bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental potential of teratocarcinoma stem cells in utero following aggregation with cleavage-stage mouse embryos
Authors: Fujii Joanne T. , Martin Gail R. 
Published: April 2021

ABSTRACT
Embryonal carcinoma cells were aggregated with cleavage stage mouse embryos, cultured briefly, and transferred as morulae to the uteri of pseudopregnant females. When midgestation foetuses were examined, many were morphologically abnormal. The severity of this abnormal development was correlated with the extent of contribution by embryonal carcinoma cells to the foetuses as indicated by GPI (glucose phosphate isomerase) analysis. This was true for all three of the cell lines studied, NG-2, PSA-1, and LT1-2D.
The clear correlation between increasingly abnormal development and more extensive participation by the embryonal carcinoma cells was not observed in control experiments in which embryos of different stages of development were aggregated together. The data therefore suggest that the embryonal carcinoma cells studied here are unable to support normal development in the absence of a substantial number of host embryonic cells. It remains unclear whether this is a consequence of the karyotypic abnormalities of the cells tested, or whether it reflects a characteristic limitation in the ability of embryonal carcinoma cells to independently direct normal development.
When aggregates were allowed to develop to term and the extent of chimaerism was examined in the live-born animals, it was found to be sporadic and limited. This is consistent with the results indicating that large contributions by embryonal carcinoma cells are not compatible with normal development at midgestation. The chimaerism observed in the liveborn animals was comparable in both frequency and in tissue distribution to that generally obtained in other studies using either the aggregation or blastocyst injection techniques..
Vascular architecture of the developing spinal cord in the rat: a suggested model
Authors: Simón-marín R. , Vilanova J. R. , Aguinagalde A. , Barberá-Guillem E. 
Published: April 2021

ABSTRACT
The vascular architecture of the developing Sprague-Dawley rat spinal cord from Ell through E16 is reported. The paraffin-embedded cord is serially sectioned in the sagittal, transversal and frontal planes and stained with PAS and methenamine silver. Serial semithin transverse sections are stained with toluidine blue. The results demonstrate two highly integrated vascular systems: one sagittally disposed in three concentric networks and the other radially oriented around the cord. The sagittal plexus is configurated by rhombohexagonal polygons. The lateral radial stem vessels anastomose with the sagittal systems at the polygonal vertex. A structural vascular model of the cord is proposed. The periodical sequence distribution of vessels in the three planes and their relationship to spinal ganglia is suggestive of a neural metamera vascularly determined.
Localization of a pigment-containing structure near the surface of Xenopus eggs which contracts in response to calcium
Authors: Merriam R. W. , Sauterer R. A. 
Published: April 2021

ABSTRACTContractions in surface structures of Xenopus eggs have been induced by application of the calcium ionophore A23187 or calcium ion. Local applications have shown that the contractile structure is present in both animal and vegetal hemispheres. It is, however, much stronger in the animal hemisphere and pigment embedded in it there defines the animal half.The injection of cytochalasin B (CB) into whole cells or the application of the antibiotic to half cells cannot prevent the induced contractions. By experimental means, the contraction of a deeper, pigment-containing structure can be uncoupled from a thin, more superficial and relatively pigment-free layer on the egg surface. By this means it has been possible to establish that the CB-resistant contraction is due, at least partially, to a structurally distinguishable layer subjacent to the outer egg cortex. Scanning and transmission electron microscopy demonstrate a dense grainy matrix near the egg surface in which pigment granules but little yolk are embedded. This structure is much thicker in the pigmented hemisphere.The presence of calcium ions in an isolation medium are shown to cause a loosening or dissolution of the structural connections between the dense, contractile structure near the surface and the cytoskeleton of the endoplasm.
Occlusion of the neural lumen in early mouse embryos analysed by light and electron microscopy
Authors: Kaufman M. H. 
Published: April 2021

ABSTRACTA histological account of neural tube occlusion during early mouse embryogenesis is presented here from an analysis of sections taken from plastic-embedded material. Because the overall pattern of neuroepithelial apposition and the duration of luminal occlusion appears to vary slightly from one embryo to another at otherwise similar stages of development, only a general guide to the events occurring in the mouse embryo between about midday on the 9th to late on the 10th day of gestation can be given. The earliest evidence of complete luminal occlusion was seen when the cephalic and caudal extremities of the neural tube were still widely open.An ultrastructural analysis of the morphological appearance of the closely apposed luminal cells in zones of partial and complete occlusion has demonstrated that occlusion is brought about initially by the interdigitation of processes from closely apposed neuroepithelial cells. This initial event is followed by direct contact over a much more extensive area between the surfaces of apposed cells with a characteristically flattened luminal border. Apposition and luminal occlusion is probably facilitated by the presence of viscous extracellular material. Finally, complete occlusion involving an extensive region of the lumen occurs. The latter phenomenon is a transient event lasting 1 or at most 2 days in the mouse. At no stage were junctional complexes observed between closely apposed neuroepithelial cells in regions in which the neural lumen appeared to be completely occluded, though they were apparent between adjacent neuroepithelial cells.Observations on the underlying mechanism(s) of cellular fusion are considered in the light of the ultrastructural findings. These results are compared with findings from analyses of various other sites of cellular fusion during embryogenesis. Attention is also drawn to the similarities and differences observed in the timing and overall pattern of events occurring during the early development of the neural tube in mouse and human embryos.
The effect of local application of retinoic acid to the anterior margin of the developing chick limb
Authors: Summerbell Dennis 
Published: April 2021

ABSTRACTLocal application of retinoic acid to the chick limb bud produces effects that are dose and/or stage dependent. Low doses and/or old stages tend to give normal limbs or perhaps one or two supernumerary digits of a more anterior character. Medium doses and/or intermediate stages tend to give full mirror-image supernumeraries with two or even three extra digits including particularly digits of a posterior character. High doses and/or early stages give limbs in which supernumerary digits fail to form or are lost, and in which even host skeletal elements are missing or reduced. The effects are graded over the full dose and/or stage range.Various explanations are discussed in the context of the current hypotheses of limb development. We conclude that one should not necessarily interpret the results as evidence that retinoids normally play a part in the control of development or regeneration.
The relationship between cleavage, DNA replication, and gene expression in the mouse 2-cell embryo
Authors: Bolton V. N. , Oades P. J. , Johnson M. H. 
Published: April 2021

ABSTRACT
The 2-cell stage of mouse embryogenesis is characterized by two phases of α-amanitin-sensitive polypeptide synthetic activity, which appear to mark the first major expression of the embryonic genome, as assessed by examination of in vitro translates of mRNA. Using populations of embryos synchronized to the first cleavage division, we have established that DNA replication takes place over the period 1 to 5 ·5 h after the first cleavage division; the two bursts of putative transcription take place before and immediately after DNA replication, and the translation products are detectable in each case within 3 –4 h. In addition, we have shown that suppression of cytokinesis and the second round of DNA replication does not affect synthesis of the α-amanitin-sensitive polypeptides, and that neither DNA replication nor the loss of maternal mRNA that take place during the 2-cell stage are dependent upon synthesis of the α-amanitin-sensitive polypeptides.
Sur l’induction et la compétence dans les relations entre l’épiblaste et le mésenchyme de la patte de Poulet
Authors: Hampé par Armand 
Published: April 2021

ABSTRACT
Dans une série d’expériences sur le rôle de l’épiblaste du bourgeon alaire, Saunders (1948) en découpe le bord épaissi et constate un arrêt de la croissance. Les seules ébauches de l’aile qui se développent sont celles qui sont déjà pré-sentes dans le mésenchyme. Les déficiences terminales sont d’autant plus accusées que l’excision est plus précoce, ce qui fait penser que l’épiblaste est responsable, d’une part de la croissance du membre et d’autre part de la déter-mination successive des divers segments: stylopode (article basal du membre), zeugopode (article intermédiaire) et autopode (article terminal, main ou pied). Mais il était cependant possible d’admettre que le mésenchyme du bourgeon décide par lui-même du segment à produire. Dans cette dernière éventualité, le rôle de l’épiblaste se bornerait à appeler le matériel cellulaire de la base.
Adenosine Triphosphatase Activity in Early Somite Tissue of the Chick Embryo
Authors: Deuchar E. M. 
Published: April 2021

ABSTRACT
Segmented somite tissue of 40 to 45-hour chick embryos (stage 11, Hamburger & Hamilton, 1951) shows a higher calcium-activated ATP-ase activity than the somite tissue that has not yet segmented at this stage. The enzyme activity is not extracted by prior treatment of the tissues with 50 per cent, glycerol, and is not localized in the mitochondrial fraction. There is no difference in magnesium-activated (mitochondrial) ATP-ase activity between segmented and non-segmented mesoderm at this stage. It is postulated that the apparent increase in calcium-activated ATP-ase at the time of segmentation may represent a synthesis of myosin or of some myosin precursor.
The Sexual Development of Salpa fusiformis (Cuvier)
Authors: Sutton Muriel F. 
Published: April 2021

ABSTRACT
The early sexual development of S. fusiformis Cuvier is described.
The fertilized egg begins to develop in the single ovarian follicle, dorsolaterally, close to the atrial epithelium. At the eight-cell stage the follicle cells (calymmocytes) proliferate rapidly and insinuate themselves between the blastomeres. Each blastomere at this point buds endogenously and the resultant seven daughter cells rapidly degenerate; a large residual cell persists. The calymmocytes continue to increase in number but their degeneration also is initiated. The follicle perforates the atrial epithelium, and is now known as the blastophore. A normal blastomere division occurs and is followed by a second phase of budding and daughter-cell degeneration. A structure, the placental knob, develops ventrally; one of its functions is to proliferate calymmocytes. The blastomeres begin to move around regularly and irregularly occurring spaces produced by calymmocyte degeneration, and, on gaining contact with each other, normal division is resumed. A medio-dorsal, neuro-chordal cell massif becomes recognizable and subsequently it moves antero-dorsally. Three regularly occurring cavities begin to develop during the neuro-chordal cell movement. They are centrally and laterally placed and will ultimately fuse and form, in part, the oozooid pharynx. The remaining blastomeres aggregate in groups which will give rise to the cloacal epithelium, remaining ectoderm, and endoderm. Mesodermal cells are not yet to be discerned with certainty. During the early stages of development of the three cavities an incubation fold develops from the adjacent atrial epithelium. It grows up around the blastophore. The aggregation of the cloacal, ectodermal, and endodermal blastomeres and the fusion of the central and lateral cavities occur after the closure of the fold.
The significance of certain phenomena, in particular of endogenous budding, are discussed. The conclusion favoured at present is that the budding process is an abnormal phase of division induced by a loss of blastomere contact.
L’Inhibition spécifique de la différenciation du cerveau des Planaires d’eau douce en régénération
Authors: Lender par Th. 
Published: April 2021

ABSTRACT
La régénération des Planaires d’eau douce est caractérisée par la formation d’un blastème dû à l’accumulation de néoblastes. Ces cellules, à caractère embryonnaire, migrent vers la blessure puis se différencient pour reconstituer les tissus excisés (Wolff & Dubois, 1947; Dubois, 1949). Les tissus de la Planaire peuvent intervenir dans les processus de différenciation en favorisant l’apparition d’un organe. Ainsi le cerveau induit la régénération des yeux de la Planaire Polycelis nigra par l’intermédiaire de substances chimiques diffusibles (Wolff & Lender, 1950; Lender, 1952, 1956a). Mais d’autre part certains auteurs ont mis en évidence des phénomènes d’inhibition dans la régénération des Planaires. Morgan (1902) etRand & Ellis (1926) constatent qu’une tête inhibe la régénération d’une autre tête chez les Planaires bicéphales. Rand & Browne (1926) et Miller (1938) empêchent la régénération de la tête en greffant une région céphalique dans la région antérieure de la Planaire opérée. Chevtchenko (1937) constate que la tête de l’hôte inhibe le développement d’une région céphalique dans un greffon de tête implanté dans la région antérieure de la Planaire. L’inhibition ne se manifeste pas si le greffon est implanté dans la région caudale. Il semble donc que la tête des Planaires d’eau douce soit capable, dans certaines conditions, d’inhiber la différenciation d’une autre tête.
The Inhibitory Action of Antimycin A in the Early Chick Embryo
Authors: McKenzie J. , Ebert J. D. 
Published: April 2021

ABSTRACT
Antimycin A, an antibiotic obtained from an undetermined species of strepto-myces, was isolated, crystallized, and described by Dunshee, Leben, Keitt, & Strong (1949), and its biological action has been studied by many workers since then. Ahmad, Schneider, & Strong (1950) demonstrated its effects on the growth and metabolism of yeast, on enzyme activities in the succinoxidase system, and on rats given the drug orally. Potter & Reif (1952) confirmed the inhibitory effect of antimycin A on the succinoxidase system in liver, suggested the presence of an ‘antimycin A-blocked factor’, identical, probably, with the ‘Slater factor’ and showed that, in certain tissues, there is an antimycin A-insensitive pathway for DPN oxidation. The same workers, Reif & Potter (1954), used the drug to characterize the pathways of DPN oxidation in different tissues. Green, Mii, & Kahout (1955) and Thorn (1956) argue from their experiments that the BAL-sensitive (Slater) factor and the antimycin A-sensitive factor are not identical.
The Skin Abnormality of ‘Ichthyosis’, a Mutant of the House Mouse
Authors: Spearman R. I. 
Published: April 2021

ABSTRACT
The skin defect ‘ichthyosis’ of the house mouse is caused by a simple recessive gene (symbol zc) which arose as a spontaneous mutation. It was first described by Carter & Phillips (1950). ‘Ichthyotic’ mice have a thin coat of very short wavy hairs together with a scaly skin. There is, however, considerable individual variation in the severity of the defect. In badly affected animals the stratum corneum of the back is shed as large flakes, and the mice may be almost bald; but in less affected mice the skin is not very scaly and there is a complete though abnormal hair cover. The tail skin has a hard smooth appearance and is less flexible than normal. In some older mice a number of depressed rings form along its length, and a portion of the tail undergoes necrosis and drops off distal to one of the constrictions.
The pattern of alkaline phosphatase activity in the developing mouse spinal cord
Authors: Kwong W. H. , Tam P. P. L. 
Published: April 2021

ABSTRACT
The localization of alkaline phosphatase activity in the lumbosacral region of the developing spinal cord was studied in 9·5-to 17·5-day mouse embryos. The activity was uniformly distributed in the pseudostratified neuroepithelium of the 9·5-day cord. In the 11-5-day cord in which the lateral motor columns were being formed, the enzymatic activity was localized in the ventrolateral sector of the cord. The enzyme-positive ventricular cells tended to be located medially whereas radially oriented enzyme-positive processes extended into the marginal layer. The 13·5-day cord displayed a similar distribution pattern, but there were many more radial processes and the enzyme-positive cells had spread laterally. Close apposition between the processes and the ventricular cells was observed. By 15·5 and 17·5 days, when the intermediate layer was fully developed and the ventricular layer had regressed to a thin ependyma, the activity had become diffusely located in the ventral half of the cord. The enzyme-positive cells and processes became less conspicuous. The silver-stained processes in the cord were found to be organized in an entirely different pattern from that of the enzyme-positive processes, suggesting that the enzyme-positive processes were not neuronal processes. The enzymatic activity found in the developing spinal cord may be associated with the migration of neuroblasts along the radially aligned processes.
Interdigital tissue chondrogenesis induced by surgical removal of the ectoderm in the embryonic chick leg bud
Authors: Hurle J. M. , Gañan Y. 
Published: April 2021

ABSTRACT
In the present work, we have analysed the possible involvement of ectodermal tissue in the control of interdigital mesenchymal cell death. Two types of experiments were performed in the stages previous to the onset of interdigital cell death: (i) removal of the AER of the interdigit; (ii) removal of the dorsal ectoderm of the interdigit. After the operation embryos were sacrificed at 10–12h intervals and the leg buds were studied by whole-mount cartilage staining, vital staining with neutral red and scanning electron microscopy.
Between stages 27 and 30, ridge removal caused a local inhibition of the growth of the interdigit. In a high percentage of the cases, ridge removal at these stages was followed 30–40 h later by the formation of ectopic nodules of cartilage in the interdigit. The incidence of ectopic cartilage formation was maximum at stage 29 (60%). In all cases, cell death took place on schedule although the intensity and extent of necrosis appeared diminished in relation to the intensity of inhibition of interdigital growth and to the presence of interdigital cartilages. Ridge removal at stage 31 did not cause inhibition of the growth of the interdigit and ectopic chondrogenesis was only detected in 3 out of 35 operated embryos.
Dorsal ectoderm removal from the proximal zone of the interdigit at stage 29 caused the chondrogenesis of the proximal interdigital mesenchyme in 6 out of 18 operated embryos. The pattern of neutral red vital staining was consistent with these results revealing a partial inhibition of interdigital cell death in the proximal zone of the interdigit.
It is proposed that under the present experimental conditions the mesenchymal cells are diverted from the death programme by a primary transformation into cartilage.
Development and degeneration of retina in rds mutant mice: observations in chimaeras of heterozygous mutant and normal genotype
Authors: Sanyal S. , Dees C. , Zeilmaker G. H. 
Published: April 2021

ABSTRACT
In homozygous rds mutant mice the photoreceptor cells lack outer segment discs and slowly degenerate. In the heterozygotes the receptor cells develop abnormal outer segments and show altered disc shedding properties as revealed by the pigment epithelial phagosome content. The receptor cells also degenerate at a slower rate than in the homozygotes. The nature of the interaction resulting in dilution of the retinal lesion in the heterozygous retina was analysed in a series of chimaeras consisting of rds/ + and +/+ genotypes, which also differed in colour genes.
In 64% of the chimaeras (18 out of 28) presence of both rds/+ and +/+ types of photoreceptors could be detected by electron microscopy. The relative proportion and patch size of the two components varied greatly between individuals but the location of the two types of photoreceptors was not related to the genotypes of the overlying pigment epithelial cells. Frequent occurrence of abnormally large phagosomes, resembling the rds/+ phenotype, was noted regularly in both rds/ + and +/+ types of pigment epithelial cells located above rds/+ types of receptors, but not in the cells of either genotype located above normal receptors. In the eyes examined at 12–18 months, localized and partial depletion of the perikaryal population in the outer nuclear layer was observed, and the location of such areas was also unrelated to the genotypes of the pigment epithelial cells. These findings confirm that the rds gene acts within the neural retina and possibly within the receptor cells and further show that the genetic interaction between the rds gene and its normal allele in the retina of the heterozygous mice takes place within the receptor cells.
Development of neural tube basal lamina during neurulation and neural crest cell emigration in the trunk of the mouse embryo
Authors: Martins-Green M. , Erickson C. A. 
Published: April 2021

ABSTRACTIn the trunk of higher vertebrates, the neural crest (NC) cells remain temporarily within the dorsal portion of the neural tube after fusion of the neural folds; shortly thereafter they emigrate, invading surrounding spaces and tissues. One of the factors postulated to be important in the initiation of migration of NC cells is the disruption of the basal lamina (BL) over the dorsal portion of the neural tube. It has been assumed by many that the BL must be discontinuous in order that the NC cells can leave the neural tube; and indeed, experiments performed in our laboratory, and by others, have shown that NC cells cannot penetrate an intact BL. Therefore, we have undertaken a systematic ultrastructural study to evaluate the condition of the BL during neural fold elevation and NC cell emigration. Our results show that: (i) BL surrounding the neural epithelium (NE) becomes progressively more extensive from neural fold to migratory stages. It first forms on the lateral portion of the neuroepithelium of the neural folds and then extends ventrally into the region adjacent to the notochord; (ii) BL becomes continuous beneath the epidermal ectoderm (EE) that overlies the NC cell region only during the terminal stages of NC cell emigration; (iii) BL does not form over the dorsal portion of the neural tube until NC emigration is terminated; and (iv) the morphology of the BL changes as development proceeds. We conclude that absence of a BL over the premigratory NC cell population in the trunk of mouse embryos is a necessary but not a sufficient condition for emigration to take place.