Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Thyroid hormone regulation of Xenopus laevis metamorphosis: functions of thyroid hormone receptors and roles of extracellular matrix remodeling (1998)
    Oxford, UK : Blackwell Science
    Wound repair and regeneration 6 (1998), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The regulatory effects of the thyroid hormone on amphibian metamorphosis is mediated by thyroid hormone receptors. Using Xenopus laevis as a model system, we and others have shown that the mRNA levels of thyroid hormone receptors and 9-cis retinoic acid receptors, which form the functional heterodimers with thyroid hormone receptors, are regulated temporally in a tissue-dependent manner so that high levels of their mRNAs are present in an organ when metamorphosis is occurring. By overexpressing thyroid hormone receptors, 9-cis retinoic acid receptors, or both into developing Xenopus embryos, we have shown that both thyroid hormone receptors and 9-cis retinoic acid receptors are required for mediating the effects of thyroid hormone on embryo development and precocious but specific regulation of the genes, which are normally regulated by thyroid hormone during metamorphosis. Analyses of the developmental expression of one class of thyroid hormone response genes, which encode extracellular matrix-degrading metalloproteinases, suggest that extra cellular remodeling plays an important role during tissue remodeling, including cell death (apoptosis) and cell proliferation and differentiation. This effect of extracellular matrix on cell behavior has been supported directly by in vitro primary cell culture experiments, in which intestinal epithelial cells undergo thyroid hormone-induced apoptosis, just like that during natural metamorphosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1524-475X.1998.60407.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Autoactivation ofXenopus thyroid hormone receptor β genes correlates with larval epithelial apoptosis and adult cell proliferation (1997)
    Springer
    Journal of biomedical science 4 (1997), S. 9-18 
    Details
    ISSN: 1423-0127
    Keywords: Thyroid hormone receptor ; Xenopus laevis ; Metamorphosis ; Apoptosis ; Cell proliferation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The thyroid hormone (T3)-dependent amphibian metamorphosis involves degeneration of larval tissues through programmed cell death (apoptosis) and concurrent proliferation and differentiation of adult cell types. As the mediators of the causative effects of T3 on metamorphosis, both thyroid hormone receptor (TR) α and β genes have been found to be expressed in different tissues during this process. In particular, theXenopus TRβ genes have been shown to be regulated by T3 at the transcriptional level and their expression correlates with organ-specific metamorphosis. We demonstrate here by in situ hybridization that theXenopus TRβ genes are regulated in a cell-type specific manner that correlates with tissue transformation. In particular, they are found to be expressed in the larval intestinal epithelial cells prior to their apoptotic degeneration and in the proliferating cells of the adult epithelium, connective tissue, and muscles. However, they are repressed again upon the differentiation of these adult cells. These results implicate that TRβ participates both in inducing apoptosis and stimulating cell proliferation during development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255588
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Demonstration of sucrase immunoreactivity of the brush border induced by duodenal mesenchyme in chick stomach endoderm (1992)
    Springer
    Development genes and evolution 201 (1992), S. 389-392 
    Details
    ISSN: 1432-041X
    Keywords: Sucrase-Brush border ; Mesenchymal induction ; Stomach endoderm ; Immunoelectron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When stomach endoderm of chick embryos was recombined and cultured with duodenal mesenchyme, the endoderm developed a brush border structure over a large area and also differentiated into mucous cells in a small area according to its own developmental fate. In the present investigation, we examined whether the induced brush border structure expressed sucrase antigen by immunoelectron microscopy using the antiserum raised against chicken sucrase. Sucrase immunoreactivity could be detected as ferritin particles in the region where the brush border was induced, whereas it was never detected on microvilli of endodermal cells which differentiated into the mucous cells. Thus, almost all of the endodermal cells could be identified as either small intestine-type cells possessing the sucrase antigen or stomach-type cells possessing mucous granules but not the sucrase antigen. The results indicate that stomach endodermal cells of chick embryos can differentiate not only morphologically but also functionally into typical intestinal epithelial cells under the inductive influence of the duodenal mesenchyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365127
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Cell-specific and spatio-temporal expression of intestinal fatty acid-binding protein gene during amphibian metamorphosis (1994)
    Springer
    Development genes and evolution 204 (1994), S. 150-155 
    Details
    ISSN: 1432-041X
    Keywords: Fatty-acid-binding protein ; Intestinal epithelium ; In situ hybridization ; Anuran metamorphosis ; Regional difference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intestinal fatty acid-binding protein (IFABP) gene is known to be regulated during Xenopus metamorphosis. To determine the relationship between its regulation and cellular differentiation during metamorphosis, we have examined the distribution of IFABP mRNA in the Xenopus digestive tract by in situ hybridization techniques. Throughout all stages examined, transcripts of IFABP gene were observed exclusively in absorptive epithelial cells of the small intestine, and they decreased in amount towards the posterior intestine. Around stage 58, just before metamorphic climax, IFABP mRNA level began to decrease in larval absorptive cells that still remained intact morphologically. Thereafter, IFABP mRNA was no longer detected among larval cells. In turn, at stage 62, IFABP mRNA became detectable in some of the newly formed adult epithelium that had not yet developed a brush border, but not in the remaining larval cells. By the end of metamorphosis, IFABP mRNA became more abundant towards the crest of intestinal folds. These results suggest that IFABP gene expression is specific for absorptive epithelial cells of the small intestine and is regionally regulated along the intestinal anterior-posterior axis in both tadpoles and frogs and also along the trough-crest axis of frog intestinal folds. In addition, our present study directly shows that IFABP mRNA level decreases in larval absorptive cells but increases in adult ones during metamorphosis, preceding morphological changes of both types of cells. Therefore, the regulation of IFABP gene is an early event during both larval epithelial cell death and adult epithelial cell differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00361110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Connective tissue is involved in adult epithelial development of the small intestine during anuran metamorphosis in vitro (1992)
    Springer
    Development genes and evolution 201 (1992), S. 322-329 
    Details
    ISSN: 1432-041X
    Keywords: Intestinal epithelium ; Anuran metamorphosis ; Organ culture ; Tissue interaction ; Regional difference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The role of connective tissue in metamorphic changes of the small intestinal epithelium inXenopus laevis tadpoles was investigated by using organ culture techniques and electron microscopy. Tissue fragments isolated from various parts of the small intestine at stage 57 were cultivated. Larval cell death of the epithelium was induced by thyroid hormone in all fragments, whereas adult epithelial development was observed only in fragments isolated from the anterior intestinal region containing the typhlosole where most of the larval connective tissue was localized. The epithelium was then cultivated in recombination with homologous or heterologous non-epithelial components. The adult epithelium developed only in recombinants containing a thick connective tissue layer from the typhlosole. There was no regional difference in the developmental potency of the epithelium itself. In all explants where adult epithelium developed, the connective tissue increased in cell density just beneath the epithelium, which was rapidly proliferating and forming typical islets. At the same time, fibroblasts possessing well-developed rough endoplasmic reticulum differentiated close to epithelial cells and often made contact with them. These results indicate that the connective tissue originating from the typhlosole plays an important role in adult epithelial development of the anuran small intestine, probably via direct cell-to-cell contacts or some factor(s) synthesized by the fibroblasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00592113
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Electron microscopical study of self-differentiation potency in the chick embryonic endoderm cultured in vitro (1983)
    Springer
    Development genes and evolution 192 (1983), S. 171-178 
    Details
    ISSN: 1432-041X
    Keywords: Differentiation ; Digestive tract ; Endoderm ; Organ culture ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The self-differentiation potency of the endoderm of the chick embryo was investigated mainly by transmission electron microscopy. Endodermal fragments isolated from 4- to 6-day stomach or small intestine were cultured in the absence of mesenchyme and were able to differentiate in vitro into organ-specific epithelia. Endodermal fragments isolated from the stomach region differentiated into a pseudo-stratified epithelium with periodic acid Schiff-positive mucous granules in the apical cytoplasm, while those from the small intestinal region differentiated into a simple columnar epithelium with a striated border which was positive in alkaline phosphatase activity. These features are comparable with those of the mucous secretory epithelium of the normal embryonic stomach and the absorptive epithelium of normal embryonic small intestine, respectively. Next, the self-differentiation potencies were investigated of the upper and lower layers of the blastoderms, at stages 1–5 of Hamburger and Hamilton (H. and H.). Both stomach-type and small-intestine-type epithelia developed only when fragments of the lower layer isolated from the blastoderms older than stage 3 of H. and H. were cultured, suggesting that cells possessing the potency to differentiate into the stomach- and small-intestine-type epithelia exist in the definitive endoderm at the beginning of its formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848687
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Chronological analysis of the intestinalization of chick stomach endoderm induced in vitro by duodenal mesenchyme (1985)
    Springer
    Development genes and evolution 194 (1985), S. 301-305 
    Details
    ISSN: 1432-041X
    Keywords: Intestinal induction ; Organ culture ; Stomach endoderm ; ultrastructure ; Cell contacts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Inductive action of duodenal mesenchyme on stomach endoderm in the chick embryo was chronologically analysed in vitro by the use of electron microscopy and immunofluorescence techniques. The behaviour of the endoderm-mesenchyme interfaces was particularly studied during the induction. In recombinates of 4-day stomach endoderm and 6-day duodenal mesenchyme, all the endodermal cells were undifferentiated at the start of cultivation. Small-intestinal sucrase antigen could first be detected on the 5th day of cultivation in one-third of the stomach endoderm, and a striated border on the 7th day. With a longer cultivation period, intestine-type cells increased in number in the stomach endoderm and the density of microvilli on the apical surface became higher. At the endoderm-mesenchyme interfaces a number of direct contacts between endodermal and mesenchymal cells were observed from the beginning to the end of cultivation. These were especially abundant in the early period before the appearance of signs of intestinal cytodifferentiation. These results suggest that the mesenchymal cells adjacent to the endodermal tissue play an important role in the intestinal induction which occurs during the early period of cultivation, probably via direct cell-to-cell contracts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01152176
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Changes in lectin-binding pattern in the digestive tract of Xenopus laevis during metamorphosis. I. Gastric region (1990)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 205 (1990), S. 1-8 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution of structural and secretory glycoconjugates in the gastric region of metamorphosing Xenopus laevis was studied by the avidin-biotinperoxidase (ABC) histochemical staining method using seven lectins (concanavalin A, Con A; Dolichos biflorus agglutinin, DBA; peanut agglutinin, PNA; Ricinus communis agglutinin I, RCA-I; soybean agglutinin, SBA; Ulex europeus agglutinin I, UEA-I; and wheat germ agglutinin, WGA). Throughout the larval period to stage 60, the epithelium consisting of surface cells and gland cells was stained in various patterns with all lectins examined, whereas the thin layer of connective tissue was positive only for RCA.-I. At the beginning of metamorphic climax, the connective tissue became stained with Con A, SBA, and WGA, and its staining pattern varied with different lectins. The region just beneath the surface cells was strongly stained only with RCA-I. With the progression of development, both the epithelium and the connective tissue gradually changed their staining patterns. The surface cells, the gland cells, and the connective tissue conspicuously changed their staining patterns, respectively, for Con A and WGA; for Con A, PNA, RCA-I, SBA, and WGA; and for Con A, RCA -I, and WGA. At the completion of metamorphosis (stage 66), mucous neck cells became clearly idpntifiable in the epithelium, and their cytoplasm was strongly stained with DBA, PNA, RCA-I, and SBA. These results indicate that lectin histochemistry can provide good criteria for distinguishing among three epithelial cell types, namely, surface cells, gland cells, and mucous neck cells, and between adult and larval cells of each type.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052050102
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Programmed cell death and heterolysis of larval epithelial cells by macrophage-like cells in the anuran small intestine in vivo and in vitro (1992)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 213 (1992), S. 185-195 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The degenerative processes in the larval small intestine of Xenopus laevis tadpoles during spontaneous metamorphosis and during thyroid hormone-induced metamorphosis in vitro were examined by electron microscopy. Around the beginning of spontaneous metamorphic climax (stages 59-61), both apoptotic bodies derived from larval epithelial cells and intraepithelial macrophage-like cells suddenly increase in number. The macrophage-like cells become rounded and enlarged because of numerous vacuoles containing the apoptotic bodies. Mitotic profiles of the macrophage-like cells, however, are localized in the connective tissue where different developmental stages of macrophage-like cells are present. After stage 62, the intraepithelial macrophage-like cells decrease in number, while large macrophage-like cells which include the apoptotic bodies and retain intact cell membranes and nuclei appear in the lumen. Degenerative changes similar to those during spontaneous metamorphosis described above could be reproduced in vitro. In tissue fragments isolated from the small intestine of stage 57 tadpoles and cultured in the presence of thyroid hormone, the number of intraepithelial macrophage-like cells reaches its maximum around the 3rd day of cultivation when the larval epithelial cells most rapidly decrease in number. These results suggest that the rapid degeneration of larval epithelial cells occurs not only because of apoptosis of the epithelial cells themselves but also from heterolysis by macrophages. The macrophages probably originate in the connective tissue, actively proliferate, migrate into the larval epithelium around the beginning of metamorphic climax, and are finally extruded into the lumen. © 1992 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052130205
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Ultrastructural changes in the intestinal connective tissue of Xenopus laevis during metamorphosis (1987)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 193 (1987), S. 13-22 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ultrastuctural changes in the intestinal connective tissue of Xenopus laevis during metamorphosis have been studied. Throughout the larval period to stage 60, the connective tissue consists of a few immature fibroblasts surrounded by a sparse extracellular matrix: few collagen fibrils are visible except close to the thin basal lamina. At the beginning of the transition from larval to adult epithelial form around stage 60, extensive changes are observed in connective tissue. The cells become more numerous and different types appear as the collagen fibrils increase in number and density. Through gaps in the thickened and extensively folded basal lamina, frequent contacts between epithelial and connective tissue cells are established. Thereafter, with the progression of fold formation, the connective tissue cells become oriented according to their position relative to the fold structure. The basal lamina beneath the adult epithelium becomes thin after stage 62, while that beneath the larval epithelium remains thick. Upon the completion of metamorphosis, the connective tissue consists mainly of typical fibroblasts with definite orientation and numerous collagen fibrils. These observations indicate that developmental changes in the connective tissue, especially in the region close to the epithelium, are closely related spatiotemporarily to the transition from the larval to the adult epithelial form. This suggests that tissue interactions between the connective tissue and the epithelium play important roles in controlling the epithelial degeneration, proliferation, and differentiation during metamorphic climax.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051930103
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...