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21.
Characterization of the Highly Autolytic Lactococcus lactis subsp. cremoris Strains CO and 2250
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Two highly autolytic Lactococcus lactis subsp. cremoris strains (CO and 2250) were selected and analyzed for their autolytic properties. Both strains showed maximum lysis when grown in M17 broth containing a limiting concentration of glucose (0.4 to 0.5%) as the carbohydrate source. Lysis did not vary greatly with pH or temperature but was reduced when strains were grown on lactose or galactose. Growth in M17 containing excess glucose (1%) prevented autolysis, although rapid lysis of L. lactis subsp. cremoris CO did occur in the presence of 1% glucose if sodium fluoride (an inhibitor of glycolysis) was added to the medium. Maximum cell lysis in a buffer system was observed early in the stationary phase, and for CO, two pH optima were observed for log-phase and stationary-phase cells (6.5 and 8.5, respectively). Autolysins were extracted from the cell wall fraction of each strain by using either 4% sodium dodecyl sulfate (SDS), 6 M guanidine hydrochloride, or 4 M lithium chloride, and their activities were analyzed by renaturing SDS-polyacrylamide gel electrophoresis on gels containing Micrococcus luteus or L. lactis subsp. cremoris CO cells as the substrate. More than one lytic band was observed on each substrate, with the major band having an apparent molecular mass of 48 kDa for CO. Each lytic band was present throughout growth and lysis. These results suggest that at least two different autolytic enzymes are present in the autolytic L. lactis subsp. cremoris strains. The presence of the lactococcal cell wall hydrolase gene, acmA (G. Buist, J. Kok, K. J. Leenhouts, M. Dabrowska, G. Venema, and A. J. Haandrikman, J. Bacteriol. 177:1554-1563, 1995), in strains 2250 and CO was confirmed by Southern hybridization. Analysis of an acmA deletion mutant of 2250 confirmed that the gene was involved in cell separation and had a role in cell lysis. 相似文献
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Claudia Schiffczyk Christina Jonas Constanze Lahmeyer Friedemann Müller Matthias W Riepe 《BMC neurology》2011,11(1):118
Background
Substituted judgment asks the proxy to decide what the patient would have decided, had he or she been competent. It is unclear whether substituted judgment of the patient's quality of life can serve as a surrogate measure in patients with dementia. 相似文献23.
alpha 1-Proteinase inhibitors (alpha 1-PIs) are members of the serpin
superfamily of proteinase inhibitors, and are important in the maintenance
of homeostasis in a wide variety of animal taxa. Previous studies have
shown that in mice (genus Mus), evolution of alpha 1-PIs is characterized
by gene amplification, region-specific concerted evolution, and rapid
accumulation of amino acid substitutions. The latter occurs primarily in
the reactive center, which is the region of the alpha 1-PI molecule that
determines the inhibitor's specificity for target proteinases. The P1
residue within the reactive center, which is methionine in so-called
orthodox alpha 1-PIs and an amino acid other than methionine in unorthodox
alpha 1-PIs, is a primary determinant of inhibitor specificity. In the
present study, we find that the expression of mRNAs encoding unorthodox
alpha 1-PIs is polymorphic within Mus species, i.e., among individuals or
inbred strains. This is in striking contrast to mRNAs that encode orthodox
alpha 1-PIs, whose concentrations are relatively invariant. The
intraspecies variations in mRNA expression represent polymorphisms in the
structure of the alpha 1- PI gene family. The results, taken together with
previously described aspects of alpha 1-PI evolution, indicate that the
dissimilar levels of polymorphism exhibited by orthodox and unorthodox
alpha 1-PIs, which likely have distinct physiological functions, may
reflect different levels of selective constraint. The significance of this
finding to the evolution of gene families is discussed.
相似文献
24.
Adam Aguirre Kenji F. Shoji Juan C. Sáez Mauricio Henríquez Andrew FG Quest 《Journal of cellular physiology》2013,228(2):485-493
Fas ligation via the ligand FasL activates the caspase‐8/caspase‐3‐dependent extrinsic death pathway. In so‐called type II cells, an additional mechanism involving tBid‐mediated caspase‐9 activation is required to efficiently trigger cell death. Other pathways linking FasL–Fas interaction to activation of the intrinsic cell death pathway remain unknown. However, ATP release and subsequent activation of purinergic P2X7 receptors (P2X7Rs) favors cell death in some cells. Here, we evaluated the possibility that ATP release downstream of caspase‐8 via pannexin1 hemichannels (Panx1 HCs) and subsequent activation of P2X7Rs participate in FasL‐stimulated cell death. Indeed, upon FasL stimulation, ATP was released from Jurkat cells in a time‐ and caspase‐8‐dependent manner. Fas and Panx1 HCs colocalized and inhibition of the latter, but not connexin hemichannels, reduced FasL‐induced ATP release. Extracellular apyrase, which hydrolyzes ATP, reduced FasL‐induced death. Also, oxidized‐ATP or Brilliant Blue G, two P2X7R blockers, reduced FasL‐induced caspase‐9 activation and cell death. These results represent the first evidence indicating that the two death receptors, Fas and P2X7R connect functionally via caspase‐8 and Panx1 HC‐mediated ATP release to promote caspase‐9/caspase‐3‐dependent cell death in lymphoid cells. Thus, a hitherto unsuspected route was uncovered connecting the extrinsic to the intrinsic pathway to amplify death signals emanating from the Fas receptor in type II cells. J. Cell. Physiol. 228: 485–493, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
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Muscle temperature was measured by telemetry in giant Atlantic bluefin tuna whilst the tuna were free-swimming in large pounds. Muscle temperature tended to remain steady at about 24°C; water temperature ranged from 9 to 17°C. Muscle temperature was much less variable than stomach temperature in these fish. Muscle temperature varied less than 3°C whereas stomach temperature varied by as much as 14°C. 相似文献
27.
The performance of fungal xylan-degrading enzyme preparations in elemental chlorine-free bleaching for Eucalyptus pulp 总被引:2,自引:0,他引:2
Medeiros RG Silva FG Salles BC Estelles RS Filho EX 《Journal of industrial microbiology & biotechnology》2002,28(4):204-206
Cellulase-free xylan-degrading enzyme preparations from Acrophialophora nainiana, Humicola grisea var. thermoidea and two Trichoderma harzianum strains were used as bleaching agents for Eucalyptus kraft pulp, prior to a chlorine dioxide and alkaline bleaching sequence. In comparison to the control sequence (performed
without xylanase pretreatment), the sequence incorporating enzyme treatment was more effective. Removal of residual lignin
was indicated by a reduction in kappa number. Overall, enzyme preparations from T. harzianum were marginally more effective in reducing pulp viscosity and chlorine chemical consumption and improving the brightness
of the kraft pulp. However, the highest reduction in pulp viscosity was mediated by the xylanase preparation from A. nainiana. Xylanase pretreatment compares very favorably with that of chemical pulping. Journal of Industrial Microbiology & Biotechnology (2002) 28, 204–206 DOI: 10.1038/sj/jim/7000227
Received 27 April 2001/ Accepted in revised form 03 November 2001 相似文献
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29.
F. G. Riepe S. Wonka C. -J. Partsch W. G. Sippell 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2001,763(1-2)
A new, simple, rapid and highly practicable automated chromatographic system for the separation, and a sensitive radioimmunoassay system for the subsequent measurement of pregnenolone and 17-hydroxypregnenolone has been developed. Pregnenolone and 17-hydroxypregnenolone were extracted with methylene chloride and separated from cross-reacting steroids by mechanised Sephadex-LH20 multi-column chromatography. Anti-pregnenolone and anti-17-hydroxypregnenolone were obtained by immunising rabbits with pregnenolone-20-oxime-BSA and 17-hydroxypregnenolone-20-oxime-BSA. The lower detection limit of the assay is 0.15 and 0.28 nmol/l for pregnenolone and 17-hydroxypregnenolone, respectively. Normal values for this assay in young male adults, in adult females, and in prepubertal boys and girls were established as a basis for the functional diagnosis of androgen excess syndromes/steroidogenesis defects. 相似文献
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