ISSN:1058-8388    

DOI:10.1002/aja.1001960402

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.1001960403

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.1001960404

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe hypothesis that cell aggregation may be driven by linear polymers in the matrix, particularly glycosaminoglycans, is revisited in light of more recent evidence. A model is proposed that extends the concept of steric exclusion to include a role in determining the directionality of cell migration and neurite extension. Recent literature is reviewed to support the conclusion that in living tissues the theoretical conditions for driving aggregation and migration by steric exclusion are met. The ability of a linear polymer to exclude cells is a function of its viscosity, which is optimum with glycosaminoglycans similar to chondroitin sulfate. It is ineffective with low viscosity glycosaminoglycans such as most heparin or heparan sulfate. Hyaluronic acid, a massive polymer, excludes cells poorly when present as an open matrix gel but forms an effective exclusion barrier when attached to the cell surface. According to a model for steric exclusion in organogenesis, when cells have a glycocalyx of linear polymer, they should disperse and migrate down a viscosity gradient of excluding matrix polymer; when they shed or internalize their surface coat in the continued presence of matrix, they should be excluded into a smaller volume and thus stimulated to aggregate. © 1993 wiley‐Liss, I

ISSN:1058-8388    

DOI:10.1002/aja.1001960405

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn continuing efforts to identify cell‐surface molecules involved in cell‐cell interactions in the developing avian retina, we identified a monoclonal antibody, the 5A11 antibody, which possessed the ability to interfere with contact‐dependent glial cell maturation in vitro. We sought to determine the molecular and biochemical identity of the glycoprotein recognized by this antibody, and using additional criteria, establish whether the 5All antigen is indeed a cell‐recognition molecule in the developing retina. Immuno‐histochemical analyses demonstrate that in the hatchling chick retina and in live cultures of embryonic retina cells, the 5A11 antigen is predominantly associated with Müller glial cells whereas little is observed on neuronal elements. Microsequencing of the major component isolated by immunoaffinity chromatography identifies the HT7 antigen (Seulberger et al.:EMBO Journal9:2151–2158, 1990), a unique member of the immunoglobulin super gene family (IGSF), as a homologous if not identical protein to the 5A11 antigen. The HT7 antibody, furthermore, recognizes affinity purified 5A11 antigen, and both the HT7 antibody and additional probes generated against the 5A11 antigen recognize a major polypeptide of 45.5 kDa and a minor band of 69 kDa on Western blots of membrane preparations from neural retina. To verify that the 5A11 antigen mediates cell‐cell recognition events in the developing neural retina, we examined the consequences of adding antibody to monolayer cultures of dissociated embryonic retina cells and to dissociated retina cells in rotation‐mediated suspension culture. Addition of the 5A11 antibody to monolayer cultures results in alteration in the development of the stereotypic arrangement of neurons and glia characterized by a reduction in the number and complexity of neural extensions upon the glial‐derived flat cells. Similarly, addition of antibodies generated against the 5A11 antigen to dissociated cells in rotation cultures significantly reduces retina cell reaggregation as monitored by computer‐assisted image analysis of cell aggregate size. These data and the identification of the 5A11 antigen as a member of the IGSF establish a role for the 5A11 antigen as a novel recognition molecule in the developing neural retina. ©

ISSN:1058-8388    

DOI:10.1002/aja.1001960406

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.1001960407

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

年代:1993

数据来源: WILEY

摘要:

AbstractCrystallins have evolved by various mechanisms that are associated with high expression of their genes in the eye lens. The diversity and pattern of crystallins among different species indicate that independent events have occurred at the molecular level during the evolution of the lens in different invertebrates (jellyfish, squid, and octopus) and vertebrates. Although it is possible that different crystallins are needed to fulfill the specific needs of individual species, the unexpectedly large array of proteins that function as crystallins and their abundance in the lens raise the possibility that selective pressures optimizing the function of certain transcription factors in the lens contribute to the recruitment of crystallins. © 1993 wiley‐Liss, I

ISSN:1058-8388    

DOI:10.1002/aja.1001960408

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.1001960409

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

年代:1993

数据来源: WILEY

摘要:

AbstractGlutamine synthetase is a differentiation marker of the neural retina, whose expression is restricted to Müller glia cells, is inducible by glucocorticoids and is dependent on tissue development. The retina tissue acquires the competence to express GS in response to glucocorticoids with development, although the level of hormone binding activity in the cells does not alter with age. Using CAT constructs that are controlled by “simple GRE” promoters we demonstrated that glucocorticoid receptor transcription activity in retina cells increases with development. The increase in receptor activity correlates directly with the increase in inducibility of the glutamine synthetase gene and inversely with the rate of retina cell proliferation. At early developmental ages, when retina cells are still proliferating, the glucocorticoid receptor is transcriptionally inactive and glutamine synthetase expression cannot be induced. Receptor activity increases progressively with development and by day 12, when cell proliferation ceases, competence for glutamine synthetase induction is high. This competence for glutamine synthetase induction can be repressed by overexpressing the oncogene v‐src, which stimulates retina cell proliferation. We discuss possible mechanisms for developmental‐dependent modulation of glucocorticoid receptor transcriptional activity. © 1993 wiley

ISSN:1058-8388    

DOI:10.1002/aja.1001960410

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe transient embryonic layers primarily composed of a periderm and subperiderm cover most regions of the chick embryo and are the first suprabasal cell layers covering the body ectoderm. This study presents evidence for regional vriation in the expression of beta keratin in the embryonic layers. Here we show that the embryonic layers covering the anterior metatarsal region of the chicken hindlimb (scutate scale forming region) produce several members of the beta keratin family of polypeptides, designated beta (β) 1–7. These specific polypeptides are later expressed in this region exclusively in the thick, cornified beta strata of mature scutate scales. In contrast to this sequence of events, the embryonic layers overlying the epidermis of the ventral foot pad (reticulate scale‐forming region) and those covering the epidermis in apteric regions of the body produce beta keratin polypeptides β1–3 and β2,3, respectively, but no subsequent expression of these proteins occurs in the mature epidermises of these regions. Furthermore, we find that the embryonic layers of the skin overlying the anterior metatasal region of birds homozygous for the mutation “scaleless” (sc/sc), which completely lack scutate scales, produce the same members of the beta keratin family, β1–7, as the embryonic layers and beta strata of normal scutate scales.Thus, the accumulation of specific beta keratin polypeptides in the developing anterior metatarsal region appears to occur in two distinct phases; first, an early region‐specific expression in cells of the embryonic layers followed by a second phase of expression which occurs in conjunction with appendage morphogenesis. The relationship between differentiation of embryonic skin and the expression of beta keratins is discussed. © 19

ISSN:1058-8388    

DOI:10.1002/aja.1001960411

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

年代:1993

数据来源: WILEY