bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat shock causes repeated segmental anomalies in the chick embryo
Authors: Primmett D. R. N. , Stern C. D. , Keynes R. J. 
Published: April 2021

ABSTRACTA single heat shock, given to 2-day-old chick embryos, can generate multiple but discrete somite and skeletal anomalies. Each of these anomalies is restricted to one, or at the most two, consecutive segments. The anomalies are separated from each other by a distance of 6–7 somites or vertebrae, or a multiple of this distance. These results argue against the ‘clock and wavefront’ model; while they support the idea of a cellular clock, they are not consistent with a single propagating wave gating cells destined to form each segment.Heat shock also alters the size and number of segments, as well as the rostrocaudal proportions of the sclerotome. The results are consistent with the rostrocaudal fate of sclerotome cells being determined during segmentation. From our observations, we speculate on the implications for regionalization of the vertebral column.
Features of embryonic induction
Authors: Jacobson Antone G. , Sater Amy K. 
Published: April 2021

ABSTRACTThe patterned distribution of different organs in the amphibian embryo begins with the establishment of two domains, the animal and vegetal regions, that differ in developmental potency. Differences amplify as inductive interactions occur across boundaries between areas of different potency. Embryonic induction establishes a temporally and spatially dynamic area of developmental potency - a morphogenetic field. The final arrangement and differentiation of cell types within the field emerge from subsequent interactions occurring primarily within the field. These principles are illustrated in a review of the induction of the lens and the heart. Recent studies show that the induction of the lens of the eye and the induction of the heart begin early in development. Most of lens inductions occurs before the formation of the optic vesicle, and the heart appears to be part of a complex of dorsal structures whose formation is dependent upon the establishment of the dorsoventral axis. Suppressive as well as inductive tissue interactions occur during the determination of both of these organs, affecting their position and time of appearance. The complex processes of induction defined by the past nine decades of experimental work present many challenging questions that can now be addressed, especially in terms of the molecular events, cellular behaviour and regulatory physiology of the responding tissue.
Patterns of fibronectin gene expression and splicing during cell migration in chicken embryos
Authors: Ffrench-Constant Charles , Hynes Richard O. 
Published: April 2021

ABSTRACT
A variety of evidence suggests that fibronectin (FN) promotes cell migration during embryogenesis, and it has been suggested that the deposition of FN along migratory pathways may also play a role in cell guidance. In order to investigate such a role for FN, it is important to determine the relative contribution of migrating and pathway-forming cells to the FN in the migratory track, as any synthesis of FN by the migrating cells might be expected to mask guidance cues provided by the exogenous FN from pathwayforming cells. We have therefore used in situ hybridization to determine in developing chicken embryos the distribution and alternative splicing of FN mRNA during three different cell migrations known to occur through FN-rich environments; neural crest cell migration, mesenchymal cell migration in the area vascu-losa and endocardial cushion cell migration in the heart. Our results show that trunk neural crest cells do not contain significant FN mRNA during their initial migration. In contrast, migrating mesenchymal cells of the area vasculosa and endocardial cushion cells both contain abundant FN mRNA. Furthermore, the FN mRNA in these migrating mesenchymal and endocardial cells appears to be spliced in a manner identical with that present in the cells adjacent to their pathways. This in vivo evidence for FN synthesis by migrating and pathway cells argues against a generalized role for exogenously produced FN as a guidance mechanism for cell migration.
Beige granules as a cell marker for clonal analysis in kidney and liver of mouse aggregation chimaeras, and three-dimensional reconstruction from serial paraffin sections
Authors: Nakatsuji Norio 
Published: April 2021

ABSTRACTAnomalous giant granules of beige (bg) mice have been used as a cell marker in the study of cell lineage of mast cells. Similar granules are known to exist in other tissues including kidney proximal tubules and liver parenchymal cells. In the present study, these granules were found to give yellow or orange autofluorescence when the tissue had been fixed with formaldehyde and embedded in paraffin. Thus, the granules can be used as a cell marker that can be visualized in serial paraffin sections without any specific histochemical staining. Chimaeric mice were produced by aggregation of 8-cell-stage embryos of beige (C57BL/ 6J-bgJ/bgJ) and A/J strains. The chimaeric liver showed beige cell patches with complicated shapes, although the patches frequently conformed to the shape of parenchymal cell cord or plate structures. In chimaeric kidney, beige cells formed coherent patches in the proximal tubules. The tubules were found to contain more than one clone. The patches frequently had long extended shapes suggesting growth of the clone along the tubule axis. Three-dimensional image reconstruction from the serial paraffin sections was carried out with the aid of a computer-assisted image analysis system, resulting in a clearer image of the patch shape.
The localization of laminin mRNA and protein in the postimplantation embryo and placenta of the mouse: anin situhybridization and immunocytochemical study
Authors: Senior Paul V. , Critchley David R. , Beck Felix , Walker Rosemary A. , Varley Jennifer M. 
Published: April 2021

ABSTRACTIn situ hybridization (ISH) and immunocytochemistry were used to localize sites of synthesis and deposition of the basement membrane glycoprotein laminin during development in the postimplantation mouse embryo and extraembryonic membranes. In addition, similar studies were performed on postnatal viscera during the first 20 days after birth. Up to 10 days post coitum, embryonic laminin synthesis was confined to parietal endoderm. In maternal tissue, intense laminin mRNA expression was detected in decidual cells in the mesometrial and antimesometrial endometrium at 5–7 days. At 10 days, uniform expression was still seen within the mesometrial endometrium, with higher levels around migrating trophoblast, but in the antimesometrial aspect expression was restricted to the basal zone. High levels of mRNA expression persisted in parietal endoderm throughout gestation but much lower levels were detected in visceral yolk sac. In the mature placenta, laminin mRNA expression was also found associated with fetal vessels in the labyrinth and giant cells at the fetal/maternal boundary. In the embryo, the external limiting membrane of the cerebral vesicles and spinal cord stained for laminin protein and detectable mRNA was found in the pia mater. Growing peripheral nerves and dorsal and ventral root fibres expressed laminin mRNA and stained for laminin protein. Laminin mRNA expression was found in ureteric buds and nephrogenic vesicles (but not in metanephric blastema) during early prenatal kidney development, and in glomeruli, Bowman’s capsule, loops of Henle and collecting duct cells at later stages of development, and after birth. All these structures possessed laminin-rich basement membrane (BM). Laminin mRNA expression fell to below detectable levels in the kidney around weaning. In the gut, laminin expression and protein staining was confined to the muscularis externa and the lamina propria during embryogenesis. After birth, the muscularis externa, muscularis mucosa and lamina propria cells corresponding to fibroblasts had detectable laminin mRNA, but in adult gut no laminin mRNA could be demonstrated in any cell type. In liver, low levels of laminin mRNA were seen in the capsule and in periportal connective tissue. After birth, laminin mRNA was associated with intrahepatic bile channels; no laminin mRNA was detected in the parenchyma and protein deposition was restricted to blood sinus BM. In the adult liver, no laminin mRNA was detected in any cell type. The developing heart showed uniform expression of laminin mRNA from 12 days to before birth. Postnatally, labelling was restricted to connective tissue cells.
The pattern of cell death infushi tarazu, a segmentation gene ofDrosophila
Authors: Magrassi Lorenzo , Lawrence Peter A. 
Published: April 2021

ABSTRACTThe pair-rule mutant, fushi tarazu, causes deletion of alternate metameres. Here we show that there is cell death in the mutant which begins at the completion of germ band extension. We map the dying cells in the epidermis; they occur scattered all over those regions that, in the wild type, would form the even-numbered parasegments and are also found in posterior parts of the odd-numbered parasegments. In the affected zones, dying and dividing cells are intermingled; we suggest that cells from these zones may still give descendents that contribute to the larval cuticle. Cell death is not limited to those cells that would normally express ftz+, suggesting that it is some indirect consequence of the abnormal situation in the mutant embryo.
Expression of injected HPRT minigene DNA in mouse embryos and its inhibition by antisense DNA
Authors: Ao Asangla , Monk Marilyn , Lovell-Badge Robin , Melton David W. 
Published: April 2021

ABSTRACTWe have used a highly sensitive biochemical micro-assay to monitor the expression of a cloned minigene for hypoxanthine phosphoribosyl transferase (HPRT, EC.2.4.2.8) in preimplantation mouse embryos. The mouse HPRT promoter and the mouse metallothionein promoter (MT-I) function equally well in embryos at the 2-cell stage whereas the viral SV40 promoter does not allow HPRT expression. Induced HPRT activity from the MT-I HPRT minigene construct occurs in cleavage embryos cultured in the presence of cadmium. In contrast, negation of enzyme expression from the injected minigene DNA is mediated by simultaneous injection of HPRT antisense DNA.
Cell lineage in the rat cerebral cortex: a study using retroviral-mediated gene transfer
Authors: Price Jack , Thurlow Linda 
Published: April 2021

ABSTRACTWe have used a retroviral vector that codes for the bacterial enzyme β-galactosidase to study cell lineage in the rat cerebral cortex. This vector has been used to label progenitor cells in the cerebral cortices of rat embryos during the period of neurogenesis. When these embryos are allowed to develop to adulthood, the clones of cells derived from the marked progenitor cells can be identified histochemically. In this way, we can ask what are the lineage relationships between different neural cell types. From these studies, we conclude that there are two distinct types of progenitor cells in the developing cortex. One generates only grey matter astrocytes, whereas the second gives rise to neurones -both pyramidal and nonpyramidal - and to another class of cells that we have tentatively identified as glial cells of the white matter. We have also been able to address the question of how neurones are dispersed in the cortex during histogenesis. It had been previously hypothesized that clonally related neurones migrated radially to form columns in the mature cortex. However, we find that clones of neurones do not form radial columns; rather, they tend to occupy the same or neighbouring cortical laminae and to be spread over several hundreds of micrometers of cortex in the horizontal dimension. This spread occurs in both mediolateral and rostro-caudal directions.
Requirements for autosomal gene activity during precellular stages of Drosophila melanogaster
Authors: Merrill Pauline T. , Sweeton Dari , Wieschaus Eric 
Published: April 2021

ABSTRACT
To identify early requirements for zygotic gene activity in Drosophila, we used compound autosomes and autosome-Y translocations to generate embryos deficient for cytologically defined portions of the genome. No obvious gross morphological defects were observed in any deficiency class until the beginning of cycle 14. Only seven autosomal regions were identified with discrete effects visible prior to the onset of gastrulation. These regions include genes with locus-specific effects on the clearing of the cortical cytoplasm during early cycle 14, (22AB), the initiation of the slow and fast phases of cellularization (26BF and 40AC, respectively), the apical-basal distribution of nuclei during cycle 14 (71C–75C) and the closing off of furrow canals during cellularization (100AC). The distal tip of the third chromosome also contains two loci (99DF and 100AC) whose deletion causes multiple nuclei to be cellularized into single cells, a phenotype similar to that produced in embryos totally lacking the X-chromosome.
Shaping and bending of the avian neural plate as analysed with a fluorescent-histochemical marker
Authors: Schoenwolf Gary C. , Sheard Philip 
Published: April 2021

Abstract
Shaping and bending of the neural plate are cardinal events of neurulation. These processes are initiated in avian embryos shortly after the onset of gastrulation and concluded concomitantly with the completion of gastrulation. The epiblast undergoes extensive morphogenetic movements during gastrulation and neurulation, but the directions, distances, rates, mechanisms and roles of such rearrangements are largely unknown. To begin to understand these morphogenetic movements, we have mapped regional displacements of the epiblast by injecting a fluorescent-histochemical marker into selected prenodal, nodal and postnodal levels of the blastoderm. Lateral epiblast regions (600 μm lateral to the midline and consisting primarily of surface epithelium) are displaced craniomedially, medial regions (300 μm lateral to the midline and consisting of neural plate and preingressed mesoderm) predominantly medially, and midline regions (consisting of neural plate and primitive streak) predominantly caudally. Displacements within the avian neural plate parallel those previously described for the amphibian neural plate. Furthermore, similar tissue displacements occur within the prenodal and postnodal levels of the avian epiblast despite the fact that neurulation is occurring in the former and gastrulation in the latter. Finally, our results show that ectodermal rudiments contained within a single crosssectional level of the embryo are a composite of cells derived from multiple craniocaudal and mediolateral levels. Thus, regional tissue displacements are important events to consider in the analysis of the early morphogenesis of axial and paraxial organ rudiments derived from the epiblast.
A whole-mount immunocytochemical analysis of the expression of the intermediate filament protein vimentin in Xenopus
Authors: Dent Joseph A. , Polson Andrew G. , Klymkowsky Michael W. 
Published: April 2021

Abstract
We have developed a whole-mount immunocytochemical method for Xenopus and used it to map the expression of the intermediate filament protein vimentin during early embryogenesis. We used two monoclonal antibodies, 14h7 and RV202. Both label vimentin filaments in Xenopus A6 cells. RV202 reacts specifically with vimentin (Mr, 55×103) on Western blots of A6 cells and embryos. 14h7 reacts with vimentin and a second, insoluble polypeptide of 57×103Afr found in A6 cells. The 57 ×103Afr polypeptide appears to be an intermediate filament protein immunochemically related to vimentin. In the whole-mount embryo, we first found vimentin at the time of neural tube closure (stage 19) in cells located at the lateral margins of the neural tube. By stage 26, these cells, which are presumably radial glia, are present along the entire length of the neural tube and in the tail bud. Cells in the optic vesicles express vimentin by stage 24. Vimentin-expressing mesenchymal cells appear on the surface of the somites at stage 22/23; these cells appear first on anterior somites and on progressively more posterior somites as development continues. Beginning at stage 24, vimentin appears in mesenchymal cells located ventral to the somites and associated with the pronephric ducts; these ventral cells first appear below the anterior somites and later appear below more posterior somites. The dorsal fin mesenchyme expresses vimentin at stage 26. In the head, both mesodermally-derived and neural-crest-derived mesenchymal tissues express vimentin by stage 26. These include the mesenchyme of the branchial arches, the mandibular arch, the corneal epithelium, the eye, the meninges and mesenchyme surrounding the otic vesicle. By stage 33, vimentin-expressing mesenchymal cells are present in the pericardial cavity and line the vitelline veins. Vimentin expression appears to be a marker for the differentiation of a subset of central nervous system cells and of head and body mesenchyme in the early Xenopus embryo.
Tissue-specific expression of c-jun and junB during organogenesis in the mouse
Authors: Wilkinson David G. , Bhatt Sangita , Ryseck Rolf-Peter , BRAVO RODRIGO 
Published: April 2021

ABSTRACT
c-jun and junB are cellular genes related to the viral oncogene v-jun and encode members of the AP-1 transcription factor gene family. These genes have been implicated in the control of the G0/G1 transition in fibroblasts. Here, we have investigated the potential roles of c-jun and junB during fetal growth and organogenesis in the mouse by in situ hybridization analysis of their expression patterns, c-jun expression is detected throughout organogenesis, and transcripts are detected in many tissues, although in restricted cell populations within developing cartilage, gut and the central nervous system (CNS). In cartilage, c-jun expression is associated with rapidly proliferating perichondrial cells, but occurs in postmitotic motor neurones in the CNS. junB expression is initiated between 14 · 5 and 17 · 5 days of development, and is restricted to differentiating epidermal cells and endodermal gut epithelium. These data suggest that c-jun and junB have distinct, tissue-specific roles in cell proliferation and differentiation during fetal development.
The segment polarity gene armadillo interacts with the wingless signaling pathway in both embryonic and adult pattern formation
Authors: Peifer Mark , Rauskolb Cordelia , Williams Michelle , Riggleman Bob , Wieschaus Eric 
Published: April 2021

ABSTRACT
The segment polarity genes of Drosophila were initially defined as genes required for pattern formation within each embryonic segment. Some of these genes also function to establish the pattern of the adult cuticle. We have examined the role of the armadillo (arm) gene in this latter process. We confirmed and extended earlier findings that arm and the segment polarity gene wingless are very similar in their effects on embryonic development. We next discuss the role of arm in pattern formation in the imaginal discs, as determined by using a pupal lethal allele, by analyzing clones of arm mutant tissue in imaginal discs, and by using a transposon carrying arm to produce adults with a reduced level of arm. Together, these experiments established that arm is required for the development of all imaginal discs. The requirement for arm varies along the dorsal-ventral and proximal—distal axes. Cells that require the highest levels of arm are those that express the wingless gene. Further, animals with reduced arm levels have phenotypes that resemble those of weak alleles of wingless. We present a description of the patterns of arm protein accumulation in imaginal discs. Finally, we discuss the implications of these results for the role of arm and wingless in pattern formation.
The emergence of sense organs in the wing disc of Drosophila
Authors: Huang Françoise , Dambly-Chaudière Christine , Ghysen Alain 
Published: April 2021

ABSTRACT
We have examined the origin of a set of precisely located sense organs in the notum and wing of Drosophila, in transformant flies where lacZ is expressed in the progenitor cells of the sense organs (the sensory mother cells) and in their progeny. Here we describe the temporal pattern of appearance and divisions of the sensory mother cells that will form the eleven macro-chaetes and the two trichoid sensilla of the notum, and five campaniform sensilla on the wing blade. The complete pattern of sensory mother cells develops in a strict sequence that extends over most of the third larval instar and the first 10 h after puparium formation. The delay between the onset of lacZ expression and the first differentiative division ranges from 30 h, in the case of the earliest mother cells, to 2 h for the latest mother cells.
The first division shows a preferential orientation which is also specific for each sensory mother cell. Up to this stage, there is no marked difference between the three types of mechanosensory organs.
Progressively restricted expression of a new homeobox-containing gene during Xenopus laevis embryogenesis
Authors: Su Ming-Wan , Suzuki Hiroaki R. , Solursh Michael , Ramirez Francesco 
Published: April 2021

ABSTRACT
We have isolated cDNAs encoding a novel Xenopus homeodomain-containing protein homologous to the mouse Hox-7.1 and the Drosophila muscle segment homeobox (msh). Northern blot and RNAase protection experiments established that transcripts of the frog gene, termed Xhox-7.1, first appear at about the beginning of gastrulation. After a rapid increase, mRNA levels plateau between the neurula and mlddle-tailbud stages, and decrease steadily thereafter. In situ hybridization localized the Xhox-7.1 message to the dorsal mesodermal mantle of gastrula stage embryos. Comparison of the hybridization patterns of progressively more anterior cross-sections of tailbud stage embryos localized the signal to the dorsal neural tube and neural crest, to specific regions of the lateral plate mesoderm, and to the cardiogenic region. By the tadpole stage, the Xhox-7.1 message appears only at specific sites in the central nervous system, such as in the dorsal hindbrain. Thus, during embryonic development levels of Xhox-7.1 expression decrease as the transcript becomes more progressively localized. Finally, evidence is presented of a distinct msh-like transcript (provisionally termed Xhox-7.1’) which begins to accumulate at early-gastrula stage, as well.