Continuous exposure of isoprenaline inhibits myoblast differentiation and fusion through PKA/ERK1/2-FOXO1 signaling pathway.

AIM: The objective of this study is to determine if exuberant sympathetic nerve activity is involved in muscle satellite cell differentiation and myoblast fusion. METHODS AND RESULTS: By using immunoassaying and western blot analyses, we found that ß1 and ß2-adrenergic receptors (AdR) were expressed in C2C12 cells. The differentiated satellite cells exhibited an increased expression of ß2-AdR, as compared with the proliferating cells. Continuous exposure of isoprenaline (ISO), a ß-AdR agonist, delayed C2C12 cell differentiation, and myoblast fusion in time- and dose-dependent manner. ISO also increased short myotube numbers while decreasing long myotube numbers, consistent with the greater reduction in MyHC1, MyHC2a, and MyHC2x expression. Moreover, continuous exposure of ISO gradually decreased the ratio of PKA RI/RII, and PKA RI activator efficiently reversed the ISO effect on C2C12 cell differentiation and myoblast fusion while PKA inhibitor H-89 deteriorated the effects. Continuous single-dose ISO increased ß1-AdR expression in C2C12 cells. More importantly, the cells showed enhanced phospho-ERK1/2 levels, resulting in increasing phospho-ß2-AdR levels while decreasing ß2-AdR levels, and the specific effects could be abolished by ERK1/2 inhibitor. Furthermore, continuous exposure of ISO induced FOXO1 nuclear translocation and increased the levels of FOXO1 in nuclear extracts while reducing pAKT, p-p38MAPK, and pFOXO1 levels. Conversely, blockade of ERK1/2 signaling partially abrogated ISO effects on AKT, p38MAPK, and FOXO1signaling, which partially restored C2C12 cell differentiation and myoblast fusion, leading to an increase in the numbers of medium myotube along with the increased expression of MyHC1 and MyHC2a. CONCLUSION: Continuous exposure of ISO impedes satellite cell differentiation and myoblast fusion, at least in part, through PKA-ERK1/2-FOXO1 signaling pathways, which were associated with the reduced ß2-AdR and increased ß1-AdR levels.

[The relationship between the effects of MTA on mRNA expression of four iconic proteins in cells of fetal rat skull and cell culture environment].

PURPOSE: To discuss the influence of MTA on mRNA expression of Cbfa1, ALP, Col-Ⅰand BGP which are 4 kinds of iconic protein in cells of fetal rats skull, and explore its influence on cell culture environment and association of changes of calcium, phosphorus. METHODS: Cells were obtained by 2 kinds of mixed enzymatic digestion for 3 steps from gestation fetal rat calvarial bone. The expression of Cbfa1mRNA, ALPmRNA, Col-1mRNA, BGP mRNA and extracellular calcium were detected. Phosphorus (P) and calcium concentration of fetal rat skull cells co-cultured with MTA for 3 weeks at different stages of cell differentiation was assessed atomic absorption spectrophotometry. The data was statistically analyzed using SPSS10.0 software package. RESULTS: At the 4th day, P3- content decreased significantly (P<0.05), while ALPmRNA in MTA group increased most greatly and was 40 times of the control group. At the 14th to 18th day, the Ca2+ and P3- content reduced significantly (P<0.05), and then the BGPmRNA in MTA group rised most greatly which was about 7.71 times of the control group. Then Cbfalpha l mRNA in MTA group increased most strongly later which was about 7.38 times of the control group. Col Ⅰ mRNA increased minimally in all time points. CONCLUSIONS: The change of P3- content may be the initiating factor when MTA promoted differentiation of fetal rats skull cells in vitro, and Ca2+ could greatly accelerate the process of mineralization when accumulated to a certain extent. At the same time, the expression of ALPmRNA, BGPmRNA, Col Ⅰ mRNA and Cbfalpha lmRNA were regulated accordingly, which is the key to explain osteogenetic mechanism of MTA.

Does trauma etiology affect the pattern of mandibular fracture?

PURPOSE: The purpose of the present study was to evaluate the relationship between trauma etiologies and anatomic sites of mandibular fractures. PATIENTS AND METHODS: The sample was composed of all patients who sustained mandibular fractures during a 10-year period (2000-2009). The patients' age and gender were recorded; the relationships between fracture etiology and pattern of mandibular fracture were also analyzed. Data analysis included the χ2 test, the Fisher exact test, the t test, and logistic regression analysis. P < 0.05 was considered significant. RESULTS: Fall at ground level had a 9.64-fold risk of mandibular condylar fractures (odds ratio, 9.64; P < 0.001). No significant relationship existed between different etiologies and symphysis fracture. All of the etiologies had a low risk to mandibular body fractures (odds radio, <1; P < 0.05). The occurrence of mandibular angle fractures was highly related to patients' age (P = 0.001). CONCLUSIONS: The pattern of mandibular fractures was highly related to patients' age and the different etiologies.

Open reduction by vestibular approach in the treatment of segmental alveolar fracture.

Fracture of the alveolar process is a common injury; the majority of alveolar fractures may be managed by closed reduction. However, some cases with severe segmental alveolar fracture cannot be reduced by close reduction, usually resulting in occlusion disturbance. This article describes open reduction by vestibular approach in the treatment of severe segmental alveolar fractures, with the aim of evaluating the prognosis. Fifteen patients with severe segmental alveolar fractures that could not be reduced by closed method were included in our case series. Open reduction by vestibular approach was performed on these patients, and the fractures were stabilized with dental arch bars or dental wires. Postoperatively, all patients achieved uneventful healing; consolidation of the fracture was confirmed clinically after 4 weeks. The technique presented is an effective treatment approach proposed for cases of severe segmental alveolar fracture that cannot be managed by closed reduction.

[The sizes of measurement files on the accuracy of electronic apex locator].

PURPOSE: To investigate the different sized measurement files on the accuracy of electronic apex locator (EAL) in vitro. METHODS: Alginate and extracted single-Ccanalled tooth were used to mimic the situation in vivo. Forty-one teeth were used. EAL Raypex 5 was applied to determine the length of the canals by 10#-40# K files. Experimental measurements and the distances (IF value) between experimental and ideal actual measurements under the same measurement environment were recorded. Paired sample F test was applied to analyze the results by using SPSS 10.0 software package. RESULTS: The results showed that at the allowance of + or - 0.5mm, the accuracy ratios were 85.4%(10#),75.6%(15#),85.4%(20#),90.2%(25#),73.2%(30#),68.3%(35#) and 63.4%(40#), respectively. While at the allowance of +0.5--1.0mm, the accuracy ratios were 87.8%(10#),87.8%(15#),90.2%(20#),97.6%(25#),97.6%(30#),97.6%(35#) and 87.8%(40#), respectively. Statistical analysis showed that there was no significant difference in accuracy between each group(P>0.05). CONCLUSION: The results suggested that it be advisable to improve the accuracy of the EAL by measuring the working length one more time with 25# K file during the preparation under this experimental environment.

[Effect of four different solutions on the accuracy of electronic apex locators].

PURPOSE: To investigate four different solutions on the accuracy of two electronic apex locators (EAL) in vitro. METHODS: 1% agar and extracted single-canaled tooth were used to mimic the situation in vivo. Forty-seven teeth were used. Two kinds of electronic apex locator, Raypex 5 and TRRY , were applied to determine the length of the canals being flooded with four different solutions. Experimental measurements and the distances(IF value) between experimental and ideal actual measurements under the same measurement environment were recorded. Paired sample t test were applied to analyze the results by using SPSS10.0 software package. RESULTS: While the canals were flooded with 0.9% NaCl, 5.25% NaOCl, human blood and 17%EDTA, the ratios of the distance within limits of +/-0.5mm were 91.5%, 91.5%, 100% and 97.8% for Raypex 5 and 95.7%, 93.5%, 93.5% and 84.8% for TRRY , respectively. There was a significant difference in accuracy between two EALs regarding blood and 17% EDTA (P<0.05). CONCLUSIONS: Both Raypex 5 and TRRY can measure root canal length accurately despite the influence of solutions under this experimental environment.

[Mandibular fracture fixed with PDLLA/nano-HA compound plates: an animal study].

OBJECTIVE: To investigate the applicability of PDLLA/nano-HA compound plates used in internal fixation of mandibular fractures. METHODS: Rabbit mandibular fracture model was used in this study. Clinical observation, the amount of callus, histological observation were studied and compared with PDLLA plates. RESULTS: All fractures were fixed rigidly. There was 1 animal experienced local inflammation and then forming fistula in the side of PDLLA plate at postoperative 2 and 3 weeks. No side-effects were found in the side of compound plates. During the early stage of bone healing, the quality of callus in the side of compound plates was apparently more than that in the other side, and histological study showed that the osteoblasts and fibroblasts were more active in the side of compound plate in the early healing stage. CONCLUSIONS: PDLLA/nano-HA compound plate has a proper degradation time. Compared with PDLLA plates, it is more effective and safer when used in mandibular fracture.