摘要:

AbstractThe midgut epithelium of larvalManduca sextais constructed of single goblet cells surrounded by a one‐cell‐thick reticulum of columnar cells. This pattern is expanded at each molt by the addition of new cells. Between molts, these epithelial cells are not dye coupled, even though gap junctions are present. Proliferating stem cells are dye coupled in small groups early in the molt. Then, at mid‐molt, the whole epithelium temporarily becomes dye coupled. This is when the new (expanded) pattern is being established. Later, at the end of the molt, the epithelium returns to the non‐coupled state. These results suggest that cell communication via gap junctions may play a role in cell patterning. © 1993 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1001970402

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe cerebellum of themeander tailmutant mouse (mea/mea) is characterized by an apparently normal cytoarchitecture posteriorly with an abrupt transition to an abnormal anterior region. Anteriorly, there is abnormal folition, a drastic reduction in the granule cells (GC) population, disorganization of the Purkinje cells (PC), and a virtual absence of Bergmann glial processes. In this paper we analyze the prenatal and postnatal development of the cerebellum in themea/meaand attempt to determine the phenotypic onset of the mutation in the anterior region. Hematoxylin and eosin stained sections reveal a morphological difference in the cerebellum of themea/meaas early as embryonic day 16 characterized by a reduction in the external granule cell layer (EGL). The reduction in the EGL becomes increasingly apparent as development proceeds. This deficit in the EGL most probably results in the absence of GC, but it is unclear at this point whether reduced migration, proliferation, and/or increased cell death is the major factor. Interestingly, immunohistochemical staining with a monoclonal antibody against parvalbumin reveals that the basket and stellate cells, which are also thought to arise from the EGL, are present in the anterior region of themea/meacerebellum. These results suggest that the lack of GC in themeander tailis due to an early expressed abnormality of the EGL. However, the presence of the basket and/or stellate cells raises some interesting questions concerning the lineage of the cerebellar microneurons. © 1993 Wiley‐Liss, I

ISSN:1058-8388    

DOI:10.1002/aja.1001970403

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe basement membrane underlying epithelium of skin is generally believed to be of epithelial origin, but a mesenchymal contribution to the basement membrane has not been directly examined. The purpose of this study was to directly evaluate both epithelial and mesenchymal contributions to the basement membrane. Fetal bovine keratinocytes cultured on the surface of collagen gels in the absence of fibroblasts did not produce an ultrastructurally recognizable basement membrane; however, when these cells were cultured in the presence of dermal fibroblasts a basement membrane at the keratinocyte‐fibroblast interface was produced after 1 week which was very similar in biochemical composition and ultrastructural appearance to dermal‐epidermal basement membrane in human skin. When dual species cultures of bovine keratinocytes and human fibroblasts were analyzed by indirect immunofluorescent microscopy (IF)1with human specific antibodies against basement membrane components, dermal fibroblasts were shown to synthesize and deposit type IV collagen, type VII collagen, and laminin in a linear manner into the basement membrane zone. Fetal bovine keratinocytes cultured in the presence or absence of fibroblasts synthesized and deposited type IV collagen, type VII collagen, laminin, K‐laminin, kalinin, and basement membrane associated heparan sulfate proteoglycan (HSPG) into the underlying basement membrane zone. In organ culture, a subpopulation of fibroblasts initially migrating from human foreskin explants was found to stain strongly for types VII and IV collagen and laminin by IF whereas after subculture all cells showed a uniform low staining. Based on these observations we propose that differentiated fibroblasts exist adjacent to epithelial tissues in vivo which produce basement membrane components and assist in basement membrane components and assist in basement membrane assembly. © 1993 Wiley‐L

ISSN:1058-8388    

DOI:10.1002/aja.1001970404

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe induction of the central nervous system in amphibian embryos is mediated both by early planar signals produced by mesoderm at the dorsal lip and later vertical signals emanating from the dorsal mesoderm after involution. We have examined the role and spatial extent of planar signals in the induction of neuronal differentiation. Planar explants that included only the deep layer of the dorsal marginal zone, comprising both the dorsal mesoderm and the contiguous dorsal ectoderm, were isolated at the beginning of gastrulation. After removal of the epithelial layer, explants were maintained in modified Danilchik's medium until mid‐neurula stages, when they were transferred to modified Danilchik's medium + 0.1% bovine serum albumin and cultured on laminin. Neurite outgrowth occurred in 90% of these planar explants. In contrast, little or no neuronal differentiation occurred in either ventral planar explants or explants of ectoderm alone. Video analysis of cell movements shows that large‐scale cell mixing does not occur between mesoderm cells and ectoderm cells in planar explants. Retrograde labelling of neuronal cell bodies indicates that cells throughout the ectoderm undergo neuronal differentiation; neurons also differentiate in cultures of distal ectoderm isolated at early neurula stages from planar explants prepared at the beginning of gastrulation. These observations indicate that planar signals act over an extended range to induce neuronal differentiation. The inductive capacity of vertical signals was examined by recombining animal caps from ultra‐violet (UV) irradiated embryos with involuted mesoderm from normal midgastrula embryos. Differentiation of either neurons or anterior neural structures occurred in 73% of vertical recombinates. Our results demonstrate that planar signals from the dorsal lip of the blastopore are capable of inducing neuronal differentiation over a considerable distance in the absence of epithelial confinement, convergence and extension, and mixing between the mesoderm and ectoderm. © 1993 Wiley‐L

ISSN:1058-8388    

DOI:10.1002/aja.1001970405

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

年代:1993

数据来源: WILEY

摘要:

AbstractSkeletal muscles are highly ordered mixtures of cell types, with each muscle having its own characteristic pattern of fiber types, connective tissues, and vasculature. The precursors of the myogenic and connective elements of a muscle are initially intermixed and are proliferating and differentiating together in a manner that generates an ordered array of mature cells. The molecular basis of myogenesis is unknown, although in vitro studies have revealed numerous putative regulators. The results obtained from in vitro studies are not easily related to in vivo myogenesis because of a lack of information about the localisation of the putative regulators in developing muscles. The objective of this paper was therefore to describe the spatial and temporal distribution of transforming growth factor beta 1 (TGF‐β1), a small peptide that affects cultured fibroblasts, myoblasts, and vascular endothelial cells. TGF‐β1‐immunoreactivity was associated with the epimysia, perimysia, and vasculature of the developing muscles. The expression of TGF‐β1 within developing muscles had a distinct spatial and temporal pattern that correlated with the fate of adjacent myotubes. Myotubes which formed prior to the expression of TGF‐β1 developed into slow fibers whereas those which formed adjacent to TGF‐β1‐containing connective tissue matured into fast fibers. The possibility that TGF‐β1 is involved in the generation of the pattern of epi‐ and perimysia and/or fiber types is discussed.

ISSN:1058-8388    

DOI:10.1002/aja.1001970406

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe know that, once rostral neurulation is completed in the neuroaxis of the chick embryo, the caudal neurocoel becomes occluded and the brain rapidly expands. However, very little is known about the mechanisms maintaining occlusion. Studies had shown that occluded neurocoels reopened in embryos treated with chelators of cations, but the reasons remained unclear and the cations unidentified. To begin defining the role of cations, this study explored the effect of Ca2+, calmodulin, and cAMP on maintaining the occluded neurocoel. Chick embryos during the natural phase of neurocoel occlusion (stage 12) were cultured in vitro with drugs known to modulate Ca2+transport, to inhibit calmodulin activity, or to elevate cAMP levels. To test if occlusion is a Ca2+‐dependent process, embryos were treated with verapamil and ionophore A23187. To test if occlusion requires calmodulin, embryos were treated with antipsychotic agents. To test if occlusion is cAMP dependent, embryos were treated with methylisobutylxanthine (MIX), forskolin (FOR), or dibutyl cyclic adenosine (DbC). Following each treatment, occlusion of the neurocoel was tested by injecting dye into the midbrain. All treatments resulted in a predominant number of precocious reopenings of the occluded neurocoels. MIX‐treated, naked neural tubes had a fourfold increase in cAMP, whereas FOR‐ and DbC‐treated neural tubes showed ten‐ and 14‐fold increases, respectively. The presence of calmodulin in the cells of the neural tube was confirmed by fluorescent tagging and3H‐chlorpromazine labelling. The combined results of this study show that occlusion of the spinal neurocoel depends on exogenous Ca2+, requires calmodulin, and is cAMP sensitive. © 1993 W

ISSN:1058-8388    

DOI:10.1002/aja.1001970407

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

年代:1993

数据来源: WILEY

摘要:

AbstractRadial glial cells, present in many parts of the embryonic vertebrate central nervous system (CNS), have been implicated in the guidance of neuroblasts from the ventricular zone to their laminar destinations. Moreover, radial glial cells may be progenitors of some CNS neurons and glia. To gain new insight into the structure and development of these cells, we have generated and characterized a panel of monoclonal antibodies that recognize radial glial cells of the chick optic tectum. Mice were immunized with hommogenates of embryonic day (E) 10 tectum, and antibodies were analyzed by immunofluorescence and immunoblotting. We describe here three pairs of antibodies. (1) H5 and a previously generated antibody, R5 (Dräger et al.,J. Neurosci. 4:2025, 1984), stain the whole extent of the radial glial cell from E7 to E20. In cultures prepared from E10 tecta, both stain a filamentous meshwork in glial cells but not in neurons. On immunoblots, both recognize a protein of ∼52 kD that is closely related (or identical) to vimentin. (2) H28 and H29 stain radial glia between E7 and E14, but not later. Moreover, H28 and H29 staining is markedly more intense in the ventricular and intermediate zones than in the laminae of the tectal plate. Both of these antibodies recognize an intracellular epitope in cultured glial cells and a protein of ∼35 kD on immunoblots. (3) H2 and H27 recognize antigens concentrated in the most superficial processes and endfeet of radial glia in late (E16–E20) embryos. They stain distinct structures in cultured glia, suggesting that they recognize distinct antigens. H27 recognizes a protein of ∼29 kD on immunoblots. Thus antibodies H5 and R5 are good markers of radial glial cells at all stages, whereas the others define antigens that are developmentally regulated and localized to discrete domains. Together, these antibodies can be used to study temporal and spatial specializations of radial glia. © 1993 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1001970408

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

年代:1993

数据来源: WILEY

ISSN:1058-8388    

DOI:10.1002/aja.1001970401

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

年代:1993

数据来源: WILEY