Loss of lamin A/C expression revealed by immuno-electron microscopy in dilated cardiomyopathy with atrioventricular block caused by<Emphasis Type="Italic"> LMNA</Emphasis> gene defects

Mutations of the LMNA gene encoding the lamin A and C nuclear envelope proteins cause an autosomal dominant form of dilated cardiomyopathy (DCM) with atrioventricular block (AVB). The aim of this study was to investigate ultrastructural nuclear membrane changes by conventional electron microscopy and protein expression by immuno-electron microscopy in the heart of patients with DCM and AVB due to LMNA gene mutations. Four immunohistochemical techniques were used: pre-embedding and post-embedding in Epon-Araldite resin and London Resin White (LRW), with and without silver enhancement. Parallel light microscopy immunohistochemistry studies were performed. Conventional electron microscopy showed a loss of integrity of the myocyte nuclei with blebs of the nuclear membrane, herniations and delamination of the nuclear lamina and nuclear pore clustering. Post-embedding LRW was the most informative technique for morphology and immuno-labelling. Immuno-labelling was almost absent in the nuclear envelope of patients with LMNA gene mutations, but intensely present in controls. The loss of labelling selectively affected myocyte nuclei; the endothelial cell nuclei were immunostained in patients and controls. Light immunohistochemistry confirmed the results. These findings confirm the hypothesis that LMNA gene defects are associated with a loss of protein expression in the selective compartment of non-cycling myocyte nuclei.     

Molecular and Microdomain Orientation in Semicrystalline Block Copolymer Thin Films by Directional Crystallization of the Solvent and Epitaxy

The directional crystallization of crystallizable organic solvents and the subsequent epitaxial crystallization of crystalline blocks onto the surface of crystalline substrates in semicrystalline block copolymers, control both molecular chain orientation of the crystalline block and the microdomain structure of the block copolymer. Thin film of semicrystalline polystyrene‐block‐poly(ethylene‐alt‐propylene)‐block‐polyethylene (PS/PEP/PE) terpolymer and polystyrene‐block‐polyethylene (PS/PE) diblock copolymer, which both contain crystallizable polyethylene (PE) blocks, have been patterned using benzoic acid (BA) and anthracene (AN) as crystallizable solvents. The directional crystallization induces orientation of the microdomains and epitaxy, due to the crystallographic matching of unit cells between the crystalline PE blocks and the crystalline organic substrates, resulting in the development of highly aligned crystalline PE blocks. The orientation of the PE crystals onto the substrate is evidenced by selected area electron diffraction and bright field transmission electron microscope images. In the case of the PS/PEP/PE terpolymer, the process induces the PS cylinders to align parallel to the b axis of the BA crystals. Long crystalline PE lamellae are oriented edge‐on on the BA surface, with the b axis of PE parallel to the b axis of BA, and parallel to the PS cylinders. In the case of the PS/PE diblock copolymer, the PE cylinders are oriented perpendicular to substrate, packed on a hexagonal lattice. Each cylinder contains precisely one crystalline PE lamella oriented edge‐on on the substrate. When BA is used, the PE lamellae inside cylinders are oriented with the b axis parallel to the b axis of BA crystals. When AN is used, due to the different epitaxial relationship between PE block and AN crystals, the PE lamellae are oriented along two equivalent directions, with the c axis parallel to the [110] and direction of AN crystals.

Schematic model of the final microstructure generated by combination of the directional crystallization and epitaxy.     

Agarose cell block: innovated technique for the processing of urine cytology for electron microscopy examination

Easy manipulation and preservation of cells in suspension through the different steps of sample processing for electron microscopy examination is essential for proper diagnosis. The author used agarose gel as an embedding media for processing cells in suspension for electron microscopic examination. The AgarCyto cell block procedure of Kerstens et al. (J Histochem Cytochem. 2000; 48: 709—718) was used to begin electron microscopic processing of exfoliated urothelial cells in voided urine or cells in suspension. Processing of agarose cell block simultaneously for light and electron microscopic examination represents a great advantage offered by this innovated technique.     

Unidirectional block in a computer model of partially coupled segments of cardiac Purkinje tissue

The initiation of a reentrant circuit requires a zone of slow conduction and a zone of unidirectional block. This study used computer model conditions under which partial coupling between segments of cardiac Purkinje tissue resulted in unidirectional block. The structure used was one-dimensional and divided into three segments: a middle segment of variable length coupled to two long (semi-infinite in concept) segments. The DiFrancesco-Noble equations represented the ionic currents of the membrane. The results show that the possibility of unidirectional block depends on the size of the middle segment and the coupling resistances between the segments. No combination of coupling resistances allowed unidirectional block for middle segments with a length of two space constants (4 mm) or longer. Unidirectional block occurred for many combinations of coupling resistances as the length of the middle segment decreased to around half a space constant (1 mm). The number of length combinations that caused unidirectional block decreased again as segment length further decreased. These results provide a possible mechanism of unidirectional block for situations where islands of viable tissue are connected through nonviable tissue, such as in a healed myocardial infarction.     

臂内侧入路臂丛阻滞麻醉的解剖学基础

目的：为臂内侧入路臂丛阻滞麻醉提供解剖学基础。方法：①尸体解剖观测臂内侧血管神经鞘；②模拟注射造影剂后X线造影和CT扫描观察造影剂扩散范围；③选择合适病例临床应用。结果：①臂内侧血管神经鞘与腋鞘相通；②臂内侧血管神经鞘注射有色液体后，鞘内各主要神经干均被染色；③造影剂可以于臂内侧鞘内向上、向下扩散；④临床应用225例，成功211例，成功率93．8％。结论：臂内侧人路臂丛阻滞麻醉具有操作简便，成功率高，无严重并发症的优点，特别适用于前臂及手部手术麻醉。     

The flickery block of ATP-dependent potassium channels of skeletal muscle by internal 4-aminopyridine

We have examined the effects of 4-aminopyridine (4-AP) on single ATP-dependent potassium channels in patches excised from frog skeletal muscle. 4-AP applied to the internal face of the membrane caused a flickery block. We could not detect any flickery block when 10 mM 4-AP was applied to the external surface of the membrane. The reduction in mean unitary current by internal 4-AP was consistent with 11 binding with a K _d of 3.3 mM at 0 mV. The block was voltage-dependent, increasing with depolarization with an effective valency of 0.57. Rate constants for blocking and unblocking by 4-AP were obtained by fitting functions to the distribution of current amplitudes. Both rate constants were voltage-dependent. At 0 mV they were 17 mM^–1 ms^–1 and 61 ms^–1. Simulation of the block using these rate constants produced a flickery block very similar to that observed experimentally.     

A way of preventing the free fatty acid concentration in the serum of rabbits from rising

A scheme of administration of nicotinic acid by mouth is suggested in order to prevent any increase in the free fatty acid concentration in the serum after intravenous injection of heparin or triiodothyronine, prolonged starvation, and thyroid feeding.Laboratory of Pathological Physiology, Institute of Experimental Endocrinology and Hormone Chemistry, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Yudaev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 78, No. 8, pp. 122–125, August, 1974.     

Diblock Copolymers Based on 1,4‐Dioxan‐2‐one and ε‐Caprolactone: Characterization and Thermal Properties

Summary: Various poly(ε‐caprolactone‐block‐1,4‐dioxan‐2‐one) (P(CL‐block‐PDX)) block copolymers were prepared according to the living/controlled ring‐opening polymerization (ROP) of 1,4‐dioxan‐2‐one (PDX) as initiated by in situ generated ω‐aluminium alkoxides poly(ε‐caprolactone) (PCL) chains in toluene at 25 °C. 1 ¹H NMR, PCS and TEM measurements have attested for the formation of colloids attributed to a growing PPDX core surrounded by a solvating PCL shell during the polymerization of PDX promoted by ω‐Al alkoxide PCL chains in toluene. The thermal behavior of the P(CL‐block‐PDX) copolymers was studied by DSC; showing two distinct melting temperatures (as well as two glass transition temperatures) similar to those of the respective homopolyesters. Finally, the thermal degradation of the P(CL‐block‐PDX) block copolymers was investigated by TGA simultaneously coupled to a FT‐IR spectrometer and a mass spectrometer for evolved gas analysis (EGA). The degradation occurred in two consecutive steps involving a first unzipping depolymerization of the PPDX blocks followed by the degradation of the PCL blocks via both ester pyrolysis and unzipping reactions.

TEM observation of P(CL‐block‐PDX) block copolyesters ( = 11 600 and = 22 100) as formed by vaporization starting from a diluted suspension in toluene/TCE mixture solvent (50/50 v/v).     

A Novel Macroinitiator for the Synthesis of Triblock Copolymers via Atom Transfer Radical Polymerization: Polystyrene‐block‐poly(bisphenol A carbonate)‐block‐polystyrene and Poly(methyl methacrylate)‐block‐poly(bisphenol A carbonate)‐block‐poly(methyl methacrylate)

Summary: Bis(hydroxy)telechelic bisphenol A polycarbonate (PC) was prepared via melt polycondensation of bisphenol A (BPA) and diphenyl carbonate (DPC) using lanthanum(III ) acetylacetonate as a catalyst for transesterification. Subsequently, the polycarbonate was converted to a bifunctional macroinitiator for atom transfer radical polymerization (ATRP) with the reagent, α‐chlorophenylacetyl chloride. The macroinitiator was used for the polymerization of styrene (S) and methyl methacrylate (MMA) to give PS‐block‐PC‐block‐PS and PMMA‐block‐PC‐block‐PMMA triblock copolymers. These block copolymers were characterized by NMR and GPC. When styrene and methyl methacrylate were used in large excess, significant shifts toward high molecular weights were observed with quantitative consumption of the macroinitiator. Several ligands were studied in combination with CuCl as the ATRP catalyst. Kinetic studies reveal the controlled nature of the polymerization reaction for all the ligands used.

Formation of a bifunctional ATRP macroinitiator by esterification of bis(hydroxy)telechelic PC with α‐chlorophenylacetyl chloride.     

Pathological Aspects of Radiofrequency Catheter Ablation of the Canine Atrioventricular Node and Bundle of His

Radiofrequency catheter ablation of the atrioventricular (AV) node or bundle of His was performed in 12 adult mongrel dogs. The aim was to create chronic incomplete AV block (first- and second-degree AV block) and to examine the histopathology of the ablated lesions. However, the late electrophysiological results (2 4 weeks follow up) were various: normal in 2 dogs, mild PR prolongation (< 50%) in 2 dogs, first-degree AV block (PR prolongation a 50%) in 2 dogs, second degree AV block in 2 dogs, complete AV block in 4 dogs. The maximally ablated area (%) of the atrioventricular conduction system in serial histologic sections from dogs with these conditions was 69%, 75%, 89.5%, 95% and 99.5%, respectively. The number of intact conduction cells at the maximally ablated site varied from 6 to 30 in the four cases of incomplete AV block. The mean ablated volume (%) of either the AV node or penetrating His bundle correlated roughly with the degree of AV block. The ablated lesions were well demarcated and almost replaced by dense fibrous tissue at 4 weeks. Interruption (3 dogs) or thinning (1 dog) of the endocardial elastic lamellae was detected, in association with endocardial thickening (mean 913 μm). Endocardial thrombi were found in 3 dogs (2 fresh, 1 organized). We conclude that radiofrequency catheter ablation does not cause severe complicated lesions. Several possible conditions for creating chronic incomplete AV block are discussed. Acta Pathol Jpn 41: 487–498, 1991.