Maps of strength of positional signalling activity in the developing chick wing bud

Development ◽  
1985 ◽  
Vol 87 (1) ◽  
pp. 163-174
Author(s):  
Lawrence S. Honig ◽  
Dennis Summerbell
Keyword(s):  
Activity Index ◽  
Temporal Distribution ◽  
Quantitative Measure ◽  
Mirror Image ◽  
Host Tissue ◽  
Limb Bud ◽  
High Reproducibility ◽  
Morphological Pattern ◽  
Initial Appearance ◽  
Wing Bud

Tissue from the posterior margin of the developing limb bud, when grafted to the anterior margin, evokes the formation of a mirror-image limb duplication from the host tissue. We present maps of the spatial and temporal distribution of this signalling activity in the chick wing bud based on a bioassay that provides a quantitative measure of the completeness of the additional structures (the strength of activity index). Activity is first detected prior to the initial appearance of the limb primordium as early as Hamburger & Hamilton stage 14. It reaches a maximum during early outgrowth of the bud at stages 19 to 25. It then declines as the limb starts to differentiate into its final morphological pattern. The design of the experiment provides serendipitous data showing that two operators can consistently perform grafts with high reproducibility between them while variability between embryos is somewhat higher. The maps of activity are of particular practical value in precisely defining for the experimental embryologist and molecular biologist those positions and stages at which peak signalling activity resides.

Myogenic cell movement in the developing avian limb bud in presence and absence of the apical ectodermal ridge (AER)

Development ◽  
1984 ◽  
Vol 80 (1) ◽  
pp. 105-125
Author(s):  
Madeleine Gumpel-Pinot ◽  
D. A. Ede ◽  
O. P. Flint
Keyword(s):  
Cell Migration ◽  
Cell Movement ◽  
Host Tissue ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Myogenic Cell ◽  
Myogenic Cells ◽  
Apical Direction ◽  
Wing Bud ◽  
Presence And Absence

Fragments of quail wing bud containing myogenic cells of somitic origin and fragments of quail sphlanchopleural tissue were introduced into the interior of the wing bud of fowl embryo hosts. No movement of graft into host tissue occurred in the control, but myogenic cells from the quail wing bud fragments underwent long migrations in an apical direction to become incorporated in the developing musculature of the host. When the apical ectodermal ridge (AER), together with some subridge mesenchyme, was removed at the time of grafting, no such cell migration occurred. The capacity of grafted myogenic cells to migrate in the presence of AER persists to H.H. stage 25, when myogenesis has begun, but premyogenic cells in the somites, which normally migrate out into the early limb bud, do not migrate when somite fragments are grafted into the wing bud. Coelomic grafts of apical and proximal wing fragments showed that apical sections of quail wing buds become invaded by myogenic cells of the host, but grafts from proximal wing bud regions do not.

Activation of Fgf-4 and HoxD gene expression by BMP-2 expressing cells in the developing chick limb

Development ◽  
1996 ◽  
Vol 122 (6) ◽  
pp. 1821-1828 ◽  
Author(s):  
D.M. Duprez ◽  
K. Kostakopoulou ◽  
P.H. Francis-West ◽  
C. Tickle ◽  
P.M. Brickell
Keyword(s):  
Gene Expression ◽  
Anterior Part ◽  
Ectopic Expression ◽  
Mirror Image ◽  
Limb Bud ◽  
Bone Morphogenetic Protein 2 ◽  
Morphogenetic Protein ◽  
Wing Bud ◽  
Hoxd Gene

Bone morphogenetic protein-2 (BMP-2) has been implicated in the polarizing region signalling pathway, which specifies pattern across the antero-posterior of the developing vertebrate limb. Retinoic acid and Sonic Hedgehog (SHH) can act as polarizing signals; when applied anteriorly in the limb bud, they induce mirror-image digit duplications and ectopic Bmp-2 expression in anterior mesenchyme. In addition, the two signals can activate Fgf-4 expression in anterior ridge and HoxD expression in anterior mesenchyme. We tested the role of BMP-2 in this signalling cascade by ectopically expressing human BMP-2 (hBMP-2) at the anterior margin of the early wing bud using a replication defective retroviral vector, and found that ectopic expression of Fgf-4 was induced in the anterior part of the apical ectodermal ridge, followed later by ectopic expression of Hoxd-11 and Hoxd-13 in anterior mesenchyme. This suggests that BMP-2 is involved in regulating Fgf-4 and HoxD gene expression in the normal limb bud. Ectopically expressed hBMP-2 also induced duplication of digit 2 and bifurcation of digit 3, but could not produce the mirror-image digit duplications obtained with SHH-expressing cells. These results suggest that BMP-2 may be involved primarily in maintenance of the ridge, and in the link between patterning and outgrowth of the limb bud.

THE ROLE OF MYELOPEROXIDASE AND NEUTROPHIL EXTRACELLULAR TRAPS IN THE PATHOGENESIS OF INFLAMMATORY BOWEL DISEASE

2021 ◽  
Vol 27 (Supplement_1) ◽  
pp. S4-S4
Author(s):  
Belal Chami ◽  
Gulfam Ahmad ◽  
Angie Schroder ◽  
Patrick San Gabriel ◽  
Paul Witting
Keyword(s):  
Disease Severity ◽  
Hypochlorous Acid ◽  
Tissue Injury ◽  
Activity Index ◽  
Critical Role ◽  
Neutrophil Migration ◽  
Sodium Sulphate ◽  
Host Tissue ◽  
Neutrophil Extracellular Trap

Abstract Neutrophils are short-lived immune cells that represent the major cell type recruited to the inflamed bowel releasing their azurophilic granules containing enzymes myeloperoxidase (MPO). Fecal and serum MPO levels has previously been shown to correlate to disease severity in IBD patients. MPO, in the presence of H2O2 and free Cl- undergoes a halogenation cycle, yielding the two-electron oxidant, hypochlorous acid (HOCl) - a potent bactericidal agent. However, chronic intestinal exposure to MPO/HOCl due to perpetual inflammation may cause secondary host-tissue injury and cell death. Neutrophil Extracellular Trap (NET)osis is a specialised form of neutrophil death where MPO is entrapped in a DNA scaffold and continues to elicit HOCl activity and may further contribute to host-tissue injury. We investigated the presence of NETs in surgically excised ileum samples from CD and healthy patients using advanced confocal microscopic techniques and found MPO, Neutrophil Elastase (NE) and Citrullinated Histone h3 (CitH3) - critical components of NET formation, individually positively correlate to the severity of histopathological intestinal injury. Furthermore, multiplex Opal™ IHC performed using LMS880 Airyscan-moduled microscopy with z-stacking revealed colocalization of NE, MPO, CitH3 and DAPI indicating the extensive presence of NETs in severely affected CD tissue. Using two pharmacological inhibitors of MPO in a dextran sodium sulphate (DSS) model of murine colitis, we demonstrated the pathological role of MPO in experimental colitis. MPO inhibitors, TEMPOL and AZD3241 delivered via daily i.p significantly rescued the course of colitis by abrogating clinical indices including body weight loss, disease activity index, inhibiting serum peroxidation, and preserving colon length, while significantly mitigating histoarchitectural damage associated with DSS-induced colitis. We also showed that MPO inhibition decreased neutrophil migration to the gut, suggesting MPO may play a role in perpetuating the inflammatory cell by further recruiting cells to the inflamed gut. Collectively, we have shown for the first time that MPO is not only an important clinical marker of disease severity but may also play a critical role in perpetuating host-tissue damage and inflammation.

Role of the chicken homeobox-containing genes GHox-4.6 and GHox-8 in the specification of positional identities during the development of normal and polydactylous chick limb buds

Development ◽  
1992 ◽  
Vol 115 (2) ◽  
pp. 629-637 ◽  
Author(s):  
C.N. Coelho ◽  
W.B. Upholt ◽  
R.A. Kosher
Keyword(s):  
Limb Development ◽  
Ectopic Expression ◽  
Limb Bud ◽  
Chick Embryos ◽  
Limb Buds ◽  
Hox Gene ◽  
Wing Bud ◽  
Coated Bead ◽  
Experimentally Induced

During early stages of normal chick limb development, the homeobox-containing (HOX) gene GHox-4.6 is expressed throughout the posterior mesoderm of the wing bud from which most of the skeletal elements including the digits will develop, whereas GHox-8 is expressed in the anterior limb bud mesoderm which will not give rise to skeletal elements. In the present study, we have examined the expression of GHox-4.6 and GHox-8 in the wing buds of two polydactylous mutant chick embryos, diplopodia-5 and talpid2, from which supernumerary digits develop from anterior limb mesoderm, and have also examined the expression of these genes in response to polarizing zone grafts and retinoic acid-coated bead implants which induce the formation of supernumerary digits from anterior limb mesoderm. We have found that the formation of supernumerary digits from the anterior mesoderm in mutant and experimentally induced polydactylous limb buds is preceded by the ectopic expression of GHox-4.6 in the anterior mesoderm and the coincident suppression of GHox-8 expression in the anterior mesoderm. These observations suggest that the anterior mesoderm of the polydactylous limb buds is “posteriorized” and support the suggestion that GHox-8 and GHox-4.6, respectively, are involved in specifying the anterior non-skeletal and posterior digit-forming regions of the limb bud. Although the anterior mesodermal domain of GHox-8 expression is severely impaired in the mutant and experimentally induced polydactylous limb buds, this gene is expressed by the prolonged, thickened apical ectodermal ridges of the polydactylous limb buds that extend along the distal anterior as well as the distal posterior mesoderm.(ABSTRACT TRUNCATED AT 250 WORDS)

The spatial and temporal distribution of polarizing activity in the flank of the pre-limb-bud stages in the chick embryo

Development ◽  
1991 ◽  
Vol 111 (3) ◽  
pp. 725-731 ◽  
Author(s):  
A. Hornbruch ◽  
L. Wolpert
Keyword(s):  
Posterior Part ◽  
Temporal Distribution ◽  
Early Embryo ◽  
Limb Bud ◽  
Posterior Edge ◽  
Limb Buds ◽  
Avian Embryos ◽  
Low Levels ◽  
Clear Change ◽  
Somitic Mesoderm

The presence of polarizing activity in the limb buds of developing avian embryos determines the pattern of the anteroposterior axis of the limbs in the adult. Maps of the spatial distribution and the strength of the signal within limb buds of different stages are well documented. Polarizing activity can also be found in Hensen's node in the early embryo. We have mapped the distribution of polarizing activity as it emerges from Hensen's node and spreads into the flank tissue of the embryo. There is a clear change in the local pattern of expression of polarizing activity between stage 8 and 18. Almost no activity is measured for stages 8 and 9. More or less uniform levels of around 10% are spread along the flank lateral to the unsegmented somitic mesoderm from somite position 12 to 22 in stage 10 embryos. Some 6 to 8 h later at stage 12, there is a distinct peak of activity at somite position 18, the middle of the wing field. This peak increases at stages 13 to 15 and its position traverses to the posterior edge of the wing field. Full strength of activity is reached shortly before the onset of limb bud formation at stage 16 to 17. Stages 16 to 18 were investigated for polarizing activity in the wing and the leg field. Low levels of polarizing activity are present in the anterior leg field at stages 16 and 17 but have disappeared by stage 18 and all activity is confined to the posterior part of the leg bud.

Reduction of the rate of outgrowth, cell density, and cell division following removal of the apical ectodermal ridge of the chick limb-bud

Development ◽  
1977 ◽  
Vol 40 (1) ◽  
pp. 1-21
Author(s):  
Dennis Summerbell
Keyword(s):  
Cell Proliferation ◽  
Cell Death ◽  
Cell Division ◽  
Cell Density ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Short Term ◽  
Density Dependent ◽  
Wing Bud

Removal of the apical ectodermal ridge causes a reduction in the rate of outgrowth of the wing-bud and the loss of distal parts. More specifically it causes a short-term increase in cell density and cell death and a decrease in the rate of cell proliferation. The evidence supports the hypothesis of density-dependent control of cell division and suggests that there may also be a mechanism regulating skeletal length at the time of differentiation. An informal model is presented to explain the observations.

Retinoic acid signaling is required during early chick limb development

Development ◽  
1996 ◽  
Vol 122 (5) ◽  
pp. 1385-1394 ◽  
Author(s):  
J.A. Helms ◽  
C.H. Kim ◽  
G. Eichele ◽  
C. Thaller
Keyword(s):  
Retinoic Acid ◽  
Limb Development ◽  
Acid Synthesis ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Retinoid Receptor ◽  
Limb Morphogenesis ◽  
Wing Bud ◽  
Zone Of Polarizing Activity

In the chick limb bud, the zone of polarizing activity controls limb patterning along the anteroposterior and proximodistal axes. Since retinoic acid can induce ectopic polarizing activity, we examined whether this molecule plays a role in the establishment of the endogenous zone of polarizing activity. Grafts of wing bud mesenchyme treated with physiologic doses of retinoic acid had weak polarizing activity but inclusion of a retinoic acid-exposed apical ectodermal ridge or of prospective wing bud ectoderm evoked strong polarizing activity. Likewise, polarizing activity of prospective wing mesenchyme was markedly enhanced by co-grafting either a retinoic acid-exposed apical ectodermal ridge or ectoderm from the wing region. This equivalence of ectoderm-mesenchyme interactions required for the establishment of polarizing activity in retinoic acid-treated wing buds and in prospective wing tissue, suggests a role of retinoic acid in the establishment of the zone of polarizing activity. We found that prospective wing bud tissue is a high-point of retinoic acid synthesis. Furthermore, retinoid receptor-specific antagonists blocked limb morphogenesis and down-regulated a polarizing signal, sonic hedgehog. Limb agenesis was reversed when antagonist-exposed wing buds were treated with retinoic acid. Our results demonstrate a role of retinoic acid in the establishment of the endogenous zone of polarizing activity.

The analysis of spatial distributions in mixed cell populations: a statistical method for detecting sorting out

Development ◽  
1971 ◽  
Vol 26 (1) ◽  
pp. 135-156
Author(s):  
R. A. Elton ◽  
C. A. Tickle
Keyword(s):  
Plant Communities ◽  
Quantitative Measure ◽  
Cell Types ◽  
Limb Bud ◽  
Cell Populations ◽  
Spatial Distributions ◽  
Mixed Cell ◽  
Mixed Aggregates ◽  
Chick Heart ◽  
Gyratory Shaker

1. This work presents a quantitative measure, α, of the degree of segregation of two cell types in sections of aggregates, and some results obtained with the measure relating to ‘sorting out’. The method is designed particularly for the case where labelling of one type of cell is incomplete, and the importance of this effect is assessed. Possible problems in formulating such a model are discussed. The measure α is compared with methods used in investigations of segregation in plant communities. 2. Segregation of chick heart and limb-bud cells in mixed aggregates has been analysed using α. In control aggregates of mixtures of labelled and unlabelled cells of one type, α is near to its random value of 1, and we suggest that the departure from random can be adequately accounted for by cell division. In mixed aggregates, significant segregation is consistently found, even in aggregates formed after 2 and 4 h. Both disaggregation procedures (EDTA, trypsin or trypsin + EDTA) and reaggregation methods (reciprocating or gyratory shaker) are found to have an effect on the degree of segregation. Possible reasons for these findings are discussed. 3. Positioning of the cells relative to the outside of aggregates is also investigated for some of the aggregates.

Cell contacts and sorting out in vivo: the behaviour of some embryonic tissues implanted into the developing chick wing

Development ◽  
1978 ◽  
Vol 48 (1) ◽  
pp. 225-237
Author(s):  
C. Tickle ◽  
M. Goodman ◽  
L. Wolpert
Keyword(s):  
Neural Tube ◽  
Cell Types ◽  
Neural Retina ◽  
Limb Bud ◽  
Embryonic Liver ◽  
Malignant Cells ◽  
Embryonic Tissues ◽  
Mixed Aggregates ◽  
Wing Bud

The interaction of cells from embryonic liver, neural retina and mesonephros with cells from limb-bud mesenchyme has been investigated in vivo by grafting these tissues into the developing chick wing-bud. The implanted cells were in all cases from quail tissue which can be recognized histologically. As embryonic liver and neural tube are tissues that sort externally to limb-bud mesenchyme in mixed aggregates, it would be expected, from a differential adhesiveness hypothesis, that heterotypic adhesions along the borders of graft and host would be favoured over cell-cell adhesions in the graft. No morphological signs of this were evident: rather the grafted cells maximized like-like contacts. The cells of the grafts, including those from control mesenchyme, did not invade into the wing. The results were the same irrespective of whether the graft was a fragment of tissue or a pellet of reaggregated cells. This supports the idea that cells within tissues are not actively moving around and also provides controls for assaying the invasiveness of other cell types, such as malignant cells into the wing.

Relationship between retinoic acid and sonic hedgehog, two polarizing signals in the chick wing bud

Development ◽  
1994 ◽  
Vol 120 (11) ◽  
pp. 3267-3274 ◽  
Author(s):  
J. Helms ◽  
C. Thaller ◽  
G. Eichele
Keyword(s):  
Retinoic Acid ◽  
Sonic Hedgehog ◽  
Positional Information ◽  
Limb Bud ◽  
Dependent Manner ◽  
All Trans Retinoic Acid ◽  
Wing Bud ◽  
Zone Of Polarizing Activity ◽  
Dose Dependent

Local application of all-trans-retinoic acid (RA) to the anterior margin of chick limb buds results in pattern duplications reminescent of those that develop after grafting cells from the zone of polarizing activity (ZPA). RA may act directly by conferring positional information to limb bud cells, or it may act indirectly by creating a polarizing region in the tissue distal to the RA source. Here we demonstrate that tissue distal to an RA-releasing bead acquires polarizing activity in a dose-dependent manner. Treatments with pharmacological (beads soaked in 330 micrograms/ml) and physiological (beads soaked in 10 micrograms/ml) doses of RA are equally capable of inducing digit pattern duplication. Additionally, both treatments induce sonic hedgehog (shh; also known as vertebrate hedgehog-1, vhh-1), a putative ZPA morphogen and Hoxd-11, a gene induced by the polarizing signal. However, tissue transplantation assays reveal that pharmacological, but not physiological, doses create a polarizing region. This differential response could be explained if physiological doses induced less shh than pharmacological doses. However, our in situ hybridization analyses demonstrate that both treatments result in similar amounts of mRNA encoding this candidate ZPA morphogen. We outline a model describing the apparently disparate effects of pharmacologic and physiological doses RA on limb bud tissue.

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