Maintaining the Constant Exposure Condition for an Acute Caenorhabditis elegans Mortality Test Using Passive Dosing

OBJECTIVES: Maintaining the constant exposure to hydrophobic organic compouds in acute toxicity tests is one of the most difficult issues in the evaluation of their toxicity and corresponding risks. Passive dosing is an emerging tool to keep constant aqueous concentration because of the overwhelming mass loaded in the dosing phase. The primary objectives of this study were to develop the constant exposure condition for an acute mortality test and to compare the performance of the passive dosing method with the conventional spiking with co-solvent. METHODS: A custom cut polydimethylsiloxane (PDMS) tubing loaded with benzyl butyl phthalate (BBP) was placed in each well of a 24-well plate containing assay medium. The rate of the release of BBP from PDMS was evaluated by measuring the change in the concentration of BBP in the assay medium. The efficiency of maintaining constant exposure condition was also evaluated using a simple two-compartment mass transport model employing a film-diffusion theory. An acute mortality test using 10 C. elegans in each well was conducted for the evaluation of the validity of passive dosing and the comparative evaluation of the passive dosing method and the conventional spiking method. RESULTS: Free concentration in the assay medium reached 95% steady state value within 2.2 hours without test organisms, indicating that this passive dosing method is useful for an acute toxicity test in 24 hours. The measured concentration after the mortality test agreed well with the estimated values from partitioning between PDMS and the assay medium. However, the difference between the nominal and the free concentration became larger as the spiked concentration approached water solubility, indicating the instability of the conventional spiking with a co-solvent. CONCLUSIONS: The results in this study support that passive dosing provides a stable exposure condition for an acute toxicity test. Thus, it is likely that more reliable toxicity assessment can be made for hydrophobic chemicals using passive dosing.

Family Membe's Caregiving Stress and Satisfaction of Care for Patients with Dementia in Long Term Care Facilities and Day Care Centers / 성인간호학회지

PURPOSE: This study was to explore family member's caregiving stress and satisfaction of care for patients with dementia in long term care facilities and day care centers. METHODS: The subjects were 129 family members of elders with dementia from ten long term care facilities and eight day care centers in Daegu and Kyungsangbukdo. Data were collected from August to October, 2007. The instruments were self administered questionnaires and included. The Family Perceptions of Caregiving Role (FPCR) and the Family Perceptions of Care Tool (FPCT) which were developed by Maas and Buckwalter (1990) and translated by Park (2002). RESULTS: Family member's care giving stress in day care centers were higher than that of long term care facilities (t=-2.89, p=.005) especially in the categories of captivity (t=-3.27, p=.001), guilty (t=-2.93, p=.004), and loss (t=-2.44, p=.016). Family member's satisfaction of care in day care centers was higher than that of long term care facilities (t=-3.21, p=.002) in the (use - categories or measures since you are referring to the instrument and delete aspects) aspects of effective management (t=-3.69, p=.000) and activity (t=-2.00, p=.045). CONCLUSION: The results of this study showed that family members' perceptions toward their care giving roles and satisfaction of care differ whether the facilities are long term care or day care centers. This study provides baseline data that could be used for improving the quality of long term care services.