Journal of Andrology
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Published-Ahead-of-Print April 1, 2006, DOI:10.2164/jandrol.05153

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Two Step Cluster Procedure After Principal Component Analysis Identifies Sperm Subpopulations in Canine Ejaculates And its Relation to Cryoresistance

Ivan Nunez-Martinez , Jose Maria Moran , and Fernando J. Pena

A two step clustering procedure, using principal component analysis derived indexes, was used to disclose sperm subpopulations within the canine ejaculate and its relationship to sperm cryoresistance. Semen from 4 dogs was frozen-thawed using a standard protocol, before freezing computer assisted sperm analysis of motility and morphometry (ISAS®) were performed, after thawing motility analysis was performed again; cryoresistance was estimated as the percent changes in progressive motility and sperm velocities after thawing. We used principal component analysis sperm derived indexes (SVI sperm velocity index, and SMI sperm motility index) and the SPSS® two step cluster method to disclose sperm subpopulations. The two step clustering procedure revealed the existence of 6 subpopulations, Subpopulations 4 and 6 were characterized by high values of both SVI (> 200 arbitrary units) and SMI (>90 arbitrary units), 2 and three by medium values (SVI; 100 to 130 and SMI, 30 to 40) and 1 and 5 were characterized by low values (SVI below 100 and SMI below 30). The distribution of sperm subpopulations was completely different among dogs. Four sperm subpopulations based in morphometric parameters of the sperm head and mid piece were revealed. VCL post thaw was explained by a model including two sperm indexes, R2 = 0.997, this is, namely explained the 99% in the variation (p<0.001) VSL and VAP post thaw were explained by models including SVI and SMI indexes. The model predicting values of VAP had a R2 = 0.98, (p<0.001) and in the one predicting VSL, R2 = 0.99 (p <0.0001).






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