Hiroshi Araya

Possibility of Long-Term Preservation of Freeze-Dried Mouse Spermatozoa

Abstract Freeze-dried mouse spermatozoa are capable of participating in normal embryonic development after injection into oocytes. When the freeze-dried spermatozoa are used as a method for storage of genetic materials, however, it is essential to assure the relevance of long-term preservation over several decades or centuries. Thus, we applied the theory of accelerated degradation kinetics to freeze-dried mouse spermatozoa. Thermal denaturation kinetics were determined based on Arrhenius plots derived from transition-state theory analysis at three elevated temperatures: 30, 40, and 50°C. Accelerated degradation kinetics were calculated by extrapolation of Arrhenius plots. This theory also is being applied to the long-term stability of drugs. The estimated rate of development to the blastocyst stage at 3 and 6 mo and at 1, 10, and 100 yr of sperm storage at 4°C were 21.60%, 7.91%, 1.00%, 0%, and 0%, respectively. At −80°C, estimated development rates to the blastocyst stage that would be expected after 100 yr of storage did not decline significantly. In addition, after 3 or 6 mo of storage at 4 or −80°C, preimplantation development of the embryos derived from intracytoplasmic sperm injection (ICSI) was examined. The actual developmental rates to the blastocyst stage from ICSI by freeze-dried sperm stored for 3 mo at 4 and −80°C were 21% and 62%, respectively, and the rates for such sperm stored for 6 mo were 13% and 59%, respectively. These results indicate that the determination of accelerated degradation kinetics can be applied to the preservation of freeze-dried mouse spermatozoa. Furthermore, for long-term preservation, freeze-dried mouse spermatozoa appear to require being kept at lower than −80°C.

An alteration in the liver microsomal membrane of the rat following paracetamol overdose

Fluorescence polarization of dansyl chloride covalently labelled microsomal membranes revealed an alteration in rat liver microsomal membranes following as a consequence of a paracetamol overdose. This suggests that dansyl chloride would be a useful probe in the study of the effects of paracetamol on microsomal membranes.