bluuebunny/crossref_metadata_2025_split huggingface dataset:
The in vitro development of blastocyst-derived embryonic stem cell lines: formation of visceral yolk sac, blood islands and myocardium
Authors: Doetschman Thomas C. , Eistetter Harald , Katz Margot , Schmidt Werner , Kemler Rolf 
Published: April 2021

ABSTRACT
The in vitro developmental potential of mouse blastocyst-derived embryonic stem cell lines has been investigated. From 3 to 8 days of suspension culture the cells form complex embryoid bodies with endoderm, basal lamina, mesoderm and ectoderm. Many are morphologically similar to embryos of the 6- to 8-day egg-cylinder stage. From 8 to 10 days of culture about half of the embryoid bodies expand into large cystic structures containing alphafoetoprotein and transferrin, thus being analagous to the visceral yolk sac of the postimplantation embryo. Approximately one third of the cystic embryoid bodies develop myocardium and when cultured in the presence of human cord serum, 30% develop blood islands, thereby exhibiting a high level of organized development at a very high frequency. Furthermore, most embryonic stem cell lines observed exhibit similar characteristics. The in vitro developmental potential of embryonic stem cell lines and the consistency with which the cells express this potential are presented as aspects which open up new approaches to the investigation of embryogenesis.
Abnormal skin development in pupoid foetus (pf/pf) mutant mice
Authors: Fisher Chris , Kollar Edward J. 
Published: April 2021

ABSTRACT
At 13 days of development the epidermis of mice homozygous for the pupoid foetus (pf/pf) mutation varies in thickness between one and ten cell layers. By 16 days of development cells from the dermis have invaded the epidermis and may be found throughout the epidermis and on its surface. Among these cells are nerve fibres and Schwann cells as well as other unidentified cells. Antibodies directed against fibronectin bind to these abnormal groups of cells in the mutant epidermis and on its surface. A basal lamina, as determined by ultrastructure and by the immuno-fluorescent localization of laminin, was always found at the interface of the mutant epidermis and the invading cell population. By 19 days of development the mutant epidermis is thickened and is permeated by a network of cells including nerve fibres, Schwann cells, blood vessels, and collagen and fibronectin-secreting cells. A basal lamina always separates these groups of invading cells from the epidermal cell population.
Dynamics of tubulin structures in Xenopus laevis oogenesis
Authors: Paleček Jiří , Habrová Věra , Nedvídek Josef , Romanovský Alexej 
Published: April 2021

ABSTRACT
The distribution of tubulin and/or tubulin-containing structures was examined in separate classes of Xenopus laevis oocytes and in germinal vesicles isolated from them. Although a monoclonal antibody has been used, the technique applied on paraffin sections does not allow clear-cut definition of the state of tubulin present (monomeric, dimeric or polymerized form); however, the probable existence of assembled microtubules is indicated by supplementary techniques, i.e. histology and immunoperoxidase staining. Immunofluorescence reveals maximum tubulin concentration in the Balbiani body and in a ring-shaped formation around the nucleus in young oocytes. The Balbiani body disintegrates in the course of vitellogenesis, granules formed from its periphery migrate into the cytoplasm and gradually fill the entire cytoplasm as radial cords. In the ring-shaped formation around the nucleus strongly fluorescent cords and fibres are formed, particularly on the future vegetal-half-facing part of the nucleus. Reorganization of tubulin may be related to the establishment of a structure directing two-way shifts (1) of cytoplasmic organelles from the Balbiani body to the cytoplasm, and (2) of yolk proteins containing endosomes derived from the endocytically active oolemma to the yolk platelets. A distinct fluorescent fibrillar network is found inside the isolated germinal vesicles,’ near the nucleus membrane. Peripheral nucleoli, often present in nuclear membrane protuberances, seem to be surrounded by this material, which is oriented along the surface, and as a basket towards the inside of the nucleus. It is assumed that the structures may participate in the transport of nucleoli from the nucleus to the cytoplasm via the nuclear envelope.
The ontogenesis of cranial neuromeres in the rat embryo : II. A transmission electron microscope study
Authors: Tuckett Fiona , Morriss-Kay Gillian M. 
Published: April 2021

ABSTRACT
The morphogenesis of rhombomeres (neuromeres) caudal to the preotic sulcus during neurulation in rat embryos is described. A model is proposed to explain the development of the characteristic neuromeric sulci and interneuromeric gyri based on the cytoskeletal elements and the kinetic behaviour of the neural epithelium.
Evidence obtained from a study of control, cytochalasin D-treated and colchicine-treated embryos, at the electron microscopic level, supports the proposed model. The longitudinally expanding cranial neural epithelium bulges between microtubule blocks present within the interneuromeric gyri, causing a bulge to develop along the line of least resistance, away from the microfilament-rich luminal border of the neuromeric sulcus region.
Autoradiographic analysis of RNA synthesis in the oocyte—nurse cell complex of the polychaete Ophryotrocha labronica
Authors: Emanuelsson Hadar 
Published: April 2021

ABSTRACT
Females of the polychaete Ophryotrocha labronica have been pulse labelled with [5-3H] uridine, and the incorporation of label into the RNA of the oocyte-nurse cell complex was followed by light and electron microscope autoradiography. Up to its regression the polyploid nurse cell displays an intense synthesis of rRNA and mRNA, which sustains an extensive production of electron-dense protein granules in it. Concomitantly rRNA and mRNA are synthesized also in the oocyte. Short-term treatment (7 h) of polychaete females with α-amanitin provokes serious disturbances of oogenesis and subsequent embryonic development, irrespective of when it is applied during oogenesis. In contrast actinomycin gives such effects only when it is applied at the onset of oogenesis.
A previous investigation has demonstrated that nurse cell granules are gradually exported through an intercellular canal to the oocyte, where a fraction of them is incorporated into the typical yolk granules. The present labelling experiments indicate that nurse cell RNA is associated with the exported yolk precursor material. From inhibition experiments with α-amanitin and from in situ hybridizations with a poly(U)probe it appears that mRNA is particularly involved.
At the final collapse of the nurse cell practically all its contents are transferred to the oocyte. From that time the ooplasm is found to contain nuage-like RNA aggregates, which in contrast to other [5-3H]uridine-labelled ooplasmic structures (yolk granules, and minor granules and aggregates) have a non-uniform distribution. The possible origin and function of these aggregates is discussed. The investigation indicates that the nurse cell has a significant export of RNA essentially similar to that from insect nurse cells.
Accumulation of pigment granules around nuclei in early embryos of Anura (Amphibia)
Authors: Kobayakawa Yoshitaka 
Published: April 2021

ABSTRACT
A dark spot was found to appear in each blastomere of the vegetal surface of blastulae of Rana rugosa, Hyla arborea. The spot divided into two before division of the blastomere, so that one new spot was allotted to each daughter cell. These dark spots were formed at early blastula stage, and persisted until the end of yolk plug stage.
Cytological observations showed that each dark spot corresponds to a mass of accumulated pigment granules around the nucleus of a blastomere. The accumulation increases with development during the cleavage period more rapidly in blastomeres of the vegetal hemisphere than in those of the animal hemisphere.
This accumulation of pigment granules around nuclei during development indicates that the granules are transported toward the nuclei during the cleavage period, suggesting some sort of directional flow of cytoplasm in blastomeres of early amphibian embryos.
Absence of a sex vesicle in meiotic foetal germ cells is consistent with an XY sex chromosome constitution
Authors: Hogg Heather , Mclaren Anne 
Published: April 2021

ABSTRACT
Sex vesicles were not seen in meiotic germ cells isolated from male and female foetal adrenals, although they were readily identified in adult male meiotic germ cells prepared by the same airdrying method. It is suggested that the failure of the XY germ cells from the male adrenals to develop a sex vesicle is due to their embarking on oogenesis rather than spermatogenesis, and that the absence of a sex vesicle does not necessarily indicate lack of a Y chromosome.
Dynamics of the control of body pattern in the development of Xenopus laevis: I. Timing and pattern in the development of dorsoanterior and posterior blastomere pairs, isolated at the 4-cell stage
Authors: Cooke Jonathan , Webber John A. 
Published: April 2021

ABSTRACT
Xenopus embryos have been selected in which the second cleavage is occuring in a frontal plane, i.e one tending to lie at right angles to the prospective plane of bilateral symmetry for the body pattern. Some of these have been used to deduce a map of the disposition of materials for the normal mesodermal pattern (the normal ‘fate map’) by injecting blastomeres to found fluorescently marked clones from 4-to 32-cell stages. Other such 4-cell embryos have been separated into two isolates across this second cleavage; in fate-map terms, prospective dorsoanterior and posterior isolates. These have been allowed to develop to control axial larval stages, with examination of the time schedule of their gastrulation movements in relation to cofertilized whole controls. The patterns of mesoderm produced have been examined and interpreted in the light of quantitative knowledge about the normal pattern, and our current understanding of the map.
A meaningful fate map exists for the egg material even at this early, essentially acellular stage, and it differs appreciably from what might have been expected in view of that traditionally shown for early gastrula stages. The patterns developed in the isolates show that at least in many eggs, widespread information that positively specifies material as to its body position is available from at most 1 h after the events that give rise to bilateral symmetry upon fertilization. This information usually leads to a mosaic development of the appropriate mesodermal part-pattern in dorsoanterior isolates, and frequently allows development that approximates to this in the reciprocal posterior part. Regulation, i.e. the replacement of removed information to specify a development more complete than the normal contribution in isolates, is not observed. The results suggest a revision of former claims for regulative ability in at least this amphibian embryo. They also imply that systems for ascribing position value (positional information) to early embryonic tissue can be diverse in dynamics, even among embryos whose body plans are obviously homologous as are those of vertebrates.
Expression of the Tcp-1 locus of the mouse during early embryogenesis
Authors: Sánchez Edwin R. , Erickson Robert P. 
Published: April 2021

ABSTRACT
The synthesis of proteins by preimplantation mouse embryos was studied by two-dimensional (2D) gel electrophoresis of proteins labelled with [35S]methionine. The product of the Tcp-1 locus of the mouse, p63/6.9, is synthesized by morula and blastocyst stage embryos, but is not detectable in 2-cell embryos. These results indicate that maternal expression (oocyte-specific) of this gene is not occurring and that this gene may be developmentally regulated. Blastocysts which are allowed to implant in vitro have rates of protein synthesis that permit fluorographs of single embryos to be performed. These embryos can be unambiguously identified for their t-complex genotype. Quantitation of the amounts of the Tcp-la and Tcp-lb allelic products in morula embryos suggested delayed expression of the paternal allele.
Amino acid transport in mouse blastocyst compartments
Authors: Miller J. G. O. , Schultz G. A. 
Published: April 2021

ABSTRACT
Properties of uptake and exchange of L-methionine associated with the compartments of the blastocyst were examined in the mouse embryo. The inner cell mass (ICM) was derived from the 102 h blastocyst by immunosurgical procedures and studied in isolation. The ICM possessed strong exchange and efflux transport character. The Vmax of transport was about one-fifth that of the intact blastocyst, but the Km (660 μM) was about 30 times as high as that of the intact blastocyst. Consequently, at a concentration of about 100 μM-methionine, the velocity of uptake into the ICM is about one-thirtieth of that into the intact blastocyst. Uptake of amino acid into the intact blastocyst was resolved into cellular and cavity components by mechanically collapsing the blastocyst following uptake of radiolabelled methionine. By this method, it was found that about 70 % of the label accumulated by the blastocyst was in the cavity.
Developmental potencies of area opaca and marginal zone areas of early chick blastoderms
Authors: Khaner Oded , Mitrani Eduardo , Eyal-Giladi Hefzibah 
Published: April 2021

ABSTRACT
The marginal zone, in pregastrulating chick blastoderms, has been defined as the intermediate ring between the epiblast proper and the most external region, the area opaca (Spratt & Haas, 1960). Azar & Eyal-Giladi (1979) have shown that the marginal zone of a stage XIII blastoderm has the capacity of regenerating an inductive layer which when in contact with a competent stage XIII epiblast can cause the formation of axial structures.
The present work demonstrates that at stage×(Eyal-Giladi & Kochav, 1976) the marginal zone can both induce and respond to its own inductive stimulus by forming an embryonic axis. By stage XIII the marginal zone seems to have lost its competence to respond to an inductive stimulus and cannot form an embryonic axis. It is further shown that at stages X-XIII the area opaca is neither competent to develop any sort of axial structures nor has the capacity to generate an inductive layer.
Epidermal development in Xenopus laevis: the definition of a monoclonal antibody to an epidermal marker
Authors: Jones Elizabeth A. 
Published: April 2021

ABSTRACT
A monoclonal antibody 2F7.C7 which identifies an epidermal antigen common to both anuían and urodele amphibia is described. This antigen has a high molecular weight and is expressed at stage first inside and then on the surface of epidermal cells. It is not expressed on presumptive nervous tissue. It is expressed on all cells of the larval epidermis including ciliated and non-ciliated cells and sucker. The relationship of the epidermal antigen to ‘epimucin’ is investigated by blocking experiments using Peanut agglutinin. These studies suggest that either the molecule recognized by 2F7.C7 is not epimucin, or that its epitope is far away from the lectin-binding site. Studies using this antibody in grafting and sandwich experiments are discussed and an overall scheme of epidermal development in Xenopus is presented.
Distribution of nuclear proteins during maturation of the Xenopus oocyte
Authors: Hausen Peter , Wang Ya Hui , Dreyer Christine , Stick Reimer , Müller Ursula , Riebesell Metta 
Published: April 2021

ABSTRACT
The internal structure of the Xenopus oocyte is reorganized during the hormone-induced egg maturation. A cytological survey of the intracellular movements and changes is described. The behaviour of the nuclear lamina protein and of three nucleoplasmic proteins during these processes was studied by immunocytology. The proteins are finally deposited in the egg in different patterns brought about by their differential behaviour during the process of maturation.
The role of gap junctions in amphibian development
Authors: Warner Anne E. 
Published: April 2021

ABSTRACT
The possibility that communication through gap junctions may be important during embryonic development has often been raised since gap junctions were first described between early embryonic cells. It is now known that this direct cell-to-cell communication pathway disappears between groups of embryonic cells with different developmental fates as the embryo progresses through development, suggesting that transfer through the gap junctional pathway may play some part in controlling events during development. Supportive evidence for a role for gap junctions comes from experiments demonstrating that the properties of gap junctions differ at the border separating each segment in insect epidermis. Recently it has been shown that the ability to exchange small dyes between cells in the amphibian embryo depends on the position of each cell with respect to the grey crescent. When communication through gap junctions is prevented, by injecting antibodies to gap junctions protein, pattern formation is severely disturbed in the non-communicating region. The paper describes experiments on the pattern of junctional communication at early stages of development of the amphibian embryo and illustrates how anti-gap junction antibodies are being used to determine when and where communication through gap junctions may play an important role during development.
The system specifying body position in the early development ofXenopus, and its response to early perturbations
Authors: Cooke Jonathan 
Published: April 2021

ABSTRACTEvidence is presented that the system setting up preliminary specifications for contributions to the axial body plan, across vegetal regions of the Xenopus embryo, acts in a widespread way at early stages. Mechanisms that regulate the spatial profile of this primary positional variable, and thus ensure the constancy and harmony of the body plans normally achieved, have lost this integrative ability by the 4-cell stage one hour after the plasm shifts that precede first cleavage and symmetrize the egg. Abnormal, partial or distorted profiles of the positional system across whole eggs or isolates, recorded by these times, are retained to give correspondingly partial or imbalanced mes/endodermal pattern at tailbud larval stages. There is evidence that subsequent ‘back-up’ positional interactions, which can heal gross positional discontinuities in isolated presumptive lateral half-eggs and so restore bilateral symmetry, also do this at the price of loss of complete pattern specification. This is probably because of an asymmetrical principle whereby relatively activated (dorsoanterior specified) material can raise the level of originally posterior material on contact, whereas the reverse interaction cannot occur. The observations are discussed in relation to apparently different behaviour in certain other amphibian embryos, and to our knowledge of other positional interactions, normal and also experimentally provoked, such as those that set up the germ layers.
The Importance of Mesenchymal Factors in the Differentiation of Chick Epidermis
Authors: McLoughlin C. B. 
Published: April 2021

ABSTRACTExperiments were undertaken to investigate the degree to which the underlying mesenchyme influences the differentiation of an epithelium. Isolated epidermis of the 5-day chick embryo was explanted in vitro in contact with three different types of mesenchyme from chick embryos of the same age. These mesenchymes were derived from the gizzard, proventriculus, and heart. In a control series epidermis was re-implanted on limb mesenchyme. In each combination the epidermis behaved in a different and characteristic way. The cellular processes by which an isolated epithelium becomes established on mesenchyme in vitro are described. In the control series, epidermis re-implanted on limb mesenchyme keratinized normally, but in contact with cartilage it degenerated. On gizzard mesenchyme epidermis is prevented from keratinizing and is induced to secrete mucus and sometimes to become ciliated. On proventriculus mesenchyme epidermis is initially prevented from keratinizing and secretes mucus, but after about 7 days it reverts to its normal differentiation and keratinizes. Expiants of heart mesenchyme become subdivided into two regions: a central myoblastic area surrounded by a zone of fibroblastic outgrowth. On the central region of myoblasts the epidermis is prevented from keratinizing and spreads to a single-layered squamous epithelium. On heart fibroblasts, however, the epidermis keratinizes more densely than in the controls. The f our types of mesenchyme differ in the nature of the intercellular material that they contain, and in the amount of epithelial spreading they permit. The various effects of the mesenchyme are probably exerted specifically by the fibroblasts, which arrange themselves in contact with the epithelium in most types of culture. These epithelio-mesenchymal interactions are discussed in relation to the initiation and maintenance of embryonic and adult differentiation. It is suggested that the intercellular material of the mesenchyme may participate in the mechanisms underlying these reactions.
Further Investigations on the Cytotoxic and Morphogenetic Effects of Some Nitrogen Mustard Derivatives
Authors: Jurand A. 
Published: April 2021

ABSTRACTPrevious experiments with TEM (triethanomelamine) on chick and mouse embryos (Jurand, 1958, 1959) have shown that some embryonic regions are more sensitive than others to its cytotoxic activity. TEM appeared to be specifically active against mesodermal structures, particularly against the somitic mesoderm, being relatively less active against other tissues. In amphibian embryos, however, the neural tube cells were the most sensitive (Waddington, 1958).
A Study of Nuclei and Intercellular Ground Substance during thein situDifferentiation of Somites inTaricha torosa
Authors: Finnegan Cyril V. 
Published: April 2021

ABSTRACTThe differentiation of T. torosa somite mesoderm between stage 25 and 15 mm. has been examined with regard to variation in nuclear morphology, mitosis, and the development of intercellular matrix. Along with conventional techniques a fluorescent Schiff reagent has been used to obtain a fluorescent Feulgen for observation of DNA pattern, and a fluorescent PAS for observation of the appearance of intercellular mucopolysaccharide. The development of three kinds of nuclear morphology (DNA pattern) and of the PAS-positive intercellular material of the differentiating somite is described. The study indicates that nuclear changes and appearance of ground substance spread laterally from the always more differentiated medial portion of the somite and that mitotic activity is frequently observed in those more superficial areas containing cells with nuclei of the first-stage DNA pattern and is not (or is rarely) observed in those more medial areas containing cells With Other DNA patterns and in which the PAS-positive intercellular material is present. It is concluded that in the differentiating somite through stage 40 there exists a superficially located population of mitotically active, presumably undifferentiated, mesoderm cells.