title: A simplified mass-transfer model for visual pigments in amphibian retinal-cone outer segments.
abstract: When radiolabeled precursors and autoradiography are used to investigate turnover of protein components in photoreceptive cone outer segments (COSs), the labeled components--primarily visual pigment molecules (opsins)--are diffusely distributed along the COS. To further assess this COS labeling pattern, we derive a simplified mass-transfer model for quantifying the contributions of advective and diffusive mechanisms to the distribution of opsins within COSs of the frog retina. Two opsin-containing regions of the COS are evaluated: the core axial array of disks and the plasmalemma. Numerical solutions of the mass-transfer model indicate three distinct stages of system evolution. In the first stage, plasmalemma diffusion is dominant. In the second stage, the plasmalemma density reaches a metastable state and transfer between the plasmalemma and disk region occurs, which is followed by an increase in density that is qualitatively similar for both regions. The final stage consists of both regions slowly evolving to the steady-state solution. Our results indicate that autoradiographic and cognate approaches for tracking labeled opsins in the COS cannot be effective methodologies for assessing new disk formation at the base of the COS.
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Weber
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina; Center for Nonlinear and Complex Systems, Duke University, Durham, North Carolina. Electronic address: laurens.howle@duke.edu.
authors.forename: Laurens E
authors.initials: LE
authors.lastname: Howle
authors.affiliation: Department of Mechanical Engineering, United States Naval Academy, Annapolis, Maryland.
authors.forename: Mark M
authors.initials: MM
authors.lastname: Murray
authors.affiliation: Departments of Cell Biology, Neurobiology, and Ophthalmology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Corless
mesh_terms: D000818:Animals; D001001:Anura / Q000378:metabolism*; D008954:Models, Biological; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism* / Q000648:ultrastructure; D055214:Retinal Photoreceptor Cell Outer Segment / Q000378:metabolism* / Q000648:ultrastructure; D012168:Retinal Pigments / Q000378:metabolism*; D012996:Solutions
chemical_list: D012168:Retinal Pigments; D012996:Solutions