Séminaire ISTerre

Magnetic nanoparticles in organisms: From bacteria to the human brain

mardi 20 mai 2025 - 10h30
Leon Kaub - udwig-Maximilians-Universität München (LMU Munich)
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Magnetite (Fe3O4) nanoparticles are ubiquitous in the environment. They are formed in igneous and metamorphic environments and are emitted from anthropogenic processes such as coal combustion and traffic. Magnetite particles are also biomineralized by microbes in soil and sediments and have even been found in tissues including the human brain. The most studied magnetite-producing organisms are magnetotactic bacteria (MTB), which use magnetite for an alignment with the geomagnetic field that guides them to their preferred habitat. While the biomineralization processes in MTB are well understood, the presence of magnetite in the brain remains enigmatic. Particles may be produced in the brain through controlled biomineralization, such as in MTB, but could also originate from imbalanced iron metabolism, or reach the brain from the outside environment as air pollution. Our magnetic measurements of postmortem human brain stems and the surrounding meninges argue for an external origin of magnetite and its translocation via blood. Extremely high magnetite levels in the brain of a subject with liver cirrhosis and hepatic iron overload support the hypothesis that blood is the main carrier. Furthermore, we found a constant concentration of single-domain magnetite in the brain with age, which could argue for internal biomineralization, but is rather explained by clearance processes that lead to steady-state magnetite levels. An observed increase in superparamagnetic particle content in individuals over 50 implies reduced clearance mechanisms in older individuals. Overall, most magnetite nanoparticles in the brain appear to undergo dynamic processes to reach and enter the brain after circulating in blood. This is concerning due to their high redox activity and surface charge, which has the potential to significantly impact health.

Equipe organisatrice : Minéralogie

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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“Minimalist seismology”: studying earthquakes with sparse instrumentation

jeudi 17 septembre 2026 - 11h00

Mathieu Causse - ISTerre

Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Stable‑to‑dynamic expansion of fault slipping area through fluid injection observed in laboratory experiments using a sub‑meter scale specimen

vendredi 18 septembre 2026 - 14h00

Takatoshi Ito  - Université de Tohoku, Japan

Equipe organisatrice : Mécanique des failles

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Apport des expériences analogiques pour la modélisation et le suivi en temps réel de la propagation du magma en profondeur : Exemple du Rift Est Africain

jeudi 1er octobre 2026 - 11h00

Virginie Pinel - ISTerre

Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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A t-on encore besoin de plaques pour expliquer la tectonique de la vallée du Rhône et des Alpes Occidentales ?

vendredi 2 octobre 2026 - 11h00

philippe VERNANT - Geosciences Montpellier

Equipe organisatrice : Tectonique active et sismicité

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 2 octobre 2026 - 14h00

Hugo Boulze - 

Equipe organisatrice : Cycle sismique et déformations transitoires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 9 octobre 2026 - 11h00

Eric Beaucé - ISTerre

Equipe organisatrice : Cycle sismique et déformations transitoires

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 20 novembre 2026 - 11h00

Farzaneh Mohammadi - ENS Paris

Equipe organisatrice : Cycle sismique et déformations transitoires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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