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  • ASTROPHYSICS  (162)
  • Life and Medical Sciences  (157)
  • INSTRUMENTATION AND PHOTOGRAPHY  (69)
  • METEOROLOGY AND CLIMATOLOGY  (69)
  • Lunar and Planetary Science and Exploration
  • Surface physics, nanoscale physics, low-dimensional systems
  • 2015-2019
  • 1995-1999
  • 1990-1994  (457)
  • 1930-1934
  • 1992  (457)
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  • 2015-2019
  • 1995-1999
  • 1990-1994  (457)
  • 1930-1934
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  • 1
    ISSN: 1040-452X
    Keywords: Embryonic stem cells ; Cell differentiation ; Pluripotency ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Ten embryonic stem (ES) cell lines from mink blastocysts were isolated and characterized. All the lines had a normal diploid karyotype; of the ten lines studied, five had the XX and five had the XY constitution. Testing of the pluripotency of the ES-like cells demonstrated that (1) among four lines of genotype XX, an X was late-replicating in three; both Xs were active in about one-third of cells of line MES8, and analysis of glucose-6-phosphate dehydrogenase revealed no dosage compensation for the X-linked gene; (2) when cultured in suspension, the majority of lines were capable of forming “simple” embryoid bodies (EB), and two only showed the capacity for forming “cystic” multilayer EBs. However, formation of ectoderm or foci of yolk sac hematopoiesis, a feature of mouse ES ceils, was not observed in the “cystic” EB; (3) when cultured as a monolayer without feeder, the ES cells differentiated into either vimentin-positive fibroblast-like cells or cytokeratin-positive epithelial-like cells (less frequently); neural cells appeared in two lines; (4) when injected into athymic mice, only one of the four tested lines gave rise to tumors. These were fibrosarcomas composed of fibrobalst-like cells, with an admixture of smooth muscular elements and stray islets of epithelial tissue; (5) when the ES cells of line MES1 were injected into 102 blastocyst cavities and subsequently transplanted into foster mathers, we obtained 30 offspring. Analysis of the biochemical markers and coat color did not demonstrate the presence of chimaeras among offspring. Thus the cell lines derived from mink blastocysts are true ES cells. However, their pluripotential capacities are restricted. © 1992 Wiley-Liss, Inc.
    Additional Material: 12 Ill.
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  • 2
    Publication Date: 2013-08-29
    Description: A short description of the program Stardust whose goal is to study the formation and properties of high temperature particles and gases, including silicate and carbonaceous materials, that are of interest in astrophysics and planetary science, is given. The international program was carried out in microgravity conditions in parabolic flight. A description of the laboratory equipment, conceived to perform experimental tests in reduced gravity conditions, and which is based on the gas evaporation technique, is given. The gas evaporation technique utilizes one or more heated crucible to vaporize solids materials (SiO, Mg) in a low pressure of inert or reactive gas inside of a vacuum bell jar. The vapor pressures of the materials are controlled by the temperature of the crucibles. The temperature and pressure of inert gas are also controlled. By varying the vapor pressure relative to the gas temperature and pressure, the conditions for substantial grain condensation can be controlled and grain formation measured using light scattering techniques. Thus the partial pressure for grain condensation, can be measured as a function of temperature. The gas evaporation technique has the advantage that complex chemical systems can be studied by using multiple crucibles each containing solid source material. Experimental results and future trends are addressed.
    Keywords: ASTROPHYSICS
    Type: ESA, Environment Observation and Climate Modelling Through International Space Projects. Columbus Eight (COSY-8): Utilisation of Earth Orbiting Laboratories; p 325-329
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  • 3
    Publication Date: 2019-06-28
    Description: Initial results are presented from airborne experiments investigating the vapor phase condensation in microgravity, carried out in the framework of the Stardust international program. Special attention is given to the design and operation of the experimental equipment, which includes the furnace for producing vapors from different materials and the cloud chamber in which the vapor nucleation occurs. A two-part mathematical model was developed to describe the transport processes in the nucleation chamber. Results obtained from three experimental series were conducted with Mg and Zn aboard NASA's KC-135 reduced-gravity research aircraft showed that nucleation front (smoke cloud) was quite different in appearance in microgravity from that typically observed at 1-g condition. The Mg and Zn particles exhibited significant differences in shape; there was some evidence of coagulation.
    Keywords: ASTROPHYSICS
    Type: IAF PAPER 92-0933
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  • 4
    Publication Date: 2019-07-12
    Description: Radio and optical positions are presented for southern hemisphere extragalactic sources from the Parkes 2.7 GHz survey. Sixty-one sources were observed with Mark III VLBI at 8.4 GHz between Tidbinbilla, Australia, and Hartebeesthoek, South Africa. The results presented are part of the effort to establish a global reference frame of 400 extragalactic radio sources. Radio positions with about 10 milliarcsec errors have been estimated for 39 sources not previously in the present radio reference frame catalog, and provisional positions were obtained for two additional sources, bringing the total number of catalog sources to 276. The principal source of error is the uncalibrated ionosphere. Of the remaining sources five were completely undetected, six were either too faint or too resolved, and nine had previous catalog positions. Optical positions on the FK5 system have also been measured for four southern sources using prime focus plates from the Anglo-Australian 4 m telescope with an accuracy of 0.06 arcsec. This raises to 40 the number of radio sources with accurately measured positions for their optical counterparts.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 103; 6 Ju
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 22 (1992), S. 117-126 
    ISSN: 0886-1544
    Keywords: algae ; cell division ; cytokinesis ; mitosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have used two monoclonal antibodies to demonstrate the presence and localization of actin in interphase and mitotic vegetative cells of the green alga Chlamydomonas reinhardtii. Commercially available monoclonal antibodies raised against smooth muscle actin (Lessard: Cell Motil. Cytoskeleton 10:349-362, 1988; Lin: Proc. Natl. Acad. Sci. USA 78:2335-2339, 1981) identify Chlamydomonasactin as a ∼43,000-Mr protein by Western immunoblot procedures. In an earlier study, Detmers and coworkers (Cell Motil. 5:415-430, 1985) first identified Chlamydomonas actin using NBD-phallacidin and an antibody raised against Dictyostelium actin; they demonstrated that F-actin is localized in the fertilization tubule of mating gametes. Here, we show by immunofluorescence that vegetative Chlamydomonas cells have an array of actin that surrounds the nucleus in interphase cells and undergoes dramatic reorganization during mitosis and cytokinesis. This includes the following: reorganization of actin to the ante- rior of the cell during preprophase; the formation of a cruciate actin band in prophase; reorganization to a single anterior actin band in metaphase; rearrange- ment forming a focus of actin anterior to the metaphase plate; reextension of the actin band in anaphase; presence of actin in the forming cleavage furrow during telophase and cytokinesis; and finally reestablishment of the interphase actin array. The studies presented here do not allow us to discriminate between G and F-actin. None the less, our observations, demonstrating dynamic reorganization of actin during the cell cycle, suggest a role for actin that may include the movement of basal bodies toward the spindle poles in mitosis and the formation of the cleavage furrow during cytokinesis. © 1992 Wiley-Liss, Inc.
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  • 6
    ISSN: 0730-2312
    Keywords: adipogenesis ; quiescence ; transcription ; mRNA ; nuclear factors ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The aim of this study was to address whether there is a fundamental difference in regulation of histone gene expression in cells that have become quiescent but retain the ability to proliferate, compared with those cells that have differentiated. We compared multiple levels of regulation of histone gene expression during 3T3-L1 pre-adipocyte differentiation. Confluent cells induced to differentiate by treatment with insulin, dexamethasone, and isobutylemethylxanthine initially exhibited an increased proliferative response compared with cells given serum alone. This initial differentiation response was associated with a twofold increase in both histone gene transcription and cellular histone mRNA levels, as well as with enhanced sequence-specific binding of nuclear factors to the proximal cell-cycle-regulatory element of the H4 histone promoter. Transforming growth factor β1, an inhibitor of 3T3-L1 differentiation, increased both the percentage of proliferating cells and the cellular levels of histone mRNA when given in addition to serum stimulation, but no enhancement of these parameters was observed upon addition of TGFβ1 to the differentiation treatment. Interestingly, although TGFβ1 enhanced binding of nuclear factors to the proximal cell cycle regulatory element of the histone promoter, these protein/DNA interactions were not associated with an increase in histone transcription. Our results are consistent with the down-regulation of histone gene expression at confluency being controlled primarily at the post-transcriptional level, in contrast to an increased involvement of transcriptional down-regulation at the onset of differentiation. © 1992 Wiley-Liss, Inc.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 50 (1992), S. 201-209 
    ISSN: 0730-2312
    Keywords: immunofluorescence staining ; DAPI ; microtubules ; chromatin ; digital image processing ; cell morphometry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Synchronized CHO-K1 cells and their dibutyryl c-AMP treated counterparts have been characterized by means of static and flow fluorescence cytometry at the level of nuclear DNA and cytoplasmic microtubules.In order to confirm earlier findings on synchronized population, Carnoy fixed and hydrolyzed, several new findings are here reported at the level of single intact cell. The fluorescence intensity of DAPI-stained glutaraldehyde fixed 2C cells correlates well with the average absorbance of the corresponding Feulgen-stained cells, thereby appearing also to be a measure of chromatin condensation during the G1 phase.In the early part of G1, the drastic alteration in anti-β tubulin immunostaining is shown to parallel microtubule depolymerization induced by calcium or colcemide.The known 1-2 h lengthening of the G1 period after reverse-transformation appears to correlate with a similar delay in the abrupt chromatin decondensation.The above results are discussed in terms of the role of microtubules and nuclear morphometry (and their coupling) in the control of cell cycle progression of transformed vs. fibroblast-like cells. © 1992 Wiley-Liss, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 48 (1992), S. 43-50 
    ISSN: 0730-2312
    Keywords: insulin/IGF-1 hybrid receptors ; autophosphorylation ; substrate phosphorylation ; protein tyrosine kinase ; in vitro assembly ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Classical insulin and IGF-1 receptors are α2β2 heterotetrameric complexes synthesized from two identical αβ half-receptor precursors [1,2]. Recent data strongly suggests, however, that nonidentical αβ half-receptor precursors can assemble to generate hybrid holoreceptor species both in vivo and in vitro [3-6,41]. This review focuses primarily on two types of hybrid receptors. The first type is an insulin/IGF-1 hybrid receptor generated by the association of an αβ insulin half-receptor with an αβ IGF-1 half-receptor. The second type is one formed from a wildtype (kinase-active) insulin or IGF-1 αβ half-receptor and a mutant (kinase-inactive) insulin αβ half-receptor. Although the functional properties of insulin/IGF-1 hybrid receptors have not yet been completely defined, wildtype/mutant hybrid receptors are essentially substrate kinase inactive [6]. These data indicate that the mutant αβ half-receptor exerts a transdominant inhibition upon the wildtype αβ half-receptor within the α2β2 holoreceptor complex. This defect in substrate kinase activity may contribute to the molecular defect underlying some syndromes of severe insulin resistance and diabetes. Heterozygous individuals expressing both wildtype and mutant tyrosine kinase-defective insulin receptor precursors demonstrate varying degrees of insulin resistance and diabetes [7-11]. In addition, cell lines which express both endogenous wildtype and transfected kinase-defective insulin receptors display markedly decreased insulin and IGF-1 sensitivity and responsiveness [12-14]. Formation of hybrid receptors which results in premature termination of insulin signal transduction may be one mechanism underlying the observation that kinase-inactive receptors inhibit the function of native receptors.
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  • 9
    ISSN: 0730-2312
    Keywords: carcinogenesis ; chemoprevention ; intermediate end point ; biomarkers ; differentiation ; growth factors ; lung cancer ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The need for validate intermediate end point markers to facilitate lung cancer chemointervention research is competing. Three major classes of lung markers are relevant for this application. Since lung cancer includes four distinct hitologies, markers that map degrees of histologic differentiation are important. Many of the markers for squamous differentiation overlap with the candidates for application in the study of head and neck cancer. Production of tissue-specific cell product especially for surfactant or CEA is of interest, because the gene structure is known and many differentiation-related polymorphisms exist. This strategy would be useful for adenomatous type of tissue. A second type of marker is the broad group of differentiation markers. The carbohydrates or blood group-like antigens comprise a representative example. Carbohydrate structures are expressed in a specific sequence during fetal processes, and this sequence appears to reverse with the development of a cancer. Retrodifferentiation of specific differentiation markers is the basis of a major effort to effect earlier lung cancer detection using sputum immunocytochemistry. The final class includes markers which affects either positive or negative aspects of growths. Candidates in this area include growth factors or their receptors or genes that regulate growth. If the intermediate end point marker reflects tumor biology and is in that casual path of tumor progression, serial observation of that parameter should indicate the success of the intervention. In all three of these examples the clinical material to be analyzed could be sputum specimens bonrchial biopsies or resected lung tissue. Systematic analysis of these markers in context of intervention trials required to validate their utility. Long term clinical follow up will demonstrate the degree of concordance between biomarkers and more traditional clinical trial end points and will establish if such tools can play a role in catalyzing the rate of prevention research. © 1992 Wiley-Liss, Inc.
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  • 10
    ISSN: 0730-2312
    Keywords: histone variant ; alternative 3′processing ; growth regulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract a variant human H2B histone gene (GL 105), previously shown to encode a 2300 nt replication independent mRNA, has been cloned. We demonstrate this gene expresses alternative mRNA regulated differentially during the hela S3 cell cycle. The H2B-GL105 gene encodes both a 500 nt cell cycle dependent mRNA and a 2300 nt constitutively expressed mRNA. The 3′ end of the cell cycle regulated mRNA terminates immediately following the region of hyphenated dyad symmetry typical of most histone mRNAs, whereas the constitutively expressed mRNA has a 1798 nt non-translated trailer that contains the same region of hyphenated dyad symmetry but is polyadenylated. The cap site for the H2B-GL105 mRNAs is located 42 nt upstream of the protein coding region. The H2B-GL105 histone gene was localized to chromosome region 1q21-1q23 by chromosomal in situ hybridization and by analysis of rodent-human somatic cell hybrids using an H2B-GL105 specific probe. The H2B-GL105 gene is paired with a functional H2A histone gene and this H2B/H2B gene pair is seperated by a bidirectionally transcribed intergenic promoter region containing consensus TATA and CCAAT boxes and an OTF-1 element. These results demonstrate that cell cycle regulated and constitutively expressed histone mRNAs can be encoded by the same gene, and indicate that alternative 3′ end processing may be an important mechanism for regulation of histone mRNA. Such control further increases the versatility by which cells can modulate the synthesis of replication-dependent as well as variant histone proteins during the cell cycle and at the onset of differentiation. © 1992 Wiley-Liss, Inc.
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