Intra-epithelial requirement of canonical Wnt signaling for tooth morphogenesis.

Multiple Wnt ligands are expressed in the developing tooth and play important and redundant functions during odontogenesis. However, the source of Wnt ligands and their targeting cells and action mechanism in tooth organogenesis remain largely elusive. Here we show that epithelial inactivation of Gpr177, the mouse Wntless (Wls) whose product regulates Wnt sorting and secretion, leads to arrest of tooth development at the early cap stage and abrogates tooth-forming capability of the dental epithelium. Gpr177 in the epithelium is necessary for the activation of canonical Wnt signaling in the dental epithelium and formation of a functional enamel knot. Epithelial deletion of Gpr177 results in defective gene expression and cellular behavior in the dental epithelium but does not alter odontogenic program in the mesenchyme. Furthermore, deletion of Axin2, a negative intracellular regulator of canonical Wnt signaling, rescues the tooth defects in mice carrying Gpr177 mutation in the dental epithelium. Together with the fact that active Wnt canonical signaling is present predominantly in the dental epithelium during tooth development, our results demonstrate that Gpr177-mediated Wnt ligands in the dental epithelium act primarily in an intra-epithelial context to regulate enamel knot formation and subsequent tooth development.

[The application of temporalis muscle flap in the salvage nasopharyngectomy for advanced recurrent nasopharyngeal carcinoma].

Objective: To summarize the application of temporalis muscle flap in the salvage nasopharyngectomy for advanced recurrent nasopharyngeal carcinoma (rNPC), and to provide guidance for the repair of extensive skull base defects in salvage rNPC. Methods: A total of 54 patients with the application of temporalis muscle flap in the salvage nasopharyngectomy for advanced rNPC were retrospectively analyzed, including 42 males and 12 females, aging from 29 to 71 years. There were 36 patients with rT3 and 18 patients with rT4. The surgical methods of temporalis muscle flap repair were summarized. The general situation, survival time and postoperative complications of patients were recorded, and the advantages and disadvantages of temporalis muscle flap were discussed. Results: The temporal muscle flap could completely cover the defect area of nasopharynx and skull base, without the need for other autologous repair materials. The follow-up period was 2 to 28 months. The survival rate of temporalis flap was 98.1% (53/54). The 1-year overall survival rate was 84.5% while 1-year progression-free survival rate was 49.0%. None of the patients had facial nerve injury. Three patients (5.6%) had necrosis of the cranial membrane required surgical intervention and four patients (7.4%) required a chonoplasty due to severe chonostril stenosis or chonostril atresia. Eleven cases (20.4%) had mouth opening restriction, chewing weakness, dysphagia and other eating difficulties. Conclusions: Temporalis muscle flap is an alternative flap for the salvage nasopharyngectomy for advanced rNPC. Temporal muscle flap shows high survival rate and wide coverage, but the surgeon should apprehend the possible complications and reduce the occurrence of them.

[Establishment of Beijing National Medical School Faculty of Dentistry].

The Beijing National Medical School Faculty of Dentistry was established in 1943. This article reviewed the files preserved in Beijing Municipal Archices and presented the early background of the establishment including the approval process, formulation of teaching plans and design of the curriculums. These historical records provide us with thought-provoking insights into the evolution of the stomatological discipline and subsequent development of various sub-disciplines, as well as the educational ideals embedded.

[3H]ouabain binding to cultured endothelial cells: effect of cholesterol enrichment.

Binding experiments were performed with [3H]ouabain on cultured human umbilical vein endothelial cells (huvEC). Saturation studies yielded a binding capacity (Bmax) of 820 +/- 81 fmole/mg pr.(n = 4) and dissociation constant (KD) of 11.7 +/- 2.1nM (n = 4) in K(+)-free buffer for specific [3H] ouabain binding on these cells. External K+ inhibited this binding in a dose-dependent manner. The mean value of Bmax is equivalent to about 4 x 10(5) sites per cell, comparable with that of smooth muscle cell. These data demonstrated the presence of specific [3H]ouabain binding linked to Na+/K+ pump, consistent with the observations of ouabain-sensitive 86Rb uptake in huvEC. Effect of cholesterol enrichment was also studied. Incubation in media supplemented with cholesterol-phospholipid liposomes of molar ratio of 2:1 for 18 hours reduced the Bmax by 31% (P < 0.05) without significantly changed the value of KD. This reduction of [3H]ouabain binding appeared to be specific for cholesterol since liposome made with pure phospholipid did not alter binding. Recent findings indicate that cholesterol-enrichment and plasma lipoproteins enhance vascular contractile response, our results suggest that the cholesterol-enrichment of endothelial cells may also indirectly affect the vascular response via disturbing the function of Na+/K+ pump.