Stability of retinol in liposomes as measured by fluorescence lifetime spectroscopy and FLIM.

Retinol shows complex photophysical properties that make it potentially useful as an exogenous or endogenous probe of membrane microenvironment, but it has not been fully explored. In this study, we use bulk fluorescence lifetime measurements and fluorescence lifetime imaging microscopy (FLIM) to examine the stability of retinol in phosphatidylcholine (PC) multilamellar and unilamellar vesicles with and without cholesterol. We find that both light and exposure to ambient temperature and oxygen contribute to retinol degradation, with the addition of an antioxidant such as butylated hydroxytoluene (BHT) essential to provide stability, especially in the absence of cholesterol. With exposure to ultraviolet light to excite its native fluorescence, retinol degrades rapidly and can photosensitize vesicles. Degradation can be measured by a decrease in fluorescence lifetime. In POPC vesicles without cholesterol, BHT leads to initially higher lifetimes compared with no BHT, but it increases the rate of photodegradation. The presence of 10 mol % cholesterol protects against this effect, and vesicles with 20 mol % cholesterol show longer lifetimes without BHT under all conditions. Because of its environmental sensitivity, retinol is interesting as a FLIM probe, but careful controls are needed to avoid degradation, and additional work is needed to optimize liposomes for food and cosmetic applications.

Louisiana Parish Health Profiles 1999: using information to drive local action.

The Parish Health Profiles 1999, published by the Department of Health and Hospitals Office of Public Health (OPH), are intended to be a source of parish-level health information to be used for community-level planning. The third edition of the Profiles uses a broader definition of health to understand the quality of life of communities. The included information represents not only health status, but also other aspects of quality of life, such as the status of local education, economy, environment, and crime and safety. The process of collecting this information yielded two additional results: strengthened relationships amongst information-providing agencies across the state and an orientation and subsequent comprehensive chapter of information on action and resources. In addition, the publication is designed to be reader friendly, with a strong emphasis on the use of the Parish Health Profiles to aid in understanding data. The Office of Public Health recognizes that the Parish Health Profiles will continue to evolve to meet the needs of their audience. In order to ensure continuous quality improvement through future editions, the Profiles are supported by an 18-month, multi-level evaluation process, ensuring consumer and user input and comment at different levels.