The incidence of myocardial bridges in heart transplants

Coronary angiograms of 64 heart transplant patients were reviewed to determine the incidence of myocardial bridges. In 33% of the patients, myocardial bridges were detected, almost exclusively across the midportion of the left anterior descending coronary artery. The incidence is higher than previously reported in the literature and is thought to be related to increased stiffness and hypertrophy of the myocardium, which facilitates angiographic detection of myocardial bridges in the transplanted heart.     

Casting of TI-6AI-4V alloy compared with pure Ti in an Ar-arc casting machine

Dental protheses of Ti are normally cast in pure Ti. Some appliances, however, require higher yield strength. Casting of Ti alloys is of interest in such cases. The objective of the present work was to study the quality of castings made of Ti-6A–4V compared with those made of pure Ti. Casting was made into a mold kept at room temperature using a MgO-Al2O3 investment. A standardized five-unit bridge was cast, consisting of two cylindrical crowns with sharp margins and three pontics. The overall mold filling was satisfactory. The margins of the casting alloys were, however, more rugged and incomplete than those of pure Ti. The most likely reason for this difference is the increased formation of dendrites in the alloy and thus more resistance to fluid flow. Furthermore, the sprue of the alloy was also found to contain some spherical, internal pores. Such pores were rare in the pure Ti castings. The surface reactions were found to be minimal for both of the materials. Increased casting deficiencies observed in the cast bridges of the Ti-6AI-4V alloy, compared with pure Ti, were: 1) the margins of the crowns in the bridge were less complete and 2) there was a tendency to an increased internal porosity, particularly in the sprues.     

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.     

Reduction and reoxidation of the neurotoxin II from the scorpion Androctonus australis Hector

Reoxidation of the totally reduced scorpion neurotoxin II from Androctonus australis Hector (four disulfide bridges) has been investigated. The totally reduced toxin was highly insoluble in neutral and alkaline conditions, which prevented the use of the usual air oxidation process for renaturation. We tested a new method in which the reduced molecules were first solubilized in 10% (v/v) acetic acid and then oxidized by air through dialysis against a series of buffers with a slow pH gradient from 2.2 to 7.0 or 8.0. In this system, up to 95% of the protein was recovered in solution. Addition of reduced and oxidized glutathione accelerated refolding and also permitted a better recovery of fully active peptide as measured by both toxicity to mice and ability to displace ¹²⁵I radiolabeled toxin II from its binding site on rat brain synaptosomal fractions. The reoxidation reaction could also be monitored directly by high pressure liquid chromatography. A strong effect of guanidine hydrochloride concentration as well as of temperature was observed both on the solubility of the reoxidation intermediates and on the refolding pathway. Finally, the method used, i.e. dialysis reoxidation with a pH gradient from 2.2 to 8.0 in 0.1 M sodium phosphate, 0.1 M sodium chloride, 20 mM guanidine hydrochloride, 1 mM oxidized and reduced glutathione allowed regeneration in high yield (70%) of a reoxidized toxin form indistinguishable from the native toxin. A minor stable and inactive molecular species (about 30%) showing a difference in mobility by electrophoresis was also detected.     

The relationship between the directions of myocardial bridges and of the branches of the coronary arteries in the human heart

Summary The variations of the direction of the myocardial bundles of the bridges over coronary arteries and branches were studied in relation to the direction of the vessels over which they are found. The investigation was performed on 82 hearts of individuals whose death was accidental and unrelated to cardiac disease. The hearts were obtained from cadavers of individuals of either sex and different racial groups, whose age ranged from 7 to 68 years. The angle between the direction of the musculature and of the vessels may explain why in some cases there is no change in the structure of the pontine portion of the wall.

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Relations entre l'axe des ponts myocardiques et les branches des artères coronaires chez l'homme

Résumé Ce travail étudie les variations de direction des fibres des ponts myocardiques et des artères coronaires et de leurs branches recouvertes par ces ponts. Les recherches ont été effectuées sur 82 coeurs de sujets décédés accidentellement et ne présentant aucune pathologie cardiaque. Ces coeurs ont été prélevés sur des sujets des deux sexes et de différents groupes raciaux dont l'âge s'échelonnait entre 7 et 68 ans. L'angle qui existe entre la direction des fibres musculaires et celle des vaisseaux peut expliquer pourquoi dans certains cas il n'y a pas de modification dans la structure de la paroi artérielle au niveau de sa portion pontée.

     

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%.     

Aggrecan,versican and type VI collagen are components of annular translamellar crossbridges in the intervertebral disc

The aim of this study was to undertake a detailed analysis of the structure of the inter and intra-lamellar regions of the annulus fibrosus. A total of 30 newborn to 6 year-old lumbar ovine intervertebral discs (IVDs) were fixed and decalcified en-bloc to avoid differential swelling artifacts during processing and vertical mid-sagittal, and horizontal 4 μm sections were cut. These were stained with toluidine blue to visualise anionic proteoglycan (PG) species, H & E for cellular morphology and picro-sirius red (viewed under polarized light) to examine collagenous organization. Immunolocalisations were also undertaken using anti-PG core-protein and glycosaminoglycan (GAG) side chain antibodies to native chondroitin sulphate (CS), Δ C-4-S and C-6-S unsaturated stubs generated by chondroitinase ABC digestion of CS, keratan sulphate (KS), and with antibodies to type I, II, VI, IX and X collagens. Trans-lamellar cross bridges (TLCBs), discontinuities in annular lamellae’s which provide transverse interconnections, stained prominently with toluidine blue in the adult IVDs but less so in the newborn IVDs. In adult discs TLCBs were evident in both the posterior and anterior AF where they extended from the outermost annular lamellae almost to the transitional zone extending across as many as eight lamellar layers displaying a characteristic circuitous, meandering, serpentine type course. There were significantly fewer TLCBs in 2 week-old compared with skeletally mature sheep and there was a further increase from 2 to 6 years. Immunolocalisation of perlecan delineated blood vessels in the TLBs of the newborn but not adult IVDs extending into the mid AF. In contrast adult but not 2 week-old TLCBs were immunpositive for C-4-S, C-6-S, KS, aggrecan, versican and type VI collagen. The change in number and matrix components of the trans-lamellar cross bridges with skeletal maturity and ageing suggest that they represent an adaptation to the complex biomechanical forces occurring in the annulus fibrosus.     

IPS Empress-2全瓷修复体的临床研究

目的评价IPS Empress-2全瓷修复体的临床效果。方法为51例患者制作了63件IPS Empress-2全瓷冠桥,戴用期为12~36个月,平均24个月,采用美国加利弗尼亚牙科协会评价标准,对修复体边缘完整性、解剖外形、颜色、表面等进行临床评价,并对修复体戴用后的菌斑指数和牙龈指数进行统计学分析。结果IPS Empress-2全瓷冠桥的满意率为96.8%,边缘位于龈上和齐龈的冠桥修复体的牙龈健康状况与对照组无统计学差异,边缘位于龈下的修复体牙龈指数记分为2的比率显著高于对照组。结论IPS Empress-2全瓷修复体的近期修复效果良好。     

Cost-effectiveness modeling of dental implant vs. bridge

Aims: We assess the cost-effectiveness of dental implant first-line strategy vs. fixed partial denture strategy in patients suffering from one single missing tooth.
Materials and methods: The model used a simulation decision framework over a 20-year period. Potential treatment switches can occur every 5 years. Transition probabilities come from literature, epidemiological reports or expert opinions. They have been programmed using specific distribution ranges to simulate the patients' and practice variability, and to take into account parameter uncertainty. Direct medical costs have been assessed according to a cost survey. Probabilistic sensitivity analyses were conducted using 5000 Monte-Carlo simulations, generating confidence intervals of model outcomes.
Results: We found that mean cost-effectiveness of the bridge strategy is higher than the implant strategy.
Conclusion: Implant as the first-line strategy appears to be the 'dominant' strategy, considering the lower overall costs and the higher success rate.