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1.
Using the sequence information from nine completely sequenced bacterial genomes, we extract 32 protein families that are
thought to contain orthologous proteins from each genome. The alignments of these 32 families are used to construct a phylogeny
with the neighbor-joining algorithm. This tree has several topological features that are different from the conventional phylogeny,
yet it is highly reliable according to its bootstrap values. Upon closer study of the individual families used, it is clear
that the strong phylogenetic signal comes from three families, at least two of which are good candidates for horizontal transfer.
The tree from the remaining 29 families consists almost entirely of noise at the level of bacterial phylum divisions, indicating
that, even with large amounts of data, it may not be possible to reconstruct the prokaryote phylogeny using standard sequence-based
methods.
Received: 22 November 1998 / Accepted: 17 February 1999 相似文献
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A universal Tree of Life (TOL) has long been a goal of molecular phylogeneticists, but reticulation at the level of genes and possibly at the levels of cells and species renders any simple interpretation of such a TOL, especially as applied to prokaryotes, problematic.One of the several ways in which microbiology puts the neo-Darwinian synthesis in jeopardy is by the threatening to “uproot the Tree of Life (TOL)” [1]. Lateral gene transfer (LGT) is much more frequent than most biologists would have imagined up until about 20 years ago, so phylogenetic trees based on sequences of different prokaryotic genes are often different. How to tease out from such conflicting data something that might correspond to a single, universal Tree of Life becomes problematic. Moreover, since many important evolutionary transitions involve lineage fusions at one level or another, the aptness of a tree (a pattern of successive bifurcations) as a summary of life’s history is uncertain [2–4]. 相似文献
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Anne M. Wolf 《Obesity (Silver Spring, Md.)》1998,6(Z1):2S-7S
From both societal and payer perspectives, the economic effect of obesity in the United States is substantial, estimated at approximately 6% of our national health expenditure and cost of care in a major health maintenance organization. The number of physician visits related to obesity has increased 88% in a 6-year period. The morbidity cost (lost productivity) and functional capability of the patient with obesity is increasing rapidly (50% increase in lost productivity, 36% increase in restricted activity, and 28% increase in number of bed-days). Cost savings of treating obesity are comparable to those of treating other chronic diseases such as coronary heart disease and diabetes. Most studies indicate that most of the direct health care costs of obesity are from type 2 diabetes, coronary heart disease and hypertension. To date, however, there have been no published reports of the cost effectiveness of the medical management of obesity treatment. In conclusion, the cost of obesity is comparable to that of other chronic diseases, yet it receives disproportionately less attention. Cost effectiveness studies need to be initiated promptly. 相似文献
5.
Ron Kagan Stephanie Allard Scott Carter 《Journal of applied animal welfare science : JAAWS》2018,21(3):59-70
ABSTRACTAnimal welfare concerns have plagued the professional zoo and aquarium field for decades. Societal differences remain concerning the well-being of animals, but it appears a shift is emerging. Scientific studies of animal welfare have dramatically increased, establishing that many previous concerns were not misguided public empathy or anthropomorphism. As a result, both zoo and aquarium animal welfare policy and science are now at the center of attention within the world’s professional zoos and aquariums. It is now possible to view a future that embraces the well-being of individual captive exotic animals, as well as that of their species, and one in which professional zoos and aquariums are dedicated equally to advancing both. Though the ethics of keeping exotic animals and animals from the wild in captivity are still a contentious subject both outside and even within the profession, this study argues. We argue that this path forward will substantially improve most zoo and aquarium animals' welfare and could significantly reduce societal concerns. If animal welfare science and policy are strongly rooted in compassion and embedded in robust accreditation systems, the basic zoo/aquarium paradigm will move toward a more thoughtful approach to the interface between visitors and animals. It starts with a fundamental commitment to the welfare of individual animals. 相似文献
6.
A method for quantitative evaluation of light sources from the point of their suitability for algal cultivation is described. Two parameters are used for the evaluation:
相似文献
(1) | amount of photons emitted in the spectral region absorbed by algae per consumed unit of electrical energy; |
(2) | fraction of photons intercept by the algae that got effectively transformed into chemical energy. |
7.
What Is Moving in the Secretory Pathway of Plants? 总被引:5,自引:2,他引:3
8.
As the molecular basis of signal propagation in the cell, proteins are regulated by perturbations, such as mechanical forces or ligand binding. The question arises how fast such a signal propagates through the protein molecular scaffold. As a first step, we have investigated numerically the dynamics of force propagation through a single (Ala) protein following a sudden increase in the stretching forces applied to its end termini. The force propagates along the backbone into the center of the chain on the picosecond scale. Both conformational and tension dynamics are found in good agreement with a coarse-grained theory of force propagation through semiflexible polymers. The speed of force propagation of 50Å ps−1 derived from these simulations is likely to determine an upper speed limit of mechanical signal transfer in allosteric proteins or molecular machines. 相似文献
9.
Rongcheng Lin Haiyang Wang 《植物学报(英文版)》2007,49(1):35-42
Arsbidopsis COP1 (Constitutive Photomorphogenic 1) defines a key repressor of photomorphogenesis in darkness by acting as an E3 ubiquitin Iigase in the nucleus, and is responsible for the targeted degradation of a number of photomorphogenesis-promoting factors, including phyA, HY5, LAF1, and HFR1. Light activation of multiple classes of photoreceptors (including both phytochromes and cryptochromes) inactivates COP1 and reduces its nuclear abundance, allowing the accumulation of these positively acting light signaling intermediates to promote photomorphogenic development. Recent studies suggest that Arabidopsis COP1 teams up with a family of SPA proteins (SPA1-SPA4) to form the physiologically active COP1-SPA E3 ubiquitin ligase complexes. These COP1-SPA complexes play overlapping and distinct functions in regulating seedling photomorphogenesis under different light conditions and adult plant growth. Further, the COP1-SPA complexes act In concert at a biochemical level with the CDD (COP10, DET1, and DDB1) complex and COP9 signalosome (CSN) to orchestrate the repression of photomorphogenesis. 相似文献
10.
Dominique Lestel 《Biosemiotics》2011,4(1):83-102
In this essay, I defend a bi-constructivist approach to ethology—a constructivist ethology assuming that each animal adopts
constructivist strategies. I put it in opposition to what I call a realist-Cartesian approach, which is currently the dominant
approach to ethology and comparative psychology. The starting point of the bi-constructivist approach can be formulated as
a shift from the classical Aristotelian question “What is an animal?” to the Spinozean question, which is much less classical
but which seems to me to be much stronger: “What are the capacities of the animal?”. Is it possible to conceptualize an ethology
which insists on interpretation and therefore on invention, innovation and creativity, rather than on causality, the monotony
of behavioural routines, and/or genetic or environmental determination? Such an ethology would be based not on the fiction
of an absent observer but on fully recognizing the necessity of an observer, who is effectively present in order to get an
observation. A pluralistic ethology does not dissociate itself from the marginal epistemologies of practitioners like animal trainers, hunters, stockbreeders etc., or, moreover, non-western experts. An ethology of this
kind is not clamped within the boundaries of purely academic epistemology, obsessed by demarcation lines between the human
and the animal. My work on the bi-constructivist approach represents a contribution towards the elaboration of an authentically
biosemiotic ethology, one which is significantly different from the mechanical ethology of today. 相似文献
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Canwei Xia Jiayu Liu Per Alström Qiao Wu Yanyun Zhang 《Ethology : formerly Zeitschrift fur Tierpsychologie》2013,119(8):653-661
Soft songs have been detected in many songbirds, but in most species, research on soft songs has lagged behind studies of broadcast songs. In this study, we describe the acoustic features of a soft song in the brownish‐flanked bush warbler Cettia fortipes. Compared with the broadcast song, the warbler's soft song was characterized by a lower minimum frequency and longer duration, and it had a higher proportion of rapid frequency modulation notes. Using playback experiments, some in combination with mounted specimens, we found different responses to soft and broadcast songs, and we found that soft song can predict aggressive escalation (attack). We conclude that the soft song is an aggressive signal in this species. 相似文献
13.
BACKGROUND TO THE DEBATE: Coronary artery disease is a major cause of death worldwide. Two very different approaches have been proposed as a way of reducing these deaths. The "high risk" approach uses tools such as risk factor scoring and carotid ultrasound to try and identify those at highest risk, and then treats them aggressively. The "population" approach aims to shift the distribution of risk factors across a population in a beneficial direction with the goal of reducing heart disease in the whole population. 相似文献
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Quantifying Landscape Spatial Pattern: What Is the State of the Art? 总被引:39,自引:0,他引:39
Eric J. Gustafson 《Ecosystems》1998,1(2):143-156
Landscape ecology is based on the premise that there are strong links between ecological pattern and ecological function and process. Ecological systems are spatially heterogeneous, exhibiting considerable complexity and variability in time and space. This variability is typically represented by categorical maps or by a collection of samples taken at specific spatial locations (point data). Categorical maps quantize variability by identifying patches that are relatively homogeneous and that exhibit a relatively abrupt transition to adjacent areas. Alternatively, point-data analysis (geostatistics) assumes that the system property is spatially continuous, making fewer assumptions about the nature of spatial structure. Each data model provides capabilities that the other does not, and they should be considered complementary. Although the concept of patches is intuitive and consistent with much of ecological theory, point-data analysis can answer two of the most critical questions in spatial pattern analysis: what is the appropriate scale to conduct the analysis, and what is the nature of the spatial structure? I review the techniques to evaluate categorical maps and spatial point data, and make observations about the interpretation of spatial pattern indices and the appropriate application of the techniques. Pattern analysis techniques are most useful when applied and interpreted in the context of the organism(s) and ecological processes of interest, and at appropriate scales, although some may be useful as coarse-filter indicators of ecosystem function. I suggest several important needs for future research, including continued investigation of scaling issues, development of indices that measure specific components of spatial pattern, and efforts to make point-data analysis more compatible with ecological theory. 相似文献
16.
Vik SB 《Journal of bioenergetics and biomembranes》2000,32(5):485-491
The ATP synthase from Escherichia coli is a prototype of the ATP synthases that are found in many bacteria, in the mitochondria of eukaryotes, and in the chloroplasts of plants. It contains eight different types of subunits that have traditionally been divided into F1, a water-soluble catalytic sector, and Fo, a membrane-bound ion transporting sector. In the current rotary model for ATP synthesis, the subunits can be divided into rotor and stator subunits. Several lines of evidence indicate that is one of the three rotor subunits, which rotate through 360 degrees. The three-dimensional structure of is known and its interactions with other subunits have been explored by several approaches. In light of recent work by our group and that of others, the role of in the ATP synthase from E. coli is discussed. 相似文献
17.
What Component of the Living Cell Is Responsible for Its Semipermeable Properties? Polarized Water or Lipids? 下载免费PDF全文
Gilbert N. Ling 《Biophysical journal》1973,13(8):807-816
A close correlation (r = +0.96) exists between the permeability (at 0°, 4°, and 25°C) of H2O and nine other hydroxylic nonelectrolytes through reversed frog skin and through synthetic cellulose-acetate sheets. By the method of least squares, the data yield the following relation: log (Pfrog skin) = 0.9900 log (Pcellulose acetate) -0.1659. Both the reversed frog skin and the cellulose-acetate sheets are semipermeable (while the lipoid membrane is not), showing higher permeability to water than to any other solute used in this series. The data offer support for the theory that it is not lipid, but water polarized in multilayers by cellular proteins, that provides the living cell with its selective surface barrier. 相似文献
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Markus Neteler Markus Metz Duccio Rocchini Annapaola Rizzoli Eleonora Flacio Luca Engeler Valeria Guidi Peter Lüthy Mauro Tonolla 《PloS one》2013,8(12)