bluuebunny/crossref_metadata_2025_split huggingface dataset:
Déterminations régionales dans l’aire cardiaque présomptive mises en évidence chez l’embryon de poulet par la méthode microélectrophysiologique
Authors: Douarin Georges Le , Obrecht Geneviève , Corabœuf Edouard 
Published: April 2021

ABSTRACT
La répartition des potentialités cardiogénétiques dans le blastoderme d’oiseau aux stades précoces du développement a été étudiée par de nombreux auteurs. Au stade du blastoderme non incubé les parties périphériques, mais non les parties centrales, peuvent fournir en culture in vitro du tissu cardiaque spontanément pulsatile (Olivo, 1928). Les cellules cardiaques présomptives sont plus abondantes dans la région postérieure que dans les régions latérales et antérieure du blastoderme (Butler, 1935). Pendant les premières heures de l’incubation l’aptitude à former du cœur est encore très largement répandue dans le blastoderme mais tend à se concentrer dans la région postérieure (Spratt, 1942). Les potentialités cardiogénétiques se localisent ensuite de part et d’autre de la ligne primitive définitive (Rudnick, 1938; Hunt, 1932). Au stade du prolongement céphalique, les limites du territoire cardiaque présomptif ont été précisées par Rawles (1936, 1943). Les deux aires cardiaques occupent alors une situation bilatérale de part et d’autre du prolongement céphalique et du tiers antérieur de la ligne primitive.
Becs-de-lièvre provoqués chez le rat par un dérivé de la pénicilline, l’hadacidine
Authors: Lejour-Jeanty Madeleine 
Published: April 2021

ABSTRACT
Il est aisé de provoquer des fentes palatines chez les Mammifères de laboratoire. L’action de la cortisone (Walker & Fraser, 1957), l’hypervitaminose A (Giroud & Martinet, 1955), la carence en niacine (Chamberlain & Nelson, 1963), par exemple, ont permis une étude détaillée de ces malformations.
Regeneration from mesenteric arteries in short-term culture
Authors: Feldman J. D. , Gardner D. L. 
Published: April 2021

ABSTRACTThe investigations which are described here were originally undertaken in order to investigate the pathogenesis of early hypertension at a time when no morphological changes were evident in adrenergic arteries on light microscopy. Evidence of functional change was therefore sought by comparing the growth patterns of cells from hypertensive and normal mesenteric arteries in culture. The study of the cells which migrated from the explants form the basis for this paper.
Modification of embryonic development of reproductive and lymphoid organs in the chick
Authors: Erickson Alan E. , Pincus Gregory 
Published: April 2021

ABSTRACT
Following the publication of Lillie’s (1917) observations and theories on the endocrine basis of the development of the bovine freemartin, experiments were initiated to determine if heterosexual gonad grafts to the chorio-alantoic membrane of chicks could stimulate formation of intersexes (Willier, 1927). Hormone extracts of testes and urine were used by Dantchakoff (1935) and Kozelka & Gallagher (1934), and synthetic hormones were tested in the chick by Wolff & Ginglinger (1935). Estrogens feminized the left gonad of male embryos and resulted in retention of Mullerian ducts in males and occasional cystic develop-ment of Mullerian ducts in females. Less extensive feminization of the left testis, dilation of Wolffian ducts, and partial deletion of Mullerian ducts occurred in androsterone-treated embryos (Wolff, 1935). Sensitivity of the genital papilla to exogenous steroids was described by Reinbold (1951). Riddle & Dunham (1942) demonstrated that a single injection of estradiol benzoate into laying birds resulted in feminization of genetic males which developed from ova released shortly thereafter. Lutz & Lutz-Ostertag (1959) described spontaneous chick freemartins developing in double-yolked eggs. Studies of individual male embryos which had access to the resources of two yolks in double-yolked eggs (Ruch, 1961) revealed the occurrence of gonadal modifications similar to those resulting from administration of estrogens or from implantation of female gonads adjacent to the genital ridge of young male embryos (Wolff, 1946–47). When heterosexual implants of gonads of sufficient size were placed on the chorioallantoic membrane, male left testes developed into ovotestes and Mullerian ducts were reduced in the female (Groenedijk-Huijbers, 1960). The immunological consequences of vascular anastomoses between bovine twins discussed by Owen (1945), and more recently by Fecheimer, Herschler & Gilmore (1963) and Goodfellow, Strong & Stewart (1965) afford an additional point of departure in studying the freemartin.
Ontogenesis of serum esterases in Mus musculus
Authors: Pantelouris E. M. , Arnason A. 
Published: April 2021

ABSTRACT
The ‘typical’ serum esterase zymogram, obtained by starch-gel electrophoresis, of adult mouse serum comprises 19 fractions, but undergoes changes related to developmental stage. The main adult fractions are already present in the 18-day foetus. Whilst most are weaker than in the adult, the reverse is true for fractions 16–19. There are also six ‘foetal esterases’ which gradually decrease and disappear after birth, at different rates. The foetus and the young animal, up to 2 weeks, have also alkaline phosphatase (1 or 2 fractions), whilst no such enzyme was detectable in the adult’s serum. Pregnancy is associated with increases in three and decreases in two adult fractions and, more characteristically, with the appearance of a strong specific pregnancy esterase. An esterase zone (6) which is always stronger in the male could be subdivided into three fractions in males and two in females. The exclusively male fraction coincides with a band of acid phosphatase activity.
The effect of embryonic partial decapitation on the developmental sequence of some proteins in the chicken
Authors: Manwell Clyde , Betz T. W. 
Published: April 2021

ABSTRACT
Partial decapitation of chick embryos at 33–36 h of incubation, ‘embryonic hypophysectomy’, markedly decreases the amount but not the electrophoretic mobility of alkaline phosphatase and a cathodal esterase, although several other esterases, acid phosphatase, lactate dehydrogenase, malate dehydrogenase, a cathepsin, lipase, haemoglobin and the major protein components extractable at low ionic strength are essentially unaffected. Electrophoresis of extracts of pituitaries of chicks just prior to hatching, at 4 days after hatching, and adults, suggests that with regard to the major proteins, which most likely include many of the protein hormones, the pituitary becomes well differentiated by hatching in normal embryos. The absence of pituitary hormones is responsible for the ‘foetal’ syndrome of partial decapitates and the reduction in bone formation may well be the result of inadequate amounts of alkaline phosphatase.
The control of growth in transplanted mammalian cartilage
Authors: Noel Janet F. 
Published: April 2021

ABSTRACT
Seven-to eight-day mouse tail vertebrae were transplanted under the renal capsules of syngeneic adult animals and allowed to grow for up to 6 months. Their curve of growth and histological pattern of ageing were similar to those of control vertebrae which had been left in their normal position on young animals.
Slices of the growth cartilage of seven-to eight-day rat tail vertebrae were similarly transplanted into adult syngeneic rats. Though some grafts failed to grow, a considerable number showed similar growth characteristics to the epiphyseal cartilage in intact control vertebrae.
These results have been used to support the view that in the mouse and rat the epiphyseal growth cartilage has a limited potential for growth. This intrinsic growth-limiting mechanism seems to be of relatively greater importance than age-dependent changes in blood hormone levels in determining the changes in the rate of growth of the vertebrae as the animals approach adulthood.
A stereoscan study of the origin of ciliated cells in the embryonic epidermis ofAmbystoma mexicanum
Authors: Billett F. S. , Courtenay T. H. 
Published: April 2021

ABSTRACTA stereoscan electron microscope has been used to survey the epidermis of axolotl embryos as it becomes ciliated. The observations are consistent with much earlier ones that ciliated cells first occur on the surface of the epidermis at about the time of the closure of the neural folds. The cells are located first in the anterior dorsal region of the embryo at about the one-somite stage. After this they rapidly increase in number and by the three-to six-somite stage ciliated cells, which are isolated from one another, are scattered over the entire surface of the embryo in numbers which approach those of much later stages (18 somites). At the earlier stage, however, most of the ciliated cells lie below the general surface of the epidermis, occupying pit-like depressions. This is in contrast to the later stage when they are raised above the surface. The observations support the view that the precursors of the ciliated cells lie beneath the outer epidermal layer of cells and that the ciliation of the embryonic surface occurs when they move into the outer layer as they complete their differentiation.
Participation of grafted nerves in amphibian limb regeneration
Authors: Wallace B. M. , Wallace H. 
Published: April 2021

ABSTRACT
Irradiated axolotl arms bearing grafts of brachial nerves can regenerate, albeit imperfectly. The origin of the regenerated tissues has been traced by means of the difference between dark and white genotypes. Although the origin of the melanophores cannot be decided in this way, their abundance identifies the genotype of the tissue they occupy. Sections of nine regenerates provide consistent evidence for the following conclusions. (1) The epidermis of the regenerate is probably an extension of the irradiated host epidermis. (2) All other tissues of the regenerate which differentiate from a mesenchymal blastema originate from the non-irradiated graft. Regeneration thus involves a true dedifferentiation and redifferentiation (i.e. a loss of determination and equivalent gain in potency for histological transformation). Irradiated cells apparently also dedifferentiate but cannot undergo the normal sequence of proliferation and redifferentiation, and so are not found in the mesodermal component of the regenerate.
The effect of progesterone and oestradiol on blastocysts cultured within the lumina of immature mouse uteri
Authors: Grant P. S. 
Published: April 2021

ABSTRACTOvariectomy-delayed blastocysts flushed from mice treated with medroxyprogesterone acetate were injected into the lumina of immature mouse uterine horns. The horns were then maintained as organ cultures for 1–3 days in media that contained either (a) ethanol or ethanol plus (6) progesterone, (c) oestradiol or (d) progesterone and oestradiol. Trophoblast invasion of the uterine stroma occurred for 13, 10 and 6 % of the eggs injected, in media that contained progesterone, progesterone plus oestradiol, and oestradiol, respectively. The uterine stromal tissue did not decidualize. Embryonic development in invading eggs usually became abnormal during the migration of the distal endoderm. Further development was impeded by the progressive collapse of the yolk cavity which allowed trophoblastic giant cells to intermingle with proximal endodermal cells. The optimal oxygen concentration for trophoblastic invasion and embryonic development in the presence of progesterone and oestradiol was between 26 and 40 %.
Estrogen-induced surface coat and enzyme changes in the implanting mouse blastocyst
Authors: Holmes P. V. , Dickson A. D. 
Published: April 2021

ABSTRACT
Blastocysts from estrogen-stimulated mice tend to be very sticky, a characteristic which can be correlated with estrogen-induced enzyme activation and changes in the surface coat of the trophoblast cells. The blastocyst surface coat was investigated using colloidal iron-Prussian blue stain. In addition, the activity of tyrosine aminotransferase was assayed histochemically in preimplantation blastocysts. The surface and enzyme changes were correlated with the presence of estrogen by investigations in normal blastocysts from intact mice before and after the endogenous estrogen surge and in delayed-implantation blastocysts from ovariectomized mice preceding and following estrogen treatment. Colloidal iron stains the surface coat of the blastocyst after, but not before, the endogenous estrogen surge and the exogenous estrogen treatment. Tyrosine aminotransferase activity also is increased considerably after estrogen induction.
Cell sorting out during the differentiation of mixtures of metabolically distinct populations ofDictyostelium discoideum
Authors: Leach C. K. , Ashworth J. M. , Garrod D. R. 
Published: April 2021

ABSTRACTThe behaviour, during the multicellular phase of the life-cycle, of amoebae of Dictyostelium discoideum grown indifferent media is described. Amoebal populations were marked by growthtemperature-sensitive genetic lesions which do not interfere with developmental phenomena. The fate of cell populations was determined by measuring the relative number of mutant and wild-type cells at various stages in the life-cycle. Cells sort out during development in such a way that they may be ordered in a sequence in which those given early in the following list preferentially appear in the spore population when mixed with those given later in the list: cells grown in axenic medium + 86 mM glucose and harvested when in the exponential phase of growth ; cells grown in axenic medium and harvested when in the exponential phase of growth ; cells grown on bacteria and harvested when in the exponential phase of growth; cells grown in axenic medium+ 86 mM glucose and harvested when in the stationary phase of growth. Chemotactic aggregation and grex migration are not essential for sorting-out to occur but, in the normal life-cycle, the cells of a grex formed from amoebae grown in different media have sorted out anteroposteriorly. The relationship between this sorting out behaviour and the mechanism of pattern formation in fruiting-body morphogenesis is discussed. Differences in density of the amoebae cannot account for the sorting out predispositions we observe.
Etude morphologique de Faction du bromure d’éthidium sur des cellules embryonnaires dePleurodeles waltliien culturein vitro
Authors: Miquel Marie-Therese , Duprat Anne-Marie 
Published: April 2021

ABSTRACTMorphological studies on the action of ethidium bromide on in vitro cultured Pleurodeles waltlii embryonic cellsEthidium bromide (EB) induces characteristic and constant nuclear changes on Pleurodeles waltlii embryonic cells cultured in vitro:At the cytoplasmic level an important alteration of the chondrioma morphology occurs and an inhibition of the utilization of yolk platelets.On the other hand EB generally inhibits neuroblast and myoblast differentiation. This inhibition appears to be reversible in myoblasts after short treatments.The chromosomal DNA synthesis (incorporation of [3H]thymidine) does not seem to be affected by EB treatments while [3H]uridine incorporation in RNAs is completely inhibited after 24 h and longer treatments.
Influence of retino-tectal innervation on cell proliferation and cell migration in the embryonic teleost tectum
Authors: Schmatolla Ernest , Erdmann Georg 
Published: April 2021

ABSTRACT
The influence of retino-tectal innervation on cell proliferation and cell migration in the optic tectum of the embryonic teleosts, Brachydanio rerio and Astyanax mexicanus, was investigated in a combined autoradiographic and experimental embryological study.
Unilateral eye Anlage removal was the method used to compare development of the affected non-optic-innervated tectum with that of its normal opposite innervated tectum.
The amount of mitosis as estimated by [3H]thymidine incorporation was not stimulated by retino-tectal innervation. Likewise no increase in cell number was found in the innervated tectum.
Cell migration and differentiation in the marginal zone was enhanced by retino-tectal innervation.
Conflicting results concerning proliferation, migration and differentiation in different species are explained by differences in time of ingrowth of the optic nerves and their depth of penetration into the tectum.
Chronological changes in the cell cycle of chick neuroepithelial cells
Authors: Wilson D. B. 
Published: April 2021

ABSTRACT
Radioautographic data obtained from a total of 103 chick embryos injected with [3H]thymidine suggest that the generation time of neuroepithelial cells in dorsolateral regions of the optic tectum increases from approximately 8 h at 3 days of incubation to 15 h at 6 days of incubation. The most marked change occurs between the 4th and 5th day, when the generation time increases from 9 to 13 h, respectively. Between the 3rd and 6th day of incubation the length of the DNA-synthetic (S) period and of the premitotic (G2) period remains fairly constant; however, the duration of mitosis (M) and of the postmitotic (GJ period appears to be prolonged.
Size determination inHydra: The roles of growth and budding
Authors: Bisbee John W. 
Published: April 2021

ABSTRACTHydra pseudoligactis cultured at 9°C for 3 – 4 weeks are one-and-a-half times larger than those cultured at 18°C. The size of Hydra is correlated with the numbers of epithelio-muscular and digestive cells in the distal portion of the animal and with the diameters of the epithelio-muscular cells in the peduncle.Counts of mitotic figures and tritiated-thymidine-labeled nuclei and determinations of increase in mass of Hydra populations suggest that the difference caused by these temperatures does not affect mitosis. At 9°C buds are initiated at a lower rate and take longer to develop than at 18°C. The surface-areas of buds raised at the two temperatures are similar.Because Hydra raised at the two temperatures have similar growth dynamics, the differences in sizes of the animals cannot be due to growth rate. The observed effect of temperature on bud initiation and development is probably relevant to the increased size of animals raised at 9°C, since these larger animals may be accumulating more cells while losing fewer to buds.
The ultrastructural effects of excess maternal vitamin A on the primitive streak stage rat embryo
Authors: Morriss Gillian M. 
Published: April 2021

ABSTRACTA single injection of 100000 i.u. vitamin A palmitate was administered to pregnant female rats on one of the days 0–14 of pregnancy. The litters were examined for malformations and prenatal death. On the basis of the results of this preliminary investigation, treatment on day 8 was selected for detailed study. Day-8 embryos were examined with the electron microscope from 2 to 24 h after maternal vitamin A administration. Ultrastructural abnormalities were: membrane swelling (cytoplasmic vacuoles, ‘budding’, nuclear membrane irregularities, general swelling leading to cell death); changes in the extra-to intracellular fluid ratio; increase in the number of lipid droplets; autophagic vacuoles; condensed and swollen mitochondria. These changes were not equally distributed among the different cell types. It is suggested that this differential effect leads to a loss of synchrony between the development of structures from the different germ layers, in addition to a general retardation. Loss of contact between mesoderm cells may delay normal migratory movements and induction of neural plate. The general retardation is related to the lower birthweights of treated embryos versus controls, and the differential effects to the subsequent abnormal morphogenesis.
Properties of the primary organization field in the embryo ofXenopus laevis: IV. Pattern formation and regulation following early inhibition of mitosis
Authors: Cooke J. 
Published: April 2021

ABSTRACTVisual observation of early blastulae, and counting of cell suspensions from the late blastula and subsequent stages of Xenopus development, have shown that exposure to either colcemid or mitomycin C can sustain blockage of the mitotic cycle, and hence prevent the normal increase in cell number. Such blockage is essentially complete within a period, following introduction of the drugs, which is short compared with the cell-cycle time normal to post-blastular stages. Although the cell-counting data do not allow a statistical demonstration, there is a suggestion that mitomycin C allows a greater proportion of cells to divide once, after its introduction, than does colcemid. This is in accord with its putative mode of action, in causing only intrachromatid cross-linkage within chromosones, but there are no data on the status of DNA replication within nuclei of the non-dividing cells under either drug. If blockage is begun not earlier than stage 10+, some 20 min after dorsal lip formation, essentially normal morphogenesis ensues up to tail-bud stages around 27, including histodifferentiation of ectodermal structures and notochord, and twitching of somitic muscle. Such embryos are described. In describing those arresting at earlier stages following blockage in blastulae, the possibility is mentioned that morphogenesis may fail for mechanical reasons due to low cell number and large cell size, rather than to lack of a normal field as such. Cell counting reveals that blocked embryos with qualitatively normal pattern formation by stages 22-24, in having a total cell number appropriate to stage 10+ or 10J, show about a seventh or an eighth of the number of cells normal to their stage. Between then and stage 27 when histogenesis, particularly of twitching muscle, is more clearly seen, the direct method of estimating cell number can no longer be used, but histology reveals no mitotic metaphases in any blocked embryos. In the same experiments, operations of two types described in previous papers are performed on early gastrulae so that regulation is required in the embryonic field after the cessation of mitosis. The results are as seen in the normal presence of the cell cycle, revealing that, in response to changes of positional information value, host material may change its presumptive differentiation tendency and final commitment, in the absence of cell division as such. There is some indication that the proportional numbers of cells assigned to different structures in an individuation field may deviate from normal when overall cell number is limiting.