基于HNSOTER的海南岛土壤有机碳储量及空间分布特征分析

基于海南岛1∶200 000土壤 地体数字化数据库（HNSOTER）,在GIS系统的支持下,对海南岛土壤有机碳储量及分布特征进行了探讨.结果表明,1）标准剖深下（0～100 cm）,海南岛土壤有机碳储量为2.78×10⁸ t.2）0～20 cm剖深土壤有机碳密度变幅在0.3～18.8 kg·m^-2之间,其中1.0～5.0 kg·m^-2密度区占总分布面积的81.2%,按面积加权均值为3.3 kg·m^-2.0～100 cm剖深的土壤有机碳密度变幅在1.0～32.1 kg·m^-2 之间,其中2.0～14.0 kg·m^-2密度区面积比重占89.7%,按面积加权均值为8.4 kg·m^-2.不同地形、岩性及土壤类型中,土壤有机碳密度分布有较大变异.3）从中部山地向外至沿海平原,土壤有机碳密度总体上呈递减趋势,但不同剖深下其分布格局仍有一定差异.0～20 cm剖深下土壤有机碳密度高值区（丰富度指数大于1）主要分布于山地以及北部玄武岩台地,0～100 cm剖深下,有机碳密度高值区（丰富度指数大于1）趋向集中于中东部山地、台地区,且其分布重心较前者明显的向东偏移.     

用RACE技术扩增并克隆牛BMP4基因3′端序列

RACE技术是一项扩增基因末端序列的新技术。该研究从牛BMP4基因出发,以牛软骨的RNA为模板,按照不同物种BMP4基因的相似性设计特异引物,运用PCR和RACE技术扩增并获得了特异片段,该片段经PCR、酶切和测序验证,证实所克隆序列为牛BMP4的3′端序列,包含有1170bp组成的开放读码框(ORF),编码389个氨基酸,3′非编码区121bp个核苷酸和poly(A)15。同源性分析结果表明,牛BMP4 cDNA最大开放读码框所推测的氨基酸序列与已知人、小鼠、大鼠、狗、羊和鸡等真核生物BMP4氨基酸序列进行比较,分别有94.5%、93.1%、91.9%、87.4%、94.2%、79%的同源性。这为克隆其他物种的BMP4基因提供了依据,同时牛骨形态发生蛋白的测序为我们更好的理解牛的生骨机理提供帮助。     

Tyrannobdella rex N. Gen. N. Sp. and the Evolutionary Origins of Mucosal Leech Infestations

Background

Leeches have gained a fearsome reputation by feeding externally on blood, often from human hosts. Orificial hirudiniasis is a condition in which a leech enters a body orifice, most often the nasopharyngeal region, but there are many cases of leeches infesting the eyes, urethra, vagina, or rectum. Several leech species particularly in Africa and Asia are well-known for their propensity to afflict humans. Because there has not previously been any data suggesting a close relationship for such geographically disparate species, this unnerving tendency to be invasive has been regarded only as a loathsome oddity and not a unifying character for a group of related organisms.

Principal Findings

A new genus and species of leech from Perú was found feeding from the nasopharynx of humans. Unlike any other leech previously described, this new taxon has but a single jaw with very large teeth. Phylogenetic analyses of nuclear and mitochondrial genes using parsimony and Bayesian inference demonstrate that the new species belongs among a larger, global clade of leeches, all of which feed from the mucosal surfaces of mammals.

Conclusions

This new species, found feeding from the upper respiratory tract of humans in Perú, clarifies an expansion of the family Praobdellidae to include the new species Tyrannobdella rex n. gen. n.sp., along with others in the genera Dinobdella, Myxobdella, Praobdella and Pintobdella. Moreover, the results clarify a single evolutionary origin of a group of leeches that specializes on mucous membranes, thus, posing a distinct threat to human health.     

Exosome secreted by MSC reduces myocardial ischemia/reperfusion injury

Human ESC-derived mesenchymal stem cell (MSC)-conditioned medium (CM) was previously shown to mediate cardioprotection during myocardial ischemia/reperfusion injury through large complexes of 50–100 nm. Here we show that these MSCs secreted 50- to 100-nm particles. These particles could be visualized by electron microscopy and were shown to be phospholipid vesicles consisting of cholesterol, sphingomyelin, and phosphatidylcholine. They contained coimmunoprecipitating exosome-associated proteins, e.g., CD81, CD9, and Alix. These particles were purified as a homogeneous population of particles with a hydrodynamic radius of 55–65 nm by size-exclusion fractionation on a HPLC. Together these observations indicated that these particles are exosomes. These purified exosomes reduced infarct size in a mouse model of myocardial ischemia/reperfusion injury. Therefore, MSC mediated its cardioprotective paracrine effect by secreting exosomes. This novel role of exosomes highlights a new perspective into intercellular mediation of tissue injury and repair, and engenders novel approaches to the development of biologics for tissue repair.     

Critical role of macrophages and their activation via MyD88-NFκB signaling in lung innate immunity to Mycoplasma pneumoniae

Mycoplasma pneumoniae (Mp), a common cause of pneumonia, is associated with asthma; however, the mechanisms underlying this association remain unclear. We investigated the cellular immune response to Mp in mice. Intranasal inoculation with Mp elicited infiltration of the lungs with neutrophils, monocytes and macrophages. Systemic depletion of macrophages, but not neutrophils, resulted in impaired clearance of Mp from the lungs. Accumulation and activation of macrophages were decreased in the lungs of MyD88(-/-) mice and clearance of Mp was impaired, indicating that MyD88 is a key signaling protein in the anti-Mp response. MyD88-dependent signaling was also required for the Mp-induced activation of NFκB, which was essential for macrophages to eliminate the microbe in vitro. Thus, MyD88-NFκB signaling in macrophages is essential for clearance of Mp from the lungs.     

Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages

Infection with the bacterial pathogen Francisella tularensis tularensis (F. tularensis) causes tularemia, a serious and debilitating disease. Francisella tularensis novicida strain U112 (abbreviated F. novicida), which is closely related to F. tularensis, is pathogenic for mice but not for man, making it an ideal model system for tularemia. Intracellular pathogens like Francisella inhibit the innate immune response, thereby avoiding immune recognition and death of the infected cell. Because activation of inflammatory pathways may lead to cell death, we reasoned that we could identify bacterial genes involved in inhibiting inflammation by isolating mutants that killed infected cells faster than the wild-type parent. We screened a comprehensive transposon library of F. novicida for mutant strains that increased the rate of cell death following infection in J774 macrophage-like cells, as compared to wild-type F. novicida. Mutations in 28 genes were identified as being hypercytotoxic to both J774 and primary macrophages of which 12 were less virulent in a mouse infection model. Surprisingly, we found that F. novicida with mutations in four genes (lpcC, manB, manC and kdtA) were taken up by and killed macrophages at a much higher rate than the parent strain, even upon treatment with cytochalasin D (cytD), a classic inhibitor of macrophage phagocytosis. At least 10-fold more mutant bacteria were internalized by macrophages as compared to the parent strain if the bacteria were first fixed with formaldehyde, suggesting a surface structure is required for the high phagocytosis rate. However, bacteria were required to be viable for macrophage toxicity. The four mutant strains do not make a complete LPS but instead have an exposed lipid A. Interestingly, other mutations that result in an exposed LPS core were not taken up at increased frequency nor did they kill host cells more than the parent. These results suggest an alternative, more efficient macrophage uptake mechanism for Francisella that requires exposure of a specific bacterial surface structure(s) but results in increased cell death following internalization of live bacteria.     

Synthesis and antitumor activity of bithienyl-pyrimidine derivatives with electrostatic binding side chains.

A series of bithienyl-pyrimidines having cationic side chain have been developed as antitumor agents. This work illustrates the overwhelming importance of the bithienyl unit for efficient DNA binding. The X-ray structure of 4-(2',2"-thien-5-yl)2-chloropyrimidine was obtained for postulating the conformation of the bithienyl-pyrimidine moiety.     

Uniconazole (S-3307) strengthens the growth and cadmium accumulation of accumulator plant Malachium aquaticum

The effects of uniconazole (S-3307) application on the growth and cadmium (Cd) accumulation of accumulator plant Malachium aquaticum (L.) Fries. were studied through a pot experiment. The application of S-3307 increased the biomass and photosynthetic pigment content of M. aquaticum in Cd-contaminated soil, and also improved the superoxide dismutase (SOD) and peroxidase (POD) activities in M. aquaticum. Application of S-3307 increased Cd content in shoots and decreased Cd content in roots of M. aquaticum, but the translocation factor (TF) of M. aquaticum increased with the increase of S-3307 concentration. For phytoextraction, the application of S-3307 increased Cd extractions by roots, shoots and whole plants of M. aquaticum, and the maxima were obtained at 75 mg L^?1 S-3307, which increased by 22.07%, 37.79% and 29.07%, respectively, compared with their respective controls. Therefore, S-3307 can be used for enhancing the Cd extraction ability of M. aquaticum, and 75 mg L^?1 S-3307 was the optimal dose.     

Protein cofactors and substrate influence Mg2+-dependent structural changes in the catalytic RNA of archaeal RNase P

The ribonucleoprotein (RNP) form of archaeal RNase P comprises one catalytic RNA and five protein cofactors. To catalyze Mg²⁺-dependent cleavage of the 5′ leader from pre-tRNAs, the catalytic (C) and specificity (S) domains of the RNase P RNA (RPR) cooperate to recognize different parts of the pre-tRNA. While ∼250–500 mM Mg²⁺ renders the archaeal RPR active without RNase P proteins (RPPs), addition of all RPPs lowers the Mg²⁺ requirement to ∼10–20 mM and improves the rate and fidelity of cleavage. To understand the Mg²⁺- and RPP-dependent structural changes that increase activity, we used pre-tRNA cleavage and ensemble FRET assays to characterize inter-domain interactions in Pyrococcus furiosus (Pfu) RPR, either alone or with RPPs ± pre-tRNA. Following splint ligation to doubly label the RPR (Cy3-RPR_{C domain} and Cy5-RPR_{S domain}), we used native mass spectrometry to verify the final product. We found that FRET correlates closely with activity, the Pfu RPR and RNase P holoenzyme (RPR + 5 RPPs) traverse different Mg²⁺-dependent paths to converge on similar functional states, and binding of the pre-tRNA by the holoenzyme influences Mg²⁺ cooperativity. Our findings highlight how Mg²⁺ and proteins in multi-subunit RNPs together favor RNA conformations in a dynamic ensemble for functional gains.