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To study the relationship between oxidative stress and mitochondrial damage during post-slaughter chilling, M. longissimus dorsi from Tan sheep was treated with the antioxidant N-acetyl-L-cysteine (NAC) solution or physiological saline and stored at 0–4 ℃. After 0, 2, 4, 6 and 8 days, the opening degree of mitochondrial permeability transition pore (MPTP), membrane potential, reactive oxygen species (ROS) content, complex I, II, III and IV activities, the activities of succinate dehydrogenase (SDH), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) content were determined, and the mitochondrial structure of myoblasts was observed under transmission electron microscopy (TEM). The results showed that the opening degree of MPTP in both the NAC and control groups gradually increased (P < 0.05) during the postmortem maturation process, and so did the ROS and MDA levels (P < 0.05). The mitochondrial membrane potential and the activities of complexes I, II, III and IV, SDH, CAT, SOD and GSH-Px showed a gradual decreasing trend (P < 0.05). It can be concluded that oxidative stress occurred in the muscle tissue of Tan sheep after slaughter, resulting in a significant increase in ROS content. Excessive ROS, exceeding the ability of the antioxidant defense system to scavenge it, could lead to an imbalance in the redox system, which could in turn accelerate the increase of ROS levels, thereby triggering the opening of MPTP and a decrease in the mitochondrial membrane potential, finally resulting in serious mitochondrial damage. However, NAC alleviated this phenomenon. Increased ROS levels impaired the normal operation of the mitochondrial electron transport chain, thus leading to increased mitochondrial damage. In addition, the lipid oxidation product MDA also damaged the function and structure of mitochondria, causing mitochondrial structural damages such as swelling and deformation, and finally leading to biological dysfunctions.

The aim of this study was to assess the effect of nitric oxide (NO)-mediated mitochondrial apoptosis on Tan sheep meat tenderness during postmortem aging. The hind leg muscle of Tan sheep was injected with 0.8% NaCl (control), 20 mmol/L aminoguanidine hydrochloride (AH) or 90 mmol/L L-arginine (L-Arg) and aged at 4 ℃ for 0, 6, 12, 24, 48, 96, and 192 h. NO and inducible nitric oxide synthase (iNOS) contents, cytochrome c (Cyt c) redox state, oxidative stress level, mitochondrial apoptotic pathways, and tenderness were measured during postmortem aging. The results indicated that at 12 and 24 h after slaughter, NO and iNOS levels were significantly higher, and ATP levels were significantly lower in the L-Arg group than in the control group (P < 0.05). At 24 and 48 h, Cyt c reduction levels and superoxide dismutase (SOD) activity were significantly higher, while the level of reactive oxygen species (ROS) was significantly lower in the AH group than in the control group (P < 0.05). From 12 to 96 h, ATP contents were significantly lower in the L-Arg group than in the control group (P < 0.05). In addition, at 24 h, Ca2+ concentration significantly increased in the L-Arg group compared with the control group (P < 0.05). At all time points except 24 h, the caspase-3 activity in the L-Arg group was significantly higher than that in the control group (P < 0.05). Moreover, it was found that the Bax/Bcl-2 ratio, pH, and myofibril fragmentation index (MFI) in the L-Arg group were significantly higher than those in the control group at all time points after slaughter (P < 0.05). Shear force was significantly lower in the L-Arg group but significantly higher in the AH group than in the control group (P < 0.05). In conclusion, NO exacerbates mitochondrial oxidative stress and directly upregulates ROS levels during the postmortem aging of Tan sheep meat, leading to a decrease in SOD activity, irreversible opening of mitochondrial permeability transition pore (MPTP), and ultimately mitochondrial damage. In addition, by controlling the redox state of Cyt c, NO indirectly activates caspase-3 activity to accelerate apoptotic energy metabolism, deplete ATP and consequently maintain myocyte homeostasis. Furthermore, NO affects the release of Ca2+, up-regulates the Bax/Bcl-2 ratio, and induces the occurrence of mitochondrial apoptotic cascade, ultimately resulting in an increase in MFI and a decrease in shear force and, consequently, improving the tenderness of Tan sheep meat.

In order to investigate the regulatory effect of B-cell lymphoma-2 (Bcl-2) on cell apoptosis and water retention in postmortem Qinchuan beef, the longissimus dorsi muscle of Qinchuan cattle was injected with either 200 μmol/L glycochenodeoxycholic acid (GCDA) or 10 μmol/L 2-ethyl-3-methylpentanamide (ABT-737) solution and aged at 4 ℃ postmortem. After 0, 6, 12, 24, 48, 72 and 120 h, the changes in Bcl-2 and Bcl-2-associated X protein (Bax) contents, the concentrations of endoplasmic reticulum and mitochondrial calcium ion, voltage-dependent anion channel protein 1 (VDAC1) expression, calpain content, the mitochondrial apoptosis pathway and water retention were determined. The results showed that at 6 h after slaughter, the Bcl-2 content of the GCDA-treated group was significantly higher than that of the control group (P < 0.01), the calcium ion concentration in the endoplasmic reticulum was significantly lower than that of the control group (P < 0.01), and cooking loss was significantly lower in both treatment groups than the control group (P < 0.05). At 12 and 24 h post-slaughter, the Bcl-2 content of the ABT-737-treated group was significantly lower than that of the control group (P < 0.01). At 12 and 120 h post-slaughter, the endoplasmic reticulum calcium ion, mitochondrial calcium ion and calpain levels in the ABT-737-treated group were significantly greater than those in the control group (P < 0.01). During 0–120 h post-slaughter, the total expression of VDAC1 in both treatment groups was lower than that in the control group. In summary, during the postmortem aging of Qinchuan beef, under the regulation of Bcl-2, calcium overload occurs through VDAC1-facilitated calcium transport, resulting in the activation of calpain, and the overloading of Ca2+ in mitochondria promotes the activation of caspase-9 and caspase-3, thus inducing cell apoptosis. The higher the degrees of cell apoptosis and caspase activation, the higher the degree of degradation of myofibrillar proteins, and the poorer the water-holding capacity of the meat.

Geomagnetic storms can cause large variations in the ionosphere, but their impacts on the mesosphere and lower thermosphere (MLT) are not well understood. Based on the Total Electron Content (TEC) data and the meteor neutral winds data over Mohe (53.5°N, 122.3°E) and Beijing (40.3°N, 116.2°E), we analyze the tidal variations during six intense geomagnetic storms from 2016 to 2021. According to the six intense geomagnetic storms, we found that intense geomagnetic storms can lead to diurnal and semidiurnal tidal enhancements in TEC, while their influences on tidal variations in the MLT region are not always captured. Responses of tidal enhancement in the MLT region to the intense geomagnetic storms are more obvious at a lower latitude at Beijing, but the tidal amplitude changes are not proportional to the Dst indices. Some semidiurnal tides are significantly enhanced prior to the onset of geomagnetic storms, which needs to be statistically investigated in the future based on additional observations. [ABSTRACT FROM AUTHOR]

Ni3Si2O5(OH)4 rods (NS) were synthesized via a hydrothermal method, employing natural wollastonite as a template. The hierarchical Ni3Si2O5(OH)4 rods exhibited vertically oriented nanosheets, resulting in a substantial increase in the specific surface area (from 2.24 m2/g to 178.4 m2/g). Subsequently, a CdS/Ni3Si2O5(OH)4 composite photocatalyst (CdS/NS) was prepared using a chemical deposition method. CdS was uniformly loaded onto the surface of the Ni3Si2O5(OH)4 nanosheets, successfully forming a heterojunction with Ni3Si2O5(OH)4. The CdS/NS photocatalyst in the presence of lactic acid as a sacrificial agent demonstrated an impressive H2 production rate of 4.05 mmol h−1 g−1, around 40 times higher than pure CdS. The photocorrosion of CdS was effectively solved after loading. After four cycles, the performance of CdS/NS remained stable, showing the potential for sustainable applications. After photoexcitation, electrons moved from Ni3Si2O5(OH)4 to the valence band of CdS, where they interacted with the holes via an enhanced interface contact. Simultaneously, electrons in CdS transitioned to its conduction band, facilitating hydrogenation. The enhanced performance was attributed to the improved CdS dispersion by Ni3Si2O5(OH)4 loading and efficient photogenerated carrier separation through the heterojunction formation. This work provides new perspectives for broadening the applications of mineral materials and developing heterojunction photocatalysts with good dispersibility and recyclability. [ABSTRACT FROM AUTHOR]

The iron content in Ni Cr Fe alloys strongly affected the properties of oxide films after 1012 h of immersion in an oxygenated simulated PWR primary water environment at 310 °C. Increasing the iron content in the alloy increased the porosity and thickness of the outer layer and the inner layer. Increasing the iron content in the alloy increased the amount of spinel needle-like oxides and decreased the amount of NiO particles in the outer layer. Cellular oxide in the inner layer was nickel-rich in the center and chromium-rich at the edge. [ABSTRACT FROM AUTHOR]

The microstructure of A508III/309L/308L weld clad and the properties of the oxide films formed in simulated pressurized water reactor primary water at 290 °C were characterized. The A508III heat-affected zone (HAZ) consisted primarily of a decarburization zone with ferrite near the fusion line and a following pearlite structure with fine grains. A high hardness region in the HAZ could be the result of C-enrichment. M 23 C 6 and M 7 C 3 precipitates were observed in element transition zone. 308L stainless steel (SS) containing ∼ 12% ferrites exhibited both ferritic-austenitic solidification mode (FA mode, δ→γ) and austenitic-ferritic solidification mode (AF mode, γ→δ), whereas 309L SS containing ∼ 9% ferrites exhibited only FA mode. The A508III surface oxide film was mainly Fe 3 O 4 in deaerated high-temperature water. The coarse grain zone covered with few oxide particles was different from other types of film on the other region of HAZ and the bulk zone. More pitting appears on 309L SS after immersion in deaerated high-temperature water due to the dissolution of inclusions. SS surface oxide films consisted primarily of spinels. The oxide film on SS was divided into two layers. Ni was concentrated mainly at the oxide/substrate interface. The oxide film formed on 309L was thicker than that on the 308L. The ferrite in the stainless steel could improve the oxidation resistance. [ABSTRACT FROM AUTHOR]