title: The dynamics of sperm detachment from epithelium in a coupled fluid-biochemical model of hyperactivated motility.
abstract: Hyperactivation in mammalian sperm is characterized by a high-amplitude, asymmetric flagellar waveform. A mechanical advantage of this hyperactivated waveform has been hypothesized to be the promotion of flagellar detachment from oviductal epithelium. In order to investigate the dynamics of a free-swimming sperm׳s binding and escaping from a surface, we present an integrative model that couples flagellar force generation and a viscous, incompressible fluid. The elastic flagellum is actuated by a preferred curvature model that depends upon an evolving calcium profile along its length. In addition, forces that arise due to elastic bonds that form and break between the flagellar head and the surface are accounted for. As in recent laboratory experiments, we find that a hyperactive waveform does result in frequent detaching and binding dynamics that is not observed for symmetric flagellar beats. Moreover, we demonstrate that flagellar behavior depends strongly on the assumptions of the bond model, suggesting the need for more experimental investigation of the biochemistry of epithelial bonding and the shedding of binding proteins on the sperm head.
authors.affiliation: Center for Computational Science and Mathematics Department, Tulane University, 6823 St. Charles Ave., New Orleans, LA 70118, USA. Electronic address: jsimons@tulane.edu.
authors.forename: Julie
authors.initials: J
authors.lastname: Simons
authors.affiliation: Department of Mathematical Sciences, Worcester Polytechnic Institute, Worcester, MA 01609, USA. Electronic address: sdolson@wpi.edu.
authors.forename: Sarah
authors.initials: S
authors.lastname: Olson
authors.affiliation: Center for Computational Science and Mathematics Department, Tulane University, 6823 St. Charles Ave., New Orleans, LA 70118, USA. Electronic address: rcortez@tulane.edu.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Cortez
authors.affiliation: Center for Computational Science and Mathematics Department, Tulane University, 6823 St. Charles Ave., New Orleans, LA 70118, USA. Electronic address: fauci@tulane.edu.
authors.forename: Lisa
authors.initials: L
authors.lastname: Fauci
mesh_terms: D000818:Animals; D002417:Cattle; D004848:Epithelium / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D013081:Sperm Motility / Q000502:physiology*; D013082:Sperm Tail / Q000502:physiology*
keywords: Hyperactivation; Regularized Stokeslets; Sperm motility; Stokes equations