bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction by acid load of the maturation of prestalk cells in Dictyostelium discoideum
Authors: Inouye Kei 
Published: April 2021

Abstract
During the process of fruiting body construction in the cellular slime mould Dictyostelium discoideum, prestalk cells become mature stalk cells in a well-controlled manner. To identify the natural inducer of stalk cell maturation, substances known to induce stalk cell differentiation under in vitro conditions, and some other related compounds, were examined for their effects in vivo on migrating slugs, the precursor structures of the fruiting bodies.
Among these substances, addition of weak acids such as CO2, and addition followed by removal of weak bases such as NH3, strikingly induced the maturation of prestalk cells in situ in slugs. On the other hand, inhibitors of the plasma membrane proton pump did not efficiently induce the maturation of prestalk cells in intact slugs. Differentiation inducing factor (DEF), an endogenous inducer of prestalk differentiation, seemed to be an even poorer inducer of stalk cell maturation when applied to intact slugs.
The activities of these substances in inducing stalk cell maturation showed a good correlation with their effects on the cytoplasmic pH (pH|) of prestalk cells; the larger the pH| drop, the stronger the induction of stalk cell maturation, suggesting a requirement for a pHi decrease for the maturation of prestalk cells. Based on these results, it was proposed that stalk cell differentiation, which is induced by DIF, is blocked halfway during normal development by (an) agent(s) that prevent(s) the decrease in pH,.
A phylogenetic interpretation of the patterns of gene expression in Drosophila embryos
Authors: Tear G. , Bate C. M. , Arias A. Martinez 
Published: April 2021

ABSTRACT
Two fundamental processes of the development of insect embryos are the generation and the morphological diversification of metameric units. In Drosophila, these processes are under the control of the products of the segmentation (generation) and the homeotic (morphological diversification) genes. Molecular studies of the activity of these genes has revealed spatial and temporal patterns of expression consistent with the requirements inferred from the mutant phenotypes but, in addition, these studies have revealed transient patterns which are difficult to reconcile with those phenotypes. It is possible that these patterns reflect ancestral regulatory elements which are still operational in more primitive insects. The validity of this interpretation can be tested by comparing the embryonic development of long germ band insects like Drosophila melanogaster with that of the more primitive short germ band insects like the locust Schistocerca gregaria and by obtaining and studying locust homologues of Drosophila segmentation and homeotic genes.
A cell lineage analysis of segmentation in the chick embryo
Authors: Stern Claudio D. , Fraser Scott E. , Keynes Roger J. , Primmett Dennis R. N. 
Published: April 2021

ABSTRACT
We have studied the lineage history of the progenitors of the somite mesoderm and of the neural tube in the chick embryo by injecting single cells with the fluorescent tracer, rhodamine-lysine-dextran. We find that, although single cells within the segmental plate give rise to discrete clones in the somites to which they contribute, neither the somites nor their component parts (sclerotome, dermatome, myotome or their rostral and caudal halves) are ‘compartments’ in the sense defined in insects. Cells in the rostral two thirds or so of the segmental plate contribute only to somite tissue and divide about every 10 h, while those in the caudal portions of this structure contribute both to the somites and to intermediate and lateral plate mesoderm derivatives. In the neural tube, the descendants of individual prospective ventral horn cells remain together within the horn, with a cycle time of 10 h.
We have also investigated the role of the cell division cycle in the formation and subsequent development of somites. A single treatment of 2-day chick embryos with heat shock or a variety of drugs that affect the cell cycle all produce repeated anomalies in the pattern of somites and vertebrae that develop subsequent to the treatment. The interval between anomalies is 6 –7 somites (or a multiple of this distance), which corresponds to 10 h. This interval is identical to that measured for the cell division cycle. Given that cell division synchrony is seen in the presomitic mesoderm, we suggest that the cell division cycle plays a role in somite formation.
Finally, we consider the mechanisms responsible for regionalization of derivatives of the somite, and conclude that it is likely that both cell interactions and cell lineage history are important in the determination of cell fates.
A note on segmentation and the scale of pattern formation in insects and in vertebrates
Authors: Cooke Jonathan 
Published: April 2021

ABSTRACT
Little or nothing was said, by workers on vertebrate somite formation at this symposium, about theories for the overall control of segment size, and thus the number of segments in the pattern. The current mood may well be that further modelling of the machinery of segmental patterning should await knowledge of the spatial patterns of synthesis of all relevant gene products, because understanding of the dynamics of segmentation in insects is only just beginning to emerge even though such knowledge for Drosophila genes is well advanced. What can be said, nevertheless, about the ‘system properties’ of the segmentation process in the two groups?
Interactions between the pair-rule genes runt, hairy, even-skipped and fushi tarazu and the establishment of periodic pattern in the Drosophila embryo
Authors: Ingham Philip , Gergen Peter 
Published: April 2021

ABSTRACT
The pair-rule genes of Drosophila play a fundamental role in the generation of periodicity in the early embryo. We have analysed the transcript distributions of runt, hairy, even-skipped and fushi tarazu in single and double mutant embryos. The results indicate a complex set of interactions between the genes during the blastoderm stage of embryogenesis.
Development of surface pattern during division in Paramecium; I. Mapping of duplication and reorganization of cortical cytoskeletal structures in the wild type
Authors: Iftode Francine , Cohen Jean , Ruiz Françoise , Rueda Antonio Torres , Chen-Shan Lily , Adoutte André , Beisson Janine 
Published: April 2021

ABSTRACT
The shape of a Paramecium is determined by the organization of its cortex which constitutes most of the cell cytoskeleton. These structures and networks are organized in relation to the approx. 4000 ciliary basal bodies present at the surface. Each basal body is the centre of a polarized and asymmetrical cortical unit. At the whole-cell level, all units are tandemly arranged in parallel rows and form a defined asymmetrical pattern with dorsoventral and anteroposterior polarities. During division, the cortex is the site of the major morphogenetic processes.
In order to analyse how the surface pattern and the shape of the cell are reconstructed at each division, we have used specific immunological and cytological probes to map, in space and time, the reorganization of each of the major cytoskeletal cortical components: basal bodies and microtubules, kinetodesmal fibres, epiplasm and outer lattice. This cytological dissection demonstrates that the surface of the dividing cell is progressively invaded by morphogenetic waves which successively and individually trigger the duplication, assembly or reorganization of each structure and which all spread from the same epicentre (oral apparatus and fission furrow) with the same shape. Furthermore, the response of units to the morphogenetic waves depends on their position on the cell. It thus appears that despite the structural local constraints within units, the development of surface pattern is controlled in an integrated manner by transcellular signals.
This paper is dedicated to the memory of T. M. Sonneborn
Distribution and possible interactions of actin-associated proteins and cell adhesion molecules of nerve growth cones
Authors: Letourneau Paul C. , Shattuck Terri A. 
Published: April 2021

ABSTRACT
Actin filaments and their interactions with cell surface molecules have key roles in tissue cell behaviour. Axonal pathfinding during embryogenesis, an especially complex cell behaviour, is based on the migration of nerve growth cones. We have used fluorescence immunocytochemistry to examine the distribution in growth cones, their filopodia and lamellipodia of several actin-associated proteins and nerve cell adhesion molecules. The leading margins of chick dorsal root ganglion nerve growth cones and their protrusions stain strongly for f-actin, filamin, a-actinin, myosin, tropomyosin, talin and vinculin. MAP2 is absent from DRG growth cones, and staining for spectrin/fodrin extends into growth cones, but not along filopodia. Thus, organization of the leading margins of growth cones may strongly resemble the leading lamella of migrating fibroblasts. The adhesion-mediating molecules integrin, LI, N-CAM and A-CAM are all found on DRG neurites and growth cones. However, filopodia stain relatively more strongly for integrin and LI than for A-CAM or N-CAM. In fact, the 180×103Mr,. form of N-CAM may be absent from most of the length of filopodia. DRG neurones cultured in cytochalasin B display differences in immunofluorescence staining which further emphasize that these adhesion molecules interact differentially with the actin filament system of migrating growth cones. Several models for neuronal morphogenesis emphasize the importance of regulation of the expression of adhesion molecules. Our results support hypotheses that cellular distribution and transmembrane interactions are key elements in the functions of these adhesion molecules during axonal pathfinding.
Potentiation by the lithium ion of morphogenetic responses to a Xenopus inducing factor
Authors: Cooke Jonathan , Symes Karen , Smith Emma J. 
Published: April 2021

ABSTRACT
We have cultured explants of Xenopus blastular animal cap tissue from embryos that had received an earlier treatment with LiCl and from their untreated siblings, in various concentrations of XTC-cell-derived mesoderm-inducing factor (XTC-MIF, Smith, 1987; Smith et al. 1988). The pretreatment with lithium that we used transforms later morphogenesis in the whole embryo to give radialized body forms with anterior/dorsal levels of structure grossly over-represented. In addition, animal caps from ‘Li+’ embryos were allowed to develop without exposure to in vitro MIF (Li+ controls) and compared with normal uninduced control explants, and explants were made from normal early blastulae but given various initial treatments with LiCl in culture.
The results confirm that the lithium ion itself will not induce mesoderm in competent, animal cap tissue of Xenopus. It does, however, enhance the responsiveness of this tissue to XTC-MIF, in a way that parallels its recently reported effect in the case of another mesoderm inducer of different character, bFGF (Slack et al. 1988). The effects observed are sufficient to imply that the altered body pattern that follows lithium treatment, in whole embryos, could be caused by modulation of the responses to an unaltered pattern of in situ inductive stimuli. We also observe evidence that appreciable inductive signals reach animal pole tissue beyond the limits of mesoderm formation in normal development.
Relatively low concentrations of MIF prevent the development of an epidermis-specific marker in dissociated blastular animal cap cells (Symes et al. 1988). When such experiments are repeated in relation to the lithium pretreatment of embryos, such treatment is seen to have sensitized the cell population, so that the MIF concentration range that assures complete suppression of the marker is reduced.
The results are discussed in relation to induction considered as pattern formation.
Expression pattern of homeobox-containing genes during chick embryogenesis
Authors: Wedden Sarah E. , PANG Kevin , Eichele Gregor 
Published: April 2021

ABSTRACT
We have isolated, sequenced and examined the expression pattern of two tandemly arranged homeobox- containing genes from the chicken. The predicted amino acid sequences of the homeodomain and the adjacent carboxyterminal portion of the protein of the first gene is virtually identical (99%) to that of murine homeobox 2.1 and hence we refer to it as Ghox 2.1 (Gallus Aomeobox). The closest mouse homologue of the second homeodomain is Hox 2.2 (95% identical within the homeobox), and hence referred to as Ghox 2.2. Northern analysis of embryonic RNA reveals major transcripts of 2 kb for Ghox 2.1 and 1·7 kb for Ghox 2.2. To investigate the transcript pattern, embryos of various stages were dissected into heads, trunks and limb buds and the RNA was analysed by Northern blotting and RNase protection assays. Ghox 2.1 transcripts are present in all three regions. Ghox 2.2 RNA is found in trunks and limb buds, but it is strikingly absent from the developing head. In situ hybridization with 35S-labelled antisense riboprobes derived from Ghox 2.1 demonstrates that this gene is expressed at high levels in spinal chord, myelencephalon and mesonephros. Dorsal root ganglia and the lung rudiment also contain Ghox 2.1 message, but in somewhat lower amounts. Mid- and forebrain, the heart, presomitic mesenchyme and notochord do not contain detectable levels of Ghox 2.1 mRNA. Of particular interest is the expression of Ghox 2.1 in a well-defined patch of mesenchymal tissue situated in an anterioproximal region of the limb bud.
In situ study of c-myc protein expression during avian development
Authors: Jaffredo T. , Vandenbunder B. , Dieterlen-Lièvre F. 
Published: April 2021

ABSTRACT
The distribution of the c-myc protein was studied in the developing embryo from the two-somite stage to embryonic day 17 (E17). A triple labelling method was used, with a polyclonal serum recognizing the human and avian c-myc proteins as the first marker followed by Hoechst 33258 for nuclear staining and the monoclonal antibody 13F4 which reveals the avian myogenic lineage. In situ hybridization was carried out at three selected stages (E3, E6 and E8), in order to compare the distribution of myc mRNA and myc protein. The c-myc protein signal was barely detectable in blastodisc nuclei during the period of somlte formation, after which it became ubiquitous in the embryonic body until E4. Myotomal cell nuclei displayed a strong signal until their organization Into premuscular masses.
On day 4, the level of c-myc protein decreased In all embryonic tissues. By doubling the antibody titre and amplifying the signal by means of the streptavidin-blotin method, c-myc could still be detected in nuclei of defined groups of cells. Such was the case in some mesenchyme-derived tissues at critical periods of or-ganogenesis, for instance in prechondrogenic condensations or hemopoietic cell foci at E6, the latter becoming negative at E9. The heart ventricle displayed a patchwork of positive and negative nuclei from E6 to E10. A myc signal restricted to the quail species was found In the wall of the carotid arteries. Cell nuclei in the nervous system displayed a detectable signal which became restricted to postmitotic neurones. In the ectoderm, the c-myc protein was generally not present after E4, except In presumptive feather buds at the time of epitheliomesenchymal interactions. Endodermal cells (such as hepatocytes, oesophageal and tracheal epithelia) did not express detectable levels of c-myc at any time.
Our results reveal a time- and tissue-specific expression of c-myc during avian development. It is noteworthy that the expression of the c-myc protein often appears dissociated from cell proliferation as shown by the absence of the signal in endodennal cells at E3-E13 as well as its presence in postmitotic neurones.
Finally, although RNA and protein are simultaneously detected in some structures such as presumptive feather buds, their expression is dissociated in endodermal tissues, notably hepatocytes, where in situ hybridization detects a large number of RNA copies with no detectable protein signal.
The correlation between patterns of dye transfer through gap junctions and future developmental fate in Xenopus: the consequences of u.v. irradiation and lithium treatment
Authors: Nagajski D. J. , Guthrie S. C. , Ford C. C. , Warner A. E. 
Published: April 2021

ABSTRACT
The correlation between cell-to-cell communication through gap junctions at the 32-cell stage and the subsequent patterning of the embryonic axis has been examined in Xenopus laevis embryos. Disturbances of embryonic axis formation were generated by exposure to u.v. irradiation at the vegetal pole before 0·6 in the cell cycle, which generates embryos with dorsal axial deficiencies. Alternatively embryos were treated with 100 mm-lithium chloride between the 2-cell and 32-cell stage, which generates embryos with ventral axial deficiencies. The cell-to-cell transfer of Lucifer Yellow was used to monitor junctional permeability. Injections were made into animal hemisphere cells, lying in tiers 1 and 2 of the 32-cell embryo, whose position relative to the future dorsoventral axis of the embryo was determined on the basis of differences in pigmentation. The frequency of Lucifer Yellow transfer in the future dorsal half of the animal hemisphere was compared with that in the future ventral half for control (untreated), u.v.-irradiated and Li-treated embryos. Injected embryos were subsequently scored for axial development for comparison with dye transfer frequencies.
In control embryos at the 32-cell stage, Lucifer Yellow transfer was both more frequent and more extensive in future dorsal regions than in future ventral regions, as observed previously. In embryos that had been u.v. irradiated before 0·6 in the first cell cycle, Lucifer transfer was the same in both light and dark regions of the animal hemisphere and at the low level characteristic of future ventral regions in normal embryos. These embryos developed with massive reductions in dorsal axial structures. Embryos irradiated after 0-8 in the first cell cycle, when u.v. irradiation no longer inhibits the cytoplasmic movements initiated at fertilization, showed a normal dorsoventral difference in Lucifer Yellow transfer and developed with normal dorsoventral polarity. Embryos exposed to 100mm-LiCl contained 1·4 mm-lithium at the end of the treatment period. The transfer of Lucifer Yellow between animal pole cells of 32-cell embryos previously treated with LiCl was the same in both light (dorsal) and dark (ventral) and at the high level characteristic of future dorsal regions in normal embryos. Such embryos subsequently developed with substantial ventral axis deficiencies. U.v.-irradiated embryos subsequently treated with lithium showed transfer rates in ventral regions equivalent to that in embryos treated with Li alone and developed with ventral axial deficiencies. We conclude that the frequency with which Lucifer Yellow transfers through gap junctions at the 32-cell stage indicates the future developmental fate of animal cells and can be used to predict the subsequent organization of the embryonic axis.
Evidence that elevated intracellular cyclic AMP triggers spore maturation in Dictyostelium
Authors: Kay Robert R. 
Published: April 2021

ABSTRACT
Spore maturation occurs during normal development in Dictyostelium when environmental influences induce a migrating slug to transform into a fruiting body. As the amoeboid prespore cells turn into refractile spores there is a burst of enzyme accumulation, including UDP-galactose epimerase, and at a later stage the exocytosis of preformed components of the spore coat. Evidence is presented here that this process is triggered by an elevated intracellular cAMP concentration.
First, a number of rapidly developing (rde) mutants, whose cAMP metabolism had been investigated previously, are shown to be able to form spores in submerged monolayers, whereas wild-type strains are not. The phenotypes of these mutants are best explained by a derepression of the signal transduction pathway utilizing intracellular cAMP.
Second and more direct, it is shown that the permeant cAMP analogues 8-Br-cAMP and 8-chlorophenylthio-cAMP, but not cAMP itself, can rapidly induce spore differentiation in wild-type amoebae incubated in submerged monolayers. These analogues also stimulate accumulation of UDP-galactose epimerase in slug cells transferred to shaken suspension.
The ability to induce spore differentiation with Br-cAMP in wild-type strains provides a new technique that can be exploited in various ways. For instance, spore differentiation in strain V12M2 is induced by 8-Br-cAMP at very low cell densities, suggesting that neither cell contact nor additional soluble inducers are necessary in these conditions. In contrast NC4 cells may require an additional inducer. Spore differentiation is inhibited by the stalk-specific inducer DIF-1 suggesting that DIF-1 inhibits a target downstream of intracellular cAMP in the signal transduction pathway inducing spore differentiation.
The durations and compositions of cell cycles in embryos of the leech, Helobdella triserialis
Authors: Bissen Shirley T. , Weisblat David A. 
Published: April 2021

Abstract
When tritiated thymidine triphosphate ([3H]TTP) or its immunohistochemically detectable analogue, bromodeoxyuridine triphosphate (BrdUTP), is injected into blastomeres of leech embryos it passes throughout the entire embryo and is rapidly incorporated (within 2 min after injection) into nuclei of cells synthesizing DNA (S phase). In the same embryos a DNA-specific stain can be used to identify cells in mitosis (M phase) or nonreplicative interphase (G1 or G2 phase) on the basis of nuclear or chromosomal morphology. Using this procedure, we have determined the lengths and compositions of the mitotic cell cycles of identifiable cells in early embryos of the leech, Helobdella triserialis, and have analysed how the cell cycles change during the first seven stages of development. The relatively short cell cycles of the early blastomeres comprise not only phases of M and S, but also postreplicative gap (G2) phases. The lengthening of the cell cycles that occurs as development progresses is primarily accomplished by an increase in the length of G2 and secondarily by an increase in the length of S and, in some instances, the addition of a prereplicative gap (G1) phase; M phase remains relatively constant. These data suggest that the durations of the cell cycles of embryonic cells are regulated by a variety of mechanisms.