bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of a cytoskeletal protein localized in the myoplasm of ascidian eggs: localization is modified during anural development
Authors: Swalla Billie J. , Badgett Marty R. , Jeffery William R. 
Published: April 2021

Abstract
The myoplasm of ascidian eggs is a localized cytoskeletal domain that is segregated to presumptive larval tail muscle cells during embryonic development. We have identified a cytoskeletal protein recognized by a vertebrate neurofilament monoclonal antibody (NN18) which is concentrated in the myoplasm in eggs and embryos of a variety of ascidian species. The NN18 antigen is localized in the periphery of unfertilized eggs, segregates with the myoplasm after fertilization, and enters the larval tail muscle cells during embryonic development. Western blots of one-dimensional and twodimensional gels showed that the major component recognized by NN18 antibody is a 55x103Mr protein (p58), which exists in at least three different isoforms. The enrichment of p58 in the Triton X-100-insoluble fraction of eggs and its reticular staining pattern in eggs and embryos suggests that it is a cytoskeletal protein. In subsequent experiments, p58 was used as a marker to determine whether changes in the myoplasm occur in eggs of anural ascidian species, i.e. those exhibiting a life cycle lacking tadpole larvae with differentiated muscle cells. Although p58 was localized in the myoplasm in eggs of four urodele ascidian species that develop into swimming tadpole larvae, this protein was distributed uniformly in eggs of three anural ascidian species. The eggs of two of these anural species contained the actin lamina, another component of the myoplasm, whereas the third anural species lacked the actin lamina. There was no defectible localization of p58 after fertilization or segregation into muscle lineage cells during cleavage of anural eggs. NN18 antigen was uniformly distributed in pre-vitellogenic oocytes and then localized in the perinuclear zone during vitellogenesis of urodele and anural ascidians. Subsequently, NN18 antigen was concentrated in the peripheral cytoplasm of post-vitellogenic oocytes and mature eggs of urodele, but not anural, ascidians. It is concluded that the myoplasm of ascidian eggs contains an intermediate filament-like cytoskeletal network which is missing in anural species that have modified or eliminated the tadpole larva.
A newt type II keratin restricted to normal and regenerating limbs and tails is responsive to retinoic acid
Authors: Ferretti Patrizia , Brockes Jeremy P. , Brown Robin 
Published: April 2021

Abstract
In order to understand the molecular mechanisms underlying the regenerative ability of the urodele limb, it is important to identify regeneration-associated proteins and to study their regulation. We have recently shown that the anti-cytokeratin monoclonal antibody LP1K reacts strongly with newt blastemal cells, while its reactivity is restricted in normal limbs. By screening a cDNA expression library from the newt blastema with LP1K, we have identified cDNA clones coding for a type II keratin (NvKH) expressed both in the mesenchyme and the specialized wound epithelium of the blastema. While the rod domain of the protein is highly conserved, the homology between NvKII and mammalian type II keratins drops markedly at the N- and C-terminal regions. The expression of this keratin was analysed by Northern blotting and RNAase protection analysis of various newt tissues, and appears to be organ specific, since it is restricted to normal and regenerating limbs and tails. In particular, we have investigated the expression of this keratin mRNA in normal and regenerating limbs. The transcript is barely detectable in the proximal portion of the normal limb, but its level is high in the distal one. After amputation, NvKH mRNA is expressed both in proximal and distal blastemas, although at higher levels distally, indicating that this keratin is regeneration associated. The NvKH transcript is detectable both in mesenchyme and in the wound epithelium of the regenerate, while no transcript is detectable in normal epidermis. The level of NvKH mRNA is markedly down-regulated both in normal and regenerating limbs following intraperitoneal injection with retinoic acid, a putative endogenous morphogen in limb regeneration.
Changes in neural and lens competence in Xenopus ectoderm: evidence for an autonomous developmental timer
Authors: Servetnick Marc , Grainger Robert M. 
Published: April 2021

ABSTRACT
The ability of a tissue to respond to induction, termed its competence, is often critical in determining both the timing of inductive interactions and the extent of induced tissue. We have examined the lens-forming competence of Xenopus embryonic ectoderm by transplanting it into the presumptive lens region of open neural plate stage embryos. We find that early gastrula ectoderm has little lens-forming competence, but instead forms neural tissue, despite its location outside the neural plate; we believe that the transplants are being neuralized by a signal originating in the host neural plate. This neural competence is not localized to a particular region within the ectoderm since both dorsal and ventral portions of early gastrula ectoderm show the same response. As ectoderm is taken from gastrulae of increasing age, its neural competence is gradually lost, while lens competence appears and then rapidly disappears during later gastrula stages. To determine whether these developmental changes in competence result from tissue interactions during gastrulation, or are due to autonomous changes within the ectoderm itself, ectoderm was removed from early gastrulae and cultured for various periods of time before transplantation. The loss of neural competence, and the gain and loss of lens competence, all occur in ectoderm cultured in vitro with approximately the same time course as seen in ectoderm in vivo. Thus, at least from the beginning of gastrulation onwards, changes in competence occur autonomously within ectoderm. We propose that there is a developmental timing mechanism in embryonic ectoderm that specifies a sequence of competences solely on the basis of the age of the ectoderm.
A chicken caudal homologue, CHox-cad, is expressed in the epiblast with posterior localization and in the early endodermal lineage
Authors: Frumkin Ayala , Rangini Zehava , Ben-Yehuda Adi , Gruenbaum Yosef , Fainsod Abraham 
Published: April 2021

ABSTRACT
CHox-cad is a chicken homeobox gene whose homeo domain is homologous to the Drosophila caudal and the murine Cdx1 genes. Based on sequence analysis of a 2.5 kb CHox-cad cDNA clone, we deduced that the primary translation product consists of 248 amino acids. Comparison between the cDNA and genomic clones revealed the presence of an intron within the CHox-cad homeodomain between amino acids 44 and 45. The onset of CHox-cad transcription correlates temporarily with the beginning of gastrulation. During primitive streak stages CHox-cad exhibits a caudally localized pattern of expression restricted to the epiblast and the primitive streak. At these stages, CHox-cad transcripts can also be detected in the definitive endoderm cells. Later in embryogenesis CHox-cad is expressed in the epithelial lining of the embryonic gut and yolk sac. After four days of chicken development, no CHox-cad transcripts could be detected. The early CHox-cad posterior expression in the germ layer undergoing gastrulation and its continuous expression in the early endodermal lineage raise the possibility of CHox-cad involvement in the establishment of the definitive endoderm.
Spontaneous immortalisation of Schwann cells in culture: short-term cultured Schwann cells secrete growth inhibitory activity
Authors: Eccleston P. Ann , Mirsky Rhona , Jessen Kristjan R. 
Published: April 2021

ABSTRACT
In the developing peripheral nerve, Schwann cells proliferate rapidly and then become quiescent, an essential step in control of Schwann cell differentiation. Cell proliferation is controlled by growth factors that can exert positive or inhibitory influences on DNA synthesis. It has been well established that neonatal Schwann cells divide very slowly in culture when separated from neurons but here we show that when culture was continued for several months some cells began to proliferate rapidly and non-clonal lines of immortalised Schwann cells were established which could be passaged for over two years. These cells had a similar molecular phenotype to short-term cultured Schwann cells, except that they expressed intracellular and cell surface fibronectin. The difference in proliferation rates between short- and long-term cultured Schwann cells appeared to be due in part to the secretion by short-term cultured Schwann cells of growth inhibitory activity since DNA synthesis of long-term, immortalised Schwann cells was inhibited by conditioned medium from short-term cultures. This conditioned medium also inhibited DNA synthesis in short-term Schwann cells stimulated to divide by glial growth factor or elevation of intracellular cAMP. The growth inhibitory activity was not detected in the medium of long-term immortalised Schwann cells, epineurial fibro-blasts, a Schwannoma (33B), astrocytes or a fibroblast-like cell-line (3T3) and it did not inhibit serum-induced DNA synthesis in epineurial fibroblasts, 33B cells or 3T3 cells. The activity was apparently distinct from trans-forming growth factor-β, activin, IL6, epidermal growth factor, atrial natriuretic peptide and gamma-interferon and was heat and acid stable, resistant to collagenase and destroyed by trypsin treatment. We raise the possibility that loss of an inhibitory autocrine loop may contribute to the rapid proliferation of long-term cultured Schwann cells and that an autocrine growth inhibitor may have a role in the cessation of Schwann cell division that precedes differentation in peripheral nerve development.
Gene regulatory factors of the sea urchin embryo: II. Two dissimilar proteins, P3A1 and P3A2, bind to the same target sites that are required for early territorial gene expression
Authors: Hoog Christer , Calzone Frank J. , Cutting Ann E. , Britten Roy J. , Davidson Eric H. 
Published: April 2021

ABSTRACT
Previous work demonstrated that a negative regulatory interaction mediated by factor(s) termed ‘P3A’ is required for correct territory-specific gene expression in the sea urchin embryo. A probe derived from a P3A target site in the skeletogenic SM50 gene of Strongylocentrotus purpuratus was used to isolate a cDNA clone coding for a factor that binds specifically to this site. This factor, called P3A1, contains two sequence elements that belong to the Zn finger class of DNA-binding motifs, and in these regions is most closely similar to the Drosophila hunchback factor. The P3A1 factor also binds to a similar target sequence in a second gene, Cyllla, expressed in embryonic aboral ectoderm. Another sea urchin embryo protein factor, P3A2, has been isolated by affinity chromatography and cloned, as described in Calzone et al. Development 112, 335–350 (1991). P3A2 footprints the same target sites in the SM50 and CyIIIa genes as does P3A1, but lacks the Zn finger sequence motifs and in amino acid sequence is almost entirely dissimilar to P3A1. A deletion analysis of P3A2 delimited the DNA-binđing region, revealing that five specific amino acids in the first P3A1 finger region and four in the second P3A1 finger region are also present in equivalent positions in P3A2. The P3A1 and P3A2 factors could function as regulatory antagonists, having evolved similar target specificities from dissimilar DNA-binding domains.
Molecular composition and development of the plant glycocalyx associated with the peribacteroid membrane of pea root nodules
Authors: Perotto Silvia , Vandenbosch Kathryn A. , Butcher Geoffrey W. , Brewin Nicholas J. 
Published: April 2021

ABSTRACT
In root nodules of pea (Pisum sativum), endosymbiotic Rhizobium bacteroids are individually enclosed by a plant-derived membrane, the peribacteroid membrane, creating an organelle-like structure termed the symbiosome. In order to investigate the structure and function of the peribacteroid membrane in plant-microbe surface interactions, monoclonal antibodies were used to identify the major antigenic components of this membrane and to investigate their cellular and tissue distribution. Immunofluorescence studies with isolated intact and ruptured symbiosomes indicated that the relevant antigens were confined to the luminal (inner) face of the peribacteroid membrane. Biochemical analysis indicated that the antibodies recognised carbohydrate epitopes associated with Golgi-derived glycoproteins and glycolipids. These glycoconjugate molecules are collectively termed the glycocalyx. Three different classes of glycocalyx antigens, reacting with different groups of monoclonal antibodies, could be distinguished. Immunolocalisation studies of longitudinal sections of pea nodules revealed enhanced expression of glycocalyx antigens in infected nodule tissue, with the three classes of antigen showing different degrees of expression in different developmental zones of the tissue. One of the classes of antigen was absent from the apical meristematic region of pea nodules but was re-expressed during cell invasion by Rhizobium and the development of peribacteroid membranes. In Phaseolus nodules, as opposed to those of Pisum, this group of antigens was entirely lacking from the central infected tissue.
Xenopus temporal retinal neurites collapse on contact with glial cells from caudal tectum in vitro
Authors: Johnston Alexander R. , Gooday Douglas J. 
Published: April 2021

ABSTRACT
Nasal and temporal retinal neurites were confronted in culture with glial cells from the rostral and caudal parts of the optic tectum and with glial cells from the diencephalon. Twenty of each of the six classes of encounter between individual growth cones and isolated glial cells were analysed by time-lapse videorecording. The results show that growth cones from the temporal retina collapse when they contact glial cells from the caudal tectum, but do not collapse when they contact glia from other areas. Growth cones of nasal retinal fibres do not collapse on contact with any of the glial types examined. This suggests that the inhibitory phenomena described by others are in part due to the cell surface characteristics of glial cells, and that there are differences between glia from the front and back of the optic tectum.
Chicken homeobox gene Msx-1: structure, expression in limb buds and effect of retinoic acid
Authors: Yokouchi Yuji , Ohsugi Kojune , Sasaki Hiroshi , Kuroiwa Atsushi 
Published: April 2021

ABSTRACT
A chicken gene carrying a homeobox highly homologous to the Drosophila muscle segment homeobox (msh) gene was isolated and designated as Msx-1. Conceptual translation from the longest ORF gave a protein of 259 amino acids lacking the conserved hexapeptide. Northern analysis detected a single 2.6 kb transcript. As early as day 2 of incubation, the transcript was detected but was not found in adult tissue. In situ hybridization analysis revealed that Msx-1 expression is closely related to a particular mesenchymal cell lineage during limb bud formation. In early stage embryos, Msx-1 was expressed in the somatopleure. When primordial mesenchyme cells for limb bud were generated from the Wolffian ridge of the somatopleure, Msx-1 expression began to diminish in the posterior half of the limb bud then in the presumptive cartilage-forming mesenchyme.
In developing limb buds, remarkable expression was seen in the apical ectodermal ridge (AER), which is responsible for the sustained outgrowth and development of the limb. The Msx-1 transcripts were found in the limb mesenchymal cells in the region covering the necrotic zone and ectodermal cells overlying such mesenchymal cells. Both ectodermal and mesenchymal expression in limb bud were rapidly suppressed by local treatment of retinoic acid which can generate mirrorimage duplication of digits. This indicates that retinoic acid alters the marginal presumptive non-cartilage forming mesenchyme cell lineage through suppression of Msx-1 expression
Pattern formation in the nematode epidermis: determination of the arrangement of peripheral sense organs in the C. elegans male tail
Authors: Baird Scott E. , Fitch David H. A. , Kassem Iman A. A. , Emmons Scott W. 
Published: April 2021

ABSTRACT
The developmental process that determines the arrangement of ray sensilla in the Caenorhabditis elegans male tail has been studied. It is shown that the adult arrangement of rays is determined by the placement of ray cells at specific sites in the epidermis of the last larval (L4) stage. Placement of ray cells at specific epidermal sites results from the generation of neurons and support cells in the epidermis near to their final positions, and the subsequent refinement of these positions by an active mechanism involving specific cellular associations. Positions of ray cells and adjacent epidermal cells have been studied during ray development by means of indirect immunofluorescence staining with an antibody to a cell junctional antigen. Mutations are described in six genes that alter the adult arrangement of the rays, frequently resulting in fusion of rays. Changes in the adult pattern of rays in mutants appear to result from prior changes in the epidermal positions of ray cells, and for two mutants it is suggested that this may be due to the inappropriate clustering of processes from neurons and support cells of adjacent rays. Development of the wild-type arrangement of rays appears to require the specification of molecular differences between the rays that affect the specificity of their cellular associations.
Effect of egg composition on the developmental capacity of androgenetic mouse embryos
Authors: Latham Keith E. , Solter Davor 
Published: April 2021

ABSTRACT
Analysis of the developmental capacities of androgenetic and gynogenetic mouse embryos (bearing two paternal or two maternal pronuclei, respectively) revealed a defect in blastocyst formation of androgenetic, but not gynogenetic, embryos that was a function of the maternal genotype. Androgenetic embryos constructed using fertilized eggs from C57BL/6 or (B6D2)F1 mice developed to the blastocyst stage at frequencies similar to those previously reported, whereas androgenetic embryos constructed with fertilized eggs from DBA/2 mice developed poorly, the majority failing to progress beyond the 16-cell stage and unable to form a blastocoel-like cavity, regardless of whether the male pronuclei were of C57BL6 or DBA/2 origin. This impaired development was observed even in androgenetic embryos constructed by transplanting two male pronuclei from fertilized DBA/2 eggs to enucleated C57BL/6 eggs, indicating that the defect cannot be explained as the lack of some essential component in the DBA/2 cytoplasm that might otherwise compensate for androgeny.
Rather, the DBA/2 egg cytoplasm apparently modifies the incoming male pronuclei differently than does C57BL/6 egg cytoplasm. Several specific alterations in the protein synthesis pattern of DBA/2 androgenones were observed that reflect a defect in the regulatory mechanisms that normally modulate the synthesis of these proteins between the 8-cell and blastocyst stages. These results are consistent with a model in which cytoplasmic factors present in the egg direct a strain dependent modification of paternal genome function in response to epigenetic modifications (genomic imprinting) established during gametogenesis and indicate that preimplantation development can be affected by these modifications at both the morphological and biochemical levels.
The determination of sense organs in Drosophila: effect of the neurogenic mutations in the embryo
Authors: Goriely Anne , Dumont Nathalie , Dambly-Chaudière Christine , Ghysen Alain 
Published: April 2021

ABSTRACT
We have examined the early pattern of sensory mother cells in embryos mutant for six different neurogenic loci. Our results show that the neurogenic loci are required to restrict the number of competent cells that will become sensory mother cells, but are not involved in controlling the localization or the position-dependent specification of competent cells. We conclude that these loci are involved in setting up a system of mutual inhibition, which transforms graded differences within the proneural clusters into an all- or-none difference between one cell, which becomes the sense organ progenitor cell, and the other cells, which remain epidermal.
Genetic approaches to inflorescence and leaf development in maize
Authors: Veit Bruce , Greene Ben , Lowe Brenda , Mathern Julie , Sinha Neelima , Vollbrecht Erik , Walko Richard , Hake Sarah 
Published: April 2021

Abstract
The application of genetic methods to the analysis of morphogenesis in maize is described. Several classes of floral mutants are differentiated through developmental studies and tests of epistasis. The results of mosaic and dosage analysis of Kn1, a dominant mutation affecting leaf development, are related to molecular studies of the gene.
Diffusible signal molecules controlling cell differentiation and patterning in Dictyostelium
Authors: Berks Mary , Traynor David , Carrin Ines , Insall Robert H. , Kay Robert R. 
Published: April 2021

Abstract
Slime moulds, such as Dictyostelium discoideum, have biochemical, physiological and probably developmental features in common with both plants and animals. During development separate Dictyostelium amoebae first aggregate into collecting centers to form small multicellular organisms which, in their slug form, can migrate over the substratum toward light. Eventually a slug culminates to form a fruiting body consisting of a cellular stalk supporting a mass of spores. Development is highly regulative, indicating that it is controlled by signalling between the cells. A number of diffusible signal molecules have been discovered, including cyclic AMP, the chemoattractant in aggregation, and DIF-1, a novel chlorinated phenyl alkanone, which acts as a specific inducer of stalk cell differentiation.
The migrating slug contains three types of precursor cell: prespore, prestalk A and prestalk B cells. Differentiation of these cells from uncommitted amoebae can be brought about in ceil cultures by cyclic AMP and DIF-1 acting in combination: cyclic AMP alone favours prespore, DIF-1 alone favours prestalk B, cyclic AMP and DIF-1 together favour prestalk A cell differentiation. There is evidence suggesting that these signals act in the same way in the intact aggregate.
A cytoplasmic DIF-1 binding protein has been discovered, whose level increases as cells become sensitive to DIF-1 and which binds DIF-1 with an affinity and specificity suggestive of a receptor. At the same time, cells are able to inactivate DIF-1 by a metabolic pathway involving at least 12 metabolites. Metabolism may also serve to produce gradients of DIF-1 in the aggregate or other signal molecules from DIF-1. Manipulation of the DIF-1 signalling system will be an important means of further elucidating its role in development.