The establishment of bilateral asymmetry in sea urchin embryos

Development ◽  
1994 ◽  
Vol 120 (2) ◽  
pp. 395-404 ◽  
Author(s):  
E. R. McCain ◽  
D. R. McClay
Keyword(s):  
Sea Urchin ◽  
Cell Separation ◽  
New Left ◽  
Lineage Tracing ◽  
Bilateral Asymmetry ◽  
Dorsoventral Axis ◽  
Adult Rudiment ◽  
Left Right Asymmetry ◽  
Relationship Of ◽  
The Relationship

Although much is known about the specification and determination of the two primary axes (animal/vegetal and dorsoventral or oral/aboral) in a number of embryos, little is understood about bilaterality. In the sea urchin, left/right asymmetry is crucial to normal development as the echinus or adult rudiment is positioned on the left side of the larva. We examined the establishment of bilateral asymmetry in Lytechnis variegatus embryos by determining the relationship of the first cleavage planes to the left/right axis. Embryos were bisected at different times to determine when the bilateral axis is committed. These lineage tracing and cell separation experiments demonstrated that the first cleavage plane divides the embryo into left and right halves, although this is conditional until after late blastula stage. The relationship between the specification of the dorsoventral axis and the bilateral axis was examined experimentally. In other species when the dorsal and ventral halves of early echinoderm embryos (preblastula) are separated, the dorsal half often reverses (180°) its dorsoventral axis. We asked whether those larvae with an inverted dorsoventral axis would shift the position of the echinus rudiment from the original left side to the new left side. If so, it would demonstrate that the larval asymmetry is dependent upon specification of the dorsoventral axis. Using a combination of lineage tracing and cell separation techniques, we show that the left/right asymmetry is specified with respect to the dorsoventral axis.

Evolutionary dissociation between cleavage, cell lineage and embryonic axes in sea urchin embryos

Development ◽  
1992 ◽  
Vol 114 (4) ◽  
pp. 931-938 ◽  
Author(s):  
J.J. Henry ◽  
K.M. Klueg ◽  
R.A. Raff
Keyword(s):  
Sea Urchin ◽  
Cleavage Plane ◽  
Cell Lineage ◽  
Frontal Plane ◽  
Individual Species ◽  
Cleavage Pattern ◽  
Embryonic Axes ◽  
Animal Pole ◽  
Dorsoventral Axis ◽  
The Relationship

Using vital dye staining and the microinjection of fluorescent cell lineage-autonomous tracers, the relationship between the first cleavage plane and the prospective larval dorsoventral axis was examined in several sea urchin species, including: Strongylocentrotus purpuratus, S. droebachiensis, Lytechinus pictus, Clypeaster rosaceus, Heliocidaris tuberculata and H. erythrogramma. The results indicate that there is no single relationship between the early cleavage pattern and the dorsoventral axis for all sea urchins; however, specific relationships exist for individual species. In S. purpuratus the first cleavage plane occurs at an angle 45 degrees clockwise with respect to the prospective dorsoventral axis in most cases, as viewed from the animal pole. On the other hand, in S. droebachiensis, L. pictus and H. tuberculata, the first cleavage plane generally corresponds with the plane of bilateral symmetry. There does not appear to be a predominant relationship between the first cleavage plane and the dorsoventral axis in C. rosaceus. In the direct-developing sea urchin H. erythrogramma the first cleavage plane bisects the dorsoventral axis through the frontal plane. Clearly, evolutionary differences have arisen in the relationship between cleavage pattern and developmental axes. Therefore, the mechanism of cell determination is not necessarily tied to any particular pattern of cell cleavage, but to an underlying framework of axial systems resident within sea urchin eggs and embryos.

“Down with 1989!”: The Peculiar Right-Wing Backlash against 1968 in Poland

2019 ◽  
Vol 33 (4) ◽  
pp. 843-860 ◽  
Author(s):  
David Ost
Keyword(s):  
Communist Party ◽  
New Left ◽  
Comparative Perspective ◽  
Right Wing ◽  
Politics Of Memory ◽  
Law And Justice ◽  
The Right ◽  
Relationship Of ◽  
The Relationship

This article is part of the special cluster titled Generation ’68 in Poland (with a Czechoslovak Comparative Perspective). Whereas much of the European right greeted the fiftieth anniversary of 1968 with a critique of its legacy, Poland’s ruling Law and Justice party was largely silent, both because 1968 did not usher in a counterculture and because the protests were directed against the communist party. And yet the Law and Justice party detests the legacy of 1968, for three reasons: 1968 was shaped by the left, ’68 activists and their values played a key role in the ensuing opposition, and because the right actually sympathizes with the communists of 1968, then dominated by nationalists. The right thus traditionally attacks the legacy of 1968 by attacking 1989 instead, when ’68’ ers played a central role and new left progressivism could finally emerge. That began changing early in 2018 when Poland’s parliament passed its Holocaust-speech law banning calumny against the “Polish Nation.” The resulting criticism brought 1968 back with a vengeance, with the right openly inhabiting the role of the national-communists, and beginning to attack Poland’s 1968 directly. Shedding new light on the diverse meanings of 1968 and the relationship of the right to national communism, the piece ends by looking at developments through Bernhard and Kubik’s theory of the politics of memory.

Anti-apartheid solidarity in the perspectives and practices of the British far left in the 1970s and 1980s

2018 ◽  
Author(s):  
Gavin Brown
Keyword(s):  
Great Britain ◽  
South African ◽  
Communist Party ◽  
Significant Role ◽  
New Left ◽  
African National Congress ◽  
South African Communist Party ◽  
National Congress ◽  
Relationship Of ◽  
The Relationship

Communists and members of the New Left were involved in the Anti-Apartheid Movement [AAM] from its origins in the Boycott Committee in the late 1950s. In its early days, the AAM welcomed support from individual communists, but was reluctant to be seen to be too close to the Communist Party. Nevertheless, members of the Communist Party of Great Britain [CPGB] played a significant role at all levels of the movement throughout its history. Fundamental to this was the relationship between the CPGB and the South African Communist Party [SACP] whose cadre played a central role in the exiled structures of the African National Congress [ANC]. In contrast to the CPGB, other left tendencies had more complicated relationships with the AAM’s leadership. This chapter examines the relationship of different far Left tendencies to the anti-apartheid struggle during the 1970s and 1980s.

scholarly journals Relación de la Asimetría Bilateral y el Déficit Bilateral con la Velocidad del Cambio de Dirección en Atletas Cadetes de Karate: Un estudio Piloto (Relationship of Bilateral Asymmetry and Bilateral Deficit with the Change of Direction Speed in Cadet Kara

Retos ◽  
2021 ◽  
Vol 42 ◽  
pp. 100-108
Author(s):  
Alex Ojeda-Aravena ◽  
Jairo Azócar-Gallardo ◽  
Tomás Herrera-Valenzuela ◽  
José Manuel García-García
Keyword(s):  
Negative Relationship ◽  
Bilateral Asymmetry ◽  
Bilateral Deficit ◽  
Change Of Direction ◽  
Explosive Strength ◽  
P 16 ◽  
Physical Abilities ◽  
Relationship Of ◽  
The Relationship ◽  
Karate Athletes

  Antecedentes: La Asimetría Bilateral (AB) y el Déficit Bilateral (DBL) y su potencial relación negativa con el rendimiento físico es actualmente estudiada, aunque la relación con la velocidad del cambio de dirección (CODS) y el sprint lineal (5-M) en atletas de karate se desconoce. Objetivo: Examinar las correlaciones entre la AB y el DBL con el CODS y 5-M, así como entre el salto horizontal con el CODS y 5-M. Métodos: Diez atletas hombres de categoría cadetes participaron voluntariamente de este estudio. Entre las habilidades físicas evaluadas se incluyeron: salto horizontal bilateral (SBJ), salto horizontal unilateral derecho (RSBJ), salto horizontal unilateral izquierdo (LSBJ), CODS y 5-M. Posteriormente, la AB y el DBL fueron calculados. Resultados: Se reportó una baja AB (5.17 ± 3.61%) y presencia de DBL (-36.9 ± 6.2 %). Correlaciones moderadas entre la AB con CODS (r = -.38; R2 = .15%; p = .30) y 5-M (r = -.47; R2 = .22%; p = .19) y entre DBL con 5-M (r = .51; R2 = .26%; p = .16) y bajas con CODS (r = .20; R2 = .04%; p = .60). Correlaciones significativas (p < .05) entre CODS con RSBJ (r = -.92; R2 = .85%; p = .00), SBJ (r = -.87; R2 = .75%; p = .00) y LSBJ (r = -.82; R2 = .67%; p = .00). Conclusiones: La AB y el DBL se relacionarían negativamente con el CODS y 5-M. Aunque, el CODS se relaciona con la fuerza explosiva horizontal bilateral y unilateral. Abstract. Background: Bilateral asymmetry (AB) and Bilateral Deficit (DBL) and their potential negative relationship with physical performance is currently studied, although the relationship with change of direction speed (CODS) and linear sprint (5-M) in karate athletes is unknown. Aim: To examine correlations between AB and DBL with CODS and 5-M, as well as between horizontal jump with CODS and 5-M. Methods: Ten male cadet athletes voluntarily participated in this study. The physical abilities assessed included: bilateral horizontal jump (SBJ), right unilateral horizontal jump (RSBJ), left unilateral horizontal jump (LSBJ), CODS and 5-M. Subsequently, AB and DBL were calculated. Results: Low AB (5.17 ± 3.61%) and presence of DBL (-36.9 ± 6.2 %) were reported. Moderate correlations between AB with CODS (r = -.38; R2 = .15%; p = .30) and 5-M (r = -.47; R2 = .22%; p = .19) and between DBL with 5-M (r = .51; R2 = .26%; p = .16) and low with CODS (r = .20; R2 = .04%; p = .60). Significant correlations (p < .05) between CODS with RSBJ (r = -.92; R2 = .85%; p = .00), SBJ (r = -.87; R2 = .75%; p = .00) and LSBJ (r = -.82; R2 = .67%; p = .00). Conclusions: AB and DBL would be negatively related to CODS and 5-M. However, CODS is related to bilateral and unilateral horizontal explosive strength.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Studies on Leukemogenic and Sarcomagenic Viruses

1970 ◽  
Vol 28 ◽  
pp. 156-157
Author(s):  
Leon Dmochowski
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Morphological Properties ◽  
Mode Of Development ◽  
Relationship Of ◽  
The Relationship

Electron microscopy has proved to be an invaluable discipline in studies on the relationship of viruses to the origin of leukemia, sarcoma, and other types of tumors in animals and man. The successful cell-free transmission of leukemia and sarcoma in mice, rats, hamsters, and cats, interpreted as due to a virus or viruses, was proved to be due to a virus on the basis of electron microscope studies. These studies demonstrated that all the types of neoplasia in animals of the species examined are produced by a virus of certain characteristic morphological properties similar, if not identical, in the mode of development in all types of neoplasia in animals, as shown in Fig. 1.

The relationship of IGE receptor topography to signaling activity in RBL-2H3 mast cells

1991 ◽  
Vol 49 ◽  
pp. 236-237
Author(s):  
J.R. Pfeiffer ◽  
J.C. Seagrave ◽  
C. Wofsy ◽  
J.M. Oliver
Keyword(s):  
Mast Cells ◽  
Protein A ◽  
Scattered Electron ◽  
Ige Receptor ◽  
Receptor Complexes ◽  
Ige Binding ◽  
Electron Imaging ◽  
Small Clusters ◽  
Relationship Of ◽  
The Relationship

In RBL-2H3 rat leukemic mast cells, crosslinking IgE-receptor complexes with anti-IgE antibody leads to degranulation. Receptor crosslinking also stimulates the redistribution of receptors on the cell surface, a process that can be observed by labeling the anti-IgE with 15 nm protein A-gold particles as described in Stump et al. (1989), followed by back-scattered electron imaging (BEI) in the scanning electron microscope. We report that anti-IgE binding stimulates the redistribution of IgE-receptor complexes at 37“C from a dispersed topography (singlets and doublets; S/D) to distributions dominated sequentially by short chains, small clusters and large aggregates of crosslinked receptors. These patterns can be observed (Figure 1), quantified (Figure 2) and analyzed statistically. Cells incubated with 1 μg/ml anti-IgE, a concentration that stimulates maximum net secretion, redistribute receptors as far as chains and small clusters during a 15 min incubation period. At 3 and 10 μg/ml anti-IgE, net secretion is reduced and the majority of receptors redistribute rapidly into clusters and large aggregates.

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