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Human Embryos (human + embryo)
Selected AbstractsThe Anatomy of the Human Embryo: A Scanning Electron-Microscope AtlasJOURNAL OF ANATOMY, Issue 5 2009Gillian Morriss-Kay No abstract is available for this article. [source] Embryonic holoprosencephaly: pathology and phenotypic variabilityCONGENITAL ANOMALIES, Issue 4 2006Shigehito Yamada ABSTRACT Holoprosencephaly (HPE) is one of the major brain anomalies caused by the failure of cleavage of the prosencephalon during the early stage of development. Over 200 cases of HPE in the Kyoto Collection of Human Embryos were observed grossly and histologically, with special emphasis on the anomalies of the brain, face and eye. The facial anomalies of HPE human embryos after Carnegie stage (CS) 18 could be classified into cyclopia, synophthalmia, ethmocephaly, cebocephaly, and premaxillary agenesis, similarly as the classical classification for postnatal cases. On the other hand, HPE embryos at CS 13,17 showed some characteristic facies which are different from those in older embryos. In the present paper, pathology and phenotypic variability in HPE embryos were discussed from the embryopathological point of view. Recently, the molecular mechanism of HPE has been clarified by the techniques of gene manipulation, and various HPE genes have been identified by gene analysis of familial HPE cases. HPE is one of the major CNS anomalies which have been extensively studied and provides a clue to the mechanisms of normal and abnormal development of craniofacial structures. [source] Feminists on the Inalienability of Human EmbryosHYPATIA, Issue 1 2006Carolyn Mcleod The feminist literature against the commodification of embryos in human embryo research includes an argument to the effect that embryos are "intimately connected" to persons, or morally inalienable from them. We explore why embryos might be inalienable to persons and why feminists might find this view appealing. But, ultimately, as feminists, we reject this view because it is inconsistent with full respect for women's reproductive autonomy and with a feminist conception of persons as relational, embodied beings. Overall, feminists should avoid claims about embryos' being inalienable to persons in arguments for or against the commodification of human embryos. [source] Human embryo and early fetus researchCLINICAL GENETICS, Issue 2 2006H Ostrer Studies of human embryos and fetuses have highlighted developmental differences between humans and model organisms. In addition to describing the normal biology of our own species, a justification in itself, studies of early human development have aided identification of candidate disease genes mapped by positional cloning strategies, understanding pathophysiology, where human disorders are not faithfully reproduced by models in other species, and, more recently, potential therapies based on human embryonic stem and embryonic germ cells. In this article, we review these applications. We also discuss when and how to study human embryo and early fetuses and some of the regulations of this research. [source] Magnetic resonance microscopy versus light microscopy in human embryology teachingCLINICAL ANATOMY, Issue 5 2004J. Puerta-Fonollá Abstract A study was carried out on the application of magnetic resonance microscopy (MRM) in teaching prenatal human development. Human embryos measuring 8 mm, 15 mm, 18.5 mm, and 22 mm were fixed in a 4% paraformaldehyde solution and sections obtained with magnetic resonance imaging (MRI) were compared to those prepared for light microscopy (LM), using the same embryos. The MRM and LM slices were of a similar quality. In the MRM sections, embryonic organs and systems were clearly visible, particularly the peripheral and central nervous systems, and the cardiovascular and digestive systems. The digitalization and clarity of the MRM images make them an ideal teaching aid that is suitable for students during the first years of a health-science degree, particularly medicine. As well as providing students with their first experience of MRM, these images allow students to access, at any time, all embryos used, to assess changes in the positions of different organs throughout their stages of development, and to acquire spatial vision, an absolute requirement in the study of human anatomy. We recommend that this technique be incorporated into the wealth of standard embryonic teaching methods already in use. Clin. Anat. 17:429,435, 2004. © 2004 Wiley-Liss, Inc. [source] Neurulation in the human embryo revisitedCONGENITAL ANOMALIES, Issue 2 2000Tomoko Nakatsu ABSTRACT It used to be widely accepted that neural tube closure in the human initiates at the level of the future neck and proceeds both cranially and caudally like zip fastener closing. This continuous closure model was recently challenged, and observation of human embryos at the neurulation stage revealed that the closure of the human neural tube initiates at multiple sites. Multi-site closure of the neural tube has been observed in many other animal species, but the initiation sites and the process of neural tube closure are variable among species. Therefore we should be careful when extrapolating the data of normal and abnormal neurulation in laboratory animals to the human. Recent studies in mouse genetics and developmental biology have shown that neural tube defects are quite heterogeneous both etiologically and pathogenetically. Gene mutations responsible for human neural tube defects are largely unknown, but molecular studies of human cases of neural tube defects and their comparison with the mouse genome data should provide a molecular basis for human neural tube defects. [source] Too much of a good thing: retinoic acid as an endogenous regulator of neural differentiation and exogenous teratogenEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003P. J. McCaffery Abstract Retinoic acid (RA) is essential for both embryonic and adult growth, activating gene transcription via specific nuclear receptors. It is generated, via a retinaldehyde intermediate, from retinol (vitamin A). RA levels require precise regulation by controlled synthesis and catabolism, and when RA concentrations deviate from normal, in either direction, abnormal growth and development occurs. This review describes: (i) how the pattern of RA metabolic enzymes controls the actions of RA; and (ii) the type of abnormalities that result when this pattern breaks down. Examples are given of RA control of the anterior/posterior axis of the hindbrain, the dorsal/ventral axis of the spinal cord, as well as certain sex-specific segments of the spinal cord, using varied animal models including mouse, quail and mosquitofish. These functions are highly sensitive to abnormal changes in RA concentration. In rodents, the control of neural patterning and differentiation are disrupted when RA concentrations are lowered, whereas inappropriately high concentrations of RA result in abnormal development of cerebellum and hindbrain nuclei. The latter parallels the malformations seen in the human embryo exposed to RA due to treatment of the mother with the acne drug Accutane (13- cis RA) and, in cases where the child survives beyond birth, a particular set of behavioural anomalies can be described. Even the adult brain may be susceptible to an imbalance of RA, particularly the hippocampus. This report shows how the properties of RA as a neural induction agent and organizer of segmentation can explain the consequences of RA depletion and overexpression. [source] The KRAB Domain of Zinc Finger Gene ZNF268: a Potential Transcriptional RepressorIUBMB LIFE, Issue 3 2003Yan Sun Abstract Nearly one-third of Krupple-type C2H2 zinc finger proteins have a krupple-associated box (KRAB) domain, which may act as a transcriptional repressor. ZNF268, which was novelty isolated from early human embryo, is a typical krupple-type C2H2 zinc finger protein with a conserved KRAB domain. In this report, the KRAB domain of ZNF268 is identified to localize in the nucleus and has transcriptional repressor activity. IUBMB Life, 55: 127-131, 2003 [source] Development of the genital ducts and external genitalia in the early human embryoJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 5 2010Yasmin Sajjad Abstract The course of development of the human genital tract is undifferentiated to the 9th week of development. At this time two symmetrical paired ducts known as the mesonephric (MD) and paramesonephric ducts (PMD) are present, which together with the urogenital sinus provide the tissue sources for internal and external genital development. Normal differentiation of the bipotential external genitalia and reproductive ducts are dependent upon the presence or absence of certain hormones. Masculinization of the internal and external genitalia during fetal development depends on the existence of two discrete testicular hormones. Testosterone secreted from Leydig cells induces the differentiation of the mesonephric ducts into the epididymis, vasa deferentia and seminal vesicles, whereas anti-Müllerian hormone (AMH) produced by Sertoli cells induces the regression of the paramesonephric ducts. The absence of AMH action in early fetal life results in the formation of the fallopian tubes, uterus and upper third of the vagina. In some target tissues, testosterone is converted to dihydrotestosterone, which is responsible for the masculinization of the urogenital sinus and external genitalia. [source] Infant Intersubjectivity: Research, Theory, and Clinical ApplicationsTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 1 2001Colwyn Trevarthen We review research evidence on the emergence and development of active " self-and-other " awareness in infancy, and examine the importance of its motives and emotions to mental health practice with children. This relates to how communication begins and develops in infancy, how it influences the individual subject's movement, perception, and learning, and how the infant's biologically grounded self-regulation of internal state and self-conscious purposefulness is sustained through active engagement with sympathetic others. Mutual selfother- consciousness is found to play the lead role in developing a child's cooperative intelligence for cultural learning and language. A variety of preconceptions have animated rival research traditions investigating infant communication and cognition. We distinguish the concept of " intersubjectivity ", and outline the history of its use in developmental research. The transforming body and brain of ahumanindividual grows in active engagement with an environment of human factors-organic at first, then psychological or inter-mental. Adaptive, human-responsive processes are generated first by interneuronal activity within the developing brain as formation of the human embryo is regulated in a support-system of maternal tissues. Neural structures are further elaborated with the benefit of intra-uterine stimuli in the foetus, then supported in the rapidly growing forebrain and cerebellum of the young child by experience of the intuitive responses of parents and other human companions. We focus particularly on intrinsic patterns and processes in pre-natal and post-natal brain maturation that anticipate psychosocial support in infancy. The operation of an intrinsic motive formation (IMF) that developed in the core of the brain before birth is evident in the tightly integrated intermodal sensory-motor coordination of a newborn infant's orienting to stimuli and preferential learning of human signals, by the temporal coherence and intrinsic rhythms of infant behaviour, especially in communication, and neonates' extraordinary capacities for reactive and evocative imitation. The correct functioning of this integrated neural motivating system is found to be essential to the development of both the infant's purposeful consciousness and his or her ability to cooperate with other persons' actions and interests, and to learn from them. The relevance of infants' inherent intersubjectivity to major child mental health issues is highlighted by examining selected areas of clinical concern. We review recent findings on postnatal depression, prematurity, autism, ADHD, specific language impairments, and central auditory processing deficits, and comment on the effcacy of interventions that aim to support intrinsic motives for intersubjective communication when these are not developing normally. [source] ALTERNATE NUCLEAR TRANSFER IS NO ALTERNATIVE FOR EMBRYONIC STEM CELL RESEARCHBIOETHICS, Issue 2 2008JOHN A. FENNEL ABSTRACT Recent developments allow for the creation of human stem cells without the creation of human embryos, a process called alternate nuclear transfer (,ANT'). Pursuing this method of stem cell research makes sense for pro-lifers if arguments for the sanctity of the human embryo do not apply to ANT. However, the technology that makes ANT possible undermines the erstwhile technical barrier between human embryos and somatic cell DNA. These advances bring home the force of hypothetical arguments about the potential of the DNA in somatic cells, showing that there is not a morally relevant difference between the potential of an embryo and the potential of the DNA in a somatic cell. Therefore, the supposed distinction between entities that are potential human life and entities that are human life does not give any support to arguments for the sanctity of the human embryo because those arguments extend value to too many entities. [source] Variability in human embryonic development and its implications for the susceptibility to environmental teratogenesisBIRTH DEFECTS RESEARCH, Issue 8 2009Kohei Shiota Abstract Considerable variability is observed in the size and developmental stage among human embryos at a given gestational age, suggesting that prenatal development does not proceed at the same speed in every embryo. Such variability in embryonic development seems to occur in many (probably all) animal species, and is probably a normal "biologic" phenomenon to some extent. In the case of humans, some other factors (e.g., maternal memory bias, difficulty in assessing the timing of ovulation and fertilization) make it more difficult to assess the developmental stage of embryos in utero. Such facts related to human embryonic development should be taken into account when the teratogenic risk of a human embryo is considered. Birth Defects Research (Part A), 2009. © 2009 Wiley-Liss, Inc. [source] The effect of fever, febrile illnesses, and heat exposures on the risk of neural tube defects in a Texas-Mexico border populationBIRTH DEFECTS RESEARCH, Issue 10 2004Lucina Suarez Abstract BACKGROUND Hyperthermia produces neural tube defects (NTDs) in a variety of animal species. Elevated maternal body temperatures may also place the developing human embryo at risk. We examined the relation between maternal hyperthermia and the development of NTDs in a high-risk Mexican-American population. METHODS Case-women were Mexican-American women with NTD-affected pregnancies who resided and delivered in any of the 14 Texas counties bordering Mexico, during 1995,2000. Control-women were randomly selected from study area residents delivering normal live births, frequency-matched to cases by hospital and year. Information on maternal fevers, febrile illnesses, exposures to heat generated from external sources, and hyperthermia-inducing activities was gathered through in-person interviews, conducted about six weeks postpartum. RESULTS The risk effect (OR) associated with maternal fever in the first trimester, compared to no fever, was 2.9 (95% CI, 1.5,5.7). Women taking fever-reducing medications showed a lower risk effect (OR, 2.4; 95% CI, 1.0,5.6) than those who did not (OR, 3.8; 95% CI, 1.4,10.9). First-trimester maternal exposures to heat devices such as hot tubs, saunas, or electric blankets were associated with an OR of 3.6 (95% CI, 1.1,15.9). Small insignificant effects were observed for activities such as cooking in a hot kitchen (OR, 1.6; 95% CI, 1.0,2.6) and working or exercising in the sun (OR, 1.4; 95% CI, 0.9,2.2). CONCLUSIONS Maternal hyperthermia increases the risk for NTD-affected offspring. Women intending to become pregnant should avoid intense heat exposures, carefully monitor and manage their febrile illnesses, and routinely consume folic acid supplements. Birth Defects Research (Part A), 2004. © 2004 Wiley-Liss, Inc. [source] Septation of the anorectal and genitourinary tracts in the human embryo: Crucial role of the catenoidal shape of the urorectal sulcusBIRTH DEFECTS RESEARCH, Issue 4 2002Daniel S. Rogers Background Previous studies of the tracheoesophageal sulcus and the sulci of the developing heart have suggested that the catenoidal or saddle-shaped configuration of the sulcus had mechanical properties that were important to developmental processes by causing regional growth limitation. We examined the development of the human perineal region to determine if a similar configuration exists in relation to the urorectal septum. We wished to re-examine the controversial issue of the role of the urorectal sulcus in the partitioning of the cloaca. Methods Digitally scanned photomicrographs of serial histologic sections of embryos from Carnegie stages 13, 15, 18, and 22, obtained from the Carnegie Embryological Collection were used. Each image was digitally stacked, aligned, and isolated using image-editing software. Images were compiled using 3-D image-visualization software (T-Vox), into full 3-D voxel-based volume renderings. Similarly, digital models were made of the urogenital sinus, anorectum, cloaca, allantois, mesonephric ducts, ureters, and kidneys by isolating their associated epithelium in each histologic section and compiling the data in T-Vox. Methods were developed to create registration models for determining the exact position and orientation of outlined structures within the embryos. Results Models were oriented and resectioned to determine the configuration of the urorectal sulcus. The results show that the urorectal sulcus maintains a catenoidal configuration during the developmental period studied and, thus, would be expected to limit caudal growth of the urorectal septum. Conclusion The observations support the concept that the urorectal septum is a passive structure that does not actively divide the cloaca into urogenital and anorectal components. Teratology 66:144,152, 2002. © 2002 Wiley-Liss, Inc. [source] Human embryo and early fetus researchCLINICAL GENETICS, Issue 2 2006H Ostrer Studies of human embryos and fetuses have highlighted developmental differences between humans and model organisms. In addition to describing the normal biology of our own species, a justification in itself, studies of early human development have aided identification of candidate disease genes mapped by positional cloning strategies, understanding pathophysiology, where human disorders are not faithfully reproduced by models in other species, and, more recently, potential therapies based on human embryonic stem and embryonic germ cells. In this article, we review these applications. We also discuss when and how to study human embryo and early fetuses and some of the regulations of this research. [source] Embryonic holoprosencephaly: pathology and phenotypic variabilityCONGENITAL ANOMALIES, Issue 4 2006Shigehito Yamada ABSTRACT Holoprosencephaly (HPE) is one of the major brain anomalies caused by the failure of cleavage of the prosencephalon during the early stage of development. Over 200 cases of HPE in the Kyoto Collection of Human Embryos were observed grossly and histologically, with special emphasis on the anomalies of the brain, face and eye. The facial anomalies of HPE human embryos after Carnegie stage (CS) 18 could be classified into cyclopia, synophthalmia, ethmocephaly, cebocephaly, and premaxillary agenesis, similarly as the classical classification for postnatal cases. On the other hand, HPE embryos at CS 13,17 showed some characteristic facies which are different from those in older embryos. In the present paper, pathology and phenotypic variability in HPE embryos were discussed from the embryopathological point of view. Recently, the molecular mechanism of HPE has been clarified by the techniques of gene manipulation, and various HPE genes have been identified by gene analysis of familial HPE cases. HPE is one of the major CNS anomalies which have been extensively studied and provides a clue to the mechanisms of normal and abnormal development of craniofacial structures. [source] Neurulation in the human embryo revisitedCONGENITAL ANOMALIES, Issue 2 2000Tomoko Nakatsu ABSTRACT It used to be widely accepted that neural tube closure in the human initiates at the level of the future neck and proceeds both cranially and caudally like zip fastener closing. This continuous closure model was recently challenged, and observation of human embryos at the neurulation stage revealed that the closure of the human neural tube initiates at multiple sites. Multi-site closure of the neural tube has been observed in many other animal species, but the initiation sites and the process of neural tube closure are variable among species. Therefore we should be careful when extrapolating the data of normal and abnormal neurulation in laboratory animals to the human. Recent studies in mouse genetics and developmental biology have shown that neural tube defects are quite heterogeneous both etiologically and pathogenetically. Gene mutations responsible for human neural tube defects are largely unknown, but molecular studies of human cases of neural tube defects and their comparison with the mouse genome data should provide a molecular basis for human neural tube defects. [source] Graphic and movie illustrations of human prenatal development and their application to embryological education based on the human embryo specimens in the Kyoto collectionDEVELOPMENTAL DYNAMICS, Issue 2 2006Shigehito Yamada Abstract Morphogenesis in the developing embryo takes place in three dimensions, and in addition, the dimension of time is another important factor in development. Therefore, the presentation of sequential morphological changes occurring in the embryo (4D visualization) is essential for understanding the complex morphogenetic events and the underlying mechanisms. Until recently, 3D visualization of embryonic structures was possible only by reconstruction from serial histological sections, which was tedious and time-consuming. During the past two decades, 3D imaging techniques have made significant advances thanks to the progress in imaging and computer technologies, computer graphics, and other related techniques. Such novel tools have enabled precise visualization of the 3D topology of embryonic structures and to demonstrate spatiotemporal 4D sequences of organogenesis. Here, we describe a project in which staged human embryos are imaged by the magnetic resonance (MR) microscope, and 3D images of embryos and their organs at each developmental stage were reconstructed based on the MR data, with the aid of computer graphics techniques. On the basis of the 3D models of staged human embryos, we constructed a data set of 3D images of human embryos and made movies to illustrate the sequential process of human morphogenesis. Furthermore, a computer-based self-learning program of human embryology is being developed for educational purposes, using the photographs, histological sections, MR images, and 3D models of staged human embryos. Developmental Dynamics 235:468,477, 2006. © 2005 Wiley-Liss, Inc. [source] Typing of the immunological system in human embryos by coelocentesisEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 5 2007Maria Concetta Renda Abstract Coelocentesis offers a new opportunity for gaining access to the human embryos from 28 d postfertilization. However, while some studies about its biochemical composition have been reported, our knowledge about immunological pattern of this compartment is still limited. For this reason, we studied the human coelomic fluids sampled from 6.6 to 10 wk of gestation. The majority of cellular population consisted in mesenchymal/epithelial cells. In fluids sampled before 10 wk we found only a preT Cell Receptor expression and an absence or a very low frequency of B lymphocytes, T lymphocytes and NK (natural killer) antigens. These preliminary data suggest that the immunological system in human embryos could be in the ideal conditions to start a process of tolerance induction. [source] Feminists on the Inalienability of Human EmbryosHYPATIA, Issue 1 2006Carolyn Mcleod The feminist literature against the commodification of embryos in human embryo research includes an argument to the effect that embryos are "intimately connected" to persons, or morally inalienable from them. We explore why embryos might be inalienable to persons and why feminists might find this view appealing. But, ultimately, as feminists, we reject this view because it is inconsistent with full respect for women's reproductive autonomy and with a feminist conception of persons as relational, embodied beings. Overall, feminists should avoid claims about embryos' being inalienable to persons in arguments for or against the commodification of human embryos. [source] Strange Anatomy: Gertrude Stein and the Avant-Garde EmbryoHYPATIA, Issue 1 2006Lynn M. Morgan Today's personable, sanitized images of human embryos and fetuses require an audience that is literally and metaphorically distanced from dead specimens. Yet scientists must handle dead specimens to produce embryological knowledge, which only then can be transformed into beautiful photographs and talking fetuses. I begin with an account of Gertrude Stein's experience making a model of a fetal brain. Her tactile encounter is contrasted to the avant-garde artistic tradition that later came to dominate embryo imagery. This essay shows the embryo visualizations portrayed in a contemporary coffee-table book about gestational development to be a remarkable political achievement predicated, in part, on keeping hidden the unsavory details of anatomical technique that transform dead specimens into icons of life. [source] Neurulation in the cranial region , normal and abnormalJOURNAL OF ANATOMY, Issue 5 2005Andrew J. Copp Abstract Cranial neurulation is the embryonic process responsible for formation of the brain primordium. In the mouse embryo, cranial neurulation is a piecemeal process with several initiation sites and two neuropores. Variation in the pattern of cranial neurulation occurs in different mouse strains, and a simpler version of this morphogenetic scheme has been described in human embryos. Exencephaly is more common in females than in males, an unexplained phenomenon seen in both mice and humans. As the cranial neural tube closes, a critical morphogenetic event is the formation of dorsolateral bending points near the neural fold tips, which enables subsequent midline fusion of the neural folds. Many mutant and gene-targeted mouse strains develop cranial neural tube defects, and analysis of the underlying molecular defects identifies several requirements for normal dorsolateral bending. These include a functional actin cytoskeleton, emigration of the cranial neural crest, spatio-temporally regulated apoptosis, and a balance between cell proliferation and the onset of neuronal differentiation. A small number of mouse mutants exhibit craniorachischisis, a combined brain and spine neurulation defect. Recent studies show that disturbance of a single molecular signalling cascade, the planar cell polarity pathway, is implicated in mutants with this defect. [source] An ontology of human developmental anatomyJOURNAL OF ANATOMY, Issue 4 2003Amy Hunter Human developmental anatomy has been organized as structured lists of the major constituent tissues present during each of Carnegie stages 1,20 (E1,E50, ,8500 anatomically defined tissue items). For each of these stages, the tissues have been organized as a hierarchy in which an individual tissue is catalogued as part of a larger tissue. Such a formal representation of knowledge is known as an ontology and this anatomical ontology can be used in databases to store, organize and search for data associated with the tissues present at each developmental stage. The anatomical data for compiling these hierarchies comes from the literature, from observations on embryos in the Patten Collection (Ann Arbor, MI, USA) and from comparisons with mouse tissues at similar stages of development. The ontology is available in three versions. The first gives hierarchies of the named tissues present at each Carnegie stage (http://www.ana.ed.ac.uk/anatomy/database/humat/) and is intended to help analyse both normal and abnormal human embryos; it carries hyperlinked notes on some ambiguities in the literature that have been clarified through analysing sectioned material. The second contains many additional subsidiary tissue domains and is intended for handling tissue-associated data (e.g. gene-expression) in a database. This version is available at the humat site and at http://genex.hgu.mrc.ac.uk/Resources/intro.html/), and has been designed to be interoperable with the ontology for mouse developmental anatomy, also available at the genex site. The third gives the second version in GO ontology syntax (with standard IDs for each tissue) and can be downloaded from both the genex and the Open Biological Ontology sites (http://obo.sourceforge.net/) [source] Separation between the digestive and the respiratory lumina during the human embryonic period: morphometric study along the tracheo-oesophageal septumJOURNAL OF ANATOMY, Issue 1 2001JOSEP NEBOT-CEGARRA An isolated tracheo-oesophageal fistula could be caused by close proximity of the epithelia of both organs (O'Rahilly & Müller, 1984; Kluth et al. 1987) at certain embryonic stages, the most frequent location being the tracheal bifurcation. Thus the relative position and degree of separation between the digestive and the respiratory tubes throughout their development may be relevant to the origin of this anomaly. The aim of this study was to analyse along the different segments of the tracheo-oesophageal septum (TES) where the closest relationship between both lumina occurred and what degree of separation was present at each segment. Computer imaging techniques were applied on cross sections of a graded series of normal human embryos (Carnegie stages (CS) 13,23). In addition, the differentiation of the primitive TES was also studied (from CS 12) by light microscopy. Between CS 13 and 16 both tubes tended to separate (phase of separation), principally at the proximal segments of the laryngopharyngeal and the tracheo-oesophageal portions of the TES. During this phase the separation between the trachea and oesophagus was wider than between the larynx and pharynx. From CS 17 to CS 23 the digestive and respiratory lumina reached their widest separation at different levels of the laryngopharyngeal portion. Below these levels they tended to come closer together, principally at the proximal segment of the tracheo-oesophageal portion, but also at the distal part of the laryngopharyngeal portion. During this phase of approximation they reached their closest relationship at the proximal (CS 17) and the distal (from CS 18) segments of the tracheo-oesophageal portion. When finally the distal segment of the trachea (which includes the bifurcation) comes closest to the oesophagus, the coats of both organs have already undergone an appreciable differentiation. According to these observations, the origin of the most frequent isolated tracheo-oesophageal fistula at the bifurcation region could not be explained from the normal development of the TES. [source] Slow programmable and ultra-rapid freezing of human embryosJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 4 2008Teraporn Vutyavanich Abstract Aim:, To compare the outcomes of slow freezing with ultra-rapid freezing (URF) of cleavage-stage human embryos on aluminum foil. Methods:, Two-cell mouse embryos were used to test our method of ultra-rapid freezing. The embryos were randomly allocated to a non-frozen control (208 embryos), and slow (204 embryos) or ultra-rapid freezing groups (204 embryos). Immediate survival rate, further cleavage and blastocyst formation were compared. After validating our ultra-rapid freezing method on mouse embryos, we applied a similar ultra-rapid freezing protocol to human embryos. Consecutive human frozen/thawed embryo transfer (FET) cycles from October 1998 to June 2005 were reviewed. The survival rate, further cleavage rate and the pregnancy outcomes were compared between the URF and slow programmable freezing. Results:, Mouse embryos in the URF group survived the freezing/thawing process better than those in the slow freezing group (93.1% vs 82.8%, P = 0.001). Blastocyst and hatching blastocyst formation of the surviving embryos were comparable in the URF and slow freezing group (59% vs 58.6%, P = 0.944 and 32.6% vs 42%, P = 0.066, respectively). There were 146 human FET cycles in the URF group and 28 cycles in the slow freezing group. The immediate survival of embryos was higher in the URF group than in the slow freezing group (87.9% and 64.3%, P < 0.001). There was no significant difference in the mean number of embryos per transfer (3.7 ± 1.3 and 3.3 ± 1.2, P = 0.178), clinical pregnancy rate per transfer (28.5% and 21.4%, P = 0.444) and implantation rate per embryo (10.98% and 10.9%, P = 0.974) in the URF or slow freezing groups. Conclusion:, Our in-house URF method gave comparable results to slow programmable freezing. Although the risk of potential contamination is a major drawback of the present ultra-rapid freezing technique, future refinement will minimize or entirely eliminate this concern. [source] KILLING EMBRYOS FOR STEM CELL RESEARCHMETAPHILOSOPHY, Issue 2-3 2007JEFF MCMAHAN Abstract: The main objection to human embryonic stem cell research is that it involves killing human embryos, which are essentially beings of the same sort that you and I are. This objection presupposes that we once existed as early embryos and that we had the same moral status then that we have now. This essay challenges both those presuppositions, but focuses primarily on the first. I argue first that these presuppositions are incompatible with widely accepted beliefs about both assisted conception and monozygotic twinning. I then argue that we never existed as embryos. If this last claim is right, killing an embryo does not kill someone like you or me but merely prevents one of us from existing. [source] Embryonic erythropoiesis in human yolk sac: Two different compartments for two different processesMICROSCOPY RESEARCH AND TECHNIQUE, Issue 12 2008Jaime Pereda Abstract The wall of 12 yolk sacs (YSs) from 17- to 50-day-old human embryos was examined by light, scanning, and transmission electron microscopy to identify the ontogeny of embryonic erythropoiesis. Initial formation of blood island with the generation of erythroid and endothelial cells was seen in the mesenchymal layer in embryos aged 17 days. A network of blood vessels containing abundant erythroblasts was identified in the YS walls of embryos aged ,24 days. At this age, erythroblasts were also identified within the embryo body. Primitive erythroblasts were the only cells present within the embryo and its YS until the end of week 5. These cells first appeared in the mesenchymal vascular plexus of the YS wall, and were then observed in the liver and other tissues of the embryo. At embryonic week 5, two compartments were identified in the YS wall; a mesodermal one in which blood vessels were formed, and an endodermal compartment in which erythrocytes were present within the endodermal vesicles. Erythrocytes were small non-nucleated cells similar to adult erythrocytes. Transmission electron microscopic observation focused on the endodermal vesicles confirmed the presence of definitive erythrocytes only at such extra vascular location. At this age, there were no definitive erythrocytes detected within the embryo. Erythrocytes started to be identified in embryonic blood vessels from week 7 onward. These findings provide information not previously described about YS erythropoiesis during early human development. Microsc. Res. Tech., 2008. © 2008 Wiley-Liss, Inc. [source] Early pathogenesis of holoprosencephaly,AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 1 2010Kohei Shiota Abstract Holoprosencephaly (HPE) is one of the most common malformations encountered in early human embryos. It is assumed that more than 90% of HPE embryos die in utero and are eliminated by spontaneous abortion. Embryonic HPE displays some characteristic craniofacial phenotypes, which are not necessarily comparable to those in postnatal HPE cases. In this article, we summarize our studies on HPE in human embryos and discuss the pathogenesis of HPE malformations. © 2010 Wiley-Liss, Inc. [source] Chromosome topology in normal and aneuploid blastomeres from human embryosPRENATAL DIAGNOSIS, Issue 12 2007Jan Diblík Abstract Objectives To find whether chromosomes 13, 16, 18, 21, 22, X and Y in blastomeres of human embryos are nonrandomly localized, whether their aneuploidy affects their localization and if eventual early inactivation of chromosome X with peripheral localization is present. Methods Relative distances from the nucleus center and edge of 1198 fluorescence in situ hybridization signals in 98 human blastomeres were measured in digital images for comparison with a mathematical model of random distribution in spherical nucleus. Results Comparison with the mathematical model revealed that localization of chromosomes 13, 16, 21, 22, X and Y in normal and aneuploid blastomeres and that of chromosome 18 in normal blastomeres was not significantly different from random distribution. Similarly, chromosome X in blastomeres with more than one X did not appear to have a preferential localization. Only chromosome 18 in aneuploid blastomeres was differently distributed (p < 0.0001) with a shift to the nuclear periphery (p = < 0.0001). Conclusions Peripheral localization of chromosome 18 in aneuploid blastomeres is related to embryo aneuploidy. Conversely, a peripheral localization of the inactive X chromosome was not found in blastomeres from 3-4 day old embryos. These results open the possibility to improve embryo selection after pre-implantation diagnosis. Copyright © 2007 John Wiley & Sons, Ltd. [source] Determination of the genetic status of cleavage-stage human embryos by microsatellite marker analysis following multiple displacement amplificationPRENATAL DIAGNOSIS, Issue 3 2007Pamela J. Renwick Abstract Objectives To analyse genotype information from cleavage-stage human embryos and assess the chromosomal status and feasibility of performing aneuploidy screening by microsatellite analysis. Methods DNA from 49 blastomeres from eight cleavage-stage human embryos was amplified using multiple displacement amplification, then tested for panels of 64 polymorphic microsatellite markers on seven different chromosomes, and for two non-polymorphic sequences on the X and Y chromosomes. Results There was an overall allele drop out (ADO) rate of 28%. Novel alleles in single cells were seen in 0.3% of amplifications, interpreted as either somatic microsatellite mutation events or ,slippage' of the MDA , 29 polymerase. Three-allele results for a single marker in a single cell were found in 0.07% of amplifications, interpreted as ,slippage' of the MDA , 29 polymerase. One apparent segmental duplication was found. Only one embryo with no normal cells was found, probably arising from the chaotic cleavage division following a triploid conception. Six embryos were mosaic, of which four had only one abnormal cell. Conclusions Abnormalities in human embryos may be present in only a single cell, leading to potentially false abnormal results at pre-implantation genetic diagnosis. ADO associated with MDA reduces the efficacy of this approach for detection of aneuploidy. Statistical analysis showed that, for ADO of 28%, seven informative markers would be required to give 95% confidence of detecting trisomic embryos. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||