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31.
Current phylogenetic tree reconstruction methods assume that there is a
single underlying tree topology for all sites along the sequence. The
presence of mosaic sequences due to recombination violates this assumption
and will cause phylogenetic methods to give misleading results due to the
imposition of a single tree topology on all sites. The detection of mosaic
sequences caused by recombination is therefore an important first step in
phylogenetic analysis. A graphical method for the detection of
recombination, based on the least squares method of phylogenetic
estimation, is presented here. This method locates putative recombination
breakpoints by moving a window along the sequence. The performance of the
method is assessed by simulation and by its application to a real data set.
相似文献
32.
We used the repetitive character of transposable elements to isolate a
non-LTR retrotransposon in Drosophila subobscura. bilbo, as we have called
it, has homology to TRIM and LOA elements. Sequence analysis showed a 5'
untranslated region (UTR), an open reading frame (ORF) with no RNA-binding
domains, a downstream ORF that had structural homology to that of the I
factor, and, finally, a 3' UTR which ended in several 5-nt repeats. The
results of our phylogenetic and structural analyses shed light on the
evolution of Drosophila non-LTR retrotransposons and support the hypothesis
that an ancestor of these elements was structurally complex.
相似文献
33.
Variation of physico-chemical parameters along a river transect through the Okavango Delta,Botswana 总被引:1,自引:0,他引:1
The Okavango Delta depends on water quantity and quality to sustain its ecosystem services. Whereas many studies have been carried out on its hydrology, few have been done on water quality in the delta. Water pH, electrical conductivity (EC), dissolved oxygen (DO), turbidity, total suspended solids (TSS) and dissolved organic carbon (DOC) were monitored at 10 sites along the Okavango–Boro–Thamalakane–Lake Ngami system almost fortnightly from June 2008 to June 2010. Water quality in the delta was generally good, despite high evapotranspiration rates which would normally produce very saline waters. Electrical conductivity and water temperature increased with distance from Mohembo to Lake Ngami, the former most likely due to evapoconcentration. In contrast, pH, DO, turbidity and TSS decreased with distance from Mohembo to Boro at the lower end of the seasonal floodplain, before increasing again to Lake Ngami. Dissolved oxygen and TSS most likely declined due to biological uptake and particle sedimentation, respectively. Strong and significant relationships were observed between TSS and turbidity and between DOC and EC, indicating that turbidity and EC could be useful proxies for routine estimations of TSS and DOC, respectively, in the delta. 相似文献
34.
The suitability of using macroinvertebrates as bioindicators of stream water quality was tested in the Mkondoa River in an agricultural area at Kilosa, using the rapid bioassessment protocol. The family biotic index (FBI) showed marked variation in water quality along the stream from values ranging from 4.1 to 5.0 in the upstream reaches, indicating good water quality, 5.3 to 5.5 in the mid-reaches and 6.0 to 6.5 in the lower reaches. The water quality index (WQI) indicated that water quality was fair (77 ± 0.98) in the upstream reach of the Mkondoa, marginal (55 ± 0.86) in the midstream reach and poor (33 ± 0.45) in the downstream reach. There were significant relationships between biological oxygen demand and dissolved oxygen and the occurrence of specific taxa, mainly Chironomus and Caenis. Significant changes in macroinvertebrate abundance were mostly related to changes in water quality. As in other parts of the world, macroinvertebrate communities proved to be good biological indicators of water quality and they should be used as bioindicators in long-term monitoring of this river. 相似文献
35.
An Improved Method for Detecting Auxin-induced Hydrogen Ion Efflux from Corn Coleoptile Segments 总被引:5,自引:2,他引:3 下载免费PDF全文
Conditions necessary to detect maximal auxin-induced H+ secretion using a macroelectrode have been investigated using corn coleoptile segments. Auxin-induced H+ secretion is strongly dependent upon oxygenation or aeration when the tissue to volume ratio is high. Cuticle disruption or removal is also necessary to detect substantial auxin-induced H+ secretion. The auxin-induced decrease in pH of the external medium is stronger when the hormone is applied to tissue in which the cuticle has been disrupted with an abrasive than when the hormone is applied to tissue from which the cuticle and epidermis have been removed by peeling. The lower detectable acidification of the external medium when using peeled segments appears to be due in part to the leakage of buffers into the medium and in part to the removal of the auxin-sensitive epidermal cells. 相似文献
36.
Gerhard Aumüller Meikel Vesper Jürgen Seitz Michael Kemme Karl Heinz Scheit 《Cell and tissue research》1988,252(2):377-384
Summary The seminal vesicles synthesize in an androgen-dependent manner a neutral protein of 13.5 kDa molecular weight that makes up about 40% of their secretion (major protein). An antiserum against this protein raised in rabbits was used to localize the antigen within the seminal vesicles. In addition to intraluminal secretion of the seminal vesicles and the ampulla of the vas deferens, ejaculated and ampullary spermatozoa revealed an intense immunoreaction, which was restricted to the neck region of the sperm head and the middle piece, while the principal piece of the tail as well as the sperm head were devoid of immunoreactive material. Comparison of spermatozoa taken from the tail of the epididymis with ampullary spermatozoa showed that about 90% of the latter, but only 10–20% of the former presented this distributional pattern of immunoreactive sites. Epididymal epithelium as well as calf seminal vesicle epithelium showed no immunoreactivity with major protein antiserum. Using a pre-embedding staining technique with gold-labeled primary or secondary antibodies, respectively, no immunostaining could be achieved at the ultrastructural level. Incubation experiments of epididymal spermatozoa in EGTA-containing solutions in the absence of calcium resulted in a gradual labilization and eventual loss of the plasma membrane of the sperm middle piece. After removal of (at least part of) the plasma membrane, bound major protein could be visualized immunohistochemically close to the mitochondria of the middle piece using a gold-labeled primary or secondary antibody. The acceptor site for major protein therefore seems to reside inside the plasma membrane of the sperm middle piece. Incubation of epididymal spermatozoa in phospholipase-containing solutions removed the acceptor site from the spermatozoa. Separation by polyacrylamide treatment of proteins from epididymal sperm cells extracted by sodium hydroxide or phospholipase treatment, subsequently transblotted on nitrocellulose sheets and directly labeled with gold-tagged major protein, demonstrated a protein duplet with a molecular weight of 65 and 67 kDa, respectively, which appears to represent the specific binder of major protein underneath the sperm surface. Binding of major protein to this 66 kDa acceptor site is regarded as a physiological event that may be related to the onset of hyperactivated sperm motility.Dedicated to Professor Dr. Th.H. Schiebler on the occasion of his 65th birthdayThis study was supported by the Deutsche Forschungsgemeinschaft (grant Au 48/7-8) 相似文献
37.
Vadim Kotov Georg Mlynek Oliver Vesper Marina Pletzer Jiri Wald Celso M. Teixeira‐Duarte Herve Celia Maria Garcia‐Alai Stephan Nussberger Susan K. Buchanan Joo H. Morais‐Cabral Christian Loew Kristina Djinovic‐Carugo Thomas C. Marlovits 《Protein science : a publication of the Protein Society》2021,30(1):201-217
38.
S J Vesper D G Dearborn I Yike W G Sorenson R A Haugland 《Applied and environmental microbiology》1999,65(7):3175-3181
Stachybotrys chartarum is an indoor air, toxigenic fungus that has been associated with a number of human and veterinary health problems. Most notable among these has been a cluster of idiopathic pulmonary hemorrhage cases that were observed in the Cleveland, Ohio, area. In this study, 16 strains of S. chartarum isolated from case (n = 8) or control (n = 8) homes in Cleveland and 12 non-Cleveland strains from diverse geographic locations were analyzed for hemolytic activity, conidial toxicity, and randomly amplified polymorphic DNA banding patterns. In tests for hemolytic activity, strains were grown at 23 degrees C on wet wallboard pieces for an 8-week test period. Conidia from these wallboard pieces were subcultured on sheep's blood agar once a week over this period and examined for growth and clearing of the medium at 37 or 23 degrees C. Five of the Cleveland strains (all from case homes) showed hemolytic activity at 37 degrees C throughout the 8-week test compared to 3 of the non-Cleveland strains. Five of the Cleveland strains, compared to two of the non-Cleveland strains, produced highly toxic conidia (>90 microgram of T2 toxin equivalents per g [wet weight] of conidia) after 10 and 30 days of growth on wet wallboard. Only 3 of the 28 strains examined both were consistently hemolytic and produced highly toxic conidia. Each of these strains was isolated from a house in Cleveland where an infant had idiopathic pulmonary hemorrhage. 相似文献
39.
40.
Hubert W. Vesper Shalender Bhasin Susan S. Tai Ravinder J. Singh Susan Ohorodnik Wael A. Salameh Raj Razdan Gary L. Myers 《Steroids》2009,74(6):498-503