基于多端元光谱混合分析方法的大兴安岭火后植被盖度恢复研究

火干扰是北方针叶林结构、功能及动态的主要调节因子之一。研究火后植被恢复对理解火干扰和生态系统的交互作用具有重要意义。火烧迹地通常由植被与基质混合组成,在中低分辨率（ > 10 m）遥感影像中表现为混合像元,因此研究亚像元尺度上植被的恢复是精确量化植被恢复的关键。本研究以2000年大兴安岭呼中自然保护区中8700 hm²火烧迹地为研究区,以两期（2014年6月1日和2010年6月22日）中分辨率Landsat ETM+影像（30 m）为基础数据,比较多端元光谱混合分析（Multiple Endmember Spectral Mixture Analysis,MESMA）和归一化植被指数（Normalized Difference Vegetation Index,NDVI）获得的植被盖度,以高分辨率（2 m）WorldView-2影像（2014年7月1日）为验证数据,对两种方法计算的植被盖度精度进行比较。结果表明,MESMA方法获得的植被盖度（R²=0.691）与传统的NDVI获得的植被盖度（R²=0.700）精度无统计差异,中烈度下获得的植被覆盖精度高于低、高火烧烈度。为验证同一端元能否运用到不同时相的Landsat影像中,本研究将从2014年影像中获取的最佳端元运用到2010年影像中获得植被盖度图,结果表明2014年与2010年得到的RMSE（均方根误差）均值分别为0.0015和0.0065,说明最佳端元可用于不同时相的影像分解。本研究表明MESMA方法可有效监测北方针叶林中火后植被盖度恢复,并可运用于时间序列遥感影像监测植被恢复动态。     

Quality of vitrified porcine immature oocytes is improved by coculture with fresh oocytes during in vitro maturation

It is essential to enhance the in vitro maturation (IVM) condition for immature oocytes after cryopreservation, particularly if limited numbers of oocytes collected from specific donors. The objective of this study was to determine if quality of vitrified porcine immature oocytes was enhanced by coculturing with fresh oocytes during IVM. To distinguish fresh versus vitrified oocytes, we used two types of coculture systems: (a) transwell two‐chamber coculture; (b) labeling and tracing fresh oocytes with CellTracker? Green CMFDA during conventional culture. Coculture systems significantly accelerated meiotic progression of vitrified oocytes and significantly increased blastocyst formation rates following parthenogenetic activation and somatic cell nuclear transfer. Reactive oxygen species generation in vitrified oocytes was ameliorated by the coculture conditions, with no significant difference between fresh and vitrified oocytes for intracellular glutathione level. Both coculture systems significantly increased rate of normal mitochondrial distribution in vitrified oocytes, but did not affect fluorescence intensity of mitochondria. The percentage of oocytes with normal endoplasmic reticulum (ER) distribution and ER fluorescence intensity were significantly higher in vitrified oocytes cocultured with fresh oocytes. After 20 hr of IVM, mRNA expression of COX2, HAS2, PTX3, and TNFAIP6 remained significantly higher in cumulus cells derived from vitrified oocytes and coculture systems significantly decreased the expression of these genes. Additionally, coculture methods prevented the reduction of mRNA expression for BMP15, ZAR1, POU5F1, and DNMT3A in vitrified oocytes. In conclusion, oocyte quality and subsequent embryo development of vitrified porcine immature oocytes were significantly improved by fresh oocyte coculture during IVM.     

黄精种子萌发及组培技术研究

研究了不同的激素对多花黄精种子的萌发及组培的影响。研究结果表明:多花黄精种子萌发的最佳激素条件为6-BA 180.0 mg/L+GA_3 60.0 mg/L,两种激素可能有交互作用;多花黄精块茎外植体的最佳灭菌时间为12 min;最佳诱导外植体愈伤组织培养基为:6-BA 2.0 mg/L+2,4-D 0.2 mg/L+MS,低浓度的6-BA利于多花黄精块茎愈伤诱导;最佳诱芽培养基为:6-BA 6.0 mg/L+NAA 0.2 mg/L+MS和6-BA 4.0 mg/L+TDZ 0.2 mg/L+NAA 0.2 mg/L+MS,低浓度的TDZ对不定芽的诱导和生长有促进作用;最佳生根培养基为:IBA 1.0 mg/L+1/2MS,但是过高浓度的IBA会抑制根的诱导。通过多花黄精的繁殖技术的研究,以期为多花黄精的快繁提供技术支持。     

Vitamin C mitigates heat damage by reducing oxidative stress,inducing HSP expression in TM4 Sertoli cells

Heat stress is a major stressor that can lead to male reproductive dysfunction. Sertoli cells play a crucial role in spermatogenesis by providing germ cells with structural and nutritional support, and contributing to blood–testis barrier formation. Vitamin C (Vc) is an antioxidant capable of neutralizing reactive oxygen species and preventing lipid peroxidation widely used because it is inexpensive and highly accessible. In the present study, we investigated the protective effect of Vc on TM4 cells following heat stress. Pretreatment with Vc could effectively inhibit apoptosis (p < 0.01), lipid peroxidation, and lactate dehydrogenase (LDH) activity. However, a significant increase in the malondialdehyde (MDA) level and LDH activity (p < 0.01) was observed in TM4 cells without Vc‐pretreatment, in conjunction with vacuole degeneration and karyopyknosis. In addition, both the messenger RNA and protein levels of CryAB, Hsp27, Hsp70, and Hsp110 substantially increased in the 3 and 12 hr recovery groups (p < 0.01). Vc also prevented microtubule aggregation following heat stress. These results suggest that pretreatment with Vc‐protected TM4 cells against heat stress by reducing the level of oxidative stress and inducing heat shock protein expression.     

Chemotherapy and cancer stem cells

Cancer stem cells are subsets of tumor cells defined through the capacity to initiate tumors and have been linked to therapeutic resistance. In this issue of Cell Stem Cell, Todaro et al. (2007) demonstrate that targeting tumor IL-4 sensitizes colon cancer stem cells to chemotherapy.     

BDCA2/Fc epsilon RI gamma complex signals through a novel BCR-like pathway in human plasmacytoid dendritic cells

Dendritic cells are equipped with lectin receptors to sense the extracellular environment and modulate cellular responses. Human plasmacytoid dendritic cells (pDCs) uniquely express blood dendritic cell antigen 2 (BDCA2) protein, a C-type lectin lacking an identifiable signaling motif. We demonstrate here that BDCA2 forms a complex with the transmembrane adapter Fc epsilon RI gamma. Through pathway analysis, we identified a comprehensive signaling machinery in human pDCs, similar to that which operates downstream of the B cell receptor (BCR), which is distinct from the system involved in T cell receptor (TCR) signaling. BDCA2 crosslinking resulted in the activation of the BCR-like cascade, which potently suppressed the ability of pDCs to produce type I interferon and other cytokines in response to Toll-like receptor ligands. Therefore, by associating with Fc epsilon RI gamma, BDCA2 activates a novel BCR-like signaling pathway to regulate the immune functions of pDCs.     

Reconstructing recombination network from sequence data: the small parsimony problem

The small parsimony problem is studied for reconstructing recombination networks from sequence data. The small parsimony problem is polynomial-time solvable for phylogenetic trees. However, the problem is proved NP-hard even for galled recombination networks. A dynamic programming algorithm is also developed to solve the small parsimony problem. It takes O(dn2(3h)) time on an input recombination network over length-d sequences in which there are h recombination and n - h tree nodes.     

Structural and biochemical insights into the regulation of protein phosphatase 2A by small t antigen of SV40

The small t antigen (ST) of DNA tumor virus SV40 facilitates cellular transformation by disrupting the functions of protein phosphatase 2A (PP2A) through a poorly defined mechanism. The crystal structure of the core domain of SV40 ST bound to the scaffolding subunit of human PP2A reveals that the ST core domain has a novel zinc-binding fold and interacts with the conserved ridge of HEAT repeats 3-6, which overlaps with the binding site for the B' (also called PR61 or B56) regulatory subunit. ST has a lower binding affinity than B' for the PP2A core enzyme. Consequently, ST does not efficiently displace B' from PP2A holoenzymes in vitro. Notably, ST inhibits PP2A phosphatase activity through its N-terminal J domain. These findings suggest that ST may function mainly by inhibiting the phosphatase activity of the PP2A core enzyme, and to a lesser extent by modulating assembly of the PP2A holoenzymes.     

Adaptive Evolution of cry Genes in Bacillus thuringiensis： Implications for Their Specificity Determination

The cry gene family, produced during the late exponential phase of growth in Bacillus thuringiensis, is a large, still-growing family of homologous genes, in which each gene encodes a protein with strong specific activity against only one or a few insect species. Extensive studies are mostly focusing on the structural and functional relationships of Cry proteins, and have revealed several residues or domains that are important for the target recognition and receptor attachment. In this study, we have employed a maximum likelihood method to detect evidence of adaptive evolution in Cry proteins, and have identified 24 positively selected residues, which are all located in Domain Ⅱ or Ⅲ. Combined with known data from mutagenesis studies, the majority of these residues, at the molecular level, contribute much to the insect specificity determination. We postulate that the potential pressures driving the diversification of Cry proteins may be in an attempt to adapt for the ＂arm race＂ between δ-endotoxins and the targeted insects, or to enlarge their target spectra, hence result in the functional divergence. The sites identified to be under positive selection would provide targets for further structural and functional analyses on Cry proteins.     

中国家蚕抗菌肽ABP-CM4在E.coli中的融合表达及活性分析

参照天然抗菌肽CM4(ABP-CM4)氨基酸序列和大肠杆菌偏爱密码子,采用rPCR法获得CM4基因后重组到表达载体pET32a上,在E.coli中融合表达。表达产物以可溶性存在,经Ni2 -NTA琼脂糖亲和层析获得融合蛋白,再经甲酸切割、亲和层析和阳离子交换层析,得到纯化的重组抗菌肽。琼脂糖扩散法和液相测定法证明了纯化的抗菌肽具有抗菌活性。