化，可能是因其产生的去甲基化作用使MSCs中处于转录失活阶段的肌分化调控基因Myf5等得以表达，从而调控MSCs向肌细胞系定向分化并逐步表达myogenin，最后分化为肌管样细胞的过程。     

高压氧干预对绿色荧光蛋白小鼠骨髓间充质干细胞培养及增殖分化的影响CSCD

目的 探讨骨髓间充质干细胞培养及高压氧对其增殖分化的影响.方法 采用全骨髓细胞贴壁培养法提取绿色荧光蛋白小鼠骨髓间充质干细胞进行培养,取P3代骨髓间充质干细胞,用神经节苷脂和胶质细胞源性神经生长因子诱导液进行成神经元样细胞诱导,并在培养及诱导时进行高压氧干预,1次/d,为高压氧干预组（高压氧组）.采用免疫荧光检测神经元特异性烯醇化酶（neuron specific enolase,NSE）表达,绘制细胞生长曲线.未进行高压氧干预的为对照组.结果 贴壁培养法分离培养骨髓间充质干细胞,经多次换液后可纯化细胞.高压氧组间充质干细胞对数生长期提前,进入平台期后细胞数量多于对照组,高压氧干预后细胞于24 h内出现轴突、树突,48 h后2组对比,高压氧组80％以上细胞出现突起,且细胞突起较长、较粗.对照组突起的细胞比例不足80％,细胞分散,突起短,未连成网状.结论 骨髓间充质干细胞全骨髓贴壁培养法操作简单,细胞繁殖能力强,经高压氧干预后骨髓间充质干细胞生长加快.在细胞诱导时联合高压氧干预,细胞分化数量多,突起长.提示高压氧能促进体外骨髓间充质干细胞向神经元样细胞增殖和分化.     

Exploring the radiosensitizing potential of magnetotherapy: a pilot study in breast cancer cells

Abstract

Aim: To explore the influence of electromagnetic fields (EMFs) on the cell cycle progression of MDA-MB-231 and MCF-7 breast cancer cell lines and to evaluate the radiosensitizing effect of magnetotherapy during therapeutic co-exposure to EMFs and radiotherapy.

Material and methods: Cells were exposed to EMFs (25, 50 and 100?Hz; 8 and 10?mT). In the co-treatment, cells were first exposed to EMFs (50?Hz/10?mT) for 30?min and then to ionizing radiation (IR) (2?Gy) 4?h later. Cell cycle progression and free radical production were evaluated by flow cytometry, while radiosensitivity was explored by colony formation assay.

Results: Generalized G1-phase arrest was found in both cell lines several hours after EMF exposure. Interestingly, a marked G1-phase delay was observed at 4?h after exposure to 50?Hz/10?mT EMFs. No cell cycle perturbation was observed after repeated exposure to EMFs. IR-derived ROS production was enhanced in EMF-exposed MCF-7 cells at 24?h post-exposure. EMF-exposed cells were more radiosensitive in comparison to sham-exposed cells.

Conclusions: These results highlight the potential benefits of concomitant treatment with magnetotherapy before radiotherapy sessions to enhance the effectiveness of breast cancer therapy. Further studies are warranted to identify the subset(s) of patients who would benefit from this multimodal treatment.     

Exposure to electromagnetic field attenuates oxygen-glucose deprivation-induced microglial cell death by reducing intracellular Ca2+ and ROS

Purpose The aim of this research was to demonstrate the protective effects of electromagnetic field (EMF) exposure on the human microglial cell line, HMO6, against ischemic cell death induced by in vitro oxygen-glucose deprivation (OGD).

Materials and methods HMO6 cells were cultured for 4?h under OGD with or without exposure to EMF with different combinations of frequencies and intensities (10, 50, or 100?Hz/1?mT and 50?Hz/0.01, 0.1, or 1?mT). Cell survival, intracellular calcium and reactive oxygen species (ROS) levels were measured.

Results OGD caused significant HMO6 cell death as well as elevation of intracellular Ca²⁺ and ROS levels. Among different combinations of EMF frequencies and intensities, 50?Hz/1?mT EMF was the most potent to attenuate OGD-induced cell death and intracellular Ca²⁺ and ROS levels. A significant but less potent protective effect was also found at 10?Hz/1?mT, whereas no protective effect was found at other combinations of EMF. A xanthine oxidase inhibitor reversed OGD-induced ROS production and cell death, while NADPH oxidase and mitochondrial respiration chain complex II inhibitors did not affect cell death.

Conclusions 50?Hz/1?mT EMF protects human microglial cells from OGD-induced cell death by interfering with OGD-induced elevation of intracellular Ca²⁺ and ROS levels, and xanthine oxidase is one of the main mediators involved in OGD-induced HMO6 cell death. Non-invasive treatment of EMF radiation may be clinically useful to attenuate hypoxic-ischemic brain injury.     

50-Hz magnetic field induces EGF-receptor clustering and activates RAS

PURPOSE: In a previous study, we found that exposure to a 50 Hz magnetic field (MF) could activate stress-activated protein kinase (SAPK) and P38 mitogen-activated protein (MAP) kinase (P38 MAPK) in Chinese hamster lung (CHL) fibroblast cells, and simultaneous exposure to a 'noise' MF of the same intensity inhibited these effects. In order to explore the possible target sites and upstream signal transduction molecules of SAPK and P38 MAPK, and further validate the interference effects of 'noise' MF on 50 Hz MF, the effects of MF exposure on clustering of epidermal growth factor (EGF) receptors and Ras protein activation were investigated. MATERIALS AND METHODS: CHL cells were exposed to a 50 Hz sinusoidal MF at 0.4 mT for different durations, and clustering of EGF receptors on cellular membrane and Ras protein activation were analyzed using immunofluorescence confocal microscopy and co-precipitation technology. EGF treatment served as the positive control. RESULTS: The results showed that, compared with sham-exposed cells, exposure to a 50 Hz MF at 0.4 mT for 5 min slightly induced EGF receptor clustering, whereas exposure for 15 min enhanced receptor clustering significantly. Corresponding to receptor clustering, Ras protein was also activated after exposure to the 50 Hz MF. Exposure to a 'noise' MF (with frequency ranges from 30 - 90 Hz) at the same intensity and durations, did not significantly affect EGF receptor clustering and Ras protein. However, by superimposing the 'noise' MF, receptor clustering and Ras activation induced by 50 Hz MF were inhibited. CONCLUSION: The results suggested that membrane receptors could be one of the most important targets where extremely low frequency (ELF) MF interacts with cells, and Ras may participate in the signal transduction process of 50 Hz MF. Furthermore, a 'noise' MF could inhibit these effects caused by ELF-MF.     

Exposure to alternating electromagnetic fields and effects on the visual and visuomotor systems

Acute effects on the visual and visuo-motor systems by exposure to electromagnetic fields (EMFs) at a frequency and amplitude similar to those produced by MR imaging gradient coils were assessed. 40 volunteers were exposed in random order to three, time varying, magnetic field gradients (0, 20 and 10 mT m(-1)r.m.s.). The waveform was 50 cycles of a 490 Hz sinusoidal waveform repeated every second with a total duration of 10 min for each trial. The EMFs were generated using an in-house designed and built magnetic gradient coil and waveform generator. During each trial, a test battery assessing the visual sensory (FACT) and visuo-motor (Pursuit Aiming II and visual tracking) neurobehavioral domains was completed by all volunteers. The sequence of these tests was assigned at random for each volunteer. Performance in these tests was analysed using linear mixed effects models adjusted for confounding factors collected in a pre-trial questionnaire. Variability of the estimates was assessed using a delete-1 jack-knife procedure. There was a trend for visuo-motor accuracy to be reduced (p = 0.06) by 1% during high exposure, but not at medium exposure. There was a weaker trend for visual contrast sensitivity to be improved by 12% and 21% during medium and high exposure, respectively, compared with the non-exposed sessions (p = 0.08). These effects did not reach 5% statistical significance within a population of 40 volunteers, but also the magnitude of these effects did not depend on single "extreme" observations.     

Non-linear dependence of the dielectric properties of chick embryo myoblast membranes exposed to a sinusoidal 50 Hz magnetic field.

Primary chick embryo myoblasts can be a useful tool for studying the developmental events which accompany myoblast differentiation, particularly myoblast membrane fusion. To determine whether the electrical properties and/or fusion in these systems are affected by 50 Hz magnetic fields, chick embryo myoblast cultures were exposed to B-field intensities ranging from 1 to 10 mT. The electrical parameters of the myoblasts, i.e. membrane conductivity, membrane permittivity and the conductivity of the cell interior (cytosol) were determined by the analysis of conductivity dispersion data in the radio frequency range (10 kHz-100 MHz). Preliminary results indicate that the time of fusion (60 h) is not affected by these fields, but that the absolute values of the two membrane electrical parameters are affected. In particular, a B-field intensity-dependent decrease was observed. The maximum effect resulted after a 1 h exposure to a magnetic flux density of about 5 mT. The conductivity of the cytosol remained unchanged. These data seem to indicate that exposure to 50 Hz magnetic fields affects both static and dynamic membrane properties in primary chick embryo myoblasts.     

Organ culture studies on the development of mouse embryo limb buds under EMF influence

PURPOSE: To investigate the effects of an electromagnetic field (EMF) on limb bud development in vitro, an organ culture system was applied. MATERIALS AND METHODS: Three test groups of amputated mouse limb buds included the experimental (E) group which received EMF (50 Hz/13.1 mT, for 2 h), a sham (Sh) group exposed to no EMF treatment and the control (C) group. The limb buds of E and Sh groups (n = 20 per group) were amputated from mouse embryos on day 11.5 of development and cultured in minimum essential medium Eagle (MEM Eagle), supplemented with 15% human embryo cord serum, for 2 days, while those of group C (n = 20) were removed on day 13.5 of development. All samples were fixed in Bouin's fluid, embedded in paraffin, serially sectioned (5 microm thick) and stained with Hematoxylin and Eosin. Limb bud measurements were performed using a scaled graticule. RESULTS: Morphological and histological examinations showed significant changes in the experimental limb bud group as compared with the sham and control groups. The growth rate in both fore and hindlimb buds in proximal-distal (P-D) and anterior-posterior (A-P) axes were significantly increased. Chondrocyte counts and mitotic figures of mesenchymal and red blood cells were significantly increased as compared with those of sham and control groups. There was also a significant reduction of mesenchymal cell counts, while no significant difference was observed in the degenerated cell counts among the three groups. CONCLUSIONS: These findings suggest that EMF, under the conditions applied, has progressive effects on the limb bud development and that both proliferation and differentiation can be stimulated in vitro.     

Effects of low intensity static electromagnetic radiofrequency fields on leiomyosarcoma and smooth muscle cell lines

In this study we investigated the effects of low intensity static radiofrequency electromagnetic field (EMF) causing no thermal effects, on leiomyosarcoma cells (LSC), isolated from tumors of fifteen Wistar rats induced via a 3,4-benzopyrene injection. Electromagnetic resonance frequencies measurements and exposure of cells to static EMF were performed by a device called multi channel dynamic exciter 100 V1 (MCDE). The LSC were exposed to electromagnetic resonance radiofrequencies (ERF) between 10 kHz to 120 kHz, for 45 min. During a 24h period, after the exposure of the LSC to ERF, there was no inhibition of cells proliferation. In contrast, at the end of a 48 h incubation period, LSC proliferation dramatically decreased by more than 98% (P<0.001). At that time, the survived LSC were only 2% of the total cell population exposed to ERF, and under the same culture conditions showed significant decrease of proliferation. These cells were exposed once again to ERF for 45 min (totally 4 sessions of exposure, of 45 min duration each) and tested using a flow cytometer. Experiments as above were repeated five times. It was found that 45% of these double exposed to ERF, LSC (EMF cells) were apoptotic and only a small percentage 2%, underwent mitosis. In order to determinate their metastatic potential, these EMF cells were also counted and tested by an aggregometer for their ability to aggregate platelets and found to maintain this ability., since they showed no difference in platelet aggregation ability compared to the LSC not exposed to ERF (control cells). In conclusion, exposure of LSC to specific ERF, decreases their proliferation rate and induces cell apoptosis. Also, the LSC that survived after exposed to ERF, had a lower proliferation rate compared to the LSC controls (P<0.05) but did not loose their potential for metastases (platelet aggregation ability). The non-malignant SMC were not affected by the EMF exposure (P<0.4). The specific ERF generated from the MCDE electronic device, used in this study, is safe for humans and animals, according to the international safety standards.     

Increased chromatid-type chromosomal aberrations in mouse m5S cells exposed to power-line frequency magnetic fields

Purpose : To investigate the induction of chromosomal aberrations in mouse m5S cells after exposure to power-line frequency magnetic fields (extremely low frequency magnetic fields; ELFMF) at high-flux densities. Material and methods : m5S cells were either untreated or pretreated during the G1 phase with mitomycin C (MMC, 1 μ M) for 1 h or 3Gy X-rays, and then exposed to ELFMF at three different flux densities (5 and 50mT at 60 Hz, 400 mT at 50 Hz) for 40 h. Unexposed control cells were incubated for the same period in a conventional CO 2 incubator. Chromosomal aberrations were analysed in the first post-treatment metaphases. Cell kinetics were assessed by DNA flow cytometry and the mitotic index. Results and conclusions : ELFMF enhanced the formation of spontaneous and MMC- or X-ray-induced chromosomal aberrations, in a flux-density-dependent manner. Statistically significant increases in the frequency of chromosomal aberrations were observed in cells exposed to 400mT ELFMF with respect to unexposed controls. The aberrations induced by ELFMF were mostly chromatid-type, not chromosome-type. The cells exposed to 400mT ELFMF exhibited a three-fold higher level of chromatid-type aberrations than did the unexposed cells. Flow cytometric and mitotic index analyses revealed that the S or G2 arrest following MMC or X-irradiation was more profound in ELFMF-exposed cells than in unexposed cells. Our results suggest that ELFMF can interfere with post-replication repair, resulting in increased levels of chromatid-type chromosomal aberrations induced spontaneously and by DNA damaging agents.     

Increased chromatid-type chromosomal aberrations in mouse m5S cells exposed to power-line frequency magnetic fields

PURPOSE: To investigate the induction of chromosomal aberrations in mouse m5S cells after exposure to power-line frequency magnetic fields (extremely low frequency magnetic fields; ELFMF) at high-flux densities. MATERIAL AND METHOD: m5S cells were either untreated or pretreated during the G1 phase with mitomycin C (MMC, 1 microM) for 1 h or 3 Gy X-rays, and then exposed to ELFMF at three different flux densities (5 and 50 mT at 60 Hz, 400 mT at 50 Hz) for 40 h. Unexposed control cells were incubated for the same period in a conventional CO2 incubator. Chromosomal aberrations were analysed in the first post-treatment metaphases. Cell kinetics were assessed by DNA flow cytometry and the mitotic index. RESULTS AND CONCLUSIONS: ELFMF enhanced the formation of spontaneous and MMC- or X-ray-induced chromosomal aberrations, in a flux-density-dependent manner. Statistically significant increases in the frequency of chromosomal aberrations were observed in cells exposed to 400 mT ELFMF with respect to unexposed controls. The aberrations induced by ELFMF were mostly chromatid-type, not chromosome-type. The cells exposed to 400 mT ELFMF exhibited a three-fold higher level of chromatid-type aberrations than did the unexposed cells. Flow cytometric and mitotic index analyses revealed that the S or G2 arrest following MMC or X-irradiation was more profound in ELFMF-exposed cells than in unexposed cells. Our results suggest that ELFMF can interfere with post-replication repair, resulting in increased levels of chromatid-type chromosomal aberrations induced spontaneously and by DNA damaging agents.     

Influence of high-frequency electromagnetic fields on different modes of cell death and gene expression

PURPOSE: International thresholds for exposure to non-ionizing radiation leading to non-thermal effects were conservatively set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The aim of this study was to examine whether biological effects such as different modes of cell death and gene expression modifications related to tumorgenesis are detectable above the threshold defined. MATERIALS AND METHODS: Human leukaemia cells (HL-60) grown in vitro were exposed to electromagnetic fields (EMF; t 1/2(r) about 1 ns; field strength about 25 times higher than the ICNIRP reference levels for occupational exposure) leading to non-thermal effects using a high-voltage-improved GTEM cell 5302 (EMCO) connected to a pulse generator NP20 (C = 1 nF, U(Load) = 20kV). HL-60 cells were harvested at 0, 24, 48 and 72 h after radiation exposure. Micronuclei, apoptosis and abnormal cells (e.g. necrosis) were determined using morphological criteria. In parallel, the expression of 1176 genes was measured using Atlas Human 1.2. Array. Based on high data reproducibility calculated from two independent experiments (> 99%), array analysis was performed. RESULTS: No significant change in apoptosis, micronucleation, abnormal cells and differential gene expression was found. CONCLUSIONS: Exposure of HL-60 cells to EMFs 25 times higher than the ICNIRP reference levels for occupational exposure failed to induce any changes in apoptosis, micronucleation, abnormal morphologies and gene expression. Further experiments using EMFs above the conservatively defined reference level set by the ICNIRP may be desirable.