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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 142 (1990), S. 592-602 
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Experiments were done on fully grown Xenopus oocytes to determine the extent and the properties of cellular water of hydration. The studies involved the osmotic shrinking and swelling of the oocytes under known osmotic pressure as well as proton NMR spectral, titration, and free induction decay analyses. Studies were done both on whole oocytes and on subcellular fractions. The results show that little if any of the oocyte water in situ has the motional or osmotic properties expected of pure "bulk" water. Four distinct water of hydration compartments were found and defined on the basis of distinct hydrogen bounding mechanisms. Some of the water in yolk platelets was found not to be in fast exchange with other water compartments. Osmotic shrinkage of oocytes caused an adaptive decrease in the bound water of hydration compartments. This osmotically induced decrease is attributed to decreased surface area available for the hydrogen bounding of water molecules on cellular proteins.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 149 (1991), S. 365-374 
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Is an intact plasma membrane responsible for keeping hemoglobin and water within the human erythrocyte? If not, what is responsible? How free is Hb to move about within the erythrocyte? To answer these questions erythrocytes were taken for phase contrast microscopy, transmission electron microscopy (TEM), determination of water-holding capacity, and proton NMR studies both before and after membrane disruption with a nonionic detergent (Brij 58). Addition of 0.2% Brij to a D2O saline solution of hemoglobin (Hb) caused particles of Hb to appear and to aggregate. This aggregation of Hb caused the amplitude of the Hb proton NMR spectra to decrease. Thus, the less mobile the Hb the lower the Hb proton spectra amplitude. Erythrocytes washed in D2O saline showed proton NMR spectra of relatively low amplitude. Addition of Brij (0.2%) to these erythrocytes caused increased Hb mobility within these erythrocytes. The TEM of fixed and thin-sectioned erythrocytes treated with Brij showed disruption of the plasma membrane of all erythrocytes regardless of whether or not they had lost Hb. Brij-permeabilized erythrocytes washed in D2O saline or in a D2O K buffer maintained a higher heavy water-holding capacity upon centrifugation as compared to nonpermeabilized erythrocytes. The TEM of Brij-treated and washed erythrocyte “shells” revealed a continuous submembrane lamina but no other evidence of cytoskeletal elements. The water-holding capacity of the erythrocyte can be accounted for by the water-holding capacity of hemoglobin. The evidence favors a relatively immobile state of Hb and of water in the erythrocyte that is not immediately dependent on an intact plasma membrane but is attributed to interactions between Hb molecules and the submembrane lamina.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The plasma membrane of erythrocytes, as of other cells, is thought to act as the barrier responsible for maintaining intracellular gradients of most ions and small molecular species between the cell and its environment. Controlled application of the nonionic detergent Brij 58 effectively opened the erythrocyte plasma membrane, as judged by electron microscopy and lipid mobilization, but the cytoplasm maintained much of its integrity for about 30 min. Release of K+ correlated well with release of protein into the surrounding medium. The results demonstrate that permeabilization of the erythrocyte plasma membrane does not result in an instantaneous equilibration of small ions, such as K+, between the cell and its environment. A comparison was made between erythrocytes treated with Brij 58 and Triton X-100. The lipid and protein solubilizing actions of Triton X-100 were not as easily separable in time as those of Brij 58. The results of treatment of the erythrocytes with different types of nonionic detergents suggest that the membranolytic and cytoplasmic protein destabilizing actions of nonionic detergents correspond with their hydrophilic-lipophilic balance numbers (HLB values). © 1994 wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 11 (1990), S. 37-45 
    ISSN: 0197-8462
    Schlagwort(e): cyclic magnetic fields ; embryogenesis ; developmental delay ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Continuous exposure of sea urchin (Strongylocentrotus purpuratus) embryos at 18°C to a cyclic 60-Hz magnetic field at 0.1 mT rms beginning 4 min after insemination caused a significant developmental delay during the subsequent 23 hours. No delay in development was recorded for periods up to 18 hours after fertilization. At 18 h, most embryos were in the mesenchyme blastula stage. At 23 h, most control embryos were in mid-gastrula whereas most magnetic-field-exposed embryos were in the early gastrula stage. Thus an estimated 1-h delay occurred between these developmental stages. The results are discussed in terms of possible magnetic-field modification of transcription as well as interference with cell migration during gastrulation. The present study extends and supports the growing body of information about potential effects of exposures to extremely-low-frequency (ELF) magnetic fields on developing organisms.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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