The problems of storing gametes and embryos

Animal and human gametes and embryos must be protected from infection durin g low temperature storage. In human, the obligatory screening of everyone w ishing to store tissue and the provision of quarantined storage when this i s impractical would minimise the risks. Straws are preferred for embryo sto rage because freezing in plastic vials is detrimental. Aseptically filled s traws do not leak dye, E. Coli or Newcastle Disease virus and even potentia lly leaky straws do not contaminate their environment when wrapped in a lay er of plastic film. Embryo viability was high after freezing in straws cont ained in a sealed plastic envelope. Storage in the vapour phase of a liquid nitrogen tank may increase the likelihood of gametes and embryos being dam aged as a result of accidental warming.