pinecone/core-2020-05-10-deduplication huggingface dataset:
Dlx5 Is a Positive Regulator of Chondrocyte Differentiation during Endochondral Ossification

AbstractThe process of endochondral ossification in which the bones of the limb are formed after generation of cartilage models is dependent on a precisely regulated program of chondrocyte maturation. Here, we show that the homeobox-containing gene Dlx5 is expressed at the onset of chondrocyte maturation during the conversion of immature proliferating chondrocytes into postmitotic hypertrophying chondrocytes, a critical step in the maturation process. Moreover, retroviral misexpression of Dlx5 during differentiation of the skeletal elements of the chick limb in vivo results in the formation of severely shortened skeletal elements that contain excessive numbers of hypertrophying chondrocytes which extend into ectopic regions, including sites normally occupied by immature chondrocytes. The expansion in the extent of hypertrophic maturation detectable histologically is accompanied by expanded and upregulated domains of expression of molecular markers of chondrocyte maturation, particularly type X collagen and osteopontin, and by expansion of mineralized cartilage matrix, which is characteristic of terminal hypertrophic differentiation. Furthermore, Dlx5 misexpression markedly reduces chondrocyte proliferation concomitant with promoting hypertrophic maturation. Taken together, these results indicate that Dlx5 is a positive regulator of chondrocyte maturation and suggest that it regulates the process at least in part by promoting conversion of immature proliferating chondrocytes into hypertrophying chondrocytes. Retroviral misexpression of Dlx5 also enhances formation of periosteal bone, which is derived from the Dlx5-expressing perichondrium that surrounds the diaphyses of the cartilage models. This suggests that Dlx5 may be involved in regulating osteoblast differentiation, as well as chondrocyte maturation, during endochondral ossification
Patterning of the Avian Intermediate Mesoderm by Lateral Plate and Axial Tissues

AbstractAmniote kidney tissue is derived from the intermediate mesoderm (IM), a strip of mesoderm that lies between the somites and the lateral plate. While much has been learned concerning the later events which regulate the differentiation of IM into tubules and other types of kidney tissue, much less is known concerning the earlier events which regulate formation of the IM itself. In the current study, the chick pronephros was used as a model system to identify tissues that play a role in patterning the IM and the critical time periods during which such patterning events take place. Explant studies revealed that the prospective pronephric IM is already specified to express kidney genes by stage 6, shortly after its gastrulation through the primitive streak, and earlier than previously reported. Transplant and explant experiments revealed that the lateral plate contains an activity that can repress IM formation in tissues that are already specified to express IM genes. In contrast, Hensen's node can promote formation of IM in the lateral plate. Paraxial tissues (presomitic mesoderm plus neural plate and notochord) were found to influence the morphogenesis of the nephric duct, but did not induce IM tissue to an appreciable extent. Combining lateral plate and paraxial tissue in vivo or in vitro led to induction of IM genes in the paraxial mesoderm but not in the lateral plate mesoderm. Based on these results and those of others, we propose a two-step model for the patterning of the IM. While tissue is still in the primitive streak, the prospective IM is relatively uncommitted. By stage 6, shortly after cells leave the primitive streak, a field of cells is generate which is specified to give rise to IM (Step 1). Subsequently, competing signals from the lateral plate and axial tissues modulate the number of cells that commit to an IM fate (Step 2)
Novel Activities of Mafb Underlie Its Dual Role in Hindbrain Segmentation and Regional Specification

AbstractThe bZip transcription factor Mafb is expressed in two segments of the developing vertebrate hindbrain: the rhombomeres 5 and 6. Loss of Mafb expression in the mouse mutant kreisler leads to elimination of r5 and to alterations of r6 regional identity. Here, we further investigated the role of Mafb in hindbrain patterning using gain-of-function experiments in the chick embryo. Our work has revealed novel functions for Mafb, including a positive autoregulatory activity, the capacity to repress Hoxb1 expression, and the capacity to synergise with or antagonise Krox20 activity. These different activities appear to be spatially restricted in the hindbrain, presumably due to interactions with other factors. Reinvestigation of the kreisler mutation indicated that it also results in an ectopic activation of Mafb in rhombomere 3, accounting for the previously described molecular alterations of this rhombomere in the mutant. Together, these data allow us to refine our view of the dual function of Mafb in both segmentation and specification of anteroposterior identity in the hindbrain
The Step-Wise Assembly of a Functional Nucleolus in Preimplantation Mouse Embryos Involves the Cajal (Coiled) Body

AbstractAfter fertilization, ribosomal RNA synthesis is silenced during a period which depends on the species. Data concerning the reassembly of a functional nucleolus remain scarce. We have examined by immunocytochemistry, Western blots, and BrUTP microinjection the dynamics of major nucleolar proteins during the first cycles of mouse embryogenesis, in relation to rDNA transcription sites and coilin, a marker of Cajal bodies. We show that: (1) the reinitiation of rDNA transcription occurs at the two-cell stage, 44–45 h after hCG injection (hphCG), at the surface of the nucleolar precursor bodies (NPBs), where the RNA polymerase I (pol I) transcription complex is recruited 4–5 h before; (2) the NPBs are not equal in their ability to support recruitment of pol I and rDNA transcription; (3) maternally inherited fibrillarin undergoes a dynamic redistribution during the second cell stage, together with coilin, leading to the assembly of the Cajal body around 40 hphCG; and (4) the pol I complex is first recruited to the Cajal body before reaching its rDNA template. We also find that fibrillarin and B23 are both directly assembled around NPBs prior to ongoing pre-rRNA synthesis. Altogether, our results reveal a role of the Cajal bodies in the building of a functional nucleolus
PAR-1 Is Required for Morphogenesis of the Caenorhabditis elegans Vulva

AbstractThe Caenorhabditis elegans vulva provides a simple model for the genetic analysis of pattern formation and organ morphogenesis during metazoan development. We have discovered an essential role for the polarity protein PAR-1 in the development of the vulva. Postembryonic RNA interference of PAR-1 causes a protruding vulva phenotype. We found that depleting PAR-1 during the development of the vulva has no detectable effect on fate specification or precursor proliferation, but instead seems to specifically alter morphogenesis. Using an apical junction-associated GFP marker, we discovered that PAR-1 depletion causes a failure of the two mirror-symmetric halves of the vulva to join into a single, coherent organ. The cells that normally form the ventral vulval rings fail to make contact or adhere and consequently form incomplete toroids, and dorsal rings adopt variably abnormal morphologies. We also found that PAR-1 undergoes a redistribution from apical junctions to basolateral domains during morphogenesis. Despite a known role for PAR-1 in cell polarity, we have observed no detectable differences in the distribution of various markers of epithelial cell polarity. We propose that PAR-1 activity at the cell cortex is critical for mediating cell shape changes, cell surface composition, or cell signaling during vulval morphogenesis
Nodal Signaling in Xenopus Gastrulae Is Cell-Autonomous and Patterned by β-Catenin

AbstractThe classical three-signal model of amphibian mesoderm induction and more recent modifications together propose that an activin-like signaling activity is uniformly distributed across the vegetal half of the Xenopus blastula and that this activity contributes to mesoderm induction. In support of this, we have previously shown that the activin-response element (DE) of the goosecoid promoter is uniformly activated across the vegetal half of midgastrula-stage embryos. Here, we further examine the nature of this activity by measuring DE activation by endogenous signals over time. We find that the spatiotemporal pattern of DE activation is much more dynamic than was previously appreciated and also conclude that DE(6X)Luc activity reflects endogenous nodal signaling in the embryo. Using both the DE(6X)Luc construct and endogenous Xbra and Xgsc expression as read-outs for nodal activity, and the cleavage-mutant version of Xnr2 (CmXnr2) to regionally suppress endogenous nodal activity, we demonstrate that nodal signals act cell-autonomously in Xenopus gastrulae. Nodal-expressing cells are unable to rescue either reporter gene activation or target gene expression in distant nodal-deficient cells, suggesting that nodals function at short range in this context. Finally, we show that DE activation by endogenous signals occurs in the absence of dorsal β-catenin-mediated signaling, but that the timing of dorsal initiation is altered. We conclude that nodal signals in Xenopus gastrulae function cell autonomously at short ranges and that the spatiotemporal pattern of this signaling along the dorsoventral axis is regulated by maternal Wnt-like signaling
Neurogenin3 Participates in Gliogenesis in the Developing Vertebrate Spinal Cord

AbstractTo study the role of basic helix–loop–helix (bHLH) transcription factors in gliogenesis, we examined whether bHLH transcription factors were expressed in glial precursor cells and participated in regulating oligodendrocyte and astrocyte development. As assessed by reverse transcription–polymerase chain reaction (RT-PCR), Neurogenin3 (Ngn3) was transiently expressed in bipotential glial cells fated to become either oligodendrocytes or astrocytes. Mice lacking Ngn3 displayed a loss of Nkx2.2 expression, a transcription factor required for proper oligodendrogliogenesis. Furthermore, a reduction in the expression of myelin basic protein (MBP), proteolipid protein (PLP), and glial fibrillary acidic protein (GFAP), markers for mature oligodendrocytes and astrocytes, was observed in the Ngn3 null mice. Overexpression of Ngn3 was sufficient to drive expression from the PLP promoter in transient cotransfection assays. Overall, the data suggest that Ngn3 may regulate glial differentiation at a developmental stage prior to the segregation of the oligodendrocyte and astrocyte lineage
Runnin' with the Dvl: Proteins That Associate with Dsh/Dvl and Their Significance to Wnt Signal Transduction

AbstractWnt proteins transmit myriad intercellular signals crucial for the development and homeostasis of metazoan animals from Hydra to human. Abnormal Wnt signaling causes a growing number of diseases, including cancer and osteoporosis. Depending on the context, a given Wnt signal may denote: cell proliferation or apoptosis; cell fate determination, differentiation, or stem cell maintenance; a variety of changes in cell behavior; and/or coordinated interactions with its neighbors. Which event(s) occur in Wnt-responsive cells depends critically on the ability of Dishevelled (Dsh)/Dvl proteins to interpret distinct types of intracellular, receptor-generated stimuli and transmit them to at least two distinct sets of effector molecules, all while apparently ignoring a third type of Wnt-generated Ca2+ signal. The three conserved domains present in Dsh/Dvl proteins uniquely function in each Wnt pathway, in part by association with 18 (and counting) Dsh/Dvl-associated proteins. The latest data suggest that Dsh/Dvl proteins organize dynamic, pathway-specific subcellular signaling complexes that ensure correct information routing, signal amplification, and dynamic control through feedback regulation. The biochemical and cell biological mechanisms by which Dsh/Dvl proteins accomplish these remarkable tasks remain obscure
Expression Profiling of Placentomegaly Associated with Nuclear Transplantation of Mouse ES Cells

AbstractTransplantation of nuclei (NT) from engineered mouse ES cells is a potentially powerful and rapid route to create knockout mice, obviating the need for matings to obtain germ-line chimeras. However, such an application is currently impossible, because NT often results in abnormalities in embryo and placenta. Although the epigenetic instability of several imprinted genes in ES cells and ES-derived NT mice has been demonstrated, it is not clear yet what causes the abnormalities. To gain perspective on the extent and types of changes, we have done gene expression profiling for mouse placentas produced by NT of ES cells and compared them with the expression profiles of placentas produced by NT of one-cell embryos. Based on microarray studies with the NIA 15K mouse cDNA collection, we report five principal aberrant events: (1) inappropriate expression of imprinted genes; (2) altered expression of regulatory genes involved in global gene expression, such as DNA methyltransferase and histone acetyltransferase; (3) increased expression of oncogenes and growth promoting genes; (4) overexpression of genes involved in placental growth, such as Plac1; and (5) identification of many novel genes overexpressed in ES-derived NT mouse placentas, including Pitrm1, a new member of the metalloprotease family. The results indicate that placentomegaly in ES-derived NT mice is associated with large-scale dysregulation of normal gene expression patterns. The study also suggests the presence of two regulatory pathways that may lead to histologically discernable placentomegaly. The discovery of groups of genes with altered expression may provide potential targets for intervention to mimic natural regulation more faithfully in NT mice
Neuronal Differentiation from Postmitotic Precursors in the Ciliary Ganglion

AbstractIn the chick ciliary ganglion, neuronal number is kept constant between St. 29 and St. 34 (E6–E8) despite a large amount of cell death. Here, we characterize the source of neurogenic cells in the ganglion as undifferentiated neural crest-derived cells. At St. 29, neurons and nonneuronal cells in the ciliary ganglion expressed the neural crest markers HNK-1 and p75NTR. Over 50% of the cells were neurons at St. 29; of the nonneuronal cells, a small population expressed glial markers, whereas the majority was undifferentiated. When placed in culture, nonneuronal cells acquired immunoreactivity for HuD, suggesting that they had commenced neuronal differentiation. The newly differentiated neurons arose from precursors that did not incorporate bromodeoxyuridine. To test whether these precursors could undergo neural differentiation in vivo, purified nonneuronal cells from St. 29 quail ganglia were transplanted into chick embryos at St. 9–14. Subsequently, quail cells expressing neuronal markers were found in the chick ciliary ganglion. The existence of this precursor pool was transient because nonneuronal cells isolated from St. 38 ganglia failed to form neurons. Since all ciliary ganglion neurons are born prior to St. 29, these results demonstrate that there are postmitotic neural crest-derived precursors in the developing ciliary ganglion that can differentiate into neurons in the appropriate environment
Fast and robust stereo matching algorithms for mining automation

The mining environment, being complex, irregular and time varying, presents a challenging prospect for stereo vision.  For this application, speed, reliability, and the ability to produce a dense depth map are of foremost importance.  This paper evaluates a number of matching techniques for possible use in a stereo vision sensor for mining automation applications. Area-based techniques have been investigated because they have the potential to yield dense maps, are amenable to fast hardware implementation, and are suited to textured scenes. In addition, two non-parametric transforms, namely, the rank and census, have been investigated. Matching algorithms using these transforms were found to have a number of clear advantages, including reliability in the presence of radiometric distortion, low computational complexity, and amenability to hardware implementation
Seasonal patterns and long-term trends in an estuarine upwelling ecosystem (Ria de Vigo, NW Spain)

16 páginas, 10 figuras, 4 tablasThermohaline properties, nutrient salts, chlorophyll a and meteorological variables have been intensively monitored since\ud
February 1987 in the Ría de Vigo (NW Spain), in order to examine the temporal variability and the relationships between\ud
these variables over different time scales. In this paper, the seasonal and the long-term components of the 1987–92 time\ud
series are analysed. The seasonal changes in thermohaline properties are forced by meteorological factors, but whereas\ud
temperature shows a well-defined annual cycle, salinity presents a higher frequency variation pattern due to the influence\ud
of upwelling–downwelling events and runoff. Nutrient concentrations change in a regular way through the seasons, so\ud
that characteristic and well-defined cycles are observed, but they are different for each nutrient and, for a given nutrient,\ud
exhibit a marked contrast between surface and bottom layers. The seasonal changes of nutrients are not explainable by\ud
advection and water column processes alone; fractionation of nutrients during recycling and, presumably, sedimentary\ud
processes should also play an important role. The annual cycle of chlorophyll a shows a bimodal pattern, which\ud
corresponds with the development of the spring and autumn blooms; even though the seasonal cycle accounts for an\ud
important amount of the observed temporal variability, variation at lower time scales is also important. Long-term trends,\ud
as a change in the mean level of the analysed time series, have been observed for most of the variables. Salinity increased\ud
and temperature decreased both for surface and bottom series. The largest trend, in terms of the percentage to the\ud
observed variability it represents, was an increase in bottom salinity. In relation to nutrient salts, there was no evidence\ud
of increasing eutrophication, although surface dissolved inorganic nitrogen, and surface and bottom phosphate increased\ud
slightly. Chlorophyll a concentration showed a decreasing trend, especially at the surface. The observed long-term trends\ud
could be attributed to changes of the meteorological factors that operate through an increase in the estuarine residual\ud
circulation.Support for this work came from CICYT project\ud
AMB 92-0165 and EC MAST project CT90-\ud
0017.Peer reviewe
A non-stationary box model to determine residual fluxes in a partially mixed estuary, based on both thermohaline properties: Application to the Ria de Arousa (NW Spain)

14 páginas, 1 apéndice, 10 figurasAn improved two-layered box model for calculating the residual fluxes in a Spanish ria is developed in the present paper.\ud
This kinematic bi-dimensional model has two characteristics that make it different to previous models. Firstly, for\ud
calculating the horizontal and vertical velocities and also vertical diffusion coefficients, the present model takes into\ud
account the distribution not only of salinity but also of temperature. Evaluation of both river discharge and heat exchange\ud
between water surface and atmosphere is required. Two sets of fluxes are computed; one for the distribution of salinity,\ud
and another for that of temperature. They are then weight-averaged according to the vertical gradient of both properties.\ud
Secondly, and due to the high density of sampling (twice a week), it is possible to introduce the non-stationary term in\ud
the convection–diffusion equation; thus, time variations of both conservative tracers are taken into account. Coherent\ud
solutions of equations are obtained in strong upwelling–downwelling and/or very low river volume situations where the\ud
estuary behaves virtually as a well-mixed estuary, and salt balance/non-stationary box models described previously were\ud
inapplicable. The strong coupling between estuarine circulation and upwelling is shown, and an equation is proposed in\ud
order to quantify this relationship. On the hypothesis of linear variation of thermohaline properties with time, fluxes at the\ud
intermediate time between two samplings were also calculated. Comparison of salinity between two stations at the mouth\ud
of the ria allows the computation of the correction due to Coriolis outward flux deflection, which was then applied to the\ud
whole riaThis work was supported\ud
by Grant MAR88-0245 of the Comision\ud
Interministerial de Ciencia y Tecnología (CICYT),\ud
and resources from the Consellería de Pesca de la\ud
Xunta de Galicia.Peer reviewe
Modelling thermohaline properties in an estuarine upwelling ecosystem (Ria de Vigo: NW Spain) using Box-Jenkins transfer function models

18 páginas, 7 tablas, 10 figurasSince 1987, twice weekly, hydrological variables have been monitored at a fixed station in the Ría de Vigo (NW Spain),\ud
aiming to examine the time scales of variability and the relationships to meteorological conditions. The present paper\ud
analyses: (1) the advantage of Box-Jenkins transfer function (TF) models (single output–multiple input), a type of linear\ud
stochastic model, to describe the dynamic behaviour of the system; and (2) the coupling between the Ría and\ud
meteorological events at the time scale of autonomy of this coastal inlet affected by the Iberian coastal upwelling,\ud
approximately a fortnightly period. In order to achieve these objectives, thermohaline properties have been used to\ud
characterize the estuarine ecosystem (output variables), while wind regime, runoff in the drainage basin and incoming\ud
solar radiation have been considered as the main forcing variables (input variables). The use of the amplitude time series,\ud
derived from principal component analysis (PCA) applied to the deseasonalized meteorological variables, is also explored\ud
as a different set of input variables.\ud
When compared with standard regression models, all TF models built to describe thermohaline behaviour had reduced\ud
residual variance. Similar TF models, as well as percentage of explained variance, were also obtained when meteorological\ud
variables or the amplitude time series were used as input variables. The fitted TF models provided an insight into the\ud
‘ inertial ’ behaviour of the system and the time scales of coupling of the system with the forcing variables. The plausible\ud
physical mechanisms which link the response of the system with the observed meteorological variability are also discussed.\ud
As could be expected, bottom thermohaline properties show a stronger inertial behaviour than the surface ones, which is\ud
particularly marked for bottom temperature. Besides, the shelf domain, by means of upwelling-downwelling events,\ud
strongly influences surface and bottom temperature, as well as bottom salinity; by contrast, surface salinity is mainly\ud
influenced by the effect of wind along the main axis of the Rı´a and runoff. In relation to the time scales of coupling\ud
between the system and the forcing variables, thermohaline properties show a dependance with the meteorological\ud
conditions in, at least, the immediately preceding fortnight period. It was concluded that: (1) TF models that incorporate\ud
meteorological information described the dynamic behaviour of the system adequately; and (2) this type of model can be\ud
useful as a first approximation to develop more sophisticated (deterministic) models, since, with the purpose of modelling\ud
any state variable of the system, both the coupling between different domains and the time scales of the interactions must\ud
be taken into accountSupport for this work came from CICYT Project\ud
AMB 92-0165Peer reviewe