Determining the mechanical properties of Rainbow Smelt (Osmerus mordax) eye tissue using atomic force microscopy (AFM)

Abstract

Hyperosmotic stress is the condition of increased cellular osmotic pressure and is linked to a number of mammalian diseases. One such disease is diabetes mellitus, which is characterized by a state of elevated blood glucose concentration which eventually can lead to such issues as a leakage of fluids from the blood vessels into the surrounding eye tissue. The resulting increase in osmotic pressure of the eye can lead to the eventual vision loss which is seen in diabetic patients. Other examples of hyperosmotic condition exist in nature, one such case being found in Rainbow Smelt. In this case, smelt are capable of surviving in colder water environments by increasing the osmotic pressure of their bodily fluids, including within the eye. This increase in osmotic pressure depresses the freezing point of their bodily fluids, allowing for adaptation to colder climates. However, the fish’s vision isn’t impacted by the hyperosmotic state. The object of this work is to study the key structural and mechanical properties of sections of rainbow smelt eye using Atomic Force Microscopy (AFM). Two subgroups of smelt were studied: ones raised in a warm water environment that show no hyperosmotic conditioning, and ones raised in a cold water environment which show elevated osmotic pressures in the eye. Comparisons between the two smelt subgroups were made in both dry and hydrated environments. By determining any key structural, mechanical, or chemical changes in the cold smelt eye, we hope to better understand the hyperosmotic conditioning that takes place within the eye.