I am sure you wondered, what stopped me from writing new blog articles. I can tell you... I am a happy and fresh hamster-mama. :D I bought a new hamster. Her name is Elsa Neumann, like the first female PhD in physics in the university of Berlin. I really love her and in the moment we train to react to her name and then climb on my hand. That needs some time. I am sorry :D Isn't it nice that there are still some big biological science question left for us to discover? One example: magnetoreception. It is proven to exist in fishes, birds, turtles, mammals, insects and bacteria. Nevertheless, we don't know how it works. Already in 1855, Alexander von Middendorff assumed that pigeons navigate with the help of the earth's magnetic field. Nevertheless, not earlier than 1960 this sense for the magnetic field was for the first time experimentally shown in European robin (see picture). And now, more than another 50 years later, we still don't know how it works. Nordmann et al. (2017) wrote a nice review about it: "Unsolved mysteries: Magnetoreception - A sense without a receptor". There they explain in detail why exploring magnetoreception is complicated and all the different theories which are discussed nowadays. Is it sensed by a mechanically sensitive magnetite-based mechanoreceptor which translates the movement of small magnetic molecules inside a cell? Such mechanism is used in magnetotactic bacteria. However, until now, nothing comparable in larger animals was found. But the search is hard, because it could be anywhere in the body. Of course, it could also be a light-sensitive and chemical based mechanism. The European robins need blue/green light for magnetic orientation. And the other way around: low frequency electromagnetic fields can change the circadian behavior (sleep-awake-cycle) which is normally controlled by light. So is there a link between light and magnetoreception? Maybe. But it could also be that there is a structure similar to the vestibular system which we use for our sense of balance. So a sort of circuit which "uses" the Faraday's law of electromagnetic induction: the movement in a fixed magnetic field would result in an electric signal which for example could be sensed y voltage-gated channels, which we find a lot in the nervous system. Everything is possible. Nothing is proven yet. Unsolved mysteries: Magnetoreception—A sense without a receptor
Gregory C. Nordmann, Tobias Hochstoeger, David A. Keays PLOS Biology (October 2017)
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Welcome back from the fall vacation break. Did you ever wonder how a leaf becomes its leaf form? Jiyan Qi et al (2017) had this question and wrote a paper about it. We know that a leaf is constructed by different tissues/parts: because of differences in gene expression the upper side (adaxial domain) looks different from the lower side (abaxial domain). But which mechanism creates the flat leaf form with upper and lower side? The bud… ergo the start of a developing leaf… is round! Jiyan Qi et al (2017) showed that “relatively simple changes in mechanical properties can account for dynamic shape changes during asymmetric leaf development”. To make a long story short: In the developing (round) leaf the lower side has a higher auxin concentration as the upper side. Auxin is a plant hormone and can lead for example to cell wall loosening by de-methyl-esterification of pectins, a major component of the primary cell wall. The lower sider gets more elastic as the upper side. This difference in elasticity leads to the leaf asymmetry. With proceeding development, the rigid zone of the upper side moves to the middle. “From a physical perspective, the stiff cells receive stronger constraints from their neighbouring […] cells, such that they prefer to grow and divide by pressing on the soft inner cells“. The leaf stretches and gets flat. Just as side note: What I like about the paper is that they use computational models to test their hypothesis if differences in cell wall stiffness and epidermal restriction can lead to the leaf asymmetry. They model what would happen if the cell wall elasticity of the upper and lower region is changed/mixed up. Then they test the model predictions by manipulating the cell wall plasticity experimentally. |
IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
März 2018
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