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result(s) for
"Tan, Yun"
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Microglial regional heterogeneity and its role in the brain
2020
Microglia have been recently shown to manifest a very interesting phenotypical heterogeneity across different regions in the mammalian central nervous system (CNS). However, the underlying mechanism and functional meaning of this phenomenon are currently unclear. Baseline diversities of adult microglia in their cell number, cellular and subcellular structures, molecular signature as well as relevant functions have been discovered. But recent transcriptomic studies using bulk RNAseq and single-cell RNAseq have produced conflicting results on region-specific signatures of microglia. It is highly speculative whether such spatial heterogeneity contributes to varying sensitivities of individual microglia to the same physiological and pathological signals in different CNS regions, and hence underlie their functional relevance for CNS disease development. This review aims to thoroughly summarize up-to-date knowledge on this specific topic and provide some insights on the potential underlying mechanisms, starting from microgliogenesis. Understanding regional heterogeneity of microglia in the context of their diverse neighboring neurons and other glia may provide an important clue for future development of innovative therapies for neuropsychiatric disorders.
Journal Article
Viral and host factors related to the clinical outcome of COVID-19
2020
In December 2019, coronavirus disease 2019 (COVID-19), which is caused by the new coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in Wuhan (Hubei province, China)
1
; it soon spread across the world. In this ongoing pandemic, public health concerns and the urgent need for effective therapeutic measures require a deep understanding of the epidemiology, transmissibility and pathogenesis of COVID-19. Here we analysed clinical, molecular and immunological data from 326 patients with confirmed SARS-CoV-2 infection in Shanghai. The genomic sequences of SARS-CoV-2, assembled from 112 high-quality samples together with sequences in the Global Initiative on Sharing All Influenza Data (GISAID) dataset, showed a stable evolution and suggested that there were two major lineages with differential exposure history during the early phase of the outbreak in Wuhan. Nevertheless, they exhibited similar virulence and clinical outcomes. Lymphocytopenia, especially reduced CD4
+
and CD8
+
T cell counts upon hospital admission, was predictive of disease progression. High levels of interleukin (IL)-6 and IL-8 during treatment were observed in patients with severe or critical disease and correlated with decreased lymphocyte count. The determinants of disease severity seemed to stem mostly from host factors such as age and lymphocytopenia (and its associated cytokine storm), whereas viral genetic variation did not significantly affect outcomes.
Genome sequences from 112 patients with confirmed SARS-CoV-2 infection showed two clades of SARS-CoV-2 virus with similar virulence and clinical outcome, and clinical data from 326 cases suggest that T cell depletion and cytokine bursts are associated with a worse prognosis.
Journal Article
Experimental and numerical simulation of loading rate effects on failure and strain energy characteristics of coal-rock composite samples
2021
The deformation and failure of coal and rock is energy-driving results according to thermodynamics. It is important to study the strain energy characteristics of coal-rock composite samples to better understand the deformation and failure mechanism of of coal-rock composite structures. In this research, laboratory tests and numerical simulation of uniaxial compressions of coal-rock composite samples were carried out with five different loading rates. The test results show that strength, deformation, acoustic emission (AE) and energy evolution of coal-rock composite sample all have obvious loading rate effects. The uniaxial compressive strength and elastic modulus increase with the increase of loading rate. And with the increase of loading rate, the AE energy at the peak strength of coal-rock composites increases first, then decreases, and then increases. With the increase of loading rate, the AE cumulative count first decreases and then increases. And the total absorption energy and dissipation energy of coal-rock composite samples show non-linear increasing trends, while release elastic strain energy increases first and then decreases. The laboratory experiments conducted on coal-rock composite samples were simulated numerically using the particle flow code (PFC). With careful selection of suitable material constitutive models for coal and rock, and accurate estimation and calibration of mechanical parameters of coal-rock composite sample, it was possible to obtain a good agreement between the laboratory experimental and numerical results. This research can provide references for understanding failure of underground coal-rock composite structure by using energy related measuring methods.
Journal Article
miR-125b-5p functions as a tumor suppressor gene partially by regulating HMGA2 in esophageal squamous cell carcinoma
by
Bai, Jie
,
Shi, Zhi-Zhou
,
Wang, Wen-Jun
in
Biology and Life Sciences
,
Breast cancer
,
Cancer genetics
2017
MicroRNAs (miRNAs) play important roles in the progression of human cancer including esophageal squamous cell carcinoma (ESCC). Although previous reports showed that miR-125b-5p was down-regulated in ESCC, the roles and mechanisms of loss of function of miR-125b-5p in ESCC were still unknown. Using microRNA microarray and GEO datasets, we found and confirmed that miR-125b-5p was down-regulated in ESCC tissues. In-vitro assays showed that ectopic miR-125b-5p expression repressed cell proliferation, migration and invasion, and induced cell senescence. We also found that miR-125b-5p reduced the expressions of cell cycle regulatory genes including CCNA2, CCND1 and CCNE1, and regulated the markers of epithelial to mesenchymal transition (EMT) including E-cadherin, N-cadherin and EMT associated transcription factor Slug, and also decreased the MMPs including MMP2, MMP7 and MMP13. Furthermore, the candidate target gene HMGA2 was negatively regulated by miR-125b-5p both in mRNA and protein levels. Importantly, knockdown of HMGA2 partially phenocopied the effects of miR-125b-5p overexpression on cell cycle regulators and EMT markers. In conclusion, our results suggested that overexpression of miR-125b-5p inhibited cell proliferation, migration and invasion partially by down-regulating HMGA2 in ESCC.
Journal Article
Ferroptosis in Carcinoma: Regulatory Mechanisms and New Method for Cancer Therapy
2019
Ferroptosis is a new form of programmed cell death with characteristic accumulation of reactive oxygen species (ROS) resulting from iron accumulation and lipid peroxidation. Ferroptosis is involved in many diseases, including cancer, and induction of ferroptosis has shown attractive antitumour activities. In this review, we summarize recent findings on the regulatory mechanisms of key regulators of ferroptosis, including the catalytic subunit solute carrier family 7 member 11 (SLC7A11), the glutathione peroxidase 4 (GPX4), p53 and non-coding RNAs, the correlations between ferroptosis and iron homeostasis or autophagy, ferroptosis-inducing agents and nanomaterials and the diagnostic and prognostic value of ferroptosis-associated genes in TCGA data.
Journal Article
Copper(I)-catalyzed diastereo- and enantio-selective construction of optically pure exocyclic allenes
2020
Among about 150 identified allenic natural products, the exocyclic allenes constitute a major subclass. Substantial efforts are devoted to the construction of axially chiral allenes, however, the strategies to prepare chiral exocyclic allenes are still rare. Herein, we show an efficient strategy for the asymmetric synthesis of chiral exocyclic allenes with the simultaneous control of axial and central chirality through copper(I)-catalyzed asymmetric intramolecular reductive coupling of 1,3-enynes to cyclohexadienones. This tandem reaction exhibits good functional group compatibility and the corresponding optically pure exocyclic allenes bearing
cis
-hydrobenzofuran,
cis
-hydroindole, and
cis
-hydroindene frameworks, are obtained with high yields (up to 99% yield), excellent diastereoselectivities (generally >20:1 dr) and enantioselectivities (mostly >99% ee). Furthermore, a gram-scale experiment and several synthetic transformations of the chiral exocyclic allenes are also presented.
Substantial efforts have been devoted to the construction of axially chiral allenes, however, the strategies to prepare chiral exocyclic allenes are still rare. This work describes a copper-catalyzed asymmetric synthesis of exocyclic allenes by simultaneous control of axial and central chirality.
Journal Article
Protein kinases PknA and PknB independently and coordinately regulate essential Mycobacterium tuberculosis physiologies and antimicrobial susceptibility
2020
The Mycobacterium tuberculosis Ser/Thr protein kinases PknA and PknB are essential for growth and have been proposed as possible drug targets. We used a titratable conditional depletion system to investigate the functions of these kinases. Depletion of PknA or PknB or both kinases resulted in growth arrest, shortening of cells, and time-dependent loss of acid-fast staining with a concomitant decrease in mycolate synthesis and accumulation of trehalose monomycolate. Depletion of PknA and/or PknB resulted in markedly increased susceptibility to β-lactam antibiotics, and to the key tuberculosis drug rifampin. Phosphoproteomic analysis showed extensive changes in protein phosphorylation in response to PknA depletion and comparatively fewer changes with PknB depletion. These results identify candidate substrates of each kinase and suggest specific and coordinate roles for PknA and PknB in regulating multiple essential physiologies. These findings support these kinases as targets for new antituberculosis drugs and provide a valuable resource for targeted investigation of mechanisms by which protein phosphorylation regulates pathways required for growth and virulence in M. tuberculosis.
Journal Article
Choroid Plexus Enlargement and Allostatic Load in Schizophrenia
2020
Although schizophrenia is a brain disorder, increasing evidence suggests that there may be body-wide involvement in this illness. However, direct evidence of brain structures involved in the presumed peripheral-central interaction in schizophrenia is still unclear. Seventy-nine previously treatment-naïve first-episode schizophrenia patients who were within 2-week antipsychotics initial stabilization, and 41 age- and sex-matched healthy controls were enrolled in the study. Group differences in subcortical brain regional structures measured by MRI and the subclinical cardiovascular, metabolic, immune, and neuroendocrine biomarkers as indexed by allostatic load, and their associations were explored. Compared with controls, patients with schizophrenia had significantly higher allostatic load (P = .001). Lateral ventricle (P < .001), choroid plexus (P < .001), and thalamus volumes (P < .001) were significantly larger, whereas amygdala volume (P = .001) was significantly smaller in patients. The choroid plexus alone was significantly correlated with higher allostatic load after age, sex, education level, and the total intracranial volume were taken into account (t = 3.60, P < .001). Allostatic load was also significantly correlated with PANSS positive (r = 0.28, P = .016) and negative (r = −0.31, P = .008) symptoms, but in opposite directions. The peripheral multisystemic and central nervous system abnormalities in schizophrenia may interact through the choroid plexus during the early stage of the illness. The choroid plexus might provide a sensitive structural biomarker to study the treatment and prevention of brain-periphery interaction abnormalities in schizophrenia.
Journal Article
Periprotein lipidomes of Saccharomyces cerevisiae provide a flexible environment for conformational changes of membrane proteins
by
Sikkema, Hendrik R
,
Jeucken, Aike
,
Moody, Branch
in
Biochemistry and Chemical Biology
,
Cell Membrane - metabolism
,
Chromatography
2020
Yeast tolerates a low pH and high solvent concentrations. The permeability of the plasma membrane (PM) for small molecules is low and lateral diffusion of proteins is slow. These findings suggest a high degree of lipid order, which raises the question of how membrane proteins function in such an environment. The yeast PM is segregated into the Micro-Compartment-of-Can1 (MCC) and Pma1 (MCP), which have different lipid compositions. We extracted proteins from these microdomains via stoichiometric capture of lipids and proteins in styrene-maleic-acid-lipid-particles (SMALPs). We purified SMALP-lipid-protein complexes by chromatography and quantitatively analyzed periprotein lipids located within the diameter defined by one SMALP. Phospholipid and sterol concentrations are similar for MCC and MCP, but sphingolipids are enriched in MCP. Ergosterol is depleted from this periprotein lipidome, whereas phosphatidylserine is enriched relative to the bulk of the plasma membrane. Direct detection of PM lipids in the 'periprotein space' supports the conclusion that proteins function in the presence of a locally disordered lipid state.
Journal Article
Mechanical and energy characteristics of coal–rock composite sample with different height ratios: a numerical study based on particle flow code
2021
To explore the differences in mechanical and energy evolution characteristics of coal–rock composite samples with different coal–rock height ratios, uniaxial compression tests of coal–rock composite samples with height ratios ranging from 4:1 to 1:4 were conducted by PFC software. A total of 7 PFC models were built and calculated. Results show that the smaller coal–rock height ratios lead to the higher elastic modulus and higher peak strength, both following exponential relationships with coal–rock height ratios, while the peak strain decreases linearly with the decrease of coal–rock height ratios. When the coal–rock height ratios decrease from 4:1 to 1:3, the fragmentation degree of coal body decreases gradually, and the failure modes are mainly of “V” type. And when the ratio is reduced to 1:4, failure mode is no longer of “V” type, the degree of coal body breaking becomes larger, and the part of rock body in the composites is also damaged. With the decrease of coal–rock height ratios, number of acoustic emission events of the composites increase first and then decrease. And U, Ue and Ud at different coal–rock height ratios exhibited similar trends, all of which increase slowly first, fast afterwards and very sharply at the peak stress points. At the peak stress point, the values of total input energy (UA) and dissipative energy (UAd) decrease firstly then increase as the coal-rock height ratios decreases and the value of elastic strain energy (UAe) decrease as coal-rock height ratios decreases. While the decrease of both UA and UAd are larger than UAe. These results can provide a useful reference for safe and efficient exploitation of coal resources.
Journal Article