摘要:

AbstractRemodeling of the extracellular matrix (ECM) is an essential component of normal development and is also involved in the pathogenesis of arthritis and the spread of cancer. The matrix metalloproteinases and their natural inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), play an important role in this context. We have isolated mouse cDNA clones encoding a novel member of the TIMP family, designated TIMP‐3. We have assigned theTimp‐3locus to the [C1–D1] region of mouse chromosome 10 using both genetic and cytogenetic methods. The conceptual translation product of theTimp‐3cDNA shows a high degree of similarity with ChIMP‐3, a recently cloned chicken metalloproteinase inhibitor, as well as significant structural similarity with the amino acid sequences of the previously isolated members of this family, TIMP‐1 and TIMP‐2. The pattern of expression ofTimp‐3in the developing mouse embryo is distinct from that previously reported forTimp‐1.Timp‐3is expressed in cartilage and skeletal muscle, in myocardium, in the skin, oral and nasal epithelium, in the newborn mouse liver, in the epithelium of some tubular structures such as the developing bronchial tree, oesophagus, colon, urogenital sinus, bile duct, in the kidney, salivary glands, and in the choroid plexus of the brain. The patterns ofTimp‐3expression in surface epithelia and in the epithelial lining of many tubular organs suggests that TIMP‐3 may be involved in regulating ECM remodeling during the folding of epithelia and during the formation, branching, and expansion of epithelial tubes. In the mouse placenta, expression is seen in the trophoblast, raising the possibility that TIMP‐3 may be involved in regulating trophoblastic invasion of the uterus. We propose a role for TIMP‐3 in musculoskeletal and cardiac development, in the morphogenesis of certain epithelial structures, and placental implantat

ISSN:1058-8388    

DOI:10.1002/aja.1002000302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractRetinoic acid induced heparin‐binding protein (RIHB) is a highly basic, soluble polypeptide of the chick embryonic extracellular matrix. We have examined the expression and localization of RIHB during very early embryogenesis by in situ hybridization and immunohistochemistry.RIHBmRNA is very weakly detectable above background in the blastodiscs of unincubated eggs. The expression increases greatly over the first 24 hours of incubation, and is observed throughout the blastodisc in all three of the germ layers following gastrulation. As neurulation occurs, the expression becomes more restricted to certain areas, notably the ectoderm, the neural folds, and especially the notochord. After the neural tube has formed the expression in the tube itself decreases dramatically, whereas the expression in the head ectoderm and the notochord persists. After 72 hours of incubation expression remains relatively high throughout most of the embryo, with higher levels of expression in regions undergoing organogenesis and lower levels in organs which have already differentiated. RIHB protein is also weakly detectable in unincubated eggs as patches of immunoreactive material between the blastodisc and the vitelline. After 6 hours of incubation small regions of basement membrane are immunoreactive. RIHB is detected in this matrix, apparently before even fibronectin. The amount of RIHB protein increases dramatically over the first 24 hours of incubation. It is found in basement membrane separating the epiblast from the hypoblast, then later in that separating the ectoderm from the mesoderm. It is also detected surrounding individual cells, especially of the ectodermal layer. During neurulation RIHB is observed in the basement membrane surrounding the neural fold and the notochord, and in the lamina separating the ectodermal, mesodermal, and endodermal layers. Later in development, RIHB is detected in the basement membrane under the epidermis, throughout the developing limbs, and in the lamina of various developing organs, such as the eye, the pulmonary bud, the intestine, and the mesonephros. These results demonstrate that RIHB is highly expressed during the early embryonic period, by all three germ layers, and is an important and very early component of the embryonic extracellular matrix. Its very broad expression and localization argue for a more general role in development than its demonstrated weak neurotrophic activity. © 1994 Wiley‐Liss,

ISSN:1058-8388    

DOI:10.1002/aja.1002000303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractDevelopment of the chick scleral ossicle was studied with respect to expression of various collagen types, cartilage matrix molecules, and osteoblastic cell surface antigens. The extra‐cellular matrix of the scleral ossicle primordium of stage 35.5 chick sclera and the mesenchyme beneath the conjunctival epithelium was immunoreactive with anti‐type II collagen antibody, giving the impression that certain materials and/or cell clusters surrounded by reactive matrix were descending from the epithelial‐mesenchymal interface to the scleral ossicle primordium. In stage 37 embryos, type II collagen immunoreactivity was restricted to the bone matrix of the scleral ossicles, and persisted through stage 39. However, at stage 41, virtually no type II collagen was detected. In contrast, strong immunostaining of type I collagen was first detected in the developing scleral ossicle at stage 37, coinciding with the formation of mineralized bone matrix. Following the extensive accumulation of type I collagen in bone matrix, type XII collagen was detected at the surface of the bone; both type I and type XII collagen immunostainings then remained. By stage 37, immunoreactivity with a pre‐osteoblastic cell surface marker was detected on cells of the scleral ossicle, and typical osteocytes were subsequently identified by both morphological and specific immunostaining techniques. Antibodies other than for type II collagen, specific to chondrogenic mesenchyme or cartilage matrix, never reacted with the scleral ossicle and its primordium during development. Taken together, these observations indicate that the scleral ossicle is a membranous bone, whose development may not require overt chondrogenesis. Implications of type II collagen distribution during the positioning of scleral ossicles and their early bone matrix formation are discussed with respect to the origin and evolution of endoskeletons in vertebrate animals. © 1994 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1002000304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractEarly neural development is a multistep process with morphologically distinct stages; however, the molecular events that underlie morphologic development are poorly understood. Retinoic acid (RA) was chosen as a teratogen to perturb development because this endogenous molecule is thought to play an integral role in normal neuraxis formation in many vertebrate species. We have examined the effects of RA on early neural patterning in the rat at three morphologically distinct stages: late streak, foregut pocket, and early somite. In this model exogenous RA exposure during mid‐gastrulation (late streak stage) leads to severe disruption of anterior neural development as determined by morphologic and molecular (Engrailed [Eu] gene expression) markers. This disruption in anterior neural development is associated with excessive cell death in the hindbrain posterior to the En expression domain. In contrast, at the time the neural folds begin to elevate (foregut pocket stage) there is a dramatic reduction in the sensitivity of anterior neural development to exogenous RA as reflected by En expression and cell death patterns. These results suggest that we have identified a major transition in the development of the anterior neuraxis that is reflected in a transition in sensitivity to RA. This transition in sensitivity demonstrates that the fundamental patterning mechanisms that separate fore‐ and midbrain from hindbrain occurs very early in neurogenesis. © 1994 Wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1002000305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper reports modelling of heart localization in the axolotl (Ambystoma mexicanum). The region of heart specification in the mesoderm defined by classical induction from the endoderm is larger than the area of final myocardial differentiation. For localizing the area of differentiation within the area of specification, we postulate a mesoderm in response to induction from the endoderm. This mechanism generates a spatial pattern for two chemicals, an activator and an inhibitor, corresponding to the area of myocardial differentiation. We postulate a diffusible chemical rescuer, which is absent in thecardiac lethalmutant, and which is a precursor to the reaction‐diffusion mechanism. The activator, inhibitor, rescuer, and product of endodermal induction are presented in an enzyme mechanism with rate equations similar to the Gierer‐Meinhardt equations. These equations were solved numerically in both one and two spatial dimensions. We have attained quantitative agreement with the experimental data for sizes of tissue regions and for times to heartbeat. Experiments modelled include wild‐type heart localization as well as both in vitro and in vivo rescue ofcardiac lethalmesoderm with wild‐type mesoderm. Based upon the parameters necessary to model heart localization, we make a series of predictions. We predict: a specific profile for the endodermal inducer gradient; the possibility of producing multiple hearts in vivo; and a greater contribution to the heart from the wild‐type mesoderm for in vivo transplants withcardiac lethalmesoderm. We make some suggestions as to the possible chemical nature of the substances in the model. We indicate that the inhibitory field and mechanochemical theories are probably not as promising as reaction‐diffusion for the mechanism of heart localization. © 1994 Wil

ISSN:1058-8388    

DOI:10.1002/aja.1002000306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIntracellular pH was measured in normal 8‐cell stage mouse embryos and in embryos from a cross between DDK females and C3H males. DDK/C3H embryos display the DDK syndrome and spontaneously begin to decompact toward the late 16‐cell stage. Ultimately, 90% fail to form blastocysts. Normal embryos have a resting intracellular pH close to neutrality. In DDK/C3H embryos a substantial proportion (46%) has an intracellular pH below 6.7. An equivalent proportion of DDK/C3H embryos was found previously to show slow communication through gap junctions at the 8‐cell stage. This is probably a consequence of low intracellular pH. In normal embryos the weak acid, butyric acid, decreased intracellular pH and slowed the transfer of Lucifer Yellow through gap junctions. Normal embryos treated with butyrate for between 1 and 6 hr beginning at the 8‐cell stage and cultured for 24 hr, reproduced the DDK/C3H phenotype. After 48 hr some butyrate treated embryos recovered, while others remained as decompacted morulae. Treatment of control and DDK/C3H 8‐cell stage embryos with dibutyryl cyclic AMP or forskolin, which will increase intracellular cyclic AMP, speeded gap junctional communication. Forskolin treatment prevented expression of the DDK syndrome in DDK/C3H embryos, although the rescue was transient and the syndrome returned when forskolin was removed. The finding that the DDK syndrome is manifested as low intracellular pH may provide clues to the molecular basis of the defect. © 1994 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1002000307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:1058-8388    

DOI:10.1002/aja.1002000301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY