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Histopathological studies of parasitic infections in fish from the natural environment of Brazilian Amazon, are quite scarce. In this study, we investigated the histopathological changes of the proximal intestine of specimens of the Amazonian fish Hoplias malabaricus infected by the hematophagous nematode Procamallanus (Spirocamallanus) paraensis. The prevalence of the infection was 60%, with an average abundance of 1.46 and an average intensity of 2.43 parasites/fish. No significant difference was observed in the prevalence of infection and fish size or sex, but larger fish showed greater infection intensity, which was also significantly higher in male hosts. Histological sections of the proximal intestine showed reduction and loss of the epithelial lining, exposure of the lamina propria where the nematode interacts with the intestine wall, through the insertion of the buccal capsule and fish cellular debris in the intestinal lumen. In addition, areas with bleeding and inflammatory infiltrate were observed, but no changes or presence of parasite structures were observed in the other tunics of the intestinal wall. [ABSTRACT FROM AUTHOR]

It is known that the insulin-like growth factor (Igf) system is involved in gonadal development and, in turn, reproduction in vertebrates. In this study, the circulating levels of Igf-1 and follicle-stimulating hormone (Fsh) were assessed as physiological signals related to gonadal maturation stage in juvenile male European sea bass at 1 year of age. The seasonal profiles of Igf-1 and Fsh were analyzed in non-precocious (NP) and precocious (PR) fish during the early onset of puberty. Subsequently, gonadal expression patterns of the three igf genes and their two receptors, igf-1r and igf-2r , were studied during their first year of life. The analysis was continued to evaluate the mRNA expression profiles of three genes (sox17 , scf , nf2) mediating spermatogenesis progression. Collectively, these results demonstrated that PR males have higher circulating levels of Igf-1 as compared to NP fish before and during the putative gonadal development period (PGD). Plasma Fsh levels were significantly higher in PR males as compared to NP fish before the start of the PGD period, although this was followed by a decrease in Fsh levels and a subsequent recovery, coinciding with the reproductive season (February). Results showed that the total variance associated with the appearance of precocity may be explained by the contribution of factors such as body size and plasma levels of Igf-1, Fsh and sex steroids in male sea bass. Expression of igfs was high during stage I, and this was significantly correlated with the expression of genes related to cell cycle progression, including sox17 , scf and nf2. Finally, the decreased expression of all these gonadal factors in precocious animals suggests their potential involvement in regulating the proliferative growth of spermatogonia and supporting cells during the early stages of spermatogenesis, thus evoking the onset of puberty in male sea bass. • Igf-1 and Fsh plasma levels are indicators of early puberty in juvenile male sea bass. • The igf/igfr system shows differential gene expression, depending on the testicular stage. • Gonadal expression of igfs is positively correlated with proliferation-related genes. • igfs , sox17 , scf and nf2 are involved in spermatogenesis progression in sea bass. [ABSTRACT FROM AUTHOR]

There are numerous fish diseases that affect the central nervous system. However, few studies have investigated the immune cells and immunological responses of fish brains. Meanwhile, microglial cells, as the brain's first line of defense, play a vital role in neuroimmunology. Furthermore, CD83 is a co-stimulatory protein that regulates immunological responses and the activation of dendritic cells and macrophages. Although CD83 expression has been linked to the initial activation of microglia in various disease scenarios in mammals, its role in teleost microglial biology remains unclear. In a recent investigation, we discovered that Ginbuna crucian carp (Gb) contains two CD83 homologs (GbCD83 and GbCD83-L). In this study, we used modified procedures of mouse-based macrophage culture from the brain and kidney to identify that GbCD83-L is highly expressed by the brain microglia-like cells and kidney-resident macrophages (KRMs) at both the protein and gene levels. Interestingly, GbCD83-L was considerably elevated in the microglia-like cells and KRMs after 24 h of lipopolysaccharide stimulation. These findings provide the first evidence of CD83 as a potential marker for active microglia and KRMs in teleosts, thus making it a crucial regulator in fish neuroimmunology and a candidate for future immunomodulatory applications in aquaculture. • Brain and kidney macrophages exhibit differences in morphology and cell behavior. • GbCD83-L is highly expressed in both microglia-like cells and kidney-resident macrophages. • GbCD83-L expression is upregulated in microglia-like cells and KRMs post-LPS stimulation. • Expression profiles suggest the potential of CD38 as an immune stimulator. [ABSTRACT FROM AUTHOR]

NLRP3 inflammasome activation is pivotal for cytokine secretion and pyroptosis in response to diverse stimuli, playing a crucial role in innate immunity. While extensively studied in mammals, the regulatory mechanisms governing NLRP3 activation in non-mammalian vertebrates remain largely unexplored. Teleosts, as basal vertebrates, represent an ideal model for exploring the evolutionary trajectory of inflammasome regulation. In this study, ABE assays, confocal microscopy, and biochemical analyses were applied to systematically characterize the mechanisms underlying NLRP3 inflammasome in teleosts, using large yellow croakers ( Larimichthys crocea , Lc ) and zebrafish ( Danio rerio , Dr ) as representative models. Our findings revealed a previously unrecognized palmitoylation-dependent regulatory mechanism essential for teleost NLRP3 activation. Specifically, zDHHC18-mediated palmitoylation at a teleost-specific cysteine residue (C946 in Lc NLRP3, C1037 in Dr NLRP3) was required for the translocation of NLRP3 to the dispersed trans-Golgi network, facilitating its subsequent recruitment to the microtubule-organizing center. This membrane trafficking was crucial for inflammasome assembly and downstream inflammatory responses. These findings provide new insights into the distinct regulatory mechanisms of NLRP3 activation in teleosts, highlighting an evolutionary divergence that contributes to innate immunity adaptation in early vertebrates.

The paraphyletic group referred to as fishes represents several extant and extinct classes that demonstrate the greatest diversity and abundance of any of the vertebrates on the Earth. Anatomically and physiologically, the systems of fish are comparable to those of other vertebrates and the thyroid and hypothalamic-pituitary-thyroid (HPT) axis are no exceptions. This article reviews the current literature on thyroid endocrinology of elasmobranch and teleost fishes with an emphasis on relevance to clinical management and highlights some of the anatomic and physiologic differences of the HPT axis in fishes., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)