title: The mechanics of hyperactivation in adhered human sperm.
abstract: Hyperactivation is an important phenomenon exhibited by mammalian sperm during the process of acquiring fertilization capacity. The majority of studies have focused on incubation-induced hyperactivation in non-human species, which typically differ in size, shape, and are more homogeneous than human sperm. We develop an alternative approach via drug-induction, using high-speed imaging and analysis of same-cell changes in the flagellar movement of adhered cells. Following stimulation with 4-aminopyridine, approximately two-thirds (21 of 34) of the cells analysed exhibited a waveform with a single characteristic frequency; in all cases, the frequency was lower than before stimulation. The remaining cells (13 of 34) exhibited a more complex motility with multiple-frequency modes. The lowest mode in all cases was lower than the frequency prior to stimulation. Flagellar bending increased in all cells following stimulation and was significantly greater in the multiple-frequency responders. Despite the increased bending, time-averaged hydrodynamic power dissipation decreased significantly when assessed across all cells, the effect being significantly greater in the multiple-frequency responders than single frequency. These results reveal the heterogeneity of responses of human sperm to a hyperactivating stimulus, the methodology being potentially useful for assessing dynamic responses to stimuli in human sperm, and physiological selection of cells for assisted reproduction.
authors.affiliation: School of Clinical and Experimental Medicine , University of Birmingham , Birmingham B15 2TT, UK ; Centre for Human Reproductive Science , Birmingham Women's NHS Foundation Trust , Birmingham B15 2TG, UK.
authors.forename: E H
authors.initials: EH
authors.lastname: Ooi
authors.affiliation: School of Mathematics , University of Birmingham , Birmingham B15 2TT, UK ; Centre for Human Reproductive Science , Birmingham Women's NHS Foundation Trust , Birmingham B15 2TG, UK ; School of Engineering and Centre for Scientific Computing , University of Warwick , Coventry CV4 7AL, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Smith
authors.affiliation: Centre for Human Reproductive Science , Birmingham Women's NHS Foundation Trust , Birmingham B15 2TG, UK ; Wolfson Centre for Mathematical Biology, Mathematical Institute , University of Oxford , Oxford OX2 6GG, UK.
authors.forename: H
authors.initials: H
authors.lastname: Gadêlha
authors.affiliation: Centre for Human Reproductive Science , Birmingham Women's NHS Foundation Trust , Birmingham B15 2TG, UK ; Wolfson Centre for Mathematical Biology, Mathematical Institute , University of Oxford , Oxford OX2 6GG, UK.
authors.forename: E A
authors.initials: EA
authors.lastname: Gaffney
authors.affiliation: School of Clinical and Experimental Medicine , University of Birmingham , Birmingham B15 2TT, UK ; Centre for Human Reproductive Science , Birmingham Women's NHS Foundation Trust , Birmingham B15 2TG, UK.
authors.forename: J
authors.initials: J
authors.lastname: Kirkman-Brown
keywords: 4-aminopyridine; binding; high-speed imaging; sperm motility