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Graduate Program in Biology

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Colin G.H. Steel

PhD (Queen's)
Professor of Biology

E-mail: csteel@yorku.ca
Web: www.yorku.ca/csteel

Research Areas: Animal Physiology: Neurobiology, Endocrinology, Physiology of Circadian Rhythms, Insect Physiology, Control of Development

Colin G.H. Steel Colin G.H. Steel

Current Research Projects 

We have current openings for new graduate students and for a junior post-doctoral fellow.

Our research is focussed on the mechanisms of communication and coordination between cells and tissues in an animal model system. We work on both the nervous system and the endocrine system, since these are the two key regulatory systems in animals. Research projects are available at molecular, cellular, tissue and whole animal levels, with the general goal of understanding physiological regulatory mechanisms. Our model system is the regulation of development and reproduction in the insect Rhodnius prolixus. This animal has many special virtues for experimentation and has been widely used in pioneering studies of physiological mechanisms. We also employ terrestrial and freshwater crustaceans, depending on which animal system will best answer our experimental questions. The various cell and tissue changes that make up growth and development are all timed to occur at particular times of the day. Therefore, our laboratory has a special interest in the mechanisms by which circadian clocks control the endocrine and nervous systems.

Using confocal laser scanning microscopy and fluorescent antibodies, we showed that the nuclear receptor for a steroid hormone that is critical for both development and reproduction (ecdysone) undergoes daily shuttling between the cytoplasm and the nucleus in target cells. This rhythmic shuttling induces time-of-day specific gene expression and therefore causes cellular rhythms in target cells. Rhythmic shuttling is caused by a circadian rhythm in the blood levels of ecdysone, measured by radio-immunoassay and HPLC. In turn, this endocrine rhythm is generated by rhythmic synthesis of ecdysone by the prothoracic glands. We found that the glands synthesise ecdysone rhythmically in organ culture and that they contain a light-sensitive circadian clock. The clock consists of a molecular oscillator in each gland cell that is based on the circadian cycling of the 'clock proteins' period and timeless.

Colin G.H. SteelThe brain synchronises these glandular clock cells with each other (and with the external world) by rhythmically releasing a neuropeptide hormone (prothoracicotropic hormone) which acts directly on the gland cells. We located specialised 'clock neurons' in the brain (which possess molecular oscillators like those in the glands) and traced their axon pathways through the brain. They make close connections with the neurons that make the neuropeptide. We found many other brain neuropeptide hormones are also released rhythmically under the control of this brain clock. Many electrophoretic, immunological and in vitro assay techniques are used to measure the neuropeptides. The brain 'clock neurons' represent a master clock for the animal. It transmits rhythmicity throughout the animal by controlling rhythmic release of neuropeptide hormones. This arrangement is astonishingly similar to the pathway found in mammals that controls rhythmic release of pituitary hormones. Our findings on the interactions between clock neurons and the endocrine system are directly applicable to mammals.

We found the vertebrate timekeeping hormone melatonin has a circadian rhythm in insect blood. As in vertebrates, the intestine produces more melatonin than the nervous system and does so in response to feeding. Feeding may be coordinated with development by gastrointestinal melatonin.

We are associated with the current active NIH project to sequence the genome of Rhodnius. Specific gene sequence data will be available over the next year that will open numerous new avenues of investigation.

Degrees

1975 D.I.C., Circadian Rhythms, Imperial College
1971 Ph.D.,Endocrinology, Queen's University
1971 M.A., Zoology, Cambridge University
1967 B.A., Zoology, Cambridge University

Honours and Awards 

Fellow, Royal Entomological Society

Scholarly and Professional Memberships 

Courses Taught 

SC/BIOL 3060  4.00          Animal Physiology I        
SC/BIOL 4310  3.00          Biological Timekeeping  
SC/NATS 1610 6.00         The Living Body
SC/BIOL 4330  3.00          Invertebrate Endocrinology

Selected Publications  

Reviews for interested students:

Steel, C.G.H. and Vafopoulou,X. (2006) Circadian orchestration of developmental hormones in the insect, Rhodnius prolixus. Comp. Biochem. Physiol. A. 144, 351-364. 

Vafopoulou,X. and Steel, C.G.H. (2005)  Circadian Organization of the Endocrine System. In:  Comprehensive Molecular Insect Science, eds. L.I. Gilbert, K. Iatrou, S. Gill.  Elsevier, Oxford.  Vol. 3, pp. 551-614.  

Steel,C.G.H. and Vafopoulou,X. (2002) Physiology of Circadian Systems. In: Insect Clocks (Saunders,D.S. with Steel,C.G.H., Vafopoulou,X., Lewis,R.D.), third edition, pp. 115-188.  Elsevier, Amsterdam

Some original research articles:

Vafopoulou,X,. Steel, C.G.H., and Terry, K.L. (2007) Neuroanatomical relations of prothoracicotropic hormone neurons with the circadian timekeeping system in the brain of larval and adult Rhodnius prolixus (Hemiptera). J. Comp. Neurol. 503, 511-524.

Vafopoulou,X., Laufer, H. and Steel, C.G.H. (2007) Spatial and temporal distribution of the ecdysteroid receptor (EcR) in haemocytes and epidermal cells during wound healing in the Crayfish, Procambarus clarkii. Gen. Comp. Endocrinol. 152, 359-370.

Shlattner,U., Vafopoulou,X., Steel, C.G.H., Hormann, R.E. and Lezzi, M. (2006) Non-genomic ecdysone effects and the invertebrate nuclear steroid hormone receptor EcR ' new role for an 'old' receptor? Molec. Cell. Endocrinol. 247, 64-72.

Vafopoulou,X. and Steel, C.G.H. (2006) Ecdysteroid hormone nuclear receptor (EcR) exhibits circadian cycling in certain tissues, but not others, during development in Rhodnius prolixus (Hemiptera). Cell Tissue Research 323, 443-455.  

Vafopoulou,X. and Steel, C.G.H. (2005) Testis ecdysiotropic peptides in Rhodnius prolixus: Biological activity and distribution in the nervous system and testis. J. Insect Physiol. 51, 1227-1239.  

Vafopoulou,X., Steel C.G.H. and Terry K.L. (2005) Ecdysteroid receptor (EcR) shows marked differences in temoral patterns between tissues during larval-adult development in Rhodnius prolixus: Correlations with haemolymph ecdysteroid titres. J. Insect Physiol. 51, 27-38.  

Gorbet, D. and Steel, C.G.H. (2003) A miniature radioimmunoassay for melatonin for use with small samples from invertebrates.  Gen. Comp. Endocrinol. 134, 193-197.