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The steady flow of lactic acid (LA) from tumor cells to the extracellular space via the monocarboxylate transporter symport system suppresses antitumor T cell immunity. However, LA is a natural energy metabolite that can be oxidized in the mitochondria and could potentially stimulate T cells. Here we show that the lactate-lowering mood stabilizer lithium carbonate (LC) can inhibit LA-mediated CD8+ T cell immunosuppression. Cytoplasmic LA increased the pumping of protons into lysosomes. LC interfered with vacuolar ATPase to block lysosomal acidification and rescue lysosomal diacylglycerol-PKCθ signaling to facilitate monocarboxylate transporter 1 localization to mitochondrial membranes, thus transporting LA into the mitochondria as an energy source for CD8+ T cells. These findings indicate that targeting LA metabolism using LC could support cancer immunotherapy.
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Antimaníacos , Ácido Láctico , Carbonato de Lítio , Mitocôndrias , Neoplasias , Humanos , Linfócitos T CD8-Positivos , Ácido Láctico/metabolismo , Carbonato de Lítio/farmacologia , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Neoplasias/metabolismo , Antimaníacos/farmacologiaAssuntos
Cocos , Glucose , Glucose/química , Adsorção , Fibras na Dieta/farmacologia , alfa-AmilasesRESUMO
Macrophages in tumors (tumor-associated macrophages, TAMs), a major population within most tumors, play key homeostatic functions by stimulating angiogenesis, enhancing tumor cell growth, and suppressing antitumor immunity. Resetting TAMs by simple, efficacious and safe approach(s) is highly desirable to enhance antitumor immunity and attenuate tumor cell malignancy. Previously, we used tumor cell-derived microparticles to package chemotherapeutic drugs (drug-MPs), which resulted in a significant treatment outcome in human malignant pleural effusions via neutrophil recruitments, implicating that drug-MPs might reset TAMs, considering the inhibitory effects of M2 macrophages on neutrophil recruitment and activation. Here, we show that drug-MPs can function as an antitumor immunomodulator by resetting TAMs with M1 phenotype and IFN-ß release. Mechanistically, drug molecules in tumor MPs activate macrophage lysosomal P450 monooxygenases, resulting in superoxide anion formation, which further amplifies lysosomal ROS production and pH value by activating lysosomal NOX2. Consequently, lysosomal Ca2+ signaling is activated, thus polarizing macrophages towards M1. Meanwhile, the drug molecules are delivered from lysosomes into the nucleus where they activate DNA sensor hnRNPA2B1 for IFN-ß production. This lysosomal-nuclear machinery fully arouses the antitumor activity of macrophages by targeting both lysosomal pH and the nuclear innate immunity. These findings highlight that drug-MPs can act as a new immunotherapeutic approach by revitalizing antitumor activity of macrophages. This mechanistic elucidation can be translated to treat malignant ascites by drug-MPs combined with PD-1 blockade.
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Antineoplásicos , Micropartículas Derivadas de Células , Ribonucleoproteínas Nucleares Heterogêneas Grupo A-B , Macrófagos , Humanos , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Lisossomos , Ribonucleoproteínas Nucleares Heterogêneas Grupo A-B/metabolismoRESUMO
Glioblastoma (GBM) is a prevalent and highly lethal form of glioma, with rapid tumor progression and frequent recurrence. Excessive outgrowth of pericytes in GBM governs the ecology of the perivascular niche, but their function in mediating chemoresistance has not been fully explored. Herein, we uncovered that pericytes potentiate DNA damage repair (DDR) in GBM cells residing in the perivascular niche, which induces temozolomide (TMZ) chemoresistance. We found that increased pericyte proportion correlates with accelerated tumor recurrence and worse prognosis. Genetic depletion of pericytes in GBM xenografts enhances TMZ-induced cytotoxicity and prolongs survival of tumor-bearing mice. Mechanistically, C-C motif chemokine ligand 5 (CCL5) secreted by pericytes activates C-C motif chemokine receptor 5 (CCR5) on GBM cells to enable DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-mediated DDR upon TMZ treatment. Disrupting CCL5-CCR5 paracrine signaling through the brain-penetrable CCR5 antagonist maraviroc (MVC) potently inhibits pericyte-promoted DDR and effectively improves the chemotherapeutic efficacy of TMZ. GBM patient-derived xenografts with high CCL5 expression benefit from combined treatment with TMZ and MVC. Our study reveals the role of pericytes as an extrinsic stimulator potentiating DDR signaling in GBM cells and suggests that targeting CCL5-CCR5 signaling could be an effective therapeutic strategy to improve chemotherapeutic efficacy against GBM.
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Glioblastoma , Animais , Linhagem Celular Tumoral , Resistencia a Medicamentos Antineoplásicos , Glioblastoma/tratamento farmacológico , Camundongos , Comunicação Parácrina , Pericitos , Temozolomida/farmacologia , Temozolomida/uso terapêutico , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The relatively poor atomic-oxygen (AO) resistance of the standard polyimide (PI) films greatly limits the wide applications in low earth orbit (LEO) environments. The introduction of polyhedral oligomeric silsesquioxane (POSS) units into the molecular structures of the PI films has been proven to be an effective procedure for enhancing the AO resistance of the PI films. In the current work, a series of POSS-substituted poly (pyromellitic anhydride-4,4'-oxydianiline) (PMDA-ODA) films (POSS-PI) with different POSS contents were synthesized via a POSS-containing diamine, N-[(heptaisobutyl-POSS)propyl]-3,5-diaminobenzamide (DABA-POSS). Subsequently, the effects of the molecular structures on the thermal, tensile, optical, and especially the AO-erosion behaviors of the POSS-PI films were investigated. The incorporation of the latent POSS substituents decreased the thermal stability and the high-temperature dimensional stability of the pristine PI-0 (PMDA-ODA) film. For instance, the PI-30 film with the DABA-POSS content of 30 wt% in the film exhibited a 5% weight loss temperature (T5%) of 512 °C and a coefficient of linear thermal expansion (CTE) of 54.6 × 10-6/K in the temperature range of 50-250 °C, respectively, which were all inferior to those of the PI-0 film (T5% = 574 °C; CTE = 28.9 × 10-6/K). In addition, the tensile properties of the POSS-containing PI films were also deteriorated, to some extent, due to the incorporation of the DABA-POSS components. The tensile strength (TS) of the POSS-PI films decreased with the order of PI-0 > PI-10 > PI-15 > PI-20 > PI-25 > PI-30, and so did the tensile modulus (TM) and the elongations at break (Eb). PI-30 showed the TS, TM, and Eb values of 75.0 MPa, 1.55 GPa, and 16.1%, respectively, which were all lower than those of the PI-0 film (TS = 131.0 MPa, TM = 1.88 GPa, Eb = 73.2%). Nevertheless, the incorporation of POSS components obviously increased the AO resistance of the PI films. All of the POSS-PI films survived from the AO exposure with the total fluence of 2.16 × 1021 atoms/cm2, while PI-0 was totally eroded under the same circumstance. The PI-30 film showed an AO erosion yield (Es) of 1.1 × 10-25 cm3/atom, which was approximately 3.67% of the PI-0 film (Es = 3.0 × 10-24 cm3/atom). Inert silica or silicate passivation layers were detected on the surface of the POSS-PI films after AO exposure, which efficiently prevented the further erosion of the under-layer materials.
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BACKGROUND: The nuclear transport system has been proposed to be indispensable for cell proliferation and invasion in cancers. Prognostic biomarkers and molecular targets in nuclear transport systems have been developed. However, no systematic analysis of genes related to nuclear transport in gliomas has been performed. An integrated prognostic classification involving mutation and nuclear transport gene signatures has not yet been explored. METHODS: In the present study, we analyzed gliomas from a training cohort (TCGA dataset, n = 660) and validation cohort (CGGA dataset, n = 668) to develop a prognostic nuclear transport gene signature and generate an integrated classification system. Gene set enrichment analysis (GSEA) showed that glioblastoma (GBM) was mainly enriched in nuclear transport progress compared to lower-grade glioma (LGG). Then, we developed a nuclear transport risk score (NTRS) for gliomas with a training cohort. NTRS was significantly correlated with clinical and genetic characteristics, including grade, age, histology, IDH status and 1p/19q codeletion, in the training and validation cohorts. RESULTS: Survival analysis revealed that patients with a higher NTRS exhibited shorter overall survival. NTRS showed better prognostic value compared to classical molecular markers, including IDH status and 1p/19q codeletion. Furthermore, univariate and multivariate analyses indicated that NTRS was an independent prognostic factor for gliomas. Enrichment map and Gene Ontology analysis demonstrated that signaling pathways related to the cell cycle were enriched in the NTRSHigh group. Subgroup survival analysis revealed that NTRS could differentiate the outcomes of low- and high-risk patients with wild-type IDH or mutant IDH and 1p/19q non-codeletion. CONCLUSIONS: NTRS is associated with poor outcomes and could be an independent prognostic marker in diffuse gliomas. Prognostic classification combined with IDH mutation, 1p/19q codeletion and NTRS could better predict the survival of glioma patients.
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Transporte Ativo do Núcleo Celular/genética , Biomarcadores Tumorais/genética , Deleção Cromossômica , Glioma/patologia , Isocitrato Desidrogenase/genética , Mutação , Transcriptoma , Adolescente , Adulto , Idoso , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Criança , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 19/genética , Feminino , Seguimentos , Regulação Neoplásica da Expressão Gênica , Glioma/genética , Glioma/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Taxa de Sobrevida , Adulto JovemRESUMO
BACKGROUND: Tumor mutational burden (TMB) is a potential biomarker for immune checkpoint therapy and prognosis. The impact of TMB on clinical outcomes and the correlation coefficient between exome sequencing and targeted sequencing in glioma have not yet been explored. METHODS: Somatic mutations in the coding regions of 897 primary gliomas and the clinical and RNA-seq data of 654 patients in The Cancer Genome Atlas (TCGA) database were analyzed as a training set, while another 286 patients in the Chinese Glioma Genome Atlas (CGGA) database were used for validation. Descriptive and correlational analyses were conducted with TMB. Enrichment map analysis and gene set enrichment analysis (GSEA) were also performed. RESULTS: TMB was higher for the group of mutant genes that are frequently mutated in glioblastomas (GBMs) and lower for the group of mutant genes that are frequently mutated in lower-grade gliomas (LGGs). Patients with a higher TMB exhibited shorter overall survival. TMB was associated with grade, age, subtype and mutations affecting genomic structure. Moreover, univariate and multivariate analyses showed that TMB was an independent prognostic factor for glioma. The signaling pathways of the cell cycle were enriched in the TMBHigh group. TMB was higher in the mismatch repair (MMR) gene mutant group than in the wild-type group, but the MMR pathway was enriched in the TMBHigh group of gliomas without mutations in classical MMR genes. The correlation between TMBs calculated through exome sequencing and targeted sequencing was moderate, and panel-based TMB was not correlated with prognosis. CONCLUSIONS: TMB is associated with poor outcomes in diffuse glioma. The high proliferative activity in the TMBHigh group could account for the shorter survival of these patients. This association was not reflected by a pan-cancer targeted sequencing panel.
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Neoplasias Encefálicas/genética , Redes Reguladoras de Genes , Glioma/genética , Mutação , Feminino , Humanos , Masculino , Prognóstico , Análise de Sequência de RNA , Análise de Sobrevida , Sequenciamento do ExomaRESUMO
In the current work, a series of black polyimide (PI) films with excellent thermal and dimensional stability at elevated temperatures were successfully developed. For this purpose, two aromatic diamines including 4,4'-iminodianline (NDA) and 2-(4-aminophenyl)-5- aminobenzimidazole (APBI) were copolymerized with pyromellitic dianhydride (PMDA) to afford PIs containing imino groups (-NH-) in the molecular structures. The referenced PI film, PI-ref, was simultaneously prepared from PMDA and 4,4'-oxydianiline (ODA). The introduction of imino groups endowed the PI films with excellent blackness and opaqueness with the optical transmittance lower than 2% at the wavelength of 600 nm at a thickness of 25 µm and lightness (L*) below 10 for the CIE (Commission International Eclairage) Lab optical parameters. Meanwhile, the introduction of rigid benzimidazole units apparently improved the thermal and dimensional stability of the PI films. The PI-d film based on PMDA and mixed diamines (NDA:APBI = 70:30, molar ratio) showed a glass transition temperature (Tg) of 445.5 °C and a coefficient of thermal expansion (CTE) of 8.9 × 10-6/K in the temperature range of 50 to 250 °C, respectively. It is obviously superior to those of the PI-a (PMDA-NDA, Tg = 431.6 °C; CTE = 18.8 × 10-6/K) and PI-ref (PMDA-ODA, Tg = 418.8 °C; CTE: 29.5 × 10-6/K) films.
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Nosema bombycis, the first identified microsporidium, causes heavy losses to the sericulture industry in China. During infection, microsporidia discharge a long and hollow polar tube, which delivers the sporoplasm into host cells. Polar tube protein 1 was the major component on the polar tube. Previously, we expressed the polar tube protein 1 from Nosema bombycis (NbPTP1) intercellularly in Drosophila S2 cells. Here, the microsporidian protein was expressed in Lepidopteran Sf9 cells. During heterologous expression, NbPTP1 protein was secreted and glycosylated. Microsporidian proliferation decreased in NbPTP1-expressing Sf9 cells. This confirms that NbPTP1 protein can interact with the host cell membrane receptor protein to facilitate microsporidian invasion.
Assuntos
Proteínas Fúngicas/genética , Nosema/fisiologia , Spodoptera/microbiologia , Animais , Proteínas Fúngicas/metabolismo , Nosema/genética , Células Sf9/microbiologiaRESUMO
Semi-alicyclic colorless and transparent polyimide (CPI) films usually suffer from the high linear coefficients of thermal expansion (CTEs) due to the intrinsic thermo-sensitive alicyclic segments in the polymers. A series of semi-alicyclic CPI films containing rigid-rod amide moieties were successfully prepared in the current work in order to reduce the CTEs of the CPI films while maintaining their original optical transparency and solution-processability. For this purpose, two alicyclic dianhydrides, hydrogenated pyromellitic anhydride (HPMDA, I), and hydrogenated 3,3',4,4'-biphenyltetracarboxylic dianhydride (HBPDA, II) were polymerized with two amide-bridged aromatic diamines, 2-methyl-4,4'-diaminobenzanilide (MeDABA, a) and 2-chloro-4,4'-diaminobenzanilide (ClDABA, b) respectively to afford four CPI resins. The derived CPI resins were all soluble in polar aprotic solvents, including N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). Flexible and tough CPI films were successfully prepared by casing the PI solutions onto glass substrates followed by thermally cured at elevated temperatures from 80 °C to 250 °C. The MeDABA derived PI-Ia (HPMDA-MeDABA) and PI-IIa (HBPDA-MeDABA) exhibited superior optical transparency compared to those derived from ClDABA (PI-Ib and PI-IIb). PI-Ia and PI-IIa showed the optical transmittances of 82.3% and 85.8% at the wavelength of 400 nm with a thickness around 25 µm, respectively. Introduction of rigid-rod amide moiety endowed the HPMDA-PI films good thermal stability at elevated temperatures with the CTE values of 33.4 × 10-6/K for PI-Ia and 27.7 × 10-6/K for PI-Ib in the temperature range of 50-250 °C. Comparatively, the HBPDA-PI films exhibited much higher CTE values. In addition, the HPMDA-PI films exhibited good thermal stability with the 5% weight loss temperatures (T5%) higher than 430 °C and glass transition temperatures (Tg) in the range of 349-351 °C.
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Enhancement of flame retardancy of a colorless and transparent semi-alicyclic polyimide (PI) film was carried out by the incorporation of phosphazene (PPZ) flame retardant (FR). For this purpose, PI-1 matrix was first synthesized from hydrogenated 3,3',4,4'-biphenyltetracarboxylic dianhydride (HBPDA) and 4,4'-oxydianiline (ODA). The soluble PI-1 resin was dissolved in N,N-dimethylacetamide (DMAc) to afford the PI-1 solution, which was then physically blended with PPZ FR with the loading amounts in the range of 0-25 wt.%. The PPZ FR exhibited good miscibility with the PI-1 matrix when its proportion was lower than 10 wt.% in the composite films. PI-3 composite film with the PPZ loading of 10 wt.% showed an optical transmittance of 75% at the wavelength of 450 nm with a thickness of 50 µm. More importantly, PI-3 exhibited a flame retardancy class of UL 94 VTM-0 and reduced total heat release (THR), heat release rate (HRR), smoke production rate (SPR), and rate of smoke release (RSR) values during combustion compared with the original PI-1 film. In addition, PI-3 film had a limiting oxygen index (LOI) of 30.9%, which is much higher than that of PI-1 matrix (LOI: 20.1%). Finally, incorporation of PPZ FR decreased the thermal stability of the PI films. The 10% weight loss temperature (T10%) and the glass transition temperature (Tg) of the PI-3 film were 411.6 °C and 227.4 °C, respectively, which were lower than those of the PI-1 matrix (T10%: 487.3 °C; Tg: 260.6 °C).
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Uniform alignment of rigid-rod liquid crystal (LC) molecules under applied voltage is critical for achievement of high-quality display for thin-film transistor-driven liquid crystal display devices (TFT-LCDs). The polymeric components that can induce the alignment of randomly aligned LC molecules are called alignment layers (ALs). In the current work, a series of organo-soluble polyimide (SPI) ALs were designed and prepared from an alicyclic dianhydride, hydrogenated 3,3',4,4'-biphenyltetracarboxylic dianhydride (HBPDA), and various aromatic diamines, including 4,4'-methylenedianiline (MDA) for SPI-1, 4,4'-aminodianiline (NDA) for SPI-2, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane (TMMDA) for SPI-3, and 3,3'-diethyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane (DMDEDA) for SPI-4. The derived SPI resins were all soluble in N-methyl-2-pyrrolidone (NMP). Four SPI alignment agents with the solid content of 6 wt.% were prepared by dissolving the SPI resins in the mixed solvent of NMP and butyl cellulose (BC) (NMP/BC = 80:20, weight ratio). Liquid crystal minicells were successfully fabricated using the developed SPI varnishes as the LC molecule alignment components. The SPI ALs showed good alignment ability for the LC molecules with the pretilt angles in the range of 1.58°-1.97°. The LC minicells exhibited good optoelectronic characteristics with voltage holding ratio (VHR) values higher than 96%. The good alignment ability of the SPI ALs is mainly attributed to the good comprehensive properties of the SPI layers, including high volume resistivity, high degree of imidization at the processing temperature (230 °C), good rubbing resistance, good thermal stability with glass transition temperatures (Tgs) higher than 260 °C, and excellent optical transparency with the transmittance higher than 97% at the wavelength of 550 nm.
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AIMS: The aim of this study was to investigate the tumor microenvironment immune types (TMIT) based on tumor cell programmed cell death ligand 1 (PD-L1) expression and tumor-infiltrating lymphocytes (TILs) distribution and whether distinct TMIT subtypes (TMIT I, PD-L1high /TILhigh ; TMIT II, PD-L1low /TILlow ; TMIT III, PD-L1high /TILlow ; and TMIT IV, PD-L1low /TILhigh ) differentially affect clinical outcomes of patients with lung adenocarcinoma (LAC) and squamous cell carcinoma (SCC). METHODS AND RESULTS: Immunohistochemistry (IHC) was applied to evaluate the expression of PD-L1 and the spatial distribution of programmed cell death 1 (PD-1) and CD8 TILs on the surgically resected specimens from 205 cases of LAC and 149 cases of SCC. PD-1 and CD8 TILs were more frequently distributed in SCC than those in LAC, regardless of their infiltrating in the tumor islets or stroma. The density of TILs was a poor prognostic factor in LAC but a favorable one in SCC. PD-L1 levels and its clinical prognostic significance differed in LAC vs SCC. LAC patients with TMIT III and SCC patients with TMIT I had the longest survival, respectively (P = .0197 and .0049). Moreover, TMIT stratification based on tumor cell PD-L1 expression and stromal CD8+ TILs could be considered as an independent prognostic factor of SCC patients' survival as determined by both univariate and multivariate analysis. CONCLUSION: Our study indicates that different type of TMIT provides its specific microenvironment with diverse impact on survival of LAC and SCC patients and highlights the importance of the integrative assessment of PD-L1 status and TILs' spatial distribution to predict patients' prognosis.
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Adenocarcinoma de Pulmão/imunologia , Carcinoma de Células Escamosas/imunologia , Neoplasias Pulmonares/imunologia , Microambiente Tumoral/imunologia , Adenocarcinoma de Pulmão/mortalidade , Adenocarcinoma de Pulmão/patologia , Adenocarcinoma de Pulmão/cirurgia , Antígeno B7-H1/imunologia , Antígeno B7-H1/metabolismo , Carcinoma de Células Escamosas/patologia , Carcinoma de Células Escamosas/cirurgia , Feminino , Humanos , Estimativa de Kaplan-Meier , Pulmão/imunologia , Pulmão/patologia , Pulmão/cirurgia , Neoplasias Pulmonares/mortalidade , Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/cirurgia , Linfócitos do Interstício Tumoral/imunologia , Masculino , Pessoa de Meia-Idade , Pneumonectomia , Prognóstico , Estudos Retrospectivos , Análise EspacialRESUMO
The polar tube protein is the major component of polar tube, and can specifically locate on the polar tube of microsporidia and plays an important role in invasion host cell. In this study, we analyzed the potential O- and Nglycosylation sites in polar tube protein 1 from Nosema bombycis. NbPTP1 was successfully cloned to eukaryotic expression vector pMT/Bip/V5-His A, involved V5 and His tags. After transfection, NbPTP1 gene could be efficiently expressed in Drosophila S2 cells. In addition, Lectin blotting and beta elimination analysis showed that NbPTP1 expressed in Drosophila S2 cells was O-glycosylation. These studies provided a basis for understanding the relationship between glycosylation and function of NbPTP1, helped us to reveal the infection mechanism of microsporidia and established effective diagnosis and prevention methods for microsporidia.
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Proteínas Fúngicas/biossíntese , Proteínas Fúngicas/química , Nosema/química , Animais , Linhagem Celular , Drosophila/citologia , Vetores Genéticos , Glicosilação , TransfecçãoRESUMO
Nosema bombycis is a destructive, obligate intracellular parasite of the Bombyx mori. In this study, a single-chain variable fragment (scFv) dependent technology is developed for the purpose of inhibiting parasite proliferation in insect cells. The scFv-G4, which we prepared from a mouse G4 monoclonal antibody, can target the N. bombycis spore wall protein 12 (NbSWP12). Indirect immunofluorescence assays showed that NbSWP12 located mainly on the outside of the N. bombycis cytoskeleton, although some of it co-localized with ß-tubulin in the meront-stage of parasites. When meront division began, NbSWP12 became concentrated at both ends of each meront. Western blotting showed that scFv-G4 could express in Sf9-III cells and recognized native NbSWP12. The transgenic Sf9-III cell line showed better resistance than the controls when challenged with N. bombycis, indicating that NbSWP12 is a promising target in this parasite and this scFv dependent strategy could be a solution for construction of N. bombycis-resistant Bombyx mori.
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Bombyx/imunologia , Resistência à Doença/imunologia , Nosema/patogenicidade , Anticorpos de Cadeia Única/imunologia , Animais , Anticorpos Monoclonais/genética , Anticorpos Monoclonais/imunologia , Western Blotting , Bombyx/genética , Bombyx/microbiologia , Clonagem Molecular , Resistência à Doença/genética , Ensaio de Imunoadsorção Enzimática , Técnica Indireta de Fluorescência para Anticorpo , Nosema/imunologia , Organismos Geneticamente Modificados , Reação em Cadeia da Polimerase em Tempo Real , Anticorpos de Cadeia Única/genéticaRESUMO
Whey protein concentrate (WPC) was oxidized by peroxyl radicals derived from 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) and the kinetics of droplet stability in O/W and W/O emulsions stabilized by oxidized WPC were evaluated by studying the micro-rheology. Degrees of protein oxidation were indicated by carbonyl concentration and emulsion types were distinguished by fluorescence microscopy. Oxidation resulted in free sulfhydryl groups degradation and surface hydrophobicity decrease. Moderate protein oxidation promoted to form diminutive droplets, which aggregated quickly to gel-network structure and decreased the motion rate of droplets, leading to the increased elasticity and viscosity, which led to better stability. Over-oxidation underwent severe droplet aggregation and sediment with increased motion rate, which resulted in instability of emulsions. The W/O emulsions of oxidized WPC were more inclined to block the motion of droplets and form a stable structure with higher viscosity, compared with the O/W emulsions.
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The impacts of protein oxidation on the droplet size and microrheology properties of casein emulsions with 20% oil content were investigated. The degree of protein oxidation was indicated by carbonyl concentration. The droplets in the emulsions of different-oxidation-degree casein had bimodal distribution, but their size altered due to oxidation. The effects of protein oxidation on the morphology, motion type, viscoelasticity, and stability of droplets were also investigated by microrheology analysis. The droplet motion was blocked by protein oxidation due to mean square displacement slope results. Solid-liquid balance values provided the liquid behavior dominating these emulsions. Oxidation of carbonyl concentration 16.72 raised the primary droplets, increased the elasticity, decreased the viscosity, and promoted the droplet motion rate, resulting in better stability of emulsions. Further oxidation promoted the aggregation of droplets and resulted in poor stability.