MiR-29c-5p regulates the function of buffalo granulosa cells to induce follicular atresia by targeting INHBA.

MicroRNAs (miRNAs) are involved in many physiological processes such as signal transduction, cell proliferation and apoptosis. Many studies have shown that miRNAs can regulate the process of follicular development. Our previous studies found that the expression of miR-29c-5p in buffalo atretic follicles was much higher than that in healthy follicles, suggesting that this miRNA may participate in the process of buffalo follicular atresia. In this study, we aim to explore to the role and molecular mechanisms of miR-29c-5p on the functions of buffalo granulosa cells (GCs). GCs cultured in vitro were transfected with miR-29c-5p mimics and its inhibitor, respectively, and it was found that the mimics significantly increased the apoptotic rate of GCs. They also inhibited the proliferation of GCs and the secretion of steroid hormones. The effect of the inhibitor was opposite to that of the mimics. MiR-29c-5p was subsequently shown to target the inhibin subunit beta A, (INHBA). Overexpression of INHBA could promote the production of activin A and inhibin A, and then reverse the effect of miR-29c-5p on buffalo GCs. In conclusion, these results suggest that miR-29c-5p promotes apoptosis and inhibits proliferation and steroidogenesis by targeting INHBA in buffalo GCs. This may ultimately promote atresia in buffalo follicles.

Targeted metabolomics analysis of bile acids and cell biology studies reveal the critical role of glycodeoxycholic acid in buffalo follicular atresia.

The follicular fluid of mammals has a high abundance of bile acids and these have proven to be closely related to the follicular atresia. However, the origin and content of bile acids in follicular fluid and its mechanisms on follicular atresia remain largely unknown. In this work, we analyzed the origin of bile acids in buffalo follicles by using cell biology studies, and quantified the subspecies of bile acids in follicular fluid from healthy follicles (HF) and atretic follicles (AF) by targeted metabolomics. The function of differential bile acids on follicular granulosa cells was also studied. The results showed that the bile acids transporters were abundantly expressed in ovarian tissues, but the rate-limiting enzymes were not, which was consistent with the inability of cultured follicular cells to convert cholesterol into bile acids. Targeted metabolomics analysis revealed thirteen differential subspecies of bile acids between HF and AF. The free bile acids were significant down-regulated and their conjugated forms were significantly up-regulated in AF as compared to HF. Finally, cell biological validation found a specific differentially conjugated bile acid, glycodeoxycholic acid (GDCA), which could promote follicular granulosa cell apoptosis and reduce steroid hormone secretion. In summary, our studies suggest that bile acids in buffalo follicles are transported from the blood rather than being synthesized within the follicles. The conjugated bile acids such as GDCA, accumulate in buffalo follicles, and may accelerate atresia by promoting apoptosis of granulosa cells and inhibiting steroid hormone production. These results will provide new clues for studying the physiological role and mechanism of bile acids involved in buffalo follicular atresia.

Theoretical Prediction Method for Erosion Damage of Horizontal Pipe by Suspended Particles in Liquid-Solid Flows.

In order to study the erosion of a pipe wall via a liquid-solid suspension flow, a two-phase flow model combined with an erosion forecasting model for multiparticle impact on horizontal pipe wall surfaces was established in this work on the basis of low-cycle fatigue theory. In the model establishment process, the effects of particle motion and material damage were considered, and a simplified method for predicting horizontal wall erosion was obtained. The calculated results showed that the particles impact the wall at a small angle of most liquid flow velocities, causing cutting erosion damage of the wall. The settling velocity and fluctuating velocity of the particles together determine the radial velocity of the particles, which affects the impact angle of the particles. The cutting erosion caused by the small-angle impact of the particles in the pipe is more likely to cause rapid loss of the wall material. Therefore, the pipe wall is usually evenly thinned.

Experimental Study on Corrosion Performance of Oil Tubing Steel in HPHT Flowing Media Containing O2 and CO2.

The high pressure and high temperature (HPHT) flow solution containing various gases and Cl- ions is one of the corrosive environments in the use of oilfield tubing and casing. The changing external environment and complex reaction processes are the main factors restricting research into this type of corrosion. To study the corrosion mechanism in the coexistence of O2 and CO2 in a flowing medium, a HPHT flow experiment was used to simulate the corrosion process of N80 steel in a complex downhole environment. After the test, the material corrosion rate, surface morphology, micromorphology, and corrosion product composition were tested. Results showed that corrosion of tubing material in a coexisting environment was significantly affected by temperature and gas concentration. The addition of O2 changes the structure of the original CO2 corrosion product and the corrosion process, thereby affecting the corrosion law, especially at high temperatures. Meanwhile, the flowing boundary layer and temperature changed the gas concentration near the wall, which changed the corrosion priority and intermediate products on the metal surface. These high temperature corrosion conclusions can provide references for the anticorrosion construction work of downhole pipe strings.

Experimental Study on Erosion⁻Corrosion of TP140 Casing Steel and 13Cr Tubing Steel in Gas⁻Solid and Liquid⁻Solid Jet Flows Containing 2 wt % NaCl.

To study the erosion⁻corrosion characteristics of TP140 casing steel and 13Cr tubing steel in oil fields, we performed gas⁻solid and liquid⁻solid jet flow experiments to control particle addition, jet angle, and flow velocity and measure erosion and corrosion components. Meanwhile, we used a standard three-electrode system to study the changes in electrochemical parameters on a metal surface in a two-phase flow containing 2 wt % NaCl. Results showed that erosion is mainly dominated by the flow velocities and impact angles of particles, and corrosion rate is mainly affected by liquid flow rate. The erosion rates of the two materials increase with flow velocity, and the critical angle of maximum erosion rate exists. Meanwhile, flow velocity growth increases the current density on the TP140 surface while reducing the corrosion potential of 13Cr, but the effect of the angle on the two parameters is relatively small. The uniform corrosion of TP140 increases the erosion rate in the range of 10⁻20%, and the pitting of 13Cr increases the erosion rate in the range of 30⁻90%, indicating that the interaction between the erosion and corrosion of stainless steel is obvious.

A New Phenomenological Model for Single Particle Erosion of Plastic Materials.

A phenomenological model for single particle erosion (SPE) of plastic materials was constructed based on the Hertzian contact theory and conservation of momentum to solve the particle impact erosion. The extrusion deformation and contact time of materials in three processes of wall elastic extrusion, elastic-plastic extrusion, and elastic recovery were discussed. Later, the critical angle for sliding contact between the particle and metal surface was calculated according to the impact angle of a particle and the corresponding critical sliding friction force of the particle. The wall indentation depths under sliding contact and no sliding contact were compared. Finally, the erosion volume of materials by impact of a single particle was gained. Moreover, a contrastive analysis on calculation results was carried out by using the gas-solid jet erosion experiment. Contact time, normal and tangential deformations of materials, as well as material erosion under sliding contact and no sliding contact in two processes of particle extrusion and rebound were gained from calculation and experiment. The constructed model showed a good agreement without involving too many empirical coefficients.

A New Method for Predicting Erosion Damage of Suddenly Contracted Pipe Impacted by Particle Cluster via CFD-DEM.

A numerical study on the erosion of particle clusters in an abrupt pipe was conducted by means of the combined computational fluid dynamics (CFD) and discrete element methods (DEM). Furthermore, a particle-wall extrusion model and a criterion for judging particle collision interference were developed to classify and calculate the erosion rate caused by different interparticle collision mechanisms in a cluster. Meanwhile, a full-scale pipe flow experiment was conducted to confirm the effect of a particle cluster on the erosion rate and to verify the calculated results. The reducing wall was made of super 13Cr stainless steel materials and the round ceramsite as an impact particle was 0.65 mm in diameter and 1850 kg/m³ in density. The results included an erosion depth, particle-wall contact parameters, and a velocity decay rate of colliding particles along the radial direction at the target surface. Subsequently, the effect of interparticle collision mechanisms on particle cluster erosion was discussed. The calculated results demonstrate that collision interference between particles during one cluster impact was more likely to appear on the surface with large particle impact angles. This collision process between the rebounded particles and the following particles not only consumed the kinetic energy but also changed the impact angle of the following particles.