Gamete cryopreservation of Australian 'old endemic' rodents – spermatozoa from the plains mouse (Pseudomys australis) and spinifex hopping mouse (Notomys alexis)

Most of the Australian ‘old endemic’ rodents have greatly reduced distributions with several species now threatened with extinction. Application of assisted reproductive technology has the potential to assist in their conservation programs in at least a few species. Here we describe an attempt to cryopreserve spermatozoa from two of these species – those of the plains mouse (Pseudomys australis) and spinifex hopping mouse (Notomys alexis), which have dramatic differences in sperm morphology. Slow and rapid freezing and three different cryoprotectant media with either raffinose, glycerol and/or skim milk were used and the results compared with those of house mouse sperm, which were used as controls. Sperm morphology, motility, membrane integrity and DNA damage were determined. Prior to cryopreservation there was a higher percentage of morphologically normal, motile, P. australis sperm than in those from N. alexis. Following cryopreservation, regardless of treatment, the percentage of motile sperm was low but it was higher when raffinose with skim milk was used as a cryoprotectant than in raffinose with glycerol albeit that minimal differences in membrane integrity or DNA damage were evident. Raffinose with skim milk should thus be used as a cryoprotectant for storing sperm of these Australian rodents in the future.

Properties of a One-Dimensional Coulomb Gas

The BBKGY equations for N identical, impenetrable, charged particles which move in one dimension and lie in a charge neutralizing background, are shown to separate into N uncoupled equations for the sequence of N reduced distributions. The potential relevant to any subgroup of s adjoining particles is that of an «-dimensional harmonic oscillator whose frequency is the plasma frequency of the aggregate. The «-particle spatial equilibrium distribution reveals that particle vibrations remain centered about fixed, uniformly distributed sites as σ/T goes from zero to infinity, where σ is particle density and T is temperature. Thus it is concluded that the system suffers no change in phase for all σ and T.