Magnetic iron compounds in the human brain: a comparison of tumour and hippocampal tissue (original) (raw)
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BioMetals, 2005
Excess iron accumulation in the brain has been shown to be related to a variety of neurodegenerative diseases. However, identification and characterization of iron compounds in human tissue is difficult because concentrations are very low. For the first time, a combination of low temperature magnetic methods was used to characterize iron compounds in tumour tissue from patients with mesial temporal lobe epilepsy (MTLE). Induced magnetization as a function of temperature was measured between 2 and 140 K after cooling in zero-field and after cooling in a 50 mT field. These curves reveal an average blocking temperature for ferritin of 10 K and an anomaly due to magnetite at 48 K. Hysteresis measurements at 5 K show a high coercivity phase that is unsaturated at 7 T, which is typical for ferritin. Magnetite concentration was determined from the saturation remanent magnetization at 77 K. Hysteresis measurements at various temperatures were used to examine the magnetic blocking of magnetite and ferritin. Our results demonstrate that low temperature magnetic measurements provide a useful and sensitive tool for the characterisation of magnetic iron compounds in human tissue.
Magnetic Deposits of Iron Oxides in the Human Brain
Nova Biotechnologica et Chimica, 2014
Deposits of iron oxides in the human brain (globus pallidus) are visible under electron microscopy as object of regular and or/irregular shape but giving sharp diffraction patterns in the transmission mode. The SQUID magnetometry reveals that the magnetization curves decline form an ideal Langevin function due to the dominating diamagnetism of organic tissue. The fitting procedure yields the quantitative characteristics of the overall magnetization curves that were further processed by statistical multivariate methods
Magnetic studies of iron-entities in human tissues
Journal of Magnetism and Magnetic Materials, 2004
Iron-entities in the human liver, brain and blood tissues have been investigated by means of EPR spectroscopy and magnetization measurements over the temperature range 4-300 K. The identification of the most typical forms of iron in the human body (i.e. isolated Fe-ions bonded in hemoglobin and transferrin as well as exchange coupled Fe-ions in nanosized ferritin cores) is presented.
Biological tissue magnetism in the frame of iron overload diseases
Journal of Magnetism and Magnetic Materials, 2007
The conspicuous magnetic properties of iron, paradoxically, rarely participate in the methods routinely employed in the clinical environment to detect iron containing species in tissues. In the organism iron is just a trace metal and it mostly occurs as part of haemoproteins or ferritin, which show paramagnetic, diamagnetic or antiferromagnetic behaviour, hence resulting in a very low contribution to the tissue susceptibility. Detailed magnetic measurements make it nowadays possible to identify such species in tissues that correspond to individuals with iron overload pathologies. Since, as alternatives to the conventional biopsy, magnetism-based noninvasive techniques to diagnose and manage such diseases are recently under development, the deep knowledge of the magnetic properties of the different forms of iron in tissues is of high applied interest. r
Journal of Inorganic Biochemistry, 2006
The magnetic properties and the ultrastructure, with special emphasis on the nanometric range, of liver tissues in an iron overload rat model have been investigated. The tissues of the animals, sacrificed at different times after a single iron dextran injection, have been characterised by magnetic AC susceptibility measurements together with transmission electron microscopy (TEM) and selected area electron diffraction (SAED) as helping techniques. It has been observed that few days after the iron administration the liver contains at least two iron species: (i) akaganéite nanoparticles, coming from iron dextran and (ii) ferrihydrite nanoparticles corresponding to ferritin. The magnetic susceptibility of the tissues depends not only on the elemental iron content but also on its distribution among chemical species, and varies in a remarkable regular manner as a function of the elapsed time since the iron administration. The results are of relevance with respect to non-invasive techniques for liver iron determination, directly or indirectly based on the magnetic susceptibility of the tissues, as biomagnetic liver susceptometry (BLS) and magnetic resonance (MRI) image treatment.
Looking for biogenic magnetite in brain ferritin using NMR relaxometry
NMR in Biomedicine, 2005
Mammalian cellular iron is stored inside the multisubunit protein ferritin, normally taking the structure of a ferrihydrite-like mineral core. It has been suggested that biogenic magnetite, which has been detected in the brain and may be related to neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, could initially form in ferritin. Indeed, as ferritin is present in the brain, the ferrihydrite core could be a precursor for biogenic magnetite formationparticularly in cases where the normal functioning of the ferritin protein is disrupted. In this work, NMR relaxometry was used to detect magnetite inside samples of ferritin extracted from normal and Alzheimer-diseased brains. The method was first calibrated with different fractions of horse spleen ferritin and synthetic magnetite particles. The relaxometry results suggest that the proportion of iron contained in brain ferritin in the form of well-crystallized magnetite instead of ferrihydrite must be < 1%, which is much less than that reported for 'magnetite-like' phase in recent transmission electron microscopy studies of similar samples. Consequently, the magnetization of this 'magnetite-like' phase must be very low compared with that of magnetite.
Using the magnetoencephalogram to noninvasively measure magnetite in the living human brain
Human Brain Mapping, 2018
During the past several decades there has been much interest in the existence of magnetite particles in the human brain and their accumulation with age. These particles also appear to play an important role in neurodegenerative diseases of the brain. However, up to now the amount and distribution of these particles has been measured only in post-mortem brain tissue. Although invivo MRI measurements do show iron compounds generally, MRI cannot separate them according to their magnetic phases, which are associated with their chemical interactions. In contrast, we here offer a new noninvasive, in-vivo method which is selectively sensitive only to particles which can be strongly magnetized. We magnetize these particles with a strong magnetic field through the head, and then measure the resulting magnetic fields, using the dcMagnetoencephalogram (dcMEG). From these data, the mass and locations of the particles can be estimated, using a distributed inverse solution. To test the method, we measured 11 healthy male subjects (ages 19-89 year). Accumulation of magnetite, in the hippocampal formation or nearby structures, was observed in the older men. These in-vivo findings agree with reports of post-mortem measurements of their locations, and of their accumulation with age. Thus, our findings allow invivo measurement of magnetite in the human brain, and possibly open the door for new studies of neurodegenerative diseases of the brain.
Physical Review B, 2006
Magnetic properties of a two-component system, consisting of horse spleen ferritin ͑HoSF͒ which contains a 5 -8 nm sized antiferromagnetic ferrihydrite ͑5Fe 2 O 3 ·9H 2 O͒ core and ferrimagnetic magnetite ͑Fe 3 O 4 ͒ nanoparticles ͑MNP͒ with an average size of 10-20 nm, have been investigated by using four different methods: induced magnetization versus ͑1͒ temperature and ͑2͒ field; ͑3͒ AC susceptibility; and ͑4͒ first-order reversal curves ͑FORC͒. All measurements were done on a mixed system of HoSF and MNP, as well as separately on the individual components. The average blocking temperature ͑T B ͒ of the mixed system at 50 mT is 15.6 K, which is a shift towards higher temperatures compared to pure HoSF ͑T B =12 K͒. The contribution of the MNP component to magnetic ordering is evident only as a separation of the zero-field-cooled and field-cooled measurement curves. ac susceptibility is dominated by the ferrimagnetic MNP and shows strong frequency dependence. The peak ac susceptibilities can be described by the Vogel-Fulcher law, indicating the influence of interactions within the system. Hysteresis measurements at 5 K show a wasp-waisted shape due to the mixture of a high coercivity phase ͑HoSF͒ with a low coercivity phase ͑MNP͒. Initial magnetization curves above T B can be fitted by a sum of Langevin functions, showing superparamagnetic behavior of both components. FORC diagrams are effective in illustrating the change from that of blocked MNP particles together with the superparamagnetic HoSF at 20 K to purely superparamagnetic behavior in both components above 50 K. We conclude that the mixed nanoparticle system is a good model for complex natural samples, such as human brain tissue.
Analysis of magnetic material in the human heart, spleen and liver
BioMetals
Isothermal remanent magnetization (IRM) acquisition and alternating field (A.F.) demagnetization analyses were performed on human heart, spleen and liver samples resected from cadavers. The magnetic properties of the samples were measured both at 77K and at 273K. A.F. demagnetization was performed at 273K. Results from the analyses of the tissue indicate the presence of ferromagnetic, fine-grained, magnetically interacting particles which, due primarily to magnetic properties, are thought to be magnetite and/or maghemite. The presence of superparamagnetic particles can be inferred from the increase in saturation IRM values when measured at 77K compared with measurements at 273K and the decay of remanent magnetization upon warming from 77K. The concentration of magnetic material (assuming it is magnetite or maghemite) in the samples varies from 13.7 ng g-1 to 343 ng g-1 , with the heart tissue generally having the highest concentration. The presence of magnetic material in these organs may have implications for the function of biogenic magnetite in the human body.