Electrophysiological effects on taste receptor cells were investigated using whole-cell patch clamp technique. The taste buds were isolated from the fungiform papilla of rat tongue. In the bath solution containingCa²⁺(10 mM), the inward Ca²⁺current(I_Ca(L))was observed. Holding potential was -60 mV. The threshold potential was -40 mV, and the peak amplitude at 0 mV was-69.8 ±11.0 pA (n=5). The I_Ca(L)was rapidly inactivated. The capacitance was 3-5 pF. The I_Ca(L)was inhibited by 78.4±4.9%(n=4, P<0.001) by MnCl₂(2 mM), and by 67.3±3.6%(n=5, P<0.001) by C_oCl₂(3 mM), but NiCl₂(40μM), an antagonist of T-type Ca²⁺channel, did not significantly affect I_{Ca (L)} (by 6.7±, 2.0%, n=4). On the other hand, nifedipine (2μM) blocked the I_Ca(L)current almost completely (by 97.2±3.2%, n=4, P<0.001), and garapamil (D-600)(1μM) inhibited it by 55.1±3.0%(n=4, P<0.001). Application of Na-saccharin (20 mM) increased I_Ca(L)by 19.6±3.1%(n=5, P<0.01). The effect was reversible. These results indicate that the slow in ward current is I_Ca(L)current, and the I_Ca(L)is enhanced by Na-saccharin, suggesting that the enhancement of I_Ca(L)would electrically transmit the signals to sensory neurons and modulate physiological functions.

View full abstract

Transforming growth factor-β(TGF-β) is a multifunctional polypeptide th at influences proliferation and differentiation in various types of cell. It has been recognized that platelets and bone are rich sources of TGF-β. However, using molecular hybridization, it has been demonstrated that periodontal cells also expressed a high level of TGF-β mRNA, relative to bone cells. This studyh as been extended on human periodontal ligament fibroblast (HPLF) by investig ating the effect of TGF-β on the synthesis of proteoglycans, which are believed to be an important factor in bone remodeling. Cells were incubated to be labeled with 35S-sulfate. The expression of proteoglycan mRNA was also observed by northern blots. Utilizing the characterized data of HPLF cells (Sommerman, M. J. et al., J. Dent. Res., 67: 66, 1988), the cells which had high alkaline phosphatase (ALP) activity were chosen. On HPLF cell-line produced predominantly the proteogl ycan II (Decorin; PG II). No stimulating effects of PG II synthesis were observed by TGF -β. However, TGF-β stimulated the expression of mRNA of proteoglycan I (Biglycan; PG I) and the synthesis of 35S-sulfate labeled PG I. According to the time course study, mRNA of PG I was increased after 12 h exposure to TGF-β. These results suggest that the PG I synthesis might be enhanced by indirect TGF-β effects and PG I synthesis is believed to be important for periodontal remodeling.

View full abstract

Relations between physical characters of foods and human preference of them were evaluated in healthy university students aged 20-25. In preference test of the material with different size at constant volume, using paired comparison test, middle size material (diameter 4.2 mm) was preferred to small size material (2.6 mm) and big size one (5.8 mm) in case of sweet and menthol taste, while in case of soda pop taste big size material (5.8 mm) was most preferred. In preference test of the material with different hardness, almost the same hardness (0.6-1.4 kg/V by texturometer) of materials was most preferred regardless of taste difference.
These results suggest that the size and hardness of food has close relations with its preference of the subjects.

View full abstract

Section of the chorda tympani nerve produced increment of androgen responses (Gland weight and esteropeptidase activity) in the rat submandibular gland. Chronic treatments with pilocarpine and bethanechol failed to prevent such increment of androgen responses in decentralized gland, implying that increased responses are not due to decreased stimulation of cholinergic receptor. The total activity of Δ4-3-ketosteroid 5α-reductase (5α-reductase) and nuclear androgen binding somewhat decreased in decentralized gland. These results suggest that the observed increment of androgen responses are induced via not only the well-known pathway of androgen action, including formation of 5a-dihydrotestosterone (5α-DHT) and its binding to nuclear androgen receptor, but also a different pathway.

View full abstract

Using trays as a convenient means of applying the gel method clinically, a newly developed freeze-dried hydroxyethylcellulose gel (abbreviated freeze-dried HEC gel method)(group III) as well as a conventional HEC gel (group II) were applied to the enamel surface of extracted teeth.
As a result, the teeth were reinforced by fluorapatite crystal formation as well as by fluoride uptake. Using the enamel and sectiond surfaces of these two groups as well as untreated teeth (group I) as targets, morphologic observations were performed by scanning electron microscopy, qualitative analysis by thin-film X-ray diffraction measuring methods, composition analysis based on infrared spectral analysis, observations based on contact microradiography as well as polarized light microscopy, elemental analysis with an electron probe microanalyzer, and qualitative analysis based on microarea X-ray diffraction.
The results suggested that, as with the conventional HEC gel, the freeze-dried HEC gel was effective when using trays in vivo as a method of generating fluorapatite and of reinforcing tooth structure.

View full abstract

For a further understanding of the gustatory function of the greater superficial petrosal nerve (GSP), effects of bilateral sectioning of the GSP and/or the chorda tympani nerves (CT) in hamsters on discriminating sucrose taste were examined through conditioned taste aversion paradigm. Licking pattern was monitored in experimental and sham control male hamsters. Once the animal was conditioned to avoid 0.1 M sucrose solution by i.p. injection of 0.5 M LiCl, the animal avoided to lick sucrose solution at higher concentration above 0.01 M. The degree of the aversion was significantly decreased when the GSP and/or the CT were sectioned bilaterally. The order of the sectioning effects was GSP+CT>GSP≥CT>sham. These results suggest that the GSP plays an important role for mediating sweet taste information, which is consistent with neurophysiological data in the hamster.

View full abstract

The curve symbol in the mandibular central incisor on the cross-sections of the tooth crown was observed quantitatively, based on the two methods by Mühlreiter. Fifty extracted incisors were examined. To identify the individual incisors as belonging to the right/left quadrant, moiré topography was applied to the proximal surface of the root before measuring. The most common morphological combination pattern of the proximal surfaces on the root was ridge-groove type (78.0%). In all teeth in the present study the mesial/distal surface could be identified from the difference of the concavo-convex level on the root surface. The cross-sectional outlines were obtained by a tht ee-dimensional measwing instrument system (VECTRON), and the measurements were made on the cross-sections output by X-Y plotter.
Comparison of the angles: When the distolabial angle is larger than the mesiolabial angle, the curve symbol is evident. On the cervical and cervical third of the tooth crown, the reverse curve symbol was evident. On the middle and incisal third of the tooth crown, the curve symbol was exhibited. Inclination of the perpendicular line: When the line perpendicular to the segment between the mesio-and disto-labial angle inclines toward the distal, the curve symbol is evident. The angle between the perpendicular line and labiolingual axis was within 5°. There tended to be a slight increase in the percentage of “distal” from the cervical to the incisal third. Therefore, the curve symbol was apt to occur near the incisal edge. On the cervical and cervical third, in any case of inclination of the perpendicular line, the mesiolabial angle was larger than the distolabial. On the middle and incisal third, when the line was toward the distal, the distolabial angle was larger than the mesiolabial, and the two methods agreed with each other. A comparison of the degree of the curve symbol judged by the angles in the three cases of the perpendicular line showed that on the every cross-section there was a general increasing trend from “mesial” to “coincident” to “distal”, and the two methods showed a similar tendency. In the relationship between the curve symbol and tooth morphology, it was suggested that the size factor correlated significantly with the curve symbol, while the shape factor did not. The curve symbol appeared more distinctly in the larger teeth.

View full abstract

The inhibition constants (K_i) for rat liver cathepsins B, H and L of three rat submandibular salivary cystatins (designated as RSC-1, RSC-2 and RSC-3), induced by chronic isoproterenol treatment, were determined. These three cystatins inhibited the enzyme activity of cathepsin L most strongly, whereas they had much larger K_i values for cathepsins B and H.

View full abstract