bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of protein polymorphisms in redwing blackbirds
Authors: Brush Alan H. , Scott Alan F. 
Published: April 2021

ABSTRACT
Breeding populations of the redwing blackbird, Agelaius phoeniceus, were studied to compare protein differences during development. Proteins which represented a minimum of ten loci were studied in egg white, embryonic, nestling and adult tissue. In starch-gel electrophoresis at several conditions of pH only ovoglobulin, ovotransferrin and general esterases were polymorphic. Tissue specificity was observed in other isozymes. These data suggest that developmental sequences of proteins may be considered an adaptative response of the organism.
Modification of muscle cell phenotype in monolayer culture by different media
Authors: Ramírez Oscar , Alemán Victor 
Published: April 2021

ABSTRACTConditions for monolayer cultures of chick skeletal muscle in a rich medium showed that non-muscle contaminants were only 20% of the population. Although the calcium content of this rich medium was 0·95 mM, multinucleate and long fibres were observed after 8 days in culture.Either in rich or in restricted media, gelatin organized the pattern of cell and fibre development in the Petri plates. Cells grown outside the gelatin boundaries looked fibroblastshaped and many were vacuolated. Gelatin did not fully prevent the growth of fibroblast-like population.Calcium in restricted media appeared to be very important for the acquisition of a definite elongated shape.The possibility of the existence of myofibro-myoblasts was supported by the finding of multinucleated fibroblast-like cells during culture in restricted medium. Epigenetic factors, such as different media in a given culture or the origin of a serum batch utilized as a component of those media, affected the fate of the cultures and might also explain the myoblastic variance observed in this and other studies reported.The capacity of phenotypic expression during the modulation change of muscle cells, in vitro, depends not only upon their genotypic origin but also on parameters such as the cell stage during this process, the type of nutrient media used and the interplay of both parameters; in vivo it depends upon specific cytological interactions.
The fine structure of the developing retina in Xenopus laevis
Authors: Dixon J. S. , Cronly-Dillon J. R. 
Published: April 2021

ABSTRACT
The fine structure of the developing retinal cells in Xenopus laevis was studied from stages 26 to 36. At all stages examined the cells contained large numbers of free ribosomes, polysomes, small mitochondria, lipid and yolk droplets and scanty granular reticulum. A basal lamina covered the smooth internal margin of the optic vesicle and also the external aspect of the germinal pigment epithelial cells.
At all stages examined zonulae adhaerentes occurred between adjacent cells at the outer aspect of the optic vesicle and maculae adhaerentes diminutae were occasionally observed. A third type of intercellular junction, characterized by a narrow gap of 3–9 nm, occurred throughout the retina up to stage 30 but only at the periphery beyond this stage. It is suggested that the disappearance of these junctions from the central portion of the retina may be correlated with retinal cell specification* which is known to occur at stage 30–31. These junctions may represent sites for the cell to cell transfer of small molecules which are required for cell differentiation. Since new cells are continually being added to the retina from the ciliary margin beyond stage 30 the persistence of junctions in this region may explain how these new cells also become specified.*
Caudal regeneration in the absence of a brain in two species of sedentary polychaetes
Authors: Hill Susan Douglas 
Published: April 2021

ABSTRACT
Evidence has been obtained showing that unlike the requirements of errant polychaetes studied by other investigators, at least two species of sedentary polychaetes, Branchiomma nigromaculata and Chaetopterus variopedatus can undergo caudal regeneration in the absence of a brain. Both Branchiomma, when maintained in a brainless condition by repeated removal of anterior segments, and Chaetopterus, when rendered brainless by amputation of cephalic segments at a level at which anterior regeneration does not occur, undergo posterior regeneration following removal of caudal segments. Animals maintained in a brainless condition for 7–10 days prior to posterior segment removal undergo normal posterior regeneration. Consequently, it appears unlikely that a circulating brain hormone present at the time of amputation is responsible. Experiments were performed on the extremely long 13th segment of Chaetopterus. An isolated posterior half of segment 13, which possesses ventral ganglia, regenerates both anteriorly and posteriorly, while the anterior half regenerates only anteriorly. That the tissues of the anterior half of segment 13 are competent to regenerate posteriorly was shown by leaving the anterior half of the segment attached to the first 12 segments. Under these conditions posterior regeneration occurred. These experiments suggest that the ventral ganglia rather than the brain are important in posterior regeneration in these species.
Les premiers stades de la formation de l’ébauche de nageoire pelvienne de Truite (Salmo fario et Salmo gairdnerí): I. Etude anatomique
Authors: Geraudie J. , François Y. 
Published: April 2021

ABSTRACT

The first stages of genesis of the pelvic fin Anlage in the Trout (Salmo fario and S. gairdnerí). I. Anatomical study
The Anlage of the pelvic fins appears in Salmo 2 weeks after the fecundation day, at the level of the somites 23-26. The mesoderm has a double origin and seems to differ in this regard from the hind limb of most of the amniotes.
The ‘initial mesenchyme’ comes from the local proliferation of the somatopleura. It will give essentially the skeletal components of dermal origin (actinotrichia and lepidotrichia). The ‘secondary mesenchyme’ is obtained by the dispersion of four ventral somitic processes that have reached and entered the initial mesenchyme blastema. The secondary mesenchyme will probably give the muscles and also the endoskeleton of the fin. The origin of the girdle is not clear. When the setting of the initial mesenchyme begins the epithelium that covers the embryo is already differentiated in an epiderm with numerous mucous cells resting on a visible basement membrane. At the apex of the pelvic bud, a localized and transitory thickening of the epiderm is produced by the increase in the height of the basal stratum. We call this structure by the name of ‘pseudo apical cap’ to stress the fact that it must be distinguished from the ‘apical cap’ described for the limb bud of amniotes.
So, the morphogenesis of the pelvic fins of Salmo shows some important particularities in the epiderm as well as in the mesoderm.
Protein synthesis during Ilyanassa development: effect of the polar lobe
Authors: Teitelman G. 
Published: April 2021

ABSTRACT
Removal of the polar lobe at the trefoil stage of the first cleavage division of Ilyanassa embryos causes abnormalities much later in development. To determine if the developmental differences between normal and delobed embryos were reflected in alterations in protein synthesis and at what stages of development these become evident, protein solutions were separated by disc electrophoresis on basic acrylamide gels. For the analysis of the newly synthesized proteins, two protein samples, one labelled with 14C and the other with 3H, were combined in the same electrophoretic column. Each was prepared from normal embryos or lobeless embryos at different stages of development.
The distribution of the two groups of differentially labelled proteins was compared by a determination, for each fraction, of the ratio of the normalized 3H/14C counts for that particular fraction (R =3H/14C). The plot of R versus fraction number was studied for various combinations of samples.
During normal development the profile of labelled proteins remains unchanged until the onset of visible differentiation. At this stage, around day 4 of development, there are changes in biosynthesis revealed by a greater emphasis on the synthesis of slow moving proteins. The profile of labelled proteins of lobeless embryos remains unchanged up to the 5th day of development. This result is correlated with the absence, in the lobeless embryos, of many of the visible differentiations.
Preliminary studies revealed that the spectrum of labelled proteins of the polar lobe is identical to the one present in lobeless embryos and in normal embryos in early stages of development. This suggests the possibility that the morphogenetic factors associated with the polar lobe are not among the newly synthesized proteins. A hypothesis is presented to account for the effects on morphogenesis and protein synthesis which are produced by removal of the polar lobe.
Morphogenetic disturbances from timed inhibitions of protein synthesis in Fundulus
Authors: Crawford Richard B. , Charles E. Wilde , Heinemann Murk H. , Hendler F. J. 
Published: April 2021

ABSTRACT
The reversible inhibition of protein synthesis at the 75 –95% level in the early zygote of Fundulus results in a specific series of developmental failures dependent upon the times of inhibitor pulse initiation. The severity of the morphogenetic failure is inversely related to the time of initiation and directly to the length of the pulse. The defects reflect the time dependent serial order of events in morphogenesis. The defects range from failure of cleavage through disorders of blastulation, failure of axiation, anencephaly to microcephaly and are entirely predictable. With the exception of cleavage failure the pattern is identical with that found using pulses of actinomycin D in a similar manner. The agent used was pactamycin, an antibiotic which reversibly inhibits amino acid incorporation into protein by disturbing the assembly of the functional ribosomal complex. The significance of time dependent protein synthesis as an active expression in morphogenesis of similarly time dependent information flow via RNA synthesis is discussed.
Effect of a proline analogue, azetidine-2-carboxylic acid, on the morphogenesis in vitro of mouse embryonic lung
Authors: Alescio T. 
Published: April 2021

ABSTRACT
A proline analogue, azetidine-2-carboxylic acid, which has been reported to selectively depress collagen biosynthesis, affects lung morphogenesis in vitro by determining differential modifications of the rate of epithelial growth and ramification activity.
Low concentrations of the analogue induce a sharp decline of the number of newly formed terminal buds, leaving the rate of global growth of the epithelial tree almost unaffected. This effect is reversed by increasing doses which appear more effective on global epithelial growth than on budding. DNA and protein content at the end of the treatment are unequally reduced. Protein concentration is more depressed with consequent rise of the DNA/protein ratio.
These results show that epithelial budding is very sensitive to the treatment with the analogue, and draw attention to collagen biosynthesis as one of the possible mechanisms by which the mesenchyme controls the spatial organization of the epithelial tree. This type of control appears relatively independent on the actual rate of epithelial cell replication, since budding is much more sensitive to the action of the drug.
Effects of erythropoietin on cell populations and macromolecular syntheses in foetal mouse erythroid cells
Authors: Paul John , Conkie David , Burgos Hugo 
Published: April 2021

ABSTRACT
The effects of erythropoietin on maturation of erythroid cells were studied in short-term cultures of foetal mouse liver. Erythropoietin-treated cultures had about 50% more cells than untreated cultures after 24 h. The increase occurred in basophilic, polychromatic and orthochromatic erythroblasts as well as in reticulocytes. A striking feature of erythropoietintreated cultures was the formation of macro-erythroblasts and macrocytes. Autoradiographic studies indicated that a maturation division was omitted in the formation of these cells and that macrocytes might be derived directly from polychromatic erythroblasts or earlier stages. These studies also indicated that there might be no more than three divisions during the normal development of orthochromatic erythroblasts from proerythroblasts in vitro. The mitotic index of proerythroblasts was raised in erythropoietin-treated cultures within 1 –2 h. Moreover, erythropoietin caused a marked elevation of DNA synthesis in proerythroblasts within the first hour of culture but effects on DNA synthesis in other cell compartments were not pronounced. In contrast, an increase in RNA synthesis was noted in proerythroblasts and basophilic and polychromatic erythroblasts; it was greatest in the two former compartments. The stimulation was noticeable, especially in the basophilic compartment, within 2 h but increased progressively throughout the first 5 –6 h. Erythropoietin did not induce an increase in total protein synthesis in cells of the normal series but macro-erythroblasts exhibited proportionately more grains.
The Effects of Ultrasonic Treatment on Embryonic Development of Drosophila melanogaster
Authors: Counce Sheila J. , Selman G. G. 
Published: April 2021

ABSTRACT
The use of ultrasonics as a tool for the experimental study of embryonic processes in Drosophila has been investigated. It has been found that developmental changes can be induced by the application of ultrasonic waves at intensities sufficiently low to obviate the possibility of cavitation damage or chemical change. The effects of ultrasonic waves of various intensities on different developmental stages has been studied by direct visual observation during treatment and in permanent preparations of sectioned material at subsequent developmental stages. Treatment at preblastodermal stages was usually followed by readjustment and normal but delayed development; in other cases death ensued without further development. Treatment of eggs in late cleavage stages with ultrasonic intensities of 0·5 to 1·2 watts/cm.2 for 30 seconds produced abnormalities of spindle, displaced centrioles, and induced polyploidy. Treatment at the syncytial blastoderm stage, with ultrasonic intensities 0·3 to 0·5 watts/cm.2 for 30 seconds, resulted in the production of a high proportion of developmental abnormalities which were classified into five different categories: (a) death without further development; (b) proliferation of cells without differentiation; (c) differentiation without organization; (d) abnormal organization; and (e) slight abnormalities in organization. The possible causes of the different types of abnormalities in embryonic development after treatment with ultrasonics are considered, and are discussed in relation to abnormalities in embryogenesis which have been produced in Dipteran embryos by other means, and in the light of the general morphogenetic situation existing in Diptera and certain other insect orders. Further applications of the method to developmental studies are suggested.
Nitrogen-Excretion in Carcinides maenas (Pennant) during the Early Stages of Regeneration
Authors: Needham A. E. 
Published: April 2021

ABSTRACT
Amputation of appendages in fasting Carcinides causes an immediate large increase in nitrogen output which then declines along an exponential type of curve, during the next 12 days or so. Superimposed on this curve are cyclic fluctuations in output, with a period of about 6 days. The excess output over the first 10 days is proportional to the normal output before operation, the relative excess being independent of diet. Later, however, carbohydrate reduces output and protein increases the short-term oscillations in output. Excess nitrogen output is related to the amount of damaged tissue remaining but not to the amount of tissue removed. It is not due entirely to the nitrogen from demolished tissues. Removal of the sinus gland region of the eye-stalks causes an increase in output greater by one order of magnitude than that due to limb-amputation. By contrast, amputation of the tips of the eyes only depresses output. Extirpation of the second antennae depressed output slightly, probably indicating that the antennal gland normally excretes nitrogen. After excision of portions of the body-wall the pattern of output differs from that following amputation of appendages, and is more similar than the latter to that following skin and bone trauma in mammals.
On the Nature of Head Malformations Obtained by Centrifuging the Eggs of Limnaea stagnalis
Authors: Raven Chr. P. , Beenakkers A. M. TH. 
Published: April 2021

ABSTRACT
Eggs of Limnaea stagnalis were centrifuged at a late 4-cell stage for 10 minutes at a centrifugal pressure of 925 × gravity. The head malformations produced by this treatment were studied. No cyclocephalic malformations were obtained. Apparently centrifuging does not produce a depression of the animal gradient-field. No median reduplications with a splitting of the apical plate were found. Hence centrifuging does not cause a strengthening of the animal gradient-field either. Lateral reductions of eyes, tentacles, and cerebral ganglia were obtained in a large percentage of the cases. They were equally distributed between both sides of the head. The frequency of lateral reductions decreases in the order: eye, tentacle, cerebral ganglion. Lateral eye reduplications occurred in a certain number of cases. They were not accompanied by a reduction of the velum. A complete splitting of the foot in two lateral halves was found in one case. The most characteristic effect of centrifugation consists of the formation of a supernumerary cerebral plate in an abnormal place. This may lie wholly in the post-trochal or in the pre-trochal region, or on the boundary between the two. As the supernumerary cerebral plate approaches one of the ‘host’ cerebral plates, the differentiation of the latter is more and more suppressed. Finally, the supernumerary plate may almost altogether supersede and replace one of the normal cerebral plates. The formation of a supernumerary cerebral plate cannot be explained by a disturbance of the animal gradient-field. The supernumerary plate appears to be superimposed upon a relatively undisturbed pattern of head organs. It is concluded that the normal pattern of head organs is controlled by a gradient-field located at early cleavage stages in the relatively immovable cortical layer. The differentiation of the cerebral plate, on the other hand, is dependent on a morphogenic substance which may be displaced by centrifugal force. In normal development, some kind of interaction between morphogenic substance and gradient-field takes place. The most simple hypothesis appears to be that the localization of the ‘cerebral plate substance’ during ooplasmic segregation is controlled by the cortical gradient-field.
The Site of Implantation of Ova in the Rat
Authors: Frazer J. F. D. 
Published: April 2021

ABSTRACT
In the rat, implantation sites on the 9th day of pregnancy were only evenly distributed along the uterine horns when there were 5 or more ova in one horn. With lesser numbers ova tended to implant in the caudal end of the horns.
Malformations déterminées par des injections de substances chimiques localisées à la tête d’embryons de poule
Authors: Ancel par P. 
Published: April 2021

ABSTRACT
Nous avons cherché à montrer dans des travaux antérieurs (Ancel, 1954) sur l’embryon de Poule, l’utilité des injections localisées en chimiotératogenèse, en particulier pour la réalisation de malformations n’existant pas à l’état spontané chez les Oiseaux comme la symélie ou rares comme l’ectrosomie. La réalisation des malformations de la tête qui fait l’objet de ce mémoire s’ajoute à ce sujet à nos résultats antérieurs. Les injections localisées à la tête d’embryons de Leghorn blanches ont été faites à l’aide d’un appareil spécial (Ancel & Rouget, 1954). Elles ont été réalisées dans les conditions suivantes.
The Development of the Ultimobranchial Body in Xenopus laevis Daudin and its Relation to the Thyroid Gland and Epithelial Bodies
Authors: Saxén Lauri , Toivonen Sulo 
Published: April 2021

ABSTRACT
The authors have investigated the formation and normal development of the ultimobranchial body and its ability to store iodine in Xenopus laevis Daudin. In this species the ultimobranchial body develops from the base of the sixth visceral pouch and forms laterally to the larynx a paired organ in which a limited number of distinct follicles are seen. The organ is formed at the beginning of metamorphosis, attains its maximal size in the middle of it, and partially degenerates at the end of metamorphosis. On the basis of the results presented it is suggested that the ultimobranchial body has its own specific secretory activity, which is evidently most highly developed during metamorphosis and weakens thereafter. Investigations with radioactive iodine (I131) have shown that the organ does not act as a thyroid gland. Neither does the ultimobranchial body form thyroid tissue or accessory epithelial bodies (parathyroid glands) during development.
On the mechanism of determination of embryonic polarity in Parascaris and Rhabditis
Authors: Tadano Yanagi , Tadano Masashi 
Published: April 2021

ABSTRACT
In an attempt to explain the determination mechanism of embryonic polarity, the relation between the behaviour of ectoplasm and the turning of the P2-cell in embryo sof Parascaris equorum, Rhabditis ikedai and Rhabditis sp., has been studied by means of centrifugation.
During cleavage of uncentrifuged eggs, extension and contraction of the cell-surface occur. These are accompanied by streaming of the ectoplasm. In the early phase of the second cleavage embryos become T-shape. Along with streaming of ectoplasm at the animal side of S2-cell in the later phase, the surface of S2-cell extends on one side and contracts on the other. Successively, P2-cell turns from the extending side of S2-cell to the contracting one, that is, in the direction of the primary streaming of ectoplasm. Thus, the embryos become rhomboidal in shape and their axes are established. The extended side of S2-cell points roughly to the ventral side of the embryo, and the other to the dorsal.
In the centrifuged embryos, extension and contraction of cell-surfaces and turning of P2-cell take place also accompanied by streaming of the ectoplasm at the centrifugal side of S2-cell.
It is concluded from these facts that the determination of embryonic polarity depends on the turning of the P2-cell by the extension and the contraction of the surfaces of S2-cell and that the direction of this turning depends on that of the primary streaming of ectoplasm in S2-cell. It is assumed that the direction of the streaming is due to the migration of the nucleus, and that the extension and contraction of cell-surfaces is based on the behaviour of the E.R. and microtubules in the ectoplasm. The tetrahedral embryo is caused by a change in the streaming of ectoplasm. The formation of a rhomboidal embryo in Rhabditis without a preceding T-stage is discussed in connection with the behaviour of the ectoplasm.
A quantitative analysis of the effect of excision of the AER from the chick limb-bud
Authors: Summerbell Dennis 
Published: April 2021

ABSTRACTThe effect of removal of the apical ectodermal ridge from the early chick limb-bud is re-examined using a new quantitative method of analysis of results. The concept of the proximo-distal sequence of laying down of parts is confirmed and evidence is presented that this proceeds as a continuous process, there being a gradual change in the level specified from one cell to another at a more distal level. The results are then interpreted in terms of the ‘progress zone’ model to show that they are both consistent with the model and that they provide an assay for one of its parameters, the rate of change of positional value with time at the tip.