Seasonal plasticity of stem embolism resistance and its potential driving factors in six temperate woody species.

The seasonal plasticity of resistance to xylem embolism has been demonstrated in leaves of some tree species, but is controversial in stems. In this study, we investigated the seasonality of stem xylem resistance to embolism in six temperate woody species (four deciduous and two evergreen tree species) that were grown at the same site. The xylem conduit anatomy, the concentrations, and ratios of the main cation in the xylem sap, as well as the content of nonstructural carbohydrates (including soluble sugars and starch) were measured in each species under each season to reveal the potential mechanisms of seasonal change in embolism resistance. The stem of all species showed increasing resistance to embolism as seasons progressed, with more vulnerable xylem in spring, but no significant adjustment in the other three seasons. The seasonal plasticity of stem embolism resistance was greater in deciduous species than in evergreen. On a seasonal scale, conduit diameter and conduit implosion resistance, the ratios of K+/Ca2+ and K+/Na+, and starch content were generally not correlated with embolism resistance, suggesting that these are probably not the main drivers of seasonal plasticity of stem embolism resistance. The seasonality of embolism resistance provides critical information for better understanding plant hydraulics in response to seasonal environments, especially under climate change.

The possible roles of OPN-regulated CEACAM1 expression in promoting the survival of activated T cells and the apoptosis of oral keratinocytes in oral lichen planus patients.

Oral lichen planus is a chronic inflammatory disorder of the oral mucosa that represents T cell-mediated autoimmune diseases. The regulation and roles of carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1), a novel immune molecule, in the immunopathogenesis of T cell-mediated autoimmune diseases remain unclear. In the current paper, CEACAM1 was found to be overexpressed in peripheral T cells and epithelial cells in oral lichen planus patients. A fraction of infiltrating inflammatory mononuclear cells in the lamina propria of the oral lichen planus mucosa also expressed CEACAM1. Importantly, for the first time, CEACAM1 expression in T cells and in normal human oral keratinocytes was demonstrated to be regulated differently by osteopontin in vitro. Furthermore, the apoptosis of oral keratinocytes and activated T cells can be markedly suppressed by CEACAM1-specific monoclonal antibodies. In conclusion, OPN-regulated CEACAM1 expression may play a critical role in the immunopathogenesis of oral lichen planus.

[The expression of Fas and bcl-2 in hamster buccal carcinogenesis].

PURPOSE: To study the expression of Fas and bcl-2 in oral carcinogenesis. METHODS: Using immunohistochemical method,we studied the expression of Fas and bcl-2 in DMBA induced hamster baccal carcinogenesis including negative control (14), hyperkeratosis (7), epithelial dysplasia (mild 12, moderate 7, severe 9), oral squamous cell carcinoma(OSCC) (25). Non-parametric test was used for statistical analysis. RESULTS: Fas was expressed in negative control consistently except stratum basale,and there was down-regulation in oral dysplasia and OSCC (chi(2)=45.576, P<0.05).bcl-2 was rarely expressed in negative control, and there was up-regulation in oral dysplasia and OSCC (chi(2)=19.433, P<0.05). CONCLUSIONS: Fas and bcl-2 may play an important role in inhibiting apoptosis coordinately, resulting in the imbalance of cell proliferation and apoptosis, which may contribute to oral carcinogenesis.

[The alteration of MTS1 gene in precancerous lesions and squamous cell carcinoma of oral mucosa].

OBJECTIVE: To investigate the expression and alteration (including homozygous deletion and mutation) of MTS1 gene in precancerous lesions and squamous cell carcinomas (SCC) of oral mucosa, and to analyse the function of MTS1 gene alteration in oral mucosal carcinogenesis. METHODS: The expression of p16 protein produced by MTS1 gene was examined with immunohistochemical SP method in 10 normal oral mucosas, 30 precancerous lesions (10 mild, 10 moderate and 10 severe dysplasia respectively) and 45 squamous cell carcinomas (SCCI18, SCCII 19, SCCIII 8). The deletion and mutation of exon1 and exon2 of MTS1 gene were examined with methods of PCR and SSCP in these same samples. RESULTS: All the precancerous lesions had p16 protein expression and no alteration of MTS1 gene. In SCC, the positive rate of p16 protein was 60.0% with 72.2% in SCCI, 57.9% in SCCII, 37.5% in SCC III, and there were no significant difference among the three groups by chi2 test (P>0.05). Gene homozygous deletion of exon1 and/or exon2 was detected in 10 cases, and gene mutation in 4 cases. The whole rate of gene alteration was 31.1% (14/45). The MTS1 gene alteration rate was 27.8% in SCCI, 31.6% in SCCII, 37.5% in SCC III and there was also no significant difference among the three groups by chi2 test (P>0.05). In SCC with local lymph nodes metastasis, MTS1 alteration rate was 57.1%, while in SCC with no lymph nodes metastasis was 8.3%, and there was significant difference by chi2 test (P<0.05). CONCLUSIONS: MTS1 gene alteration is not an early event in the carcinogenesis of oral mucosa and can not be used as a biology mark to examine oral precancerous lesions. MTS1 gene may play a certain role in the progression of oral squamous cell carcinomas.

[The experimental study of cryopreserved osteoblasts combined with BGC repairing mandibular defects in rabbits].

OBJECTIVE: The purpose of this study was to observe the biological characteristics of cultured Periosteal-derived Osteoblasts (POBs) preserved in liquid nitrogen in vitro, and to preliminarily study the osteogenetic capability of bioactive glass ceramic (BGC) combined with POBs. METHODS: The cryopreserved cells were cultured in DMEM medium and examined by morphological and histological assay. The POBs growing well in vitro were seeded into the porous BGC materials. A week later, the combined materials were implanted into the bone defects of rabbits' mandibular, the control groups were implanted into the single BGC (no cells). After 2, 4, 8, 12 weeks of operation, the specimens were respectively excised and examined by X-ray and histological chemistry. RESULTS: The cryopreserved POBs grew well in vitro and also had the tipical characteristics of mature osteoblasts. Cultured with BGC materials, the cells could attach, grow and proliferate well on the surface of most endoporous. After 4 weeks of operation, the transplanted osteoblasts began to form new osteoid or bone tissue in most pores of implanted BGC, and the bone defects were repaired better and earlier. CONCLUSION: It was practical to use the cryopreserved osteoblasts for further study on bone tissue engineering. It suggested that the "life active" bone would get more application and play a more important role in bone restoration and reconstruction.