[Exploring a new method for superimposition of pre-treatment and post-treatment mandibular digital dental casts in adults].

OBJECTIVE: To explore a cone beam computed tomography (CBCT)-independent method for mandibular digital dental cast superimposition to evaluate three-dimensional (3D) mandibular tooth movement after orthodontic treatment in adults, and to evaluate the accuracy of this method. METHODS: Fifteen post-extraction orthodontic treatment adults from the Department of Orthodontics, Peking University School and Hospital of Stomatology were included. All the patients had four first premolars extracted, and were treated with straight wire appliance. The pre- and post-treatment plaster dental casts and craniofacial CBCT scans were obtained. The plaster dental casts were transferred to digital dental casts by 3D laser scanning, and lateral cephalograms were created from the craniofacial CBCT scans by orthogonal projection. The lateral cephalogram-based mandibular digital dental cast superimposition was achieved by sequential maxillary dental cast superimposition registered on the palatal stable region, occlusal transfer, and adjustment of mandibular rotation and translation obtained from lateral cephalogram superimposition. The accuracy of the lateral cephalogram-based mandibular digital dental cast superimposition method was evaluated with the CBCT-based mandibular digital dental cast superimposition method as the standard reference. After mandibular digital dental cast superimposition using both methods, 3D coordinate system was established, and 3D displacements of the lower bilateral first molars, canines and central incisors were measured. Differences between the two superimposition methods in tooth displacement measurements were assessed using the paired t-test with the level of statistical significance set at P<0.05. RESULTS: No significant differences were found between the lateral cephalogram-based and CBCT-based mandibular digital dental cast superimposition methods in 3D displacements of the lower first molars, and sagittal and vertical displacements of the canines and central incisors; transverse displacements of the canines and central incisors differed by (0.3±0.5) mm with statistical significance. CONCLUSION: The lateral cephalogram-based mandibular digital dental cast superimposition method has the similar accuracy as the CBCT-based mandibular digital dental cast superimposition method in 3D evaluation of mandibular orthodontic tooth displacement, except for minor differences for the transverse displacements of anterior teeth. This method is applicable to adult patients with conventional orthodontic treatment records, especially the previous precious orthodontic data in the absence of CBCT scans.

Cyclic adenosine monophosphate-protein kinase A signal pathway may be involved in pulmonary aquaporin-5 expression in ischemia/reperfusion rats following deep hypothermia cardiac arrest.

We investigated the effects of cyclic adenosine monophosphate-protein kinase A (cAMP-PKA) on the expression of aquaporin 5 (AQP5) in ischemia/reperfusion (I/R) rats following deep hypothermia cardiac arrest. Wistar rats were randomly divided into: a sham control group (subjected to a sham operation); an I/R group (subjected to occlusion of the bronchial arteries and the left inferior pulmonary artery); an H89 group (subjected to occlusion of the bronchial arteries and the left inferior pulmonary vein and artery, and treated with 5 mg/kg H89 for 2 days before the study); and a forskolin group (subjected to occlusion of the bronchial arteries and the left inferior pulmonary vein and artery, and treated with 5 mg/kg forskolin for 2 days before the study). Expression levels of AQP5 mRNA and protein were determined using reverse transcription-polymerase chain reaction and western blotting. Decreased expression of AQP5 was noted in the pulmonary tissues of the I/R group compared with the sham controls. Compared to that in the control group, there was a notable decrease in AQP5 expression in the I/R group. After treating with forskolin, AQP5 expression increased in the forskolin group compared with the I/R group. In the H89 group, AQP5 expression decreased compared with the I/R group. The decreased expression of AQP5 was possibly associated with acute pulmonary injury induced by I/R. The cAMP-PKA signal pathway may be involved in the expression of AQP5 in I/R rats after deep hypothermia cardiac arrest.

The loss of Sirt1 in mouse pancreatic beta cells impairs insulin secretion by disrupting glucose sensing.

AIMS/HYPOTHESIS: Sirtuin 1 (SIRT1) has emerged as a key metabolic regulator of glucose homeostasis and insulin secretion. Enhanced SIRT1 activity has been shown to be protective against diabetes, although the mechanisms remain largely unknown. The aim of this study was to determine how SIRT1 regulates insulin secretion in the pancreatic beta cell. METHODS: Pancreatic beta cell-specific Sirt1 deletion was induced by tamoxifen injection in 9-week-old Pdx1CreER:floxSirt1 mice (Sirt1BKO). Controls were injected with vehicle. Mice were assessed metabolically via glucose challenge, insulin tolerance tests and physical variables. In parallel, Sirt1 short interfering RNA-treated MIN6 cells (SIRT1KD) and isolated Sirt1BKO islets were used to investigate the effect of SIRT1 inactivation on insulin secretion and gene expression. RESULTS: OGTTs showed impaired glucose disposal in Sirt1BKO mice due to insufficient insulin secretion. Isolated Sirt1BKO islets and SIRT1KD MIN6 cells also exhibited impaired glucose-stimulated insulin secretion. Subsequent analyses revealed impaired α-ketoisocaproic acid-induced insulin secretion and attenuated glucose-induced Ca(2+) influx, but normal insulin granule exocytosis in Sirt1BKO beta cells. Microarray studies revealed a large cluster of mitochondria-related genes, the expression of which was dysregulated in SIRT1KD MIN6 cells. Upon further analysis, we demonstrated an explicit defect in mitochondrial function: the inability to couple nutrient metabolism to mitochondrial membrane hyperpolarisation and reduced oxygen consumption rates. CONCLUSIONS/INTERPRETATION: Taken together, these findings indicate that in beta cells the deacetylase SIRT1 regulates the expression of specific mitochondria-related genes that control metabolic coupling, and that a decrease in beta cell Sirt1 expression impairs glucose sensing and insulin secretion.

Beta cell-specific Znt8 deletion in mice causes marked defects in insulin processing, crystallisation and secretion.

AIMS/HYPOTHESIS: Zinc is highly concentrated in pancreatic beta cells, is critical for normal insulin storage and may regulate glucagon secretion from alpha cells. Zinc transport family member 8 (ZnT8) is a zinc efflux transporter that is highly abundant in beta cells. Polymorphisms of ZnT8 (also known as SLC30A8) gene in man are associated with increased risk of type 2 diabetes. While global Znt8 knockout (Znt8KO) mice have been characterised, ZnT8 is also present in other islet cell types and extra-pancreatic tissues. Therefore, it is important to find ways of understanding the role of ZnT8 in beta and alpha cells without the difficulties caused by the confounding effects of ZnT8 in these other tissues. METHODS: We generated mice with beta cell-specific (Znt8BKO) and alpha cell-specific (Znt8AKO) knockout of Znt8, and performed in vivo and in vitro characterisation of the phenotypes to determine the functional and anatomical impact of ZnT8 in these cells. Thus we assessed zinc accumulation, insulin granule morphology, insulin biosynthesis and secretion, and glucose homeostasis. RESULTS: Znt8BKO mice are glucose-intolerant, have reduced beta cell zinc accumulation and atypical insulin granules. They also display reduced first-phase glucose-stimulated insulin secretion, reduced insulin processing enzyme transcripts and increased proinsulin levels. In contrast, Znt8AKO mice show no evident abnormalities in plasma glucagon and glucose homeostasis. CONCLUSIONS/INTERPRETATION: This is the first report of specific beta and alpha cell deletion of Znt8. Our data indicate that while, under the conditions studied, ZnT8 is absolutely essential for proper beta cell function, it is largely dispensable for alpha cell function.

Pressure and flow fields in the hinge region of bileaflet mechanical heart valves.

BACKGROUND AND AIM OF THE STUDY: Recent clinical thrombotic experiences with the Medtronic Parallel (MP) bileaflet heart valve have highlighted the need for new methods to assess preclinical valve hinge flow. The aim of the current study was to investigate hinge pivot flow fields in bileaflet mechanical heart valves using flow visualization in scaled x5 magnification transparent polymer models and computational fluid dynamic (CFD) analysis using CFD 2000 STORM code. METHODS: Polymeric x5 flow models of the On-X, St. Jude Medical (SJM) and MP bileaflet heart valves were constructed using laser stereolithography to replicate the interior geometry while maintaining realistic manufacturing tolerances. Each hinge flow experiment was carried out by installing the transparent x5 model in a pulsatile flow loop, which was designed according to Womersley number similitude requirements. Motions of suspended microparticles in the valve hinge area, recorded by laser imaging techniques, were used to visualize hinge flow. Experimentally measured parameters were used as input for CFD analysis. CFD simulations were made by solving the Navier-Stokes equation using a finite volume method with the pressure-based algorithm for continuity, and a pressure-implicit with splitting of operators (PISO) algorithm for pressure-velocity coupling. Moving grid methodology was employed to simulate periodic motion of the valve leaflets. CFD hinge flow results were visualized on four parallel planes at different depths in the hinge socket. The hinge flow patterns of the three types of bileaflet heart valve design are discussed. RESULTS: Prominent vortex formation and stagnant flow areas were noticed in the pivot region of the MP valve. Vortices persisted throughout both the forward- and reverse-flow phases. These flow structures were not observed in the hinge areas of the SJM and On-X valves. CONCLUSIONS: Vortex formation observed in the MP valve may contribute to the high thrombogenic potential of this valve. The absence of such vortices and areas of stagnant flow in the On-X and SJM valves indicate that hinge flow conditions in these valves do not favor mechanically induced thrombogenesis or thromboembolic events.

A microstructural flow analysis within a bileaflet mechanical heart valve hinge.

BACKGROUND AND AIMS OF THE STUDY: During recent clinical trials, the Medtronic Parallel bileaflet heart valve was found to have an unacceptable thrombosis complication rate. As patient- and material-related factors proved negative causes for this outcome, it was hypothesized that the flow fields within the valve's hinge pocket contributed to the thrombus formation. METHODS: A microstructural flow analysis within the hinge pocket is presented which uses the techniques of flow visualization, computational fluid dynamics (CFD), and laser Doppler velocimetry (LDV). The application of these techniques towards solving this problem has become possible through (i) the ability to manufacture dimensionally correct 1-X transparent heart valve housings, (ii) advances in CFD technology, and (iii) advances in LDV measurement techniques. RESULTS: This analysis showed that a vortex was present at the hinge pocket's inflow channel during forward flow and degenerated to a disturbed three-dimensional structure during reverse flow with zones of turbulent shear stress large enough to cause blood cell damage. In addition, multiple zones of flow stagnation and disturbed flow existed along the leaflet's pivot throughout the entire cardiac cycle. It was felt that these complex fluid structures created conditions which resulted in the formation of thrombus within the hinges of the Medtronic Parallel valve. These findings were supported by limited clinical explant data which illustrated early thrombus formation within the Parallel valve's hinge pocket at sites predicted by the analysis. CONCLUSIONS: This study provides, for the first time, an understanding of the detailed flow structures within the hinges of a mechanical heart valve and demonstrates an analysis technique by which future mechanical heart valve designs may be assessed for the potential of thrombus formation within the valve's hinge regions.

The identification of novel proteins that interact with the GLP-1 receptor and restrain its activity.

Glucagon-like peptide 1 receptor (GLP-1R) controls diverse physiological functions in tissues including the pancreatic islets, brain, and heart. To understand the mechanisms that control glucagon-like peptide 1 (GLP-1) signaling better, we sought to identify proteins that interact with the GLP-1R using a membrane-based split ubiquitin yeast two-hybrid (MYTH) assay. A screen of a human fetal brain cDNA prey library with an unliganded human GLP-1R as bait in yeast revealed 38 novel interactor protein candidates. These interactions were confirmed in mammalian Chinese hamster ovarian cells by coimmunoprecipitation. Immunofluorescence was used to show subcellular colocalization of the interactors with GLP-1R. Cluster analysis revealed that the interactors were primarily associated with signal transduction, metabolism, and cell development. When coexpressed with the GLP-1R in Chinese hamster ovarian cells, 15 interactors significantly altered GLP-1-induced cAMP accumulation. Surprisingly, all 15 proteins inhibited GLP-1-activated cAMP. Given GLP-1's prominent role as an incretin, we then focused on 3 novel interactors, SLC15A4, APLP1, and AP2M1, because they are highly expressed and localized to the membrane in mouse insulinoma ß-cells. Small interfering RNA-mediated knockdown of each candidate gene significantly enhanced GLP-1-induced insulin secretion. In conclusion, we have generated a novel GLP-1R-protein interactome, identifying several interactors that suppress GLP-1R signaling. We suggest that the inhibition of these interactors may serve as a novel strategy to enhance GLP-1R activity.