scholarly journals Studies on the Development of the Foregut in the Chick Blastoderm

Development ◽  
1953 ◽  
Vol 1 (2) ◽  
pp. 115-124
Author(s):  
Ruth Bellairs
Keyword(s):  
Morphological Changes ◽  
Primitive Streak ◽  
Serial Sections ◽  
Present Communication ◽  
Chick Blastoderm ◽  
Process Stage ◽  
Early Stages

Little attention has hitherto been paid to the early stages in the development of the foregut in the chick. This paper is the first of a series concerned with an investigation into how it develops during the period between the primitive streak stage and the stage of an embryo with about ten pairs of somites. The term ‘foregut’ refers throughout to the blind diverticulum extending forward into the developing head from the anterior intestinal portal. The present communication opens with a brief consideration of the gross morphological changes which take place; the rest of the paper is concerned with the location in primitive streak and head process stage blastoderms of the presumptive area from which the foregut of the ten somite embryo will develop. The following account has been compiled from the study of serial sections of twenty embryos and from the publications of Duval (1889), Adelmann (1922), and Wetzel (1929).

The Conversion of Yolk into Cytoplasm in the Chick Blastoderm as shown by Electron Microscopy

Development ◽  
1958 ◽  
Vol 6 (1) ◽  
pp. 149-161
Author(s):  
Ruth Bellairs
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Embryonic Development ◽  
Light Microscopy ◽  
Morphological Changes ◽  
Primitive Streak ◽  
Single Stage ◽  
Embryonic Cells ◽  
Chick Blastoderm ◽  
Almost All

In almost all embryos yolk becomes converted into cytoplasm. It has not previously been possible to describe in any detail the morphological changes involved in this process; indeed, when the yolk drops contained within embryonic cells are examined by light microscopy they seem to remain in much the same condition until they are suddenly used up. For this reason they have frequently been considered to be nothing but ‘inert, inactive’ stores of food. By using an electron microscope, however, it has been possible to trace some of the morphological changes which take place in the chick when intra-cellular yolk drops are converted into cytoplasm, and to show that these are not confined to a single stage of embryonic development. Moreover, the discovery of mitochondria within the yolk drops suggests that the yolk drops are not ‘inert’. The following stages have been examined: medium and long primitive streak (as defined by Waddington, 1932, and Abercrombie, 1950), head process, head fold, and 10–16 pairs of somites.

scholarly journals Studies on the Development of the Foregut in the Chick Blastoderm

Development ◽  
1953 ◽  
Vol 1 (4) ◽  
pp. 369-385
Author(s):  
Ruth Bellairs
Keyword(s):  
Tissue Culture ◽  
Morphological Changes ◽  
Primitive Streak ◽  
Dorsal Side ◽  
Reference Points ◽  
Chick Blastoderm ◽  
Plasma Clot ◽  
Morphogenetic Movements ◽  
General Expansion ◽  
External Reference

The first of this series of papers (Bellairs, 1953) outlined the morphological changes occurring in the endoderm of the chick up to the stage of about ten pairs of somites; it also showed that the presumptive foregut area in the primitive streak stage blastoderm lies around the anterior end of the primitive streak, and at a slightly later stage around the head process. The present paper is concerned with the pattern of morphogenetic movements which occur in the endoderm during the early stages of foregut development. The technique involved the use of carbon marks upon the exposed endoderm of blastoderms grown dorsal side downwards in tissue culture by the watchglass method (Waddington, 1932; Bellairs, 1953). During the period of development investigated an expansion of the blastoderm as a whole took place over the plasma clot; the use of external reference points was therefore essential, although even with such aids it was not always possible to tell whether certain displacements of marked cells were in fact merely the expression of a general expansion or were due to a specific morphogenetic migration.

Investigation on the origin of the definitive endoderm in the rat embryo

Development ◽  
1974 ◽  
Vol 32 (2) ◽  
pp. 445-459
Author(s):  
B. Levak-Švajger ◽  
A. Švajger
Keyword(s):  
Primitive Streak ◽  
Definitive Endoderm ◽  
Rat Embryo ◽  
Chick Blastoderm ◽  
Germ Layers ◽  
Kidney Capsule ◽  
Rat Embryos ◽  
Endodermal Cells ◽  
Derivatives Of

Single germ layers (or combinations of two of them) were isolated from the primitive streak and the head-fold stage rat embryos and grown for 15 days under the kidney capsule of syngeneic adult animals. The resulting teratomas were examined histologically for the presence of mature tissues, with special emphasis on derivatives of the primitive gut. Ectoderm isolated together with the initial mesodermal wings at the primitive streak stage gave rise to tissue derivatives of all three definitive germ layers. Derivatives of the primitive gut were regularly present in these grafts. At the head-fold stage, isolated ectoderm (including the region of the primitive streak) differentiated into ectodermal and mesodermal derivatives only. Endoderm isolated at the primitive streak stage did not develop when grafted and was always completely resorbed. At the head-fold stage, however, definitive endoderm differentiated into derivatives of the primitive gut if grafted together with adjacent mesoderm. These findings indirectly suggest the migration of prospective endodermal cells from the primitive ectoderm, and therefore a general analogy with the course of events during gastrulation in the chick blastoderm.

Early ontogeny of the Furongian (Cambrian) olenid trilobites Sphaerophthalmus alatus (Boeck, 1838) and Ctenopyge (Mesoctenopyge) tumida Westergård, 1922 from Bornholm, Denmark

2015 ◽  
Vol 106 (3) ◽  
pp. 171-183 ◽  
Author(s):  
Kristina Månsson ◽  
Euan N. K. Clarkson
Keyword(s):  
Morphological Changes ◽  
Early Ontogeny ◽  
Ontogenetic Development ◽  
Early Stages ◽  
Senior Synonym

ABSTRACTThe early stages in ontogenetic development are described in the co-occurring Sphaerophthalmus alatus (Boeck, 1838) and Ctenopyge (Mesoctenopyge) tumida Westergård, 1922, using fragmentary but otherwise well-preserved material from Bornholm, Denmark. The former species is a senior synonym of Ctenopyge (Eoctenopyge) angusta Westergård, 1922, as has been recently proposed, but the early stages of S. alatus from Bornholm are appreciably more spiny than those found of the same species in other places in Scandinavia, and spinosity is retained until later in development. Increasing convexity with development and other morphological changes are noted. Pygidia were previously unknown in C. (M.) tumida. Here, they are represented by early pygidia. These are shield-shaped, with a very spiny margin and a strong axial spine. The distinction between Sphaerophthalmus and Ctenopyge is discussed.

scholarly journals Experiments on the Development of the Head of the Chick Embryo

1936 ◽  
Vol 13 (2) ◽  
pp. 219-236
Author(s):  
C. H. WADDINGTON ◽  
A. COHEN
Keyword(s):  
Thin Sheet ◽  
Neural Tissue ◽  
Primitive Streak ◽  
Neural Plate ◽  
Head Region ◽  
Process Stage ◽  
Optic Vesicles ◽  
Lens Formation ◽  
Embryonic Ectoderm

1. Experiments were made on the development of the head of chicken embryos cultivated in vitro. 2. Defects in the presumptive head region of primitive streak embryos are regulated completely if the wound fills up before the histogenesis of neural tissue begins in the head-process stage. Different methods by which the hole is filled are described. 3. No repair occurs in the head-process and head-fold stages, and in this period two masses of neural tissue cannot heal together. 4. Median defects, even if repaired as regards neural tissue, cause a failure of the ventral closure of the foregut. The lateral evaginations of the gut develop typically in atypical situations. The headfold may break through and join up with the endoderm in such a way that the gut acquires an anterior opening. 5. The paired heart rudiments may develop separately. The separate vesicles begin to contract at a time appropriate to the development of the embryo as a whole. The two hearts are mirror images, the left one having the normal curvature, but the embryos do not survive long enough for the hearts to acquire a very definite shape. 6. The forebrain has a considerable capacity for repair in the early somite stages (five to twenty-five somites). One-half of the forebrain can remodel itself into a complete forebrain. In some cases the neural plate and epidermis grow together over the wound, in others the epidermis and mesenchyme make the first covering, leaving a space along the inside of which the neural tissue grows. The neural tissue may become a very thin sheet. 7. The repaired forebrain may induce the formation of a nasal placode from the non-presumptive nasal epidermis which covers the wound. 8. If the optic vesicle is entirely removed, a new one is not formed, but parts of the vesicle can regulate to complete eye-cups, either when still attached to the forebrain or after being isolated in the extra-embryonic regions of another embryo. 9. Injured optic vesicles induce lenses from the non-presumptive epidermis which grows over the wound. Transplanted optic neural tissue from embryos of about five somites induces the formation of lentoids from extra-embryonic ectoderm, but only in a small proportion of cases. 10. The presumptive lens epidermis can produce a slight thickening even when contact with the optic cup is prevented. 11. The significance of periods of minimum regulatory power for the concept of determination is discussed. 12. The data concerning lens formation are discussed in terms of the field concept.

Ectodermal patterning in the avian embryo: epidermis versus neural plate

Development ◽  
1999 ◽  
Vol 126 (1) ◽  
pp. 63-73 ◽  
Author(s):  
E. Pera ◽  
S. Stein ◽  
M. Kessel
Keyword(s):  
Chick Embryo ◽  
Neural Crest ◽  
Plate Boundary ◽  
Homeobox Gene ◽  
Primitive Streak ◽  
Neural Plate ◽  
Avian Embryo ◽  
Neural Fate ◽  
Early Stages ◽  
Two Factors

Ectodermal patterning of the chick embryo begins in the uterus and continues during gastrulation, when cells with a neural fate become restricted to the neural plate around the primitive streak, and cells fated to become the epidermis to the periphery. The prospective epidermis at early stages is characterized by the expression of the homeobox gene DLX5, which remains an epidermal marker during gastrulation and neurulation. Later, some DLX5-expressing cells become internalized into the ventral forebrain and the neural crest at the hindbrain level. We studied the mechanism of ectodermal patterning by transplantation of Hensen's nodes and prechordal plates. The DLX5 marker indicates that not only a neural plate, but also a surrounding epidermis is induced in such operations. Similar effects can be obtained with neural plate grafts. These experiments demonstrate that the induction of a DLX5-positive epidermis is triggered by the midline, and the effect is transferred via the neural plate to the periphery. By repeated extirpations of the endoderm we suppressed the formation of an endoderm/mesoderm layer under the epiblast. This led to the generation of epidermis, and to the inhibition of neuroepithelium in the naked ectoderm. This suggests a signal necessary for neural, but inhibitory for epidermal development, normally coming from the lower layers. Finally, we demonstrate that BMP4, as well as BMP2, is capable of inducing epidermal fate by distorting the epidermis-neural plate boundary. This, however, does not happen independently within the neural plate or outside the normal DLX5 domain. In the area opaca, the co-transplantation of a BMP4 bead with a node graft leads to the induction of DLX5, thus indicating the cooperation of two factors. We conclude that ectodermal patterning is achieved by signalling both from the midline and from the periphery, within the upper but also from the lower layers.

scholarly journals The early phyllosoma stages of spiny lobster Panulirus echinatus Smith, 1869 (Decapoda: Palinuridae) reared in the laboratory

2008 ◽  
Vol 68 (1) ◽  
pp. 179-186 ◽  
Author(s):  
FA. Abrunhosa ◽  
AP. Santiago ◽  
JP. Abrunhosa
Keyword(s):  
Morphological Changes ◽  
Spiny Lobster ◽  
Zoeal Stage ◽  
Water Tank ◽  
Dunaliella Viridis ◽  
Early Stages

The early stages of the Panulirus echinatus were hatched and reared in the laboratory. Ovigerous females were captured in their habitat and carefully transported to the laboratory. Larvae were transferred in a recirculation water tank at a density of 10 larvae.L-1. The larvae were fed on Artemia and gonads of mussel Brachydonts sp. Microalgae Dunaliella viridis was added at a concentration of 150 x 10(4) cell.mL-1. Larvae and exuviae of each zoeal stage were preserved in an alcohol 70% + glycerin (1:1) solution. The phyllosomas moulted eight times; the intermoulting period of each instar averaged about 7 to 10 days. The main morphological changes of each appendage were described in detail, illustrated and compared with previous reports.

scholarly journals NUCLEATING SITES FOR THE ASSEMBLY OF CYTOPLASMIC MICROTUBULES IN THE ECTODERMAL CELLS OF BLASTULAE OF ARBACIA PUNCTULATA

1970 ◽  
Vol 46 (3) ◽  
pp. 564-575 ◽  
Author(s):  
Lewis G. Tilney ◽  
Janette Goddard
Keyword(s):  
Low Temperature ◽  
Sea Urchin ◽  
Basal Body ◽  
Preliminary Report ◽  
Apical Part ◽  
Basal Region ◽  
Serial Sections ◽  
Arbacia Punctulata ◽  
Early Stages ◽  
Cytoplasmic Microtubules

In the ectodermal cells of sea urchin blastulae, the microtubules converge and appear to make contact with three distinct cytoplasmic foci or satellites associated with the basal body of the cilium. Beneath the nucleus, which lies in the apical end of the cell, the microtubules are aligned predominantly parallel to the cell's long axis and could thus make contact with the satellites as is directly suggested by observations on sections at or near the planes of the satellites. After the embryos are treated with low temperature (0°C), the microtubules disassemble; however, the satellites can still be recognized. Upon rewarming, the microtubules reappear. In early stages of reformation, when the tubules in the cell consist of short segments, tubules have only been found in the apical part of the cell. One end of each microtubule appears to make contact with its respective satellite, or is aligned so that it could contact one of the satellites, provided serial sections were cut and collected in order. After longer periods of recovery, the microtubules elongate; as before, one end of each makes contact with a satellite or is aligned so that it could attach to a satellite. Segments of microtubules seen in the basal region of the cell are aligned parallel to the long axis of the cell as in the untreated ectodermal cells and are therefore interpreted as extensions of those tubules making contact with one of the satellites. On the basis of these observations, we suggest that assembly of microtubules is initiated at the satellites. These sites, perhaps best referred to as "nucleating sites," thereby could exert considerable control over the distribution of microtubules in cells. It is hoped that this preliminary report will be followed up by a more detailed study using serial sections.

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