Virus shedding dynamics in asymptomatic and mildly symptomatic patients infected with SARS-CoV-2.

OBJECTIVES: Asymptomatic patients, together with those with mild symptoms of coronavirus disease 2019 (COVID-19), may play an important role in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission. However, the dynamics of virus shedding during the various phases of the clinical course of COVID-19 remains unclear at this stage. METHODS: A total of 18 patients found to be positive for SARS-CoV-2 infection by real-time reverse transcription PCR (RT-PCR) assay and admitted to Chongqing University Central Hospital between 29 January and 5 February 2020 were enrolled into this study. Medical data, pulmonary computed tomographic (CT) scan images and RT-PCR results were periodically collected during the patients' hospital stay. All participants were actively followed up for 2 weeks after discharge. RESULTS: A total of nine (50%) asymptomatic patients and nine (50%) patients with mild symptoms of COVID-19 were identified at admission. Six patients (66.7%) who were asymptomatic at admission developed subjective symptoms during hospitalization and were recategorized as being presymptomatic. The median duration of virus shedding was 11.5, 28 and 31 days for presymptomatic, asymptomatic and mildly symptomatic patients, separately. Seven patients (38.9%) continued to shed virus after hospital discharge. During the convalescent phase, detectable antibodies to SARS-CoV-2 and RNA were simultaneously observed in five patients (27.8%). CONCLUSIONS: Long-term virus shedding was documented in patients with mild symptoms and in asymptomatic patients. Specific antibody production to SARS-CoV-2 may not guarantee virus clearance after discharge. These observations should be considered when making decisions regarding clinical and public health, and when considering strategies for the prevention and control of SARS-CoV-2 infection.

Study on the relationship between miR-520g and the development of breast cancer.

OBJECTIVE: Breast cancer (BC) is one of the most common malignant tumors occurred in women. There is no sensitive and specific marker for early diagnosis, treatment and prognosis of breast cancer. It is suggested that miRNA may be a potential tumor marker for breast cancer. Mir-520g is considered to be associated with many tumors. This study aims to test the expression of mir-520g in peripheral blood of BC patients and healthy control. We also explored the relationship between mir-520g and several prognostic factors in breast cancer patients. PATIENTS AND METHODS: The peripheral blood of 86 cases with breast cancer (including 18 cases with stage 0, 24 cases of phase I, 20 cases of stage II, 24 cases of stage III) and 26 cases of healthy subjects were collected. The miR-520g level was measured by real-time quantitative PCR (RT qPCR) method. The correlation between plasma miR-520g level and the clinical stage, molecular subtype, receptors' expression and other factors related to the prognosis of the patients were examined. RESULTS: Plasma mir-520g expression levels were significantly higher in BC patients with lymph node metastatic and low differentiation degree grade (p = 0.033 and 0.016), and plasma miR-520g expression was significantly higher in breast cancer patients with mammary gland invasion (p < 0.01) and low expressed p53 (p = 0.0039). CONCLUSIONS: Highly expressed mir-520g is associated with lymph node metastasis and low differentiation of breast cancer, and also is associated with mammary gland invasion in breast cancer. This study suggests that mir-520g may be associated with some important prognostic factors in breast cancer patients, and may have a potential value for breast cancer marker.

Expression analysis of miRNA and target mRNAs in esophageal cancer

We aimed to investigate miRNAs and related mRNAs through a network-based approach in order to learn the crucial role that they play in the biological processes of esophageal cancer. Esophageal squamous-cell carcinoma (ESCC) and adenocarcinoma (EAC)-related miRNA and gene expression data were downloaded from the Gene Expression Omnibus database, and differentially expressed miRNAs and genes were selected. Target genes of differentially expressed miRNAs were predicted and their regulatory networks were constructed. Differentially expressed miRNA analysis selected four miRNAs associated with EAC and ESCC, among which hsa-miR-21 and hsa-miR-202 were shared by both diseases. hsa-miR-202 was reported for the first time to be associated with esophageal cancer in the present study. Differentially expressed miRNA target genes were mainly involved in cancer-related and signal-transduction pathways. Functional categories of these target genes were related to transcriptional regulation. The results may indicate potential target miRNAs and genes for future investigations of esophageal cancer.

Observation of Multi-TeV Gamma Rays from the Crab Nebula using the Tibet Air Shower Array.

The Tibet experiment, operating at Yangbajing (4300 m above sea level), is the lowest energy air shower array, and the new high-density array constructed in 1996 is sensitive to gamma-ray air showers at energies as low as 3 TeV. With this new array, the Crab Nebula was observed in multi-TeV gamma-rays and a signal was detected at the 5.5 sigma level. We also obtained the energy spectrum of gamma-rays in the energy region above 3 TeV which partially overlaps those observed with imaging atmospheric Cerenkov telescopes. The Crab spectrum observed in this energy region can be represented by the power-law fit dJ&parl0;E&parr0;&solm0;dE=&parl0;4.61+/-0.90&parr0;x10-12&parl0;E&solm0;3 TeV&parr0;-2.62+/-0.17 cm-2 s-1 TeV-1. This is the first observation of gamma-ray signals from point sources with a conventional air shower array using scintillation detectors.