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61.
Gomes JE Pesty A Gouveia-Oliveira A Cidadão AJ Plancha CE Lefèvre B 《The International journal of developmental biology》1999,43(8):839-842
The action of gonadotropins upon the oocyte is known to be crucial at later stages of follicular development in mammals. However, its influence on oocytes at early preantral stages is still a matter of debate. In the present study we evaluated the onset of mouse oocyte's capacity to exhibit calcium spikes during preantral stages of follicular development, prior to meiotic competence acquisition. In particular, through the use of confocal microscopy, we probed for the specific effects of age and gonadotropin stimulation upon the calcium dynamics of preantral follicle oocytes. We found that important developmental changes on the Ca2+ signalling mechanisms take place early during follicular development. Specifically we demonstrate that both age and gonadotropin stimulation increase the capacity of oocytes recovered from preantral follicles to exhibit calcium spikes. We propose that a strictly morphological staging of follicular development is insufficient to predict oocyte behaviour and must take in consideration animal age and gonadotropin environment. 相似文献
62.
63.
Streri A 《Somatosensory & motor research》2003,20(1):13-18
The hypothesis that the ability to coordinate information between tactual and visual modalities is present at birth and dependent on perceptual inherent structures was tested in human newborns. Using an intersensory paired-preference procedure, we showed that newborns can visually recognize the shape of an object that they have previously manipulated with their right hand, out of sight. This is an experimental evidence that newborns can extract shape information in a tactual format and transform it in a visual format before they have had the opportunity to learn from the pairings of visual and tactual experience. This is contrary to a host of theories and models of perceptual learning, both traditional (empiricist philosophers) and modern (connectionist). 相似文献
64.
Reungpatthanaphong P Marbeuf-Gueye C Le Moyec L Salerno M Garnier-Suillerot A 《Journal of bioenergetics and biomembranes》2004,36(6):533-543
The effect of low-density membrane domains on function of the plasma membrane transporter P-glycoprotéine (P-gp), involved in multidrug resistance (MDR) phenotype, has been investigated in K562/ADR cells. To this end we reversibly altered the cholesterol content of K562/ADR cells by using methyl--cyclodextrin as a cholesterol chelator and conversely we repleted them through incubation with cholesterol in culture medium. We also used the cholesterol-binding fluorochrome filipin and cholesterol oxidase. Our data show that either cholesterol depletion or complex formation with filipin resulted in a strong decrease of P-gp activity. However, when cells were incubated with cholesterol oxidase that are known to disrupt rafts, no modification of the P-gp activity was observed. In addition, using a free-detergent methodology to separate by ultracentrifugation, light, heavy, and extra heavy fractions we show that no P-gp is found in the light fraction where rafts are usually detected. Altogether, our data strongly suggest that, in this cell line, P-gp is not localized in rafts. 相似文献
65.
66.
Microtubules are cylindrical organelles that play critical roles in cell division. Their subunit protein, tubulin, is a target for various antitumor drugs. Tubulin exists as various forms, known as isotypes. In most normal cells, tubulin occurs only in the cytosol and not in the nucleus. However, we have recently reported the finding of the beta(II) isotype of tubulin in the nuclei of cultured rat kidney mesangial cells. Mesangial cells, unlike most normal cell lines, have the ability to proliferate rapidly in culture. In efforts to determine whether nuclear beta(II)-tubulin occurred in other cell lines, we examined the distribution of the beta(I), beta(II), and beta(IV) mammalian tubulin isotypes in a variety of normal and cancer human cell lines by immunofluorescence microscopy. We have found that, in the normal cell lines, all three isotypes are present only in the cytoplasm. However, the beta(II) isotype of tubulin is located not only in the cytoplasm, but also in the nuclei of the following cell lines: LNCaP prostate carcinoma, MCF-7, MDA-MB-231, MDA-MB-435, and Calc18 breast carcinoma, C6 and T98G glioma, and HeLa cells. In contrast, the beta(I) and beta(IV) isotypes, which are also synthesized in cancer cells, are not localized to the nucleus but are restricted to the cytoplasm. We have also seen beta(II) in breast cancer excisions. In most of these cells, beta(II) appears to be concentrated in the nucleoli. These results suggest that transformation may lead to localization of beta(II)-tubulin in cell nuclei, serving an as yet unknown function, and that nuclear beta(II) may be a useful marker for detection of tumor cells. 相似文献
67.
Bcl-2 family member Bfl-1/A1 sequesters truncated bid to inhibit is collaboration with pro-apoptotic Bak or Bax 总被引:11,自引:0,他引:11
Werner AB de Vries E Tait SW Bontjer I Borst J 《The Journal of biological chemistry》2002,277(25):22781-22788
Following caspase-8 mediated cleavage, a carboxyl-terminal fragment of the BH3 domain-only Bcl-2 family member Bid transmits the apoptotic signal from death receptors to mitochondria. In a screen for possible regulators of Bid, we defined Bfl-1/A1 as a potent Bid interacting protein. Bfl-1 is an anti-apoptotic Bcl-2 family member, whose preferential expression in hematopoietic cells and endothelium is controlled by inflammatory stimuli. Its mechanism of action is unknown. We find that Bfl-1 associates with both full-length Bid and truncated (t)Bid, via the Bid BH3 domain. Cellular expression of Bfl-1 confers protection against CD95- and Trail receptor-induced cytochrome c release. In vitro assays, using purified mitochondria and recombinant proteins, demonstrate that Bfl-1 binds full-length Bid, but does not interfere with its processing by caspase-8, or with its mitochondrial association. Confocal microscopy supports that Bfl-1, which at least in part constitutively localizes to mitochondria, does not impede tBid translocation. However, Bfl-1 remains tightly and selectively bound to tBid and blocks collaboration between tBid and Bax or Bak in the plane of the mitochondrial membrane, thereby preventing mitochondrial apoptotic activation. Lack of demonstrable interaction between Bfl-1 and Bak or Bax in the mitochondrial membrane suggests that Bfl-1 generally prevents the formation of a pro-apoptotic complex by sequestering BH3 domain-only proteins. 相似文献
68.
Jean-Pierre Souchard Marie-Aline Barbacanne Emmanuel Margeat Arlette Maret Fran oise Nepveu Jean-Fran ois Arnal 《Free radical research》1998,29(5):441-449
Objective and Methods Endothelium produces oxygen-derived free radicals which play a major role in vessel wall physiology and pathology. Whereas NO· production from endothelium has been extensively characterized, little is known about endothelium-derived O-·2. In the present study, we determined the O-·2 production of bovine aortic endothelial cells (BAEC) using the spin trap 5,5-dimethyl-1 pyrroline-N-oxide (DMPO) and electron spin resonance (ESR) spectroscopy.
Results An ESR adduct DMPO-OH detected in the supernatant of BAEC after stimulation with the calcium ionophore A23187 originated from the trapping of extracellular O-·2, because coincubation with superoxide dismutase (30 U/ml) completely suppressed the ESR signal, whereas catalase (2000 U/ml) had no effect. A23187 stimulated extracellular O-·2 production in a time- and dose-dependent manner. The coenzymes NADH and NADPH both increased the ESR signal, whereas a flavin antagonist, diphenylene iodonium, abolished the ESR signal. Phorbol myristate acetate potentiated, whereas bisindolylmaleimide I inhibited the A23187-stimulated O-·2 production, suggesting the involvement of protein kinase C. These signals were not altered L-NAME, a NO-synthase inhibitor, suggesting that the endogenous production of NO· did not alter O-·2 production. Finally, the amount of O-·2 generated by A23187-stimulated post-confluent BAEC was one order of magnitude higher than that evoked by rat aortic smooth muscle cells stimulated under the same conditions. 相似文献
Results An ESR adduct DMPO-OH detected in the supernatant of BAEC after stimulation with the calcium ionophore A23187 originated from the trapping of extracellular O-·2, because coincubation with superoxide dismutase (30 U/ml) completely suppressed the ESR signal, whereas catalase (2000 U/ml) had no effect. A23187 stimulated extracellular O-·2 production in a time- and dose-dependent manner. The coenzymes NADH and NADPH both increased the ESR signal, whereas a flavin antagonist, diphenylene iodonium, abolished the ESR signal. Phorbol myristate acetate potentiated, whereas bisindolylmaleimide I inhibited the A23187-stimulated O-·2 production, suggesting the involvement of protein kinase C. These signals were not altered L-NAME, a NO-synthase inhibitor, suggesting that the endogenous production of NO· did not alter O-·2 production. Finally, the amount of O-·2 generated by A23187-stimulated post-confluent BAEC was one order of magnitude higher than that evoked by rat aortic smooth muscle cells stimulated under the same conditions. 相似文献
69.
Arlette Fellous Veena Prasad Renée Ohayon Mary Ann Jordan Richard F. Ludueña 《Journal of Protein Chemistry》1994,13(4):381-391
Microtubule-associated proteins (MAPs) can promote microtubule assemblyin vitro. One of these MAPs (MAP2) consists of a short promoter domain which binds to the microtubule and promotes assembly and a long projection domain which projects out from the microtubule and may interact wth other cytoskeletal elements. We have previously shown that MAP2 and another MAP, tau, differ in their interactions with tubulin in that tau, but not MAP2, promotes extensive aggregation of tubulin into spiral clusters in the presence of vinblastine and that microtubules formed with MAP2 are more resistant than those formed with tau to the antimitotic drug maytansine [Luduena, R. F.,et al. (1984),J. Biol. Chem.
259, 12890–12898; Fellous, A.,et al. (1985),Cancer Res.
45, 5004–5010]. Here we have used chymotryptic digestion to remove the projection domain of MAP2 and examined the interaction of the digested MAP2 (ctMAP2) with tubulin in the presence of vinblastine and maytansine. We have found that ctMAP2 behaves very much like tau, but not like undigested MAP2, in the presence of vinblastine, in that ctMAP2 causes tubulin to polymerize into large clusters of spirals. In contrast, microtubule assembly in the presence of ctMAP2 is much more resistant to maytansine inhibition than is assembly in the presence of tau or undigested MAP2. Our results suggest that the projection domain of MAP2 may play a role in the interaction of tubulin with MAP2 during microtubule assembly.Abbreviations MAPs
microtubule-associated proteins
- ctMAP2
MAP2 digested with-chymotrypsin
- nMAP2
untreated MAP2
- PMSF
phenylmethylsulfonyl fluoride
- GMPCPP
guanosine-5-(,-methylene)triphosphate 相似文献
70.
Sergio Salardi Lucia Tosi Arlette Garnier-Suillerot Claudio Toniolo Gian Maria Bonora Fernando Marchiori 《Biopolymers》1982,21(6):1229-1243
The interaction of Cu(II) with the protamine clupeine YII (containing proline at the N-terminal) and with four peptides (H-Ala-Arg-OMe, H-Ala-Arg2-OMe, H-Pro-Arg-OMe, and H-Arg4-Tyr) has been studied by means of absorption, CD, and pH neasurements. The first two peptides mimic clupeine YI and Z N-terminals; the third, the clupeine YII N-terminal. At 1:1 molar ratio, clupeine YII yields two complexes: the first (I), at pH 6.6, through coordination via the N-terminal and the contiguous peptide nitrogen forming a five-membered chelate; the second (II), at pH 8.5, through the occupancy of the other two corners of the coordination square by amino nitrogens of the lateral chains. These complexes are strictly analogous and occur at the same pH as those formed with clupeine Z. Under the same conditions, all the peptides yield complex I in the first step, although the pH at which this complex is fully defined depends on the number of residues in the chain. It is 8.5 for dipeptides, decreases to 6.5 by the addition of a third residue to the chain, and remains constant when the number of residues is three or more. The amino nitrogens of lateral chains are unable to coordinate to the metal in a second step unless one additional peptide bond lies between the N-terminal residue and that containing the lateral chain bound to the metal. Thus, H-Ala-Arg-OMe and H-Pro-Arg-OMe form hydroxyl complexes in a second step (pH 11), by deprotonation of one of the water molecules coordinated to the metal; one of the lateral chains of H-Ala-Arg2-OMe is able to coordinate in a second step (pH 8.5), but it is only with H-Arg4-Tyr that a second complex (II) is obtained in which two amino nitrogens of lateral chains supersede the oxygens of water molecules in I, at pH 8.5. 相似文献