Hensen's Node Research Articles

Embryonic development of teleost Brycon orbignyanus.

Brycon orbignyanus is an important large teleost that is currently on the list of endangered species, therefore studies on its reproductive biology and embryology are fundamental to help species conservation and recovery. The objective of this research was to characterize the events that occur during extrusion, fertilization and embryonic development of the species. The samples were collected at predetermined times, fixed and processed for light microscopy and scanning electron microscopy. The greenish oocytes were spherical, had translucent chorion and a mean diameter of 1.3±0.11 mm. The eggs had well defined animal and vegetative poles approximately 18 min post-fertilization. Stages from 2 to 128 blastomeres occurred between 20 min and 3 h post-fertilization (hPF), when the morula was characterized. The blastula stage was observed between 2 and 3 hPF, and the gastrula between 3 and 7 hPF, when the embryonic shield emerged and the cellular migration with the consequent formation of epiblast and hypoblast. At 8 hPF, the formation of the neural tube, above the notochord and the encephalic region, was observed, delimiting the forebrain, mesencephalon and rhombencephalon regions. From 11 hPF onward, the optic vesicle was formed close to the forebrain and the embryo tail was well developed. The optic vesicle was observed from 12 hPF onward, and the tail showed an intense movement that culminated with the rupture of the chorion and consequent hatching of the larva at 13 hPF and 27°C.

Diagnosis, Surgical Management, and Postoperative Care for the Neonate With Sacrococcygeal Teratoma

Background Neonatal sacrococcygeal teratoma is rare occurring in approximately one in 35,000 live births with a female predominance (3:1–4:1 ratio). It is an unusual tumor that develops before birth and arises from embryologically multipotent cells from the Hensen node, which is located in the coccyx. Sacrococcygeal teratomas generally present in two distinct fashions: newborns with large predominately external masses, which are noted in utero or at the time of delivery and are rarely malignant, and older infants and young children presenting with tumors predominately confined to the pelvis with a much higher rate of malignancy. Most sacrococcygeal teratomas are now diagnosed prenatally because of the routine obstetric ultrasonagraphy. An abnormally sized uterus is typically the first sign that a sacrococcygeal teratoma may be present. The increased-sized uterus can be due to a massive tumor or polyhydramnios. Less common presentations include maternal preeclampsia. Newborns generally present with the mass protruding from the sacral region. If detected prenatally, the neonate should be considered for abdominal delivery if the mass is greater than 5 cm in size. In addition, some develop in utero high-output cardiac failure resulting in fetal hydrops and may be candidates for in utero resection. When a prenatally diagnosed sacrococcygeal teratoma is associated with fetal hydrops, the tumor can become life-threatening to both mother and baby. A classification system has been devised by Altman et al. in 1974 and is still used today. Sacrococcygeal teratomas are categorized according to their location and severity. Type I tumors are predominately external. Type II tumors present with both internal and external components. Type III tumors are predominately hidden in the pelvis with a very small external portion. Type IV tumors are entirely hidden within the pelvis. The recommended treatment of a sacrococcygeal teratoma is complete removal of the tumor by surgery performed soon after the birth. Unfortunately, there is a significant recurrence rate of 10%–20% even with complete resection. Long-term follow-up is needed, as there is a risk of malignancy and reoccurrence. Postoperative follow-up is needed during the first several years of life as bowel and bladder functions can be affected. Children should be followed through potty training to ensure that bowel and bladder functions are normal.

An obsession with the chick.

This paper provides a brief account of some aspects of the career of Ruth Bellairs using selected examples from her research publications, with the emphasis being placed on the early stages of chick embryo development, and in particular, on cell migration. Topics include the role of Hensen's node, the vitelline membrane, the structure and segmentation of somites, the tail bud and the Wolffian duct. Her research approach has involved embryo culture, experimental surgery, transmission and scanning electron microscopy, time-lapse filming and immunostaining techniques.

Neural induction by the node and placode induction by head mesoderm share an initial state resembling neural plate border and ES cells

Around the time of gastrulation in higher vertebrate embryos, inductive interactions direct cells to form central nervous system (neural plate) or sensory placodes. Grafts of different tissues into the periphery of a chicken embryo elicit different responses: Hensen's node induces a neural plate whereas the head mesoderm induces placodes. How different are these processes? Transcriptome analysis in time course reveals that both processes start by induction of a common set of genes, which later diverge. These genes are remarkably similar to those induced by an extraembryonic tissue, the hypoblast, and are normally expressed in the pregastrulation stage epiblast. Explants of this epiblast grown in the absence of further signals develop as neural plate border derivatives and eventually express lens markers. We designate this state as "preborder"; its transcriptome resembles embryonic stem cells. Finally, using sequential transplantation experiments, we show that the node, head mesoderm, and hypoblast are interchangeable to begin any of these inductions while the final outcome depends on the tissue emitting the later signals.

Expression of hLAMP-1-Positive Particles During Early Heart Development in the Chick.

Heart development requires coordinated activity of various factors, the disturbance of which can lead to congenital heart defects. Heart lectin-associated matrix protein-1 (hLAMP-1) is a matrix protein expressed within Hensen's node at Hamburger-Hamilton (HH) stage 4, in the lateral mesoderm by HH stages 5-6 and enhanced within the left pre-cardiac field at HH stage 7. At HH stages 15-16, hLAMP-1 expression is observed in the atrioventricular canal and the outflow tract. Also, the role of hLAMP-1 in induction of mesenchyme formation in chick heart has been well documented. To further elucidate the role of this molecule in heart development, we examined its expression patterns during HH stages 8-14 in the chick. In this regard, we immunostained sections of the heart during HH stages 8-14 with antibodies specific to hLAMP-1. Our results showed prominent expression of hLAMP-1-positive particles in the extracellular matrix associated with the pre-cardiac mesoderm, the endoderm, ectoderm as well as neuroectoderm at HH stages 8-9. After formation of the linear heart tube at HH stage 10, the expression of hLAMP-1-stained particles disappears in those regions of original contact between the endoderm and heart forming fields due to rupture of the dorsal mesocardium while their expression becomes confined to the arterial and venous poles of the heart tube. This expression pattern is maintained until HH stage 14. This expression pattern suggests that hLAMP-1 may be involved in the formation of the endocardial tube.

Fetal Cardiac Isomerism

During early embryogenesis, the body axes of embryo are not established until the appearance of primitive streak. During the formation of primitive node, the cilia inside the primitive node generate a consistent clockwise rotation and form a leftward hydrodyanamics which perfuse the left-side formation proteins into the future left side of embryo. If this dynamics is broken, different extents of persistent symmetry will be retained. Heterotaxy syndrome or isomerism are used to describe this spectrum of cardiac/visceral situs disorders. Since the left side is predetermined thereby right side, the left atrial isomerism is assumed more mature than the right atrial isomerism. In human fetus with left atrial isomerism, the heart generally are lacking of right-sided structures. The right-side structures including sinoatrial node, inferior vena cava, gall bladder are generally or often lacking. In fetuses with right atrial isomerism, the left-sided structures, such as returning pathway of pulmonary veins and spleen, are frequently absent. These features can be used as the clues of antenatal diagnosis. As for the outcome of atrial isomerism, the heart of left atrial isomerism is generally more developed and hence the outcome is better, unless persistent bradycardia and fetal hydrops occurred. Fetuses with right atrial isomerism generally manifested with double outlets of right ventricle, endocardial cushing defect, pulmonary stenosis and transposition of great arteries. These neonates have to receive 3-staged Norwood operation. The long-term survival is 70 % for neonates with right atrial isomerism and 80% of neonates with left atrial isomerism.

Calreticulin is a secreted BMP antagonist, expressed in Hensen's node during neural induction

Hensen's node is the “organizer” of the avian and mammalian early embryo. It has many functions, including neural induction and patterning of the ectoderm and mesoderm. Some of the signals responsible for these activities are known but these do not explain the full complexity of organizer activity. Here we undertake a functional screen to discover new secreted factors expressed by the node at this time of development. Using a Signal Sequence Trap in yeast, we identify several candidates. Here we focus on Calreticulin. We show that in addition to its known functions in intracellular Calcium regulation and protein folding, Calreticulin is secreted, it can bind to BMP4 and act as a BMP antagonist in vivo and in vitro. Calreticulin is not sufficient to account for all organizer functions but may contribute to the complexity of its activity.

META-GLARE: A meta-system for defining your own computer interpretable guideline system-Architecture and acquisition.

Several different computer-assisted management systems of computer interpretable guidelines (CIGs) have been developed by the Artificial Intelligence in Medicine community. Each CIG system is characterized by a specific formalism to represent CIGs, and usually provides a manager to acquire, consult and execute them. Though there are several commonalities between most formalisms in the literature, each formalism has its own peculiarities. The goal of our work is to provide a flexible support to the extension or definition of CIGs formalisms, and of their acquisition and execution engines. Instead of defining "yet another CIG formalism and its manager", we propose META-GLARE (META Guideline Acquisition, Representation, and Execution), a "meta"-system to define new CIG systems. In this paper, META-GLARE, a meta-system to define new CIG systems, is presented. We try to capture the commonalities among current CIG approaches, by providing (i) a general manager for the acquisition, consultation and execution of hierarchical graphs (representing the control flow of actions in CIGs), parameterized over the types of nodes and of arcs constituting it, and (ii) a library of different elementary components of guidelines nodes (actions) and arcs, in which each type definition involves the specification of how objects of this type can be acquired, consulted and executed. We provide generality and flexibility, by allowing free aggregations of such elementary components to define new primitive node and arc types. We have drawn several experiments, in which we have used META-GLARE to build a CIG system (Experiment 1 in Section 8), or to extend it (Experiments 2 and 3). Such experiments show that META-GLARE provides a useful and easy-to-use support to such tasks. For instance, re-building the Guideline Acquisition, Representation, and Execution (GLARE) system using META-GLARE required less than one day (Experiment 1). META-GLARE is a meta-system for CIGs supporting fast prototyping. Since META-GLARE provides acquisition and execution engines that are parametric over the specific CIG formalism, it supports easy update and construction of CIG systems.

Variability of quantitative morphogenetic parameters during early morphogenesis of the loach, Misgurnus fossilis L.

Analysis of normal variation in quantitative morphological characters during the early embryonic development of the loach, based on fixed material and individual developmental trajectories of living embryos, shows that the dorsoventral differentiation of the blastoderm proceeds in two stages. Initially, at the onset of epiboly, the sagittal (short) and transverse (long) blastoderm meridians are marked off, and only then, upon germ ring (GR) formation, differentiation between the opposite poles of the sagittal meridian takes place. The embryonic shield (ES) usually appears in the segment of the blastoderm where the radius of its external curvature reaches a maximum and, therefore, the active surface tension at the blastoderm boundary with the YSL (peri-blast) and yolk is the highest. In this case, the convergence of inner cells toward the future dorsal segment (leading to ES formation) is a mechanical consequence of surface tension anisotropy. The normal course of epiboly is associated with periodic changes in the curvature of the blastoderm external surface, with new structures (the dorsal segment, GR, and ES) are marked off only when the surface curvature becomes maximally uniform. Although the ES in most embryos appears within the initial dorsal segment, individual developmental trajectories have been traced where the GR starts to form at the dorsal pole of the blastoderm but the ES develops on its opposite site, at the point of GR closure. In both cases, GR formation is initiated at the point of convergence of centrifugal cell migration flows that arise in the marginal zone of the blastoderm upon GR initiation or closure.

Some knots in $S^1 \times S^2$ with lens space surgeries

We propose a classification of knots in S^1 x S^2 that admit a longitudinal surgery to a lens space. Any lens space obtainable by longitudinal surgery on some knots in S^1 x S^2 may be obtained from a Berge-Gabai knot in a Heegaard solid torus of S^1 x S^2, as observed by Rasmussen. We show that there are yet two other families of knots: those that lie on the fiber of a genus one fibered knot and the `sporadic' knots. All these knots in S^1 x S^2 are both doubly primitive and spherical braids. This classification arose from generalizing Berge's list of doubly primitive knots in S^3, though we also examine how one might develop it using Lisca's embeddings of the intersection lattices of rational homology balls bounded by lens spaces as a guide. We conjecture that our knots constitute a complete list of doubly primitive knots in S^1 x S^2 and reduce this conjecture to classifying the homology classes of knots in lens spaces admitting a longitudinal S^1 x S^2 surgery.

Organizers in Development.

An "organizer" is formally defined as a region, or group of cells in an embryo that can both induce (change the fate) and pattern (generate an organized set of structures) adjacent embryonic cells. To date, about four such regions have been demonstrated: the primary or Spemann organizer (Hensen's node in amniotes), the notochord, the zone of polarizing activity of the limb bud, and the mid-hindbrain boundary. Here we review the evidence for these and compare them with a few other regions which have been proposed to represent other organizers and we speculate on why so few such regions have been discovered.

Characterization of the Embryonic and Larval Development of Wild Pike-Barb (Luciobarbus esocinus) Biological Parameters, and the Possibility of Breeding

This study was conducted to obtain preliminary data on the possibility of breeding this species through artificial insemination and to determine the incubation period at different temperatures (°C) of hatchery water [20 (A1), 22 (A2), 25 (A3) and 26 (A4); (±1)] and to determine the morphological and larval growth parameters of L. esocinus. The blastoderm formed an embryonic shield 43 h (A1 and A2) and 36 h (A3 and A4) after insemination. The eggs hatched after 113 h (A1 and A2) and 61.5 h (A3 and A4) after insemination, and new larvae were observed. Exposing the newly fertilized eggs to various temperatures during the incubation period resulted in significantly longer duration of embryo formation, egg hatching and yolk sac consumption (h) at 20°C and 22°C than at 25°C and 26°C (P < 0.05). No significant differences were observed between eggs exposed to 20°C and 22°C and those exposed to 25°C and 26°C (P > 0.05). However, significant differences in day-degree of hatching were observed among all the groups (P < 0.05).

Sacrococcygeal teratoma in a female newborn with clinical features of trisomy 13: a case report from Central Africa

IntroductionThe objective of this report is to describe the first patient presenting clinical features of trisomy 13 in association with a sacrococcygeal teratoma.Case presentationWe present the case of a Congolese female infant born with bilateral cleft lip and palate, hypotelorism, microcephaly, and capillary hemangioma on her face. She presented with a large sacrococcygeal mass (15.0 cm ×12.0 cm ×5.0 cm) with a cystic consistency and a positive transillumination.ConclusionThis observation suggests that overexpression of certain genes on chromosome 13 may lead to tumor formation from remnant cells of Hensen’s node.

On the degeneration of tunnel numbers under a connected sum

We show that, for any integer $n\ge 3$, there is a prime knot $k$ such that (1) $k$ is not meridionally primitive, and (2) for every $m$-bridge knot $k'$ with $m\leq n$, the tunnel numbers satisfy $t(k\# k')\le t(k)$. This gives counterexamples to a conjecture of Morimoto and Moriah on tunnel number under connected sum and meridionally primitive knots.

An explanatory factor analysis on procurement risk and its multi-dimensional consequences

Article history: Received March 15, 2014 Received in revised format 28 July 2014 Accepted August 29 2014 Available online September 7 2014 Procurement risks analysis is a crucial study in supply chain risk management. According to the phenomenon of snow ball effect, if a risk occurs at the primitive node between buyer and supplier, it will be strengthened and extended throughout the entire network. Hence, it can have more disruptive influences comparing with risks that happen in further nodes. In this paper, through a case study, the most important risk factors and its multi-dimensional consequences in procurement risk analysis is derived from the literature review and implementing a Delphi method that takes into account the nine risks factors and 39 preliminary variables as risk consequences. The nine risk factors are limits of global communication, packaging and transportation, procedures and standards, sanction, supply of equipment, price of equipment, Communication, management of technology and delivery mistakes. © 2015 Growing Science Ltd. All rights reserved.

Forkhead box protein A2 and T helper type 2-mediated pulmonary inflammation.

The transcription factor forkhead box protein A2 (FOXA2, also known as hepatocyte nuclear factor 3β or transcription factor 3β), has been found to play pivotal roles in multiple phases of mammalian life, from the early development to the organofaction, and subsequently in homeostasis and metabolism in the adult. In the embryonic development period, FOXA2 is require d for the formation of the primitive node and notochord, and its absence results in embryonic lethality. Moreover, FOXA2 plays an important role not only in lung development, but also in T helper type 2 (Th2)-mediated pulmonary inflammation and goblet cell hyperplasia. In this article, the role of FOXA2 in lung development and Th2-mediated pulmonary inflammation, as well as in goblet cell hyperplasia, is reviewed. FOXA2 deletion in airway epithelium results into Th2-mediated pulmonary inflammation and goblet cell hyperplasia in developing lung. Leukotriene pathway and signal transducers and activators of transcription 6 pathway may mediate this inflammation through recruitment and activation of denditric cell during lung developments. FOXA2 is a potential treatment target for lung diseases with Th2 inflammation and goblet cell hyperplasia, such as asthma and chronic obstructive pulmonary disease.

Identification of emergent motion compartments in the amniote embryo

The tissue scale deformations (≥1mm) required to form an amniote embryo are poorly understood. Here, we studied ∼400 μm-sized explant units from gastrulating quail embryos. The explants deformed in a reproducible manner when grown using a novel vitelline membrane-based culture method. Time-lapse recordings of latent embryonic motion patterns were analyzed after disk-shaped tissue explants were excised from three specific regions near the primitive streak: 1) anterolateral epiblast, 2) posterolateral epiblast, and 3) the avian organizer (Hensen's node). The explants were cultured for 8 hours—an interval equivalent to gastrulation. Both the anterolateral and the posterolateral epiblastic explants engaged in concentric radial/centrifugal tissue expansion. In sharp contrast, Hensen's node explants displayed Cartesian-like, elongated, bipolar deformations—a pattern reminiscent of axis elongation. Time-lapse analysis of explant tissue motion patterns indicated that both cellular motility and extracellular matrix fiber (tissue) remodeling take place during the observed morphogenetic deformations. As expected, treatment of tissue explants with a selective Rho-Kinase (p160ROCK) signaling inhibitor, Y27632, completely arrested all morphogenetic movements. Microsurgical experiments revealed that lateral epiblastic tissue was dispensable for the generation of an elongated midline axis— provided that an intact organizer (node) is present. Our computational analyses suggest the possibility of delineating tissue-scale morphogenetic movements at anatomically discrete locations in the embryo. Further, tissue deformation patterns, as well as the mechanical state of the tissue, require normal actomyosin function. We conclude that amniote embryos contain tissue-scale, regionalized morphogenetic motion generators, which can be assessed using our novel computational time-lapse imaging approach. These data and future studies—using explants excised from overlapping anatomical positions—will contribute to understanding the emergent tissue flow that shapes the amniote embryo.

N-Cadherin Locks Left-Right Asymmetry by Ending the Leftward Movement of Hensen’s Node Cells

The stereotypic left-right (LR) asymmetric distribution of internal organs is due to an asymmetric molecular cascade in the lateral plate mesoderm (LPM) that is originated at the embryonic node. In chicken embryos, molecular asymmetries at Hensen's node are created by leftward cell movements that occur transiently. What terminates these movements, and, moreover, what is the impact of prolonging them on the LR asymmetry cascade? We show that leftward movements last longer when N-cadherin function is blocked and cease prematurely when N-cadherin is overexpressed on the right side of the node. The prolonged leftward movements lead to loss of asymmetric expression of fgf8 and nodal at the node region. This originates an abnormal expression of the asymmetric genes cer1 and snai1 in the LPM, resulting in mispositioned hearts. We conclude that N-cadherin stops the leftward cell movements and that this termination isan essential step in the establishment of LR asymmetry.

On manifolds with multiple lens space fillings

An irreducible \(3\)-manifold with torus boundary either is a Seifert fibered space or admits at most three lens space fillings according to the Cyclic Surgery Theorem. We examine the sharpness of this theorem by classifying the non-hyperbolic manifolds with more than one lens space filling, classifying the hyperbolic manifolds obtained by filling of the Minimally Twisted 5 Chain complement that have three lens space fillings, showing that the doubly primitive knots in \(S^3\) and \(S^1 \times S^2\) have no unexpected extra lens space surgery, and showing that the Figure Eight Knot Sister Manifold is the only non-Seifert fibered manifold with a properly embedded essential once-punctured torus and three lens space fillings.

The chicken left right organizer has nonmotile cilia which are lost in a stage‐dependent manner in the talpid3 ciliopathy

Motile cilia are an essential component of the mouse, zebrafish, and Xenopus laevis Left Right Organizers, generating nodal flow and allowing the reception and transduction of mechanosensory signals. Nonmotile primary cilia are also an important component of the Left Right Organizer's chemosensory mechanism. It has been proposed in the chicken that signaling in Hensen's node, the Left Right Organizer of the chicken, is independent of cilia, based on a lack of evidence of motile cilia or nodal flow. It is speculated that the talpid3 chicken mutant, which has normal left–right patterning despite lacking cilia at many stages of development, is proof of this hypothesis. Here, we examine the evidence for cilia in Hensen's node and find that although cilia are present; they are likely to be immotile and incapable of generating nodal flow. Furthermore, we find that early planar cell polarity patterning and ciliogenesis is normal in early talpid3 chicken embryos. We conclude that patterning and development of the early talpid3 chicken is normal, but not necessarily independent of cilia. Although it appears that Hensen's node does not require motile cilia or the generation of motile flow, there may remain a requirement for cilia in the transduction of SHH signaling.ResultsFOXJ1 is expressed at low levels in the chicken node incompatible with motile cilia generationShort cilia are present in the mesodermal cells of the chicken nodeTalpid3 chicken embryos have normal VANGL2 localization early in developmentTalpid3 chicken embryos have primary cilia early in development