bluuebunny/crossref_metadata_2025_split huggingface dataset:
Irradiated cells and blastema formation in the adult newt, Notophthalmus viridescens
Authors: Desha David L. 
Published: April 2021

ABSTRACT
This investigation primarily consisted of labeling cells in forelimbs of the newt; irradiating the labeled limb; and then inducing regeneration with a non-irradiated skin graft.
The labeled cells were obtained by injecting tritiated thymidine intraperitoneally into newts with regenerating right forelimbs. The cells in the regenerate which were undergoing DNA synthesis were labeled, and those which differentiated and ceased to divide remained labeled for long periods. The labeled regenerates were irradiated with 2000 R, and subsequently the irradiated limbs were re-amputated. Some limbs were supplied with a hind-limb skin autograft; others received no graft. The limbs without the grafts did not regenerate, whereas several of those with grafts did.
Histological studies of the blastemas of the new regenerates indicated that labeled, irradiated cells were released from the internal tissues near the amputation surface and were incorporated into the blastema. These cells presumably formed a portion of the differentiated tissues of the new regenerate. Studies were performed to verify that the labeled cells in the blastemas were derived from irradiated tissues and were not derived from extraneous sources.
This investigation substantiates reports that irradiation with 2000 R inhibits limb regeneration, and that at least some irradiated cells can contribute to a blastema formed on an irradiated limb.s
Etudes expérimentales sur le rôle des somites au cours des premiers stades du développement du membre antérieur chez l’embryon du Chélonien Emys orbicularis L.
Authors: Vasse J. 
Published: April 2021

ABSTRACT

Experimental study on the role of the somites during the early stages of development of the front limbs of the embryo of the chelonian Emys orbicularis L
Ablation of postotic somites 6—13 on one side in embryos of Emys orbicularis L. at the developmental stage when 20–23 somite pairs were present, led to arrest of forelimb-bud development in the somatopleure adjacent to the ablated somites on the operated side. Limb development in the somatopleure adjacent to intact somites on the operated side was unaffected, attaining the same stage as on the non-operated side. Ablation at later stages (25–33 somite pairs) did not prevent development of the limb adjacent to the ablated somites. When a part of the prospective somatopleure was injured, the remaining part formed a small limb-bud. When an obstacle was placed between the somatopleural mesoderm and the adjacent somite, development of the somatopleure stopped at this level.
These results corroborate those obtained from previous studies in various reptilian embryos concerning the role of the ventral somite extensions as activators of proliferation in the somatopleural mesoderm. Injury to the ventral extension alone led to serious dis-turbances in the somatopleural mesoderm adjacent to this somite.
The relation between larval and adult abnormalities in the abdominal segmentation of Calliphora erythrocephala (Diptera)
Authors: Pearson M. J. 
Published: April 2021

ABSTRACT
Early embryonic stages of Calliphora erythrocephala were X-irradiated to produce abdominal abnormalities of segmental pattern. Abnormal patterns were examined in the puparial stage: 75 (Series AA) larvae with dorsal or lateral abnormality were classified and the larval abnormality compared with the pattern of abdominal segmentation in the emerging adult fly; another 75 (Series aa) larvae were examined in dorsal, lateral and ventral aspect with respect to segmental abnormality and again in relation to abnormality in the adult.
It was observed (i) that the pattern of abdominal intersegmental membranes is not necessarily maintained through metamorphosis and may regulate to normal; (ii) that tergal abnormalities in the adult result from a failure of correct bilateral fusion of corresponding contralateral hemitergites; (iii) that reduction or displacement of scleral structures in an adult abdominal segment is correlated with deficiency or displacement of epidermal muscle insertions, and hence presumably with the histoblast anlagen which are normally associated with them. In the case of dorsal abnormalities, hemitergite differentiation is normal.
Larval abdominal abnormality patterns point to the mode of bilateral morphogenesis of the germbands in embryogenesis. The relation of adult to larval abnormalities suggests some similar independence of contralateral hemisegments at metamorphosis.
The possible developmental origin of abdominal abnormalities produced by X-irradiation of embryos is discussed, and the conclusions of the analysis of the relation between larval and adult abnormalities in Calliphora are set against the propositions of previous students of such abnormalities in Drosophila.
Gastrulation in the mouse : Growth and regionalization of the epiblast
Authors: Snow M. H. L. 
Published: April 2021

ABSTRACT
Histological determination of cell numbers in the mouse embryo between and days post coitum show that growth during this period, in which gastrulation occurs, is not uniform. Prior to primitive streak formation mean cell generation time is about 9 h. Co-incidental with the appearance of the primitive streak the embryo enters a period of rapid growth, lasting about 24 h, during which the mean cell generation time must be about 5 h in order to account for the increase in cell numbers. A more detailed study, in which variations in mitotic activity in different regions of the embryo have been analysed, has identified a small region, the so-called ‘proliferative zone’, constituting about 10 % of the whole epiblast, in which cell generation time may average as little as 2·3 h over a 24 h period. The cell generation time for other epiblast regions is estimated at about 6·5 h.
It is calculated that the proliferative zone, in the 24 h period commencing with primitive streak formation, could generate about half the cells in the -day embryo. The topographical consequences of such a rapidly expanding region in the embryo are discussed in the light of other, circumstantial evidence, and it is postulated that the cells generated in the PZ may constitute the ectoderm of later stage embryos.
Localization and synthesis of alphafoetoprotein in post-implantation mouse embryos
Authors: Dziadek M. , Adamson E. 
Published: April 2021

ABSTRACT
The localization and synthesis of alphafoetoprotein (AFP) during mouse embryogenesis were studied by immunoperoxidase and by immunoprecipitation after radioactive labelling, using an antiserum prepared against AFP. AFP is first detectable in embryos on the 7th day of gestation (7th day embryos). In 7th and 8th day embryos AFP is confined to visceral (proximal) endoderm cells around the embryonic region of the egg cylinder. Visceral extra-embryonic and parietal (distal) endoderm cells do not contain AFP. By the 9th day of gestation AFP is also present in the extra-embryonic ectoderm, mesoderm and embryonic ectoderm cells around the three cavities of the embryo. These tissues do not synthesize AFP when cultured in isolation, but can adsorb AFP when it is added to the medium. On the 12th day of gestation AFP synthesis is confined to the endoderm layer of the visceral yolk sac. It is concluded that the ability to synthesize AFP is a property which is restricted to the visceral endoderm during early post-implantation development. The presence of AFP in other tissues of the embryo appears to be due to adsorption.
Différenciation in vitro de blastodermes de Truite (Salmo irideus) dépourvus de couche enveloppante
Authors: Devillers Ch. , Colas J. , Richard L. 
Published: April 2021

ABSTRACT
L’étude structurale et fonctionnelle du blastoderme de Poisson conduit à y distinguer deux ensembles: la couche enveloppante et les blastomeres profonds. Si du seul point de vue quantitatif (volume total des cellules) la couche enveloppante est beaucoup moins importante que la masse blastomérienne, du point de vue qualitatif elle représente un élément essentiel dans le développement du blastoderme depuis le stade indivis jusqu’à la fermeture du blastopore. C’est en elle que résident les propriétés d’imperméabilité, de coordination des mouvements cellulaires, de contractilité et d’expansibilité d’ensemble du blastodisque qui entrent en jeu à divers stades de la prémorphogenèse et de la morphogenèse. Vis-à-vis de ce revêtement ‘actif’ le groupe blastomérien profond fait plutôt figure de masse inerte, ou tout au moins incohérente, incapable ‘d’initiative’ et dont les possibilités morphogénétiques, en particulier les mouvements lors de la gastrulation, ont besoin d’être coordonnées, dirigées par la couche enveloppante. Mais c’est de cet ensemble que dérive la quasi-totalité du matériel cellulaire qui édifiera l’embryon; la couche enveloppante ne constituera que l’assise la plus superficielle de l’épiderme, après avoir fourni au matériel de la zone marginale un appoint cellulaire, presque négligeable en quantité.
In vitro studies on the morphogenesis and differentiation of the mesoderm subjacent to the apical ectodermal ridge of the embryonic chick limb-bud
Authors: Kosher Robert A. , Savage Mary P. , Chan Sai-Chung 
Published: April 2021

ABSTRACT
It has been suggested that one of the major functions of the apical ectodermal ridge (AER) of the embryonic chick limb-bud is to maintain mesenchymal cells directly subjacent to it (i.e. cells extending 0·4–0·5 mm from the AER) in a labile, undifferentiated condition. We have attempted to directly test this hypothesis by subjecting the undifferentiated subridge mesoderm of stage-25 embryonic chick wing-buds to organ culture in the presence and absence of the AER and the ectoderm that normally surrounds the mesoderm dorsally and ventrally. During the period of culture, control explants comprised of the subridge mesoderm capped by the AER and surrounded by the dorsal/ventral ectoderm undergo progressive morphogenesis characterized by polarized proximal to distal outgrowth and changes in the contour of the developing explant, and ultimately form a structure grossly resembling a normal distal wing-bud tip. tin contrast, explants from which the AER and dorsal/ventral ectoderm have been removed (minus ectoderm explants) or from which just the AER has been removed (minus AER explants) form compact, rounded masses exhibiting no signs of morphogenesis. During the polarized proximal to distal outgrowth control explants undergo during the first 3 days of culture, as cells of the explant become located greater than 0·4–0·5 mm from the AER, they concomitantly undergo a sequence of changes indicative of their differentiation into cartilage. However, those cells which remain 0·4–0·5 mm from the AER during this period retain the characteristics of non-specialized mesenchymal cells. In marked contrast to control explants, virtually all of the cells of minus ectoderm explants initiate chondrogenic differentiation during the first day of culture. Cells comprising the central core of minus AER explants also initiate chondrogenic differentiation during the first day of culture, but in contrast to minus ectoderm explants, non-chondrogenic tissue types form along the periphery of the explants subjacent to the dorsal/ventral ectoderm. These results indicate that the AER maintains cells directly subjacent to it in a labile, undifferentiated condition, and that when mesenchymal cells are freed from the AER’s influence either artificially or as a result of normal polarized outgrowth, they are freed to commence cyto-differentiation. The results further suggest that the dorsal/ventral ectoderm may have an influence on the differentiation of the mesenchymal cells directly subjacent to it, once the cells have been removed from the influence of the AER.
The activity of cholinesterases during the development of Xenopus laevis
Authors: Gindi Teresa , Knowland John 
Published: April 2021

ABSTRACT
The activity of cholinesterases during the early development of Xenopus laevis has been examined, and the activity of acetylcholinesterase in particular has been distinguished from other cholinesterases. In contrast to some earlier findings, the activity of acetylcholinesterase is low at early stages and gradually increases during development. Possible reasons for the differences between the earlier results and those reported here are discussed.
Investigation of the fate of 4·5 daypost-coitummouse inner cell mass cells by blastocyst injection
Authors: Gardner R. L. , Rossant J. 
Published: April 2021

ABSTRACTTwo distinct patterns of chimaerism were found in conceptuses produced by injecting dissociated 4-5-day inner cell mass cells into genetically dissimilar blastocysts. Pattern 1 : donor cells were found in the endoderm layer of the visceral yolk sac, but not in the adjacent mesoderm layer of this organ or in the foetus itself. Pattern 2: donor cells were found in the mesoderm layer of the visceral yolk sac and/or foetus, but never in the yolk-sac endoderm as well. Primitive endoderm cells of donor inner cell masses are responsible for the first pattern and primitive ectoderm cells for the second. These results, together with those of previous studies, suggest that the entire foetus, including its endodermal components, is formed from the primitive ectoderm, and that primitive endoderm forms only extra-embryonic endoderm of the conceptus.
Marginal zone cells – the primitive streak-inducing component of the primary hypoblast in the chick
Authors: Azar Yehudit , Eyal-Giladi Hefzibah 
Published: April 2021

ABSTRACT
(1) Removal of both the area opaca and the marginal zone of the area pellucida from a blastoderm stripped of its hypoblast (type-IV operation) prevents the regeneration of a normally functioning primary hypoblast. (2) Stage-XTH E.G & K blastoderms (prior to the appearance of PS) after a type-IV operation do not form a primitive streak. (3) In older type-IV operated blastoderms in which the primitive streak has already begun to appear, the regeneration of a non-functional hypoblast did not support the normal maturation of the primitive streak, and in many cases the already existing rudimentary streak was absorbed. (4) Type-IV operated blastoderms from stage 3+ H & H and on developed normally. (5) It is concluded that the cellular contribution of the marginal zone to the primary hypoblast is instrumental in the latter’s capacity to induce a PS.
Twirler: A Mutant Affecting the Inner Ear of the House Mouse
Authors: Lyon Mary F. 
Published: April 2021

ABSTRACT
The mutant twirler, symbol Tw, of the house mouse, Mus musculus, was first recognized by the ‘waltzing’ behaviour which the heterozygotes show. It was later found to affect the morphology of the inner ear and, when homozygous, to cause death of new-born animals through harelip and cleft palate.
Experiments in vitro on the Role of Movement in the Development of Joints
Authors: Lelkes G. 
Published: April 2021

ABSTRACT
It has been pointed out by Fell & Canti (1934) as a result of their experiments in vitro concerning the early formation of the avian limb skeleton and kneejoint, that the appearance of the articular rudiment is independent of the blood- and nerve-supply as well as of mechanical influences. These authors believe that the formation of articular surfaces occurs in consequence of the differential growth of the scleroblastema (the ‘Anlage’ of the limb skeleton, skeletal rudiment) the essential factor in joint formation being the association of undifferentiated tissue with the rapidly growing chondrification centres. They emphasize, however, that only the earlier stages of joint formation can be obtained in vitro; the conditions of cultivation are not adequate for the further development of the joints. The articular rudiment disappears by secondary fusion of the cartilages of the limb skeleton. Fell & Canti mention the possibility that though mechanical movement is not necessary for the appearance of the joint, it may be an important and possibly an essential factor in its subsequent development.
The Mechanism of Hardening of the Salmonid Egg Membrane after Fertilization or Spontaneous Activation
Authors: Zotin A. I. 
Published: April 2021

ABSTRACT
The embryonic development of fishes proceeds under the protection of rigid egg membranes which preserve the embryo from mechanical injury. Salmonid fishes bury their eggs in sandy and stony ground so that they are particularly liable to mechanical damage. This is apparently the reason why the membrane of the salmonid embryo is extremely strong, resisting a load of 3–4 kg. per ovum (Gray, 1932; Hayes, 1942,1949; Hayes & Armstrong, 1942; Zotin, 1953a). This mechanical property of the membrane does not appear immediately after fertilization or activation but is preceded by a whole set of processes which are elicited in the membrane by external factors and by the fertilized or activated egg itself. Thus, according to Manery, Fisher, & Moore (1947), hardening of the egg membranes in the speckled trout sets in 2 hours after the release of the egg into water. Ca ions have been shown to be of great significance for membrane-hardening in Salvelinus fontinalis (Manery, Fisher, & Moore, 1947; Warren, Fisher, & Manery, 1947; cf. also Hoar, 1957) and Oncorhynchus keta (Kusa, 1949 a, b). In distilled water, membrane-hardening is slower than in ordinary water and is completely blocked when Ca ions are bound by 0·01 N sodium citrate or 0·02 N sodium oxalate.
Retinal pigment epithelium: pattern of proliferative activity and its regulation by intraocular pressure in postnatal rats
Authors: Stroeva O. G. , Panova I. G. 
Published: April 2021

ABSTRACT
The postnatal proliferative activity of retinal pigment epithelium (RPE) cells and its dependence on intraocular pressure were studied using pHJthymidine and [14C]thymidine autoradiography in normal and experimentally induced microphthalmic pigmented rats. The regulation of RPE growth by intraocular pressure was shown to involve the control of the number of binucleated cells by means of stimulation of cell entry into the S phase of the cell cycle. Binucleated cells in the rat RPE are formed by acy to kinetic mitoses between days 2 and 9. The significance of the postnatal proliferation and formation of binucleated cells in the RPE is discussed in terms of the specificity of the G2 phase for melanotropic hormone action on RPE differentiation.
A study of the properties, morphogenetic potencies and prospective fate of outer and inner layers of ectodermal and chordamesodermal regions during gastrulation, in various Anuran amphibians
Authors: Dettlaff T. A. 
Published: April 2021

ABSTRACTIn both the ectodermal and the chordamesodermal regions of Anuran embryos, the outer layer of cells possesses epithelial properties and has the same restricted morphogenetic potencies. It is thus interchangeable between the regions, capable of epiboly and, when underlain by notochord material, of the formation of bottle-shaped cells as at the blastoporal groove, and invagination. When taken from the chordamesoderm region, this outer layer has no inducing effect on the ectoderm of the early gastrula. In normal development the outer layer of the neural plate takes an active part in forming the neural tube cavity. It gives rise to the neuroepithelial roof of the diencephalon and medulla oblongata and, when underlain by neuroblasts that develop from the inner cell layers, to ependymal cells of the brain wall. The outer layer of the notochord material is included in the epithelial layer underlying the roof of the gastrocoel -the hypochordal plate. The inner layers of these regions consist of loosely arranged cells and normally have no epithelial properties although, when taken from the ectoderm region, they may acquire such properties upon long-term contact with the environment. However they have wide morphogenetic potencies; the differences in these potencies between cells taken from the various presumptive regions being less than the differences between outer and inner cell layers in each region. Maps are provided which show the arrangement of presumptive rudiments in the ectoderm and chordamesoderm on sagittal sections through Bombina bombina embryos in early and late gastrulation.
Genetic analysis of developmental mechanisms in hydra. VIII. Head-activation and head-inhibition potentials of a slow-budding strain (L4)
Authors: Takano Jun , Sugiyama Tsutomu 
Published: April 2021

ABSTRACT
Morphogenetic potentials involved in head formation were examined in a hydra strain (L4) which has a very low budding rate and a large polyp size, and the results were compared to those of the normal strain (105).
Hydra tissue has two types of antagonistic morphogenetic potentials which are thought to play important roles in head structure formation: the head-activation potential and the headinhibition potential. Lateral tissue transplantation (Webster & Wolpert, 1966) was used to compare the levels of the two potentials in L4 and the normal strain. It was found that the intact polyp of L4 has a nearly normal or slightly lower head-activation potential but a significantly higher head-inhibition potential than the normal strain. During the course of regeneration after head amputation, the levels of the two potentials in L4 changed in significantly different patterns from those in the normal strain. These abnormalities of the two potentials may be responsible for the developmental and morphological abnormalities in L4. The significance of these observations is discussed in light of the current hydra pattern formation models (Wolpert, Hornchurch & Clarke, 1974; Meinhardt & Gierer, 1974).
The effects of inhibition of protein glycosylation on the aggregation ofDictyostelium discoideum
Authors: Mcdonald Charles John , Sampson Jeffrey 
Published: April 2021

ABSTRACTAt concentrations greater than 10 μg ml-1 tunicamycin inhibited the incorporation of [3H]mannose into glycoproteins during the early phase of development in Dictyostelium discoideum, however, total protein synthesis was unaffected. Tunicamycin also interfered with the normal process of aggregation. In its presence small aggregates were observed at the time of normal aggregation, but amoebae failed to aggregate completely and subsequent development was inhibited. Inhibition of normal aggregation by tunicamycin was found to be reversible. The appearance of cell-associated and secreted cyclic AMP phosphodiesterase and cell-surface contact sites A was prevented by tunicamycin but cell surface cyclic AMP receptor activity developed normally in its presence. Tunicamycin also prevented amoebae from acquiring the ability to chemotact toward cyclic AMP. Addition of exogenous cyclic AMP phosphodiesterase restored the ability of amoebae to chemotact toward cyclic AMP in the presence of tunicamycin. Our data suggest that the primary block in aggregation caused by tunicamycin results from the inhibition of expression of active cyclic AMP phosphodiesterase.
An increase in cell—cell adhesion in the chick segmental plate results in a meristic pattern
Authors: Cheney Clarissa M. , Lash James W. 
Published: April 2021

ABSTRACT
Cell-cell adhesion in the anterior portion of the segmental plate plays an important role in the initiation of somitogenesis. Dissociated somites show a marked tendency to reassociate into somite-size clumps within a few hours after dissociation. Segmental plate cells show very little tendency to reassociate, even after 24 h in culture. The cells from the anterior portion of the segmental plate do show a tendency to reassociate. This supports the hypothesis that cell-cell adhesion between the cells in the anterior portion of the segmental plate plays a major role in the initiation of somitogenesis.