Magnetic material in the human hippocampus (original) (raw)
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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.
Magnetic iron compounds in the human brain: a comparison of tumour and hippocampal tissue
Journal of The Royal Society Interface, 2006
Iron is a central element in the metabolism of normal and malignant cells. Abnormalities in iron and ferritin expression have been observed in many types of cancer. Interest in characterizing iron compounds in the human brain has increased due to advances in determining a relationship between excess iron accumulation and neurological and neurodegenerative diseases. In this work, four different magnetic methods have been employed to characterize the iron phases and magnetic properties of brain tumour (meningiomas) tissues and non-tumour hippocampal tissues. Four main magnetic components can be distinguished: the diamagnetic matrix, nearly paramagnetic blood, antiferromagnetic ferrihydrite cores of ferritin and ferrimagnetic magnetite and/or maghemite. For the first time, open hysteresis loops have been observed on human brain tissue at room temperature. The hysteresis properties indicate the presence of magnetite and/or maghemite particles that exhibit stable single-domain (SD) behaviour at room temperature. A significantly higher concentration of magnetically ordered magnetite and/or maghemite and a higher estimated concentration of heme iron was found in the meningioma samples. First-order reversal curve diagrams on meningioma tissue further show that the stable SD particles are magnetostatically interacting, implying high-local concentrations (clustering) of these particles in brain tumours. These findings suggest that brain tumour tissue contains an elevated amount of remanent iron oxide phases.
Distribution of magnetic remanence carriers in the human brain
Scientific Reports, 2018
That the human brain contains magnetite is well established; however, its spatial distribution in the brain has remained unknown. We present room temperature, remanent magnetization measurements on 822 specimens from seven dissected whole human brains in order to systematically map concentrations of magnetic remanence carriers. Median saturation remanent magnetizations from the cerebellum were approximately twice as high as those from the cerebral cortex in all seven cases (statistically significantly distinct, p = 0.016). Brain stems were over two times higher in magnetization on average than the cerebral cortex. The ventral (lowermost) horizontal layer of the cerebral cortex was consistently more magnetic than the average cerebral cortex in each of the seven studied cases. Although exceptions existed, the reproducible magnetization patterns lead us to conclude that magnetite is preferentially partitioned in the human brain, specifically in the cerebellum and brain stem.
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
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.
Scientific Reports, 2021
The presence of magnetic nanoparticles (MNPs) in the human brain was attributed until recently to endogenous formation; associated with a putative navigational sense, or with pathological mishandling of brain iron within senile plaques. Conversely, an exogenous, high-temperature source of brain MNPs has been newly identified, based on their variable sizes/concentrations, rounded shapes/surface crystallites, and co-association with non-physiological metals (e.g., platinum, cobalt). Here, we examined the concentration and regional distribution of brain magnetite/maghemite, by magnetic remanence measurements of 147 samples of fresh/frozen tissues, from Alzheimer’s disease (AD) and pathologically-unremarkable brains (80–98 years at death) from the Manchester Brain Bank (MBB), UK. The magnetite/maghemite concentrations varied between individual cases, and different brain regions, with no significant difference between the AD and non-AD cases. Similarly, all the elderly MBB brains contain...
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.
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.
Magnetic investigations of human mesencephalic neuromelanin
Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, 2002
Pigmentation of neurons in substantia nigra is due to neuromelanin, a pigment that stores large amounts of iron. Human mesencephalic neuromelanin has been investigated by means of magnetic susceptibility measurements as a function of temperature. Magnetic measurements provide a physico-chemical characterization of the iron cluster buried in the organic melanin matrix and support the view that iron is not simply chelated, but rather is organized in a three-dimensional network. The paramagnetism of isolated iron ions is observed, in agreement with electron paramagnetic resonance spectroscopy. Furthermore, antiferromagnetic grains with a large size distribution function are present. These grains contain N spins coupled antiferromagnetically; however, N 1=2 spins are decoupled from the grain bulk and parallelly aligned. The latter subgrains are superparamagnetic with a blocking temperature ranging between 5 K and room temperature. This behavior has not been observed in synthetic melanin, where the paramagnetic contribution is strongly enhanced. Preliminary results on pigment isolated from patients affected by Parkinson's disease, a neurodegenerative pathology involving primarily pigmented neurons in substantia nigra pars compacta, show a lower total magnetization compared to control neuromelanin. The temperature behavior of zero field cooling and field cooling magnetizations is similar for both. The significant depletion of iron content in Parkinson's disease neuromelanin could indicate a progressive Fe migration from its storage environment to the cytosol. ß
Biogenic Magnetite in Humans and New Magnetic Resonance Hazard Questions
Measurement Science Review, 2011
The widespread use of magnetic resonance (MR) techniques in clinical practice, and recent discovery of biogenic ferrimagnetic substances in human tissue, open new questions regarding health hazards and MR. Current studies are restricted just to the induction of Faraday currents and consequent thermal effects, or 'inoffensive' interaction with static magnetic field. We outlined that magnetic energies associated with interaction of ferrimagnetic particles and MR magnetic fields can be dangerous for sensitive tissues like the human brain is. To simulate the interaction mechanism we use our 'Cube' model approach, which allows more realistic calculation of the particle's magnetic moments. Biogenic magnetite nanoparticles face during MR examination three principal fields: (i) main B 0 field, (ii) gradient field, and (iii) B 1 field. Interaction energy of biogenic magnetite nanoparticle with static magnetic field B 0 exceeds the covalent bond energy 5 times for particles from 4 nm up to 150 nm. Translation energy in gradient field exceeds biochemical bond energy for particles bigger than 50 nm. Biochemical bond disruption and particle release to the tissue environment, in the presence of all MR fields, are the most critical points of this interaction. And together with relaxation processes after application of RF pulses, they make biogenic magnetite nanoparticles a potential MR health hazard issue.