摘要:

AbstractIn the regenerating limbs of Korean salamanders,Hynobius leechii, retinoic acid (RA) induces duplication of skeletal structures in the proximodistal (PD) axis and often in the transverse axes. In the present study, the stage‐dependent effects of RA for the duplication of limb skeletal structures at two amputation levels, the distal stylopodium and the distal zeugopodium, were studied using larval limbs of Korean salamanders. The results showed that the mean level of proximalization (MLP) by RA treatment increased during the stages of dedifferentiation and early bud formation while the MLP declined thereafter in both amputation levels. The decline of the MLP at the later stages of regeneration was due to the high frequency of hypomorphic regeneration or blocked regeneration. When the effects of RA treatment at two amputation levels were compared, the overall trends were similar but the actual timing was delayed for 2–4 days in the proximal level of amputation. Furthermore, the peak level of proximalization was achieved earlier and the peak level remained longer in the distal stylopodial level of amputation compared to the distal zeugopodial level of amputation. Since the histological observations revealed that the dediferentiation period was also extended up to 2–4 days in the proximal level of amputation, the acid phosphatase activity during the course of regeneration was measured to look for a quantitative relationship between the enzyme activity and the states of dedifferentiation. The results show that the level and the duration of acid phosphatase activity in the upper arm regenerates are both higher and longer than those in the lower arm regenerates. Furthermore, RA treatment caused an increase in acid phosphatase activity. Thus our results suggest that the state of dedifferentiation might be closely linked to the extent of proximalization of regenerating limbs by RA treatment. © 1994 Wiley‐L

ISSN:1058-8388    

DOI:10.1002/aja.1001990402

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

年代:1994

数据来源: WILEY

摘要:

AbstractExpression of the muscle specific intermediate filament protein, desmin, is an early marker for chick somitic myogenesis. Somites are transient, paired, mesodermal structures adjacent to the neural tube which are formed very uniformly in a cranial to caudal fashion. The developmental somitic expression of desmin in vivo has been reported previously (Holtzer et al. [1991] “Frontiers in Muscle Research.” New York: Elsevier Science, pp 187–207; Borman and Yorde [1994] J. Histochem. Cytochem. 42:265–272). Here we explore the ability of those somitic cells which are desmin negative in vivo to successfully carry out a myogenic program of development in the absence of the surrounding embryonic microenvironment. Somites which are known to be overtly desmin negative in the embryo were explanted and cultured on collagen gels for 4 days. Immuno‐detection of desmin identified a population of somites that could support desmin positive cells in vitro as well as a population of somites that could not. The cranially located somites must remain in the embryo for a greater length of time than the caudally positioned somites prior to each being able to express desmin in vitro. In embryos of many ages there is also a population of somites unable to support desmin expression in vitro. The rate at which this ability to support somitic desmin expression in vitro progresses caudally in the embryo is significantly greater than the rate at which somites form. Notably, the detected expression of desmin in somites in vitro is parallel to the rate at which overt expression of desmin in vivo is detected. The implication for these observations with regard to the regulation of somitic myogenesis is discussed. © 1994 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1001990403

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

年代:1994

数据来源: WILEY

摘要:

AbstractRetinoic acid (RA) has been implicated in vertebrate neural pattern formation. In this paper we analysed the expression patterns of the cellular retinoic acid binding proteins (CRABP‐I and II) during early morphogenesis in normal and RA‐treated mouse embryos by whole‐mount in situ hybridization. This technique allowed a detailed analysis of the spatial and temporal changes in mRNA expression pattern. Both CRABPs were expressed in a rhombomere specific pattern; putative neural crest cells in the branchial arches expressed the CRABPs at levels corresponding to the rhombomere from which they were derived. CRABP‐II, but not CRABP‐I, was expressed in the neural epithelium caudal to the hindbrain. CRABP‐I is strongly expressed in a fine net‐like pattern which extends from the caudal diencephalon to the rostral hindbrain and remains predominantly dorsal to the lateral midline of the neural tube. This network corresponds to the pattern formed by the putative first axons of the embryonic mouse brain which are produced by the developing neurons of the mesencephalic nucleus of the trigeminal nerve. Although the expression of CRABP‐I was unaffected by a teratogenic dose of RA, CRABP‐II expression was increased slightly with no alteration in the normal spatial or temporal boundaries. These results support the suggestion that the CRABPs may play an important role in modulating endogenous RA levels, particularly in the developing nervous system and its neural crest derivatives. Furthermore, the limited ability of CRABP mRNA levels to respond to exogenous retinoids may be a factor in retinoid teratogenicity. © 19

ISSN:1058-8388    

DOI:10.1002/aja.1001990404

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe extracellular matrix plays important roles in embryogenesis. The integrin family of adhesion receptors may mediate critical cellular interactions with the extracellular matrix during development. In this study, we elucidated the developmental spatial and temporal expression pattern of the α2β1integrin heterodimer, a cell surface receptor for collagens and laminin. We generated reagents for studying the α2β1integrin and examined the developmental expression of the integrin in postimplantation mice. A partial length murine α2cDNA was isolated and the protein encoding region was found to be 82% homologous to that of the human α2cDNA. A synthetic peptide corresponding to the carboxy‐terminus of murine α2was used to generate α2‐specific antiserum. The antiserum and riboprobes derived from both the α2cDNA and the previously characterized murine β1subunit cDNA were used to determine the spatiotemporal expression of the α2subunit by immunocytochemistry and of the α2and β1mRNAs by in situ hybridization. Both approaches gave concordant results. Expression of the α2integrin subunit was observed in both the maternal and embryonic components of the placenta, namely the perivascular and basal zone decidual cells and decidual cells and spongiotrophoblasts at the maternal/embryonic junction. Expression was also observed in cells actively producing and remodeling the extracellular matrix in the maternal uterus and in the developing gut, lens, cartilage, bone, and tooth of the embryo. Generally, expression of the α2integrin subunit was found in cells entering their later stages of differentiation such as in chondrocytes as they became hypertrophic, ameloblasts and odontoblasts as they became columnar and began to secrete the matrix of the tooth, endothelial cells after they formed tubules, in the lens just prior to and during lens fiber production, and in the collecting ducts of the kidney only after full gestation. Throughout embryogenesis, β1mRNA was widely distributed and present in cell types expressing α2mRNA and protein. The developmental expression pattern of the α2β1integrin suggests roles for the integrin in placental development and matrix assembly and remodeling.

ISSN:1058-8388    

DOI:10.1002/aja.1001990405

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe distribution of adhesive molecules on surfaces of cells represents covert information for specifying positions of cells within a tissue. In insect wing epithelia where cells are arranged in two monolayers separated by an extracellular space, these adhesive molecules are found on basal and lateral surfaces of cells. Protein 3B11 is one surface protein whose expression changes in concert with movement and alignment of cells in wing monolayers ofManducaas well as with migration of tracheoles between the two monolayers of the wing. As epithelial cells segregate into periodic, transverse rows of alternating cell types (scale cells and generalized epithelial cells), the expression of 3B11 changes from a uniform distribution throughout the epithelial monolayer to a distribution correlated with a cell's final position and phenotype. Initially protein 3B11 is uniformy expressed on nonadherent surfaces of cells, but with the inception of cell rearrangement, differential expression of 3B11 on basolateral surfaces of cells—both adherent and nonadherent surfaces—becomes a function of epithelial cell type. At the completion of the cell movements associated with segregation of cell types, 3B11 is once again uniformly expressed throughout the wing epithelium. Also, as the upper and lower epithelial monolayers interact at their basal surfaces during adult development, 3B11 is expressed at the interface between the two epithelial monolayers and presumably functions in the nonspecific interaction between these monolayers. Examining the expression pattersn of this protein as well as other adhesion molecules in wing epithelia should reveal general rules about either the simplicity or the complexity of the molecular prepatterns that orchestrate overt tissue patterns in epithelial monolayers. © 1994 Wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1001990406

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

年代:1994

数据来源: WILEY

摘要:

AbstractFollowing muscle damage in adult vertebrates, myofibers can be regenerated from muscle precursor cells (satellite cells). During this process, prenatal myogenesis is recapitulated to a large extent, both morphologically and molecularly. A putative morphoregulatory molecule involved in myogenesis is M‐cadherin (Mcad), a calcium‐dependent cell adhesion protein. The expression of Mcad was studied by immunofluorescence in regenerating, denervated, and normal mouse muscles. Our results demonstrate that Mcad is present in satellite cells in normal muscle. Enhanced staining at sites of contact between satellite cells and the parent muscle fiber suggests an additional, spatially restricted expression of Mcad in muscle fibers. Mcad positive cells in normal and denervated muscles did not incorporate bromodeoxyuridine within 24 hr after injection in vivo, indicating that Mcad is expressed on mitotically quiescent satellite cells. Neural cell adhesion molecule (NCAM) co‐localized with Mcad in nearly all satellite cells in denervated muscles but rarely in intact muscles. At early stages of regeneration, Mcad was exclusively and strongly expressed in myoblasts. After fusion of myoblasts into myotubes, Mcad was down‐regulated and was barely detectable on more mature myotubes surrounded by distinct basal lamina sheaths. These observations are in line with the idea that Mcad plays a crucial role in myogenesis. In intact muscle, Mcad might function as a molecular link between satellite cell and muscle fiber. © 1994 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1001990407

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.1001990401

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

年代:1994

数据来源: WILEY