Histology, fatty acid composition, antioxidant and glycolipid metabolism, and transcriptome analyses of the acute cold stress response in Phoxinus lagowskii.

Water temperature is a crucial environmental factor that significantly affects the physiological and biochemical processes of fish. Due to the occurrence of cold events in aquaculture, it is imperative to investigate how fish respond to cold stress. This study aims to uncover the mechanisms responds to acute cold stress by conducting a comprehensive analysis of the histomorphology, glycolipid metabolic and antioxidant enzymes, fatty acid composition and transcriptome at three temperatures (16 °C, 10 °C and 4 °C) in Phoxinus lagowskii. Our results showed that cold stress not damaged muscle microstructure but caused autophagy (at 10 °C). In addition, serum glucose (Glu) and triglycerides (TG) increased during cold stress. The activities of reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), fructose phosphokinase (PFK), hexokinase (HK), pyruvate kinase (PK), and malondialdehyde (MDA) content in muscle were measured and analyzed. During cold stress, superoxide dismutase and catalase activities increased, reactive oxygen species content decreased. No significant difference in Glutathione peroxidase (GPx) activity, malondialdehyde and total cholesterol (T-CHO) contents among groups. Phosphokinase and pyruvate kinase activities decreased, and HK activity increased during cold stress. Our study resulted in the identification of a total of 25,400 genes, with 2524 genes showing differential expression across different temperature treatments. Furthermore, KEGG pathway indicated that some pathways upregulated during light cold stress (at 10 °C, including autophagy, and AMP-activated protein kinase (AMPK) signaling pathway. Additionally, circadian rhythm is among the most enriched pathways in genes up-regulated during severe cold stress (at 4 °C). Our findings offer valuable insights into how cold-water fish respond to cold stress.

Transcriptome, histological, and physiological responses of Amur sleeper (Perccottus glenii) during cold stress, freezing, and recovery.

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.

Cloning, tissue distribution, and effects of different circadian rhythms on the mRNA expression levels of circadian clock genes Per1a and Per1b in Phoxinus lagowskii.

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.

Evaluation of Pericardial Thickening and Adhesion Using High-Frequency Ultrasound.

BACKGROUND: Routine echocardiography using a standard-frequency ultrasound probe has insufficient spatial resolution to clearly visualize the parietal pericardium (PP). High-frequency ultrasound (HFU) has enhanced axial resolution. The aim of this study was to use a commercially available high-frequency linear probe to evaluate apical PP thickness (PPT) and pericardial adhesion in both normal pericardium and pericardial diseases. METHODS: From April 2002 to March 2022, 227 healthy individuals, 205 patients with apical aneurysm (AA) and 80 patients with chronic constrictive pericarditis (CP) were recruited to participate in this study. All subjects underwent both standard-frequency ultrasound and HFU to image the apical PP (APP) and pericardial adhesion. Some subjects underwent computed tomography (CT). RESULTS: Apical PPT was measured using HFU and found to be 0.60 ± 0.01 mm (0.37-0.87 mm) in normal control subjects, 1.22 ± 0.04 mm (0.48-4.53 mm) in patients with AA, and 2.91 ± 0.17 mm (1.13-9.01 mm) in patients with CP. Tiny physiologic effusions were observed in 39.2% of normal individuals. Pericardial adhesion was detected in 69.8% of patients with local pericarditis due to AA and 97.5% of patients with CP. Visibly thickened visceral pericardium was observed in six patients with CP. Apical PPT measurements obtained by HFU correlated well with those obtained by CT in those patients with CP. However, CT could clearly visualize the APP in only 45% of normal individuals and 37% of patients with AA. In 10 patients with CP, both HFU and CT demonstrated equal ability to visualize the very thickened APP. CONCLUSIONS: Apical PPT measured using HFU in normal control subjects ranged from 0.37 to 0.87 mm, consistent with previous reports from necropsy studies. HFU had higher resolution in distinguishing local pericarditis of the AA from normal individuals. HFU was superior to CT in imaging APP lesions, as CT failed to visualize the APP in more than half of both normal individuals and patients with AA. The fact that all 80 patients with CP in our study had significantly thickened APP raises doubt regarding the previously reported finding that 18% of patients with CP had normal PPT.

The effects of sustained and diel-cycling hypoxia on high-latitude fish Phoxinus lagowskii.

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.