bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pericardin, aDrosophilatype IV collagen-like protein is involved in the morphogenesis and maintenance of the heart epithelium during dorsal ectoderm closure
Authors: Chartier Aymeric , Zaffran Stéphane , Astier Martine , Sémériva Michel , Gratecos Danielle 
Published: April 2021

The steps that lead to the formation of a single primitive heart tube are highly conserved in vertebrate and invertebrate embryos. Concerted migration of the two lateral cardiogenic regions of the mesoderm and endoderm (or ectoderm in invertebrates) is required for their fusion at the midline of the embryo. Morphogenetic signals are involved in this process and the extracellular matrix has been proposed to serve as a link between the two layers of cells.Pericardin (Prc), a novel Drosophila extracellular matrix protein is a good candidate to participate in heart tube formation. The protein has the hallmarks of a type IV collagen α-chain and is mainly expressed in the pericardial cells at the onset of dorsal closure. As dorsal closure progresses, Pericardin expression becomes concentrated at the basal surface of the cardioblasts and around the pericardial cells, in close proximity to the dorsal ectoderm. Pericardin is absent from the lumen of the dorsal vessel.Genetic evidence suggests that Prc promotes the proper migration and alignment of heart cells. Df(3)vin6 embryos, as well as embryos in which prc has been silenced via RNAi, exhibit similar and significant defects in the formation of the heart epithelium. In these embryos, the heart epithelium appears disorganized during its migration to the dorsal midline. By the end of embryonic development, cardial and pericardial cells are misaligned such that small clusters of both cell types appear in the heart; these clusters of cells are associated with holes in the walls of the heart. A prc transgene can partially rescue each of these phenotypes, suggesting that prc regulates these events. Our results support, for the first time, the function of a collagen-like protein in the coordinated migration of dorsal ectoderm and heart cells.
A mitogen gradient of dorsal midline Wnts organizes growth in the CNS
Authors: Megason Sean G. , McMahon Andrew P. 
Published: April 2021

Cell cycle progression and exit must be precisely patterned during development to generate tissues of the correct size, shape and symmetry. Here we present evidence that dorsal-ventral growth of the developing spinal cord is regulated by a Wnt mitogen gradient. Wnt signaling through the β-catenin/TCF pathway positively regulates cell cycle progression and negatively regulates cell cycle exit of spinal neural precursors in part through transcriptional regulation of cyclin D1 and cyclin D2. Wnts expressed at the dorsal midline of the spinal cord, Wnt1 and Wnt3a, have mitogenic activity while more broadly expressed Wnts do not. We present several lines of evidence suggesting that dorsal midline Wnts form a dorsal to ventral concentration gradient. A growth gradient that correlates with the predicted gradient of mitogenic Wnts emerges as the neural tube grows with the proliferation rate highest dorsally and the differentiation rate highest ventrally. These data are rationalized in a ‘mitogen gradient model’ that explains how proliferation and differentiation can be patterned across a growing field of cells. Computer modeling demonstrates this model is a robust and self-regulating mechanism for patterning cell cycle regulation in a growing tissue.Supplemental data available on-line
Some effects of de-afferentation on the developing amphibian nervous system
Authors: Hughes Arthur 
Published: April 2021

ABSTRACTAn adult anuran can still walk or swim if the nerves supplying one or even two limbs are de-afferentated (Gray, 1950). However, in a developing amphibian, a limb at motile stages becomes paralysed when deprived of its sensory input. A sequence of degenerative changes then follow in the cord and in peripheral nerves.
The maturation of cortisone-treated embryonic duodenumin vitro. I. The villus
Authors: Hayes Raymond L. 
Published: April 2021

ABSTRACTMitotic expansion of the mucosa coupled with contraction of intrinsic longitudinal and circular muscle fibers produces previllous ridges on the luminal surface of the embryonic chick duodenum by the thirteenth day of incubation. Subsequently, remodelling by periodic indentation of the mucosal surface yields primitive villi which expand and elongate to form the tall, finger-like projections characterizing the absorptive surface of the mature duodenum (Hilton, 1902; Pap, 1933; Coulombre & Coulombre, 1958).
La régression du mésonéphros chez l’embryon de poulet
Authors: Salzgeber Berthe , Weber Rudolf 
Published: April 2021

ABSTRACTThe regression of the mesonephros in the chick embryo: a study of acid phosphatase and cathepsin activity analysed biochemically, histochemically, and by electron microscopyCathepsin and acid phosphatase activity and total nitrogen were determined in homogenates of mesonephros during growth (at 14 days) and regression (at 21 days). The loss of total nitrogen in this period is as much as 62%. Specific cathepsin activity, expressed as μg casein destroyed per hour per μg total nitrogen, does not change much. The increase of 19·4% observed was not significant. Specific acid phosphatase activity, expressed as 10−3μM phosphate liberated per hour per μg of total nitrogen, increases appreciably during regression. The increase between the 14th and 21st day of incubation is by 114·4%. The absolute levels of cathepsin and acid phosphatase activity are reduced during mesonephric regression by 57·6 % and 24·7 % respectively. Fractionation showed that these enzymes were solubilized during mesonephric regression. The soluble component increased by 28·4% in the case of cathepsin and by 44% in the case of acid phosphatase. Histochemical preparations for acid phosphatase and for non-specific esterases showed that these enzymes were most abundant in the apical part of the cells of the proximal tubules (secretory region with brush border). During regression, the intensity of the acid phosphatase reaction increased and large granules appear in the cells of the tubules, while the connective tissue shows cells with inclusions which could be macrophages. Electron microscopy revealed important changes in the cells of the secretory tubules during regression. On the one hand mitochondria degenerate while on the other hand cytoplasmic inclusions appear, among which are dense membranous bodies reacting positively for acid phosphatase. Mesonephric regression is compared with that of other larval and embryonic organs and its mechanism is discussed.
DNA synthesis and cell proliferation during the formation of deciduomata in mice
Authors: Zhinkin L. N. , Samoshkina N. A. 
Published: April 2021

ABSTRACTAfter ovulation and fertilization of the ovum, several typical changes occur in the uterus of pregnant mammals that are related to the implantation of the blastocyst. The formation of a deciduoma, in which endometrial cells are transformed to decidual ones, is one of these changes (Shelesnyak, 1957, 1960). Apart from an interplay of hormones the formation of a deciduoma is determined by local effects. Loeb (1907) was the first to show this by traumatizing the uterine wall. Since then the role played by hormones, histamine and other agents in the production of deciduomata has been intensively studied (Rigler & Rosenkranz, 1955; Rosenkranz & Rigler, 1958; Shelesnyak, 1959a, b, c; and many others.)
ATP level and respiration of embryos
Authors: Zotin A. I. , Faustov V. S. , Radzinskaja L. I. , Ozernyuk N. D. 
Published: April 2021

ABSTRACTA considerable increase in the rate of oxygen consumption is known to occur during the development of embryos (cf. Needham, 1931; Tuft, 1953; Brachet, 1960; Gustafson, 1965). However, the mechanism of the increase in respiration during embryonic development is still unclear. A certain correlation seems to exist between DNA synthesis and the respiration of embryos (Comita & Whiteleley, 1953; Brachet, 1960). According to Commoner (1964), this correlation is determined by a change in the level of free nucleotides in cells when the rate of DNA synthesis changes. Free nucleotides control cell metabolism, oxidative processes in particular. The ADP+P/ATP ratio is known to control the rate and direction of electron transfer in the respiratory chain (Chance & Hagihara, 1961 ; Klingenberg & Schollmeyer, 1961). The ADP/ATP system is suggested to control the rate of oxidative metabolism in fertilization (Monroy, 1965 a, b;Zotin, Milman & Faustov, 1967).
The tyrosinases of Fundulus heteroclitus at different stages of embryonic development
Authors: Spitz Leslie M. , Burnett Jean B. 
Published: April 2021

ABSTRACT
The study described here was undertaken in an effort to determine whether multiple forms of tyrosinase (EC 1.10.3.1) are present in Fundulus heteroclitus during embryonic development. If they are present, do they appear simultaneously in the course of development and do they continue to be produced and maintained without change during the part of the life cycle when tyrosinase should normally be active? Multiple forms of tyrosinase have been found in Neurospora crassa (Sussman, 1961; Fox & Burnett, 1962; Fling, Horowitz & Heinemann, 1963), mushroom (Smith & Kruger, 1962; Bouchilloux, McMahill & Mason, 1963; Jolley & Mason, 1965), potato (Patil & Zucker, 1965), Drosophila melanogaster (Lewis & Lewis, 1963; Mitchell & Weber, 1965), the eggs of Rana pipiens (Turney, 1964), goldfish (Kim & Tchen, 1962; Kim, Tchen & Chavin, 1962), hamster melanoma (Pomerantz, 1963, 1966) and mouse melanoma (Shimao, 1962; Burnett, Seiler & Brown, 1967). By using a variety of physical and chemical techniques to isolate the tyrosinases present in various organisms and organs, the investigators cited above have been able to establish numerous specific characteristics of the enzymes. Their published data suggest that in both plants and animals there may be variation in the chemical and physical characteristics of individual, enzymically active tyrosinase molecules. Experiments have not yet revealed, however, the metabolic or functional significance of the various forms of an enzyme within a single system. Since the presence of multiple forms of tyrosinase within a single system seems to be universal, it was anticipated from the outset that multiple forms of tyrosinase would be found in the embryos of Fundulus heteroclitus.
Rôle de la compétition osseuse dans la forme des os du toit cranien des Urodèles
Authors: Corsin Par Jacqueline 
Published: April 2021

ABSTRACT
Dès 1932, Troitsky chez les Mammifères, puis, en 1934 Tatarko chez les Téléostéens, ont cherché à étudier les problèmes de compétition osseuse.
Observations sur la différenciation in vitro descellules myéloïdes d’embryons de poulet
Authors: Salvatorelli Germano , Callegarini Carlo , Gulinati Anna Maria , Gardenghi Giuseppe 
Published: April 2021

ABSTRACT
Observations on the differentiation in vitro of erythropoietic cellsof the chick embryo
Erythrocytes differentiated fromexplantsof bone marrow cultured in association with embryonic chick liver by the technique of Wolff & Haffen show certain morphological and biochemical differences from those found in peripheral blood or normal bone marrow. The mean values of cell size and N/P ratio of the erythrocytes from explants are different from those of controls of corresponding age. The globin and haem content of erythrocytes fromexplantsis less than that of controls. The presence of small quantities of RNA in the cytoplasm of expiant erythrocytes is probably related to a retarded maturation process. Haemoglobin synthesised in vitro shows the same electrophoretic behaviour as that of in vivo controls.
Studies on the DNA of Xenopus laevis oocytes
Authors: Hanocq-Quertier J. , Baltus E. , Ficq A. , Brachet J. 
Published: April 2021

ABSTRACT
The existence of substantial amounts of deoxyribonucleic acid (DNA) in the cytoplasm of amphibian eggs is no longer a matter of discussion (review, Brachet, 1957). However, their intracellular distribution, role and origin remain controversial.
Etude autoradiographique du muscle strié en régénération in vivo
Authors: Reznik M. 
Published: April 2021

ABSTRACT
La régénération du muscle strié squelettique est assurée par des éléments plurinucléés qui se différencient ultérieurement en fibres plus ou moins normales. Ces structures plurinucléées peuvent affecter différentes formes. Le plus souvent, ce sont des éléments allongés contenant de nombreux noyaux disposés en file au centre d’un sarcoplasme basophile. On leur a donné des noms divers: myotubes, ‘Muskelschlâuche’, rubans musculaires. D’autres fois, des renflements massués plurinucléés se développent à l’extrémité de fibres indemnes ou de myotubes: ce sont les ‘bourgeons musculaires’. On donne le nom de ‘sarco-blastes ‘à l’ensemble des structures plurinucléées qui constituent un stade intermédiaire dans la régénération des fibres striées adultes.
The evolution of cell lineage in nematodes
Authors: Sommer Ralf J. , Carta Lynn K. , Sternberg Paul W. 
Published: April 2021

ABSTRACT
The invariant development of free-living nematodes combined with the extensive knowledge of Caenorhabditis elegans developmental biology provides an experimental system for an analysis of the evolution of developmental mechanisms. We have collected a number of new nematode species from soil samples. Most are easily cultured and their development can be analyzed at the level of individual cells using techniques standard to Caenorhabditis. So far, we have focused on differences in the development of the vulva among species of the families Rhabditidae and Panagrolaimidae. Preceding vulval development, twelve Pn cells migrate into the ventral cord and divide to produce posterior daughters [Pn.p cells] whose fates vary in a position specific manner [from Pl.p anterior to P12.p posterior]. In C. elegans hermaphrodites, P(3-8).p are tripotent and form an equivalence group. These cells can express either of two vulval fates (1° or 2°) in response to a signal from the anchor cell of the somatic gonad, or a non-vulval fate (3°), resulting in a 3°-3°-2°-Io-2°-3° pattern of cell fates. Evolutionary differences in vulval development include the number of cells in the vulval equivalence group, the number of 1° cells, the number of progeny generated by each vulval precursor cell, and the position of VPCs before morphogenesis. Examples of three Rhabditidae genera have a posterior vulva in the position of P9-P11 ectoblasts. In Cruznema tripartitum, P(5-7).p form the vulva as in Caenorhabditis, but they migrate posteriorly before dividing. Induction occurs after the gonad grows posteriorly to the position of P(5-7).p cells. In two other species, Mesorhabditis sp. PS 1179 and Teratorhabditis palmarum, we have found changes in induction and competence with respect to their presumably more C. elegans-\Wse ancestor. In Mesorhabditis, P(5-7).p form the vulva after migrating to a posterior position. However, the gonad is not required to specify the pattern of cell fates 3°-20-l°-2°-3°. Moreover, the Pn.p cells are not equivalent in their potentials to form the vulva. A regulatory constraint in this family thus forces the same set of precursors to generate the vulva, rather than more appropriately positioned Pn.p cells.
Determination in the Cranial Neural Crest of the Axolotl
Authors: Newth D. R. 
Published: April 2021

ABSTRACT
The neural folds of the Axolotl neurula transplanted homoplastically from the branchial region to the trunk give rise to cartilage in only a small proportion of cases, even where the grafts are allowed to live for very considerable periods. It is concluded that the determination of the skeletogenous component of the neural crest of the young neurula has proceeded some way, but that its cells are not yet rigidly bound to their presumptive fate.
The Effect of Environmental Factors on the Differentiation of the Allantoic Endoderm in Organ Culture
Authors: Fell Honor B. 
Published: April 2021

ABSTRACT
When the allantoic sac of the 4-day embryonic chick was grown as an organ culture in vitro, the endoderm showed great variation in its histological structure. The intact sac formed a closed vesicle lined by columnar epithelium containing many mucus-secreting goblet cells. When everted and grown in a stiff clot, the endoderm formed a tall columnar epithelium with few or no goblet cells. In a soft clot the everted sac became cystic and distended; the endoderm then resembled that of the normal chorio-allantoic membrane. In places the everted endoderm formed papillomatous, secreting outgrowths in both stiff and soft medium. It is suggested that these histological variations represent ‘modulations’ of the endoderm (Weiss).
Growth and differentiation of Tabularía cells in a chemically defined physiological medium
Authors: Burnett Allison L. , Ruffing Faith E. , Zongker June , Necco Anna 
Published: April 2021

ABSTRACT
Although hydroids have proven valuable experimental animals for studies involving polarity and regeneration, they have not been extensively used by chemical embryologists studying control mechanisms in differentiation. Ideally, hydroids should be valuable tools for such a study. Their morpohology is relatively simple since they are diploblastic; their cells achieve a high degree of specialization (cnidoblasts, nerve cells, gland and mucous cells); cell differen-tiation (and morphogenesis) from a reserve stock of interstitial or i-cells is rapid; and many species can be cultured in large numbers under controlled environmental conditions.
The respective roles of mitotic activity and of cell differentiation in Planarian regeneration
Authors: Chandebois Rosine 
Published: April 2021

ABSTRACT
Blastema formation, which is the first step of regeneration in adult Metazoa, is generally considered to be merely an accumulation of undifferentiated cells provided by mitotic activity, which occurs near the wound following amputation. Afterwards, these undifferentiated cells are thought to differentiate rapidly, thus affecting the organization of the regenerate.
Primordial germ cells in normal and transected duck blastoderms
Authors: Rogulska Teresa 
Published: April 2021

ABSTRACT
Suggestive evidence for the extragonadal origin of germ cells in birds was first presented by Swift (1914), who described primordial germ cells in the chick embryo at as early a stage as the primitive streak. According to Swift, primordial germ cells are originally located extra-embryonically in the anterior part of the blastoderm and occupy a crescent-shaped region (‘germinal crescent’) on the boundary between area opaca and area pellucida. Swift also found that primordial germ cells later enter into the blood vessels, circulate together with the blood throughout the whole blastoderm and finally penetrate into the genital ridges, where they become definitive germ cells. Swift’s views have been confirmed in numerous descriptive and experimental investigations. Among the latter, the publications of Willier (1937), Simon (1960) and Dubois (1964a,b, 1965a,b, 1966) merit special attention. Dubois finally proved that the genital ridges exert a strong chemotactic influence on the primordial germ cells.
Auto- und allotypische DifFerenzierungen aus Blastemen der Halterenscheihe von Drosophila melanogaster nach Kultur in vivo
Authors: Gehring W. , Mindek G. , Hadorn E. 
Published: April 2021

ABSTRACT
Von unserer Arbeitsgruppe wurden verschiedene Imaginalscheiben von Drosophila im Abdomen weiblicher Fliegen kultiviert (siehe Arbeiten von Hadorn und Mitarbeitern). Die Hamolymphe des Adultwirtes dient als Kultur-medium, in welchem die Blasteme proliferieren, wobei sie jedoch ihren larvalen Dificrenzierungszustand beibehalten. Die Adultdifferenzierung kann durch Rücktransplantation der Blasteme in eine Wirtslarve, mit der das Implantät die Metamorphose durchläuft, vollendet werden. Die imaginalen Strukturen des Integumentes können anschlieβend aus dem Abdomen des metamorpho-sierten Wirtes herausprapariert und untersucht werden.
The influence of the dental papilla on the development of tooth shape in embryonic mouse tooth germs
Authors: Kollar Edward J. , Baird Grace R. 
Published: April 2021

ABSTRACT
Studies of epithelio-mesenchymal interactions during embryonic organogenesis have led to a number of conclusions regarding (he nature of cellular and tissue differentiation (McLoughlin, 1963; Grobstein, 1967). For example, the importance of both the epithelium and the mesenchyme and the dependence of some systems on a limited number of specific mesenchymal tissues have been pointed out (Hilfer, 1968).
Etude expérimentale de la localisation, par rapport au plan d’amputation, de la source des cellules de régénération mésodermiques chez une Annélide Polychète (Syllis arnica Quatrefages)
Authors: Boilly B. 
Published: April 2021

ABSTRACT
Lors d’une étude histologique (Boilly, 1967a,) et ultrastructurale (Boilly, 1968a, b) des premiers stades de l’histogenèse régénératrice chez Syllis arnica Q. (Annélide Polychète), nous avons été conduits à considérer les tissus anciens (épiderme, épithélium pharyngien, épithéliums cœlomiques, épithélium intestinal) du seul segment contigu à la blessure comme étant à l’origine des trois types de cellules régénératrices (ectodermiques, mésodermiques, endodermiques) assurant l’édification du blastème. Une étude expérimentale a d’ailleurs déjà permis de confirmer le rôle histogénétique des épithéliums cœlomiques (Boilly, 1968c, d) et de l’épithélium intestinal (Boilly, 1968e), au cours de la régénération chez cette Annélide. Cependant, bien que nos observations histologiques et ultrastructurales nous conduisent à constater l’absence de migration intersegmentaire de cellules de régénération, elles ne permettent pas de démontrer la validité de cette hypothèse. Néanmoins, elles suggèrent que, parmi ces cellules, seules celles provenant des épithéliums cœlomiques (cellules régénératrices mésodermiques) seraient susceptibles de présenter un phénomène de migration. En effet, les cellules de régénération issues de l’épiderme sont sur place. D’autre part, celles provenant de l’épithélium pharyngien ou de l’épithelium intestinal ne parviennent jusqu’au niveau de section que sous la forme d’un tissu organisé et non sous celle de cellules libres, même si, au départ, les épithéliums dont elles dérivent sont éloignés du plan d’amputation; en outre, ces cellules ne participent à la régénération de leurs structures qu’au sein des tissus dont elles proviennent, sans jamais s’en échapper. Par contre, les tissus à l’origine des blastocytes mésodermiques sont les seuls à ne pas conserver leur intégrité lors de la mise en place du blastème; en conséquence, un déplacement cellulaire plus ou moins important, analogue à celui décrit chez les Oligochètes, peut être envisagé pour cette catégorie de cellules régénératrices.
Une mutation récessive (pd) déterminant la polydactylie chez Xenopus laevis D. (Batraciens anoures)
Authors: Uehlinger Verena 
Published: April 2021

ABSTRACT
Ce travail a été exécuté dans le cadre de l’analyse génétique des noyaux somatiques chez l’anoure Xenopus laevis D. (Fischberg, 1961; Fischberg & Blackler, 1963; Fischberg et al. 1964).
A new teratogenic agent applied to amphibian embryos
Authors: Levengood W. C. 
Published: April 2021

ABSTRACT
It has been demonstrated that the application of the magnetic probe to Drosophila pupae has a pronounced influence on the pattern of morphogenesis (Levengood, 1966). In addition to morphological abnormalities, there was a retardation of development which continued to occur without further treatment in succeeding generations. A theoretical basis for these disturbances has been proposed (Levengood, 1967).