bluuebunny/crossref_metadata_2025_split huggingface dataset:
Active role of embryonic facial epithelium: New evidence of cellular events in morphogenesis
Authors: Millicovsky Guillermo , Johnston Malcolm C. 
Published: April 2021

ABSTRACT
Epithelial cells of the C57B1/6J mouse embryo participate in a temporal sequence of events associated with the approximation, fusion and consolidation of components of the facial primordia into a definitive structure. These cells lose their surface microvilli, and after a brief period of quiescence they begin to fill the grooves separating facial constituents by producing a series of surface projections that increase in size and complexity as the process of fusion nears termination. Cessation of surface activity and the restoration of epithelial microvilli indicate the end of the temporal sequence. Significantly, the epithelial cells of primary palates of embryos with genetically- and phenytoin-induced cleft lip remain unchanged and do not participate in fusion. This epithelial sequence has not been described previously and we suggest that all of its steps may be critical to the normal development of the mammalian face.
The developmental capacity of blastomeres from 4- and 8-cell sheep embryos
Authors: Willadsen S. M. 
Published: April 2021

ABSTRACT
The developmental capacity of (a) single blastomeres of 4-cell embryos, (b) pairs of blastomeres of 8-cell embryos and (c) single blastomeres of 8-cell embryos was studied. The blastomeres were inserted into evacuated foreign zonae pellucidae, embedded in agar, transferred to ligated oviducts of dioestrous ewes, and recovered when their total age was to days. At lecovery the majority of embryos belonging to categories (a) and (b) had developed into small blastocysts, whereas most embryos of category (c) were vesicular forms with no clearly observable inner cell mass.
The viability of embryos which had continued their development during culture in the sheep oviduct was tested by their transfer to the uterine horns of recipient ewes which had come into oestrus on the same day as the respective embryo donors. Three lambs were produced after transfer of eight embryos of category (a) deriving from two parent embryos. These three lambs derived from a single 4-cell embryo. Nine lambs were produced after transfer of 16 embryos of category (b) deriving from four parent embryos. Four of these lambs derived from a single 8-cell embryo. When ewes which had come into oestrus one or two days after the respective embryo donors were used as recipients for 16 embryos of category (a) and 16 embryos of category (b) one and five lambs, respectively, were produced.
Finally, two lambs were produced after transfer of 31 embryos of category (c). These lambs derived from two different parent embryos.
The principal conclusions drawn from the study are that at least some individual blastomeres from 4- and 8-cell sheep embryos can give rise to an entire conceptus, and that the viability of embryos produced by blastomere separation depends more on the degree of reduction in cell number than on the stage of development at which separation is performed.
The control of somitogenesis in mouse embryos
Authors: Tam P. P. L. 
Published: April 2021

ABSTRACT
Somitogenesis in the mouse embryo commences with the generation of presumptive somitic mesoderm at the primitive streak and in the tail-bud mesenchyme. The presumptive somitic mesoderm is then organized into somite primordia in the presomitic mesoderm. These primordia undergo morphogenesis leading to the segmentation of somites at the cranial end of the presomitic mesoderm. Somite sizes at the time of segmentation vary according to the position of the somite in the body axis: the size of lumbar and sacral somites is nearly twice that of upper trunk somites and of tail somites. The size of the presomitic mesoderm, which is governed by the balance between the addition of cells at the caudal end and the removal of somites at the cranial end, changes during embryonic development.
Somitogenesis is disturbed during the compensatory growth of mouse embryos which have suffered a drastic size reduction at the primitive-streak and early-organogenesis stages. The formation of somites is retarded and the upper trunk somites are formed at a smaller size. The embryo also follows an entirely different growth profile, but a normal body size is restored by the early foetal stage. The somite number is regulated to normal and this is brought about by an altered rate of somite formation and the adjustment of somite size in proportion to the whole body size. It is proposed that axis formation and somitogenesis are related morphogenetic processes and that embryonic growth controls the kinetics of somitogenesis, namely by regulating the number of cells allocated to each somite and the rate of somite formation.
The possible mechanism of cell positioning in mouse morulae: an ultrastructural study
Authors: Sołtyńska Maria S. 
Published: April 2021

ABSTRACT
Ultrastructure of the mouse morula at the time of formation of the outer cell layer is described.
Analysis of relative positions of sister blastomeres, still connected with cytoplasmic bridge, suggests that cell division may occur both tangentially and perpendicularly in relation to the embryo surface. However, there are observations suggesting that active cell movement may be involved in cell positioning already after mitosis. These observations include: (1) the flexure of cytoplasmic bridge, (2) the presence of bundles of filaments in external blastomeres at the late cytokinesis and (3) a striking difference in loose versus tight packing of blastomeres within the embryo.
The timetable of innervation and its control in the chick wing bud
Authors: Swanson Gavin J. , Lewis Julian 
Published: April 2021

ABSTRACTHow is the timing of nerve outgrowth controlled during development? This question has been examined by grafting early limb buds between chick embryos of different ages, before innervation, and assessing the morphological pattern of nerves at later stages. Grafted limbs continued to develop according to their own timetable and were invaded by nerves from the host. Irrespective of the age of the host, the development of the pattern of innervation followed the time course appropriate to the age of the grafted limb. Young nerves in an old limb showed accelerated development; old nerves in a young limb showed retarded development. The process of innervation is apparently governed not by the intrinsic developmental timetable of the neurons, but rather by the rate of construction of pathways for them in the peripheral tissue, and by the times at which their specific targets, such as muscles, differentiate.
The retinotectal fibre pathways from normal and compound eyes in Xenopus
Authors: Fawcett J. W. , Gaze R. M. 
Published: April 2021

ABSTRACT
Horseradish peroxidase was used to demonstrate the nature of the retinotectal fibre pathways from normal eyes and from compound double nasal (NN), double temporal (TT) and double ventral (VV) eyes in Xenopus. From normal eyes, nasal fibres were widespread in the optic tract and mostly entered the tectum through the medial and lateral brachia. Ventral retinal fibres approached the tectum via the medial brachium and dorsal retinal fibres passed through the lateral brachium, while temporal retinal fibres formed a narrow band in the centre of the tract and entered the tectum directly at its rostral border.
Fibres from NN eyes formed a wide tract and strong medial and lateral brachia. Fibres from VV eyes all entered the tectum via the medial brachium and fibres from TT eyes formed a narrow tract and entered the tectum directly from its rostral extremity. Thus fibres from each type of compound eye followed pathways to the tectum that were appropriate to the embryonic origin of the retina forming the compound eye.
L’Otocyste exerce-t-il une action inductrice sur le mésenchyme somitique chez l’embryon de Poulet?
Authors: Benoit par Jean A. A. 
Published: April 2021

ABSTRACT
L’épithélium auditif induit normalement le cartilage de la capsule otique, à partir du mésenchyme céphalique, chez l’embryon de poulet (Benoit, 1955). Ce pouvoir inducteur peut-il s’exercer à l’égard du mésenchyme axial du tronc? Nous avons tenté de résoudre ce problème en greffant des otocystes au contact des somites, ou en associant otocystes et somites en culture in vitro.
Myogenic cell movement in the developing avian limb bud in presence and absence of the apical ectodermal ridge (AER)
Authors: Gumpel-Pinot Madeleine , Ede D. A. , Flint O. P. 
Published: April 2021

ABSTRACT
Fragments of quail wing bud containing myogenic cells of somitic origin and fragments of quail sphlanchopleural tissue were introduced into the interior of the wing bud of fowl embryo hosts. No movement of graft into host tissue occurred in the control, but myogenic cells from the quail wing bud fragments underwent long migrations in an apical direction to become incorporated in the developing musculature of the host. When the apical ectodermal ridge (AER), together with some subridge mesenchyme, was removed at the time of grafting, no such cell migration occurred. The capacity of grafted myogenic cells to migrate in the presence of AER persists to H.H. stage 25, when myogenesis has begun, but premyogenic cells in the somites, which normally migrate out into the early limb bud, do not migrate when somite fragments are grafted into the wing bud. Coelomic grafts of apical and proximal wing fragments showed that apical sections of quail wing buds become invaded by myogenic cells of the host, but grafts from proximal wing bud regions do not.
SEM localization of cell-surface-associated fibronectin in the cranium of chick embryos utilizing immunolatex microspheres
Authors: Meier Stephen , Drake Christopher 
Published: April 2021

ABSTRACT
Fibronectin has been localized to basement membranes and cell surfaces with the light microscope by fluorescent staining of thick sections, and with the TEM by immunoperoxidase reaction. However, these methods are limited because it is difficult to appreciate the patterned distribution of fibronectin from sectioned material. We have developed a probe for fibronectin that facilitates its identification with the SEM. Our probe consists of two parts; the first component is a derivatized methacrylate microsphere 90 nm in diameter, linked to purified sheep anti-rabbit IgG. The second component is anti-fibronectin IgG raised in rabbits. Stage-3 to -12 chick embryos were fixed and the ectoderm covering the cranial mesoderm was removed. Embryos were treated with testicular hyaluronidase, exposed to rabbit antifibronectin IgG and finally to sheep anti-rabbit IgG conjugated microspheres. As expected, the basal lamina of surface and neural ectoderm as well as the remaining fibrous ECM were heavily decorated with microspheres, whereas control embryos treated with preimmune serum were beadless. Fibronectin was localized on the cell soma and processes of primary mesenchyme as early as stage 3. In addition, it was possible to decorate to various extents, populations of prosencephalic, mesencephalic, and rhombencephalic cranial neural crest cells. Our studies suggest that fibronectin is present in the cranium of chick embryos at earlier times than heretofore realized, and that fibronectin accumulates in a cranial to caudal gradient that reflects the sequential differentiation of the embryonic axis.
Cell death in the dorsal part of the chick optic cup. Evidence for a new necrotic area
Authors: García-Porrero Juan A. , Colvée Elvira , Ojeda José L. 
Published: April 2021

ABSTRACT
The spatiotemporal pattern of morphogenetic cell death during the early development of the chick retina was studied by means of the neutral red vital staining and light microscopy. A modification of the conventional procedure of vital staining, which consisted of the injection of the dye into the neural tube lumen, was used for this purpose. In addition to the two areas of cell death known from previous literature, the first located in the ventral part of the optic cup and the second located in the insertion of the optic stalk with the diencephalon, a new area of cell death was described. This third necrotic area was located in the protruding dorsal part of the optic cup rim and was present throughout the stages 15 to 18. The area consisted of dying cells, fragments and phagocytosed cells.
We suggest that this dorsal area of cell death could stop the intense dorsal growth of the optic cup and/or reshape the optic cup rim. Moreover, this area may influence the production of cell degeneration in the dorsal part of the invaginating lens placode.
An in situ cell marker for clonal analysis of development of the extraembryonic endoderm in the mouse
Authors: Gardner R. L. 
Published: April 2021

ABSTRACT
Conditions were found for staining whole mid-gestation capsular parietal endoderms and visceral yolk sacs for malic enzyme activity that gave excellent discrimination between wildtype (Mod-1+/Mod-1+) cells and mutant (Mod-ln/Mod-ln) cells that lack the cytoplasmic form of the enzyme. Reciprocal blastocyst injection experiments were undertaken in which single primitive endoderm cells of one genotype were transplanted into embryos of the other genotype. In addition, Mod-1+/Mod-1+ early inner cell mass (ICM) cells were injected into Mod-ln/Mod-ln blastocysts, either in groups of two or three singletons or as daughter cell pairs. A substantial proportion of the resulting conceptuses showed mosaic histochemical staining in the parietal endoderm, visceral yolk sac, or in both these membranes. Stained cells were invariably intimately intermixed with unstained cells in the mosaic parietal endoderms. In contrast, one or both of two distinct patterns of staining could be discerned in mosaic visceral yolk sacs. The first, a conspicuously‘coherent’ pattern, was found to be due to endodermal chimaerism; the second, a more diffuse pattern, was attributable to chimaerism in the mesodermal layer of this membrane. The overall distribution of cells with donor staining characteristics resulting from primitive endoderm versus early ICM cell injections was consistent with findings in earlier experiments in which allozymes of glucosephosphate isomerase were used as markers.
The conspicuous lack of phenotypically intermediate cells in predominantly stained areas of mosaic membranes suggested that the histochemical difference between Mod-1+/Mod-1+ and Mod-ln/Mod-ln genotypes was cell-autonomous. This conclusion was strengthened by the results of staining mixed in vitro cultures of parietal endoderm in which presence or absence of phagocytosed melanin granules was used as an independent means of distinguishing wild type from null cells.
By substituting tetranitro blue tetrazolium for nitro blue tetrazolium in the incubation medium, satisfactory differential staining was obtained for both the extraembryonic endoderm and other tissues of earlier postimplantation wild type versus null embryos.
Finally, absence of cytoplasmic malic enzyme activity does not appear to have a significant effect on the viability or behaviour of mutant cells.
Arrest of intravitelline mitoses in Drosophila embryos by u.v. irradiation of the egg surface
Authors: Togashi Shin , Okada Masukichi 
Published: April 2021

ABSTRACT
The intravitelline mitosis in Drosophila was arrested at the anaphase within the span of a single cell cycle after irradiation with 300 nm u.v. Embryos at and before the 8-nucleus stage were influenced by the u.v. only when irradiated anteriorly, while at and after the 16-nucleus stage, embryos are sensitive to either anterior or posterior irradiation. In embryos anteriorly irradiated at or before the 8-nucleus stage all nuclei in the embryo were prevented from performing mitosis. When irradiated at or after the 16-nucleus stage, inhibition of the intravitelline mitosis is limited to the nuclei in approximately anterior-half region of embryos in anterior irradiation, and to those in approximately posterior-half region in posterior irradiation, resulting in incomplete blastoderm formation. Sites sensitive to 300 nm u.v. are postulated to be present in the peripheral cytoplasmic region of the embryo and not in the nucleus, because the half-attenuation thickness of 300 nm u.v. light for the Drosophila egg cytoplasm is and nuclei are at least 50 μm away from the periphery at the stage of irradiation. In addition lateral irradiation of a portion of an egg where there is no nucleus underneath was also effective in arresting division of nuclei in the sameegg. It is suggested that the effects of 300nm u.v. may not be conveyed to the nuclei from the periphery by simple diffusion of a substance, and a hypothesis is proposed for the involvement of cytoskeletal elements associated with the u.v. sensitive sites on the surface to the control mechanism of the intravitelline mitosis of the Drosophila embryo.
The mode of cell death associated with cavitation in teratocarcinoma-derived embryoid bodies
Authors: Boyd Sheilagh M. , Hooper M. L. , Wyllie A. H. 
Published: April 2021

ABSTRACT
Cell death occurring in embryoid bodies derived from the embryonal carcinoma cell line, PSA4, which undergo cavitation, and in those from the related cell line S2, which do not undergo cavitation, was classified as apoptosis or necrosis by ultrastructural criteria. Both modes of cell death were seen in PSA4 embryoid bodies while apoptosis alone was seen in S2 embryoid bodies. No significant difference was found between PS A4 and S2 embryoid bodies either in apoptotic incidence score or in the spatial distribution of apoptotic events. We therefore conclude that although apoptosis and tissue modelling coexist in PSA4 embryoid bodies, necrosis rather than apoptosis is causally related to formation of the cavity.
Influence of injected pluripotential (EK) cells on haploid and diploid parthenogenetic development
Authors: Kaufman M. H. , Evans M. J. , Robertson E. J. , Bradley A. 
Published: April 2021

ABSTRACT
A number of pluripotential embryo-derived EK cells were introduced into the blastocoele of haploid and diploid parthenogenetic embryos which were subsequently transferred to suitable recipients. At autopsy on day 10 or 11 of pseudopregnancy 22 % of decidua in the diploid series contained somite-stage embryos while an additional 12 % contained abnormal egg cylinder-like sacs. In the haploid series, 7 % of the decidua contained somite-stage embryos and an additional 5 % contained abnormal ‘sacs’. In ‘injected’ diploid and haploid ‘controls’ in which the zonae were pierced with an empty injection pipette 3 % and 0 % respectively of decidua in these two series contained somite-stage embryos, while an additional 17 % and 3 % respectively of decidua in these two series contained abnormal sacs. GPI analysis revealed that the EK cells were incorporated into somite-stage conceptuses in only one third of the diploids and in none of the haploid embryos. Although the presence of EK cells considerably increases the chance of normal embryonic development taking place, a detectable contribution from the EK cells into the resulting somite-stage embryo is apparently not necessary. Possible mechanisms allowing successful early post-implantation development to occur in this study are discussed.
Diploid gynogenesis in Xenopus laevis and the localization with respect to the centromere of the gene for periodic albinism a
p
Authors: Thiébaud Ch. H. , Colombelli B. , Müller W. P. 
Published: April 2021

ABSTRACT
Diploid gynogenetic Xenopus laevis were obtained by inseminating the eggs with u.v. irradiated spermatozoa, and treating them with hydrostatic pressure to inhibit the expulsion of the second polar body. A u.v. dose of 3000ergs/mm2 genetically inactivates the spermatozoa without loss of their ability to activate egg development.
The use of a genetic marker on very large samples of eggs made it possible to verify the efficiency of the methods employed. The comparison of the development of diploid gynogenetic embryos with that of haploid gynogenetic, triploid and diploid controls makes it very probable that the relatively high mortality or abnormal development obtained with the pressurized eggs is not due to partial homozygosity but rather to physical damage to the egg structure by this treatment. Altogether about 2500 developing eggs were used.
In addition diploid gynogenetic reproduction from females heterozygous for a known mutation allows the mapping of the gene concerned relative to the centromere on the basis of the recombination rate. For this experiment we used the recessive mutation causing periodic albinism (ap) and found the position of this gene to be between 44 map units from the centromere and the end of the chromosome.
Analysis of upper beak defects in chicken embryos following with retinoic acid
Authors: Tamarin A. , Crawley A. , Lee J. , Tickle C. 
Published: April 2021

ABSTRACT
Implanting inert carriers soaked in retinoic acid into the anterior margin of the developing limb of chicken embryos leads to orofacial malformations as well as affecting pattern formation in the limb. Using anion-exchange beads as carriers, and soaking solutions of 1–10 mg/ml retinoic acid, almost 100% of the embryos have malformations of the face. The effects on the treated limbs range from symmetrical patterns of duplicated digits (maximum number of digits being four) to truncations in which no digits were formed at all.
Typically, in the malformed faces the upper beak is completely absent, no nostrils are present and the front of the face forms a scalloped rim of tissue above the mouth. By reference to normal beak development, the seven bulges of tissue that make up the rim can be identified as derivatives of the masses of tissue that normally would fuse to form the upper beak. The roof of the mouth consists of three bulges of tissue flanked by widely separated palatal shelves. The defect can thus be classified as severe bilateral clefting of the primary palate.
By examining the morphology of the faces of treated embryos, the origin of the defect can be traced to failure of the frontonasal mass to enlarge. Thus, the oronasal fissures are very wide and fusion across them to form the primary palate cannot occur.
The way in which retinoic acid brings about the defect is discussed in relation to possible mechanisms involved in the production of cleft palate. The parallel is noted between the associated effects of retinoic acid on beak and limb morphogenesis and the chick mutation cpp, that also affects both face and limbs.
Characterization of exocoelomic fluid protein from rat conceptuses cultured in rat and human sera: a measure of yolk sac activity during organogenesis
Authors: Huxham I. M. , Beck F. 
Published: April 2021

ABSTRACT
Fluid from the extraembryonic coelom of 11·5-day rat embryos cultured in 100% rat serum, 100% human serum and 90% human serum supplemented with 10% rat serum between days 9·5 and 11·5 postconception were compared using polyacrylamide gel electrophoresis and crossed immunoelectrophoresis. The protein composition of the exo-coelomic fluids differed considerably from one another and from each of their respective culture sera. The majority of proteins in the exocoelom were derived from macromolecular transport but some contribution was made from protein synthesis by the conceptus. Eighteen proteins normally found in rat serum were found in the exocoelom of conceptuses cultured in 100% rat serum. Eighteen proteins were found in the exocoelom of rat conceptuses cultured in 100% human serum, of which ten were derived from human serum and eight were proteins normally found in rat serum. Analysis of fluid from conceptuses cultured in 90% human serum supplemented with 10% rat serum showed eleven human serum proteins and ten rat serum proteins. Differences in the composition of both human and rat proteins between the latter two fluids were also evident.