The red ruffed lemur, Varecia rubra (É. Geoffroy Saint-Hilaire, 1812): a comparative morphology investigation of lingual papillae and connective tissue cores.

The morphology of the lingual papillae (filiform, foliate, fungiform, and vallate papillae) and the underlying connective tissue core of the red ruffed lemur (Varecia rubra) of a strepsirrhines species were studied using light and scanning electron microscopy. The filiform papillae distributed at the root of the tongue were larger than the structures distributed at the body and apex. Six to eight vallate papillae were arranged in a Y-shape at the border between the lingual body and the lingual root. Foliate papillae were observed at the posterior lateral border of the tongue. Scanning electron microscopy revealed a primary process and numerous auxiliary processes in the epithelial layer of filiform papillae. After epithelial removal, the connective tissue core of the filiform papilla showed several protrusions surrounding an oval-shaped depression that extended slightly posteriorly, and a large, maple-shaped filiform papilla was seen in the posterior portion of the tongue. The connective tissue cores of the fungiform papillae exhibited a longitudinally ridged cylindrical structure. The connective tissue core of the foliate papillae had numerous tubular projections arranged along a groove with a salivary gland conduit at the base. As a Lemuridae species, the appearance of the fungiform and filiform papillae of the red ruffed lemur is similar to that reported in previous studies of the ring-tailed lemur, with some differences, especially in the filiform papillary connective tissue core at the base and tongue body border. These findings suggest the taxonomic and phylogenetic origins of the lemurs as well as the influence of dietary diversity.

Comparative morphology and physiology of the vocal production apparatus and the brain in the extant primates.

Objective data mainly from the comparative anatomy of various organs related to human speech and language is considered to unearth clues about the mechanisms behind language development. The two organs of the larynx and hyoid bone are considered to have evolved towards suitable positions and forms in preparation for the occurrence of the large repertoire of vocalization necessary for human speech. However, some researchers have asserted that there is no significant difference of these organs between humans and non-human primates. Speech production is dependent on the voluntary control of the respiratory, laryngeal, and vocal tract musculature. Such control is fully present in humans but only partially so in non-human primates, which appear to be able to voluntarily control only supralaryngeal articulators. Both humans and non-human primates have direct cortical innervation of motor neurons controlling the supralaryngeal vocal tract but only human appear to have direct cortical innervation of motor neurons controlling the larynx. In this review, we investigate the comparative morphology and function of the wide range of components involved in vocal production, including the larynx, the hyoid bone, the tongue, and the vocal brain. We would like to emphasize the importance of the tongue in the primary development of human speech and language. It is now time to reconsider the possibility of the tongue playing a definitive role in the emergence of human speech.

Non-invasive intravital observation of lingual surface features using sliding oral mucoscopy techniques in clinically healthy subjects.

To investigate intravital morphological features of the broader area of the lingual mucosa in clinically healthy subjects, and to attempt to evaluate subclinical conditions, we evaluated detailed intravital morphological features of the lingual mucosa using our newly developed oral contact mucoscopy techniques. Clinically healthy subjects (female: 19-22 years, average age: 20.27 years, and n = 28) were enrolled. A position indicator stain was placed on the lingual mucosal surface, and sliding images were captured and then reconstructed. In addition, the lingual mucosa was divided into six areas, and morphometry of the fungiform and filiform papillae was performed. The results were statistically analyzed. There were two morphological features among clinically healthy subjects involving the filiform papillae: the length of the papillae and the degree of biofilm (tongue coat) deposition. We defined a modified tongue coat index (mTCI) with scores ranging from 0 (tongue coating not visible) to 0.5, 1, 1.5, and 2 (thick tongue coating) for six sections of the tongue dorsum. No subjects received a score of 2. Significant differences were found in the mTCI between the six sections of the tongue dorsum, especially between the posterior areas and the lingual apex. The fungiform papillae of some subjects exhibited elongated morphological changes. Our findings suggest that magnified lingual dorsum examination of a broader area is especially important in accurate screening for subclinical or transient conditions of potential lingual mucosal diseases. For this purpose, our new oral mucoscopy and non-invasive intravital observational techniques were especially effective.

Comparative morphology of the lingual papillae and their connective tissue cores in the tongue of the Abyssinian black-and-white colobus (Colobus guereza).

We observed the morphology of the lingual papillae (filiform, fungiform, foliate, and vallate) and their underlying connective tissue cores (CTCs) in Abyssinian black-and-white colobus monkeys using light and scanning electron microscopy. The tongues of both juvenile and senescent individuals were relatively short in the rostro-caudal direction, with a rounded apex. Lingual tori were absent. Numerous filiform papillae were distributed over the entire tongue, except at the lingual root. A pair of foliate papillae was present on both the lateral and caudal margins of the corpus. Three vallate papillae were distributed on the boundary between the caudal part of the body and the root in both juvenile and senescent individuals. Based on scanning electron microscopy observations, the morphologies of the filiform papillae differed between juvenile and senescent individuals. The epithelial surface of juvenile filiform papillae had a main process, but the associated processes were weak and the underlying CTCs displayed immature morphology. In contrast, the epithelial surface of senescent filiform papillae was associated with several accessory processes, and their underlying CTCs consisted of several auxiliary cores that nearly encircled the main core, forming a concavity in the papilla. CTCs of the filiform papillae showed variable morphology. Juvenile filiform CTCs exhibited a rather primitive morphology, resembling those of the hamster, mole, and Cape hyrax while, conversely, despite the basically folivorous diet of the Abyssinian black-and-white colobus, senescent filiform CTCs resembled those found in omnivorous primates, including members of the Callitrichinae and Homoidea, and also those in Carnivora (e.g., Canidae and Felidae).

Comparative morphology of the primate tongue.

To clarify the role of the primate tongue as a means to better understand the evolution of oral function among primates - an example of adaptation within the restricted phylogenetic group - we review the morphological knowledge of the tongues of extant primates in relation to phylogenetic classification. Prosimians tongues are more effective than those of Haplorhini for taking up food with the tongue alone, because they are capable of fine movement when outside the oral cavity. However, the role of the tongue in food uptake has diminished when juxtaposed with progress in hand manipulation of food and tools in Haplorhini, especially with the manipulation of tools by Homininae. This change in the tongue from prosimians to Homininae can be regarded as degeneration in food uptake by the tongue, although the functional role of the tongue within the oral cavity has not diminished. The distribution pattern and form of lingual papillae, except foliate papillae, are very similar among all reported primates species. Although foliate papillae are generally well developed in Haplorhini, most prosimian species have no foliate papillae, or a different type of papillae that substitute for foliate papillae. There are three vallate papillae in prosimian species and the New-World macaques, Platyrrhini. These papillae exhibit an inverted V-shape and are more numerous in Old World macaques, Catarrhini. These differences seem to be the result of phylogenetic origin.

Influence of continuous use of a vacuum-forming machine for mouthguard thickness after thermoforming.

BACKGROUND/AIMS: Mouthguards can reduce the risk of sports-related injuries such as tooth fracture or avulsion, but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the effect of the continuous use of a vacuum-forming machine on mouthguard thickness. MATERIALS AND METHODS: Ethylene vinyl acetate sheets and olefin copolymer sheets were used for thermoforming with a vacuum-forming machine. The working model was trimmed to a height of 23 mm at the maxillary central incisor and 20 mm at maxillary first molar. During molding, the model was placed at the center of the vacuum unit. Three molding conditions were investigated (i) molding was carried out after the sag at the center of the softened sheet was 15 mm below the clamp (control); (ii) sheet heating started 5 minutes after the control, and molding in the same way as the control (AF5); and (iii) sheet heating started 10 minutes after the control, and molding in the same way as the control (AF10). Under each condition, vacuum forming was conducted for 30 seconds. Sheet thickness after fabrication was determined for the incisal edge, labial surface, cusp, and buccal surface using a special caliper accurate to 0.1 mm. The differences of the molding conditions on the thickness in each sheet material were analyzed by one-way analysis of variance and Bonferroni's multiple comparison tests. RESULTS: For both sheet materials, significant differences between the control and AF5 were observed at all measurement points (P<.01), but not between the control and AF10. Compared with the control, AF5 was thinner and AF10 was a similar thickness. CONCLUSION: The continuous use of a vacuum-forming machine led to a reduction in the thickness of the mouthguard. Intervals of 10 minutes are necessary to achieve consistent molding.

Effect of thermal shrinkage during thermoforming on the thickness of fabricated mouthguards: Part 2 pressure formation.

BACKGROUND: The aim of this study was to examine the effect of thermal shrinkage, which occurs during thermoforming of ethylene vinyl acetate (EVA) sheets on the thickness of mouthguards fabricated by pressure formation. MATERIALS AND METHODS: Mouthguards were fabricated from 4.0-mm-thick EVA sheets by utilizing a pressure-forming machine. Two molding conditions were compared: The sheets were placed in the thermoforming machine with the sheet extrusion direction either vertical or parallel to the model's center line. The working model was trimmed to the height of 20 mm at the cutting edge of the maxillary central incisor and 15 mm at the mesiobuccal cusp of the maxillary first molar. The sheet was pressed against the working model for 2 min where the center of the softened sheet sagged 15 mm lower than the clamp. After fabrication, the thickness of mouthguard sheets was determined for the incisal (incisal edge and labial surface) and molar (cusp and buccal surface) portions, and dimensional measurements were made. Differences in molded mouthguard thickness with the sheet orientation of extruded sheets were analyzed by Mann-Whitney U-test. RESULT: In comparison with the parallel axis orientation, the sheets in vertical orientation with the model's centerline yielded significantly higher thickness measurements at the incisal edge, labial surface, and the cusp (P < 0.01, respectively). CONCLUSION: The results suggest that the EVA sheet produced by extrusion molding in vertical axis orientation with the model's centerline can effectively reduce loss of thickness in mouthguards after pressure formation.

Shape change in mouthguard sheets during thermoforming - part 2: effect of the anteroposterior position of the model on mouthguard thickness.

BACKGROUND/AIM: Mouthguards can reduce the risk of sports-related injuries, but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the effect of model position in the molding machine on the reduction in mouthguard thickness. MATERIALS AND METHODS: Ethylene vinyl acetate sheets and olefin copolymer sheets were used for thermoforming by a pressure- or a vacuum-forming machine. The working model was trimmed to the height of 25 mm at the maxillary central incisor and 20 mm at maxillary first molar. For both pressure forming and vacuum forming, the model was placed with the anterior rim of the model positioned 40, 30, 25, 20, or 10 mm from the front of the sheet frame. An additional test was carried out at 50 mm for vacuum forming. The sheet thickness after fabrication was determined for the incisal edge, labial surface, and buccal surface using a specialized caliper. The difference of the model position on the reduction in thickness in each forming device and sheet material was analyzed by one-way analysis of variance and Bonferroni's multiple comparison tests. RESULT: The reductions in thickness at the incisal edge and labial surface were about -60% and -50%, respectively, for the distance of 25 mm from the front of forming table. That position was the same as the height of the anterior part of the model for each molding machine and sheet material. The anterior thickness after molding became greater as the distance between the model and the sheet frame became smaller. CONCLUSION: The results showed that the thickness reduction was large when the distance from the model to the frame was small. This demonstrates the importance of centering the sheet and the model to achieve the most stable molding when positioning the model in the forming unit.

Evaluation of reliability of perioral muscle pressure measurements using a newly developed device with a lip piece.

PURPOSE: We examined the reliability of measurements using a newly developed perioral muscle pressure measuring device with a lip piece in healthy adults. METHODS: Subjects were 40 healthy men (25.8 years) with normal stomatognathic function. Perioral muscle pressure measuring device with a lip piece was used to measure upper lip, lower lip and tongue pressure, and a balloon-based measurement device was used to measure tongue and cheek pressure. Each measurement was taken twice with a 1-min interval between the two measurements. We determined intra-rater reliability by using the intra-class correlation coefficient as a test of relative reliability. As a test of absolute reliability, Bland-Altman analysis was used to assess systematic bias and the 95% confidence interval of the minimal detectable change was calculated. Additionally, the coefficient of variation was calculated. The Spearman-Brown formula was calculated the number of measurements needed to achieve a confidence coefficient ≥0.9. Each set of measurements was followed by a second set that were taken 1 week later. RESULTS: All measurements showed high values of intra-class correlation coefficient. Upper lip, tongue, and cheek pressure can be determined based on a single measurement, while lower lip pressure requires averaging twice. No systematic bias was observed. The coefficients of variation of measurements were almost the same between the two devices. CONCLUSION: Measurements were highly reliable regardless of the type of perioral muscles. Our findings suggest that the method described in this study is useful as a quantitative chair side method for examining perioral muscle pressure.

Optimal heating condition of mouthguard sheet in vacuum-pressure formation: part 3 styrene-based thermoplastic elastomer.

BACKGROUND: The aim of this study was to identify suitable heating conditions of polyolefin-polystyrene co-polymer sheets in vacuum-pressure formation, monitor the sheet temperature during molding, and examine the thickness of the fabricated mouthguard. MATERIALS AND METHODS: Mouthguards were fabricated with polyolefin-polystyrene co-polymer sheets (4.0-mm thick) utilizing a vacuum/pressure-forming device, which was subjected to vacuum forming for 10 s and pressure molding for 2 min. Four heating conditions were compared, defined by the amount of sag distance of 5, 10, 15, or 20 mm from the center of the softened sheet below the clamp. The working model was trimmed to a height of 20 mm at the cutting edge of the maxillary central incisor and to a height of 15 mm at the mesiobuccal cusp of the maxillary first molar. The radiation thermometer was used to measure the sheet temperatures of the center of the heated and non-heated surfaces under each condition. The sheet thickness after fabrication was determined for the incisal and the molar portions, and dimensional measurements were obtained using a measuring device. The differences in the sheet thickness produced by the different heating conditions were analyzed by Games-Howell's multiple comparison tests. RESULTS: For condition of 5 mm sagged, the temperature on the non-heated surface did not reach a sufficient softening temperature and the thickness was smallest. Mouthguard thickness was largest in the order of 15 mm sagged condition, followed by 20 mm sagged condition and then by 10 mm sagged condition, but a statistical difference was not observed in the labial and the buccal surface among the three conditions. CONCLUSION: This study demonstrated that for sufficient softening, it was necessary to heat the sheet to obtain a sag of 10 mm or more, and that the mouthguard thickness decreased as the sag increased.

Role of the vestibular nuclear complex in facilitating the jaw-opening reflex following stimulation of the red nucleus.

According to our previous studies, stimulation of the red nucleus (RN) facilitates the low-threshold afferent-evoked jaw-opening reflex (L-JOR). It has been reported that the RN projects to the superior (SVN), lateral (LVN) and inferior vestibular (IVN) nuclei. The SVN and the LVN have reciprocal intrinsic connections with the medial vestibular nucleus (MVN). Our previous study demonstrated that stimulation of the vestibular nuclear complex (VN) modulates the L-JOR. These facts suggest that RN-induced facilitation of the L-JOR is mediated via the VN. In the present work we investigated whether electrically induced lesions of the VN, or microinjection of muscimol into the VN, affects RN-induced facilitation of the L-JOR. The L-JOR was evoked by electrical stimulation of the inferior alveolar nerve. The stimulus intensity was 1.2 times the evocation threshold. Lesions of the MVN or the LVN or the SVN, and the muscimol injection into the MVN or the LVN or the SVN, reduced the RN-induced facilitation of the L-JOR. Conversely, lesions of the IVN, and the muscimol injection into the IVN, increased the RN-induced facilitation of the L-JOR. These results suggest that the RN-induced facilitation of the L-JOR is mediated by a relay in the VN.

Shape change in mouthguard sheets during thermoforming.

BACKGROUND: The purpose of this study was to identify changes in sheet shape during thermoforming and the effect of the model position in the molding machine on fabricated mouthguard thickness. MATERIALS AND METHODS: Ethylene vinyl acetate mouthguard sheets (3.8 mm thick) were used that had cross-stripes (10 × 10 mm), and the anteroposterior and bilateral lengths were used for measurements. Two forming machines were used: a vacuum- and a pressure-forming machine, and two heating conditions were investigated that defined as the time when sagging of the softened sheet was 15 mm (H-15) and 20 mm (H-20) below the clamp, and the length of each cross-stripes was measured. The area of each lattice was calculated using Bretschneider's formula to compare changes in sheet shape for each condition. Next, mouthguards were molded by forming machine where the working model was positioned under two different conditions: with the model anterior centered in the forming unit and with the model centered. The sheet thickness after fabrication was determined for the incisal and the molar portion, and dimensional measurements were obtained using a measuring device. Differences in the thickness were analyzed by two-way analysis of variance (anova). RESULT: In both molding machines, the change in the area under H-20 was greater than H-15. While the increase in area tended to expand from the center of the sheet in concentric circles, the difference between the central and surrounding areas was only approximately 5%. For both molding machines, differences in thickness after molding due to setting position of the model were not observed. CONCLUSION: The results showed that shape changes of the sheet during thermoforming tend to concentrically and almost uniformly expand from the center and that it is important to center the sheet and the model when positioning the model in the forming unit.

Thickness of mouthguard sheets after vacuum-pressure formation: influence of mouthguard sheet material.

The aim of this study was to investigate the thickness of mouthguard sheet after vacuum-pressure formation based on the mouthguard sheet material. Three mouthguard sheet materials (4.0 mm thick) were compared: ethylene-vinyl acetate co-polymer (EVA), olefin co-polymer (OL), and polyolefin-polystyrene co-polymer (OS). The working model was made by hard gypsum that was trimmed to the height of 20 mm at the cutting edge of the maxillary central incisor and 15 mm at the mesiobuccal cusp of the maxillary first molar. Where the center of the softened sheet sagged 15 mm lower than the clamp, the sheet was pressed against the working model, followed by vacuum forming for 10 s and compression molding for 2 min. The thickness of mouthguard sheets after fabrication was determined for the incisal portion (incisal edge and labial surface) and molar portion (cusp and buccal surface), and dimensional measurements were obtained using a measuring device. Differences in the change in thickness due to sheet materials were analyzed by one-way analysis of variance (anova) followed by Bonferroni's multiple comparison tests. The OL sheet was thickest at all measurement points. At the incisal edge and cusp, thickness after formation was highest for OL, then EVA and finally OS. At the labial surface and buccal surface, the thickness after formation was highest for OL, then OS and finally EVA. This study suggested that post-fabrication mouthguard thickness differed according to sheet material, with the olefin co-polymer sheet having the smallest thickness reduction.

Method for effectively maintaining the thickness of mouthguards fabricated using EVA sheets and a circle tray: influence of grooved sheet and heating conditions.

The shapes of ethylene vinyl acetate (EVA) sheets are mainly square or round. The aim of this study was to elucidate a fabrication method that effectively maintains the thickness of the round sheet. Mouthguards were fabricated using EVA sheets (diameter 125 mm, thickness 4.0 mm) and a vacuum-forming machine. The sheet was pinched at the top and bottom and stabilized by the circle tray. Two heating conditions were compared: (i) the sheet was molded when it sagged 10 mm below the level of the sheet frame at the top of the post under normal conditions (N); and (ii) the sheet frame was lowered to and heated at 50 mm from the level of ordinary use and molded when it sagged 10 mm from the sheet frame (L). Two EVA sheet shapes were compared: an ordinary sheet (O) and a sheet with a horizontal v-shaped groove 30 mm from the anterior end (G). The height of the working model was 20 mm at the incisor point and 15 mm at the first molar. The sheet temperatures of the heating and non-heated surface were measured by the radiation thermometer. Post-molding thickness was determined for the incisal and molar portion. Differences in the thickness were analyzed using two-way anova. The temperature difference among points was smaller under condition L than under condition N. Thickness after formation was higher in condition L than in condition N, and was higher in condition G than in condition O. At the labial surface and the cusp, L-G was thickest. With the present techniques, uneven softening during heating can be improved by lowering the sheet frame and consequently reducing the reduction in the thickness of the sheet. Additionally, the thickness reduction is reduced by creating a horizontal groove on the sheet, establishing the clinical efficacy of this method.

Heating methods for reducing unevenness softening of mouthguard sheets in vacuum-pressure formation.

BACKGROUND: Unevenness in softening of the plastic sheet leads to a decrease in the mouthguard thickness during thermoforming. In this study, we examined the heating methods for reducing unevenness when softening mouthguard sheets during vacuum-pressure formation. MATERIALS AND METHODS: Ethylene vinyl acetate mouthguard sheets and olefin copolymer sheets (thickness: 4.0 mm) were used. The following three heating conditions were compared: condition A-the sheet was molded when it sagged 15 mm from the sheet frame (under normal condition); condition B-the heater was turned off when the sheet sagged by 10 mm from the frame, followed by the sheet molding when the sagging reached 15 mm below the frame; and condition C-the sheet was inverted after heating when the sheet sagged 10 mm and was molded when the sagging reached 15 mm below the frame. The sheet was heated and pressed over the model using a vacuum-pressure machine; then, 10 s of vacuum forming and 2 min of pressure molding were applied. The sheet temperatures were measured using a radiation thermometer. Thickness of the fabricated sheets was determined for the incisal and the molar portion using a measuring device. Thickness data for each condition were analyzed by one-way anova followed by Bonferroni's multiple comparison tests. RESULTS: On both sheets, condition B was smallest for temperature difference between the heated and the non-heated surface, and thicknesses after molding were greatest at all measuring portions. CONCLUSION: By comparing changes in sheet temperatures at molding and variation in thicknesses when applying the heating method using a vacuum-pressure molding machine, we found that reduced unevenness in sheet softening occurred when the heater was turned off when the sag distance of the sheet was 5 mm less than the conventional molding, and then, the sheet was pressed when the conventional sag distance was reached.

Optimal heating condition of ethylene-vinyl acetate co-polymer mouthguard sheet in vacuum-pressure formation.

BACKGROUND: The goal of the present study was to examine the thickness of mouthguards molded under a variety of heating conditions to clarify suitable conditions during vacuum-pressure forming of ethylene vinyl acetate sheets. MATERIALS AND METHODS: Mouthguards were fabricated using ethylene vinyl acetate (EVA) sheets (thickness: 4.0 mm) using a vacuum-pressure forming machine. The sheet was pressed against the working model, followed by vacuum forming for 10 s and compression molding for 2 min. Three heating conditions were investigated in which the sheet was molded when the center of the softened sheet sagged 10 mm, 15 mm, or 20 mm below the clamp (H-10, H-15, or H-20 respectively). The temperature of the sheet surface was measured using a radiation thermometer under each heating condition. The thickness of the mouthguard sheets after fabrication was determined for the incisal portion (incisal edge and labial surface) and molar portion (cusp and buccal surface), and dimensional measurements were obtained using a measuring device. Differences in thickness due to the heating condition of the sheets were analyzed by one-way analysis of variance and Bonferroni's multiple comparison tests. RESULTS: The temperature difference between the heated and non-heated surfaces was lowest under H-15. The thickness differences at incisal edge, labial surface, and cusp were determined. The thicknesses for H-10 and H-15 were greater than that for H-20, and the thicknesses for H-10 and H-15 were equivalent at all measurement points. No differences in thickness at the buccal surface were observed for the various heating conditions. CONCLUSION: The present study demonstrated that a sagging distance of 15 mm provided the most suitable forming process. The results of the present study provide a standard heating condition for EVA sheet forming.

Proposal for research and education: joint lectures and practicals on central nervous system anatomy and physiology.

We coordinated anatomy and physiology lectures and practicals to facilitate an integrated understanding of morphology and function in a basic medical science program for dental students and to reduce the time spent on basic science education. This method is a means to provide the essential information and skills in less time. The overall impression was that the practice of joint central nervous system lectures and practicals was an efficient method for students, which suggests that joint lectures might also be useful for clinical subjects. About two-thirds of students felt that the joint anatomy and physiology lecture on the central nervous system was useful and necessary in understanding the relationship between morphology and function, at least for this subject. One-third of students were neutral on the effectiveness of this method. However, the survey results suggest that improvements are needed in the method and timing of joint lectures and practicals. The present teaching approach can be further improved by conducting combined lectures in which the form and function of anatomic structures are presented by the relevant departments during the same lecture. Finally, joint lecturers and practicals offer an opportunity to increase student understanding of the importance of new research findings by the present authors and other researchers.

Three-dimensional observation of mouse tongue muscles using micro-computed tomography.

The aim of this study is to obtain information about the mouse tongue muscle rendered using micro-computed tomography (µCT) at low, middle, and high magnifications. Three-dimensional (3D) µCT is used in various fields. Most µCT observations are restricted to hard tissue in biomaterial samples. Recently, with the use of osmium tetroxide, µCT has been effectively employed to observe soft tissue; it is now believed that µCT observation of soft tissue is feasible. On the other hand, the structure of the tongue muscle has been well studied, but cross-sectional imaging enhanced by 3D rendering is lacking. We chose the mouse tongue as a soft tissue case study for µCT and generated cross-sectional images of the tongue enhanced by 3-D image rendering with histological resolution. During this observation, we developed new methods of low-magnification observation to show the relation between the tongue muscles and surrounding tissues. We also applied high-resolution µCT in high-magnification observation of muscle fiber fascicles. Our methodological techniques give the following results: (1) For low-magnification observation (field of view: 12,000 µm), pretreatment with decalcification and freeze drying is suitable for observing the area between the muscle of the tongue and the bone around the tongue using µCT. (2) For middle-magnification observation (Field of view: 3,500 µm), the use of osmium tetroxide to observe the muscle arrangement of the tongue by µCT is suitable. (3) For high-magnification observation (Field of view: 450 µm), high-resolution µCT is suitable for observation of the transversus muscle fiber fascicles.

Role of the red nucleus in suppressing the jaw-opening reflex following stimulation of the raphe magnus nucleus.

In a previous study, we found that electrical and chemical stimulation of the red nucleus (RN) suppressed the high-threshold afferent-evoked jaw-opening reflex (JOR). It has been reported that the RN receives bilaterally projection fibers from the raphe magnus nucleus (RMg), and that stimulation of the RMg inhibits the tooth pulp-evoked nociceptive JOR. These facts imply that RMg-induced inhibition of the JOR could be mediated via the RN. The present study first examines whether stimulation of the RMg suppresses the high-threshold afferent-evoked JOR. The JOR was evoked by electrical stimulation of the inferior alveolar nerve (IAN), and was recorded as the electromyographic response of the anterior belly of the digastric muscle. The stimulus intensity was 4.0 (high-threshold) times the threshold. Conditioning electrical stimulation of the RMg significantly suppressed the JOR. A further study then examined whether electrically induced lesions of the RN or microinjection of muscimol into the RN affects RMg-induced suppression of the JOR. Electrically induced lesions of the bilateral RN and microinjection of muscimol into the bilateral RN both reduced the RMg-induced suppression of the JOR. These results suggest that RMg-induced suppression of the high-threshold afferent-evoked JOR is mediated by a relay in the RN.

Function-related morphological characteristics and specialized structures of the avian tongue.

As a reflection of different life styles and environment, the tongue of vertebrates, which plays a major role in the intake and swallowing of food, displays significant morphological differences. The gross form and microscopic structure of the avian tongue differ greatly according to lifestyle. The avian tongue plays a fundamental role in many functions such as capturing, filtering, sucking and manipulating food in order to compensate absence of subsidiary organs like teeth in the oropharyngeal cavity. Variations in lingual papillae play an important role in feeding of birds, as they represent a structure similar to teeth in the upper and lower beaks and can be used to hold and direct food in the oropharyngeal cavity. Tongues of birds exhibit common as well as varying anatomical characteristics in terms of surface morphology, structure and topographical distribution of lingual papillae as well as distinct specialized structures, epithelial layers, taste buds and lingual glands. This review evaluates the important morphological peculiarities of the tongue in birds, focusing on the relationship between anatomical features and feeding functions.