The purpose of this research was to clarify the morphological changes of the apex region of the tongue in the elderly. Apexes of tongue were removed from 44 Japanese adult cadavers (64-99 years) which were contributed for dental studies at Tokyo Medical and Dental University. These specimens were fixed again with 10% formaldehyde, and then paraffin sections were made from these specimens according to a general method. After several stainings, these sections were observed with a light microscope. The results were as follows: 1) The epithelium, propria mucosae and muscle layers became thin with aging, and the boundaries between these layers became unclear. 2) The tendencies of fibrosis also became remarkable, and the arrangement and distribution of collagen fibers and elastic fibers became disordered in propria mucosae. 3) The numbers of myocytes and myofibrils tended to decrease. 4) The connective tissue which is the outer layer of nerves tended to increase. Moreover, in some nerves, the paths of each neurofibril became tangled. 5) These findings are structural features in the apex of the tongue of the elderly, involving morphological changes of layers, fibrosis, structural changes of myocytes and myofibrils, nerves and neurofibrils in this region. These changes suggest some relationships to functional disorder in motion, pain and paresthesia of the tongue.
As part of morphological research to investigate the development and function of the human dentino-enamel junction, structural features of net-like structures on the decalcified dentin surface of upper and lower incisors were observed by using stereoscopic microscope, and scanning and transmission electron microscopes. The results were as follows : 1) The net-like structures on the decalcified dentin surface were stained by hematoxylin, orange G·phosphomolybdic acid, toluidine blue and aniline blue. 2) The majority of net-like structures were covered with a membrane-like structure. 3) An individual reticulation of net-like structures corresponds to the margin of each dentin foveolus. 4) The dentin crystals situated in the vicinity of the dentinoenamel junction were larger than the crystals of usual dentin and were more closely aligned. On the other hand, the enamel crystals in this region were smaller than those in other layers of enamel. The surface dentin in the vicinity of the dentino-enamel junction seemed to be highly calcified. 5) It was possible to clearly demonstrate the outline and distribution of dentin foveolus by using certain dyes on the decalcified specimen. 6) By observing the distribution and structural features of net-like structures in detail by applying this dye method to human and animal teeth, the formation mechanism of the dentino-enamel junction and functions of those teeth were elucidated morphologically.
Calcium phosphate ceramics are widely used as bone substitutes because of their favorable biocompatibility and osteoconductivity. Some studies have reported that porous hydroxyapatite (HA), with its special structure, implanted at ectopic (non-bone) sites, exhibits osteoinductive activity. However, few studies have examined the detailed ultrastructure of mineralized tissue formed in biomaterials like HA. Therefore, it is important to examine whether the mineralized tissue exhibits structural characteristics of normal bone tissue. Thus, in this study, we subcutaneously implanted hydroxyapatite blocks (5×5×7mm) into the backs of adult dogs, and performed detailed morphological examination of the bone-like tissue formed, which showed a lamellar structure. Immunohistochemical staining revealed that the matrix fibers of the bone-like tissue were mainly composed of type I collagen. The pattern of crystal deposition in matrix fibers and the structure of osteoclast-, osteocyte-, bone-lining-, and osteoclast-like cells were similar to those of normal bone tissue and osteogenic cells, respectively. These results indicate that cellular events observed in normal bone formation and remodeling occur in bone-like tissue as well, and suggest that bone-like tissue in HA blocks is very similar to bone tissue.