bluuebunny/crossref_metadata_2025_split huggingface dataset:
An investigation of inner cell mass and trophoblast tissues following their isolation from the mouse blastocyst
Authors: Gardner R. L. , Johnson M. H. 
Published: April 2021

ABSTRACTInner cell mass (ICM) and trophoblast were isolated from -day post-coitum mouse blastocysts by microsurgery. Trophoblastic fragments formed vesicles in culture but did not aggregate with other such fragments. They proved as effective as intact blastocysts in inducing decidua in recipient uteri, but thereafter failed to proliferate. Isolated ICMs remained as solid balls of cells that readily aggregated in pairs or groups in culture but failed to induce implantation changes in receptive uteri. Possible explanations for the failure of isolated trophoblast to proliferate after implantation are discussed. It is argued that presence of ICM tissue is necessary for trophoblast proliferation, and suggested that the ICM exerts its effect by controlling development of the ectoplacental cone.
Rôle du mésoderme somitique dans le développement du plumage dorsal chez l’embryon de Poulet:II Régionalisation du mésoderme plumigène
Authors: Mauger Annick 
Published: April 2021

ABSTRACTThe role of somitic mesoderm in the development of dorsal plumage in chick embryos. II. RegionalisationTransplantation and inversion experiments were performed on the somitic mesoderm of 2-to 2·5-day chick embryos in order to study the role of regional and axial determinations in the development of the dorsal plumage.The transposition of a piece of somitic mesoderm from the posterior cervical region (where the spinal pteryla is narrow) to the thoraco-lumbar region (where it is wide) leads to a local and unilateral narrowing of the spinal pteryla at the operation site. Conversely, the transposition of somitic mesoderm from the thoraco-lumbar region to the posterior cervical region results in a local and unilateral widening of the spinal pteryla. Consequently at the time of operation the segmented or not yet segmented somitic mesoderm is already determined to give rise to a definite transverse level of the spinal pteryla.The inversion of the cephalo-caudal polarity of a piece of somitic mesoderm without the ectodermal covering, or of a portion of the axial organs deprived of the overlying ectoderm has no effect on the orientation of feather filaments and feather rows. In contrast, the inversion of the cephalo-caudal polarity of a portion of the axial organs together with the overlying ectoderm results in the development of feathers growing in a cephalad direction and feather chevrons opening towards the head of the embryo.The inversion of the dorso-ventral polarity of a piece of somitic mesoderm does not prevent the normal differentiation of feathers in the operated region.The inversion of the medio-lateral polarity of a piece of unsegmented somitic mesoderm has little effect on the development of the spinal pteryla. On the contrary, the medio-lateral inversion of a chain of somites precludes the formation of the feathers at the level of operation.The somitic mesoderm, even when segmented, is endowed with extensive regulative capacity of its axes, except for the medio-lateral polarity, which is fixed irreversibly at the time of segmentation. The regional determination of the feather-forming somitic mesoderm is acquired at an early stage, at any rate before segmentation. However, at a given transverse level of the cephalo-caudal axis, the somitic cells remain totipotent as concerns their histogenetic destiny (dermatome, myotome, or sclerotome) until after the onset of segmentation.
Investigation of the mode of nuclear control over protein synthesis in early development of loach and sea urchin
Authors: Krigsgaber Maya R. , Neyfakh A. A. 
Published: April 2021

ABSTRACT
It is shown that in loach embryos the incorporation of precursors into protein takes place in the blastoderm cells only. The change of the rate of incorporation of labelled amino acids into protein of the blastoderm separated from the yolk at successive developmental stages reflects the changes in the level of protein synthesis in intact embryos of the same developmental stages. Typical periodic changes of the intensity of protein synthesis in early embryogenesis of the loach are detected: low incorporation of amino acids at blastula stages is followed by an increase of synthesis during gastrulation and by a decrease with the onset of organogenesis.
To study the genetic control over protein synthesis at various developmental stages of loach and sea-urchin embryos the effects of ionizing radiation and long-term treatment with actinomycin D have been examined. X-Irradiation doses produce an insignificant direct effect on protein synthesis, while radiation damage of the nuclear apparatus results in a gradual but ever increasing inhibition of protein synthesis. The inhibition of RNA synthesis with actinomycin or ionizing radiation damage of the nuclei produce essentially the same effect on the intensity of protein synthesis. Protein synthesis in androgenetic haploid hybrid embryos (loach ♀ ×goldfish ♂) and in loach androgenetic haploid embryos after producing a partial elimination of chromosomes does not differ from ‘enucleated’ loach embryos completely deprived of chromosomes. These data suggest that high-polymeric RNA formed after the elimination of some chromsomes is unable to provide a normal level of protein synthesis.
Protein synthesis is not controlled by the nuclei up to the stages of early blastula (sea urchin) and of late blastula (loach), being evidently programmed in oogenesis. To provide a rapid activation of protein synthesis in the course of gastrulation in the loach the function of the nuclei has to be realized during mid-blastula stages. An increase of the rate of the incorporation of amino acids at the stages of mesenchyme blastula in the sea urchin depends on the synthesis of RNA at the early blastula. At the same time protein synthesis during gastrulation in the loach and at mesenchyme blastula in the sea urchin is much less dependent on the simultaneous RNA synthesis. Protein synthesis at these stages seems to be provided by the long-living templates and controlled by non-gene mechanisms of the regulation of translation.
Thus early embryonic differentiation in the loach and sea-urchin development is related to the activation of protein synthesis. The latter is provided by the preceding morphogenetic nuclear function, which makes protein synthesis relatively independent of simultaneous synthesis of templates that ensures subsequent development stages.
Artificial metaplasia of pigmented epithelium into retina in tadpoles and adult frogs
Authors: Lopashov G. V. , Sologub Alla A. 
Published: April 2021

ABSTRACTThe present work was aimed at investigating the possibility and conditions necessary for the artificial transformation of one tissue into another. Experiments were carried out with the pigmented epithelium of the eye in tadpoles and adult frogs of Rana temporaria. Following the removal of the mesenchyme envelopes (or their exfoliation during the experiment), pigmented epithelium transformed into retina under the influence of retina from tadpoles of the same species. This phenomenon was observed both under the cultivation of a piece of retina in a sandwich of pigmented epithelium and the transplantation of pigmented epithelium layers into the eye cavity of tadpoles. Such transformation did not occur in the absence of retinal influence. Metaplasia requires the removal of the mesenchyme envelopes, the action of the retinal agent, as well as preservation of the integrity of the pigmented epithelium layer and subsequent proliferation of its cells. The character of general control mechanisms both maintaining the stability of cell types and leading to their transformation into other cell types is discussed.
Composite eggs and Siamese twins in paedogenetic gall midges
Authors: Went Dirk F. , Camenzind René 
Published: April 2021

ABSTRACT
Several types of composite eggs were found in two species of paedogenetic gall midges. One composite egg, consisting of two blastoderms, was cultured in vitro, and its development was recorded on film. Two other composite eggs were fixed in the oocyte stage; each contained two nurse chambers, two egg chambers and one oocyte nucleus. Some other ‘eggs’ are described, which consisted merely of a nurse chamber or of one or two oocytes and of the follicular epithelium. It is argued that the formation of composite eggs and incomplete eggs must be due to errors in the formation of the oocyte-nurse cell complexes.
The article also describes three Siamese twins in larval stage which were found in two paedogenetic gall-midge species. In two twins the larvae were linked posterior-posterior, while in the third they were connected anterior-anterior. It is assumed that the Siamese twin-larvae evolved from composite eggs.
Fine structure of the apical rim—mesenchyme complex during limb morphogenesis in man
Authors: Kelley Robert O. 
Published: April 2021

ABSTRACTUltrastructure of the apical rim-basal lamina-mesenchyme complex in man duringHorizons 15-18 is correlated with the development of limbs.Apical epithelium is a complicated tissue exhibiting surface microvilli, junctional complexes, free ribosomes, elaborate Golgi centers, glycogen and scanty granular endoplasmic reticulum. The apical rim thickens during stages 15 and 16, remaining multilayered at digital tips and thinning adjacent to zones of necrosis by stages 17 and 18. Epithelial thinning may be a response to lack of ‘maintenance factor’. A continuous basal lamina is present during these stages. Collagen-like fibrils are numerous in interdigital zones of necrosis and sparse at tips of digital blastemata. The presence of oriented microfilaments in interdigital epithelium suggests active invagination during morphogenesis of fingers in man.
Spermine is major polyamine in sea urchins: studies of polyamines and their synthesis in developing sea urchins
Authors: Manen Carol-Ann , Russell Diane H. 
Published: April 2021

ABSTRACTPolyamine synthesis and accumulation was studied in several species of developing sea urchins. Most striking is the presence in the gametes of a large amount of spermine, with low amounts of putrescine and spermidine. This contrasts with the pattern of polyamines present in both micro-organisms and mammals. Micro-organisms contain mainly putrescine and spermidine and adult mammalian tissues usually contain equimolar concentrations of spermidine and spermine.During development (i.e. to gastrulation) there is a large increase in the spermidine concentration with relatively little change in either putrescine or spermine levels. After gastrulation, both spermidine and spermine concentrations are elevated. These new accumulations parallel the new synthesis of rRNA that occurs after gastrulation.Enzyme activity patterns parallel the changes detected in the concentrations of the polyamines with the exception of ornithine decarboxylase activity. This exception may be due to the rapid turnover of putrescine, the precursor for the synthesis of spermidine and spermine.
The formation of the optic fibre projection after partial tectal removal in Xenopus
Authors: Straznicky K. 
Published: April 2021

ABSTRACT
The formation of retinotectal connexions in Xenopus has been investigated by mapping the visual field projections of animals after various partial tectal removals.
Following removal of a sufficiently extensive piece of the left rostral, caudal, medial or lateral tectum with, in addition, section of the contralateral optic nerve, a consistent defect in the nasal, temporal, superior or inferior visual fields respectively was obtained. The various scotomas indicated that optic axons did not regenerate into the residual tectum from all regions of the retina. The conclusion drawn from the present experiments is that optic fibres tend to connect, in a residual half-tectum, only with appropriate tectal loci.
An ultrastructural and cytochemical study of developing small intestine in man
Authors: Kelley Robert O. 
Published: April 2021

ABSTRACT
The observations and results of this study suggest that intestinal absorptive cells possess structural and enzymic potential for function in utero. As early as the tenth postfertilization week, microvilli are differentiated, a surface coat is elaborated, alkaline phosphatase activity is localized on microvillar borders, and colloidal particles when introduced into the gut lumen in vitro are transported in vesicles from the apical cell surface to the lamina propria via extracellular spaces. In addition, cytoplasmic lipid droplets appear after administration of corn oil by injection into the gut lumen. However, the term ‘potential’ is stressed in that one can only speculate at present on what materials are absorbed from swallowed amniotic fluid in man.
Appearance of antler pedicles in early foetal life in red deer
Authors: Lincoln G. A. 
Published: April 2021

ABSTRACT
The primordial antler pedicles of red deer show a transitory enlargement in early foetal life in the male while no similar change occurs in the female. Observations on the growth rate of the reproductive tract, pituitary and adrenal glands and the content of testosterone in the gonads, indicate that the precocious development of the pedicles occurs during a phase of increased testicular activity and probably reflects a surge in testosterone secretion following sexual differentation.
The site of action of the fuzzy locus (fz) in the mouse, as determined by dermal-epidermal recombinations
Authors: Mayer Thomas C. , Mittelberger James A. , Green Margaret C. 
Published: April 2021

ABSTRACTThe site of action of the mutation fuzzy (fz) was investigated by the method of dermal- epidermal recombination. Skins from 14-day mutant and normal mouse embryos were sepa- rated into dermal and epidermal components, recombined, and grown in the mouse testis for 14 days. Grafts that contained mutant epidermis as one of the components produced many abnormal hairs characteristic of fuzzy mice. There was no observable effect of the fz locus on the dermis under the conditions of this experiment.
A quantitative study of the growth and development of the ventral root in normal and experimental conditions
Authors: Prestige M. C. , Wilson Margaret A. 
Published: April 2021

ABSTRACTThe development of the ventral root (VR) in Xenopus has been studied by electron microscopy. Total fibre counts, and counts of classes of fibres were made from large photomontages of the whole of VR 9 at × 15000. The total number of fibres in the root shows the same pattern of initial rise, peak, and subsequent decline that previous ventral horn (VH) cell counts had shown. The two curves overlay each other initially, but after the decline, there were apparently more cells than fibres. Promyelin and myelin formation was seen at the time of the decline. There was no evidence that dying axons had started to myelinate. In some animals the limb-bud was removed at the time of its first penetration by nerve fibres. The ventral roots developed normally for a week, but thereafter fibre loss was accentuated, advanced and more profound, so that after another week, no fibres were left. In these roots, no promyelin or myelin was formed. In other animals, it was shown that there is no evidence for collateral sprouting in the ventral roots during normal development. It is argued that the axons which die in normal development have already reached the limb-bud. The correspondence between axon and cell number is discussed.
Sex chimaerism and germ cell distribution in a series of chimaeric mice
Authors: McLaren Anne 
Published: April 2021

ABSTRACT
Of 30 mice born from aggregation of embryos from a multiple recessive strain with F1 embryos carrying the contrasting alleles, 4 females and 20 males proved to be overtly chimaeric. Three XX/XX females, five XY/XY males and eight XY/XX males were identified by chromosome analysis. Thus 50% of the population analysed were sex chimaeras, and all of these developed as phenotypic males, though one showed evidence of hermaphroditism. In seven XY/XX chimaeras that bred, the genetic component undergoing spermatogenesis coincided in every case with the component identified by chromosome morphology as XY. The F1 component predominated in metaphase plates derived from cultured blood cells. Comparison with direct preparations from bone marrow suggested selection in favour of F1 cells, either through differential proliferation of stem cells in vivo or differential response to phytohaemagglutinin in vitro. In XY/XX males, the percentage of XX cells detected varied from 1% to 98% in blood, and from 0% to 80% in bone marrow. Of eight ‘single-sex’ chimaeras progeny-tested (three XX/XX, five XY/XY), only one showed evidence of a mixed population of germ cells. The proportion of the two types of progeny varied significantly from litter to litter, but was unrelated to the age of the male.
An immunofluorescent study of cornea development in the chick
Authors: Ikeda A. , Maisel H. , Waggoner D. 
Published: April 2021

ABSTRACT
The developmental pattern of appearance of a structural corneal antigenic determinant was studied by immunofluorescent methods. It was first detected in the primary corneal stroma at stage 23, and thereafter spread throughout the primary and secondary stroma. This antigen was absent from Bowman’ s membrane at its initial stage of development, suggesting that this membrane is a new structure in corneal morphogenesis, and not simply a modification of the primary stroma. This study also suggests that the antigenic determinant is a carbohydrate and is secreted by the corneal epithelial cells.
Le développement du thalamus des Anoures au cours de la métamorphose
Authors: Picouet M. J. 
Published: April 2021

ABSTRACTDevelopment of the thalamus in anurans during metamorphosisA developmental study of the anuran diencephalon from stage 30 to 2 months after metamorphosis has been done. At stage 30 in Discoglossuspictus, the diencephalic wall is divided into a superior area and an inferior area, where two kinds of cellular migrations are described.Comparison with the urodele diencephalon suggests that the building of a new area (area dorsolateralis) in anurans, by means of an ‘external migration’, characterizes a level of organization which is related to the optic system in Anura. During metamorphosis, optical morphogenetic influences would come from the tectum opticum to the dorsal thalamus. It is possible that the dorsal thalamus could be involved in binocular vision by way of tectofugal fibres.Some typical anuran diencephalic nuclei (i.e. nucleus corpus geniculatum latérale) are missing or are not well differentiated (i.e. nucleus rotondus) in Discoglossus. This species gives a simplified pattern of the anuran diencephalon.
Zona pellucida denudation, blastocyst proliferation and attachment in the rat
Authors: Surani M. A. H. 
Published: April 2021

ABSTRACT
The mode of zona pellucida denudation and blastocyst proliferation and attachment was investigated in Wistar rats during day 5 of pregnancy and in ovariectomized pregnant animals given 5.0 mg progesterone daily until the 10th day, when 0.2 µg oestradiol was injected together with progesterone.
During day 5 of pregnancy, when only 5 empty zonae were detected from 32 animals, zona denudation occurred by lysis, which took 6 h. Zona denudation occurred by shedding in the ovariectomized pregnant animals; 190 empty zonae were detected from 40 animals. Oestradiol administration to the experimental animals caused lysis of the shed zonae 24-30 h after oestradiol treatment.
Air-dried preparations of the embryos showed that the blastomeres proliferated exponentially from a mean of 27.52 ± 4.0 cells per embryo at 12.00 h on day 5 of pregnancy to 53.96 ± 2.58 cells per embryo at 22.00 h, with a cell doubling time of 10 h in normal animals. In the ovariectomized animals, blastocysts were arrested at about the 100-cell stage on the 10th day. Oestradiol administration to the experimental animals did not induce mitosis; the embryos implanted without further cell division.
The number of free embryos recovered declined from a mean of 12.0 per animal at 12.00 h to 4.25 per animal at 22.00 h on day 5 of pregnancy. The number of embryos recovered from the ovariectomized animals varied between one and 11 per animal .
The results show that cell division continued in embryos within ovariectomized pregnant animals in the absence of oestrogen, until about the 100-cell stage. There was no further cell division before nidation when oestradiol was administered. The empty zonae were, however, lysed between 24 and 30 h after oestradiol treatment. The zona lytic factor appears to be oestradiol dependent and of maternal origin. A causal relationship exists between zona lysis and embryo attachment, which is independent of the number of cells per blastocyst.
Marker chromosome analysis of two mouse chimaeras
Authors: Ford C. E. , Evans E. P. , Gardner R. L. 
Published: April 2021

ABSTRACTChimaeric mice were obtained by injecting embryonic (CBA/H-T6 × PDE)F1 cells into PDE blastocysts. Three of 15 young were overt chimaeras. One female and one male chimaera survived to adulthood and after completion of test breeding, which demonstrated chimaerism in the germ cells of both, they were killed for study when aged 32 and 33 weeks respectively. Chromosome spreads were scored for the presence or absence of the T6 marker chromosome in direct preparations from bone marrow, spleen, thymus, lymph nodes, Peyer’ s patches, corneas, gut epithelium and testes. Preparations from monolayer cultures of skin, kidney, ovaiy and gut and from mitogen-stimulated blood cultures were scored in the same way.Both components of the chimaeras were identified in every one of 53 specimens studied, some of which, such as single lymph nodes, corneas and segments of gut, may not have contained more than 105 proliferating cells. This result complements published evidence for fine-grained mixture obtained in morula-aggregation chimaeras by other methods and implies extensive cell movement during embryogenesis.Results obtained from the lymphomyeloid tissues show a clear partition into two groups in respect of the proportions of host-type to donor-type cells identified. The one group consists of bone marrow, thymus and Peyer’ s patches, the other of spleen and lymph nodes. This result would be most simply explained in terms of two distinct stem cell pools and appears to conflict with the currently favoured hypothesis of a single stem cell pool for the whole lymphomyeloid complex located in bone marrow. Four groups of factors may, however, modify the relative representation of the two components in different lymphomyeloid sites: (1) The magnitude of embryonic founder populations. (2) Limited recruitment from the stem cell pool in post-natal life. (3) Variable size of clones produced by individual stem cells. (4) Differential cellular behaviour determined by genotypic differences.
Expression of homeotic mutations in duplicated and regenerated antennae ofDrosophila melanogaster
Authors: Gehring Walter J. , Schubiger Gerold 
Published: April 2021

ABSTRACTThree homeotic mutants, aristapedia (ssa and ssa-UCI) and Nasobemia (Ns) which involve antenna-leg transformations were analyzed with respect to their time of expression. In particular we studied the question of whether these mutations are expressed when the mutant cells pass through additional cell divisions in culture. Mutant antennal discs were cultured in vivo and allowed to duplicate the antennal anlage. Furthermore, regeneration of the mutant antennal anlage was obtained by culturing eye discs and a particular fragment of the eye disc. Both duplicated and regenerated antennae showed at least a partial transformation into leg structures which indicates that the mutant gene is expressed during proliferation in culture.