274 research outputs found
Generation of mouse oocytes defective in cAMP synthesis and degradation: Endogenous cyclic AMP is essential for meiotic arrest
AbstractAlthough it is established that cAMP accumulation plays a pivotal role in preventing meiotic resumption in mammalian oocytes, the mechanisms controlling cAMP levels in the female gamete have remained elusive. Both production of cAMP via GPCRs/Gs/adenylyl cyclases endogenous to the oocyte as well as diffusion from the somatic compartment through gap junctions have been implicated in maintaining cAMP at levels that preclude maturation. Here we have used a genetic approach to investigate the different biochemical pathways contributing to cAMP accumulation and maturation in mouse oocytes. Because cAMP hydrolysis is greatly decreased and cAMP accumulates above a threshold, oocytes deficient in PDE3A do not resume meiosis in vitro or in vivo, resulting in complete female infertility. In vitro, inactivation of Gs or downregulation of the GPCR GPR3 causes meiotic resumption in the Pde3a null oocytes. Crossing of Pde3aâ/â mice with Gpr3â/â mice causes partial recovery of female fertility. Unlike the complete meiotic block of the Pde3a null mice, oocyte maturation is restored in the double knockout, although it occurs prematurely as described for the Gpr3â/â mouse. The increase in cAMP that follows PDE3A ablation is not detected in double mutant oocytes, confirming that GPR3 functions upstream of PDE3A in the regulation of oocyte cAMP. Metabolic coupling between oocytes and granulosa cells was not affected in follicles from the single or double mutant mice, suggesting that diffusion of cAMP is not prevented. Finally, simultaneous ablation of GPR12, an additional receptor expressed in the oocyte, does not modify the Gpr3â/â phenotype. Taken together, these findings demonstrate that Gpr3 is epistatic to Pde3a and that fertility as well as meiotic arrest in the PDE3A-deficient oocyte is dependent on the activity of GPR3. These findings also suggest that cAMP diffusion through gap junctions or the activity of additional receptors is not sufficient by itself to maintain the meiotic arrest in the mouse oocyte
Basic tutorial tactics for virtual agents. DynaLearn, EC FP7 STREP project 231526, Deliverable D5.2
Basic tutorial tactics for virtual agents. DynaLearn, EC FP7 STREP project 231526, Deliverable D5.2
Regulation of meiotic prophase arrest in mouse oocytes by GPR3, a constitutive activator of the Gs G protein
The arrest of meiotic prophase in mouse oocytes within antral follicles requires the G protein Gs and an orphan member of the G proteinâcoupled receptor family, GPR3. To determine whether GPR3 activates Gs, the localization of Gαs in follicle-enclosed oocytes from Gpr3+/+ and Gpr3â/â mice was compared by using immunofluorescence and GαsGFP. GPR3 decreased the ratio of Gαs in the oocyte plasma membrane versus the cytoplasm and also decreased the amount of Gαs in the oocyte. Both of these properties indicate that GPR3 activates Gs. The follicle cells around the oocyte are also necessary to keep the oocyte in prophase, suggesting that they might activate GPR3. However, GPR3-dependent Gs activity was similar in follicle-enclosed and follicle-free oocytes. Thus, the maintenance of prophase arrest depends on the constitutive activity of GPR3 in the oocyte, and the follicle cell signal acts by a means other than increasing GPR3 activity
Drying Dynamics of SolutionâProcessed Perovskite ThinâFilm Photovoltaics: In Situ Characterization, Modeling, and Process Control
A key challenge for the commercialization of perovskite photovoltaics is the transfer of highâquality spin coated perovskite thinâfilms toward applying industryâscale thinâfilm deposition techniques, such as slotâdie coating, spray coating, screen printing, or inkjet printing. Due to the complexity of the formation of polycrystalline perovskite thinâfilms from the precursor solution, efficient strategies for process transfer require advancing the understanding of the involved dynamic processes. This work investigates the fundamental interrelation between the drying dynamics of the precursor solution thinâfilm and the quality of the blade coated polycrystalline perovskite thinâfilms. Precisely defined drying conditions are established using a temperatureâstabilized drying channel purged with a laminar flow of dry air. The dedicated channel is equipped with laser reflectometry at multiple probing positions, allowing for in situ monitoring of the perovskite solution thinâfilm thickness during the drying process. Based on the drying dynamics as measured at varying drying parameters, namely at varying temperature and laminar air flow velocity, a quantitative model on the drying of perovskite thinâfilms is derived. This model enables process transfer to industryâscale deposition systems beyond brute force optimization. Via this approach, homogeneous and pinholeâfree blade coated perovskite thinâfilms are fabricated, demonstrating high power conversion efficiencies of up to 19.5% (17.3% stabilized) in perovskite solar cells
Latest investigations on fluctuations, ELM filaments and turbulent transport in the SOL of ASDEX Upgrade
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