Activation of dorsal development by contact between the cortical dorsal determinant and the equatorial core cytoplasm in eggs of Xenopus laevis

Development ◽  
1997 ◽  
Vol 124 (8) ◽  
pp. 1543-1551 ◽  
Author(s):  
H. Kageura
Keyword(s):  
Xenopus Laevis ◽  
Dorsal Side ◽  
Equatorial Region ◽  
Normal Embryo ◽  
Dorsal Region ◽  
The Core ◽  
Dorsal Axis ◽  
The Future ◽  
Vegetal Pole ◽  
Cell Embryo

In eggs of Xenopus laevis, dorsal development is activated on the future dorsal side by cortical rotation, after fertilization. The immediate effect of cortical rotation is probably the transport of a dorsal determinant from the vegetal pole to the equatorial region on the future dorsal side. However, the identity and action of the dorsal determinant remain problematic. In the present experiments, individual isolated cortices from various regions of the unfertilized eggs and embryos were implanted into one of several positions of a recipient 8-cell embryo. The incidence of secondary axes was used not only to locate the cortical dorsal determinant at different times but also to locate the region of the core competent to respond to the dorsal determinant. The dorsal axis-inducing activity of the cortex occurred around the vegetal pole of the unfertilized egg. During cortical rotation, it shifted from there to a wide dorsal region. This is apparently the first evidence for the presence of a dorsal determinant in the egg cortex. The competence of the core of the 8-cell embryo was distributed in the form of gradient with the highest responsiveness at the equator. These results suggest that, in the normal embryo, dorsal development is activated by contact between the cortical dorsal determinant and the equatorial core cytoplasm, brought together through cortical rotation.

A cytoplasmic determinant for dorsal axis formation in an early embryo of Xenopus laevis

Development ◽  
1990 ◽  
Vol 110 (4) ◽  
pp. 1051-1056 ◽  
Author(s):  
M. Yuge ◽  
Y. Kobayakawa ◽  
M. Fujisue ◽  
K. Yamana
Keyword(s):  
Xenopus Laevis ◽  
Direct Evidence ◽  
Early Embryo ◽  
Dorsal Side ◽  
Axis Formation ◽  
Secondary Axis ◽  
Dorsal Axis ◽  
Cell Embryo ◽  
Dorsal Cells ◽  
Cytoplasmic Determinant

In Xenopus laevis, dorsal cells that arise at the future dorsal side of an early cleaving embryo have already acquired the ability to cause axis formation. Since the distribution of cytoplasmic components is markedly heterogeneous in an egg and embryo, it has been supposed that the dorsal cells are endowed with the activity to form axial structures by inheriting a unique cytoplasmic component or components localized in the dorsal region of an egg or embryo. However, there has been no direct evidence for this. To examine the activity of the cytoplasm of dorsal cells, we injected cytoplasm (dorsal cytoplasm) from dorsal vegetal cells of a Xenopus 16-cell embryo into ventral vegetal cells of a simultaneous recipient. The cytoplasm caused secondary axis formation in 42% of recipients. Histological examination revealed that well-developed secondary axes included notochord, as well as a neural tube and somites. However, injection of cytoplasm of ventral vegetal cells never caused secondary axis and most recipients became normal tailbud embryos. Furthermore, about two-thirds of ventral isolated halves injected with dorsal cytoplasm formed axial structures. These results show that dorsal, but not ventral, cytoplasm contains the component or components responsible for axis formation. This can be the first step towards identifying the molecular basis of dorsal axis formation.

Occurrence of dorsal axis-inducing activity around the vegetal pole of an uncleaved Xenopus egg and displacement to the equatorial region by cortical rotation

Development ◽  
1993 ◽  
Vol 118 (1) ◽  
pp. 163-170 ◽  
Author(s):  
M. Fujisue ◽  
Y. Kobayakawa ◽  
K. Yamana
Keyword(s):  
Cell Cycle ◽  
Close Association ◽  
Dorsal Side ◽  
Equatorial Region ◽  
Cell Stage ◽  
Assay Procedure ◽  
Axis Specification ◽  
Vegetal Pole ◽  
Cell Embryo ◽  
Dorsal Cells

Specification of the dorsoventral axis is a subject of great importance in amphibian embryogenesis. We have found that cytoplasm of the vegetal dorsal cells of a 16-cell embryo of Xenopus laevis, when injected into the ventral vegetal cells of a recipient at the same stage, can induce formation of a second axis. In the present experiments, using the same assay procedure, we found that the cytoplasm around the vegetal pole of an egg before cortical rotation is also active in inducing a second axis, that the activity decreases throughout the second half of the cell cycle and appears in a presumptive dorsal equatorial region at the 2- to 16-cell stages. This is the first demonstration of the localization of dorsal forming activity in any specific region of an egg. After UV irradiation, a treatment that is known to block cortical rotation and thereby inhibit axis specification, the activity remains near the vegetal pole beyond the first cell cycle and does not appear in an equatorial region, at least at the 16-cell stage. This suggests that cortical rotation or a related force is in some way involved in changes in distribution of the activity. We also found that UV-irradiated 8-cell embryos can rescue dorsal development when they are cut into halves along the first cleavage plane. Histological examination revealed that the rescued embryos have a neural tube and notochord. In the half embryo, the animal and vegetal regions came into contact during wound healing, an event that enables the activity to localize in the new equator of an embryo. Therefore this rescue suggests that, if the activity is distributed only in the equatorial region, dorsal specification occurs. In fact, the dorsal side of the rescued embryos seems to correspond to the plane through which the embryos have been cut. Based on our results, we propose (1) that a determinant that carries axis-inducing activity is first present around the vegetal pole, (2) that the determinant shifts from the vegetal pole to an equatorial region by or in close association with cortical rotation and (3) that occurrence of the determinant in the equatorial region is a prerequisite for axis specification.

Roles of Cortical and Subcortical Components in Cleavage Furrow Formation in Amphibia

1972 ◽  
Vol 11 (2) ◽  
pp. 543-556
Author(s):  
TSUYOSHI SAWAI
Keyword(s):  
Surface Layer ◽  
Xenopus Laevis ◽  
Species Specificity ◽  
Cleavage Furrow ◽  
Entire Surface ◽  
Animal Pole ◽  
The Future ◽  
Vegetal Pole ◽  
Triturus Pyrrhogaster

In the eggs of the newt, Triturus pyrrhogaster, 2 separate factors are recognized which take part in cleavage furrow formation. (1) The inductive capacity for the furrow formation by the cytoplasm lying under the cortex along the cleavage furrow (FIC); and (2) the reactivity of the overlying cortex to form a furrow in response to FIC. (1) FIC. The inductive capacity is shown by the fact that FIC induces a furrow on whichever part of the surface under which FIC is transplanted. FIC is distributed along the cleavage furrow and even extends along the future furrow plane ahead of the furrow tip. The distance FIC precedes the furrow tip is about 1.0 mm in the animal hemisphere and is less in the vegetal hemisphere. In the direction at right angles to the furrow plane, FIC does not spread more than 0.1 mm. FIC is also present in the eggs of Xenopus laevis. Species specificity of FIC for induction is not found between Triturus and Xenopus. (2) Surface layer. At the onset of the first cleavage, the reactivity of the cortex to form the furrow in answer to FIC induction is localized on the animal pole region. The reactivity of the cortex propagates medially as a belt along the surface towards the vegetal pole with the advancing tip of the cleavage furrow. After the furrow is completed, the reactivity begins to be lost from the animal pole region, and eventually over the entire surface. The reactivity, however, reappears on the animal pole region simultaneously with the second cleavage.

The correlation between patterns of dye transfer junctions and future developmental fate in Xenopus: u.v. irradiation and lithium treatment

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 747-752 ◽  
Author(s):  
D.J. Nagajski ◽  
S.C. Guthrie ◽  
C.C. Ford ◽  
A.E. Warner
Keyword(s):  
Lucifer Yellow ◽  
Lithium Treatment ◽  
Cell Communication ◽  
Embryonic Axis ◽  
Axis Formation ◽  
Dye Transfer ◽  
Cell Stage ◽  
The Future ◽  
Vegetal Pole ◽  
Cell Embryo

The correlation between cell-to-cell communication junctions at the 32-cell stage and the subsequent embryonic axis has been examined in Xenopus laevis Disturbances of embryonic axis formation were u.v. irradiation at the vegetal pole before 0.6 in the which generates embryos with dorsal axial embryos were treated with 100mM-lithium chloride 32-cell stage, which generates embryos with ventral The cell-to-cell transfer of Lucifer Yellow was used junctional permeability. Injections were made into cells, lying in tiers 1 and 2 of the 32-cell embryo, relative to the future dorsoventral axis of the embryo on the basis of differences in pigmentation. The Yellow transfer in the future dorsal half of the compared with that in the future ventral half for u.v.-irradiated and Li-treated embryos. Injected subsequently scored for axial developmenf for transfer frequencies. In control embryos at the 32- Yellow transfer was both more frequent and more dorsal regions than in future ventral regions, as In embryos that had been u.v. irradiated before 0.6 in cycle, Lucifer transfer was the same in both light and the animal hemisphere and at the low level ventral regions in normal embryos. These embryos reductions in dorsal axial structures. Embryos the first cell cycle, when u.v. irradiation no longer cytoplasmic movements initiated at fertilization, dorsoventral difference in Lucifer Yellow transfer and normal dorsoventral polarity. Embryos exposed to

The vegetal determinants required for the Spemann organizer move equatorially during the first cell cycle

Development ◽  
1996 ◽  
Vol 122 (7) ◽  
pp. 2207-2214 ◽  
Author(s):  
M. Sakai
Keyword(s):  
Cell Cycle ◽  
Formation Process ◽  
Lithium Treatment ◽  
Axis Formation ◽  
Cell Stage ◽  
Spemann Organizer ◽  
Dorsal Axis ◽  
Vegetal Pole ◽  
Organizing Center ◽  
Cell Embryo

Embryos with no dorsal axis were obtained when more than 15% of the egg surface was deleted from the vegetal pole of the early 1-cell embryo of Xenopus laevis. The timing of the deletion in the first cell cycle was critical: dorsal-deficient embryos were obtained when the deletion began before time 0.5 (50% of the first cell cycle) whereas normal dorsal axis usually formed when the deletion was done later than time 0.8. The axis deficiency could be restored by lithium treatment and the injection of vegetal but not animal cytoplasm. Bisection of the embryo at the 2-cell stage, which is known to restore the dorsal structures in the UV-ventralized embryos, had no effect on the vegetal-deleted embryos. These results show clearly that, in Xenopus, (1) the dorsal determinants (DDs) localized in the vegetal pole region at the onset of development are necessary for dorsal axis development and (2) the DDs move from the vegetal pole to a subequatorial region where they are incorporated into gastrulating cells to form the future organizing center. A model for the early axis formation process in Xenopus is proposed.

Adaptations of Time Travel Narratives in Japanese Multimedia: Nurturing Eudaimonia across Time and Space

2014 ◽  
Vol 7 (2) ◽  
pp. 136-151 ◽  
Author(s):  
Sung-Ae Lee
Keyword(s):  
Travel Narratives ◽  
Time Travel ◽  
Cultural Knowledge ◽  
Human Beings ◽  
The Core ◽  
The Past ◽  
Life Styles ◽  
Concern For Others ◽  
The Future ◽  
Live Action

To displace a character in time is to depict a character who becomes acutely conscious of his or her status as other, as she or he strives to comprehend and interact with a culture whose mentality is both familiar and different in obvious and subtle ways. Two main types of time travel pose a philosophical distinction between visiting the past with knowledge of the future and trying to inhabit the future with past cultural knowledge, but in either case the unpredictable impact a time traveller may have on another society is always a prominent theme. At the core of Japanese time travel narratives is a contrast between self-interested and eudaimonic life styles as these are reflected by the time traveller's activities. Eudaimonia is a ‘flourishing life’, a life focused on what is valuable for human beings and the grounding of that value in altruistic concern for others. In a study of multimodal narratives belonging to two sets – adaptations of Tsutsui Yasutaka's young adult novella The Girl Who Leapt Through Time and Yamazaki Mari's manga series Thermae Romae – this article examines how time travel narratives in anime and live action film affirm that eudaimonic living is always a core value to be nurtured.

The Nature of Degrowth: Theorising the Core of Nature for the Degrowth Movement

2020 ◽  
Author(s):  
Pasi Heikkurinen
Keyword(s):  
Human Nature ◽  
Culturally Sensitive ◽  
Theory And Practice ◽  
The Core ◽  
The Past ◽  
The Future ◽  
Radical Reduction ◽  
Nature Experience ◽  
Matter Energy

This article investigates human–nature relations in the light of the recent call for degrowth, a radical reduction of matter–energy throughput in over-producing and over-consuming cultures. It outlines a culturally sensitive response to a (conceived) paradox where humans embedded in nature experience alienation and estrangement from it. The article finds that if nature has a core, then the experienced distance makes sense. To describe the core of nature, three temporal lenses are employed: the core of nature as ‘the past’, ‘the future’, and ‘the present’. It is proposed that while the degrowth movement should be inclusive of temporal perspectives, the lens of the present should be emphasised to balance out the prevailing romanticism and futurism in the theory and practice of degrowth.

Pathways to Success Through Identity-Based Motivation

2015 ◽  
Author(s):  
Daphna Oyserman
Keyword(s):  
The Self ◽  
The Core ◽  
Very Young Children ◽  
The Future ◽  
Identity Based ◽  
Future Self ◽  
Fidelity Measures ◽  
The Individual ◽  
Taking Action ◽  
Minimal Effort

Everyone can imagine their future self, even very young children, and this future self is usually positive and education-linked. To make progress toward an aspired future or away from a feared future requires people to plan and take action. Unfortunately, most people often start too late and commit minimal effort to ineffective strategies that lead their attention elsewhere. As a result, their high hopes and earnest resolutions often fall short. In Pathways to Success Through Identity-Based Motivation Daphna Oyserman focuses on situational constraints and affordances that trigger or impede taking action. Focusing on when the future-self matters and how to reduce the shortfall between the self that one aspires to become and the outcomes that one actually attains, Oyserman introduces the reader to the core theoretical framework of identity-based motivation (IBM) theory. IBM theory is the prediction that people prefer to act in identity-congruent ways but that the identity-to-behavior link is opaque for a number of reasons (the future feels far away, difficulty of working on goals is misinterpreted, and strategies for attaining goals do not feel identity-congruent). Oyserman's book goes on to also include the stakes and how the importance of education comes into play as it improves the lives of the individual, their family, and their society. The framework of IBM theory and how to achieve it is broken down into three parts: how to translate identity-based motivation into a practical intervention, an outline of the intervention, and empirical evidence that it works. In addition, the book also includes an implementation manual and fidelity measures for educators utilizing this book to intervene for the improvement of academic outcomes.

China, the UN, and Human Protection

2020 ◽  
Author(s):  
Rosemary Foot
Keyword(s):  
United Nations ◽  
Public Goods ◽  
World Order ◽  
Active Engagement ◽  
Fair Share ◽  
Global Order ◽  
The Core ◽  
Short Period ◽  
The Future ◽  
The United Nations

Over a relatively short period of time, Beijing moved from passive involvement with the UN to active engagement. How are we to make sense of the People’s Republic of China’s (PRC) embrace of the UN, and what does its engagement mean in larger terms? Is it a ‘supporter’ that takes its fair share of responsibilities, or a ‘spoiler’ that seeks to transform the UN’s contribution to world order? Certainly, it is difficult to label it a ‘shirker’ in the last decade or more, given Beijing’s apparent appreciation of the UN, its provision of public goods to the organization, and its stated desire to offer ‘Chinese wisdom and a Chinese approach to solving the problems facing mankind’. This study traces questions such as these, interrogating the value of such categorization through direct focus on Beijing’s involvement in one of the most contentious areas of UN activity—human protection—contentious because the norm of human protection tips the balance away from the UN’s Westphalian state-based profile, towards the provision of greater protection for the security of individuals and their individual liberties. The argument that follows shows that, as an ever-more crucial actor within the United Nations, Beijing’s rhetoric and some of its practices are playing an increasingly important role in determining how this norm is articulated and interpreted. In some cases, the PRC is also influencing how these ideas of human protection are implemented. At stake in the questions this book tackles is both how we understand the PRC as a participant in shaping global order, and the future of some of the core norms that constitute global order.

scholarly journals The future of SIMS: Who embodies which smile and when?

2010 ◽  
Vol 33 (6) ◽  
pp. 464-480 ◽  
Author(s):  
Paula M. Niedenthal ◽  
Martial Mermillod ◽  
Marcus Maringer ◽  
Ursula Hess
Keyword(s):  
Facial Expression ◽  
Eye Contact ◽  
Initial Position ◽  
Top Down ◽  
The Core ◽  
Facial Expression Of Emotion ◽  
Expression Of Emotion ◽  
Target Article ◽  
The Future

AbstractThe set of 30 stimulating commentaries on our target article helps to define the areas of our initial position that should be reiterated or else made clearer and, more importantly, the ways in which moderators of and extensions to the SIMS can be imagined. In our response, we divide the areas of discussion into (1) a clarification of our meaning of “functional,” (2) a consideration of our proposed categories of smiles, (3) a reminder about the role of top-down processes in the interpretation of smile meaning in SIMS, (4) an evaluation of the role of eye contact in the interpretation of facial expression of emotion, and (5) an assessment of the possible moderators of the core SIMS model. We end with an appreciation of the proposed extensions to the model, and note that the future of research on the problem of the smile appears to us to be assured.

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