bluuebunny/crossref_metadata_2025_split huggingface dataset:
The hormonal control and morphology of blastocyst invasion in the mouse uterus in vitro
Authors: Grant P. S. , Ljungkvist I. , Nilsson O. 
Published: April 2021

ABSTRACT
When mature and immature uteri from ovariectomized mice were cultured in chemically defined media, blastocyst invasion occurred in the presence of progesterone but not in media containing only oestradiol.
The invaded stromal tissue did not decidualize unless the uteri were taken from mice pretreated with progesterone and oestradiol. Fibrillar material was, however, concentrated in the stromal tissue adjacent to the invasive trophoblast.
Neither progesterone nor oestradiol, had any ultrastructural effect on the endometrium of cultured uteri from ovariectomized mice, other than closure of uterine lumina in the presence of progesterone.
Embryogenesis became abnormal, probably owing to the failure of formation of a suitable implantation chamber.
Electron microscopic studies on chick limb cartilage differentiated in tissue culture
Authors: Goel Suresh C. , Jurand A. 
Published: April 2021

ABSTRACTThe hind limb-bud mesenchyme of chick embryos days old was cultured in Eagle’s Minimum Essential Medium supplemented with both horse serum and fresh chick embryo extract. Whereas no differences are seen at the light-microscope level, at the electron-microscope level the chondroblasts differentiated in tissue culture are noticeably different from those differentiated in vivo, particularly in the possession of some cytoplasmic fibrils and vacuoles. It is proposed that the secretion of the extracellular matrix alone is not sufficient to account for the pattern of cellular arrangement in a cartilaginous condensation.
Activities of haem synthetic enzymes in blood cells of pre-natal flexed-tailed (f/f) anaemic mice
Authors: Cole R. J. , Garlick J. , Cheek E. M. 
Published: April 2021

ABSTRACT
Levels of activity of δ-aminolaevulinate synthetase, δ-aminolaevulinate dehydratase, porphyrinogen synthetase and haem synthetase in circulating reticulocytes of pre-natal FL4/Re + /+ and congenitally anaemic FLl/Re f/f mice have been determined. The activities of δ-aminolaevulinate synthetase and δ -aminolaevulinate dehydratase were found to be decreased in proportion to the hypochromia observed in mature liver-derived erythrocytes in neonatal f/f mice, but activities of enzymes later in the haem synthetic pathway were relatively undisturbed. No significant differences were found in levels of haem synthetic enzymes in foetal livers of +/+ and f/f mice. These results indicate that the severe anaemia of late prenatal and neonatal f/f mice is due both to reduction in haem synthesis expressed at the reticulocyte stage of erythroid differentiation and to restricted production of erythroid progenitor cells. Retarded foetal growth and skeletal abnormalities, both characteristic of the pre-natal expression of the f/f gene complement, can also be related to reduced levels of haem synthesis, but the abnormal distribution of pigment cells seen in f/f animals appears to be a secondary effect of reduced tissue oxygenation resulting from pre-natal anaemia.
‘Immobile’ (im), a recessive lethal mutation of Xenopus laevis tadpoles
Authors: Droin A. , Beauchemin M. L. 
Published: April 2021

ABSTRACT
‘Immobile’ (im) is a recessive lethal mutation discovered in the F3 of a Xenopus (Xenopus laevis laevis) originating from a mesodermal nucleus of a neurula transplanted into an enucleated egg. The im embryos do not contract after mechanical stimulation nor do they present any spontaneous contraction from the neurula stage onwards. Development proceeds normally during the first days after which deformation of the lower jaw and tail are observed. The im tadpoles die when normal controls are at the feeding stage. Nervous and muscular tissues are histologically normal in the mutant tadpoles; at advanced stages, however, an irregularity in the path of the myofibrils is observed which is especially conspicuous in the electron microscope. Cholinesterases and ATPase are present in the mutant muscles.
Parabiosis and chimerae experiments have shown that parabionts and grafts behave according to their own genotype. Cultures of presumptive axial systems with or without ectoderm lead to the conclusion that, first of all, the abnormality is situated in the mesodermal cells and secondly that the first muscular contractions in normal Xenopus laevis are of myogenic origin. The banding pattern of the myofibrils is normal as was shown by obtaining contractions of glycerol extracted im myoblasts with ATP. It seems therefore that in this mutation, the abnormality is situated in the membranous system of the muscular cell, sarcoplasmic reticulum and/or tubular system as is probably the case in the mdg mutation of the mouse.
Progesterone-induced in vitro maturation in oocytes of Notophthalmus viridescens (Amphibia Urodela) and some observations on cytological aspects of maturation
Authors: Pilone Giuseppina Barsacchi , Humphries A. A. 
Published: April 2021

ABSTRACT
Maturation in vitro of oocytes of the newt, Notophthalmus viridescens, is inducible with progesterone after in vivo treatment of females with gonadotropin; few oocytes mature in vitro in the absence of such gonadotropin treatment. Chromosomes of most large oocytes of animals not receiving gonadotropin are still in the lampbrush condition; chromosomes from gonadotropin-treated animals are shorter and the lateral loops are less profuse and somewhat retracted. The chromosome condition, then, can be correlated with susceptibility to progesterone induction of maturation in vitro. As maturation progresses, the germinal vesicle moves toward the surface and decreases in size, with an apparent loss of nuclear material from the centripetal end. Although lateral loops of most chromosomes disappear during the changes in the germinal vesicle, profuse loops develop during this period at the sphere loci, which were previously devoid of loops.
A new in vitro system for studying secondary palate development
Authors: Brinkley L. , Basehoar G. , Branch A. , Avery J. 
Published: April 2021

ABSTRACT
An in vitro system was devised which supports palate development in partially dissected embryonic mouse heads. The heads were suspended in the culture chamber so that they were not held in a fixed orientation and were constantly surrounded with a fluid medium. Under these circumstances the developing palate must effect closure without the aid of gravitational forces. The culture medium was constantly circulated, gassed with 95 % O2, 5 % CO2 using hollow fiber gas permeation devices, and kept at 34 °C. Swiss-Webster mouse embryos of 12 days 12 –18 h (ca. 48 h prior to expected in vivo closure) or 13 days 8 –14 h (ca. 24 h prior to closure) were used to test the ability of the system to support palatal development. Embryonic heads were dissected in one of two ways before culture: brain and tongue removed, or brain, tongue and mandible removed. After 24 h in culture, preparations of either age with only the brain and tongue removed had made substantially greater progress than their counterparts with the brain, tongue and mandible removed. With only the brain and tongue removed, the palatal shelves were contacting, adhered or fused in 67 % of the older embryos, whereas most of the embryos of the same age cultured with the brain, tongue and mandible removed had shelves that were not fully elevated and still separated by a moderate gap. Thus for maximal progress in the present system, the oral cavity must be intact except for the tongue.
Cell cycle parameters in dedifferentiating iris epithelial cells
Authors: Yamada Tuneo , Roesel Marion E. , Beauchamp John J. 
Published: April 2021

ABSTRACTAfter lentectomy of the adult newt eye, non-dividing iris epithelial cells re-enter the cell cycle. Some of the iris epithelial cells become completely depigmented while they are in the cell cycle, and then differentiate into lens cells. The remaining iris epithelial cells become partially depigmented in the induced cell cycle, but resynthesize melanosomes and recover the normal state of iris epithelial cells. The two groups of cells are spatially separated within the iris epithelium. The cell cycle parameters of both groups of iris epithelial cells were estimated by a mathematical procedure on a computerized programme from the percentage of labelled mitotic cells as a function of time after peritoneal injection of [3H]methyl-thymidine on day 6 after lentectomy. The total cell cycle time was found significantly shorter in the cell population with complete depigmentation as compared with that with partial depigmentation. Based on these results the possible role of differential cell cycle time in the control of dedifferentiation was discussed. Grafting of unlabelled iris into the optic cavity of host animals injected 6 h beforehand with [3H]methyl-thymidine, followed by a study of radioactivity of iris epithelial cells of the graft demonstrated incorporation at a low level during the whole period of the experiment in which the cell cycle parameters were estimated. The data used for the estimation were corrected for the delayed incorporation.
Epithelio-mesenchymal interface during mouse kidney tubule induction in vivo
Authors: Lehtonen E. 
Published: April 2021

ABSTRACT
Transmission and scanning electron microscopy were used to study the epithet io-mesen-chymal interface between the interacting mouse ureter-bud and the metanephric mesenchyme.
The gap between the epithelial and mesenchymal cells varied in width. At the stalk of the ureter-bud the interspace was often about 1 μm, but in the inductively active areas at the tips of the branching ureter-bud epithelio-mesenchymal contacts were seen through discontinuities in the basal lamina. At these points the gap between the interacting cells was often less than 20 nm, in places less than 10 nm. The amount of electron-dense, ruthenium-red-positive material was greatest at the stalk of the ureter-bud, but only a small amount of extracellular material was found between the interacting cells at the tips.
Whether epithelio-mesenchymal cell contacts play a role in kidney tubule induction is not yet known, but their existence in the inductively active areas and their absence in inactive zones suggests that they are morphogenetically significant. The finding also obviates the need to postulate long-range transmission of inductive signals to explain this example of embryonic induction.
The formation of the gonadal ridge in Xenopus laevis: II. A scanning electron microscope study
Authors: Wylie C. C. , Bancroft M. , Heasman J. 
Published: April 2021

ABSTRACT
This paper studies the surface morphology of the developing gonadal ridge in X. laevis between stages 44 and 49 (Nieuwkoop & Faber, 1956). During this period the primordial germ cells (PGCs) move laterally from the dorsal mesentery of the gut to the position of the presumptive gonadal ridge. As they do so the coelomic lining cells lateral to the mesentery differentiate into a specialized, longitudinally orientated band, stretching nearly the full length of the dorsal mesentery on each side. The PGCs migrate beneath this band of cells, which thus becomes the germinal epithelium of the gonadal ridge. We have demonstrated by irradiation experiments that this specialized band of cells can differentiate independently, in the absence of the PGCs.
The formation of the gonadal ridge inXenopus laevis: III. The behaviour of isolated primordial germ cellsin vitro
Authors: Wylie C. C. , Roos T. B. 
Published: April 2021

ABSTRACTPrevious studies have described the morphology, including the ultrastructure, of primordial germ cells (PGCs), and the cells with which they associate to form the gonadal ridge, in Xenopus laevis. In order to test their capacity for active movement we have studied single, isolated PGCs in vitro. Time-lapse studies of these cells reveal that they are motile, using broad cytoplasmic processes. The fact that these cells are very large and easy to manipulate in vitro makes them an attractive subject of study, particularly with respect to the mechanism of their movement and the surface phenomena which guide them to the site of the gonadal ridge.
The effect of 5-bromodeoxyuridine on cell division and differentiation of preimplantation mouse embryos
Authors: Pollard D. R. , Baran M. M. , Bachvarova R. 
Published: April 2021

ABSTRACT
Mouse embryos exposed to concentrations of 5-bromodeoxyuridine (BUdR) ranging from 0·01 to 10 μg/ml in vitro for two days from the 8-cell stage exhibit a concentration-dependent decrease in the frequency of normal blastocysts and a decrease in average cell number per embryo. A 20-h exposure was adequate to achieve the full BUdR response. Both effects were eliminated in the presence of excess thymidine.
Autoradiographs demonstrated that BUdR[3H] was incorporated into DNA during the first and second day of culture. Thus, BUdR appears to act through incorporation into DNA; and, in this system, cell division is at least as sensitive to BUdR as is differentiation.
Influence of conceptus number and weight on the amount of foetal fluid in the mouse
Authors: McLaren Anne , Renfree Marilyn B. , Hensleigh Hugh C. 
Published: April 2021

ABSTRACT
The relation of extra-embryonic fluid weight to litter number and foetal and placental weight was studied in mice on the 18th day of pregnancy, in litters both of experimentally reduced and of normal number. Partial regression analysis showed that litter number and foetal weight both exerted a negative effect on fluid weight; placental weight had no significant effect. Increased foetal weight reduced weight locally; on the other hand the effect of litter number was exerted systemically, throughout both horns of the uterus.
Reorganization of retinotectal projection of compound eyes after various tectal lesions in Xenopus
Authors: Straznicky K. 
Published: April 2021

ABSTRACT
The retinotectal connexions of double nasal (NN), double temporal (TT) and double ventral (VV) eyes in juvenile Xenopus were mapped after post-metamorphic removal of the rostral, caudal, medial or lateral tectal halves with the subsequent cutting of the optic nerve of the operated eye.
A whole visual field projection occurred from NN eyes on to residual caudal tectum, from TT eyes on to residual rostral tectum and from VV eyes on to residual medial tectum. When optic fibres from NN, TT or VV eyes grew into inappropriate rostral, caudal or lateral tectal halves respectively, there was a projection deficit in the nasal and temporal or in the dorsal and ventral poles of the visual field. The persisting scotomas in the visual field indicated that only the optic fibres of the central retinal fundus had succeeded in connecting with an inappropriate tectal half whereas the peripheral optic fibres had not. The incongruous results of optic nerve regeneration obtained in the various recombinations may be taken to indicate that the assumption of early embryonic pattern regulation is inadequate to explain the findings in this experimental situation.
The nature and distribution of serologically detectable alloantigens on the preimplantation mouse embryo
Authors: Muggleton-Harris Audrey L. , Johnson Martin H. 
Published: April 2021

ABSTRACTThe nature and distribution of surface alloantigens on preimplantation mouse embryos has been examined by immunofluorescence. Non-H-2 alloantigens were detected at all stages examined, from the 2-cell to the -day blastocyst. Cleaving blastomeres, inner cell mass cells and cells of the primary trophectoderm were all positive. In Fx embryos maternal non-H-2 alloantigens were detectable at all stages, whereas paternal antigens first became evident at the 6-to 8-cell stage. No convincing evidence of the presence of alloantigens associated with the H-2 haplotype was found at any stage or on any cell type, suggesting that if these antigens are present they are in low quantity or are masked.
The distribution of melanocytes in the dorsal coats of a series of chimaeric mice
Authors: West J. D. , McLaren Anne 
Published: April 2021

ABSTRACT
Chimaeras, made by aggregating two embryos from the randomly-bred Q-strain, and X-inactivation mosaics both have similar, balanced distributions of pigmentation in the dorsal coat, while (C57BL x C3H)F1 ↔ Recessive chimaeras tend to have an unbalanced pigment distribution, with a higher proportion of F1 pigmentation in the posterior than in the anterior part of the coat. This observation can be explained if differences in the timing of the migration of the two melanocyte populations from the neural crest cause anterior-posterior differences in selection pressures.
The effect of short-term labelling in [3H] thymidine on the viability of mouse blastomeres: alone and in combination with unlabelled blastomeres
Authors: Kelly Susan J. , Rossant Janet 
Published: April 2021

ABSTRACT
A method of labelling 8-celI-stage mouse blastomeres with [3H]thymidine is described, which allows them to be followed to the late blastocyst stage and is compatible with normal postimplantation development. However, the [3H]thymidine does affect the postimplantation vigour of the cells when placed in competition with unlabelled cells in blastomere aggregates. This suggests that caution should be used in interpreting results using [3H]thymidine as a label for early mammalian cells.
Adult haemoglobin in developmentally retarded tadpoles ofXenopus laevis
Authors: Maclean Norman , Turner S. 
Published: April 2021

ABSTRACTTadpoles of Xenopus laevis reared in water containing 0·01% propylthiouracil continue to grow but fail to develop or metamorphose. The haemoglobin of such tadpoles has been extracted in buffer, converted to a cyanmet form, and run on polyacrylamide gels. The developmentally retarded tadpoles are found to possess adult-type haemoglobin rather than the tadpole type which normally characterizes their developmental stage.
Culmination in the slime mouldDictyostelium discoideumstudied with a scanning electron microscope
Authors: Watts D. J. , Treffry T. E. 
Published: April 2021

ABSTRACTMyxamoebae of Dictyostelium discoideum were allowed to develop on cellulose acetate filters, and specimens taken at various stages of fruiting body formation were prepared for study by scanning electron microscopy.In the immature fruiting body where the mass of pre-spore cells has just been lifted off the substratum by the developing stalk, the pre-spore cells are irregular in shape and are similar in appearance to cells in aggregates at earlier stages of development. As the stalk lengthens, the pre-spore cells gradually separate from one another and become rounded and elongate, but mature spores are not visible until the fruiting body reaches its maximum height. It is concluded that, contrary to previous reports, spore maturation is a slow process and is not completed until the sorus becomes pigmented.The mature stalk is surrounded by a smooth cellulose sheath but this does not envelop the cells of the basal disc, which remain discrete. The fruiting body is enclosed in a slime sheath and this may be important in holding together the mass of spores.
Activité génétique au cours de l’embryogenèse de l’OligochèteEisenia fœtida(autoradiographie à l’uracile-3H et traitement à l’actinomycine D)
Authors: Devriès J. 
Published: April 2021

ABSTRACTGene activity during embryogenesis of the earthworm Eisenia foetida ([3H]uracil autoradiography and actinomycin D treatment)Embryos of Eisenia fœtida (Spiralia) have been cultivated with [3H]uracil precursor of RNA at different stages of development from egg to gastrula. The results show that ribonucleic acid synthesis detected by autoradiography begins precociously. During segmentation messenger RNAs are produced by interphase nuclei and liberated in cytoplasm cyclically at mitosis. After the blastula stage rRNAs (nucleoli), which can migrate through the nuclear membranes, predominate. The blastomeres, which contain polar plasm and also mesoderm, already known for its controlling part in embryogenesis after gastrulation, are the seats of the increasingly important ribonucleic acid synthesis.These genetic transcriptions, which are inhibited by actinomycin D, are implicated in the determination of the blastomeres and postblastular differentiation. Only the messages required for the segmentation divisions pre-exist in the undivided egg.
Quantitation of the spatial distribution of ‘prespore vacuoles’ in pseudoplasmodia ofDictyostelium discoideum
Authors: Farnsworth Paul A. , Loomis William F. 
Published: April 2021

ABSTRACTThe axial distribution of an organelle, the prespore vacuole (PV), previously reported absent from the prestalk region, was determined in pseudoplasmodia of varying sizes, under differing conditions of photostimulation of migration.The distribution of these organelles, determined quantitatively by electron microscopy of sections from known axial locations, was found to have a spatial pattern which varied with pseudoplasmodial size. The total complement of these organelles appeared constant for any size of pseudoplasmodium under similar conditions of illumination. Increased illumination decreased the total number of the organelles.The spatial distribution of PV varies with total cell number, and the size of the region with no PV bears no relationship to the proportion of the cell mass which would form stalk cells. Similarly, the number of cells containing PV bears no fixed relationship to the number of cells which will form spores.On these grounds, the reported role of PV, that of directing or reflecting spore differentiation, appears unlikely.
The mechanism of chick blastoderm expansion
Authors: Downie J. R. 
Published: April 2021

ABSTRACT
At the time of laying, the domestic fowl blastoderm measures 4 mm across. After 4 days’ incubation, the extra-embryonic yolk-sac tissues have expanded to encompass the whole yolk mass. This expansion involves the migration over the inner surface of the vitelline membrane of a specialized band of ‘edge cells’ at the blastoderm periphery. As they move, they pull out the blastoderm behind them, setting up a considerable tension. Expansion also involves cell proliferation and changes in cell shape. This paper attempts to show how locomotion, tension, proliferation and changes in cell shape all contribute to the orderly process of expansion. As a simplification, only the extra-embryonic epiblast is considered here.
The findings are:
Expansion does not occur at a constant rate, but starts slowly, rises to a peak (over 500 μm/h) at around 3 days, and then slows as coverage of the yolk mass nears completion. During the first day of incubation, edge-cell migration produces a tension in the blastoderm. This rises to a peak at 20 –24 h, then declines. This tension may be due to an imbalance between expansion by migration and expansion by proliferation. Migration of edge cells can be affected by tension in the blastoderm, i.e. very high tension may hold them back. However, the tension level normally found in the blastoderm seems not to do so. The low rate of expansion in the first day is therefore not due to the high level of tension. It may instead be due to changes in edge-cell organization. Proliferation occurs throughout the extra-embryonic epiblast during the expansion period. It is not restricted to the blastoderm periphery. After the yolk has been covered, the epiblast continues to grow, with proliferation restricted largely to a band just distal to the advancing edge of the area vasculosa. Cell shape and arrangement change considerably during expansion. The epiblast of the unincubated embryo is a monolayer of tall cells. During expansion, these become considerably flattened so that each contributes a larger amount to yolk-sac surface area.