PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Blastoderm”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1985

Blastoderm-differential and blastoderm-specific genes of Drosophila melanogaster.

We have isolated, by molecular cloning, genes expressed differentially at the blastoderm stage of Drosophila melanogaster. Two of the blastoderm-differential genes are reexpressed at later stages, and map to single chromosomal loci 95C and 99E. The sequence at 99E is that encoding the myosin light chain 2. Two other blastoderm-differential sequences are members of multigene families (one of which is B104, or roo) and map to multiple dispersed chromosomal loci. A gastrula-differential sequence was found which maps to 71A. Most significantly, we have identified three genes encoding transcripts expressed uniquely at the blastoderm stage; these map to single chromosomal loci: 25D3, 75C, and 99D4-8. At least some of the blastoderm-differential and blastoderm-specific loci appear to be distinct from loci involved in embryonic pattern formation that have been identified in recent genetic "saturation" screens. The procedure of identifying genes specific to the blastoderm stage may thus allow the identification of genes, not previously identified by classical genetic techniques, that are involved in important embryonic processes.

Animals↗
PubMed1978

Studies on dispersed unincubated chick blastoderm cells. II. Formation of contacts and cell sorting in aggregates of unincubated chick blastoderm and heart cells.

The configuration of blastoderm-heart cell aggregates after cell sorting depended largely on the proportion of each cell type initially present in the culture. In heterotypic aggregates, blastoderm cells were always found to partially or completely surround heart cells with both cell types retaining their characteristic morphology. Specialized junctions (e.g. desmosomes) developed only between cells of the same type. These observations suggest that blastoderm cells are unable to recognize and form stable contacts with heart cells.

Animals↗
PubMed1983

Electron microscopy of DNA molecules from blastoderm nuclei and yolk granules beneath blastoderm of fertilized and unincubated chicken eggs.

The DNA molecules isolated from the blastoderm nuclei and yolk granules beneath the blastoderm of fertilized and unincubated chicken eggs were observed under electron microscope, using the DNA sample of calf thymus as control. The results showed that both nuclear and yolk DNAs are linear, and their molecules are very similar to those of thymus DNA in shape. Since chromatin was first prepared from blastoderm nuclei and yolk granules respectively and then DNA was isolated from both of chromatin samples, it could be concluded that yolk granules possess both DNA chromatin as nuclei do.

Animals↗
PubMed1983

Electron microscopic studies on the chromatin of blastoderm nuclei and yolk granules beneath blastoderm of fertilized and unincubated chicken eggs.

Chromatin prepared both from the yolk granules beneath the blastoderm and from the nuclei of the blastoderm cells of fertilized and unincubated chicken eggs was examined under electron microscope and its structure was compared. The results indicate that the above two kinds of chromatin fibers seem to have no apparent difference in structural relation and diameter. The electron microscopic appearances of the basic structures of both kinds of chromatin are all "beads-on-a-string"-shaped filaments. After the digestion of chromatin from both raw materials with DNase I, the connecting strings of chromatin fibers were cut off, only the scattered beads could be observed under electron microscope. The diameter of the scattered beads is equal to that of the beads on the chromatin fibers, and most of them are 150 A in diameter.

Animals↗
PubMed1983

Calcium-independent adhesion of extra-embryonic endoderm cells from the early chick blastoderm is inhibited by the blastoderm beta-D-galactoside-binding lectin and by beta-galactosidase.

Extra-embryonic endoderm cells from gastrulating chick embryos possess Ca2+-dependent and Ca2+-independent adhesive mechanisms. These cells also contain an endogenous beta-D-galactoside-binding lectin and cell surface receptors bearing galactose groups. The endogenous lectin inhibits cellular adhesion. To test whether the adhesive interactions involving lectin and galactose molecules are part of the Ca2+-independent or Ca2+-dependent adhesive mechanism, dissociated cells which were preincubated in beta-galactosidase were allowed to aggregate in the presence and absence of Ca2+ ions. Significant decreases in adhesion were observed in both cases. Cells were also allowed to aggregate in the presence and absence of Ca2+ ions when blastoderm lectin was present in the medium. Adhesion was decreased in both cases. The results suggest that cell surface galactose groups and the beta-D-galactoside-binding lectin are involved in Ca2+-independent adhesion.

Animals↗
PubMed2005

Origin, fate, and function of the components of the avian germ disc region and early blastoderm: role of ooplasmic determinants.

In the avian oocytal germ disc region, at the end of oogenesis, we discerned four ooplasms (alpha, beta, gamma, delta) presenting an onion-peel distribution (from peripheral and superficial to central and deep. Their fate was followed during early embryonic development. The most superficial and peripheral alpha ooplasm plays a fundamental role during cleavage. The beta ooplasm, originally localized in the peripheral region of the blastodisc, becomes mainly concentrated in the primitive streak. At the moment of bilateral symmetrization, a spatially oblique, sickle-shaped uptake of gamma and delta ooplasms occurs so that gamma and delta ooplasms become incorporated into the deeper part of the avian blastoderm. These ooplasms seem to contain ooplasmic determinants that initiate either early neurulation or gastrulation events. The early neural plate-inducing structure that forms a deep part of the blastoderm is the delta ooplasm-containing endophyll (primary hypoblast). Together with the primordial germ cells, it is derived from the superficial centrocaudal part of the nucleus of Pander, which also contains delta ooplasm. The other structure (gamma ooplasm) that is incorporated into the caudolateral deep part of the blastoderm forms Rauber's sickle. It induces gastrulation in the concavity of Rauber's sickle and blood island formation exterior to Rauber's sickle. Rauber's sickle develops by ingrowth of blastodermal cells into the gamma ooplasm, which surrounds the nucleus of Pander. Rauber's sickle constitutes the primary major organizer of the avian blastoderm and generates only extraembryonic tissues (junctional and sickle endoblast). By imparting positional information, it organizes and dominates the whole blastoderm (controlling gastrulation, neurulation, and coelom and cardiovascular system formation). Fragments of the horns of Rauber's sickle extend far cranially into the lateral quadrants of the unincubated blastoderm, so that often Rauber's sickle material forms three quarters of a circle. This finding explains the regulative capacities of isolated blastoderm parts, with the exception of the anti-sickle region and central blastoderm region, where no Rauber's sickle material is present. In avian blastoderms, there exists a competitive inhibition by Rauber's sickle on the primitive streak and neural plate-inducing effects of sickle endoblast. Avian primordial germ cells contain delta ooplasm derived from the superficial part of the nucleus of Pander. Their original deep and central ooplasmic localization has been confirmed by the use of a chicken vasa homologue. We conclude that the unincubated blastoderm consists of three elementary tissues: upper layer mainly containing beta ooplasm, endophyll containing delta ooplasm, and Rauber's sickle containing gamma ooplasm). These elementary tissues form before the three classic germ layers have developed.

Animals↗
PubMed1975

The role of microtubules in chick blastoderm expansion--a quantitative study using colchicine.

Since their discovery, cytoplasmic microtubules have been much studied in the context of cell movement and cell shape change. Much of the work has used drugs, particularly colchicine and its relatives, which break down microtubules- the so-called anti-tubulins. Colchicine and its relatives, which break down microtubules- the so-called anti-tubulins. Colchicine inhibits the orientated movements of many cell types in vitro, and disrupts cell shape change in several morphogenetic situations. The investigatiion reported here used chick blastoderm expansion in New culture in an attempt to quantify the colchicine effect on orientated cell movement. However, although colchicine could halt blastoderm expansion entirely, a simple interpretation was not possible. (1) Colchicine at concentrations capable of blocking mitosis, and of disrupting all or most of the cytoplasmic microtubules of the cells studied, inhibited blastoderm expansion, often resulting in an overall retraction of the cell sheet. (2) Though blastoderm expansion does normally involve considerable cell proliferation, the colchicine effect could not be ascribed to a block on cell division since aminopterin, which stops cell division without affecting microtubules, did not inhibit expansion. (3) Blastoderm expansion is effected by the locomotion of a specialized band of edge cells at the blastoderm periphery. These are the only cells normally attached to the vitelline membrane - the substrate for expansion. When most of the blastoderm was excised, leaving the band of edge cells, and the cultures then treated with colchicine, expansion occurred normally. The colchicine effect on blastoderm expansion could not therefore be ascribed to a direct effect on the edge cells. (4) An alternative site of action of the drug is the remaining cells of the blastoderm. These normally become progressively flatter as expansion proceeds. If flattening in these cells is even partially dependent on their cytoplasmic microtubules, disruption of these microtubules might result in the inherent contractility of the cells resisting and eventually halting edge cell migration. That cell shape in these cells is dependent on microtubules was demonstrated by treating flat blastoderm fragments with colchicine. On incubation, the area occupied by these fragments decreased by 25-30% more than controls. The significance of these results in the general context of orientated cell movements and cell shape determination is discussed, with particular emphasis on the analogous system of Fundulus epiboly.

Aminopterin↗
PubMed1997

Mixed cultures of avian blastoderm cells and the quail mesoderm cell line QCE-6 provide evidence for the pluripotentiality of early mesoderm.

During the early stages of embryogenesis, the mesoderm gives rise to cells of the cardiovascular system which include cardiac myocytes and vascular endothelial and red blood cells. We have investigated the development of these cell phenotypes using aggregate cultures of avian blastoderm cells, which replicated mesodermal cell diversification. The cell phenotypes expressed by the blastoderm cells were dependent upon the age of the blastoderm cells, with Hamburger-Hamilton stage 3 or 4 cells giving rise to endothelial and red blood cells and stage 5 cells producing endothelial and myocardial cells. To begin to understand the stage dependency of the cellular diversification of these aggregate cultures, we treated the cultures with various signaling factors that have been shown to be present in the early avian embryo. These experiments showed that stem cell factor and TGF alpha altered cell phenotypes by stimulating red blood cell and myocardial differentiation, respectively. The ability of these growth factors to shift the differentiation profile of aggregate cultures demonstrated the plasticity of early embryonic cells. To explore the diversification of individual mesodermal cells, labeled QCE-6 cells were incorporated within these blastoderm aggregate cultures. Previous studies have shown that this quail mesodermal cell line possesses characteristics of early nondifferentiated mesodermal cells and can be induced to express either myocardial or endothelial cell phenotypes (C. A. Eisenberg and D. M. Bader, 1996, Circ. Res. 78, 205-216). In the present study, we show that when these cells were cultured as a component of blastoderm cell aggregates, they differentiated into fully contractile cardiomyocytes or endothelial or red blood cells. Moreover, QCE-6 cell differentiation was in accordance with that displayed by the blastoderm cells. Specifically, QCE-6 cells differentiated into red blood cells when cultured within stage 3 or stage 4, but not stage 5, blastoderm cell aggregates. Accordingly, the differentiation of QCE-6 cells into beating cardiomyocytes only occurred when these cells were incorporated into stage 5 blastoderm cell aggregates. The identical sorting and differentiation patterns that were exhibited by QCE-6 and blastoderm cells suggest that expression of differentiated cell types within the early mesoderm is directed by the surrounding environment without immediate cellular commitment. In addition, these results provide further evidence that QCE-6 cells are representative of a multipotential mesodermal stem cell and that they possess the potential to exhibit fully differentiated cell phenotypes.

Animals↗
PubMed1990

Migration of chick blastoderm under the vitelline membrane: the role of fibronectin.

In the earliest stages of its development the chick blastoderm is a flattened disc at the surface of the yolk. It gradually increases in diameter, partially because the cells are rapidly proliferating, but also because the cells at the periphery (the margin of overgrowth) are migrating in a centrifugal direction. These cells utilize the inner surface of the vitelline membrane as their substratum. In the normal blastoderm, these cells at the edge of the spreading blastoderm are the only cells which are attached to the vitelline membrane. This investigation is concerned with the possible role played by fibronectin in the interaction between these migrating cells and the vitelline membrane. Chick blastoderms, explanted by the New (1955) technique have been treated with synthetic peptides that mimic the adhesive recognition signal of the fibronectin molecule. The pentapeptide GRGDS (containing the specific RGD cell adhesion sequence) caused the edge cells of the blastoderm to detach within minutes, and the expansion of the blastoderm was inhibited for about 4 hr. After this period there was gradual recovery and the cells reattached and spreading resumed. Examination of the margin of the blastoderm by scanning electron microscopy showed that cell processes were lost soon after treatment with GRGDS but concomitant with reattachment and the resumption of spreading, the cell processes reformed. The pentapeptide GRDGS (with the amino acids G and D inverted) produced a brief inhibition of spreading, but after an hour these blastoderms spread at the same rate as controls. Immunocytochemical staining with anti-fibronectin demonstrated that fibronectin was not only present at the interface of the edge cells and the vitelline membrane, but also between the epiblast and the hypoblast. These results indicate that tissue movement during blastoderm spreading is dependent upon fibronectin and that the specific RGD amino acid sequence, and presumably the VLA/integrin family of receptors, is involved in this embryonic morphogenetic movement.

Amino Acid Sequence↗
PubMed1986

Deoxycytidine reverses inhibition of morphogenesis by thymidine in young chick blastoderm.

Exogenous thymidine affects morphogenesis of the early chick blastoderm possibly by depleting the deoxycytidine triphosphate pool. The aim of this study is to determine whether the inhibitory action of thymidine on early chick blastoderm morphogenesis is alleviated by the removal of thymidine and/or treatment with deoxycytidine. Chick blastoderms at the full hypoblast stage develop abnormally in egg albumen containing 1.23 X 10(-3) M thymidine. Development is normal when deoxycytidine is included simultaneously in the culture medium with thymidine at equimolar concentrations. Blastoderms were cultured in egg albumen containing 15 microCi/ml thymidine [methyl-3H] or 10 microCi/ml deoxycytidine [5-3H], and 1.2 X 10(-3) M 2'-deoxycytidine or 1.23 X 10(-3) M thymidine, respectively. The culture was interrupted at timed intervals, and the amount of radioactivity associated with DNA was determined. Exogenous deoxycytidine in the culture medium caused a noticeable increase in the incorporation of 3H-thymidine, while exogenous thymidine markedly inhibited the uptake and incorporation of 3H-deoxycytidine into DNA of blastoderms. Thymidine does not inhibit the expansion of blastoderm, the migration of cells for formation of the primitive streak (PS), and the induction of axial tissues, but it interferes with the organization of these tissues to form the embryonic axis. Blastoderms show slight signs of recovery when thymidine is removed. Deoxycytidine counteracts the action of thymidine and seems to be a rate-limiting factor in normal differentiation of the early chick blastoderm.

Animals↗
PubMed1995

Spatial regulation of segment polarity gene expression in the anterior terminal region of the Drosophila blastoderm embryo.

The effects of mutations in five anterior gap genes (hkb, tll, otd, ems and btd) on the spatial expression of the segment polarity genes, wg and hh, were analyzed at the late blastoderm stage and during subsequent development. Both wg and hh are normally expressed at blastoderm stage in two broad domains anterior to the segmental stripes of the trunk region. At the blastoderm stage, each gap gene acts specifically to regulate the expression of either wg or hh in the anterior cephalic region: hkb, otd and btd regulate the anterior blastoderm expression of wg, while tll and ems regulate hh blastoderm expression. Additionally, btd is required for the first segmental stripe (mandibular segment) of both hh and wg at blastoderm stages. The subsequent segmentation of the cephalic segments (preantennal, antennal and intercalary) appears to be dependent on the overlap of the wg and hh cephalic domains as defined by these gap genes at the blastoderm stage. None of these five known gap genes are required for the activation of the labral segment domains of hh and wg, which are presumably either activated directly by maternal pathways or by an unidentified gap gene.

Animals↗
PubMed2005

The ostrich (Struthio camelus) blastoderm and embryo development following storage of eggs at various temperatures.

1. The gross morphology of blastoderms in fresh unstored ostrich eggs and in eggs subjected to different regimen of storage and incubation was studied. Then the effects of storage duration of eggs (1, 2 and 3 weeks) and storage temperature (15, 20 and 25 degrees C) on blastoderm and embryo development were investigated.2. Only incubation following overnight storage at 18 degrees C advanced blastoderm development (1.5-fold increase in diameter) to a stage comparable to hypoblast. 3. Storage of eggs at 15 or 20 degrees C did not affect blastoderm stage and size whereas, at 25 degrees C, the blastoderm doubled in size and appeared to have advanced to a primitive streak stage. Embryo development was reduced after 2 weeks of storage regardless of the storage temperature. 4. After oviposition and during pre-incubation storage the ostrich blastoderm develops progressively over time in a temperature-dependent manner towards the hypoblast stage and beyond but the viability of the blastoderm and embryo development is seriously compromised by 2 weeks of storage.

Animals↗
PubMed1997

Manipulation of blastodermal cells.

Blastodermal cells isolated from newly laid, unincubated eggs are virtually uncommitted cells that exhibit many of the properties of pluripotential stem cells. They can be transferred from donor to recipient embryos and contribute to both somatic tissues and the germline. Blastodermal cells that have been maintained in culture for 7 d express the epitopes ECMA-7 and SSEA-1, which are also expressed by mouse embryonic stem cells. After culture for up to at least 7 d, blastodermal cells retain the ability to differentiate into somatic tissues and the germline both in vivo and in vitro. Proliferation in the absence of differentiation of blastodermal cells is stimulated by the presence of Leukemia Inhibitory Factor (LIF) and other ligands that interact with the gp130 receptor, and differentiation is stimulated by exposure to retinoic acid. Blastodermal cells also possess high levels of telomerase activity, which is shared by immortalized cells and cells within the germline. Blastodermal cells can be transfected and will express foreign genes both in vivo and in vitro. Transfected cells can be isolated by fluorescence activated cell sorting and can be cryopreserved without losing their ability to contribute to either somatic tissues or the germline. These properties of blastodermal cells make them ideal vectors for introducing genetic modifications to the germline.

Alkaline Phosphatase↗
PubMed1998

Gross appearance of the turkey blastoderm at oviposition.

The blastoderm (fertilized ovum) and unfertilized germinal disc (UGD) of fresh laid eggs and eggs stored prior to incubation exhibit subtle but definable morphological variations. Such variations may lead to difficulty when attempting to determine true flock fertility based on the appearance of the blastoderm/UGD. The objectives of this study were to define and categorize such morphological variations and to determine whether sperm influence the frequency distribution of the different categories. Eleven categories of blastoderms were defined based on the relative density and appearance of the area alba, area pellucida, area opaca, and the periblast. The majority of the blastoderms were included in the first four categories. Unfertilized germinal discs were divided into six categories and were best differentiated from the blastoderms by the presence of vacuoles around its central dense area. They were also discernible from blastoderms based on their overall denser appearance. Differences in the frequency distribution of some of the UGD categories between virgin and inseminated hens may be due to the effect that supernumary sperm may have on the organization of the UGD (no fertilization but supernumary sperm present) or blastoderm (fertilized but failed to develop). It is recommended that before starting true fertility determinations during fresh egg breakouts, one should study the appearance of the UGD from virgin hens and then the blastoderm from inseminated hens. One then will learn to appreciate the subtle differences in shape and density of the blastoderm/UGD structural components.

Animals↗
PubMed1992

Distribution analysis of transferred donor cells in avian blastodermal chimeras.

Blastodermal chimeras were constructed by transferring quail cells to chick blastoderm. Contribution of donor cells to host were histologically analyzed utilizing an in situ cell marker. Of the embryos produced by injection of stage XI-XIII quail cells into stage XI-2 chick blastoderm, more than 50 percent were definite chimeras. The restriction on the spatial arrangement of donor cells was induced by varying the stage of host. Ectodermal chimerism was limited to the head region and no mesodermal chimerism was shown when the quail cells were injected into stage XI-XIII blastoderm. Mesodermal and ectodermal chimerisms were limited to the trunk, not to the head region, when the quail cells were injected into the stage XIV-2 blastoderm. In these chimeras, however, some of the injected quail cells formed ectopic epidermal cysts. Consequently, the stage XIV-2 blastoderm may become intolerant of the injected cells. Our results suggest that it is possible to obtain chimeras that have chimerism limited to a particular germ layer and region by varying the stage of donor cell injection. Injected quail cells contributed to endodermal tissues and primordial germ cells regardless of the injection site. The quail-chick blastodermal chimeras could be useful in the production of a transgenic chicken and in the investigation of immunological tolerance.

Animals↗
PubMed2001

Localization of primordial germ cells or their precursors in stage X blastoderm of chickens and their ability to differentiate into functional gametes in opposite-sex recipient gonads.

This study was performed to determine the distribution of primordial germ cells and their precursors in stage X blastoderm of chickens. The blastoderm (Barred Plymouth Rock chickens) isolated from the yolk was separated into three portions: the central disc, the marginal zone and the area opaca. The dissociated blastodermal cells derived from the central disc, marginal zone and area opaca were transferred into a recipient blastoderm (White Leghorn chicken) from which a cell cluster was removed from the centre of the central disc. The manipulated embryos were cultured in host eggshells until hatching. The chicks were raised until sexual maturity and test mated with Barred Plymouth Rock chickens to assess the donor cell contribution to the recipient germline. Germline chimaeric chickens were produced efficiently (46.7%, 7/15) when the blastodermal cells derived from the central disc were transferred into recipient embryos of the same sex, whereas no germline chimaeric chickens were produced when the blastodermal cells derived from the marginal zone or area opaca were transferred into recipient embryos of the same sex (0/12). Germline chimaeric chickens were also produced by transfer of blastodermal cells derived from the central disc (6.7%, 1/15), marginal zone (10.0%, 1/10) or area opaca (11.1%, 1/9) into recipient embryos of the opposite sex. It is concluded that primordial germ cells are induced during or shortly after stage X and that the cells derived from the central disc have the highest potential to give rise to germ cells. Cells derived from the marginal zone and area opaca can also give rise to germ cells, although the frequency is low.

Animals↗
PubMed1976

The mechanism of chick blastoderm expansion.

At the time of laying, the domestic fowl blastoderm measures 4 mm across. After 4 days' incubation, the extra-embryonic yolk-sac tissues have expanded to encompass the whole yolk mass. This expansion involves the migration over the inner surface of the vitelline membrane of a specialized band of 'edge cells' at the blastoderm periphery. As they move, they pull out the blastoderm behind them, setting up a considerable tension. Expansion also involves cell proliferation and changes in cell shape. This paper attempts to show how locomotion, tension, proliferation and changes in cell shape all contribute to the orderly process of expansion. As a simplification, only the extra-embryonic epiblast is considered here. The findings are: 1. Expansion does not occur at a constant rate, but starts slowly, rises to a peak (over 500 mum/h) at around 3 days, and then slows as coverage of the yolk mass nears completion. 2. During the first day of incubation, edge-cell migration produces a tension in the blastoderm. This rises to peak at 20-24 h, then declines. This tension may be due to an imbalance between expansion by migration and expansion by proliferation. 3. Migration of edge cells can be affected by tension in the blastoderm, i.e. very high tension may hold them back. However, the tension level normally found in the blastoderm seems not to do so. The low rate of expansion in the first day is therefore not due to the high level of tension. It may instead be due to changes in edge-cell organization. 4. Proliferation occurs throughout the extra-embryonic epiblast during the expansion period. It is not restricted to the blastoderm periphery. After the yolk has been covered, the epiblast continues to grow, with proliferation restricted largely to band just distal to the advancing edge of the area vasculosa. 5. Cell shape and arrangement change considerably during expansion. The epiblast of the unincubated embryo is a monolayer of tall cells. During expansion, these become considerably flattened so that each contributes a larger amount to yolk-sac surface area.

Animals↗