Blastoderms

Howard, K., and Ingham, P. (1986). Regulatory interactions between the segmentation genes fushi tarazu, hairy and engrailed in the Drosophila blastoderm. Cell 44 949-957. 

Muller H, Wieschaus E 1996 armadillo, bazooka, and stardust are critical for early stages in formation of the zonula adherens and maintenance of the polarized blastoderm epithelium in Drosophila. J Cell Biol 134 149-163... 

Sabin, FR (1920). Studies on the origin of blood vessels and of red blood corpuscles as seen in the living blastoderm of checks during the second day of incubation. Carnegie Inst. Wash. Pub. n°272, Contrib. Embryol. 9 214. 

Development in Drosophila and other insects follows a somewhat different pathway, as is indicated in Fig. 32-6B. The egg, which is surrounded by follicle cells and 16 nurse cells, does not divide. However, its nucleus divides repeatedly, about once every nine minutes, to form -6000 nuclei. Only then do separating membranes form to give individual cells.9,285 316 317 During the first two hours the nuclei form a syncytium, in which they are embedded in a common cytoplasm, that allows free diffusion of signaling compounds. At first the nuclei are in the center, but later most migrate to the periphery and form a single layer of cells comparable to the blastoderm of amphibian cells. A few nuclei remain in the central cavity to become yolk cells, and some at the posterior pole become separated into pole cells. 

The observations discussed so far lay out some of the desiderata of any good theory to try simultaneously to understand how position may be specified in the early embryo, and also to account for the ways in which apparently neighboring developmental programs are not spatial neighbors on the blastoderm. 

If a cell is genetically marked at about the blastoderm stage, its clonal derivatives are found not to cross a specific line on the adult wing thorax which divides the tissue into anterior and posterior compartments (Fig. 4a). If one examines a number of flies, however, one finds that clones... 

Fig. 9. Successive compartmental lines predicted on the fate map6-7 of the blastoderm by the chemical wave model, with the binary combinatorial code assignment in each compartment generated by the successive lines. A, antenna E, eye Pb, proboscis P, prothorax W, wing and mesothorax H, haltere LI, L2, L3, first, second, and third legs Abd, abdominal segments G, genital.

When initially formulated, this predicted sequence of compartmental boundaries on the egg was lately hypothetical. The data then available showed that at the blastoderm stage, compartmental boundaries appeared to isolate adjacent segments, but not the dorsal from ventral disc derivatives from the three thoracic segments, since genetically marked clones at that stage can straddle from mesothorax to mesothoracic leg.41-43-44 A short time later,44 clonal restriction lines isolate the dorsal from ventral thoracic discs thus, longitudinal lines of clonal restriction do arise on the... 

TABLE I. Predicted Relative Transdetermination Frequencies Derived from the Chemical Wave Model Applied to the Blastoderm ... 

There are two distinct phases in Drosophila embryogenesis the first precedes cellularization of the blastoderm and is associated with a cascade of interacting regulators the second occurs after cellularization and depends on intercellular signals that must be carried, at least in part, by membrane-bound proteins. We focus on some of the events occurring in the first phase because they are better understood. 

Key events in the expression of developmental regulatory genes in the blastoderm embryo. Events take place in the order shown over a period of a few hours. Measurements are based on the use of probes for detecting the transcripts of various... 

Blastoderm. The stage in embryogene-sis when a unicellular layer at the surface surrounds the yolk mass. 

Padash, B. M., Rogers, S., and Hacker, U. (2005). DRhoGEF2 regulates actin organization and contractility in the Drosophila blastoderm embryo./. Cell Biol. 168, 575-585. 

Remove the chorion from blastodermal embryos by treatment with 3% NaCIO for 2 min. 

Blastoderm Birds only Embryonic Haemoglobin synthesis... 

Spleen, liver, blastoderm 5/3-DHT 5/3-Reductase Haemoglobin synthesis The response does not primarily involve genetic transcription... 

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