bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective effect of gonadotrophins on cell coupling, nuclear maturation and protein synthesis in mammalian oocytes
Authors: Moor R. M. , Osborn J. C. , Cran D. G. , Walters D. E. 
Published: April 2021

ABSTRACTIndividual gonadotrophic hormones were used to examine the degree to which changes in intercellular coupling between somatic and germ cells initiate meiotic maturation, regulate protein synthesis or alter the ultrastructure of the ovine oocyte. Follicle Stimulating Hormone (FSH; 50 ng ml−1) suppressed intercellular coupling to the same extent as that observed during oocyte maturation in vivo. At low concentrations FSH did not, however, initiate resumption of meiosis. By contrast, luteinising hormone (LH; 100-500 ng ml−1) invariably initiated meiosis in oocytes cultured within the follicle but did not disrupt intercellular coupling. We conclude that nuclear maturation is not dependent upon the disruption of cell contact between the oocyte and the surrounding follicle cells.The profile of proteins synthesized by untreated oocytes differed greatly from that of oocytes matured for 18 h in follicles treated with a combination of FSH and LH. Pretreatment of follicles with either FSH or LH at low concentrations resulted in the synthesis of an intermediate and more variable pattern of proteins. No correlation was found between changes in protein synthesis and the extent of junctional communication between the cumulus cells and oocyte.Membrane vesiculation and lysosomal change in the transzonal processes are early structural changes associated with the suppression of intercellular coupling in oocytes. These changes in coupling probably result in the relocation of intracellular organelles in the final stages of oocyte maturation.
The secretion of proteinsin vitrofromXenopusoocytes and their accessory cells: a biochemical and morphological study
Authors: Mohun T. J. , Lane C. D. , Colman A. , Wylie C. C. 
Published: April 2021

ABSTRACTProtein secretion by Xenopus laevis oocytes and their surrounding follicular cells in vitro has been investigated using two-dimensional gel electrophoresis. Viable oocytes, devoid of follicle layers, were prepared by treatment with collagenase; they retain in full their capacity to synthesize, sequester and export secretory proteins following microinjection with heterologous messenger RNA. Both RNA-injected and normal cells export a large number of endogenous oocyte proteins and, as with heterologous secretory translation products, these proteins are found within the oocyte in a vesicle fraction. Electron microscopy indicates that secretion involves exocytotic release of cortical vesicle contents. The follicular cells themselves also seem to contribute a number of proteins to the incubation medium surrounding isolated oocytes, but the presence of follicle layers is not required for the export of endogenous oocyte proteins.
Regeneration of subnormally innervated axolotl arms
Authors: Wallace H. , Watson A. , Egar M. 
Published: April 2021

ABSTRACT
Forearms of juvenile axolotls contain about 5000 axons, of which only 25% are myelinated and visible by light microscopy. Virtually all the axons degenerate after transection of the brachial plexus, but repeated operations fail to keep the arm completely denervated. Regrown nerve fibres were detected by electron microscopy after 6 weeks of attempted denervation and related to the quantity usually considered necessary for limb regeneration. Such arms regenerated quite normally, provided their innervation had been depleted for several weeks before amputation. Among other ways of reconciling these observations to the neurotrophic theory of limb regeneration, it is suggested that tissues can adapt to deprivation of their nerve supply.
Differentiation of the yolk-sac endoderm under the influence of the digestive-tract mesenchyme
Authors: Masui Tohru 
Published: April 2021

ABSTRACT
To reveal differentiation potency of yolk-sac endoderm, this tissue from quail embryos was cultured alone or in association with digestive-tract mesenchymes of chick embryos.
When yolk-sac endoderm was cultured alone in vitro, the endoderm of the area vitellina differentiated into the yolk-sac parenchyma, but the endoderm of the extraembryonic area pellucida (EEAP) failed to differentiate into yolk-sac parenchyma, and the endoderm of the area vasculosa became necrotic.
When endoderm of the area vitellina was cultured in association with digestive-tract mesenchymes, all the endodermal cells developed into yolk-sac parenchymal cells after two days. Later, basophilic cells appeared among them, and differentiated into both mesenchymespecific epithelia and intestinal-type epithelium with a striated border, and villi were also formed. Goblet cells appeared in all types of recombinations. The endoderm of the EEAP cultured with digestive-tract mesenchymes gave similar results to that of the area vitellina. In contrast, endoderm of the area vasculosa, when cultured with digestive-tract mesenchymes, became necrotic.
The present investigation demonstrated that the endoderms of the area vitellina and of the EEAP differ in self-differentiation potency, and that their developmental fates can be modified by the influence of digestive-tract mesenchymes. These endoderms can differentiate into the mesenchyme-specific epithelia, though they often differentiate also into the intestinal-type epithelium.
Influence of serum factors on the prevalence of “normal” and “foreign” differentiation pathways in cultures of chick embryo neuroretinal cells
Authors: Pomerai D. I. De , Gali M. A. H. 
Published: April 2021

ABSTRACT
Embryonic (9-day) chick neuroretinal cells transdifferentiate extensively into lens and pigment cells during prolonged culture (4–5 weeks) in media containing foetal calf serum. Medium conditions which promote the attachment and differentiation of neural cells in other culture systems (e.g. horse serum, high glucose levels) both delay the onset and greatly reduce the extent of transdifferentiation in retinal cultures. In the presence of high glucose, horse serum (but not foetal calf serum) also favours cholinergic neuronal differentiation during the early phases of culture, as shown by the levels of choline acetyltransferase activity and accumulation of labelled choline. Substrate conditions have some effect on cholinergic differentiation (promoted by polylysine-coated dishes) but do not affect later transdifferentiation. These effects may be due in part to selective survival or growth of particular retinal cell types under the various medium conditions tested. Cultures stripped of neuronal cells contain negligible choline acetyltransferase activity, but still transdifferentiate into both lens and pigment cells, although more slowly than control cultures. Cell size distributions reveal a significant depletion of the larger cells in high glucose media with foetal calf serum, but not in those with horse serum.
Fetal murine hemopoiesis following in utero low-dose irradiation
Authors: Weinberg Sheila R. , McCarthy Emmeline G. , Macvittie Thomas J. 
Published: April 2021

ABSTRACT
The influence of in utero low-dose ionizing radiation exposure on murine hemopoietic embryogenesis was investigated. In vitro assays such as micro plasma-clot cultures and double-layer soft agar cultures served as sensitive biodosimeters to determine erythropoietic and granulopoietic injuries. Day-10·5, HA/1CR, pregnant mice were irradiated with 0, 50, 100, 150,200, or 300 rads, and day-14·5 fetal livers were studied for colony-forming unit-erythroid (CFU-E), buist-forming unit-erythroid (BFU-E), granulocyte-macrophage colony-forming cell (GM-CFC), and macrophage-colony-forming cell (M-CFC) activity. Fetuses subjected to doses of 200 rads or higher on day 10-5 of gestation responded with a decrease in day-14·5 liver cellularity, reflecting injury to the developing organ and its inability to recover to the nonirradiated values. Difference in response between erythropoietin(EPO)-dependent and EPO-independent CFU-E strongly suggests existence of two populations of erythroid progenitor cells with different radiosensitivities. A dose of 200 rads markedly reduced CFU-E recovery, and a dose of 100 rads was sufficient to reduce BFU-E recovery to almost 10% of 0-rad values. Nonirradiated day-14·5 fetal liver had more GM-CFC compared to any of the irradiated fetuses, and a dramatically reduced M-CFC recovery occurred with each increase in dose following 150 rads. Our results showed that (1) fetal liver granulopoiesis is more sensitive to radiation injury compared to erythropoiesis, and (2) fetal liver has a greater potential for erythropoiesis recovery.
Hepatic induction in the avian embryo: Specificity of reactive endoderm and inductive mesoderm
Authors: Fukuda-Taira Sumiko 
Published: April 2021

ABSTRACT
Mesoderm of precardiac and cardiac region (‘cardiac’ mesoderm) of chick, quail and mouse embryos could induce hepatic epithelium in the endoderm of the anterior half of young quail or chick embryos (anterior endoderm) in vitro as well as in vivo. No species specificity in the induction of hepatic epithelium by the ‘cardiac’ mesoderm could be observed.
The hepatic induction, was controlled strictly by tissue specificity of both endoderm and mesoderm. Replacement of the ‘cardiac’ mesoderm or the anterior endoderm by noncardiac mesoderms or endoderms other than the anterior endoderm resulted in failure of hepatic induction. Only the anterior endoderm was found to have competence for hepatic induction, indicating that it was committed, in unknown ways, to react with ‘cardiac’ mesoderm, and can properly be called pre-hepatic endoderm.
Comparison between the development of hepatic endoderm and the hepatic induction potency of ‘cardiac’ mesoderm, which was most intense during 1- to 1·5-incubation days and decreased gradually with the increase of the stage, suggests that in normal development the ‘cardiac’ mesoderm actually induces hepatic epithelium in the competent endoderm. Hepatic-induction potency remained up to 6 days, and was found in truncus arteriosus, ventricle and auricle areas and in endocardial and myocardial layers of the heart.
Effects of cystment on cells of Oxytricha fallax possessing supernumerary dorsal bristle rows
Authors: Hammersmith Robert L. , Grimes Gary W. 
Published: April 2021

ABSTRACT
The patterning and organization of new structure in eukaryotic cells can, in certain cases, be controlled by existing structure. Sonneborn illustrated this in Paramecium two ways. (1) Cells with a doublet phenotype (individual cells with almost two complete sets of cortical structures) develop true to type and are inherited, sexually and asexually, independent of changes in nuclear genotype or fluid cytoplasm (Sonneborn, 1963). (2) Inverted rows of cilia and basal bodies maintain their inverted polarity during morphogenesis and cell division, again independent of changes in nuclear genotype or fluid cytoplasm (Beisson & Sonneborn, 1965). These observations led to formulation of the concept of ‘cytotaxis’ – the organization of new structure under the influence of preexisting structure (i.e. the molecular architecture of the cell which includes visible structure) (Sonneborn, 1964,1975). Cytotaxis thus represents an informational system for pattern development and regulation which is not under direct nuclear control. Several examples of cytotaxis have been demonstrated subsequently in other cell types (Grimes, 1973c, 1976; Grimes & Adler, 1978; Grimes & L’Hernault, 1979; Hammersmith, 1976b); Ng & Frankel, 1977).
Calcium and spreading behaviour of amphibian blastula and gastrula cells
Authors: Leblanc Jacqueline , Brick Irving 
Published: April 2021

ABSTRACTCell locomotion involves several structural-functional activities: membrane extensibility, microfilament regulation and adhesive interactions. There is evidence for Ca21- requirement in all of these. Our data may clarify the role of Ca2+ in locomotion and adhesion. Morphologic and spreading responses of isolated blastula-late gastrula Rana pipiens germ layer cells to varying molar concentrations of Ca2+: 0-Ca2+, Standard Ca2+ (Barth’s Xsolution), 1·5 × and 2·0 × Std Ca2+ were viewed by S.E.M. after 1 h in culture. Ionic strength and pH were constant. All cells showed quantitative relationships between Ca2+ concentration and surface extensibility, projection formation and presumably adhesion, but with tissue- and stagespecific variations. Cells in Ca2+-free medium fail to adhere (50%), flatten or form surface projections. Cells in media with increasing Ca2+ generally formed more numerous and extensive surface projections, spread and adhered to a greater extent. In some cases there were no quantitative differences in response between 1·5 × and 2·0×standard Ca2+. Cells in suspension for 1 h in standard solution remained spherical, forming no projections. We infer from these results that both Ca2+ and contact with a physical substratum, cell-cell or cellglass are required for mobilization of the various systems involved in locomotion and adhesion. In addition, components of these systems are quantitatively activated by increased availability of Ca2+.
Somitogenesis in the amphibian Xenopus laevis: scanning electron microscopic analysis of intrasomitic cellular arrangements during somite rotation
Authors: Youn B. Woo , Malacinski George M. 
Published: April 2021

ABSTRACT
The intrasomitic changes in cell arrangement which accompany somite rotation during somitogenesis in Xenopus laevis were analysed with the scanning electron microscope (SEM). Longitudinal, horizontal fractures of whole embryos were examined at various dorsoventral levels of stage-22 to -24 embryos. Observations of the gross morphological features of somitogenesis, and the cellular changes which accompany somite segmentation and somite rotation were made. Several of these observations lead to modifications of previous models for the cellular basis of somitogenesis in Xenopus. Individual cellular rearrangements, rather than simultaneous block rotation of a whole somite, appear to be responsible for the 90° rotation of myotomal cells within a single somite.
Cellular arrangments in fused somites were also examined. Some ultraviolet-irradiated embryos displayed a complete lack of a notochord. The somites in those embryos were fused across the midline beneath the neural tube. The dorsal and ventral arms of the somites are not fused. Normal rotation occurs only in the dorsal and ventral arms while, in the majority of cases, cells in the fused region fail to rotate normally. In some cases, individual cells in the fused region undergo partial rearrangement. Those observations support the notion that individual cellular rearrangements account for the rotation of the whole somite.
Location of pre-hepatic cells in the early developmental stages of quail embryos
Authors: Fukuda-Tatra Sumiko 
Published: April 2021

ABSTRACT
The location of the pre-hepatic cells which can respond to the inductive influence of the cardiac mesoderm and differentiate to the hepatic epithelium was investigated in quail embryos between the unincubated and 8-somite stages.
These cells were found to exist in the whole area of the blastoderm of unincubated and prestreak stages. At the short-streak stage, just before the beginning of gastrulation, pre-hepatic cells are confined to the anterior part of the primitive streak. During gastrulation, pre-hepatic cells invaginate through this area of the primitive streak and enter the endoblastic layer. They are found in the anterior half of the endoblastic layer as well as in the lower half of the anterior part of the primitive streak at the medium- to definitive-streak stages. After gastrulation, they are consistently found only in the anterior half of the endoblastic layer. From the 1-somite stage, at least up to the 8-somite stage, the pre-hepatic cells are localized in the endoderm, anterior to the level of the 3rd somite.
Since the pre-hepatic cells or their progenitors were always found within the definitive endoblast which invaginates from the epiblast during gastrulation, it can be presumed that the pre-hepatic cells originate from the epiblast, invaginate through the anterior part of the primitive streak between the short- and the definitive-streak stage, and enter the definitive endoblast.
Probability aspects of supernumerary production in the regenerating limbs of the axolotl, Ambystoma mexicanum
Authors: Turner R. N. 
Published: April 2021

ABSTRACT
The applicability of deterministic models, and in particular the polar co-ordinate model of French, Bryant & Bryant (1976), to the regenerative process has been investigated by performing ipsilateral blastemal rotations of varying angle on the fore and hind limbs of the axolotl. The results show that the frequency of supernumerary production rises with increasing angle to reach a peak at 180° and then falls off more rapidly, giving rise to an asymmetric distribution curve. The position of supernumerary outgrowth also suggests a probabilistic event, there being no consistent relationship between this parameter and the angle of rotation. The polar co-ordinate model is incapable of explaining these results and the work suggests that the determinism of current regeneration models may have to be abandoned in favour of a more stochastic theory.
Carbonic anhydrase activity in the chick embryo chorioallantois: regional distribution and vitamin D regulation*
Authors: Narbaitz Roberto , Kacew Sam , Sitwell Lucian 
Published: April 2021

ABSTRACT
An electron microscopical and biochemical study of the chorionic epithelium from 16-and 17-day-old chick embryos was conducted. Using a combination of sections made either parallel or perpendicular to the chorionic surface, it was confirmed that the cell populations of the polar and equatorial regions of the membrane are different; the former contains a very reduced number of VC cells which are, contrariwise, widely distributed in the latter. This evidence was required for the interpretation of data on carbonic anhydrase activity. This enzymatic activity is known to increase in the chorioallantoic membrane at the time at which shell resorption begins but the enzyme is believed to be localized in other cell types in addition to VC cells. The results of the present experiments show that carbonic anhydrase activity is significantly higher in the region where VC cells are more frequent (equatorial) than in the region where they are rarely found (polar) and thus suggests that a substantial proportion of the activity measured in the whole membrane corresponds to VC cells.
Carbonic anhydrase activity in the equatorial region of the chorioallantoic membrane increased after 4 h and peaked 24 h after the administration of 1,25-DHCC. This time course is similar to the one on previous experiments in which serum calcium concentrations were determined after similar treatment. It is suggested that one of the effects of 1,25-DHCC on its target cells in the membrane (VC cells according to previous evidence) is to increase synthesis and/or activity of carbonic anhydrase.
Growth factors and pattern formation
Authors: Smith J. C. 
Published: April 2021

ABSTRACT
Growth and pattern formation occur simultaneously in many epimorphic fields and it has been suggested that specification of positional information is somehow linked to cell division. It is possible, therefore, that boundary regions responsible for the specification of positional information produce cell growth factors. In this paper I review the properties of some known growth factors, describe their effects on the cell cycle and discuss how they might act. In developing a convenient in vitro assay for morphogenetic factors it will be much easier to measure incorporation of [3H]thymidine into responding cells than to estimate changes in positional value.
Autonomous development of parts isolated from primitive-streak-stage mouse embryos. Is development clonal?
Authors: Snow Michael H. L. 
Published: April 2021

ABSTRACTThe relationship between growth rate and regionalization of amphibian, bird and mammalian embryos is briefly reviewed. In contrast to the others, mammals start gastrulation with few cells but accelerate cell proliferation coincidentally. Experiments are described which demonstrate (1) autonomous development of pieces isolated surgically from such mouse embryos, and (2) an absence of regeneration or regulation. Since such embryos regulate completely after chemically induced random cell death it is postulated that these results reflect developmental determination and a resulting mosaicism that suggests development may have a clonal basis. Maps are drawn, allocating positions to various tissues in the embryo.
Distal transformation in regenerating double anterior axolotl limbs
Authors: Stocum David L. 
Published: April 2021

ABSTRACT
Previous investigations have shown that axolotl double anterior thighs regenerate only a tapered extension of the femur after simple amputation, but undergo intercalary regeneration of the femur and a symmetrical tibia when a normal wrist blastema is grafted to the thigh. There are two possibilities to account for these results: (1) distal transformation in both terminal and intercalary regeneration depends upon special properties of posterior cells (such as polarizing ability) that are lacking in the anterior half of the limb, but which would be provided by the posterior half of a normal wrist blastema graft, or (2) the pattern of cellular interactions required for distal transformation during terminal regeneration is different from that required for distal transformation during intercalary regeneration.
These alternatives were tested by grafting axolotl double anterior wrist blastemas to double anterior thighs. The host thighs regenerated a femur and symmetrical tibia that structurally were the same as the bones intercalated after grafting a normal wrist blastema to a double anterior thigh. In all cases, the graft developed as a symmetrical hand comprising one to three carpals and one to two digits. These results rule out the necessity of any special properties of posterior cells for distal transformation or polarization of the anterior-posterior axis and suggest instead that distal transformation during intercalary regeneration involves a different pattern of cellular interactions than in terminal regeneration.