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41.
A likelihood approach for comparing synonymous and nonsynonymous nucleotide substitution rates, with application to the chloroplast genome 总被引:29,自引:24,他引:5
A model of DNA sequence evolution applicable to coding regions is
presented. This represents the first evolutionary model that accounts for
dependencies among nucleotides within a codon. The model uses the codon, as
opposed to the nucleotide, as the unit of evolution, and is parameterized
in terms of synonymous and nonsynonymous nucleotide substitution rates. One
of the model's advantages over those used in methods for estimating
synonymous and nonsynonymous substitution rates is that it completely
corrects for multiple hits at a codon, rather than taking a parsimony
approach and considering only pathways of minimum change between homologous
codons. Likelihood-ratio versions of the relative-rate test are constructed
and applied to data from the complete chloroplast DNA sequences of Oryza
sativa, Nicotiana tabacum, and Marchantia polymorpha. Results of these
tests confirm previous findings that substitution rates in the chloroplast
genome are subject to both lineage-specific and locus-specific effects.
Additionally, the new tests suggest tha the rate heterogeneity is due
primarily to differences in nonsynonymous substitution rates. Simulations
help confirm previous suggestions that silent sites are saturated, leaving
no evidence of heterogeneity in synonymous substitution rates.
相似文献
42.
ALEKSANDRA I. JOHANSEN ALICE EXNEROVÁ KATEŘINA HOTOVÁ SVÁDOVÁ PAVEL ŠTYS GABRIELLA GAMBERALE‐STILLE BIRGITTA S. TULLBERG 《Ecological Entomology》2010,35(5):602-610
1. Protective coloration in insects may be aposematic or cryptic, and some species change defensive strategy between instars. In Sweden, the adult striated shieldbugs Graphosoma lineatum (Heteroptera: Pentatomidae) undergo a seasonal colour change from pale brown and black striation in the pre‐hibernating adults, to red and black striation in the same post‐hibernating individuals. To the human eye the pre‐hibernating adults appear cryptic against the withered late summer vegetation, whereas the red and black post‐hibernating adults appear aposematic. This suggests a possibility of a functional colour change. However, what is cryptic to the human eye is not necessarily cryptic to a potential predator. 2. Therefore we tested the effect of coloration in adult G. lineatum on their detectability for avian predators. Great tits (Parus major) were trained to eat sunflower seeds hidden inside the emptied exoskeletons of pale or red G. lineatum. Then the detection time for both colour forms was measured in a dry vegetation environment. 3. The birds required a longer time to find the pale form of G. lineatum than the red one. The pale form appears more cryptic on withered late summer vegetation than the red form, not only to the human eye but also to avian predators. The result supports the idea that the adult individuals of G. lineatum undergo a functional change from a cryptic protective coloration to an aposematic one. 相似文献
43.
Rebekka?K?SchneiderEmail author Susanne?Ziegler Isabelle?Leisten Monica?SV?Ferreira Anne?Schumacher Bj?rn?Rath Dirk?Fahrenkamp Gerhard?Müller-Newen Martina?Crysandt Stefan?Wilop Edgar?Jost Steffen?Koschmieder Ruth?Knüchel Tim?H?Brümmendorf Patrick?Ziegler 《Journal of hematology & oncology》2014,7(1):92
We characterized bone marrow stromal cells (BMSC) from patients with pre-fibrotic myeloproliferative neoplasms (MPN). MPN-BMSC showed decreased capacity to stimulate the proliferation of colony-forming units of normal hematopoietic stem and progenitor cells and displayed increased matrix remodelling (in particular fibronectin deposition) compared to control BMSC. This finding was confirmed in pre-fibrotic MPN bone marrow biopsies in a tissue microarray (n?=?34), which stained positive for fibronectin in the absence of reticulin as a standard myelofibrosis marker. Fibronectin expression correlated significantly with reduced haemoglobin levels in MPN-patients (p?=?0.007; R2?=?0.42). Our data show significant cell-intrinsic alterations in MPN-MSC and suggest that Fibronectin expression might be applicable as a biomarker for the identification of early myelofibrotic transformation in reticulin-negative MPN. 相似文献
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45.
K P Zak M A Gruzov B M Khomenko G M Butenko S V Komissarenko L F Andrianova 《T?Sitologii?a i genetika》1985,19(4):245-249
Methods of immune electrone microscopy have revealed that OKT-3+ cells and E-RFC of human blood have a similar ultrastructure. Definite morphologic spectrum is observed within each of these fractions, that testifies to the heterogeneity of surface markers of circulating T-lymphocytes and their ultrastructure. 相似文献
46.
Mitchell SV Elkind Kristen Coates Wanling Tai Myunghee C Paik Bernadette Boden-Albala Ralph L Sacco 《BMC neurology》2006,6(1):37-6
Background
Inflammation and inflammatory biomarkers play an important role in atherosclerosis and cardiovascular disease. Little information is available, however, on time course of serum markers of inflammation after stroke. 相似文献47.
G G Ga?voronskaia D D Protvin I D Kolesnikova S V Komissarenko 《Ukrainski? biokhimicheski? zhurnal》1981,53(4):97-101
The subject of the present research is the investigation of the influence of sodium periodate on the properties of immunoglobulin G molecules. It is shown that 100 and 300 M of periodate cause a slight enhancement of the sedimentation coefficient which is a result of the higher protein density. However high concentrations (2000 M) of periodate decrease sedimentation coefficient considerably and disturb the protein structure homogeneity. Studies of the immunologic activity in the periodate-treated antibodies by the reaction of passive hemagglutination showed that in low concentrations it did not decrease significantly the activity but with an increase in the concentration up to 2000 M the activity lowered. The conjugation of antibodies with the enzyme markers was fulfilled due to periodate oxidation. The conjugates obtained were successfully used for improving sensitivity of the precipitation line in immunologic tests. 相似文献
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49.
K P Liashchenko S A Bobrovnik S V Komissarenko 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1991,(4):66-68
In experiments on guinea pigs and BALB/c mice delayed hypersensitivity to mycobacterial antigens was induced by the sensitization of the animals with live BCG or killed Mycobacterium bovis or M. avium in incomplete Freund's adjuvant. In the study of the dynamics of the development of skin reactivity to tuberculin some advantages of the sensitization of guinea pigs with live mycobacteria were revealed, while after the revaccination of the animals no development of secondary cell-mediated immune response was observed. The immunization of guinea pigs with atypical mycobacteria prior to their sensitization with BCG was found to lead to the development of higher skin reactivity to allergen prepared from atypical mycobacteria than skin reactivity to tuberculin. 相似文献
50.