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This study aimed to investigate the effects of nitric oxide (NO)-mediated hypoxia-inducible factor-1α (HIF-1α) on the glycolysis and tenderness of postmortem yak muscle and its regulatory mechanism. In this study, Yak Longissimus dorsi was injected with 0.9% saline (control), 200 μmol/L S-nitrosoglutathione (GSNO), 200 μmol/L GSNO + 100 μmol/L YC-1 (HIF-1α inhibitor) or 200 μmol/L GSNO + 50 μmol/L PD98059 and aged, and NO level, HIF-1α, mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway activation, glycolysis-related enzyme activities, and shear force of muscle were analyzed at different aging time points (3, 6, 9, 12, 24 and 72 h). The results revealed that NO levels in the GSNO group were significantly higher than those in the control group during 3–72 h (P < 0.05), reaching a peak at 6 h. ERK1/2 and p-ERK1/2 expression levels were higher in the GSNO group than the control and GSNO + PD98059 groups during 3–72 h (P < 0.05), reaching a peak at 24 h. HIF-1α expression level in the GSNO group was significantly higher than that in the control and GSNO + YC-1 groups (P < 0.05), peaking at 12 h. Hexokinase (HK), pyruvate kinase (PK) and lactate dehydrogenase (LDH) in the GSNO group reached their maximum values at 9, 12 and 12 h, respectively (P < 0.05) and were significantly higher than those in the control group; at 3, 12 and 72 h, the glycolytic potential in the GSNO group was significantly higher than that in the two other groups (P < 0.05); at 6, 9 and 72 h, the pH in the GSNO group was significantly lower than that in the other groups (P < 0.05). In addition, shear force and hematoxylin and eosin (HE) staining were used to assess the tenderness of yak meat. Shear force, myofiber cross-sectional area and diameter were lower and the space between myofibers was higher in the GSNO group than in the two other groups. In conclusion, during the early period of postmortem aging, NO mediates the MAPK/ERK signaling pathway, thereby activating HIF-1α expression and upregulating HK, PK and LDH activity, accelerating the rate of glycolysis of and reducing pH, and ultimately improving the tenderness of yak meat. The results of this study may serve as a potential regulatory mechanism for regulating the tenderness of yak meat and provide a theoretical basis for improving the theoretical system of glycolysis and tenderness during postmortem aging.

This study was conducted to investigate the regulatory mechanism of reactive oxygen species (ROS) on the glycolysis pathway of bovine muscle and its impact on meat tenderness at the early stage of postmortem cold storage. Fresh beef was treated with hydrogen peroxide (H2O2) as a major ROS, N-acetyl-L-cysteine (NAC) as an ROS scavenger, or physiological saline as a control before being stored at 4 ℃. After 0.5, 6, 12, 24, and 48 hours, the glycolysis level and tenderness indices were assessed. In addition, tandem mass tag (TMT)-labeled quantitative proteomics was used for protein identification and quantitative analysis of the samples after 24 hours and for screening of differential proteins in the glycolysis pathway. The findings showed that the glycolysis level increased significantly in the H2O2-treated group, and glycogenolysis and lactic acid accumulation were significantly higher than those in the other two groups (P < 0.05). In contrast, the glycolysis process was significantly suppressed by NAC treatment. The H2O2-treated group reached the ultimate pH after 12 hours, 12 and 36 hours earlier than the control and NAC groups, respectively. The shear force of the H2O2-treated group reached its maximum after 12 hours, and the myofibrillar fragmentation index (MFI) was significantly greater than that of the other two groups after 6–48 hours (P < 0.05), indicating that a higher ROS level can accelerate the tenderization of bovine muscle by enhancing the glycolysis capacity during postmortem refrigeration. Totally eight up-regulated proteins and two down-regulated proteins in the glycolysis pathway were identified in the H2O2-treated versus control groups after 24 hours of refrigeration. Among these proteins, the up-regulated core proteins of phosphoglycerate mutase (PGAM), enolase (ENO), and pyruvate dehydrogenase E1 subunit beta (PDHB) coordinated with the down-regulated pyruvate dehydrogenase E1 subunit alpha (PDHA) to accelerate the glycolysis process. In conclusion, ROS can speed up glycolysis and consequently improve meat tenderness by regulating the expression of key proteins in the glycolysis pathway.

This study aimed to investigate the effect of ammonia mediated hypoxia inducible factor-1α (HIF-1α) expression on mitochondrial cell apoptosis and tenderness in yak meat after slaughter. Ten mmol/L ammonium chloride (NH4Cl), 0.9% normal saline (control) and 10 mmol/L N-nitro-L-arginine methyl ester hydrochloride were used separately for treating yak Longissimus dorsi. By measuring the expression of HIF-1α, nitrogen monoxide (NO) content, energy metabolism-related enzyme activities, adenosine triphosphate (ATP) level, mitochondrial pathway of apoptosis and muscle tenderness, we explored the mechanism of cell apoptosis and tenderness change in yak meat after slaughter. The results showed that during the postmortem aging of yak meat, the expression of HIF-1α and the content of NO in each treatment group increased first and then decreased, and so did the activities of Na+-K+-ATPase, Ca2+-ATPase, caspase-9 and caspase-3 and shear stress. ATP content, the degree of mitochondrial permeability transition pore (MPTP) opening, mitochondrial membrane potential (MMP), and muscle fiber diameter and area showed a gradual downward trend, and myofibril fragmentation index (MFI) and the gap between muscle cells showed an opposite trend. During 6 to 24 h after slaughter, the expression of HIF-1α and the content of NO in the NH4Cl treatment group were significantly higher than those in the control group (P < 0.05), which were significantly higher than those in the L-NAME treatment group (P < 0.05). The ATP content in the NH4Cl group was significantly higher than that in the control and L-NAME groups during 6 to 72 h after slaughter. The activities of Na+-K+-ATPase and Ca2+-ATPase in the control group were significantly higher than those in the NH4Cl group (P < 0.05), but significantly lower than those in the L-NAME group (P < 0.05). During 6–120 h after slaughter, the opening of MPTP in the control group was significantly higher than that in the NH4Cl group (P < 0.05), but lower than that in the L-NAME group (P < 0.05). During 0 to 168 h after slaughter, the opening of MMP decreased by 47.72% in the NH4Cl group, 53.54% in the control group, and 60.05% in the L-NAME group. During 6 to 72 h after slaughter, the activities of caspase-9 and caspase-3 in the NH4Cl group were significantly lower than those in the control group (P < 0.05), which were lower than those in the L-NAME group (P < 0.05). During 6 to 120 h after slaughter, shear force and muscle fiber area and diameter in the NH4Cl group were higher than those in the control group, and MFI and the gap between muscle fibers in the NH4Cl group were lower than those in the control group, while the opposite result was observed for the L-NAME group. In conclusion, ammonia decreased the activities of Na+-K+-ATPase and Ca2+-ATPase and increased the content of ATP by up-regulating the expression of HIF-1α, which in turn regulated the energy metabolism of muscle cells and maintained the stability of the internal environment. By inhibiting the opening of MPTP and the decrease in MMP, ammonia reduced the activity of caspase-3/9, and inhibited mitochondrial cell apoptosis, thereby resulting in an increase in shear stress, a decrease in MFI and morphological changes of muscle cells, and finally causing a negative effect on the tenderness of yak meat.

The aim of this study to develop a stable anthocyanin indicator film to monitor the freshness of chilled beef. Composite anthocyanin microcapsules (CAM) were prepared and used to prepare indicator films using carrageenan (Car) and sodium carboxymethyl cellulose (CMC) as film-forming matrix with different amounts (5%, 10%, 15% and 20%, V/V) of added CAM, and the structural and physical properties of the resulting films were characterized, and their application to monitor beef freshness was investigated. The results showed that the addition of CMC significantly improved the mechanical properties, barrier properties and thermal stability of Car films. The film with 15% CAM had the highest tensile strength (17.76 MPa) and lowest water vapor transmission rate (1.35 × 10－11 g/(m·s·Pa)), and showed a tightly and orderly arranged cross-section. The Fourier transform infrared spectra showed that the components of the indicator film were structurally similar and compatible. When the indicator film was exposed to ammonia, its color changed from pink to blue-green and eventually to yellow. The indicator film was applied to monitor the freshness of beef during storage at 4 ℃. The results showed that beef reached secondary freshness and spoilage on day 4 and 7, respectively, and that the color of the indicator film changed from pink to purple and green correspondingly. In conclusion, the film with 15% CAM is the most sensitive to changes in the freshness of beef and thus can be used to detect it.

This study aimed to investigate the effect of reactive oxygen species (ROS) on early postmortem energy metabolism in bovine muscle via regulating the expression of hypoxia-inducible factor-1α (HIF-1α). The muscle samples were treated with hydrogen peroxide (H2O2), N-acetyl-L-cysteine (NAC), and normal saline (control), separately. The ROS content, proline hydroxylase (PHD) activity, phosphoinositide-3 kinase/protein kinase B (PI3K/AKT) and HIF-1α expression levels, energy metabolism, and pH were determined at 0.5, 6, 12, 24 and 48 h postmortem. The results revealed that the H2O2-treated group showed a significantly higher ROS content than the other two groups at 0.5 h postmortem (P < 0.05) and remained at a high level within 48 h, while NAC inhibited the accumulation of ROS for a short period of time (during 0.5–12 h) postmortem. The PHD activity in the H2O2-treated group was significantly lower than that in the other two groups during 0.5–48 h (P < 0.05). Meanwhile, the expression levels of PI3K from 0.5 to 12 h and phosphorylated AKT (p-AKT) from 0.5 to 6 h were significantly higher than those in the other groups (P < 0.05). Consequently, the expression level of HIF-1α in the H2O2-treated group was significantly higher than that of the other two groups during 6–48 h (P < 0.05), the rate of glycogenolysis and the rate of increase in R value were significantly faster in the H2O2-treated group during 6–24 h (P < 0.05), and the pH of the H2O2-treated group reached the limit value earlier (at 12 h). In conclusion, ROS can activate the stable expression of HIF-1α by reducing the activity of PHD and up-regulating the PI3K/AKT signaling pathway and consequently accelerate energy metabolism dominated by glycolysis and the decrease in pH in bovine muscle at the initial stage of postmortem aging, which may have a crucial impact on meat quality.

The purpose of this study was to prepare Pickering emulsions stabilized by waste jujube kernel cellulose nanocrystals (CNC) using composite essential oils (EOs) (i.e., cinnamon essential oil [CIN] combined with clove essential oil [CL]). The Pickering emulsions were blended with chitosan (CS) to generate a composite film (CS/CNC/EOs Pickering emulsions). We evaluated the mechanical properties, barrier properties, and microstructures of CS/CNC/EOs bio-based packaging films containing different concentrations of EOs. In addition, the fresh-keeping effects of the composite membranes on beef sausages were evaluated over a 12-day storage period. Notably, the EOs exhibited good compatibility with CS. With the increase in the EOs concentration, the droplet size increased, the composite films became thicker, the elongation at break decreased, the tensile strength increased, and the water vapor permeability decreased. When the composite films were used for preserving beef sausages, the antioxidant and antibacterial activity of the membranes improved as the concentration of EOs increased, effectively prolonging the shelf life of the sausages. Composite membranes with an EOs concentration of 2% exerted the best fresh-keeping effects. Overall, owing to their antioxidant and antimicrobial properties, the bio-based composite films prepared using CS/CNC/EOs Pickering emulsions demonstrated immense potential for application in the packaging of meat products. [ABSTRACT FROM AUTHOR]

Summary: In this work, deferoxamine (DFO) was injected into Tibetan sheep meat (distilled water as control) to reveal the effects of lysosomal Fe2+ on mitochondrial apoptosis and muscle tenderness. The reactive oxygen species (ROS) content, lysosomal membrane stability, cathepsins activity, mitochondrial membrane permeability transition pore (MPTP), mitochondrial membrane potential (MMP), cytochrome c (Cyt‐c) reduction level, caspase activity, myofibril fragmentation index (MFI) and shear force of Oula Tibetan sheep meat were measured at different ageing times. The results indicated that the ROS content, cathepsins activity, MPTP opening degree, lysosomal membrane stability, caspase‐3/9 activity and MFI of Tibetan sheep meat were significantly decreased after DFO treatment, whilst MMP, shear force and Cyt‐c reduction levels were noticeably increased. Furthermore, correlation analysis and principal component analysis showed that mitochondrial damage was positively correlated with meat tenderness. In sum, the study suggests that lysosomal Fe2+ may promote mitochondrial apoptosis and improve the tenderness of Tibetan sheep meat. [ABSTRACT FROM AUTHOR]

BACKGROUND: The present study aimed to investigate the effects of tremella polysaccharides on the gel properties and antioxidant activity of yak skin gelatin with a view to improving the quality of collagen jellies. The preparation of composite gels were performed by yak skin gelatin (66.7 mg mL−1) and tremella polysaccharides with different concentrations (0, 2, 4, 6, 8 mg mL−1), and finally the collagen jelly was prepared by composite gel (yak skin gelatin: 66.7 mg mL−1; tremella polysaccharides:6 mg mL−1) with the best performance. RESULTS: Tremella polysaccharides not only improved the hardness, springiness, gel strength, water holding capacity and melting temperature of yak skin gelatin, but also enhanced the composite gel's scavenging activity against ABTS radicals, DPPH radicals, O2 and OH radicals. The filling of tremella polysaccharides into the gelatin network increased the number of crosslinking sites inside the gel, which resulted in the gel network structure becoming dense and orderly. The gel particles became finer and more uniform, and the thermal stability was improved. Furthermore, the sensory score of commercially available gelatin jelly decreased more rapidly during storage compared to the composite gel jelly. CONCLUSION: The gel properties and antioxidant activity of yak skin gelatin were improved by adding tremella polysaccharides, and then the quality and storage properties of the jelly were improved, which also provided technical reference for the development of functional gel food. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Purpose: The present study was designed to investigate the resistance determinants and virulence factors of 45 Trueperella pyogenes isolates from clinical bovine mastitis in Hexi Corridor of Gansu, China. Methods: Minimum inhibitory concentrations (MICs) was tested by E-test method. Gene of antimicrobial resistance, virulence integrase and integron gene cassettes were determined by PCR and DNA sequencing. Results: The T. pyogenes isolates exhibited high resistance to streptomycin (88.9%) and tetracycline (64.4%), followed by erythromycin (15.6%) and gentamicin (13.3%). Resistance to streptomycin was most commonly encoded by aadA9 (88.9%); and to tetracycline, by tetW (64.4%). Importantly, all streptomycin-resistant isolates carried aadA9 alone or in combination with aadA1, aadA11 and strA-strB. Similarly, all tetracycline-resistant isolates harbored tetW alone or in combination with tetA33. Meanwhile, ermX was detected in 13.3% isolates, only one erythromycin-resistant isolate was not identified for this gene. Moreover, all T. pyogenes isolates carried class 1 integrons, and 17.8% of them contained gene cassettes, including arrays aadA1-aadB (4.4%), aad A24-dfrA1-ORF1 (2.2%) and aadA1 (2.2%). Furthermore, all tested isolates harbored virulent genes plo and fimA, followed by fimC (88.9%), fimE (86.6%) nanP (75.6%), nanH (40.0%), cbpA (35.6%) and fimG (6.7%). Conclusion: To our knowledge, this is the first report of integron gene cassettes of T. pyogenes isolates from bovine mastitis cases in China. These findings are useful for developing the prevention and the virulence factors of T. pyogenes could be promising candidates for vaccine antigens for bovine mastitis caused by T. pyogenes in China. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Metal nanoparticles (NPs) decorated block copolymer (BCP) hybrid nanoparticles have attracted enormous attention for their actual value in catalysis, medical therapy, and bioengineering. The confined assembly of BCPs within evaporative emulsion droplet is verified as an effective method to provide polymeric scaffolds to load metal NPs. However, to date, it remains challenging to generate different types of metal NPs decorated BCP hybrid nanoparticles. Herein, we employed the emulsion confined self‐assembly of poly(styrene‐b‐ 2‐vinylpyridine) (PS‐b‐P2VP) and the followed seed‐mediated growth of Au and palladium (Pd) NPs onto well‐defined BCP particles to design a series of Au/Pd decorated BCP hybrid nanoparticles, which exhibited excellent catalytic activity for the reduction of 4‐nitrophenol to 4‐aminophenol with the reductant of NaBH4. This work may inspire more researchers to investigate the selective decoration of different metal NPs onto the polymeric scaffolds, broadening the potential applications of the inorganic/organic hybrid nanoparticles. [ABSTRACT FROM AUTHOR]