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  • 1
    Electronic Resource
    Electronic Resource
    Nonreceptor mediated nuclear accumulation of insulin in H35 rat hepatoma cells (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 153 (1992), S. 607-613 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We previously demonstrated that insulin accumulated in the nucleus in several cell types and partially characterized the uptake mechanisms and pathways in H35 rat hepatoma cells. Nuclear accumulation of insulin was energy independent, time, temperature, and insulin concentration dependent, but apparently nonsaturable. This study investigated further the initial endocytotic pathways that contribute to the nuclear accumulation of insulin using trypsin treatment of the cells to prevent insulin binding to its plasma membrane receptor. Total cell-associated, intracellular, and nuclear insulin were compared in control and trypsin-treated H35 hepatoma cells. Trypsin treatment markedly decreased total cell-associated and intracellular insulin as well as the nuclear accumulation of insulin when cells were incubated with 2.8 ng/ml insulin. When the cells were incubated with 100 ng/ml insulin, trypsin treatment totally inhibited insulin binding to the plasma membrane for at least 90 min. However, intracellular accumulation of insulin was reduced by only 50% at 60 min, and trypsin treatment failed to inhibit the nuclear accumulation of insulin. Chemical extraction and Sephadex G-50 chromatography revealed nuclear associated insulin in trypsin-treated cells was identical to that in control cells incubated with either 2.8 or 100 ng/ml insulin. These results suggest that a nonreceptor mediated uptake pathway, i.e., fluid-phase endocytosis, contributed significantly to the nuclear accumulation of insulin at high insulin concentrations, but at lower insulin concentrations the receptor-mediated pathway predominated. No matter which initial endocytotic route was used to internalize insulin, the insulin apparently associated with the same nuclear matrix proteins. This association of insulin with the nuclear matrix may be involved in regulation of nuclear events such as cell growth and differentiation or gene transcription. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041530323
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  • 2
    Electronic Resource
    Electronic Resource
    Behavioral sensitivity of rats to extremely-low-frequency magnetic fields (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 15 (1994), S. 411-426 
    Details
    ISSN: 0197-8462
    Keywords: operant conditioning ; Pavlovian conditioning ; magnetic field ; detection ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Work in our laboratory has revealed autonomic and/or behavioral sensitivity of mice, rats, and a domestic fowl to extremely-low-frequency (ELF) or nominally static magnetic (B) fields at flux densities between 250 and 1700 μT (rms). To extend our work, an automated exposure and data-acquisition system was used with the technique of conditional suppression to assess behavioral sensitivity to time-varying B fields. Each of five rats was exposed aperiodically to a B field during 3 min warning periods that terminated in a brief electric shock. The difference between rates of lever pressing during B-field warning periods and rates during immediately antecedent, 3 min control periods was analyzed at frequencies of 7, 16, 30, 60, and 65.1 Hz. To produce equivalent induced voltages in the rat at each frequency, graded flux densities were established that ranged from 1900 μT at 7 Hz to 200 μT at 65.1 Hz. Analysis of differences in lever-pressing rates revealed that in a given session of testing the rats would increasingly suppress responding when exposed to a B field, but this trend was independent of frequency. This experiment provides evidence of behavioral sensitivity by a mammal to an ELF magnetic field. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250150505
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  • 3
    Electronic Resource
    Electronic Resource
    Exposure to 60 Hz magnetic fields in the electric utility work environment (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 15 (1994), S. 21-32 
    Details
    ISSN: 0197-8462
    Keywords: ELF ; EMF ; exposure assessment ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Research that has attempted to examine the relationship between work exposures to magnetic fields and health effects has suffered from limited exposure information. Power-frequency electric and magnetic (EM) field exposures vary substantially between industries, occupations, and individuals. In this study magnetic field data were collected for a variety of occupational categories within an electric utility. The sampling procedures emphasized craft occupations that were presumed to have higher exposures to magnetic fields. The objectives were to provide better exposure information for an ongoing cancer mortality study, examine the relationship between different summary measures of magnetic field exposure, and make available descriptive information useful for exposure reduction and worker education. Principal components analysis (PCA) and Varimax rotation were used to explore the relationships between the different summary measures among all utility workers and among the subset of electrical craft occupations. Discriminant analysis was used to assess summary measures of exposure that differentiated occupational groups. Measurements for 770 days generated a total of 42378 hours of magnetic field data. Eleven summary indices of exposure were calculated for specific occupational groups. These include arithmetic mean, geometric mean, median, 95th and 99th percentiles, and fraction of measurements exceeding .5, 1, 5, 10, and 100 μT. Electrical craft occupations had higher work exposures than non-craft occupations. Electricians and substation operators had the highest exposures among craft occupations.We identified subsets of summary measures that were intercorrelated. The first PCA axis included the geometric mean, median, and the fractions exceeding 0.5 and 1.0 μT. This set of measures also were best at discriminating occupational groups. The relevance of these findings may become more important if consistent associations are found between particular occupations and disease and particular occupations and magnetic field summary measures. Further research is needed to evaluate these exposure assessment findings. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250150107
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  • 4
    Electronic Resource
    Electronic Resource
    Functions of the IGFs in early mammalian development (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 35 (1993), S. 421-426 
    Details
    ISSN: 1040-452X
    Keywords: Preimplantation embryo ; Protein database ; Growth factors ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The identification of growth factors and/or receptors produced by mammalian embryos or present in the maternal reproductive tract is of basic interest, as well as having practical application. Early studies established that receptors binding insulin and the insulin-like growth factors (IGFs) are expressed by preimplantation mouse embryos. These studies have been confirmed at the molecular level using RT-PCR techniques. In addition, high resolution electron microscopy has shown that insulin is internalized by the cells of the blastocyst stage mouse embryo, and that immunologically intact insulin is detectable in the cells of the trophectoderm and inner cell mass. Similar studies with gold labelled IGF-I have shown that this ligand is also bound and internalized by mouse blastocysts. However, although all blastocysts express receptors that bind IGF-I on the basolateral cell surface of the trophectoderm, only 30% exhibit apically located receptors. In order to elucidate the functions of IGFs in early mouse development, we are in the process of constructing protein databases for embryos at the eight-cell and blastocyst stage. By the use of the database, it should prove possible to elucidate targets of growth factor action. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080350417
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  • 5
    Electronic Resource
    Electronic Resource
    A large scale preparative gel electrophoresis separation of α1 and α2 subunits of the voltage-gated Ca2+ channel from rabbit skeletal muscle (1994)
    Weinheim : Wiley-Blackwell
    Electrophoresis 15 (1994), S. 1186-1190 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A large-scale preparative gel electrophoresis method effectively separates individual voltage-gated calcium channel (VGCC) subunits. with high resolution, starting with up to 4 mg of rabbit skeletal muscle L-type VGCC complex. Using this method, we separated α1 and α2 subunits of rabbit skeletal muscle VGCC with a high efficiency and with protein recoveries of 83%. The separated α1 and α2 subunits eluted from the gel in a 1:1 molar ratio. The method should be applicable for separating the other VGCC subunits or subunits of other protein complexes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501501178
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