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1.
Analysis of exopolysaccharide production by Lactobacillus casei CG11, isolated from cheese. 总被引:3,自引:0,他引:3
M Kojic M Vujcic A Banina P Cocconcelli J Cerning L Topisirovic 《Applied and environmental microbiology》1992,58(12):4086-4088
Exopolysaccharide-producing Lactobacillus casei CG11 was isolated from soft, white, homemade cheese. In basal minimal medium, it produces a neutral heteropolysaccharide consisting predominantly of glucose (about 75%) and rhamnose (about 15%). Plasmid curing experiments revealed that exopolysaccharide production by strain CG11 is linked to a plasmid approximately 30 kb in size. 相似文献
2.
The process by which spiders make their mechanically superior fiber involves removal of solvent (water) from a concentrated protein solution while the solution flows through a progressively narrowing spinning canal. Our aim was to determine a possible mechanism of spider water removal by using a computational model. To develop appropriate computational techniques for modeling of solvent removal during fiber spinning, a study was first performed using a synthetic solution. In particular, the effect of solvent removal during elongational flow (also exhibited in the spinning canal of the spider) on fiber mechanical properties was examined. The study establishes a model for solvent removal during dry spinning of synthetic fibers, assuming that internal diffusion governs solvent removal and that convective resistance is small. A variable internal solvent diffusion coefficient, dependent on solvent concentration, is also taken into account in the model. An experimental setup for dry (air) spinning was used to make fibers whose diameter was on the order of those made by spiders (approximately 1 microm). Two fibers of different thickness, corresponding to different spinning conditions, were numerically modeled for solvent removal and then mechanically tested. These tests showed that the thinner fiber, which lost more solvent under elongational flow, had 5-fold better mechanical properties (elastic modulus of 100 MPa and toughness of 15 MJ/m3) than the thicker fiber. Even though the mechanical properties were far from those of dragline spider silk (modulus of 10 GPa and toughness of 150 MJ/m3), the experimental methodology and numerical principles developed for the synthetic case proved to be valuable when establishing a model for the Nephila spinning process. In this model, an assumption of rapid convective water removal at the spinning canal wall was made, with internal diffusion of water through the fiber as the governing process. Then the diffusion coefficient of water through the initial spinning solution, obtained ex vivo from the Nephila clavipes major ampullate gland, was determined and incorporated into the numerical procedure, along with the wall boundary conditions and canal geometry. Also, a typical fiber reeling speed during web making, as well as the assumption of a dry exiting fiber, were included in the model. The results show that a cross-section of spinning solution (dope), which is initially 70% water, spends 19 s in the spinning canal in order to emerge dry. While the dope cross-section traverses the canal, its velocity increases from 0.37 mm/s at the entrance to 12.5 mm/s at the canal exit. The obtained results thus indicate that simple diffusion, along with the dry wall boundary condition, is a viable mechanism for water removal during typical Nephila fiber spinning. 相似文献
3.
JY Xiong SC Li YX Sun XS Zhang ZZ Dong P Zhong XR Sun 《Biology of sport / Institute of Sport》2015,32(4):295-300
Increasing evidence suggests that physical activity could delay or attenuate the symptoms of Alzheimer''s disease (AD). But the underlying mechanisms are still not fully understood. To investigate the effect of long-term treadmill exercise on the spatial memory of AD mice and the possible role of β-amyloid, brain-derived neurotrophic factor (BDNF) and microglia in the effect, male APPswe/PS1dE9 AD mice aged 4 months were subjected to treadmill exercise for 5 months with 6 sessions per week and gradually increased load. A Morris water maze was used to evaluate the spatial memory. Expression levels of β-amyloid, BDNF and Iba-1 (a microglia marker) in brain tissue were detected by immunohistochemistry. Sedentary AD mice and wildtype C57BL/6J mice served as controls. The results showed that 5-month treadmill exercise significantly decreased the escape latencies (P < 0.01 on the 4th day) and improved the spatial memory of the AD mice in the water maze test. Meanwhile, treadmill exercise significantly increased the number of BDNF-positive cells and decreased the ratios of activated microglia in both the cerebral cortex and the hippocampus. However, treadmill exercise did not significantly alleviate the accumulation of β-amyloid in either the cerebral cortex or the hippocampus of the AD mice (P > 0.05). The study suggested that long-term treadmill exercise could improve the spatial memory of the male APPswe/PS1dE9 AD mice. The increase in BDNF-positive cells and decrease in activated microglia might underpin the beneficial effect. 相似文献
4.
Lozo J Jovcic B Kojic M Dalgalarrondo M Chobert JM Haertlé T Topisirovic L 《Current microbiology》2007,55(3):266-271
Screening the collection of natural isolates from semi-hard homemade cheese resulted in isolation and characterization of
strain Lactobacillus paracasei subsp. paracasei BGSJ2-8. The strain BGSJ2-8 harbors several important phenotypes, such as bacteriocin production, aggregation phenomenon,
and production of proteinase. Bacteriocin SJ was purified by three-step chromatography. Mass spectrometry established molecular
mass of the active peptide at 5372 Da. The auto-aggregation phenotype of wild-type (WT) strain was mediated by secreted aggregation-promoting
factor (protein of molecular mass > 200 kDa), probably acting in cooperation with other cell surface protein(s). Comparative
study of WT and its spontaneous nonaggregating derivative revealed that aggregation factor was responsible for the observed
differences in the bacteriocin and proteinase activities. Bacteriocin SJ activity and resistance to different stresses were
higher in the presence of aggregating factor. In contrast, proteinase activity was stronger in the nonaggregating derivative. 相似文献
5.
The aims of this study were to explore the use of animals in teaching and the implementation of innovative technology-based teaching practices across a small sample of universities in Eastern Europe. The research methods used were a questionnaire circulated four weeks before a workshop took place (in October 2009, in Belgrade, Serbia), as well as focused, face-to-face group discussions, led by one of the authors during the workshop. Twenty-two faculty (physiologists and pharmacologists), from 13 Eastern European countries, attended the meeting. Fourteen of the eighteen schools represented at the workshop were making use of animals, in some instances in quite large numbers, for their teaching. For example, a single department at a Romanian university used over 250 animals per annum, and at least 1130 animals were used, per annum, across all of the institutions. The species used in largest numbers were the rat (34%), frog/toad (29%), mouse (22%), rabbit (10%), guinea-pig (4%) and dog (1%). None of the universities sampled had implemented institution-wide virtual learning environments (VLEs), although there were isolated instances of local use of VLEs. There was relatively little current use of technology-based teaching and learning resources, but there was considerable enthusiasm to modernise teaching and to introduce innovative learning and teaching methods. The major perceived barrier to the introduction of replacement alternatives was the lack of versions in local languages. There was a consensus view that developing local language exemplars and evaluating their usefulness was likely to have the greatest impact on animal use, at least in the short-term. 相似文献
6.
7.
Raft-dependent endocytosis of autocrine motility factor is phosphatidylinositol 3-kinase-dependent in breast carcinoma cells 总被引:2,自引:0,他引:2
Kojic LD Joshi B Lajoie P Le PU Cox ME Turbin DA Wiseman SM Nabi IR 《The Journal of biological chemistry》2007,282(40):29305-29313
Autocrine motility factor (AMF) is internalized via a receptor-mediated, dynamin-dependent, cholesterol-sensitive raft pathway to the smooth endoplasmic reticulum that is negatively regulated by caveolin-1. Expression of AMF and its receptor (AMFR) is associated with tumor progression and malignancy; however, the extent to which the raft-dependent uptake of AMF is tumor cell-specific has yet to be addressed. By Western blot and cell surface fluorescence-activated cell sorter (FACS) analysis, AMFR expression is increased in tumorigenic MCF7 and metastatic MDA-231 and MDA-435 breast cancer cell lines relative to dysplastic MCF10A mammary epithelial cells. AMF uptake, determined by FACS measurement of protease-insensitive internalized fluorescein-conjugated AMF, was increased in MCF7 and MDA-435 cells relative to MCF-10A and caveolin-1-expressing MDA-231 cells. Uptake of fluorescein-conjugated AMF was dynamin-dependent, methyl-beta-cyclodextrin- and genistein-sensitive, reduced upon overexpression of caveolin-1 in MDA-435 cells, and increased upon short hairpin RNA reduction of caveolin-1 in MDA-231 cells. Tissue microarray analysis of invasive primary human breast carcinomas showed that AMFR expression had no impact on survival but did correlate significantly with expression of phospho-Akt. Phospho-Akt expression was increased in AMF-internalizing MCF7 and MDA-435 breast carcinoma cells. AMF uptake in these cells was reduced by phosphatidylinositol 3-kinase inhibition but not by regulators of macropinocytosis such as amiloride, phorbol ester, or actin cytoskeleton disruption by cytochalasin D. The raft-dependent endocytosis of AMF therefore follows a distinct phosphatidylinositol 3-kinase-dependent pathway that is up-regulated in more aggressive tumor cells. 相似文献
8.
Mila Ljujic Aleksandra Divac Rankov Snezana Kojic Elena Miranda Dragica Radojkovic 《Molecular biology reports》2014,41(9):6133-6141
Alpha-1 antitrypsin (AAT) gene is highly polymorphic, with a large number of rare variants whose phenotypic consequences often remain inconclusive. Studies addressing functional characteristics of AAT variants are of significant biomedical importance since deficiency and dysfunctionality of AAT are associated with liver and lung diseases. We report the results of the functional analysis of two naturally occurring AAT variants, G320R and V321F, previously identified in patients with lung disease. Neither of variants has been fully functionally characterized. In order to perform their functional analysis both variants were expressed in prokaryotic and eukaryotic systems and their intracellular localization, activity, stability, and polymerization were determined. The results of this study demonstrated that variants G320R and V321F have neither impaired activity against porcine pancreatic elastase nor propensity to form polymers. However, both variants had altered electrophoretic mobility and reduced thermostability when compared to M variant of the protein, indicating a slightly impaired secondary or tertiary structure. 相似文献
9.
The rpoS gene encodes the sigma factor which was identified in several gram-negative bacteria as a central regulator during stationary phase. rpoS gene regulation is known to respond to cell density, showing higher expression in stationary phase. For Pseudomonas aeruginosa, it has been demonstrated that the cell-density-dependent regulation response known as quorum sensing interacts with this regulatory response. Using the rpoS promoter of P. putida, we identified a genomic Tn5 insertion mutant of P. putida which showed a 90% decrease in rpoS promoter activity, resulting in less RpoS being present in a cell at stationary phase. Molecular analysis revealed that this mutant carried a Tn5 insertion in a gene, designated psrA (Pseudomonas sigma regulator), which codes for a protein (PsrA) of 26.3 kDa. PsrA contains a helix-turn-helix motif typical of DNA binding proteins and belongs to the TetR family of bacterial regulators. The homolog of the psrA gene was identified in P. aeruginosa; the protein showed 90% identity to PsrA of P. putida. A psrA::Tn5 insertion mutant of P. aeruginosa was constructed. In both Pseudomonas species, psrA was genetically linked to the SOS lexA repressor gene. Similar to what was observed for P. putida, a psrA null mutant of P. aeruginosa also showed a 90% reduction in rpoS promoter activity; both mutants could be complemented for rpoS promoter activity when the psrA gene was provided in trans. psrA mutants of both Pseudomonas species lost the ability to induce rpoS expression at stationary phase, but they retained the ability to produce quorum-sensing autoinducer molecules. PsrA was demonstrated to negatively regulate psrA gene expression in Pseudomonas and in Escherichia coli as well as to be capable of activating the rpoS promoter in E. coli. Our data suggest that PsrA is an important regulatory protein of Pseudomonas spp. involved in the regulatory cascade controlling rpoS gene regulation in response to cell density. 相似文献
10.
A single Rad52-related protein is evident by blast analysis of the Ustilago maydis genome database. Mutants created by disruption of the structural gene exhibited few discernible defects in resistance to UV, ionizing radiation, chemical alkylating or cross-linking agents. No deficiency was noted in spontaneous mutator activity, allelic recombination or meiosis. GFP-Rad51 foci were formed in rad52 cells following DNA damage, but were initially less intense than normal suggesting a possible role for Rad52 in formation of the Rad51 nucleoprotein filament. A search for interacting genes that confer a synthetic fitness phenotype with rad52 after DNA damage by UV irradiation identified the genes for Mph1, Ercc1 and the Rad51 paralogue Rec2. Testing known mutants in recombinational repair revealed an additional interaction with the BRCA2 orthologue Brh2. Suppression of the rec2 mutant's UV sensitivity by overexpressing Brh2 was found to be dependent on Rad52. The results suggest that Rad52 serves in an overlapping, compensatory role with both Rec2 and Brh2 to promote and maintain formation of the Rad51 nucleoprotein filament. 相似文献