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71.
We hypothesized that manganese deficient animals fed high vs moderate levels of polyunsaturated fat would either manifest
evidence of increased oxidative stress or would experience compensatory changes in antioxidant enzymes and/or shifts in manganese
utilization that result in decreased endogenous gut manganese losses. Rats (females in Study 1, males in Study 2,n = 8/treatment) were fed diets that contained 5 or 20% corn oil by weight and either 0.01 or 1.5 μmol manganese/g diet. In
study 2,54Mn complexed to albumin was injected into the portal vein to assess gut endogenous losses of manganese. The manganese deficient
rats:
Gut endogenous losses of manganese tended to account for a smaller proportion of absorbed manganese in rats fed high-fat diets;
otherwise fat intake had few effects on tissue manganese concentrations. 相似文献
1. | Had 30–50% lower liver, tibia, kidney, spleen, and pancreas manganese concentrations than manganese adequate rats; |
2. | Conserved manganese through ≈70-fold reductions in endogenous fecal losses of manganese; |
3. | Had lower heart manganese superoxide dismutase (MnSOD) activity; and |
4. | Experienced only two minor compensatory changes in the activity of copper-zinc superoxide dismutase (CuZnSOD) and catalase. |
72.
Oscillatory changes of the electrical resistance across the nodal complex of Nitellopsis obtusa (Desv. in Lois) J. Gr. were observed in experiments performed for 40–150 min with the use of external electrodes and microelectrodes. Three main patterns of node resistance oscillations were similar to those found for membrane potential and resistance. The presented findings indicate an oscillatory behaviour of the plasmodesmata system at the node, which may be connected with e.g. pulsatile variations in the number of open plasmodesmata. 相似文献
73.
Chang-Zhi Dong Jean-Luc Montillet Christian Triantaphylidès 《Physiologia plantarum》1994,90(2):307-312
The effects of ionizing radiation, used in post-harvest treatment of fruit and vegetables. were investigated on cultured apple cells ( Pyrus malus L. cv. Royal Red) on a short-term period. Irradiation (2 kGy) induced an increase of passive ion effluxes from cells and a decrease of cell capacity to regulate external pH. These alterations are likely due to effects on plasma membrane structure and function and were further investigated by studying the effects of irradiation on plasma membrane H+ -ATPase activity. Plasma membrane-enriched vesicles were prepared and the H+ -ATPase activity was characterized. Irradiation of the vesicles induced a dose dependent inhibition of H+ -ATPase activity. The loss of enzyme activity was immediate, even at low doses (0.5 kGy), and was not reversed by the addition of 2m M dithiothreitol. This inhibition may be the result of an irreversible oxidation of enzyme sulfhydryl moieties and/or the result of changes induced within the lipid bilayer affecting the membrane-enzyme interactions. Further analysis of the H+ -ATPase activity was carried out on vesicles obtained from irradiated cells confirming the previous results. In vivo recovery of activity was not observed within 5 h following the treatment, thus explaining the decrease of cell capacity to regulate external pH.
This rapid irreversible inhibition of the plasma membrane H+ -ATPase must be considered as one of the most important primary biochemical events occurring in irradiated plant material. 相似文献
This rapid irreversible inhibition of the plasma membrane H
74.
Hydrogen peroxide at concentrations from 0.1 to 20 μM enhances phagocytosis and oxidative burst of murine peritoneal macrophages. The activation of these macrophage functions is paralled by prolonged hyperpolarization and a transient increase in cytoplasmic free calcium concentration. All the effects are dose- and time-dependent. The results obtained for H2O2 are compared with those for a natural activator, peptide N-formyl-methionyl-leucly-phenylalanine. The data demonstrate the ability of small doses of hydrogen peroxide to stimulate macrophages through the intracellular mechanisms of ion transduction. 相似文献
75.
Summary A 3D triple resonance experiment has been designed to provide intraresidual and sequential correlations between amide nitrogens and -carbons in uniformly 13C15N-labeled proteins. In-phase 13C magnetization is transferred to the aliphatic side-chain protons via the side-chain carbons using a CC-TOCSY mixing sequence. Thus, the experiment alleviates the resonance assignment process by providing information about the amino acid type as well as establishing sequential connectivities. Leaving the carbonyl spins untouched throughout the transfer from 13C to 1H leads to E.COSY-type cross peaks, from which the 3JH
co coupling constants can be evaluated. The pulse sequence is applied to oxidized Desulfovibrio vulgaris flavodoxin. 相似文献
76.
The water fern Azolla pinnata R. Br. was fumigated for 1 week with either 25, 50 or 100 nl 1−1 SO2 . The symbiosis of Azolla with Anabaena azollae (spp.) was severely damaged by atmospheric SO2 even at concentrations as low as 25 nl 1−1 , with significant reductions in growth, reduction of C2 H2 , NH3 assimilation, protein synthesis, and heterocyst development. These disturbances appear to be mainly responsible for the extreme sensitivity of this fern to atmospheric SO2 . Changes in violaxanthin/antheraxanthin and epoxy-lutein/lutein ratios also indicate that free radical products are induced by atmospheric SO2 . These results suggest that the Azolla-Anabaena symbiotic system is a very responsive and reliable lower plant model to study the detailed effects of total sulphur deposition upon the balances between various important plant metabolic processes. 相似文献
77.
Eugenio Vitrano Antonio Cupane Maurizio Leone Valeria Militello Lorenzo Cordone Benedetto Salvato Mariano Beltramini Luigi Bubacco Gian Paolo Rocco 《European biophysics journal : EBJ》1993,22(3):157-167
In this work we report the optical absorption spectra of three cobalt-substituted derivatives of hemocyanin (He) from Carcinus maenas, in the temperature range 300–20 K. The derivatives studied are the mononuclear (Co2+)-He with a single cobalt ion in the CuA site, the binuclear (Co2+)2-He and the binuclear mixed metal (Co2+-Cu1+)-He. At low temperature three main bands are clearly resolved; the temperature dependence of their zeroth, first and second moments sheds light on the stereodynamic properties in the surroundings of the chromophore. Within the limits of the reported analysis, in the binuclear derivatives the motions coupled to the chromophore appear to be essentially harmonic in the whole temperature range investigated; moreover the data are consistent with the presence of an exogenous ligand strongly bound to the two metal ions. For the mononuclear derivative an essentially harmonic behavior is evident only up to 200 K where the data are consistent with the presence of an exogenous ligand much less strongly bound, while at higher temperatures the behavior of the spectra indicates the onset of very large anharmonic contributions to motions, that plausibly involve the above exogenous ligand and, quite likely, the entire active site.Abbreviations He
Hemocyanin
- M0
zeroth moment
- M1
first moment
- M2
second moment
- (Co2–)2-He
binuclear bicobalt hemocyanin derivative
- (Co2+)-He
mononuclear monocobalt hemocyanin derivative
- (Co2+-Cu1+)-He
binuclear mixed metals hemocyanin derivative
- LFT
ligand field theory
- CT
charge transfer
- EPR
electronic paramagnetic resonance
- XANES
X-ray absorption near edge structure
Correspondence to: L. Cordone 相似文献
78.
Robert A. Copeland 《Journal of bioenergetics and biomembranes》1993,25(2):93-102
The electronic transitions of the two heme groups of cytochromec oxidase have been resolved by application of second-derivative and cryogenic absorption spectroscopy. Both methods reveal a splitting of the ferrocytochromea Soret transition into two features at 443 and 450 nm. The relative intensity of the 450 nm feature appears to depend on the ligation state of cytochromea
3, the solution pH, and complex formation with cytochromec. The structural origin and mechanistic significance of this second Soret transition of cytochromea are discussed in terms of the electron transfer and proton translocation activities of the enzyme.Dedicated to the memory of James Carl Copeland. 相似文献
79.
Graham Palmer 《Journal of bioenergetics and biomembranes》1993,25(2):145-151
Some contemporary issues relevant to the chemistry of mammalian cytochromec oxidase are discussed. These include the optical properties of heme A and the spectroscopic consequences of the differences in side-chain substitution compared to heme B; a common fallacy concerning the electrostatic exchange interaction between cytochromea
3 and CuB; the question of the number and location of the copper components of the enzyme; and the mode of binding of ligands such as cyanide and azide. 相似文献
80.
本文研究了二类一端受外力的交联振荡器链:最邻近多相位交联振荡器链,以及多重交联振荡器链,讨论了它们产生内部传输,即各振荡器与外力具有相同频率的现象。文中近似相位差方程、指数二分性理论和中心流形理论被应用于系统的渐近近似。研究。本文得到了更符合于实际情况的神经网络CPG链动态特性分析结论。 相似文献