A circadian clock entrained by melatonin is ticking in the rat fetal adrenal.

The adrenal gland in the adult is a peripheral circadian clock involved in the coordination of energy intake and expenditure, required for adaptation to the external environment. During fetal life, a peripheral circadian clock is present in the nonhuman primate adrenal gland. Whether this extends to the fetal adrenal gland like the rat is unknown. Here we explored in vivo and in vitro whether the rat fetal adrenal is a peripheral circadian clock entrained by melatonin. We measured the 24-h changes in adrenal content of corticosterone and in the expression of clock genes Per-2 and Bmal-1 and of steroidogenic acute regulatory protein (StAR), Mt1 melatonin receptor, and early growth response protein 1 (Egr-1) expression. In culture, we explored whether oscillatory expression of these genes persisted during 48 h and the effect of a 4-h melatonin pulse on their expression. In vivo, the rat fetal adrenal gland showed circadian expression of Bmal-1 and Per-2 in antiphase (acrophases at 2200 and 1300 h, respectively) as well as of Mt1 and Egr-1. This was accompanied by circadian rhythms of corticosterone content and of StAR expression both peaking at 0600 h. The 24-h oscillatory expression of Bmal-1, Per-2, StAR, Mt1, and Egr-1 persisted during 48 h in culture; however, the antiphase between Per-2 and Bmal-1 was lost. The pulse of melatonin shifted the acrophases of all the genes studied and restored the antiphase between Per-2 and Bmal-1. Thus, in the rat, the fetal adrenal is a strong peripheral clock potentially amenable to regulation by maternal melatonin.

Risk factors associated with St. Louis encephalitis seroprevalence in two populations from Córdoba, Argentina.

St. Louis encephalitis virus (SLEV) is endemic in Argentina. The first outbreak was recorded in Córdoba during the late summer of 2005. This study analyzes the association between social and demographic factors and other variables related to exposure to mosquitoes with SLEV infection in 264 individuals who attended two health centers in the city of Córdoba during the period December 2004-January 2005. Multiple logistic regression models were used to estimate the risk coefficients. The seroprevalence was 12.9%, similar to that in previous reports. Risks of infection were associated with the presence of garbage dumps near dwellings, the practice of outdoor activities at night and place of residence. Risk for older people (60-80 years old) was moderate. The identification of risk factors related to SLEV infection would be useful to improve programs for vector control and community health.