bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of the rat conceptusin vitroand associated changes in components of culture medium
Authors: Sanyal Mrinal K. 
Published: April 2021

ABSTRACTRat conceptuses of pregnancy day 11 (embryonic age approximately 10.5 days) with embryos within the yolk and amniotic sacs and polar allantoic placental tissues were cultured by the ‘New system’ utilizing homologous serum in 60ml roller bottles with 20% O2, 5% CO2 and 75% N2 gas environment (five conceptuses/10 ml serum). Embryonic growth and development was assessed by external morphology and somite counts, and by measurement of DNA, RNA and protein contents. The embryonic growth was considerably retarded beyond 24 h when culture was extended to 48 h.During continuous culture of conceptuses for 48 h, the partial pressure of O2 in the medium decreased gradually with simultaneous increase of and decline of pH values. Glucose level was depleted considerably and small quantities of urea, uric acid and creatinine accumulated in the medium. The concentrations of electrolytes (Na+, K+, Cl-) and total Ca and P, and lactic dehydrogenase activity in the medium increased during the latter part of the 48 h culture period.The growth and differentiation of embryos were significantly improved by transferring conceptuses to fresh serum medium with 40% O2, 5% CO2 and 55 % N2 gas phase after 22–24 h culture and continuing the culture for an additional 24 h. Embryos grown in vitro for 48 h developed 39 somites and showed a tenfold increase in DNA content and a five- to seven-fold increase in RNA and protein contents, over initial values.
Morphogenetic properties of the skin in axolotl limb regeneration
Authors: Slack Jonathan M. W. 
Published: April 2021

ABSTRACT
A study has been made of the morphogenetic properties of anterior and posterior skin from the lower forelimb of the axolotl. The basic experiment consisted of a graft of a half cuff of skin from a donor to a host limb followed by a 2-week healing period, amputation through the graft, and a study of the resulting regenerate. Limbs with double posterior skin formed double posterior regenerates and, in contrast, limbs with double anterior skin formed normal or slightly hypomorphic regenerates. Posterior skin from post-metamorphic animals had a similar but weaker effect to that from ordinary axolotls.
Immunological rejection of allografts could be completely avoided if the donor limb was transplanted to the flank of the host when both were at the stage of tail-bud embryos, and the skin graft was later carried out between the supernumerary limb and one of the host limbs. This technique was used to show that immunological rejection does not affect the formation of duplicates from the limbs with double posterior skin, and to facilitate the studies of the cellular provenance of the regenerate.
The cellular composition of duplicate regenerates was studied by using both triploid donors and triploid hosts. It was shown that the posterior side of the duplications consisted wholly of host tissue and the anterior side consisted of mixed donor and host tissue. Formation of the duplicated regenerate therefore seems to involve positional reprogramming of both donor and host tissues together with metaplasia of the donor tissue.
It was not possible to inhibit the duplication-inducing property of posterior skin by treatment with a variety of enzymes.
A model based on the serial threshold theory of regeneration is advanced to explain the results. This model successfully accounts for the observed non-equivalence of anterior and posterior skin, and also explains the different regeneration behaviour of anterior and posterior half limbs, the limited regeneration of double anterior limbs, and the pattern expansion and contraction shown by regenerates from double posterior limbs.
Somite formation in cultured embryos of the snapping turtle,Chelydra serpentina
Authors: Packard David S. 
Published: April 2021

ABSTRACTA simple, reliable method for the in vitro cultivation of snapping turtle embryos was dem-onstrated. This technique was used to study somite formation in expiants containing segmental plates. Segmental plates formed a full complement of somites whether the neural tube or the neural tube and notochord was present. Explanted snapping turtle segmental plates formed an average of 6·6 ± 1·2 somites. Removal of the node region or tail bud from cultured intact embryos led to a cessation of somite formation after an additional 6·1 ± 1·8 somites had formed. These results indicate the number of somites the snapping turtle segmental plate will form. Also, the number of somites formed by explanted segmental plates showed only slight variation over a wide range of segmental plate lengths. It was concluded that while snapping turtle segmental plates formed significantly fewer somites than chicken or Japanese quail segmental plates, they were similar to the avian explants in their ability to form a consistent number of somites regardless of the length of the segmental plate.
The Mode of Growth of the Tail in Urodele Larvae
Authors: Bijtel J. Hubertha 
Published: April 2021

ABSTRACT
In the developing tail-bud of urodele larvae, the neural and the mesodermal components of the tail fold along their boundary and surround the caudal extremity of the notochord. The first growth of the tail-bud is brought about by an autonomous lengthening of the neural and the mesodermal tissues. The notochord does not have an active part in the process of the lengthening of the tail, but plays a passive role. It is a supporting organ, acting as a splint. In this way it determines the ultimate length of the tail. It is not the notochord, but the combination of the neural and the mesodermal tissues, which in the first place determines the direction in which the tail grows.
Expression of serologically detectable H-2 antigens on mid-gestation mouse embryonic tissues
Authors: Kirkwood Katrina J. , Billington W. D. 
Published: April 2021

ABSTRACTMixed haemadsorption assays using antibody-coated indicator sheep erythrocytes and mouse alloantisera revealed that major histocompatibility complex (H-2) antigens were expressed on cells of 24–72 h cultures of mid-gestation mouse embryonic skin, gut, lung, limb-bud and heart but not of embryonic gonad or kidney. The precise time of detection of H-2 antigen expression and the proportions of cells expressing these determinants depended on inbred strain, specific haplotype, tissue of origin and antiserum batch employed. In all tissues the proportion of cells expressing H-2 increased progressively from day 11–12 postcoitum onwards. The findings are discussed with respect to hypotheses concerning the possible role of major histocompatibility antigens in cellular recognition and interactions during embryogenesis.
Induction of cleft lip in cultured rat embryos by localized administration of tunicamycin
Authors: Eto Kazuhiro , Figueroa Alvaro , Tamura Gakuzo , Pratt Robert M. 
Published: April 2021

ABSTRACTWhole-embryo culture techniques have advanced to the point where the study of normal and abnormal primary palate development in vitro is possible. The purpose of this study was to ascertain whether localized administration of tunicamycin (TM) an inhibitor of protein glycosylation, into the region of the developing primary palate would induce cleft lip in culture. Rat embryos were explanted on late day 11 of gestation and cultured with open yolk sacs for 40 h. TM was administered by implanting a sterile eyelash soaked in TM into the nasal placode region. The contralateral placode was used as the control by implanting an eyelash lacking TM. Under these conditions, TM-treated placodes were found to develop cleft lip in 14 out of 15 embryos compared to 0 for the controls. These experiments demonstrate that localized administration of TM results in cleft lip formation in whole embryo culture. The technique of localized administration of drugs and teratogens in whole embryo culture should prove useful for similar studies on embryonic development.
A general cell marker for clonal analysis of Drosophila development
Authors: Lawrence Peter A. 
Published: April 2021

ABSTRACT
The mitochondrial enzyme, succinate dehydrogenase, can be localized by specific histochemical stains. A naturally occurring variant which gives heat-labile enzyme is used to map a gene responsible for succinate dehydrogenase. New alleles at the sdh locus are produced by mutagenesis and most of these are found to be homozygous lethal to flies. However, clones of cells which are homozygous for the new alleles can be produced by mitotic recombination, and are found to develop normally. If the chromosome arm bearing an sdh allele also carried brown, clones can be found in the eye. At the border of the clone the brown and sdh phenotype coincide showing that the sdh phenotype is expressed as a cell autonomous marker. Clones of sdh have been observed in the adult epidermis, the muscles, the gut, the heart and oenocytes where they display a clear phenotype. This new marker may be useful in studying the development of the internal organs of Drosophila.
Experimental evidence for autonomous action of the periodic albinism (ap) gene within developing retinal pigment cells and melanophores ofXenopus laevis
Authors: MacMillan Gillian J. 
Published: April 2021

ABSTRACTGenes which affect pigment elaboration may do so by autonomous action within the developing pigment cells or by way of tissue interactions leading to pigment cell differentiation. The site of action of the periodic albinism (ap) gene was investigated by substituting presumptive neural ectoderm of gastrulae of one genotype with uncommitted ectoderm of different genotype. Retinal pigment cells and melanophores arising from such grafts were found to differentiate according to their own genotype in spite of having spent their entire developmental history in tissues of different genotype. This finding demonstrates autonomous action of the ab gene within pigment cell derivatives and does not support recent proposals that the ap gene is involved in inductive interactions leading to melanogenesis. Experiments in which portions of presumptive dorsal mesoderm, implanted in gastrulae of different genotype, induced secondary pigment cells of host phenotype further support the proposal that the ap effect on pigment cells is not mediated by inductive interactions.
Reactivity of monoclonal antibodies against intermediate filament proteins during embryonic development
Authors: Kemler Rolf , Brûlet Philippe , Schnebelen Marie Thérèse , Gaillard Jean , Jacob François 
Published: April 2021

ABSTRACT
Monoclonal antibodies (mAbs) against a preparation of intermediate filaments from trophoblastoma cells were studied for their reactivity pattern during embryonic development and on adult tissue cells. Up to day 12 of embryonic development, epithelial cells of the three germ layers reacted with these mAbs. Later during development and in adult tissues, positive reactions could be observed only with epithelial cells derived from mesoderm and endoderm. Because of their tissue distribution, the proteins reacting with these mAbs might belong to the keratin family of intermediate filaments or they might represent a new group of intermediate filaments.
Comparative analysis of amphibian somite morphogenesis: cell rearrangement patterns during rosette formation and myoblast fusion
Authors: Youn B. Woo , Malacinski George M. 
Published: April 2021

ABSTRACTDetailed SEM observations of the changes in cellular morphology, arrangements, and contacts that occur during the process of somite formation were made in two species of urodele amphibians, Ambystoma mexicanum and Pleurodeles waltlii, and one species of anuran amphibian, Rana sphenocephala. After fixation, embryos were fractured transversely, horizontally, and parasagittally, and the intrasomitic cellular arrangement pattern was examined with the SEM. It was found that Ambystoma and Pleurodeles embryos followed exactly the same development sequence in rosette formation and myoblast fusion. Rana somites did not, however, appear to form rosettes. Those myotomal cells underwent fusion immediately after a few segmentations occurred.Patterns of cellular rearrangement were also described during urodele rosette formation at the time of somite segmentation and during myoblast fusion. Extensive changes in cell shape and orientation appeared to occur during those processes. When cells changed their orientation, they often exhibited a triangular configuration. Probable roles of these triangular-shaped cells in rosette formation and myoblast fusion are discussed.During the initial period of myoblast or myotomal cell fusion, cells first send out specialized cell processes and then establish their cell–cell contacts. The establishment of such contacts eventually leads to tight membrane appositions and fusion. Since myoblast fusion appeared to occur between two cells which were tandemly arranged in a rosette, the origin of multinuclearity in the fused cells is discussed.Finally, comparative analyses of the pattern of somite formation and subsequent muscle development were made between different species of amphibians. The possibility is discussed that patterns of somitogenesis may provide useful indicators for determining how different families of amphibians evolved.
Hypoblast induction of multiple area vasculosae, and stabilization of the area opaca vasculosa in young chick blastoderm
Authors: Zagris Nikolas 
Published: April 2021

ABSTRACTMultiple vascular areas are formed in unincubated and prestreak chick blastoderms under the influence of multiple transplanted hypoblasts. Though the transplanted hypoblasts merge into one continuous layer, they do not participate collectively in forming one streak and embryonic axis with one area vasculosa at its postero-lateral end, but each hypoblast seems to form an embryonic centre or fraction of a centre. It may be that the merged hypoblasts do not lose their individuality or that they have induced their prospective embryonic centre before merging. This is an indication that the hypoblast is able to initiate certain events to which the epiblast responds. Composite blastoderms with stage-2 host epiblasts and with two or more transplanted hypoblasts form the embryonic axis at its prospective plane and two area vasculosae, the area opaca vasculosa (a.o.v.) as in the control blastoderm, and an induced area vasculosa 180° anteriorly. However, composite blastoderms with stage-3 epiblasts and with two or more transplanted hypoblasts behave as the control blastoderms forming the embryonic axis and the a.o.v. at their prospective sites. This indicates that the typical a.o.v. in the chick blastoderm is stabilized to blood island formation at stage 3. The stage dependence which involves progressive restriction of the areas in which blood islands will develop, suggests the existence of a centre which creates organization by integrating short-lived fields. It seems that there are no particular cell groups of the unincubated blastoderm determined to form erythrocytes but that the organizing capacities of the area are necessary to induce the first early commitments of prospective erythroblasts along this course.
Lineage analysis of inner cell mass and trophectoderm using microsurgically reconstituted mouse blastocysts
Authors: Papaioannou Virginia E. 
Published: April 2021

ABSTRACTThe fate of mouse blastocyst tissues was examined following reconstitution of blastocysts from isolated inner cell mass (ICM) and trophectoderm differing for electrophoretic variants at the glucose phosphate isomerase (GPI-1) locus. A modified microsurgical method was used and a more sensitive enzyme assay allowed finer dissection of developing chimaeric conceptuses. In seven of nine cases, the extraembryonic ectoderm or the later ectoderm of the chorion was entirely of the blastocyst trophectoderm enzyme type, providing the first direct evidence that this tissue can be wholly derived from the trophectoderm. The two exceptions could represent contamination of the ICM with trophectoderm or might indicate some developmental lability of ICM cells. In addition, the results confirm the cell lineages of other tissues of the 7· 5- to 9· 5-day pc embryo and, for the first time, directly demonstrate the ICM origin of the parietal endoderm.
Enhancement of Growth of Chick Host Spleens following Chorio-allantoic Membrane Grafts of Homologous Tissues1
Authors: Mun A. M. , Kosin I. L. , Sato I. 
Published: April 2021

ABSTRACTA striking enlargement of the host chick embryo spleen was obtained following chorio-allantoic grafts of adult chicken spleen tissue. When the adult chicken spleen tissue was killed by freezing and thawing before implantation on the chorio-allantoic membrane, no enlargement of the host chick embryo spleen was observed. However, a large number of the frozen grafts failed to ‘take’. X-irradiation of the donor spleen, at a level sufficient to block or inhibit mitosis, also removed the growth-stimulating abilty of the grafted tissue in spite of the fact that the grafts were well incorporated. This suggested that donor cells capable of undergoing mitosis were necessary for producing enlarged host spleens. Because of the possibility that antibody-forming mechanisms were destroyed at these levels of irradiation, the involvement of such mechanisms in this reaction was studied. In a comparison of the effect of spleen grafts between two inbred lines of White Leghorn chickens (S and R), a lesser stimulation was obtained when spleens from 5 line chickens were implanted on S line embryos than on R line embryos. Similarly, a lesser stimulation was obtained when R spleens were implanted on R embryos than on 5 embryos. Spleens from S line chickens also evoked a greater response than spleens from R line chickens. To test the role of antibodies in this reaction, spleens from adult chickens previously injected with chick embryo spleens were implanted on the chorioallantoic membrane. In all cases (7) the spleens from the injected chickens stimulated the host embryo spleen to a significantly lesser degree than spleens from non-injected chickens. Spleens from different animal species, including the turkey, pheasant, rat, and guinea-pig, were implanted on the chorio-allantoic membrane of the early chick embryo. The turkey and pheasant spleens stimulated the host chick embryo spleens to a significantly lesser degree than adult chicken spleen in spite of the greater genetic diversity and subsequently successful incorporation in the chorio-allantoic membrane. From the available evidence the authors suggest that the enlargement of the host chick embryo spleen following chorio-allantoic membrane grafts of homologous adult chicken tissue probably involves two separate steps: (1) a stimulation which may occur in the absence of intact cells; (2) an immune-type reaction which results in necrosis of areas in the host spleen, and stunting of growth of the hatched chicks.
An Immunological Approach to the Problem of Lens Regeneration
Authors: Langman J. , Prescott B. D. 
Published: April 2021

ABSTRACTApplication of Boyd’s precipitin test showed the presence of lens antigens in extracts of pigment layer of the retina, ventral and dorsal parts of the iris, cornea, vitreous body, and in aqueous humour obtained from eyes in which the lens was removed 6-7 weeks prior to the test. Their presence was not detected in the neural layer of the retina, sclera, or in any other extra-ocular tissue (Table 1). Extracts prepared from lens-containing eyes showed exactly the same results. The number of lens antigens in these tissues was determined by the agar diffusion technique of Ouchterlony and was found to vary from 2 to 7, depending on the source of tissue used (Table 2, Plate, figs. 1-6). The antigens found in pigment layer of the retina, iris, cornea, vitreous body, and aqueous humour appeared to be identical to antigens found in the lens (Table 3, Plate, fig. 7). Since iris, pigment layer of the retina, and cornea have the property to regenerate a lens after removal of the original lens, the obtained data suggest that there is a relationship between the lens regeneration capacity and the presence of antigens identical to those of the lens.
The Submicroscopic Structure of the Drosophila Egg
Authors: Okada Eiko , Waddington C. H. 
Published: April 2021

ABSTRACT
A study has been made with the electron microscope of the structure of the growing oocyte and associated nurse and follicle cells in Drosophila melanogaster. The fully grown oocyte has a cortical plasm which is thrown into deep folds, at the base of which are small delta granules. Immediately below this is a zone of periplasm which contains: well-developed mitochondria; some ergastoplasmic elements, probably mainly tubular, though sometimes taking the form of concentric oval sheets; many alpha granules which when well fixed are irregularly star-shaped and are probably lipoidal in composition; a number of stacks of annulate lamellae. Yolk granules, which may be built of a few tens of smaller particles, are found mainly at deeper levels, and so are the electron-light and probably fluid beta granules and the rather darker gamma granules. Epsilon granules, with a definite membrane and vacuolated interior, occur mainly in the posterior end of the egg and later in the pole cells. The vitelline membrane, which in earlier stages has a spongy structure, begins to appear between oocyte and follicle cells earlier than below the nurse cells. The appearance of small vesicles in the ooplasm beneath the developing membrane suggests that it is secreted mainly by the oocyte. There is very complex folding of the membranes between oocyte and follicle cells and still more between oocyte and nurse cells. Attention is drawn to: (i) the great enlargement in the area of the nurse-cell nuclear membranes, (ii) the striking differences in appearance between the nuclear membranes in the nurse cells and follicle cells, (iii) the formation of elaborately organized ergastoplasmic structures in the cytoplasm of the degenerating nurse cells, (iv) the large number and orderly arrangement of the elements in the stacks of annulate lamellae, which is held to suggest a process of in situ synthesis.
Mesectodermal capabilities of the trunk neural crest of birds
Authors: Nakamura Harukazu , Lievre Christiane S. Ayer-Le 
Published: April 2021

ABSTRACTOrthotopic transplantation experiments have shown that in birds, under normal conditions, mesectodermal capabilities seem restricted to the cephalic neural crest down to the level of the 5th somite.In the present study the mesectodermal capabilities of trunk and lumbar neural crest were investigated at early stages of development by heterotopic, heterospecific transplantation of the neural primordium. The quail-chick nuclear marker system was used to identify the grafted cells.Mesectodermal cells did not arise from the trunk neural crest when this was implanted orthotopically, even though the neural primordium was taken early in development at the level of unsegmented plate mesoderm just anterior to Hensen’s node.Mesectodermal derivatives (connective tissues, dermis and muscle but no cartilage or bone) developed from the same trunk neural crest fragments when they were heterotopically grafted at the cephalic level and mixed with host cephalic neural crest cells. These host cephalic neural crest cells emigrated from the contralateral neural primordium when the graft was unilateral or from the fringe area of the operation in cases of bilateral transplantations.As a control, unsegmented paraxial mesoderm was inserted alongside the cephalic neural tube; its cells did not migrate ventrally in the neural crest-derived area and they differentiated in the dorsal region of the host.These results indicate that mesectodermal capabilities, though reduced, exist in the trunk neural crest at early stages of development but the differentiation of these mesectodermal derivatives is largely dependent upon environmental influences which may be found in early cephalic levels.