For the sterilization of disposable medical devices, ethylene oxide gas is used in most cases. When this sterilization method is used, ethylene oxide (EO) and its secondary products, i.e., ethylene chlorohydrin (ECH) and ethylene glycol (EG), remain in the medical devices after sterilization. If their concentration is high, these residues are liable to cause hemolytic activity and dermal or mucous membrane irritability in the human body. For this reason, in 1978 the FDA announced a proposal to regulate the residual limits of EO, ECH and EG.
Our studies were done to examine the conditions of EO sterilization from the viewpoints of the sterilization effect and the residual chemical substances and to find the optimum conditions for sterilization.
Further, the aerator was fabricated for the exclusive purpose of reducing, witl1in a brief period, the concentration of EO and other substances remaining in the medical devices after sterilization and we examined the condition of aeration by using this aerator.
As the result, it was found that a satisfactory sterilization effect could be obtained under the sterilization conditions of an EO gas concentration of 500 mg/liter, a sterilizing temperature of 55 to 60℃ and a sterilizing time of two hours, and under these conditions the concentration of the residual substances such as the EO could be made comparatively lower.
It was also clarified that the minimum required aeration conditions by using the exclusive-use aerator we1·e a temperature of 55 to 60℃ and an aeration time of 24 hours and over.
The effects of starvation and protein-deficient diet on the acute carbon tetrachloride (CCI4) induced hepatotoxicity of the mice were studied histologically and histochemically. A total of 69 male mice (C57BL/6) were used and carbon tetrachioride was administered by a single subcutaneous injection at a dose of 0.1 mg/10 g body weight after starvation for 24 hours and feeding with protein-deficient diet for one month. The changes were examined consecutively. It was shown the the CCl4-induced hepatotoxicity was exaggerated by starvation and that the regeneration after centrilobular necrosis due to CCI4 administration was retarded under this condition. In the CCl4-treated group on protein-deficient diet, the centrilobular liver cells seemed to be less responsive to CCI4.
Staining solutions of acid phosphatase and esterase group (naphthol-AS-D-chloroacetate esterase, naphthol-AS-acetate esterase and alpha-naphthyl-acetate esterase) were stored for 6 months using the freezing facilities, and the staining results were compared with those of each set of controls.
The results showed that the staining solutions of all enzymes were stable for long-term preservation (at least 6 months) in the deep freezer (-80℃) when they were stored appropriately in separated forms. In such a freezing procedure, the staining results for each enzyme did not show any decrease of positive intensity nor any non-specific staining.
Changes in the powdery composition and setting characteristics of the phosphate-bonded investment (Ceramigold) on exposure to 100% relative humidity atmosphere were investigated by means of Thermogravimetry-Differential Thermal Analysis (TG-DTA) and X-ray diffraction. The following results were obtained.
1. In the powder, NH4H2PO4 and MgO contained as the setting agents were converted into MgNH4PO4･6H2O through Mg(NH4)2H2(PO4)2･4H2O.
2. As compared with the result of the powder stored in the thermo-hygrostatic room (control=not exposed), the setting time of the mixture of the exposed powder with the colloidal silica solution decreased temporarily but increased after 4 days of exposure when the quantity of NH4H2PO4 in the powder became small and couldn’t be measured after 10 days of exposure.
3. The compressive strength and diametral tensile strength of the mixture at 2 hours increased slightly but decreased after 4 days or more of exposure and couldn’t be measured after 10 days of exposure.
4. The thermal expansion of the mixture at 800℃ produced little difference between the control and after 8 days of exposure.
As for the setting agents the process of deterioration is similar to the setting reaction. The quantity of NH4H2PO4 in the powder seems to be related to the setting time and the strength of the set investment. The quantity of MgNH4PO4･6H2O in the powder may contribute to the extreme delay of the setting reaction.