bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transfer and tissue-specific accumulation of cytoplasmic components in embryos of Caenorhabditis elegans and Rhabditis dolichura: in vivo analysis with a low-cost signal enhancement device
Authors: Bossinger Olaf , Schierenberg Einhard 
Published: April 2021

ABSTRACT
The pattern of autofluorescence in the two free-living soil nematodes Rhabditis dolichura and Caenorhabditis elegans has been compared. In C. elegans, during later embryogenesis the prospective gut cells develop a typical bluish autofluorescence as seen under UV illumination, while in Rh. dolichura a strong autofluorescence is already present in the unfertilized egg. Using a new, lowcost signal enhancement device, we have been able to follow in vivo the dramatic change in the pattern of autofluorescence during embryogenesis of Rh. dolichura. Autofluorescent material accumulates progressively in the gut primordium and disappears completely from all other cells. To investigate whether such an accumulation of cytoplasmic components also takes place in the C. elegans embryo, we labeled the cytoplasm of the egg with the fluorescing tracer dyes Lucifer Yellow (LY) or Rhodamine 6G (R6G). While LY appears to bind to yolk and progressively accumulates in the developing gut primordium, R6G does not show any such binding and remains equally distributed over all cells. Measurements in early and late stages indicate a significant increase in the volume of the gut cells during embryogenesis, while the embryo as a whole does not grow. Moreover, in cleavage-blocked 2-cell stages after development overnight, a reversal of cell size relationship to the benefit of the gut precursor cell takes place. In summary, our observations suggest a previously unknown massive transfer of yolk components in the nematode embryo from non-gut cells into lysosomes of the gut primordium, where they are further metabolized during postembryonic development.
Communication compartments in hair follicles and their implication in differentiative control
Authors: Kam Ephraim , Hodgins Malcolm B. 
Published: April 2021

ABSTRACT
Observations on hair follicles presented in this paper show that boundaries to junctional communication are formed between groups of cells following different pathways of differentiation. The patterns of junctional communication in the bulbs of rat vibrissa follicles and human hair follicles were studied by microinjection of the fluorescent tracer dye Lucifer Yellow CH. Dye spread was extensive between undifferentiated cells of the hair bulb matrix but communication boundaries were found between groups of morphologically distinct cells. For example, boundaries to dye spread were observed between undifferentiated matrix cells and cells in the early stage of differentiation into the inner root sheath, between Huxley’s and Henle’s layers in the early inner root sheath and between cells of the cuticle and cortex of the hair. Dye did not spread between epithelial cells of the hair bulb and mesenchymal cells of the connective tissue sheath or dermal papilla. The patterns of dye spread became more complex (increased boundary formation and subcompartmentation) as differentiation progressed in higher regions of the hair bulb. The observed communication can be related to previous ultrastructural studies by others on the distribution of gap junctions in the wool follicle. These results show that junctional communication, with its consequent intercellular spread of small ions and molecules, is associated with uniformity of expression and behaviour within cell populations and that interruption of communication through the formation of boundaries and communication compartments is temporally and spatially related to the production of subpopulations of cells committed to the expression of different phenotypes.
Neural induction and regionalisation in the chick embryo
Authors: Storey Kate G. , Crossley James M. , Robertis Eddy M. De , Norris Wendie E. , Stern Claudio D. 
Published: April 2021

ABSTRACT
Induction and regionalisation of the chick nervous system were investigated by transplanting Hensen’s node into the extra-embryonic region (area opaca margin) of a host embryo. Chick/quail chimaeras were used to determine the contributions of host and donor tissue to the supernumerary axis, and three molecular markers, Engrailed, neurofilaments (antibody 3A10) and XlHboxl/Hox3.3 were used to aid the identification of particular regions of the ectopic axis.
We find that the age of the node determines the regions of the nervous system that form: young nodes (stages 2-4) induce both anterior and posterior nervous system, while older nodes (stages 5-6) have reduced inducing ability and generate only posterior nervous system. By varying the age of the host embryo, we show that the competence of the epiblast to respond to neural induction declines after stage 4.
We conclude that during normal development, the initial steps of neural induction take place before stage 4 and that anteroposterior regionalisation of the nervous system may be a later process, perhaps associated with the differentiating notochord. We also speculate that the mechanisms responsible for induction of head CNS differ from those that generate the spinal cord: the trunk CNS could arise by homeogenetic induction by anterior CNS or by elongation of neural primordia that are induced very early.
Pathfinding by cranial nerve VII (facial) motorneurons in the chick hindbrain
Authors: Chang Susannah , Fan Jinhong , Nayak Jayakar 
Published: April 2021

ABSTRACTCranial nerve VII (facial) motorneurons begin extending axons through rhombomeres 4 and 5 (R4 and RS) in the chick hindbrain on the second day of incubation. Without crossing the midline, facial motorneuron axons extend laterally from a ventromedial cell body location. All facial motorneuron axons leave the hindbrain through a discrete exit site in R4. To examine the importance of the exit site in R4 on motorneuron pathfinding, we ablated R4 before motorneuron axonogenesis. We find that mechanisms intrinsic to RS direct the initial lateral orientation of RS motorneuron axons. Upon reaching a particular lateral position, all R5 motorneuron axons must turn. In normal embryos the axons all turn rostrally to reach the nerve exit in R4. In embryos with R4 ablated, sometimes the axons turn rostrally and sometimes they turn caudally. A model combining permissive fields and chemotropic cues is presented to account for our observations.
Cellular and extracellular involvement in the regeneration of the rat lower vibrissa follicle
Authors: Jahoda Colin A. B. , Horne Kenneth A. , Mauger Annick , Bard Sylviane , Sengel Philippe 
Published: April 2021

Abstract
The sequence of events leading to the reconstruction of a fibre-producing hair follicle, after microsurgical amputation of the lower follicle bulb, has been detailed by immunohistology and electron microscopy. The initial response was essentially found to be a wound reaction, in that hyperproliferative follicle epidermis quickly spread to below the level of amputation - associated with downward movement of mesenchymal (or dermal) sheath cells. Fibronectin was prominent in both dermis and epidermis at this stage and, as in wound repair, preceded laminin and type IV collagen in covering the lower dermal-epidermal junction. Once a new basal line of epidermis and a complete basement membrane were established, laminin and type IV collagen were detected below this junction and within the prospective papillaforming mesenchyme. This coincided with ultrastructural observations of profuse sub-basement membrane extracellular material in the region of new papilla formation. The glassy membrane displayed extensive ultrastructural modifications at its lower level, and these corresponded with localized variations in staining intensities for all three antibodies over time. The membrane hung below the level of the epidermis, and was crossed by migrating cells from the mesenchymal dermal sheath of the follicle - it acted to segregate the inner group of follicular dermal cells from wound fibroblasts. Extracellular matrix may be a mediator of the dermal-epidermal interactions associated with this hair follicle regeneration phenomenon.
Interactions between retinoids and TGF βs in mouse morphogenesis
Authors: Mahmood Radma , Flanders Kathleen C. , Morriss-Kay Gillian M. 
Published: April 2021

Abstract
Using immunocytochemical methods we describe the distribution of different TGF β isoforms and the effects of excess retinoic acid on their expression during early mouse embryogenesis ( days of development). In normal embryos at 9 days, intracellular TGF β1 is expressed most intensely in neuroepithelium and cardiac myocardium whereas extracellular TGF β1 is expressed in mesenchymal cells and in the endocardium of the heart. At later stages, intracellular TGF β1 becomes very restricted to the myocardium and to a limited number of head mesenchymal cells; extracellular TGF β1 continues to be expressed widely in cells of mesenchymal origin, particularly in head and trunk mesenchyme, and also in endocardium. TGF β1 is widely expressed at all stages investigated while TGF β3 is not expressed strongly in any tissue at the stages examined.
Exposure of early neural plate stage embryos to retinoic acid caused reduced expression of TGF β1 and TGF β2 proteins but had no effect on TGF β1. Intracellular TGF β1 expression was reduced in all tissues except in the myocardium, while extracellular TGF β1 was specifically reduced in neuroepithelium and cranial neural crest cells at early stages. TGF β1 was reduced in all embryonic tissues. The down-regulation of intracellular TGF β1 was observed up to 48 hours after initial exposure to retinoic acid while some downregulation of TGF β1 was still seen up to 60 hours after initial exposure.
TGF βs are known to modulate the expression of various extracellular matrix molecules involved in cell growth, differentiation and morphogenesis. The interaction between retinoic acid and TGF β is discussed in relation to morphogenesis.
Characterization of HNK-1 antigens during the formation of the avian enteric nervous system
Authors: Luider Theo M. , Peters-Van Der Sanden Marjo J. H. , Molenaar Jan C. , Tibboel Dick , Kamp Arthur W. M. Van Der , Melters Carel 
Published: April 2021

Abstract
During vertebrate embryogenesis, interaction between neural crest cells and the enteric mesenchyme gives rise to the development of the enteric nervous system. In birds, monoclonal antibody HNK-1 is a marker for neural crest cells from the entire rostrocaudal axis. In this study, we aimed to characterize the HNK-1 carrying cells and antigen(s) during the formation of the enteric nervous system in the hindgut. Immunohistological findings showed that HNK-l-positive mesenchymal cells are present in the gut prior to neural crest cell colonization. After neural crest cell colonization this cell type cannot be visualized anymore with the HNK-1 antibody. We characterized the HNK-1 antigens that are present before and after neural crest cell colonization of the hindgut. Immunoblot analysis of plasma membranes from embryonic hindgut revealed a wide array of HNK-1-carrying glycoproteins. We found that two HNK-1 antigens are present in E4 hindgut prior to neural crest cell colonization and that the expression of these antigens disappears after neural crest colonization. These two membrane glycoproteins, G-42 and G-44, have relative molecular masses of 42,000 and 44,000, respectively, and they both have isoelectric points of 5.5 under reducing conditions. We suggest that these HNK-1 antigens and the HNK-l-positive mesenchymal cells have some role in the formation of the enteric nervous system.
Expression pattern of Motch, a mouse homolog of Drosophila Notch, suggests an important role in early postimplantation mouse development
Authors: Amo Francisco Franco Del , Smith David E. , Swiatek Pamela J. , Gendron-Maguire Maureen , Greenspan Ralph J. , Mcmahon Andrew P. , Gridley Thomas 
Published: April 2021

ABSTRACT
The Notch gene of Drosophila encodes a large transmembrane protein involved in cell-cell interactions and cell fate decisions in the Drosophila embryo. To determine if a gene homologous to Drosophila Notch plays a role in early mouse development, we screened a mouse embryo cDNA library with probes from the Xenopus Notch homolog, Xotch. A partial cDNA clone encoding the mouse Notch homolog, which we have termed Motch, was used to analyze expression of the Motch gene. Motch transcripts were detected in a wide variety of adult tissues, which included derivatives of all three germ layers. Differentiation of P19 embryonal carcinoma cells into neuronal cell types resulted in increased expression of Motch RNA. In the postimplantation mouse embryo Motch transcripts were first detected in mesoderm at 7.5 days post coitum (dpc). By 8.5 dpc, transcript levels were highest in presomitic mesoderm, mesenchyme and endothelial cells, while much lower levels were detected in neuroepithelium. In contrast, at 9.5 dpc, neuroepithelium was a major site of Motch expression. Transcripts were also abundant in cell types derived from neural crest. These data suggest that the Motch gene plays multiple roles in patterning and differentiation of the early postimplantation mouse embryo.
A developmentally regulated switch in neuronal responsiveness to NCAM and N-cadherin in the rat hippocampus
Authors: Doherty Patrick , Skaper Stephen D. , Moore Stephen E. , Leon Alberta , Walsh Frank S. 
Published: April 2021

ABSTRACT
Monolayers of control 3T3 fibroblasts and 3T3 cells expressing transfected NCAM or N-cadherin have been used as a culture substratum for rat hippocampal neurons. Both NCAM and N-cadherin are expressed in the hippocampus through embryonic day 17 (E17) to postnatal day 4 (PND4); however, whereas E17 neurons responded to transfected NCAM by extending considerably longer neurites, PND4 neurons responded very poorly. The converse was true for responsiveness to N-cadherin. These data demonstrate a switch in neuronal responsiveness to NCAM and N-cadherin in the developing hippocampus. NCAM-dependent neurite outgrowth from E17 neurons was largely dependent on the presence of α2–8-linked polysialic acid (PSA) on neuronal NCAM. NCAM-dependent neurite outgrowth could be fully inhibited by pertussis toxin or a combination of L- and N-type calcium channel antagonists thus providing direct evidence concerning the nature of the second messenger pathway activated in primary neurons by cell adhesion molecules (CAMs).
Embryonic alkaline phosphatase is expressed at M-phase in the spermatogenic lineage of the mouse
Authors: Narisawa Sonoko , Hofmann Marie-Claude , Ziomek Carol A. , Luis Millán José 
Published: April 2021

ABSTRACT
We have recently cloned and characterized a novel embryonic alkaline phosphatase (EAP) expressed at the two-cell to blastocyst stage of preimplantation development in the mouse. The isozyme is re-expressed in trace amounts in the thymus, intestine and testis during adult life. In the present report, we find that EAP transcripts can be detected, by RT-PCR analysis, in very low amounts in the testes of newborn mice, but at 24 days of age EAP mRNA levels reach the highest concentrations, remaining high at 40 and even 117 days of age. We produced a synthetic peptide and a corresponding rabbit anti-peptide antiserum (Rb-1434), which was characterized by enzyme antigen immunoassays and reactivity with chinese hamster ovary cell transfectants, as reacting specifically with EAP. The Rb-1434 antibody enabled us to examine immunohistochemically what cell types in the testis are responsible for the expression of EAP during different developmental stages. No positive cells were recognized in the testis of newborns (day 0) and 8-day-old mice. Positive cells were first observed at day 15 and, at 24 days of age, many positive M-phase cells, morphologically corresponding to spermatocytes in mid to late prophase of meiotic division I, were strongly positive for EAP expression. Positive M-phase cells were also observed at 40 days and 151 days of age. Transgenic mice expressing the human GCAP isozyme in a tissue-specific manner in the testis, showed equivalent stages of M-phase figures when stained immunohistochemically with a specific rabbit polyclonal antiserum. Our results demonstrate that EAP is expressed in M-phase spermatogenic cells during postnatal development, suggesting a role for this AP isozyme during meiosis.
Why we have (only) five fingers per hand: Hox genes and the evolution of paired limbs
Authors: Tabin Clifford J. 
Published: April 2021

ABSTRACT
Limb development has long been a model system for studying vertebrate pattern formation. The advent of molecular biology has allowed the identification of some of the key genes that regulate limb morphogenesis. One important class of such genes are the homeobox-containing, or Hox genes. Understanding of the roles these genes play in development additionally provides insights into the evolution of limb pattern. Hox gene expression patterns divide the embryonic limb bud into five sectors along the anterior/posterior axis. The expression of specific Hox genes in each domain specifies the developmental fate of that region. Because there are only five distinct Hox-encoded domains across the limb bud there is a developmental constraint prohibiting the evolution of more than five different types of digits. The expression patterns of Hox genes in modern embryonic limb buds also gives clues to the shape of the ancestral fin field from which the limb evolved, hence elucidating the evolution of the tetrapod limb.
Vital dye analysis of cranial neural crest cell migration in the mouse embryo
Authors: Serbedzija George N. , Bronner-Fraser Marianne , Fraser Scott E. 
Published: April 2021

ABSTRACT
The spatial and temporal aspects of cranial neural crest cell migration in the mouse are poorly understood because of technical limitations. No reliable cell markers are available and vital staining of embryos in culture has had limited success because they develop normally for only 24 hours. Here, we circumvent these problems by combining vital dye labelling with exo utero embryological techniques. To define better the nature of cranial neural crest cell migration in the mouse embryo, premigratory cranial neural crest cells were labelled by injecting DiI into the amniotic cavity on embryonic day 8. Embryos, allowed to develop an additional 1 to 5 days exo utero in the mother before analysis, showed distinct and characteristic patterns of cranial neural crest cell migration at the different axial levels. Neural crest cells arising at the level of the forebrain migrated ventrally in a contiguous stream through the mesenchyme between the eye and the diencephalon. In the region of the midbrain, the cells migrated ventrolaterally as dispersed cells through the mesenchyme bordered by the lateral surface of the mesencephalon and the ectoderm. At the level of the hindbrain, neural crest cells migrated ventrolaterally in three subectodermal streams that were segmentally distributed. Each stream extended from the dorsal portion of the neural tube into the distal portion of the adjacent branchial arch. The order in which cranial neural crest cells populate their derivatives was determined by labelling embryos at different stages of development. Cranial neural crest cells populated their derivatives in a ventral-to-dorsal order, similar to the pattern observed at trunk levels. In order to confirm and extend the findings obtained with exo utero embryos, DiI (1,1-dioctadecyl-3,3,3′,3′-tetramethylindo-carbocyanine perchlorate) was applied focally to the neural folds of embryos, which were then cultured for 24 hours. Because the culture technique permitted increased control of the timing and location of the DiI injection, it was possible to determine the duration of cranial neural crest cell emigration from the neural tube. Cranial neural crest cell emigration from the neural folds was completed by the 11-somite stage in the region of the rostral hindbrain, the 14-somite stage in the regions of the midbrain and caudal hindbrain and not until the 16-somite stage in the region of the fore-brain. At each level, the time between the earliest and latest neural crest cells to emigrate from the neural tube appeared to be 9 hours. Some aspects of cranial neural crest cell migration were similar to those observed in avian embryos; however, the exact pathways, the timing and the axial levels that contribute to the neural crest cells were distinctly different.
Clox, a mammalian homeobox gene related to Drosophila cut, encodes DNA-binding regulatory proteins differentially expressed during development
Authors: Andres Vicente , Nadal-Ginard Bernardo , Mahdavi Vijak 
Published: April 2021

ABSTRACT
We report the isolation of a cDNA encoding a mammalian homeoprotein related to the Drosophila cut gene product, called Clox, for Cut like homeobox. In addition to the homeodomain, three 73-amino acid repeats, the so-called cut repeats, are also conserved between Cut and the mammalian counterpart described here. This conservation suggests that the cut repeat motif may define a new class of homeoproteins. Both cloned and endogenous Clox proteins are nuclear DNA-binding proteins with very similar sequence specificity. Western blot analysis revealed several distinct Clox protein species in a variety of tissues and cell types. The relative abundance of these proteins is regulated during mouse development and cell differentiation in culture. Interestingly, ∼180-190×103Mr Clox proteins predominate in early embryos and are upregulated in committed myoblasts and chondrocytes, but downregulated upon terminal differentiation. Clox DNA-binding activity is correlated with the abundance of these proteins. In contrast, larger Clox protein species (∼230-250×103Mr) are detected mainly in adult tissues and in terminally differentiated cells. Cotransfection experiments show that Clox proteins can function as repressors of tissue-specific gene transcription. Thus, Clox, like their Drosophila counterparts, are candidate regulators of cell-fate specification in diverse differentiation programs.
Determination of epithelial half-somites in skeletal morphogenesis
Authors: Goldstein Ronald S. , Kalcheim Chaya 
Published: April 2021

ABSTRACT
The segmental body plan of vertebrates arises from the metameric organization of the paraxial mesoderm into somites. Each mesodermal somite is subdivided into at least two distinct domains: rostral and caudal. The segmental pattern of dorsal root ganglia, sympathetic ganglia and nerves is imposed by differential properties of either somitic domain. In the present work, we have extended these studies by investigating the contribution of rostral or caudal-half somites to vertebral development using grafts of multiple somite halves. In both rostral and caudal somitic implants, the grafted mesoderm dissociates normally into sclerotome and dermomyotome, and the sclerotome further develops into vertebrae. However, the morphogenetic capabilities of each somitic half differ. The pedicle of the vertebral arch is almost continuous in caudal half-somite grafts and is virtually absent in rostral half-somite implants. Simi-larly, the intervertebral disk is present in rostral half-somite chimeras, and much reduced or virtually absent in caudal somite chimeras. Thus, only the caudal half cells are committed to give rise to the vertebral pedicle, and only the rostral half cells are committed to give rise to the fibrocartilage of the intervertebral disk.
Each vertebra is therefore composed of a pedicle-containing area, apparently formed by the caudal half-somite, followed by a pedicle-free zone, the intervertebral foramen, derived from the rostral somite. These data directly support the hypothesis of resegmentation, in which vertebrae arise by fusion of the caudal and rostral halves of two consecutive somites.