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排序方式: 共有110条查询结果,搜索用时 15 毫秒
1.
P D Lew A Monod K H Krause F A Waldvogel T J Biden W Schlegel 《The Journal of biological chemistry》1986,261(28):13121-13127
The generation of the two inositol trisphosphate (IP3) isomers, 1,4,5-IP3 and 1,3,4-IP3, and its relation to changes in the cytosolic free calcium concentration, [Ca2+]i, in response to the chemotactic peptide fMet-Leu-Phe was studied in the human promyelocytic cell line HL-60, induced to differentiate with dimethyl sulfoxide. Stimulation by fMet-Leu-Phe within seconds transiently elevates 1,4,5-IP3 to peak values averaging 8-fold basal levels, and leads to a concomitant rise in [Ca2+]i and to degranulation. These responses are followed by a slower and more sustained rise in 1,3,4-IP3. Alterations in [Ca2+]i modulate differentially the generation of the two IP3 isomers. At [Ca2+]i lower than 30 nM, no IP3 is generated upon fMet-Leu-Phe stimulation. Working at normal resting [Ca2+]i, but preventing the fMet-Leu-Phe induced transient rise in [Ca2+]i (by prior depletion of intracellular Ca2+ stores and working in calcium-free medium) the fMet-Leu-Phe stimulation of 1,3,4-IP3 levels is attenuated, whereas the response of 1,4,5-IP3 is not significantly altered. Maintained elevation of [Ca2+]i to micromolar levels with the Ca2+ ionophore ionomycin generates enhanced 1,3,4-IP3 levels in the absence of fMet-Leu-Phe, whereas the fMet-Leu-Phe stimulation of 1,4,5-IP3 generation is markedly inhibited. Pertussis toxin selectively abolishes the fMet-Leu-Phe-induced IP3 production, whereas ionomycin stimulation of 1,3,4-IP3 generation is unaffected. These findings indicate that in intact cells: receptor-triggered phosphatidylinositol bisphosphate phosphodiesterase activation has a minimal Ca2+ requirement, but does not depend on a previous or concomitant rise in [Ca2+]i; Ca2+ elevations above micromolar levels decrease the fMet-Leu-Phe-induced generation of 1,4,5-IP3; and 1,3,4-IP3 generation is not directly linked to receptor activation and appears to result both from increased [Ca2+]i and 1,4,5-IP3 levels. 相似文献
2.
蚕豆叶片发育与衰老过程中超氧物歧化酶活性与丙二醛含量变化 总被引:2,自引:0,他引:2
蚕豆植株叶片随茎节自上而下表现出明显的发育与衰老顺序,可作为衰老特征的是叶绿素和蛋白质含量明显下降。蚕豆叶中SOD活性主要定位于12 000× g离心后所得的上清液和叶绿体组分。衰老叶片的SOD总活性和叶绿体组分的相对活性都有所下降,SOD同工酶谱也发生了改变。O_2~ 产生速率随叶龄增大而稍上升;而MDA含量在叶片外观表现枯黄衰老征兆前就急剧上升。可能因为衰老叶片过氧化氢酶活性大幅度下降与SOD之间的不平衡,致使O_2~ 代谢中间产物累积而引起膜的损伤. 相似文献
3.
Biosynthesis of lysosomal hydrolases: their synthesis in bound polysomes and the role of co- and post-translational processing in determining their subcellular distribution 总被引:37,自引:20,他引:17 下载免费PDF全文
By in vitro translation of mRNA’s isolated from free and membrane-bound polysomes, direct evidence was obtained for the synthesis of two lysosomal hydrolases, β-glucuronidase of the rat preputial gland and cathespin D of mouse spleen, on polysomes bound to rough endoplasmic reticulum (ER) membranes. When the mRNA’s for these two proteins were translated in the presence of microsomal membranes, the in vitro synthesized polypeptides were cotranslationally glycosylated and transferred into the microsomal lumen. Polypeptides synthesized in the absence of microsomal membranes were approximately 2,000 daltons larger than the respective unglycosylated microsomal polypeptides found after short times of labeling in cultured rat liver cells treated with tunicamycin. This strongly suggests that nascent chains of the lysosomal enzymes bear transient amino terminal signals which determine synthesis on bound polysomes and are removed during the cotranslational insertion of the polypeptides into the ER membranes. In the line of cultured rat liver cells used for this work, newly synthesized lysosomal hydrolases showed a dual destination; approximately 60 percent of the microsomal polypeptides detected after short times of labeling were subsequently processed proteolytically to lower molecular weight forms characteristic of the mature enzymes. The remainder was secreted from the cells without further proteolytic processing. As previously observed by other investigations in cultured fibroblasts (A. Gonzalez-Noriega, J.H. Grubbs, V. Talkad, and W.S. Sly, 1980, J Cell Biol. 85: 839-852; A. Hasilik and E.F. Neufeld, 1980, J. Biol. Chem., 255:4937-4945.) the lysosomotropic amine chloroquine prevented the proteolytic maturation of newly synthesized hydrolases and enhanced their section. In addition, unglycosylated hydrolases synthesized in cells treated with tunicamycin were exclusively exported from the cells without undergoing proteolytic processing. These results support the notions that modified sugar residues serve as sorting out signals which address the hydrolases to their lysosomal destination and that final proteolytic cleavage of hydrolase precursors take place within lysosome itself. Structural differences in the carbohydrate chains of intracellular and secreted precursors of cathespin D were detected from their differential sensitivity to digestion with endoglycosidases H and D. These observations suggest that the hydrolases exported into the medium follow the normal secretory route and that some of their oligosaccharides are subject to modifications known to affect many secretory glycoproteins during their passage through the Golgi apparatus. 相似文献
4.
Binding of nonsuppressible insulinlike activity to human serum. Evidence for a carrier protein. 总被引:5,自引:0,他引:5
When 125I-labeled nonsuppressible insulinlike activity—soluble in acid/ethanol (NSILA-S) is incubated with human serum between 10 and 20% of the radioactivity are bound to serum proteins and can be displaced specifically by cold NSILA-S. Chromatography of the incubation mixture on Sephadex G-200 at pH 7.5 reveals three peaks of radioactivity in the large molecular weight region and a fourth one corresponding to low molecular unbound labeled NSILA-S. An excess of cold NSILA-S during preincubation leads to the disappearance of the two major large molecular weight peaks and to a concomitant increase of the peak eluting in the low molecular weight range. Binding of 125I-labeled NSILA-S is highly sensitive to small concentrations of cold NSILA-S, whereas insulin, ACTH and human growth hormone are completely ineffective in displacing bound 125I-labeled NSILA-S. NSILA-S preparations of different purity show displacement according to their specific biological activities. Furthermore, binding of 125I-labeled NSILA-S to serum pH- and time-dependent and displays saturation characteristics. Chromatography of serum on Sephadex G-200 with 0.15 m acetic acid/0.15 m NaCl localizes the binding fraction in the 50,000–70,000 molecular weight range. Boiling of serum for 5 min abolishes binding completely.These studies help explain why the molecular weight of NSILA varied considerably from one group of investigators to the other. 相似文献
5.
Jerry A. Waldvogel Silvano Benvenuti William T. Keeton Floriano Papi 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1978,128(4):297-301
Summary An attempt to repeat studies performed by Baldaccini et al. (1975b) in which pigeons exhibited predictably deviated mean vanishing bearings after prolonged exposure to deflected wind flow is reported. In four sets of pooled release data, deflections in mean bearings as predicted by the olfactory hypothesis of pigeon homing were observed. It is concluded that the time spent in such deflected-wind environments significantly alters some component of the birds' initial orientation mechanism.The authors wish to thank Howard French and Clarence Tilton for their help in construction details and André Gobert for his contributions and assistance. Our appreciation is also extended to Douglas McCorkle, Irene Brown, Michael Weiler, Sean Tunis, Angela Lui, Daniel Polikoff, and Scott Smith for their assistance in conducting test releases and in timing-in returning birds. The participation of the Italian authors was supported jointly by the Italian Ministry of Public Education and the Cassa di Risparmio di Pisa. Additional support for this study came from a National Science Foundation Grant No. BMS 75-18905 A02 to William T. Keeton. 相似文献
6.
Boric acid dust as a component of an integrated cockroach management program in confined swine production 总被引:2,自引:0,他引:2
Zurek L Gore JC Stringham SM Watson DW Waldvogel MG Schal C 《Journal of economic entomology》2003,96(4):1362-1366
Boric acid dust treatments were evaluated as a tool for the integrated management of the German cockroach, Blattella germanica (L.), in commercial confined swine production. The efficacy of boric acid dust was comparable to that of an organic residual insecticide, cyfluthrin, which is commonly used to control cockroaches in this environment. Fall treatments suppressed the cockroach population for longer durations than treatments in the Spring. Boric acid dust is an effective, inexpensive, and low risk (to animal and human health, and the environment) alternative for the management of cockroaches in livestock production systems. 相似文献
7.
Phylogenetic relationships were determined for 76 partial P-element
sequences from 14 species of the melanogaster species group within the
Drosophila subgenus Sophophora. These results are examined in the context
of the phylogeny of the species from which the sequences were isolated.
Sequences from the P-element family fall into distinct subfamilies, or
clades, which are often characteristic for particular species subgroups.
When examined locally among closely related species, the evolution of P
elements is characterized by vertical transmission, whereby the P-element
phylogeny traces the species phylogeny. On a broader scale, however, the
P-element phylogeny is not congruent with the species phylogeny. One
feature of P-element evolution in the melanogaster group is the presence of
more than one P-element subfamily, differing by as much as 36%, in the
genomes of some species. Thus, P elements from several individual species
are not monophyletic, and a likely explanation for the incongruence between
P-element and species phylogenies is provided by the comparison of
paralogous sequences. In certain instances, horizontal transfer seems to be
a valid alternative explanation for lack of congruence between species and
P-element phylogenies. The canonical P-element subfamily, which represents
the active, autonomous transposable element, is restricted to D.
melanogaster. Thus, its origin clearly lies outside of the melanogaster
species group, consistent with the earlier conclusion of recent horizontal
transfer.
相似文献
8.
Jose MG Vilar 《BMC systems biology》2010,4(1):152
Background
Cellular responses to death-promoting stimuli typically proceed through a differentiated multistage process, involving a lag phase, extensive death, and potential adaptation. Deregulation of this chain of events is at the root of many diseases. Improper adaptation is particularly important because it allows cell sub-populations to survive even in the continuous presence of death conditions, which results, among others, in the eventual failure of many targeted anticancer therapies. 相似文献9.
10.
Alessandro S Guimarães Filipe B Carmo Marcos B Heinemann Ricardo WD Portela Roberto Meyer Andrey P Lage Núbia Seyffert Anderson Miyoshi Vasco Azevedo Aurora MG Gouveia 《BMC veterinary research》2011,7(1):1-5