bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyphosphoinositlde metabolism during the fertilization wave in sea urchin eggs
Authors: Ciapa Brigitte , Borg Béatrice , Whitaker Michael 
Published: April 2021

Abstract
A transient increase in intracellular free calcium is believed to be the signal responsible for the stimulation of the egg metabolism at fertilization and the resumption of the cell cycle. We have studied how the polyphospho-inositides (PP1) turn over at fertilization in sea urchin eggs, in order to determine the relationship between the metabolism of these lipids and the calcium signal. We compare the patterns of PPI turnover that occur during the first minute following fertilization in eggs in which PPI are labelled to steady state with [3H]inositol or [3H]arachidonate with that in which PPI are labelled for a shorter period with [3H]inositol. When eggs are labelled to apparent isotopic equilibrium with either [3H]inositol or [3H]arachidonate, no early increase in [3H]PtdlnsP2occurs while Ptdins decreases slightly. On the contrary, when not labelled to isotopic equilibrium, all [3H]PPI increase during the first 15 seconds following fertilization. We find that, within seconds, fertilization triggers a 600-fold increase in the turnover of PPI, producing an amount of lnsP3 apparently sufficient to trigger calcium release. We suggest that phosphoinositi dase C and PtdlnsP kinase, responsible respectively for the hydrolysis and synthesis of PtdlnsP2, are both stimulated to a comparable degree in the first 30 seconds following fertilization and that net changes in the amount of PtdlnsP2at fertilization are very sensitive to the relative levels of activation of the two enzymes. Activating the eggs with the calcium ionophore A23187 showed that both these enzymes are sensitive to calcium, suggesting that calcium-dependent lnsP3 production might play a role in the initiation and/or the propagation of the fertilization calcium wave. A comparison of the rates of PPI turnover in fertilized and A23187-activated eggs confirms that the fertilizing sperm stimulates an early and possibly calcium-dependent increase in PtdlnsP kinase activity.
engrailedexpression in the anterior lineage compartment of the developing wing blade ofDrosophila
Authors: Blair Seth S. 
Published: April 2021

AbstractThe developing wing of Drosophila melanogaster was examined at larval and pupal stages of development to determine whether the anterior-posterior lineage boundary, as identified by lineage restrictions, was congruent with the boundaries defined by the expression of posterior-specific (engrailed, inverted), and anterior-specific (cubitus interruptus-D) genes. The lineage boundary was identified by marking mitotic recombinant clones, using an enhancer trap line with ubiquitous β-gal expression in imaginai tissues; clones of +/+ cells were identified by their lack of β-gal expression. Domains of gene expression were localized using antibodies and gene specific lacZ constructs. Surprisingly, it was found that engrailed expression extended a small distance into the anterior lineage compartment of the wing blade, as identified with anti-en/tnv mAh, anti-en polyclonal antiserum, or an en-promoter-lacZ insert, ryxho25. This anterior expression was not present in early third instar discs, but appeared during subsequent larval and pupal development. In contrast, the expression of cubitus interruptus-D, as identified using the ci-Dplac insert, appeared to be limited to the anterior lineage compartment. Thus, en expression is not limited to cells from the posterior lineage compartment, and en and ci-D activities can overlap in a region just anterior to the lineage compartment boundary in the developing wing. The lineage boundary could also be identified by a line of aligned cells in the prospective wing blade region of wandering third instar discs. A decapeniaplegic-lacZ construct was expressed in a stripe several cells anterior to the lineage boundary, and did not define or overlap into the posterior lineage compartment.
bicoid and the terminal system activate tailless expression in the early Drosophila embryo
Authors: Pignoni F. , Steingrímsson E. , Lengyel J.A. 
Published: April 2021

Abstract
In the early Drosophila embryo, the maternal terminal genes are required for formation of the acron at the anterior and the telson at the posterior. We show here that the terminal system, a signal transduction pathway active at the poles of the embryo, is required to activate transcription of the key zygotic gene tailless (tll) in two symmetrical domains. Consistent with the characterization of the tll protein as a putative transcription factor (a member of the steroid receptor superfamily) that represses segmentation genes and activates terminal-specific genes, we observe a correlation between the presence of the posterior cap of tll expression and differentiation of a telson.
While the maternal patterning systems of the Drosophila embryo function for the most part independently, the maternal anterior system, in which the bicoid (bcd) protein functions as a graded morphogen, is required together with the terminal system to establish the acron. This dual requirement is evident at the molecular level in the control of tll expression. We find that bcd and the terminal system are required together to activate the anterior-dorsal stripe of tll expression that is correlated with formation of the acron. In the absence of bcd, the anterior cap of tll expression established by the terminal system persists and an ectopic telson forms at the anterior, while in the absence of terminal system activity only an abnormal anterior stripe forms. This is the first describcd example of how, by jointly controlling expression of the same gene, two systems of positional information function together to set unique positional values.
Identification and characterization of a novel, evolutionarily conserved gene disrupted by the murine Hβ58 embryonic lethal transgene insertion
Authors: Lee James J. , Radice Glenn , Perkins Christopher P. , Costantini Frank 
Published: April 2021

Abstract
The Hβ58 transgenic mouse line carries a recessive insertional mutation that results in developmental abnormalities beginning at day 7.5 p.c. and embryonic arrest at about day 9.5. In this paper, we describe the characterization of a novel gene encoded at the Hβ58locus, whose disruption appears to be responsible for the mutant phenotype. The wild-type Hβ58 gene encodes a single 2.7 kb mRNA during embryonic and fetal development, and in many adult somatic tissues. In the mutant locus, this transcription unit is split by the transgene insertion, and one of its coding exons is deleted. Consistent with the physical disruption of the gene, the level of the Hβ58 mRNA in heterozygous mutant mouse tissues was half the normal level, indicating that the mutant allele fails to encode a stable mRNA. In situ hybridization studies revealed that expression of the wild-type Hβ58 gene begins in the oocyte, and continues throughout pre- and post-implantation embryogenesis, despite the fact that homozygous mutant embryos develop successfully through the egg cylinder stage (day 6.5 p.c.). In the early post-implantation embryo, expression of the normal Hβ58 gene is relatively low in the embryonic ectoderm, the tissue displaying the earliest phenotypic effects of the mutation, and highest in the visceral endoderm. We therefore propose that the effects of the mutation on the embryonic ectoderm may be exerted indirectly, via the visceral endoderm. Sequence analysis of Hβ58 cDNA clones revealed no homology between the 38 ×103MrHβ58 protein and other known proteins. However, the Hβ58 gene displayed extremely strong conservation between mammals and birds (&gt;96% amino acid identity), although it appeared less conserved in amphibians and invertebrates.
A genetic model for light-regulated seedling development in Arabidopsis
Authors: Chory Joanne 
Published: April 2021

Abstract
The genetic interactions among mutations that define eight distinct loci involved in light-regulated development in Arabidopsis thaliana are described. The mutations in these eight genes define two distinct phenotypic classes with opposite characteristics. Recessive mutations in either one of two genes, DET1 or DET2, result in dark-grown plants that develop as light-grown wild-type seedlings. Mutants in the second class exhibit a reduced response to light Recessive mutations in any one of five genes, HY1, HY2, HY3, HY5, or HY6 cause reduced responses to red-light Four of these genes, HY1,2,3, and 6, affect the activity of one or all of the red-light photoreceptors, the phytochromes. The HY4 gene product is involved in blue-light perception or action. The experiments described here examine how these eight genes interact to control a particular event, the switch from developmental arrest in the dark (etiolation) to growth in the light (deetiolation). The phenotypes of doubly mutant strains suggest a hierarchical regulatory network among these genes in the control of the switch from etiolated to de-etiolated growth strategies.
Secretory and inductive properties of Drosophila wingless protein in Xenopus oocytes and embryos
Authors: Chakrabarti Arthur , Matthews Glenn , Colman Alan , Dale Leslie 
Published: April 2021

Abstract
Like its vertebrate homologues, Xenopus wnt-8 and murine wnt-1, we find that Drosophila wingless (wg) protein causes axis duplication when overexpressed in embryos of Xenopus laevis after mRNA injection. In many cases, the secondary axes contain eyes and cement glands, which reflect the induction of the most dorsoanterior mesodermal type, prechordal mesoderm. We show that the extent of axis duplication is dependent on the embryonic site of expression, with ventral expression leading to a more posterior point of axis bifurcation. The observed duplications are due to de novo generation of new axes as shown by rescue of UV-irradiated embryos. The true dorsal mesoderm-inducing properties of wg protein are indicated by its ability to generate extensive duplications after mRNA injection into D-tier cells of 32-cell embryos. As revealed by lineage mapping, the majority of these D cell progeny populate the endoderm; injections into animal blastomeres at this stage are far less effective in inducing secondary axes. However, when expressed in isolated animal cap expiants, wg protein induces only ventral mesoderm, unless basic fibroblast growth factor is added, whereupon induction of muscle and occasionally notochord is seen. We conclude that in intact embryos, wg acts in concert with other factors to cause axis duplication.
Immunolocalisation studies in embryos indicate that wg protein remains localised to the blastomeres synthesizing it and has a patchy, often perinuclear distribution within these cells, although some gets to the surface. In oocytes, the pool of wg protein is entirely intracellular and relatively unstable. When the polyanion suramin is added, most of the intracellular material is recovered in the external medium.
Analysis of glia cell differentiation in the developing chick peripheral nervous system: sensory and sympathetic satellite cells express different cell surface antigens
Authors: Rüdel Christiana , Rohrer Hermann 
Published: April 2021

Abstract
To identify and analyse precursor cells of neuronal and glial cell lineages during the early development of the chick peripheral nervous system, monoclonal antibodies were raised against a population of undifferentiated cells of E6 dorsal root ganglia (DRG).
Non-neuronal cells of E6 DRG express surface antigens that are recognized by four monoclonal antibodies, G1, G2, GLI 1 and GLI 2. The proportion of non-neuronal cells in DRG that express the GLI 1 antigen is very high during ganglion formation (80% at E4) and decreases during later development (15% at E14). GLI 2 antigen is expressed only on a minority of the cells at E6 and increases with development. The G1 and G2 antigens are expressed on about 60-80% of the cells between E6 and E14. All cells that express the established glia marker O4 are also positive for the new antigens. In addition, it was demonstrated that GLI 1positive cells from early DRG, which are devoid of O4 antigen, could be induced in vitro to express the O4 antigen. Thus, the antigen-positive cells are considered as glial cells or glial precursor cells.
Surprisingly, the antigen expression by satellite cells of peripheral ganglia is dependent on the type of ganglion: antigens G1, G2 and GLI 1 were not detectable on glial cells of lumbosacral sympathetic ganglia and GLI 2 was expressed only by a small subpopulation. These results demonstrate an early immunological difference between satellite cells of sensory DRG and sympathetic ganglia. As the antigens could however be induced in vitro also in sympathetic ganglion cells, it is suggested that the specific antigen expression is due to specific environmental cues acting on precursor cells in different types of ganglia rather than to intrinsic differences between sensory and sympathetic glial precursor cells.
Cultured dermal papilla cells induce follicle formation and hair growth by transdifferentiation of an adult epidermis
Authors: Reynolds Amanda J. , Jahoda Colin A. B. 
Published: April 2021

Abstract
Adult rat pelage follicle dermal papilla cells induced follicle neogenesis and external hair growth when associated with adult footpad skin epidermis. They thus demonstrated a capacity to completely change the structural arrangement and gene expression of adult epidermis - an ability previously undocumented for cultured adult cells. Isolation chambers ensured that de novo follicle formation must have occurred by eliminating the possibility of cellular contributions, and/or inductive influences, from local skin follicles. These findings argue against previous suggestions of vibrissa follicle specificity, and imply that the potential for hair follicle induction may be common to all adult papilla cells.
The expression of neuropeptide Y immunoreactivity in the avian sympathoadrenal system conforms with two models of coexpression development for neurons and chromaffin cells
Authors: García-Arrarás José E. , Lugo-Chinchilla Ana M. , Chévere-Colón Iván 
Published: April 2021

Abstract
We have studied the expression and development of neuropeptide Y-like immunoreactivity (NPY-LI) in the sympathoadrenal system of the chicken using single and double immunocytochemical techniques and radioimmunoassay. NPY-LI is expressed by neurons of the paravertebral sympathetic ganglia and by chromaffin cells of the adrenal gland in embryonic and adult chickens. The peptide is coexpressed with catecholamin-ergic properties in neurons. In chromaffin cells, it is also expressed with immunoreactivity to somatostatin and serotonin.
We have used the expression of NPY-LI to analyze how cells that coexpress two or more neuroactive substances arrive at their final phenotype. Our results suggest that the ontogeny of coexpression in neurons of the avian paravertebral sympathetic ganglia occurs in a sequential pattern, where the expression of the peptide follows the initial expression of the “classical neurotransmitter”. In contrast, in chromaffin cells, expression of the peptides occurs concomitantly with expression of catecholamin-ergic properties or soon after. Initially, coexpression of several neuroactive substances occurs, but this is followed by further specialization where the expression of one peptide prevails over the other. We believe that the two models of coexpression shown by our results can be used to describe the ontogeny of coexpression in other cells of the nervous system.
Synaptic basal lamina contains a signal for synapse-specific transcription
Authors: Jo Sangmee Ahn , Burden Steven J. 
Published: April 2021

ABSTRACT
Nuclei in the synaptic region of multinucleated skeletal myofibers are transcriptionally distinct, since acetylcholine receptor genes are transcribed at a high rate by these nuclei, but not by nuclei elsewhere in the myofiber. Although this spatially restricted transcription pattern is presumably imposed by the motor nerve, the continuous presence of the nerve is not required, since synapsespecific transcription persists after denervation. These results suggest either that a transcriptional signal persists at synaptic sites after nerve terminals have degenerated, or that a transcriptional pattern in the myofiber, once established, is stable in the absence of a nerve-derived signal. To distinguish between these possibilities, we denervated muscle and damaged the myofibers and specialized cells located near synaptic sites, and then studied transcription of an acetylcholine receptor gene in myofibers that regenerated in their original basal lamina sheaths, but remained denervated. We show that synapse-specific transcription is re-induced in these regenerated myofibers, and we conclude that a signal for synapse-specific transcription is stably maintained in the synaptic basal lamina.
Cell fate in the shoot apical meristem of Arabidopsis thaliana
Authors: Furner Ian J. , Pumfrey Joanne E. 
Published: April 2021

ABSTRACT
Seeds of Arabidopsis thaliana, heterozygous for the alb1 mutation were treated with X-rays to generate sectors of albino tissue in the mature plants. Sectors were observed in tissues derived from L2 and L3 layers of the shoot meristem. Altogether 324 sectors were obtained affecting 512 leaves or the inflorescence. The majority of sectors affected only one or other of the first leaf pair. In later leaves, sectors were less frequent, and often affected more than one leaf. Sectors seen in the flowers almost invariably included some of the cauline leaves. Sectors in any region of the plant were of variable length and width. The axillary meristems of Arabidopsis were found to be clonally related to two or more cells near the centre of the subtending leaf. Overall the data are compatible with the idea that there are few, if any, restrictions on cell fate within the cell layers of the dry seed meristem. As in other higher plants, developmental fate could only be predicted in a general and probabilistic way. Such a pattern might be generated if the acquisition of cell fate occurred continuously as the plant grows, in a position-dependent, lineage-independent fashion. A general model of the meristem has been produced to accommodate the observations concerning the great majority of the sectors.
Transgenic mouse eggs with functional hamster sperm receptors in their zona pellucida
Authors: Kinloch Ross A. , Mortillo Steven , Wassarman Paul M. 
Published: April 2021

ABSTRACT
Sperm receptors are located in the mammalian egg extracellular coat, or zona pellucida. Mouse and hamster sperm receptor glycoproteins, mZP3 (83 × 103Mr) and hZP3 (56 × 103Mr), respectively, have very similar polypeptides (44×103Mr; 81% identical) that are glycosylated to different extents. Purified mZP3 and hZP3 can bind to mouse sperm, prevent them from binding to eggs and induce them to undergo exocytosis, the acrosome reaction, in vitro. A DNA construct that placed the hZP3 gene under the control of mZP3 gene 5 -flanking sequence was used in this report to produce two mouse lines that harbored the foreign sperm receptor transgene. In both lines, the transgene was expressed only by growing oocytes, at a level comparable to that of the endogenous mZP3 gene, and the developmental pattern of transgene expression resembled that of the mZP3 gene. In addition to mZP3, transgenic mouse oocytes synthesized and secreted a glycoprotein indistinguishable from hZP3, and incorporated both glycoproteins into a mosaic zona pellucida. Importantly, hZP3 purified from such zonae pellucidae exhibited both sperm receptor and acrosome reaction-inducing activities in vitro and, following fertilization of transgenic mouse eggs, was inactivated. These results demonstrate that a biologically active foreign sperm receptor can be synthesized and secreted by transgenic mouse oocytes, assembled into a mosaic zona pellucida, and inactivated following fertilization as part of the secondary block to polyspermy.
Differential distribution patterns of CRABP I and CRABP II transcripts during mouse embryogenesis
Authors: Ruberte Esther , Friederich Valérie , Morriss-Kay Gillian , Chambon Pierre 
Published: April 2021

ABSTRACT
We have compared the transcript distribution of cellular retinoic acid binding protein (CRABP) I and II genes in mouse embryos at various stages of development. Both CRABP transcripts are present in embryonic structures from the earliest stages studied and exhibit specific patterns of distribution, suggesting that the two retinoic acid (RA) binding proteins perform different functions during mouse embryogenesis. The CRABP I transcript distribution correlates well with structures known to be targets of excess retinoid-induced terato-genesis (e.g. neural crest cells and hindbrain), suggesting that cells expressing CRABP I are those that cannot tolerate high levels of RA for their normal developmental function. The embryonic structures expressing CRABP II transcripts include those structures that have been shown to be adversely affected by excess of retinoids, such as limbs and hindbrain, but CRABP II transcripts are also found in structures not known to be specifically vulnerable to raised RA levels. The CRABP II gene is coexpressed with retinoic acid receptor (RAR)- and cellular retinol binding protein (CRBP) I genes in a number of tissues such as the gut endoderm, hypophysis and interdigital mesenchyme, all of which are devoid of CRABP I transcripts. Interestingly, the expression of the three genes, RAR-, CRABP II and CRBP I, is induced by retinoic acid, which suggests a link between the synthesis of RA from retinol and the control of expression of subsets of RA-responsive genes. The transcript distribution of CRABP I and II is discussed in relation to the teratogenic effects of RA, and compared to the RA-sensitive pattern of expression of other important developmental genes.
Down-regulation of the POU transcription factor SCIP is an early event in oligodendrocyte differentiation in vitro
Authors: Collarini Ellen J. , Kuhn Rainer , Marshall Caroline J. , Monuki Edwin S. , Lemke Greg , Richardson William D. 
Published: April 2021

ABSTRACT
The POU-domain transcription factor SCIP (also known as Tst-1) has been implicated in the development of Schwann cells, the myelinating cells of the peripheral nervous system (PNS). We have investigated the possibility that SCIP also might play a role in the development of oligodendrocytes, the myelinating cells of the central nervous system (CNS). We purified oligodendrocyte precursors (O–2A progenitors) by immunoselection and cultured them in the presence of plateletderived growth factor (PDGF) and basic fibroblast growth factor (bFGF), which together keep O–2A progenitors proliferating and prevent oligodendrocyte differentiation. Under these culture conditions, O–2A progenitors expressed high levels of SCIP mRNA and protein, and did not express myelin-specific genes. When oligodendrocyte differentiation was initiated by withdrawing the growth factors, SCIP mRNA was rapidly down-regulated, followed by a decline in SCIP protein and the sequential activation of myelin-specific genes. Rapid down-regulation of SCIP mRNA required continued protein synthesis. In O–2A progenitors that were cultured in the presence of PDGF alone, SCIP expression declined to an intermediate level, and low levels of the myelin gene products were induced. Thus, the level of SCIP expression in O–2A progenitors is inversely related to the level of myelin gene expression, suggesting that SCIP may be involved in the developmental switch from proliferation to differentiation in the oligodendrocyte lineage. When O–2A progenitors are cultured in the presence of 10% fetal calf serum, they differentiate into type-2 astrocytes rather than oligodendrocytes. SCIP mRNA was also down-regulated in type-2 astrocytes, which do not express myelin genes, so down-regulation of SCIP seems to be more closely linked to the cessation of cell proliferation per se than the expression of a particular differentiated phenotype.