Augmented potassium current is a shared phenotype for two genetic defects associated with familial atrial fibrillation

Mutations in multiple genes have been implicated in familial atrial fibrillation (AF), but the underlying mechanisms, and thus implications for therapy, remain ill-defined. Among 231 participants in the Vanderbilt AF Registry, we found a mutation in KCNQ1 (encoding the α-subunit of slow delayed rectifier potassium current [I_Ks]) and separately a mutation in natriuretic peptide precursor A (NPPA) gene (encoding atrial natriuretic peptide, ANP), both segregating with early onset lone AF in different kindreds. The functional effects of these mutations yielded strikingly similar I_Ks “gain-of-function.” In Chinese Hamster Ovary (CHO) cells, coexpression of mutant KCNQ1 with its ancillary subunit KCNE1 generated ∼ 3-fold larger currents that activated much faster than wild-type (WT)-I_Ks. Application of the WT NPPA peptide fragment produced similar changes in WT-I_Ks, and these were exaggerated with the mutant NPPA S64R peptide fragment. Anantin, a competitive ANP receptor antagonist, completely inhibited the changes in I_Ks gating observed with NPPA S64R. Computational simulations identified accelerated transitions into open states as the mechanism for variant I_Ks gating. Incorporating these I_Ks changes into computed human atrial action potentials (AP) resulted in 37% shortening (120 vs. 192 ms at 300 ms cycle length), reflecting loss of the phase II dome which is dependent on L-type calcium channel current. We found striking functional similarities due to mutations in KCNQ1 and NPPA genes which led to I_Ks “gain-of-function”, atrial AP shortening, and consequently altered calcium current as a common mechanism between diverse familial AF syndromes.     

Toxicity of L-proline toward rat hippocampal neurons

Intrahippocampal injections of L-proline, a neutral amino acid excitant, nonselectively destroyed pyramidal and granule cells. Co-administration of equimolar kynurenate, an excitatory amino acid antagonist, markedly reduced the extent of neuronal cell death. L-Proline destroyed far more hippocampal neurons than D-proline, in keeping with its greater neuroexcitatory potency. L-Proline must therefore be added to the list of excitotoxins present in brain. Its excitotoxic action may be related to the neurological and cognitive deficits associated with hyperprolinemia.     

The transneuronal transport of proline within the mouse visual system: Some characteristics of the [H]-proline containing material

Following the intraocular injection of tritiated proline in the mouse, the progressive transport of radioactivity in the brain and the nature of the cortical material(s) to which the label is bound was examined. About 35–40% of the radioactivity that was present in the cerebral cortex at four weeks post-injection was extractable with either distilled water or various buffers. By using 0.1% SDS this value can be increased up to 94%. Polyacrylamide gel electrophoresis of the extracted proteins showed that a major part of the radioactivity is accumulated in one band of proteins. This heavily labeled band could not be identified in the homolateral parietooccipital cortex or in the frontal cortex. Similarly, SDS electrophoresis of the SDS-extracted proteins also demonstrated the presence of a major band of proteins whose molecular weight was estimated at approximately 68,000 daltons. The protein was purified by ammonium sulfate precipitation and DEAE-Sephadex separation.     

Silk-elastinlike protein polymers for matrix-mediated cancer gene therapy

Silk-elastinlike protein polymers (SELPs) are recombinant polymers designed from silk fibroin and mammalian elastin amino acid repeats. These are versatile materials that have been examined as controlled release systems for intratumoral gene delivery. SELP hydrogels comprise monodisperse and tunable polymers that have the capability to control and localize the release and expression of plasmid DNA and viruses. This article reviews recent developments in the synthesis and characterization of SELP hydrogels and their use for matrix-mediated gene delivery.     

C16orf5, a novel proline-rich gene at 16p13.3, is highly expressed in the brain

A novel gene has been characterized, designated C16orf5, with an unusually high content of proline residues (40% over 104 residues) at the N-terminus of the protein. The C-terminus of the protein is also cysteine rich with 14 cysteine residues present. Analysis using Northern and dot blots showed that the highest expression of this gene is in the brain. The gene was located on chromosome 16 at band p13.3 by FISH to metaphase chromosomes. Southern blot analysis with a human–rodent somatic cell hybrid panel showed a location between the somatic hybrid breakpoints 23HA and CY196. This gene comprises at least four exons and an open reading frame of 786 bp encoding a predicted protein of 261 amino acids. Analysis of this protein using PSORTII predicted a nuclear localization. Received: April 12, 1999 / Accepted: June 4, 1999     

Levels of type I and type III collagen in the bile duct of rats infected with Fasciola hepatica

Collagen types and their levels were compared between bile ducts from Fasciola infected rats and bile ducts from uninfected animals. Both collagen types I and III were shown to be increased in infected animals but, levels of type I increased less than type III. These results indicate that fascioliasis produces changes in the collagen composition of the bile duct that are similar to those produced in cirrhosis of the liver and other pathologic conditions including wound healing. Such observations suggest that a study of the chronology of collagen deposition in fascioliasis might provide information on the sequence of molecular events which result in bile duct hyperplasia.     

PELP1在Ⅱ型子宫内膜癌组织中的表达及其与ER相关性研究

目的:探讨脯氨酸、谷氨酸和亮氨酸富集蛋白1(PELP1)在II型子宫内膜癌中的表达及其与雌激素受体(ER)的相关性。方法:免疫组化法检测84例子宫内膜癌及40例正常子宫内膜组织中PELP1和ER表达水平并对其进行相关性分析。结果:I型子宫内膜癌及增殖期子宫内膜组织中PELP1、ER阳性表达率高于II型子宫内膜癌及分泌期子宫内膜组织,差异均有统计学意义(P0.05);II型子宫内膜癌与分泌期子宫内膜组织比较,差异均无统计学差异(P0.05)。Pearson相关分析提示,PELP1与ER在I型子宫内膜癌组织中表达量呈正相关(rs=0.348,P=0.01),而在II型子宫内膜癌组织中无相关性(rs=0.268,P=0.144)。结论:PELP1在II型子宫内膜癌组织中的表达较少,且与ER表达无明显相关性。     

Osmolyte transport in Staphylococcus aureus and the role in pathogenesis

Osmolyte transport is a pivotal part of bacterial life, particularly in high salt environments. Several low and high affinity osmolyte transport systems have been identified in various bacterial species. A lot of research has centered on characterizing the osmolyte transport systems of Gram-negative bacteria, but less has been done to characterize the same transport systems in Gram-positive bacteria. This review will focus on the previous work that has been done to understand the osmolyte transport systems in the species Staphylococcus aureus and how these transporters may serve dual functions in allowing the bacteria to survive and grow in a variety of environments, including on the surface or within humans or other animals.     

人工模拟干旱胁迫下金银花幼苗的生理适应性反应

目的研究人工模拟干旱胁迫条件下金银花幼苗的生理适应性反应,为揭示金银花植株的抗旱机制以及抗旱品种的选育提供理论依据。方法采用聚乙二醇（PEG-6000）模拟干旱胁迫处理金银花幼苗,检测幼苗体内的丙二醛（MDA）含量;超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）等保护酶活性,渗透调节物质脯氨酸（Pro）和可溶性糖含量。结果 10%、20%和30%PEG处理幼苗后120 h MDA含量分别高出对照组20.31%、28.12%和36.72%,随着PEG浓度升高,MDA含量逐渐增加。SOD、POD、CAT和APX活性总体呈现先升高后降低的趋势,各种酶对干旱胁迫的响应速率不同,CAT于干旱胁迫后立即开始启动,SOD、POD于干旱胁迫后24 h启动,而APX于干旱胁迫后48 h开始启动。Pro和可溶性糖含量均于处理后24 h开始增高,于处理后72 h达到峰值。结论随着干旱程度的增加和胁迫的延长,金银花体内膜质过氧化严重,通过增加Pro、可溶性糖的含量以及保护酶系统来抵御干旱胁迫,保护酶启动顺序为CAT、SOD、POD、APX。