bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression and function of the keratinocyte integrins
Authors: Watt Fiona M. , Jones Philip H. 
Published: April 2021

ABSTRACT
Human keratinocytes express several adhesive receptors of the integrin family. Expression is normally confined to the basal (proliferative) layer of keratinocytes, both in mature epidermis and during development. Altered expression patterns are observed during wound healing, in psoriasis and in squamous cell carcinomas. Keratinocyte integrins are subject to both transcriptional and post-translational regulation and ligand binding ability can be modulated independently of expression. Studies with cultured keratinocytes suggest a variety of functions for the receptors: adhesion to extracellular matrix proteins, intercellular adhesion, stratification, lateral migration and the regulation of terminal differentiation. Three distinct subpopulations of basal keratinocytes, with characteristics of stem cells, transit amplifying cells and cells committed to differentiate, can be distinguished on the basis of differences in integrin expression and function.
Oligodendrocyte precursor (O-2A progenitor cell) migration; a model system for the study of cell migration in the developing central nervous system
Authors: Kiernan B. W. , ffrench-Constant Charles 
Published: April 2021

ABSTRACT
Cell migration plays an important role in the development of complex multicellular organisms. The molecular mechanisms that regulate this migration are therefore of great interest. Unfortunately, however, analysis of cell migration in vertebrates is hampered by the inaccessability of the cells and the difficulty of manipulating their environment within the embryo. This review focusses on one particular migratory cell population, the oligodendrocyte precursor cell or O-2A progenitor cell, that gives rise to the myelin-forming oligodendrocytes within the CNS. These cells migrate extensively during normal development. They can be purified and grown in large numbers in cell culture, so allowing the use of reductionist approaches using cell and molecular biology techniques. Moreover, cultured cells will migrate within the CNS following transplantation. As a result, the migration of these cells in vivo can be analysed following manipulation in vitro. Taken together, we believe that the different properties of these cells makes them excellent candidates for studies addressing the control of cell migration in the developing nervous system.
puckered, a gene involved in position-specific cell differentiation in the dorsal epidermis of the Drosophila larva
Authors: Ring J. M. , Arias A. Martinez 
Published: April 2021

ABSTRACT
The final pattern of the cuticle of the Drosophila larva depends on the position-specific behaviour of the epidermal cells during their differentiation. This behaviour is dictated, in part, by the relative position of the cells during embryogenesis which allows them to receive and integrate signals from their neighbours. The translation of this ‘positional information’ into pattern might depend on the activity of genes that are able to integrate the outcome of cell interactions and tranfer it to the genes responsible for cell differentiation. Mutations in the gene puckered cause spatially restricted defects during the differentiation of the larval epidermal cells. We present data that suggests puckered may be involved in linking positional information to cell differentiation.
An immunological study on the effect of brain extract on the developing nervous tissue in the chick embryo
Authors: McCallion D. J. , Langman J. 
Published: April 2021

ABSTRACT
In previous experiments it has been shown that saline soluble extracts of adult chicken brain, when deposited on 24-to 32-hr. chick embryos, cause abnormalities of the brain and the eye. Since neither the soluble components of the brain extract, nor the chemical composition of the embryonic brain cells is known, the present study was undertaken to analyse by means of immunological techniques the soluble fractions of adult chicken brain; to study the appearance of these fractions in the course of embryonic development, and to determine the organ and species specificity of the various brain components. It was hoped that the information thus obtained might give a better understanding on the mode of action of adult tissue homogenates on the corresponding tissue in the embryo. The following results were obtained:
Adult brain extract, tested against chick brain antiserum by means of the agar diffusion technique causes the formation of five to eleven precipitin bands, indicating the presence of substantial amounts of five to eleven saline-soluble antigenic brain components. The total precipitin pattern consists of two distinct groups of bands : a group of four to eight rather vaguely defined bands, located close to the antiserum well and referred to as the ‘inner’ bands, and a group of one to three bands close to the antigen well and referred to as the ‘outer’ bands (Plate, 1,2). The antigenic brain components giving rise to the ‘inner’ bands arise during the first 5 days of development, that is the period during which neural plate formation, neural folding, and differentiation of the primitive brain vesicles occur. They have no organ specific characteristics, since they are present in identical form in all the other organs and tissues of the chick (Tables 1 and 2). The antigens giving rise to the ‘outer’ bands appear between the 5th and 12th day of development, that is the period during which the definitive cyto-architecture of the brain is established. They are also present in extracts of nervous retina, spinal cord and peripheral nerves, but are absent in all other tissues and organs of the chick. Hence, these antigens are highly specific for nervous tissue (Tables 1 and 2). The chick brain antigens causing the ‘inner’ and the ‘outer’ precipitin bands are present in antigenically identical form in brain tissue of the turkey and duck, to a lesser extent in that of some of the reptiles, but are absent in brain tissue of mammals, amphibians and fishes (Table 3). When the soluble components of the chick brain are separated by means of continuous flow electrophoresis and tested against brain antiserum, the most negatively charged fractions are found to form the ‘outer’ bands, while the positively charged molecules form the unspecific ‘inner’ precipitin bands.
The mechanism of vitamin A induced teratogenesis
Authors: Takekoshi Shoichi 
Published: April 2021

ABSTRACT
It Is generally recognized that some congenital malformations may be caused by an abnormal environment surrounding the mother in pregnancy. Many experiments have been reported concerning the teratogenesis due to various hypovitaminoses, but there are relatively few reports on teratogenesis resulting from the administration of a large quantity of vitamin. Among the latter, the best known are malformations caused by hypervitaminoses A and D.
Etude du mécanisme de la régulation dans ledéveloppement du bourgeon de membre de l’embryon de poulet
Authors: Kieny par Madeleine 
Published: April 2021

ABSTRACT
On Distingue communément deux types de régulation proximo-distale des déficiences dans le développement du bourgeon de membre: la régulation des déficiences terminales et la régulation des déficiences intermédiaires.
Permeability alterations in amphibian embryos caused by salt solution and measured by tritiated thymidine uptake
Authors: Loeffler Clarence A. , Johnston Malcolm C. 
Published: April 2021

ABSTRACT
In attempts to label the nuclei of intact amphibian embryos with tritiated thymidine we found, in agreement with other authors (Tencer, 1961; Quertier, 1962; Chibon, 1962), that when the nucleoside is dissolved in tap water or media of low salt concentration it fails to enter the embryo. However, when tritiated thymidine was either injected into the embryo or applied to isolated tissues immersed in salt solution, the marker diffused readily through the tissues. Evidently the outer surface of the amphibian embryo is furnished with a special permeability barrier which prevents or reduces the entrance of these molecules. This barrier corresponds most likely to what Holtfreter (1943a, 1943b) has described as the ‘surface coat’. In order that the results of our present experiments may be better understood some of the pertinent properties of the coat will be reviewed.
The transfer of coelomic eggs between frogs
Authors: Lavin Lora Harrer 
Published: April 2021

ABSTRACT
In the analysis of events immediately preceding and following fertilization of the frog egg, it is frequently desirable to treat the eggs with various reagents. Any such treatment must circumvent the barrier represented by the fertilization membrane and the jelly layers. These membranes can be removed from fertilized eggs mechanically or by treatment with proteolytic enzymes (Spiegel, 1951) without impairing development. However, unfertilized eggs from which the jelly has been removed mechanically cannot be fertilized by sperm unless the jelly is restored, and chemical removal of the jelly also inhibits their ability to be parthenogenically activated (Barch & Shaver, 1959). Therefore an alternative method for obtaining jelly-free eggs for treatment prior to fertilization is necessary.
The relationship between size and vascularity in the spinal cord of developing Xenopus laevis
Authors: Sims R. T. 
Published: April 2021

ABSTRACT
The ability of the blood vessels of the spinal cord to increase in number during growth without differentiation of the nerve cells was tested on six sexually immature female Xenopus and eight thyroidectomized tadpoles with suitable control animals. The mean number of blood vessels in the region of spinal cord between the origins of the second and third spinal nerves is greater in metamorphosed Xenopus which are 50 mm. long than in those which are 25 mm. long, and greater in thyroidectomized tadpoles which are 100 mm. long than in normal tadpoles at the same stage of development which are 30 mm. long. The mean number of vessels, which enter the cord from the ventral spinal artery, per unit length of spinal cord between the second and third spinal nerves is inversely proportional to the length of the cord in the metamorphosed animals, but is constant in the two groups of tadpoles. It is concluded that the ability to form new branches of the ventral spinal artery is lost during metamorphosis; the development of blood vessels in the central nervous system is not associated solely with differentiation of the nerve cells; and the histogenetic cell deaths in the developing spinal cord are not precipitated by an inadequate vascular system. The hypothesis is proposed that the growth of new blood vessels is stimulated by a humoral agent produced by the nerve tissue.
An inherited abnormality affecting the development of the yolk plasmodium and endoderm in Dermestes maculatus (Coleoptera)
Authors: Ede D. A. 
Published: April 2021

ABSTRACT
A developmental abnormality characterized most obviously by longitudinal contraction of the embryo occurred in high frequency (up to 70 per cent.) among eggs from females of a selected line of the beetle Dermestes maculatus. In the majority of the abnormal embryos dorsal closure does not occur and the embryonic material forms a boat-shaped structure beneath the yolk. Stomo-daeal and proctodaeal invaginations are formed, but the endodermal wall of the mid-gut is absent. Development is abnormal from the time of blastoderm formation. The blastoderm is not completely cut off from the underlying yolk plasmodium, to which it remains connected by strands of cytoplasm. It is suggested that the failure of the yolk plasmodium to become clearly separated from the blastoderm accounts for the contraction of the embryo and also for the absence of the endodermal layer.
Sex-dependent expression of a transcription factor, Ad4BP, regulating steroidogenic P-450 genes in the gonads during prenatal and postnatal rat development
Authors: Hatano Osamu , Takayama Koichi , Imai Tsuneo , Waterman Michael R. , Takakusu Akira , Omura Tsuneo , Morohashi Ken-ichirou 
Published: April 2021

ABSTRACT
We investigated the expression of Ad4BP (also known as SF-1), a transcription factor regulating steroidogenic P-450 genes, in the steroidogenic tissues such as adrenal glands, testes and ovaries through the prenatal and postnatal life of rats. Ad4BP was detected in the primordial adrenal glands and gonads of the 13.5 day postcoitum (d.p.c.) fetus. After the appearance of Ad4BP, a steroidogenic P-450 (P-450(SCC)) was also detected in the adrenal glands and its amount increased gradually. In the fetal gonads of 14.5 d.p.c., a significant amount of Ad4BP was detected in the somatic cells of the testes, whereas only a trace amount was present in the ovaries. The sexually dimorphic expression of Ad4BP continued throughout the neonatal age. Drastic alterations occurred during the first to third week of postnatal age accompanied by functional and structural changes of the gonads. The expression of Ad4BP in the testes attained a maximal level one week after birth and decreased markedly thereafter. By contrast, increase of Ad4BP in the ovary was detected after the first postnatal week. Expression of P-450c17 showed a good correlation with the proliferation of Leydig cells in the testes and theca cells in the ovaries. Immunohistochemical studies revealed the presence of Ad4BP in Sertoli cells as well as Leydig cells up to the pubertal age. In the adult rat testis, however, staining of Sertoli cells decreased significantly. Ad4BP was detected in granulosa, theca, corpus luteum and interstitial gland cells in the ovary although the expression levels in granulosa cells varied among follicles. It is suggested that the Müllerian inhibitory substance gene may be a target of Ad4BP since this gene has a conserved Ad4-binding site within the promoter, which is recognized by Ad4BP expressed in the fetal testes.
Transcriptional regulation of tubulin gene expression in differentiating trochoblasts during early development of Patella vulgata
Authors: Damen Wim G. M. , van Grunsven Leo A. , van Loon André E. 
Published: April 2021

ABSTRACT
The expression of α- and β-tubulin genes during the early development of the marine mollusk Patella vulgata has been investigated. From the 32-cell stage onwards, an enhanced expression of both α- and β-tubulin mRNAs was detected in the primary trochoblasts. After one additional cleavage, these cells become cleavage-arrested and then form cilia. They are the first cells to differentiate during Patella development. Later, α- and β-tubulin mRNA is also found in the accessory and secondary trochoblasts. Together these three cell-lines form the prototroch, the ciliated locomotory organ of the trochophore larva. The early and abundant expression of tubulin genes precede and accompany cilia formation in the trochoblasts and provides us with an excellent molecular differentiation marker for these cells.
Apart from the trochoblasts, tubulin gene expression was also found in other cells at some stages. At the 88-cell stage, elevated tubulin mRNA levels were found around the large nucleus of the mesodermal stem cell 4d. In later stages, tubulin gene expression was detected in the cells that form the flagella of the apical tuft and in the refractive bodies.
An α-tubulin gene was isolated and characterized. A lacZ fusion gene under control of the 5′ upstream region of this tubulin gene was microinjected into embryos at the two-cell stage. The reporter gene product was only detected in the three trochoblast cell-lines at the same time as tubulin genes were expressed in these cells.Reporter gene product was not detected in any other cells. Thus, this 5′ upstream region of this α-tubulin gene contains all the elements required for the correct spatiotemporal pattern of expression.
Progression of an inductive signal activates sporulation in Dictyostelium discoideum
Authors: Richardson Delwood L. , Loomis William F. , Kimmel Alan R. 
Published: April 2021

ABSTRACT
spiA, a marker for sporulation, is expressed during the culmination stage of Dictyostelium development, when the mass of prespore cells has moved partly up the newly formed stalk. Strains containing a full-length spiA promoter/lacZ fusion were stained for β-galactosidase activity at intervals during development. The results indicate that expression of spiA initiates in prespore cells at the prestalk/prespore boundary (near the apex) and extends downward into the prespore mass as culmination continues. A spatial gradient of staining expands from the top of the prespore mass and intensifies until the front of activation reaches the bottom, whereupon the entire region stains darkly. The spiA promoter can be deleted to within 301 bp of the transcriptional start site with no effect on the relative strength, timing or spatial localization of expression. Further 5′ deletions from −301 to −175 reduce promoter strength incrementally, although timing and spatial expression are not affected. Deletions to −159 and beyond result in inactive promoters. Treatment of early developmental structures with 8-Br-cAMP in situ activates the intracellular cAMP-dependent protein kinase (PKA) and precociously induces spiA expression and sporulation. The absence of an apparent gradient of staining in these structures suggests that PKA is equivalently activatable throughout the prespore region and that all prespore cells are competent to express spiA. Thus, we postulate that the pattern of expression of spiA reveals the progression of an inductive signal for sporulation and suggest that this signal may originate from the prestalk cells at the apex.
lag-2 may encode a signaling ligand for the GLP-1 and LIN-12 receptors of C. elegans
Authors: Henderson Samuel T. , Gao Dali , Lambie Eric J. , Kimble Judith 
Published: April 2021

ABSTRACT
The C. elegans lag-2 gene is required for several cell-cell interactions that rely on the receptors GLP-1 and LIN-12. In this paper, we report that lag-2 encodes a putative membrane protein with sequence similarity to Drosophila Delta, a proposed ligand for the Notch receptor. Furthermore, we show that the lag-2 promoter drives expression of a reporter protein in the signaling distal tip cell (DTC) of the DTC/germline interaction. By in situ hybridization, we have found that endogenous lag-2 mRNA is present in the DTC but not the germ line. One fusion protein, called LAG-2::β-gal(intra), rescues a lag-2 null mutant and can be detected in both DTC and germ line. Taking these results together, we propose that lag-2 may encode a signaling ligand for GLP-1/LIN-12 and that the entire LAG-2 protein may be taken up into the receiving cell during induction by GLP-1 and lateral signaling by LIN-12.
Positive and negative signals from mesoderm regulate the expression of mouse Otx2 in ectoderm explants
Authors: Ang Siew-Lan , Conlon Ronald A. , Jin Ou , Rossant Janet 
Published: April 2021

ABSTRACT
Otx2, a mouse homolog of the Drosophila orthodenticle gene, is first widely expressed in the epiblast but becomes progressively restricted to the anterior third of the embryo by the headfold stage. This progressive restriction corre-lates with the anterior migration of mesoderm in the embryo, suggesting that interactions with mesoderm may be involved in setting up the anterior domain of Otx2 expression in vivo. Using explant-recombination assays, we have obtained evidence that a positive signal from anterior mesendoderm is required to stabilize expression of Otx2 in vivo, whereas a negative signal from the later-forming posterior mesendoderm represses Otx2 expression in the posterior part of the embryo. We have also found that exogenous retinoic acid can mimic the effect of this negative signal and reduces the anterior domain of Otx2 expression.
The pha-4 gene is required to generate the pharyngeal primordium of Caenorhabditis elegans
Authors: Mango Susan E. , Lambie Eric J. , Kimble Judith 
Published: April 2021

ABSTRACT
In the 4-cell Caenorhabditis elegans embryo, two blastomeres are destined to generate pharyngeal cells, each by a distinct developmental strategy: one pathway is inductive, while the other is autonomous. Here, we identify the pha-4 locus. In animals lacking pha-4 activity, an early step in pharyngeal organogenesis is blocked: no pharyngeal primordium is formed and differentiated pharyngeal cells are absent. Most other tissues are generated normally in pha-4 mutants, including cells related to pharyngeal cells by cell lineage and position. Thus, pha-4 activity is required to form the pharyngeal primordium. We propose that pha-4 marks a convergence of the inductive and autonomous pathways of pharyngeal development and suggest that establishment of pharyngeal organ identity is a crucial step for pharyngeal organogenesis.
Localization of determinants for formation of the anterior-posterior axis in eggs of the ascidian Halocynthia roretzi
Authors: Nishida Hiroki 
Published: April 2021

ABSTRACT
Unfertilized eggs of the ascidian Halocynthia roretzi are radially symmetrical along the animal-vegetal axis. After fertilization, ooplasmic segregation results in formation of an anterior-posterior axis horizontally, and eggs become bilaterally symmetrical. When 8-15% of the cytoplasm of the posterior-vegetal region of the egg was removed after the second phase of ooplasmic segregation, most of the embryos completed gastrulation but developed into radialized larvae along the animal-vegetal axis with no apparent anterior-posterior axis. Removal of cytoplasm from other regions did not affect formation of this latter axis. The cleavage pattern of the embryos that were deficient in posterior-vegetal cytoplasm (PVC) exhibited radial symmetry instead of the complicated bilateral symmetry of normal embryos. Detailed comparisons of cleavage patterns revealed the duplication of the anterior cleavage pattern in the originally posterior halves of the PVC-deficient embryos. The PVC-deficent larvae lacked muscle cells, which are normally derived from the posterior blas-tomeres. Examination of the developmental fates of the early blastomeres of the PVC-deficient embryos revealed that all of the vegetal blastomeres had assumed anterior fates. These results suggest that the PVC-deficient embryos are totally anteriorized.
When posterior-vegetal cytoplasm was transplanted to the anterior-vegetal position of PVC-deficient eggs, the axial deficiency was overcome, and reversal of the anterior-posterior axis was observed. The results of transplantation of posterior-vegetal cytoplasm to the anterior-vegetal position in normal eggs demonstrated that formation of the anterior structure is suppressed by posterior-vegetal cytoplasm. These results suggest that posterior fate is specified by the presence of posterior-vegetal cytoplasm, while anterior fate is specified by the absence of posterior-vegetal cytoplasm. Thus, posterior-vegetal cytoplasm determines the anterior-posterior axis by generating the posterior cleavage pattern and conferring posterior fates on cells, as well as by inhibiting anterior fates that would otherwise occur by default.