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101.
102.
Neutrophil association and degradation of normal and acute-phase high-density lipoprotein 3. 总被引:3,自引:0,他引:3
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E G Shephard F C de Beer M C de Beer M S Jeenah G A Coetzee D R van der Westhuyzen 《The Biochemical journal》1987,248(3):919-926
The interaction of normal and acute-phase high-density lipoproteins of the subclass 3 (N-HDL3 and AP-HDL3) with human neutrophils and the accompanying degradation of HDL3 apolipoproteins have been studied in vitro. The chemical composition of normal and acute-phase HDL3 was similar except that serum amyloid A protein (apo-SAA) was a major apolipoprotein in AP-HDL3 (approx. 30% of total apolipoproteins). 125I-labelled AP-HDL3 was degraded 5-10 times faster than 125I-labelled N-HDL3 during incubation with neutrophils or neutrophil-conditioned medium. Apo-SAA, like apolipoprotein A-II (apo-A-II), was more susceptible than apolipoprotein A-I (apo-A-I) to the action of proteases released from the cells. The amounts of cell-associated AP-HDL3 apolipoproteins at saturation were up to 2.8 times greater than N-HDL3 apolipoproteins; while apo-A-I was the major cell-associated apolipoprotein when N-HDL3 was bound, apo-SAA constituted 80% of the apolipoproteins bound in the case of AP-HDL3. The associated intact apo-SAA was mostly surface-bound as it was accessible to the action of exogenous trypsin. alpha 1-Antitrypsin-resistant (alpha 1-AT-resistant) cellular degradation of AP-HDL3 apolipoproteins also occurred; experiments in which pulse-chase labelling was performed or lysosomotropic agents were used indicated that insignificant intracellular degradation occurred which points to the involvement of cell-surface proteases in this degradation. 相似文献
103.
L J Rinkel G A van der Marel J H van Boom C Altona 《European journal of biochemistry》1987,163(2):287-296
The solution conformations of the oligonucleotides d(C-C-G-A-A-T-T-C-G-G) and d(C-C-G-A-m6A-T-T-C-G-G) as a function of temperature and sample concentration were investigated by means of 1H-NMR spectroscopy. The NMR spectra revealed that, at certain combinations of temperature and low sample and salt concentration, both compounds exist as a B-DNA-type duplex slowly (on the 1H-NMR time scale) interconverting with a monomeric species. From chemical shift data and imino-proton spectra, it is concluded that the monomeric species consists of a mixture of a hairpin form in rapid equilibrium with the random-coil form. The double-helical stem of the hairpin is formed by the six terminal cytidine and guanine residues, whereas the four core residues, -A-(m6)A-T-T-, partake in the loop. Thermodynamic analysis of the chemical shift of the resonances of the monomeric species vs temperature profiles of the two decamers and mutual comparison of these profiles indicate the following: the influence of N6-methylation of residue A(5) upon the local structure of the hairpin must be small; methylation decreases the stability of the duplex relative to the monomeric species: the temperature at which the fraction duplex equals 0.5 was found to be 312 K for the parent compound and 305 K for the methylated decamer at 2 mM sample concentration; methylation does not significantly alter the stability of the hairpin form relative to the random coil form: the Tm of the hairp----n equilibrium random-coil equilibrium is 308 K for the parent compound and 306 K for the methylated decamer. A higher fraction hairpin-like structure for the N6-methylated compound is observed under identical conditions of temperature and sample concentration: at 300 K, 2 mM sample concentration, the fraction hairpin form is 0.12 for d(C-C-G-A-A-T-T-C-G-G) and 0.20 for d(C-C-G-A-m6A-T-T-C-G-G). This finding appears to be a consequence of the reduced stability of the methylated dimeric species relative to the monomeric species, and to depend upon the sodium-ion concentration: it becomes more pronounced under low-salt conditions. 相似文献
104.
We found 8-azidoadenosine 5'-diphosphate to be a phosphoryl acceptor in the enzymatic conversion of 1,3-diphosphoglyceric acid to 3-phosphoglycerate. This has allowed us to synthesize in a single-step procedure carrier-free 8-azidoadenosine 5'-[gamma-32P]triphosphate, requiring no further purification of the end product. The synthesized 8-azidoadenosine 5'-[gamma-32P]triphosphate has been characterized and shown to meet all the criteria for a specific photoreactive ATP analogue. 相似文献
105.
A milk protein, occurring in the whey fraction, has been characterized from camel milk. Determination of the primary structure reveals the existence of two related types of chain with residue differences in at least the N-terminal region. A fragment representing an N-terminal part of the protein was also recovered (heterogeneous at the same positions). The absence of cysteine residues in the protein shows that no disulphide bridges are present. The pattern of fragments and a parent protein resembles that for casein and its fragments, showing that fragments and a multiplicity of forms may be typical for different milk proteins. 相似文献
106.
Size selection of latex beads by blackfly larvae (Diptera: Simuliidae) in the laboratory 总被引:1,自引:1,他引:0
P. Schröder 《Hydrobiologia》1987,144(2):163-171
In laboratory experiments, blackfly larvae collected from a lake outlet, a woodland and a meadow stream were tested for size
selection of latex beads of < Ito > 100 μm diameters. 3 suspensions of varying proportions for each size category were supplied
to these blackfly larvae in common experiments. Comparisons between the size frequency distributions of particles supplied
and the particle compositions in the larval guts showed intra- and interspecific differences and were quantified by calculating
Jacobs' electivity index. In all species selection of larger particles increased with the larger larval instars. Although
there was a positive selectivity of small particles in some cases, the ingested proportion of large particles increases volumes
and biomasses of gut content and may be more important for larval growth than small particles. 相似文献
107.
A note on the hatching and viability ofCeriodaphnia ephippia collected from lake sediment 总被引:3,自引:3,他引:0
Christian Moritz 《Hydrobiologia》1987,145(1):309-314
Ephippia ofCeriodaphnia pulchella Sars were collected at 2 sites from successive sediment layers.
Hatching observed in the laboratory gave information about the duration of their viability. Conclusions about the hatching
situation in the lake were drawn from the ratio of intact to total ephippia at various lake depths. The results are discussed. 相似文献
108.
Synthesis and processing of alpha-galactosidase A in human fibroblasts. Evidence for different mutations in Fabry disease 总被引:6,自引:0,他引:6
P Lemansky D F Bishop R J Desnick A Hasilik K von Figura 《The Journal of biological chemistry》1987,262(5):2062-2065
The synthesis and processing of the human lysosomal enzyme alpha-galactosidase A was examined in normal and Fabry fibroblasts. In normal cells, alpha-galactosidase A was synthesized as an Mr = 50,500 precursor, which contained phosphate groups in oligosaccharide chains cleavable by endoglucosaminidase H. The precursor was processed via ill-defined intermediates to a mature Mr 46,000 form. Processing was complete within 3-7 days after synthesis. In the presence of NH4Cl and in I-cell fibroblasts, the majority of newly synthesized alpha-galactosidase A was secreted as an Mr = 52,000 form. For comparison, the processing and stability of alpha-galactosidase A were examined in fibroblasts from five unrelated patients with Fabry disease, which is caused by deficient alpha-galactosidase A activity. In one cell line, synthesis of immunologically cross-reacting polypeptides was not detectable. In another, the synthesis, processing, and stability of alpha-galactosidase A was indistinguishable from that in normal fibroblasts. In a third Fabry cell line, the mutation retarded the maturation of alpha-galactosidase A. Finally, in two cell lines, alpha-galactosidase A polypeptides were synthesized that were rapidly degraded following delivery to lysosomes. These results clearly indicate that Fabry disease comprises a heterogeneous group of mutations affecting synthesis, processing, and stability of alpha-galactosidase A. 相似文献
109.
The onset of the respiratory burst in human neutrophils. Real-time studies of H2O2 formation reveal a rapid agonist-induced transduction process 总被引:4,自引:0,他引:4
M P Wymann V von Tscharner D A Deranleau M Baggiolini 《The Journal of biological chemistry》1987,262(25):12048-12053
A real-time study of the initiation of the respiratory burst in human neutrophils was made. The cells were stimulated with fMet-Leu-Phe (fMLP) C5a, platelet-activating factor, leukotriene B4, phorbol myristate acetate (PMA), or ionomycin, and H2O2 production was determined by chemiluminescence. Identical average onset times (2.4 s) and closely comparable values for the apparent first-order rate constant (kapp) for the induction of NADPH-oxidase activity (0.21-0.29 s-1) were obtained following stimulation with fMLP, C5a, platelet-activating factor, or leukotriene B4, suggesting that different agonists act through a common transduction sequence. Much longer onset times and lower kapp values were obtained upon stimulation with PMA or ionomycin. Pretreatment with PMA consistently shortened the onset time of the neutrophil's responses to agonists by about 1 s. When H2O2 production was initiated with PMA, a subsequent stimulation with the agonist fMLP elicited an immediate response (onset time less than 0.2 s) which preceded further changes in fura-2-detected [Ca2+]i. The results are consistent with a mechanism in which agonist signals appear to be transduced by two sequences acting in concert--a rate-limiting one liberating Ca2+ and diacylglycerol and turning on the Ca2+/phospholipid-dependent enzyme protein kinase C, and an essentially instantaneous one which does not appear to require further changes in cytosolic Ca2+. 相似文献
110.
An estimation of drag in front crawl swimming 总被引:3,自引:0,他引:3
A J van der Vaart H H Savelberg G de Groot A P Hollander H M Toussaint G J van Ingen Schenau 《Journal of biomechanics》1987,20(5):543-546
Propulsive arm forces of twelve elite male swimmers during a front crawl swimming-like activity were measured. The swimmers pushed off against grips which are attached to a 23 m tube at 0.8 m under the water surface. The tube was fixed to a force transducer. Since at constant speed, mean propulsive force equals mean drag force this method also provides the mean active drag on a moving swimmer. The mean propulsive force at a speed of v = 1.48 m s-1 appeared to be 53.2 +/- 5.8 N which is two to three times smaller than what is reported by other authors for active drag but which is in agreement with values reported for passive drag on a (towed) swimmer who is not moving. Discrepancies with indirect active drag measurements are discussed. 相似文献