Intercellular bridges between megalospermatocytes in the human testis

The occurrence of intercellular bridges connecting megalospermatocytes in the human testis has been documented by means of light and electron microscopy. Thereby, the clonal character of this special form of male germ cell degeneration has been substantiated. In the course of the cellular degeneration, the intercellular bridges themselves enter a degenerative process. This process, involving the invagination and subsequent internalization of the bridge into the cytoplasm of one of the megalospermatocytes concerned, finally leads to disconnection of the cells and thus to the termination of the former clonal condition. Several clones of megalospermatocytes include additional cells which, while being bridge-connected to typical megalospermatocytes, exhibit a considerably different but likewise degenerative morphology. The cause of this occasionally occurring intraclonal heterogeneity of the megalospermatocyte morphology is discussed.     

Formation of cytotoxic transthyretin is not dependent on inter-molecular disulphide bridges commonly found within the amyloid form

Familial amyloidotic polyneuropathy (FAP) is linked to destabilising point mutations in the human plasma protein transthyretin (TTR). Consistent with similar amyloid disorders, low molecular weight TTR oligomers have been shown to exert the major cytotoxic effect. The amyloid structure of TTR contains non-native inter-molecular disulphide linkages via the cysteine at position 10 (Cys10). Moreover, substitution of Cys10 in a mouse model for TTR-amyloidosis abolishes TTR deposits, indicating an important role of Cys10 in FAP pathogenesis. However, the role of disulphide bridges in TTR cytotoxicity has not been elucidated. By probing Cys10Ser TTR variants to the human neuroblastoma SH-SY5Y cell line, we have addressed this question, and our results clearly show that formation of an inter-molecular disulphide bridge is not a pre-requisite for TTR cytotoxicity. This finding suggests that prevention of inter-molecular TTR disulphide bridges as a therapeutic intervention will not impair the cytotoxic potential of TTR.     

Silicoating: evaluation of a new method of bonding composite resin to metal

Abstract — Silicoating is a new type of pretreatment of the metal in the resin-bonded bridge technique. The size of bond strength between resin cement and silicoated metal was investigated. Different resin cements, types of metal, and grain sizes of sand used for roughening the metal surface were tested. Furthermore, the effect on the bond strength of contamination with saliva and of thermocycling was measured. There was no difference of importance between the two resin cements tested. Bond strengths obtained with Wirobond were the highest and insensible to changes in resin cement, grain size of sand, and to thermocycling. It was found that sand of the smallest grain size used brought about the highest bond strengths. Contamination with saliva did not significantly reduce the size of the bond strengths. Rinsing the metal surfaces with water or ethanol after contamination restored the bond strengths to their original magnitude. By silicoating, a greater resistance to thermocycling was obtained. Nevertheless, except for Wirobond, a fall in bond strength was measured after thermocycling. Bond strengths of the size of those between etched enamel and composite resin were measured, and the Silicoater method seems a reliable pretreatment of the metal.     

LOCATION OF DISULFIDE BRIDGES IN CARDIOTOXIN FROM THE VENOM OF FORMOSAN COBRA (NAJA NAJA ATRA)

The location of the four disulfide bridges in cardiotoxin from the venom of the Formosan cobra, Naja naja atra, was determined by isolating cystine-containing peptides from the enzymic and partial acid hydrolyzates of the intact toxin. The results indicate that the disulfide bridges are formed by half cystine residues 3–21, 14–38, 42–53, and 54–59. The amino acid sequence at the position 48–49 was revised to -Leu-Val- instead of -Val-Leu- as reported previously.     

Pathomorphology and pathogenic role of myocardial bridges in sudden cardiac death

Pathognomonic incidence of myocardial bridges during obstructive hypertrophic cardiomyopathy, hypertension, and ischemic heart disease was established. Myocardial bridges were predominantly found in the median segments of major coronary arteries with prevailence of bridge-like obstructions in the anterior interventricular branch of the left coronary artery. Typical changes in cardiac angioarchitectonics indicating pronounced inadequacy of coronary blood flow were determined depending on the segmentary directionality of bridge obstruction. The data attest to pronounced pathogenetic role of myocardial bridges in sudden cardiac death. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 138, No. 7, pp. 101–106, July, 2004     

心肌桥和壁冠状动脉的多层螺旋CT诊断及其临床意义

目的探讨心肌桥-壁冠状动脉(MB-MCA)的多层螺旋CT(MSCT)诊断和与冠脉硬化的关系。方法应用64层螺旋CT对可疑冠心病(CHD)者,行冠状动脉血管成像(CTA),3名CT诊断医师独立判断MB-MCA的存在,结果一致时确定为MB-MCA。测量壁冠状动脉(MCA)长度、肌桥(MB)厚度,结果用平均数±标准差表示,记录MB-MCA近、远段血管形态变化。根据这三项指标,提出载MB-MCA冠脉积分计算方法。确定载MB-MCA冠脉硬化情况,应用秩和统计分析,判断血管硬化与MB-MCA的关系。结果900例可疑CHD者,冠脉CTA发现MB-MCA167例(18.56%,167/900),180处。MB-MCA位于左前降支者占92.78%(167/180)。MSCT显示MCA可被心肌完全包绕(36.11%,65/180)或不完全包绕(63.89%,115/180)。MCA长度为18.7mm±10.2mm。MB厚度为1.7mm±1.2mm。70%的MCA前段和/或远段邻近血管走行迂曲成角。载MB-MCA冠脉积分评分方法MCA长度<10mm、MB不全包绕血管、邻近血管平滑,每项1分;MCA长度10~20mm、MB<1mm、邻近血管一侧成角,每项2分;MCA程度>20mm、MB>1mm、邻近血管近、远段两侧成角,每项3分。167例中,88例可见冠状动脉硬化征象(52.69%),统计学结果提示载MB-MCA冠脉硬化与MB-MCA形态积分无明显相关(u=1.234,P>0.05)。结论64层螺旋CT可用于判断MB-MCA和载MB-MCA冠脉的结构特征;临床怀疑CHD者MB-MCA检出率为18.56%;载MB-MCA冠脉硬化与MB-MCA形态积分无明显相关。     

Material Behavior and Fatigue Assessment of Old Steel Bridges of the Spanish Conventional Rail Network

This work presented salient features of the steel behavior of seven metallic bridges close to, or over, 100 years old, among the Spanish conventional rail network as well as the results of a fatigue life expectancy study. A preliminary study of the properties of the constituent materials obtained from the bridges samples was carried out followed by dynamic fatigue tests under service representative loads. Due to the steelmaking techniques in the late 19th and early 20th centuries, disperse fatigue behavior results were obtained. However, the wide safety margins with which these bridges were designed, as well as the mechanical properties of the steel (relatively good mechanical resistance but with low ductility), seem to guarantee a long fatigue life. This estimate decreases sharply with increasing loads.     

A systematic review of the survival and complication rates of resin-bonded bridges after an observation period of at least 5 years

OBJECTIVES: The objectives of this systematic review were to assess the 5-year survival of resin-bonded bridges (RBBs) and to describe the incidence of technical and biological complications. METHODS: An electronic Medline search complemented by manual searching was conducted to identify prospective and retrospective cohort studies on RBBs with a mean follow-up time of at least 5 years. Patients had to have been examined clinically at the follow-up visit. Assessment of the identified studies and data extraction were performed independently by two reviewers. Failure and complication rates were analyzed using random-effects Poissons regression models to obtain summary estimates of 5-year proportions. RESULTS: The search provided 6110 titles and 214 abstracts. Full-text analysis was performed for 93 articles, resulting in 17 studies that met the inclusion criteria. Meta-analysis of these studies indicated an estimated survival of RBBs of 87.7% (95% confidence interval (CI): 81.6-91.9%) after 5 years. The most frequent complication was debonding (loss of retention), which occurred in 19.2% (95% CI: 13.8-26.3%) of RBBs over an observation period of 5 years. The annual debonding rate for RBBs placed on posterior teeth (5.03%) tended to be higher than that for anterior-placed RBBs (3.05%). This difference, however, did not reach statistical significance (P=0.157). Biological complications, like caries on abutments and RBBs lost due to periodontitis, occurred in 1.5% of abutments and 2.1% of RBBs, respectively. CONCLUSION: Despite the high survival rate of RBBs, technical complications like debonding are frequent. This in turn means that a substantial amount of extra chair time may be needed following the incorporation of RBBs. There is thus an urgent need for studies with a follow-up time of 10 years or more, to evaluate the long-term outcomes.     

皮质外骨桥在肿瘤性假体置换术中的作用

目的探讨皮质外骨桥在预防肿瘤性假体术后松动的价值。方法自1997年至今对36例恶性骨肿瘤行瘤段切除人工关节置换术,术中将切下的软骨下骨或松质骨骨条铺放在截骨端与假体相连接处,用10-0丝线捆扎形成皮质外骨桥。结果本组患者均获得6～94个月的随访。死亡10例,3例带瘤生存,余23例无异常。1例因频发抽搐致关节脱位而行截肢术。6个月时,皮质外骨桥形成,并包绕假体周围。其余35例中,20例骨桥环绕假体与截骨断端处,10例骨桥集中在假体的后方和两侧,5例骨桥形成不明显。随访期内2例发生假体松动。结论在肿瘤型假体置换同时将骨条铺放在截骨端与假体连接处形成皮质外骨桥,可有效预防肿瘤性假体的术后松动。