bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oögenesis in the guinea-pig
Authors: Ioannou J. M. 
Published: April 2021

ABSTRACTEstimations were made of the numbers of germ cells in the guinea-pig ovary from embryonic stages to maturity. A volumetric method was used to estimate the numbers of oögonia and Oöcytes in animals aged 26 to 55 days p.c., while counts were made of the numbers of germ cells present between 60 days p.c. and 12 months p.p. Neither the mitotic activity of oögonia nor the successive stages of meiotic prophase are closely synchronized. The process of oögenesis ceases at about 50 days p.c. Large numbers of Oöcytes are found in the leptotene stage at 35 days, in zygotene at about 40 days, and in pachytene at 50 days p.c. Thereafter the proportion of Oöcytes in the diplotene phase increases, so that by a few days after birth all the Oöcytes are in this stage. By 1 month p.p., however, two types of Oöcyte in diplotene are found in large numbers. The first is comparable to the corresponding stage in rat, man and the chick, while the second displays a very contracted nucleus. The latter type rapidly gains predominance, and by 12 months p.p. 94 per cent, of the germ cells belong to it. The number of germ cells per ovary increases from about 27,000 at 30 days p.c. to reach a peak of almost 105,000 by 41 days p.c.; subsequently it declines to some 13,000 by 12 months p.p. This decline is caused by a steady process of atresia which affects germ cells from the earliest stages of development.
Transplantation of embryonic cartilage and bone on to the chorioallantois of the chick
Authors: Stephenson N. G. , Tomkins J. K. N. 
Published: April 2021

ABSTRACT
Transplantation of embryonic limb cartilage and bone to the chick chorioallantois has been carried out, using donors from the various tetrapod classes. The results may be correlated with the degree of phyletic relationship between the donor and host. Avian cartilage and bone continued to grow even when the donor was of a species and genus distinct from those of the chick host. On the other hand, when the donor belonged to another tetrapod class, only one of these embryonic tissues, namely cartilage, grew. There is a differential response of the tissues of a particular donor to a xenoplastic environment. Embryonic cartilage from amphibian, reptilian and mammalian donors will continue to grow xenoplastically when transplanted to the chick chorioallantois, whereas bone from such donors will not grow. The age factor is important in all xenoplastic results. Young donor cartilage grows well, but with increasing age there is a gradual reduction in its ability to do so. Embryonic cartilage from cold-blooded donors shows a high degree of temperature tolerance. Amphibian cartilage continues to grow xenoplastically at the chick incubation temperature (38° C.), whereas a temperature of 25° C. is known to be lethal to tadpoles of the particular donor species. Embryonic reptilian cartilage survives temperatures ranging from at least 4°C. to 38° C. The differential response of embryonic tissues to the transplantation environment is evident in development at stages much earlier than those at which immunological mechanisms are known to operate. It appears to be based on the metabolic requirements of particular tissues. The less specialized the nutritional requirements of a tissue are, the better its chances of obtaining from a xenoplastic environment the appropriate metabolites which are essential not only for its survival, but also for its continuing growth and differentiation.
Vertebral malformation in the mouse foetus caused by X-radiation of the mother during pregnancy
Authors: Murakami Ujihiro , Kameyama Yoshiro 
Published: April 2021

ABSTRACTMice of the ddN and CF1 strains were exposed to a single dose of 200 r. X-radiation between the 8th and 13th day of pregnancy, and the foetal skeletons were examined on the 19th day of pregnancy. The phenomenon of a head-to-tail gradient shift in vertebral malformations as the stage of pregnancy at radiation advanced was less marked in the result in the ddN strain, but in the CF1 strain it was of similar proportions to that obtained by hypoxia. However, after X-radiation, malformations in the cervical and thoracic vertebrae presented two peaks of susceptibility. The first peak in malformation frequency may result from an effect of X-radiation upon the early somite stage or it may be an indirect effect. The second peak may originate from a direct effect upon the primordium, i.e. upon the sclerotome itself. The incidence of cervical malformations was higher in the group treated on the 8th or 9th day, and in the group treated on the 11th day of pregnancy. The malformations presented such characteristics as enlarged rami of the posterior arch of the 1st cervical vertebra or, in the latter group, fusion of the cervical vertebrae. There were also differences in the frequency of involvement of the vertebrae in these two strains which may be due to differences in the rate of differentiation of the vertebral primordium. Other differences were seen in the incidence of cervical ribs, of absence of the 13th rib, and of lumbar ribs. Such regional differentiation seems to be influenced by the genetic constitution.
The rôle of the germinal vesicle in oöcyte maturation in anurans as revealed by the removal and transplantation of nuclei
Authors: Nikitina T. A. , Dettlaff L. A. , Stroeva O. G. 
Published: April 2021

ABSTRACTA study of nucleo-cytoplasmic interactions in pre-embryonic development, at maturation stages in particular, is of great interest. During this period ooplasmic segregation takes place, specific properties of the cortex arise, and the cytoplasm obtains information from the oöcyte nucleus which promotes the development of the embryo during all the changes related to fertilization, cleavage and blastulation (Wilson, 1925; Raven, 1961; Brachet, 1957, 1960; Briggs & King, 1959; Neyfakh, 1962).
Cytosolic interaction between deltex and Notch ankyrin repeats implicates deltex in the Notch signaling pathway
Authors: Diederich Robert J. , Matsuno Kenji , Hing Huey , Artavanis-Tsakonas Spyros 
Published: April 2021

ABSTRACT
Genetic data from Drosophila have suggested a functional relationship between the novel cytoplasmic protein encoded by the deltex locus and the transmembrane receptor encoded by Notch. We have demonstrated a direct interaction between these proteins from expression studies conducted in cultured cells, in yeast, and in the imaginal wing disc. deltex binds specifically to the Notch ankyrin repeats, a region that is crucial for Notch signaling and that constitutes the most conserved domain among Notch family members. In addition, we present a new Notch allele, Nsu42c, that is associated with a missense mutation within the fifth ankyrin repeat. In addition to representing a new class of viable Notch allele, this mutation behaves similarly to mutations of deltex and further implicates the ankyrin repeats in Notch function.
Epithelium formation in the Drosophila midgut depends on the interaction of endoderm and mesoderm
Authors: Tepass Ulrich , Hartenstein Volker 
Published: April 2021

ABSTRACT
The reorganization of mesenchymal cells into an epithelial sheet is a widely used morphogenetic process in metazoans. An example of such a process is the formation of the Drosophila larval midgut epithelium that develops through a mesenchymal-epithelial transition from endodermal midgut precursors. We have studied this process in wild type and a number of mutants that show defects in midgut epithelium formation. Our results indicate that the visceral mesoderm serves as a basal substratum to which endodermal cells have to establish direct contact in order to form an epithelium. Furthermore, we have analyzed the midgut phenotype of embryos mutant for the gene shotgun, and the results suggest that shotgun directs adhesion between midgut epithelial cells, which is independent from the adhesion between endoderm and visceral mesoderm.
The gene serpent has homeotic properties and specifies endoderm versus ectoderm within the Drosophila gut
Authors: Reuter Rolf 
Published: April 2021

ABSTRACT
The gut of Drosophila consists of ectodermally derived foregut and hindgut and endodermally derived midgut. Here I show that the gene serpent plays a key role in the development of the endoderm. serpent embryos lack the entire midgut and do not show endodermal differentiation. They gastrulate normally and form proper amnioproctodeal and anterior midgut invaginations. However, the prospective anterior midgut cells acquire properties that are usually found in ectodermal foregut cells. In the posterior region of the embryo, the prospective posterior midgut forms an additional hindgut which is contiguous with the normal hindgut and which appears to be a serial duplication, not a mere enlargement of the hindgut. The fate shifts in both the anterior and the posterior part of the srp embryo can be described in terms of homeotic transformations of anterior midgut to foregut and of posterior midgut to hindgut. serpent appears to act as a homeotic gene downstream of the terminal gap gene huckebein and to promote morphogenesis and differentiation of anterior and posterior midgut.
Localization of vasa protein to the Drosophila pole plasm is independent of its RNA-binding and helicase activities
Authors: Liang Lu , Diehl-Jones William , Lasko Paul 
Published: April 2021

ABSTRACT
The Drosophila gene vasa encodes a DEAD-box protein, which is localized during early oogenesis to the perinuclear region of the nurse cells and later to the pole plasm at the posterior end of the oocyte. Posterior localization of vasa protein depends upon the functions of four genes: capu, spir, osk and stau. We have found that localization of vasa to the perinuclear nuage is abolished in most vas alleles, but is unaffected by mutations in four genes required upstream for its pole plasm localization. Thus localization of vasa to the nuage particles is independent of the pole plasm assembly pathway. Furthermore, electron-dense nuage particles are less abundant in the cytoplasm of nurse cells from vas mutants that fail to exhibit perinuclear localization, suggesting that the formation of the nuage depends upon vas function. Eight of nine vas point mutations cause codon substitutions in a region conserved among DEADbox genes. The proteins from two mutant alleles that retain the capacity to localize to the posterior pole of the oocyte, vasO14 and vasO11, are both severely reduced in RNAbinding and -unwinding activity as compared to the wildtype protein on a variety of RNA substrates including in vitro synthesized pole plasm RNAs. Initial recruitment of vasa to the pole plasm must consequently depend upon protein-protein interactions but, once localized, vasa must bind to RNA to mediate germ cell formation.
Cortical granule biogenesis is active throughout oogenesis in sea urchins
Authors: Laidlaw Michael , Wessel Gary M. 
Published: April 2021

ABSTRACT
Cortical granules are secretory vesicles formed in the eggs of most animals and are essential for the prevention of polyspermy in these organisms. We have studied the biogenesis of cortical granules in sea urchin oocytes by identifying cDNA clones that encode proteins targeted selectively to the cortical granules. These cDNA clones were identified by an immunoscreen of a cDNA library using antibodies to proteins of the fertilization envelope. Four different mRNAs were identified, ranging from 4 kb to 13 kb in length, that encoded proteins targeted specifically to cortical granules. Accumulation of these mRNAs began very early in oogenesis, in oocytes approximately 10-15 μm in diameter, and continued throughout oogenesis. The mRNAs reached peak abundance (on a per cell basis) in germinal vesicle stage oocytes, and the accumulation of each mRNA was linear with respect to oocyte growth. During breakdown of the germinal vesicle these mRNAs were degraded so that in eggs the mRNA signals were at background levels. Antibodies generated to recombinant proteins made from each of these cDNA clones showed that in the oocyte each cognate protein appeared early in oogenesis. These proteins accumulated only in cortical granules: no accumulation was seen in the cytoplasm, in Golgi, or in other vesicles, and no heterogeneity of the contents was seen within the population of cortical granules. Using these antibodies we show that cortical granules accumulated linearly throughout oogenesis. Prior to germinal vesicle breakdown, cortical granules accumulated throughout the cytoplasm of oocytes and increased in number as the oocytes enlarged; the rate of synthesis appeared equal at each stage. At oocyte maturation the cortical granules moved to the cell periphery coincident with the complete degradation of mRNAs encoding these proteins. These results show that the genes encoding cortical granule proteins are coordinately activated throughout oogenesis and that the pathway of protein biosynthesis and targeting to these regulated secretory granules is functional throughout oogenesis in this animal.
Patterns of localization and cytoskeletal association of two vegetally localized RNAs, Vg1 and Xcat-2
Authors: Forristall Caryl , Pondel Marc , Chen Lihua , King Mary Lou 
Published: April 2021

ABSTRACT
In Xenopus, localization of a rare class of mRNAs during oogenesis is believed to initiate pattern formation in the early embryo. We have determined the pattern of RNA localization for one of these RNAs, Xcat-2, which encodes a putative RNA-binding protein related to Drosophila nanos (Mosquera, L., Forristall, C., Zhou, Y. and King, M. L. (1993) Development 117, 377-386). Xcat-2 is exclusively localized to the mitochondrial cloud in stage I oocytes, moves with this body into the vegetal cortex during stage II and, later, partitions into islands consistent with it being a component of the germ plasm. As previously shown, Vg1 is not localized to the vegetal cortex until stage IV and distributes to all vegetal blastomeres during development. We found a direct correlation between the localized condition of these RNAs and their recovery in a detergent-insoluble fraction. We present evidence suggesting that differential RNA binding to a cytoskeletal component(s) in the vegetal cortex determines the pattern of inheritance for that RNA in the embryo.
DWnt-4, a novel Drosophila Wnt gene acts downstream of homeotic complex genes in the visceral mesoderm
Authors: Graba Yacine , Gieseler Kathrin , Aragnol Denise , Laurenti Patrick , Mariol Marie-Christine , Berenger Hélene , Sagnier Thierry , Pradel Jacques 
Published: April 2021

ABSTRACT
Wnt genes encode putative cell signalling proteins which play crucial roles during development. From a library of DNA fragments associated, in vivo, with Ultrabithorax proteins, we isolated a novel Drosophila Wnt gene, DWnt-4. Neither a paralog nor an ortholog of the gene exist in the current repertoire of full-length Wnt sequences. DWnt-4 maps close (30 kb) to wingless, suggesting that the two Wnt genes derive from a duplication that occurred early in evolution, since they are significantly diverged in sequence and structure. Developmental expression of DWnt-4 partially overlaps that of wingless. The gene is transcribed following a segment polaritylike pattern in the posteriormost cells of each parasegment of the ectoderm, and at two locations that correspond to parasegments 4 and 8 of the visceral mesoderm. The control of DWnt-4 expression in the visceral mesoderm involves a network of regulatory molecules that includes Ultrabithorax and other proteins from the homeotic complex (HOM-C), as well as the TGF-β decapentaplegic gene product.
Control of Drosophila head segment identity by the bZIP homeotic gene cnc
Authors: Mohler Jym , Mahaffey James W. , Deutsch Elizabeth , Vani Kodela 
Published: April 2021

ABSTRACT
Mutational analysis of cap’n’collar (cnc), a bZIP transcription factor closely related to the mammalian erythroid factor NF-E2 (p45), indicates that it acts as a segmentspecific selector gene controlling the identity of two cephalic segments. In the mandibular segment, cnc has a classical homeotic effect: mandibular structures are missing in cnc mutant larvae and replaced with duplicate maxillary structures. We propose that cnc functions in combination with the homeotic gene Deformed to specify mandibular development. Labral structures are also missing in cnc mutant larvae, where a distinct labral primordia is not properly maintained in the developing foregut, as observed by the failure to maintain and elaborate patterns of labral-specific segment polarity gene expression. Instead, the labral primordium fuses with the esophageal primordium to contribute to formation of the esophagus. The role of cnc in labral development is reciprocal to the role of homeotic gene forkhead, which has an identical function in the maintenance of the esophageal primordium. This role of homeotic selector genes for the segment-specific maintenance of segment polarity gene expression is a unique feature of segmentation in the preoral head region of Drosophila.
Expression of the labial group Hox gene HrHox-1 and its alteration induced by retinoic acid in development of the ascidian Halocynthia roretzi
Authors: Katsuyama You , Wada Shuichi , Yasugi Sadao , Saiga Hidetoshi 
Published: April 2021

ABSTRACT
Ascidian embryogenesis shares several developmental features with vertebrates. Thus, it is presumed that some molecular mechanisms that are critical for vertebrate development may also act in the early development of ascidians. Here, we investigated expression of the ascidian labial group Hox gene HrHox-1 in the development of Halo-cynthia roretzi. HrHox-1 showed a spatially restricted expression pattern along the anterior-posterior axis, which is remarkably similar to that of the vertebrate gene, Hoxb-1. The expression of HrHox-1, however, was exclusively in tissues of ectoderm origin unlike its vertebrate counterpart. Exposure of the embryos to 10−6 M all-trans retinoic acid induced a larval phenotype with elimination of the anteriormost structures, the papillae. In this phenotype, the level of HrHox-1 expression was enhanced and ectopic expression was observed at the anterior terminal epidermis where the papillae are otherwise formed. These observations suggest that there are some conserved mechanisms in the spatial regulation of expression of labial group genes in embryogenesis of ascidians and vertebrates.
Ectopic cyclin E expression induces premature entry into S phase and disrupts pattern formation in the Drosophila eye imaginal disc
Authors: Richardson Helena , O’Keefe Louise V. , Marty Thomas 
Published: April 2021

ABSTRACT
During animal development, cell proliferation is controlled in many cases by regulation of the G1 to S phase transition. Studies of mammalian tissue culture cells have shown that the G1-specific cyclin, cyclin E, can be rate limiting for progression from G1 to S phase. During Drosophila development, down-regulation of cyclin E is required for G1 arrest in terminally differentiating embryonic epidermal cells. Whether cyclin E expression limits progression into S phase in proliferating, as opposed to differentiating, cells during development has not been investigated. Here we show that Drosophila cyclin E (DmcycE) protein is absent in G1 phase cells but appears at the onset of S phase in proliferating cells of the larval optic lobe and eye imaginal disc. We have examined cells in the eye imaginal epithelium, where a clearly defined developmentally regulated G1 to S phase transition occurs. Ectopic expression of DmcycE induces premature entry of most of these G1 cells into S phase. Thus in these cells, control of DmcycE expression is required for regulated entry into S phase. Significantly, a band of eye imaginal disc cells in G1 phase was not induced to enter S phase by ectopic expression of DmcycE. This provides evidence for additional regulatory mechanisms that operate during G1 phase to limit cell proliferation during development. These results demonstrate that the role of cyclin E in regulating progression into S phase in mammalian tissue culture cells applies to some, but not all, cells during Drosophila development. Ectopic expression of DmcycE in the eye imaginal disc disrupts normal pattern formation, highlighting the importance of coordinating cell proliferation with developmental processes for correct patterning in the developing eye. These studies establish DmcycE as a target of regulatory mechanisms that coordinate cell proliferation with other developmental events.
A Drosophila protein related to the human zinc finger transcription factor PRDII/MBPI/HIV-EP1 is required for dpp signaling
Authors: Staehling-Hampton Karen , Laughon Allen S. , Hoffmann F. Michael 
Published: April 2021

ABSTRACT
Little is known about the signal transduction pathways by which cells respond to mammalian TGF-βs or to decapentaplegic (dpp), a Drosophila TGF-β-related factor. Here we describe the genetic and molecular characterization of Drosophila schnurri (shn), a putative transcription factor implicated in dpp signaling. The shn protein has eight zinc fingers and is related to a human transcription factor, PRDII/MBPI/HIV-EP1, that binds to nuclear factor-κB-binding sites and activates transcription from the HIV long terminal repeat (LTR). shn mRNA is expressed in a dynamic pattern in the embryo that includes most of the known target tissues of dpp, including the dorsal blastoderm, the mesodermal germlayer and parasegments 4 and 7 of the midgut. Mutations in shn affect several developmental processes regulated by dpp including induction of visceral mesoderm cell fate, dorsal/ventral patterning of the lateral ectoderm and wing vein formation. Absence of shn function blocks the expanded expression of the homeodomain protein bagpipe in the embryonic mesoderm caused by ectopic dpp expression, illustrating a requirement for shn function downstream of dpp action. We conclude that shn function is critical for cells to respond properly to dpp and propose that shn protein is the first identified downstream component of the signal transduction pathway used by dpp and its receptors.
Progressive maturation of chromatin structure regulates HSP70.1 gene expression in the preimplantation mouse embryo
Authors: Thompson Eric M. , Legouy Edith , Elisabeth Christians , Renard Jean-Paul 
Published: April 2021

ABSTRACT
In the widely studied model organisms, Drosophila and Xenopus, early embryogenesis involves an extended series of nuclear divisions prior to activation of the zygotic genome. The mammalian embryo differs in that the early cleavage phase is already characterized by regulated cell cycles with specific zygotic gene expression. In the mouse, where major activation of the zygotic genome occurs at the 2-cell stage, the HSP70.1 gene is among the earliest genes to be expressed. We investigated the developmentally regulated expression of this gene during the preimplantation period, using a luciferase transgene, with or without flanking scaffold attachment regions (SARs). Cleavage stage-specific modifications in expression profiles were examined in terms of histone H4 acetylation status, topoisomerase II activity, and the localisation of HMG-I/Y, a nuclear protein with known affinity for the AT-tracts of SARs. We demonstrate that HSP70.1-associated transcription factors are not limiting, and that instead, there is a progressive maturation of chromatin structure that is directly involved in HSP70.1 regulation during early mouse development.