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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 35 (1983), S. 624-628 
    ISSN: 1432-0827
    Keywords: EGF ; DNA synthesis ; Osteoblasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Normal and malignant osteoblast-like cells in culture have been shown to possess specific, high affinity receptors for epidermal growth factor (EGF). In this study, the mitogenic response to EGF was examined in a clonal line of a rat osteogenic sarcoma (UMR 106) and in osteoblast-rich newborn rat calvarial cells. Twenty-four hour treatment of UMR 106 cells with EGF in doses ranging from 10−12 m to 2 × 10−8 m stimulated the incorporation of [3H]thymidine and DNA synthesis in a dose-dependent manner. This short-term stimulatory effect was sustained in long-term culture with a dose-dependent increase in cell proliferation by calvarial cells. A lag period of 8 h occurred before significant stimulation of [3H]thymidine incorporation was observed. Commitment to increased incorporation of [3H]thymidine required a minimum of 6 h continuous incubation with EGF. These results establish the osteoblast as a target cell for EGF action on bone.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 35 (1983), S. 294-297 
    ISSN: 1432-0827
    Keywords: Prostaglandins ; Osteoblasts ; Bone resorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The metabolism of arachidonic acid to its cyclo-oxygenase products was studied in monolayer cultures of osteoblast-rich rat calvarial cells and of clonal cell lines from a rat osteogenic sarcoma, enriched in the osteoblast phenotype. Prostanoids were measured by radioimmunoassay after extraction of media and fractionation by high pressure liquid chromatography. In both normal and malignant osteoblasts the major cyclo-oxygenase product was 6-oxo-prostaglandin F1α, the hydration product of prostacyclin, with lesser amounts of prostaglandin E2 and prostaglandin F2α. No significant thromboxane B2 was detected. Prostaglandins are thought to have a local role in the regulation of bone resorption. These results point to the possible importance of prostacyclin either in bone resorption or in some other local function, e.g., regulation of bone blood flow.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 12 (1973), S. 16-29 
    ISSN: 1432-0827
    Keywords: Bone ; Cartilage ; Culture ; Glycosaminoglycans ; Sephadex ; Collagen ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des cultures de monocouches cellulaires d'épiphyses fémorales distales d'embryons de veaux sont étudiées immédiatement après la première sub-culture, réalisée après culture primaire. L'examen au microscope optique classique montre des dépôts disséminés de matériel métachromatique: en microscopie électronique, de fines fibrilles, considérées comme des fibres de collagène, en voie de développement, ont été observées. La nature des sécrétions cellulaires a été étudiée à l'aide de précurseurs radioactifs, fractionnés sur Sephadex G200, ainsi qu'à l'aide de chromatographie par échange d'ions. La digestion enzymatique par hyaluronidase et chondroitinase AC et ABC, bactérienne et testiculaire, démontre que les cellules synthétisent 70% de glycosaminoglycanes sulfatés et 30% de glycosaminoglycanes non sulfatés. Parmi les glycosaminoglycanes, 70% sont constitués par du chondroitine-4-sulfate, 20% par du chondroitine-6-sulfate et le reste probablement par du keratane-sulfate. Les études avec des acides aminés marqués indiquent que les cellules synthétisent une protéine de poids moléculaire élevé, contenant de l'hydroxyleproline, ainsi qu'une protéine non-collagénique, mise en évidence par incorporation de tryptophane.
    Abstract: Zusammenfassung Einschichtige Zellkulturen von der distalen Femurepiphyse von Kalbsembryonen wurden nach der ersten Subkultur untersucht, welche nach der Verschmelzung der primären Kulturen angesetzt wurde. Die lichtmikroskopische Untersuchung zeigte verstreute Ablagerungen von metachromatisch gefärbtem Material; bei der Elektronenmikroskopie wurden feine Fibrillen festgestellt, welche als Collagenvorstufe angesehen wurden. Nach einer Kultur von mehreren Tagen zeigte sich eine lacunäre Anordnung der Zellen. Die Beschaffenheit der Zellsekretionen wurde mittels radioaktiv markierten Verbindungen untersucht, welche auf Sephadex G200 und durch Ionenaustausch-Chromatographie fraktioniert wurden. Die enzymatische Verdauung mit bakterieller und testikulärer Hyaluronidase und Chondroitinase-AC und-ABC zeigte, daß die Zellen 70% sulfatierte und 30% nichtsulfatierte Glycosaminoglycane synthetisierten. Die sulfatierten Glycosaminoglycane enthielten 70% Chondroitin-4-Sulfat, 20% Chondroitin-6-Sulfat, und der Rest war wahrscheinlich Keratansulfat. Untersuchungen mit markierten Aminosäuren-Vorläufern deuteten darauf hin, daß die Zellen ein Hydroxyprolinhaltiges, hochmolekuläres Protein synthetisierten und dazu etwas Eiweiß, bei dem es sich auf Grund des Tryptophaneinbaues nicht um Collagen handeln kann.
    Notes: Abstract Monolayer cell cultures from the distal femoral epiphyses of embryo calves were studied following the first subculture, which was carried out after confluence in primary culture. Light microscopic examination revealed scattered deposits of metachromatic-staining material; on electron microscopy fine fibrils considered to be developmental collagen were seen. After several days in culture lacuna-like patterns of cells were seen. The nature of the cell secretions were studied by radioactive precursors, which were fractionated on Sephadex G200 and by ion exchange chromatography. Enzyme digestion with bacterial and testicular hyaluronidase and chondroitinase-AC and-ABC revealed that the cells synthesized 70% sulphated, and 30% non-sulphated glycosaminoglycans. Of the sulphated glycosaminoglycans 70% was chondroitin-4-sulphate, 20% chondroitin-6-sulphate, and the remainder probably keratansulphate. Studies were labelled amino acid precursors suggested that the cells synthesized a high-molecular weight protein containing hydroxyproline, as well as some non-collagenous protein, shown by tryptophan incorporation
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 1 (1974), S. 0 
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: SUMMARY 1. Inorganic pyrophosphate (PPi) and diphosphonates inhibit glucagon-stimulated and fluoride-stimulated adenylate cyclase activity of rat liver.2. Concentrations of diphosphonates required to produce inhibition are lower than those of PPi, and PPi inhibited fluoride-stimulated activity to a greater extent than glucagon-stimulated activity.3. Diphosphonates have inhibitory activity in the presence and absence of an ATP regenerating system in the adenylate cyclase assay, and do not substantially affect the efficiency of the ATP regenerating system. No evidence was obtained that reversal of adenylate cyclase was responsible for PPi inhibition.4. Fluoride virtually completely inhibits pyrophosphatase activity in crude membrane preparations from rat liver, whereas glucagon has no detectable effect.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 2 (1975), S. 0 
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Incubation of parathyroid hormone with plasma membranes from rat kidney cortex resulted in rapid loss of all hormonal activity.2. Chick kidney membranes showed no ability to inactivate parathyroid hormone even with prolonged incubation.3. Biologically active, labelled parathyroid hormone was degraded to fragments by rat kidney membranes, but not by chick kidney.4. Hormone-responsive adenylate cyclase activity in a mixture of rat and chick kidney membranes was additive.5. Parathyroid hormone bound specifically to chick kidney plasma membranes.6. It is concluded that hormone inactivation during incubation has little relevance to the effectiveness of parathyroid hormone in stimulating adenylate cyclase activity in kidney, and furthermore that failure of chick kidney to metabolize the hormone is not the explanation for the greater sensitivity of this species to the hormone.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 16 (1967), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2994-3003 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sawtooth oscillations in tokamaks have been stabilized using ion cyclotron resonance heating (ICRH), but often reappear while ICRH continues. It is shown that the reappearance of sawteeth during one particular ICRH discharge in the Joint European Torus (JET) [Campbell et al., Phys. Rev. Lett. 60, 2148 (1988)] was correlated with a change of sign in the energy δW associated with m=1 internal kink displacements. To compute δW, a new analytical model is used for the distribution function of heated minority ions, which is consistent with Fokker–Planck simulations of ICRH. Minority ions have a stabilizing influence, arising from third adiabatic invariant conservation, but also contribute to a destabilizing shift of magnetic flux surfaces. As the minor radius of the q=1 surface rises, the stabilizing influence of minority ions diminishes, and the shape of the plasma cross section becomes increasingly important. It is shown that an increase in ICRH power can destabilize the kink mode: this is consistent with observations of sawteeth in JET discharges with varying levels of ICRH. It is suggested that the sawtooth-free period could be prolonged by minimizing the vertical extent of the ICRH power deposition profile.1996 American Institute of Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1623-1636 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A generalized energy principle is used to determine the effect of ion cyclotron resonant heating (ICRH) on the stability of m=1 internal kink displacements in the low-frequency limit: such displacements are associated with sawtooth oscillations. An integral expression is obtained for the contribution to the plasma energy of an ICRH-heated minority ion population with strong temperature anisotropy, which relates the former to the ICRH power input and its deposition profile. The link is provided by a realistic, but analytically tractable, new model for the distribution function of the heated ions, which is based on the approach of Stix [Nucl. Fusion 15, 737 (1975)]. Numerical evaluation of the integral expression is carried out using parameters inferred from ICRH experiments in the Joint European Torus (JET) [Campbell et al., Phys. Rev. Lett. 60, 2148 (1988)]. It is shown that the ideal m=1 internal kink is stable at values of the poloidal plasma beta βp which typically lie in the range 0.4–1, depending on the radio-frequency power input and the radius r1 of the q=1 surface. Stability is thus possible at values of βp lying significantly above the magnetohydrodynamic instability threshold ((approximately-equal-to)0.3). If the perpendicular temperature T⊥ of the hot ions exceeds the parallel temperature by a factor of 10 or more, and r1 is greater than about one-third of the plasma minor radius, trapped ions have a greater stabilizing effect than passing ions. Stabilization is most easily achieved, however, if r1 is small. The hot-ion plasma energy depends strongly on the value of T⊥, but for fixed T⊥ is insensitive to the degree of anisotropy.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 577-590 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The separation of the cylindrical tearing mode stability problem into a resistive resonant layer calculation and an external marginal ideal magnetohydrodynamic (MHD) calculation (Δ' calculation) is generalized to axisymmetric toroidal geometry. The general structure of this separation is analyzed and the marginal ideal MHD information (the toroidal generalization of Δ') required to discuss stability is isolated. This can then, in principle, be combined with relevant resonant layer calculations to determine tearing mode growth rates in realistic situations. Two examples are given: the first is an analytic treatment of toroidally coupled (m=1, n=1) and (m=2, n=1) tearing modes in a large aspect ratio torus; the second, a numerical treatment of the toroidal coupling of three tearing modes through finite pressure effects in a large aspect ratio torus. In addition, the use of a coupling integral approach for determining the stability of coupled tearing modes is discussed. Finally, the possibility of using initial value resistive MHD codes in realistic toroidal geometry to determine the necessary information from the ideal MHD marginal solution is discussed.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2909-2921 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nearly all kinetic treatments of fast wave minority heating of inhomogeneous plasma in the cyclotron range of frequencies assume the magnetic field varies in the direction perpendicular to the magnetic field. However, the toroidal magnetic field of a tokamak varies along a field line due to the rotational transform and causes a small number of trapped particles to turn in the region of cyclotron resonance. In order to include the effects of rotational transform and, hence, trapped particles in the kinetic plasma response, a simplified, concentric circle flux surface model of a tokamak is employed. The most important result of this work is the derivation of response functions for Maxwellian and bi-Maxwellian minority ions which generalize and extend previous replacement Z function forms obtained from a slab approximation of a tokamak (which also retains the variation of the strength of the magnetic field along a field line). The plasma response functions obtained include both passing and trapped ions, off-axis heating, and are valid for arbitrary minority ion concentrations. The response function for a bi-Maxwellian in the case of strong anisotropy substantially modifies the Maxwellian result. Anisotropy and the effects of toroidal geometry are illustrated graphically and tend to enter at higher toroidal mode numbers. For minority concentrations of the order or less than a critical value, the plasma response functions are used to obtain the standard transmission coefficient previously obtained for straight magnetic-field models. The expression for the transmission coefficient is shown to be valid for more general unperturbed distribution functions of pitch angle and speed on each flux surface provided k(parallel)ρ(very-much-less-than)1, where k(parallel) is the parallel wave number and ρ the minority gyroradius.
    Type of Medium: Electronic Resource
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