BACKGROUND:Post and core restoration is a common choice for tooth defects,but the repair effects of various post and core materials are different. OBJECTIVE:To evaluate the stress distribution at the post and core,tooth root,and bonding agent site of post and core models made of different elastic modulus post and core materials using finite element method. METHODS:A three-dimensional root canal treated maxillary central incisor model was built using three-dimensional modeling software,which was restored with a full ceramic crown.The post and core materials in the restoration used nanoceramic resin(elastic modulus=12.8 GPa),composite resin(elastic modulus=16 GPa),hybrid ceramic(elastic modulus=34.7 GPa),glass ceramic(elastic modulus=95 GPa),titanium alloy(elastic modulus=112 GPa),and zirconia(elastic modulus=209.3 GPa).The model was fixed in cortical bone.A 100 N concentrated force of 45° from the long axis of the tooth was applied to 1/3 of the crown and tongue side of the central incisor.The stress distribution of the post and core,dentin,and tooth-root bonding agent in the model was repaired by the maximum principal stress criterion. RESULTS AND CONCLUSION:(1)When the post and core materials with higher elastic modulus was used,the post-core stress in the repair model was more concentrated.When the elastic modulus of the post and core materials(nanoceramic resin and composite resin)was close to dentin,the stress distribution of the post and core was more uniform.The stress distribution of dentin in all restoration models was similar regardless of post and core materials.When the post and core with higher elastic modulus was used,more stress concentration was shown at the post and root bonding agent in the repair model.(2)The maximum stress values at the post and core,tooth root,and the bonding agent site of post and tooth root in the nanoceramic resin model were 31.00,33.21,and 0.51 MPa,respectively.The maximum stress values at the post and core,tooth root,and the bonding agent between the post and tooth root in the composite resin model were 36.84,33.14,and 0.59 MPa,respectively.In the mixed ceramic model,the maximum stress values at the post and core,tooth root,and the bonding agent between the post and tooth root were 64.05,32.83,and 1.00 MPa,respectively.In the glass ceramic model,the maximum stress values at the post and core,tooth root,and the bonding agent between the post and tooth root were 112.30,32.69,and 1.73 MPa,respectively.In the titanium alloy model,the maximum stress values of the post and core,tooth root,and the bonding agent between the post and tooth root were 120.00,32.17,and 1.86 MPa,respectively.In the zirconia model,the maximum stress values of the post and core,tooth root,and the bonding agent between the post and tooth root were 148.80,31.85,and 2.28 MPa,respectively.(3)The higher the elastic modulus of the post and core material,the higher the maximum stress at the post and core during restoration.The elastic modulus of the post and core material had no significant effect on the maximum stress of the dental bonding agent and dentin.

Biodegradable magnesium-based metal guided bone regeneration(GBR)membranes possess excellent me-chanical properties,biodegradability,and osteopromotive capabilities,making them ideal implants for the treatment of maxillofacial bone defects.This review summarizes the current status and future research trends related to magnesium-based GBR membranes.First,the research history and application fields of magnesium-based metals are introduced,and the advantages of the use of magnesium-based materials for GBR membranes,including their mechanical properties,bio-compatibility,osteopromotive performance,and underlying mechanisms are discussed.Finally,this review addresses the current limitations of magnesium-based GBR membranes and their applications and prospects in the field of dentistry.In conclusion,considerable advancements have been in fun-damental and translational research on magnesium-based GBR membranes,which lays a crucial foundation for the treatment of maxillofacial bone defects.

As the robotic assisted single port surgery arousing attention, a novel single-arm single-port micro-traumatic laparoscopic robotic surgical system is proposed in this study. From the perspective of the mechanics, joints with high rigidity and high reliability were utilized to realize the remote center of motion (RCM). Besides, the cost of consumables was reduced by adding the support of the rigid endoscope. From the perspective of the algorithm, high-precision motion control method and feedback force protection mechanism were implemented. The effectiveness of the aforementioned characteristics were verified by five clinical experiments of cholecystectomy. The results showed that the system is able to reduce the amount of bleeding, accelerate the patient recovery, reduce the infection risk and shorten the learning period. The robotic surgical system had significant clinical application value.
Humans ; Robotic Surgical Procedures ; Reproducibility of Results ; Laparoscopy ; Motion

OBJECTIVETo evaluate whether intraoperative autologous donation (IAD) can reduce perioperative blood transfusion for patients underwent mitral valve replacement (MVR).

METHODSA total of 318 patients received implementation of IAD from January 2011 to December 2013 were analyzed retrospectively, and compared with 517 patients of the previous 36-month period (from January 2008 to December 2012). The method of small-volume retrograde autologous priming, strict blood transfusion standard along with IAD together constituted a progressive blood-saving strategy. Statistical methods including Students' t-test, Pearson's χ(2) test, Kruskal-Wallis analysis and multivariate Logistic regression model were used for comparisons of the data.

RESULTSThere were no significant difference between IAD group and non-IAD group considering preoperative patient demographics, characteristics and preoperative comorbidities. However, IAD group significantly reduced number of patients transfused with intra/post-operative packed red-blood cell (PRBC) (55(17.0%) vs. 215 (42.1%), χ(2)=53.0, P=0.000), and had significantly reduced postoperative chest tube output (150(380) ml vs. 700(660) ml, H=195.648, P=0.000), length of stay ((16±6) d vs. (20±8)d, t=9.60, P=0.000). But hematocrit were lower in IAD group (30%±5% vs.33%±4% at end of operation, t=7.76, P=0.000; 30%±4% vs. 32%±5% at discharge, P=0.000, t=3.86). Multivariate logistic aggression analysis revealed that age, IAD and smoking history were factors influencing the probability of intra or postoperative blood transfusion.

CONCLUSIONImplementation of blood conservation strategies based on intraoperative autologous donation in mitral valve replacement surgery can significantly reduce intra/postoperative blood transfusion as well as postoperative complications.

Blood Transfusion, Autologous ; Bloodless Medical and Surgical Procedures ; Cardiac Surgical Procedures ; methods ; Hematocrit ; Humans ; Logistic Models ; Mitral Valve ; surgery ; Postoperative Complications ; Retrospective Studies

Besides the catalytic domain, some xylanases contained a non-catalytic domain which is named as carbohydrate binding module (CBM). CBM can be used to improve their binding-ability to insoluble substrates. We illustrated the importance of CBM by reviewing the source of CBMs, type of families, features of binding to insoluble substrates, specific amino acids involved in substrate-binding, linker peptides connecting the catalytic domain, and the effect of CBMs on xylanase thermostability. CBM is important for xylanase to break down complicate carbohydrates. Perspectives on engineering xylanase activity according to the characteristics of CBMs were given.
Binding Sites ; Carbohydrate Metabolism ; Catalysis ; Endo-1,4-beta Xylanases ; metabolism ; Multienzyme Complexes ; chemistry ; Substrate Specificity

BACKGROUND: It is considered traditionally that epilepsy is a kind of complicated nervous conduct disorder caused by abnormally excited neuron in different area in brain. While the research on the function of astrocyte in epileptic attack is very rare.OBJECTIVE: To study the reaction of neuron and astrocyte in medullary visceral zone after epilepsy induced by pentetrazole in rats.DESIGN: A randomized controlled experimental research.SETTING and MATERIALS: The experiment was done in the Neurosurgery Laboratory of Zhujiang Hospital Affiliated to Southern Medical University and Neuroscience Institute of Fourth Military Medical University of Chinese PLA. Fourteen healthy adult SD rats, weighing 180 - 220 g, clean grade, were provided by the Experimental Animal Center of Fourth Military Medical University of Chinese PLA.INTERVENTIONS: Distribution of neuron and astrocyte in MVZ 1 hour after epileptic attack was shown by laserconfocal microscopic technique combined with triplication immunofluorescence histochemistry of anti-Fos protein, anti-tyrosine hydroxylase(TH) and anti-glial fibrillary acidic protein(GFAP).MAIN OUTCOME MEASURES: Observation of distribution of positive cells of Fos, GFAP and TH in MVZ and relationship between GFAP positive astrocyte and neuron.RESULTS: Fos positive neurons and GFAP positive astrocytes in MVZ increased significantly. Triplication immunofluorescence histochemistry showed reaction neuron(Fos positive) closely related with reaction astrocyte(GFAP positive) . Three kinds of N-ASC compounds with different labels were found, which were TH +/Fos +/GFAP + three labeled compound, TH + /GFAP +/Fos- and Fos+/GFAP +/TH- two labeled compound.CONCLUSION: Neuron and astrocyte in MVZ reacted strongly when epilepsy attacks. N-ASC as a functional unit may regulate onset of epilepsy.

BACKGROUND: Lipopolysaccharide(LPS), as a polyclonal immune exciter, can simulate immune excitation status, which is useful in the observation of whether the catecholaminergic neurons in paraventricular nucleus of hypothalamus(PVN) projected from medullary visceral zone(MVZ) react towards LPS stimulation that is to provide a theoretical gist for the researches on the protection of brain function.OBJECTIVE: To observe whether PVN catecholaminergic neurons projected from MVZ react towards LPS stimulation for the exploration of the impacts of MVZ-PVN catecholaminergic access in "immune-to-brain communication".DESIGN: A randomized controlled study using experimental animals as subjects.SETTING: An Institute of Neurosurgery and Neurology of one Military University of Chinese PLA.MATERIALS: The study was conducted in the Department of Neurosurgery of Zhujiang Hospital affiliated to Southern Medical University and the Institute of Neurology of the Fourth Military Medical University of Chinese PLA from January to December in 2002. Ten healthy adult SD rats in cleanness grade were obtained from the experimental animal center of the Fourth Military Medical University of Chinese PLA.METHODS: WGA-HRP was injected into PVN of one side of the rat, and the immune exciter LPS was injected into the abdominal cavity after 48 hours of survival to induce immune response. Samples were stained by triple labels of WGA-HRP method and double immunohistochemical staining of anti-Fos and anti-TH antibodies.MAIN OUTCOME MEASURES: To observe the distributions and expressions of WGA-HRP labeled cells, Fos protein, and catecholaminergic neuron(labeled by TH) in MVZ.RESULTS: Seven immune-reactive(IR) positive neurons were found in MVZ, i. e., HRP, Fos or TH single labeled cells, Fos/HRP, Fos/TH or HRP/TH double labeled cells, and Fos/HRP/TH triple labeled cells. Fos/HRP double labeled neurons and Fos/HRP/TH triple labeled neurons accounted for 12. 5% and 39.6% of HRP labeled cells respectively.CONCLUSION: MVZ reacts to LPS immune stimulation, which could upload the immune message to PVN through Catecholaminergic neurons.MVZ might be a relay station in "immune-to-brain communication", which exerts immune modulatory impact through "MVZ→PVN" access.

Objective Monocular deprivation(MD) and binocular deprivation(BD) were used to examine the experience\|dependent structural plasticity of astrocytes in the central visual brain regions of young rats. Methods Pups eyelids were monocularly or binocularly sutured on postnatal day 7(P7) and maintained until 80?d,while an unoperated light experienced group was used for comparisions(L).Immunohistochemical ABC method was employed to investigate the immunoreactive changes of astrocytic bodies and processes for glial fibrillary acidic protein(GFAP) in the central visual brain regions. Results The results showed that the amount of astrocytic bodies and processes in the brain was decreased both in MD and BD groups compared to L group.The amount of GFAP\|positive immunoreactivity in the optic chiasma,optic tract,and contralateral central visual brain regions (including suprachiasmatic nucleus,lateral geniculate nucleus,occipital visual cortex,optic nerve layer of the superior colliculus and pretectal area) was significantly decreased in MD group.GFAP\|positive structures presented complementary distribution in bilateral visual cortex.For bilateral brain regions mentioned above,the amount of GFAP\|positive structures basically disappeared in BD group.There was,however,an increase in the olfactory cortex of GFAP immunoreactive in MD and BD groups. Conclusion\ The data suggested that the structure of astrocytes might be influenced by visual experience during development.

Objective To investigate the early effect of medium-dose ionic irradiation on the expression of Fos protein in the rat brain. Methods Fos protein was observed in rat brains at times ranging from 24 hours to 4 weeks after hemispheric irradiation (single-fraction maximal dose of 20Gy) with the immunohistochemical technique. Results Compared with that of the un-radiated rats,the expression of Fos protein in the irradiated brain decreased distinctly 24 hours and 1 week after irradiation.However,the quantity of Fos immunopositive cells increased gradually afterwards.At four weeks after radiation,expression of Fos protein recovered progressively in medulla oblongata and pons,in which Fos immunopositive cells were more than those in control group.In contrast,expression level of Fos protein in mesencephalon,diencephalons or telencephalon was still less compared with that of the un-irradiated rats.Conclusion The result suggested that the neuronal activity might be inhibited in certain nuclei of the rat brain in early stages after hemisphere irradiation,and this inhibitory phenomenon was more obviously in higher neural centers.

Objective To test experimentally Fluoro-Jade B(FJB) stain method for detecting degeneration of neurons in the basal ganglia. Methods Kainic acid(KA)-lesion model by stereotaxical injection of KA into striatum of rats,MPTP-lesion model by injection of MPTP into intraperitoneal cavity of mice,as well as KA-lesion model of cultured striatal cells were firstly prepared.FJB stain dye was then used to visualize degeneration of neurons in above KA-or MPTP-lesion models. Results KA-or MPTP-induced degenerative neurons including cell bodies and processes could be clearly visualized by FJB stain dye.In the brain sections,FJB-positive stained degenerative neurons were numerously observed in the striatum of KA-lesion rats and the substantia nigra pars compacta of MPTP-treated mice,but not detected in the control animals.Moreover,degenerative neurons were also detected with FJB stain in cultured striatal neurons.Semi-quantitative analysis on percentage(?s) of FJB-positive neurons constituting total cultured striatal neurons in unit area showed that degenerative neurons of KA-lesion group (8.42?1.09)% was evidently more than that of controls (3.42?0.45)%,P