Transdifferentiation of mesenchymal stem cells derived from human fetal lung to hepatocyte-like cells

The great shortage of human hepatic cells makes it desirable to generate extrahepatic stem or precursor cells. In recent years, it has been reported that human multipotential mesenchymal stem cells (hMSCs) differentiate into hepatocyte-like cells. The fetal lung is one of the largest organs containing many MSCs that can be easily obtained. Whether MSCs from fetal lung can differentiate into hepatocytes or bile duct cells is an important issue in basic medicine and clinical application. We isolated fetal lung cells, and expanded and analyzed them. At passage 4, their morphologic, immunophenotyping and cytokine secretions were similar to adult bone marrow-derived MSCs. We conclude that these cells from fetal lung are MSCs, indicating that human fetal lung is an ideal source of hMSCs. hMSCs from fetal lung induced in special differentiation medium showed homogeneous and small polygonal endothelial-like morphology, expressing weak mRNA, as well as Alb and AFP. This implies that hMSCs from fetal lung can differentiate into hepatocyte-like cells.     

一个含有乳链菌肽抗性基因的乳酸乳球菌质粒pTS50的鉴定

在添加乳链菌肽、乳糖及溴甲酚紫的M1 7选择培养基上 ,从 1 97个新鲜牛奶样品中筛选到 3株乳链菌肽抗性菌株 ,PCR扩增证实它们都含有乳链菌肽抗性基因。菌种生理生化特性鉴定及特异性 1 6SrDNAPCR扩增产物的序列测定结果表明这 3株菌都属于乳酸乳球菌乳酸亚种。质粒转化实验发现乳酸乳球菌乳酸亚种TS 1 640中的乳链菌肽抗性基因位于一个约47kb的大质粒pTS50上。BamHI、EcoRI、HindⅢ、NcoI、PstⅠ酶切分析和Southern杂交 ,进一步将乳链菌肽抗性基因定位于pTS50的一个约 1 9kbEcoRI酶切片段中     

N enrichment affects the arbuscular mycorrhizal fungi-mediated relationship between a C4 grass and a legume

Arbuscular mycorrhizal fungi (AMF) regulate soil nutrient cycling, directly supplying a host plant with nitrogen (N). AMF can also affect the outcome of interspecific interactions, but a mechanistic understanding of how soil N availability affects AMF-mediated interspecific relationships is currently lacking. We selected one dominant (Bothriochloa ischaemum; C₄ grass) and one subordinate (Lespedeza davurica; legume) species in a natural grassland climax community to investigate the mechanism by which AMF influence interspecific interaction (mixed and monoculture) under three levels of N addition (0, low, and high N addition). Under the non-N addition treatment, AMF preferentially supplied N to the roots of B. ischaemum at the expense of N uptake by L. davurica, resulting in inhibited AMF benefits for L. davurica shoot growth. Under the low N addition treatment, interspecific interaction via AMF promoted L. davurica growth. Compared to the non-N addition treatment, N addition largely mitigated the effects, both positive (for B. ischaemum) and negative (for L. davurica), of AMF-mediated interspecific interaction on plant N uptake via AMF. When soil N availability severely limited plant growth, preferential N supply to the C₄ grass by AMF was important for maintaining the abundance of the dominant species. When the N limitation for plant growth was alleviated by N addition, the interaction between AMF and soil microorganisms improved nutrient availability for the legume by stimulating activity of the enzyme responsible for soil organic matter mineralization, which is important for maintaining the abundance of the subordinate species. These data could influence strategies for maintaining biodiversity.     

白马雪山国家级自然保护区典型森林生态系统服务

生态系统服务是近年来生态学研究的热点领域,对关键区域生态系统服务的研究具有重要意义.云南省白马雪山国家级自然保护区地处青藏高原南延部分,拥有独特的地理位置,是生物多样性保护的热点区域.本文对该保护区森林生态系统的生物量与生产力、水源涵养、营养物质循环等3项服务的功能量进行了评估.结果表明:保护区森林总生物量2215.86×104t,生产力171.84×104t·a-1;水源涵养量11964.56×104m3;N、P、K年吸收量分别为26025.94t、2638.57t、12016.85 t.研究表明,保护区森林生态效益显著,对于维持当地以及周边地区的生态安全具有重要意义.     

A single residue mutation of 5-enoylpyruvylshikimate-3-phosphate synthase in Pseudomonas stutzeri enhances resistance to the herbicide glyphosate

A novel class II 5-enoylpyruvylshikimate-3-phosphate synthase (EPSPS) was identified from Pseudomonas stutzeri A1501 by complementation of an Escherichia coli auxotrophic aroA mutant. The single amino acid substitution of serine (Ser) for asparagine (Asn)-130 of the A1501 EPSPS enhanced resistance to 200 mM glyphosate. The mutated EPSPS had a 2.5-fold increase for IC(50) [glyphosate] value, a 2-fold increase for K (i) [glyphosate] value, but a K (m) [PEP] value similar to that of wild type. The effect of the single residue mutation on glyphosate resistance was also analyzed using a computer-based three-dimensional model.     

Terpenoid and phenolic metabolites from the fungus xylaria sp. associated with termite nests

Three new sesquiterpene acids, xylaric acids A-C (1-3, resp.), and a new tetralone (=3,4-dihydronaphthalen-1(2H)-one) derivative, 4, along with nine known compounds, xylaric acid D (5), hydroheptelidic acid (6), gliocladic acid (7), chlorine heptelidic acid (8), trichoderonic acid A (9), 16-(α-D-mannopyranosyloxy)isopimar-7-en-19-oic acid (10), 16-(α-D-glucopyranosyloxy)isopimar-7-en-19-oic acid (11), 5-carboxymellein (12), and naphthalen-1,8-diol 1-O-α-D-glucopyranoside (13) have been isolated from the solid culture of the ascomycete fungus Xylaria sp. associated with termite nest. The structures of these compounds were elucidated primarily by NMR experiments. The absolute configurations of compounds 1-3 and 5-9 were determined by combination of X-ray data and CD spectral analysis. The absolute configuration of 4 was assigned by Snatzke's method. Compounds 8 and 11 showed slight cytotoxicities against two cell lines A549 and SGC7901.     

Molecular dynamics simulations of migration of ions and molecules through the acetylcholine receptor channel

A dynamic model of the channel of an acetylcholine receptor in a closed state has been proposed. The channel is formed by five a-helices of subunit M2 and stabilized by the cyclic hydrocarbon (CH2)105. The migration of charged and unchanged van der Waals particles with a diameter of 7.72 A equivalent to the diameter of a hydrated sodium ion has been studied. The migration occurred by the action of external force applied to the complex along the channel axis. In the closed state, the inhibition of ions is due to two components: electrostatic interaction and steric constraints. The van der Waals channel gate is formed by residues 13'-A-Val255, B-Val261, C-Val269, D-Val255, and E-Ile264, and the negatively changed residues occurring in the upper part of the channel have a great effect on ion selectivity.     

Rapid identification and characterization of Penicillium marneffei using multiplex ligation-dependent probe amplification (MLPA) in paraffin-embedded tissue samples

Penicillium marneffei infection is a deadly disease and early diagnosis leads to prompt and appropriate antifungal therapy. To develop a sensitive method to diagnose P. marneffei infection, a multiplex ligation-dependent probe amplification (MLPA) assay was adapted. This method can rapidly and specifically detect P. marneffei DNA in cultured cells and paraffin-embedded tissue samples. Three pairs of probes were designed for amplifying the internally (intergenic) transcribed spacer (ITS) region of P. marneffei rRNA using a systematic phylogenetic analysis. These three probe sets produced three amplicons of 198, 166, and 152 bp, respectively, specific for P. marneffei. In contrast, there was only one 198 bp amplicon produced for Talaromyces stipitatus, and one 152 bp amplicon for P. funiculosum, T. intermedius and T. derxii. The probes did not amplify any other reference strains. An array of 40 P. marneffei strains isolated from human patients, bamboo rat, and the local environment was tested by using MLPA, and all were positively identified. Most importantly, P. marneffei in paraffin-embedded tissue specimens from infected human patients was positively amplified by MLPA. The sensitivity and specificity of the MLPA assay could be a useful tool for prompt diagnosis, pathogen characterization, and epidemiological studies of fungal infections.