Memoirs: The Early Development of Astropecten Irregularis, with Remarks on Duplicity in Echinoderm Larvae

1925 ◽  
Vol s2-69 (275) ◽  
pp. 519-554
Author(s):  
H. G. NEWTH
Keyword(s):  
Early Development ◽  
Normal Development ◽  
Bilateral Symmetry ◽  
Mechanical Deformation ◽  
Insufficient Evidence ◽  
Vertebrate Embryos ◽  
Pore Canals

I. (1) The normal development of Astropecten irregularis is described up to the twenty-fifth day. (2) About a third of the larvae possessed two pore-canals, and larval twinning was observed in two cases. II. There is insufficient evidence for believing that normal Echinoderm larvae possess a ‘latent’ bilateral symmetry. III. The following provisional conclusions are reached regarding duplicity in Echinoderm larvae: (1) The various kinds of duplicity form a series. (2) They are of the same nature as those found in vertebrate embryos, and are probably due to similar causes. (3) They may be determined by (a) Alteration of the polarity of the egg ; (b) Interference with processes of early development affecting gastrulation ; (c) Physiological inhibition or mechanical deformation of the tip of the archenteron. (4) Their ultimate facies, in the case of (c), is determined largely by excess or defect of nutrition.

Micromere lineages in the glossiphoniid leechHelobdella

Development ◽  
2002 ◽  
Vol 129 (3) ◽  
pp. 719-732 ◽  
Author(s):  
Françoise Z. Huang ◽  
Dongmin Kang ◽  
Felipe-Andres Ramirez-Weber ◽  
Shirley T. Bissen ◽  
David A. Weisblat
Keyword(s):  
Early Development ◽  
Normal Development ◽  
The Other ◽  
Small Cells ◽  
Spiral Cleavage ◽  
Helobdella Robusta

In leech embryos, segmental mesoderm and ectoderm arise from teloblasts by lineages that are already relatively well characterized. Here, we present data concerning the early divisions and the definitive fate maps of the micromeres, a group of 25 small cells that arise during the modified spiral cleavage in leech (Helobdella robusta) and contribute to most of the nonsegmental tissues of the adult. Three noteworthy results of this work are as follows. (1) The c′′′ and dm′ clones (3d and 3c in traditional nomenclature) give rise to a hitherto undescribed network of fibers that run from one end of the embryo to the other. (2) The clones of micromeres b′′ and b′′′ (2b and 3b in traditional nomenclature) die in normal development; the b′′ clone can be rescued to assume the normal c′′ fate if micromere c′′ or its clone are ablated in early development. (3) Two qualitative differences in micromere fates are seen between H. robusta (Sacramento) and another Helobdella sp. (Galt). First, in Helobdella sp. (Galt), the clone of micromere b′′ does not normally die, and contributes a subset of the cells arising exclusively from c′′ in H. robusta (Sacramento). Second, in Helobdella sp. (Galt), micromere c′′′ makes no definitive contribution, whereas micromere dm′ gives rise to cells equivalent to those arising from c′′′ and dm′ in H. robusta (Sacramento).

scholarly journals Mitochondrial processing peptidase activity is controlled by the processing of α-MPP during development in Dictyostelium discoideum

Microbiology ◽  
2010 ◽  
Vol 156 (4) ◽  
pp. 978-989 ◽  
Author(s):  
Koki Nagayama ◽  
Tetsuo Ohmachi
Keyword(s):  
Life Cycle ◽  
Dictyostelium Discoideum ◽  
Early Development ◽  
Normal Development ◽  
Peptidase Activity ◽  
Fruiting Bodies ◽  
Wild Type ◽  
Formation Stage ◽  
Mitochondrial Processing Peptidase ◽  
Processing Peptidase

We investigated the expression of the α subunit of the Dictyostelium mitochondrial processing peptidase (Ddα-MPP) during development. Ddα-MPP mRNA is expressed at the highest levels in vegetatively growing cells and during early development, and is markedly downregulated after 10 h of development. The Ddα-MPP protein is expressed as two forms, designated α-MPPH and α-MPPL, throughout the Dictyostelium life cycle. The larger form, α-MPPH, is cleaved to produce the functional α-MPPL form. We were not able to isolate mutants in which the α-mpp gene had been disrupted. Instead, an antisense transformant, αA2, expressing α-MPP at a lower level than the wild-type AX-3 was isolated to examine the function of the α-MPP protein. Development of the αA2 strain was normal until the slug formation stage, but the slug stage was prolonged to ∼24 h. In this prolonged slug stage, only α-MPPH was present, and α-MPPL protein and MPP activity were not detected. After 28 h, α-MPPL and MPP activity reappeared, and normal fruiting bodies were formed after a delay of approximately 8 h compared with normal development. These results indicate that MPP activity is controlled by the processing of α-MPPH to α-MPPL during development in Dictyostelium.

The system specifying body position in the early development of Xenopus, and its response to early perturbations.

Development ◽  
1985 ◽  
Vol 89 (Supplement) ◽  
pp. 69-87
Author(s):  
Jonathan Cooke
Keyword(s):  
Early Development ◽  
Body Position ◽  
Bilateral Symmetry ◽  
The Body ◽  
Spatial Profile ◽  
Cell Stage ◽  
Larval Stages ◽  
Positional System ◽  
Set Up ◽  
Pattern Specification

Evidence is presented that the system setting up preliminary specifications for contributions to the axial body plan, across vegetal regions of the Xenopus embryo, acts in a widespread way at early stages. Mechanisms that regulate the spatial profile of this primary positional variable, and thus ensure the constancy and harmony of the body plans normally achieved, have lost this integrative ability by the 4-cell stage one hour after the plasm shifts that precede first cleavage and symmetrize the egg. Abnormal, partial or distorted profiles of the positional system across whole eggs or isolates, recorded by these times, are retained to give correspondingly partial or imbalanced mes/endodermal pattern at tailbud larval stages. There is evidence that subsequent ‘back-up’ positional interactions, which can heal gross positional discontinuities in isolated presumptive lateral half-eggs and so restore bilateral symmetry, also do this at the price of loss of complete pattern specification. This is probably because of an asymmetrical principle whereby relatively activated (dorsoanterior specified) material can raise the level of originally posterior material on contact, whereas the reverse interaction cannot occur. The observations are discussed in relation to apparently different behaviour in certain other amphibian embryos, and to our knowledge of other positional interactions, normal and also experimentally provoked, such as those that set up the germ layers.

scholarly journals Reproduction and the Early Development of Vertebrates in Space: Problems, Results, Opportunities

Life ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 109
Author(s):  
Alexandra Proshchina ◽  
Victoria Gulimova ◽  
Anastasia Kharlamova ◽  
Yuliya Krivova ◽  
Nadezhda Besova ◽  
...  
Keyword(s):  
Developmental Biology ◽  
Cell Proliferation ◽  
Early Development ◽  
Space Flight ◽  
Morphological Changes ◽  
Vertebrate Development ◽  
The Moon ◽  
Adaptive Changes ◽  
Space Flights ◽  
Vertebrate Embryos

Humans and animals adapt to space flight conditions. However, the adaptive changes of fully formed organisms differ radically from the responses of vertebrate embryos, foetuses, and larvae to space flight. Development is associated with active cell proliferation and the formation of organs and systems. The instability of these processes is well known. Over 20 years has passed since the last systematic experiments on vertebrate reproduction and development in space flight. At the same time, programs are being prepared for the exploration of Mars and the Moon, which justifies further investigations into space flight’s impact on vertebrate development. This review focuses on various aspects of reproduction and early development of vertebrates in space flights. The results of various experiments on fishes, amphibians, reptiles, birds and mammals are described. The experiments in which our team took part and ontogeny of the vertebrate nervous and special sensory systems are considered in more detail. Possible causes of morphological changes are also discussed. Research on evolutionarily and taxonomically different models can advance the understanding of reproduction in microgravity. Reptiles, in particular, geckos, due to their special features, can be a promising object of space developmental biology.

scholarly journals The tolerance to hypoxia is defined by a time-sensitive response of the gene regulatory network in sea urchin embryos

2020 ◽  
Author(s):  
Majed Layous ◽  
Lama Khalaily ◽  
Tsvia Gildor ◽  
Smadar Ben-Tabou de-Leon
Keyword(s):  
Gene Regulatory Network ◽  
Early Development ◽  
Sea Urchin ◽  
Regulatory Network ◽  
Normal Development ◽  
Oxygen Level ◽  
Sea Urchin Embryo ◽  
Tolerance To Hypoxia ◽  
Vegf Pathway ◽  
Gene Regulatory

AbstractDeoxygenation, the reduction of oxygen level in the oceans induced by global warming and anthropogenic disturbances, is a major threat to marine life. This change in oxygen level could be especially harmful to marine embryos that utilize endogenous hypoxia and redox gradients as morphogens during normal development. Here we show that the tolerance to hypoxic conditions changes between different developmental stages of the sea urchin embryo, due to the structure of the gene regulatory networks (GRNs). We demonstrate that during normal development, bone morphogenetic protein (BMP) pathway restricts the activity of the vascular endothelial growth factor (VEGF) pathway to two lateral domains and by that controls proper skeletal patterning. Hypoxia applied during early development strongly perturbs the activity of Nodal and BMP pathways that affect VEGF pathway, dorsal-ventral (DV) and skeletogenic patterning. These pathways are largely unaffected by hypoxia applied after DV axis formation. We propose that the use of redox and hypoxia as morphogens makes the sea urchin embryo highly sensitive to environmental hypoxia during early development, but the GRN structure provides higher tolerance to hypoxia at later stages.Summary statementThe use of hypoxia and redox gradients as morphogens makes sea urchin early development sensitive to environmental hypoxia. This sensitivity decreases later, due to the structure of the gene regulatory network.

The relation of the two blastomeres to the polar lobe in Dentalium

Development ◽  
1968 ◽  
Vol 20 (1) ◽  
pp. 101-105
Author(s):  
N. H. Verdonk
Keyword(s):  
Normal Development ◽  
Bilateral Symmetry ◽  
Polar Lobe ◽  
Posterior Side ◽  
First Case

Experiments on the influence of the polar lobe on the development of molluscs have shown that after removal of the polar lobe cleavage is radially symmetrical and indications of bilateral symmetry do not appear (Wilson, 1904: Dentalium; Clement, 1952: Ilyanassa). In normal development the polar lobe fuses with one of the two cells of the trefoil stage, and this cell becomes the posterior side of the embryo. The question now arises whether the polar lobe fuses in an arbitrary way with one of the blastomeres at first cleavage, which then becomes the CD cell. Another possibility is that one of the two blastomeres at the trefoil stage is already predetermined to become the CD cell, with which the polar lobe always fuses. In the first case dorsoventrality is determined epigenetically; in the second case it is preformed. Morgan (1936) tried to solve this question by removing one of the blastomeres at the trefoil stage in Ilyanassa.

scholarly journals PRC2 and EHMT1 regulate H3K27me2 and H3K27me3 establishment across the zygote genome

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Tie-Gang Meng ◽  
Qian Zhou ◽  
Xue-Shan Ma ◽  
Xiao-Yu Liu ◽  
Qing-Ren Meng ◽  
...  
Keyword(s):  
Early Development ◽  
Transcriptional Repression ◽  
Normal Development ◽  
De Novo ◽  
Micrococcal Nuclease ◽  
Regulatory Mechanisms ◽  
Facultative Heterochromatin ◽  
Mouse Zygotes ◽  
Essential Prerequisite

AbstractThe formation of zygote is the beginning of mammalian life, and dynamic epigenetic modifications are essential for mammalian normal development. H3K27 di-methylation (H3K27me2) and H3K27 tri-methylation (H3K27me3) are marks of facultative heterochromatin which maintains transcriptional repression established during early development in many eukaryotes. However, the mechanism underlying establishment and regulation of epigenetic asymmetry in the zygote remains obscure. Here we show that maternal EZH2 is required for the establishment of H3K27me3 in mouse zygotes. However, combined immunostaining with ULI-NChIP-seq (ultra-low-input micrococcal nuclease-based native ChIP-seq) shows that EZH1 could partially safeguard the role of EZH2 in the formation of H3K27me2. Meanwhile, we identify that EHMT1 is involved in the establishment of H3K27me2, and that H3K27me2 might be an essential prerequisite for the following de novo H3K27me3 modification on the male pronucleus. In this work, we clarify the establishment and regulatory mechanisms of H3K27me2 and H3K27me3 in mouse zygotes.

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