ABSTRACT
Puccinellia tenuiflora is a typical salt-excluding halophytic grass with excellent salt tolerance. Plasma membrane Na+/H+ transporter SOS1, HKT-type protein and tonoplast Na+/H+ antiporter NHX1 are key Na+ transporters involved in plant salt tolerance. Based on our previous research, we had proposed a function model for these transporters in Na+ homeostasis according to the expression of PtSOS1 and Na+, K+ levels in P. tenuiflora responding to salt stress. Here, we analyzed the expression patterns of PtSOS1, PtHKT1;5, and PtNHX1 in P. tenuiflora under 25 and 150 mM NaCl to further validate this model by combining previous physiological characteristics. Results showed that the expressions of PtSOS1 and PtHKT1;5 in roots were significantly induced and peaked at 6 h under both 25 and 150 mM NaCl. Compared to the control, the expression of PtSOS1 significantly increased by 5.8-folds, while that of PtHKT1;5 increased only by 1.2-folds in roots under 25 mM NaCl; on the contrary, the expression of PtSOS1 increased by 1.4-folds, whereas that of PtHKT1;5 increased by 2.2-folds in roots under 150 mM NaCl. In addition, PtNHX1 was induced instantaneously under 25 mM NaCl, while its expression was much higher and more persistent in shoots under 150 mM NaCl. These results provide stronger evidences for the previous hypothesis and extend the model which highlights that SOS1, HKT1;5, and NHX1 synergistically regulate Na+ homeostasis by controlling Na+ transport systems at the whole-plant level under both lower and higher salt conditions. Under mild salinity, PtNHX1 in shoots compartmentalized Na+ into vacuole slowly, and vacuole potential capacity for sequestering Na+ would enhance Na+ loading into the xylem of roots by PtSOS1 through feedback regulation; and consequently, Na+ could be transported from roots to shoots by transpiration stream for osmotic adjustment. While under severe salinity, Na+ was rapidly sequestrated into vacuoles of mesophyll cells by PtNHX1 and the vacuole capacity became saturated for sequestering more Na+, which in turn regulated long-distance Na+ transport from roots to shoots. As a result, the expression of PtHKT1;5 was strongly induced so that the excessive Na+ was unloaded from xylem into xylem parenchyma cells by PtHKT1;5.
ABSTRACT
PURPOSE: To evaluate the effect of overlaying titanium mesh with concentrate growth factors(CGF) for rebuilding severe buccal bone defect of anterior maxilla when used in association with dental implantation. METHODS: Twenty patients with severe buccal bone defect of maxilla were selected. A total of 25 dental implants were placed, including 5 cases in bilateral central incisor area and 15 cases in unilateral central incisor area. After implantation, the defects were treated with Bio-oss and Bio-guid in conjunction with fixation of titanium mesh and then CGF technology was used. Two-stage surgery was carried out after 6 months of submerged healing, and permanent prosthesis was used 3 months after temporary restoration. The repairs of the defect were observed at the second stage surgery. The height of margin bone around implants and the thickness of bone at implants lingual side were measured, at the time of the second stage operation, and 3, 6, 12, 18 months after permanent restoration. The differences were analyzed by SPSS 19.0 software package with multi-sample nonparametric test and Fierdman test. RESULTS: At the time of second operation, the bone plate at lingual side was completely reconstructed, and new bone was formed at the top of implants. Clinical measurements showed that the averaged thickness of bone at lingual side was (2.69±0.154) mm at that time. Three, 6, 12, 18 months after restoration, the values were (2.67±0.152) mm, (2.66±0.153) mm, (2.65±0.153) mm, (2.65±0.151) mm, respectively. Implant-abutment junction was used as a base line to assess vertical bone absorption, the marginal bone of implant neck at lingual side was all inferior to the base line, the distance was (0.02±0.048) mm, (0.69±0.085) mmï¼(0.87±0.019) mm, (0.87±0.013) mm, respectively. Statistical analysis showed the thickness of bone of labial side decreased significantly over time after permanent restoration (P<0.01). Likewise, the height of marginal bone was also decreased significantly (P<0.01). However, the difference between them at 12 months and 18 months was not statistically significant (P>0.05). CONCLUSIONS: The results indicate that bone augmentation at maxilla can be achieved using titanium mesh in conjunction with CGF. The height and thickness of newly formed bone at the implant neck margin will be stabilized after 1 year. This method is worthy of wide clinical application.