The influence of Zn on signaling pathways and attachment of Mytilus galloprovincialis haemocytes to extracellular matrix proteins

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This digital document is a journal article from Comparative Biochemistry and Physiology, Part C, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The present study investigates the cytotoxic mechanisms induced by zinc (Zn) in haemocytes of mussel Mytilus galloprovincialis. Haemocytes play a key role in the immune defence of mussels. Micromolar concentration of Zn (50 @mM) play an important role in the elevation of pHi and increase in Na^+ influx in haemocytes. The observed effects were inhibited by the Na^+/H^+ exchanger (NHE) inhibitor, ethyl-N-isopropyl-amiloride (EIPA). Furthermore, our results showed that Zn caused an increase in O”2^- production that was reversed after NHE inhibition. Phorbol ester (PMA) caused a significant rise both in pHi and Na^+ influx as well as in O”2^- production. These effects were reversed by calphostin C. Our results indicated that Zn also enhanced haemocyte attachment to both BSA and laminin which was reversed by EIPA and calphostin C. The enhancement of haemocytes attachment to both BSA and laminin after Zn suggests that it is likely to play a signal role in cytoskeleton-dependent process of cell growth and migration in mussel M. galloprovincialis haemocytes. We conclude that Zn induces a signaling pathway with the involvement of NHE, PKC, O”2^- and @a”1- and @b-adrenergic receptors.

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Cloning of anthozoan fluorescent protein genes

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This digital document is a journal article from Comparative Biochemistry and Physiology, Part C, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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Many cnidarians display vivid fluorescence under proper lighting conditions. In general, these colors are due to the presence of fluorescent proteins similar to the green fluorescent protein (GFP) originally isolated from the hydrozoan medusa Aequorea victoria (Cnidaria: Hydrozoa). To optimize the search for new fluorescent proteins (FPs), a technique was developed that allows for the rapid cloning and screening of FP genes without the need for a prior knowledge of gene sequence. Using this method, four new FP genes were cloned, a green from Montastraea cavernosa (Anthozoa: Scleractinia: Faviidae), a cyan from Pocillopora damicornis (Anthozoa: Scleractinia: Pocilloporidae), a cyan from Discosoma striata (Anthozoa: Corallimorpharia), and a red from a second Discosoma species. Two additional green FPs were cloned, one from M. cavernosa and one from its congener Montastraea faveolata, from purified cDNA using PCR primers designed for the first M. cavernosa green FP. Each FP has recognizable amino acid sequence motifs that place them conclusively in the GFP protein family. Mutation of these products using a low-stringency PCR protocol followed by screening of large numbers of bacterial colonies allowed rapid creation of mutants with a variety of characteristics, including changes in color, maturation time, and brightness. An enhanced version of the new red FP, DspR1+, matures faster at 30 ^oC than the commercially available DsRed but matures slower than DsRed at 37 ^oC. One of the M. cavernosa green FPs, McaG2, is highly resistant to photobleaching and has a fluorescence quantum yield approximately twice that of EGFP-1.

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The functional consequences of paraoxon exposure in central neurones of

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This digital document is a journal article from Comparative Biochemistry and Physiology, Part C, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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Toxicity of paraoxon has been attributed to inhibition of cholinesterase, but little is known about its direct action on ionic channels. The effects of paraoxon (0.3 @mM-0.6 @mM) were studied on the firing behaviour of snail neurones. Paraoxon significantly increased the frequency of spontaneously generated action potentials, shortened the afterhyperpolarization (AHP) and decreased the precision of firing. Short periods of high frequency-evoked trains of action potentials led to an accumulation in the depth and duration of post-train AHPs that was evidenced as an increase in time to resumption of autonomous activity. The delay time in autonomous activity initiation was linearly related to the frequency of spikes in the preceding train and the slope of the curve significantly decreased by paraoxon. The paraoxon induced hyperexcitability and its depressant effect on the AHP and the post-train AHP were not blocked by atropine and hexamethonium. Calcium spikes were elicited in a Na^+ free Ringer containing voltage dependent potassium channel blockers. Paraoxon significantly decreased the duration of calcium spikes and following AHP and increased the frequency of spikes. These findings suggest that a reduction in calcium influx during action potential may decrease the activation of calcium dependent potassium channels that participate in AHP generation and act as a mechanism of paraoxon induced hyperexcitability.

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Interactive effects of naphthalene treatment and the onset of vitellogenesis on energy metabolism in liver and gonad, and plasma steroid hormones of rainbow … Biochemistry and Physiology, Part C]

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This digital document is a journal article from Comparative Biochemistry and Physiology, Part C, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The purpose of the study was to assess in female fish the possible interaction between treatment with a polycyclic aromatic hydrocarbon (PAH) like naphthalene and the onset of vitellogenesis. In a first experiment, female rainbow trout (Oncorhynchus mykiss) at stages 2-3 (previtellogenesis) or 4 (early vitellogenesis) were intraperitoneally injected (2 @ml g^-^1) with vegetable oil alone (control) or containing naphthalene (50 mg kg^-^1) to be sampled 3 h later. A second experiment was similarly designed but using fish intraperitoneally implanted (10 @ml g^-^1) with slow-release coconut oil implants alone (control) or containing 50 mg naphthalene kg^-^1 body mass that were sampled 3 days after injection. On each sampling time, plasma levels of cortisol and 17@b-estradiol, and several metabolic parameters in plasma, liver and gonad were assessed. In controls, early vitellogenic fish compared with previtellogenic fish displayed changes that in some cases are confirmatory of previous studies whereas in other cases provide new information in plasma (increased amino acid levels), liver (decreased capacity for exporting glucose and reduced amino acid levels) and gonad (decreased amino acid levels). Naphthalene treatment produced in previtellogenic fish decreased 17@b-estradiol levels in plasma, increased plasma glucose or decreased liver gluconeogenic capacity whereas no major effects were noticed on parameters involved in lipid, amino acid and lactate metabolism. Differential effects of naphthalene treatment were noticed in early vitellogenic fish such as decreased 17@b-estradiol and glucose levels in plasma, increased hexokinase and glucokinase and lack of changes in fructose 1,6-bisphosphatase activities in liver, and a lower decrease of amino acid levels in gonad. Those alterations produced by naphthalene treatment resulted in a decreased capacity for covering the energy demand of vitellogenesis in liver and gonad that could contribute to a delay and/or impairment of the onset of maturation.

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Trace metal burdens and expression of heat stable low molecular mass proteins in the female asteroid Coscinasterias muricata – Fluctuations throughout … Biochemistry and Physiology, Part C]

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This digital document is a journal article from Comparative Biochemistry and Physiology, Part C, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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Concentrations of the essential trace metals copper and zinc were measured in the pyloric caeca of female Coscinasterias muricata sampled from Port Phillip Bay, Victoria, Australia at monthly intervals for 15 months. Results indicate that the concentrations of these metals appear to be regulated by the reproductive cycle. Peaks in zinc concentration occurred simultaneously with peaks in progesterone concentration in the pyloric caeca. These findings suggest that zinc plays a role in gametogenesis and ovarian development. Fluctuations in pyloric caeca copper concentration appear inversely related to the pyloric caecal index and associated with oocyte diameter, indicative of a role for this metal in oogenesis. The levels of cytosolic heat stable low molecular mass (LMM) proteins were examined throughout the sampling period. Heat stable LMM proteins (metallothionein-like) of 12 kDa and 7.5 kDa (apparent molecular mass) and the concentrations of copper appear to be related; although the exact nature of these proteins remains unknown. No such relationship was observed between the levels of heat stable LMM proteins and zinc.

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