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951.
David M. Grossnickle Meng Chen James G. A. Wauer Spencer K. Pevsner Lucas N. Weaver Qing-Jin Meng Di Liu Yu-Guang Zhang Zhe-Xi Luo 《Evolution; international journal of organic evolution》2020,74(12):2662-2680
Ecology and biomechanics play central roles in the generation of phenotypic diversity. When unrelated taxa invade a similar ecological niche, biomechanical demands can drive convergent morphological transformations. Thus, examining convergence helps to elucidate the key catalysts of phenotypic change. Gliding mammals are often presented as a classic case of convergent evolution because they independently evolved in numerous clades, each possessing patagia (“wing” membranes) that generate lift during gliding. We use phylogenetic comparative methods to test whether the skeletal morphologies of the six clades of extant gliding mammals demonstrate convergence. Our results indicate that glider skeletons are convergent, with glider groups consistently evolving proportionally longer, more gracile limbs than arborealists, likely to increase patagial surface area. Nonetheless, we interpret gliders to represent incomplete convergence because (1) evolutionary model-fitting analyses do not indicate strong selective pressures for glider trait optima, (2) the three marsupial glider groups diverge rather than converge, and (3) the gliding groups remain separated in morphospace (rather than converging on a single morphotype), which is reflected by an unexpectedly high level of morphological disparity. That glider skeletons are morphologically diverse is further demonstrated by fossil gliders from the Mesozoic Era, which possess unique skeletal characteristics that are absent in extant gliders. Glider morphologies may be strongly influenced by factors such as body size and attachment location of patagia on the forelimb, which can vary among clades. Thus, convergence in gliders appears to be driven by a simple lengthening of the limbs, whereas additional skeletal traits reflect nuances of the gliding apparatus that are distinct among different evolutionary lineages. Our unexpected results add to growing evidence that incomplete convergence is prevalent in vertebrate clades, even among classic cases of convergence, and they highlight the importance of examining form-function relationships in light of phylogeny, biomechanics, and the fossil record. 相似文献
952.
The fatty acid composition from mycelia of Streptomyces hygroscopicus strains was studied. A significant proportion of C18 : 2 was found in cultures. High levels of C16 : 0 , iso-C16 : 0 and C18 : 1 were also detected in all S. hygroscopicus strains. The different representatives of S. hygroscopicus had almost the same proportion of unsaturated fatty acids. Certain shifts in the amount of iso, anteiso and straight-chain fatty acids in some cultures were revealed. This might be explained by the adaptation capability of strains belonging to one species to form a variety of available fatty acids determined by particular cell membrane composition favouring certain antibiotic biosynthesis. 相似文献
953.
954.
955.
Addition of purified colicin Ib to whole Escherichia coli cells or cytoplasmic membrane vesicles inhibits their subsequent ability to generate a membrane potential. In addition, this colicin is shown to bring about a voltage-dependent increase in the conductance of an artificial planar bilayer membrane prepared from soybean phospholipids. This results from the formation of ion-permeable channels. These data provide strong evidence that the depolarization of Escherichia coli cells by this colicin results from an Ib-induced increase in membrane permeability to ions. 相似文献
956.
Gowrishankar TR Esser AT Vasilkoski Z Smith KC Weaver JC 《Biochemical and biophysical research communications》2006,341(4):1266-1276
Conventional electroporation (EP) by 0.1 to 1 kV/cm pulses longer than 100 micros, and supra-electroporation by 10 to 300 kV/cm pulses shorter than 1 micros cause different cellular effects. Conventional EP delivers DNA, proteins, small drugs, and fluorescent indicators across the plasma membrane (PM) and causes moderate levels of phosphatidylserine (PS) translocation at the PM. We hypothesize that supra-EP is central to intracellular effects such as apoptosis induction and higher levels of PS translocation. Our cell system model has 20,000 interconnected local models for small areas of the PM and organelle membranes, small regions of aqueous media, appropriate resting potentials, and the asymptotic EP model. Conventional EP primarily affects the PM, but with a hint of endoplasmic reticulum involvement. Supra-EP can involve all of a cell's membrane at the largest fields. Conventional EP fields tend to go around cells, but supra-EP fields go through cells, extensively penetrating organelles. 相似文献
957.
Adaptation and increased susceptibility to infection associated with constitutive expression of misfolded SP-C 总被引:5,自引:0,他引:5
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Mutations in the gene encoding SP-C (surfactant protein C; SFTPC) have been linked to interstitial lung disease (ILD) in children and adults. Expression of the index mutation, SP-C(Deltaexon4), in transiently transfected cells and type II cells of transgenic mice resulted in misfolding of the proprotein, activation of endoplasmic reticulum (ER) stress pathways, and cytotoxicity. In this study, we show that stably transfected cells adapted to chronic ER stress imposed by the constitutive expression of SP-C(Deltaexon4) via an NF-kappaB-dependent pathway. However, the infection of cells expressing SP-C(Deltaexon4) with respiratory syncytial virus resulted in significantly enhanced cytotoxicity associated with accumulation of the mutant proprotein, pronounced activation of the unfolded protein response, and cell death. Adaptation to chronic ER stress imposed by misfolded SP-C was associated with increased susceptibility to viral-induced cell death. The wide variability in the age of onset of ILD in patients with SFTPC mutations may be related to environmental insults that ultimately overwhelm the homeostatic cytoprotective response. 相似文献
958.
Critical structure-function determinants within the N-terminal region of pulmonary surfactant protein SP-B 总被引:1,自引:0,他引:1
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Surfactant protein SP-B is absolutely required for the surface activity of pulmonary surfactant and postnatal lung function. The results of a previous study indicated that the N-terminal segment of SP-B, comprising residues 1–9, is specifically required for surface activity, and suggested that prolines 2, 4, and 6 as well as tryptophan 9, may constitute essential structural motifs for protein function. In this work, we assessed the role of these two motifs in promoting the formation and maintenance of surface-active films. Three synthetic peptides were synthesized including a peptide corresponding to the N-terminal 37 amino acids of native SP-B and two variants in which prolines 2, 4, 6, or tryptophan 9 were substituted by alanines. All three synthetic peptides were surface-active, as expected from their amphipathic structure. The peptides were also able to insert into dipalmitoylphosphatidylcholine/palmitoyloleoylphosphatidylglycerol (7:3 w/w ratio) monolayers preformed at pressures >30 mN/m, indicating that they perturb and insert into membranes. Substitution of alanine for tryptophan at position 9 significantly decreased both the rate of adsorption/insertion of the peptide into the interface and reinsertion of surface-active material excluded from the film during successive compression-expansion cycles. Substitution of alanines for prolines at positions 2, 4, and 6 did not produce substantial changes in the rate of adsorption/insertion; however, reinsertion of surface-active material into the expanding interface film was not as effective as in the presence of the nativelike peptide. These results suggest that W9 is critical for optimal interface affinity, whereas prolines may promote a conformation that facilitates rapid insertion of the peptide into phospholipid monolayers compressed to the highest pressures during compression-expansion cycling. 相似文献
959.
It is proposed to obtain effective Lipari–Szabo order parameters and local correlation times for relaxation vectors of protein
13CO nuclei by carrying out a 13CO-R1 auto relaxation experiment, a transverse CSA/dipolar cross correlation and a transverse 13CO CSA/13CO–15N CSA/dipolar cross correlation experiment. Given the global rotational correlation time from 15N relaxation experiments, a new program COMFORD (CO-Modelfree Fitting Of Relaxation Data) is presented to fit the 13CO data to an effective order parameter , an effective local correlation time and the orientation of the CSA tensor with respect to the molecular frame. It is shown
that the effective is least sensitive to rotational fluctuations about an imaginary axis and most sensitive to rotational fluctuations about an imaginary axis parallel to the NH bond direction. As such, the
information is fully complementary to the 15N relaxation order parameter, which is least sensitive to fluctuations about the NH axis and most sensitive to fluctuations
about the axis. The new paradigm is applied on data of Ca2+ saturated Calmodulin, and on available literature data for Ubiquitin. Our data indicate that the order parameters rapport on slower, and sometimes different, motions than the 15N relaxation order parameters. The CO local correlation times correlate well with the calmodulin’s secondary structure.
Electronic Supplementary Material Supplementary material is available to authorized users in the online version of this article at . 相似文献
960.
Pioli PA Weaver LK Schaefer TM Wright JA Wira CR Guyre PM 《Journal of immunology (Baltimore, Md. : 1950)》2006,176(11):6647-6655
The uterine endometrium coordinates a wide spectrum of physiologic and immunologic functions, including endometrial receptivity and implantation as well as defense against sexually transmitted pathogens. Macrophages and epithelial cells cooperatively mediate innate host defense against bacterial invasion through the generation of immunologic effectors, including cytokines and antimicrobial peptides. In this study, we demonstrate that stimulation of peripheral blood monocytes and uterine macrophages with bacterial LPS induces the production of biologically active proinflammatory IL-1beta. High doses of estradiol enhance LPS-induced IL-1beta expression in an estrogen receptor-dependent manner. Furthermore, both peripheral blood monocyte- and uterine macrophage-derived IL-1beta induce secretion of antimicrobial human beta-defensin 2 by uterine epithelial cells. These data indicate dynamic immunologic interaction between uterine macrophages and epithelial cells and implicate a role for estradiol in the modulation of the immune response. 相似文献