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PubMed2004

The apical and basal environments of the retinal pigment epithelium regulate the maturation of tight junctions during development.

A culture model has been established to study the gradual development of tight junctions during the embryogenesis of the chick retinal pigment epithelium. This study asks how closely the culture model reflects normal development and how the composition, structure and function of embryonic tight junctions are affected by the apical and basal environments. The study focused on the expression of claudins, the fine-structure of tight junctional strands and the transepithelial electrical resistance. Between embryonic days 7 and 14, patches of junctional strands gradually expanded and coalesced to form a continuous junction, in vivo. Although there was a corresponding increase in claudin expression, different claudins appeared at different times. In culture, the apical and basal environments acted synergistically to promote a continuous network of tight junctions with higher electrical resistance. Independently, pituitary extract or the secretory products of either embryonic fibroblasts or the retina promoted the formation of tight junctions. In combination, three effects were identified. With basally placed fibroblast conditioned medium, apical retinal medium increased transepithelial electrical resistance by affecting structure alone. With basally placed pituitary extract, apical retinal conditioned medium increased transepithelial electrical resistance by affecting structure and by modulating claudin expression in a manner that was consistent with development in vivo. Although embryonic day 7 and 14 cultures in retinal medium exhibited similar structure, the transepithelial electrical resistance of the embryonic day 14 cultures was higher. This higher transepithelial electrical resistance correlated with differences in claudin expression and localization. Therefore, this experimental model can isolate the effects of retinal secretions on structure and claudin expression, and can help us to determine how claudins affect function when structure is held constant.

Animals↗
PubMed2004

Morphological and immunohistochemical analysis of ductal plate malformation: correlation with fetal liver.

AIMS: Ductal plate malformation (DPM) is the persistence of excess of embryonic bile duct structures in the portal tracts. Most of the congenital diseases of intrahepatic bile ducts represent examples of DPM at different levels of the biliary tree. The aim of the present study was to evaluate the histopathological spectrum and immunohistochemical properties of DPM in various paediatric liver diseases and compare them with those of the normal embryonic ductal plates of human fetuses. METHODS AND RESULTS: All paediatric liver biopsies and autopsied livers of infant deaths and stillbirths over a 5-year period (between 1996 and June 2001) were subjected to histopathological examination to identify ductal plate malformations. A detailed immunohistochemical analysis was carried out in 35 cases of ductal plate malformation and 25 abortuses by using antibodies against cytokeratin (CK)7, 8, 18 and 19, CD34 and type IV collagen. Thirty-nine cases of ductal plate malformation were identified which consisted of extrahepatic biliary atresia with DPM (n = 20), isolated congenital hepatic fibrosis (n = 9), autosomal recessive polycystic kidney disease (n = 5), congenital hepatic fibrosis with autosomal polycystic kidney disease (n = 2), Caroli's syndrome (n = 2) and one case of Ivemark's syndrome. The ductal plate cells stained with CK7, 8, 18 and 19 but not with CD34. CONCLUSION: DPM was present in all intrahepatic bile duct diseases included in this study and in about 26% of cases of extrahepatic biliary atresia. The cytokeratin immunophenotype of the ductal plate in pathological conditions is similar to that of normal embryonic ductal plates of fetuses after 20 weeks of gestation.

Antigens, CD34↗
PubMedDate not supplied

Determination of the structure of the RNA complex of a double-stranded RNA-binding domain from Drosophila Staufen protein.

We have determined using NMR the structure of the complex between the third double-stranded RNA-binding domain (dsRBD3) of Drosophila Staufen protein and a RNA stem-loop with optimal binding properties in vitro. This work was designed to understand how dsRBD proteins bind RNA and to investigate the role of Staufen dsRBDs in the localization of maternal RNAs during early embryonic development. The structure determination was challenging, because of weak, nonsequence specific binding and residual conformational flexibility at the RNA-protein interface. In order to overcome the problems originated by the weak interaction, we used both new and more traditional approaches to obtain distance and orientation information for the protein and RNA components of the complex. The resulting structure allowed the verification of aspects of RNA recognition by dsRBDs matching the information obtained by a related crystallographic study. We were also able to generate new observations that are likely to be relevant to dsRBD-RNA binding and to the physiological role of Staufen protein.

Animals↗
PubMedDate not supplied

Effects of removal of the statoacoustic ganglion complex upon the growing otocyst.

An experiment was designed to answer the question as to whether or not the neural elements of the statoacoustic ganglion complex have a trophic effect upon the histodifferentiation of the sensory structures of the embryonic mouse inner ear anlage as it develops in vitro. The embryonic inner ear anlage with associated otic mesenchyme and statoacoustic ganglion complex was excised from 11, 12, and 13-day CBA/C57 mouse embryos. The inner ear explants of each gestational age group were further divided into two groups: the first group "A" (with) statoacoustic ganglion was explanted to the organ culture system without further surgical intervention; the second group "B" (without) statoacoustic ganglion underwent further surgical manipulation during which their statoacoustic ganglion complexes were dissected away prior to explantation to in vitro. The explanted embryonic inner ears were allowed to develope in organ culture until the equivalent of gestation day 21 in vivo was reached for each group; then all cultures were fixed and histologically processed and stained by a nerve fiber stain, in combination with a stain for glucoprotein membranes. Each specimen was code labeled and scored for histodifferentiation of sensory structures. Light microscopic observations confirmed that in group "A" cultures, statoacoustic ganglion neurons and their nerve fibers were present in association with the developed sensory structures; neither ganglion cell neurons nor their nerve fibers were found to be present in the sensory structures that developed in the group "B" organ culture specimens. Quantification revealed no consistent trend of greater occurrence of any sensory structure in the groups of explants analyzed. The presence of such a trend would have signified the probable existence of a trophic effect of the statoacoustic ganglion neural elements upon development of inner ear sensory structures in the group "A" explants of the 11, 12, and 13-day embryo inner ear organ culture specimens when compared to the aganglionic group "B" cultures. Microscopic comparison of the sensory structures and their sensory hair cells that developed in the organ cultures revealed no differences in the quality of the histodifferentiation of eithergroup "A" or goup "B" explants. A base to apex pattern of histodifferentiation of the organ of Corti sensory structures, which has been described to occur in vivo, was noted to occur in the in vitro developed cochlear ducts of all of the explanted inner ears without respect to whether neural elements were present ("A") or absent ("B") during development. It was concluded from the quantification of histodifferentiation data and the above observation on the pattern of differentiation of Corti's organ that no trophic effect of neural elements of the statoacoustic ganglion complex influencing the histodifferentiation of sensory structures of 11, 12, and 13-gestation day mouse embryo inner ear explants as they differentiate in vitro could be demonstrated.

Animals↗
PubMed1999

Expression of apoptosis in the developing human cephalic region during the embryonic and early fetal period.

The aim of our work was to study the expression of apoptosis in the cephalic region in human embryonic and fetal material. Twelve human embryos and fetuses were processed by routine histological technique and then studied using the Boehringer-Mannheim Company kit for TUNNEL technique. Rich appearance of apoptotic cells was typical for mesenchyme and for tissues of the mesenchymal origin. Dispersed or focal occurrence of apoptotic cells was described in nervous system and some orofacial structures during the embryonic period. During the early fetal period occurrence of apoptosis decreased and only rare apoptotic nuclei were visible in studied areas. Often they failed at all.

Apoptosis↗
PubMed2005

Placentation in the Mexican lizard Sceloporus mucronatus (Squamata: Phrynosomatidae).

We used light microscopy to study placental structure of the lizard Sceloporus mucronatus throughout 6 months of embryonic development. Three stages of placental development could be assigned to embryos based on the arrangement of the extraembryonic membranes. A highly vascular choriovitelline placenta was present in the embryonic hemisphere and a nonvascular bilaminar omphalopleure covered most of the abembryonic hemisphere of the egg during embryonic Stages 10-28. A chorioallantoic placenta replaced the choriovitelline placenta by embryonic Stage 29 and an omphaloplacenta covered the abembryonic hemisphere at this stage. The combination of these two placental types occurred in Stage 29-36 embryos. The final stage of placentation, embryonic Stages 37-40, was characterized by an omphalallantoic placenta in the abembryonic hemisphere and a chorioallantoic placenta in the embryonic hemisphere of the egg. The choriovitelline and chorioallantoic placentae are well vascularized, with closely apposed maternal and embryonic blood vessels. These structures are the most likely sites of respiratory exchange. In contrast, the omphaloplacenta and omphalallantoic placentae contain cuboidal or columnar epithelia and these structures may function in histotrophic exchange. Placentation of S. mucronatus is similar to that of predominantly lecithotrophic species in other squamate lineages suggesting that the evolution of this placental morphology is a response to similar factors and is independent of phylogeny.

Animals↗
PubMed1991

Intracellular sperm/egg interactions in Drosophila: a three-dimensional structural analysis of a paternal product in the developing egg.

During fertilization in Drosophila, a single 1.75 mm long sperm enters the egg through the anterior end. Using a sperm-specific monoclonal antibody and indirect immunofluorescence of whole fixed eggs and embryos, intracellular interactions between the sperm and egg are examined as they occur inside the fertilized egg. The sperm nucleus remains attached to the axoneme throughout the entire process of fertilization including the stages of pronuclear maturation, pronuclear fusion and karyogamy indicating an intracellular function for the sperm during these stages. Optical sections and three-dimensional reconstructions of whole mount specimens reveal that a stereotypically folded structure forms during fertilization strongly suggesting that this structure positions the male pronucleus in the proper region of the egg in anticipation of pronuclear fusion. This, and the appearance of regional structural changes in the sperm upon entry suggests that sperm are localized via specific interactions with the maternal cytoplasm. Following fertilization and during the ensuing cleavage divisions, the sperm remains intact and localized at the anterior end of the egg. During cellular blastoderm formation the sperm tail is sequestered into the anterior yolk area where it continues to persist well into embryonic development. This structural analysis identifies intracellular sperm/egg interactions as an important aspect of fertilization, and provides a unique model system for the study of sperm/egg interactions not presently available in other systems.

Animals↗
PubMed1986

Complete nucleotide and encoded amino acid sequence of a mammalian myosin heavy chain gene. Evidence against intron-dependent evolution of the rod.

The complete nucleotide sequence and exon/intron structure of the rat embryonic skeletal muscle myosin heavy chain (MHC) gene has been determined. This gene comprises 24 X 10(3) bases of DNA and is split into 41 exons. The exons encode a 6035 nucleotide (nt) long mRNA consisting of 90 nt of 5' untranslated, 5820 nt of protein coding and 125 nt of 3' untranslated sequence. The rat embryonic MHC polypeptide is encoded by exons 3 to 41 and contains 1939 amino acid residues with a calculated Mr of 223,900. Its amino acid sequence displays the structural features typical for all sarcomeric MHCs, i.e. an amino-terminal "globular" head region and a carboxy-terminal alpha-helical rod portion that shows the characteristics of a coiled coil with a superimposed 28-residue repeat pattern interrupted at only four positions by "skip" residues. The complex structure of the rat embryonic MHC gene and the conservation of intron locations in this and other MHC genes are indicative of a highly split ancestral sarcomeric MHC gene. Introns in the rat embryonic gene interrupt the coding sequence at the boundaries separating the proteolytic subfragments of the head, but not at the head/rod junction or between the 28-residue repeats present within the rod. Therefore, there is little evidence for exon shuffling and intron-dependent evolution by gene duplication as a mechanism for the generation of the ancestral MHC gene. Rather, intron insertion into a previously non-split ancestral MHC rod gene consisting of multiple tandemly arranged 28-residue-encoding repeats, or convergent evolution of an originally non-repetitive ancestral MHC rod gene must account for the observed structure of the rod-encoding portion of present-day MHC genes.

Amino Acid Sequence↗
PubMed1985

The trophotaenial placenta of a viviparous goodeid fish. II. Ultrastructure of trophotaeniae, the embryonic component.

Embryos of the viviparous goodeid fish Ameca spendens develop within the ovarian lumen, where they establish a placental association with the maternal organism and undergo a 15,000% increase in embryonic dry weight. The placenta consists of an embryonic component, the trophotaeniae, and a maternal component, the internal ovarian epithelium. Examination with light microscopy and with transmission and scanning electron microscopy reveals that trophotaeniae of A. splendens are extraembryonic membranes consisting of five ribbon-like processes originating from a tube-like mass of tissue that extends outward from the perianal region of developing embryos. There are two sets of lateral processes and a longer single median process. Trophotaeniae possess an outer epithelium that surrounds a highly vascularized core of loose connective tissue. Epithelial cells possess apical microvilli and a pronounced endocytotic apparatus. Cells of the trophotaenial epithelium are either tightly apposed along their lateral margins or separated by enlarged intercellular spaces. Regions of the trophotaenial epithelium possessing enlarged intercellular spaces are distributed in patches. The trophotaenial epithelium is continuous with the embryonic hindgut epithelium and is considered to be derived from it. Comparison of trophotaenial morphology in A. splendens with that reported in Xenotoca eiseni reveals differences in histological organization. The former possess unsheathed trophotaeniae, whereas the latter are sheathed. We postulate that the apposition of trophotaenial epithelium to the internal ovarian epithelium constitutes a placental association equivalent to a noninvasive, epithelioform of an inverted yolk sac placenta. Structural relationships of embryonic and maternal tissues of the trophotaenial placenta are discussed in relation to maternal-embryonic nutrient transfer processes.

Animals↗
PubMed1966

Electron microscopy: attachment sites between connective tissue cells.

Regions of attachment have been observed between connective tissue cells from four different structures: fibroblasts in embryonic and fetal tendons, fibroblasts in fetal ligamentum nuchae, odontoblasts, and osteoblasts. Morpho logically these sites appear to be focal and to consist of an approximation of the plasma membranes of adjacent cells to within approximately 200 A. In the region of approximation both the extracellular space and the cytoplasm adjacent to the plasmalemma are increased in density. We have postulated a role for these sites in the maintenance of structural integrity.

Animals↗
PubMed1980

Effect of aminoguanidine on chick embryonic liver during organ culture.

The addition of 10(-3) M aminoguanidine to culture medium caused no significant effect on the ultrastructure of cytoplasmic organellae in chick embryonic liver cells during organ culture but produced unique alterations in the nucleolar ultrastructure, such as increased density of protein matrix, increase of granular components, and fragmentation of nucleolar constituents. A high dose of aminoguanidine led the cultured liver cells to necrosis. Aminoguanidine also inhibited RNA synthesis rather than DNA synthesis in the cells. These results suggest that this agent may induce primary inhibition of RNA synthesis accompanied with significant changes of nucleolar structure in chick embryonic liver cells.

Animals↗
PubMed1990

Ultrasound in the first trimester of pregnancy.

High-resolution sonography, including transvesical and endovaginal techniques, has resulted in enhanced visualization of embryonic and extraembryonic structures. With endovaginal sonography, the gestational sac may be seen within the decidua at about 4.5 weeks menstrual age. The yolk sac is the first structure to be seen within the gestational sac, and confirms the presence of a gestational sac rather than a decidual cast. The embryo is identified by endovaginal sonography early in the 6th week, and cardiac activity is routinely identified by a crown-rump length of 3 to 5 mm. On endovaginal sonography, absent cardiac activity in an embryo having a crown-rump length of greater than 3 to 5 mm indicates embryonic death. With endovaginal scanning, a gestational sac of greater than 8 mm without a yolk sac, or greater than 16 mm without an embryo, also indicates a nonviable pregnancy. Routine sonography primarily to assess the menstrual age should be performed in the second trimester, when added clinically relevant information may be obtained. Although it is possible to diagnose some anomalies in the first trimester, most remain second trimester sonographic diagnoses.

Congenital Abnormalities↗
PubMedDate not supplied

The timecourse of neuronal connections of the rotundoectostriatal pathway in chicks (Gallus gallus) during embryogenesis: a retrograde transport study.

The avian retinotectofugal pathway has been suggested to be homologous to the mammalian retinotectofugal pathway. The projection of the nucleus rotundus upon the ectostriatum is equivalent to that of the pulvinar nucleus upon the extrastriate cortex in mammals. In this system, the optic tectum relays retinal input to the nucleus rotundus, which then ascends to the ectostriatum of the telencephalon. Given the fact that the chick retinotectofugal system becomes mature early during development, the present study attempted to investigate the timecourse of neuronal connections of the embryonic rotundoectostriatal pathway. We used multiple injections of cholera toxin B subunit (CTb) in the ectostriatum of chick embryos to retrogradely trace projections to the nucleus rotundus. We found CTb-labeled neurons in the nucleus rotundus at embryonic day 7.5-8. By embryonic day 8-8.5, increased numbers of CTb-labeled neurons were seen in the nucleus rotundus. It was noted that the time of this initial connection between the nucleus rotundus and the ectostriatum is nearly synchronous with that of the retinotectal and tectorotundal pathways, respectively (Crossland et al., 1975; Thanos & Bonhoeffer, 1987; Wu et al., 2000). These findings, combined with the present study, suggest that the retinotectofugal system becomes established, at least at a structural level, by embryonic day E8.

Animals↗
PubMed1982

Differentiation of the metameric pattern in the embryonic axis of the mouse. II. Somitomeric organization of the presomitic mesoderm.

The formation of the embryonic axis is brought about by the continuous recruitment of cells from the primitive streak, and at later stages from the tail bud. Presumptive somitic cells are first incorporated into presomitic mesoderm before they emerge as metamerically arranged somites. When the presomitic mesoderm was examined in stereo with the scanning electron microscope (SEM), mesenchymal cells were found to be already organized into segmental units. These segmental units are called somitomeres because of their striking similarity to structures in the embryonic axis of the chick embryo described by Meier [16]. Cells within the somitomere are arranged in concentric whorls about a core center, bisected by a medio-lateral seam which subdivides the cell population into anterior and posterior halves. The concentric configuration of the cells is most easily observed along the medial face of the presomitic mesoderm when it is generally wedge-shaped. Even tough the units are tandemly contiguous, somitomeric interfaces are distinguished by abrupt change in cellular orientation. Despite a nearly two-fold fluctuation in the overall size of the presomitic mesoderm during embryonic development, a relatively constant number of somitomeres (six) is found in tandem sequence. Somitomeric maturation culminating in somite formation involves compaction of the cell population, more orderly alignment of cells, reduction in extracellular space, and changes in the shape of the somitomere concomitant with neurulation. Though the more mature somitomere is about 70% the size of the most recently formed somitomere at the caudal end of the presomitic mesoderm, the average size of each somitomere is adjusted proportionally to the overall length of the presomitic mesoderm. In vitro culture of the presomitic mesoderm shows a direct developmental lineage between the somitomere and the somite, suggesting that somite formation is a morphologic manifestation of a somitomeric pattern laid down at an earlier stage in development. The somitomeric pattern in the paraxial mesoderm is the earliest recognizable morphologic evidence of metamerism in the embryonic axis. This pattern is later emulated by other tissues that are topographically associated with the paraxial mesoderm.

Animals↗
PubMed1976

[Progressive character of embryogenesis in placental animals].

The article presents evidence of the placental animals being isolated from the rest of higher vertebrates according to many peculiarities of their structure and the embryonic development. The most important of these signs are the following: female genital tracts are disposed to the inside from the urinary tracts (in embryos the Müller's canals are on the inner side of the wolffian ducts); in placental animals there are no tertiary egg sheaths which are physiologically substituted for the trophoblast; the provisory organs reveal great variability; the allantoid placenta performs not only metabolic but also endocrinous functions. The evolution of peculiarities of the structure and development characteristic of placental animals was performed by a series of successive aromorphous phenomena. Theri mighty adaptive radiation is the result of greater perfectness of placental animals.

Adaptation, Biological↗
PubMed2005

Intra-abdominal ovarian-type mucinous cystadenoma associated with fallopian tube-like structure and aberrant epididymal tissue in a male patient.

Ovarian-type mucinous tumors may occasionally occur in the retroperitoneum, pancreas, and liver exclusively or almost exclusively in women. In men, only few cases of such neoplasms arising within or around the testis have been reported. We describe a unique case of an ovarian-type mucinous cystadenoma occurring in the peritoneal cavity of a 65-year-old male patient with secondary adrenocortical insufficiency and hypogonadism. There was a typical fallopian tube enclosed in the capsule of the tumor. Contiguous to that, accessory ectopic epididymal tissue was found. We have interpreted this case as the result of a minor disorder of embryonic development involving structures of both müllerian and wolffian origin. The disproportion of sexual hormones might have had a role in inducing intra-abdominal müllerian remnants to give rise to the mucinous cystadenoma.

Aged↗
PubMed2005

Posterior expression of nanos orthologs during embryonic and larval development of the anthozoan Nematostella vectensis.

Cnidarians are primitive animals located in a basal position in the phylogenetic tree of the Animal Kingdom, as an outgroup of the Bilaterians. Therefore, studies on cnidarian developmental biology may illustrate how fundamental developmental processes have originated and changed during animal evolution. A particular example of this is the establishment of polarity along the body axes, which is under the control of a number of developmental genes, most of them conserved in evolution and playing similar roles in diverged species. Concerning the anterior-posterior axis, genetic and molecular studies on Drosophila have shown that the nanos gene plays an essential role in defining posterior structures during early embryonic development. Here we report the isolation of two nanos orthologs in the anthozoan Nematostella vectensis. We show that nanos mRNA is asymmetrically distributed in the fertilized egg and this asymmetry is maintained during embryonic development. At gastrula and planula larva stages, nanos expression is permanently associated with posterior body regions. These results, together with our previous analysis in the hydrozoan Podocoryne carnea, indicate that posterior nanos expression during development is a conserved feature among cnidarians. Therefore, the potential role of cnidarian nanos in defining axial polarity as a posterior determinant would represent an ancestral trait in the Animal Kingdom.

Amino Acid Sequence↗
PubMed2002

Formation of multiple hearts in mice following deletion of beta-catenin in the embryonic endoderm.

Using Cre/loxP, we conditionally inactivated the beta-catenin gene in cells of structures that exhibit important embryonic organizer functions: the visceral endoderm, the node, the notochord, and the definitive endoderm. Mesoderm formation was not affected in the mutant embryos, but the node was missing, patterning of the head and trunk was affected, and no notochord or somites were formed. Surprisingly, deletion of beta-catenin in the definitive endoderm led to the formation of multiple hearts all along the anterior-posterior (A/P) axis of the embryo. Ectopic hearts developed in parallel with the normal heart in regions of ectopic Bmp2 expression. We provide evidence that ablation of beta-catenin in embryonic endoderm changes cell fate from endoderm to precardiac mesoderm, consistent with the existence of bipotential mesendodermal progenitors in mouse embryos.

Animals↗