Objective:To investigate the stress distribution surrounding an implant under different thickness of cancellous bone and cortical bone,and to analyze the influence of thickness ratio and total thickness of bone tissues on the reliability of an implant.Methods:By using the commercial finite element method software Abaqus, a simplified three-dimensional model of a jawbone consisting of a cancellous bone,a cortical bone,an implant,and a ceramic crown was constructed,and then the computation was performed.Under the condition that the system was loaded by lateral and normal stresses, the influence of thickness ratio and total thickness of cancellous bone and cortical bone in the stress distribution surrounding the implant was studied,where the thickness ratios were 3∶1, 2∶1, 1∶1, 1∶2, and 1∶3;the total thickness were 0.5, 1.0, 2.0, 3.0 and 4.0 mm, respectively. Results:The maximum stresses on the cortical bone,the cancellous bone as well as the implant were all found to decrease with the increasing of the total thickness of cortical and cancellous bones,with a higher decreasing rate in the range between 0.5-2.0 mm and a lower decreasing rate between 2.0-4.0 mm. More importantly, the maximum value of stress in the cortical bone within the neck region of the implant was observed to increase dramatically via reducing the total thickness below 2 mm, while it was increased insignificantly when the total thickness was above 2.0 mm. Conclusion:The thickness ratio and the total thickness of cancellous bone and cortical bone have strong influence in the stress distribution surrounding the implant.In dental implantation surgery, the total thickness of cancellous bone and cortical bone should be at least 2 mm, and therefore 2 mm is an optimal value.

Objective To describe the clinical application of microvascular anastomotic device in head and neck reconstruction.Methods From July,2013 to November,2013,microvascular free flaps were transferred to reconstruct the defects simultaneously after tumor resection of head and neck region in 12 cases in Department of Oral and Maxillofacial Surgery,Peking University School of Stomatology.Microvascular anastomotic coupling devices (MACD) were used in vascular anastomosis.The clinical data were collected and analyzed,including the selection of free flap,diameter of donor and recipient vessels,type of MACD,time of anastomosis,instant patency of anastomosis.The flap was monitored closely after operation and the final survival rate was calculated.Results Twelve microvascular free flaps were done in this series,including 6 fibula flaps,4 forearm flaps and 2 anterolateral thigh flaps.Totally 17 MACD were used by end-to-end anastomosis in this series,including 5 arterial anastomosis and 12 venous anastomosis.The anastomose time using MACD was from 4 to 10 minutes,with a median time 6.8 minutes.The instant patency rate of anastomosis was 100％.There were some blood leakages near the anastomotic stoma in 1 arterial anastomosis using MACD.It was resolved successfully by changing a new MACD.Conclusion Our primary clinical experience showed that the MACD was well suited to the microvascular reconstruction of head and neck defect.The feasibility and reliability was confirmed by our clinical cases.It should be recommended as a safe,fast and reliable adjuvant anastomotic instrument for free tissue transfer.

A gap is found between the existing quality of care,and social expectations and the PDCA model.Peking University People's Hospital applied the quality control circle in building a supervision platform for medical quality and sustained improvement of civilized services.This study demonstrated the efforts in this regard made by the hospital,and the major outcomes of the platform in its 6-year practice in identifying service defects,optimizing service processes and sustained improvement of medical services.In addition,it also shared insights on enhanced real-time supervision,standardized management,and long-term mechanisms of the hospital.

Salmonella is the main food-borne pathogen that causes food poisoning and gastroenteritis in human and ani-mals .The type III secretion system in Salmonella has played an important role in the invasion of host cell .In recent years ,the research of the composition ,assembly and related pathogenesis of Salmonella T3SS have made some progress .This article re-views the composition and assembly of Salmonella type III secretion system ,which could provide further study the pathogene-sis of Salmonella and also the new strategies and methods toward the treatment and prevention of Salmonella infections .

Five hundred and twelve patients with psudohypertrophic muscular dystrophy underwent rapidly minimally invasive muscle biopsy with TZ semi-automatic biopsy needle under intravenous anesthesia. Three hundred and seventy nine samples were taken from quadriceps femoris muscle, while other 133 samples were taken from the deltoid muscle. The pathological diagnosis was obtained in all patients and there were no complications after biopsy. The results indicated that this method was simple, safe, effective, indolent, and minimally invasive. The obtained muscle samples can meet the request of histopathological and immunohistochemical examination and the method should be recommended for clinical applicatioa.

Objective To investigate the anti-apoptotic effect of gene A20 in treatment of trau-matic brain injury (TBI). Methods Thirty-five Sprague-Dawley rats were made severe TBI models and assigned randomly to experimental group and control group (35 rats in each group). After severe TBI, the rats in experimental group were injected with liposome-pcDNA3.1-A20 and those in control group injected with liposome pcDNA3.1-A20 at 30 minutes after severe TBI. The animals in both groups were sacrificed to remove the brain of five rats from each group at 12, 24, 48, 72 and 168 hours for sec-tioning. The expression of A20 and neurocyte apoptosis were defined by immunohistological method and TUNEL accordingly. The other ten rats were testified for neurological function at 1,2, 3 and 4 weeks af-ter TBI. Results The expression of A20 in experimental group was higher than that in control group, with statistical differences (P < 0. 01). The peak neurocyte apoptosis was found at 72 hours after TBI. The number of apoptosis cells in experimental group was lower than that in control group at 12, 24, 48 and 72 hours afte TBI (P < 0.01 or 0.05). At the 4th week after TBI, the neurological function in exper-imental group was better than that in control group (P < 0.05). Conclusion Gene therapy with A20 may have anti-apoptosis effect and exert neuroprotective effect on severe TBI.

AIM: To clarify the protective effect of long-term administration of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor fluvastatin on ventricular remodeling after myocardial infarction (MI) in rats and its mechanisms. METHODS: Myocardial infarction were established by ligated left coronary anterior artery in SD rats, 24 hours after the operation, the survival rats were treated by gavage fluvastatin (20 mg?kg~(-1)?d~(-1)) or distilled water for 8 weeks. Doppler echocardiography, homodynamic and cardiac histomorphometry were used to assess the ventricular remodeling and cardiac function. The plasma levels of total cholesterol (Tch), creatinine (Cr), glutamic-oxal (o) acetic transaminase (AST), lipid peroxidation (LPO), glutathione perioxidase (GSH-PX), nitrogen monoxide (NO_2~-/NO_3~-) were detected. RESULTS: The Tch, Cr and AST were not significant difference in groups. Left ventricular end-diastole pressure, right relative weight, left ventricular posterior wall thickness, collagen volume fraction and the lung weight were decreased in AMI+fluvastatin group compared to AMI group (P

Objective: To investigate the prevalence of current smoking and smoking cessation, and identify the influencing factors among hypertensive patients in Nanshan District, Shenzhen City, so as to provide insights into smoking control among hypertensive patients. Methods: The demographic features, life style, status of smoking and smoking cessation in hypertensive patients were collected from 69 community health centers in Nanshan District from 2017 to 2019. The gender- and age-specific prevalence of smoking and smoking cessation was estimated among hypertensive patients, and the factors affecting hypertensive patients' smoking and smoking cessation were identified using a multivariable logistic regression model. Results: Totally 4 385 patients with hypertension were enrolled, with a mean age of (58.41±11.19) years, and the participants included 2 265 men (51.65%) and 2 120 women (48.35%). There were 724 current smokers, and the prevalence of current smoking was 16.51%, with 29.71% prevalence in males and 2.41% in females. There were 424 hypertensive patients quitting smoking, and the prevalence of smoking cessation was 36.93%, with 38.20% prevalence in males. Multivariable logistic regression analysis identified male ( OR=12.885, 95%CI: 9.567-17.354 ) and drinking ( OR=2.567, 95%CI: 2.118-3.111 ) as facilitating factors for current smoking among hypertensive patients, and increasing age (OR=0.723, 95%CI: 0.642-0.815) and high exercise frequency (OR=0.881, 95%CI: 0.817-0.950) as barrier factors, while male ( OR=7.309, 95%CI: 3.304-16.165), increasing age ( OR=1.381, 95%CI: 1.120-1.703 ), unmarried ( OR=1.819, 95%CI: 1.329-2.490 ), divorced ( OR=7.837, 95%CI: 1.254-48.975 ), retired ( OR=1.545, 95%CI: 1.095-2.180 ), unemployed (OR=1.801, 95%CI: 1.057-3.066), and high exercise frequency ( OR=1.221, 95%CI: 1.096-1.360 ) were identified as facilitating factors for smoking cessation among hypertensive patients and widowed ( OR=0.285, 95%CI: 0.089-0.906 ), high educational level ( OR=0.766, 95%CI: 0.619-0.949 ), and drinking ( OR=0.488, 95%CI: 0.368-0.647 ) as barrier factors. Conclusions The prevalence of smoking is lower, and the prevalence of smoking cessation is higher among hypertensive patients than among general populations in Nanshan District. Young and middle-aged, employed, widowed men with a high educational level are key populations for tobacco control, and alcohol consumption control and intensified exercises are important measures to reduce the prevalence of smoking and improve the prevalence of smoking cessation.

AIM: To determine the relevance of NADPH oxidase subunit p22hox and the expression of superoxide anion on ventricular remodeling in myocardial infarction (MI) rats. METHODS: MI of Sprague-Dawley rats were established by left anterior descenting coronary artery ligation. 8 weeks after MI, Doppler echocardiography, hemodynamic study and histomorphometry were performed to analyze the ventricular remodeling. The level of thiobarbituric acid reactive substance in plasma and myocardium were measured, and the distribution of superoxide anion was observed with laser scanning confocal microscope. The expression of p22phox mRNA and protein level was detected by RT-PCR and immunohistochemistry. RESULTS: The left ventricular remodeling was significant in MI rats, also the level of thiobarbituric acid reactive substance increased in the plasma and non-infarcted myocardium. The expressions of p22-phox mRNA and protein levels, and superoxide anion increased in infarcted and non-infarcted myocardium in MI rats. CONCLUSION: Our results suggest that the expression of NADPH oxidase and its derived superoxide anion may take part in left ventricular remodeling through oxidative stresss after MI.

Clustered regularly interspaced short palindromic repeats (CRISPR) is an acquired immune system existing in archaea and bacteria with the long-term process of evolutionary.CRISPR/Cas9 gene editing system is a new type of gene editing technology developed based on the system.CRISPR/Cas9 is a more efficient method for gene targeting than the previous methods.It has been successfully applied for gene-modified of eukaryotes since 2012,but the reports about pathogenic microorgaisms are rarely.Here,the research progress in the structure,mechanism of CRISPR/Cas9 system and its applications on pathogenic microorgaisms is reviewed.