Dr. Michael E. Geusz
Ph.D., Vanderbilt University Circadian rhythms of cells LSC (419)372- mgeusz@bgnet.bgsu.edu Research and Personal Page

Research Interests:: Many organisms show a daily rhythm in behavior and physiology because of their endogenous circadian pacemakers. These circadian clocks enable animals to predict when daily changes will occur in their environment, which is of obvious adaptive value. They also synchronize multiple rhythmic internal processes. In humans, the circadian system is prominent in daily regulation of sleep, blood pressure, immune responses, alertness, and numerous other behaviors. My lab is focused on the mechanisms of these biological clocks and how their timing adjusts to daily cycles of light and dark in the environment. We rely on in vitro and in vivo systems to study the major circadian pacemaker in mammals, the suprachiasmatic nucleus of the hypothalamus. We use bioluminescent transgenic mice expressing the firefly luciferase gene, imaging, pharmacology, immunocytochemistry, and electrical recording of neural impulses to characterize the cells generating circadian rhythms.

Selected Publications:

Collaco, A, and Geusz, M.E. (2003) Imaging whole body immediate-early gene expression in haired and hairless transgenic mice. BMC Physiology 3: 8-19.

Sigworth, L. A., Liao, L., Chandler, T. R., and Geusz, M.E. (2003) Luciferase expression controlled by a viral gene promoter in a mammalian circadian pacemaker. NeuroReport 14: 443-447.

Geusz, M.E. (2001) Bioluminescence imaging of gene expression in living cells and tissues. In: Methods in Cellular Imaging. Basics of Fluorescence, Fluorophores, Microscopy and Detectors. A. Periasamy, (ed.) Oxford Univ. Press, New York .395-408

Nunemaker, C.S., DeFazio, R.A., Geusz, M.E., Herzog, E.D., Pitts, G.R., Moenter, S.M. (2001) Long-term recordings of networks of immortalized gonadotropin-releasing hormone neurons reveal spontaneous episodic patterns of action potential firing. J Neurophysiology.86:86-93

Liao, L. and Geusz, M.E. (2001) Luciferase bioluminescence enables real-time imaging of mammalian gene expression. The Spectrum. 14: 15-20

Sigworth, L.A., Chandler, T.R., Liao, L., and Geusz, M.E. (2000). Luciferase imaging reveals distinct patterns of gene regulation in live brain slices. In: Bioluminescence and Chemiluminescence 2000. J. F. Case, P.J. Herring, B.H. Robison, SHD Haddock, LJ Kricka, PE Stanley (eds.) World Scientific, Singapore.185-188

Tosini, G. Doyle, S., Geusz, M.E., and Menaker, M. (2000) Induction of photosensitivity in neonatal rat pineal gland. Proceedings of the National Academy of Sciences (USA) 97: 11540-11544.

Geusz, M.E., Fletcher C., Block, G.D., Straume, M., Copeland, N.G., Jenkins, N.A., Kay, S.A., Day, R.N. (1997) Long-term monitoring of circadian rhythms in c-fos gene expression from suprachiasmatic nucleus cultures. Current Biology 7: 758-766.

Herzog, E.D., Geusz, M.E., Khalsa, S.B., Straume, M., and Block, G.D. (1997) Circadian rhythms in mouse suprachiasmatic nucleus explants on multimicroelectrode plates. Brain Research 757: 285-290.

Geusz, M.E., Foster, R.G., DeGrip, W.J., and Block, G.D. (1997) Opsin-like immunoreactivity in the circadian pacemaker neurons and photoreceptors in the eye of the opisthobranch mollusk Bulla. Cell and Tissue Research 287: 203-210.

Block, G., Geusz, M., Khalsa, S., Michel, S. (1995) A clockwork Bulla: Cellular study of a model circadian system. Seminars in the Neurosciences 7: 37-42.

Geusz, M.E., and Block, G.D. (1994) Intracellular calcium in the entrainment pathway of molluscan circadian pacemakers. Neuroscience and Biobehavioral Reviews 18: 555-561.

Tominaga, K., M.E. Geusz, S. Michel, and S.T. Inouye. (1994) Calcium imaging in organotypic cultures of the rat suprachiasmatic nucleus. NeuroReport 5: 1901-1905.

Geusz, M.E., Michel, S. and Block, G.D. (1994) Intracellular calcium responses of circadian pacemaker neurons measured with fura-2. Brain Research 638: 109-116.

Michel, S., Geusz, M.E., Zaritsky, J.J., and Block, G.D. (1993) Circadian rhythm in membrane conductance expressed in isolated neurons. Science 259: 239-241.

Block, G. D., Khalsa, S. B. S., McMahon, G. D., Michel, S., and Geusz, M. E. (1993) Cellular mechanisms of biological timekeeping. International Review of Cytology 146: 83-144.

Geusz, M.E., and Block, G.D. (1992) The retinal cells generating the circadian small spikes in the Bulla optic nerve. Journal of Biological Rhythms 7: 255-268.

Geusz, M.E., and Page, T.L. (1991) An opsin-based photopigment mediates phase shifts of the Bulla circadian pacemaker. Journal of Comparative Physiology A 168: 565-570.

Geusz, M.E., and Page, T.L. (1990) The circadian rhythm and photosensitivity of small impulses of the Bulla eye. Journal of Comparative Physiology A 166: 795-801.