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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.
SPERMIOGENESIS IN WILD TYPE AND IN A MALE STERILITY MUTANT OF DROSOPHILA MELANOGASTER 总被引:3,自引:1,他引:2
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Jane Rearick Shoup 《The Journal of cell biology》1967,32(3):663-675
Spermiogenesis in the translocation heterozygote T (1; 2H) 25(20) y l 25/FM6 has been studied with the electron microscope and compared with that in wild type males. It appears that the genetic lesion in the male sterility mutant is associated primarily with a failure in differentiation of the head. In wild type flies, the spermatid nucleus assumes a conchoidal shape; chromatin accumulates along the convex surface. Adjacent to the concave surface a large bundle of microtubules runs parallel to the long axis of the spermatid. A single row of microtubules is juxtaposed against the convex surface of the head. As differentiation proceeds, the nucleus elongates, chromatin condenses, and the nucleus is compacted to a final diameter of about 0.3 µ. In the sterile mutant the spermatid nucleus has an irregular or wedge-shaped profile and no concavity is formed, nor is the bundle of microtubules observed. The row of microtubules, however, is usually present around the periphery. The change from lysine-rich to arginine-rich histone in mature wild type sperm does not occur in the sterile male. The substructure of the axial filament and mitochondrial derivatives, however, are similar to those in wild type. 相似文献
5.
INTRODUCTI0NThedifferentiati0nofcelIsalongthemonocyte-macr0phagepathwayandthesig-nalsinvo1vedinthesecel1sacquiringtheabilitytokilltum0rcellsarenotfllllyundersto0d.Wehavebeenstudingamoleculewhichappearst0beanimportantmemberofthecytokinenetworkinvo1vedintheregulati0nmonocyteactivation.ThiscytokinetermedP48wasisolatedfr0mthehllmannullcellleukemiacell1ineReh.IthasbeenpurifiedtohomogeneityandfOundtobedistinctfrominterferongamma,col0nystimulatingfactors(CSFs)andTNFalphaalldbeta[1,2].Func-ti… 相似文献
6.
S A Shoup W W Johnston H F Siegler J W Tello J Schlom D D Bigner S H Bigner 《Acta cytologica》1990,34(3):385-392
Five antibodies, 2D.1 (pan-leukocyte), AE-1,3 (anti-keratin), B72.3 (anti-carcinoma), ME 1-14 (alpha-chondroitin sulfate proteoglycan) and polyclonal S-100 protein (P-S100), were tested to determine if this panel could be used immunocytochemically to differentiate melanoma from nonmelanoma. A total of 161 cases were evaluated: 145 fine needle aspirates of various body sites and 16 effusions, consisting of 52 melanomas, 41 adenocarcinomas, 11 squamous cell carcinomas, 14 undifferentiated carcinomas, 8 small cell carcinomas, 8 miscellaneous carcinomas, 8 primary central nervous system (CNS) tumors, 7 lymphomas/leukemias, 4 sarcomas and 8 benign effusions. The 52 melanomas were stained by ME 1-14 (in 31 cases) and by P-S100 (in 39 cases), but not by B72.3, AE-1,3 or 2D.1. The 82 carcinomas reacted with P-S100 (in 25 cases), B72.3 (in 37 cases), AE-1,3 (in 68 cases) and 2D.1 (in 1 case), but not with ME 1-14. Lymphomas were stained only by 2D.1 (5 of 7 cases). The eight primary CNS tumors reacted solely with ME1-14 (in 3 cases) and P-S100 (in 3 cases). The eight benign effusions exhibited staining by ME 1-14 (in 1 case), P-S100 (in 1 case), AE-1,3 (in 3 cases) and 2D.1 (in 8 cases), but not by B72.3. Thirty-six cases (including 11 melanomas) failed to stain with any antibody. In summary, 41 of 52 melanomas and 4 of 8 CNS tumors stained with ME1-14, P-S100 or both and were negative for B72.3, AE-1,3 and 2D.1. Only 2 of 101 other nonmelanomas exhibited this pattern. Thus, this panel distinguishes melanoma from other neoplastic and nonneoplastic processes in the majority of cases. 相似文献
7.
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
8.
Abstract. 1. Stage-specific survival and recruitment of spruce budworm were measured by frequent sampling of foliage in four outbreak populations over a 15-year period in Ontario and Quebec, Canada.
2. Patterns of change in population density during the outbreak collapse phase were closely linked to changes in survival of the late immature stages, and were determined largely by the impact of natural enemies.
3. Host-plant feedback also contributed significantly to survival patterns throughout the outbreak: annual defoliation influenced survival of fourth and fifth instars and fecundity while cumulative defoliation influenced survival of the very early larval stages (first and second) via impacts on stand condition.
4. Inclusion of this host-plant feedback reveals spruce budworm population dynamics as a function of density-related trophic interactions that vary in their order and strength of influence over time. This view re-introduces the importance of forest interactions as a component of dynamics of the spruce budworm. 相似文献
2. Patterns of change in population density during the outbreak collapse phase were closely linked to changes in survival of the late immature stages, and were determined largely by the impact of natural enemies.
3. Host-plant feedback also contributed significantly to survival patterns throughout the outbreak: annual defoliation influenced survival of fourth and fifth instars and fecundity while cumulative defoliation influenced survival of the very early larval stages (first and second) via impacts on stand condition.
4. Inclusion of this host-plant feedback reveals spruce budworm population dynamics as a function of density-related trophic interactions that vary in their order and strength of influence over time. This view re-introduces the importance of forest interactions as a component of dynamics of the spruce budworm. 相似文献
9.
Arielle Brooks Daniel Shoup Lauren Kustigian Jason Puchalla Chavela M. Carr Hays S. Rye 《PloS one》2015,10(3)
Vital cellular processes, from cell growth to synaptic transmission, rely on membrane-bounded carriers and vesicles to transport molecular cargo to and from specific intracellular compartments throughout the cell. Compartment-specific proteins are required for the final step, membrane fission, which releases the transport carrier from the intracellular compartment. The role of fission proteins, especially at intracellular locations and in non-neuronal cells, while informed by the dynamin-1 paradigm, remains to be resolved. In this study, we introduce a highly sensitive approach for the identification and analysis of membrane fission machinery, called burst analysis spectroscopy (BAS). BAS is a single particle, free-solution approach, well suited for quantitative measurements of membrane dynamics. Here, we use BAS to analyze membrane fission induced by the potent, fission-active ENTH domain of epsin. Using this method, we obtained temperature-dependent, time-resolved measurements of liposome size and concentration changes, even at sub-micromolar concentration of the epsin ENTH domain. We also uncovered, at 37°C, fission activity for the full-length epsin protein, supporting the argument that the membrane-fission activity observed with the ENTH domain represents a native function of the full-length epsin protein. 相似文献
10.
L. DA S. PONTES J.-F. SOUSSANA† F. LOUAULT D. ANDUEZA‡ P. CARRÈRE 《Functional ecology》2007,21(5):844-853