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To efficiently produce seedlings in aquaculture farms, it is essential to control the ratio of males and females by sex distinguishing. On the other hand, the concentration of 11-ketotestosterone (11-KT), which is contained in the plasma, would be an excellent indicator that is significantly different between males and female fish.However, the concentration of 11-KT is challenging to measure due to its low concentration. In this study, we attempted to develop a high-sense biosensor system enhanced by single-walled carbon nanotubes (SWCNTs) with high conductivity and improved the efficiency and accuracy of fish gender determination. First, a self-assembled monolayer (SAM)was formed on the surface of a disk-type gold electrode, and an anti-rabbit IgG was immobilized on the SAM end.Next, an anti-11-KT antibody was immobilized on this IgG antibody, and then SWCNTs were immobilized on the electrode surface to fabricate the biosensor.Then, we attempted to quantify 11-KT by analyzing the minor electrochemical changes on the electrode surface before and after the reaction of an anti-11-KT antibody with 11-KT as an antigen by cyclic voltammetry.Next, after examining the influence of various conditions (temperature, pH, reaction time) on the response value of this sensor, the specificity of the sensor using other hormones was confirmed.Furthermore, as an application of this sensor to the actual sample, the 11-KT concentration in a Nile tilapia (Oreochromis niloticus) plasma was measured and correlated with the measurement value obtained by the conventional method (ELISA) was compared., source:https://doi.org/10.1016/j.sbsr.2022.100474, source:https://www.elsevier.com

To efficiently produce seedlings in aquaculture farms, it is essential to control the ratio of males and females by sex distinguishing. On the other hand, the concentration of 11-ketotestosterone (11-KT), which is contained in the plasma, would be an excellent indicator that is significantly different between males and female fish.However, the concentration of 11-KT is challenging to measure due to its low concentration. In this study, we attempted to develop a high-sense biosensor system enhanced by single-walled carbon nanotubes (SWCNTs) with high conductivity and improved the efficiency and accuracy of fish gender determination. First, a self-assembled monolayer (SAM)was formed on the surface of a disk-type gold electrode, and an anti-rabbit IgG was immobilized on the SAM end.Next, an anti-11-KT antibody was immobilized on this IgG antibody, and then SWCNTs were immobilized on the electrode surface to fabricate the biosensor.Then, we attempted to quantify 11-KT by analyzing the minor electrochemical changes on the electrode surface before and after the reaction of an anti-11-KT antibody with 11-KT as an antigen by cyclic voltammetry.Next, after examining the influence of various conditions (temperature, pH, reaction time) on the response value of this sensor, the specificity of the sensor using other hormones was confirmed.Furthermore, as an application of this sensor to the actual sample, the 11-KT concentration in a Nile tilapia (Oreochromis niloticus) plasma was measured and correlated with the measurement value obtained by the conventional method (ELISA) was compared., source:https://doi.org/10.1016/j.sbsr.2022.100474, source:https://www.elsevier.com

Retinoic acid (RA) is crucial for mammalian spermatogonia differentiation, and stimulates Stra8 expression, a gene required for meiosis. Certain fish species, including zebrafish, have lost the stra8 gene. While RA still seems important for spermatogenesis in fish, it is not known which stage(s) respond to RA or whether its effects are integrated into the endocrine regulation of spermatogenesis. In zebrafish, RA promoted spermatogonia differentiation, supported androgen-stimulated meiosis, and reduced spermatocyte and spermatid apoptosis. Follicle-stimulating hormone (Fsh) stimulated RA production. Expressing a dominant-negative RA receptor variant in germ cells clearly disturbed spermatogenesis but meiosis and spermiogenesis still took place, although sperm quality was low in 6-month-old adults. This condition also activated Leydig cells. Three months later, spermatogenesis apparently had recovered, but doubling of testis weight demonstrated hypertrophy, apoptosis/DNA damage among spermatids was high and sperm quality remained low. We conclude that RA signaling is important for zebrafish spermatogenesis but is not of crucial relevance. As Fsh stimulates androgen and RA production, germ cell-mediated, RA-dependent reduction of Leydig cell activity may form a hitherto unknown intratesticular negative-feedback loop.

Leptin modulates all levels of the reproductive endocrine axis in mammals, and in turn, both leptin and the leptin receptor are regulated by sex steroids. The aim of this study was to investigate if sex steroids regulate the leptin system also in fish. Immature one-year old male Atlantic salmon parr were implanted with Silclear capsules that were either empty or filled with 11-ketoandrostenedione (11 KA) or testosterone (T) and the effects of 35-days treatment were investigated on measures of maturation, gene expression of leptin (lepa1, lepa2), leptin receptor (lepra1) and circulating plasma leptin. Both 11-KA and T stimulated the reproductive axis by increasing testes weight and up-regulated pituitary lh-beta mRNA levels and for T also fsh-beta. T up-regulated transcription levels of lepa1 and lepra1 in the pituitary, while 11-KA had no effect. Leptin receptor expression in the testis was unaltered by either androgen. T up-regulated lepa1 mRNA levels significantly also in the liver, but had no effect on lepa2, and 11 KA did not affect hepatic gene expression of either lepa1 or lepa2. Plasma leptin levels did not differ significantly between treatments. The results indicate that androgens regulate gene expression of leptin and the leptin receptor in different tissues in fish and that the effects of leptin might be tissue specific considering plasma levels remained unaltered. Overall, the results suggest a role for leptin in fish reproduction, where sex steroids are able to regulate components of the leptin system differentially in liver and important tissues of the reproductive axis.

Leptin modulates all levels of the reproductive endocrine axis in mammals, and in turn, both leptin and the leptin receptor are regulated by sex steroids. The aim of this study was to investigate if sex steroids regulate the leptin system also in fish. Immature one-year old male Atlantic salmon parr were implanted with Silclear capsules that were either empty or filled with 11-ketoandrostenedione (11 KA) or testosterone (T) and the effects of 35-days treatment were investigated on measures of maturation, gene expression of leptin (lepa1, lepa2), leptin receptor (lepra1) and circulating plasma leptin. Both 11-KA and T stimulated the reproductive axis by increasing testes weight and up-regulated pituitary lh-beta mRNA levels and for T also fsh-beta. T up-regulated transcription levels of lepa1 and lepra1 in the pituitary, while 11-KA had no effect. Leptin receptor expression in the testis was unaltered by either androgen. T up-regulated lepa1 mRNA levels significantly also in the liver, but had no effect on lepa2, and 11 KA did not affect hepatic gene expression of either lepa1 or lepa2. Plasma leptin levels did not differ significantly between treatments. The results indicate that androgens regulate gene expression of leptin and the leptin receptor in different tissues in fish and that the effects of leptin might be tissue specific considering plasma levels remained unaltered. Overall, the results suggest a role for leptin in fish reproduction, where sex steroids are able to regulate components of the leptin system differentially in liver and important tissues of the reproductive axis.

Mature male Pacific salmon (Oncorhynchus spp.) develop a hooknose, as a secondary male sexual characteristic, during the spawning period. It is likely that androgens regulate hooknose formation. However, endocrinological and histochemical details about the relationship between androgens and hooknose formation are poorly understood. In this study, we performed assays of serum androgens, detection of androgen receptor (AR) in hooknose tissues, external morphological measurement of hooknose-related lengths, and microscopic observation of hooknose tissues of pink salmon (O. gorbuscha) at different stages of sexual maturation. Expression of the ar beta gene was detected in hooknose tissues of males but not females. The elongation of these tissues was mediated directly via androgens. Serum 11-ketotestosterone (11-KT) concentrations indicated a significant positive correlation with both jaw lengths during sexual maturation of males. In the upper jaw, cartilage tissue developed during hooknose formation, and AR-immunoreactive chondrocytes were located in the rostal-vetral regions of hooknose cartilage in maturing male. The chondrocytes in maturing males before entering into rivers exhibited rich cytoplasm with high cell activity than at other sexual development stages. On the other hand, in the lower jaw, the development of the spongiosa-like bone meshworks. AR-immunoreactivity was detected in a proportion of the osteocytes and osteoblast-like cells in the spongiosa-like bone meshworks. These results indicate that hooknose formation in pink salmon, which is associated with the buildup of a structure with sufficient strength that it can be used to attack other males on the spawning ground, is regulated by 11-KT. (C) 2018 Elsevier Inc. All rights reserved.

Mature male Pacific salmon (Oncorhynchus spp.) develop a hooknose, as a secondary male sexual characteristic, during the spawning period. It is likely that androgens regulate hooknose formation. However, endocrinological and histochemical details about the relationship between androgens and hooknose formation are poorly understood. In this study, we performed assays of serum androgens, detection of androgen receptor (AR) in hooknose tissues, external morphological measurement of hooknose-related lengths, and microscopic observation of hooknose tissues of pink salmon (O. gorbuscha) at different stages of sexual maturation. Expression of the ar beta gene was detected in hooknose tissues of males but not females. The elongation of these tissues was mediated directly via androgens. Serum 11-ketotestosterone (11-KT) concentrations indicated a significant positive correlation with both jaw lengths during sexual maturation of males. In the upper jaw, cartilage tissue developed during hooknose formation, and AR-immunoreactive chondrocytes were located in the rostal-vetral regions of hooknose cartilage in maturing male. The chondrocytes in maturing males before entering into rivers exhibited rich cytoplasm with high cell activity than at other sexual development stages. On the other hand, in the lower jaw, the development of the spongiosa-like bone meshworks. AR-immunoreactivity was detected in a proportion of the osteocytes and osteoblast-like cells in the spongiosa-like bone meshworks. These results indicate that hooknose formation in pink salmon, which is associated with the buildup of a structure with sufficient strength that it can be used to attack other males on the spawning ground, is regulated by 11-KT. (C) 2018 Elsevier Inc. All rights reserved.

We collected examined and analyzed 1378 fish of 99 species from 47 sites in the Mississippi River basin (MRB) during 1995 and from a reference site in 1996. The sampling sites in the MRB represented National Contaminant Biomonitoring Program (NCBP) stations situated at key points on major rivers and National Water Quality Assessment Program (NAWQA) stations located on lower-order rivers and streams in the Eastern Iowa Basins (FIB) and Mississippi Embayment (MSE) Study Units. The reference site was the water supply system of the USGS-Leetown Science Center in rural Jefferson County WV Common carp (Cyprinus carpio; carp) and black basses (Micropterus spp., bass) the targeted species together represented 82% of the fish collected. Each fish was examined in the field for externally and internally visible gross lesions selected organs were weighed to compute various ponderal and organo-somatic indices and selected tissues and fluids were obtained and preserved for analysis of biomarkers. Fish health indicators included splenic macrophage aggregates lysozyme activity and hispathological anlysis of liver kidney and of liver tissues. Reproductive biomarkers included analysis of plasma concentrations of vitellogenin (vtg) and the sex steroid hormones 17beta-estradiol (E2) and 11-ketotestosterone (11- kt), and the histological determination of percent oocyte atresia (in female fish) and gonadal stage. Hepatic ethoxyresorufin O-deethylase (EROD) activity was also measured. Composite samples of whole fish from each station were grouped by species and gender and analyzed for persistent organochlorine and elemental contaminants and for dioxin-like activity (TCDD-EQ) using the H411E rat hepatoma cell bioassay., The original document contains color images.

This document describes the suite of biological methods of the U.S. Geological Survey Biomonitoring of Environmental Status and Trends program for monitoring chemical contaminants and their effects on fish. The methods, which were selected by panels of experts, are being field-tested in rivers of the Mississippi River, Columbia River, and Rio Grande basins. General health biomarkers include a health assessment index based on gross observation; histopathological examination of selected organs and tissues; condition factor; and the heptosomatic and splenosomatic indices. Immune system indicators are plasma lysozyme activity and measures of splenic macrophage aggregates. Reproductive biomarkers include plasma concentrations of sex steroids hormones (17beta-estradiaol and 11-ketotestosterone) and vitellogenin, gonadal histopathology (including reproductive stage and, in females, gonadal atresia), and the gonadosomatic index. Indicators of exposure to polycyclic aromatic and polyhalogenated hydrocarbons are the H4IIE rat hepatoma cell bioassay (performed on solvent extracts of composite fish samples) and hepatic ethoxyresorufin-O-deethylase activity. Stable nitrogen isotope ratios are used to assess the trophic position of the fish and their exposure to sewage and other animal wastes. For each indicator we describe endpoints(s) and methods, and discuss the indicator's value and limitations for contaminant monitoring and assessment.

In Europe, the study of the relationship between nutritional conditions and reproduction in captivity of marine fish has focused on sea bass, Dicentrarchus labrax, gilthead sea bream, Sparus aurata, and turbot, Scophthalmus maximus three economically important species. However, in these species, there are very few studies on the nutritional influence on the male reproductive condition, as well as on dietary effects on sperm quality. In the sea bass, we have shown that deficiencies in dietary protein and w-3 fatty acids notably influence the female reproductive process, both at the brain and the ovarian level, which may affect the survival and viability of eggs and larvae (Kah et al., 1994; Cerd`a et al., 1995). We present here, for the first time in this species, evidence for long-term dietary effects on the levels of circulating androgens, which were observed in fish fed low dietary fatty acids during two consecutive reproductive cycles.