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71.
The photosynthetic response of trees to rising CO2 concentrations largely depends on source-sink relations, in addition to differences in responsiveness by species, genotype, and functional group. Previous studies on elevated CO2 responses in trees have either doubled the gas concentration (>700 μmol mol−1) or used single large addition of CO2 (500-600 μmol mol−1). In this study, Gmelina arborea, a fast growing tropical deciduous tree species, was selected to determine the photosynthetic efficiency, growth response and overall source-sink relations under near elevated atmospheric CO2 concentration (460 μmol mol−1). Net photosynthetic rate of Gmelina was ∼30% higher in plants grown in elevated CO2 compared with ambient CO2-grown plants. The elevated CO2 concentration also had significant effect on photochemical and biochemical capacities evidenced by changes in FV/FM, ABS/CSm, ET0/CSm and RuBPcase activity. The study also revealed that elevated CO2 conditions significantly increased absolute growth rate, above ground biomass and carbon sequestration potential in Gmelina which sequestered ∼2100 g tree−1 carbon after 120 days of treatment when compared to ambient CO2-grown plants. Our data indicate that young Gmelina could accumulate significant biomass and escape acclimatory down-regulation of photosynthesis due to high source-sink capacity even with an increase of 100 μmol mol−1 CO2. 相似文献
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The present study was undertaken to characterize leaf gas exchange physiology and photoacclimation characteristics in drought-stressed mulberry cultivar V1 (Morus indica L.) grown under the hot semi-arid steppe agroclimate of Southern India. The experiment was conducted in year 2009 during peak summer months (April–June). Mulberry plants, grown in short rotation coppice system, were subjected to two irrigation regimes: the control plot received a regulated full-rate irrigation (weekly 2–3 times) and the drought-stressed plot received a regulated deficit irrigation (irrigated only once in a fortnight). Net photosynthesis, transpiration, stomatal conductance, leaf water potential (ΨL) and photosytem-II (PS II) efficiency were examined. In spite of significant down-regulation in leaf gas exchange, the drought-stressed stands still exhibited a considerable rate of photosynthesis along with significant concomitant decrease in ΨL, more conspicuously during midday (12.00–13.00 h) depicting rather low stomatal control on ΨL, a behavior characterized as ‘anisohydric’. The PS II structural and functional integrity was well-maintained, even in the drought-stressed plants. However, apparent photoacclimatory changes were recorded in drought-exposed stands including decrease in electron transport and enhanced thermal dissipation from PS II. Overall, our data demonstrate some of the important driving leaf-level mechanisms adopted by mulberry cultivar V1 to tolerate drought stress and sustain photosynthesis. 相似文献
74.
Hadley KC Borrelli MJ Lepock JR McLaurin J Croul SE Guha A Chakrabartty A 《Cell stress & chaperones》2011,16(5):549-561
The inability of cells to maintain protein folding homeostasis is implicated in the development of neurodegenerative diseases,
malignant transformation, and aging. We find that multiphoton fluorescence imaging of 1-anilinonaphthalene-8-sulfonate (ANS)
can be used to assess cellular responses to protein misfolding stresses. ANS is relatively nontoxic and enters live cells
and cells or tissues fixed in formalin. In an animal model of Alzheimer’s disease, ANS fluorescence imaging of brain tissue
sections reveals the binding of ANS to fibrillar deposits of amyloid peptide (Aβ) in amyloid plaques and in cerebrovascular
amyloid. ANS imaging also highlights non-amyloid deposits of glial fibrillary acidic protein in brain tumors. Cultured cells
under normal growth conditions possess a number of ANS-binding structures. High levels of ANS fluorescence are associated
with the endoplasmic reticulum (ER), Golgi, and lysosomes—regions of protein folding and degradation. Nuclei are virtually
devoid of ANS binding sites. Additional ANS binding is triggered by hyperthermia, thermal lesioning, proteasome inhibition,
and induction of ER stress. We also use multiphoton imaging of ANS binding to follow the in vivo recovery of cells from protein-damaging
insults over time. We find that ANS fluorescence tracks with the binding of the molecular chaperone Hsp70 in compartments
where Hsp70 is present. ANS highlights the sensitivity of specific cellular targets, including the nucleus and particularly
the nucleolus, to thermal stress and proteasome inhibition. Multiphoton imaging of ANS binding should be a useful probe for
monitoring protein misfolding stress in cells. 相似文献
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Xu Gao Avirup Guha Benjamin Buck Dilesh Patel Melissa J. Snider Michael Boyd Muhammad Afzal Auroa Badin Hemant Godara Zhenguo Liu Jaret Tyler Raul Weiss Steven Kalbfleisch John Hummel Ralph Augostini Mahmoud Houmsse Emile G. Daoud 《Indian pacing and electrophysiology journal》2018,18(2):68-72
Background
Expert opinion recommends performing exercise testing with initiation of Class Ic antiarrhythmic medication.Objective
To evaluate the rate and reason for discontinuation of Ic agent within the first year of follow up, with particular attention to rate of proarrhythmia and the value of routine treadmill testing.Methods
This is a single center retrospective cohort study including consecutive patients with atrial arrhythmias who were initiated on a Class Ic agent from 2011 to 2016. Data was collated from chart review and pharmacy database.Results
The study population included 300 patients (55% male, mean age 61; mean ejection fraction, 56%) started on flecainide (n = 153; 51%) and propafenone (n = 147; 49%). Drug initiation was completed while hospitalized on telemetry and the staff electrophysiologists directed dosing. There was one proarrhythmic event during initiation (0.3%). The primary reason for not being discharged on Ic agent was due to detection of proarrhythmia (n = 15) or ischemia (n = 1) with treadmill testing (5.3%). Exercise testing was the single significant variable to affect the decision to discontinue Ic drug, p < 0.0001 (95% CI: 1.89–6.08%). During follow up, the primary reason for discontinuation of Ic agent was lack of efficacy, 32%.Conclusions
With proper screening, initiation of Class Ic agent is associated with very low rate of proarrhythmia. Treadmill testing is of incremental value and should be completed in all patients after loading Class Ic antiarrhythmic. 相似文献80.
C A Hasselbacher E Rusinova E Waxman R Rusinova R A Kohanski W Lam A Guha J Du T C Lin I Polikarpov et al. 《Biophysical journal》1995,69(1):20-29
The local environments of the four tryptophan residues of the extracellular domain of human tissue factor (sTF) were assessed from difference absorption and fluorescence spectra. The difference spectra were derived by subtracting spectra from single Trp-to-Phe or Trp-to-Tyr replacement mutants from the corresponding spectrum of the wild-type protein. Each of the mutants was capable of enhancing the proteolytic activity of factor VIIa showing that the mutations did not introduce major structural changes, although the mutants were more susceptible to denaturation by guanidinium chloride. The difference spectra indicate that the Trp residues are buried to different extents within the protein matrix. This evaluation was compared with the x-ray crystal structure of sTF. There is excellent agreement between predictions from the difference spectra and the environments of the Trp residues observed in the x-ray crystal structure, demonstrating that difference absorption and particularly fluorescence spectra derived from functional single-Trp replacement mutants can be used to obtain information about the local environments of individual Trp residues in multi-tryptophan proteins. 相似文献