The ampC ?-lactamases gene in Escherichia coli(E.coli) is different from other Gram-negative bacteria.E.coli contains a chromosomal ampC gene which has a weak promoter as well as a transcriptional attenuator.The promoter of the ampC gene in E.coli is part of the preceding frd operon,the attenuator of the ampC gene is a transcription terminator for the frd operon.The ampC regulatory gene,ampR,is absent.Strains carrying the wild-type gene produce a low basal amount of AmpC.Studies on the molecular basis of AmpC overproduction in E.coli have shown that some hyperproducers contain mutation in the promoter region and/or attenautor and/or ampC-coding region of ampC,while others contain more than one copy of ampC.Acquisition of a stronger promoter or insertion of an insertion element containing promoter sequences or regulatory gene ampR has also been proposed as the molecular basis of hyperproduction of AmpC in some E.coli strains.Plasmid-mediated AmpC ?-lactamases have been discovered frequently in E.coli strains.This is another reason for hyperproduction of AmpC ?-lactamases.

Objective To investigate the effects of small interfering RNA (siRNA) silencing Nanog gene on the ability of migration and invasion of the human lung adenocarcinoma A549 cells. Methods The human lung adenocarcinoma A549 cells were transfected with siRNA targeting Nanog gene , and three experiment groups were set up. The expression level of Nanog was detected using reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. Cell migration was examined by wound healing assay and cell invasion was detected by Transwell assay. Results The Nanog silencing cell group (A549-siNanog) showed much lower level of Nanog mRNA and protein (0.40 ± 0.06, 0.50 ± 0.03) than A549-siNC cell group (0.97 ± 0.03, 0.85 ± 0.02; P < 0.05) under RT-PCR and Western blot analysis. Meanwhile, the wounded area filled rate and the number of invaded cells of A549-siNanog cell group (57% ± 0.04, 69.60 ± 17.14) were decreased significantly compared to A549-siNC cell group (95% ± 0.02, 209.60 ± 15.40; P < 0.05). Conclusion siRNA targeting human Nanog could specially suppress the expression of Nanog gene in lung adenocarcinoma A549 cells. In this way, it couldsignificantly reduce the capability of migration and invasion of A549 cells.

Objective To study the effect of the inhibitor of apoptosis protein,Livin on proliferation and multi?drug resistance of lung adenocarcino?ma cells A549. Methods A549 cells were transfected with the eukaryotic expression vector pcDNA3.1?Livin. A549 cell clone with stable expres?sion of Livin was obtained through G418 screening. Expressions of Livin mRNA and protein in the transfected cells were respectively measured by re?verse transcription polymerase chain reaction(RT?PCR)and Western blot. The distribution of cell cycle phase was determined using flow cytometry. The level of P?gp mRNA and protein in A549 cells transfected with pcDNA3.1?Livin was detected by RT?PCR and Western blot. The analysis of multi?drug resistance of A549 treated with different chemotherapeutics was performed by MTT. Results The mRNA and protein expressions of Liv?in were both significantly increased in the transfected A549 cells. The flow cytometry analysis showed there was higher percentage of S phase and low?er percentage of G0/G1 phase in A549 cells transfected with pcDNA3.1?Livin. Compared with control groups,the expression of P?gp mRNA and pro?tein was increased in A549 cells transfected with pcDNA3.1?Livin,which showed a higher drug resistance and lower sensitivity to chemotherapic drugs such as ADM,MTX,CTX,and DDP(P<0.05). Conclusion Overexpression of Livin could enhance the proliferation of A549 cells,and high expression of P?gp caused by Livin could serve as one of the causes for multi?drug resistance in lung adenocarcinoma against chemotherapies.

Objective To establish the isodose curves and dose calculation models of()~(125)I seed plane implantation using the three-dimensional treatment planning system(3D-TPS). Methods The isodose cures of 1 000 cGy,3 000 cGy,6 000 cGy,9 000 cGy,12 000 cGy,15 000 cGy,and 20 000 cGy and dose calculation models of triangular,quadrilateral,hexagon,and dodecagon patterns of()~(125)I seed plane implantation were created using the 3D-TPS.The isocenter dose pattern of 0,0.5,1.0,1.5,2.0,2.5,3.0,and 4.0 cm from the plane center was calculated with 3D-CRT. Results The study showed that if doses were less than 10 Gy at 2.0 cm,2.5 cm,3.0 cm and 4.0 cm apart from the center of triangular,quadrilateral,hexagon,and dodecagon patterns and the distance was beyond 1 cm between seeds,there was a low dose region in the centeral point. Conclusions The study showed that the isodose distribution curves and dose calculation models in plane implantation were primarily established using the seed implantation 3D-TPS.

Objective To observe the multi-segmental cervical spondylotic myelopathy with simple anterior or posterior joint pre-and post-operative prognosis of spinal cord function improved and the status, explore co-operation after the clinical efficacy and complications. Methods The clinical data of 298 cases of multi-segmental cervical spondylotic myelopathy with anterior or posterior of the simple pre-and post-joint surgery from January 2001 to January 2008 were retrospectively analyzed. The clinical efficacy, titanium anterior cervical decompression and fusion surgery net implanted titanium plate fixation 121 cases, posterior open-door laminoplasty 112 cases, 65 cases of combined surgery before and after. JOA score line of spinal cord function and somatosensory evoked potential, as compared 3 groups after surgical efficacy. Results All patients were followed-up 1- 7 years, averaged (4.7±1.4) years. The anterior cervical decompression and fusion surgery titanium mesh implanted titanium plate fixation to improve the rate was 78.1%, excellent and good rate was 72.7%(88/121). Posterior open-door laminoplasty to improve the rate was 70.6%, excellent and good rate was 66.1% (74/112), there was statistically significant between them (P < 0.05). After anterior surgery, improving rate was 86.7%, excellent and good rate was 83.1% (54/65). Anterior and posterior combined surgery before and after comparison was significant (P < 0.05), regardless of near-term results, long-term effects were better than that of anterior or posterior surgery. Conclusions The spinal cord in the treatment of multi-segmental operation of cervical spondylosis after anterior surgery is obviously superior to the efficacy of anterior or posterior surgery alone. Spinal stability anterior, posterior, after a joint operation before the lower one by one.

Objective To investigate the effect and underlying mechanism of single,fractioned and continuous low dose rate radiation on CL187 colorectal cancer cell line.Methods CL187 cells were exposed to 6 MV X-rays at a high dose rate of 4 Gy/min and 125Ⅰ seed at a low dose rate of 2.77 cGy/h with three groups:single dose radiation group (SDR),fractioned dose radiation group (FDR) by 2 Gy/f,and continuous low dose rate radiation group (CLDR).The radiation doses were 0,2,4 and 8 Gy.Total cell number and cell viability were determined by trypan blue.Clone forming assay was used to evaluate the cell proliferation ability.The percentage of apoptosis cells was analyzed by flow cytometry.Western blot was used to detect the protein expression levels of PHLPP2,PTEN and Bax.Results Compared with SDR and FDR groups,the total cell number and survival fraction of CLDR group decreased.The relative biological effect (RBE) for 125Ⅰ seeds compared with 6 MV X-rays was 1.41.The percentage of apoptosis cells of CLDR group was significantly increased (t =-15.08,-11.99,P ＜ 0.05).The expression level of Bax increased in CLDR group,while no obvious changes were observed on PHLPP2 and PTEN among three groups.Conclusions The expression level of PHLPP2 increaseS in SDR,FDR and CLDR group,while it seems that it was not influenced by dose rate.The expression level of Bax increased in three groups,while more colorectal CL187 cells in CLDR group may be killed due to the increase of Bax expression.

Objective To investigate the effect of cetuximab (C225) on the radiosensitivity of colorectal cancer cells CL187 and underlying mechanism.Methods Cell survival was detected by colony forming assay.The levels of apoptosis and cell cycle distribution were determined by flow cytometer.The mitotic ratio was measured by Wright' s-Giemsa mixed coloring method.The protein levels of Bax and Bcl2 were detected by Western blot.Results The sensitizing enhancement ratio of C225 was approximately 1.4.C225 treatment and 125I seed radiation induced G1 cell cycle arrest individually.C225 increased the radiation-induced apoptosis (t =6.6,P ＜ 0.05) and cellular Bax/Bcl-2 ratio (t =9.4,P ＜ 0.05),but did not increase radiation-induced G1 arrest.In addition,there was no difference in mitotic index among different groups.Conclusions C225 sensitizes CL187 to 125I seed irradiation,which might be related with increase of radiation-induced apoptosis.

Objective To investigate the effect of C225 on DNA repair and molecular pathways in CL187 colorectal cancer cells after irradiated by 125Ⅰ radioactive seeds.Methods In the experiment involved were four groups:control group,100 nmol/L C225 treatment group,125Ⅰ radioactive seeds continuous low-dose rate irradiation group and C225 combined with 125Ⅰ radioactive seeds continuous lowdose rate irradiation group.Cells were collected at 48 h after 4 Gy irradiation,and γH2AX foci/cell and γH2AX foci positive cells were counted with immunofluorescence.At the same time,DNA repair proteins were detected by Western blot.Cells were lyzed immediately after 4 Gy irradiation,and changs in EGFR downstream signaling molecules were detected by Western blot.Results Compared with 125Ⅰ seeds irradiated cells,cells treated with C225 and 125Ⅰ seeds irradiation showed more γH2AX foci per cell (t =8.0,P =0.05),and more γH2AX foci positive cells (t =6.8,P ＜ 0.05) and less expression of Ku70 (t =6.6,P ＜ 0.05) and DNA-PKcs (t =5.6,P ＜ 0.05).Combined with 125Ⅰ-CLDR irradiation,C225 reduced cellular EGFR level(t =4.9,P ＜0.05) and inhibited the activation of Akt(t =5.5,P ＜0.05).Conclusions In the condition of 125Ⅰ seeds irradiation,C225 reduced the expression of Ku70 and DNA-PKcs,inhibited the activation of Akt and attenuated the DNA damage repair capacity in CL187 colorectal cancer cells.

Objective To investigate the inhibition effect of continuous low dose rate radiation by 125Ⅰ radioactive seeds on Hep-2 cells and the corresponding mechanisms.Methods Hep-2 cells were divided into three groups,control group,single dose radiation group with high dose rate form X-rays (SDR) and continuous low dose rate radiation by 125Ⅰ seeds group (125Ⅰ-CLDR).After exposure to SDR and 125Ⅰ-CLDR,colony formation assay was used to determine the radiosensitivity and RBE,trypan blue exclusion assay was used to determine cell proliferation,and flow cytometry was used to detect cell apoptosis and cell cycle arrest.Results The radiosensitivity of Hep-2 cells to 125Ⅰ-CLDR was higher than that to SDR.The RBE of 125Ⅰ-CLDR versus SDR was approximately 1.61.The α/β ratio of 125Ⅰ-CLDR group was higher than that of SDR group.Both SDR and 125Ⅰ-CLDR inhibited cell proliferation (t =30.9,40.7,P＜0.05),in which 125Ⅰ-CLDR was stronger than SDR (t =9.8,P＜0.05).In addition,the incidences of apoptosis and G2/M arrest induced by125Ⅰ-CLDR were also stronger than those induced by SDR (t =5.8,19.8,P ＜ 0.05).Conclusions 125Ⅰ-CLDR generates more serious inhibition effects than SDR on reducing cellular DNA repair capacity,inducing cell apoptosis and G2/M arrest and inhibiting proliferation of Hep-2 cells.

Objective To evaluate the efficacy and adverse reactions of CT-guided 125I radioactive seed implantation in treatment of locally recurrent rectal cancer (LRRC).Methods Thirty patients with LRRC who refused operation or were unable to endure pelvic radiotherapy received 125I seed implantation under CT guidance.Three-dimensional treatment planning system was used to calculate the number,activity,and dose of the seeds needed.The activity of seeds ranged from 14.8 to 29.6 MBq with a median of 25.9 MBq,the seed numbers ranged from 33 to 137 with a median of 74.5,the prescription doses ranged from120-160 Gy,and the actual verification dose D90 ranged from 75.91 to 159.32 Gy with a median of 119.77 Gy.Dosimetric verification by CT scanning was conducted immediately after the treatment.Follow-up was conducted for 15.2 months(4.2-35.0 months).Results The follow-up rate was 93.3％.The pain relief rate was 95.2％.The overall response rate was 50.0％,including a complete response rate of 13.3％ and a partial response rate of 36.7％.The 1-and 2-year local control rates were 30.0％ and 8.0％ respectively.The median local control survival time was 7.8 month.The 1-and 2-year survival rates were 66.5％ and 32.9％ respectively.The median overall survival time was 21.5 months.Complications,mainly adverse effects of skin and urinary system (frequent urination,urgent urination,and dysuria) occurred in 6 patients with a rate of 20.0％.Conclusions Minimally invasive and with satisfying efficacy and tolerable complications,CT-guided 125I radioactive seed implantation is a favorable option for treatment of LRRC,especially for the patients who have undergone previous pelvic radiation.