Effect of DNA damage caused by cryopreservation of spermatozoa using a modified Single cell gell electrophoresis in the freshwater catfish Pangasianodon hypophthalmus(Fowler,1936)

Objective:To detect the integrity of sperm DNA in the catfish Pangasianodon hypophthalmus cryopreserved with Hanks balanced salt solution,5%-30%dimethyl acetamide(DMA)using the single-cell gel electrophoresis in order to test how sperm cryopreservation affected nuclear DNA stability.Methods:Electrophoresis was conducted for 60 min at 130 mA and 15 V.The comet images were analyzed using software CometScore 1.5,and parameters such as comet length,tail length and percentage DNA in the tail were obtained.Then the comet rate and damage coefficient were calculated.Results:There were no significant differences in motility,comet rate and damage coefficient between fresh sperm and cryopreserved sperm stored in 5%,10%,15%and 20%DMA,while the sperm cryopreserved with 25%and 30%DMA had lower motility,higher comet length and damage coefficients than those of fresh sperm.Conclusions:There was positive correlation between comet rate of cryopreserved sperm and the concentration of DMA.The toxicity of cryoprotectant is the main factor for DNA damage in cryopreserved sperm.

Preliminary studies on the cryopreservation of spermatozoa in the fresh water fish common carp(Cyprinus carpio L.)

Objective:To investigate the effects of various extenders containing different cryoprotectants on post-thaw viability,motility and scanning electron microscopic study of frozen spermatozoa from carp.Methods:cryopreservation has been achieved using extender and cryoprotectants like dimethylacetamide After screening a variety of cryoprotectants and extenders,a protocol for the 5%-20%at appropriate dilution ratio(1:10).For all experimental tests,the motility and viability percentage of spermatozoa were examined after storage of 5 d at 4℃.Results:The maximum motility of 75%has been observed with 10%dimethyl sulfoxide.Scanning electron microscopic studies on normal and cryopreserved spermatozoa showed prominent head,middle piece and different segments of flagellum.There were no significant deformities noticed on the surface topography of cryopreserved spermatozoa.Conclusions:Thus the results clearly documented that cryoprotectant 10%dimethyl sulfoxide affords better cryopreservation at 4℃for the spermatozoa of Cyprinus carpio.