bluuebunny/crossref_metadata_2025_split huggingface dataset:
Re-evaluation of the presence of multiple haemoglobins during the ontogenesis of the chicken: Electrophoretic and chromatographic characterization, polypeptide composition and immunochemical properties
Authors: Schalekamp M. , Schalekamp M. , Goor D. Van , Slingerland R. 
Published: April 2021

ABSTRACT
Haemolysates of red blood cells from embryos of several developmental stages ranging from 2 to 21 incubation days and from post-hatching chickens of various age groups were analysed by ion-exchange chromatography, agar-and starch-gel electrophoresis, immunoelectrophoresis with specific antisera and polypeptide chain electrophoresis.
With these methods two adult (A1 and A2) and six embryonic (E1–E6 haemoglobin types were identified. Antisera specific for the major adult haemoglobins (A1 and A2) as well as antisera specific for the major embryonic haemoglobins (E3, E4) could be prepared. Throughout embryogenesis the haemoglobin types contribute in varying amounts to the total haemoglobin pattern. Three periods of haemoglobin synthesis could be recognized, the transition between these periods occurred at the 6th and 12th incubation day. The first period is characterized by the presence of two major embryonic haemoglobins (E3 and E4) and two minor embryonic haemoglobins (E2 and E5). During the second period E3 and E4 are largely replaced by a major adult haemoglobin (A2) and a new embryonic haemoglobin (E1). The third period is characterized by the appearance of a second adult haemoglobin (A1) and a new minor embryonic haemoglobin (E6) with a concomitant decrease of E2 and E5. At the time of hatching two embryonic haemoglobins (E1 and E6) are still present.
Besides A1 and A2, several minor haemoglobin fractions were inconsistently found in adult chickens. Evidence has been obtained that these additional fractions are reflecting a so called minor heterogeneity or separation artifacts.
The haemoglobins A1, A2 and E1 –E6 show different polypeptide chain compositions. Three embryo-specific chains could be demonstrated (β E2E5, γE4 and δ E3). The production of the polypeptide chains appears to be correlated with the aforementioned periods of haemoglobin synthesis.
The genetic and morphological implications of the findings are discussed.
Study of yolk-sac endoderm organogenesis in the chick using a specific enzyme (cysteine lyase) as a marker of cell differentiation
Authors: Bennett Nelly 
Published: April 2021

ABSTRACTThe detection of a specific enzyme (cysteine lyase) of the yolk-sac endoderm by a very sensitive method is employed to characterize cell differentiation during the early stages of endoderm organogenesis in the chick.The first cells to contain active cysteine lyase are found in the germ wall at the primitive streak stage.In vivo observations establish a relation between the morphological specialization and organization of endodermal cells, their loss of mitotic activity and the increase in cysteine lyase activity. They suggest an influence of the mesoderm on endoderm differentiation.In vitro experiments confirm the existence in the yolk-sac endoderm of an incompatibility between cell proliferation and differentiation, as well as the action of the mesoderm on both the structural organization of the endoblast and the appearance of cysteine lyase; this last action seems to be due mainly to blood cells; chicken and rabbit blood cells are equally active.The problems of the origin of the endoderm and of the interactions occurring during the organogenesis of the yolk-sac endoderm are discussed.
A histochemical study of sulphated glycosaminoglycans associated with the somites of the chick embryo
Authors: O’hare M. J. 
Published: April 2021

ABSTRACT
A histochemical analysis has been made of sulphated glycosaminoglycans (mucopoly-saccharides) associated with chick embryo somites before and after the onset of overt cartilage differentiation. The sulphated glycosaminoglycans were distinguished and resolved into different types by the use of alcian blue at low pH and alcian blue ‘critical electrolyte con-centration’ staining combined with hyaluronidase digestion.
The newly formed somites are bounded on their dorsal, ventral, and medial surfaces by basement membrane material as they are delimited from the unsegmented paraxial mesoderm Such epithelial basement membrane material, which was first detected in association with the epiblast/mesoderm boundary in the stage-4 embryo, was found to contain a major chondroitin sulphate A/C fraction and a minor chondroitin sulphate B fraction. The notochord sheath contained similar sulphated glycosaminoglycans.
Sulphated glycosaminoglycans were first detected between cells of the somite ‘core’ at stage 14 and were subsequently seen to accumulate around the cells of the developing sclero-tome and later around cells of the dermatome; the myotome was devoid of such material at these stages (stage 14–20). These pre-cartilaginous sulphated glycosaminoglycans were also of the chondroitin sulphate A/C plus chondroitin sulphate B types.
In contrast, the matrix material of newly forming vertebral cartilage, which was first seen in the anterior region of stage 21 embryos, was distinguished by its lack of a hyaluronidase-resistant sulphated glycosaminoglycan component, and therefore presumably contained only chondroitin sulphates A/C. Much later in development (after stage 33) small amounts of sulphated glycosaminoglycan with the staining properties of keratan sulphate were found in the perichordal and subperichondrial regions of the vertebral cartilage.
An experimental study of eye development in the cephalopod Loligo vulgaris: determination and regulation during formation of the primary optic vesicle
Authors: Marthy H.-J. 
Published: April 2021

ABSTRACT
By a series of explantation, transplantation (yolk syncytium left intact) and incision experiments done with the eye rudiment during the stages VI –IX (Naef, 1923) it is concluded that the yolk syncytium does not induce the differentiation of ‘the outer layer of cells’ from stage VI on as suggested by Arnold (1965 b). From the explantation and transplantation experiments the author draws the conclusion that there exists, from stage VI on, in the ‘outer layer of cells’ on each side of the embryo, an area which contains all factors necessary for eye formation and which manifests itself, under experimental conditions, in regulation. The explanted eye rudiment shows in vitro autonomous differentiation capacity only if nutritional conditions are sufficient. The incision experiments elucidate the role of ‘contractile elements’ in organogenesis. Arnold’s results are discussed.
Développement des organes lymphoïdes chez l’Amphibien UrodèleTriturus alpestrisLaur.; tolérance des allogreffes après la thymectomie larvaire
Authors: Tournefier Annick 
Published: April 2021

ABSTRACTThe development of lymphoid organs in the urodele amphibian Triturus alpestris Laur.; skin allograft tolerance after larval thymectomyThe first part of this work is an attempt to extend anatomical knowledge of lymphoid organ differentiation: thymus, spleen and liver in Triturus alpestris Laur.The purpose of the second part is to compare a first-set allograft reaction in normal adult newts (100% rejection) and the allograft reaction of larval-thymectomized adult newts. Thymectomy was performed on 39 newts in the tenth week of their life at a known stage of their splenic and thymic differentiation. These thymectomized newts were grafted 18 months later with two different adult skin grafts. A daily observation of the 78 grafts showed that larval thymectomy induced 72% of tolerance.However, 11 newts rejected their grafts in the same way as normal adult newts, but with a longer median survival time (36 days instead of 23 or 27 days). In five of these newts, dissection showed one or two functional thymic nodules and the allograft rejection was due to an incomplete larval thymectomy.In the six other newts, one thymic nodule was found, so the rejection was probably because the thymectomy was too late. Triturus alpestris Laur., like other urodeles, has no bonemarrow, and splenic lymphocytes are probably, for the most part, of thymic origin.Lymphocytes first appear in the spleen during ths ninth week of larval life. If thymectomy is performed at the end of the tenth week, splenic differentiation is completed and the spleen may substitute for thymus function in allograft rejection.
Contribution expérimentale à l’étude de la formation de l’endoblaste chez les Oiseaux
Authors: Lutz par Hubert 
Published: April 2021

ABSTRACT
The technique of marking the unincubated duck blastoderm with fine particles of Chinese ink leads to the following conclusions:
there exist superficial morphogenetic movements during the first few hours of incubation; surface material rolls round the posterior, lateral, and anterior margins; there is a direct continuity between extra-embryonic and embryonic endoblast.
The endoblastic layer forms therefore by surface material rolling round the posterior, lateral, and anterior margins.
Post-Partum Changes in the Uterus of the Rat
Authors: Warbrick James G. 
Published: April 2021

ABSTRACT
Rats were killed at intervals from 0 hours to 5 days after littering. Some of the changes that occur in the uterus during this period were studied. The area of endometrium left devoid of epithelium by the separation of the placenta was re-epithelialized by cells which spread in from the existing marginal epithelium. There was no evidence of a transformation of stromal into epithelial cells. The migrating epithelial cells did not contain glycogen and their cytoplasmic content of ribonucleic acid was reduced. Re-epithelialization of the sites was completed within 36 hours. There was vacuolation of the epithelial cells which was most marked from between 24 to 36 hours after littering. The changes in the rats’ uterus are compared with those occurring in some other mammals.
The Reversibility of the Effect of Hypervitaminosis A on Embryonic Limb Bones Cultivated in vitro
Authors: Herbertson M. A. 
Published: April 2021

ABSTRACT
Experiments were made to study the reversibility of the effects of hyper-vitaminosis A on embryonic long-bones in vitro. Limb-bone rudiments from 6-to 7-day chick embryos were cultivated by the watch-glass method, first in medium to which excess vitamin A had been added and then in normal medium. Suitable controls were also grown. The excess vitamin arrested the growth of the explants and caused the cartilage matrix to shrink and lose its basophilia and metachromasia. The extent of the damage depended upon the length of time spent in + A medium, the concentration of the vitamin, the stage of development of the rudiment when explanted, and the particular rudiment treated. The degree of recovery was related to the severity of the changes produced by the vitamin. In the shaft these changes were arrested but there was no restora-tion of lost matrix; the cells appeared healthy but resembled osteoblasts rather than normal hypertrophic chondroblasts. The epiphyses also partially recovered and began to enlarge again when transferred to normal medium; they had a high mitotic rate in comparison with the normal controls.
An ultrastructural study of germ plasm in spermatogenesis ofXenopus lœvis
Authors: Kerr J. B. , Dixon K. E. 
Published: April 2021

ABSTRACTSpermatogonia and primary diplotene and zygotene spermatocytes contain an electron-dense, finely granular substance which is usually closely associated with mitochondria; small patches of this substance also occur close to the nuclear membrane, often in the nuclear pores, and within the nucleus of primary spermatogonia. The fine structure of this substance is very similar to the fine structure of germ plasm in other stages of development, and since an ontogenetic continuity with germ plasm can be demonstrated, it was concluded that this substance is also germ plasm. The substance disappears about pachytene, earlier than in oogenesis where it persists until mid-diplotene, a difference which may be due to the fact that the oocyte stores large quantities of germ plasm in its cortex for the next generation of primordial germ cells. If the presence of the substance in the nuclear pores and within the nucleus is an indicator of synthesis of germ plasm, then synthesis stops in the secondary spermatogonium, which correlates with the subsequent absence of germ plasm from the pachytene spermatocyte stages. It is suggested that the function of the germ plasm in specifying germ line cells is carried out between the gastrula stage and the beginning of meiosis. The three events which take place during this period are (i) the migration of the presumptive primordial germ cells from the endoderm to the genital ridges, (ii) mitosis of the primordial germ cells and subsequently of the oogonia and spermatogonia in the developing gonads and (iii) preparations for meiosis. It is suggested that the mechanism of action of the germ plasm may be in the control of one or more of these processes. Other types of granular cytoplasmic deposits are also described, and their possible relationship to germ plasm discussed.
Mise en évidence de glycogène et d’une activité de la glycogène synthétase dans l’ébauche hépatique aux stades précoces du développement embryonnaire chez le poulet
Authors: Houssaint Elisabeth , Douarin Nicole M. Le 
Published: April 2021

ABSTRACTDetection of glycogen and glycogen synthetase activity in the hepatic primordium of chick embryo at early developmental stagesGlycogen has been detected cytochemically in the chick hepatic primordium at early developmental stages. The cytochemical methods used are PAS according to Hotchkiss & MacManus after fixation by Gendre’s fluid at —20 °C and rapid dehydration at 4 °C and Thiery’s technique for polysaccharide detection at the electron microscopic level. Previous authors reported that glycogen appears in the hepatocytes during the sixth or seventh day of incubation in the chick embryo. In fact, the more sensitive methods used here show that this substance is present in the determined presumptive hepatic endoderm as early as the 20-somite stage, some hours before the formation of the primary hepatic bud. Glycogen is present in an approximately constant amount in the differentiating hepatic endoderm as β particles (according to Drochmans’ nomenclature) from the 20-somite stage to the sixth day of incubation. Then the hepatocyte glycogen content increases rapidly as had previously been shown by biochemical methods and a rosettes appear in the cell. A glycogen synthetase activity has been detected at the end of the fourth day of incubation (96 h). This activity increases sharply from the sixth day of incubation to reach a maximal value at .12 days and then decreases until hatching. The possible regulatory mechanisms of glycogen synthesis in differentiating liver cells of avian embryos are discussed.
Trophoblastic factors involved in lysis of the blastocyst coverings and in implantation in the rabbit: observations on inversely orientated blastocysts
Authors: Denker H.-W. 
Published: April 2021

ABSTRACTLysis of the blastocyst coverings in the rabbit normally starts at the abembryonic hemisphere of the blastocyst facing the antimesometrial endometrium. Theoretically, this restricted effect could be caused by factors locally produced by abembryonic trophoblast, anti-mesometrial endometrium, or a combination of them. Blastocysts abnormally implanting with reversed orientation exhibit lysis of blastocyst coverings in the abembryonic hemisphere despite the absence of antimesometrial endometrium, and they do not show lysis in the embryonic hemisphere despite its contact with antimesometrial endometrium. Accordingly, it appears that lysis of blastocyst coverings is attributable to a factor localized in the abembryonic hemisphere of the blastocyst. Blastocyst protease activity was found to be maximal there in all blastocysts, whether oriented normally or reversed. The origin and role of this enzyme and other factors are discussed.
L’architecture des centres visuels diencéphaliques et pretectaux du poussin deGallus domesticusL. Etude expérimentale
Authors: Raffin J.-P. 
Published: April 2021

ABSTRACTThe architecture of the diencephalic and pretectal visual centres in Gallus domesticus L. An experimental studyThe effects of bilateral optic vesicle removal on the main diencephalic and pretectal visual centres have been studied from the 15th day of incubation till the 15th day after hatching.Some centres (nucleus lateralis anterior, nucleus geniculatus lateralis dorsalis and ventralis, nucleus griseums tectalis and nucleus pretectalis principalis) show a variable degree of disorganisation and reduction in size. Others (nucleus ectomammillaris, nucleus superficialis synencephali) have already disappeared on the 15th day of incubation. The nucleus rotundus, though not recognized as an optic projection centre, is also affected by optic vesicle removal. No true neuronal degeneration could be observed in these structures.A survey of chicken optic projections suggests that some may be only transitory, disappearing in the adult. A comparison of these results with those of other authors leads one to consider the morphogenetic influence of the optic pathways on the visual centres.
Studies on the gastrulation of amphibian embryos : pseudopodia in the gastrula ofBufo bufojaponicus and their significance to gastrulation
Authors: Nakatsuji Norio 
Published: April 2021

ABSTRACTThe course of gastrulation in embryos of Bufo bufo japonicus was studied by use of 1 μm Epon sections. It was observed that the cells of the presumptive pharyngeal endoderm and mesoderm form pseudopodia coinciding with their invagination. Some of the inner cells of the ectodermal layer also form pseudopodia. The cells of the endodermal mass and the surface of the embryo rarely form such structures. The observed pseudopodia seem to correspond to the hitherto reported pseudopodia formed by the dissociated cells from the gastrula of amphibians. Formation of the pseudopodia seems to suggest that the invagination of the presumptive pharyngeal endoderm and mesoderm is brought about by active migration of the individual cells along the inner surface of the ectodermal layer.
Induction de la tolérance aux allogreffes de peau dans les chimères de l’amphibien modèle,Pleurodeles waltliiMichah.
Authors: Goujon P. 
Published: April 2021

ABSTRACTInduction of skin allograft tolerance in chimaeras of urodele amphibian, Pleurodeles waltlii MichahAllogenic chimaeras were produced in Pleurodeles waltlii (Amphibian, Urodele) by associating the anterior and the posterior parts of two different embryos. A reciprocal exchange between two homologue embryos gave rise to reciprocal allogenic chimaeras.Skin grafts performed in the adult stage between two reciprocal chimaeras are always tolerated. On the other hand, when two skin grafts coming from the anterior and the posterior part of one chimaera are grafted on a common host, one of them may be tolerated and the other rejected : each part of a chimaera keeps its own antigenicity.In allogenic chimaeras, the average natural tolerance for skin allografts is 30 % higher than in sibling controls.
Differentiation in vitro of larval cell types from early embryonic cells of Drosophila melanogaster
Authors: Shields Glen , Dübendorfer Andreas , Sang James H. 
Published: April 2021

ABSTRACT
A variety of cell types develop when cells of h Drosophila embryos are cultured in an improved medium. Nerve, muscle, fat-body, chitin-secreting, and macrophage-like cells (possibly haemocytes) appear in the first 24 h and mature over the next week. Tracheal, imaginai disc, a second stage of the macrophage-like, and a number of unidentified fibroblastic and epithelial cells appear in the 2nd and 3rd week, following a resumption of cell multiplication. There is some organization of some of the cell types into higher structures.
Structural basis of the functional development of the retina in the cichlid Tilapia leucosticta (teleostei)
Authors: Grün Gerd 
Published: April 2021

ABSTRACT
The differentiation of retinal cells has been studied with special reference to the formation of functionally important structures. Three phases could be revealed: from day 3 to day 6 retinal cells in the mostly advanced central part show signs of general cell differentiation (formation of ribosomes, endoplasmic reticulum, mitochondria). In the second phase from day 6 to day 9 characteristic nerve cell structures appear (neurites, dendrites, synapses, receptor outer and inner segments). In the last phase from day 9 to day 12 these special structures attain their final, mature appearance, synapses seem ready for function, dendritic invaginations and synaptic ribbons are formed, twin cones become arranged in mosaic patterns. This developmental order conforms to a gradient running from the ganglion cells to the receptors. Neurites and dendrites appear in the ganglion cells on day 3, in the intermediate neuron layer not before day 4. The horizontal cells are the last ones to differentiate out of the intermediate neurons. The inner plexiform layer synapses are structurally mature before those from the outer plexiform layer. The receptor inner and outer segments differentiate from the 5th day up to the time the young fish is able to see (day 13). The last structures to appear are dendritic invaginations and synaptic ribbons in the receptor terminals, and the twin cone mosaic. It is assumed that the ability to see is achieved only when these structures have been formed.
Differentiation of photoreceptors in cultured optic vesicles from embryos of Rana esculenta
Authors: Caravita S. , Cataldi E. 
Published: April 2021

ABSTRACT
Optic vesicles from embryos of Rana esculenta at a stage corresponding to stage 19 in the development of Ranapipiens were cultured for 15 days. The eyes which differentiated in vitro were much smaller than controls of the same age, due partly to the absence of the vitreous body. In many specimens a well-stratified retina surrounded by a layer of pigmented cells was found. The features of all the components of the retinal layers are described.
The complete differentiation of photoreceptors, including their outer segments, is the most interesting result obtained in these organ cultures, and is in contrast with the observations previously reported for retinal tissue cultures. The authors suggest that the source of the material (amphibia instead of birds or mammals) is the main reason for this discrepancy. Frog embryo cells are practically self-sufficient since they are endowed with nutritional substances, amongst which Vit. A and antioxidative agents (Vit. E and ascorbic acid) have been indicated as the most important factors for the structural organization and integrity of the outer segments. The role played by the pigment epithelium is also discussed.
Autoradiographic studies of t
n
/t
nmouse embryos
Authors: Nadijcka Mary , Hillman Nina 
Published: April 2021

ABSTRACT
High-resolution autoradiographic studies were used to determine whether t12/t12 and tw32/tw32 mouse embryos synthesize the excessive lipid which distinguishes these embryos prior to their death. The studies show that the tn homozygotes synthesize neutral lipid which is stored in intracellular lipid droplets. Cholesterol and phospholipid precursors are not incorporated into these droplets.