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1.
Specific mitochondrial incorporation of 10 N-nonyl acridine orange (NAO) is demonstrated by subcellular fractionation of rat hepatocytes. Moreover, comparative studies with NAO and rhodamine 123 (Rh 123) prove that acridine orange-derivative uptake is independent of transmembrane mitochondrial potential, a property allowing its utilization for the assessment of mitochondrial membrane mass modifications under various physiological states. Using NAO and Rh 123, we have respectively followed the biosynthesis of mitochondrial membrane and its assembly under a functional state during the L1210 cell cycle. Their evolution occurs in two stages according to a well-defined sequential order. Mitochondrial biogenesis, as revealed by NAO incorporation, occurs essentially in the G1 phase (probably mitochondrion enlargement) but also starts in late S phase (probably mitochondrion division). The increased amount of functional mitochondrial membrane, monitored by Rh 123 uptake, is emphasized in late G1 (prerequisite to DNA synthesis) and during G2M phases (prerequisite to mitosis). This alternative succession of phases displays the existence of a time-lag between the biosynthesis of mitochondrial membrane and its functional organization. Such an analysis confirms the potential of the NAO probe to evaluate mitochondrial membrane mass changes in various biological fields. 相似文献
2.
Capsule Woodpigeon Columba palumbus nest-tree selection is affected by human disturbance, grazing and tree characteristics. Aims To determine the characteristics of trees used for nesting by Woodpigeons under two levels of grazing and disturbance in a Holm oak Middle Atlas forest, Morocco. Methods Woodpigeon nest-tree selection was investigated in highly disturbed and less-disturbed sites over two years (2010 and 2011). The features of nest-tree characteristics were determined by comparing the characteristics of trees used for nesting to those of randomly selected trees. Results Tree physical characteristics, grazing intensity and level of human disturbance were the main factors determining selection for nest-trees. Woodpigeons chose nesting trees that were greater in height, larger in DBH, lower in base of the live crown, in denser stands and at greater distance from tracks. Conclusions Forest management for Woodpigeon nest habitat selection should focus on controlling the access of vehicles especially trucks, introducing a rotating system of forest utilization for grazing and maintaining (without extending) the cereal crops. These recommendations may assist land managers to plan for continued persistence of this species in Middle Atlas forests. 相似文献
3.
Spa32 regulates a switch in substrate specificity of the type III secreton of Shigella flexneri from needle components to Ipa proteins
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Magdalena J Hachani A Chamekh M Jouihri N Gounon P Blocker A Allaoui A 《Journal of bacteriology》2002,184(13):3433-3441
Type III secretion systems (TTSS) are essential virulence determinants of many gram-negative bacteria and serve, upon physical contact with target cells, to translocate bacterial proteins directly across eukaryotic cell membranes. The Shigella TTSS is encoded by the mxi/spa loci located on its virulence plasmid. By electron microscopy secretons are visualized as tripartite with an external needle, a transmembrane domain, and a cytoplasmic bulb. In the present study, we generated a Shigella spa32 mutant and studied its phenotype. The spa32 gene shows low sequence homology to Salmonella TTSS1 invJ/spaN and to flagellar fliK. The spa32 mutant, like the wild-type strain, secreted the Ipas and IpgD, which are normally secreted via the TTSS, at low levels into the growth medium. However, unlike the wild-type strain, the spa32 mutant could neither be induced to secrete the Ipas and IpgD instantaneously upon addition of Congo red nor penetrate HeLa cells in vitro. Additionally, the Spa32 protein is secreted in large amounts by the TTSS during exponential growth but not upon Congo red induction. Interestingly, electron microscopy analysis of the spa32 mutant revealed that the needle of its secretons were up to 10 times longer than those of the wild type. In addition, in the absence of induction, the spa32 mutant secreted normal levels of MxiI but a large excess of MxiH. Taken together, our data indicate that the spa32 mutant presents a novel phenotype and that the primary defect of the mutant may be its inability to regulate or control secretion of MxiH. 相似文献
4.
Abderrahman El Maarouf Damali Moyo-Lee Yaw Theresa Lindhout Damien D. Pearse Warren Wakarchuk Urs Rutishauser 《The Journal of biological chemistry》2012,287(39):32770-32779
In vertebrates, polysialic acid (PSA) is typically added to the neural cell adhesion molecule (NCAM) in the Golgi by PST or STX polysialyltransferase. PSA promotes plasticity, and its enhanced expression by viral delivery of the PST or STX gene has been shown to promote cellular processes that are useful for repair of the injured adult nervous system. Here we demonstrate a new strategy for PSA induction on cells involving addition of a purified polysialyltransferase from Neisseria meningitidis (PSTNm) to the extracellular environment. In the presence of its donor substrate (CMP-Neu5Ac), PSTNm synthesized PSA directly on surfaces of various cell types in culture, including Chinese hamster ovary cells, chicken DF1 fibroblasts, primary rat Schwann cells, and mouse embryonic stem cells. Similarly, injection of PSTNm and donor in vivo was able to produce PSA in different adult brain regions, including the cerebral cortex, striatum, and spinal cord. PSA synthesis by PSTNm requires the presence of the donor CMP-Neu5Ac, and the product could be degraded by the PSA-specific endoneuraminidase-N. Although PSTNm was able to add PSA to NCAM, most of its product was attached to other cell surface proteins. Nevertheless, the PSTNm-induced PSA displayed the ability to attenuate cell adhesion, promote neurite outgrowth, and enhance cell migration as has been reported for endogenous PSA-NCAM. Polysialylation by PSTNm occurred in vivo in less than 2.5 h, persisted in tissues, and then decreased within a few weeks. Together these characteristics suggest that a PSTNm-based approach may provide a valuable alternative to PST gene therapy. 相似文献
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6.
Abderrahman Khila Ehab Abouheif Locke Rowe 《Evolution; international journal of organic evolution》2014,68(8):2159-2170
Invasion of new ecological habitats is often associated with lineage diversification, yet the genetic changes underlying invasions and radiations are poorly understood. Over 200 million years ago, the semi‐aquatic insects invaded water surface from a common terrestrial ancestor and diversified to exploit a wide array of niches. Here, we uncover the changes in regulation and function of the gene Ultrabithorax associated with both the invasion of water surface and the subsequent diversification of the group. In the common ancestor of the semi‐aquatic insects, a novel deployment of Ubx protein in the mid‐legs increased their length, thereby enhancing their role in water surface walking. In derived lineages that specialize in rowing on the open water, additional changes in the timing of Ubx expression further elongated the mid‐legs thereby facilitating their function as oars. In addition, Ubx protein function was selectively reversed to shorten specific rear‐leg segments, thereby enabling their function as rudders. These changes in Ubx have generated distinct niche‐specialized morphologies that account for the remarkable diversification of the semi‐aquatic insects. Therefore, changes in the regulation and function of a key developmental gene may facilitate both the morphological change necessary to transition to novel habitats and fuel subsequent morphological diversification. 相似文献
7.
Mliji el M Hamadi F Latrache H Cohen N El Ghmari A Timinouni M 《The new microbiologica》2007,30(1):19-27
The formation of biofilm is a universal bacterial survival strategy. Biofilms occur on inert and living support in the natural environment and in industrial installations. This microenvironment leads to the horizontal transfer of genetic material between bacteria by physical contact. In order to evaluate the relationship between biofilm-forming capabilities, surface characteristics and plasmid content we purified from Salmonella a plasmid conferring resistance to cephalosporin and transferred it by electroporation to E.coli DH10B originally unable to form biofilm in inert surface. We demonstrated the association between a plasmid conferring resistance to expanded-spectrum cephalosporin and biofilm formation. We also noted that this plasmid influences the cell surface properties and cell motility. 相似文献
8.
Léonard R Lhernould S Carlué M Fleurat P Maftah A Costa G 《Glycoconjugate journal》2005,22(1-2):71-78
1,4-Fucosylation has been recently detected in Arabidopsis thaliana [Léonard et al. (2002), Glycobiology 12: 299–306], and corresponding enzymes have also been characterized in Beta vulgaris [Bakker et al. (2001), FEBS Lett, 507: 307–312], and Lycopersicum aesculentum [Wilson (2001), Glycoconjugate J., 18: 439–447]. Here we demonstrated fucosyltransferase activity (FucT) in Silene alba cells and tissues. The Fuc linkage to GlcNAc residues of the lactosamine moiety of the Type I acceptor was confirmed by mass spectrometry experiments. Lea-glycoconjugates are found in the Golgi apparatus and plasma membrane of plant cells. In planta, the highest levels of activity were detected in seedlings, young roots and male flowers. The enzyme was stable up to 45C and the optimum pH of reaction was 8.0. The enzyme required Mg2+ or Mn2+ for activity and was inhibited by Zn2+ and ethylenediaminetetraacetic acid. Chemical modification of the enzyme with group-selective reagents revealed that selective modifications of arginine and lysine residues had no effect on enzyme activity. However the enzyme contains histidine and tryptophan residues that are essential for its activity. In contrast to human FUT3, the S. alba 4-FucT was insensitive to N-ethylmaleimide (NEM) treatment. Measurement of enzyme activity in S. alba cell fractions indicated that the enzyme is bound to microsomal membranes, furthermore a soluble isoform of the protein may be present. Published in 2005. 相似文献
9.
We consider a stage-structured model of a harvested fish population and we are interested in the problem of estimating the
unknown stock state for each class. The model used in this work to describe the dynamical evolution of the population is a
discrete time system including a nonlinear recruitment relationship. To estimate the stock state, we build an observer for
the considered fish model. This observer is an auxiliary dynamical system that uses the catch data over each time interval
and gives a dynamical estimate of the stock state for each stage class. The observer works well even if the recruitment function
in the considered model is not well known. The same problem for an age-structured model has been addressed in a previous work
(Ngom et al., Math. Biosci. Eng. 5(2):337–354, 2008). 相似文献
10.
Blanchet X Péré-Brissaud A Duprat N Pinault E Delourme D Ouali A Combet C Maftah A Pélissier P Brémaud L 《Protein science : a publication of the Protein Society》2012,21(7):977-986
The family of serpins is known to fold into a metastable state that is required for the proteinase inhibition mechanism. One of the consequences of this conformational flexibility is the tendency of some mutated serpins to form polymers, which occur through the insertion of the reactive center loop of one serpin molecule into the A-sheet of another. This "A-sheet polymerization" has remained an attractive explanation for the molecular mechanism of serpinopathies. Polymerization of serpins can also take place in vitro under certain conditions (e.g., pH or temperature). Surprisingly, on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, bovSERPINA3-3 extracted from skeletal muscle or expressed in Escherichia coli was mainly observed as a homodimer. Here, in this report, by site-directed mutagenesis of recombinant bovSERPINA3-3, with substitution D371A, we demonstrate the importance of D371 for the intermolecular linkage observed in denaturing and reducing conditions. This residue influences the electrophoretic and conformational properties of bovSERPINA3-3. By structural modeling of mature bovSERPINA3-3, we propose a new "non-A-sheet swap" model of serpin homodimer in which D371 is involved at the molecular interface. 相似文献