摘要:

AbstractS‐crystallins are the predominant soluble proteins of the squid lens. Of these, S‐III crystallin is the major component and S‐I and S‐II crystallin are the minor lens components. The lens has a posterior and anterior segment, each derived from separate groups of ectodermal cells referred to as lentigenic cells. In the present study, the appearance of S‐crystallins during the development of the lens ofLoligo opalescenswas followed by immuno‐cytochemistry. S‐crystallins of the lens and lentigenic cells were first observed at day 17 (Arnold stage 27) of embryogenesis. S‐crystallins were not confined to a single region, but were present in the middle group (group 2) of lentigenic cells, the posterior lens primordium, and the processes connecting the lentigenic cells and the posterior lens primordium. Two days later (Arnold stage 28), the S‐crystallins were also observed in the anterior group (group 1) of lentigenic cells, the anterior lens primordium, and the processes connecting the cells with the anterior lens primordium. Thus, during development, S‐crystallins accumulate first in the posterior lens primordium and subsequently in the anterior lens primordium and their respective lentigenic cells and connecting lentigenic processes. Incubated sections of the adult lens and lentigenic cells also show specific immuno‐peroxidase staining when compared with controls. This evidence in combination with a recent investigation (West [1993] Ph.D. dissertation), which indicates that the cephalopod lens continues to grow throughout adulthood, suggests that squid lens crystallins are synthesized during adulthood.

ISSN:1058-8388    

DOI:10.1002/aja.1001990202

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

年代:1994

数据来源: WILEY

摘要:

AbstractCurly tail mouse mutant embryos (ct/ct) develop spinal neural tube defects (NTD) in 54% of cases, comprising isolated tail flexion defects and spina bifida with tail flexion defects. Both types of spinal NTD result from delayed closure of the posterior neuropore (PNP). Previous studies (Seller et al. [1979] Proc. R. Soc. Lond. Biol. 206:95–107; Seller and Perkins [1982]Prenat. Diagn. 2:297–300) described a paradoxial effect of retinoic acid (RA) on the phenotypic expression of thectmutation: Treatment with low doses of RA on day 8 of gestation increased the incidence of total NTD, whereas low doses of RA administered on day 9 resulted in reduced incidence of total NTD. In order to investigate further the reported preventive effect of RA, we have carried out detailed analyses of the effects of maternal treatment with 5 mg/kg RA on the incidence of NTD at different developmental stages, and on the development and growth ofct/ctembryos. We found that 5 mg/kg RA reduces the incidence of spinal NTD in a stage‐specific manner, without increasing the incidence of cranial NTD. The effect of RA is specific: There were no other alterations in morphogenesis, growth, development, resorption rate, or litter size. RA was more effective in the prevention of isolated tail flexion defects than of spina bifida. Prevention of isolated tail flexion defects was maximal (50% reduction) when RA was administered between 10 days 4 hours and 10 days 8 hours post coitum (p.c.) inclusive (24 to 34 somite stage). In contrast, maximal prevention of spina bifida (36%) resulted from RA administration at 10 days 8 hours p.c.; decreased PNP size in treated embryos, compared with control embryos, was evident by 6 hours after the treatment at the 27 to 31 somite stage. The preventive effect of RA on spina bifida was related to maternal phenotype: By comparison with phenotypically straighttailed mothers, curly‐tailed mothers had a greater incidence of spina bifida among their offspring, and this incidence was unresponsive to RA. This result suggests that additional factors, such as modifier genes, modulating phenotypic expression of thectgene, may be present in thectmutant stock. Here we show that the RA prevention of spinal NTD is a specific effect. Hence it is plausible that this prevention of spinal NTD by RA is mediated via nuclear retinoic acid receptors. © 1994 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1001990203

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe Drosophila genenanosis required for two processes. During oogenesis,nanosfunction is required for the continued production of egg chambers, andnanosis expressed in the early germarium. During embryogenesis,nanosis required maternally to specify abdominal segmentation.Nanosshares this latter function with nine other genes, collectively known as the posterior group. Of this group,nanosencodes a determinant, and is localized as an RNA to the posterior pole of early embryos. This RNA is translated to form a gradient of nanos protein with highest concentrations at the posterior. Analysis of the distribution ofnanosgene products in embryos mutant for posterior group genes shows that eight of these genes are required for localization, but not stability, of thenanosRNA. Embryos mutant for posterior group alleles which produce weak abdominal phenotypes show reduced amounts of localizednanosRNA. This correlation betweennanosRNA localization and abdominal phenotype suggests thatnanosacts as a localization‐dependent posterior determinant. Localization ofnanosis not affected by mutations inbicoidortorso, confirming that the three maternal systems of anterior‐posterior determination initially act independently. © 1994 Wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1001990204

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

年代:1994

数据来源: WILEY

摘要:

AbstractTwo contrasting substrates,Drosophilalaminin and human vitronectin, caused determined primaryDrosophilaembryo cells to follow alternate intermediate differentiation steps without affecting the final outcome of differentiation. Integrin αPS2βPS3was essential for the initial spreading of myocytes on vitronectin: focal contacts rich in βPS3integrins formed and were connected by actin‐ and myosin‐containing stress fibers. While αPS2βPS3was unnecessary for myotube formation on laminin, it was required for the subsequent change to a sarcomeric cytoarchitecture. The differentiating primary cultures synthesized integrins and assembled them into detergent‐insoluble, cytoskeleton‐associated complexes. Collagen IV, laminin, glutactin, papilin, and other other extracellular matrix proteins were made primarily by hemocytes and were secreted into the medium. Further differentiation within the cultures was influenced by secreted components and by later addition of vitronectin or bovine serum. Comparison of the differentiation of various cell types on the two substrates showed that vitronectin provided a selective advantage for the differentiation of myocytes, with enrichment over epithelia, epidermal cells, and neurites. © 1994 Wi

ISSN:1058-8388    

DOI:10.1002/aja.1001990205

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

年代:1994

数据来源: WILEY

摘要:

AbstractType II collagen, generally considered to be characteristic of cartilage, has been localized in specific non‐cartilaginous structures during embryogenesis and development of the skeleton. Type II procollagen is synthesized in two different forms generated by alternative splicing of exon 2 in the precursor mRNA transcript. One form (type IIA procollagen) contains a large cysteine‐rich domain in the NH2‐terminal propeptide, while the second form (type IIB procollagen) does not. These two forms are spatially expressed during development and chondrogenesis with the type IIB procollagen mRNA primarily expressed by chondrocytes while the IIA form is expressed in chondroprogenitor cells (Sandell et al. [1991] J. Cell Biol. 114:1307–1319). The present study demonstrates that the early non‐cartilage expression, by somites, mesenchymal and epithelial cells, is predominately the alternate splice form, type IIA procollagen mRNA. Later in development, the type IIB mRNA splice form is expressed by chondrocytes. During the development of intramembranous bones, such as the mandible, type IIA procollagen mRNA is also expressed. In this tissue, the splice form does not switch to type IIB mRNA and no cartilage is formed. These results show that expression of type IIA mRNA, whether by epithelial or mesenchymal cells, precedes formation of overt skeletal structures. © 1994 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1001990206

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe development of skin appendages such as hair, feathers, and teeth is brought about by reciprocal interactions between epidermal and mesenchymal tissues and is thought to be influenced in part by cell adhesion molecules and components of the extracellular matrix. The developmental distributions of tenascin, neural cell adhesion molecule (NCAM), E‐cadherin, intercellular adhesion molecule 1 (ICAM‐1), chondroitin sulfate proteoglycan (CSPG), and the heparan sulfate proteoglycan perlecan were studied in relation to hair follicle morphogenesis in fetal human skin. Tenascin first appeared in developing skin in focal concentrations at the epidermal‐mesenchymal interface, just prior to, and presumably correlated with, hair follicle initiation. Tenascin immunostaining remained prominent in the basement membrane zone and extracellular matrix of the follicle sheath during subsequent morphogenetic stages. Two forms of tenascin (Mr250 × 103and 280–300 × 103), were revealed by Western blots of skin extracts. NCAM immunolabeling was initially present throughout the dermis, and became progressively restricted to the dermal condensation and the follicle sheath. Western blot analysis revealed an isoform of NCAM (Mr160 × 103) which lacked polysialic acid. At all stages, E‐cadherin staining was diminished on follicle cells situated adjacent to the basement membrane, relative to cells in the follicle interior. Follicle‐specific immunostaining for ICAM‐1 was transient, appearing only at the pre‐germ and hair germ stages of development. Antibodies to three distinct CSPG determinants revealed unique immunolabeling patterns following follicle initiation: One CSPG epitope co‐distributed with tenascin in the follicle basement membrane and follicle sheath extracellular matrix; one CSPG epitope was similarly expressed, and was also found on follicle epithelial cells; and the third CSPG determinant was noticeably absent from the follicle sheath during elongation of the developing appendage. Perlecan was concentrated in the dermal papilla, in addition to its distribution in all skin basement membranes. A model for how these diverse molecules may inter/act to influence human hair follicle morphogenesis is presented. ©

ISSN:1058-8388    

DOI:10.1002/aja.1001990207

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

年代:1994

数据来源: WILEY

摘要:

AbstractGap junctions which comprise a family of proteins called connexins have been implicated in the morphogenesis of the chick limb bud. We have examined the expression patterns of two members of the connexin family, connexin43 (Cx43) and connexin42 (Cx42), during the early development of the chick limb bud and embryo by in situ hybridization. Cx43 mRNA is expressed in high amounts in the apical ectodermal ridge (AER), which promotes the outgrowth of the mesodermal cells of the limb bud, and in the ectopic AER of the limb buds of polydactylousdiplopodia‐5 mutant embryos. In contrast, little Cx43 expression is detectable in nonridge limb ectoderm at early stages of limb development. These results suggest that Cx43 gap junctions may integrate the activity of the cells comprising the AER and compartmentalize them into a functionally distinct entity capable of directing limb outgrowth. In addition, Cx43 exhibits high expression in the posterior subridge mesoderm of the early limb bud that is growing out in response to the AER, but little expression in the anterior mesoderm. This graded distribution of Cx43 transcripts correlates with a functional gradient of gap junctional communication along the anteroposterior (AP) axis, and suggests that Cx43 gap junctions may be involved in pattern formation across the AP axis. At later stages of development, Cx43 is transiently expressed in high amounts in the precartilage condensations of the carpals and metacarpals, at a time when critical cell‐cell interactions are occurring that trigger cartilage differentiation. In contrast, in the developing limb, Cx42 is expressed exclusively by the central artery. In the remainder of the chick embryo, Cx42 is expressed in high amounts by the vessels comprising the arterial vasculature, but is not expressed by the venous vasculature. Thus, Cx42 gap junctions may be involved in specification of the arterial vasculature of the limb and embryo. Cx42, but not Cx43, is expressed in the ventricle of the heart, and by cells along the intrasclerotomal fissure that separates the rostral and caudal halves of the sclerotome of somites into distinct communication compartments. © 1994 Wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1001990208

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.1001990209

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

年代:1994

数据来源: WILEY