bluuebunny/crossref_metadata_2025_split huggingface dataset:
Drosophila puckered regulates Fos/Jun levels during follicle cell morphogenesis
Authors: Dobens Leonard L. , Martín-Blanco Enrique , Martínez-Arias Alfonso , Kafatos Fotis C. , Raftery Laurel A. 
Published: April 2021

ABSTRACT
puckered (puc) encodes a VH1-like phosphatase that down- regulates Jun kinase (JNK) activity during dorsal closure of the Drosophila embryo. We report a role for puc in follicle cell morphogenesis during oogenesis. puc mRNA accumulates preferentially in the centripetally migrating follicle cells and cells of the elongating dorsal appendages. Proper levels of Puc activity in the follicle cells are critical for the production of a normal egg: either reduced or increased Puc activity result in incomplete nurse cell dumping and aberrant dorsal appendages. Phenotypes associated with puc mutant follicle cells include altered DE- cadherin expression in the follicle cells and a failure of nurse cell dumping to coordinate with dorsal appendage elongation, leading to the formation of cup-shaped egg chambers. The JNK pathway target A251-lacZ showed cell- type-specific differences in its regulation by puc and by the small GTPase DRac1. puc mutant cells displayed region- specific ectopic expression of the A251-lacZ enhancer trap whereas overexpression of a transgene encoding Puc was sufficient to suppress lacZ expression in a cell autonomous fashion. Strikingly, decreased or increased puc function leads to a corresponding increase or decrease, respectively, of Fos and Jun protein levels. Taken together, these data indicate that puc modulates gene expression responses by antagonizing a Rho GTPase signal transduction pathway that stabilizes the AP-1 transcription factor. Consistent with this, overexpression of a dominant negative DRac1 resulted in lower levels of Fos/Jun.
Ontogeny of haemoglobin in the chicken
Authors: Manwell Clyde , Baker C. M. Ann , Betz T. W. 
Published: April 2021

ABSTRACT
The controversy as to whether haemoglobin embryology in the chicken involves qualitative or merely quantitative changes is settled by the observation of consistent electrophoretic differences between the haemoglobins of early embryos and the haemoglobins of foetuses, chicks and adult chickens. Studies on polypeptide chain composition indicate that the multiple haemoglobins of 3-to 5-day incubation embryos are A2C2, B2C2 and D2F2. The major and minor haemoglobins of foetuses and adult chickens are A2F2 and A2E2. Thus, although embryos and adults have no haemoglobins in common, they appear to have two kinds of polypeptide chains in common, A and F. Embryos have three unique polypeptide chain types and adults have one, on the basis of differences in electrophoretic mobility. Some degree of polypeptide chain interchange occurs with at least one of the chicken haemoglobins in that one of the adult haemoglobins will hybridize with human adult haemoglobin, α 2β 2. Although two of the three 3-to 5-day chick embryonic haemoglobin components have one of their polypeptide chain types in common with the major adult haemoglobin, the oxygen equilibria and Bohr effect of adult and early embryonic haemoglobin are very different. Chick embryo haemoglobin has an extremely high oxygen affinity and a Bohr effect only two-thirds that of the adult. The haemoglobin ‘switchover’ at the end of day 5 of incubation is not paralleled by changes in erythrocyte esterases, lactate dehydrogenase or malate dehydrogenase isoenzymes.
The control of muscle and cartilage development in the chick limb: the role of differential vascularization
Authors: Caplan Arnold I. , Koutroupas Steven 
Published: April 2021

ABSTRACT
The results of previous studies on the effects of nicotinamide levels on chick limb mesodermal cell expression have indicated that there may exist a metabolic gradient situated radially across the limb which has a controlling influence on whether a limb cell will differentiate into either a myogenic or chondrogenic phenotype. This study investigates the possible role of the vascular pattern in establishing such a metabolic gradient. Observations are reported which show that prospective myogenic and chondrogenic areas become differentially vascularized before the onset of molecular differentiation, thus indicating that the vascular pattern is capable of establishing metabolic gradients across the limb. Furthermore, predictions based on these results have been tested and verified in vitro. The hypothesis is presented that the spatial differentiation of cartilage and muscle in the developing chick limb is under the controlling influence of gradients of metabolic potential which can be established by the differential vascularization of the limb.
The differentiation of the chick chorionic epithelium: an experimental study
Authors: Narbaitz Roberto , Tellier Pierre P. 
Published: April 2021

ABSTRACT
An electron microscopical study of the chorionic epithelium under two different experimental situations was conducted in order to gain knowledge on the mechanisms controlling the differentiation of ‘calcium-absorbing’ cells. In chorioallantoic membranes from 10-day-old embryos cultured on a semi-synthetic medium, the chorion became avascular but ‘calcium-absorbing’ cells differentiated, showing that the differentiation of these cells is not dependent on the vascular changes which in vivo occur simultaneously.
The number of ‘calcium-absorbing’ cells was much larger in the explants cultured on parathyroid hormone-enriched medium than in controls, indicating that the hormone is capable of stimulating their differentiation. Since it is known that parathyroid glands are active at the time in which ‘calcium-absorbing’ cells normally appear, our results suggest that the hormone may be the normal inductor of their differentiation.
Finally, a small number of ‘calcium-absorbing’ cells differentiated in vivo in a portion of chorion which had been artificially separated from the shell membranes, showing that their differentiation does not depend on the proximity of the external source of calcium.
Origine des ceintures scapulaires et pelviennes chez l’embryon d’oiseau
Authors: Chevallier Alain 
Published: April 2021

ABSTRACT
The development and the origin of the pectoral and pelvic girdles have been studied in bird embryos by homo- or heterotopic transplantations of somitic and somatopleural mesoderm.
Experiments consisted in implanting a piece of somitic or of somitic and somatopleural mesoderm obtained from a 2-to 2 · 5-day quail or chick embryo into a chick host of equal age.
Results showed that the scapula derives from the somitic mesoderm, while clavicle, coracoid, sternum and pelvic girdle originate from the somatopleural mesoderm.
The longitudinal span of the territories of the various skeletal elements, expressed as the number of the corresponding somites, was found to be as follows: scapula 15 – 24, clavicle 10 – 15, coracoid .15 – 17, sternum 12 – 26, and pelvic girdle 26 – 32.
It was also demonstrated that both somitic and somatopleural mesoderm are regionalized as early as 2 days of incubation, prior to somitic segmentation, with respect to their ability to give rise to the skeletal elements of the girdles.
These results were compared to those acquired previously concerning the other morphogenetic potentialities (vertebrae, ribs, limb musculature, dorsal plumage) of the para-axial and lateral mesoderm.
Bristle patterns and compartment boundaries in the tarsi ofDrosophila
Authors: Lawrence Peter A. , Struhl Gary , Morata Gines 
Published: April 2021

ABSTRACTWe describe cell lineage of the tarsus of wild-type Drosophila. Large Minute+ clones were made to map the position of the antero-posterior compartment boundary in all three tarsi. The tarsus is mirror symmetric, but the compartment boundary does not coincide with the mirror plane. This boundary runs along the dorsal and the ventral rows of bristles which are immediately posterior to the mirror plane; elements in these rows being made by both anterior and posterior polyclones. The provenance of bristles and bracts suggests that the bristle cells move into their final positions. The homoeotic mutation engrailed affects only the posterior compartments of all three tarsi. The mutations bithorax and postbithorax affect only the anterior and posterior compartments of the third legs, respectively, transforming them into homologous compartments of the second leg. These results support the selector gene model of development (Garcia-Bellido, 1975) and emphasize that collaboration between polyclones is important in pattern formation.
Experimental analysis of control mechanisms in somite segmentation in avian embryos.: I. Reduction of material at the blastula stage in Coturnix coturnix japonica
Authors: Veini Marianne , Bellairs Ruth 
Published: April 2021

ABSTRACT
The blastulae of unincubated eggs of the quail, Coturnix coturnix japonica, have been bisected in ovo, using the technique of Lutz (1949). Some embryos were harvested after 24 h and found to possess two primitive streaks. Most were fixed at 48 h or 72 h. Some were found to have regulated to form almost normal single axes, whilst others had developed into duplicitas anterior embryos, separate twins or collided axes. All three types of twinned embryos were smaller than the control embryos. The number of somites was not however reduced in the shorter embryos. This finding corresponds with a similar result obtained by Cooke (1975) who reported that if a Xenopus blastula is reduced in size, it nevertheless develops the correct number of somites.
The quail however adjusts the shape of the individual somites so that they fit into the reduced body length, whereas Xenopus reduces the size of somites. No miniaturized somites were ever seen in these quail embryos.
As a result of the present experiments, it was concluded that the length of incubation time does not directly control the rate of somite formation, because different numbers of somites were found in twins which possessed identical genomes and had developed in almost the same environment for identical periods. In addition, the size of the area pellucida does not appear to control somite formation. Probably, the most important influence is the regression of the node.
The mechanism of feather pattern development in the chick: I. The time of determination of feather position
Authors: Davidson Duncan 
Published: April 2021

ABSTRACT
A regular array of feather primordia covers chick dorsal skin in vivo. The pattern develops over a period of 2 days as a morphogenetic wave sweeps across either side of the back of the chick, forming successive anteroposterior rows of primordia.
This paper describes a new method for the culture of chick skin which allows the development of large areas of the feather pattern to be investigated experimentally. Skin is cultured on a substratum of hydrated collagen; since the collagen is transparent, feather primordium development can be observed in detail.
The new method has been used to investigate the problem of when the positions of feathers are determined. I show that during the time when the first few rows of primordia are forming, skin taken from just lateral to the most recently formed row can be caused to form an increased number of primordia per row by stretching it anteroposteriorly. This result indicates that the positions of feathers are determined sequentially along an invisible wave which moves just ahead of the visible wave of primordium morphogenesis.
X-chromosome instability in pluripotential stem cell lines derived from parthenogenetic embryos
Authors: Robertson E. J. , Evans M. J. , Kaufman M. H. 
Published: April 2021

ABSTRACT
The karyotype of six pluripotential stem cell lines derived from haploid and two additional lines derived from diploid parthenogenetic embryos is described. All these lines are diploid and possess a normal autosomal complement. The stage at which diploidization of the haploid cells occurs is not yet known. The XX-chromosome complement in these lines is unstable, although in two haploid-derived lines and one diploid-derived line many normal XX-bearing cells are found in early cultures. All of the lines so far examined either become XO (rarely), or a single X chromosome shows a deletion in the distal region. The extent of this deletion varies between lines, but the position of the breakpoint appears to be constant for a given line. We suggest that these cytogenetic findings raise the possibility that a single deletion event occurring at an early stage during the isolation of these lines may confer a selective advantage to those cells carrying the deleted X chromosome.
The development of facial motoneurones in the mouse — neuronal death and the innervation of the facial muscles
Authors: Ashwell K. W. , Watson C. R. R. 
Published: April 2021

ABSTRACT
The relationship between neuronal death and the formation of patterned connections was studied in the facial neuromuscular system of foetal, neonatal, and adult mice. The facial neuromuscular system was selected because two large, widely separated, facial muscles (the nasolabial and posterior auricular muscles) are innervated by clearly separated parts of the the facial motor nucleus in the adult mouse. The number of motorneurones in the facial nucleus was counted in Nissl-stained sections at different stages of development. Over 6400 neurones were present in the facial nucleus at day 17 p.c. (post-coitum). After day 17 p.c. the number of neurones fell rapidly and only 2000 cells remain in the adult nucleus. This represents a loss of 68 %, most of which occurs between days 18 and 20 p.c. Neurones with pyknotic nuclei are seen on day 17p.c. and are most numerous on day 18p.c. This leads us to believe that the fall in neurone numbers is due to cell death.
Indirect evidence provided by acetylcholinesterase histochemistry (time of earliest reaction in the facial muscles) and horseradish peroxide (HRP) tracing studies (time of earliest transport) indicate that facial motorneurone axons innervate the facial musculature before the period of cell death: diffuse acetylcholinesterase activity first appeared inthe auricular muscles at day 15 p.c. and in the nasolabial muscles at day 17 p.c. ; retrograde transport of HRP from the auricular and nasolabial muscles to the facial nucleus cannot be reliably demonstrated before day 17 p.c.
We assessed the topography of early facial neuromuscular innervation by making HRP injections into nasolabial and posterior auricular muscles of embryonic and neonatal mice. Injections of HRP at day 17 p.c. (the day before cell loss commenced) showed that the nasolabial muscle and posterior auricular muscles were innervated by the same subnuclei of the facial nucleus as in the adult - except that there was a small number (1-5 %) of labelled cells located in parts of the nucleus not consistent with the adult innervation pattern. These data indicate that, except for a small number of neurones, topographically organized connections in the facial neuromuscular system are established before the period of cell death. We conclude that motoneurone cell death does not play a major role in the establishment of topographically organized connections in this system.
Synthesis of globin chains in the erythropoietic sites of the early chick embryo
Authors: Fucci L. , Cirotto C. , Tomei L. , Geraci G. 
Published: April 2021

ABSTRACT
The synthesis of globins in the chick embryo before the onset of circulation has been studied in situ by specific immunofluorescence labelling of embryonic sections and by labelling newly synthesized proteins in ovo and in vitro in embryonic explants with [3Hjleucine.
The presence of major primitive haemoglobins is observed by 28 h of incubation. The minor primitive haemoglobins become detectable by immunofluorescence after 40 h of development, shortly before the onset of circulation. 3H-labelling shows that one definitive a chain is synthesized, though in low concentration, from the initial globin detection. The other definitive a chain is observed in embryos of at least 40 h of development. The relative concentration of the two definitive α chains changes rapidly with development indicating a specific mechanism of regulation.
An erythropoietic site is observed in the wall of the dorsal aorta in embryos of about 45–50 h of development. From the initial detection, those cells contain all four primitive embryonic haemoglobins, in contrast to what is observed for the cells of the blood islands.
The form and structure of supernumerary hindlimbs formed following skin grafting and nerve deviation in the newt Triturus cristatus
Authors: Reynolds Susan , Holder Nigel , Fernandes Manuel 
Published: April 2021

ABSTRACT
The results of a series of skin grafting experiments performed on the hindlimb of the newt Triturus cristatus are described. In an attempt to limit the position of origin and the complexity of supernumerary limb outgrowths four experimental features were varied. These were 1) size of skin grafts; 2) their position of origin; 3) the position to which they were grafted; and 4) the presence or absence of nerves of two different sizes at the graft site. The degree of distal outgrowth and the pattern of the supernumerary structures in the anterior to posterior and dorsal to ventral axes were assessed. The results are discussed in terms of the control of pattern regulation in localized populations of limb blastema cells.
Autonomous cortical activity in mouse eggs controlled by a cytoplasmic clock
Authors: Waksmundzka Małgorzata , Krysiak Elżbieta , Karasiewicz Jolanta , Czołowska Renata , Tarkowski Andrzej K. 
Published: April 2021

ABSTRACT
Mouse eggs of Swiss albino origin, both parthenogenetic and fertilized, were bisected into nucleate (NHs) and anucleate halves (AHs) and observed in vitro (semicontinuous observations) for up to 40 h for possible manifestations of cortical activity. Three experimental groups were studied: (1) Non-fertilized eggs activated 17h after administration of hCG with a heatshock and bisected 4h later. (2) Non-fertilized eggs first bisected, and the resulting sister halves activated 17 h after administration of hCG with ethyl alcohol. (3) In vivo fertilized eggs bisected 27 h after administration of hCG into an AH and a binucleate half. Parthenogenetic eggs (intact, zona-free, and incompletely bisected), and fertilized eggs collected 17, 20, and 27 h after administration of hCG were also studied.
In the middle of the first cell cycle the cell surface in all types of cells studied changed from smooth to slightly undulate. In nucleate cells the surface deformations lasted for several hours and disappeared shortly before the first mitosis. In contrast, in AHs the indentations of the cell surface deepened, and developed into manifold furrows, thus leading to fragmentation. However, in 20 % of AHs fragmentation was partially or completely reversed. The incidence and the intensity of fragmentation were lower, and its reversibility was more common in AHs carrying the 2nd polar body. We suggest that the interphase nucleus, i.e. the pronucleus in whole eggs and NHs, and the 2nd polar body nucleus (if 2nd polary body is attached to an AH) exerts a moderating effect on cortical activity. However, the initiation of cortical activity is nucleus-independent, as shown by the behaviour of AHs separated before activation. We believe that the observed phenomena reflect autonomous cortical activity which is regulated by a cytoplasmic clock.
Mutational analysis of patterning of oral structures in Tetrahymena: I. Effects of increased size on organization
Authors: Frankel Joseph , Jenkins Leslie M. , Bakowska Julita , Nelsen E. Marlo 
Published: April 2021

ABSTRACT
The oral apparatus (OA) of the ciliated protozoan Tetrahymena thermophila consists of four ordered arrays of ciliary units. In wild-type cells, these arrays are constant in spatial organization and vary little in size except during extreme starvation. Recessive mutations at five gene loci are known to increase the size of the OA. They do this by increasing the length of the ciliary arrays, without affecting their width and often without increasing their number beyond the usual four. Comparison of the oral arrays over a large range of sizes has revealed: (1) that the lengths of the anterior two of three parallel arrays (membranelles) are rather tightly coordinated; (2) that the specific basal body configurations resulting from remodelling of the membranelles are only slightly affected by large changes in lengths of membranelles; and (3) that the third membranelle is restricted to a nearly constant length, except in the very largest OAs in which the structure is lengthened but interrupted by a gap in the middle. This gap may reveal the spatial extent of a putative zone of basal body regression. These phenomena are not specific to any of the genotypes utilized in this investigation; the effect of the mutations is to loosen quantitative restrictions and thus reveal underlying associations and constraints.
Size regulation in the mouse embryo
Authors: Rands G. F. 
Published: April 2021

ABSTRACT
The development of mouse embryos formed by the aggregation of four 8-cell-stage eggs was analysed in comparison with control single embryos. The analysis revealed that: Quadruple aggregates undergo size regulation over several days, starting before implantation and being completed by 6·5 days post coitum.The attainment of recognizable postimplantation morphological stages is independent of size.Regulation is not brought about by disproportionate alterations in the size of the internal cavities.Regulation in both inner cell mass (ICM) and trophectoderm derivatives is completed between 5·5 and 6·5 days post coitum.Despite the abnormal proportions of ICM and trophectoderm in quadruple blastocysts, the proportions of the tissues derived from them are already normal by 5·5 days.
The possibility that down regulation in size of aggregate embryos occurs as a consequence of limited nutrient supply is discussed.
Basal laminar thinning in branching morphogenesis of the chick lung as demonstrated by lectin probes
Authors: Gallagher Betty C. 
Published: April 2021

ABSTRACT
Three lectins, wheat germ agglutinin (WGA), soybean agglutinin (SBA) and Ricinis communis agglutinin I (RCA), were used to study the basement membrane of developing chick lungs. Thinning of the basement membrane at the tips of newly formed bronchi was visualized with all three lectins, but was particularly evident using SBA. Control sections established the ability of the lectins to stain hyaluronic acid and chondroitin sulphate. Neuraminidase, bovine testes hyaluronidase and Streptomyces hyaluronidase removed some of the staining, but none were able to affect the staining of the basement membrane. Possible explanations for this are discussed in the text. Incorporation of [3H]thymidine is enhanced at the tips relative to the interbud area in stage-30 lungs, extending previous studies on stage-26 lungs. Evidence has been presented here which demonstrates that mechanisms of morphogenesis used in avian embryos are similar to those already elucidated in work on mammalian embryos.
Analysis of the cytosolic proteins of chick embryo gonads by two-dimensional gel electrophoresis
Authors: Samsel J. , Lorber B. , Petit A. , Weniger J.-P. 
Published: April 2021

ABSTRACT
Gonads and mesonephros dissected from normal chick embryos, as well as a blood sample, were labelled in vitro with [35S]methionine and [14C]leucine. The patterns of cytosolic protein synthesis of the different tissues were analysed using two-dimensional (2-D) polyacrylamide gel electrophoresis. Three developmental stages, i.e. 8, 12 and 17 days of incubation, were investigated.
Five sex-specific proteins were detected in the male and two in the female. In the testis, only one protein is already present at the 8-day stage. In the ovary, one protein exists since the 8-day stage, but it is also synthesized in the mesonephros. The second ovary-specific protein appeared only at the 12-day stage.