人气管普孢子虫基因组中MITEs转座子的鉴定及进化分析

利用生物信息学方法,首次在人气管普孢子虫( Trachipleistophorahominis )基因组内鉴定到 9 个 MITEs 家族ThME1~ThME9 ,共 123 个拷贝, MITEs 转座子的长度均小于 600bp 。根据靶位点重复序列( Targetsiteduplication ,TSD )的不同,将 ThME1 归 属 于 Tc1 / Mariner 超 家 族, ThME2 和 ThME3 归 属 于 PIF / Harbinger 超 家 族, ThME5 和ThME6 归属于 CACTA 超家族(超家族的名字用正体较好,下同),其余家族归为新家族。分析发现,人气管普孢子虫中的所有 MITEs 家族的吉布斯自由能均小于 0 ,表明 MITEs 家族具有形成二级结构的潜能,有利于该家族在基因组上转座。人气管普孢子虫 MITEs 家族在基因组的插入时间估计在 0~800 万年内,而且这种插入在基因组中是随机的,没有位置偏向性,并发现 2 个 MITEs 转座子拷贝插入到基因编码区内部。上述结果为进一步研究微孢子虫 MITEs 转座子的起源以及功能奠定了基础。
     

No cold dust within the supernova remnant Cassiopeia A

A large amount (about three solar masses) of cold (18 K) dust in the prototypical type II supernova remnant Cassiopeia A was recently reported. It was concluded that dust production in type II supernovae can explain how the large quantities (approximately 10(8) solar masses) of dust observed in the most distant quasars could have been produced within only 700 million years after the Big Bang. Foreground clouds of interstellar material, however, complicate the interpretation of the earlier submillimetre observations of Cas A. Here we report far-infrared and molecular line observations that demonstrate that most of the detected submillimetre emission originates from interstellar dust in a molecular cloud complex located in the line of sight between the Earth and Cas A, and is therefore not associated with the remnant. The argument that type II supernovae produce copious amounts of dust is not supported by the case of Cas A, which previously appeared to provide the best evidence for this possibility.     

残余奥氏体定量分析的特殊方法

在一般情况下 ,残余奥氏体的定量分析选用奥氏体的 311线条作为测量的依据 ,但在特殊情况下 ,奥氏体的 311线条极不明显 ,难以测定 .本文介绍在特殊情况下进行残余奥氏体定量分析的方法     

A novel route for ATP acquisition by the remnant mitochondria of Encephalitozoon cuniculi

Mitochondria use transport proteins of the eukaryotic mitochondrial carrier family (MCF) to mediate the exchange of diverse substrates, including ATP, with the host cell cytosol. According to classical endosymbiosis theory, insertion of a host-nuclear-encoded MCF transporter into the protomitochondrion was the key step that allowed the host cell to harvest ATP from the enslaved endosymbiont. Notably the genome of the microsporidian Encephalitozoon cuniculi has lost all of its genes for MCF proteins. This raises the question of how the recently discovered microsporidian remnant mitochondrion, called a mitosome, acquires ATP to support protein import and other predicted ATP-dependent activities. The E. cuniculi genome does contain four genes for an unrelated type of nucleotide transporter used by plastids and bacterial intracellular parasites, such as Rickettsia and Chlamydia, to import ATP from the cytosol of their eukaryotic host cells. The inference is that E. cuniculi also uses these proteins to steal ATP from its eukaryotic host to sustain its lifestyle as an obligate intracellular parasite. Here we show that, consistent with this hypothesis, all four E. cuniculi transporters can transport ATP, and three of them are expressed on the surface of the parasite when it is living inside host cells. The fourth transporter co-locates with mitochondrial Hsp70 to the E. cuniculi mitosome. Thus, uniquely among eukaryotes, the traditional relationship between mitochondrion and host has been subverted in E. cuniculi, by reductive evolution and analogous gene replacement. Instead of the mitosome providing the parasite cytosol with ATP, the parasite cytosol now seems to provide ATP for the organelle.     

High-energy particle acceleration in the shell of a supernova remnant

A significant fraction of the energy density of the interstellar medium is in the form of high-energy charged particles (cosmic rays). The origin of these particles remains uncertain. Although it is generally accepted that the only sources capable of supplying the energy required to accelerate the bulk of Galactic cosmic rays are supernova explosions, and even though the mechanism of particle acceleration in expanding supernova remnant (SNR) shocks is thought to be well understood theoretically, unequivocal evidence for the production of high-energy particles in supernova shells has proven remarkably hard to find. Here we report on observations of the SNR RX J1713.7 - 3946 (G347.3 - 0.5), which was discovered by ROSAT in the X-ray spectrum and later claimed as a source of high-energy gamma-rays of TeV energies (1 TeV = 10(12) eV). We present a TeV gamma-ray image of the SNR: the spatially resolved remnant has a shell morphology similar to that seen in X-rays, which demonstrates that very-high-energy particles are accelerated there. The energy spectrum indicates efficient acceleration of charged particles to energies beyond 100 TeV, consistent with current ideas of particle acceleration in young SNR shocks.     

空调冷凝器、蒸发器残留水分量检测系统

本文介绍了空调冷凝器、蒸发器残留水分量检测系统的组成和工作原理、技术指标、系统的工艺过程，最后说明了系统的考核和应用情况。     

人芽囊原虫在RPMI1640及LES培养中的比较

寻求一种在人芽囊原虫培养方面比传统的洛克氏液 鸡蛋 血清培养基(Locke′s egg serummedium ,LES)更优越的培养基 ,建立人芽囊原虫的纯培养系 ,为进一步研究人芽囊原虫的各种特性奠定基础 .将从临床获得的腹泻病人粪便标本分别接种于RPMI164 0及LES两种培养基中进行人芽囊原虫的培养 ,观察人芽囊原虫在两种培养基内的生长趋势和形态结构 ,比较两种培养基的优缺点 .结果表明 ,RPMI164 0培养管中的虫体密度比较高 ;RPMI164 0培养基中的虫体存活时间比较长 ;RPMI164 0培养基内可见空泡型、颗粒型、复分裂型和似包囊型 .结论表明 ,RPMI164 0培养基比LES培养基在人芽囊原虫的培养方面更优越 .     

Extremely fast acceleration of cosmic rays in a supernova remnant

Galactic cosmic rays (CRs) are widely believed to be accelerated by shock waves associated with the expansion of supernova ejecta into the interstellar medium. A key issue in this long-standing conjecture is a theoretical prediction that the interstellar magnetic field can be substantially amplified at the shock of a young supernova remnant (SNR) through magnetohydrodynamic waves generated by cosmic rays. Here we report a discovery of the brightening and decay of X-ray hot spots in the shell of the SNR RX J1713.7-3946 on a one-year timescale. This rapid variability shows that the X-rays are produced by ultrarelativistic electrons through a synchrotron process and that electron acceleration does indeed take place in a strongly magnetized environment, indicating amplification of the magnetic field by a factor of more than 100. The X-ray variability also implies that we have witnessed the ongoing shock-acceleration of electrons in real time. Independently, broadband X-ray spectrometric measurements of RX J1713.7-3946 indicate that electron acceleration proceeds in the most effective ('Bohm-diffusion') regime. Taken together, these two results provide a strong argument for acceleration of protons and nuclei to energies of 1 PeV (10(15) eV) and beyond in young supernova remnants.     

Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation

Giardia intestinalis (syn. lamblia) is one of the most widespread intestinal protozoan pathogens worldwide, causing hundreds of thousands of cases of diarrhoea each year. Giardia is a member of the diplomonads, often described as an ancient protist group whose primitive nature is suggested by the lack of typical eukaryotic organelles (for example, mitochondria, peroxisomes), the presence of a poorly developed endomembrane system and by their early branching in a number of gene phylogenies. The discovery of nuclear genes of putative mitochondrial ancestry in Giardia and the recent identification of mitochondrial remnant organelles in amitochondrial protists such as Entamoeba histolytica and Trachipleistophora hominis suggest that the eukaryotic amitochondrial state is not a primitive condition but is rather the result of reductive evolution. Using an in vitro protein reconstitution assay and specific antibodies against IscS and IscU--two mitochondrial marker proteins involved in iron-sulphur cluster biosynthesis--here we demonstrate that Giardia contains mitochondrial remnant organelles (mitosomes) bounded by double membranes that function in iron-sulphur protein maturation. Our results indicate that Giardia is not primitively amitochondrial and that it has retained a functional organelle derived from the original mitochondrial endosymbiont.     

The acceleration of cosmic-ray protons in the supernova remnant RX J1713.7-3946

Protons with energies up to approximately 10(15) eV are the main component of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking. Electrons are known to be accelerated to cosmic-ray energies in supernova remnants, and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (pi(0)), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in gamma-rays with a particular spectral-energy distribution. Here we report the observation of cascade showers of optical photons resulting from gamma-rays at energies of approximately 10(12) eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms.     

A forty-kilodalton protein of the inner membrane is the mitochondrial calcium uniporter

Mitochondrial Ca(2+) homeostasis has a key role in the regulation of aerobic metabolism and cell survival, but the molecular identity of the Ca(2+) channel, the mitochondrial calcium uniporter, is still unknown. Here we have identified in silico a protein (named MCU) that shares tissue distribution with MICU1 (also known as CBARA1), a recently characterized uniporter regulator, is present in organisms in which mitochondrial Ca(2+) uptake was demonstrated and whose sequence includes two transmembrane domains. Short interfering RNA (siRNA) silencing of MCU in HeLa cells markedly reduced mitochondrial Ca(2+) uptake. MCU overexpression doubled the matrix Ca(2+) concentration increase evoked by inositol 1,4,5-trisphosphate-generating agonists, thus significantly buffering the cytosolic elevation. The purified MCU protein showed channel activity in planar lipid bilayers, with electrophysiological properties and inhibitor sensitivity of the uniporter. A mutant MCU, in which two negatively charged residues of the putative pore-forming region were replaced, had no channel activity and reduced agonist-dependent matrix Ca(2+) concentration transients when overexpressed in HeLa cells. Overall, these data demonstrate that the 40-kDa protein identified is the channel responsible for ruthenium-red-sensitive mitochondrial Ca(2+) uptake, thus providing a molecular basis for this process of utmost physiological and pathological relevance.     

A family of mitochondrial proteins involved in bioenergetICS and biogenesis

The respiratory chain complexes of mitochondria consist of many different subunits, of which only a few partake directly in electron transport. The functions of the subunits that do not contain prosthetic groups are largely unknown. The cytochrome reductase complex of Neurospora crassa, for examine, consists of nine different subunits, of which the peripheral membrane proteins I and II (ref.3) that are located on the matrix side of the mitochondrial inner membrane are the largest subunits devoid of redox centres. Significantly, a cytochrome reductase fraction lacking these two subunits was inactive in electron transfer, and in yeast mutants with defective genes for either of the two subunits, assembly of the reductase is disrupted. Most mitochondrial proteins are imported into the mitochondrion as precursor proteins, and two proteins are necessary for cleaving their presequences, namely the matrix processing peptidase (MPP) and the processing enhancing protein (PEP), the latter strongly stimulating the activity of the former. Temperature-sensitive yeast mutants, which are affected in PEP or MPP, accumulate precursors at the nonpermissive temperature. We report here that subunit I of the cytochrome reductase can be grouped as members of the same protein family.     

An absence of ex-companion stars in the type Ia supernova remnant SNR 0509-67.5

A type Ia supernova is thought to begin with the explosion of a white dwarf star. The explosion could be triggered by the merger of two white dwarfs (a 'double-degenerate' origin), or by mass transfer from a companion star (the 'single-degenerate' path). The identity of the progenitor is still controversial; for example, a recent argument against the single-degenerate origin has been widely rejected. One way to distinguish between the double- and single-degenerate progenitors is to look at the centre of a known type Ia supernova remnant to see whether any former companion star is present. A likely ex-companion star for the progenitor of the supernova observed by Tycho Brahe has been identified, but that claim is still controversial. Here we report that the central region of the supernova remnant SNR 0509-67.5 (the site of a type Ia supernova 400?±?50 years ago, based on its light echo) in the Large Magellanic Cloud contains no ex-companion star to a visual magnitude limit of 26.9 (an absolute magnitude of M(V) = +8.4) within a region of radius 1.43 arcseconds. (This corresponds to the 3σ maximum distance to which a companion could have been 'kicked' by the explosion.) This lack of any ex-companion star to deep limits rules out all published single-degenerate models for this supernova. The only remaining possibility is that the progenitor of this particular type Ia supernova was a double-degenerate system.     

Deletions of muscle mitochondrial DNA in patients with mitochondrial myopathies

In vitro studies of muscle mitochondrial metabolism in patients with mitochondrial myopathy have identified a variety of functional defects of the mitochondrial respiratory chain, predominantly affecting complex I (NADH-CoQ reductase) or complex III (ubiquinol-cytochrome c reductase) in adult cases. These two enzymes consist of approximately 36 subunits, eight of which are encoded by mitochondrial DNA (mtDNA). The increased incidence of maternal, as opposed to paternal, transmission in familial mitochondrial myopathy suggests that these disorders may be caused by mutations of mtDNA. Multiple restriction endonuclease analysis of leukocyte mtDNA from patients with the disease, and their relatives, showed no differences in cleavage patterns between affected and unaffected individuals in any single maternal line. When muscle mtDNA was studied, nine of 25 patients were found to have two populations of muscle mtDNA, one of which had deletions of up to 7 kilobases in length. These observations demonstrate that mtDNA heteroplasmy can occur in man and that human disease may be associated with defects of the mitochondrial genome.     

线圈残余曲率与织物外观形态关系的研究

分析了织物中线圈的形态 ,推导出了线圈残余曲率与纱线细度、纱线机械性能及成圈机件尺寸之间的关系式 .在理论分析和实践的基础上讨论了线圈的残余曲率与织物外观形态和尺寸间的关系