bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental control of N-CAM sialylation state by Golgi sialyltransferase isoforms
Authors: Breen Kieran C. , Regan Ciaran M. 
Published: April 2021

ABSTRACTA rat brain Golgi sialyltransferase activity capable of the differentiation-dependent control of N-CAM sialylation state is described. The specific activity of Golgi sialyltransferase was found to be developmentally regulated with respect to both endogenous and exogenous protein acceptors, with a particular elevation on postnatal days 10-12 when the heavily sialylated or ‘embryonic’ form of N-CAM is re-expressed. The subsequent developmental decrease in activity was associated with a significant decrease in apparent Km for the CMP-NeuNAc substrate, but not for the asialofetuin exogenous acceptor, which could not be attributed to the temporal expression of an endogenous competitive inhibitor. The apparent Vmax remained constant for CMP-NeuNAc but was significantly reduced for asialofetuin. Sialyltransferase activity, which was optimal at pH 7·0 – 7·5, was also modulated by various cations. Zinc abolished enzyme function, in contrast to ferric ions which stimulated activity fourfold-sevenfold. The marked activation of the adult form of the enzyme by potassium and magnesium ions, together with the alterations in kinetic constants, suggested this activity to be distinct from that derived from postnatal day-12 tissue. The kinetics of [l4C]sialic acid incorporation into immunoprecipitated N-CAM demonstrated the individual polypeptides to be sialylated, possibly by addition of polysialosyl units, in a developmental sequence. The presence of four distinct sialyltransferase activities was demonstrated by non-denaturing gel electrophoresis followed by solid-phase enzyme assay. These isoforms were temporally expressed during development, two being correlated with the postnatal reexpression of the ‘embryonic’ form of N-CAM.
Determination of somite cells: independence of cell differentiation and morphogenesis
Authors: Aoyama Hirohiko , Asamoto Ken 
Published: April 2021

ABSTRACTSomites are mesodermal structures which appear transiently in vertebrates in the course of their development. Cells situated ventromedially in a somite differentiate into the sclerotome, which gives rise to cartilage, while the other part of the somite differentiates into dermomyotome which gives rise to muscle and dermis. The sclerotome is further divided into a rostral half, where neural crest cells settle and motor nerves grow, and a caudal half. To find out when these axes are determined and how they rule later development, especially the morphogenesis of cartilage derived from the somites, we transplanted the newly formed three caudal somites of 2·5-day-old quail embryos into chick embryos of about the same age, with reversal of some axes. The results were summarized as follows. (1) When transplantation reversed only the dorsoventral axis, one day after the operation the two caudal somites gave rise to normal dermomyotomes and sclerotomes, while the most rostral somite gave rise to a sclerotome abnormally situated just beneath ectoderm. These results suggest that the dorsoventral axis was not determined when the somites were formed, but began to be determined about three hours after their formation. (2) When the transplantation reversed only the rostrocaudal axis, two days after the operation the rudiments of dorsal root ganglia were formed at the caudal (originally rostral) halves of the transplanted sclerotomes. The rostrocaudal axis of the somites had therefore been determined when the somites were formed. (3) When the transplantation reversed both the dorsoventral and the rostrocaudal axes, two days after the operation, sclerotomes derived from the prospective dermomyotomal region of the somites were shown to keep their original rostrocaudal axis, judging from the position of the rudiments of ganglia. Combined with results 1 and 2, this suggested that the fate of the sclerotomal cells along the rostrocaudal axis was determined previously and independently of the determination of somite cell differentiation into dermomyotome and sclerotome. (4) In the 9·5-day-old chimeric embryos with rostrocaudally reversed somites, the morphology of vertebrae and ribs derived from the explanted somites were reversed along the rostrocaudal axis. The morphology of cartilage derived from the somites was shown to be determined intrinsically in the somites by the time these were formed from the segmental plate. The rostrocaudal pattern of the vertebral column is therefore controlled by factors intrinsic to the somitic mesoderm, and not by interactions between this mesoderm and the notochord and/or neural tube, arising after segmentation.
Mechanism of erythropoietin action on the erythroid progenitor cells induced from murine erythroleukemia cells (TSA8)
Authors: Matsui Hiroaki Fukumoto Yasuhisa , Obinata Masuo 
Published: April 2021

Abstract
Erythropoietin is a well-known erythroid differentiation and growth factor, but the mechanism of its action is not well understood. In this work, we have examined its mechanism of action on the erythropoietin-responsive murine erythroleukemia cells (TSA8). TSA8 cells become responsive to erythropoietin after induction with DMSO. Stimulatory effects on erythropoietin response are observed with the addition of compounds affecting the cAMP level such as forskolin, phosphodiesterase inhibitor and cholera toxin only in the presence of erythropoietin. cAMP analogues themselves show no stimulatory effect on TSA8 cells, nor does erythropoietin increase cAMP level in the cells. Thus, it is suggested that cAMP does not act as a direct second messenger for signal transduction through erythropoietin receptors, but as a stimulator of the erythropoietin receptor pathway and/or as a second messenger in combination with the receptor pathway. The mechanism for acquisition of responsiveness to growth and differentiation factors of progenitor cells is discussed.
Periodic segmental anomalies induced by heat shock in the chick embryo are associated with the cell cycle
Authors: Primmett D. R. N. , Norris W. E. , Carlson G. J. , Keynes R. J. , Stern C. D. 
Published: April 2021

Abstract
This study provides evidence that cells destined to segment together into somites have a degree of cell division synchrony. We have measured the duration of the cell division cycle in somite and segmental plate cells of the chick embryo as 9·5 h using [3H]thymidine pulse-and-chase. Treatment of embryos with any of a variety of inhibitors known to affect the cell division cycle causes discrete periodic segmental anomalies: these anomalies appear about 6–7 somites after treatment and, in some cases, a second anomaly is observed 6 to 7 somites after the first. Since somites take 1·5 h to form, the 6- to 7-somite interval corresponds to about 9–10 h, which is the duration of the cell cycle as determined in these experiments. The anomalies are similar to those seen after heat shock of 2-day chick embryos. Heat shock and some of the other treatments induce the expression of heatshock proteins (hsp); however, since neither the expression nor the distribution of these proteins relate to the presence or distribution of anomalies seen, we conclude that hsps are not responsible for the pattern of segmental anomalies observed. The production of periodic segmental anomalies appears to be linked to the cell cycle. A simple model is proposed, in which we suggest that the cell division cycle is involved directly in gating cells that will segment together.
Presence of basic fibroblast growth factor in the early Xenopus embryo
Authors: Slack J. M. W. , Isaacs H. V. 
Published: April 2021

Abstract
Mesoderm-inducing activity can be extracted from Xenopus embryos, eggs or whole ovary. It binds to heparin and can be neutralized by heparin or anti-bFGF but not by anti-TGFβ. Two molecular forms can be identified by Western blotting and have molecular weights of about 19 and 14K. The content in embryos is about 7 units g-1 (approximately 7 ng ml-1) which would be sufficient for it to be acting as an endogenous inducer of ventral mesoderm. Attempts to detect TGFβ-like inducing factors in embryos were not successful.
Cell rearrangement and segmentation in Xenopus: direct observation of cultured explants
Authors: Wilson Paul A. , Oster George , Keller Ray 
Published: April 2021

Abstract
We make use of a novel system of explant culture and high resolution video-film recording to analyse for the first time the cell behaviour underlying convergent extension and segmentation in the somitic mesoderm of Xenopus. We find that a sequence of activities sweeps through the somitic mesoderm from anterior to posterior during gastrulation and neurulation, beginning with radial cell intercalation or thinning, continuing with mediolateral intercalation and cell elongation, and culminating in segmentation and somite rotation. Radial intercalation at the posterior tip lengthens the tissue, while mediolateral intercalation farther anterior converges it toward the midline. This extension of the somitic mesoderm helps to elongate the dorsal side of intact neurulae. By separating tissues, we demonstrate that cell rearrangement is independent of the notochord, but radial intercalation - and thus the bulk of extension - requires the presence of an epithelium, either endodermal or ectodermal. Segmentation, on the other hand, can proceed in somitic mesoderm isolated at the end of gastrulation. Finally, we discuss the relationship between cell rearrangement and segmentation.
Embryonic development of Xenopus studied in a cell culture system with tissue-specific monoclonal antibodies
Authors: Mitani Shohei , Okamoto Harumasa 
Published: April 2021

Abstract
An in vitro microculture system of early gastrula cells of Xenopus laevis has been developed; deep layer cells from the lateral marginal zone (prospective somite region) or ventral ectoderm (prospective epidermis region) were fully dissociated, and the desired number of each (1–100) was distributed into a microculture well and cultured under appropriate conditions. When examined with the tissue-specific Mabs (Mul for muscle and E3 for epidermis, respectively), a substantial portion of the deep layer cells from the two regions followed their respective normal embryonic fates. It was found that reproducible cellular differentiation was dependent on the intimate reaggregation of dissociated cells and on the size of the resultant aggregate. About 20 lateral marginal zone cells were found to be sufficient, when put into a culture well, for supporting successful muscle differentiation, whereas about 100 ventral ectoderm cells were necessary for epidermal differentiation.
Xwnt-8, a Xenopus Wnt-1/int-1-related gene responsive to mesoderminducing growth factors, may play a role in ventral mesodermal patterning during embryogenesis
Authors: Christian Jan L. , Mcmahon Jill A. , Mcmahon Andrew P. , Moon Randall T. 
Published: April 2021

ABSTRACT
In amphibian embryos, formation of the basic body plan depends on positional differences in the mesoderm. Although peptide growth factors involved in mesoderm induction have tentatively been identified, additional signals are required to generate pattern in this tissue. We have isolated a Xenopus cDNA for a Wnt-1 related gene, designated Xwnt-8, which is activated in ‘response to mesoderm-inducing growth factors. Xwnt-8 transcripts are transiently expressed, being most abundant during gastrulation at which time expression is confined primarily to ventral mesodermal cells. Embryos dor-soanteriórized by exposure to lithium exhibit greatly reduced levels of Xwnt-8 mRNA, supporting a correlation between Xwnt-8 expression and a ventral mesodermal cell fate. Surprisingly, ectopic expression of Xwnt-8 in embryos causes a dorsoanterior-enhanced phenotype. These findings suggest that Awni-S may be a secondary signalling agent which is produced in response to mesoderm-inducing factors and is involved in the early steps of mesodermal patterning.
Lineage of neurons and glia in chick dorsal root ganglia: analysis in vivo with a recombinant retrovirus
Authors: Frank Eric , Sanes Joshua R. 
Published: April 2021

ABSTRACT
We used retrovirus-mediated gene transfer to study the lineage of neural crest cells in chick embryos. Individual crest cells were infected before they migrated from the neural tube, and their clonal progeny were subsequently revealed in sensory ganglia and associated structures by a histochemical stain for the viral gene product (lacZ). We found that crest cells were multipotential in several respects. (1) Many clones contained both ventrolateral (VL) and dorsomedial (DM) neurons, which had been suggested to be lineally distinct. (2) Many clones contained both large and small neurons, which are known to innervate distinct targets. (3) Many clones contained multiple glial subtypes, e.g. both Schwann cells, which ensheath axons, and satellite cells, which ensheath neuronal somata. (4) Many clones contained both neurons and glial cells. On the other hand, a sizeable minority of clones was homogenous, e.g. they contained only neurons or only glial cells – suggesting that some progenitors may be, or become, restricted in potential. Finally, this study provides the first opportunity to compare directly the two methods currently available for tracing cell lineage in vertebrate embryos, retroviral infection and tracer injection: our results and those of Bronner-Fraser and Fraser (1989), who used the latter method, provide complementary but consistent views of crest lineage.
Neurothelin: molecular characteristics and developmental regulation in the chick CNS
Authors: Schlosshauer Burkhard 
Published: April 2021

ABSTRACT
Neurothelin has recently been identified as a cell surface protein specific for chick endothelial cells forming the blood-brain barrier. Neurons of the adult brain are essentially devoid of neurothelin. In contrast, neurons of the chick retina, which lack blood vessels and accessory astrocytes, express neurothelin. Here we demonstrate that during chick brain development initially neurothelin is expressed probably in all neuroblasts. With proceeding cytodifferentiation, such as vascularization and gliogenesis, brain neurons become neurothelin negative. Coincidentally the endothelial cells forming the blood-brain barrier start to synthesize neurothelin. In contrast to brain neurons, in retina neurons, neurothelin expression increases by one order of magnitude during the course of histogenesis. Coculturing of chick retinal cells with purified rat astrocytes in vitro results in reduction of neural neurothelin expression as quantified by ELISA. Conversely, disruption of the glia-neuron interactions by culturing brain neurons as individualized cells in vitro leads to a reexpression of neurothelin. This is consistent with the hypothesis that astrocytes inhibit neurothelin expression in neurons.
Biochemical characterization classifies neurothelin as an integral membrane protein. Temperature-induced-detergent phase separation, phospholipase C digestion and sodium carbonate treatment were employed to distinguish between integral membrane proteins, lipid- anchored proteins and peripheral membrane proteins. Two-dimensional gel electrophoresis reveals an isoelectric point of about 6.4 for neurothelin. Polysaccharide analysis by glycosidase digestion and lectin binding indicates that neurothelin is highly glycosylated. The relative molecular mass of glycosylated neurothelin is 41 × 103, whereas the peptide backbone is only 25 × 103.
The very strict spatiotemporal regulation of neurothelin expression in the central nervous system suggests that neurothelin fulfils possibly a crucial function such as transport of low relative molecular mass components that are essential for neuronal metabolism. The proposed biological activity of neurothelin might be specifically affected by some of its distinct biochemical features.
Mutations in a newly identified Drosophila melanogaster gene, mago nashi, disrupt germ cell formation and result in the formation of mirror-image symmetrical double abdomen embryos
Authors: Boswell Robert E. , Prout Mary E. , Steichen Jessica C. 
Published: April 2021

Summary
The mago nashi (mago) locus is a newly identified strict maternal effect, grandchildless-like, gene in Drosophila melanogaster. In homozygous mutant mago females reared at 17°C, mago+ function is reduced, the inviable embryos lack abdominal segments and 84–98 % of the embryos die. In contrast, at 25°C, some mago alleles produce a novel gene product capable of inducing the formation of symmetrical double abdomen embryos. Reciprocal temperature-shift experiments indicate that the temperature-sensitive period is during oogenetic stages 7–14. Furthermore, embryos collected from mago1 homozygous females contain no apparent func- tional posterior determinants in the posterior pole. In viable F1 progeny from mago mutant females, regardless of genotype and temperature, polar granules are reduced or absent and germ cells fail to form (the grandchildless-like phentoype). Thus, we propose that the mago+ product is a component of the posterior determinative system, required during oogenesis, both for germ cell determination and delineation of the longitudinal axis of the embryo.
Microtubules mediate the localization of bicoid RNA during Drosophila oogenesis
Authors: Pokrywka Nancy Jo , Stephenson Edwin C. 
Published: April 2021

ABSTRACT
We have examined cytoskeletal requirements for bicoid (bed) RNA localization during Drosophila oogenesis, bed is an anterior morphogen whose proper function relies on the localization of its messenger RNA to the anterior cortex of the egg. Drugs that depolymerize microtubules perturb all aspects of bed RNA localization. During recovery from drug treatment, bed RNA relocalizes to the oocyte cortex, suggesting that the localization machinery is a component of the cortical cytoskeleton.
Taxol, a drug that stabilizes microtubules, also effectively disrupts bed RNA localization, and the effects of taxol treatments on exuperantia and swallow mutants suggest general roles for these gene products in the multi-step bed RNA localization process.
Developmental regulation of creatine kinase gene expression by myogenic factors in embryonic mouse and chick skeletal muscle
Authors: Lyons Gary E. , Mühlebach Stephan , Moser Andrea , Masood Rizwan , Paterson Bruce M. , Buckingham Margaret E. , Perriard Jean-Claude 
Published: April 2021

ABSTRACT
The B isoform of creatine kinase (BCK), which is expressed at a high level in embryonic neural tissues, is also expressed abundantly in developing striated muscle and is an early marker for skeletal myogenesis. Using isoform-specific 35S-labeled antisense cRNA probes for in situ hybridization, we have detected BCK mRNAs in embryonic mouse and chick myotomes, the first skeletal muscle masses to form in developing embryos. These transcripts are detectable, as soon as myotomes are morphologically distinguishable. BCK is expressed at high levels in both skeletal and cardiac muscle in mouse and chick embryos. In the mouse, BCK transcript levels fall off rapidly in striated muscle shortly after the onset of MCK gene expression.
The M isoform of creatine kinase (MCK), the striated muscle-specific isoform, is expressed later than BCK. In the mouse, BCK transcripts are expressed in myotomes at 8.5 days post coitum (p.c.), but MCK transcripts are not detected before 13 days p.c. In the chick, BCK mRNAs are present at Hamburger-Hamilton stage 13, but MCK mRNAs are not detected before stage 19.
We have compared the patterns of expression of the CK genes with those of myogenic differentiation factor genes, which are thought to regulate skeletal musclespecific gene expression. In the chick, both CMD1, first detected at stage 13, and myogenin, first detected at stage 15, are present prior to MCK, which begins to be expressed at stage 19. Unlike the mouse embryo, CMD1, the chick homologue of MyoDl, is expressed before chick myogenin. In the mouse, myogenin, first detected at 8.5 daysp.c., is expressed at the same time as BCK in myotomes. Both myogenin and MyoDl, which begins to be detected two days later than myogenin, are expressed at least two days before MCK.
It has been proposed that the myogenic factors, MyoDl and myogenin, directly regulate MCK gene expression in the mouse by binding to its enhancer. However, our results show that MCK transcripts are not detected until well after MyoDl and myogenin mRNAs are expressed, suggesting that these factors by themselves are not sufficient to initiate MCK gene expression.
Biologically active kit ligand growth factor is produced by mouse Sertoli cells and is defective in Sld mutant mice
Authors: Tajima Youichi , Onoue Hitoshi , Kitamura Yukihiko , Nishimune Yoshhake 
Published: April 2021

ABSTRACT
In order to define the role of Kit ligand (KL) growth factor encoded at the mouse steel (SI) locus in spermatogenesis, we have examined its production in Sertoli cells. As a measure KL growth factor bioactivity, the ability to support proliferation and maintenance of mast cells was used in co-culture with primary mouse Sertoli cells. On the rertoli cells derived from +/+ and Wv/Wv mice, +/+ mast cells proliferated and were supported for more than 2 weeks, but not W/Wv mast cells. In contrast, Sertoli cells from Sld/Sld mice could not support + /+ mast cell proliferation under similar conditions. The supportive effect required close-range interaction of Sertoli cells with cultured mast cells. These results indicate that Sertoli cells derived from +/+ and Wv/Wv but not Sld/Sld mutant mice produce biologically active KL growth factor as a membranebound form. The biologically active KL of Sertoli cells may also play an important role in germ cell growth and differentiation.
The beginning of pattern formation in theDrosophilacompound eye: the morphogenetic furrow and the second mitotic wave
Authors: Wolff Tanya , Ready Donald F. 
Published: April 2021

ABSTRACTEvents in the morphogenetic furrow set the stage for all subsequent compound eye development in Drosophila. The periodic pattern of the adult eye begins in the furrow with the spaced initiation of ommatidial rudi- ments, the preclusters. A wave of mitosis closely follows the furrow. A cell-by-cell analysis reveals details of these events.Early stages of ommatidial assembly can be resolved using a lead sulfide stain. Overt ommatidial organization begins in the morphogenetic furrow as cells gather into periodically spaced concentric aggregates. A stereotyped sequence of cell rearrangements converts these aggre- gates into preclusters. In the furrow, new rows of ommatidia are initiated at the equator and grow as new clusters are added to the peripheral ends.Mitotic labeling using BrdU feeds shows that all cells not incorporated into a precluster divide. BrdU injec- tions show that cells divide roughly simultaneously between two adjacent rows of ommatidia.