Egg activation events are regulated by the duration of a sustained [Ca2+]cyt signal in the mouse

AbstractAlthough the dynamics of oscillations of cytosolic Ca2+ concentration ([Ca2+]cyt) play important roles in early mammalian development, the impact of the duration when [Ca2+]cyt is elevated is not known. To determine the sensitivity of fertilization-associated responses [i.e., cortical granule exocytosis, resumption of the cell cycle, Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity, recruitment of maternal mRNAs] and developmental competence of the parthenotes to the duration of a [Ca2+]cyt transient, unfertilized mouse eggs were subjected to a prolonged [Ca2+]cyt change for 15, 25, or 50 min by means of repetitive Ca2+ electropermeabilization at 2-min intervals. The initiation and completion of fertilization-associated responses are correlated with the duration of time in which the [Ca2+]cyt is elevated, with the exception that autonomous CaMKII activity is down-regulated with prolonged elevated [Ca2+]cyt. Activated eggs from 25- or 50-min treatments readily develop to the blastocyst stage with no sign of apoptosis or necrosis and some implant. Ca2+ influx into unfertilized eggs causes neither Ca2+ release from intracellular stores nor rapid removal of cytosolic Ca2+. Thus, the total Ca2+ signal input appears to be an important regulatory parameter that ensures completion of fertilization-associated events and oocytes have a surprising degree of tolerance for a prolonged change in [Ca2+]cyt

Adult Body Weight Is Programmed by a Redox-Regulated and Energy-Dependent Process during the Pronuclear Stage in Mouse

In mammals fertilization triggers a series of Ca2+ oscillations that not only are essential for events of egg activation but also stimulate oxidative phosphorylation. Little is known, however, about the relationship between quantitative changes in egg metabolism and specific long-term effects in offspring. This study assessed whether post-natal growth is modulated by early transient changes in NAD(P)H and FAD2+ in zygotes. We report that experimentally manipulating the redox potential of fertilized eggs during the pronuclear (PN) stage affects post-natal body weight. Exogenous pyruvate induces NAD(P)H oxidation and stimulates mitochondrial activity with resulting offspring that are persistently and significantly smaller than controls. Exogenous lactate stimulates NAD+ reduction and impairs mitochondrial activity, and produces offspring that are smaller than controls at weaning but catch up after weaning. Cytosolic alkalization increases NAD(P)+ reduction and offspring of normal birth-weight become significantly and persistently larger than controls. These results constitute the first report that post-natal growth rate is ultimately linked to modulation of NAD(P)H and FAD2+ concentration as early as the PN stage

Production par transplantation embryonnaire de veaux monozygotes. Aspects zootechniques.

National audienc

Production par transplantation embryonnaire de veaux monozygotes. Aspects zootechniques.

National audienc

Bacterial sensors based on <I>Acidithiobacillus ferrooxidans</I> Part II. Cr(VI) determination

International audienceThe aerobic acidophilic bacterium Acidithiobacillus ferrooxidans oxidizes Fe2+ and S2O32 ions by consuming oxygen. An amperometric biosensor was designed including an oxygen probe as transducer and a recognition element immobilized by a suitable home-made membrane. This biosensor was used for the indirect amperometric determination of Cr2O72 ions owing to methods based on a mediator (Fe2+) or titration. Using the mediator, the biosensor response versus Cr2O72 was linear up to 0.4 mmol L1, with a response time of, respectively, 51 s (2 × 105 mol L1 Cr2O72) and 61 s (6 × 105 mol L1 Cr2O72). The method sensitivity was 816 μA L mol1. Response time and measurement sensitivity depended on membrane material and technique for biomass immobilization. For example, their values were 90 s200 μA L mol1 when using a glass-felt membrane and 540 s4.95 μA L mol1 with a carbon felt one to determine a concentration of 2 × 105 mol L1 Cr2O72. For the titration method, the biosensor is used to determine the equivalence point. The relative error of quantitative analysis was lower than 5%

Bacterial sensors based on <I>Acidithiobacillus ferrooxidans</I> Part I. Fe²⁺ and S₂O₃² determination

International audienceAn amperometric bacterial sensor with current response to Fe2+ and S2O32– ions has been designed by immobilizing an acidophilic biomass of Acidithiobacillus ferrooxidans on a multi disk flat-front oxygen probe. The bacterial layer was located between the oxygen probe and a membrane of cellulose. A filtration technique was used to yield the bacterial membranes having reproducible activity. The decrease of O2 flow across the bacterial layer is proportional to the concentration of the dosed species. The dynamic range appeared to be linear for the Fe2+ ions up to 2.5 mmol L–1 with a detection limit of 9 × 10–7 mol L–1 and a sensitivity of 0.25 A L mol–1. The response of the biosensor is 84 s for a determination of 2 × 10–4 mol L–1 Fe2+. Optimizing the Fe2+ determination by A. ferrooxidans sensor was carried out owing to Design of Experiments (DOE) methodology and empirical modelling. The optimal response was thus obtained for a pH of 3.4, at 35 °C under 290 rpm solution stirring. S2O32– concentration was determined at pH 4.7, so avoiding its decomposition. The concentration range was linear up to 0.6 mmol L–1. Sensitivity was 0.20 A L mol–1 with a response time of 207 s for a 2 × 10–4 mol L–1 S2O32– concentration

Variabilité fonctionnelle des signaux Ca2+ de la fécondation : un critère prédictif du développement embryonnaire

absen

<I>Acidithiobacillus ferrooxidans</I> fixation on mercuric surfaces ant its application in stripping voltammetry

International audienceThe adsorption (fixation) of bacteria Acidithiobacillus ferrooxidans on Hg and Cu metallic surfaces was qualitatively studied owing to two independent methods: frequency measurement using a quartz crystal microbalance and light absorption measuring at the Hg/bacterial culture interface. A method using a dropping mercury electrode (DME) allowed quantifying this bacterial fixation. Determining the superficial tension at Hg/bacterial culture interface led to determine bacteria adsorption on Hg through the Gibbs isotherm. A modified stripping voltammetry was proposed taking benefit of both bacterial adsorption on Hg surface and metal fixation capacity on biomass. Metal preconcentration on the biologically modified Hg electrode appeared to improve the measurement sensitivity of differential pulse anodic stripping voltammetry (DPASV). The height of the detected peaks was thus increased of 17.6% for copper, 48.4% for lead, and 132% for cadmium determinations compared to those obtained with an unmodified mercury electrode. Such augmentation depended on bulk bacteria concentration and bacteria preconcentration

Early differential miRNA expression following in vitro fertilization of mouse eggs incubated in two standard culture media

absen