bluuebunny/crossref_metadata_2025_split huggingface dataset:
Embryonic vascular development: immunohistochemical identification of the origin and subsequent morphogenesis of the major vessel primordia in quail embryos
Authors: Coffin J. Douglas , Poole Thomas J. 
Published: April 2021

AbstractThe development of the embryonic vasculature is examined here using a monoclonal antibody, QH-1, capable of labelling the presumptive endothelial cells of Japanese quail embryos. Antibody labelling is first seen within the embryo proper at the 1-somite stage. Scattered labelling of single cells appears ventral to the somites and at the lateral edges of the anterior intestinal portal. The dorsal aorta soon forms a continuous cord at the ventrolateral edge of the somites and continues into the head to fuse with the ventral aorta forming the first aortic arch by the 6-somite stage. The rudiments of the endocardium fuse at the midline above the anterior intestinal portal by the 3-somite stage and the ventral aorta extends craniad. Intersomitic arteries begin to sprout off of the dorsal aorta at the 7-somite stage. The posterior cardinal vein forms from single cells which segregate from somatic mesoderm at the 7-somite stage to form a loose plexus which moves mediad and wraps around the developing Wolffian duct in later stages. These studies suggest two modes of origin of embryonic blood vessels. The dorsal aortae and cardinal veins apparently arise in situ by the local segregation of presumptive endothelial cells from the mesoderm. The intersomitic arteries, vertebral arteries and cephalic vasculature arise by sprouts from these early vessel rudiments. There also seems to be some cell migration in the morphogenesis of endocardium, ventral aorta and aortic arches. The extent of presumptive endothelial migration in these cases, however, needs to be clarified by microsurgical intervention.
Evidence for axonal ‘decision regions’ in the axolotl peripheral nervous system
Authors: Wilson Steve , Holder Nigel 
Published: April 2021

AbstractHorseradish peroxidase (HRP) was employed to analyse the spatial organization of axons within nerves of the axolotl peripheral nervous system. HRP applications to the lateral motor column, spinal nerves and muscle nerve branches were examined after orthograde or retrograde transport. Axons change relative positions at particular limb regions, notably at the limb plexi, but also at branch points at other limb levels. Such areas of axon reorganization (termed ‘decision regions’ in line with Tosney & Landmesser (1985)J. Neurosci. 5, 2345) are interspersed by lengths of nerve in which axons run parallel to one another. A decision region is also described which involves only axons destined for axial musculature. The detailed anatomy of axon groups is discussed in terms of the likely mechanisms responsible for its formation during development. We conclude that, despite considerable variation in nerve pattern not seen in higher vertebrates, neuromuscular specificity in the axolotl limb is established largely by local pathway cues guiding axons to their appropriate targets.
In situ hybridization reveals differential spatial distribution of mRNAs for type I and type II collagen in the chick limb bud
Authors: Devlin C. J. , Brickell P. M. , Taylor E. R. , Hornbruch A. , Craig R. K. , Wolpert L. 
Published: April 2021

Abstract
During limb development, type I collagen disappears from the region where cartilage develops and synthesis of type II collagen, which is characteristic of cartilage, begins. In situ hybridization using antisense RNA probes was used to investigate the spatial localization of type I and type II collagen mRNAs. The distribution of the mRNA for type II collagen corresponded well with the pattern of type II collagen synthesis, suggesting control at the level of transcription and mRNA accumulation. In contrast, the pattern of mRNA for type I collagen remained more or less uniform and did not correspond with the synthesis of the protein, suggesting control primarily at the level of translation or of RNA processing.
Dietary components modulate yolk protein gene transcription in Drosophila melanogaster
Authors: Bownes Mary , Scott Ann , As Alan Shirr 
Published: April 2021

Abstract
The three yolk proteins of Drosophila melanogaster begin to be synthesized at eclosion. Transcription of the genes is regulated by the genes tra, tra-2 and dsx and also by the insect hormones, juvenile hormone and 20-hydroxyecdysone. We show that there is yet another level of control which is dependent upon feeding. Females that are starved from eclosion show a basal level of yolk protein gene transcription, which is rapidly increased when a complete diet is supplied. We show that the effect is not due to incorrect development of the fat body and is unlikely to be solely due to a general effect on protein synthesis. Later in development, cessation of feeding leads to selective inhibition of yolk protein synthesis and hence egg production.
The effects of starvation can be partially overcome by 20-hydroxyecdysone, juvenile hormone, casein, amino acid mix or sucrose, but only a complete medium or live yeast brings about total recovery. Using ypl-Adh fusions (fusions of the promoter region of ypl to the structural gene for Adh), the DNA sequence required for this diet-enhanced transcription has been located within an 890 bp fragment upstream of the ypl gene. The insect hormones do not operate on this same DNA fragment.
Nuclear and cytoplasmic localization of newly synthesized proteins in the early mouse embryo
Authors: Howlett S. K. , Barton S. C. , Norris M. L. , Surani M. A. H. 
Published: April 2021

Abstract
1-, 2- and 4-cell mouse embryos were labelled with [35S]methionine and the newly synthesized proteins from isolated nuclei were compared with those from cytoplasts and total embryos. There were distinct subsets of translation products present within nuclei compared to those that remained in the cytoplasm. There was no detectable evidence for differences in the presence of newly synthesized proteins in the male and female pronuclei. However, different new proteins associated with nuclei over the time that the embryonic genome becomes active.
Role of segment polarity genes in the definition and maintenance of cell states in the Drosophila embryo
Authors: Arias A. Martinez , Baker N. E. , Ingham P. W. 
Published: April 2021

Abstract
Segment polarity genes are expressed and required in restricted domains within each metameric unit of the Drosophila embryo. We have used the expression of two segment polarity genes engrailed (en) and wingless (wg) to monitor the effects of segment polarity mutants on the basic metameric pattern. Absence of patched (ptc) or naked (nkd) functions triggers a novel sequence of en and wg patterns. In addition, although wg and en are not expressed on the same cells absence of either one has effects on the expression of the other. These observations, together with an analysis of mutant phenotypes during development, lead us to suggest that positional information is encoded in cell states defined and maintained by the activity of segment polarity gene products.
Secretion of collagen types I and II by epithelial and endothelial cells in the developing chick cornea demonstrated byin situhybridization and immunohistochemistry
Authors: Hayashi Masando , Ninomiya Yoshifumi , Hayashi Kimiko , Linsenmayer Thomas F. , Olsen Bjorn R. , Trelstad Robert L. 
Published: April 2021

AbstractCells involved in the synthesis of collagen types I and II in the cornea of developing chick embryos have been studied by using in situ hybridization and immunohistochemistry. Corneas processed for in situ hybridization with the type I and II collagen probes demonstrated specific mRNAs in the epithelium of embryos at stage 18 with an increase at stages between 26 and 31, and then gradual decrease to the background level in the next several days. In the endothelium, a small amount of specific mRNA was recognized through these stages. In the stroma, only sections hybridized with the type I probe demonstrated mRNA in fibroblasts. Immunostaining demonstrated specific collagen types in the stroma at sites which were closely associated with cells containing specific mRNAs. Both collagens type I and II were present beneath the epithelium as narrow bands at stage 18; as the thicker primary stroma at stages 20 and 26; and as subepithelial, subendothelial and stromal staining at stage 31. Thereafter, type I collagen was increased in the stroma but it was also noted in the subepithelial and, to a lesser degree, subendothelial regions, whereas type II collagen was gradually confined to the subendothelial matrix. Electron microscopic examination of sections from 5-day-old (stage-27) embryo corneas using antibodies against the carboxyl propeptides of type I and II procollagens revealed the presence of these procollagens within the cisternae of the endoplasmic reticulum and Golgi vesicles in both epithelial and endothelial cells. In the epithelial cells both the periderm and basal cells contained these procollagens within the cytoplasmic organelles. These results indicate that not only the epithelial cells, but also the endothelial cells secrete collagen types I and II during the formation of the primary corneal stroma and for several days after invasion of fibroblasts.
Mechanisms of vertebrate segmentation
Authors: Keynes Roger J. , Stern Claudio D. 
Published: April 2021

Abstract
That all higher organisms possess some segmental organization during their development is presumably no coincidence. Segmentation appears to be an important developmental strategy with which to build and diversify different body regions. It can be studied at many levels, ranging from molecule and genome, through cells and their interactions, to morphogenesis and whole body pattern; and there is no compelling reason for thinking that the study of any one level will prove more revealing than that of any other. The study of vertebrate segmentation in fact provides a particularly good example of this philosophy. The application of classical and molecular genetic analysis to Drosophila development (reviewed by Akam, 1987) has yielded a large amount of information about the genes that play a role in the development of segmental patterns in this organism. Springing directly from this analysis comes the hope that similar methods applied to vertebrate development, exemplified by the discovery of the homeobox in the vertebrate genome, will be just as successful. But will the identification of vertebrate segmentation genes complete our understanding of the segmentation process? We believe not, and our chief purpose in this review is to identify and discuss the variety of different levels at which one can approach the major events involved.
Myoblast migration specifically inhibited in the chick embryo by grafted CSAT hybridoma cells secreting an anti-integrin antibody
Authors: Jaffredo T. , Horwitz A. F. , Buck C. A. , Rong P. M. , Dieterlen-Lievre F. 
Published: April 2021

Abstract
We report a teratological method in which mouse hybridoma cells are grafted into a chick host. CSAT (Cell Substratum ATtachment) hybridoma was used. It produces an antibody directed against the avian integrin complex. The grafts were performed during the second and third days of incubation either at the level of the somites or in the coelom of the chick embryo. The anomalies were revealed by means of a monoclonal antibody that recognizes myogenic cells as soon as they become committed in the myotome. When embryos were grafted at the level of the somites, body wall muscles failed to develop on the side of the graft only. After coelomic grafting, total agenesis of abdominal muscles was induced.
The anomalies were specific since the engraftment of three control hybridoma clones induced no change in muscle formation. These control hybridomas produce antibodies directed against the same molecular complex but not against the same epitope as CSAT.
The injection of hybridoma cells in an embryo appears as a method of general interest to determine the long-term consequences of perturbing a specific developmental process.
Pattern of the insulin-like growth factor II gene expression during rat embryogenesis
Authors: Stylianopoulou Fotini , Efstratiadis Argiris , Herbert Joseph , Pintar John 
Published: April 2021

AbstractThe rat insulin-like growth factor II (IGF-II) gene, encoding a fetal somatomedin, expresses a family of transcripts in embryonic/fetal tissues, and also in the adult choroid plexus and the leptomeninges. We have localized IGF-II gene transcripts in sections of rat embryos of embryonic days 10–16 by performing in situ hybridization. These transcripts are present in the head mesenchyme, formed from both the mesoderm and the cephalic portion of the neural crest, and also in the majority of other tissues of mesodermal origin, predominantly those derived from the somites and the lateral mesoderm. Intense labelling was detected in muscle cells, and their precursors, throughout the examined stages, whereas in chondrocytes the initial high level of hybridization declined substantially prior to ossification. IGF-II gene transcripts are also present in derivatives of other germ layers, but in restricted sites. Thus, from the derivatives of the endoderm, only the liver and the bronchial epithelium yielded hybridization signals. Ectoderm-derived tissues, including the central and peripheral nervous system, were negative for hybridization, with the exception of the choroid plexus, the newly forming pituitary rudiment and, to a lesser extent, the auditory placode. The pattern of IGF-II gene expression during embryogenesis overlaps significantly with the reported distribution of immunohistochemically detected TGF-β1. A paracrine/autocrine role for IGF-II in the developmental process is discussed.
Tissue- and stage-specific control of homeotic and segmentation gene expression in Drosophila embryos by the polyhomeotic gene
Authors: Dura Jean-Maurice , Ingham Philip 
Published: April 2021

Abstract
The distributions of the products of the homeotic genes Sex combs reduced (Scr) and Ultrabithorax (Ubx) and of the segmentation genes, fushi tarazu (ftz), even skipped (eve) and engrailed (en) have been monitored in polyhomeotic (ph) mutant embryos. None of the genes monitored show abnormal expression at the blastoderm stage in the absence of zygotic ph expression. Both Scr and Ubx are ectopically expressed in the epidermis of ph embryos, confirming the earlier proposal, based on genetic analysis, that ph+ acts as a negative regulator of Antennapedia (ANT-C) and bithorax (BX-C) complex genes.
At the shortened germ band stage, en is also ectopically expressed, mainly in the anterior region of each segment. In contrast to these effects in the epidermis, the expression of en, Ubx, Scr and ftz is largely or completely suppressed in the central nervous system, whereas eve becomes ectopically expressed in most neurones.
Cycling cytoplasmic factors that promote mitosis in the cultured 2-cell mouse embryo
Authors: Pratt H. P. M. , Muggleton-Harris A. L. 
Published: April 2021

ABSTRACT
A cytoplasmic component(s), previously shown to rescue the ‘blocked’ 2-cell mouse embryo in vitro, has been demonstrated to peak in activity during the transition between G2 and M phase and decline thereafter. The possible significance of this component(s) in the regulation of cleavage of the cultured
Complete sequence andin vitroexpression of a tissue-specific phosphatidylinositol-linked N-CAM isoform from skeletal muscle
Authors: Barton C. Howard , Dickson George , Gower Hilary J. , Rowett Lewis H. , Putt Wendy , Elsom Vicki , Moore Stephen E. , Goridis Christo , Walsh Frank S. 
Published: April 2021

ABSTRACTNeural cell adhesion molecules (N-CAMs) are a family of cell surface sialoglycoproteins encoded by a single copy gene. A full-length cDNA clone that encodes a nontransmembrane phosphatidylinositol (PI) linked N-CAM of Mr125×103 has been isolated from a human skeletal muscle cDNA library. The deduced protein sequence encodes a polypeptide of 761 amino acids and is highly homologous to the N-CAM isoform in brain of Mr120×103. The size difference between the 125×103Mr. skeletal muscle form and the 120× 103Mr N-CAM form from brain is accounted for by the insertion of a block of 37 amino acids called MSD1, in the extracellular domain of the muscle form. Transient expression of the human cDNA in COS cells results in cell surface N-CAM expression via a putative covalent attachment to PI-containing phospholipid. Linked in vitro transcription and translation experiments followed by immunoprecipitation with anti-N-CAM antibodies demonstrate that the full-length clone of 761 amino acid coding potential produces a core polypeptide of Mr110×103 which is processed by microsomal membranes to yield a 122× 103Mr species. Taken together, these results demonstrate that the cloned cDNA sequence encodes a lipid-linked, PI-specific phospholipase C releasable surface isoform of N-CAM with core glycopeptide molecular weight corresponding to the authentic muscle 125×103Mr N-CAM isoform. This is the first direct correlation of cDNA and deduced protein sequence with a known PI-linked N-CAM isoform from skeletal muscle.
The developmental potential of parthenogenetically derived cells in chimeric mouse embryos: implications for action of imprinted genes
Authors: Clarke Hugh J. , Varmuza Susannah , Prideaux Valerie R. , Rossant Janet 
Published: April 2021

ABSTRACTParthenogenetic embryos of mice die shortly after implantation and characteristically contain poorly developed extraembryonic tissue. To investigate the basis of the abnormal development of parthenotes, we combined them with normal embryos to produce chimeras and examined the distribution of the parthenogenetically derived cells during preimplantation and early postimplantation development. The parthenogenetic embryos were derived from a transgenic mouse line bearing a large insert, which allowed these cells to be identified in histological sections using in situ hybridization. At the blastocyst stage, the parthenogenetic embryos contributed cells to the trophectoderm (TE) and inner cell mass (ICM) of chimeras. By 6·5 days, however, in almost every embryo, parthenogenetically derived cells were not detected in the extraembryonic trophoblast tissue descended from the TE. In contrast, parthenogenetically derived cells could contribute to all descendants of the ICM of 6·5 and 7·5-day chimeras, including the extraembryonic visceral and parietal endoderm. Quantitative analysis of the degree of chimerism in the embryonic ectoderm at 6·5–7·5 days indicated that parthenogenetically derived cells could contribute as extensively as normal cells. These results indicate that normal trophoblast development requires gene expression from the paternally inherited genome before 6·5 days of embryogenesis. Tissues of the ICM lineage, however, apparently can develop independently of the paternal genome at least to 7·5 days of embryogenesis. Comparison of these results with those of others suggests that the influence of imprinted genes is manifested at different times and in a variety of tissues during development.
Isolation and characterization of novel mutants of Arabidopsis thaliana defective in flower development
Authors: Komaki Masako K. , Okada Kiyotaka , Nishino Eisho , Shimura Yoshiro 
Published: April 2021

ABSTRACT
We have isolated a number of mutants of Arabidopsis thaliana, a member of the mustard family, that have defects in flower development and morphogenesis. Of these, five mutants have been extensively characterized. Two mutants (Fl-40, Fl-48) lacking petals show homeotic conversion of sepals to carpels. One mutant (Fl-54) displays highly variable phenotypes, including several types of homeotic variations, loss or distorted positions of the floral organs as well as abnormal structures on the inflorescence. Two other mutants (Fl-82, Fl-89) show aberrant structures in the pistils.
Genetic analyses have revealed that these mutations are single and recessive, except for one mutant whose mutational loci still remain to be determined. These mutants may prove useful for the analysis of the genetic control of flower development and morphogenesis in the higher plant.
Two DIF-inducible, prestalk-specific mRNAs of Dictyostelium encode extracellular matrix proteins of the slug
Authors: Mcrobbie Stuart J. , Jermyn Keith A. , Duffy Karen , Blight Kenneth , Williams Jeffrey G. 
Published: April 2021

ABSTRACT
The migratory slug of Dictyostelium discoideum is surrounded by, and continuously synthesizes, an extracellular protein-cellulose matrix known as the slime sheath which is deposited on the substratum as a trail marking the slug’s progress. We show that the stalk-specific proteins, ST310 and ST430, are exclusively located in the slime sheath and trail and that fusion genes, containing upstream sequences from the cognate genes, direct correct mRNA accumulation during development and correct localization of the fusion protein.
Immunoelectron microscopy shows the ST310 and ST430 proteins to be present throughout the entire thickness of the slime sheath and almost totally absent from the cells of the slug. The genes that encode the ST310 and ST430 polypeptides are inducible by DIF, a stalk-specific inducing agent, and the mRNAs are highly enriched in prestalk over prespore cells. The production of these extracellular proteins by prestalk cells suggests that, in a manner somewhat analogous to that of extracellular matrix proteins of higher eukaryotes, the anterior region of the slug may be responsible for the continuous deposition of a track, along which the slug cells migrate. In the mature culminant, the ST310, and possibly the ST430, protein form part of the stalk tube and stalk cell wall. Therefore, the results also show that there are proteins common to both slime trail and stalk tube, indicating a possible precursor-product relationship between these chemically similar integuments.
A cell-type-specific abnormality of cell proliferation in mutant (curly tail) mouse embryos developing spinal neural tube defects
Authors: Copp Andrew J. , Brook Frances A. , Roberts Heather J. 
Published: April 2021

ABSTRACTThe mouse mutant curly tail (ct) provides a model system for studies of neurulation mechanisms. 60 % of ct/ct embryos develop spinal neural tube defects (NTD) as a result of delayed neurulation at the posterior neuropore whereas the remaining 40 % of embryos develop normally. In order to investigate the role of cell proliferation during mouse neurulation, cell cycle parameters were studied in curly tail embryos developing spinal NTD and in their normally developing litter-mates. Measurements were made of mitotic index, median length of S-phase and percent reduction of labelling index during a [3H]thymidine pulse-chase experiment. These independent measures of cell proliferation rate indicate a reduced rate of proliferation of gut endoderm and notochord cells in the neuropore region of embryos developing spinal NTD compared with normally developing controls. The incidence of cell death and the relative frequency of mitotic spindle orientations does not differ consistently between normal and abnormal embryos. These results suggest a mechanism of spinal NTD pathogenesis in curly tail embryos based on failure of normal cell proliferation in gut endoderm and notochord.