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In this study, the effects of different freezing methods and temperatures (freezer at −20 and −50 ℃, and liquid nitrogen at −50 and −80 ℃) on the water-holding capacity and structural properties of myofibrillar proteins from the hind leg muscle of Rana nigromaculata were investigated. The results showed that the time required for hind legs frozen in freezer at −20 and −50 ℃ and with liquid nitrogen at −50 and −80 ℃ to pass through the zone of maximum ice crystal formation temperature (−1 to −5 ℃) were 91.5, 57.0, 1.5 and 0.5 min, respectively. Compared with the freezer freezing groups, the liquid nitrogen freezing groups exhibited reduced thawing loss, increased content of immobilized water, and decreased content of free water. Compared with fresh samples, the water-holding capacity, solubility, total sulfhydryl content and endogenous fluorescence intensity of myofibrillar proteins decreased significantly after freezing, and the particle size, surface hydrophobicity and relative content of random coil showed an increasing trend. In the −50 ℃ liquid nitrogen freezing group, the water-holding capacity, protein solubility, total sulfhydryl content and endogenous fluorescence intensity decreased by 8.10%, 9.57%, 10.50% and 67.36%, respectively, and the volume average particle size, surface hydrophobicity and random coil content increased by 100.05%, 82.24% and 13.65%, respectively; these changes were significantly lower than those in the other freezing groups (P < 0.05). The degree of myofibrillar protein denaturation in the −80 ℃ liquid nitrogen freezing group was significantly lower than that in the −20 ℃ freezer freezing group, but higher than that in the −50 ℃ liquid nitrogen freezing group (P < 0.05). According to the results of scanning electron microscopy (SEM), muscle fibers were more tightly and regularly arranged in the −50 ℃ freezer freezing and −50 ℃ liquid nitrogen freezing groups, while those in the −80 ℃ liquid nitrogen freezing group were arranged regularly but slightly cracked, and those frozen in the −20 ℃ freezer freezing group were obviously broken. These findings indicate that liquid nitrogen freezing can slow down the migration of water in the hind leg muscle of R. nigromaculata and effectively inhibit the cold denaturation of myofibrillar proteins, the effect being more pronounced at −50 ℃ than at −80 ℃.

Phyllostachys praecox shoots were frozen using liquid nitrogen at –60, –90 or –120 ℃ to an internal temperature of –18 ℃, or frozen at –90 ℃ to an internal temperature of –6, –12 or –18 ℃, vacuum-packed and stored in a freezer at –18 ℃ for 24 weeks. In order to analyze the effect of liquid nitrogen freezing on physiological and biochemical characteristics of P. praecox shoots during frozen storage, L-phenylalanine ammonialyase (PAL) and peroxidase (POD) activities, total phenolic content, relative electrical conductivity, and water state were measured and ice crystal structure and cell morphology were observed. The results showed that with increasing freezing time, the PAL and POD activities, total phenolic content, and peak area of free water in all six groups decreased significantly (P 0.05). The PAL and POD activities and relative conductivity of P. praecox shoots frozen at –6 ℃ were higher than those frozen at –12 and –18 ℃, and the size of ice crystals was smaller and the degree of cell damage was greater in P. praecox shoots frozen at –6 ℃ than at –12 and –18 ℃. The difference between P. praecox shoots frozen at –12 and –18 ℃ was not significant (P > 0.05). Collectively, these findings indicated that the most suitable liquid nitrogen freezing conditions of P. praecox shoots are –90 and –12 ℃ for freezing and internal temperature, respectively.

In this study, the effects of the addition of different amounts of salt (0%, 1%, 2% and 3%) at five stages of processing: raw shrimp, blanching, marination, soaking for 2 h and soaking at 4 ℃ for 24 h, on the quality and volatile flavor compounds of marinated crayfish were investigated. The results showed that L* values increased and then decreased as the processing stages proceeded, while a* and b* values both continued to increase. But salt addition had little effect on the color difference. Additionally, moisture content decreased and then increased, and was affected little by salt addition. For 1%, 2% and 3% salt addition, hardness, elasticity, chewiness and adhesion showed an initial increasing and subsequent decreasing trend. Without salt addition, hardness and chewiness continued to increase. For each group, elasticity and cohesiveness increased and then did not show any significant change. The electronic nose results could be roughly divided into four parts, raw shrimp and blanching, marination, soaking for 2 h, and soaking at 4 ℃ for 24 h. There were also some differences between the less and more salt addition groups. The electronic tongue results showed that as salt addition increased or the processing stages proceeded, saltiness, astringency, and umami taste increased, and other taste attributes changed little. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis showed that salt addition and marination had a positive effect on the volatile flavor of crayfish. However, excessive salt addition and too long processing time were detrimental to volatile flavors. In conclusion, the addition of salt and processing stages can affect the quality and flavor of marinated crayfish.

Abstract Bronchopulmonary dysplasia (BPD) is characterized by alveolar dysplasia, and evidence indicates that interferon regulatory factor 4 (IRF4) is involved in the pathogenesis of various inflammatory lung diseases. Nonetheless, the significance and mechanism of IRF4 in BPD remain unelucidated. Consequently, we established a mouse model of BPD through hyperoxia exposure, and ELISA was employed to measure interleukin-17 A (IL-17 A) and interleukin-6 (IL-6) expression levels in lung tissues. Western blotting was adopted to determine the expression of IRF4, surfactant protein C (SP-C), and podoplanin (T1α) in lung tissues. Flow cytometry was utilized for analyzing the percentages of FOXP3+ regulatory T cells (Tregs) and FOXP3+RORγt+ Tregs in CD4+ T cells in lung tissues to clarify the underlying mechanism. Our findings revealed that BPD mice exhibited disordered lung tissue structure, elevated IRF4 expression, decreased SP-C and T1α expression, increased IL-17 A and IL-6 levels, reduced proportion of FOXP3+ Tregs, and increased proportion of FOXP3+RORγt+ Tregs. For the purpose of further elucidating the effect of IRF4 on Treg phenotype switching induced by hyperoxia in lung tissues, we exposed neonatal mice with IRF4 knockout to hyperoxia. These mice exhibited regular lung tissue structure, increased proportion of FOXP3+ Tregs, reduced proportion of FOXP3+RORγt+ Tregs, elevated SP-C and T1α expression, and decreased IL-17 A and IL-6 levels. In conclusion, our findings demonstrate that IRF4-mediated Treg phenotype switching in lung tissues exacerbates alveolar epithelial cell injury under hyperoxia exposure.

In recent years, ultrasound has been widely used in the food industry as a promising non-thermal, green technology, but the exact effect of ultrasound on the physicochemical properties of myofibrillar proteins from Procambarus clarkii is not clear yet. This study investigated the effect of high-intensity ultrasound treatment at 300 W power and 20 kHz frequency for 0, 4, 8, 12 and 16 min during homogenization on the structure and physicochemical properties of myofibrillar proteins from Procambarus clarkii. The results showed that ultrasound treatment decreased the turbidity and mean particle size of myofibrillar proteins significantly (P < 0.05), but initially increased and then decreased the solubility and absolute value of ζ-potential, demonstrating altered degree of protein aggregation. The surface hydrophobicity and endogenous fluorescence intensity initially increased and then decreased with increasing treatment time; the total sulfhydryl group content significantly decreased (P < 0.05) while the carbonyl group content significantly increased (P < 0.05), demonstrating changes in the tertiary structure and a certain degree of protein denaturation. In addition, the relative contents of α-helix and random coil increased first and then decreased, whereas the opposite trend was observed for the proportion of β-sheet, indicating changes in the secondary structure. These results showed that high-intensity ultrasound treatment could affect the physicochemical properties, structure and aggregation degree of myofibrillar proteins from crayfish meat, which could provide a reference for the application of ultrasound as an auxiliary approach in the processing and storage of crayfish.

Objective To investigate the dynamic changes of leukotriene C4 (LTC4), type 2 innate lymphoid cell(ILC2) and related cytokines (IL-4, IL-5 and IL-13) in the lung tissue of mice with bronchopulmonary dysplasia (BPD). Methods C57BL / 6 mice were randomly divided into air group and hyperoxia group.The hyperoxia group was exposed to 85% oxygen for 1, 7 and 14 days to replicate the BPD model.HE staining microscopy was used to observe the pathological changes of the lung tissue of mice. The percentages of ILC2 and CysLT1R+ILC2 were detected by flow cytometry.The contents of LTC4, IL-4, IL-5 and IL-13 were detected by ELISA.Western blot was used to detect the expression of LTC4-C synthase (LTC4S).RT-qPCR was used to detect the mRNA expression of LTC4S and cysteine leukotriene type 1 receptor (CysLT1R). Results Compared with air group, the percentage of ILC2 and CysLT1R+ILC2 in hyperoxia group and the expression of CysLT1R mRNA all increased(P＜0.05);The expression of IL-4, IL-5 and IL-13 in the hyperoxia group increased and were higher than those in the air group at the same time point (P＜0.05);LTC4 content, LTC4S protein and mRNA expression were significantly increased in hyperoxia group (P＜0.05). Conclusions In BPD, LTC4 increases and may induce the increase of ILC2 and related cytokines (IL-4, IL-5 and IL-13) through CysLT1R.

In this paper, based on first-principles theory, we investigated the properties of the multiferroic VSi2P4/Al2S3 van der Waals (vdW) heterostructure (HS), in which VSi2P4 and Al2S3 are ferromagnetic (FM) and ferroelectric (FE) materials, respectively. Our results show that the properties of the VSi2P4 layer can be effectively manipulated by reversing the ferroelectric polarized state of the Al2S3 layer (P↑ and P↓). Specifically, for P↓ Al2S3, VSi2P4 preserves the semiconductor nature and the intrinsic valley polarization in the conduction band. However, for P↑ Al2S3, the VSi2P4 sublayer is changed to a half-metal, and the valley polarization in the conduction band is submerged in trivial bands. Our findings provide an effective way for nonvolatile electrical control of the electronics and valleytronics of 2D ferromagnetic materials. [ABSTRACT FROM AUTHOR]