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51.
52.
Biosynthesis and action of nitric oxide in mammalian cells 总被引:26,自引:0,他引:26
Nitric oxide (NO) can act as a vasorelaxant, a modulator of neurotransmission and a defence against pathogens. However, under certain conditions, NO can also have damaging effects to cells. Whether NO is useful or harmful depends on its chemical fate, and on the rate and location of its production. Here, we discuss progress in NO chemistry and the enzymology of NO synthases, and we will also attempt to explai its actions in the cardiovascular, nervous and immune systems. 相似文献
53.
Roland Prinzinger Jörg-Peter Kleim Werner Schroth Bernd Schierwater 《Journal of Ornithology》1997,138(3):291-296
In 1899Reichenow described an african bushshrike in juvenile plumage as a new species. He named itLaniarius dubiosus. DNA from type material (feathers and skin) was extracted and DNA sequences from the mitochondrial Cyt-b gene were analysed. Comparisons of DNA-sequences from other bushshrikes (including the type-specimen from Luehder's bushshrikeLaniarius lühderi) support the judgement that dubiosus does not represent a full species rather than a representative of the western subspecies of the Luehder's bushshrikeLaniarius luehderi.
Zusammenfassung Der vonReichenow (1899) als neue Art beschriebene, sich im Jugendkleid befindliche BuschwürgerLaniarius dubiosus ist nach DNA-Sequenzanalysen des mitochondrialen Cyt-b Genes mit hoher Wahrscheinlichkeit ein Jungvogel der westlichen Rasse des BraunscheitelwürgersLaniarius lühderi. Auf der Basis eines DNA-Stammbaumes von sieben verschiedenen Buschwürgern ist der 1991 neu beschriebeneLaniarius liberatus am wenigsten eng mitL. dubiosus verwandt.相似文献
54.
Interleukin 1β-converting Enzyme Related Proteases/Caspases Are Involved in TRAIL-induced Apoptosis of Myeloma and Leukemia Cells 下载免费PDF全文
Sara M. Mariani Bernd Matiba Elena A. Armandola Peter H. Krammer 《The Journal of cell biology》1997,137(1):221-229
The Fas/APO-1/CD95 ligand (CD95L) and the recently cloned TRAIL ligand belong to the TNFfamily and share the ability to induce apoptosis in sensitive target cells. Little information is available on the degree of functional redundancy between these two ligands in terms of target selectivity and intracellular signalling pathway(s). To address these issues, we have expressed and characterized recombinant mouse TRAIL. Specific detection with newly developed rabbit anti-TRAIL antibodies showed that the functional TRAIL molecule released into the supernatant of recombinant baculovirus-infected Sf9 cells is very similar to that associated with the membrane fraction of Sf9 cells. CD95L resistant myeloma cells were found to be sensitive to TRAIL, displaying apoptotic features similar to those of the CD95L- and TRAIL-sensitive T leukemia cells Jurkat. To assess if IL-1β-converting enzyme (ICE) and/or ICE-related proteases (IRPs) (caspases) are involved in TRAIL-induced apoptosis of both cell types, peptide inhibition experiments were performed. The irreversible IRP/caspase-inhibitor AcYVAD-cmk and the reversible IRP/caspase-inhibitor Ac-DEVD-CHO blocked the morphological changes, disorganization of plasma membrane phospholipids, DNA fragmentation, and loss of cell viability associated with TRAIL-induced apoptosis. In addition, cells undergoing TRAIL-mediated apoptosis displayed cleavage of poly(ADP)-ribose polymerase (PARP) that was completely blocked by Ac-DEVD-CHO.
These results indicate that TRAIL seems to complement the activity of the CD95 system as it allows cells, otherwise resistant, to undergo apoptosis triggered by specific extracellular ligands. Conversely, however, induction of apoptosis in sensitive cells by TRAIL involves IRPs/caspases in a fashion similar to CD95L. Thus, differential sensitivity to CD95L and TRAIL seems to map to the proximal signaling events associated with receptor triggering.
相似文献55.
The peptide bond formation of alanine (ala), ala + glycine (gly), ala + diglycine (gly2), and ala + gly cyclic anhydride (cyc-gly2) in drying/wetting cycles at 80°C was studied. Silica, alumina, and representative smectites—montmorillonite and hectorite—were
used as catalysts, and the dependence of reaction yields on the available amount of water in the reaction systems was evaluated.
Silica and alumina catalyze the formation of oligopeptide mainly in temperature fluctuation experiments, whereas higher amounts
of water in the reaction system support clay-catalyzed reactions. Silica and alumina are much more efficient for amino acid
dimerization than clays. Whereas only 0.1% of ala oligomerized on hectorite and no reaction proceeded on montmorillonite,
about 0.9 and 3.8% alanine converted into its dimer and cyclic anhydride on silica and alumina, respectively. Clay minerals,
on the other hand, seem to more efficiently catalyze peptide chain elongation than amino acid dimerization. The reaction yields
of ala-gly-gly and gly-gly-ala from ala + gly2 and ala + cyc-gly2 reached about 0.3% on montmorillonite and 1.0% on hectorite. The possible mechanisms of these reactions and the relevance
of the results for prebiotic chemistry are discussed.
Received: 15 December 1996 / Accepted: 1 May 1997 相似文献
56.
Sorichter Stephan; Mair Johannes; Koller Arnold; Gebert Walter; Rama Daniel; Calzolari Charles; Artner-Dworzak Erika; Puschendorf Bernd 《Journal of applied physiology》1997,83(4):1076-1082
Sorichter, Stephan, Johannes Mair, Arnold Koller, WalterGebert, Daniel Rama, Charles Calzolari, Erika Artner-Dworzak, and BerndPuschendorf. Skeletal troponin I as a marker of exercise-inducedmuscle damage. J. Appl. Physiol.83(4): 1076-1082, 1997.The utility of skeletal troponin I (sTnI)as a plasma marker of skeletal muscle damage after exercise wascompared against creatine kinase (CK), myoglobin (Mb), and myosin heavychain (MHC) fragments. These markers were serially measured in normalphysical education teacher trainees after four different exerciseregimens: 20 min of level or downhill (16% decline) running(intensity: 70% maximal O2uptake), high-force eccentric contractions (70 repetitions), orhigh-force isokinetic concentric contractions of the quadriceps group(40 repetitions). Eccentrically biased exercise (downhill running andeccentric contractions) promoted greater increases in all parameters.The highest plasma concentration were found after downhill running{median peaks: 309 U/l CK concentration ([CK])}, 466 µg/l Mb concentration([Mb]), 1,021 µU/l MHC concentration ([MHC]),and 27.3 µg/l sTnI concentration ([sTnI]). Level running produced a moderate response (median peaks: 178 U/l [CK],98 µg/l [Mb], 501 µU/l [MHC], and 6.6 µg/l [sTnI]), whereas the concentric contraction protocoldid not elicit significant changes in any of the markers assayed. sTnIincreased and peaked in parallel to CK and stayed elevated (>2.2µg/l) for at least 1-2 days after exercise. In contrast to MHC,sTnI is an initial, specific marker of exercise-induced muscle injury,which may be partly explained by their different intracellularcompartmentation with essentially no (MHC <0.1%) or a small solublepool (sTnI: median 3.4%). 相似文献
57.
HPLC-analysis of algal pigments: comparison of columns,column properties and eluents 总被引:1,自引:0,他引:1
The effects of columns (Nucleosil C18ODS, MZ-PAH, YMC-PACK C30), column properties (inner diameters of 4 mm, 3 mm and 2 mm, pore-width 10 nm and 30 nm) and eluents (methanol, acetonitrile,
acetone, water) were tested on the separation of algal pigments. The length of columns was 250 mm and particle size was 5
μm. Flow rates and gradients were adjusted to optimize peak separation; remaining chromatographic conditions were kept constant.
The resolution of chromatographic systems was tested with pigment standards and various algal cultures. Total flow rate and
retention times decreased with decreasing inner diameter, whereas pressure, sensitivity and peak-width increased. Pore width
had negligible effects on the chromatographic separation of pigments under the test conditions. Only with acetonitrile as
eluent were all the taxonomically important pigments resolved adequately: zeaxanthin (Cyanophyceae), lutein (Chlorophyceae),
fucoxanthin (Bacillariopyceae), alloxanthin (Cryptophyceae), peridinin (Dinophyceae). 相似文献
58.
Ouabain-blocked toad urinary bladders were maintained in Na+-free mucosal solutions, and a depolarizing solution of high K+ activity containing only 5 mM Na+ on the serosal side. Exposure to mucosal sodium (20 mM activity) evoked a transient amiloride-blockable inward current, which decayed to near zero within one hour. The apical sodium conductance increased in the initial phase of the current decay and decreased in the second phase. The conductance decrease required Ca2+ to be present on the serosal side and was more rapid when the mucosal Na+ activity was higher. At 20 mM mucosal Na+ and 3 mM serosal Ca2+ the initial (maximal) rate of inhibition amounted to 20% in 10 min. The conductance decrease could be accelerated by raising the serosal Ca2+ activity to 10 mM. The inhibition reversed on lowering the serosal Ca2+ to 3 μM and, in addition, the mucosal Na+ to zero. Exposure of the mucosal surface to the ionophore nystatin abolished the Ca2+ sensitivity of the transcellular conductance, showing that the Ca2+-sensitive conductance resides in the apical membrane. The data imply that in the K+-depolarized epithelia, cellular Ca2+, taken up from the serosal medium by means of a Na+-Ca2+ antiport, cause feedback inhibition by blockage of apical Na+ channels. However, the rate of inhibition is small, such that this regulatory mechanism will have little effect at 1 mM serosal Ca2+ and less than 20 mM cellular Na+. 相似文献
59.
Abstract A micro method for the isolation and characterization of the penicillin-binding sites in penicillin-binding proteins (PBPs) was developed. Only 10 nmol of a pure PBP are required for the whole procedure which is based on high-pressure liquid chromatography (HPLC). We showed that serine 44 in PBP 5 from Escherichia coli binds penicillin covalently. 相似文献
60.
Four strains of obligately thermophilic Bacilli capable of growing with carbon monoxide as a sole carbon and energy source were isolated from settling ponds of a sugar factory. Most of them could be identified as strains of Bacillus schlegelii on the basis of cell wall composition, DNA homology menaquinone and DNA base content. Growth with CO was very fast (t
d
=3 h) and was optimal at 65°C. No growth occurred below 50°C. As with the mesophilic carboxydotrophs, hydrogen plus carbon dioxide could also serve as autotrophic substrates. Growth of the isolates with CO depended on the presence of molybdenum in the growth medium. This suggested CO oxidase in the newly isolated Bacilli being a molybdenum hydroxylase similar to the enzymes from the mesophilic carboxydotrophs. Some data characterizing the CO-oxidizing activity in extracts of the thermophilic isolates are also provided.This paper is respectively dedicated to Professor Dr. H. G. Schlegel on the occasion of his 60th birthday 相似文献