bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in the patterns of collagens and fibronectin during limb-bud chondrogenesis
Authors: Dessau W. , Mark H. Von Der , Mark K. Von Der , Fischer S. 
Published: April 2021

ABSTRACTThe distribution and sequence of appearance of fibronectin and of type-I and type-II collagen in the developing cartilage models of embryonic chick hind-limb buds was studied by immunofluorescence, using specific antibodies directed against these proteins. Fibronectin and type-I collagen are evenly distributed throughout the intercellular space of the mesenchyme prior to condensation of core mesenchyme of the limb anlage and formation of the cartilage blastema. With the onset of the condensation process fibronectin and type-I collagen appear to increase in the cartilage blastema compared to the surrounding loose mesenchyme, reaching a maximal density at the time of cartilage differentiation. The latter process is marked by the appearance of type-II collagen in the cartilage blastema. As cartilage differentiation progresses, type-I collagen is gradually replaced by type-II collagen; fibronectin disappears and is completely absent from mature cartilage.The transient appearance of type-I collagen and fibronectin suggests a temporal role in cell-matrix or cell-cell interactions in chondrogenesis, since it had been shown that (a) type-I collagen substrates stimulate cell proliferation and cartilage differentiation in limb-bud mesenchyme cell cultures; (b) fibronectin mediates attachment of cells to collagen substrates; and (c) fibronectin is directly involved in cellular interactions in chondrocyte cultures.
Is there a ventral neural ridge in chick embryos? Implications for the origin of adenohypophyseal and other APUD cells
Authors: Levy N. B. , Andrew Ann , Rawdon B. B. , Kramer Beverley 
Published: April 2021

ABSTRACT
Two- to ten-somite chick embryos were studied in order to ascertain whether, as has been proposed, there exists a ‘ventral neural ridge’ which gives rise to the hypophyseal (Rathke’s) pouch. Serial sections and stereo-microscopy were used.
The neural ridges arch around the rostral end of the embryo onto the ventral surface of the head, but no evidence was found for their extension to form a ‘ventral neural ridge’ reaching the stomodaeum: in fact a considerable expanse of non-thickened surface ectoderm was seen to separate the ventral portions of the neural ridges from the stomodaeum. The thickening of neural ectoderm which does appear on the ventral surface of the head results from apposition and fusion of the opposite neural ridges flanking the neural plate and thus the tip of the anterior neuropore – the classically accepted mode of closure of the neuropore.
These findings are in accord with the generally accepted concept of the origin of the hypophyseal pouch rather than with its derivation from a ‘ventral neural ridge’.
No sign of neural crest formation was encountered ventrally; this observation excludes the possibility that endocrine cells of the APUD series could originate from neural crest in this region.
The ontogeny of erythropoiesis in the mouse detected by the erythroid colony-forming technique: II. Transition in erythropoietin sensitivity during development
Authors: Rich Ivan N. , Kubanek Bernhard 
Published: April 2021

ABSTRACT
The erythroid colony-forming technique has been used to study the erythropoietin (Ep) sensitivity of CFU-E during ontogenesis. Evidence is provided which indicates that an age-related decreasing Ep sensitivity of CFU-E occurs as the animal develops. In addition, an intermediate Ep-sensitive CFU-E population represented by the 2-day-old neonate is present during the transition from foetus to adult. The Ep sensitivity of the foetal, neonatal and adult CFU-E populations is shown to be an intrinsic property of these populations.
Differentiation of glomerular filter and tubular reabsorption apparatus during foetal development of the rat kidney
Authors: Schaeverbeke Jean , Cheignon Madeleine 
Published: April 2021

ABSTRACT
Differentiation of the glomerulus and the proximal tubule was studied in the rat foetus, especially with regard to the development of the protein filtration-reabsorption apparatus. Filtration starts several days before full differentiation of the glomerulus, when the glomerular basement membrane consists of a thin lamina alongside the podocyte membrane. Endocytosis is functional from this time, but fusion between endocytic vesicles and lysosome-like bodies occurs 2 days later. Foetal urine electrophoresis shows the presence of many proteins, including high molecular weight ones, this proteinuria seeming chiefly due to the immaturity of the glomerular barrier.
Erythroid cell differentiation in unincubated chick blastoderm in culture
Authors: Zagris Nikolas 
Published: April 2021

ABSTRACT
Morphologically distinct erythroid cell types characteristic of the primitive and the definitive erythroid cell lines, and embryonic and adult haemoglobins are produced when the unincubated chick blastoderm is cultured ventral side down on a filter raft to inhibit morphogenetic movements and subsequent primitive-streak formation mechanically in serum-free minimal essential medium. The primitive and definitive erythroid cell populations appear consecutively in culture even though there is no axis formation nor apparent morphogenesis. The information to produce both the early and late haemoglobins and erythroid cell types is independent of axis formation and of specific extra-embryonic influences, such as progressive induction exerted by the yolk mass.
Actin synthesis during the early development of Xenopus laevis
Authors: Sturgess E. A. , Ballantine J. E. M. , Woodland H. R. , Mohun P. R. , Lane C. D. , Dimitriadis G. J. 
Published: April 2021

ABSTRACT
Cytoskeletal β and γ-actin are amongst the most rapidly made proteins of oocytes, blastulae and later embryonic stages of Xenopus laevis but, relative to other proteins, the rate of synthesis is low in the egg or cleaving embryo, although the messenger RNA is present in comparable amounts at the different stages. Actin synthesis therefore involves post-transcriptional regulation, α-actin, the actin class characteristic of striated muscle cells, is first detectable in late gastrulae and it is an abundant newly synthesized protein from the neurula stage onwards. mRNA template activity for this protein is not detectable before the gastrula stage. Thus a-actin synthesis probably reflects new gene action, confined to part of the embryo, for α-actin only appears in the section which includes presumptive skeletal muscle cells. It therefore constitutes the earliest cyto-specific protein so far demonstrated in Amphibia. When tadpole tail poly(A)-containing mRNA is injected into oocytes and eggs α-actin synthesis is seen in both cases. Extensive evidence for the identification of the actins is presented. This is based on location of synthesis, DNase-I binding and partial peptide mapping.
Cellular morphology in haploid amphibian embryos
Authors: Ellinger Mark S. , Murphy Judith A. 
Published: April 2021

ABSTRACT
External surfaces of haploid and diploid embryos of Bombina orientalis were examined with the scanning electron microscope to determine the possible contribution of cellular morphology to the amphibian haploid syndrome. Cellular anomalies were prevalent in all surface areas of haploid embryos. The epithelium appeared uneven due to the displacement of ciliated cells and the rounded apical surfaces of the non-ciliated cells. The ratio of ciliated to non-ciliated cells was altered in comparison to diploid embryos. Cells of the gill filaments and adhesive organs were abnormal in morphology, and the adhesive organs themselves were fused into a single large rudiment in haploid embryos. Uniformity of cell size was markedly reduced in head regions of haploid embryos with severe microcephaly. Haploid and diploid embryos elaborated mucoid matrices over the surface cells when removed from the fertilization envelope.
It is apparent that aberrant cellular morphologies are widespread in haploid embryos, and it is likely that these defects are major contributors to the gross morphological anomalies of the haploid syndrome.
Positional information around the segments of the cockroach leg
Authors: French Vernon 
Published: April 2021

ABSTRACT
Epidermal cells from different circumferential positions around the femur of Blabera craniifer can interact to form an intercalary regenerate consisting of that section of the circumference normally separating graft and host positions, by the shorter route. This result is extended to other leg segments; the tibia and coxa (TT and CC Grafts). Grafting strips of integument from the tibia (TF Grafts) or the coxa (CF Grafts) to a corresponding position on the host femur results in simple healing. Grafting to a non-corresponding position leads to intercalation of the shorter intermediate arc of circumference, composed partly of graftsegment and partly of host-segment structures. These results show that the same continuous sequence of positional values is distributed around the circumferences of the coxa, femur and tibia. Cellular interactions along the edges of strip-grafts obey the Shortest Intercalation Rule.
At the ends of strip-grafts intercalation usually restores continuity of positional values where possible but, when a complete circumference is generated, a supernumerary distal regenerate is usually formed. This is in general agreement with the Complete Circle Rule and the exceptions are discussed.
In intercalary regeneration following the intersegmental strip-grafts, the host femur cells seem unable to intercalate beyond two positions (posterior/internal and posterior/external). These lineage restrictions operating during regeneration indicate that the cockroach leg, like the Drosophila leg disc, may consist of an anterior and a (smaller) posterior ‘compartment’.
Cell membrane regions in preimplantation mouse embryos
Authors: Izquierdo L. , López T. , Marticorena P. 
Published: April 2021

ABSTRACTCell membrane regions characterized by alkaline phosphatase activity are described in cleaving mouse embryos and early blastocysts. Enzyme activity is demonstrated by light and electron microscopy, from the late 4-cell stage onwards, on the cell surfaces between blastomeres but not on the outer surface of the embryo. Experiments with dissociated morulae show that this is probably not an artifact due to the retention of the enzyme reaction product between the blastomeres. With the electron microscope the activity is also demonstrated in crystalloid bodies within the cytoplasm. The localization and growth during cleavage of cell membrane regions with enzyme activity is interpreted as the result of new cell membrane formation and/or as a relation of the crystalloid bodies with the cell membrane through the cortical system of microtubules and filaments.
The Forces Producing Neural Closure in Amphibia
Authors: Selman G. G. 
Published: April 2021

ABSTRACTIt has been shown by Smith (1946), working with trout eggs, that when an embryo develops the heat lost to the surroundings is balanced by the loss in the calorific value of its energy-rich storage substances. Other workers (e.g. Shearer, 1922) have shown that the heat lost by eggs and developing embryos is approximately equal to the available energy deduced from the observed respiration. It would seem, therefore, that only a very small fraction of the energy known to be available to the embryo from its aerobic metabolism can be stored as potential energy in the visible pattern of tissue structures which the embryo progressively develops. It has sometimes been concluded from this that little energy can be required for morphogenesis. This conclusion is doubtless true, but the argument is unsound, because no knowledge of the energy balance between the total energy being released by the embryo and the energy being lost to the surroundings can tell us anything about the work which may be required to overcome a potential energy barrier. For instance, consider this example which is used here as a simple illustration of the argument rather than as a model of what actually happens. It is conceivable that when a newt embryo gastrulates, considerable work must be done in so deforming the cells against their own elasticity that the blastula tissue may pass through the narrow blastopore opening. To perform such work energy is required from the chemical energy source; it will be stored as potential energy by deformed cells as they pass through the blastopore; yet when the constriction is passed, the cells relax to their equilibrium shapes once more and the energy is dissipated as heat. In such a case a knowledge of the energy-balance could tell us nothing about the work done in gastrulation. On the other hand, if we knew about the forces required to deform the cells we should be able to estimate the work required for gastrulation, using this particu-lar model for the process.
A definite number of aphidicolin-sensitive cell-cyclic events are required for acetylcholinesterase development in the presumptive muscle cells of the ascidian embryos
Authors: Satoh Noriyuki , Ikegami Susumu 
Published: April 2021

ABSTRACTIn order to determine whether or not a crucial number of DNA replications are prerequisite for cellular differentiation, we have studied development of a tissue-specific enzyme, muscle acetylcholinesterase (AChE) in the presumptive muscle cells of cleavage-arrested ascidian embryos. Embryos were cleavage-arrested with cytochalasin B (an inhibitor of cytokinesis) and aphidicolin (an inhibitor of DNA synthesis). The 64-ceIl-stage embryos which had been permanently cleavage-arrested with cytochalasin B developed AChE in all the eight presumptive muscle cells, but the same stage embryos which had been prevented from undergoing further divisions by simultaneous treatment with aphidicolin and cytochalasin did not produce AChE at all. Cytochalasin-arrested 76-cell-stage embryos were able to differentiate AChE in the ten presumptive muscle cells, while aphidicolin-cytochalasin-arrested 76-cell stages in as many as four cells. The early gastrulae which had been arrested with cytochalasin B produced AChE in all the sixteen presumptive muscle cells, while the same stage embryos arrested with aphidicolin and cytochalasin in as many as twelve cells. Cytochalasin-arrested late gastrulae developed AChE in twenty blastomeres, while aphidicolin-cytochalasin-arrested late gastrulae in eighteen cells.The presumptive muscle cells at these four stages consist of those of three different (seventh, eighth, and ninth) generations, and the relative positions of the blastomeres in the cleavage-arrested embryos remained fixed. Judging from the relative positions of the blastomeres, the AChE-producing cells in aphidicolin-cytochalasin-arrested embryos were always at eighth or ninth generation, while those with no AChE activity were certainly at seventh generation. Based on these findings it was supposed that aphidicolin-sensitive cell-cyclic events, presumably DNA replication, are closely associated with AChE development and that the eighth cleavage cycle may be ‘quantal’ for the histospecific enzyme development.
Morphologic aspects of adhesion and spreading behavior of amphibian blastula and gastrula cells
Authors: LeBlanc Jacqueline , Brick Irving 
Published: April 2021

ABSTRACT
By means of SEM we have examined spreading and adhesive behavior of cells isolated from superficial and deep regions of germ layers from blastula to late gastrula in Rana pipiens embryos. Each of the cell populations sampled show adhesive and spreading characteristics distinctive for each region and stage which we interpret as demonstrating the following:
From blastula through late gastrula, cells from each region have already acquired the ability to express surface morphologic and adhesive features independently of their association with their neighbors, i.e. autonomously. The distinctive spreading and adhesive characteristics for each tissue sub-population suggest kinetic properties seemingly related to their in vivo morphogenetic movements, epiboly or invagination. The appearance within germ layers of two subpopulations between blastula to mid-gastrula, suggests early intratissue inductive interactions. The outermost, superficial cells from each germ layer show proximal and distal surface differences which may reflect adhesive differentials as postulated by Steinberg (1970) for presumptive ectoderm cells. With the exception of superficial cell proximal and distal differentiation, freshly disaggregated cells do not show morphologic characteristics seen in corresponding cells spreading for one hour.
Abnormal overgrowth of chick embryos treated withp-nitrophenylβ-D-xyloside at early stages of development
Authors: Oohira Atsuhiko , Nogami Hiroshi , Nakanishi Yasuo 
Published: April 2021

ABSTRACTThe effect of p-nitrophenyl β-D-xyloside, an inhibitor of proteoglycan biosynthesis, on the growth of chick embryos was studied by injection of the single dose of 1.0mg/egg into fertile eggs on day 3. Embryos examined on day 10 had systemic edema, and were increased not only in wet weight (142% of the non-treated embryos) but also in dry weight (125%). No skeletal malformations were observed in the treated embryos. The glycosaminoglycan content in the treated embryos began to increase 6 h after treatment and reached the maximum level (174% of the non-treated) after 3 days, while the DNA and protein content began to increase 12 h after treatment and reached the maximum level (about 140%) within 3 days. p-Nitrophenyl α-D-xyloside, p-nitrophenyl β-D-galactoside, and a mixture of p-nitrophenol and D-xylose produced neither the abnormal overgrowth nor the edematous change of chick embryos.When fertile eggs were treated with 1·0 mg/egg of p-nitrophenyl β-D-xyloside on day 6, the increase in wet and dry weights was also observed in all surviving embryos. On the contrary, treatment on day 9 resulted in the slight reduction of embryonic growth in addition to the systemic edema. Both embryos treated on day 3 and on day 6 contained glycosaminoglycans rich in chondroitin 6-sulfate, whereas the embryos treated on day 9 contained glycosaminoglycans rich in undersulfated chondroitin sulfates. These findings seem to support the view that glycosaminoglycans play an important role in the regulation of embryonic growth.
Presence of multipotential hemopoietic cells in teratocarcinoma cultures
Authors: Cudennec Claude A. , Johnson Gregory R. 
Published: April 2021

ABSTRACT
Previous investigations have shown that the teratocarcinoma line PCC3/A/1 is able to differentiate in vitro to produce red blood cells of the primitive hemopoietic cell population of the mouse embryo. The present paper demonstrates the presence in the same cultures of multipotential cells capable of giving rise to colonies containing erythrocytes, macrophages, and megakaryocytes when stimulated by pokeweed-mitogen spleen-cell conditioned medium.
Erythropoiesis and haemoglobin ontogeny in the turtle Emys orbicularis L
Authors: Vasse J. , Beaupain D. 
Published: April 2021

ABSTRACT
The erythropoietic sites and developmental patterns of haemoglobins have been investigated during ontogeny of Emys orbicularis. The yolk-sac blood islands seem to be the unique erythropoietic site during most of embryonic life. Bone marrow haemopoiesis is first observed in young turtles aged one year. The cortical haemopoietic layer of the liver appears involved mainly in granulopoiesis. There is no morphologically well-defined series of primitive or definitive erythrocytes. Rather there is a gradual shift in size from a mean length of 17·4μm in embryos to 19·9μm in the adult. However the size of erythrocytes is highly variable at all stages. Three haemoglobins of adult type and three haemoglobins of embryonic type have been identified by electrophoretic separation. It seems that one haemoglobin is synthesized during the whole life. Embryonic haemoglobins persist for more than a year after hatching while the typically adult haemoglobins appear shortly before hatching.
Enzymo- and immunocytochemical analyses of the differentiation of liver cells in the prenatal mouse
Authors: Shiojiri Nobuyoshi 
Published: April 2021

ABSTRACTDifferentiation of the endodermal cells of the mouse liver was studied enzymo- and immunocytochemically by analyzing the cellular localization of alphafoeto protein (AFP), glycogen, and alkaline phosphatase (ALP) and 5’-nucleotidase (5′-Nase) activities.In 8-5-day foetuses, AFP appears in some endodermal cells of the anterior intestinal portal region. The cells of the cranial diverticulum contain much AFP at 9-5 days, while those of the caudal diverticulum contain less AFP. In 9·5- to 15·5-day foetuses, hepatocytes are intensely fluorescent for AFP. After 16·5 days less-positive hepatocytes increase in number. AFP is still present in a few hepatocytes of 14-day-old postnatal mice. ALP and 5′-Nase activities appear in a small proportion of hepatocytes at 13·5 and 14·5 days of embryonal life, respectively. At 15-5 days, many hepatocytes possess these enzyme activities, and initiate accumulation of glycogen. AFP-containing hepatocytes type I (gestation day 9·5–16·5) successively acquire ALP and 5′-Nase activities and accumulate glycogen, and then differentiate into hepatocytes type II after gestation day 17·5. Endodermal cells constituting lumen structures in the liver trabeculae are the precursor of the intrahepatic bile duct cells. They possess much AFP, but no glycogen and no ALP activity, and are similar to hepatocytes type I. Since immature hepatic duct cells also possess much AFP, but no glycogen, and no ALP and 5′-Nase activities, they are similar to endodermal cells of the lumen structures. Therefore, that the endodermal cells of the lumen structures are the intermediate cells between hepatocytes type I and hepatic duct cells may be conceivable.
Cell interactions and endoderm differentiation in cultured mouse embryos
Authors: Hogan Brigid L. M. , Tilly Rita 
Published: April 2021

ABSTRACT
Morphological and biochemical evidence is presented that the visceral extraembryonic endoderm of the 6·5-day mouse embryo will differentiate into parietal endoderm when cultured in contact with extraembryonic ectoderm undergoing transition into trophoblast giant cells. Egg cylinders from 6·5-day embryos were dissected into embryonic and extraembryonic halves and cultured in suspension in vitro for up to 7 days. After 4 days, the endoderm cells of the extraembryonic fragments morphologically resemble parietal endoderm, are associated with a thick basement membrane and synthesize large amounts of the matrix proteins laminin and Type IV procollagen. A similar transition in phenotype is not seen in the endoderm of embryonic fragments, nor in visceral extraembryonic endoderm cells cultured in isolation. In another series of experiments, complete egg cylinders were dissected free of visceral endoderm ovei lying the extraembryonic ectoderm and then cultured in vitro. The visceral endoderm cells which recolonize the surface of the extraembryonic ectoderm develop a parietal endoderm phenotype and lay down a thick basement membrane. These results suggest that the differentiation of the extraembryonic endoderm of the early mouse embryo into visceral and parietal phenotypes can be influenced by local cell-cell or cell-substrate interactions, and is not determined solely by cell lineage.