bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protein synthetic patterns of tissues in the early chick embryo
Authors: Lovell-Badge Robin H. , Evans Martin J. , Bellairs Ruth 
Published: April 2021

ABSTRACT
Tissues dissected from early chick embryos were labelled in vitro with [35S]methionine, and their patterns of polypeptide synthesis investigated using the technique of two-dimensional (2-D) polyacrylamide gel electrophoresis. Apart from providing a preliminary description of the molecular changes associated with the processes of gastrulation and segmentation in the chick embryo, this study has revealed a number of polypeptides that may be useful as markers of cell type or function.
The protein synthetic patterns of hypoblast from early and late gastrulae (stages 2 and 4, respectively: Hamburger & Hamilton, 1951) and of definitive endoblast and junctional endoblast from late gastrulae all resemble one another closely, but differ markedly from that of the epiblast at either stage. The lower layer tissues are characterized by the presence of eleven polypeptides that are largely absent from the epiblast. These findings are discussed with reference to current theories on the origins of the lower layer tissues.
Comparisons between the 2-D patterns for tissues dissected from gastrulae and from embryos undergoing segmentation (stage 12) have revealed ten polypeptides showing stage-specific rather than tissue-specific expression. Apart from these ten polypeptides, the 2-D patterns for epiblast and ectoderm were practically identical, and distinguishable from those of other tissues by a lack of any unique polypeptides. On the other hand, stage-4 endoblast and stage-12 endoderm differed in the expression of many polypeptides.
One polypeptide was found that may be considered as a marker of mesodermal cell type, as it was present in lateral plate, segmental plate and somitic mesoderm, but not in tissues of the other germ layers. Lateral plate could be distinguished from the other mesodermal tissues in the expression of a number of polypeptides, but the similarity in the 2-D patterns for segmental plate and somites suggest that the separation of somites from the anterior end of the segmental plate is not accompanied by the synthesis of new polypeptides.
Growth stimulation of the immature chick oviduct by androgens : the vagina as a new target tissue
Authors: Grau Yves , Reichhart Jean-Marc , Thiebold Jean 
Published: April 2021

ABSTRACT
Testosterone when injected alone stimulates growth of the vagina but is inactive upon the other segments of the oviduct of the immature chicken. This action of testosterone can already be detected in embryos: it is expressed by the beginning of differentiation of the vaginal mesenchyme cells into smooth muscle cells. In the treated immature chicken, stimulation of growth is considerable and is specifically caused by androgens (testosterone and 5-α-dihydrotestos-terone); the vaginal mesenchyme differentiates into two smooth muscular layers and vaginal epithelium cells differentiate into ciliated cells and goblets cells. [3H]testosterone binding has been found in the vagina of the immature chicken (data not shown). The characteristics of testosterone binding to cytoplasmic components of the chick vagina are consistent with its identity as a testosterone receptor.
Pattern regulation in fragments of Drosophila wing discs which show variable wound healing
Authors: Dale Leslie , Bownes Mary 
Published: April 2021

ABSTRACT
When complementary fragments of the imaginal wing disc of Drosophila are cultured for several days prior to inducing metamorphosis, usually one fragment will regenerate while the second duplicates. It has been proposed that wound healing plays an important part in disc regulation by initiating cell proliferation and determining the mode of regulation (regeneration/ duplication). To test the latter proposal 15 types of wing disc fragments were examined for variability both in the mode of wound healing and the mode of pattern regulation. Two modes of wound healing were observed, regular - the two wound edges heal with each other, and irregular - each wound edge heals with itself. When cultured separately fragments that healed regularly regenerated, while fragments that healed irregularly duplicated. This suggests that the mode of wound healing determines the mode of pattern regulation.
Trophectodermal carcinoma: mouse teratocarcinoma-derived tumour stem cells differentiating into trophoblastic and yolk sac elements
Authors: Damjanov I. , Damjanov A. , Andrews P. W. 
Published: April 2021

ABSTRACT
The retransplantable tumour line derived from a spontaneous ovarian murine teratocarcinoma (Fekete & Ferigno, 1952) was cloned and characterized using light and electron microscopic and immunohistochemical techniques. Grown in ascites, the tumour consisted predominantly of stem cells and a small number of differentiated derivatives. The stem cells expressed surface reactivity with antibody to SSEA-3 and Forssman antigen, alkaline phosphatase, focal cytoplasmic reactivity with antibody to SSEA-1, and varying amounts of cytoplasmic glycogen and 3 betahydroxysteroid dehydrogenase. Their cytoskeleton reacted with antibodies to keratin and vimen-tin. The differentiated derivatives formed approximately 5–15 % of the total cell population in ascites and appeared either as giant cells or were characterized by their reactivity with antibodies to H-2 or α-foetoprotein or intracellular and pericellular laminin or high levels of 3 betahydroxysteroid dehydrogenase activity. Solid tumours produced from subcutaneously injected cells had a variegated appearance suggesting, that like the limited differentiation in the ascites, the stem cells can give rise to trophoblastic, as well as parietal and visceral yolk sac elements. On the basis of the presented data the tumour stem cells were considered as representing malignant equivalents of the common precursor of trophoblastic, visceral and parietal yolk sac cells most likely corresponding to trophectoderm. Accordingly, the tumour was designated as trophectodermal carcinoma.
Pioneering and pathfinding by an identified neuron in the embryonic leech
Authors: Kuwada John Y. 
Published: April 2021

ABSTRACT
Numerous investigations of pathfinding by embryonic neurons, including many leech neurons, have demonstrated that pathfinding is precise. Neurons project the correct number of growth cones which grow to their target areas by making specific choices along the way. However, one leech mechanosensory neuron, the dorsal P (PD) neuron, is unusual in the sense that it initially projects an excessive number of growth cones. One of the growth cones will form the peripheral axon while the others are eliminated. This suggests that PD is one of the earliest neurons to project a peripheral axon, i.e., it may pioneer a peripheral nerve, and that it searches with its multiple growth cones for an external cue which can guide it to its target area. Examination of the early PD axon with light and electon microscopy reveals that it indeed is the first growth cone in its nerve and that it grows in contact with a large non-neuronal (DV) cell until it reaches its target area. The DV cell has a unique morphology and location: a large cell body with thin flat processes extending from the edge of the ganglion to the target area of the PD. It is also present with its unique morphology prior to axonal outgrowth by the PD neuron. These features suggest that the DV cell may be an attractive substrate and/or axonal guidance cue for the PD peripheral axon and therefore for the entire peripheral nerve.
In vitro analysis of interactions between sensory neurons and skin: evidence for selective innervation of dermis and epidermis
Authors: Verna J.-M. 
Published: April 2021

ABSTRACT
Axons from dorsal root ganglion cells cultured in a serum-free medium on poly-L-lysine or collagen substrates interact differently with dermis and epidermis. The orientation of neurite growth is not changed by encountering mesenchymal cells migrating from the outgrowth zone of a dermal explant, and neurites form close membrane associations with some dermal cells; in contrast, neurites strongly avoid epidermis and deviate around the edge of an epidermal explant. When cultures are grown on polylysine this avoidance behaviour occurs at a distance from the epidermis. It is suppressed in the presence of necrotic epidermal cells. We suggest that this avoidance is due to epidermal diffusible factor(s) which bind preferentially to polylysine. The possibility of an absence of specific recognition cues between neurites and epidermal cells is discussed.
In vitro differentiation of neuronal precursor cells from amphibian late gastrulae: morphological, immunocytochemical studies, biosynthesis, accumulation and uptake of neurotransmitters
Authors: Duprat Anne-Marie , Kan Paulette , Foulquier Françoise , Weber Michel 
Published: April 2021

ABSTRACT
Neuronal differentiation has been studied in dissociated cell cultures from early neurulae of Pleurodeles waltl and Ambystoma mexicanum. Cocultures were prepared from the neural primordium and underlying chordamesoderm. NP and NF cultures were prepared from isolated neural plate and neural folds, respectively.
Neuronal precursors in NP and NF cultures had distinctive aggregation properties already evident after 1–2 days in culture. After 10–15 days, mature neurones and synapses were observed by electron microscopy in the three culture types. The expression of neurofilament polypeptides and tetanus-toxin-binding sites was also present in these cultures. A small percentage of neurones contained cytochemically detectable catecholamine. Many neurones took up tritiated dopamine with a high affinity.
Quantitative measurement of [3H]acetylcholine synthesis and storage from [3H]choline were negative at the early neurula stage and in 5 to 15-day-old NF cultures, and remained low in 5 to 15-day-old NP cultures. Acetylcholine production in cocultures increased linearly with time and was always much higher than in NP cultures.
These results suggest that, at the early neurula stage, some neuronal precursors have acquired the capacity to express a high degree of morphological and biochemical differentiation even in the absence of further chordamesoderm influence. However, the chordamesodermal cells in the cultures increased acetylcholine synthesis.
An allelic difference determines reciprocal patterns of expression of binding sites for Dolichos biflorus lectin in inbred strains of mice
Authors: Ponder Bruce A. J. , Festing Michael F. W. , Wilkinson Maureen M. 
Published: April 2021

ABSTRACT
We used staining of tissue sections by lectin conjugates to screen inbred strains of mice for polymorphisms which could be used as histological markers of chimaerism. We found one polymorphism, which involves reciprocal patterns of expression of binding sites for the N-acetyl-galactosamine-binding lectins from Dolichos biflorus (DBA), Helixpomatia (HPA) and Wisteria floribunda (WFA) on intestinal epithelium and vascular endothelium. The polymorphism is due to alleles at a single locus, designated Dlb-1 (for Dolichos lectin binding). Of 29 inbred strains examined, 3 are D1b-1a (type strain RIII-ro; gut epithelium - ve, vascular endothelium + ve), and 26 are D1b-1b (type strain C57BL/6J; gut epithelium + ve, vascular endothelium − ve). In RIII-ro and C57BL/6J embryos, the polymorphic difference is not clearly present until day 11 of gestation. Before then, embryos of both strains express binding sites on gut epithelium and on endothelium.
The temporal and tissue-specific patterns of expression of lectin-binding sites may result from differences in expression of an N-acetyl galactosaminosyl transferase. If so, elucidation of the genetic basis of the polymorphism might provide an insight into the mechanisms of developmental regulation of glycosyltransferase activity.
Embryonic axis orientation in the mouse and its correlation with blastocyst relationships to the uterus: II. Relationships from 4¼ to 9½ days
Authors: Smith L. J. 
Published: April 2021

ABSTRACT
Each of the three primary axes of the primitive streak ( days p.cf) to C-shaped ( days) stage mouse embryo has a specific relationship to the uterine horn axes. By a retrograde analysis of younger sectioned embryos it has been possible to construct an axis fate map for the implanting day blastocyst and to show how its implantation in one or the other of two specific orientations to the ends and walls of the horn leads to these embryo-horn relationships. The implanting blastocyst axis fate map can be related to an axis fate map of the attached blastocyst (Smith, 1980) since these too are in one or the other of two orientations to the ends and walls of the horn. It is suggested that the asymmetries of the attached and implanting blastocysts that allowed the distinctive attachment and implantation orientations to be recognized, are the initial expressions of a three-dimensional system of positional information that is present in the attached blastocyst.
A model for chondrogenic condensations in the developing limb: the role of extracellular matrix and cell tractions
Authors: Oster G. F. , Murray J. D. , Maini P. K. 
Published: April 2021

ABSTRACT
The hyaluronate component of the extracellular matrix is a powerfully hydrophilic polymer, capable of osmotically swelling and deswelling by a volume factor of 5 or more. At the time of cartilage condensation in the limb bud the chondrocytes start to produce hyaluronidase, an enzyme which degrades hyaluronate. The consequent deswelling brings the chondrocytes closer together -close enough for intercellular cell tractions to become effective and intercellular junctions to form. By analysing the physicochemical situation we show how these processes, principally the coupling of the osmotic deswelling with cellular traction forces, can produce cartilage condensation patterns resembling those in the early limb bud. In distinction from our earlier model for chondrogenic condensations this mechanism does not depend on cell motions other than convective transport by contraction.
The cytoskeleton of Xenopus oocytes and its role in development
Authors: Wylie C. C. , Brown Derek , Godsave S. F. , Quarmby J. , Heasman Janet 
Published: April 2021

ABSTRACT
Much is known about determinative events in early amphibian embryos, perhaps more than any other animal group. However, as yet, little attention has been focused on the cytoarchitecture of the oocyte, and the way in which this could regulate asymmetries in the egg, which in turn could lead to developmentally important interactions.
The changing cytoarchitecture of the Xenopus oocyte is described with the emphasis on the following: - firstly the polarity; the oocyte is not radially symmetrical at early stages of oogenesis, but shows marked polarity. Secondly, several cytoskeletal elements change their distribution during oogenesis, and again during maturation to form a fertilizable egg. Thirdly, monoclonal antibody methods show that the oocyte develops several asymmetries which are retained in the egg and early embryo, and may be lineage related.
Cell lineage labels and region-specific markers in the analysis of inductive interactions
Authors: Smith J. C. , Dale L. , Slack J. M. W. 
Published: April 2021

ABSTRACT
This paper reviews work with cell lineage labels and cell-type specific markers in the analysis of inductive interactions in early amphibian development. Our results provide clear evidence for the existence of three such interactions. Mesodermal induction occurs in the early blastula and results from the action of vegetal pole cells on the animal hemisphere. At least two mesodermal rudiments are formed, one dorsal and one ventral. During the next interaction, which we call dorsalization, the ventral mesodermal rudiment becomes subdivided into several territories under the influence of the dorsal marginal zone, or organizer. Finally, during gastrulation, the involuting organizer induces neural tissue from the overlying ectoderm. This interaction is called neural induction.
Although these phenomena can readily be demonstrated under experimental conditions, direct evidence that they occur in normal development awaits an understanding of the molecular basis of induction.
Development of Haemoglobin by De-embryonated Chick Blastoderms Cultured in vitro and the Effect of Abnormal RNA upon its Synthesis
Authors: O′ Brien B. R. A. 
Published: April 2021

ABSTRACT
A simple in vitro histogenesis is described in which the protein haemoglobin is synthesized in the developing blood-islands of a de-embryonated blastoderm. The spread of the blastoderm which follows de-embryonation when it is cultured on the vitelline membrane according to the New technique is eliminated by transfer to an agar gel medium. Cell-division and differentiation in the blood-islands was not inhibited to the same extent as it was in the other tissues present. The erythroblasts multiply, differentiate, and synthesize haemoglobin. The RNA base analogue and antimetabolite 8-azaguanine effectively blocks the synthesis of haemoglobin up to but not including developmental stage 8 on the Hamburger-Hamilton scale. Stages 9 and 10 synthesize haemoglobin in the presence of this analogue. The inhibition by 8-azaguanine is in part removed when the normal base guanine is included with it in the medium. The inhibition is not removed to any extent by incubation with guanine either before or after contact with azaguanine. It is concluded that there is a period in developmental stage 8 of only 1 or 2 hours that represents the border line between RNA analogue inhibition and non-inhibition. It is considered that during this period the RNA associated mechanisms or templates for haemoglobin production begin to operate. The amino-acid analogue fluorophenylalanine but not thienylalanine inhibited haemoglobin synthesis. Incubation following de-embryonation in RNAse had little effect on the synthesis. Chloramphenicol proved to be ineffective as an inhibitor of protein synthesis in this system. The data presented are discussed in relation to the sequence in which haemoglobin becomes detectable in the nucleolus, the nucleus, and the cytoplasm of the developing erythroblast. Haemoglobin development is observed directly in the living system and histochemically by the peroxidatic oxidation of o-dianisidine.
Atypical Spindles in Reinnervated Rat Muscles
Authors: Hník P. , Zelená J. 
Published: April 2021

ABSTRACT
In young rats, following lesions of a peripheral nerve at birth, immature muscle spindles disintegrate during a short transition period (Zelená, 1957), and even after several months of reinnervation the reinnervated muscles are usually found to contain no spindles (Zelená & HNÍK, 1960). Nevertheless, occasional small spindles of atypical structure are observed in some of these muscles. In the present report, the structure and morphological characteristics of these atypical spindles were studied and compared with normal spindles. Since differences in fast and slow muscles may include differences in muscle receptors (Voss, 1937; Maruseva, 1947; Hagbarth & Wohlfahrt, 1952; Freimann, 1953; Cooper, 1960), the number, size, and distribution of spindles were studied in two muscles representing the two functional groups.
Development of gynogenetic and parthenogenetic inner cell mass and trophectoderm tissues in reconstituted blastocysts in the mouse.
Authors: Barton Sheila C. , Adams Catharine A. , Norris M. L. , Surani M. A. H. 
Published: April 2021

ABSTRACT
The developmental potential of inner cell mass (ICM) and trophectoderm (TE) derived from parthenogenetic or biparental gynogenetic embryos was examined in reconstituted blastocysts with normal TE or ICM, respectively. The results demonstrate that when a normal ICM was introduced inside a trophectoderm vesicle derived from parthenogenetic or gynogenetic blastocysts, postimplantation development was characterized by the almost complete failure of trophoblast proliferation and without compensating cellular contribution from the normal ICM to the outer trophoblast lineage. Consequently, the normal ICMs also failed to develop adequately and only a few retarded embryos were detected on day 11–12 of pregnancy. In most respects, development of these reconstituted blastocysts resembled that obtained with unoperated gynogenetic and a parthenogenetic blastocyst. By contrast, an ICM from a parthenogenetic or gynogenetic embryo introduced inside a normal trophectoderm vesicle induced substantial proliferation of the trophoblast but again without a detectable cellular contribution from the ICM to the outer trophoblast lineage. However, with the improved development of the trophoblast, both the parthenogenetic and gynogenetic ICMs developed substantially better and without a detectable cellular contribution from the TE to the embryo. Almost all the embryos developed at least up to the 25-somite stage and many of them reached the 30- to 40-somite stage. Some of the most advanced day-11 and -12 gynogenones and parthenogenones yet seen have now been obtained in this way. Nevertheless, all the embryos were still smaller than the equivalent control embryos and showed signs of some tissue degeneration. The yolk sac was also suboptimal with poor blood supply and may need to be improved to obtain further improvement in the development of the embryos. The combined results demonstrate that the trophoblast proliferates very poorly even in the presence of a normal ICM, if the TE tissue lacks a paternal genome. However, ICM tissues which lack a paternal genome can develop to an advanced embryonic stage if they are introduced inside a normal trophectoderm vesicle. The results give further insight into the differential roles of maternal and paternal genomes during development of the embryo and extraembryonic tissues in the mouse.
Temporal and spatial aspects of the gradual migration of primordial germ cells from the epiblast into the germinal crescent in the avian embryo
Authors: Ginsburg Malka , Eyal-Giladi Hefzibah 
Published: April 2021

ABSTRACT
The migration of the PGCs from a stage XIII epiblast into the germinal crescent of a stage 10 chick blastoderm was experimentally investigated. Considerable numbers of PGCs start to come down from the epiblastic layer at stage XII–XIII and continue to do so in relatively smaller numbers until stage 6. The earliest PGCs land on the primary hypoblast and probably are carried by it into the GC. The PGCs that descend at relatively later stages land on the mesodermal wings and are either carried by them passively, or move actively into the GC. After the removal of the lower layer from stage 4 and older blastoderms, there is no regeneration of a GC in the blastoderm. Other consequences of this operation are that the mesodermal wings do not spread anteriorly as in normal controls and the PGCs that are still in the mesodermal domain are trapped. PGCs were found in expiants of the lower layer and of the mesoderm. No identifiable PGCs were encountered in expiants of the PS.
Formation of pattern in regenerating tissue pieces of Hydra attenuata
Authors: Bode Patricia Macauley , Bode Hans R. 
Published: April 2021

ABSTRACT
The tentacles in hydra have characteristics of both spacing patterns and number-regulating patterns in that their number under some circumstances changes with the size of the animal and under others does not. To determine which type of processes could yield these results, an extensive analysis was undertaken of the size parameters pertinent to tentacle formation. To do this pieces of tissue, varying in shape and spanning a 30-fold size range, were excised and allowed to regenerate into complete animals. Three separate mechanisms were found to combine which resulted in the final number of tentacles: (1) the spread of the two-part head pattern to produce a competent band of tissue of a given size where the tentacles could form; (2) initiation of tentacle-forming centres by a spacing mechanism and (3) growth of the tentacles to a size proportional to the size of the animal.