Optimal analysis conditions for sperm motility parameters with a CASA system in a passerine bird, Passer montanus

Background:Sperm motility parameters,which can be measured objectively and repeatedly by a computer-assisted sperm analysis(CASA)system,are important indicators of sperm quality.However,the sperm motility parameters assessed by a CASA system can be affected by various factors,including instrument components and settings,sperm preparation or analysis procedures.To date,no standardized protocol is available that would permit to assess sperm kinetic characteristics in passerine birds and this lack precludes any comparison of sperm swimming ability and sperm quality across species.Methods:In this study,we chose the Tree Sparrow(Passer montanus)as the object to evaluate sperm motility parameters,including sperm motility,sperm velocity and sperm movement trajectory,at different analysis time,temperatures and pH using the WLJY-9000 CASA system.Results:Sperm motility parameters remained statistically unchanged at 1‒9 min.Progressive motility was similar at 38℃ and 40℃,but a greater percentage of slow progressive sperm was detected at 38℃ compared to 40℃ and 42℃.Additionally,progressive motility was lower and immotility was higher at 42℃than 38℃and/or 40℃(close to the body temperature of the Tree Sparrow).The percentages of rapid progressive sperm,progressive sperm and immotile sperm were statistically similar at pH 7.0,7.5 and 8.0 with the exception of lower percentage of progressive sperm at pH 7.0 compared to pH 7.5.In addition,slower sperm velocity and worse sperm movement trajectory were found at pH 6.0 and 9.0 than those at pH 8.0,7.5 or 7.0.Conclusions:Our study indicates that the ideal conditions for sperm motility parameters assessment in Tree Sparrow are obtained between 1 and 9 min after dilution,an environment at body temperature(40℃)and a pH around 7.5-8.0.The results of this study provide a reference for the evaluation of sperm characteristics and sperm quality using a CASA system in passerine birds.

Nonlinear dynamics of cell migration in anisotropic microenvironment

Cell migration in anisotropic microenvironment plays an important role in the development of normal tissues and organs as well as neoplasm progression,e.g.,osteogenic differentiation of embryonic stem cells was facilitated on stiffer substrates,indicating that the mechanical signals greatly affect both early and terminal differentiation of embryonic stem cells.However,the effect of anisotropy on cell migration dynamics,in particular,in terms of acceleration profiles which is important for recognizing dynamics modes of cell migration and analyzing the regulation mechanisms of microenvironment in mechanical signal transmission,has not been systematically investigated.In this work,we firstly rigorously investigate and quantify the differences between persistent random walk and anisotropic persistent random walk models based on the analysis of cell migration trajectories and velocity auto-covariance function,both qualitatively and quantitatively.Secondly,we introduce the concepts of positive and negative anisotropy based on the motility parameters to study the effect of anisotropy on acceleration profiles,especially the nonlinear decrease and non-monotonic behaviors.We particularly elaborate and discuss the mechanisms,and physical insights of non-monotonic behaviors in the case of positive anisotropy,focusing on the force exerted on migrating cells.Finally,we analyze two types of in vitro cell migration experiments and verify the universality of nonlinear decrease and the consistence of non-monotonic behaviors with numerical results.We conclude that the anisotropy of microenvironment is the cause of the non-monotonic and nonlinear dynamics,and the anisotropic persistent random walk can be as a suitable tool to analyze in vitro cell migration with different combinations of motility parameters.Our analysis provides new insights into the dynamics of cell migration in complex microenvironment,which also has implications in tissue engineering and cancer research.