[Clinical electroretinography in veterinary medicine. 2. Progressive retinal atrophy and hemeralopia].
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Biomedical subjects
A Reichenbach
Publications and source records attributed to A Reichenbach.
[Clinical retinography in veterinary medicine. 1. Methodological principles and normal values].
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Changes in membrane-associated proteins during sporulation in Bacillus subtilis.
Membrane proteins from vegetative and sporulating cells of Bacillus subtilis were separated by the two-dimensional gel electrophoresis system using isoelectric focusing and sodium dodecyl sulfate/polyacrylamide gel electrophoresis (O'Farrell technique). Membrane proteins were isolated according to published procedures. The gels were stained with Coomassie blue. Three different concentrations of proteins were analyzed to detect even minor constituents. Over two hundred different membrane proteins were identified in vegetative cells by their isoelectric point (pI) and molecular weight (Mr). Analysis of membrane proteins from cells harvested during and at the end of logarithmic growth (A600 approximately equal to 0.8; T0) and every hour thereafter until T4 showed that in the wild-type strain 55 proteins are degraded mostly at the beginning or sporulation. Many others (76 proteins) are newly synthesized during sporulation. About 16 proteins are synthesized at times during sporulation but again degraded within 1 h or less. Others (uncertain proteins, 65) are degraded and resynthesized again. This observation is in agreement with experiments previously published by Andreoli et al. [Andreoli, A. J., Kao, M., Chui, R., Cabrera, J., and Wong, S. K. S (1981) in Sporulation and Germination (Levinson, H. S., Sonenshein, A. L., and Tipper, D. J., eds) pp. 168-173, American Society for Microbiology, Washington] using Bacillus cereus. Experiments with the early blocked asporogenous mutant JH 649 (spoOF) showed that few proteins (40%) are degraded and even fewer (30%) are newly synthesized between A600 approximately equal to 0.8 and T4. Protease inhibitors (phenylmethylsulfonyl fluoride, EDTA, o-phenanthroline) have no effect on the protein patterns. The experiments presented here show that proteins involved in differentiation in B. subtilis can be identified by the two-dimensional gel electrophoresis system and with the aid of asporogenous mutants. In order to assure that no cytoplasmic proteins are contaminating the membrane preparations, several cytoplasmic enzyme activities have been measured. Their concentration was found to be always below 0.005% of total protein, which is below the level of detection by Coomassie blue staining.
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The glutamate-isolated mass receptor potential of the frog's retina. III. Calcium dependence.
The mass receptor potential of excised frog retinas was isolated by superfusion of the tissue with modified Ringer solutions containing sodium glutamate. The changes in the potential amplitude due to the variation of the calcium concentration were measured. Step by step reduction of the calcium concentration from 2 to 0.05 mM caused a mass receptor potential increase up to threefold; further calcium lowering diminished the amplitudes. Rods and cones, however, seemed to react in different ways to changed calcium concentrations. The responses to red light stimuli and the so-called rapid decay of the glutamate-isolated potentials, both generated mainly by cones, disappeared in calcium free solutions. Both the responses to green light stimuli and the so-called remaining part of mass receptor potentials, however, i.e. the potentials produced mainly by rods, were still larger in calcium free solutions compared to those in 2 mM calcium solutions. Changing the calcium concentration of the solutions altered both the Sodium and the potassium dependence of the mass receptor potential, and that differently for rods und cones. The results are used to support the hypothesis that calcium acts as internal transmitter in vertebrate photoreceptors. This view is confirmed by interpretation and critical comparison of data taken from the literature.
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Preparation of isolated Müller cells of the mammalian (rabbit) retina.
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Quantitative properties of Müller cells in rabbit retina as revealed by histochemical demonstration of NADH-diaphorase activity.
Müller cells in rabbit retina were selectively stained by demonstrating NADH-diaphorase activity. After the sections were measured by light microscopy, the following properties of Müller cells were found: (a) independent of the retinal localization, one Müller cell corresponds with a retinal volume of 15,000 microns 3, i.e., with 11 photoreceptor cells, 2 neurons of the inner nuclear layer, and 0.3-1 ganglion cells; (b) the Müller cell population represents about 6.8% of the total retinal volume; (c) the sorbitol accumulation of Müller cells in diabetic retinopathy is said to be unable to cause osmotic damage.
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The glutamate-isolated mass receptor potential of the frog's retina. I. General properties and intensity dependence.
The glutamate-isolated mass receptor potential of the superfused frog's retina was investigated in order to find a method for discrimination of both rod and cone contribution to the sum response. After mesopic white light stimuli the potential showed a biphasic decay with a rapid and a slow part, respectively. Regarding threshold, saturation, light adaptation, and time course, the rapid decay is shown to correspond to the cone response. The remaining part of mass receptor potential, on the other hand, resembled the rod response in all these properties. This analysis provides the basis for studying the cation dependence of rod and cone receptor potentials with the stable mass receptor potentials. Moreover, the time course of the rod's light response is discussed to draw some conclusions regarding the internal transmission in rod photoreceptors.
Action Potentials↗
The glutamate-isolated mass receptor potential of the frog's retina. II. Sodium and potassium dependence.
The mass receptor potential of superfused frog retinas was isolated by means of sodium glutamate. The changes of the potential amplitudes due to the variation of sodium and potassium concentration were measured. Lithium and choline were tested as osmotic substitutes. In both lithium and choline containing solutions the mass receptor potential amplitude varied in direct linear proportion to the logarithm of the sodium concentration, and in inverse linear proportion to the logarithm of the potassium concentration. To obtain stable potentials, however, it was necessary to enhance the glucose content to 50 mM in lithium solutions. Choline is shown to be more suitable for an osmotic substitute than lithium. The effects of sodium and potassium on the mass receptor potential were strongly dependent on intensity and wavelength of the stimulus light. Both the responses to red light stimuli or strong white lights showed only a slight sodium and potassium dependence; the same was evident for the so-called rapid decay of the potentials. The responses to green light stimuli or dim white ones and the so-called remaining part, however, were strongly reduced in high potassium or low sodium concentrations. These results suggest that the retinal rod activity is more dependent on the ionic composition of superfusing solutions than that of the cones under the given experimental conditions. This might be caused by the faster reaction of the cone membrane pumps.
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Horizontal cells of the rabbit retina: some quantitative properties revealed by selective staining.
Horizontal cells of the rabbit retina were selectively stained by demonstration of beta-hydroxybutyrate dehydrogenase activity. Thereafter, the size of the cell bodies, the distance between neighbouring cells, and the number of cells per mm2 were measured. In the area centralis, the horizontal cell bodies occupy only 4.2% of the total retinal area; in the far periphery, however, 12.8% of the retinal area consist of horizontal cell bodies. Furthermore, the horizontal cells of the retinal periphery have much larger cell bodies as compared with those of the retinal center. The far periphery, for these reasons, is concluded to be the optimal region for intracellular microelectrode recordings from rabbit retinal horizontal cells.
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[Electrophysiological studies on the spectral sensitivity of the photoreceptors of the frog retina].
A new method for potential measurements is proposed to study the spectral sensitivity of more than two different types of photoreceptors by means of the mass receptor potential of the isolated retina. The studies were carried out on retinas of animals belonging to the European waterfrog group: Rana ridibunda, R. lessonae and R. esculenta. We were able to demonstrate two different spectral types of rods and two different types of cone responses in each retina. In connection with morphological findings the european waterfrogs are suggested to possess the same types of photoreceptors as Rana pipiens. The question is discussed whether the different types of both rods and cones show different thresholds.
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Photoreceptor layer composition in the retina of the frog (Rana esculenta).
Retinas of Rana esculenta frogs were studied by light and electron microscopy in order to establish the photoreceptor layer composition. We found 56% red rods, 9% green rods, 19% single cones, and 16% double cones. This work provides the morphological basis for electrophysiological investigations concerning the mass receptor potential of isolated Rana esculenta retinas.
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[Topography of the quail retina].
Retinas of quails (Coturnix coturnix japonica) were studied by light microscopy. By this, an area centralis with high cell density could be demonstrated. Moreover, in the posterior-superior retina there exists a region of moderate cell density containing a central red field with a high concentration of cones with red oil droplets. The results suggest the quail to be able to fix objects lateral to its head and in front of its bill in direction of picking.
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[Changed retinal cell content in diabetics (author's transl)].
A quantitative exploration of retinal cell content was carried out in diabetics and metabolically healthy controls of the same age and sex distribution. After diabetes of 6 years duration there was a drastic diminution of cells in the ganglion cell layer of the central retinal area, while the number of cells of the inner nuclear layer was slightly reduced and that of the outer nuclear layer was still unchanged. The periphery of short duration diabetic retinae showed a normal cell content in all nuclear layers. In long-term diabetes (about 10 years), significant diminutions in cell numbers were found in all layers of both the retinal center and periphery. The described cell deficits are accounted for by disturbances of retinal microcirculation. After a relatively short duration of diabetes, blood flow interruptions in the area supplied by the central retinal artery occur; in long-term diabetics the chorioidal vessels are also affected. Connexions between the cell-deficit pattern and functional (electrophysiological) findings are discussed.
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[Demonstration of subcomponents of PIII in the ERG of isolated rabbit retina using sodium asparaginate].
Experiments on the sum potential to dark flashes after eliminating the positive components by low temperature (25 degrees C) and low content of plasma (10% instead of 50%) in the perfusion fluid have shown that the cornea-negative component PIII is extensively reduced by application of 10 mM sodium aspartate. The existence of an aspartate sensitive PIII-subcomponent, which was first discovered by intraretinal records, is not in agreement with the opinion that the whole PIII represents receptor activity. Fast and slow PIII-subcomponents are also discernible in the cornea-negative PIII - recorded with cross-electrodes - by their time course without and with adding sodium aspartate. The fast subcomponents are demonstrable in a rough approximation by condenser-coupling the amplifier (t = 0.3 sec). Changing the temperature from 22 degrees C to 27 degrees C the temperature quotient amounts to 1,3 for the fast subcomponents, and to 2.1 for the whole PIII including the slow subcomponents.
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What do retinal müller (glial) cells do for their neuronal 'small siblings'?
Müller (radial glial) cells are the predominant glia of the vertebrate retina. They arise, together with rod photoreceptor cells, bipolar cells, and a subset of amacrine cells, from common precursor cells during a late proliferative phase. One Müller cell and a species-specific number of such neurons seem to form a columnar unit within the retinal tissue. In contrast, 'extracolumnar neurons' (ganglion cells, cone photoreceptor cells, horizontal cells, and another subset of amacrine cells) are born and start differentiation before most Müller cells are generated. It may be essential for such neurons to develop metabolic capacities sufficient to support their own survival, whereas late-born ('columnar') neurons seem to depend on a nursing function of their 'sisterly' Müller cell. Thus, out of the cell types within a retinal column it is exclusively the Müller cell that possesses the enzymes for glycogen metabolism. We present evidence that Müller cells express functional insulin receptors. Furthermore, isolated Müller cells rapidly hydrolyse glycogen when they are exposed to an elevated extracellular K+ ion concentration, a signal that is involved in the regulation of neuronal-glial metabolic cooperation in the brain. Müller cells are also thought to be essential for rapid and effective retinal K+ homeostasis. We present patch-clamp measurements on Müller cells of various vertebrate species that all demonstrate inwardly rectifying K+ channels; this type of channel is well-suited to mediate spatial buffering currents. A mathematical model is presented that allows estimation of Müller cell-mediated K+ currents. A simulation analysis shows that these currents greatly limit lateral spread of excitation beyond the borders of light-stimulated retinal columns, and thus help to maintain visual acuity.
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Development of dendritic trees of rabbit retinal alpha ganglion cells: relation to differential retinal growth.
To provide a quantitative description of the postnatal development of dendritic trees in alpha ganglion cells of the rabbit retina, these cells were stained either by intracellular injection of Lucifer yellow or by application of the lipophilic dye DiI. This was done at three developmental stages: postnatal day (P) 8/9, P 16/17, and in adults. For different retinal locations we quantified the alpha cell dendritic field area, the number of dendritic branch points, and the average dendritic length between branch points. According to the alpha cell location, the data were collected in three groups representing the retinal center, midperiphery, and far periphery, respectively. The data were then correlated with the postnatal retinal expansion which is known to differ among the above topographic regions of the retinae (Reichenbach et al., 1993). Our results show that the growth of alpha ganglion cell dendrites is not proportional to, but significantly exceeds, that of the local retinal tissue. Between P 8/9 and adulthood, the area of central alpha cells increases almost six-fold from 26,000 to 144,000 microns 2 (retinal expansion: 2.2-fold), and that of peripheral cells more than 15-fold from 35,000 to 556,000 microns 2 (retinal expansion: four-fold). During this period, the coverage factor of alpha cell dendritic fields increases about three-fold, and reaches adult levels of about 3 (retinal center) and 2.2 (periphery), respectively. The number of dendritic branch points remains nearly constant, and the distance between them increases by a factor close to the square root of the factor by which the dendritic field area grows. Thus, it appears that, from the second postnatal week on, dendritic trees of rabbit alpha ganglion cells increase by intense "interstitial growth," rather than by outgrowth of (new) dendritic branches. This growth pattern is different from that of some other rabbit retinal ganglion cell types, and of alpha ganglion cells of the cat retina, whose dendritic trees expand at a rate equal to or less than that of the surrounding retinal tissue. The consequences for synaptic contacts with bipolar and amacrine cells are discussed; they suggest a high degree of synaptic plasticity during normal postnatal retinal growth.
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Development of the rabbit retina, III: Differential retinal growth, and density of projection neurons and interneurons.
To provide a quantitative description of postnatal retinal expansion in rabbits, a new procedure was developed to map the retinae, which cover the inner surface of hemispheres or parts of rotation ellipsoids, in situ, onto a single plane. This method, as well as the known distribution of Müller cells per unit retinal surface area, were used to estimate the redistribution of specific subpopulations of Müller cells within different topographic regions of the retinae. Müller cells are known to exist as a stable population of cells 1 week after birth and can therefore be used as "markers" for determining tissue expansion. Our results show that differential retinal expansion occurs during development. Peripheral retinal regions expand at least twice as much as the central ones. Furthermore, there is a greater vertical than horizontal expansion. This differential retinal expansion leads to a corresponding redistribution of 5-hydroxytryptamine (5-HT) accumulating amacrine cells. Differential retinal expansion, however, does not account for all of the changes in the centro-peripheral density gradient of cells in the ganglion cell layer (GCL)--mostly retinal ganglion cells--during postnatal development. The changes in the ganglion cell layer were evaluated in Nissl-stained wholemount retinal preparations. Additionally, the difference between expansion-related redistribution of cells in the GCL and Müller cells was confirmed in wholemount preparations where Müller cells (identified as vimentin positive) and cells in the GCL (identified by fluorescent supravital dyes) were simultaneously labeled. It is assumed that many of the ganglion cells within the retinal center are not translocated during retinal expansion, possibly because their axons are fixed. In contrast, 5-HT accumulating amacrine cells--which are interneurons without a retinofugal axon--display a passive redistribution together with the surrounding retinal tissue.
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Changes of the organotypic retinal organization in Borna virus-infected Lewis rats.
Retinae of Borna disease virus (BDV)-infected Lewis rats were investigated with emphasis on long-term changes in organotypic tissue organization and glia-neuron relationship. Virus inoculation was attained via intracerebral BDV injection. Following survival times ranging between two and eight months, the retinal thickness was reduced up to one third of that of controls. Photoreceptor segments were completely extinguished and the number of neurons was dramatically reduced. The typical laminar organization of the retina was largely dissolved. Electron microscopy revealed severe spongy degeneration. Large numbers of activated microglia and macrophages were found, both cell types performing very active phagocytosis. The microglial cells expressed an extraordinary phenotype as characterized by large numbers of processes, with some of them penetrating the endfeet of Müller cells and others establishing highly complex interdigitations with vacuolized swellings and endings of neuronal processes. Müller cells were not reduced in number but displayed clear indications of gliosis such as alterations in the immunoreactivity for filament proteins and glutamine synthetase, significantly thickened stem processes, and an altered pattern of K(+) currents in patch-clamp recordings. These findings demonstrate for the first time long-term neuron-glia interactions in the retina of BDV-infected rats. Moreover, the data contribute to our knowledge on structural and functional alterations accompanying persisting virus infection in the central nervous system.
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