ABSTRACT
Existing methods are not able to monitor accurately the penetration of cryoprotective solvents (CPS) into intact tissues. In this study, NMR imaging is shown to be a noninvasive nondestructive way to measure penetration rates and effective diffusion coefficients of Me2SO into samples of rat kidney and rat liver tissues. This new method is unique in that the measurements obtained are not averaged over the entire tissue volume but may be made at any site in the tissue. Measurements of penetration rates yield values which are similar to literature values, and the effective diffusion coefficients fall within the expected range. The images also suggest an explanation of why CPSs fail to completely protect organs from freezing damage.
Subject(s)
Cryopreservation/methods , Cryoprotective Agents/pharmacokinetics , Dimethyl Sulfoxide/pharmacokinetics , Organ Preservation/methods , Animals , Blood Vessels/metabolism , Diffusion , In Vitro Techniques , Kidney/anatomy & histology , Kidney/blood supply , Kidney/metabolism , Kinetics , Liver/anatomy & histology , Liver/blood supply , Liver/metabolism , Magnetic Resonance Spectroscopy , Models, Biological , Nonlinear Dynamics , Rats , Solvents , Tissue DistributionABSTRACT
According to a 1992 national survey, more than 95 percent of general dentists in the United States purchased malpractice insurance. The authors evaluated the survey findings to identify factors that had the greatest effect on dentists' insurance premium costs. Premiums were higher for dentists who had been the subject of previous complaints or claims, as well as for those who owned their practices. States with fewer lawyers had lower premiums. Finally, state limits on use of dental hygienists, number of offices and the extent of water fluoridation also affected premium levels.
