bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental manipulations of early Drosophila embryos: II. Adult and embryonic defects resulting from the removal of blastoderm cells by pricking
Authors: Bownes Mary , Sang J. H. 
Published: April 2021

ABSTRACT
Cells were removed from three regions (anterior, mid-lateral and posterior) of Drosophila eggs at blastoderm formation, by pricking. Embryonic defects were generally correlated with the site of damage, as is also found with microcautery and with u.v. irradiation. But many structures can develop autonomously, independently of surrounding damage. Most hatching adults were normal, suggesting that there may be mechanisms which permit compensation for cell loss. Malformed or missing adult structures are those expected from the fate map obtained from studies of genetic mosaics.
The anionic binding-sites at the cell surface after tissue dissociation and during the early phases of cell reaggregation
Authors: Caravita Silvia , Zacchei Anna Maria 
Published: April 2021

ABSTRACT
The fixation of dissociated chick embryonic cells in the presence of ruthenium red or alcian blue revealed a remarkable reduction in the binding of these cations to cell surfaces following tryptic digestion at 37 °C, but not after trypsin used at 4 °C or EDTA.
The reconstitution of anionic sites present over the cell plasma membrane was studied in retina, liver and heart cells from embryos of different ages, cultivated according to a method which promotes cell reaggregation. All these cells regenerated ruthenium red-stainability within the first hour of culture. Culturing at 15 °C, substitution of saline for the culture medium or addition of puromycin or of neuraminidase to the culture media did not affect this restitutive process. Neuraminidase and hyaluronidase digestion were not able to alter the ruthenium red-binding, once it was present.
From these data and from the reports available in the literature it has been concluded that the anionic binding-sites cannot be identified with the cell surface coat, and probably not with sialic acids, which require active metabolic processes and a much longer time interval for regeneration. The presence of these sites probably favours the formation of initial cell contacts but is not sufficient for cell reaggregation.
Extent and properties of the regeneration field in the larval legs of cockroaches (Leucophaea maderae):II. Confirmation by transplantation experiments
Authors: Bohn Horst 
Published: April 2021

ABSTRACT
The investigation of the regeneration field of the larval legs of cockroaches (Leucophaea maderae), which commenced in a previous paper with extirpation experiments, has been continued by transplantation experiments. The extirpation experiments showed that there are two regions near the leg which are indispensable for leg regeneration: the basal sclerites, and the membranous region extending behind the leg up to the spiracle of the next segment, called Teg-inducing membrane’ (LIM). The LIM is followed by ‘sclerite-inducing membrane’ (SIM) which, upon contact with sclerites, only allows formation of sclerite structures.
The results of the extirpation experiments have been confirmed by transplantation experiments. When the whole leg including the basal sclerites is removed, no leg regeneration occurs. The regenerative ability can be restored by implantation of part of the basal sclerites (for instance, the trochantin), but leg regeneration takes place only when the implantation area is covered by LIM. When the sclerites are transplanted to a region which is covered by SIM only additional basal sclerites are formed.
Whole sets of basal sclerites have been implanted at different distances behind the uninjured hindleg. Additional legs are regenerated only in the anterior half of the membranous field extending between the hindleg and the first abdominal segment. Thus, there is a distribution of LIM and SIM in the region of the hindleg, similar to that near the midleg.
Whole sets of basal sclerites have been implanted at various sites on the dorsal or ventral surfaces of the abdomen. Legs are formed on both surfaces, but only when the transplanted sclerites contact the intersegmental membranes. This means that the intersegmental membranes of the abdomen also have leg-inducing capacities.
The implantation of a trochantin into a field of LIM is followed by the development of two regenerates -a normal one at the posterior border of the field, and one with reverse anterior-posterior polarity at the anterior border. When the trochantin is transplanted together with the praecoxa in a similar way, only one normal regenerate is formed at the posterior margin of the trochantin. The praecoxa prevents contact of the anterior margin of the trochantin with LIM, and contact of the anterior margin of the praecoxa with LIM does not promote leg regeneration.
Regeneration and growth control in Nereis: III. Separation of wound healing and segment regeneration by experimental endocrine manipulation
Authors: Golding D. W. 
Published: April 2021

ABSTRACT
Loss of posterior segments from immature Nereis is followed by the associated processes of wound healing and segment regeneration. In the absence of a hormone secreted by the brain, wound healing alone ensues. However, proliferation of segments can be initiated by intracoelomic implantation of a living brain (removed from a donor) during the course of wound healing or subsequent to its completion. In this way, wound healing and regenerative growth can be separated experimentally. Wound hormones may have a role in wound healing, but are probably not involved in the initiation of segment regeneration in Nereis. However, developments at the site of the wound which follow loss of posterior segments in the absence of regeneration progressively reduce the regenerative activity which follows subsequent brain implantation. The nature of the changes is unknown. Maintenance in a decerebrate condition also reduces regenerative capacity. This effect is independent of changes at the wound and may be due to accelerated maturation.
Parthenogenetic activation of rhesus monkey follicular oocytesin vitro
Authors: Abramczuk Jan , Stark Richard A. , Konwinski Marian , Solter Davor , Mastroianni Luigi , Koprowski Hilary 
Published: April 2021

ABSTRACTRhesus monkey follicular oocytes obtained from gonadotropin-injected animals were treated with hyaluronidase and cultured in Whitten’s medium. Of 74 oocytes beyond germinal vesicle stage, 57 were activated. Twenty-one of the activated oocytes cleaved one to three times. Behavior in culture and the values of relative Feulgen-DNA content in nuclei of six normally cleaved 6-to 10-cell parthenogenones showed that four resulted from the activation of primary oocytes, one from a secondary oocyte, and one from a primary polyploid oocyte. One parthenogenone with four pronuclei, and two with a single pronucleus (without extrusion of the first and second polar bodies in either case) were also observed.
Etude expérimentale sur les premiers stades du développement du membre antérieur chez l’embryon du Chélonien Emys orbicularis L.: détermination en mosaïque et régulation
Authors: Vasse J. 
Published: April 2021

ABSTRACTExperimental study on the early stages of development of the front limbs of the embryo of the chelonian Emys orbicularis L. : mosaic determination and regulationAblation of postotic somites 6– 13 on one side in embryos of Emys orbicularis L. or injury to the adjacent somatopleure at the developmental stage when 15– 21 somite pairs were present, led to arrest of forelimb-bud development in this part of the somatopleure on the operated side. Limb development in the remaining part of prospective somatopleure on the operated side was investigated 5– 11 days after the operation.When this part of somatopleure was adjacent to cranial somites 6– 9 or 6-10, the development stopped at the start of the apical crest as in Anguis or Scelotes forelimb-buds. A part of somatopleure adjacent to caudal somites 8– 12, 9– 12 or 10– 12 developed into a normal limb with three segments; a part of somatopleure adjacent to 1– 2 somites only, developed into a reduced limb, scarcely swelling.Each somitic level developed in relation to its initial regional determination dependent on position in the cephalocaudal axis; to its environment (cranial or caudal bud) and to the quantity of somatopleural material in the bud.
Glycosaminoglycan localization and role in maintenance of tissue spaces in the early chick embryo1
Authors: Fisher Marilyn , Solursh Michael 
Published: April 2021

ABSTRACTComparison of sections stained with Alcian blue at pH 1·0 or 2·5 demonstrates the distribution of sulfated and non-sulfated glycosaminoglycans in the extracellular matrix of the stage-8 (Hamburger & Hamilton, 1951) chick embryo. Both types of GAG are present in basement membranes throughout the embryo. Treatment of sections with Streptomyces hyaluronidase, reported to be specific for hyaluronic acid, prior to staining with Alcian blue at pH 2·5 reveals that hyaluronate is an important constituent of the extracellular matrix in basement membranes and in intercellular spaces within the mesoderm. Hyaluronate is shown to be the predominant glycosaminoglycan in the matrix of the head mesenchyme. In addition, examination by SEM and light microscopy of embryos after treatment in ovo with hyaluronidase shows that removal of hyaluronate from living embryos results in a dramatic decrease in cell-free spaces and a weakening of the association between mesoderm and ectoderm in the head.
Morphogenèse de l’épiderme imaginai de l’abdomen de Calliphora erythrocephala (Insecte, Diptère)
Authors: Bautz Anne-Marie 
Published: April 2021

ABSTRACT
The morphogenesis of the abdominal epidermis in Calliphora erythrocephala begins by a cellular proliferation which proceeds slowly in larvae and rapidly in pupae. This allows histoblasts to glide and invade the whole abdominal surface.
As soon as the new epidermal sheet has become continuous, differentiation begins. Generalized epidermal cells show an intense activity which leads to the deposition of imaginai cuticle from the 6th day after pupation onwards. After cuticle deposition they darken and become inactive although they remain alive, even after emergence.
Trichogen and tormogen cells are even more active than generalized epidermal cells, especially the trichogen cell in which polyribosomes and microtubules are abundant. The former are possibly involved in microtubule synthesis. After cuticle deposition the trichogen and tormogen cells undergo degeneration. Their nuclei contract, rough endoplasmic reticulum breaks down and cytoplasm breaks up into fragments through infoldings which proliferate from the plasma membrane. Finally only generalized epidermal cells and sensory cells remain alive in the adult.
The influence of the lower beak on the interorbital septum-prenasal process complex in the chick embryo
Authors: Wouterlood F. G. , Pelt W. Van 
Published: April 2021

ABSTRACTThe effect of removal of the lower beak on the development of the interorbital septum-prenasal process (ISPP) complex was studied in chick embryos. In normal development the angle between the ventral contour of the interorbital septum and the long axis of the prenasal process increases. At the same time the angle between the ventral contour of the interorbital septum and the basal plate increases.After surgical removal of the prospective lower beak at stage 29, the position of the entire ISPP complex was altered in stage-38 embryos and the prenasal process showed elongation. In stage-38 embryos in which the prospective upper beak had been removed at stage 29, Meckel’s cartilage was elongated. It is concluded that straightening of the angle between the ventral contour of the interorbital septum and the long axis of the prenasal process is not influenced by the lower beak, whereas the position of the entire ISPP complex and the size of the prenasal process are under the epigenetic influence of the lower beak. The position and size of Meckel’s cartilage are under the epigenetic influence of the upper beak.
Role of the somitic mesoderm in the development of the thorax in bird embryos
Authors: Chevallier Alain 
Published: April 2021

ABSTRACT
The regional embryonic origin of trunk and limb musculature was determined through heterospecific homotopic or heterotopic transplantations of quail somitic or somitic-somatopleural mesoderm into chick hosts, and through localized X-irradiation of the somitic mesoderm. Experiments were performed on 2-day embryos.
Results show that the myoblastic component of all truncal and appendicular muscles is of somitic origin. Intra- and perimuscular connective tissue as well as tendons are of somatopleural origin. X-ray destruction of the somitic mesoderm at and beyond the wing level resulted in the complete or almost complete absence of musculature in the wing and corresponding truncal region.
The mapping of the cephalocaudal origin of the various muscles was found to be as follows:
In the heterotopic transplantations, the grafted somitic mesoderm gave rise to site-specific morphogenesis, irrespective of the cephalocaudal level of its origin. This result demonstrates that, at 2 days of incubation, the myogenic somitic cells are not regionalized.
Sorting out behaviour of disaggregated cells in the absence of morphogenesis inDictyostelium discoideum
Authors: Tasaka M. , Takeuchi I. 
Published: April 2021

ABSTRACTCells disaggregated from slugs of Dictyostelium discoideum were cultured in Bonner’s salt solution in roller tubes. Cells rapidly stuck together to form an amorphous loose agglutinate which was later transformed into a spheroidal tight agglutinate surrounded by slime sheath material. Prespore cells in the loose agglutinate underwent partial dedifferentiation by starting to decompose their specific antigen until formation of the tight agglutinate, in which the antigen was resynthesized. During the process, there was some decrease in the proportion of prespore cells.Changes in the distribution of prespore and prestalk cells in the agglutinates were examined by using immunocytochemical staining. They were randomly distributed in the early agglutinates, but became well separated in 4 h agglutinates in such a way that prestalk cells were completely enveloped by prespore cells. Prestalk cells later came outside to be partially enveloped and finally occupied a hemisphere side by side with prespore cells. During the process, cells in one or two outer layers differentiated into prestalk or stalk cells. Similar changes in the distribution pattern were observed, when labelled prestalk cells were cultured with unlabelled prespore cells and their distribution in co-agglutinates was followed by autoradiography. It was concluded from these results that the majorities of prestalk and prespore cells isolated from slugs are sorted out in agglutinates without changing their original cell types, and that the sorting-out occurs in the complete absence of polar structures and movement of the cell mass. The distribution patterns in agglutinates of prestalk and prespore cells were discussed with reference to intercellular adhesion among/between them.
Nitrogen Excretion in Developing Chick Embryos
Authors: Fisher James R. , Eakin Robert E. 
Published: April 2021

ABSTRACT
An analysis, more extensive than hitherto, has been made of nitrogen excretion in developing chicks. It was found that the concentration of ammonia in the allantoic fluid was constant from the 5th to the 11th day and equalled the concentration in the extra-allantoic fluids, e.g. yolk. The increase into total ammonia content of the allantois during development is apparently due to the increase in volume of the organ and not to excretion by the embryo. The concentration of urea in the allantoic fluid increases during development and injected urea concentrates in that organ. The total amount and concentration of uric acid in allantoic fluid increases during development. The ratio of urea nitrogen to uric-acid nitrogen is relatively constant from the 6th to the 11th day of development indicating that no major shift from urea excretion to uric-acid excretion occurs. No urease activity was observed even in the blastodiscs of unincubated eggs. The distribution of arginase activity in 7-day-old chicks did not resemble that of ureotelic organisms. Activity of heads, bodies, and livers were essentially the same. From these results it was concluded that ammonia is not an excretion product and that the developing chick does not pass through either a typical ammonotelic or ureotelic stage of excretion.
The Pulmonary Return as an Agent in the Final Development of the Atrium in Rana Temporaria
Authors: Simons J. R. 
Published: April 2021

ABSTRACT
The lungs of tadpoles of R. temporaria were removed at an early stage (12 mm.) in order to ascertain the effect on the development of the atrium and the interauricular septum of the heart. Serial sections of the hearts of experimental and control tadpoles at three comparable stages of development between the operation and metamorphosis were prepared. The operation causes a reduction in the absolute volume of the atrium. When it is first formed, the left auricle in the normal tadpole averages 25 per cent, of the total atrial volume but, as growth proceeds, it comes to average about one-third of the total atrial volume by the time metamorphosis occurs. In the experimental tadpoles the left auricle, when first formed, averaged about one-fifth of the total atrial volume and maintained a similar proportion throughout development to metamorphosis. The presence of the pulmonary return is thus necessary for the normal enlargement of the proportional volume of the left auricle. The obliteration of the pulmonary return did not affect the origin and normal development of the interauricular septum.
The effect of cell killing by X-irradiation on pattern formation in the chick limb
Authors: Wolpert L. , Tickle C. , Sampford M. , Lewis J. H. 
Published: April 2021

ABSTRACTIt has been suggested that positional information along the proximo-distal axis of the limb-bud is specified by time spent in the progress zone. Mesenchyme cells have been killed by X-irradiation, reducing the rate cells leave the zone. The time spent there by some cells is thus increased. When limbs, stage 18/19, stage 21, or tips of stage 24, are treated with increasing doses of X-irradiation, from 1000 rads to 2500 rads proximal structures are progressively lost, whereas distal ones - the digits - are relatively unaffected. There was no evidence for intercalation of missing parts. These effects are due to killing or damage of mesenchyme cells: the ectoderm is not affected at these doses. The results are consistent with a quantitative analysis based on the progress zone model, in which viable cells repopulate the progress zone and gradually restore it to normal as non-dividing cells are diluted out. It is suggested that any treatment causing damage to the mesenchyme at early stages will give similar results.The mesenchyme cells appear to be surprisingly resistant to radiation damage. The form of the limb-bud is not altered by damaging the mesenchyme. Differences in the development of structures at similar proximo-distal levels, following irradiation, is considered in terms of the requirement of a threshold number of cells.
The zone of polarizing activity: evidence for a role in normal chick limb morphogenesis
Authors: Summerbell Dennis 
Published: April 2021

ABSTRACTWhen an impermeable barrier is placed so as to divide the early chick limb-bud into anterior and posterior parts then development continues only on one side of the barrier. The detailed results are inconsistent with mosaic development. They can readily be explained by supposing that pattern is specified by the concentration of a diffusible morphogen controlled by the zone of polarizing activity. A simulation of appropriate concentration profiles is presented and its relevance to similar experiments published elsewhere is discussed. It seems probable that the zone of polarizing activity is active during normal development.
Inhibition of tooth germ differentiationin vitroby diazo-oxo-norleucine (DON)
Authors: Hurmerinta Kirsti , Thesleff Irma , Saxén Lauri 
Published: April 2021

ABSTRACTMolar tooth germs from mouse embryos were studied in a Trowell-type organ culture. After 5 days of culture the odontoblasts had secreted predentine and the ameloblasts had differentiated. When cultured in the presence of 10 – 50 μ M diazo-oxo-norleucine (DON), which is a glutamine analogue, the differentiation of odontoblasts was inhibited, but the teeth looked otherwise healthy. When DON was added after 2 days of culture in control medium (at this time the odontoblasts in the cuspal area were already differentiated), it did not inhibit predentine secretion, ameloblast differentiation, nor enamel secretion. However, this was seen only in the cuspal area and the boundary to the undifferentiated, more cervical cells was distinct.The results support the concept that the mechanism of the differentiation of odontoblasts is different from that of the ameloblasts. We have shown earlier that a close association between the basement membrane and the mesenchymal cells is required for odontoblast differentiation. Because DON interferes with glycosaminoglycan and glycoprotein synthesis we suggest that DON inhibits odontoblast differentiation by affecting the mesenchymal cell surface and/or the basement membrane.
Interaction between inner cell mass and trophectoderm of the mouse blastocyst : II. The fate of the polar trophectoderm
Authors: Copp A. J. 
Published: April 2021

ABSTRACT
Selective labelling of polar trophectoderm cells in early mouse blastocysts has allowed the fate of polar cells to be followed during in vitro and in vivo blastocyst development. Results show that there is cell movement from polar to mural regions as blastocysts grow. This indicates that trophectoderm cells directly opposite the inner cell mass are the oldest mural cells. However, after implantation polar cells invaginate into the blastocoelic cavity and contribute to the extra-embryonic ectoderm. It is suggested that the morphogenetic changes occurring in the mouse embryo at implantation result from the maintenance of a balance between (a) regional differences in rates of cellular proliferation, and (b) mechanical constraints on the direction in which growth can occur.
Factors regulating the degree and extent of experimental chimaerism in the mouse
Authors: Mystkowska Ewa T. , Ożdżeński Wacław , Niemierkos Anna 
Published: April 2021

ABSTRACT
The degree of chimaerism of the coat, bone marrow and cornea in mouse chimaeras obtained by aggregation of an albino inbred embryo of A strain with an AxCBA-T6T6 hybrid was investigated. Out of 21 individuals born, 18 were chimaeras. Statistically significant correlation has been demonstrated between chimaerism of the coat, bone marrow and the cornea. The contribution of the two components appears to be affected by two factors: first, variable participation of the two components in the embryonic ectoderm of the chimaeric egg cylinder, and second, the rate of proliferation of the two cell lines.
A photometric method is described which permits the quantitative evaluation of coat chimaerism. The method is sensitive and reliable.
Rôle de la sérotonine et des catecholamines dans la régénération de la planaire Polycelis tenuis
Authors: Franquinet R. 
Published: April 2021

ABSTRACT
During traumatic regeneration of Planaria Polycelis tenuis, determination of serotonin, noradrenaline and dopamine levels revealed important variations of serotonin and catecholamines from the time of excision. The use of specific inhibitors of these hormones delayed regeneration whereas simultaneous addition of an hormone and its antagonist restores a standard time of regeneration. Serotonin acts through adenylate cyclase system. Results allow us to assume that dopamine acts through the same mechanism. The action of noradrenaline is so far not elucidated although propranolol (β antagonist) delays or inhibits completely regeneration.