Search

Mitochondrial dysfunction, which results in the overproduction of oxygen free radicals, is a crucial mechanism underlying cerebral ischemia-reperfusion injury. 4'-Hydroxyl-2-substituted phenylnitronyl nitroxide (HPN), which is an antioxidant and free radical scavenger, can effectively scavenge oxygen free radicals, suggesting its potential as a protective agent against cerebral ischemia-reperfusion injury. In this study, we investigated the effects of HPN on mitochondrial function and apoptosis following cerebral ischemia/reperfusion injury in rats. Healthy adult SD rats were chosen as the experimental subjects, and the rat ischemia/reperfusion injury model was generated using the modified Zea Longa method. The administration of HPN significantly enhanced the activity of endogenous antioxidant enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT). Additionally, HPN effectively preserved the morphology and function of mitochondria, reduced the protein and gene expression of Caspase-3 and Bax, increased the protein and gene expression of Bcl-2, mitigated neuronal apoptosis, improved neurological deficits, and decreased the volume of cerebral infarction. Of interest, the protective effect on brain tissue was more evident with increasing doses of HPN. These findings indicate that HPN can serve as an effective protective agent against cerebral ischemia-reperfusion injury., (Copyright © 2024 IBRO. Published by Elsevier Inc. All rights reserved.)

Oxidative stress has been considered to be closely related to spaceflight-induced bone loss; however, mechanism is elusive and there are no effective countermeasures. Using cultured rat calvarial osteoblasts exposed to microgravity simulated by a random positioning machine, this study addressed the hypotheses that microgravity-induced shortening of primary cilia leads to oxidative stress and that primary cilium protection prevents oxidative stress and osteogenesis loss. Microgravity was found to induce oxidative stress (as represented by increased levels of reactive oxygen species (ROS) and malondialdehyde production, and decreased activities of antioxidant enzymes), which was perfectly replicated in osteoblasts growing in NG with abrogated primary cilia (created by transfection of an interfering RNA), suggesting the possibility that shortening of primary cilia leads to oxidative stress. Oxidative stress was accompanied by mitochondrial dysfunction (represented by increased mitochondrial ROS and decreased mitochondrial membrane potential) and intracellular Ca 2+ overload, and the latter was found to be caused by increased activity of Ca 2+ channel transient receptor potential vanilloid 4 (TRPV4), as also evidenced by TRPV4 agonist GSK1016790A-elicited Ca 2+ influx. Supplementation of HC-067047, a specific antagonist of TRPV4, attenuated microgravity-induced mitochondrial dysfunction, oxidative stress, and osteogenesis loss. Although TRPV4 was found localized in primary cilia and expressed at low levels in NG, microgravity-induced shortening of primary cilia led to increased TRPV4 levels and Ca 2+ influx. When primary cilia were protected by miR-129-3p overexpression or supplementation with a natural flavonoid moslosooflavone, microgravity-induced increased TRPV4 expression, mitochondrial dysfunction, oxidative stress, and osteogenesis loss were all prevented. Our data revealed a new mechanism that primary cilia function as a controller for TRPV4 expression. Microgravity-induced injury on primary cilia leads to increased expression and overactive channel of TRPV4, causing intracellular Ca 2+ overload and oxidative stress, and primary cilium protection could be an effective countermeasure against microgravity-induced oxidative stress and loss of osteogenic potential of osteoblasts., (© 2023 Wiley Periodicals LLC.)

The dense canopy of rice causes attenuation of droplet dispersion during pesticide application. The canopy-opening device can increase droplet deposition in the middle and lower canopy of rice by causing disturbance to the rice canopy. However, the conditions for use of the canopy-opening device are difficult to determine. Rice morphological structure parameters and material parameters were measured to study the movement mechanism of the rice stems under the action of the canopy-opening device, and the canopy-opening process was then simulated using the explicit dynamic method. The simulation scene of the rice canopy-opening process considered the combination of three different heights and three different driving velocities of the canopy-opening device. The movement mechanism of the rice stems under the operation of the canopy-opening device was investigated, and the entire movement process was separated into two stages: contact and oscillation. The simulation results and high-speed photography experimental results show a strong correlation, with a correlation coefficient of 0.733. The simulation results indicate that when the canopy-opening device is closer to the ground and the driving velocity is higher, the disturbance to the rice stem during the contact stage is stronger. However, for the oscillation stage, there exists a critical value for both the height and driving velocity of the canopy-opening device. During the oscillation stage, there is a critical value for both the height and driving velocity of the canopy-opening device. The numerical-based explicit dynamics approach was employed in this work to investigate the rice canopy motion mechanism, and this study has a definite reference value for the investigation of complicated motion mechanisms in the field crop production process., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Jing, Wei, Song and Wang.)

P-TEFb, a heterodimer of the kinase CDK9 and Cyclin T1, is a critical regulator of promoter-proximal pause release of Pol II in metazoans. It is capable of forming three larger complexes, including the super elongation complex (SEC), the BRD4/P-TEFb complex and the 7SK snRNP. In the SEC or the BRD4/P-TEFb complex, P-TEFb is enzymatically active, while in the 7SK snRNP, its activity is inhibited. The SEC consists of AFF1 or 4, ENL or AF9, ELL1, 2 or 3 and EAF1 or 2 in addition to P-TEFb, the only subunit with catalytic activity, and the noncatalytic subunits have been found to be able to regulate pause release through P-TEFb. We and others recently found that AFF1, ENL and AF9 are capable of regulating transcriptional initiation, but it is unknown yet whether AFF4 is also capable of doing so. With respect to the gene regulation selectivity of the SEC and the BRD4/P-TEFb complex, one recent study showed that in human DLD-1 cells, the SEC only regulates pause release of heat shock (HS) genes, whereas the BRD4/P-TEFb complex regulates pause release of the rest of the genes. However, it is unclear whether those mechanisms are general. In this study for the purpose of further understanding the role of AFF4 in transcriptional regulation, we found that AFF4 knockdown by RNA interference in human HEL cells decreased not only cellular level but also global chromatin occupancy of CTD serine 2 phosphorylated Pol II. Direct target genes of AFF4 were identified by RNA-seq and CUT&Tag. Notably, we found by ChIP-seq and PRO-seq that AFF4 loss also increased promoter-proximal pause of Pol II on several hundred HS and thousands of non-HS genes. Mechanistically, AFF4 promotes pause release likely by facilitating the binding of P-TEFb to Pol II. These results suggest that extent of the impact of AFF4 on pause release is likely to be context-dependent or cell-type dependent.

Objective: To evaluate the diagnostic efficacy of stress-strain index (SSI) for different stages or degrees of keratoconus and changes of SSI and stiffness parameter A1 (SPA1) after corneal collagen cross-linking (CXL) surgery. Methods: Cross-sectional study and retrospective case series study. Ninety-four patients (113 eyes) diagnosed as clinical keratoconus (CKC) in Qingdao Eye Hospital from July 2019 to August 2021 were enrolled in the CKC group, including 69 males and 25 females, aged (20.82±4.53) years, and further divided into subgroups of mild (35 patients, 36 eyes), moderate (36 patients, 40 eyes) and severe (33 patients, 37 eyes) CKC. Fifty-six unaffected eyes of monocular keratoconus patients were enrolled in the subclinical keratoconus (SKC) group. Ninety-one healthy subjects (91 eyes) were recruited as the control group. All subjects were examined by Pentacam topography and Corvis ST measurements to obtain mean keratometry, maximal keratometry, deformation amplitude (DA) ratio at 2 mm, integrated radius (IR), Ambrósio's relational thickness to the horizontal profile, corneal central thickness, SPA1 and SSI for comparison. Forty-eight CKC patients (65 eyes) underwent CXL surgery, and the above parameters were recorded before and 3, 6 and 12 months after operation. Data were analyzed by the ANOVA test, Kruskal-Wallis H test, paired sample test, receiver operating characteristic curves and Pearson correlation. Results: The value of SPA1 in the SKC group accounted for 85.53% (87.92±12.38 vs. 102.79±11.74; t =-6.614, P <0.001) compared with the control group, but the value of SSI had no difference in the two groups ( t =0.105, P =0.916). The value of SPA1 in the CKC group accounted for 52.87% (54.35±14.70 vs. 102.79±11.74; t =25.985, P <0.001) compared with the control group. The value of SSI in the CKC group accounted for 67.96% (0.70±0.14 vs. 1.03±0.14; t =-15.305, P <0.001) compared with the control group. The more severe the disease was, the smaller the SPA1 and SSI values were 64.27±12.12, 55.22±12.23, 43.75±12.33; 0.78±0.14, 0.71±0.11, 0.61±0.09, and there were significant statistical differences among groups (mild vs. moderate, mild vs. severe, moderate vs. severe; SPA1: t =3.257, -7.249, -4.159; all P <0.001. SSI: t =2.383, 5.065, 2.798; P =0.018,<0.001,=0.006). Receiver operating characteristic analysis showed that SPA1 had good diagnostic efficiency for subclinical patients [area under curve (AUC)=0.802], while the SSI had no diagnostic value ( P =0.802). SPA1 had better diagnostic efficiency than the SSI for keratoconus in different stages, especially in the mild CKC and SKC groups (AUC: 0.914 vs. 0.847). The SSI had a significant positive correlation with SPA1 and a significant negative correlation with DA ratio and IR in the control, SKC and CKC groups ( r =0.278, 0.368, 0.550; r =-0.346, -0.462, -0.547; r =-0.612, -0.591, -0.718; P <0.01). For patients who received CXL, maximal keratometry decreased significantly at 6 and 12 months postoperatively ( t =4.029, 3.633; all P <0.001), whereas SPA1 increased significantly ( t =-3.960, -4.500; all P <0.001). However, the SSI only increased significantly at 3 months ( t =-2.577, P =0.012) and returned to the preoperative level at 6 and 12 months postoperatively, with no statistical difference compared with the preoperative level ( t =-0.544, -0.257; P =0.589, 0.798). Conclusions: While there was no significant change in the SSI of SKC, the SSI of CKC decreased, and the more severe the disease was, the smaller the value was. The SSI was significantly and consistently correlated with DA ratio, IR and SPA1. The SSI compared with SPA1 had a lower degree of identification in different stages and degrees of keratoconus. The consistency of SPA1 with clinical effects after CXL surgery was higher than that of the SSI parameter.