No abstract

No abstract

ContentsIn recent years, there has been an increased interest in new preservation techniques that facilitate sperm storage and distribution, with freeze-drying (FD) having been proposed as an alternative method for sperm preservation and maintenance of genetic resources in different animal species. FD is a method in which frozen material is dried by sublimation of ice, thereby involving a direct transition from a solid (ice) to a vapour (gas) phase. One of the main advantages of FD is that nitrogen and dry ice are no longer required for the storage and shipment of frozen sperm, which can be stored at room temperature or 4°C, thereby resulting in enormous reductions in storage and shipping costs. Unlike sperm cryopreserved after gradual freezing, the sperm membrane may be further damaged by both snap-freezing and drying stresses during the FD procedure. As mammalian spermatozoa lose their motility, viability and, at least partially, their DNA integrity when freeze-dried, they must be microinjected into an oocyte by intracytoplasmic sperm injection (ICSI). Although the efficiency of ICSI is limited when freeze-dried spermatozoa are used, embryos and live offspring can be produced. DNA fragmentation in freezedried spermatozoa is one of the main causes of failure of embryonic development and successful pregnancy. In this regard, it has been suggested that endonucleases are among the leading causes of DNA fragmentation in spermatozoa along with oxidative stress caused by the release of reactive oxygen species (ROS). Many factors influence the FD process, and it is not clear how FD affects specific components of sperm from different animal species. As such, a sound understanding of the FD process would result in increased production of embryos and/or live offspring. The aim of this review was to study the various stages and techniques used in the FD process and to further evaluate the results obtained.

In this study, we investigated the protective ability of the addition of two antioxidant herb extracts, mate tea and lemon balm, on boar epididymal frozen-thawed spermatozoa quality. Testes from mature boars were collected at local slaughterhouse, and sperm samples from epididymis were recovered by flushing. Spermatozoa were cryopreserved in lactose-egg yolk buffer supplemented with various concentrations of lemon balm and mate tea (0, 2.5, 5 and 10 g l(-1) ) using the straw-freezing procedure. Motion parameters, acrosome and plasma membrane integrity, lipoperoxidation levels and DNA oxidative damage (8-hydroxy-2'-deoxyguanosine base lesion) were evaluated. There were no differences among experimental groups with regard to motility characteristics, viability, acrosome and plasma membrane integrity; however, the highest concentration of lemon balm produced significant (P < 0.05) improvement in curvilinear trajectory, straightness and amplitude of lateral head displacement after thawing. The supplementation of freezing extender with mate tea and lemon balm reduced sperm lipid membrane peroxidation, and only mate tea protected DNA against oxidative damage during cryopreservation at 120 min post-thawing (P < 0.05). Mate tea experimental extender at concentration of 10 g l(-1) showed the lowest percentage of sperm oxidised DNA and malondialdehyde generation; thus, mate tea is a potential candidate such as antioxidant compound on boar sperm cryopreservation medium.

No abstract