bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence inductrice de l’encéphale embryonnaire sur le développement du crâne chez le poulet: II. Influence de l’excision de la chorde et des territoires encéphaliques moyen et postérieur sur le développement crânien
Authors: Schowing Par Jean
Published: April 2021

The inductive influence of the embryonic brain upon the development of the skull in the fowl. II. The effect of removal of notochord and of mid-and hind-brain material upon cranial development

The notochord and the mid-and hind-brain of chick embryos 48 h old were removed with the following consequences.

Excision of the notochord alone leads to a reduction of the basal plate and basioccipital. The other bones of the head are unaffected by the operation. Excision of the mesencephalon alone has a minor effect on the skull. Its action on cranial differentiation is weaker than that of the other parts of the brain. Excision of the rhombencephalon alone leads to a reduction of parietals, which disappear after excision of both mesencephalon and rhombencephalon. In both cases, the basal plate is reduced. Development fails completely if the notochord is excised with the brain tissue. If both rhombencephalon and anterior medullary tube are excised, the parietals are reduced and the lateral and dorsal parts of the occipital complex disappear. The basioccipital and basal plate are differentiated, but remain small. These experiments demonstrate that cranial vault differentiation depends on the brain and show the role of the notochord in the development of the cartilaginous cranial floor.
The effect of removing the polar lobe in centrifuged eggs of Dentalium
Authors: Verdonk N. H.
Published: April 2021

Classical evidence for the existence of morphogenetic substances was provided by experiments with spiralian eggs possessing a polar lobe: Ilyanassa (Crampton, 1896; Clement, 1952, 1956, 1962); Dentalium (Wilson, 1904); Chaetopterus (Tyler, 1930); Sabellaria (Hatt, 1932; Novikoff, 1938); and Mytilus (Rattenbury & Berg, 1954). Eggs from which the polar lobe had been removed developed into embryos with specific abnormalities. In Dentalium, after removal of the polar lobe at the trefoil stage, a trochophore larva is formed without post-trochal region and apical tuft. Removal of the polar lobe at second cleavage causes a larva without post-trochal region, but with an apical tuft. Wilson concluded that specific cytoplasmic materials essential to the formation of the apical tuft are contained in the first but no longer in the second polar lobe.
Mise en évidence du rôle inducteur de l’encéphale dans l’ostéogenèse du crâne embryonnai re du poulet
Authors: Schowing Par Jean
Published: April 2021

Nos expériences d’excision des différents territoires encéphaliques (Schowing, 1959, 1961, 1967) mettent en évidence l’importance du rôle des structures nerveuses dans la différenciation du squelette crânien. Le mécanisme de cette action inductrice, ainsi que la nature de l’inducteur, est mal connu.
Influence inductrice de l’encéphale embryonnaire sur le développement du crâne chez le Poulet: I. Influence de l’excision des territoires nerveux antérieurs sur le développement crânien
Authors: Schowing Par Jean
Published: April 2021

The inductive influence of the embryonic brain upon the development of the skull in the fowl. I. The effect of removal of anterior neural material upon cranial development

Chick embryos 48 h old and possessing 10-20 somites were subjected to the removal of different parts of the brain.

Removal of the prosencephalon alone leads to a reduction of the frontal bones. The other bones of the skull are unaffected. The frontals disappear if both prosencephalon and mesencephalon are excised. Both frontal and parietal bones disappear if the brain is completely removed. In this case, the squamosals alone remain, but are reduced. The cranial floor is also changed. If both brain and anterior medullary tube are excised, not only the frontals and parietals disappear, but also the supraoccipitals. At the same time, the cranial floor is reduced. Depending upon the presence or absence of the face, the palatines are normal or reduced and the parasphenoidal rostrum is present or absent. In the absence of notochord, the cranial floor is reduced or lacks some pieces, particularly basisphenoid and basioccipital. The cranial vault depends directly on the brain which is necessary for its differentiation. The palatines and the parasphenoidal rostrum are independent of nervous tissue but both depend upon the presence of the face. The basisphenoid and the basioccipital are influenced by both neural tube and notochord. This suggests that the latter has an important role, worthy of further study.
Ultracentrifugal and electrophoretic analysis of the water-soluble fraction of chick embryo yolk
Authors: Carinci P. , Manzoli-Guidotti L.
Published: April 2021

Ultracentrifugal and electrophoretic analysis of chick embryo yolk water-soluble fraction (WSF) has been carried out using fertile non-incubated eggs and at 10, 15 and 21 days incubation. Ultracentrifugal and electrophoretic analysis of WSF globulins has been carried out at the same incubation stages. The ultracentrifugal and electrophoretic patterns of both the WSF and its globulin components at 10 days incubation are very similar to those observed in non-incubated eggs. Ultracentrifugal and electrophoretic patterns at 15 and 21 days incubation undergo marked changes due to the appearance of egg-white proteins in the yolk. The significance of these findings in relation to embryogenesis is discussed.
Analysis of the development of the nervous system of the zebrafish, Brachydanio rerio: I. The normal morphology and development of the spinal cord and ganglia of the zebrafish
Authors: Weis Judith Shulman
Published: April 2021

In embryos and young fry of the zebrafish, Brachydanio rerio, the sensory function of the nervous system is fulfilled by a primitive transitory system of Rohon-Beard cells. These are replaced 2 or 3 weeks after hatching by the developing spinal ganglia. The spinal ganglia are typically tear-drop-shaped and occupy a dorsolateral position relative to the spinal cord, with the exception of the first three pairs of ganglia which are large, round, and lie ventrolateral to the cord. As the fish grow, the spinal ganglia grow in size, due to an increase in cell size, and an increase in cell number. This is different from the situation in mammals and chicks, for example, in which the number of cells reached in embryonic stages remains constant, and growth of ganglia is achieved only by means of cell enlargement.
Differentiation ofalkaline phosphatase and glucose-6-phosphatedehydrogenase in rat yolk-sac
Authors: Johnson E. Marshall , Spinuzzi Ralph
Published: April 2021

Electrophoretic and biochemical techniques were applied to homogenates of the visceral yolk-sac of rat embryos at various gestational ages. Alkaline phosphatase was shown by starch gel electrophoresis of normal yolk-sacs to undergo specific sequential changes from day 10 to day 20 of gestation. The isozyme repertory on any given day of gestation was achieved by deletions from, or additions to, that of the previous day. Glucose-6-phosphate dehydrogenase was shown, by polyacrylamide gel electrophoresis of normal yolk-sacs, to achieve early in gestation a qualitatively constant number of enzyme forms. Quantitative changes among the enzyme forms occurred as gestation proceeded. A teratogenic folic acid deficiency resulted in the delayed appearance of some enzyme forms as well as the premature disappearance of others in the two enzyme systems studied. The effects of the treatment were selective in that not all of the enzyme forms of the treated material were affected.
The origin of vertebrate limbs
Authors: Coates Michael I.
Published: April 2021

The earliest tetrapod limbs are polydactylous, morphologically varied and do not conform to an archetypal pattern. These discoveries, combined with the unravelling of limb developmental morphogenetic and regulatory mechanisms, have prompted a re-examination of vertebrate limb evolution. The rich fossil record of vertebrate fins/limbs, although restricted to skeletal tissues, exceeds the morphological diversity of the extant biota, and a systematic approach to limb evolution produces an informative picture of evolutionary change. A composite framework of several phylogenetic hypotheses is presented incorporating living and fossil taxa, including the first report of an acanthodian metapterygium and a new reconstruction of the axial skeleton and caudal fin of Acanthostega gunnari. Although significant nodes in vertebrate phylogeny remain poorly resolved, clear patterns of morphogenetic evolution emerge: median fin origination and elaboration initially precedes that of paired fins; pectoral fins initially precede pelvic fin development; evolving patterns of fin distribution, skeletal tissue diversity and structural complexity become decoupled with increased taxonomic divergence. Transformational sequences apparent from the fish tetrapod transition are reiterated among extant lungfishes, indicating further directions for comparative experimental research. The evolutionary diversification of vertebrate fin and limb patterns challenges a simple linkage between Hox gene conservation, expression and morphology. A phylogenetic framework is necessary in order to distinguish shared from derived characters in experimental model regulatory systems. Hox and related genomic evolution may include convergent patterns underlying functional and morphological diversification. Brachydanio is suggested as an example where tail-driven patterning demands may have converged with the regulation of highly differentiated limbs in tetrapods.
Growth factors in development: the role of TGF-β related polypeptide signalling molecules in embryogenesis
Authors: Hogan Brigid L. M. , Blessing Manfred , Winnier Glenn E. , Suzuki Noboru , Jones C. Michael
Published: April 2021

Embryonic induction, the process by which signals from one cell population influence the fate of another, plays an essential role in the development of all organisms so far studied. In many cases, the signalling molecules belong to large families of highly conserved proteins, originally iden- tified as mammalian growth factors. The largest known family is related to Transforming Growth Factor-β (TGF-β related to Transforming Growth Factor-β and currently consists of at least 24 different members.

Genetic studies in Drosophila on the TGF-β related gene, decapentaplegic (dpp), reveal the existence of conserved mechanisms regulating both the expression of the protein during development and the way in which it interacts with other signalling molecules to generate pattern within embryonic tissues. Comparative studies on another TGF-β related gene, known as Bone Morphogenetic Protein-4 (BMP-4), in Xenopus and mouse point to a conserved role in specifying posteroventral mesoderm during gastrula- tion. Analysis of other polypeptide signalling molecules during gastrulation suggests that their interaction in the generation of the overall body plan has also been conserved during vertebrate evolution.
Les effets de la centrifugation sur la blastula et la jeune gastrula des Amphibiens
Authors: Pasteels J.
Published: April 2021

Nous avons montré dans les deux premiers mémoires de cette série que la centrifugation aux stades blastula et jeune gastrula peut provoquer une activation de redoblaste-, c’est à dire que sans aucune intervention d’un inducteur éventuel, l’ectoblaste constitue des tissus nerveux et neuroïdes, de la chorde, des somites, du pronéphros. Le caractère autonome de cette activité a pu être démontré par des expériences d’explantations (Pasteels, 1953a, p. 15) ou de greffes, soit homoplastiques (Pasteels, 1953a, p. 16), soit hétéroplastiques (Pasteels, 1953a, p. 17).
The Inducing Action of the Bone-marrow of the Guinea-pig after Alcohol and Heat Treatment in Implantation and Explantation Experiments with Embryos of Triturus
Authors: Toivonen Sulo
Published: April 2021

In previous implantation experiments (Toivonen, 1953) the alcohol-treated bone-marrow of the guinea-pig had proved to be a very specific inductor of mesodermal structures. 2.The same material has been treated in addition for 10 minutes in hot water at 80°-90° C. and then used as inductor in implantation experiments with whole gastrulae of Triturus vulgaris. The results of this experiment show that the previous mesodermal activity of the inductor has completely disappeared; it now induces purely epidermal formations, such as lenses, lentoids, and balancers. In explantation experiments with the ‘sandwich’ method the alcohol-treated bone-marrow tissue has induced the same mesodermal structures as in the previous series with whole gastrulae. Heat-treated bone-marrow has induced in the ‘sandwiches’ normal epidermis in the neighbourhood of the inductor, and in addition lentoids and balancerlike formations. Because the previously very strong mesodermal activity of the inductor has disappeared as a result of the heat treatment and the treated inductor has only been able to exert a weak epidermal activity, it is assumed that the heat treatment has inactivated the independent, thermolabile mesodermal agent, and the epidermal agents, which are present in the inductor, have consequently been enabled to exert their own effect. The chemical nature of the mesoderm-inducing agent is discussed; and also the similarity of the tissue-specific agents which presumably regulate regeneration in adult vertebrates and the embryonic inducing agent.
The Relation of the Interrenal Blastema to the Origin of the Somatic Tissues of the Gonad in Frog Tadpoles
Authors: Vannini Enrico , Sabbadin Armando
Published: April 2021

In frog tadpoles the interrenal blastema proliferates from the lateral plates in the zone where the splanchnopleures meet to form the dorsal mesentery. At first the interrenal proliferation appears distinct and separate from the mesonephric blastemata which, in the form of nephrogenic cords, occupy a more lateral site. In later stages the interrenal blastema moves dorsally from its site of origin to join secondarily, under the aorta, the medial faces of the mesonephric blastemata, which are now differentiating their tubular structures. The interrenal blastema in early stages contracts relationships with the primordial germ-cells, when the latter form a median unpaired genital ridge at the mesenteric root; and it provides these cells with the first somatic follicular elements, which will then take part in the genesis of the gonadal cortex. A further participation of the interrenal blastema in the constitution of the gonadal cortex is also observed later, at the stage when paired genital ridges lie one at each side of the dorsal mesentery. In this stage interrenal cells descend towards the gonadal primordia, moving down along the walls of the vena cava, and penetrate between the germ-cells, contributing further to the formation of their follicles. The interrenal blastema later continues to penetrate into the gonadal rudiment, now providing only medullary tissue. Such embryological relationships between the interrenal blastema and the somatic cortical and medullary tissues of the gonads suggest the following points. (a) They appear to be in accord with the chemical and physiological likeness of the steroid hormones which will be secreted by these tissues in the adult. (b) They further suggest that sex differentiation of the Amphibian gonads is not based on a predetermined antagonism between a cortical and a medullary somatic tissue, each different from the beginning both in activity and in embryonic origin. On the contrary, the common embryological derivation of these territories agrees very well with their reported power of partly modulating themselves in either an ovarian or a testicular direction, according to the gonadal sex differentiation. The feminizing potentiality of the cortex on the one hand, and the masculinizing potentiality of the medulla on the other hand, seem thus to establish themselves little by little, during the process of gonad differentiation, under the activity of the genetical factors of sex determination. Analogous powers of transforming their morphogenetic destinies seem also to have already been reported, by other workers, for the cells lying in the boundary zone between the interrenal and the mesonephric blastemata. All the blastemata of the urogenital area, which have a mesodermal origin, seem therefore to be endowed with a certain degree of pluripotentiality, their definitive morphogenetical determination being gradually attained in the course of development.
Les injections localisées en chimiotératogenèse
Authors: Ancel P.
Published: April 2021

Localized injections of chemical substances on to young chick embryos have provided new data on the determination of the teratogenic dose, on the sensitivity of certain embryonic rudiments, on the mode of teratogenic action of various chemical substances and on certain problems of embryonic mechanisms.
A quantitative approach to the detection of nuclear activity after differential damage to nucleus and cytoplasm in early development
Authors: Neyfakh A. A. , Rott N. N.
Published: April 2021

For studying nucleo-cytoplasmic relations during development various selective influences on the nucleus and cytoplasm are widely used as the main method of experimental analysis. However, the application of such techniques presents difficulties both in obtaining evidence that shows the specificity of a nuclear or cytoplasmic effect by a chosen agent and in the quantitative evaluation of the extent of damage.
The role of acid phosphatase in the fusion of the secondary palate
Authors: Angelici D. , Pourtois M.
Published: April 2021

Complete closure of the secondary palate must progress through two con-secutive events: the converging movement of the palatal shelves and their subsequent fusion at the line of contact. Each step is indispensable in normal palatal development since, theoretically, a palatal cleft might be the consequence of a failure of either.
Changes in the rate of cell divisions in the course of early development of diploid and haploid loach embryos
Authors: Rott N. N. , Sheveleva G. A.
Published: April 2021

The period of development preceding gastrulation can be divided into two stages. The first is characterized by rapid synchronous cell division. True interphase, which is characterized by the fusion of karyomers and the occurrence of a nucleolus, is absent at this stage. During the second stage the rate of cell division decreases and divisions are asynchronous.
La colonisation des ébauches gonadiques par les cellules germinales de l’embryon de Poulet, en culture in vitro
Authors: Dubois Regis
Published: April 2021

Chez les Vertébrés, la ségrégation de la lignée germinale s’effectue dès les stades les plus précoces du développement. Les cellules germinales primordiales (CGP) apparaissent toujours hors des gonades et se trouvent souvent localisées dans des territoires bien délimités, plus ou moins éloignés des ébauches gonadiques présomptives. La destinée des gonocytes étant liée de façon irréductible à leur installation dans les ébauches génitales, ces cellules entreprennent, à chaque génération, une migration qui les conduit infailliblement aux épithéliums germinatifs.
The effect of rubella and herpesvirus hominis on the pre- and post-implantation stages of pregnancy in laboratory animals
Authors: Oxford J. S. , Sutton R. N. P.
Published: April 2021

The teratogenic effect of rubella virus in humans has now been well documented (Ingalls, Plotkin, Meyer & Parkman, 1967) and virus isolation studies have suggested that rubella virus causes embryopathy by actually infecting the cells of the developing foetus (Alford, Neva & Weller, 1964). However, a laboratory animal model is required for controlled studies of the teratogenic activity of rubella virus and for the assessment of possible preventative measures. Such an animal system would also be useful for screening attenuated rubella vaccine strains for teratogenic properties. Pregnant primates have been used in preliminary experiments with rubella virus (Parkman, Phillips & Meyer, 1965) but suffer from the disadvantages of size, expense and difficulty of mating. Both the hamster (Ferm&Kilham, 1965) and the rabbit (Gibson, Staples & Newberne, 1966) have proved useful animals for the investigation of teratogenic agents. We have described previously the adaptation of strains of rubella virus to small laboratory animals (Oxford & Schild, 1966; Oxford, 1967) and wish now to report studies of the infection of rabbits and hamsters with rubella virus in the early stages of pregnancy.
Immunoelectrophoresis of egg and plasma proteins during development of the house sparrow, Passer domesticus
Authors: Bush Francis M. , Seibert Charlene A.
Published: April 2021

Differentiation of plasma proteins in avian embryology has been analysed by electrophoresis (Brandt, Clegg & Andrews, 1951; Schechtman, 1952; Heim & Schechtman, 1954; Weller & Schechtman, 1962). Information has been obtained on affinities between plasma and egg proteins by electrophoretic studies (Wise, Ketterer & Hansen, 1964) and by immunochemical studies (Kaminski & Durieux, 1956; Williams, 1962a; Stratil, 1967; Zaccheo & Grossi, 1967).
Endocrine influences on growth and pigmentation of embryonic down feather cells
Authors: Johnson Leland G.
Published: April 2021

Rawles (1960) and Hamilton (1952) have outlined the development of the down feather. Details of the development and interaction of the epidermal constituents and melanocytes of the down feather were reported by Watterson (1942) and Goff (1949) described the development of the mesodermal portions of the feather.
Ultrastructure et cytochimie ultrastructurale de la vésicule germinative et du cytoplasme périnucléaire de l’oocyte mûr de Xenopus laevis
Authors: Gansen Par P. Van , Schram A.
Published: April 2021

Les oocytes et les œufs de Batraciens constituent, depuis longtemps, un material de choix pour les embryologistes. Au cours de ces dernières années, les phénomènes initiaux du développement embryonnaire ont été étudiés avec toute la précision que permettent les techniques biochimiques et cytochimiques actuelles. En particulier, l’étude de la maturation des oocytes de Batraciens a été reprise par plusieurs auteurs depuis que ce phénomène peut être obtenu in vitro (Dettlaff, Nikitina & Stroeva, 1964; Dettlaff, 1966; Brachet, 1965a, b, 1967; Smith, Ecker &. Subtelny, 1966). Brachet a mis en évidence l’apparition, au cours de la maturation, de grains Feulgen-positifs distincts des chromosomes, dans le suc nucléaire de Rana, de Xenopus et de Bufo ainsi que dans le cytoplasme périnucléaire des oocytes de Bufo. Ces grains se rassemblent dans le cytoplasme cortical, puis ils disparaissent (Brachet, 1965a).
Extra-uterine development of mouse blastocysts cultured in vitro from early cleavage stages
Authors: Billington W. D. , Graham C. F. , McLaren Anne
Published: April 2021

Many experiments indicate that oviducal mouse eggs are unable to form embryonic tissues following transplantation to extra-uterine sites; they give rise only to trophoblast and extra-embryonic membranes (Fawcett, Wislocki & Waldo, 1947; Fawcett, 1950; Chester-Jones, 1951; Whitten, 1958; Kirby, 1962; Billington, 1965). Possible rare exceptions exist in the reports by Runner (1947) and Stevens (1967). In contrast, about a quarter of uterine blastocysts form mor-phologically normal embryos when similarly transplanted (Kirby, 1963; Billington, 1965). The conditions under which the mouse eggs reach the blastocyst stage may also have developmental consequences. Eggs cultured in vitro to the blastocyst stage (Whitten, 1956) or tube-locked blastocysts (Kirby, 1962) did not develop embryonic tissue in extra-uterine sites, but were capable of complete development following transfer to a receptive uterus.
Etude cytochimique, an microscope électronique, des structures à ARN et du glycogène dans le cytoplasme des oocytes de Xenopus laevis
Authors: Thomas Christian
Published: April 2021

Ayant entrepris une étude de l’évolution des structures ribosomales au cours de l’oogenèse chez Xenopus laevis, nous avons montré, dans un précédent travail (Thomas, 1967), qu’un constituant fibrillo-granulaire est présent dans le cytoplasme des oocytes tout au long de leur croissance:

(1) Le cytoplasme des oocytes de moins de 300 μ ne contient pas, ou peu, de ribosomes typiques; il montre un matériel fibrillaire et granulaire, d’environ 10 à 20 Å de diamètre, plus ou moins dispersé suivant le stade, fréquemment agencé en travées.

(2) De nombreux corpuscules d’aspect ribosomal, reliés entre eux par des travées, apparaissent au début de la vitellogenèse. Ces corpuscules et les travées qui les relient sont constitués de fibrilles et de granules identiques au matériel trouvé dans les oocytes de moins de 300 μ.

(3) Des corpuscules d’aspect ribosomal, non réunis par des travées et dont la structure est formée de fibrilles et de granules de 10 à 20 Å de diamètre, sont présents dans les oocytes de 700 et de 1000 μ. Ils sont disséminés dans le cytoplasme parmi les granules β de glycogène. Cet ensemble d’observations nous a conduit à l’idée que les ribosomes s’édifieraient progressivement, dans le cytoplasme oocytaire, par la condensation d’unités élémentaires présentes dans les jeunes oocytes de Xenopus laevis. Le présent travail a pour but d’apporter des arguments cytochimiques, à l’échelle de l’ultrastructure, en faveur de cette hypothèse, en employant des techniques mettant spécifiquement en évidence les structures à ARN, soit par une coloration sélective, soit par une digestion enzymatique spécifique. Ce travail a été complété par une étude cytochimique du glycogène dans les gros oocytes (1000 μ).
Differentiation potencies of the young chick blastoderm as revealed by different manipulations: I. Folding experiments and position effects of the culture medium
Authors: Eyal-Giladi Hefzibah
Published: April 2021

An earlier study has demonstrated both the equipotentiality and the lability of the very young unincubated chick blastoderm (Eyal-Giladi & Spratt, 1965). It was observed that when a central cut was made in a blastoderm of this age, an embryo tended to form along the cut edge and the original embryo-forming centre at the prospective posterior side was suppressed. As the blastoderms grow older, the embryo-forming potency as expressed by the reaction to the cut is gradually lost from the central area, becomes confined to the marginal zone, and within it gradually to its posterior region.
The mitotic pattern of the embryonic epidermis of chick during scale morphogenesis
Authors: Yohro Takesi
Published: April 2021

The epidermis of the chick embryo has been widely used for in vitro studies of many developmental problems (Matoltsy, 1960; Billingham & Silvers, 1963). The present attempt to determine the proliferation rate of chick embryonic epidermal cells was expected to provide a base for experimental studies, but a preliminary mitotic count revealed that the number of mitoses varied greatly in different areas. This suggested accumulation of mitoses in some restricted parts of the epidermis, and so a mapping experiment was carried out to determine the distribution of mitoses in this material. The characteristic mitotic pattern which was discovered is described and discussed.
Effects of β-mercaptoethanol on the fine structure of the neural plate cells of the chick embryo
Authors: Messier Paul-Emil
Published: April 2021

In the course of his studies on mitosis in sea-urchin eggs, Mazia (1958 a, b) first used mercaptoethanol (HS-CH2 -CH2 OH) in biological research. This strongly reducing sulphydryl reagent penetrates easily into living cells and is relatively non-toxic. In an extensive series of studies Brachet and coworkers, using this substance, have illustrated its remarkable inhibitory effects on regeneration in a large variety of biological specimens, including nucleate or anucleate fragments of Acetabularia mediterrenea, cephalic regions of Planaria, the tail bud of tadpoles (Brachet, 1959) and bud regeneration in Hydra (Descotils-Heernu, Quertier & Brachet, 1961). Moreover, light-microscope and biochemical studies have shown that mercaptoethanol is a powerful inhibitor of neurulation, both in amphibians (Brachet, 1959,1963; Brachet et al. 1961 ; Malpoix, Quertier & Brachet, 1963; Pohl & Quertier, 1963) and chick embryos (Pohl & Brachet, 1962; Pohl & Quertier, 1963).
Haemoglobins of the foetal and adult rat: sites of synthesis and the effects of erythropoietin
Authors: Hunter J. A. , Paul J.
Published: April 2021

Early studies on rat haemoglobins indicated the existence of several components (Gratzer & Allison, 1960). Seven components were found in the blood of adult random-bred Wistar rats by CM-cellulose chromatography; their rates of synthesis appeared unaltered during erythroid cell maturation (Brada & Tobiska, 1964). A 5-component electrophoretic pattern found in some randombred Wistar rats was considered to be a combination of two 4-component patterns observed in two inbred strains (Marinkovic, Martinovic & Kanazir, 1967). A 4-component electrophoretic pattern was also reported by Cole,

Hunter & Paul (1968). During gestation the number of components resolved in this buffer system increased from 1 at 13 days to 4 at 15 days; the pattern appeared identical to that of the adult from 18 days onward.
Formation de novo and development of neuromuscular junctions in vitro
Authors: Veneroni Giorgio , Murray Margaret R.
Published: April 2021

The purpose of this study has been to examine, by means of isolation in vitro, the conditions under which neuromyal junctions develop. More than a hundred years ago Doyère (1840) observed in the water-bear Milnesium tardigradum that the nerve fibers terminate in characteristic eminences of muscle fibers. This observation, made on an arthropod, stimulated research into the connexion between muscle and nerve fiber, and resulted in abandonment of the older concept that motor nerves after having formed loops around the muscles return to the central nervous system as sensory pathways. Although investigations during the intervening century have identified and characterized morphologically the ‘motor end plate’ (as it was designated by Krause, 1863), and have revealed microscopic and fine-structural differences between types of motor endings, there is as yet no general agreement on the respective roles played by nerve, muscle and ambient influences in the development of the neuromuscular junction.
Cytotoxicity of lens antisera to dissociated chick neural retina cells in tissue culture
Authors: Braverman Max , Cohen Carl , Katoh Arthur
Published: April 2021

Immunoprecipitation techniques have shown that characteristic lens proteins can be found in many tissues of the chick eye. Langman & Prescott (1959), Maisel & Langman (1961a), Maisel (1962) and Maisel & Harmison (1963), among others, have demonstrated antigens cross-reacting with adult chick lens antisera in iris, pigmented retina, cornea and aqueous and vitreous humour. Maisel (1963) suggested that lens antigens are present in neural retina, but the presence of lens antigens in this tissue has not been firmly established, and a number of investigators reporting lens antigens in other ocular tissues have not found them in the neuro-retina. [For reviews of immunological investigations on the development and ubiquity of lens proteins see Langman (1959a, b), Maisel & Langman (1961b), Rabaey (1962), Woedereman (1961), Zwaan (1963), Ikeda & Zwaan (1966, 1967), Zwaan & Ikeda (1968) and Clayton, Campbell & Truman (1968).]
Transfert de cellules germinales primordiales de Dindon à l’embryon de Poulet par injection intravasculaire
Authors: Reynaud Georges
Published: April 2021

Les recherches descriptives et expérimentales concernant l’étude des rapports entre soma et germen, suscitées par les théories de Nussbaum (1880) et de Weismann (1885), ont montré que chez la plupart des Métazoaires — et notamment chez la quasi totalité des Vertébrés — le soma et le germen constituent des lignées cellulaires déjà distinctes au début du développement puisque la destruction des éléments germinaux entraîne la stérilité sexuelle définitive des individus. La ségrégation complète et irréversible des lignées somatique et germinale n’implique pas pour autant leur indépendance métabolique. Des travaux portant sur la différenciation des cellules germinales et la maturation des gamètes ont en effet démontré qu’elles nécessitent un apport de substances provenant des tissus somatiques de la gonade. Dès lors, on pouvait se demander si certaines de ces substances n’étaient pas porteuses d’information. La résolution expérimentale de ce problème nécessitait la colonisation d’un tissu somatique de gonade par des cellules germinales de spécificité zoologique différente.
Activité hormonale des gonades d’embryons de Poulet hypophysectomisés
Authors: Akram Hémayatollah , Weniger Jean-Pierre
Published: April 2021

Si, pour les uns, l’hypophysectomie, chez l’embryon de Poulet, ne retentit aucunement sur le développement des gonades (Wolff & Stoll, 1937; Van Deth, Van Limborgh & Van Faassen, 1956), pour les autres, elle entraîne la raréfaction du tissu interstitiel testiculaire et l’amincissement du cortex ovarien (Fugo, 1940; Vogel, 1957; Betz, 1967). Nous n’entrerons pas dans ce débat. Nous avons visé un autre point.
Formation et rôle des nucléoles des ovocytes de Trituras helvéticas Raz — Etude autoradiographique et ultramicroscopique
Authors: Sanchez Simone
Published: April 2021

La présence d’un très grand nombre de nucléoles dans la vésicule germinative des Amphibiens, et l’évolution de cette population nucléolaire au cours de l’ovogénèse est un phénomène particulier qui a déjà suscité de nombreux travaux. MacGregor (1965) a résumé les résultats obtenus par différents auteurs et rapportés ses propres observations sur la formation des nucléoles chez les Amphibiens de différentes espèces. Il ressort de l’analyse faite par cet auteur que deux mécanismes généraux déterminent l’état multinucléolé des ovocytes d’Amphibiens, soit que les chromosomes plumeux élaborent des corps nucléo-laires qui viennent grossir la population des nucléoles d’origine, soit que la fragmentation des nucléoles d’origine conduise à une multiplication de ces derniers, sans qu’une élaboration nouvelle intervienne. Mais, quelle qu’en soit l’origine, les nucléoles néoformés apparaissent, aux yeux de cet auteur, parfaite-ment identiques aux nucléoles originels. Par contre, Gall (1968) montre que l’apparition des organisateurs nucléolaires et de l’ADN qui constitue ces organisateurs, a lieu au cours du stade pachytène de la méiose, et la multiplica-tion nucléolaire qui suit, s’effectue en liaison avec ces organisateurs. Ces observations suggèrent que la population des nucléoles typiques est fixée dès les premiers stades de la méiose. Cependant, de très nombreux corps nucléo-laires apparaissent au stade diplotène suivant, dans les ovocytes d’Amphibiens. Chez Xenopus laevis, Van Gansen & Schram (1968) distingue, à la fin de ce stade, trois types de nucléoles: des nucléoles typiques, des micronucléoles, et des nucléoles à protubérances à partir desquels se formeraient les seconds. Nucléoles typiques et micronucléoles se caractérisent différemment par les techniques cytochimiques. Des examens ultrastructuraux et cytochimiques poussés ont permis d’établir d’une manière sûre la constitution et la fonction métabolique des nucléoles (Miller, 1962, 1964, 1966; MacGregor, 1967; Lane, 1967; Van Gansen & Schram, 1968). Deux zones distinctes composent tout nucléole typique: l’une est fibreuse, l’autre granulaire. Les précurseurs tritiés de l’ARN apparaissent d’abord dans le matériel fibreux où s’effectuerait la synthèse d’une partie de l’ARN au contact de l’ADN de l’organisateur nucléolaire. L’ARN synthétisé serait ensuite transféré dans le cortex granulaire. Par contre, les micronucléoles non basophiles décrits par Van Gansen & Schram (1968) sont constitués d’un matériel compact fibrillo-granulaire dense.
Communications intercellulaires dans les ovarioles de Dytiscus marginalis L
Authors: Steinert G. , Urbani E.
Published: April 2021

L’un des aspects intéressants de l’oogénèse de Dytiscus marginalis est la formation, à partir d’une même oogonie, et au cours de quatre mitoses différen-tielles, d’un oocyte et de quinze cellules nourricières. Dès la première mitose différentielle, le noyau de l’oocyte se caractérise par la présence d’une masse de chromatine qui lui est propre et ne se retrouve donc pas dans les cellules nourricières (Giardina, 1901). Cette masse Feulgen positive de la vésicule germi-native se désagrège assez vite et se fragmente de plus en plus au cours de la période d’accroissement de l’oocyte tandis qu’augmente parallèlement la quan-tité de RNA présente dans son noyau (Urbani, 1950; Urbani & Russo-Caia, 1964; Bier & Ribbert, 1966; Kaori Kato, 1968).
The effect of thyroid function on hemoglobin differentiation in the chick
Authors: Atherton Robert W.
Published: April 2021

The switching off of the synthesis of embryonic hemoglobin (EHb) and the turning on of adult hemoglobin (AHb) synthesis has served as one of several major examples of biochemical differentiation. However, the control mechanisms underlying this transformation remained elusive, except in the case of Rana catesbeiana (Moss &Ingram, 1965, 1968a, b) where the classical thyroxine-induced metamorphosis effected a precocious shift from EHb to AHb. In the chick embryo such a dramatic metamorphosis does not occur, but a change from EHb to AHb can be detected electrophoretically on the sixth day of incubation (Hashimoto &Wilt, 1966; Manwell, Baker &Betz, 1966).
Effects of a mesoderm-inducing factor on early chick embryos
Authors: Deuchar E. M.
Published: April 2021

During recent years Tiedemann and his co-workers have developed methods for extracting and purifying neural and mesoderm-inducing factors from homogenates of 9-day-old chick embryos (see Tiedemann, 1966). One type of extract, obtained initially by phenol treatment of material precipitated with ammonium sulphate from a pyrophosphate extract of chick embryos (Tiedemann, 1959) appeared to induce mesoderm in a high proportion of cases, when implanted into Triturus gastrulae. It has been purified by chromatography on CM-cellulose (Tiedemann, 1959; Tiedemann, Kesselring, Becker & Tiedemann, 1961) and by electrophoresis on Dextran gel (Kocher-Becker, Tiedemann & Tiedemann, 1965). Triturus larvae which have received implants of mesoderminducing factor at the gastrula stage show extra notochord, muscle and kidney within their ventrolateral mesoderm. From the illustrations in these authors’ papers, there can be no doubt at all as to the identity of these induced tissues. Since, however, they develop within areas that would normally have formed mesoderm of another kind, one may infer that in these cases there has been no transformation of cells other than mesoderm : rather, the type of mesoderm has been altered to somite myoblasts, chorda and kidney cells instead of lateral mesothelium. In tests by the ‘sandwich’ technique (Holtfreter, 1933) however, which were evidently also used but not reported in detail (Tiedemann, 1959) any mesoderm that formed would have to be by transformation of ectoderm cells. In earlier experiments on the effects of a crude protein extract from chick embryos on isolated amphibian ectoderm in tissue culture (Becker, Tiedemann & Tiedemann, 1959) transformations into mesenchyme, myoblasts and chorda cells were certainly shown to occur. It seems then that a ‘mesoderm inductor’ may have two kinds of effect: an enhancement of the growth of mesoderm, transforming it also into more dorsal, axial tissues; and a transformation of ectoderm into cells of all mesoderm types. Whether or not endoderm cells can be transformed by the inductor is not fully clear: Kocher-Becker et al. (1965) described an apparent migration of endoderm cells outwards over the surface of Triturus gastrulae which contained implants of highly purified mesoderm inductor, but they interpreted this as due to ectoderm transformation (with a resultant increase in affinity between ectoderm and endoderm) rather than suggesting that the endoderm itself had acquired any mesoderm-like properties.
The role of movement in the development of joints and related structures: the head and neck in the chick embryo
Authors: Murray P. D. F. , Drachm Daniel B.
Published: April 2021

Skeletal muscle contractions are necessary during embryonic life for the normal development of joints. The general features of joint development in immobile limbs were first studied with the techniques of grafting and organ culture. (Murray, 1926; Murray & Selby, 1930; Fell, 1925; Fell & Canti, 1934; Hamburger & Waugh, 1940; Lelkes, 1958). However, these methods of necessity entail a drastic alteration in the environment of the developing articulations, which may result in gross distortions of the skeletal structures themselves. More recently, neuromuscular blocking agents have been used to produce paralysis of chick embryos in ovo. When administered intravenously, these pharmacological substances produce profound paralysis, which may be continued for prolonged periods during embryonic development (Drachman & Coulombre, 1962a, b).
The differentiation capacity of isolated loach (Misgurnus fossilis L.) blastoderm
Authors: Kostomarova Alla A.
Published: April 2021

Experiments on the capacity of the isolated teleost blastoderm to undergo development when cultivated in vitro have revealed species differences in the time of initiation of blastoderm differentiation. Thus the Fundulus blastoderm acquires the ability to develop after being separated from the yolk at the stage of 32 blastomeres (Oppenheimer, 1936) while the blastoderms of pike and of salmon differentiate only after isolation at the blastula stage (Devillers, 1947). These differences have been interpreted as the result of a different ratio between the volume of the cytoplasm and the yolk (Tung, Chang, & Tung 1945); the initiation of the capacity of the blastoderm to develop in vitro being interpreted as a result of the passage of some substances required for differentiation from the yolk into the blastoderm (Oppenheimer, 1936). This hypothesis of Oppen - heimer was substantiated by other authors (Tung et al. 1945; Tung, Wu & Tung, 1955; Devillers, 1952), although the nature of these hypothetical substances, the time and the mode of their passage from the yolk into the blastoderm is still unknown.
Metabolic gradients and morphological polarization in embryonic development of hydroid polypes
Authors: Belousov L. V. , Ostroumova T. V.
Published: April 2021

One of the main problems of modern embryology is the problem of relations between morphogenetic and metabolic processes. For several decades this problem was studied under the influence of the theory of physiological gradients and of some of its modifications (Child, 1941; Dalcq & Pasteels, 1938). The general principle of these conceptions was that the processes of cell differentiation were strictly determined by previous regional metabolic conditions (metabolic, or physiological gradients). The gradients were supposed in their turn to be determined by the heterogeneity of the embryo’s environment. Therefore, a simple and non-reversible chain of relationships was postulated: heterogeneity of environment ⟶ graded metabolic differences ⟶ regional differences at the cellular or supracellular levels. No possibility of any kind of inverse relations—that is, influence of cellular and supracellular events upon the metabolic processes—was taken into account in these conceptions.
The primary action of lithium chloride on morphogenesis in Lymnaea stagnalis
Authors: Elbers P. F.
Published: April 2021

In Lymnaea stagnalis, as in sea urchins, lithium ions cause disturbances of development, notably exogastrulation and head malformations (Raven, 1942). As the effect of a Li-treatment presents itself only after several hours or days of development, the question was raised of the site and the nature of the primary action of the ion in the egg cells, even though it had never been proved that Li actually enters the cells.
Les cellules germinales du Canard chez des embryons normaux et des embryons de régulation. Etude des jeunes stades du développement
Authors: Fargeix Noel
Published: April 2021

Chez de nombreux Invertébrés et Vertébrés, les cellules germinales, destinées à la reproduction, apparaissent à des stades précoces du développement embryonnaire, dans des régions souvent éloignées des ébauches gonadiques. Tel est le cas en particulier chez les Oiseaux où ces cellules peuvent être identifiées dans les régions antérieures et latérales de l’aire extra-embryonnaire, dès le stage de la ligne primitive, ainsi que l’a observé Swift en 1914. Par la suite, ces cellules sont transportées dans l’embryon par le système circulatoire, ce qui a été démontré expérimentalement par Simon en 1960. Puis, elles colonisent les ébauches gonadiques, grâce à l’effet attractif qu’exercent ces ébauches; ceci a été mis en évidence récemment par Dubois (1964a, b, 1965a, b, 1966, 1968). Or, en 1947, Wolff & Lutz mettaient au point une technique de fissuration in ovo du blastoderme d’Oiseau, permettant d’obtenir des embryons de régulation à partir de différentes régions du blastoderme, et, en 1949, à la suite d’une étude histologique d’embryons jumeaux de Canard, obtenus par cette technique, Lutz constatait que de tels embryons présentaient des gonades renfermant de nombreux gonocytes. 11 soulignait alors que ce fait posait le problème de l’origine des cellules germinales. Différentes interprétations de ce résultat peuvent être envisagées. Au moment de l’intervention expérimentale, c’est à dire au stage non incubé, les cellules germinales seraient réparties dans tout le blastoderme, aussi bien dans la moitié postérieure que dans la moitié antérieure; dans ces conditions, la localisation des cellules germinales dans le croissant de Swift, au stade de la ligne primitive, serait secondaire; ou bien, ce matériel ne serait pas encore déterminé; ou enfin, les cellules germinales seraient transportées de l’un dans l’autre des embryons jumeaux par le système circulatoire puisque c’est là le mode normal de migration de ces cellules. A la suite de ces observations, il était donc intéressant d’effectuer une étude plus détaillée de la lignée germinale chez les embryons de régulation: tel est le but de ces recherches entreprises depuis plusieurs années sur l’œuf de Cane. Nous rapportons ici les résultats d’une étude comparée de la lignée germinale d’embryons normaux de Canard et d’embryons de régulation, issus de différentes parties du blastoderme. Le stage de ces divers embryons s’échelonne depuis la ligne primitive jusqu’à 15 paires de somites. A ces jeunes stades du développement, l’appareil circulatoire ne peut pas encore être tenu pour responsable de la répartition des cellules germinales entre des embryons jumeaux. I1 devrait être possible ainsi de préciser dans quelle mesure des régions différentes d’un blastoderme peuvent donner naissance à des embryons contenant des cellules germinales.
The fate of the zona pellucida in mice
Authors: McLaren Anne
Published: April 2021

In mice and rats, the egg is surrounded by a mucoprotein coat, the zona pellucida, which is lost shortly before implantation. The mechanism of loss has long been a matter of controversy. In rats, loss of the zona has variously been reported to be by lysis (Defrise, 1933; Dickson, 1963) or by an active hatching mechanism (Dickmann & Noyes, 1961). A similar lack of unanimity is encountered in discussions on the mechanism of loss of the mouse zona pellucida in utero, though, under conditions of in vitro culture, the hatching of blastocysts from the zona has been not only observed, but even filmed (Cole & Paul, 1965; Cole, 1967).