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51.
Roger F. Castilho Paulo C. Carvalho-Alves Anibal E. Vercesi Sérgio T. Ferreira 《Molecular and cellular biochemistry》1996,159(2):105-114
The major protein in the sarcoplasmic reticulum (SR) membrane is the Ca2+ transporting ATPase which carries out active Ca2+ pumping at the expense of ATP hydrolysis. The aim of this work was to elucidate the mechanisms by which oxidative stress induced by Fenton's reaction (Fe2+ + H2O2 HO· + OH–+ Fe3+) alters the function of SR. ATP hydrolysis by both SR vesicles (SRV) and purified ATPase was inhibited in a dose-dependent manner in the presence of 0–1.5 MM H2O2 plus 50 M Fe2+ and 6 mM ascorbate. Ca2+ uptake carried out by the Ca2+-ATPase in SRV was also inhibited in parallel. The inhibition of hydrolysis and Ca2+ uptake was not prevented by butylhydroxytoluene (BHT) at concentrations which significantly blocked formation of thiobarbituric acid-reactive substances (TBARS), suggesting that inhibition of the ATPase was not due to lipid peroxidation of the SR membrane. In addition, dithiothreitol (DTT) did not prevent inhibition of either ATPase activity or Ca2+ uptake, suggesting that inhibition was not related to oxidation of ATPase thiols. The passive efflux of 45Ca2+ from pre-loaded SR vesicles was greatly increased by oxidative stress and this effect could be only partially prevented (ca 20%) by addition of BHT or DTT. Trifluoperazine (which specifically binds to the Ca2+-ATPase, causing conformational changes in the enzyme) fully protected the ATPase activity against oxidative damage. These results suggest that the alterations in function observed upon oxidation of SRV are mainly due to direct effects on the Ca2+-ATPase. Electrophoretic analysis of oxidized Ca2+-ATPase revealed a decrease in intensity of the silver-stained 110 kDa Ca2+-ATPase band and the appearance of low molecular weight peptides (MW < 100 kDa) and high molecular weight protein aggregates. Presence of DTT during oxidation prevented the appearance of protein aggregates and caused a simultaneous increase in the amount of low molecular weight peptides. We propose that impairment of function of the Ca2+-pump may be related to aminoacid oxidation and fragmentation of the protein.Abbreviations AcP
acetylphosphate
- BHT
butylhydroxytoluene
- DTT
dithiothreitol
- Hepes
4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid
- SDS
sodium dodecyl sulfate
- SDS-PAGE
polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate
- SR
sarcoplasmic reticulum
- SRV
sarcoplasmic reticulum vesicles
- TBA
thiobarbituric acid
- TBARS
thiobarbituric acid-reactive substances
- TFP
trifluoperazine 相似文献
52.
Applications of intrinsic fluorescence measurements in the study of Ca2+-transport ATPases are reviewed. Since the initial reports showing that the fluorescence emission was sensitive to Ca2+ binding, a substantial amount of work has focused on the use of both steady-state and time-resolved fluorescence spectroscopy to investigate structure-function relationships in sarcoplasmic reticulum and plasma membrane Ca2+-ATPases. These studies have revealed ligand-induced conformational changes, as well as provided information on protein-protein, protein-solvent and/or protein-lipid interactions in different functional states of these proteins. The main results of these studies, as well as possible future prospects are discussed. 相似文献
53.
Fernando Pliego-Alfaro Mary Joy R. Monsalud Richard E. Litz Dennis J. Gray Pamela A. Moon 《Plant Cell, Tissue and Organ Culture》1996,44(1):63-70
Inhibition of mango somatic embryo growth was inducedin vitro by treatments for 4 or more weeks with abscisic acid (0–100 M ABA) with and without high osmolarity provided by mannitol (0–10%). High osmolarity and ABA significantly affected somatic embryo length, precocious germination and the production of good quality secondary somatic embryos. High osmolarity also affected root elongation. Abscisic acid was more effective in suppressing growth and development of 0.5 cm-length somatic embryos than smaller somatic embryos. Development beyond the heart stage was significantly inhibited by both ABA and mannitol treatments. The recovery of good quality somatic embryos was enhanced by high levels of ABA (100 M) with and without mannitol (0–5%). Somatic embryos that had been pulsed with ABA were partially desiccated at different relative humidities. Weight loss was affected only by relative humidity; and ABA did not enhance desiccation tolerance.Abbreviations ABA
Abscisic acid
- 2,4-D
2,4-Dichlorophenoxyacetic acid
- MM1
Mango maturation medium
- RH
Relative humidity 相似文献
54.
Jose Pontón Fernando L. Hernando Maria Dolores Moragues Pedro L. Barea Mara Gerloni Stefania Conti Paola Fisicaro Cristina Cantelli Luciano Polonelli 《Mycopathologia》1996,133(2):89-94
The presence of heat shock mannoproteins (HSMPs) reactive with sIgA was demonstrated in several C. albicans strains. The subculture of the C. albicans isolated from mucosal surfaces on Sabouraud's dextrose agar at 25 °C switched off the HSMP expression. A re-expression of the HSMPs was obtained in the same medium by shifting the temperature of incubation to 37 °C. However, expression of HSMPs in two strains isolated from deep infections was maintained during several subcultures on Sabouraud's dextrose agar at 25 °C. A glycoprotein of 200 kDa seemed to be the main HSMP reacting with vaginal sIgA. The data presented in this study suggest that factors other than temperature can influence the expression of C. albicans HSMPs and therefore these antigens should be referred as stress mannoproteins.Abbreviations HSMPs
heat shock mannoproteins
- MAb
monoclonal antibody
- sIgA
secretory IgA 相似文献
55.
56.
Antonio Balas Felix Garcia-Sanchez Fernando Gomez-Reino Jose L. Vicario 《Immunogenetics》1994,39(6):452-452
Correspondence to: J. L. Vicario. 相似文献
57.
R. F. M. van Steveninck A. Babare D. R. Fernando M. E. van Steveninck 《Plant and Soil》1994,167(1):157-164
Plant species adapted to soils enriched with heavy metals often accumulate these metals in their above or below ground organs. In this study, electron probe microanalysis of fractured, quench-frozen root specimens of common crop species shows that an appreciable quantity of Zn can be bound as Zn phytate (myo-inositolkis-hexaphosphate) within small vacuoles of cells in the root elongation zone of lucerne, soybean, lupins, tomato, rapeseed, cabbage, radish, maize and wheat exposed to high levels of Zn (80–300 M). Globular deposits of Zn phytate are most frequently observed in the endodermis of dicotyledonous species and in the pericycle of monocotyledonous species, but may also occur in the stele and inner cortex after prolonged exposure to toxic levels of Zn. The deposits could not be found in Zn-treated sunflower, field peas and Italian ryegrass. In three crop species, lucerne, soybean and maize, Zn-induced phytate globules were frequent, but exposure of roots to 30 M Cd did not induce the formation of Cd-containing globular deposits as observed inLemna minor (Van Steveninck et al., 1990a, 1992). Simultaneous Zn and Cd treatment induced the formation of Zn phytate globules as effectively as Zn alone, and Cd was not detected in the deposits. 相似文献
58.
Cllia Ferreira Adriana N. Capella Roberta Sitnik Walter R. Terra 《Archives of insect biochemistry and physiology》1994,26(4):299-313
In the midgut of Spodoptera frugiperda larvae, subcellular fractionation data suggest that aminopeptidase and part of amylase, carboxypeptidase A, dipeptidase, and trypsin are bound to the microvillar membranes; that major amounts of soluble dipeptidase, cellobiase, and maltase are trapped in the cell glycocalyx; and finally that soluble carboxypeptidase, amylase, and trypsin occur in intracellular vesicles. Most luminal acetylglucosaminidase is soluble and restricted to the ectoperitrophic contents. Aminopeptidase occurs in minor amounts bound to membranes both in the ectoperitrophic contents and incorporated in the peritrophic membrane. Amylase, carboxypeptidase A, and trypsin are found in minor amounts in the ectoperitrophic contents (both soluble and membrane-bound) and in major amounts in the peritrophic membrane with contents. Part of the activities recovered in the last mentioned contents corresponds to enzyme molecules incorporated in the peritrophic membrane. The results suggest that initial digestion is carried out in major amounts by enzymes in the endoperitrophic space and, in minor amounts, by enzymes immobilized in the peritrophic membrane. Intermediate and final digestion occur at the ectoperitrophic space or at the surface of midgut cells. The results also lend support to the hypothesis that amylase and trypsin are derived from membrane-bound forms, are released in soluble form by a microapocrine mechanism, and are partly incorporated into the peritrophic membrane. © 1994 Wiley-Liss, Inc. 相似文献
59.
Parasites of all kinds affect the behaviour of their hosts, often making them more susceptible to predators. The associated
loss in expected future reproductive success of infected hosts will vary among individuals, with younger ones having more
lose than older ones. For this reason, young hosts would benefit more by opposing the effects of parasites than old ones.
In a laboratory study, the effects of the trematode Telogaster opisthorchis on the anti-predator responses of the upland bully (Gobiomorphus breviceps) and of the common river galaxias (Galaxias vulgaris) were examined in relation to fish age. In a bully population where parasites were very abundant, the magnitude of the fish's
anti-predator responses decreased as the number of parasites per fish increased, and this effect was significantly more pronounced
in age 2 + and, to a lesser extent, age 3 + fish than in age 1 + fish. In another bully population where parasites were 10
times less abundant, similar effects were noticeable but not significant, whereas no effects of parasites on the responses
of galaxiids to predators were apparent. Differences in the abundance of parasites and in their sites of infection in fish
may explain the variability among host populations or species. However, in the bully population with high parasite abundance,
parasitism has age-dependent effects on responses to predators, providing some support for the prediction that young fish
with high expected future reproductive success invest more energy into opposing the effects of parasites than do older fish. 相似文献
60.
The presence of an adenylate translocator in the envelope membranesof proplastids isolated from the cultured cells of tobacco (Nicotianatabacum L. cv. BY2) was examined by means of transport experimentsusing the silicone oil filtering centrifugation technique. Itwas observed that proplastids can import [3H]ATP, [3H]ADP, [3H]AMPand less specifically ADP-[14C]Glc which can eventually be usedfor starch biosynthesis. The effects of specific inhibitorsof the mitochondrial adenylate translocator, i.e. atractyloside,bongkrekic acid and carboxyatractyloside were tested. Similarto the case of amyloplasts isolated from the cultured cellsof sycamore and chloroplasts isolated from spinach leaves, onlyATP and ADP-Glc uptake were shown to be partially inhibitedby carboxyatractyloside. On the other hand, neither atractylosidenor bongkrekic acid exerted a significant inhibitory effecton adenylate uptake. (Received August 8, 1992; Accepted November 26, 1992) 相似文献