HIF-2α Inhibits Ameloblast Differentiation via Hey2 in Tooth Development

Enamel is the highly mineralized outer layer of teeth; the cells responsible for enamel formation are ameloblasts. Local hypoxia and hypoxia inducible factor (HIF) in embryonic tissues are important to promote normal organogenesis. However, hypoxic state in tooth germs and the roles of HIF in ameloblast differentiation have not been understood. The aim of this study is to clarify the role of HIF in ameloblast differentiation during tooth germ development. We found that tooth germs were under hypoxia and HIF-1α and HIF-2α were expressed in tooth germs in embryonic mice. Then, we used HIF inhibitors to evaluate the function of HIF during tooth germ development. The HIF-2α inhibitor significantly decreased the size of tooth germs in organ culture, while the HIF-1α inhibitor did not apparently affect the size of tooth germs. The HIF-2α inhibitor enhanced the expression of amelogenin, a marker of ameloblast differentiation, in the tooth germs in organ culture and rat dental epithelial SF2 cells. Moreover, we found that the HIF-2α inhibitor-stimulating amelogenin expression was regulated by hes-related family basic helix-loop-helix transcription factor with YRPW motif 2(Hey2) in SF2 cells. These findings suggest that the HIF-2α-Hey2 axis plays an important role in ameloblast differentiation during tooth germ development.

Occlusal Force and Condylar Motion in Patients with Anterior Open Bite

Patients with open bite often show a weak occlusal force and temporomandibular disorders (TMDs). If these are the main cause of open bite, it may be hypothesized that both pre-pubertal and adult open-bite patients would show a weak occlusal force and abnormal condylar motion. The purpose of this study was to test this hypothesis. Test group subjects consisted of 13 consecutive pre-pubertal and 13 adult patients with anterior open bite. They were compared with age-matched normal subjects. The adult open-bite group showed a weaker occlusal force and a shorter range of condylar motion compared with the control subjects. In the pre-pubertal subjects, however, there were no significant differences in the occlusal force and range of condylar motion between the open-bite and control groups. Therefore, these results suggest that a weak occlusal force or TMDs may not be the main cause of open bite.

Denervation Resulting in Dento-Alveolar Ankylosis Associated with Decreased Malassez Epithelium

Inferior alveolar nerve denervation causes appreciable decreases in the distribution of epithelial rests of Malassez. To explore roles of the Malassez epithelium, we attempted to evaluate possible changes in dento-alveolar tissues surrounding this epithelium by experimental denervation. We found that denervation led to dento-alveolar ankylosis with a decrease in the width of the periodontal spaces. Interestingly, with regeneration of the Malassez epithelium 10 weeks after the denervation, the periodontal space width showed a correspondingly significant increase. These findings suggest that the Malassez epithelium may be involved in the maintenance of periodontal space and that sensory innervation might be indirectly associated with it. In addition, it is of interest that denervation activated root resorption of the coronal root surface and that the consequently resorbed lacunae were repaired by cellular cementum. It is suggested that Malassez epithelium may negatively regulate root resorption and induce acellular cementum formation.

Increase of Galanin in Trigeminal Ganglion during Tooth Movement

It is known that nerve fibers containing neuropeptides such as galanin increase in the periodontal ligament during experimental tooth movement. However, the origin of galanin-containing nerve fibers in the periodontal ligament remains unclear. This study was conducted to examine our hypothesis that the increased galanin nerve fibers have a sensory neuronal origin, and that the peptide is associated with pain transmission and/or periodontal ligament remodeling during experimental tooth movement. In control rats, galanin-immunoreactive trigeminal ganglion cells were very rare and were observed predominantly in small ganglion cells. After 3 days of experimental tooth movement, galanin-immunoreactive trigeminal ganglion cells significantly increased, and the most marked increase was observed at 5 days after experimental tooth movement. Furthermore, their cell size spectrum also significantly changed after 3 and 5 days of movement: Medium-sized and large trigeminal ganglion cells began expressing, and continued to express, galanin until 14 days after experimental tooth movement. These findings suggest that the increase of galanin in the periodontal ligament during experimental tooth movement at least partially originates from trigeminal ganglion neurons and may play a role in pain transmission and/or periodontal remodeling.

Resin monomers act as adjuvants in Ni-induced allergic dermatitis in vivo

Resin monomers (RMs) are inflammatory agents and are thought to cause allergic contact dermatitis (ACD). However, mouse models are lacking, possibly because of the weak antigenicities of RMs. We previously reported that inflammatory substances can promote the allergic dermatitis (AD) induced by intradermally injected nickel (Ni-AD) in mice. Here, we examined the effects of RMs on Ni-AD. To sensitize mice to Ni, a mixture containing non-toxic concentrations of NiCl2 and an RM [either methyl methacrylate (MMA) or 2-hydroxyethyl methacrylate (HEMA)] was injected intraperitoneally or into ear-pinnae intradermally. Ten days later, a mixture containing various concentrations of NiCl2 and/or an RM was intradermally injected into ear-pinnae, and ear-swelling was measured. In adoptive transfer experiments, spleen cells from sensitized mice were transferred intravenously into non-sensitized recipients, and 24 h later NiCl2 was challenged to ear-pinnae. Whether injected intraperitoneally or intradermally, RM plus NiCl2 mixtures were effective in sensitizing mice to Ni. AD-inducing Ni concentrations were greatly reduced in the presence of MMA or HEMA (at the sensitization step from 10 mM to 5 or 50 µM, respectively, and at the elicitation step from 10 µM to 10 or 100 nM, respectively). These effects of RMs were weaker in IL-1-knockout mice and in macrophage-depleted mice. Cell-transfer experiments in IL-1-knockout mice indicated that both the sensitization and elicitation steps depended on IL-1. Challenge with an RM alone did not induce allergic ear-swelling in mice given the same RM + NiCl2 10 days before the challenge. These results suggest that RMs act as adjuvants, not as antigens, to promote Ni-AD by reducing the AD-inducing concentration of Ni, and that IL-1 and macrophages are critically important for the adjuvant effects. We speculate that what were previously thought of as "RM-ACD" might include ACD caused by antigens other than RMs that have undergone promotion by the adjuvant effects of RMs.

Gap-junction-mediated Communication in Human Periodontal Ligament Cells

Periodontal tissue homeostasis depends on a complex cellular network that conveys cell-cell communication. Gap junctions (GJs), one of the intercellular communication systems, are found between adjacent human periodontal ligament (hPDL) cells; however, the functional GJ coupling between hPDL cells has not yet been elucidated. In this study, we investigated functional gap-junction-mediated intercellular communication in isolated primary hPDL cells. SEM images indicated that the cells were in contact with each other via dendritic processes, and also showed high anti-connexin43 (Cx43) immunoreactivity on these processes. Gap-junctional intercellular communication (GJIC) among hPDL cells was assessed by fluorescence recovery after a photobleaching (FRAP) analysis, which exhibited dye coupling between hPDL cells, and was remarkably down-regulated when the cells were treated with a GJ blocker. Additionally, we examined GJs under hypoxic stress. The fluorescence recovery and expression levels of Cx43 decreased time-dependently under the hypoxic condition. Exposure to GJ inhibitor or hypoxia increased RANKL expression, and decreased OPG expression. This study shows that GJIC is responsible for hPDL cells and that its activity is reduced under hypoxia. This is consistent with the possible role of hPDL cells in regulating the biochemical reactions in response to changes in the hypoxic environment.

An anti-c-Fms antibody inhibits osteoclastogenesis in a mouse periodontitis model

OBJECTIVE

Bacterial lipopolysaccharide (LPS) can induce inflammatory bone loss such as periodontal disease. The formation of osteoclasts depends on macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor kb ligand (RANKL). It has recently been reported that administration of an antibody of the M-CSF receptor c-Fms completely blocked osteoclastogenesis and bone erosion induced by LPS in mouse calvaria. In this study, the effect of antibody against c-Fms in the mouse periodontitis model by injection of LPS was investigated.

MATERIALS AND METHODS

C57BL6/J mice were injected with LPS and anti-c-Fms antibody into the mesial gingiva of the first molar in the left mandible. Histological sections of periodontal tissue were stained for tartrate-resistant acid phosphatase, and osteoclast numbers and ratio of alveolar bone resorption determined.

RESULTS

The number of osteoclasts and ratio of alveolar bone resorption in mice administered both LPS and anti-c-Fms antibody was lower than those in mice administered LPS alone. The expression of RANKL receptor, RANK, was inhibited by the anti-c-Fms antibody in periodontal tissue.

CONCLUSION

M-CSF and/or its receptor are potential therapeutic targets for the treatment of bone resorption, caused by LPS, in periodontitis. Injection of an anti-c-Fms antibody might be useful for inhibition of pathological bone resorption in periodontitis.

Orthodontic miniscrew failure rate and root proximity, insertion angle, bone contact length, and bone density

OBJECTIVES

To test the hypothesis that there is no significant correlation between miniscrew failure rate and root proximity, insertion angle, bone contact length, and bone density.

SETTING AND SAMPLE POPULATION

This study included 107 patients in whom 190 miniscrews had been placed from April 2008 to October 2009 in Tohoku University Hospital (Sendai, Japan).

MATERIALS AND METHODS

Cone beam computed tomography scans (CBCT) and periapical radiographs were taken before and after miniscrew placement. Differences in root proximity, screw insertion angle, bone contact length, and bone density were statistically compared; comparisons were also made between the CBCT images and periapical radiographs.

RESULTS

A significantly higher success rate was observed in the maxilla than in the mandible. The distance between the miniscrew and the root surface was significantly smaller in the failure group. There were no significant differences in the insertion angle, bone contact length, or bone density between the success group and the failure group. The concordance rate between the periapical dental radiographs and CBCT images was 46.5%.

CONCLUSION

While bone contact length, miniscrew angle, and bone density did not exert major effects on miniscrew failure, root proximity was the factor that most affected miniscrew failure, especially for miniscrews placed in the mandible. CBCT was superior to periapical dental X-rays for evaluating the proximity of miniscrews to the root. Correction of the X-ray attenuation coefficient value was necessary for measuring bone density using CBCT.

Effects of CO2 laser irradiation of the gingiva during tooth movement

Patients often feel pain or discomfort in response to orthodontic force. It was hypothesized that CO(2) laser irradiation may reduce the early responses to nociceptive stimuli during tooth movement. The distribution of Fos-immunoreactive (Fos-IR) neurons in the medullary dorsal horn of rats was evaluated. Two hrs after tooth movement, Fos-IR neurons in the ipsilateral part of the medullary dorsal horn increased significantly. CO(2) laser irradiation to the gingiva just after tooth movement caused a significant decrease of Fos-IR neurons. PGP 9.5- and CGRP-positive nerve fibers were observed in the PDL of all study groups. The maximum temperature below the mucosa during CO(2) laser irradiation was less than 40 degrees C. It was suggested that CO(2) laser irradiation reduced the early responses to nociceptive stimuli during tooth movement and might not have adverse effects on periodontal tissue.

CTGF and apoptosis in mouse osteocytes induced by tooth movement

It is known that experimental tooth movement stimulates the gene expression of connective tissue growth factor (CTGF) and induces apoptosis in osteocytes in rats. We hypothesized that there is a relationship between CTGF expression and the induction of apoptosis in osteocytes, to play a significant role in triggering bone remodeling during experimental tooth movement. In this study, CTGF mRNA expression was detected at 2 hours in osteocytes on the pressure side, followed by apoptosis at 6 hours after tooth movement in mice. The number of empty lacunae significantly increased on day 1 after mechanical stimulation. Thereafter, the number of osteoclasts significantly increased on the pressure side of the alveolar bone on day 3. Tooth movement increased rapidly on day 10. These findings suggest that CTGF expression, followed by apoptosis in osteocytes in response to mechanical stimulation, might play a significant role in triggering bone remodeling during tooth movement.

Brain-derived neurotrophic factor-immunoreactive primary sensory neurons in the rat trigeminal ganglion and trigeminal sensory nuclei

Immunohistochemistry for brain-derived neurotrophic factor (BDNF) was performed on the rat trigeminal ganglion (TG). The immunoreactivity (IR) was detected in 46% of TG neurons. These neurons were mostly small- or medium-sized (range, 149.7-1246.3 microm2; mean +/- SD = 373.4 +/- 151.6 microm2). A double immunofluorescence method also revealed that 54% of BDNF-immunoreactive (IR) neurons were immunoreactive for calcitonin-gene-related peptide. In addition, 93% of BDNF-IR TG neurons contained vanilloid receptor subtype 1. However, the co-expression of BDNF and vanilloid receptor 1-like receptor was very rare (less than 1%). In the trigeminal sensory nuclei, laminae II of the medullary dorsal horn was abundant in presumed BDNF-IR axon terminals. Such profiles were also detected in the dorsolateral part of the subnucleus oralis. The retrograde tracing and immunohistochemical methods demonstrated that BDNF-IR was common among cutaneous TG neurons (47%) but not tooth pulp TG neurons (13%). The present study indicates that BDNF-IR TG neurons have unmyelinated axons and project to the superficial medullary dorsal horn. It is likely that BDNF-containing neurons in both the trigeminal and spinal sensory systems have similarities in morphology and function. However, the content of BDNF in TG neurons probably depends on their peripheral targets. BDNF seems to convey nociceptive cutaneous input to the trigeminal sensory nuclei.

VR1-, VRL-1- and P2X3 receptor-immunoreactive innervation of the rat temporomandibular joint

Immunohistochemistry for vanilloid receptor subtype 1 (VR1), vanilloid receptor 1-like receptor (VRL-1) and P2X3 receptor was performed in the rat temporomandibular joint (TMJ). Blood vessels in the articular disk and capsule, the synovial membrane and the fibrous tissue around the condylar process were innervated by VR1- or P2X3 receptor-immunoreactive (ir) nerve fibers. However, VRL-1-immunoreactivity (ir) could not be detected in the TMJ. Retrograde tracing and immunohistochemical methods revealed that 25%, 41% and 52% of TMJ neurons in the trigeminal ganglion (TG) exhibited VR1-, VRL-1- and P2X3 receptor-ir, respectively. VR1-ir TMJ neurons were mostly small to medium-sized, whereas VRL-1- and P2X3 receptor-ir TMJ neurons were predominantly medium-sized to large. In addition, 73%, 28% and 44% of VR1-, VRL-1- and P2X3 receptor-ir TMJ neurons, respectively, coexpressed calcitonin gene-related peptide (CGRP)-ir. The present study suggests that the TMJ has abundant nociceptors which respond to vanilloid compounds, protons, heat and extracellular ATP.

Galanin-immunoreactive nerve fibers in the periodontal ligament during experimental tooth movement

Neuropeptides have been suggested to play a role in pain transmission during orthodontic tooth movement. We examined this hypothesis by examining the effect of orthodontic tooth movement on the expression of galanin (GAL)-immunoreactive (ir) nerve fibers in the periodontal ligament (PDL) of one mesial root (MR) and two distal roots (DRs) of the rat maxillary first molar. In control rats, GAL-ir fibers were very rare in the PDL. One day after the insertion of the elastic band, the number of GAL-ir fibers increased, becoming most numerous at 3 days. From 5 to 28 days, GAL-ir fibers tended to decrease. Electron microscopic observation showed that all of the GAL-ir fibers were unmyelinated. These findings suggest that GAL-containing nerve fibers in the PDL may play an important role in the response of the tissue to experimental tooth movement.

The use of small titanium screws for orthodontic anchorage

The use of conventional dental implants for orthodontic anchorage is limited by their large size. The purpose of this study was to quantify the histomorphometric properties of the bone-implant interface to analyze the use of small titanium screws as an orthodontic anchorage and to establish an adequate healing period. Overall, successful rigid osseous fixation was achieved by 97% of the 96 implants placed in 8 dogs and 100% of the elastomeric chain-loaded implants. All of the loaded implants remained integrated. Mandibular implants had significantly higher bone-implant contact than maxillary implants. Within each arch, the significant histomorphometric indices noted for the "three-week unloaded" healing group were: increased labeling incidence, higher woven-to-lamellar-bone ratio, and increased osseous contact. Analysis of these data indicates that small titanium screws were able to function as rigid osseous anchorage against orthodontic load for 3 months with a minimal (under 3 weeks) healing period.

CTGF/Hcs24 induces chondrocyte differentiation through a p38 mitogen-activated protein kinase (p38MAPK), and proliferation through a p44/42 MAPK/extracellular-signal regulated kinase (ERK)

Connective tissue growth factor/hypertrophic chondrocyte specific gene product 24 (CTGF/Hcs24) promotes proliferation and differentiation of chondrocytes in culture. We investigated the roles of two major types of mitogen activated protein kinase (MAPK) in the promotion of proliferation and differentiation by CTGF/Hcs24. Here we report the effects of the MAPKK/MEK 1/2 inhibitor, PD098059, and p38 MAPK inhibitor, SB203580, in a human chondrosarcoma-derived chondrocytic cell line (HCS-2/8) and rabbit growth cartilage (RGC) cells treated with CTGF/Hcs24. In the proliferation phase, CTGF/Hcs24 induced a approximately fivefold increase in the phosphorylation of p44/42 MAPK/ERK and a approximately twofold increase in that of p38 MAPK in an in vivo kinase assay. These inhibitors of MAPKK and MAPK suppressed phosphorylation of ets-like gene-1 (Elk-1) and nuclear activating transcription factor-2 (Atf-2) induced by CTGF/Hcs24 in a dose-dependent manner, respectively. Western blot analysis showed that phosphorylation of ERK was induced from 30 to 60 min and phosphorylation of p38 MAPK from 10 to 15 min after the addition of CTGF/Hcs24 in confluence HCS-2/8 cells. PD098059 suppressed the DNA synthesis of HCS-2/8 cells and RGC cells, while SB203580 did not. On the other hand, the p38 MAPK inhibitor, SB203580, completely inhibited the CTGF/Hcs24-induced synthesis of proteoglycans in HCS-2/8 cells and RGC cells but the MEK1/2 inhibitor, PD098059, did not. These results suggest that ERK mediates the CTGF/Hcs24-induced proliferation of chondrocytes, and that p38 MAPK mediates the CTGF/Hcs24-induced differentiation of chondrocytes.

Osteopontin-immunoreactivity in the rat trigeminal ganglion and trigeminal sensory nuclei

Osteopontin-immunoreactivity (OPN-ir) was examined in the oro-facial tissues and trigeminal sensory nuclei (principal sensory nucleus and spinal trigeminal nucleus) to ascertain the peripheral ending and central projection of OPN-containing primary sensory neurons in the trigeminal ganglion (TG). No staining was observed using mouse monoclonal anti-OPN antibody preabsorbed with recombinant mature OPN. OPN-immunoreactive (ir) peripheral endings were classified into two types: encapsulated and unencapsulated types. Unencapsulated endings were subdivided into two types: simple and complex types. Simple endings were characterized by the thin neurite that was usually devoid of ramification. These endings were seen in the hard plate and gingiva. The complex type was characterized by the thick ramified neurite, and observed in the vibrissa, hard palate, and molar periodontal ligament. Encapsulated endings were found only in the hard palate. The trigeminal sensory nuclei contained OPN-ir cell bodies and neuropil. The neuropil was devoid of ir in laminae I and II of the medullary dorsal horn (MDH), and had various staining intensities in other regions of the trigeminal sensory nuclei. Transection of the infraorbital and inferior alveolar nerves caused an increase of OPN-ir intensity in ipsilateral TG neurons. The staining intensity of the neuropil also increased in the trigeminal sensory nuclei ipsilateral to the neurotomy excepting laminae I and II of the MDH. The present study indicates that OPN-ir primary sensory neurons in the TG innervate encapsulated and unencapsulated corpuscular endings. Such neurons probably project their central terminals to the trigeminal sensory nuclei except for the superficial laminae of the MDH.

Dentocraniofacial morphology of 12 Japanese subjects with unilateral cleft lip and palate with a severe Class III malocclusion: a cephalometric study at the pretreatment stage of surgical orthodontic treatment

OBJECTIVE

The present study clarifies the dentocraniofacial morphology of patients with cleft lip and palate (CLP) with severe Class III malocclusion prior to surgical orthodontic treatment.

METHODS

The sample was 12 Japanese male subjects with repaired complete unilateral CLP (surgical CLP group; 21.2 +/- 1.92 years in mean age). Two sets of patients without CLP Class III malocclusion, consisting of 19 male subjects treated by surgical orthodontic treatment (surgical Class III group; 23.4 +/- 6.35 years in mean age) and 14 male subjects treated by nonsurgical orthodontic treatment (nonsurgical Class III group; 18.7 +/- 3.49 years in mean age) were used as controls. Analyses were performed using lateral and posteroanterior (P-A) cephalograms.

RESULTS

(1) The surgical CLP group showed significantly smaller values for overjet, SNA angle, and inclination of the maxillary incisor as compared with those of the surgical and nonsurgical Class III controls. The values of SNB, mandibular effective length, and ramus height in the surgical CLP group were significantly smaller than those of the surgical Class III group but were similar to those of the nonsurgical Class III group. (2) The mandible and the upper and lower dental arches deviated laterally toward the cleft side. The displacement of the mandible was correlated with that of the maxilla. These results show that CLP patients who required surgical orthodontic treatment had a characteristic dentocraniofacial morphology, compared to controls without CLP with Class III malocclusion.

Influences of ovariectomy on experimental tooth movement in the rat

Estrogen withdrawal, which is important in the pathogenesis of post-menopausal osteoporosis, accelerates bone metabolism with a negative calcium balance. Therefore, it is hypothesized that estrogen deficiency could affect the rate of experimental tooth movement and alveolar bone remodeling. Six-week-old rats received a bilateral ovariectomy (OVX) or sham operation. Fourteen days later, rats were subjected to lateral tooth movement in the upper molar with nickel-titanium wire of 10 g of force. OVX significantly increased the rate of experimental tooth movement from 12 days after experimental tooth movement (p < 0.001). Eighteen days after the start of tooth movement, bone histomorphometry demonstrated that OVX significantly elevated the osteoblast surface, osteoclast surface, and number of osteoclasts (p < 0.05) in the alveolar bone. These findings indicated that estrogen deficiency caused significantly rapid orthodontic tooth movement, and that the acceleration of tooth movement could be due to the further activation of alveolar bone turnover.

Activation of the bulbospinal serotonergic system during experimental tooth movement in the rat

Experimental tooth movement is known to induce characteristic delayed and continuous nociception. Nociceptive somatic stimuli activate endogenous pain control systems such as descending monoaminergic pathways, which modulate the transmission of ascending sensory messages. To test the hypothesis that bulbospinal serotonergic pathways modulate subchronic nociception, we assayed the medulla at the level of the subnucleus caudalis and peri-aqueductal grey by high-performance liquid chromatography with electrochemical detection for the serotonin (5-hydroxytryptamine, 5-HT) and its metabolite (5-hydroxyindoleacetic acid, 5-HIAA) 24 hrs after the onset of experimental tooth movement. Experimental tooth movement significantly increased 5-HT and 5-HIAA levels, and 5-HIAA/5-HT, an index of serotonin turnover, in the medulla, and 5-HIAA level and 5-HIAA/5-HT in the peri-aqueductal grey, indicating that nociception induced by experimental tooth movement activates the bulbospinal serotonergic pathway.

An approach to enhance the interface adhesion between an orthodontic plastic bracket and adhesive

For the purpose of improving the degree of success of plastic bracket bonding, based on the analysis of the chemical components of plastic brackets, a systematic method for the treatment of the adhesive surface of plastic brackets was introduced in this study. After sandblasting the adhesive surfaces of two commercially available plastic brackets (Spirit and Clear Bracket), a favourable surface treatment was obtained with the application of a silane coupling agent, gamma-methacryloxy propyl trimethoxy silane. The findings showed that (i) the fillers added to the plastic brackets were glass fillers with Si-OH groups distributed on their surfaces; (ii) sandblasting of the bracket surface resulted in exposure of the glass fillers; (iii) combined with sandblasting, silane coupling treatment significantly increased the bond strength (P < 0.05), which was adequate to withstand the forces generated during orthodontic therapy; and (iv) treatment with sandblasting and silane coupling 24 hours before direct bonding did not cause a significant reduction in bond strength. It is concluded that sandblasting and silane coupling treatment offers the benefit of increasing the in vitro bond strength of plastic brackets for orthodontic application.

Deglutitive movement of the tongue under local anesthesia

The purpose of the present study was to investigate whether or not sensory input from the tongue affects deglutitive tongue movement. Subjects were seven healthy volunteers with anesthetic applied to the surface of the tongue (surface group) and seven healthy volunteers with the lingual nerve blocked by anesthetic (blocked group). We established six stages in deglutition and analyzed deglutitive tongue movement and the time between the respective stages by cineradiography before and after anesthesia. After anesthesia in both surface and blocked groups, deglutitive tongue movement slowed and bolus movement was delayed. The deglutitive tongue tip retreated in the blocked group. These results suggest that delay of tongue movement by anesthesia causes weak bolus propulsion and that deglutitive tongue tip position is affected by sensory deprivation of the tongue or the region innervated by the inferior alveolar nerve.

Condylar motion in patients with reduced anterior disc displacement

The influence of reduced anterior disc displacement on condylar motion has not been fully examined in young adults. Reduced anterior disc displacement was hypothesized to inhibit condylar motion. Using a six-degrees-of-freedom jaw-tracking system, we recorded bilateral condylar motion during maximum open-close jaw movement and gum-chewing on both sides in ten young adults with unilateral reduced anterior disc displacement and in ten control subjects without temporomandibular disorders. The bilateral condylar motion during both maximum open-close jaw movement and chewing on the disc-displacement side was inhibited in the test group. The condylar motion on the disc-displacement side during chewing on the non-disc-displacement side was also inhibited in the test group. These results suggest that the limitation of condylar motion on the disc-displacement side may influence condylar motion on the non-disc-displacement side during maximum open-close jaw movement, and mastication on the disc-displacement side in young adults.

Histological reaction to hydroxyapatite in the middle ear of rats

OBJECTIVE

Present study was performed to evaluate the histological response of rat middle ear mucosa following implantation of Apaceram granules, a synthetic dense hydroxyapatite [Ca10(PO4)6(OH)2], prepared from commercially available synthetic auditory ossicle, and to assess the precise histological response of the rat middle ear to implantation of Apaceram granules, by microscopic examination of mucosal tissue at various time points after implantation.

METHODS

Apaceram granules were implanted in the temporal bulla of 32 rats. As control, sham surgery was performed in a group of ten rats. Bulla specimens were removed at 1, 3, 7, 14, and 30 days after surgery in the implant and control groups, and at 90, 180 and 300 days in the implant group. Specimens were decalcified, sectioned at a thickness of 6 microm, and stained with haematoxylin and eosin, and Mallory's azan for histological examination of mucosal tissue.

RESULTS

Evidence of inflammatory reaction was slightly greater in the implant group than in controls. Lymphocyte and macrophage counts were higher in the implant group 1 day after surgery, but decreased to similar levels by day 3, and continued to decrease thereafter, and few were observed in the implant group at 300 days. Neutrophils observed at 1 day after surgery were not evident in either group at 3 days. Gradual fibrosis development continued in both groups over all time points studied. Foreign body giant cells were never observed in either group. No bony reaction was observed in any specimen.

CONCLUSION

The results of this study suggest that Apaceram is biocompatible and suitable for reconstructive ear surgery.

Gene and protein expression of brain-derived neurotrophic factor and TrkB in bone and cartilage

Gene and protein expressions of brain-derived neurotrophic factor (BDNF) and TrkB, the high-affinity receptor of BDNF, were investigated in the femur and mandibular condyle of rats by in situ hybridization and immunohistochemistry. BDNF and TrkB mRNA showed overlapped expression in chondrocytes in proliferating and mature zones of the epiphyseal growth plate cartilage and mandibular condylar cartilage, and in cuboidal-shaped active osteoblasts at the site of endochondral and intramembranous ossification and in trabecular bone. Expression of BDNF protein also showed a similar localization. The present study suggests that BDNF may participate in regulating the development and remodeling of bony tissue in the developing rat.

Mitogenic effects of neutrophins on a periodontal ligament cell line

Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) are three representative neurotrophins responsible for the differentiation and survival of neurons, and their high-affinity receptors are tropomyosin-receptor-kinase (TRK)A, TRKB, and TRKC, respectively. In this study, we investigated the expression of neurotrophins in a mouse periodontal ligament cell line (MPL), by reverse transcription-polymerase chain-reaction (RT-PCR) and enzyme-linked immunoabsorbent assay (ELISA). We also studied the expression of TRK receptors on MPL by immunostaining and the effects of neurotrophins on the proliferation of MPL, with a hypothesis of autocrine mechanism of neurotrophins. Each neurotrophin and TRK receptor was expressed, and neurotrophins enhanced the proliferation of MPL. These findings suggest that the MPL has functional neurotrophin receptors involved in an autocrine function of neurotrophins. The expression level of neurotrophins and TRKs showed the reverse pattern, and we propose an auto-regulatory mechanism of ligands and receptors in accordance with the level of synthesized neurotrophins.

A three-dimensional distribution of osteocyte processes revealed by the combination of confocal laser scanning microscopy and differential interference contrast microscopy

Osteocytes are the most numerous cells in bone, embedded within the mineralized bone matrix. Their slender cytoplasmic processes form a complex intercellular network. In addition, these processes are thought to be important structures in the response to mechanical stress. This study provides an extensive analysis of the three-dimensional structure of the osteocyte and its processes in 16-day-old embryonic chick calvariae, based on nondestructive subsurface histotomography using both confocal laser scanning (CLS) microscopy and differential interference contrast (DIC) microscopy. OB7.3, a chicken osteocyte-specific monoclonal antibody, and Texas Red-X-conjugated phalloidin were used to confirm the osteocyte phenotype and to identify whole cells in the calvariae, respectively. Serial CLS images revealed morphological changes in bone cells up to 20 microm in depth. Osteocytes had widely spread their processes into the osteoblast layer, and we found for the first time that some of these processes had elongated to the vascular-facing surface of the osteoblast layer. Furthermore, stereotype images reconstructed from CLS images could show the three-dimensional distribution of these processes. Using the stereopair image, we could evaluate the frequency of processes between osteocytes and osteoblasts. Complementation of DIC microscopy revealed canaliculi and lacunae with high contrast. The distributional pattern of canaliculi generally coincided with that of the osteocyte processes. We consider that the combination method of CLS microscopy and DIC microscopy using a laser scanning microscope is a very useful new technical approach for investigating osteocytes in bone.

Motion of the human mandibular condyle during mastication

It has been reported that loading to the mandible during closing movement makes the condylar path move more in the superior direction than that during the free closing movement. In this study, the hypothesis was tested that the displacement of the condyle on the chewing side is greater in the direction of the mandibular fossa than that on the non-chewing side. Using a six-degrees-of-freedom jaw movement recording system, we recorded condylar motion in 12 healthy adults without TMD, during the chewing of a large hard gummy jelly. The maximum displacements at the condyle on the chewing side from the maximum intercuspation (CO) position were significantly larger in the superior and medial directions at the initial stage and in the posterior direction at all stages (0.5 mm, 0.5 mm, and 0.6 mm, respectively) than those on the non-chewing side (0.0 mm, 0.1 mm, and 0.1 mm, respectively). This suggests that, in healthy adults, the condyles at CO are located in a position such that excessive load is not applied to the temporomandibular joint when there are the aforementioned displacements.

Mechanical stimulation induces CTGF expression in rat osteocytes

Connective tissue growth factor (CTGF), which is encoded by an immediate early gene and a member of the CCN family, has been shown to be expressed in osteoblasts, fibroblasts, and chondrocytes. Although CTGF is expressed in bone and cartilage tissues, we tested the hypothesis that CTGF is regulated in mechanotransduction. In the alveolar bone during experimental tooth movement, CTGF mRNA was expressed in osteoblasts and in osteocytes localized around the periodontal ligament under control conditions. Interestingly, 12 hrs after the start of experimental tooth movement, the expression of CTGF mRNA in osteocytes and osteoblasts became more intense around the periodontal ligament, and the intense expression of CTGF extended to osteocytes situated deep in alveolar bone matrix apart from periodontal ligament in both tension and compression sides. Our present findings indicate that CTGF could play a role in regulation of osteocyte function during the mechanical stimulation of bone.

Peripheral neuroglial death induced by cisplatin administration in newborn rats

To determine the target of cytotoxicity of cisplatin (CDDP), we injected newborn rats with 2 mg/kg CDDP and examined the trigeminal ganglion for possible cell death. A nick translation method for DNA fragmentation revealed CDDP-induced glial cell death. DNA fragmentation was detected in both Schwann cells and satellite cells. Satellite cell death was observed as early as 0.5 day after injection, most frequent at 1-3 days and subsided thereafter. The incidence of neuronal death was very low and comparable to that observed in vehicle control rats. CDDP has selective toxicity to peripheral glial cells, though the damage did not culminate in cell death in adults. The glial toxicity may contribute to clinical symptoms of CDDP neuropathy.

Medullary monoamine levels during experimental tooth movement

We investigated possible influence of nociception induced by experimental tooth movement on the medullary monoaminergic inhibitory systems. Forty-eight hours after the start of the experimental tooth movement, significant increases in dorsal serotonin (5-HT), dopamine (DA), norepinephrine (NE), 5-hydroxyindoleacetic acid (5-HIAA), and dihydroxyphenylacetic acid (DOPAC) levels were detected with ipsilateral dominance. These results suggest that the nociception induced by experimental tooth movement might be under modulation of serotonergic, noradrenergic, and dopaminergic systems.

Local and chronic application of PTH accelerates tooth movement in rats

We previously reported that whereas systemic continuous infusion of parathyroid hormone (PTH) accelerated orthodontic tooth movement, systemic but intermittent injection of PTH did not increase the rate of tooth movement. Analysis of these data suggested that continuous administration of PTH could be applicable for orthodontic therapy. In the present study, we investigated whether local and chronic application of PTH(1-34) would accelerate orthodontic tooth movement. To increase the residence time of PTH in the injected area, we used methylcellulose (MC) gel (2% W/V) for a slow-release formulation of PTH. MC gel containing PTH (PTH-MC) continuously released biologically active PTH into the acceptor medium for more than 72 hrs in vitro. When male rats received a local injection of PTH-MC into the subperiosteum in the mesio-palatal region of the maxillary first molar (M1) every other day, M1 movement, which was mesially drawn by an orthodontic coil spring attached to the maxillary incisors, was accelerated in a dose-dependent manner. PTH-MC injection at 1 microg/400 g body weight caused a 1.6-fold increase in the rate of tooth movement. The acceleration of tooth movement by PTH-MC injection was marked on days 6, 9, and 12. Local injection of PTH dissolved in saline without MC did not significantly accelerate tooth movement on day 6 or later. Histological examination revealed active osteoclastic bone resorption and a widened periodontal space on the compression side of the periodontal tissue in the PTH-MC-injected rats. These results suggest that local injection of PTH in a slow-release formulation is applicable to orthodontic therapy.

Long-term changes in dentoskeletal pattern in a case with Beckwith-Wiedemann syndrome following tongue reduction and orthodontic treatment

Long-term changes in the dentoskeletal pattern in a 6-year-old Japanese girl with Beckwith-Wiedemann syndrome were demonstrated. The patient showed macroglossia, which is the most common symptom of the syndrome, protruded lower lip, mandibular protrusion and anterior open bite. The jaw base relationship improved to skeletal Class I and the molar relationship to Angle Class I at the early preadolescent period following tongue reduction and phase I orthodontic treatment using a chin cap and tongue crib. Optimum intercuspation of teeth was achieved after edgewise treatment without orthognathic surgery, and a skeletal Class I apical base relationship and good facial profile were maintained after the retention period of 2 years. This case report suggests that early orthodontic treatment with tongue reduction can be effective in a case with Beckwith-Wiedemann syndrome to improve an abnormal dentoskeletal pattern.

A cineradiographic study of deglutitive tongue movement and nasopharyngeal closure in patients with anterior open bite

The purpose of this study was to investigate the movement of the tip and the dorsal surface of the tongue during deglutition in patients with anterior open bite using cineradiography. The subjects were 10 female patients with anterior open bites and 10 female controls with normal overbites. By cineradiography we established 7 stages of tongue movement and bolus position during deglutition and analyzed the tongue position, tongue movement and the time. The tongue-tip position was more protrusive during deglutition in anterior open bite than in the controls. After the head of the bolus arrived at the opening of the esophagus, the rear part of the dorsal surface of the tongue demonstrated slower movement in patients with anterior open bite than in controls. The nasopharynx closed earlier in patients with anterior open bite than in controls. It is suggested that anterior open bite patients had compensatory coordination of tongue movement, soft palate movement and pharyngeal constrictor muscle activity during deglutition.

Epithelial rests of Malassez express immunoreactivity of TrkA and its distribution is regulated by sensory nerve innervation

The periodontal ligament is the connective tissue that fills the space between the tooth and its bony socket. It is abundantly innervated by the sensory and sympathetic nerves. We first investigated the immunoreactivity of TrkA, which is a high-affinity receptor of nerve growth factor (NGF), in the periodontal ligament of rats. Immunoreactivity was observed at the epithelial cells in the cervical and furcation regions of the molars. These epithelial cells, which gather together to form clusters or networks, are known as the epithelial rests of Malassez. Immunoreactivity was not observed in other non-neuronal cells, such as osteoblasts, fibroblasts, odontoblasts, cementoblasts, endothelial cells, and/or osteoclasts. On the basis of these findings, we investigated the possible involvement of sensory nerve innervation in the immunoreactivity of the epithelial cells. Denervation of the inferior alveolar nerve resulted in a marked decrease in the distribution area and size of the clusters of immunoreactive cells compared with those of sham-operated rats. These findings suggest that sensory nerve innervation may have a regulatory role in maintenance of the epithelial rests of Malassez expressing TrkA in the periodontal ligament.

Inferior alveolar nerve transection inhibits increase in osteoclast appearance during experimental tooth movement

To evaluate the role of sensory nerve innervation in alveolar bone remodeling during experimental tooth movement, we investigated histomorphometrically the influence of sensory nerve denervation on bone metabolism. Seven days after inferior alveolar nerve (IAN) transection or a sham operation in rats, orthodontic force was applied to the animals by inserting an elastic module interproximally between the lower first molar and second molar. Twenty-four hours after the application of the orthodontic force, osteoclast number, osteoclast surface, and osteoblast surface were measured on the trabecular bone surface in the interradicular septum of the lower second molar. The distribution of sensory nerve fibers immunoreactive to antibody against calcitonin gene-related peptide (CGRP) was also evaluated. In the sham-operated rats, CGRP-immunoreactive nerves were observed to be distributed along the blood vessels in the trabecular alveolar bone. Experimental tooth movement resulted in a fivefold increase in the number of osteoclasts and in increased immunoreactivity of nerves to anti-CGRP in the trabecular bone. However, IAN transection depleted the immunoreactivity to anti-CGRP and reduced the osteoclast number and osteoclast surface significantly. On the other hand, in the rats that were not subjected to experimental tooth movement, there was no significant difference in osteoclast number between sham-operated and IAN-transected rats. Significant changes were not observed in osteoblast surfaces associated with experimental tooth movement or nerve transection. These findings suggest that sensory nerves play an important role in regulating bone resorptive activity during experimental tooth movement.

Molecular events caused by mechanical stress in bone

The shape of bone changes as a result of bone remodeling corresponding to physical circumstances such as mechanical stress. The tissue which receives the loaded mechanical stress most efficiently is bone matrix. Recent studies revealed the function of osteocytes as mechanosensors in the early stage of bone remodeling. Loaded mechanical stress is converted to a series of biochemical reactions, and finally activates osteoclasts and osteoblasts to cause bone resorption and formation. Biochemical and molecular biological studies have recently resulted in the identification of the gene of which expression level is changed by mechanical stress. Nitric oxide (NO) and cAMP is secreted in response to mechanical stress in the immediate early stage. Genes encoding enzymes such as glutamate/aspartate transporter (GLAST), nitric oxide synthetase (NOS) and prostaglandin G/H synthetase (PGHS-2) are identified as mechanical stress-responsive. The expression level of IGF-I is enhanced under the control of PTH/PTHrP. The expression of c-fos is increased by loading of mechanical stress. AP1, a heterodimer of c-FOS/c-JUN, functions as a transcription factor of downstream gene(s). Elements including AP1 sites, cyclic AMP response elements (CRE) and shear stress response elements (SSRE) are found in the promoter region of mechanical stress-response genes. The enhanced expression of osteopontin (OPN) in the osteocytes of bone resorption sites was demonstrated by in situ hybridization and immunohistochemistry and transdifferentiation of chondrocytes with the abundant expression of BMP-2 and -4 in the process of distraction osteogenesis was observed.

Orthodontic treatment for a patient with Pierre-Robin sequence complicated by juvenile periodontitis

OBJECTIVE

To arrest the advancement of periodontitis.

PATIENT

A 17-year-old boy diagnosed with Pierre-Robin sequence at birth exhibited localized juvenile periodontitis. Severe bone loss and mobile teeth were localized in the incisors and molars, which were irregularly positioned, possibly associated with a residual scar from palatoplasty for a soft palate cleft at an early age.

CONCLUSION

Combined orthodontic-periodontic-prosthodontic treatment arrested the advancement of the periodontitis and established a stable occlusion.

The difference in temporal distribution of c-Fos immunoreactive neurons between the medullary dorsal horn and the trigeminal subnucleus oralis in the rat following experimental tooth movement

The difference in temporal distribution of c-Fos-immunoreactivity (Fos-IR) was assessed in the medullary dorsal horn (MDH) and in the dorsomedial part of the trigeminal subnucleus oralis (Vodm) following experimental tooth movement of the rat maxillary molars. The number of MDH c-Fos-immunoreactive neurons increased bilaterally at 2 h and decreased markedly by 12 h, and then increased again with a small peak at 48 h. In contrast, Vodm c-Fos expression was not up-regulated until 12 h, but increased in number after 24 h, which increase lasted until 72 h. These findings indicate that experimental tooth movement induced nociceptive c-Fos response in a biphasic manner. Furthermore, the later response appeared after 24 h, and lasted for a few days, mainly manifested in the Vodm during experimental tooth movement.

Shear bond strengths of orthodontic plastic brackets

The purpose of the present study was to evaluate the shear bond strengths of plastic brackets and the influences of the bracket filler contents on the bonding. The shear bond strengths of 4 plastic brackets (Spirit; Spirit MB; Clear Bracket; Aesthetic-Line) bonded to enamel with 4 orthodontic adhesives (Orthomite Superbond; System 1+; Transbond XT; and Kurasper-F) were compared with the strength of a conventional metal bracket. The findings of this study indicated the following: (1) shear bond strength of the 4 plastic brackets was significantly lower than that of the conventional metal brackets (P <.05), with most of the values ranging from 3 MPa to 6 MPa; (2) when comparing the bond strengths of plastic brackets, Aesthetic-Line had the largest value followed by Spirit MB, Spirit, and Clear Bracket, and when the plastic brackets were bonded with Orthomite Superbond, they showed relatively stronger bond strengths than when bonded with the other adhesives. Clear Bracket showed relatively lower values especially when bonded with System 1+; (3) the application of primer did not increase the durability of the bond strengths when bonding Spirit and Clear brackets; and (4) fillers contained in each plastic bracket ranging from 9.18% to 19. 52% were fairly well distributed and showed the same morphology of a fiber type 10 microm in diameter with different lengths. The filler concentration tended to correlate with the bond strength. The exposed fillers on the bracket base surface may play a more important role in plastic bracket adhesion than the macro-morphology of the base surface.

Parathyroid hormone-activated volume-sensitive calcium influx pathways in mechanically loaded osteocytes

This paper documents for the first time a volume-sensitive Ca(2+) influx pathway in osteocytes, which transmits loading-induced signals into bone formation. Stretch loading by swelling rat and chicken osteocytes in hypo-osmotic solution induced a rapid and progressive increase of cytosolic calcium concentration, [Ca(2+)](i). The influx of extracellular Ca(2+) explains the increased [Ca(2+)](i) that paralleled the increase in the mean cell volume. Gadolinium chloride (Gd(3+)), an inhibitor of stretch- activated cation channels, blocked the [Ca(2+)](i) increase caused by hypotonic solutions. Also, the expression of alpha1C subunit of voltage-operated L-type Ca(2+) channels (alpha1C) is required for the hypotonicity-induced [Ca(2+)](i) increase judging from the effect of alpha1C antisense oligodeoxynucleotides. Parathyroid hormone (PTH) specifically potentiated the hypotonicity-induced [Ca(2+)](i) increase in a dose-dependent manner through the activation of adenyl cyclase. The increases induced by both PTH and hypotonicity were observed primarily in the processes of the osteocytes. In cyclically stretched osteocytes on flexible-bottomed plates, PTH also synergistically elevated the insulin-like growth factor-1 mRNA level. Furthermore, Gd(3+) and alpha1C antisense significantly inhibited the stretch-induced insulin-like growth factor-1 mRNA elevation. The volume-sensitive calcium influx pathways of osteocytes represent a mechanism by which PTH potentiates mechanical responsiveness, an important aspect of bone formation.

Thickness of fibrous capsule after implantation of hydroxyapatite in subcutaneous tissue in rats

The present study evaluates in rats the histomorphometrical thickness of fibrous capsules that surround hydroxyapatite (HA) disks after implantation. HA disks were implanted into the subcutaneous tissue of 79 rats for 1 day to 20 months. Decalcified histological sections stained with hematoxylin and eosin were examined. Fibrous capsule thickness (FCT) was measured using an objective micrometer. On the fourteenth day, primary fibrous capsules formed around implants. From that time point FCT increased with time of implantation. Within a given sample, FCT differed from one portion of the fibrous capsule to another, depending on which site faced the disks. FCT was thickest at the upper and lower portions of the disks, thinner at the lateral portions, and thinnest at the upper and lower ring-shaped portions. Two possible explanations for the above findings are discussed in this paper: (1) The area of contact between disk and tissue differs. (2) Chemical stimulation of implanted material caused by demineralization and remineralization may result from the varying thicknesses of fibrous capsules. FCT from upper and lower portions of HA disks increased by over 200% in the first 10 months and steadily increased about 20% over the next 10 months. Many studies have concluded that HA is useful for reconstructive surgery, so the long-term effects of FCT need further study.

Role of osteopontin in bone remodeling caused by mechanical stress

Changes in the number and proportion of osteopontin mRNA (Opn) expressing osteocytes and osteoclasts caused by the mechanical stress applied during experimental tooth movement were examined in the present study. Opn expression was detected in the osteocytes on the pressure side at the early stage, and gradually spread to those on the tension side and also to the osteoblasts and bone-lining cells in the alveolar bone. Only 3.3% of the osteocytes located on the pressure side expressed Opn in the interradicular septum of control rats; in contrast, the value was increased to 87.5% at 48 h after the initiation of tooth movement. These results indicate that these cells responded to mechanical stress loaded on the bone with expression of the osteopontin gene. Following the increased expression of Opn in these cells, a 17-fold greater number of osteoclasts compared with the control and numerous resorption pits were observed on the pressure side of the alveolar bone. Injection of arginine-glycine-aspartic acid-serine peptide but not that of arginine-glycine-glutamic acid-serine peptide strongly inhibited the increase in the number of osteoclasts. Furthermore, an in vitro migration assay demonstrated the chemotactic activity of osteopontin (OPN) on the precursor of osteoclasts. Our study strongly suggests that OPN is an important factor triggering bone remodeling caused by mechanical stress.

Apoptotic cascade of neurons in the subcortical sensory relay nuclei following the neonatal infraorbital nerve transection

A terminal transferase-mediated dUTP nick end labeling (TUNEL) method was utilized for detection of neuronal death in the subcortical relay nuclei of the trigeminosensory system following the infraorbital nerve transection in newborn rats. At 18-24 h after injury, numerous TUNEL-positive profiles were found within the ventroposteromedial thalamic nucleus (VPM) contralateral to the injury, whereas the VPM on the ipsilateral side and of the age-matched normal control contained only a few profiles per section. Electron microscopy revealed that the TUNEL-positive profiles were apoptotic neurons. The ventral part of the ipsilateral brainstem sensory trigeminal nuclear complex (the nucleus principalis, and the subnuclei oralis and interpolaris) exhibited statistically significant 65-70% increase in number of apoptotic neurons compared to the contralateral side. Taken together with our previous study [T. Sugimoto, C. Xiao, H. Ichikawa, Neonatal primary neuronal death induced by capsaicin and axotomy involves an apoptotic mechanism, Brain Res. 807 (1998) 147-154], the present results demonstrated a cascade of apoptosis in the primary, secondary and tertiary order sensory neurons along the neuroaxis.

Electron microscopic demonstration of nick end-labeled DNA fragments during capsaicin-induced apoptosis of trigeminal primary neurons in neonatal rats

DNA fragmentation was induced in the trigeminal ganglion of newborn rats by subcutaneous capsaicin injection (50 mg/kg). Twenty-four hours later, numerous roundish profiles were intensely labeled by both a DNA polymerase I-mediated nick translation method and a terminal transferase-mediated tailing method. Direct electron microscopic examination of labeled profiles indicated that the labeled profiles were neurons at earlier stages of apoptosis. DNA fragmentation signal was first detected in the nucleoplasm and later spread to the cytoplasm. The cell finally disintegrated forming many small apoptotic bodies. DNA fragmentation signal in the apoptotic bodies was readily labeled by the tailing but not the translation method.