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  • 2005-2009
  • 1965-1969  (111)
  • Physical Chemistry  (56)
  • Cat  (55)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 264 (1969), S. 406-419 
    ISSN: 1432-1912
    Schlagwort(e): Intestinal Absorption ; Cardiac Glycosides ; Blood of Portal Vein ; Intestinal Lymph ; Cat ; Intestinale Resorption ; Herzglykoside ; Portalvenenblut ; Darmlymphe ; Katze
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. The cardiac glyoosides digitoxin, ouabain, digoxin and peruvosid labelled with3H were injected into tied intestinal loops of anaesthetized cats in situ. The absorbed glycosides were measured in the blood of the portal vein and in the intestinal lymph. At the same time the3H-activity was measured in the blood of the peripheral circulation, in the bile and in the urine. 2. Calculation of the amount of glycosides totally absorbed from the3H-concentration in the blood of the portal vein and the circulation volume (bubble-flow-meter) gave the following absorption rates as a percentage of the administered dose per hour: digitoxin 56%, digoxin 42%, peruvosid 26% and ouabain 10%. 3. The amount of glycosides passing into the lymph during 1 hour was found to be only 0.006 to 0.02% of the amount offered. In lymph3H-activity cannot be measured earlier than 5 min after the administration of the labelled glycosides. The3H-concentration in the lymph did not equal that measured in the blood of the peripheral circulation until at least 1 hour after the administration and always remained below the3H-concentration of the blood in the portal vein. This proportion remained unchanged even if digitoxin was administered as an emulsion in oil instead of an aqueous solution. From the time course of3H-concentration it might be concluded that the glycosides do not pass directly to the lymph after absorption but indirectly by way of the blood. 4. The amount of glycoside excreted in the bile is for peruvosid 15,5% of the amount absorbed, for ouabain 1,9%, for digoxin 1,4% and for digitoxin 0,8%. The3H-activity excreted in urine is very small and can be disregarded. 5. Chromatographic analyses of the bile revealed, that in the case of digoxin, 4/5 of the amount excreted were unchanged, in the case of digitoxin and ouabain 2/3 and in the case of peruvosid only 1/4. In the lumen of the tied intestinal loops and in the tissue of the small intestine the glycosides were hardly metabolised.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 128 (1969), S. 28-39 
    ISSN: 1432-0568
    Schlagwort(e): Arterial supply ; Corpus callosum ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung An 27 Katzen beiderlei Geschlechts wurde die Blutversorgung des Corpus callosum untersucht. Dabei wurden folgende Befunde erhoben: Der Balken der Katze wird im Bereich des Rostrum und Genu sowie im vorderen und mittleren Truncuabschnitt aus der Arteria cerebri anterior versorgt und zwar über Äste, die den Arteriae pericallosae und den Arteriae genu corporis callosi entstammen. Diese Äste wurden als Arteriae callosi superiores und inferiores bezeichnet. Lediglich im hinteren Truncusabschnitt und im Splenium erfolgt die Versorgung neben Ästen der A. pericall. auch über solche der Arteriae cerebri mediae und posteriores. Die Blutgefäße treten dolchartig in den Balken ein, teilen sich dann baumartig weiter auf und gehen in ein Capillarnetz über, das in Richtung des Nervenfaserverlaufes ausgezogen ist. Auf in der Literatur bereits bekannte, aber oft vernachlässigte Besonderheiten der Arteria carotis interna und des Circulus arteriosus wird hingewiesen.
    Notizen: Summary In investigations on 27 cats of both sexes, the arterial supply of the corpus callosum was studied. The findings are as follows: In the region comprising rostrum and genu as well as in the fore and middle trunk sections, blood supplied by branches of the arteriae pericallosae and the arteriae genu corporis callosi which originate from the arteria cerebri anterior. These branches were designated arteriae callosi superiores and inferiores. However, in the posterior section of the trunk and in the splenium the blood is supplied by branches of the aa. pericall. and, in addition, by branches of the arteriae cerebri media and posteriores. The blood vessels penetrate the corpus callosum in bayonet fashion, then arborise and finally become a capillary network which is elongated in the direction of the course of the nerve fibres. Attention is drawn to peculiarities of the arteria carotis interna and the circle of Willis which, although known in the literature, are rarely referred to.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 128 (1969), S. 222-234 
    ISSN: 1432-0568
    Schlagwort(e): Postnatal development ; Fixation ; Neuroglia ; Corpus callosum ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Gehirne von Tieren aus 4 verschieden alten Würfen junger Katzen wurden teils lebensfrisch durch Perfusion, teils nach 24 Std durch Immersion fixiert und für Vergleichsuntersuchungen in Paraffin eingebettet. Bei Betrachtung der Gliazellen des Corpus callosum ergab sich: 1. Nach Perfusionsfixierung sind die Kerne der Gliazellen groß und elliptisch. Sie sind wasserklar und haben eine scharf gezeichnete Chromatinstruktur. Nach Immersionsfixierung 24 Std p.m. sind die Kerne dagegen klein und rund, homogen dunkel gefärbt und haben ein kaum zu erkennendes Chromatingerüst. 2. Nach Perfusionsfixierung sieht man im Balken der ganz jungen Tiere zahlreiche Mitosen. Sie fehlen bei den durch Immersion fixierten Geschwistertieren desselben Wurfes. 3. Die nach verschiedener Fixierung beobachteten Unterschiede in der Form der Gliazellkerne werden durch Messungen der Quer- und Längsachsen erfaßt.
    Notizen: Summary In four litters of young cats, some of the brains were fixed by perfusion and the others by immersion. The material was embedded in paraffin and the neuroglia was investigated in sections through the corpus callosum. It was found that: 1. After fixation by perfusion the nuclei of the glia cells are large and elliptic. The caryoplasm is clear and there is a distinct structure of the chromatin. After fixation by immersion the nuclei of the same cells are small and round. The caryoplasm is dense and the structure of the chromatin is not clearly visible. 2. After fixation by perfusion mitotic figures are present. They are absent in the brains fixed by immersion. 3. Following different fixation, there are differences in the shape of the nuclei of the glial cells. These differences have been investigated in detail by measuring the diameters of the nuclei.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-1106
    Schlagwort(e): Lateral cervical nucleus ; Midbrain lesions ; Nauta method ; Ultrastructural investigation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The lateral cervical nucleus (LCN) has been studied with the light and electron microscope after midbrain lesions in kittens of different ages, and in adult cats. It has been shown that nerve cells remain within the contralateral LCN after hemisection of the midbrain. performed on 1 day old kittens. The estimated number of these remaining cells was 3–19% in the different cases. No fibers descending to the LCN from levels rostral to the midbrain could be demonstrated in adult cats with the Nauta technique. A combined Nauta and electron microscopical investigation was performed on kittens operated on at different ages and allowed to survive varying times postoperatively. At the operations the LCN-axons were transected at midbrain level. The Nauta investigation demonstrated silver impregnation of degenerating LCN-neurons on the affected side of the same type as has been described recently in other neuronal systems following axonal transection. The ultrastructural study revealed electron dense degenerating dendrites and probably also nerve cells within the LCN. The dense degenerative changes were very similar to the dense degeneration in terminal boutons following transection of parent axons. The potential value of the findings for electron microscopical research in neuroanatomy is discussed. The results in terms of connections of the LCN are discussed in the light of known anatomical and physiological data of the LCN.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 7 (1969), S. 143-157 
    ISSN: 1432-1106
    Schlagwort(e): Reticular formation ; Convergence ; Inhibition ; Cat ; Chloralose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung 1. Ein konditionierender corticaler Reiz inhibiert den somatischen Startlereflex bei Katzen unter Chloralosenarkose für eine Dauer von mehr als 200 ms. Die Interaktionen zwischen beiden Reizen laufen in der bulbären und pontinen Formatio reticularis ab. 2. Dem Startlereflex liegt eine polysynaptische Erregungsschleife zugrunde, die die bulbäre und pontine Formatio reticularis durchzieht. Die Resistenz der reticulären Neurone gegenüber repetitiver Stimulation wurde als Kriterium ihrer funktionellen Lokalisation auf dem polysynaptischen Reflexbogen gewertet. 3. Die corticale Inhibition wird im Verlaufe der polysynaptischen Erregungsschleife zunehmend stärker. Neurone, die von den Startlereflexafferenzen direkt erregt werden, werden durch den corticalen Reiz nicht inhibiert. Dies schliebt eine präsynaptische Inhibition der reticulopetalen Fasersysteme aus.
    Notizen: Summary 1. The startle reflex evoked by cutaneous stimulation in cats under chloralose anesthesia is inhibited for more than 200 ms by a conditioning cortical volley. The interaction between the cutaneous and the cortical volley takes place in the bulbar and pontine reticular formation. 2. The startle reflex involves a series of reticular neurones. Resistance to repetitive stimulation has been determined to evaluate the functional localization of each neurone within this polysynaptic path. 3. Inhibition following the cortical volley becomes increasingly more effective along the course of the polysynaptic path and is completed within 5–6 ms. Reticular neurones excited directly by the spino-reticular afferents are not inhibited, thus excluding a presynaptic inhibition of the spinoreticular fibres.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 9 (1969), S. 284-306 
    ISSN: 1432-1106
    Schlagwort(e): Cutaneous receptive fields ; Spinal cord ; Cat ; Pain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Examination of cutaneous receptive fields (RFs) of lamina 5 cells in the lumbar spinal cord of decerebrate cats shows them to have three distinct zones with respect to mechanical and electrical stimulation. The mean response rate to both mechanical and electrical stimulation in zone 1 increases steadily up to the highest strengths used; in zone 2, surrounding zone 1 mainly proximally, mild stimuli reduce the mean rate, stronger stimuli increase it; in zone 3, mainly proximal to zone 2, all stimuli reduce the rate. Temporally, zone 1, electric shocks near threshold produce bursts of firing followed by inhibition. With increased stimulus strength, the bursts lengthen to a second or more. In zones 2 and 3, inhibition at all strengths is preceded at higher strengths by bursts of firing. Cold-blocking the spinal cord at lower thoracic levels reversibly increases the ongoing activity of these cells, increases the area of zones 1 and 2, and almost completely suppresses all inhibition. Stimulation of dorsal columns and threshold stimulation of distant dorsal roots inhibits ongoing and induced activity. Barbiturate decreases ongoing activity and the duration of firing produced by cutaneous electrical stimulation but does not decrease inhibition. These results are consistent with a model in which low-threshold fibres are excitatory only over a small central area of the RF of a lamina 5 cell (zone 1), high threshold fibres are excitatory over a larger area (zones 1 and 2), and low threshold fibres are inhibitory over the entire receptive field (zones 1, 2 and 3) with a slower time-course. This inhibition is tonically enhanced by descending influences in the decerebrate cat. It is suggested that the high and low threshold fibres correspond approximately to the small and large diametre fibres whose balance is the basis for the coding of pain in the theory of melzack and wall.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 7 (1969), S. 195-213 
    ISSN: 1432-1106
    Schlagwort(e): Corpus callosum ; EEG synchronization ; Homolateral sensory evoked potentials ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Spontaneous EEG-patterns and evoked potentials (EP's) of symmetrical cortical areas were recorded in chronic and acute cats before and after section of the corpus callosum, the commissura anterior and posterior and the massa intermedia. The spontaneous EEG was recorded without and with anesthesia, EP's after electrical stimulation of the fore-paws only during nembutal anesthesia. — No changes in the bilateral coordination of spontaneous and evoked EEG-patterns could be seen after commissurotomy (CT). The bilateral coherence of EEG-waves as revealed by cross-correlation is low already in the normal cats and does not change significantly after CT. The values of cross-correlation coefficients at T = ± 15 msec vary during one EEG-record between -0.25 and +0.25 in the somatosensory, suprasylvian and temporal areas (mean values slightly above 0). In the visual area occasionally positive values between 0.5 and 0.8 were seen, but also here a large variation was found in all animals and the mean values were below 0.1. No consistent phase shift between both sides was observed. EEG-patterns like spindles or arousal, still occurred together in both hemispheres after CT, the variability of their exact beginning or end was the same as in controls. Spontaneous spindles often lasted longer after section of the massa intermedia. Homolateral EP's in the somato-sensory area were still present after CT. Rhythmical afterdischarges could be restricted to the contralateral somato-sensory cortex even before CT.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 9 (1969), S. 30-52 
    ISSN: 1432-1106
    Schlagwort(e): Climbing fibers ; Mossy fibers ; Vestibulo-cerebellar input ; Cat ; Frog ; Golgi cell inhibition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. Field and unitary potentials evoked in the vestibulo-cerebellum of frog and cat following vestibular nerve stimulation were recorded with microelectrodes and correlated with their site of origin in the various layers of the cerebellar cortex. 2. In the frog, primary vestibular fibers project both as mossy and as climbing fibers onto the cerebellar auricular lobe. Secondary vestibulo-cerebellar fibers seem to end exclusively as mossy fibers in the auriculum. As a consequence of this dual projection, extra- and intracellular recordings from Purkinje cells in the auricular lobe show two kinds of responses to vestibular nerve stimulation: a) graded, repetitive firing mediated through mossy fiber-granule cell-parallel fiber pathways, and b) all-or-none burst responses caused by monosynaptic impingement of vestibular climbing fibers on Purkinje cells. 3. The field and unitary potentials evoked in the cat nodulus, flocculus and uvula following vestibular nerve stimulation are shown to be generated by mossy fibers exclusively. Considerable convergence of the two labyrinthine mossy fiber inputs to a given cerebellar area was found. 4. Interaction of contralateral and ipsilateral mossy fiber input at the level of the flocculus suggests that Golgi cell inhibition might operate not only as a simple inhibitory feedback loop, but also as a complex gating operator at the granule layer. 5. No short latency climbing fiber activation of Purkinje cells was observed following VIIIth nerve stimulation. Stimulation of the contralateral inferior olive evoked short latency climbing fiber EPSPs in Purkinje cells of the vestibulo-cerebellum. Suggestions are made as to the possible role of mossy and climbing fiber inputs to this area of the cerebellum.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 9 (1969), S. 96-115 
    ISSN: 1432-1106
    Schlagwort(e): Pyramidal tract ; Fusimotor Neurons ; Forelimb ; Extensor ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effects of cortical stimulation upon dynamic and static sensitivities of the sensory endings in muscle spindles have been analyzed. 63 single afferent fibers from the muscle spindles of the forelimb extensors: M. flexor carpi radialis, M. flexor digitorum communis and M. palmaris longus were isolated in dorsal root filaments in 20 adult cats under chloralose-urethane anesthesia. They were identified by their response to stimulation of the median nerve. 1. Surface anodal repetitive stimulation of the anterior sigmoid gyrus was found to produce an enhancement of static response of single Group II fibers. Effective area was localized in a restricted region which corresponded to the forelimb motor area. The effect was obtained without any concomitant muscle contraction. Similarly, the stimulation increased the resting discharges of the Group Ia fibers from the same muscles. 2. Stimulation of the same area in the cerebral cortex was also found to increase the dynamic sensitivities of primary sensory endings. The increase was revealed by an enhancement of initial burst discharge during relaxation period of a twitch contraction caused by median nerve stimulation. 3. These results indicate that stimulation of the forelimb motor area has a facilitatory effect on both the static and dynamic fusimotor neurons innervating the muscle spindles of the test muscles. 4. The effects were reproduced in pyramidal tract preparations in which the brainstem was cut either at the level of the midbrain except for the cerebral peduncle or at the level of caudal medulla oblongata sparing the pyramid. 5. The threshold for the fusimotor effects was less than 1.3–1.5 times threshold of the pyramidal tract discharge, when the best spot for eliciting the fusimotor response was chosen. These results indicate that the effects of cortical stimulation are mainly mediated by the fast conducting pyramidal tract fibers.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 9 (1969), S. 307-324 
    ISSN: 1432-1106
    Schlagwort(e): Muscle spindle ; Gamma motor control ; Mesencephalic reticular formation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Effects of repetitive stimulation of the mesencephalic reticular formation (MRF) on the static discharge and dynamic sensitivity of muscle spindle primary endings (soleus muscle) were studied in cats anaesthetized with Halothane (Fluothane). By progressive increasing the depth of anaesthesia three different fusimotor effects could be observed: 1. A static effect; the static discharge of the primary endings was strongly increased; the response to phasic stretch was decreased or remained unaltered. 2. A dynamic effect; the dynamic sensitivity of the primary endings was powerfully increased while the rate of discharge under static conditions was only slightly augmented. 3. A depressant effect; the static discharge and the dynamic sensitivity of primary endings were decreased. Repeated stimulation elicited successive static and dynamic effects. No specific regions within the MRF could be related to a particular effect.
    Materialart: Digitale Medien
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  • 11
    ISSN: 1432-1106
    Schlagwort(e): Muscle spindle ; Gamma motor control ; Reticular formations ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. During a progressive increase of Fluothane (Halothane) anaesthesia, repetitive stimulation of the mesencephalic retioular formation (MRF) produces several fusimotor effects — static, dynamic or depressant — on primary endings of soleus muscle spindles (Vedel et Mouillac-Baudevin 1969). 2. Transection of the brain immediately rostral to the site of stimulation may increase the dynamic effect but does not alter the static or the depressant effects. 3. A section of the rubrospinal tract does not modify the fusimotor effects elicited by stimulation of the MRF. 4. Transections of the spinal cord have shown that the pathways responsible for the transmission of these effects are mainly situated in the ipsilateral ventral and ventrolateral funiculi which contain the efferent fibers from the pontine reticular formation (PRF), from the bulbar reticular formation (BRF) and from the vestibular nucleus. 5. Contra and ipsilateral PRF stimulation produces the static fusimotor effect; contralateral stimulation from a small anterior region produces the dynamic effect. 6. Stimulation of the lateral part of the ipsilateral BRF elicits the dynamic effect while stimulation of the medial part elicits the static effect.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 9 (1969), S. 164-182 
    ISSN: 1432-1106
    Schlagwort(e): Emotional behaviour ; Hypothalamus ; Electricalstimulation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. In order to compare the selective value of repetitive cathodal pulses of 8 c.p.s. and of continuous sine-wave alternating currents of 5000 c.p.s. (middle frequency current) when applied to brain tissue, explorations were made in the region of the hypothalamus that had yielded defence and/or flight reactions in earlier experiments. The region was explored by stimulating each point in turn with both current forms. At the same time measurement was made of the impedance of the brain tissue, and the effects produced by altering the time of rise of the middle frequency current on threshold of responses were also studied. The experiments were carried out on unanaesthetized, freely moving cats. 2. Both stimulation types produced affective (“emotional”) responses. The patterns elicited by low frequency cathodal pulse stimulation were often associated with stimulus-bound phasic muscle activity, i.e., flapping of ears, and twitching of whiskers, or, rotation of the head. Such extraneous motor effects were rarely obtained when continuous middle frequency currents were applied, and were tonic in character when present. 3. Mapping of reactive points revealed that the area producing defence or flight following middle frequency stimulation is smaller in size than the field delimited by means of repetitive cathodal pulse stimulation. These results strongly suggest that spread of current can be reduced by using middle frequency current stimulation. This apparently local (and hence highly selective) action is paralleled by a lower impedance of the brain tissue to the rapidly changing polarity of this current. 4. The hissing (and/or growling) associated with the defence pattern showed adaptation to suddenly rising middle frequency currents of 30 secs duration. An increase in threshold of hissing occurred when the time of rise of the current was prolonged. Flight, in contrast, was obtained at the same critical intensity regardless of the time of rise of current. 5. The nature of the stimulatory action of middle frequency current (examined in the peripheral nerve by Wyss) and the advantages presented by this new method of brain stimulation are briefly discussed.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 7 (1969), S. 32-50 
    ISSN: 1432-1106
    Schlagwort(e): Lateral cervical nucleus ; Spinal lesions ; Ultrastructural investigation ; Degenerating boutons ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The ultrastructure of terminal degeneration within the lateral cervical nucleus (LCN) after transection of its spinal afferent fibers 2 days–2 years earlier is described. The degeneration after 2 days was of both the neurofilamentous and dense type. The highest number of degenerating terminals, about 15%, was found after 4–5 days. Then most of the degenerating boutons were of the dense type. The degenerating terminals had synaptic contact with cell bodies and dendrites of LCN-neurons. Removal of the degenerating boutons seemed to be effected by a phagocytic cell present in increased number compared to the normal LCN. In cases with long survival times an increase in the number of astroglial filaments was observed. In an animal where the spinal afferents to the LCN had been cut 2 years earlier a decrease in medium size of the neurons was observed. The amount of dendritic spines was also considerably smaller than normally.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 7 (1969), S. 68-83 
    ISSN: 1432-1106
    Schlagwort(e): Medial geniculate body ; Inhibition ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. Inhibitory activity in the cat medial geniculate body (MG) was examined by stimulating electrically and acoustically the input and output of the MG. 2. A longer and more profound depression of excitability occurs following a click-evoked potential in the MG than in the inferior colliculus (IC) in both anesthetized and unanesthetized states. Recovery is cyclic in the barbiturate MG preparation. 3. Electrical stimulation of the brachium of the inferior colliculus (BIG) evokes a field potential in the MG consisting of clearly distinguishable presynaptic and postsynaptic components. The presynaptic component recovers rapidly, while the postsynaptic component requires 100–200 msec for full recovery. This depression of excitability is localized within the MG since cortical ablation does not alter its occurrence. 4. Stimulation of the BIC mimics the effects of click stimulation on single units. Excitatory, inhibitory and reverberatory responses are evoked by the BIC shock. Suppression of single unit activity correlates with the depression of excitability following a BIC-evoked field response. 5. Cortical stimulation can evoke antidromic and trans-synaptic unit responses in the MG, as well as causing a variety of inhibitory effects and reverberation. In view of the fact that cortical ablation does not impair the recording of these responses to afferent stimuli, it is suggested that the cortical-evoked responses are at least partly mediated by antidromic conduction to MG. 6. Evidence is presented that inhibitory effects of both afferent and cortical stimulation are due to active inhibition of MG unit activity. Speculations are made as to the mechanisms producing inhibition and reverberation in the MG.
    Materialart: Digitale Medien
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  • 15
    ISSN: 1432-1106
    Schlagwort(e): Electron microscopy ; Pontine nuclei ; Experimental neuroanatomy ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The electron microscopical changes occurring in the pontine nuclei following unilateral lesions of the primary sensorimotor cortex have been studied in 7 cats with a survival time from 2–23 days. A description is also given of the fine structure of the pontine regions in receipt of the fibres. These regions are shown in Fig. 1. The study shows that the boutons are practically only in synaptic contact with dendrites. The bouton density on these is only 16%. The boutons are of the en passage and terminal type, with the latter as the most common (Figs. 4a-e). The synaptic vesicles are rounded or elongated. The formaldehyde fixed material had 17.8% boutons with vesicles of the elongated type; the material fixed with a mixture of formaldehyde and glutaraldehyde had only 11.5% of such boutons. The degenerating boutons show the dark type of reaction and the majority of the corticopontine fibres are of the type shown in Figs. 4d and 4e. Astrocytes and microglial cells participate in the removal of degenerating boutons and terminal fibres. Degenerating boutons are present even at the 23 day stage and some have apparently only started to degenerate.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 8 (1969), S. 79-96 
    ISSN: 1432-1106
    Schlagwort(e): Evoked potential thresholds ; Factor analysis ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Zur Beschreibung von Korrelationen zwischen zahlreichen elektrophysiologischen Daten aus verschiedenen Hirngebieten wurde eine Faktorenanalyse nach der Hauptachsenmethode gerechnet. Ausgangsmaterial dieser Analyse waren Schwellen subcortical ausgelöster und abgeleiteter Antwortpotentiale auf Einzelreize. Das resultierende Faktorenmuster ermöglicht ein quantitatives Konzept der Schwellendetermination subcorticaler Reizantworten und zugleich ein Modell von Funktionsbeziehungen zwischen einigen Hirnstrukturen. Die Reizungen und Ableitungen erfolgten bei 35 encéphale isolé-Katzen mit Hilfe bipolarer Elektroden in folgenden Arealen: Amygdala, Hippocampus, Septum, N. dorsomedialis Thalami, Hypothalamus posterior und Formatio reticularis mesencephali. Es wurden 435 Korrelationskoeffizienten zwischen den Schwellen von 30 subcorticalen Verbindungen gebildet und zum Zwecke einer Datenreduktion durch eine Matrix von 5 Faktoren reproduziert. 1. Jeder Faktor repräsentierte hohe Schwellenkorrelationen zwischen den efferenten Projektionen jeweils eines Kerngebietes. Demnach nimmt im allgemeinen die Aktivität des Reizortes den größten Einfluß auf die Schwelle eines Antwortpotentials. Diese Hypothese ist durch pharmakologische Untersuchungen belegt worden [27] 2. Kovariationen von Reizantworten mit identischen Ableiteorten ergaben sich ausnahmslos, wenn die Latenzzeiten mehr als 11 msec betrugen. 3. Zusätzlich zeigte die Faktorenmatrix Schwellenkorrelationen zwischen: a) den hypothalamischen Efferenzen und mehreren hippokampalen Afferenzen langer Latenz (positive Korrelationen) b) retikulo-limbischen Verbindungen und „primären” Efferenzen von Amygdala und Hippocampus (positive Korrelationen) c) Antwortpotentialen, die durch Reizung der Formatio reticularis, und solchen, die durch Reizung des N. Amygdalae ausgelöst waren (negative Korrelationen) d) den Efferenzen des N. dorsomedialis Thalami und limbischen Projektionen langer Latenz zur mesencephalen Formatio reticularis (positive Korrelationen) Die Interpretation dieser Zusammenhänge bestätigt und erweitert einige bekannte Modelle von Beziehungen zwischen subcorticalen Kerngebieten. Abschließend wird mit Rücksicht auf die Linearität der mathematischen Methode die Anwendbarkeit der Faktorenanalyse auf Schwellen von Reizantworten diskutiert.
    Notizen: Summary In 35 cats (encéphale isolé) evoked responses were elicited and recorded with bipolar electrodes from the amygdala, hippocampus, septum, dorsomedial thalamic nucleus, posterior hypothalamus, and mesencephalic reticular formation. Correlations between the thresholds of responses in different areas following stimulation of other areas were described by a factor analysis according to the principal axis method. 435 coefficients of correlation were calculated and reproduced by a matrix of 5 factors for the purpose of data reduction. Each factor represented high threshold correlations between the efferent projections of one region, which suggests that the activity of the stimulated site exerts a major influence on the evoked potential threshold. This is supported by pharmacological studies [27, 49]. Covariations of responses recorded in the same nucleus were always found, if the latencies exceeded 11 msec. The factor matrix indicated threshold correlations between: the efferent projections of the hypothalamus and several long latency afferent projections to the hippocampus (positive correlations); reticulo-limbic connections and “primary” efferent connections of the amygdala and hippocampus (positive correlations); evoked potentials following reticular and amygdaloid stimulation (negative correlations); the efferent projections of the dorsomedial thalamic nucleus and long latency limbic projections to the mesencephalic reticular formation (positive correlations). The interpretation of these relationships confirms and extends some well known models of relations between subcortical regions. The applicability of factor analysis to evoked potential thresholds is discussed with regard to the linearity of the mathematical method.
    Materialart: Digitale Medien
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  • 17
    ISSN: 1432-1106
    Schlagwort(e): Emotional Behaviour ; Hypothalamus ; Electrical stimulation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. The results presented in the present paper are an extension of preceding work devoted to exploration of the hypothalamic defence and flight fields using coaxial electrodes with small cathode. In 33 cats simultaneous stimulation was applied to two points which upon single stimulation had yielded defence, flight, or defence and flight respectively. Results were compared with those produced at either point alone. In 2 cats combined stimulation of a defence and a flight point was carried out with a stuffed cat present. 2. The latencies and rates of the vocal effects associated with defence (growling and hissing), and the latencies of flight (jump from the table) were measured. 3. Simultaneous stimulation of two points which had yielded defence, or of two points which had yielded flight resulted in facilitation (spatial summation) of the effects evoked: a more complete defence response associated with decrease of the latencies and increase in the rates of the vocal effects; decrease of flight latencies and increase of flight impetuosity. 4. Simultaneous stimulation of a defence point which had yielded growling at lower threshold than hissing, and of a point which had yielded flight resulted in facilitation of hissing. Growling and flight were often suppressed; when they occurred, latencies were lengthened and growling rates were increased somewhat. 5. Stimulation of a defence point with a dummy present produces striking (fending off). Simultaneous stimulation of a flight point resulted in facilitation of both hissing and striking. 6. It is concluded that the complex patterns obtained when defence is combined with flight are the result of facilitatory and inhibitory interaction between the elements of the individual patterns.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 8 (1969), S. 37-52 
    ISSN: 1432-1106
    Schlagwort(e): Retinal Ganglion Cells ; Spatial Summation ; Center Inhibition ; Dynamic Organisation of Receptive Fields ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung 1. An retinalen Ganglienzellen der Katze wurde die räumliche Summation im receptiven Feldzentrum (KFZ) bei Dunkeladaptation und Helladaptation durch mittelpunktzentrierte Lichtreize verschiedener Flächengrößen untersucht. Als Kriterium dienten die Entladungsraten der ersten 200 und 500 msec nach Licht-an oder Licht-aus. Das Summationsverhalten wurde sowohl für Einzelneurone als auch gruppenstatistisch für die beiden Neuronen-Systeme B (on-Zentrum) und D (off-Zentrum) untersucht. 2. Die räumliche Summation ist auf den inneren Bereich des RFZ beschränkt: bei on-Zentrum-Neuronen steigt die Entladungsrate nur bis zu Reizflächen, die etwa 1/5 der Fläche des RFZ belichten, bei off-Zentrum-Neuronen bis zu Reizflachen von ca. 1/10 des RFZ. Bei Variation der Reizfläche zwischen 20 und 100% der Fläche des RFZ bleibt das Entladungsniveau konstant (asymptotischer Verlauf der Summationskurve). 3. Die Begrenzung der räumlichen Summation auf einen kleinen Bereich des RFZ beweist eine bereits im Feldzentrum wirksame Hemmung. Diese Zentrum-Inhibition begrenzt die Erregungssummation im RFZ bei zunehmender Flächengröße des Lichtreizes. 4. On- und off-Zentrum-Neurone unterscheiden sich in beiden Adaptationszuständen in der Höhe des Entladungsniveaus. Die Entladungsraten der on-Zentrum-Neurone nach Licht-an übertreffen um ein Mehrfaches die Entladungsraten der off-Zentrum-Neurone nach Licht-aus. Die Unterschiede sind gruppenstatistisch hoch signifikant. Die interneuronale Variabilität der Entladungsraten ist bei den onZentrum Neuronen erheblich geringer als bei den off-Zentrum-Neuronen. 5. Dunkel -und Helladaptation führt zu signifikantem Unterschied der Entladungsraten: bei Helladaptation liegt die Impulsrate beider Neuronentypen höher als bei Dunkeladaptation und der Summationsbereich ist um 5–10% größer. 6. Für die mathematische Beschreibung der Summationsverläufe ist die Hyperbel besser geeignet als die logarithmische und Potenzfunktion. Logarithmus- und Potenzfunktionen beschreiben den konstanten asymptotischen Teil der Summationskurven ungenügend und eigenen sich nur für den Kurventeil im innersten Summationsbereich. Die Bedeutung der Befunde für eine dynamische Interpretation der visuellen Feldorganisation und mögliche Beziehungen zur lateralen Umfeldhemmung werden diskutiert.
    Notizen: Summary 1. Spatial summation of suprathreshold light stimuli within receptive field centers (RFZ) of retinal ganglion cells was investigated during dark and light adaptation in cats. The mean discharge rates for 200 and 500 msec following light on or off were the computed response criteria. The summation effects were analyzed for single neurones and statistically for grouped neuron populations of the two neuronal subsystems B (on-center-neurones) and D (off-center-neurones). 2. Spatial summation is restricted to a small part of the RFZ. On-centerneurones increase their on-discharge rates with increasing spot sizes, only if the stimulus illuminates less than 1/5 of the RFZ. The summating area of the off-centerneurones is smaller (about 1/10 of the RFZ). 3. The limitation of spatial summation to a small part of the RFZ indicates the existance of inhibition within the RFZ. This center-inhibition sets a constant limit for excitation summation in the RFZ. 4. The mean neuronal response rates for the 2 subsystems show significant differences: The on-discharges of the on-center-neurones exceed the off-discharges of the off-center-neurones by a factor of 3–5. These highly significant differences occur at both adaptation levels and are not due to different spontaneous activity. Interneuronal response variability of the off-center-neurones was twice as large as that of the on-center-neurones. 5. Change from dark to light adaptation had only a small but significant influence on summation properties. The poststimulus discharge rates were higher during light adaptation and the summating area was slightly larger (about 5–10%). 6. A comparative curve fitting procedure for three suitable mathematical functions revealed that the hyperbola describes the neuronal summation curves better than a logarithmic or power function. The latter do not fit the constant asymptotic part of the curve. The significance of the results for a dynamic interpretation of the organisation of visual receptive fields is discussed.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 8 (1969), S. 53-65 
    ISSN: 1432-1106
    Schlagwort(e): Lateral geniculate body ; Spatial summation ; Off-center-characteristics ; Geniculate transfer ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung 1. Die räumliche Summation im receptiven Feldzentrum von Neuronen des Corpus geniculatum laterale (CG-L) wird beschrieben und mit entsprechenden Untersuchungen an retinalen Ganglienzellen verglichen. Neben größerer interneuronaler Variabilität ergeben sich ausgeprägtere Unterschiede der Summationseigenschaften der on-und off-Zentrum-Neurone. Der effektive Summationsbereich von etwa 1/5 der Fläche des RFZ ist in Retina und CGL etwa gleich. 2. Die on-Zentrum-Neurone des CGL zeigen in beiden Adaptationszuständen einen ähnlichen Summationsverlauf wie in der Retina. Das Entladungsnieau ist im CGL jedoch erheblich geringer und nicht durch Unterschiede in der Spontanaktivität zu erklären. 3. Die Mehrzahl der off-Zentrum-Neurone des CGL zeigt bei DA inverse Summationsverläufe wie in der Retina: durchgehende Verminderung der Entladungsrate der off-Antworten bei Vergrößerung der Reizfläche im RFZ. Eine kleine Gruppe zeigt einen parabelförmigen Summationsverlauf mit Entladungszunahme bis zu Reizflächen von 10–30% der Fläche des RFZ und darauffolgender Entladungsminderung. Bei Helladaptation zeigen fast alle off-Zentrum-Neurone diesen Parabelverlauf. Das durchschnittliche Entladungsniveau ist von dem retinaler offZentrum-Neurone nicht signifikant verschieden. 4. Die interneuronale Variabilität der Summationsvorgänge im RFZ von CGLNeuronen ist gegenüber den retinalen Ganglienzellen deutlich größer. Dies gilt insbesondere für die off-Zentrum-Neurone. Das Summationsverhalten von CGLNeuronen läßt sich daher nicht wie in der Retina durch einen Funktionstyp beschreiben. 5. Die Befunde sprechen für eine Transformation des retinalen Eingangs der off-Zentrum-Neurone im CGL, während die on-Zentrum-Neurone außer der bekannten Frequenzuntersetzung keine wesentliche Umformung erkennen lassen.
    Notizen: Summary 1. Spatial summation in the receptive field center of neurones of the lateral geniculate body (CGL) is limited by inhibition to a small part of field center. Variations of stimulus size are only effective if the stimulus is smaller than about 1/5 of the area of receptive field center. Thus, the active summating area of the field center in the CGL corresponds to that of the retina. Geniculate neurones, however, show less homogeneous responses and the summation properties of the two neuronal subsystems (on-center-and off-center-cells), show greater differences than in the retina. 2. The form of summation curves for the on-center-neurones of the CGL is similar to those of the retina at both adaptation levels. However, the average responses rates in the CGL are considerably lower. This is not due to differences of spontaneous activity. 3. The summation characteristics of off-responses of off-center-neurones of the CGL are quite different from those in the retina. In dark adaptation the majority of CGL neurones respond with decreasing discharge rates to increasing spot-sizes within the field center. A small number show an initial increase of discharge rates up to stimulus sizes of about 1/10 of the receptive field center before a decrease occurs. This parabolic summation type is typical for most off-center-neurones in light adaptation. The mean discharge levels are the same as those of the retinal offcenter-neurones. 4. The higher interneuronal variability of summation curves especially of the off-center-neurones of the CGL indicates a more complex determination of the discharge properties of CGL neurones. This functional differentiation of single neurones is congruent with the more complex structural and synaptic organisation in CGL. 5. With respect to spatial summation, the results indicate a transformation of the retinal input of the off-center-neurones at the geniculate level, whereas the oncenter-neurones are nearly unchanged.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Psychopharmacology 14 (1969), S. 164-166 
    ISSN: 1432-2072
    Schlagwort(e): Benperidolum ; Cat ; Extrapyramidal Side Effect ; EEG ; Toxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Daily doses of 1–10 mg Benperidol were given perorally to cats during 26 months. The general behaviour and the EEG were unchanged during the treatment, in particular no signs of dyskinesia were observed. After discontinuation of the administration, the behaviour and the EEG of the animals stayed normal. Thus no lasting and irreversible side effects could be observed.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Psychopharmacology 15 (1969), S. 382-391 
    ISSN: 1432-2072
    Schlagwort(e): LSD ; Retina ; LGN ; Single Unit Activity ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effect of LSD 25 (i. v. injection) on the spontaneous and evoked activity of the visual system was investigated in cats. 50 γ/kg did not change significantly the ERG and the visual cortical evoked potential. The spontaneous discharge rate of 14 out of 21 retinal ganglion cells showed an increase which reached its maximum within 20–30 min and which could still be present 1 hour following the injection. One third of the retinal units showed a slight depression of their spontaneous dischaRge rate with about the same time course. Single units of the LGN showed about the same behaviour. The response to light stimulation was slightly increased in some units and light induced inhibition was slightly shortened. The possible mechanism of the LSD-effect on retinal ganglion cell activity is discussed.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 309 (1969), S. 285-309 
    ISSN: 1432-2013
    Schlagwort(e): Labyrinthine Stimulation ; Types of Abducens Neurones ; Frequency Analysis ; Cat ; Labyrinthreizung ; Abducensneurone ; Frequenzanalyse ; Katze
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Single cell activity was recorded extracellularly from neurones in cat's abducens nuclei in unanesthetized, decerebrate preparations. Two types of neurones were found. i) The motoneurones (type IIA) increased their firing linearly or exponentially to contralateral constant angular accelerations and decreased firing to ipsilateral rotation. The increased frequency was maintained at a constant level without any sign of adaptation. This constant level of maximum frequency was proportional to the logarithm of the acceleration applied. No significant differences of the frequency responses of tonic and silent motoneurones were found. The conduction velocities of the axons of spontaneously firing type IIA cells were slower than in silent neurones. Electrical stimulation of the contralateral VIIIth nerve led to activation of the type IIA cells; stimulation of the ipsilateral nerve resulted in inhibition of both spontaneous discharge and antidromic invasion of the motoneurones. ii) The type IA units increased their firing rate to ipsilateral rotation and ceased to discharge in response to contralateral rotation. They never were excited antidromically by stimulation of the VIth nerve. However, they were excited by stimulation of the ipsilateral VIIIth nerve. Their possible functional role in the vestibulo-ocular system was discussed.
    Materialart: Digitale Medien
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  • 23
    ISSN: 1432-2013
    Schlagwort(e): Cat ; Decerebration ; Afferents to Respiratory Centers ; Medulla Oblongata ; Reticular Formation ; Katze ; Decerebrierung ; Afferenzen zu Atemzentren ; Medulla oblongata ; Formatio reticularis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung An 11 intercolliculär decerebrierten Katzen wurde geziegt, daß Kälteblockade eines eng umschriebenen Feldes auf der ventralen Oberfläche der Medulla oblongata, wie früher für anaesthesierte Tiere beschrieben, zu Atemstillstand führt, wenn die kontralaterale Stelle auf der Medulla oblongata, die Sinusnerven und die Vagi ausgeschaltet sind. Zu Atemstillstand kam es auch, wenn statt der Kälteblockade 2% Novocain durch lokale Superfusion bei gleichzeitiger Gegenspülung der Umgebung mit künstlichem Liquor angewandt wurde, oder wenn ein mit 1% Novocain getränkter Tupfer lokal aufgelegt wurde. Außerdem führte Kälteblockade zu Atemstillstand, wenn durch kontinuierliche auch während der Kälteblockade anhaltende elektrische Reizung eines N. femoralis oder hinterer Lumbalwurzeln an decerebrierten Katzen oder des Hypothalamus an einer anaesthesierten Katze Steigerungen der Ventilation ausgelöst worden waren. Elektrische Reizung eines Sinusnerven führte zu Atemsteigerungen. Bei Sinusnervenreizung während eines durch Kälteblockade ausgelösten Atemstillstands kam es zu rhythmischer Atmung. Aus diesen Untersuchungen wird geschlossen, daß mit der Ausschaltung der beschriebenen Felder auf der ventralen Oberfläche der Medulla oblongata am sonst desafferentierten Tier die Gesamtheit der für die zentrale CO2-Empfindlichkeit verantwortlichen Strukturen erfaßt ist, daß nach Ausschaltung der zentralen und der peripheren Chemosensibilität eine unspezifische Aktivierung der Atmungszentren unwirksam ist und daß die Atmungszentren zur Ausbildung einer rhythmischen Atmung von spezifischen Antrieben abhängig sind.
    Notizen: Summary It was shown in 11 decerebrated cats, that cooling of a small and well defined area on the ventral surface of the medulla will cause respiratory arrest if the contralateral area of the medulla, the vagi and sinus nerves are eliminated. This confirms earlier observations obtained in anesthetized cats. Apnea was also produced by local superfusion of 2% procain with simultaneous flushing of the immediate surrounding area with mock spinal fluid. Local application of a small sponge soaked with 1% procain had the same effect. Electrical stimulation of femoral nerves or posterior roots which results in hyperventilation on the decerebrated cat failed to show any effect during periods of cold blockade. There was no respiratory response to direct stimulation of the hypothalamus in an anesthetized cat during cooling. Electrical stimulation of one sinus nerve caused an increase of ventilation. Sinus nerve stimulation during apnea induced by cold blockade resulted in rhythmical respiration. It is concluded from these experiments: Blocking of the area under discussion on the ventral surface of the medulla, inhibits all structures responsible for the central CO2-sensitivity in the deafferentiated animal. There was no response to non-specific stimuli of the respiratory center after elimination of central and peripheral chemosensitivity. The respiratory centers apparently depend on specific stimuli to support rhythmical respiration.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 8 (1969), S. 113-129 
    ISSN: 1432-1106
    Schlagwort(e): Emotional behaviour ; Hypothalamus ; Electrical stimulation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. Affective behaviour patterns produced by electrical stimulation of the hypothalamus were studied in unanaesthetized, freely-moving cats. Bipolar stimulation with coaxial electrodes and small cathode was used to elicit defence, attack or flight. The development of these responses was studied by varying stimulation strength. In some experiments a stuffed animal was introduced in order to study the reactions of the cat to changes in the environment during stimulation. 2. The following responses were evoked at threshold intensity: (i) growling reaction; (ii) hissing reaction; (iii) two types of flight — type a preceded by hastily looking to and fro as if in search of an exit, type b preceded by inspection of surroundings, in most cases associated with sniffing. 3. Increasing stimulation 1.5 times threshold often yielded combined patterns. At points yielding the growling reaction a defence response in which growls alternated with hisses was obtained. The points yielding flight type a sometimes yielded hissing followed by flight. Increasing stimulation at hissing points yielded either a defence reaction or the combined effect hissing-flight. 4. The growling reactions were obtained from the tuber region. The hissing responses were obtained from points above the tuber. The flight reactions, type a, were produced from the intermediate zone extending from the level of the preoptic area to the mamillary bodies and type b from the caudo-lateral hypothalamus. 5. The reactions of the cats to a dummy during stimulation varied depending on the type of response which had been evoked in the absence of the dummy. The defence reaction was converted into threatening and striking of the dummy, the combined effects into threatening, striking or biting, culminating in sudden flight. The dummy was ignored during stimulation of points yielding flight type a, but examined by sniffing during stimulation of points yielding flight type b.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 8 (1969), S. 219-231 
    ISSN: 1432-1106
    Schlagwort(e): Cerebral cortex in vitro ; Chloride transport ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The kinetics of the uptake of chloride by slices of cat cerebral cortex incubated in vitro have been studied for a wide range of concentrations of chloride and potassium in the incubation media. 1. In studies with 36Cl at a constant concentration of external K+, the rate of entry of chloride into slices of cat cerebral cortex (after equilibration with the fluid of the extracellular space) followed Michaelis-Menten kinetics with Vmax=7.7 μmoles/g/min and Km=245 mM. The kinetic data so described differ significantly from a curve describing simple diffusion (P 〈 0.02). 2. A clear dependence on concentration of K+ in the incubation medium was demonstrated. When external chloride was held constant at 6.8 mM and concentrations of potassium were varied over a range of 27–100 mM, the apparent rate of entry of chloride followed Michaelis-Menten kinetics with Vmax=0.191 μmoles/ g/min and Km=30.3 mM. 3. Under similar equilibrium conditions, the rate of influx of chloride was not statistically different from the rate of efflux, and the value for extracellular space (355 μl/g) derived by extrapolation from efflux data was of an identical order of magnitude to the value (352 μl/g) obtained from influx data. These values are essentially identical to those previously determined for chloride space of cat cerebral cortex in vivo (Bourke, Greenberg and Tower 1965). 4. The total, membrane-delimited content of chloride in cerebral cortex, as defined in these studies in vitro, was a function of the concentration of K+ in the incubation medium.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 8 (1969), S. 232-248 
    ISSN: 1432-1106
    Schlagwort(e): Cerebral cortex in vitro ; Edema ; Fluid compartmentation ; Chloride transport ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The ionic parameters of incubation media which foster both the development and subsequent reduction of swelling of slices of cerebral cortex under isosmotic conditions of incubation in vitro are described. A linear relationship between increasing chloride concentrations in incubation media and progressive swelling of tissue slices (under conditions of constant temperature and K+ concentrations and isotonicity of incubation media) is demonstrated. Subsequent reduction of chloride concentration in incubation media together with reciprocal replacement by isethionate is associated with significant and characteristic reduction in the volume of tissue swelling when all other conditions of incubation, including isotonicity of the media, are kept constant. The ionic composition of the fluid of swelling under different conditions of incubation is derived together with the ionic composition and expected transmembrane potentials of the neuronal compartment of cerebral cortex in vitro. Mechanisms involved in the development and subsequent reduction of swelling of cerebral cortex in vitro are discussed, and proposals for possible clinical applications are suggested.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 262 (1969), S. 73-86 
    ISSN: 1432-1912
    Schlagwort(e): Strophanthidine Derivatives ; Toxicity ; Absorption ; Guinea-Pig ; Cat ; Strophanthidinderivate ; Toxicität ; Resorption ; Meerschweinchen ; Katze
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wurde die Wirksamkeit verschiedener Ester und Äther von Helveticosid und Helveticosol bei i.v. und intraduodenaler Zufuhr an Katzen und Meerschweinchen geprüft. 1. Bei i.v. Dauerinfusion waren Helveticosol und seine Derivate bei Meerschweinchen etwa doppelt so wirksam wie die analogen Helveticosidverbindungen. Bei der Katze bestand kein Unterschied. Die Monomethyläther Cymarin und Cymarol waren gleich oder sogar stärker wirksam, alle übrigen Derivate deutlich schwächer als die Ausgangssubstanzen. 2. Die tödlichen Dosen bei intraduodenaler Injektion lagen beim Meerschweinchen für einige Substanzen in gleicher Größenordnung oder niedriger als die Titer bei i.v. Infusion. Diese hohe enterale Wirksamkeit kann bei Helveticosid und seinen Derivaten durch eine Reduktion zu dem wirksameren Helveticosol, bei Estern außerdem durch eine Hydrolyse zu wirksameren Glykosiden vorgetäuscht werden. 3. Bei intraduodenaler Infusion an Katzen waren alle geprüften Ester und Äther wirksamer als Helveticosid und Helveticosol. Die aus dem Verhältnis der toxischen Dosen bei i.v. und intraduodenaler Infusion berechnete enterale Wirksamkeit lag zwischen 20 und 50%. 4. Unterschiede in der Dauer der intraduodenalen Infusion bei Katzen lassen sich berücksichtigen, wenn man von der theoretischen Annahme einer exponentiellen und vollständigen Resorption ausgeht und die Halbwertszeit für die Resorption berechnet. Die minimale Resorptionsgeschwindigkeit lag bei einigen Derivaten in gleicher Größenordnung wie bei Digoxin und Digitoxin. Es wird auf den Unterschied zwischen der auf Grund der pharmakologischen Wirkung bestimmten relativen enteralen Wirksamkeit und der Resorptionsquote hingewiesen. Letztere ist für die Verläßlichkeit der therapeutischen Wirkung eines Glykosids bei oraler Gabe maßgebend.
    Notizen: Summary The efficacy of several esters and ethers of Helveticosid and Helveticosol was assayed by intravenous and intraduodenal administration to cats and guinea-pigs. 1. In guinea-pigs, Helveticosol and its derivatives were approximately twice as active on intravenous infusion as the analogous derivatives of Helveticosid; in cats there was no significant difference. The monomethylethers Cymarin and Cymarol were equally or slightly more potent, all other derivatives were weaker than the original compound. 2. In guinea-pigs the lethal doses of some compounds on intraduodenal injection were equal to or even lower than those on intravenous infusion. This may partly be accounted for by a reduction of Helveticosid and its derivatives to the more potent Helveticosol analogues, partly by a hydrolysis of the esters, yielding compounds of higher activity. 3. On intraduodenal infusion in cats, all the investigated esters and ethers were more active than Helveticosid and Helveticosol. The relative enteral activity calculated from the ratio of the toxic doses on intravenous and intraduodenal infusion varied between 20 and 50%. 4. Due to a delayed absorption from the gastrointestinal tract, the toxic dose falls with a reduced speed of intraduodenal infusion. Assuming an exponential and complete absorption, the half time of absorption was calculated. For some of the compounds investigated, the speed of absorption was comparable to that of Digoxin and Digitoxin. The difference between the relative enteral activities determined by comparing equiactive doses on enteral and parenteral administration and the percentages of the glycosides which are absorbed from the gastrointestinal tract is pointed out. The latter is of prime importance for obtaining reproducible effects after enteral administration.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 101 (1969), S. 607-620 
    ISSN: 1432-0878
    Schlagwort(e): Glandula bulbourethralis ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Das Parenchym der Glandula bulbourethralis der Katze besteht aus weitlumigen, gebuchteten intraglandulären Gängen, in welche kurze, englumige, zumeist unverzweigte Tubuli einmünden. Der Drüse fehlt eine äußere Organkapsel, so daß ihre peripheren Tubuli stellenweise direkt zwischen den Fasern des quergestreiften M. bulboglandularis liegen. Die Drüsentubuli und die Buchten der intraglandulären Gänge sind mit einem einschichtigen Zylinderepithel ausgekleidet, auf den Gangfalten ist das Epithel abschnittsweise mehrreihig, Die sezernierende Epitheloberfläche ist durch die Ausbildung von interzellulären Sekretkapillaren vergrößert. Breite Zwischenzellspalten (Durchmesser etwa 1,5μ), in welche schlanke interdigitierende Cytoplasmafortsätze hineinragen, erstrecken sich von der Basalmembran bis kurz unter das Tubulusbzw. Ganglumen. Die lumenseitigen Zellgrenzen tragen einige stummelförmige Mikrovilli und besitzen zerklüftete Außenkonturen, die durch glykogenreiche Cytoplasmaprojektionen bedingt sind. Alle Epithelzellen sind reich an Mitochondrien. Die supranuklearen Abschnitte der meisten Gang- und Tubuluszellen enthalten Sekretgranula, welche im Elektronenmikroskop unterschiedliche optische Dichten aufweisen können. Die Granula enthalten ein PAS-positives, neuraminsäurehaltiges epitheliales Muzin, das in einzelnen Sekretkörnchen auch eine histochemische Reaktion auf Sulfatgruppen gibt. Alle Epithelzellen reagieren sehr stark auf unspezifische Esterase und stark auf β-D-Glucuronidase, β-D-Glactosidase sowie die Enzyme des Citronensäurezyklus, der Glykolyse und der Atmungskette (NAD-ICDH, SDH, ALD, LDH, ADH, GDH, NADH-T-Red, Cyt-Ox).
    Notizen: Summary The bulbourethral glands of sexually mature male cats are studied with the light and electron microscope. The parenchyma consists of spacious, sinus-like intraglandular ducts and short, narrow, mostly unbranched tubular endpieces. The gland has no complete connective tissue capsule, consequently some of the peripheral tubules are situated directly in between the fibers of the surrounding bulboglandularis muscle. The endpieces and the sinus of the intraglandular ducts are lined by a simple columnar epithelium, whereas the folds of the ducts are generally covered by a low pseudostratified epithelium. The secretory surface of the cells is increased by intercellular canaliculi which communicate with the gland lumen. These canaliculi are identified on the light microscopic level by their strong 5′-nucleotidase activity. Furthermore widened intercellular spaces (approximately 1,5 μ in diameter) filled with slender, interdigitating cytoplasmic processes extend from the basal lamina to the apical junctional complexes. The luminal cell pole exhibits some short microvilli and forms irregularly shaped, glycogen containing protrusions. Within the cytoplasm of the gland cells numerous spherical mitochondria, some dense bodies, a typical Golgi apparatus, free ribosomes and a poorly developed endoplasmic reticulum are to be observed. Secretory granules which can be grouped into three types on the basis of their electron density occur in the supranuclear regions of most of the cells. According to histochemical tests all granules contain a periodate reactive sialomucin and some of them also sulfate groups. The glandular parenchyma is site of an exceptionally strong unspecific esterase activity and is rich in β-D-glucuronidase, β-D-glactosidase, aldolase, α-glycerophosphate dehydrogenase, lactate dehydrogenase, alcohol dehydrogenase, NAD-dependent isocitrate dehydrogenase, succinate dehydrogenase and cytochrome oxydase.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 585-587 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969) 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 31
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 1-1 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 3-9 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: C—Cl and C—C bond energies in the chloroethanes and C—H, C—Cl, and C—C bond energies in the chloroethyl radicals are calculated from known heats of formation of chloroethanes and chloroethylenes and known C—H bond energies in chloroethanes.The results obtained show a dependence of bond energy on the isomeric structure of the molecules and radicals and on the type of bond broken (primary, secondary, or tertiary). Heats of formation and bond energies estimated from group property additivity rules are in close agreement with experimental values.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
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  • 33
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 11-27 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A study of the pressure dependence of the C5 products from the reaction of cis-butene-2 and methylene is reported. Methylene was produced by the photolysis of diazomethane with 4358 Å light at 23° or 56°, and by photolysis of ketene with 3200 Å radiation at 23° or 100°. The change with increasing pressure of the relative amounts of the characteristically “triplet products” (trans-1,2-dimethylcyclopropane, trans-pentene-2 (TP2), and 3-methylbutene-1 (3MB1)) and “singlet products” (cis-1,2-dimethylcyclopropane (CDMC) and cis-pentene-2 (CP2)) are discussed. The behavior is reminiscent of that found in 3CH2-cis-butene-2 systems and can be interpreted in terms of the rapid rate of rearrangement of an initial triplet diradical product component, due to 3CH2, relative to the slower rate and readier collisional stabilization of an initial vibrationally-excited dimethyl cyclopropane product component, due to 1CH2. Relative rates of reactions of 1CH2 with allylic CH:vinyl CH:C=C in the neat liquid were, for diazomethane, 1:1.1:7.2 and, for ketene, 1:1.2:6.7.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 34
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The use of iodine monochloride (ICl) as a thermal source of chlorine atoms in known concentration is discussed with particular reference to the suppression, by large excesses of iodine, of the chain processes normally associated with chlorine atom reactions. The kinetics and mechanism of the reaction of ICl with hydrogen are presented in a study covering the temperature range 205-337°C, and the pressure ranges: ICl, 6-20 torr; I2, 3-13 torr; and H2, 9-520 torr. The reaction, followed spectrophotometrically in a static system, is shown to be homogeneous, first order in ICl and in H2, and inverse half-order in I2, over several half-lifetimes of the ICl, yielding HCl as the sole product. The rate data obtained in this work for the reaction are combined with the critically evaluated results of other workers in an Arrhenius plot covering the temperature range 286-730°C, and three orders-of-magnitude in the rate constant, yielding the results, log k1/(1/mole sec) = 10.68-5.26/θ, where θ = 2.303RT in kcal/mole. This value of k1 is lower by a factor of about two than that proposed in a recent review by Fettis and Knox, and is clearly at variance by a factor of two or more with the most recent data of Clyne and Stedman.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 35
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The temperature-jump method has been used to determine the nickel(II)- and cobalt(II)-arginine complexation kinetics. In the pH range studied, the neutral form of the ligand, HL, is the attacking, as well as the complexed, ligand species. The reactions reported on are of the type where n = 1, 2, 3 and M is Ni or Co. At 25° and ionic strength 0.1M the association rate constants are: for nickel(II) k1 = 2.3 × 103(±20%), k2 = 2.4 × 104(±20%), k3 = 3.5 × 104(±40%) M-1 sec-1; for cobalt(II) k1 = 1.5 × 105(±20%), k2 = 8.7 × 105(±20%), k3 = 2.0 × 105(±40%) M-1 sec-1. Arginine binds to metal ions less well than homologous chelating agents due to the electrostatic repulsion arising from the positively charged terminus of the zwitterion. Kinetically, the effect appears in the association rate constants with nickel reactions more strongly influenced than cobalt.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 36
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The spectrophotometric determination of the rate of iodine atom catalyzed geometrical isomerization of diiodoethylene in the gas phase from 502.8 to 609.1°K leads to a rate constant for the bimolecular reaction between I and trans-diiodoethylene of log kt-c(M-1 sec-1) = 8.85 ± 0.12 - (11.01 ± 0.30)/θ. Estimates of the entropy and enthalpy change for the addition of I atoms to trans-diiodoethylene (process a.b) lead to log Ka.b(M-1) = -2.99 - 4.0/θ, and thus to log kc (sec-1) = log kt-c - log Kab = 11.8 -7.0/θ for the rate constant for rotation about the single bond in the adduct radical. The theory for calculation of the rotation rate constant is presented and it is shown that while the exact value depends on the barrier height, a value of 6.8 kcal/mole for this quantity leads to log k (sec-1) = 11.8 -6.7/θ. The activation energy points to a better value of the group contribution to heat of formation of the group C-(I)2(H)(C) than one based on bond additivity.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 69-87 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The title reactions have been investigated in a fast flow system at pressures of about 2 torr and temperatures between 12 and 132°C. The following Arrhenius equations are derived for reaction (2) where the units of k2 are l/mole sec and of E2, cal/mole, and the limits are the 95% confidence limits assuming random errors.These equations are in good agreement with those which can be derived from previous investigations.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 38
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 105-111 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction between carbon monoxide and atomic oxygen was studied in a gas flow over a temperature range of 136 to 230°C at atmospheric pressure. The rate constant of this reaction, considered to be one for a second-order reaction, was found to decrease with increasing temperature and to depend on the ratio of O2 to CO that was varied from 0.11 to 2.69. A conclusion was made that under the experimental conditions the reaction was third order The rate constant of this reaction was determined for a mixture of O2 and CO and it was found that the efficiency of O2 as particle M is four times that of CO.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 39
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 113-126 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Rates of solvolysis of benzyl chloride and of substituted benzyl chlorides have been measured in an acetone-water mixture (acetone mole fraction 0.147) at pressures ranging from atmospheric to 1 kbar. Pressure studies have also been made for p-methyl benzyl chloride in various acetone-water mixtures. Measurements have also been made of the partial molar volumes of the reactants. The plots of log k against pressure are fitted to a second-degree polynomial in P, and values of ΔV
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 40
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The method of molecular-modulation spectrometry for studying photochemical reactions has been applied to methyl nitrite photolysis. The infrared absorption of the nitroxyl radical HNO has been observed in the gas phase at 3300 cm-1. Under the present experimental conditions the steady-state concentration of HNO under steady illumination was 1.1 × 1012 particles/cc, and the observed modulation amplitude was 4.5 × 1010 particles/cc. At 25°C and 1 atm of nitrogen, the cross section for infrared absorption by HNO at 3300 cm-1 is 1.7 × 10-19 cm2. The rate constant ratio b/c was found to be 8.0. From the literature value of the rate constant d , the observed rate constant for the reaction is e = (5 ± 1) × 10-11 cc/particle sec.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969) 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 42
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 147-156 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The spectrophotometric determination of the rate of pyrolysis of 1,2-diiodoethylene from 305.8 to 435.0° (with additional data on the addition of iodine to acetylene from 198.1 to 331.6°) has resulted in the observation of both a (in part heterogeneous) unimolecular process (A), and an iodine atom catalyzed process (B). For the homogeneous unimolecular process, log (kA/sec-1) ≈ 12.5-46/θ would appear to be reasonable, while log (kB/M-1 sec-1) = 11.8-23.9/θ, where θ = 2.303RT in kcal/mole.It is suggested that a donor-acceptor complex intermediate may explain the observed rate constant of process B and analogous reactions in other systems.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 43
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 133-146 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The thermal isomerization of the title compounds was studied in the vapor phase. Over the temperature range from 445.1 to 477.5°K, 1,4-dimethylbicyclo[2.2.0]hexane underwent a homogeneous unimolecular reaction to 2,5-dimethyl-1,5-hexadiene, the rate constants being represented by the equation: k = 1.86 × 1011 exp (-31000 ± 1800/RT) sec-1. Over the temperature range from 630.0 to 662.2°K, 1,4-dimethylbicyclo[2.1.1]-hexane also underwent a unimolecular isomerization to the same product, the rate constants being given by the equation: k = 8.91 × 1014 exp (-56000 ± 900/RT) sec-1. The pyrolysis of 1,4-dimethylbicyclo[2.1.0]pentane gave 1,3-dimethylcyclopentene-1 and 2,4-dimethyl-1,4-pentadiene in the ratio of 9:1. The former reaction was influenced by surface effects but the latter was not. The rate constants for the formation of 2,4-dimethyl-1,4-pentadiene fitted the equation: k = 1.66 × 1017 exp (-57400 ± 3100/RT) sec-1. The effect of the two methyl groups at the bridgehead positions in these molecules in influencing the rate of decomposition is discussed in terms of the non-bonded repulsive forces between the substituents.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 157-170 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Isotope effects, general acid catalysis, and relative reactivities show that proton transfer to one of the unsaturated carbon atoms is rate determining for the acidolysis of unsaturated alkylmercuric halides. For compounds, R1R2C=CHHgX, substitution of CH3 for H at R1 or R2 leads to an acceleration of a factor of ∼ 30. This relatively small acceleration, the relative facility of the reactions, and the magnitude of the Br- catalytic terms, suggests an olefin-mercuric halide complex as the product of the rate-determining step, rather than a simple carbonium ion.The Brøonsted catalysis law is obeyed with a variety of carboxylic acids, giving an ∝ of 0.69 ± 0.04, but acids of other structures give substantially deviant catalytic coefficients, in a pattern similar to that generated by other A-SE2 reactions. The acetic acid catalytic coefficient is larger by a factor of 102 than that predicted if it were due to specific hydronium ion-general base catalysis instead of true general acid catalysis.The overall solvent isotope effect, kH/kD, is 2.55 ± 0.10. The competitive isotope effect, κH/κD, is 6.84 ± 0.06. Taken with a model in which the proton is transferred directly from the H3O+ unit of the aquated proton to the substrate, these are sufficient to successfully predict the rate at all intermediate isotopic compositions.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 45
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 171-191 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The thermal decomposition of azomethane-d6 has been studied. There is a short chain reaction, and measurements have been made of the rate of production of N2, CD4, and C2D6. A mechanism is suggested which accounts for these results fairly well. A comparison is made with some similar results of Forst for azomethane. Measurements have also been made of the reaction inhibited by NO. It is believed that the N2 production, extrapolated to zero NO pressure, measures the rate of the initial step CD3N2CD3 → 2 CD3 + N2. This has an activation energy at high pressures of 50.7 kcal per mole and an Arrhenius A·factor of 1015.49 sec-1. This is to be compared to values of 55.5 and 1017.3 found by Forst and Rice for CH3N2CH3 → 2 CH3 + N2. The pressure fall-off behavior for CD3N2CD3 → 2 CD3 + N2 has also been investigated and compared to the theoretical curves, which seem to fit satisfactorily except at the lowest pressure, where experimental errors may be large. Unexpectedly, the fall-off curve crosses that for CH3N2CH3 → 2 CH3 + N2. It is suggested that the extrapolation to zero NO pressure may not be entirely correct in the CH3N2CH3 case where the chain is longer than with CD3N2CD3. It is believed that the decomposition of azomethane-d6 is a better example for unimolecular-rate theory than is that of azomethane.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 46
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 193-207 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: t-Butylperoxy α-phenylisobutyrate (I) decomposes thermally by concerted formation of carbon dioxide, t-butoxy, and cumyl radicals. Radical pair return in the solvent cage therefore does not affect the observed rate of decomposition, but is readily determined by means of galvinoxyl and other scavengers. In a series of 15 solvents the rate constant varies over a 2.8 fold range, being fastest in aromatic solvents. In the same solvent series the relative rates of diffusion and combination of radicals, measured by the cage effect, change by tenfold and are largely determined by the viscosity of the solvent. In all solvents of η 〉 8 mP, the reciprocal of the cage effect is a linear function of (T1/2/η), as recently observed for trifluoromethyl and methyl radicals [16]. This property of the cage effect provides a test by which it can be distinguished from other processes that reduce the efficiency of free-radical production from an initiator.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 47
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 279-282 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
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  • 48
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of ozonation of C2H4 and C2H2 have been studied in the gas phase from -40 to -95°C (C2H4) and +10 to -30°C (C2H2). The O3 concentrations were near 10-4 M, and the hydrocarbons were present in 2- to 25-fold excess. A few experiments with propylene were also carried out. The reactions were followed by observing the rate of decay of O3 absorption at 2537 Å. Reaction stoichiometries and effects of added O2 were investigated. The second-order rate constant for C2H4 was log k(M-1 sec-1) = (6.3 ± 0.2) - (4.7 ± 0.2)/θ (θ = 2.3RT). The rate was independent of the presence of excess O2. Rate measurements for C3H6 were less accurate because of aerosol interference. Combined with room temperature measurements of other workers, the C3H6 rate constant was log k(M-1 sec-1) = (6.0 ± 0.4) - (3.2 ± 0.6)/θ. The C2H2 rate constant was log k(M-1 sec-1) = (9.5 ± 0.4) - (10.8 ± 0.4)/θ. In the case of C3H6 the major product was propylene ozonide. Ethylene did not yield the ozonide, and the products of the O3-C2H4 and O3-C2H2 reactions were not identified. Pre-exponential factors for the olefin reactions are consistent with a five-membered ring transition state formed by 1,3 dipolar cycloaddition of O3. For C2H2, however, the much higher observed A factor suggests a different mechanism. Possible transition states for the O3-C2H2 reaction are discussed.
    Zusätzliches Material: 5 Ill.
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  • 49
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969) 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 50
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Methods are presented for rapidly estimating the entropies and heat capacities of free radicals from the known S0 and Cp0 of structurally similar compounds. The methods consist of estimating the differences due to changes in mass, vibration frequencies, spin, symmetry, and changes in rotational barriers. Tables of contributions to S0 and Cp0 by different frequencies over the temperature range 300-1500°K are presented to facilitate the tabulation of the above differences. Conjugated radicals, such as benzyl and allyl, are included. It is shown that the greatest uncertainties in the estimates arise from uncertainties in the barriers to rotation in the radicals.The results are applied to kinetic data on the pyrolysis of branched hydrocarbons and the reverse reactions of radical recombination. Major discrepancies exist in these data which can be nearly reconciled by postulating improbably high rotational barriers of 8 kcal for CH3 rotation in isopropyl and t-butyl radicals.It is shown that radical thermochemistry can be fitted into group schemes and tables of groups values are given for the rapid estimation of ΔHf0, S0, and Cp0 for different organic radicals, including those containing sulfur, oxygen, and nitrogen.
    Zusätzliches Material: 5 Tab.
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  • 51
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The rate of the reaction CH2I2 + HI ⇆ CH3I + I2 has been followed spectrophotometrically from 201.0 to 311.2°. The rate constant for the reaction fits the equation, log (k1/M-1 sec-1) = 11.45 ± 0.18 - (15.11 ± 0.44)/θ. This value, combined with the assumption that E2 = 0 ± 1 kcal/mole, leads to ΔHf298° (CH2I, g) = 55.0 ± 1.6 kcal/mole and DH298° (H—CH2I) = 103.8 ± 1.6 kcal/mole.The kinetics of the disproportionation, 2 CH3I ⇆ CH4 + CH2I2 were studied at 331° and are compatible with the above values.
    Zusätzliches Material: 6 Ill.
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  • 52
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Several hydrocarbons have been pyrolyzed in a single pulse shock tube. Rate parameters for the main bond breaking step have been found to be \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left\{{{\rm iC}_3 {\rm H}_7 {-\!-} {\rm CH}\left({{\rm CH}_3} \right){\rm CH} {\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}} {\rm CH}_2 \longrightarrow {\rm iC}_3 {\rm H}_7 \cdot + \cdot {\rm CH}\left({{\rm CH}_3} \right){\rm CH} {\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}} {\rm CH}_2} \right\} = 10^{15.70} \exp \left({{{- 32,500} \mathord{\left/ {\vphantom {{- 32,500} T}} \right. \kern-\nulldelimiterspace} T}} \right)\sec ^{- 1} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left\{{{\rm iC}_3 {\rm H}_7 {-\!-} {\rm C}\left({{\rm CH}_3} \right)_2 {\rm C}_2 {\rm H}_5 \longrightarrow {\rm iC}_3 {\rm H}_7 \cdot + \cdot {\rm C}\left({{\rm CH}_3} \right)_2 {\rm C}_2 {\rm H}_5} \right\} = 10^{16.15} \exp \left({{{- 35,900} \mathord{\left/ {\vphantom {{- 35,900} T}} \right. \kern-\nulldelimiterspace} T}} \right)\sec ^{- 1} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left\{{{\rm C}_2 {\rm H}_5 {-\!-} {\rm C}\left({{\rm CH}_3} \right)_2 {\rm C}_2 {\rm H}_5 \longrightarrow {\rm C}_2 {\rm H}_5 \cdot + \cdot {\rm C}\left({{\rm CH}_3} \right)_2 {\rm C}_2 {\rm H}_5} \right\} = 10^{16.57} \exp \left({{{- 38,800} \mathord{\left/ {\vphantom {{- 38,800} T}} \right. \kern-\nulldelimiterspace} T}} \right)\sec ^{- 1} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left\{{{\rm iC}_3 {\rm H}_7 {-\!-} {\rm CH}_2 {\rm C}_6 {\rm H}_5 \longrightarrow {\rm iC}_3 {\rm H}_7 \cdot + \cdot {\rm CH}_2 {\rm C}_6 {\rm H}_5} \right\} = 10^{15.23} \exp \left({{{- 34,800} \mathord{\left/ {\vphantom {{- 34,800} T}} \right. \kern-\nulldelimiterspace} T}} \right)\sec ^{- 1} $$\end{document} In combination with similar studies carried out earlier and through application of the well-established experimental rule (kr2(AB)/kr(AA)kr(BB))1/2 ∼ 2 where A and B are radicals and the rate constants are for the combination of these radicals, rate parameters for the thermal decomposition of all the hydrocarbons formed from any pair of the following radicals: methyl, ethyl, isopropyl, t-butyl, t-amyl, allyl, methylallyl, and benzyl have been calculated. The available calculated and experimental values of the decomposition rate constants are in excellent agreement. It appears that, with the possible exception of reactions involving the ejection of methyl radicals, the frequency factors per bond are nearly constant, depending only upon the type of carbon-carbon bond that is being broken. These values are all lower than those expected from the radical recombination rates.Heats of formation of ethyl, t-amyl, benzyl, methylallyl, n-propyl, s-butyl, isobutyl, neopentyl, and 3-pentyl radicals have been derived.Rate parameters for the decomposition of some simple ketones and ethers have also been estimated.
    Zusätzliches Material: 6 Ill.
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  • 53
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the photoinitiated reductions of methyl iodide and carbon tetrachloride by tri-n-butylgermanium hydride in cyclohexane at 25°C have been studied and absolute rate constants have been measured. Rate constants for the combination of CH3ċ and CCl3ċ radicals are equal within experimental error and are also equal to the values found for the self-reactions of most non-polymeric radicals in low viscosity solvents, i.e. ∼1-3 × 109 M-1 sec-1.Rate constants for hydrogen atom abstraction by CH3ċ and CCl3ċ radicals are both ∼1-2 × 105 M-1 sec-1. Tri-n-butyltin hydride is about 10-20 times as good a hydrogen donor to alkyl radicals as is tri-n-butylgermanium hydride.The strength of the germanium-hydrogen bond, D(n-Bu3Ge-H) is estimated to be approximately 84 kcal/mole.
    Zusätzliches Material: 1 Ill.
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  • 54
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 353-356 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 325-337 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the thermally and radiation initiated chain reaction between trichloroethylene and cyclopentane to produce 1,1-dichlorovinylcyclopentane and hydrogen chloride have been investigated in the temperature range 250-360°C at high pressure in the gas phase. The rate governing step in the chain is (k3 = 3.3 × 109 exp -(4800/RT) cc mole-1 sec -1). The rate of the unimolecular decomposition of trichloroethylene is 1.4 × 1014 exp -(61,200/RT) sec-1.
    Zusätzliches Material: 5 Ill.
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  • 56
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 297-314 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The gas phase, nitric oxide catalyzed positional isomerization of 3-methylene-1,5,5-trimethylcyclohexene (MTC) into 1,3,5,5-tetramethyl-1,3-cyclohexadiene (TECD) has been studied for temperatures ranging between 296° and 425°C. The major reaction was first order with respect to nitric oxide and to MTC.The major side product, mesitylene, usually amounted to less than 10% of the TECD isomer formed. Only at high temperatures and large conversions has up to 20% been observed.Conditioned pyrex or quartz vessels coated with KCl have been used. The nitric oxide catalyzed isomerization is apparently a homogeneous process, as demonstrated by the insensitivity of the observed rate constants towards a 15-fold increase in the surface to volume ratio of the reaction vessels. However, a residual, presumably heterogeneous, thermal isomerization of the starting material could not be eliminated. Good mass balances were obtained for both NO and hydrocarbons.After correcting for the thermally induced conversion the observed rate constants for the nitric oxide catalyzed isomerization yield log k1 (1 mole-1 sec-1) = (10.7 ± 0.2) - (37.3 ± 0.9)/θ where θ is 2.303 × 10-3 RT (kcal mole-1). Plotting log k1 versus the ratio of the starting materials (MTC/NO)0 it was found that for temperatures ≥ 365°C the rate constants were systematically too high.Using extrapolated values for the higher temperature range yields the more reliable corrected Arrhenius equation log k1corr = 8.6 - 31.7/θ. The reaction mechanism is outlined and the implications with respect to the stabilization energy generated in the MTCċ radical intermediate and the activation energy of the backreaction MTCċ + HNO are discussed.Using for the activation energy E-1 of the backreaction (Rċ + HNO) a literature value of 9.2 ± 0.9 kcal mole-1 reported for the cyclohexadiene—1,3—system, this yields 23.4 ± 2 kcal mole-1 for the stabilization energy in the methylenecyclohexenyl radical, which is to be compared with the corresponding values for the allyl (10.2 ± 1.4), methallyl (12.6 ± 1) pentadienyl (15.4 ± 1) and cyclohexadienyl (24.6 ± 0.7) radicals.The pre-exponential factor agrees well with the value of (8.4 ± 0.2) reported by Shaw and co-workers for the similar reaction of NO with 1,3-cyclohexadiene. It is noteworthy that HNO, acting as sole hydrogen donor in the system, is surprisingly stable under the reaction conditions used. Nitrous oxide, HCN, H2O and N2 are observed in the product mixture of experiments carried out to high conversions at higher temperatures.
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  • 57
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 339-351 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The following Arrhenius parameters have been determined for the hydrogen-abstraction reactions: R + (CH3)4Si → RH + (CH3)3SiCH3 TextRTemp. (°K)E (kcal/mole)Log A (mole-1 cc sec-1)Log k(400°K) (mole-1 cc sec-1)CF3330-4337.23 ± 0.0911.90 ± 0.057.95CH3396-47610.23 ± 0.3611.55 ± 0.185.68CD3396-49610.36 ± 0.1211.84 ± 0.066.20C2H5423-52211.40 ± 0.4811.88 ± 0.225.68The activation energies are in keeping with the strengths of the bonds formed during the reaction. By comparison with the activation energies for the analogous reactions of neopentane it is estimated that D((CH3)3SiCH2—H) ≃ 97 kcal/mole.The A factors for the above series of reactions fall within the range predicted by transition-state theory for this type of process and the validity of previous results of Kerr, Slater, and Young is seriously in doubt.
    Zusätzliches Material: 2 Ill.
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  • 58
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 357-359 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
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  • 59
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969) 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 60
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 391-399 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the presence of elementary iodine, isobutyl iodide (2-methyl-1-iodopropane) undergoes isotopic exchange and also decomposes with production of additional iodine. Both reactions are approximately first order in isobutyl iodide and half order in iodine molecules. In degassed hexachlorobutadiene at 160°, the rate constants for exchange and decomposition are 7.5 × 10-6 and 11.4 × 10-6 (liter/mole)1/2sec-1, respectively. The decomposition is probably initiated by iodine atom abstraction of a β hydrogen atom, but comparison with rates for related compounds indicates that this hydrogen abstraction does not contribute significantly to the mechanism of exchange.
    Zusätzliches Material: 1 Tab.
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  • 61
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics and mechanism of the reaction between iodine and dimethyl ether (DME) have been studied spectrophotometrically from 515-630°K over the pressure ranges, I2 3.8-18.9 torr and DME 39.6-592 torr in a static system. The rate-determining step is, where k1 is given by log (k1/M-1 sec-1) = 11.5 ± 0.3 - 23.2 ± 0.7/θ, with θ = 2.303RT in kcal/mole. The ratio k2/k-1, is given by log (k2/k-1) = -0.05 ± 0.19 + (0.9 ± 0.45)/θ, whence the carbon-hydrogen bond dissociation energy, DH° (H—CH2OCH3) = 93.3 ± 1 kcal/mole. From this, ΔH°f(CH2OCH3) = -2.8 kcal and DH°(CH3—OCH2) = 9.1 kcal/mole.Some nmr and uv spectral features of iodomethyl ether are reported.
    Zusätzliches Material: 3 Ill.
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  • 62
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 371-380 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Arrhenius parameters have been determined for the hydrogen-abstraction reactions: R + SiHCl3 + RH + SiCl3 TextRTemp (°K)E(kcal/mole)Log A(mole-1 cc sec-1)Log k(400°K) (mole-1 cc sec-1)CF3323-4615.98 ± 0.0611.77 ± 0.038.50CH3333-4434.30 ± 0.0810.83 ± 0.044.48C2H5314-4135.32 ± 0.0711.54 ± 0.048.63The trend in activation energies ECH3 〈 EC2H5 〈 ECF3 is interpreted as indicating a polar effect in the reaction of CF3 with SiHCl3 and the similar reactivities of all three radicals appear to be due to the high exothermicity of the reactions.The A Factors for the reactions are normal for hydrogen abstraction reactions of free radicals. The previous results of Kerr, Slater, and Young for CH3 abstracting an H atom from SiHCl3 have been amended.
    Zusätzliches Material: 2 Ill.
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  • 63
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 361-370 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Stable nitroxide radicals and ESR techniques have been used to investigate rotational and translational motions of molecules in the liquid state. It is found that for hydrocarbons and molecules with low polarity the rotational frequencies are about an order of magnitude faster than translational encounters. Arrhenius parameters are reported for the rates of both types of processes. A scheme is given for the relation of these motions to radical recombination in solution and also to reactions requiring activation energy. The consequences of this scheme are examined.Such important properties as hydrodynamic fluidity, thermal conductivity, processes of extraction and solution, occurring in the liquid phase as well as at the interface are determined by mobility of particles in the liquid. The problem of molecular mobility is of essential significance for the kinetics of chemical and chemico-physical processes in the liquid phase.Application of both ESR techniques and stable nitroxide radicals for kinetic studies of molecular motions in liquids and the correlation between molecular mobility and the kinetic parameters of liquid-phase radical reactions have been studied in the present paper.
    Zusätzliches Material: 4 Ill.
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  • 64
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969) 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 65
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 413-425 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The photolysis of pentafluoroacetone has been investigated in the 3130 Å region, from room temperature to 360°C. The ΦCO varies from 0.7 to 0.9 over this range, and the decomposition is represented by CF2HCOCF3 → CF2H + CO + CF3. The disproportionation/combination ratio for CF3 and CF2H (→ CF3H + CF2) radicals is found to be 0.09. Arrhenius parameters for hydrogen atom abstraction from the ketone are log10A = 12.7 (units are mole-1 cc sec-1) and E = 14.3 kcal mole-1 for CF2H, and log10A = 12.1 and E = 11.8, for CF3 radicals. At low pressures HF elimination reactions are observed from the vibrationally excited fluoroethanes, C2F5H* and C2F4H2*, formed in the system. A rough estimate of the activation energy for the process C2F5H → C2F4 + HF of 60-65 kcal mole-1 is made.
    Zusätzliches Material: 3 Ill.
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  • 66
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The activating effects of a number of unsaturated groups and a cyclopropyl group have been evaluated in a solvent free system by determining the absolute rate constants, and energies and entropies of activation in the vapor phase pyrolysis of secondary and tertiary esters of the type RC(R′CH3) OAc where R′ = H or CH3 and R = c-Pr, i-Pr, CH3, CH2=CH, CH2=CHCH2, C6H5; the cyclopropyl showed only a moderate activating effect. The results are in contrast to the very significant activating effect of a cyclopropyl group in solvolysis of cyclopropylcarbinyl derivatives. Apparently marked activation by this group occurs only when a highly developed positive center forms adjacent to it. The lack of marked activation by the cyclopropyl group supports a mechanism for ester pyrolysis which involves a modest, but detectable, charge separation in the transition state [2] but questions a mechanism in which an intimate ion-pair was proposed [3].
    Zusätzliches Material: 1 Ill.
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  • 67
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The gas phase reaction I2 + HCOOCH3 → HI + CH3I + CO2 has been studied spectrophotometrically in a static system over the pressure ranges I2 (6-39 torr) and HCOOMe (28-360 torr). In the temperature range 293-356°, the initial rate of disappearance of I2 is first order in [HCOOMe] and half-order in [I2]. The rate determining step is where k1 is given by \documentclass{article}\pagestyle{empty}\begin{document}$$\log _{10} \left({k_1 /{\rm M}^{- 1} \sec ^{- 1}} \right) = \left({9.6 \pm 0.3} \right) - \left({22.4 \pm 0.8} \right)/\theta $$\end{document} where θ = 2.303 RT in kcal/mole. This activation energy gives a carbonyl C—H bond strength of 92.7 kcal/mole. At 356° there was no evidence of abstraction of a methoxy hydrogen, so a lower limit of 100 kcal/mole may be placed on this C—H bond strength. These ester C—H bond strengths are discussed in relation to comparable values in aldehydes and ethers.
    Zusätzliches Material: 1 Ill.
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  • 68
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 439-450 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The relative rates of addition of difluorocarbene to a series of methyl-substituted olefins have been determined and correlated with similar data for dichlorocarbene, chlorofluorocarbene and ground-state oxygen atoms. The electrophilic nature and stabilization of difluorocarbene by the fluorine substituents is discussed. Relative activation energies for the difluorocyclopropane-forming reaction have been estimated and correlated with properties of the olefins as derived from molecular orbital theory.
    Zusätzliches Material: 4 Ill.
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  • 69
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 451-458 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Data on the kinetics of S2F10 pyrolysis, which gives SF4 + SF6, have been reinterpreted to give a value for the equilibrium constant of S2F10 ⇆ SF4 + SF6. This, together with statistical estimates of the entropy and heat capacity of S2F10, can be used to give for this reaction values of ΔH298° = 19.7 ± 1.0 kcal/mole and ΔS300° = 47.6 ± 2 gibbs/mole. ΔHf°(S2F10) = -494 kcal/mole. A compatible mechanism is shown to be S2F10 ⇆ 2SF5 (fast); 2SF5 ⇆ SF6 + SF4 (slow) with step 2 rate-determining. The overall, best first order rate constant is proposed as kmeas = 1017.42-43.0/θ sec-1 = K1k2, where θ = 2.303RT in kcal/mole.Independent measurements of δHf° and S° for the SF5 radical, permits the evaluation of the equilibrium constant K1 = 108.92-(27.1 ± 6)/θ l./mole-sec and yields k2 = 108.50-15.9/θ l./mole-sec. The observed homogeneous catalysis by NO and CHCl = CHCl can be explained in terms of a direct abstraction of F from S2F10 : C + S2F10 → CF + S2F9, followed by S2F9 → SF5 + SF4 and SF5 + CF ⇆ SF6 + C (C ≡ NO or C2H2Cl2).
    Zusätzliches Material: 1 Ill.
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  • 70
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 479-481 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 71
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 473-477 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The gas phase isomerization of 1,1-dimethyl-2-vinylcyclopropane to cis-2-methylhexa-1,4-diene has been studied in a static system. The isomerization is homogeneous and kinetically first order. The rate constants were independent of initial reactant pressure in the range 0.6 to 2 torr and of added nitrogen up to 180 torr. Rate constants determined at 10 temperatures in the range 200 to 254°C fitted the Arrhenius equation k = 1011.41±0.02 exp (-33,540 ± 47 cal/RT) sec-1The low A factor and activation energy are consistent with a concerted 1,5-hydrogen migration via a “tight” cyclic transition complex.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 72
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 459-472 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The intramolecular elimination of isobutene from 2-d1-triisobutylaluminum has been studied in the gas phase for temperatures ranging between 102.4 and 184.6°C. The reaction is apparently homogeneous and obeys the first order rate law, yielding the following Arrhenius relationship: \documentclass{article}\pagestyle{empty}\begin{document}$$ \log \,k_{{\rm el}im} \left( {\sec ^{ - 1} } \right) = 11.1 - {{27.2} \mathord{\left/ {\vphantom {{27.2} {\theta \,{\rm where}\,\theta \,{\rm equals}\,4.58 \times 10^{ - 3} }}} \right. \kern-\nulldelimiterspace} {\theta \,{\rm where}\,\theta \,{\rm equals}\,4.58 \times 10^{ - 3} }}T\left( {{}^ \circ {\rm K}} \right)\,{\rm in}\,{\rm units}\,{\rm of}\,{{{\rm kcal}} \mathord{\left/ {\vphantom {{{\rm kcal}} {{\rm mole}{\rm .}}}} \right. \kern-\nulldelimiterspace} {{\rm mole}{\rm .}}} $$\end{document} Excess ethylene was added to the starting material in order to avoid complications from the backreaction. The cyclic 4-center nature of the transition state proposed earlier has been unequivocally demonstrated by deuterium labelling. Mass-spectral analyses show that the isobutene formed contains no deuterium. The hydrolyses products of the mixed trialkylaluminum formed during the reaction consist of monodeuteroethane and 2-d1-isobutane. The observed negative entropy of activation of ∼12 cal/°-mole agrees with prediction and implies a reasonably tight transition state structure. Combined with the corresponding data for the non deuterized Al(i-bu)3 reported earlier, these data result in a primary kinetic deuterium isotope effect of kH/kD = 1.3 × 100.6/θ corresponding to a ratio of the isotopic rate constants of 3.7 at 25°C. This result is in excellent agreement with a predicted value of 1.4 × 100.7/θ and it is in line with literature data on similar reactions involving cyclic transition state complexes.
    Zusätzliches Material: 1 Ill.
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  • 73
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 483-486 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 74
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 487-492 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969) 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 76
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 493-494 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 77
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 78
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 499-508 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the gas phase bond isomerization of allyl fluoride, allyl chloride and allyl bromide, catalyzed by HBr and ultraviolet light, has been studied in the temperature range of 150-250° and at pressures of 3.5 to 50 mm. The reactions are very clean, first order in allyl halide and HBr, and have a light intensity exponent of unity. A quantum yield for allyl chloride of 3200 indicates a chain reaction. Dilution with inert gases is almost without effect, indicating that excited state intermediates are not involved. A small wall effect is observed. The evidence indicates a free radical reaction, involving hydrogen abstractions by bromine atoms, with replacement at the other end of the allylic radical.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 79
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By photolyzing (CF2H)2CO and (CFH2)2CO the hydrogen atom abstraction reactions of CF2H radicals with (CF2H)2CO, H2, D2, CH4, C2H6, n—C4H10 and iso—C4H10, and the reactions of CFH2 radicals with (CFH2)2CO and n—C4H10, have been studied. Arrhenius parameters for these reactions are compared with related systems. From a knowledge of the activation energies for the forward and reverse reactions a value of the bond dissociation energy, D(CF2H—H) = 97.4 ± 1.3 kcal mole-1 at a mean temperature of 543°K is obtained. This value is subject to much uncertainty due to possible compensation effects in the Arrhenius parameters. These effects are discussed for this and the other reactions, and the data suggest that D(CF2H—H) is approximately 100 kcal mole-1, and that D(CFH2—H) is very similar. Other literature data tend to confirm these approximate values.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 80
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 527-539 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This review presents in tabular and graphical form rate data on the reactions of atomic oxygen (O3P) with methane and ethane. The reliability of these data is discussed and suggested values of the rate constants are given over specified temperature intervals. Specific values are given for 298 and 1000°K.
    Zusätzliches Material: 2 Ill.
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  • 81
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 581-583 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 82
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 551-569 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A detailed kinetic model of the HCl chemical laser produced by the flash photolytically initiated H2—Cl2 explosion is described, and the results of computer calculations on such a system are discussed. It is shown that currently accepted values of the various rate constants, supplemented in a few cases by reasonable estimates of previously unmeasured rate constants, are adequate to approximate the observed laser behavior of this system. It is also shown that the chemistry of such a system is extremely complex, and exhibits a high degree of coupling between one reaction and another; therefore, great care is required to extract kinetic data from the optical behavior of such laser systems. It is further argued that different hydrogen halide lasers may behave quite differently from each other, depending on the relative magnitudes of the various rate constants involved.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 541-549 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The thermal dissociation of COS was investigated in shock waves with argon as carrier gas. The concentration was varied between 0.05 and 0.5% COS in argon, the total density from 2.5 × 10-5 mole/cm3 to 2.5 × 10-3 mole/cm3. Temperatures between 1500°K and 3100°K were applied.For the reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm COS}\left({^1 \Sigma} \right)\mathop {\longrightarrow}\limits^{K_{\rm 1}} {\rm CO}\left({^1 \Sigma ^ +} \right) + {\rm S}\left({^3 P} \right) $$\end{document} the rate constant was found to be \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{10} \approx 10^{14.2} \exp - \left({\frac{{61000}}{{RT}}} \right) \quad\quad ({\rm cm}^3 {\rm mole}^{- 1} \sec ^{- 1}) $$\end{document} in the low pressure range of the unimolecular reaction and \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{1\infty} \approx 10^{11.6} \exp - \left({\frac{{61000}}{{RT}}} \right) \quad\quad (\sec ^{- 1}) $$\end{document} in the high pressure range.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 571-580 
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The addition of methyl radicals to tetrafluoroethylene in the gas phase has been studied over the temperature range 80-180°C, using a material balance method. \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm CH}_{\rm 3} + {\rm C}_2 {\rm F}_{\rm 4} \to {\rm CH}_3 {\rm C}_2 {\rm F}_4 $$\end{document}Arrhenius parameters of 1011.95±0.23 (mole-1 cm3 sec-1) and 5.7 ± 0.4 (kcal/mole) have been measured for the addition reaction.Electrophilic reagents such as O or CF3 appear to react almost equally readily with ethylene and tetrafluoroethylene but methyl radicals add much more rapidly to tetrafluoroethylene than to ethylene, the difference in reactivity being principally due to an activation energy difference of ∼2 kcal/mole.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 127 (1968), S. 221-231 
    ISSN: 1432-0568
    Schlagwort(e): Marginal glia ; Superficial nerve cells ; Brain stem ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung An Paraffinschnitten durch perfusionsfixierte Gehirne von erwachsenen Katzen werden in der Glia marginalis des Hirnstamms unterschiedlich gebaute Bezirke beschrieben. Es wird gezeigt, daß über dem Nucleus paragigantocellularis und über dem Ncl. “z” swischen den Fasern der Glia marginalis Nervenzellen liegen. Über dem erstgenannten Kern stellen diese Zellen möglicherweise das morphologische Substrat der chemosensiblen Felder dar, die durch die physiologischen Untersuchungen von Loeschcke, Mitchell u.a. bekannt geworden sind.
    Notizen: Summary In the marginal glia covering the brain stem of the cat, regional differences are described in paraffin sections of brains which had been fixed by perfusion of Bouin's fluid. It is shown that between the glia fibres covering the nucleus paragigantocellularis and the nucleus “z” there are nerve cells. It is suggested that in the region of the nucleus paragiganto-cellularis these cells are the morphological substrate of a chemosensible zone described in physiological experiments by Loeschcke, Mitchell and others.
    Materialart: Digitale Medien
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 127 (1968), S. 138-144 
    ISSN: 1432-0568
    Schlagwort(e): Capillary density ; Postnatal development ; Corpus callosum ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung An Paraffinschnitten durch das Corpus callosum perfusionsfixierter Gehirne von 19 Katzen im Alter von einem Tag bis zu 2 1/2 Jahren wurde das Capillarvolumen bestimmt. Es beträgt bei der neugeborenen Katze 0,81 Vol.-%. In der 2. Lebenswoche beginnt eine Zunahme, die in der 5. Woche ein Maximum von 2,92 Vol.-% erreicht. Im Verlauf der 6. Woche setzt eine zunächst rasche, von der 7. Woche an aber nur noch langsam verlaufende Abnahme ein, bis bei einem Lebensalter von etwa 1 Jahr ein für das erwachsene Tier charakteristischer Wert um 1,5 Vol.-% erreicht wird. Die Abnahme des Capillarvolumens hängt mit der Markscheidenbildung und der dadurch bedingten Zunahme des Fasermaterials zusammen.
    Notizen: Summary Postnatal changes of capillary density have been determined in paraffin sections through the corpus callosum of 19 cats. At birth the capillary density amounts to 0.81 vol.-%. In the 2nd week of postnatal life it begins to increase and reaches a maximum of 2.92 vol.-% in the 5th week. From the 6th week onwards there is an initially steep and later on less pronounced decrease until at an age of about 1 year a value of about 1.5 vol.-% is reached, which is maintained in adult life. — The decrease in the percentage of capillary volume seen after the 5th week is caused by the rapid increase in fibrous material due to myelination.
    Materialart: Digitale Medien
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  • 87
    ISSN: 1432-0533
    Schlagwort(e): Alumina Cream ; Intracerebral Injection ; Pathology of Growing Brain ; Myelination ; Demyelination ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Zum Studium der Reaktion des jugendlichen und erwachsenen Gehirnes auf einen chronischen Reiz wurden bei Katzen verschiedenen Lebensalters intracerebrale Injektionen von Aluminiumhydroxyd vorgenommen. Die Tiere wurden nach Überlebenszeiten von 7 Tagen, 40 Tagen und 3 Monaten durch Perfusion mit Bouinscher Lösung getötet. Die histologische Untersuchung der Gehirne ergab eine Reihe von Unterschieden, je nachdem ob die Injektion vor oder nach der Markscheidenbildung erfolgt war. Besonders auffällig war der Befund, daß in der noch unmyelinisierten weißen Substanz jugendlicher Tiere kein Hirnödem und keine Gliose auftritt. Obgleich durch fluorescenzmikroskopische Untersuchungen gezeigt werden konnte, daß das Aluminium von der Injektionsstelle aus weit in das umgebende Hirngewebe eindringt und dort über lange Zeit festgehalten wird, werden bei den jungen Tieren die Markscheiden später bis in die unmittelbare Umgebung des Herdes normal angelegt. Bei erwachsenen Tieren kam es dagegen in der Nachbarschaft des Herdes stets zu einem starkem Ödem der weißen Substanz, zum Zerfall der Markscheiden und zu einer ausgebreiteten Gliose. Weitere Unterschiede in der Reaktionsweise des Gehirnes jugendlicher und erwachsener Tiere, die den Cortex und insbesondere die marginale Gliafaserschicht betreffen, werden im einzelnen beschrieben und diskutiert.
    Notizen: Summary In order to compare the reaction to chronic irritation of young and adult brain intracerebral injections of alumina cream were made in cats of various ages. The animals were killed by perfusion with Bouin's fluid after a survival time of 7 days, 40 days, and 3 months. Histological investigation revealed gross differences in the reaction according to whether the intracerebral injections had been made before or after myelination. Particularly striking was the finding that in the non-myelinated white matter of young animals there was no edema and no subsequent gliosis. Although alumina, as evidenced by fluorescence microscopy after staining with Morin, spreads into the tissue surrounding the focus, subsequent myelination appeared to be normal even in regions close to the site of injection. In contrast, injection into the brains of adult animals was followed by edema, widespread demyelination and gliosis of the white matter near the site of injection. Further differences between young and adult animals were found in the reaction of the grey matter and particularly of the marginal glia.
    Materialart: Digitale Medien
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 5 (1968), S. 326-340 
    ISSN: 1432-1106
    Schlagwort(e): Subcellular fractionation ; Parallel fiber axons ; Cerebellum ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Fractionation of the cat cerebellum has revealed that the parallel fibers of the cerebellar cortex break into two types of fragments which can be recognized in thin sections and in suspensions of negatively stained material. Fragmented material correlates well with electron micrographs of parallel fibers in situ. Parallel fiber axons and their bulbous presynaptic expansions sediment mainly into two subfractions. One unique layer consists of the intersynaptic tubular pieces of parallel fiber axons. Another layer is enriched in the synaptic portions which make contact with Purkinje spines. The possible contaminants of these fractions are discussed. These fractions may permit analysis of the chemical organization of conducting vis à vis synaptic membranes from a known anatomical source. This material was presented as a preliminary report at the Sixth Annual Meeting of the American Society for Cell Biology, November 1966, and is contained in J. Cell. Biol. 31, 52A, 1966.
    Materialart: Digitale Medien
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  • 89
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 6 (1968), S. 234-246 
    ISSN: 1432-1106
    Schlagwort(e): Tactile discrimination ; Dorsal column-medial lemniscus ; Spino-cervico-thalamic tract ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The role of two spinal sensory pathways, the dorsal column (DC) pathway and the spino-cervico-thalamic tract (SCTT), involved in tactile discrimination was studied. Pour lesion groups of cats (DC lesion, SCTT lesion, combined DC and SCTT lesion, and sham-operated) were tested to discriminate various degrees of roughness. Animals with either the SCTT or the combined lesions performed at around 50–60% level under all the conditions tested. On the other hand, those with the DC lesion and sham-operations generally attained 80–100% level of performance. A difference between the DC group and sham-operated group was found in their rate of learning and ability for finer discrimination. These results are interpreted as an indication that a duplicity in transmission of tactile sensation exists, the DC pathway being more specific than the SCTT.
    Materialart: Digitale Medien
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 5 (1968), S. 55-60 
    ISSN: 1432-1106
    Schlagwort(e): EEG frequency ; Regional cortical blood flow ; Isotope measurements ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The EEG frequency content in cats, anaesthetized by Nembutal and artificially ventilated, was altered by means of injections of either additional Nembutal or of Metrazol. The EEG in cerveau isolé preparations was also changed in the same way. The regional cortical blood flow was determined by means of the 85Krypton technique. A high correlation was found between the frequency content of the EEG, measured by means of manual frequency analysis, and the regional cortical blood flow. The cortical blood flow increased when the mean frequency increased, and vice versa. A similar correlation was found when the EEG mean frequency was changed by means of sensory stimulation.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 5 (1968), S. 61-71 
    ISSN: 1432-1106
    Schlagwort(e): EEG frequency ; Regional cortical blood flow ; Isotope measurements ; Effects of hypoxia ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. The relationship between cortical blood flow and the frequency content of the EEG was studied in a circumscribed area of the exposed cerebral cortex in cats under nitrous oxide-oxygen anaesthesia. Autoregulation of the cortical blood flow was also tested during step-changes of the arterial blood pressure. Observations were made before and after an episode of severe hypoxia. 2. An episode of systemic hypoxia disrupted the normal high correlation between cortical blood flow and EEG frequency content. In the post-hypoxic period cortical flows of up to about three times normal values were recorded together with brain swelling and a slow wave EEG. The hyperemia and swelling subsided during 1–2 h after the hypoxic episode, and were accompanied by partial or complete recovery of the EEG. In the post-hypoxic period a defective autoregulation of the cortical blood flow to changes in the systemic blood pressure was demonstrated. 3. The cerebral post-hypoxic state with hyperaemia, brain swelling, EEG depression, and loss of autoregulation of blood flow, is probably caused by an accumulation of anaerobic metabolites which lead to cerebral tissue acidosis.
    Materialart: Digitale Medien
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  • 92
    ISSN: 1432-1106
    Schlagwort(e): Cerebral cortex ; Thalamus ; Cat ; Nauta
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The corticothalamic projections from the gyrus proreus and the medial wall of the rostral hemisphere have been studied in the cat with the silver method of Nauta. The gyrus proreus projects upon the following nuclei (for abbreviations, see list on page 133), ipsilateral R, VA, VM, VL, MD, Pc, CL, CM, Pf, VPM, VPMpc. VPI and to the contralateral principal nucleus of the trigeminal nerve. The medial wall of the rostral hemisphere projects bilaterally upon R, VA, VM, VL, MD, Pc, CL, CM, Pf, VPM, VPMpc, VPI, VPL, the dorsal column nuclei and the principal nucleus of the trigeminal nerve. The ipsilateral thalamic projection is more abundant than the contralateral. The latter appears to increase in amount as the lesion is placed successively more ventrally on the medial wall of the rostral hemisphere. Some degenerating fibers cross in the corpus callosum and descend in the contralateral internal capsule but the majority cross in the dorsal part of the anterior commissure and reach the medial aspect of the anterior limb of the contralateral internal capsule. A somatotopical organization of the medial wall of the rostral hemisphere has been demonstrated. The rostrocaudal part projects upon the ipsilateral VPL lateralis (VPLl) and nucleus cuneatus and the contralateral nucleus gracilis and VPL medialis (VPLm). The caudal part of this cortical area sends fibers bilaterally to VPM, VPMpc, and the principal nucleus of the trigeminal nerve. The intermediate part, which also includes agranular cortex on the medial wall, projects upon ispsilateral VPLm and nucleus gracilis and upon contralateral VPLl and nucleus cuneatus. — The fibers to the ventro-basal complex, dorsal column nuclei and the principal nucleus of the trigeminal nerve are rather thick. The corticofugal fibers to the other thalamic nuclei are quite thin. — The findings are discussed in light of relevant anatomical and physiological observations in the literature and special emphasis has been laid on reported observations on the “supplementary motor” area.
    Materialart: Digitale Medien
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 5 (1968), S. 153-172 
    ISSN: 1432-1106
    Schlagwort(e): SII ; Thalamus ; Cat ; Somatotopical localization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The corticothalamic projection from the anterior ectosylvian gyrus in the cat has been studied with the silver impregnation method of Nauta. The second somatosensory cortical area (SII) projects upon the ipsilateral nucleus ventralis posterolateralis (VPL), nucleus ventralis posteromedialis (VPM), the posterior thalamic region (PO) and to a slight extent upon the reticular nucleus of the thalamus (R), the centrum medianum (CM), the parvocellular part of VPM (VPMpc) and the nucleus ventralis posterior inferior (VPI). A somatotopical arrangement in the projection upon the ventro-basal (VB) complex has been demonstrated and a topical arrangement in the corticothalamic fibers from SII to PO is also evident. The transitional area between SII and the second auditory cortex sends fibers mainly to the entire magnocellular part of the medial geniculate body (MGmc) and to a lesser degree to the principal division of this nucleus (MGp). The corticofugal fibers from SII follow various and rather complicated circuitous routes before they end in the different thalamic nuclei. The experimental findings are discussed in the light of recent anatomical and physiological observations. It is shown that zones B and C of SII which have been shown by Carreras and Andersson (1963) to possess a large number of place and modality specific neurons project upon the VB-complex. On the other hand, zone A which contains a majority of place and modality unspecific neurons sends its fibers exclusively to PO. Finally the problem of thalamocortical projections to SII is briefly discussed.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 5 (1968), S. 210-234 
    ISSN: 1432-1106
    Schlagwort(e): Sensorimotor cortex ; Pontine nuclei ; Somatotopical localization ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Small lesions (in some cases bilateral) were made in the cerebral primary sensorimotor region in altogether 21 adult cats and the ensuing degeneration in the pontine nuclei was studied with the silver impregnation methods of Nauta and Glees. Using thermocoagulation it was possible to obtain lesions restricted entirely to particular cortical regions (for example the “hindlimb region” in the posterior sigmoid gyrus). The main results are as follows: 1. All parts of the primary sensorimotor region send fibres to the pontine nuclei. The projections from the posterior part of the posterior sigmoid gyrus and the posterior part of the coronal gyrus are relatively scanty. 2. The cortical “motor” area (the anterior sigmoid gyrus and the anterior part of the coronal gyrus) and the “sensory” area (the posterior sigmoid gyrus and the posterior part of the coronal gyrus) do not project to identical pontine regions, although both projections are organized in principally the same way. 3. The “motor” and “sensory” areas both project in a somatotopical manner onto two longitudinally oriented sharply delimited columns. In both projections one column is located medial and one lateral to the longitudinal fibre bundles of the corticospinal and corticobulbar tracts. Within the medial columns the “hindlimb” is represented ventrally with “face” most dorsally, within the lateral columns the “hindlimb” is located most caudally, with “forelimb” and “face” successively more rostrally. 4. The present results are in agreement with physiological observations on the cerebrocerebellar relations, but show that the pontine projection from the primary sensorimotor cortex is organized in a more complex manner than hitherto assumed.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 4 (1968), S. 321-329 
    ISSN: 1432-1106
    Schlagwort(e): Temperature ; Interval histograms ; Optic nerve ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung In 13 Katzen wurde die Aktivität von 128 Einzelfasern des N. opticus bei Temperaturen zwischen 27 und 39° C abgeleitet und direkt einer Intervallanalyse zugeführt. Die Durchschnittsfrequenz sank mit abnehmender Temperatur von 56/sec bei 39–37° C auf 21/sec unter 29° C. Bei Temperaturen über 35° C wurden nur unimodale oder zweigipfelige Verteilungen mit gehäuften Mehrfachentladungen gefunden. Unter 35° C traten multimodale Intervallhistogramme und Übergangstypen auf, bei denen einer Verteilung mehrere Gipfel aufgesetzt erschienen. Unter 29° C wurden nur mehrgipfelige Verteilungen beobachtet. In der phasischen Reaktion der Neurone wurden mit der Temperaturabnahme Latenzen länger und Hemmungen stärker. Unter 30° C konnte der Reaktionstyp des Neurons oft nicht mehr erkannt werden. Das vermehrte Auftreten multimodaler Verteilungen bei niedrigen Temperaturen ließe sich durch Verminderung von Interaktionen in der Retina erklären. Die Anregung zu dieser Untersuchung wurde von Herrn Professor Dr. Hans Bornschein gegeben.
    Notizen: Summary The activity of 128 single fibers of the optic nerve was recorded in 13 cats at temperatures between 27 and 39° C. Nonsequential interval histograms were computed on line. Decreasing temperature diminished the mean frequency of the fiber activity from 56/sec at 37–39° C to 21/sec below 29° C. Above 35° C the histograms were unimodal or bimodal, the first peak caused by repetitive discharges. Below 35° C multimodal histograms appeared; in some distributions several peaks were superimposed. At temperatures below 29° C only multimodal distributions were obtained. The phasic response of the neurons to light showed an increase of latency and of inhibition according to the decrease of temperature. Often the type of the response of the neuron could not be recognized below 30° C. During hypothermia interactions in the retina may be reduced and this may explain why multimodal distributions occur more frequently.
    Materialart: Digitale Medien
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 299 (1968), S. 261-284 
    ISSN: 1432-2013
    Schlagwort(e): Cat ; Electrophysiology ; Single Units ; Bulbar Trigeminal Nuclei ; Katze ; Elektrophysiologie ; Einzelneurone ; Bulbäre Trigeminuskerne
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung 1. Funktionelle Eigenschaften der excitatorischen Verbindungen von Cortex, Thalamus und Peripherie zu 438 Neuronen der bulbären Trigeminuskerne wurden untersucht. Es konnten Beziehungen zwischen den Latenzzeiten der Antworten auf ipsilaterale, periphere Einzelreize, contralaterale thalamische Einzel- und Serienreize (N. ventralis posteromedialis) und contralaterale corticale Einzel- und Serienreize (somatosensorisches Projektionsgebiet S I, S II) nachgewiesen werden. 2. Für die Gesamtheit der Neurone wurde mit zunehmender Latenzzeit der Entladung auf periphere Reize eine Zunahme der prozentualen Ansprechbarkeit und der Latenzzeit der Antwort auf zentrale Reize beobachtet. 3. Die Neurone, deren periphere, thalamische und corticale Antworten Reizfrequenzen von 50 Hz und mehr folgten, hatten im Mittel kürzere periphere Latenzzeiten als Neurone, die Reizfrequenzen von 50 Hz nicht folgten. 4. Bulbäre Neurone, die mit thalamischen Reizen antidrom erregt wurden (lemniscale Neurone), unterschieden sich im Mittel von den übrigen Neuronen durch kürzere Latenzzeiten für periphere und zentrale Reize. 5. Es wurden lemniscale Neurone beobachtet, die mit corticalen Reizen monosynaptisch erregt werden konnten. 6. Neurone mit kleinen peripheren rezeptiven Feldern hatten im Mittel kürzere Latenzzeiten auf periphere Reize als Neurone mit großen rezeptiven Feldern. 7. Die periphere Reizantwort von Neuronen konnte durch vorausgehende thalamische und corticale Reize gehemmt werden. Im Mittel wurde die Hemmung bei Neuronen mit Latenzzeiten auf periphere Reize häufiger beobachtet. 8. Mögliche Bahnen, die an der Übertragung thalamo-bulbärer Effekte beteiligt sind, wurden diskutiert und schematisch dargestellt. Die Ergebnisse wurden mit statistischen Methoden geprüft.
    Notizen: Summary 1. Functional properties of excitatory connections from cortex, thalamus and periphery to a total of 438 trigeminal bulbar neurons of the cat have been investigated extracellularly. For the sample considered, correlations between latency of response to ipsilateral electrical single stimuli, contralateral electrical thalamic single and serial stimuli (N. ventralis posteromedialis) and also contralateral electrical cortical single and serial stimuli (somatosensory areas S I, S II) were established. 2. With increasing peripheral latency of response, the percentage of neurons responding to central stimulation increased as well. 3. Neurons following thalamic, cortical or peripheral stimulation frequencies of 50 cps or more showed in the average shorter latencies of response compared with neurons that could not be driven with 50 cps stimulation. 4. Bulbar neurons antidromically invaded by stimulation of the thalamus showed shorter latencies to peripheral, thalamic and cortical stimuli compared with other neurons. 5. Lemniscal neurons that could be activated monosynaptically by cortical stimulation have been observed. 6. Neurons with a small peripheral receptive field had in the average a shorter latency to peripheral stimuli than neurons with a large receptive field. 7. Responses to peripheral stimuli could be inhibited by preceding thalamic and cortical stimuli. 8. Possible pathways that are involved in transmission of thalamo-bulbar effects have been discussed and schematically represented. 9. All results have been examined by means of statistical methods.
    Materialart: Digitale Medien
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 303 (1968), S. 173-180 
    ISSN: 1432-2013
    Schlagwort(e): Hippocampus ; Corpus geniculatum laterale ; Katze ; Mikroelektrophorese ; Acetylcholin ; Hippocampus ; Lateral Geniculate Body ; Cat ; Microelectrophoresis ; Acetylcholine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary 1. Hippocampal and lateral geniculate neurones in anaesthetized cats (Chloralose-Urethane) were examined with multibarrelled microelectrodes, testing their responsiveness to microelectrophoretic application of acetylcholine and photic stimulation. 2. In the ventral hippocampus and in the lateral geniculate body 60% of all neurones responded to acetylcholine. 3. Hippocampal neurones were activated with relatively short delay, often less than 1 sec. By contrast, lateral geniculate neurones responded with a latency period of 2–12 sec. The recovery time after acetylcholine-microelectrophoresis was found to be 10–20 sec in both regions. 4. The response of hippocampal and lateral geniculate neurones to photic stimulation was enhanced by local application of acetylcholine; even during phenobarbital depression the photic responses were restored by acetylcholinemicroelectrophoresis.
    Notizen: Zusammenfassung 1. Neurone im Gebiet des Hippocampus und des Corpus geniculatum laterale der mit Chloralose-Urethan narkotisierten Katze wurden mit mehrkanüligen Mikroelektroden auf ihre Ansprechbarkeit auf mikroelektrophoretisch appliziertes Acetylcholin und auf optische Reizung untersucht. 2. Im ventralen Hippocampus und im Corpus geniculatum laterale wurden 60% aller untersuchten Neurone durch Acetylcholin aktiviert. 3. Die Neurone des Hippocampus wurden nach relative kurzer Latenz, oft weniger als 1 sec, aktiviert. Neurone des Corpus geniculatum laterale dagegen zeigten eine Latenz von 2–12 sec. Die Zeit nach der Mikroelektrophorese bis zur Wiedererreichung der normalen Aktivität betrug 10–20 sec für beide Gebiete. 4. Die Acetylcholin-Mikroelektrophorese verstärkte die Reizantwort der Neurone des Hippocampus und des Corpus geniculatum laterale auf visuelle Reizung. Die nach Phenobarbital abgeschwächte Antwort auf visuelle Reizung wurde durch Acetylcholin-Mikroelektrophorese wieder verstärkt.
    Materialart: Digitale Medien
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    European archives of psychiatry and clinical neuroscience 211 (1968), S. 43-62 
    ISSN: 1433-8491
    Schlagwort(e): Neuronal activity ; EEG-cortex ; Hypoglycemia ; Cat ; Neuronale Aktivität ; EEG-Cortex ; Hypoglykämie ; Katze
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung 1. An Katzen wurden EEG-Veränderungen durch Hypoglykämie hervorgerufen und mit den Aktivitätsveränderungen corticaler Neurone verglichen, wie sie sich bei intracellulären und „quasi-intracellulären“ Ableitungen darstellen. Es zeigte sich, daß pathologische EEG-Veränderungen erst bei niedrigen Blutzuckerwerten (zwischen 30 und 25 mg-%) auftreten und daß es erst bei Werten unter 10–15 mg-% zur elektrischen Stille kommt. 2. Während des flachen, desynchronisierten EEG des wachen Hirns vor Hypoglykämie lassen sich keine Beziehungen zwischen den kleinen EEG- und statistisch verteilten Zellpotentialen nachweisen. — Während der regelmäßigen 8–10/sec- Spindelgruppen, die bei tiefer Hypoglykämie häufig zu beobachten sind, findet sich eine enge Korrelation zwischen den einzelnen Oberflächen-negativen Spindelwellen und Zelldepolarisationen, die meist unterschwellig sind. 3. Bei den langsamen Wellen der δ-Frequenz finden sich ähnliche, aber weniger enge Korrelationen für die flachen, „monomorphen“ δ-Wellen. Andere Formen von langsamen Potentialkomplexen des Cortiocogramms, die im Tintenschreiber als „polymorphe“ δ-Wellen imponieren können, zeigen etwas andere, aber für den einzelnen Wellenkomplex jeweils konstante Beziehungen zur Zellaktivität. 4. Die steilen Wellen wurden unterteilt in primär positive und in primär negative bi- (oder auch tri-)phasische Potentiale. Die primäre Phase der primär-positiven steilen Potentiale ist im Durchschnitt kürzer (unter 20–40 msec) als die negative Phase der primär-negativen Phase (über 100 msec). Die meist überschwellige Zelldepolarisation, die in der Regel zu einer kurzen Gruppenentladung führt, fällt mit der primären Phase, also entweder der positiven oder der negativen zusammen. Die Phasenkoppelung, d. h. die „Synchronisation“ mit dem EEG-Potential, ist jedoch im Fall der primär-positiven Phase enger und die Dauer der Depolarisation kürzer als im Fall der primär-negativen steilen Potentiale. Diese Befunde werden als Hinweis auf eine stärkere Synchronisation der Aktivität der corticalen Nervenzellpopulation im Fall der primär-positiven steilen Potentiale gewertet. 5. Die verschieden engen Phasenkoppelungen und die je nach Steilheit der Wellen wechselnden Phasenbeziehungen zwischen Zellaktivierung und oberflächennegativen resp. -positiven Potentialen werden an Hand eines einfachen Modells der Elektrogenese von EEG-Potentialen erklärt, das den Synchronisationsgrad cortico-petaler und cortico-fugaler Faseraktivität sowie die Summation postsynaptischer Potentiale corticaler Neurone berücksichtigt.
    Notizen: Summary 1. The EEG, recorded monopolarly from the pial surface, was investigated during insuline induced hypoglycemia in acute cats and compared with the activity of cortical cells recorded with intra or “quasi-intracellular” electrodes. 2. Pathological changes of the EEG were observed only when the blood glucose fell below 25–30 mg-%. Electrical silence was observed at blood glucose levels below 15–10 mg-%. 3. The essentially flat, “desynchronized” EEG of the awake animal before hypoglycemia did not show any relation between the small, irregular fast EEG- potentials and the statistically distributed cellular potentials. —During the regular 8–10/sec spindles (Fig. 3) a close correlation was found between the single surface- negative spindle waves and the mostly subthreshold compound cellular EPSP's. 4. Slow waves of δ-frequency showed similar but less close correlations, if the waves were of regular appearance comparable to “monomorphic” δ-waves (Fig.4A). Other forms of slow complex potentials (Fig.4B and C), which correspond to “polymorphic” δ-waves in an EEG-record (e.g. Fig.4C and Fig.2d) may show different relations between cellular and EEG-activity which were, however, consistent for each type of complex wave. 5. Sharp waves were divided into primary positive and primary negative bi- (or tri-)phasic potentials. The primary positive phase was always shorter (below 20–40 msec) than the primary negative phase (above 100 msec). The mostly suprathreshold cellular depolarization, which may lead to a short burst of discharge, coincided with the primary, i.e. either the primary positive or the primary negative phase (Fig. 7 shows records from the same cell and different EEG-phenomena). The phase coupling, i.e. the “synchronization” with the EEG-potential, is closer in the primary positive than the primary negative waves, and the duration of the cellular depolarization is also shorter in the former case (compare Fig.7B I–III with 7B IV). This can be interpreted as stronger synchronization of cellular activity during the short primary positive waves. 6. A causal relation between cortical neuronal activity and EEG-potentials is assumed. Differences in the closeness of phase coupling and the changing phase relation between cellular and EEG-activity according to the form and steepness of cortical EEG-potentials are explained by a simple model of electrogenesis of EEG-potentials, which takes in account the degree of synchronization of corticopetal and cortico-fugal fibre activity as well as the summation of postsynaptic potentials of cortical neurones.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    European archives of psychiatry and clinical neuroscience 211 (1968), S. 155-169 
    ISSN: 1433-8491
    Schlagwort(e): Sleep EEG ; Experimental Epilepsy ; Cat ; Schlaf-EEG ; Experimentelle Epilepsie ; Katze
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Frage der Wacho- der Schlaf-Aktivierung der fokalen Epilepsien wird bei 20 epileptischen Katzen im chronischen Experiment untersucht (Kopeloff-Methode). Die Narben wurden im Nucleus amygdaloideus (Pars basolateralis), Hippocampus dorsalis, Formatio reticularis mesencephali, Isocortex gesetzt. Bei einer Untersuchungsdauer der einzelnen Tiere zwischen 3 und 60 Tagen, wurden insgesamt 442 Std in Polygraphie (EEG, EMG, Augenbewegungen) abgeleitet. Die Tiere zeigten innerhalb der ersten 7 Tage Krampfpotentiale im EEG und die meisten ab der 2. Woche Krampfanfälle. Bei Katzen mit subcorticalen Narben war keine Veränderung der Dauer, der Verteilung und der Organisation der einzelnen Schlafstadien nachweisbar. Die im Ruhe-EEG vorhandenen Paroxysmen wurden während des langsamen Schlafes nicht aktiviert und fokalisiert. Im paradoxen Schlaf waren die Krampfpotentiale völlig desaktiviert, es traten einzelne Spindeln auf. Die Tiere mit Narben im Isocortex zeigten im langsamen Schlaf seltene Paroxysmen. Während der häufigeren kurzen Phasen des paradoxen Schlafes war eine Fokalisierung der Spitzen im Bereich der Läsion nachweisbar, jedoch, keine Aktivierung. Bei allen Tieren war die ausgeprägteste Aktivierung der Krampfbereitschft stets in dem von uns als „Wach mit motorischer Inaktivität“ bezeichnete Phase zu bemerken. Daher wird angenommen, daß dieser Zustand bei der Katze mit dem Einschlafstadium des Menschen vergleichbar ist.
    Notizen: Summary The activation of focal epileptic activities during wakefulness, slow and REM sleep was studied in chronic experiments in 20 epileptic cats (Kopeloff's method). The lesions were produced in the nucleus amygdaloideus (pars basolateralis), hippocampus dorsalis, formatio reticularis mesencephali and in the isocortex. Each animal was observed from between 3 to 60 days and a total of 442 hours of polygraphy (E.E.G., E.M.G, Eye movements) were recorded. Within the first 7 days all animals showed E.E.G paroxysms and most of them showed seizures from the beginning of the second week. In those cats with subcortical lesions there was no change detected in the duration, distribution and organisation of the different sleep phases. The paroxysmal E.E.G activity seen in the wakeful animal were not activated or focalised during slow-wave sleep; in REM sleep the paroxysms disappeared completely, only a few spindles were seen. Animals with lesions in the isocortex rarely showed paroxysms during the slow wave sleep. However, during REM sleep a clear focalisation was seen, although there was no additional activation in the area of the lesion. In all animals the most significant of the paroxysms was seen during a state which we should like to describe as; “Awake without any motor activity”. It is assumed that this state corresponds to the state of falling asleep in man.
    Materialart: Digitale Medien
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 3 (1967), S. 117-134 
    ISSN: 1432-1106
    Schlagwort(e): Supraspinal effects ; Extrapyramidal pathways ; Spinal activity ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Effects of stimulation of the sensorimotor cortex on activity of the lumbosacral cord were studied in pyramidotomized cats. The following actions initiated by corticofugal volleys were found: 1. postsynaptic effects on motoneurones, mainly excitatory in flexor motoneurones and inhibitory or excitatory in extensor motoneurones, 2. facilitation of spinal reflexes to motoneurones at an interneuronal level, 3. depolarization of presynaptic terminals of group Ib and cutaneous fibres. The latencies of the earliest cortical effects on motoneurones as indicated by modification of monosynaptic reflexes or PSPs were 9–12 msec. Experiments with lesions of different spinal tracts suggest that the effects on motoneurones are mediated mainly by pathways in the ventral part of the lateral funiculus (probably reticulospinal), the facilitation of reflex transmission by pathways in the dorsal part of the lateral funiculus (probably rubrospinal) and primary afferent depolarization by both the former and the latter pathways. The strongest cortical effects were evoked by stimulation of an area around the postcruciate dimple.
    Materialart: Digitale Medien
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