bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell adhesion and movement in relation to the developing limb pattern in normal and talpid
3 mutant chick embryos
Authors: Ede D. A. , Agerbak G. S. 
Published: April 2021

ABSTRACT
Descriptive studies of the talpid2 chick embryonic lethal mutant (ta3//a3) have suggested that the multiple effects produced by this gene are of mesodermal origin, and that they arise from defective mesenchymal cell movement and condensation (Ede & Kelly, 1964a, b). It may be argued that condensation in vivo is comparable to cell reaggregation of dissociated cells in vitro, and that defects in the former are likely to be reflected in the latter. In this case it should be possible to obtain experimental verification of this effect of the gene at the cellular level, using the quantitative methods for assessing aggregation developed by Moscona (1961a, b) and Curtis & Greaves (1965). The experiments reported here show a clear genetic effect upon cell adhesion in the wing-bud mesenchyme of the talpid3 mutant.
An electron-microscope study of centrioles in differentiating motor neuroblasts
Authors: Lyser Katherine M. 
Published: April 2021

ABSTRACT
Mature neurons with centrioles were first described at the end of the nine-teenth century and have been observed in many animals (see Cajal, 1911; Ariens Kappers, Huber & Crosby, 1936). As mitosis rarely, if ever, occurs after morphological differentiation of the neuroblast begins, the function of the centrioles in nerve cells posed a problem which has yet to be resolved. Held (1909) described centrosomes in differentiating neuroblasts as being associated with the ‘fibrillogenous zone’, which suggests a role for the centriole in the differen-tiation of neurofibrils.
The effect of hydrocortisone acetate on the development of mouse embryos
Authors: Jurand A. 
Published: April 2021

ABSTRACT
Hydrocortisone (Kendall’s compound F, 17-hydroxycorticosterone, Cortisol) and cortisone (Kendall’s compound E, 17-hydroxy-ll-dehydrocorticosterone) have been widely used in medicine for about 20 years, first as adrenal hormones in substitution therapy. Since the discovery of Hench, Kendal, Slocumb & Polley (1949) that cortisone is beneficial against a wide range of rheumatic diseases and against all forms of arthritis, many more types of diseases have been added in later years to the list of ailments curable with cortisone, namely bronchitis, bronchial asthma, pulmonary tuberculosis, colitis, various inflammatory conditions and certain skin, blood and eye diseases. Hydrocortisone is used against the same diseases as cortisone; in fact, it is believed that cortisone becomes pharmacologically active only after conversion to hydrocortisone in the liver (Cope, 1964). Particularly in the inflammatory conditions cortisone must be converted to hydrocortisone to become antiphlogistic (Applezweig, 1962).
Enzyme ontogeny in normal and hemimelic limbs of mice
Authors: Long Sally Y. , Johnson E. Marshall 
Published: April 2021

ABSTRACT
The appearance of electrophoretically separable isozyme patterns is specific both to type of tissue and to its stage of development (Markert & Moller, 1959), In abnormally developing embryonic systems there are alterations in the time of initial appearance and the persistence of isozymes from a variety of metabolic areas (Johnson &Spinuzzi, 1966, 1968). In malformed embryos from folic-acid-deficient rats the altered zymogram patterns of esterases from abnormal limbs were different from those of abnormal kidneys, yet differentiation of zymograms from the normal hearts of these embryos was unaltered. This implies a correlation between altered tissue-specific zymogram patterns and abnormally developing systems, though no causal relationship has as yet been shown (Johnson, 1968), Moreover, when tibial hemimelia in the rat was elicited by two different teratogens—a folic acid antagonist, 9-methylpteryol-glutamic acid (PGA), and the alkylating agent N-nitroso-iV-methylurea (NNMU)—there were similar changes in the non-specific esterases after electrophoretic separation of homo-genates from the defective limbs (Johnson & Lambert, 1968).
Nucleic acid and protein synthesis and pattern regulation in hydra: II Effect of inhibition of nucleic acid and protein synthesis on hypostome formation
Authors: Clarkson S. G. 
Published: April 2021

ABSTRACT
In a previous paper (Clarkson, 1969) data were presented which indicate that hypostome determination is accompanied by a large and rapid burst of RNA synthesis, a slight stimulation of protein synthesis, and no increase in DNA synthesis. More direct evidence concerning the relative importance of these metabolic activities in hypostome determination is reported in this paper.
RNA synthesis in the early embryogenesis of a fish (Misgurnus fossilis)
Authors: Kafiani C. A. , Timofeeva M. J. , Neyfakh A. A. , Melnikova N. L. , Rachkus J. A. 
Published: April 2021

ABSTRACT
Synthesis of ribonucleic acids in early embryos has been extensively studied during recent years in a number of laboratories and has been shown to begin shortly after fertilization (Kafiani, Tatarskaya & Kanopkayte, 1958; Wilt, 1963; Brown & Littna, 1964; Decroly, Cape & Brachet, 1964; Glišin & Glišin, 1964; Kafiani & Timofeeva, 1964, 1965; Nemer & Infant, 1965). Early embryos of Xenopus (Brown & Gurdon, 1964; Brown & Littna, 1964, 1966) and of sea urchins (Wilt, 1963; Glišin & Glišin, 1964; Nemer & Infant, 1965) synthesize up to gastrula stage predominantly or exclusively polydisperse RNA of a non-ribosomal nature usually referred to as DNA-like RNA (dRNA).
Myogenesis in chick embryo somites in vitro
Authors: Ellison M. L. , Ambrose E. J. , Easty G. C. 
Published: April 2021

ABSTRACT
Evidence from a number of studies (e.g. Holtzer, 1964; Coon & Cahn, 1966; Konigsberg, 1963) has suggested that the differentiation of some types of cells in vitro may be influenced by environmental factors. Culture conditions can permit or prevent the phenotypic expression of characteristics already determined in the cells.
The influence of the nucleus on sequential determination in frog ectoderm following induction by lithium ion
Authors: Ansevin Krystyna D. 
Published: April 2021

ABSTRACT
It appears certain that the process of cellular differentiation is an outcome of interactions between the cell nucleus and cell cytoplasm. Differentiation of embryonic amphibian ectoderm involves two fairly distinct phases: during the first short period an inductor (or some intrinsic factor, if an inductor is absent) determines the course of future differentiation in a multipotential cell; during the second, longer interval of time presumably a complex sequence of reactions leads to physiological and morphological differentiation. Little is known about the nature of reactions which take place during the first phase when the cells become developmentally determined by the inductor. It appears that the first step in translation of the inductive instruction in the competent cell is accomplished during the first 2 or 3 h following the treatment with the inductor (Ansevin, 1966). The step is not actinomycin-sensitive (Ansevin, 1965), as was shown by cells that completely recovered after actinomycin treatment (in conditions when it was unlikely that they could have failed to take up some inhibitor). This suggests that transcription of RNA does not have to occur during cell determination, but it does not exclude the possibility that induction removes biological repressors from specific genes which thus become available to direct cellular differentiation along a specific line. Barth (1965) has drawn attention to a striking similarity between the power of several inorganic ions to bind to DNA and the capacity of the same ions to act as embryonic inductors. He suggested that ions might compete with histones for active sites on DNA molecules, and by binding on these sites protect the molecules from the inactivating action of histones.
Differentiation capacities of the prospective tail somite region of the neural plate in the embryos of Ambystoma mexicanum
Authors: Niazi I. A. 
Published: April 2021

ABSTRACT
The hind part of the neural plate in amphibian embryos has a mesodermal significance although it occupies an ectodermal position till late neurula stage. In anurans it gives rise to the posterior tail somites (Smithberg, 1954) and in urodeles the somites of the posterior trunk region and of the entire tail together with several other mesodermal structures (Bijtel, 1931; Nakamura, 1938; Aufsess, 1941; Spofford, 1945; Chuang, 1947; Ford, 1949). Presence of mesoderm in the neural plate is an interesting developmental problem. During normal gastrulation this region is at first underlaid by the future anterior part of the archenteric roof which exerts a neuralizing inductive influence. It is only later that the posterior part of the notochord with its mesodermalizing influence comes to lie under it. According to Eyal-Giladi (1954), who worked on gastrula stages of the Axolotl, even a short and transient contact of the invaginating archenteric roof with the overlying ectoderm produces archencephalic induction in the latter. It is therefore relevant to ask whether the posterior part of the neural plate does or does not pass through a phase of neuralization before assuming mesodermal properties. This specific question has not been investigated although a number of workers have studied the determination, differentition capacities or inductive properties of the caudal portion of the neural plate in amphibians (Bytinski-Salz, 1931; Bijtel, 1936, 1958; Chuang, 1947; Nakamura, 1947; Spofford, 1948; Smithberg, 1954). Spofford (1948) demonstrated that in Ambystoma mexicanum neurulae the tail notochord induces the overlying ectoderm to acquire mesodermal properties. He replaced the posterior part of the neural plate by a piece of competent ectoderm which itself had never been subjected to the influence of a neural inductor. This technique could demonstrate that, under experimental conditions, the so-called transformation or mesodermalization need not be preceded by activation or neuralization. These results, however, do not show whether this is also true during normal embryogenesis.
Nouvelles observations sur les facteurs qui contrôlent l’érythropoïèse in vitro
Authors: Salvatorelli Germano 
Published: April 2021

ABSTRACT
Nous avons démontré précédemment que l’association de fragments de foie embryonnaire à des expiants de moelle osseuse de poulet s’est montrée très favorable au maintien du processus de l’érythropoïèse médullaire. Dans ces conditions expérimentales en effet, même après 15 jours de culture la structure et la composition cellulaire des expiants sont comparables à celles existant in vivo. En particulier, en ce qui concerne la série rouge tous les stades de la différencia-tion cellulaire depuis la cellule souche jusqu’à la cellule sanguine mûre sont présents dans nos expiants et dans des proportions comparables à celles qu’on retrouve dans la moelle osseuse normale.
The formation of somites in Xenopus
Authors: Hamilton Louie 
Published: April 2021

ABSTRACT
The cell movements and contacts in somite formation in Xenopus are unusual. The vertebrate somite as seen in section is traditionally described as a rosette and is formed by pinching off a group of cells from the paraxial mesoderm; these cells then increase intercellular contacts. Typical rosettes with cells radiating from the myocoel may be seen in the Axolotl (Fig. 1 A). Not all the cells of a rosette have the same fate. The lateral ones become dermis and spread out under the epidermis forming a continuous sheet with their counterparts from neighbouring somites. The majority of the somitic cells, which are myotomal, will elongate antero-posteriorly and fuse end to end with other cells of the same somite (Przybylski & Blumberg, 1966; Riabova, 1966). In this way myotubes are formed which stretch from one end of the somite to the other and obliterate the myocoel. Somites are formed in an orderly anterior-posterior succession.
Histogenesis of lymphoid organs in larvae of the South African clawed toad, Xenopus laevis (Daudin)
Authors: Manning Margaret J. , Horton John D. 
Published: April 2021

ABSTRACT
Before embarking on a study of the lymphoid system of an amphibian larva, it is necessary to realize that lymphoid tissue may occur in many organs of the body and that in all immature vertebrates and in adult poikilotherms separation of lymphoid tissue from myeloid tissue is incomplete (Yoffey, 1960). Jordan (1938) reviewed the early work on the haemopoietic tissues of Amphibia.
Le rôle du mésoderme somitique dans la morphogenèse précoce des membres de l’embryon de Poulet
Authors: Pinot Par Madeleine 
Published: April 2021

ABSTRACT
La morphogenèse des membres a fait l’objet de nombreux travaux chez l’embryon de Poulet. Les recherches récentes concernent surtout les processus intervenant après l’apparition de l’ébauche du membre, et conduisant à sa morphologie définitive. Le premier stade de développement du membre consiste en une condensation localisée du mésoderme de la somatopleure. Par la suite seulement, l’ectoderme sus-jacent acquiert un aspect morphologique particulier: une crête épaissie à l’extrémité distale. Les causes de la condensation initiale du mésoderme ne sont pas connues. Le rôle déterminant du constituant mésodermique comme initiateur du développement du membre a été clairement mis en évidence par Kieny (1959, 1960). Le constituant mésodermique isolé, greffé sous l’ectoderme du flanc, peut induire la formation d’une crête apicale dans l’ectoderme sus-jacent, et provoquer ainsi le développement d’un membre surnuméraire. A quel moment et sous quelles influences le mésoderme acquiert-il cette propriété ?
The inhibitory effect of tetracycline on osteogenesis in organ culture
Authors: Kaitila Ilkka , Wartiovaara Jorma , Laitinen Ossi , Saxén Lauri 
Published: April 2021

ABSTRACT
Two characteristics of the tetracycline-group antibiotics have recently focused the special attention of teratologists: these drugs are known to pass readily across the placental ‘barrier’ (Charles, 1954; Frost & Villanueva, 1960; Gibbons & Reichelderfer, 1960; Hughes, Lee & Flood, 1965; Simpson, Burnette & Bawden, 1967), and they are incorporated into the foetal skeleton, where they may remain for long periods and can be detected owing to their brilliant fluorescence (Rail, Loo, Lane & Kelly, 1957; Milch, Rail & Tobie, 1957, 1958; Bevelander, Rolle & Cohlan, 1961; Urist & Ibsen, 1963; Michelson, 1964). The question of whether they exert a harmful effect on bone formation and mineralization in mammals, however, is still a matter of controversy. There is no doubt that tetracycline interferes with mineralization of the skeletal tissue in certain lower vertebrates (Bevelander, Goldberg & Nakahara, 1960; Bevelander & Cohlan, 1962), and prevents calcification of mammalian bones in organ culture (Saxén, 1966a, b). Reports of in vivo studies in mammalian species have yielded more confusing results.
The role of the zona pellucida in the development of mouse eggs in vivo
Authors: Modlński Jacek A. 
Published: April 2021

ABSTRACT
Up to the present time the function and significance of the zona pellucida in the development of mammalian eggs has not been fully explained. Zona-free mouse eggs will develop in vitro from the 2-cell stage, or later, up to the blastocyst stage (Tarkowski, 1961; Mintz, 1962; Gwatkin, 1963). Single blastomeres isolated at the 2-cell (Mulnard, 1965), 4- and 8-cell stage (Tarkowski & Wrób-lewska, 1967) will also develop in vitro up to the blastocyst stage. Similar experiments on development in vitro of 1- and 2-cell rabbit eggs (Edwards, 1964) showed that in this species also cleavage can occur when the zona pellucida is absent, although the blastomeres exhibit a tendency to fall away from each other.
The role of neurohumours in early embryogenesis
Authors: Buznikov G. A. , Kost A. N. , Kucherova N. F. , Mndzhoyan A. L. , Suvorov N. N. , Berdysheva L. V. 
Published: April 2021

ABSTRACT
In previous papers (Buznikov, Chudakova & Zvezdina, 1964; Buznikov, Chudakova, Berdysheva & Vyazmina, 1968) we reported that fertilized eggs of the sea-urchin Strongylocentrotus dröbachiensis synthesized a number of neurohumours, such as serotonin (5-hydroxytryptamine, 5-HT), acetylcholine (ACh), adrenalin (A), noradrenalin (NA) and dopamine. Synthesis of 5-HT was also demonstrated in the fertilized eggs of the loach Misgurnus fossilis and some marine Invertebrata. In experiments with sea-urchin embryos we were able to trace regular changes in the level of 5-HT, ACh, A and NA, related to the first cleavage divisions. This early onset of neurohumour synthesis, as well as regular changes in their level, suggests their direct involvement in the regulation of the first cleavage divisions.
Cleavage rate of mouse embryos in vivo and in vitro
Authors: Bowman Patricia , McLaren Anne 
Published: April 2021

ABSTRACT
Mouse embryos (Q strain) developing in vivo from the 2-cell to the blastocyst stage showed a constant cell doubling time of about 10 h. Embryos cultured in vitro over the same period showed a rate of cleavage which was initially almost as great as in the reproductive tract, but subsequently declined to give a doubling time of about 24 h. Addition of oestrogen to the culture medium increased the diameter of blastocysts but did not increase cell number.
Thyroid hormone effects on chick scale morphogenesis and keratinization
Authors: Lawrenz Nancy K. , Johnson Leland G. 
Published: April 2021

ABSTRACT
The effects of thiourea injection on scale development were studied in New Hampshire Red × White Leghorn Cross chick embryos.
Normal morphogenesis and keratinization of scales were significantly delayed in thioureatreated specimens. Subsequent thyroxine injection resulted in normal or even precocious scale development.
The thyroid hormone responsiveness of scale development is discussed in relation to other studies of endocrine effects on differentiation of skin and skin derivatives.
Effect of temperature differentials upon reconstitution of embryonic primordia in Ambystoma
Authors: Piatt Jean 
Published: April 2021

ABSTRACT
Eggs of Ambystoma maculatum in early stages of development were separated into two groups and maintained at 5 and 14 °C, respectively. In one series of animals comprising both temperature groups, the right otic vesicle was extirpated at stage 27. In another series the right forelimb disc was extirpated at stage 30. Following operation, animals of both groups were kept at 18 °C. Frequency and extent of reconstitution were compared between the two temperature groups.
The 5° group was superior to the 14° group in the number of ears and forelimbs reconstituted. The extent of ear reconstitution and the initial quality of forelimb reconstitution were also superior in the 5° group. Statistical analysis of the data indicates that the difference between the two temperature groups is highly significant in both series.
It is concluded that a slower pre-operative rate of development, caused by hypothermia, enhances the regenerative capacity of both ear and forelimb fields in the salamander embryo.
Influence de la thiourée sur la charge en glycogène du foie de l’embryon de poulet
Authors: Daugéras Nicole 
Published: April 2021

ABSTRACT

Influence of thiourea on the glycogen content of the liver of the chick embryo
In the developing chick embryo, liver glycogen appears on the sixth day of incubation. The glycogen content increases from the sixth day, but decreases on the twelfth day before increasing again.
This decrease on day 12 might be related to the onset of thyroid activity, which would be responsible for an increased rate of utilization of the substrates.
An antithyroid drug, thiourea, has been injected on day 6·0. The liver glycogen concentration of the thiourea-treated chick embryos was determined from the tenth to the fifteenth days and compared with that of the control embryos.
Etude de l’origine et de la différenciation du pharynx au cours de la régénération chez l’annélide Eisenia fœtida
Authors: Chapron Claude 
Published: April 2021

ABSTRACT
Study of the origin and differentiation of the pharynx during regeneration in Eisenia foetida (Annelida)
A study has been made in Eisenia foetida of the regeneration of the pharynx, a complex organ with an epithelium, muscular fibres and glandular cells. We have investigated the origin of these constituents and analysed the ultrastructural aspects of their differentiation.
The epithelium derives from oesophageal endoderm and not from stomodeal ectoderm as during embryogenesis. Muscular fibres form from myoblasts which result from dedifferentiation of the muscular coats of the alimentary canal and dorsal vessel. Glandular elements come from the peritoneal coat of the dorsal vessel, and in particular from stem cells of chlora-gogen cells.
Each of these cellular classes synthesizes specific substances but this differentiation is always preceded by a period in which all the three cell types undergo similar modifications. They change shape to the adult form, then the electron density of the cytoplasm diminishes considerably.
A general hypothesis is formulated to try to explain these preliminary phenomena of differentiation. An inducer would determine a modification in the cell surface which would become permeable to enzymes. These enzymes would be able to hydrolyse the ‘coat’ of inactive mRNA pre-existing in the cells. Then the mRNA would control the synthesis of specific proteins.
The analysis of spatial distributions in mixed cell populations: a statistical method for detecting sorting out
Authors: Elton R. A. , Tickle C. A. 
Published: April 2021

ABSTRACT
This work presents a quantitative measure, α, of the degree of segregation of two cell types in sections of aggregates, and some results obtained with the measure relating to ‘sorting out’. The method is designed particularly for the case where labelling of one type of cell is incomplete, and the importance of this effect is assessed. Possible problems in formulating such a model are discussed. The measure α is compared with methods used in investigations of segregation in plant communities. Segregation of chick heart and limb-bud cells in mixed aggregates has been analysed using α. In control aggregates of mixtures of labelled and unlabelled cells of one type, α is near to its random value of 1, and we suggest that the departure from random can be adequately accounted for by cell division. In mixed aggregates, significant segregation is consistently found, even in aggregates formed after 2 and 4 h. Both disaggregation procedures (EDTA, trypsin or trypsin+ EDTA) and reaggregation methods (reciprocating or gyratory shaker) are found to have an effect on the degree of segregation. Possible reasons for these findings are discussed. Positioning of the cells relative to the outside of aggregates is also investigated for some of the aggregates.
Stimulation of haem synthesis by erythropoietin in mouse yolk-sac-stage embryonic cells
Authors: Bateman A. E. , Cole R. J. 
Published: April 2021

ABSTRACT
Cultures of disaggregated cells from mouse embryos at the stage of yolk-sac erythropoiesis have been used to test sensitivity of primary erythroid cells to erythropoietin, the hormone which controls adult red cell production. Synthesis of haem was stimulated by 89% in cells of 8-day embryos, 23 % in cells of 9-day embryos and by 19% in peripheral nucleated blood cells of 12-day embryos. Differentiation of primary embryonic erythroid cells may therefore be controlled by erythropoietin in situ. The haem precursor δ-aminolaevulinic acid (ALA) did not stimulate haem synthesis under similar conditions.