Astrogeology 13 - Lunar crater morphology and relative age determination of lunar geologic units Interagency report

Lunar crater morphology and age classification syste

Geologic application of thermal-inertia mapping from satellite

The author has identified the following significant results. Two night-time thermal images of the Powder River Basin, Wyoming distinctly show a major thermal feature. This feature is substantially coincident with a drainage divide and the southward facing slope appears cooler, suggesting a lower thermal inertia. An initial examination of regional geologic maps provides no clear evidence to suggest what type of geologic feature or structure may be present, although it can be noted that its northeastern end passes directly through Lead, South Dakota where the Homestake Gold Mine is located

Molecular medicine of microRNAs: structure, function and implications for diabetes

MicroRNAs (miRNAs) are a family of endogenous small noncoding RNA molecules, of 19–28 nucleotides in length. In humans, up to 3% of all genes are estimated to encode these evolutionarily conserved sequences. miRNAs are thought to control expression of thousands of target mRNAs. Mammalian miRNAs generally negatively regulate gene expression by repressing translation, possibly through effects on mRNA stability and compartmentalisation, and/or the translation process itself. An extensive range of in silico and experimental techniques have been applied to our understanding of the occurrence and functional relevance of such sequences, and antisense technologies have been successfully used to control miRNA expression in vitro and in vivo. Interestingly, miRNAs have been identified in both normal and pathological conditions, including differentiation and development, metabolism, proliferation, cell death, viral infection and cancer. Of specific relevance and excitement to the area of diabetes research, miRNA regulation has been implicated in insulin secretion from pancreatic β-cells, diabetic heart conditions and nephropathy. Further analyses of miRNAs in vitro and in vivo will, undoubtedly, enable us determine their potential to be exploited as therapeutic targets in diabetes

Geologic applications of thermal-inertia mapping from satellite

In the Powder River Basin, Wyo., narrow geologic units having thermal inertias which contrast with their surroundings can be discriminated in optimal images. A few subtle thermal inertia anomalies coincide with areas of helium leakage believed to be associated with deep oil and gas concentrations. The most important results involved delineation of tectonic framework elements some of which were not previously recognized. Thermal and thermal inertia images also permit mapping of geomorphic textural domains. A thermal lineament appears to reveal a basement discontinuity which involves the Homestake Mine in the Black Hill, a zone of Tertiary igneous activity and facies control in oil producing horizons. Applications of these data to the Cabeza Prieta, Ariz., area illustrate their potential for igneous rock type discrimination. Extension to Yellowstone National Park resulted in the detection of additional structural information but surface hydrothermal features could not be distinguished with any confidence. A thermal inertia mapping algorithm, a fast and accurate image registration technique, and an efficient topographic slope and elevation correction method were developed

Geologic application of thermal-inertia mapping from satellite

The author has identified the following significant results. Approximately 400 miles of low altitude scanner data of good quality was acquired over the Powder River Basin between 13-16 Oct. 1978. Radiometric and meteorological data from three ground stations were also acquired in support of low altitude U.S.G.S. overflights

GATA believe it: new essential regulators of pancreas development

Understanding the transcriptional mechanisms that underlie pancreas formation is central to the efforts to develop novel regenerative therapies for type 1 diabetes. Recently, mutations in the transcription factor GATA6 were unexpectedly shown to be the most common cause of human pancreas agenesis. In this issue of the JCI, Carrasco et al. and Xuan et al. investigate the role of Gata6 and its paralogue Gata4 in mouse embryonic pancreas and show that GATA factors are essential regulators of the proliferation, morphogenesis, and differentiation of multipotent pancreatic progenitors.Fil: Rodríguez Seguí, Santiago Andrés. Institut d’Investigacions Biomèdiques August Pi I Sunyer; España. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Akerman, Ildem. Institut d’Investigacions Biomèdiques August Pi I Sunyer; EspañaFil: Ferrer, Jorge. Institut d’Investigacions Biomèdiques August Pi I Sunyer; Españ

The Development of Xenopus tropicalis Transgenic Lines and their Use in Studying Lens Developmental Timing in Living Embryos

The generation of reporter lines for observing lens differentiation in vivo demonstrates a new strategy for embryological manipulation and allows us to address a long-standing question concerning the timing of the onset of differentiation. Xenopus tropicalis was used to make GFP reporter lines with &#;1-crystallin promoter elements directing GFP expression within the early lens. X. tropicalis is a close relative of X. laevis that shares the same ease of tissue manipulation with the added benefits of a diploid genome and faster life cycle. The efficiency of the Xenopus transgenic technique was improved in order to generate greater numbers of normal, adult transgenic animals and to facilitate in vivo analysis of the crystallin promoter. This transgene is transmitted through the germline, providing an accurate and consistent way to monitor lens differentiation. This line permitted us to distinguish models for how the onset of differentiation is controlled: by a process intrinsic to differentiating tissue or one dependent on external cues. This experiment would not have been feasible without the sensitivity and accuracy provided by the in vivo reporter. We find that, in specified lens ectoderm transplanted from neural tube stage donors to younger neural-plate-stage hosts, the onset of differentiation, as measured by expression of the crystallin/GFP transgene, is delayed by an average of 4.4 hours. When specified lens ectoderm is explanted into culture, the delay was an average of 16.3 hours relative to control embryos. These data suggest that the onset of differentiation in specified ectoderm can be altered by the environment and imply that this onset is normally controlled by external cues rather than by an intrinsic mechanism

Hepatocyte Nuclear Factor 3beta is Involved in Pancreatic Beta-Cell-Specific Transcription of the PDX-1 Gene

The mammalian homeobox gene pdx-1 is expressed in pluripotent precursor cells in the dorsal and ventral pancreatic bud and duodenal endoderm, which will produce the pancreas and the rostral duodenum. In the adult, pdx-1 is expressed principally within insulin-secreting pancreatic islet b cells and cells of the duodenal epithelium. Our objective in this study was to localize sequences within the mouse pdx-1 gene mediating selective expression within the islet. Studies of transgenic mice in which a genomic fragment of the mouse pdx-1 gene from kb 24.5 to 18.2 was used to drive a b-galactosidase reporter showed that the control sequences sufficient for appropriate developmental and adult specific expression were contained within this region. Three nuclease-hypersensitive sites, located between bp 22560 and 21880 (site 1), bp 21330 and 2800 (site 2), and bp 2260 and 1180 (site 3), were identified within the 5*-flanking region of the endogenous pdx-1 gene. Pancreatic b-cell-specific expression was shown to be controlled by sequences within site 1 from an analysis of the expression pattern of various pdx-1–herpes simplex virus thymidine kinase promoter expression constructs in transfected b-cell and non-b-cell lines. Furthermore, we also established that this region was important in vivo by demonstrating that expression from a site 1-driven b-galactosidase reporter construct was directed to islet b-cells in transgenic mice. The activity of the site 1-driven constructs was reduced substantially in b-cell lines by mutating a hepatocyte nuclear factor 3 (HNF3)-like site located between nucleotides 22007 and 21996. Gel shift analysis indicated that HNF3b present in islet b cells binds to this element. Immunohistochemical studies revealed that HNF3b was present within the nuclei of almost all islet b cells and subsets of pancreatic acinar cells. Together, these results suggest that HNF3b, a key regulator of endodermal cell lineage development, plays an essential role in the cell-type-specific transcription of the pdx-1 gene in the pancreas

PDX-1 is Required for Posterior Poregut Patterning and Differentiation of the Pancreas and Duodenum

The Xenopus homeobox gene, XlHbox8, has been proposed to be involved in endodermal differentiation, specifically in pancreatic and duodenal development (Wright et al., 1988. Development 105, 787-794). To test this hypothesis directly, the mouse homolog, pdx-1, was cloned and gene targeting was used to produce two separate null alleles. In one, the second pdx-1 exon, including homeobox sequences, was replaced by a neomycin resistance cassette. In the second, a lacZ reporter was fused in-frame with the N-terminus of PDX-1, replacing most of the homeodomain. Neonatal $pdx{-}1\ {-}/{-}$ mice for both mutations are apancreatic, in confirmation of the report by Jonsson et al. (Jonsson. J., Carlsson, L., Edlund, T. and Edlund, H. 1994. Nature 371, 606-609.). However, the data presented in this dissertation show that the pancreatic buds form in homozygous mutants, with the dorsal bud undergoing limited proliferation and outgrowth to form a small, irregularly branched, ductular tree. No insulin or amylase-positive cells are found in these outgrowths, but glucagon-expressing GLUT2-positive cells are found. The rostral duodenum suffers a local absence of the normal columnar epithelial lining, villi, and Brunner\u27s glands, which are replaced by a GLUT2-positive cuboidal epithelium resembling the bile duct lining. The abundance of enteroendocrine cells in the rostral duodenal villi is greatly reduced in pdx-$1\ {-}/{-}$ embryos. The PDX-1/$\beta$-galactosidase fusion allele is expressed in the pancreatic and duodenal cells in the absence of functional PDX-1, and the majority of these cells express PDX-1/$\beta$-galactosidase fusion protein into perinatal stages without changes in the boundaries or levels of expression. These results are discussed in terms of a role for pdx-1 in posterior foregut patterning, specifically in the differentiation of the pancreas and rostral duodenum

Inhibition of activin/nodal signalling is necessary for pancreatic differentiation of human pluripotent stem cells

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