bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of the optic nerve inXenopus laevisIL Gliogenesis, myelination and metamorphic remodelling
Authors: Cima Charles , Grant Philip 
Published: April 2021

ABSTRACTWe studied the time of origin, development and location of glial elements in the developing optic nerve of Xenopus with light and electron microscopy. The first cells acting as a primitive glia are ependymal cells lying dorsal to the chiasmatic optic nerve (CON) at Nieuwkoop & Faber (1956) NF stage 39. Later (stage 47/48), immature astrocyte cell bodies migrate from the periphery of the middle optic nerve (MON) into the central fibre mass along cytoplasmic processes extending from the outer glia limitans. Shortly thereafter, oligodendrocyte cell bodies appear in the centre of the fibre mass and myelination begins, first in the middle of the MON, spreading from the centre distally towards the chiasm and proximally to the retina. In late tadpoles myelinated fibres appear first in the CON then in the retinal optic nerve (RON) increasing markedly in juveniles and adults. Segment-specific patterns of glia and myelination appear during optic nerve development. During metamorphic climax, the optic nerve shortens (Cullen & Webster, 1979), a process involving myelin and axon remodelling primarily in the MON. Neither the profound changes during metamorphosis, nor the processes of gliogenesis and myelination significantly alter the underlying chronotopic ordering in the tadpole nerve. In juvenile and adult optic nerves, however, as myelination and gliogenesis increase, and as more axons mature and grow in diameter, the dorsoventral chronotopic arrangement of axons becomes less apparent.
The patterns of protein synthesis during foetal and neonatal organ development in the mouse are remarkably similar
Authors: Van Blerkom Jonathan , Janzen Richard , Runner Meredith N. 
Published: April 2021

ABSTRACTThe extent to which differential gene expressions can be correlated with organ development was examined at the level of protein synthesis during pre- and postnatal development in the mouse. High resolution, equilibrium, two-dimensional polyacrylamide gel electrophoresis detected, for each of five to ten successive stages for each of seven organ systems, between 850 and 1000 separate newly synthesized proteins. The possibility that the 1000 detectable proteins synthesized at any one time during organ development represent a sampling bias was contra-indicated (a) because a different and larger population of [14C]- amino acid-incorporating protein syntheses gave similar results and (b) because nonequilibrium isoelectricfocusing, electrophoresis, isoelectric points between pH 5·5 and 8·7, confirmed the results from yet a different population of protein syntheses. Within limits of the sampling of protein syntheses, the entire period of organ development examined proceeds with altered expression of small proportion of the total proteins being synthesized. While all protein changes were stage specific, approximately three organ-specific protein syntheses were detected per organ system.One family of five protein syntheses seen in 16-day foetuses had homologous primary structures and presumably are keratins derived from a single genomic expression. These selected stage-specific protein syntheses examined by electrophoresis of partial proteolytic digests disclosed a programme for post-translational changes in protein syntheses. The current observations indicate that the examined pre- and postnatal organ development of the seven organs occurs in the presence of greater than 99% similarity among proteins synthesized in the same and different organ systems. Functional differentiation during organogenesis, therefore, occurs in the presence of less than 1 % change in qualitative or quantitative switch in protein syntheses. Evidence is presented to indicate that even this remarkably small number of changes in protein syntheses during functional organ differentiation may be derived from an even smaller subset of gene expressions. Collectively, the data suggest that explanatory mechanisms for molecular organogenesis must encompass both selective gene expressions along with post-translational programmed events.
Induction de cartilage in vitro par l’extrait d’otocystes d’embryons de Poulet
Authors: Benoit par Jean A. A. 
Published: April 2021

ABSTRACT
En 1937 De Beer, dans The Development of the Vertebrate Skull, posait le problème suivant: ‘Can extracts of auditory vesicles induce the formation of cartilage in vitro? in vivo?’ (p. 514). Nous pensons avoir trouvé une réponse à la première question: l’extrait d’otocystes induit in vitro la formation de cartilage à partir du mésenchyme otique, chez l’embryon de Poulet.
The Distribution of Sulphur in the Differentiating Visceral Cartilage of Xenopus
Authors: Okada T. S. , Sirlin J. L. 
Published: April 2021

ABSTRACT
The incorporation of sulphate into tissues of Xenopus embryos in various developmental stages was studied by means of autoradiography. Particularly high uptake was demonstrated in the precartilages as well as in the differentiated cartilages. In the earlier stages, when no intercellular matrix has yet been deposited, the tracer is mainly in the cytoplasm of precartilaginous cells, while it is mainly in the matrix and especially in the immediate periphery of the chondrocytes of the differentiated cartilaginous tissue. The movement of tracer stored in the cytoplasm to the intercellular matrix accompanies the histogenesis of cartilage.
Influence of the Supra-oesophageal Ganglion on Posterior Regeneration in Nereis diversicolor
Authors: Clark R. B. , Bonney D. G. 
Published: April 2021

ABSTRACT
Extirpation of the supra-oesophageal ganglion of N. diversicolor before the removal of a number of posterior segments inhibits the formation of new segments. At most, a new pygidium is regenerated. Extirpation of the supra-oesophageal ganglion 3 days after the removal of a number of posterior segments retards but does not inhibit segment-formation. An increase in the quantity of neurosecretory material produced by cells in certain nuclei of the brain of regenerating worms becomes detectable about 12 hours after the posterior segments have been removed. Nereis resembles lumbricid oligochaetes in that the supra-oesophageal ganglion plays an essential role during the initial phases of regeneration, but that once regeneration is initiated, its importance declines.
Aberrant Nerve Fibres in Human Development
Authors: Boyd J. D. , Hughes A. F. W. 
Published: April 2021

ABSTRACT
Attention is drawn to the regular, though transient, presence of aberrant nerve fibres (fibres égarées) in three different regions of human embryos and foetuses. One of these regions is the cartilaginous basisphenoid into which fibres from the abducens nerves pass. The other two regions are the epithelial cord, known as the organ of Chievitz, and, in male specimens, the epithelium of the fused paramesonephric ducts. The possible causes for the atypical behaviour of the aberrant nerve fibres is discussed. It is tentatively suggested that the abducens nerve fibres may be attracted medially by some influence emanating from the cranial end of the notochord. For the aberrant fibres in the uterus masculinas and in Chievitz’s organ the neurotropic attraction is presumed to emanate from the constituent epithelia of the two structures.
Studies on Embryonic Determination of the Harlequin-fly, Chironomus dorsalis : I. Effects of centrifugation and of its Combination with Constriction and Puncturing
Authors: Yajima Hideo 
Published: April 2021

ABSTRACTBy centrifuging, alone or in combination with constricting and puncturing of the egg, the embryonic determination in the harlequin-fly C. dorsalis has been studied. In eggs centrifuged moderately, three zones were distinguished: a centrifugal yolk zone, a centripetal oil zone, and an intermediate zone consisting of cytoplasm with nuclei. The mode of redistribution of the constituents of the centrifuged eggs differs according to the developmental stage at the time of centrifugation and to the centrifugal force. The strata of weakly centrifuged eggs begin to mix with each other immediately after centrifugation. Redistribution of the constituents of strongly centrifuged eggs always occurs in a definite way, even though the redistribution after centrifuging at the nuclear division stage does not take place until later, in the nuclear migration stage, while the cytoplasm of eggs centrifuged during and after nuclear migration begins to migrate as soon as the centrifuge is stopped. By centrifuging the eggs at the nuclear division stage, various types of malformation related to the direction of centrifugation are caused. These malformations are characterized by having duplicated parts. The frequency of occurrence of the malformations increases with increase in the centrifugal force. The structure of the double monsters is further modified by separating a part of the yolk or oil in the centrifuged eggs by strong centrifuging or by constricting, and by removing a part of the cytoplasm from the centrifuged eggs by puncturing. Modification always occurs in the mid-part of the double monster in the form of loss of segments. The number of omitted segments depends on the volume of the separated or the removed part. By applying two successive centrifugations in reverse directions it was found that a causal relationship between the direction of centrifugation before nuclear migration and the resulting malformation type is established at about the nuclear migration stage. From late centrifugation, two other groups of malformations resulted which are different from those obtained by early treatment. Those of the first group, which were caused by centrifuging at the syncytial blastoderm stage, are characterized by having a defect on the centrifugal side and no duplicated parts. Those of the second group were obtained from eggs centrifuged at the cellular blastoderm stage. In the extreme degree of this malformation the cells which reach the final level of differentiation are not organized into an embryo, forming instead small tissue masses. The specific features of the embryonic development of C. dorsalis, particularly thorax development, and the more general problem of the relation of the mode of development of Chironomus to that of other Dipterans, are discussed.
Colour pattern modification by coldshock in Lepidoptera
Authors: Nijhout H. Frederik 
Published: April 2021

ABSTRACT
When young pupae of Vanessa cardui, V. virginiensis and Precis coenia (Lepidoptera: Nymphalidae) are exposed to severe coldshock many develop aberrant adult wing patterns. For each species, a synchronous cohort of experimental animals always develops a broad range of aberrant pattern morphologies but these can always be arranged in a single unbranched morphological series. When such phenotypic series are compared, between species and between wing surfaces within a species (each wing surface usually bears a different colour pattern), many parallel modifications and trends become evident. These parallelisms reveal certain homologies of pattern elements and suggest that a common physiology underlies the development of a considerable diversity of normal and aberrant colour patterns. The case is made that the phenotypic series produced may represent either a series of sequential stages in colour pattern determination or, a series of quantitatively different ‘interpretations’ of an established gradient system. Colour pattern morphoclines reveal which patterns are developmentally ‘adjacent’ to one another and may therefore prove useful in elucidating the evolution of patterns.
The distribution of fibres in the optic tract after contralateral translocation of an eye in Xenopus
Authors: Taylor J. S. H. , Willshaw D. J. , Gaze R. M. 
Published: April 2021

ABSTRACT
In Xenopus embryos of stage 30 the right eye was translocated, without rotation, to a left host orbit. Shortly after metamorphosis the visuotectal projection through the operated eye was mapped electrophysiologically and shown to be normal dorsoventrally but reversed nasotemporally. Labelling of small groups of retinal axons with HRP showed that the fibre trajectories from dorsal and ventral retina were normal, whereas fibres from nasally placed retina had diencephalic pathways and tectal terminations typical of temporal fibres, and fibres from temporally placed retina had diencephalic pathways and tectal terminations typical of nasal fibres. Thus from just beyond the chiasma the fibres had already achieved the major uniaxial rearrangement necessary to establish a normal tract distribution despite the eye translocation. The fibre rearrangement required to permit the formation of a nasotemporally inverted visuotectal projection appears, therefore, to occur not on the tectum or in the optic tract, but either within the nerve or at the chiasma.
The behaviour of growing axons invading developing chick wing buds with dorsoventral or anteroposterior axis reversed
Authors: Stirling R. Victoria , Summerbell Dennis 
Published: April 2021

ABSTRACT
The trajectories of motor axons innervating chick wings reversed about the DV or AP axis before axon invasion were analysed after retrograde filling by HRP injection into biceps or triceps muscles. Chick-quail chimaeras showed that the plane of reversal for flank operations was proximal to the confluence of the 14th, 15th, and 16th spinal roots as they form the plexus. The shoulder reversal plane was distal to the plexus.
In dorsoventral (DV) reversed wings at both shoulder or flank level, the motor axons do not alter their course as they enter the graft. They therefore innervate by passive deployment any target that they encounter. In anteroposterior (AP) reversed wings at both shoulder or flank level, the motor axons clearly corrected their position in the nerve tract after entering the graft and innervated appropriate targets. The innervation of appropriate targets in AP shoulder reversals shows that axons are sensitive to AP mismatch distal to the plexus. Since axons were displaced similar distances from their normal routes in flank DV and AP reversals, the difference in behaviour suggests that they respond to mismatch in the AP but not the DV axis.
Experimental analysis of the role of the ZPA in the development of the wing buds of wingless (ws) mutant embryos
Authors: Wilson D. J. , Hinchliffe J. R. 
Published: April 2021

ABSTRACT
Phenotypically wingless (ws) chick embryos have wing buds characterized by the spreading of mesenchymal cell death in an anterior-to-posterior direction beginning at stage 19. It has been argued that this may reflect the absence of a functional polarizing zone (ZPA). When tested by preaxial grafting into normal wing buds (stages 20 –21), wingless ZPAs (stage 18 –19) had duplicating properties identical with those of normal ZPAs. Equally, normal chick or quail ZPA (stages 20 –22) grafted into the posterior margin of wingless wing buds (stages 18 –20) failed to inhibit the pattern of cell death or to evoke any improvement in their developmental performance. The wingless (ws) condition is not, therefore, due to a ZPA deficiency. Possible explanations are the prior programming for cell death of the wingless mesenchyme, or somitic deficiency, but it appears more likely that the mutant limb mesenchyme fails to transmit or respond to factor(s) produced by the ZPA.
The cell lineage of the muscles of the Drosophila head
Authors: Raghavan K. Vijay , Pinto Ludwin 
Published: April 2021

ABSTRACT
Using a cell marker mutation the cell lineage of the muscles of the Drosophila head are traced out. Three sets of muscles separated by lineage restrictions are observed, even when cells are marked as early as the blastoderm stage. Each set underlies the derivatives of one of the three pairs of imaginal discs which differentiate to form the epidermis of the adult head. Clones of the homoeotic mutation engrailed (enIO) were apparently normal in the muscles of the head. The muscle clone frequency, at the blastoderm stage, in each hemisegment of the fly is similar, indicating an equal partitioning of cells during segmentation.
Cell surface markers to monitor the process of visceral endoderm differentiation from embryonal carcinoma cells: identification of the stage sensitive to high concentration of retinoic acid
Authors: Sato Masahiro , Ozawa Masayuki , Hamada Hiroshi , Kasai Masataka , Tokunaga Tohru , Muramatsu Takashi 
Published: April 2021

ABSTRACT
Two cell surface antigens, brushin and FT-1 were effective in analysis of the process of visceral endoderm differentiation. Brushin was detected on both primitive and visceral endoderm, while FT-1 was detected only on visceral endoderm. When aggregates of N4-1 embryonal carcinoma cells were exposed to 10–8 M-retinoic acid for more than 2 days, external cells differentiated to multilayered and vacuolized visceral endoderm. However, aggregates treated with 10–6M-retinoic acid developed an endoderm layer, which remained one cell thick and was not vacuolized. Cell surface properties of the endoderm cells indicated that the high concentration of retinoic acid inhibited the differentiation pathway at the stage between primitive endoderm cells and visceral endoderm cells. By pulsed exposure to 10–6 M-retinoic acid, the period sensitive to the high concentration of retinoic acid was shown to be around day 4 after the initial exposure to retinoic acid.
Regeneration from isolated half limbs in the upper arm of the axolotl
Authors: Wigmore Peter , Holder Nigel 
Published: April 2021

ABSTRACT
A technique enabling the isolation of half limb stumps using strips of skin from the head is described. Using this technique posterior, anterior, dorsal and ventral halves of the upper arms of axolotls were constructed. All halves produced regenerates and regional differences were shown in the regenerative and regulative abilites of the different halves. Posterior half stumps regenerated limbs with a mean digit number of 3·9 and had a normal dorsoventral muscle pattern. Anterior halves produced hypomorphic limbs with a mean digit number of 1·2 while dorsal and ventral halves produced an average of 3·8 and 2·6 respectively. Regenerates from dorsal half stumps had a normal dorsoventral axis but the majority of those from ventral halves were either double ventral or had little muscle on the dorsal side of the limb.
An analysis of protein synthesis patterns during early embryogenesis of the urodele - Ambystoma mexicanum
Authors: Meuler Debbie Crise , Malacinski George M. 
Published: April 2021

ABSTRACT
Changes in protein synthesis during early Ambystoma mexicanum (axolotl) embryogenesis were monitored using two-dimensional (2-D) polyacrylamide gel electrophoresis. No change in synthesis patterns during progesterone-induced oocyte maturation was detected. In oocytes matured in vivo (unfertilized eggs), however, the synthesis of several oogenetic proteins ceased, only to be resumed later in development. At fertilization, one novel non-oogenetic protein was found. A cleavage-specific protein was also detected.
Dramatic changes in protein synthesis patterns were detected at gastrulation in axolotl embryos. About 10% of the proteins synthesized at earlier stages ceased synthesis at gastrulation. Another 10% of the proteins synthesized during gastrulation were novel. A gastrulation-specific protein was also detected. After gastrulation additional novel nonoogenetic proteins were synthesized for most stages examined. A pronounced increase in the number of novel proteins synthesized was observed at the onset of neurulation and during neural fold fusion. Some of those proteins were specific to dorsal or axial structure tissue (AST) and some were specific to ventral or non-axial structure tissue (NAST).
Actin and tubulin synthesis was also monitored during axolotl development. While the cytoplasmic γ- and β-actins were synthesized at all stages, muscle-specific α-actin synthesis began at the head-process stage (stage 23/25).
Evidence for the role of fibronectin in amphibian gastrulation
Authors: Boucaut J. C. , Darribere T. , Li Shi De , Boulekbache H. , Yamada K. M. , Thiery J. P. 
Published: April 2021

ABSTRACT
In amphibian embryos, fibronectin (FN) assembles as a fibrillar network on the roof of the blastocoel cavity, preceding mesodermal cell migration. Local inversion of the ectoderm to produce a site where no FN is available prevents mesodermal cell migration. Microinjection of monovalent antibodies to FN arrests gastrulation. A complete inhibition of mesodermal cell migration is obtained after microinjection of a synthetic peptide containing the cell binding site sequence of FN. Prevention of interactions between receptors and FN appears to be the primary cause for blockage of gastrulation.
A review of the theories of vertebrate neurulation and their relationship to the mechanics of neural tube birth defects*
Authors: Gordon Richard 
Published: April 2021

ABSTRACTAll of the published theories of neurulation, (some of them forgotten but never disproved), are reviewed for the purpose of assessing just where we are in coming to a satisfactory explanation of this critical step in the formation of the brain and spinal cord, whose occasional failure leads to neural tube birth defects. A new approach to evaluating these theories is introduced, namely finite element analysis, along with a discussion of its promise and present limitations.‘To think that heredity will build organic beings without mechanical means is a piece of unscientific mysticism’ (His, 1888).
Placental Grafts in Rats
Authors: Payne J. M. , Payne Sylvia 
Published: April 2021

ABSTRACTYolk sacs from rat placental membranes taken on the 14th or 15th day of pregnancy grew and differentiated in a remarkable manner when transplanted into the mother’s omentum. A variety of tissues developed within them, including mucus-secreting cysts, epidermoid cysts, cartilage, and bone. The mucus-secreting cysts were surrounded by smooth muscle and closely resembled intes-tine; they probably arose from the endoderm and mesoderm of the yolk sac. The epidermoids could have originated either from amnion remnants included accidentally in the transplant, or from metaplasia of the yolk-sac endoderm. It is obscure whether the cartilage and bone developed from host or graft. Transplants were rarely successful when removed from rats at the 11th or 18th day of gestation.Similar results were obtained when the hosts were other stock rats, either normal or ovariectomized females or males.The grafts were well tolerated by the hosts and homograft reactions did not occur. Members of the rat stock used would not tolerate adult skin homografts in the omentum, but transplants of foetal skin and bone grew and differentiated well. It is concluded that the tolerance of yolk-sac membranes is not a charac-teristic peculiar to placental tissue, but is part of a wider phenomenon of toler-ance to foetal tissues in general.
Topography of the Presumptive Rudiments in the Endoderm of the Anuran Neurula
Authors: Tahara Y. , Nakamura O. 
Published: April 2021

ABSTRACT
The topography of the presumptive rudiments of the endodermal organs in the neurula of R. nigromaculata nigromaculata was studied by local vital staining. The results obtained are summarized in Text-fig. 22. The main portion of the fore-gut develops into the pharynx, oesophagus, stomach, and the anterior half of the duodenum. The lateral and ventral walls of the liver diverticulum give rise not only to the liver, but also to the gall-bladder, the bile-duct, and the ventral pancreas. The dorsal pancreas is derived from the dorsal and lateral archenteric walls at the boundary between fore-gut and mid-gut. The yolk mass subjacent to the mid-gut is the material for the small intestine and the posterior half of the duodenum. The whole endoderm originally lining the mid-gut is incorporated into the dorsal wall in consequence of the closure of the archenteron and the perforation of the definitive cavity of the intestine through the yolk mass. The hind-gut mostly forms the rectum; only a small portion at the margin of the blastopore becomes the post-anal gut.