RESUMEN

Freeze tolerance is a survival strategy employed by some ectotherms living in extremely cold environments. Some fish in extremely cold areas can recover from their frozen state, but they also have to endure cold stress. Amur sleeper (Perccottus glenii) can recover from a completely frozen state. To explore the response of freeze-resistant fish to low temperatures, we analyzed histological alterations, and antioxidant and carbohydrate-lipid metabolizing enzymes of P. glenii under low temperatures. So far, sensory genes regulating P. glenii during cold stress, freezing, and recovery have not been identified. Ultrastructure results indicated that glycogen content and mitochondrial ridge decreased during cold stress and freezing, whereas the number of endoplasmic reticulum increased during recovery. Plasma glucose and glycerol levels of the three treatment groups significantly increased. Lactate dehydrogenase and pyruvate kinase levels significantly increased during cold stress and freezing, and hexokinase levels significantly increased during cold stress. In total, 30,560 unigenes were found (average length 1724 bp, N50 2843 bp). In addition, 7370 differentially expressed genes (DEGs; including 2938 upregulated genes and 4432 downregulated genes) were identified. KEGG analysis revealed that the DEGs were enriched in carbohydrate and lipid metabolism, lipid synthesis, immune system, and anti-apoptosis. Genes involved in glycolysis and phospholipid metabolism were significantly upregulated during cold stress; genes related to circadian rhythm, oxidative phosphorylation, and lipid synthesis were significantly upregulated during freezing; and genes involved in the immune system and anti-apoptosis were significantly upregulated during recovery. Our results attempt to offer new insights into the physiological mechanisms of complex adaptation in P. glenii and provide useful information for future studies on the mechanism underlying freezing/recovery in animals.

Asunto(s)

RESUMEN

This study describes the cloning and characterization of Period 1a and Period 1b genes and the analysis of their mRNA and protein expression in Amur minnow (Phoxinus lagowskii) after exposure to different light cycles. The full-length P. lagowskii Per1a and Per1b genes encode proteins consisting of 1393 and 1409 amino acids, and share high homology with the per1 genes of other freshwater fish species. The Per1a and Per1b genes were widely expressed within the brain, eye, and peripheral tissues. The acrophase of the Per1a gene in the pituitary gland occurred during the dark phase at ZT15 (zeitgeber time 15, 12 L: 12 D) and ZT18 (8 L, 16 D), whereas the acrophase of the Per1b gene in the pituitary gland was observed during the light phase. Our study suggests that the expression of Per1a and Per1b in P. lagowskii varied depending on differences in circadian rhythm patterns. The results of our dual-luciferase reporter assays demonstrated that the P. lagowskii Per1b gene enhances the activation of NF-κB. This study is the first to examine the circadian clock gene Per1a and Per1b in the high-latitude fish P. lagowskii, offering valuable insights into the effects of different light periods on this fish species.

Asunto(s)

RESUMEN

High-latitude fish are subjected to sustained and diel-cycling hypoxia. Oxygen deficiency could pose a serious threat to fish, but little information is available regarding the response mechanisms employed by high-latitude fish to sustained and diel-cycling hypoxia. In this study, a combination of transcriptomics and metabolomics were used to examine the molecular response mechanisms actioned by sustained and diel-cycling hypoxia in the high-latitude fish, Phoxinus lagowskii. P. lagowskii was divided into normoxic control (6.0-7.0 mg/L dissolved oxygen), sustained (1.5 mg/L dissolved oxygen), and diel-cycling hypoxic treatment (6.0-7.0 mg/L between 07:00-21:00, and 3.0-4.0 mg/L between 21:00-07:00) tanks for 28 days. Differentially expressed genes (DEGs) and significantly different metabolites (DMs) related to digestive proteases, lipid metabolism, estrogen signaling pathway, steroid hormone biosynthesis, glutathione metabolism, and tryptophan metabolism were identified from comparative metabolomic and transcriptomic data expression profiles within the liver. The current study found that P. lagowskii had significantly different responses between sustained and diel-cycling hypoxia. P. lagowskii faced with sustained hypoxia may enhance their tolerance capacity through phospholipid and glutathione metabolism. Our data provide new insights into the high latitude fish coping with changes in hypoxia and warrants further investigation into these potentially important genes and metabolites.

Asunto(s)

RESUMEN

Nitrogen-doped reduced graphene oxide-metal(metal oxides) nanoparticle (N-rGO-M(MO) NPs, M = Fe, MO: M = Co, Mn) composites were prepared through a facile and general method at high temperature (800 °C). M(MO) were well-dispersed and tightly anchored on graphene sheets, which were doped with nitrogen simultaneously and further loaded with Pt nanoparticles. Those results showed a more positive onset potential, higher cathodic density, and higher electron transfer number for the ORR in alkaline media. Furthermore, N-rGO-metal(metal oxides)-Pt (N-rGO-M(MO)-Pt) nanoparticles show better durability than the commercial Pt/C catalyst, and can be used as promising potential materials in practical applications.