Proteolysis by MMP20 Prevents Aberrant Mineralization in Secretory Enamel.

The present study was conducted to investigate the role of proteolysis by matrix metalloproteinase 20 (MMP20) in regulating the initial formation of the enamel mineral structure during the secretory stage of amelogenesis, utilizing Mmp20-null mice that lack this essential protease. Ultrathin sagittal sections of maxillary incisors from 8-wk-old wild-type (WT), Mmp20-null (KO), and heterozygous (HET) littermates were prepared. Secretory-stage enamel ultrastructures from each genotype as a function of development were compared using transmission electron microscopy, selected area electron diffraction, and Raman microspectroscopy.

Treatment of Sleep Disturbance May Reduce the Risk of Future Probable Alzheimer's Disease.

Objective: This study explored two research questions: (a) Does sleep medication neutralize or provide a protective effect against the hazard of Alzheimer's disease (AD)? (b) Do apolipoprotein (APOE) e4 carriers reporting a sleep disturbance experience an increased risk of AD?

Method: This study is a secondary analysis of the National Alzheimer's Coordinating Center's Uniform Data Set ( n = 6,782) using Cox proportional hazards regression.

Results: Sleep disturbance was significantly associated with eventual AD development. Among the subset of participants taking general sleep medications, no relationship between sleep disturbance and eventual AD was observed.