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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annals of hematology 53 (1986), S. 437-441 
    ISSN: 1432-0584
    Keywords: Acute myeloic leukemia ; Glutathione ; Ascorbic acid ; ESR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Electron spin resonance (ESR) spectra of lyophilized erythrocytes obtained from patients with acute myeloic leukemia (AML) show, in comparison to controls, a characteristic change especially in the low-field region of the spectrum concomitant with a reduction of the spin concentration. This effect can be simulated by addition of SH-containing substances (e.g. reduced glutathione or cysteine) to healthy erythrocytes. S-S containing compounds exhibit no effect. Since SH-containing substances can hardly permeate plasma membranes, the membrane surface seems to be defective in the case of “AML” erythrocytes. Furthermore, it can be concluded that the concentration of SH-containing substances, such as cysteine, is increased in the plasma of AML-patients, which could be confirmed by HPLC-measurements. In the case of a successful treatment of the patients with alexan, daunoblastin, and thioguanine the spin concentration increased again and the resulting ESR spectrum is very similar to the control spectrum. It should be pointed out, that the ascorbic acid concentration is very low in both plasma and erythrocytes of AML patients.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0584
    Keywords: LeukÄmie ; Erythrozyten-Membran ; ESR ; Atomabsorption ; AscorbinsÄure ; Leukemia ; Erythrocyte ghosts ; ESR ; Atomic absorption ; Ascorbic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The effect of ascorbic acid on white ghosts of erythrocytes and plasma has been investigated by means of ESR spectroscopy. Since the spectra obtained are identical to the one obtained with leukemic blood, it is concluded that the receptor for vitamin C has to be searched for in membrane and plasma as well. Determination of Cu and Fe by means of atomic absorption spectroscopy revealed that both of the metals are also present in the membrane. In the case of copper, it must exist there as a protein which has not been identified yet. Oxidizing substances, such as KMnO4, reverse the effect produced by ascorbic acid.
    Notes: Zusammenfassung Die Wirkung von AscorbinsÄure auf Erythrozyten-Membran (white ghosts) und Plasma ist mittels der ESR-Spektroskopie untersucht worden. Da die erhaltenen Spektren identisch mit denen sind, die von leukÄmischem Blut erhalten wurden, wird angenommen, da\ der Rezeptor für Vitamin C sowohl in der Membran als auch im Plasma vorhanden sein mu\. Cu- und Fe-Bestimmungen mittels der Atomabsorptionsspektroskopie ergaben, da\ beide Metalle auch in der Membran vorhanden sind. Im Falle des Kupfers mu\ es dort als ein Protein vorliegen, das noch nicht identifiziert wurde. Oxidierende Substanzen, wie z. B. KMnO4, bewirken eine Umkehr des durch die AscorbinsÄure erzeugten Effektes.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0584
    Keywords: ESR ; LeukÄmie ; AscorbinsÄure ; Antioxidanzien ; oxidierende Substanzen ; ESR ; Leukemia ; Ascorbic acid ; Antioxidants ; Oxidizing agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Addition of ascorbic acid to native blood or to erythrocytes and leukocytes of healthy persons results in an ESR spectrum which is identical to the one obtained with blood or its fractions of leukemic patients. After an initial increase the spin concentration decreases at higher (〉 100 mM) concentrations of ascorbic acid. These findings confirm observations made thus far that cancerous tissue, finally, exhibits a lower spin concentration and a higher concentration of antioxidants than its corresponding healthy tissue. Application of oxidizing substances, such as KMnO4 or CuCl2, to erythrocytes either before or after administration of vitamin C compensates the effect of the latter substance depending, of course, on the concentration used. The effect produced by ascorbic acid on blood and its fractions seems to be unique since neither vitamin E or vitamin A or catechol and its amines noradrenaline, adrenaline, dopamine, and its precursor amino acid dopa, cytochrome c, FMN, NADH, Na2S2O4, ethylenglycol, glyceraldehyde, or tyrosine produce this effect. Ascorbic acid seems to play, thus, an important role in the balance of health and disease, as has been pointed out by Szent-Györgyi [16]. Its possible receptor(s) and its implication in the formation of cancer, or at least leukemia, will be discussed in detail elsewhere [9].
    Notes: Zusammenfassung Eine Zugabe von AscorbinsÄure zu nativem Blut oder zu Erythrozyten und Leukozyten von gesunden Personen ergibt ein ESR-Spektrum, das identisch zu dem ist, welches mit Blut oder seinen Fraktionen von LeukÄmie-Patienten erhalten wird. Nach einer anfÄnglichen Zunahme nimmt die Spin-Konzentration bei höheren (〉 100mM) AscorbinsÄure-Konzentrationen wieder ab. Diese Ergebnisse bestÄtigen bisherige Beobachtungen, wonach Krebsgewebe im fortgeschrittenen Stadium eine niedrigere Spin-Konzentration und eine grö\ere Konzentration an Antioxidanzien als das dazugehörige gesunde Gewebe besitzt. Eine Zugabe von oxidierenden Substanzen, wie z. B. KMnO4 oder CuCl2, zu Erythrozyten entweder vor oder nach Vitamin C Zugabe kompensiert den Effekt der letzteren Substanz, was natürlich von der gebrauchten Konzentration abhÄngt. Der durch AscorbinsÄure an Blut und seinen Fraktionen erzeugte Effekt scheint spezifisch zu sein, da weder Vitamin E nach Vitamin A oder Catechol und seine Amine Noradrenalin, Adrenalin, Dopamin und sein VorlÄufer, die AminosÄure Dopa, Cytochrom c, FMN, NADH, Na2S2O4, Äthylenglykol, Glyzeraldehyd oder Tyrosin diesen Effekt erzeugen.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: Renshaw cells ; Motor axons ; Random stimulation ; Synaptic transmission ; Facilitation ; Depression ; Time constants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In 9 adult anaesthetized cats, 22 lumbosacral Renshaw cells recorded with NaCl-filled micropipettes were activated by random stimulation of ventral roots or peripheral nerves. The stimulus patterns had mean rates of 9.5–13 or 20–23 or 45 pulses per second and were pseudo-Poisson; short intervals below ca. 5 ms (except in two cases) were excluded. The Renshaw cell responses were evaluated by two kinds of peristimulus-time histograms (PSTHs). “Conventional” PSTHs were calculated by averaging the Renshaw cell discharge with respect to all the stimuli in a train. These PSTHs showed an early excitatory response which was often followed by a longer-lasting slight reduction of the discharge probability. These two response components were positively correlated. “Conditional” PSTHs were determined by averaging the Renshaw cell discharge with respect to the second (“test”) stimulus in pairs of stimuli which were separated by varied intervals, δ. The direct effect of the first “conditional” response was subtracted from the excitation following the second (“test”) stimulus so as to isolate the effect caused by the second stimulus per se. After such a correction, the effect of the first “conditioning” stimulus showed pure depression, pure facilitation or mixed facilitation/depression. Analysis of such conditioning curves yielded two time constants of facilitation (ranges: ca. 4–35 ms and 93–102 ms) and two of depression (ranges: ca. 7–25 ms and 50–161 ms). It is concluded that these time constants are compatible with processes of short-term synaptic plasticity known from other synapses. Other processes such as afterhyperpolarization and mutual inhibition probably are of less importance.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Red nucleus ; Renshaw cells ; Moto-neurone-Renshaw cell linkage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The red nucleus region was stereotaxically stimulated with short trains of high-frequency alternating current pulses in anaesthetized cats. The effects were studied, in contralateral lumbar segments, on the responses of microrecorded individual Renshaw cells (RCs) to antidromic or orthodromic test shocks of ventral root or muscle nerve fibres. Monosynaptic reflexes (MRs) of their motoneurone pools were recorded from one of the cut lumbar ventral roots. Averages of 10–20 replicate test responses of the RC (converted into instantaneous frequency curves, IFCs) and of the MR shapes were computed and graphically displayed. 2. Orthodromic (afferent) test shocks induced simultaneously MRs as well as responses of a RC belonging to the same motor pool. From their paired records at systematically varied shock strengths, whole “linkage characteristics” of the relation between the two events could be obtained, representing the functional linkage from the motoraxon collaterals to the RC under study. The overall result of rubral conditioning was a change in the course of the characteristic, which indicated a reduction of this linkage (= relative inhibition of the RC against its recurrent input). 3. Sequential trials with test shocks of constant, submaximal strength were performed with 45 individual RCs. The clearest results were obtained with RC responses to antidromic ventral root shocks: 65% of the RCs were partially inhibited by rubral conditioning. Interposed minor facilitory subcomponents could be seen in the course of inhibited IFCs. Mixed sequences of manifest inhibitory/facilitory effects were observed in 11%; reversed sequences (facilitory/inhibitory) did not occur. A pure but weak facilitation was found in only one case, paralleled by an increase of the MR. RCs belonging to either extensor or flexor motor pools were affected about equally. A little over 20% of the tested RCs remained uninfluenced by rubral stimulation. 4. The MRs, induced by constant, submaximal, orthodromic test shocks, were usually enhanced with only few exceptions, by rubral stimulation. The effects on the orthodromic RC responses were mainly inhibitory, but could be more or less masked by the concurrent increase of the MR, providing a stronger recurrent input to the RC. Such inhibition could be uncovered, however, by observing the above described linkage change. 5. Variation of several parameters of rubral conditioning (train duration, timing of train with respect to test shock, strength of train) modified the inhibitory effects on antidromic RC responses to a certain extent without changing their principal character. Higher conditioning strengths frequently induced mass discharges of previously silent motoneurones, but at the same time an increased inhibition of the concurrent RC responses. 6. Spontaneous RC activity (in the absence of test stimuli) occurred infrequently and was weak and interrupted by silent periods. When this persisted long enough for testing repeated rubral stimulation, a strong initial inhibition lasting up to several hundred ms was found, sometimes followed by some oscillations of the average discharge rate. 7. The predominant combination of concurrent effects of the conditioning, namely, inhibition of RCs and facilitation of motoneurones, indicated independent (and mostly divergent) control of the two target neurones by the red nucleus. It is concluded that in this way the RCs can be flexibly and transiently decoupled to some degree from their recurrent motoneuronal input.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 21 (1974), S. 353-360 
    ISSN: 1432-1106
    Keywords: Renshaw cells ; Muscle stretch ; Phasic tonic motoneurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary a) Renshaw cells (RC) were recorded during ramp stretch of the GS muscle. In 90% of the analysed cells, the frequency and duration of the phasic response were enhanced by increases in both the length and rate of stretch. b) The tonic response, which was observed in about 30% of the analysed cells, increased at higher stretch lengths. c) After application of the cholinergic blocking agent mecamylamine or after severance of the GS nerve, the Renshaw stretch response was abolished. d) The results lend some support to the hypothesis that RCs are triggered predominantly by large phasic motoneurones. The smaller tonic motoneurones seem to provide some supporting background input to the RCs.
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  • 7
    ISSN: 1432-1106
    Keywords: Ramp-and-hold stretches ; Ia inhibitory interneurones ; Renshaw cells ; Reciprocal inhibition ; Recurrent facilitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of ramp stretches applied to triceps surae muscle on the discharge patterns of single Ia inhibitory interneurones, monosynaptically invaded from various nerves, were studied in either decerebrate or anesthetized cats. Interneurones which received direct excitatory Ia input from the stretched muscle exhibited augmented activity both during the dynamic and static phase of stretch, which was, however, interrupted by a transient inhibitory influence during the dynamic phase of stretch. The influences on Ia inhibitory interneurones, monosynaptically invaded from hamstring or tibial nerve, were exclusively inhibitory. These stretch-induced inhibitions were better demonstrable in decerebrate than in anesthetized preparations. The timing of the discharge patterns of additionally recorded Renshaw cells during stretch, and the disappearance or reduction of the above described inhibitory effects after administration of DHE, strongly support the idea that these inhibitory actions are caused by Renshaw inhibition. In Ia inhibitory interneurones, monosynaptically activated from the antagonistic peroneal nerve, stretch induced also pronounced inhibitory effects, which were most probably caused by mutual inhibition between Ia inhibitory interneurones. The suppression of agonistic Ia inhibitory interneurone activity below the tonic resting activity corresponded to an enhancement of the monosynaptic reflex amplitude of the antagonistic motoneurone pool. The findings suggest that normal orthodromic activation of Renshaw cells, and consequently the recurrent inhibition of the Ia inhibitory interneurones, is predominantly linked with rapid phasic, rather than slow tonic, motoneuronal firing. The functional role of this mechanism for the performance of rapidly alternating movements and the damping of ballistic agonist contractions is discussed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 10 (1983), S. 197-204 
    ISSN: 1432-1017
    Keywords: Ascorbic acid ; ESR ; Na+ ; K+
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract ESR investigations on lyophilized systems have shown that the signal at g = 2.005 can be explained by an interaction between Na+ or K+ and the anionic ascorbyl radical. The unpaired electron is probably localized near the C(4) region and is produced by a cleavage of an H atom belonging to a water molecule bound tightly to C(4). Experiments on aqueous samples revealed that ascorbic acid in its radical configuration and in its highest concentration exists only at physiological pH and temperature. An additional splitting is obtained by the ring formation between C(3) and C(6)-OH. The coupling constants of the triplets produced by the CH2-6 protons differ between ascorbic acid and isoascorbic acid. Thus, the ESR technique can be applied for an easy distinction between these two epimers.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 10 (1983), S. 205-210 
    ISSN: 1432-1017
    Keywords: Ascorbic acid ; Na+/K+-transport ; ESR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Ascorbic acid/isoascorbic acid are present as radicals at physiological pH with the unpaired electron located in the C(4) region. Since a distinction can be made between both types of radicals, the electron spin resonance technique can be used for discrimination between the epimers of vitamin C. The radical has a cyclic side-chain structure which is formed by the hydrogen bond C(3)-O− ... HO-C(6) (≈ 2.7 kJ) and which engulfs Na+ or K+ in the case of the ascorbyl or the isoascorbyl radical, respectively. The radicals Na-ASC and K-Iso-ASC are electroneutral. Red. glutathione affects both types of radicals by restoring the original electronic configuration at C(4) without changing the electroneutral bicyclic structure. In this way, the mobile carriers Na-ASC and K-Iso-ASC can transport Na+ and K+ across membranes. Its highest efficiency is around 37
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2013
    Keywords: Random inputs ; Cross-correlation ; Nonlinear analysis ; Synchronous inputs ; Renshaw cells ; Dorsal horn neurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We here present a method to study the interaction of parallel neural input channels regarding their effects on a neurone. In particular, the method allows to disclose the effects of oligosynaptic pathways that may exist in parallel to direct monosynaptic connections to the cell. Two (or more) inputs (nerves) are stimulated with random patterns of stimuli. The response of the cell to these patterns is evaluated by the computation of peristimulus-time histograms (PSTHs). One of the two stimulus trains is selected as the one to yield reference events for the PSTH computation. From this stimulus train are selected those stimuli as reference events which are preceded, at defined mean intervals, by stimuli in the same or a parallel channel. These “conditioning” stimuli are determined (1) separately from each single stimulus train and (2) concomitantly from the two trains as events occurring simultaneously in both. The effects exerted by these various conditioning events on the effects of the “test” pulses on the cell response yield insights into the interactions between the two (or more) inputs. These methods are demonstrated on spinal Renshaw cells activated by independent random stimulation of two muscle nerves and on dorsal horn neurones responding to cutaneous nerve stimulation.
    Type of Medium: Electronic Resource
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