bluuebunny/crossref_metadata_2025_split huggingface dataset:
Colonization of the post-umbilical bowel by cells derived from the sacral neural crest: direct tracing of cell migration using an intercalating probe and a replication-deficient retrovirus
Authors: Pomeranz Howard D. , Rothman Taube P. , Gershon Michael D. 
Published: April 2021

ABSTRACT
Experiments were done to test the hypothesis that the avian gut is colonized by cells derived from both vagal and sacral regions of the neural crest. A fluorescent dye, dil (l,l-dioctadecyl-3,3,3′,3′-tetramethylmdocarbocya-nine perchlorate), and a replication-deficient retrovirus (LZ10; Galileo et al. 1990) were employed as tracers. Since LZ10 was constructed with lacZ of E. coli as a reporter gene, infected cells were identified by demonstrating β-galactosidase immunoreactivity. Dil and LZ10 were injected between the neural tube and surface ectoderm (before the migration of crest cells away from the injection sites) at vagal, truncal (dil only), or sacral axial levels. The bowel was examined 4 days later in order to allow crest-derived cells sufficient time to migrate to the gut. Following injections of either tracer into the vagal crest, labelled cells were found in the gizzard and duodenum.’When dil or LZ10 was injected into the sacral crest, labelled cells were seen in the postumbilical bowel and ganglion of Remak. In the hindgut, marked cells were concentrated in the mesenchyme, just internal to the serosa, and were never observed rostral to the umbilicus. No fluorescent cells were ever found in the bowel following truncal injections of dil, although such cells were observed in sympathetic ganglia. Labelled cells were always found in dorsal root ganglia, no matter which tracer or level of the crest was injected. In embryos injected with LZ10, infected cells in the gut and dorsal root ganglia displayed a neural crest marker (NC-1 immunoreactivity). These observations confirm that the gut is colonized by cells from the sacral as well as the vagal region of the neural crest and that the émigrés from the sacral crest are confined to the post-umbilical bowel.
An extensive 3′ cis-regulatory region directs the imaginal disk expression of decapentaplegic, a member of the TGF-β family in Drosophila
Authors: Blackman Ronald K. , Sanicola Michele , Raftery Laurel A. , Gillevet Trudy , Gelbart William M. 
Published: April 2021

ABSTRACT
The decapentaplegic (dpp) gene in Drosophila melanogaster encodes a TGF-β-like signalling molecule that is expressed in a complex and changing pattern during development. One of dpp’s contributions is to proximal-distal outgrowth of the adult appendages, structures derived from the larval imaginal disks. Appendage specific mutations of dpp fall in a 20 kb interval 3’ to the known dpp transcripts. Here, we directly test the hypothesis that these mutations define an extended 3’ cis-regulatory region. By analysis of germ-line transformants expressing a reporter gene, we show that sequences from this portion of the gene, termed the dppdisk region, are capable of directing expression comparable to that defined by RNA in situ hybridization. We localize two intervals of the dppdisk region that appear to account for much of the dpp spatial pattern in imaginal disks and discuss the positions of these important elements in terms of the genetics of dpp. Finally, we provide evidence to suggest that one of our constructs expresses β-galactosidase in the early imaginal disk primordia in the embryo, at approximately the time when they are set aside from surrounding larval epidermal tissues. Thus, dpp may be involved directly in the determination of the imaginal disks.
An analysis of culmination in Dictyostelium using prestalk and stalk-specific cell autonomous markers
Authors: Jermyn K. A. , Williams J. G. 
Published: April 2021

ABSTRACT
The ecmA (pDd63) and ecmB (pDd56) genes encode extracellular matrix proteins of the slime sheath and stalk tube of Dictyostelium discoideum. Using fusion genes containing the promoter of one or other gene coupled to an immunologically detectable reporter, we previously identified two classes of prestalk cells in the tip of the migrating slug; a central core of pstB cells, which express the ecmB gene, surrounded by pstA cells, which express the ecmA gene. PstB cells lie at the position where stalk tube formation is initiated at culmination and we show that they act as its founders. As culmination proceeds, pstA cells transform into pstB cells by activating the ecmB gene as they enter the stalk tube. The prespore region of the slug contains a population of cells, termed anterior-like cells (ALC), which have the characteristics of prestalk cells. We show that the ecmA and ecmB genes are expressed at a low level in ALC during slug migration and that their expression in these cells is greatly elevated during culmination. Previous observations have shown that ALC sort to surround the prespore cells during culmination (Sternfeld and David, 1982Devi Biol. 93, 111-118) and we find just such a distribution for pstB cells. We believe that the ecmB protein plays a structural role in the stalk tube and its presence, as a cradle around the spore head, suggests that it may play a further function, perhaps in ensuring integrity of the spore mass during elevation. If this interpretation is correct, then a primary role of anterior-like cells may be to form these structures at culmination.
We previously identified a third class of prestalk cells, pstO cells, which lie behind pstA cells in the slug anterior and which appeared to express neither the ecmA nor the ecmB gene. Using B-galactosidase fusion constructs, which give more sensitive detection of gene expression, we now find that these cells express the ecmA gene but at a much lower level than pstA cells. We also show that expression of the ecmA gene becomes uniformly high throughout the prestalk zone when slugs are allowed to migrate in the light. Overhead light favours culmination and it may be that increased expression of the ecmA gene in the pst ‘O’ region is a preparatory step in the process.
Molecular cloning and expression of a novel homeobox gene AHox1 of the ascidian, Halocynthia roretzi
Authors: Saiga Hidetoshi , Mizokami Atsushi , Makabe Kazuhiro W. , Satoh Noriyuki , Mita Takashi 
Published: April 2021

ABSTRACT
We have isolated a novel ascidian homeobox gene, designated AHoxl, by screening the genomic DNA of Halocynthia roretzi with the Bombyx mori Antennapedia type homeobox as a probe. The AHoxl gene encodes a protein that consists of 741 amino acids. The homeobox of AHoxl is interrupted by 2 introns each of which is about 300 bp in length and it shows about 70 % similarity at a deduced amino acid level to that of Drosophila H2.0. This suggests that AHoxl is one of the most diverged homeobox genes so far characterized. Northern blot hybridization with an AHoxl probe showed the presence of single transcripts approximately 2.8 kb in length in larvae, juveniles and some adult tissues. The expression of AHoxl is scarcely detected during the course of early development but it increases to a moderate level at the larval stage. After metamorphosis, the level of AHoxl expression increases as development proceeds. In situ hybridization to the juvenile 7 days after metamorphosis showed that the site of AHoxl expression is the epithelium of digestive tract. Among the adult tissues examined, digestive tract, digestive gland and coelomic cells were the major sites of the expression of AHoxl. In gonad, body wall muscle and pharyngeal epithelium, the expression of AHoxl is relatively weak. These results suggest that AHoxl is primarily expressed in the tissues of endodermal origin and that the gene expression may be associated with differentiation of the endodermal tissues.
Decrease in DNA methylase activity during preimplantation development in the mouse
Authors: Monk M. , Adams R. L. P. , Rinaldi A. 
Published: April 2021

ABSTRACT
During early mouse development, there are large-scale changes in DNA methylation. These changes may be due to the availability or stability of the enzyme, DNA methyltransferase (methylase), which is responsible for maintenance of DNA methylation. A microassay for methylase activity in preimplantation embryos shows that the level of maternally inherited enzyme is extremely high in the egg and that this activity is stable for the first three cleavage divisions. However, from the 8-cell to the blastocyst stage, there is a marked and absolute decrease in enzyme activity.
Homologous patterns in the embryonic development of the peripheral nervous system in the grasshopper Schistocerca gregaria and the fly Drosophila melanogaster
Authors: Meier Thomas , Chabaud Fabienne , Reichert Heinrich 
Published: April 2021

ABSTRACT
To determine the generality of developmental mechanisms involved in the construction of the insect nervous system, the embryonic development of the peripheral nervous system in the grasshopper Schistocerca gregaria was characterized at the level of identified neurons and nerve branches and then compared to that previously described from the fly Drosophila melanogaster. For this, immunocytochemistry using a neuron-specific antibody was carried out on staged grasshopper embryos. Our results show that initially a simple peripheral nerve scaffolding is established in each segment of the animal. This scaffolding consists of a pair of intersegmental nerves that are formed by identified afferent and efferent pioneer neurons and a pair of segmental nerves that are formed by afferent pioneers situated in limb buds. Subsequently, identified sets of sensory neurons differentiate in a stereotyped spatiotemporal pattern in dorsal, lateral and ventral clusters in each segment and project their axons onto these nerves. Although segmentspecific differences exist, serial homologs of the developing nerves and sensory neurons can be identified. A comparison of these results with those obtained from Drosophila shows that virtually the same pattern of peripheral nerves and sensory structures is formed in both species. This indicates that the construction of the peripheral nervous system in extremely divergent modern insects relies on conserved developmental mechanisms that evolved in ancestral insects over 300 million years ago.
Patterning the vertebrate head: murine Hox 2 genes mark distinct subpopulations of premigratory and migrating cranial neural crest
Authors: Hunt Paul , Wilkinson David , Krumlauf Robb 
Published: April 2021

ABSTRACT
The structures of the face in vertebrates are largely derived from neural crest. There is some evidence to suggest that the form of the facial pattern is determined by the crest, and that it is specified before migration as to the structures that it is able to form. The neural crest is able to control the form of surrounding, non-neural crest tissues by an instructive interaction. Some of this cranial crest is derived from a region of the hindbrain that expresses Hox 2 homeobox genes in an overlapping and segment-restricted pattern.
We have found that neurogenic and mesenchymal neural crest expresses Hox 2 genes from its point of origin beside the neural plate, during migration and after migration has ceased and that rhombomeres 3 and 5 do not have any expressing neural crest beside them. Each branchial arch expresses a different combination or code of Hox genes in a segment-restricted way.
The surface ectoderm over the arches initially does not express Hox genes, and later adopts an expression pattern that reflects that of neural crest that has come to underlie it. We suggest that initially the neural plate and neural crest are spatially specified, while the surface ectoderm is unpatterned. Subsequently some positional information could be transferred to the surface ectoderm as a result of an interaction with the neural crest.
Given that the role of the homologous genes in insects is position specification, and that neural crest is imprinted before migration, we suggest that Hox 2 genes are providing part of this positional information to the neural crest and hence are involved in patterning the structures of the branchial arches.
The roles of pyruvate, lactate and glucose during preimplantation development of embryos from F1 hybrid mice in vitro
Authors: Brown J. J. G. , Whittingham D. G. 
Published: April 2021

ABSTRACT
Embryos of certain inbred mouse strains, and their F1 hybrids, are able to develop from the 1-cell to blastocyst stage in simple chemically defined media containing lactate (L), pyruvate (P) and glucose (G). The individual roles of these substrates in supporting complete preimplantation development in vitro was examined with 1-cell F2 embryos from B6CBF1 hybrid mice. Embryos collected between 26 and 27 h post hCG were cultured in medium containing L, P, LP or LPG. After 50 h in culture, the proportions developing to the morula stage were 1%, 83%, 94% and 100%, respectively. In combination, lactate and pyruvate appeared to act synergistically and both the rate and level of development to the morula stage were unaffected by the absence of glucose. After a further 46 h in culture, only the embryos grown in the presence of glucose developed into blastocysts. In LP medium, embryos arrested at the compacted morula stage late on day 3 of development.
As culture continued in the absence of glucose, embryos decompacted (≈82 h post hCG) and subsequently degenerated. Exposure to medium containing glucose for the first, second or third 24 h period in culture was sufficient to support the morula-to-blastocyst transition. Glucose still supported this transition when embryos were transferred to LPG medium 3h after the completion of compaction (76 h post hCG), but was ineffective 6 h later (82 h post hCG) once decompaction had commenced. We conclude that lactate and pyruvate together are able to support normal development of 1-cell F2 embryos to the morula stage in vitro, but that glucose is an essential component of the culture medium for development to the blastocyst stage.
Expression of the fibroblast growth factor-5 gene in the mouse embryo
Authors: Haub Olivia , Goldfarb Mitchell 
Published: April 2021

ABSTRACT
Fibroblast growth factors (FGFs) are structurally related mitogens that can regulate the differentiation of a wide variety of cells. As a step towards elucidating the developmental roles played by one of these factors, we have used in situ hybridization methods to examine expression of the murine Fgf-5 gene during embryogenesis. Fgf-5 RNA was detected at seven distinct sites in the developing mouse embryo: (1) postimplantation epiblast (embryonic day , (2) lateral splanchnic mesoderm , (3) lateral somatic mesoderm , (4) myotomes , (5) mastication muscle , (6) limb mesenchyme , and (7) acoustic ganglion . At several of these sites, expression is spatially restricted within the tissues. We offer several hypotheses regarding the roles of FGF-5 in murine development.
Proteinases of the mammary gland: developmental regulation in vivo and vectorial secretion in culture
Authors: Talhouk Rabih S. , Chin Jennie R. , Unemori Elaine N. , Werb Zena , Bissell Mina J. 
Published: April 2021

ABSTRACT
The extracellular matrix (ECM) is an important regulator of mammary epithelial cell function both in vivo and in culture. Substantial remodeling of ECM accompanies the structural changes in the mammary gland during gestation, lactation and involution. However, little is known about the nature of the enzymes and the processes involved. We have characterized and studied the regulation of cell-associated and secreted mammary gland proteinases active at neutral pH that may be involved in degradation of the ECM during the different stages of mammary development. Mammary tissue extracts from virgin and pregnant CD-I mice resolved by zymography contained three major proteinases of 60K (K=103Mr), 68K and 70K that degraded denatured collagen. These three gelatinases were completely inhibited by the tissue inhibitor of metalloproteinases. Proteolytic activity was lowest during lactation especially for the 60K gelatinase which was shown to be the activated form of the 68K gelatinase. The activated 60K form decreased prior to parturition but increased markedly after the first two days of involution. An additional gelatin-degrading proteinase of 130K was expressed during the first three days of involution and differed from the other gelatinases by its lack of inhibition by the tissue inhibitor of metalloproteinases.
The activity of the casein-degrading proteinases was lowest during lactation. Three caseinolytic activities were detected in mammary tissue extracts. A novel 26K cell-associated caseinase - a serine arginine-esterase - was modulated at different stages of mammary development. The other caseinases, at 92K and a larger than 100K, were not developmentally regulated. To find out which cell type produced the proteinases in the mammary gland, we isolated and cultured mouse mammary epithelial cells. Cells cultured on different substrata produced the full spectrum of gelatinases and caseinases seen in the whole gland thus implicating the epithelial cells as a major source of these enzymes. Analysis of proteinases secreted by cells grown on a reconstituted basement membrane showed that gelatinases were secreted preferentially in the direction of the basement membrane. The temporal pattern of expression of these proteinases and the basal secretion of gelatinases by epithelial cells suggest their involvement in the remodelling of the extracellular matrix during the different stages of mammary development and thus modulation of mammary cell function.
The embryonic origin of imaginal discs in Drosophila
Authors: Bate Michael , Arias Alfonso Martinez 
Published: April 2021

ABSTRACT
The thoracic imaginal discs of Drosophila melanogaster can be observed during embryogenesis as clusters of cells with particular shapes, sizes and behaviours. These structures can be detected soon after germ band shortening and their development appears to be tightly linked to that of the larval epidermis.
Substitution for mesenchyme by basement-membrane-like substratum and epidermal growth factor in inducing branching morphogenesis of mouse salivary epithelium
Authors: Nogawa Hiroyuki , Takahashi Yu 
Published: April 2021

ABSTRACT
Mouse salivary epithelium cannot undergo branching morphogenesis in the absence of the surrounding mesenchyme. To clarify the nature of the mesenchymal influence on the epithelium, we have investigated the culture conditions in which the epithelium could normally branch in the absence of mesenchymal cells. Combination of basement-membrane-like substratum (Matrigel) and epidermal growth factor (EGF) could substitute for the mesenchyme, the epithelium showing typical branching morphogenesis. Transforming growth factor a had the same effect as EGF. Matrigel plus basic fibroblast growth factor or transforming growth factor β1 and collagen gel plus EGF were not sufficient to support the branching of the epithelium. These results clearly reveal that the role of mesenchyme in salivary morphogenesis is both to provide the epithelium with an appropriate substratum and to accelerate growth of the epithelium.
Identification of multiple stages in the conversion of maize meristems from vegetative to floral development
Authors: Irish Erin E. , Nelson Timothy M. 
Published: April 2021

ABSTRACT
Vegetative growth in most lines of maize is terminated at a predictable stage in development by the conversion of the shoot apical meristem into an inflorescence, the tassel. The conversion from vegetative to floral development is under developmental control, the basis of which is obscure. We have assayed the developmental potential of the shoot apical meristem in order to identify the stage at which it is determined to form a tassel. We show, using shoot apex culture, that meristems are not determined to form a tassel until after all vegetative nodes have been initiated. We also show that floral determination is a separate, later event in the development of a maize inflorescence. Intermediate stages can be distinguished in which the meristem is determinate and has the phyllotaxis of a tassel when cultured but develops vegetative shoots from buds that normally give rise to sets of florets.
Differential stability of expression of similarly specified endogenous and exogenous genes in the sea urchin embryo
Authors: Livant Donna L. , Hough-Evans Barbara R. , Moore James G. , Britten Roy J. , Davidson Eric H. 
Published: April 2021

ABSTRACT
The object of these experiments was to determine whether competitive titration in vivo of factors required for expression of the Cyllla · CAT fusion gene would affect expression of the endogenous Cyllla gene in the same embryos. Earlier work showed that expression of this fusion gene after injection into sea urchin eggs is stoichiometrically reduced when low molar excesses of DNA fragments containing only its regulatory domain are coinjected. In order to compare endogenous (i.e. Cyllla) and exogenous (i.e. Cyllla · CAT) expression simultaneously in embryos bearing excess competitor regulatory DNA, we developed, and here describe, a new procedure for generating transgenic sea urchin embryos in which all of the cells in many embryos, and most in others, bear the exogenous DNA. Such large reduction of mosaicism can be achieved by multiple injection of the exogenous DNA fragments into fertilized eggs. Using this method, we demonstrate that at a level of competitor DNA incorporation which reduces Cyllla·CAT expression by 85%, endogenous Cyllla mRNA levels are wholly unaffected. Nor is spatial expression of the endogenous Cyllla gene disturbed. Since the Cyllla · CAT genes are properly expressed under control of the Cyllla regulatory sequences, they must participate in the same set of necessary DNA-protein interactions. However, we infer from the results that we report here that the regulatory complexes in the endogenous Cyllla gene are greatly stabilized relative to those of the exogenous Cyllla · CAT genes.
Restricted spatial and temporal expression of G-protein α subunits during Drosophila embryogenesis
Authors: Wolfgang William J. , Quan Franklin , Thambi Nina , Forte Michael 
Published: April 2021

ABSTRACT
Of the known signal transduction mechanisms, the most evolutionarily ancient is mediated by a family of heterotrimeric guanine nucleotide binding proteins or G proteins. In simple organisms, this form of sensory transduction is used exclusively to convey signals of developmental consequence. In metazoan organisms, however, the developmental role of G-protein-coupled sensory transduction has been more difficult to elucidate because of the wide variety of signals (peptides, small molecules, odorants, hormones, etc.) that use this form of sensory transduction. We have begun to examine the role of G-protein-coupled signaling during development by investigating the expression during Drosophila embryogenesis of a limited set of G proteins. Since these proteins are a common component of all G-protein-coupled signaling systems, their developmental pattern of expression should indicate when and where programmed changes in gene activity are initiated by, or involve the participation of, G-protein-coupled signaling events. We have focused on the spatial and temporal expression pattern of three different Drosophila G-protein α subunits by northern blot analysis, in situ hybridization and immunocytochemistry using antibodies directed to peptides specifically found in each α subunit. From the spatial and temporal restriction of the expression of each protein, our results suggest that different forms of G-protein-coupled sensory transduction may mediate developmental interactions during both early and late stages of embryogenesis and may participate in a variety of specific developmental processes such as the establishment of embryonic position, the ontogeny of the nervous system and organogenesis.