scholarly journals The stopping response of Xenopus laevis embryos: pharmacology and intracellular physiology of rhythmic spinal neurones and hindbrain neurones

1992 ◽  
Vol 169 (1) ◽  
pp. 65-86 ◽  
Author(s):  
K. M. Boothby ◽  
A. Roberts
Keyword(s):  
Xenopus Laevis ◽  
Kynurenic Acid ◽  
Excitatory Amino Acid ◽  
Pattern Generator ◽  
Cement Gland ◽  
Intracellular Recordings ◽  
Pressure Sensitive ◽  
Inhibitory Postsynaptic Potentials ◽  
Spinal Neurones ◽  
Xenopus Laevis Embryos

1. Xenopus laevis embryos stop swimming in response to pressure on the cement gland. This behaviour and ‘fictive’ stopping are blocked by bicuculline (10 mumol 1(−1)), tubocurarine (110 mumol 1(−1)) and kynurenic acid (0.5 mmol 1(−1)). 2. Intracellular recordings from spinal neurones active during swimming have shown that pressure on the cement gland evokes compound, chloride-dependent inhibitory postsynaptic potentials (IPSPs). These are blocked by bicuculline, tubocurarine and kynurenic acid, but are unaffected by strychnine (2 mumol 1(−1)). 3. When the cement gland is pressed, trigeminal ganglion activity precedes both the IPSPs and the termination of ‘fictive’ swimming activity recorded in rhythmic spinal neurones. The trigeminal discharge is unaffected by the antagonists bicuculline, tubocurarine, kynurenic acid and strychnine. 4. Intracellular recordings from the hindbrain have revealed neurones that are normally silent, but rhythmically inhibited during ‘fictive’ swimming. In these neurones pressure on the cement gland evokes depolarising potentials, often with one or more spikes. 5. We propose that the stopping response depends on the excitation of pressure-sensitive trigeminal receptors which innervate the cement gland. These release an excitatory amino acid to excite brainstem GABAergic reticulospinal neurones, which inhibit spinal neurones to turn off the central pattern generator for swimming. There may also be a less direct pathway.

Cement gland as the adhesion organ in Xenopus laevis embryos

2012 ◽  
Vol 43 (1) ◽  
pp. 1-11 ◽  
Author(s):  
E. S. Pshennikova ◽  
A. S. Voronina
Keyword(s):  
Xenopus Laevis ◽  
Cement Gland ◽  
Xenopus Laevis Embryos

Cholinergic contribution to excitation in a spinal locomotor central pattern generator in Xenopus embryos

1995 ◽  
Vol 73 (3) ◽  
pp. 1013-1019 ◽  
Author(s):  
R. Perrins ◽  
A. Roberts
Keyword(s):  
Spinal Cord ◽  
Central Pattern Generator ◽  
Excitatory Amino Acid ◽  
Pattern Generator ◽  
Excitatory Input ◽  
Intracellular Recordings ◽  
Electrical Excitation ◽  
Spinal Interneurons ◽  
Xenopus Embryos ◽  
Spike Firing

1. We have investigated whether in Xenopus embryos, spinal interneurons of the central pattern generator (CPG) receive cholinergic or electrical excitatory input during swimming. The functions of cholinergic excitation during swimming were also investigated. 2. Intracellular recordings were made from rhythmically active presumed premotor interneurons in the dorsal third of the spinal cord. After locally blocking inhibitory potentials with 2 microM strychnine and 40 microM bicuculline, the reliability of spike firing and the amplitude of fast, on-cycle, excitatory postsynaptic potentials (EPSPs) underlying the single on-cycle spikes were measured during fictive swimming. 3. The nicotinic antagonists d-tubocurarine and dihydro-beta-erythroidine (DH beta E, both 10 microM) reversibly reduced the reliability of the spike firing during swimming and reduced the amplitude of the on-cycle EPSP by 16%. DH beta E also reduced the EPSP amplitude in spinalized embryos by 22%. These results indicate that interneurons receive rhythmic cholinergic excitation from a source within the spinal cord. 4. Combined applications of nicotinic and excitatory amino acid (EAA) antagonists or cadmium (Cd2+, 100-200 microM) resulted in complete block of the fast EPSP, suggesting that interneurons do not receive electrical excitation. 5. The nicotinic antagonists mecamylamine and d-tubocurarine (both 5 microM) reduced the duration of episodes of fictive swimming recorded from the ventral roots, in spinal embryos. When applied in the middle of a long episode, d-tubocurarine decreased the swimming frequency, ruling out an effect on the initiation pathway. The cholinesterase inhibitor eserine (10 microM) increased the duration of swimming episodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential gene expression in the anterior neural plate during gastrulation of Xenopus laevis

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 779-786 ◽  
Author(s):  
M. Jamrich ◽  
S. Sato
Keyword(s):  
Gene Expression ◽  
Xenopus Laevis ◽  
Neural Induction ◽  
Neural Plate ◽  
Cement Gland ◽  
Cdna Clones ◽  
Differential Gene ◽  
Anteroposterior Polarity ◽  
Xenopus Laevis Embryos ◽  
Anterior Neural Plate

We have isolated three cDNA clones that are preferentially expressed in the cement gland of early Xenopus laevis embryos. These clones were used to study processes involved in the induction of this secretory organ. Results obtained show that the induction of this gland coincides with the process of neural induction. Genes specific for the cement gland are expressed very early in the anterior neural plate of stage-12 embryos. This suggests that the anteroposterior polarity of the neural plate is already established during gastrulation. At later stages of development, two of the three genes have secondary sites of expression. The expression of these genes can be induced in isolated animal caps by incubation in 10 mM-NH4Cl, a treatment that is known to induce cement glands.

Responses of young Xenopus laevis tadpoles to light dimming: possible roles for the pineal eye

2000 ◽  
Vol 203 (12) ◽  
pp. 1857-1867 ◽  
Author(s):  
D. Jamieson ◽  
A. Roberts
Keyword(s):  
Xenopus Laevis ◽  
Water Column ◽  
Central Pattern Generator ◽  
Water Surface ◽  
Pattern Generator ◽  
Cement Gland ◽  
Solid Objects ◽  
Floating Objects ◽  
Behavioural Significance

When the light is dimmed, the pineal eye of hatchling Xenopus laevis tadpoles excites the central pattern generator for swimming, but the behavioural significance of pineal excitation is unclear. We show that tadpoles spend 99 % of their time hanging from the surface meniscus or solid objects using mucus secreted by a cement gland on the head. Attachment inhibits swimming, but unattached tadpoles swim spontaneously. Provided that their pineal eye is intact, they attach closer to the water surface in the dark than in the light and attach preferentially to the underside of floating objects that cast shadows. Dimming causes tadpoles swimming horizontally to turn upwards and is very effective in initiating upward swimming in unattached tadpoles. Similar pineal-dependent responses during swimming are present up to stage 44. Pinealectomy blocks responses to dimming at all stages. Recordings from immobilised tadpoles reveal that light dimming induces faster fictive swimming and that pineal activity is increased for up to 20 min during sustained light dimming. We suggest that the increase in pineal discharge during dimming increases the probability of upward swimming and, in this way, increases the probability of tadpoles attaching to objects higher in the water column that cast shadows.

Xenopus laevis cement gland as an experimental model for embryonic differentiation

Development ◽  
1975 ◽  
Vol 33 (4) ◽  
pp. 969-978
Author(s):  
J. J. Picard
Keyword(s):  
Xenopus Laevis ◽  
Ammonium Chloride ◽  
Superficial Layer ◽  
Cement Gland ◽  
Physiological Salt Solution ◽  
Adjacent Layer ◽  
Gland Tissue ◽  
Total Tissue ◽  
Xenopus Laevis Embryos

Explants of the blastocoelic roof of Xenopus laevis embryos were incubated for 6 h in Holtfreter solution containing 10 mm ammonium chloride and 10 mM sodium bicarbonate. After this incubation they were transferred for 5 days to Barth's physiological salt solution. Under these conditions the explants underwent differentiation into cement gland tissue. The ability to produce cement gland was highest when explants were dissected from young gastrulae (stage 10). Explants from younger and older embryos displayed much smaller cement glands. There is no difference in the response of ventral or dorsal portions of the blastocoelic roof of stage-10 embryos under these in vitro conditions involving ammonium chloride stimulation. Although the treatment changed the fate of some ectoblastic tissues, it was unable to force endodermal or mesodermal tissues of the blastoporal lip to differentiate into cement gland. The amount of cement gland in the ectoblastic explants varied according to the egg-batch and on the average accounted for 55 % of the total tissue. The remaining tissue was undifferentiated. Most of this undifferentiated tissue originates from the adjacent layer of the ectoblast. Therefore it may be estimated that the cement gland accounts for 80 to 100 % of the volume of the competent superficial layer.

scholarly journals Iron nanoparticle bio-interactions evaluated in Xenopus laevis embryos, a model for studying the safety of ingested nanoparticles

2019 ◽  
Vol 14 (2) ◽  
pp. 196-213
Author(s):  
Patrizia Bonfanti ◽  
Anita Colombo ◽  
Melissa Saibene ◽  
Luisa Fiandra ◽  
Ilaria Armenia ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Iron Nanoparticle ◽  
Xenopus Laevis Embryos ◽  
Ingested Nanoparticles
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