bluuebunny/crossref_metadata_2025_split huggingface dataset:
The site of action of the ichthyosis locus (ic) in the mouse, as determined by dermal-epidermal recombinations
Authors: Green Margaret C. , Alpert Barbara N. , Mayer Thomas C. 
Published: April 2021

ABSTRACTSkin of 14-day ic/ic and +/+ embryos was separated into dermal and epidermal layers using trypsin, and recombined in the combinations + / + epidermis with + / + dermis, + / + epidermis with ic/ic dermis, ic/ic epidermis with +/+ dermis, and ic/ic epidermis with ic/ic dermis. The recombined tissues were implanted in adult histocompatible testes and allowed to grow for 2 weeks. The type of hair that developed in the grafts corresponded to the genotype of the epidermis, and was not influenced by the genotype of the dermis. We conclude that the ic locus acts in the epidermis.
Potentialites hématopoïétiques de tissus embryonnaires et adultes analysees par greffe à des poussins irradiés
Authors: Samarut Jacques , Nigon Victor 
Published: April 2021

ABSTRACT

Differentiation of haemopoietic tissues from embryos and adults injected into irradiated chickens
Irradiated chicken are injected with haemopoietic tissues from adult or 11-day-old embryos. Development of stem cells gives rise to well-defined erythrocytic colonies on the surface of the tibial marrow. Erythropoietic production appears to be similar from adult marrow and embryonic blood stem cells; production from injected vitelline stem cells seems to be between 3 and 4 times higher than that of adult marrow stem cells. Results are discussed on the basis of two hypotheses:
–existence of an extramedullary erythropoietic site in the host after vitelline cells grafting;
–development of vitelline stem cells in the host marrow with kinetic patterns different from those of grafted adult marrow or embryonic blood stem cells.
Anyway, the 11-day-old embryo appears to contain at least two types of blood stem cells with distinctive properties. Developmental origin, relationship and future of these different stem cells remain to be analysed.
Rôle du mésoderme somitique dans le développement de la cage thoracique de 1 embryon d’oiseau. I. Origine du segment sternal et mécanismes de la différenciation des côtes
Authors: Chevallier Alain 
Published: April 2021

ABSTRACT

Role of the somitic mesoderm in the development of the rib cage of bird embryos

I
Origin of the sternal component and conditions for the development of the ribs
The developmental origin of the sternal component of the ribs and the conditions for the development of the rib cage have been elucidated in bird embryos.
Experiments consisted in homo-or heterospecific transplantations of 2-day-old quail or chick embryo somitic mesoderm into chick hosts of the same age in ortho-or heterotopic position along the cephalo-caudal axis.
Results show that vertebral halves, ribs (not only their vertebral segment, but also their sternal component when they possess one), the trunk and intercostal muscles, as well as at least part of the scapula originate exclusively from the somitic material, while the sternum, ventral muscles and the other parts of the pectoral girdle are derived from the somatopleural mesoderm.
The development of the rib basket is subjected to following rules:
—only the somitic mesoderm of the prospective thoracic region (somites 19–26) is able to give rise to ribs.
—only the somitic mesoderm of the posterior thoracic region (somites 22–26) is able to develop ribs with a sternal component.
—the vertebral component of ribs can develop outside the thoracic region.
—contrariwise, the sternal component can form only in the vicinity of the sternal anlage, i.e. within about three somites in front and rear of the normal limits of the thoracic region.
It is concluded that the somitic mesoderm is already regionalized at a stage slightly pre-ceding its metamerization and that the somatopleural territory of the sternum plays a morphogenetic role in the development of the sternal component of ribs, although it does not make a cellular contribution to their construction.
Différenciation in vitro de cartilage à partir des crêtes neurales céphaliques chez Pleurodeles waltlii Michah
Authors: Corsin Jacqueline 
Published: April 2021

ABSTRACT

In vitro differentiation of cartilage from cephalic neural crest of Pleurodeles waltlii Michah
Parts of cephalic neural crest of Pleurodeles waltlii have been cultivated in vitro alone or in explants containing other cellular components. It was hoped that these experiments would establish under what conditions cephalic neural crest cells can differentiate into chondroblasts. It has been demonstrated that this differentiation is possible only under the influence of the dorsal mesoderm and foregut endoderm.
It appears that neural crest cells are relatively pluripotent and progressively differentiate in response to local environmental factors.
Limb development in mouse embryos: protection against teratogenic effects of 6-diazo-5-oxo-L-norleucine (DON) in vivo and in vitro
Authors: Greene R. M. , Kochhar D. M. 
Published: April 2021

ABSTRACT
The glutamine analogue, 6-diazo-5-oxo-L-norleucine (DON), has been shown to inhibit biosynthesis of purines and glycosaminoglycans, presumably by blocking the glutaminedependent steps in the biosynthetic pathways. The teratogenic potential of DON on the developing mouse limb-bud in vivo and in vitro was studied in an attempt to discriminate whether DON is exerting its teratogenic effect by interfering with glycosaminoglycan or purine metabolism.
A single intramuscular injection of DON (0·5 mg/kg) to ICR/DUB mice on day 10 of gestation resulted in 76% resorption, while fetuses surviving to day 17 exhibited growth retardation, median cleft lip, and limb malformations. Concurrent administration of L-glutamine (250 mg/kg) provided no protection against resorption or malformations, while 5-aminoimidazolecarboxamide (A1C, 250 mg/kg) decreased the resorption rate to 34% without significantly altering the incidence of malformations. Injection of DON alone on day 11 resulted in 87% of fetuses exhibiting limb malformations, with only 2% resorption. Concurrent injection of A1C decreased the frequency of limb malformations to 32%. L-Glutamine, D-glucosamine, or inosinic acid were without any protective effect in vivo.
DON (5 µgml medium) added in vitro to organ cultures of day 11 mouse limb-buds caused all limbs to evidence cartilage abnormalities. In this system, either L-glutamine or D-glucosamine (0·5 mg/ml medium) provided protection against DON effects while A1C (0·5 mg/ml medium) offered no protection in vitro.
These data suggest that DON exerts its effects in vivo by interfering with purine metabolism while in vitro its teratogenic action may be interruption of glycosaminoglycan biosynthesis. This may reflect upon the relative importance of growth and differentiation to limb development in vivo and in vitro. These data infer that limb development in vitro relies more on the differentiative process (differentiation of cartilage) than on growth, whereas limb development in vivo is dependent, at this stage, to a greater extent on growth for normal phenotypic expression.
The distribution of non-synaptic intercellular junctions during neurone differentiation in the developing spinal cord of the clawed toad
Authors: Hayes Brian P. , Roberts Alan 
Published: April 2021

ABSTRACT
The distribution of intercellular junctions, other than synapses and their precursors, has been described in the developing spinal cord of Xenopus laevis between the neurula and free swimming tadpole stages. At the neurocoel, ventricular cells are joined in the apical contact zone by a sequence of junctions which usually has one or more intermediate junctions but often also includes close appositions, gap junctions and desmosomes. This apical complex is more diverse than that reported in other vertebrate embryos and between ependymal cells in the adult central nervous system. Gap junctions are also found between ventricular cells and their processes near the external cord surface. However, no other special junctions occur in this location under the basement lamella which surrounds the cord. Punctate intermediate junctions are generally distributed between undifferentiated and differentiating cells and their processes but were not found in neuropil after stage 28. These results are discussed in relation to cell movements during neural differentiation, possible effects on the freedom of movement of ions and molecules through extracellular pathways in the embryo, and possible inter-cytoplasmic pathways via gap junctions which may be responsible for the physiologically observed electrical coupling between neural tube cells.
Positional information and pattern formation in Hydra. Dynamics of regions away from the boundary
Authors: Hicklin J. , Hornbruch A. , Wolpert L. 
Published: April 2021

ABSTRACT
The dynamics of regions away from the head-end boundary have been investigated by a variety of assays, and the changes appear to be slow. If, for example, a head end is grafted onto a peduncle to give H/56F, region 5 does not become a region 1 within 72 h. Such results support a gradient type model, and exclude a head end inducing a region 1 in the tissue adjacent to it. The changes can be interpreted if the positional value were effectively slowly diffusible: about 10 times more slowly than the positional signal. These results also have implications for studies on polarity reversal.
An analysis of the condensation process during chondrogenesis in the embryonic chick hind limb
Authors: Thorogood P. V. , Hinchliffe J. R. 
Published: April 2021

ABSTRACT
An analysis has been made of the pre-cartilaginous condensation stage in the development of the femur and tibia/fibula skeletal blastemata of the embryonic chick hind limb. Light microscopy serial sections were used to ‘map’ the mesenchymal cell condensations of both myogenic and chondrogenic anlagen in the limb-bud from stages 22 to 26 (Hamburger & Hamilton, 1951). Cell counts reveal that an increase in mesenchymal cell number per unit area occurs in the central chondrogenic locus at stage 24 prior to matrix formation. Electron microscopy, using a simultaneous double fixation with osmium and glutaraldehyde, reveals that the pre-chondrogenic cells are characterized by large areas of close surface contact between adjacent cells, as compared with the extensive intercellular spaces associated with undifferentiated mesenchymal cells. The results are discussed and related to other investigations of in vivo chondrogenesis and to analyses of cellular events during in vitro chondrogenesis. These observations are consistent with the theory that condensations are formed by a process of aggregation rather than by localized increased mitosis.
Differentiation in vitro of innervated tail regenerates in larval Ambystoma
Authors: Globus Morton , Liversage Richard A. 
Published: April 2021

ABSTRACT
Larval Ambystoma tail regenerates, innervated by the intact spinal cord, were cultured with their epidermal covering in modified Parker’s medium (CMRL-1415) and the morphological integrity of the explanted regenerates was maintained with consistent success. The results show that the larval urodele tail blastema is capable of undergoing growth and differentiation when isolated in vitro and regeneration follows the normal in vivo pattern. A diffuse aggregate of blastema cells, which extended caudally from the cut end of the notochord at the time of explantation, underwent differentiation in vitro in the presence of the regenerating spinal cord. The importance of the nerve in regeneration is discussed in relation to the in vitro system.
Haploid mouse embryos obtained by microsurgical removal of one pronucleus
Authors: Modliński Jacek A. 
Published: April 2021

ABSTRACTA pronucleus can be microsurgically removed from the fertilized mouse egg. Out of 145 haploid eggs obtained by this method and transplanted into the oviduct of pseudopregnant recipients, 36 multicellular embryos were recovered on the 4th or 5th day. On the 4th day all embryos were morulae composed of 8-50 cells, with the majority containing 8-16 cells. After an additional 24 h in vivo or in vitro the cell number increased considerably, sometimes up to as many as 80. Out of 36 multicellular embryos only one developed into a blastocyst while the others remained at the morula stage. Karyological investigations confirmed that the embryos were haploid and revealed that all were gynogenetic. Possible reasons for the absence of the androgenones and for the scarcity of blastocysts are discussed.
Developmental precocity in transferred mouse embryos influencing the teratogen response to salicylate
Authors: Marsk L. , Larsson K. S. , Kjellberg M. 
Published: April 2021

ABSTRACT
Asynchronous blastocyst transfer, supposed to equalize the developmental stage of native and alien embryos during the organogenic period, was used as a tool in a teratological investigation.
A spurious protection by the transfer as such was shown to depend on a persisting asynchrony between native and alien foetuses. The initial difference of 24 h was not nullified, but decreased to 8 h. This difference allowed transferred foetuses to pass the period of maximum sensitivity before salicylate treatment.
The structural and functional development of the retina in larval Xenopus
Authors: Chung S. H. , Stirling R. Victoria , Gaze R. M. , Land M. , Stirling R. Victoria 
Published: April 2021

ABSTRACT
The structural transformations of the larval Xenopus retina at successive stages of development, and concomitant changes in response characteristics of retinal ganglion cells, were studied using histological and electrophysiological techniques. The first sign of visually evoked electrical responses appears at about the time when the ganglion cells spread out into a single layer and shortly after the inner and outer plexiform layers become discernible. Initially giving simple ‘on’ responses, the cells progressively change their response characteristics and become ‘event’ units. Subsequently, ‘dimming’ units can be identified. Throughout larval life, response properties of these two types become more distinct from one another and approximate to those found in the adult. So do the arborization patterns of the dendritic trees of the ganglion cells. Two types of branching patterns are identifiable in Golgi preparations. Around metamorphic climax, a new type of ganglion cell appears, coinciding with the emergence of ‘sustained’ units electro physiologically. After metamorphosis, the retina still grows both in thickness (mainly in the inner plexiform layer) and diameter. The three unit types change such that they come to show pronounced inhibitory effects from the peripheral visual field on the receptive field and each unit type acquires a distinct pattern of endogenous discharge.
Xenopus laevis cement gland as an experimental model for embryonic differentiation
Authors: Picard J. J. 
Published: April 2021

ABSTRACT
Explants of the blastocoelic roof of Xenopus laevis embryos were incubated for 6 h in Holtfreter solution containing 10 mM ammonium chloride and 10 HIM sodium bicarbonate. After this incubation they were transferred for 5 days to Barth’s physiological salt solution. Under these conditions the explants underwent differentiation into cement gland tissue. The ability to produce cement gland was highest when explants were dissected from young gastrulae (stage 10). Explants from younger and older embryos displayed much smaller cement glands.
There is no difference in the response of ventral or dorsal portions of the blastocoelic roof of stage-10 embryos under these in vitro conditions involving ammonium chloride stimulation. Although the treatment changed the fate of some ectoblastic tissues, it was unable to force endodermal or mesodermal tissues of the blastoporal lip to differentiate into cement gland.
The amount of cement gland in the ectoblastic explants varied according to the egg-batch and on the average accounted for 55 % of the total tissue. The remaining tissue was undifferentiated. Most of this undifferentiated tissue originates from the adjacent layer of the ectoblast. Therefore it may be estimated that the cement gland accounts for 80 to 100 % of the volume of the competent superficial layer.
Investigation of the determinative state of the mouse inner cell mass
Authors: Rossant J. 
Published: April 2021

ABSTRACTInner cell masses (ICMs) were dissected from and day mouse blastocysts and inserted into empty zonae before transfer to the oviducts of pseudopregnant mice. The ICMs survived in the oviduct for at least 2 days with little evidence of reduction in cell number. After 1 day, isolated day ICMs were still viable, since they could form chimaeras when injected into day blastocysts. However, no evidence of trophoblast formation could be detected in any of the isolated ICMs, despite exposure of some of their cells to ‘outside’ conditions. This is further evidence that ICM cells, although not overtly differentiated, are determined by days. Although no trophoblast was formed, day ICMs formed an outer endoderm layer after 1 day in the oviduct, as judged by light and electron microscopical evidence. It is suggested that cell position may be important in endoderm differentiation.
Ultrastructural identification of extracellular matrix and cell surface components during limb morphogenesis in man
Authors: Kelley Robert O. 
Published: April 2021

ABSTRACT
Development of the human hand plate (stages 16–17) has been analyzed with emphasis on differentiation of elements within the extracellular matrix and the composition of the mesenchymal cell surface. The epithelial-mesenchymal interface contains a basal lamina and a sublaminar matrix exhibiting: (a) collagen fibrils with characteristic 63–64 nm banding; (6) non-banded filaments, 10—15 nm in diameter; (c) ruthenium red-positive particles, 12—15 nm in diameter; and (&lt;7) attenuated threads, 3·5–5·0 nm in diameter which interconnect particles, fibrils, filaments and the basal lamina. Processes of mesenchymal cells penetrate this matrix network. In addition to staining with ruthenium red, components of basal laminae bind to ferritin-conjugated Concanavalin A, greatest binding being localized on the mesenchymal surface of the lamina. Asymmetry of binding is removed by incubation of exposed laminae with trypsin (5 /μg/ml). Regional differences in these staining and binding characteristics within the subepithelial matrix have not been observed in the hand plate. However, precartilaginous extracellular zones deep within the plate are notably unstructured in comparison to the sublaminar region. Ruthenium red-positive materials at mesenchymal cell surfaces display sensitivity to testicular hyaluronidase, Pronase and trypsin but resist removal with neuraminidase and EDTA. These features of the substrate in situ may be important in the regulation of mesenchymal cell behavior during limb morphogenesis in man.
Immunofluorescence studies on amphibian myoblast differentiation
Authors: Duprat A. M. , Romanov’sky A. , Hurychová D. , Machá J. 
Published: April 2021

ABSTRACT
Differentiating myoblasts from urodele amphibians were cultivated in vitro and treated by immunofluorescence techniques and (or) inhibitors of RNA and protein syntheses. These experiments lead to the conclusion that the differentiation of these cells is directed by long-lived m-RNAs which are already present in morphologically undifferentiated cells and may act for at least 6 days.
Contrary to observations on cultivated myogenic cells from other groups, the fusion of urodele myoblasts is not a prerequisite for a normal and functional differentiation (contractions) since isolated myoblasts differentiate quite normally.
The appearance and further evolution of myosin and actin occur synchronously in this biological system.
Analysis of gene expression during development in the homeotic mutant Contrabithorax of Drosophila melanogaster
Authors: Morata Gines 
Published: April 2021

ABSTRACT
Contrabithorax, a mutant of the bithorax system in Drosophila melanogaster produces a partial homeotic transformation of mesothorax (wing) into metathorax (haltere). The wing of a fly homozygous or heterozygous for the mutant is a mosaic of wing and haltere structures. A genetic analysis of the mutant suggests that its phenotype is due to some form of derepression in the wing of two other genes of the bithorax system (bithorax and postbithorax) which are not normally active there. This repression is not complete. The activity of the two genes is below the normal level resulting in only a partial transformation of wing into haltere.
Clones of marked cells were generated by X-rays and were found to include both transformed (haltere) and untransformed (wing) territory; this was true even for those generated late in development. Thus the final expression of a cell depends not on its immediate ancestry but perhaps on the level of the products of the wild-type alleles of bithorax and postbithorax.
The role of microtubules in chick blastoderm expansion—a quantitative study using colchicine
Authors: Downie J. R. 
Published: April 2021

ABSTRACT
Since their discovery, cytoplasmic microtubules have been much studied in the context of cell movement and cell shape change. Much of the work has used drugs, particularly colchicine and its relatives, which break down microtubules - the so-called anti-tubulins. Colchicine inhibits the orientated movements of many cell types in vitro, and disrupts cell shape change in several morphogenetic situations.
The investigation reported here used chick blastoderm expansion in New culture in an attempt to quantify the colchicine effect on orientated cell movement. However, although colchicine could halt blastoderm expansion entirely, a simple interpretation was not possible. Colchicine at concentrations capable of blocking mitosis, and of disrupting all or most of the cytoplasmic microtubules of the cells studied, inhibited blastoderm expansion, often resulting in an overall retraction of the cell sheet.Though blastoderm expansion does normally involve considerable cell proliferation, the colchicine effect could not be ascribed to a block on cell division since aminopterin, which stops cell division without affecting microtubules, did not inhibit expansion.Blastoderm expansion is effected by the locomotion of a specialized band of edge cells at the blastoderm periphery. These are the only cells normally attached to the vitelline membrane - the substrate for expansion. When most of the blastoderm was excised, leaving the band of edge cells, and the cultures then treated with colchicine, expansion occurred normally. The colchicine effect on blastoderm expansion could not therefore be ascribed to a direct effect on the edge cells.An alternative site of action of the drug is the remaining cells of the blastoderm. These normally become progressively flatter as expansion proceeds. If flattening in these cells is even partially dependent on their cytoplasmic microtubules, disruption of these microtubules might result in the inherent contractility of the cells resisting and eventually halting edge cell migration. That cell shape in these cells is dependent on microtubules was demonstrated by treating flat blastoderm fragments with colchicine. On incubation, the area occupied by these fragments decreased by 25-30 % more than controls.
The significance of these results in the general context of orientated cell movements and cell shape determination is discussed, with particular emphasis on the analogous system of Fundulus epiboly.