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  • 1
    Electronic Resource
    Electronic Resource
    Engagement of the Osteoclast Integrin αvβ3 by Osteopontin Stimulates Phosphatidylinositol 3-Hydroxyl Kinase Activityb (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 760 (1995), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1995.tb44627.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of Phorbol Ester, Cyclic Nucleotides, and Ionomycin on Ion Transport and Brush-Border Topography in Cultured Renal Proximal Tubular Cells (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 494 (1987), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1987.tb29525.x
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  • 3
    Electronic Resource
    Electronic Resource
    Hormone-Like Activity of Human Thrombin (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 485 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb34595.x
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  • 4
    Electronic Resource
    Electronic Resource
    Parathyroid hormone-induced changes of the brush border topography and cytoskeleton in cultured renal proximal tubular cells (1986)
    Springer
    The journal of membrane biology 92 (1986), S. 151-162 
    Details
    ISSN: 1432-1424
    Keywords: kidney ; parathyroid hormone ; angiotensin II ; calcium ; brush border ; cytoskeleton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In order to examine the possibility of parathyroid hormone-mediated ultrastructural rearrangements in target epithelium, isolated canine renal proximal tubular cells were grown on a collagen-coated semipermeable membrane in a defined medium. Scanning and transmission electron microscopy of these monolayers revealed abundant microvilli. Exposure of the proximal tubular cells to parathyroid hormone resulted in a biphasic changes involving: (1) dramatic shortening and rarefaction of microvilli within 1 min; and (2) recovery of microvillar topography after 5 min. A similar shortening of microvilli was observed following exposure to ionomycin, whereas incubation with cyclic AMP resulted in an elongation of microvilli. Parathyroid hormone stimulated cyclic AMP production and increased cytoplasmic free calcium concentration in cultured proximal tubular cells. Pretreatment of cells with a calmodulin inhibitor abolished the effect of parathyroid hormone on brush border topography. Shortening of microvilli was associated with a disappearance of microvillar core filaments. Staining of F-actin with fluoresceinphalloidin showed that parathyroid hormone resulted in fragmentation of stress fibers. It is concluded that parathyroid hormoneinduced cell activation involves cytoplasmic-free calcium, calmodulin, and the cytoskeleton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870704
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  • 5
    Electronic Resource
    Electronic Resource
    Transcytosis in cultured proximal tubular cells (1986)
    Springer
    The journal of membrane biology 93 (1986), S. 237-247 
    Details
    ISSN: 1432-1424
    Keywords: pinocytosis ; proximal tubule ; Lucifer Yellow ; quin-2 ; 1-oleoyl-2-acetyl-glycerol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Studies were designed to examine fluid-phase pinocytosis in proximal tubular cells. Canine proximal tubules were obtained from the band IV of Percoll® gradient centrifugation of the dispersed renal cortex, and were seeded on collagen-coated polycarbonate membranes. Integrity of monolayers was confirmed by electrophysiologic measurements, and by scanning electron microscopy. At confluence cell monolayers were studied in Ussing chambers. The rate of transfer of a marker of fluidphase pinocytosis, Lucifer Yellow CH, from the luminal to the basolateral bath was three times higher than that occurring in the opposite direction. Fluorescence microscopy demonstrated that Lucifer Yellow was trapped exclusively in the vesicular compartment. Electron microscopy of the monolayers incubated with cationized ferritin added to the luminal or to the basolateral bath revealed that endocytic vesicles were formed only at the luminal surface. Luminal-to-basolateral transfer of Lucifer Yellow was almost completely blocked at 0°C, and was significantly diminished by K+ depletion. Transcytosis of Lucifer Yellow was stimulated twofold by 1-oleoyl-2-acetyl-glycerol. Transfer of quin-2 acetoxymethylester across the monolayer was used as a marker of the paracellular pathway, demonstrating the lack of directional selectivity of this transport route. In summary, vectorial fluid-phase pinocytosis in proximal tubular cells represents an additional mechanism contributing to fluid transport in this segment of the nephron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871178
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  • 6
    Electronic Resource
    Electronic Resource
    Ca2+ uptake by endoplasmic reticulum of renal cortex. II. Effects of uninephrectomy and parathyroidectomy (1992)
    Springer
    Calcified tissue international 51 (1992), S. 42-47 
    Details
    ISSN: 1432-0827
    Keywords: Kidney ; Endoplasmic reticulum ; Calcium ; In vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Calcium uptake by the endoplasmic reticulum (ER) is important for cellular calcium homeostasis, yet its regulation in nonmuscle cells is poorly understood. We reported that Ca2+ uptake by a light fraction of canine renal cortical ER (LER) is stimulated by protein kinase C in vitro. Here we describe conditions in vivo that stimulated renal cortical LER Ca2+ uptake. Thirty minutes after contralateral nephrectomy in the dog, 45Ca2+ uptake into renal cortical LER was increased 42% above control LER. There was no difference in LER Ca2+ uptake 24 hours after uninephrectomy. Acute denervation did not reproduce the increase in LER 45Ca2+ uptake seen at 30 minutes after uninephrectomy, nor did prior thyroparathyroidectomy abolish it. Forty-eight hours after thyroparathyroidectomy, 45Ca2+ uptake activity into renal cortical LER was decreased ≈sevenfold. In a proximal tubular cell line (LLC-PK1), 30-minute incubation with 12-O-tetradecanoylphorbol-13-acetate doubled 45Ca2+ uptake into a nonmitochondrial pool. Pretreatment with epidermal growth factor halved ER Ca2+ uptake, whereas insulin-like growth factor and growth hormone, alone or in combination, had no effect. Our data suggest that Ca2+ uptake into renal cortical ER is stimulated acutely during compensatory renal growth, perhaps through protein kinase C, and is stimulated chronically by parathyroid hormone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296216
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  • 7
    Electronic Resource
    Electronic Resource
    Ca2+ uptake by endoplasmic reticulum of renal cortex. I. Ionic requirements and regulation in vitro (1992)
    Springer
    Calcified tissue international 51 (1992), S. 35-41 
    Details
    ISSN: 1432-0827
    Keywords: Kidney ; Endoplasmic reticulum ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A subcellular fraction enriched in cytochrome c reductase (7.9-fold) and relatively de-enriched (0.64-fold) in Na+/K+-ATPase was prepared from canine kidney cortex by sucrose density gradient ultracentrifugation. It was shown by electron microscopy to consist primarily of a light fraction of endoplasmic reticulum (LER). LER vesicles displayed ATP-dependent 45Ca2+ uptake that was insensitive to 10 mM KCN or NaN3, and was promptly released by 20 μM A23187 or ionomycin. Inositol-1,4,5-trisphosphate (IP3) appeared to produce a time-dependent release of 45Ca2+. Vanadate inhibited 45Ca2+ uptake with a Ki≈0.3 mM, further suggesting that the activity resided in the ER rather than the plasma membrane. 45Ca2+ uptake by LER, at 5 μM total [Ca2+], displayed a strong dependence on divalent cations (Mg2+〉Co2+〉Mn2+≫Ba2+≥Cd2+≥Sr2+, present at 2 mM) as well as on monovalent cations (Na+≥K++Na+ 〉K+〉Li+〉choline+), and anions (Cl-〉acetate-≥NO3 -≥F-〉H2PO4 -≫gluconate-≥oxalate=≫SO4 =). It had a fairly narrow pH optimum (7.25–7.50). Preincubation (10 min) of LER vesicles with 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated LER Ca2+ uptake; this effect was enhanced in the presence of renal cytosol [5% (vol/vol)]. However, Ca2+ uptake was not affected by preincubation with dibutyryl cyclic AMP, calmodulin, or 1,25-(OH)2-vitamin D3, either in the absence or presence of renal cytosol. Thus, the Mg2+-ATP dependent 45Ca2+ uptake activity of this canine renal cortical LER fraction displays modulation by IP3, TPA, and pH that appears to be physiologically relevant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296215
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  • 8
    Electronic Resource
    Electronic Resource
    Monitoring cytosolic calcium in parathyroid hormone target cells: Osteoblasts and renal epithelia (1991)
    Springer
    Methods in cell science 13 (1991), S. 217-227 
    Details
    ISSN: 1573-0603
    Keywords: monolayer kidney culture ; intracellular calcium ; fluorescent dyes ; photon counting ; video image analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe methods for measuring cytosolic-free calcium concentrations [Ca2+]i in cell monolayers, using the calcium-sensitive fluorescent probe fura-2. The system is based on a commercially available microspectrofluorometer, to which some additional hardware has been added to improve memory capability and time-resolution. Cells grown on glass cover slips can be observed and studied through an inverted microscope, coupled to the fluorometer. [Ca2+]i can be monitored in real-time by either photon counting or video image analysis. These two techniques can be used selectively to take full advantage of their respective potentials: photon counting provides high sensitivity and time-resolution for experiments on single cells, whereas video imaging offers a spatial resolution of the calcium signal among the cell population and within single cells. The method can be applied to both primary cultures of dispersed proximal tubular cells as well as to immortalized or transformed cell lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02388130
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  • 9
    Electronic Resource
    Electronic Resource
    Membrane potential and cation content of osteoblast-like cells (UMR 106) assessed by fluorescent dyes (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 131 (1987), S. 434-441 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A number of cellular functions have recently been associated with alterations of the membrane potential in non-excitable cells. To assess the electrophysiologic regulation of osteoblast function, a method for measuring the membrane potential (Em) of a rat osteogenic sarcoma cell line (UMR 106) by the voltage-sensitive oxonol dye di-BA-C4(3) was developed. The fluorescent signal of di-BA-C4(3) was calibrated through a null point method using the protonophore FCCP. At null point, Em is equivalent to H+ equilibrium potential, and may be calculated by the Nernst equation. Intracellular pH (pHi) changes induced by the protonophore were monitored using BCECF, a pH-sensitive fluorescent probe. In the presence of FCCP, intracellular pH was found to be linearly correlated to extracellular pH (pHo). Therefore, the value of pHi at null point was extrapolated as well. With this technique, we estimated the plasma membrane potential of the “putative” rat osteoblasts (UMR 106) as - 28.3 ± 4.0 mV (n = 10). This method corrected the 16% overestimation of Em derived from the assumption that pHi does not change during the calibration procedure, as described in previous studies employing pH null point techniques. With null point methods, using BCECF and the carboxylic ionophores nigericin and monensin, intracellular concentrations of potassium and sodium were also measured and found to be 125 ± 0.7 mM (n = 3) and 24 ± 5.3 mM (n = 3), respectively. Although the Em of UMR 106 cells was dependent on extracellular potassium concentration, these cells did not behave as a potassium electrode. The sodium/potassium permeability ratio, calculated by the Goldman equation, was estimated at 0.317. This high membrane permeability to sodium may contribute to the genesis of the low plasma membrane potential of UMR 106 cells.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041310316
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  • 10
    Electronic Resource
    Electronic Resource
    Alpha1-adrenergic stimulation and cytoplasmic free calcium concentration in cultured renal proximal tubular cells: Evidence for compartmentalization of quin-2 and fura-2 (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 128 (1986), S. 466-474 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study was designed to examine the role of changes in cytoplasmic free calcium concentration ([Ca2+]i) during the response to α1-adrenergic agonists in cultured renal proximal tubular cells. Experiments were carried out on primary cultures of canine proximal tubular cells grown in defined culture medium on a solid support, on collagen-coated polycarbonate membranes, or on collagen-coated glass coverslips. Quin-2 and fura-2 were used to monitor [Ca2+]i. The basal level of [Ca2+]i was 101 nM, as measured with quin-2, and 122 nM, as determined using fura-2. Fluorescence flow cytometry revealed that about 85% of the population of proximal tubular cells responded to phenylephrine with an increase in [Ca2+]i. Phenylephrine (10-5 M) caused an immediate actual increase in [Ca2+]i by 18 and 24%, as determined with quin-2 and fura-2, respectively, with the peak increase in [Ca2+]i averaging 22% and 44% over the basal level (180-300 sec). This effect did not require extracellular calcium. The effect of phenylephrine was abolished by prazosin and verapamil. Fluorescence microscopy of quin-2 or fura-2 loaded cells revealed punctate areas of fluorescence within the cytoplasm suggesting vesicular uptake of the dyes. Pinocytotic entrapment of the dyes was demonstrated by the transfer of cell-impermeant fura-2 across tubular cell monolayers mounted in Ussing chambers. The transfer of the dye was similar to that of a marker of fluid-phase pinocytosis, Lucifer Yellow (LY). This pinocytotic entrapment of Ca2+-indicators would lead to underestimation of the actual calcium transients. Microfluorometric study of single proximal tubular cells “scrape-loaded” with fura-2 revealed a four-fold increase in [Ca2+]i concentration following stimulation with phenylephrine.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041280316
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