Norimichi Nakamoto

Functional role of acetylcholine and the expression of cholinergic receptors and components in osteoblasts

Recent studies have indicated that acetylcholine (ACh) plays a vital role in various tissues, while the role of ACh in bone metabolism remains unclear. Here we demonstrated that ACh induced cell proliferation and reduced alkaline phosphatase (ALP) activity via nicotinic (nAChRs) and muscarinic acetylcholine receptors (mAChRs) in osteoblasts. We detected mRNA expression of several nAChRs and mAChRs. Furthermore, we showed that cholinergic components were up‐regulated and subunits/subtypes of acetylcholine receptors altered during osteoblast differentiation. To our knowledge, this is the first report demonstrating that osteoblasts express specific acetylcholine receptors and cholinergic components and that ACh plays a possible role in regulating the proliferation and differentiation of osteoblasts.

Nicotine induces cell proliferation in association with cyclin D1 up-regulation and inhibits cell differentiation in association with p53 regulation in a murine pre-osteoblastic cell line.

Recent studies have suggested that nicotine critically affects bone metabolism. Many studies have examined the effects of nicotine on proliferation and differentiation, but the underlying molecular mechanisms remain unclear. We examined cell cycle regulators involved in the proliferation and differentiation of MC3T3-E1 cells. Nicotine induced cell proliferation in association with p53 down-regulation and cyclin D1 up-regulation. In differentiated cells, nicotine reduced alkaline phosphatase activity and mineralized nodule formation in dose-dependent manners. Furthermore, p53 expression was sustained in nicotine-treated cells during differentiation. These findings indicate that nicotine promotes the cell cycle and inhibits differentiation in association with p53 regulation in pre-osteoblastic cells.

Proteomics-based identification of novel proteins in temporal tendons of patients with masticatory muscle tendon--aponeurosis hyperplasia.

Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is a new disease associated with limited mouth opening that is often misdiagnosed as a temporomandibular disorder; subsequently, patients are mistakenly treated with irreversible operations. Due to the poor presentation and characterization of symptoms, the underlying pathological conditions remain unclear. We have previously conducted a proteomic analysis of tendons derived from one MMTAH subject and one facial deformity subject using two-dimensional fluorescence difference gel electrophoresis and liquid chromatography coupled with tandem mass spectrometry. However, the results were obtained for only one subject. The aim of the present study was to confirm the expression of specific molecules in tendon tissues from multiple subjects with MMTAH by applying two-dimensional polyacrylamide gel electrophoresis with matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Of the 19 proteins identified in tendons from both MMTAH and facial deformity patients, fibrinogen fragment D and beta-crystallin A4 were up-regulated, whereas myosin light chain 4 was down-regulated in MMTAH. We also found fibrinogen to be expressed robustly in tendon tissues of MMTAH patients. Our data provide the possibility that the distinctive expression of these novel proteins is associated with the pathology of MMTAH.

A randomized controlled trial assessing the effectiveness of professional oral care by dental hygienists

OBJECTIVES This study was designed to compare professional oral care (POC) by a dental hygienist with tooth brushing and mouth rinsing by patients themselves according to the instructions of a nurse (control). METHODS Forty patients were randomly assigned to either the POC group (n = 20) or control group (n = 20). The presence of plaque and bacteria was assessed clinically. RESULTS One patient in the POC group and three patients in the control group dropped out because of exacerbation of underlying disease or death. Plaque control record scores were significantly lower in the POC group than in the control group on the fifth hospital day and the day of discharge. There was no significant difference between the groups in the detection rate of Candida species; and nosocomial pathogens on either day. CONCLUSIONS Professional oral care by a dental hygienist is more effective than tooth brushing and mouth rinsing by patients themselves according to the instructions of a nurse.

Masticatory muscle tendon-aponeurosis hyperplasia exhibits heterotopic calcification in tendons.

OBJECTIVE Masticatory muscle tendon-aponeurosis hyperplasia is a new disease entity associated with limited mouth opening. In this study, we analyzed the microstructural characteristics of muscles and tendons in masticatory muscle tendon-aponeurosis hyperplasia by electron microscopy and energy-dispersive X-ray analysis to determine the elemental composition. METHODS Histological analysis was performed to detect the calcification. Transmission electron microscopy and scanning electron microscopy were conducted to clarify the microstructural characteristics of muscles and tendons. Energy-dispersive X-ray microanalysis was performed to identify the distribution of elements. RESULTS Mineralized nodules were observed in tendon tissues of masticatory muscle tendon-aponeurosis hyperplasia as compared with facial deformity. Electron microscopy revealed that the muscle and tendon tissues in masticatory muscle tendon-aponeurosis hyperplasia showed degenerative changes and distinctive histological findings as compared with tissues in facial deformity. We found that Ca, P, and Si were detected only in masticatory muscle tendon-aponeurosis hyperplasia. CONCLUSION We demonstrated that masticatory muscle tendon-aponeurosis hyperplasia exhibits heterotopic calcification in tendon tissues.

Preliminary results of a study comparing conventional radiography with phase-contrast radiography for assessing root morphology of mandibular third molars

OBJECTIVES The aim of this study was to evaluate the usefulness of phase-contrast radiography for assessing root morphology of mandibular third molars in comparison with conventional radiography. METHODS We studied 37 extracted mandibular third molars. One oral surgeon compared the number of roots and root curvature of the extracted teeth on conventional radiographs with those on phase-contrast images. RESULTS The number of roots and root curvature on conventional images differed significantly from those on phase-contrast images. CONCLUSIONS Our results suggest the possibility that phase-contrast radiography is more useful than conventional radiography for assessing the root morphology of mandibular third molars.