Effect of different surface treatments on the crystal structure and properties of zirconia / 北京大学学报(医学版)

OBJECTIVE@#To investigate the effects of 3 surface different treatments on the crystal structure, shear bond strength,roughness value and flexural strength of zirconia.@*METHODS@#The zirconia specimens were prepared and randomly divided into 4 groups and received the following treatments: (1) blank control group,the specimens without treatments; (2)sandblasting with alumina group, sandblasting the specimens with 110 μm alumina particles for 21 s as working pressure 0.25 MPa and working distance 10 mm; (3)laser etching group, coating the surface of the specimens with graphite powder and using Er:Yttrium Aluminum Garnet (Er:YAG) laser to irradiate the surface 30 s; (4) hot-etching group, putting the specimens in a closed reactor within a 1:1 mixture of 40% (mass traction) nitric acid and 68%(mass traction) hydrofluoric acid liquid, the reaction of 30 min in a water bath at 100 degrees centigrade. The changes of crystal structure, shear bond strength(SBS) and flexural strength of zirconia after different surface treatments were tested.@*RESULTS@#The X-ray diffractometer (XRD) patterns showed that the volume percentage of monoclinic phase of the 4 groups was 0.91%, 12.50%, 6.64% and 17.81% respectively. The roughness value for the four groups were as follows: blank control group,(0.29±0.01) μm; sandblasting with alumina group, (1.05±0.11) μ m; laser etching group, (0.73±0.04) μm; hot-etching group, (1.31±0.06) μm, respectively(P<0.05). Mean SBS was (7.09±0.46) MPa in blank control group, (12.14±1.51) MPa in sandblasting with alumina group, (8.82±0.74) MPa in laser etching group and (11.97±0.99) MPa in hot-etching group. There was no statistically significant difference between sandblasting with alumina group and hot-etching group (P>0.05), but the difference between the other groups were statistically significant(P<0.05). Mean three-point bending was (933.70±44.13) MPa in blank control group, (850.95±60.66) MPa in sandblasting with alumina group, (771.53±68.08) MPa in laser etching group and (766.27±57.49) MPa in hot-etching group. There was no statistically significant difference between sandblasting with alumina group and hot-etching group (P>0.05), but the difference between the other groups were statistically significant (P<0.05).@*CONCLUSION@#After different surface treatments, the surface of zirconia has changed from tetrago-nal to monoclinic phases in varying degrees. In addition, surface treatments could improve the bond strength of zirconia to resin cement, and also lead to a decrease in the flexural strength of zirconia.

Cloning and bioinformatics analysis of recombinant methyl-accepting chemotaxis signal transduction protein of Helicobacter hepaticus / 南方医科大学学报

<p><b>OBJECTIVE</b>To clone the gene encoding methyl-accepting chemotaxis signal transduction protein (MCSTP) of Helicobacter hepaticus and analyze the gene structures using bioinformatics methods.</p><p><b>METHODS</b>With the specific primer of Helicobacter hepaticus MCSTP c1977, MCSTP gene was amplified by PCR from the genomic DNA of Helicobacter hepaticus and ligated to the prokaryotic expression vector pET22b(+). After sequencing, the sequence homology and structural feature of MCSTP gene were analyzed by bioinformatics method.</p><p><b>RESULTS</b>A 99% similarity was identified between MCSTP gene cloned and its counterpart in standard Helicobacter hepaticus strain ATCC51449 genome DNA published by GenBank, with only a replacement of A by T at 1160 bp. A low homology was found in the MCSTP genes between Helicobacter hepaticus, Campylobacter jejuni and Helicobacter pylori by bioinformatics analysis, suggesting the specificity of MCSTP gene in Helicobacter hepaticus among the microbes.</p><p><b>CONCLUSION</b>The prokaryotic expression plasmid pET22b(+)/MCSTP is constructed successfully, and the bioinformatics analysis provided evidences and clues for further study of the biological functions and pathogenic mechanism of MCSTP.</p>

Isolation and characterization of the first strain of Helicobacter hepaticus in China / 南方医科大学学报

Helicobacter hepaticus is nongastric helicobacter that can reside in the hepatobiliary and intestinal systems of many animal hosts, leading to proliferative hepatitis, hepatocellular carcinoma, typhlitis, and colonitis. In this study, the intestinal mucosa was isolated from BALB/c mice to prepare tissue homogenate and spread onto selective C jejuni blood agar plates for incubation in the presence of trimethoprim, vancomycin, and polymyxin at 37 degrees Celsius; under microaerobic conditions in vented jars containing 5% O2, 10%CO2, and 85% N2. The bacteria were identified morphologically and biochemically. Gene sequence analysis of the 16s rRNA confirmed the presence of Helicobacter hepaticus, and the success in isolating this bacteria may have significant implications for studies of nongastric helicobacter.

Expression of heat-shock transcription factor 1 and X-linked inhibitor of apoptosis protein-associated factor-1 in gastrointestinal cancer / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the expressions of X-linked inhibitor of apoptosis protein (XIAP)-associated factor-1 (XAFI) and heat-shock transcription factor 1 (HSF1) and their relationship in human gastrointestinal cancers.</p><p><b>METHODS</b>Immunoblotting was used to analyze the expressions of HSF1 and XAF1 in gastric and colon cancer tissues and in gastrointestinal cancer cells. The gastrointestinal cancer cells were tranfected with a eukaryotic expression vector containing HSF1 gene fragment or subjected to RNA interference to induce up- or down-regulation of HSF1 expression, and the consequence changes in XAF1 expression in the cells was measured. XAF1 expression was also assayed in the cells after stress stimulation for HSF1 expression.</p><p><b>RESULTS</b>The expression of HSF1 was higher in gastrointestinal cancer tissues than in normal tissues. The expression of XAF1 and HSF1 was inversely correlated in the cancer cell lines, and stress stimuli of the cells up-regulated the expression of HSF1 but down-regulated XAF1 expression.</p><p><b>CONCLUSION</b>HSF1 expression is increased in gastrointestinal cancer tissues to result in suppressed expression of XAF1, which may be one of the reasons for the low expression of XAF1 in association with the defect of the apoptosis mechanisms in the cancer cells</p>

Expression of HSF1 and XAF1 in gastro-intestinal cancer / 南方医科大学学报

<p><b>OBJECTIVE</b>X-linked inhibitor of apoptosis protein (XIAP) To gastrointestinal (GI) investigate the expression of XAF1 and heat-shock transcription factors 1 èHSF1éand their relationship in human gastrointestinal cancers.</p><p><b>METHODS</b>Immunoblotting was used to analyze the expression of HSF1 and XAF1 in either gastric or colon cancer tissue and GI cancer cell line. Transient expression of the HSF1-containing vector in GI cell lines and RNA interference were used to up/down-regulae the expression of the HSF1, and the subsequent expression of XAF1 was measured.</p><p><b>RESULTS</b>The expression of HSF1 was higher in GI cancers than in normal tissues. The expression of XAF1 and HSF1 was negatively correlated in GI cancer cell lines. Stress stimuli up-regulated the expression of HSF1 while the alteration of XAF1 expression was negatively correlated with HSF1 expression.</p><p><b>CONCLUSION</b>The high expression of HSF1 in GI cancers is associated with suppressed expression of XAF1, which can be one of the mechanisms for low-expression of XAF1 and insufficient apoptosis in GI cancers.</p>

Short hairpin RNA-mediated survivin gene silencing inhibits invasion and metastasis of human colon carcinoma cell line SW480 in vitro / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of short hairpin RNA (shRNA) targeting survivin on adhesion and invasion of human colon carcinoma cell line SW480 in vitro.</p><p><b>METHODS</b>According to the sequence of the coding region of survivin gene, two strings of 19 nucleotides of inverted sequence flanking the loop sequence of two complementary 9-base oligonucleotides were designed and synthesized to prepare the hairpin construct as the DNA templates for the target shRNA. The shRNA templates were cloned into shRNA expression vector pRNAT-U6.1/Neo, and the resulted vector pRNAT-U6.1/Neo-survivin was transfected into SW480 cells using Lipofectamine 2000. Western blotting was performed to evaluate survivin gene silencing induced by shRNA transfection at the protein level, and the biological behaviors of the SW480 cells were investigated by cell-matrix adhesion, invasion and gelatin-zymography assays.</p><p><b>RESULTS</b>Western blotting revealed significantly lowered survivin protein expression in transfected SW480 cells, and survivin gene silencing induced by shRNA significantly suppressed the metastatic potential of SW480 cells in association with suppressed MMPs activity.</p><p><b>CONCLUSIONS</b>Survivin may play an important role in modulating human colorectal carcinoma cell invasion and metastasis, and survivin gene silencing can inhibit human colorectal cancer cell invasion and the production of MMP-2 and MMP-9. Survivin may affect invasion and metastasis of human colorectal carcinoma cells via regulating the production of MMPs.</p>

Construction of the attenuated Salmonella typhimurium strain expressing Helicobacter pylori conservative region of adhesin antigen / 生物工程学报

To construct a non-resistance and attenuated Salmonella typhimurium strain which expresses conservative region of adhesin(AB) of Helicobacter pylori(Hp). The AB gene was amplified by PCR and inserted into the expression vector pYA248 containing asd gene and was introduceded into the delta Cya, delta Crp, delta Asd attenuated Salmonella typhimurium strain by twice transformations, which is a balanced lethal recombinant. Bridged ELISA method was used to measure AB expressed in sonicate and culture supernatant. According to Meacock's way and growth curve, stability of the recombinant is evaluated. Semi-lethal capacity test was used to evaluate the safty of recombinant. Results showed S. typhimurium X4072(pYA248-AB) was constructed successfully, recombinant X4072(pYA248- AB) content of supernatant serum was higher than that of thallus lytic liquor confirmed by bridged ELISA, and after recombinant pYA248- AB cultured 100 generation without selection pressure, all the recombinant germ selected randomly can grow, and the AB antigen was positive by ELISA detection. The growth curve of the recombinant germ showed that the growth state of X4072(pYA248) and X4072(pYA248- AB) were coincidence on the whole, and the survival rate of C57BL/6 was still 100%, 30 days after taking X4072(pYA248- AB) 1.0 x 10(10)cfu. orally. Non-resistance S. typhimurium X4072(pYA248- AB) was constructed successfully. The recombinant plasmid was stable indicated by in vitro experiment. And the recombinant strain was safe confirmed by animal experiment. This live vaccine strain is worthy to be considered as a new live oral vaccine candidate against Hp infection.

Contribution of eukaryotic initiation factor-4E inhibition to heparanase expression and activity in human colon adenocarcinoma cell line LS-174T / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To determine whether the eukaryotic initiation factor-4E (eIF-4E) is involved in the cap-dependent translational regulation of heparanase and study the correlation between heparanase expression and metastatic potential of LS-174T cells.</p><p><b>METHODS</b>The protein and mRNA levels of inhibited eIF-4E were tested by Western blot and RT-PCR. Heparanase activity was defined as the ability to degrade high molecular weight (40-100 000) radiolabeled ((35)S) heparan sulfate (HS) substrate into low molecular weight (5-15 000) HS fragments. The invasive potential of tumor cells in vitro was observed by Matrigel invasion assay system.</p><p><b>RESULTS</b>The 20-mer antisense oligonucleotide (asODN) against eIF-4E specifically and significantly inhibited eIF-4E expression at both transcriptional and translational levels. The expression and the activity of heparanase were effectively lowered, which further decreased the invasive potential of LS-174T.</p><p><b>CONCLUSION</b>eIF-4E, probably being involved in translational regulation of heparanase in colon adenocarcinoma cell line LS-174T, can be a particularly interesting target for heparanase regulation, based on of its critical function.</p>