Biology subjects

Sun, K.

Publications and source records attributed to Sun, K..

5 recordsLinked to original sources

bioRxiv2018

Transient Overexpression of VEGF-A in Adipose Tissue Promotes Energy Expenditure via Activation of the Sympathetic Nervous System

Adipose-derived VEGF-A stimulates functional blood vessel formation in obese fat pads which in turn facilitates healthy expansion of the adipose tissue. However, the detailed mechanism(s) governing the process remains largely unknown. Here, we investigated the role of sympathetic nervous system activation in the process. To this end, we induced overexpression of VEGF-A in an adipose-specific doxycycline (Dox)-inducible transgenic mouse model for a short period of time during high fat-diet (HFD) feeding. We found that local overexpression of VEGF-A in adipose tissue stimulated lipolysis and browning rapidly after Dox induction. Immunofluorescent staining against tyrosine hydroxylase (TH) indicated higher levels of sympathetic innervation in adipose tissue of transgenic mice. In response to the increased norepinephrine (NE) level, expression of {beta}3-andrenoceptor was significantly upregulated and the downstream protein kinase A (PKA) pathway was activated, as indicated by the enhanced phosphorylation of the whole PKA substrates, in particular the hormone sensitive lipase (HSL) in adipocytes. As the result, the adipose tissue exhibited increased lipolysis, browning, and energy expenditure. Importantly, all these effects were abolished upon the treatment with {beta}3-adrenoceptor antagonist SR59230A. Collectively, these results demonstrate that transient overexpressed VEGF-A activates sympathetic nervous system which hence promotes lipolysis and browning in adipose tissue.

physiology↗

bioRxiv2018

Impact of exogenous nitrogen on cyanobacterial abundance and community in oil-contaminated sediment mesocosms

High concentrations of crude oil are toxic to cyanobacteria but can facilitate the emergence of cyanobacterial aggregation at an appropriate concentration range; however, the exact inducing factor has never been clearly elucidated. We hypothesized that increasing exposure to elevated concentrations of nitrogen would inhibit the accumulation of cyanobacteria in oil-contaminated sediments. To test this hypothesis, we simulated an oil spill in estuarine sediment microcosms with and without the removal of nitrogen limitation by supplementation of exogenous nitrogen. An integrated MiSeq sequencing of 16S rRNA gene analysis along with metatranscriptome sequence was performed to achieve a comprehensive study of cyanobacterial blooms. The number of cyanobacterial sequences increased over time in both oil-contaminated and non-oil-contaminated sediments at different time points after 42 days of incubation. And, supplementation with a nitrogen resource could accelerate cyanobacterial blooms under uncontaminated microcosms but delay the bloom phenomenon and reduce the cyanobacterial abundance to a great degree when exposed to oil. Our results clearly illustrated that nitrogen limitation was a vital driver of the increased abundance of cyanobacteria in oil-contaminated mesocosms. In addition, the abundance and compositions of blooming cyanobacteria varied significantly among the different treatment groups, and Oscillatoria may play a potential and non-negligible role in oil-contaminated mesocosms.

microbiology↗

bioRxiv2018

Quantifying the risk of local Zika virus transmission in the continental US during the 2015-2016 ZIKV epidemic

BackgroundLocal mosquito-borne Zika virus (ZIKV) transmission has been reported in two counties of the continental United State (US), prompting the issuance of travel, prevention, and testing guidance across the continental US. Large uncertainty, however, surrounds the quantification of the actual risk of ZIKV introduction and autochthonous transmission across different areas of the US.\n\nMethodWe present a framework for the projection of ZIKV autochthonous transmission in the continental US during the 2015-2016 epidemic, using a data-driven stochastic and spatial epidemic model accounting for seasonal, environmental and detailed population data. The model generates an ensemble of travel-related case counts and simulate their potential to trigger local transmission at individual level.\n\nResultsWe estimate the risk of ZIKV introduction and local transmission at the county level and at the 0.025{degrees} x 0.025{degrees} cell level across the continental US. We provide a risk measure based on the probability of observing local transmission in a specific location during a ZIKV epidemic modeled after the one observed during the years 2015-2016. The high spatial and temporal resolutions of the model allow us to generate statistical estimates of the number of ZIKV introductions leading to local transmission in each location. We find that the risk is spatially heterogeneously distributed and concentrated in a few specific areas that account for less than 1% of the continental US population. Locations in Texas and Florida that have actually experienced local ZIKV transmission are among the places at highest risk according to our results. We also provide an analysis of the key determinants for local transmission, and identify the key introduction routes and their contributions to ZIKV spread in the continental US.\n\nConclusionsThis framework provides quantitative risk estimates, fully captures the stochas-ticity of ZIKV introduction events, and is not biased by the under-ascertainment of cases due to asymptomatic infections. It provides general information on key risk determinants and data with potential uses in defining public health recommendations and guidance about ZIKV risk in the US.

epidemiology↗

bioRxiv2018

A compromised gsdf signaling leads to gamatogenesis confusion and subfertility in medaka

Summary statementGsdf signals trigger the gamatogenesis, alter the somatic expression of Fsh/Lh receptors and brain type aromatase in medaka brain and gonad.\n\nAbstractGonadal soma-derived factor (gsdf) and anti-Mullerian hormone (amh) are somatic male determinants in several species of teleosts, although the mechanisms by which they trigger the indifferent germ cells into the male pathway remain unknown. This study aimed to decipher the roles of gsdf/amh in directing the sexual fate of germ cells using medaka as a model. Transgenic lines (TgcryG) that restrictively and persistently express a Gsdf-Gfp fusion protein in the lens and the hypothalamus-pituitary-gonad (HPG) axis, were generated under the control of a mouse {gamma}F-crystallin promoter. A high frequency (44.4%) of XX male sex reversals was obtained in TgcryG lines, indicating that signals of gsdf-expressing cells in HPG were enough for the spermatogenesis activation in the genetic females. Furthermore, all TgcryG XY individuals with endogenous gsdf depletion (named Sissy) displayed intersex (100%) with enlarged ovotestis in contrast to a giant ovary developed in XY gsdf deficiency. The heterogeneous expression of gsdf led to the confusion of gamatogenesis and ovotestis development, similar to some hotei (amhr2) mutants, suggests that the signaling balance of gsdf/amh is essential for proper gamatogenesis, maintaining sex steroid production and gonadotropin secretion, which are evolutionarily conserved across phyla.

evolutionary biology↗

bioRxiv2017

Preliminary results of models to predict areas in the Americas with increased likelihood of Zika virus transmission in 2017.

Numerous Zika virus vaccines are being developed. However, identifying sites to evaluate the efficacy of a Zika virus vaccine is challenging due to the general decrease in Zika virus activity. We compare results from three different modeling approaches to estimate areas that may have increased relative risk of Zika virus transmission during 2017. The analysis focused on eight priority countries (i.e., Brazil, Colombia, Costa Rica, Dominican Republic, Ecuador, Mexico, Panama, and Peru). The models projected low incidence rates during 2017 for all locations in the priority countries but identified several subnational areas that may have increased relative risk of Zika virus transmission in 2017. Given the projected low incidence of disease, the total number of participants, number of study sites, or duration of study follow-up may need to be increased to meet the efficacy study endpoints.

epidemiology↗