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1.
Knud IB Christensen 《Nordic Journal of Botany》1983,2(6):537-548
Crataegus curvisepala Lindm., C. laevigata (Poiret) DC. and C. monogyna Jacq. (Rosaceae) form hybrid complexes in Denmark due to introgression. C. palmstruchii Lindm. seems to be variously introgressed individuals of C. laevigata. C. eremitagensis Raunk., C. raavadensis Raunk. and C. schumacheri Raunk. apparently belong to C. curvisepala x laevigata. The delimitation between C. curvisepala x laevigata and C. laevigata x monogyna is discussed. 相似文献
2.
Andersen OM Christensen PA Christensen LL Jacobsen C Moestrup SK Etzerodt M Thogersen HC 《Biochemistry》2000,39(35):10627-10633
The low-density lipoprotein receptor-related protein (LRP) is a large surface receptor that mediates binding and internalization of a large number of structurally and functionally unrelated ligands. The ligand binding sites are located in clusters of complement-type repeats (CR), where the general absence of mutual binding competition suggests that different ligands map to distinct sites. Binding of alpha(2)-macroglobulin-protease complexes to the LRP is mediated by the receptor binding domain (RBD) of alpha(2)-macroglobulin (alpha(2)M). To determine the major binding epitope(s) in the LRP, we generated a complete set of tandem CR proteins spanning the second cluster of CR domains, and identified a binding site for alpha(2)M in the N-terminal part of the cluster comprising CR3-CR6, using ligand blotting and surface plasmon resonance (SPR) analysis. The specific site involved in alpha(2)M recognition resides in the fourth CR domain, CR4, whereas another site is identified in CR5. An acidic epitope in CR4 is identified as important for binding alpha(2)M by mutagenesis and SPR analysis. The formation of the complex between the rat alpha(1)-macroglobulin RBD and CR domain pairs is characterized by analytical size-exclusion chromatography, which demonstrates a sufficiently strong interaction between the alpha(1)M RBD and CR34 or CR45 for the isolation of a complex. 相似文献
3.
ZBARSKYIB 《Cell research》1998,8(2):99-103
The nonchromatin proteinous residue of the cell nucleus was revealed in our laboratory as early as in 1948 and then identified by light and electron microscopy as residual nucleoli,intranuclear network and nuclear envelope before 1960,This structure termed afterwards as “nuclear residue“,“nuclear skeleton“,“nuclear cage“,“nuclear carcass“etc.,was much later(in 1974) isolated,studied and entitled as “nuclear matrix“ by Berezney and Coffey,to whom the discovery of this residual structure is often wronly ascribed.The real history of nuclear matrix manifestation is reported in this paper. 相似文献
4.
JUAN DIEGO IBÁÑEZ‐ÁLAMO MANUEL SOLER 《Biological journal of the Linnean Society. Linnean Society of London》2010,101(4):759-766
Urbanization, one of the most extreme land‐use alterations, is currently spreading, and the number of species confronting these changes is increasing. However, contradictory results of previous studies impede a clear interpretation of which selective pressure (nest predation or food limitation) is more important in urban habitats compared with natural situations, and whether birds can confront them by adjusting their life‐history strategies. We investigated life‐history syndromes of three common blackbird (Turdus merula) populations differing in their human influence (urban, rural, and woodland). We analysed daily nest predation and nestling starvation rates to assess the relative importance of these selection pressures in each habitat. Simultaneously, several life‐history traits were investigated to determine if T. merula seem adapted to their main source of selection. Food limitation was more important in the city, whereas nest predation was the most important selective force in the forest. The rural habitat was characterized by an intermediate influence of these two factors. Life‐history syndromes, as the covariation of a suite of traits, confirmed these results because T. merula seem well adapted to the main cause of selection in each habitat. Our results are consistent with urbanization imposing new challenges on birds, and that they adaptively respond to them. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 759–766. 相似文献
5.
Kantyka T Plaza K Koziel J Florczyk D Stennicke HR Thogersen IB Enghild JJ Silverman GA Pak SC Potempa J 《Biological chemistry》2011,392(5):483-489
Bacterial proteases are considered virulence factors and it is presumed that by abrogating their activity, host endogenous protease inhibitors play a role in host defense against invading pathogens. Here we present data showing that Staphylococcus aureus cysteine proteases (staphopains) are efficiently inhibited by Squamous Cell Carcinoma Antigen 1 (SCCA1), an epithelial-derived serpin. The high association rate constant (k(ass)) for inhibitory complex formation (1.9×10(4) m/s and 5.8×10(4) m/s for staphopain A and staphopain B interaction with SCCA1, respectively), strongly suggests that SCCA1 can regulate staphopain activity in vivo at epithelial surfaces infected/colonized by S. aureus. The mechanism of staphopain inhibition by SCCA1 is apparently the same for serpin interaction with target serine proteases whereby the formation of a covalent complex result in cleavage of the inhibitory reactive site peptide bond and associated release of the C-terminal serpin fragment. Interestingly, the SCCA1 reactive site closely resembles a motif in the reactive site loop of native S. aureus-derived inhibitors of the staphopains (staphostatins). Given that S. aureus is a major pathogen of epithelial surfaces, we suggest that SCCA1 functions to temper the virulence of this bacterium by inhibiting the staphopains. 相似文献
6.
IB Masters MM Eastburn PW Francis R Wootton PV Zimmerman RS Ware AB Chang 《Respiratory research》2005,6(1):16
Background
Flexible video bronchoscopes, in particular the Olympus BF Type 3C160, are commonly used in pediatric respiratory medicine. There is no data on the magnification and distortion effects of these bronchoscopes yet important clinical decisions are made from the images. The aim of this study was to systematically describe the magnification and distortion of flexible bronchoscope images taken at various distances from the object.Methods
Using images of known objects and processing these by digital video and computer programs both magnification and distortion scales were derived.Results
Magnification changes as a linear function between 100 mm (×1) and 10 mm (×9.55) and then as an exponential function between 10 mm and 3 mm (×40) from the object. Magnification depends on the axis of orientation of the object to the optic axis or geometrical axis of the bronchoscope. Magnification also varies across the field of view with the central magnification being 39% greater than at the periphery of the field of view at 15 mm from the object. However, in the paediatric situation the diameter of the orifices is usually less than 10 mm and thus this limits the exposure to these peripheral limits of magnification reduction. Intraclass correlations for measurements and repeatability studies between instruments are very high, r = 0.96. Distortion occurs as both barrel and geometric types but both types are heterogeneous across the field of view. Distortion of geometric type ranges up to 30% at 3 mm from the object but may be as low as 5% depending on the position of the object in relation to the optic axis.Conclusion
We conclude that the optimal working distance range is between 40 and 10 mm from the object. However the clinician should be cognisant of both variations in magnification and distortion in clinical judgements. 相似文献7.
Florian Veillard Maryta Sztukowska Danuta Mizgalska Mirosław Ksiazek John Houston Barbara Potempa Jan J. Enghild Ida B. Thogersen F. Xavier Gomis-Rüth Ky-Anh Nguyen Jan Potempa 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Arginine-specific (RgpB and RgpA) and lysine-specific (Kgp) gingipains are secretory cysteine proteinases of Porphyromonas gingivalis that act as important virulence factors for the organism. They are translated as zymogens with both N- and C-terminal extensions, which are proteolytically cleaved during secretion. In this report, we describe and characterize inhibition of the gingipains by their N-terminal prodomains to maintain latency during their export through the cellular compartments.Methods
Recombinant forms of various prodomains (PD) were analyzed for their interaction with mature gingipains. The kinetics of their inhibition of proteolytic activity along with the formation of stable inhibitory complexes with native gingipains was studied by gel filtration, native PAGE and substrate hydrolysis.Results
PDRgpB and PDRgpA formed tight complexes with arginine-specific gingipains (Ki in the range from 6.2 nM to 0.85 nM). In contrast, PDKgp showed no inhibitory activity. A conserved Arg-102 residue in PDRgpB and PDRgpA was recognized as the P1 residue. Mutation of Arg-102 to Lys reduced inhibitory potency of PDRgpB by one order of magnitude while its substitutions with Ala, Gln or Gly totally abolished the PD inhibitory activity. Covalent modification of the catalytic cysteine with tosyl-l-Lys-chloromethylketone (TLCK) or H-D-Phe-Arg-chloromethylketone did not affect formation of the stable complex.Conclusion
Latency of arginine-specific progingipains is efficiently exerted by N-terminal prodomains thus protecting the periplasm from potentially damaging effect of prematurely activated gingipains.General significance
Blocking progingipain activation may offer an attractive strategy to attenuate P. gingivalis pathogenicity. 相似文献8.
The partition matrix: exploring variable phylogenetic signals along nucleotide sequence alignments 总被引:6,自引:2,他引:4
The partition matrix is a graphical tool for comparative analysis of
nucleotide sequences following alignment. It is particularly useful for
investigating the divergent phylogenies of sequence regions undergoing
reticulate evolution. A partition matrix is generated by determining the
consistency of the parsimoniously informative sites in a set of aligned
sequences with the binary partitions inferred from the sequences. Since the
linear order of sites is maintained, the matrix can be used to assess
whether the distribution of sites either supporting or conflicting with
particular partitions changes along the length of the alignment. The
usefulness of the matrix in allowing visual identification of differences
in evolutionary history among regions depends on the order in which
partitions are shown; several suitable ordering schemes are proposed. We
demonstrate the use of the partition matrix in interpreting the evolution
of the pseudoautosomal boundary region on the sex chromosome of catarrhine
primates. Its routine use should help to avoid attempts to derive single
phylogenies from sequences whose evolution has been reticulate and to
identify the gene conversion or recombination events underlying the
reticulation. The method is relatively fast. It is exploratory, and it can
form the basis for more formal analysis, which we discuss.
相似文献
9.
The regulatory role of protons in hyphal tip growth was investigated by using membrane-permeant weak acids to acidify cytoplasm of the oomycete Saprolegnia ferax. Acetic acid decreased cytoplasmic pH from approximately pH 7.2 to 6.8, as shown by SNARF-1 measurements of cytoplasmic pH. Inhibition of growth in a dose-dependent manner by acetic, propionic, and isobutyric acid was accompanied by changes in positioning and morphology of mitochondria and nuclei, condensation of chromatin, disruptions in peripheral actin, and increases in hyphal diameter. These cellular alterations were fully reversible, and during recovery, major cytoplasmic movements and extensive apical vacuolations were observed. The results are consistent with proton regulation of the cytoskeleton, nuclear matrix, and/or chromosomes. However, a macroscopic cytoplasmic gradient of H+ in hyphae was not revealed by SNARF-1, indicating that if such a H+ gradient were required, it must occur at a finer level than we detected. 相似文献
10.
The campound 3-methyleneoxindole was synthesized and tested in three “biological systems for auxin activity: Root initarion in pea stem currings, extension growth of etiolated pea stem segments and Avena first internodes. In none of the systems was found any effect — positive or negative of methyleneoxindole. It thus seems improbable that the compound participates in the growth regulation of these plants. 相似文献