ClO_2毒性研究

ClO_2是一种可以代替液氯的新型消毒剂。本文通过金鱼毒性实验,确定了ClO_2用于饮水消毒的安全浓度;通过小白鼠急性经口毒性实验,确定了ClO_2属实际无毒型水处理剂。     

Glycine-receptor immunoreactivity in retinal bipolar cells is postsynaptic to glycinergic and GABAergic amacrine cell synapses.

Glycinergic innervation of the synaptic terminals of mixed rod-cone bipolar cells in the goldfish retina was investigated by electron microscopical immunocytochemistry with presynaptic and postsynaptic markers for glycinergic neurons: a monoclonal antibody (mAb 7A) against the 93 kDa subunit of the strychnine-sensitive glycine receptor and polyclonal antisera against a glycine/BSA conjugate. Conventional "glycinergic" synaptic contacts, made by amacrine cell processes, accounted for 7-10% of the input to the bipolar cell terminals, whether determined by glycine receptor immunoreactivity (GlyR-IR) or glycine-IR. In addition to the conventional synapses, the large bipolar cell terminals in the proximal inner plexiform layer (type Mb) gave rise to spinules (spine-like protrusions) that invaginated into presynaptic amacrine cell processes. Although 85% of the spinules were GlyR-IR, no spinules were postsynaptic to glycine-IR processes; yet 86% of the spinules were postsynaptic to GAD-IR processes, suggesting that the GlyR-IR spinules were postsynaptic to GABAergic terminals. Furthermore, a single amacrine cell process could make two synapses with an Mb terminal: a GlyR-IR contact onto a spinule and a conventional synapse that was not GlyR-IR. We suggest that glycinergic innervation of bipolar cell terminals involves conventional glycinergic synapses as well as an unconventional situation in which GABA and glycine may interact in as yet undetermined manner, perhaps by potentiation.     

Norepinephrine regulation of growth hormone release from goldfish pituitary cells. I. Involvement of alpha2 adrenoreceptor and interactions with dopamine and salmon gonadotropin-releasing hormone

Adrenergic regulation of growth hormone (GH) release in the goldfish was examined in vitro using dispersed goldfish pituitary cells under column perifusion. Norepinephrine and epinephrine suppressed basal GH release from goldfish pituitary cells in a reversible and dose-dependent manner. At high doses, a transient rebound of GH release was observed after termination of norepinephrine and epinephrine treatment. In this study, the dose-dependence of adrenergic inhibition on basal GH release was mimicked by the alpha2 agonists clonidine and UK14304. Basal GH secretion, however, was not affected by the beta agonist isoproterenol and alpha1 agonist methoxamine. In addition, the inhibitory actions of norepinephrine and clonidine on basal GH release were blocked by the alpha2 antagonists yohimbine and RX821002. The beta antagonist propranolol and alpha1 antagonists prasozin and benoxathian were not effective in this respect. Salmon gonadotropin-releasing hormone (sGnRH) and dopamine, two known GH-releasing factors in fish, stimulated GH release from goldfish pituitary cells and their GH-releasing actions were inhibited by simultaneous treatment with norepinephrine. Furthermore, the GH rebound after norepinephrine treatment was significantly enhanced by prior exposure to sGnRH and this effect was not observed with dopamine treatment. These results, taken together, suggest that in the goldfish adrenergic input at the pituitary level inhibit basal GH release through activation of alpha2 adrenoreceptors. This alpha2 inhibitory influence may interact with dopaminergic and GnRH input to regulate GH secretion from goldfish pituitary cells. The 'post-inhibition' GH rebound after NE treatment and its sensitivity to sGnRH potentiation may also represent a novel mechanism for GH regulation in fish.     

Norepinephrine regulation of growth hormone release from goldfish pituitary cells. II. Intracellular sites of action

Previous results suggest that norepinephrine decreases growth hormone (GH) release in goldfish by means of alpha-2 adrenoceptor activation. The intracellular mechanisms by which norepinephrine inhibits GH release were examined in the present study using dispersed goldfish pituitary cells. In 2-h static incubation experiments, norepinephrine and the alpha-2 agonist clonidine decreased basal GH release and the GH responses to stimulation by the dopamine D1 agonist SKF38393 and two native gonadotropin-releasing hormones (GnRH). Norepinephrine also reduced GH responses to the adenylate cyclase activator forskolin, two protein kinase C (PKC) activators (phorbol ester and synthetic diacylglycerol), and two Ca2+ ionophores (ionomycin and A23187). Similarly, norepinephrine applied as a 1-h pulse in cell column perifusion experiments reduced basal GH release and abolished the GH response to a 5-min pulse of arachidonic acid. In goldfish, D1-stimulated GH release is mediated by AC-, arachidonic acid-and Ca2+-dependent pathways, whereas GnRH action is coupled to PKC-and Ca2+-dependent mechanisms. These results suggest that norepinephrine activation of alpha-2 receptors inhibits ligand-induced GH secretion by actions subsequent to activation of these second messenger cascades. To further characterize norepinephrine mechanisms of action on unstimulated hormone release, the ability of norepinephrine and an alpha-2 agonist to affect activation of two second messenger cascades under basal conditions was also investigated. Static incubation with clonidine reduced cAMP production in a time-and dose-dependent manner, suggesting that norepinephrine inhibitory action can also be expressed at the level of cAMP production. Resting intracellular free calcium levels in single, identified goldfish somatotropes was unaffected by norepinephrine. However, the inhibitory effects of norepinephrine on basal GH secretion was not observed in the presence of a voltage-sensitive Ca2+ channel agonist. Whether these channels are targets for norepinephrine action on unstimulated GH release requires further investigation.     

Accumulation and toxicity of CuO and ZnO nanoparticles through waterborne and dietary exposure of goldfish (Carassius auratus)

Dietary and waterborne exposure to copper oxide (CuO) and zinc oxide (ZnO) nanoparticles (NPs) was conducted using a simplified model of an aquatic food chain consisting of zooplankton (Artemia salina) and goldfish (Carassius auratus) to determine bioaccumulation, toxic effects, and particle transport through trophic levels. Artemia contaminated with NPs were used as food in dietary exposure. Fish were exposed to suspensions of the NPs in waterborne exposure. ICP‐MS analysis showed that accumulation primarily occurred in the intestine, followed by the gills and liver. Dietary uptake was lower, but was found to be a potential pathway for transport of NPs to higher organisms. Waterborne exposure resulted in about a 10‐fold higher accumulation in the intestine. The heart, brain, and muscle tissue had no significant Cu or Zn. However, concentrations in muscle increased with NP concentration, which was ascribed to bioaccumulation of Cu and Zn released from NPs. Free Cu concentration in the medium was always higher than that of Zn, indicating CuO NPs dissolved more readily. ZnO NPs were relatively benign, even in waterborne exposure (p ≥ 0.05). In contrast, CuO NPs were toxic. Malondialdehyde levels in the liver and gills increased substantially (p < 0.05). Despite lower Cu accumulation, the liver exhibited significant oxidative stress, which could be from chronic exposure to Cu ions. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 119–128, 2015.     

Effects of season, temperature, and photoperiod on plasma melatonin rhythms in the goldfish, Carassius auratus

Abstract: Effects of season, environmental temperature, and photoperiod on plasma melatonin concentrations were studied in the goldfish, Carassius auratus. When goldfish were reared under natural conditions, melatonin levels at mid-dark exhibited seasonal changes, with higher levels obtained in June and September than in December and March. When fish were kept under light: dark (LD) cycle of 12: 12 at 5, 15, or 25°C during March-April, temperature-dependent increases in melatonin levels at mid-dark were observed. When animals were maintained under LD 16: 8 or LD 8: 16 in combination with temperature changes (5, 15, and 25°C) during January-February, the duration of nocturnal elevation in melatonin was controlled by the length of the scotophase while the amplitude was influenced by environmental temperature. These results indicate that plasma melatonin profiles in the goldfish exhibit seasonal changes that are regulated by both photoperiod and temperature.     

Comparison of Retinal Degeneration in the Normal Goldfish and the Megalophthalmic Black Moor Goldfish after Optic Nerve Transection and Lens Extraction

A comparison in retinal degeneration was studied in the normal goldfish and the megalophthalmic goldfish after optic nerve transection or lens extraction by the TUNEL (Terminal transferase-mediated dUTP nick end labeling) technique. A significant number of TUNEL positive cells appeared in both cases 7 days after injury, with a more prominent result in the megalophthalmic eye. Lens extraction, had less apoptotic cell death in the experimental retinas.     

Hexavalent chromium‐induced multiple biomarker responses in liver and kidney of goldfish,Carassius auratus

Hexavalent chromium [Cr (VI)] is a constituent of chromite ore. Although it is known to have several industrial and technological applications, its release into the aquatic environment as a result of chemical spill or inadequate waste discharge may hamper the health of aquatic organisms. In this study, we have investigated the effects of Cr (VI) on multiple biomarkers responses in goldfish under subchronic exposure conditions. Laboratory‐acclimatized fish were exposed to 4.25 ppm and 8.57 ppm Cr (VI) for four weeks using a continuous flow‐through system. During exposure, fish samples were collected on a weekly basis and analyzed for multiple biomarkers including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), metallothionein (MT), and total protein in liver and kidney. Study results indicated that the CAT activity and total protein levels in Cr (VI) ‐ treated goldfish did not significantly differ (P > 0.05) from their respective controls during experimentation. However, highly significant up‐regulations (P < 0.05) of SOD, GPx, and MT expression in Cr (VI) ‐ treated goldfish were recorded at different exposure times depending on Cr (VI) concentration, test organ, and/or biomarker of interest. For example, significantly higher liver GPx levels were found at weeks 2 and 3 in the 4.25 ppm concentration, and at weeks 3 and 4 in the 8.57 ppm, while kidney GPx levels were significantly higher at weeks 1, 2 and 3 in the 4.25 ppm concentration, and at weeks 2, 3 and 4 in the 8.57 ppm concentration. In summary, Cr (VI)‐induced oxidative stress was characterized by statistically significant increases in SOD, GPx, and MT expression in goldfish tissues; with the kidney showing a relatively higher sensitivity to Cr (VI) toxicity compared with the liver. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2011.     

Pharmacological characterisation of the goldfish somatostatin sst5 receptor

Somatostatin (somatotropin release inhibiting factor, SRIF), exerts its effects via specific G protein coupled receptors of which five subtypes have been cloned (sst1-5). Recently, SRIF receptors have also been cloned from fish tissues. In this study, goldfish sst5 receptors (gfsst5) were expressed and characterised in the Chinese hamster lung fibroblast cell line, that harbours the luciferase reporter gene driven by the serum responsive element (CCL39-SRE-Luci). The agonist radioligands [125I]-LTT-SRIF-28 ([Leu8, DTrp22, 125I-Tyr25]SRIF-28) and [125I][Tyr10]cortistatin-14 labelled similar receptor densities with high affinity and in a saturable manner (pKd: 9.99-9.71; Bmax: 300-350 fmol mg-1). 5'-Guanylyl-imidodiphosphate inhibited radioligand binding to some degree (38.5-57.9%). In competition binding studies, the pharmacological profile of SRIF binding sites defined with [125I]LTT-SRIF-28 and [125I][Tyr10]cortistatin-14 correlated significantly (r2=0.97, n=20). Pharmacological profiles of human and mouse sst5 receptors expressed in CCL39 cells correlated markedly less with those of the gfsst5 profile (r2=0.52-0.78, n > or = b16). Functional expression of the gfsst5 receptor was examined by measurement of agonist-induced luciferase expression and stimulation of [35S]GTPgammaS ([35S]guanosine 5'-O-(3-thiotriphosphate) binding. Profiles were similar to those achieved in radioligand binding studies (r2=0.81-0.93, n=20), although relative potency (pEC50) was reduced compared to pKd values. Relative efficacy profiles of luciferase expression and [35S]GTPgammaS binding, were rather divergent (r2=0.48, n=20) with peptides showing full agonism at one pathway and absence of agonism at the other. BIM 23056 (D-Phe-Phe-Tyr-D-Trp-Lys-Val-Phe-D-Nal-NH2) acted as an antagonist on the effects of SRIF-14 (pKB=6.74 +/- 0.23) on stimulation of [35S]GTPgammaS binding. Pertussis toxin abolished the effect of SRIF-14 on luciferase expression and [35S]GTPgammaS binding suggesting coupling of the receptor to G(i)/G(o) proteins. In summary, the present studies demonstrate that the gfsst5 receptor has a similar pharmacological profile and transductional properties to mammalian sst5 receptors. The difference in efficacy profiles defined using different functional assays suggests numerous, agonist specific, conformational receptor states, and/or ligand-dependent receptor trafficking.     

Pathway choice by regenerating optic fibers following tectal lobectomy in the goldfish: Inferences from the study of gliosis in tectal efferent bundles

Cell counts in various fiber bundles of the goldfish brain have demonstrated a profound, but transient gliosis of tectal (and pretectal) efferent pathways following removal of a tectal lobe. In the majority of cases, the pathways which underwent gliosis were also those which were penetrated by regenerating optic fibers which had been sectioned by the tectal surgery. However, the dorsal trunk of the horizontal commissure on the intact side of the brain showed only a minimal gliotic response but was consistently innervated by the optic fibers. Conversely, the ansate commissure and the crossed tectobulbar tract invariably demonstrated a marked gliotic response but only rarely received more than minimal innervation by the regenerating fibers.These observations are discussed with regard to the modifications which they demand of the hypothesis that degenerating axon bundles in the goldfish brain are in some way attractive to regenerating axons.