test Browse by Author Names Browse by Titles of Works Browse by Subjects of Works Browse by Issue Dates of Works

Advanced Search
& Collections
Issue Date   
Sign on to:   
Receive email
My Account
authorized users
Edit Profile   
About T-Space   

T-Space at The University of Toronto Libraries >
School of Graduate Studies - Theses >
Master >

Please use this identifier to cite or link to this item: http://hdl.handle.net/1807/30571

Title: An Examination of the Free Hormone Hypothesis through Phylogenetic Comparison of Glucocorticoid and Corticosteroid-binding Globulin Levels Among the Vertebrates
Authors: Desantis, Lanna
Advisor: Boonstra, Rudy
Department: Ecology and Evolutionary Biology
Keywords: Glaucomys
HPA axis
stress physiology
field endocrinology
natural populations
Issue Date: 7-Dec-2011
Abstract: The “Free Hormone Hypothesis” posits that only free, unbound hormone is biologically active and available to tissues. Conventional biomedical wisdom proposes that corticosteroid-binding globulin (CBG) normally binds 90-95% of blood glucocorticoid (GC), rendering it unavailable to tissues. Under chronic stress, GC levels greatly exceed binding capacity resulting in impaired bodily function and reduced fitness. However, under normal conditions in northern and southern flying squirrels, less than 10% of GC is bound, presenting a major challenge to the hypothesis. To assess the extent of variation in these properties among vertebrates, I compared all species (88) with known GC and CBG and levels. 92% conform reasonably to known convention. Flying squirrels appear as extreme species, as do New World monkeys, yet both groups evolved from ancestors that followed normal convention. I speculate as to how this state evolved and persisted through time.
URI: http://hdl.handle.net/1807/30571
Appears in Collections:Master

Files in This Item:

File Description SizeFormat
Desantis_Lanna_M_201111_MSc_DatatableSupplementary Data Table277.5 kBMicrosoft Excel
Desantis_Lanna_M_201111_MSc_thesis.pdfMain Thesis2.53 MBAdobe PDF

Items in T-Space are protected by copyright, with all rights reserved, unless otherwise indicated.