Cardiac responses to hypoxia: the role of pyruvate dehydrogenase complex in carbohydrate utilisation

Accelerated carbohydrate utilisation and suppressed lipid oxidative metabolism are hallmarks of heart failure (HF). Hypoxia mimics failing heart metabolic reprogramming and has been suggested to play a role in cardiac metabolic switch. One aspect of the regulation of cardiac energy metabolism is the pyruvate dehydrogenase complex (PDC). Hypoxia inducible factor (HIF) signalling is thought regulate hypoxia-induced adaptations. HIF transcriptional activity is controlled by prolyl hydroxylase domain (PHD) protein and factor inhibiting HIF (FIH-1). In chapter 3 revealed that relative to baseline, acute hypoxia increased cardiac lactate efflux and suppressed fatty acid oxidation (FAO) rates in non-treated isolated mouse hearts with final cardiac recovery being 63% of baseline values. Hypoxic and post-hypoxic PDC activation, via dichloroacetate (DCA), decreased cardiac lactate release and FAO during reoxygenation, but failed to improve cardiac recovery relative to control hearts. Chapter 4 sought to establish how chronic hypoxia (11%) upregulates cardiac glycolytic flux, determined via 3H-glucose. Findings of this chapter indicate that of four enzymes considered to set the pace of glycolysis, upregulated pyruvate kinase (PK) flux, appears to explain accelerated hypoxia-induced cardiac glycolytic flux. Western blotting analysis revealed increased PK M2 protein isoform. Sustained hypoxia increased pentose phosphate pathway (PPP) flux, but left lactate accumulation unaltered. Chapter 5 examined the role of sustained in vivo hypoxia in modulating cardiac tolerance to subsequent acute H/R injury and chronic PDC activation in modifying hypoxic heart tolerance to acute injury. Chronic hypoxia reduced cardiac tolerance to H/R injury accompanied by increased glycolytic flux and lactate efflux during reoxygenation injury. Chronic PDC activation improved hypoxic heart tolerance to the acute injury and normalized cardiac metabolic flux and reduced tissue lactate accumulation during reoxygenation, indicative of increased carbohydrate oxidation. Collectively, the data appear to imply that forced carbohydrate oxidation normalizes hypoxic heart recovery from acute injury. In chapter 6 we demonstrated that global FIH-1 deletion increased isolated heart glycolytic flux at baseline and during reoxygenated. FIH-1 KO hearts displayed increased reoxygenated hexokinase (HK) and PK activities, but no changes in PK protein isoforms. Functional analysis revealed that FIH-1 deficiency does not affect isolated heart function at baseline and in response to acute injury. Acute PDC activation does not appear to improve cardiac function during acute hypoxic stress. Conversely, chronic PDC activation normalized, via restored metabolic flux, cardiac tolerance to acute injury following sustained in vivo hypoxia. Furthermore, the present thesis revealed increased PPP flux following sustained in vivo hypoxia, and proposed a pivotal role PKM2 may play in the regulation of hypoxic heart carbohydrate metabolism. In addition, we identified FIH-1 as a novel regulator of cardiac carbohydrate metabolism at baseline and following acute hypoxic injury

Disk emission and atmospheric absorption lines in black hole candidate 4U 1630-472

We re-analyzed SUZAKU data of the black hole candidate 4U 1630-472 being in the high/soft state. We show that the continuum X-ray spectrum of 4U 1630-472 with iron absorption lines can be satisfactorily modeled by the spectrum from an accretion disk atmosphere. Absorption lines of highly ionized iron originating in hot accretion disk atmosphere can be an alternative or complementary explanation to the wind model usually favored for these type of sources. We model continuum and line spectra using a single model. Absorption lines of highly ionized iron can origin in upper parts of the disk atmosphere which is intrinsically hot due to high disk temperature. Iron line profiles computed with natural, thermal and pressure broadenings match very well observations. We showed that the accretion disk atmosphere can effectively produce iron absorption lines observed in 4U 1630-472 spectrum. Absorption line arising in accretion disk atmosphere is the important part of the observed line profile, even if there are also other mechanisms responsible for the absorption features. Nevertheless, the wind theory can be an artifact of the fitting procedure, when the continuum and lines are fitted as separate model components.Comment: 10 pages, 4 figures, accepted by Astronomy and Astrophysic

Influence of CMV/EBV Serostatus on Respiratory Infection Incidence During 4 Months of Winter Training in a Student Cohort of Endurance Athletes

The purpose of this study was to examine the influence of previous infection with cytomegalovirus (CMV) or Epstein Barr virus (EBV) on the incidence, severity and duration of upper respiratory tract illness (URTI) episodes in endurance athletes during a 4-month winter training period. Blood samples were obtained from 236 healthy subjects (186 males, 70 females) who were engaged in regular sports training (predominantly endurance-based activities such as running, cycling, swimming, triathlon, team games and racquet sports) at the start of the study period for CMV and EBV serostatus analysis. Their baseline characteristics were (mean ± SD) age: 21 ± 2 years, body mass: 73.5 ± 11.2 kg, height: 176.5 ± 9.3 cm, body mass index 23.6 ± 2.2 kg/m2. Weekly training and daily illness logs were kept. Self-reported weekly training duration averaged 9.6 ± 5.2 h/week and 4.0 ± 1.6% of the cohort experienced a URTI episode each week. Twenty-five percent of the subject cohort were CMV positive with a similar proportion in males (24%) and females (26%) whereas 84% of the subject cohort were EBV positive with a similar proportion in males (84%) and females (83%). In addition, 21% of the subject cohort were both CMV and EBV positive (CMV+EBV+) whereas 13% of the subject cohort had no prior CMV or EBV infection (CMV-EBV-). With regard to CMV/EBV serostatus, the results indicated that there was no difference in the proportion of subjects who presented with symptoms of infection between CMV/EBV positive and negative groups. Athletes with previous CMV infection had fewer URTI symptom days during the study period than those with no previous infection [mean and interquartile range (IQR), positives 2 (0-7) days, negatives 4 (1-9) days, P = 0.033] and EBV serostatus had no influence on URTI episode incidence, severity or duration. Moreover, we found that athletes with prior infection of both CMV and EBV had fewer URTI episodes and symptom days than athletes who were seronegative for both CMV and EBV [mean (IQR), URTI episodes: positives 0 (0-1), negatives 1 (0-2), P = 0.04; symptom days: positives 2 (0-7), negatives 8 (2-12), P = 0.01]. The reasons for this are still unclear but could be related to the previously reported elevated T cytotoxic cell response to exercise in individuals with positive CMV serostatus. Previous coinfection with CMV and EBV might promote protective immune surveillance to lower the risk of URTI

The Architecture And Dynamics Of Gene Regulatory Networks Directing Cell-Fate Choice During Murine Hematopoiesis

Mammals produce hundreds of billions of new blood cells every day througha process known as hematopoiesis. Hematopoiesis starts with stem cells that develop into all the different types of cells found in blood by changing their genome-wide gene expression. The remodeling of genome-wide gene expression can be primarily attributed to a special class of proteins called transcription factors (TFs) that can activate or repress other genes, including genes encoding TFs. TFs and their targets therefore form recurrent networks called gene regulatory networks (GRNs). GRNs are crucial during physiological developmental processes, such as hematopoiesis, while abnormalities in the regulatory interactions of GRNs can be detrimental to the organisms. To this day we do not know all the key compo-nents that comprise hematopoietic GRNs or the complete set of their regulatory interactions. Inference of GRNs directly from genetic experiments is low throughput and labor intensive, while computational inference of comprehensive GRNs is challenging due to high processing times. This dissertation focuses on deriving the architecture and the dynamics of hematopoietic GRNs from genome-wide gene expression data obtained from high-resolution time-series experiments. The dissertation also aims to address the technical challenge of speeding up the process of GRN inference. Here GRNs are inferred and modeled using gene circuits, a data-driven method based on Ordinary Differential Equations (ODEs). In gene circuits, the rate of change of a gene product depends on regulatory influences from other genes encoded as a set of parameters that are inferred from time-series data. A twelve-gene GRN comprising genes encoding key TFs and cytokine receptors involved in erythrocyte-neutrophil differentiation was inferred from a high-resolution time-series dataset of the in vitro differentiation of a multipotential cell line. The inferred GRN architecture agreed with prior empirical evidence and pre- dicted novel regulatory interactions. The inferred GRN model was also able to predict the outcome of perturbation experiments, suggesting an accurate inference of GRN architecture. The dynamics of the inferred GRN suggested an alternative explanation to the currently accepted sequence of regulatory events during neutrophil differentiation. The analysis of the model implied that two TFs, C/EBPα and Gfi1, initiate cell-fate choice in the neutrophil lineage, while PU.1, believed to be a master regulator of all white-blood cells, is activated only later. This inference was confirmed in a single-cell RNA-Seq dataset from mouse bone marrow, in which PU.1 upregulation was preceded by C/EBPα and Gfi1 upregulation. This dissertation also presents an analysis of a high-temporal resolution genome-wide gene expression dataset of in vitro macrophage-neutrophil differentiation. Analysis of these data reveal that genome-wide gene expression during differentiation is highly dynamic and complex. A large-scale transition is observed around 8h and shown to be related to wide-spread physiological remodeling of the cells. The genes associated by myeloid differentiation mainly change during the first 4 hours, implying that the cell-fate decision takes place in the first four hours of differentiation. The dissertation also presents a new classification-based model-training technique that addresses the challenge of the high computational cost of inferring GRNs. This method, called Fast Inference of Gene Regulation (FIGR), is demonstrated to be two orders magnitude faster than global non-linear optimization techniques and its computational complexity scales much better with GRN size. This work has demonstrated the feasibility of simulating relatively large realistic GRNs using a dynamical and mechanistically accurate model coupled to high-resolution time series data and that such models can yield novel biological insight. Taken together with the macrophage-neutrophil dataset and the computationally efficient GRN inference methodology, this work should open up new avenues for modeling more comprehensive GRNs in hematopoiesis and the broader field of developmental biology

Imidazolidine-4-one derivatives in the search for novel chemosensitizers of Staphylococcus aureus MRSA : synthesis, biological evaluation and molecular modeling studies

A series of amine derivatives of 5-aromatic imidazolidine-4-ones (7–19), representing three subgroups: piperazine derivatives of 5-arylideneimidazolones (7–13), piperazine derivatives of 5-arylideneimidazolidine-2,4-dione (14–16) and primary amines of 5-naphthyl-5-methylimidazolidine-2,4-diones (17–19), was evaluated for their ability to improve antibiotics effectiveness in two strains of Gram-positive Staphylococcus aureus: ATCC 25923 (a reference strain) and MRSA (methicillin resistant S. aureus) HEMSA 5 (a resistant clinical isolate). The latter compounds (17–19) were obtained by 4-step synthesis using Bucherer-Bergs condensation, two-phase bromoalkylation and Gabriel reactions. The naphthalen derivative: (Z)-5-(naphthalen-2-ylmethylene)-2-(piperazin-1-yl)-3H-imidazol-4(5H)-one (10) was the most potent in combination with β-lactam antibiotics and ciprofloxacin against the resistant strain. The high potency to increase efficacy of oxacillin was noted for (Z)-5-(anthracen-10-ylmethylene)-2-(piperazin-1-yl)-3H-imidazol-4(5H)one (12) too. In order to explain the mechanism of action of the compounds 10 and 12, docking studies with the use of crystal structures of a penicillin binding protein (PBP2a) and MecR1 were carried out. Their outcomes suggested that the most probable mechanism of action of the active compounds is the interaction with MecR1. Molecular dynamic experiments performed for the active compounds and compound 13 (structurally similar to 12) supported this hypothesis and provided possible explanation of activity dependencies of the tested compounds in terms of the restoration of antibiotic efficacy in S. aureus MRSA HEMSA 5

How to make a better magnet? Insertion of additional bridging ligands into a magnetic coordination polymer

A three-dimensional cyanide-bridged coordination polymer based on FeII (S = 2) and NbIV (S = 1/2) {[FeII(H2O)2]2[NbIV(CN)8]·4H2O}n (Fe2Nb) was modified at the self-assembly stage by inserting an additional formate HCOO− bridge into its cyanide framework. The resulting mixed-bridged {(NH4)[(H2O)FeII-(μ-HCOO)-FeII(H2O)][NbIV(CN)8]·3H2O}n (Fe2NbHCOO) exhibited additional FeII-HCOO-FeII structural motifs connecting each of the two FeII centers. The insertion of HCOO− was possible due to the substitution of some of the aqua ligands and crystallization water molecules in the parent framework by formate anions and ammonium cations. The formate molecular bridge not only shortened the distance between FeII ions in Fe2NbHCOO from 6.609 Å to 6.141 Å, but also created additional magnetic interaction pathways between the magnetic centers, resulting in an increase in the long range magnetic ordering temperature from 43 K for Fe2Nb to 58 K. The mixed-bridged Fe2NbHCOO also showed a much broader magnetic hysteresis loop of 0.102 T, compared to 0.013 T for Fe2Nb

Enhancement of pure titanium localized corrosion resistance by anodic oxidation

The corrosion behavior of commercially pure titanium (UNS R50400) was investigated in presence of aggressive, bromides containing, species; reported to cause severer localized corrosion compared to chlorides. To enhance localized corrosion resistance of the metal, several surface treatments were performed. Samples anodized at potentials between 10 V and 200 V were characterized in term of oxide thickness and morphology and tested with potentiodynamic analyses in NH4Br. This treatment was found to greatly enhance corrosion resistance of titanium but it suffers localized removal of the oxide due to wrong handling of the part before their installation. For this reason, another treatment, suitable for in-situ surface recovering was developed through chemical oxidation in NaOH 10 M

The underexplored field of lanthanide complexes with helicene ligands : towards chiral lanthanide single molecule magnets

The effective combination of chirality and magnetism in a single crystalline material can lead to fascinating cross-effects, such as magneto-chiral dichroism. Among a large variety of chiral ligands utilized in the design and synthesis of chiral magnetic materials, helicenes seem to be the most appealing ones, due to the exceptionally high specific rotation values that reach thousands of deg·cm3·g−1·dm−1, which is two orders of magnitude higher than for compounds with chiral carbon atoms. Despite the sizeable family of transition metal complexes with helicene-type ligands, there are only a few examples of such complexes with lanthanide ions. In this mini-review, we describe the most recent developments in the field of lanthanide-based complexes with helicene-type ligands and summarize insights regarding the further exploration of this family of compounds towards multifunctional chiral lanthanide single molecule magnets (Ln-SMMs)