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991.
Cooperative interaction of EWS with CREB-binding protein selectively activates hepatocyte nuclear factor 4-mediated transcription 总被引:1,自引:0,他引:1
992.
Pinto LZ Laure MA Bitondi MM Hartfelder K Simões ZL 《The International journal of developmental biology》2003,47(5):385-388
The reorganization of the ventral nerve cord (VNC) during metamorphosis of M. quadrifasciata was observed to be characterized by shortening of connectives and subsequent fusion of the 2nd and 3rd thoracic and the 1st abdominal ganglia. Also, the 5th to 7th abdominal ganglia came into very close contact. These changes were accompanied by increasing levels of endogenous ecdysteroids, as determined by a radioimmunoassay. Incubation of VNC in the presence of 5 microg 20-hydroxyecdysone, caused significant shortening of connectives in the thoracic region, but not in the abdomen, evidencing a segment-specific response to this hormone. Cell death in the ventral ganglia was revealed by transmission electron microscopy and TUNEL-reaction. Detection of labeled cells in the region where contiguous ganglia come into close contact suggests that programmed cell death is involved in ganglionic fusion. 相似文献
993.
Freire AC Aoyama H Haun M Ferreira CV 《Journal of enzyme inhibition and medicinal chemistry》2003,18(5):425-429
Protein phosphatases are signalling molecules that regulate a variety of fundamental cellular processes including cell growth, metabolism and apoptosis. The aim of this work was to correlate the cytotoxicity of pervanadate and okadaic acid on HL60 cells and their effect on the phosphatase obtained from these cells. The cytotoxicity of these protein phosphatase inhibitors was evaluated on HL60 cells using phosphatase activity, protein quantification and MTT reduction as indices. The major phosphatase presents in the cellular extract showed high activity (80%) and affinity (Km = 0.08 mM) to tyrosine phosphate in relation to p-nitrophenyl phosphate (pNPP)-(Km = 0.51 mM). Total phosphatase (pNPP) was inhibited in the presence of 10 mM vanadate (98%), 200 microM pervanadate (95%) and 100 microM p-chloromercuribenzoate (80%) but okadaic acid caused a slight increase in enzyme activity (25%). When the HL60 cells were treated with the phosphatase inhibitors (pervanadate and okadaic acid) for 24hours, only 20% residual activity was observed in presence of 200 microM pervanadate, whereas in the presence of okadaic acid this inhibitory effect was not observed. However, in respect to mitochondrial function, cell viability decreased about 80% in the presence of 100 nM okadaic acid. The total protein content was decreased 25% when the cells were treated with 100 nM okadaic acid in combination with 200 microM pervanadate. Our results suggest that both phosphatase inhibitors presented different mechanisms of action on HL60 cells. However, their effect on the cell redox status have to be considered. 相似文献
994.
995.
996.
Pacheco Thaynara L. Monné Marcela L. Vaz-de-Mello Fernando Z. Ahrens Dirk 《Organisms Diversity & Evolution》2022,22(3):733-748
Organisms Diversity & Evolution - Two unusual scarab species discovered from two localities in the Amazonian Basin are described. We used comparative morphology and phylogenetic analysis to... 相似文献
997.
El Mecherfi Kamel-Eddine Lupi Roberta Cherkaoui Mehdi Albuquerque Marcela A. C. Todorov Svetoslav Dimitrov Tranquet Olivier Klingebiel Caroline Rogniaux Hélène Denery-Papini Sandra Onno Bernard de Melo Franco Bernadette Dora Gombossy Larré Colette 《Probiotics and antimicrobial proteins》2022,14(5):779-791
Probiotics and Antimicrobial Proteins - Wheat is a worldwide staple food, yet some people suffer from strong immunological reactions after ingesting wheat-based products. Lactic acid bacteria (LAB)... 相似文献
998.
Nitric oxide (NO) generation by soybean (Glycine max, var ADM 4800) chloroplasts was studied by electron paramagnetic resonance (EPR) spin-trapping technique.1 Both nitrite and L-arginine (arg) are the required substrates for enzymatic activities considered as possible sources of NO in plants. Soybean chloroplasts showed a NO production of 3.2 ± 0.2 nmol min−1 mg−1 protein in the presence of 1 mM NaNO2. Chloroplasts incubated with 1 mM arg showed a NO production of 0.76 ± 0.04 nmol min−1 mg−1 protein. This production was inhibited when chloroplasts were incubated in presence of NOS-inhibitors L-NAME and L-NNA. In vitro exposure of chloroplasts to a NO-donor (GSNO) decreased both ascorbyl radical content and the activity of ascorbate peroxidase, without modification of the total ascorbate content. Exposure of the isolated chloroplasts to a NO-donor decreased lipid radical content in membranes, however, incubation in the presence of 25 µM peroxynitrite (ONOO−) led to an increase in lipid-derived radicals (34%). The effect of ONOO− on protein oxidation was determined by western blotting, showing an increase in carbonyl content either in stroma or thylakoid proteins as compared to control. Taken as a whole, NO seems to be an endogenous metabolite in soybean chloroplasts and reactive nitrogen species could exert either antioxidant or prooxidant effects on chloroplasts, since both a decreased lipid radical content in membranes and a decrease in the activity of ascorbate peroxidase were observed after exposure to a NO donor.Key Words: ascorbate, ascorbate peroxidase, chloroplasts, nitric oxide, peroxynitriteThe origin of nitric oxide (NO) in plants under aerobic conditions is currently under study. Although plants with low level of arginine shows arg-stimulated NO accumulation,2 the mechanism for arginine-dependent NO synthesis in plants is still unknown, because the detection of an animal-type NOS remains elusive to date.3,4 Even though assimilatory nitrate reductase is an enzymatic source of NO, its role in vivo would be limited by both its cytosolic localization which difficult the availability for nitrite, and the relative high Km for nitrite (100 µM).5Chloroplasts have been previously marked as NO sources based in nonquantitative studies employing fluorescence microscopy6,7 and immunogold electron microscopy.8 In our work we employed an specific technique (EPR, electron paramagnetic resonance with spin trap9) to detect NO as an endogenous metabolite and to quantify its generation in the presence of different substrates. In order to gain insight on the mechanism leading to NO production both nitrite-dependent and arg-dependent pathways were evaluated. In the presence of 1 mM arg and 0.1 mM NADPH the rate of NO generation was 0.76 ± 0.04 nmol min−1 mg−1 prot (arg-dependent synthesis). The synthesis of NO resulted completely blocked in the presence of arg analogs (L-NAME and L-NNA). It is important to point out that the content of arg in the chloroplasts stroma is high as compared to the content of other amino acids (56.7 ± 0.8 nmol mg−1 prot), suggesting that this pathway could be operative under physiological conditions.Soybean chloroplasts showed a NO production of 3.2 ± 0.2 nmol min−1 mg−1 prot in the presence of 1 mM NaNO2. Furthermore, NO generation was detected in the presence of nitrite concentrations as low as 25 mM. Since nitrite-dependent NO generation resulted inhibited by 50% by the addition of DCMU, and no NO generation was measured in the stroma fraction, thylakoidal electron transport seems to be a key feature in NO synthesis.According to this scenario and assuming that the two independent pathways for NO generation in chloroplasts are operative, the total rate of production of NO could be understood as the generation by the activity of an arg-dependent enzyme and by a NO2− dependent pathway, as indicated by eq. 1.(1)Regarding the NO disappearance, from a kinetic point of view, the rate of the reaction of NO with O2− to generate peroxynitrite seems to be the main pathway, since the reaction is diffusionally controlled. Thus, the rate of disappearance of NO could be estimated from the rate of generation of ONOO− (eq. 2); however, other reactions should be considered under nonphysiological conditions.(2)NO generation rate should be equal to NO consumption rate in order to keep a physiological NO steady state concentration (eq. 3)(3)Thus, replacing NO generation and disappearance rates by those rates indicated in equations 1 and 2,
(4)
The data obtained under unrestricted availability of substrates, indicate a generation rate of NO by the activity of a NOS-like enzyme of 13 × 10−9 M s−1. Chloroplastic NO generation rate in the presence of 100 µM NO2− was 14 × 10−9 M s−1. Thus, according to equation 1, the rate of generation of NO is approximately 3 × 10−8 M s−1. Assuming a steady state concentration for O2− of 1 nM in chloroplasts10 and a rate constant (k) of 6.9 × 109 M−1 s−1 for the reaction between O2− and NO,11 a steady state concentration of 4 nM for NO in the chloroplast could be estimated. Since under in vivo conditions chloroplasts may content the required substrates for the NO synthesis, the assays presented here strongly suggest that a feasible NO production could take place inside the chloroplasts. However, nonsupplemented chloroplasts did not show any NO-dependent EPR signal. This observation agrees with the fact that NO steady state concentration under physiological conditions as was calculated here (4 nM) is below the EPR detection limit (500 nM).12Further studies should be performed to characterize NO oxidative effects on chloroplasts. Scavenging of O2− and H2O2 is essential for chloroplasts to maintain their ability to fix CO2 since several enzymes in the CO2-reduction cycle are sensitive to active oxygen species.13 These organelles lacking catalase, contain a significant peroxidase activity.14 H2O2-reduction catalized by ascorbate peroxidase (AP) lead to ascorbate oxidation and produces ascorbyl radical (A.).15 In isolated chloroplast the content of A.. was evaluated in DMSO based extract by EPR16. Quantification of EPR signals indicated that A. content in control chloroplasts (123 ± 5 pmol mg−1 prot) decreased after exposure to NO (Fig. 1). The total content of ascorbate, assessed by an HPLC technique17 in chloroplasts isolated from soybean leaves exposed to NO was not significantly different from the measured content in chloroplasts not exposed to the NO donor (Fig. 1). The activity of AP was significantly decreased by 48, 53 and 54% after exposure of the chloroplasts to NO-donor. Previous data suggested that AP could be inactivated by NO via oxidation of functional thiols.18 Besides, the reversible inhibition of AP could be due to the formation of Fe-nitrosyl complexes between NO and the Fe atom of the heme group, as it was previously described for NO-mediated activation of guanylate cyclase and the inhibition of cytochrome P450 and catalase in mammals.19 The data presented here showed that in isolated chloroplasts exposed to a NO donor, there could be either a limited damage associated to the decrease in the content of A.. or an increased cellular deterioration by the decrease in the activity of the enzyme responsible for the scavenging of H2O2.Open in a separate windowFigure 1Ascorbate metabolism in soybean chloroplasts after NO exposure. A.. content (▪), ascorbate content (▪), and AP activity (*) as a function of the exposure of isolated chloroplasts to GSNO in the presence of 50 µM DTT. * = significantly different at p ≥ 0.05 from the value obtained in the absence of GSNO + 50 µM DTT.Thus, in situ generation of NO could play a protective role in preventing the oxidation of chloroplastic lipids; however, the reaction of NO with O2− leading to ONOO− production may result in a potential source of damage or as it is shown here by the significant decrease of the AP activity that consumes H2O2. NO is a suitable candidate to modulate cellular H2O2 level through the chloroplast function, as an initial step to regulate complex metabolic pathways directed to activate physiological responses, defense pathways or deleterious effects in the cytosol. Furthermore, an integrated study on the effect of nitrogen reactive species is required under stress conditions to characterize the metabolic pathways involved in the resulting cellular damage. 相似文献
999.
Mouse-human chimeric antibodies composed of murine variable (V) and human (C) chains are useful therapeutic reagents. Consequently, we investigated whether heterologous C-regions from mice and humans affected specificity and affinity, and determined the contribution of C(H) glycosylation to antigen binding. The interaction of a 12-mer peptide mimetic with monoclonal antibody (mAb) 18B7 to Cryptococcus neoformans glucuronoxylomannan, and its chimeric (ch) and deglycosylated forms were studied by surface plasmon resonance. The equilibrium and rate association constants for the chAb were higher than for mAb 18B7. V region affinity was not affected by C(H) region glycosylation whereas heterologous C region of the same isotype altered the Ab binding affinity and the specificity for self-antigens. Structural models displayed local differences that implied changes on the connectivity of residues. These findings suggest that V region conformational changes can be dictated by the C(H) domains through an allosteric effect involving networks of highly connected amino acids. 相似文献
1000.
Pereira Áurea Marcela de Souza de Farias Daniely Rayane Bezerra de Queiroz Blenda Brito Nobre Michelangela Suelleny de Caldas Cavalcanti Mônica Tejo Salles Hévila Oliveira dos Santos Karina Maria Olbrich de Medeiros Ana Claudia Dantas Florentino Eliane Rolim Alonso Buriti Flávia Carolina 《Probiotics and antimicrobial proteins》2019,11(1):273-282
Probiotics and Antimicrobial Proteins - The potential for reusability of whey is of concern due to its substantial nutritional value and, second, in view of the need to reduce environmental impact.... 相似文献