scholarly journals Characterization of convergent thickening, a major convergence force producing morphogenic movement in amphibians

2018 ◽  
Author(s):  
David Shook ◽  
Jason Wen ◽  
Ana Rolo ◽  
Brian Francica ◽  
Destiny Dobins ◽  
...  
Keyword(s):  
Interfacial Tension ◽  
Surface Area ◽  
Marginal Zone ◽  
Tensile Force ◽  
African Clawed Frog ◽  
Radial Dimension ◽  
Morphogenic Process ◽  
Clawed Frog

SUMMARYWe characterize the morphogenic process of convergent thickening (CT), which occurs in the involuting marginal zone (IMZ) during gastrulation of Xenopus, the African clawed frog. CT was described previously as the tendency of explants of the ventral IMZ of Xenopus to converge their circumblastoporal dimension and thicken their radial dimension (Keller and Danilchik 1988). Here we show that CT occurs from the onset of gastrulation, initially throughout the pre-involution IMZ. We suggest that CT is driven by an increase in the interfacial tension between the deep IMZ and its epithelium, resulting in cells of the deep IMZ tending to minimize their surface area. In explants, this results in a progressive shortening (convergence) of the IMZ along its longer mediolateral axis and thickening in the orthogonal planes, and can generate tensile force (Shook et al. 2018). In vivo, convergence of the annular IMZ generates circumferential tension, closing the blastopore. These results provide the first clear example of a tensile morphogenic force from a Holtfreterian/Steinbergian change in tissue affinity.

scholarly journals Androgen-Induced Vocal Transformation in Adult Female African Clawed Frogs

2005 ◽  
Vol 94 (1) ◽  
pp. 415-428 ◽  
Author(s):  
Kristen A. Potter ◽  
Tina Bose ◽  
Ayako Yamaguchi
Keyword(s):  
Neural Systems ◽  
Behavioral Modification ◽  
Female Adult ◽  
African Clawed Frog ◽  
Soma Size ◽  
Behavioral Transformations ◽  
Clawed Frog ◽  
Muscle Contractile ◽  
Laryngeal Motoneurons

Sex-specific behaviors of some vertebrates are reversible by androgen administered in adulthood. Such behavioral transformations in adulthood provide opportunities to identify how neural systems reconfigure to produce sex-specific behavior. In this study, we focused on the vocalizations of the African clawed frog, Xenopus laevis. Male and female adult Xenopus produce sexually distinct vocalizations; males produce series of rapid clicks, whereas females produce slow trains of clicks. The differences in click rate can be reduced to differences in the firing rate of laryngeal motoneurons in vivo. This behavioral dimorphism is accompanied by various sex-specific characteristics throughout the vocal pathways, including functionally distinct laryngeal muscles and motoneurons in the sexes. In this study, we first determined whether and how testosterone (T) modifies the vocalizations of adult females and then examined changes underlying the behavioral modification at the laryngeal muscle and motoneuron levels. Our results show that, in response to T, the vocalizations of females were transformed within 13 wk. Vocal transformation was preceded by complete masculinization of muscle contractile properties and motoneuron soma size by the fourth week of T treatment, which suggests that the vocal pathways' peripheral components masculinize earlier than the behavior. Therefore the rate of transformation of vocal behavior must reflect a functional transformation of neurons in the central vocal pathways, which leads to the generation of male-like motor rhythms.

scholarly journals Endogenous Serotonin Acts on 5-HT2C-Like Receptors in Key Vocal Areas of the Brain Stem to Initiate Vocalizations in Xenopus laevis

2010 ◽  
Vol 103 (2) ◽  
pp. 648-658 ◽  
Author(s):  
Heather J. Yu ◽  
Ayako Yamaguchi
Keyword(s):  
Xenopus Laevis ◽  
Brain Stem ◽  
Motor Nucleus ◽  
African Clawed Frog ◽  
In Vivo Release ◽  
Rhythmic Behaviors ◽  
Clawed Frog ◽  
The Brain

Serotonin initiates various rhythmic behaviors in vertebrates. Previously we have shown that serotonergic neurons innervate the central vocal pathway in the African clawed frog ( Xenopus laevis ). We also discovered that exogenous serotonin applied to isolated brains in vitro activates fictive vocalizations by activating 5-HT2C-like receptors. In this study, we examined the location of 5-HT2C-like receptors and determined whether endogenously released serotonin also initiates vocalizations by activating 5-HT2C-like receptors in male Xenopus brains. To this end, we first identified the specific location of 5-HT2C-like receptors using immunohistochemistry. We next examined which of the populations of neurons that express 5-HT2C-like receptors are functionally relevant for initiating fictive vocalizations by applying a 5-HT2C receptor agonist to brains transected at various levels. Of four populations of immunopositive neurons, we showed that 5-HT2C-like receptors located in two areas of the brain stem vocal circuit, the raphe nucleus and motor nucleus IX-X, initiate fictive vocalizations. We next showed that endogenous serotonin can also activate fictive vocalizations by increasing the extracellular concentration of endogenous serotonin using a selective serotonin reuptake inhibitor (SSRI). The SSRI-induced vocal initiation is also mediated by activation of 5-HT2C-like receptors because blockade of these receptors prevents fictive vocalization. The results suggest that in vivo release of serotonin initiates male vocalizations by activating 5-HT2C-like receptors in the brain stem vocal nuclei.

scholarly journals Trialkyltin Rexinoid-X Receptor Agonists Selectively Potentiate Thyroid Hormone Induced Programs of Xenopus laevis Metamorphosis

Endocrinology ◽  
2016 ◽  
Vol 157 (7) ◽  
pp. 2712-2723 ◽  
Author(s):  
Brenda J. Mengeling ◽  
Albertinka J. Murk ◽  
J. David Furlow
Keyword(s):  
Thyroid Hormone ◽  
Xenopus Laevis ◽  
Caspase 3 ◽  
Target Genes ◽  
Luciferase Reporter ◽  
In Vivo Model ◽  
Reporter Cell ◽  
African Clawed Frog ◽  
Clawed Frog

The trialkyltins tributyltin (TBT) and triphenyltin (TPT) can function as rexinoid-X receptor (RXR) agonists. We recently showed that RXR agonists can alter thyroid hormone (TH) signaling in a mammalian pituitary TH-responsive reporter cell line, GH3.TRE-Luc. The prevalence of TBT and TPT in the environment prompted us to test whether they could also affect TH signaling. Both trialkyltins induced the integrated luciferase reporter alone and potentiated TH activation at low doses. Trimethyltin, which is not an RXR agonist, did not. We turned to a simple, robust, and specific in vivo model system of TH action: metamorphosis of Xenopus laevis, the African clawed frog. Using a precocious metamorphosis assay, we found that 1nM TBT and TPT, but not trimethyltin, greatly potentiated the effect of TH treatment on resorption phenotypes of the tail, which is lost at metamorphosis, and in the head, which undergoes extensive remodeling including gill loss. Consistent with these responses, TH-induced caspase-3 activation in the tail was enhanced by cotreatment with TBT. Induction of a transgenic reporter gene and endogenous collagenase 3 (mmp13) and fibroblast-activating protein-α (fap) genes were not induced by TBT alone, but TH induction was significantly potentiated by TBT. However, induction of other TH receptor target genes such as TRβ and deiodinase 3 by TH were not affected by TBT cotreatment. These data indicate that trialkyltins that can function as RXR agonists can selectively potentiate gene expression and resultant morphological programs directed by TH signaling in vivo.

scholarly journals Expression and characterization of the bacterial mechanosensitive channel MscS in Xenopus laevis oocytes

2011 ◽  
Vol 138 (6) ◽  
pp. 641-649 ◽  
Author(s):  
Grigory Maksaev ◽  
Elizabeth S. Haswell
Keyword(s):  
Xenopus Laevis ◽  
Single Channel ◽  
Ease Of Use ◽  
Mechanosensitive Channel ◽  
Xenopus Laevis Oocytes ◽  
E Coli ◽  
African Clawed Frog ◽  
Clawed Frog ◽  
Small Conductance

We have successfully expressed and characterized mechanosensitive channel of small conductance (MscS) from Escherichia coli in oocytes of the African clawed frog, Xenopus laevis. MscS expressed in oocytes has the same single-channel conductance and voltage dependence as the channel in its native environment. Two hallmarks of MscS activity, the presence of conducting substates at high potentials and reversible adaptation to a sustained stimulus, are also exhibited by oocyte-expressed MscS. In addition to its ease of use, the oocyte system allows the user to work with relatively large patches, which could be an advantage for the visualization of membrane deformation. Furthermore, MscS can now be compared directly to its eukaryotic homologues or to other mechanosensitive channels that are not easily studied in E. coli.

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