bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell behaviour in a polygonal cell sheet
Authors: Honda H. , Kodama R. , Takeuchi T. , Yamanaka H. , Watanabe K. , Eguchi G. 
Published: April 2021

ABSTRACT
Cell monolayers on culture dishes were divided into two groups: tensile monolayers and non-tensile ones. In the development of an epithelium, a non-tensile cell monolayer turns into a tightly bound tensile one. Detection of these states was carried out by using the boundary shortening procedure, a computer-based geometrical method to show how much the polygonal cell boundary contracts.
Non-tensile monolayers were divided further into two groups according to their motility: a fluctuating monolayer in which cells move laterally, and a stable monolayer in which cells are immobilized. Quantitative determination of cell motility was performed by analysing timelapse cellular patterns.
These computer-based geometrical analyses enabled us to divide monolayers into three groups: tensile stable monolayers, non-tensile stable monolayers and fluctuating monolayers, and this study therefore gives an insight into the way in which changing conformations of cells may be assayed.
Syndactyly induced by Janus Green B in the embryonic chick leg bud: a reexamination
Authors: Fernandez-Teran M. A. , Hurle J. M. 
Published: April 2021

ABSTRACT
In an attempt to clarify the mechanism of production of the syndactyly induced by Janus Green B (JGB) we have studied the morphology and structural modifications of the chick embryo leg bud after JGB administration by means of (1) neutral red vital staining, (2) whole-mount cartilage staining and β) light microscopy and transmission and scanning electron microscopy. The results show that the well-known inhibition of interdigital cell death is accompanied by a precocious alteration of the epithelial tissue and especially of the epithelial-mesenchymal interface. 24 h after JGB administration the cells of the AER reduce the number of junctions and the basal ectodermal cells are detached into the mesenchymal tissue in zones in which the basal lamina undergoes disruption. In addition the interdigital mesenchymal cells diverted from the dying program are able to undergo a rapid differentiation into cartilage.
It is proposed that the mechanism of production of JGB-induced syndactyly might be due to an alteration of the normal epithelial-mesenchymal interactions rather than to a direct inhibitory effect of the JGB on the dying program.
Changes in antibody and complement production in Xenopus laevis during postmetamorphic development revealed in a primary in vivo or in vitro antibody response
Authors: Lallone R. L. , Chambers M. R. , Horton J. D. 
Published: April 2021

ABSTRACT
Xenopus laevis (G-line) mounts a primary plaque forming cell (PFC) response either in vivo or in vitro following challenge with foreign erythrocytes. Methods are described for generating and assaying the response, which specify criteria such as antigen dose, antigen choice, response kinetics, and complement source. The results suggest that at the peak of the primary response (approximately day 6), animals of different ages produce predomi-nantly different ‘classes’ of antibody which display markedly different complement-fixing characteristics. Antibodies produced by larvae and 4-month-old postmetamorphic animals appear here to be unable to fix either guinea pig complement (GPC′) or adult Xenopus complement, but can readily fix complement from 6-month-old Xenopus. The proportion of spleen PFC’s producing antibody capable of fixing GPC′ progressively increases from about six months to 18 months of age. Possible explanations for such ontogenetic changes are discussed.
Investigation of variability among mouse aggregation chimaeras and X-chromosome inactivation mosaics
Authors: West John D. , Bücher Theodor , Linke Ingrid M. , Dünnwald Manfred 
Published: April 2021

ABSTRACT
Mouse aggregation chimaeras were produced by aggregating C3H/HeH and C3H/HeHa-PgZc-la/Ws embryos. At mid-term the proportions of the two cell populations in these conceptuses and the X-inactivation mosaic female progeny of C3H/HeH ♀ × C3H/HeHa-PgZi-7′7Ws ♂ matings were estimated using quantitative electrophoresis of phosphoglycerate kinase (PGK-1) allozymes. The percentage of PGK-1B was more variable in the foetus, amnion and yolk sac mesoderm of the chimaeras than in the corresponding tissues of the mosaic conceptuses. Positive correlations were found for the percentage of PGK-1B between these three primitive ectoderm tissues in both chimaeras and mosaics and between the two primitive endoderm tissues (yolk sac endoderm and parietal endoderm) of the chimaeras. There was no significant correlation between the primitive ectoderm and primitive endoderm tissues of the chimaeras. The results suggest that unequal allocation of cell populations to the primitive ectoderm and primitive endoderm considerably increases the variability among chimaeras but variation probably exists before this segregation occurs. The variation that arises before and at this allocation event is present before X-chromosome inactivation occurs in the primitive ectoderm lineage and explains why the proportions of the two cell populations are more variable among chimaeras than mosaics. Additional variation arises within the primitive ectoderm lineage, after X-inactivation. This variation may be greater in chimaeras than mosaics but the evidence is inconclusive. The results also have some bearing on the nature of the allocation of cells to the primitive ectoderm and primitive endoderm lineages and the timing of X-chromosome inactivation in the primitive ectoderm lineage.
Morphological and experimental studies of the somitomeric organization of the segmental plate in snapping turtle embryos
Authors: Packard David S. , Meier Stephen 
Published: April 2021

ABSTRACT
The segmental plate mesoderm of snapping turtle embryos (Chelydra serpentina) was examined with stereoscanning electron microscopy imaging. A metameric pattern was detected along the entire length of the segmental plates. This pattern consisted of a tandem sequence of mesodermal units, called somitomeres. Each somitomere was oval to cubic in shape and the processes of the constituent mesodermal cells tended to be arranged in concentric rings about the centre of the somitomere. Several experiments from a previous study (Packard, 1980b) of snapping turtle segmental plates were repeated, but, instead of culturing the explants and observing the numbers of somites that formed, the explants were fixed immediately for scanning electron microscopy and the number of somitomeres was counted. The segmental plates were found to contain an average of 6·5 ± 0·7 somitomeres, which is almost identical to the average number of somites formed by such segmental plates when cultured (6·6 ± 1·2). Furthermore, the number of somitomeres was identical in right and left explants removed from the same embryo, and the number of somitomeres was consistent regardless of the length of the segmental plate. Both of these observations are identical to those made previously for somite formation in culture. This association between numbers of somitomeres and somites strongly suggests that one gives rise to the other. Finally, it was demonstrated that for each somite formed by a segmental plate in culture, the segmental plate contained one less somitomere. This showed in a direct manner that turtle somitomeres become somites. It was concluded that the segmental plate mesoderm of snapping turtle embryos is already segmented, and that the ‘segmentation’ seen under a dissecting microscope is actually the final stage of somitomere differentiation into an epithelial somite.
Development of synapses between identified sensory neurones and giant interneurones in the cockroach Periplaneta americana
Authors: Blagburn J. M. , Beadle D. J. , Sattelle D. B. 
Published: April 2021

ABSTRACT
The cereal afferent, giant interneurone pathway in Periplaneta americana was used as a model for synapse formation. The morphology of the two identified filiform hair sensory neurones (FHSNs) and of two giant interneurones (Gl 2 and Gl 3) was followed throughout embryogenesis by cobalt injection. The FHSN axons enter the CNS at the 45 % stage of embryogenesis, branch at 50 % and form complete arborizations by 70 %. The giant interneurones send out a primary dendrite at 45%. Secondary branches form between 50% and 60% and elaboration of the branching pattern takes place until 80 % embryogenesis. At early stages the FHSN axons are within filopodial range of Gl dendrites which may use these sensory processes as guidance cues.
Synapse formation between the main FHSN axon shafts and Gl dendrites was investigated by injection of the latter with HRP. From 55 % to 65 % the process is initiated by desmosome-like filopodial contacts, with subsequent vesicle clustering and formation of a small synaptic density. Numbers of contacts did not significantly increase after about 70 %, but the number of synapses doubled between 65 % and 75 %, with each Gl process becoming postsynaptic to two FHSN synapses and the presynaptic densities lengthening to become bars. From 75 % embryogenesis to hatching there is a further small increase in synaptic bar length.
In the first instar GI3 is postsynaptic to both FHSN axons, whereas GI2 forms very few synapses with the axon of the lateral FHSN (LFHSN). This imbalance of contacts is present throughout synaptogenesis, apart from some early filopodial contacts. Gl 3 forms synapses with the lateral side of the LFHSN axon from 60 % embryogenesis but these are totally absent at hatching. The growth of glia along this side of the axon during the last 30 % of development appears to be associated with degeneration of synapses in this region.
Thus, as the dendrites of the GIs grow to form a miniature version of the adult without loss of branches, there is little evidence of an initial overproduction of FHSN-GI synapses. Similarly there is no evidence that Gl 2 forms ‘incorrect’ synapses with the axon of LFHSN. However, Gl 3 contacts are removed from an inappropriate region of a correct synaptic partner, LFHSN.
Regeneration of axolotl hindlimbs bearing surgically created discontinuities in the anterior—posterior axis
Authors: Holder Nigel , Weekes Charleston 
Published: April 2021

ABSTRACT
The pattern regulation process in amphibian limbs has been examined with respect to the presence of discontinuities in the anterior–posterior (a–p) axis. Limbs bearing such discontinuities were surgically created by contralateral exchange of either dorsal or ventral half thighs and these limbs were then amputated immediately after surgery. The results demonstrate that a–p discontinuities lead to the formation of extra limb structures during distal outgrowth in contrast to the mosaic behaviour of comparable limb stumps which contain dorsal–ventral (d–v) discontinuities (Holder & Weekes, 1984). It is evident, therefore, that pattern regulation in the transverse limb axes is accomplished by basically different mechanisms.
The structure of the limbs in the present study was examined in Victoria-blue-stained wholemounts and serial sections. The results allow some discussion of the basic mechanisms for pattern regulation in the two transverse limb axes and the relationship between them.
Target cell surface glycoconjugates and neural induction in an amphibian
Authors: Gualandris Lydie , Rouge Pierre , Duprat Anne-Marie 
Published: April 2021

ABSTRACT
The possible involvement of target membrane specific receptor(s) in the transmission of the neural signal leading to activation of the intracellular machinery involved in the process of neural determination, has been examined using lectin probes (Con A, succinylated-ConA, LcA, PsA and SB A). Not only Con A binding sites but many different glycoconjugated molecules (α-D-galactose, N-acetyl-D-galactosamine, α-D-fucose, N-acetyl-D-glucosamine, etc.) would have to be involved, if neural receptor(s) are invoked to explain initiation of neural induction. We show here that the close involvement of such receptor molecules in neural induction is so far hypothetical and remains to be demonstrated. Moreover we are inclined to the view of Barth and others who suggested that ionic fluxes and physicochemical and electrophysiological properties of the target membrane could play a crucial role in neural induction.
Polyneuronal innervation of an adult and embryonic lobster muscle
Authors: Govind C. K. , Stephens Philip J. , Eisen Judith S. 
Published: April 2021

ABSTRACT
Motor innervation of the deep extensor muscle in the abdomen of lobsters (Homarus americanus) was compared in adults and embryos using electrophysiological techniques. There is widespread innervation of the adult muscle by the common excitor and inhibitor axons and regionally restricted or private innervation by three more excitor axons. In the embryo the earliest sign of functional innervation revealed a single inhibitory and two to three excitatory axons thus denoting simultaneous innervation by the full complement of axons. In corroboration, serial-section electron microscopy revealed several axon profiles invading the embryonic deep extensor muscles and giving rise to well-defined neuromuscular synapses with presynaptic dense bars. Innervation patterns to homologous regions of the embryonic and adult muscles were similar, consisting of a few large inhibitory synapses and many small excitatory ones. Consequently the adult pattern of polyneuronal innervation occurs simultaneously and in toto during embryonic development.
Serine metabolism in rat embryos undergoing organogenesis
Authors: Rowe Peter B. , Kalaizis Annette 
Published: April 2021

ABSTRACT
Rat embryos (9·5 days gestation) were cultured for 48 h in heat-inactivated homologous serum containing [3-14C] serine. Analysis of the distribution of the radioactive label in the conceptus demonstrated that almost one half of the incorporated serine was cleaved to provide one-carbon units for the synthesis of purine and pyrimidine nucleotides. Analysis of the free amino acids in the serum, the exocoelomic fluid and the cells of the yolk sac and the embryo showed that there was a variably selective increase in the concentration of amino acids in the exocoelomic fluid compared with the serum and a significant decrease in the specific radioactivity of the free serine within the conceptus which was the highest in the yolk sac and lowest in the embryo. These findings would support the concept of yolk sac lysosomal degradation of medium serum protein as a major source of amino acids supplying almost 86 % of that required during this phase of embryonic development.
The specific radioactivity of purine bases in cellular nucleotides, RNA and DNA was similar to that of the free serine in both yolk sac and embryo. This indicated that an alternative, as yet unidentified source of one-carbon units was available for purine nucleotide biosynthesis.
Analysis of the cellular purine nucleotides revealed low ATP/GTP ratios in both the embryo and its yolk sac and this may be related to the undifferentiated state of many of the cells of the conceptus.
Sequence and regulation of morphological and molecular events during the first cell cycle of mouse embryogenesis
Authors: Howlett Sarah K. , Bolton Virginia N. 
Published: April 2021

ABSTRACT
Mouse oocytes were fertilized in vitro and the precise timing and sequence of morphological and molecular events occurring during the first cell cycle were investigated. The timing of development through the first cell cycle was found to be initiated by an event associated with sperm penetration rather than with germinal vesicle breakdown. DNA replication is initiated randomly in either pronucleus of a given egg, beginning approximately 11 h post insemination (hpi), and S phase lasting 6−7 h in both. Careful study of polypeptide synthetic profiles revealed three classes of changes in polypeptide synthesis during the first few hours of development: fertilization-independent, fertilization-accelerated, and fertilization-dependent. Pulse-chase experiments and in vitro translation of extracted mRNA showed that the changes in polypeptide synthetic profile result from differential mRNA activation, differential polypeptide turnover and post-translational modifications. These results support the notion that following ovulation, development is controlled at two levels. An endogenous (oocyte) programme, set in train by the terminal events of oocyte maturation, may regulate the ‘housekeeping’ functions of the egg, while sperm penetration activates a further endogenous (fertilization) programme, which may serve to initiate subsequent embryogenesis.
The ontogenesis of cranial neuromeres in the rat embryo I. A scanning electron microscope and kinetic study
Authors: Tuckett Fiona , Lim Lynette , Morriss-Kay Gillian M. 
Published: April 2021

ABSTRACT
The development of the cranial neuromeres, rostral to the level of the first somite, in rat embryos during neurulation is described. Examination of scanning electron micrographs of 4-, 8-, 12- and 16-somite-stage embryos has shown that the neuromeres develop in a strictly ordered pattern but the sequence is not ordered in either a rostrocaudal or caudorostral direction. The two mesomeres are shown to develop by subdivision of a previously formed mesomere, whilst the rhombomeres develop independently of each other. At the completion of cranial neurulation two mesomeres and nine rhombomeres (including the preotic sulcus) but no prosomeres are identifiable.
A direct correlation of the position of peaks in mitotic index along the embryonic axis with the position of sulci on the surface of the neural epithelium, was not possible. However, it is suggested that the mitotic index peak is the initial means of identifying a neuromere, and once the neuromere is expressed morphologically as a surface sulcus the mitotic index returns to its basal level.
Does the oral apparatus of the ciliate Stentor inhibit oral development by release of a diffusible substance?
Authors: De Terra Noël 
Published: April 2021

ABSTRACT
In the ciliate Stentor, many thousands of basal bodies assemble on the ventral cell surface to form a new oral apparatus during cell division, regeneration and reorganization (oral replacement during interphase). During interphase, oral development is normally inhibited by the presence of the anteriorly placed oral apparatus. A glass needle was used to cut the oral apparatus of interphase stentors in two so that the parts remained intact but separate at the anterior end of the cell. These cells initiated basal body assembly and oral development, usually within 8 h. Basal body assembly can therefore result from disconnection of fibrous structures within the oral apparatus but is unlikely to be regulated by an inhibitor diffusing from it.
Adhesiveness of mouse primordial germ cells to follicular and Sertoli cell monolayers
Authors: Felici Massimo De , Siracusa Gregorio 
Published: April 2021

ABSTRACT
The adhesiveness of female and male mouse primordial germ cells (PGCs) to somatic cell monolayers of various origin has been studied in the definite conditions of an in vitro system. PGCs were isolated from the gonads of embryos of various post coital ages according to the method of De Felici & McLaren (1982), and seeded on the cell monolayers. PGCs from 12·5 to 15·5 days post coitum (dpc) embryos specifically adhered to Sertoli and follicular cells obtained from adult gonads. The percentage of female PGCs which adhered to follicular cell monolayers was significantly higher than that of male PGCs. No significant adhesion was seen between PGCs and somatic cell monolayers obtained from various embryonic and adult tissues.
The results obtained indicate that the simple in vitro assay described in the present paper might help to characterize the cellular interactions between somatic and germ cells during gonadal development.
Teratogenic Activity of Several Closely Related Disazo Dyes on the Developing Chick Embryo
Authors: Beaudoin Allan R. 
Published: April 2021

ABSTRACT
Thet eratogenic activity of several disazo dyes during rat embryogenesis has been investigated by Wilson (1955). In addition to the marked teratogenicity of trypan blue Wilson also demonstrated that Evans blue was moderately active and that Niagara blue 4B and Niagara sky blue 6B were possibly active. On the other hand, several other closely related disazo dyes such as Congo red and azo blue were found to cause no malformations in the surviving offspring.
The Block to Polyspermy in Sturgeon and Trout with Special Reference to the Role of Cortical Granules (Alveoli)
Authors: Ginsburg A. S. 
Published: April 2021

ABSTRACT
Treatment of sturgeon eggs with the polyspermy-inducers urethane, ethyl ether, and acetone prolongs the latent period of the cortical reaction and apparently retards the actual secretion of the cortical granules. On activation of sturgeon eggs by pricking and of trout eggs by immersion in water, they lose their fertilizability at the moment of the discharge of cortical granules (the content of the alveoli) in the micropylar region. Before this no decrease in ability of the egg cytoplasm to accept a spermatozoon is observed. After removal of the perivitelline fluid (containing substances discharged from the cortical alveoli) penetration of numerous spermatozoa into activated trout eggs becomes possible. Perivitelline fluid of trout causes an agglutination of spermatozoa. The data obtained provide evidence that the block to polyspermy in fishes is a one-step process realized by means of the discharge of cortical granules (the content of the alveoli).
The Serum Proteins of the Rat During Development
Authors: Heim Werner G. 
Published: April 2021

ABSTRACT
The sera of rats at various stages of development from the 17th day of gestation to adulthood were examined by paper electrophoresis. A component distinct from, and of higher mobility than, the bulk of the albumin was found at the 17th and 18th days of development. However, the mobility of this component is well within the limits of mobility of adult albumin. Evidence supporting the existence of a component in the beta-globulin region specific to the perinatal animal is presented. Gamma globulin and an asymmetry associated with it were demonstrable in all stages examined. The possible relation of this asymmetry to eta globulin is discussed. Problems concerning the physiology of the foetus arising from the changes in the relative concentrations of the serum proteins are pointed out.