The clinical performance of hybrid bridges delivered by undergraduate dental students: a retrospective study

The aim of this study was to retrospectively analyse the clinical performance of hybrid bridges and their effect on periodontal health. All the bridges in this study were delivered by undergraduate dental students at the University Dental School and Hospital Cork. The recall protocol took the form of a questionnaire and a full clinical examination of the abutments, retainers and contra lateral control teeth. In all, 22 patients with 25 bridges were examined. The periodontal response was generally favourable and soft tissue alteration was minimal. The outcome of the performance hybrid bridges is not encouraging, as 32% (8) of the bridges failed and 68% (17) were in service with a mean duration of clinical service of 48 months.     

Glutathione accelerates sodium channel inactivation in excised rat axonal membrane patches

The effects of glutathione were studied on the gating behaviour of sodium channels in membrane patches of rat axons. Depolarizing pulses from –120 to –40 mV elicited sodium currents of up to 500 pA, indicating the simultaneous activation of up to 250 sodium channels. Inactivation of these channels in the excised, inside-out configuration was fitted by two time constants ( _h1=0.81 ms; _h2= 5.03 ms) and open time histograms at 0 mV revealed a biexponential distribution of channel openings ( _short=0.28 ms; _long=3.68 ms). Both, the slow time constant of inactivation and the long lasting single channel openings disappeared after addition of the reducing agent glutathione (2–5 mM) to the bathing solution. Sodium channels of excised patches with glutathione present on the cytoplasmatic face of the membrane had inactivation kinetics similar to channels recorded in the cell-attached configuration. These observations indicate that redox processes may contribute to the gating of axonal sodium channels.     

Cyclic disulfide analogues of the complement component C3a Synthesis and conformational investigations

The flexible C-terminal region of the anaphylatoxic peptide C3a was reported to contain the receptor binding site. To elucidate the receptor binding conformation of the C-terminus, as well as to examine a synthetic approach to potential C3a-antagonists, 26 cyclic disulfide bridged C3a analogues were synthesized. Solid phase peptide synthesis was performed on different polymeric supports by individual peptide synthesis, with Fmoc strategy, and simultaneous multiple peptide synthesis, using Boc and Fmoc strategies. Both strategies gave open-chain peptides in comparable yields. Syntheses using the Boc strategy employed the HF-labile 4(methoxy)benzyl group (Mob) for β-thiol protection of cysteine; in contrast, the TFA-stable protecting groups, acetamidomethyl (Acm) and trityl (Trt), were chosen for syntheses employing Fmoc strategy. Ring closure reactions by iodine oxidation were carried out starting from protected (Acm/Acm, Trt/Acm) or unprotected dithiols. The resulting cyclic C3a analogues were characterized by HPLC, amino acid analysis, and FAB-MS. Conformational investigations using CD spectroscopy and theoretical structural investigations by means of molecular dynamics calculations revealed that slight variations in sequence result in pronounced conformational consequences. The potential of cyclic C3a analogues to activate or to desensitize guinea pig platelets, a standard test system for biological activities of anaphylatoxic peptides like C3a, revealed relatively low activities for cyclic peptides (<0.1% C3a activity). N-terminal acylation with cationic, arginine-rich sequences like YRRGR- led to amplified biological effects. Three of the synthesized peptides, namely CAALCLAR (P1), YRRGR°CGGLCLAR (P5) and YRRGRAhx°CGGLCLAR (P8), point in the direction of C3a antagonists.     

Cystine peptides Antiparallel β-sheet conformation of the cyclic biscystine pep tide [Boc-Cys-Ala-Cys-NHCH3]2

The crystal structure analysis of the cyclic biscystine peptide [Boc-Cys¹-Ala²-Cys³-NHCH₃]₂ with two disulfide bridges confirms the antiparallel β-sheet conformation for the molecule as proposed for the conformation in solution. The molecule has exact twofold rotation symmetry. The 22-membered ring contains two transannular NH ? OC hydrogen bonds and two additional NH ? OC bonds are formed at both ends of the molecule between the terminal (CH₃)₃COCO and NHCH₃ groups. The antiparallel peptide strands are distorted from a regularly pleated sheet, caused mainly by the L-Ala residue in which φ=– 155° and ψ= 162°. In the disulfide bridge C^α (1)-C^β (1)-S(1)-(3′)-C^β(3′)-C^α(3′), S—S = 2.030 Å, angles C^β SS = 107° and 105°, and the torsional angles are –49, –104, +99, –81, –61°, respectively. The biscystine peptide crystallizes in space group C2 with a = 14.555(2) Å, b = 10.854(2) Å, c = 16.512(2)Å, and β= 101.34(1) with one-half formula unit of C₃₀H₅₂N₈O₁₀S₄· 2(CH₃)₂SO per asymmetric unit. Least-squares refinement of 1375 reflections observed with |F| > 3σ(F) yielded an R factor of 7.2%.     

多层螺旋CT冠状动脉成像技术在诊断冠状动脉壁血管-心肌桥的临床应用

目的：分析壁血管-心肌桥（MB—MCA）在16层螺旋CT（MSCT）冠状动脉（简称冠脉）成像的图像特征。方法：通过回顾性分析经MSCT检查临床疑似冠心病（CHD）患者300例中检出的67例MB—MCA影像学特点,并判断MB—MCA与动脉粥样硬化的关系。结果：MB—MCA在MSCT的检出率为22．3％,最常出现在左前降支,壁血管平均长度为13．1mm,心肌桥厚度为1．6mm,合并临近血管动脉粥样硬化为29.9％。结论：MSCT可用于判断MB—MCA的结构特点;MB—MCA与动脉粥样硬化有相关性。     

Fully synthetic immunogens

The bis-cysteinyl hinge-fragment 225–232 of human IgG1 has been extended at the N- or C-terminus with Nle¹⁵-desamido-human-little-gastrin-[5-17] and Nle¹⁵-human-little-gastrin-[5-17]-NH₂, respectively. Thermodynamically controlled air oxidation of the resulting bis-cysteinyl-peptides led to the predominant formation of the corresponding dimers in parallel alignment despite the incorporation of the immunoglobulin-unrelated gastrin-sequences. These surprising results confirm the high degree of structural information inherent in the hinge-sequence and its intrinsic tendency to fold into the correct structure in terms of cysteine pairings. This protein subdomain-the hinge-peptide-is therefore well suited as core molecule for the design of fully synthetic immunogens with multiple attachment of antigenic determinants.     

Pathology of mitosis after recovery of cells from metaphase block

Experiments on fibroblast-like Chinese hamster cells showed that agents inducing c-mitosis (colchicine, colcemid, low temperature) give rise to two distinct effects: stathmokinetic and radiomimetic. Toward the time of reversibility of the first of these effects, the second becomes clearly manifested as bridge formation. The appearance of this pathological form is evidently due to disturbance of cell nucleoprotein metabolism during c-mitosis.Institute of Human Morphology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 87, No. 6, pp. 587–589, June, 1979.     

高速铁路三塔斜拉桥车桥动力分析

进行了高速铁路南京越江方案中三塔斜拉桥的车桥耦合振动分析.分析采用有限元等数值计算方法,建立了车桥动力学方程.计算结果表明,三塔斜拉桥方案具有较好的动力性能,基本满足行车安全和乘客舒适性的要求.还指出,只要桥梁的自振频率远离列车的激励频率,按静力计算的桥梁横向和竖向刚度一般都能满足现有规定的要求.