Somitogenesis in amphibian embryos

Development ◽  
1979 ◽  
Vol 51 (1) ◽  
pp. 27-50
Author(s):  
Murray Pearson ◽  
Tom Elsdale
Keyword(s):  
Heat Shock ◽  
Xenopus Laevis ◽  
Rana Temporaria ◽  
The Body ◽  
Body Axis ◽  
Cellular Mechanics ◽  
Cellular Processes ◽  
Cellular Change ◽  
Somite Formation ◽  
Heat Shocks

Somitogenesis is described in two species of anuran amphibians, Xenopus laevis and Rana temporaria, in which the cellular mechanics of somite formation are distinctly different. Heat shocks are employed to demonstrate a wave of cellular change which precedes somite formation down the body axis. This prior wave is shown to be kinematic. It is not a propagated wave. It is a consequence of the temporal activities of the cells laid out in space, but there is no evidence that these activities depend upon an interpretation of their position. Heat shocks cause characteristic segmental abnormalities over a zone of somites which is formed several hours after the shock. Evidence from double heat shock experiments suggests that the pattern of abnormality is the result of (i) a disturbance of co-ordination between pre-somitic cells, and (ii) the time available to those cells for recovery before they are recruited into a segmental pre-pattern at the time of passage of the prior wave. It is a temporal coordination that is disturbed and subsequently recovered following a heat shock. This temporal co-ordination of pre-somitic cells does not depend upon position along the axis. The evidence for two physiologically independent temporal patterns of cellular processes, which interact to specify the segmental pattern of somites (their size, shape and number), gives experimental support for the theoretical account of somitogenesis proposed by Cooke & Zeeman (1976).

scholarly journals MYC activity is required for maintenance of the Neuromesodermal Progenitor signalling network and for correct timing of segmentation clock gene oscillations

2017 ◽  
Author(s):  
Ioanna Mastromina ◽  
Laure Verrier ◽  
Kate G. Storey ◽  
J. Kim Dale
Keyword(s):  
Cell Cycle Progression ◽  
The Body ◽  
Body Axis ◽  
Cellular Functions ◽  
Segmentation Clock ◽  
Signalling Network ◽  
Undifferentiated State ◽  
Somite Formation ◽  
Axis Elongation ◽  
And Function

AbstractThe Myc transcriptional regulators are implicated in a range of cellular functions, including proliferation, cell cycle progression, metabolism and pluripotency maintenance. Here, we investigated the expression, regulation and function of Myc during mouse embryonic axis elongation and segmentation. Expression of both cMyc and MycN in the domains where neuromesodermal progenitors (NMPs) and underlying caudal pre-somitic mesoderm (cPSM) cells reside is coincident WNT and FGF signals; factors known to maintain progenitors in an undifferentiated state. Pharmacological inhibition of MYC activity, downregulates expression of WNT/FGF components. In turn, we find that cMyc expression is WNT, FGF and NOTCH regulated, placing it centrally in the signalling circuit that operates in the tail end that both sustains progenitors and drives maturation of the PSM into somites. Interfering with MYC function in the PSM, where it displays oscillatory expression, delays the timing of segmentation clock oscillations and thus of somite formation. In summary, we identify Myc as a component that links NMP maintenance and PSM maturation during the body axis elongation stages of mouse embryogenesis.Summary StatementMYC operates in a positive feedback loop with WNT/FGF signals to maintain the progenitors which facilitate body axis elongation while its activity is crucial for timing of the segmentation clock.

scholarly journals Development of a new method for assessing otolith function in mice using three-dimensional binocular analysis of the otolith-ocular reflex

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shotaro Harada ◽  
Takao Imai ◽  
Yasumitsu Takimoto ◽  
Yumi Ohta ◽  
Takashi Sato ◽  
...  
Keyword(s):  
Eye Movement ◽  
Three Dimensional ◽  
Vertical Component ◽  
Inertial Force ◽  
Linear Acceleration ◽  
The Body ◽  
Body Axis ◽  
Gravitational Acceleration ◽  
Ocular Reflex ◽  
Translational Movement

AbstractIn the interaural direction, translational linear acceleration is loaded during lateral translational movement and gravitational acceleration is loaded during lateral tilting movement. These two types of acceleration induce eye movements via two kinds of otolith-ocular reflexes to compensate for movement and maintain clear vision: horizontal eye movement during translational movement, and torsional eye movement (torsion) during tilting movement. Although the two types of acceleration cannot be discriminated, the two otolith-ocular reflexes can distinguish them effectively. In the current study, we tested whether lateral-eyed mice exhibit both of these otolith-ocular reflexes. In addition, we propose a new index for assessing the otolith-ocular reflex in mice. During lateral translational movement, mice did not show appropriate horizontal eye movement, but exhibited unnecessary vertical torsion-like eye movement that compensated for the angle between the body axis and gravito-inertial acceleration (GIA; i.e., the sum of gravity and inertial force due to movement) by interpreting GIA as gravity. Using the new index (amplitude of vertical component of eye movement)/(angle between body axis and GIA), the mouse otolith-ocular reflex can be assessed without determining whether the otolith-ocular reflex is induced during translational movement or during tilting movement.

The Caenorhabditis elegans gene lin-44 controls the polarity of asymmetric cell divisions

Development ◽  
1994 ◽  
Vol 120 (5) ◽  
pp. 1035-1047 ◽  
Author(s):  
M.A. Herman ◽  
H.R. Horvitz
Keyword(s):  
Caenorhabditis Elegans ◽  
The Body ◽  
Body Axis ◽  
Nematode Caenorhabditis Elegans ◽  
Asymmetric Cell Divisions ◽  
Cell Divisions ◽  
Sister Cells

The generation and orientation of cellular and organismic polarity are fundamental aspects of development. Mutations in the gene lin-44 of the nematode Caenorhabditis elegans reverse both the relative positions of specific sister cells and the apparent polarities of these cells. Thus, lin-44 mutants appear to generate polar cells but to misorient these cells along the body axis of the animal. We postulate that lin-44 acts to specify the orientation of polar cells.

Head positioning control in a gravito-inertial field and in normal gravity

2004 ◽  
Vol 14 (4) ◽  
pp. 321-333
Author(s):  
Frédéric Sarès ◽  
Christophe Bourdin ◽  
Jean-Michel Prieur ◽  
Jean-Louis Vercher ◽  
Jean-Pierre Menu ◽  
...  
Keyword(s):  
Inertial Force ◽  
The Body ◽  
Body Axis ◽  
Positioning Control ◽  
Head Positioning ◽  
Subject Variability ◽  
Visual Frame ◽  
Vector Orientation ◽  
The Right ◽  
Within Subject Variability

The way in which the head is controlled in roll was investigated by dissociating the body axis and the gravito-inertial force orientation. Seated subjects (N = 8) were requested to align their head with their trunk, 30° to the left, 30° to the right or with the gravito-inertial vector, before, during (Per Rotation), after off-center rotation and on a tilted chair without rotation (Tilted). The gravito-inertial vector angle during rotation and the chair tilt angle were identical (17°). The subjects were either in total darkness or facing a visual frame that was fixed to the trunk. Both final error and within-subject variability of head positioning increased when the body axis and the gravito-inertial vector were dissociated (Per Rotation and Tilted). However, the behavior was different depending on whether the subjects were in the Tilted or Per Rotation conditions. The presentation of the visual frame reduced the within-subject variability and modified the perception of the gravito-inertial vector's orientation on the tilted chair. As head positioning with respect to the body and sensing of the gravito-inertial vector are modified when body axis and gravito-inertial vector orientation are dissociated, the observed decrease in performance while executing motor tasks in a gravito-inertial field may be at least in part attributed to the inaccurate sensing of head position.

scholarly journals Impacts of three glyphosate formulations on gonadal development of Xenopus laevis

2021 ◽  
Vol 5 ◽  
pp. 239784732110314
Author(s):  
Oluwaseun O Babalola ◽  
J Christoff Truter ◽  
Johannes H van Wyk
Keyword(s):  
Xenopus Laevis ◽  
Body Mass ◽  
Reproductive System ◽  
Sex Ratios ◽  
Gonadal Development ◽  
Application Rate ◽  
Amphibian Declines ◽  
The Body ◽  
Pesticide Pollution ◽  
Glyphosate Formulations

The emergence of widespread morphological malformations in the reproductive system of wildlife is generating increasing concerns. This concern is because the observed malformities may be linked to pollution by pesticides and other chemicals. The amphibian declines, for example, have been linked to pesticide pollution among other factors. Using an extended Xenopus Metamorphosis Assay protocol, until the tadpoles metamorphosized, the exposure impacts of three glyphosate formulations, namely, Roundup, Kilo Max and Enviro Glyphosate, were assessed on the reproductive system of Xenopus laevis, vis-a-vis the body mass, sex ratios and morphological malformations as endpoints. The exposure concentrations ranged between 0.2–0.6 mg/L, 0.9–28 mg/L and 90–280 mg/L for Roundup, Enviro Glyphosate, and Kilo Max, respectively. Both Kilo Max and Enviro Glyphosate formulations significantly reduced the body mass of the metamorphs compared to the control. In sex ratios, only Kilo Max altered the percentage sex ratio of the treated frogs at a ratio of 68:32 (F:M) compared to 50:50 ratio in the control. In reproductive malformations, the three formulations showed abnormality index range of 22.3–49%, 17.5–37.5% and 20–30% for the Kilo Max, Enviro Glyphosate and Roundup formulations, respectively, compared to 7.5% in the control. Observed reproductive malformations include mixed sex, translucence, aplasia, segmented hypertrophy and segmented aplasia and translucence. This result indicates that some of the glyphosate formulations have the capacity to cause widespread reproductive malformations in a way that could reduce the reproductive fitness of the amphibian. Care must therefore be taken to reduce the application rate of these formulations, particularly in aquatic environments.

scholarly journals Mitochondrial responses towards intermittent heat shocks in the Eastern Oyster, Crassostrea virginica

2021 ◽  
Author(s):  
Georges Hraoui ◽  
Sophie Breton ◽  
Gilles Miron ◽  
Luc H. Boudreau ◽  
Florence Hunter-Manseau ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Heat Shock ◽  
Crassostrea Virginica ◽  
Heat Waves ◽  
Physiological Stress ◽  
Eastern Oyster ◽  
Emission Rates ◽  
Mitochondrial Functions ◽  
Heat Shocks ◽  
Single Stress

Frequent heat waves caused by climate change can cause physiological stress in many animals, particularly in sessile ectotherms such as bivalves. Most studies characterizing thermal stress in bivalves focus on evaluating the responses to a single stress event. This does not accurately reflect the reality faced by bivalves which are often subject to intermittent heat waves. Here, we investigated the effect of intermittent heat stress on mitochondrial functions of Eastern oyster Crassostrea virginica which play a key role in setting ectotherms’ thermal tolerance. Specifically, we measured changes in mitochondrial oxygen consumption and H2O2 emission rates before, during and after intermittent 7.5°C heat shocks in oysters acclimated to 15°C and 22.5°C. Our results showed that oxygen consumption was impaired following the first heat shock at both acclimation temperatures. After the second heat shock, results for oysters acclimated to 15°C indicated a return to normal. However, oysters acclimated to 22.5°C struggled more with the compounding effects of intermittent heat shocks as denoted with an increase contribution of FAD-linked substrates to mitochondrial respiration as well as high levels of H2O2 emission rates. However, both acclimated populations showed signs of potential recovery ten days after the second heat shock, reflecting a surprising resilience to heat waves by C. virginica. Thus, this study highlights the important role of acclimation in oyster's capacity to weather intermittent heat shock.

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