Yersinia ruckeri Infection and Enteric Redmouth Disease among Endangered Chinese Sturgeons, China, 2022.

During October 2022, enteric redmouth disease (ERM) affected Chinese sturgeons at a farm in Hubei, China, causing mass mortality. Affected fish exhibited characteristic red mouth and intestinal inflammation. Investigation led to isolation of a prominent bacterial strain, zhx1, from the internal organs and intestines of affected fish. Artificial infection experiments confirmed the role of zhx1 as the pathogen responsible for the deaths. The primary pathologic manifestations consisted of degeneration, necrosis, and inflammatory reactions, resulting in multiple organ dysfunction and death. Whole-genome sequencing of the bacteria identified zhx1 as Yersinia ruckeri, which possesses 135 drug-resistance genes and 443 virulence factor-related genes. Drug-susceptibility testing of zhx1 demonstrated high sensitivity to chloramphenicol and florfenicol but varying degrees of resistance to 18 other antimicrobial drugs. Identifying the pathogenic bacteria associated with ERM in Chinese sturgeons establishes a theoretical foundation for the effective prevention and control of this disease.

Comparative transcriptome analysis reveals expression signatures of albino Russian sturgeon, Acipenseriformes gueldenstaedtii.

Albinism is a genetically inherited condition that is caused by a series of genetic abnormalities leading to a reduction in melanin production. Russian sturgeon is one of the most valuable freshwater fish species worldwide, and albino individuals have been found in fish farms. Due to its complicated genome and scarce genome-wide genetic resources, the underlying molecular basis of albinism in Russian sturgeon is unknown. In the present study, we first generated transcriptome profile of Acipenser gueldenstaedtii using pooled tissues, which provided reliable reference sequences for future molecular genetic studies. A total of 369,441 contigs were assembled, corresponding to 32,965 unique genes. A comparative analysis of the transcripts from the skin of albino and wildtype individuals was conducted afterwards. A total of 785 unique genes were differentially expressed, including the upregulation of 385 genes and the downregulation of 400 genes in albino individuals. The expression pattern of 16 selected differentially expressed genes was validated using qRT-PCR. Additional annotation, GO enrichment analysis and gene pathway analysis indicated that the melanogenesis pathway may be interrupted in albinism. Eight potential causative genes that were highly likely to be responsible for sturgeon albinism were identified, including Dct, Tyrp1b, Slc45a2, Ctns, Pmela, Pmelb, Cd63, and Bloc1s3, which were found to be significantly down-regulated in albino Russian sturgeon. Moreover, a sliding window analysis of the ratio of nonsynonymous to synonymous nucleotide substitution rates (Ka/Ks) ratios indicated that seven out of the eight genes underwent positive selection during evolution. Our results provide a valuable basis for understanding the molecular mechanism of albinism in fish species and will facilitate future genetic selection and breeding of sturgeon with market-favored traits in aquaculture.

Genome-wide characterization of Toll-like receptor gene family in common carp (Cyprinus carpio) and their involvement in host immune response to Aeromonas hydrophila infection.

The Toll-like receptor (TLR) gene family is a class of conserved pattern recognition receptors, which play an essential role in innate immunity providing efficient defense against invading microbial pathogens. Although TLRs have been extensively characterized in both invertebrates and vertebrates, a comprehensive analysis of TLRs in common carp is lacking. In the present study, we have conducted the first genome-wide systematic analysis of common carp (Cyprinus carpio) TLR genes. A set of 27 common carp TLR genes were identified and characterized. Sequence similarity analysis, functional domain prediction and phylogenetic analysis supported their annotation and orthologies. By examining the gene copy number of TLR genes across several vertebrates, gene duplications and losses were observed. The expression patterns of TLR genes were examined during early developmental stages and in various healthy tissues, and the results showed that TLR genes were ubiquitously expressed, indicating a likely role in maintaining homeostasis. Moreover, the differential expression of TLRs was examined after Aeromons hydrophila infection, and showed that most TLR genes were induced, with diverse patterns. TLR1, TLR4-2, TLR4-3, TLR22-2, TLR22-3 were significantly up-regulated at minimum one timepoint, whereas TLR2-1, TLR4-1, TLR7-1 and TLR7-2 were significantly down-regulated. Our results suggested that TLR genes play critical roles in the common carp immune response. Collectively, our findings provide fundamental genomic resources for future studies on fish disease management and disease-resistance selective breeding strategy development.

[Effects of adrenergic receptor agonists injected into hippocampus on cellular immune function].

AIM AND METHODS: The effect of intrahippocampal microinjection of noradrenaline (NA) and its receptors antagonists and agonists on cellular immune functions were investigated in normal and adrenalectomy rat by determine the proliferative activity of Con A-stimulated splenic lymphocytes in MTT method and natural killer (NK) cell activity. RESULTS: (1) In normal group, the proliferative activity of Con A-Stimulated splenic lymphocytes were inhibited and the activity of NK cell were reduced with microinjection NA and beta1-, beta2-adrenergic receptor agonists Dobutamine (Dob, 4 microl, 6.0 x 10(-3) moL/L), Metaproterenol (Met, 4 microl, 8.0 x 10(-3) mol/L), compared with their intensity of effect, NA > Met > Dob; the immunosuppression effect induced by NA was partly hindered by alpha- and beta-receptor antagonists, phentolamine (Phen, 2 microl, 1.6 x 10(-2) mol/L) and propranolol (Prop, 2 microl, 1.6 x 10(-3) mol/L), and the action of Prop was more evident. (2) In adrenalectomy group, immunosuppression effect induced by NA was unconspicuous. CONCLUSION: The results suggested that NA in hippocampus could inhibit distinctly cellular immune functions, which was predominantly mediated by beta2- adrenergic receptor with a minor contribution of beta1- and alpha- adrenergic receptors. Moreover, keeping intact construction and function of adrenal gland have an important role in the effect of NA on cellular immune function.