Distinct conformations of the protein complex p97-Ufd1-Npl4 revealed by electron cryomicroscopy

p97 is a key regulator of numerous cellular pathways and associates with ubiquitin-binding adaptors to remodel ubiquitin-modified substrate proteins. How adaptor binding to p97 is coordinated and how adaptors contribute to substrate remodeling is unclear. Here we present the 3D electron cryomicroscopy reconstructions of the major Ufd1-Npl4 adaptor in complex with p97. Our reconstructions show that p97-Ufd1-Npl4 is highly dynamic and that Ufd1-Npl4 assumes distinct positions relative to the p97 ring upon addition of nucleotide. Our results suggest a model for substrate remodeling by p97 and also explains how p97-Ufd1-Npl4 could form other complexes in a hierarchical model of p97-cofactor assembly.     

Dicyanovinylnaphthalenes for neuroimaging of amyloids and relationships of electronic structures and geometries to binding affinities

The positron-emission tomography (PET) probe 2-(1-[6-[(2-fluoroethyl)(methyl)amino]-2-naphthyl]ethylidene) (FDDNP) is used for the noninvasive brain imaging of amyloid-β (Aβ) and other amyloid aggregates present in Alzheimer’s disease and other neurodegenerative diseases. A series of FDDNP analogs has been synthesized and characterized using spectroscopic and computational methods. The binding affinities of these molecules have been measured experimentally and explained through the use of a computational model. The analogs were created by systematically modifying the donor and the acceptor sides of FDDNP to learn the structural requirements for optimal binding to Aβ aggregates. FDDNP and its analogs are neutral, environmentally sensitive, fluorescent molecules with high dipole moments, as evidenced by their spectroscopic properties and dipole moment calculations. The preferred solution-state conformation of these compounds is directly related to the binding affinities. The extreme cases were a nonplanar analog t-butyl-FDDNP, which shows low binding affinity for Aβ aggregates (520 nM K_i) in vitro and a nearly planar tricyclic analog cDDNP, which displayed the highest binding affinity (10 pM K_i). Using a previously published X-ray crystallographic model of 1,1-dicyano-2-[6-(dimethylamino)naphthalen-2-yl]propene (DDNP) bound to an amyloidogenic Aβ peptide model, we show that the binding affinity is inversely related to the distortion energy necessary to avoid steric clashes along the internal surface of the binding channel.     

Conformational state of the MscS mechanosensitive channel in solution revealed by pulsed electron–electron double resonance (PELDOR) spectroscopy

The heptameric mechanosensitive channel of small conductance (MscS) provides a critical function in Escherichia coli where it opens in response to increased bilayer tension. Three approaches have defined different closed and open structures of the channel, resulting in mutually incompatible models of gating. We have attached spin labels to cysteine mutants on key secondary structural elements specifically chosen to discriminate between the competing models. The resulting pulsed electron–electron double resonance (PELDOR) spectra matched predicted distance distributions for the open crystal structure of MscS. The fit for the predictions by structural models of MscS derived by other techniques was not convincing. The assignment of MscS as open in detergent by PELDOR was unexpected but is supported by two crystal structures of spin-labeled MscS. PELDOR is therefore shown to be a powerful experimental tool to interrogate the conformation of transmembrane regions of integral membrane proteins.     

Late-onset intermittent fasting dietary restriction as a potential intervention to retard age-associated brain function impairments in male rats

Lifelong dietary restriction (DR) is known to have many potential beneficial effects on brain function as well as delaying the onset of neurological diseases. In the present investigation, the effect of late-onset short-term intermittent fasting dietary restriction (IF-DR) regimen was studied on motor coordination and cognitive ability of ageing male rats. These animals were further used to estimate protein carbonyl content and mitochondrial complex I-IV activity in different regions of brain and peripheral organs, and the degree of age-related impairment and reversion by late-onset short-term IF-DR was compared with their levels in 3-month-old young rats. The results of improvement in motor coordination by rotarod test and cognitive skills by Morris water maze in IF-DR rats were found to be positively correlated with the decline in the oxidative molecular damage to proteins and enhanced mitochondrial complex IV activity in different regions of ageing brain as well as peripheral organs. The work was further extended to study the expression of synaptic plasticity-related proteins, such as synaptophysin, calcineurin and CaM kinase II to explore the molecular basis of IF-DR regimen to improve cognitive function. These results suggest that even late-onset short-term IF-DR regimen have the potential to retard age-associated detrimental effects, such as cognitive and motor performance as well as oxidative molecular damage to proteins.     

Autologous Platelet Rich Plasma After Third Molar Surgery: A Comparative Study

Purpose

This study is an attempt to evaluate the use of autologous platelet rich plasma (PRP) to promote wound healing and osseous regeneration in human third molar extraction sockets.

Materials and method

PRP was prepared after two centrifugation and the gelling agent used was freshly prepared 10% calcium chloride.PRP gel was placed in one of the extracted sockets of bilateral impacted mandibular third molars. IOPA Xrays were used to evaluate the wound dehiscence, probing depth, bone density & alveolar bone level after 1st, 2nd and 7th day and 3rd & 6th month respectively.

Results

On evaluation, it was found that PRP grafted sockets showed dehiscence in 8% cases. The decrease in alveolar bone level was highly significant in PRP grafted sockets in 3rd and 6th month post operatively. There was significant difference between pre-operative density of adjacent bone and bone formed in extraction sockets at 3rd and 6th month in PRP grafted sockets. There was significant reduction in probing depth from initial period to 3 and 6 months in both the groups, but PRP grafted sockets showed greater decrease in probing depth.

Conclusion

PRP is an inexpensive and widely available modality to minimize postoperative complication and enhance both hard and soft tissue healing potentials. This autologous product eliminates concern about immunogenic reaction and disease transmission. Its beneficial outcomes in dental clinic, including decrease in bleeding and rapid wound healing hold promise for further procedures.PRP is thus a new application in tissue engineering and developing area for clinician and researchers.     

不同皮肤扩张方式对皮瓣的超微结构和回缩率的影响

目的研究反复快速扩张、单纯快速扩张及常规扩张对皮瓣的超微结构和回缩率的影响,以探讨适合于临床的最佳皮肤扩张方式。方法用兔制备动物模型,随机将动物分为反复快速扩张组(A组)、单纯快速扩张组(B组)、常规扩张组(C组)、植入不扩组(D组)和正常对照组(E组),扩张后分别维持1周、2周、3周、4周以及6周,透射电镜下观察扩张皮瓣超微结构的变化,分格测量法计算回缩率。结果透射电镜观察:维持扩张1周后,A、B、C三组的基底细胞胞质可见少量的表面张力细丝,基底膜部分断裂,成纤维细胞胞质内,有丰富的粗面内质网,线粒体数量明显增加,A组的细胞功能最为活跃;维持扩张4周后,A、B、C三组基底膜基本恢复,成纤维细胞胞质内,细胞器数量明显减少,线粒体大部分嵴或膜融合。回缩率比较:A、B、C及D组在相同扩张维持期,回缩率均高于E组;A、B、C组回缩率随时间延长均呈下降趋势;A、C组与B组比较,维持1、2、3和4周,回缩率均下降;A组与C组比较,维持1和2周,回缩率增加。结论采用反复快速扩张方式,能获取回缩率及质量相同的皮瓣,并可缩短疗程。     

Podoplanin在口腔鳞状细胞癌中的表达及与淋巴结转移的关系

目的:采用淋巴管特异性标志物podoplanin标记口腔鳞癌组织和正常口腔组织中的淋巴管,并计数淋巴管密度(lymphatic vessel density,LVD)值,探讨口腔鳞癌及癌周淋巴管密度与淋巴结转移的相关性及可能机制。方法:采用免疫组织化学方法检测21例正常口腔黏膜组织和88例口腔鳞癌患者组织的podoplanin表达;用podoplanin标记淋巴管,并计数口腔鳞癌和癌周组织的淋巴管密度。采用SPSS13.0软件包对数据进行t检验,分析正常组织和癌组织、淋巴结转移组和未转移组的淋巴管密度(癌周、癌内)。结果:口腔鳞癌及癌周组织的淋巴管密度均高于正常口腔黏膜组织,有显著差异(P<0.05)。癌组织内淋巴管小而闭锁,癌组织周围的淋巴管大而扩张;淋巴结转移组的癌周淋巴管密度(14.270±4.610)显著高于无转移组(9.450±2.411),差异具有显著性(P<0.05),癌组织淋巴管密度在2组间无显著差异。结论:口腔鳞癌患者癌周淋巴管的生成可能是影响区域淋巴结转移的重要因素。     

The role of single immediate loading implant in long class IV Kennedy mandibular partial denture

Background: The treatment of long‐span Kennedy class IV considers a prosthodontic challenge. This study evaluated the integrity of principle abutments in long Kennedy class IV clinically and radiographically, when rehabilitated with conventional metallic partial denture as a control group and mandibular partial overdentures supported with single immediately loaded implant in symphyseal as a study group. Material and Methods: Twelve male patients were divided randomly allotted into two equal groups. First group patients received removable metallic partial denture, whereas in the second group, patients received partial overdentures supported with single immediately loaded implant in symphyseal region. The partial dentures design in both groups was the same. Long‐cone paralleling technique and transmission densitometer were used at the time of denture insertion, 3, 6, and 12 months. Gingival index, bone loss, and optical density were measured for principle abutments during the follow‐up. Results: A significant reduction in bone loss and density were detected in group II comparing with group I. Gingival index had no significant change (p‐value < 0.05). Conclusion: A single symphyseal implant in long span class IV Kennedy can play a pivotal role to improve the integrity of the principle abutments and alveolar bone support.     

牙龈卟啉单胞菌感染血管平滑肌细胞的超微结构观察

目的:观察牙龈卟啉单胞菌(Porphyromonas gingivalis,Pg)对大鼠胸大动脉平滑肌细胞黏附及入侵情况,探讨Pg对血管平滑肌细胞的损伤途径,为牙周病在动脉粥样硬化发病机制中的研究提供依据.方法:用感染复数(multiplicity of infection,MOD为100∶1 Pg感染大鼠胸大动脉平滑肌细胞,分别于8、16 h TEM观察Pg对血管平滑肌细胞的黏附和入侵能力.结果:Pg感染大鼠胸大动脉平滑肌细胞16h时,Pg能利用表面菌毛黏附于血管平滑肌细胞表面并入侵胞质内.结论:Pg能够黏附于大鼠胸大动脉平滑肌细胞,并入侵细胞质,定植于细胞内.     

儿童前牙区牙槽骨和基骨骨密度的锥形束CT测量

目的评估儿童前牙区上下颌牙槽骨和基骨的骨密度。方法选择138例患者的锥形束CT扫描图像,以亨斯菲尔德单位(X线衰减单位Hu)来测定其上下颌切牙区、尖牙区牙槽嵴和基骨骨密质及骨松质的骨密度。结果上颌切牙区左右两侧相同部位间的骨密度值相比较,差异没有统计学意义(P>0.05);下颌切牙区左右两侧相同部位的骨密度值相比较,基骨区舌侧骨密质的骨密度值差异有统计学意义(P=0.012);上颌尖牙区左右两侧相同部位的骨密度值相比较,差异没有统计学意义(P>0.05);下颌尖牙区左右两侧相同部位的骨密度值相比较,牙槽骨和基骨区骨松质的骨密度值差异有统计学意义,P值分别为0.046和0.002。结论本研究可为前牙区微螺旋种植体植入位置和方法提供一定的数据。