bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epithelial autolysis during implantation of the mouse blastocyst: an ultrastructural study
Authors: El-Shershaby A. M. , Hinchliffe J. R. 
Published: April 2021

ABSTRACTAn ultrastructural investigation was made of cell death in the uterine epithelium during the implantation of the mouse blastocyst. Cell death occurs in two phases: (i) early individual cell death, and (ii) later general cell death.Individual dead epithelial cells are phagocytosed and digested by trophoblast cells. At 95 h post coitum (p.c.) there are 1–4 dead cells; at 105 h and 113 h, 6–8 dead cells, and at 116 h, 2–3 dead cells. No lysosomal involvement could be identified in the death of these cells.The general breakdown of the uterine epithelium around the implanting blastocyst is first recognizable at the ultrastructural level at 113 hp.c., and continues until the adjacent deteriorated epithelium has been phagocytosed by the trophoblast cells at 119 h p.c. Ultrastructurally, from I13h p.c. cytoplasmic portions of epithelial cells are trapped within cytosegrosomes, and there is an increase in size of the dense lysosomal bodies found in viable epithelial cells at 105 h p.c. The dense bodies, which are positively stained for acid phosphatase enzyme at 105 h p.c., increase in diameter approximately 3–5 times between 105 h p.c. and 119 h p.c. These results provide evidence of intracellular digestion of small portions of the cytoplasm possibly through the formation of cytosegrosomes which then fuse with residual bodies already present. Thus the evidence favours a process of autolytic breakdown of the uterine epithelium around the implanting blastocyst.
The function of the ectodermal apical ridge and distinctive characteristics of adjacent distal mesoderm in the avian wing-bud
Authors: Cairns John M. 
Published: April 2021

ABSTRACT
Blocks of mesoderm about 0 ·1 mm in diameter were isolated from various regions of chick wing-buds of stages 17 through 22 and cultured individually, or sometimes in pairs, wells. Cell deaths had occurred after 10 h of culture in those explants that had come from the region associated with the thickest part of the ectodermal ridge, and after 11 –12 h in all other mesoderm. When the adjacent ectodermal ridge was left attached to the mesodermal block there were almost no cell deaths for up to 24 h of culture. When the dorsal ectoderm immediately proximal to the apical ridge was left attached, but no ridge was present, cell deaths occurred just as they did in mesoderm with no ectoderm. When a number (usually six) of complete ridges were suspended in a wire basket at the top of a well, cell deaths did not occur in a test mesodermal block at the bottom of the well (six of eight cases). These experiments support previous evidence for a special function of the ectodermal apical ridge in limb morphogenesis, and indicate that there is a chemical messenger.
The cells that migrated from distal mesodermal explants (the band up to 0 ·15 mm from the apical ridge) differed sharply in morphology and behavior from those coming from explants from any more proximal region. Within the proximal mesoderm there was a less striking variation along the antero-posterior axis. These observations reveal that there is present even at early stages a detailed pattern within the mesoderm of the limb-bud. The particularly striking and distinctive characteristics of that mesoderm closest to the apical ectodermal ridge provide new possibilities for the understanding of the function of the ridge in limb morphogenesis.
Mitochondrial and other ultrastructural changes in the developing Habrobracon embryo
Authors: Amy Robert L. 
Published: April 2021

ABSTRACT
Cells of the wasp, Habrobracon juglandis, were studied by electron microscopy with the view to comparing ultrastructural changes, especially those found in mitochondria, that occur during the first two-thirds of the 29 h embryonic period. In 1-to 2-h embryos (the earliest studied) mitochondria are distributed principally in the periplasm and typically are arranged in clumps with their long axes parallel to each other. Based on a study of profiles occurring in thin sections, most appear to be elongate with poorly developed cristae, have dense matrices and are longer than those of later stages. At 3 –4 h of age, in incipient blastoderm cells, the mitochondria are distributed throughout the cytoplasm with 40% located lateral to the nuclei and 42 % concentrated in a subnuclear position. Most (81 %) exhibit spherical profiles, with well-developed cristae and less dense matrices than those found at earlier ages. In fully formed blastodermal cells (7 –8 h), mitochondria are similar morphologically except that a lower percentage (53 %) are spherical; almost half (48 %) have migrated to a supranuclear location. In early gastrula cells (11 –12 h) no significant variations from the blastoderm condition were apparent. Mitochondria in the oldest cells studied (18 – 19 h) show somewhat greater structural complexity and variability. The number per cell section is drastically reduced compared to earlier ages, but this, at least in part, is related to a reduction in cell size. Changes observed in other cellular constituents are also described. Comparisons are made with similar variations reported in other developing organisms and their possible significance is discussed.
The development of animals homozygous for a mutation causing periodic albinism (a
p) in Xenopus laevis
Authors: Hoperskaya Olga A. 
Published: April 2021

ABSTRACT
This paper describes the development of a mutant strain associated with periodic albinism (ap) in the clawed toad Xenopus laevis. The most outstanding feature of this mutation is the instability of the albino state. In the course of the development there is a succession of three periods of pigment expression: (1) complete absence of melanin pigment, (2) appearance of melanin in the pigmented epithelium of the eyes and in small quantities in skin melanophores, (3) disappearance of most pigment granules. Repeated spawnings show that the mutant syndrome is inherited as a recessive trait. Possible ways of analysing pigment cell differentiation with the use of the mutation described are discussed.
Adult amphibian epidermal proteins: biochemical characterization and developmental appearance
Authors: Reeves O. Raymond 
Published: April 2021

ABSTRACT
The keratin-like proteins (KLPs) from the epidermis of adult frogs of the species Xenopus laevis have been isolated and biochemically characterized by means of polyacrylamide gel electrophoresis, amino acid analysis, tryptic peptide mapping, amino-terminal end-group analysis and isoelectric focusing. One particular protein fraction of rather unusual amino acid composition found only in epidermal tissue was isolated in quantity by preparative gel electrophoresis and monospecific antibodies prepared against it. Using this anti-KLP antibody preparation it was possible to show that at least one kind of keratin-like protein characteristic of the adult epidermis first appears within the larval epidermis during metamorphosis. This is the first reported biochemical characterization of a tissue-specific protein from adult amphibian skin.
In vitro differentiation of a homogeneous cell population—the epidermis of Xenopus laevis
Authors: Reeves O. R. , Laskey R. A. 
Published: April 2021

ABSTRACT
A simple culture technique is described for obtaining homogeneous populations of differentiating epidermal cells from adult amphibian skin. This population of cells continues its normal differentiation, namely keratinization, in vitro. By the third day of culture more than 99·9 % of the cells in the population contain immunoreactive keratin. During the next 5 –7 days of culture these cells synthesize increasing amounts of a tissue-specific keratin-like protein until this protein constitutes more than 25 % of the total extractable carboxymethylated proteins of these cells. Under the conditions described cell division does not occur during the course of differentiation. When vitamin A is added to the culture medium the rate of keratinization is decreased; when its antagonist citral is added, keratinization is accelerated. These factors influence only the rate but not the direction of differentiation.
Diploid parthenogenetic mouse embryos produced by heat-shock and Cytochalasin B
Authors: Bałakier Hanna , Tarkowski Andrzej K. 
Published: April 2021

ABSTRACTSwiss albino and C57BL/10 eggs from induced ovulations, and spontaneously ovulated A eggs, were activated in vitro by a heat shock of 44 °C for 5 or 7·5 min and cultured in the presence of 10 μg/ml of Cytochalasin B (CB) for 5-8 h. The activation rate was about 70% in Swiss albino, 40% in C57BL and 90% in A eggs. CB suppressed second polar body (2P.B.) formation in over 90% of activated eggs, with the majority containing two pronuclei. When eggs were placed in CB-free medium their surface became wrinkled and they formed protrusions of various sizes, which in some eggs detached to form enucleate or pronucleate cytoplasmic fragments; some eggs broke down completely into fragments. In most eggs, however, the surface smoothed out in a few hours and suppression of 2P.B. appeared to be permanent. The rate of development of these eggs after transplantation to the oviduct was delayed in terms both of cell divisions and of the time of blastocyst formation. Out of 41 implants collected on the 8th–10th day of pregnancy only two healthy looking egg-cylinders were found on the 8th and 9th day; both were retarded, at the stage characteristic for the 7th day of normal development. The reasons for delayed preimplantation development and low implantation rate are discussed. The present experiments corroborate earlier observations that parthenogenetic mouse embryos, even if diploid, rarely survive in the uterus beyond the egg-cylinder stage.
Ultrastructural observations of lethal yellow (A
y
/A
y
) mouse embryos
Authors: Calarco Patricia G. , Pedersen Roger A. 
Published: April 2021

ABSTRACT
A V /A V embryos were identified by the presence of large excluded blastomeres (Pedersen, 1974) and examined cytologically and ultrastructurally. Cell organelles, inclusions and junctions in the excluded blastomeres were compared with those of non-excluded cells of Av/Av embryos and control embryos. Excluded blastomeres always had the fine structural characteristics of earlier developmental stages and may have arrested at the 4-to 8-cell stage or slightly later. Interior cells (inner cell mass) were observed in all mutant blastocysts. Non-excluded cells of Av/Av embryos were normal until degenerative changes appear in the late blastocyst stage. The mode of action of the + Av gene was not determined, but evidence from this study and others indicates that the effects of + Av gene action occur over a wide range of time in early cleavage and implantation.
Réversibilité de la dédifférenciation observée dans les cultures cellulaires de foie embryonnaire d’oiseau
Authors: Houssaint E. 
Published: April 2021

ABSTRACTReversibility of the morphological and functional dedifferentiation occurring in cultures of avian embryonic liver cellsPrimary cell cultures are established from 8-day quail embryo livers. During the first three days the culture is made up of areas of epithelial-like cells and scattered fibroblasts. The cytoplasm of the epithelial cells shows a high glycogen content as detected by the PAS reaction controlled with salivary amylase digestion. During the following days an important increase in the number of fibroblastic cells is observed. After 6–7 days of cultivation, the epithelial cells have disappeared and the culture is entirely fibroblastic. PAS technique does not show any trace of glycogen in these cultures which have been prolonged up to 45 days.Six-to 45-day primary cultures entirely made up of fibroblasts were associated with hepatic or pulmonary mesenchyme in organotypic culture for 3–4 days. In some cases the explant was first cultivated in vitro for 2 days and then grafted into a 5-day-old chick embryo on the chorioallantoic membrane for 6 days. In the secondary cultures hepatocytes showing an epithelial arrangement and a high glycogen content were observed.It appears from this observation that some of the primary culture fibroblasts are in fact dedifferentiated parenchymal cells. Such a dedifferentiation is a reversible phenomenon since the cells retain the ability to express their initial determination if they are placed in convenient environmental conditions. The role of the specific tissular arrangement in the stability of the differentiated state is discussed.
Implantation and early postimplantation development of the bank vole Clethrionomys glareolus, Schreber
Authors: Ławożdżeński Wac , Mystkowska Ewa T. 
Published: April 2021

ABSTRACT
The development of the bank vole Clethrionomys glareolus is described from implantation to the formation of the foetal membranes. The embryonic development of this species combines features of primitive rodent species, for example Geomys bursarius and highly specialized ones, for example Mus musculus. The egg-cylinder is formed by invagination into the blastocoelic cavity of the inner cell mass and polar trophoblast overlying it; this resembles in many respects the early stages of development of primitive species. The fully formed egg-cylinder, however, resembles that of the mouse and the formation of foetal membranes is also similar to that in Muridae. It is concluded that in the bank vole and also in other rodents, the extra-embryonic ectoderm of the egg-cylinder is derived from the polar trophoblast rather than from the inner cell mass.
Increased production of genetic mosaics inHabrobracon juglandisby cold shock of newly oviposited eggs
Authors: Petters R. M. , Grosch D. S. 
Published: April 2021

ABSTRACTEggs from an ebony stock exposed to 5·5 °C prior to syngamy exhibited increased production of genetic mosaics in comparison with untreated eggs from the same females. No increase in mosaic production occurred for cold-shocked cleavage-stage embryos from the ebony stock or from pre-cleavage cold-shocked eggs from a wild-type stock. Heat shock of pre-syngamy eggs also failed to increase the production of genetic mosaics. These findings are consistent with predictions based on the post-cleavage fertilization theory of mosaic origin in Habrobracon or with a hypothesis of differential mortality.
Patches in the livers of chimaeric mice
Authors: West J. D. 
Published: April 2021

ABSTRACTSections of adult chimaeric livers have been histochemically stained for β-glucuronidase activity and patches of two cell populations visualized. A one-dimensional clonal analysis has been used to estimate the number of coherent clones in the adult liver. The data are consistent with a total of 9–22 million regular, coherent clones, comprising 10–34 nuclei, or a smaller number of irregular, branched coherent clones. Both of these alternatives suggest considerable cell mixing during liver morphogenesis.
A simplified procedure for preparing myogenic cells for culture
Authors: Caplan Arnold I. 
Published: April 2021

ABSTRACTA procedure involving mechanical agitation referred to as vortexing is compared to a trypsin procedure for obtaining myogenic cells for culture. The vortex procedure appears to be at least as useful as the trypsin procedure and has several advantages including speed, the elimination of chemical disruptive agent, elimination of collagen coating of culture dishes and earlier onset of fusion.
Fish swimbladder: an excellent mesodermal inductor in primary embryonic induction
Authors: Kawakami Izumi 
Published: April 2021

ABSTRACTSwimbladder of the crucian carp, Carassius auratus, was found to be better as a vegetali-zing tissue than other tissues, such as guinea-pig bone marrow, when presumptive ectoderm of Trituras gastrulae was used as reacting tissue.Swimbladder usually induced assemblies of highly organized mesodermal tissues, such as notochord, somites and pronephric tubules, some of which were covered by mesodermal epithelium without an epidermal covering.A special character of the effect of swimbladder was the rather frequent induction of solid balls of undifferentiated cells, which were identified as mesodermal or mesodermal and probably endodermal. These findings show that swimbladder has a strong and fast spreading vegetalizing effect on the responding presumptive ectoderm.
Direct exposure of mouse embryonic limb-buds to 5-bromodeoxyuridinein vitroand its effect on chondrogenesis: increasing resistance to the analog at successive stages of development
Authors: Agnish Narsingh D. , Kochhar Devendra M. 
Published: April 2021

ABSTRACTThe inhibitory effect of 5-bromodeoxyuridine (BudR)-an analog of thymidine-on embryonic mouse limb-buds was studied in vitro employing an organ-culture system. The effect was found to be dose-related and also depended on the developmental stage of the donor embryos. Limbs at an early stage of development (early 11th-day embryos, somite stage 26 –29) were extremely sensitive to the analog. Treatment with low levels (2 –4 μg ml) and for a relatively short period of time in culture (2-3 days) completely and irreversibly suppressed chondrogenesis in these explants. Limbs from older embryos (somite stage 40 and up) were found to be much less sensitive to the inhibitory effect of the drug; a prolonged exposure to a much higher dose (100 –150 μg ml) resulted in an incomplete suppression of chondrogencsis. Only a 20% inhibition was observed in the cultures of limbs from mid-13th-day mouse embryos. After continuous growth in vitro, the limbs became progressively resistant to the analog and towards the end of the culture period had become refractory to the drug. The time of complete insensitivity appeared earlier in the cultures of the limbs taken from older embryos than in the explants of younger limbs. These studies show that as limbs continue to differentiate in vivo or in vitro, they become increasingly resistant to the inhibitory effect of BudR. in at least as far as the effect on the process of chondrogenesis is concerned. It is suggested that the relative sensitivity or insensitivity to the inhibitory effect of BudR may prove to be a useful parameter in evaluating the developmental stage of an organ.
Evidence that blood pressure controls heart rate in the chick embryo prior to neural control
Authors: Rajala G. M. , Kalbfleisch J. H. , Kaplan S. 
Published: April 2021

ABSTRACT
Blood, pressure increases will increase heart rate in intact chick embryos, prior to the development of neural control. Similarly, in surgically isolated hearts, increases in intraventricular fluid pressure will increase the rate of beat. However, fluid pressure applied equally to both interior and exterior surfaces of the isolated heart does not result in increased heart rate. Therefore, we conclude that the increased pressure stretches the heart muscle and that this stretch stimulates the increased heart rate.
While heart rate is clearly influenced by blood pressure, the reverse is not true. Propranolol reduces the heart rate to about half normal in intact embryos but does not significantly alter the blood pressure.
A method for enucleating oocytes ofXenopus laevis
Authors: Ford C. C. , Gurdon J. B. 
Published: April 2021

ABSTRACTA method is described for the enucleation and complete healing of Xenopus oocytes so that the enucleated oocytes withstand multiple injections and culture for several days. The oocytes are defolliculated and enucleated manually and allowed to heal in a potassium phosphate buffer. Oocytes enucleated in this way support RNA synthesis by injected HeLa-cell nuclei 3 days later. This method is valuable in providing a low-background system in which transcription of injected nuclei can be studied.
Evaluation of the technique of immunosurgery for the isolation of inner cell masses from mouse blastocysts
Authors: Handyside A. H. , Barton S. C. 
Published: April 2021

ABSTRACTInner cell masses (ICMs) immunosurgically-isolated from -day mouse blastocysts were examined for trophoblast cell contamination and developmental capacity. Blastocysts were preincubated in rabbit anti-mouse antiserum, washed thoroughly and then incubated in complement. The ICMs were then easily dissected by drawing through a fine pipette.Various experiments confirmed that the trophectoderm had been completely removed by this treatment. Firstly, the ICMs did not bind a fluorescein-conjugated antibody directed against rabbit IgG, indicating the absence of cells exposed to the rabbit antiserum during the immunosurgical procedure. Secondly, ICMs dissected from blastocysts preincubated in a suspension of melanin granules did not include any of the trophoblast cells that had phagocytosed the granules. And, thirdly, the protein synthetic profile of these ICMs was similar to microsurgically dissected ICMs, and in particular, trophoblast specific spots were absent.The developmental capacity of immunosurgically-isolated ICMs was tested by injecting them into blastocysts and transferring to the uterus of -day pseudopregnant recipients. Extensive chimaerism was detected in the majority of implants, 5-6 days after transfer, but only in ICM-derived tissues. This demonstrates both the lack of trophoblast cell contamination and functional viability of these ICMs.
The Time and Place of Fertilization of the Golden Hamster Egg
Authors: Strauss Fritz 
Published: April 2021

ABSTRACT
The middle and caudal third of the ampulla tubae are the regions where most of the eggs of Mesocricetus auratus Waterhouse are fertilized. The earliest fertilization resulting from evening matings prior to ovulation (assuming the ovulation peak to be at 3 a.m.) were obtained at 2 hours after ovulation. When copulation occurred the morning after ovulation, fertilized ova were not obtained at 2 hours after mating, but they were at 4 hours. The time of fertilization is most frequently between the 2nd and 10th hour after ovulation. About 91 per cent, of the eggs are fertilized during this period. On the basis of existing data it is not possible to speak of a family-specific or even an order-specific fertilization site for the mammalian egg.
The Initial Formation and Subsequent Development of the Double Visual Cells in Amphibia
Authors: Saxén Lauri 
Published: April 2021

ABSTRACT
The investigation deals with the development and structure of the double visual cells of two amphibians, Rana temporaria and Trituras vulgaris. The double cells of these species, which belong to the ‘double cone’ type described by previous investigators, are encountered later in development than the single visual cells. They are formed through the fusion of two visual cell progenitors. The results support the theory previously advanced by the present author that the accessory component is a rod-like receptor. Thus the name ‘double cone’ gives an erroneous impression both with regard to the origin of this cell, and probably also with regard to its function. The glycogen droplet in the accessory component, the paraboloid, is apparently a lens-like organ. The function of the double cell is still, however, open to speculation.