Effects of four kinds of electromagnetic fields (EMF) with different frequency spectrum bands on ovariectomized osteoporosis in mice.

Electromagnetic fields (EMF) was considered as a non-invasive modality for treatment of osteoporosis while the effects were diverse with EMF parameters in time domain. In present study, we extended analysis of EMF characteristics from time domain to frequency domain, aiming to investigate effects of four kinds of EMF (LP (1-100 Hz), BP (100-3,000 Hz), HP (3,000-50,000 Hz) and AP (1-50,000 Hz)) on ovariectomized (OVX) osteoporosis (OP) in mice. Forty-eight 3-month-old female BALB/c mice were equally assigned to Sham, OVX, OVX + LP, OVX + BP, OVX + HP and OVX + AP groups (n = 8). After 8-week exposure (3 h/day), LP and BP significantly increased serum bone formation markers and osteogenesis-related gene expressions compared with OVX. Bedsides, LP and BP also slightly increased bone resorption activity compared with OVX, evidenced by increased RANKL/OPG ratio. HP sharply decreased serum bone formation and resporption markers and osteogenesis and osteoclastogenesis related gene expressions compared with OVX. AP had accumulative effects of LP, BP and HP, which significantly increased bone formation and decreased bone resporption activity compared with OVX. As a result, LP, BP and HP exposure did not later deterioration of bone mass, microarchitecture and mechanical strength in OVX mice with OP. However, AP stimulation attenuated OVX-induced bone loss.

Effects of extremely low frequency pulsed magnetic fields on diabetic nephropathy in streptozotocin-treated rats.

BACKGROUND: Extremely low frequency pulsed magnetic fields (ELFPMF) have been shown to induce Faraday currents and measurable effects on biological systems. A kind of very high frequency electromagnetic field was reported that it improved the symptoms of diabetic nephropathy (DN) which is a major complication of diabetes. However, few studies have examined the effects of ELFPMF DN at the present. The present study was designed to investigate the effects of ELFPMF on DN in streptozotocin (STZ)-induced type 1 diabetic rats. METHODS: Adult male SD rats were randomly divided into three weight-matched groups: Control (non-diabetic rats without DN), DN + ELFPMF (diabetic rats with DN exposed to ELFPMF, 8 h/days, 6 weeks) and DN (diabetic rats with DN exposed to sham ELFPMF). Renal morphology was examined by light and electron microscopy, vascular endothelial growth factor (VEGF)-A and connective tissue growth factor (CTGF) were measured by enzyme linked immune sorbent assay. RESULTS: After 6 weeks' ELFPMF exposure, alterations of hyperglycemia and weight loss in STZ-treated rats with DN were not found, while both positive and negative effects of ELFPMF on the development of DN in diabetic rats were observed. The positive one was that ELFPMF exposure attenuated the pathological alterations in renal structure observed in STZ-treated rats with DN, which were demonstrated by slighter glomerular and tubule-interstitial lesions examined by light microscopy and slighter damage to glomerular basement membrane and podocyte foot processes examined by electron microscopy. And then, the negative one was that ELFPMF stimulation statistically significantly decreased renal expression of VEGF-A and statistically significantly increased renal expression of CTGF in diabetic rats with DN, which might partially aggravate the symptoms of DN. CONCLUSION: Both positive and negative effects of ELFPMF on the development of DN in diabetic rats were observed. The positive effect induced by ELFPMF might play a dominant role in the procession of DN in diabetic rats, and it is suggested that the positive effect should be derived from the correction of pathogenic diabetes-induced mediators.

Circadian rhythm affects the preventive role of pulsed electromagnetic fields on ovariectomy-induced osteoporosis in rats.

Pulsed electromagnetic fields (PEMF) have been proved effective in the prevention of osteoporosis both experimentally and clinically. Chronotherapy studies have shown that circadian rhythm (CR) played an important role in the occurrence, development and treatment of several diseases. CR has also been recognized as an essential feature of bone metabolism. Therefore, it is of therapeutic significance to investigate the impact of CR on the efficacy of PEMF in the prevention of osteoporosis. However, this issue has never been discussed previously. The objective of this study was to systematically evaluate the impact of CR on the preventive effect of PEMF on osteoporosis in rats. Thirty-two 3 month old female Sprague-Dawley rats were randomly divided into four different groups: sham-operated control (Sham), ovariectomy (OVX), OVX with PEMF stimulation in daytime (OVX+DPEMF) and OVX with PEMF stimulation in nighttime (OVX+NPEMF) groups. The OVX+DPEMF and OVX+NPEMF groups were subjected to daily PEMF exposure on the 2nd post-operative day, from 9:00 to 15:00, and 0:00 to 6:00, respectively. After 12 weeks, the OVX+DPEMF group presented better efficacy in prevention against OVX-induced bone loss and deterioration of trabecular bone architecture compared with the OVX+NPEMF group. This was evidenced by the increased levels of femoral bone mineral density, trabecular area percentage, trabecular thickness, trabecular number and decreased trabecular separation. Furthermore, the bone turnover biomarkers (serum alkaline phosphatase, serum bone Gla protein and urinary deoxypyridinoline) and the dynamic histomorphometric parameters reflecting the trabecular osteoblast and osteoclast activity (bone formation rate with bone volume as referent, osteoclast number, etc.) in the OVX+DPEMF group decreased to a larger extent compared with the OVX+NPEMF group. In conclusion, the results indicated that CR was an important factor determining the preventive effect of PEMF on osteoporosis and PEMF exposure in the daytime presented better stimulus efficacy in rats. The findings might be helpful for the efficacious use of PEMF mediations, evaluation of PEMF action and experimental design in the future studies of biological effect of electromagnetic fields.

Alimentary hyperlipemia of rabbits is affected by exposure to low-intensity pulsed magnetic fields.

An experimental study was carried out in rabbits to investigate the effects of exposing rabbits to low-intensity pulsed magnetic fields (PMFs) on alimentary hyperlipemia. Thirty female white big ear rabbits were randomly divided into three groups. The normal group was fed with a standard chow diet and the other two groups (hyperlipid and magnetic) were fed with the chow diet supplemented with cholesterol, yolk powder and lard. The magnetic group was exposed to 15 Hz pulsed magnetic fields. After 8 weeks, levels of blood lipid and indices of hemorheology were examined. In addition, histomorphologic changes of hepatic and myocardial tissues were compared across the groups respectively. Compared with the hyperlipid group, hemorheology indices of the magnetic group reduced significantly from 12.80% to 38.05% (P < 0.01) indicating lower blood viscosity. Similarly, compared with the hyperlipid group, the levels of total cholesterol and triglycerides in the magnetic group decreased 40.52% and 52.42% (P < 0.01). On the contrary, high density lipoprotein (HDL) value obviously increased 66.67% (P < 0.01). Furthermore, compared with the control group, the values of triglycerides and HDL of the magnetic group did not show statistical differences (P > 0.05). The deposit of fatty material on the inner lining of thoracic aorta wall of the magnetic group was significantly lighter than that of the hyperlipid group. Numerous aggregation of lipoids emerged among myocardial myofibrils in the hyperlipid group, while no notable change was found in both the magnetic and control group. The results indicate that low-intensity PMFs could be helpful for the treatment of alimentary hyperlipemia.