title: Trajectory variance and autocorrelations within single-sperm tracks as population-level descriptors of sperm track complexity, predictability, and energy-generating ability.
abstract: The objectives of the present study were to develop an alternative  theoretical approach to the analysis of sperm motility and to develop motility  parameters that would complement those more commonly used in current  computer-assisted semen analysis procedures. We have defined a set of  parameters and have tested them using boar spermatozoa undergoing  bicarbonate-induced motility activation. The new parameters were calculated  for a series of (x,y) coordinates of sperm head positions recorded at each  move along the trajectory. The parameters were: mean velocity (MV), immobility  ratio, fractal dimension (FD), the variance of the steplengths (VAR), and 2  autocorrelation function coefficients of the step-length time series for lags  1 and 2 (C(1) and C(2)). MV measures the  average speed along the trajectory, and VAR is a measure of displacement  variability that can be related to the specific mean (per step) kinetic energy  of the spermatozoon. All of the parameters except MV and FD were affected by  the sampling frequency (25 vs 50 Hz); inappropriately high sampling frequency  in relation to magnification resulted in step-lengths between successive  frames that were below the resolution threshold of the imaging system. The  autocorrelation functions were especially informative; discrimination between  sperm subpopulations was obvious within simple histogram formats, and complex  statistical analyses were not needed for their identification.
authors.affiliation: Estación Experimental de Zonas Aridas, Consejo Superior de Investigaciones Científicas, Almería, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Abaigar
authors.forename: Javier
authors.initials: J
authors.lastname: Barbero
authors.forename: William V
authors.initials: WV
authors.lastname: Holt
mesh_terms: D000818:Animals; D057205:Automation, Laboratory; D017709:Fractals; D007091:Image Processing, Computer-Assisted; D008297:Male; D018715:Microscopy, Video; D008954:Models, Biological; D015203:Reproducibility of Results; D017693:Sodium Bicarbonate / Q000494:pharmacology; D013077:Sperm Head / Q000502:physiology; D013081:Sperm Motility / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D013997:Time Factors
chemical_list: D017693:Sodium Bicarbonate