Branchial nitrogen cycle symbionts can remove ammonia in fish gills.

Knowledge of the mechanisms by which fish excrete their metabolic nitrogenous waste and insights into nitrogen cycling in aquaculture systems is of utmost importance to improve the sustainable commercial production of fish. In fish, most nitrogenous waste is excreted via the gills as ammonia, a potentially toxic nitrogenous compound. In this study; activity assays, physiological experiments, molecular analysis and microscopy were used to show that the gills of fish harbor a unique combination of hitherto overlooked nitrogen-cycle microorganisms that can theoretically detoxify excreted ammonia by converting it into inert dinitrogen gas.

Low oxygen tolerance of different life stages of temperate freshwater fish species.

Data on low dissolved oxygen (DO₂) tolerance of freshwater fish species of north-western Europe were used to create species sensitivity distributions (SSD). Lowest observed effect concentrations (LOEC) and 100% lethal concentrations (LC₁₀₀) data were collected from the scientific literature. Comparisons were made among life stages as well as between native and exotic species.

The effects of arachidonic acid on the endocrine and osmoregulatory response of tilapia (Oreochromis mossambicus) acclimated to seawater and subjected to confinement stress.

In previous studies in freshwater tilapia (Oreochromis mossambicus), dietary supplementation with arachidonic acid (ArA; 20:4n - 6) had considerable, opposing effects on the main ion-transporting enzyme Na(+)/K(+)-ATPase in gills and kidneys and changed the release of osmoregulatory hormones, such as cortisol. The present study was performed to assess the influence of dietary ArA on (1) the osmoregulatory capacity of tilapia acclimated to seawater (SW) (34‰) and (2) the osmoregulatory imbalance associated with acute stress. The increased ambient salinity was associated with significant alterations in the tissue fatty acid composition, particularly the n - 6 polyunsaturated fatty acids (PUFAs).

Cellular responses in the skin of the gilthead sea bream Sparus aurata L. and the sea bass Dicentrarchus labrax (L.) exposed to high ammonia.

Adult gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax were exposed for 24 and 48 h, respectively, to two concentrations of ammonia each (mean values of 3·34 and 13·10 mg l(-1) TA-N in S. aurata; 2·99 and 11·90 mg l(-1) TA-N in D. labrax).

Transcriptional analysis of the common carp (Cyprinus carpio L.) immune response to the fish louse Argulus japonicus Thiele (Crustacea: Branchiura).

In the present study we investigated changes in transcription levels of a panel of selected immune relevant genes in peripheral blood leucocytes (PBL) and skin samples collected from carp exposed to larval Argulus japonicus. We show that in skin up-regulation of gene transcription of the chemokine CXCa, and to a lesser extent the chemokine receptor CXCR1 and the cytokine TNFalpha, are good indicators of parasite-induced skin damage at 2 days post-parasite exposure. Up-regulation of gene transcription corresponded well with an increase in leucocytes, probably neutrophilic granulocyte numbers in skin samples collected at the sites of infection.

Calcium homeostasis in low and high calcium water acclimatized Oreochromis mossambicus exposed to ambient and dietary cadmium.

The effects of cadmium administered via ambient water (10 microg/l) or food (10 microgCd/fish/day) on plasma calcium, corpuscles of Stannius and bony tissues of Oreochromis mossambicus acclimated to low calcium (0.2 mM) and high calcium (0.8 mM) water were studied for 2, 4, 14 and 35 days.

Metabolic and thyroidal response in air-breathing perch (Anabas testudineus) to water-borne kerosene.

To address the physiological compensatory adaptations in air-breathing fish to a toxicant, we studied the metabolite pattern, serum and liver enzymes and thyroidal response in a tropical air-breathing perch, Anabas testudineus (kept at 30 degrees C in a 12-h L:D cycle) after exposing the fish for 48h to the water-soluble fraction of kerosene. The concentrations of serum glucose (P <0.05), triglycerides (P <0.

Opercular epithelial cells: a simple approach for in vitro studies of cellular responses in fish.

This study evaluated the efficacy of fish opercular external (skin) and inner (opercular membrane) epithelium as an in vitro model for toxic and other substances studies. The rainbow trout (Oncorhynchus mykiss) operculum was cultured in 12-well dishes containing sterile Leibovitz 15 (L-15) supplemented with glutamine medium during 24h at 9 degrees C, and the effect of copper, a toxic agent, and/or cortisol, an endogenous agent, on the epithelial cells was analyzed using light microscopy techniques. The opercula were submitted to four treatments: (i) control (Cont), L-15 medium only, (ii) 0.

The acute stress response of red porgy, Pagrus pagrus, kept on a red or white background.

The skin colour of red porgy, Pagrus pagrus, can be modified by exposure to different background colours. Red and white background colours brighten the dark skin colour that develops under common culture conditions in red porgy. To assess whether skin colour is also modified by aquaculture related handling stress, we subjected red porgy to 5 min of netting stress combined with air exposure.

Plasma alpha-MSH and acetylated beta-endorphin levels following stress vary according to CRH sensitivity of the pituitary melanotropes in common carp, Cyprinus carpio.

Pituitary melanotropes release alpha-melanocyte-stimulating hormone (alpha-MSH) and acetylated beta-endorphin (NAc beta-end) during stress responses. However, effects of stressors on plasma concentrations of these hormones are highly inconsistent among fish species. Here, we show that also within a species, the common carp (Cyprinus carpio), fish sometimes respond with elevated alpha-MSH and NAc beta-end plasma levels, and at other times not.

Arachidonic acid reduces the stress response of gilthead seabream Sparus aurata L.

In this study the influence of the dietary level of the fatty acid arachidonic acid (ArA, 20:4n-6) was determined on the acute stress response and osmoregulation of adult gilthead seabream Sparus aurata L. Seabream were fed a diet containing either 0.9% or 2.

A short-term in vitro gill culture system to study the effects of toxic (copper) and non-toxic (cortisol) stressors on the rainbow trout, Oncorhynchus mykiss (Walbaum).

A short-term (24 h) method of gill filament culture system was developed to predict the effects of environmental contamination and stress in fish. Gill culture system containing two or three rainbow trout gill filaments in sterile glutamine supplemented Leibovitz 15 (L-15) media was submitted for 24 h to six different treatments: (i) CONT (control, medium only); (ii) CORT (cortisol, 0.28 microM cortisol); (iii) BLOCK (glucocorticoid receptor blocker, 14 microM RU 486); (iv) CORT+BLOCK (cortisol and blocker, 0.

Localization, expression and control of adrenocorticotropic hormone in the nucleus preopticus and pituitary gland of common carp (Cyprinus carpio L.).

Adrenocorticotropic hormone (ACTH) takes a central role in the hypothalamo-pituitary-interrenal axis (HPI axis), which is activated during stress. ACTH is produced by the corticotrope cells of the pituitary pars distalis (PD) and is under control of factors from the nucleus preopticus (NPO). The distribution of ACTH in the hypothalamo-pituitary system in common carp (Cyprinus carpio L.

Corticotropin-releasing hormone in the teleost stress response: rapid appearance of the peptide in plasma of tilapia (Oreochromis mossambicus).

High concentrations (up to 600 pg/ml) of corticotropin-releasing hormone (CRH) were detected in plasma of the teleost fish Oreochromis mossambicus (tilapia) when screening peripheral tissues of tilapia exposed to stress. Notably, the plasma CRH response to stressors in tilapia is much more pronounced than that in higher vertebrates, such as rats. After characterisation by RIA, by spiking plasma with synthetic tilapia CRH and by methanol-acid extraction, it is concluded that the immunoreactive (ir) material in plasma represents tilapia CRH(1-41).

Cortisol influences the host-parasite interaction between the rainbow trout (Oncorhynchus mykiss) and the crustacean ectoparasite Argulus japonicus.

The host-parasite interaction between the rainbow trout Oncorhynchus mykiss and the fish louse Argulus japonicus was investigated by administering low levels of dietary cortisol before infecting the fish with low numbers of the parasite. After 24 h, the dietary cortisol treatment elevated blood cortisol and glucose levels and stimulated the synthesis of secretory granules in the upper layer of skin cells. Infection with 6 lice per fish caused skin infiltration by lymphocytes, also in areas without parasites.

Differential release of alpha-melanophore stimulating hormone isoforms by the pituitary gland of red porgy, Pagrus pagrus.

The best known actions of the pleiotrope alpha-melanophore stimulating hormone (alpha-MSH) are skin pigment regulation and corticotrope actions in the response to chronic stress. Stress-induced and enhanced release of alpha-MSH may therefore influence skin pigmentation and stress physiology simultaneously. The release of alpha-MSH is under multiple control by hypothalamic hormones and neurotransmitters.

Exposure to water from the lower Rhine induces a stress response in the rainbow trout Oncorhynchus mykiss.

The water quality of the river Rhine has improved in recent years and populations of salmonids are increasing. Nevertheless at present, the water from the lower Rhine still contains a complex mixture of low levels of many pollutants and it is not known whether exposure to such water is stressful to salmonid fish. For 31 days we continuously exposed the trout Oncorhynchus mykiss to water from the lower Rhine in the Netherlands and measured a variety of physiological, biochemical, and histological parameters, including the stress parameters cortisol and glucose.

Effects of acetylsalicylic acid treatment on thyroid hormones, prolactins, and the stress response of tilapia (Oreochromis mossambicus).

The cyclooxygenase (COX) pathway converts arachidonic acid (ArA) into prostaglandins (PGs), which interact with the stress response in mammals and possibly in fish as well. Acetylsalicylic acid (ASA) is a COX inhibitor and was used to characterize the effects of PGs on the release of several hormones and the stress response of tilapia (Oreochromis mossambicus). Plasma PGE2 was significantly reduced at 100 mg ASA/kg body wt, and both basal PGE2 and cortisol levels correlated negatively with plasma salicylate.

Organ-related distribution of phospholemman in the spiny dogfish Squalus acanthias.

The distribution of phospholemman among nine different organs of the spiny dogfish (Squalus acanthias) has been determined on the basis of Western blotting of microsomal material. Only rectal gland (100%), brain (43%), heart (18%), and kidney (19%) (abundancies as percent of the concentration in rectal gland) contained the protein, but not gill and colon. The relative abundance in the brain makes this organ a preferential test system for phospholemman in fishes that lack a rectal gland like teleosts.

Cloning of a proopiomelanocortin cDNA from the pituitary gland of the sea bass (Dicentrarchus labrax) and assessment of mRNA expression in different tissues by means of real-time PCR.

Proopiomelanocortin (POMC) cDNA was cloned from sea bass (Dicentrarchus labrax) pituitary gland. A 743 nucleotide sequence was obtained coding for the following sequences flanked by sets of proteolytic cleavage sites: ACTH (Ser(88)-Met(127)), alpha-MSH (Ser(88)-Gly(102)), CLIP (Pro(106)-Met(127)), beta-LPH (Glu(131)-Gln(208)), gamma-LPH (Glu(131)-Ser(175)), beta-MSH (Asp(159)-Ser(175)), and beta-endorphin (Tyr(178)-Gln(208)). No region homologous to gamma-MSH/joining peptide (a tetrapod POMC feature) was found.

Temperature-induced changes in thyrotropin-releasing hormone sensitivity in carp melanotropes.

This study investigates whether thyrotropin-releasing hormone (TRH), alpha-melanocyte-stimulating hormone (alpha-MSH) and N-acetyl beta-endorphin (NAc beta-END), or the thyroid hormones thyroxine (T4) and 3,5,3'-triiodothyronine (T3) are involved in the physiological response to temperature changes in the poikilotherm common carp (CYPRINUS CARPIO). Carps were either subjected to a rapid cold exposure or acclimated over time to three different temperatures. Acute cold exposure did not influence blood plasma alpha-MSH concentrations.

Distribution and quantification of corticotropin-releasing hormone (CRH) in the brain of the teleost fish Oreochromis mossambicus (tilapia).

The recent characterization of the corticotropin-releasing hormone (CRH) prehormone of the fish tilapia (Oreochromis mossambicus) showed that more variation exists between vertebrate CRH amino acid sequences than recognized before. The present study investigates whether the deviating composition of tilapia CRH coincides with an atypical distribution of CRH in the brain. For this purpose we applied immunohistochemistry, as well as radioimmunoassay (RIA) quantification in brain slices.

Corticotropin-releasing hormone (CRH) in the teleost fish Oreochromis mossambicus (tilapia): in vitro release and brain distribution determined by a novel radioimmunoassay.

The quantitative distribution of corticotropin-releasing hormone (CRH) in the brain and pituitary of the fish Oreochromis mossambicus (tilapia) was studied following the validation of a radioimmunoassay. Compared to the pituitary content, the brain contained 20 times more CRH. Eighty percent of the total brain content was located outside the hypothalamus, particularly in the telencephalon.

Characterization of primary culture of rainbow trout (Oncorhynchus mykiss) skin explants: growth, cell composition, proliferation, and apoptosis.

A trout (Oncorhynchus mykiss) epidermal skin primary explant system was evaluated over 8 d by light and electron microscopy. Three distinct regions of the explant outgrowth were identified on the basis of cell composition. The area immediately adjacent to the founder tissue contained mainly small migrating cells and mucous cells.