Astrid v. Lützow

Off-effekt und negative ERG-komponente des enukleierten bulbus und der isolierten retina des kaninchens I. Einfluss Der Reizparameter

Zusammenfassung Der Einfluss der Temperatur (10–35 °C) auf das ERG intakter enukleierter Bulbi (in O 2 -durchperlter Tyrodelosung) und isolierter umstromter Netzhautstucke von 12 Kaninchen wurde untersucht. Die Reiz und Registrierbedingungen waren die gleichen wie bei den vorhergehenden Untersuchungen bei Raumtemperatur (19°–22°C). Da das ERG der isolierten Netzhaut unter optimalen Versuchsbedingungen bei 30°C eine ausgepragte b-Welle enthielt, musste zur Isolierung der negativen Komponente P III eine plasmafreie Umstromungsflussigkeit verwendet werden. Die Belichtungsantwort der negativen Komponente (on-Effekt) vergrosserte bei beiden Praparationsarten mit steigender Temperatur ihre Amplitude und ihre Steilheit. Langerdauernde Erwarmung schadigte das Bulbuspraparat. Die nach Belichtungsende einsetzende Ruckkehr zur Basislinie (off-Effekt) wurde durch Temperaturerhohung ebenfalls beschleunigt. Dieser Ruckkehr war bei der isolierten Netzhaut eine rasche positive Schwankunguberlagert, die unter den gegebenen Versuchsbedingungen durch Unterkuhlen eliminiert werden konnte. Ihre Auspragung war vom Vorhandensein einer b-Welle unabhangig. Gelegentlich konnte ein langsames positives Potential beobachtet werden, das nach Belichtungsende kurzer Reize (1 sec) weiter zunahm und nach langen Reizen einen off-Effekt und anschliessende Ruckkehr zur Basislinie zeigte. Es verhielt sich wie das positive Spiegelbild der langsamen Phase von P III und konnte bei Verwendung von kurzen Reizen eine b-Welle vortauschen. Seinem zeitlichen Verlauf nach kommt es als Grundkomponente der c-Welle (P I) in Frage.

Die Bedeutung von Plasmafaktoren für die isolierte umströmte Kaninchennetzhaut

Theb-wave in the electroretinogram of the isolated retina of the rabbit can be completely preserved by addition of plasma to the perfusing fluid. The plasma factor is a non-protein (heat-stable, molecular size <24Å), and was found in the plasma of rabbit, man, and horse.Theb-wave in the electroretinogram of the isolated retina of the rabbit can be completely preserved by addition of plasma to the perfusing fluid. The plasma factor is a non-protein (heat-stable, molecular size <24A), and was found in the plasma of rabbit, man, and horse.

Der Nachweis des Barbiturateffektes an der isolierten Warmblüternetzhaut

Barbiturates cause an increase of the ERG amplitude in the isolated perfused retina of the rabbit as well as in the eye of the intact animal. Therefore, this effect cannot be transmitted by centrifugal fibres in the optic nerve.

Das elektronenblitz-ERG der isolierten warmblüternetzhaut—II. Einfluss von intensität und temperatur auf die positiven wellen

The influences of light intensity and temperature on the initial positive waves in the ERG of isolated mammalian retinae were investigated. In an intensity range of 4 log units in rabbit, dog and guinea pig peak times between 32 and 12 msec were found. Varying temperatures peak times between34 ± 3.19 msec (20°) and14 ± 4.13 msec (35°) were measured (corresponding toQ10 of 2.3 for temperatures between 20° and 30° in the rabbit. The slower wave of cat and ground squirrel (peak time about 60 msec) did not decrease significantly with increased intensity; a similar independance is known from the human x-wavein situ. Decrease of temperature abolishes the “x-wave” irreversibly revealing the initial positive potential (Q10 = 2.5).

A second order model of the optic generator potential and its relation to Stevens' power function

SummaryThe component PIII of the electroretinogram representing the optic generator potential was recorded after stimulation with short stimuli with different light intensity. It is shown that the impulse response function of a linear second order model with intensity-dependent coefficients can be well fit to the recordings. Two of its parameters, after logarithmic transformations, are linearly dependent on the luminance while the third parameter varies only within a small interval. It is therefore possible to describe the relation between PIII and luminance in a linearized second order model. Furthermore, both the type of the function relating the gain of the model to the luminance and its exponent are nearly identical with the psychophysic function relating luminance to subjective brightness. Further physiological implications are also considered.

Das elektronenblitz-ERG der isolierten warmblüternetzhaut—I. Die inititalen positiven wellen des blitz-ERG

The ERGs of isolated mammalian retinae (european ground squirrel, guinea pig rabbit, cat, dog) were investigated using photographic flash stimuli. Besidesa- andb-waves in cat and ground squirrel a positive wave (peak time 60 msec at 30°)—corresponding to the photopicb-wave in man, was demonstrated. In the retinae of all animals—except ground squirrel—a fast positive hump (peak time About 20 msec) was found obviously corresponding to the first oscillatory potentialin situ. Application of IAA in the rabbit resulted in progressive abolition ofb-wave and later humps. In the retinae of rabbit and guinea pig another small positive hump (peak time 45 msec) is described.

Zur Ausschaltung des Becquereleffektes in der Elektroretinographie

Distortion of the electroretinogram by Becquerel effect may be excluded by using carbon rod instead of metallic wire in connecting the electrode.

A mathematical model of slow PIII of the ERG: Variation of stimulus duration

Light stimulation of a vertebrate retina induces an interruption of the Na’ inward current into the outer segments of photoreceptors (Penn and Hagins, 1969). Concomitantly [K’] decreases in the extracellular space of the photoreceptor layer (Tomita, 1976; Oakley and Green, 1976). It is hypothesized that the Na’ influx into photoreceptors is accompanied by a K‘ efBux. keeping a constant extracellular [K’] in the dark. Light reduces this outflow while the Na’,/K’ pump situated in the inner ‘segment membrane (Matsuura et al., 1978) continues to remove K’ from the extracellular space. It has been shown recently, that blocking the pump actually diminishes the light induced decrease of extracellular [K+] (Oakley et al., 1979). The [K’] sink seems to be mainly produced by rod activity and has been assumed to give rise to the Miiller cell hyperpolarization (Witkovsky et al., 1975) which can be recorded as slow P III in the gross ERG. Taking into account the different underlying mechanisms in the present investigation slow P III as recorded from an isolated rabbit eye bulb was modelled by a set of two exponential functions, which were fit independently to the potential changes occurring at light onset and offset respectively.

Effect of azide on the ERG of the isolated mammalian retina.

SummaryAzide, which is known to affect the pigment epithelium strongly may be assumed to cause damage to the receptors, which are functionally connected to the pigment epithelium. To check this hypothesis the effect of azide on the ERG was investigated. An isolated retina preparation was used as in this preparation the P III component, which contains considerable receptor contribution, can be isolated.In 2 series of experiments the effects of azide on the P III and the complete ERG were investigated. Depending on the concentration azide was shown to abolish the b-wave, to cause delay and amplitude diminution of the P III and enhance a positive component in the off-effect.A number of plausible sites of origin of these azide effects on the ERG changes are discussed.

Nachweis des Azid-Potentials an der isolierten Kaninchennetzhaut

In the isolated rabbit retina, application of azide produces a positive potential as was demonstrated in situ byNoell. The amplitude of this effect is about 1/5 to 1/10 of the amplitudes described in situ. The results support the assumption that the azide potential is produced partly in the pigment epithelium but to some extent also within the retina.