Adolescent and young adult women's use of emergency contraception.

STUDY OBJECTIVE: To determine differences in the use of emergency contraception (EC) between adolescent (11-17 years old) and young adult women (18-24 years old) in an insured, population based cohort. DESIGN AND PARTICIPANTS: Females 11-24 years old were divided into two groups: adolescents (11-17) and young adults (18-24) at their first captured EC prescription fill. A medical record review followed. MAIN OUTCOME MEASURES: The main outcomes of our study were reason for EC use, timing of EC use, and repeat use. Chi-square tests were used to compare dichotomous variables between groups by age and for ever vs repeat use. An independent t-test was used to compare continuous variables. A person-time analysis was used to compare rates of repeat use. RESULTS: 344 women were identified as having filled at least one prescription for an EC drug. Among ever users, adolescents were more likely than young adults to cite no contraception as their reason for seeking EC (30% for 11-17 and 24% for 18-24 year olds; P = 0.38). For both ever and repeat users, young adults reported condom failure as their main reason for seeking EC. We calculated t-tests on the hours since unprotected sex. For adolescents the mean was 42 hours and for young adults the mean was 34 hours (P = 0.13). Both are within the recommended 72-hour window for administration and were not significantly different. The rate of repeat use was essentially the same for both age groups. CONCLUSIONS: We found that adolescent use of EC was similar to young adult use and support the recommendation that 17-year-olds have behind-the-counter access to EC.

An electron transfer dependent membrane potential in chromaffin-vesicle ghosts.

Adrenal medullary chromaffin-vesicle membranes contain a transmembrane electron carrier that may provide reducing equivalents for intravesicular dopamine beta-hydroxylase in vivo. This electron transfer system can generate a membrane potential (inside positive) across resealed chromaffin-vesicle membranes (ghosts) by passing electrons from an internal electron donor to an external electron acceptor. Both ascorbic acid and isoascorbic acid are suitable electron donors. As an electron acceptor, ferricyanide elicits a transient increase in membrane potential at physiological temperatures. A stable membrane potential can be produced by coupling the chromaffin-vesicle electron-transfer system to cytochrome oxidase by using cytochrome c. The membrane potential is generated by transferring electrons from the internal electron donor to cytochrome c. Cytochrome c is then reoxidized by cytochrome oxidase. In this coupled system, the rate of electron transfer can be measured as the rate of oxygen consumption. The chromaffin-vesicle electron-transfer system reduces cytochrome c relatively slowly, but the rate is greatly accelerated by low concentrations of ferrocyanide. Accordingly, stable electron transfer dependent membrane potentials require cytochrome c, oxygen, and ferrocyanide. They are abolished by the cytochrome oxidase inhibitor cyanide. This membrane potential drives reserpine-sensitive norepinephrine transport, confirming the location of the electron-transfer system in the chromaffin-vesicle membrane. This also demonstrates the potential usefulness of the electron transfer driven membrane potential for studying energy-linked processes in this membrane.