To date, measurements of root canals have been performed two-dimensionally. Thus, measuring the diameter of curved root canals was difficult. Recently, micro-computed tomography (micro-CT) has enabled the measurement of any cross-sectional subject, therefore, it has often been applied to teeth and bones. In this study, we have measured the detailed diameter of the apical foramen of buccal and lingual canals in the maxillary first premolar using micro-CT. Eight maxillary first premolars were obtained from patients (4 males, 4 females) at the age of forty. Reconstructed three-dimensional images of each root canal were sliced orthogonally at 12 μm intervals, and the major and minor axes were measured on the sliced images. Measurements were taken up to a distance of 1.68 mm from the root apex. The narrowest point of the root canal was defined as the point where the minor axis was the smallest. The flatness ratio was also determined by dividing the major axis by the minor axis. The narrowest points of the buccal and lingual canals were located at 1.20 mm and 1.08 mm from the root apex, respectively. The flatness ratios of the buccal and lingual canals were 136.7% and 150.2%, respectively. The narrowest point of both the buccal and lingual canals was located approximately 1 mm from the root apex, and the data of the flatness ratios indicated that the lingual canal was more flat than the buccal canal at the apical third of the root canal. Micro-CT has been shown to be a useful tool for performing detailed measurements of root canal structures.

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Adenosine and ATP have been implicated in the regulation of inflammatory responses. Furthermore, adenosine and ATP affect cell growth, cell differentiation, and apoptosis. The aim of this study was to evaluate the differentiation-inducing effects of adenosine and ATP on human monocytic leukemia U937 cells. Adenosine at 10^-3M markedly induced differentiation in leukemia U937 cells as assessed by evaluating the expression of CD11b. Similarly, ATP at 10^-4 and 10^-3M significantly induced differentiation in U937 cells. Simultaneously, adenosine at 10^-3M and ATP at 10^-4 and 10^-3M significantly inhibited the cell number in U937 cells. Next, we evaluated the effects of adenosine and ATP on U937 cells differentiated by differentiation inducers all-trans retinoic acid (ATRA), 1, 25-dihydroxy-vitamin D₃ (VD₃) and phorbol 12-myristate 13-acetate (PMA). Interestingly, adenosine at 10^-4 and 10^-3M significantly potentiated ATRA-induced CD11b expression. However, ATRA failed to affect adenosine at 10^-3M-induced CD11b expression. Similarly, ATP at 10^-4 and 10^-3M significantly potentiated ATRA-induced CD11b expression. In addition, ATRA potentiated ATP-induced CD11b expression. In contrast, VD₃ and PMA further increased the expression of CD11b in the presence of adenosine or ATP, respectively. These results suggest that adenosine and ATP may induce differentiation in human leukemia U937 cells, and may further increase ATRA-induced differentiation in U937 cells.

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Although several morphological studies of main excretory duct of the submandibular gland have been performed, few reports present immunohistochemical data. Some epithelial cells or basal cells contain dense granules of an array shape by electron microscopic observation. However, the details of granulated cells have not been clarified immunohistochemically. In this study, both protein gene product 9.5 (PGP 9.5) and chromogranin or serotonin immunoreactive cells in the main excretory duct (MED) of the rat submandibular gland were observed. Some nerve endings were also observed among the epithelium of the MED. Therefore, the modifying mechanism of primary saliva in the MED may be regulated by both serotonergic nerve and endocrine cells with serotonin.

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We developed a biofilm model with artificial food supplementation (AFS), which was more similar to food intake in the human oral cavity, for the elucidation of pathogenic mechanisms and biofilm formation, and the evaluation of active agents. A five-organism bacterial consortium containing Streptococcus mutans was grown in a chemostat-type system with continuous supplementation of basal medium containing mucin (BMM). Biofilms formed on the surfaces of saliva-coated hydroxyapatite discs. As periodic application of AFS, the entire volume of culturing media was replaced with a sucrose-supplemented broth and re-incubated for 30 min. Then, the media were refilled with fresh BMM every 12 h. For comparison with the AFS biofilm, the sucrose pulses (SP) biofilm model, which is without any intermittent replacement cultures, was established by referring to previously reported biofilm models. The biological and physical properties of the biofilms generated by AFS and SP were evaluated. The results showed that the bacterial composition, amount of carbohydrate, pH responses, and structure of the AFS biofilm were more similar to those of in vivo or in situ dental plaque biofilms, compared with those of the SP biofilm. Additional experiments showed that the same bacterial growth patterns were reproducible in the AFS biofilm. Consequently, utilization of this newly developed biofilm model will lead to a better understanding of the pathogenic mechanisms in biofilm formation, and will be useful for the evaluation of active agents.

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15-Deoxy-Δ^12,14-prostaglandin J₂ (15dPGJ₂), which is a ligand for peroxisome proliferator-activated receptor γ (PPARγ), induced apoptosis of several human tumors including gastric, lung, colon, prostate and breast. However, the role of PPARγ signals in other types of cancer cells such as leukemia, except solid cancer cells, is still unclear. The aim of this study was to evaluate the ability of 15dPGJ₂ on the proliferation of the human T cell leukemia cell line MOLT-4F. 15dPGJ₂ at 5 μM stimulated proliferation in MOLT-4F at 1 to 3 days after incubation. In contrast, 15dPGJ₂ at concentrations of above 10 μM inhibited proliferation. PGD₂, PGJ₂ and Δ¹²-PGJ₂ (ΔPGJ₂), which are precursors of 15dPGJ₂, had similarly proliferative effects, whereas they showed anti-proliferative effects at high concentrations. Both SB203580, a p38 mitogen-activated protein kinase (MAPK) inhibitor, and LY294002, a phosphoinositide 3-kinase (PI3K) inhibitor, prevented proliferation accelerated by 15dPGJ₂ and its three precursors in MOLT-4F. In contrast, PD98059, an extracellular signal-related kinase 1/2 inhibitor, did not affect proliferation accelerated by 15dPGJ₂ and its three precursors. Immunoblotting analysis revealed that PGD₂ at 5 μM, PGJ₂ at 5 μM, ΔPGJ₂ at 1 μM and 15dPGJ₂ at 5 μM potentiated the expression of cyclin A, without affecting the expression of Cdk inhibitors including p18, p21, and p27 in MOLT-4F. These results suggest that PGD₂, PGJ₂, ΔPGJ₂ and 15dPGJ₂ may, through the activation of p38 MAPK and/or PI3K, potentiate the expression of cyclin A, leading to acceleration of proliferation in MOLT-4F.

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GABA(A) receptors are abundantly present in the trigeminal mesencephalic nucleus (Vmes) neurons involved in the senses of the masticatory muscle spindles and periodontal pressoreceptors. It has been reported that GABA(A) receptors may show internalization, which indicates the intracellular uptake of them after binding to an agonist. The internalization of GABA(A) receptors may be involved in the chewing motion-regulating mechanism. In this study, to investigate the internalization of GABA(A) receptors in Vmes, I analyzed the fluorescence intensity of neurons by fluorescence staining of Vmes neurons using immunohistochemical procedures. In Vmes neurons from rats treated with an agonist, the fluorescence intensity of a fluorescence-labeled secondary antibody was attenuated. Attenuation of fluorescence intensity indicating the presence of GABA(A) receptors suggested that administration of the agonist induced internalization of GABA(A) receptors. Furthermore, there was no attenuation of fluorescence intensity 6 hours after administration of the agonist, suggesting that attenuation of fluorescence intensity is not associated with drug administration-related irreversible cell injury.

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In observations of Suncus cranial specimens, tissue sections of the temporomandibular joint, and dissected sections of the temporomandibular joint articular surface and temporal muscle, the relationship between the temporal muscle and cranial morphology was evaluated.
Morphology of the calvaria in the origin of the temporal muscle and that of the coronoid process in the insertion of the temporal muscle corresponded to marked development of the temporal muscle. The temporal muscle was composed of superior, middle, and inferior muscle bundles. The superior and inferior muscle bundles vertically overlapped the middle muscle bundles. Most of the muscle fibers were inserted in the thick fascia of the middle muscle bundle. The middle muscle bundle originated from the calvaria, ran in the horizontal outer anterior direction, and was inserted in the coroniod process. From the composition and course of the three muscle bundles of the temporal muscle, it was speculated that the main action of the temporal muscle was to pull the mandibular bone coronoid process in the horizontal inner posterior direction. This action of the temporal muscle influenced a series of bone morphology ranging from the inner surface of the coronoid process to the temporomandibular joint via the condylar process. From the articulatory direction of the superior and inferior joints of the temporomandibular joint, the size of the articular surface, and the presence of the articular disc, it was speculated that, in the temporomandibular joint, posterior-inferior inner action caused by the temporal muscle and articulation is received with the inferior joint as the fulcrum, in response to the mandibular supero-inferior movement caused by the condylar antero-posterior movement in the superior joint.

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Microfocus X-ray computed tomography (μCT) is becoming widely used in various research fields relevant to the oral sciences. This technology, in conjunction with computer-assisted 3D reconstruction and quantitative structural analysis, is most suitable for investigating hard tissues in a non-invasive way. Despite this recognition, it still remains a concern whether the data acquisition process is conducted properly and accurately in order to ensure the reproducibility of 3D imaging and the determination of structural parameters such as bone volume (BV) and surface area (BS). In this report, we aim to provide an overview of the experimental procedures and conditions that are necessary for optimizing the acquisition of gray-scale CT images and their conversion into digital images (TIFF or JPEG) prior to 3D reconstruction and measurements. Towards these objectives, we collected μCT images of a 4-week-old mouse temporomandibular joint using a μCT apparatus (Nittetsu ELEX Co., ELE-SCAN model). Data proceedings and measurements were conducted using software (RATOC System Engineering Co., TRI-BON and TRI-SRF2). Special care was taken in optimizing experimental conditions and variables, e.g., X-ray tube voltage and current, selection of an adequate shiftvalue to compensate the mismatching between the specimen-rotating center and incident X-ray beam, and window level and width for contrast adjustment. The results of our empirical approach showed that careful selection of the experimental conditions and computation variables ensures the high quality of the 3D images and the accuracy and reproducibility of the quantitative measurements. The magnitude of errors associated with each of the determined structural parameters was confirmed to be within 3% of the determinations. Further knowledge and refinement of μCT technology and data acquisition will help to improve our understanding of the architecture and dynamic modeling of hard tissues.

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