Hensen's Node Research Articles

Bilateral cellular flows display asymmetry prior to left-right organizer formation in amniote gastrulation.

Bilaterians are defined by a bilaterally symmetrical body plan. Vertebrates exhibit external bilateral symmetry but display left-right (LR) asymmetry in their internal organs. Amniote embryos switch patterning of internal organs from bilateral symmetry to LR-asymmetry, but the initiation of LR symmetry breaking is not well understood. Using chick embryo as a model system due to its easy accessibility and similarity to human development, our biophysical approaches to quantify cellular flows inferred that LR symmetry breaking occurs prior to the formation of Hensen's node, a LR organizer, which serves as a signaling center for LR patterning-gene programs. Our work demonstrates that quantitative biophysical parameters can help unravel the initiation of LR symmetry breaking, suggesting involvement of physical mechanisms in this critical biological patterning process.

Pyridaben inhibits cell cycle progression and delays early embryonic development in zebrafish (Danio rerio)

Pyridaben is a broad-spectrum, contact-killing acaricide that can be used to control a variety of harmful food and plant mites. Pyridaben displays cardiotoxicity and liver toxicity toward fish, but the effects on fish embryonic development have not been characterized. We exposed early zebrafish embryos to 20, 30, and 40 μg/L concentrations of pyridaben. The exposure caused developmental abnormalities, including delayed embryonic shield formation, yolk sac resorption, decreases in body length, reduced pigmentation, and delays in hatching. Pyridaben caused a significant increase in the transcription level of the endoderm marker foxa2, but the transcription levels of the ectoderm development marker foxb1a and the mesoderm development marker snaila were not significantly altered. The transcription levels of the genes SOX17 in early embryos were significantly reduced. After exposure to pyridaben, catalase (CAT) activity and glutathione (GSH) content were increased, and cyclin D1, that is involved in early embryonic development, was abnormally expressed. This study shows that pyridaben causes anomalous development in zebrafish embryos by interfering with the cell cycle order of early embryonic development and inducing excessive oxidative stress. Colivelin, an agonist of the STAT3 signaling pathway, acted as a salvage drug to restore the cell cycle order during embryonic development following exposure to pyridaben. Thus, the toxic effects may be caused by pyridaben’s regulation of the STAT3 signaling pathway.

A gene regulatory network for neural induction.

During early vertebrate development, signals from a special region of the embryo, the organizer, can redirect the fate of non-neural ectoderm cells to form a complete, patterned nervous system. This is called neural induction and has generally been imagined as a single signalling event, causing a switch of fate. Here, we undertake a comprehensive analysis, in very fine time course, of the events following exposure of competent ectoderm of the chick to the organizer (the tip of the primitive streak, Hensen's node). Using transcriptomics and epigenomics we generate a gene regulatory network comprising 175 transcriptional regulators and 5614 predicted interactions between them, with fine temporal dynamics from initial exposure to the signals to expression of mature neural plate markers. Using in situ hybridization, single-cell RNA-sequencing, and reporter assays, we show that the gene regulatory hierarchy of responses to a grafted organizer closely resembles the events of normal neural plate development. The study is accompanied by an extensive resource, including information about conservation of the predicted enhancers in other vertebrates.

Surgical management of neonatal Sacrococcygeal teratoma in a tertiary care center of Eastern Nepal: An observational cross-sectional study in a resource-limited setting

BackgroundDespite being an uncommon tumor, sacrococcygeal teratoma (SCT) is the most prevalent among newborns. SCT comprises tissue generated from many germ layers. It develops from Hensen's node's totipotent cells. The objective of our study was to determine the epidemiology and management of neonatal sacrococcygeal teratoma in the tertiary care center of Nepal in a resource-limited setting. MethodsIt is a retrospective cross-sectional study that includes all cases of neonatal SCT admitted and treated in the department of Pediatrics and Neurosurgery, B. P. Koirala Institute of Health Sciences, over the period from July 2017 to December 2021. The primary endpoint was to determine the epidemiological profile of neonates with SCT, their surgical management, and their complications. ResultsOur investigation included a total of 15 patients. Nine of the fifteen cases were female (60%) and six were male (40%). Six newborns (40%) were diagnosed with SCT antenatally and were referred to our tertiary care institution for delivery. The size of the SCT varied ranging from less than 8 cm to greater than 11 cm. Surgical excision was performed. Only 1 case (6.6 %) expired due to complications. ConclusionsIn our context, SCT is the most prevalent tumor in babies. Even with limited resources, great surgical results with a high level of satisfaction in patients and caregivers may be accomplished with sound clinical judgment and competency of the surgeons and clinicians. Prenatal diagnosis should be encouraged.

The embryonic node behaves as an instructive stem cell niche for axial elongation

In warm-blooded vertebrate embryos (mammals and birds), the axial tissues of the body form from a growth zone at the tail end, Hensen's node, which generates neural, mesodermal, and endodermal structures along the midline. While most cells only pass through this region, the node has been suggested to contain a small population of resident stem cells. However, it is unknown whether the rest of the node constitutes an instructive niche that specifies this self-renewal behavior. Here, we use heterotopic transplantation of groups and single cells and show that cells not destined to enter the node can become resident and self-renew. Long-term resident cells are restricted to the posterior part of the node and single-cell RNA-sequencing reveals that the majority of these resident cells preferentially express G2/M phase cell-cycle-related genes. These results provide strong evidence that the node functions as a niche to maintain self-renewal of axial progenitors.

Jointly primitive knots and surgeries between lens spaces

Jointly primitive knots and surgeries between lens spaces

Embryonic and Larval Development of Thai Pangas Pangasianodon Hypopthalmus (Sauvage, 1878) Under Hatchery Condition

The embryonic and larval development of Pangasianodon hypophthalmus was investigated during peak spawning periods (May-July 2019). The fertilized eggs were adhesive and spherical with a greenish‐brown egg capsule. The yolk sac was yellowish‐brown in color and 1.00–1.70 mm in diameter. The first cleavage stage, embryonic shield, head, tail region, neural grooves and somites were apparent after fourteen hours post‐fertilization. The ranges of incubation period were from 18.00-20.00 hrs at a temperature of 26-30°C. The newly hatched larvae were transparent and light yellowish in color with a body length of 2.98–3.10 mm. Eye pigment appeared and the heart started to work within 12-16 hrs of hatching. The mouth became well developed at the age of 24 hrs; barbules were prominent, elongated and look like threads. The yolk sac was fully absorbed and the palatine teeth were fully increased during the 3 days pro‐larval stage. The stomach became functional and aerial respiration started after 3 days of larval development. After 72 hrs, the young fry was well‐developed, and appeared an adult, and length was measured up to 7.20±0.02 mm. When daily ration of pangas larvae is insufficient cannibalism was recorded. This study must be supportive for researcher and nursery owner on the biology and ecology of the fish, which might be helpful for appropriate measure of sustainable nursery, rearing and management technology of pangas. Bangladesh J. Zool. 49(1): 147-159, 2021

SACROCOCCYGEAL TERATOMA : A RARE ENTITY

Teratomas are composed of tissues derived from ectoderm, mesoderm, and endoderm. Sacrococcygeal teratomas are developed from the totipotential cells of primitive knot which is a remnant of the primitive streak in the coccygeal region. With the incidence of 1/35000–1/40000 live birth, sacrococcygeal teratoma is considered as the most common germ cell tumor in the neonatal period and infancy. Sacrococcygeal teratoma shows female preponderance with male to female ratio 1:4 . AIMS AND OBJECTIVES: To study clinical presentation and management of sacrocoocygeal teratoma in paediatric age group. CASE REPORT: A seven year old child presented to our tertiary care hospital with a swelling of size 20 x 10 cm in sacrococcygeal region Which was initially smaller in size about 6 X 3cm and have gradually progressed to the present size swelling was soft to rm in consistency, patient was subject to MRI pelvis which was suggestive of solid cystic swelling in sacrococcygeal region of size 20 X 15 cm with maintained fat planes with rectum and adjacent organs. Patients was subjected to surgery in which the teratoma was removed of size 20 x 15 cm along with coccygectomy was done intraoperatively there was no involvement of rectum or other organs or pelvic walls. Child recovered well post operatively and the histopathological report conrmed the diagnosis of sacrococcygeal teratomawith solid cytic compoments.

A New Systematic GDI Circuit Synthesis Using MUX Based Decomposition Algorithm and Binary Decision Diagram for Low Power ASIC Circuit Design

The advances in the new process technology characteristically come with a multitude of new design variables and hence a new set of challenges for the designers to understand the impact of circuit design. During the last decade, widespread deliberations have been specified to the usage of Gate Diffusion Input (GDI) networks in the design of digital core systems; however the logic design has been constructed using transistor-level. Till now there is no specific approach is available for synthesizing GDI circuit that incorporated the impact of signal arrangement and circuit technology. Creation of standard cell library for GDI technique becomes an utmost imperative. In this research work, a regimented synthesis algorithm have been proposed to minimize power and augment performance of the digital circuits through two approaches MUX based decomposition algorithm and Binary Decision Diagram (BDD). The primitive nodes are implemented by GDI logic and CMOS logic for level restoration circuit. This research work is targeted to design sub-micron GDI library which is suitable for the 180 ​nm and 90 ​nm 6-metal layer CMOS n-well process which is offered by MOSIS. The principal focus is to engender a comprehensive library including the core number of essential primitive cells, depicting the detailed layout and transistor-level schematic views of every cell in 180nm and 90 ​nm process, in order to use them as a completely synthesizable library. The signal connectivity models for GDI are presented using MUX and BDD approach. The synthesis of ISCAS Combinational bench mark circuit in CMOS, PTL and GDI technique is also examined in this work along with buffer inclusion procedure for GDI technique.

Temporal Modulations of NODAL, BMP, and WNT Signals Guide the Spatial Patterning in Self-Organized Human Ectoderm Tissues

Summary Developmental biology studies using model organisms suggest that the emergence of spatial patterning in the ectoderm is mediated by the morphogen gradients. However, it is still unclear whether the morphogen gradient is necessary and dominates the cell spatial patterning, particularly in human genetic background. Here, we demonstrate that human pluripotent stem cells can self-organize to concentric rings of all major cell types in ectoderm when cultured on micropatterned surfaces in a chemically defined condition. We reveal that modulating the dynamics of NODAL, BMP, and WNT signals is sufficient to control the spatial order of different cell types. Our mathematical model suggests that changes in wavelength and phase of signaling patterns formed via reaction-diffusion may be the mechanism by which temporal information is translated into spatial information. Together, our work demonstrates that in vitro human ectoderm microtissues have great potential in understanding the mechanisms of early-stage human development.

Primary lymph node gastrinoma: a case report and review of the literature

BackgroundGastrinoma is a rare form of neuroendocrine neoplasm. The presence of a primary lymph node localization of gastrinoma is a much debated and controversial topic in the literature, as regards whether these cases represent metastatic disease from an as yet unidentified primary tumor, or the de novo occurrence of a gastrinoma in a lymph node.Case presentationWe report the case of a 24-year-old male with intense epigastric pain treated at the beginning with high dose proton pump inhibitors. Further workup with CT and subsequent laparotomy revealed a single peripancreatic lymph node. Histological examination highlighted a well-differentiated neuroendocrine tumor.ConclusionThis case underlines that the primitive lymph node gastrinoma is a distinct nosological entity with a precise location in the context of rare neuroendocrine tumors that should be considered when specific symptoms are associated with the identification of isolated lymph nodes, after excluding any possible primitive locations of neoplastic localization.

A Vague Gluteal Swelling in a Neonate: Challenges in Its Diagnosis and Management. Short Title-Sacroccoygeal Teratoma

Sacro coccygeal teratoma (SCT) is the most common extra gonadal neoplasm in the pre sacral area occurring in neonatal period. They mostly occur in the midline with a female preponderance. They are usually attached to coccyx, They are believed to be arising from totipotent cells that originate from primitive knot (Hensen’s node), hence are usually attached to coccyx. Infection in a sacrococcygeal teratoma has been rarely reported. Here is a report of a case of vague gluteal mass in a neonate and challenges in its diagnosis and management.

Морфологические особенности черноморского калкана (Scophthalmus maeoticus) в период эмбрионального развития

Черноморский калкан Scophthalmus maeoticus (Pallas, 1814) — ценный промысловый вид рыб и перспективный объект промышленной марикультуры. Потенциальная плодовитость калкана оценивается в 3–13 млн икринок, однако смертность потомства на ранних стадиях развития в море очень высока (до 90 %). В природе пелагическая икра калкана после оплодотворения поднимается к поверхностному слою моря через 2–3 ч. Она является частью нейстона до вылупления, и эмбриогенез происходит в поверхностных водах. Калкан наиболее уязвим на ранних стадиях своего развития: практически незащищённый эмбрион подвергается разнообразным неблагоприятным воздействиям. Выживаемость и физиологическое состояние личинок на этапе вылупления и до перехода к экзогенному питанию зависят от нормы морфологических характеристик зародышей в процессе их развития. Целью нашей работы было изучить нормы изменений морфологических характеристик калкана в период эмбриогенеза. Представлены результаты морфологического анализа стадий развития калкана от оплодотворения икры до выклева на основании исследования интактных икринок (более 2000 экз.) из разных партий, инкубированных в экспериментальных условиях. Для детального исследования морфологических структур эмбрионов проведена их фото- и видеосъёмка с помощью цифровой фотокамеры Canon PowerShot A720, подсоединённой к стереомикроскопу МБС-10 при увеличении 8×4, и аналоговой видеокамеры, подсоединённой к инвертированному микроскопу Nikon Eclipse TS100 при увеличении ×4, ×10, ×40. Морфологические особенности, характерные для последовательных стадий развития черноморского калкана (до и после оплодотворения, дробления, бластуляции, гаструляции, эпиболии и нейруляции, вплоть до выклева), представлены серией цифровых фотографий с описанием трансформирующихся эмбриональных структур. Оплодотворённые пелагические икринки калкана, покрытые прозрачными оболочками, имеют диаметр от (1,26 ± 0,14) до (1,31 ± 0,15) мм, равномерно распределённый желток и одну круглую прозрачную жировую каплю 0,20–0,21 мм в диаметре, расположенную в верхней части желтка. Временны́е интервалы эмбрионального развития калкана в оптимальном для его эмбриогенеза температурном диапазоне (+14…+16 °C) представлены в единицах относительного времени (временнόго отрезка от оплодотворения до момента появления структуры, выраженного в процентах от общей длительности эмбриогенеза, % RT). Дробление начинается в возрасте 2,5 % RT. Десинхронизация деления клеток зародыша калкана, свидетельствующая о начале их дифференциации, наступает между 6-м и 7-м делением; бластодиск насчитывает около 128 бластомеров с плотными межклеточными контактами. В течение 10–11-го митотического деления (512–1024 клеток, около 12 % RT) происходит формирование желточного синцитиального слоя, контролирующего эпиболию, спецификацию клеток и морфогенез зародыша. В процессе гаструляции образуется зародышевое кольцо (21 % RT), от которого около 25 % RT выделяется зародышевый щиток. К 31 % RT достигается 50 % эпиболии. В период 40–45 % RT на протяжении 70–75 % эпиболии возникает нейральный киль, различимы нотохорда и глазные пузыри, начинается сегментация, появляется Купферов пузырёк. К завершению эпиболии (49 % RT) сформированы глазные бокалы, в туловище эмбриона более 20 пар сомитов. К 60 % RT исчезает Купферов пузырёк и образуется хвостовая почка, в глазных бокалах формируются линзовые плакоды. К 65 % RT происходит вакуолизация нотохорды, образуются миотомы и начинается рост хвостового отдела. К 70–75 % RT хвостовой отдел туловища эмбриона отделяется от желточного мешка. Около 80 % RT начинается нейромышечная моторика эмбриона; сердце слабо пульсирует; хвост эмбриона охватывает более 60 % поверхности желточного мешка; дифференцируются ксантофоры, придающие телу эмбриона розоватый оттенок. К 90–95 % RT у эмбриона калкана чётко очерчены непигментированные глазные чаши с хрусталиками; образовано по 3 симметричные слуховые камеры с отолитами; в туловище 33–38 сомитов; в дерме присутствуют меланофоры и ксантофоры; эмбрион совершает резкие движения хвостовым отделом и туловищем. Перед выклевом оболочка икринки становится эластичной, растягивается и разрывается в области головы. При +14…+16 °C выклев наступает через 114–94 ч после оплодотворения соответственно. У выклюнувшейся билатерально-симметричной личинки калкана (со стандартной длиной тела от (2,53 ± 0,13) до (2,91 ± 0,10) мм) сформированы все органы, глаза непигментированы, кишечный тракт закрыт; в течение 3–5 суток она развивается за счёт желточных запасов. Описания морфологических изменений эмбриона калкана при правильном развитии могут быть использованы для разработки критериев оценки качества развивающейся икры как в естественной среде обитания, так и в условиях культивирования.

Topo2Vec: A Novel Node Embedding Generation Based on Network Topology for Link Prediction

Link prediction of a scale-free network has become relevant for problems relating to social network analysis, recommendation system, and in the domain of bioinformatics. In recently proposed approaches, the sampling of nodes of a network is done by simulating random walk. The generated node samples are used to train a neural network to learn the contextual information through an embedding vector. This method has gained popularity as the embedding vector is produced from the primitive node adjacency information and has achieved an outstanding performance. In this article, a naive and scalable approach for generating the node samples based on the principle of goal-oriented greedy searching has been proposed. The generated node samples have low noisy structures, which can represent the relation of edges of the network in a better way, compared to the state-of-the-art methods. Consequently, better representation of feature embedding of nodes of the network is generated from the samples. The learned feature vectors are used for solving the link prediction problem using a pairwise kernel support vector machine (SVM) classifier, which is computationally and spatially expensive in nature. Therefore, as an alternative, we have chosen to deploy a random forest (RF) classifier with a new algebraic operation to obtain the symmetric pairwise feature representation of a node pair. We demonstrated the efficacy of the proposed Topo2vec by testing it against the state-of-the-art network context generation algorithms in several real-world networks. Altogether, the proposed Topo2vec algorithm is a new method for solving the link prediction problem with entirely different settings.

Matrix-filled microcavities in the emerging avian left-right organizer.

Hensen node of the amniote embryo plays a central role in multiple developmental processes, especially in induction and formation of axial organs. In the chick, it is asymmetrical in shape and has recently been considered to represent the left-right organizer. As mechanisms of breaking the initial left-right symmetry of the embryo are still ill-understood, analyzing the node's microarchitecture may provide insights into functional links between symmetry breaking and asymmetric morphology. In the course of a light- and electron-microscopic study addressing this issue we discovered novel intercellular matrix-filled cavities in the node of the chick during gastrulation and during early neurulation stages; measuring up to 45 μm, they are surrounded by densely packed cells and filled with nanoscale fibrils, which immunostaining suggests to consist of the basement membrane-related proteins fibronectin and perlecan. The cavities emerge immediately prior to node formation in the epiblast layer adjacent to the tip of the primitive streak and later, with emerging node asymmetry, they are predominantly located in the right part of the node. Almost identical morphological features of microcavities were found in the duck node. We address these cavities as "nodal microcavities" and propose their content to be involved in the function of the avian node by mediating morphogen signaling and storage.

Migrasomes provide regional cues for organ morphogenesis during zebrafish gastrulation.

Migrasomes are recently identified vesicular organelles that form on retraction fibres behind migrating cells. Whether migrasomes are present in vivo and, if so, the function of migrasomes in living organisms is unknown. Here, we show that migrasomes are formed during zebrafish gastrulation and signalling molecules, such as chemokines, are enriched in migrasomes. We further demonstrate that Tspan4 and Tspan7 are required for migrasome formation. Organ morphogenesis is impaired in zebrafish MZtspan4a and MZtspan7 mutants. Mechanistically, migrasomes are enriched on a cavity underneath the embryonic shield where they serve as chemoattractants to ensure the correct positioning of dorsal forerunner cells vegetally next to the embryonic shield, thereby affecting organ morphogenesis. Our study shows that migrasomes are signalling organelles that provide specific biochemical information to coordinate organ morphogenesis.

Compound heterozygous Pkd1l1 variants in a family with two fetuses affected by heterotaxy and complex Chd

Heterotaxy and congenital heart defects associated with pathogenic variants in the PKD1L1 gene (autosomal visceral heterotaxy type 8, MIM 617205) has been reported in only four individuals from three unrelated families. We describe a further family with two affected fetuses and novel compound heterozygous pathogenic variants in PKD1L1.PKD1L1 has been shown to function in the ciliary sensation of nodal flow at the embryo primitive node and in the restriction of NODAL signalling to the left lateral.plate mesoderm, mechanisms involved in the development of laterality in vertebrates.Individuals affected with this autosomal recessive condition have variable thoracic and abdominal situs. Features of CHD and other anomalies vary between and within families.

Sacrococcygeal teratoma with unilateral renal agenesis, spinal dysraphism, lumbar hernia, CTEV and natal teeth

We report a unique case of unilateral renal agenesis, spinal dysraphism, lumbar hernia, congenital talipes equino varus, and natal teeth associated with sacrococcygeal teratoma (SCT). The occurrence of this rare association in a neonate has not been reported in the literature. The theory of defective mesenchymal precursor cells from primitive node may explain the presence of associated malformations (related to defective mesenchyme) and presence of SCT.

Knockdown of Mns1 Increases Susceptibility to Craniofacial Defects Following Gastrulation-Stage Alcohol Exposure in Mice.

MNS1 (meiosis-specific nuclear structural protein 1) is necessary for motile cilia function, such as sperm flagella or those found in the embryonic primitive node. While little is known regarding the function or expression pattern of MNS1 in the embryo, co-immunoprecipitation experiments in sperm have determined that MNS1 interacts with ciliary proteins, which are also important during development. Establishment of morphogenic gradients is dependent on normal ciliary motion in the primitive node beginning during gastrulation (gestational day [GD] 7 in the mouse, second-third week of pregnancy in humans), a critical window for face, eye, and brain development and particularly susceptible to perturbations of developmental signals. The current study investigates the role of Mns1 in craniofacial defects associated with gastrulation-stage alcohol exposure. On GD7, pregnant Mns1+/- dams were administered 2 doses of ethanol (5.8g/kg total) or vehicle 4hours apart to target gastrulation. On GD17, fetuses were examined for ocular defects by scoring each eye on a scale from 1 to 7 (1=normal, 2 to 7=defects escalating in severity). Craniofacial and brain abnormalities were also assessed. Prenatal alcohol exposure (PAE) significantly increased the rate of defects in wild-type fetuses, as PAE fetuses had an incidence rate of 41.18% compared to a 10% incidence rate in controls. Furthermore, PAE interacted with genotype to significantly increase the defect rate and severity in Mns1+/- (64.29%) and Mns1-/- mice (92.31%). PAE Mns1-/- fetuses with severe eye defects also presented with craniofacial dysmorphologies characteristic of fetal alcohol syndrome and midline tissue loss in the brain, palate, and nasal septum. These data demonstrate that a partial or complete knockdown of Mns1 interacts with PAE to increase the susceptibility to ocular defects and correlating craniofacial and brain anomalies, likely though interaction of alcohol with motile cilia function. These results further our understanding of genetic risk factors that may underlie susceptibility to teratogenic exposures.

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.