In order to elucidate the mechanisms of bone @entity730 , embryonic @entity35 calvariae treated with chemical or cryo-fixation were observed using transmission electron microscopy by three techniques: fine structures, various cvtochemical localizations including nonspecific proteoglycan, decorin, @entity12006 , hyaluronan, @entity4972 ( @entity4972 ), and @entity12912 , as well as the elemental mapping of @entity460 and @entity3151 by energy-filtering electron microscopy. In the calvariae, the @entity730 sequence ran as follows crystallization within matrix vesicles, formation of calcified nodules, collagen @entity730 , and finally the establishment of an expansive calcified matrix. The osteoid contained an abundance of mesh-like fibers of proteoglycans, including decorin, @entity12006 , and hyaluronan, around collagen fibrils approximately 50 nm in diameter. @entity460 tended to localize at the proteoglycan sites, while @entity3151 was often mapped to the collagen fibril-structures in the osteoid. @entity460 / @entity3151 co-localization was found in and around the calcified nodules, where @entity4972 and small sized proteoglycans were observed. During this stage, native proteoglycans surrounding the collagen fibrils disappeared, with the collagen fibrils fusing laterally, and attaining a diameter of more than 400nm. The calcified nodules expanded to occupy the entire space made available by the collagen fibril-fusion, following @entity12912 accumulation in the calcified nodule/collagen fibril border. In conclusion, crystals present within the matrix vesicles became calcified nodules, in a process induced by the co-localization of @entity460 and @entity3151 . @entity4972 and proteoglycans may participate in the @entity460 / @entity3151 co-localization. Decreases in the native proteoglycans, and the lateral fusion of collagen fibrils are thought to be involved in the expansion of calcified areas, followed by @entity12912 -mediated collagen @entity730 .

Ultrastructural analysis of bone XXXX by using energy-filtering transmission electron microscopy.

@entity4972 :: ('MESH:C562645', 'Disease') :: ['ALP', 'alkaline phosphatase'] @entity12006 :: ('MESH:D002809', 'Chemical') :: ['chondroitin 4-sulfate'] @entity730 :: ('MESH:D002114', 'Disease') :: ['calcification'] @entity12912 :: ('24791(Tax:10116)', 'Gene') :: ['osteonectin'] @entity460 :: ('MESH:D002118', 'Chemical') :: ['calcium', 'Calcium'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity3151 :: ('MESH:D010758', 'Chemical') :: ['phosphorus']
@entity730 :: (MESH:D002114,Disease) :: ['calcification']
