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排序方式: 共有189条查询结果,搜索用时 15 毫秒
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Kim M. Plummer Sarah J. Clark Lana M. Ellis Ashwini Loganathan Taha H. Al-Samarrai Erik H.A. Rikkerink Patrick A. Sullivan Matthew D. Templeton Peter C. Farley 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(3):265-274
Peptidases have been implicated in the pathogenicity of fungi that cause disease in plants. Expression of the secreted aspartic peptidase gene (gcsap), of a Glomerella cingulata isolate pathogenic on apples, is induced during appressorium formation. To determine whether the secreted aspartic peptidase (GcSAP) is essential to pathogenicity, gcsap was disrupted using a vector containing a 637 bp fragment of genomic DNA that encodes the sequence spanning the two active site aspartic acid (Asp) residues. To ensure that the truncated gcsap gene products could not have residual peptidase activity the codons for the active site residues Asp112 and Asp297 were both mutated to histidine residues. Both PCR and Southern analysis confirmed disruption of gcsap. Neither gcsap mRNA nor GcSAP activity was detected in the disruption mutant. Pathogenicity tests on fruit from three apple cultivars showed that GcSAP was not required for pathogenicity. The disruption mutant grew on medium containing protein as the sole source of nitrogen because G. cingulata secretes a previously undetected peptidase(s). A serine peptidase that had a pH optimum between pH 7.0 and 8.0 and a K
m of 0.25 mM for the synthetic substrate succinyl-Ala–Ala–Pro–Phe-p-nitroanilide was identified. 相似文献
3.
Assessment of corneal thickness,intraocular pressure,optical corneal diameter,and axial globe dimensions in Miniature Horses 总被引:1,自引:0,他引:1
OBJECTIVE: To determine corneal thickness, intraocular pressure (IOP), and horizontal and vertical corneal diameter (HCD and VCD) and to obtain axial measurements of the anterior chamber depth (ACD), crystalline lens thickness (CLT), vitreous chamber depth (VtCD), and axial globe length (AGL) in eyes of Miniature Horses. ANIMALS: 41 healthy Miniature Horses. PROCEDURE: Ocular component measurements were obtained via ultrasonic pachymetry, applanation tonometry, ultrasound, and by use of a Jameson caliper. RESULTS: Mean IOP and corneal thickness for all eyes were 26.0 mm Hg and 785.6 microm, respectively. There was no correlation of age with IOP or corneal thickness and no difference in these variables between right and left eyes or between females and males. Mean HCD andVCD were 25.8 and 19.4 mm, respectively; although there were no differences between sexes or between right and left eyes, there was positive correlation of optical corneal diameters with increasing age. Mean ACD, CLT, VtCD, and AGL were smaller in Miniature Horses (5.6, 10.0, 18.1, and 33.7 mm, respectively), compared with values for full-sized horses; there was no difference in these variables between sexes or between right and left eyes in Miniature Horses, but they were correlated with increasing age. CONCLUSIONS AND CLINICAL RELEVANCE: In Miniature Horses, corneal thickness and IOP are similar to values reported for full-sized horses and do not increase with advancing age. Vertical corneal diameter, HCD, and AGL increase until 5, 7, and 2 years of age, respectively. 相似文献
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文章通过对内蒙古大兴安岭林区培育大径材的目的、意义、必要性及方法等方面的分析,论述了大径级材培育是促进林区生态、经济和社会协调发展的有力措施。 相似文献
6.
AIDS: an international perspective 总被引:17,自引:0,他引:17
P Piot F A Plummer F S Mhalu J L Lamboray J Chin J M Mann 《Science (New York, N.Y.)》1988,239(4840):573-579
The acquired immunodeficiency syndrome (AIDS) and infection with the human immunodeficiency virus type 1 (HIV-1) constitute a worldwide public health problem. Whereas in Europe and in most of the Americas transmission of HIV-1 has occurred predominantly among homosexual men and intravenous drug abusers, in Africa a distinct epidemiologic pattern has emerged that indicates that HIV-1 infection is mainly heterosexually acquired. Heterosexual transmission appears to be increasing in some parts of Latin America and the Caribbean, and possibly in the United States. In addition to HIV-1, at least one other human retrovirus, namely HIV-2, has been implicated as a cause of AIDS in Africa and Europe. Factors that influence heterosexual transmission of HIV-1 include genital ulcerations, early or late stages of HIV-1 infection in the index case, and possibly oral contraception and immune activation. The rate of perinatal transmission is enhanced when the mother's illness is more advanced. AIDS and HIV-1 infection may have a significant impact not only on public health, but also on the demography and socioeconomic conditions of some developing countries. Programs for the prevention and control of AIDS should be an immediate priority in all countries. 相似文献
7.
We propose an isotopic fractionation mechanism, based on photolytic destruction, to explain the 15N/14N and 18O/16O fractionation of stratospheric nitrous oxide (N2O) and reconcile laboratory experiments with atmospheric observations. The theory predicts that (i) the isotopomers 15N14N16O and 14N15N16O have very different isotopic fractionations in the stratosphere, and (ii) laboratory photolysis experiments conducted at 205 nanometers should better simulate the observed isotopic fractionation of stratospheric N2O. Modeling results indicate that there is no compelling reason to invoke a significant chemical source of N2O in the middle atmosphere and that individual N2O isotopomers might be useful tracers of stratospheric air parcel motion. 相似文献
8.
PT Sprunger L Petersen EW Plummer E Laegsgaard F Besenbacher 《Science (New York, N.Y.)》1997,275(5307):1764-1767
Large-amplitude electron density oscillations were observed on a Be(0001) surface by means of variable-temperature scanning tunneling microscopy. Fourier transforms of the images showed a ring of radius 2kF, where kF is the Fermi wave vector of the Be(0001) surface state. This wavelength was expected from Friedel oscillations caused by electronic screening of surface defects, but the amplitude of the waves for energies near the Fermi energy was anomalously large and inconsistent with the Friedel concept of screening. The enhanced amplitude of the waves must be a many-body effect, either in the electron gas (possibly an incipient charge density wave) or in the response of the lattice (electron-phonon coupling). 相似文献
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