Objective:To compare the differences between suspension and adherent cells of MDCK cell line in the isolation of influenza virus, and to explore the application prospects of MDCK cell suspension.Methods:Determination of viable cell density and cell specific growth rate were recorded by cell count. The WHO recommended vaccine strains were used for virus infection experiments. After five passages, hemagglutination titers were detected, while the sequencing analysis of their HA and NA genes revealed the mutation frequency.Results:The 24-hour and 48-hour viable cell density of the cell suspension was more stable than that of adherent cells. The cell suspension achieved an HA titer of 1∶256 or higher in the third generation, while adherent cells had no titer. In the fourth and fifth generations, one amino acid site mutation was found in the HA gene of H3N2 and BV subtypes of influenza virus cultured in the cell suspension, while no gene mutation was found in adherent cells in two passages. There were no mutations in the whole NA gene.Conclusions:Suspension of MDCK cells have more stable growth and higher efficiency in virus isolation than adherent cells, meanwhile there was a low rate of virus mutation during continuous passage. This study demonstrated the feasibility of this suspension of MDCK cells for influenza vaccine production based on cell culture technology.

Objective:To analyze the genetic and molecular characteristics of H9N2 subtype avian influenza viruses from external environment and humans in Anhui Province from 2013 to 2022.Methods:Environmental samples and human samples were collected from Anhui influenza surveillance network laboratory. Sixty-three strains of virus were isolated in chicken embryos. RT-PCR was used to amplify the virus and whole genome sequencing was performed. To construct gene evolutionary tree and analyze its genetic characteristics and potential glycosylation sites.Results:The hemagglutinin (HA) gene belongs to the 9.2.4.5 clade, and the protein cleavage sites are mostly " PSRSSR\GL". The neuraminidase (NA) gene, basic protein-1(PB1) gene, acidic protein (PA) gene, non-structural protein (NS) gene and nucleoprotein (NP) gene belong to the F/98 clade, the matrix protein (MP) gene belongs to the G1/97 clade, and the basic protein-2 (PB2) gene belongs to the ST/7488 clade. Mutations of T155N, R164Q, H183N, T189D/V, A190V/T and Q226L occurred in HA protein, deletion of NA protein occurred at 62-64 sites, and mutations of T271A, I292V/M and E627V/L occurred in PB2 protein. At the same time, mutations of K356R and S409N occurred in the PA protein.Conclusions:The H9N2 subtype avian influenza viruses collected from external environment and human sources in Anhui province from 2013 to 2022 belong to the same evolutionary branch, and amino acid site mutations suggest that the virus shows a tendency to gradually adapt to the mammalian host environment. Therefore, further studies on the adaptive evolution of the virus and related monitoring work are needed.

Objective:To prepare a phase-change lipid nanoparticle modified by tumor homing membrane-penetrating peptide (tLyP-1) and carrying paclitaxel (PTX) engineered by metal polyphenol network (TA-Fe 3+ ), and evaluate the therapeutic effects of tumor targeting, ultrasound/photoacoustic imaging and photothermal combined chemotherapy in vitro. Methods:Phase-change lipid nanoparticles (t-P@TFP) with TA-Fe 3+ engineered PTX mediated by tLyP-1 were prepared by solvent replacement method, thin film hydration method and double emulsification method. Its detection and characterization, in vitro targeting ability, photothermal conversion ability, in vitro photoacoustic and ultrasonic imaging ability, CCK-8 method, cell live and death double staining method and flow cytometry method were used to detect the safety of nanoparticles and the killing effects of different nanoparticles on 4T1 cells. Results:t-P@TFP nanoparticles were successfully prepared. Transmission electron microscopy showed that the nanoparticles were spherical with uniform shape and size, with a particle size of (209.8±1.56)nm and a potential of (-25.9±1.36)mV. Laser confocal scanning microscopy showed that t-P@TFP nanoparticles could gather around 4T1 cells in a targeted manner. It had an efficient photothermal conversion effect, and nanoparticles could quickly become microbubbles after being irradiated by near-infrared laser, which enhanced the in vitro ultrasonic imaging effect; The photoacoustic signal of nanoparticles increased with the increase of concentration. CCK-8 method, double staining of living and dead cells and flow cytometry showed that t-P@TFP combined photothermal chemotherapy had the best anti-tumor effect. Conclusions:t-P@TFP nanoparticles are successfully prepared. The nanoparticles have good targeting ability for photoacoustic and ultrasonic imaging and have good photothermal effect, killing breast cancer cells, which is expected to realize the integration of diagnosis and treatment.

BACKGROUNDIn recent years, computers have been intensively used at home. In contrast to paper-based books and documents, computer screen is self-illuminated with larger screen-background luminance difference, which greatly induces visual discomfort. To compensate for that, one effective solution is to offer an additional background luminance. In this study, we investigated whether and to what extent additional background lighting is needed in looking at a computer display comfortably.

METHODSIn this study, 60 healthy children aged from 9 to 12 years and 58 adults aged from 21 to 39 years participated in the experiments. They were asked to choose their most preferred background luminance intensities at three screen luminance levels. The data were analyzed by Matlab (R2012b) and SPSS 20.0.

RESULTSBoth children and adult participants selected a non-dark background as their comfortable lighting condition when watching a computer display (children: t (59) = 22.0, P < 0.01, adults: t (57) = 15.5, P < 0.01). Comparatively, children preferred brighter background in general ( F (1,116) = 7.0, P < 0.01). More importantly, participants' preferred background luminance levels were linearly correlated with screen luminance intensities (children: slope = 0.97, R(2) = 0.98; adults: slope = 0.38, R(2) = 1.00).

CONCLUSIONThese results indicate that varying background luminance to maintain screen-background luminance ratio is beneficial to human visual comfort.

Adult ; Child ; Computers ; Contrast Sensitivity ; physiology ; Female ; Humans ; Lighting ; Male ; Myopia ; prevention & control ; Young Adult