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PubMed1986

Normal epithelial branching morphogenesis in the absence of collagen I.

Interstitial collagens are thought to mediate epithelial-mesenchymal interactions during organogenesis. We have used the collagen I-deficient mouse mutant Mov13 to directly investigate the role of this major representative of the interstitial collagens in epithelial branching morphogenesis. Since homozygous embryos die at midgestation, we have studied the development of organ rudiments from Mov13 homozygous (i.e., collagen I-deficient), heterozygous, and wild-type embryos in culture. Development of all explants, including lung, kidney, salivary glands, pancreas, and skin, was normal by light and electron microscopic criteria and was independent of the genotype of the donor embryo. Metabolic labeling and immune staining verified the complete absence of collagen I in homozygous explants while revealing substantial production of collagens III and V in explants of all three genotypes. These results indicate either that collagen I has no role in the morphogenesis of these organs, or that its function is shared, or can be substituted for, by other fibrillar collagens.

Animals↗
PubMed1987

Milk protein expression and ductal morphogenesis in the mammary gland in vitro: hormone-dependent and -independent phases of adipocyte-mammary epithelial cell interaction.

Epithelial cell differentiation frequently occurs in situ in conjunction with supporting mesenchyme or connective tissue. In embryonic development the importance of the supporting mesenchyme for cytodifferentiation and morphogenesis has been demonstrated in several epithelial tissues, but the importance of epithelial-connective tissue interactions is less well studied in adult epithelial organs. We have investigated the interaction of adult mammary epithelial cells with adipocytes, which compose the normal supporting connective tissue in the mammary gland. Mammary epithelial cells from mice in various physiological states were cultured on cellular substrates of adipocytes formed from cells of the 3T3-L1 preadipocyte cell line. We found that there were two distinct phases to the interaction of epithelial cells with adipocytes. Cytodifferentiation of the epithelial cells and milk protein production were dependent on lactogenic hormones (insulin, hydrocortisone, and prolactin), whereas ductal morphogenesis was lactogenic hormone independent. When cultured on preadipocytes or adipocytes, mammary epithelial cells from never pregnant, pregnant, lactating, and involuting mice responded to lactogenic hormones rapidly by producing and secreting large amounts of alpha-, beta-, and gamma-casein and alpha-lactalbumin. This response was seen in individual as well as in clusters of epithelial cells, but was not seen if the same cells were cultured on tissue culture dishes without adipocytes, on fibroblasts (human newborn foreskin fibroblasts) or in the presence of adipocytes but in the absence of lactogenic hormones. Continued incubation of mammary epithelial cells on adipocytes in the presence or absence of lactogenic hormones resulted in the formation of a branching ductal system. Mammary epithelial cells in ducts that formed in the absence of lactogenic hormones produced no casein, but rapidly synthesized casein when subsequently exposed to these hormones. Ultrastructural studies revealed that the formation of a basement membrane occurs only in co-cultures of mammary epithelium with adipocytes or preadipocytes. Ultrastructural changes associated with secretion occurred only in the presence of lactogenic hormones. We propose that growth and formation of a ductal system in vitro can occur in the absence of lactogenic hormones, but that certain environment-associated events must occur if the epithelium is to become responsive to lactogenic hormones and undergo the cytodifferentiation associated with lactation.

Adipose Tissue↗
PubMed1988

Genes expressed during imaginal disc morphogenesis: IMP-E1, a gene associated with epithelial cell rearrangement.

A unique set of genes that encodes hormone-inducible transcripts found on membrane-bound polysomes is expressed during ecdysone-dependent morphogenesis of Drosophila imaginal discs cultured in vitro. The pattern of expression of one of these genes, IMP-E1, was analyzed in tissues from late third instar larvae and white prepupae by hybridization of asymmetric RNA probes to tissue sections. The IMP-E1 transcript was detected in all anterior and posterior imaginal discs except the ommatidial region of the imaginal eye disc. Within the imaginal leg disc, the IMP-E1 transcript is expressed more abundantly in the proximal than in the distal portions of the epithelium. The distribution of transcripts is consistent with the hypothesis that the IMP-E1 gene product is involved in the cell rearrangements associated with morphogenesis of the disc epithelium. The IMP-E1 transcript is also expressed at pupariation in glial cell layers that ensheath the brain. This glial cell transcript is the same size (7.5 kb) and polarity as the imaginal disc transcript, and is also transcribed in response to 20-hydroxyecdysone. Similarities between the morphogenetic changes in imaginal disc and glial cell layers during metamorphosis are discussed.

Animals↗
PubMed1989

Retinoic acid improves epidermal morphogenesis.

Hyper- and hypovitaminosis A both provoke epithelial pathologies in animals and humans. This suggests that a critical level of retinoic acid (RA) is required in vivo for the maintenance of normal architecture and function of these tissues. However, no beneficial, but only adverse effects of RA on epithelia have been so far observed in vitro. For instance, addition of RA to keratinocyte cultures has been shown to inhibit epidermal differentiation while this process is stimulated by serum delipidization, which reduces RA concentration in the medium. Assuming that the previous failure to demonstrate beneficial effects of RA on the epidermal phenotype in vitro was due to culture conditions too far from the in vivo conditions we decided to reevaluate the effect of RA in a culture system optimized for epidermal morphogenesis: the "emerged dermal equivalent." When human keratinocytes were grown in such a system with total fetal calf serum, the resulting epithelium was very similar to normal epidermis. But when delipidized serum was used, the epithelium was abnormal in the direction of excessive maturation (hyperkeratosis). When physiological concentrations of RA (10(-9) and 10(-8) M) were added to the delipidized serum supplement, a normal architecture (orthokeratosis) was restored. However, as classically described in the literature, higher RA concentrations (greater than 10(-7) M) reduced epidermal maturation and produced parakeratosis. Thus, although it is unquestionable that RA reduces the synthesis of epidermal-specific differentiation markers, an optimal epidermal morphogenesis seems to be achieved only in the presence of a critical RA concentration.

Cell Differentiation↗
PubMed1989

Mutations that disrupt the morphogenesis and localization of a sperm-specific organelle in Caenorhabditis elegans.

Nematode sperm contain unusual organelles, membranous organelles, which undergo dramatic morphological changes during spermatogenesis. Early in spermatogenesis, the membranous organelle functions to transport sperm specific components to the spermatids; later, during the formation of the crawling spermatozoa, it adds new components to the cell surface as it fuses with the plasma membrane. Genetic analysis of spermatogenesis in the nematode Caenorhabditis elegans has revealed mutations that specifically disrupt the proper cellular localization and morphogenesis of this organelle. In animals homozygous for the either the known deficiency hcDf1 or the probable deficiency h12, the membranes of the membranous organelles are aberrantly covered with ribosomes. A mutation in the spermatogenesis-defective spe-10 gene causes severe defects in the morphogenesis of a fibrous body-membranous organelle complex. In both cases, these mutations also disrupt the proper localization of both nuclei and membranous organelles in haploid spermatids and spermatozoa.

Animals↗
PubMed1990

Inhibition of mouse mammary ductal morphogenesis and down-regulation of the EGF receptor by epidermal growth factor.

EGF, initially demonstrated to be a potent mitogen for a variety of cell types, has more recently been shown to inhibit proliferation of several cell lines. Few studies, however, have addressed the effects of EGF on growth and morphogenesis of tissues in vivo, particularly with regard to EGF as a possible inhibitor. We now demonstrate that EGF treatment of vigorously growing mammary ducts, administered directly to the glands by slow release plastic implants, inhibited normal ductal growth. Inhibition was restricted to the region around the implant and untreated glands in the same animal were normal, indicating direct effects of EGF. EGF-treated end buds were smaller and demonstrated reduced levels of DNA synthesis, although remnants of a stem (cap) cell layer persisted. Full inhibition of growth occurred within 3 days of implantation and required extended exposure to EGF, since treatment of 5 hr or less had no effect on ductal growth. At the lower inhibitory doses tested, growth resumed within 8 days, indicating reversibility of inhibition. No lobuloalveolar or hyperplastic response was seen. 125I-EGF autoradiography revealed that ductal growth inhibition was preceded by the disappearance of EGF receptors located in the cap cell layer of the end bud epithelium and in stromal cells adjacent to the buds. These results, in conjunction with our previous evidence demonstrating the growth-stimulatory effect by EGF on nonproliferating mammary ducts, suggest a growth regulatory role for EGF in mouse mammary ductal morphogenesis.

Aging↗
PubMed1983

Involvement of Tetrahymena intermediate filament protein, a 49K protein, in the oral morphogenesis.

To study the biological function of Tetrahymena intermediate-type filament protein (a 49K protein), we examined the immunofluorescence localization of 49K protein within Tetrahymena cells. The results showed that the immunofluorescence was localized in the oral apparatus, mitochondria and mucocysts. Among them, the fluorescence in the oral apparatus was of high interest in its unique region and vicissitude in the cell cycle: a tau-shaped region of the oral apparatus intensely fluoresced during interphase, but the fluorescence completely disappeared during dividing phase. The tau-shaped region corresponded to 'posterior connectives' and the root part of 'deep fiber', to the conjunction parts of microtubule bundles. In the those parts, there was electron-dense material in the microtubule bundles. Hence, it is conceivable that 49K protein corresponds to the dense material and has a function of microtubule bundle conjunction. On the other hand, disappearance of immunofluorescence from the old oral apparatus of most dividing cells reflected the oral apparatus regression and remodelling which have been known as necessary sequential events in the cell cycle. We observed that oral fluorescence disappeared concurrently with the onset of oral regression and of constriction of division furrow, whereas at a late dividing stage immunofluorescence began to appear simultaneously in both new and old oral apparatus. Thus, the 49K protein may play a crucial role(s) not only in the morphogenesis of oral primordia but also in the transient morphogenesis in the old oral system.

Animals↗
PubMed1987

Immunoelectron microscopy of Rift Valley fever viral morphogenesis in primary rat hepatocytes.

The morphogenesis of the hepatotropic phlebovirus Rift Valley fever virus (RVFV) has been examined by immuno-electron microscopy in primary hepatocyte cultures derived from genetically susceptible and resistant rat strains. RVFV replicates in both cell types with growth kinetics comparable with those seen in other permissive cells. However, in contrast to that has been observed in other cell types, RVFV replication in hepatocytes is associated with maturation at cellular surface membranes in addition to the smooth internal membranes of the Golgi and endoplasmic reticulum. Envelope acquisition at surface membranes occurred primarily on basolateral membranes. The events occurring in RVFV morphogenesis were indistinguishable in hepatocytes from resistant and susceptible animals; however, hepatocytes from susceptible animals produced significantly higher titers of virus.

Animals↗
PubMed1987

Expression of fibronectin and laminin in fetal male gonads in vivo and in vitro with and without testicular morphogenesis.

Sertoli cell differentiation occurs in vitro, even when testicular morphogenesis is inhibited by addition of serum to the culture medium (Magre, S. and A. Jost: Proc. Natl. Acad. Sci. USA 81, 7831-7834 (1984]. Using indirect immunohistochemical technique, we have studied the expression of fibronectin and laminin in gonads lacking testicular morphogenesis, as compared to in vivo controls and gonads cultured in synthetic medium. In undifferentiated gonads in vivo, fibronectin and laminin are distributed uniformly in the blastema. If testicular differentiation occurs in vivo, laminin is detected only in the basement membranes; when it occurs in vitro, laminin is found both in the basement membranes and among the stromal tissue. In gonads without seminiferous cords (cultured in serum-supplemented medium), fibronectin and laminin are both present, they are uniformly distributed among the gonadal cells.

Animals↗
PubMed1992

Epimorphin: a mesenchymal protein essential for epithelial morphogenesis.

A novel 150 kd protein expressed on the surface of mesenchymal cells of mouse embryonic tissues was identified. A monoclonal antibody to this molecule inhibited various processes of epithelial morphogenesis, such as hair follicle growth and lung epithelial tubular formation, in organ cultures of these tissues. Sequence analysis of cDNA encoding this protein revealed that it had 289 amino acids with a hydrophobic stretch at the C-terminus. NIH 3T3 cells transfected with the cDNA of this protein expressed the exogenous 150 kd protein on their surface. When lung epithelial cells were cocultured with these transfected cells, they showed normal tubular morphogenesis, but not with untransfected NIH 3T3 cells. These results indicate that this protein, termed epimorphin, plays a central role in epithelial-mesenchymal interactions.

Amino Acid Sequence↗
PubMed1985

Does triiodothyronine influence the morphogenesis of fetal mouse mesencephalic dopaminergic neurons cultured in chemically defined medium?

Serum-free cultures of mouse mesencephalic cells were used for studying the influence of triiodothyronine (T3) on the morphogenesis of dopaminergic neurons. Supplementation of culture medium with T3 (10(-9) M) did not modify the number, but increased the size of the perikarya without affecting the neurite density of mesencephalic dopamine (DA) neurons. Furthermore, T3 had no effect on the uptake of [3H]DA in these cultures. These findings, taken together with previous results obtained with hypothalamic cell cultures, show that T3 affects the morphogenesis of mesencephalic DA neurons in a different manner than that of hypothalamus and that the perikarya size on the one hand, and the neurite elongation on the other hand, seem to be independently regulated by T3.

Animals↗
PubMed1998

Expression of epithelial-cadherin, alpha-catenin and beta-catenin during human intrahepatic bile duct development: a possible role in bile duct morphogenesis.

BACKGROUND/AIMS: Cell adhesion molecules play an important role in the morphogenesis of developing organs. However, little is known about their expression during intrahepatic bile duct development. METHODS: We immunohistochemically investigated the expression of E-cadherin (E-Cad), alpha-catenin (A-Cat) and beta-catenin (B-Cat) during human intrahepatic bile duct development, using 31 fetal livers of various gestational ages. The developmental stages of bile ducts were classified into the ductal plate, migrating biliary cells (remodeling stage), and immature bile ducts (remodeled stage). RESULTS: E-Cad was broadly and strongly expressed in the ductal plate with a cytoplasmic pattern, heterogeneously and weakly expressed in the migrating biliary cells with a cytoplasmic pattern, and broadly and strongly expressed in immature bile ducts with a membranous pattern. A-Cat was broadly and strongly expressed in the ductal plate with a membrane pattern, broadly and moderately expressed in the migrating biliary cells with a membranous pattern, and broadly and strongly expressed in immature bile ducts with a membranous pattern. In contrast, expression of B-Cat was weak or slight in the ductal plate, but B-Cat was expressed broadly and strongly with a membranous pattern in migrating biliary cells and in immature bile ducts. Immature hepatocytes rarely expressed E-Cad and A-Cat, but expressed B-Cat with a membranous pattern throughout development. CONCLUSIONS: These results suggest that E-Cad, A-Cat and B-Cat are involved in the normal developmental morphogenesis of human intrahepatic bile ducts.

Bile Ducts, Intrahepatic↗
PubMed1996

Activation of dopaminergic D1 receptors promotes morphogenesis of developing striatal neurons.

The early dopaminergic input from the midbrain may play an important role in the development of the basal ganglia. We therefore investigated whether and how dopamine affects the morphogenesis of striatal target neurons. Dissociated cell cultures of embryonic day 17 rat striatum were raised for seven days. Cells were then incubated with dopamine or various receptor-specific ligands for 1 h. At various times after termination of the treatment, cells were immunostained for growth-associated protein-43. Morphological parameters including numbers of growth cones, length of neurites, number of bifurcations, and neuronal soma size were assessed by means of a computer-based morphometric device. Treatment with dopamine in low concentrations as well as with the D1-like receptor agonist SKF 38393 increased the numbers of growth cones and neurite length and arborization. The morphogenetic effect took several hours to evolve and remained stable for at least 24 h. It could be blocked by the D1-like receptor antagonist SCH 23390 or by cycloheximide but not by pretreatment of the cultures with tetrodotoxin. The D2-like receptor agonist quinpirole had no effect on the morphological parameters and did not contribute to that of SKF 38393. Dopamine and SKF 38393 but not quinpirole also induced an increase in the number of neurons immunoreactive for Fos-like proteins. However, this effect was restricted to growth-associated protein-43-negative neurons. This is the first observation of a positive regulatory effect of D1-like receptors on neuronal morphogenesis. We conclude that the changes reflect true differentiation rather than short-term modulation of cellular properties and that c-fos induction is not an obligatory step in the transduction pathway coupling D1-like receptors to neurite outgrowth. Our results suggest that the differentiation of embryonic striatal neurons is promoted by the dopaminergic nigrostriatal projection through D1-like receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1990

Proteolytic balance and capillary morphogenesis.

Angiogenesis is the process by which new capillary blood vessels are formed from preexisting vessels. A number of components of this morphogenetic process, including endothelial cell invasion and capillary lumen formation, are believed to be dependent on tightly controlled proteolytic degradation of the extracellular matrix. The critical importance of an appropriate balance between proteases and protease inhibitors in these processes is suggested by two sets of observations. Firstly, that extracellular matrix invasion and capillary lumen formation are inhibited in the presence of an excess of protease inhibitors. Secondly, that when unchecked by protease inhibitors, excessive proteolysis is incompatible with normal capillary morphogenesis. These results clearly suggest that a precisely regulated proteolytic balance is necessary for normal capillary morphogenesis.

Animals↗
PubMed1990

Susceptibility of epithelia to directive influences of mesenchymes during organogenesis: uncoupling of morphogenesis and cytodifferentiation.

Morphogenesis and functional cytodifferentiation are two major events in organogenesis, and normally they take place inseparably either in vivo or in vitro conditions. In this article, we reviewed a series of our recent results on mesenchymal-epithelial interactions in organogenesis of digestive organs, urogenital organs and the skin of avian and mammalian embryos, giving special attention to the importance of the responses of epithelia to the directive influences of mesoderms and also to the uncoupling of morphogenesis and cytodifferentiation, which has often been observed during the course of these studies.

Animals↗
PubMed1995

Activin disrupts epithelial branching morphogenesis in developing glandular organs of the mouse.

We report that activin profoundly alters epithelial branching morphogenesis of embryonic mouse salivary gland, pancreas and kidney rudiments in culture, indicating that it may play a role as a morphogen during mammalian organogenesis. In developing pancreas and salivary gland rudiments, activin causes severe disruption of normal lobulation patterns of the epithelium whereas follistatin, an activin-binding protein, counteracts the effect of activin. In the kidney, activin delays branching of the ureter bud and reduces the number of secondary branches. TGF-beta induces a pattern of aberrant branching in the ureter bud derived epithelium distinct from that seen for activin. Reverse-transcriptase polymerase chain reaction, Northern hybridization and in situ hybridization analyses indicate that these developing tissues express the mRNA transcripts for activin subunits, follistatin or activin receptors. Our results are suggestive of a potential role for the activin-follistatin system as an intrinsic regulator of epithelial branching morphogenesis during mammalian organogenesis.

Activin Receptors↗
PubMed1994

Expression of collagen alpha 1(IV), laminin and nidogen genes in the embryonic mouse lung: implications for branching morphogenesis.

The patterns of laminin A, B1, B2, nidogen and collagen alpha 1(IV) gene expression in the embryonic mouse lung were determined using in situ hybridization histochemistry at a stage when branching morphogenesis is taking place. Collagen alpha 1(IV), laminin B1 and B2 genes were expressed throughout the mesenchyme and epithelium. Nidogen gene expression was uniform throughout the mesenchyme but was not detected in epithelial cells. Laminin A mRNA was localized to cells closely associated with a basement membrane at the epithelial-mesenchymal interface. However, expression of the laminin A gene was limited to the mesenchymal cells in bronchial regions and to epithelial cells in distal terminal lobules. We propose that the pattern of laminin A gene expression in different regions of the developing lung will influence the structure of the basement membrane at the epithelial-mesenchymal interface and thus have a role in branching morphogenesis.

Animals↗
PubMed1994

The cold-sensitive period for frizzled in the development of wing hair polarity ends prior to the start of hair morphogenesis.

The function of the frizzled (fz) gene is essential for the development of the normal pattern of hairs on the Drosophila wing. In the absence of fz function hairs develop, but they display an abnormal polarity. Mutations in fz result in an altered subcellular location for the assembly of the F-actin filled prehair that becomes the adult cuticular hair. This observation led to the suggestion that fz and other tissue polarity genes form a regulatory pathway that controls the initiation of prehairs. We have isolated a cold-sensitive fz allele and found that the cold-sensitive period for fz in the pupal wing starts in the early pupae and ends prior to the first sign of prehair morphogenesis. This cold-sensitive mutation is due to a missense mutation in a putative transmembrane domain. Western blot analysis shows that the accumulation of the mutant protein is not cold sensitive, consistent with the supposition that it is the activity of the mutant protein that is cold sensitive. Our data argue that fz has a regulatory function in specifying where the prehair forms, but no role in the actual morphogenesis of the prehair.

Actins↗