Thyroid disruption by technical decabromodiphenyl ether (DE-83R) at low concentrations in Xenopus laevis

2010 ◽  
Vol 22 (5) ◽  
pp. 744-751 ◽  
Author(s):  
Xiaofei Qin ◽  
Xijuan Xia ◽  
Zhongzhi Yang ◽  
Shishuai Yan ◽  
Yaxian Zhao ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Decabromodiphenyl Ether ◽  
Low Concentrations ◽  
Thyroid Disruption

scholarly journals Developmental changes of purinergic control of intestinal motor activity during metamorphosis in the African clawed frog, Xenopus laevis

2007 ◽  
Vol 292 (5) ◽  
pp. R1916-R1925 ◽  
Author(s):  
Monika Sundqvist
Keyword(s):  
Xenopus Laevis ◽  
Motor Activity ◽  
Receptor Antagonist ◽  
Circular Muscle ◽  
Developmental Changes ◽  
Disulfonic Acid ◽  
Developmental Phase ◽  
African Clawed Frog ◽  
Low Concentrations ◽  
Clawed Frog

Little is known about the purinergic regulation of intestinal motor activity in amphibians. Purinergic control of intestinal motility is subject to changes during development in mammals. The aim of this study was to investigate purinergic control of intestinal smooth muscle in the amphibian Xenopus laevis and explore possible changes in this system during the developmental phase of metamorphosis. Effects of purinergic compounds on mean force and contraction frequency in intestinal circular muscle strips from prometamorphic, metamorphic, and juvenile animals were investigated. Before metamorphosis, low concentrations of ATP reduced motor activity, whereas the effects were reversed at higher concentrations. ATP-induced relaxation was not inhibited by the P2-receptor antagonist pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS) but was blocked by the ecto-nucleotidase inhibitor 6- N, N-diethyl-d-β,γ-dibromomethylene ATP ( ARL67256 ), indicating that an ATP-derived metabolite mediated the relaxation response at this stage. Adenosine induced relaxation before, during, and after metamorphosis, which was blocked by the A1-receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). The stable ATP-analog adenosine 5′-[γ-thio]-triphosphate (ATPγS) and 2-methylthioATP (2-MeSATP) elicited contractions in the circular muscle strips in prometamorphic tadpoles. However, in juvenile froglets, 2-MeSATP caused relaxation, as did ATPγS at low concentrations. The P2Y11/P2X1-receptor antagonist NF157 antagonized the ATPγS-induced relaxation. The P2X-preferring agonist α-β-methyleneadenosine 5′-triphosphate (α-β-MeATP) evoked PPADS-sensitive increases in mean force at all stages investigated. This study demonstrates the existence of an adenosine A1-like receptor mediating relaxation and a P2X-like receptor mediating contraction in the X. laevis gut before, during, and after metamorphosis. Furthermore, the development of a P2Y11-like receptor-mediated relaxation during metamorphosis is shown.

scholarly journals Upstream domains of the Xenopus laevis rDNA promoter are revealed in microinjected oocytes.

1986 ◽  
Vol 6 (4) ◽  
pp. 1228-1234 ◽  
Author(s):  
J Windle ◽  
B Sollner-Webb
Keyword(s):  
Xenopus Laevis ◽  
Dna Sequences ◽  
Promoter Region ◽  
Core Promoter ◽  
Rrna Genes ◽  
Deletion Mutants ◽  
Low Concentrations ◽  
Upstream Promoter ◽  
Polymerase I ◽  
Vector Dna

The DNA sequences involved in promoting transcription of the Xenopus laevis rRNA genes were determined by microinjecting a series of deletion mutants into oocyte nuclei. A very small promoter region is sufficient to direct efficient transcription when templates are microinjected at high rDNA concentration, since 5'delta- 9 and 3'delta +6 templates are fully active. However, as the concentration of injected template is decreased, an increasing requirement for upstream domains, extending to nucleotide approximately -170, is observed. The major downstream border of the required region does not change. This apparently expanding 5' promoter border results from the fact that, as the rDNA concentration is decreased, transcription from templates lacking the upstream promoter domain falls off much more sharply than does transcription from a complete promoter. In fact, the deleted promoters are virtually inactive below a threshold rDNA concentration. It is indeed the rDNA concentration that is important, for coinjected vector DNA does not increase the level of transcription obtained from low concentrations of the 5' deletions. From these data we conclude that polymerase I transcription factors can recognize and initiate transcription from a small core promoter domain, but that sequences extending upstream to nucleotide approximately -170 increase the efficiency of initiation. A model is presented that could account for these results.

scholarly journals Thyroid Disruption by Di-n-Butyl Phthalate (DBP) and Mono-n-Butyl Phthalate (MBP) in Xenopus laevis

PLoS ONE ◽  
2011 ◽  
Vol 6 (4) ◽  
pp. e19159 ◽  
Author(s):  
Ouxi Shen ◽  
Wei Wu ◽  
Guizhen Du ◽  
Renping Liu ◽  
Lugang Yu ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Thyroid Disruption ◽  
Butyl Phthalate

Thyroid disruption effects of environmental level perfluorooctane sulfonates (PFOS) in Xenopus laevis

Ecotoxicology ◽  
2011 ◽  
Vol 20 (8) ◽  
pp. 2069-2078 ◽  
Author(s):  
Yan Cheng ◽  
Yuan Cui ◽  
Hui-ming Chen ◽  
Wen-ping Xie
Keyword(s):  
Xenopus Laevis ◽  
Thyroid Disruption ◽  
Environmental Level

Effects of Antidepressants on G Protein–coupled Receptor Signaling and Viability in Xenopus laevis  Oocytes

2003 ◽  
Vol 99 (4) ◽  
pp. 911-917 ◽  
Author(s):  
Danja Strümper ◽  
Marcel E. Durieux ◽  
Barbara Tröster ◽  
Klaus Hahnenkamp ◽  
Cristina Vitan ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
G Protein ◽  
Lysophosphatidic Acid ◽  
Local Anesthetics ◽  
Xenopus Laevis Oocytes ◽  
Receptor Signaling ◽  
G Protein Coupled Receptor ◽  
Prolonged Incubation ◽  
Low Concentrations ◽  
G Protein Coupled

Background Tricyclic antidepressants are structurally related to local anesthetics, suggesting that part of their analgesic action may result from properties shared with local anesthetics. Because local anesthetics block G protein-coupled receptor signaling (which explains, in part, their inflammatory modulating properties), the authors studied whether antidepressants have similar effects. Methods Peak Ca-activated Cl currents induced in Xenopus laevis oocytes by lysophosphatidic acid (10(-4) m) were measured using a voltage clamp. The effects of a 30-, 120-, or 240-min incubation in amitriptyline, nortriptyline, imipramine, or fluoxetine were determined. Results After a 30-min incubation, low concentrations (10(-7)-10(-5) m) of antidepressants had no effect on lysophosphatidic acid-induced currents. After prolonged incubation, only amitriptyline or nortriptyline inhibited lysophosphatidic acid signaling (each to 58% of the control response at 10(-7) m after 240 min). At low concentrations, none of the compounds induced membrane damage (defined as a holding current of > 1 microA, 2% in control cells). Imipramine at 10(-3) m induced damage in 100% of oocytes, and fluoxetine at 10(-4) m induced damage in 71% of oocytes (P < 0.05 vs. control). Amitriptyline and nortriptyline had no effect. Conclusions These findings are in part different from those obtained with local anesthetics and suggest that interference with G protein-coupled signaling might explain, in part, the analgesic properties of some antidepressants. However, use of antidepressants in high concentrations may be associated with cellular toxicity.

MELANOPHORE-STIMULATING HORMONE-MELATONIN ANTAGONISM IN RELATION TO COLOUR CHANGE IN XENOPUS LAEVIS

1971 ◽  
Vol 49 (4) ◽  
pp. 573-580 ◽  
Author(s):  
KAY DIERST-DAVIES ◽  
F. W. LANDGREBE ◽  
G. M. MITCHELL
Keyword(s):  
Xenopus Laevis ◽  
Dose Response ◽  
Colour Change ◽  
Response Curves ◽  
Low Concentrations ◽  
Wide Range ◽  
Dose Response Curves ◽  
Normal Light ◽  
Melanophore Stimulating Hormone ◽  
Stimulating Hormone

SUMMARY Experiments on colour change of Xenopus laevis were performed to investigate the possibility that melatonin is the physiological antagonist to melanophore-stimulating hormone (MSH). Various amounts of substandard (SS) extract of ox posterior pituitary plus melatonin were injected into the dorsal lymph sac of adult male Xenopus laevis. Normal light-adapted, completely hypophysectomized, and anterior lobectomized animals were used. Dose—response curves were obtained for different SS dosages over a wide range of melatonin concentrations. Melatonin at very low concentrations inhibited the darkening reaction to both injected SS and endogenous MSH. In all cases more melatonin was required to inhibit the effect of SS in hypophysectomized than in normal animals. The results indicate that melatonin may be a physiological MSH antagonist in Xenopus laevis and the pituitary either contains some lightening factor itself ( Hogben's 'W' substance?) or has control over another organ (pineal gland?) where a lightening factor may be present. The unusual linear-logarithmic dose—response curves are discussed.

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