bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mesoderm-inducing properties of INT-2 and kFGF: two oncogene-encoded growth factors related to FGF
Authors: Paterno G. D. , Gillespie L. L. , Dixon M. S. , Slack J. M. W. , Heath J. K. 
Published: April 2021

Abstract
Many theories of neoplasia suggest that oncogenic transformations result from aberrations in the control mechanisms which normally regulate growth and differentiation during embryonic development. It has recently become clear that many proto-oncogenes are differentially expressed during embryonic development and may thus be important embryonic regulatory molecules. We report here that the products of two transforming oncogenes int-2 and hst / ks (now called kfgf) can, with different potencies, induce mesoderm formation in isolated Xenopus laevis animal pole explants and stimulate DNA synthesis in mammalian fibroblasts. The results suggest that these proteins may function as mesoderm inducers in mammalian embryogenesis and that similar receptor/signalling pathways may be utilized for developmental and oncogenic processes. Finally, we have shown that the Xenopus assay system used in this study provides a powerful screen for protein factors that are active in development.
Gene expression during mammalian oogenesis and early embryogenesis: quantification of three messenger RNAs abundant in fully grown mouse oocytes
Authors: Roller R. J. , Kinloch R. A. , Hiraoka B. Y. , Li S. S.-L. , Wassarman P. M. 
Published: April 2021

ABSTRACT
Ribonuclease protection assays have been used to quantitatively assess changes in steady-state levels of specific mRNAs during oogenesis and early embryogenesis in mice. The mRNAs encode ZP3 (a glycoprotein that serves as a sperm receptor), LDH-B (heart-type lactate dehydrogenase), and MOM-1 (a protein of unknown function). MOM-1 and LDH-B are expressed in a variety of adult mouse tissues and midgestation embryos, whereas ZP3 expression is restricted completely to oocytes. All three mRNAs are expressed by growing mouse oocytes and accumulate to unusually high levels in fully grown oocytes as compared to somatic cells; 240000, 200000 and 74000 copies mRNA per fully grown oocyte for ZP3, LDH-B and MOM-1, respectively. Steady-state levels of LDH-B and MOM-1 mRNA undergo a modest decline (∼20–40 %) during ovulation when fully grown oocytes become unfertilized eggs and, in general, mirror the reported change in poly(A)+RNA levels during this period of development. On the other hand, the level of ZP3 mRNA declines dramatically (∼98%) during ovulation, from ∼240000 copies per oocyte to ∼5000 copies per unfertilized egg, and ZP3 mRNA is undetectable in fertilized eggs (&lt;1000 copies per fertilized egg). MOM-1 mRNA is expressed at relatively low levels in morulae ∼2000 copies per embryo) and blastocysts ∼5000 copies per embryo), whereas ZP3 mRNA remains undetectable (&lt;1000 copies per embryo) at these stages of preimplantation development. These findings are discussed in the context of overall gene expression during oocyte growth, meiotic maturation and early embryogenesis in mice.
Expression of N-CAM precedes neural induction in Pleurodeles waltl (Urodele, amphibian)
Authors: Saint-Jeannet Jean-Pierre , Foulquier Françoise , Goridis Christo , Duprat Anne-Marie 
Published: April 2021

ABSTRACT
The appearance and localization of N-CAM during neural induction were studied in Pleurodeles waltl embryos and compared with recent contradictory results reported in Xenopus laevis.
A monoclonal antibody raised against mouse N-CAM was used. In the nervous system of Pleurodeles, it recognized two glycoproteins of 180 and 140 xlO3 which are the Pleurodeles equivalent of N-CAM-180 and -140.
Using this probe for immunohistochemistry and immunocytochemistry, we showed that N-CAM was already expressed in presumptive ectoderm at the early gastrula stage. In late gastrula embryos, a slight increase in staining was observed in the neurectoderm, whereas the labelling persisted in the noninduced ectoderm.
When induced ectodermal cells were isolated at the late gastrula stage and cultured in vitro up to 14 days, a faint polarized labelling of cells was observed initially. During differentiation, the staining increased and became progressively restricted to differentiating neurons.
Development and phenotypic variability of genetically identical half mouse embryos
Authors: Papaioannou Virginia E. , Mkandawire John , Biggers John D. 
Published: April 2021

ABSTRACT
The growth and development of three groups of genetically identical F1 C57BL/6J♀ × SJL/J♂ mice were compared to examine whether embryo manipulation affects subsequent postnatal growth and development of mammalian embryos: (1) controls - the natural offspring of timed matings, (2) transferred controls - offspring from 2-cell embryos transferred to recipients 1 day asynchronous, and (3) transferred half embryos - offspring developing from one blastomere from the 2-cell stage transferred to recipients 1 day asynchronous. The recipients were C57BL/6J females. No differences were found in the age at eye opening and vaginal opening. At 5 days after birth the median body weights of the controls were lower than the weights of the transferred groups. This result could be explained by the larger litter size in the control group. The overall variances of the body weights did not differ between the groups. By the second week after birth a marked increase in overall variances of body weights of the transferred groups, compared with the control group, was observed. At 5 days after birth, the median tail lengths did not differ between groups, and overall variances were the same. By the second week, the overall variances of the tail lengths of the transferred groups were significantly greater than that of the control group. Possibly the increased overall variances of the body weight and the tail length of the transferred groups are related to the smaller litter size in these groups which affects competition for food and the ambient temperature in the nest. The overall results suggest newborn mice that have developed from half embryos have compensated for their initial deficiency. The intraclass correlation coefficients for body weight and tail length are approximately the same in all groups. Thus, producing artificial identical twins by embryo bisection may not affect their potential usefulness in the design of experiments.
Gene regulation during cartilage differentiation: temporal and spatial expression of link protein and cartilage matrix protein in the developing limb
Authors: Stirpe Norine S. , Goetinck Paul F. 
Published: April 2021

ABSTRACT
The temporal and spatial expression of link protein and cartilage matrix protein genes was defined during chondrogenesis in the developing chick embryonic wing bud, using RNA in situ hybridization. For comparison, the expression of genes encoding type II collagen and cartilage proteoglycan core protein was also examined. Link protein transcripts are first detected at stage 25 of Hamburger and Hamilton, together with proteoglycan core protein transcripts. Type II collagen transcripts were first detected as early as stage 23 whereas cartilage matrix protein transcripts could not be detected before stage 26. The results of the study indicate that the temporal expression of the genes for cartilage matrix protein and type II collagen are independent of each other and also independent of that for link protein and proteoglycan core protein.
Complementary patterns of expression of c-ets 1, c-myb and c-myc in the blood-forming system of the chick embryo
Authors: Vandenbunder B. , Pardanaud L. , Jaffredo T. , Mirabel M. A. , Stehelin D. 
Published: April 2021

ABSTRACT
We have used in situ hybridization to study the spatial and temporal distribution of the transcription of three cellular oncogenes encoding DNA-binding proteins, c-ets 1, c-myb and c-myc during the development of the chick embryo.
c-ets 1 mRNA expression appears linked to the mesodermal lineage and is strongly expressed in early endothelia; it subsequently becomes restricted to small vessel endothelia. Hemopoietic cells in extraembryonic blood islands at E2 express c-ets 1, while intraembryonic hemopoietic cells in aortic clusters (E3) and paraaortic foci (E6) express c-myb. c-myc transcripts are detected in cells undergoing hemopoiesis in both these extraembryonic and intraembryonic sites. Outside the blood forming system, c-myc is transcribed in a large variety of cells; c-ets 1 displays tissue-specific expression in groups of mesodermal cells engaged in morphogenetic processes and appears excluded from all epithelia; finally the expression of c-myb is the most tightly linked to hemopoietic cells. In any case, it is clear that these three oncogenes display complementary expression in endothelial and hemopoietic cells where their patterns are modulated in relationship to multiplication and differentiation.
Retinoic acid inhibits growth in agarose of early chick embryonic cells and may be involved in regulation of axis formation
Authors: Mitrani Eduardo , Shimoni Yael 
Published: April 2021

ABSTRACT
The mechanisms involved in the generation of axial structures in the chick are well documented, yet, little is known about the actual factors that generate such a complex pattern. The recent demonstrations that all-trans-retinoic acid (RA) acts as a morphogen during limb development (Thaller and Eichele, 1987) lead us to examine whether during axis formation in the developing chick, RA could be one of the factors involved. We now show that retinoic acid can block a very unusual property of normal early chick embryonic cells, mainly their capacity to grow in semisolid medium. We also present experiments that suggest that RA may play a direct role during axis formation in the developing chick.
Spatially ordered transcription of regulatory DNA in the bithorax complex of Drosophila
Authors: Sánchez-herrero Ernesto , Akam Michael 
Published: April 2021

ABSTRACT
The identities of the second through ninth abdominal segments of Drosophila are specified by two genes of the bithorax complex (BX-C), abdominal-A (abd-A) and Abdominal B (Abd-B). The correct deployment of these two genes requires an extensive region (the iab region) located between the two protein-coding transcription units. We show here that one iab mutation affects the pattern of expression of Abd-B. We also show that most or all of the DNA in this regulatory iab region is transcribed. In blastoderm stage embryos we can define three distinct domains within the iab DNA, each transcribed in a region that extends from a characteristic anterior limit to the posterior end of the segmented part of the embryo. The anterior limits of expression for the three regions are colinear with the sequence of the domains on the chromosome, and lie at about two-segment intervals. We suggest that these early transcription patterns reflect the initial activation of the BX-C.
Mitogenic effect of muscle on the neuroepithelium of the developing spinal cord
Authors: Fontaine-Pérus Josiane C. , Chanconie Marcelle , Le Douarin Nicole M. , Gershon Michael D. , Rothman Taube P. 
Published: April 2021

ABSTRACT
A previous study revealed that segments of bowel grafted between the neural tube and somites of a younger chick host embryo would induce a unilateral increase in cellularity of the host’s neural tube. The current experiments were done to test the hypotheses that muscle tissue in the wall of the gut is responsible for this growth-promoting effect and that the spinal cord enlargement is the result of a mitogenic action on the neuroepithelium. Fragments of skeletal (E8–15) or cardiac muscle (E4–14) were removed from quail embryos and grafted between the neural tube and somites of chick host embryos (E2). Both skeletal and cardiac muscle grafts mimicked the effect of bowel and induced an increase in cell number as well as a unilateral enlargement of the region of the host’s neural tube immediately adjacent to the grafts. The growth-promoting effect of muscle-containing grafts was restricted to the neural tube itself and was not seen in proximate dorsal root or sympathetic ganglia. The action of the grafts of muscle was neither species-nor class-specific, since enlargement of the neural tube was observed following implantation of fetal mouse skeletal muscle into quail hosts. Grafts of skeletal muscle or gut increased the number of cells taking up [3H]thymidine in the host’s neuroepithelium as early as 9h following implantation of a graft. The increase in the number of cells entering the S phase of the cell cycle preceded the increase in cell number. These observations demonstrate that muscle-containing tissues can increase the rate of proliferation of neuroepithelial cells when these tissues are experimentally placed together.
Presence of cdc2+-like proteins in the preimplantation mouse embryo
Authors: McConnell Josie , Lee Melanie 
Published: April 2021

ABSTRACT
An antibody raised against a portion of the human equivalent of the yeast cdc2+ protein reacts with a 34K protein in mouse cell lines and early embryonic cells. Western blot analysis coupled with phosphatase treatment of material collected from the early preimplantation embryo has shown that the murine cdc2+ homologue does not correspond to the previously described newly synthesised proteins that are phosphorylated in a cell-cycle-dependent fashion [Howlett, 1986]. The cdc2+-like protein is converted into a slower migrating form on entry into S-phase and is further modified during G2 prior to mitosis. Studies of embryos that are held in extended periods of M-phase, i.e. unfertilised eggs or 1-cell embryos treated with nocodazole, demonstrate that the cdc2+-like protein becomes demodified in these cells.
Sex determination in the germ line of Drosophila depends on genetic signals and inductive somatic factors*
Authors: Nöthiger Rolf , Jonglez Martine , Leuthold Margrit , Meier-Gerschwiler Pia , Weber Thomas 
Published: April 2021

ABSTRACT
We have analyzed the mechanism of sex determination in the germ line of Drosophila by manipulating three parameters: (1) the ratio of X-chromosomes to sets of autosomes (X: A); (2) the state of activity of the gene Sexlethal (Sxl), and (3) the sex of the gonadal soma. To this end, animals with a ratio of 2X:2A and 2X:3A were sexually transformed into pseudomales by mutations at the sex-determining genes Sxl (Sex-lethal), tra (transformer), tra-2 (transformer-2), or dsx (double-sex). Animals with the karyotype 2X;3A were also transformed into pseudofemales by the constitutive mutation SxlM1. The sexual phenotype of the gonads and of the germ cells was assessed by phase-contrast microscopy.
Confirming the conclusions of Steinmann-Zwicky et al. (Cell 57, 157, 1989), we found that all three parameters affect sex determination in germ cells. In contrast to the soma in which sex determination is completely cell-autonomous, sex determination in the germ line has a non-autonomous component inasmuch as the sex of the soma can influence the sexual pathway of the germ cells. Somatic induction has a clear effect on 2X; 2A germ cells that carry a Sxl+ allele. These cells, which form eggs in an ovary, can enter spermatogenesis in testes. Mutations that cause partial loss of function or gain of function of Sxl thwart somatic induction and, independently of the sex of the soma, dictate spermatogenesis or oogenesis, respectively. Somatic induction has a much weaker effect on 2X;3A germ cells. This ratio is essentially a male signal for germ cells which consistently enter spermatogenesis in testes, even when they carry SxlMl. In a female soma, however, Sxl™1 enables the 2X;3A germ cells to form almost normal eggs.
Our results show that sex determination in the germ line is more complex than in the soma. They provide further evidence that the state of Sxl, the key gene for sex determination and dosage compensation in the soma, also determines the sex of the germ cells, and that, in the germ line, the state of activity of Sxl is regulated not only by the X: A ratio, but also by somatic inductive stimuli.
The zygotic control of Drosophila pair-rule gene expression: I. A search for new pair-rule regulatory loci
Authors: Vavra Stephanie H. , Carroll Sean B. 
Published: April 2021

ABSTRACT
The examination of pair-rule gene expression in wildtype and segmentation mutant embryos has identified many, but not necessarily all, of the elements of the regulatory system that establish their periodic patterns. Here we have conducted a new type of search for previously unknown regulators of these genes by examining pair-rule gene expression in blastoderm embryos lacking parts of or entire chromosomes. This method has the advantage of direct inspection of abnormal pair-rule gene patterns without relying upon mutagenesis or interpretation of larval phenotypes for the identification of segmentation genes. From these experiments we conclude that: (i) most zygotically required regulators of the fushi tarazu (ftz), even-skipped (eve) and hairy (h) pair-rule genes have been identified, except for one or more loci we have uncovered on chromosome arm 2L; (ii) the repression of the ftz and eve genes in the anterior third of the embryo is under maternal, not zygotic control; and (iii) there are no general zygotically required activators of pair-rule gene expression. The results suggest that the molecular basis of pair-rule gene regulation can be pursued with greater confidence now that most key trans-acting factors are already in hand.
The origin of secondary myotubes in mammalian skeletal muscles: ultrastructural studies
Authors: Duxson M. J. , Usson Y. , Harris A. J. 
Published: April 2021

ABSTRACT
The distribution of secondary myotubes and undifferentiated mononucleated cells (presumed to be myoblasts) within foetal IVth lumbrical muscles of the rat was analyzed with serial section electron microscopy. In all myotube clusters for which the innervation zone was located, every secondary myotube overlapped the endplate region of the primary myotube. No secondary myotubes were ever demonstrated to occur at a distance from the primary myotube innervation zone. This indicates that new secondary myotubes begin to form only in the innervation zone of the muscle. Some young secondary myotubes made direct contact with a nerve terminal, but we cannot say if this is true for all developing secondary myotubes. Myoblasts were not clustered near the innervation zone, but were uniformly distributed throughout the muscle. Myoblasts were frequently interposed between a primary and a secondary myotube, in equally close proximity to both cell membranes. We conclude that specificity in myoblast-myotube fusion does not depend on restrictions in the physical distribution of myoblasts within the muscle, and therefore must reflect more subtle mechanisms for intercellular recognition.
Positional information revisited
Authors: Wolpert Lewis 
Published: April 2021

ABSTRACT
Positional information has been suggested to play a central role in pattern formation during development. The strong version of positional information states that there is a cell parameter, positional value, which is related to position as in a coordinate system and which determines cell differentiation. A weaker version merely emphasises position as a key determinant in cell development and differentiation. There is evidence for boundaries and orthogonal axes playing an important role in positional systems. A positional signal is distinguished from an inductive interaction because the former specifies multiple states, confers polarity, and can act over a long range. A gradient in a diffusible morphogen is just one way of specifying position. There is now good evidence in several systems for substances which may be the morphogen for positional signalling. The product of the bicoid gene in early Drosophila development is the best prospect. Retinoic acid is unique in its ability to alter positional value and may also be a morphogen. The best evidence for positional value, a concept fundamental to positional information, remains a biological assay based on grafting. The idea of positional value uncouples differentiation and position, and allows considerable freedom for patterning. It is not clear whether positional value or differentiation involves a combinatorial mechanism.
Interpretation of positional information remains a central problem. There is good evidence that cells can respond differentially to less than a two-fold change in concentration of a chemical signal. It may be that interpretation involves listing the sites at which a particular class of cell differentiation will occur. The problem is made less severe when blocks of cells are specified together as in mechanisms based on an isomorphic prepattern. Isomorphic prepatterns could establish repeated structures which are equivalent and which are then made non-equivalent by positional information. This would enable local differences to develop. The combination of these two mechanisms may be widespread.
There is evidence that positional signals within a single animal and in related animals are conserved. It is not clear just how wide this conservation is, but it is at phylotypic stages, rather than in eggs, that similarity might be expected. It is nevertheless impressive that the polar coordinate model can be applied to regulation in systems as diverse as insects, vertebrates and protozoa. The molecular basis of positional signalling is just becoming accessible; the molecular basis of positional value is still awaited.
A brief personal history of positional information is provided in an appendix.
The development of a simple scaffold of axon tracts in the brain of the embryonic zebrafish, Brachydanio rerio
Authors: Wilson Stephen W. , Ross Linda S. , Parrett Timothy , Easter Stephen S. 
Published: April 2021

ABSTRACT
We have examined neuronal differentiation and the formation of axon tracts in the embryonic forebrain and midbrain of the zebrafish, between 1 and 2 days postfertilisation. Axons were visualised with three techniques; immunocytochemistry (using HNK-1 and antiacetylated tubulin antibodies) and horseradish peroxidase (HRP) labelling in whole-mounted brains, and transmission electron microscopy. Differentiation was monitored by histochemical staining for acetylcholinesterase (AChE).
These independent methods demonstrated that a simple grid of tracts and commissures forms the initial axon scaffold of the brain. At 1 day, the olfactory nerve, four commissures, their associated tracts and three other non-commissural tracts are present. By 2 days, these tracts and commissures have all greatly enlarged and, in addition, the optic nerve and tract, and three new commissures and their associated tracts have been added.
Small applications of HRP at various sites revealed the origins and projections of some of these earliest axons. Retrogradely labelled cell bodies originated from regions that were also positive for AChE activity. At 1 day, HRP-labelled axons were traced: (1) from the olfactory placode through the olfactory nerve to the dorsal telencephalon; (2) from the telencephalon into the tract of the anterior commissure and also to the postoptic region of the diencephalon; (3) from the hindbrain through the ventral midbrain and diencephalon to the postoptic commissure; (4) from the dorsal diencephalon (in or near the epiphysis) to the tract of the postoptic commissure; (5) from ventral and rostral midbrain through the posterior commissure. Three new projections were demonstrated at 2 days: (1) from the retina through the tract of the postoptic commissure to the tectum; (2) from the telencephalon to the contralateral diencephalon; and (3) from the telencephalon to the ventral flexure.
These results show that at 1 day, the zebrafish brain is impressively simple, with a few small, well-separated tracts but by 2 days the brain is already considerably more complex. Most of the additional axons added onto pre-existent tracts rather than pioneered new ones supporting the notion that other axons play a crucial role in the guidance of early central nervous system (CNS) axons.