Although boar spermatozoa have a relatively low water permeability in the presence of CPAs (0.120 |xm/min/atm, in the presence of DMSO), compared to other cell types such as murine oocytes (0.80 (xm/min/atm in the presence of DMSO) regarding intracellular ice formation, the cells also have a counterbalancing low intracellular water volume (31%) , and a very high surface area:volume ratio (surface area:volume = 156 |xm2:26.3 |xm3) . Therefore, the low probability of intracellular ice formation even when relatively high cooling rates are used appears consistent with the complete biophysical characteristics of these cells. Therefore, these data suggest that the majority of cell loss predicted at high cooling rates is not associated with intracellular ice formation but is due to excessive cell swelling upon rapid warming. This predicted cell loss is greater when EG rather than glycerol is used as the CPA for sperm cryopreservation. This finding presents a complex dilemma. buy ortho tri-cyclen
The CPA that has been found to have the highest permeability (EG), and therefore has been predicted to be most optimal for minimizing cell volume excursions upon its addition and removal, also has the highest associated temperature dependence, resulting in potentially damaging cell swelling when rapid cooling and warming rates are used. These data indicate a three-way interaction among CPA type, cooling rate, and warming rate. Therefore, in developing new cryopreservation protocols, it may be most effective to prioritize selection of CPA type first (using the highest PCPA as the criterion) and use as high a concentration of that CPA as the cell type of interest will tolerate upon addition and removal (using osmotic tolerance limits as criteria).