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Guerra, P. A., Gegear, R. J., & Reppert, S. M. (2014). A magnetic compass aids monarch butterfly migration. Nat Commun, 5, 4164.
Abstract: Convincing evidence that migrant monarch butterflies (Danaus plexippus) use a magnetic compass to aid their fall migration has been lacking from the spectacular navigational capabilities of this species. Here we use flight simulator studies to show that migrants indeed possess an inclination magnetic compass to help direct their flight equatorward in the fall. The use of this inclination compass is light-dependent utilizing ultraviolet-A/blue light between 380 and 420 nm. Notably, the significance of light <420 nm for inclination compass function was not considered in previous monarch studies. The antennae are important for the inclination compass because they appear to contain light-sensitive magnetosensors. For migratory monarchs, the inclination compass may serve as an important orientation mechanism when directional daylight cues are unavailable and may also augment time-compensated sun compass orientation for appropriate directionality throughout the migration.
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Solov'yov, I. A., Domratcheva, T., & Schulten, K. (2014). Separation of photo-induced radical pair in cryptochrome to a functionally critical distance. Sci Rep, 4, 3845.
Abstract: Cryptochrome is a blue light receptor that acts as a sensor for the geomagnetic field and assists many animals in long-range navigation. The magnetoreceptor function arises from light-induced formation of a radical pair through electron transfer between a flavin cofactor (FAD) and a triad of tryptophan residues. Here, this electron transfer is investigated by quantum chemical and classical molecular dynamics calculations. The results reveal how sequential electron transfer, assisted by rearrangement of polar side groups in the cryptochrome interior, can yield a FAD-Trp radical pair state with the FAD and Trp partners separated beyond a critical distance. The large radical pair separation reached establishes cryptochrome's sensitivity to the geomagnetic field through weakening of distance-dependent exchange and dipole-dipole interactions. It is estimated that the key secondary electron transfer step can overcome in speed both recombination (electron back-transfer) and proton transfer involving the radical pair reached after primary electron transfer.
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Sulpizio, M., Falone, S., Amicarelli, F., Marchisio, M., Di Giuseppe, F., Eleuterio, E., et al. (2011). Molecular basis underlying the biological effects elicited by extremely low-frequency magnetic field (ELF-MF) on neuroblastoma cells. J Cell Biochem, 112(12), 3797–3806.
Abstract: Extremely low-frequency magnetic fields (ELF-MFs) may affect human health because of the possible associations with leukemia but also with cancer, cardiovascular, and neurological disorders. In the present work, human SH-SY5Y neuroblastoma cells were exposed to a 50 Hz, 1 mT sinusoidal ELF-MF at three different times, that is, 5 days (T5), 10 days (T10), and 15 days (T15) and then the effects of ELF-MF on proteome expression and biological behavior were investigated. Through comparative analysis between treated and control samples, we analyzed the proteome changes induced by ELF-MF exposure. Nine new proteins resolved in sample after a 15-day treatment were involved in a cellular defense mechanism and/or in cellular organization and proliferation such as peroxiredoxin isoenzymes (2, 3, and 6), 3-mercaptopyruvate sulfurtransferase, actin cytoplasmatic 2, t-complex protein subunit beta, ropporin-1A, and profilin-2 and spindlin-1. Our results indicated that ELF-MFs exposure altered the proliferative status and other important cell biology-related parameters, such as cell growth pattern, and cytoskeletal organization. These findings support our hypothesis that ELF radiation could trigger a shift toward a more invasive phenotype.
Keywords: Cell Line, Tumor; Cell Proliferation; Cell Survival; Humans; Immunohistochemistry; *Magnetics; Neuroblastoma/*pathology; Proteome
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Thun-Battersby, S., Mevissen, M., & Loscher, W. (1999). Exposure of Sprague-Dawley rats to a 50-Hertz, 100-microTesla magnetic field for 27 weeks facilitates mammary tumorigenesis in the 7,12-dimethylbenz[a]-anthracene model of breast cancer. Cancer Res, 59(15), 3627–3633.
Abstract: We have shown previously (W. Loscher et al., Cancer Lett., 71: 75-81, 1993; M. Mevissen et al., Carcinogenesis (Lond.), 17: 903-910, 1996) that 50-Hz magnetic fields (MFs) of low [50 or 100 microTesla (T)] flux density enhance mammary gland tumor development and growth in the 7,12-dimethylbenz[a]anthracene (DMBA) model of breast cancer in female Sprague Dawley rats. In these previous experiments, groups of rats were given 20 mg of DMBA (four weekly gavage doses of 5 mg each) and were MF- or sham-exposed for 13 weeks. The objective of the present study was to examine whether the use of a lower dose of DMBA (10 instead of 20 mg per rat), MF exposure of the rats before DMBA injection, and the increase of the MF exposure period after DMBA application to 26 weeks enhance the effect of MF on tumor development and growth. A group 99 rats was exposed to a homogeneous, horizontally polarized 100-microT MF of 50-Hz for 24 h/day for 7 days/week; another group of 99 rats was sham-exposed under the same environmental conditions as the MF-exposed rats. The exposure chambers were identical for MF-exposed and sham-exposed animals. The age of the rats was 45-49 days at the onset of exposure; duration of MF or sham exposure was 27 weeks. DMBA was administered p.o. at a dose of 10 mg/rat after 1 week of MF or sham exposure. The animals were palpated once weekly from week 6 onwards to assess the development of mammary tumors. At the end of the exposure period, the animals were killed for the determination of number and volume and histological verification of mammary tumors. All of the recordings were done in a blinded fashion; i.e., the investigators were not aware which animals were MF- or sham-exposed. Mammary tumor development and growth was significantly enhanced by MF exposure, the most marked effect on tumor incidence (190% above sham control) being observed 13 weeks after DMBA administration. At the time of necropsy, i.e., 26 weeks after DMBA administration, the incidence of histologically verified mammary tumors was 50.5% in controls and 64.7% in MF-exposed rats, the difference being statistically significant. More marked intergroup differences were recorded when tumor incidence was separately evaluated for each of the six mammary complexes, the most pronounced MF effect on tumor incidence being seen in the cranial thoracic complex. The data substantiate that, at least under the experimental conditions used in our laboratory, 50-Hz, 100-microT MF exposure significantly facilitates the development and growth of mammary tumors in the DMBA rat model of breast cancer.
Keywords: 9,10-Dimethyl-1,2-benzanthracene/administration & dosage/*toxicity; Adenocarcinoma/chemically induced/*etiology/pathology; Adenoma/chemically induced/etiology/pathology; Animals; Carcinogens/administration & dosage/*toxicity; Circadian Rhythm; *Cocarcinogenesis; Dose-Response Relationship, Drug; Electromagnetic Phenomena; Female; Fibroadenoma/chemically induced/etiology/pathology; Magnetics/*adverse effects; Mammary Neoplasms, Experimental/chemically induced/*etiology/pathology; Melatonin/deficiency/physiology; Models, Biological; Neoplasms, Radiation-Induced/chemically induced/*etiology/pathology; Organ Specificity; Ornithine Decarboxylase/physiology; Rats; Rats, Sprague-Dawley; Time Factors
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Hoffman, A. E., Zheng, T., Stevens, R. G., Ba, Y., Zhang, Y., Leaderer, D., et al. (2009). Clock-Cancer Connection in Non-Hodgkin's Lymphoma: A Genetic Association Study and Pathway Analysis of the Circadian Gene Cryptochrome 2. Cancer Research, 69(8), 3605–3613.
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