An intact pituitary vasopressin system is critical for building a robust circadian clock in the suprachiasmatic nucleus.

The circadian clock is a biological timekeeping system that oscillates with a circa-24-h period, reset by environmental timing cues, especially light, to the 24-h day-night cycle. In mammals, a "central" clock in the hypothalamic suprachiasmatic nucleus (SCN) synchronizes "peripheral" clocks throughout the body to regulate behavior, metabolism, and physiology. A key feature of the clock's oscillation is resistance to abrupt perturbations, but the mechanisms underlying such robustness are not well understood. Here, we probe clock robustness to unexpected photic perturbation by measuring the speed of reentrainment of the murine locomotor rhythm after an abrupt advance of the light-dark cycle. Using an intersectional genetic approach, we implicate a critical role for arginine vasopressin pathways, both central within the SCN and peripheral from the anterior pituitary.

Effects of Benzalkonium Chloride and Preservative-Free Composition on the Corneal Epithelium Cells.

Purpose: Benzalkonium Chloride (BAK) is reported to have the potential to damage the cornea. We developed a composition with broad-spectrum antimicrobial activity without preservatives by combining trometamol, boric acid, and ethylenediaminetetraacetic acid (TBE). This study aimed at evaluating the corneal damage caused by TBE and comparing it with that caused by BAK. Methods: SV40-immortalized human corneal epithelial cell line (HCE-T) was treated with BAK or TBE, and the cell viability was measured. The exposure time that caused 50% cell death (CDT50) was calculated. Transepithelial electrical resistance (TEER) was measured before and after treatment with BAK or TBE. Occludin was detected with immunostaining and Western blotting after treatment with BAK or TBE. The effect of BAK or TBE on membrane-associated mucins was evaluated with rose bengal (RB) staining. Results: In the BAK group, cell viability decreased in a dose-dependent manner. The viability of the TBE group was significantly greater than that of the BAK group. The CDT50 of the TBE group is greater than that of the BAK groups. In the BAK groups, the recovery of TEER was delayed in a dose-dependent manner, whereas in the TBE group, the recovery occurred earlier. Localization of occludin was disrupted, and the amount of occludin was significantly reduced among the cells exposed to BAK. The area stained with RB in the BAK groups increased, whereas that in the TBE group did not increase. Conclusion: These results suggest that the application of TBE would be useful for developing preservative-free ophthalmic preparations that offer both sufficient safety and antimicrobial activity.