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1.
2.
MAJOR CLADES OF THE ANGIOSPERMS 总被引:2,自引:0,他引:2
ROLF DAHLGREN KÅRE BREMER 《Cladistics : the international journal of the Willi Hennig Society》1985,1(4):349-368
Abstract— Our knowledge of fundamental angiosperm interrelationships is still very incomplete. The absence of a narrowly circumscribed gymnosperm outgroup, ideally the sister group, makes character evaluation, necessary for a cladistic analysis, difficult. According to current views the superorder Magnoliiflorae with a number of other groups, for example the monocotyledons, may represent a complex of families near the base of the angiosperms. Interrelationships of groups within the monocotyledons are much better understood than those between groups within the dicotyledons. A cladogram of monocotyledon orders based on earlier work by R. Dahlgren, H. T. Clifford, and F. N. Rasmussen is presented. A data matrix for a sample of the angiosperms with 61 characters for 49 taxa, mostly magnoliifloran and related families, is presented. The characters are polarized mainly according to the current view that the primitive angiosperm morphotype is a woody dicotyledon with strobiloid flowers. As an alternative the matrix is adjusted following W. C. Burger's conjecture that the primitive angiosperm was a herbaceous monocotyledon with trimerous flowers. Both matrices were run in a computerized parsimony analysis, resulting in numerous equally parsimonious solutions. This result is illustrative of the great homoplasy in the available character information, and also of how little actually is known about fundamental angiosperm interrelationships or phylogeny. 相似文献
3.
Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution 总被引:1,自引:0,他引:1
In order to study the relationships among mammalian alpha-globin genes, we
have determined the sequence of the 3' flanking region of the human alpha 1
globin gene and have made pairwise comparisons between sequenced
alpha-globin genes. The flanking regions were examined in detail because
sequence matches in these regions could be interpreted with the least
complication from the gene duplications and conversions that have occurred
frequently in mammalian alpha-like globin gene clusters. We found good
matches between the flanking regions of human alpha 1 and rabbit alpha 1,
human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and
horse alpha 1 and goat II alpha. These matches were used to align the
alpha-globin genes in gene clusters from different mammals. This alignment
shows that genes at equivalent positions in the gene clusters of different
mammals can be functional or nonfunctional, depending on whether they
corrected against a functional alpha-globin gene in recent evolutionary
history. The number of alpha-globin genes (including pseudogenes) appears
to differ among species, although highly divergent pseudogenes may not have
been detected in all species examined. Although matching sequences could be
found in interspecies comparisons of the flanking regions of alpha- globin
genes, these matches are not as extensive as those found in the flanking
regions of mammalian beta-like globin genes. This observation suggests that
the noncoding sequences in the mammalian alpha-globin gene clusters are
evolving at a faster rate than those in the beta-like globin gene clusters.
The proposed faster rate of evolution fits with the poor conservation of
the genetic linkage map around alpha-globin gene clusters when compared to
that of the beta-like globin gene clusters. Analysis of the 3' flanking
regions of alpha-globin genes has revealed a conserved sequence
approximately 100-150 bp 3' to the polyadenylation site; this sequence may
be involved in the expression or regulation of alpha-globin genes.
相似文献
4.
INTRODUCTI0NThedifferentiati0nofcelIsalongthemonocyte-macr0phagepathwayandthesig-nalsinvo1vedinthesecel1sacquiringtheabilitytokilltum0rcellsarenotfllllyundersto0d.Wehavebeenstudingamoleculewhichappearst0beanimportantmemberofthecytokinenetworkinvo1vedintheregulati0nmonocyteactivation.ThiscytokinetermedP48wasisolatedfr0mthehllmannullcellleukemiacell1ineReh.IthasbeenpurifiedtohomogeneityandfOundtobedistinctfrominterferongamma,col0nystimulatingfactors(CSFs)andTNFalphaalldbeta[1,2].Func-ti… 相似文献
5.
D Restrepo Y Okada J H Teeter L D Lowry B Cowart J G Brand 《Biophysical journal》1993,64(6):1961-1966
The sense of smell allows terrestrial animals to collect information about the chemical nature of their environment through the detection of airborne molecules. In humans smell is believed to play an important role in protecting the organism from environmental hazards such as fire, gas leaks and spoiled food, in determining the flavor of foods, and perhaps in infant-parent bonding. In addition, the study of human olfaction is relevant to a number of medical problems that result in olfactory dysfunction, which can affect nutritional state, and to the study of the etiology of neurodegenerative diseases which manifest themselves in the olfactory epithelium. Although much is known about behavioral aspects of human olfaction, little is understood about the underlying cellular mechanisms in humans. Here we report that viable human olfactory neurons (HON) can be isolated from olfactory tissue biopsies, and we find that HON respond to odorants with an increase in intracellular calcium concentration ([Cai]). 相似文献
6.
Perception of several bitter-tasting compounds was tested in52 subjects. Stable individual differences in the perceivedintensity of the bitterness of suprathreshold concentrationsof quinine sulfate (QSO4) and urea were found. Whereas 18 subjectsjudged selected concentrations of these compounds to be equallybitter, 17 found QSO4 to be more bitter than urea, and 17 foundurea to be more bitter than QSO4. These reliable individualdifferences were significantly related to threshold sensitivityto QSO4; that is, individuals who perceived QSO4 to be moreintense than urea at suprathreshold concentrations also hadlower QSO4 thresholds than did those who perceived urea to bemore intense than QSO4. There appeared to be no relationshipbetween the relative perceived intensities of these compoundsand rating of the bitterness of PROP (6-n-propylthiouracil).However, QSO4-sensitive individuals tended to find the bitternessof suprathreshold caffeine and sucrose octaacetate to be greaterthan that of suprathreshold magnesium sulfate, whereas the reversewas true for urea-sensitive individuals. This pattern parallelsthe pattern of cross-adaptation among these compounds reportedby other investigators. These results are consistent with theexistence of multiple bitter transduction sequences and suggestthat individual differences in response to various bitter compoundsmay reflect differences in teh relative availability of specifictransduction sequences. 相似文献
7.
Marissa A. LeBlanc Gregory D. Fairn Sarah B. Russo Ola Czyz Vanina Zaremberg L. Ashley Cowart Christopher R. McMaster 《PloS one》2013,8(4)
The oxysterol binding protein family are amphitropic proteins that bind oxysterols, sterols, and possibly phosphoinositides, in a conserved binding pocket. The Saccharomyces cerevisiae oxysterol binding protein family member Kes1 (also known as Osh4) also binds phosphoinositides on a distinct surface of the protein from the conserved binding pocket. In this study, we determine that the oxysterol binding protein family member Kes1 is required to maintain the ratio of complex sphingolipids and levels of ceramide, sphingosine-phosphate and sphingosine. This inability to maintain normal sphingolipid homeostasis resulted in misdistribution of Pma1, a protein that requires normal sphingolipid synthesis to occur to partition into membrane rafts at the Golgi for its trafficking to the plasma membrane. 相似文献
8.
Under natural conditions, plants are subjected to continuous changes of irradiance that drive variations of stomatal conductance to water vapour (gs). We propose a dynamic model to predict the temporal response of gs at the leaf level using an asymmetric sigmoid function with a unique parameter describing time constants for increasing and decreasing gs. The model parameters were adjusted to observed data using Approximate Bayesian Computation. We tested the model performance for (1) instant changes of irradiance; or (2) continuous and controlled variations of irradiance simulating diurnal time courses. Compared with the two mostly used steady‐state models, our dynamic model described daily time courses of gs with a higher accuracy. In particular, it was able to describe the hysteresis of gs responses to increasing/decreasing irradiance and the resulting rapid variations of intrinsic water‐use efficiency. Compared to the mechanistic model of temporal responses of gs by Kirschbaum, Gross & Pearcy, for which time constants were estimated with a large variance, our model estimated time constants with a higher precision. It is expected to improve predictions of water loss and water‐use efficiency in higher scale models by using a small number of parameters. 相似文献
9.
Jessica S. Ross Wei Hu Bess Rosen Ashley J. Snider Lina M. Obeid L. Ashley Cowart 《The Journal of biological chemistry》2013,288(31):22193-22206
We previously demonstrated that sphingosine kinase 1 (Sphk1) expression and activity are up-regulated by exogenous palmitate (PAL) in a skeletal muscle model system and in diet-induced obesity in mice; however, potential functions and in vivo relevance of this have not been addressed. Here, we aimed to determine the mechanism by which PAL regulates SphK1 in muscle, and to determine potential roles for its product, sphingosine-1-phosphate (S1P), in muscle biology in the context of obesity. Cloning and analysis of the mouse Sphk1 promoter revealed a peroxisome proliferator-activated receptor (PPAR) α cis-element that mediated activation of a reporter under control of the Sphk1 promoter; direct interaction of PPARα was demonstrated by chromatin immunoprecipitation. PAL treatment induced the proinflammatory cytokine interleukin (IL)-6 in a manner dependent on SphK1, and this was attenuated by inhibition of the sphingosine-1-phosphate receptor 3 (S1PR3). Diet-induced obesity in mice demonstrated that IL-6 expression in muscle, but not adipose tissue, increased in obesity, but this was attenuated in Sphk1−/− mice. Moreover, plasma IL-6 levels were significantly decreased in obese Sphk1−/− mice relative to obese wild type mice, and muscle, but not adipose tissue IL-6 signaling was activated. These data indicate that PPARα regulates Sphk1 expression in the context of fatty acid oversupply and links PAL to muscle IL-6 production. Moreover, this function of SphK1 in diet-induced obesity suggests a potential role for SphK1 in obesity-associated pathological outcomes. 相似文献
10.
Cowart M Pratt JK Stewart AO Bennani YL Esbenshade TA Hancock AA 《Bioorganic & medicinal chemistry letters》2004,14(3):689-693
2-aminoethylbenzofurans constitute a new class of H(3) antagonists that are more rotationally constrained than most previously reported H(3) antagonists. They retain high potency at human and rat receptors, with efficient CNS penetration observed in 35. The SAR of the basic amine moiety was compared in three different series of analogues. The greatest potency was found in analogues bearing a 2-methylpyrrolidine, a 2,5-dimethylpyrrolidine, or a 2,6-dimethylpiperidine. 相似文献