The present studies were performed to investigate the healing process of the tooth extraction wound in whole body irradiated rats and to clarify the effect of irradiation on bone metabolism.
107 Wistar rats of about 100g body weight were used and divided into 3 groups.Whole body irradiated rats were given single exposure with a dose of 8 Gy.The region of the left upper molars of local irradiated rats as controls, was exposed to 8 Gy.On the 7th day after irradiation, the left upper first molar of each rat was extracted.The rats were sacrificed at intervals of 1 day to 14 days after extraction.Non-irradiated rats were sacrificed at the same intervals after extraction.The maxillary bone including the extraction wound was evaluated, histologically, hiscometrically and ultrastructurally.
From the histolgical and histometrical findings, the difference of the healing process between non-irradiated rats and locally irradiated rats is not significant.
In whole body irradiated rats, the healing process especially in the socket was disturbed. The osteoblastic new bone formation following production of granulation tissue was interfered with. Ultrasturacturally, the cytoplasmic organellae were poorly developed in the osteoblast and osteoid formation was reduced in the socket.But periosteal new bone formation was same as that of the locally irradiated rats.
In whole body irradiated rats, the osteoclasts in the interradicular alveolar bone were decreased and have smaller nuclei, compared with non-irradiated and locally irradiated rats.Histometrically, the amount of bone loss was decreased in whole body irraeiated rats.Ultrastructurally, the cyoplasmic organellae and ruffled border were poorly developed in the osteoclasts of whole body irradiated rats.
The findings suggest that irradiation induced cytological changes not only in osteoblasts but also in osteoclasts and these changes resulted in the delayed healing of extraction wound.

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The effect of passive jaw depression on SI neurons driven by electrical stimulation of the temporomandibular joint (TMJD. neurons) were studied in anesthetizts cats. A total of 89 TMJD. neurons were analyzed in this study. Twenty three TMJD. neurons increased in their firequency following depression of the mandible (Fa-type TMJD. neurons) and 4 of them decreased in firing frequency (Dp-type TMJD. neurons). On the other hand, 62 of them did not change in their firing frequency during depression of the mandible (Non-type TMJD. neurons). The majority of the Fa-type neurons were distributed in laminae III-V of area 3a and lamina III of area 3b, whereas Dp-type TMJD. neurons were in laminae III and V of area 3a. The time to peak firing frequency and threshold intensity of Fa-type neurons after electrical stimulation of the temporomandibular joint were significantly shorter and lower than those of Non-type neurons. Fa-type neurons were classified as Fa-sus. types which showed sustained responses during depression of the mandible and Fa-tran. types which showed transient responses during depression of the mandible. Almost all of the Fa-sus. type neurons increased firing frequency following an increase in the velocity of jaw movement. On the other hand, Fa-tran, type neurons did not change in their firing frequency with relation to the velocity of jaw movement.
These findings suggest that Fa-sus. type neurons may function to encode the velocity of jaw movement, whereas Fa-tran. type neurons may have a relationship to perception of jaw movement.

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It has been reported that bone type alkaline phosphatase (ALP) has a higher activity in human periodontal ligament fibroblasts (HPLF) than that of other soft connective tissue cells, such as gingiva and skin 6broblasts.Since the ALP activity of HPLF is markedly stimulated by 1, 25 (OH) ₂D₃, which incidentally is one of the characters of osteoblasts, it was suggested that HPLF is an osteoblastic. fi broblast. These findings led us to the further characterization of osteoblastic features of HPLF in order to mderstand the physiological function of HPLF.
In this study, the anchorage-independent colony formation assay, biosynthesis of secreted phosphoproteins and gene expression using specific probes (cDNA) of TGF-β, liver/bcne/kidney ALP, 2ar/osteopontin and SPARC/osteonectin were investigated. Human gingival cells (Gin-1), human pulp clone cell (593C1) and rat osteoblastic cells (A₁₁, ROS17/2.8) were used to compare with HPLF.
The findings were as follows: conditioned media from HPLF were able to induce colony formation similar to that of A₁₁ and ROS17/2.8, indicating that HPLF secreted a TGF-β-like factor. The radio-labeled osteopontins were synthesized with Mrs.45K and 67K in ROS17/2.8, while the proteins were not detected in HPLF. Finally, a higher expression of mRNAs of ALP, TGF-βand SPARC mRNA were revealed in HPLF by the northern blot analysis, but no 2ar mRNA was detected.
In conclusion, these results indicate that HPLF presents osteoblastic characters based on the gene expression of ALP, TGF-βand SPARC. However, the biosynthesis of phosphoprotein was found to be distinct from osteoblastic cells.

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Activities of acid phosphatase (ACPase) and tartrate-reristant acid phosphatase (TRAP) of multinucleated giant cells (MGCs) responding to hydroxyapatite (HA) implanted in rat jaw bone and subcutaneous tissue were studied by enzyme histochemistry.In the jaw bone, MGCs had ruffled border-like structures on the surface of HA.Both ACPase and TRAP activity were also detected in the cytoplasm of MGCs.Morphological and histochemical features of these MGCs closely resembled those of osteoclasts in the jaw bone.Moreover, both enzyme activities were observed in the mononuclear cells around the MGCs.On the other hand, MGCs in subcutaneous tissue had elongated the flattened cytoplasm along HA surface, and both enzyme activities were basely detected.Also many mononuclear cells that did not show TRAP activity were observed around these MGCs.The present results raise the possibility that the histological environment of the site for HA implantation may play a role in the regulation of the biological characteristics of MGCs responding to HA.

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After investigating the standard error of a plane glass electrode pH meter for a thin layer sample, the pH of human resting saliva collected between the tongue apex and the hard palate with a piece of neutral paper was studied in the following ways.
1.When a subject performed maximum forced nose breathing for 15 sec, the pH of the mixed saliva was little changed.In contrast it rose by about 0.2 points after the maximum forced mouth breathing for 15 sec.Thus, the following measurement was performed under conditions avoiding the error caused by mouth breathing and vigorous conversation.
2.The average pH value of the mixed saliva collected in the morning was significantly lower than that of samples (n=5) collected during the daytime.
3.The mean pH value of the mixed saliva from 5 diurnal cycles collected from a single subject indicated a reproducible diurnal change which appeared to consist of 1) a short-lasting variation (about ± 0.5 points) during 0.5-1.5h after food-intake, and 2) a long-lasting variation (about-1 point) alternating from daytime to night time.
4. A significant finding was an abrupt increase in the pH level observed when changing from the covered mode to the uncovered mode.This increase appeared due to the [HCO₃^-] lchange in the saliva and its peak came at approximately 4min after changing the mode of measurement.

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We have examined the effects of buthionine sulfoximine (BSO) mediated glutathione (GSH) depletion in melphalan (L-PAM), chlorambucil (CLB), nimustin (ACNU), adriamycin (ADR), bleomycin (BLM), mitomycin C (MMC) and cisplatin (CDDP) cytotoxicity to cultured, human tongue squamous cell carcinoma (SCC-25) cells and human osteoblast like osteosarcoma (SaOS-2) cells.
The treatment of BSO reduced the level of intracellular GSH without cellular toxicity. The remarkable enhancement of L-PAM and CLB cytotoxicities were shown by the treatment of BSO in both SCC-25 cells and SaOS-2 cells. The values of IC3o of L-PAM and CLB were approximately 2.5 to 4.5-fold lower in the BSO-treated cells, as compared to control cells. However, there was almost no difference between BSO-treated and control cells in the cytotoxicities of ACNU, ADR, BLM, MMC and CDDP of both cell lines. These data indicate that BSO treatment potentiates the cytotoxicity of L-PAM and CLB, but not in other drugs in SCC-25 and SaOS-2 cells. The results suggest that the combination chemotherapy of L-PAM and CLB and non-cytotoxic, GSH-modulating agent is worthy for the treatment of neoplasms.

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We evaluated the effect of streptozotocin-induced diabetes on the structures of dermatan sulfate (DS) and heparan sulfate (HS) prepared from rat submandibular gland glycosaminoglycans (GAGs). GAGs were isolated and purified from the submandibular glands of diabetic and age-matched control rats by standard procedures. DS and HS were prepared from GAG by chondroitinase AC and ABC digestions. The unsaturated disaccharides produced from DS and HS by enzymatic digestion were separated and identified by HPLC. The unsaturated disaccharides from DS in normal rats had ΔDi-4 S as its main component and ΔDi-6 S and ΔDi-0 S as subcomponents. The proportion of ΔDi-4 S increased in diabetes along with a decrease in ΔDi-0 S. The unsaturated disaccharides from HS in normal rats were identified as ΔDi_HS-0 S, which was the main component, and ΔDi_HS-6 S and ΔDi_HS-NS, which were subcomponents. However, the ratio of the peak height of ΔDi_HS-0 S to that of ΔDi_HS-6 S increased in diabetes. This suggests that diabetes causes a reduction in the non-sulfated portion of the DS chain, and an increase in the non-sulfated portion of the HS chain.

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The present study was performed to obtain direct eviden ce of MPNSS (methylprednisolone sodium succinate) on the growth retardation of hard tissues in rats. For this purpose, different doses of MPNSS were injected intraperitoneally to the rat (daily administration of 2.0 mg/kg, 14 times and alternate-day administration of 10.0 mg/kg, 14 times). To the age-matched control animals, 0.9 % NaCl solution was injected. The body weight was measured daily. Wet weight of the adrenal gland was measured and the lengths of upper jaw (diastema) and tibia were also measured with dial calipers. In addition, the rate of the incisal dentine formation was measured with a chronological-labelling method using tetracycline. The right tibia was used for measuring the defatted -dry weight and the ash weight. To detect changes in calcium homeostasis, contents of calcium and phosphorus in the plasma were analysed. Following treatment with MPNSS, the weight loss, atrophy of the adrenal gland and retardation of bone growth were detected in both experimental groups.On the other hand, osteoporosis could not be recognized by contact-microradiography. It was confirmed that reduction of the growth rates was greater in the daily injected group than in the alternate-day injected one. In conclusion, the present study showed a direct inhibitory effect of MPNSS on bone growth in growing young rats. It is suggested that a larger dose of glucocorticoids could be given more effectively with less side effects of the drug by an alternate-day administration.

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