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Sheeba, Caroline J. « Mechanisms of vertebrate embryo segmentation ». Seminars in Cell & ; Developmental Biology 49 (janvier 2016) : 57–58. http://dx.doi.org/10.1016/j.semcdb.2016.01.041.
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Kornberg, Thomas B., et Tetsuya Tabata. « Segmentation of the Drosophila embryo ». Current Opinion in Genetics & ; Development 3, no 4 (janvier 1993) : 585–93. http://dx.doi.org/10.1016/0959-437x(93)90094-6.
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Borman, W. H., et D. E. Yorde. « Analysis of chick somite myogenesis by in situ confocal microscopy of desmin expression. » Journal of Histochemistry & ; Cytochemistry 42, no 2 (février 1994) : 265–72. http://dx.doi.org/10.1177/42.2.8288867.
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We explored the relationship in chick embryos between somitogenesis and the onset of somite myogenesis by immunodetection of the muscle-specific intermediate filament protein desmin. Early somite desmin expression was detected by whole-mount in situ confocal microscopy. No detectable somite desmin was observed in embryos of 15 somites (Stage 12) or younger. In embryos having between 16 and 26 somites (Stages 12-15), desmin could be detected in somites positioned increasingly more caudal in the embryo. Finally, in embryos of 27 somites (Stage 16) and older, somite desmin expression was consistently present in all but the caudal-most six somites. Although the rate of somite formation is fairly constant, the rate of observed somite desmin expression progressing caudally in the embryo is greater initially than the rate of segmentation. After an embryo has formed about 27 somites, the rate of desmin appearance parallels the rate of segmentation at a distance of about six somites. This result suggests that very early somite myogenesis is not linked to somitogenesis.
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Osborne, H. B., C. Gautier-Courteille, A. Graindorge, C. Barreau, Y. Audic, R. Thuret, N. Pollet et L. Paillard. « Post-transcriptional regulation in Xenopus embryos : role and targets of EDEN-BP ». Biochemical Society Transactions 33, no 6 (26 octobre 2005) : 1541–43. http://dx.doi.org/10.1042/bst0331541.
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EDEN (embryo deadenylation element)-dependent deadenylation is a regulatory process that was initially identified in Xenopus laevis early embryos and was subsequently shown to exist in Drosophila oocytes. Recent data showed that this regulatory process is required for somitic segmentation in Xenopus. Inactivation of EDEN-BP (EDEN-binding protein) causes severe segmentation defects, and the expression of segmentation markers in the Notch signalling pathway is disrupted. We showed that the mRNA encoding XSu(H) (Xenopus suppressor of hairless), a protein central to the Notch pathway, is regulated by EDEN-BP. Our data also indicate that other segmentation RNAs are targets for EDEN-BP. To identify new EDEN-BP targets, a microarray analysis has been undertaken.
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Sparrow, D. B., W. C. Jen, S. Kotecha, N. Towers, C. Kintner et T. J. Mohun. « Thylacine 1 is expressed segmentally within the paraxial mesoderm of the Xenopus embryo and interacts with the Notch pathway ». Development 125, no 11 (1 juin 1998) : 2041–51. http://dx.doi.org/10.1242/dev.125.11.2041.
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The presomitic mesoderm of vertebrates undergoes a process of segmentation in which cell-cell interactions mediated by the Notch family of receptors and their associated ligands are involved. The vertebrate homologues of Drosophila Δ are expressed in a dynamic, segmental pattern within the presomitic mesoderm, and alterations in the function of these genes leads to a perturbed pattern of somite segmentation. In this study we have characterised Thylacine 1 which encodes a basic helix-loop-helix class transcription activator. Expression of Thylacine is restricted to the presomitic mesoderm, localising to the anterior half of several somitomeres in register with domains of X-Delta-2 expression. Ectopic expression of Thylacine in embryos causes segmentation defects similar to those seen in embryos in which Notch signalling is altered, and these embryos also show severe disruption in the expression patterns of the marker genes X-Delta-2 and X-ESR5 within the presomitic mesoderm. Finally, the expression of Thylacine is altered in embryos when Notch signalling is perturbed. These observations suggest strongly that Thylacine 1 has a role in the segmentation pathway of the Xenopus embryo, by interacting with the Notch signalling pathway.
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Weisblat, David A. « Segmentation and commitment in the leech embryo ». Cell 42, no 3 (octobre 1985) : 701–2. http://dx.doi.org/10.1016/0092-8674(85)90264-8.
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Davidson, Duncan. « Segmentation in frogs ». Development 104, Supplement (1 octobre 1988) : 221–29. http://dx.doi.org/10.1242/dev.104.supplement.221.
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This paper reviews evidence relating to the question, at what stage in the development of the frog embryo are segment boundaries specified? Current evidence leads to the hypothesis that a spatiotemporal series of cell states leading to segmentation is continuously initiated at a position 200 to 300 μm from the posterior end of the presomitic mesoderm, about nine somite intervals before the formation of a definitive somite. The evidence suggests, though by no means proves, that segment boundaries are specified close to this time. This hypothesis relies critically on evidence concerning the effects of disruptive agents, the extent of cell mixing prior to the early gastrula stage, fate-map data, and a comparison with development in the mouse where a similar fate map can be related to morphological evidence of somitomeric segmentation. Evidence regarding the organization of the posterior, undifferentiated zone of the mesoderm in the frog embryo indicates that the cells are not proliferating rapidly, but are undergoing cell movements and rearrangements associated with caudal extension. The speculation that the segment pattern derives from inductive interactions in this region is discussed.
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Zhang, Kun, Hongbin Zhang, Huiyu Zhou, Danny Crookes, Ling Li, Yeqin Shao et Dong Liu. « Zebrafish Embryo Vessel Segmentation Using a Novel Dual ResUNet Model ». Computational Intelligence and Neuroscience 2019 (3 février 2019) : 1–14. http://dx.doi.org/10.1155/2019/8214975.
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Zebrafish embryo fluorescent vessel analysis, which aims to automatically investigate the pathogenesis of diseases, has attracted much attention in medical imaging. Zebrafish vessel segmentation is a fairly challenging task, which requires distinguishing foreground and background vessels from the 3D projection images. Recently, there has been a trend to introduce domain knowledge to deep learning algorithms for handling complex environment segmentation problems with accurate achievements. In this paper, a novel dual deep learning framework called Dual ResUNet is developed to conduct zebrafish embryo fluorescent vessel segmentation. To avoid the loss of spatial and identity information, the U-Net model is extended to a dual model with a new residual unit. To achieve stable and robust segmentation performance, our proposed approach merges domain knowledge with a novel contour term and shape constraint. We compare our method qualitatively and quantitatively with several standard segmentation models. Our experimental results show that the proposed method achieves better results than the state-of-art segmentation methods. By investigating the quality of the vessel segmentation, we come to the conclusion that our Dual ResUNet model can learn the characteristic features in those cases where fluorescent protein is deficient or blood vessels are overlapped and achieves robust performance in complicated environments.
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Maia-Fernandes, Ana Cristina, Ana Martins-Jesus, Nísia Borralho-Martins, Tomás Pais-de-Azevedo, Ramiro Magno, Isabel Duarte et Raquel P. Andrade. « Spatio-temporal dynamics of early somite segmentation in the chicken embryo ». PLOS ONE 19, no 4 (18 avril 2024) : e0297853. http://dx.doi.org/10.1371/journal.pone.0297853.
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During vertebrate embryo development, the body is progressively segmented along the anterior-posterior (A-P) axis early in development. The rate of somite formation is controlled by the somitogenesis embryo clock (EC), which was first described as gene expression oscillations of hairy1 (hes4) in the presomitic mesoderm of chick embryos with 15–20 somites. Here, the EC displays the same periodicity as somite formation, 90 min, whereas the posterior-most somites (44–52) only arise every 150 minutes, matched by a corresponding slower pace of the EC. Evidence suggests that the rostral-most somites are formed faster, however, their periodicity and the EC expression dynamics in these early stages are unknown. In this study, we used time-lapse imaging of chicken embryos from primitive streak to somitogenesis stages with high temporal resolution (3-minute intervals). We measured the length between the anterior-most and the last formed somitic clefts in each captured frame and developed a simple algorithm to automatically infer both the length and time of formation of each somite. We found that the occipital somites (up to somite 5) form at an average rate of 75 minutes, while somites 6 onwards are formed approximately every 90 minutes. We also assessed the expression dynamics of hairy1 using half-embryo explants cultured for different periods of time. This showed that EC hairy1 expression is highly dynamic prior to somitogenesis and assumes a clear oscillatory behaviour as the first somites are formed. Importantly, using ex ovo culture and live-imaging techniques, we showed that the hairy1 expression pattern recapitulates with the formation of each new pair of somites, indicating that somite segmentation is coupled with EC oscillations since the onset of somitogenesis.
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Resende, Tatiana P., Raquel P. Andrade et Isabel Palmeirim. « Timing Embryo Segmentation : Dynamics and Regulatory Mechanisms of the Vertebrate Segmentation Clock ». BioMed Research International 2014 (2014) : 1–12. http://dx.doi.org/10.1155/2014/718683.
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All vertebrate species present a segmented body, easily observed in the vertebrate column and its associated components, which provides a high degree of motility to the adult body and efficient protection of the internal organs. The sequential formation of the segmented precursors of the vertebral column during embryonic development, the somites, is governed by an oscillating genetic network, the somitogenesis molecular clock. Herein, we provide an overview of the molecular clock operating during somite formation and its underlying molecular regulatory mechanisms. Human congenital vertebral malformations have been associated with perturbations in these oscillatory mechanisms. Thus, a better comprehension of the molecular mechanisms regulating somite formation is required in order to fully understand the origin of human skeletal malformations.
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Suhirman, Suhirman, Shoffan Saifullah, Ahmad Tri Hidayat et Rr Hajar Puji Sejati. « Otsu Method for Chicken Egg Embryo Detection based-on Increase Image Quality ». MATRIK : Jurnal Manajemen, Teknik Informatika dan Rekayasa Komputer 21, no 2 (31 mars 2022) : 417–28. http://dx.doi.org/10.30812/matrik.v21i2.1724.
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Detection of chicken egg embryos using image processing has limitations and needs some processes for improvement. By human vision, the previous process used binoculars and candling using light/beams directed at the chicken eggs in the incubator. In this study, we propose the application of image segmentation using the Otsu method in detecting chicken egg embryos. This method uses image segmentation with increased image quality (preprocessing) by several methods such as resizing, grayscaling, image adjustment, and image enhancement. These processes produce a better image and can be used for input in the segmentation process. In addition, this study compares several segmentation methods in detecting chicken egg embryos, such as thresholding, Otsu basic, and k-means clustering. The results show that our proposed method produced segmentation images to detect chicken egg embryos of 200 datasets images. This method has a faster process and can create a uniform segmentation than other methods. However, other methods can also detect chicken egg embryos. The method’s accuracy proposed in this study increased by 1.5% compared to other methods. In addition, the resulting SSIM value has a percentage close to and more than 90%, which means that the segmentation of the results obtained can be used to detect chicken egg embryos.
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Wang, Shengke, Junyu Dong, Xin Sun, Jiahua Wu et Ping Zou. « Probabilistic Index Maps Model Based Embryo Images Segmentation ». Journal of Medical Imaging and Health Informatics 5, no 2 (1 avril 2015) : 317–21. http://dx.doi.org/10.1166/jmihi.2015.1393.
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WU, TAO, JIANFENG LU, YANTING LU, TIANMING LIU et JINGYU YANG. « Embryo zebrafish segmentation using an improved hybrid method ». Journal of Microscopy 250, no 1 (15 février 2013) : 68–75. http://dx.doi.org/10.1111/jmi.12019.
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Jäckle, Herbert, Eveline Seifert, Anette Preiss et Urs B. Rosenberg. « Probing gene activity in Drosophila embryos ». Development 97, Supplement (1 octobre 1986) : 157–68. http://dx.doi.org/10.1242/dev.97.supplement.157.
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The segmentation pattern of the Drosophila wild-type embryo is characterized by a number of easily identifiable cuticular structures. They include skeletal elements of the involuted head and ventral denticle belts that define by size, pattern and orientation the anterior part of the three thoracic and eight abdominal segments. Further landmarks such as sensory organs and the posterior tracheal endings (‘Filzkörper’), in combination with the denticle belts, allow one to unequivocally determine the polarity and quality of each segment in preparations of the larval cuticle (see Fig. 1D). The segmentation pattern of Drosophila is established at about blastoderm stage and it requires both maternally and zygotically active genes. Genetic analysis has identified a number of genes with zygotic activity that regulate key steps during pattern formation. Mutations in these genes cause specific defects in the segmental pattern of the embryo that allow the definition of classes of segmentation genes required for the subdivision of the embryo into segmental units (Nüsslein-Volhard & Wieschaus, 1980).
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Ambrosio, L., A. P. Mahowald et N. Perrimon. « l(1)pole hole is required maternally for pattern formation in the terminal regions of the embryo ». Development 106, no 1 (1 mai 1989) : 145–58. http://dx.doi.org/10.1242/dev.106.1.145.
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Maternal expression of the l(1)pole hole (l(1)ph) gene product is required for the development of the Drosophila embryo. When maternal l(1)ph+ activity is absent, alterations in the embryonic fate map occur as visualized by the expression of segmentation genes fushitarazu and engrailed. If both maternal and zygotic activity is absent, embryos degenerate around 7 h of development. If only maternal activity is missing, embryos complete embryogenesis and show deletions of both anterior and posterior structures. Anteriorly, structures originating from labral and acron head regions are missing. Posteriorly, abdominal segments A8, 9 and 10, the telson and the proctodeum are missing. Similar pattern deletions are observed in embryos derived from the terminal class of female sterile mutations. Thus, the maternal l(1)ph+ gene product is required for the establishment of cell identities at the anterior and posterior poles of the Drosophila embryo.
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Tsai, C., et J. P. Gergen. « Gap gene properties of the pair-rule gene runt during Drosophila segmentation ». Development 120, no 6 (1 juin 1994) : 1671–83. http://dx.doi.org/10.1242/dev.120.6.1671.
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The Drosophila Runt protein is a member of a new family of transcriptional regulators that have important roles in processes extending from pattern formation in insect embryos to leukemogenesis in humans. We used ectopic expression to investigate runt's function in the pathway of Drosophila segmentation. Transient over-expression of runt under the control of a Drosophila heat-shock promoter caused stripe-specific defects in the expression patterns of the pair-rule genes hairy and even-skipped but had a more uniform effect on the secondary pair-rule gene fushi tarazu. Surprisingly, the expression of the gap segmentation genes, which are upstream of runt in the segmentation hierarchy was also altered in hs/runt embryos. A subset of these effects were interpreted as due to an antagonistic effect of runt on transcriptional activation by the maternal morphogen bicoid. In support of this, expression of synthetic reporter gene constructs containing oligomerized binding sites for the Bicoid protein was reduced in hs/runt embryos. Finally, genetic experiments demonstrated that regulation of gap gene expression by runt is a normal component of the regulatory program that generates the segmented body pattern of the Drosophila embryo.
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Mushtaq, Abeer, Maria Mumtaz, Ali Raza, Nema Salem et Muhammad Naveed Yasir. « Artificial Intelligence-Based Detection of Human Embryo Components for Assisted Reproduction by In Vitro Fertilization ». Sensors 22, no 19 (29 septembre 2022) : 7418. http://dx.doi.org/10.3390/s22197418.
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Assisted reproductive technology is helping humans by addressing infertility using different medical procedures that help in a successful pregnancy. In vitro fertilization (IVF) is one of those assisted reproduction methods in which the sperm and eggs are combined outside the human body in a specialized environment and kept for growth. Assisted reproductive technology is helping humans by addressing infertility using different medical procedures that help in a successful pregnancy. The morphology of the embryological components is highly related to the success of the assisted reproduction procedure. In approximately 3–5 days, the embryo transforms into the blastocyst. To prevent the multiple-birth risk and to increase the chance of pregnancy the embryologist manually analyzes the blastocyst components and selects valuable embryos to transfer to the women’s uterus. The manual microscopic analysis of blastocyst components, such as trophectoderm, zona pellucida, blastocoel,and inner cell mass, is time-consuming and requires keen expertise to select a viable embryo. Artificial intelligence is easing medical procedures by the successful implementation of deep learning algorithms that mimic the medical doctor’s knowledge to provide a better diagnostic procedure that helps in reducing the diagnostic burden. The deep learning-based automatic detection of these blastocyst components can help to analyze the morphological properties to select viable embryos. This research presents a deep learning-based embryo component segmentation network (ECS-Net) that accurately detects trophectoderm, zona pellucida, blastocoel, and inner cell mass for embryological analysis. The proposed method (ECS-Net) is based on a shallow deep segmentation network that uses two separate streams produced by a base convolutional block and a depth-wise separable convolutional block. Both streams are densely concatenated in combination with two dense skip paths to produce powerful features before and after upsampling. The proposed ECS-Net is evaluated on a publicly available microscopic blastocyst image dataset, the experimental segmentation results confirm the efficacy of the proposed method. The proposed ECS-Net is providing a mean Jaccard Index (Mean JI) of 85.93% for embryological analysis.
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Tykarska, Teresa. « Rape embryogenesis. II. Development of embryo proper ». Acta Societatis Botanicorum Poloniae 48, no 3 (2015) : 391–421. http://dx.doi.org/10.5586/asbp.1979.033.
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It was found in the continued studies on rape embryogenesis, started by the description of the proembryo (Tykarska, 1976) that the development of embryo is extremely regular and based on differentiating divisions. It appeared that the transverse segmentation boundary and cell walls separating the mother cells of the histogens in the proembryo can be distinguished in all the later stages of the embryo. The border between the cytoledons and epicotyl part of the embryonal axis, and the hypocotyl corresponds to the segmentation boundary between layer l and layer l' at the octant stage. As border between the hypocotyl and radicle was assumed the upper boundary of the root cap reaching usually to the level of the boundary between segments II and III of dermatogen and periblem. The apical meristem of the shoot forms from dermatogen and the periaxial cells of the globular embryo subepidermis. The promeristem of the radicle constists of 3 layers of initial cells surrounding on all sides the inactive layer of central binding cells.
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Mee, Jane E., et Vernon French. « Disruption of segmentation in a short germ insect embryo ». Development 96, no 1 (1 juillet 1986) : 267–94. http://dx.doi.org/10.1242/dev.96.1.267.
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A heat shock (of 15min at 48° C) given to early embryos of the locust, Schistocerca gregaria, results in localized abnormalities in the segment pattern subsequently formed. Most defects involve two consecutive segments of the thorax or abdomen, and these are analysed in detail. The abdominal defects fall into three main classes each of which involves the absence of a particular region of the segment pair and, in one class, duplication of the region which remains. The thoracic defects similarly involve absence of parts of the segments and the formation of a single limb base from which one, two, or three limbs develop. Heat shock may result in the absence of parts of segments in two distinct ways. It may interfere with the process of segmentation or it may delete parts of already formed segment primordia. These possibilities are discussed although, at present, neither can be excluded. The duplication observed in some abdominal disruptions and the formation of triple limbs indicates that the absence of parts of embryonic segments is followed by pattern regulation similar to that occurring in regeneration studies on larval segments and appendages of other insects. Two out of the three classes of abnormality can be explained in terms of intercalary regeneration restoring pattern continuity, but it is possible that discontinuities persist in the remaining class.
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Mee, Jane E., et Vernon French. « Disruption of segmentation in a short germ insect embryo ». Development 96, no 1 (1 juillet 1986) : 245–66. http://dx.doi.org/10.1242/dev.96.1.245.
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The effect of heat shock (15 min at 48 °C) on segmentation has been investigated in the short germ embryo of the locust (Schistocerca gregaria). Prior to formation of the germ anlage and at the disc stage heat shock considerably reduced the survival of eggs but appeared to have little effect upon segmentation. At later stages heat shock had no effect on survival but resulted in disruptions of the segmental pattern. The location of abnormal segments depended upon the stage at heat shock and the number affected depended on its severity. A constant number of normal segments developed between the last segment visible at the time of heat shock and the first abnormal segment. These results are similar to the disruptions observed in amphibian somites following heat shock. However, different parts of the segment pattern varied in their response; the head segments were very rarely affected, and disrupted regions rarely started in the middle abdomen (segments A5 and A6). The results are discussed in relation to two models (the clock and wavefront and progress zone models) that have been proposed as an explanation for the specification of the somite pattern in amphibians.
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Vallade, Jean, François Bugnon et Zhour Ibannain. « Interprétation morphologique de l'embryon chez les Embryophytes, avec application au cas des Graminées (Poaceae) ». Canadian Journal of Botany 71, no 2 (1 février 1993) : 256–72. http://dx.doi.org/10.1139/b93-027.
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A new interpretation of the Monocotyledoneae embryo is presented following a reinvestigation of the fundamental transformations characterizing the evolution of the zygote to a plantlet, in the Archegoniatae division or Embryophyta subkingdom (including Bryophyta). The following elementary processes of embryogenesis were analysed: segmentation, territorial differentiation, histogen differentiation, and organic differentiation, the latter being related to the formation of terminal meristems. Embryos belonging to very different systematic groups are compared by a diagram showing the development of the essential parts of the embryo body. From the different data collected, a diagram is proposed to represent the embryo of the Gramineae. This includes (i) a foot area (scutellum) homologous to that of Ruppia and those of various Pteridophyta; the foot differentiation also affects a part of the rising cotyledon; (ii) a cotyledon with a coleoptilary sheath; (iii) a lateral primary caulinar meristem (shoot apex); (iv) a primary root (radicle), which is endogenous because the organic differentiation do not reach the outside of the body; (v) a coleorhiza, thallin residue of the proembryonic stage, separated from the root by a space arising from the delamination of one of the main proembryo cell walls. Key words: embryogenesis, embryo differentiation, Embryophyta, Monocotyledoneae, Gramineae.
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Hart, Marilyn C., Lei Wang et Douglas E. Coulter. « Comparison of the Structure and Expression of odd-skipped and Two Related Genes That Encode a New Family of Zinc Finger Proteins in Drosophila ». Genetics 144, no 1 (1 septembre 1996) : 171–82. http://dx.doi.org/10.1093/genetics/144.1.171.
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Abstract The odd-skipped (odd) gene, which was identified on the basis of a pair-rule segmentation phenotype in mutant embryos, is initially expressed in the Drosophila embryo in seven pair-rule stripes, but later exhibits a segment polarity-like pattern for which no phenotypic correlate is apparent. We have molecularly characterized two embryonically expressed odd-cognate genes, sob and bowel (bowl), that encode proteins with highly conserved C2H2 zinc fingers. While the Sob and Bowl proteins each contain five tandem fingers, the Odd protein lacks a fifth (C-terminal) finger and is also less conserved among the four common fingers. Reminiscent of many segmentation gene paralogues, the closely linked odd and sob genes are expressed during embryogenesis in similar striped patterns; in contrast, the less-tightly linked bowlgene is expressed in a distinctly different pattern at the termini of the early embryo. Although our results indicate that odd and sob are more likely than bowl to share overlapping developmental roles, some functional divergence between the Odd and Sob proteins is suggested by the absence of homology outside the zinc fingers, and also by amino acid substitutions in the Odd zinc fingers at positions that appear to be constrained in Sob and Bowl.
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Thirupathi, Yasotha, Pratheesh Mankuzhy, Vikash Chandra et G. Taru Sharma. « Warrants of cryopreservation in assisted reproductive technology amidst COVID-19 pandemic ». Journal of Reproductive Healthcare and Medicine 2 (22 février 2021) : 49–54. http://dx.doi.org/10.25259/jrhm_38_2020.
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Cryopreservation plays a central role in assisted reproductive technology (ART) by allowing in vitro fertilization (IVF) cycle segmentation, banking of supernumerary gametes, embryos, and fertility preservation. The identification of viral receptors on gametes and embryos raises serious concerns for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) patients who are interested in preserving fertility. The complications caused by the SARS-CoV-2 on IVF and embryo safety are yet to be explored. Scanty information is available so far regarding the risk of cryopreservation of biological materials used in ART. Here, we highlight the risks of cryopreservation in ART and safety measures to follow amidst the COVID-19 pandemic.
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Walrad, Pegine B., Saiyu Hang et J. Peter Gergen. « Hairless is a cofactor for Runt-dependent transcriptional regulation ». Molecular Biology of the Cell 22, no 8 (15 avril 2011) : 1364–74. http://dx.doi.org/10.1091/mbc.e10-06-0483.
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Runt is a vital transcriptional regulator in the developmental pathway responsible for segmentation in the Drosophila embryo. Runt activates or represses transcription in a manner that is dependent on both cellular context and the specific downstream target. Here we identify Hairless (H) as a Runt-interacting molecule that functions during segmentation. We find that H is important for maintenance of engrailed (en) repression as was previously demonstrated for Groucho (Gro), Rpd3, and CtBP. H also contributes to the Runt-dependent repression of sloppy-paired-1 (slp1), a role that is not shared with these other corepressors. We further find distinct roles for these different corepressors in the regulation of other Runt targets in the early Drosophila embryo. These findings, coupled with observations on the distinct functional requirements for Runt in regulating these several different targets, indicate that Runt-dependent regulation in the Drosophila blastoderm embryo relies on unique, target-gene-specific molecular interactions.
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Carroll, S. B., G. M. Winslow, V. J. Twombly et M. P. Scott. « Genes that control dorsoventral polarity affect gene expression along the anteroposterior axis of the Drosophila embryo ». Development 99, no 3 (1 mars 1987) : 327–32. http://dx.doi.org/10.1242/dev.99.3.327.
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At least 13 genes control the establishment of dorsoventral polarity in the Drosophila embryo and more than 30 genes control the anteroposterior pattern of body segments. Each group of genes is thought to control pattern formation along one body axis, independently of the other group. We have used the expression of the fushi tarazu (ftz) segmentation gene as a positional marker to investigate the relationship between the dorsoventral and anteroposterior axes. The ftz gene is normally expressed in seven transverse stripes. Changes in the striped pattern in embryos mutant for other genes (or progeny of females homozygous for maternal-effect mutations) can reveal alterations of cell fate resulting from such mutations. We show that in the absence of any of ten maternal-effect dorsoventral polarity gene functions, the characteristic stripes of ftz protein are altered. Normally there is a difference between ftz stripe spacing on the dorsal and ventral sides of the embryo; in dorsalized mutant embryos the ftz stripes appear to be altered so that dorsal-type spacing occurs on all sides of the embryo. These results indicate that cells respond to dorsoventral positional information in establishing early patterns of gene expression along the anteroposterior axis and that there may be more significant interactions between the different axes of positional information than previously determined.
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Stern, Claudio D., Scott E. Fraser, Roger J. Keynes et Dennis R. N. Primmett. « A cell lineage analysis of segmentation in the chick embryo ». Development 104, Supplement (1 octobre 1988) : 231–44. http://dx.doi.org/10.1242/dev.104.supplement.231.
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We have studied the lineage history of the progenitors of the somite mesoderm and of the neural tube in the chick embryo by injecting single cells with the fluorescent tracer, rhodamine-lysine-dextran. We find that, although single cells within the segmental plate give rise to discrete clones in the somites to which they contribute, neither the somites nor their component parts (sclerotome, dermatome, myotome or their rostral and caudal halves) are `compartments' in the sense defined in insects. Cells in the rostral two thirds or so of the segmental plate contribute only to somite tissue and divide about every 10 h, while those in the caudal portions of this structure contribute both to the somites and to intermediate and lateral plate mesoderm derivatives. In the neural tube, the descendants of individual prospective ventral horn cells remain together within the horn, with a cycle time of 10 h. We have also investigated the role of the cell division cycle in the formation and subsequent development of somites. A single treatment of 2-day chick embryos with heat shock or a variety of drugs that affect the cell cycle all produce repeated anomalies in the pattern of somites and vertebrae that develop subsequent to the treatment. The interval between anomalies is 6-7 somites (or a multiple of this distance), which corresponds to 10 h. This interval is identical to that measured for the cell division cycle. Given that cell division synchrony is seen in the presomitic mesoderm, we suggest that the cell division cycle plays a role in somite formation. Finally, we consider the mechanisms responsible for regionalization of derivatives of the somite, and conclude that it is likely that both cell interactions and cell lineage history are important in the determination of cell fates.
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UYSAL, Nefise, Tahir Koray YOZGATLI, Ecem Nur YILDIZCAN, Emre KAR, Murat GEZER et Ercan BAŞTU. « Comparison of U-Net Based Models for Human Embryo Segmentation ». Bilişim Teknolojileri Dergisi 15, no 1 (31 janvier 2022) : 35–44. http://dx.doi.org/10.17671/gazibtd.949430.
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Sidhu, Simarjot S., et James K. Mills. « Automated 3D blastomere segmentation and injection for early-stage embryo ». International Journal of Mechatronics and Automation 7, no 3 (2020) : 122. http://dx.doi.org/10.1504/ijma.2020.10031293.
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Sidhu, Simarjot S., et James K. Mills. « Automated 3D blastomere segmentation and injection for early-stage embryo ». International Journal of Mechatronics and Automation 7, no 3 (2020) : 122. http://dx.doi.org/10.1504/ijma.2020.109059.
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Rad, Reza Moradi, Parvaneh Saeedi, Jason Au et Jon Havelock. « Trophectoderm segmentation in human embryo images via inceptioned U-Net ». Medical Image Analysis 62 (mai 2020) : 101612. http://dx.doi.org/10.1016/j.media.2019.101612.
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Nakao, Hajime. « Anterior and posterior centers jointly regulate Bombyx embryo body segmentation ». Developmental Biology 371, no 2 (novembre 2012) : 293–301. http://dx.doi.org/10.1016/j.ydbio.2012.08.029.
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Zhu, Zhihui, Kai Yang et YuTing He. « Research on Detection of Fertility of Group Hatching Eggs Based on Adaptive Image Segmentation ». Applied Engineering in Agriculture 38, no 2 (2022) : 283–91. http://dx.doi.org/10.13031/aea.14849.
Texte intégralRésumé :
HighlightsAn adaptive group eggs segmentation was proposed, which separates a single egg from the group eggs image.Key color features and texture features were extracted from the RGB and HSI histograms, respectively.The Support Vector Machine (SVM) model and Least Squares Support Vector Machine (LS-SVM) model were built to distinguish infertile egg and dead-embryo egg, respectively.LS-SVM model reached 100% accuracy for infertile eggs on day 4 of incubation, and dead-embryo eggs on day 10 of incubation.Abstract. For the incubation factory, it is of vital importance to detect infertile eggs and dead-embryo eggs in the industrial egg trays as early as possible. In this article, an activity detection computer vision system was proposed and evaluated. Due to the dense layout of eggs in industrial egg trays, the image segmentation task to separate each single egg becomes difficult. To this end, an adaptive image segmentation method for group eggs was proposed. Firstly, the binary image was obtained by the Canny operator using dynamic threshold and processed to reduce redundant information. Then ellipse fitting was employed to obtain the egg contour of the single egg. Moreover, the Red, Green, Blue (RGB) and Hue, Saturation, Intensity (HSI) histograms were selected for feature extraction. According to the analysis on color features and texture features of the images, 13 features [positions for peak values of R and I in histogram, peak values of G and I within histogram, averages of R and G, variances of R and G, contrast, roughness, inverse different moment (IDM), correlation and angular second moment (ASM)] were chosen as the criterion for detecting dead-embryo eggs. Meanwhile, 12 features (positions for peak values of R, G, H, and I in histogram, averages of R and G, slope and variance of G, contrast, roughness, IDM, and correlation) were selected for detecting infertile eggs. Lastly, the Support Vector Machine (SVM) model and Lease Squares Support Vector Machine (LS-SVM) model were built to distinguish infertile egg and dead-embryo egg, respectively. According to the comparison, the LS-SVM model reached higher accuracy in determining infertile egg and dead-embryo egg than the SVM model, with less time consumed. The LS-SVM model reached 100% accuracy in detection for infertile eggs on day 4 of incubation, as well as for dead-embryo eggs on day 10 of incubation. The result demonstrated that the proposed method can conduct the activity detection for group eggs both accurately and fast, which meets the commercial requirement for non-destructive detection in the hatchery industry. Keywords: Adaptive image segmentation, Computer vision, Fertility, Group hatching eggs, LS-SVM, Non-destructive detection, SVM
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Akiyama-Oda, Yasuko, et Hiroki Oda. « Hedgehog signaling controls segmentation dynamics and diversity via msx1 in a spider embryo ». Science Advances 6, no 37 (septembre 2020) : eaba7261. http://dx.doi.org/10.1126/sciadv.aba7261.
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Hedgehog (Hh) signaling plays fundamental roles in animal body patterning. Understanding its mechanistic complexity requires simple tractable systems that can be used for these studies. In the early spider embryo, Hh signaling mediates the formation of overall anterior-posterior polarity, yet it remains unclear what mechanisms link the initial Hh signaling activity with body axis segmentation, in which distinct periodic stripe-forming dynamics occur depending on the body region. We performed genome-wide searches for genes that transcriptionally respond to altered states of Hh signaling. Characterization of genes negatively regulated by Hh signaling suggested that msx1, encoding a conserved transcription factor, functions as a key segmentation gene. Knockdown of msx1 prevented all dynamic processes causing spatial repetition of stripes, including temporally repetitive oscillations and bi-splitting, and temporally nonrepetitive tri-splitting. Thus, Hh signaling controls segmentation dynamics and diversity via msx1. These genome-wide data from an invertebrate illuminate novel mechanistic features of Hh-based patterning.
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Jen, W. C., D. Wettstein, D. Turner, A. Chitnis et C. Kintner. « The Notch ligand, X-Delta-2, mediates segmentation of the paraxial mesoderm in Xenopus embryos ». Development 124, no 6 (15 mars 1997) : 1169–78. http://dx.doi.org/10.1242/dev.124.6.1169.
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Segmentation of the vertebrate embryo begins when the paraxial mesoderm is subdivided into somites, through a process that remains poorly understood. To study this process, we have characterized X-Delta-2, which encodes the second Xenopus homolog of Drosophila Delta. Strikingly, X-Delta-2 is expressed within the presomitic mesoderm in a set of stripes that corresponds to prospective somitic boundaries, suggesting that Notch signaling within this region establishes a segmental prepattern prior to somitogenesis. To test this idea, we introduced antimorphic forms of X-Delta-2 and Xenopus Suppressor of Hairless (X-Su(H)) into embryos, and assayed the effects of these antimorphs on somite formation. In embryos expressing these antimorphs, the paraxial mesoderm differentiated normally into somitic tissue, but failed to segment properly. Both antimorphs also disrupted the segmental expression of X-Delta-2 and Hairy2A, a basic helix-loop-helix (bHLH) gene, within the presomitic mesoderm. These observations suggest that X-Delta-2, via X-Notch-1, plays a role in segmentation, by mediating cell-cell interactions that underlie the formation of a segmental prepattern prior to somitogenesis.
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Kraut, R., et M. Levine. « Mutually repressive interactions between the gap genes giant and Kruppel define middle body regions of the Drosophila embryo ». Development 111, no 2 (1 février 1991) : 611–21. http://dx.doi.org/10.1242/dev.111.2.611.
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The gap genes play a key role in establishing pair-rule and homeotic stripes of gene expression in the Drosophila embryo. There is mounting evidence that overlapping gradients of gap gene expression are crucial for this process. Here we present evidence that the segmentation gene giant is a bona fide gap gene that is likely to act in concert with hunchback, Kruppel and knirps to initiate stripes of gene expression. We show that Kruppel and giant are expressed in complementary, non-overlapping sets of cells in the early embryo. These complementary patterns depend on mutually repressive interactions between the two genes. Ectopic expression of giant in early embryos results in the selective repression of Kruppel, and advanced-stage embryos show cuticular defects similar to those observed in Kruppel- mutants. This result and others suggest that the strongest regulatory interactions occur among those gap genes expressed in nonadjacent domains. We propose that the precisely balanced overlapping gradients of gap gene expression depend on these strong regulatory interactions, coupled with weak interactions between neighboring genes.
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Mlodzik, M., G. Gibson et W. J. Gehring. « Effects of ectopic expression of caudal during Drosophila development ». Development 109, no 2 (1 juin 1990) : 271–77. http://dx.doi.org/10.1242/dev.109.2.271.
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The effects of heat-shock-induced ectopic expression of the homeobox gene caudal (cad) at all stages of Drosophila development have been examined. Presence of cad protein (CAD) at the anterior end of cellular blastoderm embryos was found to disrupt head development and segmentation, due to alteration of the expression of segmentation genes such as fushi tarazu and engrailed, as well as repression of head-determining genes such as Deformed. These results support the conclusion that, while CAD is probably required to activate transcription of fushi tarazu in the posterior half of the embryo, it should not be expressed in the anterior half prior to gastrulation, and thus suggest a role for the CAD gradient. Ectopic expression of CAD at later stages of development has no obvious effects on embryogenesis or imaginal disc development, suggesting that the homeotic genes of the Antennapedia and Bithorax Complexes are almost completely epistatic to caudal.
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Saifullah, Shoffan, Andiko Putro Suryotomo et Yuhefizar. « Detection of Chicken Egg Embryos using BW Image Segmentation and Edge Detection Methods ». Jurnal RESTI (Rekayasa Sistem dan Teknologi Informasi) 5, no 6 (30 décembre 2021) : 1062–69. http://dx.doi.org/10.29207/resti.v5i6.3540.
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This study aims to identify chicken egg embryos with the concept of image processing. This concept uses input and output in images. Thus the identification process, which was originally carried out using manual observation, was developed by computerization. Digital images are applied in identification by various image preprocessing, image segmentation, and edge detection methods. Based on these three methods, image processing has three processes: image grayscaling (convert to a grayscale image), image adjustment, and image enhancement. Image adjustment aims to clarify the image based on color correction. Meanwhile, image enhancement improves image quality, using histogram equalization (HE) and Contrast Limited Adaptive Histogram Equalization methods (CLAHE). Specifically for the image enhancement method, the CLAHE-HE combination is used for the improvement process. At the end of the process, the method used is edge detection. In this method, there is a comparison of various edge detection operators such as Roberts, Prewitt, Sobel, and canny. The results of edge detection using these four methods have the SSIM value respectively 0.9403; 0.9392; 0.9394; 0.9402. These results indicate that the SSIM values of the four operators have the same or nearly the same value. Thus, the edge detection method can provide good edge detection results and be implemented because the SSIM value is close to 1.00 (more than 0.93). Image segmentation detected object (egg and embryo), and the continued process by edge detection showed clearly edge of egg and embryo.
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Limbourg-Bouchon, B., D. Busson et C. Lamour-Isnard. « Interactions between fused, a segment-polarity gene in Drosophila, and other segmentation genes ». Development 112, no 2 (1 juin 1991) : 417–29. http://dx.doi.org/10.1242/dev.112.2.417.
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Fused (fu) is a segment polarity gene whose product is maternally required in the posterior part of each segment. To define further the role of fused and determine how it interacts with other segmentation genes, we examined the phenotypes obtained by combining fused with mutations of pair rule, homeotic and other segment polarity loci. When it was possible, we also looked at the distribution of corresponding proteins in fused mutant embryos. We observed that fused-naked (fu;nkd) double mutant embryos display a phenotypic suppression of simple mutant phenotypes: both naked cuticle and denticle belts, which would normally have been deleted by one of the two mutants alone, were restored. In fused mutant embryos, engrailed (en) and wingless (wg) expression was normal until germ band extension, but partially and completely disappeared respectively during germ band retraction. In the fu;nkd double mutant embryo, en was expressed as in nkd mutant at germ band extension, but later this expression was restricted and became normal at germ band retraction. On the contrary, wg expression disappeared as in fu simple mutant embryos. We conclude that the requirements for fused, naked and wingless activities for normal segmental patterning are not absolute, and propose mechanisms by which these genes interact to specify anterior and posterior cell fates.
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Lehmann, Ruth, et Hans Georg Frohnhöfer. « Segmental polarity and identity in the abdomen of Drosophila is controlled by the relative position of gap gene expression ». Development 107, Supplement (1 avril 1989) : 21–29. http://dx.doi.org/10.1242/dev.107.supplement.21.
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The establishment of the segmental pattern in the Drosophila embryo is directed by three sets of maternal genes: the anterior, the terminal and the posterior group of genes. Embryos derived from females mutant for one of the posterior group genes lack abdominal segmentation. This phenotype can be rescued by transplantation of posterior pole plasm into the abdominal region of mutant embryos. We transplanted posterior pole plasm into the middle of embryos mutant either for the posterior, the anterior and posterior, or all three maternal systems and monitored the segmentation pattern as well as the expression of the zygotic gap gene Krüppel in control and injected embryos. We conclude that polarity and identity of the abdominal segments do not depend on the relative concentration of posterior activity but rather on the position of gap gene expression. By changing the pattern of gap gene expression, the orientation of the abdomen can be reversed. These experiments suggest that maternal gene products act in a strictly hierarchical manner. The function of the maternal gene products becomes dispensable once the position of the zygotically expressed gap genes is determined. Subsequently the gap genes will control the pattern of the pair-rule and segment polarity genes.
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Bastiaansen, Wietske A. P., Melek Rousian, Régine P. M. Steegers-Theunissen, Wiro J. Niessen, Anton H. J. Koning et Stefan Klein. « Multi-Atlas Segmentation and Spatial Alignment of the Human Embryo in First Trimester 3D Ultrasound ». Machine Learning for Biomedical Imaging 1, PIPPI 2021 (14 juillet 2022) : 1–31. http://dx.doi.org/10.59275/j.melba.2022-cb15.
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Segmentation and spatial alignment of ultrasound imaging data acquired in the in first trimester are crucial for monitoring early human embryonic growth and development throughout this crucial period of life. Current approaches are either manual or semi-automatic and are therefore very time-consuming and prone to errors. To automate these tasks, we propose a multi-atlas framework for automatic segmentation and spatial alignment of the embryo using deep learning with minimal supervision. Our framework learns to register the embryo to an atlas, which consists of the ultrasound images acquired at a range of gestational ages, segmented and spatially aligned to a predefined standard orientation. From this, we can derive the segmentation of the embryo and put the embryo in standard orientation. Ultrasound images acquired at 8+0 till 12+6 weeks gestational age were used and eight pregnancies were selected as atlas images. We evaluated different fusion strategies to incorporate multiple atlases: 1) training the framework using atlas images from a single subject, 2) training the framework with data of all available atlases and 3) ensembling of the frameworks trained per subject. To evaluate the performance, we calculated the Dice score over the test set. We found that training the framework using all available atlases outperformed ensembling and gave similar results compared to the best of all frameworks trained on a single subject. Furthermore, we found that selecting images from the four atlases closest in gestational age out of all available atlases, regardless of the individual quality, gave the best results with a median Dice score of $0.72$. We conclude that our framework can accurately segment and spatially align the embryo in first trimester 3D ultrasound images and is robust for the variation in quality that existed in the available atlases. Our code is publicly available at: <a href='https://github.com/wapbastiaansen/multi-atlas-seg-reg'>https://github.com/wapbastiaansen/multi-atlas-seg-reg</a>
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Ishaq, Muhammad, Salman Raza, Hunza Rehar, Shan e. Zain ul Abadeen, Dildar Hussain, Rizwan Ali Naqvi et Seung-Won Lee. « Assisting the Human Embryo Viability Assessment by Deep Learning for In Vitro Fertilization ». Mathematics 11, no 9 (24 avril 2023) : 2023. http://dx.doi.org/10.3390/math11092023.
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The increasing global infertility rate is a matter of significant concern. In vitro fertilization (IVF) significantly minimizes infertility by providing an alternative clinical means of becoming pregnant. The success of IVF mainly depends on the assessment and analysis of human blastocyst components such as the blastocoel (BC), zona pellucida (ZP), inner cell mass (ICM), and trophectoderm (TE). Embryologists perform a morphological assessment of the blastocyst components for the selection of potential embryos to be used in the IVF process. Manual assessment of blastocyst components is time-consuming, subjective, and prone to errors. Therefore, artificial intelligence (AI)-based methods are highly desirable for enhancing the success rate and efficiency of IVF. In this study, a novel feature-supplementation-based blastocyst segmentation network (FSBS-Net) has been developed to deliver higher segmentation accuracy for blastocyst components with less computational overhead compared with state-of-the-art methods. FSBS-Net uses an effective feature supplementation mechanism along with ascending channel convolutional blocks to accurately detect the pixels of the blastocyst components with minimal spatial loss. The proposed method was evaluated using an open database for human blastocyst component segmentation, and it outperformed state-of-the-art methods in terms of both segmentation accuracy and computational efficiency. FSBS-Net segmented the BC, ZP, ICM, TE, and background with intersections over union (IoU) values of 89.15, 85.80, 85.55, 80.17, and 95.61%, respectively. In addition, FSBS-Net achieved a mean IoU for all categories of 87.26% with only 2.01 million trainable parameters. The experimental results demonstrate that the proposed method could be very helpful in assisting embryologists in the morphological assessment of human blastocyst components.
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Duk, Maria A., Vitaly V. Gursky, Maria G. Samsonova et Svetlana Yu Surkova. « Application of Domain- and Genotype-Specific Models to Infer Post-Transcriptional Regulation of Segmentation Gene Expression in Drosophila ». Life 11, no 11 (13 novembre 2021) : 1232. http://dx.doi.org/10.3390/life11111232.
Texte intégralRésumé :
Unlike transcriptional regulation, the post-transcriptional mechanisms underlying zygotic segmentation gene expression in early Drosophila embryo have been insufficiently investigated. Condition-specific post-transcriptional regulation plays an important role in the development of many organisms. Our recent study revealed the domain- and genotype-specific differences between mRNA and the protein expression of Drosophila hb, gt, and eve genes in cleavage cycle 14A. Here, we use this dataset and the dynamic mathematical model to recapitulate protein expression from the corresponding mRNA patterns. The condition-specific nonuniformity in parameter values is further interpreted in terms of possible post-transcriptional modifications. For hb expression in wild-type embryos, our results predict the position-specific differences in protein production. The protein synthesis rate parameter is significantly higher in hb anterior domain compared to the posterior domain. The parameter sets describing Gt protein dynamics in wild-type embryos and Kr mutants are genotype-specific. The spatial discrepancy between gt mRNA and protein posterior expression in Kr mutants is well reproduced by the whole axis model, thus rejecting the involvement of post-transcriptional mechanisms. Our models fail to describe the full dynamics of eve expression, presumably due to its complex shape and the variable time delays between mRNA and protein patterns, which likely require a more complex model. Overall, our modeling approach enables the prediction of regulatory scenarios underlying the condition-specific differences between mRNA and protein expression in early embryo.
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Jäckle, Herbert, Ulrike Gaul et Norbert Redemann. « Regulation and putative function of the Drosophila gap gene Krüppel ». Development 104, Supplement (1 octobre 1988) : 29–34. http://dx.doi.org/10.1242/dev.104.supplement.29.
Texte intégralRésumé :
The Drosophila segmentation gene Krüppel (Kr) is expressed in a broad band of cells that covers about four-segment primordia in the blastoderm embryo. Examination of size and position of the Kr protein domain in various mutant embryos revealed that the establishment of the domain of Kr gene expression is under the control of the maternal effect pattern organizers which act at the poles. The lack of Kr activity causes a gap in the segment pattern of the embryo which is about twice the size of the Kr expression domain and extends posterior to it. This indicates that Kr activity per se is not directly responsible for the establishment of the pattern elements which are deleted in the mutant embryo. Examination of the molecular lesions in four Kr alleles indicated that each of them is a point mutant within the coding sequence of the Kr gene and each mutation results in a different replacement of a single amino acid within the `finger domain' of the Kr protein. Thus, this region of the Kr protein is essential for Kr function. Since this portion of the Kr protein shares structural homology with the DNA-binding domain of several transcription factors, we propose that Kr acts as a transcription factor on subordinate genes that process the spatial cues provided by Kr activity to establish eventually the segments in the central region of the embryo.
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Irvine, K. D., et E. Wieschaus. « Cell intercalation during Drosophila germband extension and its regulation by pair-rule segmentation genes ». Development 120, no 4 (1 avril 1994) : 827–41. http://dx.doi.org/10.1242/dev.120.4.827.
Texte intégralRésumé :
After the onset of gastrulation, the Drosophila germband undergoes a morphological change in which its length along the anterior-posterior axis increases over two-and-a-half fold while its width along the dorsal-ventral axis simultaneously narrows. The behavior of individual cells during germband extension was investigated by epi-illumination and time-lapse video microscopy of living embryos. Cells intercalate between their dorsal and ventral neighbors during extension, increasing the number of cells along the anterior-posterior axis while decreasing the number of cells along the dorsal-ventral axis. Mutations that reduce segmental subdivision of the embryo along the anterior-posterior axis decrease both germband extension and its associated cell intercalation. In contrast, cell intercalation and germband extension are still detected in embryos that lack dorsal-ventral polarity. Characterization of germband extension and cell intercalation in mutant embryos with altered segmentation gene expression indicates that these processes are regionally autonomous and are dependent upon the establishment of striped expression patterns for certain pair-rule genes. Based on these observations, we propose a model for germband extension in which cell intercalation results from the establishment of adhesive differences between stripes of cells by pair-rule genes.
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Read, D., T. Nishigaki et J. L. Manley. « The Drosophila even-skipped promoter is transcribed in a stage-specific manner in vitro and contains multiple, overlapping factor-binding sites ». Molecular and Cellular Biology 10, no 8 (août 1990) : 4334–44. http://dx.doi.org/10.1128/mcb.10.8.4334-4344.1990.
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To investigate the factors contributing to regulation of expression of the Drosophila segmentation gene even-skipped (eve), we have analyzed both the in vitro transcription and eve-promoter-binding proteins in embryo extracts. We show that the eve promoter is accurately and efficiently expressed in nuclear extracts derived from Drosophila embryos and that transcription is more efficient in extracts prepared from embryos at early stages of development than in those from older embryos, broadly reproducing the temporal pattern of expression observed in vivo. This stage-specific expression is dependent on sequences upstream of the eve transcription start site which contain multiple binding sites for at least two distinct proteins present in embryo nuclei. One of these proteins, the binding sites for which correspond to the sequences required for stage-specific expression, appears to be the previously described GAGA factor. Although the binding activity of the GAGA factor remains constant, the level of the binding activity of the other protein, which we have called the TCCT factor, changes during the course of embryogenesis. Activity is first detected 3 to 5 h after fertilization and decreases during later stages of embryogenesis. We discuss the possibility that the TCCT factor plays a role in the maintenance or refinement of the eve expression pattern.
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Read, D., T. Nishigaki et J. L. Manley. « The Drosophila even-skipped promoter is transcribed in a stage-specific manner in vitro and contains multiple, overlapping factor-binding sites. » Molecular and Cellular Biology 10, no 8 (août 1990) : 4334–44. http://dx.doi.org/10.1128/mcb.10.8.4334.
Texte intégralRésumé :
To investigate the factors contributing to regulation of expression of the Drosophila segmentation gene even-skipped (eve), we have analyzed both the in vitro transcription and eve-promoter-binding proteins in embryo extracts. We show that the eve promoter is accurately and efficiently expressed in nuclear extracts derived from Drosophila embryos and that transcription is more efficient in extracts prepared from embryos at early stages of development than in those from older embryos, broadly reproducing the temporal pattern of expression observed in vivo. This stage-specific expression is dependent on sequences upstream of the eve transcription start site which contain multiple binding sites for at least two distinct proteins present in embryo nuclei. One of these proteins, the binding sites for which correspond to the sequences required for stage-specific expression, appears to be the previously described GAGA factor. Although the binding activity of the GAGA factor remains constant, the level of the binding activity of the other protein, which we have called the TCCT factor, changes during the course of embryogenesis. Activity is first detected 3 to 5 h after fertilization and decreases during later stages of embryogenesis. We discuss the possibility that the TCCT factor plays a role in the maintenance or refinement of the eve expression pattern.
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Qaleh, Ali Zeynali Aaq. « Segmentation of Cells from 3-D Confocal Images of Live Embryo ». International Journal of Intelligent Information Systems 3, no 6 (2014) : 45. http://dx.doi.org/10.11648/j.ijiis.s.2014030601.18.
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Sanders, E. J., et E. Cheung. « Ethanol treatment induces a delayed segmentation anomaly in the chick embryo ». Teratology 41, no 3 (mars 1990) : 289–97. http://dx.doi.org/10.1002/tera.1420410306.
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Gustavson, Elizabeth, Andrew S. Goldsborough, Zehra Ali et Thomas B. Kornberg. « The Drosophila engrailed and invected Genes : Partners in Regulation, Expression and Function ». Genetics 142, no 3 (1 mars 1996) : 893–906. http://dx.doi.org/10.1093/genetics/142.3.893.
Texte intégralRésumé :
Abstract We isolated and characterized numerous engrailed and invected alleles. Among the deficiencies we isolated, a mutant lacking invected sequences was viable and phenotypically normal, a mutant lacking engrailed was an embryo lethal and had slight segmentation defects, and a mutant lacking both engrailed and invected was most severely affected. In seven engrailed alleles, mutations caused translation to terminate prematurely in the central or C-terminal portion of the coding sequence, resulting in embryonic lethality and segmentation defects. Both engrailed and invected expression declined prematurely in these mutant embryos. In wild-type embryos, engrailed and invected are juxtaposed and are expressed in essentially identical patterns. A breakpoint mutant that separates the mgrailed and invected transcription units parceled different aspects of the expression pattern to engrailed or invected. We also found that both genes cause similar defects when expressed ectopically and that the protein products of both genes act to repress transcription in cultured cells. We propose that the varied phenotypes of the engrailed alleles can be explained by the differential effects these mutants have on the combination of engrailed and invected activities, that engrailed and invected share a regulatory region, and that they encode redundant functions.
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Vavra, S. H., et S. B. Carroll. « The zygotic control of Drosophila pair-rule gene expression. I. A search for new pair-rule regulatory loci ». Development 107, no 3 (1 novembre 1989) : 663–72. http://dx.doi.org/10.1242/dev.107.3.663.
Texte intégralRésumé :
The examination of pair-rule gene expression in wild-type and segmentation mutant embryos has identified many, but not necessarily all, of the elements of the regulatory system that establish their periodic patterns. Here we have conducted a new type of search for previously unknown regulators of these genes by examining pair-rule gene expression in blastoderm embryos lacking parts of or entire chromosomes. This method has the advantage of direct inspection of abnormal pair-rule gene patterns without relying upon mutagenesis or interpretation of larval phenotypes for the identification of segmentation genes. From these experiments we conclude that: (i) most zygotically required regulators of the fushi tarazu (ftz), even-skipped (eve) and hairy (h) pair-rule genes have been identified, except for one or more loci we have uncovered on chromosome arm 2L; (ii) the repression of the ftz and eve genes in the anterior third of the embryo is under maternal, not zygotic control; and (iii) there are no general zygotically required activators of pair-rule gene expression. The results suggest that the molecular basis of pair-rule gene regulation can be pursued with greater confidence now that most key trans-acting factors are already in hand.