Hemoglobin is an oxygen-dependent glutathione buffer adapting the intracellular reduced glutathione levels to oxygen availability

Fast changes in environmental oxygen availability translate into shifts in mitochondrial free radical production. An increase in intraerythrocytic reduced glutathione (GSH) during deoxygenation would support the detoxification of exogenous oxidants released into the circulation from hypoxic peripheral tissues. Although reported, the mechanism behind this acute oxygen-dependent regulation of GSH in red blood cells remains unknown. This study explores the role of hemoglobin (Hb) in the oxygen-dependent modulation of GSH levels in red blood cells. We have demonstrated that a decrease in Hb O2 saturation to 50% or less observed in healthy humans while at high altitude, or in red blood cell suspensions results in rising of the intraerythrocytic GSH level that is proportional to the reduction in Hb O2 saturation. This effect was not caused by the stimulation of GSH de novo synthesis or its release during deglutathionylation of Hb's cysteines. Using isothermal titration calorimetry and in silico modeling, we observed the non-covalent binding of four molecules of GSH to oxy-Hb and the release of two of them upon deoxygenation. Localization of the GSH binding sites within the Hb molecule was identified. Oxygen-dependent binding of GSH to oxy-Hb and its release upon deoxygenation occurred reciprocally to the binding and release of 2,3-bisphosphoglycerate. Furthermore, noncovalent binding of GSH to Hb moderately increased Hb oxygen affinity. Taken together, our findings have identified an adaptive mechanism by which red blood cells may provide an advanced antioxidant defense to respond to oxidative challenges immediately upon deoxygenation

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Oxygenation state of hemoglobin defines dynamics of water molecules in its vicinity

This study focuses on assessing the possible impact of changes in hemoglobin (Hb) oxygenation on the state of water in its hydration shell as it contributes to red blood cell deformability. Microwave Dielectric Spectroscopy (MDS) was used to monitor the changes in interactions between water molecules and Hb, the number of water molecules in the protein hydration shell, and the dynamics of pre-protein water in response to the transition of Hb from the tense (T) to the relaxed (R) state, and vice versa. Measurements were performed for Hb solutions of different concentrations (5 g/dl-30 g/dl) in phosphate-buffered saline buffer. Cole-Cole parameters of the main water relaxation peak in terms of interactions of water molecules (dipole-dipole/ionic dipole) during the oxygenation-deoxygenation cycle were used to analyze the obtained data. The water mobility-represented by α as a function of ln τ-differed dramatically between the R (oxygenated) state and the T (deoxygenated) state of Hb at physiologically relevant concentrations (30 g/dl-35 g/dl or 4.5 mM-5.5 mM). At these concentrations, oxygenated hemoglobin was characterized by substantially lower mobility of water in the hydration shell, measured as an increase in relaxation time, compared to deoxyhemoglobin. This change indicated an increase in red blood cell cytosolic viscosity when cells were oxygenated and a decrease in viscosity upon deoxygenation. Information provided by MDS on the intraerythrocytic water state of intact red blood cells reflects its interaction with all of the cytosolic components, making these measurements powerful predictors of the changes in the rheological properties of red blood cells, regardless of the cause

Donor age and red cell age contribute to the variance in lorrca indices in healthy donors for next generation ektacytometry: a pilot study

The ability of red blood cells (RBCs) to transport gases, their lifespan as well as their rheological properties invariably depend on the deformability, hydration, and membrane stability of these cells, which can be measured by Laser optical rotational red cell analyser (Lorrca® Maxsis, RR Mechatronics). The osmoscan mode of Lorrca is currently used in diagnosis of rare anemias in clinical laboratories. However, a broad range of normal values for healthy subjects reduces the sensitivity of this method for diagnosis of mild disease phenotype. In this pilot study, we explored the impact of age and gender of 45 healthy donors, as well as RBC age on the Lorrca indices. Whereas gender did not affect the Lorrca indices in our study, the age donors had a profound effect on the O_hyper parameter. To study the impact of RBC age on the osmoscan parameters, we have isolated low (L)-, medium (M)-, or high (H)- density fractions enriched with young, mature, and senescent RBCs, respectively, and evaluated the influence of RBC age-related properties, such as density, morphology, and redox state, on the osmoscan indices. As before, O_hyper was the most sensitive parameter, dropping markedly with an increase in RBC density and age. Senescence was associated with a decrease in deformability (EI_max) and tolerability to low and high osmolatites (Area). L-fraction was enriched with reticulocytes and cells with high projected area and EMA staining, but also contained a small number of cells small in projected area and most likely, terminally senescent. L-fraction was on average slightly less deformable than mature cells. The cells from the L-fraction produced more oxidants and NO than all other fractions. However, RBCs from the L-fraction contained maximal levels of reduced thiols compared to other fractions. Our study suggests that reference values for O_hyper should be age-stratified, and, most probably, corrected for the average RBC age. Further multi-center study is required to validate these suggestions before implementing them into clinical practice

Differences in selected blood parameters between brachycephalic and non-brachycephalic dogs

IntroductionCranial and upper-airway anatomy of short-nosed, flat-faced brachycephalic dogs predisposes them to brachycephalic obstructive airway syndrome (BOAS). Periodic apnoea increased inspiratory resistance, and an inability to thermoregulate effectively are characteristic of BOAS, but internationally accepted objective markers of BOAS severity are missing. The objective of this study was to compare the selected blood parameters between non-brachycephalic (NC) and brachycephalic (BC) dogs, exploring the possibility of developing a blood test for BOAS severity grading in the future.MethodsWe evaluated blood biochemistry, complete blood cell counts, red blood cell (RBC) indices, reticulocyte counts, a blood-born marker of intermittent hypoxia (glutathione, NO production), RBC hydration, deformability, and blood markers of metabolic changes and stress between BC (n = 18) and NC (meso- and dolichocephalic, n = 22) dogs.ResultsReticulocyte counts and the abundance of middle-fluorescence immature reticulocytes were significantly (p < 0.05) higher in BC dogs compared to NC dogs. BC dogs had significantly more NO-derived NO2-/NO3- in plasma than NC dogs. RBCs of BC dogs were shedding significantly more membrane, as follows from the intensity of eosin maleimide staining, and had a significantly higher mean corpuscular hemoglobin concentration than NC dogs. Intracellular reduced glutathione content in RBCs of BC dogs was significantly lower, while plasma lactate was significantly higher in BC dogs compared to NC dogs. Plasma cholesterol and triglycerides were significantly lower, and cortisol was significantly higher in BC dogs compared to NC dogs. Eosinophil counts were significantly lower and the neutrophil-to-lymphocyte ratio was higher in BC dogs compared to NC dogs.DiscussionTaken together, our findings suggest that the brachycephalic phenotype in dogs is associated with alterations at the level of blood cells and, systemically, with oxidation and metabolic changes. The parameters identified within this study should be further investigated for their potential as objective indicators for BOAS

New Liquid Fraction Measurement Methodology for Phase Change Material Analysis Based on X-Ray Computed Tomography

To tackle the climate change, it is of fundamental importance to develop more efficient systems to convert and manage the energy. Latent Thermal Energy Storage systems (LTESs), which are based on Phase Change Materials (PCMs) present many interesting features that can lead us to achieve energy sustainability. In fact, these systems can be employed in many applications (e.g., HVAC, buildings thermal management, thermal energy recovery). To use those materials, it is crucial to understand and monitor their phase-change behaviour. However, the evaluation of two-phase systems is still difficult because of their intrinsic complexity and transient behaviour.In the present study, a new methodology to measure liquid fraction is proposed. It is based on X-ray Computed Tomography (XCT), which is used to follow the solidification process of eicosane. The XCT and acquisition settings were optimised to ensure the maximum contrast between the phases. Then, the solidification process of eicosane was dynamically studied and the volumetric liquid fraction extracted. Finally, via Ansys Fluent software, a CFD model, based on the enthalpy-porosity method, was developed to simulate the solidification of eicosane. The numerical results were compared against the experimental data, showing excellent agreement. This novel experimental methodology opens new possibilities to characterize and understand the solid-liquid phase transition process of PCMs, by directly observing and quantifying the solid/liquid phase evolution in time, the volumetric shrinkage, the presence/formation of voids and the different phases which might occur during the phase-change process.+ ID der Publikation: hslu_96778 + Art des Beitrages: Wissenschaftliche Medien + Sprache: Englisch + Letzte Aktualisierung: 2023-09-27 15:12:5