I investigated the distribution of nociceptive neurons responding to masseteric nerve stimulation in the nucleus ventralis posteromedialis proper (VPM) and intralaminar (IL) nuclei of the thalamus. The activity of single thalamic neurons in cats anesthetized with urethane and chloralose was assessed extracellularly. Thirty neurons with masseteric inputs were observed around the periphery (shell region) of the posterior half of the VPM, and most of these were excited by mechanical stimulation in the contralateral trigeminal integument. Of these, 20 neurons displayed a graded response to touch, pressure, and noxious mechanical stimulation to the center of the receptive field, while the surrounding area was responsive only to noxious mechanical stimulation. They were therefore considered to be wide dynamic range (WDR) neurons, and were located more anteriorly in the VPM. The other 10 neurons responded only to noxious mechanical stimulation. Twenty-six neurons were found in the nuclei centralis lateralis and parafascicularis of the IL nuclei, and most of these were excited by noxious stimulation of the spinal nerve territory. Some of the VPM and IL neurons responded to injection of 3% NaCl solution into the masseter. These findings suggest that masseteric inputs, such as masseteric pain information, are mainly conveyed to the cortex via WDR neurons and IL nociceptive neurons.

View full abstract

Epidermal growth factor (EGF) is produced in the human salivary glands and excreted in human saliva. Recently, EGF has attracted interest owing to its association with carcinoma. Cytokeratin 19 (CK19) is an especially intriguing member of the CK intermediate filament a superfamily. CK 19 tends to reflect the state of differetiation of tumors. For example, the expression of CK 19 is more intense in poorly differentiated lesions than in other lesions. First, we confirmed that the oral squamous cell carcinoma cell line HSC-3 expressed CK 19 mRNA by Northern blot analysis. Secondly, we examined the relationship between CK 19 and EGF in HSC-3 cells. Morphology and expression of CK 19 mRNA were observed in the cells with and without EGF. The results suggest that EGF may modulate the morphology and expression of CK 19 nRNA of HSC-3 cells.

View full abstract

We investigated how effectively the oral age index evaluates the oral health level. The index was used for seven consecutive years during oral health checkups of adults working in a company that provided oral health care for their employees. The oral age index more accurately evaluated the level of oral health in the people in this group than did the DMFT index which is a quantitative measure of dental diseases. Furthermore, the oral age of adult group was preserved to be younger than chronological age by providing consecutive oral health care service. Based on these results the evaluation of the oral age indicated that consecutive oral health care service is required to improve oral health level. A person with a younger oral age than chronological age can be said to be in good oral heath. The oral age index can be used as a target for individuals or groups to improve their oral health level.

View full abstract

We conducted a cross-sectional study to determine if dental caries experience is a risk indicator for periodontal disease. The subjects were 27, 683 adults who received an oral examinations after the Kobe earthquake in 1995. The results showed that in every age groups, the percentage of teeth with Community Periodontal Index (CPI) 0 code were significantly in the following order : decayed teeth (DT)<filled teeth (FT)<sound teeth. On the contrary, the percentage of teeth with CPI 3 or 4 code were significantly in the following order : sound teeth<filled teeth (FT)<decayed teeth (DT). On the other hand, there was correlation between CPI code and DMFT. In each DMFT component, DT increased with the increase of CPI code especially in 20-29 age group, while FT didn't change with increase of CPI code. With stepwise logistic regression analysis of CPI code 3 or 4 in 20-29 age group, DT indicated the highest odds ratio in the independent variables (DT, MT, FT and gender). The results showed a strong correlation between DT and periodontal health, especially in the 20-29 age group. This indicates that DT can be used as a risk indicator for periodontal disease.

View full abstract

We studied the effect of high concentrated fluoride on enamel subsurface lesions. Enamel specimens 3mm in diameter were prepared from extracted human incisors using a hollow core drill. The specimens were highly polished and subsurface lesions were produced by immersion in a demineralizing solution for 24 hours. The specimens were treated with acid phosphate fluoride (APF) solution and then washed in 1 M KOH solution. The samples were analyzed by atomic force microscope (AFM), electron spectroscope for chemical analysis (ESCA), SEM and x-ray microanalyzer (XMA). We found that treatment with a high concentration of APF improved the enamel to be calcium fluoride like-materials at only to a depth 5 μm from the surface, but did not alter the entire subsurface lesion. When this improvement was washed in KOH, calcium fluoride like-materials were eliminated from the surface. This elimination may make the subsurface lesion decrease acid resistance. This suggests that it is necessary a fluoride treatment program to aid in maintaining calcium fluoride like-materials formed at the surface layer of the subsurface lesion.

View full abstract

We investigated the relationship between the human life span and the life of the average tooth. Although Japanese woman live longer than men, the opposite is true for their teeth. We also found that longevity was different for each tooth. During the six years from 1987 to 1993 the increase in longevity of the average Japanese tooth was three times greater than the increase in the average life span. In order for people to achieve the goal of having 20 teeth by age 80, we must consider different preventive measures for each tooth.

View full abstract

We observed the process of carcinogensis in a rat tongue carcinoma model induced by oral administration of 4 NQO, and correlated cell proliferation and vasculogenesis by immunohistochemical methods. As carcinogenesis progressed, the PCNA labeling index and microvessel density were both increased, and there was a significant correlation in their kinetics (0.896). Microvessels appeared to be irregular and their density was increased in epithelial dysplasia compared with normal epithelia. During early invasional carcinomas and invasional carcinomas, microvessels were localized around the cancer nests, appeared more irregular, and had increased density. These data suggest tumor cell proliferation and vasculogenesis are dependent on the interrelation of the tumor cell and tumor stroma in the rat tongue carcinoma model induced by oral administration of 4 NQO.

View full abstract

Using a model of acute-phase infarction of the middle cerebral artery (MCA) in rats, we evaluated the effect of sevoflurane anesthesia on cerebral autoregulation. The capacity for cerebral autoregulation, as assessed by the relative slope ratio (RS) between mean arterial pressure (MAP) and cerebral blood flow, was evaluated in exsanguinated rats (Group I), rats under deep anesthesia with sevoflurane (Group II), and rats with MCA infarction under deep anesthesia with sevoflurane (Group III). Although the animals in Groups I and II exhibited similar RS within the range of 40 to 110 mmHg MAP, the ratio in Group III was higher than in the other two (p<0.05). These findings suggest that cerebral autoregulation deteriorates during the acute phase of cerebral ischemia.

View full abstract

I investigated the distribution and functional properties of nociceptive neurons responding to masseteric nerve stimulation in the nucleus ventralis posteromedialis proper (VPM) and intralaminar (IL) nuclei of the thalamus. The activity of single thalamic neurons in cats anesthetized with urethane-chloralose was assessed extracellularly. Thirty-two neurons with masseteric input observed around the periphery of the posterior half of the VPM responded to noxious mechanical stimulation. They were therefore considered to be nociceptive specific (NS) and wide dynamic range (WDR) neurons. Twenty-six neurons were found in the nuclei parafascicularis and centralis lateralis of the IL nuclei. These finding suggest that masseteric input, such as masseteric pain information, is conveyed to the cortex via NS and WDR neurons, and IL nociceptive neurons.

View full abstract

We investigated the effect of green tea on cellular proliferation and telomerase activity in the human oral squamous cell carcinoma cell lines HSC-4 (well differentiated) and HSC-3 (poorly differentiated). HSC-4 and HSC-3 cells were incubated following treatment with or without (-)-epigallocatechin-3-gallate (EGCG), and with or without (-)-epicatechin (EC), at various concentrations. Although EC did not significantly inhibit cellular proliferation in either cell line, EGCG inhibited it in a dose and time dependent manner. Although the telomerase activity of HSC-3 cells was not inhibited, that of HSC-4 was inhibited in a dose and time dependent manner. When HSC-4 cells were treated with EC in the presence of EGCG, there was a synergism in the inhibition of cellular proliferation, telomerase activity and the expressions of hTERT and MMP-9 mRNA. These results indicated that antitumor effects of green tea are closely related to telomerase activity in well differentiated oral squamous cell carcinoma.

View full abstract

[in Japanese]

View full abstract