pinecone/core-2020-05-10-deduplication huggingface dataset:
Ontogeny of Basal and Regulated Proopiomelanocortin-Derived Peptide Secretion from Fetal and Neonatal Pituitary Intermediate Lobe Cells: Melanotrophs Exhibit Transient Glucocorticoid Responses during Development

AbstractProopiomelanocortin (POMC)-producing cells comprise nearly 100% of the adult rat intermediate lobe (IL) hormone-producing cells. Secretion by these cells in the adult is primarily under negative regulation by dopamine. Although the POMC-derived peptide α-MSH has been detected in plasma of fetal rats, the secretory capability of fetal melanotrophs has not yet been examined directly. Here we have used the reverse hemolytic plaque assay to assess, at the single-cell level, basal and regulated release by melanotrophs from fetal and early postnatal ages. Basal secretion was detected at the earliest age examined [Embryonic Day 17.5 (e17.5)], but CRH (10−8M) stimulated secretion was not observed until e19.5. As development proceded, CRH increased both individual plaque sizes and the percentage of melanotrophs stimulated to secrete. An unexpected, transient inhibition of CRH stimulated release from melanotrophs by dexamethasone (DEX, 10−6M) was observed from e19.5–p2 (postnatal Day 2). By p3, however, DEX no longer inhibited melanotroph secretion while inhibition of CRH-stimulated release from p3 corticotrophs was readily detected. The dopamine agonist ergocryptine (ERG, 10−6M) inhibited basal secretion from melanotrophs, but not corticotrophs, at all ages examined. Taken together, these results indicate that melanotrophs undergo a maturation process in which they are initially nonresponsive to CRH, next possess functional CRH and steroid receptors, and finally, undergo functional uncoupling of steroid receptors which characterizes the adult IL. The loss of steroid-mediated inhibition of stimulated secretion parallels the arrival of catecholaminergic input into the IL. In contrast, the early response of melanotrophs to dopaminergic agonists, which can be detected 1 week prior to arrival of catecholaminergic fibers into the neurointermediate lobe, appears to be an intrinsic feature of these cells that is never present in corticotrophs
Expression of the Ubiquitin-Conjugating DNA Repair Enzymes HHR6A and B Suggests a Role in Spermatogenesis and Chromatin Modification

AbstractRAD6,a member of the expanding family of ubiquitin-conjugating (E2) enzymes, functions in the so-called “N-rule” protein breakdown pathway ofSaccharomyces cerevisiae. In vitro,the protein can attach one or multiple ubiquitin (Ub) moieties to histones H2A and B and trigger their E3-dependent degradation. Rad6 mutants display a remarkably pleiotropic phenotype, implicating the protein in DNA damage-induced mutagenesis, postreplication repair, repression of retrotransposition, and sporulation. RAD6 transcription is strongly induced upon UV exposure and in meiosis, suggesting that it is part of a damage-induced response pathway and that it is involved in meiotic recombination. It is postulated that the protein exerts its functions by modulating chromatin structure. Previously, we have cloned two human homologs of this gene (designated HHR6A and HHR6B) and demonstrated that they partially complement the yeast defect. Here we present a detailed characterisation of their expression at the transcript and protein levels. Both HHR6 proteins, resolved by 2-dimensional immunoblot analysis, are expressed in all mammalian tissues and cell types examined, indicating that both genes are functional and constitutively expressed. Although the proteins are highly conserved, the UV induction present in yeast is not preserved, pointing to important differences in damage response between yeast and mammals. Absence of alterations in HHR6 transcripts or protein upon heat shock and during the cell cycle suggests that the proteins are not involved in stress response or cell cycle regulation. Elevated levels of HHR6 transcripts and proteins were found in testis. Enhanced HHR6 expression did not coincide with meiotic recombination but with the replacement of histones by transition proteins. Immunohistochemistry demonstrated that the HHR6 proteins are located in the nucleus, consistent with a functional link with chromatin. Electron microscopy combined with immunogold labeling revealed a preferential localisation of HHR6 in euchromatin areas, suggesting that the protein is associated with transcriptionally active regions. Our findings support the idea that both HHR6 genes have overlapping, constitutive functions related to chromatin conformation and that they have a specific role in spermatogenesis, involving Ub-mediated histone degradation
First Blood Vessels in the Avian Neural Tube Are Formed by a Combination of Dorsal Angioblast Immigration and Ventral Sprouting of Endothelial Cells

AbstractWe studied the early pattern of neural tube (NT) vascularization in quail embryos and chick–quail chimeras. Angioblasts appeared first in the dorsal third at Hamburger and Hamilton (HH) stage 19 as single, migrating cells. Their distribution did not correspond to a segmental pattern. After this initial dorsal immigration, endothelial sprouts invaded the NT on either side of the floor plate (HH stage 21). These cells remained continuous with their arterial vascular sources, connected to the venous perineural vascular plexus at HH-stage 22, and formed the first perfused vessels of the NT at HH-stage 23. The same pattern of angiotrophic vascularization was observed in a craniocaudal sequence starting caudal to the rhombencephalic NT. Extremely long filopodia were observed on sprouting cells, extending toward the central canal and the mantle layer. The exclusively extraneuroectodermal origin of angioblastic cells was demonstrated with chick–quail chimeras. Following replacement of quail NT by chick NT graft, angioblast and sprout distribution in chimeras was the same as in controls. We conclude that the NT receives its first blood vessels by a combination of two different processes, dorsal immigration of isolated migrating angioblastic cells and ventral sprouting of endothelial cells, which derive from perfused vessels. The dorsal invasive angioblasts contribute to the developing intraneural vascular plexus after having traversed the neural tube. The initial distribution of blood vessels within the neuroepithelium corresponds to intrinsic random motility of angioblastic cells; a more regular pattern is seen later. The floor plate apparently prohibits connections between sprouts in both NT sides, whereas in the dorsal NT, such a separating effect on the migrating angioblasts does not exist
Effects of the Transcription Inhibitor Actinomycin D on Postzygotic Development ofTetrahymena thermophilaConjugants

AbstractDuringTetrahymena thermophilaconjugation, new somatic macronuclei develop from a common zygotic nucleus derived from meiotic products of the germline, and the old parental somatic nucleus is destroyed. The transcription inhibitor actinomycin D disrupts many events of postzygotic conjugation (cycloheximide causes indistinguishable effects). Early treatment causes a block of all postzygotic development, suggesting a transcription requirement for conjugants to pass a checkpoint, allowing entry into postzygotic development. Thereafter, pair separation, resorption of the old macronucleus, and elimination of one of the new micronuclei are blocked if actinomycin D is added at least 1.5 hr before each of these events normally occurs. Treatment just before DNA rearrangements in the developing macronuclei (anlagen) causes aberrant anlage DNA loss, suggesting that this DNA loss may be caused by inhibition of gene expression involved in genome rearrangements. DNA loss, and correlated lethality, appear to require previous gene expression, since actinomycin D added earlier causes cells to arrest in development without anlage DNA loss, and these conjugants can (at some frequency) complete conjugation and make viable progeny once actinomycin D is removed. The old macronucleus already had been inactivated before most actinomycin D treatments were initiated, indicating that the various induced defects we observed are the result of inhibition of postzygotic gene expression, presumably in anlagen. The defects induced by actinomycin D are similar to defects previously observed in conjugants harboring nullisomic germline deficiencies but proficient old macronuclei
The Distribution of Collapsin-1 mRNA in the Developing Chick Nervous System

AbstractCollapsin-1 is a secreted glycoprotein that inhibits the extension of specific growth conesin vitro.It has been hypothesized to serve as a repulsive guidance cue for extending growth conesin vivo.Here we report the distribution of collapsin-1 message as demonstrated byin situhybridization using digoxigenin-labeled RNA probes in wholemounts and tissue sections. In the early chick brain collapsin-1 is expressed in specific regions of the retina, the olfactory bulb, and the diencephalon. In the hindbrain collapsin-1 is first expressed in rhombomere 5 and later in bilaterally symmetric rostrocaudal stripes. Collapsin-1 is expressed in high levels in the ventral horn of the spinal cord and in ventricular stripes that extend rostrally to the hindbrain. In the periphery, collapsin-1 is expressed in the dermamyotome and in ectoderm and epidermis. Based on collapsin's expression patterns we tested axons extending from explants of ventral spinal cord and olfactory bulb for sensitivity to collapsin and show that the former are sensitive to collapsin wheras the latter are not. The distribution of collapsin mRNA is consistent with it playing a role in the organization of sensory axonal projections within the spinal cord and skin
Developmental and Tissue-Specific Regulation of the Murine Cardiac Actin Genein VivoDepends on Distinct Skeletal and Cardiac Muscle-Specific Enhancer Elements in Addition to the Proximal Promoter

AbstractCardiac actin is an early marker of cardiac and skeletal muscle lineages in the mouse. After birth, the gene is down-regulated in skeletal muscle. High-level expression of the murine cardiac actin gene in skeletal myotubesin vitroinvolves distal (−7.8/−7.0 kb) and proximal (−5.4/−3.5 kb) enhancer sequences as well as the proximal promoter (−0.7/+0.1 kb). Transgenic mice carrying annlacZreporter gene under the control of different fragments of the upstream region of the cardiac actin gene were generated. This analysis led to the conclusions that (1) the proximal promoter is a weak but tissue specific elementin vivo,(2) consistent high-level expression in skeletal muscle depends on the presence of at least one of the enhancers, (3) expression in adult cardiac muscle requires a cardiac enhancer located in the (−5.4/−0.7 kb) region, and (4) a construct containing these three elements gives a strong specific expression of the transgene in the heart throughout the life of the animal and in embryonic skeletal muscle. All transgenes tested reproduce the down-regulation observed in adult skeletal muscle for the cardiac actin gene. Nonuniform expression of these transgenes in the heart may mark cardiomyocytes derived from different cardiac progenitors
Proneural and Neurogenic Genes Control Specification and Morphogenesis of Stomatogastric Nerve Cell Precursors inDrosophila

AbstractThe stomatogastric nervous system (SNS) of theDrosophilaembryo develops from a placode which appears in the stomodeal epithelium. Most cells of this placode invaginate as three pouches (the iSNSPs) into the interior of the embryo. After separating from the stomodeum, the SNS pouches transiently form epithelial vesicles and eventually dissociate into solid clusters of cells which migrate on the foregut epithelium and differentiate into the neurons of the SNS. Prior and during iSNSP invagination, two small subpopulations of SNSPs (dSNSPs and tSNSPs) delaminate as individual cells from the SNS placode (Hartensteinet al.,1994). The results presented in this paper show that the neurogenic and proneural genes are expressed and required during all phases of SNS development to control the number, pattern, and structural characteristics of the SNSP subpopulations. First, loss-of-function mutations of the proneural and gain-of-function mutations of the neurogenic genes result in the absence or reduction of delaminating SNSPs; loss of function of neurogenic genes leads to the overproduction of d/tSNSPs and a loss of iSNSPs. Second, both proneural and neurogenic genes are involved in the invagination and dissociation of iSNSPs. Reduction of neurogenic gene function leads to a premature dissociation of iSNSPs; gain of neurogenic gene function blocks invagination and dissociation of these cells. Since all iSNSPs form a homogenous population with regard to their differentiative fate as SNS neurons, these results indicate that lateral inhibition is not a necessary aspect of the developmental process controlled by neurogenic and proneural gene function
Cell Autonomous Expression of Perlecan and Plasticity of Cell Shape in Embryonic Muscle ofCaenorhabditis elegans

AbstractPerlecan, a component of the extracellular matrix (ECM), is essential for myofilament formation and muscle attachment inCaenorhabditis elegans.We show here that perlecan is a product of muscle and that it behaves in a cell autonomous fashion. That is, perlecan expressed in an individual muscle cell does not spread beyond the borders of the ECM underlying that cell. Using a polyclonal antibody that recognizes all isoforms of perlecan, we demonstrate that this protein first appears extracellularly at the comma stage (approx. 350 min) of development. We also show that during morphogenesis muscle cells have a heretofore undescribed plasticity of shape. This ability to regulate cell shape allows cells within a muscle quadrant to compensate for missing cells and to form a functional quadrant. A dramatic example of this morphological flexibility can be observed in animals in which the D blastomere has been removed by laser ablation. Such animals, lacking 20 of the 81 embryonic body wall muscle cells, can survive to become viable adult animals indistinguishable from wildtype animals. This demonstrates that the assembly of an embryo via a stereotypic lineage does not preclude a more general regulation during morphogenesis. It appears that embryos are flexible enough to immediately compensate for drastic alterations in tissue composition, a feature of development that may be of general importance during evolution
orthodenticleIs Required for Photoreceptor Cell Development in theDrosophilaEye

AbstractDrosophilaphotoreceptor cells (R cells) develop from the eye imaginal disc during the third instar larval stage and acquire their adult morphology during pupation. We show thatorthodenticle(otd), a homeobox gene, is required for R-cell morphogenesis during pupation.otdUV-insensitive(otduvi) is a hypomorphic allele ofotdthat only affects R-cell development. The R-cell rhabdomeres are disorganized inotduvi, and there is a disruption of proximal–distal development in the eye. Theotdgenomic structure was determined and resulted in the identification of a deletion in the third intron ofotduvi. Sequences encompassing this deletion are able to direct expression of thelacZreporter gene at all stages of the developing visual system, including the photosensitive cells of Bolwig's organ, the ocelli, and the adult eye. The third intron enhancer is the primary regulatory element controllingotdin the R cells and is not under the control of theglassgene
Hensen's Node from Vitamin A-Deficient Quail Embryo Induces Chick Limb Bud Duplication and Retains Its Normal Asymmetric Expression ofSonic hedgehog(Shh)

AbstractBoth Hensen's node, the organizer center in chick embryo, and exogenous retinoic acid are known to induce limb duplication when grafted or applied to the host chick limb bud. Retinoic acid is known to be present in the node and has been proposed as the putative morphogen for chick limb development. Here, we report that Hensen's node from vitamin A-deficient quail embryo induces limb duplication in the host chick embryo similar to that induced by the node from vitamin A-sufficient control embryos. We also demonstrate that the expression ofSonic hedgehog(Shh), recently shown to be the mediator of polarizing activity in the chick limb bud, is not affected by the endogenous vitamin A status of the embryo. Furthermore, whole-mountin situhybridization revealed asymmetry ofShhexpression in the Hensen's node of both vitamin A-sufficient and -deficient quail embryos. Retinoids were not detectable in the eggs from which vitamin A-deficient embryos were obtained. Extracts from normal embryos induced a level of expression of reporter gene equivalent to the presence of 3.4 pg of active retinoids per embryo, while those from vitamin A-deficient embryos induced a baseline level of reporter gene expression similar to that of the controls. Our studies suggest that endogenous retinoic acid is not involved inShhexpression nor in regulating its asymmetry during normal early avian embryogenesis and support the current view that endogenous retinoic acid may not be a direct morphogen for limb bud duplication
Formation and Maturation of the Calcium Release Apparatus in Developing and Adult Avian Myocardium

AbstractMuscle fibers release large amounts of calcium from an internal compartment, the sarcoplasmic reticulum (SR), during activation. Two proteins are involved in this process and its control: plasma membrane calcium channels, or dihydropyridine receptors (DHPRs), and SR calcium release channels, or ryanodine receptors (RyRs). The two proteins form part of a structural complex, perhaps unique to muscle cells, which allows an interaction between plasma membrane and SR, resulting in calcium release from the latter. The surface–SR interaction is a step in the coupling between electrical events in the plasma membrane and contraction (excitation–contraction coupling). The structural complexes have been called calcium release units. One key to further understanding the control of calcium homeostasis in muscle is knowledge of how DHPRs and RyRs assemble into calcium release units. We have studied the development of avian myocardium, using immunocytochemistry to locate DHPRs and RyRs and electron microscopy to follow the formation of calcium release units containing feet (RyRs) and large membrane particles (presumably DHPRs). We find that the initial step is a docking of SR vesicles to the plasma membrane, followed by the appearance of feet in the junctional gap between SR and plasma membrane. Feet aggregate in ordered arrays, and the arrays increase in size until they fill the entire junctional gap. Clustering of membrane particles, presumably DHPRs, is apparently coupled to clustering of feet, since the two junction components assemble within patches of membrane of approximately equal size and containing an approximately constant ratio of particles to feet. Thus, despite the fact that no evidence exists for a direct interaction between DHPRs and RyRs in cardiac muscle, some mechanism exists to ensure that the two molecules are clustered in proximity to each other and in the appropriate proportion
Skeletal Myogenesis: The Preferred Pathway of Chick Embryo Epiblast Cellsin Vitro

AbstractThe epiblast layer of the chick embryo gives rise to all embryonic tissues.In vitroanalyses were carried out to determine whether epiblast cells could form skeletal muscle prior to entry into the primitive streak. Epiblasts were separated from the mesoderm, hypoblast, and primitive streak, dissociated to produce a single cell suspension, and plated at high density. Myogenesis began on the first day in culture, and by the fifth day most cells had differentiated into skeletal muscle. Some cells differentiated without replicating. MyoD messenger RNA was present in epiblast tissue and translated in practically all cells in culture. Cells from regions of the epiblast which do not form muscle later in the embryo did soin vitro.Epiblasts cultured for 2 days as an intact epithelium, or in the presence of the mesoderm and hypoblast, did not undergo myogenesis. These findings demonstrate that myogenic potential is wide-spread within the primitive streak stage epiblast, and that muscle differentiation, which occurs relatively autonomously in culture, can be prevented by cell and tissue interactions
Unmasking mRNA in Clam Oocytes: Role of Phosphorylation of a 3′ UTR Masking Element-Binding Protein at Fertilization

AbstractDuring meiotic maturation or after fertilization of invertebrate and vertebrate oocytes, many of the quiescent stored mRNAs are recruited into polysomes. In the clam,Spisula solidissima,such masked messages include the abundant mRNAs encoding cyclin A and the small subunit of ribonucleotide reductase. We have previously shown that mRNA-specific unmasking of these two messages can be achievedin vitro,in oocyte cell-free extracts, by the addition of antisense RNAs corresponding to a fairly short (130–140 nucleotides) segment in their cognate 3′ untranslated regions. We postulated that the antisense RNAs prevented the binding of a masking repressor protein (Standartet al.,1990). Here we report UV-crosslinking and gel retardation studies which show that the masking portions of the translationally regulated mRNAs bind an oocyte protein of 82 kDa (p82), which is phosphorylated after fertilization. This modification was accompanied by altered RNP complex formation in gel retardation assays. These changes presumably reflect the activation of translation of the masked mRNAs. The role of p82 phosphorylation in maternal mRNA unmasking was assessed in a novelin vitroactivation system developed from clam oocytes, based upon the natural rise in pH which accompanies fertilization. Concomitant with mRNA unmasking, several kinases, including cdc2 and MAP kinases were activated in this system, as was p82 phosphorylation. Inhibitors of serine/threonine kinases, including 6-DMAP, staurosporine, and H7 inhibited p82 phosphorylation, whereas inhibitors of tyrosine kinases, protein kinase C, cAMP-dependent protein kinase, and p70s6kdid not prevent this modification. A specific inhibitor of cdc2 kinase, p27Kip1, prevented p82 phosphorylation and translational activation, strongly suggesting that p82 modification is required for unmasking
Expression of the Actin Gene Family in Embryos of the Sea UrchinLytechinus pictus

AbstractThe genome of the sea urchinLytechinus pictusincludes genes encoding four cytoskeletal actins LpC1–4 and the muscle actin LpM. Gene-specific probes corresponding to 3′ noncoding termini have been used to characterize their patterns of expression byin situhybridization. The gene encoding LpC1 actin, which is most similar in sequence to theStrongylocentrotus purpuratusCyI actin, has a complex developmental profile of expression. LpC1 transcripts become prominent in the archenteron and secondary mesenchyme cells of embryos, as well as in adult testis and ovary. The LpC2 actin gene is predominantly expressed in aboral ectoderm of embryos, similarly to the pattern of expression of its closest relatives inS. purpuratus,the SpCyIIIa and SpCyIIIb actin genes. The LpC3 actin gene is expressed at low levels in secondary mesenchyme cells. The LpC4 actin gene is expressed in a subset of primary mesenchyme cells which may be actively engaged in skeletogenesis. Transcripts of the LpM gene accumulate in esophageal muscle cells beginning during gastrulation before overt differentiation. Each of theL. pictusactin genes has a distinct pattern of expression, none of which is identical to that of anyS. purpuratusactin gene. These results indicate that the regulation of expression of members of the actin gene family, even those likely to have common ancestors, has diverged as these sea urchin species diverged