Peta-electron volt gamma-ray emission from the Crab Nebula

The Crab Nebula is a bright source of gamma rays powered by the Crab Pulsar's rotational energy through the formation and termination of a relativistic electron-positron wind. We report the detection of gamma rays from this source with energies from 5 × 10^-4 to 1.1 peta-electron volts with a spectrum showing gradual steepening over three energy decades. The ultrahigh-energy photons imply the presence of a peta-electron volt electron accelerator (a pevatron) in the nebula, with an acceleration rate exceeding 15% of the theoretical limit. We constrain the pevatron's size between 0.025 and 0.1 parsecs and the magnetic field to ≈110 microgauss. The production rate of peta-electron volt electrons, 2.5 × 10³⁶ ergs per second, constitutes 0.5% of the pulsar spin-down luminosity, although we cannot exclude a contribution of peta-electron volt protons to the production of the highest-energy gamma rays.

Extended Very-High-Energy Gamma-Ray Emission Surrounding PSR J0622+3749 Observed by LHAASO-KM2A

We report the discovery of an extended very-high-energy (VHE) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar PSR J0622+3749 with the Large High-Altitude Air Shower Observatory (LHAASO). The source is detected with a significance of 8.2σ for E>25  TeV assuming a Gaussian template. The best-fit location is (right ascension, declination) =(95.47°±0.11°,37.92°±0.09°), and the extension is 0.40°±0.07°. The energy spectrum can be described by a power-law spectrum with an index of -2.92±0.17_{stat}±0.02_{sys}. No clear extended multiwavelength counterpart of the LHAASO source has been found from the radio to sub-TeV bands. The LHAASO observations are consistent with the scenario that VHE electrons escaped from the pulsar, diffused in the interstellar medium, and scattered the interstellar radiation field. If interpreted as the pulsar halo scenario, the diffusion coefficient, inferred for electrons with median energies of ∼160  TeV, is consistent with those obtained from the extended halos around Geminga and Monogem and much smaller than that derived from cosmic ray secondaries. The LHAASO discovery of this source thus likely enriches the class of so-called pulsar halos and confirms that high-energy particles generally diffuse very slowly in the disturbed medium around pulsars.

Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources

The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10¹⁵ electronvolts) indicates the existence of the so-called PeVatrons-cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays¹. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref. ²). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane^3-6, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.

New ^{59}Fe Stellar Decay Rate with Implications for the ^{60}Fe Radioactivity in Massive Stars

The discrepancy between observations from γ-ray astronomy of the ^{60}Fe/^{26}Al γ-ray flux ratio and recent calculations is an unresolved puzzle in nuclear astrophysics. The stellar β-decay rate of ^{59}Fe is one of the major nuclear uncertainties impeding us from a precise prediction. The important Gamow-Teller strengths from the low-lying states in ^{59}Fe to the ^{59}Co ground state are measured for the first time using the exclusive measurement of the ^{59}Co(t,^{3}He+γ)^{59}Fe charge-exchange reaction. The new stellar decay rate of ^{59}Fe is a factor of 3.5±1.1 larger than the currently adopted rate at T=1.2  GK. Stellar evolution calculations show that the ^{60}Fe production yield of an 18 solar mass star is decreased significantly by 40% when using the new rate. Our result eliminates one of the major nuclear uncertainties in the predicted yield of ^{60}Fe and alleviates the existing discrepancy of the ^{60}Fe/^{26}Al ratio.

Acceleration of Brain TOF-MRA with Compressed Sensitivity Encoding: A Multicenter Clinical Study

BACKGROUND AND PURPOSE

The clinical practice of three-dimensional TOF-MRA, despite its capability in brain artery assessment, has been hampered by the relatively long scan time, while recent developments in fast imaging techniques with random undersampling has shed light on an improved balance between image quality and imaging speed. Our aim was to evaluate the effectiveness of TOF-MRA accelerated by compressed sensitivity encoding and to identify the optimal acceleration factors for routine clinical use.

MATERIALS AND METHODS

One hundred subjects, enrolled at 5 centers, underwent 8 brain TOF-MRA sequences: 5 sequences using compressed sensitivity encoding with acceleration factors of 2, 4, 6, 8, and 10 (CS2, CS4, CS6, CS8, and CS10), 2 using sensitivity encoding with factors of 2 and 4 (SF2 and SF4), and 1 without acceleration as a reference sequence (RS). Five large arteries, 6 medium arteries, and 6 small arteries were evaluated quantitatively (reconstructed signal intensity, structural similarity, contrast ratio) and qualitatively (scores on arteries, artifacts, overall image quality, and diagnostic confidence for aneurysm and stenosis). Comparisons were performed among the 8 sequences.

RESULTS

The quantitative measurements showed that the reconstructed signal intensities of the assessed arteries and the structural similarity consistently decreased as the compressed sensitivity encoding acceleration factor increased, and no significant difference was found for the contrast ratios in pair-wise comparisons among SF2, CS2, and CS4. Qualitative evaluations showed no significant difference in pair-wise comparisons among RS, SF2, and CS2 (P > .05). The visualization of all the assessed arteries was acceptable for CS2 and CS4, while 2 small arteries in images of CS6 were not reliably displayed, and the visualization of large arteries was acceptable in images of CS8 and CS10.

CONCLUSIONS

CS4 is recommended for routine brain TOF-MRA with balanced image quality and acquisition time; CS6, for examinations when small arteries are not evaluated; and CS10, for fast visualization of large arteries.

ZEB2-AS1 regulates the expression of TAB3 and promotes the development of colon cancer by adsorbing microRNA-188

OBJECTIVE

This study aimed to explore the possible role and mechanism of lncRNA ZEB2-AS1 in the pathogenesis of colon cancer (CCa).

PATIENTS AND METHODS

The expression level of ZEB2-AS1 in 41 colon cancer tissue samples and 25 normal tissues was detected by qRT-PCR, and appropriate colon cancer cell lines were screened for in vitro experiments. Subcellular localization of ZEB2-AS1 was examined. After ZEB2-AS1 was transfected into colon cancer cells by liposome method, the cell proliferation, migration ability, and cell apoptosis percentage were evaluated by CCK-8 test, transwell assay, and flow cytometry, respectively. In addition, bioinformatics was applied to detect the target genes of microRNA-188. The Luciferase gene reporter assay was then performed to analyze the relative activity of Luciferase between microRNA-188 and TAB3 or ZEB2-AS1. At the same time, the control sequence, microRNA-188 mimics, microRNA-188 mimics+ ZEB2-AS1, si-TAB3, and microRNA-188 inhibitor+ si-TAB3 were respectively transfected into cells to further verify the interaction between TAB3 and microRNA-188 or ZEB2-AS1. Besides, the glucose and lactate levels were measured to explore their roles in glycolysis.

RESULTS

The expression of ZEB2-AS1 in colon cancer tissues and cells was significantly higher than that in normal ones, and ZEB2-AS1 was confirmed to be mostly located in the cytoplasm. In addition, ZEB2-AS1 overexpression could enhance the cell proliferation rate and migration ability as well as reduce the cell apoptosis, which could be reversed by microRNA-188 overexpression. In addition, bioinformatics prediction and Dual-Luciferase reporter assays revealed that ZEB2-AS1 could bind to microRNA-188, which could directly target TAB3. At the same time, it was found that the overexpression of ZEB2-AS1 and low expression of microRNA-188 promoted glycolysis, while the opposite result was observed after overexpression of microRNA-188 and low expression of TAB3.

CONCLUSIONS

The expression of ZEB2-AS1 is significantly increased in colon cancer tissues and cells, which can promote the proliferation, migration, and promote apoptosis of colon cancer cells. It may be involved in the development of this cancer through the process of glycolysis regulated by microRNA-188/TAB3.

[Comparative study on metagenomics of esophageal flora in elderly and middle-aged esophageal squamous cell carcinoma patients]

Objective: To explore the flora characteristics and differences of esophageal tissues between elderly esophageal squamous cell carcinoma (ESCC) patients and young and middle-aged ESCC patients, so as to assist in studying the potential biomarkers of elderly ESCC patients. Methods: In this study, a retrospective study was adopted. 72 ESCC patients diagnosed in Taihe Hospital, Shiyan City, Hubei Province from July 2018 to July 2019 were selected, including 49 patients in the elderly group (≥ 60 years old, 40 males and 9 females), 23 patients in the young and middle-aged group (<60 years old, 21 males and 2 females). In the same period, 20 healthy persons without abnormal gastroscopy in endoscopy center were selected as the control group (aged 35-78 years old, median age 57 years old, 16 males and 4 females). The genomic DNA was extracted from the affected esophageal tissues of patients with ESCC and the middle esophageal samples of the control group. The V4 hypervariable region of bacterial 16SrRNA gene sequence was amplified. Illumina HiSeq sequencing technology was adopted. The flora characteristics of elderly, young and middle-aged ESCC patients was compared and analyzed. QIIME and Rstudio software were used to analyze the sequence data, and nonparametric Kruskal-Wallis test or Wilcoxon rank sum test were used for statistical methods. Results: Shannon index [5.17 (4.53, 5.95) vs. 4.79 (3.74, 5.97)], Simpson index [0.94 (0.91, 0.96) vs. 0.92 (0.83, 0.96)] and Chao1 index [343.55 (259.76, 570.59) vs. 329.16 (268.88, 648.00)] were similar in flora of two groups, and there was no significant difference (Z=-0.791, -1.057, -0.380, all P>0.05). There was no significant difference in β-diversity between the elderly group and the young and middle-aged group (PC1=19.14%, PC2=6.95%, P_PC1=0.67, P_PC2=0.42). At the phyla level, the top 5 phyla in abundance were as follows: Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria and Fusobacteria in the young and middle-aged group, while the top 5 phyla in abundance were as follows: Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria and Actinobacteria in the elderly group; the significant difference between the two groups was Fusobacteria (Q=0.596, P<0.05). At the genus level, the top 5 genera in the young and middle-aged group in abundance were as follows: Prevotella, Bacteroides, Streptococcus, Selenomonas and Veillonella. In the elderly group, Prevotella, Bacteroides, Streptococcus, Selenomonas and Haemophilus were the top 5 in abundance, and there were significant difference in Fusobacterium between the two groups (Q=0.938, P<0.05). PICRUSt function prediction showed that the abundance of Aminoacyl.tRNA.biosynthesis, Nucleotide.excision.repair, RNA.polymerase, Ribosome, Clavulanic.acid.biosynthesis, Photosynthesis and Photosynthesis. proteins in the elderly group were lower than those in the young and middle-aged group (all Q=0.734, P<0.05). Conclusion: There is no significant difference in α-diversity and β-diversity between elderly ESCC patients and young and middle-aged patients, but the abundance of Fusobacterium flora increased.

From One- to Two-Magnon Excitations in the S=3/2 Magnet β-CaCr_{2}O_{4}

We apply neutron spectroscopy to measure the magnetic dynamics in the S=3/2 magnet β-CaCr_{2}O_{4} (T_{N}=21  K). The low-energy fluctuations, in the ordered state, resemble large-S linear spin waves from the incommensurate ground state. However, at higher energy transfers, these semiclassical and harmonic dynamics are replaced by an energy and momentum broadened continuum of excitations. Applying kinematic constraints required for energy and momentum conservation, sum rules of neutron scattering, and comparison against exact diagonalization calculations, we show that the dynamics at high-energy transfers resemble low-S one-dimensional quantum fluctuations. β-CaCr_{2}O_{4} represents an example of a magnet at the border between classical Néel and quantum phases, displaying dual characteristics.

Controlled expression of lysis gene E by a mutant of the promoter pL of the thermo-inducible λcI857-pL system

AIMS

To identify a lambda promoter pL mutant that could extend the thermal stability of the thermo-inducible λcI857-pR/pL system and to evaluate the effects of the modified system for the controlled expression of lysis gene E during the production of bacterial ghosts (BGs).

METHODS AND RESULTS

The promoter pL mutant was identified by random mutagenesis and site-directed mutagenesis. The results showed that a T → 35C mutation in the pL promoter was responsible for the phenotype alteration. Under the same induction conditions, the lysis rates of the modified lytic system on Escherichia coli and Salmonella enteritidis were significantly lower than that of the control, while the lysis rates of Escherichia coli with the thermo-inducible lytic system were significantly higher than that of S. enteritidis with the corresponding plasmid (P < 0·05).

CONCLUSIONS

Increasing the heat stability of the thermo-inducible lytic systems decreased lysis efficiency during the production of BGs. There exist differences in the lysis efficiency of thermo-inducible lytic systems between different bacterial strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings enrich current knowledge about modifications to thermo-inducible systems and provide a reference for the application of these modified systems for the production of BGs and controlled gene expression in bacteria.

The effect of Clostridium tyrobutyricum Spo0A overexpression in the intestine of mice

Clostridium tyrobutyricum shows probiotic properties and can affect the composition of gut microbiota and regulate the intestinal immune system. Compared with other probiotics, this spore-producing bacterium shows unparalleled advantages in commercial production. In addition to being resistant to extreme living environments for extended periods, its endophytic spores are implicated in inhibiting cancer cell growth. We speculated that C. tyrobutyricum spores can also promote gut health, which mean it can maintain intestinal homeostasis. To date, the beneficial effects of C. tyrobutyricum spores on gut health have not been reported. In this study, a Spo0A-overexpressing C. tyrobutyricum strain was developed to increase spore production, and its probiotic effects on the gut were assessed. Compared with the wild-type, the engineered strain showed significantly increased sporulation rates. Mice administered with the engineered strain exhibited enhanced intestinal villi and the villus height/crypt depth ratio, weight gain and improved Firmicutes/Bacteroidetes ratio to facilitate intestinal homeostasis. This study demonstrated for the first time that enhanced spore production in C. tyrobutyricum can improve intestinal homeostasis, which is advantageous for its commercial application in food and pharmaceutical industry.

MicroRNA-1271 inhibits the progression of papillary thyroid carcinoma by targeting IRS1 and inactivating AKT pathway

OBJECTIVE

The important role of microRNA-1271 (miR-1271) has been identified in human diseases and cancers. However, the biological function of miR-1271 remains ambiguous in papillary thyroid carcinoma (PTC). Therefore, the specific role of miR-1271 was investigated in PTC.

PATIENTS AND METHODS

The expressions of miR-1271 and insulin receptor substrate 1 (IRS1) were detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) assay. The protein expression of the genes was measured by Western blot analysis. The function of miR-1271 was investigated using methyl thiazolyl tetrazolium (MTT) and transwell assays. The Dual-Luciferase assay was used to observe the relationship between miR-1271 and IRS1.

RESULTS

MiR-1271 was downregulated in PTC tissues. Moreover, overexpression of miR-1271 suppressed migration, invasion and proliferation of PTC cells. Furthermore, IRS1 was indicated as a direct target gene of miR-1271 and knockdown of IRS1 inhibited cell migration, invasion and proliferation in PTC. In addition, miR-1271 inhibited the progression of PTC by targeting IRS1. Besides that, miR-1271 blocked the epithelial-mesenchymal transition (EMT) and protein kinase B (AKT) pathway in PTC.

CONCLUSIONS

MiR-1271 inhibited the progression of PTC by targeting IRS1 and blocking EMT and AKT pathway.

Prognostic gene expression signature for high-grade serous ovarian cancer

BACKGROUND

Median overall survival (OS) for women with high-grade serous ovarian cancer (HGSOC) is ∼4 years, yet survival varies widely between patients. There are no well-established, gene expression signatures associated with prognosis. The aim of this study was to develop a robust prognostic signature for OS in patients with HGSOC.

PATIENTS AND METHODS

Expression of 513 genes, selected from a meta-analysis of 1455 tumours and other candidates, was measured using NanoString technology from formalin-fixed paraffin-embedded tumour tissue collected from 3769 women with HGSOC from multiple studies. Elastic net regularization for survival analysis was applied to develop a prognostic model for 5-year OS, trained on 2702 tumours from 15 studies and evaluated on an independent set of 1067 tumours from six studies.

RESULTS

Expression levels of 276 genes were associated with OS (false discovery rate < 0.05) in covariate-adjusted single-gene analyses. The top five genes were TAP1, ZFHX4, CXCL9, FBN1 and PTGER3 (P < 0.001). The best performing prognostic signature included 101 genes enriched in pathways with treatment implications. Each gain of one standard deviation in the gene expression score conferred a greater than twofold increase in risk of death [hazard ratio (HR) 2.35, 95% confidence interval (CI) 2.02-2.71; P < 0.001]. Median survival [HR (95% CI)] by gene expression score quintile was 9.5 (8.3 to -), 5.4 (4.6-7.0), 3.8 (3.3-4.6), 3.2 (2.9-3.7) and 2.3 (2.1-2.6) years.

CONCLUSION

The OTTA-SPOT (Ovarian Tumor Tissue Analysis consortium - Stratified Prognosis of Ovarian Tumours) gene expression signature may improve risk stratification in clinical trials by identifying patients who are least likely to achieve 5-year survival. The identified novel genes associated with the outcome may also yield opportunities for the development of targeted therapeutic approaches.

The effectiveness and safety of thromboprophylaxis in cancer patients based on Khorana score: a meta-analysis and systematic review of randomized controlled trials

INTRODUCTION

Cancer patients receiving chemotherapy are a high risk of VTE, yet the importance of thromboprophylaxis for cancer patients that are at high risk of developing VTE is still controversial.

AIM

To calculate the benefits and harms of thromboprophylaxis, compared to placebo, in ambulatory high-risk cancer patients that are receiving chemotherapy.

METHODS

We searched PubMed, Embase, Web of Science, the Cochrane Library, Cochrane Central Register of Controlled Trials, Chinese Biomedical Literature Database, WANFANG Data, Chinese National Knowledge Infrastructure and Chinese Scientific Journal Database for randomized controlled trials (RCTs) describing benefits and harms of thromboprophylaxis. Statistical analysis was performed using Stata software (version 15.1).

RESULTS

We included six studies, which contained a total of 3240 cancer patients with thromboprophylaxis and 2874 cancer patients without thromboprophylaxis. Thromboprophylaxis was effective in high-risk patients with two points or higher (RR 0.51, 95% CI 0.36-0.71, I² = 0.0%, P = 0.526). It was associated with an increase in bleeding events (RR 1.65, 95% CI 1.14-2.40, I² = 0.0%, P = 0.498) and was mainly efficient in reducing the risk of pulmonary embolism (RR 0.56, 95% CI 0.33-0.96, I² = 0.0%, P = 0.263). The risk of major (RR 1.85, 95% CI 0.87-3.94, I² = 0.0%, P = 0.888) and non-major (RR 1.59, 95% CI 0.96-2.62, I² = 16.3%, P = 0.303) bleeding showed no significant difference with or without thromboprophylaxis. There was no reduction in all-cause mortality with thromboprophylaxis (RR 0.95, 95% CI 0.78-1.18, I² = 22.0%, P = 0.277).

CONCLUSION

Thromoboprophylaxis is effective and safe in cancer patients that are at high risk for developing VTE with chemotherapy.