Wolf-Dieter Heiss

The Value of Regional Cerebral Blood Flow Measurements Compared to Angiography in the Assessment of Obstructive Neck Vessel Disease

In 50 patients with internal carotid artery occlusion and 40 patients with internal carotid artery stenosis hemispheric and regional cerebral blood flow (rCBF) was measured by the 133Xenon clearance method, rCBF was evaluated according to the presence of ischemic or hyperemic foci and to the level of regional perfusion alteration. The degree of collateral circula tion and diameter of stenosis were determined from the angiograms. The clinical symptoms were expressed in a score of motor deficiencies. In internal carotid artery occlusion no correla tion of motor deficiency index with angiographically demonstrable collateral circulation was detectable, but there was good correlation with hemispheric CBF and an excellent correlation (P < 0.001) with the rCBF parameters. In internal carotid artery stenosis no correlation existed between motor deficiency and the degree of stenosis or hemispheric CBF, but good correlation was observed between motor deficiency and the rCBF parameters (P < 0.01). According to these findings, angiographical demonstration of collateral circulation and of stenosis does not provide as accurate information on impending or already developed tissue in farction as does rCBF measurement. Presence of hyperemic foci and lack of ischemic foci were related to lesser motor disturbances. Borderlines of 30 ml/100 gm per minute for threatening tissue ischemia and of 25 ml/100 gm per minute for present tissue ischemia are established. Some points favor the thromboembolic theory of infarction in internal carotid artery stenosis.

Daueraktivita¨t retinaler neurone unter einwirkung von strychnin und pikrotoxin

Abstract The activity of 141 single fibers of the optic nerve was studied in seven cats. The units were classified according to their response to short light stimuli. The tonic activity was recorded on tape and from these data nonsequential interval histograms were computed. Three types of interval histograms could be obtained from the spontaneous activity in darkness: 1, Unimodal scew distributions. 2, Histograms with two peaks; the first peak was related to the repeated appearance of bursts in the discharge. 3, Multimodal distributions; the maxima occurring in regular distance of integral multiples of the first peak. During constant diffuse illumination of different intensity (0.88, 15.4 and 220 cd/m 2 ) three possible variations of the maintained activity were observed: 1, The activity was diminished in relation to the intensity of illumination. 2, The maintained discharge rate was not changed by illumination. 3, The activity was increased during illumination. On-center-neurons showed all three possible variations, in off-center-neurons reduction of activity dominated significantly. Therefore, off-center-neurons may be responsible for the overall reduction of retinal activity during continuous illumination. After intravenous injection of strychnine (0.25–0.8 mg/kg) the spontaneous activity was significantly increased. The same types of interval histograms as for the controls could be observed. The tonic and phasic reaction due to light stimulation were similar to those of units not being influenced by strychnine. A low dosage of picrotoxin (0.3 mg/kg) decreased the activity in some neurons; higher dosage (0.6–1.5 mg/kg) accelerated the discharge significantly. With respect to the types of interval histograms and the change of maintained activity during illumination no significant difference to the controls was found. Higher dosage of Picrotoxin increased inhibitory effect of short light stimulation: In some neurons this effect could be so strong, that the response of the unit appeared to be inversed. The inhibition was not extinguished by simultaneous application of strychnine and picrotoxin. According to these results the existence of three different mechanisms of inhibition in the retina may be assumed.

Contribution to the Hemodynamics of Arterial Venous Malformations

In three cases of arteriovenous malformations (AVMs), and in one postoperative case, the passage of an I.V.-administered 99m-Technetium bolus through the brain and the 133Xenon clearance after intracarotid injection from different brain areas were observed, using a scintillation camera-1600 channel memorydigital magnetic tape unit. Regional cerebral blood flow values from contiguous areas down to 12 mm lateral lengths were calculated. In two cases computer-calculated cerebral blood flow maps are presented. Areas surrounding the AVMs revealed relatively high CBF values, while the blood flow in more distant parts of the hemisphere was decreased. Areas of low CBF values were detected also in the postoperative case with ligation of vessels. The initial part of the washout curves showed over all AVMs shunt peaks up to 88% of the initial activity. Shunt peaks detected also over most parts of the involved hemisphere are explained by arterio-arterial shunt connections. Their flow, centripetally directed to AVM, may cause the observed pattern of higher and lower flow values, indicating that the Xenon washout may be sensitive not only to capillary flow. Conclusions are drawn that the Xenon-clearance technique provides detection of the hemodynamic influence, but not of the shunt volume of AVMs.

Die wirkung von psychopharmaka auf die aktivität retinaler neurone

Abstract Using microelectrodes the activity of a total of 328 single fibers of the optic nerve was recorded in 37 cats. The influence of Chlorpromazin, Butyrylperazine, Chlorprothixen, Spiroperidol, Desipramin, Amitriptyline and Diazepam on spontaneous and light induced activity was investigated. With increasing doses of the psycho-pharmacological agents the spontaneous activity decreased significantly. Diazepam altered the type of nonsequential interval histograms: In spite of the decreased frequency the histograms were uni- or bimodal under the influence of the studied drugs except Diazepam. With this substance multimodal distributions appeared. The phasic response of the neurons to light stimuli was only slightly altered. Under the influence of Desipramin and Amitriptyline strong reactions to the stimuli without any spontaneous activity of the fibers were observed. The results in connection with the findings of other investigators show a direct influence of psycho-pharmacological agents on the neural net of the retina. The results support the assumption of the existence of synaptic transmitters in addition to acetylcholine and catecholamines.

Die wirkung von psychopharmaka auf visuell evozierte potentiale der katze

Abstract Visually evoked potentials were recorded from the visual cortex of 25 cats and the changes due to the influence of Chlorpromazin, Butyrylperazin, Chlorprothixen, Haloperidol, Desipramin, Amitriptyline and Diazepam were investigated. The latencies of the responses increased with increasing doses of the agents, the on-responscs in the evoked potentials of most of the animals were enlarged. In some experiments off-responses could be seen only under the influence of psychopharmacological drugs; in most animals the amplitude of the off-responses increased according to higher dosage. The visually evoked potentials were accentuated under the influence of these drugs. The effects may be interpreted as caused by reduction of activating influences from other parts of the brain to the visual cortex and by the decrease of spontaneous activity in the primary afferent system.

Die aktivität von Einzelfasern des nervus opticus bei verschiedenen temperaturen

SummaryThe 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.ZusammenfassungIn 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.

Single Fibers of Cat Optic Nerve:"Thresholds" to Light

Absolute thresholds of 39 single fibers of the optic nerves of 20 cats were determined by inspection of post-stimulus time histograms, each com puted from the responses to 60 to 100 identical flashes of white light. The values found—from 1.1 x 10-7 to 6.8 x 10-6 candella per square meter (nits)—agree well with psychophysi cal thresholds found in previous in vestigations.

Retinale Impulsaktivität und Elektroretinogramm unter dem Einfluss von Desipramin

The influence of Desipramin on ERG and optic nerve activity (42 single neurons) was studied in 8 cats. The drug strongly suppressed the spontaneous activity of the neurons, leaving the response to illumination practically uninfluenced. Thec-wave of the ERG was increased. There is little doubt about a pure retinal origin of the effects.The influence of Desipramin on ERG and optic nerve activity (42 single neurons) was studied in 8 cats. The drug strongly suppressed the spontaneous activity of the neurons, leaving the response to illumination practically uninfluenced. Thec-wave of the ERG was increased. There is little doubt about a pure retinal origin of the effects.

Participation of retinal mechanisms in DMT hallucinations

Intravenöse Injektionen von DMT (1–5 mg/kg) bewirkten neben einer Verkleinerung der visuell evozierten corticalen Potentiale und der lichtinduzierten phasischen Reaktionen retinaler Neurone auch eine starke Verminderung der Spontanaktivität in Einzelfasern des N. opticus. Die Befunde sprechen für eine Beteiligung retinaler Mechanismen beim Zustandekommen optischer Halluzinationen und lassen 5-HT als retinalen Transmitter vermuten.