Embryonic enhancers in the dpp disk region regulate a second round of Dpp signaling from the dorsal ectoderm to the mesoderm that represses Zfh-1 expression in a subset of pericardial cells

The steps that lead to the formation of a single primitive heart tube are highly conserved in vertebrate and invertebrate embryos. Concerted migration of the two lateral cardiogenic regions of the mesoderm and endoderm (or ectoderm in invertebrates) is required for their fusion at the midline of the embryo. Morphogenetic signals are involved in this process and the extracellular matrix has been proposed to serve as a link between the two layers of cells.Pericardin (Prc), a novel Drosophila extracellular matrix protein is a good candidate to participate in heart tube formation. The protein has the hallmarks of a type IV collagen α-chain and is mainly expressed in the pericardial cells at the onset of dorsal closure. As dorsal closure progresses, Pericardin expression becomes concentrated at the basal surface of the cardioblasts and around the pericardial cells, in close proximity to the dorsal ectoderm. Pericardin is absent from the lumen of the dorsal vessel.Genetic evidence suggests that Prc promotes the proper migration and alignment of heart cells. Df(3)vin6 embryos, as well as embryos in which prc has been silenced via RNAi, exhibit similar and significant defects in the formation of the heart epithelium. In these embryos, the heart epithelium appears disorganized during its migration to the dorsal midline. By the end of embryonic development, cardial and pericardial cells are misaligned such that small clusters of both cell types appear in the heart; these clusters of cells are associated with holes in the walls of the heart. A prc transgene can partially rescue each of these phenotypes, suggesting that prc regulates these events. Our results support, for the first time, the function of a collagen-like protein in the coordinated migration of dorsal ectoderm and heart cells.

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4U 1608–52 as a quasi-persistent X-ray source

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psaa099 ◽

2020 ◽

Vol 72 (6) ◽

Author(s):

Vojtěch Šimon

Keyword(s):

Accretion Disk ◽

Time Segment ◽

X Ray ◽

Band Emission ◽

Heating And Cooling ◽

Soft State ◽

Cyclic Variations ◽

Low Mass ◽

X Ray Binaries ◽

Disk Region

Abstract 4U 1608–52 is a soft X-ray transient. The analysis presented here of a particular part of its X-ray activity uses observations of RXTE/ASM and Swift/BAT. We show a time segment (MJD 54262–MJD 55090) (828 d) in which 4U 1608–52 behaved as a quasi-persistent X-ray source with a series of bumps, with a complicated relation between the evolution of fluxes in the soft (1.5–12 keV) and the hard (15–50 keV) X-ray regions. We ascribe these bumps to a series of propagations of heating and cooling fronts over the inner disk region without any transitions to the true quiescence. 4U 1608–52 oscillated around the boundary between the dominance of the Comptonized component and the dominance of the multicolor accretion disk in its luminosity. Only some of the bumps in this series were accompanied by a transition from the hard to the soft state; if it occurred, it displayed a strong hysteresis effect. The hard-band emission with the dominant Comptonized component was present for most of this active state and showed a cycle of about 40 d. We argue that the cyclic variations of flux come from the inner disk region, not, e.g., from a jet. We also discuss the observed behavior of 4U 1608–52 in the context of other quasi-persistent low-mass X-ray binaries.

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Dpp signaling thresholds in the dorsal ectoderm of the Drosophila embryo

Development ◽

10.1242/dev.127.15.3305 ◽

2000 ◽

Vol 127 (15) ◽

pp. 3305-3312 ◽

Cited By ~ 5

Author(s):

H.L. Ashe ◽

M. Mannervik ◽

M. Levine

Keyword(s):

Gene Expression ◽

Target Genes ◽

Histone Acetyltransferase ◽

Cell Types ◽

Drosophila Embryo ◽

Present Evidence ◽

Drosophila Homolog ◽

Dorsal Ectoderm ◽

Transgenic Embryos ◽

Different Cell Types

The dorsal ectoderm of the Drosophila embryo is subdivided into different cell types by an activity gradient of two TGF(β) signaling molecules, Decapentaplegic (Dpp) and Screw (Scw). Patterning responses to this gradient depend on a secreted inhibitor, Short gastrulation (Sog) and a newly identified transcriptional repressor, Brinker (Brk), which are expressed in neurogenic regions that abut the dorsal ectoderm. Here we examine the expression of a number of Dpp target genes in transgenic embryos that contain ectopic stripes of Dpp, Sog and Brk expression. These studies suggest that the Dpp/Scw activity gradient directly specifies at least three distinct thresholds of gene expression in the dorsal ectoderm of gastrulating embryos. Brk was found to repress two target genes, tailup and pannier, that exhibit different limits of expression within the dorsal ectoderm. These results suggest that the Sog inhibitor and Brk repressor work in concert to establish sharp dorsolateral limits of gene expression. We also present evidence that the activation of Dpp/Scw target genes depends on the Drosophila homolog of the CBP histone acetyltransferase.

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The Pericardial Cells of Drosophila melanogaster

Journal of Cell Science ◽

10.1242/jcs.s3-106.75.261 ◽

1965 ◽

Vol s3-106 (75) ◽

pp. 261-268

Author(s):

R. P. MILLS ◽

R. C. KING

Keyword(s):

Endothelial Cells ◽

Drosophila Melanogaster ◽

Adult Female ◽

Toxic Compounds ◽

Pericardial Cells ◽

Pericardial Cell

The ultrastructure of the pericardial cells of adult female Drosophila melanogaster is illustrated. The data presented suggest that the pericardial cell internalizes by pinocytosis complex and possibly toxic compounds present in suspension in the haemolymph. These compounds are broken down to soluble molecules within lysosome-like vacuoles. The pericardial cells thus behave like the reticulo-endothelial cells of mammals.

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Interdigital tissue chondrogenesis induced by surgical removal of the ectoderm in the embryonic chick leg bud

Development ◽

10.1242/dev.94.1.231 ◽

1986 ◽

Vol 94 (1) ◽

pp. 231-244

Author(s):

J. M. Hurle ◽

Y. Gañan

Keyword(s):

Cell Death ◽

Vital Staining ◽

Mesenchymal Cell ◽

Neutral Red ◽

Surgical Removal ◽

Experimental Conditions ◽

Local Inhibition ◽

Dorsal Ectoderm ◽

Interdigital Cell Death ◽

Proximal Zone

In the present work, we have analysed the possible involvement of ectodermal tissue in the control of interdigital mesenchymal cell death. Two types of experiments were performed in the stages previous to the onset of interdigital cell death: (i) removal of the AER of the interdigit; (ii) removal of the dorsal ectoderm of the interdigit. After the operation embryos were sacrificed at 10–12h intervals and the leg buds were studied by whole-mount cartilage staining, vital staining with neutral red and scanning electron microscopy. Between stages 27 and 30, ridge removal caused a local inhibition of the growth of the interdigit. In a high percentage of the cases, ridge removal at these stages was followed 30–40 h later by the formation of ectopic nodules of cartilage in the interdigit. The incidence of ectopic cartilage formation was maximum at stage 29 (60%). In all cases, cell death took place on schedule although the intensity and extent of necrosis appeared diminished in relation to the intensity of inhibition of interdigital growth and to the presence of interdigital cartilages. Ridge removal at stage 31 did not cause inhibition of the growth of the interdigit and ectopic chondrogenesis was only detected in 3 out of 35 operated embryos. Dorsal ectoderm removal from the proximal zone of the interdigit at stage 29 caused the chondrogenesis of the proximal interdigital mesenchyme in 6 out of 18 operated embryos. The pattern of neutral red vital staining was consistent with these results revealing a partial inhibition of interdigital cell death in the proximal zone of the interdigit. It is proposed that under the present experimental conditions the mesenchymal cells are diverted from the death programme by a primary transformation into cartilage.

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Time variable funnel flows

Proceedings of the International Astronomical Union ◽

10.1017/s174392130700943x ◽

2007 ◽

Vol 3 (S243) ◽

pp. 71-82 ◽

Cited By ~ 2

Author(s):

Silvia H. P. Alencar

Keyword(s):

Field Configuration ◽

Time Variable ◽

T Tauri Stars ◽

Magnetic Field Configuration ◽

Accretion Process ◽

T Tauri ◽

Model Predictions ◽

The Magnetic Field ◽

Disk Region ◽

Magnetospheric Accretion

AbstractMagnetospheric accretion models are the current consensus to explain the main observed characteristics of classical T Tauri stars. In recent years the concept of a static magnetosphere has been challenged by synoptic studies of classical T Tauri stars that show strong evidence for the accretion process to be dynamic on several timescales and governed by changes in the magnetic field configuration. At the same time numerical simulation results predict evolving funnel flows due to the interaction between the stellar magnetosphere and the inner disk region. In this contribution we will focus on the main recent observational evidences for time variable funnel flows and compare them with model predictions.

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The somatic-visceral subdivision of the embryonic mesoderm is initiated by dorsal gradient thresholds in Drosophila

Development ◽

10.1242/dev.121.7.2107 ◽

1995 ◽

Vol 121 (7) ◽

pp. 2107-2116 ◽

Cited By ~ 5

Author(s):

K. Maggert ◽

M. Levine ◽

M. Frasch

Keyword(s):

Expression Pattern ◽

Target Genes ◽

Substantial Reduction ◽

Drosophila Embryo ◽

Germ Layers ◽

Cardiac Tissues ◽

Early Drosophila Embryo ◽

Dorsal Ectoderm ◽

Lateral Mesoderm

The maternal dorsal regulatory gradient initiates the differentiation of the mesoderm, neuroectoderm and dorsal ectoderm in the early Drosophila embryo. Two primary dorsal target genes, snail (sna) and decapentaplegic (dpp), define the limits of the presumptive mesoderm and dorsal ectoderm, respectively. Normally, the sna expression pattern encompasses 18–20 cells in ventral and ventrolateral regions. Here we show that narrowing the sna pattern results in fewer invaginated cells. As a result, the mesoderm fails to extend into lateral regions so that fewer cells come into contact with dpp-expressing regions of the dorsal ectoderm. This leads to a substantial reduction in visceral and cardiac tissues, consistent with recent studies suggesting that dpp induces lateral mesoderm. These results also suggest that the dorsal regulatory gradient defines the limits of inductive interactions between germ layers after gastrulation. We discuss the parallels between the subdivision of the mesoderm and dorsal ectoderm.

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ladybird, a new component of the cardiogenic pathway in Drosophila required for diversification of heart precursors

Development ◽

10.1242/dev.124.18.3471 ◽

1997 ◽

Vol 124 (18) ◽

pp. 3471-3479 ◽

Cited By ~ 10

Author(s):

K. Jagla ◽

M. Frasch ◽

T. Jagla ◽

G. Dretzen ◽

F. Bellard ◽

...

Keyword(s):

Late Phase ◽

Heart Cell ◽

Heart Cells ◽

Neurogenic Genes ◽

Pericardial Cells ◽

Wingless Signaling ◽

Heart Formation ◽

Repeated Pattern ◽

Pericardial Cell

The embryonic heart precursors of Drosophila are arranged in a repeated pattern of segmental units. There is growing evidence that the development of individual elements of this pattern depends on both mesoderm intrinsic patterning information and inductive signals from the ectoderm. In this study, we demonstrate that two homeobox genes, ladybird early and ladybird late, are involved in the cardiogenic pathway in Drosophila. Their expression is specific to a subset of cardioblast and pericardial cell precursors and is critically dependent on mesodermal tinman function, epidermal Wingless signaling and the coordinate action of neurogenic genes. Negative regulation by hedgehog is required to restrict ladybird expression to two out of six cardioblasts in each hemisegment. Overexpression of ladybird causes a hyperplasia of heart precursors and alters the identity of even-skipped-positive pericardial cells. Loss of ladybird function leads to the opposite transformation, suggesting that ladybird participates in the determination of heart lineages and is required to specify the identities of subpopulations of heart cells. We find that both early Wingless signaling and ladybird-dependent late Wingless signaling are required for proper heart formation. Thus, we propose that ladybird plays a dual role in cardiogenesis: (i) during the early phase, it is involved in specification of a segmental subset of heart precursors as a component of the cardiogenic tinman-cascade and (ii) during the late phase, it is needed for maintaining wingless activity and thereby sustaining the heart pattern process. These events result in a diversification of heart cell identities within each segment.

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The Localization of Alkaline Phosphatase during the Post-embryonic Development of Drosophila melanogaster

Journal of Cell Science ◽

10.1242/jcs.s3-91.13.89 ◽

1950 ◽

Vol s3-91 (13) ◽

pp. 89-105

Author(s):

T. YAO

Keyword(s):

Alkaline Phosphatase ◽

Drosophila Melanogaster ◽

Embryonic Development ◽

Phosphatase Activity ◽

Alkaline Phosphatase Activity ◽

Larval Instar ◽

Morphological Evidence ◽

Simultaneous Increase ◽

Endocrine Organs ◽

Pericardial Cells

1. The localization of alkaline phosphatase during the post-embryonic development of Drosophila melanogaster has been described. 2. In the larvae, nuclear phosphatase is always demonstrable, but cytoplasmic phosphatase shows a more restricted distribution. Salivary glands, mid-gut, Malpighian tubes, and pericardial cells are richest in cytoplasmic phosphatase. 3. The larva prior to puparium formation is characterized by a decrease of alkaline phosphatase in the internal organs with a simultaneous increase in the hypodermis. 4. The phosphatase data support the view that the prepupa is actually an intrapuparial larval instar. 5. Pupation is accompanied, by a very noticeable increase of alkaline phosphatase which is mainly confined to the cytoplasm. The high enzyme activity is maintained for the first day and a half after head eversion: there is a subsequent decline until at the time of emergence most organs are inactive. However, certain organs retain their alkaline phosphatase activity. 6. As in embryogenesis, alkaline phosphatase seems to be more concerned with histo-differentiation than with chemo-differentiation. 7. Alkaline phosphatase (and also acid phosphatase) actively participates in the process of histolysis or cellular degeneration. 8. The alkaline phosphatase activity of the pericardial cells, together with other morphological evidence, indicates that these cells are endocrine organs which play important roles in Drosophila metamorphosis. 9. Cytochemical evidence suggests that alkaline phosphatase in Drosophila is probably playing a part in the carriage of organic substances across the membrane barrier.

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Positive and negative signals modulate formation of the Xenopus cement gland

Development ◽

10.1242/dev.122.9.2739 ◽

1996 ◽

Vol 122 (9) ◽

pp. 2739-2750 ◽

Cited By ~ 5

Author(s):

L. Bradley ◽

D. Wainstock ◽

H. Sive

Keyword(s):

Potent Inhibitor ◽

Neural Plate ◽

Cement Gland ◽

Cell Interactions ◽

Potent Inducer ◽

Negative Cell ◽

Complex Process ◽

Dorsal Mesoderm ◽

Dorsal Ectoderm ◽

Early Gastrula

The cement gland is a simple secretory organ that marks the anterior-most dorsal ectoderm in Xenopus embryos. In this study, we examine the timing of cement gland induction and the cell interactions that contribute to cement gland formation. Firstly, we show that the outer ectodermal layer, from which the cement gland arises, becomes specified as cement gland by mid-gastrula. Curiously, at early gastrula, the inner layer of the dorsal ectoderm, which does not contribute to the mature cement gland, is strongly and transiently specified as cement gland. Secondly, we show that the mid-gastrula dorsoanterior yolky endoderm, which comes to underlie the cement gland primordium, is a potent inducer of cement gland formation and patterning. The cement gland itself has an anteroposterior pattern, with the gene XA expressed only posteriorly. Dorsoanterior yolky endoderm greatly enhances formation of large, patterned cement glands in partially induced anterodorsal ectoderm, but is unable to induce cement gland in naive animal caps. Neural tissue is induced less frequently than cement gland by the dorsoanterior yolky endoderm, suggesting that the endoderm induces cement gland directly. Thirdly, we demonstrate that the ventral ectoderm adjacent to the cement gland attenuates cement gland differentiation late during gastrulation. The more distant ventral mesendoderm is also a potent inhibitor of cement gland formation. These are the first data showing that normal ventral tissues can inhibit cement gland differentiation and suggest that cement gland size and position may be partly regulated by negative signals. Previous work has shown that cement gland can be induced by neural plate and by dorsal mesoderm. Together, these data suggest that cement gland induction is a complex process regulated by multiple positive and negative cell interactions.

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