bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Immuno-embryological Study on the Chick Lens
Authors: Maisel Harry , Langman Jan 
Published: April 2021

ABSTRACTThe purpose of this experiment was to analyse location and time of appearance of lens proteins during lens development.Applying the agar-diffusion technique of Ouchterlony the adult lens was found to contain substantial amounts of at least seven soluble antigenic substances, grouped into three main fractions and referred to as Fractions I, II, and III. While Fraction I consists of one antigenic substance, Fraction II contains at least four components and Fraction III usually two components. Fraction I appears to be identical to the protein alpha crystallin (m.w. approximately 1,000,000) as prepared by continuous-flow electrophoresis and tested on homogeneity and identity by ultracentrifugation and paper electrophoresis. It is detected in the epithelial cells of the lens placode before the appearance of any other lens antigens and is thus considered to be the first lens protein to arise during organogenesis. The importance of this protein for lens development is also shown by its presence in the lens of representative species of the vertebrate series and by its presence in iris, retina, and cornea—that is, those tissues which show the capacity to form a lens after removal of the original lens. Fraction II appears to be identical to beta crystallin (m.w. approximately 200,000) and is characterized by at least four closely related antigenic subfractions, which appear at the onset of differentiation and growth of the nuclear lens fibres. As it is localized in the nucleus of the lens, the typical site of con genital cataracts, it is believed to be the main target for teratogenic factors such as German measles virus, which causes a cataract only if acting during differentiation and growth of the nuclear lens fibres. Fraction III appears to be identical to gamma crystallin (m.w. approximately 60,000) and is the last lens antigen to arise during lens development. Its morphological position could not be determined.
The Blood-Vessels of the Developing Spinal Cord of Xenopus laevis
Authors: Sims R. T. 
Published: April 2021

ABSTRACT
The blood-vessels of the developing spinal cord of X. laevis have been studied from stage 45 to stage 66 by the injection technique. Within the substance of the cord the first vessels injected were found at stage 46, and individual vessels were not constant in position or time of appearance. The vascular network is formed by dichotomous branching and joining of vessels. Estimates of the number of vascular segments (i.e. between branches) per mm.3 of spinal cord and the total length of vessel per mm.3 showed that the latter increased during development while the former did not. It is concluded that the vascularity of the spinal cord increases as differentiation of the cord proceeds and is brought about by increasing the average length of the vascular segments.
L’Action de l’irradiation ultraviolette sur le métabolisme des acides nucléiques dans l’embryon de Poulet
Authors: Barbieri par Francisco D. 
Published: April 2021

ABSTRACT
The incorporation of labelled adenine in the neural plate of ultra-violet irradiated chick embryos has been studied. It has been confirmed that small doses of radiation inhibit the closure of the neural folds. The incorporation of adenine increases immediately after radiation and decreases one hour after the treatment. There is a significant increase of the mitotic index during this first hour. In the light of previous results it is possible to attribute the inhibition of closure of the neural folds to some alteration in the metabolism of nucleic acids or proteins.
Investigations of the Germ-plasm in Relation to Nuclear Transplantation
Authors: Berardino Marie A. Di 
Published: April 2021

ABSTRACTPrimordial germ-cells in R. pipiens mid-blastula and early gastrula stages were detected in serial sections, because these cells contained a stainable component, the germ-plasm. Their location was of prime interest in determining whether or not the nuclei of primordial germ-cells had been used in previous transplantation studies (King et al., 1959; Briggs & King, 1960). In the mid-blastula and early gastrula stages the primordial germ-cells were confined to the vegetal hemisphere. The majority of these cells was situated in the upper-third of the vegetal hemisphere. An intracellular displacement of the germ-plasm occurred between mid-blastula and early gastrula stages. The number and location of the primordial germ-cells suggest that only in rare cases could a nucleus from one of these cells have been transplanted in the previous studies, and such cases would probably have been undetectable. What appears most significant is that nuclei derived from cells not containing germ-plasm are capable of giving rise to larvae whose gonads contain numerous auxocytes.
Serologically Active Groups of Amphibian Embryos
Authors: Inoue Kazuko 
Published: April 2021

ABSTRACTUsing the embryos of T. pyrrhogaster, the activity gradients of serologically active surface groups of protein molecules were analysed in buffered saline soluble (S) fractions of early embryonic stages against anti-S-fraction sera. Titrimetric methods were utilized in determination of the relative degree of participation of each group in the antigen-antibody reaction, as evidenced by inhibition of precipitation subsequent to inactivation of specific surface groups. Use was made of the blocking reagents p-chlor omer cur i benzo ate, monoiodoacetamide, cysteine, iodine, tyrosinase, 2,4-dinitrofluorobenzene, phenyl isocyanate, benzoyl chloride, and diazonium compounds in evaluating the reactivity of the sulphydryl, disulphide, phenol, imidazol, and amino groups. In the S-fractions, low activity of SS—SH groups and of the phenol groups is perceptible in the large oocyte; after fertilization the activity of all groups increases rapidly. The curve of SH activity culminates in the blastula; that of SS shows perceptible activity in the morula, wanes in the blastula, and then again rises to a maximum in the early gastrula. The gradient of activity of the phenol groups reaches its peak in the late gastrula stage. The amino and imidazol groups demonstrate maximum activity in the neurula and tail-bud stages of development.
Experiments on the Maternal-Foetal Barrier in the Mouse
Authors: Finegold Milton , Michie Donald 
Published: April 2021

ABSTRACTLeakage of chromium-labelled erythrocytes from the circulation of pregnant mice into the foetal circulation could not be detected, either following X-irradiation at various dose-levels and gestational stages or in untreated pregnancies. Two exceptions were encountered out of a total of 279 foetuses examined. This was taken as an estimate of the spontaneous incidence of transplacental leakage of maternal erythrocytes and contrasted with the relatively high incidence encountered in the human species.
Experiments on the Maternal-Foetal Barrier in the Mouse: II. A Test for the Transmission of Maternal Serum Albumin into the Foetal Circulation following X-irradiation
Authors: Knobel D. P. , Michie Donald 
Published: April 2021

ABSTRACT
Serum albumin labelled with Evans blue did not pass from the maternal into the foetal circulation in 13 pregnant mice, of which 7 had received 300 r. X-irra-diation at stages ranging from day 13 to day 19, and 6 were untreated. The bearing of this result on studies of placental permeability in other species is considered.
L’Influence de divers mésenchymes sur la différenciation de l’épithélium pulmonaire de l’embryon de Poulet en culture in vitro
Authors: Dameron par Florence 
Published: April 2021

ABSTRACT
Le poumon embryonnaire de Poulet prélevé à 5 jours d’incubation offre l’aspect d’un petit sac mésenchymateux enveloppant un conduit épithélial qui présente deux ou trois dilatations. Les deux ébauches entrent en contact l’une avec l’autre pour édifier l’organe.
Retinoic acid and pattern formation in the developing chick wing: SEM and quantitative studies of early effects on the apical ectodermal ridge and bud outgrowth
Authors: Lee J. , Tickle C. 
Published: April 2021

ABSTRACT
When retinoic acid is locally applied to the anterior margin of developing chick wing buds on ion-exchange beads, dose-dependent changes in the skeletal pattern result. At low doses, additional digits develop. At high doses, there is thinning of the symmetrical wing. Local application of retinoic acid to the apex of the bud also leads to pattern changes, but in contrast normal wing patterns are almost always obtained following application posteriorly. These effects are manifest at 6–7 days after the operation although only a brief exposure (14–20 h) to retinoic acid is required. Therefore the morphology of wing buds was studied at shorter times after the start of treatment.
The local application of retinoic acid to the wing bud margin leads to changes in extent of the apical ridge that can be detected at 24 h after application. The behaviour of the apical ridge with varying doses and positions of retinoic acid application has been analysed quantitatively and dose response curves obtained. At low doses of retinoic acid, the length of the apical ridge increases or remains constant, but then progressively decreases with higher doses. The progressive obliteration of the ridge starts first near the bead and then involves more distant parts of the bud. Thus the region of the ridge affected depends on the position at which the retinoic acid is applied.
We propose that these effects on the apical ridge reflect dose-dependent responses to the local concentration of retinoic acid that varies with distance from the source. At high doses, the apical ridge disappears but at low doses it is maintained. Since grafts of polarizing region tissue also have a graded effect on ridge morphology, a possible interpretation of the retinoic acid effects is that tissue adjacent to the source is converted into polarizing region tissue. Alternatively, retinoic acid may act directly on the ridge cells.
The changes in the extent of the apical ridge produced by retinoic acid lead to different forms of bud outgrowth. The form of the outgrowth depends on the dose of retinoic acid, the position of application and the interaction between the effects of the local source of retinoic acid and those of the polarizing region of the host bud. These considerations give some insights into why anterior application of retinoic acid leads to the development of additional digits whereas posterior application generally gives normal wings.
Cleavage and gastrulation in the egg-brooding, marsupial frog, Gastrotheca riobambae
Authors: Elinson Richard P. , Pino Eugenia M. Del 
Published: April 2021

ABSTRACT
The marsupial frog Gastrotheca riobambae has several reproductive adaptations, most prominent of which is the incubation of the embryo in a pouch on the mother’s back. We have followed cleavage and gastrulation by microscopical observation and by vital staining, and have found several alterations in these processes which may reflect the reproductive adaptations. The large, yolky egg has a cap of yolk-poor cytoplasm at the animal pole which is incorporated into a translucent blastocoel roof consisting of a single cell layer. The epithelium of the yolk sac is derived from the roof. The inconspicuous blastoporal lips form near the vegetal pole from cells of the marginal region. Gastrulation movements include the epibolic stretching of the surface towards the blastopore and a contraction of the vegetal surface. The blastoporal lips close over a small archenteron, and the cells of the lips become the embryonic disc, a discrete group of small cells which give rise to most of the embryo’s body. The great size difference between animal and vegetal blastomeres during cleavage, the single-celled blastocoel roof, the dissociation in time between archenteron formation and its expansion, the embryonic disc and the slow development distinguish G. riobambae embryos from those of other frogs. The importance of the marginal region which produces the embryonic disc and the unimportance of the most animal region whose fate is primarily yolk sac emphasizes the role of the marginal region in amphibian development.
Interactions between neurites and somite cells: inhibition and stimulation of nerve growth in the chick embryo
Authors: Stern Claudio D. , Sisodiya Sanjay M. , Keynes Roger J. 
Published: April 2021

ABSTRACT
After neural processes emerge from the neural tube in the chick embryo, their growth is restricted to the cranial halves of the neighbouring somites. In this study we have developed an in vitro system to model the interactions between these tissue types. Pioneer neurites display a hierarchy of preferences in terms of the substrates they can grow on. As expected, tissue culture plastic does not support neural outgrowth, but this can be overcome by coating the plastic substrate with either collagen or poly-L-lysine. Neural crest, cranial half somite, and a number of other tissues support growth well, while caudal half somite and tail bud mesenchyme do so to a much smaller extent.
The binding pattern of a variety of lectins was assessed in cryostat sections of embryos and in cultured cells of the above tissues. It was found that peanut agglutinin can discriminate between cranial and caudal sclerotome both in vitro and in the embryo, since it binds preferentially to caudal sclerotome in both cases. This difference is expressed as soon as the sclerotome forms.
The significance of these findings is twofold: first, they show that the interactions that take place during peripheral neural segmentation can be modelled in vitro; second, they represent the first instance of a molecular difference between the cranial and caudal halves of the sclerotome, detectable both in culture and in the embryo.
The effects of local application of retinoic acid on limb development and regeneration in tadpoles of Xenopus laevis
Authors: Scadding S. R. , Maden M. 
Published: April 2021

ABSTRACT
Vitamin A can have different effects on developing and regenerating limbs depending on the mode of administration. Previous work has demonstrated the differential effect of retinol palmitate on limb development and regeneration in Xenopus laevis. The purpose of the present investigation was to determine the effects of vitamin A on limb development and regeneration in Xenopus when administered by a local implantation method. Xenopus tadpoles had both hindlimbs implanted with either a block of silastin carrying retinoic acid or an anion exchange resin bead carrying retinoic acid and then the right hindlimb was amputated and the effect of the retinoic acid on limb development and regeneration was studied. The results showed that in developing hindlimbs the effects of silastin implants carrying retinoic acid was to cause skeletal reductions or deletions similar to those induced by immersion of the tadpole in retinol palmitate. On the other hand, in regenerating hindlimbs, the silastin implants caused a range of skeletal reductions and deletions as well as occasional accessory structures but notably induced no proximodistal (PD) duplications, unlike the effect of immersion in retinol palmitate where PD duplications were a common response. Implantation of anion exchange resin beads carrying retinoic acid had no significant effect on either development or regeneration beyond stage 50, presumably because the dose of the retinoic acid was so low. Thus the results suggest that the mode of administration of vitamin A has a very significant influence on its effects. The significance of this observation for vitamin A experiments on limbs is discussed.
Changes in patterns of protein synthesis in axolotl oocytes during progesterone-induced maturation
Authors: Gautier Jean , Tencer Renée 
Published: April 2021

ABSTRACT
Patterns of protein phosphorylation and synthesis during axolotl (Ambystoma mexicanum) oocyte maturation were studied by incorporation of [32P]orthophosphate and [35S]methionine into polypeptides, followed by two-dimensional gel electrophoresis. Various alterations were observed after progesterone treatment: de novo appearance of [35S]methionine-labelled polypeptides, a quantitative increase in previously synthesized proteins and a quantitative decrease in or disappearance of other previously synthesized proteins. Changes in 32P- and 35S-labelling were observed very early during maturation. Neither prior oocyte enucleation nor α-amanitin treatment had a significant effect on these changes. Stimulation with MPF provided the same final protein pattern as PG treatment. However, cholera toxin inhibited all the changes seen during maturation. Comparisons between the patterns of [35S]methionine- and [32P]phosphate-labelling provide further information on the biochemical events that take place during oocyte maturation.
Mechanism of polar body formation in the mouse oocyte: an interaction between the chromosomes, the cytoskeleton and the plasma membrane*
Authors: Maro Bernard , Johnson Martin H. , Webb Michelle , Flach Gin 
Published: April 2021

ABSTRACT
The influence of mouse oocyte chromosomes on their immediate environment has been investigated following their dispersal by dissolution of the metaphase spindle with nocodazole. Small clusters of chromosomes become redistributed around the egg cortex in a microfilamentdependent process. Each cluster has the capacity, on removal from nocodazole, to organize a spindle that rotates to yield a polar body. In this process of spindle formation, the chromosome clusters are able both to promote tubulin polymerization in their vicinity and to recruit microtubule-organizing centres (MTOCs) which organize the polymerized tubulin into spindles. In addition each oocyte chromosome cluster, as well as the non-dispersed sperm-derived haploid group of chromosomes, induces a focal accumulation of subcortical actin (corresponding to a filamentous area devoid of organelles) and a loss of surface Concanavalin A binding activity (corresponding to a loss of surface microvilli) in the overlying cortex. This induction ceases with the formation of pronuclei whether or not the pronuclei migrate centrally. Pronuclear formation is sensitive to the action of nocodazole for up to 2–4h postinsemination, and pronuclear migration is totally sensitive to the drug. If pronuclei are blocked in a peripheral location by nocodazole they are associated with an elevation in Con A binding activity of the overlying membrane which corresponds to an area of the surface rich in blebby microvilli.
Effect of experimentally induced calcium deficiency on development, metabolism and liver morphogenesis of the chick embryo
Authors: Ono Tamao , Tuan Rocky S. 
Published: April 2021

ABSTRACT
To study the effects of systemic calcium deficiency on embryonic development, chick embryos maintained in long-term shell-less cultures were compared to control embryos incubated in ovo with respect to various parameters of metabolism and growth. After incubation day 14, retarded growth and development were apparent in shell-less embryos which exhibited severe hypocalcaemia and hyperphosphataemia. A development-specific necrosis of the liver tissues was observed in both shell-less and control embryos, but the frequency and extent of tissue abnormality were significantly greater in the former. Serum levels of lactate dehydrogenase and alkaline phosphatase were considerably elevated in shell-less embryos. Electrophoretic analysis revealed that the relative levels of two major serum proteins were also altered in shell-less embryos.
Cleavage in vitro following destruction of some blastomeres in the marsupial Antechinus stuartii (Macleay)
Authors: Selwood Lynne 
Published: April 2021

ABSTRACT
The effect of destruction of some blastomeres on subsequent cleavage in vitro was investigated in the marsupial Antechinus stuartii. Blastomeres were killed by puncturing with a fine glass needle. The positions of the punctured and surviving blastomeres were recorded with respect to the yolk mass and defects on the shell membrane. Blastomeres were punctured in 2-cell, 4-cell, 14-cell, 16-cell and 22-cell embryos. Subsequent development of the embryos was followed in vitro. Embryos developed at a normal rate after destruction of some blastomeres. Puncturing of the shell, mucoid layer and zona pellucida, without damage to blastomeres, did not affect subsequent development. The embryos developed in accordance with the proportion of surviving blastomeres. Embryos with half of the blastomeres surviving developed as embryos with half the zona pellucida lined by blastomeres. Embryos with 1/4 of the blastomeres destroyed developed as 3/4 embryos. It is not known, without transfer into surrogate mothers, whether these fractional embryos were capable of developing into complete embryos.
Bud induction in decapitated Hydra attenuata by 5-azacytidine: a morphological study
Authors: Petrocellis L. De , Maharajan V. , Petrocellis B. De , Minei R. 
Published: April 2021

ABSTRACT
The effect of 5-azacytidine (5-azaCR) on head regeneration and budding in hydra are reported. Hydra attenuata were exposed to various doses of 5-azaCR for 48 h and then decapitated and cultured. Head regeneration and bud formation were observed for 12 days after decapitation. Untreated control hydra regenerated heads within 7 to 8 days of decapitation with a budding index of 0·2. Buds invariably arose in the normal budding zone (below the gastric region).
In the group treated with 0·8mM-5-azaCR, 9 days after decapitation head regeneration was seen in only 13 % of animals, and an average of two buds per hydra were formed, most of which were in the vicinity of the distal end. Induction of budding was also seen in the animals that regenerated heads.
In animals exposed to 1 mM-5-azaCR three main types of responses were observed 9 days after decapitation. (1) 44% of the animals regenerated normal heads; about half of them developed at least one bud and these buds originated in the budding zone. (2) 17·5% of the animals developed abnormal, long hypostome-like structures with single or bifurcated tentacles at their tips. There were at least two buds per animal and they were invariably at abnormal sites. (3) 32 % of the animals failed to regenerate heads, although they developed two buds. 87 % of these buds originated in abnormal sites of the body column and a large number (72%) did not detach even by the 12th day after decapitation.
Both 5 and 10 mM of 5-azaCR were toxic to the animals; the survivors formed large globeshaped heads. Bud induction was seen in 60% and 28% of animals in the 5 and 10 mM groups, respectively.
These observations demonstrate that 5-azaCR induces bud formation in hydra at doses that inhibit head regeneration. This bud induction might be due to a specific expression of gene products responsible for bud formation.
Myoblasts and notochord influence the orientation of somitic myoblasts from Xenopus laevis
Authors: Mccaig Colin D. 
Published: April 2021

ABSTRACT
The orientation of developing myoblasts extending a bipolar axis in the presence of explanted myoblasts or whole notochord has been studied in vitro. Myoblasts tended to elongate perpendicular to the lines of diffusion of substances from these tissues. A slow-release source of agar impregnated with medium conditioned by segmented somitic myoblast or notochord also caused myoblasts to elongate perpendicular to the lines of diffusion from the source. Medium conditioned by neural tube cells or unsegmented mesoderm cells did not influence the orientation of myoblasts.
It is concluded that somites and notochord release diffusible substances in vitro which are capable of directing the orientation of developing myoblasts. In vivo, a somite-derived material could play a role in determining the direction of myoblast elongation in the presomitic mesoderm. An interaction between somite and notochord-derived secretions could influence the rotation of presomitic myoblasts to form a segmented somite.