Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Blink rate. Uppercase letters refer to comparisons within groups between time points; lowercase letters indicate comparisons between groups at the same time point; different letters indicate values that differ significantly (P < 0.001). Data are shown as mean values; bar, 1 SD.
