Differential Exoproteome and Biochemical Characterisation of Neoparamoeba perurans

Infection with the protozoan ectoparasite Neoparamoeba perurans, the causative agent of AGD, remains a global threat to salmonid farming. This study aimed to analyse the exoproteome of both an attenuated and virulent N. perurans isolate using proteomics and cytotoxicity testing. A disproportionate presence of proteins from the co-cultured microbiota of N. perurans was revealed on searching an amalgamated database of bacterial, N. perurans and Amoebozoa proteins. LC‑MS/MS identified 33 differentially expressed proteins, the majority of which were upregulated in the attenuated exoproteome. Proteins of putative interest found in both exoproteomes were maltoporin, ferrichrome-iron receptor, and putative ferric enterobactin receptor. Protease activity remained significantly elevated in the attenuated exoproteome compared with the virulent exoproteome. Similarly, the attenuated exoproteome had a significantly higher cytotoxic effect on rainbow trout gill cell line (RTgill W1) cells compared with the virulent exoproteome. The presence of a phosphatase and serine protease in the virulent exoproteome may facilitate AGD infection but do not appear to be key players in causing cytotoxicity. Altogether, this study reveals prolonged culture of N. perurans affects the exoproteome composition in favour of nutritional acquisition, and that the current culturing protocol for virulent N. perurans does not facilitate the secretion of virulence factors.

Subtoxic dose of lithium cobalt oxide nanosheets impacts critical molecular pathways in trout gill epithelial cells

Global transcriptomics uncovered key molecular processes impacted by subtoxic dose of lithium cobalt oxide nanoparticles, indicating cellular attempts to restore energy and oxygen balance.

Tricellular tight junction-associated angulins in the gill epithelium of rainbow trout

Molecular physiology of the tricellular tight junction (tTJ)-associated proteins lipolysis-stimulated lipoprotein receptor ( lsr, = angulin-1) and an immunoglobulin-like domain-containing receptor ( ildr2, ≈angulin-3) was examined in model trout gill epithelia. Transcripts encoding lsr and ildr2 are broadly expressed in trout organs. A reduction in lsr and ildr2 mRNA abundance was observed during and after confluence in flask-cultured gill cells. In contrast, as high-resistance and low-permeability characteristics developed in a model gill epithelium cultured on permeable polyethylene terephthalate membrane inserts, lsr and ildr2 transcript abundance increased. However, as epithelia entered the developmental plateau phase, lsr abundance returned to initial values, while ildr2 transcript abundance remained elevated. When mitochondrion-rich cells were introduced to model preparations, lsr mRNA abundance was unaltered and ildr2 mRNA abundance significantly increased. Transcript abundance of ildr2 was not altered in association with corticosteroid-induced tightening of the gill epithelium, while lsr mRNA abundance decreased. Transcriptional knockdown of the tTJ protein tricelluin (Tric) reduced Tric abundance, increased gill epithelium permeability, and increased lsr without significantly altering ildr2 transcript abundance. Data suggest that angulins contribute to fish gill epithelium barrier properties but that Lsr and Ildr2 seem likely to play different roles. This is because ildr2 typically exhibited increased abundance in association with decreased model permeability, while lsr abundance changed in a manner that suggested a role in Tric recruitment to the tTJ.

Characterization of the histologic appearance of normal gill tissue using special staining techniques

Anatomic pathologists are familiar with stains used in light microscopy to identify cells, storage products, tissue deposits, and pathogens. Assessment of the surrounding tissue with special stains may reveal aspects of interest for the tissue or the species. We illustrate the expected staining characteristics of normal rainbow trout gill tissue with routine hematoxylin and eosin and 18 other histochemical stains.