Biology subjects

Si, H.

Publications and source records attributed to Si, H..

22 records · Page 2Linked to original sources

bioRxiv2020

Cdc42 is required for lymphatic branching, maturation and valve formation during embryonic development

Cdc42, a Ras-related GTPase that regulates the actin cytoskeleton, was recently shown to play an indispensable role in vasculogenesis and endothelial cell (EC) survival. Here, we determined whether Cdc42 also contributes to lymphatic development by generated two different Cdc42 knockout mice lines by crossing Cdc42/flox mice with either vascular endothelial cadherin-Cre (Cdh5-Cre) mice or Prox1-CreERT2 mice. Our results demonstrated that depleting ECs of Cdc42 expression resulted in embryonic lethality with severe edema. Whole-mount immunofluorescence staining of both knockout embryos showed that the deletion of Cdc42 in ECs impaired lymphatic vessel branching and that the lymphatic lumen size significantly increased. Moreover, we found that the inactivation of Cdc42 compromised mesenteric collecting lymphatic vessel maturation and prevented valve formation. We go on to show that Cdc42 can be activated by vascular endothelial growth factor c (VEGFc) in cultured human dermal lymphatic ECs (HDLECs), and that knocking down Cdc42 expression in these cells using siRNA decreased VEGFc-induced focal adhesion kinase (FAK) phosphorylation. These findings, when taken together with the fact that inactivating FAK plus one allele of Cdc42 in ECs was sufficient to recapitulate the phenotypes of the Cdc42 EC knockout embryos, suggests that Cdc42 and FAK interact genetically during lymphatic development. In addition, Cdc42 and FAK regulated signal transduction is essential for blood and lymphatic vessel separation. Taken together, our data highlights the important role played by Cdc42 in the development of the lymphatic system.

developmental biology↗

bioRxiv2019

Heterologous expression of Stlac2, a laccase isozyme of Setosphearia turcica, and the ability of decolorization of malachite green

Laccases can catalyze monoelectronic oxidation and have shown to have an increasing value in industrial application. In this study, as identified by Native-PAGE and ESI-MS/MS, ascomycetous fungus Setosphaeria turcica produced three laccase isozymes: Stlac1, Stlac2, and Stlac6. Stlac2 was heterologously expressed in both eukaryotic and prokaryotic expression systems. The eukaryotic recombinant Stlac2 expressed in Pichia pastoris was inactive, and also showed a higher molecular weight than predicted because of glycosylation. The depression of laccase activity was attributable to the incorrect glycosylation at Asn97. Stlac2 expressed in Escherichia coli and after being renaturated from the inclusion body, the recombinant Stlac2 exhibited activity of 28.23 U/mg with 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as the substrate. The highest activity was observed at pH of 4.5 and the temperature of 60 {degrees}C. The activity of recombinant Stlac2 was inhibited by 10 mM Na+, Mg2+, Ca2+, Mn2+, and increased by 10 mM of Fe3+ with a relatively activity of 315% compared with no addition. Cu2+ did not affect enzyme activity. Recombinant Stlac2 was capable of decolorizing 67.08% of 20 mg/L malachite green in 15 min without any mediators. It is suggested that Stlac2 has potential industrial applications. ImportanceSetosphaeria turcica, an ascomycetous fungus causes northern corn leaf blight, product three laccase isozymes identified by Native-PAGE and ESI-MS/MS. The major expression laccase gene StLAC2 was expression in both eukaryotic and prokaryotic expression systems, which found incorrect glycosylation at Asn97 may result in the depression of laccase activity. The heterologous laccase Stlac2 decolorize organic dye malachite green, which had a potential industrial application.

bioengineering↗

bioRxiv2018

Antibacterial activity of total flavonoids from Ilex rotunda Thunb. and different antibacterials on different multidrug-resistant bacteria alone or in combination

The problem of bacterial resistance is becoming more and more serious, which has become an urgent problem to be solved in human and veterinary. One approach to control and delay bacterial resistance is combination therapy in which antibiotics are given together with other antimicrobial or non-antimicrobial agents. Studies have shown that flavonoids from Traditional Chinese medicine (TCM) possess a high level of antibacterial activity against antibiotic resistant strains. The aim of this study was to evaluate the antibacterial effects of a combined therapy of total flavonoids from Ilex rotunda Thunb. and antibiotics against seven kinds of veterinary bacteria which were multidrug resistance bacteria. A microdilution checkerboard method was used to determine the minimal inhibitory concentrations of both types of antimicrobials, alone and in combination. The fractional inhibitory concentration index was calculated and used to classify observed collective antibacterial activity as synergistic, additive, indifferent or antagonistic.\n\nFrom the performed tests, the total flavonoids and antimicrobial agents were combined to inhibit different multidrug-resistant bacteria, such as Escherichia coli, Streptococcus, Pseudomonas aeruginosa, Enterococcus faecalis, Proteus vulgaris, Staphylococcus aureus, Acinetobacter baumannii. For these bacteria, total flavonoids from Ilex Rotunda Thunb. presented synergistic or additive with different antibiotics and had a certain antibacterial effect on the separated multidrug-resistant bacteria. The study shows total flavonoids from Ilex rotunda Thunb. have potential as adjuvants for the treatment of animal bacterial diseases.

microbiology↗

bioRxiv2018

Lead-DBS v2: Toward a comprehensive pipeline for deep brain stimulation imaging

Deep brain stimulation (DBS) is a highly efficacious treatment option for movement disorders and a growing number of other indications are investigated in clinical trials. To ensure optimal treatment outcome, exact electrode placement is required. Moreover, to analyze the relationship between electrode location and clinical results, a precise reconstruction of electrode placement is required, posing specific challenges to the field of neuroimaging. Since 2014 the open source toolbox Lead-DBS is available, which aims at facilitating this process. The tool has since become a popular platform for DBS imaging. With support of a broad community of researchers worldwide, methods have been continuously updated and complemented by new tools for tasks such as multispectral nonlinear registration, structural / functional connectivity analyses, brain shift correction, reconstruction of microelectrode recordings and orientation detection of segmented DBS leads. The rapid development and emergence of these methods in DBS data analysis require us to revisit and revise the pipelines introduced in the original methods publication. Here we demonstrate the updated DBS and connectome pipelines of Lead-DBS using a single patient example with state-of-the-art high-field imaging as well as a retrospective cohort of patients scanned in a typical clinical setting at 1.5T. Imaging data of the 3T example patient is co-registered using five algorithms and nonlinearly warped into template space using ten approaches for comparative purposes. After reconstruction of DBS electrodes (which is possible using three methods and a specific refinement tool), the volume of tissue activated is calculated for two DBS settings using four distinct models and various parameters. Finally, four whole-brain tractography algorithms are applied to the patients preoperative diffusion MRI data and structural as well as functional connectivity between the stimulation volume and other brain areas are estimated using a total of eight approaches and datasets. In addition, we demonstrate impact of selected preprocessing strategies on the retrospective sample of 51 PD patients. We compare the amount of variance in clinical improvement that can be explained by the computer model depending on the method of choice.\n\nThis work represents a multi-institutional collaborative effort to develop a comprehensive, open source pipeline for DBS imaging and connectomics, which has already empowered several studies, and may facilitate a variety of future studies in the field.

neuroscience↗