Neuroectodermal origin of avian hypothalamo-hypophyseal complex: the role of the ventral neural ridge

Development ◽  
1975 ◽  
Vol 34 (2) ◽  
pp. 311-325
Author(s):  
T. Takor Takor ◽  
A. G. E. Pearse
Keyword(s):  
The Other ◽  
Avian Embryo ◽  
Chick Embryos ◽  
White Leghorn ◽  
Optic Chiasma ◽  
Somite Stage ◽  
White Leghorn Chick ◽  
Caudal Portion ◽  
Neuroectodermal Origin

Embryonic discs from White Leghorn chick embryos (presomite to 12-somite stages) were examined in serial transverse and longitudinal sections. Later stages, up to 21 days, were also examined. The following observations were made: (1) Lateral folding rather than head folding is the mechanism by which the avian embryo is delimited. The process takes place at two terminal points, one cephalic the other caudal. (2) Thickening of the ventral ectoderm around the tip of the presumptive anterior neuropore, beginning at the 4-somite stage, subsequently extends the dorsal neural ridge to form a ventral neural ridge. (3) The cephalic portion of the ventral neural ridge, extending from anterior neuropore to optic chiasma, is mainly incorporated into the alar plates of the diencephalon. (4) The caudal portion, extending from optic chiasma to the stomodeum, gives rise to Rathke's pouch and thus to the adenohypophysis. We conclude that the latter is to be regarded as of neuroectodermal rather than ectodermal (stomodeal) origin, and that some or all of the neuroendocrine nuclei of the hypothalamus are similarly derived from the neuroectoderm of the neural ridge. The hypothalamo-hypophyseal complex is thus to be regarded as a single rather than a composite entity.

The development of hepatogenic potency in the endoderm of quail embryos

Development ◽  
1979 ◽  
Vol 52 (1) ◽  
pp. 49-62
Author(s):  
Sumiko Fukuda
Keyword(s):  
Digestive Tract ◽  
The Other ◽  
Chick Embryos ◽  
Posterior Half ◽  
Coelomic Cavity ◽  
Somite Stage ◽  
Anterior Half ◽  
Other Hand ◽  
Cardiac Region ◽  
Cardiac Mesenchyme

Hepatogenic potency of the endoderm is detectable in the anterior half of the endoderm of quail embryos older than 2-somite stage when endodermal fragments are cultured with or without heterologous chick mesenchymes, in the coelomic cavity of 3-day chick embryos. On the other hand, the posterior half of the endoderm never has hepatogenic potency. The hepatogenic potency of the endoderm is gradually stabilised with increasing age. However, expression of hepatogenesis can be affected when the endoderm is associated with inductively active digestive tract mesenchymes. Mesenchyme taken from the presumptive cardiac region (‘cardiac’ mesenchyme) of chick embryos is necessary for the uncommitted anterior endoderm to acquire hepatogenic potency, and this effect is specific for the ‘cardiac’ mesenchyme. The ‘cardiac’ mesenchyme, however, fails to induce hepatic epithelium in the allantoic endoderm, which can differentiate heterotypically when cultured in combination with digestive tract mesenchymes. The evidence presented in this study suggests that the effect of ‘cardiac’ mesenchyme on the acquisition of hepatogenic potency in the endoderm is limited.

scholarly journals Immunocytochemical studies of cardiac myofibrillogenesis in early chick embryos. II. Generation of alpha-actinin dots within titin spots at the time of the first myofibril formation.

1987 ◽  
Vol 105 (6) ◽  
pp. 2795-2801 ◽  
Author(s):  
K T Tokuyasu ◽  
P A Maher
Keyword(s):  
The Other ◽  
Chick Embryos ◽  
Initial Length ◽  
Electron Microscopic ◽  
Somite Stage ◽  
Dense Bodies ◽  
Whole Mount ◽  
Ultrathin Sections ◽  
Per Se ◽  
Immunocytochemical Studies

In whole mount preparations of the 9 somite stage chick embryonic hearts that were immunofluorescently double labeled for titin and alpha-actinin, presumptive myofibrils were recognized as rows of several periodically aligned titin spots. Within these titin spots, smaller alpha-actinin dots were observed. These periodical arrangements of titin spots and alpha-actinin dots were not found in the 7 somite stage hearts. In wide myofibrils in the 10 somite stage hearts, the alpha-actinin dots and titin spots simultaneously became 'lines.' To study the ultrastructural features of the titin-positive regions in the 6-9 somite stage hearts, the thoracic portions of the embryos were immunofluorescently labeled for titin and embedded in resin. Ultrathin sections were mounted on electron microscopic grids and examined in immunofluorescence optics. The titin-positive regions thus identified were then examined in the electron microscope. No readily discernable specific ultrastructural features were found in titin-positive regions of the 6 somite stage cardiac primodia. Examination of the sections of the 9 somite stage hearts, on the other hand, revealed the occasional presence of small dense bodies, Z bodies, in the titin-positive regions. These observations strongly suggest that these Z bodies are the ultrastructural counterparts of the alpha-actinin dots seen by immunofluorescence optics and that they are formed nearly at the time of the formation of the first myofibrils. In some of the nascent myofibrils the Z bodies were found to be considerably narrower than the myofibrils, implying that the Z bodies are required not for the assembly of myofibrils per se but for their stabilization. Immunofluorescent labeling for titin and alpha-actinin revealed that the length of the shortest sarcomeres in the first myofibrils is approximately 1.5 micron, approximately the width of the A bands of mature myofibrils. The possibility that the A bands might define the initial length of nascent sarcomeres was indicated.

The Fine Structure of the Normal Chorio-Allantoic Membrane of the Chick-Embryo

1962 ◽  
Vol s3-103 (61) ◽  
pp. 17-23
Author(s):  
S.R. S. RANGAN ◽  
SATYAVATI M. SIRSAT
Keyword(s):  
Fine Structure ◽  
Chick Embryo ◽  
Potassium Permanganate ◽  
Osmium Tetroxide ◽  
Cell Membranes ◽  
Chick Embryos ◽  
White Leghorn ◽  
White Leghorn Chick ◽  
Lipid Inclusions ◽  
General Appearance

The chorio-allantoic membranes of White Leghorn chick embryos at 10 to 12 days after laying were fixed in Palade's buffered osmium tetroxide or in Luft's potassium permanganate. After fixation in these two ways the general appearance is similar, but there are differences in certain tissue elements. Cell membranes are well preserved after fixation in KMnCv Certain lipid inclusions in the cytoplasm of the cells of the allantoic layer are well seen after fixation by OsO4, but not after KMnO4; in their places empty vacuoles are seen. Details of the structure of the red blood-corpuscles are more clearly seen after fixation in KMnO4.

Consequences of somite manipulation on the pattern of dorsal root ganglion development

Development ◽  
1989 ◽  
Vol 106 (1) ◽  
pp. 85-93 ◽  
Author(s):  
C. Kalcheim ◽  
M.A. Teillet
Keyword(s):  
Dorsal Root Ganglion ◽  
Neural Crest ◽  
Dorsal Root Ganglia ◽  
Neural Tube ◽  
Dorsal Root ◽  
Neural Crest Cells ◽  
The Other ◽  
Avian Embryo ◽  
Chick Embryos ◽  
Somitic Mesoderm

We have investigated dorsal root ganglion formation, in the avian embryo, as a function of the composition of the paraxial somitic mesoderm. Three or four contiguous young somites were unilaterally removed from chick embryos and replaced by multiple cranial or caudal half-somites from quail embryos. Migration of neural crest cells and formation of DRG were subsequently visualized both by the HNK-1 antibody and the Feulgen nuclear stain. At advanced migratory stages (as defined by Teillet et al. Devl Biol. 120, 329–347 1987), neural crest cells apposed to the dorsolateral faces of the neural tube were distributed in a continuous, nonsegmented pattern that was indistinguishable on unoperated sides and on sides into which either half of the somites had been grafted. In contrast, ventrolaterally, neural crest cells were distributed segmentally close to the neural tube and within the cranial part of each normal sclerotome, whereas they displayed a nonsegmental distribution when the graft involved multiple cranial half-somites or were virtually absent when multiple caudal half-somites had been implanted. In spite of the identical dorsal distribution of neural crest cells in all embryos, profound differences in the size and segmentation of DRG were observed during gangliogenesis (E4–9) according to the type of graft that had been performed. Thus when the implant consisted of compound cranial half-somites, giant, coalesced ganglia developed, encompassing the entire length of the graft. On the other hand, very small, dorsally located ganglia with irregular segmentation were seen at the level corresponding to the graft of multiple caudal half-somites. We conclude that normal morphogenesis of dorsal root ganglia depends upon the craniocaudal integrity of the somites.

Dexamethasone Effect on Embryonic Chick Respiratory Epithelium

1982 ◽  
Vol 40 ◽  
pp. 248-249
Author(s):  
M.R. Richter ◽  
R.V. Blystone
Keyword(s):  
Lung Development ◽  
Critical Role ◽  
Respiratory Epithelium ◽  
Chick Embryos ◽  
Embryonic Chick ◽  
White Leghorn ◽  
Lung Maturation ◽  
Synthetic Analogs ◽  
Lung Physiology ◽  
Avian Lung

Dexamethasone and other synthetic analogs of corticosteroids have been employed clinically as enhancers of lung development. The mechanism(s) by which this steroid induction of later lung maturation operates is not clear. This study reports the effect on lung epithelia of dexamethasone administered at different intervals during development. White Leghorn chick embryos were used so as to remove possible maternal and placental influences on the exogenously applied steroid. Avian lung architecture does vary from mammals; however, respiratory surfactant produced by the lung epithelia serves an equally critical role in avian lung physiology.

Plasma Levels of Protein S, Protein C, and Factor X: Effects of Sex, Hormonal State and Age

1995 ◽  
Vol 74 (05) ◽  
pp. 1271-1275 ◽  
Author(s):  
C M A Henkens ◽  
V J J Bom ◽  
W van der Schaaf ◽  
P M Pelsma ◽  
C Th Smit Sibinga ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Postmenopausal Women ◽  
Protein C ◽  
Blood Donors ◽  
Premenopausal Women ◽  
Protein S ◽  
The Other ◽  
Factor X ◽  
Normal Ranges

SummaryWe measured total and free protein S (PS), protein C (PC) and factor X (FX) in 393 healthy blood donors to assess differences in relation to sex, hormonal state and age. All measured proteins were lower in women as compared to men, as were levels in premenopausal women as compared to postmenopausal women. Multiple regression analysis showed that both age and subgroup (men, pre- and postmenopausal women) were of significance for the levels of total and free PS and PC, the subgroup effect being caused by the differences between the premenopausal women and the other groups. This indicates a role of sex-hormones, most likely estrogens, in the regulation of levels of pro- and anticoagulant factors under physiologic conditions. These differences should be taken into account in daily clinical practice and may necessitate different normal ranges for men, pre- and postmenopausal women.

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