bluuebunny/crossref_metadata_2025_split huggingface dataset:
The oviduct as a barrier to exogenous thymidine in the early development of the mouse embryo
Authors: Dyban A. P. , Samoshkina Natalia A. , Mystkowska Ewa B. 
Published: April 2021

ABSTRACT
Mouse embryos are able to use exogenous thymidine during cleavage stages in vivo if the thymidine is injected directly into the oviduct.
DNA synthesis during cleavage occurs asynchronously and the intensity of DNA synthesis in the blastomeres of the same embryo varies. At all stages, the label in some nuclei is distributed unevenly, suggesting that some chromosomes may be heterochromatinized very early in development.
Epidermal metaplasia of proamnionic epithelium induced by dorsal skin dermis in the chick embryo
Authors: Mizuno Takeo 
Published: April 2021

ABSTRACT
Proamnionic epithelium of the chick embryo cultivated directly on Wolff and Haffen’s medium in the absence of mesenchymes fails to differentiate. Cultivation of the dorsal dermis of 6 ·5-day chick embryos in the absence of epithelium also results in lack of differentiation of dermal cells.
When proamnionic epithelium taken from embryos before the 10-somite stage is cultivated combined with dorsal dermis of 6 ·5-day embryos for 6 days, the epithelium invariably undergoes metaplastic changes, forming stratified epidermis, sometimes with keratinized superficial layer. The underlying dermal cells are condensed and this often leads to the formation of feather germ-like structures.
The competence of the epithelium for changing into the epidermis is gradually lost after the 10-somite stage, and the dorsal dermis from 8 ·5-day embryos is not very effective in inducing the epidermal metaplasia.
Proamnionic epithelium cultivated on heat-killed dorsal dermis seems healthy but shows no sign of differentiation. Dorsal dermis combined with heat-killed proamnionic epithelium spreads and remains almost undifferentiated. These observations suggest that reciprocal induction mechanisms are involved in the epithelial and dermal differentiation.
Cultivation of proamnionic epithelium with various heterologous mesenchymes or fragments of embryonic organs shows that this epithelium is only competent for epidermal differentiation when combined with dorsal dermis.
When proamnion (proamnionic epithelium plus hypoblast) is directly combined with 6 ·5-day dorsal dermis it undergoes metaplastic changes. The same result is obtained when inverted (upside-down) proamnion is combined with the dermis. Hypoblast does not seem to affect the inductive interaction between the epithelium and the dorsal dermis.
Chondrogenesis in chick embryo somites grafted with adjacent and heterologous tissues
Authors: O’hare M. J. 
Published: April 2021

ABSTRACT
A variety of heterologous tissues have been tested for the ability to promote cartilage differentiation in isolated chick-embryo somites, using a modified chorioallantoic grafting technique. Of the 12 tissues tested only 3- and 4-day embryonic ectoderm promoted somite chondrogenesis in somites that fail to chondrify when grafted in isolation. This activity of ectoderm was evident in grafts of somites isolated with adjacent ectoderm, and in grafts of somites recombined with ectoderm derived from several sources. Four-day embryonic limbbud ectoderm, including the apical ridge, was capable of promoting somite chondrogenesis, but to no greater extent than dorsal trunk ectoderm of the same age. It is suggested that the ability of embryonic ectoderm to promote cartilage differentiation in isolated somites is associated with its ability to synthesize basement membrane material (sulphated glycosaminoglycans and collagen), in association with adjacent somite mesoderm.
Ultrastructural changes during transition of larval to adult intersegmental muscle at metamorphosis in the blowfly Calliphora erythrocephala
Authors: Crossley A. C. 
Published: April 2021

ABSTRACT
Dissolution of the contractile apparatus derived from larval muscle occurs when pupal morphogenetic movements are complete, but a residual myofibre remains. Synapses with nerves are retained by degenerating myofibres, although the nerves are not structurally normal. Within the myofibre, the appearance of several types of unit membrane aggregate is coincident with the disappearance of normal sarcoplasmic reticulum. One type of aggregate consists of stacked cisternae, separated by a gap of 300 Å which is traversed by a three-dimensional connecting lattice of regularly arranged rods. These latticed cisternae appear to be derived from sarcoplasmic reticulum, and they interconnect with smooth-surfaced cisternae. Structures akin to latticed cisternae have been described by others in a variety of cells. Of particular interest is a report of their formation as a result of denervation in rat muscle. This report, coupled with the evidence presented here, suggests that latticed cisternae are indicative of changed nervous stimuli in degenerating muscle.
Changes in the membrane systems are rapidly followed by resorption of the myofilaments. Thick myofilaments disappear first, followed by thin myofilaments, with the eventual disappearance of Z-discs completing the dissolution of the sarcomere. No evidence was obtained for the segregation of myofilaments in membrane-bound vacuoles, or for the presence of lysosomes in muscle at this time. It is suggested that these observations are consistent with theories developed by others for retention of protein structure, rather than disassembly into amino acids, at metamorphosis in insects.
Formation of surface blebs is correlated with loss of organelles to the haemolymph. Morphological evidence supports the proposition that coated vesicles are involved in exchange of proteins with the haemolymph, shortly before adult myofilaments form.
Insect myoblast fine structure is described. The bipolar shape of these cells is shown to be associated with an oriented fascicle of microtubules. Attention is drawn to the plasma membrane of the myoblast, which bears folds at the points where flexion of the cell can be demonstrated by time-lapse microscopy. Myoblasts do not contain recognizable microfilaments other than microtubules.
Fusion of free-floating myoblasts with the residual myofibre is demonstrated by light and electron microscopy, and the stages of fusion are described. Ultrastructual manifestation of a cell recognition process was not detected. The process of multinucleation of developing muscle cells in insects is directly comparable with myoblast fusion in vertebrate cells. How ever, in Calliphora the resulting myofibre contains two classes of nucleus, easily recognizable on basis of size. The structure of these nuclear classes, and the role played by each in adult myofibril formation, is investigated in an accompanying paper.
Immunochemical study of hypoxanthine-dehydrogenase in different organs of the chick
Authors: Croisille Yvon 
Published: April 2021

ABSTRACT
Immunotitration of hypoxanthine-dehydrogenase confirms earlier findings according to which, in the liver, HXDH activity stays low throughout embryonic life and increases suddenly at the period of hatching.
Whether from liver, kidney, intestine, pancreas or mesonephros, HXDH appears to have the same electrophoretic mobility (in agar, agarose and starch gels), the same molecular weight (estimated to be about 290000 by Sephadex G 200 filtration) and the same immunochemical properties (as tested with 24 anti-liver, 18 anti-kidney, and 4 anti-mesonephros sera).
Various attempts to interfere with HXDH synthesis in vivo or in vitro (injection of substrate or liver extracts; explantation of fragments of mesonephros, metanephros or intestine from 9-to 12-day-old chick embryos on substrate-containing culture media; direct association of tissues containing high and low levels of enzyme) have so far failed.
Rôle du nerf et du territoire cutané dans le développement des corpuscules de Herbst et de Grandry
Authors: Saxod Raymond 
Published: April 2021

ABSTRACT

Role of nerve and cutaneous tissue in the development of Herbst’s and Grandrfs corpuscles
Frontal buds or pieces of the bill of duck and chick embryos have been explanted on the chorioallantoic membrane, transplanted as homo- or xeno-plastic grafts to the flank, the frontal bud and the limb bud of early host embryos, or associated as coelomic grafts with various isolated nerve sources. Results show that :
These results are discussed in connexion with what is known about peripheric sense organs in vertebrates. A schematic model is proposed for the mechanism of the morphogenesis of the corpuscles.
Cell movements in morphogenesis of hydroid polypes
Authors: Beloussov L. V. , Badenko L. A. , Katchurin A. L. , Kurilo (Filatcheva) L. F. 
Published: April 2021

ABSTRACT
Growth, morphogenesis and cell movements were studied in Obelia loveni, O. geniculata and Dynamena pumila with the use of time-lapse cinematography, visual observations of vitally stained objects and by histological techniques. Growth pulsations with the period around 14 min and the amplitude around 15 μm exist in Dynamena pumila and with the period 5–8 min and amplitude up to 5 μm in Obelia loveni. It was demonstrated that the rhythm of growth pulsations does not coincide with the rhythm of periodical contractions of the proximal part of coenosarc. The distalwards movements of individual cells in the ectoderm of growing stems and hydranth rudiments are described. A considerable variability in the rates of movements of ectodermal cells has been demonstrated. Different kinds of cell reorientations in developing rudiments are described. As a rule, they precede the alterations of growth directions or of rudiment shapes. The mechanisms involved in deformations of epithelial layers are discussed. The possibility of the existence of passive, elastico-plastic structures in the deforming epithelial sheets is suggested.
The role of neurohumours in early embryogenesis
Authors: Buznikov G. A. , Sakharova A. V. , Manukhin B. N. , Markova L. N. 
Published: April 2021

ABSTRACT
The 5-hydroxytryptamine concentration changes insignificantly in the course of each of the first cleavage divisions, except at prometaphase when a sharp short-term fall occurs. According to the data obtained by the simplified gaseous formaldehyde method of Falck and Hillarp, 5-HT is present in all embryonic and larval cells up to the stage of prism. In plutei 5-HT is detected by this method only in the digestive tube, ventral ciliary band and possibly in pigment cells. According to the data obtained by the aqueous formaldehyde method, at the gastrula stage 5-HT is localized in the archenteron and vegetative ectoderm and at the stages of prism and pluteus in cells of the digestive tube, ventral ciliary band and, possibly, in pigment cells. The aqueous method gives negative results at pregastrular developmental stages.
On the basis of the data obtained a suggestion is put forward about the presence of two 5-HT pools in developing sea-urchin embryos and larvae. It is suggested that the first of them, not detected by the aqueous method and present in embryos beginning from the earliest developmental stages, performs intracellular regulatory functions whose character is discussed. The second pool detected by the aqueous method arises with the onset of gastrulation and appears to be related to morphogenetic processes.
Cytodifferentiation of the mouse secondary palate in vitro: morphological, biochemical, and histochemical aspects
Authors: Idoyaga-Vargas Victor , Nasjleti Carlos E. , Azcurra Julio M. 
Published: April 2021

ABSTRACT
Previous investigations had indicated that the epithelial cells at the medial surface of the palate differentiate prior to fusion. An increase in adhesiveness and signs of partial autolysis were reported to be part of the differentiation. It was not determined, however, whether or not the autolytic processes may result in the total lysis of the cells, even if fusion is prevented. This problem was approached in the present investigation by culturing shelves in isolation, thus preventing fusion. The morphological properties of the presumptive fusing cells were then observed during and after the actual time of fusion. Differentiation was assessed in vivo at equivalent developmental ages. In addition, the role of the lysosomes in the process of fusion was investigated. This was done by measuring the activities of two lysosomal enzymes, glucosaminidase and arylsulfatase, before, during, and after fusion in vivo and at the equivalent times in vitro. Glucosaminidase activity was also localized histochemically.
The in vitro and in vivo differentiation were similar. The cells of the mesenchyme produced intramembranous bone and loose mesenchyme. The nasal surface differentiated into a pseudostratified columnar ciliated epithelium, while the oral surface became stratified squamous epithelium. At the medial surface, however, the morphological changes during fusion in vivo were different from those observed at the equivalent time in vitro. Few, if any, of the presumptive fusing cells forming a bi-layered or multilayered epithelium degenerated in the explants, while many cells forming the epithelial seam in vivo underwent complete degeneration. In addition, after fusion, the medial surface of the palatal expiants was covered by a stratified squamous and/or pseudostratified columnar ciliated epithelia. In vivo, the mesenchyme merged as a consequence of the total destruction of the seam. The specific activity of glucosaminidase increased progressively, reaching a peak three days after fusion. In all cases no statistically significant differences were found between the in vivo and in vitro values. Arylsulfatase specific activity remained the same both in vivo and in vitro. Histochemically glucosaminidase activity was localized in the cells undergoing degeneration during fusion. It is concluded that fusion is a necessary condition for the completion of the autolysis of the presumptive fusing cells. The cells may alter their developmental fate, forming a stratified squamous and/or pseudostratified columnar epithelia, if fusion is prevented.
Neurotrophic dependence of macromolecular synthesis in the early limb regenerate of the newt, Triturus
Authors: Singer Marcus , Caston J. Douglas 
Published: April 2021

ABSTRACT
The well-documented nerve dependence of limb regeneration in the newt was analysed by study of accumulation of newly synthesized macromolecules following denervation. The specific activity of RNA and DNA in the denervated early regenerate bud was determined following intraperitoneal injection of [3H]-uridine and [3H]-thymidine. Results showed an outburst in the incorporation into RNA and DNA which reached a peak 3 h after denervation for the former and 7 h for the latter. There was then a decline in incorporation to a plateau about 50-60% of the control non-denervated side within 48 h. Combining these results with our previous demonstration of a similar outburst in the accumulation of newly synthesized protein with a peak at 4 h, the sequence of the outbursts was in order RNA, protein and DNA. The results are interpreted to mean that the nerve influences either macromolecular synthesis or macromolecular processing and turnover, and therefore accumulation in the regenerate.
Properties of the primary organization field in the embryo ofXenopus laevisI. Autonomy of cell behaviour at the site of initial organizer formation
Authors: Cooke J. 
Published: April 2021

ABSTRACTThe work presented, in this and the subsequent papers of a series, was begun in order to re-examine the properties of the amphibian primary embryonic field, in the light of current theories concerning the nature of individuation fields in developing animal systems. A detailed description is given of the basic operation whose results are described in this and the subsequent paper. This involves the transplantation, into a late blastula or stage-10 gastrula host, of a supernumerary stage-10 organizer region. The consequences of such operations during the following 4–6 h, up to the late gastrula stage, are also described.Evidence is presented that, from a time some 2·5 h before the organizer site first becomes externally visible, its presumptive region is immune from interference by the proximity of another, implanted organizer, even one which is itself 2·5 h older. That is to say, the final site of development of host organizer activity is not altered by the presence of such an implant.Pairs of early organizers at comparable stages of activity appear to set up competing fields of cellular orientation and immigration, which show a fairly sharp boundary at their interface. This is most obvious for pairs of organizers fairly close together, since the cell polarization and stretching is most pronounced in the region near to the apex of the field, i.e. the initial site of cell immigration. Independent initial fields of immigration due to two organizers can reliably be distinguished in cases where they are as little as 30° of angular distance apart in the marginal zone of the host.These results are to be considered in relation to those of Paper II, for the same series of operations, where the final patterns of cell differentiation are studied, and to those of Paper III, where evidence is given for the development of autonomous polarity in the region of the organizer.
Rôle du mésoderme somitique dans le développement du plumage dorsal chez l’embryon de Poulet:I. Origine, capacités de régulation et détermination du mésoderme plumigène
Authors: Mauger Annick 
Published: April 2021

ABSTRACTThe role of somitic mesoderm in the development of dorsal plumage in chick embryos. I. Origin, regulation capacity and determinationThe role of somitic mesoderm in the development of the dorsal plumage has been studied in chick embryos. The operations were performed at 2–2·5 days of incubation.The replacement of a portion of somitic mesoderm by somitic mesoderm labelled with [3H] thymidine or obtained from Japanese quail embryos (whose nuclei bear distinctive specific markers) showed that cells originating from the dermatomes build up the dermis of the dorsal skin only. They do not migrate farther than approximately midway down the flank. Beyond this limit, dermal cells originate from the somatopleural mesoderm.The unsegmented somitic mesoderm is capable of extensive regulation, which leads to the development of a dorsal plumage, normal in the number and arrangement of its feathers according to the characteristic pattern of the spinal pteryla. Uni-or bilateral excision of segmented somitic mesoderm resulted in dorsal plumage deficiencies, the extent and frequency of which was related to the state of differentiation of the excised mesoderm. Thus, the excision of somites generally led to an incomplete spinal pteryla (absence of feather rows, apteria). However, the somitic mesoderm is still capable of regulation even though it has already undergone its differentiation into dermatome, myotome and sclerotome. These results show that somitic mesoderm retains its regulative capacity, even though it has already acquired its feather-forming determination.The replacement of unsegmented somitic mesoderm by various implants (agar, tantalum, gut, neural tube, somatopleural mesoderm), intended to block the regulation processes, abolished the differentiation of the spinal feathers on the operated side. In some cases, the implantation of somatopleural mesoderm resulted in the formation of a supernumerary tract. No tissue other than somitic mesoderm -not even the somatopleural mesoderm, which is normally in part feather-forming -is able to give rise to region-specific spinal pteryla dermis.The excision and replacement of somitic mesoderm prevented the differentiation of dense dermis, whereas these operations had no effect on the early histogenesis of the epidermis, with the formation of arches and anchor filaments.
Energy metabolism in isolated rat embryo hearts: effect of metabolic inhibitors
Authors: Cox Steven J. , Gunberg David L. 
Published: April 2021

ABSTRACTHearts isolated from 11-and 12-day rat embryos were incubated in a simple salt solution to which was added the metabolic inhibitors iodoacetate, malonate, 2,4-dinitrophenol or trypan blue. Comparisons were made between the two age-groups and it was observed that both 11-and 12-day hearts exhibited depressed contractile activity with the glycolytic inhibitor iodoacetate. Malonate did not depress contraction rate in the younger hearts but significantly depressed the rate in the older hearts. A greater inhibitory action on the older hearts as compared with the younger hearts was also produced by 2,4-dinitrophenol. These results were interpreted as further evidence of a shift in dependence on pathways other than glycolysis between days 11 and 12 of development.The teratogenic agent trypan blue was shown to depress contraction rate when added to the incubation medium. This effect could be reversed by adding glycolytic intermediates such as fructose-l,6-diphosphate or alpha glycerophosphate. These results were suggestive of a direct inhibitory effect of trypan blue either on glucose uptake or its complete catabolism.
Evidence for a two-step mechanism operating duringin vitromouse kidney tubulogenesis
Authors: Gossens Carol L. , Unsworth Brian R. 
Published: April 2021

ABSTRACTThe process of kidney tubulogenesis was investigated in mouse metanephrogenic mesenchyme, differentiating in tissue culture under the influence of an inductive stimulus from embryonic mouse brain. The metanephrogenic mesenchyme was separated from the brain by a membrane filter. The time of exposure to the inductive stimulus was controlled by removing the brain from the filter.Restricting the period of transfilter association of metanephrogenic mesenchyme and brain resulted in incomplete tubulogenesis. A 30 h interaction time with brain led to the formation of small tubules. These small tubules were at an unstable stage of differentiation, and regressed during the 6-day culture period. Stabilization and elongation was achieved by the addition of mesenchymal tissues or chick embryo extract. Induction was clearly not a one-time triggering event, and as the degree of differentiation increased so the specificity for mesenchymal requirement decreased.Embryo extract did not mimick the inductive event that initiated tubulogenesis, but supported the later stages of tubulogenesis. This was interpreted to indicate a certain specificity in the induction reaction.The incidence of tubule elongation was related to both the initial mass of metanephrogenic mesenchyme and to the total contact time with brain. The greater the initial mass of mesenchymal tissue, the less contact time with brain needed for complete tubulogenesis.The morphology of the elongated tubules depended on the nature of the mesenchyme with which the small tubules were associated. This suggested that the expression of tubule morphology may be under the control of the surrounding mesenchymal cells. Possible mechanisms operating during tubule elongation were discussed.It was concluded that an integrated two-step mechanism was operating during kidney tubulogenesis. The first step, cell condensation, was induced by contact with brain. The second step, tubule elongation, was dependent upon the association of the condensates with the surrounding non-induced mesenchymal cells.