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  • 1
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Energy dispersive x-ray microanalysis measured the Na, K, Cl, P, Mg, S, and Ca contents (mM/kg dry weight) in the nucleus, yolk-free cytoplasm, and yolk platelets of Rana pipiens oocytes quick frozen in the ovary. The data revealed that significant content changes occur in frog oocytes during intraovarian growth. All elements but Ca changed in content in the nucleus and cytoplasm, while in the yolk platelet only Na content did not change. A nucleus to cytoplasm K gradient develops and increases in magnitude during oocyte growth. The data from this and previous reports lead to the hypothesis that intra-oocytic water and elements undergo changes in state during oocyte growth and that three subcellular Na compartments exist.
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  • 2
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Crystalline lenses provided good material to study and measure the properties of cellular water. Different methods were used to establish the extent and properties of nonbulk water in mammalian lenses. These methods include: NMR titration analysis, a test of the osmotic properties, a test of dye exclusion In lenses with intact cell membranes and in lenses with disrupted cell membranes, and the water-holding capacity of lenses subjected to 40,000 × g for 1 hour with intact cell membranes and in lenses with disrupted cell membranes. The data from these methods, as well as other data from the literature, lead to the conclusion that most, if not all, of the water in lens cells (up to 2.2 g water/g dry mass) has motional and osmotic properties that distinguish it from bulk water. These findings call into question the common and convenient assumption that all but a small proportion of cellular water is like that in dilute solution.
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ultrastructural observations in combination with electron probe X-ray microanalysis on detergent (Brij 58) permeabilized (disruption of the plasma membrane) nucleated chicken erythrocytes support the view that a large fraction of cytoplasmic and nuclear K+ is not freely diffusible and that adsorption of K+ on detergent released mobilizable proteins exists within the cell. The data also suggest that the detergent proteins are normally immobilized by a detergent-resistant cytoskeleton so that they are not immediately free to diffuse from the cell for several minutes after detergent disruption of the plasma membrane.
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The release of sodium and potassium and the uptake of sucrose molecules was studied in pig lenses incubated in isosmotic sucrose solution in either the presence or absence of 1% Triton X-100 (a non-ionic detergent). This Triton X-100 treatment has been shown to cause severe disruptions of cell membrane integrity. If sodium and potassium were free in the lens fibers as in a dilute aqueous solution, they would be expected to diffuse three to four times faster than sucrose. However, measurements of sodium and potassium release and sucrose uptake in the Triton X-100 treated lenses show a 1:1 equilibration. When pig lenses were incubated in the same solution without detergent, the sucrose uptake was significantly less than the potassium and sodium release. It is postulated that a slow, detergent mediated collapse of protein-water-ion interactions within the lens is the rate-limiting step of the observed equilibration of monovalent cations and sucrose molecules.
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  • 5
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this study, the intracellular concentrations of six elements (mmole/kg dry weight) were directly measured in the muscle fibers of pectoralis major muscles of eight week old, genetically dystrophic and normal chickens by the X-ray microanalysis technique. The extent of muscle degeneration was evaluated by morphometric measurements of muscle fiber diameter and other histological changes. A significant increase in the concentration of intracellular sodium and chlorine was evident in dystrophic muscles. The concentration of intracellular sodium was 127.0 ± 35.0 in the muscle fibers of dystrophic chicks compared to 65.7 ± 16.5 in normal controls. The concentration of chlorine was 90.5 ± 27.5 and 54.1 ± 5.5 in the muscle fibers of dystrophic and normal chicks respectively. The intracellular concentrations of potassium, magnesium, phosphorous, and sulfur remained unchanged in the dystrophic condition. Morphometric studies revealed that the dystrophic pectoralis muscles contain fewer but thicker fibers per unit area compared to normal pectoralis muscles. The importance of these findings are discussed in relation to the results of earlier investigations.
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  • 6
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fully grown oocytes 1.2mm in diameter were removed from Xenopus laevis ovaries and were exposed to progesterone (2.5 μg/ml in Ringer's solution) to induce completion of the first maturation division or germinal vesicle breakdown (GVBD). This process required 5.5 ± 0.5 hr. Neither oocyte vo ume nor water content was observed to change throughout muturation. At selected times, the oocytes were quick frozen in liquid propane and cryosectioned. The sections were freeze-dried, and analyzed for K, Na, Cl, P, S, and Mg in millimolar per kilogram dry weight content in the nucleus and the yolk-free cytoplasm using electron probe X-ray microanalysis. Unstimulated oocytes showed significant nuclear to yolk-free cytoplasmic content gradients (N/C ratio) for the following elements: K (1.84), P (0.65), and S (1.56), but significant N/C content gradients were not found for Na and Mg. By 10 min after progesterone stimulation, a significant change in the N/C ratio of the following elements had occurred due to a rapid increase in nuclear content: K (2.29), Cl (2011). A significant N/C ratio for Mg (1.35) had developed by 10 min after progesterone stimulation and a significant N/C ratio for Na (2.07) had developed by 45 min. In addition the following elements showed significant content increases in both the nucleus and the yolk-free cytoplasm from the time prior to progesterone stimulation to the time just prior to GVBD at 240 min: K, Na, Cl, P, S, and Mg. Nuclear magnetic reasonance measurements of the spin-lattice relaxation time (T1) of water proton in oocytes showed a sinificant increase in the T1 time after progesterone exposure. The changes in N/C ratios of specific elements and in the physical parameter of water proton relaxation time suggest that progesterone is responsible for inducing changes in the physicochemical interactions between various macromolecules, specific elements, and water.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 116 (1983), S. 409-414 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Erythrocyte populations from newborn and mature mice were characterized according to: size; ultrastructural features; water content; concentration of intraerythrocyte elements including Na, Cl, K, P, S, Mg, and Fe; and the spin-lattice (T1) and spin-spin relaxation times of water protons as measured by nuclear magnetic resonance (NMR) spectroscopy. A significant increase in the T2 time from 142 ± 3 msec to 184 ± 3 msec occurred during erythrocyte maturation. This change in T2 time was correlated with a change from a polyribosome-rich hemoglobin-poor cell type to a polyribosome-absent hemoglobin-rich cell type. The change in T2 time could also be correlated to a significantly higher K and P concentration in the mature erythrocytes. The change in T2 time was not correlated to a change in cellular water content or to the concentration of any of the other elements measured by electron probe X-ray microanalysis. If the NMR relaxation times of water molecules truly reflect their average motional freedom, then the findings suggest that greater water ordering interaction occurs in the ribosome containing immature erythrocyte.
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  • 8
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study concerned changes in the motional properties of cellular water during the first cell cycle of fertilized sea urchin eggs (Lytechinus variegatus). There was a significant decrease in proton NMR T1 relaxation time and in cytoplasmic ice crystal growth during mitosis and a significant increase in T1 time and cytoplasmic ice crystal size during cleavage. This was not caused by egg water content changes as reflected by egg volume measurements. Removal of both the fertilization membrane and the hyaline layer shortly after fertilization did not alter the pattern of T1 time changes at mitosis and cleavage as compared to whole eggs; thus, the pattern of T1 time changes was attributed to intracellular events. Treatment of fertilized eggs with cytochalasin B, an inhibitor of actin polymerization, did not block the fall in T1 time at mitosis, but did block cytokinesis and the increase in T1 time, which normally occurred at cleavage. A significant pattern of actin disassembly and reassembly at mitosis and cytokinesis was found by studies on the total amount of monomeric actin (G actin) using the DNase I assay. This led to the hypothesis that the observed changes in T1 time and ice crystal size during the first cell cycle were due to the depolymerization and polymerization of cytoplasmic actin. To test this, the effect of the in vitro polymerization of purified actin on the T1 time and on ice crystal growth was examined. It was concluded that changes in the T1 time and ice crystal growth upon polymerization of actin in vitro resembled the changes seen in vivo. These results suggest that changes in the motional properties of cytoplasmic water during the first cell cycle are due, at least in part, to the state of polymerization of cytoplasmic actin.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS The present report describes a simple and useful method for synchronizing mass cultures of the ciliate Tetrahymena pyriformis. The method employs a nutritional approach which involves starvation of the cells in a non-nutrient phosphate buffer followed by refeeding with an enriched nutritional growth medium. It takes 240 minutes after refeeding before the first cells start to divide. Radioautographic and DNA determinations taken together show that starved cells are stalled in the GI nuclear DNA condition and that essentially all of the cells replicate their DNA prior to their first cell division.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. Heat shock and stationary-phase conditions both cause fusion of nucleoli. In both cases the process is reversed when the cell is returned to normal physiological growth conditions. Fusion of nucleoli during the cell cycle of logarithmically growing cells was not observed. Likewise, fusion of nucleoli was not observed when the Padilla and Cameron(8) method of synchronization was used. The macronuclei of cells synchronized by the 1 cold-shock per cycle method(8) more closely resembled macronuclei of log-phase cells than did the macronuclei of cells synchronized by the Scherbaum and Zeuthen(12) heat-shock method.
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