We investigated the intra-articular pressure-volume relation and the methodology for measuring intra-articular pressure (IAP) in both the monkey knee joint and the human temporomandibular joint. Two catheters were inserted into the monkey's knee joint with an external transducer on one path through the catheter and a microsyringe on the other. Measurement of the IAP was made by the rapid bolus injection technique, and values for the intra-articular pressure-volume relation were calculated. Measurements included IAP before volume injection (Po), peak IAP caused by volume injection (Pp), and the intra-articular pressure volume index (IAPVI) calculated as ⊿V/log (Pp/Po). We obtained the pressure-volume (P-V) relationship from changes in IAP after injection of physiological saline into the articular cavity of the monkey knee joint. The parameter ⊿/log(Pp/Po) seemed to be a useful index for characterization of the internal pressure environment of the articular cavity. We termed this the intra-articular pressure-volume index (IAPVI), and measured its value for the human temporomandibular joint (TMJ). IAPVI was calculated. The IAPVI in the normal human TMJ was constant irrespective of the baseline pressure level (Po). In addition, IAPVI was lower in patients with internal derangement of the TMJ (anterior disk displacement without reduction) than in normal subjects. These results suggest that IAPVI is useful for evaluating the physical characteristics of the TMJ cavity, and for diagnosing internal derangement of the TMJ.

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We developed a sensitive method based on amplification of cytokeratin(CK)8 mRNA using the reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot hybridization for detection of cervical lymph node micrometastases from oral squamous cell carcinoma (SCC). CK8 RT-PCR showed that CK8 mRNA expressed in all of the 10 primary oral SCCs we tested, but not in any of 5 normal lymph nodes, indicating that CK8 mRNA is a good target of RT-PCR for the detection of lymph node micrometastases in oral cancer. We compared the detectability of lymph node metastases with CK8 RT-PCR, Southern blot hybridization and conventional histological examination, using 70 lymph nodes obtained from 10 oral SCC patients. CK8 mRNA was detected in all of the 8 lymph nodes which were histologically metastasis-positive. In addition, 5 (8%) out of the 62 histologically metastasis-negative nodes gave a CK8 product detectable with ethidium staining. On Southern blot hybridization with ^<32>P labeled CK8 cDNA, a 11 (18%) of the lymph nodes that had been judged negative by histology gave positive signals, indicating that these lymph nodes contained micrometastases which could not be detected histologically. These results demonstrate that CK8 RT-PCR is a more sensitive method than histological examination for the detection of lymph node micrometastases in oral SCC.

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Rats with non-insulin-dependent diabetes mellitus (NIDDM) induced by neonatal streptozotocin injection are a useful animal model. We administered an intraperitoneal injection at 65 mg/kg of streptozotocin dissolved in 0.05 M citrate buffer at pH 4.5 to neonatal rats with naturally occurring gingivitis rat (ODUS/Odu). Injections were done either at birth (day 0) or day 1 (n-STZ). Another group was administered the same volume of STZ 2 weeks after birth (I-STZ), and the control group received an injection of citrate buffer only. We measured blood glucose, body weight, serum triglycerides and pocket probing depths for the three groups. We also examined the extent of gingivitis among the n-STZ, I-STZ and control groups, and monitored macrophage function. After 18 weeks, the I-STZ group had significantly higher levels of blood glucose (p<0.001) and serum triglycerides than the other two groups. At 18 weeks the I-STZ group showed significantly lower body weight than either the n-STZ animals or the controls (p<0.001). Pocket probing depths of the I-STZ group were slightly increased compared with the n-STZ (p<0.05) and control (p<0.05) groups. At 18 weeks, macrophage chemotaxis in 1 : 20 and 1 : 40 zymosan activated serum was significantly greater in I-STZ than in the control group (p<0.05). The same was true for superoxide anion production measured by stimulation with phorbol myristate acetate and Ca ionophore A 23187 (p<0.001). These findings suggest that n-STZ rats have resistance to STZ. Based on blood glucose, body weight, pocket probing depths and serum triglycerides in the n-STZ group, we concluded that STZ affects the immune system.

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In order to determine how Ca affects the growth of rat incisors, three-week old male rats were divided into four groups and fed controlled diets for three weeks. Group 1 was fed a low calcium diet for 13 days followed by a standard diet; group 2 was fed a standard diet for 13 days followed by a low calcium diet; group 3 was fed a low calcium diet only ; and the control group was fed a standard diet only. Dentin growth was examined using the tetracycline (TC) labeling method. A confocal laser scanning microscope (CLSM) was employed to examine the pattern of TC labeling, to measure the thickness and area of the layers between each two labeling lines, and to measure the cross-sectional areas of the incisors and dental pulps. In addition, body weight and serum Ca and serum P levels were measured to investigate their relationship to the amount of mineralized tissue growth in the dentin. After the diet changed, a marked increase in body weight was observed in group 1 and a gradual increase in the rats of group 2. Compared with the controls, the increase in group 3 was slow and gradual. The observed values for serum Ca in group 3 were significantly lower than in the controls. Group 3 had the highest values for cross-sectional area of the dental pulp. No significant differences were observed for the cross-sectional area of incisors among the four groups. Furthermore, group 1 showed a prominent increase in both thickness and area of mineralized tissue, after alteration of the diet. A slow and gradual reduction in both thickness and area were observed in group 2 after changing the diet. The thickness and area of mineralized tissue growth observed in group 3 were significantly lower than in the controls. These results suggest that the amount of Ca ingested has a profound effect on dentin growth in rats.

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Thalamic nociceptive neurons receiving afferent inputs from the tooth pulp (TP) were recorded from the nucleus ventralis posteromedialis proper (VPM) of cats anesthetized with urethane and chloralose. We investigated the effects of cervical vagus nerve (CVN) stimulation on the responses of TP neurons in the VPM and observed 31 tooth pulp specific (TPS) neurons and 15 wide dynamic range (WDR) neurons with TP inputs around the periphery (shell region) of the posterior half of the VPM. Of these neurons, 22 TPS and 11 WDR neurons were excited by electrical stimulation of trigeminothalamic tract (TTT) fibers in the trigeminal medial lemniscus. We used a conditioning-test paradigm to examine the effects of CVN stimulation on the responses of VPM neurons to electrical stimulation of TP and of TTT. Inhibition of the responses was observed in 17 TPS and 8 WDR neurons. Local anesthetic block of the mesencephalic periaqueductal gray (PAG) and/or nucleus raphe dorsalis (NRD) markedly eliminated the inhibitory effects of CVN stimulation on the responses of TPS and WDR neurons to TTT stimulation, and had a limited inhibitory effect on the response of these neurons to TP stimulation. These results suggest that vagal afferents were able to activate the ascending antinociceptive pathway from the PAG/NRD to the VPM, as well as activating the descending antinociceptive system that acts on the lower brain stem. In addition, vagal afferent inputs to the PAG/NRD, which may be relayed through the nucleus of the solitary tract, acted as an afferent mechanism that triggered this ascending antinociceptive system.

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We investigated the ability of the internal jugular venous valve (IJVV) to buffer the transmission of pressure to the cerebral venous system during intrathoracic hypertension, by analyzing its transvalvular pressure gradients. The subjects were seven patients who underwent general anesthesia for oral surgery. After induction of anesthesia, one catheter was percutaneously inserted into the superior bulb of the internal jugular vein and another into the superior vena cava via the subclavian vein. These catheters were used to simultaneously monitor the internal jugular venous pressure (IJVP) and the superior vena caval pressure (SVCP). Pressure waves were recorded during intrathoracic hypertension caused by coughing at emergence. We examined the relationship of SVCP with the difference (⊿P) between variations in SVCP and IJVP. The SVCP had a positive linear correlation with ⊿P (⊿P mmHg=0.69 ・ SVCP-10.25, n = 101, r=0.837). Even when the SVCP increased significantly (>50 mmHg), the elevation in IJVP was suppressed, suggesting that the IJVV is usually competent during sudden increases in intrathoracic pressure.

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We investigated the presence or absence and timing of BNB failure using various neuro pathic pain models : the complete Freund's adjuvant neuritis (CFA) model, the Hashimoto model, the axotomy model, and the chronic constriction nerve injury (CCI) model. In addition, we investigated whether thalidomide inhibited BNB failure. The CFA model did not show BNB failure. However, all rats had BNB failure 21 days after surgery with the Hashimoto model. In the axotomy model, all rats showed BNB failure 14 days after surgery. With the CCI model, they all had BNB failure 12 hours after surgery. Furthermore, administration of thalidomide to the CCI model more markedly inhibited BNB failure at a higher dose or when administration was started earlier.

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We examined the effect of clonidine with complete Freund's adjuvant (CFA) on neuritis in Sprague-Dawley rats using behavior assays. The animals were anesthetized and the common sciatic nerves were exposed bilaterally after intraperitoneal injection of 50μg/kg clonidine or saline. The left nerve was wrapped in a band of sterile hemostatic oxidized cellulose saturated with 50μL CFA. The right nerve was only exposed. Intraperitoneal injection of clonidine or saline were administered every 12 hours for a total of eight times. The response of the rats was checked 12 hours after the last injection. We found that cold-allodynia and mechano-hyperalgesia, but not mechano-allodynia, were depressed in the rats that had received clonidine.

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Using cats anesthetized with urethane and chloralose, we studied the responses evoked by electrical stimulation of tooth pulp (TP), muscle nerves and visceral afferent input through the greater splanchnic nerve, by noxious and innocuous mechanical stimulation of muscle, cutaneous and subcutaneous tissues, and by injection of algesic chemicals (hypertonic saline) into the masseter and splenius muscles. The responses were investigated in single neurons located in the nucleus ventralis posteromedialis proper (VPM) and the intralaminar nuclei (IL). Using chemical and noxious mechanical stimuli of the masseter muscle, we were able to excite 17 VPM neurons that could be functionally classified on the basis of their cutaneous receptive field properties as nociceptive specific (NS), tooth pulp specific (TPS), or wide dynamic range (WDR) neurons. We were able to excite 23 IL neurons, which had a complex receptive field, sometimes covering half of the body surface, using the same stimuli. The VPM and IL nociceptive neurons receiving muscle as well as cutaneous or TP afferent inputs had receptive field properties comparable to those previously described for thalamic nociceptive neurons. The VPM nociceptive neurons were located around the periphery of the posterior half of the VPM. These neurons generally had larger cutaneous receptive fields than neurons unresponsive to muscle afferent stimulation, and WDR neurons were located more anteriorly than NS neurons. The IL neurons had a more extensive receptive field than the VPM neurons, and the receptive fields were predominantly located in subcutaneous rather than cutaneous tissues. The muscle afferent inputs were considered to be predominantly of a nociceptive character for three reasons. They had a high threshold for most of the neuronal responses evoked by electrical stimulation of the muscle afferents. They had a preferential responsiveness to the muscle afferent stimulation of neurons that were functionally identified as cutaneous nociceptive neurons. In addition, there was responsiveness of the neurons excited by electrical stimulation of the muscle nerves, by noxious mechanical stimulation of the muscle, and by injection of algesic chemicals into the muscles. This study provided the first detailed analysis of the response of functionally identified thalamic neurons to natural and electrical stimulation of masseter muscle afferent input. The data indicate that many VPM and IL nociceptive neurons also relay high-threshold muscle afferent inputs and so may play a role in deep craniofacial pain as well as in superficial pain. We concluded that there are regions within the VPM and IL of cats that are capable of processing nociceptive information from the masseter muscle. (J Osaka Dent Univ 2003 ; 37(1) : 65-73)

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We investigated the factors affecting functional patterns in the transitional stage from mastication to swallowing. Thirty-one subjects were divided into four groups based on occlusal support, age and whether they wore dentures. Subjects were instructed to masticate and swallow ten grams of steamed rice. Tongue and mandibular movements were recorded using ultrasound diagnostic equipment and a mandibular kinesiograph. Analysis revealed that the onset of oral transit followed the onset of bracing activity by the teeth and mandible in all subjects. We also found that although the posterior occlusal support of natural molars and the use of dentures were very important to the duration of oral transit, age was not so significant. Moreover, we found that although the duration of oral transit was shortened by placing dentures in patients who had lost all posterior occlusal support, the duration was still longer than in dentate persons.

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Dental arch form and tooth position are influenced by perioral forces, especially those of the tongue and lip. We measured tongue and lip forces against the maxillary and mandibular left central incisors in open bite patients who had a tongue thrust habit. The open bite patients were then compared with normal subjects and the relationship between these forces and craniofacial morphology was examined. Lateral cephalograms of 10 open bite patients and 8 normal subjects were analyzed. Lip and tongue forces were measured at the center of the labial surface, the cervix of the lingual surface, and near the edge of the lingual surface on the maxillary and mandibular left central incisors. Lip and tongue forces at rest were recorded for all the measurement points. On swallowing, the maximum force, time quadrature of force, and averaged force were recorded for all measurement points. Also, on the lingual surface the ratio of forces near the edge to forces on the cervix was calculated for each measurement item. Forces at rest, the maximum force, time quadrature, averaged force, and each ratio were compared for the open bite patients and normal subjects using the Student's t-test. On swallowing, forces of all measurement items on the cervix of the maxillary central incisors were smaller than normal while those on the cervix of the mandibular were larger. Among open bite patients, craniofacial morphology and the tongue forces against the mandibular central incisors on swallowing were compared using correlation analysis. A high correlation was seen between tongue force and occlusal plane angle, interincisal angle, and L1 to mandibular plane angle. These results suggest that the tongue position lowers during swallowing, while the occlusal plane angle and L1 to mandibular plane angle increase. However, the interincisal angle becomes smaller. As the tongue position lowers on swallowing, there is a possibility of it causing changes in the alveolus, which determines the labial inclination of the mandibular central incisors.

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Pressure is exerted against the violinist's mandible while playing the instrument. I compared the craniofacial morphology of violinists with that of patients with mandibular deformities using standardized frontal cephalograms. The subjects included 10 violinists and 15 patients with mandibular deformities. I collected data for the zygoma line, mastoidate line, anterior nasal spine to menton line, condylion line, antegonion notch line and the maxillary molar line. Correlation analysis was done on all of these lines. Among violin players, there was a correlation at p<0.01 between the antegonion notch line and the zygoma line. There was a correlation at p<0.05 between the antegonion notch line and anterior nasal spine to menton line. The same was true for the antegonion notch line and condylion line. Among mandibular deformity patients, a correlation was observed at p<0.01 between the antegonion notch line and anterior nasal spine to menton line. Correlation for the condylion line and the zygoma line was significant at the same level. There was a correlation at p<0.05 between the antegonion notch line and maxillary molar line. These results indicate that the temporal bone of violinists is deformed in a similar manner to that of patients who use a chin cap. However, the temporal bone of mandibular deformity patients is not deformed.

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