Differential effects of repeated immobilization stress in early vs. late postnatal period on stress-induced corticosterone response in adult rats

This study was performed in order to determine how immobilization stress in the early postnatal period or in the late postnatal period affects growth in the developing rat, and the response of the hypothalamus-pituitary-adrenocortical (HPA) axis in adult rats subjected to subsequent novel stresses. In addition, the effects of maternal deprivation (MD) within the same period of exposure to immobilization stress were also examined. We used two different types of immobilization stress and two different types of MD: immobilization stress for 30 min per day from postnatal day 7 (P7) to P13 (IS-E group); immobilization stress for 30 min from P15 to P21 (IS-L group); MD for 30 min per day from P7 to P13 (MD-E group); and MD for 30 min per day from P15 to P21 (MD-L group). The IS-E group showed a significant reduction in body weight that was maintained until at least P40 when compared with the control group. On the other hand, the IS-L group showed a significant reduction in body weight at only postnatal day (P) 20 when compared with the control group. Furthermore, the IS-E group showed a larger HPA response to novel stress than the IS-L and control groups in adulthood. The MD-E group showed a significant reduction in body weight that was maintained until at least P20 when compared with the control group, but did not show a larger HPA response to novel stress, except at T30 (30 min after exposure to novel stress) than the control group in adulthood. The MD-L group did not show a significant reduction in body weight or increased HPA response when compared with control rats. These results suggest that repeated immobilization stress, but not MD, in the early postnatal period induces long-term effects on growth and HPA response to novel stress in adulthood. (C) 2012 Elsevier Ireland Ltd. All rights reserved

Calcium Charge and Release of Conventional Glass-Ionomer Cement Containing Nanoporous Silica

The aim of this study was to evaluate calcium charge and release of conventional glass-ionomer cement (GIC) containing nanoporous silica (NPS). Experimental specimens were divided into two groups: the control (GIC containing no NPS) and GIC-NPS (GIC containing 10 wt % NPS). The specimens were immersed in calcium chloride solutions of 5 wt % calcium concentration for 24 h at 37 degrees C, whereupon the calcium ion release of the specimens was measured. The calcium ion release behavior of GIC-NPS after immersion in the calcium solution was significantly greater than that of the control. Scanning electron microscopy and electron-dispersive X-ray spectroscopy results indicated that calcium penetrated inside the GIC-NPS specimen, while the calcium was primarily localized on the surface of the control specimen. It was demonstrated that NPS markedly improved the calcium charge and release property of GIC

Bone morphogenetic protein-2 down-regulates miR-206 expression by blocking its maturation process

MicroRNAs (miRNAs) are small non-coding RNAs that are emerging as important post-transcriptional gene regulators. miR-206 is unique in that it is expressed only in skeletal muscle, including the myoblastic C2C12 cell line. In C2C12 cells, miR-206 expression was reduced dramatically after bone morphogenetic protein (BMP)-2 treatment. The down-regulation of miR-206 expression was also observed after co-transfection with constitutively-active Smad1 and Smad4, which are the intracellular signaling molecules of the BMP pathway. BMP-2 also reduced miR-206 expression in the presence of α-amanitin in a similar manner to that in the absence of α-amanitin. Moreover, the expression of pri-miR-206 was increased upon BMP-2 treatment for 6 hours compared to that in the absence of BMP-2. These results suggested that BMP-2 down-regulates miR-206 expression at the post-transcriptional level, by inhibiting the processing of pri-miR-206 into mature miR-206, and that BMP-2 could regulate miRNA biogenesis by a novel mechanism

Wnt/β-catenin signaling and osteoprotegerin

Wnt/β-catenin signaling plays an important role in the developing skeletal system. Our previous studies demonstrated that Wnt/β-catenin signaling inhibits the ability of bone morphogenetic protein (BMP)-2 to suppress myotube formation in the multipotent mesenchymal cell line C2C12 and that this inhibition is mediated by Id1. In this study, we examined the role of intracellular signaling by Wnt/β-catenin and BMP-2 in regulating the expression of osteoprotegerin (OPG) and of the receptor activator of NFkB ligand (RANKL). OPG expression was induced by Wnt/β-catenin signaling in C2C12 cells and osteoblastic MC3T3-E1 cells. Silencing of glycogen synthase kinase-3β also increased OPG expression. In contrast, RANKL expression was suppressed by Wnt/β-catenin signaling. In a transfection assay, β-catenin induced the activity of a reporter gene, a 1.5 kilobase fragment of the 5’-flanking region of the OPG gene. Deletion and mutation analyses revealed that Wnt/β-catenin signaling regulates transcription of OPG via a promoter region containing two Wnt/β-catenin responsive sites. BMP-2 enhanced Wnt/β-catenin-dependent transcriptional activation of the OPG promoter. In response to BMP-2 stimulation, Smad 1 and 4 interacted with these Wnt/β-catenin responsive sites. These results show that the regulation of OPG expression is mediated through two transcription pathways that involve the OPG promoter

Root canal treatment of traumatized permanent teeth with external root resorption

External root resorption is an important challenge in the preservation of traumatized teeth. External root resorption is observed in cases of replanted teeth from dental trauma. Root canal dressing containing calcium hydroxide (Ca(OH)2) is one recommended clinical approach for external root resorption treatment. However, complete control of external resorption may not be possible due to certain factors, such as the smear layer, which is formed by reaming and filing during root canal treatments. The smear layer plugs dentinal tubules and inhibits the effects of Ca(OH)2 as a root canal dressing material. Our study showed that root canal irrigation with ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) with an ultrasonic device is the most effective method to remove the smear layer. Additionally, we observed an alkaline environment at the outer root surface due to ion diffusion from Ca(OH)2 following this treatment. As a result, the combined use of EDTA and NaOCl with an ultrasonic device for root canal irrigation led to good control of external root resorption

Impacted mandibular primary second molar: A case report

We present a case of 6-year- and 10-month-old boy with an impacted primary molar. An x-ray photograph revealed the impacted mandibular right primary second molar with small hard tissue on the crown of the tooth as an obstacle. We extracted the small hard tissue and the mandibular right primary second molar. A histopathological examination of the obstacle revealed a tooth germ containing dental papilla, dentin, and enamel. The obstacle was diagnosed as the tooth germ of the mandibular right second premolar. In conclusion, the early detection of impacted primary molars is important for children's healthy growth and development. (C) 2022 The Authors. Published by Elsevier Ltd on behalf of Japanese Society of Pediatric Dentistry

Cytotoxicity of Strengthened Glass-ionomer Cement by Compounding Short Fibers with CaO-P2O5-SiO2-Al2O3 Glass.

The purpose of this study was to clarify whether the short glass fibers of CaO-P2O5-SiO2-Al2O3 (CPSA) glass possessed the ability to reinforce conventional glass-ionomer cement (GIC). Biocompatibility of the set GIC mixed with short CPSA glass fibers was evaluated in a cell culture cytotoxicity test. Moreover, the rate of release fluoride ions from GIC mixed with short glass fibers was measured. The powder of a conventional GIC was mixed with short CPSA glass fibers (diameter, 9.7±2.1 μm; aspect ratio, 5.0±0.9) before mixing with the liquid of the GIC. Set cements of 40 mass% short CPSA glass fibers mixed with GIC powders showed maximum values of 18 MPa in diametral tensile strength (DTS) after aging for 24 hours due to the effects of specific shape of short glass fibers and reactivity between the mixing liquid and short glass fibers. The cytotoxicity of these cements to rat pulpal cells tested by cellular activity showed that the set GIC disks (13 mm in dia. × 1 mm in thickness) with 40 mass% short CPSA glass fibers had cell activity as that of the set GIC or a cell culture coverslip used as control. Moreover, the addition of short glass fibers to GIC did not disturb the release of fluoride from the specimens

Effects of N-acetylcysteine on root resorption after tooth replantation

In the case of complete luxation with dental trauma, delayed replantation leads to a higher probability of root resorption. We evaluated the efficacy of N-acetylcysteine (NAC) as a root canal medication for trauma-associated root resorption. A rat dental trauma model was used. In the test group, mesial root pulpectomy was carried out after tooth extraction. NAC was applied as a root canal medication followed by replantation. We euthanized the rats after two weeks, excised the maxilla, and prepared thin sections, followed by H-E and TRAP staining. Furthermore, RAW264.7 cells were treated with RANKL and NAC. The effects of NAC on osteoclast differentiation were investigated by determining the numbers of osteoclasts and nuclei and quantifying osteoclast-related mRNA expression levels by real-time PCR. The level of root resorption and number of odontoclasts tended to be lower in the NAC groups than in the control group. In terms of osteoclast differentiation, the total number of osteoclasts was lower in both the 5 and 10 mmol/L NAC groups than in the control group. Real-time PCR revealed that the expression levels of RANK, NFATc1, DC-STAMP, CD47, and cathepsin K were lower in the 10 mmol/L NAC group. NAC tended to inhibit root resorption and reduce the number of odontoclasts. NAC also inhibited the expression of osteoclast-related genes. Overall, NAC reduced the number of odontoclasts, inhibited bone resorption, and influenced the inhibition of osteoclast differentiation, fusion, and functions. Therefore, we suggest that NAC may be beneficial in the treatment of root resorption. (C) 2020 Japanese Society of Pediatric Dentistry. Published by Elsevier Ltd. All rights reserved

Simple and Rapid Conductive Preparation of Wet Biological Samples for SEM Observation: Use of an Asymmetrical Choline-like Room Temperature Ionic Liquid as a Visualizing Agent

In this study, we prepared a hydrophilic, choline-like room temperature ionic liquid (RTIL), and investigated its use as an electroconductive pretreatment for scanning electron microscopy (SEM) investigations of wet biological samples. Wet biological samples generally require pretreatment before SEM observation because of their properties. Conventional pretreatment methods consist of multiple tedious steps that take from several hours, to a day or more. In contrast, our pretreatment only requires the samples to be immersed in an RTIL. This gives the sample suitable electroconductivity for SEM analysis, which can then be carried outperformed rapidly. In addition, samples pretreated with RTILs can remain wet even in the vacuum chamber of SEM. This property allows morphological observation of wet biological samples in "a life-like manner" because our method avoids the chemical fixation, dehydrogation and drying processes required by conventional pretreatment. Moreover, some samples can be successfully visualized after pretreatment using RTILs without dilution. These results suggest that this method can allow simple and rapid conductive pretreatment of wet biological and insulating samples without optimizing their concentrations