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PubMed1985

[Death of myocardiocytes and destruction of their structures during embryonic histogenesis].

By means of light and electron microscopy, death of cardiomyocytes and their structures has been studied in the myocardium of chick (the 4th-20th days of incubation) and in rat (the 14th-20th days of embryogenesis) embryos. The same processes have been studied after a single and repeated injections of insulin and 5-fluorauracyl to the chick embryos (into the air chamber of the egg). In the myocardium of the chick and rat embryos atrophy of some muscle cells takes place as a demonstration of histogenetic (physiological) death characterized by changes in nucleo- and cytoplasm according to the "dark" type. Under the effect of 5-fluorauracyl the same type of cardiomyocyte death is observed; differences with the control are but quantitative ones. When the chick embryo is affected with cytotoxic concentrations of insulin, together with histogenetic death of the cardiomyocytes (the "dark" type) the death according to the "light" type also takes place. Under the effect of both insulin and 5-fluorauracyl the destructive processes in the cardiomyocytes are manifested greater than in the control. This is a morphological manifestation of certain disturbances in processes of physiological restoration at the cellular level.

Animals↗

PubMed1990

Primary structure and embryonic expression pattern of the mouse Hox-4.3 homeobox gene.

We report the cloning, genomic localization, primary structure and developmental expression pattern of the novel mouse Hox-4.3 gene. This gene is located within the HOX-4(5) complex, at a position which classifies it as a member of the Hox-3.1 and -2.4 subfamily, the DNA and predicted protein sequences further confirmed this classification. Hox-4.3 has a primary structure characteristic of a Hox gene but, in addition, contains several monotonic stretches of amino acids, one of the 'paired'-like type. As expected from its presence and position within the complex. Hox-4.3 is developmentally expressed in structures of either mesodermal or neurectodermal origin located or derived from below a precise craniocaudal level. However, a very important offset between anteroposterior boundaries within neuroectoderm versus mesoderm derivatives is observed. Like other genes of the HOX-4(5) complex, Hox-4.3 is expressed in developing limbs and gonads, suggesting that 'cluster specificity' could be a feature of the HOX network.

Amino Acid Sequence↗

PubMed1987

Embryonic pig hemoglobins Gower I (zeta 2 epsilon 2), Gower II (alpha 2 epsilon 2), Heide I (zeta 2 theta 2) and Heide II (alpha 2 theta 2): oxygen-binding functions related to structure and embryonic oxygen supply.

The common pig lacks a fetal hemoglobin but has four embryonic hemoglobins: Gower I (zeta 2 epsilon 2), Gower II (alpha 2 epsilon 2), Heide I (zeta 2 theta 2) and Heide II (alpha 2 theta 2) as well as adult Hb A (alpha 2 beta 2) and the amino acid sequence for each of the five constituent polypeptide chains has been established. The oxygenation characteristics of the five components, measured in relation to pH, temperature and the erythrocytic ligand 2,3-diphosphoglycerate (DPG), together with the changes in their relative concentrations during early embryonic life, are given. The findings indicate a progressive decrease in maternal-fetal oxygen affinity difference and thus in oxygen transfer efficacy at a given diffusion gradient that correlates with the development of the gas exchange structures. The functional properties of the individual hemoglobins are additionally discussed in relation to molecular structure.

2,3-Diphosphoglycerate↗

PubMed2006

Derivation and characterization of gut-like structures from embryonic stem cells.

Embryonic stem (ES) cells have a pluripotent ability to differentiate into a variety of cell lineages of all three embryonic germ layers in vitro. The hanging drop culture of ES cell suspension in the absence of leukemia inhibitory factor induces aggregation and differentiation of the cells into simple or cystic embryoid bodies (EBs). After 6 d of hanging drop culture, the resulting EBs are plated onto plastic dishes for the outgrowth culture. At d 21 after outgrowth culture, cell populations of EBs can give rise to three-dimensional gut-like structures that exhibit spontaneous contraction and highly coordinated peristalsis. The gut-like structures have large lumens surrounded by three layers: epithelium, lamina propria, and muscularis. Ganglia are scattered along the periphery, and interstitial cells of Cajal are distributed among the smooth muscle cells. The fundamental process of formation of the in vitro organized gut-like structures is similar to embryonic gastrointestinal development in vivo. The EBs at the 6-d egg-cylinder stage may have the potential to regulate developmental programs associated with cell lineage commitment and provide an appropriate microenvironment to differentiate ES cells into enteric derivatives of all three embryonic germ layers and reproduce the gut organization process in vitro.

Animals↗

PubMed1994

Endovaginal ultrasonographic measurement of early embryonic size as a means of assessing gestational age.

Crown-rump length has consistently been found to be the most accurate method of determining gestational age in the first trimester. The original regression curve established by Robinson in 1973 with static arm scanners remains the one most widely employed. New endovaginal ultrasonographic probes afford a degree of detail that allows embryonic structures to be seen as soon as they are distinct from the yolk sac. Previously, measurements of very early embryonic structures have mistakenly been labeled crown-rump lengths. There has been widespread use of nomograms constructed from regression curves, where the bulk of the data were derived from small fetuses and then such curves extrapolated back to embryos of very small size. The purpose of this study was to establish a nomogram for gestational age assessment by measuring early embryos prior to the development of a "crown" or "rump." This present study consisted of 143 patients. To be included they had to have had no history of any prior bleeding, and all were delivered of singleton infants within 2 weeks of their estimated delivery date by last menstrual period. All had a single early embryonic size measurement between 1 and 25 mm using high-frequency endovaginal probes. Regression analysis revealed a linear equation of Gestational age (days) = early embryonic size (mm) + 42 with a correlation coefficient r = 0.87; 95% confidence limit = +/- 3 days. We conclude that using high-frequency vaginal ultrasonographic probes and having a better understanding of embryonic anatomic stages allow for the construction of a nomogram of gestational age derived from measurements of early embryonic size prior to development of a crown-rump length.

Anthropometry↗

PubMed2005

Multicellular structures developing during maize microspore culture express endosperm and embryo-specific genes and show different embryogenic potentialities.

During maize pollen embryogenesis, a range of multicellular structures are formed. Using different approaches, the "nature" of these structures has been determined in terms of their embryogenic potential. In situ molecular identification techniques for gene transcripts and products, and a novel cell tracking system indicated the presence of embryogenic (embryo-like structures, ELS) and non-embryogenic (callus-like structures, CLS) structures that occurred for short periods within the cultures. Some multicellular structures with a compact appearance generated embryos. RT-PCR and fluorescence in situ hybridization (FISH) with confocal microscopy techniques using specific gene markers of the endosperm (ZmESR2, ZmAE3) and embryo (LTP2 and ZmOCL1, ZmOCL3) revealed "embryo" and "endosperm" potentialities in these various multicellular structures present in the cultures. The results presented here showed distinct and specific patterns of gene expression. Altogether, the results demonstrate the presence of different molecules on both embryonic and non-embryonic structures. Their possible roles are discussed in the context of a parallel between embryo/endosperm interactions in planta and embryonic and non-embryonic structure interrelations under in vitro conditions.

Biomarkers↗

PubMed1997

Involvement of hepatocyte growth factor in formation of bronchoalveolar structures in embryonic rat lung in primary culture.

To clarify the role of hepatocyte growth factor (HGF) in embryonic lung development, organoids from fetal rat lung were cultured in collagen gels with or without HGF antisense oligonucleotides. Cyst-like structures formed within 24 h in organoids isolated from fetuses after 14 days' gestation, but this was abolished by the oligonucleotide addition, apparently by interference with the endogenous expression of HGF. Electron microscopy revealed two types of structure: an alveolar type characterized by osmiophilic lamellar bodies in the cytoplasm and lumen, and a bronchial type consisting of epithelial cells bearing microvilli on their apical surfaces. HGF mRNA was detectable from day 14 in fetal lung by RT-PCR. Our results suggest that HGF plays, coordinately with its expression, a crucial role in the morphogenesis of both alveolar and bronchial epithelia in the rat fetal lung.

Animals↗

PubMed1997

Ontogeny of prohormone convertases in rat prenatal development.

It has been well established that peptide precursors usually undergo limited proteolysis at pairs or single basic amino acids during their biosynthetic process. This posttranslational modification paradigm is common for numerous membrane-spanning and secreted proteins, neuropeptides, and peptide hormones of physiological significance, in which endoproteolytic cleavage is invariably essential for the accurate biosynthesis and full activity of the mature products. Establishment of an effective peptide profile is dependent on not only the presence of peptide precursor, but also the presence and the enzymatic specificities of cleavage enzymes. We have, therefore, characterized the spatial and temporal patterns of six subtilisin-like serine endoproteases known to be involved in proprotein processing, including furin, PC1, PC2, PC4, PC5, and PACE4, in rat prenatal development and related the results to the expression patterns of several peptide precursors. We have observed largely distinct and sometimes complementary expression patterns of individual PCs in various embryonic structures, suggesting PCs may be functionally distinct in processing different sets of proprotein substrates in development. From these studies, numerous tentative enzyme-substrate relationships in various embryonic structures have been proposed and should encourage more studies to test the in vitro cleavage potentialities of individual PCs toward these precursors. In the future, knowledge gained from these studies, when combined with insights gained from in vivo perturbation and genetic ablation studies, should lead to final comprehensive understanding of specific precursors cleaved by specific enzymes at specific cleavage sites in known spatial and temporal expression patterns during development.

Animals↗

PubMed1976

In vitro development of secondary blastodiscs from dispersed blastoderm cells of Gallus domesticus.

A study of the in vitro growth of embryonic structures from dispersed blastoderm cells is reported. The specific type of blastoderm cells with the capability of growing on the coverslip developed into the discoidal embryonic structures resembling those of avian species. The glass surface was apparently an initiator of differentiation into at least three types of cells specifically distributed in the blastodisc. Groups of structures formed were evaluated at 6, 12, 24 and 36 hours to study the developmental pattern in vitro and to estimate the number of cells per structure. Microscopic examination of the area pellucida revealed that all three basic germ layers were established after 24 hours of incubation in vitro. The 36 hour stage was represented by bulky growth of mesodermal-like cells and changes in hypoblast layer where some of the cells degenerated and some were transformed to mesenchymal spindle-like cells.

Animals↗

PubMed2002

Mixl1 is required for axial mesendoderm morphogenesis and patterning in the murine embryo.

In Xenopus, the Mix/Bix family of homeobox genes has been implicated in mesendoderm development. Mixl1 is the only known murine member of this family. To examine the role of Mixl1 in murine embryogenesis, we used gene targeting to create mice bearing a null mutation of Mixl1. Homozygous Mixl1 mutant embryos can be distinguished from their littermates by a marked thickening of the primitive streak. By the early somite stage, embryonic development is arrested, with the formation of abnormal head folds, foreshortened body axis, absence of heart tube and gut, deficient paraxial mesoderm, and an enlarged midline tissue mass that replaces the notochord. Development of extra-embryonic structures is generally normal except that the allantois is often disproportionately large for the size of the mutant embryo. In chimeras, Mixl1(-/-) mutant cells can contribute to all embryonic structures, with the exception of the hindgut, suggesting that Mixl1 activity is most crucial for endodermal differentiation. Mixl1 is therefore required for the morphogenesis of axial mesoderm, the heart and the gut during embryogenesis.

Animals↗

PubMed1999

Development of a morphologically-based scoring system for postimplantation New Zealand White rabbit embryos.

Rodent whole-embryo culture (WEC) systems are well-established, as are several corresponding morphological scoring systems. Recently, WEC techniques for rabbits have been developed, creating the need for a morphological evaluation system in this species. Consequently, we developed a gestational-age-based quantitative morphology evaluation system for rabbit embryos. Detailed descriptions of 21 embryonic structures, as collected from gestational day (gd) 9-13 rabbit embryos, formed the basis for this evaluation system. These descriptions were then developed into specific criteria for assigning numerical scores to quantify the degree of development of each embryonic structure. The overall morphologic score was calculated as the average of the individual structure scores. To make the system as informative as possible, the numerical scale of the scoring system was gestationally age-based (i.e., range of potential scores was 9.0-13.0). The scoring system was then applied in the evaluation of New Zealand White (NZW) rabbit embryos explanted on gd 9 and cultured for 48 hr. Embryos grown in vitro developed normally, but at a slightly slower rate in vitro than in vivo, as evidenced by the lower morphology score (10.4 in vitro, 11.0 in vivo) and measures of growth (somite number, total protein, and head length). This work firmly establishes the normal archetype of embryonic development in the gd 9-13 NZW rabbit and provides an important tool for the advancement of mechanistic studies of rabbit embryos developing both in vivo and in vitro.

Allantois↗

PubMed1992

Differential distribution patterns of CRABP I and CRABP II transcripts during mouse embryogenesis.

We have compared the transcript distribution of cellular retinoic acid binding protein (CRABP) I and II genes in mouse embryos at various stages of development. Both CRABP transcripts are present in embryonic structures from the earliest stages studied and exhibit specific patterns of distribution, suggesting that the two retinoic acid (RA) binding proteins perform different functions during mouse embryogenesis. The CRABP I transcript distribution correlates well with structures known to be targets of excess retinoid-induced teratogenesis (e.g. neural crest cells and hindbrain), suggesting that cells expressing CRABP I are those that cannot tolerate high levels of RA for their normal developmental function. The embryonic structures expressing CRABP II transcripts include those structures that have been shown to be adversely affected by excess of retinoids, such as limbs and hindbrain, but CRABP II transcripts are also found in structures not known to be specifically vulnerable to raised RA levels. The CRABP II gene is coexpressed with retinoic acid receptor (RAR)-beta and cellular retinol binding protein (CRBP) I genes in a number of tissues such as the gut endoderm, hypophysis and interdigital mesenchyme, all of which are devoid of CRABP I transcripts. Interestingly, the expression of the three genes, RAR-beta, CRABP II and CRBP I, is induced by retinoic acid, which suggests a link between the synthesis of RA from retinol and the control of expression of subsets of RA-responsive genes. The transcript distribution of CRABP I and II is discussed in relation to the teratogenic effects of RA, and compared to the RA-sensitive pattern of expression of other important developmental genes.

Abnormalities, Drug-Induced↗

PubMed1999

Genomic structure and embryonic expression of the Xenopus winged helix factors XFD-13/13'.

We have isolated the gene, its corresponding cDNA and a closely related cDNA encoding the Xenopus winged helix factors XFD-13' and XFD-13, respectively. XFD-13/13' are regarded as pseudo-alleles and, based upon a comparison of sequences and genomic structures, represent the Xenopus orthologues to mammalian FREAC-1/HFH-8. XFD-13/13' genes are not transcribed during oogenesis, zygotic transcription starts at late gastrula/early neurula and transcripts persist throughout embryogenesis. Expression is found within head derived neural crest cells and the dorsolateral plate (DLP). At later developmental stages, cell populations of the DLP migrate to the ventral region but exclude the most posterior part. Since they are subsequently found to accumulate in vessel like structures, we suggest that these cells represent hematopoietic/endothelial progenitor cells.

Amino Acid Sequence↗

PubMed2002

Genomic structure and embryonic expression of estrogen receptor beta a (ERbetaa) in zebrafish (Danio rerio).

Estrogenic steroid hormones mediate complex actions important in both embryonic and adult life. The hormones signal through ligand-inducible transcription factors known as estrogen receptors (ERs). In this study, we have isolated a zebrafish estrogen receptor with homology to human estrogen receptor beta (ERbeta). This zebrafish ERbeta (ERbetaa) has a conserved genomic structure of eight coding exons with boundaries similar to those of human ERbeta. The coding exon structures of two other zebrafish estrogen receptors (ERalpha and ERbetab) are presented as well. We also analyzed 3.3 kb of the promoter region and identified numerous putative transcription factor binding sites, including SP1 and ER half sites. Zebrafish ERbetaa message RNA is maternally loaded, but quickly degraded after fertilization, as detected by reverse transcriptase polymerase chain reaction. ERbetaa transcripts are detected again between 24 and 48 h post fertilization. These results indicate that ERbeta has been highly conserved during evolution and is likely used during later embryogenesis in zebrafish. Future identification of the expression levels and patterns of this and other estrogen receptors in zebrafish will allow a better understanding of estrogen signaling during embryogenesis.

Amino Acid Sequence↗

PubMed2005

Experimentally produced diploid-triploid mouse chimaeras develop up to adulthood.

Spontaneous diploid-triploid chimaeras occur sporadically in various mammalian species including man, but so far have never been produced experimentally. In order to get a deeper insight into the developmental consequences of this anomaly, we have developed two procedures that enabled for the first time to produce routinely diploid-triploid embryos, foetuses, and animals in the mouse. These procedures are: (1) aggregation of cleaving diploid embryos with triploid embryos produced by suppression of the second polar body in zygotes, and (2) fusion of a haploid karyoplast with one blastomere of the two-cell diploid embryos. The first procedure yielded 23 living and 6 dead postimplantation embryos and foetuses (age: 8th-19th day) out of which 22 were chimaeric. In addition, three chimaeric neonates reached adulthood. Two animals were fertile, and one--an overt chimaera--was an infertile male. The rate of postimplantation development of aggregation chimaeras was normal or only slightly retarded, and with one exception the foetuses were morphologically normal. Generally, the highest contribution of the 3n component in extra-embryonic structures was noted in the yolk sac, and usually it was higher than its contribution to the organs of the body. Chimaerism was most often noted in the liver, the heart, the intestine, and the lungs. Participation of triploid cells to all tissues studied, both in the body and in extra-embryonic structures, appeared to decrease slightly as development progressed. The second procedure yielded 10 foetuses and 6 adults. Three foetuses were chimaeric. Six fertile adults were probably non-chimaeras: the triploid component was absent in the coat and in the blood.

Animals↗

PubMed2003

Gene structure and embryonic expression of mouse COP9 signalosome subunit 8 (Csn8).

Csn8 is the smallest subunit of the constitutively photomorphogenic 9 (COP9) signalosome (CSN), which consists of eight distinct components. CSN is homologous to the lid subcomplex of the 26S proteasome and is a regulator of the ubiquitin-proteasome pathway. Murine Csn8 is an ortholog of Arabidopsis COP9, which was originally identified as a key regulator of photomorphogenic development. CSN is essential for the viability of plants and flies, but the role of this conserved protein complex in development of vertebrate animals remains obscure. We report the genomic structure of murine Csn8 gene and the expression pattern of Csn8 during early embryo development. Mouse Csn8 protein contains 209 amino acid residues and is encoded by a single gene located on chromosome 1. Csn8 is expressed in embryonic stem (ES) cells and throughout early embryo development from zygote, preimplantation embryos, to post-implantation embryos. Immunostaining studies revealed that Csn8 is predominantly present in the inner cell mass (ICM) of E3.5 blastocyst and is widely expressed in E9.5-day embryos.

Amino Acid Sequence↗

PubMed2006

Graphic and movie illustrations of human prenatal development and their application to embryological education based on the human embryo specimens in the Kyoto collection.

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.

Anatomy, Artistic↗

PubMed2001

Patterning mechanisms controlling vertebrate limb development.

Vertebrate limb buds are embryonic structures for which much molecular and cellular data are known regarding the mechanisms that control pattern formation during development. Specialized regions of the developing limb bud, such as the zone of polarizing activity (ZPA), the apical ectodermal ridge (AER), and the non-ridge ectoderm, direct and coordinate the development of the limb bud along the anterior-posterior (AP), dorsal-ventral (DV), and proximal-distal (PD) axes, giving rise to a stereotyped pattern of elements well conserved among tetrapods. In recent years, specific gene functions have been shown to mediate the organizing and patterning activities of the ZPA, the AER, and the non-ridge ectoderm. The analysis of these gene functions has revealed the existence of complex interactions between signaling pathways operated by secreted factors of the HH, TGF-beta/BMP, WNT, and FGF superfamilies, which interact with many other genetic networks to control limb positioning, outgrowth, and patterning. The study of limb development has helped to establish paradigms for the analysis of pattern formation in many other embryonic structures and organs.

Animals↗