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Early diagnosis and intervention are pivotal in reducing colorectal cancer (CRC) incidence and enhancing patient outcomes. In this study, we focused on three genes, AQP8, GUCA2B, and SPIB, which exhibit high coexpression and play crucial roles in suppressing early-stage CRC. Our objective was to identify key miRNAs that can mitigate CRC tumorigenesis and modulate the coexpression network involving these genes. We conducted a comprehensive analysis using large-scale tissue mRNA data from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus to validate the coexpression of AQP8, GUCA2B, and SPIB, and to assess their diagnostic and prognostic significance in CRC. The mRNA-miRNA interactions were examined using MiRNet and the Encyclopedia of RNA Interactomes. Furthermore, using various molecular techniques, we conducted miRNA inhibitor transfection experiments in HCT116 cells to evaluate their effects on cell growth, migration, and gene/protein expression. Our findings revealed that, compared with normal tissues, AQP8, GUCA2B, and SPIB exhibited high coexpression and were downregulated in CRC, particularly during tumorigenesis. OncoMirs, hsa-miR-182-5p, and hsa-miR-27a-3p, were predicted to regulate these genes. MiRNA inhibition experiments in HCT116 cells demonstrated the inhibitory effects of miR-27a-3p and miR-182-5p on GUCA2B mRNA and protein expression. These miRNAs promoted the proliferation of CRC cells, possibly through their involvement in the GUCA2B-GUCY2C axis, which is known to promote tumor growth. While the expressions of AQP8 and SPIB were barely detectable, their regulatory relationship with hsa-miR-182-5p remained inconclusive. Our study confirms that hsa-miR-27a-3p and hsa-miR-182-5p are oncomiRs in CRC. These miRNAs may contribute to GUCY2C dysregulation by downregulating GUCA2B, which encodes uroguanylin. Consequently, hsa-miR-182-5p and hsa-miR-27a-3p show promise as potential targets for early intervention and treatment in the early stages of CRC.
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The mortality of sepsis and septic shock remains high worldwide. Neutrophil extracellular traps (NETs) release is a major cause of organ failure and mortality in sepsis. Targeting Gasdermin D (GSDMD) can restrain NETs formation, which is promising for sepsis management. However, no medicine is identified without severe safety concerns for this purpose. Xuebijing injection (XBJ) has been demonstrated to alleviate the clinical symptoms of COVID-19 and sepsis patients, but there are not enough animal studies to reveal its mechanisms in depth. Therefore, we wondered whether XBJ relieved pulmonary damage in sepsis by suppressing NETs formation and adopted a clinically relevant polymicrobial infection model to test this hypothesis. Firstly, XBJ effectively reversed lung injury caused by sepsis and restrained neutrophils recruitment to lung by down-regulating proinflammatory chemokines, such as CSF-3, CXCL-2, and CXCR-2. Strikingly, we found that XBJ significantly reduced the expressions of NETs component proteins, including citrullinated histone H3 (CitH3), myeloperoxidase (MPO), and neutrophil elastase (NE). GSDMD contributes to the production of NETs in sepsis. Notably, XBJ exhibited a reduced effect on the expressions of GSDMD and its upstream regulators. Besides, we also revealed that XBJ reversed NETs formation by inhibiting the expressions of GSDMD-related genes. Collectively, we demonstrated XBJ protected against sepsis-induced lung injury by reversing GSDMD-related pathway to inhibit NETs formation.
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AIMS: In the present study, we investigated the roles of renin-angiotensin system (RAS) activation and imbalance of matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in cold-induced stroke during chronic hypertension, as well as the protective effects of captopril and recombinant human TIMP-1 (rhTIMP-1). MAIN METHODS: Rats were randomly assigned to sham; 2-kidney, 2-clip (2K-2C); 2K-2Câ¯+â¯captopril, and 2K-2Câ¯+â¯rhTIMP-1 groups. After blood pressure values had stabilized, each group was randomly divided into an acute cold exposure (ACE) group (12-h light at 22⯰C/12-h dark at 4⯰C) and a non-acute cold exposure (NACE) group (12-h light/12-h dark at 22⯰C), each of which underwent three cycles of exposure. Captopril treatment was administered via gavage (50â¯mg/kg/d), while rhTIMP-1 treatment was administered via the tail vein (60⯵g/kg/36â¯h). KEY FINDINGS: In the 2K-2C group, angiotensin II (AngII) and MMP-9 levels increased in both the plasma and cortex, while no such changes in TIMP-1 expression were observed. Cold exposure further upregulated AngII and MMP-9 levels and increased stroke incidence. Captopril and rhTIMP-1 treatment inhibited MMP-9 expression and activation and decreased stroke incidence in response to cold exposure. SIGNIFICANCE: The present study is the first to demonstrate that cold exposure exacerbates imbalance between MMP-9 and TIMP-1 by activating the RAS, which may be critical in the initiation of stroke during chronic hypertension. In addition, our results suggest that captopril and rhTIMP-1 exert protective effects against cold-induced stroke by ameliorating MMP-9/TIMP-1 imbalance.
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Metaloproteinasa 9 de la Matriz/metabolismo , Sistema Renina-Angiotensina/fisiología , Accidente Cerebrovascular/metabolismo , Inhibidor Tisular de Metaloproteinasa-1/metabolismo , Angiotensina II/metabolismo , Animales , Presión Sanguínea/efectos de los fármacos , Captopril/metabolismo , Captopril/farmacología , Proteínas de Ciclo Celular/metabolismo , Frío/efectos adversos , Humanos , Riñón/metabolismo , Masculino , Metaloproteinasa 1 de la Matriz/metabolismo , Metaloproteinasa 2 de la Matriz/metabolismo , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes/farmacología , Sistema Renina-Angiotensina/genética , Accidente Cerebrovascular/fisiopatología , Inhibidor Tisular de Metaloproteinasa-1/farmacología , Inhibidor Tisular de Metaloproteinasa-2RESUMEN
Sepsis and septic shock threaten the survival of millions of patients in the intensive care unit. Secondary fungal infections significantly increased the risk of mortality in sepsis patients. Chinese medicine Xuebijing injection (XBJ) has been routinely used as an add-on treatment to sepsis and septic shock in China. Our network pharmacology analysis predicted that XBJ also influences fungal infection, consisting with results of pioneer clinical studies. We conducted in vivo and in vitro experiments to verify this prediction. To our surprise, XBJ rescued mice from lethal Candida sepsis in a disseminated Candida albicans infection model and abolished the colonization of C. albicans in kidneys. Although XBJ did not inhibit the growth and the virulence of C. albicans in vitro, it enhanced the viability of 293T cells upon C. albicans insults. Further RNA-seq analysis revealed that XBJ activated the endoplasmic reticulum (ER) stress pathway upon C. albicans infection. Western blot confirmed that XBJ maintained the expression of GRP78 in the presence of C. albicans. Interestingly, key active ingredients in XBJ (C0127) mirrored the effects of XBJ. C0127 not only rescued mice from lethal Candida sepsis and prevented the colonization of C. albicans in kidneys, but also sustained the survival of kidney epithelial cells partially by maintaining the expression of GRP78. These results suggested that XBJ may prevent fungal infection in sepsis patients. Pre-activation of ER stress pathway is a novel strategy to control C. albicans infection. Network pharmacology may accelerate drug development in the field of infectious diseases.
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BiOBr nanosheets are important photocatalytic nanomaterials. However, their biological effects remain to be explored. In this study, we investigated the antifungal effect of BiOBr nanosheets on Candida albicans. Strikingly, the nanosheets strongly inhibited the growth of C. albicans [IC50=(96±4.7) mg/L], hyphal development and biofilm formation. Compareed to the antifungal effect of the cationic surfactant cetyltrimethylammonium bromide, the inhibitory effect of the nanosheets on fungal pathogen was attributed to cetyltrimethylammonium bromide adsorbed by the nanosheets. Thermal gravity analysis and cetyltrimethylammonium bromide release experiment indicated that only 0.42% cetyltrimethylammonium bromide on BiOBr nanosheets was released. Taken together, this study uncovers the contribution of surfactant released from the nanosheets to their antifungal activity.
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We analyze the performance of high dynamic range liquid crystal displays (LCDs) using a two-dimensional local dimming mini-LED backlight. The halo effect of such a HDR display system is investigated by both numerical simulation and human visual perception experiment. The halo effect is mainly governed by two factors: intrinsic LCD contrast ratio (CR) and dimming zone number. Based on our results, to suppress the halo effect to indistinguishable level, a LCD with CR≈5000:1 requires about 200 local dimming zones, while for a LCD with CR≈2000:1 the required dimming zone number is over 3000. Our model provides useful guidelines to optimize the mini-LED backlit LCDs for achieving dynamic contrast ratio comparable to organic LED displays.
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We develop a rigorous model to simulate an LCD's contrast ratio (CR) and viewing angle by considering the depolarization effect in thin-film transistor substrate, LC layer, color filter (CF) array, etc. To mitigate the depolarization effect, we propose a new device structure by adding a thin in-cell polarizer between LC layer and CF array. Based on the analysis using our new model, the maximum CR of a multi-domain vertical alignment (MVA) LCD can reach > 20,000:1, while for the fringe-field switching (FFS) mode it can reach > 3000:1. We also discuss other approaches to further enhance the CR. Our model is a powerful tool to analyze the CR degradation mechanism and to guide the future LCD device and material optimizations.
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We report a vertically-aligned liquid crystal display (LCD) device with submillisecond response time, high transmittance, and low operation voltage. The top substrate has a common electrode, while the bottom substrate consists of hole-patterned fringing-field-switching (FFS) pixel electrodes. A negative dielectric anisotropy LC is employed. In the voltage-on state, the LC directors are reoriented by the fringing fields surrounding the hole area and by the longitudinal and fringe fields outside the hole area. After design optimization, we are able to achieve 85% peak transmittance under crossed circular polarizers. During the relaxation process, the standing walls exert a strong restoring force, leading to submillisecond gray-to-gray response time. Moreover, this device enables high resolution density because only one thin-film transistor per pixel is needed and the bottom FFS electrode has built-in capacitor. This device is particularly attractive for the emerging virtual reality displays.
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Metastasis accounts for the high mortality rate associated with colorectal cancer (CRC), but metastasis regulators are not fully understood. To identify a novel gene involved in tumor metastasis, we used oligonucleotide microarrays, transcriptome distance analyses, and machine learning algorithms to determine links between primary and metastatic colorectal cancers. Aminopeptidase A (APA; also known as ENPEP) was selected as our focus because its relationship with colorectal cancer requires clarification. Higher APA mRNA levels were observed in patients in advanced stages of cancer, suggesting a correlation between ENPEP and degree of malignancy. Our data also indicate that APA overexpression in CRC cells induced cell migration, invasion, anchorage-independent capability, and mesenchyme-like characteristics (e.g., EMT markers). We also observed TWIST induction in APA-overexpressing SW480 cells and TWIST down-regulation in HT29 cells knocked down with APA. Both APA silencing and impaired APA activity were found to reduce migratory capacity, cancer anchorage, stemness properties, and drug resistance in vitro and in vivo. We therefore suggest that APA enzymatic activity affects tumor initiation and cancer malignancy in a TWIST-dependent manner. Results from RT-qPCR and the immunohistochemical staining of specimens taken from CRC patients indicate a significant correlation between APA and TWIST. According to data from SurvExpress analyses of TWIST1 and APA mRNA expression profiles, high APA and TWIST expression are positively correlated with poor CRC prognosis. APA may act as a prognostic factor and/or therapeutic target for CRC metastasis and recurrence.
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Transformación Celular Neoplásica/metabolismo , Neoplasias Colorrectales/metabolismo , Glutamil Aminopeptidasa/metabolismo , Células Madre Neoplásicas/metabolismo , Proteínas Nucleares/biosíntesis , Proteína 1 Relacionada con Twist/biosíntesis , Animales , Transformación Celular Neoplásica/patología , Neoplasias Colorrectales/mortalidad , Neoplasias Colorrectales/patología , Técnica del Anticuerpo Fluorescente , Regulación Neoplásica de la Expresión Génica/fisiología , Xenoinjertos , Humanos , Estimación de Kaplan-Meier , Ratones , Ratones Endogámicos BALB C , Mutagénesis Sitio-Dirigida , Células Madre Neoplásicas/patología , Análisis de Secuencia por Matrices de Oligonucleótidos , Modelos de Riesgos Proporcionales , Reacción en Cadena en Tiempo Real de la Polimerasa , Análisis de Matrices Tisulares , Regulación hacia ArribaRESUMEN
We propose to add a functional reflective polarizer (FRP) in the backlight unit to suppress the crosstalk between red, green and blue color filters of a liquid crystal display (LCD) panel. When incorporated with a commercial two-phosphor-converted white light-emitting diode (2pc-WLED), the color gamut of the LCD can be improved from 92% to 115% NTSC standard, which is comparable to the cadmium-based quantum dot (QD) backlight. If a narrow-band color filter is employed, the color gamut can be further enhanced to 135% NTSC. Our design offers an alternative approach to QDs, while keeping low cost and long lifetime. Such a simple yet efficient approach would find widespread applications for enlarging the color gamut of LCDs.
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In 2009, a swine-origin influenza A virus - A(H1N1)pdm09 - emerged and has became a pandemic strain circulating worldwide. The hemagglutinin (HA) of influenza virus is a potential target for the development of anti-viral therapeutic agents. Here, we generated mAbs by immunization of baculovirus-insect expressing trimeric recombinant HA of the A(H1N1)pdm09 strain. Results indicated that the mAbs recognized two novel neutralizing and protective epitopes-"STAS" and "FRSK" which located near Cb and Ca1 antigenic regions respectively and were conserved in almost 2009-2016 influenza H1N1 stains. The mAb 12E11 demonstrated higher protective efficacy than mAb 8B10 in mice challenge assay. Both mAb pretreatments significantly reduced virus titers and pro-inflammatory cytokines in mice lung postinfection (p < 0.01), and showed prophylactic and therapeutic efficacies even 48 h postinfection (p < 0.05). Combination therapy using the mAbs with oseltamivir pre- and post-treatment showed synergistic therapeutic effect in mice model (p < 0.01). Further investigation for clinical application in humans is warranted.
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Anticuerpos Monoclonales/uso terapéutico , Anticuerpos Antivirales/uso terapéutico , Inmunoterapia/métodos , Subtipo H1N1 del Virus de la Influenza A/inmunología , Gripe Humana/inmunología , Infecciones por Orthomyxoviridae/terapia , Vacunas Virales/inmunología , Animales , Anticuerpos Monoclonales/aislamiento & purificación , Anticuerpos Antivirales/aislamiento & purificación , Terapia Combinada , Perros , Sinergismo Farmacológico , Glicoproteínas Hemaglutininas del Virus de la Influenza/inmunología , Humanos , Epítopos Inmunodominantes/inmunología , Células de Riñón Canino Madin Darby , Ratones , Ratones Endogámicos BALB C , Infecciones por Orthomyxoviridae/inmunología , Oseltamivir/uso terapéutico , Multimerización de Proteína , PorcinosRESUMEN
In this study, we analyze how a backlight's peak wavelength, full-width at half-maximum (FWHM), and color filters affect the color gamut of a liquid crystal display (LCD) device and establish a theoretical limit, even if the FWHM approaches 1 nm. To overcome this limit, we propose a new backlight system incorporating a functional reflective polarizer and a patterned half-wave plate to decouple the polarization states of the blue light and the green/red lights. As a result, the crosstalk between three primary colors is greatly suppressed, and the color gamut is significantly widened. In the experiment, we prepare a white-light source using a blue light-emitting diode (LED) to pump green perovskite polymer film and red quantum dots and demonstrate an exceedingly large color gamut (95.8% Rec. 2020 in Commission internationale de l'éclairage (CIE) 1931 color space and 97.3% Rec. 2020 in CIE 1976 color space) with commercial high-efficiency color filters. These results are beyond the color gamut limit achievable by a conventional LCD. Our design works equally well for other light sources, such as a 2-phosphor-converted white LED.
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We propose a high dynamic range (HDR) liquid crystal display (LCD) with pixel-level local dimming. The device structure consists of a pixelated LCD dimming panel to control the backlight intensity entering the master LCD panel. According to our analysis and test cell experiment, this dual-panel display system possesses exceedingly high contrast ratio (> 1,000,000:1) and high bit-depth (> 14 bits) at merely 5 volts. Meanwhile, to mitigate the Moiré effect induced by the cascaded thin-film transistor (TFT) backplanes, we separate the two LCD panels with a polarization-dependent scattering film. The pros and cons of this HDR display are discussed.
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OBJECTIVE: The purpose of the current study was to investigate the effect of the dosing time on the pharmacokinetics of erlotinib and the circadian rhythms of the metabolism enzymes in tumor-bearing mice. METHODS: Female C57BL mice were randomly assigned to six groups. Erlotinib was orally administrated to the mice in each group at six different times of day. The plasma concentration of erlotinib was determined through a high-performance liquid-chromatographic assay, and the total mRNA was extracted from liver tissues to determine the expression of the mRNA of the related drug metabolism enzymes by qRT-PCR. RESULTS: The results indicated that AUC0-24 h and MRT0-24 h were the lowest in the 20:00 group (P < 0.01). T max of the 13 HALO (hour after light onset), 17 HALO and 21 HALO groups was higher than that of the 1 HALO and 5 HALO groups (P < 0.01). CL of the light-phase groups was lower than that of the dark-phase groups (P < 0.01). The peak value of C max appeared in the 5 HALO group (P < 0.01). The mRNA levels of Cyp3a11, Cyp3a13 and Cyp1a2 were generally higher during the afternoon and the dark phase. CONCLUSION: Circadian rhythm plays a critical role in the pharmacokinetics of erlotinib in mice, and the mechanisms may be attributed to gene expression rhythms of drug-metabolizing enzymes in liver tissues.
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Ritmo Circadiano/fisiología , Clorhidrato de Erlotinib/metabolismo , Clorhidrato de Erlotinib/farmacocinética , Neoplasias/metabolismo , Administración Oral , Animales , Cronofarmacocinética , Femenino , Hígado/metabolismo , Ratones , Ratones Endogámicos C57BL , ARN Mensajero/metabolismoRESUMEN
BACKGROUND: The swine-origin influenza A (H1N1) virus (S-OIV) has come to the forefront since 2009 and was identified as a new reassortant strain. The hemagglutinin (HA) glycoprotein mediates virus binding, contains antigenic regions recognized by neutralizing antibodies, and is associated with viral cross-species infection and adaption. The comparison study of codon usage preferences in influenza viral genomes was less extensive. In this study, we used codon usage pattern analyses to validate the adaption and origins of S-OIV. METHODS: Codon usage pattern was used to estimate the host adaption of S-OIVs. Phylogenetic analysis of the HA gene was conducted to understand the phylogeny of H1N1 viruses isolated from different hosts. Amino acid signature pattern on antigenic sites of HA was analyzed to understand the antigenic characteristics. RESULTS: Results of phylogenetic analyses of HA gene indicate that S-OIVs group in identical clusters. The synonymous codon usage pattern analyses indicate that the effective number of codons versus GC content at the third codon position in the HA1 gene slightly differ from those in swine H1N1 and gradually adapted to human. Our data indicate that S-OIV evolution occurred according to positive selection within these antigenic regions. A comparison of antigenic site amino acids reveals similar signature patterns between S-OIV and 1918 human influenza strains. CONCLUSION: This study proposes a new and effective way to gain a better understanding of the features of the S-OIV genome and evolutionary processes based on the codon usage pattern. It is useful to trace influenza viral origins and cross-species virus transmission.
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Glicoproteínas Hemaglutininas del Virus de la Influenza/genética , Especificidad del Huésped/genética , Subtipo H1N1 del Virus de la Influenza A/genética , Gripe Humana/virología , Acoplamiento Viral , Sustitución de Aminoácidos/genética , Animales , Composición de Base/genética , Codón/genética , Genoma Viral/genética , Humanos , Filogenia , Porcinos , Enfermedades de los Porcinos/virologíaRESUMEN
We propose a versatile design approach of engineered diffuser based on freeform optics that can tailor the light distribution of a liquid crystal display (LCD) to meet different applications. The proposed LCD system consists of a quasi-directional backlight, liquid crystal panel, and an engineered diffuser. It offers high efficiency, wide view, high contrast, as well as low ambient light reflection. For large size LCDs, we design a wide view diffuser to match the light distribution with state-of-the-art organic light emitting diode (OLED) TV. For mobile displays, we design a diffuser to replicate current LCD performance. Our design can also provide flattop light intensity distribution for privacy protection. These exemplary designs prove that our engineered diffuser is versatile for different applications.
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Candida albicans is the most common fungal pathogen of mucosal infections and invasive diseases in immuno-compromised humans. The abilities of yeast-hyphal growth and white-opaque switching affect C. albicans physiology and virulence. Here, we showed that C. albicans Aft2 regulator was required for embedded filamentous growth and opaque cell-type formation. Under low-temperature matrix embedded conditions, Aft2 functioned downstream of Czf1-mediated pathway and was required for invasive filamentation. Moreover, deletion of AFT2 significantly reduced opaque cell-type formation under N-acetylglucosamine (GlcNAc) inducing conditions. Ectopic expression of CZF1 slightly increased the white-opaque switching frequency in the aft2Δ/Δ mutant, but did not completely restore to wild-type levels, suggesting that Czf1 at least partially bypassed the essential requirement for Aft2 in response to opaque-inducing cues. In addition, multiple environmental cues altered AFT2 mRNA and protein levels, such as low temperature, physical environment and GlcNAc. Although the absence of Czf1 or Efg1 also increased the expression level of AFT2 gene, deletion of CZF1 remarkably reduced the stability of Aft2 protein. Furthermore, C. albicans Aft2 physically interacted with Czf1 under all tested conditions, whereas the interaction between Aft2 and Efg1 was barely detectable under embedded conditions, supporting the hypothesis that Aft2, together with Czf1, contributed to activate filamentous growth by antagonizing Efg1-mediated repression under matrix-embedded conditions.
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Factor de Transcripción Activador 2/genética , Factor de Transcripción Activador 2/metabolismo , Candida albicans/crecimiento & desarrollo , Proteínas de Unión al ADN/metabolismo , Proteínas Fúngicas/metabolismo , Factores de Transcripción/metabolismo , Acetilglucosamina/farmacología , Factor de Transcripción Activador 2/química , Candida albicans/efectos de los fármacos , Candida albicans/genética , Proteínas Fúngicas/genética , Regulación Fúngica de la Expresión Génica , Humanos , Estabilidad Proteica , Transducción de Señal , Temperatura , Factores de Transcripción/genéticaRESUMEN
We investigated the protective effects of lentinan against damages to chronic and low-dose radiation (CL-radiation) by using mouse models. The mice were randomized divided into four groups: normal control mice (Ctr), mice exposed to radiation (Rad), irradiated mice treated with low-dose lentinan (0.1mg/(kg.d), RL), and irradiated mice treated with high-dose lentinan (0.5mg/(kg.d), RH). All the mice were injected intraperitoneally once a day at a dose of 0.5mL (Ctr and Rad with normal sodium while RL and RH with lentinan). The success of radiation models was confirmed by HE stain and cell morphology by a transmission electron microscope (TEM). On the basis of radiation models, we investigated the expression of proteins on the membrane of splenic cells through MALDI-TOF-MS/MS. The results demonstrated that both RT-radiation and lentinan affected the expression of membrane proteins, but lentinan protected the splenic cells and tissue from the injuries caused by CL-radiation. Therefore, we speculated that CL-radiation mainly damages the genetic materials and membrane-bound proteins, while lentinan protects membrane-bound proteins by regulating signal transduction and the appearance of the cells.
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Lentinano/farmacología , Linfocitos/efectos de los fármacos , Linfocitos/efectos de la radiación , Proteínas de la Membrana/metabolismo , Protectores contra Radiación/farmacología , Animales , Linfocitos/metabolismo , Masculino , Ratones , Bazo/citología , Irradiación Corporal TotalRESUMEN
Here we investigated the regulation of Pichia pastoris desaturase genes by low temperature and exogenous fatty acids in the late-exponential phase at the transcriptional level. Time-course studies of gene expression showed that mRNA levels of four desaturase genes were rapidly and transiently enhanced by low temperature and suppressed by exogenous oleic acid. Stearic acid showed no obvious repression of mRNA levels of Fad12 and Fad15 and a slight increase in Fad9A and Fad9B mRNA levels. Using a promoter-reporter gene construct, we demonstrated that the pFAD15 promoter activity was induced by low temperature in a time-dependent manner and reduced in a dose- and time-dependent manner by unsaturated fatty acids. Also, there was no absolute correlation between mRNA abundance and production of corresponding fatty acids. Disruption of Spt23 resulted in a decrease in transcript levels of Fad9A and Fad9B, but had little effect on the other desaturase genes. Consistent with these observations, a decrease in the relative amount of oleic acid (OLA) and an increase in the relative content of linoleic acid and ALA with different degrees were clearly observed in the stationary phase cells of ΔSpt23 mutant. Further analysis showed that the effect of low-temperature activation and OLA inhibition on expression of Fad9A and Fad9B seemed to disappear after disruption of the Spt23 gene, which indicated that Spt23p is essential for the expression of two Δ9-desaturase genes internally and probably involved in the regulation of Δ9-desaturase genes transcription in response to external stimuli, and thereby plays a role in the synthesis of OLA.
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Ácido Graso Desaturasas/genética , Regulación Enzimológica de la Expresión Génica/genética , Pichia/enzimología , Transcripción Genética/genética , Ácido Graso Desaturasas/metabolismo , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Ácido Oléico/farmacología , Pichia/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Relación Estructura-Actividad , Temperatura , Transcripción Genética/efectos de los fármacosRESUMEN
Unsaturated fatty acids (UFAs), including oleic acid (OA, C18:1n-9), linoleic acid (LA, C18:2n-6) and α-linolenic acid (ALA, C18:3n-3), are major components of membrane lipids in Pichia pastoris GS115. In order to clarify the biosynthesis pathway of UFAs on the molecular level and investigate their possible roles in growth and development of this strain, we here report modified strains with disrupted desaturase gene by homologous recombination. Gas chromatography analysis of fatty acid composition in the corresponding mutants confirmed that ∆(12)-desaturase encoded by Fad12 was responsible for the formation of LA, and ALA was synthesized by ∆(15)-desaturase encoded by Fad15. Simultaneous deletion of Fad9A and Fad9B was lethal and supplementation of OA could restore growth, indicating that possibly both Fad9A and Fad9B encoded ∆(9)-desaturase that converted SA into OA. Phenotypic analysis demonstrated that wild type and Fad15 mutant grew at almost the same rate, Fad12 mutant grew much slower than these two strains. Moreover, OA was positively correlated to cold tolerance and ethanol tolerance of GS115, whereas LA and ALA did not affect cold tolerance and ethanol tolerance of it. In addition, we showed that tolerance of GS115 to high concentration of methanol was independent of these three UFAs.