CircRNA circ_POLA2 overexpression suppresses cell apoptosis by downregulating PTEN in glioblastoma.

The oncogenic role of circ_POLA2 has only been explored in lung cancer, whereas the role of which in glioblastoma (GBM) is unclear. Our research explored the involvement of circ_POLA2 in GBM. Circ_POLA2 and phosphatasetensinhomolog (PTEN) mRNA levels in GBM and paired nontumor tissues collected from 58 GBM patients were analyzed by real-time quantitative PCR (RT-qPCR). Circ_POLA2 and PTEN were overexpressed in GBM cells to study their interaction by RT-qPCR and Western blot. The roles of circ_POLA2 and PTEN in regulating GBM cell apoptosis were explored using cell apoptosis assay. Our data revealed that circ_POLA2 was upregulated and PTEN was downregulated in GBM. PTEN showed an inverse correlation to circ_POLA2 across GBM tissues, In GBM cells, circ_POLA2 overexpression decreased PTEN accumulation, but PTEN overexpression failed to significantly affect circ_POLA2 expression. Moreover, PTEN reduced the inhibitory effects of circ_POLA2 on GBM cell apoptosis. Circ_POLA2 is overexpressed in MCL and might promote GBM cell apoptosis through downregulating PTEN.

Dry Friction Properties of Diamond-Coated Silicon Carbide.

Dry friction between seal faces, caused by unstable or extreme operating conditions, significantly affects the running stability and service life of mechanical seals. Therefore, in this work, nanocrystalline diamond (NCD) coatings were prepared on the surface of silicon carbide (SiC) seal rings by hot filament chemical vapor deposition (HFCVD). The friction test results under dry environment reveals that the coefficient of friction (COF) of SiC-NCD seal pairs is about 0.07-0.09, which were reduced by 83-86% compared to SiC-SiC seal pairs. The wear rate of SiC-NCD seal pairs is relatively low, ranging from 1.13 × 10-7 mm3/N·m to 3.26 × 10-7 mm3/N·m under different test conditions, which is due to the fact that the NCD coatings prevent adhesive and abrasive wear between the SiC seal rings. The analysis and observation of the wear tracks illustrate that the excellent tribological performance of the SiC-NCD seal pairs is due to a self-lubricating amorphous layer formed on the worn surface. In conclusion, this work highlights a pathway to enable mechanical seals to satisfy the high application requirements under highly parametric working conditions.

Prognosis and Influencing Factors of Early Microsurgery for Severe Hypertensive Brainstem Hemorrhage.

Objective: To investigate the prognosis and influencing factors of early microsurgery for severe hypertensive brainstem hemorrhage. Methods: The clinical data of 19 patients with severe hypertensive brainstem hemorrhage treated in the Department of Neurosurgery of the Second Affiliated Hospital of Shandong First Medical University between January 2018 and December 2021 were retrospectively analyzed. The clinical efficacy and risk factors affecting the prognosis were analyzed by chi-square test and multivariate logistic regression. Results: A total of 19 patients with severe hypertensive brainstem hemorrhage were treated by early microsurgery, including 14 cases by subtemporal approach and 5 cases by retrosigmoid approach. After 3 months of follow-up, 6 patients died and 13 patients survived. The 30-day and 90-day mortality rates were 21.1% and 31.6%, respectively, and the good prognosis rate was 15.4%. Univariate analysis showed that hematoma volume and hematoma clearance rate might be the factors affecting the prognosis of patients with severe hypertensive brainstem hemorrhage; the observed difference was statistically significant (P < 0.05). Multivariate logistic regression analysis further confirmed that hematoma volume was an independent factor affecting the death of patients with brainstem hemorrhage (P < 0.05), while hematoma volume (B: 2.909, OR: 18.332, 95% CI: 1.020-329.458, P: 0.048) was a risk factor. Conclusion: Hematoma volume resulted as an independent factor affecting the death of patients with severe hypertensive brainstem hemorrhage. Early microsurgical clearance of brainstem hematoma contributed to reducing the 30-day and 90-day mortality and improving the prognosis of patients.

Blocking cerebral lymphatic drainage deteriorates cerebral oxidative injury in rats with subarachnoid hemorrhage.

Substances and fluid in the brain and subarachnoid spaces may be drained into extracranial lymphatics. This study aimed to investigate the possible role of cerebral lymphatic drainage in the process of cerebral injury following subarachnoid hemorrhage (SAH). Wistar rats were divided into non-SAH, SAH, and SAH plus cervical lymphatic blockage (SAH + CLB) groups. Autologous arterial hemolysate was injected into rats' cisterna magna to induce SAH. At time of 24 and 72 h after SAH, the rats were sacrificed for serum lactate dehydrogenase (LDH) activity, brain tissue superoxide dismutase (SOD) activity, and brain tissue malonaldehyde (MDA) content detection. It was found that serum LDH activity increased in rats of SAH group comparing with non-SAH group. SAH also resulted in decreased brain tissue SOD activity and increased brain tissue MDA content. In rats of SAH + CLB group, the increase of serum LDH activity was to a lager extent. Meanwhile, brain tissue SOD activity decreased and MDA content increased to a lager extent, as compared with SAH group. It was concluded that blockage of cerebral lymphatic drainage deteriorates cerebral oxidative injury after SAH, indicating cerebral lymphatic drainage may exert intrinsic protective effects against cerebral injury following SAH.

Decreasing Resistivity of Silicon Carbide Ceramics by Incorporation of Graphene.

Silicon carbide (SiC) ceramic is an ideal material for mechanical seal because of its super hardness, high strength, low friction coefficient, good thermal conductivity, and resistance to friction and wear. However, due to relatively high resistivity of SiC ceramic, the triboelectric charge caused by rubbing of mechanical seal end-faces could not be released. It is terrible that the accumulation of triboelectric charge could cause electrochemical corrosion, which would accelerate wear. To decrease the resistivity of SiC ceramic is a desire for improving the performance of mechanical seal. In this research, decreasing resistivity of pressureless sintered SiC ceramic was investigated by conductive pathways through semiconductive grains in a body by incorporation of graphene, which has an extremely low resistivity. With the increasing of graphene from 0 to 2 wt.%, the volume resistivity of SiC ceramics sintered with graphene decreased logarithmically from >106 to around 200 Ω·cm, and the bulk density decreased gradually, from 3.132 to 3.039 g/cm3. In order to meet the requirements of mechanical seal, SiC ceramic sintered with 1 wt.% of graphene, for which the volume resistivity is of 397 Ω·cm, the bulk density is of 3.076 g/cm3, and the flexural strength is of 364 MPa, was optimized when all properties were taken into consideration. It is possible to fabricate low-resistivity SiC ceramic as a useful friction pair material for mechanical seal in a special condition, without excessive loss of their excellent mechanical properties by the introduction of partially connected graphene as conductive pathway into semiconducting ceramic.

Brain edema and protein expression of c-Fos and c-Jun in the brain after diffused brain injury.

OBJECTIVE: To investigate brain edema and protein expression of c-Fos and c-Jun in brain after diffuse brain injury, and to investigate the pathological change after brain injury, which may provide evidence for the clinical treatment of diffused brain injury. METHODS: Marmarou method was used to establish the diffuse brain injury in rats. RESULTS: After diffused brain injury, brain water content increased at 1 h, reached the peak at 1 d and remained at a high level at 7 d when compared with control group. One day after injury, diffuse subarachnoid hemorrhage was observed in the brain. HE staining showed vascular swelling and bleeding at the cortex and corpus callosum at 1 d. ß-APP expression was found at the brainstem, hippocampus, thalamus, corpus callosum and periventricular regions. Pathological examination of ultrathin sections showed evidence edema and fracture of axons at 3 d after brain injury. The brain injury caused severe cerebral ischemia. The c-Fos and c-Jun expression increased at 1 h. The c-Fos expression peaked at 3 h (P < 0.05), then reduced, reached a maximal level again at 3 d (P < 0.05), and reduced significantly at 7 d but remained at a higher level when compared with control group (P < 0.05). The number of c-Jun positive cells peaked at 6 h (P < 0.05), then reduced, reached a maximal level again at 3 d and reduced markedly but still remained at a higher level when compared with control group (P < 0.05). CONCLUSION: After diffuse brain injury, brain water content and c-Fos/c-Jun expression change over time.

Intranasal delivery of calcitonin gene-related peptide reduces cerebral vasospasm in rats.

Cerebral vasospasm is the primary cause of sequelae and poor clinical conditions of subarachnoid hemorrhage (SAH); therefore, it is imperative to relieve vasospasm and improve cerebral blood supply. Calcitonin gene-related peptide (CGRP) is a potent vasodilator that is normally released by trigeminal sensory fibers but depleted following SAH. We propose that intranasal application may be an effective way to deliver CGRP to the brain and ameliorate vasospasm after SAH. In this study, we intranasally applied CGRP to rats and induced SAH by double-injection of autologous blood into the cisterna magna. Compared to intravenous injection, intranasal delivery led to a 10-fold higher level of CGRP in the brain. Intranasal CGRP significantly ameliorated vasospasm, improved cerebral blood flow, and reduced cortical and endothelial cell death. Moreover, CGRP increased the levels of vascular endothelial growth factor and stimulated angiogenesis. Altogether, our data demonstrate that intranasal CGRP delivery is a promising method for moderating vasospasm and reducing the associated ischemic brain injury after SAH in rats, and suggest that it may be a potential approach in clinic.