miR-302a-3p suppresses melanoma cell progression via targeting METTL3

The miRNA-302 family plays a critical role in carcinogenesis. As an enzyme that regulates the N6-methyladenosine modification, methyltransferase-like 3 (METTL3) plays important roles in the development and progression of various tumours. However, the upstream regulatory mechanisms of METTL3 in melanoma have not yet been fully investigated. Herein, we investigated the functions of miR-302a-3p and its target RNA METTL3 on proliferation, apoptosis, and invasion of melanoma. Quantitative real-time PCR and immunofluorescence staining were used to measure the expression of METTL3 mRNA and protein level after transfection. miR-302a-3p expression was determined by quantitative reverse transcription-PCR. The cell proliferation, cell cycle progression, apoptosis, colony formation, migration, and cell invasion ability were determined using MTT assay, propidium iodide (PI) staining, Annexin V/PI flow cytometry, plate clone assay, and Transwell migration and invasion assays, respectively. Melanoma cell metastasis was also evaluated using an in vivo model. The effect of METTL3 on the phosphorylation of PI3K and AKT was measured with western blot analysis. Our results showed that miR-302a-3p was significantly downregulated in melanoma and exerted a tumour suppressive role against melanoma progression. We identified METTL3 as a direct target of miR-302a-3p in melanoma cells using bioinformatics analysis and luciferase assay. Furthermore, the enforced overexpression of METTL3 promoted the proliferation, cell cycle progression, cell invasion, migration, expression of epithelial-to-mesenchymal transition markers, and the PI3K-AKT signalling pathway as well as suppressed the apoptosis of melanoma cells. Meanwhile, silencing the expression of METTL3 with specific shRNA demonstrated reverse outcomes of the above phenotypes in melanoma cells. By rescue experiments, we found that the restoration of METTL3 expression in miR-302a-3p-overexpressing melanoma cells successfully recovered the miR-302a-3p-mediated melanoma suppression. The in vivo results also showed that miR-302a-3p substantially inhibited melanoma cell growth and metastasis. In summary, this study demonstrated that miR-302a-3p targets METTL3 and plays tumour suppressive roles in the proliferation, apoptosis, invasion, and migration of melanoma cells.

Melatonin ameliorates microvessel abnormalities in the cerebral cortex and hippocampus in a rat model of Alzheimer's disease

Melatonin can attenuate cardiac microvascular ischemia/reperfusion injury, but it remains unclear whether melatonin can also ameliorate cerebral microvascular abnormalities. Rat models of Alzheimer’s disease were established by six intracerebroventricular injections of amyloid-beta 1–42, administered once every other day. Melatonin (30 mg/kg) was intraperitoneally administered for 13 successive days, with the first dose given 24 hours prior to the first administration of amyloid-beta 1–42. Melatonin ameliorated learning and memory impairments in the Morris water maze test, improved the morphology of microvessels in the cerebral cortex and hippocampus, increased microvessel density, alleviated pathological injuries of cerebral neurons, and decreased the expression of vascular endothelial growth factor and vascular endothelial growth factor receptors 1 and 2. These findings suggest that melatonin can improve microvessel abnormalities in the cerebral cortex and hippocampus by lowering the expression of vascular endothelial growth factor and its receptors, thereby improving the cognitive function of patients with Alzheimer’s disease. This study was approved by the Animal Care and Use Committee of Jinzhou Medical University, China (approval No. 2019015) on December 6, 2018.

[Angiotensin II type 1 receptor autoantibody induces myocardial fibrosis by activating cardiac fibroblasts]

Myocardial fibrosis (MF) is an important pathological process of cardiac remodeling in patients with heart failure; however its etiology has not been clear. It has been known that the angiotensin II type 1 receptor autoantibody (AT1-AA) is present in patients with heart failure, but it is unclear whether this antibody directly causes MF. In this study, we investigated the role of AT1-AA in MF and its effects on cardiac fibroblasts (CFs). The AT1-AA positive rat model was established by active immunization method, and the measurement of indexes were made in the 8th week after active immunity. The results of heart echocardiography showed that the cardiac systolic and diastolic functions of AT1-AA positive rats were impaired with reduced left ventricular wall thickness and enlarged heart chambers. HE staining results showed that the myocardial fibers were disorganized and ruptured, and Masson staining revealed that the area of collagen fibers around the myocardium and coronary arteries was significantly increased in AT1-AA positive group compared with that of the control group (P < 0.05). Moreover, primary CFs isolated from neonatal rats were cultured and treated with AT1-AA for 48 h. CCK-8 and immunofluorescence staining results showed that AT1-AA enhanced proliferation rate of CFs (P < 0.001), and Western blot results showed that AT1-AA significantly increased expressions of collagen I (Col I), Col III, matrix metalloproteinase-2 (MMP-2) and MMP-9 in CFs (all P < 0.05). Taken together, these results suggest that AT1-AA may induce MF and cardiac dysfunction via activating CFs.

Direct precision frequency measurement and correction technology with double ADC

A new method of direct precision frequency measurement is proposed in this paper, which uses the clock cursor effect between the sampling clock signal and input signal and ADC (analog to digital converter) quantization error suppression technique in the background of digital measurement with double ADC. On this basis, a precision frequency corrector is designed. Compared with the traditional frequency synthesizer, this device takes the non-standard frequency signal of the crystal oscillator as the reference to realize the standard frequency signal output through the frequency correction function. Meanwhile, the output signal is obviously narrower in range, from 0.0001 Hz to 0.1 Hz. The frequency corrector can also realize the second stability of less than 3 × 10^-12 and a small frequency correction of 10^-11 orders of magnitude.

[Estimation of sparse vegetation coverage in arid region based on hyperspectral mixed pixel decomposition]

Based on Hyperion hyperspectral image data, the image-derived shifting sand, false-Gobi spectra, and field-measured sparse vegetation spectra were taken as endmembers, and the sparse vegetation coverage (< 40%) in Minqin oasis-desert transitional zone of Gansu Province was estimated by using fully constrained linear spectral mixture model (LSMM) and non-constrained LSMM, respectively. The results showed that the sparse vegetation fraction based on fully constrained LSMM described the actual sparse vegetation distribution. The differences between sparse vegetation fraction and field-measured vegetation coverage were less than 5% for all samples, and the RMSE was 3.0681. However, the sparse vegetation fraction based on non-constrained LSMM was lower than the field-measured vegetation coverage obviously, and the correlation between them was poor, with a low R2 of 0.5855. Compared with McGwire's corresponding research, the sparse vegetation coverage estimation in this study was more accurate and reliable, having expansive prospect for application in the future.