Decreased plasma levels of nitric oxide metabolites, angiotensin II, and aldosterone in spontaneously hypertensive rats exposed to 5 mT static magnetic field

Transcranial Magneto-Acoustic Stimulation Protects Synaptic Rehabilitation from Amyloid-Beta Plaques via Regulation of Microglial Functions

Transcranial magneto-acoustic stimulation (TMAS), which is characterized by high spatiotemporal resolution and high penetrability, is a non-invasive neuromodulation technology based on the magnetic-acoustic coupling effect. To reveal the effects of TMAS treatment on amyloid-beta (Aβ) plaque and synaptic plasticity in Alzheimer's disease, we conducted a comparative analysis of TMAS and transcranial ultrasound stimulation (TUS) based on acoustic effects in 5xFAD mice and BV2 microglia cells. We found that the TMAS-TUS treatment effectively reduced amyloid plaque loads and plaque-associated neurotoxicity. Additionally, TMAS-TUS treatment ameliorated impairments in long-term memory formation and long-term potentiation. Moreover, TMAS-TUS treatment stimulated microglial proliferation and migration while enhancing the phagocytosis and clearance of Aβ. In 5xFAD mice with induced microglial exhaustion, TMAS-TUS treatment-mediated Aβ plaque reduction, synaptic rehabilitation improvement, and the increase in phospho-AKT levels were diminished. Overall, our study highlights that stimulation of hippocampal microglia by TMAS treatment can induce anti-cognitive impairment effects via PI3K-AKT signaling, providing hope for the development of new strategies for an adjuvant therapy for Alzheimer's disease.

Effect of Magnetohydrodynamic on Cutaneous Wound Healing in Rat Model

Background: Exogenous electrical stimulation of the skin may mimic its endogenous bioelectric currents. In this study, a combination of direct current (DC) and magnetic field (MF) was investigated in the excision of the rat wound model. Methods: A circular wound was created on the posterior of the neck, and an electrode was fixed in the wound center. Rats were divided into sham, DC (600 µA), MF (~0.8 T), and magnet-direct current (MDC) groups. The study was conducted in 14 days with 20-min treatment daily. Results: The DC and MDC groups had higher healing percentages (P < 0.01) with mean differences of -13.42 and -15.63, respectively. Direct current on days 2, 5, and 6, and MDC on days 8, 9, 10, 11, 12, and 13 showed higher wound closing. In the DC-treated group, angiogenesis was improved on day 7. In MDC-treated rats, angiogenesis and fibroplasia were improved on day 13. The MF and MDC groups had lower granulation thicknesses on day 7. Granulation thickness increased on day 13 in the MF and MDC groups, while it decreased in the DC group. Direct current treatment improved healing in the first half of the study period, whereas MDC enhanced it in the second half, overtaking DC. From day 7, the magnet group started to overtake the control group slightly in the last four days. Conclusions: To accelerate wound healing, we suggest applying DC in the first days of wounding and MDC in the following days.

Electromagnetic Field as a Treatment for Cerebral Ischemic Stroke

Cerebral stroke is a leading cause of death and adult-acquired disability worldwide. To this date, treatment options are limited; hence, the search for new therapeutic approaches continues. Electromagnetic fields (EMFs) affect a wide variety of biological processes and accumulating evidence shows their potential as a treatment for ischemic stroke. Based on their characteristics, they can be divided into stationary, pulsed, and sinusoidal EMF. The aim of this review is to provide an extensive literature overview ranging from in vitro to even clinical studies within the field of ischemic stroke of all EMF types. A thorough comparison between EMF types and their effects is provided, as well as an overview of the signal pathways activated in cell types relevant for ischemic stroke such as neurons, microglia, astrocytes, and endothelial cells. We also discuss which steps have to be taken to improve their therapeutic efficacy in the frame of the clinical translation of this promising therapy.

Biological and health-related effects of weak static magnetic fields (≤ 1 mT) in humans and vertebrates: A systematic review

Background

There is a rapid development in technologies that generate weak static magnetic fields (SMF) including high-voltage direct current (HVDC) lines, systems operating with batteries, such as electric cars, and devices using permanent magnets. However, few reviews on the effects of such fields on biological systems have been prepared and none of these evaluations have had a particular focus on weak SMF (≤ 1 mT). The aim of this review was to systematically analyze and evaluate possible effects of weak SMF (≤ 1 mT) on biological functioning and to provide an update on the current state of research.

Methods

This review was prepared in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. Methodological limitations in individual studies were assessed using the Office of Health Assessment and Translation (OHAT) Risk-of-Bias Rating Tool.

Results

Eleven studies fulfilled the eligibility criteria and were included in this review. All included studies were experimental animal studies as no human studies were among the eligible articles. Eight of the eleven studies reported responses of rat, rabbits and quails to weak SMF exposure that were expressed as altered melatonin biosynthesis, reduced locomotor activity, altered vasomotion and blood pressure, transient changes in blood pressure-related biochemical parameters, or in the level of neurotransmitters and increases in enzyme activities. It remained largely unclear from the interpretation of the results whether the reported effects in the evaluated studies were beneficial or detrimental for health.

Conclusion

The available evidence from the literature reviewed is not sufficient to draw a conclusion for biological and health-related effects of exposure to weak SMF. There was a lack of homogeneity regarding the exposed biological systems and the examined endpoints as well as a lack of scientific rigor in most reviewed studies which lowered credibility in the reported results. We therefore encourage further and more systematic research in this area. Any new studies should particularly address effects of exposure to SMF on biological functioning in humans to evaluate whether SMF pose a risk to human health.

The impact of pulsed electromagnetic field therapy on blood pressure and circulating nitric oxide levels: a double blind, randomized study in subjects with metabolic syndrome

Purpose: Regulation of blood pressure (BP) is important in reducing the risk for cardiovascular disease. There is growing interest in non-pharmacological methods to treat BP including a novel approach using pulsed electromagnetic field therapy (PEMF). PEMF therapy has been proposed to impact physiological function at the cellular and tissue level and one possible mechanism is through an impact on endothelial function and nitric oxide (NO) related pathways. The focus of the present study was to evaluate the effect of PEMF on BP and NO in subjects with mild to moderate metabolic syndrome.Materials and methods: For 12 weeks, 23 subjects underwent PEMF therapy and 21 subjects underwent sham therapy. BP was measured at rest and near the end of submaximal exercise pre- and 12 week post-therapy. Additionally, plasma NO was measured at similar time points.Results: The PEMF demonstrated an increase in NO after therapy (p = .04) but SHAM did not (p = .37). For resting BP, there were no differences in systolic BP (SBP), diastolic BP (DBP) or mean arterial pressure (MAP) between groups (p > .05). During exercise, PEMF had a reduction in peak SBP (p = .04), but not SHAM (p = .57). PEMF demonstrated significant relationships between baseline SBP and change in SBP following therapy (r = -0.71, p < .01) and between MAP and change in MAP following therapy (r = -0.60, p < .01), but no such relationships were found in SHAM. Subjects with resting hypertension (SBP ≥140 mmHg) in PEMF (n = 11) had significant reductions in SBP, DBP and MAP when compared to SHAM with hypertension (n = 9) (p < .05). In this sub-group analysis, PEMF demonstrated lowered peak SBP (p = .04) at a given exercise load (p = .40) but SHAM did not (p > .05).Conclusion: PEMF may increase plasma NO availability and improve BP at rest and during exercise. However, this beneficial effect appears to be more pronounced in subjects with existing hypertension.

On the mechanism of the cell cycle control of suspension-cultured tobacco cells after exposure to static magnetic field

One of the main sites of the magnetic fields influence on living cells is the cell cycle. The intensity of this influence however, varies depending on the cell type and the duration of the treatment. Suspension of cultured tobacco cells (Nicotiana tabacum cv. Barley 21) were synchronized via sucrose starvation at their stationary growth phase. The cells were then exposed to 0.2 m T SMF up to 24 h. The progression of different cell cycle phases was monitored through flow cytometry in a time course manner. Expression of cell cycle controlling genes and amounts of certain signaling molecules were measured as well. Exposure to SMF delayed G1.S transition which was accompanied by decrease of cyclin-dependent kinases A (CDK A) and D-type cyclin, but an increase in the adenylyl cyclase (AC), transcription factor E2F, retinoblastoma protein (Rbp), and CDK-inhibitor protein 21 (p21) transcript accumulation. Exposure to SMF also increased the contents of nitric oxide (NO), hydrogen peroxide (H2O2), and salicylic acid (SA), compared to the control group. The results suggest a signaling pathway triggered by SMF starting from accumulation of NO and H2O2 followed by downstream events including the increase of cyclic nucleotides and subsequent decrease of both CDKA and CycD.

Static magnetic field reduces blood pressure short-term variability and enhances baro-receptor reflex sensitivity in spontaneously hypertensive rats

PURPOSE

It has been shown that chronic exposure of young spontaneously hypertensive rats (SHR) to static magnetic field (SMF) delays the development of overt hypertension. Therefore the aim of the present work was to investigate the effects of SMF on autonomic cardiovascular control in adult spontaneously hypertensive rats.

MATERIALS AND METHODS

Experiments were performed in freely moving spontaneously hypertensive rats equipped with femoral arterial catheter for blood pressure recording. Spontaneously hypertensive rats were exposed for 30 days to upward-oriented SMF (n = 17) or downward-oriented SMF (n = 17) of 16 mT intensity. A control group of spontaneously hypertensive rats (n = 17) was not exposed to SMF. Neurogenic cardiovascular control was evaluated by spectral analysis of arterial blood pressure and heart rate short-term variability and baro-receptor reflex sensitivity using the sequence method.

RESULTS

Exposure of spontaneously hypertensive rats to both upward- and downward-oriented SMF significantly reduced arterial blood pressure and enhanced baro-receptor reflex sensitivity. Downward-oriented SMF reduced heart rate, too. SMF of either orientation reduced systolic blood pressure variability in very low frequency domain while downward-oriented SMF also reduced low-frequency and increased high frequency domains.

CONCLUSION

It follows that prolonged exposure to SMF is beneficial for neurogenic cardiovascular control in hypertension.

Pulsed electromagnetic field therapy promotes healing and microcirculation of chronic diabetic foot ulcers: a pilot study

OBJECTIVE

To examine the effects of pulsed electromagnetic field (PEMF) therapy on promoting the healing and microcirculation of chronic diabetic foot ulcers.

DESIGN

A randomized, double-blind, placebo-controlled clinical trial on a homogenous subset of chronic diabetic foot ulcers.

SETTING

Hospital and university.

PATIENTS

Thirteen subjects (7 in the PEMF group and 6 in the control group) diagnosed with type 2 diabetes and had unsatisfactory healing of ulcer(s) in the preceding 4 weeks were recruited.

INTERVENTIONS

Subjects were randomly allocated to receive either active PEMF therapy (duration: 60 minutes; frequency: 12 Hz; intensity: 12 Gauss) or nonactive PEMF for 14 sessions within 3 weeks.

MAIN OUTCOME MEASURES

Assessment on wound closure, wound depth, and microcirculation were performed at the baseline, end of the treatment period, and 1-month follow-up.

MAIN RESULTS

By the end of the treatment period, there was an 18% decrease in wound size in the active PEMF group as compared with a 10% decrease in the control group. The PEMF group demonstrated significant cumulative increase in cutaneous capillary blood velocity (by 28%) and 14% increase in capillary diameter. In contrast, the control group showed a decrease in both capillary blood velocity and diameter.

CONCLUSION

In this study, PEMF therapy seemed to accelerate wound healing and improve microcirculation.

Pentoxifylline and electromagnetic field improved bone fracture healing in rats

Background

The aim of this study was to evaluate the effects of a phosphodiesterase inhibitor pentoxifylline (PTX), electromagnetic fields (EMFs), and a mixture of both materials on bone fracture healing in a rat model.

Materials and methods

Eighty male Wistar rats were randomly divided into four groups: Group A, femur fracture model with no treatment; Group B, femur fracture model treated with PTX 50 mg/kg/day intraperitoneal injection; Group C, femur fracture model treated with EMF 1.5±0.2 Mt/50 Hz/6 hours/day; and Group D, femur fracture model treated with PTX 50 mg/kg/day intraperitoneal injection and EMF 1.5±0.2 Mt/50 Hz/6 hours/day.

Results

Bone fracture healing was significantly better in Group B and Group C compared to Group A (P<0.05), but Group D did not show better bone fracture healing than Group A (P>0.05).

Conclusion

It can be concluded that both a specific EMF and PTX had a positive effect on bone fracture healing but when used in combination, may not be beneficial.

Increased vascular permeability in the circumventricular organs of adult rat brain due to stimulation by extremely low frequency magnetic fields

It has been demonstrated that the exposure of biological systems to magnetic fields (MFs) can produce several beneficial effects: tissue recovery in chronic wounds, re-establishment of blood circulation after tissue ischemia or in necrotic tissues, improvement after epileptic episodes, angiogenesis, etc. In the current study, the effects of extremely low frequency (ELF) MF on the capillaries of some circumventricular organs (CVOs) are demonstrated; a vasodilator effect is reported as well as an increase in their permeability to non-liposoluble substances. For this study, 96 Wistar male rats (250 g body mass) were used and divided into three groups of 32 rats each: a control group (no treatment); a sham ELF-MF group; and an experimental group subjected to ELF-MF (120 Hz harmonic waves and 0.66 mT, root mean square) by the use of Helmholtz coils. All animals were administered colloidal carbon (CC) intravenously to study, through optical and transmission electron microscopy, the capillary permeability in CVOs and the blood-brain barrier (BBB) in brain areas. An increase in capillary permeability to CC was detected in the ELF-MF-exposed group as well as a significant increase in vascular area (capillary vasodilation); none of these effects were observed in individuals of the control and sham ELF-MF groups. It is important to investigate the mechanisms involved in the phenomena reported here in order to explain the effects of ELF-MF on brain vasculature.

Strontium hexaferrite nanomagnets suspended in a cosmetic preparation: a convenient tool to evaluate the biological effects of surface magnetism on human skin

BACKGROUND/PURPOSE

Magnetic therapy has been popular for ages, but its therapeutic abilities remain to be demonstrated. We aimed to develop a homogeneous, stable dispersion of magnetic nanoparticles in a skin-care preparation, as a tool to analyze the biological and physiological effects of superficial magnetism in skin.

METHODS

SrFe(12)O(19) nanoparticles were generated by ultrasound, dispersed in glycerol, stabilized in Dermud cream and permanently magnetized. The magnetic cream was applied on the epidermis of human skin organ cultures. The effects on UV-induced cell toxicity, apoptosis and inflammatory cytokine expression were analyzed. A clinical test was performed to check skin moisturization.

RESULTS

Nanomagnets were found to be homogenously and stably dispersed. After magnetization, the preparation generated a magnetic field of 1-2 G. Upon cream application, no cytotoxicity and no impairment of cellular vitality were found after 24 and 48 h, respectively. The anti-apoptotic and anti-inflammatory properties of Dermud were not modified, but its long-term effect on moisturization in vivo was slightly increased.

CONCLUSION

Nanomagnetic Dermud cream can be used as a tool to analyze the biological effects of nanomagnets dispersed on the skin surface at the cellular and molecular levels, thus allowing to explore the possible therapeutic uses of superficial magnetism for skin care.

Extremely low frequency pulsed electromagnetic field designed for antinociception does not affect microvascular responsiveness to the vasodilator acetylcholine

A 225 microT, extremely low frequency, pulsed electromagnetic field (PEMF) that was designed for the induction of antinociception, was tested for its effectiveness to influence blood flow within the skeletal microvasculature of a male Sprague-Dawley rat model (n = 103). Acetylcholine (0.1, 1.0, or 10 mM) was used to perturb normal blood flow and to delineate differential effects of the PEMF, based on degree of vessel dilation. After both 30 and 60 min of PEMF exposure, we report no effects on peak perfusion response to acetylcholine (with only 0.2% of the group difference attributed to exposure). Spectral analysis of blood flow data was generated to obtain information related to myogenic activity (0.15-0.40 Hz), respiratory rate (0.4-2.0 Hz), and heart rate (2.0-7.0 Hz), including the peak frequency within each of the three frequency regions identified above, peak power, full width at half maximum (FWHM), and mean within band. No significant effects due to exposure were observed on myogenic activity of examined blood vessels, or on heart rate parameters. Anesthesia-induced respiratory depression was, however, significantly reduced following PEMF exposure compared to shams (although exposure only accounted for 9.4% of the group difference). This set of data suggest that there are no significant acute physiological effects of 225 microT PEMF after 30 and 60 min of exposure on peak blood flow, heart rate, and myogenic activity, but perhaps a small attenuation effect on anesthetic-induced respiratory depression.

Magnetic Field Therapy: A Review

There is increasing interest in using permanent magnets for therapeutic purposes encouraged by basic science publications and clinical reports. Magnetotherapy provides a non invasive, safe, and easy method to directly treat the site of injury, the source of pain and inflammation, and other types of disease. The physiological bases for the use of magnetic fields for tissue repair as well as physical principles of dosimetry and application of various magnetic fields are subjects of this review. Analysis of the magnetic and electromagnetic stimulation is followed by a discussion of the advantage of magnetic field stimulation compared with electric current and electric field stimulation.

Alteration of nitric oxide production in rats exposed to a prolonged, extremely low-frequency magnetic field

The purpose of this study is to investigate the possible effect of an extremely low-frequency magnetic field (ELF-MF) on nitric oxide (NO) level. In this study, 27 male Sprague-Dawley rats were used. The rats were divided into three groups: two experimental and one control (sham-exposed). The first and second experimental group (n = 10) were exposed to 100 microT and 500 microT ELF-MF during 10 months, 2 h a day, respectively, and the third (n = 7) group was treated like an experimental group except for ELF-MF exposure in methacrylate boxes. After ELF-MF and sham exposure, serum nitrite levels were measured by Griess reaction. A significant reduction was observed in nitrite levels among the first and second experimental groups of rats and sham-exposed rats after exposure for 10 months, 2 h a day, to ELF-MF of 100 and 500 microT (p < 0.01). These results suggest that prolonged ELF-MF exposure at intensities of exposure limits, determined by ICNIRP for public and occupational, may reduce NO production probably affected by NO generation pathways.

Chronic static magnetic field exposure alters microvessel enlargement resulting from surgical intervention

Magnetic field therapy has recently become a widely used complementary/alternative medicine for the treatment of vascular, as well as other musculoskeletal pathologies, including soft tissue injuries. Recent studies in our laboratory and others have suggested that acute static magnetic field (SMF) exposure can have a modulatory influence on the microvasculature, acting to normalize vascular function; however, the effect of chronic SMF exposure has not been investigated. This study aimed to measure, for the first time, the adaptive microvascular response to a chronic 7-day continuous magnetic field exposure. Murine dorsal skinfold chambers were applied on day 0, and neodymium static magnets (or size and weight-matched shams) were affixed to the chambers at day 0, where they remained until day 7. Separate analysis of arteriolar and venular diameters revealed that chronic SMF application significantly abrogated the luminal diameter expansion observed in sham-treated networks. Magnet-treated venular diameters were significantly reduced at day 4 and day 7 (34.3 and 54.4%, respectively) compared with sham-treated vessels. Arteriolar diameters were also significantly reduced by magnet treatment at day 7 (50%), but not significantly at day 4 (31.6%), although the same trend was evident. Venular functional length density was also significantly reduced (60%) by chronic field application. These results suggest that chronic SMF exposure can alter the adaptive microvascular remodeling response to mechanical injury, thus supporting the further study of chronic application of SMFs for the treatment of vascular pathologies involving the dysregulation of microvascular structure.

A literature review: The effects of magnetic field exposure on blood flow and blood vessels in the microvasculature

The effect of magnetic field (MF) exposure on microcirculation and microvasculature is not clear or widely explored. In the limited body of data that exists, there are contradictions as to the effects of MFs on blood perfusion and pressure. Approximately half of the cited studies indicate a vasodilatory effect of MFs; the remaining half indicate that MFs could trigger either vasodilation or vasoconstriction depending on initial vessel tone. Few studies indicate that MFs cause a decrease in perfusion or no effect. There is a further lack of investigation into the cellular effects of MFs on microcirculation and microvasculature. The role of nitric oxide (NO) in mediating microcirculatory MF effects has been minimally explored and results are mixed, with four studies supporting an increase in NO activity, one supporting a biphasic effect, and five indicating no effect. MF effects on angiogenesis are also reported: seven studies supporting an increase and two a decrease. Possible reasons for these contradictions are explored. This review also considers the effects of magnetic resonance imaging (MRI) and anesthetics on microcirculation. Recommendations for future work include studies aimed at the cellular/mechanistic level, studies involving perfusion measurements both during and post-exposure, studies testing the effect of MFs on anesthetics, and investigation into the microcirculatory effects of MRI.

Effects of 12 mT static magnetic field on sympathetic agonist-induced hypertension in wistar rats

We investigated the combined effects of a moderate-intensity static magnetic field (SMF) and two different sympathetic agonists, an alpha(1)-adrenoceptor agonist, phenylephrine and a beta(1)-adrenoceptor agonist, dobutamine, which induced hypertension and different hemodynamics in Wistar rats. Five-week-old male rats were continuously exposed to the SMF intensity of 12 mT (B(max)) with the peak spatial gradient of 3 mT/mm for 10 weeks. A loop-shaped flexible rubber magnet was adjusted to fit snugly around the neck region of a rat (diameter-adjustable to an animal size). Sham exposure was performed using a dummy magnet. Six experimental groups of six animals each were examined: (1) sham exposure with intraperitoneal (ip) saline injection (control); (2) SMF exposure with ip saline injection (SMF); (3) sham exposure with ip phenylephrine (1.0 microg/g) injection (PE); (4) SMF exposure with ip phenylephrine injection (SMF + PE); (5) sham exposure with ip dobutamine (4.0 microg/g) injection (DOB); (6) SMF exposure with ip dobutamine injection (SMF + DOB). Fifteen minutes after the injection of each agent, the first set of parameters, arterial blood pressure (BP) and heart rate (HR), the second set of parameters, skin blood flow (SBF) and skin blood velocity (SBV), or the third set of parameters, the number of rearing (exploratory behavior) responses and body weight was monitored. Each agent was administered three times a week for 10 weeks, and each set of parameters was monitored on different days, once a week. The dose of phenylephrine significantly increased BP and decreased HR, SBF, SBV, and the number of rearing responses in the PE group compared with those in the respective age-matched control group. The dose of dobutamine significantly increased BP and HR, increased SBF, SBV, and the number of rearing responses in the DOB group compared with those in the control group. Continuous neck exposure to the SMF alone for up to 10 weeks induced no significant changes in any of the measured cardiovascular and behavioral parameters. The SMF exposure for at least 2 weeks (1) significantly depressed phenylephrine effects on BP, SBF, SBV, and rearing activity (SMF + PE group vs. PE group); (2) significantly depressed dobutamine effects on BP, SBF, and SBV, and suppressed dobutamine-induced increase in the rearing activity (SMF + DOB group vs. DOB group). These results suggest that continuous neck exposure to 12 mT SMF for at least 2 weeks may depress or suppress sympathetic agonists-induced hypertension, hemodynamics, and behavioral changes by modulating sympathetic nerve activity.

Effects of a moderate-intensity static magnetic field on VEGF-A stimulated endothelial capillary tubule formation in vitro

Effects of a moderate-intensity static magnetic field (SMF) on the early-stage development of endothelial capillary tubule formation were examined during the initial cell growth periods using co-cultured human umbilical vein endothelial cells and human diploid fibroblasts. The co-cultured cells within a well (16 mm in diameter) were exposed to SMF intensity up to 120 mT (Bmax) with the maximum spatial gradient of 21 mT/mm using a disc-shaped permanent magnet (16 mm in diameter and 2.5 mm in height) for up to 10 days. Control exposure was performed without magnet. Some vascular endothelial cells were treated with vascular endothelial growth factor (VEGF)-A (10 ng/ml) to promote the tubule formation every 2-3 days. Four experimental protocols were performed: (1) non-exposure (control); (2) SMF exposure alone; (3) non-exposure with VEGF-A; (4) SMF exposure with VEGF-A. Photomicrographs of tubule cells immunostained with an anti-platelet-endothelial cell adhesion molecule-1 (PECAM-1 [CD31[) antibody as a pan-endothelial marker, were analyzed after culture at 37 degrees C for 4, 7, and 10 days. The mean values of the area density and the length of tubules (related mainly to arteriogenesis) as well as the number of bifurcations (related mainly to angiogenesis) were determined as parameters of tubule formation and were compared between the groups. After a 10 day incubation, in the peripheral part of the culture wells, SMF alone significantly promoted the tubule formation in terms of the area density and the length of tubules, compared with control group. In the central part of the wells, however, SMF did not cause any significant changes in the parameters of tubule formation. After a 7 day incubation, VEGF-A significantly promoted all the parameters of tubule formation in any part of the wells, compared with control group. With regard to the synergistic effects of SMF and VEGF-A on tubule formation, after a 10 day incubation, SMF significantly promoted the VEGF-A-increased area density and length of tubules in the peripheral part of the wells, compared with the VEGF-A treatment alone. However, SMF did not induce any significant changes in the VEGF-A-increased number of bifurcations in any part of the wells. The tubule cells observed in the wells had elongated, spindle-like shapes, and the direction of cell elongation was random, irrespective of the presence and direction of SMF. These findings suggest that the application of SMF to intact or VEGF-A-stimulated vascular endothelial cells leads mainly to promote or enhance arteriogenesis in the peripheral part of the wells, where the spatial gradient increases relative to the central part. The effects of SMF on the VEGF-A-enhanced tubule formation appear to be synergistic or additive in arteriogenesis but not in angiogenesis.

Effects of neck exposure to 5.5 mT static magnetic field on pharmacologically modulated blood pressure in conscious rabbits

Static magnetic fields (SMF) in the millitesla (mT) range have been reported to modulate microcirculatory hemodynamics and/or blood pressure (BP) under pharmacologically modified state in mammals. This study was designed to investigate the acute effects of local application of a SMF to neck or pelvic region under pharmacologically modulated BP; norepinephrine (NE)-induced hypertension as well as an L-type voltage-gated Ca(2+) channel blocker, nicardipine (NIC)-induced hypotension in conscious rabbits. Magnetic flux densities were up to 5.5 mT and the spatial magnetic gradient peaked in neck (carotid sinus baroreceptor) region at the level of approximately 0.06 mT/mm. The duration of exposure was 30 min (including 10 min of pretreatment) and the effects on BP were investigated up to 100 min postexposure. Baroreflex sensitivity (BRS) was estimated from invasive recordings of systolic BP and pulse interval. Neck exposure to 5.5 mT significantly attenuated the pharmacologically induced vasoconstriction or vasodilation, and subsequently suppressed the increase or decrease in BP compared with sham exposure. In contrast, pelvic exposure to 5.5 mT did not significantly antagonized NE-elevated BP or NIC-reduced BP. The neck exposure to 5.5 mT has a biphasic and restorative effect on vascular tone and BP acting to normalize the tone and BP. The neck exposure to 5.5 mT caused a significant increase in BRS in NE-elevated BP compared with sham exposure. The buffering effects of the SMF on increased hemodynamic variability under NE-induced high vascular tone and NIC-induced low vascular tone might be, in part, dependent on baroreflex pathways, which could modulate NE-mediated response in conjunction with Ca(2+) dynamics.

Exposure to a moderate intensity static magnetic field enhances the hypotensive effect of a calcium channel blocker in spontaneously hypertensive rats

We investigated the combined effects of a moderate intensity static magnetic field (SMF) and an L-type voltage-gated Ca(2+) channel blocker, nicardipine in stroke-resistant spontaneously hypertensive rats during the development of hypertension. Five-week-old male rats were exposed to SMF intensity up to 180 mT (B(max)) with a peak spatial gradient of 133 mT/mm for 14 weeks. Four experimental groups of 14 animals each were examined: (1) sham exposure with intraperitoneal (ip) saline injection (control); (2) SMF exposure with ip saline injection (SMF); (3) sham exposure with ip nicardipine injection (NIC); (4) SMF exposure with ip nicardipine injection (SMF + NIC). A disc-shaped permanent magnet or a dummy magnet was implanted in the vicinity adjacent to the left carotid sinus baroreceptor region in the neck of each rat. Nicardipine (2 mg/kg ip) was administered three times a week for 14 weeks, and then 15 min after each injection, arterial blood pressure (BP), heart rate (HR), baroreflex sensitivity (BRS), skin blood flow (SBF), skin blood velocity (SBV), plasma nitric oxide (NO) metabolites (NO(x) = NO(2) (-) + NO(3) (-)), plasma catecholamine levels and behavioral parameters of a functional observational battery were monitored. The action of nicardipine significantly decreased BP, and increased HR, SBF, SBV, plasma epinephrine and norepinephrine in the NIC group compared with the control respective age-matched group without changing plasma NO(x) levels. Neck exposure to SMF alone for 5-8 weeks significantly suppressed or retarded the development of hypertension together with increased BRS in SMF group. Furthermore, the exposure to SMF for 1-8 weeks significantly promoted the nicardipine-induced BP decrease in the SMF + NIC group compared with the respective NIC group. Moreover, the SMF induced a significant increase in plasma NO(x) in the nicardipine-induced hypotension. There were no significant differences in any of the physiological or behavioral parameters measured between the SMF + NIC and the NIC groups, nor between the SMF and the control groups. These results suggest that the SMF may enhance nicardipine-induced hypotension by more effectively antagonizing the Ca(2+) influx through the Ca(2+) channels compared with the NIC treatment alone. Furthermore, the enhanced antihypertensive effects of the SMF on the nicardipine-treated group appear to be partially related to the increased NO(x). Theoretical considerations suggest that the applied SMF (B(max) 40 mT, 0 Hz) can be converted into a changing magnetic field (B(max) 30-40 mT, 5.7-6.5 Hz or 7.5-8.3 Hz) in the baroreceptor region by means of the carotid artery pulsation. Therefore, we propose that the moderate intensity changing magnetic field, i.e., the magnetic field modulated by the pulse rate, may influence the activity of baroreceptor and baroreflex function.