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D J Bird

Publications and source records attributed to D J Bird.

At least 19 recordsLinked to original sources
PubMed2003

Bile metabolites of polycyclic aromatic hydrocarbons (PAHs) in European eels Anguilla anguilla from United Kingdom estuaries.

A total of 94 European eels (Anguilla anguilla) were collected from five estuaries in the UK. The deconjugated metabolites of polycyclic aromatic hydrocarbons (PAHs) in the bile of the eels were separated using HPLC. Six PAH metabolites were identified: 1-hydroxy (1-OH) metabolites of phenanthrene, pyrene and chrysene; and the 1-OH, 3-OH and 7,8 dihydrodiol metabolites of benzo[a]pyrene (BaP). The mean concentration of the six metabolites was greatest in eels from the Tyne (49 microM) followed by the Wear (33 microM), Tees (19 microM), Thames (4 microM) and Severn (2 microM) estuaries. Although 1-OH pyrene was always the dominant compound, there were significant differences (P<0.05) between sites and between estuaries for some metabolites. Normalising the molar concentration of the bile metabolites to the bile biliverdin absorbance reduced sample variation. When the metabolites identified were each expressed as a percentage of the total detected, the metabolite profile was characteristic for each estuary.

Anguilla↗
PubMed2002

Bile metabolites of polycyclic aromatic hydrocarbons in three species of fish from the Severn Estuary.

Six metabolites of polycyclic aromatic hydrocarbons (PAHs) were identified and quantified from the bile of 31 common eels (Anguilla anguilla), 29 European flounders (Pleuronectes flesus), and 15 conger eels (Conger conger) collected from the Severn Estuary and Bristol Channel during 1997. The bile metabolites were deconjugated by enzymatic hydrolysis and separated by reverse-phase HPLC with fluorescence detection. The major metabolite present in all fish was 1-hydroxy pyrene (75-94% of all metabolites detected) with lower proportions of 1-hydroxy chrysene (2-15%) and 1-hydroxy phenanthrene (2-8%), and small amounts of three benzo[a]pyrene derivatives (<3%). Metabolite concentrations (normalized to biliverdin content) were significantly higher in common eels than in the other two species and tended to be higher in all species at the beginning of the year than at the end. The data confirm the importance of 1-hydroxy pyrene as the key PAH metabolite in fish bile and suggest that the common eel is an ideal species for monitoring PAHs in estuarine environments.

Animals↗
PubMed2001

The distribution of melanin-concentrating hormone in the lamprey brain.

In addition to its novel, colour-regulating hormonal role in teleosts, the melanin-concentrating hormone (MCH) serves as a neuromodulatory peptide in all vertebrate brains. In gnathostome vertebrates, it is produced in several neuronal cell groups in the hypothalamus. The present work examines the organisation of the MCH system in the brain of lampreys, which separated from gnathostome vertebrates at an early stage in evolution. In all three lamprey genera examined-Petromyzon, Lampetra, and Geotria spp.-MCH perikarya were found in one major anatomical site, the periventricular dorsal hypothalamic nucleus of the posterior hypothalamus. Axons from these cell bodies projected medially into the ventricular cavity, and laterally to the neuropile of the lateral hypothalamus. From here, they extended anteriorly and posteriorly to the fore- and hindbrain. Other fibres extended dorsomedially to the habenular nucleus. In Lampetra, but not in Petromyzon, MCH fibres were seen in the pituitary neurohypophysis, most prominantly above the proximal pars distalis. The hypothalamic region in which the MCH perikarya are found forms part of the paraventricular organ (PVO), which is rich in monoamines and other neuropeptides. The association of MCH neurones with the PVO, which occurs also in many other nonmammalian vertebrates, may reflect the primary location of the MCH system. These MCH neurones were present in ammocoetes, postmetamorphic juveniles, and adults. They were more heavily granulated in adults than in young lampreys but showed no marked change in secretory appearance associated with metamorphosis or experimental osmotic challenge to indicate a role in feeding or osmoregulation. In sexually maturing Lampetra fluviatilis, however, a second group of small MCH neurones became detectable in the telencephalon, suggesting a potential role in reproduction and/or behaviour.

Animals↗
PubMed2001

Assessing chemical toxicity with the bioluminescent photobacterium (Vibrio fischeri): a comparison of three commercial systems.

The inhibition of light emitted by the bioluminescent bacterium, Vibrio fischeri, is the basis for several toxicity bioassays. The inhibitory effects of 81 chemicals, after 5 min contact time, were studied at eight concentrations using reagents from three commercial assay systems (ToxAlert 10, Microtox and LUMIStox). Solubility in water was the limiting factor in determining the selection of chemicals for study. The effective nominal concentrations (EC) resulting in 20, 50 and 80% inhibition were determined using Ln dose/Ln gamma plots and the results obtained for each system were compared by linear regression. The chemical concentrations producing 10-90% inhibition extended over 9 orders of magnitude and ranged from a minimum of 0.001 ppm to a maximum of 1,000,000 ppm. The toxicity of many chemicals was apparently related to their pH in solution and at high chemical concentrations, to osmotic imbalance. The fact that the same operator tested the same solutions simultaneously on three different systems reduced sources of error and variability and improved the consistency and reliability of the results. Only five compounds gave EC 50s that varied more than three-fold between assays. These data provide comparisons of toxicity that have not been previously available and demonstrate that, when used under standardised conditions, these bioluminescence-based toxicity assays produce very similar results.

Hydrogen-Ion Concentration↗
PubMed2001

Hepatic metallothionein as a biomaker for metal contamination: age effects and seasonal variation in European flounders (Pleuronectes flesus) from the Severn Estuary and Bristol Channel.

Hepatic concentrations of metallothionein [MT] and three metals (Cu, Zn, Cd) were determined in 242 European flounders (Pleuronectes flesus) collected from power stations at Oldbury-upon-Severn and Hinkley Point, located in Severn Estuary and Bristol Channel, UK, respectively, between March 1996 and February 1998. A model involving three-factor analysis of variance (ANOVA) was used to examine variation in MT and metal concentrations with respect to season, year and site; with age-class included as a covariate in the analysis. Hepatic concentrations of MT and Cd (and to some degree, Cu, but not Zn) increased significantly with age. The model explained 38, 25, 17 and 26% of the variation in MT, Cu, Zn and Cd, respectively, with significant effects due to season, and to a lesser extent, to year. Site was only a significant factor for Cd which was higher in fish from Hinkley. Correlation between the individual concentration of MT and each metal alone, or in combination, was poor, and explained only an additional 3.0% of the residual variation in MT, most of which was attributable to Cu (2.7%). Compared to other industrialised estuaries, Cd concentrations were high (>20 micro g-1 in some individuals). The study emphasises the importance of seasonal variation and other factors in biomonitoring programmes and highlights the limitations of using [MT] as a biomarker for metal contamination in flounders from the Severn Estuary.

Age Factors↗
PubMed2001

Towards the development of molecularly imprinted polymer based screen-printed sensors for metabolites of PAHs.

This paper describes the fabrication of a sensor for 1-hydroxypyrene (1-OHP) based on a screen-printed carbon electrode (SPCE) modified with a molecularly imprinted polymer (MIP); 1-OHP was chosen as a model metabolite of polyaromatic hydrocarbons (PAHs). It was shown that 1-OHP could be readily oxidised at a plain SPCE and the electrochemical mechanism was found to involve an ECE (electron transfer-chemical reaction-electron transfer) process. The MIP for 1-OHP was prepared using only divinylbenzene (DVB) and styrene as monomers and the binding was only based on hydrophobic interactions. Batch binding studies revealed that optimum uptake of 1-OHP by the MIP occurred from solutions containing 35% water in methanol. Selectivity of the binding sites in the MIP was examined by performing uptake studies in the same solution containing either phenol or 1-naphthol; the specific binding of 1-OHP was twenty times greater than the former and five times greater than the latter. Preliminary calibration studies were performed with the MIP-SPCE using a two-step approach; accumulation was carried out in 35% water in methanol followed by measurement in 50% methanol-0.025 mol dm(-3) phosphate buffer pH 12. This two-step non-competitive affinity assay gave encouraging results and indicated potential for use in pollution studies.

Journal Article↗
PubMed2000

Modulation of the fish immune system by hormones.

Immune-neuroendocrine interactions in fish, as in mammals, have become a focus of considerable interest, with the modulation of immune responses by hormones receiving particular attention. Cortisol, growth hormone (GH), prolactin (PRL), reproductive hormones, melanin-concentrating hormone (MCH) and proopiomelanocortin (POMC)-derived peptides have all been shown to influence immune functions in a number of fish species. This review summarises the known effects of these hormones on the fish immune system, as well as the often complex interactions between different hormones. The possible implications for fish health, with respect to aquaculture and the changes in immunocompetence that take place during different stages in the fish life cycle are also discussed.

Animals↗
PubMed2000

Supernatants from leucocytes treated with melanin-concentrating hormone (MCH) and alpha-melanocyte stimulating hormone (alpha-MSH) have a stimulatory effect on rainbow trout (Oncorhynchus mykiss) phagocytes in vitro.

Melanin-concentrating hormone (MCH) and alpha-melanocyte stimulating hormone (alpha-MSH) are widespread vertebrate neuropeptides. In teleost fish the peptides are involved in the hormonal control of skin pigmentation, but they have also been shown to modulate corticosteroid secretion in both fish and mammals. alpha-MSH has additional potent anti-inflammatory actions in mammals and both peptides stimulate leucocyte phagocytosis in rainbow trout in vitro. The effects of these peptides on phagocytosis and the release of immunomodulatory factors by rainbow trout head kidney leucocytes were investigated in vitro. Neither MCH nor alpha-MSH had any effect on the adherence of phagocytes to glass slides or the activity of isolated phagocytes. When added to mixed leucocyte suspensions, however, MCH (50 and 100nM) and alpha-MSH (1 and 10nM) significantly increased the percentage of cells undergoing phagocytosis and MCH (50nM), but not alpha-MSH, stimulated the phagocytic index. In subsequent experiments, isolated phagocytes were exposed to supernatants derived from mixed leucocyte suspensions exposed to MCH (50 and 100nM) and alpha-MSH (1 and 10nM). Supernatants from leucocytes exposed to all doses of the peptides significantly increased the percentage phagocytosis and those from cells stimulated with MCH (100nM) and alpha-MSH (1 and 10nM) increased the phagocytic index of the phagocytes. The results suggest that cells other than phagocytes are required for MCH and alpha-MSH to exert their stimulatory effects on trout phagocytic cells through the release of one or more macrophage-activating factors.

Animals↗
PubMed2000

Catalytic properties of CYP1A isoforms in the liver of an agnathan (Lampetra fluviatilis) and two species of teleost (Pleuronectes flesus, Anguilla anguilla).

The catalytic activity of CYP1A isoforms and the effect of mammalian CYP1A-specific inhibitors in liver S9 fractions were studied in an agnathan (River lamprey, Lampetra fluviatilis, 30-33 cm) and in two species of teleost fish (European flounder, Pleuronectes flesus, 11-18 cm and common eel, Anguilla anguilla, 31-48 cm). Ethoxyresorufin O-deethylation (EROD), caffeine N-demethylation/C-oxidation and phenacetin O-deethylation (POD) activity increased 3-4-fold in flounders and 17-46-fold in eels, 5 days after fish were injected (i.p.) with 100 mg kg(-1) benzo(a)pyrene (B[a]P). In lampreys, basal EROD activity was very low and no increase in activity was observed following exposure to B[a]P. While the apparent Michaelis constant (K(m)) for each assay showed only small changes after B[a]P injection, maximum reaction velocity (V(max)) values increased by up to 19- and 84-fold for EROD activity, 4- and 35-fold for caffeine-related metabolism and 4- and 19-fold for POD activity in flounders and eels, respectively. The mammalian CYP1A2 inhibitor furafylline (50 microM-1 mM) reduced activity in the EROD, caffeine and POD assays to 65, 21 and 20% of control values in flounders and to 85, 10 and 5% of control values in eels, respectively. By contrast, low concentrations (0.025-0.050 microM) of the mammalian CYP1A1 inhibitor ellipticine completely abolished EROD activity, but had no effect (up to 1 mM) on caffeine metabolism or POD activity in either species. While the inhibitor studies strongly suggest that two separate enzymes are present in flounders and eels, the monophasic Michaelis-Menten kinetics obtained in all the assays imply that only a single CYP1A protein is present that has substrate and inhibitor specificities characteristic of both mammalian CYP1A1 and CYP1A2 isoforms.

Anguilla↗
PubMed1996

In the trout, CRH and AVT synergize to stimulate ACTH release.

Anterior pituitaries of the rainbow trout (Oncorhynchus mykiss) were incubated with graded concentrations of arginine vasotocin (AVT) or synthetic rat corticotrophin-releasing hormone (rCRH-41), alone or in combination, and the ACTH secreted into the medium was measured by a sensitive cytochemical bioassay. The aim was to determine the relative potencies of the two secretogogues and whether, in this fish species, they act synergistically. Rat CRF-41 and AVT both produced concentration-dependent increases in ACTH release. The minimum effective concentration for both peptides was approximately 1 nM but, at higher concentrations, the efficacy of CRF-41 was greater than that of AVT. Clear evidence of synergy between the two peptides was obtained. The response of the trout thus falls in line with observations in mammals and contrasts with findings for the goldfish.

Adrenocorticotropic Hormone↗
PubMed1996

Neoplastic transformation of prostatic and urogenital epithelium by the polyoma virus middle T gene.

Male transgenic mice expressing the polyomavirus middle T (PyV-MT) gene exhibited growth and developmental abnormalities in prostatic and other urogenital epithelium. Expression of PyV-MT was directed to these tissues by a novel, androgen-inducible expression vector based on the rat C3(1) gene. Epithelial growth disturbances (hyperplasia, dysplasia, and invasive carcinoma) were observed in the ventral and dorsal prostate, coagulating gland, epididymis, and vas deferens. The abnormalities were characterized by histological disorganization, nuclear pleomorphism, increased mitoses, and abnormal DNA content. Transgene transcription was detected in affected tissues, indicating that the C3(1)-based vector targeted androgen-sensitive urogenital tissues, especially the prostate. These results demonstrated that expression of a gene, the protein of which is known to interact with cellular proteins involved in signal transduction, dramatically disrupted urogenital growth and development.

Animals↗
PubMed1989

An immunological study of the secretory activity of neurons producing melanin-concentrating hormone in a teleost.

The melanin-concentrating hormone is a general vertebrate neurosecretory peptide which, in bony fish, serves as a neurohypophysial hormone influencing pigmentary changes in response to background colour. Young carp were reared for six months in white- or black-coloured tanks to determine how this would influence the development of the neurons producing the peptide. Cytological criteria and radioimmunoassay of tissue extracts showed that the background markedly influenced the synthetic activity of these neurons. In carp reared in black tanks, the perikarya were small and poorly granulated, with small nuclei and often undetectable nucleoli. Transfer of such fish to a white tank for six days caused no significant change in hormone content but cytological criteria suggested an increased activity of some of the neurons. In fish reared on a white background, over 50% of these neurons showed a greatly enhanced synthetic activity, while radioimmunoassays showed significantly higher concentrations of immunoreactive peptide in their hypothalami but not in their pituitary glands. After such fish were moved to black tanks for six days, the neuropeptide content of the hypothalamus and pituitary gland was significantly increased. Histologically, this was reflected in the amount of immunostainable granulation in both sites but cell nuclear size was not decreased. These changes are interpreted in terms of changes of hormone synthesis and release. The observations provide evidence that the activity of many but not necessarily all of the neurons producing melanin-concentrating hormone in the carp hypothalamus is controlled by background colour.

Animals↗
PubMed1989

Immunocytochemical demonstration of melanin-concentrating hormone and proopiomelanocortin-like products in the brain of the trout and carp.

Immunocytochemistry on frozen sections revealed that in both the trout and the carp, parvocellular neurones located in the medial basal hypothalamus (medial nucleus lateralis tuberis) were immunostained by antisera against three molecules known to be derived from the proopiomelanocortin (POMC) molecule, viz: alpha-melanocyte-stimulating hormone (alpha MSH), ACTH, and salmonid NPP--the whole N-terminal sequence preceding ACTH in the POMC precursor. Axons from these neurones extended into various regions of the brain but did not appear to project into the pituitary gland. Antiserum against salmonid melanin-concentrating hormone (MCH) immunostained magnocellular neurones in the lateral basal hypothalamus (lateral nucleus lateralis tuberis). Axons from some of these neurones projected into the brain while other axons extended into the pituitary gland. In the carp, but not in the trout, some MCH neurones were also immunostained by antisera against alpha MSH but not by antisera against the other POMC molecules.

Animals↗
PubMed1988

Opioid binding sites in the fish brain: an autoradiographic study.

Cryostat sections of trout brains were incubated with tritiated opioid ligands (5 nM [3H]etorphine or 4 nM D-[3H]Ala2, Met5 enkephalinamide) with the initial aim of locating opioid binding sites associated with the hypothalamo-pituitary axis. Naloxone-displaceable binding was observed in all regions of the brain, with a density ranking order of cerebellum greater than telencephalon greater than optic tectum greater than hypothalamus greater than brain stem greater than pituitary gland. Within the hypothalamus and pituitary gland binding was unexpectedly low, apart from a slightly enhanced binding anteriorly in the preoptic region and posteriorly associated with presumptive sensory fibres. A similar distribution of opioid binding sites was seen in the eel and lamprey brain. The high level of opioid binding in the cerebellum permitted a tentative identification of opioid subtypes using [3H]etorphine binding to membrane preparations from trout cerebellum. Scatchard analysis indicated the presence of a single class of high-affinity binding sites with a density of 0.38 pmol/mg protein and affinity constant (KD) of 2.6 nM. Displacement by unlabelled ligands suggested the existence of mu and/or kappa receptors.

Anguilla↗