bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of viable chimaeras by aggregation between teratocarcinomas and preimplantation mouse embryos
Authors: Stewart C. L. 
Published: April 2021

ABSTRACTThe formation of viable teratocarcinoma-adult chimaeras, by aggregation rather than by microinjection, is described. Aggregation chimaeras were produced using two pluripotential EC cell lines, PSA-l/NG-2 and PSA-4/TG12. The frequency and distribution of chimaerism were assessed, for the EC cells, in conceptuses recovered from in utero and in adults. In utero 37% of the morphologically normal conceptuses formed from PSA-l/NG-2 aggregations and 73 % of the morphologically normal conceptuses produced from PSA-4/TG12 aggregations were found to be chimaeric. However, the frequency of chimaeric adults formed from both cell lines was lower. The reason for this discrepancy appeared to be that in the chimaeric conceptuses, the predominant tissues colonized by the EC cells were the extraembryonic membranes.
Scanning electron microscopy of gastrulation in a sea urchin (Anthocidaris crassispina)
Authors: Amemiya Shonan , Akasaka Koji , Terayama Hiroshi 
Published: April 2021

ABSTRACT
Gastrulation in Anthocidaris was investigated by observing the inside and the outside of embryos by scanning electron microscopy.
Furrows which possibly reflect changes in intercellular interactions were observed on the outer surface (hyaline layer side) of embryos twice in development: firstly at the time of primary mesenchyme cell formation, and secondly at the time of vegetal plate indentation. In the latter case, the cells within and surrounding the vegetal plate appeared to change their shapes differently; the former (within the plate) having broader surfaces on the blasto-coel side whereas the latter (surrounding the plate) having broader surfaces on the hyaline layer side. This suggests that the first phase of indentation may be mediated by the autonomous change of cell shape and intercellular adhesiveness, accompanied by an autonomous cell movement in the vegetal pole region.
Although some pseudopodial linkages were observed between secondary mesenchyme cells on the top of the invaginating archenteron and the animal pole in the mid-gastrula and later stage embryos, they were thinner and smaller in number as compared to those in the Pseudocentrotus embryos. The rate of invagination appeared rather constant throughout gastrulation in contrast to the accelerated invagination in other embryos with larger blasto-coel cavities. Moreover, the number of columnar cells on the dissected surface of embryos remained unaltered.
These findings suggest that the secondary mesenchyme cells may act as a linker between the archenteron tip and the animal pole, but they may not generate major motive forces for archenteron invagination at least in the Anthocidaris embryos.
Developmental effects of some newly inducedUltrabithoraxalleles ofDrosophila
Authors: Kerridge Stephen , Morata Gines 
Published: April 2021

ABSTRACTNine X-ray-induced mutations of the bithorax complex (BX-C) have been isolated and characterized. They all show the typical features of the Ultrabithorax mutations. They are homozygous lethal, produce a slight enlargement of the haltere in heterozygous condition and fail to complement the mutations at the bx, bxd and pbx loci. Some of them are associated with chromosomal aberrations in the regions 89E 1-4, where the BX-C lies, while others appear normal cytologically.The effect of six of these mutants in the adult cuticle has been studied, producing mutant marked clones in heterozygous individuals. The clones were generated by X-radiation at two points in development: the blastoderm stage and the second larval period. In all cases mutant clones showed the same phenotype: clones appearing in the dorsal structures transform metathorax and first abdominal segment towards mesothorax. That is the additive effect of bx, bxd and pbx mutations. Clones in the legs, if induced during the larval period, show an effect homologous to that seen in the dorsal structures. However, when produced at blastoderm they show in addition a transformation of the posterior second (mesothoracic) and third (metathoracic) legs into the posterior first (prothoracic) leg. This transformation, named postprothorax (ppx) has been recently described for the alleles Ubx130 and Ubx1 (Morata & Kerridge, 1981) and appears to be general for the Ubx mutations.It is concluded that the realm of action of the Ubx gene is defined by part of the meso-thoracic segment (posterior second leg compartment) and the entire metathoracic and first abdominal segments.
Cell membrane regionalization in early mouse embryos as demonstrated by 5′ -nucleotidase activity
Authors: Izquierdo L. , Ebensperger C. 
Published: April 2021

ABSTRACTThe distribution of 5’-nucleotidase activity in pre-implantation mouse embryos is studied by means of a cytochemical method adapted from Uusitalo & Karnovsky (1977). The enzyme activity is detected, from the 4-cell stage up to the morula stage, on discrete patches of the cell membane between blastomeres. Appropriate controls show that this distribution is not a localization artifact due to selective retention of the enzyme reaction product in the narrow interblastomeric spaces. In early blastocysts, as the blastocoel expands the enzyme activity on its lining disappears. The external surface of the trophectoderm in early blastocysts lacks any enzyme activity, whereas in late blastocysts a strong enzyme activity is detected at the embryonic trophectoderm, decreasing in intensity towards the opposite pole of the embryo.These results are compared to previous observations by other authors and the differences are mainly ascribed to differences in the cytochemical procedure employed.We conclude that during cleavage a gradual cell membrane regionalization unfolds, revealing a pattern that may be related to morphogenesis; in particular, to the localization of zonular tight junctions around the peripheral blastomeres of the morula (Izquierdo, 1977; Izquierdo, López & Marticorena, 1980).
Neural tube development in mutant(curly tail)and normal mouse embryos: the timing of posterior neuropore closurein vivoandin vitro
Authors: Copp A. J. , Seller M. J. , Polani P. E. 
Published: April 2021

ABSTRACTA dye-injection technique has been used to determine the developmental stage at which posterior neuropore (PNP) closure occurs in normal and mutant curly tail mouse embryos. In vivo, the majority of non-mutant embryos undergo PNP closure between 30 and 34 somites whereas approximately 50% of all mutant embryos show delayed closure, and around 20% maintain an open PNP even at advanced stages of development. A similar result has been found for embryos developing in vitro from the headfold stage. Later in development, 50-60% of mutant embryos in vivo develop tail flexion defects, and 15-20% lumbosacral myeloschisis. This supports the view that delayed PNP closure is the mftin developmental lesion leading to the appearance of caudal neural tube defects in curly tail mice. The neural tube is closed in the region of tail flexion defects, but it is locally over-expanded and abnormal in position. The significance of these observations is discussed in relation to possible mechanisms of development of lumbosacral and caudal neural tube defects. This paper constitutes the first demonstration of the development of a genetically induced malformation in vitro.
The effects of chlorcyclizine-induced alterations of glycosaminoglycans on mouse palatal shelf elevation in vivo and in vitro
Authors: Brinkley Linda L. , Vickerman Mary M. 
Published: April 2021

ABSTRACT
To define whether glycosaminoglycans play a role in palatal shelf movement, we studied the morphology and elevation behaviour of chlorcyclizine-treated mouse palatal shelves. Chlorcyclizine treatment was used because this agent enhances degradation of the palatal glycosaminoglycans, hyaluronate and chondroitin sulphates, with little or no effect on their synthesis. Use of in vitro and in vivo experiments enabled us to control the complicating effects of other factors on elevation.
Drug-administration resulted in a reduction in shelf size, as measured by cross-sectional surface area, in the posterior two-thirds of the palatal shelf. In vivo shelf reorientation was also inhibited. When elevation behaviour was observed in vitro, pronounced regional variation was noted. The anterior third of the shelf was able to reorient, the posterior two-thirds was not. This region also showed distinct histological changes as compared to controls. Mesenchymal cells were rounded with prominent nuclei and nucleoli and were more densely packed than in controls.
These results suggest that for at least the posterior two-thirds of the palatal shelf, the intrinsic reorientation ability may in large part be linked to the acquisition of a specific temporal and spatial distribution of hyaluronate and possibly other matrix components.
Mutations affecting the indirect flight muscles ofDrosophila melanogaster
Authors: Deak Ilan I. , Bellamy Paul R. , Bienz Marianne , Dubuis Yvonne , Fenner Elke , Gollin Michael , Rähmi Andreas , Ramp Theodor , Reinhardt Christoph A. , Cotton Beata 
Published: April 2021

ABSTRACTThe development of the indirect flight muscles of Drosophila melanogaster was studied by analysing mutations that cause flightlessness. Twenty-five mutations on the X-chromosome and two on the third chromosome were examined. The X-chromosomal mutations form ten complementation units. The ten loci were assigned preliminary map positions by meiotic recombination and deficiencies and duplications. The two autosomal mutations represent two genes. Gynandromorph analyses suggest that many of these mutations have their primary effect in the presumptive thoracic muscle region of the embryo. The mutations cause a variety of characteristic defects, such as absence of the bulk of the thoracic muscle mass, or absence of only one of the two fibrillar muscle groups. Electronmicroscopic studies of sixteen mutants representing all twelve loci reveal abnormal myofibrillar organization in some of these mutants, e.g. aberrant or missing Z-bands, or absence of the thin filaments. Mutant protein patterns, obtained by SDS-polyacrylamide gel electrophoresis, show the following differences from wild type: ten mutants are characterized by absence or reduction of the 54 K protein, and most mutants exhibit a reduction and modification of the 80 and 90 K proteins. The absence or reduction of the 54 K protein was strongly correlated with aberrant Z-bands.
Genetical and Developmental Studies on Droopy-eared Mice
Authors: Curry G. A. 
Published: April 2021

ABSTRACT
Droopy-ear is a single, recessive, autosomal gene with full penetrance. Droopy-ear is linked to Varitint p27 ± 3·2, but segregates independently of the other genes tested. In adult droopy-eared mice the areas of specific abnormalities are the occiput and the shoulder girdle. The rest of the skeleton shows immaturity of form, and disproportionate shortening of the limb bones. The anomalies of the adult skeleton are traced back, through a delay in ossification, to a delay in chondrification and localized areas of abnormal cartilage, and thus back to disturbed mesenchymal condensations, which in some cases are also thin. Certain of the abnormalities, in particular the splitting of the dens epistrophei into two parts, one of which may be attached to the basioccipital, strongly recall the anatomical situation in the more primitive vertebrates. Some anomalies of the internal bone structure are described. The droopy-ear syndrome is considered in relation to the syndromes of the other mouse mutants whose mesenchymal condensations are disturbed. The similarities of the droopy-ear syndrome with some conditions in other chondrodystrophic disorders is noted. The theories concerning the localization of specific abnormalities are discussed in relation to droopy-ear.
Dimensions of the Notochord and Somites in Embryos of Xenopus laevis Treated with Thiocyanate
Authors: Ranzi Silvio , Gavarosi Gianna 
Published: April 2021

ABSTRACT
As a result of previous research, Ranzi & Tamini (1939) pointed out that the notochord of Amphibian embryos of several species treated with sodium thiocyanate (NaSCN) solutions is larger than the notochord of control embryos. Later, several substances were identified which cause enlargement of the notochord: full data and a complete review of the literature on this subject are given by Ranzi & Citterio (1954) and Ranzi (1957). A careful statistical study on the number of nuclei in Rana escalenta embryos was carried out by Corti (1950). In embryos which had been treated for 24 hours with 0·05 M NaSCN, from the late blastula stage onwards, she found 1233 ±28 nuclei at the tail-bud stage, whereas the controls reared in spring-water had only 1107 ± 24 nuclei: these two sets of data are significantly different (standard error of the difference ±37).
The First Appearance of Specific Antigens during the Induction of the Lens1
Authors: Langman Jan 
Published: April 2021

ABSTRACT
Presumptive lens ectoderm with associated eye-cup from 5 – 17-somite chick embryos was explanted in ‘normal’ medium, ‘anti-myosin’ medium, and a medium containing lens antibodies. The control explants in ‘normal’ and ‘anti-myosin’ medium showed lens formation in 80-100 per cent, of the cases (Text-fig. 1); the explants in ‘anti-lens’ medium showed degeneration and necrosis of the future lens area, indicating the presence of substances (lens antigens) capable of reacting with lens antibodies (Text-fig. 1). Explants from embryos with 18 or more somites in ‘anti-lens’ medium formed lenses as the controls. Presumptive lens ectoderm without the associated eye-cup from 7 – 20-somite embryos was cultured on a ‘normal’ and ‘anti-lens’ medium. The controls showed epithelial membranous outgrowth in 80 –100 per cent, of the explants (Text-fig. 3; Table 1). Explants on ‘anti-lens’ medium showed outgrowth similar to controls when obtained from embryos younger than 11 and older than 17 somites, but showed degeneration when obtained from 11-to 17-somite embryos, indicating the formation of the first reacting substances (lens antigens) at the 11-somite stage (Text-fig. 3; Table 1). The ‘first-stage’ lens antigens are formed at the 11-somite stage, shortly after the adhesion between eye-cup and presumptive lens ectoderm has been established (9 somites) and shortly before the morphological changes characterized by loss of vacuolization, nuclear orientation, and palisade phenomenon appear (13 – 19 somites).
The Passage of Urea and Creatinine across the Placenta of the Pig
Authors: Zweymüller E. , Widdowson E. M. , Mccance R. A. 
Published: April 2021

ABSTRACTThe concentration of ‘creatinine chromogens’ in the serum of the foetal pig at term may be over three times that in the maternal serum. The concentrations of urea were always about the same. The values for these chromogens in piglet sera fell to the adult level in the day following birth. Fructose was the only chromogen other than creatinine found in piglet serum by chromatography. Pyruvic acid was not the cause of the difference. It is concluded, therefore, that the chromogens were mostly true creatinine, and that the pig’s placenta is less ‘permeable’ to it than to urea.
Morphogenetic Events in Normal and Synchronously Dividing Tetrahymena
Authors: Williams Norman E. , Scherbaum Otto H. 
Published: April 2021

ABSTRACT
A study of differentiation in the ectoplasmic cortex of T. pyriformis GL subjected to the standard temperature cycling for the induction of synchronous binary fission has demonstrated an arrest in development which occurs in all cells at a characteristic point in the cell cycle. After treatment all cells were found to possess anarchic fields of kinetosomes in the stomatogenic region, indicating 100 per cent, synchrony. The cells remain in this condition for a period of 50 –55 minutes after the last heat shock. During this time no changes other than in increase in the size of the macronuclear chromatin granules could be detected. At the end of the period of arrested development morphogenesis resumes and binary fission continues in synchrony. The degree of synchrony is somewhat reduced as development proceeds, resulting in about 85 per cent, synchrony at the time of cytoplasmic constriction. In order to facilitate analysis of morphogenesis in synchronously dividing Tetrahymena, a series of four developmental stages has been defined. Based on work which has confirmed available descriptions of stomatogenesis and macronuclear fission, the sequence includes new data on development of the somatic ciliature. All observations, including quantitative consideration of the somatic kinetosomes, ciliary meridians, and contractile vacuole pores has indicated that, aside from synchrony and the period of arrested development, the morphogenetic events in synchronized organisms are fundamentally no different from these processes in untreated cultures. Growth of the organism, growth of the macronucleus, and morphogenesis are to some extent dissociated in synchronized cultures of Tetrahymena. During the heat treatment morphogenesis is blocked while cell and macronuclear growth continues. After treatment and prior to the synchronous cytoplasmic constriction there is a significant increase in mean nuclear volume with no significant increase in total cell volume. After resumption of development in synchronized cultures morphogenesis proceeds unaccompanied by any increase in cellular volume. In addition, it is believed that the nuclear increase occurs during the period of arrested development and not during the subsequent period of development. The use of protargol staining promises to be of value in studies of ciliate morphogenesis. Of those structures in and on the ciliate cortex, protargol appears to be highly specific for kinetosomes. In addition to this the cilia and ciliary membranes are revealed by this technique.
A Study of Environmental Influences on the Size of the Pronephros and Related Structures in Triturus helveticus
Authors: Fox H. 
Published: April 2021

ABSTRACT
Triturus helveticus embryos were reared from a stage equivalent to Harrison stage 24–26 for Ambystoma punctatum, in a variety of media for 15 days, and the pronephric systems were quantitatively analysed. The lumen volumes and internal surface areas of the tubules of decapsulated embryos were smaller than those of capsulated embryos. The pronephric tissue volumes and glomus volumes of decapsulated embryos reared in full-strength Holtfreter solution were smaller than when they were reared in one-tenth-strength Holtfreter solution. All measurements of pronephric components (except nuclear length) were significantly and considerably greater in decapsulated specimens reared in distilled water than in decapsulated embryos reared in full-strength Holtfreter solution. Pronephroi of decapsulated embryos reared in calcium-free one-tenth strength Holtfreter solution had a significantly smaller lumen volume and internal surface area of the tubules than those of controls. Pronephroi of decapsulated embryos reared in 0·5 per cent, urea in one-tenth-strength Holtfreter solution had slight, but significant, superiority in length and cell volume, but a smaller lumen volume, than those of controls. Comparison of the pronephric measurements of two unrelated collections of T. helveticus showed significant intra-specific differences.
Appearance of Antigens during Development of the Lens
Authors: Langman Jan 
Published: April 2021

ABSTRACTThe double diffusion technique of Ouchterlony, based on the differential diffusion of a mixture of antigens in an agar gel, was used to study the formation of lens antigens during development of the chick embryo and to correlate chemical and morphological differentiation. Aqueous extracts prepared from lenses of 50-, 60-, 72-, and 96-hour, and 10-day embryos, and from new-born and young adult chickens, were tested with antiserum prepared with 10 per cent, adult chicken lens extract. The gradual appearance of 1–7 precipitin bands, indicating the corresponding formation of substantial amounts of up to 7-lens antigens, was noted during embryonic development. The number of bands formed was dependent upon the age of the embryos providing the lens extracts. The first appearing lens antigen causing a precipitin band was found in 50-hour lens extract (18-24 somites). The appearance of new precipitin bands in the course of development, indicating the formation of new lens antigens, preceded or coincided with the appearance of morphological structures indicating synthesis of new protein. Precipitin bands formed during the first stages of development (bands 2, 3, and 4 in Plate 1, fig. 2a and Plate 2, fig. 3a) were caused by antigens identical to those present in the later stages (Plate 2, figs. 5a, 6a, 1a). The molecular weight of the first formed antigens appeared to be higher than that of the antigens formed later in development.
Mitotic Pattern in the Chick Pronephric Duct
Authors: Overton Jane 
Published: April 2021

ABSTRACT
Studies carried out on the stage 14 chick embryo indicate that in normal and in colchicine-treated embryos mitotic frequency is greatest towards the posterior tip of the elongating pronephric duct. Although the mitotic frequency in the duct tip is high compared to that in the duct at more cephalic levels, it is similar to that in other mesodermal regions at the same level. Distortions of the embryo which occur with colchicine treatment suggest that migratory activity is prominent towards the duct tip, and emphasize the dependence of normal morphology of the duct on tensions in the blastoderm.
Recherches sur les malformations déterminées par le refroidissement temporaire de l’œuf de poule et compatibles avec la vie des Poussins
Authors: Ancel P. 
Published: April 2021

ABSTRACT
Nous avons signalé dans un travail antérieur (Ancel, 1958) portant sur 699 œufs que le refroidissement de l’œuf de poule à différentes périodes de l’incubation pendant deux ou trois jours donnait naissance à des malformations des paupières, du bec et des membres. Un petit nombre d’embryons avaient été prélevés seulement après le 17ème jour de l’incubation. Dans le présent travail, nous avons cherché à savoir si certaines des malformations ainsi obtenues étaient compatibles avec la vie des poussins.
The Pigment Cell System in the Light Sussex Fowl
Authors: Cohen J. 
Published: April 2021

ABSTRACTThe pigmentation pattern of the Light Sussex fowl is described and considered as a case of ‘partial pigmentation’. By the use of tissue-culture methods it has been demonstrated that a competent pigment cell system occurs in the white plumage of the Light Sussex embryo and adult. Papilla transplantation experiments were used to evaluate the role of the epidermis in determining the fate of these pigment cells. The results obtained indicate strongly that the epidermis determines whether or not the equipotential pigment cells shall or shall not produce pigment in vivo. It is concluded that the pigment cell system of the Light Sussex responds to certain conditions in vivo and in vitro by the production of sufficient pigment to colour feather, and to other conditions by the production of insufficient pigment.
Tolerance of Skin Grafts produced by Various Adult Cells, Soluble Extracts, and Embryonic Cells
Authors: Terasaki P. I. 
Published: April 2021

ABSTRACT
Tolerance of skin homografts was studied after the injection of various adult cells and soluble tissue extracts into newly hatched or embryonic chicks. Tolerance (measured by the proportion of surviving skin homografts 30 days after transplantation) was induced in 50 per cent, or more of the chicks injected with diluted whole blood, blood lymphocytes, blood monocytes, and thymocytes. Since monocytes and thymocytes do not produce a ‘graft against host’ reaction it follows that tolerance to homografts can be induced by adult cells without the complications associated with runt disease. Tolerance could not be induced with cell-free extracts of known antigenic potency. Analysis by the tolerance test of the appearance of adult-type iso-antigens during embryonic development shows that they are detectable by the 4th day of embryonic life.