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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 9 (1988), S. 159-166 
    ISSN: 0197-8462
    Keywords: Lorentz force ; Maxwell stress ; threshold field strength ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Static magnetic fields affect the diffusion of biological particles in solutions through the Lorentz force and Maxwell stress. These effects were analyzed theoretically to estimate the threshold field strength for these effects. Our results show that the Lorentz force suppresses the diffusion of charged particles such as Na+, K+, Ca2+, Cl-, and plasma proteins. However, the threshold is so high, i.e., more than 104 T, that the Lorentz force does not affect the ion diffusion at typical field strengths (a few Tesla at most). Since the threshold of gradient fields for producing a change in ion diffusion through the Maxwell stress is more than 105 T2/m for paramagnetic molecules (FeCl3, O2) and plasma proteins, their diffusion would be unaffected by typical gradient fields (100 T2/m at most) and even by high gradient fields (less than 105 T2/m) used in magnetic separation techniques. In contrast, movement of deoxygenated erythrocytes and FeCl3 colloids (more than 103 molecules) is influenced by the usual gradient fields due to a volume effect.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 399-410 
    ISSN: 0197-8462
    Keywords: magnet ; magnetic field ; tissue culture ; exposure system ; biological effects ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A magnetic field generator constructed of rare earth-cobalt magnets is proposed for examining the biological effects of static magnetic fields (less than 1 T) on tissue cultures. Important quantities of a magnetic field from a biological-effects viewpoint, ie, its strength and the product of strength and gradient, are analysed. A practical procedure for designing the generator with optimum parameters is given. Also, parameters are determined which will yield a sinusoidal spatial field distribution.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 6 (1982), S. 215-223 
    ISSN: 0148-7280
    Keywords: spermatozoon ; egg ; fertilization ; in vitro ; incorporation ; cincmatography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Cumulus-free mouse eggs were placed on microscope slides and inseminated with capacitated mouse spermatozoa. Fertilization could then be observed through the phase contrast microscope and recorded by time-lapse cinematography. Following the penetration of the fertilizing spermatozoon through the zona pellucida and the fusion of the sperm head with the vitelline membrane, the entire sperm tail gradually entered the vitellus. The time required for tail incorporation into the vitellus as measured in 49 eggs varied from 3 h 3 min to 5 h 49 min, with a mean time of 4 h 23 min. When tail incorporation began, the greater part of the flagellum was still outside the zona pellucida; occasionally it slipped into the perivitelline space, but generally it remained outside the zona and shortened by degrees as incorporation proceeded. The motility of the fertilizing spermatozoon declined abruptly very soon after fusion of the sperm head with the vitellus and remained at a very low level during the 3-6 h required for tail incorporation. Sperm motility, therefore, does not appear to be the main determinant in tail incorporation and the primary mechanism responsible for it remains unclear. As the sperm tail slowly entered the vitellus, the second meiotic division was completed with concomitant extrusion of the second polar body. Key stages in second polar body formation were correlated with events in tail incorporation. Differences between fertilization in vitro and in vivo are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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