黄土高原子午岭种子植物区系特征研究

黄土高原子午岭位于黄土高原中部半湿润半干旱过渡带(107°30′~109°40′E,33°50′~36°50′N)。其在植被分区上隶属于泛北极植物区、中国-日本森林植物亚区的华北地区黄土高原植物亚地区。区内共有种子植物94科361属689种,分别占黄土高原区种子植物总数的63.95%、41.78%和21.37%。其中大科、大属在区系组成中起着非常重要的作用。该区种子植物属包含15个分布区类型及12个变型,其中北温带分布、旧世界温带分布、泛热带分布、东亚分布等成分占有重要地位。其种子植物区系的基本特征是:植物种类相对丰富;多种地理成分交汇、过渡特征明显;区系组成以华北成分为主体,温带成分占优势;沿纬度梯度地理成分差异显著,垂直分布带谱不明显;区系成分新老并存,特有化程度低。     

Inhibition of Syk promotes chemical reprogramming of fibroblasts via metabolic rewiring and H2S production

Chemical compounds have recently been introduced as alternative and non‐integrating inducers of pluripotent stem cell fate. However, chemical reprogramming is hampered by low efficiency and the molecular mechanisms remain poorly characterized. Here, we show that inhibition of spleen tyrosine kinase (Syk) by R406 significantly promotes mouse chemical reprogramming. Mechanistically, R406 alleviates Syk / calcineurin (Cn) / nuclear factor of activated T cells (NFAT) signaling‐mediated suppression of glycine, serine, and threonine metabolic genes and dependent metabolites. Syk inhibition upregulates glycine level and downstream transsulfuration cysteine biosynthesis, promoting cysteine metabolism and cellular hydrogen sulfide (H₂S) production. This metabolic rewiring decreased oxidative phosphorylation and ROS levels, enhancing chemical reprogramming. In sum, our study identifies Syk‐Cn‐NFAT signaling axis as a new barrier of chemical reprogramming and suggests metabolic rewiring and redox homeostasis as important opportunities for controlling cell fates.     

Aptamer directly evolved from live cells recognizes membrane bound immunoglobin heavy mu chain in Burkitt's lymphoma cells

The identification of tumor related cell membrane protein targets is important in understanding tumor progression, the development of new diagnostic tools, and potentially for identifying new therapeutic targets. Here we present a novel strategy for identifying proteins that are altered in their expression levels in a diseased cell using cell specific aptamers. Using an intact viable B-cell Burkitt's lymphoma cell line (Ramos cells) as the target, we have selected aptamers that recognize cell membrane proteins with high affinity. Among the selected aptamers that showed different recognition patterns with different cell lines of leukemia, the aptamer TD05 showed binding with Ramos cells. By chemically modifying TD05 to covalently cross-link with its target on Ramos cells to capture and to enrich the target receptors using streptavidin coated magnetic beads followed by mass spectrometry, we were able to identify membrane bound immunoglobin heavy mu chain as the target for TD05 aptamer. Immunoglobin heavy mu chain is a major component of the B-cell antigen receptor, which is expressed in Burkitt's lymphoma cells. This study demonstrates that this two step strategy, the development of high quality aptamer probes and then the identification of their target proteins, can be used to discover new disease related potential markers and thus enhance tumor diagnosis and therapy. The aptamer based strategy will enable effective molecular elucidation of disease related biomarkers and other interesting molecules.     

Formation of homogeneous unilamellar liposomes from an interdigitated matrix

Phospholipid-ethanol-aqueous mixtures containing bilayer-forming lipids and 20-50 wt.% of water form viscous gels. Further hydration of these gels results in the formation of liposomes whose morphology depends upon the lipid type. Upon hydration of gels containing mixtures of the lipids 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), small homogeneous and unilamellar liposomes were produced. In contrast, hydration of gels containing only POPC resulted in formation of large multilamellar liposomes. Likewise, mulitlamellar liposomes resulted when this method was applied to form highly fusogenic liposomes comprised of the novel negatively charged N-acyl-phosphatidylethanolamine (NAPE) mixed with di-oleoyl-phosphatidylcholine (DOPC) (7:3) [T. Shangguan, C.C. Pak, S. Ali, A.S. Janoff, P. Meers, Cation-dependent fusogenicity of an N-acyl phosphatidylethanolamine, Biochim. Biophys. Acta 1368 (1998) 171-183]. In all cases, the measured aqueous entrapment efficiencies were relatively high. To better understand how the molecular organization of these various gels affects liposome morphology, we examined samples by freeze-fracture transmission electron microscopy and X-ray diffraction. We found that phospholipid-ethanol-water gels are comprised of highly organized stacks of lamellae. A distinct feature of the gel samples that result in small unilamellar liposomes is the combination of acyl chain interdigitation and net electrostatic charge. We speculate that the mechanism of unilamellar liposome formation proceeds via formation of stalk contacts between neighboring layers similar to membrane hemifusion intermediates, and the high aqueous entrapment efficiencies make this liposome formation process attractive for use in drug delivery applications.     

Mechanomics analysis of hESCs under combined mechanical shear,stretch, and compression

Biomechanics and Modeling in Mechanobiology - Human embryonic stem cells (hESCs) can differentiate to three germ layers within biochemical and biomechanical niches. The complicated mechanical...     

Sera from patients with type 2 diabetes and neuropathy induce autophagy and colocalization with mitochondria in SY5Y cells

The etiology of diabetic neuropathy is multifactorial and not fully elucidated, although oxidative stress and mitochondrial dysfunction are major factors. We reported previously that complement-inactivated sera from type 2 diabetic patients with neuropathy induce apoptosis in cultured neuronal cells, possibly through an autoimmune immunoglobulin-mediated pathway. Recent evidence supports an emerging role for autophagy in a variety of diseases. Here we report that exposure of human neuroblastoma SH-SY5Y cells to sera from type 2 diabetic patients with neuropathy is associated with increased levels of autophagosomes that is likely mediated by increased titers of IgM or IgG autoimmune immunoglobulins. The increased presence of macroautophagic vesicles was monitored using a specific immunohistochemical marker for autophagosomes, anti-LC3-II immunoreactivity, as well as the immunohistochemical signal for beclin-1, and was associated with increased co-localization with mitochondria in the cells exposed to diabetic neuropathic sera. We also report that dorsal root ganglia removed from streptozotocin-induced diabetic rats exhibit increased levels of autophagosomes and co-localization with mitochondria in neuronal soma, concurrent with enhanced binding of IgG and IgM autoimmune immunoglobulins. To our knowledge, this is the first evidence that the presence of autophagosomes is increased by a serum factor, likely autoantibody(ies) in a pathological condition. Stimulation of autophagy by an autoantibody-mediated pathway can provide a critical link between the immune system and the loss of function and eventual demise of neuronal tissue in type 2 diabetes.     

General Cell-Binding Activity of Intramolecular G-Quadruplexes with Parallel Structure

G-quadruplexes (G4s) are four-stranded nucleic acid structures adopted by some repetitive guanine-rich sequences. Putative G-quadruplex-forming sequences (PQSs) are highly prevalent in human genome. Recently some G4s have been reported to have cancer-selective antiproliferative activity. A G4 DNA, AS1411, is currently in phase II clinical trials as an anticancer agent, which is reported to bind tumor cells by targeting surface nucleolin. AS1411 also has been extensively investigated as a target-recognition element for cancer cell specific drug delivery or cancer cell imaging. Here we show that, in addition to AS1411, intramolecular G4s with parallel structure (including PQSs in genes) have general binding activity to many cell lines with different affinity. The binding of these G4s compete with each other, and their targets are certain cellular surface proteins. The tested G4s exhibit enhanced cellular uptake than non-G4 sequences. This uptake may be through the endosome/lysosome pathway, but it is independent of cellular binding of the G4s. The tested G4s also show selective antiproliferative activity that is independent of their cellular binding. Our findings provide new insight into the molecular recognition of G4s by cells; offer new clues for understanding the functions of G4s in vivo, and may extend the potential applications of G4s.     

Construction of a BmNPV polyhedrin-plus Bac-to-Bac baculovirus expression system for application in silkworm, Bombyx mori

The baculovirus expression vector system is one of the most powerful and versatile eukaryotic expression systems available. However, as the recombinant baculovirus is usually generated by replacing the foreign gene into the polyhedrin locus, the resulting polyhedrin-negative virus is less infectious to the host larvae when administered via oral ingestion. This limits the large-scale production of the recombinant protein, as the host larvae can only be inoculated through dorsal injection, which is a laborious task. In this paper, we describe a new Bombyx mori nucleopolyhedrovirus polyhedrin-plus Bac-to-Bac baculovirus expression system for application in silkworm, B. mori. In this system, the foreign gene and the polyhedrin are co-expressed, and polyhedra are produced as in the wild-type virus, and thus the recombinant baculovirus can be used directly via oral infection. It effectively improves the efficiency of the baculovirus expression system and also widens the application of baculovirus in other fields, such as the development of new biological insecticides.     

A mammary repopulating cell population characterized in mammary anlagen reveals essential mammary stroma for morphogenesis

The cells with mammary repopulating capability can achieve mammary gland morphogenesis in a suitable cellular microenvironment. Using cell surface markers of CD24, CD29 and CD49f, mouse mammary repopulating unit (MRU) has been identified in adult mammary epithelium and late embryonic mammary bud epithelium. However, embryonic MRU remains to be fully characterized at earlier mammary anlagen stage. Here we isolated discrete populations of E14.5 mouse mammary anlagen cells. Only Lin⁻CD24^medCD29⁺ cell population was predicted as E14.5 MRU by examining their capacities of forming mammosphere and repopulating cleared mammary fat pad in vivo. However, when we characterized gene expressions of this E14.5 cell population by comparing with adult mouse MRU (Lin⁻CD24⁺CD29^hi), the gene profiling of these two cell populations exhibited great differences. Real-time PCR and immunostaining assays uncovered that E14.5 Lin⁻CD24^medCD29⁺ cell population was a heterogeneous stroma-enriched cell population. Then, limiting dilutions and single-cell assays also confirmed that E14.5 Lin⁻CD24^medCD29⁺ cell population possessed low proportion of stem cells. In summary, heterogeneous Lin⁻CD24^medCD29⁺ cell population exhibited mammary repopulating ability in E14.5 mammary anlagen, implying that only suitable mammary stroma could enable mammary gland morphogenesis, which relied on the interaction between rare stem cells and microenvironment.