AbstractsBiology & Animal Science

This thesis focuses on optimization techniques for transport process during the cryopreservation of biological systems. In the first part of this thesis, a well established shape independent Differential Scanning Calorimeter (DSC) technique was used to measure the dehydration response during freezing of Pacific oyster sperm cells. Volumetric shrinkage during freezing of diploid and tetraploid pacific oyster sperm cell suspensions was obtained at cooling rates of 5 and 20 ˚C/min in the presence of extracellular ice and CPAs. By fitting a model of water transport to the experimentally obtained volumetric shrinkage data the best fit membrane permeability parameters (L_pg and E_Lp) were determined. The simulation results were analyzed to predict the amount of water left in the cell after dehydration ceased, in the absence of IIF and the "optimal cooling rates" for diploid and tetraploid pacific oyster sperm cryopreservation. The second part of this thesis, a generic mathematical model based on a 2 parameter Kedem and Katchalsky formulation was developed to simulate the coupled solute and solvent transport in arbitrary tissue sections. Osmotic responses of various tissue cells within the artificial tissue are predicted by the numerical model with three model parameters: permeability of the tissue cell membrane to water (L_p) permeability of the tissue cell membrane to the solute or CPA (ω) and the diffusion coefficient of the solute or CPA in the vascular space (D). By fitting the model results with published experimental data on solute/water concentrations at various locations within an artificial tissue, we were able to determine the permeability parameters of embedded tissue cells in the presence of Me₂SO. The permeability parameters obtained in the present study represent the first such effort for embedded tissue cells.