THE PRESENCE OF HEMOLYTIC,CYTOLYTIC AND COMPLEMENT-BINDING SUBSTANCES IN EXTRACTS OF ENDAMOEBA HISTOLYTICA     

Craig CF 《Science (New York, N.Y.)》1927,65(1695):620

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The proteasome of Mycobacterium tuberculosis is required for resistance to nitric oxide     

Darwin KH  Ehrt S  Gutierrez-Ramos JC  Weich N  Nathan CF 《Science (New York, N.Y.)》2003,302(5652):1963-1966

The production of nitric oxide and other reactive nitrogen intermediates (RNI) by macrophages helps to control infection by Mycobacterium tuberculosis (Mtb). However, the protection is imperfect and infection persists. To identify genes that Mtb requires to resist RNI, we screened 10,100 Mtb transposon mutants for hypersusceptibility to acidified nitrite. We found 12 mutants with insertions in seven genes representing six pathways, including the repair of DNA (uvrB) and the synthesis of a flavin cofactor (fbiC). Five mutants had insertions in proteasome-associated genes. An Mtb mutant deficient in a presumptive proteasomal adenosine triphosphatase was attenuated in mice, and exposure to proteasomal protease inhibitors markedly sensitized wild-type Mtb to RNI. Thus, the mycobacterial proteasome serves as a defense against oxidative or nitrosative stress.  相似文献   

Structure of the uncleaved human H1 hemagglutinin from the extinct 1918 influenza virus     

Stevens J  Corper AL  Basler CF  Taubenberger JK  Palese P  Wilson IA 《Science (New York, N.Y.)》2004,303(5665):1866-1870

The 1918 "Spanish" influenza pandemic represents the largest recorded outbreak of any infectious disease. The crystal structure of the uncleaved precursor of the major surface antigen of the extinct 1918 virus was determined at 3.0 angstrom resolution after reassembly of the hemagglutinin gene from viral RNA fragments preserved in 1918 formalin-fixed lung tissues. A narrow avian-like receptor-binding site, two previously unobserved histidine patches, and a less exposed surface loop at the cleavage site that activates viral membrane fusion reveal structural features primarily found in avian viruses, which may have contributed to the extraordinarily high infectivity and mortality rates observed during 1918.  相似文献   

Neural systems responding to degrees of uncertainty in human decision-making     

Hsu M  Bhatt M  Adolphs R  Tranel D  Camerer CF 《Science (New York, N.Y.)》2005,310(5754):1680-1683

Much is known about how people make decisions under varying levels of probability (risk). Less is known about the neural basis of decision-making when probabilities are uncertain because of missing information (ambiguity). In decision theory, ambiguity about probabilities should not affect choices. Using functional brain imaging, we show that the level of ambiguity in choices correlates positively with activation in the amygdala and orbitofrontal cortex, and negatively with a striatal system. Moreover, striatal activity correlates positively with expected reward. Neurological subjects with orbitofrontal lesions were insensitive to the level of ambiguity and risk in behavioral choices. These data suggest a general neural circuit responding to degrees of uncertainty, contrary to decision theory.  相似文献   

Large magnetic anisotropy of a single atomic spin embedded in a surface molecular network     

Hirjibehedin CF  Lin CY  Otte AF  Ternes M  Lutz CP  Jones BA  Heinrich AJ 《Science (New York, N.Y.)》2007,317(5842):1199-1203

Magnetic anisotropy allows magnets to maintain their direction of magnetization over time. Using a scanning tunneling microscope to observe spin excitations, we determined the orientation and strength of the anisotropies of individual iron and manganese atoms on a thin layer of copper nitride. The relative intensities of the inelastic tunneling processes are consistent with dipolar interactions, as seen for inelastic neutron scattering. First-principles calculations indicate that the magnetic atoms become incorporated into a polar covalent surface molecular network in the copper nitride. These structures, which provide atom-by-atom accessibility via local probes, have the potential for engineering anisotropies large enough to produce stable magnetization at low temperatures for a single atomic spin.  相似文献   

Venus's southern polar vortex reveals precessing circulation     

Luz D  Berry DL  Piccioni G  Drossart P  Politi R  Wilson CF  Erard S  Nuccilli F 《Science (New York, N.Y.)》2011,332(6029):577-580

Initial images of Venus's south pole by the Venus Express mission have shown the presence of a bright, highly variable vortex, similar to that at the planet's north pole. Using high-resolution infrared measurements of polar winds from the Venus Express Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a center of rotation displaced from the geographic south pole by ~3 degrees of latitude and that drifts around the pole with a period of 5 to 10 Earth days. This is indicative of a nonsymmetric and varying precession of the polar atmospheric circulation with respect to the planetary axis.  相似文献   

Crystallography of the hexagonal ferrites     

Kohn JA  Eckart DW  Cook CF 《Science (New York, N.Y.)》1971,172(3983):519-525

The hexagonal ferrites form an unusual group of complex, ferrimagnetic oxides embodying some 60 known crystal structures. These include phases for which the structural unit cell is larger than that in any known inorganic materials. The various hexagonal ferrite modifications fall into two distinct structural series, each formed by the ordered interlayering (stacking) of two discrete building blocks; these blocks stack along the c crystallographic axis in varying ratios and varying permutations to form strictly coherent, reproducible crystal structures. This mixed-layering aspect of the hexagonal ferrites permits direct, visual observation of the sequence of their subunit-cell stacking elements, after etching, by means of electron microscopy. The sequence of stacked blocks in such structures constitutes the only information lacking for a complete, three-dimensional structure determination. Direct access to this information provides an immediate, unique solution of the crystal structure problem in each case and thereby avoids the dilemmas of a classical diffraction approach to such large unit cells. Ferrite structures with hexagonal c dimensions of 1455 and 1577 angstroms have been uniquely solved by direct electron microscopic readout of surface etch features. One must exercise caution, however, in generalizing these findings to other materials. The method is successful in the case of the hexagonal ferrites because these are mixed-layer structures, wherein the building blocks react at different rates to a specific etchant. Mixed-layer systems are not uncommon in crystallography, and it is likely that similar techniques can be developed for other such materials. Regardless of the validity of this prognosis, however, it is quite evident that high-resolution replica electron microscopy is a most promising tool for the direct observation of surface structure on an ultramicro scale. During the studies reported here replica resolution capability was improved to about 10 angstroms; final resolution is limited by the particle size of the platinum shadowing material. Careful control of experimental conditions during replica preparation or an alternate choice of shadowing material, or both, might reasonably improve the resolution by a factor of 2. This resolution is within the range of most unit cell dimensions and approaches interatomic distances in solid-state materials. The potential of such an experimental capability needs no elaboration.  相似文献   

Monothiol glutaredoxin cDNA from Taiwanofungus camphorata: a novel CGFS-type glutaredoxin possessing glutathione reductase activity     

Ken CF  Chen IJ  Lin CT  Liu SM  Wen L  Lin CT 《Journal of agricultural and food chemistry》2011,59(8):3828-3835

Glutaredoxins (Grxs) play important roles in the redox system via reduced glutathione as a reductant. A TcmonoGrx cDNA (1039 bp, EU158772) encoding a putative monothiol Grx was cloned from Taiwanofungus camphorata (formerly named Antrodia camphorata). The deduced amino acid sequence is conserved among the reported monothiol Grxs. Two 3-D homology structures of the TcmonoGrx based on known structures of human Grx3 (pdb: 2DIY_A) and Mus musculus Grx3 (pdb: 1WIK_A) have been created. To characterize the TcmonoGrx protein, the coding region was subcloned into an expression vector pET-20b(+) and transformed into E. coli C41(DE3). The recombinant His6-tagged TcmonoGrx was overexpressed and purified by Ni(2+)-nitrilotriacetic acid Sepharose. The purified enzyme showed a predominant band on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited glutathione reductase (GR) activity via dithionitrobenzoate (DTNB) assay. The Michaelis constant (K(M)) values for GSSG and NADPH were 0.064 and 0.041 mM, respectively. The enzyme's half-life of deactivation at 60 °C was 10.5 min, and its thermal inactivation rate constant (k(d)) was 5.37 × 10(-2) min(-1). The enzyme was active under a broad pH range from 6 to 8. The enzyme retained 50% activity after trypsin digestion at 37 °C for 40 min. Both mutants C(40)→S(40) and C(165)→S(165) lost 40-50% GR activity, whereas the mutant S(168)→C(168) showed a 20% increase in its GR activity.  相似文献   

5-Lipoxygenase expression in benign and malignant canine prostate tissues     

Goodman LA  Jarrett CL  Krunkosky TM  Budsberg SC  Northrup NC  Saba CF  LeRoy BE 《Veterinary and comparative oncology》2011,9(2):149-157

5-Lipoxygenase (5-LO) is overexpressed in human prostate carcinomas (PCs), and its inhibition decreases proliferation and induces apoptosis in prostate cancer cell lines. We hypothesized that 5-LO would be overexpressed in canine PC compared with benign prostate tissue and may be important in the pathogenesis of the disease. Immunoblot analysis of canine PC and benign prostatic hyperplasia (BPH) tissues demonstrated 5-LO expression in both. 5-LO immunohistochemical staining was not significantly different within the stromal or epithelial components of canine primary PC, BPH or suppurative prostatitis, suggesting that differential expression of this enzyme does not occur in these conditions. The percentage of tumour cells expressing 5-LO was significantly lower in metastatic PC lesions compared with primary PC (P < 0.0001). This decreased expression may indicate down-regulation or altered expression of the enzyme with progression of canine PC to a metastatic phenotype.  相似文献   

Toxoplasma gondii in Switzerland: a serosurvey based on meat juice analysis of slaughtered pigs, wild boar, sheep and cattle     

Berger-Schoch AE  Bernet D  Doherr MG  Gottstein B  Frey CF 《Zoonoses and public health》2011,58(7):472-478

Toxoplasmosis is one of the most important zoonotic diseases worldwide and is caused by the protozoan Toxoplasma gondii. Besides vertical infection during pregnancy, humans can get infected post-natally either by peroral uptake of sporulated Toxoplasma oocysts or by ingestion of tissue cysts upon consumption of raw or undercooked meat. The aim of this study was to approximate the risk of human infection via meat consumption by estimating the seroprevalence of T. gondii in slaughtered animals in Switzerland and to compare data with prevalences assessed 10 years ago. The study included pigs, cattle, sheep and wild boar of different age groups and housing conditions whenever possible and applicable. A P-30-ELISA was used to detect T. gondii-specific antibodies and to determine seroprevalences in meat juice of slaughtered animals. A total of 270 domestic pigs (120 adults, 50 finishing, 100 free-ranging animals), 150 wild boars, 250 sheep (150 adults, 100 lambs) and 406 cattle (47 calves, 129 heifers, 100 bulls, 130 adult cows) were tested. Seropositivity increased with the age of the assessed animals. Independent of the age-group, the overall seroprevalence was lowest in wild boars (6.7%), followed by pigs (23.3%), cattle (45.6%) and sheep (61.6%), respectively. Conventional fattening pigs and free-ranging pigs surprisingly had comparable seroprevalences (14.0% and 13.0%, respectively). Unlike in other European countries, where generally a decrease in the number of seropositive animals had been observed, we found that the prevalence of seropositive animals, when compared with that of 10 years ago, had increased for most species/age groups. Conclusively, the results demonstrated a high seroprevalence of T. gondii in animals slaughtered for meat production and revealed that increasing age of the animals is a more important risk factor than housing conditions in Switzerland.  相似文献