bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production élective de la phocomélie sous Finfluence d’ypérite azotée, chez l’embryon de Poulet: IL—Etude histologique des bourgeons de membres au cours du développement
Authors: Salzgeber par Berthe 
Published: April 2021

ABSTRACT
The production of phocomelia in the chick embryo by the action of nitrogen mustard. IL Histological study of developing limb buds Nitrogen mustard at a concentration of 3x 10−4M was administered to chick embryos of days incubation (stages 18-20 of Hamburger & Hamilton). The solution was deposited either over the whole embryo or locally on the limb rudiments. Some limb buds were examined in situ during the period 24-48 h after the administration and were subject to examination at autopsy at the 11th day of incubation. Others, both wing and leg-buds, were taken for histological examination at times between 1 h and 120 h of the beginning of treatment. The first detectable morphological lesions appear between 24 and 30 h of the administration of the nitrogen mustard. The growth of the bud is inhibited and haematomata of varying sizes are seen at the centre of the bud or near its base. Histological study of limb rudiments fixed within the first hours or days of treatment gives a more detailed picture of the changes suffered by them. The dense central mesenchyme with small cell nuclei is replaced by a vacuolated tissue with large cell nuclei. Forty hours after treatment the disorganization of the limb bud is characterized by the absence of the central mesenchymal condensation and the presence of lacunae, of vacuoles and pyknotic nuclei. Chondrogenesis is inhibited or delayed. Four or five days after treatment there is a reorganization of the limb rudiment. The distal structures appear, as do nodules of precartilaginous cells and muscle rudiments. Nerves and blood vessels enter the limb which is of reduced size. In those cases where the mesoderm is greatly reduced the buds degenerate. This gives rise to ectromelia, the complete absence of limbs. The ectoderm, including the apical cap, develops normally in most cases. In cases of extreme mesodermal atrophy the ectodermal covering shows signs of degeneration. These results suggest a specific action of nitrogen mustard on mesodermal structures. They are compared with the results of other authors and their relevance to problems of mesodermal-ectodermal interactions is discussed.
The effect of mitomycin C on developing chicken embryos
Authors: Kury George , Craig John M. 
Published: April 2021

ABSTRACT
The effect of mitomycin C before completion of organogenesis was studied in chicken embryos. The injection of mitomycin C into the yolk sac produced developmental anomalies which varied with the time of injection. Embryos treated on the 3rd day of development (2–16 μg/egg) had retardation of growth, bilateral microphthalmia, cerebral hemorrhage, malformations of lower extremities, lower beak and defect of calvarium. Specimens treated on the 4th day of development (2–28 μg/egg) had retardation of growth, abnormalities of beak, lower extremities and calvarium. Histological examination of viable embryos sacrificed 2–6 days after injection revealed necrotic changes involving the developing retina, lens, cerebral vesicles, mesenchyme and heart. Histological examination of 19-to 20-day-old treated embryos showed depression of hematopoietic and osteoblastic tissues. The skeletal abnormalities produced included shortening and curvature, deformity of the bones of lower extremities, especially the tibia. Absence of other bones of the lower extremities was also encountered.
Ectopic regeneration of whiskers in the hooded rat from implanted lengths of vibrissa follicle wall
Authors: Oliver R. F. 
Published: April 2021

ABSTRACT
A method is described for isolating and removing lengths of follicle wall, composed of the inner root sheath, outer root sheath and mesenchymal layer, from vibrissa follicles. These segments of follicle wall were transplanted into ear skin and, in one case, into an ovarian capsule. Seven of the thirteen implants originally dissected from the lower third of the follicle produced short whiskers up to 6 mm in length. Two further implants had also regenerated dermal papillae but not whiskers. The dermal papillae regenerated at the proximal end of the implants and appeared to derive from cells from the mesenchymal layer. None of the four implants obtained from above the lower third of the follicle regenerated dermal papillae or produced whiskers. The outer root sheaths of all of the implants which did not regenerate papillae or whiskers did, however, maintain their typical histological character. The possibility that maintenance of the implants was dependent on the presence of the mesenchymal layer is discussed. Whisker growth from transplanted lengths of follicle wall logically isolates the outer root sheath and/or the mesenchymal layer as the essential prerequisites for papilla regeneration.
The differentiation of epidermis:I. The interrelationship of epidermis and dermis in embryonic chicken skin
Authors: Dodson J. W. 
Published: April 2021

ABSTRACT
Experiments were made on the tarso-metatarsal skin of 12-day chicken embryos to determine the relative importance of different dermal constituents for the continued growth and differentiation of the epidermis. The two tissues were separated after exposure to Versene and the isolated epidermis was either recombined with the dermis which had previously been subjected to various treatments, or explanted on different gels, including acetic acid-extracted collagen. After growth in organ culture on natural medium, the explants were examined histologically. The isolated epidermis did not survive in culture when laid directly on a plasma-embryo extract clot, but it grew and keratinized when placed with the basal surface downwards on dermis killed by freezing and thawing or on a gel of collagen; when frozen-killed dermis was trypsinized, the epidermis differentiated at first, but then degenerated. The epidermis did not survive on heat-killed dermis, on agar, alginate, or fibrin gels, nor on Gelfilm. The epidermis survived on Millipore filter only in the presence of an increased concentration of embryo extract, when it differentiated to form a s. corneum. A periodic acid-Schiff-reactive basement membrane was formed in the absence of living dermal cells. It is concluded that, under the conditions of the experiments, the survival of embryonic chicken epidermis as an organized, keratinizing tissue depends on the contact of the basal surface with a suitable substratum, but not on the presence of living dermal cells. In the normal substratum provided by the dermis, both collagen and trypsin-labile ground substance are required by the epidermis, yet a gel of collagen can provide a suitable surface on which the epidermis is capable of normal differentiation in vitro. It has been suggested therefore that the epidermis reacts to the flat surface of collagen gels in the same way as to the extracellular moiety of the dermis.
Aspects of the development of yolk spheres in the hen’s oöcyte, studied by electron microscopy
Authors: Bellairs Ruth 
Published: April 2021

ABSTRACT
Yolk-sphere formation in the hen’s oöcyte has been studied by electron microscopy using the following stages: Balbiani body present, Balbiani body dispersed, large vesicles visible, well-defined yolk present. A detailed description is given of each stage. Raw materials from which the yolk is formed appear to enter the oöcyte in two ways. The first is probably by pinocytosis, the second by specialized pieces of follicle cell apparently becoming engulfed by the oöcyte. These pieces of follicle cell have been described in detail elsewhere under the name of ‘lining bodies’. Prior to yolk formation the mitochondria and Golgi bodies migrate to the periphery of the oöcyte, the numbers of free lipid drops in the cytoplasm become reduced and two new structures appear in the oöcyte. These are respectively electron-dense particles measuring 300 Å in diameter and specialized structures that may be termed ‘yolk spindles ‘. The latter are about 700 Å in T.S. and contain within them a rod that is about 50 Å in diameter. The yolk spheres develop from large, membrane-bounded vesicles that appear in the ooplasm. There is no direct evidence as to the origin of these vesicles though several alternative suggestions are made. Yolk spindles cluster around some of the large vesicles and appear to become incorporated into them. It is suggested that the yolk spindles influence the large vesicles to transform into primary yolk spheres, though the mechanism is not understood. As the large vesicles become recognizable as primordial yolk spheres, they acquire osmiophilic subdroplets as well as more granular material. Frequently they also contain many 300 Å dense particles, as well as degenerating lining bodies. The mechanism by which these materials enter the primordial yolk spheres is unknown. Each yolk sphere within the oöcyte is surrounded by a well-defined unit membrane. By the time the egg is laid, however, it has become difficult to demonstrate this membrane. It is suggested in this paper that the unit membrane of the yolk sphere retains its normal appearance so long as it remains in contact with living cytoplasmic structures. This contact is retained only until the oöcyte is about 2·5 mm in diameter, for at about that time the nucleus and cytoplasmic components stream up to the animal pole where they remain.
Studies on growth of the mink blastocyst
Authors: Daniel Joseph C. 
Published: April 2021

ABSTRACT
Mink blastocysts grew in vitro when the culture medium contained estrone or ergosterol, but the growth was slow and of short duration, and believed to be the product of fluid uptake rather than cell proliferation.
Ergosterol failed to shorten the gestation period when administered to mink during the delay phase of pregnancy, the same failure having been reported earlier with estrogen.
Mink blastocysts did not grow in vitro in medium containing other vitamins, enzymes known or suspected to be present in uterine fluids, a variety of energy sources, rabbit uterine or blastocyst fluids or when transplanted to the uterus of 3-to 4-day pregnant rabbits.
A factor inhibiting blastocyst growth is believed to exist in the mink because rabbit blastocysts cease growing and collapse when retained in culture medium whose mink serum component is 5% or higher. Dialysis does not remove the factor.
Collapsed mink blastocysts can reconstitute to their original fluid-filled state in vitro.
Studies on the haemopoietic stem cells of mouse foetal liver
Authors: Silini G. , Pozzi L. V. , Pons S. 
Published: April 2021

ABSTRACT
Cells obtained from the blood-forming organs of donor animals and injected, under appropriate conditions, into heavily irradiated mice, can colonize, among other organs, the spleen of the hosts, giving rise to discrete and differentiated nodules of haemopoietic tissue (Till & McCulloch, 1961). It has been demonstrated that the number of nodules is directly proportional to the number of injected cells and that such nodules may be regarded as clones arising from single cells (Till & McCulloch, 1961; Becker, McCulloch & Till, 1963). The postulate of classical haematological theories (Maximov & Bloom, 1934; Ferrata, 1935) that a proportion of the cells in blood-forming organs is capable of indefinite division with renewal of the stem line and of differentiation into mature blood cells has thus been experimentally demonstrated.
Temperature and other environmental effects on ammocoete organs in culture
Authors: Stephenson E. M. , Potter I. C. 
Published: April 2021

ABSTRACTWhole hearts of ammocoete larvae of Mor dada mordax were cultured at temperatures ranging from 37 to 5 °C. Rapid death of cultures occurred at 37 °C. A temperature of 30 °C was ultimately lethal but viability as indicated by heart beat could be maintained for up to 6 days. Total viability was usually maintained in temperatures from 25 to 5 °C. Rate of heart beat varied in absolute values but the relative pattern in relationship to incubation temperatures was more or less constant. The optimal temperature was 25 °C. Cell outgrowth occurred at 25, 20 and 15 °C. The optimal temperature for rate of outgrowth appeared to be 25 °C, but cultures at 20 °C were also satisfactory. Chopped kidney and liver explants were also cultured. Successful outgrowth was obtained from almost all kidney cultures at 25 and 20 °C. Outgrowth from liver was extremely rare and occurred only at 25 and 20 °C. Successful outgrowth was obtained in media lacking any homologous component. Dilution of standard media by approximately 10 % appeared to be necessary for outgrowth but viability could be maintained in undiluted media. A correlation appears to exist between the upper limit of temperature suitable for maintenance of ammocoete tissues in vitro and the highest temperatures encountered by the whole animals in their natural environment.
Promoting activity of extracellular materials on sponge cell reaggregation
Authors: Maclennan A. P. , Dodd R. Y. 
Published: April 2021

ABSTRACTA number of species of sponge showed enhanced aggregation behaviour in the presence of cell extracts prepared under defined conditions previously found suitable for other sponges. The promoting activity of one such preparation appeared to be based on a minor component of the total extract. The specificity of promotion was of a low order and led to mixed aggregate formation from species that segregated specifically in unpromoted mixtures. The observations are discussed in relation to the known antigenic relationships of the cell surfaces of the species examined.
Morphology and development of theDrosophilaeye
Authors: Hanly E. W. , Hemmert Wynn H. 
Published: April 2021

ABSTRACTThe morphological changes which take place in the differentiation of the adult Drosophila eye from the larval imaginal disc have been described from a histological and cytological standpoint by Shatoury (1956, 1963) and Shatoury & Waddington (1957). In addition, Gottschewski (1960), Gottschewski & Querner (1961), and Schneider (1964) have studied these processes in eyes and brains in vitro. These latter workers removed eye-antennal anlage with associated structures, and placed them in culture media. Under these conditions, the imaginal discs can apparently undergo most of the normal differentiation processes, finally attaining nearly all of the adult morphology.
Development of explanted rat embryos in circulating medium
Authors: New D. A. T. 
Published: April 2021

ABSTRACTA method is described for growing post-implantation rat embryos, explanted with their embryonic membranes, in circulating medium. Embryos cultured by this method grow to about five times the maximum weight attainable in static medium in watch-glasses. Homologous serum, equilibrated with 95 % O2/5 % CO2, has proved to be a satisfactory culture medium, and it makes no difference whether the serum is from pregnant or non-pregnant animals. Good development is obtained in 2–3 ml serum per embryo, and little or no improvement is gained by using more than this. About 50 % of embryos explanted at 7–15 somites develop to 30-to 35-somite stages and synthesize O·3–O·5mg protein during the period in culture. Further development of these embryos appears to be prevented by the abnormal formation of a large blood vessel bypassing the allantoic placenta. About 50 % of embryos explanted at 22–28 somites develop to 40–46 somite stages and synthesize about 1–1·5 mg protein. Embryos explanted at more than 45 somites do not develop. The rate of flow of the circulating medium is critical. Embryos explanted at 7–15 somites develop much better in serum flowing at 1 ml/min (= 2 cm/min through the embryo chamber) than at 10 ml/min. Embryos explanted at 22–28 somites develop much better in serum flowing at &gt; 10 ml/min than at 1 ml/min.
On the orientation of the implanting blastocyst
Authors: Kirby D. R. S. , Potts D. M. , Wilson I. B. 
Published: April 2021

ABSTRACTThe sequence of events in the orientation of the blastocyst is described. Six a priori mechanisms for orientating the blastocyst are presented. It is concluded that the only mechanism fulfilling the available morphological and experimental observations is one in which the inner cell mass is free to travel round the inside of the trophoblast shell once the latter has become fixed to the uterine epithelium.
Effects of histones on morphogenesis and differentiation in chick embryos
Authors: Malpoix P. , Emelinckx A. 
Published: April 2021

ABSTRACTThe transcription of DNA is known to be inhibited in vitro by the presence of histones. This has been shown to be true for isolated nuclei, isolated chromatin, or for DNA alone (Bonner & Huang, 1962; Bonner, Huang & Gilden, 1963; Allfrey & Mirsky, 1963 ; Allfrey, Faulkner & Mirsky, 1964; Sonnenberg & Zubay, 1965). The masking of genomic sites in adult differentiated tissues seems the most probable explanation of the expression of only a fraction of the adult genome (Paul & Gilmour, 1966). Affinities have been observed between certain base sequences in DNA and certain fractions of histones (Liau, Hnilica & Hurlbert, 1965; Skalka, Fowler, Andre & Hurwitz, 1966; Tan, 1966), yet the remarkable similarity in composition between the histones of different species and organs of the same species does not encourage the idea that histones are specific repressors of genomic function. Many authors (Zalokar, 1964; Goldberg & Atchley, 1966; Frenster 1967) have proposed hypotheses tending to reconcile the apparent non-specificity of the relation between DNA and histones and their intervention in gene function : it is thought that polyanions (RNAs, phosphoproteins, phospholipids, non-histone proteins or hormones) may remove histones from binding sites and release specific single-stranded sequences of DNA for transcription.
The developmental potentialities of regeneration blastema cell nuclei as determined by nuclear transplantation
Authors: Burgess Ann M. C. 
Published: April 2021

ABSTRACTFormerly, many embryologists believed that the blastema cells in regenerating amphibian tails and limbs arose from a reserve of undifferentiated cells, but since the work of Hertwig (1927) and Butler (1935) few modern investigators would support this view. Others have suggested that blastema cells are of epidermal origin (Godlewski, 1928; Rose, 1948). However, this idea has largely fallen into disrepute following the investigations of Karczmar & Berg (1951), Chalkley (1954) and Hay & Fischman (1961). There is now abundant evidence that blastema cells arise by the dedifferentiation of some of the stump tissues, in particular the stump muscle and cartilage (Thornton, 1938 a, b;, Hay, 1958,1959, 1962; Hay & Fischman, 1961), and that contributions may also arise from fibroblasts when they are present.
The experimental induction of whisker growth in the hooded rat by implantation of dermal papillae
Authors: Oliver R. F. 
Published: April 2021

ABSTRACTDermal papillae are regenerated and whiskers are produced after the experimental removal of up to the lower third of the vibrissa follicle, but if more of the follicle is removed neither event occurs (Oliver, 1966 a, b). Similarly, when lengths of the lower third of the vibrissa follicle wall are transplanted into ear skin, whiskers are again produced, but not if lengths of wall are taken from within the upper two-thirds of the follicle (Oliver, 1967). From these experiments it was clear that the outer root sheath and the adherent mesenchymal layer, from which the new papillae are apparently derived, are the essential tissues in the regeneration process.
Analysis of the development of the nervous system of the zebrafish, Brachydanio rerio: II. The effect of nerve growth factor and its antiserum on the nervous system of the zebrafish
Authors: Weis Judith Shulman 
Published: April 2021

ABSTRACT
When a nerve growth factor isolated from mouse submaxillary salivary glands is injected into young zebrafish, Brachydanio rerio, it causes enlargement of spinal ganglia due to hypertrophy and hyperplasia. A large part of the response is due to hyperplasia, as compared with that of chicks and mammals, in which the response is primarily hypertrophy of cells. The nature of the response to NGF corresponds to the chief method of normal growth of ganglia in this species. Sympathetic ganglia of B. rerio are also markedly enlarged by treatment with the nerve growth factor. Injections of a specific antiserum to the nerve growth factor cause a reduction in size of the spinal ganglia of the zebrafish. This decrease in size is due to a reduction in the cell population of the ganglia, while the cells in the reduced ganglion appear normal. An effect of antiserum has previously been noted in other animals, but only on sympathetic ganglia.
Glandular metaplasia of hair follicles and other responses to vitamin A excess in cultures of rodent skin
Authors: Hardy Margaret H. 
Published: April 2021

ABSTRACT
This paper reports the effects of excess vitamin A on the development of hair follicles in organotypic cultures of embryonic mouse skin. Pieces of trunk skin, upper lip and lower jaw were cultivated on the surface of a clot of adult cock plasma and chicken embryo extract in slide preparations for 11 – 14 days. Changes in individual living follicles were observed daily and the findings confirmed from complete serial sections. In skin from the trunk of -day embryos the pelage follicles were initiated and underwent some normal differentiation, both in the presence and absence of added vitamin A (6·2 – 37·5 i.u./ml.). In skin from the trunk of 15-day embryos the pelage follicles differentiated normally for 4 days in both treated and untreated groups but then regressed in the vitamin-treated groups (12·5, 25·0 i.u./ml.), while normal differentiation continued and some keratinized hairs were formed in the control groups. Vibrissal follicles in the upper lip from a -day embryo differentiated normally for 4 days in excess vitamin A (12·5 i.u./ml.), and then some follicles became misshapen and developed gland-like lateral buds, while follicles in the control explant continued normal development and produced many keratinized hairs. All the vibrissal follicles originally present in four explants of upper Up from 14-day embryos differentiated normally for about 3 days in excess vitamin A (12·5 i.u./ml.) and then showed metaplastic changes. Many of them underwent a complete glandular metaplasia, being transformed into compound tubular glands with branching duct systems, terminal ‘alveolar’ swellings and occasional signs of mucous secretion. Some follicles retained traces of the original structure, and in a few the follicle eventually recovered its capacity for normal differentiation, producing simultaneously a small keratinized hair and a vigorously growing gland. The metaplastic glands were unlike any normal mammalian skin glands but resembled immature salivary glands. At the time of initiation of the metaplasia there was also an increase in the secretion of sebum or sebum-like material in the same hair follicles. In the control group without excess vitamin A the follicles continued normal differentiation and hair production until the experiment was terminated, and there was no metaplasia. Most of the vibrissal follicles in the explants of upper lip from 15-day embryos continued normal differentiation in the presence of excess vitamin A (12·5 i.u./ml.), although a higher proportion of the hairs were abnormal in structure than in the control group. In excess vitamin A a few of the initially least advanced follicles underwent glandular metaplasia, but no metaplasia was observed in the control group. Some of the differences between the behaviour of explants from embryos of different ages could be explained by the hypothesis that there is only a relatively short critical stage in follicle development during which vitamin A is capable of inducing metaplasia.