bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Developmental Origin of Hereditary Absence of Otoliths in Mice
Authors: Lyon Mary F. 
Published: April 2021

ABSTRACT
Hereditary absence of otoliths occurs in some mice homozygous for the mutant pallid. The development of the ears of pallid mice, with and without otoliths, was compared with that of normal mice. In ears lacking otoliths all parts of the developing otoliths could be detected, except the calcium salts. Abnormality was first detected at days’ gestation, when the normal birefringence due to calcium salts did not appear; from days some ears of pallid mice showed a normal layer of calcium granules while others lacked it. The gelatinous layer of the otolith matrix appeared at the normal time, and was normal in amount, position, and staining reactions. The granular matrix was not clearly present at the earliest stages, and days, at which it is normally seen. From days, however, abnormal ears contained free debris which, from its staining reactions, was interpreted as granular matrix. This debris was found in the sacculus and later the endolym-phatic sac. At and days’ gestation ears lacking otoliths showed hydrops of the cochlear duct, sacculus, and endolymphatic duct. Possible mechanisms for the failure of calcification and for the hydrops are discussed. All ears of pallid mice lacked pigment from the secretory regions. The ears of six other mouse mutants, some affecting pigment, and others affecting hearing and behaviour but not pigment, were examined for pigmenta-tion. The pigment of the ear paralleled that of the eyes, and there was no correla-tion between lack of ear pigment and presence of behaviour defects.
The Effect of Prior Intravenous Injections of Dissociated Epidermal Cells and Blood on the Survival of Skin Homografts in Rabbits
Authors: Billingham R. E. , Sparrow E. M. 
Published: April 2021

ABSTRACT
A study has been made of the effect of prior intravenous injections of living homologous dissociated epidermal cells and blood-cells on the survival of skin homografts subsequently transplanted from the cell donors in rabbits. These treatments failed to elicit an immune response resulting in the accelerated breakdown of the skin homografts, even when a massive dosage of homologous blood was administered. On the contrary, in a high proportion of animals injected with their intended donors’ epidermal cells it was found that the host’s capacity to react against the skin homografts was abrogated to an extent that actually increased their survival by a factor of 2 or 3. This prolongation of survival is not merely the outcome of the non-specific treatment of a host with epidermal cells as such, since pre-treatment of animals with suspensions of their own epidermal cells was ineffective in prolonging the survival of homografts. This modification in the host’s response was not obtained by the administration of epidermal cell suspensions by other routes; when the cells were injected intradermally a state of immunity was elicited, and their intraperitoneal injection was without demonstrable effect. The injection of living cells was found to be obligatory since cells killed by freezing and thawing before their injection had no effect on the course of the homograft reaction. The injection of homologous blood gave results comparable with those obtained with epidermal cell suspensions, although they were not as consistent. Evidence is presented suggesting that a state of immunity towards grafts of homologous skin may be evoked by prior intradermal injections of epidermal cell washings not containing intact living cells. Possible explanations and affinities of the induced abrogation of a host’s immunological response to skin homografts are discussed, as well as its possible implications.
The Development of the Neural Tube of the Chick Embryo. A Study with the Ultraviolet Microscope
Authors: Hughes Arthur 
Published: April 2021

ABSTRACTThe development of the spinal cord and dorsal root ganglia of the chick has been studied by ultraviolet photomicrography of sections at 2,537 Å. The results have been compared with material treated by standard neurohistological methods. In the ultraviolet negatives cytoplasmic density for unit thickness of section has been measured for ependymal and ventral horn cells, and also in the neuro-blasts of the dorsal root ganglia. The density of the mitotic figures in the ependymal layer has also been measured. The changes in cytoplasmic density in developing neurones closely parallel those in the RNA concentration of the whole embryo. In the developing neurone a high density of RNA is seen within the cyto-plasm for some days after the cell has first differentiated. This then falls and later rises slowly once again as Nissl substance is laid down. Experiments on the effect of ribonuclease on ependymal mitotic figures and the cytoplasm of neuroblasts are described.
A New Technique for the Cultivation of the Chick Embryo in vitro
Authors: New D. A. T. 
Published: April 2021

ABSTRACT
A new technique is described for the cultivation of chick embryos in vitro. It consists essentially in supporting the explanted blastoderm on a piece of vitel-line membrane stretched across a glass ring. The nutrient medium is fluid albumen. Primitive streak blastoderms explanted by this technique: (a) frequently develop as far as the formation of a functional blood circulation, together with flexion and torsion of the embryo; (b) show normal expansion across the vitelline membrane; (c) develop at a normal rate until after the 20-somite stage.
Mitotic cell death and delay of mitotic activity in guinea-pig embryos following brief maternal hyperthermia
Authors: Edwards M. J. , Mulley R. , Ring Shiela , Wanner R. A. 
Published: April 2021

ABSTRACTPregnant guinea-pigs were exposed to an environmental temperature of 42·0–42·5 °C for 1 h on day 21 of gestation. Their embryos were removed at periods from 45 min of heating to 48 h following exposure. Histological preparations of embryos showed clumping of nuclear chromatin and subsequent death of cells which were at about the stage of mitosis. Affected cells were particularly numerous in the central nervous system. Further mitotic activity was inhibited for 6–8 h. Squash preparations of the telencephalon at 1 h after heating showed an increase from 3 to 86 % in the number of mitotic cells showing damage in the form of nuclear clumping; this number fell progressively to 30% by 24 h after heating. The proportion of cells in various stages of mitosis changed considerably at 1–8 h after heating, but had returned to pre-heating values by 24 h. The proportion of cells in prophase fell markedly, while the proportion of metaphase cells was doubled at 4 h after heating, indicating blocks to the cell generation cycle before prophase and in metaphase.
Analyse expérimentale de la régulation du nombre des cellules germinales après déficience gonadique chez le poulet
Authors: Didier Par Eliane , Fargeix Noël , Bergeaud Yves 
Published: April 2021

ABSTRACTExperimental study of the regulation of the number of germ cells following gonadial deficiency in the chickColonization of the genital ridges by germ cells was quantitatively studied in control chick embryos killed at stages 25–29, and in embryos in which a surgical excision of the gonad presumptive area was made previously on the second day.In operated embryos which show a more or less perfect agenesis of one gonad, the number of germ cells counted in genital ridges is lower than the number of germ cells estimated in the same stages of control embryos. The deficit is greater for left gonadic agenesis. The decrease in the total number of germ cells is essentially due to a reduction in the cells colonizing the deficient gonad. There is no excess of germ cells observed in the control gonad.Accordingly, a right side operation strengthens the asymmetry of germ cells distribution, whereas a left side one reduces it.Thus, in birds the regulation of the number of germ cells and the quantitative control of colonisation of the gonads is at the gonad level.
The neural cell cycle in the looptail (Lp) mutant mouse
Authors: Wilson Doris B. , Center E. M. 
Published: April 2021

ABSTRACTThe cell cycle of mesencephalic ventricular cells was studied by means of tritiated thymidine radioautography during normal and abnormal development in the looptail (Lp) mutant mouse. The total generation time, DNA-synthetic (S), premitotic (G2), mitotic (M), and postmitotic (G1) periods were compared in looptail homozygotes (Lp/Lp) which exhibit neural dysraphism and in their normal littermates ( + / + ) at 10 and 11 days’ gestation. Both normal and abnormal embryos showed a chronological lengthening of the generation time between the 10th and 11th day. However, the generation time in the 10-day abnormal brains was 4·5 h longer than that in normal littermates, and the difference was the result of an increase mainly in the M and G1 periods. At 11 days of gestation the generation time in the abnormal brains increased by 5·0 h over that of the normal brains. Since the cell cycle was actually prolonged in the defective brains, the increased numbers of mitotic figures which characterize the looptail homozygote brain during early development appear to reflect the lengthening of the mitotic period rather than increased proliferation.
Fine structural study of cell migration in the early mesoderm of normal and mutant mouse embryos (T-locus:t9/t9)
Authors: Spiegelman Martha , Bennett Dorothea 
Published: April 2021

ABSTRACTMouse embryos homozygous for the t9-allele exhibit an enlarged primitive streak, scanty mesoderm, and aberrant axial organization by the eighth day of development and die by the tenth day.Light and electron microscopic observations of sections through mesodermal cells of these mutant embryos reveal sheet-like arrangements of cells rather than the array of stellate individual cells seen in mesoderm of normal embryos. The abnormal mesodermal cells usually display lobate pseudopodia instead of the filiform pseudopodia typical of normal mesodermal cells. These lobopodia do not possess the subsurface microfilaments characteristic of filopodia. Cellular junctions such as those regularly seen between adjacent filpopodia of normal mesodermal cells occur only very rarely between neighboring lobopodia of mutant mesodermal cells.The deficiency of mesoderm may be due to the failure of cells to form the cellular associations typical of gastrulation and to move normally from the primitive streak which consequently becomes enlarged due to the accumulation of apparently immobilized cells. Those few cells which do attain the proper location nevertheless do not appear well-differentiated. Their abnormalities of cell shape, cellular translocation, and cellular interactions may be related to a lack of microfilament cytostructure and surface adhesiveness.
Studies on effects of 5-bromodeoxyuridine on the development of explanted early chick embryos
Authors: Lee H. , Deshpande A. K. , Kalmus G. W. 
Published: April 2021

ABSTRACTChick embryos were explanted at stages ranging from the definitive streak to one-somite and cultured for 19–21 h on thin albumen with or without 5-bromodeoxyuridine (BrdU) (2–12 μg/ml). BrdU primarily inhibited neurulation which was found to be stage dependent. If exposed to BrdU at the definitive streak stage, it resulted in an open brain region; if treatment was delayed until the head-process stage, it inhibited the closure of the midbrain and, to some extent, the hindbrain, but the forebrain closure was mostly unaffected. BrdU had no appreciable effect on later stages. It was also found that BrdU inevitably inhibited somite formation when exposed to 8 μg/ml or higher concentrations. The blastodermal expansion, heart development, and blood island formation were usually not affected.Cytological changes were observed in adversely affected tissues, particularly the neural tissue. BrdU produced nuclear enlargement and clumped metaphase, but did not cause extensive necrosis.The grafting experiments showed that an increase in the concentration of BrdU from 4 to 12 μg/ml progressively inhibited the self-differentiation of Hensen’s node grafts. However, BrdU (8 μg/ml) had no significant effect on the inducing capacity of node grafts nor the competence of the epiblast.Autoradiographic studies showed that the application of BrdU, at 6 μg/ml or lower, caused no obvious variations in the incorporation of [3H]uridine into chick embryonic cells. BrdU, at .10—12 μg/ml, selectively inhibited the uptake of [3H]uridine in the neural tissue.
The effect of 5-bromodeoxyuridine on early mouse embryosin vitro
Authors: Garner Wendy 
Published: April 2021

ABSTRACTThe effect of 5-bromodeoxyuridine (BudR) on the development of cleavage stage mouse embryos has been examined. The analogue was found to have a deleterious effect at relatively low doses on survival to blastocyst, and to a lesser extent on trophoblast outgrowth in supple- mented medium. No tendency to suppress differentiation rather than cell division was detected. Possible mechanisms for the BudR effect are discussed.
Microfilaments in the external surface layer of the early amphibian embryo
Authors: Perry Margaret M. 
Published: April 2021

ABSTRACTA comparison was made by transmission electron microscopy of the microfilaments in the surface layers of the early embryos of Triturus alpestris and Xenopus laevis at stages of development up to neurulation. Actin-like filaments which bound heavy meromyosin (HMM) were found in cell extracts of all stages, but were comparatively rare in the newly fertilized egg. Ten nm microfilaments were present throughout development in Xenopus, and from the mid-neurula stage in Triturus. Both kinds of microfilament were located in the circumferences of superficial ectoderm cells at the level of the apical junctions, the .10 nm microfilaments in association with desmosomes which began to develop before gastrulation in Xenopus. The accumulations of microfilaments in the apical constrictions, which form in ectoderm cells of Triturus early gastrulae when dissociated in a calcium-free medium, suggest that they are contractile elements. In the absence of such accumulations in the cell apices, the reverse curling exhibited by Xenopus ectodermal explants is attributed rather to a separation of the cells’ lateral borders. Cytochalasin B (5 μg/ml) caused ectodermal explants from the early gastrulae of both species to disaggregate. With the rupture of the apical junctions there was a disorganization of the associated microfilamentous layer.
The determination of polarity in the developing insect retina
Authors: Lawrence P. A. , Shelton P. M. J. 
Published: April 2021

ABSTRACT
The retina in Oncopeltus fasciatus is a polarized structure in which all ommatidia are orientated the same way. By a series of grafting experiments we have shown that the orientation of ommatidia is partly dependent upon the orientation of the epidermis from which they develop and partly on the orientation of the host eye. Grafts which invert the dorsoventral axis of the presumptive eye epidermis do not disrupt the orientation of the nascent ommatidia. Grafts which are rotated by 90° or 180° produce altered patterns of orientation. The polarity of the epidermis is to some extent conserved in these cases. Significantly ommatidia at the graft/host border take up orientations intermediate between the extremes found in the graft and host. Small rotated grafts assume the polarity of the host retina. These results are compared with the effects of similar grafts on developing insect bristle patterns.
The development of the retinotectal projection inXenopuswith one compound eye
Authors: Feldman Joan D. , Gaze R. M. 
Published: April 2021

ABSTRACTDouble-nasal and double-temporal compound eyes were constructed in Xenopus embryos at stages 32 and 37/38. A particular half was removed from the host eye anlage and replaced with the opposite half-eye from the contralateral side of a donor embryo. Control operations consisted of removing a half-eye and replacing it with a similar half from the ipsilateral side of the donor embryo. Whereas in control animals, each half-eye projected its fibres to the appropriate half-tectum, in operated animals each half of the compound eye spread its optic terminals across the entire rostrocaudal extent of the dorsal tectal surface.The area of tectal surface covered by ganglion fibre terminals was similar in operated animals mapped at successive stages of development to that previously observed in normal animals at equivalent stages. Therefore the factors responsible for the extended distribution of fibre terminals from each half of a compound eye must exist at least from mid-tadpole life, and thereafter be continuously present throughout development.
Restoration of the capacity to form pole cells in u.v.-irradiatedDrosophilaembryos
Authors: Warn Richard 
Published: April 2021

ABSTRACTInjection of pole plasm into u.v.-irradiated posterior poles of early Drosophila embryos leads to the restoration of the capacity to form pole cells in nearly half of the recipients. The effect is specific, since cytoplasm from the anterior tip has no such result. In most cases only a small number (between 1 and 5) of discrete pole cells are formed. However, a large number of pole cell fragments with or without nuclei occur. Occasionally pole cells were formed outside the area of the originally irradiated pole plasm. This happened when material was injected more anteriorly than usual. Thus polar cytoplasm contains some factor(s) necessary for the formation of pole cells.
The matrix of the optic vesicle-presumptive lens interface during induction of the lens in the chicken embryo
Authors: Hendrix Richard W. , Zwaan Johan 
Published: April 2021

ABSTRACTThe cell coats of the presumptive lens cells and the extracellular interface between the lens rudiment and optic vesicle were investigated in the chicken embryo throughout the period during which lens induction is presumed to take place.Histochemical methods showed that the cell coats contained both glycoproteins and glycos-aminoglycans. Autoradiography after [3H]glucosamine injection indicated incorporation of the precursor with subsequent localization primarily at the cell surface. No obvious changes in the properties of the coat were noted with the progression of early lens morphogenesis.The extracellular matrix at the interface between ectoderm and optic vesicle also contained glycoprotein and glycosaminoglycan. There was a heavy concentration of [3H]glucosamine-containing macromolecules in the area. Electron microscopy revealed that the interface consisted of the basement membrane systems of lens and optic vesicle, fused with their external fibrillar layers. In contrast to the findings on cell coats, the density of the interfacial matrix increases appreciably during the lens induction period. Evidence suggests that the cells of the two ocular epithelia are themselves the source of the matrix materials.It is proposed that the macromolecules excreted by the epithelial cells into the interface interact at different concentrations to form aggregates of various structure by a process of self-assembly. This may be reflected in the different ultrastructure of the layers of the inter-facial matrix.Quantitative changes in the density of the matrix, leading to increased adhesion between lens rudiment and optic vesicle, may restrict the lateral spreading of the lens cells and so fix the basal area of the lens rudiment. This, together with continued cell replication, may produce the cell crowding, placode formation and invagination characteristic of lens morphogenesis.
Nicotinamide adenine dinucleotide levels in chick limb mesodermal cells in vitro: effects of 3-acetylpyridine and nicotinamide
Authors: Rosenberg Martin J. , Caplan Arnold I. 
Published: April 2021

ABSTRACT
The studies reported here show that in cultures of developing mesodermal cells, chondrogenic expression is associated with a progressive decline in cellular NAD+ levels. Furthermore, reduced cellular NAD+ levels resulting from exposure to the nicotinamide analog 3-acetyl-pyridine are correlated with a 2- to 100-fold potentiation of chondrogenic expression. Conversely, elevated NAD+ levels resulting from exposure to nicotinamide alone are correlated with inhibition of chondrogenic expression. These data are consistent with the hypothesis that pyridine nucleotides, or some derivative thereof, play a central role in the control of muscle and cartilage development in embryonic chick limbs.
The development of embryos in the uteri of mice treated with actinomycin D before implantation
Authors: Finn C. A. , Bredl J. C. S. 
Published: April 2021

ABSTRACT
This investigation follows the development of embryos in the uteri of mice in which the differentiation of the implantation chamber has been retarded by the administration of actinomycin D before implantation.
For the first 48 h after the induction of implantation both embryonic and extra-embryonic parts of the blastocyst develop, but after 72 h the embryonic parts cease to grow and die. The giant cells and other extra-embryonic tissues, on the other hand, continue to develop for a much longer period, up to 288 h.
It is suggested that the actinomycin D, by delaying the formation of the implantation chamber in the endometrium, interferes with the formation of a proper functional connection between the trophoblast and endometrium with the result that the embryo receives insufficient nutrition for its development.
Immunochemical analysis of water-soluble antigens of chick retina in the course of embryogenesis
Authors: Mikhailov A. T. , Barabanov V. M. 
Published: April 2021

ABSTRACTWater-soluble antigens of chick retina were investigated using rabbit antisera to total extract and to individual electrophoretic fractions of retinal extract by methods of immunoelectrophoresis and Ouchterlony precipitation test. In the retina of the adult chick six serum and eleven tissue antigens were demonstrated. The tissue antigens of the retina comprised one organ-specific antigen and ten inter-organ antigens which were characterized by nonuniform distribution in tissues and organs of adult chick. Three antigens out of these were found only in tissues of the eye (retina, iris) and in the brain - inter-organ antigens of ‘narrow’ specificity. The other seven inter-organ antigens were found in tissues of brain and eye, as well as in various tissues and organs of hens - inter-organ antigens of ‘broad’ specificity.A high degree of antigen similarity between retina and iris was observed. Anti-retina sera in chick lens could detect only inter-organ antigens of ‘broad’ specificity.In the course of embryogenesis the first to appear in the developing retina were interorgan antigens of ‘broad’ specificity (on 3rd day of incubation). Formation of antigens of this group was completed by the 9th day of incubation. On the contrary, inter-organ antigens of ‘narrow’ specificity appeared later, in the period of histogenesis of retina (from 5 to 18 days of incubation). The organ-specific antigen of retina was found by 7th day of incubation.One of the inter-organ retinal antigens of ‘narrow’ specificity (retina-iris-brain) appeared in the developing chick brain at the same time as in retina - on 10th—11 th day of incubation. Using the indirect immunofluorescence antibody technique this antigen was identified in the cytoplasm of retinal cells and brain neurones, but was not detected in the nerve fibres.