Xenopus laevis oocyte maturation is affected by metal chlorides

Author: Marin, M.; Slaby, S.; Marchand, G.; Demuynck, S.; Friscourt, N.; Gelaude, A.; Lemiere, S.; Bodart, J.-F. Description: Few studies have been conducted using Xenopus laevis germ cells as oocytes, though these cells offer many advantages allowing both electrophysiological studies and morphological examination. Our aim was to investigate the effects of metal (cadmium, lead, cobalt and zinc) exposures using cell biology approaches. First, cell survival was evaluated with both phenotypical and electrophysiological approaches. Secondly, the effect of metals on oocyte maturation was assessed with morphological observations and electrophysiological recordings. From…

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Vital dye mapping of the gastrula and neurula of Xenopus laevis. I. Prospective areas and morphogenetic movements of the superficial layer

Author: Keller, R.E. Description: The disposition of prospective areas and the course of morphogenetic movements during gastrulation and neurulation were investigated by vital staining. The prospective lining of the archenteron, the prospective neural area, and the prospective epidermal area are represented on the surface of the early gastrula. The prospective lining of the archenteron occupies the area within 65–70° of the vegetal pole and is divided into prospective archenteron roof and prospective archenteron floor by the blastopore pigment line which functions as the locus of invagination. A crescent-shaped neural area…

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PeIA-5466: A Novel Peptide Antagonist Containing Non-natural Amino Acids That Selectively Targets alpha3beta2 Nicotinic Acetylcholine Receptors

Author: Hone, A.J.; Fisher, F.; Christensen, S.; Gajewiak, J.; Larkin, D.; Whiteaker, P.; McIntosh, J.M. Description: Pharmacologically distinguishing alpha3beta2 nicotinic acetylcholine receptors (nAChRs) from closely related subtypes, particularly alpha6beta2, has been challenging due to the lack of subtype-selective ligands. We created analogs of alpha-conotoxin (alpha-Ctx) PeIA to identify ligand-receptor interactions that could be exploited to selectively increase potency and selectivity for alpha3beta2 nAChRs. A series of PeIA analogs were synthesized by replacing amino acid residues in the second disulfide loop with standard or nonstandard residues and assessing their activity on…

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Using Cognitive Dissonance to Encourage Water Conservation

Author: Dickerson, C.A.; Thibodeau, R.; Aronson, E.; Miller, D. Description: In a field experiment on water conservation, we aroused dissonance in patrons of the campus recreation facility by making them feel hypocritical about their showering habits. Using a 2 × 2 factorial design, we manipulated subjects “mindfulness” that they had sometimes wasted water while showering, and then varied whether they made a “public commitment” urging other people to take shorter showers. The “hypocrisy” condition–in which subjects made the public commitment after being reminded of their past behavior–was expected to be…

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p53 mutations in human cancers

Author: Hollstein, M.; Sidransky, D.; Vogelstein, B.; Harris, C.C. Description: Mutations in the evolutionarily conserved codons of the p53 tumor suppressor gene are common in diverse types of human cancer. The p53 mutational spectrum differs among cancers of the colon, lung, esophagus, breast, liver, brain, reticuloendothelial tissues, and hemopoietic tissues. Analysis of these mutations can provide clues to the etiology of these diverse tumors and to the function of specific regions of p53. Transitions predominate in colon, brain, and lymphoid malignancies, whereas G:C to T:A transversions are the most frequent…

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Modulation of human GABAA and glycine receptor currents by menthol and related monoterpenoids

Author: Hall, A.C.; Turcotte, C.M.; Betts, B.A.; Yeung, W.-Y.; Agyeman, A.S.; Burk, L.A. Description: Effects of common monoterpenoid alcohols and ketones were investigated on recombinant human gamma-aminobutyric acid A (GABAA; alpha1beta2gamma2s) and glycine (alpha1 homomers) receptors expressed in Xenopus oocytes. GABA currents were enhanced by coapplications of 10-300 microM: (+)-menthol>(-)-menthol>(-)-borneol>>(-)-menthone=camphor enantiomers>carvone enantiomers, with menthol acting stereoselectively. By contrast, thujone diastereomers inhibited GABAA receptor currents while glycine currents were only markedly potentiated by menthol. Positive modulation by (+)-menthol was explored given its pronounced effects (e.g., at 100 microM, GABA and glycine…

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Subunit-dependent block by isoflurane of wild-type and mutant alpha(1)S270H GABA(A) receptor currents in Xenopus oocytes

Author: Hall, A.C.; Stevens, R.J.N.; Betts, B.A.; Yeung, W.-Y.; Kelley, J.C.; Harrison, N.L. Description: The volatile anesthetic isoflurane both prolongs and reduces the amplitude of GABA-mediated inhibitory postsynaptic currents (IPSCs) recorded in neurons. To explore the latter effect, we investigated isoflurane-induced inhibition of steady-state desensitized GABA currents in Xenopus oocytes expressing wild-type alpha(1)beta(2), alpha(1)beta(2)gamma(2s), mutant alpha(1)(S270H)beta(2) (serine to histidine at residue 270) or alpha(1)(S270H)beta(2)gamma(2s) receptors. The alpha(1) serine 270 site in TM2 (second transmembrane domain of the subunit) is postulated as a binding site for some volatile agents and is…

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The effects of isoflurane on desensitized wild-type and alpha 1(S270H) gamma-aminobutyric acid type A receptors

Author: Hall, A.C.; Rowan, K.C.; Stevens, R.J.N.; Kelley, J.C.; Harrison, N.L. Description: gamma-aminobutyric acid type A receptors (GABA(A)-R) mediate synaptic inhibition and meet many pharmacological criteria required of important general anesthetic targets. During synaptic transmission GABA release is sufficient to saturate, maximally activate, and transiently desensitize postsynaptic GABA(A)-Rs. The resulting inhibitory postsynaptic currents (IPSCs) are prolonged by volatile anesthetics like isoflurane. We investigated the effects of isoflurane on maximally activated and desensitized GABA(A)-R currents expressed in Xenopus oocytes. Wild-type alpha(1)beta(2) and alpha(1)beta(2)gamma(2s) receptors were exposed to 600 microM GABA until…

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Cyclohexanol analogues are positive modulators of GABA(A) receptor currents and act as general anaesthetics in vivo

Author: Hall, A.C.; Griffith, T.N.; Tsikolia, M.; Kotey, F.O.; Gill, N.; Humbert, D.J.; Watt, E.E.; Yermolina, Y.A.; Goel, S.; El-Ghendy, B.; Hall, C.D. Description: GABA(A) receptors meet all the pharmacological criteria required to be considered important general anaesthetic targets. In the following study, the modulatory effects of various commercially available and novel cyclohexanols were investigated on recombinant human gamma-aminobutyric acid (GABA(A), alpha(1)beta(2)gamma(2s)) receptors expressed in Xenopus oocytes, and compared to the modulatory effects on GABA currents observed with exposures to the intravenous anaesthetic agent, propofol. Submaximal EC(20) GABA currents were…

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Teratogenic assessment of four solvents using the frog embryo teratogenesis assay–xenopus (FETAX)

Author: Dresser, T.H.; Rivera, E.R.; Hoffmann, F.J.; Finch, R.A. Description: The Frog Embryo Teratogenesis Assay-Xenopus (FETAX) was used to assess the teratogenic potential of four solvents. Embryos of the South African clawed frog, Xenopus laevis, were exposed for 96 h to ethanol, dimethyl sulfoxide (DMSO), formamide or glycerol formal. Exposure groups were maintained using a static renewal system in which the exposure media were changed at 24-h intervals. Survival was monitored at 24-h intervals. Length, as an indicator of growth effects, and developmental malformations were determined at the end of…

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