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1.
2.
Johannes H. P. Hackstein Theo A. van Alen 《Evolution; international journal of organic evolution》1996,50(2):559-572
It has been assumed that the feeding habits of vertebrates predispose the variety of intestinal differentiations and the composition of the microbial biota living in their intestinal tracts. Consequently, the presence of methanogenic bacteria in the various differentiations of the large intestine and the foregut of herbivorous vertebrates had been attributed primarily to the existence of anaerobic habitats and the availability of carbon dioxide and hydrogen originating from the fermentative microbial digestion of plant-based diets. However, Australian ratites, many murids, and several New World primates lack methanogens, despite their intestinal differentiations and their vegetarian feeding habits. Crocodiles, giant snakes, aardvarks, and ant-eaters on the other hand release significant amounts of methane. A determination of methane emissions by 253 vertebrate species confirmed that competence for intestinal methanogenic bacteria is shared by related species and higher taxa, irrespective of different feeding habits. In “methanogenic” branches of the evolutionary tree, a variety of differentiations of the large intestine evolved and, in some cases, differentiations of the foregut. In contrast, the lack of competence for methanogens in chiropterans/insectivores and carnivores apparently has precluded the evolution of specialized fermenting differentiations of the digestive tract. Our observations reveal that the presence of intestinal methanogenic bacteria is under phylogenetic rather than dietary control: competence for intestinal methanogenic bacteria is a plesiomorphic (primitive-shared) character among reptiles, birds, and mammals. This competence for methanogenic bacteria has been crucial for the evolution of the amniotes. 相似文献
3.
Detecting non-neutral heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence 总被引:11,自引:4,他引:7
Natural selection, in the form of balancing selection or selective sweeps,
can result in a decoupling of the amounts of molecular polymorphism and
divergence. Thus natural selection can cause some areas of DNA sequence to
have greater silent polymorphism, relative to divergence between species,
than other areas. It would be useful to have a statistical test for
heterogeneity in the polymorphism to divergence ratio across a region of
DNA sequence, one that could identify heterogeneity greater than that
expected from the neutral processes of mutation, drift, and recombination.
The only currently available test requires that a region be arbitrarily
divided into sections that are compared with each other, and the
subjectivity of this division could be problematic. Here a test is proposed
in which runs of polymorphic and fixed sites are counted, where a "run" is
a set of one or more sites of one type preceded and followed by the other
type. The number of runs is smaller than otherwise expected if
polymorphisms are clumped together. By simulating neutral evolution and
comparing the observed number of runs to the simulations, a statistical
test is possible which does not require any a priori decisions about
subdivision.
相似文献
4.
Holger Hackstein Gerhard Jahn Holger Kirchner Gregor Bein 《Histochemistry and cell biology》1996,106(2):229-234
Radioactive in situ hybridization techniques or enzymatic detection procedures of hapten-modified human cytomegalovirus (HCMV)
probes have been widely used for studying the infection of peripheral blood leukocytes with HCMV. This report describes significant
improvements in terms of signal resolution which can be obtained by applying a highly sensitive fluorescence in situ hybridization
(FISH) technique in conjunction with a large subgenomic HCMV DNA probe. Three cosmid clones spanning 119.1 kb of the HCMV
genome (230 kb) were used to construct the digoxigenin-11-dUTP-labeled probe which was found to be superior to a total HCMV
probe representing the entire genome. Crucial hybridization parameters were analyzed systematically in order to ensure optimal
resolution power and sensitivity. The protocol was successfully applied to HCMV-infected fibroblasts and peripheral blood
leukocytes of 12 transplant patients and unambiguously facilitated the precise intracellular localization of HCMV genomes
in infected cells. Because of its excellent resolution properties, accompanied by the virtual absence by any background staining,
we recommend the use of this protocol as a sensitive approach for further virological analyses of the interactions between
HCMV and peripheral blood leukocytes at the single-cell level.
Accepted: 16 February 1996 相似文献
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7.
Kasthuri Kannayiram Vidhya Rekha Umapathy Y Chamundeswari JH Fathima Ramajayam Govindan Chella Perumal Palanisamy Vishnu Priya Veeraraghavan Selvaraj Jayaraman Ponnulakshmi Rajagopal 《Bioinformation》2022,18(3):80
Diabetes mellitus is a group of metabolic disorders that has risen to become the third most common cause in humans in recent years. The development of new bioactive substances from natural sources is a relatively new area. Flavonoids are believed to have a variety of beneficial properties in nature, including anti-inflammatory, antimicrobial, anticancer, antioxidant, neuroprotective, and anti-HIV properties. 15 naturally occurring flavonoids docked with the selected target aldose reductase. We report the optimal binding of Acumitin, Agathisflavone, Agehoustin B, and alpha-Toxicarol with aldose reductase for further consideration in drug discovery for T2DM. 相似文献
8.
Ali C Akyildiz Lambert Speelman Harald van Brummelen Miguel A Gutiérrez Renu Virmani Aad van der Lugt Anton FW van der Steen Jolanda J Wentzel Frank JH Gijsen 《Biomedical engineering online》2011,10(1):25
Background
Rupture of the cap of a vulnerable plaque present in a coronary vessel may cause myocardial infarction and death. Cap rupture occurs when the peak cap stress exceeds the cap strength. The mechanical stress within a cap depends on the plaque morphology and the material characteristics of the plaque components. A parametric study was conducted to assess the effect of intima stiffness and plaque morphology on peak cap stress. 相似文献9.
Holger Hackstein Sabine Kranz Anne Lippitsch Andreas Wachtendorf Olivia Kershaw Achim D Gruber Gabriela Michel Jürgen Lohmeyer Gregor Bein Nelli Baal Susanne Herold 《Respiratory research》2013,14(1):91
Background
Klebsiella pneumoniae is a leading cause of severe hospital-acquired respiratory tract infections and death but little is known regarding the modulation of respiratory dendritic cell (DC) subsets. Plasmacytoid DC (pDC) are specialized type 1 interferon producing cells and considered to be classical mediators of antiviral immunity.Method
By using multiparameter flow cytometry analysis we have analysed the modulation of respiratory DC subsets after intratracheal Klebsiella pneumonia infection.Results
Data indicate that pDCs and MoDC were markedly elevated in the post acute pneumonia phase when compared to mock-infected controls. Analysis of draining mediastinal lymph nodes revealed a rapid increase of activated CD103+ DC, CD11b+ DC and MoDC within 48 h post infection. Lung pDC identification during bacterial pneumonia was confirmed by extended phenotyping for 120G8, mPDCA-1 and Siglec-H expression and by demonstration of high Interferon-alpha producing capacity after cell sorting. Cytokine expression analysis of ex vivo-sorted respiratory DC subpopulations from infected animals revealed elevated Interferon-alpha in pDC, elevated IFN-gamma, IL-4 and IL-13 in CD103+ DC and IL-19 and IL-12p35 in CD11b+ DC subsets in comparison to CD11c+ MHC-class IIlow cells indicating distinct functional roles. Antigen-specific naive CD4+ T cell stimulatory capacity of purified respiratory DC subsets was analysed in a model system with purified ovalbumin T cell receptor transgenic naive CD4+ responder T cells and respiratory DC subsets, pulsed with ovalbumin and matured with Klebsiella pneumoniae lysate. CD103+ DC and CD11b+ DC subsets represented the most potent naive CD4+ T helper cell activators.Conclusion
These results provide novel insight into the activation of respiratory DC subsets during Klebsiella pneumonia infection. The detection of increased respiratory pDC numbers in bacterial pneumonia may indicate possible novel pDC functions with respect to lung repair and regeneration. 相似文献10.
Janine JH Oosterhof G Jolanda Elving Ietse Stokroos Arie van nieuw Amerongen Henny C van der Mei Henk J Busscher 《Biofouling》2013,29(6):347-353
The integrity of biofilms on voice prostheses used to rehabilitate speech in laryngectomized patients causes unwanted increases in airflow resistance, impeding speech. Biofilm integrity is ensured by extracellular polymeric substances (EPS). This study aimed to determine whether synthetic salivary peptides or mucolytics, including N-acetylcysteine and ascorbic acid, influence the integrity of voice prosthetic biofilms. Biofilms were grown on voice prostheses in an artificial throat model and exposed to synthetic salivary peptides, mucolytics and two different antiseptics (chlorhexidine and Triclosan). Synthetic salivary peptides did not reduce the air flow resistance of voice prostheses after biofilm formation. Although both chlorhexidine and Triclosan reduced microbial numbers on the prostheses, only the Triclosan-containing positive control reduced the air flow resistance. Unlike ascorbic acid, the mucolytic N-acetylcysteine removed most EPS from the biofilms and induced a decrease in air flow resistance. 相似文献