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  • 1
    Electronic Resource
    Electronic Resource
    Stimulus-induced changes in extracellular Na+ and Cl− concentration in relation to changes in the size of the extracellular space (1982)
    Springer
    Experimental brain research 46 (1982), S. 73-84 
    Details
    ISSN: 1432-1106
    Keywords: Extracellular space ; Na+ and Cl− concentration ; Effects of metabolism on osmolarity ; Epilepsy ; Cerebral cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Extracellular Na+- and Cl−-concentrations ([Na+]o, [Cl−]o) were recorded with ion-selective microelectrodes during repetitive stimulation and stimulus-induced self-sustained neuronal afterdischarges (SAD) in the sensorimotor cortex of cats. In all cortical layers [Na+]o initially decreased by 4–7 mM. In depths of more than 600 μm below the cortical surface such decreases usually turned into increases of 2–6 mM during the course of the SADs, whereas in superficial layers [Na+]o never rose above its resting level. [Cl−]o always showed an increase in the course of the SADs often preceded by an initial small decrease. The average increase at a depth of 1,000 μm was about 7 mM. [Cl−]o reached peak values at about the end of the ictal period, whereas [Na+]o reached its maximum shortly after the end of the SAD, at times when [K+]o was still elevated above the baseline concentration. These data indicate that the extracellular osmolarity can increase during SAD by up to 30 mM. Such an increase in osmolarity can be explained by an increase in the number of intracellular particles, caused by cleavage of larger molecules during enhanced metabolism. This could lead to cell-swelling due to passive water influx from the extracellular space (ES). However, the resulting reduction of the size of the ES is calculated to be less than 10% for an increase in intracellular osmolarity by 30 mOsm. This value is too small as compared to previously measured ES-reductions under similar conditions (i.e., 30% reduction at 1,000 μm; Dietzel et al. 1980). Reductions of the size of the ES that accompany the observed changes in the ionic environment, are quantitatively explained on the basis of the extended glial buffering mechanism described in the preceding paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238100
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  • 2
    Electronic Resource
    Electronic Resource
    Transient changes in the size of the extracellular space in the sensorimotor cortex of cats in relation to stimulus-induced changes in potassium concentration (1980)
    Springer
    Experimental brain research 40 (1980), S. 432-439 
    Details
    ISSN: 1432-1106
    Keywords: Extracellular space ; K+ regulation ; Spatial K+ buffering ; Epilepsy ; Cerebral cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The time course of local changes of the extracellular space (ES) was investigated by measuring concentration changes of repeatedly injected tetramethylammonium (TMA+) and choline (Ch+) ions for which cell membranes are largely impermeable. After stimulus-induced extracellular [K+] elevations the δ[TMA+] and δ[Ch+] signals recorded with nominally K+-selective liquid ion-exchanger microelectrodes increased by up to 100%, thus indicating a reduction of the ES down to one half of its initial size. The shrinkage was maximal at sites where the K+ release into the ES was also largest. At very superficial and deep layers, however, considerable increases in extracellular K+ concentration were not accompanied by significant reductions in the ES. These findings can be explained as a consequence of K+ movement through spatially extended cell structures. Calculations based on a model combining the spatial buffer mechanism of Kuffler and Nicholls (1966) to osmolarity changes caused by selective K+ transport through primarily K+ permeable membranes support this concept. Following stimulation additional iontophoretically induced [K+]o rises were reduced in amplitude by up to 35%, even at sites where maximal decreases of the ES were observed. This emphasizes the importance of active uptake for K+ clearance out of the ES.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236151
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  • 3
    Electronic Resource
    Electronic Resource
    81. Strömungsmessungen am Vineberg-Sewell-Implantat im akuten Versuch (1971)
    Springer
    Langenbeck's archives of surgery 329 (1971), S. 230-231 
    Details
    ISSN: 1435-2451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bis heute ist umstritten, ob sofort nach der Implantation der A. mammaria interna (AMI) ein Einstrom von Blut in den Herzmuskel erfolgt oder welche Faktoren sonst für das Offenbleiben der AMI im Intervall zwischen Einpflanzung und Kollateralgefäßanschluß verantwortlich sind. Nach der an der Cleveland Clinic standardisierten Technik wurden bei 14 Hunden Vineberg-Sewell-Implantate in die Vorderwand des linken Ventrikels eingepflanzt und mit einem elektromagnetischen Flowmeter Mittelfluß und pulsatile Strömung bestimmt. Nach der Einpflanzung wurde eine allenfalls minimale Strömung (durchschnittlich 0,6 ml/min) beobachtet, die sich zwanglos durch die Eigendurchblutung der extramyokardialen Gefäßstielstrecke erklären läßt. Im frischen Implantat finden aber ständig erhebliche Verschiebungen der Blutsäule statt, die durch die Wechsel wirkung zwischen den von der Aorta her wirkenden Flußkräften und den auf die intramyokardiale Gefäßstrecke wirkenden Kontraktionskräften hervorgerufen werden. Beim Fehlen eines initialen Abstroms ist die Konzeption Vinebergs, wonach die Implantate durch den sofortigen Abstrom von Blut über die myokardialen Sinusoide offengehalten werden, entschieden in Frage gestellt. Ein unmittelbarer Revascularisationseffekt vor Ausbildung mammariokoronarer Kollateralen ist nicht vorstellbar.
    Notes: Summary Despite widespread clinical application of the Vineberg operation some basic principles of indirect myocardial revascularization are poorly understood. The influence of initial flow on implant patency has been questioned; flow measurements in the early postimplantation period show a considerable variety of results. Vineberg-Sewell-implants were inserted into the anterolateral wall of the left ventricle in 14 dogs. Mean flows and phasic flows were determined. Following implantation mean flow averaged 0.6 ml/min (0–2 ml/min) being reduced to 0.2 ml/min after 90 min. This minimal forward flow is easily explained by the back flow in the internal mammary vein draining capillary flow from the extramyocardial portion of the pedicle. However, there was significant to-and-fro motion in the newly implanted arteries with marked backflow in early systole, forward flow in late systole, early diastolic retrograde flow and positive flow during late diastole, this to-and-fro motion being produced by the interaction of flow forces and ventricular contraction forces acting upon the intramural segment of the implanted systemic artery. Our results suggest that Vineberg's conception regarding immediate implant flow and run-off into the myocardial sinusoids as the main source of implant patency in the postoperative period is not valid. Accordingly an immediate revascularization effect does not seem possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01770498
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  • 4
    Electronic Resource
    Electronic Resource
    Kern-Trockenmassen und Kern-Volumina in der regenerierenden Rattenleber (1962)
    Springer
    Naturwissenschaften 49 (1962), S. 235-236 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00628013
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  • 5
    Electronic Resource
    Electronic Resource
    Activation characteristics of the calcium-dependent outward potassium current in Helix (1982)
    Springer
    Pflügers Archiv 394 (1982), S. 70-77 
    Details
    ISSN: 1432-2013
    Keywords: Calcium ; Cell membrane permeability ; Helix (snails) ; Ion-channels ; Models ; Neurons ; Potassium ; Voltage clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The activation of calcium-dependent outward potassium current [IK(Ca)] by shortlasting Ca2+ inward currents was studied. These Ca2+ currents were produced either by small depolarizing pulses preceding the larger depolarizations or by interposed repolarizations (I.R.s) starting from depolarized membrane potentials. IK(Ca) then develops with a potential-invariant time course (half time 6–12 ms) and the normally bell-shaped isochronal IK(Ca)/V curve, measured at between 30 and 300 ms, is straightened. However, these Ca2+-injecting pulses, of any amplitude and duration, do not increase the steady-state conductance to values beyond those measured with single step depolarizations to lower potentials. varied in length, activation of IK(Ca) increased linearly with the during depolarization to near the supposed calcium equilibrium potential with no further Ca2+ influx. When I.R.s are varied in length, activation of I(Ca) increases linearly with the amount of Ca2+ current. Fading of activation during I.R. follows a time course nearly ten times slower than activation and is not expressed in tail currents. The time course of IK(Ca) is described by a function defined only by voltage parameters of activation combined with a minimum activation time constant which is similar to that found in tail currents. Peak location and general form of the IK(Ca)/V relationship for times up to several hundred milliseconds are well predicted without the necessity to explicitly account for actual calcium entry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01108310
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  • 6
    Electronic Resource
    Electronic Resource
    Properties of a calcium- and voltage-activated potassium current in Helix pomatia neurons (1982)
    Springer
    Pflügers Archiv 394 (1982), S. 61-69 
    Details
    ISSN: 1432-2013
    Keywords: Action potentials ; Calcium channels ; Cell membrane permeability ; Helix (snails) ; Neurons ; Potassium channels ; Potassium-selective electrode ; Voltage clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A calcium- and voltage-dependent current was found to be the principal outward current in identified Helix neurons. The current depends on the presence of [Ca2+]0, with half maximal activation at 1 mM [Ca2+]0, and it saturates beyond about 5 mM. The current is termed IK(Ca) since the charge carried by it corresponds to the amount of potassium ions transferred from the cell interior, as determined from the increase in K+ concentration in the external volume with K+ liquid ion-exchanger microelectrodes. IK(Ca) is characterized by bell shaped isochronal I/V curves. The peaks of these curves move from +30 mV to about +70 mV with an increase of the time of measurement from 30–200 ms. IK(Ca) rise times have a minimum of 10–15 ms at low depolarization around 0 mV, but increase about exponentially with more positive potentials. A tenfold decrease in [Ca2+]0 over the range of 30 to 0.3 mM also produces an increase in rise time, equivalent to a positive shift of potential by 20 mV. On repolarization of the membrane IK(Ca) disappears much faster than the intracellularly accumulated Ca2+, with a time constant which is similar to the minimum activation time constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01108309
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  • 7
    Electronic Resource
    Electronic Resource
    The time courses of intracellular free calcium and related electrical effects after injection of CaCl2 into neurons of the snail,Helix pomatia (1981)
    Springer
    Pflügers Archiv 391 (1981), S. 242-251 
    Details
    ISSN: 1432-2013
    Keywords: Calcium ; Cell membrane permeability ; Ion channels ; Ion-selective electrode ; Helix (snails) ; Microinjections ; Neurons ; Potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Controlled quantities of 100 mM aqueous CaCl2 solutions were pressure injected into voltage-clamped neurons with a resolution of 10−11 1. Ca2+-selective microelectrodes monitored the time course of changes in [Ca2+]i. At a membrane potential of −50 mV CaCl2 quantities in the range of 1% of the cell volume induced an inward current, associated with a conductance increase and having an equilibrium potential between −20 and +20 mV, which accompanied the rise in [Ca2+]i. An artifactual origin of the inward current by the injection procedure or by calcium screening of membrane sites could be excluded. The calcium-induced hyperpolarizing conductance, producing an outward current at −50 mV, followed the inward current and reached maximum during the late decline in [Ca2+]i. In most cases its development was separated from the inward current by an intermediate relative decrease of the membrane conductance. Neither of the two transient conductance increases showed a particular dependence on voltage. Renewed Ca2+ injection quickly decreased the calcium-induced hyperpolarizing conductance for several seconds. Ca2+ injections below 0.05% of the cell volume mostly produced pure outward currents or hyperpolarizing responses. Partial substitution of extracellular CaCl2 by NiCl2 decreased the hyperpolarizing response but not the initial inward current. The immediate effects of increased [Ca2+]i are activation of a depolarizing conductance and the partial block of the late hyperpolarizing conductance. The latter is probably produced through intermediate steps after increasing [Ca2+ i.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00596178
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  • 8
    Electronic Resource
    Electronic Resource
    Activation characteristics of the calcium-dependent outward potassium current in helix (1982)
    Springer
    Pflügers Archiv 394 (1982), S. 277-277 
    Details
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00589105
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  • 9
    Electronic Resource
    Electronic Resource
    Zur Kenntnis des kolloidalen Silbers (1905)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 45 (1905), S. 77-80 
    Details
    ISSN: 0863-1778
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19050450110
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  • 10
    Electronic Resource
    Electronic Resource
    Weitere Beiträge zur Kenntnis anorganischer Kolloide (1905)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 44 (1905), S. 225-228 
    Details
    ISSN: 0863-1778
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19050440117
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