Biogenic Monoamines in Early Embryos of Sea Urchins

1981 ◽  
Vol 4 (4) ◽  
pp. 322-328 ◽  
Author(s):  
B.N. Manukhin ◽  
E.V. Volina ◽  
L.N. Markova ◽  
L. Rakić ◽  
G.A. Buznikov
Keyword(s):  
Sea Urchins ◽  
Biogenic Monoamines ◽  
Early Embryos

Histochemical study of biogenic monoamines in early (“Prenervous”) and late embryos of sea urchins

1985 ◽  
Vol 3 (5) ◽  
pp. 493-495 ◽  
Author(s):  
L.N. Markova ◽  
G.A. Buznikov ◽  
N. Kovačević ◽  
L. Rakić ◽  
N.B. Salimova ◽  
...  
Keyword(s):  
Histochemical Study ◽  
Sea Urchins ◽  
Biogenic Monoamines

RNA synthesis in the early embryogenesis of a fish (Misgurnus fossilis)

Development ◽  
1969 ◽  
Vol 21 (2) ◽  
pp. 295-308
Author(s):  
C. A. Kafiani ◽  
M. J. Timofeeva ◽  
A. A. Neyfakh ◽  
N. L. Melnikova ◽  
J. A. Rachkus
Keyword(s):  
Rna Synthesis ◽  
Animal Species ◽  
Sea Urchins ◽  
Early Embryogenesis ◽  
Gastrula Stage ◽  
Cell Nuclei ◽  
Ribonucleic Acids ◽  
Early Embryos ◽  
Apparent Conflict ◽  
Misgurnus Fossilis

Synthesis of ribonucleic acids in early embryos has been extensively studied during recent years in a number of laboratories and has been shown to begin shortly after fertilization (Kafiani, Tatarskaya & Kanopkayte, 1958; Wilt, 1963; Brown & Littna, 1964; Decroly, Cape & Brachet, 1964; Glišin & Glišin, 1964; Kafiani & Timofeeva, 1964, 1965; Nemer & Infant, 1965). Early embryos of Xenopus (Brown & Gurdon, 1964; Brown & Littna, 1964, 1966) and of sea urchins (Wilt, 1963; Glišin & Glišin, 1964; Nemer & Infant, 1965) synthesize up to gastrula stage predominantly or exclusively polydisperse RNA of a nonribosomal nature usually referred to as DNA-like RNA (dRNA). The occurrence of continuous dRNA synthesis in early embryogenesis is in apparent conflict with the periodicity of the 'morphogenetic function' of cell nuclei found by one of us (Neyfakh, 1959, 1961, 1964, 1965) in embryos of a number of animal species.

Electrical coupling of blastomeres in early embryos of ascidians and sea urchins

1982 ◽  
Vol 140 (2) ◽  
pp. 457-461 ◽  
Author(s):  
B DALE ◽  
A DESANTIS ◽  
G ORTOLANI ◽  
M RASOTTO ◽  
L SANTELLA
Keyword(s):  
Sea Urchins ◽  
Electrical Coupling ◽  
Early Embryos

scholarly journals Physical constraints on early blastomere packings

2020 ◽  
Author(s):  
James Giammona ◽  
Otger Campàs
Keyword(s):  
Developmental Stages ◽  
Sea Urchins ◽  
Physical Parameters ◽  
Cell Stage ◽  
Physical Constraints ◽  
C Elegans ◽  
Deformable Particles ◽  
Early Embryos ◽  
Square Configuration ◽  
The Right

AbstractAt very early embryonic stages, when embryos are composed of just a few cells, establishing the correct packing arrangements (contacts) between cells is essential for the proper development of the organism. As early as the 4-cell stage, the observed cellular packings in different species are distinct and, in many cases, differ from the equilibrium packings expected for simple adherent and deformable particles. It is unclear what are the specific roles that different physical parameters, such as the forces between blastomeres, their division times, orientation of cell division and embryonic confinement, play in the control of these packing configurations. Here we simulate the non-equilibrium dynamics of cells in early embryos and systematically study how these different parameters affect embryonic packings at the 4-cell stage. In the absence of embryo confinement, we find that cellular packings are not robust, with multiple packing configurations simultaneously possible and very sensitive to parameter changes. Our results indicate that the geometry of the embryo confinement determines the packing configurations at the 4-cell stage, removing degeneracy in the possible packing configurations and overriding division rules in most cases. Overall, these results indicate that physical confinement of the embryo is essential to robustly specify proper cellular arrangements at very early developmental stages.Author summaryAt the initial stages of embryogenesis, the precise arrangement of cells in the embryo is critical to ensure that each cell gets the right chemical and physical signals to guide the formation of the organism. Even when the embryo is made of only four cells, different species feature varying cellular arrangements: cells in mouse embryos arrange as a tetrahedron, in the nematode worm C. elegans cells make a diamond and in sea urchins cells arrange in a square configuration. How do cells in embryos of different species control their arrangements? Using computer simulations, we studied how cell divisions, physical contacts between cells and the confinement of the embryo by an eggshell affect the arrangements of cells when the embryos have only 4 cells. We find that the shape of the confining eggshell plays a key role in controlling the cell arrangements, removing unwanted arrangements and robustly specifying the proper contacts between cells. Our results highlight the important roles of embryonic confinement in establishing the proper cell-cell contacts as the embryo starts to develop.

scholarly journals Cyclin D and cdk4 Are Required for Normal Development beyond the Blastula Stage in Sea Urchin Embryos

2002 ◽  
Vol 22 (13) ◽  
pp. 4863-4875 ◽  
Author(s):  
Jennifer C. Moore ◽  
Jan L. Sumerel ◽  
Bradley J. Schnackenberg ◽  
Jason A. Nichols ◽  
Athula Wikramanayake ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Normal Development ◽  
Sea Urchins ◽  
Ectopic Expression ◽  
Cyclin D ◽  
Blastula Stage ◽  
Cell Stage ◽  
Cell Cycles ◽  
Early Embryos ◽  
Cdk4 Expression

ABSTRACT cdk4 mRNA and protein are constitutively expressed in sea urchin eggs and throughout embryonic development. In contrast, cyclin D mRNA is barely detectable in eggs and early embryos, when the cell cycles consist of alternating S and M phases. Cyclin D mRNA increases dramatically in embryos at the early blastula stage and remains at a constant level throughout embryogenesis. An increase in cdk4 kinase activity occurs concomitantly with the increase in cyclin D mRNA. Ectopic expression of cyclin D mRNA in eggs arrests development before the 16-cell stage and causes eventual embryonic death, suggesting that activation of cyclin D/cdk4 in cleavage cell cycles is lethal to the embryo. In contrast, blocking cyclin D or cdk4 expression with morpholino antisense oligonucleotides results in normal development of early gastrula-stage embryos but abnormal, asymmetric larvae. These results suggest that in sea urchins, cyclin D and cdk4 are required for normal development and perhaps the patterning of the developing embryo, but may not be directly involved in regulating entry into the cell cycle.

scholarly journals The spindle assembly checkpoint functions during early development in non-chordate embryos

2019 ◽  
Author(s):  
Janet Chenevert ◽  
Marianne Roca ◽  
Lydia Besnardeau ◽  
Antonella Ruggiero ◽  
Dalileh Nabi ◽  
...  
Keyword(s):  
Early Development ◽  
Spindle Assembly Checkpoint ◽  
Sea Urchins ◽  
Volume Ratio ◽  
Spindle Assembly ◽  
Eukaryotic Cells ◽  
Embryonic Cells ◽  
Checkpoint Response ◽  
Early Embryos ◽  
Spindle Microtubules

In eukaryotic cells, a spindle assembly checkpoint (SAC) ensures accurate chromosome segregation. This control mechanism monitors proper attachment of chromosomes to spindle microtubules and delays mitotic progression if connections are erroneous or absent. The SAC operates in all eukaryotic cells tested so far, but is thought to be relaxed during early embryonic development in animals. Here, we evaluate the checkpoint response to lack of kinetochore-spindle microtubule interactions in early embryos of diverse animal species from the main metazoan groups. Our analysis shows that there are two classes of embryos, either proficient or deficient for SAC activation during cleavage. Sea urchins, mussels and jellyfish embryos show a prolonged mitotic block in the absence of spindle microtubules from the first cleavage division, while ascidian and amphioxus embryos, like those of Xenopus and zebrafish, continue mitotic cycling without delay. SAC competence during early development shows no correlation with cell size, chromosome number or kinetochore to cell volume ratio, ruling out the hypothesis that lack of checkpoint activity in early embryos is due to the large egg volume. Our results instead indicate that there is no inherent incompatibility between SAC activity and large fast-dividing embryonic cells. We suggest that SAC proficiency is the default situation of metazoan embryos, and that SAC activity is specifically silenced in chordate species with fast dividing embryos.

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.

Fate of sperm membrane in fertilized ova

1993 ◽  
Vol 51 ◽  
pp. 40-41
Author(s):  
Frank J. Longo
Keyword(s):  
Electron Microscopy ◽  
Electrical Activity ◽  
Sea Urchins ◽  
Morphological Changes ◽  
Integrated System ◽  
Electrophysiological Recording ◽  
Experimental Conditions ◽  
The Status ◽  
Sperm Membrane ◽  
Temporal And Spatial

Measurement of the egg's electrical activity, the fertilization potential or the activation current (in voltage clamped eggs), provides a means of detecting the earliest perceivable response of the egg to the fertilizing sperm. By using the electrical physiological record as a “real time” indicator of the instant of electrical continuity between the gametes, eggs can be inseminated with sperm at lower, more physiological densities, thereby assuring that only one sperm interacts with the egg. Integrating techniques of intracellular electrophysiological recording, video-imaging, and electron microscopy, we are able to identify the fertilizing sperm precisely and correlate the status of gamete organelles with the first indication (fertilization potential/activation current) of the egg's response to the attached sperm. Hence, this integrated system provides improved temporal and spatial resolution of morphological changes at the site of gamete interaction, under a variety of experimental conditions. Using these integrated techniques, we have investigated when sperm-egg plasma membrane fusion occurs in sea urchins with respect to the onset of the egg's change in electrical activity.

Sign in / Sign up

Export Citation Format

Share Document