Predictive value of pulmonary function testing in the evaluation of pulmonary hypertension in sarcoidosis

Background In sarcoidosis patients, pulmonary hypertension (PH) is associated with significant morbidity and mortality. Early identification of sarcoidosis-associated pulmonary hypertension (SAPH) has substantial clinical implications. While a number of pulmonary function testing (PFT) variables have been associated with SAPH, the optimal use of PFT’s in screening for SAPH is unknown. Objectives To examine the predictive value of PFT’s for echocardiographic PH in a cohort of sarcoidosis patients. Methods We conducted a retrospective cohort study of patients with sarcoidosis from a single center over a period of five years. All consecutive adult patients with a diagnosis of biopsy-proven sarcoidosis (determined by review of the medical chart) who underwent PFT and echocardiographic testing were included. Echocardiographic risk of PH (either intermediate or high) was determined by the presence of echocardiographic PH signs and tricuspid regurgitant jet velocity. Data analysis was performed using multivariate logistic regression analysis with least absolute shrinkage and selection operator. Results Of the 156 patients included in the study, 42 (27%) met the criteria for echocardiographic PH. Roughly equal proportions met the criteria for intermediate risk (45%) as did for high risk of PH (55%). The percent predicted of diffusion capacity for carbon monoxide (%DLCO) and forced vital capacity (%FVC) were predictive of echocardiographic PH. No other PFT variables outperformed these two markers, and the incorporation of additional PFT variables failed to significantly enhance the model. Conclusions The %FVC and %DLCO emerged as being predictive of echocardiographic PH in this cohort of biopsy-proven sarcoidosis patients. Potentially reflecting the multifactorial pathogenesis of PH in sarcoidosis, incorporation of other PFT variables failed to enhance screening for PH in this population

Phycocyanin: One Complex, Two States, Two Functions

Solar energy captured by pigments embedded in light-harvesting complexes can be transferred to neighboring pigments, dissipated, or emitted as fluorescence. Only when it reaches a reaction center is the excitation energy stabilized in the form of a charge separation and converted into chemical energy. Well-directed and regulated energy transfer within the network of pigments is therefore of crucial importance for the success of the photosynthetic processes. Using single-molecule spectroscopy, we show that phycocyanin can dynamically switch between two spectrally distinct states originating from two different conformations. Unexpectedly, one of the two states has a red-shifted emission spectrum. This state is not involved in energy dissipation; instead, we propose that it is involved in direct energy transfer to photosystem I. Finally, our findings suggest that the function of linker proteins in phycobilisomes is to stabilize one state or the other, thus controlling the light-harvesting functions of phycocyanin

Development of potentiometric ion sensors based on insertion materials as sensitive element

We have demonstrated the feasibility of developing stable Li+ potentiometric sensors, using a composite plastic technology as electrode support. Both triphylite LiFePO4- and FePO4-based sensors display good Li+ sensing properties (reversibility, stability, linearity in the serum Li+ concentration range). Besides, the reversible insertion of various cations (Na+, K+, Mg2+) into the FePO4 host structure was unraveled, providing the necessary information to clearly demonstrate that, within these materials, the sensing mechanism is nested in the ability of the structure to undergo cation insertion/deinsertion reactions. This process was shown to be governed by the Nernst's law. To our knowledge, besides the LiMn2O4/MnO2 spinel-type system, the LiFePO4/FePO4 constitutes the second example of a sensor based on this mechanism. © 2003 Elsevier Science B.V. All rights reserved

Switching an Individual Phycobilisome Off and On

Photosynthetic organisms have found various smart ways to cope with unexpected changes in light conditions. In many cyanobacteria, the lethal effects of a sudden increase in light intensity are mitigated mainly by the interaction between phycobilisomes (PBs) and the orange carotenoid protein (OCP). The latter senses high light intensities by means of photoactivation and triggers thermal energy dissipation from the PBs. Due to the brightness of their emission, PBs can be characterized at the level of individual complexes. Here, energy dissipation from individual PBs was reversibly switched on and off using only light and OCP. We reveal the presence of quasistable intermediate states during the binding and unbinding of OCP to PB, with a spectroscopic signature indicative of transient decoupling of some of the PB rods during docking of OCP. Real-time control of emission from individual PBs has the potential to contribute to the development of new super-resolution imaging techniques

Phycocyanin: One Complex, Two States, Two Functions

Solar energy captured by pigments embedded in light-harvesting complexes can be transferred to neighboring pigments, dissipated, or emitted as fluorescence. Only when it reaches a reaction center is the excitation energy stabilized in the form of a charge separation and converted into chemical energy. Well-directed and regulated energy transfer within the network of pigments is therefore of crucial importance for the success of the photosynthetic processes. Using single-molecule spectroscopy, we show that phycocyanin can dynamically switch between two spectrally distinct states originating from two different conformations. Unexpectedly, one of the two states has a red-shifted emission spectrum. This state is not involved in energy dissipation; instead, we propose that it is involved in direct energy transfer to photosystem I. Finally, our findings suggest that the function of linker proteins in phycobilisomes is to stabilize one state or the other, thus controlling the light-harvesting functions of phycocyanin

Resolving the contribution of the uncoupled phycobilisomes to cyanobacterial pulse-amplitude modulated (PAM) fluorometry signals.

International audiencePulse-amplitude modulated (PAM) fluorometry is extensively used to characterize photosynthetic organisms on the slow time-scale (1-1000 s). The saturation pulse method allows determination of the quantum yields of maximal (F(M)) and minimal fluorescence (F(0)), parameters related to the activity of the photosynthetic apparatus. Also, when the sample undergoes a certain light treatment during the measurement, the fluorescence quantum yields of the unquenched and the quenched states can be determined. In the case of cyanobacteria, however, the recorded fluorescence does not exclusively stem from the chlorophyll a in photosystem II (PSII). The phycobilins, the pigments of the cyanobacterial light-harvesting complexes, the phycobilisomes (PB), also contribute to the PAM signal, and therefore, F(0) and F(M) are no longer related to PSII only. We present a functional model that takes into account the presence of several fluorescent species whose concentrations can be resolved provided their fluorescence quantum yields are known. Data analysis of PAM measurements on in vivo cells of our model organism Synechocystis PCC6803 is discussed. Three different components are found necessary to fit the data: uncoupled PB (PB(free)), PB-PSII complexes, and free PSI. The free PSII contribution was negligible. The PB(free) contribution substantially increased in the mutants that lack the core terminal emitter subunits allophycocyanin D or allophycocyanin F. A positive correlation was found between the amount of PB(free) and the rate constants describing the binding of the activated orange carotenoid protein to PB, responsible for non-photochemical quenching