Effects of low frequency electromagnetic fields on the chondrogenic differentiation of human mesenchymal stem cells

Electromagnetic fields (EMF) have been shown to exert beneficial effects on cartilage tissue. Nowadays, differentiated human mesenchymal stem cells (hMSCs) are discussed as an alternative approach for cartilage repair. Therefore, the aim of this study was to examine the impact of EMF on hMSCs during chondrogenic differentiation. HMSCs at cell passages five and six were differentiated in pellet cultures in vitro under the addition of human fibroblast growth factor 2 (FGF‐2) and human transforming growth factor‐β₃ (TGF‐β₃). Cultures were exposed to homogeneous sinusoidal extremely low‐frequency magnetic fields (5 mT) produced by a solenoid or were kept in a control system. After 3 weeks of culture, chondrogenesis was assessed by toluidine blue and safranin‐O staining, immunohistochemistry, quantitative real‐time polymerase chain reaction (PCR) for cartilage‐specific proteins, and a DMMB dye‐binding assay for glycosaminoglycans. Under EMF, hMSCs showed a significant increase in collagen type II expression at passage 6. Aggrecan and SOX9 expression did not change significantly after EMF exposure. Collagen type X expression decreased under electromagnetic stimulation. Pellet cultures at passage 5 that had been treated with EMF provided a higher glycosaminoglycan (GAG)/DNA content than cultures that had not been exposed to EMF. Chondrogenic differentiation of hMSCs may be improved by EMF regarding collagen type II expression and GAG content of cultures. EMF might be a way to stimulate and maintain chondrogenesis of hMSCs and, therefore, provide a new step in regenerative medicine regarding tissue engineering of cartilage. Bioelectromagnetics 32:283–290, 2011. © 2010 Wiley‐Liss, Inc.     

Effects of low frequency electric fields on the sedimentation rate of human blood. Preliminary observations

The erythrocyte sedimentation rate (ESR) of human blood samples exposed to electric fields at frequencies ranging from 1 Hz to 100 kHz was measured. Statistically significant differences in ESR were found between the exposed and the control samples at most of the frequencies used. The results suggest a possible nonlinear dependence of the effect on frequency, the threshold field strength varying from about 25 V/m to about 5 kV/m.     

Responses of the spider Argiope aurantia to low frequency phasic and continuous vibrations

I maintained female orb-weaving spiders, Argiope aurantia, in the laboratory and subjected them to low frequency phasic and continuous transverse vibrations of known frequency, amplitude, and position on the web. Stimuli were administered for periods of 1 min and all behaviour recorded. Pumping was associated with tactile contact to the spider's abdomen. Pumping increased with increasing frequency of phasic stimuli delivered to the web surface. Attack increased linearly with the log of stimulus frequencies between 0 and 14 Hz for stimuli delivered to the catching spiral. Dropping occurred only when high frequencies and amplitudes of stimuli were administered to the spider's abdomen and the hub of the web.     

Effects of extremely low frequency electromagnetic fields on health

This paper gives a brief review of the physical interaction and bio-effects of exposure to extremely low frequency (ELF) electromagnetic fields (EMF) along with guidelines on limits of exposure to 50/60 Hz electric and magnetic fields.     

Effects of low frequency cyclic mechanical stretching on osteoclastogenesis

Bone cells are continuously exposed to mechanical deformations originating from movement. Mechanical stimulation at fundamental frequencies associated with most frequent normal locomotion (0.167–10 Hz) has been reported to suppress differentiation of osteoclasts. However, the effects of very low frequency (0.01 Hz) stimulation (which could be a frequency component of normal movement and also relevant to locomotion of movement-impaired individuals) on osteoclasts are poorly understood. We examined differentiation of osteoclasts from mouse bone marrow precursors and RAW 264.7 monocytes cultured on an extendable silicone surface that was dynamically stretched at 0.01 Hz. Three stimulation regimes were applied: (i) continuously during 4 days of differentiation, (ii) non-continuously, 8 h/day for 4 days, and (iii) post-differentiation, when stimulation was applied for 24 h after osteoclasts were noted. Low frequency mechanical stimulation did not inhibit osteoclastogenesis. Moreover, the expression of osteoclast marker genes was upregulated in mechanically stimulated cells compared to static control. Conditioned medium collected from osteoclast cultures stimulated non-continuously or post-differentiation induced differentiation of osteoclast precursors plated in standard tissue culture plates. Extracellular signal-regulated kinase (ERK) phosphorylation was increased in mechanically-stimulated cultures compared to static control. Thus, low frequency mechanical stimulation has qualitatively different effects on osteoclast formation compared to stimulation associated with the fundamental frequencies of normal movement.     

Effects of electromagnetic fields of low frequency and low intensity on rat metabolism

A series of experiments on rats have been performed, to study the effects of long time (50 days) exposure to electromagnetic fields of extremely low frequency (ELF, i.e. less than 100 Hz) and amplitude (non thermal), testing whether the metabolic processes would be affected. The background lies on recent observations on the behaviour of isolated enzymes in vitro exposed to EFL fields. In these experiments, the cyclotron (or Larmor) frequency of the metallic ion has been used to "stimulate" the metalloproteins redox-active site, thus obtaining a clear variation of the enzyme functionality. In this paper we have extended for the first time the check to more complex animal metabolism. The novelty of this approach implies that a large amount of data had to be analyzed since it was not possible, in principle, to select only a few parameters among all the potential effects. Several biochemical parameters have been evaluated by comparing their values during the periods of exposure (field ON) and non exposure (field OFF). The evidence that long term exposure to electromagnetic fields with a well defined frequency may have relevant effects on parameters such as body weight, blood glucose and fatty acid metabolism has been obtained.     

The biological effect of extremely low frequency electromagnetic fields and vibrations on barley seed hydration and germination

The changes of wet and dry weights and germination of barley seed in different periods of its swelling in nontreated (control), extremely low frequency electromagnetic fields (ELF EMF) )-treated, and extremely low frequency vibrations (ELFV)-treated cold (4 degrees C) and warm (20 degrees C) distilled water (DW) were studied. The metabolic-dependent seed hydration, dry weight dissolving, germination, and water binding in seed were modulated by preliminary EMF- and ELFV-treated DW. Frequency "windows" for the effect of EMF and ELFV on seed hydration, solubility, water binding in seed, and germination were discovered. These "windows" were different for EMF and ELFV, as well as in various phases of seed swelling. It is suggested that EMF-induced water structure modification has a different biological effect on the process of seed hydration, solubility, water binding in seed, and germination compared to ELFV.     

Effects of extremely low frequency electromagnetic fields on membrane-associated enzymes

The effects of extremely low frequency electromagnetic fields of 75 Hz were studied on different membrane-associated enzymes. Only the activities of three enzymes out of seven exposed to the field decreased approximately of about 54-61% with field amplitudes above a threshold of 73-151 microT depending on the enzyme. The same field had no effect on the activities of either integral membrane enzymes such as Ca,ATPase, Na/K,ATPase, and succinic dehydrogenase or peripheral membrane enzymes such as photoreceptor PDE. The decrease in enzymatic activity of the field-sensitive enzymes was independent of the time of permanence in the field and was completely reversible. When these enzymes were solubilized with Triton, no effect of the field was obtained on the enzymatic activity, suggesting the crucial role of the membrane in determining the conditions for enzyme inactivation. The role of the particular linkage of the field-sensitive enzymes to the membranes is also discussed.     

Preliminary measurements of the sensitivity of the vibrissae of Harbour seals (Phoca vitulina) to low frequency vibrations

The sensitivity of the vibrissae of three Harbour seals ( Phoca vitulina ) to vibrations ranging between 50 and 1000 Hz was estimated using standard psychophysical techniques. Their vibrissae are relatively insensitive at the lower frequencies tested, however, vibrations which displaced the animal's whiskers by less than one micron were perceptible at 1000 Hz. Further preliminary tests indicated that the animals can use their vibrissae to perceive vibrations beyond this frequency. It is hypothesized that marine mammals can use their whiskers to detect the large amplitude water displacements propagated by objects vibrating at low frequencies. This ability would permit the animal to determine various properties of objects moving underwater without having to touch them.     

Effects of low frequency electromagnetic field on proliferation of human epidermal stem cells: An in vitro study

To investigate the effects of low frequency electromagnetic fields (EMF) on the proliferation of epidermal stem cells, human epidermal stem cells (hESC) were isolated, expanded ex vivo, and then exposed to a low frequency EMF. The test and control cells were placed under the same environment. The test cells were exposed for 30 min/day to a 5 mT low frequency EMF at 1, 10, and 50 Hz for 3, 5, or 7 days. The effects of low frequency EMF on cell proliferation, cell cycle, and cell‐surface antigen phenotype were investigated. Low frequency EMF significantly enhanced the proliferation of hESC in the culture medium in a frequency‐dependent manner, with the highest cell proliferation rate at 50 Hz (P < 0.05). Exposure to a low frequency EMF significantly increased the percentage of cells at the S phase of the cell cycle, coupled with a decrease in the percentage of cells in the G1 phase (P < 0.05) but the effect was not frequency dependent. The percentage of CD29⁺/CD71^? cells remained unchanged in the low frequency EMF‐exposed hESC. The results suggested that low frequency EMF influenced hESC proliferation in vitro, and this effect was related to the increased proportion of cells at the S phase. Bioelectromagnetics 34:74–80, 2013. © 2012 Wiley Periodicals, Inc.     

Effects of low frequency pulsed electrical current on keratinocytes in vitro

The effects of low frequency pulsed electrical current on epidermal repair in vitro were examined. Charge-balanced current stimuli proposed for chronic wound treatment were tested on skin keratinocytes cultured at an air-liquid interface on dead human dermis. Results imply that the balance between proliferation and differentiation in electrically treated samples is significantly modified in favor of differentiation. More advanced differentiation, shown through epidermal histology, was obtained in cultures exposed to electrical current, whereas the culture growth, the result of keratinocyte migration and proliferation, was greater in control samples. Bioelectromagnetics 18:250–254, 1997. © 1997 Wiley-Liss, Inc.     

Effects of UV-irradiation on the SCE frequency in human lymphocyte cultures

UV-irradiation (254 nm) was found to induce a smaller increase of SCE in human lymphocytes than in human fibroblasts and CHO cells. The UV-induced SCE frequency in human lymphocytes was not influenced by the duration between irradiation and the subsequent S-phase. UV-irradiated lymphocytes showed a slightly more than additive response to the SCE-inducing effect of HN2 and acetaldehyde in comparison with non-irradiated cells. The UV-induced SCE frequency was similar in lymphocyte cultures containing 20 and 100 microM of BrdUrd. The results suggest that human lymphocytes are relatively insensitive to the SCE-inducing effect of UV-irradiation, and that SCE-inducing damage caused by UV is not removed during the G1 phase in these cells.     

极低频电磁场对植物及人体细胞生长的影响

通过体外模拟一定强度的极低频电磁场对洋葱根尖分生组织细胞和人肺成纤维细胞分别处理不同时间后,采用根部生长量的测定、细胞增殖测定、荧光染色分析、单细胞凝胶电泳分析等方法对极低频电磁场的细胞生物效应进行了探讨;初步研究了极低频电磁场对细胞增殖分化、凋亡、DNA损伤等方面的影响。结果发现不同场强的电磁场对细胞增殖有明显影响,且与温度和处理时间有相关性。     

Effects of extremely low frequency (50 Hz) magnetic field on morphological and biochemical properties of human keratinocytes

We investigated the effects on human keratinocytes (HaCaT) of exposure to a sinusoidal magnetic field of 2 mT (50 Hz). These cells are a good model for studying interaction of nonionising radiation, because they are not shielded from fields in vivo and also because they are resistant to both mechanical and thermal stimuli. We performed scanning microscopy which showed modification in shape and morphology in exposed cells. This modification is related to differential actin distribution as revealed by phalloidin fluorescence analysis. Moreover, the exposed cells show increased clonogenic capacity, as well as increased cellular growth as showed by clonogenicity assays and growth curves. Indirect immunofluorescence analysis using a fluorescent antibody against involucrin and beta4 integrin, which are respectively differentiation and adhesion markers, revealed an increase of involucrin expression and segregation of beta4 integrin in the cell membrane in cells exposed to 50 Hz; a higher percentage of the exposed cells shows a modified pattern of adhesion and differentiation markers. We also present evidence that exposure of HaCaT cells can interfere with protein kinase activity. Our observations confirm the hypothesis that electromagnetic fields at 50 Hz may modify cell membrane morphology and interfere with initiation of the signal cascade pathway and cellular adhesion.     

Effects of extremely low frequency electromagnetic field on the health of workers in automotive industry

Objective. To observe the effects of extremely low frequency electromagnetic fields (ELF-EMFs) in automotive industry on occupational workers. Methods. A total of 704 workers were investigated, and 374 workers were chosen and divided into two groups (control group and exposure group) according to the inclusive criteria, namely male with age 20–40 years old and ≥ 2 years of exposure. The intensities of ELF-EMFs and noise were detected with EFA-300 Field Analyzer (Narda company, Pfullingen, Germany) and AWA5610D integrating sound level meter (Hangzhou Aihua Instruments Co., Ltd, Hangzhou, China), respectively. Survey data were collected by questionnaire, and the physical check-up was done in hospital. All the data were input into SPSS17.0 software (SPSS Inc, Chicago, USA), and the appropriate statistic analyses were carried out. Results. The intensity of EMFs in exposure group was significantly higher than that in control group (p < 0.05), while the noise in two workplaces showed no difference (p>0.05). The survey data collected by questionnaires showed that the symptoms of loss of hair in exposure group were significantly different as compared with that in control group (p < 0.05). The check-up parameters of cardiovascular, liver and hematology system showed significant differences between the two groups (p < 0.05). Conclusions. Survey and check-up data suggest that exposure to ELF-EMFs might have effects on the nervous, cardiovascular, liver, and hematology system of workers.     

极低频磁场对人肝癌细胞生长、代谢及细胞周期的影响

目的研究一定参数的极低频磁场对人肝癌细胞(SK-HEP-1)在诸多方面的影响。方法在整个SK-HEP-1细胞的培养周期中用50Hz,20mT的极低频磁场对其进行作用,并检测作用后细胞的增殖活性、生长动力学、代谢以及细胞周期的变化。结果50Hz,20mT的极低频磁场对SK-HEP-1细胞的生长与代谢有抑制作用,并能阻碍其有丝分裂的进行。结论50Hz,20mT的极低频磁场为治疗人类恶性肿瘤提供了一种可能的手段。     

极低频磁场对人肝癌细胞生长、代谢及细胞周期的影响

目的：研究一定参数的极低频磁场对人肝癌细胞（SK-HEP-1）在诸多方面的影响。方法：在整个SK-HEP-1细胞的培养周期中用50Hz,20mT的极低频磁场对其进行作用,并检测作用后细胞的增殖活性、生长动力学、代谢以及细胞周期的变化。结果：50Hz．20mT的极低频磁场对SK-HEP-1细胞的生长与代谢有抑制作用,并能阻碍其有丝分裂的进行。结论：50Hz,20mT的极低频磁场为治疗人类恶性肿瘤提供了一种可能的手段。     

Quaternary structures and low frequency molecular vibrations of haems of deoxy and oxyhaemoglobin studied by resonance Raman scattering

The influence of quaternary structure on the low frequency molecular vibrations of the haem within deoxyhaemoglobin (deoxy Hb) and Oxyhaemoglobin (oxy Hb) was studied by resonance Raman scattering. The FeO₂ stretching frequency was essentially identical between the high affinity (R) state (Hb A) and low affinity (T) state (Hb Kansas and Hb M Milwaukee with inositol hexaphosphate). However in deoxy Hb, only one of the polarized lines showed an appreciable frequency shift upon switch of quaternary structure, i.e. 215 to 218 cm^?1 for the T state (Hb A, des-His(146β) Hb, and des-Arg(141α) Hb (pH 6.5)) and 220 to 221 cm^?1 for the R state (des-Arg(141α) Hb (pH 9.0), des-His(146β)-Arg(141α) Hb and NES des-Arg(141α) Hb). Based on the observed ⁵⁴Fe isotopic frequency shift of the corresponding Raman lines of deoxy Hb A (214 → 217 cm^?1), of deoxy NES des-Arg Hb (220 → 223 cm^?1), of the protoporphyrinato-Fe(II)-(2-methylimidazole) complex in the ferrous high spin state (207 → 211 cm^?1) and of deoxymyoglobin (220 → 222 cm^?1) (Kitagawa et al., 1979), and on substitution of perdeuterated for protonated 2-methylimidazole in the deoxygenated picket fence complex (T_pivPP)Fe²⁺ (2-MeIm) (209 → 206 cm^?1), and on the results of normal co-ordinates calculation carried out previously, we proposed that the 216 cm^?1 line of deoxy Hb is associated primarily with the FeN_ε(HisF8) stretching mode and accordingly that the FeN_ε(HisF8) bond is stretched in the T state due to a strain exerted by globin.     

Effect of low frequency modulated microwave exposure on human EEG: individual sensitivity

The aim of this study was to evaluate the effect of modulated microwave exposure on human EEG of individual subjects. The experiments were carried out on four different groups of healthy volunteers. The 450 MHz microwave radiation modulated at 7 Hz (first group, 19 subjects), 14 and 21 Hz (second group, 13 subjects), 40 and 70 Hz (third group, 15 subjects), 217 and 1000 Hz (fourth group, 19 subjects) frequencies was applied. The field power density at the scalp was 0.16 mW/cm(2). The calculated spatial peak SAR averaged over 1 g was 0.303 W/kg. Ten cycles of the exposure (1 min off and 1 min on) at fixed modulation frequencies were applied. All subjects completed the experimental protocols with exposure and sham. The exposed and sham-exposed subjects were randomly assigned. A computer also randomly assigned the succession of modulation frequencies. Our results showed that microwave exposure increased the EEG energy. Relative changes in the EEG beta1 power in P3-P4 channels were selected for evaluation of individual sensitivity. The rate of subjects significantly affected is similar in all groups except for the 1000 Hz group: in first group 3 subjects (16%) at 7 Hz modulation; in second group 4 subjects (31%) at 14 Hz modulation and 3 subjects (23%) at 21 Hz modulation; in third group 3 subjects (20%) at 40 Hz and 2 subjects (13%) at 70 Hz modulation; in fourth group 3 subjects (16%) at 217 Hz and 0 subjects at 1000 Hz modulation frequency.