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Daniel G. Cyr

Toxicologie/biologie cellulaire/moléculaire

Effets des contaminants environnementaux sur le système reproducteur mâle

Research Interest

Our laboratory is interested understanding the role of cell-cell interaction in the epididymis and their importance in creating a luminal environment suitable for sperm maturation. We are also interested in the effects of environmental toxicants and their effects on cell-cell interaction and in the development and function of male reproductive function.

Regulation on intercellular communication

Intercellular gap junctions are essential structural components that allow direct communication between neighboring cells. Gap junctional communication is therefore critical for coordinating cellular function within complex epithelia. In the male reproductive tract, gap junctional communication is essential for the exchange of cellular messengers necessary for spermatogenesis in the testis and for the coordination of sperm maturation in the epididymis. A crucial aspect of sperm maturation is the fact that the epididymal epithelium must coordinate the different regions of epididymis in order to modify the luminal environment necessary for sperm maturation. Our objectives are to understand the role and regulation of gap junctional communication in the epididymis and the role of this cellular communication in sperm maturation. In the short-term objectives are to target the gap junctional proteins, connexins, and correlate their level of expression to both the physiological and structural integrity of the epididymis, in order understand the role of gap junctions in coordinating epithelial function and sperm maturation.

Epididymal tight junctions and the blood-epididymal barrier

The creation and maintenance of microenvironments within biological systems are crucial for the development and function of specialized cells within complex organisms. These microenvironments are created by tight junctions between cells which form an impenetrable seal, thereby forcing receptor mediated transport across cells and creating specific environments. These cellular barriers exist in the brain, retina, thymus, intestine, and kidney, as well as in male reproductive tissues such as the testis and epididymis. Understanding the regulation of proteins responsible for the maintenance of these barriers is necessary, as tight junctions undergo rapid alterations in diseases such as celiac disease, Crohn's disease, renal diseases, asthma, cystic fibrosis and breast cancer. In male reproductive tissues, the microenvironments formed by tight junctions are essential for spermatogenesis in the testis and for sperm maturation in the epididymis. While unexplained male infertility results from multiple causes, studies in rats have shown that infertility in ageing males is accompanied by a loss of tight junctions in the epididymis. Given the crucial nature of tight junctions in both normal physiological processes and in widespread pathologies, including male infertility, our objective is to understand the factors regulating the formation of the tight junctions responsible for the formation of the blood-epididymal barrier, a key determinant of male fertility.

Effects of endocrine disruptors on fish reproduction

We have shown that fish in the St. Lawrence River are exposed to environmental estrogens. This contamination originates in the Ottawa River. Other sources of estrogenic contamination include the Montreal Urban Community's sewage effluent. Contamination of aquatic ecosystems by estrogenic substances can be associated with a variety of chemical contaminants. While exposure to estrogenic contamination can be monitored by measuring the expression of vitellogenin (VTG) in male and immature fish, there has been relatively limited information on the significance of induced VTG on gonadal development and reproductive fitness in males. A difficulty in assessing the effects of endocrine disrupting chemicals (EDCs) on fish reproduction stems from the fact that there are a limited number of tools available to assess testicular development in fish. The development of such tools is critical for understanding the effects of EDCs on the testis. Given the extent of the contamination of the St. Lawrence by EDCs, and the site specific effects we have characterized in the past, this represents an ideal ecosystem model in which to develop tools needed to assess the effects of EDCs on the testis, and to establish specific effects associated with the contamination of the St. Lawrence. We have developed a variety of biomarkers to study the effects of EDCs on male reproduction. These include sperm motility, and markers of spermatogenesis and sex reversal. We have shown that sperm number and motility is altered in spottail shiners captured at sites where male shiners have elevated hepatic VTG mRNA levels. We are currently interested to further establish the effects of EDCs, on semen quality using a laboratory based approach and to determine the effects of EDCs on both spermatogenesis and sex determination using a field-based sampling approach

 

Biography

Dr. Cyr is a graduate of Concordia University where he received a B.Sc. (Hons) and M.Sc. (Biology) and from the University of Manitoba where he received a Ph.D. (Zoology). Following four years of postdoctoral studies at McGill University (Pharmacology), Dr. Cyr worked as a scientist for Health Canada (1992-93) and the Department of Fisheries and Oceans (1993-97).

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Daniel Cyr et les mécanismes cellulaires du système reproducteur masculin ...

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Daniel G. Cyr, professeur au Centre INRS-Institut Armand-Frappier

Daniel G. Cyr, professeur au Centre INRS-Institut Armand-Frappier

Daniel G. Cyr, professeur au Centre INRS-Institut Armand-Frappier

Daniel G. Cyr, professeur au Centre INRS-Institut Armand-Frappier