The fine structures of the sublingual and interpapillar surfaces of the human tongue were examined by light microscopy, and scanning and transmission electron microscopies. After consent, specimens of the normal median area of the tongue were obtained during surgery. The patterns of microridges on the sublingual and interpapillar epithelial surfaces were similar, but the structure of the longitudinal sections of microridges in the sublingual and interpapillar epithelial cells differed. Long microridges with many branches were abundant in the sublingual area, but from the lingual apex to the lingual body, the proportion, height and number of microridge branches of interpapillar epithelial cells gradually decreased. The width of the interpapillar epithelial cell microridges was least in the lingual apex. The differences in microridge shape between the sublingual and interpapillar epithelial cells may be related to differences in retention of mucus, cell stretching and mechanical forces, reflecting the functions of the respective regions.

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We attempted to separate several oligo peptides, including arginine, from human whole saliva and to confirm the presence of sialin (GGKR). The methanol soluble fraction of whole saliva was subjected to gel filtration on a Bio-Gel P-6 column. Fraction III (material estimated to weigh less than 10, 000 Da) was ultrafiltrated to remove a greater than 5, 000 Da fraction, and analysed using affinity chromatography on an anhydrotrypsin agarose column. After the adsorbed fraction was separated by reversed-phase highperformance liquid chromatography (RP-HPLC), fourteen peptides were purified using the same column. The results of amino acid analysis indicated that the ten oligo peptides were present as a histidine-rich arginine peptide. Sequencing of the 5 major peptides revealed that the low molecular weight arginine peptides were derived from proteolysis of the histatins. The molecular weight of the major arginine peptides ranged from 800 to 1, 600 Da. Based on the present results, sialin was not detected.

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To investigate the effect of ingested food texture on tongue activity during mastication in humans, the electromyographic (EMG) activity was recorded by surface electrodes from the skin over the mylohyoid muscle (MH), masseter muscle (M) and anterior digastric muscle (Da) during mastication ofthree kinds of food (gumi candy: G, peanuts: P, rice cake: RC) in eleven adult subjects. The texture ofthese foods was measured according to the texture profile analysis. P was the hardest food, while RC was the most adhesive of the three. The amplitude of M-EMG decreased significantly during P mastication, while the amplitude of Da-EMG decreased significantly according to the progress of mastication of G, P and RC. The amplitude of MH-EMG decreased significantly during mastication of G. In contrast, the amplitude of MH-EMG increased significantly during mastication of P and RC, with an especially marked increase in amplitude observed in the late stage of chewing during mastication of RC. These results suggest that tongue activity in the late stage of chewing just before swallowing may be affected by the texture of the triturated food in the oral cavity.

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This study observed interodontoblastic fibers (IOF) in human circumpulpal dentin by light and electron microscopy, in order to discuss their ultrastructure and connection with predentin. The IOF was connected with both pulpal and predentinal fibers in all pulpal areas of human teeth. The IOF connected with the predentin either at the intertubular dentin or the edges of dentinal tubule openings. There were three types of IOF in both cases: one where fibrils of the IOF radiate and intermingle with predentinal fibrils (transitional type); one where fibrils of the IOF penetrate predentin without radiating (penetrative type); and one where fibrils of the IOF show features of both of the above types (mixture type). The transitional and mixture types were evenly distributed in the coronal area. The penetrative type was common at intertubular dentin in the root and chamber floor areas. The IOF in the roots and chamber floors were thicker than IOF in the coronal area. The IOF in the roof of the pulp chamber, in particular, presented a fine detailed network. Odontoblasts showed a pseudostratified epithelium-like arrangement in the coronal area, while there was a more simple arrangement in the root and chamber floor areas.
It is suggested that the thickness of the IOF, sites, and types of IOF-predentin connections are closely associated with the arrangement of odontoblasts, and that the IOF observed in this study corresponds to Korff's fibers.

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In the present report, we outline a procedure using an adsorption model that permits the assessment of the surface pool of calcium in enamel and synthetic apatites. Enamel samples at various developmental stages were obtained from porcine unerupted incisors, as well as human erupted dentition. The dissected enamel samples were freeze-dried, pulverized, and finally treated by plasma ashing (decomposition of organic matter). For references free from organic matter, synthetic hydroxyapatite and Mg-containing carbonatoapatite were also included. Each of the samples was equilibrated in solutions containing various initial concentrations of Ca²⁺, Mg²⁺ and Na+ as nitrate salts. Following equilibration, the total concentrations and activities of the calcium and magnesium ions in the experimental solution were determined. Experimental data on the calcium adsorption onto the crystals were interpreted on the basis of the Langmuir-type model for binary systems, assuming competition of Ca²⁺ and Mg²⁺ for the same adsorption sites on the crystal surfaces. The results supported the presence of two distinct types of surface calcium: one corresponded to the same pool competing in adsorption with Mg ions, while the other was labile in nature, and was displaced easily from the solid with water. From a biological point of view, it is interesting to point out that the surface pools of calcium varied with tissue development, most probably reflecting the composition (particularly Ca²⁺ and Mg²⁺ activities) of the fluid responsible for biomineralization.

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Carbonation of biological apatites is a common, not exceptional, phenomenon in vertebrate teeth and bones. In order to explain this ubiquitous phenomenon, we previously postulated that carbonatoapatite is the stable mineral phase in mineralizing milieu having certain CO₂ partial pressures. The current work using Fourier-transformed infrared spectroscopy, in conjunction with the use of ¹³CO₃ as probes, shows that a carbonatoapatite precipitates concomitantly with the dissolution of human enamel mineral. The substitution of CO₃^2- into both PO4^3- (B-type) and OH- (A-type) sites of apatite lattices were realized in the dissolution/precipitation processes. The results also verified that the lability of carbonate as reported for immature enamel is almost eliminated from human enamel of the erupted dentition. The overall results support our working hypothesis concerning the carbonation of bioapatites and their stability in mineralizing milieus.

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It has been suggested that calcitonin gene-related peptide (CGRP) -positive nerve fibers in rat junctional epithelium (JE) originate from the trigeminal ganglion. However, their nature and function remain unclear. Furthermore, species generality of the JE innervation has not yet been established. Recently, it has been reported that peripheral sensory nerve terminals generally possess Na⁺, K⁺-ATPase (Na⁺-pump) in their axonal cell membranes. The present study thus aimed to confirm whether the CGRP-positive nerve terminals in the JE also possess Na⁺, K⁺-ATPase and if the innervation to JE is common in all mammals. The existence of Na⁺, K⁺-ATPase in rat JE nerves was comparatively assessed by immunohistochemistry using polyclonal antisera against a rat brain Na⁺, K⁺-ATPase β1 subunit, human protein gene product 9.5 (PGP 9.5) and synthetic rat CGRP. No positive immunoreaction for Na⁺, K⁺-ATPase β1 subunit was demonstrated on the CGRP-positive nerve fibers in JE, in spite of positive reactions in the axon terminals of the free nerve endings, lamellated corpuscles and Merkel cell-neurite complexes in oral mucosal areas of the same section. The innervation to JEs of the mouse, gerbil, dog and monkey was examined by immunohistochemistry using polyclonal antisera against CGRP and PGP 9.5. Although JEs of the mouse and gerbil contained nerve fibers positive for both CGRP and PGP 9.5, no similar fibers were detected in the JEs of the dog and monkey. These results indicate that dense innervation in the junctional epithelium is possibly a species-specific phenomenon in rodents.

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