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81.
The single, basal pyrenoids of Gonium quadratum Pringsheim ex Nozaki and G. pectorale Müller (Goniaceae, Chlorophyta) differed in appearance when vegetative colonies were cultured photoheterotrophically in medium containing sodium acetate. Chloroplasts of G. quadratum had distinct pyrenoids when grown in medium without major carbon compounds. However, the pyrenoids degenerated and were markedly reduced in size when such cells were inoculated into a medium containing 400 mg·L?1 of sodium acetate. No pyrenoids were visible under the light microscope; however, with electron microscopy small pyrenoids and electron-dense bodies were visible within the degenerating chloroplasts, which had only single layers of thylakoid lamellae at the periphery. The chloroplasts subsequently developed distinct pyrenoids and several layers of thylakoid lamellae as the culture aged. In contrast, vegetative cells of G. pectorale always showed distinct pyrenoids when cells were inoculated into medium containing sodium acetate, sodium pyruvic acid, sodium lactate, and/or yeast extract. Therefore, we propose two terms, “unstable pyrenoids” and “stable pyrenoids,” for pyrenoids of G. quadratum and G. pectorale, respectively. Chloroplasts of the colonial green flagellates should thus be examined under various culture conditions in order to determine whether their pyrenoids are unstable or stable when pyrenoids are used as taxonomic indicators. Immunogold electron microscopy showed that the ratios of gold particle density of ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCO) between pyrenoid matrix and chloroplast stroma in G. quadratum grown in medium with or without sodium acetate were lower than those of G. pectorale. Heavy labeling by anti-RuBisCO was observed in both the electron-dense bodies and pyrenoid matrix of G. quadratum. This is the first electron microscopic demonstration of degeneration and development of both pyrenoids and thylakoid lamellae in the chloroplast as a function of culture condition in green algae. 相似文献
82.
The involvement of a vanadate-sensitive ATPase in plasma membranes of a salt tolerant cyanobacterium
Rachel Gabbay-Azaria Uri Pick Gozal Ben-Hayyim Elisha Tel-Or 《Physiologia plantarum》1994,90(4):692-698
Plasma membranes of the marine cyanobacterium Spirulina subsalsa were tested for ATPase activity, and for involvement in salt stress. Transition of cells from saline to hypersaline medium enhances the respiratory activity associated with extrusion of Na+ and Cl− , and persisting salt stress induces synthesis of respiratory enzymes in the plasma membranes. The membranes possess an ATPase, specific for ATP and Mg2+ and sensitive to orthovanadate and dicyclohexylcarbodiimide. Immunoblot analysis of plasma membrane polypeptides from Spirulina subsalsa with anti- Arabidopsis H+ -ATPase serum identified a single polypeptide of 100 kDa, which cross-reacted with the antibodies. An unusual feature of this ATPase is a specific stimulation by Na+ ions. Prolonged adaptation of S. subsals cells to hypersaline conditions induced an increase in ATPase activity in subsequent plasma membrane preparations, as well as a higher content of the 100 kDa polypeptide. It is suggested that the ATPase investigated is an H+ -pump, which is involved in extrusion of Na+ and in conferring resistance to salt stress. 相似文献
83.
84.
Tomonari Tsutsumi Tetsuyuki Kobayashi Hiroshi Ueda Emiko Yamauchi Shiro Watanabe Harumi Okuyama 《Neurochemical research》1994,19(4):399-406
A membrane preparation from rat brain catalyzed the hydrolysis of [2-3H]glycerol-labeled lysophosphatidylinositol (lysoPI) to yield monoacylglycerol (MG) and inositolphosphates. This phospholipase C activity had an optimal pH of 8.2. The membrane preparation did not require the addition of Ca2+ for its maximum activity, but the activity was inhibited by addition of 0.1 mM EDTA to the assay mixture and was restored by simultaneous addition of 0.2 mM Ca2+. The activity was found to be localized in synaptic plasma membranes prepared by Ficoll and Percoll density gradients. The phospholipase C was highly specific for lysoPI; diacylglycerol formation from phosphatidylinositol, and MG formation from lysophosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidylserine were below 5% of that observed with lysoPI under the conditions used. We concluded that there is a pathway for phosphatidylinositol metabolism in brain synaptic membranes which is different from the well-characterized phosphoinositide-specific phospholipase C pathway.Abbreviations PI
phosphatidylinositol
- lysoPI
lysophosphatidylinositol
- lysoPI-PLC
lysophosphoinositide-specific phospholipase C
- PI-PLC
phosphoinositide-specific phospholipase C
- MG
monoacylglycerol
- PLC
phospholipase C
To whom to address reprint requests. 相似文献
85.
C. Cafè C. Torri S. Gatti D. Adinolfi P. Gaetani R. Rodriguez Y. Baena F. Marzatico 《Neurochemical research》1994,19(12):1551-1555
Non-synaptosomal and synaptosomal mitochondrial membrane-linked enzymatic activities, NADH-cytochrome c reductase rotenone insensitive (marker of the outer membrane) and cytochrome oxidase (marker of the inner membrane), were measured in rat brain hippocampus and striatum immediately after and 1, 4, and 7 days following the induction of complete transient ischemia (15 min) by the four vessel occlusion method. Furthermore citrate synthetase activity was measured with and without Triton X-100 in order to qualitatively evaluate the membrane permeability. Nonsynaptosomal mitochondrial membranes showed reduction of both activities only in the late reperfusion phase: NADH-CCRRi decreased in striatal mitochondria after 4–7 days and only after 7 days in the hippocampus. COX activity decreased only in striatal mitochondria 7 days after ischemia. Non-synaptosomal mitochondrial membrane permeability did not show changes. Synaptosomal mitochondria showed a decrease of NADH-CCRRi only at 7 days of reperfusion both in hippocampus and striatum, while COX activity decreased only during ischemia and returned to normal levels in the following days in the two areas considered. In summary, free mitochondria showed insensitiveness to ischemia but they risulted damaged in the late reperfusion phase, while mitochondria from the synaptic terminal showed ischemic damage, partially restored during reperfusion. The striatal mitochondria showed a major susceptibility to ischemia/repefusion damage, showing changes earlier than the hippocampal ones. 相似文献
86.
Synaptic plasma membranes (SPM) from the brain are known to have specific binding sites for several steroid hormones, but the mechanisms of membrane transduction of steroid signals is not understood. In this study, corticosterone was found to prevent temperature-dependent dissociation of endogenous calmodlin (CaM) from highly purified SPM from rat cerebral cortex. The steroid stabilizes Ca2+-dependent membrane binding of endogenous CaM (78% of total CaM), whereas Ca2+-independent binding of CaM (the other 22%) is not affected. The stabilization of membrane binding of endogenous CaM by corticosterone is concentration-dependent, with the maximal effect occurring at steroid concentration of 1 M. The EC50 is estimated as 130 nM, which is almost identical to the Kd of specific binding of the steroid to SPM (120 nM) reported previously. The effect in stabilizing membrane binding of CaM is specific to corticosterone and other glucocorticoids (cortisol, dexamethasone and triamcinolone); gonadal steroids (17-estradiol, progesterone and testosterone) are ineffective. Furthermore, corticosterone administration in vivo (2 mg/kg, i.p.) produced a rapid increase of CaM content in SPM, occurring within 5 min after steroid injection and persisting for at least 20 min. Since CaM mediates a variety of biochemical processes in synaptic membranes, we hypothesize that the effect of glucocorticoids in promoting membrane binding of CaM may lead to a cascade of consequences in synaptic membrane function.Special issue dedicated to Dr. Sidney Ochs. 相似文献
87.
88.
Effects of osmotic preconditioning on nuclear replication activity in seeds of pepper (Capsicum annuum) 总被引:1,自引:0,他引:1
Sergio Lanteri H. Lieke Kraak C. H. Ric De Vos Raoul J. Bino 《Physiologia plantarum》1993,89(3):433-440
Routing of cytosolically synthesized precursor proteins into chloroplasts is a specific process which involves a multitude of soluble and membrane components. In this review we wil1 focus on early events of the translocation pathway of nuclear coded plastidic precursor proteins and compare import routes for polypeptide of the outer chloroplast envelope to that of internal chloroplast compartments. A number of proteins housed in the chloroplast envelopes have been implied to be involved in the translocation process, but so far a certain function has not been assigned to any of these proteins. The only exception could be an envelope localized hsc 70 homologue which could retain the import competence of a precursor protein in transit into the organelle. 相似文献
89.
Recent advances in the understanding of polyamine functions during plant development 总被引:15,自引:0,他引:15
Suggested roles for polyamine function, and the evidence for these functions, is reviewed. These include membrane stabilization, free radical scavenging, effects on DNA, RNA and protein synthesis, effects on the activities of RNase, protease and other enzymes, the interaction with ethylene biosynthesis, and effects on second messengers. It is concluded that in addition to interacting with plant hormones, polyamines are able to modulate plant development through a fundamental mechanism(s) common to all living organisms.Abbreviations ACC
1-aminocyclopropane-1-carboxylic acid
- ADC
arginine decarboxylase
- Chl
chlorophyll
- DAP
diaminopropane
- DFMA
DL--difluoromethylarginine
- DFMO
DL--difluoromethylornithine
- PAs
polyamines
- Put
putrescine
- SAM
S-adenosylmethionine
- Spd
spermidine
- Spm
spermine 相似文献
90.
Fourier transform infrared spectroscopic study of ion binding and intramolecular interactions in the polar head of digalactosyldiacylglycerol 总被引:2,自引:0,他引:2
Lipid bilayers composed of digalactosyldiacyl-glycerol (DGDG), that is, Galp1-6Galp1-3DAG, a non-ionic lipid of the thylakoid membrane of chloroplasts, aggregate in aqueous media containing mono- and divalent cations in amounts above a threshold concentration (Ct) of about 1.0, 4.7 and 10.0 mM for Ca2+, Mg2+ and Na+, respectively. In this work, we found that above Ct the DGDG membranes do not undergo fusion and that the aggregation can be reversed, or disrupted. This means that the perturbation induced by the salts results from adsorption, or complexation of the ions in the polar head of DGDG. To investigate this question, we used Fourier transform infrared (FTIR) spectroscopy to identify the molecular sites in DGDG which are modified by interaction, or adduct formation with CaCl2, MgCl2 and NaCl. We also determined whether the ions affect the intramolecular hydrogen bonding between the sn2 ester C = O and the carbon-6 of the -anomer of galactose (Gal). The major conclusions are: (i) the salts do not affect, at least directly, the, ester carbonyl region of DGDG, (ii) the most probable sites of binding, or adsorption, for the ions are the ring oxygen, and (iii) the ring hydroxyls are the sites of either ion complexation or intra- and intermolecular H-bonding in interacting DGDG membranes. Within this framework, the complexation of the ions with Gal might induce total or partial dehydration of the galactolipid headgroup and thus provides the means to overcome the repulsive hydration forces that hinder aggregation of the DGDG membranes.Abbreviations DGDG
digalactosyldiacylglycerol
- EDTA
ethylenediaminetetracetic acid
- FTIR
Fourier transform infrared
- Gal
galactose
- GIDG
D-glucosyldiacylglycerol
- Glyc
glycerol
- LHCII
chloroplast light harvesting complex II
- MGDG
monogalactosyldiacylglycerol
- PC
phosphatidylcholine
- PG
phosphatidylglycerol
- PS
phosphatidylserine
- SQDG
sulfoquinovosyl-diacylglycerol
Correspondence to: M. Fragata 相似文献