Brain Res. Bull. (1996) vol. 39: 255-259
Jon Dobson and Paola Grassi
DOBSON, J. and GRASSI, P. Magnetic properties of human hippocampal tissue - evaluation of artefact and contamination sources BRAIN RES. BULL. - In order to investigate the possibility that post mortem chemical alteration or contamination is responsible for recent results indicating the presence of magnetite in human brain tissue and to determine whether magnetite is present in living brain tissue, we examined tissue samples resected from six patients during amygdalo-hippocampectomy operations. The tissue samples were sealed in sterilized vials in the operating theater and placed into liquid nitrogen directly after removal to prevent changes in tissue chemistry after the death of the brain cells. The low temperature magnetic properties of the tissue were measured in order to determine the presence of ferro- or ferrimagnetic material in the tissue. The results of these experiments indicate that magnetite is present in the tissue. In addition, results of experiments designed to control for airborne contamination and contamination during cauterization of vessels during surgery indicate that these are not significant sources of magnetite contamination in the tissue.
Biochem. Biophys. Res. Comm. (1996) 227(3):718-723
Jon Dobson and Tim St. Pierre
The ferromagnetic transduction model proposed by Kirschvink (1) suggests that the coupling of biogenic magnetite particles in the human brain to mechanosensitive membrane ion gates may provide a mechanism for interactions of environmental magnetic fields with humans. Extremely low frequency alternating magnetic fields primarily were considered, and in the model A.C. fields with frequencies below 10 Hz should have minimal effect. We show that pulsed fields, square waves and D.C. fields also could force open the membrane gates long enough to disrupt normal neurophysiological processes. The model may therefore be extended to explain results obtained in studies of epileptic patients which show effects on the central nervous system from low frequency square wave and D.C. magnetic fields. In addition, the model also may provide a plausible mechanism linking exposure to magnetic fields from discontinuous transmission cellular telephones and disruption of normal cellular processes in the human brain.
Brain Res. Bull. (1995) 36/2: 149-153
J.R. Dunn, M. Fuller, J. Zoeger, J. Dobson, F. Heller, J. Hammann, E. Caine and B.M. Moskowitz
DUNN, J.R., M. FULLER, J. ZOEGER, J. DOBSON, F. HELLER, J. HAMMANN, E. CAINE, and B.M. MOSKOWITZ, Magnetic material in the Human Hippocampus, BRAIN RES. BULL. Magnetic analyses of hippocampal material from deceased normal and epileptic subjects, and from the surgically removed epileptogenic zone of a living patient have been carried out. All had magnetic characteristics similar to those reported for other parts of the brain (6). These characteristics along with low temperature analysis indicate that the magnetic material is present in a wide range of grain sizes. The low temperature analysis also revealed the presence of magnetite through manifestation of its low temperature transition. The wide range of grain sizes is similar to magnetite produced extracellularly by the GS-15 strain of bacteria and unlike that found in magnetotactic bacteria MV-1, which has a restricted grain size range. Optical microscopy of slices revealed rare 5 to 10 micron clusters of finer opaque particles, which were demonstrated with Magnetic Force Microscopy to be magnetic. One of these was shown with EDAX to contain Al, Ca, Fe, and K, with approximate weight percentages of 55, 19, 19, and 5 respectively.