Miami-Dade County Public Schools is the fourth largest school district in the United States, comprised of 392 schools, 345,000 students and over 40,000 employees. Located at the southern end of the Florida peninsula, the school district stretches over 2,000 square miles of diverse and vibrant communities ranging from rural and suburban to urban cities and municipalities. A truly global community, district students speak 56 different languages and represent 160 countries.
Superintendent Alberto M. Carvalho has led the school district since the fall of 2008. During his tenure, the district has received state and national recognition for unprecedented increases in student achievement and graduation rates.
Calcium triggers the secretion of histamine from mast cells after previous exposure to sodium fluoride. The secretory process can be divided into a fluoride-activation step and a calcium-induced secretory step. It was observed that the fluoride-activation step is accompanied by an elevation of cyclic adenosine monophosphate (cAMP) levels within the cells. The attained high levels of cAMP persist during histamine release. It was further found that catecholamines do not markedly alter the fluoride-induced histamine release. It was also confirmed that the second, but not the first, step in sodium fluoride-induced histamine secretion is inhibited by theophylline.  Vasodilation and increased permeability of capillaries are a result of both H1 and H2 receptor types.