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  • ASTROPHYSICS  (208)
  • Life and Medical Sciences  (94)
  • Humans  (92)
  • 1990-1994  (394)
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  • 1990  (394)
  • 1
    Electronic Resource
    Electronic Resource
    A simple model for calculating residential 60-Hz magnetic fields (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 11 (1990), S. 283-296 
    Details
    ISSN: 0197-8462
    Keywords: grounding currents ; ELF ; exposure assessment ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A model is presented that permits the calculation of densities of 60-Hz magnetic fields throughout a residence from only a few measurements. We assume that residential magnetic fields are produced by sources external to the house and by the residential grounding circuit. The field from external sources is measured with a single probe. The field produced by the grounding circuit is calculated from the current flowing in the circuit and its geometry. The two fields are combined to give a prediction of the total field at any point in the house. A data-acquisition system was built to record the magnitude and phase of the grounding current and the field from external sources. The model's predictions were compared with measurements of the total magnetic field at a single location in 23 houses; a correlation coefficient of .87 was obtained, indicating that the model has good predictive capability. A more detailed study that was carried out in one house permitted comparisons of measurements with the model's predictions at locations throughout the house. Again, quite reasonable agreement was found. We also investigated the temporal variability of field readings in this house. Daily magnetic field averages were found to be considerably more stable than hourly averages. Finally, we demonstrate the use of the model in creating a profile of the magnetic fields in a home.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250110405
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  • 2
    Electronic Resource
    Electronic Resource
    Changes in the mitochondrial calcium influx and efflux properties are responsible for the decline in sperm calcium during epididymal maturation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 25 (1990), S. 186-194 
    Details
    ISSN: 1040-452X
    Keywords: Intracellular calcium ; Intracellular pH ; Mitochondira ; Epididymal sperm ; Bovine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: This study was undertaken to determine the role of calcium ion, a key regulator of the intensity and form of motility in mature demembranated sperm, in the development of motility during passage through the bovine epididymis. Cellular calcium levels in bovine caput and cauda epididymal spermatozoa were measured with three different techniques. 45Ca2+ uptake measurements revealed that net calcium uptake and Ca2+-Ca2+ exchange in caput spermatozoa were about 2 to 3 times higher than in caudal spermatozoa. Intracellular free calcium determination with the calcium fluorophore Fura 2 showed that the levels were 6 times higher in caput spermatozoa. The values for caput and caudal sperm were 875±55 nM (n = 15) and 155±6 nM (n = 24), respectively. Total cellular calcium levels quantitated by atomic absorption were 626±30 (n = 48) and 304±19 (n = 46) ng/108 sperm in caput and caudal epididymal sperm, respectively. At least one of the reasons for the high calcium content of caput epididymal sperm is the result of a higher rate and extent of mitochondrial calcium accumulation in caput compared to caudal sperm. Mitochondrial calcium uptake rates measured in digitonin permeabilized cells revealed uptake rates 2- to 3-fold higher in caput compared to caudal sperm. However, mitochondrial calcium efflux rates were identical in caput and caudal epididymal sperm. The efflux rates in both cell types were unaffected by external sodium levels but were found to be proportional to pH. Alkalinization or acidification of internal pH of intact sperm resulted in a corresponding lowering or elevation of cytoplasmic free calcium levels. We propose that external calcium has access to sperm only via the mitochondria (Vijayaraghavan and Hoskins: Cell Calcium 10:241-253, 1989) and that this mitochondrial calcium is subsequently redistributed into the cytoplasmic space as a function of the internal pH. We document for the first time that changes in mitochondrial calcium handling properties are important in epididymal sperm maturation and suggest that the acquisition of sperm motility in the epididymis could be related to these changes in sperm calcium handling properties.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080250212
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  • 3
    Electronic Resource
    Electronic Resource
    Stimulation of plasma membrane and matrix vesicle enzyme activity by transforming growth factor-β in osteosarcoma cell cultures (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 145 (1990), S. 200-206 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Transforming growth factor-β (TGFβ) serves an important role in extracellular matrix formation by stimulating the production of numerous extracellular matrix proteins by connective tissue cells and by osteoblasts or bone-forming cells. TGFβ has been shown to stimulate alkaline phosphatase (ALPase) activity in the rat osteoblast-like osteosarcoma cell line ROS 17/2.8. Previous studies have shown that this enzyme is elevated during calcification of bone and that it is enriched in matrix vesicles, an extracellular organelle associated with initial hydroxyapatite formation. To test the hypothesis that TGFβ plays a role in regulating mineral deposition in the matrix, the effects of TGFβ on ALPase and phospholipase A2, two enzymes associated with mineralization, were examined. ROS 17/2.8 cells were cultured at high and low density with recombinant human TGFβ (0.1-10 ng/ml) to examine the influence of cell maturation on response to TGFβ. Maximal stimulation of ALPase activity in the low density cultures was seen at 5 ng/ml; in high-density cultures, there was further stimulation at 10 ng/ml. There was a dose-dependent increase in ALPase activity seen in the matrix vesicles and plasma membranes in both types of cultures. Matrix vesicle ALPase exhibited a greater response to factor than did the plasma membrane enzyme. However, in low density cultures, the two membrane fractions exhibited a parallel response with greatest activity consistently in the matrix vesicles. There was a dose-dependent increase in phospholipase A2-specific activity in the plasma membranes and matrix vesicles of both high- and low-density cultures. In agreement with previous studies, TGFβ inhibited cellular proliferation 50%. The results show that addition of TGFβ stimulates the activity of enzymes associated with calcification. The effect of TGFβ is dependent on the stage of maturation of the cell. This study indicates that TGFβ may play an important role in induced bone formation, calcification, and fracture repair in addition to its role in promoting chondrogenesis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041450203
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  • 4
    Electronic Resource
    Electronic Resource
    Osteoblasts display receptors for and responses to leukemia-inhibitory factor (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 145 (1990), S. 110-119 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Specific binding of leukemia-inhibitory factor (LIF) to osteoblasts, but not multinucleated osteoclasts, was demonstrated by receptor autoradiography by *using cells isolated from newborn rat long bones. The clonal rat osteogenic sarcoma cells, UMR 106-06, which have several phenotypic properties of osteoblasts, expressed 300 LIF receptors per cell, with an apparent KD of 60 pM. Treatment of calvarial osteoblasts or UMR 106-01 cells with LIF resulted in a dose-dependent inhibition of plasminogen activator (PA) activity. Both calvarial osteoblasts and osteogenic sarcoma cells were shown by Western blotting and reverse fibrin autography to produce plasminogen activator inhibitor-1 (PAI-1), the production of which was increased by LIF treatment. Northern blot analysis revealed that LIF treatment resulted in a rapid (peak 1 hour), dose-dependent increase in mRNA for PAI-1. LIF treatment of the preosteoblast cell line, UMR 201, enhanced the alkaline phosphatase response of these cells to retinoic acid. Each of the osteoblast-like cell types (calvarial osteoblasts, UMR 106-06, and UMR 201) was shown to produce LIF by bioassay and, by using the polymerase chain reaction (PCR), was shown to express low levels of mRNA for LIF. These data establish that cells of the osteoblast lineage are targets for LIF action. The reported anabolic effects of this cytokine on bone formation in vivo could be related to inhibition of protease activity. LIF may be an important paracrine modulator in bone, or perhaps an autocrine one, based on the evidence for its production by osteoblasts and osteoblast-like cells.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041450116
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  • 5
    Electronic Resource
    Electronic Resource
    Purification of δ-aminolevulinate dehydratase from genetically engineered yeast (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 6 (1990), S. 319-330 
    Details
    ISSN: 0749-503X
    Keywords: δ-Aminolevulinate dehydratase purification ; Saccharomyces cerevisiae HEM2 transformants ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Saccharomyces cerevisiae transformed with a multicopy plasmid carrying the yeast structural gene HEM2, which codes for δ-aminolevulinate dehydratase, was enriched 20-fold in the enzyme. Beginning with cell-free extracts of transformed cells, the dehydratase was purified 193-fold to near-homogeneity. This represents a 3900-fold purification relative to the enzyme activity in normal, untransformed yeast cells. The specific activity of the purified enzyme was 16·2 μmol h-1 per mg protein at pH 9·4 and 37·5°C. In most respects the yeast enzyme resembles mammalian enzymes. It is a homo-octamer with an apparent Mr, of 275 000, as determined by centrifugation in glycerol density gradients, and under denaturing conditions behaved as a single subunit of Mr ≃ 37 000. The enzyme requires reduced thiol compounds to maintain full activity, and maximum activity was obtained in the presence of 1·0 mM-Zn2+. It is sensitive to inhibition by the heavy metal ions Pb2+ and Cu2+. The enzyme exhibits Michaelis-Menten kinetics and has an apparent Km of 0·359 mM. Like dehydratases from animal tissues, the yeast enzyme is rather thermostable. During the purification process an enhancement in total δ-aminolevulinate dehydratase activity suggested the possibility that removal of an inhibitor of the enzyme could be occurring.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320060405
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  • 6
    Electronic Resource
    Electronic Resource
    Importance of alignment between local DC magnetic field and an oscillating magnetic field in responses of brain tissue in vitro and in vivo (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 11 (1990), S. 159-167 
    Details
    ISSN: 0197-8462
    Keywords: magnetic resonance ; ionic resonance ; calcium efflux ; behavior ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The frequency dependence of the electric and magnetic (EM)-field-induced release of calcium ions from an in vitro brain tissue preparation has been shown to be a function of the density of the local DC magnetic field (BdC). In this study, we demonstrate that the relative orientation of the Bdc and the magnetic component (Bac) of a 315-Hz EM signal (15 Vrms/m and 61 nTrms) are crucial for the induced release to be observed. The induced release occurs only when the Bdc and the Bac are perpendicular, and not when they are parallel. This finding is consistent with a magnetic resonance-like transduction mechanism for the conversion of EM energy into a physicochemical change, and contrasts with the requirement for parallel Bdc and Bac components in the diatom-mobility experiments of Smith et al. A review of the exposure conditions in the rat behavioral experiments conducted by Thomas et al. identifies unhydrated calcium and zinc ions as alternatives to lithium ions as candidates for interaction under parallel magnetic-field orientations but fails to reject perpendicular orientations as an alternative basis for the phenomenon. Investigators that attempt to confirm the rat behavioral experiments should be aware of the conflicting exposure conditions that can be assumed to be operative, and they should design their experiments to test all conditions accordingly.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250110207
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  • 7
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    Isotope-edited NMR of cyclosporin A bound to cyclophilin: evidence for a trans 9,10 amide bond (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-12-07
    Description: The binding of a 13C-labeled cyclosporin A (CsA) analog to cyclophilin (peptidyl prolyl isomerase) was examined by means of isotope-edited nuclear magnetic resonance (NMR) techniques. A trans 9,10 peptide bond was adopted when CsA was bound to cyclophilin, in contrast to the cis 9,10 peptide bond found in the crystalline and solution conformations of CsA. Furthermore, nuclear Overhauser effects (NOEs) were observed between the zeta 3 and epsilon 3 protons of the methylleucine (MeLeu) residue at position 9 of CsA and tryptophan121 (Trp121) and phenylalanine (Phe) protons of cyclophilin, suggesting that the MeLeu9 residue of CsA interacts with cyclophilin. These results illustrate the power of isotope-edited NMR techniques for rapidly providing useful information about the conformations and active site environment of inhibitors bound to their target enzymes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fesik, S W -- Gampe, R T Jr -- Holzman, T F -- Egan, D A -- Edalji, R -- Luly, J R -- Simmer, R -- Helfrich, R -- Kishore, V -- Rich, D H -- New York, N.Y. -- Science. 1990 Dec 7;250(4986):1406-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Pharmaceutical Discovery Division, Abbott Laboratories, Abbott Park, IL 60064.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2255910" target="_blank"〉PubMed〈/a〉
    Keywords: Amides ; Amino Acid Isomerases/chemistry/*metabolism ; Carbon Isotopes ; Carrier Proteins/chemistry/*metabolism ; Cyclosporins/chemistry/*metabolism ; Escherichia coli/genetics ; Humans ; Leucine/analogs & derivatives/chemistry ; Magnetic Resonance Spectroscopy/methods ; Peptidylprolyl Isomerase ; Phenylalanine/chemistry ; Protein Binding ; Protein Conformation ; Recombinant Proteins/chemistry/metabolism ; Tryptophan/chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    RAG-1 and RAG-2, adjacent genes that synergistically activate V(D)J recombination (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-06-22
    Description: The vast repertoire of immunoglobulins and T cell receptors is generated, in part, by V(D)J recombination, a series of genomic rearrangements that occur specifically in developing lymphocytes. The recombination activating gene, RAG-1, which is a gene expressed exclusively in maturing lymphoid cells, was previously isolated. RAG-1 inefficiently induced V(D)J recombinase activity when transfected into fibroblasts, but cotransfection with an adjacent gene, RAG-2, has resulted in at least a 1000-fold increase in the frequency of recombination. The 2.1-kilobase RAG-2 complementary DNA encodes a putative protein of 527 amino acids whose sequence is unrelated to that of RAG-1. Like RAG-1, RAG-2 is conserved between species that carry out V(D)J recombination, and its expression pattern correlates precisely with that of V(D)J recombinase activity. In addition to being located just 8 kilobases apart, these convergently transcribed genes are unusual in that most, if not all, of their coding and 3' untranslated sequences are contained in single exons. RAG-1 and RAG-2 might activate the expression of the V(D)J recombinase but, more likely, they directly participate in the recombination reaction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Oettinger, M A -- Schatz, D G -- Gorka, C -- Baltimore, D -- GM39458/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 Jun 22;248(4962):1517-23.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Whitehead Institute for Biomedical Research, Cambridge, MA 02142.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2360047" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Base Sequence ; Biological Evolution ; Cattle ; Cell Line ; Chickens ; Cricetinae ; DNA/*genetics ; DNA Nucleotidyltransferases/*genetics ; *DNA-Binding Proteins ; Dogs ; Female ; *Gene Rearrangement, B-Lymphocyte ; *Gene Rearrangement, T-Lymphocyte ; *Homeodomain Proteins ; Humans ; Male ; Mice ; Molecular Sequence Data ; *Multigene Family ; Nuclear Proteins ; Nucleic Acid Hybridization ; Opossums ; Proteins/*genetics ; Rabbits ; Recombination, Genetic/*genetics ; Restriction Mapping ; Transfection ; Turtles ; VDJ Recombinases
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    Protease nexin-II (amyloid beta-protein precursor): a platelet alpha-granule protein (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-05-11
    Description: Protease nexin-II (PN-II) [amyloid beta-protein precursor (APP)] and the amyloid beta-protein are major constituents of neuritic plaques and cerebrovascular deposits in individuals with Alzheimer's disease and Down syndrome. Both the brain and the circulation have been implicated as sources of these molecules, although they have not been detected in blood. Human platelets have now been found to contain relatively large amounts of PN-II/APP. Platelet PN-II/APP was localized in platelet alpha-granules and was secreted upon platelet activation. Because PN-II/APP is a potent protease inhibitor and possesses growth factor activity, these results implicate PN-II/APP in wound repair. In certain disease states, alterations in platelet release and processing and clearance of PN-II/APP and its derived fragments could lead to pathological accumulation of these proteins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Van Nostrand, W E -- Schmaier, A H -- Farrow, J S -- Cunningham, D D -- GM-31609/GM/NIGMS NIH HHS/ -- HL01615/HL/NHLBI NIH HHS/ -- HL35553/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1990 May 11;248(4956):745-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Molecular Genetics, University of California, Irvine 92717.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2110384" target="_blank"〉PubMed〈/a〉
    Keywords: Amyloid/*blood/isolation & purification ; Amyloid beta-Peptides/*blood/isolation & purification ; Amyloid beta-Protein Precursor ; Antibodies, Monoclonal ; Blood Platelets/*chemistry ; Cell Fractionation ; Cytoplasmic Granules/*chemistry ; Epidermal Growth Factor/blood ; Humans ; Immunoblotting ; Plasminogen Inactivators/blood ; Platelet Activation ; Protein Precursors/*blood/isolation & purification
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    A new arbovirus from Aedes albopictus, an Asian mosquito established in the United States (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-12-21
    Description: Ten strains of a new arbovirus belonging to the Bunyamwera group (Bunyaviridae) were recovered from field-collected Aedes albopictus mosquitoes in Potosi, Missouri. This evidence indicates that this species may serve as an arbovirus vector in the United States. The urban-suburban distribution, aggressive biting behavior, and broad viral susceptibility of Ae. albopictus may lead to the transmission of viruses of known public health importance and perhaps of viruses hitherto not transmitted to humans because of the feeding pattern of their usual vectors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Francy, D B -- Karabatsos, N -- Wesson, D M -- Moore, C G Jr -- Lazuick, J S -- Niebylski, M L -- Tsai, T F -- Craig, G B Jr -- New York, N.Y. -- Science. 1990 Dec 21;250(4988):1738-40.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Vector-Borne Infectious Diseases, Centers for Disease Control, U.S. Public Health Service, Fort Collins, CO 80522.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2270489" target="_blank"〉PubMed〈/a〉
    Keywords: Aedes/*microbiology ; Animals ; Arboviruses/*isolation & purification ; Asia ; Humans ; Insect Vectors ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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