bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temporal and spatial selection against parthenogenetic cells during development of fetal chimeras
Authors: Fundele Reinald H. , Norris Michael L. , Barton Sheila C. , Fehlau Monika , Howlett Sarah K. , Mills Walter E. , Surani M. Azim 
Published: April 2021

ABSTRACT
The fate of parthenogenetic cells was investigated during development of fetal and early postnatal chimeras. On day 13 of embryonic development, considerable contribution of parthenogenetic cells was observed in all tissues of chimeric embryos, although selection against parthenogenetic cells seemed to start before day 13. Between days 13 and 15 of development, parthenogenetic cells came under severe selective pressure, which was most striking in tongue. The disappearance of parthenogenetic cells from tongue coincided with the beginning of myoblast fusion in this tissue. Severe selection against parthenogenetic cells was also observed in pancreas and liver, although in the latter, parthenogenetic cells were eliminated later than in skeletal muscle or pancreas. In other tissues, parthenogenetic cells may persist and participate to a considerable extent throughout the gestation period and beyond, although a significant decrease was observed in all tissues. Parthenogen-etic↔fertilized chimeras were significantly smaller than their non-chimeric littermates at all developmental stages. These results suggest that the absence of paternal chromosomes is largely incompatible with the maintenance of specific differentiated cell types. Furthermore, paternally derived genes seem to be involved in the regulation of proliferation of all cell types, as indicated by the drastic growth deceleration of parthenogen-etic↔fertilized chimeras and the overall decrease of parthenogenetic cells during fetal development. Chromosomal imprinting may have a role in maintaining a balance between cell growth and differentiation during embryonic development.
The major exception to the selective elimination of parthenogenetic cells appear to be the germ cells; viable offspring derived from parthenogenetic oocytes were detected, sometimes at a high frequency in litters of female parthenogenetic↔fertilized chimeras.
Melanization in albino mice transformed by introducing cloned mouse tyrosinase gene
Authors: Tanaka Satoshi , Yamamoto Hiroaki , Takeuchi Sakae , Takeuchi Takuji 
Published: April 2021

Abstract
We introduced a mouse tyrosinase minigene, mg-Tyrs-J, in which the authentic genomic 5′ non-coding flanking sequence was fused to a mouse tyrosinase cDNA, into fertilized eggs of albino mice.
Of the 25 animals that developed from the injected eggs, four mice exhibited pigmented hair and eyes. Histological analysis of the transgenic mice revealed that the melanogenesis was restricted to hair bulbs and eyes.
These results suggest that this minigene encodes active tyrosinase protein and that its 5′ flanking region contains the sequences regulating expression of mouse tyrosinase gene. This is the first report of a successful expression of tyrosinase gene and of pigment production in transgenic mice.
Mesoderm induction and the control of gastrulation in Xenopus laevis: the roles of fibronectin and integrins
Authors: Smith J. C. , Symes K. , Hynes R. O. , DeSimone D. 
Published: April 2021

Abstract
Exposure of isolated Xenopus animal pole ectoderm to the XTC mesoderm-inducing factor (XTC-MIF) causes the tissue to undergo gastrulation-like movements. In this paper, we take advantage of this observation to investigate the control of various aspects of gastrulation in Xenopus.
Blastomeres derived from induced animal pole regions are able, like marginal zone cells, but unlike control animal pole blastomeres, to spread and migrate on a fibronectin-coated surface. Dispersed animal pole cells are also able to respond to XTC-MIF in this way; this is one of the few mesoderm-specific responses to induction that has been observed in single cells.
The ability of induced animal pole cells to spread on fibronectin is abolished by the peptide GRGDSP. However, the elongation of intact explants is unaffected by this peptide. This may indicate that fibronectin-me-diated cell migration is not required for convergent extension.
We have investigated the molecular basis of XTC-MIF-induced gastrulation-like movements by measuring rates of synthesis of fibronectin and of the integrin fit chain in induced and control explants. No significant differences were observed, and this suggests that gastrulation is not initiated simply by control of synthesis of these molecules. In future work, we intend to investigate synthesis of other integrin subunits and to examine possible post-translational modifications to fibronectin and the integrins.
Effect of the X-linked gene Tabby (Ta) on eyelid opening and incisor eruption in neonatal mice is opposite to that of epidermal growth factor
Authors: Kapalanga Joachim , Blecher Stan R. 
Published: April 2021

Abstract
Studies on eyelid opening and incisor eruption in 216 neonatal Tabby (Ta)-bearlng mice and wildtype controls (35 Ta/Y, 62 +/Y, 30 Ta/Ta, 57 Ta/+ and 32 +/+) showed that in animals hemizygous and homozygous for Ta, the timing of eyelid opening and incisor eruption was significantly delayed (P&lt;0.05). It was also observed that once open, the eyes of mutant pups do not remain open for long but soon close again for several days before reopening. An iterative eyes open-eyes closed process seems to continue beyond puberty. Studies In 25 epidermal growth factor (EGF)-treated mutants and 23 saline-treated controls showed that neonatal EGF injections (4μg g-1 body weight per day) reversed the delayed timing of eyelid opening and incisor eruption in hemizy gote and homozygote Tabby mice. However, both mutant and wildtype EGF-treated mice also showed the eyes open-eyes closed cycle, whereas untreated nonmutant mice did not. Because Tabby appears to be genetically homologous to the gene for human X-linked hypohidrotic ectodermal dysplasia, these results may have potential clinical significance. The eyes open-eyes closed cycle may involve cycling levels of EGF receptor; since the gene for this receptor shows homology with an oncogene, this system may be useful in studies on genetic control of oncogene function.
How embryos work: a comparative view of diverse modes of cell fate specification
Authors: Davidson Eric H. 
Published: April 2021

Abstract
Embryonic processes in the nematode C. elegans, the gastropod mollusc Ilyanassa, the dipteran Drosophila, the echinoid Strongylocentrotus purpuratus, the ascidian Ciona, the anuran Xenopus, the teleost Brachydanio and mouse are compared with respect to a series of parameters such as invariant or variable cleavage, the means by which the embryonic axes are set up, egg anisotropies and reliance on conditional or on autonomous specification processes. A molecular interpretation of these modes of specification of cell fate in the embryo is proposed, in terms of spatial modifications of gene regulatory factors. On this basis, classically defined phenomena such as regulative development and cytoplasmic localization can be interpreted at a mechanistic level, and the enormous differences between different forms of embryogenesis in the Animal Kingdom can be considered within a common mechanistic framework. Differential spatial expression of histospecific genes is considered in terms of the structure of the gene regulatory network that will be required in embryos that utilize cell–cell interaction, autonomous vs conditional specification and maternal spatial information to differing extents. It is concluded that the regulatory architectures according to which the programs of gene expression are organized are special to each form of development, and that common regulatory principles are to be found only at lower levels, such as those at which the control regions of histospecific structural genes operate.
Sialoconjugates and development of the tail bud
Authors: Griffith C. M. , Wiley M. J. 
Published: April 2021

Abstract
Using lectin histochemistry, we have previously shown that there are alterations in the distribution of glycoconjugates in the tail bud of chick embryos that parallel the developmental sequence of the caudal axis. If glycoconjugates or the cells bearing them play a role in caudal axial development, then, restriction of their availability by binding with lectins would be expected to produce abnormalities of caudal development. In the present study, we treated embryos at various stages of tail bud development by microinjection with a variety of lectins. Administration of WGA by sub-blastodermal injection resulted in high incidences of secondary neural tube and notochordal abnormalities in lectin-treated embryos. The incidence of malformations was dependent upon both the dose of WGA received and the stage of development at the time of treatment. Using an anti-WGA antibody, we have also shown binding of the lectin in regions where defects were found. The lectin WGA binds to the sialic acid residues of glycoconjugates and to yV-acetylglucosamine. Treatment of embryos with Limu-lus polyphemus lectin (LPL), which also binds to sialic acid, produced results similar to those of WGA. Treatments using lectins with other sugar-binding specificities, including succinylated WGA (with N-acetylglucosamine specificity only) produced defects that differed from those produced by WGA and LPL, and only with the administration of much higher doses. The results suggest that glycoconjugates in general and sialocopjugates in particular, or the cells carrying them, may have a role in caudal axial development.
Maternal messenger RNA distribution in silkmoth eggs: I. Clone Ec4B is associated with the cortical cytoskeleton
Authors: Kastern William H. , Watson Cornelius A. , Berry Spencer J. 
Published: April 2021

Abstract
We have constructed a cDNA library from mature egg RNA of the silkmoth, Hyalophora cecropia. Differential screening of the library using cDNA made against mRNAs from the yolky cytoplasm (soluble fraction) and the cortical cytoplasm (cytoskeletal-associated or cortical fraction) resulted in several clones that hybridized to a higher degree to the cDNA from the cytoskeletal-associated fraction. We selected and analyzed the clone giving the strongest signal (designated Ec4b) for its distribution in situ and found that it bound to mRNAs in the nurse cell cytoplasm, in the cortex and in the follicle cells of oocytes. Hybridization of the insert from Ec4b to both detergent-soluble and -insoluble (cortical) RNA on dot blots further supported the observation that the mRNA corresponding to Ec4b was enriched in this cytoskeletal fraction. The mRNA for Ec4b was approximately 500 bases long and the gene seems to be a member of a large multigene family in the H. cecropia genome. Analyses of the nucleotide and amino acid sequences reveal similarity to lepidopteran chorion genes and a lesser but convincing similarity to vertebrate cytokeratins. The filter and in situ hybridization data point to the association of specific messenger RNAs with the cortical cytoskeleton of silkmoth oocytes. Aspects of the structure of the protein encoded by this mRNA suggest that it is a structural component necessary for formation of the cellular blastoderm of the embryo. The association of this maternal mRNA with the cortical cytoskeleton presents the interesting possibility that mRNA bound to the cytoskeleton may be capable of participating in the synthesis of new cytoskeleton or related structures during blastoderm formation. Such an association between maternal mRNA and the cytoskeleton may indicate a general mechanism for the spatial distribution of determinative elements in eggs.
Sex-linked dosage-sensitive modifiers as imprinting genes
Authors: Sapienza Carmen 
Published: April 2021

ABSTRACT
It is proposed that differential genome imprinting is the result of dosage-sensitive modifier genes located on the sex chromosomes. Parallels between variegating position-effects in Drosophila, the phenotype elicited by transgenes in the mouse and data from several pediatric tumors indicate that the net result of the activity of such modifier genes is often cellular mosaicism in the expression of affected alleles. The mechanism by which inactivation of affected alleles is achieved is proposed to be through the formation of heterochromatic domains.
Because the relevant sex-linked modifying loci are dosage sensitive in their activity, differential imprinting will occur even within homogeneous genetic backgrounds. The presence of allelic variants at these loci in non-inbred populations will give rise to variation in the observed expressivity and mode of inheritance of affected traits.
Gene expression and parental dominance in hybrid plants
Authors: Heslop-Harrison J. S. 
Published: April 2021

ABSTRACT
Genomic imprinting, where the genes from one parent have different expression properties to those of the other parent, occurs in plants. It has potentially significant consequences because of the importance of hybrids in plant evolution and plant breeding, and provides a mechanism that can hide genetic variation for many generations. The study of nuclear organization shows that chromosome and genome position relates to imprinting in F1 hybrids, with peripheral genomes tending to be expressed preferentially. In some inbred, polyploid hybrids, such as Triticale (a wheat x rye hybrid), treatment with the demethylation agent azacytidine releases hidden variation, which was perhaps lost because of imprinting phenomena.
Acellularity of starfish embryonic mesenchyme cells as shown in vitro
Authors: Kaneko Hiroyuki , Takaichi Shigeko , Yamamoto Masamichi , Dan-Sohkawa Marina 
Published: April 2021

ABSTRACT
Embryonic mesenchyme cells of the starfish are shown to be unexpectedly fusogenic in vitro. When archenteron complexes (archenterons and varying portions of the extracellular matrix {ECM} surrounding them) are isolated from starfish embryos and inoculated in sea water containing 4 % newborn bovine serum, the mesenchyme cells form large syncytia on the substratum underneath each archenteron. These syncytia break into smaller fragments interconnected by fine cell processes within 24 h. These networks have been studied morphologically, dynamically and ultrastructurally and found to lack cell borders between the constituent fragments. These fragments contain various numbers of nuclei ranging from 0 to 6 or more and move about constantly over the substratum, sometimes breaking into two and sometimes fusing with neighbouring fragments, so that the overall pattern of the network changes constantly. Our results also indicate that the network is threedimensional i.e. it has crossing sites, the frequency of which seems to depend on the amount of the ECM excreted on the substratum. A similar network pattern is found among mesenchyme cells in vivo, which suggests that the features found in vitro reflect those in vivo.
Neurogenic and antineurogenic effects from modifications at the Notch locus
Authors: Palka J. , Schubiger M. , Schwaninger H. 
Published: April 2021

ABSTRACT
The best studied mutations at the Notch locus produce a neurogenic phenotype, with a massive overgrowth of the nervous system at the expense of epidermis. We report here that, in the development of the adult peripheral nervous system, the Abruptex alleles of Notch have the opposite phenotype, namely an underproduction of sensory organs or sensilla. This arises primarily not from an arrest of the lineages that produce sensilla, from the degeneration of sensillar cells, or from the transformation into neurons of cells that normally secrete the cuticular components of a sensillum (as can happen in Notch alleles). Rather, our evidence argues strongly that the sensillar mother cells never form. This implies that the Notch protein plays a role in the process that first generates a difference between sensillar mother cells and ordinary epidermal cells. The number of sensilla formed on the wing of flies carrying multiple doses of Notch* is virtually the same as that of wild type, i.e. the Abruptex phenotype is not reproduced to any significant extent. This suggests that the single amino acid substitutions that occur in Abruptex mutants confer on the protein some functionally distinctive feature, possibly more powerful intermolecular binding or altered stability.
Neurogenesis in the insect enteric nervous system: generation of pre-migratory neurons from an epithelial placode
Authors: Copenhaver* Philip F. , Taghert Paul H. 
Published: April 2021

ABSTRACT
The enteric plexus (EP) is a major division of the enteric nervous system (ENS) in the moth Manduca sexta and contains a dispersed population of about 360 bipolar neurons, the EP cells. Previously we showed that embryonic EP cells achieve their mature distributions by extensive migration along the gut surface and then display position-specific phenotypes. We now demonstrate that the entire EP cell population is generated from an ectodermal placode that invaginates from the embryonic foregut. Individual EP cells become post-mitotic just as they leave the epithelium, but their terminal differentiation is subsequently delayed until after their migratory dispersal. Clonal analysis by injection of lineage-tracing dyes has shown that the EP cell population is derived from a large number of placodal cells, each of which contributes a limited number of neurons to the ENS. Placodally derived clones produce neurons exclusively, while clones arising from cells adjacent to the placode are incorporated into the gut epithelium. These results indicate that neurogenesis in the insect ENS involves a developmental strategy that is distinct from that seen in the insect CNS and which resembles the generation of certain cell classes in the vertebrate nervous system.
Identification of zona- and fucoidan-binding proteins in guinea-pig spermatozoa and mechanism of recognition
Authors: Jones Roy , Williams Rachel M. 
Published: April 2021

ABSTRACT
Binding of guinea-pig spermatozoa to the zona pelluclda of homologous eggs has been reported to involve ‘receptors’ on the inner acrosomal membrane (Huang et al. 1981). These receptors can be blocked by sulphated polysaccharides such as fucoidan (Huang and Yanagimachi, 1984). The aims of the present investigation were to identify these putative zona receptors using 1251-fucoidan as a probe and examine their mechanism of recognition. Results show that 1251-fucoidan binds to several proteins extracted from guinea-pig spermatozoa with molecular m of 95, 60, 48, 34, 30 and 18-20xloJ (K) on SOS-PAGE. The 48K, 34K and 30K components represent Jroacrosln and two forms of acrosin, respectively. 1 1-zona pelluclda glycoproteins also bound strongly to the 48K, 34K and 30K sperm proteins. The other high and low mass binding proteins were not positively identified but cytochemlcal experiments with fluorescelnamine-fucoidan and FITC-soybean trypsin inhibitor indicate that they are intraacrosomal. The mechanism of binding of 1251-fucoidan to proacrosin/acrosln (and also the 95K, 60K and 18K-20K components) involves multiple sulphate groups on the polysaccharlde in a specific orientation to allow them to interact with basic residues on the protein. It is suggested that guinea-pig spermatozoa retain sufficient proacrosin/acrosin bound to the inner acrosomal membrane after the acrosome reaction to mediate binding to the zona pellucida and that functionally proacrosin is analogous to sea urchin bindin.
The role of the nucleocytoplasmic ratio in development regulation of the early mouse embryo
Authors: Evsikov S. V. , Morozova L. M. , Solomko A. P. 
Published: April 2021

ABSTRACT
The hypothesis suggesting that the blastocoele is able to form only at a definite nucleocytoplasmic ratio was tested. We compared the development of preimplantation mouse embryos under different conditions. The results demonstrated that the start of cavitation is not dependent on the number of cell divisions. Thus, a definite nucleocytoplasmic ratio is not required for blastocoele formation to start. Our studies on embryos with microsurgically altered cytoplasm content provided evidence for the following biological clock mechanism: a change in the cell program of morphogenesis needs definite concentration of the products of a previous genetic program.
Fibroblast growth factor during mesoderm induction in the early chick embryo
Authors: Mitrani E. , Gruenbaum Y. , Shohat H. , Ziv T. 
Published: April 2021

ABSTRACT
A chick genomic clone that reveals a high degree of homology to the mammalian and Xenopus bFGF gene has been isolated. The pattern of expression of bFGF has been examined during early chick embryogenesis. RNA blot analysis revealed that chick bFGF is already transcribed at pregastrula stages. Immunolabeling analysis indicated that bFGF protein is present at these early developmental stages and is distributed evenly in the epiblast, hypoblast and marginal zone of the chick blastula. Substances that can inhibit FGF action were applied to early chick blastoderms grown in vitro under defined culture conditions (DCM). Both heparin and suramin were capable of blocking the formation of mesodermal structures in a dose-dependent manner. Our results indicate that FGF-like substances may need to be present for axial structures to develop although they may be acting earlier during the induction of non-axial mesoderm.
The micropyle: a sperm guidance system in teleost fertilization
Authors: Amanze Diala , Iyengar Arati 
Published: April 2021

ABSTRACT
The micropylar region of the Rosy barb, Barbus conchonius, egg consists of 7-10 grooves and ridges, which drain directly into a funnel-shaped vestibule, the only point on the chorion through which sperm-egg contact is achieved during fertilization. Results of time-lapse video microscope study and computer-aided analysis of sperm motility pattern in the micropylar region showed that the fertilizing sperm, usually the first to enter the micropylar region, always travelled preferentially along the grooves into the micropylar pit. Subsequently, 86% of sperm arriving the micropylar region within 30 s travelled preferentially along the grooves into the immediate vicinity of the micropylar pit. The sperm guidance role of the micropylar region was calculated to enhance chances of egg penetration/fertilization by as much as 99.7% once sperm were within the micropylar region, possibly in response to some form of chemo-attractant(s) from the egg. Sperm agglutination postfertilization was also found to occur preferentially along the grooves. Results of our in vitro fertilization experiments showed association between point of sperm entry and blastodisc formation: the blastodisc formed directly beneath the micropyle in all undisturbed eggs.
The influence of cell interactions and tissue mass on differentiation of sea urchin mesomeres*
Authors: Khanert Oded , Wilt Fred 
Published: April 2021

ABSTRACT
The developmental potential of different blastomeres of the sea urchin embryo was re-examined. We have employed a new method to isolate substantial numbers of different kinds of blastomeres from 16-cell-stage embryos, and we have used newly available molecular markers to analyze possible vegetal differentiation. We have found that, while isolated mesomere pairs behave according to the classical expectations and develop into ectodermal vesicles, there is a clear effect of reaggregat ing two or more mesomere pairs. They survive better in long-term culture and, after prolonged periods, they display an astonishing ability to express vegetal differen tiation. We also combined mesomeres with stained micromeres or macromeres from the vegetal hemi sphere. Although induction of guts and spicules was observed, there was little if any effect of varying the ratio of different blastomeres on the kinds of differentiation obtained.