Unicellular cyanobacteria Synechocystis 6803 were fixed using high-pressure freezing (HPF) and freeze substitution without any chemical cross-linkers. Immunoelectron microscopy of these cells showed that five sequen...
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Unicellular cyanobacteria Synechocystis 6803 were fixed using high-pressure freezing (HPF) and freeze substitution without any chemical cross-linkers. Immunoelectron microscopy of these cells showed that five sequential enzymes of the Calvin cycle (phosphoriboisomerase, phosphoribulokinase, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), 3-phosphoglyceratekinase and glyceraldehyde-3-phosphate dehydrogenase) and the catalytic portion of the chloroplast H^+-ATP synthase (CF1) are located adjacent to the thylakoid membranes. Cell-free extracts of Synechocystis were processed by ultracentrifugation to isolate thylakoid fractions sedimenting at 40 000, 90 000, and 150 000 g. Among these, the 150 000-g fraction showed the highest linked activity of the above five sequential Calvin cycle enzymes and also the highest coordinated activity of light and dark reactions as assessed by ribose-5-phosphate (R-5-P) +ADP dependent CO2 fixation. Immunogold labeling of this membrane fraction confirmed the presence of the above five enzymes as well as the catalytic portion of the CF1 ATP synthase. Notably, the protein A-gold labeling of the thylakoids was observed without use of chemical cross-linkers and in spite of the normal washing steps used during standard immunolabeling. The results showed that soluble Calvin cycle enzymes might be organized along the thylakoid membranes.
Despite serving as a major inorganic nitrogen source for plants,ammonium causes toxicity at elevated con-centrations,inhibiting root elongation early *** previous studies have shown that ammonium-inhibited root develo...
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Despite serving as a major inorganic nitrogen source for plants,ammonium causes toxicity at elevated con-centrations,inhibiting root elongation early *** previous studies have shown that ammonium-inhibited root development relates to ammonium uptake and formation of reactive oxygen species(ROS)in roots,it remains unclear about the mechanisms underlying the repression of root growth and how plants cope with this inhibitory effect of *** this study,we demonstrate that ammonium-induced apo-plastic acidification co-localizes with Fe precipitation and hydrogen peroxide(H_(2)O_(2))accumulation along the stele of the elongation and differentiation zone in root tips,indicating Fe-dependent ROS *** screening ammonium sensitivity in T-DNA insertion lines of ammonium-responsive genes,we identified PDX1.1,which is upregulated by ammonium in the root stele and whose product catalyzes de novo biosyn-thesis of vitamin *** growth of pdx1.1 mutants is hypersensitive to ammonium,while chemical complementation or overexpression of PDX1.1 restores root *** salvage strategy requires non-phosphorylated forms of vitamin B6 that are able to quench ROS and rescue root growth from ammo-nium ***,these results suggest that PDX1.1-mediated synthesis of non-phosphorylated B6 vitamers acts as a primary strategy to protect roots from ammonium-dependent ROS formation.
Background:The presence and extent of structural changes in the brain as a consequence of Parkinson’s disease(PD)is still poorly ***:High-resolution 3-tesla T1-weighted structural magnetic resonance images in sixty-f...
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Background:The presence and extent of structural changes in the brain as a consequence of Parkinson’s disease(PD)is still poorly ***:High-resolution 3-tesla T1-weighted structural magnetic resonance images in sixty-five PD and 27 age-matched healthy control participants were ***,caudate,and intracranial volumes were manually traced in the axial plane of 3D reconstructed *** nuclei volumes were normalized to intracranial volume for statistical *** status was assessed using the Unified Parkinson’s Disease Rating Scale and Hoehn and Yahr *** status was assessed using global status tests and detailed neuropsychological ***:Both caudate and putamen volumes were smaller in PD brains compared to controls after adjusting for age and *** volumes were reduced by 11%(p=0.001)and putamen volumes by 8.1%(p=0.025).PD striatal volumes were not found to be significantly correlated with cognitive or motor ***:Small,but significant reductions in the volume of both the caudate and putamen occur in PD *** reductions are independent of the effects of age and gender,however the relation of these reductions to the functional loss of dopamine,which is characteristic of PD,remains unclear.
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