Cooperative function of ammonium polyacrylate with antifreeze protein type I.

Activity of antifreeze proteins (AFPs) and antifreeze glycoproteins (AFGPs) is often determined by thermal hysteresis, which is the difference between the melting temperature and the nonequilibrium freezing temperature of ice in AF(G)P solutions. In this study, we confirmed that thermal hysteresis of AFP type I is significantly enhanced by a cooperative function of ammonium polyacrylate (NH4PA). Thermal hysteresis of mixtures of AFP type I and NH4PA was much larger than the sum of each thermal hysteresis of AFP type I and NH4PA alone. In mixed solutions of AFP type I and NH4PA in the thermal hysteresis region, hexagonal pyramidal-shaped pits densely formed on ice surfaces close to the basal planes. The experimental results suggest that the cooperative function of NH4PA with AFP type I was caused either by the increase in adsorption sites of AFP type I on ice or by the adsorption of AFP type I aggregates on ice.

[Shock absorption of mouthguard materials--influence of temperature conditions and shore hardness on shock absorption].

PURPOSE: To consider changes in the physical properties of mouthguard materials with the change of temperature, shock-absorbing examination and Shore hardness measurement of existing MG materials and other elastic materials were carried out. METHODS: Both examinations were done under two temperature conditions: at room temperature (25 degrees C) and simulated intraoral temperature (37 degrees C). In addition, a comparative study of the relation between Shore hardness and shock absorption of the materials was made. A self-made drop impact machine was used for the shock-absorbing examination. The thickness of a sample was assumed to be 3 mm. The loading was applied by dropping 3 kinds of steel ball, phi 10 mm (4.0 g), phi 15 mm (13.7 g), and phi 20 mm (32.6 g) from a height of 60 cm. The shock absorption of all materials was compared by the maximum impact force. Shore hardness was measured based on the JIS standard. RESULTS: The shock absorption of each material showed a different tendency depending on the loading condition. Furthermore, the shock absorption of the same material showed different results depending on the temperature condition. Shore hardness measurements tended to show low values with the condition of 37 degrees C for all materials. CONCLUSION: From the relation between shock absorption and Shore hardness, it was confirmed that there is a correlation between hardness and the maximum impact force in the materials that showed shock absorption by elastic deformation. Some materials showed high shock absorption compared with existing MG materials.

Evaluation of corneal damage caused by iodine preparations using human corneal epithelial cells.

PURPOSE: To compare the cytotoxicity of povidone-iodine solution (PVP-I) with that of polyvinyl alcohol-iodine solution (PAI) for ophthalmic use. METHODS: Cells of the human corneal epithelial cell line HCE-T were exposed to various dilutions of PVP-I or PAI, and the cytotoxicity of these two antiseptics was evaluated. The relative toxicities of PVP-I and PAI were also investigated following the inactivation of iodine by achromatization with sodium thiosulfate. RESULTS: PVP-I and PAI had equivalent antiseptic effects, but the cytotoxicity of PVP-I diluted 16-fold was higher than that of PAI diluted 6-fold. Following inactivation of iodine with sodium thiosulfate, the cytotoxicity of PVP-I remained concentration dependent, whereas PAI exhibited a low toxicity that was similar to the effect of saline on cell viability. Exposure to lauromacrogol, a surfactant used in PVP-I, in solution at concentrations of 1-1000 mg/mL clearly resulted in corneal cytotoxicity. The PVP-I and PAI solutions had a pH value of 4.0 and 5.2, respectively. HCE-T cells were significantly more viable at pH 7 than at pH 1-6. CONCLUSION: To avoid corneal damage, preoperative antisepsis of the surgical field should be accomplished with PAI diluted 6-fold, rather than with PVP-I diluted 16-fold. The toxicity of the iodine compound stems primarily from the available iodine concentration and partly from its pH, surfactant and osmolality. Further clinical investigations are required in order to determine the optimal concentrations for use.