bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential binding of gold-labeled zona pellucida glycoproteins mZP2 and mZP3 to mouse sperm membrane compartments
Authors: Mortillo Steven , Wassarman Paul M. 
Published: April 2021

ABSTRACT
Egg zona pellucida glycoproteins mZP3 and mZP2 serve as primary and secondary sperm receptors, respectively, during initial stages of fertilization in mice [Wassarman (1988) A. Rev. Biochem. 57, 415–442]. These receptors interact with complementary egg-binding proteins (EBPs) located on the sperm surface to support speciesspecific gamete adhesion. Results of whole-mount autoradiographic experiments suggest that purified egg mZP3 and mZP2 bind preferentially to acrosome-intact (Al) and acrosome-reacted (AR) sperm heads, respectively [Bleil and Wassarman (1986)J. Cell Biol. 102, 1363–1371]. Here, we used purified egg mZP2, egg mZP3 and fetuin, which were coupled directly to colloidal gold (‘gold-probes’), to examine binding of these glycoproteins to membrane compartments of Al and AR sperm by transmission electron microscopy. mZP3 gold-probes were found associated primarily with plasma membrane overlying the acrosomal and post- acrosomal regions of Al sperm heads. They were also found associated with plasma membrane overlying the post-acrosomal region of AR sperm heads. mZP2 gold- probes were found associated primarily with inner acrosomal membrane of AR sperm heads, although some gold was associated with outer acrosomal membrane of Al sperm that had holes in plasma membrane overlying the acrosome. Fetuin gold-probes, used to assess background levels of binding, were bound at relatively low levels to plasma membrane and inner acrosomal membrane of Al and AR sperm, respectively. None of the gold-probes exhibited significant binding to sperm tails, or to red blood cells and residual bodies present in sperm preparations. These results provide further evidence that mZP2 and mZP3 bind preferentially to heads of AR and Al sperm, respectively. Furthermore, they demonstrate that mZP2 and mZP3 bind preferentially to different sperm membrane compartments and permit quantitative assessment of the distribution and abundance of EBPs on sperm.
Spatiotemporal expression of three gap junction gene products involved in fetomaternai communication during rat pregnancy
Authors: Risek Boris , Gilula Norton B. 
Published: April 2021

ABSTRACT
The expression of three different members of the gap junction multigene family, ax (Cx43), ft (Cx32), and p2 (Cx26), was analysed in the rat implantation chamber (a structural unit containing fetal, extraembryonic and maternal components within the pregnant uterus) during mid-and late stages of gestation as well as in the delivering, post-partum and non-pregnant uterus. A differential, spatiotemporal and cell-type-specific regulation of gap junctional coexpression was observed for Pi and p2 • ″ a ″ epithelia examined (visceral, luminal and glandular), as well as for a, and ft in decidual cells and keratinocytes of the fetal epidermis, aj antigen was detected in the mesometrial stroma, mesometrial myometrium, connective tissue, mesothelia of the amnion and visceral yolk sac and in the allantoic mesodermal layer throughout gestation. In addition, expression of at in the placental basal zone and trophoblast giant cells coincided with the differentiation of these cells, fi expression was observed prominently in the chorionic villi of the placental labyrinth. The presence of Pi and P2 in the visceral epithelium (visceral yolk sac=the primary route for embryonic nourishment prior to the formation of the chorioallantoic placenta) and p2 in the chorionic villi (placental barrier=the major fetomaternai exchange route) suggests that gap junctions have an important role in fetomaternai communication.
Expression of syndecan, a putative low affinity fibroblast growth factor receptor, in the early mouse embryo
Authors: Sutherland A. E. , Sanderson R. D. , Mayes M. , Seibert M. , Calarco P. G. , Damsky C. H. , Bernfield M. 
Published: April 2021

Summary
Syndecan is an integral membrane proteoglycan that binds cells to several interstitial extracellular matrix components and binds to basic fibroblast growth factor (bFGF) thus promoting bFGF association with its high- affinity receptor. We find that syndecan expression undergoes striking spatial and temporal changes during the period from the early cleavage through the late gastrula stages in the mouse embryo. Syndecan is detected initially at the 4-cell stage. Between the 4-cell and late morula stages, syndecan is present intracellularly and on the external surfaces of the blastomeres but is absent from regions of cell – cell contact. At the blastocyst stage, syndecan is first detected at cell – cell boundaries throughout the embryo and then, at the time of endoderm segregation, becomes restricted to the first site of matrix accumulation within the embryo, the interface between the primitive ectoderm and primitive endoderm. During gastrulation, syndecan is distributed uniformly on the basolateral cell surfaces of the embryonic ectoderm and definitive embryonic endoderm, but is expressed with an anteroposterior asymmetry on the surface of embryonic mesoderm cells, suggesting that it contributes to the process of mesoderm specification. In the extraembryonic region, syndecan is not detectable on most cells of the central core of the ectopiacental cone, but is strongly expressed by cells undergoing trophoblast giant cell differentiation and remains prominent on differentiated giant cells, suggesting a role in placental development. Immunoprecipitation studies indicate that the size of the syndecan core protein, although larger than that found in adult tissues (75 versus 69×l03Mr), does not change during periimplantation development. The size distribution of the intact proteoglycan does change, however, indicating developmental alterations in its glycosaminoglycan composition. These results indicate potential roles for syndecan in epithelial organization of the embryonic ectoderm, in differential axial patterning of the embryonic mesoderm and in trophoblast giant cell function.
Abbreviations: DGD, diethylene glycol distearate; bFGF, basic fibroblast growth factor; GAG, glycosaminoglycan; mAb, monoclonal antibody; PEG, polyethylene glycol.
Clonal analysis of astrocyte diversity in neonatal rat spinal cord cultures
Authors: Miller Robert H. , Szigeti Vilma 
Published: April 2021

Summary
Within the mammalian CNS, astrocytes appear to be a heterogeneous class of cells. To assay the number of distinct types of astrocytes in the rat spinal cord, cell lineage and phenotypic analyses were carried out on cultures from newborn rat spinal cord and five distinct types of astrocytes were observed. Proliferating precur- sors for each class of astrocyte were isolated by low density culture and shown to give rise to 5 distinct and morphologically homogeneous clusters of GFAP+ astro- cytes. Immunocytochemical analysis with antibodies A2B5 and Ran-2, which identify different glial lineages in optic nerve cultures, demonstrated that many clusters included both A2B5+ and A2B5− cells. Similarly, many clusters also possessed a mixture of Ran-2 + and Ran-2− cells, suggesting that in spinal cord cultures, in contrast to optic nerve cultures, expression of these antigens is regulated by individual cells rather than by cell lineage.
Single-cell cloning studies, revealed that the abun- dance and proliferative capacity of individual astrocyte precursors differed depending on the type of astrocyte. To assay the effects of a complex cellular environment on the composition of astrocyte clones, lineage analysis was performed in complete spinal cord cultures using a replication deficient retrovirus. Although similar mor- phologically homogeneous clones of cells to those seen with single-cell clones were observed, the proliferative capacity and relative abundance of the distinct astrocyte precursors differed from that seen in single-cell cloning studies. Together these observations suggest that in spinal cord, gliogenesis is considerably more complex than in the optic nerve and that cultures of newborn rat spinal cord contain multiple, distinct populations of astrocytes.
Development of the indirect flight muscles of Drosophila
Authors: Fernandes Joyce , Bate Michael , Vijayraghavan K. 
Published: April 2021

ABSTRACT
We have followed the pupal development of the indirect flight muscles (IFMs) of Drosophila melanogaster. At the onset of metamorphosis larval muscles start to histolyze, with the exception of a specific set of thoracic muscles. Myoblasts surround these persisting larval muscles and begin the formation of one group of adult indirect flight muscles, the dorsal longitudinal muscles. We show that the other group of indirect flight muscles, the dorsoventral muscles, develops simultaneously but without the use of larval templates. By morphological criteria and by patterns of specific gene expression, our experiments define events in IFM development.
Elements of the fruitless locus regulate development of the muscle of Lawrence, a male-specific structure in the abdomen of Drosophila melanogaster adults
Authors: Gailey Donald A. , Taylor Barbara J. , Hall Jeffrey C. 
Published: April 2021

ABSTRACT
A genetically defined element of the fruitless (fru) locus in Drosophila melanogaster regulates the development of a male-specific muscle spanning the fifth abdominal segment in adult males, the ‘muscle of Lawrence’ (MOL). The region is defined by two cytological deletions, each with a breakpoint that co-maps with previously described mutant courtship phenotypes at cytogenetic interval 91B on the third chromosome. Flies that carry both of these deletions are viable, and males express abnormalities of courtship similar to those caused by the fru inversion breakpoint at 91B. In addition, these double-deletion males show the complete absence of the MOL, suggesting that they have little or no gene expression of a postulated MOL determinant; the musculature in the fifth abdominal segment of these mutants to indistinguishable from that of a normal female. Other mutant combinations that produce fruitless courtship phenotypes -including deletion and inversion breakpoints, and a marked transposon inserted at 91B -produce intermediate forms of the MOL. A new genetic variant, induced by imprecise excision of the marked transposon, is homozygous lethal and disrupts fru functions related to courtship and the MOL. The MOL is shown to be dispensable for fertility and is therefore not the causative factor of fru-induced behavioral sterility. These genetic variants and their phenotypic results are discussed with regard to a model for the organization of the fru locus.
Developmental changes in the subcellular distribution of the 43K (v1) polypeptides in Torpedo marmorata electrocyte: support for a role in acetylcholine receptor stabilization
Authors: Nghiêm Hoàng-Oanh , Hill Joseph , Changeux Jean-Pierre 
Published: April 2021

ABSTRACT
Analysis of the relative amounts of the acetylcholine receptors (AChR) and of the 43K protein present in the membrane of developing electrocyte shows that massive accumulation of 43K protein is not required for induction of early AChR clustering. Furthermore, we demonstrate the existence of cytosol- and membrane-associated 43K polypeptide pools in Torpedo electrocyte. Epitope analysis shows that both pools of 43K protein are related to the long mRNA transcript and share similar antigenic determinants distributed throughout the protein sequence. Their partition between the cytosol and membrane fractions abruptly increases in favor of the membrane during the postsynaptic maturation phase of development, supporting a role for 43K protein in the stabilization and maintenance of the postsynaptic domain.
Avian neural crest cell attachment to laminin: involvement of divalent cation dependent and independent integrins
Authors: Lallier Thomas , Bronner-Fraser Marianne 
Published: April 2021

ABSTRACT
The mechanisms of neural crest cell interaction with laminin were explored using a quantitative cell attachment assay. With increasing substratum concentrations, an increasing percentage of neural crest cells adhere to laminin. Cell adhesion at all substratum concentrations was inhibited by the CSAT antibody, which recognizes the chick β1, subunit of integrin, suggesting that β1integrins mediate neural crest cell interactions with laminin. The HNK-1 antibody, which recognizes a carbohydrate epitope, inhibited neural crest cell attachment to laminin at low coating concentrations (&gt;1 μgml−1; Low-LM), but not at high coating concentration of laminin (10 μgml−1; High-LM). Attachment to Low-LM occurred in the absence of divalent cations, whereas attachment to High-LM required &gt;0.1 mM Ca2+ or Mn2+. Neural crest cell adherence to the E8 fragment of laminin, derived from its long arm, was similar to that on intact laminin at high and low coating concentrations, suggesting that this fragment contains the neural crest cell binding site(s). The HNK-1 antibody recognizes a protein of 165 000 Mr which is also found in immunoprecipitates using antibodies against the β1subunit of integrin and is likely to be an integrin a subunit or an integrin-associated protein. Our results suggest that the HNK-1 epitope on neural crest cells is present on or associated with a novel or differentially glycosylated form of β1-integrin, which recognizes laminin in the apparent absence of divalent cations. We conclude that neural crest cells have at least two functionally independent means of attachment to laminin which are revealed at different substratum concentrations and/or conformations of laminin.
The murine H19 gene is activated during embryonic stem cell differentiation in vitro and at the time of implantation in the developing embryo
Authors: Poirier Francoise , Chan C.-T. J. , Timmons Paula M. , Robertson Elizabeth J. , Evans Martin J. , Rigby Peter W. J. 
Published: April 2021

ABSTRACT
The differentiation in vitro of murine embryonic stem cells to embryoid bodies mimicks events that occur in vivo shortly before and after embryonic implantation. We have used this system, together with differential cDNA cloning, to identify genes the expression of which is regulated during early embryogenesis. Here we describe the isolation of several such cDNA clones, one of which corresponds to the gene H19. This gene is activated in extraembryonic cell types at the time of implantation, suggesting that it may play a role at this stage of development, and is subsequently expressed in all of the cells of the mid-gestation embryo with the striking exception of most of those of the developing central and peripheral nervous systems. After birth, expression of this gene ceases or is dramatically reduced in all tissues.
A target-derived chemoattractant controls the development of the corticopontine projection by a novel mechanism of axon targeting
Authors: O’leary D. D. M. , Heffner C. D. , Kutka L. , López-Mascaraque L. , Missias A. , Reinoso B. S. 
Published: April 2021

Abstract
Here, we review our studies in rats of target recognition by developing cortical axons focusing on their innervation of the basilar pons, a major hindbrain target. The corticopontine projection develops by a ‘delayed interstitial budding’ of collaterals from layer 5 corticospinal axons, rather than by a direct ingrowth of primary axons or by bifurcation of the growth cone. Branches form de novo from the axon cylinder in the pathway overlying the basilar pons and extend directly into it. Cocultures of cortex and basilar pons in 3-dimensional collagen matrices show that a diffusible chemotropic signal released by the basilar pons directs the growth of collateral branches from layer 5 axons in a target and neuron specific manner. ‘Delayed’ co-cultures suggest that a diffusible, pontine-derived signal also initiates the selective branching of layer 5 axons. In vivo experiments support this chemotropic mechanism. First, corticospinal axons form collateral branches at novel locations directly over ectopic aggregations of basilar pontine neurons induced by X-irradiation; no branches form at positions that would normally overlie the appropriate region of basilar pons which is absent because of the X-irradiation. Thus, the basilar pons, rather than local cues in the axon pathway, appears to control the location of corticospinal axon branching. Second, in a series of experiments in which different subsets of corticospinal axons are prevented from innervating the basilar pons, remaining corticospinal axons extend collaterals in a directed manner to regions of the basilar pons deprived of cortical input, a behavior consistent with a response to a diffusible chemoattractant emanating from these regions. In conclusion, our findings suggest that a diffusible, target-derived chemotropic molecule(s) underlies target recognition in this developing system by initiating the formation and directing the growth of pontine collateral branches of primary layer 5 corticospinal axons.
Motoneuronal development in the embryonic zebrafish
Authors: Eisen Judith S. 
Published: April 2021

Abstract
To learn how neurons find their appropriate targets, we have studied two populations of motoneurons in the embryonic zebrafish: primary motoneurons, individually identified cells whose growth cones pioneer the first nerve pathways in the muscle, and secondary motoneurons, cells which develop later and whose growth cones apparently extend along the axons of the primary motoneurons. Transplantation studies of single, identified primary motoneurons suggest that commitment of these cells to innervate their cell-specific muscle territories may be a multistep process in which they are first committed to be motoneurons and are later committed to extend axons along specific pathways. Ablation studies suggest that interactions among the primary motoneurons are unlikely to be necessary for proper pathfinding or commitment. However, interactions with the primary motoneurons may be important for proper development of the secondary motoneurons.
The developmental fate of the cephalic mesoderm in quail-chick chimeras
Authors: Couly Gérard F. , Coltey Pierre M. , Le Douarin Nicole M. 
Published: April 2021

ABSTRACT
The developmental fate of the cephalic paraxial and prechordal mesoderm at the late neorula stage (3- somite) in the avian embryo has been investigated by using the isotopic, isochronic substitution technique between quail and chick embryos. The territories involved in the operation were especially tiny and the size of the transplants was of about 150 by 50 to 60 μm. At that stage, the neural crest cells have not yet started migrating and the fate of mesodermal cells exclusively was under scrutiny. The prechordal mesoderm was found to give rise to the following ocular muscles: musculus rectus ventraUs and medialis and musculus oblicus verttralis. The paraxial mesoderm was separated in two longitudinal bands: one median, lying upon the cephalic vesicles (median paraxial mesoderm - MPM); one lateral, lying upon the foregut (lateral paraxial mesoderm - LPM). The former yields the three other ocular muscles, contributes to mesencephalic meninges and has essentially skeletogenic potencies. It contributes to the corpus sphenoid bone, the orbitosphenoid bone and the otic capsules; the rest of the facial skeleton is of neural crest origin. At 3-somite stage, MPM is represented by a few cells only. The LPM is more abundant at that stage and has essentially myogenic potencies with also some contribution to connective tissue. However, most of the connective cells associated with the facial and hypobranchial muscles are of neural crest origin.
The more important result of this work was to show that the cephalic mesoderm does not form dermis. This function is taken over by neural crest cells, which form both the skeleton and dermis of the face. If one draws a parallel between the so-called “somitomeres” of the head and the trunk somites, it appears that skeletogenic potencies are reduced in the former, which in constrast have kept their myogenic capacities, whilst the forma­tion of skeleton and dermis has been essentially taken over by the neural crest in the course of evolution of the vertebrate head.
Induction and repression of mammalian achaete-scute homologue (MASH) gene expression during neuronal differentiation of P19 embryonal carcinoma cells
Authors: Johnson Jane E. , Zimmerman Kathryn , Saito Tetsuichiro , Anderson David J. 
Published: April 2021

ABSTRACT
MASH1 and MASH2, mammalian homologues of the Drosophila neural determination genes achaete-scute, are members of the basic helix-loop-helix (bHLH) family of transcription factors. We show here that murine P19 embryonal carcinoma cells can be used as a model system to study the regulation and function of these genes. MASHl and MASHl display complementary patterns of expression during the retinoic-acid-induced neuronal differentiation of P19 cells. MASHl mRNA is undetectable in undifferentiated P19 cells but is induced to high levels by retinoic acid coincident with neuronal differentiation. In contrast, MASHl mRNA is expressed in undifferentiated P19 cells and is repressed by retinoic acid treatment. These complementary expression patterns suggest distinct functions for MASHl and MASH2 in development, despite their sequence homology. In retinoic-acid-treated P19 cells, MASHl protein expression precedes and then overlaps expression of neuronal markers. However, MASHl is expressed by a smaller proportion of cells than expresses such markers.
MASHl immunoreactivity is not detected in differentiated cells displaying a neuronal morphology, suggesting that its expression is transient. These features of MASHl expression are similar to those observed in vivo, and suggest that P19 cells represent a good model system in which to study the regulation of this gene. Forced expression of MASHl was achieved in undifferentiated P19 cells by transfection of a cDNA expression construct. The transfected cells expressing exogenous MASHl protein contained E-box-binding activity that could be supershifted by an anti-MASHl antibody, but exhibited no detectable phenotypic changes. Thus, unlike myogenic bHLH genes, such as MyoD, which are sufficient to induce muscle differentiation, expression of MASHl appears insufficient to promote neurogenesis.
Metalloproteinases mediate extracellular matrix degradation by cells from mouse blastocyst outgrowths
Authors: Behrendtsen Ole , Alexander Caroline M. , Werb Zena 
Published: April 2021

ABSTRACT
The maintenance and developmental remodeling of extracellular matrix is crucial to such processes as uterine implantation and the cell migratory events of morphogenesis. When mouse blastocysts are placed in culture they adhere to extracellular matrix, and trophoblast giant cells migrate out onto the matrix and degrade it. The secretion of functional proteinases by developing mouse embryos increases dramatically at the time of implantation. By zymography we identified the major secreted gelatin-degrading proteinase, also known as type IV collagenase, as one migrating at 92 × 103Mr. Several casein-degrading proteinases were also secreted. The tissue inhibitor of metalloproteinases (TIMP) inhibited all of the embryo-derived proteinases detected by gelatin gel zymography, indicating that they are metalloproteinases, whereas TIMP did not inhibit all of the caseinases. Urokinase was also secreted. Addition of TIMP at 5·500 nM effectively inhibited the degradation of matrix by the trophoblast outgrowths. Blocking antibodies directed against 92 × 103Mr gelatinase abolished matrix degradation by the trophoblast cells. These observations suggest that several metalloproteinases are regulated in early development and that 92 × 103Mr gelatinase, in particular, has a rate-limiting function in degradation of the maternal extracellular matrix by trophoblast cells.