Biomedical subjects

Shoogo Ueno

Publications and source records attributed to Shoogo Ueno.

At least 19 recordsLinked to original sources

PubMed2006

Effects of pulsed magnetic stimulation on tumor development and immune functions in mice.

We investigated the effects of pulsed magnetic stimulation on tumor development processes and immune functions in mice. A circular coil (inner diameter = 15 mm, outer diameter = 75 mm) was used in the experiments. Stimulus conditions were pulse width = 238 micros, peak magnetic field = 0.25 T (at the center of the coil), frequency = 25 pulses/s, 1,000 pulses/sample/day and magnetically induced eddy currents in mice = 0.79-1.54 A/m(2). In an animal study, B16-BL6 melanoma model mice were exposed to the pulsed magnetic stimulation for 16 days from the day of injection of cancer cells. A tumor growth study revealed a significant tumor weight decrease in the stimulated group (54% of the sham group). In a cellular study, B16-BL6 cells were also exposed to the magnetic field (1,000 pulses/sample, and eddy currents at the bottom of the dish = 2.36-2.90 A/m(2)); however, the magnetically induced eddy currents had no effect on cell viabilities. Cytokine production in mouse spleens was measured to analyze the immunomodulatory effect after the pulsed magnetic stimulation. tumor necrosis factor (TNF-alpha) production in mouse spleens was significantly activated after the exposure of the stimulus condition described above. These results showed the first evidence of the anti-tumor effect and immunomodulatory effects brought about by the application of repetitive magnetic stimulation and also suggested the possible relationship between anti-tumor effects and the increase of TNF-alpha levels caused by pulsed magnetic stimulation.

Animals↗

PubMed2006

Cleavage and survival of Xenopus embryos exposed to 8 T static magnetic fields in a rotating clinostat.

In this study, we examined cleavage and survival of fertilized Xenopus embryos exposed to 8 T static magnetic fields (SMFs). We investigated fertilized Xenopus embryos exposed to magnetic field either in static chamber or in a rotating culture system. Our results showed that the exposure to the strong magnetic field of 8 T changed the third cleavage furrow from the usual horizontal one to a perpendicular one; however, when the direction of gravity was randomized by exposing embryos to magnetic field in a rotating culture system, the third cleavage furrow were formed horizontally, a finding which suggests that the observed distortion of the third cleavage furrow in magnetism-exposed embryos was accomplished by altering gravity effects which were elicited by diamagnetic force due to high gradient magnetic field. Our results also showed that the exposure to the strong magnetic field did not damage survival. These results demonstrate that SMF and altering gravity cause distortion of the third cleavage furrow and show that effects of exposing cleavage embryos to magnetic field were transient and did not affect the post-cleavage development. We also showed that strong magnetic field is not hazardous to the cleavage and blastula-gastrula transition of developing embryonic cells.

Animals↗

PubMed2006

Retrograde cerebral perfusion with intermittent pressure augmentation provides adequate neuroprotection: diffusion- and perfusion-weighted magnetic resonance imaging study in an experimental canine model.

OBJECTIVE: Diffusion- and perfusion-weighted magnetic resonance imaging can identify ischemic brain injury in the hyperacute stage. For neuroprotection during thoracic aortic surgery, we developed a novel retrograde cerebral perfusion with intermittent pressure augmentation. The purpose of this study was to assess the efficiency of this novel method for neuroprotection in real time by using diffusion- and perfusion-weighted magnetic resonance imaging. METHODS: Sixteen beagle dogs were randomly divided into 4 groups: the antegrade selective cerebral perfusion group (n = 4; antegrade selective cerebral perfusion at a flow rate of 10 mL x kg(-1) x min(-1)); the intermittent retrograde cerebral perfusion group (n = 4; retrograde cerebral perfusion at a baseline pressure of 15 mm Hg with intermittent pressure augmentation to 45 mm Hg every 30 seconds); the conventional retrograde cerebral perfusion group (n = 4; conventional retrograde cerebral perfusion at a fixed pressure of 25 mm Hg); and the circulatory arrest group (n = 4; only circulatory arrest). Diffusion- and perfusion-weighted magnetic resonance images were acquired during each session of cerebral perfusion. Regions of interest were defined, and the apparent diffusion coefficient and relative regional cerebral blood volume were calculated in these regions of interest. Finally, the brain was evaluated for its histopathologic damage score. RESULTS: The best apparent diffusion coefficient values were observed in the intermittent retrograde cerebral perfusion group in all the regions of interest, although the relative regional cerebral blood volume values were mostly lower than those in the antegrade selective cerebral perfusion group. The total Histopathologic Damage Score (0, normal; 32, worst) in the intermittent retrograde cerebral perfusion group (8.0 +/- 0.6) was significantly lower than that in the conventional retrograde cerebral perfusion (17.5 +/- 1.7; P < .01) and circulatory arrest (25 +/- 1.0; P < 0.01) groups and was equivalent to that in the antegrade selective cerebral perfusion group (7.8 +/- 0.8; P = .9). CONCLUSION: Intermittent retrograde cerebral perfusion provides adequate neuroprotection by allowing high apparent diffusion coefficient values to be maintained.

Animals↗

PubMed2006

The state of the art of nanobioscience in Japan.

This paper reviews a part of the state of the art of nanobioscience in Japan. The importance of combination and integration of interdisciplinary principles is emphasized for the development of nanobioscience. Biomagnetics, biomechanics, nanomachining, self-replicating cell model, neuronal network, drug delivery system, and tissue engineering are discussed.

Biological Science Disciplines↗

PubMed2006

Estimation of membrane permeability and intracellular diffusion coefficients.

We propose a method for estimating membrane permeability and the intracellular diffusion coefficient using pulsed-gradient spin-echo measurement in combination with numerical simulation. The diffusion signal attenuation of leukocytes was measured with 4pi(2)q(2)(Delta-delta/3) values up to 6000 s/mm(2). For numerical simulations, the cell was modeled as a 15 x 15 microm(2) square with various membrane permeabilities and intracellular diffusion coefficients. Minimization of the difference in signal attenuations between the measurement and the simulation enabled estimations of these unknown parameters for the leukocytes. A cell sample of 2.17 x 10(8) cells/mL had a membrane permeability and an intracellular diffusion coefficient of 23 mum/s and 8.9 x 10(-4) mm(2)/s, respectively.

Cell Membrane Permeability↗

PubMed2005

Evaluation of diffusional anisotropy and microscopic structure in skeletal muscles using magnetic resonance.

The pulsed-gradient spin-echo (PGSE) nuclear magnetic resonance (NMR) method is used for detecting the diffusion of water molecules in biological tissues. Because tissues generally have diffusional anisotropy, their diffusion properties are denoted by a tensor. In this study, we evaluated the diffusional anisotropy and microscopic structure in atrophied skeletal muscles using the PGSE NMR method. The left sciatic nerve was severed in twelve 9-week-old rats. Neurotomy caused neurogenic muscular atrophy at the left gastrocnemius. At 2, 4 and 8 weeks after neurotomy, magnetic resonance signals were selectively acquired from a 2 x 2 x 2 mm(3) voxel, which was located on the left gastrocnemius. The diffusion tensor, the mean diffusivity (MD) and the fractional anisotropy (FA) were calculated from the signals. A theoretical model of the diffusion in muscles was derived from Tanner's equation. The muscle fiber diameter was estimated by fitting the model to the measured signals. The measurements were also performed for normal rats as controls. No significant difference was found in the MD and the estimated intracellular diffusion coefficient between the control group and the denervated group. The denervated group had significantly higher FA compared with the control group (P<.05). The estimated muscle fiber diameter of the denervated group was significantly smaller than the estimated value of the control group (P<.05). These differences were found at 8 weeks after neurotomy. The proposed method is effective for evaluating changes in the microscopic structure of skeletal muscles.

Analysis of Variance↗

PubMed2005

Acquisition of ischemic tolerance by repetitive transcranial magnetic stimulation in the rat hippocampus.

We investigated the acquisition of ischemic tolerance in the rat hippocampus using repetitive transcranial magnetic stimulation (rTMS). Rats received 1000 pulses/day for 7 days, and the field excitatory postsynaptic potentials were measured in the hippocampal CA1. After slices were exposed to ischemic conditions, long-term potentiation (LTP) was induced. The LTP of the stimulated group was enhanced compared with the LTP of the sham control group in each ischemic condition, suggesting that rTMS has the potential to protect hippocampal function from ischemia.

Animals↗

PubMed2005

Micropatterning of cells using modulated magnetic fields.

A new technique of cell micropatterning was presented. Mouse osteoblast cells (MC3T3-E1) were seeded on a substrate whose surface was exposed to a periodically modulated magnetic field (a line pattern with a 200- or 600-microm pitch) produced by a field modulator inserted into a homogeneous magnetic field of 1 T generated by an electromagnet. The cells were trapped consistent with the line profile of the modulated field. The trapping efficiency was enhanced by adding Mn(II)EDTA (paramagnetic) to the cultivation medium. The cells were subsequently incubated in the magnetic field. The same technique was applied to whole blood to pattern red blood cells.

3T3 Cells↗

PubMed2005

Short term exposure to 1439 MHz pulsed TDMA field does not alter melatonin synthesis in rats.

The widespread use of the mobile phone has initiated many studies on the possible adverse effects of a high frequency electromagnetic field (EMF), which is used in mobile phones. A low frequency EMF is reported to suppress melatonin synthesis. The aim of this study was to clarify the effects on melatonin synthesis in rats after short term exposure to a 1439 MHz time division multiple access (TDMA) EMF. The average specific absorption ratio (SAR) of the brain was 7.5 W/kg, and the average SARs of the whole body were 1.9 and 2.0 W/kg for male and female rats, respectively. A total of 208 male and female rats were investigated. After acclimatization to a 12 h light-dark (LD) cycle, serum and pineal melatonin levels together with pineal serotonin level under a dark condition (less than 1 lux) were examined by radioimmunoassay. No significant differences in melatonin and serotonin levels were observed between the exposure, sham, and cage control groups. These results suggest that short term exposure to a 1439 MHz TDMA EMF, which is about four times stronger than that emitted by mobile phones, does not alter melatonin and serotonin synthesis in rats. Further investigations on the effects of long term exposure are warranted.

Animals↗

PubMed2004

Strong static magnetic field effects on yeast proliferation and distribution.

The present study focuses on the effects of gradient magnetic fields on the behavior of yeast, such as its proliferation and mass distribution, and evaluates the effects of magnetism on materials in the yeast culture system. Yeast, Saccharomyces cerevisiae, was incubated in a liquid medium under magnetic fields (flux density B = 14 T). When yeast in a tube was exposed to 9-14 T magnetic fields with a maximum flux density gradient of dB/dx = 94 T/m, where x is the space coordinate, the rate of yeast proliferation under the magnetic fields decreased after 16 h of incubation compared to that of the control group. The physical properties of the yeast culture system were investigated to discover the mechanism responsible for the observed deceleration in yeast proliferation under magnetic fields. Gas pressure inside the yeast culture flask was compared with and without exposure to a magnetic field. The results suggested that the gas pressure inside a flask with 6 T, 60 T/m slowly increased in comparison to the pressure inside a control tube. Due to the diamagnetism of water (medium solution) and yeast, the liquid surface distinctly inclined under gradient magnetic fields, and the hydrostatic force in suspension was strengthened by the diamagnetic forces. In addition, magnetophoresis of the yeast cells in the medium solution exhibited localization of the yeast sedimentation pattern. The roles of magnetically changed gas-transport processes, hydrostatic pressures acting on the yeast, and changes in the distribution of the yeast sedimentation, as well as the possible effects of magnetic fields on yeast respiratory systems in the observed disturbance of the proliferation are discussed.

Cell Proliferation↗

PubMed2004

Dominance of the left oblique view in activating the cortical network for face recognition.

Faces in portraits are often depicted from the left 3/4 view (an oblique view of the face that is intermediate between the frontal view and left profile). Here, we used functional magnetic resonance imaging (fMRI) to show that, compared with photographs of right 3/4 views of familiar faces, photographs of left 3/4 views of the same faces elicited stronger neural responses in the right middle occipital/inferior parietal cortex, and right inferior frontal gyrus; which are known to be involved in face recognition. By contrast, there was no differential activation in the temporal cortex including the superior temporal sulcus and fusiform gyrus, which are thought to process face-related visual stimuli at a stage that precedes recognition. We suggest that the preference for the left 3/4 view of faces was produced at a later stage of facial information processing that involves attention or memory retrieval.

Adult↗

PubMed2004

Genotoxic effects of strong static magnetic fields in DNA-repair defective mutants of Drosophila melanogaster.

To assess the possibility that strong static magnetic fields cause DNA damage and mutation, we examined the genotoxic effects of magnetic field exposure by using the somatic mutation and recombination test system in DNA repair-proficient and -deficient strains of Drosophila melanogaster. A postreplication repair-defective mutation mei-41D5 and/or a nucleotide excision repair-defective mutation mei-9(a) was introduced into the conventional loss of the heterozygosity assay system by the use of mwh +/ + flr transheterozygotes, and were exposed to static magnetic fields of up to 14 Tesla (T). We found that exposure to 2, 5, or 14 T fields for 24 h caused a statistically significant enhancement in somatic recombination frequency in the postreplication repair-deficient flies, whereas the frequency remained unchanged in the nucleotide excision repair-deficient flies and in the DNA repair-proficient flies after exposure. An increase linearly dependent on the flux density was observed between 0.5 T and 2 T, but it was saturated at exposure levels over 2 T. These findings suggest that exposure to high-density magnetic fields induce somatic recombination in Drosophila and that the dose-response relationship is not linear.

Animals↗

PubMed2004

Dependence of the spin-spin relaxation time of water in collagen gels on collagen fiber directions.

In this study, we investigated the effect of structural differences in collagen fibers in relation to the spin-spin (T2) relaxation time of surrounding water molecules. We propose a simple experimental model of the magic angle effect based on magnetically oriented collagen gels. Experiments were performed with a 4.7T magnetic resonance imaging (MRI) system with a quadrature radio frequency coil operated at 200 MHz for 1H resonance. Collagen gels were polymerized from collagen solutions exposed to a 4.7T magnetic field for 120 min. The T2 relaxation time was measured with the Carr-Purcell-Meiboom-Gill (CPMG) sequence. The apparent diffusion coefficient (ADC) was measured with the stimulated echo acquisition mode (STEAM) sequence with a motion-probing gradient (MPG). Orienting the collagen fibers at an angle of about 55 degrees to the main magnetic field caused an increase in the T2 relaxation times of water molecules in the collagen gels. The ADC in the direction parallel to the fibers was larger than that in the direction perpendicular to the fibers. The increase in the T2 relaxation time and ADC are attributed to a change in the magnetic interaction between the water molecules and collagen fibers.

Anisotropy↗

PubMed2004

Detection of weak magnetic fields induced by electrical currents with MRI: theoretical and practical limits of sensitivity.

Detection of weak magnetic fields induced by neuronal electrical activities with magnetic resonance imaging (MRI) is a potentially effective method for functional imaging of the brain. In this study, we compared the theoretical and practical limits of sensitivity for detecting weak magnetic fields with a columnar phantom. The theoretical limit of sensitivity was estimated from signal and noise intensities in magnetic resonance images. The theoretical limit of sensitivity was approximately 10(-8)T. The practical limit was 10 times the theoretical limit. The dependence of the theoretical limit of sensitivity on acquisition parameters, such as the repetition time (TR), echo time (TE), number of pixels, and spectral width, was quantitatively evaluated. The results indicated the existence of an optimal value in T(E)/T2*.

Brain Mapping↗

PubMed2003

The effect of repetitive transcranial magnetic stimulation on long-term potentiation in rat hippocampus depends on stimulus intensity.

We investigated the effect of repetitive transcranial magnetic stimulation (rTMS) on long-term potentiation (LTP) in the rat hippocampus. Rats were magnetically stimulated at a rate of 1000 pulses/day for 7 days by a round coil, in which the peak magnetic fields at the center of the coil were 0.75 and 1.00 T. LTP enhancement was observed only in the 0.75-T rTMS group, while no change was observed in the 1.00-T rTMS group. These results suggest that the effect of rTMS on LTP depends on the stimulus intensity.

Animals↗

PubMed2003

Control of orientation of rat Schwann cells using an 8-T static magnetic field.

Schwann cells aid in neuronal regeneration in the peripheral nervous system via guiding the regrowth of axons. In this study, we investigated the magnetic orientation of Schwann cells, and of a mixture of Schwann cells and collagen, after an 8-tesla magnetic field exposure. We obtained cultured Schwann cells from dissected sciatic nerves of neonatal rats. After 60 h of magnetic field exposure, Schwann cells oriented parallel to the magnetic fields. In contrast, the mixture of Schwann cells and collagen, Schwann cells oriented in the direction perpendicular to the magnetic field after 2 h of magnetic field exposure. In this case, Schwann cells aligned along the collagen fiber oriented by magnetic fields. The magnetic control of Schwann cell alignment is useful in medical engineering applications such as nerve regeneration.

Animals↗

PubMed2003

1439 MHz pulsed TDMA fields affect performance of rats in a T-maze task only when body temperature is elevated.

This study sought to clarify the effects of exposure to electromagnetic waves (EMW) used in cellular phones on learning and memory processes. Sprague-Dawley rats were exposed for either 1 h daily for 4 days or for 4 weeks to a pulsed 1439 MHz time division multiple access (TDMA) field in a carousel type exposure system. At the brain, average specific absorption rate (SAR) was 7.5 W/kg, and the whole body average SAR was 1.7 W/kg. Other subjects were exposed at the brain average SAR of 25 W/kg and the whole body average SAR of 5.7 W/kg for 45 min daily for 4 days. Learning and memory were evaluated by reversal learning in a food rewarded T-maze, in which rats learned the location of food (right or left) by using environmental cues. The animals exposed to EMW with the brain average SAR of 25 W/kg for 4 days showed statistically significant decreases in the transition in number of correct choices in the reversal task, compared to sham exposed or cage control animals. However, rats exposed to the brain average SAR of 7.5 W/kg for either 4 days or for 4 weeks showed no T-maze performance impairments. Intraperitoneal temperatures, as measured by a fiber optic thermometer, increased in the rats exposed to the brain average SAR of 25 W/kg but remained the same for the brain average SAR of 7.5 W/kg. The SAR of a standard cellular phone is restricted to a maximum of 2 W/kg averaged over 10 g tissue. These results suggest that the exposure to a TDMA field at levels about four times stronger than emitted by cellular phones does not affect the learning and memory processes when there are no thermal effects.

Animals↗

PubMed2003

Skin temperature changes induced by strong static magnetic field exposure.

High intensity static magnetic fields, when applied to the whole body of the anesthetized rat, have previously been reported to decrease skin temperature. The hypothesis of the present study was that in diamagnetic water, molecules in the air play significant roles in the mechanism of skin temperature decrease. We used a horizontal cylindrical superconducting magnet. The magnet produced 8 T at its center. A thermistor probe was inserted in a subcutaneous pocket of the anesthetized rats to measure skin temperature. Animals (n=10) were placed in an open plastic holder in which the ambient air was free to move in any direction (group I). Animals (n=10) were placed in a closed holder in which the air circulation toward the direction of weak magnetic field was restricted (group II). Each holder was connected to a hydrometer to measure humidity around the animal in the holder. The data acquisition phase consisted of a 5 min baseline interval, followed by inserting the animal together with the holder into the center of the magnet bore for a 5 min exposure and a 5 min postexposure period outside the bore. In group I, skin temperature and humidity around the animal significantly decreased during exposure, followed by recovery after exposure. In group II, skin temperature and humidity did not decrease during the measurement. The skin temperature decrease was closely related to the decrease in humidity around the body of the animal in the holder, and the changes were completely blocked by restricting the air circulation in the direction of the bore entrance. Possible mechanisms responsible for the decrease in skin temperature may be associated with magnetically induced movement of water vapor at the skin surface, leading to skin temperature decrease.

Adaptation, Physiological↗