bluuebunny/crossref_metadata_2025_split huggingface dataset:
04 and A007-sulfatide antibodies bind to embryonic Schwann cells prior to the appearance of galactocerebroside; regulation of the antigen by axon-Schwann cell signals and cyclic AMP
Authors: Mirsky Rhona , Dubois Cathérine , Morgan Louise , Jessen Kristján R. 
Published: April 2021

ABSTRACT
In the rat sciatic nerve, the relationship between Schwann cells, axons, the extracellular matrix and perineurial sheath cells undergoes extensive modification between embryo day 15 and the onset of myelination during the first postnatal day. Little is known about molecular changes in Schwann cells in this important prenatal period.
In the present paper, we use immunofluorescence to study the prenatal development and postnatal regulation of the antigen(s) recognized by the 04 monoclonal antibody and a well-characterized rat monoclonal antibody to sulfatide, A007. We show that, in a series of immunochemlcal tests, the 04 antibody recognizes only sulfatide in neonatal and adult rat nerves. Both antibodies first bind to Schwann cells in the sciatic nerve at embryo day 16-17, and all Schwann cells bind both antibodies at birth. In the adult nerve, both nonmyellnforming and myelin-formlng cells are labelled with the antibodies. Schwann cells dissociated from embryo day 15 nerves and cultured in the absence of axons develop neither 04 nor A007 binding on schedule, and 04-positive and A007-positive Schwann cells from postnatal nerves lose the ability to bind these antibodies during the first few days in culture. Schwann cells in the distal stump of transected nerves also sharply down-regulate cell surface binding of 04. High numbers of 04-positive or A007-positive Schwann cells reappear in cultures treated with agents that mimic or elevate intracellular cAMP. We conclude that two anti-sulfatide antibodies 04 and A007, recognize an antigen, probably sulfatide, that appears very early in Schwann cell development (one to two days prior to galactocerebroside) but is nevertheless subject to upregulation by axonal contact or elevation of intracellular cAMP.
Curvature and spiral geometry in aggregation patterns of Dictyostelium discoideum
Authors: Foerster P. , Müller S. C. , Hess B. 
Published: April 2021

ABSTRACT
Aggregation patterns of the slime mould Dictyostelium discoideum were recorded using dark-field equipment combined with video techniques. Computerized image processing allowed the analysis of wave collision structures, expanding concentric circles and rotating spirals in terms of wave velocity and front geometry, as previously done in the Belousov-Zhabotinskii reaction, a chemical system showing similar patterns. We verified the linear relationship between the normal velocity and the curvature of wave fronts predicted by a reactiondiffusion model. The proportionality factor, which in this case is the diffusion coefficient of the chemical signal transmitter cAMP establishing communication between the cells, was determined to be 0.66×10−5cm2s-1. From measurements of positively curved circular waves, we could roughly estimate the critical radius of wave propagation (∽200//m); which means that up to 500 cells are necessary to form a center of an aggregation structure. Furthermore, we analyzed the geometrical parameters of spiral wave patterns and estimated the core radius ro to be ≈300 μm.
Colocalization of TGF-beta 1 and collagen I and III, fibronectin and glycosaminoglycans during lung branching morphogenesis*
Authors: Heine Ursula I. , Munoz Eliana F. , Flanders Kathleen C. , Roberts Anita B. , Sporn Michael B. 
Published: April 2021

ABSTRACT
The possible in vivo role of TGF-beta 1 in regulating various proteins of the extracellular matrix, including fibronectin, collagen I and III, and glycosaminoglycans, was examined by immunohistochemical methods during critical stages of lung morphogenesis in the 11-to 18-day-old mouse embryo. Sections of Bouin-fixed, paraf-fin-embedded whole embryos were exposed to polyclonal antibodies specific to synthetic peptides present in the precursor part of TGF-beta 1 (pro-TGF-beta 1), in the processed TGF-beta 1 (antibody CC), collagen J and HI, fibronectin, followed by the PAP or ABC technique to visualize the location of the antibody. GAG were stained with Alcian Blue 8GX. Our results indicate colocalization of TGF-beta 1 expression and that of matrix proteins in the developing lung when branching morphogenesis (cleft formation) and tissue stabilization occur. The presence of TGF-beta 1 at the epithelialmesenchymal interfaces of stalks and clefts at a time when matrix proteins can first be visualized in these areas, suggests a direct participation of the growth factor in the development of the basic architecture of the lung.
Expression of a homeobox gene product in normal and mutant zebrafish embryos: evolution of the tetrapod body plan
Authors: Molven Anders , Wright Christopher V. E. , Bremiller Ruth , Robertis Eddy M. De , Kimmel Charles B. 
Published: April 2021

ABSTRACT
An antibody was used to detect antigens in zebrafish that appear to be homologous to the frog homeodomain-containing protein XIHbox 1. These antigens show a restricted expression in the anteroposterior axis and an anteroposterior gradient in the pectoral fin bud, consistent with the distribution of XIHbox 1 protein in frog and mouse embryos. In the somitic mesoderm, a sharp anterior limit of expression coincides exactly with the boundary between somites 4 and 5, and the protein level fades out posteriorly. A similar, graded expression of the antigen is seen within the series of Rohon-Beard sensory neurons of the CNS. We also immunostained the mutant spt-1 (‘spadetail’), in which the trunk mesoderm is greatly depleted and disorganized in the region of XIHbox 1 expression. The defects stem from misdirected cell movements during gastrulation, but nevertheless, newly recruited cells that partially refill the trunk mesoderm express the antigen within the normal span of the anteroposterior axis. This finding suggests that the mutation does not delete positional information required for activation of the XIHbox 1 gene.
Sex determination in loggerhead turtles: differential expression of two hnRNP proteins
Authors: Harry Jenny L. , Williams Keith L. , Briscoe David A. 
Published: April 2021

ABSTRACT
Sex determination in the loggerhead turtle, Caretta caretta, is controlled by incubation temperature during a critical period of embryogenesis. As heat-shock gene expression is temperature-dependent and has been shown to be associated with early developmental regulation in several organisms, we studied the constitutive expression of hsp70 and hsp90 in embryonic brain and urinogenital tissues to see if these proteins are differentially expressed during the sex-determining period in embryos incubated at male- (26 °C) and female-(32 °C) determining temperatures. The level of expression of hsp70 and hsp90, as determined from monoclonal antibody staining, is similar in both sexes during the sexdetermining period. However, AC88, a monoclonal antibody that identifies hsp90 in several systems, recognised two additional protein bands (Mr 42 and 46xl(r), which are differentially expressed in the urinogenital tissue. of developing male and female embryos during the sex-determining period. While the 42K and 46K proteins appear in the urinogenital tissue of developing female (32 °C) embryos until stage 25, they are not expressed in the male (26 °C) urinogenital system after stage 24. Subsequent experiments have identified both turtle proteins as heterogeneous nuclear ribonucleoprotein particles (hnRNPs). As several hnRNP proteins have specific RNA-binding sites and are involved in mRNA processing reactions, the 46K protein may mediate post- transcriptional control of specific RNA transcripts required for sexual differentiation in C. caretta.
Differential growth of facial primordia in chick embryos: responses of facial mesenchyme to basic fibroblast growth factor (bFGF) and serum in micromass culture
Authors: Richman Joy M. , Crosby Zoe 
Published: April 2021

ABSTRACT
Differential growth of the three major facial primordia, the frontonasal mass, maxilla and mandible, results in a characteristic face shape. Abnormal growth of any of the primordia can lead to facial defects. In order to dissect out the factors that control growth, we developed a functional assay for cell proliferation using micromass culture and defined medium. Cell number was determined over a 4 day period and BrdU incorporation was used to determine the percentage of cells in S-phase. In defined medium, cell number progressively decreases and proliferation is very reduced in cultures of cells from all three primordia. When foetal calf serum was added, frontonasal mass cell number triples, mandible doubles and maxilla increases by half. The number of cells in S-phase increased in every case but the final cell number reflects a balance between proliferation and cell loss from the culture. The addition of basic fibroblast growth factor (bFGF) to defined medium leads to an increase in cell number in the frontonasal mass, while the cell number of mandibular and maxillary cultures is relatively unaffected. The percentage of cells in S-phase is highest in frontonasal mass cultures. Serum and bFGF both increase chondrogenesis in frontonasal mass cultures when compared to defined medium. In contrast in mandibular cultures, serum does not change the amount of cartilage and with bFGF chondrogenesis is reduced. The coordination of the changes in proliferation and differentiation in frontonasal mass cultures suggest that either these two processes are independently stimulated to the same extent or a single subpopulation of cells is stimulated to divide and differentiate into chondrocytes. The different responses of the populations of individual facial primordia to growth factors may contribute to differential growth in vivo and also be linked to the generation of facial defects.
The anterior extent of dorsal development of the Xenopus embryonic axis depends on the quantity of organizer in the late blastula
Authors: Stewart Ronald M. , Gerhart John C. 
Published: April 2021

ABSTRACT
In amphibian gastrulae, the cell population of the organizer region of the marginal zone (MZ) establishes morphogenesis and patterning within itself and within surrounding regions of the MZ, presumptive neurecto-derm, and archenteron roof. We have tested the effects on pattern of reducing the amount of organizer region by recombining halves of Xenopus laevis late blastulae cut at different angles from the bilateral plane. When regions within 30° of the dorsal midline are excluded from recombinants, ventralized embryos develop lacking the entire anterior-posterior sequence of dorsal structures, suggesting that the organizer is only 60° wide (centered on the dorsal midline) at the late blastula stage. As more and more dorsal MZ (organizer) is included in the recombinant, progressively more anterior dorsal structures are formed. In all cases, when any dorsal structures are missing they are deleted serially from the anterior end. Thus, we suggest that the amount (lateral width) of the organizer in the MZ determines the anterior extent of dorsal development.
Developmental potential of neural crest-derived cells migrating from segments of developing quail bowel back-grafted into younger chick host embryos
Authors: Rothman Taube P. , Douarin Nicole M. Le , Fontaine-Pérus Josiane C. , Gershon Michael D. 
Published: April 2021

ABSTRACT
The technique of back-transplantation was used to investigate the developmental potential of neural crest-derived cells that have migrated to and colonized the avian bowel. Segments of quail bowel (removed at E4) were grafted between the somites and neural tube of younger (E2) chick host embryos. Grafts were placed at a truncal level, adjacent to somites 14 –24. Initial experiments, done in vitro, confirmed that crest-derived cells are capable of migrating out of segments of foregut explanted at E4. The foregut, which at E4 has been colonized by cells derived from the vagal crest, served as the donor tissue. Comparative observations were made following grafts of control tissues, which included hindgut, lung primordia, mesonephros and limb bud. Additional experiments were done with chimeric bowel in which only the crest-derived cells were of quail origin. Targets in the host embryos colonized by crest-derived cells from the foregut grafts included the neural tube, spinal roots and ganglia, peripheral nerves, sympathetic ganglia and the adrenals, but not the gut. Donor cells in these target organs were immunostained by the monoclonal antibody, NC-1, indicating that they were crest-derived and developing along neural or glial lineages. Some of the crest-derived cells (NC-l-immunoreactive) that left the bowel and reached sympathetic ganglia, but not peripheral nerves or dorsal root ganglia, co-expressed tyrosine hydroxylase immunoreactivity, a neural characteristic never expressed by crest-derived cells in the avian gut. None of the cells leaving enteric back-grafts produced pigment. Cells of mesodermal origin were also found to leave donor explants and aggregate in dermis and feather germs near the grafts. These observations indicate that crest-derived cells, having previously migrated to the bowel, retain the ability to migrate to distant sites in a younger embryo. The routes taken by these cells appear to reflect, not their previous migratory experience, but the level of the host embryo into which the graft is placed. Some of the population of crest-derived cells that leave the back-transplanted gut remain capable of expressing phenotypes that they do not express within the bowel in situ, but which are appropriate for the site in the host embryo to which they migrate.
Localization of vasa, a component of Drosophila polar granules, in maternal-effect mutants that alter embryonic anteroposterior polarity
Authors: Hay Bruce , Jan Lily Yeh , Jan Yuh Nung 
Published: April 2021

ABSTRACT
Cytoplasm at the posterior pole of the early Drosophila embryo, known as polar plasm, serves as a source of information necessary for germ cell determination and for specification of the abdominal region. Likely candidates for cytoplasmic elements important in one or both of these processes are polar granules, organelles concentrated in the cortical cytoplasm of the posterior pole. Females homozygous for any one of the maternal-effect mutations, tudor, oskar, staufen, vasa, or valois give rise to embryos that lack localized polar granules, fail to form the germ cell lineage and have abdominal segment deletions. Using antibodies against a polar granule component, the vasa protein, we find that vasa synthesis or localization is affected by these mutations. In vasa mutants, synthesis of vasa protein is absent or severely restricted. In oskar and staufen mutant females, vasa synthesis appears normal, but the vasa protein is not localized. In tudor and valois mutant females, vasa is localized to the posterior pole of oocytes, but this localization is lost following egg activation. In addition to the posterior localized vasa, there is a low level of vasa distributed throughout the embryo. A function for this distributed vasa is postulated based on the observation that embryos from Bicaudal-D mothers, in which abdominal determinants are incorrectly localized to the anterior pole, do not show any ectopic vasa localization, though abdomen development at the anterior end depends on the amount of vasa protein in the embryo.
Stable lines of transgenic zebrafish exhibit reproducible patterns of transgene expression
Authors: Stuart Gary W. , V1Elkind Juergen R. , Mcmurray James V. , Westerfield Monte 
Published: April 2021

ABSTRACT
To study the frequency of germ-line transformation and to examine the reproducibility of tissue-specific trans gene expression, we produced several lines of transgenic zebrafish expressing a recombinant chloramphenicol acetyltransferase (CAT) gene. Supercoiled plasmids containing both Rous sarcoma virus and SV-40 pro moter sequences upstream of the CAT coding region were injected into zebrafish embryos prior to first cleavage. CAT activity could be detected in batches of injected embryos as early as 8 h and up to at least 12 days post-fertilization. Approximately 18 % of injected fish raised to maturity exhibited CAT activity in their fins, and approximately 5 % of injected fish became stable germ-line transformants. Breeding studies indicated that although transgenic founder fish were frequently germ-line mosaics, transgenic individuals of subsequent generations were fully hemizygous for the transgene marker. The transgenes present in the F] progeny of four independent lines were relatively well expressed in fin and skin, while lower levels of expression were observed in heart, gill and muscle. Little or no CAT expression was observed in the brain, liver and gonad. A monoclonal antibody directed against the CAT gene product consistently revealed variegated patterns of CAT expression in ectodermally derived fin epidermal cells in three of these lines. These results show that it is possible to efficiently produce stable germ-line trans formants of the zebrafish and to observe reproducible tissue-specific patterns of transgene expression in this organism. Possible mechanisms for the variegated ex pression observed within tissues are also considered.
Differential expression of TGF beta isoforms in murine palatogenesis
Authors: Fitzpatrick David R. , Denhez Fabienne , Kondaiah Paturu , Akhurst Rosemary J. 
Published: April 2021

ABSTRACT
We have studied the expression of genes encoding transforming growth factors (TGFs) beta1, beta2 and beta3 during development of the secondary palate in the mouse from 11.5 to 15.5 days postcoitum using in situ hybridisation. The RNA detected at the earliest developmental stage is TGF beta3, which is localised in the epithelial component of the vertical palatal shelf. This expression continues in the horizontal palatal shelf, predominantly in the medial edge epithelium, and is lost as the epithelial seam disrupts, soon after palatal shelf fusion. TGF betal RNA is expressed with the same epithelial pattern as TGF beta3, but is not detectable until the horizontal palatal shelf stage. TGF beta2 RNA is localised to the palatal mesenchyme underlying the medial edge epithelia in the horizontal shelves and in the early postfusion palate. The temporal and spatial distribution of TGF betal, beta! and beta3 RNAs in the developing palate, together with a knowledge of in vitro TGF beta biological activities, suggests an important role for TGF beta isoforms in this developmental pro cess.
Protein kinase C and progesterone-induced maturation in Xenopus oocytes
Authors: Varnold Robert L. , Smith L. Dennis 
Published: April 2021

ABSTRACT
Though progesterone-induced maturation has been studied extensively in Xenopus oocytes, the mechanism whereby the prophase block arrest is released is not well understood. The current hypothesis suggests that a reduction in cAMP and subsequent inactivation of cAMP-dependent protein kinase is responsible for reentry into the cell cycle. However, several lines of evidence indicate that maturation can be induced with out a concomitant reduction in cAMP. We show that the mass of diacylglycérol in whole oocytes and plasma membranes decreases 29% and 10% respectively, within the first 15 sec after the addition of progesterone. Diacylglycerol in plasma membranes further decreased 59 % by 5 min. We also show that the protein kinase C inhibitors sphingosine and staurosporine can induce oocyte maturation. In addition, the synthetic diglycer ide, DiC8, and microinjected PKC can inhibit or delay progesterone-induced maturation. These results together suggest that a transient decrease in protein kinase C activity may regulate entry into the cell cycle. The mechanism whereby DAG is decreased in response to progesterone is unclear. Initial studies show that progesterone leads to a decrease in IP3 suggesting that progesterone may act by reducing the hydrolysis of PIP2. On the other hand, progesterone caused a de crease in the amount of [3H]arachidonate labelling in DAG during the same time suggesting that progesterone may stimulate lipase activity. The relationship between postulated changes in the PKC pathway and those hypothesized for the PKA pathway are discussed.
XY female mice resulting from a heritable mutation in the primary testis determining gene, Tdy
Authors: Lovell-Badge Robin , Robertson Elizabeth 
Published: April 2021

ABSTRACT
Chimeric mice constructed with XY embryonic stem (ES) cells that had been multiply infected with a retro viral vector were used in a genetic screen to look for mutations affecting the sex determination pathway in mice. From a small number of chimeras screened one was identified that gave rise to a low proportion of XY females amongst his offspring. Analysis of the segregat ing patterns of retroviral insertions demonstrated that the mutation was found in a subset of the offspring derived from one originally infected ES cell. However, the mutation appeared to have occurred subsequent to the infection. Some of the XY females proved to be fertile, and the mutant phenotype was found to segregate exclusively with the Y chromosome. Analysis of the offspring also confirmed the absence of any retroviral insertion that could be correlated with the mutation.
Further characterisation of the Y chromosome carry ing the mutation by karyotypic analysis, and by Southern blotting with a range of Y-specific DNA probes suggested that there has been no gross deletion or rearrangement of the Y carrying the mutation. There also appeared to be no loss of Y-specific gene functions apart from that of testis determination. Moreover, the mutation is complemented by Sxr‘, the minimum portion of the mouse Y known to carry Tdy. From the phenotype and deduced location of the mutation, we conclude that it is within the Tdy locus. This is the first such mutation to be described in mice.
The marginal zone and its contribution to the hypoblast and primitive streak of the chick embryo
Authors: Stern Claudio D. 
Published: April 2021

ABSTRACT
The marginal zone of the chick embryo has been shown to play an important role in the formation of the hypoblast and of the primitive streak. In this study, time-lapse filming, fate mapping, ablation and trans plantation experiments were combined to study its contribution to these structures. It was found that the deep (endodermal) portion of the posterior marginal zone contributes to the hypoblast and to the junctional endoblast, while the epiblast portion of the same region contributes to the epiblast of the primitive streak and to the definitive (gut) endoderm derived from it. Within the deep part of the posterior marginal zone, a subpopu lation of HNK-l-positive cells contributes to the hypo blast.
Removal of the deep part of the marginal zone prevents regeneration of the hypoblast but not the formation of a primitive streak. Removal of both layers of the marginal zone leads to a primitive streak of abnormal morphology but mesendodermal cells never the less differentiate.
These results show that the two main properties of the posterior marginal zone (contributing to the hypoblast and controlling the site of primitive streak formation) are separable, and reside in different germ layers. This conclusion does not support the idea that the influence of the posterior marginal zone on the development of axial structures is due to it being the source of secondary hypoblast cells.