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  • 1
    Electronic Resource
    Electronic Resource
    Oscillations in oxygen tension and insulin release of individual pancreatic ob/ob mouse islets (2000)
    Springer
    Diabetologia 43 (2000), S. 1313-1318 
    Details
    ISSN: 1432-0428
    Keywords: Keywords Oscillation, metabolism, oxygen tension, insulin release, islet, glucose, tolbutamide, heterogeneity, Clark electrode, ELISA.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. The role of beta-cell metabolism for generation of oscillatory insulin release was investigated by simultaneous measurements of oxygen tension (pO2) and insulin release from individual islets of Langerhans.¶Methods. Individual islets isolated from the ob/ob-mice were perifused. Insulin in the perifusate was measured with a sensitive ELISA and pO2 with a modified Clark-type electrode inserted into the islets.¶Results. In the presence of 3 mmol/l d-glucose, pO2 was 102 ± 9 mmHg and oscillatory (0.26 ± 0.04 oscillations/min). Corresponding insulin measurements showed oscillatory release with similar periodicity (0.25 ± 0.02 oscillations/min). When the d-glucose concentration was increased to 11 mmol/l, pO2 decreased by 30 % to 72 ± 10 mmHg with maintained frequency of the oscillations. Corresponding insulin secretory rate rose from 5 ± 2 to 131 ± 16 pmol · g–1· s–1 leaving the frequency of the insulin pulses unaffected. The magnitude of glucose-induced change in pO2 varied between islets but was positively correlated to the amount of insulin released (r 2 = 0.85). When 1 mmol/l tolbutamide was added to the perifusion medium containing 11 mmol/l glucose no change in average oscillatory pO2 was observed despite a doubling in the secretory rate. When 8 mmol/l 3-oxymethyl glucose was added to perifusion medium containing 3 mmol/l d-glucose, neither pO2 nor insulin release of the islets were changed. Temporal analysis of oscillations in pO2 and insulin release revealed that maximum respiration correlated to maximum or close to maximum insulin release.¶Conclusion/interpretation. The temporal relation between oscillations in pO2 and insulin release supports a role for metabolic oscillations in the generation of pulsatile insulin release. [Diabetologia (2000) 43: 1313–1318]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250051528
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Ethanol on γ-Aminobutyric Acid and Glycine Receptor-Coupled Cl− Fluxes in Rat Brain Synaptoneurosomes (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 57 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Chloride fluxes in Synaptoneurosomes in response to additions of γ-aminobutyric acid, glycine, and ethanol were measured using a chloride-sensitive fluorescent probe 6-methoxy-N-(3-sulfopropyl) quinolinium (SPQ). The C1− gradient was directed outward by bathing cells in a medium low in C1− concentration. The Synaptoneurosomes responded to both γ-aminobutyric acid and glycine by outflow of C1− ions, as judged from an increase in SPQ fluorescence. These effects were inhibited by picrotoxin and strychnine, respectively. Ethanol also produced an outflow of C1− ions from the Synaptoneurosomes. Both picrotoxin and strychnine inhibited this effect. When the antagonists were used together, the inhibiting effect was additive. These results indicate that ethanol affects both γ-aminobutyric acid and glycine receptor-linked chloride fluxes in the rat brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb03764.x
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  • 3
    Electronic Resource
    Electronic Resource
    Dual modulation of calcium channel current via recombinant α2-adrenoceptors in pheochromocytoma (PC-12) cells (1997)
    Springer
    Pflügers Archiv 435 (1997), S. 280-285 
    Details
    ISSN: 1432-2013
    Keywords: Key words Calcium channels ; α2-Adrenoceptors ; G proteins ; Dexmedetomidine ; PC-12 cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The ability of recombinant rat α2D-and α2B-adrenoceptors expressed in nerve-growth-factor-differentiated pheochromocytoma PC-12 cells to modulate Ca2+ currents, recorded by the whole-cell patch-clamp technique, has been studied. Ca2+ currents in different cells were either reversibly reduced or increased by dexmedetomidine, an α2-adrenergic agonist, in a concentration-dependent manner. Pertussis toxin pretreatment reduced the number of cells that showed an inhibitory response and reduced the magnitude of inhibition. In cells expressing the α2B-adrenoceptor, pertussis toxin increased the proportion of cells from which a stimulatory effect on Ca2+ currents could be recorded. The magnitude of the inhibitory responses was unaffected but the stimulatory responses were considerably reduced by the dihydropyridine Ca2+ channel blocker nifedipine (5 μM). All effects of dexmedetomidine were reversible upon wash-out and inhibited by the antagonist rauwolscine. The results support the idea that modulation of voltage-dependent Ca2+ channels in transfected PC-12 cells is mediated by activation of recombinant α2D- and α2B-adrenoceptors. This receptor activation predominantly causes inhibition of dihydropyridine-insensitive Ca2+ channels via pertussis-toxin-sensitive G proteins. Additionally receptor activation can also lead to stimulation of dihydropyridine-sensitive Ca2+ channels via pertussis-toxin-insensitive mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050513
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  • 4
    Electronic Resource
    Electronic Resource
    Endogenous γ-l-glutamylglutamate is a partial agonist at the N-methyl-d-aspartate receptors in cultured cerebellar granule cells (1995)
    Springer
    Neurochemical research 20 (1995), S. 1471-1476 
    Details
    ISSN: 1573-6903
    Keywords: Cerebellar neurons ; N-methyl-d-aspartate receptors ; γ-l-glutamylglutamate ; intracellular Ca2+ depolarization ; Mg2+ dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract γ-l-Glutamylglutamate (LGG), an endogenous constituent of the brain, reduced the glutamateevoked increase in intracellular Ca2+ in cultured cerebellar granule cells. The extent and properties of this inhibition were different at different Mg2+ concentrations. The intracellular Ca2+ response to NMDA was slightly enhanced by 0.1 mM LGG in normal (1.3 mM) Mg2+ medium, but in Mg2+-free medium LGG was stimulatory at low (0.1–1 μM) NMDA and inhibitory at high (0.1–1 mM) NMDA concentrations. In the absence of Mg2+, LGG alone increased cytosolic free Ca2+ and depolarized the cells. These effects were potentiated by glycine and blocked by extracellular Mg2+, 2-amino-5-phosphonopentanoate (APV), 7-chlorokynurenate, 3-amino-1-hydroxypyrrolidin-2-one (HA-966) and 5,7-dinitroquinoxaline-2,3-dione (MNQX). The results indicate that LGG is a partial NMDA agonist. On the other hand, the non-NMDA antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitroquinoxaline-2,3-dione (DNQX) also inhibited the effects of LGG. This indicates an involvement of non-NMDA receptors in the actions of LGG. The consequent depolarization may also contribute to the activation of NMDA receptor-governed ionophores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00970596
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  • 5
    Electronic Resource
    Electronic Resource
    Electron-dense precipitates in glomus cells of rat carotid body after fixation in glutaraldehyde and pyroantimonate-osmium tetroxide mixture as possible indicators of calcium localization (1981)
    Springer
    Cell & tissue research 217 (1981), S. 93-104 
    Details
    ISSN: 1432-0878
    Keywords: Carotid body ; Calcium ; Granular vesicles ; Exocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An attempt was made to study the subcellular localization of calcium in carotid body glomus cells of adult rats using fixation with glutaraldehyde followed by treatment with a mixture of pyroantimonate and osmium tetroxide. Precipitates were seen as electron-dense particles (EDP) in the glomus cells, mostly within membrane-bound organelles, such as dense-cored vesicles, mitochondria, small clear vesicles, multivesicular bodies, and especially in lysosomes. However, EDP were also seen in the nuclei and in the free cytoplasm of the glomus cells and even outside them. Preincubation of carotid bodies in media containing calcium and either high potassium or calcium-ionophore A 23187 resulted in a marked increase in the general precipitation pattern, there being an increased amount of EDP both in the glomus cell nuclei and in the cytoplasm. Dense-cored vesicles more often showed precipitates than those in the controls. Some dense-cored vesicles contained multiple precipitates, typically located in the electron-lucent area between core and vesicle membrane. Extensive diffusion of ions probably occurred during fixation before precipitation, making the localization of calcium and other precipitating cations unreliable. However, it is possible that precipitates, which were regularly seen in the dense-cored vesicles, may reflect the content of bound calcium. The possible significance of calcium in glomus cell function is discussed, and the need for more adequate methods is emphasized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233829
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  • 6
    Electronic Resource
    Electronic Resource
    Endocytotic uptake of cationized ferritin tracer into glomus cells dissociated from the adult rat carotid body (1982)
    Springer
    Cell & tissue research 226 (1982), S. 37-49 
    Details
    ISSN: 1432-0878
    Keywords: Carotid body ; Glomus cells ; Endocytosis ; Cationized ferritin ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Glomus cells from carotid bodies of adult rats dissociated by means of collagenase or collagenase + trypsin were used to study by electron microscopy the endocytotic uptake of cationized ferritin (CF) tracer into subcellular compartments. The glomus cells were incubated with the tracer (1) in a basic salt medium (BM), or (2) in the BM into which calcium ionophore A23187 had been added, or (3) in a potassium-rich medium. Incubation of the cells in BM containing CF for 30 min resulted in attachment of the tracer to the cell membrane and uptake of a few solitary tracer particles into small vesicles and multivesicular bodies. No uptake into the cisternae of the Golgi apparatus was observed. Further incubation in BM containing CF for another 30 min resulted in increased uptake of the tracer into small vesicles and multivesicular bodies. A similar pattern of uptake was observed when the dissociated glomus cells were first preincubated in BM with CF for 30 min and then incubated for 1 min or 30 min in the BM solution containing both the ionophore and CF. Upon such incubation, CF particles were seen to penetrate into coated pits and sites of exocytosis at the cell surface. When the 30-min preincubation in BM was followed by incubation in a CF-containing potassium-rich medium for 15–30 min, uptake into vesicles, small lysosomes and occasionally also into profiles of the smooth endoplasmic reticulum was seen. Endocytotic mechanisms of the glomus cells are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217080
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of long-term (72 hr) calcium content during mitogen activation of cultured human T lymphocytes (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 123 (1985), S. 46-50 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In vitro stimulation of human blood lymphocytes with mitogen resulted in an increased intracellular content of Ca2+ per unit cell volume. This increase in Ca2+ content of lectin-activated cells reached a maximum after 24 hr of culture and thereafter slowly declined. Brief treatment of cells at 24 hr of culture with the Ca2+ ionophore A23187 in combination with EGTA resulted in a larger release of Ca2+ from cells in mitogen-stimulated cultures than from cells in control cultures. This indicates that the Ca2+ is accumulated intracellularly but is readily exchangeable. At 24 hr of culture the increase in cellular Ca2+ correlated well with the proliferative response as measured by 3H-thymidine incorporation. Ca2+ influx at 24 and 48 hr of culture was markedly enhanced in the mitogenically stimulated cells as compared either to cells cultured for 1 and 72 hr or cells cultured without mitogen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041230108
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