bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and differentiationin vitroofDrosophilaimaginal disc cells from dissociated early embryos
Authors: Dübendorfer Andreas , Shields Glen , Sang James H. 
Published: April 2021

ABSTRACTEmbryos of Drosophila melanogaster, 6-8 h after oviposition, were dissociated and the cells cultured in vitro. Besides larval cell types, imaginal disc cells, assembled and growing in bloated monolayered vesicles, were obtained.The cells of these vesicles become competent to differentiate adult structures when treated with a-ecdysone or ecdysterone in vitro. Recognizable patterns of the adult fly are not formed though. If metamorphosis of imaginal cell vesicles from in vitro-cultures is induced in vivo by transplantation into host larvae of various ages within the third larval instar, recognizable patterns can differentiate provided the host larva does not metamorphose prior to 2 days after transplantation. The frequency of specific patterns in the implants can be increased by providing 9 days of culture in vivo (adult host flies) before metamorphosis. Passage through the third larval instar is not essential for these cells to produce identifiable patterns since culture in adult flies alone can achieve this. The quality of the differentiated pattern is not correlated with the extent of cell proliferation in the cultured tissues.The problem of pattern specification in vitro and in vivo is discussed.
Positional information and pattern regulation in Hydra. Dynamics of regions at the boundary
Authors: Hicklin J. , Hornbruch A. , Wolpert L. 
Published: April 2021

ABSTRACT
The dynamics of boundary regions have been investigated mainly by axial grafting and with the emphasis on the head end. The time to resist inhibition of head-end formation and the ability to inhibit head-end formation have been assayed under a variety of conditions. The times increase with distance from the head end. The times required by a boundary region to acquire the inhibitory properties of a head end are longer than those required to acquire resistance to inhibition. Determination of a head end is faster at a cut surface and at higher temperatures. The results are discussed in terms of a model involving two gradients. Some anomalous results are reported.
Le rôle du système nerveux au cours de la régénération du bras chez une Etoile de mer: Asterina gibbosa Penn. (Echinoderme, Astéride)
Authors: Huet Michel 
Published: April 2021

ABSTRACT
In Asterina gibbosa regeneration of a cut-off arm tip cannot occur if the radial nerve has been removed. This regeneration needs the presence of the oral nerve ring connected with the radial nerve intact up to the level of the wound tissues. The oral nerve ring can be considered as a central nervous system. Exposure of the radial nerve to irradiation induces a delay in regeneration. These data suggest there is a stimulation from the oral nerve ring up to the wound tissues. When the tissues involved in regeneration, except for the radial nerve, have been destroyed by irradiation, regeneration is inhibited. Stimulation by a healthy radial nerve is necessary to maintain differentiation and growth of the blasternal cells. The amount of blasternal growth and differentiation depends on the time when the radial nerve ceases to stimulate regeneration. The action of the nervous system is needed throughout the whole course of regeneration.
Studies of t6/t6 mouse embryos
Authors: Nadijcka Mary , Hillman Nina 
Published: April 2021

ABSTRACT
The phenocritical period of the t6/t6 genome extends from the late blastocyst substages through the elongated egg-cylinder stage, whereas the lethal period begins at the short eggcylinder stage and extends through the elongated egg-cylinder stage. Most of the homozygous mouse embryos die during the short egg-cylinder stage. The viable egg-cylinder-staged t6/t6 embryos can be distinguished from their phenotypically wild-type litter-mates at both the light and electron microscopic levels. The distinguishing characteristics of these embryos are aberrantly arrangedentodermal cells,excessive cytoplasmic lipid and crystal-containing mitochondria. These same features are also characteristic of those mutant embryos which are developmentally arrested at both the short and elongated egg-cylinder stages. Over 50% of the t6/t6 embryos can be identified as early as the late blastocyst substages by the presence of large, electron-dense cytoplasmic lipid droplets.
ATP metabolism in t
n
/t
n mouse embryos
Authors: Ginsberg Leonard , Hillman Nina 
Published: April 2021

ABSTRACT
Total ATP, ATP/ADP ratios, and the rates of synthesis and turnover of ATP were determined for t12-, tw32- and T+/T+-litters at the 2-cell, 4-cell, 8-cell, early morula, late morula and late blastocyst stages. The results show that tn-litters have excessive rates of ATP metabolism up to the cleavage stage immediately before the stage of lethality for most tw32/tw32embryos (early morula) and most t12/t12 embryos (late morula); mutant ATP metabolism then falls below control levels. After the death of the tn homozygotes, ATP metabolism in the tn-litters (composed of only T+/T+ and T+/tn embryos) returns to control levels. These data are discussed in relation to the phenotypes of the homozygous tn embryos.
Myogenesis in the trunk and leg during development of the tadpole of Xenopus laevis (Daudin 1802)
Authors: Muntz Louise 
Published: April 2021

ABSTRACT
Xenopus embryos pass through five behavioural stages between the end of neurulation (stage 20) and the accomplishment of free swimming (stage 33). These are (I) non-motile (stage 20 – 22) when the myotome muscle begins to differentiate; (II) pre-motile (stage 22 – 24) when the first striated fibrils are visible and contractions are possible; (III) early flexure (stage 24 – 27) when reflex responses are given and peripheral nerves are present; (IV) early swimming (stage 28 – 33); and (V) free swimming (stage 32 – 46) when co-ordinated swimming is possible but the myotome muscles are still uninucleate. At the onset of metamorphosis (stage 48 – 50) the myotome muscle becomes multinucleate, possibly by fusion with satellite cells at the ends of the fibres, and has the appearance of adult skeletal muscle.
The hind limb of Xenopus passes through similar behavioural stages but at a later stage in development: (i) non-motile (stage 48 – 52) when little differentiation of the limb-bud has occurred but nerves are present; (ii) pre-motile (stage 53 – 54) when the limb trembles and muscles are just beginning to acquire striated fibrils; (iii) motile (stage 55 – 58) when the limb can make stepping movements and the muscles are striated and multinucleate; and (iv) fully functional (stage 60 – 63) when the limbs are fully differentiated. Unlike the myotome muscle the limb muscle becomes multinucleate before striated myofibrils are assembled.
By stage 60 myotome and limb muscle are similar in appearance except that the myotome muscle has larger fibres with fewer nuclei than the limb muscle.
In Xenopus, myotome and limb muscle become multinucleate at more or less the same time in the development of the tadpole. In the myotome this is long after contractility and nervous control have appeared, in the limb it precedes the formation of striated fibrils and the ability to contract. It is suggested that the difference in development of the myotome and limb muscles with respect to the stage at which they become multinucleate may be due to some substance produced just before or during metamorphosis.
Effets biologiques de solutions de protéines chromatiniennes non histoniques sur un système embryonnaire en différenciation in vitro
Authors: Mathieu C. , Duprat A. M. , Dupuy M. H. , Ferrer P. , Zalta J. P. , Beetschen J. C. 
Published: April 2021

ABSTRACT

Biological effects of solutions of non-histone chromatin-associated proteins on cell differentiation in vitro
Nuclear non-histone (NNH) proteins, both chromatin-associated and otherwise, have been prepared in defined conditions, either from nuclei or from washed chromatin. When these NNH proteins are homospecific, they produce inhibitory effects on morphological differentiation of embryonic Urodelan Amphibian cells cultivated in vitro. When they are heterospecific, on the contrary, they have no action on the differentiation of those cells. It is concluded that the effects of the non-histone proteins on cell differentiation depend upon the relationship between the animal species which is used to provide the proteins and that used to provide the reactive material.
In vitro studies of limb regeneration in adult Diemictylus viridescens: Neural dependence of blastema cells for growth and differentiation
Authors: Globus Morton , Liversage Richard A. 
Published: April 2021

ABSTRACT
Explants of 99 adult newt forelimb blastemata (21-to 24-day regenerates) were cultured, with and without implanted dorsal root ganglia, in modified Parker’s medium (CMRL-1415) for periods of 72 – 144 h. Growth and differentiation of the cultured blastemata were compared with ganglionated and non-ganglionated controls fixed at the start of the culture period.
The results of these experiments establish that implanted spinal ganglia are able to sustain growth and differentiation of forelimb blastemata in vitro: active proliferation amongst the blastema cells was found to be correlated with the presence of an implanted ganglion. In addition, the blastema cells exhibited a differential growth response which was most pronounced when the ganglion was eccentrically implanted 2 – 3 days before explantation of the limb regenerate.
These results suggest that a causal relationship exists between the position of the implanted ganglion and the localization of growth within the blastema. The nerve influence, believed to be mediated by a chemical factor(s), was localized in the region of the implanted neurons, indicating that a close association between the nerves and the responding blastema cells is essential for normal growth. The importance of the physical presence of nerves for the cultivation of blastemata in vitro is emphasized.
Positional information and pattern regulation in hydra: enzyme profiles
Authors: Baquer Najma Zaheer , McLean Patricia , Hornbruch Amata , Wolpert L. 
Published: April 2021

ABSTRACTCertain key enzymes of alternative pathways of glucose metabolism, of amino acid metabolism and of redox systems have been measured in hydra and this profile compared with mammalian differentiated tissues with a view to locating pathways of specific importance in hydra. There was a marked constant proportionality in the major part of the enzymes investigated, the profile suggested a metabolic pattern geared to utilization of amino acids as a carbon source for biosynthesis and energy production and to the production and conservation of pyruvate. The importance of conversion to ionized forms was noted. The most notable specific proportion changes were the exceptionally low lactate dehydrogenase, malic enzyme and the relatively high citrate synthase. The proximal-distal gradients in hydra were examined and these gradients suggested a switch to a more anaerobic type of metabolism and an elevation of the pentose phosphate pathway as the basal region was approached. Measurements of the formation of 14CO2 from specifically labelled glucose provided additional evidence for the functional activity and polarity of the pentose phosphate pathway in hydra. The effect of oligomycin, which can reverse polarity in hydra, had a significant effect on gradients of enzymes eliminating all except that observed for G6P dehydrogenase. The profile suggested a movement towards a more anaerobic type of metabolism, in keeping with the known biochemical action of this inhibitor. It is suggested that redox states and/or phosphorylation states may be featured in the positional information of cells in hydra.
Proportionality in the pattern of differentiation of the cellular slime mouldDictyostelium discoideumand the time of its determination
Authors: Farnsworth Paul A. 
Published: April 2021

ABSTRACTA quantitative measure of the proportionality of the pattern of cell differentiation is obtained by separating populations of fruiting bodies into stalks and spores and determining the ratio of their dry weights.The effect of incubation temperature on the proportion of a population which becomes stalk cells is determined.The time of determination of this proportion is then indicated by the time in the developmental sequence at which a temperature shift fails to alter it.The results show that the temperatures of growth, aggregation and migration have no effect on the pattern of differentiation and that temperature alterations during early culmination alter the pattern of differentiation.This result demonstrates that the pattern of differentiation is not determined during the migrating slug stage, and it is suggested that the axial inhomogeneities seen in the slug are not directly related to the terminal pattern of differentiation of the fruiting body as has been previously suggested.
On the determination of the dorso-ventral polarity inXenopus laevisembryos
Authors: Landström Ulf , Løvtrup Søren 
Published: April 2021

ABSTRACTWhen embryos, or dorsal or ventral half-embryos, of Xenopus laevis are subjected to unilateral restriction of oxygen supply, the posterior end will always appear at the aerobic side, while the development of the anterior end, oriented towards the anaerobic side, will be partly suppressed. The shorter the time treatment lasts, the more normal the development will be. When the restriction of oxygen effects an inversion of the dorso-ventral polarity, development is retarded, otherwise not. Measurements of oxygen consumption show a substantial reduction in the experimental embryos, as compared with normal ones. The change in oxygen consumption in inverted embryos is delayed relative to non-inverted ones, but there is no significant difference in the total consumption of oxygen. Our results support the idea that the dorso-ventral polarity is associated with a gradient in oxygen consumption, and various kinds of evidence suggest that oxygen consumption is, in part, required for the formation of Ruffini’s flask-cells, responsible for the initiation of invagination. It is suggested that the basic mechanisms involved in the determination of the normal, and the inverted, dorso-ventral polarity are fundamentally different, the latter being in fact an induction of a new polarity.
Parthenogenetic activation of mouse oocytes following avertin anaesthesia
Authors: Kaufman M. H. 
Published: April 2021

ABSTRACT
Avertin anaesthesia induced mouse eggs to become activated parthenogenetically. An increasing incidence of activation was observed when females were anaesthetized 6·5, 9 and 13 h after ovulation, reaching a maximum of 45·8 %. In a spontaneously ovulating group approximately 12·5 % of all the eggs ovulated, or 27·3 % of all the eggs activated evoked a decidual response, and the presence of implanting embryos was confirmed histologically. These findings demonstrate a new and simple method of inducing post-implantation parthenogenetic development in the mouse, and stress the necessity of taking into account the possible consequences of anaesthesia in the early post-ovulatory period.
Xenopus laeviscement gland as an experimental model for embryonic differentiation
Authors: Picard J. J. 
Published: April 2021

ABSTRACTEctoblastic cells explanted from the animal pole of young Xenopus laevis gastrulae have been cultured in vitro. When these cells were cultured for five days in standard salt solutions they formed atypical epidermis. When they were first submitted for 6 h to Holtfreter solution containing ammonium chloride and then transferred for five days in standard Barth’s solution they underwent differentiation into typical cement gland tissue.The optimum concentration of ammonium chloride was 10 mM. Below and above this concentration the resulting cement glands had a smaller volume.The optimum duration for the initial stimulation with 10 mM ammonium chloride in Holtfreter solution was 6 h. Shorter stimulation times produced only small cement glands. Longer initial incubations in ammonium chloride resulted in progressive dissociation of the explants.To obtain the best differentiation into cement gland it appeared that the pH of the ammonium chloride solution should be between 7·5 and 7·7.When the stimulation is performed under these optimum conditions the cement gland measured after five days of culture accounts for 80–90 ° % of the explanted tissue. This means that all or almost all of the competent superficial layer of the ectoblastic cells underwent differentiation into cement gland. No other differentiated tissue was observed in the explants. The cement gland is a very simple organ containing only one single cell type. The gland obtained under the described in vitro conditions is therefore proposed as an experimental model for biochemical studies on early embryonic differentiation.
Mesenchymal derivatives of the neural crest: analysis of chimaeric quail and chick embryos
Authors: Lièvre C. S. Le , Douarin N. M. Le 
Published: April 2021

ABSTRACT
Interspecific grafts of neural tube and associated neural crest (NC) have been made between quail and chick embryos. Structural differences of the interphase nucleus in the two species make it possible to identify quail from chick cells in the chimaeras after Feulgen-Rossenbeck’s staining and at the electron microscope level. Owing to the stability of the natural quail nuclear marker labelling, migration pattern and developmental fate of the grafted NC cells could be followed in the host embryo. In previous work it has been demonstrated that the visceral skeleton derives entirely from NC mesenchyme and the various levels of the neural axis from which visceral cartilages and bones originate have been established. In the present work, the contribution to the lower jaw and pharynx of NC mesenchymal derivatives other than bones and cartilages has been studied. It is shown that the dermis in the face and ventrolateral side of the neck has a neural origin. The wall of the large arteries deriving from the branchial arches (systemic aorta, pulmonary arteries, brachiocephalic trunks and common carotid arteries) are entirely made up of mesectodermal cells except for the endothelial epithelium which is mesodermal in origin. The presence in the wall of the common carotid arteries of fluorogenic monoamines-containing cells is demon-strated using the formol-induced-fluorescence technique. Like the secretory cells of the carotid body, the fluorescent cells of the carotid artery wall originate from the rhomb-encephalic NC.
Connective tissue of the lower jaw, tongue and ventrolateral part of the neck originate from the neural crest. Mesectoderm participate in the formation of the glands associated with the tongue and pharynx (lingual gland, thymus, thyroid, parathyroids) giving their mesenchymal component. On the other hand, as demonstrated previously by our group, NC cells are the main cellular component of the UB since they give rise to the calcitonin-producing cells. The wall of the oesophagus and trachea is of mesodermal origin, but adipose tissue around the trachea and parasympathetic enteric ganglia of the digestive tube derives from NC. NC cells participate in the formation of striated muscles of the branchial arches and differentiate there into connective and muscle cells.
It appears from this study that the differentiating capabilities are similar in mesenchymal and mesectodermal cells with the exception of blood vessel endothelia which in our experiments are always of host origin in mesectoderm-derived tissues.
The capacity of the NC to give rise to mesenchymal derivatives is restricted to the cephalic neural axis down to the level of the 5th somite in both chick and quail embryos.
La localisation du matériel germinal dans le blastoderme non incube de l’oeuf de cane: étude à l’aide des irradiations aux rayons X
Authors: Fargeix Noël 
Published: April 2021

ABSTRACT
Le problème de l’origine des cellules germinales primordiales (CGP) des Oiseaux a suscité de très nombreuses recherches tant histologiques qu’expérimentales et il est maintenant bien établi qu’à partir du stade de la ligne primitive, ces cellules sont situées, au moins pour la grande majorité d’entre elles, dans les régions antérieures et latérales de l’aire extra-embryonnaire (croissant germinal de Swift, 1914). Quant à la localisation du matériel germinal à des stades antérieurs, elle est plus difficile à préciser.
The effect of u.v. irradiation of the vegetal pole of Xenopus laevis eggs on the presumptive primordial germ cells
Authors: Züst Brigitta , Dixon K. E. 
Published: April 2021

ABSTRACT
The initial effect of u.v. irradiation of the vegetal pole was to inhibit cleavage in the vegetal hemisphere although karyokinesis was not substantially affected. In this way a syncytium formed in the vegetal hemisphere which broke down into individual cells some time between morula and late blastula. The movement of the germ plasm from the peripheral cortical regions into the interior of the egg was not appreciably delayed although aggregation of the germ plasm did not take place until the individual presumptive primordial germ cells were formed when the syncytium broke down. The method of segregation of the germ plasm and formation of the presumptive primordial germ cells was therefore very different in irradiated embryos from the normal orderly processes which depend on normal cleavage patterns. After neurula, the number of presumptive primordial germ cells declined rapidly and at stage 43/44, when the genital ridges in normal embryos contain primordial germ cells, the genital ridges in irradiated embryos were sterile. These results raise the question whether derangement of the segregation of the presumptive primordial germ cells is solely responsible for the later abnormalities in the cell lineage or whether u.v. irradiation affects the germ plasm and therefore indirectly the germ cells.
Adult deficiencies and duplications of head and thoracic structures resulting from microcautery of blastoderm stage Drosophila embryos
Authors: Bownes Mary 
Published: April 2021

ABSTRACT
Drosophila embryos were damaged by microcautery at the cellular blastoderm stage at the sites of presumptive imaginal cells, identified from fate maps. The resulting adults were analyzed for abnormal structures. Cautery of any of the presumptive imaginal regions can lead to defects in the adult cuticle, though the majority of adults which hatch are morphologically normal. The abnormal adults had one or more discs either deleted, incompletely formed, or misarranged. Several of the structures which were incomplete had duplicated regions. The results suggest that, from the time of their initial formation in the cellular blastoderm, a group of cells determined to be an ‘adult’ structure possesses a gradient of developmental capacity which is expressed by certain regions duplicating and other cells regenerating. The types of duplications found were similar to those resulting from other experimental treatments of imaginal discs at later stages in development, indicating that the presumptive imaginal disc cells, when they are first established in the cellular blastoderm, have a similar organization to mature imaginal discs.