Enzymatic preparation of high specific activity radiolabeled (I)-L-5-methyltetrahydropteroylglutamate

5-CH₃[G-³H]H₄PteGlu (sp act 5.0 Ci/nmol) was synthesized by direct enzymatic reduction of [G-³H]PteGlu by dihydropteroylglutamate reductase to H₄PteGlu. The latter was reacted with formaldehyde to give 5,10-CH₂-H₄-PteGlu which was reduced to the final product by sodium borohydride. A single chromatographic step on TEAE-cellulose afforded 5-CH₃[G-³H]H₄PteGlu in high yield at a radiochemical purity of about 99%.     

Chromosome polymorphisms track trans‐Atlantic divergence and secondary contact in Atlantic salmon

Pleistocene glaciations drove repeated range contractions and expansions shaping contemporary intraspecific diversity. Atlantic salmon (Salmo salar) in the western and eastern Atlantic diverged >600,000 years before present, with the two lineages isolated in different southern refugia during glacial maxima, driving trans‐Atlantic genomic and karyotypic divergence. Here, we investigate the genomic consequences of glacial isolation and trans‐Atlantic secondary contact using 108,870 single nucleotide polymorphisms genotyped in 80 North American and European populations. Throughout North America, we identified extensive interindividual variation and discrete linkage blocks within and between chromosomes with known trans‐Atlantic differences in rearrangements: Ssa01/Ssa23 translocation and Ssa08/Ssa29 fusion. Spatial genetic analyses suggest independence of rearrangements, with Ssa01/Ssa23 showing high European introgression (>50%) in northern populations indicative of post‐glacial trans‐Atlantic secondary contact, contrasting with low European ancestry genome‐wide (3%). Ssa08/Ssa29 showed greater intrapopulation diversity, suggesting a derived chromosome fusion polymorphism that evolved within North America. Evidence of potential selection on both genomic regions suggests that the adaptive role of rearrangements warrants further investigation in Atlantic salmon. Our study highlights how Pleistocene glaciations can influence large‐scale intraspecific variation in genomic architecture of northern species.     

Developing synthetic conical nanopores for biosensing applications

In this review we bring together recent results from our group focused towards the development of biosensors from single conically-shaped artificial nanopores. The nanopores, used in the work presented here, were prepared using the track-etch process. The fabrication of track-etched conical nanopores has been optimized to allow for single nanopores with reproducible dimensions to be prepared. We have also demonstrated techniques that allow for easy and controllable manipulation of nanopore geometry (e.g., cone angle). We will consider the ion transport properties of the conical nanopores and factors that affect these properties. Methods for introducing functions that mimic biological ion channels, such as voltage-gating, into these nanopores will also be addressed. Three prototype sensors developed from single conical nanopores will be presented. In the first two sensors, the single conical nanopores function as resistive-pulse sensors and detect the presence of analytes as current-blockade events in the ion current. The third sensor functions in an on/off mode, much like a ligand-gated ion channel. In the presence of a target analyte, the ion current permanently shuts off.     

游仆虫信息素Er-1和Er-2对四膜虫的种间作用

信息素是生物体向外释放的化学物质,在细胞及生物体中具有种内信息传递的生理学功能。信息素这一类分子广泛分布于系统发生史中,它们的特异活性在单细胞生物、昆虫以及脊椎动物中均有报道。脊椎动物中信息素的信号传输已被证实是一嗅觉依赖过程,7TM-受体被认为是信号传输过程中的信号转换器。在低等单细胞生物(例如:来可夫游仆虫)的细胞膜上存在有信息素异构体,作为信息素分子的有效结合位点而行使其功能。本研究主要探讨单细胞的信息素(Er-1和Er-2)的基础细胞生理学作用是仅限于产生该信息素的物种,还是对其它的原生动物(例如:四膜虫)或对系统发育中分类地位较高的细胞(例如:MRC5成纤维细胞或J774巨噬细胞)均具有调节活性。研究结果表明,游仆虫的两种信息素对梨形四膜虫GL的生长调节有显著不同的作用:当信息素浓度为10-11M时,Er-1具有正调控作用,而Er-2具有抑制剂的作用。这两种配体的趋化作用也有很不同:Er-1具有一种广范的化学排斥特性,而Er-2具有一个双峰的化学吸引剂的性质。计算机检测发现,与Er-2的作用不同,Er-1可略微降低被测细胞的游动速率。趋化现象的选择特性表明Er-2信息素的受体有一种“短期”的特性;而Er-1是不能选择任何亚种群的,这也支持了我们先前的研究数据,即这两种信息素在四膜虫GL内产生两种不同的信号。四膜虫对信息素特异性的反应表明四膜虫能辨别非常近似但带有微小差异的配体(如Er-1和Er-2的电荷差异)。     

Type VI collagen induces cardiac myofibroblast differentiation: implications for postinfarction remodeling

Cardiac fibroblast (CF) proliferation and differentiation into hypersecretory myofibroblasts can lead to excessive extracellular matrix (ECM) production and cardiac fibrosis. In turn, the ECM produced can potentially activate CFs via distinct feedback mechanisms. To assess how specific ECM components influence CF activation, isolated CFs were plated on specific collagen substrates (type I, III, and VI collagens) before functional assays were carried out. The type VI collagen substrate potently induced myofibroblast differentiation but had little effect on CF proliferation. Conversely, the type I and III collagen substrates did not affect differentiation but caused significant induction of proliferation (type I, 240.7 +/- 10.3%, and type III, 271.7 +/- 21.8% of basal). Type I collagen activated ERK1/2, whereas type III collagen did not. Treatment of CFs with angiotensin II, a potent mitogen of CFs, enhanced the growth observed on types I and III collagen but not on the type VI collagen substrate. Using an in vivo model of myocardial infarction (MI), we measured changes in type VI collagen expression and myofibroblast differentiation after post-MI remodeling. Concurrent elevations in type VI collagen and myofibroblast content were evident in the infarcted myocardium 20-wk post-MI. Overall, types I and III collagen stimulate CF proliferation, whereas type VI collagen plays a potentially novel role in cardiac remodeling through facilitation of myofibroblast differentiation.