Dr.Le Bihan Abstract En2
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35th HONDA PRIZE Commemorative Symposium Abstract of the Commemorative Speech Ecotechnology of the water molecule in biology and medicine" Denis Le Bihan At the onset of the 21st century humankind is focusing its attention on a very small molecule made of three atoms, one carbon atom and two oxygen atoms. Controlling CO2 in the atmosphere is becoming a major goal, economically, socially, politically. Yet, there is another small molecule, also made of three atoms, one oxygen atom and two hydrogen atoms, which is going to play a similarly prominent role if not more in the near future. While an excessive concentration of CO2 might be harmful to life on earth as we know it, H2O, especially in its liquid form, the “Blue Gold”, is just indispensable to our lives. Over the past centuries lack of access to water has triggered death, through drought, famine or even wars. The preservation of the quality and abundance of drinking water will become a major challenge for nations during this century. This is no surprise. Water makes 60 to 70% of the human body weight and is crucial to the working of the biological machinery. Different organisms have adopted different strategies in the way they get the most out of water, depending on their environment, and water contributes to the biodiversity. Faulty mechanisms in the use of water by tissues may lead to severe diseases or death. In the mid 1980s it was shown that diffusion of water in the brain could be imaged using Magnetic Resonance Imaging (MRI). During their random displacements water molecules probe tissue structure at a microscopic scale, thus providing unique information on the functional architecture of tissues. A dramatic application of diffusion MRI has been acute brain ischemia, following the discovery that water diffusion drops immediately after the onset of an ischemic event, when brain cells undergo swelling through cytotoxic edema. With its unmatched sensitivity water diffusion MRI provides patients with the opportunity to receive suitable treatment at a stage when brain tissue might still be salvageable, thus avoiding them terrible handicaps. On the other hand, it was found that water diffusion is anisotropic in white matter, because axon membranes limit molecular movement perpendicularly to the fibers. This feature can be exploited to produce stunning maps of the orientation in space of the white matter tracks and brain connections in just a few minutes, as well as to provide information on white track microstructure and integrity. With water diffusion MRI it has been shown that some psychiatric disorders, such as schizophrenia might result from faulty brain connection. Water diffusion can also give clues on the cellular organization within lesions in many organs, such as brain, breast, liver or prostate. As such, diffusion MRI is now being used for an accurate and early diagnosis of cancer, or to monitor treatment effects. Clearly, water deserves to be seen as the prime “biological molecule” and its importance should not be forgotten and taken for granted. .