Elizabeth Yokum


Presentation: 9:00-10:15 a.m., Kennedy Union Ballroom



Download Project (1.3 MB)


Cope’s gray treefrog Dryophytes chrysoscelis belongs to a select group of vertebrates that survives the winter by tolerating repeated freezing and thawing of body water. One of the ways that D. chrysoscelis survives these freeze-thaw cycles is by using a complex system of chemical cryoprotectants to prevent cells from freezing and to maintain homeostasis of body fluids. We hypothesized that an additional mechanism that enables freeze tolerance is the modification of cellular membrane lipid composition during cold acclimation, thereby optimizing cellular biophysical properties and function in preparation for freezing. To evaluate that hypothesis, cellular membranes were prepared from liver, skeletal muscle, and blood cells of wild-caught male treefrogs that were cold-acclimated to 5°C (cold) or maintained at 22°C as the (warm) control group. 1H-NMR analysis was used to quantify relative abundance of membrane cholesterol and to characterize phospholipid fatty acids. Principal components statistical analysis indicates that membrane lipid profiles are tissue-specific, but that membrane lipids were affected by cold acclimation in liver tissue only. In liver, both free and esterified membrane cholesterol was elevated in the cold by 2-fold and 1.4-fold, respectively (P < 0.05). Fatty acid characterization revealed that chain length did not vary between groups (P = 0.46), but total fatty acid unsaturation (i.e. number of double bonds) was nearly doubled in cold frogs compared to the warm control (P < 0.05). Both mono and polyunsaturated fatty acids are more abundant in the cold group and the ω-6 fatty acid linoleic acid was more than 2-fold greater in membranes from cold frogs (P < 0.05). These specific modifications in liver membrane lipid composition support our hypothesis and would likely enhance cellular freeze tolerance in the cold. Surprisingly, membrane lipids were not similarly adapted in blood cells or muscle, indicating that membrane adaptation may be tissue-specific or adapted during freezing conditions.

Publication Date


Project Designation

Graduate Research

Primary Advisor

Carissa Krane, Jeremy Erb

Primary Advisor's Department



Stander Symposium, College of Arts and Sciences

Institutional Learning Goals

Scholarship; Practical Wisdom; Critical Evaluation of Our Times

NMR-Based Lipid Analysis Indicates Cellular Membrane Lipids in Liver, but Not Skeletal Muscle or Blood Cells, Are Cold-Adapted in the Freeze-Tolerant Treefrog <em>Dryophytes chrysoscelis</em>