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Dennis


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What the USFDA has to say
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U. S. Food and Drug Administration
Center for Food Safety and Applied Nutrition
June 2, 2000


Kinetics of Microbial Inactivation for Alternative Food Processing Technologies
Oscillating Magnetic Fields
(Table of Contents)


Scope of Deliverables


This section reports the effects of magnetic fields on microbial populations. Mechanisms of inactivation and critical process factors are described. Results of microbial testing experiments are controversial. Consistent results concerning the efficacy of this method are needed before its potential use as a food preservation method is assessed.


1. Definition, Description and Applications


Static (SMF) and oscillating (OMF) magnetic fields have been explored for their potential as microbial inactivation methods. For SMF, the magnetic field intensity is constant with time, while an OMF is applied in the form of constant amplitude or decaying amplitude sinusoidal waves. The magnetic field may be homogeneous or heterogeneous. In a homogeneous magnetic field, the field intensity B is uniform in the area enclosed by the magnetic field coil, while in a heterogeneous field, B is nonuniform, with the intensities decreasing as distances from the center of the coil increases. OMF applied in the form of pulses reverses the charge for each pulse, and the intensity of each pulse decreases with time to about 10% of the initial intensity (Pothakamury and others 1993).


Preservation of foods with OMF involves sealing food in a plastic bag and subjecting it to 1 to 100 pulses in an OMF with a frequency between 5 to 500 kHz at temperatures in the range of 0 to 50 oC for a total exposure time ranging from 25 to 100 ms. Frequencies higher than 500 kHz are less effective for microbial inactivation and tend to heat the food material (Barbosa-Cánovas and others1998). Magnetic field treatments are carried out at atmospheric pressure and at moderate temperatures. The temperature of the food increases 2-5 oC. According to Hoffman (1985) exposure to magnetic fields causes inhibition in the growth and reproduction of microorganisms. OMF of intensity of 5 to 50 telsa (T) and frequency of 5 to 500 kHz was applied and reduced the number of microorganisms by at least 2-log cycles. Within the magnetic field of 5-50 T, the amount of energy per oscillation coupled to 1 dipole in the DNA is 10-2 to 10-3 eV (Hoffman 1985). OMF of this intensity can be generated using: (1) superconducting coils; (2) coils which produce DC fields; or (3) coils energized by the discharge of energy stored in a capacitor (Gersdof and others 1983). Inhibition or stimulation of the growth of microorganisms exposed to magnetic fields may be a result of the magnetic fields themselves or the induced electric fields. The latter is measured in terms of induced electric field strength and induced current density. To differentiate between electric field and magnetic field effects, a cylindrical enclosure containing cells and a medium that can be adapted to in vitro studies employing uniform, single-phase, extremely low frequency (ELF) magnetic fields is recommended.


2. Inactivation of Microorganisms


Yoshimura (1989) classified the effects of magnetic fields on microbial growth and reproduction as (1) inhibitory, (2) stimulatory and (3) none observable. Pothakamury and others (1993) summarized the effect of magnetic fields on microorganisms as shown in Table 1.


Table 1. Effect of magnetic fields on microorganisms.






Microorganism



Type of


Magnetic fileda



Field


Strength


(T)



Frequency


of pulse


(Hz)



Effect



Reference




Wine yeast cell



Heterogeneous


Smagnetic field



0.04



0



Growth inhibited when exposed for 5, 20, 25, 60, 120, or 150 min; no inhibition for 10, 15, 17 min exposure



 


Kimball (1937)




Wine yeast cell



Heterogeneous


Smagnetic field



1.1



0



No effect for 5, 10, 20, 40 or 80 min exposure



Kimball (1937)




Serratia marcescens



Heterogeneous


Smagnetic field



1.5



-



Growth rate remains same as in controls up to 6 h; growth rate decreases between 6 and 7 h and again increases between 8 and 10 h; at 10 h cell population same as in controls



Gerenscer


and others (1962)




Staphylococcus aureus



Heterogeneous


Smagnetic field



1.5



0



Growth rate increases between 3 and 6 h; then decreases between 6 and 7 h; cell population at 7 h is same as controls



Gerenscer


and others (1962)




Saccharomyces cerevisiae



Heterogeneous


Smagnetic field



0.465



0



Rate of reproduction reduced, incubated for 24, 48 or 72 h



Van Nostrand


and others(1967)




Escherichia coli



Smagnetic field



0.3



0



Growth simulated



Moore (1979)




Halobacterium halobium,


Bacillus subtilis



Smagnetic field



0.015


0.03


0.06



0



Growth inhibited



Moore (1979)




Pseudomonas aeruginosa,


Candida albicans



Omagnetic field



0.015


0.03


0.06



0.1-0.3



Growth simulated; stimulation increases with increase in frequency



Moore (1979)




E. coli



Omagnetic field



0.15



0.05



Inactivation of cells when concentration was 100 cells/mL



Moore (1979)




Streptococcus themophilus in milk



Omagnetic field



12.0



6,000


(1 pulse)



Cell population reduced from 25,000 cells/ml to 970



Moore (1979)




Saccharomyces in yogurt



Omagnetic field



40.0



416,000


(10 pulses)



Cell population reduced from 3,500 cells/ml to 25



Hofmann (1985)




Saccharomyces in orange juice



Omagnetic field



40.0



416,000


(1 pulse)



Cell population reduced from 25,000 cells/ml to 6



Hofmann (1985)




Mold spores



Omagnetic field



7.5



8,500


(1 pulse)



Population reduced from 3,000 spores/ml to 1



Hofmann (1985)




Saccharomyces cerevisiae



 


Smagnetic field



0.56



0



Decreased growth rate; interaction between temperature and magnetic field only during the logarithmic phase



 


Van Nostrand


and others (1967)


aSmagnetic field = static magnetic field; Omagnetic field = oscillating magnetic field


Hoffman (1985) reported on the inactivation of microorganisms with OMF in milk, yogurt, orange juice, and bread roll dough. According to Hoffman (1985) only 1 pulse of OMF was adequate to reduce the bacterial population between 102 and 103 cfu/g. The intensity of the magnetic field required to achieve these effects varied between 2-25 T and a frequency range from 5-500 Hz.


A review of the literature shows that inconsistent results have been obtained on the effect of OMF on microbial growth (Table 1). In some cases OMF stimulated or inhibited microbial growth and, in others, it had no effect on microbial growth. The results presented in Table 1 show that, although not well understood, the effect of magnetic fields on the microbial population of foods may depend on the magnetic field intensity, number of pulses, frequency and property of the food (that is, resistivity, electrical conductivity, and thickness of the foodstuff).


3. Mechanisms of Microbial Inactivation


SMF or OMF may have some potential to inactivate microorganisms in food. Pothakamury and others (1993) reported 2 theories to explain the inactivation mechanisms for cells placed in SMF or OMF. The first theory stated that a "weak" OMF could loosen the bonds between ions and proteins. Many proteins vital to the cell metabolism contain ions. In the presence of a steady background magnetic field such as that of the earth, the biological effects of OMF are more pronounced around particular frequencies, the cyclotron resonance frequency of ions (Coughlan and Hall 1990).


An ion entering a magnetic field B at velocity v experiences a force F given by:


An ion entering a magnetic field B at velocity v experiences a force F     (1)

Figure 1 shows the movement of a charged particle in a magnetic field. When v and B are parallel, F is zero. When v is normal to B, the ion moves in a circular path ( Fig. 2). For other orientations between n and B, the ions move in a helical path ( Fig. 3). The frequency at which the ions revolve in the magnetic field is known as the ion's gyrofrequency n , which depends on the charge/mass ratio of the ion and the magnetic field intensity:


n = q B / (2 π m) (2)


where q is the charge and m is the mass of the ion. Cyclotron resonance occurs when n is equal to the frequency of the magnetic field. At 50 µ T, the resonance frequency of Na+ and Ca+ is 33.33 and 38.7 Hz, respectively. At cyclotron resonance, energy is transferred selectively from the magnetic field to the ions with n equivalent to frequency of the magnetic field. The interaction site of the magnetic field is the ions in the cell, and they transmit the effects of magnetic fields from the interaction site to other cells, tissues, and organs.


A second theory considers the effect of SMF and OMF on calcium ions bound in calcium-binding proteins, such as calmodulin. The calcium ions continually vibrate about an equilibrium position in the binding site of calmodulin. A steady magnetic field to calmodulin causes the plane of vibration to rotate, or proceed in the direction of magnetic field at a frequency that is exactly = of the cyclotron frequency of the bound calcium. Adding a "wobbling" magnetic field at the cyclotron frequency disturbs the precision to such an extent that it loosens the bond between the calcium ion and the calmodulin (Pothakamury and others 1993).


Hoffman (1985) suggested that the inactivation of microorganisms may be based on the theory that the OMF may couple energy into the magnetically active parts of large critical molecules such as DNA. Within 5-50 T range, the amount of energy per oscillation coupled to 1 dipole in the DNA is 10-2 to 10-3 eV. Several oscillations and collective assembly of enough local activation may result in the breakdown of covalent bonds in the DNA molecule and inhibition of the growth of microorganisms (Pothakamury and others 1993).





Charged particle in a magnetic field.

Figure 1. Charged particle in a magnetic field.





Charged particle in a magnetic field when V is normal to B.

Figure 2. Charged particle in a magnetic field when V is normal to B.





Charged particle in a magnetic field when V makes an arbitrary angle with B.

Figure 3. Charged particle in a magnetic field when V makes an arbitrary angle with B.

The work of San-Martin and others (1999) shows that an externally applied electromagnetic signal at frequencies close to a given resonance and parallel to an SMF ( Fig. 4) may couple to the corresponding ionic species in such a way as to selectively transfer energy to these ions and thus indirectly to the metabolic activities in which they are involved. The earth's total field ranges from 25 to 70 µ T. Most of the slightly and double charged ions of biological interest have corresponding gyrofrequencies in the ELF range 10 to 100 Hz for this field strength.





Required AC and DC magnetic field orientation to achieve ion cyclotron.

Figure 4. Required AC and DC magnetic field orientation to achieve ion cyclotron.


4. Validation/Critical Process Factors


The critical process factors affecting the inactivation of microbial populations by magnetic fields are not completely understood. Some factors believed to influence microbial inactivation include magnetic field intensity, electrical resistivity, and microbial growth stage.


4.1. Magnetic Field


Exposure to a magnetic field may stimulate or inhibit the growth and reproduction of microorganisms. A single pulse of intensity of 5 to 50 T and frequency of 5 to 500 kHz generally reduces the number of microorganisms by at least 2-log cycles (Hoffman 1985). High intensity magnetic fields can affect membrane fluidity and other properties of cells (Frankel and Liburdy 1995). Inconsistent results of other inactivation studies (see Table 1), however, make it impossible to clearly state the microbial inactivation efficiency of magnetic field or to make any predictions about its effects on microbial populations.


4.2. Electrical Resistivity


For microorganisms to be inactivated by OMF, foods need to have a high electrical resistivity (greater than 10 to 25 ohms-cm). The applied magnetic field intensity depends on the electrical resistivities and thickness of the food being magnetized, with larger magnetic fields intensities used with products with large resistivity and thickness.


4.3. Microbial Growth Stage


Tsuchiya and others (1996), working with homogeneous (7 T) and inhomogeneous (5.2 to 6.1 T and 3.2 to 6.7 T) magnetic fields, found a growth stage dependent response of Escherichia coli bacterial cultures. The ratio of cells under magnetic field to cells under geomagnetic field was less than 1 during the first 6 h of treatment and greater than 1 after 24 h. These authors also found that cell survival was greater under inhomogeneous compared with homogeneous fields. Based on the assumption that magnetic fields could act as a stress factor, cells collected after 30 min of incubation under magnetic field treatment (lag or early lag growth phase) or in the stationary phase after long-term magnetic field treatment were heated to 54 oC. No differences were observed between the treated and control samples. Little else is known about the effect of microbial growth stage on susceptibility to magnetic fields.


5. Process Deviations


Data acquisition systems must be installed in the processing area to monitor and control the power source, number of pulses, and frequencies applied to the food. Food composition, temperature, size of unit, among other factors also would require control and monitoring to assure constant treatments. Any deviation from the specified conditions such as temperature changes must be continuously recorded and appropriate responses taken. If the system shuts down or fails to deliver the described treatment during processing, the food must be reprocessed to assure quality and safety.


6. Research Needs


There is a significant lack of information on the ability of OMF treatment to inactivate pathogenic microorganisms and surrogates. A main area that needs to be elucidated is the confirmation that magnetic field treatment is an effective process to inactivate microbes. Once this is established, significant data gaps still must be closed before this technology can be safely and practically applied to food preservation. Some of the more significant research needs are:




    • Identify key resistant pathogens.
    • Establish the effects of magnetic fields on microbial inactivation.
    • Elucidate the destruction kinetics of magnetic fields.
    • Determine the mechanism of action of magnetic fields.
    • Determine critical process factors and effects on microbial inactivation.
    • Validate the process and evaluate indicator organisms and appropriate surrogates.
    • Identify process deviations and determine ways to address them.

GLOSSARY


A complete list of definitions regarding all the technologies is located at the end of this document.


Cyclotron resonance. Phenomenon that occurs when the frequency of revolving ions induced by a specific magnetic field intensity is similar to the frequency of that magnetic field and parallel to it. In these instances, energy may be transferred to the ions, affecting cell metabolic activities.


Cyclotron. An accelerator in which particles move in spiral paths in a constant.


Dipole. For oscillating magnetic fields, a magnetic particle that contains a *north* and *south* magnetic pole.


Gyrofrequency. Frequency at which the ions revolve in a magnetic field.


Heterogeneous magnetic field. Magnetic field that exhibits a gradient depending on the nature of the magnet.


Homogeneous magnetic field. Magnetic field with a constant strength over space.


Magnetic flux density. Force that an electromagnetic source exerts on charged particles. Magnetic flux density is measured in Telsa (1 Telsa =104 gauss).


Oscillating magnetic field. Fields generated with electromagnets of alternating current. The intensity varies periodically according to the frequency and type of wave in the magnet.


Sinusoidal Wave. A mode of propagation of the magnetic field.


Static magnetic field. Magnetic fields with a constant strength over time.


Telsa. Unit to express magnetic flux density (B). 1 Telsa (T) = 104 gauss.



REFERENCES


Barbosa-Cánovas, G.V., Pothakamury, U.R., and Barry, G.S. 1994. State of the art technologies for the stabilization of foods by non-thermal processes: physical methods. In: Barbosa-Cánovas, G.V., and Welti-Chanes, J.(eds.), Food Preservation by Moisture control. Lancaster, Technomic Publishing.pp. 423-532.


Barbosa-Cánovas, G.V., Gongora-Nieto, M.M., and Swanson, B.G. 1998. Nonthermal electrical methods in food preservation. Food Sci. Int. 4(5):363-370.


Coughlan, A., Hall, N. 1990. How magnetic field can influence your ions? New Scientist. 8(4):30


Frankel, R. B. and Liburdy, R. P. 1995. Biological effects of static magnetic fields. In Handbook of Biological Effects of Electromagnetic Fields. Polk, C. and Postow, E. (Ed). 2nd Ed. CRC Press. Boca Raton, FL


Gerencser, V.F., Barnothy, M.F., and Barnothy, J.M. 1962. Inhibition of bacterial growth by magnetic fields. Nature, 196:539-541.


Gersdorf, R., deBoer, F.R., Wolfrat, J.C., Muller, F.A., Roeland, L.W. 1983. The high magnetic facility of the University of Amsterdam, high field magnetism. Proceedings International symposium on High Field Magnetism. Osaka, Japan. 277-287


Hofmann, G.A. 1985. Deactivation of microorganisms by an oscillating magnetic field. U.S. Patent 4,524,079.


Kimball, G.C. 1937. The growth of yeast on a magnetic fields. J. Bacteriol. 35:109-122.


Moore, R.L. 1979. Biological effects of magnetic fields. Studies with microorganisms. Can. J. Microbiol., 25:1145-1151.


Pothakamury, U.R., Barbosa-Cánovas, G.V., and Swanson, B.G. (1993). Magnetic-field inactivation of microorganisms and generation of biological changes. Food Technol. 47(12):85-93.


San-Martin, M.F., Harte, F.M., Barbosa-Cánovas, G.V., and Swanson, B.G. 1999. Magnetic field as a potential non-thermal technology for the inactivation of microorganisms. Washington State University, Biological Systems Engineering, Pullman, WA., USA. (Unpublished).


Tsuchiya, K., Nakamura, K., Okuno, K., Ano, T. and Shoda, M. 1996. Effect of homogeneous and inhomogeneous high magnetic fields on the growth of Escherichia coli. J Ferment Bioeng 81(4):343-346.


Van Nostran, F.E., Reynolds, R.J. and Hedrick, H.G. 1967. Effects of a high magnetic field at different osmotic pressures and temperatures on multiplication of Saccharomyces cerevisiae. Appl Microbiol. 15: 561-563.


Yoshimura, N. 1989. Application of magnetic action for sterilization of food. Shokukin Kihatsu 24(3):46-48.



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Anonymous

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I don't think I'm signed in, so this is Fish.


Looking at this, I've found a few things in table 1 interesting.

Of all the bacteria listed, the only major pathogens are S. aureus, E. coli, and P. aeruginosa. Both S. aureus and P. aeruginosa had growh either stimulated or no less than controls. There were 2 listings for E.coli, one had stimulated growth and one didn't. However, only a few strains of E. coli are actually pathogenic, so it's hard to tell how effective it is against bacterial pathogens.

The fungi studied (yeast, molds, Candida, and Saccharomyces) are the same. The ones primarily used for alchol are affected, but not the pathogen (Candida albicans).


Based on this, it looks like the OSM doesn't kill the pathogens, just the normal everday bacteria and yeasts that aren't harmful.


I think this statement says it all:

There is a significant lack of information on the ability of OMF treatment to inactivate pathogenic microorganisms and surrogates.

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Dennis


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Fish 16 people were cured out of 16 using the rife. I found another FDA message and my puter froze that further supported the basic workings of the rife machine....i had trouble finding it.again. I tried posting it with this one and it froze.

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Anonymous

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quote:
Originally posted by: Dennis
"Fish 16 people were cured out of 16 using the rife. I found another FDA message and my puter froze that further supported the basic workings of the rife machine....i had trouble finding it.again. I tried posting it with this one and it froze."




Where does it say 16 of 16 people survived?? In the article above?? Perhaps I missed it.

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Anonymous

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searches on Pubmed (journal database) turned up these abstracts in a search for 'oscillating magnetic fields'...http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed

I briefly scanned some of the abstracts and picked some that might pertain to this topic.



Photochem Photobiol Sci. 2003 Jun;2(6):637-48. Related Articles, Links

Interactions of zero-frequency and oscillating magnetic fields with biostructures and biosystems.

Volpe P.

Department of Biology, University of Rome Tor Vergata, Rome, Italy. volpe@bio.uniroma2.it

This review points to the investigations concerning the effects of zero-frequency (DC) and oscillating (AC) magnetic fields (MFs) on living matter, and especially those exerted by weak DC and low-frequency/low-intensity AC MFs. Starting from the analysis of observations on the action of natural magnetic storms (MSs) or periodic geomagnetic field (GMF) variations on bacteria, plants and animals, which led to an increasing interest in MFs in general, this survey pays particular attention to the background knowledge regarding the action of artificial MFs not only at the ionic, molecular or macromolecular levels, but also at the levels of subcellular regions, in vitro cycling cells, in situ functioning tissues or organs and total bodies or entire populations. The significance of some crucial findings concerning, for instance, the MF-dependence of the nuclear or cellular volumes, rate of cell proliferation vs. that of cell death, extent of necrosis vs. that of apoptosis and cell membrane fluidity, is judged by comparing the results obtained in a solenoid (SLD), where an MF can be added to a GMF, with those obtained in a magnetically shielded room (MSR), where the MFs can be partially attenuated or null. This comparative criterion is required because the differences detected in the behaviour of the experimental samples against that of the controls are rather small per se and also because the evaluation of the data often depends upon the peculiarity of the methodologies used. Therefore, only very small differences are observed in estimating the MF-dependence of the expression of a single gene or of the rates of total DNA replication, RNA transcription and protein translation. The review considers the MF-dependence of the interactions between host eukaryotic cells and infecting bacteria, while documentation of the harmful effects of the MFs on specific life processes is reported; cases of favourable action of the MFs on a number of biological functions are also evidenced. In the framework of studies on the origin and adaptation of life on Earth or in the Universe, theoretical insights paving the way to elucidate the mechanisms of the MF interactions with biostructures and biosystems are considered.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12859147


Mechanism for action of electromagnetic fields on cells.

Panagopoulos DJ, Karabarbounis A, Margaritis LH.

Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens GR-15784, Greece. dlpanagop@cc.uac.gr

A biophysical model for the action of oscillating electric fields on cells, presented by us before [Biochem. Biophys. Res. Commun. 272(3) (2000) 634-640], is extended now to include oscillating magnetic fields as well, extended to include the most active biological conditions, and also to explain why pulsed electromagnetic fields can be more active biologically than continuous ones. According to the present theory, the low frequency fields are the most bioactive ones. The basic mechanism is the forced-vibration of all the free ions on the surface of a cell's plasma membrane, caused by an external oscillating field. We have shown that this coherent vibration of electric charge is able to irregularly gate electrosensitive channels on the plasma membrane and thus cause disruption of the cell's electrochemical balance and function [Biochem. Biophys. Res. Commun. 272(3) (2000) 634-640]. It seems that this simple idea can be easily extended now and looks very likely to be able to give a realistic basis for the explanation of a wide range of electromagnetic field bioeffects.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12379225


A mechanism for action of oscillating electric fields on cells.

Panagopoulos DJ, Messini N, Karabarbounis A, Philippetis AL, Margaritis LH.

Department of Cell Biology and Biophysics, Athens University, Greece. dpanagop@cc.uoa.gr

The biological effects of electromagnetic fields have seriously concerned the scientific community and the public as well in the past decades as more and more evidence has accumulated about the hazardous consequences of so-called "electromagnetic pollution." This theoretical model is based on the simple hypothesis that an oscillating external electric field will exert an oscillating force to each of the free ions that exist on both sides of all plasma membranes and that can move across the membranes through transmembrane proteins. This external oscillating force will cause a forced vibration of each free ion. When the amplitude of the ions' forced vibration transcends some critical value, the oscillating ions can give a false signal for opening or closing channels that are voltage gated (or even mechanically gated), in this way disordering the electrochemical balance of the plasma membrane and consequently the whole cell function. Copyright 2000 Academic Press.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10860806


An imposed oscillating electrical field improves the recovery of function in neurologically complete paraplegic dogs.

Borgens RB, Toombs JP, Breur G, Widmer WR, Waters D, Harbath AM, March P, Adams LG.

Department of Basic Medical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana 47907, USA. cpr@vet.purdue.edu

We show that an applied electric field in which the polarity is reversed every 15 minutes can improve the outcome from severe, acute spinal cord injury in dogs. This study utilized naturally injured, neurologically complete paraplegic dogs as a model for human spinal cord injury. The recovery of paraplegic dogs treated with oscillating electric field stimulation (OFS) (approximately 500 to 600 microV/mm; n = 20) was compared with that of sham-treated animals (n = 14). Active and sham stimulators were fabricated in West Lafayette, Indiana. They were coded, randomized, sterilized, and packaged in Warsaw, Indiana, and returned to Purdue University for blinded surgical implantation. The stimulators were of a previously unpublished design and meet the requirements for phase I human clinical testing. All dogs were treated within 18 days of the onset of paraplegia. During the experimental applications, all received the highest standard of conventional management, including surgical decompression, spinal stabilization (if required), and acute administration of methylprednisolone sodium succinate. A radiologic and neurologic examination was performed on every dog entering the study, the latter consisting of standard reflex testing, urologic tests, urodynamic testing, tests for deep and superficial pain appreciation, proprioceptive placing of the hind limbs, ambulation, and evoked potential testing. Dogs were evaluated before and after surgery and at 6 weeks and 6 months after surgery. A greater proportion of experimentally treated dogs than of sham-treated animals showed improvement in every category of functional evaluation at both the 6-week and 6-month recheck, with no reverse trend. Statistical significance was not reached in comparisons of some individual categories of functional evaluation between sham-treated and OFS-treated dogs (ambulation, proprioceptive placing); an early trend towards significance was shown in others (deep pain), and significance was reached in evaluations of superficial pain appreciation. An average of all individual scores for all categories of blinded behavioral evaluation (combined neurologic score) was used to compare group outcomes. At the 6-month recheck period, the combined neurologic score of OFS-treated dogs was significantly better than that of control dogs (p = 0.047; Mann-Whitney, two-tailed).

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10447075


Cytoplasmic Ca2+ oscillations in human leukemia T-cells are reduced by 50 Hz magnetic fields.

Galvanovskis J, Sandblom J, Bergqvist B, Galt S, Hamnerius Y.

Department of Medical Biophysics, University of Goteborg, Sweden. galvanov@clavicula.mednet.gu.se

The effect of 50 Hz magnetic fields on the cytosolic calcium oscillator in Jurkat E6.1 cells was investigated for field strengths within the range from 0 to 0.40 mT root mean square. The intracellular Ca2+ concentration data were collected for single Jurkat cells that exhibited a sustained spiking for at least 1 h while repeatedly exposing them to an alternating magnetic field in 10-min intervals interposed with nonexposure intervals of the same length. The obtained data were analysed by computing spectral densities of the Ca2+ oscillating patterns for each of these 10-min intervals. For every single-cell experiment the spectra of all exposure as well as nonexposure periods were then averaged separately. A comparison between the resulting averages showed that the total spectral power of the cytosolic Ca2+ oscillator was reduced by exposure of the cells to an alternating magnetic field and that the effect increased in an explicit dose-response manner. The same relationship was observed within the 0-10 mHz (10 x 10(-3) Hz) subinterval of the Ca2+ oscillation spectrum. For subintervals at higher frequencies, the change caused by the exposure to the magnetic field was not significant.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10407511


Increase in radiation-induced HPRT gene mutation frequency after nonthermal exposure to nonionizing 60 Hz electromagnetic fields.

Walleczek J, Shiu EC, Hahn GM.

Department of Radiation Oncology, Stanford University Medical School, California 94305-5403, USA.

It is widely accepted that moderate levels of nonionizing electric or magnetic fields, for example 50/60 Hz magnetic fields of about 1 mT, are not mutagenic. However, it is not known whether such fields can enhance the action of known mutagens. To explore this question, a stringent experimental protocol, which included blinding and systematic negative controls, was implemented, minimizing the possibility of observer bias or experimental artifacts. As a model system, we chose to measure mutation frequencies induced by 2 Gy gamma rays in the redox-sensitive hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene in Chinese hamster ovary cells. We tested whether a 12-h exposure to a 60 Hz sinusoidally oscillating magnetic-flux density (Brms = 0.7 mT) could affect the mutagenic effects of ionizing radiation on the HPRT gene locus. We determined that the magnetic-field exposure induced an approximate 1.8-fold increase in HPRT mutation frequency. Additional experiments at Brms = 0.23 and 0.47 mT revealed that the effect was reduced at lower flux densities. The field exposure did not enhance radiation-induced cytotoxicity or mutation frequencies in cells not exposed to ionizing radiation. These results suggest that moderate-strength, oscillating magnetic fields may act as an enhancer of mutagenesis in mammalian cells.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10190502


Relationship between field strength and abnormal development in chick embryos exposed to 50 Hz magnetic fields.

Juutilainen J, Laara E, Saali K.

Department of Environmental Hygiene, University of Kuopio, Finland.

Chick embryos were exposed to sinusoidally oscillating 50 Hz magnetic fields during their first 2 days of development. In the first series of experiments magnetic field strengths of 0.1, 0.3, 1 and 10 A/m were used. The percentage of abnormal embryos (% AE) was 16 per cent in the sham-exposed control group. % AE was increased at 1 A/m (29 per cent) and 10 A/m (32 per cent), but not at 0.1 A/m (16 per cent) or 0.3 A/m (14 per cent). In the second series of experiments field strengths of 0.4, 0.6, 0.9 and 1.35 A/m were used. % AE was 17 per cent in the control group, 10 per cent at 0.4 A/m, 19 per cent at 0.6 A/m, 17 per cent at 0.9 A/m and 36 per cent at 1.35 A/m. Only the 1.35 A/m group was significantly different from the controls. The results of this study suggest that exposure of chick embryos to a 50 Hz magnetic field causes abnormal development, and that no abnormalities are induced below a threshold between 0.9 and 1 A/m.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=3500146

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