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  • 1
    Electronic Resource
    Electronic Resource
    The Simian Virus 40 Large T Antigen Does Not Inhibit Translation of the 14-kDa Myelin Basic Protein mRNA in Reticulocyte Lysates or in Transfected Cells (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 64 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Viral T antigens are transcription factors that have been suspected of inhibiting expression of the myelin basic protein (MBP) mRNA at the translational level in vitro and in vivo. The effect of simian virus 40 (SV40) large T antigen (T-ag) was examined on the translation of the 14-kDa MBP mRNA in reticulocyte lysates and on MBP expression after transfection into cells that express SV40 T-ag. SV40 T-ag did not inhibit translation of 14-kDa MBP cRNAs in cell-free translations even at 30 µM (∼600 µg/ml) T-ag. Permanent transfection of COS-1 cells (which endogenously express SV40 T-ag) with the 14-kDa MBP cDNA resulted in the expression of the 14-kDa MBP as determined by western blot analysis. Permanent transfection of N20.1 cells, an oligodendrocyte line immortalized with a temperature-sensitive SV40 T-ag, with the 14-kDa MBP cDNA construct also resulted in the expression of the 14-kDa MBP under conditions in which the cells expressed functional SV40 T-ag. These results indicate that SV40 T-ag does not prevent expression of the MBP gene at the translational level and that in those immortalized oligodendrocyte lines that express MBP mRNA, but not MBP protein, some factor other than the SV40 large T-ag is responsible for the posttranscriptional regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.64020928.x
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement of clottability of fibrin polymers using magnetic orientation : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4708-4710 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fibrin polymers, as a kind of diamagnetic material, are oriented parallel to the direction of magnetic fields. We investigated the polymerization of partially digested fibrinogens in an 8 T magnetic field in order to observe the clotting ability of various sizes of fibrinogen fractions using a magnetic orientation technique. We purified high-molecular weight fraction (F1) and low-molecular weight fraction from human fibrinogen (F2). Fibrin gels were formed in an 8 T magnetic field for 9 h, and transmittancies were measured to evaluate the degree of magnetic orientation. The results show that a lack at the C-terminal half of one Aα chain did not affect the magnetic orientation of fibrin. We also investigated the effect of the digestion of fibrinogen by plasmin on the magnetic orientation of fibrin. The result shows that partially digested fibrin molecules also orient in an 8 T magnetic field. However, the degree of magnetic orientation significantly decreases when fragment X and fragment Y appear. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361647
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  • 3
    Electronic Resource
    Electronic Resource
    Catalytic activity of catalase under strong magnetic fields of up to 8 T : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4705-4707 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The question of whether or not magnetic fields affect enzymatic activity is of considerable interest in biomagnetics and biochemistry. This study focuses on whether magnetically related enzymatic activities can be affected by magnetic fields. We examined the effect of magnetic fields of up to 8 T on catalytic decomposition of hydrogen peroxide (H2O2). We observed changes in absorbance of reaction mixture of hydrogen peroxide and catalase at 240 nm, during and after magnetic field exposures. When the reaction mixture was not treated with nitrogen-gas bubbling, it was observed that the initial reaction rate of the reaction which was exposed to magnetic fields of up to 8 T was 50%–85% lower than the control data. This magnetic field effect was not observed, however, when the reaction mixture was bubbled with nitrogen gas to remove the dissolved oxygen molecules which were produced in the solution. We also measured concentration of dissolved oxygen which was produced by the decomposition of hydrogen peroxide. Dissolved oxygen concentration in the reaction mixture which was exposed to magnetic fields increased 20%–25% compared to the control solution. The results of the present study indicate that magnetic fields affect dynamic movement of oxygen bubbles which are produced in the reaction mixture by the decomposition of hydrogen peroxide, but not the catalytic activity of catalase itself. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361646
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  • 4
    Electronic Resource
    Electronic Resource
    Quenching of flames by magnetic fields (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1243-1245 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experiment has been demonstrated to show a phenomenon involving quenching of candle flames using magnetic fields. An electromagnet with a pair of columnar magnetic poles in which inner sidepieces were hollowed out was used. Magnetic fields of 1.5 T at the brim gave a gradient of 50–300 T/m in the direction perpendicular to the pole axis when the distance of the airgap was in a range of 5–10 mm. A candle was burned in the hollowed space between magnetic poles, and candle flames were exposed to magnetic fields. The flames were quenched a few seconds after the onset of field exposures. A model, called a "magnetic curtain,'' was introduced to explain this phenomenon. It is assumed that the magnetic curtain is a wall of air which is formed by magnetic fields. The magnetic curtain, which is also called an "air curtain,'' blocks air flow in and out of the hollowed space. The interception of oxygen by the magnetic curtain quenches flames. The magnetic curtain also presses back flames and other gases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343016
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  • 5
    Electronic Resource
    Electronic Resource
    Localized stimulation of neural tissues in the brain by means of a paired configuration of time-varying magnetic fields (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5862-5864 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method of localized stimulation of the human brain is proposed. The basic idea is to concentrate induced eddy currents locally in the vicinity of a target in the cortex by a pair of coils which are positioned outside the head so that time-varying magnetic fields pass through the head in the opposite directions around a target. The eddy currents induced at the target are expected to flow together, which results in an increased current flow at the target. Spatial distributions of induced eddy currents are calculated in cubical and spherical volume conductor models by a finite element method. The results show that the current vectors make themselves two vortexes which flow together at the target. The current density at the target makes a peak which is higher by 2–3 times than current densities at nontarget regions. The validity of the proposed method is demonstrated by experiments using frog nerve-muscle preparations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342181
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  • 6
    Electronic Resource
    Electronic Resource
    Current source imaging for high spatial resolution magnetocardiography in normal and abnormal rat cardiac muscles (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6205-6207 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The purpose of our study was to identify the current source produced by acute ischemia and infarction. We measured magnetocardiograms (MCG) and electrocardiograms (ECG) of five male rats using a high-resolution dc superconducting quantum interference device gradiometer in a magnetically shielded room after performing coronary artery occlusion. The spatial resolution of the detecting magnetic field of our system is higher than the typical system, thus permitting the measurement of magnetic fields in small animals. Distribution of the magnetic fields B(t) and distribution of |rot B(t)|, which corresponded to the distribution of the current source, were imaged by 12-channel MCGs. As a result, the distribution of current source changes in the affected area of the myocardium during the ST segment, and amplitude of the peak significantly increased after occlusion. Our system can be used to help clarify the mechanism of the ST shift related to severe heart disease. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372655
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  • 7
    Electronic Resource
    Electronic Resource
    Quenching of flames by magnetic fields (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6030-6030 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of magnetic fields on combustion of alcohol with the aid of platinum catalysis have been studied to simulate in part the oxidation of organic matter in the living body, and it has been found that the combustion reactions are influenced by magnetic fields. It has also been observed that candle flames are pressed down by magnetic fields of higher intensities when flames are exposed to gradient magnetic fields in a range 20–200 T/m under 0.5–1.4 T. Apart from the combustion experiments, flows of carbon dioxide, oxygen, nitrogen, and argon gases were exposed to magnetic fields up to 2.2 T and 300 T/m. The flows of these gases were blocked or disturbed by the magnetic fields. The purpose of the present study is to clarify the mechanisms for the phenomena observed in the experiments of magnetic effects on combustion and gas flow. An electromagnet with a pair of columnar magnetic poles of which inner sidepieces were hollowed out was used. The magnetic fields of 1.5 T at the brim gave a gradient of 50–100 T/m in the direction perpendicular to the pole axis when the distance of the airgap was in a range 5–10 mm. A candle was burned in the hollowed space between magnetic poles, and candle flames were exposed to magnetic fields. The flames were quenched in a few seconds after the onset of field exposures. Oxygen gas as a paramagnetic molecule can be attracted to the magnetic fields of higher intensities. However, under the intensities of magnetic fields concerned, oxygen gases are not concentrated but are aligned so as to make a "wall of oxygen'' or an "air curtain.'' The air curtain, which is also called the "magnetic curtain,'' blocks air flow into and out of the hollowed space. The interception of oxygen by magnetic curtain quenches flames. The magnetic curtain also presses back flames and other gases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342142
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  • 8
    Electronic Resource
    Electronic Resource
    Spinal reflex evoked by a pair of opposing pulsed magnetic fields : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6019-6021 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A noninvasive method of magnetic stimulation of the spinal roots was designed. The basic idea is to concentrate induced eddy currents in a target by a pair of opposing pulsed magnetic fields. A figure-eight coil was positioned outside the median of the back so that time varying magnetic fields pass through the body in opposite directions around the target. Magnetic stimulation of the spinal roots of human and a rabbit was carried out. It was found that each spine level can be stimulated selectively, producing electromyographic waves related to both the H-reflex and M-wave. The results indicate that the M-wave can be produced by currents flowing either in the rostral or caudal direction, whereas the H-reflex is only generated by currents flowing in the caudal direction. The H-reflex elicited by magnetic stimulation of nerves in the vicinity of the spine becomes a new tool in diagnosis of neuromuscular system diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347798
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  • 9
    Electronic Resource
    Electronic Resource
    Source analysis of MEG activities during sleep (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6023-6023 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present study focuses on magnetic fields of the brain activities during sleep, in particular on K-complexes, vertex waves, and sleep spindles in human subjects. We analyzed these waveforms based on both topographic EEG (electroencephalographic) maps and magnetic fields measurements, called MEGs (magnetoencephalograms). The components of magnetic fields perpendicular to the surface of the head were measured using a dc SQUID magnetometer with a second derivative gradiometer. In our computer simulation, the head is assumed to be a homogeneous spherical volume conductor, with electric sources of brain activity modeled as current dipoles. Comparison of computer simulations with the measured data, particularly the MEG, suggests that the source of K-complexes can be modeled by two current dipoles. A source for the vertex wave is modeled by a single current dipole which orients along the body axis out of the head. By again measuring the simultaneous MEG and EEG signals, it is possible to uniquely determine the orientation of this dipole, particularly when it is tilted slightly off-axis. In sleep stage 2, fast waves of magnetic fields consistently appeared, but EEG spindles appeared intermittently. The results suggest that there exist sources which are undetectable by electrical measurement but are detectable by magnetic-field measurement. Such source can be described by a pair of opposing dipoles of which directions are oppositely oriented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347802
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  • 10
    Electronic Resource
    Electronic Resource
    Mechanism of orientation of stimulating currents in magnetic brain stimulation (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6023-6023 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We made a functional map of the human motor cortex related to the hand and foot areas by stimulating the human brain with a focused magnetic pulse. We observed that each functional area in the cortex has an optimum direction for which stimulating currents can produce neural excitation. The present report focuses on the mechanism which is responsible for producing this anisotropic response to brain stimulation. We first obtained a functional map of the brain related to the left ADM (abductor digiti minimi muscles). When the stimulating currents were aligned in the direction from the left to the right hemisphere, clear EMG (electromyographic) responses were obtained only from the left ADM to magnetic stimulation of both hemisphere. When the stimulating currents were aligned in the direction from the right to the left hemisphere, clear EMG signals were obtained only from the right ADM to magnetic stimulation of both hemisphere. The functional maps of the brain were sensitive to changes in the direction of the stimulating currents. To explain the phenomena obtained in the experiments, we developed a model of neural excitation elicited by magnetic stimulation. When eddy currents which are induced by pulsed magnetic fields flow in the direction from soma to the distal part of neural fiber, depolarized area in the distal part are excited, and the membrane excitation propagates along the nerve fiber. In contrast, when the induced currents flow in the direction from the distal part to soma, hyperpolarized parts block or inhibit neural excitation even if the depolarized parts near the soma can be excited. The model explains our observation that the orientation of the induced current vectors reflect both the functional and anatomical organization of the neural fibers in the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347801
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