bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pollen-specific gene expression in transgenic plants: coordinate regulation of two different tomato gene promoters during microsporogenesis
Authors: Twell David , Yamaguchi Judy , Mccormick Sheila 
Published: April 2021

ABSTRACT
To investigate the regulation of gene expression during male gametophyte development, we analyzed the pro moter activity of two different genes (LAT52 and LAT59) from tomato, isolated on the basis of their anther-specific expression. In transgenic tomato, tobacco and Arabidopsis plants containing the LAT52 promoter region fused to the β-glucuronidase (GUS) gene, GUS activity was restricted to pollen. Transgenic tomato, tobacco and Arabidopsis plants containing the LAT59 promoter region fused to GUS also showed very high levels of GUS activity in pollen. However, low levels of expression of the LAT59 promoter construct were also detected in seeds and roots. With both constructs, the appearance of GUS activity in developing anthers was correlated with the onset of microspore mitosis and increased progressively until anthesis (pollen shed). Our results demonstrate co-ordinate regulation of the LAT52 and LAT59 promoters in developing microspores and suggest that the mechanisms that regulate pollen-specific gene expression are evolutionarily conserved.
Sperm-egg Association and its Relationship to the Activation of the Egg in Salmonid Fishes
Authors: Ginsburg Anna S. 
Published: April 2021

ABSTRACT
A study has been made of the initial stage of fertilization in Salmonids, using the lake trout Salmo trutta L. morpha lacustris Linné and the salmon S. salar L. morpha sebago Girard. Lake trout spermatozoa are activated by coelomic fluid and by Ringer solution; in these media they retain their motility and fertilizing capacity much longer than in water.At the moment when the spermatozoa kept in coelomic fluid or Ringer solution lose their fertilizing capacity, they are not reactivated by the addition of water. After a period of ‘rest’, however, a proportion of them acquires motility upon the addition of water which leads to a partial restoration of the fertilizing capacity of the sperm suspension.When trout and salmon eggs are inseminated in coelomic fluid or Ringer solution, the union of the gametes is achieved without egg activation. A cytological investigation shows that the spermatozoon reaches the cortical egg layer along the micropylar canal and the anterior part of its head gets embedded in the cytoplasm.When trout spermatozoa are placed into egg water or other media containing products of egg secretion no changes resembling the extrusion of the acrosome filament are seen with the electron microscope. This supports previous data on the absence of the acrosome in salmonid spermatozoa.The development of eggs inseminated in coelomic fluid or Ringer solution is initiated by immersion into water. The involvement of the fertilizing spermatozoon in development is possible upon egg activation for up to several days after insemination. To achieve such an effect, a brief exposure to water is necessary (this varies from 10 to 70 sec. for different eggs).Normal development of the egg may be achieved upon its activation either after or before insemination (the only limitation being the fact that the penetration of the spermatozoon in the activated egg is possible only before the expulsion of the contents of the cortical alveoli in the micropylar region).When water pretreated eggs are inseminated in calcium-free medium, no involvement of the spermatozoon in development takes place.The latent period of the cortical reaction on activation of trout eggs by water (from the moment of appearance of changes setting the process in train until the beginning of the expulsion of the contents of the cortical alveoli) in the bulk of the eggs takes 40–50 sec. at 3 ·0°C and 30–40 sec. at 8 · 9°C.The phenomena of union of the gametes and egg activation in salmonid fishes are to a considerable degree autonomous : they can easily be separated in time and combined in any sequence. This is related to the peculiarities of the mechanism of sperm-egg interaction.
bicoid mRNA localization signal: phylogenetic conservation of function and RNA secondary structure
Authors: Macdonald Paul M. 
Published: April 2021

Abstract
Transcripts of the bicoid (bcd) gene are localized to the anterior pole of the Drosophila oocyte, thereby allowing formation in the embryo of an anteroposterior gradient of the bcd protein morphogen. We previously showed that a 630 nucleotide portion of the 3′ noncoding region of the bcd mRNA is necessary for this localization, and is sufficient to confer anterior localization on a heterologous transcript. Here I have used a comparative analysis to begin to more precisely define the cis-acting mRNA localization signal. The bcd genes from six additional Drosophila species were cloned, and DNA of the 3′ noncoding regions sequenced. Three of these regions were tested interspecifically for mRNA localization in D. melanogaster and each functioned correctly; these regions must therefore contain the cis-acting signal. The primary sequences, which are up to 50 % divergent from the D. melanogaster gene, show patchy homology throughout most of the region. Interestingly, all seven species can potentially form a large stereotypic secondary structure. This structure is a likely candidate for the localization signal and can be used for the rational design of mutations to test that possibility.
The Drosophila transcript encoded by the β-amyloid protein precursor-like gene is restricted to the nervous system
Authors: Martin-Morris Linda E. , White Kalpana 
Published: April 2021

Abstract
We have molecularly delineated a Drosophila β-amyloid protein precursor-like (Appl) gene and analyzed its pattern of expression. Appl defines a new locus within the IB division of the X-chromosome, a region previously shown to be important for neural development. The genomic limits of the Appl gene were defined by mapping of the Appl cDNAs. The Appl transcript spans ∼38kb (1kb=103 base-pairs) of genomic DNA. Genomic regions surrounding the first two exons were sequenced. The first exon contains 78 nucleotides of the coding sequence and is separated from the second exon by a ∼21 kb intron. The second exon is 171 nucleotides long and is separated from the third exon by a ∼7 kb intron.
We present in situ RNA localization data that demonstrate that the Appl transcript is found in post-mitotic neurons in all developmental stages, in the central and peripheral nervous systems. Within the nervous system transcripts are not observed in neuroblasts, newly generated neurons and at least one class of presumed glial cells. The temporal and spatial specificity of Appl expression suggests that the gene product has a function that is common to most neurons.
Appl cDNA predicts an 886-amino acid polypeptide that exhibits strong sequence similarity to the human β-amyloid protein precursor (APP) (Rosen et al. 1989). In this paper, we compare the Appl gene expression with the pattern of expression of the β-amyloid protein precursor (APP) gene in mammals. Furthermore, we suggest that during evolution, a neural-specific function encoded by the APP gene has been selectively maintained.
Distribution and migration pathways of HNK-1-immunoreactive neural crest cells in teleost fish embryos
Authors: Sadaghiani Bahram , Vielkind Juergen R. 
Published: April 2021

Abstract
Whole mounts and cross-sections of embryos from three species of teleost fish were immunostained with the HNK-1 monoclonal antibody, which recognizes an epitope on migrating neural crest cells. A similar distribution and migration was found in all three species. The crest cells in the head express the HNK-1 epitope after they have segregated from the neural keel. The truncal neural crest cells begin to express the epitope while they still reside in the dorsal region of the neural keel; this has not been observed in other vertebrates. The cephalic and anterior truncal neural crest cells migrate under the ectoderm; the cephalic cells then enter into the gill arches and the anterior truncal cells into the mesentery of the digestive tract where they cease migration. These cephalic and anterior trunk pathways are similar to those described in Xenopus and chick. The neural crest cells of the trunk, after segregation, accumulate in the dorsal wedges between the somites, however, unlike in chick and rat, they do not migrate in the anterior halves of the somites but predominantly between the neural tube and the somites, the major pathway observed in carp and amphibians; some cells migrate over the somites. The HNK-1 staining of whole-mount embryos revealed a structure resembling the Rohon-Beard and extramedullary cells, the primary sensory system in amphibians. Such a system has not been described in fish.
Expression of extracellular matrix-degrading metalloproteinases and metalloproteinase inhibitors is developmentally regulated during endoderm differentiation of embryonal carcinoma cells
Authors: Adler Richard R. , Brenner Carol A. , Werb Zena 
Published: April 2021

Abstract
The differentiation of F9 and PSA-1 embryonal carcinoma cells to embryoid bodies composed of a mixture of parietal and visceral endoderm was accompanied by changes in their secretion of metalloproteinases. Differentiation was induced by retinoic acid and dibutyryl cyclic AMP (for F9 cells) or by removing cells from a substrate of feeder cells to alter cell-cell interaction and adhesion (for. PSA-1 cells). The embryoid bodies attached to gelatin-coated dishes, and the parietal endoderm cells spread out over the matrix. The differentiated cells secreted specific gelatin- and casein-degrading proteinases, including enzymes that comigrated with proenzyme forms of collagenase and stromelysin. Total proteinase activity as well as specific collagenase activity increased with the time of differentiation. All of the gelatin- and casein-degrading proteinases detectable by substrate gel zymography were inhibited by inhibitors of metalloproteinases but not by inhibitors of serine or cysteine proteinases, indicating that they were metalloproteinases. Both cell lines showed increased collagenolytic activity, which was activated by treatment with plasmin. In addition, both cell lines showed increased secretion of specific metalloproteinase inhibitors, including tissue inhibitor of metalloproteinases, with differentiation. Analysis of mRNA from undifferentiated and differentiated F9 cells by RNA blot analysis or reverse transcription coupled with the polymerase chain reaction showed that increased expression of genes for collagenase, stromelysin and tissue inhibitor of metalloproteinases is associated with differentiation of these cells. These results suggest that the expression of extracellular matrix-degrading metalloproteinases and their inhibitors is developmentally regulated during the differentiation and spreading of the parietal endoderm.
Receptors for epidermal growth factor and insulin-like growth factor-I on preimplantation trophoderm of the pig
Authors: Corps A. N. , Brigstock D. R. , Littlewood C. J. , Brown K. D. 
Published: April 2021

Abstract
12sI-labelled epidermal growth factor (125I-EGF) and 125I-labelled insulin-like growth factor-I (12SI-IGF-I) bound to trophodenn cells from pig blastocysts obtained on days 15 –19 of pregnancy. Specific binding was detected on freshly isolated cell suspensions and on cells cultured for several days. The binding of 12SI-EGF was inhibited by increasing concentrations of EGF, but not by various other growth factors and hormones. Chemical cross-linking of 12SI-EGF to its receptors using disuccinimidyl suberate (DSS) revealed a radiolabelled band of relative molecular mass 160 000, similar to that identified as the EGF receptor in other cell types. The binding of l2iI-IGF-I was inhibited by both IGF-I and insulin, indicating that the receptors were either type I IGF receptors or insulin receptors. Cross-linking of f25I-IGF-I to serum-free supernatants from trophoderm cultures showed that the cells secreted an IGF-binding protein, giving a complex of relative molecular mass about 45 000. The presence of receptors for EGF and IGF/insulin suggests that these factors could be involved in regulating the growth and development of the early blastocyst.
All-or-none craniorachischisis in Loop-tail mutant mouse chimeras
Authors: Musci Teresa S. , Mullen Richard J. 
Published: April 2021

Abstract
Mouse embryos homozygous for the mutant gene Looptail (Lp) are characterized by craniorachischisis, an open neural tube extending from the midbrain to the tail. In the present study, experimental chimeric mice containing mixtures of genetically mutant (from Lp/ + ×Lp/ + matings) and genetically normal cells were produced. Our aim was to determine whether a ‘rescue,’ phenotypic gradient, or intermediate expression (i.e. alternating areas of open and closed neural tube) would be observed in these chimeras. We report our analyses of Loop-tail mutant chimeras (n=82) by gross examination, progeny testing and quantitative analysis of glucose phosphate isomerase (GPI) isozyme levels. An all-or-none craniorachischisis in Loop-tail mutant chimeras was observed. Two multicolored adult chimeras, without any gross evidence of a neural tube defect, were shown to be homozygous Loop-tail chimeras (Lp/Lp↔+/+) by progeny testing. These results indicate that the normal phenotype can be expressed in the presence of mutant cells. Conversely, six neonates with craniorachischisis were shown to be chimeras by GPI analyses. These results show that the full mutant phenotype can be expressed even when one-third to one-half of the cells are genotypically wild-type. This study did not determine which tissue is primarily responsible for the defective neurulation in this mutant, but suggests that a ‘threshold’ mechanism underlies the Loop-tail mutant phenotype. In some chimeras that threshold is not reached and the neural tube remains open, whereas in other chimeras the threshold is reached and the neural tube closes completely.
Invasive equine trophoblast expresses conventional class I Major Histocompatibility Complex antigens
Authors: Donaldson William L. , Zhang Chonghui H. , Oriol Julio G. , Antczak Douglas F. 
Published: April 2021

Abstract
Monoclonal antibodies and alloantisera were used in an indirect immunohistochemical assay to determine the expression of class I and class II Major Histocompatibility Complex (MHC) antigens by equine placental cells and the endometrial tissues at the fetal-maternal interface. MHC class I antigens were expressed at high density on the surface of the trophoblast cells of the chorionic girdle at days 32–36, just prior to their invasion of the endometrium. The mature gonadotrophin-secreting cells of the endometrial cups, which are derived from the chorionic girdle cells, had greatly reduced levels of MHC class I antigen expression while no MHC class I antigens were detectable on the non-invasive trophoblast cells of the allantochorion, except in small isolated patches. MHC class I antigens inununo-precipitated from chorionic girdle cells with either monoclonal antibodies or alloantisera had a relative molecular mass of 44 000, which was identical to that of MHC class I antigens precipitated from lymphocytes with the same reagents. MHC class H antigens were not detected on any trophoblast cells, although they were expressed at high levels by the endometrial glandular and lumenal epithelium immediately bordering the endometrial cups. MHC class I antigens were also expressed at high levels by endometrial tissues in the area of the cups. The high level of MHC class I antigen expression by endometrial glands within and bordering the cups was in sharp contrast to the greatly reduced class I antigen expression by the mature endometrial cup cells themselves. Polymorphic, paternal, MHC class I antigens that are expressed by the invasive trophoblast cells of the chorionic girdle probably provide the antigenic signal for maternal anti-fetal alloantibody production in early horse pregnancy. Reduced expression of these antigens by terminally differentiated endometrial cup cells may represent a strategy for the protection of the conceptus from maternal immunological attack and destruction that is distinct from prevention of primary maternal sensitization.
NGF mRNA expression in developing cutaneous epithelium related to innervation density
Authors: Harper Sarah , Davies Alun M. 
Published: April 2021

ABSTRACT
To determine if the initial level of NGF mRNA in developing cutaneous epithelium is correlated with its final innervation density, we measured the concentration of NGF mRNA in the epithelia of the maxillary, mandibular and ophthalmic territories of trigeminal ganglion in the embryonic mouse. At the onset of neuronal death in the ganglion there were marked differences in the concentration of NGF mRNA in these epithelia: the level was highest in the epithelium of the densely innervated maxillary territory, it was lower in the epithelium of the moderately innervated mandibular territory and was lowest in the epithelium of the sparsely innervated ophthalmic territory. These regional differences in the level of NGF mRNA during the early stages of target field innervation suggest that the level of NGF production in target field cells, rather than regional differences in the access of innervating neurons to NGF, governs the number of neurons that survive. Because the same percentage cell death occurs in each of the subsets of trigeminal neurons that innervate the maxillary, mandibular and ophthalmic territories, regional differences in NGF synthesis are not responsible for establishing differences in innervation density, rather they maintain differences that arise earlier in development.
Regulations in the induction of the organized neural system in amphibian embryos
Authors: Yamada Tuneo 
Published: April 2021

Abstract
Some of the recent data on the induction of the neural system in amphibian embryos are reviewed, utilizing a model, according to which two basic events regulate in this system: (1) ectodermal dorsalization, which occurs all over the induced region of the ectoderm and is responsible for the neural and mesectodermal pathways and (2) caudalization, which occurs only on the posterior level of dorsalized ectoderm and is responsible for the posterior mode of induced differentiation, functioning as a gradient with the apex at the posterior end of the embryo. Dorsalization of ectoderm can be caused by treatment with Con A or TPA, both of which are potential mitogens. Not only after the treatment with TPA, but also during normal dorsalization, the activation of protein kinase C occurs in responding cells. The possibility is suggested that an early step of mitogenic transmembrane signal transduction induced by a growth factor regulates dorsalization in intact embryos. Ectodermal dorsalization is responsible for the appearance of neuronal and glial cell lineages, and independent of the ECM network formed on the internal surface of the responding ectoderm during gastrulation. In caudalization, a series of experiments suggests that the regulatory role is played by the transcript of the mesodermal posterior homeobox gene, Xhox 3. The expression of this gene in time and location closely coincides with the pattern of convergent extension, one type of morphogenetic movement, which is expressed in a posterior-anterior gradient. This directed cell motility is responsible for the formation of the body axis of vertebrates, and was shown to be involved in caudalization by earlier induction experiments in urodele embryos. Thus clues have been obtained for regulation in dorsalization and caudalization, paving the way for understanding the inductive action of the organizer.
Development and persistence of catecholaminergic neurons in cultured explants of fetal murine vagus nerves and bowel
Authors: Baetge G. , Schneider K. A. , Gershon M. D. 
Published: April 2021

Abstract
Transient catecholaminergic (TC) cells have been found to appear in the vagal pathway and bowel of fetal mice and rats. It has been proposed that these cells are migrating vagal crest-derived precursors of enteric neurons that lose their catecholaminergic properties when they terminally differentiate. In the current experiments, segments of fetal mouse gut were explanted before (day E9) TC cells or any neural markers could be detected in situ. Tyrosine hydroxylase (TH)-immuno-reactive neurons developed in vitro in 4/12 such explants; therefore, cells with a catecholaminergic potential are present in the gut of at least some animals prior to the in situ expression of this phenotype. The neurogenic potential of cells in the vagal pathway was similarly tested by studying cultures of explanted vagus nerves (day Ell). These studies revealed that neural precursors were present in the vagi and gave rise in vitro to neurons that displayed acetylcholinesterase (AChE) activity and neuron-specific enolase (NSE) immunoreactivity. A subset of these neural precursors were capable of migrating and formed satellite ganglia at a distance from the explants. Coincident expression of NSE and TH immunoreactivities was observed, indicating that at least some of the neurons that developed in vitro were derived from TC cells. Vagal TC cells, therefore, are neurogenic. Catecholaminergic cells did not disappear from cultured explants of vagus nerves or gut provided that these tissues contained TC cells at the time of explantation. Instead, catecholaminergic neurons developed and persisted in vitro for as long as cultures were maintained. These neurons contained aromatic L-amino acid decarboxylase as well as TH, NSE and neurofilament immunoreactivities. In contrast, if the bowel was explanted after the in situ disappearance of TC cells, catecholaminergic cells did not arise in the cultures. These experiments indicate that the period of time during which a catecholaminergic phenotype is expressed by neural precursors in the fetal vagal pathway and gut is not fixed, but can be changed by altering the environment of the cells as occurs when the bowel is grown in vitro’, moreover, contact with non-neuronal cells within the bowel is not by itself sufficient to inactivate catecholaminergic expression. The nature of the signal responsible for loss of the catecholaminergic phenotype in situ remains to be determined; however, the persistence of catecholaminergic expression in vitro should facilitate the investigation of this signal. expression, enteric nervous system.
Hormone-sensitive stages in the sexual differentiation of laryngeal muscle fiber number in Xenopus laevis
Authors: Marin Melanie L. , Tobias Martha L. , Kelley Darcy B. 
Published: April 2021

Abstract
The number of muscle fibers in the vocal organ of the adult male African clawed frog, Xenopus laevis, exceeds that of adult females. This sex difference is the result of rapid fiber addition in males between the end of metamorphosis, post-metamorphic stage 0 (PM0) and PM2. At PM0, male and female frogs have similar numbers of laryngeal muscle fibers. Males then add more muscle fibers than females and achieve an adult value that is 1.7 times the female number. Males castrated at PM0 have the same fiber number as females. Ovariectomy at PM0 does not alter muscle fiber addition in females. Gonadectomy at PM2 has no effect on fiber addition in either sex. Females attain masculine muscle fiber number if their ovaries are replaced with a testis at metamorphosis. Exogenous testosterone treatment at PM0 significantly increases fiber number in females but not in males. Exogenous testosterone given at PM2 has no effect on fiber number in females but decreases fiber number in males. We conclude that the testes are necessary for the marked addition of laryngeal muscle fibers seen in male X. laevis between PM0 and PM2. The masculine pattern of muscle fiber addition can be induced in females provided with a testis. Androgen secretion from the testes most probably accounts for masculinization of laryngeal muscle fiber number. After PM2, androgens are no longer necessary for muscle fiber addition and cannot increase fiber number in females.