[Finite element analysis of maxillary anterior teeth retraction of posterior teeth with different alveolar bone absorption heights under orthodontic force].

OBJECTIVE: This study applied the direct orthodontic force system to explore the applicability of the finite element method in the simulation of alveolar bone absorption and analyze periodontal stress distribution and the overall displacement trend. METHODS: The horizontal balanced alveolar bones of model 2, 3 and 4 were reduced by 2, 4, and 6 mm by deleting elements in reference to the established height of the normal alveolar bone model 1. Then, stress distribution on the posterior set of teeth and initial total tooth displacement under the simulated load of 1.47 N of orthodontic force were investigated. RESULTS: The total displacement of posterior teeth increased and parodontium Von Mises stress gradually increased as the alveolar bone height decreased. The total displacement trend and parodontium stress drastically increased when alveolar bone absorp-tion reached the height of 4 mm. CONCLUSIONS: When treating patients with alveolar bone loss, stress should be avoided or drasti-cally reduced to prevent irreversible damage to periodontal tissue and to improve the quality of medical treatment.

A coumarin-based two-photon probe for hydrogen peroxide.

A new fluorescence probe was developed for hydrogen peroxide (H2O2) detection based on donor-excited photo induced electron transfer (D-PET) mechanism, together with the benzil as a quenching and recognizing moiety. The benzil could convert to benzoic anhydride via a Baeyer-Villiger type reaction in the presence of H2O2, followed by hydrolysis of benzoicanhydride to give benzoic acid, and the fluorophore released. The probe was synthesized by a 6-step procedure starting from 4-(diethylamino)salicylaldehyde. A density functional theory (DFT) calculation was performed to demonstrate that the benzil was a fluorescence quencher. The probe was evaluated in both one-photon and two-photon mode, and it exhibited high selectivity toward H2O2 over other reactive oxygen species and high sensitivity with a detection limit of 0.09 µM. Furthermore, the probe was successfully applied to cell imaging of intracellular H2O2 levels with one-photon microscopy and two-photon microscopy. The superior properties of the probe made it of great potential use in more chemical and biological researches.

[Expression of vascular endothelial growth factor A and C in human breast cancer and their significance].

BACKGROUND & OBJECTIVE: Vascular endothelial growth factor (VEGF) family is related to angiogenesis. VEGF-A and VEGF-C are closely related to tumorigenesis and lymphatic metastasis. This study was to detect the expression of VEGF-A and VEGF-C in breast cancer, and explore their correlation to cell proliferation, microvessel density (MVD), and lymphatic metastasis of breast cancer. METHODS: The expression of VEGF-A, VEGF-C, proliferating cell nuclear antigen (PCNA), and CD34 in 98 samples of breast cancer were detected by SP immunohistochemistry. RESULTS: The positive rate of VEGF-A was 85.7%; that of VEGF-C was 90.8%. The positive rates of VEGF-A and VEGF-C were significantly higher in cancers with lymph node metastasis than in cancers without lymph node metastasis (P<0.05). The positive rate of PCNA was 98.0%; its expression level was increased with the expression levels of VEGF-A and VEGF-C (r=0.432, P=0.000; r=0.294, P=0.001). MVD was significantly higher in cancers with lymph node metastasis than in cancers without lymph node metastasis(64.26+/-26.40 vs. 50.29+/-29.35, P<0.05). MVD was positively correlated to the expression of VEGF-A (r=0.327, P<0.001), but had no correlation to VEGF-C (r=0.123, P>0.05). CONCLUSIONS: VEGF-A mainly mediates angiogenesis, cell proliferation, and metastasis of human breast cancer. VEGF-C promotes cell proliferation of human breast cancer; it is correlated to lymph node metastasis, but has no correlation to MVD.