SEARCH · Search PubMed

Results for “Germ Layers”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources

PubMed1996

The tumor suppressor gene Brca1 is required for embryonic cellular proliferation in the mouse.

Mutations of the BRCA1 gone in humans are associated with predisposition to breast and ovarian cancers. We show here that Brca1+/- mice are normal and fertile and lack tumors by age eleven months. Homozygous Brca1(5-6) mutant mice die before day 7.5 of embryogenesis. Mutant embryos are poorly developed, with no evidence of mesoderm formation. The extraembryonic region is abnormal, but aggregation with wild-type tetraploid embryos does not rescue the lethality. In vivo, mutant embryos do not exhibit increased apoptosis but show reduced cell proliferation accompanied by decreased expression of cyclin E and mdm-2, a regulator of p53 activity. The expression of cyclin-dependent kinase inhibitor p21 is dramatically increased in the mutant embryos. Buttressing these in vivo observations is the fact that mutant blastocyst growth is grossly impaired in vitro. Thus, the death of Brca1(5-6) mutant embryos prior to gastrulation may be due to a failure of the proliferative burst required for the development of the different germ layers.

Alternative Splicing↗

PubMed1998

Smad2 signaling in extraembryonic tissues determines anterior-posterior polarity of the early mouse embryo.

Smad proteins transmit TGFbeta signals from the cell surface to the nucleus. Here we analyze Smad2 mutant embryos created using ES cell technology. Smad2 function is not required for mesoderm production per se, but, rather unexpectedly, in the absence of Smad2 the entire epiblast adopts a mesodermal fate giving rise to a normal yolk sac and fetal blood cells. In contrast, Smad2 mutants entirely lack tissues of the embryonic germ layers. Smad2 signals serve to restrict the site of primitive streak formation and establish anterior-posterior identity within the epiblast. Chimera experiments demonstrate these essential activities are contributed by the extraembryonic tissues. Thus, the extraembryonic tissues play critical roles in establishing the body plan during early mouse development.

Animals↗

PubMedDate not supplied

Human embryonic stem cells derived without feeder cells.

BACKGROUND: Human embryonic stem cells are likely to play an important role in the future of regenerative medicine. However, exposure of existing human embryonic stem-cell lines to live animal cells and serum risks contamination with pathogens that could lead to human health risks. We aimed to derive an embryonic stem-cell line without exposure to cells or serum. METHODS: Frozen cleavage-stage embryos were thawed and cultured to the blastocyst stage. Inner cell masses were isolated by immunosurgery and plated onto extracellular-matrix-coated plates that can be easily sterilised. Six established human embryonic stem-cell lines were also maintained with this serum and feeder free culture system. FINDINGS: A new stem-cell line was derived from human embryos under completely cell and serum free conditions. The cells maintained normal karyotype and markers of pluripotency, including octamer binding protein 4 (Oct-4), stage-specific embryonic antigen (SSEA)-3, SSEA-4, tumour-rejection antigen (TRA)-1-60, TRA-1-81, and alkaline phosphatase. After more than 6 months of undifferentiated proliferation, these cells retained the potential to form derivatives of all three embryonic germ layers both in vitro and in teratomas. These properties were also successfully maintained (for more than 30 passages) with the established stem-cell lines. INTERPRETATION: This system eliminates exposure of human embryonic stem cells and their progeny to animal and human feeder layers, and thus the risk of contamination with pathogenic agents capable of transmitting diseases to patients.

Animals↗

PubMed2001

Chromosome analysis and comparison of the benign cystic and malignant squamous component of an ovarian teratoma.

Teratoma, the most common ovarian germ-cell tumor, presumably arises from a single germ cell and is composed of tissues representing all germ layers (ectoderm, mesoderm, and endoderm). Benign cystic teratomas (dermoid cyst) represent over 95% of ovarian teratomas and are comprised of entirely mature adult tissues. When malignant, almost all mature teratomas contain squamous carcinoma. We report for the first time the karyotypic comparison of an ovarian teratoma in a 36-year-old female with tissue separately taken from the benign cystic and malignant squamous components. The malignant squamous component revealed two distinct karyotypic populations: one diploid and the other polyploid. Both, however, demonstrated two common markers. The polyploid population also demonstrated numerous additional abnormalities with multiple copies of chromosome 20. Though many of the chromosomal aberrations were unique to the benign component, several karyotypes showed the same markers noted in the malignant squamous component. The significance of this finding is that it may serve to identify those histologically benign teratomas destined to undergo malignant transformation.

Adult↗

PubMed1984

Waardenburg's syndrome: a case report with CT scanning and cochleovestibular evaluation.

The Waardenburg's syndrome, a congenital ectodermal germ layer defect of autosomal dominant inheritance with variable phenotypic expressivity consists of 6 major characteristics: dystopia canthorum, broad nasal root, hypoplasia of the medial eyebrow, heterochromia irides, white forelock, and congenital deafness. Twelve additional characteristics have been reported including meningocele, atresia of the esophagus, and Hirshsprung's disease supporting an early hypothesis that the neural crest is the embryonic site linking defects of the cervical sympathic system with pigmentary abnormalities and inner ear anomalies. Congenital deafness reported in 20% of Waardenburg patients, and the most disabling characteristic, has been associated with ENG abnormalities in 30% of these deaf patients. A congenitally deaf young person with Waardenburg's syndrome is examined for basic cause of episodic vertiginous symptoms. Diagnostic assistance from previous investigations is lacking because they have not involved state-of-the-art functional evaluations or correlations of behavioral and radiographic findings. In this patient, high-resolution computerized tomography failed to demonstrate bony labyrinthine anomalies. Functional cochleovestibular analysis revealed a bilateral profound sensorineural hearing loss and a unilateral weakness in oculomotor responses to caloric stimulations. Repeated measurements of ocular counterroll show variations compatible with intermittent otolithic dysfunctioning. These findings are consistent with a diagnosis of an acquired active unilateral peripheral vestibular disorder. Some of the technical issues underlying the derivation of this conclusion are discussed.

Abnormalities, Multiple↗

PubMed1997

A nasopharyngeal dermoid causing neonatal airway obstruction.

A case of neonatal respiratory distress due to a pedunculated nasopharyngeal dermoid is presented with its MRI assessment. The dermoid was removed without complications. Nasopharyngeal teratomas are uncommon, consisting of tissues from all three germ layers with varying degrees of differentiation. Symptoms arise during the neonatal period and are associated with airway obstruction. MRI can be performed for contemporary assessment. The first goal of management is to establish a safe and protected airway using complete surgical excision.

Airway Obstruction↗

PubMed1997

Genomic structure and embryonic expression of the rat type 1 vasoactive intestinal polypeptide receptor gene.

The genomic structure of the rat vasoactive intestinal polypeptide type 1 receptor (VIPR I) gene was characterized using polymerase chain reactions (PCR) and DNA sequencing. These studies show that the rat VIPR I gene spans more than 20 kb of DNA sequence and includes thirteen exons separated by twelve introns, ranging from 0.2 to 4.5 kb. VIP is known to play an important role early in embryonic development. To elucidate the receptor-mediated biological functions of VIP in development, the temporal and spatial expression of VIPR I during rat embryonic development was examined in this study. Using in situ hybridization histochemistry with 35S-labeled riboprobe, VIPR I mRNA was detected as early as embryonic day 11 (E11), in the neuroepithelium, foregut, heart and in cells lining the blood vessels. From E14 through E18, VIPR I mRNA was detected in multiple tissues derived from all three germ layers. These include neuronal cells in brain and spinal cord (ectoderm); smooth muscle cells of intestines, cells lining the wall of the heart and blood vessels, kidney, adrenal gland (mesoderm); epithelial cells of airway and of liver (endoderm). The early onset and wide tissue expression of VIPR I suggests that binding of VIP to this receptor may play an important role in rat embryonic development.

Animals↗

PubMed2000

The EGF-CFC gene family in vertebrate development.

EGF-CFC genes encode extracellular proteins that play key roles in intercellular signaling pathways during vertebrate embryogenesis. Mutations in zebrafish and mouse EGF-CFC genes lead to defects in germ-layer formation, anterior-posterior axis orientation and left-right axis specification. In addition, members of the EGF-CFC family have been implicated in carcinogenesis. Although formerly regarded as signaling molecules that are distant relatives of epidermal growth factor (EGF), recent findings indicate that EGF-CFC proteins act as essential cofactors for Nodal, a member of the transforming growth factor beta (TGF-beta) family. Here, we review molecular genetic evidence from mouse and zebrafish on biological and biochemical roles of the EGF-CFC family, and discuss differing models for EGF-CFC protein function.

Amino Acid Sequence↗

PubMed1995

Mouse embryonic hematopoiesis.

The hematopoietic system of vertebrates is derived from the mesodermal germ layer in early embryogenesis. Various animal models have been used for the study of hematopoiesis, from early stages in the visceral yolk sac or its analog, to the later stages where hematopoiesis is observed in intraembryonic areas surrounding the aorta, genital ridge and pro/mesonephros. Using the mouse as a model, we describe what is known about mammalian embryonic hematopoiesis and put it in the context of hematopoietic cell formation in avian, amphibian and fish embryos. Evolutionary comparisons and recent experimental evidence show that there are two embryonic sites of developing hematopoietic activity in the mouse before fetal liver hematopoiesis and suggest that, during ontogeny, two successive waves of hematopoietic activity may contribute to the blood system of the adult.

Animals↗

PubMed2003

Fox's in development and disease.

Since the first forkhead (Fox) gene was identified, the importance of this family of transcription factors has increased steadily with the discoveries of the diverse range of developmental processes that they regulate in eukaryotes. Among other processes, the Fox factors are important in the establishment of the body axis and the development of tissues from all three germ layers. In this article, we present some of the recent data on this gene family with reference to selected phenotypes observed in patients and model organisms, and the sensitivity of developmental processes to alterations in forkhead gene dosage.

Animals↗

PubMed2000

Endoderm development: from patterning to organogenesis.

Although the ectoderm and mesoderm have been the focus of intensive work in the recent era of studies on the molecular control of vertebrate development, the endoderm has received less attention. Because signaling must occur between germ layers in order to achieve a properly organized body, our understanding of the coordinated development of all organs requires a more thorough consideration of the endoderm and its derivatives. This review focuses on present knowledge and perspectives concerning endoderm patterning and organogenesis. Some of the classical embryology of the endoderm is discussed and the progress and deficiencies in cellular and molecular studies are noted.

Animals↗

PubMed2002

The psychological puzzle presented by physiological acts.

Physiological acts present the puzzle that we are unable to explain how we performed them, how we solved the technical difficulties involved in their execution. For instance, when we sing, we produce various musical notes by changing the shape of the larynx. The normal person does not even know what the larynx looks like, let alone its configurations corresponding to various notes and the combination of the 19 muscles acting on the larynx that has to be activated to bring about the required configuration. Some psychologists offer the explanation that the technical details are worked out by a computer-like mechanism. But how could a computer start controlled cell proliferation in the repair of an injury? Another idea (originally put forward by Leibniz around 1700) is the complex character of the mind. The mind may incorporate a multitude of personalities. Subordinate personalities, some, perhaps, specialising on various tasks, may carry out the orders of the commanding personality. Objection: most physiological tasks, for instance digestion or the fight against invading microorganisms, are completely unconscious. The 'myself' personality could not even issue commands regarding the repair of injuries or the fight against microorganisms. PROPOSED SOLUTION: At an early stage of evolution the body of a higher animal divides itself into three compartments, each specialising on a different task of life. The three parts correspond to the entoderm, mesoderm and ectoderm appearing at an early part of ontogenetic development. The task of the entoderm is metabolism, that of the mesoderm mainly the mechanical aspects of life, that of the ectoderm gathering information from and reacting to the outside world. Each of these is probably of a composite character. The myself personality is the equivalent of the ectoderm, not of the whole body. The technical details of its commands are worked out by subordinate personalities. So are the commands of the mesodermal and entodermal divisions. Dreams could be attempts of communication between the germ layers.

Humans↗

PubMed1998

Chromatin structure and functional analysis of the mouse HNF3alpha gene.

The transcription factor HNF3alpha is a member of the winged-helix family of regulatory proteins. It is expressed in the definitive endoderm, notochord, and neural tube in embryos, but in the adult is expressed primarily in endoderm-derived tissues such as liver, lung, and pancreas. We present here the cloning of the mouse HNF3alpha gene and a characterization of its chromatin structure and regulatory sequences. The HNF3alpha gene is encoded by two exons and its transcription initiates at multiple start sites at a TATA-less promoter that is highly conserved between mouse and rat. We found different patterns of DNaseI hypersensitive sites in HNF3alpha gene chromatin in different adult tissues in which HNF3alpha is expressed, suggesting distinct regulatory mechanisms occurring within different tissue derivatives of the endoderm germ layer. Cell transfection data indicate that sequences spanning certain upstream hypersensitive sites can enhance transcription from the HNF3alpha promoter, but only when stably integrated into chromatin and not when transiently transfected. The results suggest a complex regulatory interplay between distinct genetic regulatory sequences that function specifically in chromatin.

Animals↗

PubMed1999

Identification of a Drosophila homologue to vertebrate Crk by interaction with MBC.

The vertebrate adapter protein termed Crk was initially identified from the chicken CT10 retrovirus on the basis of its transforming activity (Mayer et al., 1988. Nature 332, 272-275). We have identified a Drosophila protein with homology to vertebrate Crk, termed dCRK, by interaction with the protein encoded by the Drosophila myoblast city (mbc) gene. The dCRK protein has extensive homology to the both the Crk-II form of vertebrate Crk and the Crk-related protein CRKL, and includes one SH2 domain followed by two SH3 domains. A single protein of approx. 37kDa is detected in extracts from embryos, and Northern analysis revealed a single transcript of 1.3kb. The dCrk mRNA is abundant throughout embryogenesis, declines during the larval stages, and reappears during pupation. In addition, maternally-provided transcripts have been detected. During embryogenesis, the spatial distribution of this transcript is relatively broad and appears to include all germ layers. Finally, dCrk is located on the fourth chromosome, approximately at cytological position 101F-102A.

Adaptor Proteins, Signal Transducing↗

PubMed1996

Development of bovine and porcine embryonic teratomas in athymic mice.

Inner cell masses (ICM) and embryonic discs from bovine and porcine blastocysts of various ages were transplanted under the kidney capsule of athymic (nude) mice to evaluate growth of teratocarcinomas containing both differentiated tissues and undifferentiated stem cells. Inner cell masses were isolated immunosurgically from Day 8, Day 9 and Day 10 porcine blastocysts and from Day 8, Day 10 and Day 12 bovine blastocysts. Embryonic discs were mechanically dissected from Day 11 and Day 12 porcine embryos and from Day 14 bovine embryos. Day 6 egg cylinders were dissected from BALB/C embryos and from hybrid embryos of a cross between BALB/C and an outbred strain of mouse. Two to four ICM, embryonic discs or egg cylinders were transplanted under the kidney capsule of each athymic host. After 8 weeks, graft hosts were killed and their tumors removed, fixed and prepared for histological and immunohistochemical examination. Embryonic teratomas developed at high frequency from murine egg cylinders and from Day 11 and Day 12 porcine and Day 14 bovine embryos. Tumors were observed only infrequently from younger bovine and porcine blastocysts. Murine embryonic tumors were composed of numerous differentiated cell types of ectodermal, mesodermal and endodermal origins, but representation of the three embryonic germ layers was somewhat more restricted in bovine and porcine embryonic tumors. No undifferentiated stem cells were detected in tumors of any of the three species. These results demonstrate that teratomas will develop from bovine and porcine embryos when grafted to an immunocompromised host, but the presence of undifferentiated teratocarcinoma stem cells from these species has yet to be achieved.

Animals↗

PubMed2001

Embryonic stem cells as an in vitro model for mutagenicity, cytotoxicity and embryotoxicity studies: present state and future prospects.

Primary cultures or established cell lines of vertebrates are commonly used to analyse the mutagenic, embryotoxic or teratogenic potential of environmental factors, drugs and xenobiotics in vitro. However, these cellular systems do not include developmental processes from early embryonic stages up to terminally differentiated cell types. An alternative approach has been offered by permanent lines of pluripotent stem cells of embryonic origin, such as embryonic carcinoma (EC), embryonic stem (ES) and embryonic germ (EG) cells. The undifferentiated stem cell lines are characterized by nearly unlimited self-renewal capacity and have been shown to differentiate in vitro into cells of all three primary germ layers. Pluripotent embryonic stem cell lines recapitulate cellular developmental processes and gene expression patterns of early embryogenesis during in vitro differentiation, data which are summarized in this review. In addition, recent studies are presented which investigated mutagenic, cytotoxic and embryotoxic effects of chemical substances using in vitro systems of pluripotent embryonic stem cells. Furthermore, an outlook is given on future molecular technologies using embryonic stem cells in developmental toxicology and embryotoxicology.

Animal Testing Alternatives↗

PubMed2002

The use of quantitative image analysis in the assessment of in vitro embryotoxicity endpoints based on a novel embryonic stem cell clone with endoderm-related GFP expression.

The capacity of pluripotent embryonic stem cells (ESC) to differentiate in vitro into various tissues provides the opportunity to develop an in vitro assay for investigating mechanisms of developmental toxicity. ESC clones carrying tissue specific reporter gene constructs are currently being developed. The clones should allow the quantification of the effects of chemicals on the development of germ layers and main target tissues. We report the establishment of the alpha-fetoprotein_GFP/D3 reporter gene clone: alpha-fetoprotein (AFP) enhancers and the homologous promoter regulate green fluorescent protein (GFP) expression in cells of the D3-ESC clone. AFP was used as a marker for endodermal cells. Differentiation of this clone via embryoid bodies (EBs, spheroids of cells) leads to green fluorescence on the surfaces of EBs. AFP- related GFP expression was confirmed. An easy and quick image analysis-based endpoint measurement was developed for quantifying low amounts of cells expressing GFP. As demonstrated with the embryotoxic chemical diphenylhydantoin, image analysis can be used to distinguish between a general effect on EB growth and a specific effect on the development of GFP-positive endodermal cells. Endoderm development was inhibited at a different dose than cardiomyocyte development.

Animal Testing Alternatives↗

PubMedDate not supplied

Conjoined gastric and mediastinal benign cystic teratomas. Case report of a rare occurrence and review of literature.

Teratomas are embryonal neoplasms which arise from totipotential cells and contain elements from all three germ layers (ectoderm, mesoderm, and the endoderm). Simultaneous occurrence of mediastinal and gastric teratomas in infants has not been reported, although gastric teratomas extending into the mediastinum have been reported twice in literature. We report here a case in which a gastric cystic teratoma was connected to its mediastinal counterpart with a pedicle. The pertinent literature is reviewed.

Diagnostic Imaging↗