bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the notochord on proliferation and differentiation in the neural tube of the chick embryo
Authors: van Straaten H. W. M. , Hekking J. W. M. , Beursgens J. P. W. M. , Terwindt-Rouwenhorst E. , Drukker J. 
Published: April 2021

ABSTRACT
After implantation of a notochord fragment lateral to the neural tube in a 2-day chick embryo, at 4 days the ipsilateral neural tube half was increased in size and axons left the neural tube in a broad dorsoventral area (van Straaten et al. 1985). This enlargement appears to coincide with an increased area of AChE-positive basal plate neuroblasts, as determined with scan-cytophotometry. The effect was ipsilateral and local: clear effects were seen only when the implant was localized less than 80 μm from the neural tube and over 120 μm from the ventral notochord. In order to investigate the expected enhancement of proliferation, the mitotic density and the number of cells at the site of the implant at 3 days was determined and the mitotic index calculated. All three parameters showed an increase. It was coneluded that the cell cycle was shorter in the implant area relative to the control area, at least during the third day. At 4 days the number of cells was still increased, predominantly in the basal plate. It appeared that the numerical increase was for the larger part due to neuroblasts. The synergism of two notochords thus resulted in enhancement of proliferation and differentiation in the neural tube. It is suggested that the notochord merely regulates and arranges the surrounding sclerenchymal cells, which are the effective cells in the regulation of neural tube development.
Analysis of function of the pair-rule genes hairy, even-skipped and fushi tarazu in mosaic Drosophiia embryos
Authors: Lawrence Peter A. , Johnston Paul 
Published: April 2021

ABSTRACT
We report the first attempt of its kind to study genetic interactions using young Drosophila embryos that are mosaic for wildtype and mutant cells. Using nuclear transplantation we make mosaic embryos in which a patch of cells lacks a particular segmentation gene, A. With antibodies, we than look at the expression of another gene that is known to be downstream of gene A, with respect to the cells in the patch. We have examples of patches of hairy cells (where we monitor the effect on fushi tarazu (ftz) expression), even-skipped (monitoring ftz) and ftz (monitoring engrailed and Ultrabithorax).
Our main finding is that the dependence of engrailed expression on the ftz gene is strictly cell-autonomous. This result goes some way towards explaining the dependence of Ultrabithorax expression on ftz, a dependence we show to be locally cell-autonomous within parts of parasegments 6 and 8 but non autonomous within parasegment 7.
Molecular approaches to vertebrate limb morphogenesis
Authors: Smith Susan M. , Pang Kevin , Sundin Olof , Wedden Sarah E. , Thaller Christina , Eichele Gregor 
Published: April 2021

ABSTRACT
It has long been proposed that concentration gradients of morphogens provide cues to specify cell fate in embryonic fields. Recent work jn a variety of vertebrate systems give bona fide evidence that retinoic acid, the biologically active form of vitamin A, is a candidate for such a morphogen. In the developing chick wing, for example, locally applied retinoic acid triggers striking changes in the pattern along the anteroposterior axis. Instead of giving rise to a wing with the normal 234 digit pattern, wing buds treated with retinoic acid develop a 432234 mirror-image symmetrical digit pattern.
For this review, we focus on three aspects of limb morphogenesis. (1) We summarize the experimental evidence supporting the notion that retinoic acid is a candidate morphogen. (2) Limb buds contain high levels of cellular retinoic-acid-binding protein (CRABP). Using order of magnitude calculations, we evaluate how the concentration of CRABP might affect the occupancy state of the retinoic acid receptor. (3) We discuss the spatio-temporal expression pattern of homeobox-con-taining genes in the developing limb and speculate about the possibility that retinoic acid influences the pattern of expression of homeobox genes.
Genetics of intercellular signalling in C. elegans
Authors: Austin Judith , Maine Eleanor M. , Kimble Judith 
Published: April 2021

ABSTRACT
Cell-cell interactions play a significant role in controlling cell fate during development of the nematode Caenorhabditis elegans. It has been found that two genes, glp-1 and lin-12, are required for many of these decisions, glp-1 is required for induction of mitotic proliferation in the germline by the somatic distal tip cell and for induction of the anterior pharynx early in embryogenesis, lin-12 is required for the interactions between cells of equivalent developmental potential, which allow them to take on different fates. Comparison of these two genes on a molecular level indicates that they are similar in sequence and organization, suggesting that the mechanisms of these two different sets of cell-cell interactions are similar.
Role of the neuropeptide head activator for growth and development in hydra and mammals
Authors: Schaller H. Chica , Hoffmeister Sabine A. H. , Dübel Stefan 
Published: April 2021

ABSTRACT
In hydra, HA is produced by nerve cells and released into the intercellular space bound to large-molecular-weight carrier(s). By additional interaction with extracellular matrix components and selfinactivation by dimérisation, a local action is ensured. HA acts as a mitogen on all dividing cell types in hydra forcing them to pass through G2, divide, and either start a new round of cell division or terminally differentiate. In addition, HA is required for head-specific determination and differentiation processes. To become a head-specific nerve cell, for example, an interstitial stem cell requires HA in early S-phase to become determined to the nerve cell pathway, in late G2 to progress through mitosis, and/or in Gj to differentiate to a head-, and not to a foot-, specific nerve cell. HA (with identical amino acid sequence) occurs in other animals including mammals. In mammals, it is produced by nerve or endocrine cells and it probably acts, as in hydra, on nerve-precursor cells. On the neural cell line NH15-CA2 and on the pituitary cell line AtT20, HA acts as mitogen by stimulating cells arrested in G2 to enter mitosis. The presence of HA early in neural development and in abnormal neural development, such as in brain and neuroendocrine tumors, are consistent with a function in growth control for HA in mammals.
Profile of a mammalian sperm receptor1,2
Authors: Wassarman Paul M. 
Published: April 2021

ABSTRACT
Complementary molecules on the surface of eggs and sperm are responsible for species-specific interactions between gametes during fertilization in both plants and animals. In this essay, several aspects of current research on the mouse egg receptor for sperm, a zona pellucida glycoprotein called ZP3, are addressed. These include the structure, synthesis, and functions of the sperm receptor during oogenesis and fertilization in mice. Several conclusions are drawn from available information. These include (/) ZP3 is a member of a unique class of glycoproteins found exclusively in the extracellular coat (zona pellucida) of mammalian eggs. (If) ZP3 gene expression is an example of oocyte-specific and, therefore, sex-specific gene expression during mammalian development. (Ill) ZP3 is a structural glycoprotein Involved in assembly of the egg extracellular coat during mammalian oogenesis. (ZV) ZP3 is a sperm receptor involved in carbohydrate-mediated gamete recognition and adhesion during mammalian fertilization. (V) ZP3 is an inducer of sperm exocytosis (acrosome reaction) during mammalian fertilization. (Vf) ZP3 participates in the secondary block to polyspermy following fertilization in mammals. (VII) The extracellular coat of other mammalian eggs contains a glycoprotein that is functionally analogous to mouse ZP3. The unique nature, highly restricted expression, and multiple roles of ZP3 during mammalian development make this glycoprotein a particularly attractive subject for investigation at both the cellular and molecular levels.
Glue protein genes in Drosophila virilis: their organization, developmental control of transcription and specific mRNA degradation
Authors: Swida Ulrike , Lucka Lothar , Kress Horst 
Published: April 2021

Abstract
The gene Lgp-1, which is localized in the intermoult puff 16A of D. virilis polytene chromosomes, encodes the major larval glue protein lgp-1. The gene consists of two exons interrupted by a short intron. In the 5′ flanking region of Lgp-1, we find putative ecdysone receptor binding sites and two proximal conserved sequence motifs which are possibly involved in gene regulation. The amino acid sequence deduced from the DNA sequence reveals a relationship to the 68C glue protein family of D. melanogaster. The size of the Lgp-1 transcripts decreases in late third instar larvae concomitantly with their disappearance. This is caused by deadenylation followed by distinct nucleolytic attacks in the 3′untranslated region. Preliminary data suggest the presence of another glue protein gene in the 16A puff region which is related to the Lgp-1 gene.
A two-step model for the localization of maternal mRNA in Xenopus oocytes: Involvement of microtubules and microfilaments in the translocation and anchoring of Vg1 mRNA
Authors: Yisraeli Joel K. , Sokol Sergei , Melton D. A. 
Published: April 2021

Abstract
In an effort to understand how polarity is established in Xenopus oocytes, we have analyzed the process of localization of the maternal mRNA, vg1. In fully grown oocytes, vg1 mRNA is tightly localized at the vegetal cortex. Biochemical fractionation shows that the mRNA is preferentially associated with a detergent-insoluble subcellular fraction. The use of cytoskeletal inhibitors suggests that (1) microtubules are involved in the translocation of the message to the vegetal hemisphere and (2) microfilaments are important for the anchoring of the message at the cortex. Furthermore, immunohistochemistry reveals that a cytoplasmic microtubule array exists during translocation. These results suggest a role for the cytoskeleton in localizing information in the oocyte.
Genital ridges exert long-range effects on mouse primordial germ cell numbers and direction of migration in culture
Authors: Godin Isabelle , Wylie Christopher , Heasman Janet 
Published: April 2021

Abstract
The functional gametes of all vertebrates first arise in the early embryo as a migratory population of cells, the primordial germ cells (PGCs). These migrate to, and colonise, the genital ridges (GR) during the early organogenesis period, giving rise to the complete differentiating gonad. PGCs first become visible by alkaline phosphatase staining in the root of the developing allantois at 8.5 days post coltum (dpc). At 9.5 dpc they are found in the wall of the hind-gut and, during the following three days, they migrate along the hind-gut mesentery to the dorsal body wall, and then to the genital ridges. By 12.5 dpc, the great majority of PGCs have colonised the genital ridges. During this period the number of PGCs increases from less than 100 to approximately 4000.
In a previous paper (Donovan et al. 1986), we showed that 10.5 dpc PGCs can be explanted from the hind-gut mesentery, and will spread and migrate on feeder cell layers. We showed also that the intrinsic ability of PGCs to spread and migrate changes as they colonise the genital ridges. In this paper, we examine extrinsic factors that control PGC behaviour in vitro. Using PGCs taken from 8.5 dpc embryos, at the beginning of their migratory phase, we show that culture medium conditioned by 10.5 dpc genital ridges causes an increase in the number of PGCs in these cultures. We also show that PGCs migrate towards 10.5 dpc genital ridges in preference to other explanted organs.
These experiments show that genital ridges exert long-range effects on the migrating population of PGCs. They also suggest that tropic factors released from the genital ridges play a role in PGC guidance.
Requirements for integrins during Drosophila development
Authors: Zusman Susan , Patel-King Ramila S. , Ffrench-Constant Charles , Hynes Richard O. 
Published: April 2021

Abstract
The common subunit of the PS antigens of Drosophila is homologous with vertebrate integrins and is encoded by the lethal(1)myospheroid gene. We have generated flies mosaic for wild-type and mutant alleles of lethal-(1) myospheroid using adult gynandromorphs and radiation-induced somatic crossing over. The defects observed in the gynandromorphs demonstrate widespread requirements for PS integrins during development especially in ventrally derived structures, which also show strong expression of PS β integrin. Smaller lethal(1)myo-spheroid clones induced during larval development result in blister and vein defects in the wings and aberrant development of photoreceptor cells, demonstrating roles for PS integrins during development of both wings and eyes. PS integrins are required for the close apposition of the dorsal and ventral wing epithelia and for the proper arrangement of photoreceptor cells. However, many other adhesive and morphogenetic processes proceed normally in the absence of integrins containing the fl subunit encoded by lethal(1)myospheroid.
Position-specific activity of the Hox1.1 promoter in transgenic mice
Authors: Püschel Andreas W. , Balling Rudi , Gruss Peter 
Published: April 2021

Abstract
During development, positional values have to be assigned to groups of cells. The murine Hox genes are a class of genes that are predicted to be involved at some stage in this process. During embryogenesis they are expressed in distinct overlapping region- and stagespecific patterns and therefore must be regulated in response to positional information. In this study, we have analysed the activity of Hox1.1 promoter sequences in transgenic mice. The use of lacZ as a marker allows a detailed analysis of expression at the single cell level during early embryonic development. We show that 3.6 kbp of promoter and 1.7 kbp of 3’ sequences provide sufficient regulatory information to express a transgene in a spatial and temporal manner indistinguishable from the endogenous Hox1.1 gene during the period of development when Hox1.1 expression Is established. The activation occurs in a strict order in specific ectodermal and mesodermal domains. Within each of these domains the transgene is activated over a period of four hours apparently randomly in single cells. In a following second period, Hox1.1 and transgene expression patterns diverge. In this period, transgene expression persists in many mesodermally derived cells that do not express Hox1.1 indicating the absence of a negative regulatory element in the transgene. The anterior boundary of transgene expression is identical to that of Hox1.1. However, no posterior boundary of transgene expression is set, suggesting that a separate element absent from the transgene specifies this boundary.
TGF beta in murine morphogenetic processes: the early embryo and cardiogenesis
Authors: Akhurst Rosemary J. , Lehnert Sigrid A. , Faissner Andreas , Duffie Elizabeth 
Published: April 2021

Abstract
The tissue distribution of TGF beta-1 RNA was examined within whole mouse embryos from implantation to 10.5 days gestational age and, in the developing heart, up to 8 days postpartum. The earliest high level expression of TGF beta-1 RNA is at 7.0 days postcoUum ip.c.) in the cardiac mesoderm. At 8.0 days gestational age, cardiac TGF beta-1 RNA expression is limited to endocardia! cells. By 9.5 days p.c, this expression pattern becomes regionalised to those cells that overlie cardiac cushion tissue. High TGF beta-1 RNA levels continue to persist in endothelial cells of the heart valves until approximately one week postpartum.
The TGF beta-1 RNA distribution was compared with the extracellular distributions of polypeptides for TGF beta and Jl/tenascin. As previously reported, endothelial expression of TGF beta-1 RNA is correlated with mesenchymal expression of TGF beta polypeptide, suggesting a paracrine mode of action for this growth factor in cardiac development. Minor discrepancies in the distributions of TGF beta-1 RNA and the extracellular form of the TGF beta polypeptide suggest that translational or post-translational control of protein levels occurs and/or the possibility that the antibody used may also recognise other members of the TGF beta polypeptide family.
A correlation between endothelial TGF beta-1 expression and distribution of Jl/tenascin in the mesenchyme gives further support to the proposition that the biological effects of TGF beta-1 may, in part, be mediated by Jl/tenascin.
Regulation of fission yeast mating-type interconversion by chromosome imprinting
Authors: Klar Amar J. S. 
Published: April 2021

ABSTRACT
Mating types of the fission yeast Schizosaccharomyces pombe interchange nonrandomly in a cell lineage so that only one cell among four granddaughters of a cell ever switches, and the sister of the newly switched cell switches efficiently in consecutive cell divisions, thereby producing chains of recurrent switching. The programme of cellular differentiation is mediated by inheritance of parental DNA chains at the mating type locus (matl) by progeny cells. This review summarizes recent results suggesting that two types of imprinting events at the matl locus are required to generate the specific pattern of switching in a cell lineage. One of those is a site- and strand-specific event that is required before the mat1 locus can be cleaved in vivo. The other is a double-stranded break at matl that is healed by gene conversion in the progeny cells resulting in switching the matl locus.
Gametic imprinting in maize in relation to the angiosperm life cycle
Authors: Kermicle Jerry L. , Alleman Mary 
Published: April 2021

ABSTRACT
Differences in the activity of maternally and paternally derived genomes in maize endosperm have been observed at three levels of genetic manipulation. When the balance of entire chromosome sets departs from the standard ratio of two of maternal origin to one of paternal origin, development is impaired, often leading to seed failure. At the level of individual chromosomes, absence of a paternal representative for 8 of the 19 chromosome arms tested causes a marked reduction in kernel size. Replacement of the missing arms by ones of maternal origin does not complement this defect. At the gene level, some alleles of R confer solid coloration on the aleurone layer when transmitted maternally but patchy coloration (mottled) when transmitted via pollen. In contrast with the endosperm, no effect of parentage on R phenotype has been detected in embryonic and seedling tissues. Furthermore, gynogenetic and androgenetic haploid plants are viable in maize and are similar in appearance. The detection of parental effects in the endosperm, but not the embryo, points to the few cell divisions of the gametophytes as a critical stage in imprinting. Chromosomally based epigenetic variation originating at this stage would be reflected as imprinting effects. A separate fertilization establishes a line of genetic descent in the embryo that appears to be relatively free of imprinted genes.
Fusion between myoblasts and adult muscle fibers promotes remodeling of fibers into myotubes in vitro
Authors: Hinterberger Timothy J. , Barald Kate F. 
Published: April 2021

ABSTRACT
Muscle satellite cells are residual embryonic myoblast precursors responsible for muscle growth and regeneration. In order to examine the role of satellite cells in the initial events of muscle regeneration, we placed individual mature rat muscle fibers in vitro along with their satellite cells. When the satellite cells were allowed to proliferate, they produced populations of myoblasts that fused together to form myotubes on the laminin substrate. These myoblasts and myotubes also fused with the adult fibers. When they did so, the fibers lost their adult morphology, and by 8 days in vitro, essentially all of them were remodeled into structures resembling embryonic myotubes. However, when proliferating satellite cells were eliminated by exposure to cytosine arabinoside (araC), the vast majority of fibers retained their adult shape. Addition of C2C12 cells (a myoblast line derived from adult mouse satellite cells) to araC-treated fiber cultures resulted in their fusion with the rat muscle fibers and restored the ability of the fibers to remodel, whereas addition of either a fibroblast cell line or a transformed, non-fusing variant of C2C12 cells, or addition of conditioned medium from C2C12 cells, failed to do so. These results imply that myoblast fusion is responsible for triggering adult fiber remodeling in vitro.
Expression of J1 / ten asci n in the crypt-villus unit of adult mouse small intestine: implications for its role in epithelial cell shedding
Authors: Probstmeier Rainer , Martini Rudolf , Schachner Melitta 
Published: April 2021

ABSTRACT
The localization of the extracellular matrix recognition molecule J1/tenascin was investigated in the cryptvillus unit of the adult mouse ileum by immunoelectron microscopic techniques. In the villus region, J1/tenascin was detected strongly in the extracellular matrix (ECM) between fibroblasts of the lamina propria. It was generally absent in the ECM at the interface between sub-epithelial fibroblasts and intestinal epithelium, except for some restricted areas along the epithelial basal lamina of villi, but not of crypts. These restricted areas corresponded approximately to the basal part of one epithelial cell. In J1/tenascin-positive areas, epithelial cells contacted the basal lamina with numerous microvillus-like processes, whereas in J1/tenascin-negative areas the basal surface membranes of epithelial cells contacted their basal lamina in a smooth and continuous apposition. In order to characterize the functional role of J1/tenascin in the interaction between epithelial cells and ECM, the intestinal epithelial cell line HT-29 was tested for its ability to adhere to different ECM components. Cells adhered to substratum-immobilized fi bronectin, laminin and collagen types I to IV, but not to J1/tenascin. When laminin or collagen types I to IV were mixed with J1/tenascin, cell adhesion was as effective as without J1/tenascin. However, adhesion was completely abolished when cells were offered a mixture of fibronectin and J1/tenascin as substratum. The ability of J1/tenascin to reduce the adhesion of intestinal epithelial cells to their fibronectin-containing basal lamina suggests that J1/tenascin may be involved in the process of physiological cell shedding from the villus.
Guidance of commissural growth cones at the floor plate in embryonic rat spinal cord
Authors: Bovolenta Paola , Dodd Jane 
Published: April 2021

ABSTRACT
The floor plate of the embryonic rat spinal cord has been proposed to act as an intermediate target that plays a role in the pattern of extension of commissural axons. To begin to examine the role of the floor plate in axon guidance at the midline, we have studied the precision of the commissural axon projection to and across the floor plate during development. To delineate the pathway, the fluorescent carbocyanine dye, Di-I, has been used as a probe. We show that commissural axons traverse the floor plate and turn rostrally at its contralateral border with remarkable precision. Axons were not observed to turn ipsilaterally and turned only upon reaching the contralateral edge of the floor plate. Virtually all com missural axons follow this route. The morphology of commissural growth cones was also examined. As they encountered the floor plate, commissural growth cones became larger and increased in complexity. The reorientation of axons in register with the floor plate boundary and the change in the morphological properties of commissural growth cones as they traverse the midline suggest that the floor plate may act as a guidepost with functions similar to cells that have been implicated in axon guidance in invertebrates.