PV/Wind Hybrid Energy System, Modeling and Simulation at variable weather conditions

This paper presents a modeling and simulation of a grid-connected wind / PV hybrid power system under variable weather conditions. This system includes a wind turbine system, a PV system that shares a DC bus, and no battery. The paper contains an overview of the hybrid system and some previous studies; it presents a brief overview of each component used for this system. Signal distortion remains the great obstacle when connecting to the grid, so the system architecture and its proposed control are also introduced to reduce the distortion of electrical signals to an acceptable value. A simulation of the system’s operation with specific weather conditions in three different modes was performed using the MATLAB Simulink to describe the effect of these weather conditions on the production of electrical energy. Simulation results show how these weather conditions affect the operation of this hybrid system. An acceptable distortion value of the produced current signals has also been reached. These results present an evaluation of the dynamic performance of this system under the proposed working conditions. It also shows the energy exchange with the grid

Etude des gènes nucléaires dans quatre cas de déficits en complexe III de la chaîne respiratoire

PARIS-BIUP (751062107) / SudocSudocFranceF

Role of Sex Hormones on Brain Mitochondrial Function, with Special Reference to Aging and Neurodegenerative Diseases

The mitochondria have a fundamental role in both cellular energy supply and oxidative stress regulation and are target of the effects of sex steroids, particularly the neuroprotective ones. Aging is associated with a decline in the levels of different steroid hormones, and this decrease may underline some neural dysfunctions. Besides, modifications in mitochondrial functions associated with aging processes are also well documented. In this review, we will discuss studies that describe the modifications of brain mitochondrial function and of steroid levels associated with physiological aging and with neurodegenerative diseases. A special emphasis will be placed on describing and discussing our recent findings concerning the concomitant study of mitochondrial function (oxidative phosphorylation, oxidative stress) and brain steroid levels in both young (3-month-old) and aged (20-month-old) male and female mice

Steroids in Stroke with Special Reference to Progesterone

International audienceBoth sex and steroid hormones are important to consider in human ischemic stroke and its experimental models. Stroke initiates a cascade of changes that lead to neural cell death, but also activates endogenous protective processes that counter the deleterious consequences of ischemia. Steroids may be part of these cerebroprotective processes. One option to provide cerebroprotection is to reinforce these intrinsic protective mechanisms. In the current review, we first summarize studies describing sex differences and the influence of steroid hormones in stroke. We then present and discuss our recent results concerning differential changes in endogenous steroid levels in the brains of male and female mice and the importance of progesterone receptors (PR) during the early phase after stroke. In the third part, we give an overview of experimental studies, including ours, that provide evidence for the pleiotropic beneficial effects of progesterone and its promising cerebroprotective potential in stroke. We also highlight the key role of PR signaling as well as potential additional mechanisms by which progesterone may provide cerebroprotection

Mutation in the AGK gene in two siblings with unusual Sengers syndrome

International audienc

Association of the CAG repeat polymorphism in mitochondrial polymerase gamma (POLG1) with male infertility: A case-control study in an Algerian population

Polymorphisms in the mitochondrial DNA polymerase gamma (POLG) have been speculated to be associated with male infertility. The main objective of our study was to assess the possible association of CAG repeat polymorphism in POLG1 gene and male infertility in Algerian population. Genomic DNA from 89 infertile men and 84 controls was extracted using salting-out method. CAG repeat polymorphism was analyzed by the automated direct sequencing protocol. Statistical analysis was performed by Epi-info® (v6.0) software. A significant association with male infertility was found for CAG repeat polymorphism in heterozygous genotypes (10/ ≠ 10 vs 10/10: OR = 2.00 [0.99 - 4.05], p = 0.03; “infertile vs control groups”; 10/≠10 vs 10/10: OR = 3.75 [1.20- 11.96], p=0.01 “oligoasthenoteratospermic group”). Also, the results showed a significant association between the morbid allele (≠10) and male infertility (2.07 [01.07 - 04.02], p = 0.01). Our results showed that POLG1 CAG repeat polymorphism might be a risk factor for male infertility in Algerian population. Investigations with larger sample sizes and representative population-based cases and matched controls are needed to validate our results. Les polymorphismes de l'ADN polymérase gamma mitochondriale (POLG) ont été supposés être associés à l'infertilité masculine. L'objectif principal de notre étude était d'évaluer l'association possible du polymorphisme de répétition CAG dans le gène POLG1 et l'infertilité masculine dans la population algérienne. L'ADN génomique de 89 hommes stériles et 84 témoins a été extrait en utilisant la méthode de salting-out. Le polymorphisme de répétition CAG a été analysé par le protocole de séquençage direct automatisé. L'analyse statistique a été réalisée par le logiciel Epi-info® (v6.0). Une association significative avec l'infertilité masculine a été trouvée pour le polymorphisme de répétition CAG dans les génotypes hétérozygotes (10 / ≠ 10 vs 10/10: OR = 2,00 [0,99 -4,05], p = 0,03; «infertiles vs groupes témoins»; 10 / ≠ 10 vs 10/10: OR = 3,75 [1,20-11,96], p = 0,01 «groupe oligoasthénotératospermique»). De plus, les résultats ont montré une association significative entre l'allèle morbide (≠ 10) et l'infertilité masculine (2,07 [1.07-4.02], p = 0.01). Nos résultats ont montré que le polymorphisme répété de POLG1 CAG pourrait être un facteur de risque d'infertilité masculine dans la population algérienne. Des enquêtes avec des échantillons de plus grande taille et des cas représentatifs basés sur la population et des témois appariés sont nécessaires pour valider nos résultats

Intranasal administration of progesterone: A potential efficient route of delivery for cerebroprotection after acute brain injuries

International audienceProgesterone has been shown to be cerebroprotective in different experimental models of brain injuries and neurodegenerative diseases. The preclinical data provided great hope for its use in humans. The failure of Phase 3 clinical trials to demonstrate the cerebroprotective efficiency of progesterone in traumatic brain injury (TBI) patients emphasizes that different aspects of the design of both experimental and clinical studies should be reviewed and refined. One important aspect to consider is to test different routes of delivery of therapeutic agents. Several studies have shown that the intranasal delivery of drugs could be used in different experimental models of central nervous system diseases. In this review, we will summarize the pharmacokinetic characteristics and practical advantages of intranasal delivery of progesterone. A special emphasis will be placed on describing and discussing our recent findings showing that intranasal delivery of progesterone after transient focal cerebral ischemia: 1) improved motor functions; 2) reduced infarct volume, neuronal loss, blood brain barrier disruption; and 3) reduced brain mitochondrial dysfunctions. Our data suggest that intranasal delivery of progesterone is a potential efficient, safe and non-stressful mode of administration that warrants evaluation for cerebroprotection in patients with brain injuries. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury"

Defects in maintenance of mitochondrial DNA are associated with intramitochondrial nucleotide imbalances

Defects in mtDNA maintenance range from fatal multisystem childhood diseases, such as Alpers syndrome, to milder diseases in adults, including mtDNA depletion syndromes (MDS) and familial progressive external ophthalmoplegia (adPEO). Most are associated with defects in genes involved in mitochondrial deoxynucleotide metabolism or utilization, such as mutations in thymidine kinase 2 (TK2) as well as the mtDNA replicative helicase, Twinkle and gamma polymerase (POLG). We have developed an in vitro system to measure incorporation of radiolabelled dNTPs into mitochondria of saponin permeabilized cells. We used this to compare the rates of mtDNA synthesis in cells from 12 patients with diseases of mtDNA maintenance. We observed reduced incorporation of exogenous α 32P-dTTP in fibroblasts from a patient with Alpers syndrome associated with the A467T substitution in POLG, a patient with dGK mutations, and a patient with mtDNA depletion of unknown origin compared to controls. However, incorporation of α 32P-dTTP relative to either cell doubling time or α 32P-dCTP incorporation was increased in patients with thymidine kinase deficiency of PEO as the result of TWINKLE mutations compared with controls. The specific activity of newly synthesized mtDNA depends on the size of the endogenous pool diluting the exogenous labelled nucleotide. Our result is consistent with a deficiency in the intramitochondrial pool of dTTP relative to dCTP in cells from patients with TK2 deficiency and TWINKLE mutations. Such DNA precursor asymmetry could cause pausing of the replication complex and hence exacerbate the propensity for age-related mtDNA mutations. Because deviations from the normal concentrations of dNTPs are known to be mutagenic, we suggest that intramitochondrial nucleotide imbalance could underlie the multiple mtDNA mutations observed in these patients

Resveratrol attenuates oxidative stress in mitochondrial Complex I deficiency: Involvement of SIRT3

International audienceThe pathophysiological mechanisms underlying Complex I (CI) deficiencies are understood only partially which severely limits the treatment of this common, devastating, mitochondrial disorder. Recently, we have shown that resveratrol (RSV), a natural polyphenol, has beneficial effects on CI deficiency of nuclear origin. Here, we demonstrate that RSV is able to correct the biochemical defect in oxygen consumption in five of thirteen CI-deficient patient cell lines. Other beneficial effects of RSV include a decrease of total intracellular ROS and the up-regulation of the expression of mitochondrial superoxide dismutase (SOD2) protein, a key antioxidant defense enzyme. The molecular mechanisms leading to the up-regulation of SOD2 protein expression by RSV require the estrogen receptor (ER) and the estrogen-related receptor alpha (ERRα). Although RSV increases the level of SOD2 protein in patients' fibroblasts, the enzyme activity is not increased, in contrast to normal fibroblasts. This led us to hypothesize that SOD2 enzyme activity is regulated post-translationally. This regulation involves SIRT3, a mitochondrial NAD þ-dependent deacetylase and is critically dependent on NAD þ levels. Taken together, our data show that the metabolic effects of RSV combined with its antioxidant capacities makes RSV particularly interesting as a candidate molecule for the therapy of CI deficiencies

Respiratory Chain Defects May Present Only with Hypoglycemia

International audienceHypoglycemia occasionally results from oxidative phosphorylation deficiency, associated with liver failure. Conversely, in some cases of respiratory chain defect, the impairment in glucose metabolism occurs with normal hepatic function. The mechanism for this hypoglycemia remains poorly understood. We report here three unrelated children with hypoglycemia as the presenting symptom associated with oxidative phosphorylation deficiency but without liver dysfunction. Two patients had, respectively, complex III and complex IV deficiency and presented with long fast hypoglycemia. During a fasting test, the first patient showed evidence for impaired gluconeogenesis (progressive increase of plasma lactate and no decrease of alanine levels), whereas the second patient appeared to have impaired fatty acid oxidation (hypoketotic hypoglycemia with increased levels of non esterified fatty acids). The third patient presented with both long and short fast hypoglycemia related to complex IV deficiency. The mechanism of hypoglycemia for this patient may have been partly related to GH insufficiency, whereas impaired glycogen metabolism possibly accounted for short fast hypoglycemia. We suggest that hypoglycemia can be the presenting symptom for respiratory chain defects, through the possible reduction in cofactors resulting from oxidative phosphorylation deficiency, and that respiratory chain defects should therefore be considered in the differential diagnosis of hypoglycemia