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Biomedical subjects

E Zrenner

Publications and source records attributed to E Zrenner.

At least 235 records · Page 13Linked to original sources
PubMed1986

The influence of phosphodiesterase inhibitors on ERG and optic nerve response of the cat.

Reversible changes in electroretinograms (ERG) and optic nerve responses (ONR), induced by various concentrations of four different types of phosphodiesterase (PDE)-inhibitors, were recorded from arterially perfused, isolated cat eyes. In the dark-adapted eye, the implicit time of the PIII-component of the ERG, isolated by temporary hypoxia, showed a dose-dependent increase after the injection of PDE-inhibitors into the ophthalmociliary artery. The PIII-amplitude increased in response to small doses of PDE-inhibitors, whereas higher doses led to an amplitude decrease. Rod b-wave amplitude and implicit time showed similar alterations. An amplitude increase could not be observed in the rod ONR. In the light-adapted eye, 440 nm and 555 nm cones were functionally separated by means of chromatic adaptation. Their ERG and ONR implicit times were prolonged under PDE-inhibition. The amplitude behaviour of both types of cones showed a different concentration dependency. Certain concentrations of PDE-inhibitors depressed the short-wavelength sensitive cone, while, at the same time, sensitizing the long-wavelength sensitive cone. The amplitude increase of the L-cone b-wave was accompanied by a response increase of tonic ganglion cells in the ONR.

Animals↗
PubMed1984

[Increased radiation exposure of the retina following implantation of intraocular lenses and its prevention using colorless filter glasses].

By measurement of spectral sensitivity functions it was shown that the irradiation of the retina with short visible wavelengths increases by a factor of 20 after implantation of intraocular lenses. According to recent investigations, the possibility of photochemical retinal damage and the development of macular degeneration is thereby increased considerably. It is discussed to what extent the Irvine-Gass-Norton syndrome observed in a particular patient two years after operation is associated with increased retinal irradiation. A protective glass filter is described which brings the spectral sensitivity function of pseudophakic patients down into the physiological range without changing color vision and brightness sensation; moreover, it provides a high degree of protection against phototoxic UV radiation, to which (according to Williams et al.; 1983) pseudophakic patients are 300 times more exposed.

Aphakia, Postcataract↗
PubMed1984

Cone mechanisms and their colour-opponent interaction in monkeys and cat.

Cone mechanisms and colour opponency were investigated in 108 recordings from tonic ganglion cells of the rhesus monkey retina and 265 recordings from ganglion cells of the cat retina. Colour-opponent cells input from short and longer wavelength sensitive cones can be found in both species in about equal proportions (6-8%). Although cells with opponency between middle and long-wavelength sensitive cones are very common in monkey (49%), they are rare in the cat (4%); usually the opponency of the latter can only be detected with strong chromatic adapting lights suppressing the dominant mechanism, while in monkey colour opponency is usually revealed under neutral adapting conditions. These differences between both species in processing chromatic stimuli can help to explain certain types of colour vision deficiencies in man.

Animals↗
PubMed1983

Intracellular recordings from a biplexiform ganglion cell in macaque retina, stained with horseradish peroxidase.

A biplexiform ganglion cell, which is characterized by dendritic contacts with rods, has been penetrated with an HRP-filled microelectrode in the retina of Macaca fascicularis. Its fine curvy axon could be traced to the optic disc. One of several dendritic processes ascended through all retinal layers and ended in the layer of rod spherules. Under all conditions of chromatic adaption, the cell produced depolarizing responses with a rapid onset and a slow decay. Besides a strong rod input the recordings indicate signals from at least two spectrally different cone mechanisms.

Animals↗
PubMed1979

Enchancement of luminance flicker by color-opponent mechanisms.

Color-opponent ganglion cells in the monkey retina respond to luminance flicker at high temporal frequencies. Color opponency, which makes these cells so selective of wavelength at low temporal frequencies, is progressively lost at high frequencies. This loss is due to a frequency-dependent phase shift between the responses of spectrally different center and surround mechanisms in the receptive field of each of these cells. Center and surround responses, which are antagonistic at low temporal frequencies, become synergistic at high ones, making these cells most responsive at high frequencies to those wavelengths to which they are least responsive at low frequencies. This phenomenon can explain the differences between chromatic and luminance flicker in human vision.

Animals↗
PubMed1979

Blue-sensitive cones of the cat produce a rodlike electroretinogram.

Two cone mechanisms are identifiable in the strongly yellow light-adapted electroretinogram (ERG) of the arterially perfused cat eye. One has its maximum spectral sensitivity near 555 nm; the other has its maximum near 450 nm. The former cone system produces a much larger signal with characteristics of a typical cone or inhibitory ERG. The latter cone system produces a small, saturable signal (less than 5 microV) which resembles a rodlike or excitatory ERC. The results imply that the latter ERG is generated by blue-sensitive cones, which form a small fraction of the total cone population and share some physiological and perhaps anatomical properties of rods.

Animals↗