bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vitronectin regulates Sonic hedgehog activity during cerebellum development through CREB phosphorylation
Authors: Pons Sebastián , Luis Trejo José , Ramón Martínez-Morales Juan , Martí Elisa 
Published: April 2021

ABSTRACT
During development of the cerebellum, Sonic hedgehog (SHH) is expressed in migrating and settled Purkinje neurons and is directly responsible for proliferation of granule cell precursors in the external germinal layer. We have previously demonstrated that SHH interacts with vitronectin in the differentiation of spinal motor neurons. Here, we analysed whether similar interactions between SHH and extracellular matrix glycoproteins regulate subsequent steps of granule cell development. Laminins and their integrin receptor subunit α6 accumulate in the outer most external germinal layer where proliferation of granule cell precursors is maximal. Consistent with this expression pattern, laminin significantly increases SHH-induced proliferation in primary cultures of cerebellar granule cells. Vitronectin and its integrin receptor subunits αv are expressed in the inner part of the external germinal layer where granule cell precursors exit the cell cycle and commence differentiation. In cultures, vitronectin is able to overcome SHH-induced proliferation, thus allowing granule cell differentiation. Our studies indicate that the pathway in granule cell precursors responsible for the conversion of a proliferative SHH-mediated response to a differentiation signal depends on CREB. Vitronectin stimulates phosphorylation of cyclic-AMP responsive element-binding protein (CREB), and over-expression of CREB is sufficient to induce granule cell differentiation in the presence of SHH. Taken together, these data suggest that granule neuron differentiation is regulated by the vitronectin-induced phosphorylation of CREB, a critical event that terminates SHH-mediated proliferation and permits the differentiation program to proceed in these cells.
Overexpression of Hoxc13 in differentiating keratinocytes results in downregulation of a novel hair keratin gene cluster and alopecia
Authors: Tkatchenko Andrei V. , Visconti Richard P. , Shang Lijuan , Papenbrock Thomas , Pruett Nathanael D. , Ito Tatsuya , Ogawa Makio , Awgulewitsch Alexander 
Published: April 2021

ABSTRACTStudying the roles of Hox genes in normal and pathological development of skin and hair requires identification of downstream target genes in genetically defined animal models. We show that transgenic mice overexpressing Hoxc13 in differentiating keratinocytes of hair follicles develop alopecia, accompanied by a progressive pathological skin condition that resembles ichthyosis. Large-scale analysis of differential gene expression in postnatal skin of these mice identified 16 previously unknown and 13 known genes as presumptive Hoxc13 targets. The majority of these targets are downregulated and belong to a subgroup of genes that encode hair-specific keratin-associated proteins (KAPs). Genomic mapping using a mouse hamster radiation hybrid panel showed these genes to reside in a novel KAP gene cluster on mouse chromosome 16 in a region of conserved linkage with human chromosome 21q22.11. Furthermore, data obtained by Hoxc13/lacZ reporter gene analysis in mice that overexpress Hoxc13 suggest negative autoregulatory feedback control of Hoxc13 expression levels, thus providing an entry point for elucidating currently unknown mechanisms that are required for regulating quantitative levels of Hox gene expression. Combined, these results provide a framework for understanding molecular mechanisms of Hoxc13 function in hair growth and development.
The retinoic acid signaling pathway regulates anterior/posterior patterning in the nerve cord and pharynx of amphioxus, a chordate lacking neural crest
Authors: Escriva Hector , Holland Nicholas D. , Gronemeyer Hinrich , Laudet Vincent , Holland Linda Z. 
Published: April 2021

Amphioxus, the closest living invertebrate relative of the vertebrates, has a notochord, segmental axial musculature, pharyngeal gill slits and dorsal hollow nerve cord, but lacks neural crest. In amphioxus, as in vertebrates, exogenous retinoic acid (RA) posteriorizes the embryo. The mouth and gill slits never form, AmphiPax1, which is normally downregulated where gill slits form, remains upregulated and AmphiHox1 expression shifts anteriorly in the nerve cord. To dissect the role of RA signaling in patterning chordate embryos, we have cloned the single retinoic acid receptor (AmphiRAR), retinoid X receptor (AmphiRXR) and an orphan receptor (AmphiTR2/4) from amphioxus. AmphiTR2/4 inhibits AmphiRAR-AmphiRXR-mediated transactivation in the presence of RA by competing for DR5 or IR7 retinoic acid response elements (RAREs). The 5′ untranslated region of AmphiTR2/4 contains an IR7 element, suggesting possible auto- and RA-regulation. The patterns of AmphiTR2/4 and AmphiRAR expression during embryogenesis are largely complementary: AmphiTR2/4 is strongly expressed in the cerebral vesicle (homologous to the diencephalon plus anterior midbrain), while AmphiRAR expression is high in the equivalent of the hindbrain and spinal cord. Similarly, while AmphiTR2/4 is expressed most strongly in the anterior and posterior thirds of the endoderm, the highest AmphiRAR expression is in the middle third. Expression of AmphiRAR is upregulated by exogenous RA and completely downregulated by the RA antagonist BMS009. Moreover, BMS009 expands the pharynx posteriorly; the first three gill slit primordia are elongated and shifted posteriorly, but do not penetrate, and additional, non-penetrating gill slit primordia are induced. Thus, in an organism without neural crest, initiation and penetration of gill slits appear to be separate events mediated by distinct levels of RA signaling in the pharyngeal endoderm. Although these compounds have little effect on levels of AmphiTR2/4 expression, RA shifts pharyngeal expression of AmphiTR2/4 anteriorly, while BMS009 extends it posteriorly. Collectively, our results suggest a model for anteroposterior patterning of the amphioxus nerve cord and pharynx, which is probably applicable to vertebrates as well, in which a low anterior level of AmphiRAR (caused, at least in part, by competitive inhibition by AmphiTR2/4) is necessary for patterning the forebrain and formation of gill slits, the posterior extent of both being set by a sharp increase in the level of AmphiRAR.Supplemental data available on-line
The migration of cerebellar rhombic lip derivatives
Authors: Gilthorpe Jonathan D. , Papantoniou Elli-Kalliopi , Chédotal Alain , Lumsden Andrew , Wingate Richard J. T. 
Published: April 2021

We have used cell labelling, co-culture and time-lapse confocal microscopy to investigate tangential neuronal migration from the rhombic lip. Cerebellar rhombic lip derivatives demonstrate a temporal organisation with respect to their morphology and response to migration cues. Early born cells, which migrate into ventral rhombomere 1, have a single long leading process that turns at the midline and becomes an axon. Later born granule cell precursors also migrate ventrally but halt at the lateral edge of the cerebellum, correlating with a loss of sensitivity to netrin 1 and expression of Robo2. The rhombic lip and ventral midline express Slit2 and both early and late migrants are repelled by sources of Slit2 in co-culture. These studies reveal an intimate relationship between birthdate, response to migration cues and neuronal fate in an identified population of migratory cells. The use of axons in navigating cell movement suggests that tangential migration is an elaboration of the normal process of axon extension.Movies available on-line
Action of heart and liver RNA on the differentiation of segments of chick blastoderms
Authors: Butros Joseph 
Published: April 2021

ABSTRACT
RNA was prepared from chick embryo hearts and livers respectively by a modified procedure of Kirby. Post-nodal fragments, obtained by transecting definite streak or heard process blastoderms at 0·2 mm. posterior to the primitive pit and trimmed to 1 × 1 mm.2, were cultured for 8 days on a basic medium containing TC 199, whole egg suspension, embryo extract, agar and penicillin. Half of the cultured pieces received one drop of either RNA twice daily; the other pieces were given a drop of the solvent. Heart RNA promoted twitching in localized areas. Differentiation of myoblasts and nerve fibres was enhanced. Liver RNA stimulated the folding of the entoderm layer and modification of the cells to columnar, goblet form. The results are discussed in the fight of current literature on transformation in cells of higher organisms.
A histochemical study of sex inversion produced by estradiol in chick embryos
Authors: Narbaitz Roberto , Teitelman Gladys 
Published: April 2021

ABSTRACT
Forty-five White Leghorn chick embryos were injected on the 4th incubation day with 0·1 mg. estradiol benzoate. Some of them were dissected on the 9th day, their gonads being studied with the digitonine histochemical technique for cholesterol. The rest were dissected either on the 10 th or on the 13th day and used for Δ5-β-hydroxysteroid dehydrogenase histochemical determination. In both groups genetic sex was determined by a chromosome study made on liver cells. The gonads belonging to male embryos contained interstitial cells with cholesterol and enzymatic activity comparable in amount and distribution to those found in normal ovaries. The gonads of female embryos contained apparently normal enzymatic activity but gave negative results with the digitonine technique. Additional experiments were made in order to analyse this fact further. The differentiation, in male embryos, of estrogen-producing cells through the action of estrogens is inferred from our results, and this is explained by supposing that in these cells differentiation is normally inhibited in males by some kind of genetically controlled factor. The action of estradiol would consist in counteracting this inhibition.
Germ-cell transfer and sex ratio in Xenopus laevis
Authors: Blackler A. W. 
Published: April 2021

ABSTRACT
Primordial germ cells have been grafted from one neurula to another in Xenopus laevis by means of the technique of Blackler & Fischberg (1961). A nuclear marker enabled tadpoles derived from graft material to be identified, after surviving animals had been raised to sexual maturity and bred.
The examination of sex ratio in groups of tadpoles has revealed that male gonocytes were sex-reversed in ovaries and vice versa, with eventual production of functional gametes. About half of all transfers made involved grafts between neurulae of unlike sex. It is evident that females of genetic constitution WW are viable in this toad, as well as sperm of constitution W.
The nature of the earliest spontaneous activity of the chick embryo
Authors: Alconero Barbara B. 
Published: April 2021

ABSTRACT
Two types of grafts from 3-day chick embryos were grown on the chorioallantoic membrane of a 9-day-old chick embryo: six isolated somites, 14−20; and six somites 14−20, with adjacent spinal cord. The activity of these noninnervated and innervated grafts was observed during their growth on the membrane. No activity was observed at any time in the fifteen grafts of six somites grafted without spinal cord; but spontaneous twitching could be observed in twenty out of thirty-three grafts which contained sections of the spinal cord. Histological examination confirmed that the twenty active transplants each contained a segment of spinal cord, and large nerve fibers could be traced to the muscle tissue in the grafts. The failure of the other thirteen grafts to show contraction is accounted for either by the absence of well differentiated muscles or by the absence of nerves invading them. The muscle of the non-innervated, inactive pieces showed the same amount of differentiation as that of the innervated active grafts. The activity observed in the innervated muscle tissue shows three different patterns : regular, with a periodicity similar to that of the intact embryo ; irregular and isolated twitches, i.e. less than six twitches in the 10-min. observation period. It is concluded that the spontaneous motility of muscle developing on the chorioallantoic membrane is neurogenic and not myogenic. This finding supports the view that the spontaneous motility observed in vivo is neurogenic from its beginning.
An electrophoretic analysis of proteins of cellular sap in normal and hybrid frog embryos
Authors: Shore Richard E. 
Published: April 2021

ABSTRACT
The degree of abnormality found in amphibian interspecies hybrids varies from one species pair to another, and may also differ between reciprocal matings (Moore, 1955). Although some general ideas exist about the mechanism of arrest and the course of abnormal development, our knowledge is far from complete. One major aspect of development which has received attention only at the gross level is the nature and diversity of those proteins which compose the greater part of the cytoplasmic sap, the ‘soluble’ proteins in the sense of this paper (see below). This paper reports the results of studies on the development of normal (Ranapipiens) and gastrula-arrested hybrid (R. pipiens ♀×R. sylvatica ♁) amphibian embryos.
The development of the spinal cord examined by autoradiography
Authors: Martin Alexander , Langman Jan 
Published: April 2021

ABSTRACT
The wall of a recently closed neural tube is generally considered to consist of three concentric layers. Surrounding the lumen is found the ependymal zone characterized by large pale cells known as the germinal cells of His (1889). These cells are believed to give rise to the neuroblasts and some of the spongioblasts. Soon after formation the neuroblasts move away from the lumen to enter a densely packed nucleated zone referred to as the mantle layer. This layer consisting of spongioblasts and neuroblasts ultimately gives rise to the gray matter of the spinal cord. The outermost layer, known as the marginal layer, contains the fibres of the developing neuroblasts and later forms the white matter.
Action de la vitamine et de l’antivitamine B6 sur le développement de l’embryon de poulet
Authors: Conti par G. , Milio G. 
Published: April 2021

ABSTRACT
Le groupe des vitamines B6 comporte trois substances distinctes: la pyridoxine, qui est un dérivé de la pyridine; la pyridoxamine et le pyridoxal qui dérivent de la pyridoxine. Tous les organismes utilisent le pyridoxal; certains utilisent également la pyridoxine, d’autres la pyridoxamine, d’autres enfin (le rat, par exemple), utilisent les trois substances. Cette constatation a fait penser que la substance réellement active serait le pyridoxal, et que seuls certains organismes pourraient former de la pyridoxine, de la pyridoxamine ou les deux substances. De plus, le pyridoxal, sous forme d’ester phosphorique (pyridoxalphosphate) déploie une action importante comme co-enzyme dans de nombreux complexes enzymatiques actifs dans le métabolisme des acides aminés; parmi ces complexes, il faut citer les transaminases, les aminoacide-décarboxylases, les déshydratases, les désulfhydrases, les racémases, l’histaminase et les tryptophanases.
Action de la vitamine et de l’antivitamine B6 sur le myocarde d’embryon de poulet cultivé in vitro
Authors: Conti par G. , Milio G. 
Published: April 2021

ABSTRACT
Nous avons essayé les effets de la vitamine (PX) et de l’antivitamine B6 (DPX) sur des organes d’embryons de poulet cultivés in vitro; et cela dans le but de voir si l’action inhibitrice de la DPX se manifestait sur la croissance in vitro des organes et si cette action inhibitrice éventuelle pouvait être annulée, ou du moins partiellement empêchée, par l’adjonction simultanée de la vitamine B6 au milieu de culture.
The susceptibility of the offspring of alloxan-diabetic mice to a teratogen
Authors: Takano Kiichi , Tanimura Takashi , Nishimura Hideo 
Published: April 2021

ABSTRACT
Maternal diabetes, or pre-diabetes, has been considered as a possible factor in the aetiology of human congenital malformations by several investigators (De Costa, 1955; Hoet et al., 1960; Hiekkala & Koskenoja, 1961; Nicholson & De Maria, 1963; Pederson et al., 1964; Lenz & Maier, 1964). However, a few authors have reported no increase in the incidence of anomalies among infants of diabetic women (Given et al., 1950; Hall & Tillman, 1951; Rubin & Murphy, 1958). Alloxan-induced maternal diabetes in animals has also been studied, and an increase of stillbirth and foetal macrosomia has usually been recognized (Davis et al., 1947; Lindan & Morgans, 1950; Bartelheimer & Kloos, 1952; Angervall, 1959; Solomon, 1959; Kim et al., 1960; Loveeia/., 1960; Koskenoja 1961). The incidence of malformations, however, was not increased in most cases, the exception being those reported by Ross & Spector (1952), Fujimoto et al. (1958) and Watanabe & Ingalls (1963).
Différenciation des épithéliums du tube digestif in vitro
Authors: Soriano par Luis 
Published: April 2021

ABSTRACT
Nous avons démontré que l’épithelium de l’œsophage de l’embryon de Souris, prélevé à 12 jours de gestation et cultivé in vitro, montre une différenciation accélérée par rapport à celle observée dans le développement normal (Soriano et coll., 1964). Ces résultats ont été obtenus en utilisant une modification de la méthode de Trowell (1954).
The maturation of cortisone-treated embryonic duodenum in vitro. II. The striated border
Authors: Hayes Raymond L. 
Published: April 2021

ABSTRACT
Regulation of the morphological and physiological maturation of embryonic duodenal mucosa by adrenocorticoid hormones has been demonstrated with a variety of techniques. Single injections of cortisone acetate (Moog & Richardson, 1955; Moog & Thomas, 1957); multiple daily administrations of cortisone (Moog & Ford, 1957; Moog, 1959); or in vitro maintenance of duodenal fragments with adrenal steroids (Moog & Nehari, 1954; Moog & Kirsch, 1955) all accelerate morphogenesis and the onset of alkaline phosphatase activity in this tissue.
Obtention expérimentale de Cyclopes parfaits par microchirurgie chez l’embryon de Poulet. Etude histologique
Authors: Schowing par Jean 
Published: April 2021

ABSTRACT
La cyclopie parfaite peut être définie comme une anomalie de développement caractérisée par la présence d’un seul œil situé au milieu de la face, dans la position normalement occupée par le nez.
Experimental studies on the columella-capsular interrelationship in the turtle Chelydra serpentina
Authors: Toerien M. J. 
Published: April 2021

ABSTRACT
The reciprocal effect of two neighbouring structures of different origins on each other during development is of considerable interest to the embryologist. Such a relationship exists between the columella auris and the auditory capsule in the vicinity of the fenestra ovalis. This particular relationship, in addition, embraces an aspect of fundamental importance to the morphologist viz. the possible derivation of part of the columella from the capsule.
Action of rat submaxillary gland extracts on neural tube growth in organ culture
Authors: Adler Ruben , Narbaitz Roberto 
Published: April 2021

ABSTRACT
Organ cultures of portions of chick embryo neural tube together with surrounding tissues, were made in order to test the action of other tissues in nearby culture, and of organ extracts added to the medium. Expiants four somites long, dissected from embryos at Stages 11 to 13 (Hamburger & Hamilton), developed and differentiated normally in vitro. Pieces of limb bud from older embryos, added to the expiants, fused with them and differentiated as usual. The addition of the limb bud pieces did not influence the size of the cultured neural tube. The addition of submaxillary gland extract to the medium produced during the first 6 hours of culture a dorsal opening of the neural tubes and, thereafter, an exuberant and irregular growth of them. Other organ extracts, purified ‘nerve growth factor’ and iodine treated submaxillary gland extract failed to produce the same action. The presence in submaxillary extracts of an active factor independent of ‘nerve growth factor’ and protease activity is deduced from our results.
Effet de la fécondation sur 1’utrastructure du cytoplasme périphérique de l’œuf de Xenopus laevis
Authors: Van Gansen P. 
Published: April 2021

ABSTRACT
Cet article fait suite à celui où nous avons décrit et discuté les modifications provoquées par la maturation dans l’ultrastructure de l’œuf ovarien (Van Gansen, 1966). Nous y avions indiqué dans quelles perspectives ce travail était entrepris (Brachet, 1964, 1965b).
pH-dependence of the inducing activity of lithium ion
Authors: Masui Yoshio 
Published: April 2021

ABSTRACT
Using ectodermal explants isolated from early gastrulae of Triturus pyrrhogaster, the inductive effect of lithium ion was examined at different pH’s and under the influence of neuralizing substances. Treatment with 0·06 M-LiCl brought about the differentiation of axial mesoderm together with neuralization and the production of yolk-laden tissues which sometimes formed gut-like structures. The neuralization and mesodermalization were brought about with minimum frequency by treatment carried out near pH 5·0, but they increased when treatment was carried out at alkaline or acid pH. On the contrary, the production of yolk-laden tissue was brought about with maximum frequency by the treatment near pH 6·0 and decreased as the pH at which the treatment was done was raised or lowered. Treatment with alkaline NaCl solution carried out after the treatment with LiCl solution was found to be effective in enhancement of mesodermalization, but the same treatment carried out before the LiCl treatment had no effect on incidence of mesodermalization. Treatment with LiCl solution containing calcium or magnesium ion which alone have a weak neuralizing action brought about considerable increase of the mesodermalization near neutral pH. On the other hand, zinc and ammonium ions and urea, which act as strong neuralizing agents, had an inhibitory effect or mesodermalization by lithium ion. The results are discussed in relation to the significance of the influence of pH and neuralizing agents on the mesodermalizing effect of lithium ion, and it is suggested that these agents sensitize the mesodermal competence of the ectoderm to the inductive action of the ion, resulting in enhancement of the mesodermalization.