ID Number		2427
Study Type		In Vivo
Model		Studies of bird behavior and other endpoints upon EMF exposure.
Details		AUTHORS' ABSTRACT: Engels et al. 2014 (IEEE #5808): Electromagnetic noise is emitted everywhere humans use electronic devices. For decades, it has been hotly debated whether man-made electric and magnetic fields affect biological processes, including human health. So far, no putative effect of anthropogenic electromagnetic noise at intensities below the guidelines adopted by the World Health Organization has withstood the test of independent replication under truly blinded experimental conditions. No effect has therefore been widely accepted as scientifically proven. Here we show that migratory birds are unable to use their magnetic compass in the presence of urban electromagnetic noise. When European robins, Erithacus rubecula, were exposed to the background electromagnetic noise present in unscreened wooden huts at the University of Oldenburg campus, they could not orient using their magnetic compass. Their magnetic orientation capabilities reappeared in electrically grounded, aluminium-screened huts, which attenuated electromagnetic noise in the frequency range from 50kHz to 5 MHz by approximately two orders of magnitude. When the grounding was removed or when broadband electromagnetic noise was deliberately generated inside the screened and grounded huts, the birds again lost their magnetic orientation capabilities. The disruptive effect of radiofrequency electromagnetic fields is not confined to a narrow frequency band and birds tested far from sources of electromagnetic noise required no screening to orient with their magnetic compass. These fully double blinded tests document a reproducible effect of anthropogenic electromagnetic noise on the behaviour of an intact vertebrate. AUTHOR'S ABSTRACT: Kirschvink 2014 (IEEE #5809): Weak radio waves in the medium-wave band are sufficient to disrupt geomagnetic orientation in migratory birds, according to a particularly well-controlled study. But the underlying biophysics remains a puzzle. AUTHORS' ABSTRACT: Efimova and Hore 2008 (IEEE #6457): It is not yet understood how migratory birds sense the Earth's magnetic field as a source of compass information. One suggestion is that the magnetoreceptor involves a photochemical reaction whose product yields are sensitive to external magnetic fields. Specifically, a flavin-tryptophan radical pair is supposedly formed by photoinduced sequential electron transfer along a chain of three tryptophan residues in a cryptochrome flavoprotein immobilized in the retina. The electron Zeeman interaction with the Earth's magnetic field ( approximately 50 microT), modulated by anisotropic magnetic interactions within the radicals, causes the product yields to depend on the orientation of the receptor. According to well-established theory, the radicals would need to be separated by >3.5 nm in order that interradical spin-spin interactions are weak enough to permit a approximately 50 microT field to have a significant effect. Using quantum mechanical simulations, it is shown here that substantial changes in product yields can nevertheless be expected at the much smaller separation of 2.0 +/- 0.2 nm where the effects of exchange and dipolar interactions partially cancel. The terminal flavin-tryptophan radical pair in cryptochrome has a separation of approximately 1.9 nm and is thus ideally placed to act as a magnetoreceptor for the compass mechanism. AUTHORS' ABSTRACT: Hore and Mouritsen 2016 (IEEE #6605): Although it has been known for almost half a century that migratory birds can detect the direction of the Earth's magnetic field, the primary sensory mechanism behind this remarkable feat is still unclear. The leading hypothesis centers on radical pairs-magnetically sensitive chemical intermediates formed by photoexcitation of cryptochrome proteins in the retina. Our primary aim here is to explain the chemical and physical aspects of the radical-pair mechanism to biologists and the biological and chemical aspects to physicists. In doing so, we review the current state of knowledge on magnetoreception mechanisms. We dare to hope that this tutorial will stimulate new interdisciplinary experimental and theoretical work that will shed much-needed additional light on this fascinating problem in sensory biology.
Findings		Effects
Status		Completed With Publication
Principal Investigator
Funding Agency		?????
Country
References		Engels, S et al. Nature. , (2014) 509:353-356 Kirschvink, JL Nature., (2014) 509:574-575 Efimova, O et al. Biophys J., (2008) 94:1565-1574 Hore, PJ et al. Annu Rev Biophys., (2016) 45:299-344 Albaqami, M et al. Scientific Reports., (2020) 10:11260- Kattnig, DR et al. Nat Chem., (2016) 8:384-391 Muheim, R et al. Proc Natl Acad Sci U S A., (2016) 113:1654-1659 Nimpf, S et al. Curr Biol., (2019) 29:4052-4059 Akbari, H et al. J Environ Health Sci Eng. , (2021) 19:1827-1833 Nath, A et al. Urban Ecosyst. , (2022) 25:1279-1295 Nyirenda, VR et al. Biologia. , (2022) 77:2237-2249
Comments